Patent GB-858554-A (GB)
Title: Improvements in or relating to hydraulic couplings
IPC: F16D31/02
Filed: 1957-12-14
Abstract: 858,554. Hydraulic couplings. FRASER, W. Dec. 2, 1958 [Dec. 14, 1957], No. 38955/57. Class 69 (2). An hydraulic coupling for transmitting power from one shaft to another of the kind having on one shaft 14 a casing 11, 12 provided with a cam track 13b to reciprocate pistons 24 in radially-disposed cylinders 23 in a casing 21 on the other shaft 20, with the flow of oil passing into and out of the cylinders upon relative rotation of the shafts controlled by a valve 42, is characterized by the casing 11, 12 being shaped with an annular mid-region AB of substantial oil capacity having a larger radius which is greater than the radius of the largest circle passing through the apertures of replenishment valves 46 for keeping the cylinders filled with oil, and a smaller radius which is smaller than the radius of the smallest circle passing through the apertures, the remaining portions of the casing providing an air capacity radially within the mid-region when the oil is in the rotary condition and above the midregion when the oil is in the static condition, whereby the apertures of the replenishment valves are submerged in all conditions of the coupling. The cam track 13b of the coupling, which may be similar to that described in Specification 569,787, is of elliptic configuration and formed on a member 13 secured between portions 11, 12 of the outer casing bolted to the shaft 14 which may be connected to an internalcombustion engine, a ring 15 secured to the casing being provided for starting purposes. The cam track, together with a guide track 29, co-operate with shoes 28 pivotally connected to the pistons 24 which are urged outwardly by springs 26. The cylinders 23 have ports 23a leading to aligned ports 21b in the inner casing 21 which are of circular, triangular or other shape depending upon the operation of the coupling and lead into a chamber 21a within the casing. The ports 21b can be opened or closed to control the flow of oil to and from the cylinders 23 by axial movement of the valve 42 which is pinned to a rod 40 axially movable in the shaft 14 or the shaft 20 by a pin fitted into a bore 40a in the rod engaging a sleeve on the shaft 20, the pin moving in a slot 20b in the shaft; when the ports 21b are closed, the flow of oil to and from the cylinders is restricted and reaction occurs between the shoes 28 and cam track to communicate the drive from the shaft 14 to the shaft 20. The coupling is filled with oil to the level of a filler plug 48 and the casing is shaped with portions 11i, 12i to provide the annular mid-region AB of substantial oil capacity. In the static condition, the level of oil is above the apertures of the replenishment valves which are of the non-return type and consist of members 46 axially movable in bores 23a in the walls of the cylinders 23. The portions of the casing 11o, 12o above the filler provide an air space of relatively small axial length to accommodate expansion of the oil caused by heating. In the rotary condition, the oil is thrown centrifugally outwards and a spaee radially inwards of the apertures provides the air space, a flange 22g on the inner and/or outer casing assisting in keeping the apertures of the valves immersed. A float 40a on the rod 40 and a pressure relief valve 43 provide an outlet for air and/or oil from the chamber 21a. In other embodiments, a plurality of cam tracks may be arranged one beside the other, each track reciprocating a corresponding group of pistons and arranged out of phase with each other, and the cylinders 23 connected to an annular groove in the valve 42 which is axially displaceable to move the groove into and out of alignment with the cylinders to control the coupling. The inlet ducts of the replenishment valves may be formed with spring-loaded telescopic tubes so that under centrifugal action the tips of the tubes move radially outwards into the oil.