Patent GB-748354-A (GB)
Title: Improvements relating to push-button electric switch mechanism
IPC: H01H13/72
Filed: 1953-05-06
Abstract: 748,354. Switches held set and freed mechanically; electrically-released switches. JELSON ELECTRIC, Ltd., and MOULSON, J. P. July 6, 1954 [May 6, 1953; Nov. 14, 1953]. Nos. 12541/53 and 31642/53. Class 38(5) A switching device is formed of two two-pole switches each latched closed by a respective push-button and released, either by a third push-button common to both switches, or by a common bimetal strip deflected by a heating element. The device, Figs. 1, 5, 9, comprises a pair of casings 7 mounted back-toback with a space therebetween each casing containing the movable contact blade 20 of one pole of each switch, the blades 20 of each switch being operated by a transverse insulating bar 17 having slotted ends 18 to receive the blades. The bars 17 are carried by a two-armed lever 16 pivoted at 9 between the casings 7 and extend through arcuate casing slots 19. Pushbuttons 3, 4 pivoted to the lever 16 at 15 have shoulders 12 supported on coiled springs 13 retained between the ends of openings 14 formed in the opposed walls of the casings 7. A centre button 5 biased upwardly by a leaf spring 35 has a pin 32 co-operating with a U-shaped slot 28 in the lever 16, and in the "off" position of the switches, shown, the pin 32 abuts a lug 29 at the slot centre. On depression of a button 3 or 4 the lever 16 pivots at 9 to engage the blades 20 of one switch with their fixed contacts 23, the springs 13 are compressed, and the pin 32 moves into one limb of the slot 28. Thus the lever 16 is locked against rotation and the unpressed button 3 or 4 cannot be depressed to close the blades 20 of the other switch. To reset the device the button 5 is pressed whereupon the springs 13 restore the lever 16. The device may be alternatively reset by a bimetal strip 37 connected to the lower end 36 of the button 5 and which deflects downwards when heated by a winding 39. In a modification, Fig. 10, in which both switches may be closed at the same time, each push-button 3, 4 is connected to a separate lever 16a, 16b pivoted at 43, carrying a bar 17, and each lever has a right-angle slot 40 cooperating with a pin 41 on a respective latch lever 42 pivoted at 42a. The other ends of levers 42 are bifurcated to embrace the push-buttons 3, 4 and engage the springs 13. When a button 3 or 4 is pressed the pin 41 is moved into the vertical limb of the slot 40 and the switch is thus latched closed, release being performed by a shoulder 44 on the button 5 which engages the pin 41. In another construction, Figs. 15, 20, 22, in which both switches may be closed at the same time, the buttons 3 ... 5 and latching mechanism are enclosed in a central metal casing A and the switch contacts enclosed in two-insulating casings B situated on either side of the casing A. Each button 3, 4 has a lever plate 50, 50a carrying an insulating contact-operating bar 63 and is pivoted at 51, 51a, the pivot pin 51 or 51a of one lever passing through a slot 52a or 52 of the other lever. The levers have registering openings 54, 55, each opening 54 having a notch 56 for co-operating with a respective spring-biased latching pawl 57 pivoted at 58. When, e.g., button 4 is pressed, as shown, its lever 50a is pivoted against the bias of a spring 61a, and pawl 57 moves into the notch 56 to latch the lever and hold the contact blades 66 of one switch against the fixed contacts 69. To reset the switch the button 5 is pressed against a spring 72 so that a shoulder 73 therein engages the pawl top 74 and the spring 61a restores the lever. The device may be reset by a bimetal strip (Fig. 14, not shown) which acts on a notch 77 on the button 5 in the manner described with reference to Figs. 1, 5, 9. The blades 66 carry auxiliary blades 86 which complete auxiliary circuits with fixed contacts 84 when the contacts 66, 69 are closed. To prevent both switches being closed at the same time, the levers 50, 50a may be modified, Fig. 24, by the addition of a lug 86 and a shoulder 85: Thus if the lever 50a is operated, its shoulder 85 by engaging the lug 86 of the lever 50 prevents operation of the latter. In a further modification, Fig. 26, which permits either switch to be closed alone or both switches to be closed but only in a certain order, the lever 50 has a lug 86 and lever 50a has a projection 87. If the lever 50a is first operated the projection 87 moves beneath the lug 86 and prevents operation of the lever 50, as shown. If, however, lever 50 is first operated, the lug 86 is received in the recess 88 beneath the projection 87 when the lever 50a is subsequently operated.