Vacuum valve

A vacuum valve comprises a valve housing which has an inlet opening and an outlet opening penetrating opposite walls of the valve housing, a valve seat surrounding the inlet opening, and a closure unit which is arranged in an interior space of the valve housing and which has a valve plate which is adjustable between an open position in which it releases the inlet opening, an intermediate position in which it covers the inlet opening but is lifted from the valve seat, and a closed position in which it covers the inlet opening and is pressed against the valve seat, and at least one adjusting piston which is arranged in an interior space of the closure unit and, for the purpose of adjusting the valve plate between its intermediate position and its closed position, is displaceable in direction of its longitudinal center axis between a passive position in which the valve plate is in its intermediate position and an active position in which the valve plate is in its closed position. At least one work space of the closure unit that can be acted upon by pressure gas for displacing the at least one adjusting piston into its active position is bounded by a diaphragm seal. At least one tappet is arranged at the adjusting piston and is guided out of the interior space of the closure unit through an opening and is supported directly or indirectly at the valve housing when the adjusting piston is displaced from its passive position into its active position.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority of Austrian Application No. A 1022/2006, filed Jun. 16, 2006, the complete disclosure of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

a) Field of the Invention

The invention is directed to a vacuum valve comprising a valve housing which has an inlet opening and an outlet opening which penetrate opposite walls of the valve housing, a valve seat surrounding the inlet opening, and a closure unit which is arranged in an interior space of the valve housing and which has a valve plate which is adjustable between an open position in which it releases the inlet opening, an intermediate position in which it covers the inlet opening but is lifted from the valve seat, and a closed position in which it covers the inlet opening and is pressed against the valve seat, and at least one adjusting piston which is arranged in an interior space of the closure unit and, for the purpose of adjusting the valve plate between its intermediate position and its closed position, is displaceable in direction of its longitudinal center axis between a passive position in which the valve plate is in its intermediate position and an active position in which the valve plate is in its closed position. At least one work space of the closure unit that can be acted upon by pressure gas for displacing at least one adjusting piston into its active position is bounded by a diaphragm seal.

b) Description of the Related Art

A vacuum valve in which a valve plate is displaceable between its intermediate position and its closed position by means of an adjusting piston arranged in an interior space of a closure unit is known from U.S. Pat. No. 6,561,484 B2. The closure unit comprises the valve plate and a supporting plate. The valve plate and the supporting plate can be anchored against the valve housing between the inner surfaces of the valve housing in the area around the inlet opening and the outlet opening by means of the adjusting piston. A receiving housing for the adjusting piston can be arranged at the supporting plate or at the valve plate. Sealing rings acting between the adjusting piston and the receiving housing are provided for forming work spaces which are acted upon by pressure to displace the adjusting piston. At least one sealing bellows extends between the valve plate and the supporting plate in some of the embodiment forms. In addition to embodiment forms in which the closure unit is displaceable linearly for adjusting between its open position and its intermediate position, embodiment forms constructed in the manner of a pendulum valve are also described. In these embodiment forms, the carrying arm at which the closure unit is arranged is swivelable around a swiveling axis for displacing the closure unit between its open position and its intermediate position.

Another valve in which a valve plate is displaceable between its intermediate position and its closed position by means of a adjusting piston arranged in an interior space of a closure unit is known from US 2004/0079915 A1. In this case also, work spaces which can be acted upon by pressure gas for displacing the adjusting piston are sealed by flexible sealing rings.

U.S. Pat. No. 6,776,394 B2 discloses a pendulum valve in which cylinder bore holes in which adjusting pistons are arranged are formed in the valve housing. Tappets can be displaced by the adjusting pistons in order to press the valve plate against the valve seat in the closed position of the valve plate. The adjusting pistons are likewise sealed relative to the walls of the cylinder spaces by sealing rings.

A vacuum valve of the type mentioned above is known from the embodiment example shown in FIG. 5 of DE 19 857 201 A1. Tensioning cylinders serve as lifting bodies for pressing valve plates against a valve housing. The tensioning cylinders are sealed relative to a base body of the closure unit by diaphragm seals.

It is known from U.S. Pat. No. 5,975,492 A to press valve plates against valve seats of the valve housing by means of an actuator arranged in an interior space of the closure unit. The actuator comprises plates which are pressed together so as to be tight against pressure by high-grade steel bellows (seeFIG. 21).

Further, adjusting elements with diaphragm pistons are known from other applications as vacuum valves, for example, in automobile engineering in connection with brake cylinders or in fixture construction for clamping parts, i.e., workpieces to be clamped.

OBJECT AND SUMMARY OF THE INVENTION

It is the primary object of the invention to provide an advantageous, compact vacuum valve of the type mentioned above in which the sealed state can be maintained over a long period of time in the event of loss of pressure gas.

According to the invention, this object is met by a vacuum valve comprising a valve housing which has an inlet opening and an outlet opening which penetrate opposite walls of the valve housing, a valve seat surrounding the inlet opening, and a closure unit which is arranged in an interior space of the valve housing and which has a valve plate which is adjustable between an open position in which it releases the inlet opening, an intermediate position in which it covers the inlet opening but is lifted from the valve seat, and a closed position in which it covers the inlet opening and is pressed against the valve seat, and at least one adjusting piston which is arranged in an interior space of the closure unit and, for the purpose of adjusting the valve plate between its intermediate position and its closed position, is displaceable in direction of its longitudinal center axis between a passive position in which the valve plate is in its intermediate position and an active position in which the valve plate is in its closed position, wherein at least one work space of the closure unit that can be acted upon by pressure gas for displacing at least one adjusting piston into its active position is bounded by a diaphragm seal, and wherein at least one tappet is arranged at the adjusting piston on the side facing the outlet opening, this at least one tappet being guided out of the interior space of the closure unit through an opening and being supported directly or indirectly at the valve housing in the area next to the outlet opening for pressing the valve plate against the valve seat when the adjusting piston is displaced from its passive position into its active position.

Because the work space serving for the displacement of the adjusting piston into its active position is sealed by a diaphragm seal, a high degree of tightness of this work space can be achieved. Accordingly, the sealed state of the vacuum valve is maintained for a long period of time in the event of an outage of the pressure gas in the closed position of the valve plate.

Further, by means of the construction according to the invention, the vacuum valve can be constructed in a compact manner with respect to the dimensioning of the valve housing between the inlet opening and outlet opening.

In an advantageous embodiment form of the invention, the diaphragm seal is disk-shaped and is tightly connected in the area of its circumferential edge to the adjusting piston and, in a middle portion, is held in contact with the inner surface of a wall of the receiving housing for the adjusting piston. It is also conceivable and possible for the disk-shaped diaphragm to be connected in the area of its circumferential edge in a vacuum-tight manner to the wall and held so that its middle portion contacts the adjusting piston. Further, the diaphragm could also be annular and connected at its outer circumferential edge in a vacuum-tight manner to the adjusting piston or to the wall and at its inner circumferential wall to the other of these two parts.

At least one portion of the diaphragm, preferably an annular portion adjoining its outer circumferential edge, is made of a flexible plastics material.

A vacuum valve according to the invention can be constructed economically due to its small quantity of parts. Further, maintenance periods can be spread out over a longer time due to low wear.

In an advantageous manner, a work space which is acted upon by pressure gas can be sealed relative to a remaining area of the interior space of the closure unit by the diaphragm seal, and this remaining area of the interior space of the closure unit can be sealed relative to the vacuum area of the vacuum valve. Accordingly, this remaining area of the interior space of the closure unit can be connected to the atmosphere or evacuated. This remaining area of the interior space of the closure unit accordingly forms a safety space between the work space that is sealed by the diaphragm seal and the vacuum area of the vacuum valve to prevent pressure gas from flowing out into the vacuum area of the vacuum valve in case of a leak in the work space that is acted upon by pressure gas.

Further advantages and details of the invention are described in the following with reference to the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT EXAMPLES

An embodiment example of a vacuum valve according to the invention is shown inFIGS. 1 to 17. The vacuum valve has a valve housing1with an inlet opening2and an outlet opening3which penetrate opposite walls4,5of the valve housing1. A valve seat6surrounds the inlet opening2, which is formed by a sealing surface in the present embodiment example, at the inner surface of the wall4having the inlet opening2.

A closure unit8comprising a valve plate9is arranged in an interior space7of the valve housing1. In the present embodiment example, the valve plate9has a flexible sealing ring10for contacting the valve seat16in the closed state of the vacuum valve. It is also conceivable and possible in principle to arrange the sealing ring at the valve seat6and a sealing surface cooperating with the sealing ring at the valve plate9.

In this embodiment example, the vacuum valve is designed as a pendulum valve and the closure unit8is arranged at an arm12which is swivelable around a swiveling axis11. A rotary drive13serves to swivel the arm12by means of the shaft21at which the arm12is arranged. By means of the rotary drive13, the closure unit8and therefore the valve plate9can be swiveled between a position (FIG. 1) in which the inlet opening2is released and in which the vacuum valve is in its completely open state and a position in which it covers the inlet opening2viewed in direction of the longitudinal axis14of the inlet opening2(seeFIG. 5). Since the valve plate9is initially lifted from the valve seat6, this position is referred to within the present framework as the intermediate position.FIGS. 2 to 4show a middle position between the open position and the intermediate position.

The closure unit8further comprises a rigid adjusting piston5which is arranged in an interior space16of a receiving housing of the closure unit8. In the present embodiment example, a wall of this receiving housing is formed by the valve plate9. The valve plate9is arranged in another part of the receiving housing, preferably so as to be removable, e.g., by screws, and is accordingly sealed relative to this other part by means of a sealing ring51(see, e.g.,FIG. 11andFIG. 12). A wall17of the receiving housing located opposite to the valve plate9has openings for the passage of tappets18which are arranged at the adjusting piston15on the side of the adjusting piston15remote of the valve plate9. The passage through which the tappet18exits from the interior space16is preferably sealed, e.g., by means of bellows19.

The adjustment of the valve plate9between its intermediate position and its closed position, in which it covers the inlet opening2viewed in direction of the longitudinal axis14of the inlet opening2and is pressed against the valve seat6, is carried out by means of the adjusting piston15. For this purpose, the adjusting piston15is displaced in direction of its longitudinal center axis20between a passive position (FIGS. 6,10,12) and an active position (FIGS. 7 to 9and11). When the adjusting piston15is displaced from its passive position to its active position, the tappets18, which are initially at a distance from the wall5of the valve housing1having the outlet opening3, run against the inner surface of this wall5and consequently displace the valve plate9in direction of the longitudinal axis14of the inlet opening2, or in direction of the longitudinal center axis20of the adjusting piston15, until it is pressed against the valve seat. In so doing, the shaft21at which the arm12is arranged moves in direction of its longitudinal axis. A displacement of the shaft21of this kind is known in pendulum valves. For example, the shaft21has in the area of its end remote of the closure unit8an external toothing with which a toothed wheel of the rotary drive13engages, which external toothing can be displaced relative to the toothed wheel in longitudinal direction of the shaft21.

The longitudinal axis14of the inlet opening2preferably extends parallel to the longitudinal axis of the inlet opening3. These longitudinal axes preferably coincide. In the present embodiment example, the inlet opening2and the outlet opening3have the same diameter, which is preferable.

The longitudinal axis14of the inlet opening2and the longitudinal center axis20of the adjusting piston15are preferably parallel to one another. In the present embodiment example, these axes coincide in the closed position of the valve plate9.

In the area of their free ends, the tappets18preferably have flexible stop elements for running against the wall5.

Work spaces22,23are acted upon by pressure gas for displacing the adjusting piston15between its passive position and its active position. The work spaces22,23are sealed by means of diaphragm seals24,25. The diaphragm seals24,25are plate-shaped in this embodiment example and are tightly connected in the area of their circumferential edge to the respective side surface of the adjusting piston15. In the simplified views inFIGS. 6 and 7, this connection is not shown in detail. An embodiment example for a connection of this kind is shown inFIGS. 11 to 13. In this embodiment, the adjusting piston15has an annular groove26in which a projection27of the respective diaphragm seal24,25projects. The tight fastening to the adjusting piston15is achieved by means of a holding ring28and a clamping ring29which holds the holding ring in a position in which it is pressed against the diaphragm seal24,25and which is supported at an undercut shoulder of the adjusting piston15.

In a middle portion30, the diaphragm seal24is held in contact against the inner surface of the wall17of the closure unit8and the diaphragm seal25is held in contact against the inner surface of the valve plate9.

In the simplified views shown inFIGS. 6 and 7, these middle portions30are shown only by thickened areas. For example, they could be glued to the inner surface of the wall17or valve plate9. However, the diaphragm seal24,25is preferably rigid in this middle portion30and a pin31serves to hold it in contact with the inner surface of the wall17or valve plate9. This pin31is oriented in direction of the longitudinal center axis20of the adjusting piston15and penetrates a preferably central opening in the adjusting piston15relative to which it is sealed, for example, by means of a flexible sealing ring32. Further, the adjusting piston15is preferably provided with a sliding bush33surrounding this opening.

To hold the diaphragm seals24,25in contact with the inner surface of the wall17or valve plate9along their entire middle portion30by means of the pin31, the diaphragm seals24,25are rigidly constructed in this middle potion30. A flexible, resilient annular portion34adjoins the circumferential edge.

It is conceivable and possible to construct the middle portion30, in its entirety, from a rigid material, for example, metal. A plate-shaped metal part35is preferably coated with a flexible plastic or embedded in a flexible plastic in this middle portion30as is shown inFIGS. 11,12and16,17. The flexible plastic is preferably vulcanized on the plate-shaped metal part35.

The flexible plastic of the diaphragm seals24,25is preferably an elastomer or a thermoplastic elastomer.

The construction corresponds in principle to that described below with reference to another embodiment example shown inFIGS. 28 to 31. In the area of the annular portion34, the diaphragm seal24,25is made entirely of flexible plastic, preferably the same flexible plastic that is vulcanized on the metal part35in the middle portion30.

Pressure gas channels37,38extending through the receiving housing for the adjusting piston15serve for supplying pressure gas to the work spaces22,23. In the views according toFIG. 6andFIG. 7, a pressure gas channel37extends through the wall17and a pressure gas channel38extends through the valve plate9. The pressure gas channels37,38are continued by holes in the middle portions30of the diaphragm seals24,25and open through these into the work spaces22,23.

Compressed air or nitrogen under pressure, for example, are preferably used as pressure gas.

However, it is preferable that the two pressure gas channels37,38extend through the wall17, and the pressure gas channel38is continued by a hole through the middle portion30of the diaphragm seal24and a channel39which extends in the pin31and which exits at the circumference of the pin31in the area of the work space23(seeFIGS. 11,12,16and17).

The pressure gas channels37,38preferably extend through flat pipes40,41which are introduced in recesses of the wall17and whose interiors communicate with the holes in the diaphragm seal24by bore holes through their walls. The holes in the diaphragm seal24are preferably sealed relative to the pipes40,41by sealing beads of the diaphragm seal24which are pressed against the pipes40,41.

For the sake of simplicity, the diaphragm seal25can be constructed identical to diaphragm seal24.

The adjusting piston15can also be guided by the pin31. Additional guides can be provided in the area of the circumference of the adjusting piston15if required (see guide pins52inFIGS. 9 and 10).

The pressure gas channels37,38are continued by pressure gas channels, not shown in the drawing, in the shaft21so that the work spaces22,23can be acted upon by pressure outside the valve housing1.

For displacing the valve plate9from its intermediate position to its closed position, pressure gas channel38is acted upon by pressure gas and pressure gas channel37is connected to atmospheric pressure so that the work space23is charged and the adjusting piston15is displaced from its passive position into its active position. To return to the intermediate position, pressure gas channel37is acted upon by pressure gas and pressure gas channel38is connected to atmospheric pressure so that the work space22is charged and the adjusting piston15is returned to its passive position.

When the adjusting piston15is adjusted from its passive position to its active position, and vice versa, there is an elastic deformation of the diaphragm seals24,25in the area of their annular portions34. The annular portions34preferably enclose an angle between 0° and 45° with the plane of the adjusting piston15over the entire adjustment area. On the other hand, there is no deformation of the diaphragm seals24,25in the area of their middle portions30.

It is also conceivable and possible that the diaphragm seals24,25are fastened in the area of their circumferential edge to the inner surface of the wall17or valve plate9. In the middle portion, they could be fastened to the respective surface of the adjusting piston15or pressed against the adjusting piston15in that the work space22,23sealed by them is acted upon by pressure.

It is basically conceivable and possible also that the diaphragm seals24,25are constructed annularly, i.e., only the outer portion34described above is provided, and fastened to the adjusting piston15on one side and to the inner surface of the wall17or valve plate9on the other side so as to be connected to these parts in a vacuum-tight manner in each instance. They would then be formed of flexible plastic36in their entirety and would preferably enclose an angle between 0° and 45° with the principal plane of the adjusting piston15over the entire adjustment area of the adjusting piston15.

Accordingly, in the plate-shaped construction of the diaphragm seals24,25as well as in an annular construction of the diaphragm seals, the work spaces22,23are bounded by the diaphragm seals24,25in radial direction with reference to the longitudinal center axis20of the adjusting piston15.

The work spaces22,23are sealed from the rest of the area of the interior16of the closure unit8by the diaphragm seals24,25. This remaining area of the interior space16of the closure unit8is preferably sealed from the vacuum area of the valve; for example, bellows19are provided for the tappets18as was shown and described above. This remaining area of the interior space16can preferably be connected to the atmosphere by a conduit that is not shown in the drawings. It is also conceivable and possible to evacuate this remaining area of the interior space. Accordingly, the pressure of the pressure gas acting upon the adjusting piston15is separated from the vacuum area by the intermediary of a space which is at atmospheric pressure or is evacuated. This represents an additional safety function of the vacuum valve.

FIGS. 18 and 19show a simplified view of a somewhat modified embodiment form in which the pin31is sealed from the adjusting piston15by a diaphragm seal42. These diaphragm seals are annular and are fastened to the pin31on one side and to the adjusting piston15on the other side and are sealed relative to these parts. Accordingly, there are no longer any dynamic seals in this construction; rather, all of the seals are formed as static seals.

As is shown inFIGS. 20 and 21, springs43can also be provided for restoring the adjusting piston15to its passive position from its active position. Accordingly, the work space22and the diaphragm seal24sealing this work space are omitted in this embodiment example. Therefore, a single-action adjusting piston15is provided in this embodiment example instead of the dual-action adjusting piston described above. Again, the pressure gas preferably impinges on the work space23through which the adjusting piston15is displaced into its active position through a bore hole through the pin31. The pin31is supported at its end remote of the work space23by a seal44at the pipe41and, therefore, indirectly at the wall17.

Also, in this embodiment example the work space23is sealed from the rest of the area of the interior space16of the closure unit8by the diaphragm seal25. The rest of the area of the interior space16is preferably connected to atmospheric pressure or is pumped out (via a channel which is not shown in the drawings).

In the embodiment example shown inFIGS. 22 to 31, the closure unit8is displaced linearly (in a straight line) between the open position of the valve plate9and the intermediate position of the valve plate9. For this purpose, for example, it is arranged at a valve rod45which is displaceable in its longitudinal direction by means of a linear drive, for example, a piston-cylinder unit46which is shown schematically inFIGS. 22 and 24.

The inlet opening2and outlet opening3in the valve housing1and the valve plate9have a rectangular shape in this embodiment form. The closure unit8comprises, for example, three adjusting pistons15. More or fewer adjusting pistons15can also be provided. Each adjusting piston15is constructed as a dual-action piston in a manner analogous to that described above in connection with the embodiment example according toFIGS. 1 to 17, and diaphragm seals24,25serve to seal the work spaces. Again, a respective adjusting piston15could be restored to its passive position from its active position through at least one spring and the diaphragm seals24could again be dispensed with in this case.

The adjusting pistons15have circumferential contours deviating from the circular shape considered in the direction of their longitudinal center axis20(FIGS. 22 to 25). They are provided with projecting portions47at opposite locations in circumferential direction. A tappet18is arranged at the adjusting piston15in the area of a respective projecting portion47. These tappets are again guided out of the receiving housing for the adjusting pistons15through bore holes and serve for pressing the valve plate9against the valve seat6in the active position of the adjusting pistons15.

The same adjusting pistons15in different rotational positions can be used for inlet and outlet openings of different widths (seeFIGS. 22 and 24). The receiving housing for the adjusting pistons15is adapted to the respective corresponding width of the inlet opening2and outlet opening3.

In order to supply pressure gas through the opening48of the diaphragm seal24for different rotational positions of the adjusting pistons15and with those of the diaphragm seals24,25arranged at the latter, this opening48is shaped as an elongated hole extending along a circular arc.

This opening is preferably closed by flexible plastics material for the diaphragm seal24as is shown inFIGS. 29 and 31.

The diaphragm seals24,25are again formed of flexible plastic in the annular portion34and are rigidly constructed in a middle portion30. For this purpose, a metal part35is embedded in the flexible plastics material in the middle portion or is at least partially surrounded by it as can be seen fromFIGS. 30 and 31. The flexible plastics material extends along the side of the metal part35facing the inner surface of the wall17or the valve plate9and preferably also along the opposite surface of the metal part35in a radial outer portion of the metal part35.

FIG. 27shows guides49for the adjusting pistons15which are arranged in the area of the circumferential edge of a respective adjusting piston15.

FIGS. 32 and 33show another embodiment example of the diaphragm seal24. In the middle portion, the diaphragm seal is constructed in the manner described above with reference toFIGS. 30 and 31. In this embodiment form, the annular portion34is constructed in the manner of a rolling diaphragm and it carries out a kind of rolling movement when the adjusting piston15is displaced, i.e., the area of the portion34which is arc-shaped in cross section is displaced along this portion34.

The diaphragm seal25can be constructed in an analogous manner, and the opening48can be closed (corresponding toFIG. 31).

Rolling diaphragms of the kind mentioned above can be used in all of the described embodiment forms for the diaphragm seal24and/or for the diaphragm seal25.

Various modifications of the embodiment examples shown herein are conceivable and possible without departing from the scope of the invention. For example, a plurality of pins31could be provided. Also, more or fewer tappets18can be provided. Also, a plate-shaped contact pressing element could be arranged at the ends of the tappets18remote of the adjusting piston15for contacting the inner surface of the wall5of the valve housing1. In this case, the tappets18are supported by the plate-shaped contact pressing element indirectly at the valve housing1in the area next to the outlet opening3. In this case, only one individual, preferably centrally arranged, tappet18could also be provided.

Further, the valve plate could also be arranged at the end of the at least one tappet18remote of the adjusting piston15and can be pressed against the valve seat6by the adjusting piston15. In this case, the wall of the receiving housing for the at least one adjusting piston15which is located opposite from the wall17that is penetrated by the at least one tappet18would contact the inner surface of the wall5of the valve housing1having the outlet opening3in the active position of the at least one adjusting piston15in the area around the outlet opening3and would transmit the reaction force to the valve housing1.

As follows from the preceding description, the range of the invention is not limited to the embodiment examples shown herein, but rather should be defined with reference to the appended claims together with their full range of possible equivalents.

While the preceding description and drawings show the invention, it is obvious to a person skilled in the art that various modifications can be carried out without departing from the spirit of and field of the invention.

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