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Agricultural and Biosystems EngineeringPublications Agricultural and Biosystems Engineering
1978
Development of a Blade Guard for MowingWesley F. BucheleIowa State University
William I. BaldwinIowa State University
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Development of ? Blade Guard for Rotary Mowers
Wesley F. Buchele, William H. Baldwin FELLOW
ASAE
ABSTRACT
A N analysis of rotary lawn mower accident statistics showed that measures must be undertaken to
reduce or to guard against the hazards of operating these machines.
A cantilever rod blade guard was designed, built, developed, and tested. The rotary mower, when equipped with a blade guard, mowed the lawn satisfactorily and yet, when encountering a test object (a dressed chicken), passed over it without inflicting injury to the test object.
INTRODUCTION
The walking (push and self-propelled) and riding rotary mowers are used to cut grass on household lawns. The larger, self-propelling, forward mounted, midmounted and three-point-hitch rear mounted, tractor-operated rotary mowers are used to cut grass and weeds on household and commercial company lawns, highways right-of-ways and medians and farms and rangelands of the nation.
They all operate on the same principle; a powered, sharp, rapid rotating, horizontal blade impact cuts the stems at prepherial velocities of 45.72 to 60.96 m/s (9,000 to 21,000 fpm) and throws the cut material outside the tip-circle described by the rotating blade. Although the rotary mower performs a useful service, it must be treated as an extremely dangerous machine by the operator and the bystanders. Design engineers and potential owners and operators should become aware of the hazardous nature of the functional component, the sharp, rapidly rotating blade.
The purpose of this paper is to present the history of safety research, accident statistics, governmental activities and the design and development of a blade guard for rotary lawn mowers.
HISTORY OF ROTARY MOWERS
White (1964) recorded the history of lawn mowing from the time when grazing sheep or hand sickles were used for manicuring the expansive lawns of palaces, manor houses, and bowling greens to the popular use of the rotary mower of today.
Bolen (1935) was issued a patent on ^ ^o* " "otary mower on Oct. 15, 1935.
TABLE 1. INJURIES REPORTED BY MANNER OF INJURY (MCCLURE,
1959) .
Article was reviewed and approved for publication by the Power and Machinery Division of ASAE. Presented as ASAE Paper No. 75-5520.
Journal Paper No. J-8364 of the Iowa Agriculture and Home Economics Experiment Station, Ames, IA. Project No. 1941.
The authors are: WESLEY F. BUCHELE, Professor, and WILLIAM H. BALDWIN, Technician, Agricultural Engineering Dept., Iowa State University, Ames.
Number Percent
Total injuries Blade con tac t Thrown objects
794 553 241
100 69.6 30.4
An electrically driven rotary mower is on display at the Pioneer Village, Minden, Nebraska. An information sign states that one of the first manufacturers of rotary mowers was the Hanks Foundry of Kensington, Kansas, in 1938, and that rotary mowers first became popular in the South before they were accepted in the North. White (1964) and Silbereis (1965) state that rotary mowers became popular during World War II because of the shortage of steel, which was required for the manufacturing of reel mowers. Rotary mowers also were better suited for mowing uneven terrain than the reel mower.
THE INJURY POTENTIAL OF THE ROTARY MOWER
The injury potential of rotary mowers was identified by medical doctors Irvine (1954), McClure (1957), White (1957), Furnas (1959), and Grosfeld et al. (1970). After treating numerous lawn mower accident patients, these doctors published articles in medical journals and in the Home Safety Reveiw (published by the National Safety Council) concerning what they had observed in their practices.
Witt and Lamp (1965) stated that design engineers have a "moral obligation to help reduce" rotary mower accidents.
McClure (1959) studied the injury mechanism of walking rotary mowers involved in 794 accidents as shown in Table 1.
The eyes were injured in 16 percent of the thrown-objects accidents. This rate of injury is much higher than the percentage of area of the body involved. He found permanent disability resulted from 14 percent of the accidents.
McConnell et al. (1965, 1967, 1968, 1970) and Knapp et al. (1961, 1965, 1969) made numerous in-depth studies of rotary lawn mower accidents, conducted research, and built, installed, and tested safety devices for rotary mowers. McConnell (1970) tabulated the type of accidents associated with 102 riding rotary lawn mower accidents as shown in Table 2.
He found that 28 percent of the accidents resulted from the victim being hit by a thrown object or being struck by some part of the machine other than the blade. Blade-contact accidents accounted for 72 percent of the total.
1978—TRANSACTIONS of the ASAE 227
TABLE 2. TYPE OF RIDING ROTARY LAWN MOWER ACCIDENTS.
Number of accidents
Unsafe acts of opera tor Malfunction of machine Thrown objects Non operat ional Run-over Back-over Stability
102
26 24
6 2 4
12 28
MO
WE
z <> <cn
O - J 1IIA
I 3"
< _,
NN
UA
1944 1948 1952 1956 1960 1964 1968 1972 1976 YEAR
FIG. 1 Annual sale of all types of lawn mowers in the U.S.
ANNUAL RIDING LAWN MOWER SALES
1944 1948 1952 1956 1960 1964 1968 1972 YEAR
FIG. 2 Annual sale of riding lawn mowers in the U.S. [below 20 hp engines].
Although McConnell does not list the percentage of permanent injuries, he does state that 46 of the 102 accidents were amputations and that four were fatal accidents, for a total of approximately 51 percent disability and deaths, much higher than for walking mowers.
McConnell (1970) studied the run-over and back-over accidents. He stated, 'The run-over accident is one in which the victim, a bystander, or in some cases, the operator, is struck by the machine. It is distinguished from the back-over accident in that it occurs while the machine is traveling forward.
"The back-over accidents are the most tragic and, typically, have the following elements in common. First, the victim is usually a small child between the ages of 1 and 5 who suffers an amputation (of a leg). Second, the operator of the mower is either a parent, brother, or sister. Third, the mishaps occur as the machine is being operated in reverse. It is easy to visualize, not only the severity of the trauma, but also the mental anguish of the operator who feels an extreme sense of guilt."
A mathematical treatment of the injury potential of the sharp, rapidly blade was made by Park and DeMuth (1975). They found that the kinetic energy (KE) developed by a 0.6604 m long (26 in.), 1.59 kg (3.5 lb) blade rotating at 3000 rpm was 2803.5 J (2100 ft-lb). The angular momentum was 2579.22 J sec (161 lb-in.-sec), and the tip velocity of the blade was 103.74 m/s (20,420.35 fpm) or 373.46 km/h (232 mph). They found that the blade rotating with a tip velocity of 373.46 km/h (232 mph), was equivalent in injury potential to a 0.53 kg (1.17 lb) missile traveling at the same speed.
DEVELOPMENT OF SAFETY SPECIFICATIONS BY THE MOWER MANUFACTURING INDUSTRY
The American Standard Safety Specifications for Power Lawn Mowers, B71.1, approved by the American Standards Association (ASA, 1960) on June 23, 1960, limited the tip speed of the blade to 106.68 m/s (21,000 fpm) and called for the enclosure of the blade except at the discharge chute at the front of the mower.
The rotary lawn mower industry reduced the revolutions per minute of the blade from 106.68 m/s (21,000) to 96.52 m/s (19,000 fpm) by the approval of the U.S.A. Standard Safety Specifications for Power Lawn Mowers by the United States of America Standards Institute (USASI, 1968) on Oct. 10, 1968.
The mower industry began assembling discharge chute deflectors on walking and riding mowers and trailing deflectors on walking mowers in the early 1970's.
American National Standard Safety Specification for power lawn mowers, lawn and garden tractors, ANSI B 71.1-1972 was approved on March 31, 1972 by the American National Standard Institute. While the previous safety specification contain both design and performance specification, the latter document contained, for the most part, performance specifications.
An ANSI B 71.1a-1974 supplement to the ANSI B 71.1-1972 was approved April 1974.
LAWN MOWER PRODUCTION STATISTICS
The number of mowers shipped by lawn mower manufacturers is recorded by the Outdoor Power Equipment Institute (OPEI, 1973) and is published each year in November.
The growth of rotary mower sales has been phenomenal. Sales increased from 35,000 units per year in 1939 to more than 7.5 million in 1974 and are increasing at the present rate of 250,000 units per year as shown in Fig. 1. Sales of riding lawn mowers were relatively slow until 1968. There was a rapid increase in sales in 1969, and more than 1 million has been sold each year since that time, as shown in Fig. 2. The number of riding lawn mowers sold is included in the total number of lawn mower sales in Fig. 1.
The accumulation of lawn mowers on the American lawns is shown in Fig. 3. There were approximately 40 million walking mowers and 7 million riding mowers in the United States in 1973. This figure shows a steady accumulation of lawn mowers in America of about 2 million per year, and there is no sign of the market becoming saturated. Most homeowners who purchase riding lawn mowers continue to own walking lawn mowers for trimming around shrubbery, bushes, and other tight places. Even though the riding rotary lawn
^ B01 LAWN MOWERS IN AMERICAN HOMES
ig44 1948 1952 1956 1960 1964 1968 1972
FIG. 3 The accumulation of all types of lawn mowers on the lawns of American homes.
228 TRANSACTIONS of the AS AE—1978
mower takes over some of the jobs, there will continue to be a need for the walking lawn mower. The area mowed has tended to increase with the number of mowers sold; the mower owners are mowing areas never mowed before, including steep slopes, rough land, etc.
LAWN MOWER ACCIDENT STATISTICS
The statistics concerning power accidents have been sketchy. Accident statistics were developed by insurance companies and were published by the Wall Street Journal, National Safety Council, and other organizations interested in safety (Table 3). These basic estimates were organized into magazine articles and published, as shown in Table 4, by other publishing houses. These data are plotted in Fig. 4. High and low estimate lines were drawn through the data.
The rate of lawn mower accidents per 100,000 population for the data published in Table 4 was determined
3 0 0 L LAWN MOWER ACCIDENTS
1944 1948 1952 195B 19BD 19B4 1968 1972 YEAR
FIG. 4 The high and low estimate of all types of reportable lawn mower accidents in the U.S.
TABLE 3. THE BASIC ESTIMATES OF THE TOTAL NUMBER OF LAWN MOWER ACCIDENTS IN THE UNITED STATES.
1959 1960 1955 1968 1971
Accident/year
79,400 80,000 35,000
140,000 180,000
Accident rate/l00,000 populations
39.11 43.84
70.71 85.71
Publications Year Data gathered
The Wall Street Journal 1960 The Wall Street Journal 1960 Family Safety, N.S.C. 1963 The Wall Street Journal 1970 Good Housekeeping 1970
Insurance companies Insurance companies Insurance companies U.S. Dept. of HEW Ralph Nader estimates
TABLE 4. SOURCE OF STATISTICS CONCERNING ROTARY LAWN MOWER ACCIDENTS.
Statistic year
1956
1956
1955
1959
1960
1960
1962
1963
1964
1964
1968
1968
1968
1969
1969 1971
Estimated No. of accidents
10,000
10,000
35,000
70,400
80,000
80,000
80,000
75,000
75,000
50,000 to
80,000
55,000 to
80,000 140,000
140,000
140,000 180,000
Title of article
Accident injuries associated with rotary lawn mowers
Danger: power mower
Hidden dangers of your power mowers
The power mower industry
The power mower industry
Safety with power lawn mowers
Hidden danger of your power mowers
Lawn and garden tractors and outdoor power equipment
Power mower injuries
Power mowers take mounting injury toll among suburbanites
Final report of the national commission on product safety
Ralph Nader reports
Reference
U.S. Dept. of HEW, 1964
Today's Health, pp. 34-35, 1958
Family Safety, National Safety
Council, pp. 5-6, Summer 1963 The Wall Street Journal, Front page, July 14, 1960 The Wall Street Journal, Front page, July 14, 1960 Consumer's Bulletin, p. 10, June, 1961 Popular Gardening, pp. 48-51, 1963 Family Safety, National Safety
Council pp. 5-6, Summer 1963 Consumer's Bulletin p. 22, April 1965 Agricultural Engineer
ing pp. 436-437, Aug., 1965
Journal of Iowa Medical Society pp. 500-501, June, 1969 Consumer's Report p. 378, July 1969
The Wall Street Journal, Front page, May 14, 1970 Consumer's Bulletin, p. 19, Oct. 1972
p. 29 Good Housekeeping, 1972
Author
William V. White
Dennis Orphan
Robert H. Witt and Benson J. Lamp L. W. Knapp, W. H. McConnell Franklin H. Top
Source quoted
Numerous
Dr. William L. White
Insurance
Insurance Co.
Insurance Co.
Insurance Co.
Injury Control Program Section of U.S. Public Health Service Public Health Survey
U.S. Dept. HEW
Dept. of HEW
Dept. of HEW Dept. of HEW
1978—TRANSACTIONS of the ASAE 229
in 600 DC
O 500
g q 400
L RATE OF LAWN MOWER ACCIDENTS
ig44 1948 1952 195B 19B0 1964 1968 1972 YEAR
FIG. 5 The high and low estimates rate of lawn mower accidents per 100,000 mowers. This estimate is made by dividing data from Fig. 4 by Fig. 3 and multiplying by 100,000.
by dividing the number of accidents by the population of the area covered and multiplying by 100,000 and as shown in Table 5. This table shows a wide variation among locations.
The number of accidents for a given year, as shown in Fig. 4, was divided by the accumulated number of lawn mowers in the United States, shown in Fig. 3, and multiplied by 100,000 to produce the rate of accidents per 100,000 mowers, which is plotted in Fig. 5. The graph shows that the accident rate of the lawn mowers had topped out at approximately 500 accidents per 100,000 lawn mowers in 1974. This means that one person in five who mows grass with a rotary mower for 40 yr will receive a reportable accident from his lawn mower sometimes within his life.
The data in Table 5 can only be compared directly with the data in Fig. 5 when it is multiplied by eight (there w?s only one lawn mower per eight people in 1962). This mathematical manipulation shows that Dayton, Ohio was suffering a high rate of 1,000 accidents per 100,000 mowers per year in 1962. It also seems that the survey of the other areas did not pick up all the injuries suffered by people mowing lawns.
THE NATIONAL ELECTRONIC INJURY SURVEILLANCE SYSTEM (NEISS)
The Injury Data and Control Center of the Bureau of Product Safety of the Food and Drug Administration, which was organized in 1969, was transferred to the Bureau of Epidemiology on May 19, 1973, when the Consumer Product Safety Commission was activated.
One hundred and nineteen cooperating hospitals were statistically selected to supply information at 2 a.m. by code on the telephone concerning each person treated in the emergency room during the proceding 24 hr.
A study of The National Electronic Injury Surveillance System data (NEISS) for fiscal years 1972, 1973, 1974, 1975 (Table 6) (A) shows the number of accidents treated in the emergency rooms of cooperating hospitals for each fiscal year for each type of power lawn mower and (B) gives an estimate of the total treated in all emergency rooms of hospitals in the country. (Fiscal year 1973 is July 1, 1972-June 30, 1973).
The number of actual accidents are extrapolated to
TABLE 5. SUMMARY OF LAWN MOWER ACCIDENT SURVEY INFORMATION.
Area Year Accidents/year Estimated size of Rate of lawn mower population studied accidents/100,000 people
Dayton, Ohio 6 Iowa counties Pittsburg, PA State of Georgia
1962 1963 and 1964 1956 1955 and 1956
300 62.5 89
794
240,000 234,480
1,500,000 3,444,578
125 26.65
5.93 23.35
TABLE 6. SUMMARY OF NEISS DATA FOR POWER LAWN MOWERS.
1401
1405
1418
1419
1420
1421
1422
1437
1439
Product code
Power mowers, type not specified
Garden tractors
Power mowers, rotary gasoline
Power mowers, rotary
Power mowers, reel, gasoline
Power mowers, reel, electric
Power mowers, riding
Power mowers, riding gasoline
Lawn mowers not otherwise specified
Total
1973
A
1,594
101
3 6 2
29
39
11
100
2,236
B
38,279
3,082
11,117
579
1,310
204
5,910
60,481
Fiscal year
1974
A
1,478
83
349
19
35
6
89
2,057
B
38,089
2,244
10,506
464
881
343
3,815
56,342
1975
525
87
201
12
13
4
5
1,454
2,355
A—Number of accidents treated in the emergency rooms of the cooperating 119 hospitals
B—Estimated number of accident treated in all the emergency rooms in the nation.
230 TRANSACTIONS of the ASAE—1978
estimate the number treated in the nation's emergency rooms by multiplying by a factor unique for each machine.
An estimate of the total number of accidents in the country is found by dividing the number treated in the nation's emergency room by 0.38, (the percentage of all accident cases treated in emergency rooms of hospitals).
The total estimated number of lawn mower accidents are approximately: for fiscal year 1972—152,000; 1973— 159,000; 1974—148,000. The NEISS estimates of lawn mower accidents is slightly less than the low-estimate line drawn before the author was aware of the NEISS data.
ACTIVITIES OF THE CONSUMER PRODUCT SAFETY COMMISSION
The National Commission on Product Safety (Elkind, 1970) appointed by President Johnson on March 28, 1968, issued its final report on June 30, 1970. The commission concluded that rotary mowers were hazardous machines, that injuries from power mowers have increased in proportion to the numbers and use of the machines, and that the safety specifications for powered lawn mowers offered insufficient protection to the consumer. The commission concluded, "unless the . . . safety standard for rotary mowers is corrected, Federal intervention is called for to require adoption of less hazardous designs and possible recall or reconstruction of hazardous mowers currently in use".
The Consumer Product Safety Commission (CPSC, 1974), which was appointed by President Nixon on Oct. 27, 1972, conducted a hazard analysis of the in-depth investigations of the accidents by the Bureau of Epidemiology of the CPSC and of the accident statistics gathered by NEISS. The CPSC published (CPSC, 1974) the following statement: "The Consumer Product Safety Commission has made preliminary determination (a) the hazards associated with power lawn mowers, lawn tractors, and lawn and garden tractors (all hereinafter referred to as power lawn mowers) present unreasonable risk of death or injury and (b) that one or more consumer product safety standards are necessary to eliminate or reduce those unreasonable risks of injury."
The CPSC after rejecting existing safety specifications and safety standards extended an invitation to become "offerers" to all standards-writing organizations. They were requested to submit existing standards or to offer to develop one or more safety standards for power lawn mowers.
The CPSC received four offers to write standards and selected the offer of Consumers Union. The proposed lawn mower safety standard was written by Consumers Union with the cooperation and help of the OPEI, the mower manufacturing industry, private consultants, and university personnel and was submitted to CPSC on July 17, 1975. This standard has been evaluated by Stanford Research Institute to determine its effect on the price of mowers and on the industry.
DESIGN AND DEVELOPMENT OF A BLADE GUARD FOR ROTARY MOWERS
Proposed means of preventing contact with the sharp, rotating blade are:
1978—TRANSACTIONS of the ASAE
1 Extend skirt of blade cover below blade. 2 Make discharge chute longer than the length of
the forepart of the foot. 3 Install noninjury blade. 4 Install bumper that declutches and brakes blade
when activated by foreign body. 5 Install cow catcher, which pushes foreign bodies
out of the way of the mower. 6 Install a blade guard. An analysis of these means of preventing injury by
the sharp, rotating blade shows that the skirt of the blade does indeed, when properly designed and operated on level ground, act as a cow catcher, but would not prevent an injury when the mower falls on a person. The skirt of the blade cover, of course, may not always be successful in preventing blade contact. Body parts slip or roll under the skirt and the wheels while riding over the body, may lift the skirt over the body parts.
The design of the blade clutch and brake system, although complicated, would be safe when activated, but would not prevent an injury in a case of a mower fall-on-a-person accident.
The noninjury blade (Kepkan, 1975) is now under development (Nov. 1975) but was not known to the author when this research was initiated. The grass-cutting ability of the noninjury blade has not been evaluated by the author, nor has the injury potential in case of the run over or the fall-on-accident been determined. Of the proposed safety measures, only the blade guard would prevent injury in case of a run-over, back-over, or fall-on accident. It is simple in design and does not involve any complex mechanisms; it is always in place ready to prevent injury in case of an accident.
The program of developing a blade guard began in the fall of 1973.
DEVELOPMENT PROGRAM
A grill guard that completely covered the blade was constructed for the 21-in. walking mower owned by the author. Grass mowing tests showed that the grill rods pushed the grass down against the ground and prevented contact between the grass and the blade.
To bring the grass into contact with the sharp rotating blade, comb teeth were welded to the front of the rods. The teeth straightened up the grass, and the grass in this position was cut by the mower, Fig. 6. But grass hairpinned around the teeth and clogged the front of the mower. The comb teeth were removed, and a program of opening an area around the front of the mower was begun by reducing the length of the grill rods and evaluating by mowing tests.
FIG. 6 Comb teeth attached to rods of grill guard.
231
FIG. 7 The final results of the first grill guard which permitted a satisfactory job of mowing grass. The rear rods were not removed on later models. U.S. patent.
FIG. 10 Worms eye view of cantilever rod guard. Note unrestricted movement of hair pinned grass into the sharp rotating blade.
FIG. 8 Underside view of mower with short rod blade guard assembled in place on a riding lawn mower. Note area swept by sharpened part of blade was not protected. U.S. patent.
[B] Reciprocating knife and guard of farm mower.
[A] Rotary blade and guard of rotary lawn mower.
FIG. 11 The arrangement and the spacial arrangement of the knife and guard of the rotary mower and farm mower.
FIG. 9 Underside view of cantilevered rod guard assembled onto walking rotary mower.
FIG. 12 Underside view of riding mower equipped with cantilevered rod blade guard. Note position of added bumper ahead of blade cover.
Successful mowing was accomplished when the unprotected front area was increased (by shortening the grill rods) to that swept by the sharpened part of the rotating blade as it swung through the front arc. The points of the shortened rods were sharpened to a point to pick up grass as shown in Fig. 7. The guard reduced the area of contact to approximately 20 percent of an unguarded mower. A guard was built for a riding mower as shown in Fig. 8 (See U.S. Patent No. 3,917,199). Comparative mowing tests proved that a satisfactory job of mowing could be accomplished with a guarded mower. Dressed chickens, purchased from the supermarket, were used as test objects to determine the injury potential during run-over and back-over tests. The results showed that the unguarded mower caused complete destruction of the bird while, with the guarded mower, the bird only lost a leg, or a wing, or slices of white meat from the breast.
The test showed that it takes time for an accident to happen, and the blade guard reduced the number of times the blade actually struck the test object to only two or three hits instead of twenty to thirty hits as with an unguarded mower.
Development was continued during the fall of 1974 on a new theory of guarding to further reduce blade-contact injury in the event of run-over, back-over, or mower-fall-on accidents.
The grill guard was redesigned to include cantilever grill bars extending forward of the blade cover skirt (as shown in Fig. 9 and 10). The bars were cantilevered from the guard ring and contained the upper half of a spearpoint on the front of the bar and set with the rear
portion of the spear just outside the tip circle of the sharp rotating blade.
The objective of the half spear point was to comb the grass as shown in Fig. 10 and raise any grass that hair-pinned over the point and to pass it back into the path of the sharp, rotating blade, where it was cut and thrown down the discharge chute.
The arrangement and spacial relationship of the rotating knife and guard of the rotary mower shown in Fig. 11a is strikingly similar to that of the reciprocating knife and guard of the farm shown in l i b .
A bumper (shown in Fig. 12 and Fig. 13) was placed ahead of the spear points on riding mowers to protect the points in the event of collision with rocks or stumps.
The guard ring shown in Fig. 9 and Fig. 12 was placed concentric with the center of the blade, between the blade and the grill guard, and was welded to each rod of the grill guard. The diameter of the guard ring was slightly less than the unsharpened center section of the blade.
The width of the guard ring was approximately equal to the distance between the grill bars and the unsharpened section of the rotary blade. Its purpose was to press the rotating blade upward and out of the way of the grill rods whenever an upward force was exerted against the grill guard.
Whenever an upward force was exerted against the outer portion of a single grill rod, the spear point of the single grill bar pressed upward against the bottom of the skirt of the blade cover. This also prevented contact between rod and blade.
232 TRANSACTIONS of the AS AE—1978
FIG. 13 Close view of spear points of cantilever blade guard. Note position of bumper set ahead to protect the spear points.
FIG. 14 Quality of mowing job done by unguarded [top left] and mower [left] guarded with cantilevered rod guard.
FIG. 15 Start of unguarded run over test. A dressed 1 1/2 lb chicken was laid in front of
TEST PROGRAM AND CONCLUSIONS
Mowing tests were conducted with the unguarded mower and with a mower equipped with a cantilever rod guard. The quality of the job of mowing as shown in Fig. 14 was similar, except that the spearpoints seemed to rake the lawn as they moved through the grass and lift matted grass into the mower leaving the lawn with a raked appearance. The author mowed his lawn during the 1975 season with the walking mower equipped with the blade guard. The pushing force was noticeably greater when the experimental guard was installed, but the extra drag should not pose a problem with self-propelled or riding lawn mowers.
Run-over and back-over tests with a test object were conducted with the cantilevered rod blade guard. Fig. 15 shows the position of the test object (chicken) at start of test. Fig. 16 shows the results of the unguarded walking mower run-over test. The unguarded walking mower back-over test was similar. Fig. 17 shows the results of a guarded mower run-over test. The back-over guarded test results were similar to Fig. 17.
These tests show that the grill guard equipped with cantilevered spearpoints can satisfactorily mow grass and yet provide protection in the event of a back-over or run-over accident.
Cantilever rod blade guards were then built for the cutting sections of midmounted and front-mounted riding rotary lawn mowers.
Patent applications of the short rod and the cantilevered rod blade guards have been filed in the U.S. Patent Office by the Iowa State University Research Foundation.
References 1 ASA. 1960. American Standard Safety Specification for Power
' N <-
FIG. 16 Results of unguarded run over test showing condition of chicken. Chicken was thrown out the discharge chute.
Lawn Mowers. B71.1—1960. 10 East 40th Street, New York, NY 10016. June 23.
2 Bolen, Harry W. 1935. Powered Rotary Mower, U.S. Patent No. 2,017, 524.
3 CPSC. 1974. Consumer Product Safety Commission. Power Lawn Equipment, Proceedings for Development Safety Standard. Federal Register vol. 39 N144, pages 26662-26664. July 22, 1974.
4 Eklind, Arnold B. 1970. Final report of the National Commission on Product Safety. U.S. Government Printing Office, pages 28-30.
5 Furnas, David W. 1959. Projected injury from power lawn mowers. United States Armed Forces Medical Journal, X(2):235-237.
6 Grosfeld, Jay L., Thomas S. Morse, and Edward J. Eyring. 1970. Arch surgery, Vol. 100, pages 582-583.
7 Irvine, Vincent M. 1954. High-speed rotary lawn mower injuries. General Practitioner, July.
8 Kepkan. 1975. Personal correspondent. 9 Knapp, L. W. and W. H. McConnell. 1965. Designing the
rotary power lawn mower for safety. ASAE Paper 65-652, ASAE, St. Joseph, MI 49085.
10 Knapp, L. W. 1961. Man-machine relationship in tractor accidents. ASAE Paper No. 61-128, ASAE, St. Joseph, MI 49085.
11 Knapp, L. W. and J. T. Parks. 1969. Small tractor operator position and safety behavior. 51:456-459.
12 McClure, John N. Jr. 1959. Power lawn mower injuries are preventable. Southern Medical Journal, vol. 52, pages 1254-1257.
13 McClure, John N. 1957. Power lawn mower injuries. Home safety review. Published by the National Safety Council. March.
14 McConnell, William H. 1970. Analysis of 102 riding lawn mower injury cases. ASAE Paper No. 70-664, ASAE, St. Joseph, MI 49085.
15 McConnell William H. 1968. The engineer's responsibility in riding mower design. AGRICULTURAL ENGINEERING 49(8) :454-455.
16 Connell, W. H. and L. W. Knapp. 1965. Epidemiology of rotary power lawn mower injuries. Bulletin No. 9, Institute of Agricultural Medicine, The University of Iowa.
17 McConnell, W. H. 1967. Injury associated with the use of riding rotary lawn mowing equipment. ASAE Paper No. 67-663, ASAE, St. Joseph, MI 49085.
18 Neiss. 1972, 1973, 1974, 1975. Neiss News published by the Bureau Epidemiology, Consumer Product Safety Commission. National Injury Information Clearinghouse. Washington, DC 20207.
19 OPEL 1973. November news release. Outdoor Power Equip-(Continued on page 238)
FIG. 17 Result of guarded run over test original position of chicken was similar to Fig. 16.
1978—TRANSACTIONS of the ASAE
trated zone, or applied in a layer. In light of the above, three important conclusions
can be drawn from the results of this study: 1 Any of the herbicide placements used in this test
which tended to maximize weed control effectiveness resulted in some early season crop injury.
2 Seedling injury at the higher chemical concentration was greater than seedling injury with the low concentration level of herbicide applied.
3 The herbicides, dinitramine and trifluralin, drastically injured cotton and soybean seedlings when these chemicals were sprayed in a layer at the seed level after the seeds were planted. The previous conclusions, obviously, are valid only for the two herbicides and two crops included in this study.
The significance of the seedling injury will normally depend upon growing conditions during the early season. Previous studies have shown that under favorable conditions, the crop tends to overcome the early injury and grows satisfactorily. However, under adverse conditions, the effects of the early injury may be magnified.
The results also show a significant effect due to herbicide, since dinitramine produced more injury than trifluralin in all cases. A significant interaction between herbicide and crop resulted primarily from the greater injury to soybeans than to cotton by dinitramine.
The need for further research is clearly indicated by some other significant interactions. The treatment-herbicide interaction was highly significant for germination, average plant height, and green weight of plants after 12 days in the low concentration study.
ment Institute , Inc., Suite 903-905, 1725K Strict, N.W., Washington, DC 20006.
20 Park, William H. and William E. DeMuth, Jr. 1975. Wounding capacity of rotary lawn mowers. The Journal of Trauma, 15(l):36-38.
21 Silbereis, Joseph A. 1965. Moving ahead with safety. ASAE Paper 65-111, ASAE, St. Joseph, MI 49085.
22 Strauss, Bertrum and George Papritz. 1975. Proposed safety standards for power lawn mowers. Published by Consumers Union of the United States, Inc.
23 USASI. 1968. USA standard safety specifications for power
These results would indicate that different chemicals may need to be applied with different techniques to minimize crop injury.
The treatment-crop interaction on average plant height after 12 days was highly significant in all three tests. Again, these results indicate that different placement techniques may be required for different crops in order to minimize seedling stunting.
References 1 Davis, J. B., T. H. Garner, A. G. Jordan, B. K. Webb, and
B. J. Gossett. 1975. Injected trifluralin and fluometuron compared to disk incorporation and spray overlay. ASAE Paper No. 75-1068, ASAE, St. Joseph, MI 49085.
2 Garner, T. H., B. K. Webb, W. K. Whitehead, B. J. Gossett, and C. E. Rieck. 1971. Reduction of carrier and technical rates in the application of soil incorporated herbicides through low-volume application and increased uniformity. Annual progress report for Cooperative Agreement Number 69-149, South Carolina Agricultural Experiment Station, Clemson University, Clemson, South Carolina.
3 Jordan, A. G., T. H. Garner, B. K. Webb, J. B. Davis, and B. J. Gossett. 1974. Development and evaluation of a herbicide injector/planter. Paper presented at Southeast Region Meeting of ASAE in Memphis.
4 Oliver, L. R., and R. E. Frans. 1965. Influence of trifluralin rate and depth of incorporation on cotton and soybean lateral root development. Proceedings Southern Weed Conference 18:85-87.
5 Talbert, R. E. 1965. Effects of trifluralin on soybean root development. Proceedings Southern Weed Science 18:652.
6 Talbert, R. E., and R. E. Frans. 1968. Studies of factors influencing the selectivity of trifluralin and nitralin. Proceedings Southern Weed Conference 21:337.
7 Whitehead, W. K., T. H. Garner, B. K. Webb. 1968. Influence of trifluralin incorporation uniformity on weed control effectiveness. ASAE Paper No. 68-647, ASAE, St. Joseph, MI 49085.
lawn mowers. B71-1-1968. 1430 Broadway, New York 10018. Oct. 10. 24 White, William L. 1957. The menace of the rotary lawn mower.
American Journal of Surgery, 93:674-675. 25 White, William V. 1964. Accidental injuries associated with
rotary lawn mowers. PB-194 181. U.S. Department of Health, Education, and Welfare, Washington, DC.
26 Witt, Robert H. and Benson J. Lamp. (1965). Lawn and garden tractors and outdoor power equipment. AGRICULTURAL ENGINEERING 46(8):436-437, 447.
Guard for Rotary Mower (Continued from page 233)
238 TRANSACTIONS of the ASAE—1978