GB810075A - Shaft positioning clutch device - Google Patents

Abstract

810,075. Stopping shafts in predetermined positions. COLLINS RADIO CO. April 18, 1957 [Sept. 25, 1956], No. 12763/57. Class 80 (2). A coupling device between a driving member and an output shaft comprises a jamming roller-type ratchet clutch surrounding a torquelimiting clutch on the output shaft, the cage for the jamming rollers being formed with a raw-toothed shoulder and the output shaft having locking means controlled by a first pawl which co-operates with a second pawl engageable with the sawteeth, friction means having substantially less torque capacity than the clutch being provided between the driving member and the roller clutch cage. Drive from a cylindrical driving member 41 is transmitted to an output shaft 11, required to be positioned in predetermined positions, through a roller ratchet clutch comprising the bore of the driving member 41, rollers 51 in a cage 36 and a collar member 21 having flats 22 on its periphery. The bore 23 of the collar 21 is splined to engage plates 28 of a torque limiting coupling whose intermediate plates 27 are splined to the output shaft 11, the coupling being axially loaded by a spring washer 29 and circlip 31 in a groove 32 of the shaft 11. The cage 36 for the clutch rollers is formed with a saw-toothed shoulder 38 and a light frictional drag between the member 41 and the shoulder 38 is provided by a felt washer 47. The shaft 11 extends through a support plate 10 and has a notched stop-wheel 17 fixed to the end 16, the notches 64 of the wheel 17 being engageable by a pawl 63 pivoted on a spindle 62 and actuated by a relay 66. A second pawl 71 pivoted by a slot 72 on the spindle 62 is engageable with the saw-tooth 38, the pawl being loaded laterally by a spring 76. During normal running the drive from a gear 46, integral with the member 41 is transmitted to the shaft 11 through the roller clutch and the torque limiting coupling, the two pawls 63, 71 being held disengaged by the relay 66. When the shaft 11 has been rotated to a desired position the relay 66 is de-energized and pawl 63 drops into a notch 64 to lock the shaft 11, this produces slip in the coupling 27, 28 for a small part of a revolution until the pawl 71 drops behind one saw-tooth of the flange 38. Pawl 71 then moves the length of the slot 72 until it abuts the pivot 62, whereupon the pawl produces disengagement of the roller clutch and stops the torque loading on the coupling 27, 28. As the roller clutch releases, the spring 76 acting through the pawl 71 moves the roller clutch cage into a mid-position of non- engagement such that the member 41 rotates freely with only light friction between it and the shoulder 38. This light frictional drive is used to engage the roller clutch on re-engagement of the drive by energizing the relay 66. In a second embodiment two saw-tooth shoulders are provided of opposite hand to provide drive in either direction. Specification 660,939, [Group XXXVIII], is referred to.