Patent GB-1387636-A (GB)
Title: Mechanical transmission devices
IPC: F16D41/00
Filed: 1971-10-02
Abstract: 1387636 Automatic spring- or gravity-applied brakes; one-way acting selectively R GOOLD 30 Oct 1972 [2 Oct 1971] 45944/71 Heading F2E A self-locking movement transmission device comprises a plurality of locking elements (e.g. 22, Figs. 1, 4) carried by a first member (e.g. 10) and a movable release cam (e.g. 24) having a neutral position in which the locking elements are in jamming engagement with one or more co-operating surfaces (e.g. 18, Fig. 2) on a second member (e.g. 12) to lock the second member relative to the first member, the release cam being movable selectively from the neutral position to displace one or more selected locking elements out of jamming engagement and release the second member for selective movement by means of the cam. In Figs. 1, 2, 4, first member 10 is a fixed housing carrying locking elements 22 tapered in both radial senses and urged radially inwards by springs 23. Second member 12 is a driven member, and release cam 24 is provided on a control member 11 which serves as a driving member. As shown, driven member 12 has an integral flange 15 with a generally-frusto-conical face on which are formed two diametricallyopposite symmetrical portions 18 which are raised above the general level of face 17 but merge into it at their edges. The locking elements 22 are located between face 17 and an end wall 20 on housing 10, and are urged radially outwards by two cam lobes 25 on cam 24. Members 12 and 11 have a spigot-and-socket engagement including pairs of shoulders 13, 14, which when the device is at rest are respectively separated by a small angle a, so that at all times the lobes 25 are axially aligned with portions 18, or very nearly so. (The separation at rest is effected by spring 27 and balls 26). Radial grooves, not shown, in the surface of end wall 20 permit radial movement of elements 22 but prevent rotational movement about axis A-A. In operation, if any attempt is made to rotate driven member 12 directly, from rest, such rotati on is prevented by inter-engagement of flange 15, elements 22 and end wall 20. If, however, rotation of control member 11 is attempted, initial rotation of it through angle a is sufficient to initiate un-jamming of elements 22 adjacent to lobes 25, after which elements 22 are successively urged outwards by lobes 25, and member 11 drives member 12 by inter-engagement of shoulders 13, 14. This action can take place in either direction of rotation. The device may form part of a steering shaft. In Figs. 6, 7, first member 110 is a fixed housing, second member 112 (on the right of Fig. 6) is a slidable bolt, and two locking elements 122 (one on each side of the bolt) are each mounted in the housing 110 by a pin-and-slot connection and biased by springs or gravity into jamming engagement with bevelled faces 117 on the bolt. A release cam 124 on a control member 111 straddles the base of the bolt and the neutral position of the cam relative to the bolt is represented by spacing a between member 111 and the inner end of the bolt, such position being normally maintained by a spring (not illustrated). In operation, when member 111 is moved to the right a distance a, bolt 112 is engaged, cam 124 has released elements 122, and the bolt may thus be moved. At any position the control member may be released, whereupon it is restored to its neutral position relative to the bolt, and the bolt is locked automatically.