GB2074680A

GB2074680A - Overload protection relay valve

Info

Publication number: GB2074680A
Application number: GB8112689A
Authority: GB
Original assignee: Graubremse GmbH
Current assignee: Graubremse GmbH
Priority date: 1980-04-26
Filing date: 1981-04-24
Publication date: 1981-11-04
Also published as: IT1137462B; FR2482029A1; FR2482029B1; ES502077A0; YU107681A; IT8121373A0; GB2074680B; DE3016200C2; DE3016200A1; ES8202740A1

Abstract

Overload protection relay valve (12) for combined service and spring-loaded brakes of vehicles, in particular road vehicles, comprising a pressure storage chamber (36), a brake chamber (33), and a first control chamber (27) and a second control chamber (30), it being possible for compressed air to be admitted to the pressure storage chamber (36) from a storage reservoir (6), for the pressure for releasing the spring-loaded brake to be admitted to the brake chamber 33), for the braking pressure of the service brake to be admitted to one control chamber (30) and for the control pressure of the spring- loaded brake to be admitted to the other control (27), and a relay piston (22, 22', 22''), which is driven by the pressure in one of the control chambers and which actuates a double valve body (34), by which the brake chamber (33) can be connected either to the pressure storage chamber (36) or to the atmosphere, wherein, in addition to its partial working area (26) associated with one control chamber (27), the relay piston (22, 22' and 22'') comprises on the same side a second partial working area (29) which is associated with the other control chamber (30). <IMAGE>

Description

SPECIFICATION Overload protection relay valve The invention is based on an overload protection relay valve of the type indicated in the pre-characterising section of Claim 1. An overload protection relay valve of this is known from German Auslegeschrift 1,814,722. Two relay pistons are provided in an axial tandem arrangement, one control chamber of which pistons can be controlled via the service brake and the other control chamber of which can be controlled via the control pressure of the hand brake valve. Since the service brake performs a positive operation and the auxiliary brake and/or parking brake a negative operation, addition of the control pressures is avoided when the two brakes are actuated simultaneously. This prevents the maximum permitted brake power of the two brakes from being exceeded.The two relay pistons, which are in an axial tandem arrangement and are guided in a common cylinder, comprise various working areas which are of different sizes.

These differing sizes occur automatically as a result of the design of the arrangement. Since the control chamber between the two relay pistons drives firstly the rearside of one relay piston and, secondly the front side of the other relay piston, these two relay pistons must have the same external diameter. However, the rear side of the lower relay piston, the partial working area of which adjoins the brake chamber, is designed smaller because the circular surface of the outlet seat of the double valve body is effectively omitted.

Therefore an intensification of pressure is incorporated in this connection. For the purpose of controlling the control chamber between the two relay pistons, the upper relay piston loossesses a seal so that its working area pro > ;ided on the front side is smaller than the working area on the front side of the lower relay piston. This means finally that the partial working areas which are driven by the two control pressures are unequal in size so that there is a different intensification or reduction with respect to each control pressure. The control pressures are thus subjected to unequal treatment, which can lead to difficulties with the release of the spring-loaded brake.

The object underlying the invention is to develop the overload protection relay valve of the type described in the introduction so that there is complete freedom of design with respect to the intensification or reduction of pressures on the inlet side in relation to the pressure on the outlet side. It should therefore be possible, in particular, for the partial working areas which are associated with the two control chambers to be of equal size and/or for the pressure to be adapted to the release pressure, which is determined by the springloaded accumulator, by intensification or reduction.

This is achieved in accordance with the invention by the features of the characterising section in combination with the features of the pre-characterising section of Claim 1. This makes it possible for the partial working areas to be designed independently of one another, and in particular to be of equal size so that the two control pressures are treated equally.

These two partial working areas can also be selected independently of the partial working areas driven via the brake chamber so that any desired pressure intensification and reduction can be achieved. In contrast to prior art, movement of the relay piston in the subject of the application results whenever the auxiliary and/or parking brake is actuated and whenever the service brake is actuated so that there is virtually no danger of this piston jamming.

Moreover, the stress on the seals between the various partial working areas is more favourable than in the prior art.

According to Claim 2 it is possible for this third partial working area (31) to be dimensioned independently of the other two partial working areas (26, 29) on the front side of the relay piston. In addition, there is obtained the special advantage that the intermediate chamber (46), which is formed in this manner, is connected to the atmosphere, the control chamber (30) which is nearest to the brake chamber (33) being separated from the said brake chamber (33) by the two seals (45, 25). Since the intermediate chamber is always connected to the atmosphere, slight leakages at the two seals (45, 25) mentioned cannot have such an adverse effect as when only one seal is provided between the control chamber (30) and the brake chamber (33).

According to Claim 3 a pressure intensification of 1:1 is achieved.

According to Claim 4 it is possible for the relay piston to be designed in one piece. In the case of the relay piston being part of multi-part design according to Claim 5 or 6, the number of seals can be increased. According to Claim 7 a favourable method of bleeding is provided. According to Claim 8 the air which flows into and out of the intermediate chamber is used as a means of damping the movements of the relay piston. This counteracts in particular the chatter of the relay piston.

Exemplary embodiments of the invention are described below. In the drawing: Figure 1 shows a circuit of the combined service brake and spring-loaded brake system with the overload protection relay valve, Figure 2 shows a half section of a first embodiment of the overload protection relay valve, Figure 3 shows a half section of a further embodiment of the overload protection relay valve, and Figure 4 shows a section through a third embodiment of the overload protection relay valve.

The brake system shown in Fig. 1 has a compressor 1, a pressure regulator 2, a fourcircuit safety valve 3, three air reservoirs 4, 5, 6, a dual-circuit brake valve 7 for the service brake, a handbake valve 8 for the auxiliary brake and/or parking brake, a trailer control valve 9, an automatically load-sensitive brake pressure regulator 1 0, a test valve 11, and overload protection relay valve 12, a dia phragm-type cylinder . 3 for the front axle, a diaphragm-type/spring-loaded brake cylinder 1 4 for the rear axle and a coupling head 1 5 for the supply line and a coupling head 1 6 for the brake line.The individual units are connected to one another by the illustrated connecting lines, a supply line 1 7 from the compressed air storage reservoir 6 of the third circuit, a control line 18 from the handbrake valve 8 and a control line 1 9 from the dualcircuit brake valve 7 leading to the overload protection relay valve 1 2. From the overload protection relay valve 12, the two lines 20 lead to the spring-loaded part of each combined diaphragm-type/spring-loaded brake cylinder 14. It goes without saying that the auxiliary brake and/or parking brake operates indirectly with the aid of the handbrake valve 8, that is a braking action is initiated in the combined diaphragm-type/spring-loaded brake cylinder 14 by bleeding the line 18.On the other hand, the service brake operates with a positive control signal; the springloaded part is released or kept in the released position by an increase of pressure in the line 1 9 which leads finally to a braking action via the diaphragm part of the combined diaphragm-type/spring-loaded brake cylinder 1 4.

The overload protection relay valve 1 2 according to Fig. 2 possesses a housing 21 in which a relay piston 22 is slidably mounted.

The relay piston 22 is designed in one piece, and carries at its lower end an outlet seat 23.

Associated with the piston are the seals 24 and 25. On the front side of the relay piston 22, the first partial working area 26 is enclosed in the form of a circular surface by the seal 24, and defines the first control chamber 27 which is permanently connected to the connecting branch 28 to which, for example, the hand brake valve 8 is connected via the line 1 8. On the same front side of the relay piston 22 there is provided between the seals 24 and 25 the second partial working area 29, which is in the form of a circular surface and which defines the second control chamber 30 to which the line 1 9 or the dual-circuit brake valve 7 is connected by its control line outlet.In this case the line 1 9 leads to a connecting branch 51 which forms a permanent connection to the second control chamber 1 3 by means of a channel 52. On its rear side the relay piston 22 has a third partial working area 31 and a fourth partial working area 32 which, as a result of a seal having been removed, are permanently connected to one another and define a brake chamber 33.

The third partial working area 31 is a circular face which is formed as a result of the difference between the diameters of the removed seal and of the outlet seat 23. Likewise, the fourth partial working area 32 is also a circuit lar face corresponding to the difference between the diameters of the seal 25 and of the removed seal. The geometric dimensions can be selected, for example, so that the first partial working area 26 and the second partial working area 29 are of equal size, whilst the partial working areas 31 and 32, which are driven via the brake chamber 33, are smaller by the circular area of the outlet seat 23 than the sum of the partial working areas 26 and 29. In this case a pressure reduction of approximately 1:2 is achieved.

Spring-mounted in the housing 21 is a double valve body 34 which combines with a drawn-in edge 35 of the housing to form the inlet valve 34, 35 and with the outlet valve 23 to form the outlet valve 34, 23. A pressure storage chamber 36 is permanently connected via the branch 37 to the line 1 7 leading to the compressed air storage reservoir 6. The double valve body 34 is of hollow form and has mounted thereon a sealing cover 38 through which the removed air passes into the atmosphere via a flap valve 39. The double valve body 34 is supported on the cover 38 via a spring 40. On the other hand, the brake chamber 33 leads to one or a plurality of connecting branches 41, from which the lines 20 branch and lead to the spring-loaded part of the diaphragm-type/spring-loaded brake cylinder 14.In the cover 38 there is provided a compensator chamber 42 which is permanently connected to the brake chamber 33 via bores 43 and a channel 44.

The compensator chamber 42 serves to relieve the pressure on the double valve body 34. The difference in area between the inlet seat, which is formed by the projecting edge 35 of the housing, and the outlet seat 23- is compensated or overcompensated.

In the embodiment of the overload protection relay valve according to Fig. 3, a seal 45 is fitted into the relay piston 22', thereby separating the third partial working area 31 from the fourth partial working area 32. In this case an intermediate chamber 46, which is permanently connected to the atmosphere via a channel 47 and a jet 48 inserted therein, is separated from the brake chamber 33. In the embodiment accoding to Fig. 3 the geometrical dimensions can be selected so that the first partial working area 26, the second partial working area 29 and the third partial working area 31 are of exactly the same size. The relay piston 22' can in this case be divided radially and provided with an annular piston 22" which carries a further seal 49. The annular piston 22" bears against the remaining part of the relay piston 22' via the stop 50.

In the embodiment of the overload protection relay valve 1 2 according to Fig. 4, the relay piston is divided axially so that in this case the piston part 22"" is a working corrlponent part of the relay piston 22"'. It goes without saying that the combined use of the radially divided arrangement according to Fig.

3 and the axially divided arrangement accotd- ing to Fig. 4 is also possible. When the seals 24 and 25 illustrated in Fig. 4 lie on the same diameter, then, for example, the first partial working area 26 and the second partial working area 29 can be of the same size and the third partial working area 31 can be comparatively smaller by the area of the outlet seat 23. Thus the two control pressures are treated equally and a slight pressure intensification is incorporated.

The overload protection relay valve 1 2 according to Figs. 2 to 4 are shown in an airfree state. This means that the handbrake valve 8 is switched to bleeding of the line 1 8 so that the spring-loaded part of the combined diaphragm-type/spring-loaded brake cylinder 14 has the effect of a parking brake. To release the parking brake, the hand brake valve 8 is switched over so that air is admitted to the first control chamber 27 via the line 1 8. The relay piston 22 or 22' and 22" or 22"' and 22""' thus moves downwards.The outlet valve 34, 32 is closed and the inlet valve 34, 35 opened so that the stored pressure formed in the pressure storage chamber 36 can pass into the brake chamber 33 and, from there, via the line 20 to the combined spring-loaded brake cylinders 1 4 so that the latter are released. The release pressure on the outlet side acts at the same time upon the third partial working area 31 or, as shown in 2, 2, on the third and fourth partial working areas 31 and 32. As a result of the pressure intensification selected in the embodiment according to Fig. 2, it is possible, for example, for the pressure to be accurately adapted to the release power, which is predetermined by the spring-loaded part of the combined brake cylinder, or to the release pressure.

If operation of the service brake is initiated when the parking brake is released, compressed air passes through the line 19, connecting branch 51, and the channel 52 into the second control chamber 30. As the auxiliary brake and/or parking brake had been previously released, no further reaction takes place in this case.

If, on the other hand, the auxiliary brake and/or parking brake is actuated to produce a braking action when the service brake has been released, then the first control chamber 27 has also been bled so that finally the brake chamber 33, having been bled, is also connected to the atmosphere. Consequently, the preloaded spring of the auxiliary and/or parkirig brake can have a braking effect. If the service brake is now also actuated, that is if cOntrol pressure is conveyed to the second control chamber 30, then the relay piston 22 or its parts 22' and 22" or 22"' and 22"" also move downwards so that the outlet valve 24, 23 is closed and the inlet valve 34, 35 is opened. This means that brake release pres stire for the spring-loaded part is in turn conveyed from the outlet side into the brake chamber 33 so that the auxiliary and/or park ihg brake is released. Addition of brake pres sores does not occur therefore on the combined spring-loaded brake cylinder 1 4. It goes without saying that addition of the brake pressures does not occur on the spring-loaded brake cylinder, even when the actuating sequence is reversed, that is when a braking action is first to be initiated via the service brake and an additional braking action is to be subsequently initiated via the auxiliary brake.

Claims

1. Overload protection relay valve (12) for combined service and spring-loaded brakes of vehicles, in particular road vehicles, comprising a pressure storage chamber (36), a brake chamber (33), and a first control chamber (27) and a second control chamber (30), it being possible for compressed air to be admitted to the pressure storage chamber (36) from a storage reservoir (6), for the pressure for releasing the spring-loaded brake to be admitted to the brake chamber (33), for the braking pressure of the service brake to be admitted to one control chamber (30) and for the control pressure of the spring-loaded brake to be admitted to the other control chamber (27), and a relay piston, which is driven by the pressure in one of the control chambers and which actuates a double valve body (34), by which the brake chamber (33) can be connected either to the pressure storage chamber (36) or to the atmosphere, characterised in that, in addition to its partial working area (26) associated with one control chamber (27), the relay piston (22; 22' and 22"; 22"' and 22"") comprises on the same side a second partial working area (29) which is associated with the other control chamber (30).

2. Overload protection relay valve according to Claim 1, characterised in that, on its rear side facing the brake chamber (33), the relay piston (22' and 22"; 22"' and 22"") comprises two partial working areas(31, 32) separated by a seal (45), it being possible for one (31) of these working areas to be driven by the pressure in the brake chamber (33) and for the other (32) to be driven by the atmosphere. (Fig. 3 or 4)

3. Overload protection relay valve according to Claims 1 and 2, characterised in that the two partial working areas (26, 29) on the front side and the partial working area (31), which is driven by the presssure in the brake chamber (33), are each designed to be equal in size.

4. Overload protection relay valve according to Claims 1 and 2, characterised in that the front and rear sides of the relay piston (22' and 22" or 22"' and 22"") are each in the form of a stop piston. (Fig. 3 or 4)

5. Overload protection relay valve according to one or more of Claims 1 to 4, characterised in that the relay piston (22' and 22" or 22"' and 22"") consists of two or more parts which are supported on one another with the aid of stops (50, 50'). (Fig. 3 or 4)

6. Overload protection relay valve according to Claim 5, characterised in that an annular piston (22") is provided on the front side of the relay piston (22') to form the second partial working area (29). (Fig. 3)

7. Overload protection relay valve according to Claim 5, characterised in that the relay piston (22"' and 22"") is divided in the axial direction, and that the part (22"") of the piston facing the brake chamber (33) is of the hollow form for bleeding an intermediate chamber (46) associated with the fourth partial working area (32). (Fig. 4)

8. Overload protection relay valve according to Claim 6 or 7, characterised in that a jet (48) is provided in the channel (47) formed by the hollow part of the piston. (Fig. 3 or 4)

9. An overload protection relay valve for combined service and spring-loaded brakes of vehicles, substantially as herein described with reference to Figs. 2, 3 or 4 of the accompanying drawings.