EP1220993A2

EP1220993A2 - Safety valve

Info

Publication number: EP1220993A2
Application number: EP00974333A
Authority: EP
Inventors: Stefan Pfund; Günter Baldauf
Original assignee: IMI Norgren Herion Fluidtronic GmbH and Co KG
Current assignee: Norgren GmbH
Priority date: 1999-10-15
Filing date: 2000-09-28
Publication date: 2002-07-10
Anticipated expiration: 2020-09-28
Also published as: EP1220993B1; JP2003512579A; WO2001029429A2; WO2001029429A3; DE50007312D1; DE19949874B4; JP4643100B2; DE19949874A1; ES2223604T3; US6758241B1

Abstract

The invention relates to a safety valve for consumers driven by compressed air, comprising two directional valves connected in parallel, each having a working piston and a valve head which is connected to the latter. Each of said valves can be operated by a pilot valve allocated to it. Both valve heads are guided in a respective bore of the valve housing and the two bores are interconnected in a crosswise manner via two cross-channels. The valve seat of the first pilot valve is connected by a pilot channel to one of the cross-channels, which originates in the bore of one of the valve heads and the valve seat of the second pilot valve is connected by another pilot channel to the other cross-channel, which originates in the bore of the other valve head. Said safety valve is characterised in that at each of two interconnected points on the two directional valves, a compressed-air driven switching element is provided, by means of which the safety valve can be closed at these two points in case of a difference in pressure and at least one of the two switching elements can only be reactivated by external compressed-air driven actuation.

Description

safety valve

The invention relates to a safety valve for compressed air-operated consumers according to the preamble of claim 1.

Such a safety valve can be found, for example, in DE 30 05 547 C2 and DE 196 22 198 AI.

Such safety valves are used, for example, to actuate clutches and brakes on presses. In the event of a malfunction in which the two directional valves assume different switching positions, the inlet is blocked in such safety valves and the line leading to the consumer is vented. tet, so that there is no residual pressure in the latter. In order to determine such a malfunction and to switch off the system, it is provided in the safety valve resulting from DE 30 05 547 C2 that the control air for the pilot valves should not be taken directly from the inlet, but from cross ducts, which contain the two holes in which the valve disks are guided , connect with each other crosswise. This enables constant dynamic self-monitoring of the safety valve.

The object of the invention is to develop a safety valve of the generic type in such a way that the valve can be reset or switched on again in a simple manner, preferably without the aid of electrical switching elements, after the fault has been eliminated.

This object is achieved by the features of claim 1 and has the advantage that the safety valve can be blocked not only in the event of a malfunction of one of the two directional valves, but also by external actuation of the switching element, for example by key switch or manually or by removing the entire system pressure can be switched on again. Further advantages and refinements of the invention are the subject of the dependent claims.

For example, it is particularly advantageous that each switching element has a device for dynamic monitoring of pressure differences in at least two Pressure lines with a piston-cylinder unit, which connects the inlet of one of the two directional control valves with the atmosphere at different pressures in the two pressure lines. By connecting the input of one of the two directional control valves to the atmosphere, an unintentional and unwanted restarting of the safety valve is avoided.

The switching element is preferably arranged in one of the pilot channels.

Further advantages and features of the invention are the subject of the following description and the drawing.

The drawing shows:

Figure 1 is a sectional view of a safety valve according to the invention in the rest position.

Figure 2 shows the safety valve in the switch position.

3 shows the safety valve in a faulty switching;

4 shows the safety valve after the fault has occurred and is stored in the rest position;

5 shows the reset of the error in the safety valve shown in FIGS. 1 to 4;

6 shows a monitoring device used in a safety valve according to the invention of pressure differences in two pressure lines in the rest position and

Fig. 7 shows the device shown in Fig. 6 in the storage position.

A safety valve 10, shown in FIGS. 1 to 5, comprises a housing 12 in which two directional valves are arranged in parallel. Each of the two directional control valves has a working piston 16a and 16b and a valve disk 18a, 18b firmly connected to it. The housing 12 has an inlet connection 20 for compressed air, a return connection 22 and a consumer connection 24. Each of the directional control valves is assigned an electromagnetically switchable pilot valve 26a or 26b with valve seats 28a or 28b and ventilation openings 30a or 30b. The piston-shaped valve plates 18a, 18b are guided in bores 36a, 36b of the housing 12. This opens and closes valve seats 34a, 34b. Valve seats 32a, 32b are opened and closed by working pistons 16a, 16b.

The two valve disks 18a, 18b have transverse bores 38 which open into an annular channel 42a or 42b.

Furthermore, two channels 46a, 46b, hereinafter referred to as cross channels, are formed in the housing 12, through which the two bores 36a, 36b can be mutually connected. Pilot channels 48a, 48b branch off from these cross channels 46a, 46b Storage chambers 60a, 60b and devices for dynamic monitoring of pressure differences, to be described in more detail below, hereinafter called storage valves 70a, 70b for short, lead to the valve seats 28a, 28b of the pilot valves 26a, 26b. Channels 50a and 50b also lead from the pilot valves to the working pistons 16a, 16b and to their working chambers 14a, 14b.

The storage valves 70a, 70b are connected in such a way that the storage valve 70a assigned to one directional control valve 26a or one of the two directional control valves connected in parallel has a first input line 71a, which is connected on the one hand to an electromagnetically actuated valve 72a and on the other hand to the input line 73b of the other storage valve 70b and a second input line 73a connected to the storage chamber 60b. The storage valve 70b assigned to the other directional control valve has an input line 71b, which is connected on the one hand to an electromagnetically actuated valve 72b and on the other hand to the second input line 73a of the other storage valve 70a, whereas its second input line 73b is connected to the first input line 71a of the storage valve 70a , The storage valves 70a, 70b are thus also connected crosswise via the storage chambers 60a, 60b via the channels 48a and 48b to the directional valves arranged in parallel. To understand the functioning of the safety valve, the functioning of the storage valves 70a, 70b is first explained with reference to FIGS. 6 and 7.

The storage valve for dynamic monitoring and storage of pressure differences, shown in FIGS. 6 and 7, comprises a housing 200 having a connection 207 which is connected to the second input lines 73a and 73b and a connection 211 which is connected to the first input lines 71a and 71b is connected. A piston 202 is displaceable in the housing 200 in an opening of the housing 200 against the restoring force of restoring springs 205.

The accumulator valve further includes a port 208 and a port 210, the port 208 depending on the position of the piston 202 with either the port

207 or with the connection 210, which in turn is connected to the atmosphere. The connection

208 is connected to the pilot valves 26a, 26b in the safety valve shown in FIGS. 1 to 5, whereas the connection 210 is connected to the return line 22 or the atmosphere.

The piston 202 is closed on its side facing away from the return springs 205 by a membrane 201 which is fastened in the housing 200 and forms an effective pressure surface AI with which the piston 201 can be acted upon by a pressure prevailing at the connection 211. On the side of the piston 202 facing the spring 205, the effective pressure surface is formed by the larger pressure surface A2 of the piston 202 formed on this side by a seat 209. In addition, the pressure surface can also be formed by a piston with a sealing element, which can be a lip ring, for example.

The spring force generated by the return springs 205 holds the piston 202 in its rest position shown in FIG. 6. For this purpose, the piston 202 has sealing surfaces 203 on its side facing away from the return springs 205, which cooperate with the valve seat 209.

On its side facing the return springs 205, the piston 202 also has a sealing surface 204 which interacts with a valve seat 206.

The storage valve stores a signal whenever there is a pressure at port 211 and no pressure at port 207, or when there is a pressure difference here, as will be described in more detail below.

If the two connections 207 and 211 are pressurized, the piston 202 remains in its rest position shown in FIG. 6. The spring force of the return springs 205 and the pressure force on the surface A2, which is generated by the fluid pressure at the connection 207 and acts on the valve seat 209, result in a resultant force in the rest position, which the piston 202 hold against a force caused by the fluid pressure that occurs on the membrane 201. It is understood that the two effective areas AI, A2 and the spring constant are chosen so that the effective area A2 minus the effective area AI at the same pressure at the connections 207 and 211 result in a pressure force that is chosen so that the piston 202 remains in its rest position. In this rest position, the same fluid pressure is present at connection 208 as at connection 207. As mentioned above, connection 210 is connected to the atmosphere or return line 22.

The memory function of the memory valve is as follows. If the fluid pressure at port 207 and thus at port 208 drops - a pressure difference can be determined by the interaction of the area AI, A2 and the spring force of the springs 205, at which a storage process is to be initiated - the spring force remains (only) and the resulting force from the lower pressure opposite port 211 at ports 207, 208 to hold piston 202 in its rest position. However, since the pressure force applied to the diaphragm 201 outweighs the spring force and the resulting force from the lower pressure compared to the connection 211 at the connections 207, 208, since the connection 211 is still pressurized, the piston 202 moves into the in 7 storage position shown downward in the direction of the valve seat 206 with the surface A3. If a fluid pressure is again present at the connection 207 and 208 or the pressure rises again, only a small upward force arises, which is formed from the product "seat A3 of the valve seat 206 times fluid pressure". The seat surface A3 of the valve seat 206 is dimensioned so that this force together with the force generated by the return springs 205 is not sufficient to move the piston 202 against the downward force which is formed by the product "fluid pressure times membrane surface AI" , A pressure equalization between connection 207 and 211 does not lead to a reset or deletion of the memory function of the device in the rest position. The pressure difference that has occurred remains, to a certain extent, stored by the position of the piston which connects port 208 through port 210 to the atmosphere.

Resetting the storage valve, i.e. an extinguishing function can only be achieved in that the space above the diaphragm 201 is vented through the connection 211, so that the springs 205 and the fluid pressure applied to the seat surface A3 move the piston 202 upwards again into its initial or rest position. In this case the stored signal is deleted. The venting, as described below in connection with FIGS. 1 to 5, can take place via the electromagnetically actuated reset valves 72a or 72b.

1 to 5, the same reference numerals designate identical elements. The safety valve works as follows. In Fig. 1 the safety valve is shown in the rest position. In the rest position, the pilot valves 26a, 26b are closed and the working chambers 14a, 14b of the working pistons 16a, 16b are vented via the channels 50a, 50b and the ventilation openings 30a, 30b of the pilot valves 26a, 26b. The valve plates 18a, 18b are thus pressed by the compression springs 80a and 80b (and the pressure medium) against the seats 34a, 34b and close them. The valve seats 32a and 32b of the working pistons are open, so that the consumer connection 24 to the return connection 22 is vented. If the pilot valves 26a, 26b are now switched over, as shown in FIG. 2, their valve seats 28a, 28b are opened and their ventilation opening 30a, 30b is closed. The volume of the pilot channels 48a, 48b of the storage chambers 60a, 60b and of the second connecting lines 73a, 73b and the connecting lines 75a, 75b of the storage valves 70a, 70b is selected to be so large that those in the pilot channels 48a, 48b and the storage chambers 60a, 60b and the second connecting lines 73a, 73b and the connecting lines 75a, 75b, compressed air which flows via the valve seats 28a, 28b and the channels 50a, 50b into the working chambers 14a and 14b of the working pistons 16a, 16b, is sufficient for the working pistons 16a, 16b to switch over so that they assume the position shown in FIG. 2, in which the valve seats 32a, 32b of the working pistons are closed and the valve seats 34a, 34b of the valve disks 18a, 18b are open. In this case, the compressed air flows from the inlet 20 into the hollow bored valve plates 18a, 18b, from there through the cross bores 38 into the ring channels 42a, 42b, then through the cross channels 46a, 46b into the ring channels 40a, 40b and from there through the Valve seats 34a, 34b through the consumer port 24 to the consumer. At the same time, the compressed air flows from the cross channels 46a, 46b or from the ring channels 40a, 40b into the pilot channels 48a, 48b, into the storage chambers 60a, 60b and towards the storage valves 70a, 70b, both the input line 71a and 71b respectively the inlet line 73a and 73b of the storage valves 70a and 70b are also pressurized with compressed air under the same pressure. In this state, the storage valves 70a, 70b are in the rest position described above, so that the valve seats 28a and 28b are filled with compressed air, which are under the full inlet pressure, around the working pistons 16a, 16b of the valves arranged in parallel via the lines 50a, Hold 50b in switch position. If the pilot valves 26a, 26b are now switched over again and their valve seats 28a, 28b are closed, then the ventilation openings 30a, 30b are opened and the working chambers 14a, 14b of the working pistons 16a, 16b via the ventilation openings 30a, 30b of the pilot valves and the channels 50a and 50b vented.

The two directional control valves are then switched back to the rest position shown in FIG. 1, since the working pistons 16a, 16b are no longer acted upon by the compressed air and therefore the springs 80a, 80b control the valves. Press tilt plates 18a, 18b onto their valve seats 34a, 34b. The pilot channels 48a and 48b are filled with compressed air which has the full inlet pressure, so that when this compressed air is switched again, the working pistons 16a, 16b are switched back to the position shown in FIG. 2.

In the case of a malfunction shown in FIG. 3, it was assumed that the magnet of the pilot valve 26a is excited, whereas the magnet of the pilot valve 26b is not excited. The valve seat 28a is thus opened, but the valve seat 28b is closed. The working piston 16a is supplied with compressed air via the pilot control channel 48b and the second input line 73a, the storage valve 70a, the line 75a, the valve seat 28a and the channel 50a and is switched to the position shown in FIG. 3, while the working piston 16b is not switched over , The valve seat 34b is thus closed, but the valve seat 34a is open. In this position, however, no compressed air can flow to the valve seat 34a, since the cross channel 46a leading to the valve seat 34a is closed by the piston-shaped valve plate 18b. The consumer port 24 is vented to the return 32 via the open valve seat 32b. A pressure build-up at the consumer connection 24 is excluded.

Compressed air enters through the valve plate 18a via the transverse bore 38 and the ring channel 42a into the cross channel 46b, but since the valve plate 18b is in the closed position, it cannot continue there. stream. However, the working piston 16a remains supplied with the full inflow via the pilot channel 48b connected to the cross channel 46b.

The pilot channel 48a, on the other hand, is vented to the return 22 via the ring channel 40a and the open valve seats 34a and 32b, so that no pressure can build up in the pilot channel 48a and any pressure on the return pressure, e.g. Atmospheric pressure is reduced.

Due to the switching of the storage valves 70a, 70b, the storage valve 70a is in its rest position in this case, in which the line 73a is connected via the line 75a to the valve seat 28a of the solenoid valve 26a, so that the valve seat 28a via the pilot line 48b and the storage chamber 60b is pressurized with fluid under pressure. The storage valve 70b, on the other hand, has changed over to its storage position, since the same pressure is not present in the two lines 71b and 73b. Namely, while there is no pressure in line 73b, since this line is connected to the return 22 via the storage chamber 60a and the pilot channel 48a and is thus vented, the line 71b is via the storage chamber 60b via the lines 48b, 46b, the ring channel 42a and the transverse bore 38 is connected to the inlet connection 20 for compressed air. In this case, the connection 210 (see FIGS. 6 and 7) of the storage valve 70b is connected to the atmosphere via the line 74b. Should the pilot valve 26b still be switched in some way If the valve seat 28b were opened, the working piston 16b would not be able to be switched over, since the channel 50b is connected to the line 74b in this case via the channels 75b and the memory valve 70b which remains in the storage position.

Even if the working piston 16a would return to its rest position, as shown in FIG. 4, the error would remain stored, since the storage valve 70b would remain in its position shown in FIG. 3 even in this case, although the pressure conditions on it Storage valve 70b in the line 71b and 73b would be balanced. Only when the storage valve is reset, by actuating the reset valve 72 as shown in Fig. 5, i.e. when the line 71b is vented and the storage valve 70b returns to its rest position, the safety valve can be operated again. This reset can be done, for example, by a key switch or by another manual operation.

The device can also be reset by switching off the system pressure. This can e.g. the solenoid valve or the mechanically operated valve, which is actuated, for example, by means of a key switch, is eliminated.

Claims

claims

1.Safety valve for compressed air-operated consumers with two parallel-connected, one working piston (16a, 16b) and one valve valve connected to it, each of which can be switched by a pilot valve (26a, 26b) assigned to it, the two valve plates each are each guided in a bore of the valve housing and these two bores are connected to one another by means of two cross channels (46a, 46b), and the valve seat (28a) of the first pilot valve (26a) is connected to the one cross channel via a pilot channel (48b) ( 46b), which extends from the bore (36b) of one valve plate (18b), and that the valve seat (28b) of the second pilot valve (26b) is connected to the other cross channel (46a) via a further pilot channel (48a), which starts from the bore (36a) of the other valve plate (18a), characterized in that at two mutually assigned points each of the two We valves each a compressed air-operated switching element is provided, by means of which the safety valve can be blocked at different pressures at these two points and can only be switched on again by external compressed air-operated actuation of at least one of the two switching elements.

2. Safety valve according to claim 1, characterized in that the one switching element is arranged in each case in a pilot channel, the two points being inputs of the switching elements, which are each connected crosswise to the corresponding inputs of the other switching element.

3. Safety valve according to claim 2, characterized in that each switching element is a device for dynamic monitoring of pressure difference in at least two pressure lines with a piston-cylinder unit, which connect one of the two directional control valves to the atmosphere at different pressures in the two pressure lines.

4. Safety valve according to claim 3, characterized in that the device for dynamic monitoring of pressure differences in the at least two pressure lines comprises a piston-cylinder unit, with two opposite, differently sized effective pressure areas (AI, A2), one of which through the one pressure line and the other of which can be pressurized with fluid under pressure through the other pressure line and with a piston ben (202), which is movable against the restoring force of at least one restoring spring (205) such that, at the same pressure in the two pressure lines, the restoring force of the at least one restoring spring (205) together with the pressure surface facing the at least one restoring spring (205) (A2) applied pressure force is just as large as the pressure force applied to the pressure surface (AI) facing away from the return spring (205), so that the piston-cylinder unit remains in its rest position, and that the piston-cylinder unit with only a brief reduction in the the pressure force applied to the at least one return spring (205) passes into a storage position in which the pressure force (AI) applied to the pressure surface facing away from the at least one return spring (205) is greater than the sum of the spring force and that on a third entry surface (A3) when reapplied with pressurized flu id applied pressure force and that the piston-cylinder unit from the storage position can only be returned to the rest position by removing the pressure acting on the pressure surface (AI) facing away from the return spring (205).

5. Safety valve according to claim 4, characterized in that on the at least one return spring (205) facing away from the arranged pressure surface (AI) is formed by an actuating membrane (201) of the piston-cylinder unit.

6. Safety valve according to claim 4, characterized in that the pressure surface (AI) arranged on the side facing away from the at least one return spring (205) is formed by a sealing element, preferably a lip ring, of a piston of the piston-cylinder unit.

7. Safety valve according to one of claims 4 to 6, characterized in that the piston-cylinder unit has at least two connections (208, 210), one of which is connected to the atmosphere and the other in the rest position of the piston-cylinder unit with that of the at least one Return spring (205) facing connection (207) is connected and in the storage position of the piston-cylinder unit is connected to the connection (210) connected to the atmosphere.

8. Safety valve according to one of claims 4 to 6, characterized in that the pressure force acting on the at least one return spring (205) facing away from the pressure surface (AI) can be reduced by a solenoid valve or by a mechanically actuated valve or by removing the system pressure.