GB1297841A - - Google Patents

Abstract

1297841 Screwdrivers K TOTSU 25 Feb 1970 [6 Aug 1969] 9112/70 Heading B3N A portable electric screwdriver 10, Figs. 1 and 2 comprises a handle 12 housing an electric motor 16, a driven shaft 22 and a clutch mechanism 36, the screwdriver being adapted to be driven by the electric motor until a predetermined resistance is reached, whereat the screwdriver is operated manually from the handle through clutch 36, which drives shaft 22. The motor shaft 18 is connected to an intermediate shaft 20, which in turn is releasably coupled to shaft 22 by a split pin 28 in the shaft 22 which is located in a bore 24 in shaft 20, and a diametric slot and key connection 20, 30. Shafts 20, 22 may be formed on a single shaft. Clutch 36 is formed as a coil which is connected at one end to handle 12, and at the other end to a collar 34 connected to shaft 20. In operation, a push button 38 is actuated so that motor 16 drives in a screw 68, Fig. 10 (not shown), and tends to open the coils of clutch 36. When a predetermined torque is reached motor 16 stops, and handle 12 is rotated so as to wind-up the clutch and further tighten the screw. Collar 34, Fig. 5, is rotatable relative to shaft 20, and has ridges (40), Fig. 6 (not shown), or balls (54), Fig. 7 (not shown), which co-operate with recesses (44) in a second collar 42 rotatably fixed but axially slidable on shaft 20 to provide a clutch drive, override of the clutch is varied by screwing a nut so as to vary the tension in a spring 50. A planetary reduction gear may be provided between the motor and shaft 22. The screwdriver tip 56 comprises a bore and slot 60 58, Fig. 8, into which a driver bit 62 is fitted, a resilient screw-holding member 64 being provided.