Patent GB-985090-A (GB)
Title: Improvements relating to motor-vehicle transmission mechanisms
Inventor: HILL CLAUDE
IPC: F16H61/02
Filed: 1961-02-09
Abstract: 985,090. Differential gear; ratchet clutches. HARRY FERGUSON RESEARCH Ltd. Jan. 31, 1962 [Feb. 9, 1961], No. 4799/61. Headings F2C and F2D. [Also in Division B7] Relates to a motor vehicle limited-slip central differential gear engine-driven through an hydraulic torque converter, if desired, and a reversing gear and interposed between front and rear propeller shafts driving front and rear axle conventional inter-roadwheel differential gears, wherein two one-way friction clutches 32, 33 are disposed between a shaft 30 geared at 24 to one of the propeller shafts (e.g., as described, the rear) and members 34, 35 geared at 25, 26 to the central differential input, the gears 24, 25, 26 providing different ratios so that under normal conditions the shaft 30 is overrun by the member 34 and overruns the member 35, whilst the clutches 32, 33 engage to limit differential action when there is a tendency for, respectively, the rear wheels to spin (or the front wheels to lock) and the front wheels to spin (or the rear wheels to lock). In such a differential gear the clutches 32, 33 comprise friction plates alternately splined to presser plates 40 helically threaded in the members 34, 35 and the shaft 30 and interposed between said presser plates and abutment plates 43A, B, and a mechanical control device normally supporting the abutment plates in their spacedapart operative position for forward driving is movable to withdraw its support and thereby disable the clutches during reverse driving. The members 34, 35 are a rotatable fit in a cover 42 which carries stop rings 34A, 35A cooperating with rings 37 to limit the helical movements of the presser plates 40. Resilient cushions 40A between plates 40B and the gears 25, 26 prevent overspacing of the friction plates in their released condition. The abutment plates 43A, 43B, are circumferentially located on each other by bushes 44 and pockets 44A and are loaded by light springs 45 to provide frictional drag. The mechanical control device comprises a radial wedge 50 engaging inclined faces on the abutment plates and a cam rod 51 normally rightwardly urged by a spring 58 against a stop 56 to radially cam and support the wedge by its slope 70 and cone 53 respectively. A ratchet toothed member 63 splined on the shaft 30 engages the rod 51. A complementary ratchet toothed member 64 is supported in a one-way roller detent 65 permitting rotation in the forward direction only and has a brake cone 67. During reverse drive, the member 64 is stationed and, due to the ratchet teeth, the brake cone 67 is rightwardly cammed into engagement with the fixed casing to relieve the detent 65 and the member 63 and the rod 51 are leftwardly cammed to remove the support of the wedge 50 from the abutment plates 43A, 43B and disable the clutches. On restoration of forward drive the member 63 rotates the member 64 and the wedge 50 is cammed back into its supporting position. The tips of the ratchet teeth are flattened to prevent their biting into each other on forward drive restoration. Under normal forward drive conditions a spring-loaded plunger 61 relieves engagement of the brake cone 67.