EP2095199A2

EP2095199A2 - Valve device

Info

Publication number: EP2095199A2
Application number: EP07725397A
Authority: EP
Inventors: Johannes Volzer; Wolfang Mechler; Markus Weber; Bernd Kärcher
Original assignee: Festo SE and Co KG
Current assignee: Festo SE and Co KG
Priority date: 2007-05-21
Filing date: 2007-05-21
Publication date: 2009-09-02
Also published as: WO2008141661A2; WO2008141661A3

Abstract

The invention relates to a valve device having a valve unit comprising a valve chamber (13) in which a valve member (14) is movable by means of a servo drive (15) between an open position and a closed position in which the valve member (14) contacts a valve seat (19) with a contact force to close off the passage through the valve chamber (13) in a fluid-tight manner and corresponding sealing surfaces on the valve member (14) and the valve seat (19) are pressed against each other, said valve device also having a control device (21) coupled to the servo drive (15) for controlling the contact force, the control device (21) having a force transducer (22) for capturing the force acting on the valve member (14), the force being transmitted via transfer means to a pressure sensor (23) present outside of the valve chamber (13).

Description

valve means

The invention relates to a valve device, comprising a valve unit having a valve chamber in which a valve member by means of an actuator between an open position and a closed position, in which the valve member for fluid-tight closing of the passage through the valve chamber with contact force to a valve seat comes into contact and corresponding sealing surfaces on valve member and valve seat are pressed together, is movable, and with a coupled to the actuator control means for controlling the contact pressure.

From DE 10 2005 031 411 Al a valve device of the type mentioned is known, which has a valve which is located in a passageway between two vacuum chambers. The valve is designed as a slide valve, wherein a valve slide in its closed position blocks the passage through the passageway fluid-tight. On the valve spool is a seal, which is pressed when closing with a contact force on a valve seat. The contact pressure required to achieve a sealing effect depends largely on the differential pressure between the two vacuum chambers. At a smaller differential pressure, a smaller contact force is required to achieve the desired sealing effect, while at a larger differential pressure accordingly a larger contact force is necessary. It each vacuum chamber is assigned a pressure sensor, so that the differential pressure between the two vacuum chambers can be determined. Via a control unit, which is coupled to the actuator, the contact pressure can then be controlled in dependence on the determined differential pressure. In concrete terms, this means that the closing position of the valve spool is defined defined as a function of the determined differential pressure.

However, the lo ratios in the passage are not taken into account in such differential pressure measurements. For example, frictions that are not taken into account occur there, so that such measurements are faulty.

Measurements which are carried out directly at the point of action, that is to say at the valve slide or valve member itself, have the disadvantage that a complex signal-conducting signal to be sealed off from the enclosed valve chamber is necessary. Even wireless signal transmission out of the valve chamber is not reliable or even impossible due to the signal-shielding housing material of the valve chamber.

20 lent.

The object of the invention is to provide a valve device of the type mentioned, with which the contact pressure when closing the valve member can be controlled reliably and with simple means.

2s This object is achieved by a valve device having the features of independent claim 1. Further developments of the invention are shown in the subclaims.

The valve device according to the invention is characterized in that the control device has a valve element arranged on the valve element. Neten load cell for receiving the force acting on the valve member, wherein the force via transmission medium to a pressure sensor located outside the valve chamber is transferable. The force acting on the valve member can be the contact pressure force on contact with the sealing surface on the valve seat or, in the case of a position of the valve member lifted off the valve seat, the force acting on the valve chamber due to the pressure conditions in the valve chamber.

The measurement is thus carried out directly at the point of action, namely on the valve member, which is pressed when closing with contact force on the valve seat. However, the pressure sensor is located outside the valve chamber, so that cable routing from the valve chamber is avoided when the signal is transmitted by cable. High temperatures can prevail in the valve chamber, which can impair the functionality of a pressure sensor arranged in the valve chamber. If the pressure sensor is located outside the valve chamber, this problem does not arise.

The transmission means serving for force transmission between the force transducer and the pressure sensor can be formed by at least one fluid column, in particular a fluid column, coupled on the one hand to the force transducer and, on the other hand, to the pressure sensor. The incompressibility of the liquid causes a direct, independent of the transmission medium power transmission. As a liquid, for example, oil, preferably hydraulic oil, may be provided.

Alternatively, it is possible that as transmission means at least one on the one hand with the force transducer and on the other hand with the pressure sensor coupled rigid transmission member, for example in the form of a plunger, is provided. In a further development of the invention, the transmission means are arranged in a projecting into the valve chamber via a passage output member of the actuator. Conveniently, a fluid-operated working cylinder is provided as the actuator, which has a cylinder housing in which a fluidbeaufschlagter working piston is movably guided, which in turn is connected to a the output member forming piston rod. Alternatively, however, it is also possible to use an electric linear drive, for example a linear motor, as the actuator.

In an alternative arrangement, the transmission means can be arranged in a sensor carrier projecting beyond a passage into the valve chamber and receiving the pressure sensor in a region outside the valve chamber. This offers the advantage that standard actuators can be used, to each of which the sensor carrier can be attached.

The pressure sensor is located outside the valve chamber. As already mentioned above, it can be attached to a sensor carrier. Alternatively, it is possible that the pressure sensor is seated on the actuator, for example on the output member, during

Use of a working cylinder is thus attached to the Kobenstange. Alternatively, when using a working cylinder, it is possible to integrate the pressure sensor into the piston.

In a particularly preferred manner, the load cell is formed by a bellows which hermetically seals a fluid-filled pressure chamber. Conveniently, a fluid-filled bellows is used. In principle, other types of force sensors can also be used, for example a deformation body with strain gauges (DMS) or the like. The force transducer is expediently located at the connection point between valve member and driven member or sensor carrier. By varying the force application surface of the force transducer, different force translations are possible between the force acting on the valve member and the force transmitted by the force transducer to the pressure sensor.

In a development of the invention, a control module is provided for processing signals transmitted by the pressure sensor by means of signal transmission and corresponding to actual actual contact forces, and for controlling the actuator. Since the pressure sensor is located outside the valve chamber, a simple, cable-controlled signal transmission from the pressure sensor to the control module is also possible. Alternatively, a wireless signal transmission, in particular signal transmission by means of radio, conceivable.

Appropriately, located on the sealing surface on the valve member, an elastic seal which is claimed when pressing the valve member to the valve seat. By the measures described above, the contact pressure can now be controlled, so that the elastic seal is not damaged when hitting the corresponding sealing surface on the valve seat.

The valve device may further comprise a passageway which connects two working chambers, for example vacuum chambers, to each other. In the passageway, the valve chamber of the valve unit may be arranged.

Preferred embodiments of the invention are illustrated in the drawings and will be explained in more detail below. In the drawing show: 1 shows a schematic representation of a first embodiment of the valve device according to the invention, wherein only a part of the valve unit is shown,

FIG. 2 shows an enlarged view of the valve device of FIG. 1 with all the components of the valve unit in a schematic illustration,

Figure 3 shows a second embodiment of the valve device according to the invention in a schematic representation and

Figure 4 shows a third embodiment of the valve device according to the invention in a schematic representation.

Figures 1 and 2 show a first embodiment of the valve device 11 according to the invention the heart of the valve device 11 is a valve unit 12, which could also be referred to as a process valve. The valve unit 12 has a valve chamber 13, in which a valve member 14 by means of an actuator 15 between an open position and a closed position is movable. Conveniently, the valve chamber 13 is located in a passage 16 which connects two working chambers 17, 18 with each other. In the working chambers 17, 18 process gases may be located. An exchange is possible via the passage 16. The task of the valve unit 12 is, if necessary, to close the passage through the passageway 16 in a fluid-tight manner.

For this purpose, the valve member 14 is moved by means of the actuator 15 in its closed position, in which it comes with contact pressure on a valve seat 19 to the plant. In this case, mutually corresponding sealing surfaces are pressed together. The Valve member-side sealing surface is formed by an elastic seal 20 which is attached to the outside of the valve member 14, in particular vulcanized to the outside. As shown in particular in Figure 1, the valve member 14 may have a wedge-shaped cross section, wherein the tip of the valve member 14 is immersed in the closed position in the corresponding thereto also wedge-shaped valve seat 19.

If the valve member is moved too fast, that is, with too high a pressing force into the closed position, there is the risk that the seal 20 will be damaged. On the other hand, a minimum contact pressure is necessary in order to achieve a fluid-tight seal of the through-channel 16. Furthermore, in the passage, depending on the differential pressure between the two working chambers 17, 18 often very different pressure conditions exist, which must be taken into account during the closing process.

It is therefore necessary to move the valve member 14 with a defined contact force in its closed position. A control device 21 is used to set a defined contact force. This comprises a force transducer 22 for receiving the force acting on the valve member 14 which can be transmitted via transmission means to a pressure sensor 23 located outside the valve chamber 13.

As a load cell, a bellows is provided, which hermetically seals a liquid-filled pressure chamber. The liquid used here is oil. The transmission means are also formed in this case by a liquid column 29, which communicates on the one hand with the pressure chamber of the bellows and on the other hand with the

Pressure sensor 23 is coupled. As a liquid is also here Used oil. The bellows is located at the junction between valve member 14 and a driven member 24 of the actuator 15th

The actuator 15 is shown here by way of example in the form of a fluid-operated working cylinder, which has a cylinder housing 25 in which a working piston 26 which can be loaded with fluid is movably guided. The working piston 26 is connected to a piston rod which forms the output member 24 and which projects into the valve chamber 13 via a passage 28 which is sealed by means of a seal 27. As mentioned, the bellows is located at the piston-remote end of the piston rod.

As shown in FIGS. 1 and 2, the liquid column 29 according to the first exemplary embodiment is located inside the hollow piston rod. The piston rod can pass through the rear side of the cylinder housing 25, in which case the pressure sensor 23 is seated on the bellows-distal end of the piston rod. It can also be provided two piston rods, of which a first piston rod connects the bellows with the piston and the other piston rod connecting the piston with the pressure sensor 23. In an alternative, not shown, the pressure sensor may also be located in the working piston. A continuation of the piston rod or a second piston rod is then not necessary.

The pressure sensor 23 comprises a P / U converter, which detects the force transmitted by the liquid column 29 in the form of a pressure and converts it into a voltage.

Further, a control module 30 is provided, which receives the voltage signals of the pressure sensor 23 and the working cylinder conveniently via a control valve (not shown) controls. The signal transmission from the pressure sensor 23 to the control module 30 is carried out according to the first embodiment by cable. Alternatively, however, a wireless or wireless signal transmission would be possible.

Figure 3 shows a second embodiment of the invention. It differs from the first exemplary embodiment described above in that a sensor carrier 31 is provided, which protrudes into the valve chamber 13 via a passage 28 which is sealed by means of a seal 27. The senlo sorträger 31 carries on the one hand the bellows, which in turn is in contact with the valve member 14, while on the other hand is coupled to the piston rod of the working cylinder. Furthermore, the pressure sensor 23 is fastened to the sensor carrier 31, to be precise in an area located outside of the valve chamber 13. The pressure space of the bellows and the pressure sensor are in turn connected to each other by means of a liquid column 29, wherein the liquid column 29 is located in a channel 32 formed in the sensor carrier 31. The signal transmission from the pressure sensor 23 to the likewise

20 existing control module 30 is done by cable.

Finally, FIG. 4 shows a third exemplary embodiment of the invention, which is constructed identically to the second exemplary embodiment, with the exception that the signal transmission from the pressure sensor 23 to the control module 30 takes place by means of radio.

25 The function of the valve device is described in more detail below:

The valve member 14 is initially in its open position shown in Figure 1. In this case, the valve member 14 has moved completely out of the through-channel 16, so that there is no flow resistance for flow in the through-channel 16. forming process fluid. To close the valve chamber 13 and the passage through the passage 16 now the working cylinder is activated, wherein the piston rod remote side of the piston 26 with fluid, in particular with compressed air is applied, so that the piston, for example, as shown in Figures 2 to 4, after is moved above, whereby the piston rod extends out of the working cylinder and the valve member 14 is moved in the direction of the valve seat 19. According to a first variant, the speed with which the valve member 14 moves in the direction of the valve seat is chosen to be relatively high, but only until the seal 20 located on the valve member contacts the sealing surface on the valve seat 19. If the valve member 14 is now moved further, the contact pressure increases. The actual contact pressure is transmitted to the pressure chamber of the bellows and from there via the liquid column 29 to the pressure sensor 23. The actual contact pressure is detected as a contact pressure and converted into a corresponding voltage signal. This voltage signal is then transmitted by cable or wireless to the control module 30, where a comparison of the actual contact pressure with a minimum contact force and a maximum contact force takes place. The minimum contact pressure must be exceeded for a fluid-tight seal of the valve chamber 13 takes place. The maximum contact pressure must not be exceeded, otherwise the elastic seal 20 will be damaged. As already mentioned, the contact pressure also depends on the pressure conditions in the passage, which are also taken into account, as they ultimately represent nothing else than a force acting on the valve member 14. Is the minimum

Pressing force falls below, the valve member 14 is moved further in the direction of the valve seat 19. Exceeding the Maximal -Anpresskraft is not possible, since a constant adjustment of the actual contact force with this maximum value takes place. Overall, this makes it possible to bring the valve member with defined contact force in its closed position. It is ensured that the valve chamber and thus the passage through the passage 16 is sealed fluid-tight and on the other hand, there is no risk that the elastic seal 20 is damaged.

Furthermore, it is advantageous to measure directly at the point of action, thereby avoiding measurement errors that occur due to ignoring the conditions prevailing in the passage 16. Further measurement errors are prevented by the fact that the pressure sensor 23 is seated outside the valve chamber 13, whereby it is protected from high temperatures and aggressive process media. The position of the pressure sensor 23 also brings the advantage that a complex cable management out of the valve chamber 13 out - in this case, in turn, should pay attention to the fluid tightness of the cable gland - be avoided. In addition, the position of the pressure sensor 23 outside the valve chamber 13 opens the possibility of wireless signal transmission to the control module 30. If the pressure sensor 23 within the valve chamber 13 would be due to the valve chamber 13 surrounding, shielding material wireless signal transmission only limited or not possible ,

Claims

claims

A valve device, comprising a valve unit (12) having a valve chamber (13) in which a valve member (14) by means of an actuator (15) between an open position and a closed position in which the valve member (14)

5 fluid-tight closing of the passage through the valve chamber (13) with contact pressure on a valve seat (19) comes to rest and corresponding sealing surfaces on valve member (14) and valve seat (19) are pressed together, is movable, and with a with the actuator (15) coupled control device (21) for controlling the contact force, characterized in that the control device has a force sensor (22) arranged on the valve member (14) for receiving the force acting on the valve member (14), which is transmitted via transmission means (29 ) is transferable to a pressure sensor (23) located outside the valve chamber (13).

2. Valve device according to claim 1, characterized in that as a transmission means at least one on the one hand with the force transducer (22) and on the other hand with the pressure sensor (23) coupled fluid column, in particular liquid

20 column (29), is provided.

3. Valve device according to claim 1, characterized in that as a transmission means at least one on the one hand with the force transducer (22) and on the other hand with the pressure sensor (23) coupled rigid transfer member is provided.

4. Valve device according to one of the preceding claims, characterized in that the transmission means in

5 a via a passage (28) in the Ventilkamtner (13) projecting output member (24) of the actuator (15) are arranged.

5. Valve device according to one of claims 1 to 3, characterized in that the transmission means in a lo via a passage (28) in the valve chamber (13) projecting, the pressure sensor (23) in a region outside the valve chamber (13) receiving the sensor carrier (31) are arranged.

6. Valve device according to one of claims 1 to 4, da- i5 characterized in that the pressure sensor (23) on the actuator (15) sits.

7. Valve device according to one of the preceding claims, characterized in that the force transducer is formed by a bellows, which is a fluid-filled pressure

20 hermetically seals tightly.

8. Valve device according to one of the preceding claims, characterized in that the actuator (15) is formed by a fluid-operated working cylinder having a cylinder housing (25) in which a fluidbeaufschlagba

25 rer working piston (26) is movably guided, which in turn is connected to a the output member (24) forming the piston rod.

9. Valve device according to one of the preceding claims, characterized in that a control module (30) is provided for processing from the pressure sensor (23) by means of signal transmission, respectively actual Ists contact forces corresponding signals and for driving the actuator (15).

10. Valve device according to claim 9, characterized in that a cable-controlled signal transmission is provided.

11. Valve device according to claim 9 or 10, characterized in that a wireless signal transmission, in particular signal transmission by radio, is provided.

12. Valve device according to one of the preceding claims, characterized in that the sealing surface on the valve i5 member (14) by an elastic seal (20) is formed.

13. Valve device according to one of the preceding claims, characterized by a two working chambers (17, 18) interconnecting passageway (16) in which the valve chamber (13) of the valve unit (14) is arranged.