Patent GB-930252-A (GB)
Title: Accelerator pedal controlled full power brake system for vehicles
Inventor: HOLLAND FRANCIS JOSEPH
IPC: B60T11/10
Filed: 1960-09-29
Abstract: 930,252. Fluid-pressure brakes. F. J. HOLLAND. Sept. 29, 1960, No. 33428/60. Class 103(1). [Also in Groups XXIX and XXXI] A power braking system for vehicles comprises an hydraulic slave cylinder 42 having an outlet 124 connected to the brake operating mechanism associated with the vehicle wheels 10, 12, a variable fluid pressure control device in the form of a transducer valve (Fig. 4) having a fluid pressure inlet and a variable pressure outlet connected to the slave cylinder drive, a movable regulator in the variable fluid pressure control device is operable by a signal force applied thereto to regulate the fluid pressure output from the latter, and a movable operating arrangement in the form of a sensing valve (Fig. 10) is connected to the variable signal power supply to provide a signal force to the movable regulator in proportion to the position of the operating arrangement. In the air suspended system disclosed in Fig. 1 a conventional hydraulic master cylinder braking system is shown including a master cylinder 26 and connection 24 leading to the fluid pressure lines to the wheel brake cylinders 18 of the vehicle wheels 10, 12 the master cylinder 26 being operated by a conventional brake pedal 32. A secondary braking system is also provided controlled from the position of the conventional accelerator pedal 38 by means of an overlay pedal 400 which functions to control the operation of a sensing valve 380 (Fig. 10) to provide a vacuum signal from a vacuum source such as the engine manifold 606 and a reservoir 614, the magnitude of the signal being proportional to the position of the overlay pedal in its range of movement. A switching valve (Fig. 12) 550 mounted on the vehicle dashboard is inserted between the vacuum source and the sensing valve 380. This vacuum signal functions to control the operation of a transducer valve (Fig. 4) which meters, in proportion to the signal, a source of vacuum to a vacuum-operated power unit 40 which supplies a proportional hydraulic fluid pressure to the wheel brake cylinders 18. Sensing valve (Fig. 10).-This valve provides a connection between the vacuum source via conduit 618 connected to inlet 366 of sensing valve and outlet conduit 616 connecetd to outlet 398 of the sensing valve leading to the signal chamber 158 of the transducer valve (Fig. 4). Spring-loaded valve 358 is normally open to allow free passage of fluid between inlet 366 and outlet 398 of the sensing valve when the overlay pedal 400 is in its fully release position shown in Fig. 1 whereby actuating rod 380 is moved outwardly against action of spring 384 when the brakes are to be fully applied. Atmospheric valve connection 368 is closed in this condition of the sensing valve. When the magnitude of vacuum in the controlled vacuum chamber 396 of the sensing valve reaches a value at which the force exerted by it on a diaphragm 342 matches the counter force of the spring 384, the diaphragm and its attached stem assembly is moved towards the left closing the vacuum valve seat 358 and maintaining the atmospheric valve 368 closed to provide a condition wherein the sensing valve is in a state of equilibrium. When the overlay pedal 400 is rotated to its position wherein it engages the underlying accelerator pedal 38 the actuating rod 380 is retracted inwardly to its maximum limit by spring 384 to close the vacuum seat 358 and open the air valve 368 to release the brakes. Transducer valve (Fig. 4).-This valve comprises a diaphragm means 156 separating a chamber 160 communicating with the atmosphere from a chamber 158 receiving the signal vacuum via connection 164. The diaphragm moves under differential pressure in chambers 158, 160 to close pilot and secondary valve members 200, 192 and open pilot and secondary valve members 202, 204 to permit vacuum to flow from connection 176 leading to the inlet manifold via conduit 604 to vacuum chamber 56 of the power unit via connection 234 and conduit 602 to actuate the power unit. The hydraulic pressure developed by the power unit is fed back through connection 218 to act on valve extension 178 connected to the diaphragm member 156 to provide a balancing force on the diaphragm 156. Fig. 6 shows an alternative means for applying a variable signal pressure to the diaphragm 156 by means of a solenoid coil 250 controlled by a variable resistance 260 operated by a plunger 270 connected to the overlay pedal 272 attached to the accelerator pedal 38. This embodiment obviates the need for the sensing valve device (Fig. 10). Switching valve (Fig. 12).-This valve is mounted on the vehicle dashboard 588 and is operable by the driver from the position shown wherein the connection between the vacuum source 606, 614 via connection 572 is in connection with the sensing valve via conduit 618 and vacuum outlet 580 of the switching valve to a position in which the valve seat 576 is moved into connection with the valve seat 574 to isolate the sensing valve from the vacuum source. An automatic parking brake is provided by a solenoid-operated check valve 590 mounted in the hydraulic fuel line leading from the outlet of the power unit 42 to the wheel brake cylinders 18 and a vacuum switch 592 is inserted in the vacuum supply system such that when the vacuum in reservoir 614 decreases the solenoidoperated check valve is caused to close thus sealing the hydraulic line against further reduction of hydraulic pressure at the wheel cylinders to maintain the wheel brake set. An alternative embodiment is disclosed in the Specification wherein in place of the air suspended system disclosed in Fig. 1 a vacuum suspended system is described having two fluid pressure power units 40 one supplying hydraulic fluid to one set of wheels and the other supplying hydraulic fluid to the other set of wheels.