GB490812A - Improvements in or relating to time switches - Google Patents

Abstract

490,812. Time switches. BRITISH SANGAMO CO., Ltd., BUTHERUS, F. R., GILLIVER, G., and TAGG, G. F. Feb. 18, 1937, Nos. 4946 and 28354. [Class 38 (v)] A time switch for heavy currents has a fixed contact 17 comprising a mercury pot of the kind described in Specification 415,128, and the moving contact plunger 26 is connected to a lever 29, which is pivoted at 30, and has a lug 32 for engagement by pins 34 on a rotatable disc 35 fixed on a spindle 36. Thus rotation of the spindle 36 in six steps, moves lever 29 alternately " on and " off." The rotation of the spindle is effected by an oscillating alternating current motor 46, the armature 42 of which carries pawl 47 engaging a ratchet wheel 48 on the spindle 36. The motor is energized by a time switch (not shown) of the kind described in Specification 473,186, and the motor runs until spindle 36 has been rotated one step. At this time a projection SO on disc 35 moves a lever 51 to open the motor circuit. At the same time a second projection 50 on a second disc 35 has been removed from a second lever 52 to prepare an alternative circuit which is closed by change over contacts in the time switch, when the next operation takes place. As an alternative, the shaft 36 may be driven by a continuously running motor through an electromagnetic clutch the operating coil of which is connected in circuit in the same manner as the motor 46. As a further modification, the shaft 36 may be stepped round by ratchet and pawl mechanism driven by a solenoid periodically energized for short intervals by the time switch. In this case the time switch mechanism is as shown in Fig. 8. The tappet of a time switch engages the part 62 to move lever 60 clockwise and then release it. It returns and a pawl 63 engages a tooth of ratchet 64 to move cam 65 to allow contacts 68 to close. Arm 60a is carried down with arm 60 but only returns after an interval due to pawl 71 engaging a retarding gear train 72. When arm 60a returns pawl 63a engages ratchet 64a and moves cam 65a further step to open contacts 68. Thus contacts 68 are only closed for a short time, sufficient to operate the solenoid. An indicator arm 19, Fig. 6, projecting through a scale plate 20 is driven by a snail cam 37 on spindle 36 and indicates which of the switching positions the shaft is in. The switch can also be operated manually by means of a lever 21 having a pawl 77 engaging a ratchet 76 on shaft 36. The shaft 36 may operate any number of contacts. Specifications 415,128 and 473,186 are referred to.