GB2289319A

GB2289319A - Flow control valve

Info

Publication number: GB2289319A
Application number: GB9508557A
Authority: GB
Inventors: Hugo Frei; Peter Keller; Martin Boesch
Original assignee: Balzers AG
Current assignee: OC Oerlikon Balzers AG
Priority date: 1994-05-09
Filing date: 1995-04-27
Publication date: 1995-11-15
Anticipated expiration: 2015-04-27
Also published as: CH689735A5; FR2719647A1; FR2719647B1; GB9508557D0; DE19508691A1; GB2289319B

Description

2289319 TITLE VALVE

DESCRIPTION Inventive Field

The present invention relates to a valve, in particular a vacuum valve.

Background Art

In vacuum valves, which have an opening or closure member that includes a valve stem together with a valve disc, as well as in slide valves, in which a slide plate is moved in the plane of the opening to be controlled by the valve, it is customary to actuate the opening movement with remotecontrolled driving elements, for example, by pneumatic, hydraulic, or electromagnetic means, whereas, in contrast, the closing movement is spring- actuated, such that, for example in case of electrical power failure, the valve shifts into the safe closed position.

Accordingly, the locking spring must be dimensioned such that the necessary sealing force is produced on the valve seat, whether this is along a circular sealing means around the opening of the valve seat, or against a linear sealing means of a slide valve. Especially in the case of circular sealing means, additional forces, operating in the opening direction caused by pressure differentials, must be accommodated.

Figure 1 depicts by the example of a schematically depicted valve, especially a vacuum valve with valve stem 1 and valve disc 3, a known valve with locking spring 5 and an opening driver 7, which acts against the force of the locking spring. Numeral 9 denotes the ring-shaped sealing region, 11 denotes a metal bellows, used for vacuum applications, which seals driver 7 and particularly locking spring 5 against the vacuum connection the valve is supposed to open and close. Mechanical springs always exhibit a restoring force that increases with increasing compression displacement.

Accordingly, as shown on the right of Figure 1, as the lift X of the valve disc increases, the spring force increases in the closing direction. At x = 0, i.e., a closed valve, the spring acts with closing force F1 corresponding to the requisite sealing force. Although valve locking springs conventionally have a relatively flat characteristic curve, so far as installation conditions permit, the spring force acting on the valve disc in the opening direction increases to a value F2 at the usual working lift s. The value F2 is usually approximately 20%, to 305%, higher than the spring force F, in the closed position, which ensures the requisite sealing force in the sealing region 9.

Thus, the opening drivers 7 must act against force F2, although only F,, the functionally active spring force at x 0, would be necessary. This results in drivers 7 that are larger and consume more power, and in correspondingly larger valves.

If the driver 7 is an electromagnetic unit, then it must be further considered that the electric driving current increases quadratically with the expended force, i.e., it increases proportionally with the square of (F2 - F,). The task of the present invention is eliminating the described disadvantage in a valve as described above, especially in a vacuum valve.

The Invention The invention provides a valve in which a driven member moves away from and closes against a sealing region associated with a valve seat to open and close the valve respectively, characterized in including:

two faces one connected to the valve seat and one to the (L) between the faces is at a is closed against the sealing driven member such that a gap minimum when the driven member region; and means for producing a magnetic field (H) to cause attraction between the faces and bias the driven member towards the sealing region.

Because of the minimal air gap between the f aces when the driven member is in the closed poisition, the magnetic force is at a maximum there, but decreases as the valve is opened.

Thus, the driving unit for opening the valve, whether electromagnetic, pneumatic, or hydraulic, can be constructed smaller, such that such a unit can be designed for lower power consumption or for lower driving- medium pressure. it need only be designed for the maximum opposing force, the magnetic sealing force.

The self-closing function is retained in that, in the case of failure of the driving energy, the magnetic force continues to close the valve.

Moreover, because known locking springs are relatively long, the valve constructed according to thepresent invention can be shorter. Even failures, such as a spring failure in known locking-spring valves, need not be considered because the availability of the magnetic force is essentially uninterruptable. Because the field-determined magnetic force exists along the air gap, there is an optimal distribution of sealing pressure on the sealing means. In contrast to a locking spring, the magnetic force reaches its maximum at the minimum air gap (which may be no air gap at all) i.e., in the closed position. The structural force-producing members, and the air gap can be designed anywhere along the movement path of the closure/opening member, which provides great flexibility concerning the valve construction and application of the invention to current valve designs.

Therefore, the magnetic force can, for example, act directly on the valve disc, in that a permanent-magnet arrangement or an electromagnet arrangement may be disposed on the valve disc or on the valve seat, and correspondingly, the opposing part constructed from lightly magnetic material. The magnet/air-gap arrangement can also be disposed along a valve stem or, in a slide valve, along the lateral sliding guides.

Claims

Preferred embodiments of valves, especially vacuum valves, according to

the invention are specified in Claims 2 through 9.

The invention will be explained, by example, in conjunction with the Figures.

Therein depict:

Fig. 2 schematically the basic according to the invention; principle of a valve Fig. 3 based on the principle of Fig. 2, a preferred embodiment of a valve according to the invention, in which the closing lift is traversed by spring action before reaching the closed position; Fig. 4 based on the principle of Fig. 2, potentially also implemented according to Fig. 3, a preferred embodiment of movement attenuation of the closure/opening member of the valve, in order to prevent chatter; Fig. 5 a further embodiment of a valve according to the invention, analogous to the representations in Figs. 2-4, in which the closing force and, thereby, also the sealing force, is controlled as a function of the lift; Fig. 6 in partial sectional view, a currently preferred embodiment of a valve according to the invention.

v oll First, the basic principle of the invention will be explained with reference to Figures 2-5.

From these, a person skilled in the art could derive a large number of different possible implementations, of which a currently realized version is presented in Fig. 6.

According to the schematic functional representation of Fig. 2, a valve basically comprises a stationary frame of reference, usually a housing 10, with a sealing region 12, also with an opening/closure member 14, with its own sealing region 17, which is forced against the sealing region 12 in the direction of double-arrow K.

The driving system for moving the closure/opening member 14, especially in the opened position, which could be an electromagnetic, pneumatic, or hydraulic driving unit, is not depicted in Figures 2-5.

on the closure/opening member 14 and the stationary housing 10 there are, respectively, a face 160 and a face 16u, which between themselves f orm. an air gap L in the movement direction K. As shown, the faces 16 are oriented perpendicularly to direction K and are substantially flat.

However, depending on the desired design of the air gap, they can be arcuate. The opposing faces are in the flow of a magnetic field H, preferably but not necessarily a static magnetic field. The magnetic system 18 generating the magnetic field H is, as represented by dashed lines, coupled either with the movement of member 14 or with the stationary housing 10. The faces 160 and 16u, permeated by the magnetic field H, are either magnetised solely by the magnetic system 18 itself, or comprise lightly magnetic material, such that the member 14 is f orced toward the sealing region 12 by the magnetic force F.

The magnetic system 18 is preferably a permanent magnet -6 arrangement, but it can also be an electromagnet arrangement or a combination of permanent and electromagnets.

If, as in Fig. 1, the lift of the member 14 starting from the closed position is designated by x, then the closing f orce F, starting from the closed position at x = 0, is qualitatively represented by the decreasing value in Fig. 2.

It is entirely possible to drive the member 14, as driving member, through the entire closure lift, i.e., from the open position at x = p to the closed position at x = 0, by means of the magnetic system 18. However, in many cases, it is simpler, for design reasons, to employ the ef feet of the inventive magnetic system only in the region where member 14 approaches its closed position.

For this purpose, as shown in Fig. 3, which corresponds to Fig. 2 and includes the same position symbols, it is suggested that a locking spring 20, supported on the wall of housing 10, be allowed to act on the member 14, the sole purpose of the spring 20 being to overcome the friction between member 14 and the stationary housing 10, and to drive the member into a predetermined region proximate to the sealing region 12, where the magnetic system 18, as designed according to the invention, assumes the residual closing and ensures the sealing force.

As was evident in the explanations of Figures 2 and 3, the placement of the faces 160 and 16u can be selected according to the valve design and may vary widely depending on this design. For example, the faces could be formed directly on a valve disc 160, and a valve seat 16u.

As indicated by the direction of the closing force, shown in principle in Fig. 2, the member 14 is increasingly accelerated by the magnetic force F towards the sealing region 12. In order to prevent chatter as member 14 reaches its closed position ( x = 0), an elastic damping 1 A member 22 is provided according to Fig. 4, which corresponds to the representations of Figures 2 and 3. The elastic damping member 22 acts on member 14, on the one hand, and rests against the housing wall, on the other. Thus, as qualitatively represented by the dashed line in Fig. 2, a damping of the progressively accelerated movement of member 14 is achieved in the region proximate to the sealing region 12, so that chatter is avoided.

In a preferred embodiment, the elasticity in sealing region 12 and/or in the sealing members of sealing region 17 of the moving-member, such as in O-Ring seals, can be directly utilized as an elastic damping member 22. The magnetic closing force acts against their elasticity in the final, proximate region at the sealing position. Figure 4 depicts an embodiment in which by means of a spring member the magnetic closing force F, especially as the member 14 approaches the sealing region 12, distinguished from the magnetic force characteristic, can be optimally adapted i.e., a damping of the closing force is carried out as a function of the lift x.

Furthermore, according to Fig. 5, this can also be realized by utilizing a permanent/electromagnetic system 18a to a far more flexible extent. For this purpose, a lift detector 24 is provided, whose output signal s(x) depends on the lift x of member 14. The output signal s(x) of detector 24 is linearly or nonlinearly amplified by a processing unit 26, and controls the electromagnetic current I of the electromagnets provided in unit 18a. The detector 24 can very simply be an electric switching section which closes as member 14 approaches sealing region 12, and thereby permits electric current to the electromagnet arrangement.

Such a switching section, for example, can be realized simply in the closure region of the member 14, for example, by utilizing member 14 itself as the switching section, in order to activate the electromagnet arrangement or partially electromagnetic arrangement of unit 18a.

Figure 6 depicts as example a currently preferred embodiment example of a valve according to the invention in the form of a vacuum valve. An armature 30 is disposed so as to be axially slidable on the valve stem 14a, which stem forms part of the opening/closure member 14 of Figures 24. The armature 30 is driven by the field of a coil arrangement 32. The armature 30 acts in the opening direction on a shoulder 14b of the valve stem 14a in order to lift up the latter, and the armature is tiltably disposed on the valve stem 14a, so that the bore 30b of the armature has some clearance relative to the smaller diameter of the section of valve stem 14a. As a result, when the valve is in the opened position, the upper front face of the armature 30 can come into contact flat with the opposing face 30c.

The armature 30, which operates simultaneously as a damping piston, slides along a cylinder bore 43, sealing by means of seals 34, and defines thereby cylinder chambers 340 and 34u, depending on its position.

A first inlet/outlet line 36u leads into the lower chamber 34u, a second inlet/outlet line 360 leads into the upper chamber 340. As final flow control elements, filters of selectable flow rate values are inserted into the inlet/outlet lines 36. As shown by the dashed lines 38, an overflow line is incorporated into the armature 30, in addition to or instead of lines 36. A filter of given flow rate value, preferably changeable, is inserted in the overflow line.

The valve stem 14a acts on a valve disc 40, which supports a locking spring 42 resting against the housing wall. The valve disc 40, which is also part of the closure/opening member 14 as shown in Figures 2-4, closes or opens a connection between lines 44 and 46 of a vacuum system. The i vacuum system is enclosed by means of a metal bellows 48 relative to the valve stem 14a with locking spring 42 and dampening unit/driving unit.

A permanent magnet ring 50 is inserted in the sealing region around the opening of line 44 to be closed. This corresponds to the case of Figures 2-4 in which the magnetic system 18 is attached to the housing 10. The valve disc 40 comprises f or example sof t iron so that it is drawn to the valve seat by the magnetic ring 50. In order to avoid chatter, consistent with the embodiments of Figure 4, a seal 52, which would be included anyway, is located at the valve disc, as depicted, or at the valve seat, or combined, in such a way that the magnetic force of magnet 50 acts only with a compressing effect against the elasticity of the sealing arrangement 52 during the end of the closure phase, thus avoiding chatter.

It is understood that it is readily possible to provide the magnet arrangement at the valve disc; or, in magnet arrangements that acts in the closing direction, attached either to the housing wall or to the valve stem/disc; the system can comprise permanent and/or electromagnets, and/or the magnet arrangement for generating closing power can be disposed along the valve stem 14a according to convenience of implementation.

Thus, in the versions depicted in Figure 6, it would be readily possible to provide the magnet arrangement on armature 30, as represented by dashed lines at 50a but to operate the armature 30 in the closing direction against a stop on the valve stem 14a.

The locking spring 42 acts only with low force on the valve disc 40, solely in order to move the valve disc into the region near the ring magnet 50, thereby overcoming friction. The actual sealing closure, at least in principle, is achieved by the action of magnet 50 on valve disc 40.

CLAIMS 1. A valve in which a driven member (14, 14a, 40), moves away from and closes against a sealing region associated with a valve seat to open and close the valve respectively, characterized in including:

two f aces (16u, 160) one connected to the valve seat and one to the driven member (14, 14a, 40) such that a gap (L) between the faces is at a minimum when the driven member is closed against the sealing region; and means f or producing a magnetic f ield (H) to cause attraction between the faces and bias the driven member towards the sealing region.
2. A valve according to claim 1, wherein the f aces (16u, 160) lie substantially in planes perpendicular to the direction of movement of the driven member (14, 14a, 40).
3. A valve according to claim 1 or claim 2, wherein the means for producing the magnetic field includes a permanent magnetic system (18, 50) and/or an elecMmagnetic system (18a) attached to at least one of the faces (160, 16u).
4. A valve according to any of claims 1 to 3, wherein the magnetic field (H) is controlled by a control signal (s(x)), which is dependent on the distance (x) between a sealing region of the member (14, 14a, 40) and the sealing region associated with the valve seat.
5. A valve according to any of claims 1 to 4, wherein the driven member (14) includes a slide plate of a slide valve, and the sealing region includes a linear sealing member (12).
6. A valve according to any of claims 1 to 4, wherein the driven member (14a, 40) includes a valve stem (14a) and a valve disc (40).
7 7. A valve according to any of claims 1 to 6, immediately before or during closure against the region, the driven member acts against an elastic (22, 52) which biases the driven member in an opening direction.

wherein sealing member
8. A valve according to claim 7, wherein the elastic member comprises an elastic sealing member (52) on the driven member (14, 14a, 40) and/or at the sealing region (12).
9. A valve according to any of claims 1 to 8, wherein a locking spring (20, 42) acts on the driven member (14, 14a 40) in the closing direction, to bias the driven member towards an effective region of the magnetic field (H).
10. A valve according to any of claims 1 to 9, wherein the valve is implemented as a vacuum valve.
11. A valve substantially as described herein with reference to figure 6 of the drawings.