GB772382A - Rotary impact tool with inertia responsive torque control - Google Patents

Abstract

772,382. Screwing-up and unscrewing nuts &c. CHICAGO PNEUMATIC TOOL CO. April 15, 1955 [April 26, 1954], No. 10894/55. Class 83 (3). [Also in Groups XXIV and XXXVII] An impact-tool comprises an anvil 38, a rotatable shaft 31 having intermittent rotarymovement together with the hammer 57, and driving a flywheel 95 through a flexible-connection, and automatic means to discontinue rotation of the hammer responsive to relative movement between the flywheel and shaft due to sudden deceleration of the latter. The toolbody comprises a clutch-housing 18 having a radially-extending handle, a motor-housing 19 and a control-housing and handle 20. The direction of rotation of the pneumatic-motor 23 is controlled by a lever 36 and valve 35. The motor rotates a cam 44 engaging a pivoted member 57P carrying a double-headed hammer 57R, 57L engaging the anvil 38 on the toolholding shaft 39. When resistance to rotation occurs, the hammer swings about the pivot 56 and, as shown in Fig. 5, rotates about the anvil until an impact occurs as the faces 57S, 41 meet. The impact causes rotation of the flywheel 95 relatively to the motor-shaft 31. The flywheel is connected to the shaft by balls 98 in co-operating grooves with helical faces 97R, 99R in the flywheel and in a cam-sleeve 93 axially-movable on the shaft. When an impact is of sufficient duration and force, the flywheel causes the sleeve 93 to move axially to stop the motor by releasing a trigger 87 holding open an air-supply valve 66. Axial movement of the sleeve is resisted by a spring 101 adjusted by a screw 106 against a torque-setting dial. The trigger is re-set by releasing the starting-button 64 so that a spring 81 can return the valve 66 to its lowest position. In a modified tool, the flywheel itself moves axially at each impact. Modifications may be made in the helical faces of the grooves containing the balls 98 so that the motor will be cut-off by a lower impact when screwing-up than when unscrewing. Alternatively, one face of the groove may be of zeroangle, so that the automatic cut-off is not actuated and the loosening of a bolt is manually controlled. The tool may be of the accumulator-type, the flywheel then being driven by a spindle &c. which starts and stops with the hammer, instead of by the motor. It may also be electrically-driven so that the torque-control actuates a switch instead of a valve. Specification 619,796 is referred to.