GB1587826A - Multi-current hydraulic brake apparatus - Google Patents

Description

(54) MULTI-CIRCUIT HYDRAULIC BRAKE APPARATUS (71) We, BENDIX WESTINGHOUSE LIMITED, a Company incorporated under the Laws of Great Britain, of Douglas Road, Kingswood, Bristol, England, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to multi-circuit hydraulic brake apparatus.

According to the present invention there is provided an air over hydraulic brake apparatus including for respective circuits first and second hydraulic master cylinders constructionally arranged substantially parallel and side-by-side, but such that respective air pressure operable actuators for the said master cylinders are opposingly mounted thereto.

In order that the present invention may be more clearly understood and readily carried into effect, the same will be further described by way of example with reference to the accompanying drawings of which Figure 1 illustrates a side view of a multi-circuit air-over-hydraulic master cylinder arrangement utilising the present invention and Figure 2 illustrates a part-sectional view of the master cylinder arrangement of Figure 1.

Figure 3 illustrates a sectional view of the hydraulic master cylinder of the apparatus of Figure 1 and Figure 2.

It will be understood that the arrangement to be described is adapted to be operated by air pressure from a dual foot valve with independent supply circuits to each section of the valve from respective reservoirs. The reservoirs may be charged by a single compressor via respective charging check valves. The arrangement may be mounted beneath the chassis of a vehicle remotely from the foot valve and reservoirs and the discrete hydraulic pressure outputs are fed to respective brake actuator circuits.

These brake actuator circuits may be arranged to feed front and rear wheels' brakes or they may feed dual circuit actuators on some or all wheels as required.

Referring now to Figure 1, this shows a central main single body of material in the form of casting denoted by reference 1, which includes two hydraulic master cylinders, the internal components of which are shown in greater detail in Figure 3, to be described later. The lines of action "A" and "B" (shown dotted in Figure 2) on the hydraulic master cylinders being substantially parallel but mutually opposing, that is the master cylinders are mounted together so that they are operable by forces applied at opposite ends of the main casting 1. The main casting 1 has respective flanges 2 and 3 with provision to receive twin mounting studs 4 and 5 of an air-operated actuator 6 and studs 7 and 8 of an air-operated actuator 9.As will be seen more clearly from the view of Figure 1, the lines of action "A" and "B" of the air-operated actuators on the hydraulic master cylinders in the central casting 1, are laterally displaced. Mounted on the central casting 1 there is also a twin hydraulic fluid feed tank 10 with a common replenishing cover 11 and an internal division which provides effectively a pair of independent reservoirs for the two hydraulic circuits fed by the respective master cylinders.

Referring especially to Figure 2, it will be seen that the air actuators are as shown with reference to the actuator 6, of conventional internal construction and comprise a lightly spring-loaded diaphragm piston 14 urged by a spring 15 against a diaphragm 16, the region on the other side of the diaphragm 16 being provided with an air input port 17.

The diaphragm piston rod 18 engages within a socket formed in the piston 19 of the respective hydraulic master cylinder, which itself is internally spring-biassed by a spring 21 (Figure 3) in the hydraulic fluid chamber.

The usual input port and compensating ports communicating with the respective reservoir in the tank 10 are provided together with a suitable check valve incorporated at the output port to retain a small pressure in the hydraulic pipe leading from this master cylinder to the slave cylinders connected thereto. The other half of the arrangement is identical and requires no further description.

As is clearly shown in Figure 2, the arrangement affords a compact arrangement of dual hydraulic master cylinders and respective air-operated actuators and suitable mounting brackets denoted by reference MB1 and MB2 can be clamped by means of the existing pairs of studs, 4, 5 and 6, 7 of the respective actuators between flanges of the central casting and the plane surfaces of the actuators 6 and 9 through which respective actuator rods such as 18 extend.

Referring to Figure 3, the pistion 19 of the sectioned hydraulic master cylinder portion is slideable within a cylinder 20 and is urged rightwards towards the associated air operated actuator by a biassing spring 21.

The right-hand end of the piston is provided with a suitable piston seal 22 which prevents the egress of fluid past this end of the piston and the piston is provided with a reduced diameter central portion 23, the lefthand flange of which engages with the operating end 25 of a tilting valve 28 which, in the extreme position shown, is thereby rendered open to provide communication with cylinder 20 from the reservoir. The lefthand end of the hydraulic master cylinder is provided with a check valve, the movable member of which is denoted by reference 26 and the spring of which is denoted by reference 27, this valve being provided with a central lightly-loaded valve member 29 through which hydraulic pressure is transmissible upon a leftward force being exerted upon the piston 19.

In operation, upon such a leftward force on the piston 19, the piston moves and the tilting valve 28 becomes seated. The fluid pressure which is then generated leftward of the seal 22 by the piston is therefore transmitted through the check valve to the associated brake circuit. On release of the piston 19, the check valve, formed of components 26 and 27, retains a predetermined residual pressure in the brake circuits for the purposes of maintaining the various piston seals in the circuit in good contact with the bores in which they operate.

Principally, these piston seals are the slave cylinder piston seals of the brakes.

For convenience, both master cylinders of the pair are fed from a common chamber 10 which is suitably divided by a partition 34 to provide effectively independent sources of fluid for the two hydraulic master cylinders.

As shown in Figure 3, this common chamber 10 is provided in its cap 32 with a suitable indicator float 30, the stem 31 of which projects, through a suitable splash-over protection arrangement, to provide an indication by its position as shown dotted at 33, that the chamber 10 is full to the appropriate level. Any appreciable loss of fluid via either master cylinder causes the float 30 to drop and thereby indicate that attention to the hydraulic fluid is required.

It will be appreciated from the foregoing that the input ports such as 17 of the air actuators of the multi-circuit arrangement are connected to the outputs of a multicircuit driver-operated foot valve provided on the vehicle and the hydraulic outputs at ports are connected directly to the slaving components of actuators for the various dual circuit brake units on the vehicle.

These may be disc, drum, or other brake units.

It will further be appreciated that the relative sizes of the diaphragms of the air operated actuators 6 and 9 can be chosen to provide the desired degree of force amplification as between the driver's foot valve and the slave units.

WHAT WE CLAIM IS: 1. An air over hydraulic brake apparatus including for respective circuits first and second hydraulic master cylinders constructionally arranged substantially parallel and side-by-side, but such that respective air pressure operable actuators for the said master cylinders are opposingly mounted thereto.

2. An hydraulic brake apparatus as claimed in Claim 1 or 2, the hydraulic master cylinders being formed in a single body of material.

3. An hydraulic brake apparatus as claimed in Claim 3, wherein said single body of material is a casting.

4. An hydraulic brake apparatus as claimed in Claim 1, 2 or 3, including a mounting bracket attachable by fixing means common to the fixing also of a said air actuator to the respective hydraulic master cylinders.

5. A multi-circuit hydraulic brake apparatus substantially as described herein, with reference to Figures 1, 2 and 3 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. respective hydraulic master cylinder, which itself is internally spring-biassed by a spring 21 (Figure 3) in the hydraulic fluid chamber. The usual input port and compensating ports communicating with the respective reservoir in the tank 10 are provided together with a suitable check valve incorporated at the output port to retain a small pressure in the hydraulic pipe leading from this master cylinder to the slave cylinders connected thereto. The other half of the arrangement is identical and requires no further description. As is clearly shown in Figure 2, the arrangement affords a compact arrangement of dual hydraulic master cylinders and respective air-operated actuators and suitable mounting brackets denoted by reference MB1 and MB2 can be clamped by means of the existing pairs of studs, 4, 5 and 6, 7 of the respective actuators between flanges of the central casting and the plane surfaces of the actuators 6 and 9 through which respective actuator rods such as 18 extend. Referring to Figure 3, the pistion 19 of the sectioned hydraulic master cylinder portion is slideable within a cylinder 20 and is urged rightwards towards the associated air operated actuator by a biassing spring 21. The right-hand end of the piston is provided with a suitable piston seal 22 which prevents the egress of fluid past this end of the piston and the piston is provided with a reduced diameter central portion 23, the lefthand flange of which engages with the operating end 25 of a tilting valve 28 which, in the extreme position shown, is thereby rendered open to provide communication with cylinder 20 from the reservoir. The lefthand end of the hydraulic master cylinder is provided with a check valve, the movable member of which is denoted by reference 26 and the spring of which is denoted by reference 27, this valve being provided with a central lightly-loaded valve member 29 through which hydraulic pressure is transmissible upon a leftward force being exerted upon the piston 19. In operation, upon such a leftward force on the piston 19, the piston moves and the tilting valve 28 becomes seated. The fluid pressure which is then generated leftward of the seal 22 by the piston is therefore transmitted through the check valve to the associated brake circuit. On release of the piston 19, the check valve, formed of components 26 and 27, retains a predetermined residual pressure in the brake circuits for the purposes of maintaining the various piston seals in the circuit in good contact with the bores in which they operate. Principally, these piston seals are the slave cylinder piston seals of the brakes. For convenience, both master cylinders of the pair are fed from a common chamber 10 which is suitably divided by a partition 34 to provide effectively independent sources of fluid for the two hydraulic master cylinders. As shown in Figure 3, this common chamber 10 is provided in its cap 32 with a suitable indicator float 30, the stem 31 of which projects, through a suitable splash-over protection arrangement, to provide an indication by its position as shown dotted at 33, that the chamber 10 is full to the appropriate level. Any appreciable loss of fluid via either master cylinder causes the float 30 to drop and thereby indicate that attention to the hydraulic fluid is required. It will be appreciated from the foregoing that the input ports such as 17 of the air actuators of the multi-circuit arrangement are connected to the outputs of a multicircuit driver-operated foot valve provided on the vehicle and the hydraulic outputs at ports are connected directly to the slaving components of actuators for the various dual circuit brake units on the vehicle. These may be disc, drum, or other brake units. It will further be appreciated that the relative sizes of the diaphragms of the air operated actuators 6 and 9 can be chosen to provide the desired degree of force amplification as between the driver's foot valve and the slave units. WHAT WE CLAIM IS:

1. An air over hydraulic brake apparatus including for respective circuits first and second hydraulic master cylinders constructionally arranged substantially parallel and side-by-side, but such that respective air pressure operable actuators for the said master cylinders are opposingly mounted thereto.

2. An hydraulic brake apparatus as claimed in Claim 1 or 2, the hydraulic master cylinders being formed in a single body of material.

3. An hydraulic brake apparatus as claimed in Claim 3, wherein said single body of material is a casting.

4. An hydraulic brake apparatus as claimed in Claim 1, 2 or 3, including a mounting bracket attachable by fixing means common to the fixing also of a said air actuator to the respective hydraulic master cylinders.

5. A multi-circuit hydraulic brake apparatus substantially as described herein, with reference to Figures 1, 2 and 3 of the accompanying drawings.