Patent GB-899114-A (GB)
Title: Torque release and shut off device for rotary pneumatic tools
IPC: B25B23/145
Filed: 1960-08-18
Abstract: 899,114. Screwing-up nuts and bolts. CHICAGO PNEUMATIC TOOL CO. Aug. 18, 1960 [Oct. 1, 1959], No. 28653/60. Class 83 (3). [Also in Group XXIV] A power tool for transmitting controlled torque to a driven element such as a nut, bolt or screw, has a pneumatic motor connected to a work spindle by an overload release clutch which is completely disengaged when a predetermined torque is attained and the supply of compressed air to the motor is simultaneously cut off. The clutch remains disengaged until the operator intervenes to reset the tool. As shown in Figs. 1 and 8, a hand-held tool comprises a sliding vane motor unit 21 driven by compressed air supplied through an inlet 95 to a chamber 93 in a hollow handle 94 of the tool. A valve 97 is manually depressable to admit air to a chamber 98 and is spring loaded for return movement. Chamber 98 supplies air to the motor under the control of a poppet valve 27. Exhaust from the motor passes through a port 113 and ports 114 of an exhaust deflector 115 to the atmosphere. The rotor shaft 41 of the motor unit 21 is fast with an upper clutch member 44, a lower clutch member 49 being formed with a shaft 58 which drives the work spindle through epicyclic reduction gearing. A number of rollers 51 are rotatably mounted in an annular groove in the driving clutch member 44 and co-operate with pockets formed in the driven member 49 between intervening teeth 57. A spring 26 biases the driven member 49 upwardly so that the pockets accommodate the rollers 51. In operation, upon reaching a predetermined torque, the rollers ride out of the pockets, forcing the member 49 downwardly. The poppet valve 27 has a stem 119 connected to a thrust rod 28 passing through a bore in the rotor shaft 41 and contacting the bottom of the recess in the shaft of the driven clutch member 49. When the clutch is fully engaged the poppet valve 27 is held clear of its seat and a surrounding shoulder 122, the valve being lightly biased downwardly by the pressure acting on the unbalanced area of the valve which is equal to the area of the stem 119. When the member 49 is cammed downwardly on overload, the lower edge of the poppet valve is close to the upper edge of the shoulder 122, restricting the passage of air so that the pressure at the underside of the poppet valve is suddenly decreased. The valve is thus moved downwardly and acts through the thrust rod 28 to completely disengage the driven clutch member 49, and the valve engages its seat 103 and cuts off the air flow to the motor. As long as the valve 97 is held open the clutch remains disengaged and the motor at rest. To reset the tool the operator must release the valve 97 to cut off the air supply to chamber 98 which then vents through a restricted passage 124 in the poppet valve and thence through the motor to the atmosphere. The reduction in pressure permits spring 26 to expand to unseat the poppet valve and re-engage the clutch. The loading of the spring 26 is adjustable to vary the maximum torque transmissible. The spring, which acts on the lower clutch member 49 through a cup 72 and a bearing 74, reacts on a nut 76 screwing on to a fixed boss 73 and having ears 86 engaging longitudinal slots in a sleeve 81 formed with teeth 84 engaging a bevel gear 83 rotatably mounted in the tool housing and turned by a key insertable in a socket 82. The position of the ears 86 can be read off on a scale marked on the housing to enable the torque setting of the clutch to be readily adjusted. In a modification a stationary tool 125 forms one of a gang of multiple nut setters. The upper and lower clutch members 129, 133 are formed with clutch teeth. Air is supplied through a control valve 159 to a manifold 161 provided with a plurality of lines 162 connected with the tools (only one being shown). The air passes directly to a poppet valve chamber 163, and thence through a non-return valve 173 to the motor rotor. As before, the reduction in pressure beneath the poppet valve which occurs when the clutch partially disengages, unbalances the poppet valve which is then seated and acts through the thrust rod to completely disengage the clutch. The arrangements for adjusting the spring loading of the clutch are also modified. The spring acts between the lower clutch member 133 and a cup 135 slidable on a shaft 134 fast with the lower clutch member. The cup is mounted by means of a bearing 136 in a ring 137 having ears 138 passing through vertical slots 139 in the tool housing. An internally threaded adjusting collar 141 engages projecting threads on the ears 138 whereby the ring can be adjusted axially to vary the spring loading. The tool is one of a gang of similar tools which are each mounted by a flange 192 on a common mounting plate 193 and supplied with compressed air through a common manifold 161. When an individual tool 125 has reached its torque setting its clutch disengages and its motor stops without effecting operation of the other tools of the gang. When all the tools have come to a stop they may be simultaneously reset by turning the valve 159 to its " vent " position ; on subsequently returning the valve to its " on " position the motors of all the tools will start simultaneously.