Patent GB-919296-A (GB)
Title: Improvements in centrifugal clutches
IPC: F16D43/18
Filed: 1960-07-29
Abstract: 919,296. Friction clutches; clutch combinations; ratchet clutches. ZAVODY 9. KVETNA, NARODNI PODNIK. July 29, 1960 [Aug. 3, 1959], No. 26597/60. Class 80 (2). In a centrifugal friction clutch particularly for single track motor vehicles, lined clutch shoes 5 having conical friction surfaces 5<SP>1</SP> and pivoted on a driving carrier 2 are centrifugally moved, to a limited extent, against return springs 7, to engage corresponding friction surfaces of one or two driven clutch plates 12, 16; the plate 12 (or carrier 2) is acted on by a pressure spring 14 to axially urge the friction surfaces together and by a device controlled by means not shown and comprising a cam 20, a plate 19 and studs 18 to axially disengage the clutch independently of speed; and a cam or screw device 21, 22 acting on the plate 12 (the carrier 2, or the plate 16) axially urges the friction surfaces together when the driven shaft 9 overruns the driving shaft 1. As shown, the driven shaft 9, carrying a pinion 35 meshing a wheel 36, is free on the driving shaft 1 which has the carrier 2 splined thereon. Alternatively, the driving and driven shafts may be arranged as coaxial shafts following in line. The clutch plates 12, 16 are rotatably connected to the driven shaft 9 by projections 13, 17 engaging slots 11 in a drum 10 secured to the driven shaft 9. The axial movement of the plate 12 is limited by a stop 15. The plate 16 is axially fixed. The cam device comprises a cam 21 fixed to the driven shaft 9 and a cam 22 rotatably free on the driving shaft and frictionally connected thereto by a drag spring 23. Alternatively, the cam 22 may be fixed to the driving shaft, the cam 21 being rotatably free and frictionally connected to the driven shaft by the drag spring. In operation, on increase of driving shaft speed the shoes 5 are centrifugally outwardly moved until they engage the conical surfaces of the plates 12, 16. On further speed increase the shoes are displaced by a small axial movement of the carrier 2 towards the plate 12 which is axially moved against the spring 14 for full clutch engagement. Further outward shoe movement is prevented by engagement of shoe stops 24 in carrier slots. For towed starting or engine braking, when the driven shaft overruns the driving shaft, the drag spring connected cam 22 moves the cam 21, the drum 10 and hence, through the spring 14, the plate 12 towards the shoes 5 whereby the conical friction surfaces of shoes and clutch plates are engaged. As soon as driving shafts speed equals driven shaft speed the cam device is inoperative. In Fig. 7, auxiliary friction surfaces 26 on both the shoes and clutch plates, the angle α of which surfaces is greater than the angle # of the main friction surfaces, reduce cam-urged axial shift of the plate 12 and provide a disengaging speed lower than engaging speed on vehicle deceleration since disengagement of the main friction surfaces due to drop in driving shaft speed is prevented by cam-urged engagement when the driven shaft overruns. If α < 90 degrees the auxiliary friction surfaces 26 may be arranged to provide gradual clutch engagement at starting, the surfaces 26 contacting the plates 12, 16 first and permitting slipping before full clutch engagement is attained when the main friction surfaces 5<SP>1</SP> contact their corresponding plate surfaces on axial movement of the plate 12 against the spring 14. In Figs. 5 and 6 (not shown) progressive engagement is provided by pivoted auxiliary masses which act on the shoes for final engagement following slipping contact by the shoes only. The auxiliary masses and return springs are arranged to provide a difference between engaging and disengaging speeds. In Fig. 5 the auxiliary masses bear against the backs of the shoes, whereas in Fig. 6 smaller auxiliary masses swinging in a diametrically opposite direction to their corresponding shoes each comprise the long arm of a lever, the short arm of which bears against the free end of the corresponding shoe. In Fig. 8 (not shown), dispensing with the drum 10, the plate 12 is splined on the driven shaft 9 and the plate 16, rotatably connected to the plate 12 by means of the studs 18 of the disengaging device, is acted on by the cam device 21, 22. For low torque requirements, a single plate 12 is arranged between the drum 10 and the carrier 2, the plate 16 being dispensed with. The carrier may be axially fixed or movable, with the plate 12 respectively axially movable or fixed, the axially movable member being acted on by the pressure spring, and the cam and disengaging devices. Alternatively, both carrier and plate may be axially movable, the pressure spring and disengaging device acting on one member and the cam device acting on the other.