Vacuum valve

Abstract

To provide a vacuum valve which can be surely operated and has higher energy efficiency.SOLUTION: The vacuum valve includes: a valve housing defining a passage connecting a first opening and a second opening of the valve housing; a valve body and a complementary seat disposed in the passage, the valve body and the complementary seat comprising a sealing member. The valve body being movable in a linear axial direction along an open position and a closed position. The valve body comprises: a valve body and a complementary seat cooperating with the seat in a closed position to hermetically close the first opening; and an electromechanical actuation unit for actuation of the valve body, the actuation unit comprising: a mechanical conversion unit comprising an electric motor, an input drivingly connected with the electric motor and an output drivingly connected with the valve body, wherein the mechanical conversion unit comprises an electromechanical actuation unit for converting a rotational output of the electric motor into a linear movement of the output to move the valve body in an axial direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a vacuum valve for a medium, high or ultra-high vacuum system.A further aspect of the invention relates to a method of operating a vacuum valve. [Background technology]

[0002] Medium, high and ultra-high vacuum systems are used in many technical fields and in industrial and scientific applications. -9 Such vacuums, in the Pa range, place very high requirements on the design of the components used in such systems. In particular, the valves of such systems must meet high standards, as they must be able to reliably prevent gas leakage when in the closed state.

[0003] Conventional vacuum valves are based on pneumatic or solenoid actuators. Although such valves are generally reliable, a significant amount of energy is required to operate the valve and to hold it in an open or closed position. However, energy efficiency is becoming an increasingly important issue due to environmental, cost, and other considerations. Summary of the Invention [Problem to be solved by the invention]

[0004] It is therefore an object of the present invention to provide a vacuum valve which is reliably operable and more energy efficient. [Means for solving the problem]

[0005] According to a first aspect of the present invention there is provided a vacuum valve for a medium, high or ultra-high vacuum system, the vacuum valve comprising: a valve housing defining a passageway connecting a first opening and a second opening of the valve housing; a valve disc and a complementary seat disposed in the passage, at least one of the valve disc and the complementary seat comprising a sealing member, the valve disc being linearly axially movable along an open position and a closed position, the valve disc cooperating with the seat in the closed position to hermetically close a first opening; an electromechanical actuation unit for actuating the valve disc, the actuation unit comprising an electric motor, a mechanical transformation unit having an input part drivingly connected to the electric motor, and an output part drivingly connected to the valve disc, the mechanical transformation unit transforming a rotational output of the electric motor into a linear motion of the output part to axially move the valve disc; Equipped with.

[0006] Such an electromechanical actuation unit can be very compact and efficiently converts the input electrical energy into an actuation movement of the valve disc. Due to the relatively low energy consumption of the vacuum valve according to the invention, it does not necessarily have to be supplied with power via the power grid for its operation. It may operate from a battery or capacitor source or may be equipped with solar panels.

[0007] The motor may be, for example, an in-runner or out-runner type brushed or brushless motor (such as a stepper motor). The motor alternatives provide flexibility in identifying the solution with the best overall characteristics.

[0008] Furthermore, the electromechanical actuation unit allows the valve disc to assume not only the open or closed position, but also any intermediate position. Suitable control of the motor, for example provided by an internal or external control unit, makes it possible to further influence the dynamics of the valve disc's movement during the opening and closing of the valve.

[0009] At least one of the valve disc and the seat may include a plurality of sealing members.

[0010] According to one embodiment of the present invention, the mechanical conversion unit comprises a lead screw cooperating with a nut element. Such a conversion unit is inexpensive and can be easily scaled to meet practical requirements.

[0011] For example, the output may comprise a nut element, which is moved axially by rotation of a lead screw provided directly or indirectly by an electric motor, although it is also conceivable to provide an axially movable screw, which holds the nut element in an axially fixed position.

[0012] According to one embodiment, at least one first elastic element, e.g. a spring, is provided, which is supported by the valve housing and acts on the valve body such that a force is applied to the valve body, urging it axially to the closed position. This force is a biasing force supporting the closing movement of the valve body. This means that less torque is provided by the electric motor to generate the desired closing force during the closing movement of the valve body. As a result, said motor can be smaller in size and / or the energy required to operate the valve is reduced.

[0013] According to one embodiment, the valve disc is axially movable relative to the output, in other words the valve disc is not fixedly attached to the output in order to allow compensation of thermal effects and / or minor inaccuracies of the operation of the electromechanical actuation unit, in particular the electric motor.

[0014] The electromechanical actuation mechanism may comprise at least one second elastic element, e.g. a spring, supported by the output and acting on the valve disc such that a force is exerted on the valve disc urging it axially away from the output, this biasing force serving to provide the compensation.

[0015] The output and the valve disc may be coupled by a coupling unit which limits the relative axial movement of the output and the valve disc, the coupling unit being provided to ensure that the valve disc moves together with the output when the maximum allowable spatial separation of these parts is reached, in particular when the vacuum valve is opened.

[0016] In embodiments comprising both first and second elastomeric elements, the first elastomeric element may have a higher elasticity than the second elastomeric element to obtain the desired valve characteristics.

[0017] According to one embodiment, the output part is held rotatably fixed by a guiding device. The guiding device may comprise a protrusion cooperating with an axially extending guiding slot or groove. Alternative guiding concepts may also be employed, for example guiding rails and / or guiding based on the outer (non-rotationally symmetric) shape of the output part.

[0018] According to one embodiment, the electric motor and the input are drivingly coupled via at least one reduction drive. Such a reduction drive makes it possible to optimize the thrust and the linear actuator speed. This may comprise, for example, gears, belts and / or pulley wheels. However, a direct drive may also be used, in which the output member of the motor is directly coupled to the input of the mechanical conversion unit.

[0019] According to one embodiment, the electromechanical actuation unit comprises at least one locking device and / or locking function for locking the output or the valve body in a desired axial position. The locking function may be provided by the mechanical conversion unit or by the reduction drive, if present. For example, the mechanical conversion unit and / or the reduction drive have self-locking properties, for example due to the specific design of its mechanical parts. However, it is also conceivable that multiple locking devices or functions are provided in order to obtain design alternatives for improving packaging, cycle life and energy efficiency. Locking methods include mechanical, electrical and electromechanical concepts. An electric motor may be used as a locking device and then function as an electric locking device. An electric clamp break is an example of an electromechanical locking device.

[0020] The self-locking concept is associated with many specific advantages, such as reduced time-averaged power consumption and reduced wear on the electric motor, the converter unit of the valve and the associated control unit (electronics). In particular, the electric motor can be put into standby mode or even completely shut down if the electromechanical actuating unit is in a self-locked state. In this case, specific holding breaks or active control of the motor are also dispensed with. A further advantage is also that the valve is maintained in its current state during a power failure, e.g. in the open, closed or intermediate position of the valve disc.

[0021] According to one embodiment, a position sensor is provided to detect the position of the output and / or the valve disc. Such a sensor makes it possible to provide a closed loop control such that data provided by the sensor can be used to control the electric motor. The sensor may be an encoder, an optical sensor, a Hall effect based sensor, or any other suitable sensor.

[0022] With information regarding the position of the output and / or valve disc, the dynamics of the electromechanical actuation unit can be determined and adapted as needed by controlling the electric motor accordingly, and the valve disc can be easily placed in a desired intermediate position to control the gas flow dynamics within the vacuum system to affect, suppress or enhance pressure time profiles, pressure spikes, gas velocities, flow induced debris generation and movement, and pump inlet pressure.

[0023] It is also possible to provide open-loop control of the motor: for example the actuation unit comprises a stepper motor equipped with a step counter, the data provided by the counter being an indication of the actual position or state of the output.

[0024] According to a second aspect of the present invention there is provided a vacuum valve for a medium, high or ultra-high vacuum system, the vacuum valve being adapted to: a valve housing defining a passageway connecting a first opening and a second opening of the valve housing; a valve disc and a complementary seat disposed in the passageway, the valve disc and the complementary seat comprising a sealing member, the valve disc being linearly movable between an open position and a closed position, the valve disc cooperating with the seat in the closed position to close a passageway of the vacuum enclosure; an actuation unit for actuating the valve body; a sealing member having at least one of a non-circular shape in a cross section perpendicular to the first opening, being hollow, having a PTFE material or coating, and having a fluoroelastomer material or coating; The hollow material carrying the seal member, the applied material, and / or the fluoroelastomer material may have a circular shape.

[0025] The use of such a sealing member (a "low force seal"), which compresses at a relatively low force and / or provides suitable sealing properties when subjected to relatively low forces, helps to reduce the energy required to actuate the valve. The concept according to the second aspect of the invention can be combined with a vacuum valve according to the first aspect of the invention, and vice versa.

[0026] According to one embodiment, first and second seal members are provided, where the first seal member is fixed to the valve body and the second seal member is fixed to the housing. The first and second seal members may be arranged to contact when the valve is closed. In this embodiment, both seal members compress against each other when the valve body moves to the closed position. The seal-to-seal compression provides a more reliable seal than seal-to-metal compression in most cases for a given compression force. Or stated differently, the force required to obtain a proper sealing of the valve is relatively low.

[0027] The first and second sealing members may be fixed to the corresponding components by vulcanization. The sealing members may be PTFE and / or fluoroelastomer materials and may be coatings on the valve body and / or seat.

[0028] The vacuum valve according to the first and / or second aspect of the invention may comprise an actuation unit comprising an energy storage unit for supplying electrical energy to the electric motor. A suitable energy storage unit (e.g. a battery pack) allows the electric motor to be operated for a significant period of time without the need to be connected to a power grid, so that the concept according to the invention leads to a valve with reduced energy consumption. If the control unit provided for controlling the motor and / or monitoring the state of the valve has no wired connection (e.g. a wireless data connection may be envisaged), the operation of the valve may be completely cordless.

[0029] According to a third aspect of the present invention, there is provided a method of operating a vacuum valve, in particular according to the embodiment described above, said vacuum valve comprising: a valve housing defining a passageway connecting a first opening and a second opening of the valve housing; a valve disc and a complementary seat disposed in the passageway, the valve disc and the complementary seat having a sealing member, the valve disc being linearly axially movable along an open position and a closed position, the valve disc cooperating with the seat in the closed position to hermetically close a first opening; an electromechanical actuation unit for actuating the valve disc, the actuation unit comprising an electric motor, a mechanical transformation unit having an input part drivingly connected to the electric motor, and an output part drivingly connected to the valve disc, the mechanical transformation unit transforming a rotational output of the electric motor into a linear motion of the output part to axially move the valve disc; The method for operating a vacuum valve, comprising: The electric motor is operated during movement of the disc to the closed position such that the disc's velocity is reduced at least one of before and during contact of the disc with the seat.

[0030] In particular, if a seal is provided on the disc, the velocity will decrease before the seal contacts the seat. If a seal is provided on the seat, the velocity may decrease before the disc contacts the seal. If seals are provided on both the seat and the disc, the velocity of the disc may decrease before the seals collide with each other.

[0031] In a manner of speaking, the reduction in the valve disc's velocity provides a "soft landing" of the disc on its complementary seat. The slower approach of the disc reduces stress on the sealing members and reduces the induction of wear. Furthermore, the selection of an appropriate velocity profile minimizes the generation of vibrations during valve closure. This also reduces the generation and transport of fine debris particles within the valve that can cause serious problems when introduced into a vacuum system.

[0032] According to one embodiment of the method, the motor is operated such that movement of the disc from the open position to the closed position takes longer than movement of the disc from the closed position to the open position, and in particular the motor is operated such that compression of the seal member during movement of the disc to the closed position takes longer than decompression of the seal member during movement of the disc out of the closed position.

[0033] When opening a valve, the problems of vibration and stress on the seals, seats and disc are less pronounced, so it can be opened faster than it can be closed, thereby proving the dynamic properties of the valve. This is especially true for the decompression of the seals.

[0034] According to an embodiment of the method, the electric motor is operated in the closed position of the valve disc such that the force acting on the sealing member does not fall below a predefined threshold. This measure ensures that the valve is closed. The force acting on the sealing member may be determined based on data provided by at least one of force, strain or temperature sensors. In particular, data provided by appropriately positioned force or strain sensors may be used to directly determine the force acting on the sealing member. An indirect determination of the force is also possible, for example by estimating the force based on the temperature of the valve housing, the seat, the actuation unit and / or the valve disc. According to an embodiment, the force acting on the sealing member is determined based on operating variables of the electric motor. Such an indirect determination of the force may be based on measured motor current or voltage data. For example, the current required for the rotation of the motor through a certain angle (for example an angle less than 5°) can be used to estimate the force acting on the sealing member, since the current is essentially proportional to the force acting on the sealing member.

[0035] Other sensors that may optionally be provided to monitor the state of the vacuum valve may provide a source of data for determining or estimating the above-mentioned forces. The thresholds may be fixed values ​​or may be determined based on operational variables of the valve and / or vacuum system. [Brief description of the drawings]

[0036] [Figure 1] FIG. 1 shows a first embodiment of a vacuum valve in cross section. [Diagram 2] FIG. 2 shows a cross-section of the first embodiment in a perspective view. [Diagram 3] FIG. 3 shows a perspective view of the first embodiment. [Figure 4] FIG. 4 illustrates a schematic diagram of a second embodiment of the vacuum valve. [Diagram 5] FIG. 5 shows a schematic top view of the second embodiment. [Figure 6] FIG. 6 shows a schematic diagram of a third embodiment of the vacuum valve. [Figure 7] FIG. 7 shows a schematic top view of the third embodiment. [Figure 8]Figure 8 shows a flow chart visualizing the approach to optimizing the design of a vacuum valve. [Figure 9] FIG. 9 shows a first embodiment of a method for operating a vacuum valve. [Figure 10] FIG. 10 shows a second embodiment of a method for operating the vacuum valve. [Figure 11] FIG. 11 shows a first embodiment of a low force seal member. [Figure 12] FIG. 12 shows a second embodiment of a low force seal member in uncompressed and compressed conditions. [Figure 13] FIG. 13 shows one embodiment of the coupling unit. [Figure 14] FIG. 14 shows a third embodiment of a low force seal arrangement in the uncompressed condition. [Figure 15] FIG. 15 shows a fourth embodiment of the vacuum valve in a perspective view. [Figure 16] FIG. 16 shows an enlarged portion of FIG. [Figure 17] FIG. 17 shows a fourth embodiment in cross section. [Figure 18] FIG. 18 shows an enlarged portion of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] 1, 2 and 3 show a vacuum valve 10 with a housing 12. The housing 12 comprises a bottom part 14 which defines a first chamber 16 with a first opening 18 and a second opening 20. Both openings 18, 20 are connected to flange sections 22a, 22b which allow the vacuum valve 10 to be integrated into medium, high or ultra-high vacuum systems. The upper side of the chamber 16 is covered by a wall element 24 which abuts against a wall 26 of a guide device 28. The wall 26 forms a second chamber 32 together with a cover element 30. In other words, the multi-part housing 12 defines two chambers 16, 32 which respectively house a valve body (poppet 50) for sealing the opening 18 and the main components required for its operation, as explained below. The chamber 16 essentially serves as a passage between the openings 18, 20.

[0038] The second chamber 32 houses an electric motor 34 which is drivingly connected via a reduction drive 36 having a lead screw 38. The reduction drive 36 may comprise, for example, a spur gear, a worm gear and / or a planetary gear. The lead screw 38 cooperates with a nut 40 such that, when the electric motor 34 is actuated to rotate the lead screw 38, the nut 40 moves axially (axial movement AM) as a projection 42 of the nut 40 engages an axial slot 44 in the guide device 28 preventing the nut 40 from rotating.

[0039] The nut 40 is fixedly connected to a sleeve 46. The sleeve 46 is provided with a first spring element 47 which is supported by an inner shoulder of the sleeve 46 and acts on a tip element 48 which in turn contacts a poppet 50 which includes a seal 52. The seal 52 may be, for example, a conventional O-ring or a low force seal as described above and further below.

[0040] The second spring element 54 is supported by an axial projection 56 of the guide device 28 which projects into the first chamber 16 through an opening in the wall element 24. The second spring element 54 acts on the poppet 50 urging it downwardly towards the opening 18. The second spring element 54 is surrounded by a bellows 58 which radially surrounds the lower part of the sleeve 46 while isolating the second spring element from the interior of the first chamber 16.

[0041] When the valve 10 is closed, the electric motor 34 is started and drives the lead screw 38. The rotation of the lead screw 38 causes a downward axial movement of the nut 40, thereby pushing the sleeve 46 downward. This movement is transmitted via a first spring element 47 and a tip element 48 on the poppet 50, which is not fixedly connected to the sleeve 46. This movement is supported by a second spring element 54, which is pre-compressed. The force provided by the spring element 54 therefore acts parallel to the thrust force applied to the poppet 50 by the lead screw mechanism 38, 40, which converts the rotation of the lead screw 38 into an axial translation of the parts 40, 46, 47, 48 and 50. The second spring element 54 therefore reduces the torque required to create said axial translation, and the energy consumption of the electric motor 34 is reduced. A further advantage is that the electric motor 34 can be of a relatively small size, especially if the reduction drive 36 is appropriately selected.

[0042] When the seal 52 contacts the seat 60 surrounding the opening 18, it begins to compress, initiating the process of sealing the opening 18. At a given point, the compression of the seal 52 plateaus and the poppet 50 stops axial movement. The poppet 50 is now in a closed position. Since there is a clearance between the poppet 50 and the sleeve 46, it does not hurt to run the motor 34 for a short time. This will only cause the clearance to decrease and the first spring element 47 to compress further.

[0043] If open loop control of the motor 34 (e.g. a stepper motor) is provided, small inaccuracies in the motor control can be compensated for by the clearance. Of course, position sensors may be provided to monitor the position of any of the components 40, 46, 47 and 50 so that closed loop control of the motor 34 can be provided.

[0044] If the lead screw mechanism 38, 40 and / or the reduction drive 36 have a self-locking design, no energy is required to hold the poppet 50 in the closed position. The spring elements 47, 54 press the poppet 50 against the seat 60. In this situation, the above clearance also compensates for differential thermal expansion and / or stress relaxation of the valve 10 components.

[0045] To open the valve 10, the lead screw 38 is rotated in the opposite direction by appropriate control of the electric motor 34, thereby inducing the sleeve 46, which is fixed to the nut 40, to move upward. Initially, the poppet 50 is still pushed downward by the spring elements 47, 54. However, as the sleeve 46 retracts, the gap between the sleeve 46 and the poppet 50 is enlarged and the force provided by the first spring element 47 acting on the poppet 50 is reduced. A coupling mechanism, detailed below, couples the poppet 50 to the sleeve 46 when the maximum gap is reached. The poppet 50 then moves upward together with the sleeve 46 against the force applied by the spring element 54 until it reaches an end position that defines the "fully open" condition. However, any desired intermediate position between the closed and fully open positions may be assumed by the poppet 50.

[0046] 4 shows a schematic representation of a second embodiment of the vacuum valve 10. The electric motor 34 is arranged coaxially with a reduction drive 36 which in turn is coupled via a belt 62 and pulleys 64, 66 with a lead screw 38. The lead screw 38 cooperates with a nut 40 which is fixedly connected to a rod 68 carrying a poppet 50 with a seal 52. Axial guidance is provided in this embodiment by a guide element 70 which protrudes through a guide opening 72 in the nut 40. By way of analogy, the guide element 70 functions as a guide rail. Details regarding the chamber 16 have been omitted for the sake of clarity.

[0047] In this configuration, the stroke S of the poppet is parallel to the axial movement AM of the nut 40 during operation of the valve 10, except that both the stroke S and the axial movement AM are in the axial direction.

[0048] 5 shows in a top view that the rotation axis RA1 of the pulley 64 (and the electric motor 34), the rotation axis RA2 of the pulley 66 and the lead screw 38, and the axial projection of the rod 68 are essentially arranged on the diagonal line D of the cover 30. This arrangement is simple and compact.

[0049] An alternative compact arrangement is shown in Figures 6 and 7. The lead screw 38 is carried by a bearing support 74 with bearings 76. It is driven by an electric motor 34 connected to a reduction drive 36 which drives an output gear 78 which meshes with an input gear 80 fixed to the lead screw 38. The lead screw 38 cooperates with an axially movable but rotationally fixed nut 40 which is connected to a poppet 50 by a rod 68. In this embodiment, the stroke S, the input gear 80 and the axial movement AM and rotation axis RA2 of the lead screw 38 are arranged coaxially.

[0050] Figure 8 shows a flow chart for visualizing an exemplary approach of how to optimize the design of a vacuum valve according to the invention and adapt it to market requirements. Important goals, besides energy efficiency, are optimized flow conductance, optimized actuation motion and dynamics, compact size, low impact velocity at valve closure, temperature stability, reliable self-locking properties, reproducible duty cycle, etc. Non-performance-related issues such as packaging, cost, manufacturability, etc. may also be considered during valve optimization.

[0051] The leftmost flow requires the desired flow conductance through the valve as input A1. Appropriate variables, such as the poppet or seal diameter and poppet stroke, are selected (A2) and lead to the actual flow conductance (A3). The variables are editable to change A3.

[0052] The next flow on the right requires the input of the desired seal material (B1). Then, variables relating to further properties of the seal are selected in step B2, e.g. its diameter, cross section, elasticity, and variables describing how it will be held (e.g. the shape of the groove in which the seal is placed, influencing the response due to relative thermal expansion). This information leads to further insights regarding the expected actual squeeze force and / or the actual squeeze force of the seal exerted (B3). Depending on this information, the above variables may be edited, allowing the properties of the first spring element 47 to be optimized (B4).

[0053] The next flow on the right requires as inputs the desired actuation profile for example linear motion and thrust of the poppet 50, the desired torque and rotation speed as well as the desired self-locking force (C1). Relevant variables are for example the diameter of the lead screw and / or the characteristic friction between the lead screw and the nut (C2). This leads, among other things, to the actual linear motion and thrust response of the driving torque and rotation speed of the relevant parts. Further insight into the actual squeezing force and the actual self-locking force is obtained (C3). This allows the characteristics of the second spring element 54 to be optimized (C4).

[0054] In the rightmost flow there is a constraint (D1) of the desired motor type, such as brushed motor (D2), stepper motor (D3), inrunner (D4), outrunner (D5). The relevant variables are e.g. motor torque, offered rotational speed, and variables related to duty cycle or duty cycle definition (D6). This leads to the actual required or expected value of actual "power in" (D7). The selection of the appropriate motor can be optimized based on the relevant variables.

[0055] In D8 it must be determined whether a reduced speed drive or equivalent is required or desired. The relevant variables here are the actual torque and rotational speed provided to actuate the valve, and the reduction ratio (D9) that leads to the actual self-locking force expected (D10).

[0056] It should be emphasized that the above optimization flows are only exemplary in nature. Additional and / or modified optimization approaches may be employed. The order in which the optimization flows are executed may be freely selected.

[0057] FIG. 9 shows an exemplary duty cycle of a pre-sent vacuum valve according to the invention in a position (P) versus time (t) diagram. At time t=0, the poppet 50 of the valve is in a fully open position (position P1). When the motor 34 is activated, the poppet 50 is accelerated and moves relatively quickly towards the seat 60. The speed of the poppet 50 is actively reduced already before the seal 52 starts to compress. This is reflected by the smaller slope of the dashed movement curve before the contact seal 52 with the seat 60 (seal contact SC, position P2). During the compression of the seal 52, the speed of the poppet 50 is further reduced until it reaches zero 0 at the closed position (position P3, time t1). The seal 52 is compressed by an amount indicated by SR (squeezed range). The valve is appropriately controlled such that metal-to-metal contact (MMC) between the poppet 50 and the seat 60 is avoided. The approach outlined above results in a "soft landing" of the poppet 50 while closing the valve.

[0058] If one or more components of the electromechanical actuation unit, such as at least one of the lead screw mechanisms 38, 40 and the reduction drive 36, have self-locking characteristics, maintaining the poppet 50 in a closed position does not require the supply of electrical energy to the motor 34.

[0059] The opening of the vacuum valve begins at time t2 (P4). As previously noted, the problem of creating vibrations and / or stresses in the seal member 52, seat 60, and / or valve body 50 is significantly less pronounced when the valve is opened than when it is closed. Thus, the poppet 50 is allowed to accelerate rapidly. As a result, the decompression of the seal 52 occurs much faster than its compression.

[0060] In the embodiment shown, the poppet 50 has already reached its maximum speed when the seal 52 loses contact with the seat 60 (position P5). It moves further away from the seat 60 until it again reaches the fully open position (P3 at t6).

[0061] From the above it follows that the duty cycle of the valve according to the invention can be asymmetrical with respect to opening and closing. In the above example, closing the valve (from 0 to t1) takes longer than opening the valve (from t2 to t3). This concept can be easily implemented by an electromechanical actuation unit of the vacuum valve according to the invention, which allows very precise control of the position and dynamics of the valve body, the poppet. It also allows the design of suitable position-time and / or thrust profiles for each application.

[0062] FIG. 10 shows the effects occurring in the closed state of the valve in a diagram of force (F) versus time (t). The horizontal dashed line indicates the minimum thrust force (Fmin) that must be exerted on the seal 52 to ensure a proper seal. This value is below the squeeze force F1 obtained after normal or proper closure of the valve. Differential thermal expansion of the valve's components can lead to a reduction in the thrust or squeeze force (see ΔT). If this effect is detected, it is possible to compensate for said effect by an appropriate response (see actuator response AR) to keep the force in the desired seal squeeze range SR1, for example by monitoring the position of the poppet 50 or other components of the actuation unit with a suitable sensor, by actuating the electric motor 34. Stress relaxation of the involved mechanical components can be another source of reduction of the force exerted on the seal 52 (see StR).

[0063] A reduction in the energy consumption of the vacuum valve can also be achieved, independent of the nature of the actuating unit, by using so-called "low force seals", i.e. seals that can be adequately compressed by applying a relatively small force and / or seals that already have low force sealing properties.

[0064] Seals with PTFE material or application and / or seals with fluoroelastomer material or application are examples of such low-force seals. The required properties can also be obtained by the selection of a non-circular shape away from the circular cross section of the seal. For example, a diamond-shaped seal 52 (placed in a groove 82 and not compressed) as depicted on the left side of FIG. 12 deforms to a higher extent than a conventional O-ring of comparable dimensions when a given force is applied (FIG. 12, right side). This effect is enhanced if the seal 52 is at least partially hollow (see FIG. 11). Suitable hollow seals or seals with a softer core may also have shapes different from the diamond-shaped geometric shape shown in FIG. 11.

[0065] One exemplary embodiment of the mechanism for coupling the poppet 52 and sleeve 46 is shown in Figure 13. In the open state of the valve, the poppet 50 is pushed away from the sleeve 46 by the spring-loaded tip element 48, resulting in a gap 84 between the parts. In this state, the protrusions of the fingers 86 of the sleeve 46 engage the upper ends of the grooves 88 of the poppet 50, which hold it in this position. In the closed state of the valve, the poppet 50 is moved towards the sleeve 46 (the situation shown in Figure 13) to compensate for effects resulting, for example, from slight inaccuracies in the motor control and / or gradual seal compression and / or thermal effects.

[0066] During valve opening, sleeve 46 moves upwardly while poppet 50 remains pressed against seat 60 by spring elements 47, 54. Only when the projection of finger 86 engages the upper end of groove 86 will poppet 50 be actively lifted from seat 60.

[0067] It should be readily apparent that there are numerous alternative mechanisms that can provide the same or similar type of coupling.

[0068] Figure 14 shows a further embodiment of a low force seal. It comprises seals 52a, 52b arranged on the poppet 50 and seat 60, respectively, in a non-compressed state. During valve closing, the seals 52a, 52b are brought into contact with each other and gradually compressed. As already mentioned above, a lower force is required to obtain a proper seal of such a valve than is required with conventional arrangements.

[0069] Figures 15 to 18 show a miniature vacuum valve 10 having an axially movable lead screw 38a cooperating with an axially fixed nut 40a which is driven in rotation by an electric motor 34a disposed between axial walls 90a, 90b.

[0070] Activation of the motor 34a rotates the nut 40a, which in turn causes axial movement of the lead screw 38a, which is fixed to the axial wall 90a and prevented from rotating by the projection 42a engaging the axial groove 44a of the lead screw 38a. Functionally equivalent mechanisms are contemplated.

[0071] The valve 10 can be operated in a similar manner to the valves of the embodiments described above. Furthermore, it should be noted that individual features described in connection with one embodiment may be implemented in other embodiments as appropriate. This is particularly true for the functionality provided by the spring elements 47, 54 described in connection with the embodiment shown in Figures 1 and 2. [Explanation of symbols]

[0072] 10 Vacuum valve 12. Chassis 14 Bottom 16 Room 1 18 First Opening 20 Second Opening 22a, 22b flange section 24 Wall Elements 26 Wall section 28 Guidance device 32 Room 2 36 Reduction drive unit 38, 38a Lead screw 40, 40a Nut 42, 42a protrusion 44, 44a Axial slot or groove 46 Sleeves 47 First spring element 48 Tip Element 50 Poppet 52, 52a, 52b Sealing part 54 Second spring element 56 Axial protrusion 58 Bellows 60 seats 62 Belt 64, 66 Pulley 68 Rod part 70 Guidance elements 72 Guide opening 74 Bearing Support 76 Bearings 78 Output Gear 80 Input Gear 82 Groove 84 Gap 86 fingers 88 Groove 90a, 90b axis wall AM Axial Movement S Stroke RA1, RA2 Rotation axis D Diagonal P position t time SC Seal Contact SR, SR1 Compression range MMC metal-to-metal contact StR Stress relief F force

Claims

1. 1. A vacuum valve for medium, high and ultra-high vacuum systems, comprising: a valve housing defining a passageway connecting a first opening and a second opening of the valve housing; a valve disc and a complementary seat disposed in the passageway, the valve disc and the complementary seat having a sealing member, the valve disc being linearly axially movable along an open position and a closed position, the valve disc cooperating with the seat in the closed position to hermetically close a first opening; an electromechanical actuation unit for actuating the valve disc, the actuation unit comprising an electric motor and a mechanical transformation unit having an input part drivingly connected to the electric motor and an output part drivingly connected to the valve disc, the mechanical transformation unit transforming a rotational output of the electric motor into a linear motion of the output part to axially move the valve disc; A vacuum valve comprising:

2. The vacuum valve according to claim 1 , wherein the mechanical conversion unit comprises a lead screw cooperating with a nut element.

3. The vacuum valve of claim 2 , wherein the output comprises the nut element.

4. 4. A vacuum valve as claimed in any one of claims 1 to 3, wherein at least one first resilient element is provided which is supported by the valve housing and which acts to urge the valve disc axially to a closed position when a force is applied to the valve disc.

5. The valve body is movable in a linear axial direction relative to the output portion. A vacuum valve according to any one of claims 1 to 4.

6. 6. The vacuum valve of claim 5, wherein the electromechanical actuation mechanism comprises at least one second resilient element supported by the output and acting on the valve disc such that a force is exerted on the valve disc urging it axially away from the output.

7. The vacuum valve according to claim 5 , wherein the output portion and the valve body are coupled by a coupling unit that limits relative axial movement of the output portion and the valve body.

8. 7. A vacuum valve according to claims 4 and 6, wherein the first elastic element has a higher elasticity than the second elastic element.

9. The output portion is rotatably fixed and held by a guide device. A vacuum valve according to any one of claims 1 to 8.

10. 10. The vacuum valve of claim 9, wherein the guide means comprises an axially extending protrusion cooperating with a guide slot or groove.

11. 11. A vacuum valve according to any one of claims 1 to 10, wherein the electric motor and the input are drivingly coupled via at least one reduction drive.

12. 12. The vacuum valve according to claim 1, wherein the electromechanical actuation unit comprises at least one locking device and / or locking function for locking the output or the valve body in a desired axial position.

13. The vacuum valve according to claim 12, wherein the mechanical conversion unit has a self-locking property.

14. 14. The vacuum valve according to claim 1, further comprising a position sensor for detecting a position of at least one of the output portion and the valve body.

15. 1. A vacuum valve for a medium, high or ultra-high vacuum system, comprising: a valve housing defining a passageway connecting a first opening and a second opening of the valve housing; a valve disc and a complementary seat disposed in the passageway, the valve disc and the complementary seat comprising a sealing member, the valve disc being linearly movable between an open position and a closed position, the valve disc cooperating with the seat in the closed position to close a passageway of the vacuum enclosure; an actuation unit for actuating the valve body; a seal member having at least one of a non-circular shape in a cross section perpendicular to the first opening, being hollow, having a PTFE material or coating, and having a fluoroelastomer material or coating; The vacuum valve.

16. The actuation unit comprises an energy storage unit which supplies electrical energy to the electric motor. A vacuum valve according to any one of claims 1 to 15.

17. A method for operating a vacuum valve, comprising: a valve housing defining a passageway connecting a first opening and a second opening of the valve housing; a valve disc and a complementary seat disposed in the passageway, the valve disc and the complementary seat having a sealing member, the valve disc being linearly axially movable along an open position and a closed position, the valve disc cooperating with the seat in the closed position to hermetically close a first opening; an electromechanical actuation unit for actuating the valve disc, the actuation unit comprising an electric motor, a mechanical transformation unit having an input part drivingly connected to the electric motor, and an output part drivingly connected to the valve disc, the mechanical transformation unit transforming a rotational output of the electric motor into a linear motion of the output part to axially move the valve disc; The method for operating a vacuum valve, comprising:

16. A method of operating a vacuum valve, wherein the electric motor is operated during movement of the disc to a closed position such that the velocity of the disc is reduced at least one of before and during contact of the disc with the seat.

18. 20. The method of claim 17, wherein the motor is operated such that movement of the valve disc from an open position to a closed position takes longer than movement of the valve disc from a closed position to an open position.

19. 19. A method according to claim 17 or 18, wherein the motor is operated such that compression of the seal member as the valve disc moves to a closed position takes longer than decompression of the seal member while the valve disc moves from a closed position.

20. 20. A method according to any one of claims 17, 18 or 19, wherein the electric motor is operated in a closed position of the valve disc such that the force acting on the seal member does not fall below a predetermined threshold.

21. 21. The method of claim 20, wherein the force acting on the seal member is determined based on data provided by at least one of a force, strain or temperature sensor.

22. 22. The method of claim 21, wherein the force acting on the seal member is determined based on an operational variable of the electric motor.

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