GB1563144A - Multi-circuit protection valve - Google Patents

Description

(54) MIJLTI-CIRCUIT PROTECTION VALVE (77) We, WABCO WESTINGHOUSE GMBH a German Company, of 3000 Hannover 91, Postfach 91 1280, German Federal Republic, 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 multicircuit protection valve means for multi-circuit brake systems, particularly for motor vehicles.

Multicircuit protection valve means have the object of maintaining the braking pressure in the remaining intact circuit or circuits in the event of failure of one brake circuit or several brake circuits.

In the following, the expression "protection valve" is intended to mean a valve which presents a predetermined pressure gradient in a fluid pressure feed line up to a given set pressure downstream thereof whereupon it "opens" and ceases to present such gradient.

When a number of such valves are used in "closing" lines to a number of reservoirs, failure of the pressure in one reservoir will therefore still leave the or each other reservoir chargeable to a pressure corresponding to the set pressure of the protection valve of the failed circuit.

In, for example, a four-circuit protection valve means, two circuits I and II are allocated to the two service brake circuits of the brake system, circuit III supplies the auxiliary brake system and a trailer brake system with compressed air whilst circuit IV safeguards a so called ancillary load.

In the German Auslegeschrift No. 2005 727 is disclosed a threecircuit protection valve means which is similar to the above mentioned four-circuit protection valve means both in construction and operation, whereby the circuits I to III supply the same brake circuits as above.Both the four-circuit protection valve means and the three-circuit protection valve means are designed such, that the pressurisation of circuits I and II is given precedence, i.e. the circuits III and IV or circuit III are pressurised with compressed air only after one of the service brake circuits has attained the predetermined supply or storage pressure, which means that the vehicle can only be put into motion after a pressure for safeguarding proper braking has been built up reliably in at least one of the service brake circuits and the pressure level in the auxiliary or ancillary brake circuit is adequately high to release the spring brake actuators associated therewith.

These protection valve means exhibit however the drawback that, as the result of adjustment and manufacturing tolerances, it is not possible to guarantee that the intact line circuits of the brake system can be pressured (starting) from atmospheric pressure when one line circuit is faulty, because control of the shut-off members of the protection valves on the protection valve means are subject to compressed air pressure from the pressure supply side as well as from the line circuit side.

Accordingly the opening and closing pressures not only differ from one another but the opening pressure are also dependent on the pressure conditions prevailing on the line circuit side.

If, for example, the relief valve for the defective circuit has the lowest opening pressure, the case may arise, in which none of the intact circuits is further pressurised because the compressed air escapes to atmosphere through the valve in the defective circuit.

The German Offenlegungsschrift No.

2206975 discloses three- and fourcircuk protection valve means in which this drawback is removed by means which, in the event of failure of one circuit, enable charging from 0 bar to be effected in the intact circuits by the by-passing of every protection valve with a by-pass line in which are arranged in series a throttle and a non-return valve opening towards the line circuit Since however in the case of such a protection valve means all circuits are connected in parallel, the provision of preferential pressurisation of one of the service circuits gives rise to the need for an expensive design feature comprising an additional shut-off valve in the or each of the by-pass lines of the circuit(s) to be pressurised later which additional shutoff valve opens depending upon the opening of the relief valve in the (or each) other line circuit.

It is thus desirable to provide a three-circuit or four-circuit protection valve means which combines the positive characteristics of known valve means, namely the preferential pressurising of the circuits I and II and the pressurising from 0 bar of the intact circuit in the event of failure of one circuit, and which meets the conditions for such preferential charging without requiring the expensive provision of additional shut-off valves.

According to one aspect of this invention there is provided multi-circuit protection valve means for a multi-circuit, pressure-medium operable braking system, particularly for a motor vehicle, comprising: a pressure-medium inlet for connection to a pressure-medium source; first and second pressure-medium outlets for connection respectively to first and second service braking circuits of the system; a third pressure-medium outlet for connec tion to an auxiliary brake and/or ancillary load circuit of the system; first and second protection valves arranged to permit pressure-medium flow from the inlet to said first and second outlets respectively when a predetermined pressure difference across the respective valve is exceeded;; first and second by-pass passages across the first and second valves respectively, each by-pass passage including in series a throttle and a non-return valve; a connecting passage interconnecting the first and second outlets and including the first and second non-return valves; another passage, leading to said third outlet from said connecting passage between the said first and second non-return valves, and including a third protection valve arranged to permit pressure-medium flow therethrough to said third outlet when a predetermined pressure difference across said third valve is exceeded; and a third by-pass passage across said third protection valve between the inlet and said third outlet, the third by-pass passage including in series a throttle and a non-return valve.

By way of example, an embodiment of this invention will now be described with reference to the accompanying drawing which is a schematic block diagram of a protection valve according to this invention.

As a basis for the illustrated embodiment a three-circuit or four-circuit protection valve of series design is taken, i.e. the third circuit or the third and fourth circuit is arranged behind the two parallel first circuits which are the service brake circuits, whereby, even with poor adjustment and manufacturing tolerances, the circuits disposed behind the service brake circuit and having no additional circuit members, will always be pressured after at least one of the first two circuits has attained a fixed pressure level. Such a three-circuit protection valve has been disclosed in German Auslegeschrift No. 2005 727.

The four-circuit protection valve means illustrated diagrammatically in Fig. 1 is encIosed by a housing represented by the chain-dotted outline and is connected through a main supply line 2 with an air compressor (not shown).

A main closing line 3a connected with the main supply line 2 runs through a protection valve 4 and a main closing line 3b to the first load or service circuit I, and a main closing line 5a likewise connected to the main line 2 runs through a second protection valve 6 and a main closing line 5b to the second load or service circuit II. A main closing line 7a branches off from the main closing line 3b and runs through a third protection valve 8 and a main closing line 7b to the third load circuit III. A main closing line 9a branches off from the main closing line 5b and runs through a fourth protection valve 10 and a main closing line 9b to provide a connection with the fourth load circuit IV.By means of the line 11 which the two main closing lines 7a and 9a all load circuits are connected with one another, i.e.

circuits I and II are interconnected by line 11, circuits I and III are interconnected (other than by line 11), circuits II and IV are interconnected (other than by line 11), circuits III and IV are interconnected by line 11, and the circuits I and IV and the circuits I and III are also connected to one another (via line 11).

Non-return valves 12 and 13 are inserted in the main closing lines 7a and 9a respectively between the circuits 1 and III and the circuits II and IV.

The protection valves 4, 6, 8 and 10 are by-passed by by-pass lines 14, 15, 16 and 17, the by-pass lines 14 and 16 branching off the main closing line 3a and joining the main closing lines 3b and 7b respectively (leading to the load circuits I and III) behind the protection valves 4 and 8, and the by-pass lines 15 and 17 branching off the main closing line 5a and joining the main closing lines 5b and 9b respectively (leading to the load circuits II and IV) behind the protection valves 6 and 10. In each of the by-pass lines 14, 15, 16 and 17 there are arranged in series one throttle 18, 19, 20 and 21 respectively and one non-return valve 22, 23, 24 and 25 respectively, each non-return valve being open towards the load circuits.

In normal operation, compressed air from the air compressor entering the protection valve means 1 through the main line 2 passes through the main closing lines 3a and 5a and, after attaining the respective pressures or safe pressures, valves 4 and 6 are opened by the pressure building up downstream of them in the main closing lines 3b and 5b. This pressure build up in the lines 3b and 5b is generated because part of the compressed air flows through the by-pass lines 14 and 15 into the respective main closing lines 3b and Sb until valves 4 and 6 open.

The compressed air flows on through the opened valves 4 and 6 through the main closing lines 3b and 5b into the load or service circuits I and II.

The compressed air reaching simultaneously the main closing lines 7a and 9a branching off the main closing lines 3b and 5b flows through the main closing lines 7b and 9b into the load circuits III and IV after the protection valves 8 and 10 have been opened, whereby the opening is likewise supported by the pressure building up through the by-pass lines 16 and 17 behind the valves 8 and 10.

If, for example, a service brake circuit connected to circuit I were to fail due to a leak, replenishment compressed air fed from the air compressor will initially escape into the leaking circuit. The pressure in the second intact service brake circuit connected to circuit II drops simultaneously to the preset opening pressure of the faulty circuit. If the pressure in the intact service brake circuit is subsequently reduced by withdrawal of air the pressure in it will be made up by the opening pressure of the faulty circuit I. In contrast, the pressure in circuits III and IV is initially maintained at its original level by th nonreturn-valves 24 and 25.Should the pressure in one of the circuits III or IV fall below the preset opening pressure of the faulty circuit as the result of a withdrawal of air, the circuit is replenished until a pressure equalling the preset opening pressures of the faulty circuit is attained.

The safeguarding of the pressures in circuits I, III and IV in the event of failure of circuit II proceeds in the same way.

In the event of failure e.g. of circuit III the pressure in the circuits I, II and IV will fall to the preset opening pressure of the faulty circuit and will be maintained at that level. If air is withdrawn from circuits I, II and IV precipitating a pressure drop, these circuits will be re-pressurised to the preset opening pressure of the faulty circuit.

The safeguarding of the pressure in the circuits I, II and III in the event of failure of circuit IV proceeds in the same way.

In the event of the circuit pressure of I or II falling below the opening pressure of the valves 4 and 6, the intact circuit is safeguarded against the faulty or defective circuit by the non-return valves 12 and 13.

In the event of failure of one of the circuits I and II the arrangement of the non-return valves 12 and 13 prevents compressed air from escaping from the parallel intact circuit through the lines 7a-1 1-9a or 9a-1 1-7a through the defective circuit.

The description of the mode of operation shows clearly that precedence is normally given to the pressurisation of the circuits I and II by the series circuit design even without provision of an additional circuit member specifically to provide this function. Only after compressed air flows through the opened valves 4 or 6 into the service circuits I or II, where the service brake pressure is built up, is it possible to build up a pressure which is sufficient to open the valves 8 and 10 so that the circuits III and IV will be pressurised after the circuits I and/or II.

Apart from this functional aspect of the protection valve 1, which is met by the means described above, the valve fulfils another need arising from the various adjustment and manufacturing tolerances and relating to the pressurising of the intact circuit from 0 bar in the event of another circuit failure, in that a by-pass line comprising series-connected throttle and non-return valves is provided in respect of each protection valve.

The provision of these by-pass lines allows the uniform and accelerated pressurising from atmospheric pressure of all load circuits. This is because the compressed air entering the load circuits aids the opening of the protection valves. In the event of a load circuit failing due to leakage, its protection valve closes as the result of the drop in pressure to atmospheric pressure on the load side until the intact load circuits are pressurised up to the opening pressure of the valve in the defective circuit independent from the initial pressure prevaiilng in the intact load circuits. Since only a small amount of air is able to escape during this period through the by-pass lines of the defective circuit there is no major energy loss. The pressurising of the intact circuits is ensured even on simultaneous leakages in several circuits.

The diagrammatically illustrated four-circuit protection valve means 1 according to the invention thus combines the advantages of the two protection valve arrangements referred to in the descriptive introduction as representative of the prior state of the art, and in its function of protecting the compressed air brake system and the associated ancillary load compressed air system does not exhibit the described drawbacks characterising said two prior art protection valves.

The descriptions of said embodiment can apply analogously also to a three-circuit protection valve arrangement and to a pro tection valve with more than four circuits.

WHAT WE CLAIM IS:- 1. Multi-circuit protection valve means for a multi-circuit, pressure-medium operable braking system, particularly for a motor vehicle, comprising: a pressure-medium inlet for connection to a pressure-medium source; first and second pressure-medium outlets for

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

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. pressure build up in the lines 3b and 5b is generated because part of the compressed air flows through the by-pass lines 14 and 15 into the respective main closing lines 3b and Sb until valves 4 and 6 open. The compressed air flows on through the opened valves 4 and 6 through the main closing lines 3b and 5b into the load or service circuits I and II. The compressed air reaching simultaneously the main closing lines 7a and 9a branching off the main closing lines 3b and 5b flows through the main closing lines 7b and 9b into the load circuits III and IV after the protection valves 8 and 10 have been opened, whereby the opening is likewise supported by the pressure building up through the by-pass lines 16 and 17 behind the valves 8 and 10. If, for example, a service brake circuit connected to circuit I were to fail due to a leak, replenishment compressed air fed from the air compressor will initially escape into the leaking circuit. The pressure in the second intact service brake circuit connected to circuit II drops simultaneously to the preset opening pressure of the faulty circuit. If the pressure in the intact service brake circuit is subsequently reduced by withdrawal of air the pressure in it will be made up by the opening pressure of the faulty circuit I. In contrast, the pressure in circuits III and IV is initially maintained at its original level by th nonreturn-valves 24 and 25.Should the pressure in one of the circuits III or IV fall below the preset opening pressure of the faulty circuit as the result of a withdrawal of air, the circuit is replenished until a pressure equalling the preset opening pressures of the faulty circuit is attained. The safeguarding of the pressures in circuits I, III and IV in the event of failure of circuit II proceeds in the same way. In the event of failure e.g. of circuit III the pressure in the circuits I, II and IV will fall to the preset opening pressure of the faulty circuit and will be maintained at that level. If air is withdrawn from circuits I, II and IV precipitating a pressure drop, these circuits will be re-pressurised to the preset opening pressure of the faulty circuit. The safeguarding of the pressure in the circuits I, II and III in the event of failure of circuit IV proceeds in the same way. In the event of the circuit pressure of I or II falling below the opening pressure of the valves 4 and 6, the intact circuit is safeguarded against the faulty or defective circuit by the non-return valves 12 and 13. In the event of failure of one of the circuits I and II the arrangement of the non-return valves 12 and 13 prevents compressed air from escaping from the parallel intact circuit through the lines 7a-1 1-9a or 9a-1 1-7a through the defective circuit. The description of the mode of operation shows clearly that precedence is normally given to the pressurisation of the circuits I and II by the series circuit design even without provision of an additional circuit member specifically to provide this function. Only after compressed air flows through the opened valves 4 or 6 into the service circuits I or II, where the service brake pressure is built up, is it possible to build up a pressure which is sufficient to open the valves 8 and 10 so that the circuits III and IV will be pressurised after the circuits I and/or II. Apart from this functional aspect of the protection valve 1, which is met by the means described above, the valve fulfils another need arising from the various adjustment and manufacturing tolerances and relating to the pressurising of the intact circuit from 0 bar in the event of another circuit failure, in that a by-pass line comprising series-connected throttle and non-return valves is provided in respect of each protection valve. The provision of these by-pass lines allows the uniform and accelerated pressurising from atmospheric pressure of all load circuits. This is because the compressed air entering the load circuits aids the opening of the protection valves. In the event of a load circuit failing due to leakage, its protection valve closes as the result of the drop in pressure to atmospheric pressure on the load side until the intact load circuits are pressurised up to the opening pressure of the valve in the defective circuit independent from the initial pressure prevaiilng in the intact load circuits. Since only a small amount of air is able to escape during this period through the by-pass lines of the defective circuit there is no major energy loss. The pressurising of the intact circuits is ensured even on simultaneous leakages in several circuits. The diagrammatically illustrated four-circuit protection valve means 1 according to the invention thus combines the advantages of the two protection valve arrangements referred to in the descriptive introduction as representative of the prior state of the art, and in its function of protecting the compressed air brake system and the associated ancillary load compressed air system does not exhibit the described drawbacks characterising said two prior art protection valves. The descriptions of said embodiment can apply analogously also to a three-circuit protection valve arrangement and to a pro tection valve with more than four circuits. WHAT WE CLAIM IS:-

1. Multi-circuit protection valve means for a multi-circuit, pressure-medium operable braking system, particularly for a motor vehicle, comprising: a pressure-medium inlet for connection to a pressure-medium source; first and second pressure-medium outlets for

connection respectively to first and second service braking circuits of the system; a third pressure-medium outlet for connecuon to an auxiliary brake and/or ancillary load circuit of the system; first and second protection valves arranged to permit pressure-medium flow therethrough from the inlet to said first and second outlets respectively when a predetermined pressure difference across the respective valve is exceeded; first and second by-pass passages across the first and second valves respectively, each by-pass passage including in series a throttle and a non-return valve; a connecting passage interconnecting the first and second outlets and including first and second non-return valves;; another passage, leading to said third outlet from said connecting passage between the said first and second non-return valves, and inciud- ing a third protection valve arranged to permit pressure-medium flow therethrough to said third outlet when a predetermined pressure difference across the said third valve is exceeded; and a third by-pass passage across said third protection valve between the inlet and said third outlet, the third by-pass passage including in series a throttle and a non-return valve.

2. Protection valve means according to Claim 1, wherein at least one further pressuremedium outlet is provided for connection to a further auxiliary brake and/or ancillary load circuit of the system, the or each further outlet has a further passage leading therefrom to said connecting passage between the first and non-return valves, the or each said further passage includes a further protection valve arranged to permit pressure-medium flow therethrough to the associated further outlet when a predetermined pressure difference across that further protection valve is exceeded, and wherein the or each said further outlet is connected to the inlet by an associated further by-pass passage including in series a throttle valve and a non-return valve.

3. Protection valve means according to Claim 1 or Claim 2, comprising: a number, one or more, of other pressure-medium outlets for connection to a like number of other service braking circuits respectively; a like number of other protection valves each arranged to permit pressure-medium flow therethrough between the inlet and the or an associated one of the said other outlets when a predetermined pressure difference across the respective protection valve is exceeded; a like number of other by-pass passages across the or an associated one of the said other relief valves respectively, the or each said other by-pass passage including in series a throttle and a non-return valve; and another non return valve between the or each said other outlet and said connecting passage between said first and second non-return valves.

4. Protection valve means according to any preceding Claim, wherein each non-return valve in a by-pass passage is arranged to prevent retum flow of pressure-medium therethrough to the inlet.

5. Protection valve means according to any preceding Claim, wherein the throttle and non-return valve of one or more of said by-pass passages are arranged such that pressure-medium flow through that by-pass passage from the inlet passes first through the throttle and then through to the non-return valve.

6. Protection valve means according to any one of Claims 1 to 4, wherein the throttle and non-return valve of one or more of said bypass passages are arranged such that pressuremedium flow through that by-pass passage from the inlet passes first through the nonretum valve and then through the throttle.

7. Four-circuit protection valve means sub stantially as herein described with reference to the accompanying drawing.

8. A mulit-circuit, pressure-medium operable braking system, particularly for a motor vehicle, the system including protection valve means according to any preceding Claim.

9. A motor vehicle having a braking system according to Claim 8.