Patent GB-753933-A (GB)
Title: Hydraulic brake mechanism for motor vehicles for facilitating starting of the vehicles on up-hill roads
IPC: B60T11/10
Filed: 1954-06-04
Abstract: 753,933. Hydraulic brakes. FIAT SOC. PER AZIONI., and BALDWIN, P. S. June 4, 1954 [June 9, 1953], No. 16644/54. Class 103 (1). [Also in Group XXXI] An hydraulic brake mechanism for a motor vehicle is of the type comprising a double acting valve 17, interposed between the master cylinder and the brake cylinders, the valve 17 having means actuated by means of a lever 43 whereby back-flow of fluid from the wheel brake cylinders to the master cylinders is prevented, the lever 43 being connected to a clutch pedal 62 and held in its position corresponding to release of said valve by a spring, such as 44, the brake mechanism being characterized in that the connection between the lever 43 and the clutch pedal 62 is such that the lever 43 is not actuated by downward movement of the clutch pedal during which the clutch is disconnected, but only by a supplementary downward stroke of the pedal during which the lever 43 is displaced against the action of the spring 44 to actuate the valve and prevent the backflow of fluid. Fluid under pressure can pass from the brake master cylinder 1 to the valve 17 by means of a connection formed from bolts 6 and 11, and a bush 7, bores through which communicate with an entry port 15 in the valve 17. At the end of the valve 17 opposite to the entry port 15 is a hollow plug 20 and a collar 22 which distributes fluid to the brake cylinders. The inner end of the plug 20 carries a resilient ring 29 the outer cylindrical surface of which is rounded and lies inside a perforated skirt 33 projecting from the rim of a tumbler shaped member 30. An annular surface on the member 30 can abut against the resilient ring 29 to prevent back-flow of fluid outwardly through the perforations in the skirt 33 and along grooves 38 cut axially in the outer surface of the member 30. Inside the member 30 lies a cylindrical member 34 abutting the end of plug 20 and being formed with radial bores 37 which come from an inner cavity 36 and communicate with axial grooves 59 cut in the outer surface of the member 34. An expandible ring 50 is carried on a post on the member 34 and can be compressed between the members 34 and 30 to prevent back-flow of fluid from the interior of member 30 outwardly through an aperture 31 in its base but at the same time permit flow in the opposite direction, viz. from the master cylinder 1 to the brake cylinders. The member 30 is pressed against both the resilient rings 29 and 50 by means of a spring 41 which can be deflected by back-flow of fluid from the brake cylinders and permit relief of the brakes. To prevent back-flow from the brake cylinders a cup-shaped member 39, with axial grooves in its outer surface to pass fluid, is pressed directly on to the bottom of the member 30 by means of a cam 42 rotated by the lever 43. To rotate the lever 43 against the spring 44, a pin and slot connection is made with the clutch pedal 62 such that movement of the pin within the slot from position A to B, Fig. 1, is sufficient to declutch the vehicle, while further movement to position C against the spring 44 actuates the cam 42 to prevent back-flow of fluid through the valve 17, but nevertheless, by virtue of the expandible ring 50, permits flow of fluid to the brake cylinders. The spring 44 may be replaced by a spring 70, shown in dotted lines. Alternative arrangements for the resilient ring 29 are given in Figs. 3 and 6 (not shown). In one arrangement the ring 29 surrounds a skirt on the end of the tumbler shaped member 30 which floats inside the valve casing and has a conical annular portion to abut and tend to contract the ring 29. In the other arrangement the resilient ring 29 is retained in a peripheral groove on a projection on the plug 20 and a skirt on the tumbler shaped member 30 passes over the projection to abut the exposed outer peripheral portion of the ring. In this arrangement also, the cup-shaped member 39 may be dispensed with, the cam 42 being made to act directly on the bottom of the tumbler-shaped member 30. In all constructions, as it is not greatly stressed, the member 34 may be made of synthetic resin.