Patent GB-641313-A (GB)
Title: Improvements in push-button devices for use in controlling electric circuits
IPC: H01H7/12
Filed: 1948-03-19
Abstract: 641,313. Press-button retractive switches; controllers HEATON, F., and HEATON, A. R. March 19, 1948, No. 8180. [Classes 38 (iii) and 38(v)] A push-button switch comprises a toothed quadrant 13 (or sliding rack) which is rotated (or slid) against a returning spring 22 when the button 10 is pressed and rotates a toothed pinion 17 positively connected to a switch arm 20 so that the latter moves from a position 'bridging contacts 35, 36 to bridge contacts 34, 37. Also connected to the pinion is a ratchet wheel 21 engaged by a pawl 25 on a toothed wheel 23 rotatable on the same axis 'as the pinion. Actuation of the switch as above causes the teeth of the ratchet to freewheel over the pawl and when pressure is released from button 10, spring 22 causes wheel 23 to be driven by the ratchet and pawl which in turn drives a clockwork train, the last wheel 27 thereof having escapement mechanism imparting a time delay to th switch arm in returning to its initial position. Fig. 4 shows the application of the switch to a star-delta starter for an A.C. motor. Closure of an isolator switch 38 and movement of the push-button switch-arm 20 to bridge contacts 34, 37 by pressing button 10 completes a circuit from a supply contact 50 through the contacts 37, 34, contacts 83, 81 of a stop switch 82, a trip switch 80 and the energizing coil 52 of a triple-pole contactor 51. The latter closes and connects the supply to one end of each of the coils 59, 60, 61 of the motor, the other ends being short-circuited by a switch 93. The coils are thus star-connected. Closing of switch 51 also closes an auxiliary switch 51a which completes a holding circuit through contacts 63, 62, contacts 89, 86 on an inching switch, stop switch 82, trip switch 80 and coil 52. Release of the button 10 causes arm 20 to reconnect the contacts 35, 36 after the time lag produced by the clockwork train. A circuit is then completed from switch 51a through contact points 89, 86, 87, 83, 81, 80, 36a, 36, 35, 110a, 101a and the energizing coil 71 of a second triple-pole contactor 70. The latter closes and in so doing opens the short-circuiting switch 93. When the contactor 70 is completely closed the coils 59, 60, 61 are connected in delta. To inch the motor, the inching switch arm 88 is rotated to bridge contacts 87, 91. The holding circuit cannot now be completed and current flows from terminal 50 through points 37, 91, 87, 83, 81, 80 and the coil 52. Thus the contactor 51 will close to start the motor in star but the latter will stop as soon as pressure is released on the inching switch button. To stop the motor in any circumstances switch 82 is operated to open contacts 81, 83. The push-button switch can also be adapted to the starting of a D.C. motor, M, Fig. 7. In this case the arm 20 constantly engages a curved contact c at one end, the other end moving over contacts C<SP>1</SP>-C<SP>4</SP>. Closure of the isolated switch A and pressure on the button 10 to cause the arm 20 to bridge contacts c, c', closes a circuit from the contacts of an auxiliary switch B on switch A through arm 20, the contacts e<SP>1</SP>, e<SP>2</SP> of a stop switch E and the coil L<SP>4</SP> of a double-pole switch D having an auxiliary switch d. Switch D closes and current flows through the starting resistances R<SP>1</SP>-R<SP>3</SP>, the motor armature and field F. Meanwhile as the motor starts up, the button 10 having been released, the arm 20 is returning retarded by its time lag device. Switch D remains closed over a holding circuit d, inching switch contacts J<SP>1</SP>-J<SP>3</SP> contacts e<SP>2</SP>, e<SP>1</SP> and coil L<SP>4</SP>. When arm 20 reaches contact c<SP>2</SP> current flows from d through J<SP>1</SP>, J<SP>2</SP>, e<SP>2</SP>, c, c<SP>2</SP> and a relay coil L<SP>1</SP> which closes a switch S<SP>1</SP> and short-circuits one of the starting resistances R<SP>1</SP>. Switches S<SP>2</SP>, S<SP>3</SP> are closed in turn by relays L<SP>2</SP>, L<SP>3</SP> operated by the arm 20 engaging contacts c<SP>3</SP>, c<SP>4</SP> respectively thereby short-circuiting all the starting resistances, switch S<SP>3</SP> remaining closed to maintain the connection of the motor across the supply. The inching and stopping switches J and E operate similarly to those in the previous example.