GB2056605A - Dual-line trailer brake valve assembly with load-dependent operation - Google Patents

Abstract

A combined emergency brake valve and load responsive relay brake valve assembly includes a relay valve control piston 2, 3 mounted on a control rod 4 and an emergency brake device having a piston 9. The emergency piston 9 is mounted in a freely floating manner on the control rod 4 and is normally biased by emergency line pressure from line 15 (and also by a spring 58 in Figure 2) against a stop 57 on the assembly housing. A spring- biased triple valve element 18 is slidably mounted in the piston 9. The housing has an edge 23 defining a valve seat and defining with the element 18 on inlet valve between a reservoir 17 and a brake cylinder 30. An annular axial extension 27 of the control rod 4 defines with the same valve element 18 an exhaust valve. The inlet valve is opened either by relay piston 2, 3 in response to increasing braking pressure at inlet 8 or by piston 9 on decrease in reservoir line 15 pressure. <IMAGE>

Description

SPECIFICATION Dual-line trailer brake valve assembly with loaddependent operation The invention relates to a dual-line trailer brake valve with load-dependent operation, thus including relay action and an emergency brake device, comprising a valve element, which is resiliently suspended and forms, together with a stationary housing, an inlet valve and, together with an extension of the control piston of the relay valve, forms an outlet valve.

A dual-line trailer brake valve of this type is known from German Offenlegungsschrift 1,966,569. In this valve, a control unit and a balancing unit are produced, each possessing separate pistons and acting, forward or backwards on the load-dependent adjusting device at the angle of 90~. The valve element, which forms a part of the inlet valve and of the outlet valve, is resiliently suspended in the housing and delimits a space in which compressed air from the reservoir container of the trailer is continuously present. The control piston which is provided is designed in the form of separate sections, the outer annular piston being guided on the inner piston and tied to it via a spring.This arrangement allows a sudden increase in the deployment of the brake pressure to be achieved, the outer annular piston then ceasing to be effective on coming to rest against a stop. An emergency brake device is, so to say, flanged onto this dual-line trailer brake valve, this emergency brake device possessing a switching piston, guided by springs, this switching piston being subjected, in the usual manner, to the compressed air from the reservoir container on the one side, and to the compressed air from the reservoir line on the other side. In the event of fracture of the reservoir line, this switching piston directs compressed air onto the control piston in the sense of emergency braking. The known dual-line trailer brake valve consists of a large number of individual parts and is a relatively complex assembly.The emergency brake device is designed as a completely separate, flanged-on-section, so that the emergency brake device can be said to be integrated only to a very limited extent.

German Auslegeschrift 1,630,189 discloses an adjustable load-dependent brake valve for the compressed air brake systems of vehicle trailers, that is to say also a dual-line trailer brake valve, but with its load-dependent adjustment being resettable, to various selectable positions, only by hand. In this valve, the emergency brake device is designed as an emergency brake piston, which is arranged in axial alignment with the control piston and influences the latter via a mechanical extension. On the other hand, a combined inlet and outlet valve is separately provided in the housing of this trailer brake valve, the load-dependent adjustment being applied to this combined valve via a rocking beam, this beam also actuating the valve. This two-axes design is also relatively complex. No provision is made for a sudden increase in pressure, so that the reaction stage is comparatively large.

On the other hand, a brake force regulatorfor compressed air brakes, which is controlled in relation to axle load, is.known from the German Patent Specification 1,229,865, which regulation is preferably employed in conjunction with an initiating brake on the trailer side. In this relatively simple type of design, a control piston is provided, which controls the deployment of the trailer braking during indirect braking in normal operation and also in the event of emergency braking. This valve functions indirectly. The control rod is designed as a tension rod, a balancing piston being provided on this tension rod in a manner allowing the former two float freely.When an initiating brake is connected, the brake force regulator functions with a relay action, but this relay action is lost if the brake force regulator is employed in combination with a dual-line brake. In this case, the connections are altered in such a manner that the control- and emergency-brake piston, in the case of single-line connection, becomes a control piston in the case of dual-line connection, the emergency brake device ceasing to be effective. An additional impulse source, or auxiliary valve, for example a trailer brake valve, is necessary.

The object on which the invention is based is, starting from a dual-line trailer brake valve of the type initially described, to indicate a simplified type of design, in spite of which simplification none of the following functions are dispensed with: relay action, load-dependent adjustment and emergency brake action, in the case of an integrated dual-line trailer brake valve.

This object is achieved, according to the invention, by locating the valve element inside the emergency brake device, the latter being designed in the form of an emergency brake piston, and by fitting the emergency brake piston between the control piston and the inlet valve, the emergency brake piston floating freely on a control rod and being preloaded against a stop located on the housing. In the design of a dual-line trailer brake valve with load-dependent operation, the invention has recourse, in a surprising manner, to the design of a brake force regulator which is controlled in relation to axle load, of a type employed particularly for initiating brake systems.

By arranging the emergency brake piston between the control piston and the inlet valve, and by providing an additional housing wall, neither the relay action nor the emergency brake action surprisingly, is lost. The double valve element is suspended in the emergency brake piston, so that the control piston can be designed, in a particularly simple manner, as a stepped piston, for the purpose of achieving, for example, a very rapid build-up of pressure, in particular a sudden increase in pressure.

The valve according to the invention possesses the further advantage that it can also be applied in the case of an initiating brake system. An additional advantage consists in the fact that the loaddependent force, occurring on braking, is securely set by mechanical means, so that no setting shift occurs as a result of bouncing or the like.

The emergency brake piston is designed either as a stepped piston and or is loaded with a spring, in oder to preload it in opposition to its direction of operation. This design has the advantage that the emergency braking does not occur whenever compressed air is consumed, but only when a very particular decrease in pressure occurs.

The stepped piston can possess two different external diameters, each being fitted with a seal, the space between the two seals being connected to the atmosphere. By means of the arrangement and design of these two different external diameters, it is much more effectively possible, using comparatively small external diameters, to provide different working areas on the two faces of the stepped piston, in such a manner for example, that the working area facing the emergency brake chamber is approximately twice as large as the working area facing the reservoir chamber. Byvirtue of this arrangement, the emergency braking commences only when the pressure falls to a pressure which is significantly below the pressure in the reservoir container on the trailer, that is to say, for example, in the event of a fall in pressure in the reservoir line and emergency brake chamber to half of the level of the reservoir pressure in the reservoir container on the trailer, and in the reservoir chamber; nevertheless, the emergency brake piston can be produced with an external diameter that is small in comparison to the balancing piston. Preferably, no spring is located inside the emergency brake chamber, so that no force component remains on the large surface of the emergency brake piston in the event of complete loss of airfrom the reservoir line. The configuration ofthe emergency brake piston is thus substantially independent of the configuration of the balancing piston.

The emergency brake piston can possess one or more seals on the same internal diameter. However, the stepped piston may also additionally possess two different internal diameters, each being fitted with a seal, and the space between the two seals may also be connected to the atmosphere. The ratio of the surfaces can also be adjusted in this manner, -although only to a small extent.

Due to the design of the stepped piston with two sealed external diameters, it is no longer possible, without greater expense, to maintain the inflow to the reservoir container on the trailer with the aid of bypass gaiters. The stepped piston accordingly possesses at least one opening between the emergency brake chamber and the reservoir cham ber, in which a non-return valve is provided. This valve is constructed so that it opens in the direction of the reservoir chamber. By this means, a very simple air supply to the reservoir container on the trailer is achieved.

To influence the progressiveness of the deployed brake pressure, particularly of the emergency brake pressure, the ratio of the surface area of the emergency brake piston to the surface area of the balancing piston may be equal to, smaller than, or greater than 1.

The control piston is attached to the control rod, the latter being designed as a tension rod. The connection may be fixed or positive locking. A balancing piston can be fitted on the extension of the control piston, in a manner allowing itto float freely, in a constructionally simple manner.

For the purpose of achieving a very rapid buildup of pressure, in particular a sudden increase in pressure, the control piston can be designed in the form of separate sections, the two pistons being tied together via a spring. However, it is also possible to apply reverse flow to the balancing piston only via a bypass valve, or this method can be applied concurrently.

The invention is further described with the aid of three preferred illustrative embodiments. In the figures, Figure 1 shows a longitudinal section through the dual-line trailer brake valve in a first embodiment, Figure 2 shows a longitudinal section through the dual-line trailer brake valve in a second embodiment and Figure 3 shows a longitudinal section through the dual-line trailer brake valve in a third embodiment.

Inside a housing 1, which is advantageously designed in the form of several parts, a divided control piston 2,3 is guided in a slideably displaceable and sealed manner. The control piston 2,3 consists of an inner piston 2, which is located, in a sealed manner, on a hollow control rod 4, whilst the outer annular piston 3 is tied to the piston 2 via the spring 5. The brake chamber 6 is located beneath the control piston 2,3, this brake chamber being continuously connected to the brake line 8 via the connection 7.

The emergency brake piston 9 is mounted inside the central part of the trailer brake valve, on the hollow control rod 4, in a sealed and freely floating manner. The emergency brake piston 9 rests against a stop 10 on the hollows control rod 4, and subdivides the housing into an emergency brake chamber 11 and a reservoirchamber 12, an annular gaiter, which can act as a bypass in one direction and forms a non-return valve 13, being located on the emergency brake piston 9. The emergency brake chamber 11 is permanently connected to the reservoir line 15, via the connection 40. The reservoir chamber 12 is connected to the compressed air reservoir container 17 on the trailer, via the connection 16.

Inside the emergency brake piston 9, the valve element 18 is suspended by means of the spring 19.

The emergency brake piston 9 is configured as a stepped piston, by means of the seals 20 and 21, which are located on a different diameter. On the other hand, the reservoir chamber 12 is delimited by a housing wall 22, which terminates in a turned-in housing edge 23, which forms, together with the valve element 18, the inlet valve 18. The hollow control rod 4 is led, in a sealed manner, through the emergency brake piston 9 by means of the seal 20.

A stop 57 is provided, securely fixed to the housing, against which the emergency brake piston 9, which is designed as a stepped piston, is pre loaded via the pressure from the reservoir line 15 acting thereon. The preload can be changed or increased by means of a spring 58 (Figure 2).

A balancing piston 24 is guided inside the housing, in a sliding and sealed manner, beneath the housing wall 22. The seal 25 seals with respect to the housing, whilst the seal 26 slides along the extension 27 and there fulfils its sealing function. At its upper end, the extension 27 forms, together with the valve element 18, the outlet valve 18,27. The balancing chamber 28 is formed between the housing wall 22 and the balancing piston 24, this chamber being permanently connected to the brake cylinders 30, via the connection 29. The balancing piston 24 is coupled to the extension 27, and to the hollow control rod 4, via the spring 31.

The extension 27 can also be designed to be integral with the hollow control rod 4, the hollow control rod 4 continuing downwards into the region of a lever-transmission device 32, which transmits forces. For this purpose, a flat iron bar 33 is attached to the hollow control rod 4, both to the right and to the left of the lever-transmission device 32, these bars engaging, in turn, with the lowest lever 34. The lever 34 rotates about the axle 35, which is securely fixed to the housing. The upper lever 36 rotates about the axle 37, which is securely fixed to the housing, whilst the central lever 38 carries a roller 39, the relative position of which, between the levers 34 and 36, can be altered. This alteration is achieved by means of a mechanical linkage 40,41, pivoting about the rotation axis 42.A stop for the lever 41 is formed by means of the setting screw 43, which is used for setting the transmission ratio while the vehicle is empty. The hollow control rod 4, which is designed as a tension rod, possesses a passage 44 in its interior, which passes into a transverse bore 45 at the Iwoer end of the control rod. An annular space 46 is created between this control rod 4 and the extension 27. The extension 27 possesses a transverse bore 47, thereby ensuring venting via a flutter valve 48.

Beneath the balancing piston 24, a pressure piece 49 is loosely mounted, which is supported by the lever 36 on the one side and, on the other side, comes into contact with the stop 50 of the balancing piston 24 when a brake pressure is deployed and the balancing chamber 28 is correspondingly pressurised, so that a balancing force is transmitted.

The duai-line trailer brake valve functions in the following manner: Figure 1 shows the brakes-off position. The brake line 8 and the brake chamber 6 are vented. Compressed air has entered the emergency brake chamber 11 via the reservoir line 15, and has thence entered the reservoir chamber 12, via the annular gaiter 13. In this manner, the compressed air container 17 on the trailer is charged with compressed air. In the reservoir chamber 12, this compressed air is in contact with the inlet valve 18,23, this valve being closed. The outlet valve 18, 27 is open, so that not only the brake cylinders 30 are connected to the atmosphere, via the hollow control rod 4 and its passage 44, but also the space above the control piston 2, 3, together with the internal space of the emergency brake piston 9.In this condition, no force can be applied to the levertransmission device 32, for which reason a transmission ratio is readily set, via the linkage 40, 41, corresponding to a lateral displacement of the roller 39, this transmission ratio corresponding to the load condition of the vehicle. Figure 1 shows the relative position when the vehicle is unloaded.

When the operating brake in the motor vehicle is actuated, a control pulse subsequently arrives also in the brake line 8, so that the pressure in the brake chamber 6 rises and pressure is thus applied to the lower side of the control piston 2, 3. Since the entire working surface of the control piston 2,3 is available, the valve reacts quickly, in that the outlet valve 18, 27 is closed. At this time, the control rod 4 functions as a tension rod. Immediately afterwards, the inlet valve 18,23 is opened. Compressed air from the reservoir chamber 12 is thereby directed, via the balancing chamber 28, to the brake cylinders 30. The outer annular piston 3 comes into contact with a stop associated with the housing 1. The pressure now rises in the balancing chamber 28, so that the balancing piston 24 comes into contact, via its stop 50, with the pressure piece 49.The pressure piece 49 exerts a force on the lever 36, this force being correspondingly transmitted by means of the lever transmission device 32 and applied to the control rod 4. This force attempts to pull the hollow control rod 4 and the inner piston 2 downwards, against the force in the brake chamber 6. A very rapid build-up of pressure, in particular a sudden increase in pressure, occurs, the magnitude of which is determined by the strength of the spring 5. It should also be understood that the preload strength of the spring 5 can also be designed to be adjustable. As more pressure is deployed,a cut-off position is finally reached, in which the spring 5 is partially compressed and, most important of all, both the inlet valve 18,23 and the outlet valve 18,27 are closed.Due to the fact that force is applied to the lever transmission device 32, the currently set transmission ratio is securely locked by mechanical means, so that no displacement of the roller 29 occurs during the braking process. Consequently, no pressure variations occur in the pressure which is deployed.

If a still higher control pressure is directed into the brake chamber 6, the inlet valve 18,23 reopens, until a new cut-off position is reached. In the case of maximum braking with a fully loaded vehicle, a position is finally reached, in which the inlet valve 18,23 remains open, so that the entire reservoir pressure is directed, from the container 17, into the brake cylinders 30.

When braking ends, the brake chamber 6 is vented, so that the outlet valve 18, 27 is opened, the inlet valve 18,23 being closed. In this manner, the brake cylinders 30 are vented via the balancing chamber 28, so that the parts reassume the position shown.

In the event of a fracture in the reservoir line 15, emergency braking commences, due to the fact that the emergency brake chamber 11 is vented. Since the emergency brake piston 9 is designed in the form of a stepped piston, the emergency brake does not react immediately, but only after a prescribed reduction of pressure in the emergency brake chamber 11, so that the reservoir pressure in the reservoir chamber 12 has an opportunity to lift the emergency brake piston 9, thereby closing the outlet valve 18,27 and opening the inlet valve 18,23, by means of the stop 10 on the control rod 4. In this case also, balanced braking occurs, corresponding to the load condition of the vehicle. Braking of the trailer on parking is achieved in the same way, by means of this emergency brake device.By means of a shunting valve, which is not shown but which can also, if appropriate, be flanged onto the valve shown, this braking can be released or reapplied, at will, for shunting purposes.

The embodiment of the dual-line trailer brake valve according to Figure 2 corresponds, in its essential construction, to that of Figure 1. Only an additional housing wall 51 is provide, which separates the balancing chamber 28 and the pressure deployment chamber 52, the latter being connected to the brake cylinders 30 via the connection 29. A connecting line 53 leads from the pressure deployment chamber 52, via the balancing piston 24, to the balancing chamber 28. A spring-loaded bypass valve 54, allowing reverse flow, is inserted in this connecting line 53. In this bypass valve, the valve element 55 is supported on the adjustable spring 56. By this means, on deploying a brake pressure, a reaction initially occurs in the balancing chamber 28, that is to say a force presses down on the balancing piston 27.

Only when the deployed brake pressure exceeds the force of the spring 56, so that the bypass valve 54 opens, does a balancing action occur. A sudden increase in pressure can be achieved simply by providing this bypass valve, so that it is not absolutely necessary to design the control piston 2,3 in the form of two separate sections. However, both measures can be applied beside each other, supporting each other and with a partly overlapping effect.

In the embodiment of the trailer brake valve according to Figure 3, the emergency brake piston 9 possesses at least one opening 59, which passes through the piston from the emergency brake chamber 11 to the reservoir chamber 12 and in which a bypass gaiter 60 acts in a manner whereby the complete assembly forms the non-return valve 13. A plurality of openings 59 can, of course, be provided, distributed over the circumference. The openings 59 can be covered by a filter 61, in order, by this means, to filter the compressed air which is fed to the reservoir container of the trailer.

It is essential that the emergency brake piston 9, which is designed in the form of a stepped piston, possess two outer diameters of different sizes, these diameters being defined and located by the seals 62 and 63. It should be understood that the housing 1 is correspondingly stepped at this position. A space 64 is formed between the two seals 62 and 63, this space being connected to the atmosphere and to the venting, via a passage 65 provided in the emergency brake piston 9.

By means of the outer diameters, which can be selected, and according to the seals 62 and 63, the emergency brake piston 9, which is designed in the form of a stepped piston, is provided with two working areas, their sizes differing as much as possible and which are chosen in accordance with the required transmission ratio. In doing so, it is readily possible to design the emergency brake piston in such a mannerthat emergency braking is triggered in the event of a pressure drop of 3 to 4 bars in the reservoir line. Other pressure levels can, of course, be selected.

A stop 57 is provided, which is securely attached to the housing and against which the emergency brake piston 9, which is designed as a stepped piston, is preloaded in via the pressure exerted on it from the reservoir line 15.

The dual-line trailer brake valve according to Figure 3 functions analogously to the embodiment according to Figure 1.

Claims (11)

1. Dual-line brake valve assembly with loaddependent operation including a relay valve having a control piston, an emergency brake device, a valve element, which is resiliently mounted and forms, together with a stationary housing edge, an inlet valve and, together with an extension of the control piston of the relay valve, forms an outlet valve, wherein the valve element is located inside the emergency brake device, the latter being in the form of an emergency brake piston and being fitted between the control piston and the inlet valve, freely floating on a control rod and preloaded against a stop, the latter being securely fixed to the housing.

2. Dual-line trailer brake valve assembly according to Claim 1, wherein the emergency brake piston is loaded with a spring (58) in order to preload ft in opposition to its direction of operation.

3. Dual-line trailer brake valve assembly according to Claim 1 or 2, wherein the emergency brake piston is stepped to have two portions with different external diameters, each portion being fitted with a seal, the space between the two seals being vented to atmosphere.

4. Dual-line trailer brake valve assembly according to Claim 3, wherein the stepped piston additionally possesses two portions with different internal diameters, each being fitted with a seal, the space between the two seals being connected to the atmosphere.

5. Dual-line trailer brake valve assembly according to Claim 3 or 4, wherein the stepped piston possesses an opening between an emergency brake chamber and a reservoir chamber of the assembly, a non-return valve being fitted in the opening.

6. Dual-line trailer brake valve assembly according to any preceding Claim having a balancing piston for providing progressive application of emergency brake pressure by the emergency brake piston.

7. Dual-line trailer brake valve assembly according to any one of claims 1 to 6, wherein the control piston of the relay valve is attached to the control rod, the latter being in the form of a tension rod, a balancing piston being fitted on an extension of the control piston, in a manner allowing it to floatfreely.

8. Dual-line trailer brake valve assembly according to any preceding Claim, wherein the control piston has two separate sections, for the purpose of achieving a very rapid build-up of pressure, the two sections being tied together via a spring.

9. Dual-line trailer brake valve assembly according to Claim 8, wherein reverse flow can be applid to the balancing piston only via a bypass valve.

10. Dual-line trailer brake valve assembly according to any preceding Claim, wherein the control rod is hollow and unite all the spaces which are to be connected to atmosphere.

11. Dual-line trailer brake valve assembly contructed substantially as herein described with reference to Figure 1, Figure 2 or Figure 3 of the accompanying drawings.