GB1340005A - Handtools such as screwdrivers - Google Patents

Abstract

1340005 Powered screwdrivers E COOKEYARBOROUGH 12 June 1972 [22 June 1971] 29137/71 Heading B3N A tool, in particular a screwdriver, has a casing 1 with a spindle 3 rotatable therein, driven by a member piston 8, reciprocable by fluid pressure air, admitted into the casing. Movement of the piston causes the spindle to rotate through screw-threaded engagement therebetween. Rotation of the piston is stopped by having a key, keyway engagement between the piston and the casing or by having the crosssections of the two parts non-circular. Air passes in Fig. 1, to either side of the piston by a passageway 9 or a passageway 10 and an axial duct 11 in the spindle. Air control is through a spool valve 32. At a predetermined torque a relief valve 33 can be activated to release air to operate a piston 35 to raise valve 32 by way of arm 36 and thus reverse the pressure. As illustrated the spindle is mounted so as to allow a degree of end float or axial play. The tool may have an arrangement at its lower end whereby a coarser thread, groove 16, allows further turning of a workpiece than can be achieved by spindle 3. This is brought about by axial movement of the piston and spindle 3. In the embodiment of Fig. 5 an extension 102 of piston 8 slides through a partition 101 and engages the spindle 3 via a ratchet mechanism and a nut 105. The tool operates in much the same way as the embodiment in Fig. 1 except that parts 108, 109 enable the automatic continuous reciprocation of the piston assembly as long as the fluid pressure is applied by way of an on-off finger valve. Specification 1,338,139 is referred to.