Patent GB-1282420-A (GB)
Title: Drive unit
Inventor: SIMONS WALFORD JOHN LOUIS
IPC: F16D71/00
Filed: 1968-11-22
Abstract: 1282420 Stopping machines at definite positions; positive detents; spring mechanisms ROTAX Ltd 12 Nov 1969 [22 Nov 1968] 55522/68 Headings F2E and F2S A drive unit which transmits intermittent rotary motion includes a driving shaft 12, a fixed member 13 and movable member 14 thereon, a brake construction 20, 21, 22, and a spring 16, wherein the brake is appled to prevent member 14 from rotating while shaft 12 and member 13 drive it to the left against the spring, after which the brake is released to permit the spring to push member 14 (now rotating) back to its first position, shaft 12 not rotating in this phase; this sequence is repeated as often as necessary. Input shaft 12 extends from the extreme left of Fig. 2 to the region of a planet carrier 26. A collar 13, with triangular recesses 18, Fig. 3, is secured to the shaft, while a bushing is both axially slidable and rotatable on the shaft. Bushing 14 has at its outermost periphery teeth which engage axially-extending slots provided in the inner periphery of an annular member 15, Fig. 2, which is journalled for angular movement within housing 11, but which may be prevented from rotating by a brake in the form of a ratchet 22, the axiallymovable part of which is associated with an armature 21, spring-loaded to the left and co-operating with a solenoid 20 on its right. In operation, the solenoid is de-energized, and rotation of shaft 12 is initiated by an electric motor, (not shown). Bushing 14 is prevented from rotating because annular member 15 is temporarily fixed, so the bushing must slide to the left from its first position to its second position, such sliding being effected by interengagement of recesses 18 on collar 13 with complementary projections 19 on bushing 14. When bushing 14 makes contact with a stop member 17, Fig. 2 fixed to shaft 12, the bushing and member 15 together prevent further angular movement of the collar 13 and therefore of the shaft. The driving motor must thereupon be de-energized and solenoid winding 20 energized. Brake 22 now being released, a spring 16, lying between stop member 17 and bushing 14, can now force bushing 14 to the right, the bushing being forced to rotate by inter-engagement of parts 18, 19 and causing annular member 15 to rotate with it. When bushing 14 reaches its first position the cycle may be repeated. Preferably the electric motor above referred to incorporates an electromagnetic brake which is energized when the motor is de-energized, and vice versa. Also, when the motor brake is energized (and shaft 12 is thus at rest), solenoid winding 20 of brake 22 is energized, releasing brake 22. For automatic re-setting of the drive unit to its first position a switch-operating member 23, Fig. 2, may be provided to contact a part mounted on bushing 14, these being included in an appropriate circuit. A further switch may sense when the bushing has reattained its first position and be incorporated into the circuit so that more-or less continuous incremental angular movement is obtained. Fig. 2 includes an output reduction gear box and clutch 9, wherein shaft 12 is provided with gear teeth defining a sun wheel. Annulus 24 is coupled to a multi-plate friction clutch 25 and the drive to shaft 27 of the device is taken from planet-carrier 26. Normally clutch 25 does not slip, but in the event of electrical failure shaft 27 may be rotated by hand whereupon clutch 25 slips to permit angular rotation of annulus 24. Stop member 17 may be axially adjustable.