4626 4630.output

* GB785033 (A)

Description: GB785033 (A) ? 1957-10-23

Improvements in or relating to electric control devices for furnaces

Description of GB785033 (A)

PATENT SPECIFICATION Date of filing Complete Specification July 18, 1955. Application Date July 16, 1954. 785,035 No 20805/54. Complete Specification Published Oct 23, 1957. Index at Acceptance:-Classes 40 ( 6), R 3 (A 1: Bil); and 75 ( 1), TE, TG 22, TJ. International Classification: -F 23 d, f H 03 f. COMPLETE SPECIFICATION Improvements in or relating to Electric Control Devices for Furnaces We, ORMISTON MEIKLE, British Subject, of "High Trees ", 64, Butts Green Road, Hornchurch, in the County of Essex, LEONARD PERCIVAL FIANDER, British Subject, of 25, Zealand Avenue, Harmondsworth, West Drayton, in the County of Middlesex, and DOUGLAS JA Ci K GODFREE ANDREWS, British Subject, of 56, Biggin 1 ill, Upper Norwood, London, S E 19, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: - This invention relates to an electric control device for an oil-burning or gas burning furnace, which can be employed in conjunction with thermostats or other devices responsive to conditions in the furnace to control the normal operation of the furnace and also to provide adequate safeguards in the event of failure of the furnace to operate satisfactorily. The invention has for its primary object to provide an improved electric control device for this purpose of simple and robust construction which will operate efficiently and reliably to effect the desired control. The control device according to the present invention comprises two

electric relays respectively energised from the anode circuits of two electronic discharge devices each having a control grid, a capacitance-resistance timing circuit connected to the control grid of each electronic device, and means whereby each relay controls the application of potential to the timing circuit associated with the electronic device energising the other relay, the arrangement being such that the time delay controlled by the first relay and preceding operation of the second relay is initiated by the energisation of such first relay whilst the time delay controlled by the second relay and preceding operation of the first relay is initiated by the deenergisation of such second relay. The device is preferably such that, when it is required (for example as the result of the lPrice 3 s 6 d l operation of a thermostat) to bring the furnace burner into operation, the first relay is energised (provided that the time delay controlled by the second relay has meanwhile expired) and acts on operation to energise the fuel-supply means for the burner Preferably, such second relay, on operation after the time delay initiated by the first relay, acts to deenergise the first relay unless meanwhile a flame-responsive device operative when the burner has satisfactorily ignited has completed a holding circuit for the first relay. Conveniently, if the said holding circuit has been completed, the two relays remain energised until the furnace temperature has been raised by the burner to the desired level, whereupon a thermostat operates to deenergise both relays The arrangement is preferably such that, after deenergisation of the first relay by the second relay in the event of failure of the flame-responsive device to complete its holding circuit, the second relay remains energised and thereby locks the control device against further operation until a manually-controlled switch is operated to deenergise the second relay. Whilst the burner may be ignited in other ways, it is often convenient, especially in an oil-burning furnace, to control such ignition electrically over a circuit which is completed on energisation of the first relay, such circuit being broken on energisation of the second relay. The electronic device may take various forms but in one convenient arrangement are combined together in a single envelope in the form of a double triode. A preferred arrangement of electronic control device according to the invention is illustrated diagrammatically in the accompanying drawing and will be described, for convenience with reference to its use in controlling an oilburning furnace, in which the fuel supply to the burner and also a fan for providing the necessary draught are controlled by an electric motor A (hereinafter termed "the burner

motor ") and the fuel-air mixture is ignited by means of an electric spark controlled through an ignition transformer B, the furnace also being provided with a flame-responsive device C for determining whether the burner has satisfactorily ignited Such device may consist, for example, of a thermostat directly exposed to the heat of the flame or of a photocell exposed to the light from the flame or of a contact device responsive to the electrical conductivity of the flame In addition, there will usually be a number of devices responsive to the temperature and other conditions in the furnace or in chambers or vessels or passages directly or indirectly heated by the furnace. Such devices indicated at D may include, for instance, furnace thermostats, flue thermostats, hot-water thermostats (in the case of boilers or water-heaters), steam pressure responsive devices ( in the case of steam generators), room thermostats (when the furnace is used for heating a building) and so on, the term " controlling thermostat " being used in the following description as a collective term representative of such devices. The electric control device itself, in this arrangement, comprises a double triede E, consisting of two triodes F F' F' and G G' G 2 in a single envelope with a common heater E' for the two cathodes, two timing circuits H H' and J J', and two electromagnetic relays K and L. Each timing circuit consists of a capacitance H or J in parallel with a resistance H' or Jl, the two timing circuits respectively being series connected in the grid circuits of the two triodes The second timing circuit J J 1, associated with the second triode G G' G, has its resistance J' variable so that its time delay can be adjusted, for example from one to sixty seconds, to suit requirements, whilst the first timing circuit H H' can have a fixed time delay, of say two minutes. The first relay K is series-connected in the anode circuit of the first triode F F' F 2, and has a smoothing capacitance K' connected across it, and the second relay L also provided with a smoothing capacitance L' is similarly energised from the anode circuit of the second triode G G' G 2. The first relay K controls five contacts, three of which I KA; K' are normally open when relay is deenergised, whilst the other two K 2 K' are each in the form of change-over contacts The terms " normally open " and " normally closed " are used herein with reference to a relay contact or contacts to indicate the state of such contact or contacts when the relay is deenergised, for example when the burner is out of action. One of these change-over contacts K 2 controls the application of potential to the second timing circuit J I', such circuit being connected when the relay K is deenergised to the positive pole of a

supply source M through a resistance J, and when the relay K is energised to the negative pole of such source, such negative pole also being directly connected to the cathodes F G 2 of the two triodes. The other change-over contact K' in the 70 de-energised position controls the energising circuit to a lockout lamp N and alarm device (not shown), and in the energised position controls the energising circuit to a burner motor A The change-over arm of this contact K' is 75 connected to a positive busbar M' which is energised from the positive pole of the source M, when the first relay is energised, through one of the three normally open contacts K'. Another of the normally-open contacts K' of 80 the first relay K is connected between the positive pole of the source M and the " cold " contact C' of the flame-responsive device C, and serves in normal operating conditions, as will be described later, to provide a temporary 85 holding circuit for the first relay K under the control of the second relay L, before a main holding circuit for the relay K becomes operative. The remaining normally-open contact K of 90 the first relay K is connected between the "hot" contact C' of the flame-responsive device C and the free end of the coil of the first relay K (that is the end remote from the anode F of the first triode), and serves as a 95 holding contact for completing the main holding circuit for the first relay K in normal operating conditions. The supply to the flame-responsive device C for energisation of its hot and cold contact C' i ? C 2 in accordance with the operation of such device is taken from the positive pole of the source M through the controlling thermostat D. The second relay L has one normally closed 105 contact L' and two change-over contacts LW La. The normally-closed contact L controls the energising circuit from the positive busbar M 1 to the ignition transformer B 110 One of the change-over contacts L 2 controls the application of potential to the first timing circuit H H', such circuit being connected when the second relay L is deenergised to the negative pole of the source M and when 115 the relay is energised to the positive pole of the source M through a resistance H The other change-over contact L' connects the cold contact C 2 of the flame-responsive device C when the second relay L is deener 120 gised to the free end of the first relay coil K, and w her the second relay L is energised to the free end of the second relay L and to the positive busbar M' This contact L' is so arranged that on energisation of the relay L it 125 does not open its normally-closed contact until after it has closed its normally-open contact. The manner in which the control device controls the normal operation

of the furnace will first be described, starting from the con 130 -2 785,033 the grid G' is at a negative potential below the cut-off value of the valve G G' G' to an extent determined by the building up of charge on the capacitor J during the period when grid current was flowing At the end of the time 70 delay, the capacitance J will have become sufficiently discharged to increase the grid potential to a value above the cut-off potential which will permit the second triode G G' G' to supply sufficient anode current to energise the 75 second relay L, causing such relay to operate. This time delay is set in accordance with the furnace characteristics to provide adequate time for the burner to ignite satisfactorily but insufficient time for risk of danger in the event 80 of failure to ignite. It will first be assumed that the burner does ignite satisfactorily and that the flame-responsive device C moves over to its hot-contact C, thus making the main holding circuit through 85 contacts K' for the first relay K, within the chosen time delay At the end of the time delay, the second relay L operates and breaks at one contact of the change-over contact L' the temporary holding circuit for the first relay 90 K (which however remains energised because its main holding circuit has meanwhile been completed), the second relay L also making its own holding circuit through the other contact of the change-over contact L' The energising 95 circuit to the ignition transformer B is broken at contact Lo, since there is no further need for ignition, once the burner flame is properly established At the same time, the first timing circuit H H' is transferred at contact L' from 100 the negative pole of the source M to the positive pole and thus at once charges up the capacitance H and puts a positive potential on the grid F' sufficient to cause the valve F F' F 2 to pass grid current The corresponding 105 reduction in anode current however does not cause decnergisation of the first relay K, although if the first relay had been deenergised it would prevent the reenergisation thereof owing to the difference between the holding 110 current and the lifting current of the relay. The two relays K L are therefore both energised, and this condition continues and keeps the burner in operation, thus gradually heating the furnace up again When the critical maxi 115 mum temperature is reached, the controlling thermostat D breaks the connection from the positive pole of the source M to the flameresponsive device C, and thus breaks the holding circuit for the first relay K which immedi 120 ately moves to its deenergised position This breaks at contact K' the circuit to the burner motor A and cuts the burner out of action and also at contact K' deenergises the positive busbar M' and breaks the circuit to the second 125 relay L, thus deenergising that relay At the

same time, the second timing circuit J pl is transferred at contact K' from the negative pole to the positive pole of the source, thus restoring the valve G G' G 2 to the condition 130 dition (shown in the drawing) in which the burner is out of action and the furnace is gradually cooling after previous operation of the burner At this stage both relays K L are deenergised, and the second timing circut J J' is connected to the positive pole of the source M so that the positive potential on the grid of the second triode G G' G' ensures that such valve is not in condition to supply anode current sufficient for the actuation of the second relay L In these conditions, the capacitor J becomes charged by the grid current which flows in the timing circuit J J', the grid side of the condenser J being at a positive potential somewhat less than that of the side of such condenser J remote from the grid to an extent determined by the potential difference developed across the resistance I 1 of the timing circuit J J' The first timing circuit H H' is, however, connected to the negative pole of the source M and, provided that it has been so connected long enough to cover the two minute time delay required for discharge of its condenser H, the grid F' of the first triode F F' F' is at such a potential that the valve is in condition to supply sufficient anode current for the immediate actuation of the first relay K as soon as its energising circuit is completed. When the furnace cools to the critical minimum temperature at which the controlling thermostat D operates, such operation will supply current from the positive pole of the source M through the flame-responsive device C to the cold contact C 2 thereof and thence through the change-over contact L' on the second relay L to the free end of the first relay K, thus completing the energising circuit of the first relay K and causing such relay to operate This will prepare through contact K' the mhain holding circuit for this relay to the hot contact C' of the flame-responsive device C, and also complete through contact K' the temporary holding circuit for the relay K so as to keep the relay energised when the flame-responsive device C breaks the connection to its cold contact C 2 The positive busbar M' will be energised through contact K' from the positive pole of the source M 1, thus preparing the energising circuit to the second relay L and completing through contacts K' K' the energising circuits to the burner motor A and through contact K' to the ignition transformer B, thus supplying fuel to the burner and operating the ignition device therefor At the same time, the second timing device J I' will be disconnected at contact K 2 from the positive pole of the source M and connected to the negative pole, thus immediately bringing the side of the capacitance J remote from the grid G' of the valve G G' G' to zero potential and initiating the time delay by allowing the charge on the

capacitance to leak away slowly through the resistance J' It should be mentioned that at the beginning of such time delay 785,033 785,033 in which it cannot permit reactuation of the relay L. The deenergisation of the second relay L prepares at contact L 3 the energising circuit for the first relay K and also at contact L' the energising circuit for the ignition transformer B, neither of these circuits however at this stage being connected to the positive pole of the source M At the same time, the first timing circuit H H' is transferred at contact L 2 from the positive pole to the negative pole of the source M, thus permitting the capacitance H to discharge slowly and initiating the two-minute time delay This brings the control device back into condition for restarting when the furnace has cooled down sufficiently for operation of the controlling thermostat D, provided that the two-minute time delay has meanwhile elapsed It should again be mentioned that at the beginning of the two-minute time delay the grid F' of the triode F F' F 2 is at a negative potential below the cut-off value to an extent determined by the charge built up on the capacitance H during the period when grid current was flowing in the timing circuit H He. If now after starting or restarting, the burner fails to ignite satisfactorily, or if the burner does ignite but the flame-responsive device C fails to move over to its hot contact Cl, the main holding circuit for the first relay K through contact IK' will not be completed before expiration of the time delay of the second timing circuit J J In such case, the second relay L will be energised at the end of the time delay of the second timing circuit I J' and will immediately break at contact L' the energising circuit for the first relay K, thus deenergising that relay This at once breaks the circuit to the burner motor A and cuts off the fuel supply to the burner, there-by preventing the accumulation of the dangerous quantity of the unignited fuel-air mixture in the furnace At the same time the first relay K breaks the direct connection from the positive pole of the source M to the positive busbar Ml, but an alternative connection to this busbar remains completed through the cold contact C 2 of the flame-responsive device C and through the holding contact L of the second relay L The second timing device J 1 l is also transferred back to the positive pole of the source M, the positive potential on the grid G' of the valve G G' G 2 being such as to allow the valve to permit sufficient anode current to flow to leave the second relay L actuated but insufficient to cause re-actuation thereof if such relay is deenergised The deenergisation of the first relay K also completes the connection from the positive busbar Ml to the lock-out lamp N and alarm, so that warning is given that the burner has been locked out Thus, during the lockout condition the first relay K is deenergised

but the second relay L remains energised, and the control circuit remains in the condition until some positive action is taken to deenergise the second relay L. For this purpose, a manually-operated switch O is provided in the main lead from the 70 positive pole of the source M to the control device This switch O is normally held closed by spring action, but can be operated when required to break the supply circuit momentarily When this switch is operated, it will 75 cause the second relay L to be deenergised. This, as above mentioned, prepares the circuits for restarting, but also transfers the first timing circuits H HI to the negative pole of the source, thus permitting the capacitance H to 80 discharge slowly during the two-minute time delay The control device remains locked out until this time delay expires, when the control device is ready to be restarted automatically by the controlling thermostat 85 A safety relay P is preferably provided to guard against failure of the relay L to operate its contacts for any reason when energised at the end of the time delay of the timing circuit J JF Such failure would leave the relay K con 90 tinuously energised and might create dangerous conditions in the furnace The relay P has a time delay considerably longer than that of the timing circuit J Il, and is energised when contacts KI' and L' are both closed If 95 contact L' fails to open, the relay P opens the main supply circuit at its contact Pl and deenergises the relay K. It will be appreciated that the foregoing arrangement has been described by way of 100 example only and may be modified in various ways within the scope of the invention Thus, for instance, if the furnace is arranged to give automatic ignition (for example by the provision of a permanently lighted gas pilot jet), 1 5 the control device would be modified to omit the control circuit for the ignition transformer B Again, in some instances, as for example in the case of a gas-burning furnace, the burner motor A would not need to drive a fuel-supply 110 pump, since the normal pressure of the gas mains would suffice, and such burner motor could be omitted altogether, if adequate provision is available for securing a proper draught in the furnace, the control circuit for the 115 burner motor however still being retained for the purpose of operating a gas-supply tap Further, although a double triode will usually be preferred, two separate triodes may be used or more generally two separate electronic dis 120 charge devices having control grids. Again the foregoing arrangement is more especially intended for use with light oils, but can readily be adapted for use with heavy oils by the addition of further devices, including 125 an oil preheater provided with a heater thermostat and a safety trip thermostat, as

well as a further controlling thermostat for preventing starting unless a minimum oil temperature has been attained In such case, it is usually desir 130 785,033 able to add further circuits to the control device for energising indicating lamps to indicate whether the oil heater is in operation or has been tripped out.

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* GB785034 (A)

Description: GB785034 (A) ? 1957-10-23

Multiple position beam tube


PATENT SPECIFICATION 785,034 d, O Ha SB A Date of Application and filing Complete Specification July 22, 1954. No 21442154. Application made in United States of America on July 24, 1953. (Patent of Addition to No 759,153 dated May 29, 1953). Complete Specification Published Oct 23, 1957. Index at Acceptance: -Class 39 ( 1), D 4 (A 1: A 7: D 1: F 6 B: G 1: 'G 3: K 3), D( 10 A 1: 17 A 2 B: 18 C: 34). International Classification: -HO 1 j. COMPLETE SPECIFICATION Multiple Position Beam Tube We, BURROUGHS CORPORATION, a corporation organised under the laws of the State of Michigan, United States of America, of Main Offices, 6071, Second Avenue, Detroit, Michigan, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the

following statement:This invention relates to improvements in or modifications of the electron discharge device which forms the subject of our Letters Patent No 759,153. In the aforesaid patent, there is described and claimed an electron discharge apparatus adapted to form and direct an electron beam in which electrons follow trochoidal paths through the action of crossed electrostatic and magnetic fields to cause selective impingement of the beam on a plurality of collector electrodes, said electron discharge device comprising a hermetically sealed envelope housing a source of electrons adapted to emit a beam of electrons, and a first electrode structure spaced from the electron source and constituted by a plurality of spaced beam forming or control spade electrodes spaced from each other to define passageways therebetween into which the electron beam may be directed and locked, in which there is provided a second electrode structure spaced from the first electrode structure and disposed on the side thereof remote from said electron source and constituted by a plurality of beam collector electrodes arranged with respect to the control electrodes of the first structure so that each collector electrode has at least one beam receiving area overlying the passage way between two adjacent spade electrodes or two or more beam receiving areas each overlying a different passageway and disposed to receive the electron beam directed through the associated passageway, and in which there is also provided a beam switching structure situated intermediate the spade electrode structure and the beam collector electrode structure and spaced therefrom, the beam switching structure and the collector lprice 35 6 d 1 electrodes being so constructed and arranged as to permit electron flow to the beam receiving areas of the collector electrodes and to produce an output from the collector electrodes that indicates the passageway through which the beam is passing, said beam switching structure including one or more distinct portions associated with respective juxtaposed spade electrodes and collector electrodes and serving to effect, when suitably excited, the switching of the beam from one passageway to another. Apparatus according to the aforesaid patent can be used with advantage in code conversion systems, switching and multiplexing applications for either modulated or unmodulated signals, counting and computing devices, and similar applications requiring high speed beam switching and especially in such applications where external circuitry is desired to be simplified or equipment should be compact. In addition to these uses, one particularly suitable application of an electron discharge device according to the present invention is in counting and computing devices. According to the present invention, there is provided an improvement

in or modification of an electron discharge apparatus as claimed in our Letters Patent No 759,153, which comprises providing one or more collector electrodes each of which collector electrodes is placed in front of only one of the passages defined between two adjacent spade electrodes. One or more apertures may be provided in the beam switching structure, all of which are disposed in front of a single passageway between two adjacent spade electrodes Where a single aperture is provided, it is preferably in the form of a slot. In some applications, it is advantageous to provide a plurality of slots in the beam switching structure, each slot being disposed in front of a respective passageway between two adjacent spade electrodes, and in other applications, a slot may be provided for every passageway formed by the spade electrodes. The slots may vary in size or they may be substantially identical in which case they are preferably of approximately the same length 785,034 as the electron emissive portion of thile cathode. It is preferred to shape each collector electrode similarly to the shape of the associated slot, the area of the collector electrode being at least as large as the area of the slot, and to place the collector electrode in front of its associated slot so as to intercept substantially all the electrons passing therethrough. When the slots are varied in area, the lengths of successive slots may differ by regular increments. In order to prevent cross coupling between collector electrodes, suppressor electrodes maintained at the potential of the cathode may be provided adjacent each of the collector electrodes. The spade electrodes, beam switching structure and collector electrodes may be arranged in successive lines, but preferably, they are concentrically arranged about the cathode, the collector electrodes being angularly displaced from a position in alignment with the associated aperture or apertures and the cathode so as to intercept substantially all the electrons passing through the aperture or apertures in a curved path. It is preferred to provide a spade resistance within the tube envelope adjacent each spade electrode. Tubes made in accordance with the present invention are especially useful as counting or switching tubes For example, a decade counter tube in which an output signal is derived in only one of ten beam positions, can be provided by slotting the beam switching structure at only one of ten beam positions of the tube and having a single collector electrode opposite the slot. Because variations in output voltage have relatively little effect on tube operating stability, tubes made in accordance with the present

invention are suitable for use in multiplexing or other switching operations, for example, where modulation of the electron beam takes place. Further, because multiple position beam tubes made in accordance with the present invention have few critical spacings and are comprised of parts which may be easily and economically fabricated, the tubes may be easily assembled and economically produced. There will now be described by way of example only, a preferred embodiment of the invention with reference to the accompanying drawings in which: Fig 1 is a perspective view, partly broken away, illustrating an electrode structure for use in a multiple-position beam tube having ten individual output electrodes in accordance with the present invention; Fig 2 is a top plan view of the tube shown in Fig 1; Fig 3 is an exploded view of the tube shown in Fig 1; Fig 4 is a perspective view of a modification of the anode 32 shown in Fig 3; Fig 5 is a plan view of a modification of the tube shown in Fig 1; Fig 6 is a plan view of a modification of the tube mount assembly shown in Fig 1; and 70 Fig 7 is an isometric view, partly broken away, of a mount assembly constructed in accordance with the present invention and adapted for use as a decade counter tube. In the mount assembly illustrated in Fig 1 75 and shown in more detail in Figs 2 and 3, the arrangement of anode slots and collector electrodes is utilized to provide a multiple position beam tube which is especially useful as a switching or counting tube 80 Multiple position beam tubes are described and claimed in our Patent No 759,153 and the construction and mode of operation of electron discharge apparatus according to the present invention are similar to those described in the 85 above patent. Like the coding tube described in Patent No. 759,153, the tube shown in Figs 1, 2 and 3 has an elongated thermionic cathode 24 which is centrally disposed within a hermetically 90 sealed envelope 22 and is surrounded by a substantially cylindrical array of elongated troughshaped spades A sleeve type cylindrical anode 32 ' of larger diameter than the spade array is disposed coaxially and concentrically with 95 respect thereto The anode has elongated slots 341, equal in number to the number of beam positions of the tube, disposed substantially in parallel alignment with the cathode 24 and so located with respect to the space between o 100 adjoining pairs of spades that a substantial part of the electron beam locked in on any one spade will pass through one of the slots 34 '. In the embodiment shown in Fig 2 the slots are disposed directly in line with the space 105 between each pair of adjoining spades However, in view of the fact that the electron beam usually approaches the slcts in a slightly curved path, it is possible to pass a larger

percentage of the beam through the slots if the latter are 110 offset circumferentially slightly with respect to the spaces between the spades In such case the direction in which the slots are offset should be opposite to the direction of rotation of the electron beam 115 In order to provide a separate output from every beam position, individual collector electrodes 36 ' are disposed opposite each slot 34 ' in the anode 321 and the side of the anode which is opposite to the spades 26 While the 120 collector electrodes 36 ' are aligned with the space between the adjacent spades as are the slots 34 ' in the anode 32 ', the collector electrodes 36 ' like the slots 341 may be circumferentially displaced slightly with respect to the 125 spades and in the same direction as the slots 341 are displaced in order to permit a larger portion of the electron beam to impinge thereon Fig 5 shows the offset anode slots and collector electrode arrangement 130 785,034 Leads (not shown) to the individual spades, individual collector electodes, anodes, and cathode are brought out through the stem 124 (which may be of glass) to the base pins 46. The switching time required to move the beam from one position to another may be made more uniform if the spade resistors 64 are located within the tube envelope One such arrangement of the spade resistors 64 is shown in Figs 1 and 2, in which each of the resistors 64 is disposed between the sides of the spade 26 to which the individual resistor is connected Because the resistors 64 are connected directly to the spades in this arrangement, lead capacitances are minimised and have much less effect on the switching time between individual beam positions than if leads were provided to resistors located outside the tube. Other advantages accrue by the use of resistors which are located inside the tube envelope. All the resistors operate at the same temperature and are unaffected by change in humidity. Because the resistors operate in a vacuum, they may have a larger wattage rating per unit physical size without burning out and consequently result in a saving in space which is an important advantage where equipment is to be miniaturized However, the increase in switching speed and the uniformity of wave shape achieved through the use of the internal spade impedance elements 64 is more than sufficient reason to justify their use In addition to the advantageous increase in switching speed made possible by the use of internal spade resistors, the switching time from one beam position to another is made more uniform Such uniformity becomes important when it is considered that in many applications a discrete pulse width is required to switch the position of the beam Variations in spade impedance would result in changes in the pulse widths required to

switch the beam from position to position Thus, the pulse width required to switch the beam to an " average " beam position might, for example, be too short to switch the beam to another position or long enough to advance the beam two positions if only a very short pulse width is required for switching from one position to another. Further, a reduction in the number of leads which must pass through the tube envelope may be achieved if the switching of the beam is to be accomplished by means other than pulsing the spade electrodes If the spades are not used to switch the electron beam from one position to another, individual spade leads are unnecessary and the internally mounted spade resistors are connected to a common lead which may be connected to the source of spade operating potential. A quantized or stepped output from the tube of Figs 1, 2, or 3 may be obtained if the anode 32 shown in Fig 4 is substituted for the slotted anode shown in those figures The slot length is varied to control the amount of output current available at the collector electrode of each beam position The quantized or stepped output could, of course, be achieved by varying either dimension of the slots 3411. Another variation of the tube shown in Fig 70 1 is shown in Fig 7 In that structure the anode 32 is slotted at only one beam position, providing a decade counter tube having an output in only one of the ten beam positions. The spade resistors 64 shown in Fig 7 are 75 similar to those in Fig 1. The anode 32 as shown in each of the embodiments of the present invention, acts as an electrostatic shield between the collector electrodes and spades, thus allowing the col 80 lector electrode output to vary to a greater extent than was formerly possible without the collector electrode field extending inwardly to such an extent that it causes the beam to switch The positioning of the collector elec 85 trodes beyond the spades rather than between them also reduces the effect of the collector electrode field on beam switching stability. Further, this arrangement isolates the collector electrode from adjoining spades both capa 90 citywise and physically Reduction in spadeto-spade capacitance (through the collector electrode) results in improved beam switching characteristics which result in the unmodulated output wave more nearly resembling a square 95 wave The physical isolation of spades and collector electrodes permits collector electrodes having larger areas to be used, thus permitting larger power outputs "Fringe" electrons near the edge of the electron beam impinge 100 on the anode 32 and thus are not free to escape to adjoining electrodes and cause cross talk. The anode 32 and collector electrodes 36 may advantageously be

composed of materials which are poor secondary electron emitters or 105 the electrodes may be provided with a coating which reduces the secondary emission capabilities of the material. Fig 6 shows an electrode configuration which is similar to that shown in Fig 2, but 110 has suppressor electrodes 126 disposed between adjacent collector electrodes These suppressor electrodes, which are illustrated as elongated rods; are normally maintained at or near to cathode potential and tend to repel 115 stray electrons which do not impinge on the intended collector electrode or any other electrons which might, under the influence of the magnetic field or the positive field, on adjacent collector electrodes, tend to impinge on adja 120 cent collector electrodes and cause cross talk. The suppressors 126 may be connected to the cathode inside the tube or they may be provided with a common lead through the tube envelope in order that they may be biased in 125 any desired manner. While specific embodiments of the present invention have been described, it will be apparent that this invention is by no means limited to the exact forms illustrated or the 130 use indicated, but that many variations may be made in the particular structure used and the purpose for which it is employed without departing from the scope of the invention as set forth in the appended claims For example, the spade electrodes, beam switching structure and collector electrodes may be arranged in successive lines instead of concentrically about the cathode, in a similar manner as described in Patent No 759,153 for a "straight line" version of a multiple position beam tube.


* GB785035 (A)

Description: GB785035 (A) ? 1957-10-23

Improvements in closed circuit turbine power plants


PATENT SPECIFICATION Inventors: ALEXANDER VELLAN and JEAN CRISTESCOU 785035 Date of filing Complete Specification: Jan 6, 1955. Application Date: Aug 3, 1954. No 22463/54. Complete Specification Published: Oct 23, 1957. Index at acceptance:-Classes 110 ( 3), B 2 M 6; and 122 ( 3), A 7 X. International Classification:-F Olc F 02 h. COMPLETE SPECIFICATION Improvements in Closed Circuit Turbine Power Plants We, C V PRIME MOVERS LIMITED, a British Company, of Bilbao House, 36/38, New Broad Street, London, E C 2, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to closed circuit turbine power plants for heat recovery from low temperature heat sources, either waste heat or natural heat, using a low boiling point working fluid such as carbon dioxide, sulphur dioxide, or ammonia which is gaseous at normal pressures and temperatures It is the object of the invention to provide an improved plant of this character. Specific examples of natural low grade heat and residual or waste heat sources are springs and mine water as natural heat sources, and exhaust steam or other exhaust gases of power or industrial plants, the temperature level of which is not high enough to produce mechanical energy by conventional means A further natural source of heat is solar heat Also waste heat appearing as residual heat in burnt gases or fluids resulting from chemical reactions or eventually released from an industrial process (including nuclear plants) may be utilized. It is known that certain low boiling point media, if confined, attain fairly high pressures when heated to temperatures of from 500 C. to 200 WC The following figures show the pressures attained at relatively low levels of temperature by suitable low boiling point media, which are given as examples. Ammonia (NH,) attains a pressure of 90 atms abs for a temperature level of + 130 'C. Sulphur dioxide (SO,) attains a pressure of atms abs for a temperature level of + 130 WC. Carbon dioxide (CO,) attains a pressure of 130 atms abs for a temperature level of + 6 WC _ O ^ The invention consists in a power plant for heat recovery from low temperature heat sources comprising a

closed circuit containing a low boiling point working fluid which is gaseous at normal temperature and pressure, means for transferring heat from a low temperature heat source, the temperature lev of which does not exceed 200 C G, to, the working fluid, a turbine deriving mechanical power from expansion of the working fluid, means for transferring heat from the working fluid exhausted fromn the turbine to a cooling agent, and a pump for raising the pressure of the working fluid prior to the transfer of hept thereto from the heat source to' a pressure substantially greater than the critical pressure of the fluid, the heat source being a heat exchanger whereby the reception of heat by the working fluid is substantially evenly distributed over the working temperature range of the cycle, and the rejection of heat by the working fluid to the cooling agent taking place substantially at the minimum temperature of the working cycle. The invention also consists in a power plant for heat recovery from low temperature heat sources, comprising a closed circuit containing carbon dioxide as a working fluid, means for transferring heat from a low temperature heat source, the temperature level of which does not exceed 200 C, to the working fluid, a turbine deriving mechanical power from the expansion of the working fluid, means for transferring heat from the working fluid exhausted from the turbine to, a cooling agent, and a pum D for raising the pressure of the working fluid prior to the transfer of heat thereto from the heat source to a pressure substantially greater than the critical pressure of the working fluid. In the accompanying drawing, Figure 1 is a diagrammatic view of one form of power plant according to, the invention; Figure 2 is a temperature-entropy diagram. Referring to Figure 1, the reference numeral 2 785,035 1 generally indicates a closed circuit in which is confined carbon dioxide, for example, as the working fluid The circuit comprises piping and includes an expansion turbine 2, the piping extending from the turbine exhaust to a part 4 of the piping which extends through a heat exchanger 5 where it is in direct contact with exhaust steam or waste gases at a low temperature level, for example at 60 C ( 140 F) The exhaust steam flows through the heat exchanger 5 contra to the direction of flow of the working fluid in the part 4 of the piping and said part 4 may be of coiled or serpentine form or may be replaced by a bank of tubes The arrow heads show the direction of flow of the working fluid and of the exhaust steam As an alternative instead of the employment of exhaust steam a solar heater may be employed directly to heat said part of the piping, or a solar heater may heat a fluid which flows through the heat exchanger 5 In operation the working fluid after being heated in that part 4 of the piping which extends through the heat exchanger 5 whereby its temperature and

pressure are raised, will flow to the inlet of the expansion turbine 2 to drive the same In its passage through the turbine thle worlng flu' d expands so that its temperature and pressure are lowered before exhaust from the turbine A part 11 of the piping leading from the turbine exhaust extends through a secondary heat exchanger 12 in which the exhausted gaseous carbon dioxide is partially cooled and its pressure is reduced The partly cooled exhaust gas then flows in the piping to a part thereof which extends through another cooler 13 whereby the gaseous carbon dioxide is converted to the liquid phase and collects in a closed vessel 14 A pump 15 forces liquid from the vessel through piping, a part 16 of which extends through the secondary heat exchanger 12 where it is partially heated and from thence it flows to the part of the piping 4 in the primary heat exchanger 5 Cooling liquid for the cooler 13 may be fed by a pump 17 from a supply 18 and returned by way of a spray 19. Performance figures, for prime-movers such as described, may be estimated by means of the T p diagram (temperature-entropy), for C 02 The results as calculated by N G T E. (Pyestock, Hants), are tabulated below, for three distinct cases, namely: Case 1-Summer running, with a minimum C 02 cycle temperature of 25 C. ( 77 F), corresponding to a minimum pressure of 63 5 atms. Case 2-Winter running, with a minimum C 02 cycle temperature of 15 C. ( 59 F) corresponding to a minimum pressure of 50 atms. Case 3-" Refrigerated" (liquid air) running, with a minimum C 02 cycle temperature of -55 C ( 131 F), corresponding to a minimum pressure of 6 atms. In all three cases ( 1), ( 2) and ( 3) above, initial conditions of temperature and pressure are identical, namely 180 C ( 356 F) and atms. Figure 2 is the termperature entropy diagram for a plant according to Figure 1 using carbon dioxide with a maximum cycle tempri'atue' of 180 C and a maximum cycle pressure of 150 atmospheres. The following table is derived from the relevant Tl, diagrams. PERFORMANCE DATA TABLE Case 1 Case 2 Case 3 1 Max C 02 cycle temperature C 180 C 180 C 180 C. 2 Max C 02 cycle pressure atmuns 150 Atms 150 Atms 150 Atms 3 Min C 02 cycle temperature C 25 C 15 ' C -55 C. 4 Mlin C 02 cycle pressure atms 63 4 Atms 50 Atms 6 Atms Yield of power per pound per second of C 02, KW 19 7 KW 26 5 KW 68 2 KW 6 Cycle efficiency % 14 1 % 19 1 o 29 3 % 7 Supply-of heat per pound per second of C 02 circulated CHU 51 8 CHU 63 7 CHU 121 0 CHU 8 Extraction of heat per pound per second of C 02 circulated, CHU 51 8 CHU 54 CHU 85 6 CHU 785,035 from the C 02, T-0 diagram, as a, practical example,

it follows that in order to produce, say 1000 KW, and assuming that: Ordinary steam turbines and closed-cycle gas turbines (air), may not function under conditions as given in the above table. From the above performance figures derived Max C 02 cycle temperature T 1 C = + 180 C ( 356 F) Max C 02 cycle pressure Pl atms = 150 ATMS Min C 02 cycle temperature T 2 C = + 15 C ( 59 F) Min C 02 cycle pressure P 2 atms = 50 ATMS, the following conditions will arise. It will be seen that the example ( 1000 KW) is taken for winter running conditions These conditions have been selected as located between the two extreme conditions, viz Summer running (+ 25 C) and "refrigerated" running ( 55 C) (-67 F) A minimum C 02 cycle temperature of + 15 C ( 590 F) is reasonably correct over a wide range of territories and for the best part of the year. Let W =yield of power per pound per second of C 02 in KW W = 1000 KW (assumed) m = 26 5 KW per pound per second of C 02 (from table above) 01 = 63 7 CHU, supply of heat per pound per second of C 02 circulated (from above table) 02 = 54 CHU extraction of heat per pound per second of CO 2 circulated (from above table) 0 A 1 =supply of heat per pound per second of CO, circulated for 1000 KW 0 '2 =extraction of heat per pound per second of CO, circulated for 1000 KW M =lb/sec of CO, for 1000 KW We have: W 1000 M = = m 26 5 = 37 7 lbs/sec of C 02, for 1000 KW. 011 = 63 7 x 37 7 = 2401 49 CHU per second per pound of C 02 circulated and 0 '2 = 54 x 37 7 = 2035 8 CHU per pound per second of C 02 circulated. The above value of M= 37 7 does not allow for cooling-cycle losses and pressure losses, in the C 02 cycle, due to the heat exchanger. Allowances have been made concerning the expansion in the turbine, when establishing the figure of 26 5 KW. In other words, under conditions as assumed, in order to generate 1000 KW it is necessary to circulate 37 7 lbs/sec of C 02 in the closed circuit of the prime-mover, neglecting losses as indicated above. In the same way for "Summer" running (+ 250 C) ( + 77 F) we have: W 1000 M=_=m 19 7 = 50 7 lbs/sec of C 02 for 1000 KW. and for "refrigerated" (-55 C) running we have: W 1000 M=-= m 68 2 = + 14 6 lbs/sec of C 02 for 1000 KW. The same remarks apply regarding losses as above. As an example, if a pump be used under conditions of Winter running (+ 15 C minimum cycle temperature) the work in HP necessary for the return of the working fluid in a unit intended to, generate 1000 KW will be given by HO Wp= 8 n Where: H = 1033 metres of water = 100 auns. Q= 17 1 Kg/sec = 37 7 lbs/sec for 1000 KW 8 = 0 81 sp wt of liquid C

02 Kg/1 =Conversion factor Substituting we have: 0.81 x 17 1 x 1033 W: 192 5 HP = 142 KW Assuming an efficiency of pump of = 65 % we have Work done= 218 KW necessary for the return of 37 7 lbs/sec of C 02 in the closed circuit, producing 1000 KW in the prime-mover. Net output of prime-mover 1000 218 = 782 KW Also, referring to one pound of C 02 circulated per second, giving 26 5 KW, the work done to return, by means of a pump, the working fluid, will be 218 -= 5 8 KW 37.7 Thus, net output per pound of C 02 per sec. circulated will be: 100 26.5 5 8 = 20 7 KW.


* GB785036 (A)

Description: GB785036 (A) ? 1957-10-23

Improvements in and relating to speed regulating and current limit motorcontrol systems


PATENT SPECIFICATION 78590363 o Date of Application and filing Complete Specification Aug 17, 1954. No 23904/54. Application made in United States of America on Aug 26, 1953. Complete Specification Published Oct 23, 1957. Index at Acceptance:-Class 38 ( 4), R( 4: 33 D 2: 61: 62: 67: 112 A). International Classification: -GO 5 c. COMPLETE SPECIFICATION Improvements in and relating to Speed Regulating and' Current Limit Motor Control Systems We, IGRANIC ELECTRIC COMPANY LIMITED, a British

Company of Elstow Road, Bedford, in the County of Bedford, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: - This invention relates to speed regulators and current limit motor control systems. The present invention provides an improved speed regulating, find current limit control system characterised by low steady state error, relatively high system stability and sharp current limit action. The invention also provides a voltage comparison circuit for the speed regulating control element of a regulator which automatically limits the voltage difference which may be developed across such element to protect the 2 (v same against excessive voltage. The invention further provides a voltage comparison circuit for the current limit control element of the aforementioned regulator in which the motor current signal voltage is supplemented by a portion of the voltage difference in the voltage comparison circuit for the speed regulating control element for increasing the sharpness of current limit action. Other features and advantages of the invention will hereinafter appear. The invention consists broadly of a control system for ian electric motor, wherein said motor drives a generator and said generator is included in a circuit with a source of reference voltage and a control winding of an amplifying Regulator, for subjecting said control winding to the voltage difference between said source and said generator, and the voltage supplied to the armature of said motor is varied according to the output of said amplifying regulator, an element, rendered conductive upon attainment of a given voltage difference, being adapted to shunt a greater portion of the current of said circuit around said control winding. The accompanying drawings illustrate prelPdce 3 s 6 d l ferred embodiments of the invention which will now be described by way of example only. In the drawings, 50 Figure 1 is a diagrammatic showing of a rectified alternating current control system for a D C motor incorporating the invention. Figure 2 depicts a modification of a part of the control system of Figure 1, and 55 Figure 3 is a diagrammatic showing of an adjustable voltage drive incorporating the invention. Referring to Figure 1 the numeral 5 generally designates la transformer having a primary 60 winding 6, which may be assumed to be connected to a suitable source of alternating voltage supply, and having secondary windings 7, 8, 9 and 10 Secondary winding 7 is

provided with end terminals 7 a and 7 b% centre tap ter 65 minal 7 and intermediate tap terminals 7 ' and 7 End terminal 7 a is connected in series with an input winding lla of a current transformer 11 to the anode 12 b of a gas filled thermionic valve 12, which is also provided with a cathode 70 12 a and a control electrode 120 End terminal 7 b is connected in series with another input winding 11 b of current transformer 11 to the anode 13 b of a valve 13, like valve 12 Tube 13 is also provided with a cathode 13 a and a 75 control electrode 13 The cathodes 12 a and 13 a of valves 12 and 13 are connected together to one terminal of armature 14 a of a direct current motor 14 The other armature terminal of motor 14 is connected to centre tap terminal 80 of secondary winding 7. The control electrodes 120 and 13 e of valves 12 and 13 are connected together, in series with a secondary winding 15 b of a transformer 15, which has a primary winding 15 a Second 85 ary winding 15 b has a centre tap terminal 150 which is connected to the point common to cathodes 12 a and 13 a and the first mentioned motor armature terminal A filter capacitor 16 is connected between the control electrode 120 90 and the cathode 12 a of valve 12, and a similar filter capacitor 17 is connected between the control electrode 130 and cathode 13 a of valve 13. 785,036 The primary winding 15 i of transformer 15 is connected at one end terminal to centre tap terminal 7 of secondary winding 7 P and is connected at its other end terminal in series with A C windings 18 a and 18 b of a saturable reactor 18 to intermediate tap terminal 7 of winding 7 The point common between winding 15 a and 181 is connected in series with a resistor 19 to intermediate tap terminal 7 d of winding 7 As will be apparent, winding 15 ' of transformer 15, windings 183 ' and 18 b of saturable reactor 18, and resistor 19 comprise a phase shift network, whereby, in accordance with the energization of D C winding 15 of reactor 18, the potential applied on the control electrode of valves 12 and 13 may be shifted in time-phase with respect to the potentials applied to the anodes The energizaion of the D C winding 18 ' of reactor 18 will be hereinafter described. Motor 14 is provided with a shunt field 14 b which is connected to the D C terminals of a full-wave rectifier bridge 20 The A C terminals of rectifier bridge 20 are connected to the end terminals of the aforementioned secondary winding 8 of transformer 5. Armature 14 A of motor 14 is mechanically connected to a tachometer generator 21, which is connected at its low potential armature terminal to the low potential armature terminal of a tachometer generator 22, which may be assumed to be driven by a machine element with whose speed motor 14 is to be regulated or matched Tachometer generator 22 is connected at its high potential armature terminal in

series with a D C control winding 23 a of a self-saturating magnetic amplifier 23, a halfwave rectifier 24, which preferably has no appreciable threshold conducting voltage in the forward direction, such as for example a germanium diode a resistor 25 and the resistance element of a voltage divider 26 to the high potential armature terminal of tachometer generator 21 A half-wave rectifier 27 is connected at its input terminal to the point common between the high potential armature terminal of tachometer generator 22 and winding 23 % and is connected at its output terminal to the point intermediate, the resistor 25 and voltage divider 26. As will be apparent the voltage difference between tachometer 22 and tachometer 21 is impressed across the winding 23 a of magnetic amplifier 23, whenever the potential of tachometer 22 is higher than the potential of tachometer generator 21 Rectifier 24 prevents reverse flow through winding 23 a in the event there is reduction in the output voltage of tachometer generator 22 below that of tachometer generator 21. Rectifier 27 acts to limit the voltage which will appear across the series circuit comprising winding 23 a, rectifier 24 and resistor 25, and rectifier 27 is so chosen that it will commence to conduct only when the voltage across it exceeds a certain value as determined by the voltage rating of winding 23 a Thus, any attempt to increase the voltage across rectifier 27 results in most of the current flowing through rectifier 27 and appearing as a voltage 70 drop across the resistance element voltage divider 26 By proper selection of the ohmic value of resistor 25 it is thus possible to keep the voltage across winding 23 a to a very low level. This not only protects winding 23 a during 75 accelerating and deceleration of motor 14, but also limits the level of ampere turns which may be developed by winding 23 a in magnetic amplifier 23. Amplifier 23 is provided with A C main 80 windings 23 Y and 23 ', which are connected at corresponding ends to one end terminal of the aforementioned secondary winding 9 of transformer 5 The other end of winding 23 e is connected to the output terminal of the half 85 wave rectifier 230, whose input terminal is connected to the output terminal 23 f Terminal 23 f is connected to the input terminal of a half-wave rectifier 23 whose output terminal is connected to the other end terminal of secondary 90 winding 9 The other end of winding 23 d is connected in series with the input terminal of a half-wave rectifier 23 h, whose output terminal is connected to the output terminal 23 Y. Terminal 23 i is connected to the output ter 95 minal of a half-wave rectifier 23 k whose input terminal is connected to the last mentioned end terminal of the secondary winding 9 Output terminals 23 f and 23 i

of amplifier 23 are connected to the end terminals of control 100 winding 18 ' of saturable reactor 18 The control system as thus far described provides speed regulating control of motor 14 The system is additionally provided with current limit control which will now be described 105 Amplifier 23 is provided with another D C. control winding 23 b, which is connected at one end in series with a resistor 28 to the high potential D C terminal of a full-wave bridge rectifier 29, whose output terminal is 110 connected to adjusting element 26 a of voltage divider resistor 26 Winding 23 b is connected at its other end in series with a resistor 30 and a half-wave rectifier 31 to the adjusting element 32 ' of a potentiometer 32, which has a 115 resistance element 32 " Resistance element 321 of potentiometer 32 is connected across the D.C terminals of a full wave bridge rectifier 33 The A C terminals of rectifier 29 are connected to the end terminals of output wind 120 ing 1 le of current transformer 11 The A C. terminals of rectifier 33 are connected to the end terminals of the aforementioned secondary winding 10 of transformer 5 Rectifier 29 has connected across its D C terminals a 125 smoothing capacitor 34, and rectifier 33 has a smoothing capacitor 35 connected across its D.C terminals. As will be apparent, the voltage across the control winding 23 b of amplifier 23 is the 130 785,036 difference between, on the one hand, the D C. reference voltage between the adjusting element 32 a and the left hand end of resistance 32 b of potentiometer 32, and, on the other hand, a variable D C voltage which is the sum of the variable voltage derived from winding 110 of current transformer 11 and rectifier 29, plus the variable voltage obtaining between the adjusting element 26 a and the right hand end of the resistance element of voltage divider 26 Thus, whenever the magnitude of such variable D C voltage is greater than the D C reference voltage, current will flow through winding 23 b to develop ampere turns, which may be assumed to counteract the ampere turns developed by control winding 230 and thereby decrease the output of amplifier 23, or even turn the latter off The rectifier 31 prevents current flow in the reverse direction, thereby preventing winding 23 b acting cumulatively with winding 23 a. The operation of the system of Fig 1 as a whole will now be described. Assume that motor 14 is rotating at the desired speed but with practically no load. Now let it be assumed that the armature 14 a of motor 14 is gradually loaded up This of course results in slow-down of armature speed. Accordingly, the output voltage of tachometer generator 21 decreases resulting in a voltage difference across control winding 230 which

increases the output voltage across terminals 231 and 23 ' of amplifier 23 Thus the voltage across D C winding 18 of saturable reactor 18 is increased, thereby decreasing the impedance of A C windings 18 i and 18 b Consequently the alternating voltage applied to control electrodes 12 and 130 of valves 12 and 13 will be shifted more in-phase with the anode potentials of such valves and thus the latter will conduct over a greater portion of their conducting half cycles, thereby increasing the current supplied to armature 140 of the motor Motor 14 will consequently increase in speed aiid the output of tachometer generator 21 will increase, thereby decreasing the voltage difference across winding 23 a of amplifier 23 to decrease the output of the latter Ultimately, the system will stabilize with motor 14 running at a speed only slightly less than its aforementioned no load speed. During the aforementioned action of the control system, the current flowing through valves 12 and 13, and hence through windings 11 a and 1 b of current transformer 11, causes a voltage to be developed across capacitor 34. As long as the voltage across capacitor 34 is less than the voltage across the low potential side of the resistance element 32 b of potentiometer 32 no current will flow in control winding 23 b because of the blocking action C 9 rectifier 31 If the current flowing through valves 12 and 13 increases sufficiently so that the voltage across capacitor 34 exceeds the reference voltage afforded by potentiometer 32, then the current which flows in winding 23 b will tend to reduce the voltage output of amplifier 23, and hence the voltage output to armature 14 a of the motor. Reduction in the applied voltage on the 70 motor armature tends to decrease the motor speed, and hence the speed and voltage output of tachometer generator 21 The resultant increase in differential voltage across winding 230 will tend to increase the voltage output 75 to the motor armature to maintain the speed, which action is opposed to the aforementioned action produced by the increasing current flow in tubes 12 and 13. Since the current limit action is a safety 80 feature it is made to predominate over the speed regulating action To further limit the speed regulating action, when excessive values of current are reached in the motor armature current, rectifier 27 conducts to limit the 85 differential voltage applied across winding 23 a, and a voltage proportional to the excess differential voltage, appearing across the resistance element of voltage divider 26 is added to the voltage appearing across capacitor 34 to aid 90 in current limit action This summation of voltages during current limit action results in a very definite current value, above which, the control system is responsive

only to the current limit portion of the control system, and 95 the output voltage of amplifier 23 is decreased to whatever value is necessary to maintain the current flowing in the motor armature at the limiting value Below such limiting value, the control system is responsive only to the speed 1001 regulating portion thereof. While in the system of Figure 1 the tachometer generator 22 has been described as a source of reference voltage in the speed regulating voltage comparison circuit, it will be 105 apparent that any other suitable source of D C. reference voltage, such as for example the series connected battery 37 and adjustable resistor 38 shown in Figure 2 can be used in place thereof 110 In Figure 3 there is shown a form of the speed regulating and current limit control system as applied to Ward Leonard drive It will be noted that elements of the system in Figure 3, which are identical to those in Figure 115 1 are given corresponding reference numerals. The Ward Leonard drive comprises a D C. motor 40, having an armature 40 a connected in a loop-circuit with the armature 410 of a D.C generator 41 D C control windings 420 120 and 42 b of a saturable reactor 42 are connected in series in the loop-circuit, and provide a source of current limit signal. Motor 40 is provided with a shunt field winding 40 T which is connected at one end in 125 series with an adjustable resistor 43 to the input D C terminal of a full-wave rectifier bridge 44 and is connected at its other end to the output D C terminal of rectifier 44 Rectifier 44 has its A C terminals connected to a 130 785,036 secondary winding 45 of a transformer 46, having a primary winding 47 which may be assumed to be connected to a suitable source of alternating voltage supply Transformer 46 is provided with other secondary windings 48, 49 and 50 Generator 41 is provided with a shunt field winding 41 b which is connected to output terminals 23 f and 23 ' of amplifier 23. Saturable reactor 42 is provided with a pair of series connected A C winding 420 and 42 d, and one end thereof is connected to one end terminal of secondary winding 48 while the other end of such series connected windings is connected to one A C terminal of rectifier 29 The other A C terminal of rectifier 29 is connected to the other end terminal of secondary winding 48. Secondary winding 49 provides the source of A C input for amplifier 23, with one end terminal being connected to corresponding ends of windings 23 c and 23 d, and the other end terminal being connected to the output and input terminals of rectifiers 23: and 23 k, respectively The A C terminals of rectifier 33 are connected to the end terminals of secondary winding 50.

The operation of the speed regulating and current limit portions of the control system of Figure 3 will be like that of the embodiment of Figure 1, except that their effect on the motor 40 will be intermediately through control of armature voltage of generator 41.


* GB785037 (A)

Description: GB785037 (A) ? 1957-10-23

Improvements in or relating to electromagnetic brakes


PATENT SPECIFICATION PATENT SPECIFICATION 785,037 Date of Application and filing Complete Specification: Aug 20, 1954. No 24287/54. Application made in United States of America on Nov 27, 1953. Complete Specification Published: Oct 23, 1957. Index at acceptancie -Classes 12 ( 3), C 5 B 3 C; 65 ( 2), F( 1 G: 3 E: 3 F); and 103 ( 1), E 2 E, E 2 M 1 (B 3 A: B 4 G: E 4: E 6: E 7: F 2: K 2). International Classification:-F 06 d, n. COMPLETE SPEGIIFI'CATION Improvements in or relating to Electromagnetic Brakes We, IGRANIC ELECTRIC COMPANY, LIMITED, a British Company of, 'Elstow Road, Bedford in the County of Bedford, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: - This invention relates to electromagnetic brakes and has for one of

its objects the provision of an improved brake having brake shoe operating parts which can be easily removed to facilitate repair and replacement of various brake parts Other objects and advantages wilt appear hereinafter. According to the invention there is provided an electromagnetically operated friction brake in which at least one brake shoe, supported from a base, is moved into and out of engagement with a brake drum by the pivoting action of a member pivotally mounted on said, base and actuated by an energisable magnet carried by said base, the pivotal mounting of said member on said base being effected by means of a flexible strap attaching said member to said base. Other features and advantages of the invention will become apparent from the following description of one particular embodiment given by way of example only, with reference to the accompanying drawings, in which:Figure 1 is a side elevational view of an electromagnetic external shoe drum brake embodying the present invention, several of the parts thereof being shown in section,. Figure 2 is an end view of the brake shown in Figure 1 and, Figure 3 is a fragmentary sectional view taken substantially along line 3-3, of Figure 1. Like reference characters indicate corresponding parts throughout the several views of the drawings. Referring to Figure 1, it illustrates a brake drum 1 to be secured to a motor or other lPrice 3 s 6 d 1 device to be bralked, opposed brake shoes 2 and 3 for frictionally engaging said drum on opposite sides thereof, and upwardly extending levers 4 and 5 to support and operate said shoes respectively The lower ends of levers 4 and 5 are pivatally mounted on a base 6, and an electromagnet 7 also mounted on said base 6 is provided for operation of said levers. Electromagnet 7 is provided with a field element including an energizing winding 8 and co-operating armature members 9 and 10 arranged on opposite sides thereof Armature is pivotally mounted on base 6 and is operatively connected to' lever 4 by a link 11. Said link 11 is attached to armature member by means of pin, 12, and to lever 4 by means of pairs of nuts 13 and 14 and springs as shown in Figure 1 'Such connection between link 11 and lever 4 provides adjustability as is well known in the electromagnetic brake art Armature member 9 is also pivotally mounted on a base 6 an& is operatively connected to lever 5 thxough adjustable spacing means to be hereinafter described Energizing winding 8 is completely, encased by side plates 1,6, ring member 17, cover strap 118, and support plate 19 Cover strap 18 is fastened to support plate 19 'by means of threaded studs 20 and nuts 20 a Said studs are welded to strap 18 ' in any well known manner As shown in Figure 2, support plate 19 is firmly

attached to base 6 by means of bolts 21 extending flange portions of base 6 and threadingly engaging said support plate 19. As shown in Figure 1, armature members 9 and 10 are positioned in elongated shallow recesses formed in base 6 and are pivotally mounted therein by means of straps 22 formed of resilient material such as spring steel. Bolts 23 are provided, for attaching said straps 22 to armature members 9 and 10 and to base member 6. Adjustable spring means 24 are provided for effecting separation of armature members 9 and 10 whenever energizing winding 8 is in an unenergized state Such spring means is well known in the electromagnetic brake art and permits adjustment of the compressive force of the operating spring in a well known manner Also provided in electromagnet 7 is a spacer 25 and sealing strap 26, each of which functions in a well known manner. o 10 The adjustable spacing means between lever and, armature member 9 comprises an Lshaped mounting bracket 27, bolt 28, nut 29, and wedge-shaped spacer block 30 Member 27 is attached as shown in Figure 1 to lever 5 by any suitable means such as by welding. It is believedl apparent that bracket 27 need not be a separate element but could be formed integral with lever 5 Bolt 28 extends through an opening formed in member 27 and threadedly engages spacer block 30 A compression spring 31 and sleeve 32 are provided to retain nut 29, which is welded to bolt 28, in abutting relation with the L-shaped, bracket 27 By this means the relative position of armature member 9 and lever 5 can be varied by turning bolt 28 to move spacer block 30. Each of the brake shoes 2 and 3 is attached to its respective operating lever 4 and 5 by means of a pair of bolts 33 the shanks of which extend through clearance openings in the operating lever and threadedly engage the brake shoe Such openings in levers 4 and 5 are elongated vertically to permit adjustment of the brake shoes in a vertical plane. The lower end portion of each of said operating levers 4 and 5 is formed into a segment of a cylinder 34 As shown in Figure 1, base 6 is formed with a surface complemental to said cylinder segment 34 to thus co-operate therewith as a roller and socket joint As illustrated in Figures 1 and 3, said cylinder segments 34 are provided with recesses for retention of pins 35 Said pins 35 ft into openings 36 a formed in mounting plates 36 Said 4 plates 36 are mounted on base 6 by means of bolts 37 as shown in Figures 1 and 3 Thus, operating levers 4 and 5 can be pivotally moved relatively to base 6 while maintaining a high degree of bearing surface between cylinder segments 34 and said base 6.

The bearing surfaces of segments 34 and base 6 are lubricated by means of an absorbent material such as felt saturated with a suitable lubricant and disposed between the respective operating levers 4 and 5, and base 6, as shown in Figure 1 A small bracket 38 and screws, such as shown at 39 in 'Figure 1, retain the absorbent material in such position The arrangement is preferably such that upon brake releasing pivotal movement of the operating levers 4 and, 5 relatively to base 6 associated therewith acts to compress slightly the absorbent material associated therewith to thus emit some of the lubricant which flows into the aforementioned roller and socket joints It is further seen that the absorbent material acts as a seal to prevent foreign matter from entering the joint and causing damage to the bearing surfaces. It is apparent that each operating lever 4 70 and 5 can be removed by simply detaching one of the mounting plates 36 from base 6 and sliding the operating lever outwardly for a distance of approximately one inch in a direction parallel to the axis of drum 1, and 75 then lifting the same free of the other brake elements.


4626 4630.output

Law