Patent GB-623134-A (GB)
Title: Improvements in and relating to electric switches
IPC: H01H19/62
Filed: 1947-04-17
Abstract: 623,134. Mechanical switches. BRITISH THOMSON-HOUSTON CO., Ltd. April 17, 1947, No. 10237. Convention date, April 17, 1946. [Class 38(v)] A switching device comprises contacts which are closed and opened by the longitudinal movement of a shaft in opposite directions and a number of other contacts which are closed in succession by the rotation of the shaft and opened in succession in reverse order by rotation of the shaft in the opposite direction. A pawl and ratchet mechanism ensures that the shaft can only be rotated in one direction for each longitudinal position of the shaft. Fig. 2 shows an exploded view of the device in which the shaft 1 can be moved axially by a knob 2 to actuate contacts 5, 6, 7, 8 of a switch A, rotation of the shaft actuating the contacts of a number of rotary switches of which only one, B, is shown. The pawl and ratchet mechanism is shown at 35 and in exploded view in Fig. 3. A spring ball 31 and indented wheel 30 indicate that the knob 2 has been turned from one switching position to another. The switch A comprises two interconnected fixed contacts 5, 6 and. movable contacts 7, 8 mounted loosely on carriages 9 supported on pivots passing through openings 10. The contacts 7, 8 carry posts 15 which pass loosely through openings in the carriages 9 and are surrounded by springs 14 and terminate in rounded heads 16. The carriages carry terminals 12, and springs 13 bias the contacts 7, 8 into engagement with the contacts 5, 6. The contacts are opened by axial movement of a member 17 on the shaft 1 which in one position presses the heads 16 to open the contacts and in another position allows the contacts to close under the influence of the springs 13. The member 17 is formed with two grooves 18, 19 to receive the heads 16 in the two positions of the member 17 the size of the grooves being such as to give the heads 16 the required movements. The member 17 slides on a shaft 22 on which is mounted the rotary part of the switch B which comprises fixed and movable contacts 5, 6, 7, 8 mounted similarly to the contacts of switch A except that the springs 13 are omitted and the terminal 12 are connected to contacts 7, 8 by flexible leads 21. On the shaft 22 is an opening cam 23 having risers 24 for engaging the heads 16, and two closing cams 25, 26 having risers 27 for engaging extensions 28 on the carriages 9<SP>1</SP>. In the position shown the contacts are open and on a clockwise movement of the knob 2 the cams 24 leave the heads 16 and the cams 27 engage the extensions 28 and close the contacts. A number of switches, B, may be arranged on the shaft 22 and the cams arranged so that all the switches are closed simultaneously and opened in succession. A device for preventing closure of the switches B before switch A is closed and for preventing switches B from being opened before A is opened comprises a hub 35 fixed to the shaft 1 and carrying a spring-pressed pawl 34 which engages in one or other of oppositely constructed ratchet openings in fixed plates 44, 45 separated by a plate 46 having an opening with notches 48, 49 corresponding to the end notches in the plates 44, 45. The shaft 1 can thus be moved axially to actuate switch A only when it has been turned to actuate switches B and the pawl 34 has reached the end of its travel in either direction so that it can be passed through one or other of the notches 48, 49. Fig. 4 shows an alternative device for allowing the shaft 1 to be turned in only one direction for each of its two axial positions. The shaft carries a coned member 60 up which a spring 62 can ride when the shaft is moved axially. The end 63 of the spring is fixed and the end 61 is secured to a rocking shaft 56 carrying a double-ended pawl 54 engaging a ratchet wheel 53 slidable on the shaft 1 which can thus be rotated in one direction only according to the end of the pawl that is in engagement with the wheel 53. Axial movement of the shaft causes the spring 62 to ride up or down the cone 60 and tilt the shaft 56 to actuate the pawl 54.