Bush Cutter Research Articles

Muscle fatigue related to human posture using a brush cutter for landscape gardening: a preliminary study

Brush cutters are widely used in Chinese landscape gardening and agricultural laboring which leads the operators being exposed to many risks. Low back pain (LBP) is particularly common and can lead to substantial personal, community and financial burdens. The aim of the presented study was to measure the activity and function of each torso muscle of the operator when using the bush cutter, so as to evaluate the muscle injury of the operator during using several common brush cutters for different landscape tasks. The human postures of 6 workers using 2 types of brush cutters in the 3 working conditions were recorded and measured by using a surface electromyography (sEMG) system and a camera. The test results were compared by t-test and sign test. The effect of human posture on the sEMG signal of trunk muscles in different working condition were analyzed by ANOVA. In the 3 working conditions, except for the left trapezius muscle, the muscle load of operating the backpack brush cutter is higher than that of operating side-mounted brush cutter. When operating the side-mounted backpack brush cutter, the force on both sides of the trapezius muscle is uneven, the load of the left trapezius muscle is >25%, and the maximum value is >30%. The results highlighted significant differences in the effects of different working postures on the muscle activities of workers' trunk. Safe operation standards should therefore be taken to protect the exposed workers and to improve the industrial design of irrigation cutters to prevent the occurrence of occupational diseases. Med Pr. 2022;73(3):201-7.

林内作業時の粉塵環境について : チェーンソー,プロセッサおよび刈払機作業時の粉塵濃度

林内作業時の粉塵環境について : チェーンソー,プロセッサおよび刈払機作業時の粉塵濃度

Результаты исследований фрезерного кустореза в производственных условиях

Результаты исследований фрезерного кустореза в производственных условиях

Модернизация фрезерного кустореза

The shoots design of supporting device allowing to raise completeness of vegetation cutting and to increase the bush cutter efficiency is developed. We propose the idea to give the working body reciprocating movement. This movement will be carried out by hydraulic cylinders mounted on frame of bush cutter. The bush cutter is equipped with two milling cutters on the sides of which are located two hydraulic cylinders. When removing young growth bush cutters are the most widely adopted having a working body in the form of a cylindrical cutter.

1F2-4 やじろべえ式刈払機による草刈り作業負担の軽減に関する実験的検証

1F2-4 やじろべえ式刈払機による草刈り作業負担の軽減に関する実験的検証

Working Posture When Weeding with a Bush Cutter on Slopes

Working Posture When Weeding with a Bush Cutter on Slopes

Being shot by a bush cutter

Being shot by a bush cutter

The Reverse Rotation of the Bush Cutter Head and Its Relevant Problems

The Reverse Rotation of the Bush Cutter Head and Its Relevant Problems

Soil Hardness in No-tilled Field with Cover Crop Residue Mulch and Early Growth of Machine-planted Soybean

Soil hardness in no-tilled field with cover crop residue mulch and early growth of machine-planted soybeanHairy vetch and barley were cultivated for a cover crop at the University Farm of Niigata University, from October 1999. HV was killed by rotary mower (bush cutter) and roller, and barley was mowed by a reciprocal mower and flail mower on June 29, 2000. The soil hardness was reduced in the cover crop residue mulch field compared with the no-tilled field without the cover residue mulch, however, there was a difference in the amount of soil hardness reduction among cover crop residue mulches. In the field covered with rotary mower-killed HV, soil hardness was reduced most effectively. In the barley residue mulch field, some soybean seeds were not well settled in the planting furrows because the soil surface was hard. In HV residue mulch field, planting furrows were formed at the regular depth of 2-3cm, and the soybean seeds were well settled in the furrows. However, soil covering was insufficient in the HV residue mulch field. In addition, at the area with a large amount of HV residue, furrow formation was not complete. The frequency of stand establishment of soybeans in the cover crop residue mulch field was 50-60%, compared with the rotary tilled field without cover crop residue. The growth of soybeans in the field covered with rotary mower-killed HV residue was similar to that in the tilled field. It is necessary to establish the mechanical system in the soil covering after the seeds settle in the furrow when operating a sowing machine in a cover crop residue mulch field.

夏作カバークロップを利用した有機栽培ブロッコリの生産性

Organic broccoli was grown in the fall of 2001 and 2002 at the Experimental Farm, Ibaraki University. The objective was to determine the yield responses, food qualities, and weeds suppression in a no-till production system in which mulch treatments included cover crops of forage soybean and Japanese millet as compared with the conventional cultivation production system. Two different killing cover crop methods that were the use of bush cutter and hammer knife mower, were applied to all mulch treatments.Millet cover crop biomass showed the highest value that the ranged from 580kg/10a to 636kg/10a. Soybean N contents showed the highest value that the ranged 2.8kgN/10a to 6.3kgN/10a. Yields and head mass increased for millet mulch at an early harvest stage in both years. However, total yields were no significant differences between cover crop mulches and the conventional cultivation system. Broccoli sugar contents for millet mulch showed higher values compare with other treatment, and nitrate contents usually showed the lowest value. On the other hands, broccoli nitrate content for soybean mulch usually showed higher values comparewith other treatment. These results suggest that millet mulch would be an appropriate technique for organic broccoli production system because that would provide adequate soil nutrient condition.

Occupational Disease Induced by Hand Transmitted Vibration — The Relationship between Characteristics of Case and Kind of Tool

In statistics of workers' accidents under the Compensation Law in Japan, the number of cases of occupational disease due to hand-arm vibration in private enterprises was 2,120 from 1994 to 1997. These consisted of 712 cases (33.6%) by rock drill operation, 372 (17.5%) by chain saw, 323 (15.2%) by pick hammer, 241 (11.4%) by concrete vibrator, 80 (3.8%) by concrete breaker, 61 (2.9%) by bush cutter, 50 (2.4%) by chipping hammer, and 51 (2.4%) by portable grinder, among others. The clinical features of vibration disease differ greatly with the kind of tool. Each tool has its own characteristic of an engineering nature, which, combined with many factors in operation at the workplace, will induce characteristic clinical features. Nine cases from our laboratory cases are discussed in this connection.

The Evaluation of Vibration Exposure in the Operation of Chain Saws and Bush Cutters

The evaluation of vibration exposure has had three aims for the prevention of vibration syndrome among Japanese forest workers using chain saws and bush cutters. The first was to introduce exposure time regulation in chain saw and bush cutter operation, the second to improve the chain saw and bush cutter, and the third to find effective tests for the early diagnosis of vibration syndrome. For the first aim, correlations between vibration exposure time (minutes, hours, days and years) and physiological effects including subjective symptoms were observed. From the results, new effective regulations were introduced. For the second aim, existing and new chainsaws and bush cutters were compared in terms of vibration acceleration level and changes of physiological function between before and after chain saw and bush cutter operation. Those results promoted the improvement of chain saws and bush cutters. For the third aim, correlations between vibration exposure dose and physical examination results were analyzed. From the analysis, effective tests relating closely with vibration exposure dose were obtained.

固定刃付き刈払機刈刃に関する研究 第２報 刈払い性能及び作業者の筋負担への固定刃形状の影響

The mowing efficiency, resistance force imposed on the bush cutter control shaft, and burden on the operator's muscle were investigated and compared with conventional blades to discover a shape of the fixed blade which is suitable for mowing weeds and grass. The following is a summary of the results of the investigation.1) Mowing efficiency of the 23-tooth fixed blade is higher and more stabilized than that of 19-tooth and 45-tooth fixed blade, with engine speed of over 6, 500rpm in operation.2) The pitch of the cutting edge of the 45-tooth fixed blade is too small to cut all the grass and inevitable inching operation results in a conspicuous decline of mowing efficiency, especially in a higher range of running speed of the rotary blade.3) The fixed blade having 19 teeth has a cutting edge of a wide pitch, so that it takes in a large amount of grass stems. However, it supports only part of the stems, and most of them are pushed down by the rotating cutting blade before they are cut. To prevent this, it is necessary to reduce the amount of grass for the fixed blade to take in. For this reason, mowing is done by slowing the travel speed of the bush cutter. Consequently, the mowing efficiency did not increase in this test, too.4) The degree of mowing resistance inflicted on the control shaft in directions of right and left, and up and down was measured. With the fixed blade, the resistance on the right and left side was on the lowest level with engine speed of about 6, 500rpm in operation and the resistance increased with the engine speed below and above 6, 500rpm. This phenomenon is reverse to that of mowing efficiency. The phenomenon can be explained as follows. (1) While a lower engine speed allows the cutter to take in more grass stems, the cutting capability can not catch up with the fast speed of the cutter movement which is set in the experiment. (2) A faster engine speed accelerates the rotary speed of the blade which causes some grass stems to be pushed by the outer periphery of the blade. The above phenomenon was more conspicuous with 19-tooth and 45-tooth fixed blades than with 23-tooth fixed blade.5) The degree of mowing resistance on the control shaft in directions of up and down was the same on different types of the fixed blade. With the fixed blades, the resistance was on the puls (up) side, the reason being that the grass stems, after being cut, worked to push the bottom of the rotary blade upward. With an ordinary cutting blade, the resistance was on the minus (down) side, the reason being that the grass was cut down and left on the cutting blade. The grass accumulated on the blade worked to push the blade downward.6) Surface electro-Myogram on 8 points of the operators shoulders and arms was measured. With both of the fixed blade and ordinary blade, a strong electric emission was recognized on the left shoulder muscle (M. trapezius), where the suspension belt is placed and on the arms muscles (M. branchioradialis), the area to support cutter's handle operation. The electric emission signifies muscle strain.7) Electric emission from the left M. trapezius and left M. branchiordialis in using an ordinary blade, was less than that in using the fixed blade, because the weight of cutting head of the ordinary blade was lighter than that of the fixed blade by about 0.5kg. But, the emission from the right side muscles, in using the ordinary blade, was more than that in using the fixed blade. The increased electric emission from the right side muscles in judged to be attributed to the increased mowing resistance (in directions of up and down) caused by the grass clippings accumulated on the blade, and to bending and twisting for arms to throw the grass clipping on the blade. To ascertain the judgment, the weight of the cutting head of the ordinary blade was adjusted to the same weight as of the fixed blade, to make comparison in the electro-myogram.

Studies on the Bush Cutter equipped with a Fixed Blade (3)

To assess the degree of safety to the machine operators, we checked into the conditions of cut grass and pebbles scattered in operation of two types of bush cutter, one the cutter with a specially designed fixed (stationary) blade and the other an ordinary blade of 8-tooth and nylon wire. The major results obtained are summarized as follows.1) After mowing Digitaria adscendens Henr. in the experiment, were checked into the traces of cut pieces of the grass and the grass juice left on the operator's clothes. In the use of nylon wire cutter, which cuts the grass with centrifugal force, the traces were conspicous on the operator's waist and below. In 30 minute operation, operator's right and left knees accounted for about 80% of the entire area of the traces(trace area of cut objects cm2/100cm2). In the use of the cutter with a fixed blade and an ordinary 8-tooth blade, scattering of the cut grass was less. Scattering was much less (ratio of trace area 0.1%) with the fixed blade cutter which is designed to reduce the rotating speed of the cutter blade to about 1/3 of that of an ordinary blade.2) Scattering of ceramic triangular pyramids (DIN specification) from the fixed blade cutter was less than that of an ordinary 8-tooth blade. The result is due to the lower rotating speed of the cutter blade of the former cutter and also to the crushed objects being contained or being prevented from scattering by the fixed blade.3) Scattering direction tended to be in the left side of the operator with all of the fixed blade cutter, an ordinary 8-tooth blade and nylon wire cutter. Scattering density number of scattered objects in the operator's position with the fixed blade cutter was down to half (1/2) of that of an ordinary 8-tooth blade and nylon wire cutter.4) Scattering height with the fixed blade cutter and an ordinary 8-tooth blade cutter was less than 50cm. Scattering density at each designated height in the operator's position was lower for the fixed blade cutter than that of an ordinary 8-tooth blade cutter which leads us to determine that the danger from scattered objects decreases in using the former type of the machine.

固定刃付き刈払機刈刃に関する研究 第１報 作業性の実態

For the purpose of preventing frequent stone accidents in using bush cutter, we have developed a new cutting system equipped with a fixed blade upper the rotary blade, which is designed to catch grass and cut the way a pair of shears do. Experiments were carried out to know the mowing efficiency and the physical stress on the operators in mowing work. The results were compared with conventional bush cutters (8-cutter blade) without a fixed blade. The major results obtained are summarized as follows.1) In test mowing of oat grass, with a new cutter equipped with the fixed blade, a slightly mowing efficiency was obtained. The lower rate of mowing efficiency can be attributed to the following factors. (1) Diameter of the rotary blade is smaller than that of 8-teeth blade by 4mm. (2) The cutter head including gear case and blades is heavier than that of 8-teeth blade by about 70%, which may affect mowing operation adversely. (3) Engine was set at high speed of 8, 000rpm, which might have caused the cutter blades to catch less grass, resulting in slower movement of the bush cutter.2) With the new cutting system, higher mowing efficiency was obtained with engine speed 6, 000rpm (peripherals speed of the rotary blade 21m/sec) than with 8, 000rpm (29m/sec). The lower engine speed allowed the cutter to catch more grass and cut grass with better performance. The result was in contrast to the phenomenon with ordinary bush cutters.3) Relation between a degree of abrasion on the rotary blade and mowing efficiency was investigated. A used blade with abrasion of about R 0.5 allowed the cutter to catch more grass and to yield higher mowing efficiency than with a new blade.4) Ordinary cutter blade yield higher mowing efficiency in mowing grass with low cutting load. However, the efficiency declined steeply in mowing thick grass in high density and with high moisture. In Contrast, the new cutting system maintained a stabilized mowing efficiency without being affected by the degree of grass density.5) The effect of using the new cutting system on the extent of operator's physical stress was also studied. Weight of the cutter head is heavier than that of conventional machines by about 70%, which caused slightly heavier pyhsical stress on the operator.6) In test mowing with machines equipped with cutter heads of the same weight, heart rates with an ordinary blade increased by 144%, and that with the new cutting system by 138%. Lower rate as observed for the latter was believed to have resulted from moment of inertia and self rotating angular velocity which were less than for an ordinary blade by about 1/2 and 1/3 respectively, corresponding to reduction of about 1/6 in gyroscopic couple force generated on the new cutting system blade. Reduced gyroscopic couple made it easier to operate the machine and reduced pysical stress on the operator.7) Rate of increase in heart rates in operating the cutting system to mow along concrete wall fence was smaller. Rotary blade of the system, smaller in diameter than that of the fixed blade on top, worked to prevent itself to hit concrete wall and to spatter concrete debris. Also, it worked to prevent the machine to get swung back on hitting the wall. All this resulted in reducing the degree of pyhsical and mental stress on the operator.

Numerical Simulation Using the Engineering Workstation Application to the Bush Cutter and the ROPS

Numerical Simulation Using the Engineering Workstation Application to the Bush Cutter and the ROPS

飛び石事故防止のための受刃付き刈払機刈刃の試作

To prevent stone accidents, several modifications have been made to a conventional bush cutter head. One of the modification is to mount a shear bar with counter edges over the conventional blade (counter edge cutting type).Another modification is to put two notched blades, one over the other, and to reciprocally reverse the blade (relative cutting type).Tests were conducted in relation to stone scattering, operation efficiency and energy required to cut stems of weed, and result were compared with impact cutting type bush cutter without counter edges.1) Because the counter edges obstructed stone scattering, the percentage of stones scattered toward the operator by the counter edge cutting type bush cutter was half of that of the impact cutting type.2) The percentage of stones scattered by the counter edge type decreased with the decrease of the blade rotating speed, and the direction of stone scattering tends to shift on the left-hand side of the operator, making it safer to use the counter edge type.3) The work efficiency for the impact cutting type rapidly decreased as the rotating speed of blade decreases to 5, 000rpm or less, where that of the counter edge type decreased a little with the slow rotating speed.4) For the counter edge cutter type, the energy to cut single stems of Golden-rod decreased with the decrease in the blade rotating speed, and with the increase in the blade traveling speed. Impact cutting has been shown to impart energy to the stem due to stem deflection and also to suffer energy loss from stem due to blade friction, Hence, impact cutting type would be expected to require more energy than counter edge type.5) For cutting of young rice plants, the effect of increasing clearance between the blade and counter edge was small over a range of clearance in practice. The young rice plants shearing abilities of the counter edge and relative cutting type were superior to that of the impact cutting type. More than 90% of rice plants were sheared by relative cutting type even at the low level of peripheral speed, 5-15m/s.Since these cutter heads has a complicated structure, it is evident that more work using different approaches is necessary.

人間工学手法による往復動刃型刈払機の作業分析

In oder to prevent stone accidents, a mowing test was conducted to evaluate the performance of a reciprocating mower type bush cutter which were newly developed. This was compared with a rotating disc type.Some of our findings may be summarized as follows:1) With the reciprocating type cutter, most of the struck stones were not scattered. therefore the operator has no need to worry about mowing work.2) When the reciprocating type cutter struck against stones, the amount of GSR was much less than that obtained by using the rotating blade, which means that the mental stress of the operator was greatly reduced.3) The reciprocating type cutter has an disadvantage over the rotating type cutter in the amount of work done. It's work efficiency on level field and slope was about 80% of the rotating type cutter.4) The RMR for an operator on level field was 4.5 and 3.3 at a working width of 150cm respectively for the reciprocating type and the rotating type. The RMR on slope was 5.4 and 5.7 respectively for the reciprocating type and the rotating type.5) In mowing work using reciprocating type, grass was mown one way only. In addition, the bottom of the blade contacted with mown grass and trailed producing additional operating resistance.6) The optimum mowing width was considered to be 100cm from the results obtained in the test of surface EMG, RMR and work efficiency.

Studies on Trial Piano-wire Blades of Bush Cutter (IV)

Studies on Trial Piano-wire Blades of Bush Cutter (IV)

The recent status of vibration hazards among workers at the state forests in Hokkaido (author's transl)

In order to make clear the recent status of vibration hazards among workers belonging to the national forestry bureau in northern Hokkaido, a special health examination was carried out on 417 chain saw operators and 443 bush cutter operators. The results obtained are as follows: 1. Seven point seven percent of chain saw operators and 5.6% of bush cutter operators were diagnosed as suffering from vibration hazards. Distribution of the cases in chain saw operators was 50% in grade I, 31.2% in grade II and 18.8% in grade III, while in bush cutter operators it was 20% in grade I, 60.0% in grade II and 20.0% in grade III. 2. Six new patients were found in this special health examination. 3. Twenty-two of 76 authorized patients, who had been treated with periodical therapy and prohibited from the operation of vibratory tools until this special health examination, were diagnosed as having recovered their health because of the existance of no symptoms concerning vibration hazards. 4. Pains on pressure of the muscles were complained of at the upper arm, forearm, chest and at the back in 12.4% of chain saw and bush cutter operators. Deformities of the elbow, hand and finger joints were recognized in 12.6% of the workers, and ulnar nerve paralysis was recognized in 1.0% of them. 5. Occupational hearing loss and lumbago were diagnosed in 20.2% and 14.7% of the chain saw and bush cutter workers, respectively.