GB725571A - Improvements in or relating to clutches and clutch assemblies - Google Patents

Abstract

725,571. Friction clutches. BORG-WARNER CORPORATION. Feb. 4, 1953 [Feb. 6, 1952], No. 3147/53. Class 80 (2). To prevent idle drag due to centrifugal pressure of residual oil in the pressurechamber C of a hydraulically-applied friction clutch 38, supplied through passages 42, 51, 67 by an input-driven pump P, the idle-speed pressure of which is insufficient to cause clutch engagement, the engaging piston 23 has a bleed hole 69, leading to a back space 70, the rear of which has an outwardly divergent opening X, defined by the inclined rear face 25a of the piston and the adjacent clutch disc 38, which latter is a conically-dished Belleville spring-plate with its raised inner periphery contacting the piston. Centrifugal idle pressure is thus free to drain at X, but normal engaging pressure distorts the Belleville clutch-disc over centre to close the escape X and cause build up of engaging pressure. Others of the clutch discs 38 splined to the outer input member 22 may also be Belleville spring plates flattened under engaging load, the complementary discs 37 splined to the inner output member 27 being flat. A central spring 36 assists the Belleville plates for clutch-release. Overriding mariual control is provided by a valve V which is a combined control and relief valve, the closure member 47 of which is turned manually through a cable 65 to either of two positions for exhausting at 54, 52 or shutting off exhaust respectively, from the pressure-passage 42. Excess pump-pressure moves the closure-member 47 axially against a spring 61 to exhaust the pressure-passage 42 at the same port 54. The clutch is used in an automatic transmission on a vehicle.