GB2079882A - Relay valves for trailer brakes - Google Patents

Abstract

A dual-line trailer brake valve with a relay action incorporates a charging valve 25, 26 by which the trailer reservoir 13 is charged from the supply line 3. The charging valve is supplied from an inlet chamber 22 and opens when pressure in the chamber reaches a predetermined value. Air flows to the inlet chamber from supply line 3 or from reservoir 13 through non-return valves 23, 31. The inlet chamber also supplies the relay valve elements 19, 20, 21, leading to brake actuator 5. <IMAGE>

Description

SPECIFICATION Dual-line trailer brake valve The invention relates to a dual-line trailer brake valve of the type mentioned in the precharacterising clause of Claim 1. The trailer brake valve can be intended for one circuit and can be used with a single function in a single-circuit system or with a double function in a dual-circuit system. The trailer brake valve can, however, also be a dual-circuit brake valve. As a rule, a trailer brake valve of this type should also have an emergency brake device.

A dual-line trailer brake valve of this type is known from German Patent Specification 2,326,708. It possesses a control piston which can be caused to respond via the brake line and the extension of which forms, with the valve body, the outlet valve. The control piston of the relay valve is subjected on its underside to the brake pressure deployed. Provided on the housing of the trailer brake valve is a first connection for the supply line which is brought from the supply coupling-head and in which, for example, a T-piece is provided, in the case of a dual-circuit system. A further connection to the trailer brake valve serves to provide a line from the inlet valve to the compressed-air reservoir vessel, and vice versa.In the known trailer brake valve, a pressuremaintenance safeguard is provided by locating an overflow valve between the line brought from the supply coupling-head and the inlet valve of the trailer brake valve. Such a pressure-maintenance safeguard protects against a defect in the line leading to the compressed-air reservoir vessel, specifically in such a way that, in the case of such a defect, the trailer brake valve of this one circuit fails, that is to say, braking can no longer be carried out, but the trailer brake valve of the other circuit can be operated according to the opening pressure of the overflow valve. If, on the other hand, a defect occurs in the supply line brought from the coupling-head to the one connection, then emergency braking operations are initiated.

A similarly designed trailer brake valve is known from German Patent Specification 2,342,542, which also shows a dual-circuit design of the trailer brake valve. Here, also, an overflow valve or two such overflow valves are arranged integrally, only the sequence between the valve body, supported via a spring, of the overflow valve and a non-return valve being interchanged in comparison with German Patent Specification 2,326,708.

German Patent Specification 1,555,608 makes known a dual-circuit dual-line braking system for trailer vehicles, twin single-circuit brake valves being arranged within the system and the supply line being brought via a T-piece to the two trailer brake valves. This has the advantage that, in the case of a defect in this supply line, emergency braking is triggered in both circuits. In the case of a defect in the brake line, emergency braking is triggered in both brake circuits, indirectly via the heavy goods vehicle. However, a disadvantage is that, in the case of a defect in one of the two supply circuits on the trailer, that is to say, between the respective inlet valve of the trailer brake valve and the respective associated compressed-air reservoir vessel, braking can no longer be carried out, and, indeed, neither an operational nor an emergency braking.The intact circuit automatically executes emergency braking operations, so that the axle in question runs hot.

The intact circuit cannot be resupplied; to that extent, it is a system which can be exhausted.

French Patent Specification 1,401,647 also shows a dual-circuit dual-line trailer brake system with two trailer brake valves each having a singlecircuit design. Here, there is located in the supply line to these two trailer brake valves, a dual-circuit protection valve, at which the branching of the supply line takes place. The location of this dualcircuit protection valve at this point has the advantage that, when a defect occurs in a supply circuit after this branching, the other supply circuit can be resupplied up to the opening pressure of the overflow valve in the dual-circuit protection valve. A disadvantage is that, in the case of a defect before the dual-circuit protection valve, no emergency braking occurs, since the closing pressure of the overflow valves is higher than the control pressure of the emergency brake. Such a system is, therefore, dangerous in this respect.

All these system have, among other things, also the disadvantage that they cannot be used in single-circuit trailer brake systems, because their effect is always such that, when a defect occurs, the respective trailer brake valve is separated from the connection to the trailer supply line and consequently becomes ineffective. Therefore, such a pressure-maintenance safeguard is pointless in a single-circuit system, since the effect of the respective single circuit is consequently no longer provided, despite the pressure-maintenance safeguard.

The object on which the invention is based is to develop further a trailer brake valve of the type described in the introduction -- with a singlecircuit or dual-circuit design - in such a way that, in the case of a defect in the line leading from the trailer brake valve to the compressed-air vessel, an emergency operation of the brake circuit in question can be maintained.

According to the invention, this is achieved, due to the fact that an overflow valve which permits return flow is provided, in or on the trailer brake valve, in the line leading from the inlet valve to the compressed-air reservoir vessel. Although overflow valves which permit return flow are known, nevertheless no valves of any kind have hitherto been located in the line between the inlet valve and the compressed-air reservoir vessel. The overflow valve which permits return flow can be arranged and integrated according to the invention in such a way that a known valve of this type is brought directly into communication with the connection on the housing of the trailer brake valve, to which the line leading to the reservoir vessel is conventionally connected.In this way, a line between the trailer brake valve and the overflow valve is avoided, so that, also, a defect cannot occur there. The defect is assumed to be in the line actually provided to the compressed-air reservoir vessel. However, it is also possible to install the overflow valve, which permits return flow, inside the trailer brake, valve, that is to say, to integrate it into the latter and to accommodate it in a common housing with the conventional components of the trailer brake valve. It is important that it must be an overflow valve which permits return flow, so that stored air can flow out of the compressed-air vessel to the inlet valve of the trailer brake valve even when the overflow valve has closed.

The overflow valve with its valve body having two partial working areas, on the one hand, and a non-return valve permitting the return flow, on the other hand, are arranged in parallel branches, so that the non-return valve lets compressed air through in the opposite direction when the overflow valve is closed. However, when the reservoir vessel is being filled, the non-return valve is closed, and the compressed air must flow via the opened valve body of the overflow valve.

In the case of constructional integration, the valve body of the overflow valve can be arranged coaxially to the control piston. It is also possible for the emergency brake piston of the emergency brake device to have a drawn-in margin which interacts with the valve body of the overflow valve.

Some exemplary embodiments of the invention are illustrated in the drawings and are described further below. In the drawings: Figure 1 shows a section through the dual-line trailer brake valve in a first embodiment, Figure 2 shows a section through the trailer brake valve in the design as a load-dependent brake force regulator, and Figure 3 shows a section through a dualcircuit trailer brake valve.

The trailer brake valve illustrated in Figure 1 has a housing 1 which appropriately consists of several parts. The housing 1 possesses a connection 2 for a supply line 3 which is brought from the supply coupling-head, a connection 4 for a line 6 leading to the brake cylinders 5, a connection 7 for a brake line 8 and a connection 9 for a hand brake valve 10, as well as a connection 11 for a line 12 leading to a compressed-air reservoir vessel 13. This trailer brake valve is designed intrinsically for a single-circuit trailer braking system. However, it can, of course, also be designed with a double function, so as to be an integral part of a dual-circuit braking system.

A control piston 14 is guided in the housing 1 in a leak-proof manner, so that this piston divides off a control chamber 15 and a balancing chamber 1 6 which is in permanent communication, by means of the connection 4, via the line 6 with the brake cylinders 5.

Also guided in a sliding and leak-proof manner in the housing 1 of the trailer brake valve is an emergency brake piston 1 7 which is preloaded relative to a spring 19, via the supply line 3, in an emergency brake chamber 1 8. The emergency brake piston possesses a drawn-in margin 1 9 which, together with the double valve body 20 suspended resiliently therein, forms an inlet valve 19,20.Provided on the control piston 14 is an extension 21 which, together with the double valve body 20, forms an outlet valve 20, 21. The double valve body 20 separates off, in the emergency brake piston 17, an inlet chamber 22 which can receive a flow via the supply line 3, thes connection 2, the emergency brake chamber 18 and an annular gaiter 23, which acts as a nonreturn valve, as well as a bore 24.

The emergency brake piston 1 7 has a further drawn-in margin 25 which, together with a valve body 26, supported on a spring 27 on the emergency brake piston 17, forms an overflow valve 25, 26. The force of the spring 26 is adjustable, so that the opening and the closing pressure can be adjusted by means of the spring force.Formed between the emergency brake piston 1 7 and the valve body 26 is an overflow chamber 28 which adjoins via a bore 29 an annular groove 30 which is in permanent communication with the connection 11 and, consequently, with the line 12 to the compressedair reservoir vessel 1 3. From the inlet chamber 22, the one branch of a line is formed via the opened overflow valve 25, 26, into the overflow chamber 28 and via the bore 29 into the annular groove 30.

A parallel line branch leads, in the opposite direction, from the annular groove 30, via an annular gaiter 31 which can act as a bypass in this direction, to the bore 24, and consequently to the inlet chamber 22. The annular gaiter 31 represents a non-return valve, namely the nonreturn valve of the overflow valve 25, 26, 31 which permits return flow. The connection 9 of the hand brake 10 also receives compressed air via the annular groove 30.

The trailer brake valve is vented, after the outlet valve 20, 21, through the hollow double valve body 20 into an outlet chamber 32 and thence through the perforated head of the emergency brake piston 17, via a flutter valve 33, into the atmosphere.

The trailer brake valve functions as follows: In the operating position, as illustrated in Figure 1, supply air has been brought via the supply line 3.

As a result of being applied to the emergency brake piston 1 7 in the emergency brake chamber 18, this supply air has preloaded the said piston against the force of the spring 1 9, the inlet valve 19, 20 being closed and the outlet valve 20, 21 < being opened. At the same time, compressed air has flowed past the annular gaiter 23 into the inlet chamber 22. The pressure in the inlet chamber 22; has still not reached the opening pressure of the overflow valve 25, 26, that is to say, the. valve body 26 is subjected to the supply air only on a first partial working area 34.Only when the pressure reaches the set opening pressure of the overflow valve 25, 26 does the overflow valve 25, 26 open, and the compressed air is now also additionally applied to a second partial working area 35 of the valve body 26. As a result, the overflow valve 25, 26 will open and remain opened. The supply pressure builds up in the reservoir vessel 13. The brake line 8 is vented.

If braking now takes place, compressed air is fed via the brake line 8 into the control chamber 1 5 and to the control piston 14, so that the latter is moved downwards. The outlet valve 20, 21 closes and the inlet valve 1 9, 20 is opened, so that the compressed air can pass out of the inlet chamber 22 via the balancing chamber 1 6, the connection 4 and the line 6 to the brake cylinders 5. More braking air will flow into the inlet chamber 22, depending on the pressure conditions, via the annular gaiter 23 and/or the annular gaiter 31.

If a defect occurs in the line 1 2 or on the compressed-air reservoir vessel 13, the pressure also drops in the overflow chamber 28 and, when the overflow valve 25, 26 is opened, also in the inlet chamber 22. This occurs until the set closing pressure of the overflow valve 25, 26 is reached, so that, after the overflow valve has closed, the pressure in the overflow chamber 28 is further reduced, but not the pressure in the inlet chamber 22. Via the supply line 3 and the annular gaiter 23, compressed air can, at any time, be resupplied to the inlet chamber 22, specifically up to the level of the opening pressure of the overflow valve 25, 26.

This means that, even in the case of a such a defect, braking operations can be carried out via the brake line as a control line, and in any desired number, the brake pressure deployed being merely limited or lowered according to the opening pressure of the overflow valve. On the other hand, however, in the case of an intact system, that is to say, no defect in the line 12, the functioning of the emergency brake device is ensured and is not prejudiced.

In the exemplary embodiment of Figure 2, parts having a similar function are provided with the same reference numerals. Here, the emergency brake piston 1 7 is not loaded on a spring, but via the pressure of the reservoir vessel 13. This pressure acts in the inlet chamber 22 before the inlet valve 19, 20, the drawn-in margin 19 being formed and provided here on the housing side.

Here, also, the extension 21 of the control piston 14 forms the outlet valve 20, 21 with the double valve body 20. A further special feature provided here is that the control piston 1 4 is surrounded by a leading piston 36 which acts, via a spring 37, over part of the range, so that, in this way, a sudden increase in pressure is effected, in order to compensate the efficiency of the wheel brake.

Furthermore, this trailer brake valve is also designed simultaneously as a brake force regulator working in a load-dependent manner, in that appropriate parts are arranged integrally in the housing 1. In this case, the extension 21 of the outlet valve 20, 21 is adjusted vertically via an actuating mechanism 38 controlled in a loaddependent manner. A separate balancing piston 39 is also provided, in addition to the control piston 14.

Here, the overflow valve which permits return flow is screwed into the connection 11, so that a corresponding piece of line is avoided between it and the inlet valve 1 9, 20 or the inlet chamber 22, with the result that, even there, there is no danger of a break in the line. The only piece of line is the line 12 to the compressed-air reservoir vessel 13, this line being connected after the overflow valve which permits return flow. Instead of screwing-in the overflow valve which permits return flow, this can, of course, also be cast, with its housing, simultaneously onto the housing 1 of the trailer brake valve. Here, again, the valve body 26' and the adjustable spring 27' are provided in the overflow valve which permits return flow.The two partial working areas 34' and 35' are provided on the valve body 26', the partial working area 34' which receives the flow first being located on the outside in this case. A non-return valve 31' is provided in a parallel line branch, so that compressed air can then pass out of the reservoir vessel 13, in the opposite direction, also into the inlet chamber 22, when the overflow valve 25', 26' is closed. In this embodiment also, more compressed air can flow in the inlet chamber 22 either via the supply line 3 and the annular gaiter 23, which can act as a bypass in one direction, on the emergency brake piston 1 7, or else out of the supply vessel 13.

The trailer brake valve illustrated in Figure 3 is intended for a dual-circuit system. Located in a sliding and leak-proof manner in the housing 1 is a combined supply and control piston 40 in which the two double valve bodies 20, 20' are suspended resiliently. The piston 40 possesses two drawn-in margins 1 9, 1 9' which, together with the double valve bodies 20, 20', form the two inlet valves 19, 20 and 19', 20' of the two circuits.

From the inlet valve 1 9, 20, the brake chamber 1 6 leads to the connection 4, from which the line 6 to the brake cylinder 5 of the first circuit is branched.

Analogously, the brake chamber 16' leads to the brake cylinder 5' of the second circuit. The inlet chambers 22 and 22' are formed at the inlet valves. Connectad after the connection 2 is a nonreturn valve 41 which leads via a bore 42 to the inlet chamber 22. For the other circuit, the supply line 3 is brought to the connection 2', at which there is likewise located a non-return valve 41' leading via a bore 42' to the inlet chamber 22'.

Arranged in a sliding and leak-proof manner in the combined piston 40 are the two valve bodies 26 and 26', to which drawn-in margins 27 and 27' on the piston 40 are assigned. Formed here, again, are overflow chambers 28 and 28' which lead via bores 29 and 29' to the connections 11 and 11', the lines 12 and 12' of which lead to the compressed-air reservoirs 13 and 13'. Annular gaiters 31 and 31', which can act as bypasses in one direction, and over which the inlet chambers 22 and 22' can be supplied with compressed air from the reservoir vessels 1 3 and 13', are again provided, parallel to each of these paths.

The balancing space 16' is divrded off by a fixed inserted wall 43. Here, the emergency brake piston 17 is mounted underneath this wall 43 and is supported on the spring 19. The emergency brake chamber 18 is supplied with compressed air via a bore 44 and a channel 45 from the connection 2', specifically before the non-return valve 41'.

Here, again, the first partial working areas 34 and 34' and the second partial working areas 35 and 35' are provided on the valve bodies 26 and 26' of the two overflow valves 25, 26 and 25', 26'. The valve bodies 26 and 26' are here supported against one another via a common spring 27'.

The mode of action of this dual-circuit trailer brake valve is analogous and is evident to a person skilled in the art. Here, also, overflow valves 25,26 or 25', 26' which permit return flow 31 or 31' are provided for the first and the second circuit. Functioning is analogous to that of the exemplary embodiment according to Figure 1.

Despite the arrangement of only one emergency piston 17, emergency braking is deployed in both circuits in the case of a defect. On the other hand, however, emergency operation can remain maintained when a defect occurs in the line 12 or the line 12'.

Claims (4)

1. Dual-line trailer brake valve with a relay action and, if appropriate, an emergency brake device, with a resiliently suspended valve body which forms, with one edge, an inlet valve and, with an extension of a control piston of the relay valve, an outlet valve, and with a connection for a supply line brought from a supply coupling-head and with a further connection for a line leading from the inlet valve to a compressed-air reservoi'r vessel, characterised in that an overflow valve which permits return flow (25,26,31 or 25', 26', 31') is provided, in or on the trailer brake valve, i the line (12 or 12') leading from the inlet valve (19, 20 or 19', 20') to the compressed-air reservoir vessel (13 or 13').

2. Dual-line trailer brake valve according to Claim 1, characterised in that, on the one hand, the overflow valve (25, 26 or 25', 26') with its valve body (26, 26') having two partial working areas (34, 35 or 34', 35') and, on the other hand, a non-return valve (31 or 31') permitting the return flow are arranged in parallel branches.

3. Dual-line trailer brake valve according to Claims 1 and 2, characterised in that the valve body (25, 25') of the overflow valve is arranged coaxially to the control piston (14).

4. A dual-line trailer brake valve according to Claim 3, characterised in that the emergency brake piston (17) of the emergency brake device has a drawn-in margin (25) which interacts with the valve body (26) of the overflow valve.