Patent GB-566619-A (GB)
Title: Improvements in or relating to time-controlled electric switch-operating mechanisms
IPC: G04C23/34
Filed: 1943-08-25
Abstract: 566,619. Ratchet gearing. BRITISH VACUUM CLEANER & ENGINEERING CO., Ltd., and WHITESIDE, H. J. Aug. 25, 1943, No. 13866. [Class 80 (iii)] [Also in Group XXXVII] A time-switch suitable for controlling factory sirens, where the programme varies throughout the week, comprises a periodically-actuated member connected to the switch-proper, a device for locking the switch open, and timecontrolled means for unlocking the locking device and consisting of an intermittently advanced rotary disc (or discs) having notches into which enter means having engagement with the locking device, the arrangement being that on such engagement the switch is allowed to close under control of the periodicallyactuated member. A 24-hour disc 29 is rotated step-by-step at minutes-intervals by gearing 25 ... 27 from a ratchet wheel 12 engaged by pins on a driving arm 14 and retaining arm 19, the former being pivoted to an extension 11 of a frame 9 which is pivoted at 10 and carries an armature 8, the arrangement being that the pin 15 is advanced to engage the next ratchettooth by attraction of the armature, whereas on release of the latter a spring 24 steps the ratchet wheel round. The electromagnet 7 is energized at minute-intervals either by a master clock or, as shown, by a switch 6 cam-operated from a synchronous motor 4. The disc-periphery is notched at appropriate places 30 to receive a detent 35 on a lever 36, the latter having a further detent 38 cooperating with a second 7-day disc 37 driven from gearing 27 by means which advance it one step hourly. Disc 37 exerts an over-riding control so as to prevent operation at certain times, for example, weekends, and carries a raised part which engages detent 38 to prevent the lever 36 from rotating. The moment of operation can be determined to still finer limits by a wheel 81 on the shaft 13 of ratchet wheel 12, the wheel 81 having notches 82 at 5-minute intervals cooperating with detent 35. The detent lever 36 is fast on a shaft 60 carrying a trip lever 59, a projection 67 on which normally engages a pin 66 on a lever 61 adjustably carrying a mercury switch 71. Lever 61 is linked at 77 to an arm 75 on a rotatable sleeve, another arm 76 on which is normally engaged by a step 78 on the extension 11. In operation, when the detent lever 36 falls, lever 59 releases lever 61, but not until the next attraction of the armature 8 does extension 11 move its stop 78, so allowing spring 79 to rotate lever 61 about pivot 61a and close the switch. The latter is preferably of the type which retards the rupture of the circuit, notwithstanding the immediate return of the container to the " off position. During the closing movement of lever 61,-a pin 64 thereon lifts the trip lever 59 into position for a pin 70 thereon to be engaged by a spring pawl 68, so allowing the pin 66 on the returning lever 61 to pass under projection 67, the pin 66 then engaging the pawl 68 to free the lever 59 which resumes the position shown. The timing disc can be set by a lever 85, Fig. 1, rotating a cam 84 between the arms 14, 19 so as to disconnect the drive, a part 86 on lever 85 engaging the detent lever 36 during the operation. To facilitate such setting, a clock 88 is driven from wheel 25 through gearing 89. The discs are both removably secured to their spindles for interchange purposes. The drive for disc 37, Fig. 9, 10 comprises a gear-wheel 50 meshing with gear 27 and rotatable on a sleeve 47 which is fast on a stub shaft 44 rotatable in a barrel 41 adjustably carried on the frame. The shaft-end is formed as a pinion 45 seated in a cup bearing 46 in the frame and meshing with a wheel 55 on the disc-shaft. Sleeve 47 also carries a plate 48 which is cut away at 49 to receive a stud 51 on gear 50, and has pivoted to it at 52b a pawl 52 engaging a ratchet wheel 43 fast on barrel 41. Stud 51 and a stud 54 on pawl 52 are interconnected by a spring 53 coiled about the barrel 41. In operation, stud 51 is caused, by anticlockwise rotation of wheel 50, to traverse the recess 49 and ride up the part 52a of the pawl 52 to rock it out of engagement with the ratchet wheel, the tensioned spring 53 advancing the pawl into engagement with the next tooth and transmitting motion to disc 37.