Patent GB-606128-A (GB)
Title: Hydraulic brake system
IPC: B60T11/10
Filed: 1945-09-06
Abstract: 606,128. Fluid-pressure-operated brakes. TIMKEN-DETROIT AXLE CO. Sept. 6, 1945, No. 22948. Convention date, Oct. 30, 1944. [Class 103 (i)] [Also in Group XXVIII] A vehicle brake system comprises a hydraulic pump driven by a road wheel of the vehicle through driving gear put into engagement by a manually-operated master cylinder to boost the pressure initially applied to the brake cylinders directly by the master cylinder. A separate system may be provided for a tractor vehicle and a trailer coupled thereto, these systems being controlled by the same or byseparate manual levers. A four-wheeled tractor coupled to a two-wheeled trailer is shown. The tractor system comprises a master cylinder 18 with pedal 20, connected by pipe 24 to a pump 26 which may be driven by the drive shaft and is connected bv pipe 22 to wheel brake cylinders 10. The trailer system comprises a master cylinder 44 on the trailer operated by a hand lever 46 through a hydraulic, Bowden wire or other connection 50 and connected by pipe 42 to a pump 52 connected to brake cylinders 28 by pipe 40. The master cylinder 44 may instead be connected to the pedal 20 in such a manner as to be operated in advance of the cylinder 18. A lanyard may be connected to the tractor and to a latch on the master cylinder 44 whereby in the event of a break-away of the trailer a spring is released to apply the trailer brakes. The pumps 26, 52 each comprise a plunger 56, Figs. 3, 5, slidable in a cylindrical extension 70 of the cap 68 and normally urged by a spring 66 to the position shown in which the plunger is disengaged from a cam 58 secured to the hub 98 of a road wheel. The arrangement shown is for a trailer wheel, the cam being disposed within the brake drum 112 and the pump 52 being bolted to the axle flange 116 which also carries the anchor plate 114 for the brake shoes 136. The brakes may be such as described in Specification 598,626. The pump carries an oil deflector 130 having a lip which extends into a baffle 128 secured to the brake drum, whereby the brake is protected from the escape bf oil. The plunger 56- and cap 68 carry non-return valves 78, 82. Pipes 40, 42 are connected respectively at 84, 86. When the master cylinder 44 is operated, liquid is initially supplied therefrom directly to the trailer brake cylinders 28 by pipe 42, passages 86, 74, 76, valves 78, 82 and pipes 85, 40 until the fluid pressure acting on the plunger 56 is sufficient to move it against the pressure of spring 66 to engage the cam 58, the increased volume of the piston chamber 70<SP>1</SP> being filled from the pipe 42. During the return stroke of the plunger effected by the cam, liquid is forced from chamber 70<SP>1</SP> past the valve 82 to the brake cylinders 28. To enable the operator to " feel " the pressure applied in the brake cylinders, a device 91 is disposed between the pipe 42 and the pump 52 and comprises a piston 251, Fig. 7, upon which the brake cylinder pressure acts through pipe 206 and carrying a valve 248 through which the liquid supplied from the master cylinder 44 passes to the pipe 89 and the pump. Release of the brakes is effected by a valve 87 which byepasses the pump and which comprises a valve proper spring-mounted in the tubular rod of a piston upon which the pressure in the pipe 42 acts to seat the valve on the end of the pipe 207. The spring of the valve acts as a safety-valve to limit the brake pressure. The liquid returns through the piston-rod and piston to the master cylinder.