Ergonomics - Atlas Copco

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1.5 m/s 2 . For a grinding machine with a rigid mass loaded support handle, readings were down to around 0.5 m/s 2 . We decided, however, to provide the machine with a lighter plastic handle, thus saving 0.4 kg in weight. Isolation of vibration with a dominant direction When designing this type of percussive hand tool, one of the tasks is to develop a damping system that can transfer high feed forces over a soft mass spring system. One source of vibration is the forward and return action of the impact piston. This action causes alternating pressures on the front and rear parts of the piston, with cor- responding oscillating reactionary forces on the machine housing. The isolation built into the machine also has to be soft. The impact frequency for these tools often lies around 30 Hz, therefore the isolation system must have a natural frequency of its own that is well below this frequency. The mass of the machine cannot be in- creased too much without adversely affect- ing the design, therefore the spring must be soft. The damping system on <strong>Atlas</strong> <strong>Copco</strong> Fig. 3.17 Analysis of the grinder in running mode as seen from the front end. Above left: the machine is fitted with a stiff handle moving in phase. Below left: the machine is fitted with an anti-vibration handle moving out of phase. The question is, which solution is the best? 111
112 RRH machines serves two functions. It acts as a mass spring system to isolate vibra- tions, while conveying feed forces from the handle to the process. The mobile cylinder and valve system are housed in a low-friction bearing in the machine housing. At one end of the cylinder there is a servo piston. When the hammer is fitted with a riveting die and pressed against a rivet, the first task of the damping system is to transfer feed force applied to the handle to the rivet. When force is applied, the servo piston moves backwards inside the tool, gradually exposing an inlet hole into a volume in the handle. At the same time, it gradually closes an outlet hole. Air pressure in the volume in the handle then increases until there is a balance between the inlet and outlet flow. Pressure acting on the damping piston produces a force that corresponds to the feed force. If the feed force increases or decreases, the system responds with a cor- responding pressure change. This change has a limiting frequency of about 5 Hz. With faster changes, such as the impact rate of the hammer, the system will not have time for air pressure changes in the volume. Thus, that volume of air now acts as a spring, the handle is a mass and the system has efficient vibration isolation (weighted value
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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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2 Working with high feed forces req
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2 Working areas of a standing works
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2 body is lifted or tilted, or the
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30 The team is an important factor
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32 Grinders Grinders and sanders ar
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34 HanDle DeSiGn The hand grips on
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36 DUSt anD oil Although the machin
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38 Working environment In general,
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40 SHoCK reaCtion Sudden changes in
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42 practice. Sometimes the chisel h
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44 SHoCK reaCtion These tools do no
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46 heavy, assembly work is often hi
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48 depends on its inertia. The same
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50 bolts. Unfortunately there are a
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52 The low reaction torque in impul
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54 the working environment A typica
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56 Today, the angle nutrunner can b
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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 and 76: 74 Fig. 3.3 The same feed force app
Page 77 and 78: 76 Pushing and pulling Pushing a to
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
Page 101 and 102: 100 High motor power and fast clutc
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
Page 111: 110 In the GTG 40 grinding machine,
Page 115 and 116: 114 be noted that declared values b
Page 117 and 118: 116 Noise Noise was the first envir
Page 119 and 120: 118 value for 8 hours’ exposure t
Page 121 and 122: 120 We can start by looking at the
Page 123 and 124: 122 This is done with a minimum inc
Page 125 and 126: 124 microphones at a distance of 1
Page 127 and 128: 126 coated with dust or damaged by
Page 129 and 130: 128 This method has not been used b
Page 131 and 132: 130 tool cabinet. Many workplaces h
Page 133 and 134: 132 lubrication. Made from a compos
Page 135 and 136: 134 Grinder GTG 40 F085 The relevan
Page 137 and 138: 136 were simulated by fitting a whe
Page 139 and 140: 138 Drill LBB 26 EPX-060 The releva
Page 141 and 142: 140 applied to the center of the dr
Page 143 and 144: 142 Chipping hammer RRF 31 The rele
Page 145 and 146: 144 SHOCK REACTION There are no sho
Page 147 and 148: 146 Riveting hammer RRH 06 The rele
Page 149 and 150: 148 WEIGHT The weight is 1.3 kg, sc
Page 151 and 152: 150 Screwdriver LUM 22 PR4 The rele
Page 153 and 154: 152 This gives a score of 9. In pra
Page 155 and 156: 154 Impulse nutrunner EP9 PTX80-HR1
Page 157 and 158: 156 Due to friction in the hydrauli
Page 159 and 160: 158 Electric nutrunner ETP ST32-05-
Page 161 and 162: 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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