Patent GB-163413-A (GB)
Title: Improvements in electric plug fittings
IPC: H01R13/70
Filed: 1920-02-04
Abstract: 163,413. Evans, W. E., and Dant, D. W. Feb. 4, 1920. Plug and two-part couplings combined with electric switches; binding-posts and terminals; couplings.-An electric plug fitting comprises two or more pairs or sets of external contact elements each adapted for engagement with counterpart coupling contacts and a switch device for connecting the leads from the fitting to the pair or set employed for the time being. According to the Provisional Specification the switch may be hand-operated, but preferably it is automatically actuated upon effecting the coupling. A rectangular apertured insulating body is fitted with tightly-fitting covers, the latter carrying the lead terminals 15, 16 and the switch. No terminal 15 may have an upstanding lug which assists in positioning the lead, relieves the strain on it and minimizes risk of detachment. Two sets of contact elements. are mounted on the sides of the body and may be of different types or sizes, one preferably consisting of a bayonet or screw plug. According to Fig. 1 the opposite sides 2, 3 of the body carry plug pins 8, 9 and a bayonet coupling 10 respectively. The plug 8 is mounted on a plate 7<1> which may have a series of holes to vary the pitch of the plugs whilst according to the Provisional Specification the plugs may be exchangeable for others of a different gauge or may be clamped in position with one end bearing upon a contact plate so as to enable the pitch to be varied. The contact elements 8, 11 are permanently connected together. The terminal 15 is put into connection with them by a spring 15<1> on the former which engages the member connecting them together. The switch is pivotally mounted on the terminal 16 which consists of two plates with upstanding parts 22, 23 the upper one 22 having a slot 25 and being pivoted at 21 so that the lead is gripped between the upstanding parts and secured by a screw 24 clamping the plates together. The switch comprises a conducting arm in contact with the pivot 21 and gripping an insulating arm 27. A spring 30 holds the conducting arm normally in engagement with the base of the plug 9 so that the plugs 8, 9 are normally in circuit with the leads. The bayonet contact-member 29 is slidingiy mounted in the bodv and held extended as shown by the spring 30 and arm 27 so that the coupling 10 is normally out of circuit. On inserting the coupling 10 into a socket the member 29 operates the switch which disconnects the plug 9 before the parts are fully engaged. The member 29 then engages the head of the terminal screw 24 and finally the contact 11 engages its counterpart contact and the connection is complete. The disengagement of the coupling 10 preferably disconnects the contact 11 first and so prevents sparking at the terminal screw 24. A form having three pairs of contact elements and an automatic switch is also described, an additional pair of plugs of different gauge to the plugs 8, 9 being mounted on the part 5 of the body. One of the plugs is slidably mounted and normally thrust outwards by a spring and it carries an insulating cone which works between the arm 27 and contact member 29 to actuate the switch automatically when required and to maintain the contact 29 in extended position except when the bayonet coupling is in use. The switch according to the Provisional Specification comprises a spring arm actuated by a spindle within a fixed cam sleeve. The inner end of one contact member of such coupling is recessed to form a switch pole and the cam acts upon turning the spindle so as to lift the arm out of each groove and lower it into the other.