Abstract: A limited slip differential gear assembly has a rotating housing containing meshing spur gears each turning a gear element which is externally helically toothed. Each gear element meshes with its own externally-toothed gear member which has a larger diameter and drives one of two output shafts between which differential movement is to take place. The meshing helical gear teeth have the characteristic that the efficiency of drive transmission in opposite directions is different and this provides the limited slip. As the axes of rotation of all rotating parts of the assembly are parallel, reduced constructional and operating costs result.

Abstract: A start-up coupling engages progressively in two stages. During the first stage drive is transmitted from an input shaft (3) along respective paths (8,7,9,12,11,10,25 and 26; and, 19,20,19 and 32) to helically-toothed rollers (27,30) which mesh but are designed to be incapable of transmitting drive between them, or of doing so very inefficiently. The rollers (27,30) are mounted in an oil-filled chamber (18) in a casing (1) integral with an output shaft (2). During the first hydraulic stage of engagement, oil pockets between their oppositely-moving teeth (28,31) prevent them from engaging as the phase of one roller (27) is progressively changed by a centrifugal adjustment (4) against the bias of a torque cell (19). However, increasing frictional resistance in the oil pockets causes the rollers (27,30) to exert an increasing rotational torque on the casing (1).

Abstract: A torque limiting mechanism has two locking members (1 31, 137) designed to be incapable of transmitting drive between them but having meshing spiral teeth (132, 138). The members are in a rotatable frame (127) and are respectively driven by radially toothed gears (128, 124) having an idler gear (125) between them. One radially toothed gear (124) is splined (at 123) to a section of a drive shaft (110) of reduced diameter so that it twists in torsion when an input driving torque is applied to the shaft (110). Gear lash exists between the radially toothed gears (124, 125 and 128) which is overcome by the twist of the shaft (110) if the applied torque is big enough. When this occurs, synchronous drive from the input shaft (110) is applied to both locking members (131, 137) so that they rotate together. The applied torque necessary to achieve this is determined by the position of one gear (124) on the spline (123) and this is controlled by a lever (114).