GB1596063A

GB1596063A - Brake valve

Info

Publication number: GB1596063A
Application number: GB5262/78A
Authority: GB
Original assignee: Wabco Fahrzeugbremsen GmbH
Current assignee: Wabco Fahrzeugbremsen GmbH
Priority date: 1977-02-17
Filing date: 1978-02-09
Publication date: 1981-08-19
Also published as: NL188628C; NL7801211A; ATA49478A; SE7800225L; IT7867324A0; DE2706757B2; AT374422B; JPS6137136B2; NL188628B; FR2380923A1; IT1203170B; CH627979A5; JPS53102469A; FR2380923B1; SE435362B; DE2706757A1

Abstract

The brake valve, actuable by way of a tappet, is equipped with a preloaded spring (10) which is supported on a piston (4) and a displaceable spring plate (8). The spring plate (8) has a central funnel-shaped recess (16), the lower terminating surface (18) of which is of spherical design. In this recess (16) a tappet (20), connected so that it is directly rotatable with the brake operating pedal, is arranged, the end face (22) of which is designed to be complementary to the surface (18) of the recess (16). The tappet (20) is thereby capable of moving in three dimensions. This also results in a smaller overall length and reduced valve wear. <IMAGE>

Description

(54) BRAKE VALVE (71) We, WABCO FAHRZEUG BREMSEN, GMBH (formerly known as Wabco Westinghouse GMBH.), a German Company of, Am Lindener Rafen 21, 3000 Hannover 91, 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 brake valve for a vehicle.

Motor vehicle brake valves are known which are actuated by a lever, a thrust member of the lever acting on a further thrust member arranged in an expanding bellows, this second thrust member being guided in a carrier plate and acting on a spring plate of a rubber spring which in turn acts on a piston that actuates the valve.

This known type of brake valve has various disadvantages, the main one being the additional friction of the thrust member in the carrier plate. The rubber spring used always exhibits lack of uniformity and, since it is operated rigidly, as it were, by the thrust member, the lack of uniformity means that the piston may be subjected to tilting moments, which causes increased friction and increased wear as well as impaired graduation. Moreover, the known type of valve is relatively long overall, on account of the additional thrust member and the additional carrier plate, and this involves higher construction costs.

Motor vehicle brake valves that are actuated by a push rod are also known, the push rod being arranged in a recess of a thrust member arranged in an expanding bellows, this thrust member being guided in a carrier plate. As in the case of the brake valve that is actuated by a lever, the thrust member acts by way of a spring plate on a rubber spring which in turn acts on a piston that actuates the valves.

This known push rod-actuated brake valve has, essentially, the same disadvantages as those of the lever actuated brake valve described above. The large overall length which means that the valve usually has to be housed only outside the drivels cab and actuated remotely by means of levers and rods, is particularly obvious disadvantages of this brake valve.

The present invention provides a vehicle brake valve including a valve member operable by a piston, and a resilient member supported between the piston and a support plate which has a central recess in which a valve actuating member is supported, the support plate having peripheral portions with convex outer faces by which the support plate is displaceably guided in a bore of the piston.

Preferably, the recess in the support plate is a funnel-shaped bore with a spherical end.

Advantageously, the working point, working line or working surface of the actuating member in the recess of the support plate, when viewed in the direction of operation of the actuating member, is behind the surface of the support plate.

In an embodiment of the invention, the support plate has a projection which extends in the direction of operation into the resilient member and is engageable with the piston to define a rest position of the support plate at the end of the path of the resilient member.

The invention will now be described in more detail with the aid of the attached drawings which show, by way of example, an embodiment of the invention. In the drawings: Fig. 1 shows a brake valve constructed according to the invention, partly in crosssection, and Fig. 2 shows the brake valve of Fig. 1 when installed, that is, coupled with a brake pedal.

Fig. 1 shows a brake valve constructed according to the invention. A piston 4 for operating a valve member, which is not shown in more detail, is arranged in a housing 2. The piston 4 has a stepped central bore 6 in which there is arranged a spring plate 8 on which a spring 10, in the form of an annular rubber spring, is supported against a supporting surface 11. The spring 10 is further supported, as shown, on the piston 4. A circlip 12 holds the spring plate substantially around its periphery and in such a manner that it is biased towards the spring 10.

The spring plate 8 is guided against the wall of the bore 6 of the piston 4 by an annular flange 14 provided with crowned or spherical outer faces 13. The spring plate 8 has a central, funnel-shaped recess 16, the lower end surface 18 of which is spherical.

In this recess 16 there is arranged a push rod 20, the end surface 22 of which is of a shape complementary to that of surfaces 18 and which is guided to the outside of the valve by a collar placed thereover as a result of which three-dimensional movement is imparted to the push rod.

The working point of the push rod 20 on the spring plate in the recess 16 is so selected that, as seen in the drawing, it lies beneath the support surface 11 thus imparting a tractive force to the spring plate which receives a self-stabilising motion by means of which skewed positioning and possible jamming of the spring plate 8 is avoided; this is also aided by the lateral guidance of the spring plate 8 by means of the annular flange 14.

A further improvement in self-stabilisation may be achieved by arranging that the working point of the push rod 20, in the recess, lies in the middle third of the length of the external diameter of the piston.

The spring plate 8 is also provided with a projection 24 extending through the spring 10, with which the spring plate may come to rest at the end of the spring path against the piston 4.

When a brake operating member, for example a brake pedal (not shown) is operated, the push rod 20 in the drawing is moved downwards and transmits the move ment, by means of the spring plate 8 and the spring 10, to the piston 4 which descends against the force of a pre-tensioning spring 26 and actuates the valve (not shown). When the brake pedal is released, the spring 10 presses the spring plate upwards again and the piston 4 follows this movement under the influence of the spring 26.

It can be seen from Fig. 2 that the valve is designed for a dual circuit brake system.

The transfer member for transmitting the movement of a brake pedal 32 is a single push rod 34 which is coupled at 36 to the one short lever 38 of the pedal. The brake pedal itself pivots about a centre of rotation 40. To show the position of certain components more clearly, the position of the spring plate 44 (corresponding to plate 8 in Fig. 1) together with its recess 46, is indicated by a broken line beneath an expanding bellows 42.

In the brake valve shown in Fig. 1 the central recess 16 permits the use of only one push rod 20 which is operated directly, for example by means of the brake operating member normally present, without additional rods and additional guides because the recess already provides a reliable bearing. This enables a substantially smaller overall length to be achieved so that the brake valves may then be housed in the driver's cab and, because actuating levers or additional actuating rods can be dispensed with, the installation costs may be substantially reduced.

Fewer actuating members and joints as well as the absence of special supporting and guiding parts enable friction and hysteresis to be reduced and the graduation of the valve to be improved. More particularly, when the push rod 20, which is directly supported in the recess 16, is rotatably connected to a brake operating member (e.g. a brake pedal) as illustrated in Fig. 2 then an arrangement is achieved having altogether only two places of friction.

The reduction in friction is further aided by forming the closed end of the recess 16 with a sperical shape and by shaping the end of the push rod 20 in a complementary manner: this also helps bring about an improvement in guidance.

Simple installation of the spring plate 8 to pre-tension the spring 10 is achieved through the use of the circlip 12 to hold the spring plate in place around its periphery.

Good radial guidance of the spring plate 8 is achieved by guiding the spring plate by its peripheral portions in the bore 6 of the piston, and the convex shaping of the faces of these peripheral portions assists in preventing the spring plate becoming skewed and jammed, which could occur as a result of tolerances and lack of uniformity of the spring 10.

The provision of the projection 24 on the spring plate 8 ensures that, even when the spring plate is overloaded, it is subject to very low stress; the plate can, accordingly, have relatively small dimensions without there being the risk of damage.

WHAT WE CLAIM IS: 1. A vehicle brake valve including a valve member operable by a piston, and a resilient member supported between the piston and a support plate which has a central recess in which a valve actuating member is supported, the support plate having peripheral portions with convex outer faces by which the support plate is displaceably-guided in a bore of the piston.

2. A brake valve according to claim 1, in which the valve actuating member is a push rod.

3. A brake valve according to claim 1 or claim 2, in which the valve actuating member is directly and rotatably connectable to the vehicle brake pedal.

4. A brake valve according to any one of the preceding claims in which the recess in the support plate is a funnel-shaped bore with a spherical end.

5. A brake valve according to claim 4, in which the bore is a blind bore.

6. A brake valve according to any one of the

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

Claims

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

wall of the bore 6 of the piston 4 by an annular flange 14 provided with crowned or spherical outer faces 13. The spring plate 8 has a central, funnel-shaped recess 16, the lower end surface 18 of which is spherical.

In this recess 16 there is arranged a push rod 20, the end surface 22 of which is of a shape complementary to that of surfaces 18 and which is guided to the outside of the valve by a collar placed thereover as a result of which three-dimensional movement is imparted to the push rod.

The working point of the push rod 20 on the spring plate in the recess

16 is so selected that, as seen in the drawing, it lies beneath the support surface

11 thus imparting a tractive force to the spring plate which receives a self-stabilising motion by means of which skewed positioning and possible jamming of the spring plate 8 is avoided; this is also aided by the lateral guidance of the spring plate 8 by means of the annular flange 14.

A further improvement in self-stabilisation may be achieved by arranging that the working point of the push rod 20, in the recess, lies in the middle third of the length of the external diameter of the piston.

The spring plate 8 is also provided with a projection 24 extending through the spring 10, with which the spring plate may come to rest at the end of the spring path against the piston 4.

When a brake operating member, for example a brake pedal (not shown) is operated, the push rod 20 in the drawing is moved downwards and transmits the move ment, by means of the spring plate 8 and the spring 10, to the piston 4 which descends against the force of a pre-tensioning spring

26 and actuates the valve (not shown). When the brake pedal is released, the spring 10 presses the spring plate upwards again and the piston 4 follows this movement under the influence of the spring 26.

It can be seen from Fig. 2 that the valve is designed for a dual circuit brake system.

The transfer member for transmitting the movement of a brake pedal 32 is a single push rod 34 which is coupled at 36 to the one short lever 38 of the pedal. The brake pedal itself pivots about a centre of rotation 40. To show the position of certain components more clearly, the position of the spring plate

44 (corresponding to plate 8 in Fig. 1) together with its recess 46, is indicated by a broken line beneath an expanding bellows 42.

In the brake valve shown in Fig. 1 the central recess 16 permits the use of only one push rod 20 which is operated directly, for example by means of the brake operating member normally present, without additional rods and additional guides because the recess already provides a reliable bearing. This enables a substantially smaller overall length to be achieved so that the brake valves may then be housed in the driver's cab and, because actuating levers or additional actuating rods can be dispensed with, the installation costs may be substantially reduced.

Fewer actuating members and joints as well as the absence of special supporting and guiding parts enable friction and hysteresis to be reduced and the graduation of the valve to be improved. More particularly, when the push rod 20, which is directly supported in the recess 16, is rotatably connected to a brake operating member (e.g. a brake pedal) as illustrated in Fig. 2 then an arrangement is achieved having altogether only two places of friction.

The reduction in friction is further aided by forming the closed end of the recess 16 with a sperical shape and by shaping the end of the push rod 20 in a complementary manner: this also helps bring about an improvement in guidance.

Simple installation of the spring plate 8 to pre-tension the spring 10 is achieved through the use of the circlip 12 to hold the spring plate in place around its periphery.

Good radial guidance of the spring plate 8 is achieved by guiding the spring plate by its peripheral portions in the bore 6 of the piston, and the convex shaping of the faces of these peripheral portions assists in preventing the spring plate becoming skewed and jammed, which could occur as a result of tolerances and lack of uniformity of the spring 10.

The provision of the projection 24 on the spring plate 8 ensures that, even when the spring plate is overloaded, it is subject to very low stress; the plate can, accordingly, have relatively small dimensions without there being the risk of damage.

WHAT WE CLAIM IS: 1. A vehicle brake valve including a valve member operable by a piston, and a resilient member supported between the piston and a support plate which has a central recess in which a valve actuating member is supported, the support plate having peripheral portions with convex outer faces by which the support plate is displaceably-guided in a bore of the piston.
2. A brake valve according to claim 1, in which the valve actuating member is a push rod.
3. A brake valve according to claim 1 or claim 2, in which the valve actuating member is directly and rotatably connectable to the vehicle brake pedal.
4. A brake valve according to any one of the preceding claims in which the recess in the support plate is a funnel-shaped bore with a spherical end.
5. A brake valve according to claim 4, in which the bore is a blind bore.
6. A brake valve according to any one of the

preceding claims, in which the working point, working line or working surface of the actuating member in the recess of the support plate, when viewed in the direction of operation of the actuating member, is behind the surface of the support plate.
7. A brake valve according to claim 6, in which the working point, working line or working surface of the actuating member in the recess lies in the middle third of the length of the external diameter of the piston.
8. A brake valve according to any one of the preceding claims, in which the support plate is pre-tensioned and held in place around its periphery with the aid of a circlip.
9. A brake valve according to any one of the preceding claims, in which the support plate has a projection which extends in the direction of operation into the resilient member and is engageable with the piston to define a rest position of the support plate at the end of the path of the resilient member.
10. A vehicle brake valve substantially as described herein with reference to, and as shown in, the accompanying drawings.