GB1571334A

GB1571334A - Brake systems

Info

Publication number: GB1571334A
Application number: GB1333977A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1976-03-31
Filing date: 1977-03-30
Publication date: 1980-07-16

Description

(54) IMPROVEMENTS IN BRAKE SYSTEMS (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 invention relates to a hand-brake valve unit for a compressed air brake system for a motor vehicle.

It has been proposed to provide a brake system having a spring-loaded brake cylinder whose energy-storing spring, is controlled by a double-seat valve in a hand-brake valve unit with means for checking the braking action of only a portion of the motor vehicle brake system, (see Wabco Publication 826 000-027, September 1967 Issue). In this system, the double-seat valve for the spring-loaded brake and a valve for the checking device are arranged adjacent to one another in a common housing of the hand-brake valve unit. Although the two valves are actuated by way of a common hand lever, they have separate actuating cams and push rods, thus rendering their control very complicated.

The first object of the invention is to sim plify actuation in a hand-brake valve unit of this type.

Furthermore, it is proposed in the said publication to construct the hand-brake valve unit such that the brake on a tractor vehicle remains in its applied state when the brake on a trailer is released for the purpose of testing it.

A further object of the invention is to pro vide, in the hand-brake valve unit, isolating means which ensures that the spring-loaded brake on the tractor vehicle can remain in its applied state whilst the trailer control valve is actuated again for the purpose of releasing the trailer brake.

According to the present invention there is provided a hand valve, for a compressed air braking system for motor vehicles, having an inlet port supplied with air from a compressed air source, a first outlet port for connection with a spring-loaded brake cylinder, a second outlet port for connection with a trailer control valve and a further port leading to atmosphere, a double seat valve controlled by an actuating linkage, the inlet port being connected in a running position to the first and second outlet ports, and the first and second outlet ports being isolated from the inlet port and vented to atmosphere in a braking position, the valve further comprising an isolating member arranged coaxially with the actuating linkage and having an additional valve seat adapted to engage the double seat valve for isolating the said first and second outlet ports from one another and at the same time venting the first outlet port to atmosphere upon movement of the actuating linkage to a test position.

The invention is further described by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagram of a twin-line com pressed air brake system, and Figure 2 is a section through a hand brake valve unit.

An external force, dual-circuit, twin-line brake system has a compressor 1 which sup plies compressed air to two reservoirs 5 and 6, a secondary load 7 and a trailer supply line 8 by way of a pressure regulator 2, an anti frosting pump 3 and a four-circuit protective valve 4. The two reservoirs 5 and 6 have two associated service brake circuits I and II which can supply compressed air to a front wheel brake cylinder 10 and a rear wheel brake cylinder 11 by way of a foot-operated dual circuit brake valve 9. Compressed air lines 12 and 13 of the two brake circuits I and II are connected to a trailer control valve 14 to which is also connected a third line 15 leading from a spring-loaded brake circuit having a hand brake valve unit 16 and two springloaded brake cylinders 17 and 18.The springs of the spring-loaded brake cylinders 17 and 18 act in a direction to apply the brakes, e.g.

for parking and emergency braking and compressed air is applied to these cylinders to compress the springs and thereby release the brakes. The spring-loaded brake circuit is supplied with compressed air from the third circuit comprising the trailer supply line 8 by way of a non-return valve 19. It is obvious that a relay valve can also be used in the spring-loaded brake circuit, so that the springloaded brake cylinders are not directly actuated by the hand brake valve unit 16. Finally, a second supply line connection 7' leads to the hand brake valve unit 16, from the fourth circuit, leading to the secondary load 7.

A supply line coupling head 20 is located at the end of the trailer supply line 8, and a line 21 leads from the trailer control valve 14 to a brake line coupling head 22. Furthermore, a branch line 23 leads from the supply line coupling head 20 to the trailer brake valve 14.

Finally, a first brake line 24 and a second brake line 25 lead from the hand brake valve unit 16 to the spring-loaded brake cylinders 17 and 18, the two lines 24 and 25 being isolated from one another by means of a two-position non-return valve 26.

The hand brake valve unit 16 is shown in section in Figure 2.

The hand brake valve unit 16 has a housing 27 which has a multiply stepped through bore 28.

A second housing 29 is attached to the housing 27 and accommodates a three port, two position valve 30. The housing 29 of the three-port, twoposition valve has a supply connection 31 for the line 7', a connection 32 for the brake line 25, and an atmospheric air connection 33. The three-port, two-position valve 30 acts as a shutoff valve and is in the form of a double-seat valve which, as is illustrated, normally maintains communication between the supply line 7' and the brake line 25 and, when in its other end position, shuts off the supply line 7' and connects the brake line 25 to the atmosphere.

The housing 27 having an inlet port for connection with the supply line, a first outlet port for connection with a spring loaded brake cylinder, a second outlet port for connection with a trailer control valve, and a port leading to atmosphere.

A double-seat valve 34 is also provided in the other housing 27 and, when in its illustrated position, establishes communication between the supply line, incorporating the non-return valve 19, and the trailer control valve (connection 35, line 15) as well as the brake line 24 (connection 36), which double-seat valve can assume another position in which the supply line connection for the trailer control valve 14 and for the brake line 24 is interrupted and in which communication can be established with the atmosphere (connection 37).

An isolating member 38 is provided in the housing 27 between the connection 36 and the connection 35 and carries a valve seat 39 at its end facing the double-seat valve 34. The double seat valve 34 has a first valve seat 40 which is formed by the rim of a mushroom-shaped element 41 and which, head downwards, is slipped from below onto one end of a rod 42 of an actuating linkage 43 which extends coaxially through the entire valve unit 16.

When the double-seat valve 34 is in its illustrated initial position, a closure plate 44 rests on the valve seat 40 and can cooperate with a second valve seat 46 of the double-seat valve 34 which is provided on a piston 45. The closure plate 44 and the first valve seat 40 thereby form an outlet valve 40/44, and the closure plate 44 and the second valve seat 46 form an inlet valve 44/46 for monitoring the spring-loaded brake cylinders 17 and 18 and the trailer control valve 14. A spring biases the closure plate 44 towards the first valve seat 40.

The valve seat 39 disposed on the isolating member 38 is a third valve seat which cooperates with the double-seat valve 34 and which is arranged coaxially of the actuating linkage 43. The significance of the valve seat 39 will be explained later. Its inner diameter is sufficiently large to admit the first valve seat 40 without the passage of air through an axial bore 47 in the isolating member 38 being obstructed by the edge of the valve seat 40.

The axial bore 47 is supplemented by a radial opening 48.

A rod 49 of the actuating linkage 43 passes through the isolating member 38 and extends into the second housing 29 and its bottom end carries a movable valve seat 50 of the three-port, two-position valve 30. The valve 30 also has a fixed seat 51, and the two seats 50 and 51 are intended to cooperate with a closure plate 52. A cover 53 mounted on the top of the first housing 27 is provided with a securing flange 54 for the valve unit 16. The cover 53 accommodates a spindle 55 which is provided with an eccentric 56 and which is rotatable by means of a hand lever 57. A spring-loaded sleeve 58 is mounted coaxially on the lever 57 and its end 59 facing the valve unit 16 abuts against a stop 60 in the cover 53 after the lever 57 has passed through a first angle a of traverse. The stop 60 is cleared by pulling the lever 57., whereupon the end 59 of the sleeve passes across the stop 60. The lever 57 can then continue its travel and pass through an angle ss of traverse.

The actuating linkage 43 has an associated sleeve 61 which is arranged in the cover 53 and which is acted upon by the eccentric 56. A screw-threaded portion 62 of the rod 42 is inserted into the sleeve 61 and carries a nut 63 which is prevented from turning by means of the sleeve 61. The top end of the rod 42 is provided with a slot 64. The slot 64 and the nut 63 enable the effective length of the rod 42 to be caried by means of a screwdriver.

A graduation spring 65 is arranged in the housing 27 and, when the piston 45 is in its illustrated position, is stressed by the piston 45 by virtue of the fact that the piston 45 is acted upon from below by the pressure in the springloaded brake line 24 and in the line 15 leading to the trailer control valve 14. The force of the gradation spring 65 when the latter is effective can be adjusted indirectly by rotating the rod 42. Thus, a limit to the release pressure of the spring-loaded brake can be achieved. The pressure level which is established is dependent upon the force of the spring 65 which is in turn dependent upon the working position of the two valve seats 46 and 40 of the double seat valve 34 as adjusted by the rod 42.The piston 45 carries a bracket 66 through the centre of which passes the rod 42 and which, together with the bottom end of the sleeve 61, forms a stop 61/66. The chamber housing the spring 65 is connected with the atmospheric connection 37 via the passageway (shown dotted in Figure 2) and with a central opening in the closure plate 44 through holes (not shown) in the bracket 69.

The brake system described operates in the following manner: 1. Travelling or running position When in the travelling or running position, the three port, two position valve 30 has established communication between the line 25 and the supply line 7', and the double seat valve 34 has established communication between the first outlet port spring-loaded brake line 24 and the inlet port for the trailer supply line 8. Both sides of the two-position nonreturn valve 26 are subjected to supply pressure which is also applied to the spring-loaded brake cylinders 17 and 18 where in stresses the energy-storing springs and releases the brakes.

If one of the two lines 24 or 25 should fail, the brake remains in its released state, since the non-return valve 26 shuts off the defective line.

In the illustrated travelling position of the lever 57, the valve 30 blocks operation of the spring-loaded brakes. This ensures that the spring-loaded brakes do not respond in an uncontrolled manner if the supply pressure drops or fails.

2. Unblocking (three-port, two-position valve 30) Upon actuating the lever 57 a certain distance from the travelling position, the eccentric 56 urges the actuating linkage 43 downwardly.

The three-port, two-position valve 30 is thereby changed over from its position in which it blocks the vent from the line 25 in the first instance by means of the rods 42 and 49. Thus, air can escape from the line 25 to the atmosphere by way of the connection 33. However, the energy-storing springs in the spring-loaded brake cylinders 17 and 18 do not yet respond, since the valve 34 is not yet changed over so that the pressure still exists in the line 24 and the non-return valve 26 merely shuts off the line 25.

In the event of a fracture in the springloaded brake line 24, the three-port, twoposition valve 30 acts as an emergency release valve, so that the spring-loaded brake can be released even when a defect of this type occurs.

3. Braking The double-seat valve 34 is changed over upon further actuation of the lever 57 in the range of the angle a of traverse. The inlet valve 44/46 is closed and the outlet valve 40/44 is opened. Thus, the first outlet for the springloaded brake line 24 is also vented, and the spring-loaded brakes become effective. The second outlet for the line 15 leading to the trailer control valve is also vented, so that the brakes are also applied on the trailer. The gradation spring 65 monitors the release of the pressure from the line 24 since this pressure acts against the spring 65. This ensures that the braking operation is effected in a sensitive manner. The brake lever 58 reaches the stop 60 when the brakes are fully applied, the residual pressure in the line 24 being determined by the adjustment of the rod 62.

A latching position can be provided at this location.

4. Testing If a test is to be made to determine whether the spring-loaded brake device installed on the tractor vehicle is sufficiently effective to brake the entire vehicle/trailer combination by itself, i.e. without the trailer brake, the trailer brake has to be released again when the springloaded brake is applied.

For this purpose, the lever 57 is pulled outwardly, so that the end 59 of the sleeve can pass across the stop 60. The lever 57 can now pass through the angle p of traverse. The following then occurs in the brake valve unit: The actuating linkage 43 completes the final part of its stroke, and the sleeve 61 abuts against the bracket 66. 3y virtue of this stop 61/66 on the actuating linkage 43, a positive connection is established with the piston 45 which moves the inlet valve seat 46 further downwardly. The closure plate 44 abutting against the seat 46 follows this movement and reaches the third valve seat 39 disposed on the isolating member 38. When in this position, the line 15 leading to the trailer control valve 14 is pressurized again, while the spring-loaded brakes remain vented.The lever 57 automatically returns to the full braking position from the test position.

The actuating linkage 43 acts upon the valves in a pressing manner when the lever 57 is swung through the angles oe and ss of traverse in the braking direction. Thus, it is possible to transmit force by means of simple rods 42 and 49.

WHAT WE CLAIM IS: 1. A hand valve, for a compressed air braking system for motor vehicles, having an inlet port supplied with air from a compressed air source, a first outlet port for connection with a spring-loaded brake cylinder, a second outlet port for connection with a trailer control valve and a further port leading to atmosphere, a double seat valve controlled by an actuating linkage, the inlet port being connected in a running position to the first and second outlet ports, and the first and second outlet ports being isolated from the inlet port and vented to atmosphere in a braking position, the valve further comprising an isolating member arranged coaxially with the actuating linkage and having an additional valve seat adapted to engage the double seat valve for isolating the said first and second outlet ports from one another and at the same time venting the first outlet port to atmosphere upon movement of the actuating linkage to a test position.

2. A valve unit for a brake system as claimed in claim 1 which has a brake lever wllich after overcoming an obstruction or a resistance can be swung into an end position which constitutes the test position of the hand brake valve unit.

3. A valve unit for a brake system as claimed in claim 2 in which a movable inlet seat of the double-seat valve is displaceable by a member, movable by the brake lever, coming into abutment with a member having said inlet seat thereon as said lever is brought into said test position, whereby a closure member of the double seat valve is permitted to engage said additional valve seat and is lifted from the inlet seat.

4. A valve unit for a brake system as claimed in claim 3 in which the inlet seat of the double seat valve is provided on a piston movable in conjunction with the actuating linkage by virtue of the member movable by the brake lever, engaging the piston.

5. A valve unit for a brake system as claimed in any of claims 1 to 3, in which the actuating linkage is designed for actuating the brakes by applying a compressive force and in which a three-port, two-position valve, acting as a cut-out and as an emergency release valve for the motor vehicle brake, is also provided and is actuable before the changing-over between the running and braking positions of the double-seat valve.

6. A valve unit for a brake system as claimed in any of claims 1 to 5 in which a gradation spring of variable stress is provided and its spring force determines the release pressure of the spring-loaded brake at any given time.

7. A brake system fitted with a hand-brake valve unit as claimed in any of claims 5 or 6, in which two brake lines lead from the hand-brake valve unit to the spring-loaded brake cylinders, and a common two-position non-return valve is interposed between each brake line and the brake cylinders.

8. A hand-brake valve unit for a compressed air brake system constructed substantially as herein described with reference to and as illustrated in Figure 2 of the accompanying drawings - 9. A compressed air brake system for a motor vehicle constructed and adapted to operate substantially as herein described with reference to and as illustrated in the accompanying drawings.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. possible to transmit force by means of simple rods 42 and 49. WHAT WE CLAIM IS:

1. A hand valve, for a compressed air braking system for motor vehicles, having an inlet port supplied with air from a compressed air source, a first outlet port for connection with a spring-loaded brake cylinder, a second outlet port for connection with a trailer control valve and a further port leading to atmosphere, a double seat valve controlled by an actuating linkage, the inlet port being connected in a running position to the first and second outlet ports, and the first and second outlet ports being isolated from the inlet port and vented to atmosphere in a braking position, the valve further comprising an isolating member arranged coaxially with the actuating linkage and having an additional valve seat adapted to engage the double seat valve for isolating the said first and second outlet ports from one another and at the same time venting the first outlet port to atmosphere upon movement of the actuating linkage to a test position.

8. A hand-brake valve unit for a compressed air brake system constructed substantially as herein described with reference to and as illustrated in Figure 2 of the accompanying drawings -

9. A compressed air brake system for a motor vehicle constructed and adapted to operate substantially as herein described with reference to and as illustrated in the accompanying drawings.