GB2136602A

GB2136602A - Compressed air supply device for compressed-air systems

Info

Publication number: GB2136602A
Application number: GB08406288A
Authority: GB
Inventors: Klaus Jenner; Gunther Strobel
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1983-03-10
Filing date: 1984-03-09
Publication date: 1984-09-19
Also published as: GB8406288D0; SE8401323D0; SE8401323L; FR2542389B1; DE3308547A1; FR2542389A1; GB2136602B

Abstract

A compressed air supply device for compressed-air systems, such as pneumatic brake or door actuating systems, is proposed and comprises an air compressor (11), an air drier (12) connected downstream thereof, and a pressure regulator (14) connected to the outlet of the air drier, in which device, for the purpose of completely regenerating the drying agent during the shut-off phase of the pressure regulator (14), the pressure regulator (14) has a change-over valve (20) which, when in its operating position, connects the outlet of the pressure regulator to a control line (13) of the air drier (12), and a safety valve (19) controlled independently of the change-over valve (20). <IMAGE>

Description

SPECIFICATION Compressed air supply device for compressed-air systems The invention relates to a compressed air supply device for compressed-air systems, such as pneumatic brake or door actuating systems, comprising an air compressor, an air drier connected to the outlet thereof, and a pressure regulator-which is disposed downstream of the air drier and which has a pressure valve and a change-over valve, particular- ly a three-port, two-position valve, which has a return spring and which is conrolled by the pressure at the outlet of the pressure regulator and which, when in its operating position, connects the pressure regulator port to the air drier.

In a known compressed air supply device of this kind, the pressure valve, adjustable by spring force, is subjected to control pressures in the form of the pressure at the inlet of the pressure valve on the one hand and, on the other hand, the pressure at the outlet of the change-over valve when the latter is in its operating position, for which purpose that port of the change-over valve which is connected to the regeneration air return line of the air drier is connected to one of two control inlets of the pressure valve. The pressure valve is normally closed. The inlet of the pressure valve communicates with the atmosphere by way of a throttling cross section when the change-over valve is in its operating position or in its change-over position, and also when an admissible over-pressure in the compressed air supply device reaches a value exceeding the operating pressure.When the operating pressure of, for example, 8 bar is reached inthe compressed-air system, and hence in the compressed air supply device, the change-over valve assumes its operating position from its rest or normal position in which the regeneration air return line leading to the air drier is shut off. The pressure valve is also opened as soon as the change-over valve changes over and hence the regeneration air return line is connected to the outlet of the pressure regulator.

The air drier is at the same time changed over, so that the regeneration air from the return line can flow through the air drier and from the air drier into the atmosphere. The air compressor is operating in its no-load phase.

When the pressure regulator is in this switching position, a portion of the residual volume of dried air located between the air drier and the outlet of the pressure regulator flows to the air drier by way of the change-over valve and the regeneration air return line, and a portion emerges directly by way of the venting outlet of the pressure valve. As a result of this splitting-up of the flow of air, only a small quantity of regenertion air flows through the air drier during the shut-off phase of the pressure regulator or during the no-load phase of the air compressor, and is frequently insufficient to regenerate the drying agent. Hence, the regeneration of the drying agent effected during the no-load phase of the air drier is incomplete, that is to say, when the changeover valve has shut off the pressure regulator.

In contrast to this, the present invention provides a compressed air supply device in which the pressure valve is a safety valve controlled independently of the change-over valve and consequently has the advantage that, by virtue of decoupling the control of the pressure valve from the change-over valve, the former no longer opens upon shutting-off of the pressure regulator as a result of reaching the operating pressure. As a result of this, direct communication with the atmosphere is not established during the shut-off phase of the pressure regulator.

The entire quantity of the dried residual air can only flow into the atmosphere by way of the regeneration air return line and the air drier. This larger quantity of dry air available for regeneration substantially improves the regeneration of the drying agent during the shut-off phase of the pressure regulator, that is to say, during the no-load phase of the air compressor. The pressure valve is only a safety valve which opens at a predeterminable excess pressure lying above the shut-off pressure of the pressure regulator, and hence direct communication with the atmosphere is established.

Preferably a non-return valve is connected directly upstream of the outlet of the pressure regulator. The change-over valve, safety valve and non-return valve are preferably disposed in a common housing. The same housing may also have disposed therein at least one air filter.

The invention will be further described with reference to an embodiment illustrated in the drawings, in which: Figure 1 is a block circuit diagram of a compressed air supply device for a compressed-air brake system of the invention; and Figure 2 is a block circuit diagram of a pressure regulator of the compressed air supply device of Figure 1.

The compressed air supply device, illustrated diagrammatically as a block circuit diagram in the drawings, serves to supply compressed-air systems, a pneumatic brake system in the present instance, with compressed air. The compressed air accumulators (not illustrated) of the pneumatic brake system are filled by way of a known four-circuit protective valve 10 to which two service brake circuits, a parking brake and trailer circuit and a secondary load circuit, are connected.

The compressed air supply device has an air compressor 11, an air drier 12 which is connected to the outlet thereof and has a control line 13, and a pressure regulator 14 whose inlet 1 is connected to the outlet of the air drier 12, and whose outlet 21 is connected to the four-circuit protective valve 10 of the compressed-air brake system.

Two air filters 15 and 16 and a non-return valve 17 are connected in series between the inlet 1 and the outlet 21 in the pressure regulator 14. The shut-off direction of the non-return valve is from the outlet 21 to the inlet 1. A branch line 18 leads from the junction of the two air filters 15 and 16 to a venting outlet 3 of the pressure regulator 14 by way of a pressure valve in the form of a safety valve 19. A pneumatically controlled change-over valve 20 is connected to the outlet of the non-return valve 17, that is to say, upstream of the outlet 21 of the pressure regulator, and, in the present instance is in the form of a three-port, two-position valve having a return spring.The control inlet and also one port of the three-port, two-position valve 20 are connected to the outlet 21 of the pressure regulator, while the other port of the three-port, two-positon valve 20, which is connected to the above-mentioned first port when the valve is in its operating or change-over position, is connected to the control line 13 of the air drier 12 by way of an outlet 23 of the pressure regulator 14. When the three-port, two-position valve 20 is in its normal or basic position, the outlet 23, connected to the control line 13, of the pressure regulator 14 is vented. The change-over valve 20, the safety valve 19, the non-return valve 17 and the two airfilters 15 and 16 are disposed in a common housing 22 which is symbolized by a dash-dot border in Figure 2.

The mode of operation of the compressed air supply device is as follows: The air compressor 11 draws in air during the delivery phase, compresses it and conveys it to the four-circuit protective valve 10 by way of the air drier 12 and the pressure regulator 14, that is to say, through the air filters 15 and 16 and the non-return valve 17 in the present instance. When the pressure at the inlet of the four-circuit protective valve 10 reaches a pressure of, for example, 7 bar, the four-circuit protective valve 10 opens and the compressed air accumulators of the compressed-air brake system (not illustrated) are stressed.The drying agent in the air drier 12 extracts moisture from the compressed air flowing through the air drier 12 and absorbs it, and the moisture content of the drying agent increases and thereby gradually reduces the drying capacity of the drying agent. The shut-off phase of the pressure regulator 14 is used to regenerate the drying agent. The air compressor 11 is changed over to no-load when the pressure in the compressed air reservoirs of the brake system reaches the operating pressure. This pressure, which also appears at the outlet of the pressure regulator 14, changes over the change-over valve 20, whereby the outlet 21 of the pressure regulator is connected to the air drier 12.

The air drier 12 is at the same time change over, so that all the air upstream of the non-return valve 17 then flows through the drying agent in the air drier and can emerge directly into the atmosphere at a venting outlet of the air drier 12. The air, in the order of magnitude of 1 to 2 litres, which is present between the air drier 12 and the outlet 21 of the pressure regulator upon change-over of the change: over valve 20, and which has been dried as a result of flowing through the air drier 12 during the delivery phase of the air compressor 11, then flows through the air drier 12 and absorbs moisture from the drying agent. The drying agent is regenerated and is thereby able to extract moisture again from the compressed air flowing through the air drier 12 during the following delivery phase of the air compressor 11.

The pressure at the outlet of the non-return valve 17, that is to say, at the outlet 21 of the pressure regulator, also drops as soon as the pressure in the compressed air brake system drops below operating pressure as a result of, for example, actuation of the brake system. As a result of this pressure reduction, the return spring of the change-over valve 20 can return the latter to its basic position. The control line 13 is isolated from the outlet 21 of the pressure regulator and is vented. The air compressor 11 is changed over to its delivery phase, and the air drier 12 is also changed over such that compressed air from the air compressor 11 can then flow through the air drier 12 towards the inlet 1 of the pressure regulator 14 The safety valve 19 inthe pressure regulator 14 fulfils a safety function. In the event of damage, it prevents the pressure in the compressed air supply device from increasing substantially in excess of the shut-off pressure of the pressure regulator, that is to say, the pressure at which the change-over valve 20 is changed over.

Claims

1. A compressed air supply device for compressed-air systems, such as pneumatic brake and door actuating systems, comprising an air compressor, an air drier connected to the outlet thereof, and a pressure regulator which is disposed downstream of the air drier and which has a pressure valve and a change-over valve, particularly a three-port, twoposition valve, which has a return spring and which is controlled by the pressure at the outlet of the pressure regulator and which, when in its operating position, connects the pressure regulator port to the air drier, characterised in that the pressure valve is a safety valve controlled independently of the changeover valve.

2. A device as claimed in claim 1, characterised in that a non-return valve is connected directly upstream of the outlet of the pressure regulator.

3. A device as claimed in claim 2, characterised in that the change-over valve, safety valve and non-return valve are disposed in a common housing.

4. A device as claimed in claim 3, in which the housing also has disposed therein at least one air filter.

5. A device as claimed in claim 1, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.