Patent GB-588640-A (GB)
Title: Improvements in electrical control mechanism
IPC: H03J1/18
Filed: 1945-02-09
Abstract: 588,640. Change-speed gearing. GENERAL ELECTRIC CO., Ltd., and ROSE, W. R. Feb. 9, 1945, No. 3365. [Class 80 (ii)] A three-speed epicyclic gear 133 between a reversible D.C. electric motor 13 and a radiotuning condenser 55 is controlled by a stepwise oscillating-armature type electric ratchet-motor 86, 92, 97, driving a selector camshaft 64 which also carries additional cams 84, 85 for operating contacts 71, 72, 73, 74 for de-energizing the camshaft-motor 97 after a ratio has been established. Both motor circuits are controlled automatically as described in Specification 576,161, [Group XXXVIII], and the output shaft 28 of the gear drives the condenser-shaft 51 through irreversible worm-gearing 50 and a final-drive claw-clutch 57, disengagement of which latter, also under control of the selector camshaft 64, causes a permanent-biassing spiral spring 54 to return the condenser to a starting position ready for a fresh adjustment. The change-speed gear comprises a driving sun 30, driven by the main motor 13 through a slip-coupling 16 and worm-gear 15, and a driven sun 31, secured to the output shaft 28. For highest speed (direct drive) a knifeedged toothed clutch 34 operated through a central spring-loaded push-rod 38 and bellcrank 71, directly connects the driving and driven suns 30, 31. A moderate-ratio first reduction is obtained by releasing the clutch 34 and holding the planet-carrier 133 by a pivoted knife-edged stop 42, engageable with pointed teeth on a stopwheel 45 integral with the carrier 133. A highratio second reduction is obtained by releasing the carrier and holding, by means of a similar pivoted stop 42A and wheel 45A, a reaction-sun 32, which has a slightly larger number of teeth or slightly greater diameter than the driven sun 31 and engages a double-width planet 135 common with the sun 31. The clutch-operating bellcrank 71 and the reaction-stops 42, 42A are actuated by cams 67, 68, 69 respectively, secured on the selector camshaft 64, and all acting through blade-springs, e.g., 47. A fourth cam 70 operates the final-drive clutch 57. The camshaft motor comprises a pivoted spring-loaded armature 92, Fig. 3, oscillated by a magnet, the winding 97 of which is fed through contacts 99 which are opened by the armature at each attraction-stroke, the armature having a pawl 88 which drives a ratchet-wheel 86 on the camshaft 64. The sequence for changing the condenser setting from the starting position shown is as follows. A reversing-switch 105, Fig. 5, is closed to supply current to the main motor 13 and also to a magnet-winding 17 to release a detent 18 normally positively locking the motorshaft 14. At the same time a switch 101, Fig. 5, is closed to energize the camshaft-motor 97 through the camshaft-controlled contacts 71, which are initially closed, and the camshaft 64 is then driven until its cams 67, 70 engage the direct and final drive clutches 34, 57. The cam 84 then opens the contacts 71 de-energizing the camshaft-motor 97. The main motor 13 continues to drives the condenser 55 in direct-drive until the required setting is approached, whereupon a switch 102, Fig. 5, is automatically closed to energize the camshaft motor 97 through the contacts 72. The camshaft 64 is then stepped further until its cam 67 disengages the directdrive clutch 34 and cam 68 engages the planetcarrier stop 42, whereupon the cam 84 opens the contact 72, de-energizing the camshaft-motor 97. Drive is now at first reduced ratio until the condenser is at a predetermined angle from the final position, when switch 105, Fig. 5, is closed, energizing the camshaft-motor 97 through contacts 73, whereupon the cam 68 releases the planet-carrier stop 42 and the cam 69 engages the reaction-sun stop 42A, after which the cam 85 opens the contacts 73, de-energizing the camshaftmotor 97. The condenser 55 is now driven at the high-ratio creeping speed in either direction as required under control of the reversing- switch 105, Fig. 5, until the exact condensersetting is reached, whereupon the main motor 13 is de-energized and the positive-stop 18 reengaged to lock the gearing. To return the condenser 55 to the starting position of its range ready for a fresh adjustment, the switch 104, Fig. 5, is closed, energizing the camshaft motor 97 through the contacts 74, which are at this time closed, whereupon the cams 69, 70 release the reaction-sun stop 42A and the final-drive clutch 57, after which the cam 85 opens the contacts 74, de-energizing the camshaft-motor 97 and the cams 84, 85 close the contacts 71, 72, 73 ready for the next adjustment. On release of the final-drive clutch 57 the condenser 55 is returned to its starting position by the biassing spring 54 which acts constantly in the return direction and serves also to take up backlash in the gearing. The return speed is controlled by an escapement 100. To prevent overtravel of the condenser in the forward direction a cam 106 on the final-drive clutch-member 57 rides up a fixed projection 107, disengaging the clutch 57. The automatic control of the switches 101 ... 105 is described in Specification 576,161 above referred to.