Patent GB-203101-A (GB)
Title: Improvements relating to electric switches, circuit breakers and the like
IPC: H01H71/52
Filed: 1922-06-23
Abstract: 203,101. Ferguson Pailin, Ltd., and Pailin, G. June 23, 1922. Automatic circuit-breakers of the loose handle type have overload trip gear which, to open the switch, releases the energy stored in a spring by the recoupling movement of the switch handle preliminary to closing the switch, the released energy serving in turn to release the locking device which holds the switch closed. In the construction shown in Figs. 1 and 3 in which the mechanism and the rectilinearly-moving contact-arm a carrying the contacts, not shown, are in the closed position a slide d is guided upon the arm a and accommodates, in a slot a ball c which normally engages a groove b in the arm thereby serving to couple the slide and arm together. The ball is retained in the slot by a roller k pivoted in a stirrup piece i, itself pivoted at its lower end to the slide. To the same pivot pin on the slide a catch lever s is connected, which normally bears at its outer end against a rack t and at its inner end against a pin u on the stirrup member. In closing the switch from the position indicated in dotted lines in Fig. 1, the handle f is moved downwards thereby operating the toggle links g, hand moving the slide and with it the contact arm, locked to it by the ball c, until the overset position is reached. If the handle is moved with a jerky movement or if the operating pressure is temporarily removed the weight of the sliding parts reading through the rack t presses the upper end of the catch s against the pin u, thereby deflecting the stirrup piece and releasing the connection between the slide and the contact arm, allowing the contact arm to return to its off position under the weight of the moving parts. The contact arm is automatically released by deflecting the stirrup member which carries a lateral extension m in engagement with a tripping bridge n mounted on parallel movement links w under the control of the spring y. The right-hand link w is connected with a tripping arm 3 the upper end of which lies in the path of the weighted end 4 of a bell-crank lever 4, 5, Fig. 5, pivoted at 6. The end 11 cf the lever 4, 5 moves in a slot in the latching bell-crank lever 9, 10, which is retained in the position shown by the tripping detent 12, thereby retaining the lever 4, 5 against the action of the spring 7. When the detent 12 is rotated by the action of any one of three overload armatures associated with overload coils in the three phases the lever 4, 5 swings round, strikes the tripping arm 3, which lifts the tripping bridge thereby displacing the stirrup and releasing the switch arm from its armature with the driving slide. To reset the switch, the operating handle is reversed, thereby carrying the slide to the left. In this movement a roller upon the slide engages a lever 22 the upper end of which restores the bell-crank 4, 5 to the position shown in Fig. 5, where it is retained, if there is no overload on the system, by the latching lever 9, 10 which passes under the detent 12. Thus the first part of the reclosing movement, while the switch is still open, serves to tension the tripping spring 7 which acts, through the arm 3 and the stirrup to release the switch when the detent 12 is rotated. To complete the closure the handle movement is reversed, and the slide, now in driving connection with the switch arm drives the switch to the closed position. In the modified construction shown in Fig. 14, the latching lever 10 forms part of one of the parallel links w of the tripping bridge n. The arm 3 is replaced by a link m having a pin and slot connection with the stirrup. The tripping spring 30 is located between a link w and a point on the tripping bridge and is strained in the resetting movement (the first part of which is from left to right) as before.