GB1593243A - Brake cylinders for motor vehicles - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO BRAKE CYLINDERS FOR MOTOR VEHICLES (71) We, ROBERT BOSCH GMBH, a German Company of Postfach 50, 7 Stuttgart 1, Federal Republic of Germany, 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: The present invention relates to brake cylinders for motor vehicles and more particularly to brake cylinders for dual-circuit brake systems.

A two-way valve is fitted to a springloaded brake cylinder to prevent uncontrolled application of a spring-loaded brake in case of damage to brake lines connected to the spring-loaded brake cylinders. A disadvantage of one known brake system from the point of view of reliability of operation is, however, that, on normal braking by means of a spring-loaded brake, the two-way valves always remain in the same terminal position.

If a leak should develop in one of the brake lines, valve closure members of the two-way valves may have become jammed owing to rusting, resulting in failure of the safety arrangements, and failure, or uncontrolled application, of the spring-loaded brake.

According to the present invention there is provided a brake cylinder for motor vehicles, in which a two-way valve communicating with the cylinder has two inlet connections which are provided with valve seats either one or other, but not both simultaneously, of which can be closed by a respective one of two valve closure portions, said connections being adapted to be connected to two separate brake lines protected from one another pressure-wise, and has a piston which normally occupies a closure position of one of the two valve closure portions and which in use is slightly movable in response to pressure variations in the respective brake line through which pressure is applied to the piston.

A spring-loaded brake cylinder embodying the present invention can have the advantage that its two-way valve is provided with valve closure portions which are displaced on every normal operation of the brake, in order to prevent them from becoming jammed due to rust or corrosion. The reliability of the system can thereby be improved.

The invention will be further described by way of example with reference to the accompanying drawings in which: Figure 1 is a diagrammatic arrangement of a brake system, and Figure 2 is an axial section to a larger scale of a two-way valve applied to a spring-loaded brake cylinder of Figure 1.

A brake system includes a compressor 1 which supplies compressed air to two reservoirs 3 and 4 through a pressure regulator 2.

A respective supply line 5, 6 connects each reservoir 3, 4 to a brake valve 7, in the form of a valve assembly having at least two valves (not shown) arranged parallel with each other. At least one of the valves is movable by displacing an operating lever 8 in the direction of operation shown by an arrow.

Such valve unit can be very compact and save space and weight.

Two brake lines 9 and 10 which are protected from one another pressure-wise in the brake valve are connected to respective outputs of the brake valve 7, and are both connected to two valves 11 and 12, each of which is associated with a respective spring-loaded brake cylinder 13, 14, with whose housing it is integrally formed.

As is shown to a larger scale in Figure 2, each two-way valve 11, 12 has a respective closure portion 16, 16' cooperating with a respective non-return valve seat 15, 15' for controlling the brake line 10, the respective valve closure portion 16, 16' being formed onapiston 17, 17'.

At its other end each piston 17, 17' has a second valve closure portion 18, 18', which cooperates with a second non-return valve seat 19, 19' to control the brake line 9. Each non-return valve seat 15, 15'; 19, 19' is formed by a respective seat member 22, 22'; 20, 20', comprising an annular seal having a region which is resiliently yielding in a direction axially of the piston. This region is formed by an O-ring seal; 23, 23'; 21, 21' or by a ring similar to an O-ring seal. Alternatively, however, the annular seal, with its resiliently yielding region, may be arranged on the piston 17, 17'. The brake valve 7 may be so constructed that the brake line 10 is the main brake line. The piston 17, 17' is then normally, as shown in the drawings, in its right-hand terminal position.In this position, however, it is subject to continual variation of pressure, since the pressure in the brake line 10 is reduced on braking.

The brake system operates as follows: The spring-loaded brake cylinder 13, 14 may be charged not only via the line 9 but also via the line 10. When each spring-loaded brake cylinder is charged, the portion 17, 17' remains lifted from the non-return valve seat 15, 15' and the non-return valve seat 19, 19' remains closed. On normal braking, air is exhausted from the brake line 10 via the brake valve 7, and the spring-loaded brake is applied. Owing to the pressure differences thus created, the piston 17, 17' in its terminal position shown, is moved against the resilient O-ring seal 21, 21' whereby it is prevented from becoming jammed as a result of rusting.

In the event of the brake line 10 being broken, the pistons 17, 17' move to their other terminal positions, in which the nonreturn valve seats 15, 15' close the faulty line 10 and air can still be supplied to the springloaded brake cylinders 13 and 14 via the brake line 9.

The two-way valves 11 and 12 are preferably so constructed that their O-ring seals 23, 23' also permit slight movement of the pistons 17, 17' in their other terminal positions.

Alternately, however, since this position of the piston 17, 17' occurs only very rarely, namely, in the event of a line failure, the resilient O-ring seals may, for economy, be omitted from the non-return valve seats 15, 15' which only then come into operation.

In the event of the brake line 9 being broken, the pressure in the spring-loaded cylinders closes the non-return valve seats 19, 19', and, as previously described, air is supplied via the brake line 10.

If a reservoir 3 or 4, or a supply line 5 or 6, should fail, the brake system is not detrimentally affected except for the loss of air.

Whenever the brakes are operated, the pistons 17, 17', owing to their being resiliently supported, are moved slightly, so that they cannot become jammed due to rust or corrosion.

It is evident that the possibility of a fault occurring in a brake system embodying the present invention is substantially eliminated.

Jamming of the pistons of the two-way valves owing to rust or corrosion can be prevented.

Faulty operation of the brakes is consequently substantially precluded.

The invention is usable preferably in spring-loaded brake systems. Clearly, however, it is also advantageous for more usual brakes.

WHAT WE CLAIM IS: 1. A brake cylinder for motor vehicles, in which a two-way valve communicating with the cylinder has two inlet connections which are provided with valve seats either one or other, but not both simultaneously, of which can be closed by a respective one of two valve closure portions, said connections being adapted to be connected to two separate brake lines protected from one another pressure-wise, and has a piston which normally occupies a closure position of one of the two valve closure portions and which in use is slightly movable in response to pressure variations in the respective brake line through which pressure is applied to the piston.

2. A brake cylinder as claimed in claim 1, in which at least the said one valve closure portion or the corresponding valve seat has an annular seal with a region which is resiliently yielding in a direction axially of the piston.

3. A brake cylinder as claimed in claim 2, in which the resiliently yielding region is formed by a ring which is or is similar to an O-ring seal.

4. A brake cylinder as claimed in any preceding claim, in which said valve portions are portions of said piston.

5. A brake cylinder as claimed in any preceding claim, which is a spring-loaded braked cylinder.

6. A brake cylinder as claimed in any preceding claim in which the two separate brake lines protected from one another emanate from a common brake valve.

7. A brake cylinder for a spring-loaded brake for a motor vehicle, constructed and arranged and adopted to be operated substantially as hereinbefore particularly described with reference to and as illustrated in the accompanying drawings.

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

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. cooperates with a second non-return valve seat 19, 19' to control the brake line 9. Each non-return valve seat 15, 15'; 19, 19' is formed by a respective seat member 22, 22'; 20, 20', comprising an annular seal having a region which is resiliently yielding in a direction axially of the piston. This region is formed by an O-ring seal; 23, 23'; 21, 21' or by a ring similar to an O-ring seal. Alternatively, however, the annular seal, with its resiliently yielding region, may be arranged on the piston 17, 17'. The brake valve 7 may be so constructed that the brake line 10 is the main brake line. The piston 17, 17' is then normally, as shown in the drawings, in its right-hand terminal position.In this position, however, it is subject to continual variation of pressure, since the pressure in the brake line 10 is reduced on braking. The brake system operates as follows: The spring-loaded brake cylinder 13, 14 may be charged not only via the line 9 but also via the line 10. When each spring-loaded brake cylinder is charged, the portion 17, 17' remains lifted from the non-return valve seat 15, 15' and the non-return valve seat 19, 19' remains closed. On normal braking, air is exhausted from the brake line 10 via the brake valve 7, and the spring-loaded brake is applied. Owing to the pressure differences thus created, the piston 17, 17' in its terminal position shown, is moved against the resilient O-ring seal 21, 21' whereby it is prevented from becoming jammed as a result of rusting. In the event of the brake line 10 being broken, the pistons 17, 17' move to their other terminal positions, in which the nonreturn valve seats 15, 15' close the faulty line 10 and air can still be supplied to the springloaded brake cylinders 13 and 14 via the brake line 9. The two-way valves 11 and 12 are preferably so constructed that their O-ring seals 23, 23' also permit slight movement of the pistons 17, 17' in their other terminal positions. Alternately, however, since this position of the piston 17, 17' occurs only very rarely, namely, in the event of a line failure, the resilient O-ring seals may, for economy, be omitted from the non-return valve seats 15, 15' which only then come into operation. In the event of the brake line 9 being broken, the pressure in the spring-loaded cylinders closes the non-return valve seats 19, 19', and, as previously described, air is supplied via the brake line 10. If a reservoir 3 or 4, or a supply line 5 or 6, should fail, the brake system is not detrimentally affected except for the loss of air. Whenever the brakes are operated, the pistons 17, 17', owing to their being resiliently supported, are moved slightly, so that they cannot become jammed due to rust or corrosion. It is evident that the possibility of a fault occurring in a brake system embodying the present invention is substantially eliminated. Jamming of the pistons of the two-way valves owing to rust or corrosion can be prevented. Faulty operation of the brakes is consequently substantially precluded. The invention is usable preferably in spring-loaded brake systems. Clearly, however, it is also advantageous for more usual brakes. WHAT WE CLAIM IS:

1. A brake cylinder for motor vehicles, in which a two-way valve communicating with the cylinder has two inlet connections which are provided with valve seats either one or other, but not both simultaneously, of which can be closed by a respective one of two valve closure portions, said connections being adapted to be connected to two separate brake lines protected from one another pressure-wise, and has a piston which normally occupies a closure position of one of the two valve closure portions and which in use is slightly movable in response to pressure variations in the respective brake line through which pressure is applied to the piston.

2. A brake cylinder as claimed in claim 1, in which at least the said one valve closure portion or the corresponding valve seat has an annular seal with a region which is resiliently yielding in a direction axially of the piston.

3. A brake cylinder as claimed in claim 2, in which the resiliently yielding region is formed by a ring which is or is similar to an O-ring seal.

4. A brake cylinder as claimed in any preceding claim, in which said valve portions are portions of said piston.

5. A brake cylinder as claimed in any preceding claim, which is a spring-loaded braked cylinder.

6. A brake cylinder as claimed in any preceding claim in which the two separate brake lines protected from one another emanate from a common brake valve.

7. A brake cylinder for a spring-loaded brake for a motor vehicle, constructed and arranged and adopted to be operated substantially as hereinbefore particularly described with reference to and as illustrated in the accompanying drawings.