Ergonomics - Atlas Copco

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Human force generating capacity The above actions are limited by the force generating capacities of individual operators. A common measure of their capacity is muscular strength, i.e., the maximal force that a group of muscles can develop under prescribed conditions. Since the muscles must be activated voluntarily, some authorities refer to muscular strength as producing Maximum Voluntary Contraction (MVC) levels. In this regard, the measured strength values, even with well-motivated subjects are probably below the physiological tolerance of the muscle-tendon-bone system, thus providing a safety factor against over-exertion. The extent of this “safety factor” is not really known, but it could be as great as 30%. However, epidemiological studies have shown that when a job requires more exertion than a person would give voluntarily, there is a much greater risk of injury. Normal muscle strength values are usually obtained from volunteers belonging to specified groups (e.g., male, female, working population, domestic population, etc.) under prescribed conditions. It should be noted that there are substantial individual variations in muscular capacity data – the strongest is 6-8 times stronger than the weakest. Of the many factors which may influence muscular strength, gender accounts for the largest difference in average strength values. The strength of the average woman is approximately two-thirds that of the average man. This average covers the capacities of many different muscles. The strength of the different muscles in the hand-arm-shoulder system of a woman can be anywhere between 35% and 80% of that of a man. Age is another factor which influences muscular strength. In general, a person’s strength appears to be at its peak in the late twenties and early thirties, declining there- after. In an average population, strength at age 40 appears to be approximately 5% less, and at age 60, 20% less than in the late twenties. Physical differences, such as weight and stature, also influence muscular strength. However, physical dimensions alone are not a reliable guide to strength. Thus, if a certain amount of strength is required to perform a given task safely, choosing an operator based on size, shape or weight alone will not be enough. Muscle strength values for different arm operations have been obtained from various population groups. These can serve as guide- lines for hand tool designers when they decide the feed force and reaction force of the tools. 75
76 Pushing and pulling Pushing a tool forward is one of the most common operations in hand-held power tool applications. For the majority of the working population the maximal capacity to ap- ply force by pushing forward may be set at 275 N for a male seated operator in optimal working conditions. During the action of pushing forward, the relatively strong muscles of the arm – the biceps, brachialis and triceps – come into play. Therefore, the operator can gener- ate much greater force than when pushing inwards, outwards, upwards or downwards. Correspondings force capacity limits can be found in Table.3.2. Wrist torque Forearm supination refers to rotating the forearm clockwise, as in the action of tighten- ing a screw. Forearm pronation is rotating the Standing postures Men Women Push forward straight arm 450 340 Pull backward 400 300 Push down straight arm 600 450 Radial lift up 50 30 Ulnar push down 75 50 Dorsal push 75 50 Palmar push 55 35 Sitting postures Men Women Push forward straight arm 275 180 Pull backward 250 170 Radial lift up 50 30 Ulnar push down 75 50 Dorsal push 75 50 Palmar push 55 35 Table 3.2 Maximal Voluntary Contraction (MVC) values with forces in Newton (N). These are practical values based on scientific results and experience. Pull backwards Push forward Radial lift up Ulnar push down Palmar push Dorsal push Fig. 3.5 Definitions of the force values given in Table 3.2.
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Power Tool Ergonomics E V A L U A T
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Acknowledgements While doing resear
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How to get the best out of this boo
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Work with international standards I
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Good ergonomics is good economics W
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10 SOCIOLOGY INDUSTRIAL SOCIOLOGY S
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12 Work organization No organizatio
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1 outside the production system, an
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1 A seated operator usually has goo
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1 without stretching the trunk. The
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20 The arm sling as a preventive me
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22 Extreme working postures in real
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Page 31 and 32: 30 The team is an important factor
Page 33 and 34: 32 Grinders Grinders and sanders ar
Page 35 and 36: 34 HanDle DeSiGn The hand grips on
Page 37 and 38: 36 DUSt anD oil Although the machin
Page 39 and 40: 38 Working environment In general,
Page 41 and 42: 40 SHoCK reaCtion Sudden changes in
Page 43 and 44: 42 practice. Sometimes the chisel h
Page 45 and 46: 44 SHoCK reaCtion These tools do no
Page 47 and 48: 46 heavy, assembly work is often hi
Page 49 and 50: 48 depends on its inertia. The same
Page 51 and 52: 50 bolts. Unfortunately there are a
Page 53 and 54: 52 The low reaction torque in impul
Page 55 and 56: 54 the working environment A typica
Page 57 and 58: 56 Today, the angle nutrunner can b
Page 59 and 60: 58 High torque nutrunners for use w
Page 61 and 62: 60 Wheel nuts on trucks and buses a
Page 63 and 64: 62 Introduction A basic ergonomic p
Page 65 and 66: 64 Handle design The handle of a ha
Page 67 and 68: 66 Arteries Veins (superficial) Vei
Page 69 and 70: 68 Handle size Since a tool handle
Page 71 and 72: 70 However, if the texture is too c
Page 73 and 74: 72 Bibliography Chaffin, D.B. and A
Page 75: 74 Fig. 3.3 The same feed force app
Page 79 and 80: 78 the object, the shape of the obj
Page 81 and 82: 80 Safety factor a 2 Frequency of t
Page 83 and 84: 82 Comments for different tool type
Page 85 and 86: 84 The trigger is either operated b
Page 87 and 88: 86 used in one handed operations. T
Page 89 and 90: 88 Weight The weight of a hand-held
Page 91 and 92: 90 stability of grip, the center of
Page 93 and 94: 92 Temperature Hand-held power tool
Page 95 and 96: 94 To ensure physical comfort durin
Page 97 and 98: 96 Score 40 30 20 10 0 Bibliography
Page 99 and 100: 98 the dynamic properties of the ma
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Page 103 and 104: 102 Score 40 30 20 10 0 shock react
Page 105 and 106: 104 piezo-electric crystal. When th
Page 107 and 108: 106 EN 50144 and EN 60745. Both ISO
Page 109 and 110: 108 hole of the wheel are wider tha
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Page 113 and 114: 112 RRH machines serves two functio
Page 115 and 116: 114 be noted that declared values b
Page 117 and 118: 116 Noise Noise was the first envir
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Page 121 and 122: 120 We can start by looking at the
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126 coated with dust or damaged by
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128 This method has not been used b
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130 tool cabinet. Many workplaces h
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132 lubrication. Made from a compos
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134 Grinder GTG 40 F085 The relevan
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136 were simulated by fitting a whe
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138 Drill LBB 26 EPX-060 The releva
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140 applied to the center of the dr
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142 Chipping hammer RRF 31 The rele
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144 SHOCK REACTION There are no sho
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146 Riveting hammer RRH 06 The rele
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148 WEIGHT The weight is 1.3 kg, sc
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150 Screwdriver LUM 22 PR4 The rele
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152 This gives a score of 9. In pra
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154 Impulse nutrunner EP9 PTX80-HR1
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156 Due to friction in the hydrauli
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158 Electric nutrunner ETP ST32-05-
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160 WEIGHT The electric nutrunner i
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162 Angle nutrunner LTV 29 R30-10 T
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164 operator equal to installed tor
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166 Electric angle nutrunner Tensor
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168 WEIGHT The electric nutrunner i
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170 High torque nutrunner LTP 51 Th
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172 Score 40 30 20 10 0 NOISE The d
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Ergonomics - Atlas Copco

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