Patent GB-587763-A (GB)
Title: Improvements in electrical switching devices
IPC: H01H3/20
Filed: 1945-01-16
Abstract: 587,763. Retractive switches ; latching switches. GENERAL ELECTRIC CO., Ltd., and HARRISON, W. J. D. Jan. 16, 1945, No. 1357. [Class 38 (v)] A switch is closed by a rectilinear or rotary movement of a member followed by a similar movement in the opposite direction. Alternatively the switch may be constructed to open by the two movements of the actuating member. When the switch has been closed a separate movement by a catch is required to re-open it. This catch may be controlled by a selector device which renders the main actuating member effective only when the selector device is in a certain position. Fig. 1 shows a switch in which contacts 10 and 10a are normally kept apart by a blade 9 which abuts against the arm of the contact 10. The blade 9 is kept in the raised position by two cam surfaces 3, 8 formed respectively on a member 2 carrying a knob 1 and a member 6 which is slidable on the member 2. When the knob 1 is pushed the member 2 slides in the frame 7 and is returned by a spring 14 to its initial position when pressure is removed. Projecting from the member 2 are pins 4 which engage in slots 5 in the member 6 which is thus carried with the member 2 when the knob 1 is pushed inwards. During this movement of the parts, the final position of which is shown in Fig. 2, the blade 9 rides over the flat portions of the surfaces 3, 8 and the position of the contacts 10, 10a is maintained. Below the sliding members is spring blade 11 with a catch 12 at its free end which engages the end of member 6 when this has reached its final position. When the pressure on knob 1 is removed the member 3 returns to its original position but member 6 is retained in its inward position by the catch 12. A depression is thus formed between the cam surfaces 3, 8 as shown in Fig. 3, which allows the blade 9 to drop and the contacts 10, 10a to close. The switch is re-opened by pressing a finger 13 on the blade 11 and thus releasing the catch 12. The member 6 then returns to its original position under the influence of a spring 15 and the blade 9 raised to open the contacts. The finger 13 may be controlled by a lever arrangement, Fig. 4 (not shown) in which one arm of the lever is spring-pressed into contact with the periphery of a cam wheel. In certain positions of the wheel the finger is depressed permanently and the switch cannot be closed by operation of the knob 1. The spindle of the wheel may actuate a second switch and more than one finger 13 may be provided to release the catch 12 all the fingers being controlled by cam wheels. When any one of the wheels is rotated to depress its finger 13 the switch will open, and all the wheels must be in a position to allow the catch 12 to engage the member 6 before the switch can be closed by actuation of the knob 1. Fig. 5 (not shown) illustrates a modification in which the sliding members 2, 6 are replaced by rotary discs provided with cam surfaces 3, 8 which when separated form a depression in which the end of the blade 9 drops. The disc 2 is fast on its spindle 1 and carries a pin 4 engaging in a slot in the disc 6 and both discs are urged towards their initial positions by springs. When the spindle 1 is rotated both discs turn together but when the spindle is released the disc 6 is retained by a catch 11 which can be released by a finger 13.