Patent GB-994429-A (GB)
Title: One-way clutch
IPC: F16D41/06
Filed: 1961-09-04
Abstract: 994,429. Ratchet clutches. ARTHUR D. LITTLE Inc. Sept. 4, 1961 [Sept. 8, 1960; Aug. 9, 1961], No. 31675/61. Heading F2C. A ratchet clutch comprises an inner race and an outer race, defining a space within which gripper means is located, one of the races having a substantially circular surface in contact with a corresponding arcuate surface on the gripper means and the other of said races having a contoured cam surface also in contact with a corresponding surface on the gripper means, and means maintaining the surfaces of the gripper means against the co-operating surfaces of the races, the circulararcuate pairs of engaging surfaces being so formed as to develop a greater frictional force than the cam-container pairs of engaging surfaces. The cam-contoured surfaces may be coated with a material having a low coefficient of friction, such as polytetrafluoroethylene. Alternatively, the frictional force developed between the circular-arcuate engaging surfaces is increased by interengaging wedges and grooves. In one form, wedging shoes 18, Fig. 2, between a cylindrical inner race 16 and a contoured outer race 10, have the friction between the outer race and the shoes reduced by coating the contoured surfaces on the race with an epoxy resin and the co-operating surface 20 of each wedge with polytetrafluoroethylene. The coacting surfaces of the inner race 16 and of the wedging shoes 18, which parts may be made of, e.g. steel, are untreated. The wedges 18 are biased to engage their coacting friction surfaces by, e.g. springs 26 on the wedges engaging shoulders on the cam surfaces. Alternatively, the wedges 18 may be biased towards their engaged positions by spring-biased plungers 30 coacting with cam faces 32 formed on the wedge ends. As a further modification, wedges 24 may bias the wedges 18 into engagement, or the wedges 18 may be mounted on the outer race 10 by wires 28. A small spring 33, which may be of bimetallic construction, carried by each wedge 18, may coact with a film of lubricating oil on the inner race 16 to engage the clutch with falling temperature, corresponding to increasing oil viscosity. To obtain increasing frictional force between the wedges 18 and the race 16, each wedge 36, Fig. 4, may be formed with inclined faces. The number of wedges may be reduced. In one form, only two wedges 35, Fig. 5, co-operate with a shaft 14 and an outer race 10. In this construction, the outer race 10 comprises a disc to which are welded at right angles strips 17. In another form, Fig. 6 (not shown), a single wedge extending over nearly 360 degrees is used. In another modification, Fig. 7 (not shown), a cam surface is formed on an inner race, and the outer race, formed with a groove or grooves, is cylindrical. In one modification, wedges 36, Fig. 8, have truncated grooves for engagement by correspondingly shaped projections on the inner circular race 14. Each wedge may be formed in two parts separated along a plane perpendicular to the main clutch axis, Fig. 9 (not shown), or in four parts, Fig. 10 (not shown). The projections and grooves may be of regular or irregular cross-sectional shape, Figs. 11-13 (not shown), on outer circular surfaces. Oil grooves may be provided on one or other of the races or on the frictional engaging surfaces of the wedges, Figs. 15, 17 (not shown). In another form, wedges 66, Fig. 16, which are cammed outwards by contoured surfaces 65a to engage the cylindrical surface of an outer rate 64, are restrained from increasing the engaging force with increasing speed and centrifugal force by masses 71 pivoting at 72 on the inner race 65 and having pins 74 coacting with the wedges. Thus excessive wear at high speed on the friction surfaces is prevented.