GB446140A - Improvements in or relating to switches more especially for electrically operated hand tools - Google Patents

Abstract

446,140. Snap-action switches; actuating controllers. ARMSTRONG, J. J. V., 12, Church Street, Liverpool.-(Bosch Akt.- Ges., R. ; 4, Militõrstrasse, Stuttgart, Germany) May 28, 1935, No. 15474. [A Specification was laid open to inspection under Sect. 91 of the Acts, Nov. 30, 1935.] [Classes 38 (iii) and 38 (v)] A switch mounted in the handle of an electrically operated tool such as a drill comprises an operating lever 17, a longitudinally movable rod 3 operated through snap-action mechanism by movement of the lever 17 and a contact carrying member 4 which is carried by the rod 3 and may be rotated into one of two selected positions by movement of a lever 8. The rod 3 passes through a partition 1a which separates the mechanical and electrical parts of the switch. The lever 17 carries a fork 22 which embraces the axle 19 of two rollers on a spring-link 12 that pivots about a fixed axis 13. The rollers run along a fixed surface 16a, Fig. 10, having a hump 16b which is reached by the rollers at the point of maximum compression of the spring 14 of the spring link, so that an additional kick is given to the snapaction. The rocker 12 moves in a recess 3b on the rod 3 moving the latter rapidly by engaging an end of the recess. Premature movement is prevented by a ball 20. In the form shown, adapted to control the motor of a drill, the member 4 carries a circle of six contact studs 4a ... f, three of which are adapted to engage three pairs of fixed contacts 11 on a base 26 when the rod 3 is moved downwards by operation of the handle 17. Before this movement is made, the member 4 may be moved into one of two positions by operation of the lever 8 which carries an arm 9, a slot in which is engaged by a stud 10 on a disc 5 connected to the member 4 by a pin 6 so as to allow longitudinal but not rotary relative movement between the members 4, 5. This selects the three contacts 4a ... f, which will come opposite the contacts 11 and engage them when the rod 3 is moved downwards. The three-phase motor is thus caused to rotate one way or the other as will be seen from Fig. 6. The arm 9 is sector-shaped and adapted to engage a notch 3d in the rod 3 preventing movement of the latter if the lever 8 is in an intermediate position between its two end positions. Movement of the lever 8 is similarly prevented when the rod 3 is in its lower position.