Abstract:
A vacuum valve, including a valve housing, which has a passage having an axis, a seat that surrounds the passage and that lies in a first plane, and a counter seat that surrounds the passage and that lies in a second plane that forms a wedge shape with the first plane, and including a closure device, which can be moved between an open position in which the passage is released and a closed position in which the passage is sealed and which has a closure plate parallel to the first plane and a counter plate parallel to the second plane, and including a valve rod, which has a longitudinal axis and which carries the closure device and which can be moved in a straight line. In order to spread apart the closure plate and the counter plate, the closure device includes a spreading unit, which lies between the closure plate and the counter plate and which can be moved in the closing direction of the valve rod relative to the closure plate and the counter plate, and a support part, which is movably guided relative to the spreading unit and which is connected to the closure plate and/or the counter plate.

Description:
BACKGROUND 
     The invention relates to a vacuum valve comprising a valve housing which has a passage having an axis, a seat surrounding the passage located in a first plane, and a counter seat surrounding the passage located in a second plane, with the first and the second planes being arranged to form a wedge-shape in reference to each other and each forming an angle in reference to the axis of the passage, an open position releasing the passage, and a closed position in which the passage is sealed, an adjustable closure device with a closure plate, which in the closed position of the closure device is pressed to the seat and here is aligned parallel in reference to the first plane, and a counter plate, which in the closed position of the closure device is pressed against the counter seat and is here aligned parallel in reference to the second plane, and a valve rod with a longitudinal axis and supporting the closure device, which for the adjustment of the closure device from its open position into its closed position and back is displaceable in a straight line in a closing direction parallel in reference to the longitudinal axis of the valve rod and against the closing direction. 
     Such a vacuum valve comprising a seat and a counter seat located in first and second planes arranged in a wedge-shape in reference to each other and in the closed state of the vacuum valve pressed against the closure plate and a counter plate is known from U.S. Pat. No. 4,301,993 A. The closure plate and the counter plate are fastened at fastening plates, which are connected to each other via an arched connection plate, engaged by the valve rod. When closing the vacuum valve the fastening plates are first moved by the valve rod and, when the closure plate and the counter plate are positioned opposite the seat and counter seat, hindered by approaching a stop at a counter stop, fixed at the valve housing, from any further motion, subsequently the valve rod impressing into the arched connection plate and thus the closure plate and the counter plate are pressed apart and thereby being slightly deflected and pressed against the seat and the counter seat. In this construction is it hardly possible to keep the production tolerances sufficiently low, and additionally changes of the mutual position of the different parts can develop over time due to use. 
     A vacuum valve is known from U.S. Pat. No. 6,056,267 A in which the valve rod is fixed at the compression element, which has a diagonal surface, which cooperates with a diagonal surface of the closure device in order to press a closure plate to a seat in the closed state of the vacuum valve. Due to the fact that the closure force has to be transferred via the valve rod a very stiff construction is required, in which the valve rod must be embodied appropriately massively. 
     A vacuum valve with a wedge-shaped closure member is discernible from U.S. Pat. No. 6,367,770 B1. The closure member comprises lateral surfaces approaching each other in a wedge-shaped fashion, at which seals are arranged, which in the closed state of the valve also contact sealing surfaces of the valve seat arranged wedge-shaped in reference to each other. The closing of the vacuum valve occurs with only little closing force, with in case of an applied differential pressure one of the seals is compressed with one of the sealing surfaces. Another vacuum valve with a wedge-shaped closure member is discernible from U.S. Pat. No. 7,011,294 B1. When closing the vacuum valve the closure member is guided in a gliding fashion in reference to the valve housing by gliding parts arranged at the closure member in the last section of its displacement motion. Another vacuum valve with a wedge-shaped closure member is discernible from U.S. Pat. No. 4,548,386. The wedge-shaped closure member comprises two plates supported by a valve rod. A recess is located therebetween, in which a ring is arranged. The ring and the walls of the recess exhibit a wedge-shaped cross-section. By the wedge-shaped ring arranged in the wedge-shaped recess the plates can be adjusted in their position to the seat and the counter seat of the valve housing. Disadvantages of the vacuum valves of prior art with wedge-shaped closure members are, among other things, that either a sealing of the vacuum valve is achieved only by an applied differential pressure or relatively strong shearing forces are applied upon the respective seal leading to wear and tear of the seal and the production of particles. 
     Blocking slides are discernible from DE 455907 C and DE 1962121 A1, in which closure plates, arranged wedge-shaped in reference to each other, are pressed against appropriately arranged valve seats by a wedge located therebetween during the closing process. 
     In slide valves known from U.S. Pat. No. 4,779,649 A the seats for the closure plate and the counter plate are located in parallel planes. The areas of the closure plate and the counter plate facing each other are aligned wedge-shaped in reference to each other and cooperate with a wedge arranged between them, which presses the closure plate and the counter plate against the seat and the counter seat in order to close the valve. The closure plate and the counter plate are impinged by spring elements in the direction towards each other. 
     Additionally, slide valves are known comprising a closure plate and a counter plate, which are located parallel in reference to each other and with a spreading unit being arranged between them. When closing the vacuum valve the closure plate and the counter plate first are moved by the valve rod in their longitudinal direction and then, upon approaching a stop connected to the closure plate and the counter plate, to a counter stop, fixed at the valve housing are spread apart by the spreading unit engaged by the valve rod, which is further displaced in order to be pressed against the seat and the counter seat of the vacuum valve. For this purpose different embodiments of spreading units are known, as discernible for example from U.S. Pat. No. 4,560,141 A and DE 3 028 786 A1. From the latter publication an embodiment is discernible in which the spreading unit shows a wedge-shaped embodiment and cooperates via interposed rolls with wedge-shaped areas of the closure plate and the counter plate, embodied at sides of the closure plate and counter plate facing each other by way of recesses. With regards to the production tolerances in this construction sufficient stroke must be provided for pressing the closure plate and the counter plate to the seat and the counter seat. However, particles are created over the entire stroke when spreading the plate and the counter plate apart. In order to reduce the stroke very small production tolerances had to be achieved and the stiffness had to be high, which leads to respectively high costs. 
     SUMMARY 
     The objective of the invention is to provide a vacuum valve of the type mentioned at the outset, in which only a minor stroke of the closure plate and the counter plate for pressing the closure plate and the counter plate to the seat and the counter seat can be achieved by the spreading unit in a cost-effective embodiment. 
     In the vacuum valve of the invention the closure plate and the counter plate are located in the closed position of the closure device as well as in its open position parallel in reference to the seat and/or the counter seat, with the planes of the seat and the counter seat and thus also the closure plate and the counter plate being positioned wedge-shaped in reference to each other and each showing an angle in reference to the axis of the passage. 
     Here, they are inclined in reference to the perpendicular alignment in reference to the axis of the passage by opposite angles, preferably of equal size. Preferably the angles formed by the planes of the seat and the counter seat with the axis of the passage amount to more than 45°, preferably more than 70°. The angle formed by these two planes in reference to each other amounts preferably to less than 45°, particularly less than 20°. 
     The spreading unit fastened at the valve rod comprises a first spreading surface aligned parallel in reference to the plane of the seat and a second spreading surface aligned parallel in reference to the plane of the counter seat. The first and the second spreading surfaces are therefore parallel in reference to the closure plate and/or the counter plate. In order to spread apart the closure plate and the counter plate in order to press the closure plate to the seat and the counter plate to the counter seat the spreading unit is displaceable in reference to the closure plate and the counter plate in the closing direction of the valve rod, aligned parallel in reference to the longitudinal axis of the valve rod. 
     When closing the vacuum valve, the valve rod, starting from a first position, in which the closure unit is in its opened position and releases the passage, is displaced in the closing direction aligned parallel in reference to the longitudinal direction of the valve rod to a second position, in which the closure unit is inserted into the passage of the vacuum valve, into a third position, in which the closure unit is in its closed position. Advantageously, in the second position of the valve rod, when the stop of the closure device abuts a counter stop fixed at the valve housing and thus the closure plate and the counter plate are blocked from any further displacement in the closing direction of the valve rod, the closure plate is spaced apart from the seat and the counter plate from the counter seat. In a further displacement of the valve rod from its second position into its third position the spreading unit is displaced in reference to the closure plate and the counter plate in the closing direction of the valve rod and thus the closure plate and the counter plate are spread apart from each other and pressed to the seat and/or counter seat in order to seal the passage. 
     By the wedge-shaped arrangement of the seat and counter seat as well as the closure plate and the counter plate the distances shown between the closure plate and the counter plate from the seat and/or counter seat in the second position of the valve rod may be designed relatively small, preferably amount to less than 2 mm. The stroke of the plate and the counter plate performed thereby between the second and the third position of the valve rod is therefore appropriately small. 
     The spreading apart of the closure plate and the counter plate by the spreading unit occurs by a parallel displacement of the closure plate and the counter plate parallel in reference to the passage. By this parallel displacement the mutual distance of the closure plate and the counter plate is increased. 
     The first and second spreading surfaces of the spreading unit may cooperate directly with the closure plate and/or the counter plate for spreading the closure plate and the counter plate by contacting the respective compression surface of the closure plate and the counter plate. The compression surface of the closure plate is here located parallel in reference to the first plane and the compression surface of the counter plate parallel in reference to the second plane. However, it is also possible to interpose transmission elements between the first and the second spreading surfaces and the closure plate and the counter plate. For example, a roller bearing may be provided for each, with its roller bodies rolling on the one side at the respective spreading surface, and on the other side at the respective compression surface. The cooperation between the first spreading surface and the closure plate and/or between the second spreading surface and the counter plate for spreading apart the closure plate and the counter plate may therefore be indirect as well. 
     According to the invention, the closure device further comprises at least one support part, guided displaceable in reference to the spreading unit in the direction of the longitudinal axis of the valve rod, which is connected to the closure plate and/or the counter plate in a fixed manner in reference to the direction of the longitudinal axis of the valve rod. This way, an advantageous guidance of the closure plate and the counter plate is achieved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Additional advantages and details of the invention are explained in greater detail based on the attached drawings. Shown are: 
         FIG. 1  is a perspective view of a vacuum valve according to the invention in the closed state; 
         FIGS. 2 and 3  are a front view and a side view of the vacuum valve of  FIG. 1 ; 
         FIG. 4  is a cross-section along a line  4 - 4  of  FIG. 2 ; 
         FIG. 5  is an enlarged detail from  FIG. 4 ; 
         FIG. 6  is a perspective view according to  FIG. 1  in the opened state of the vacuum valve; 
         FIG. 7  is a cross-section similar to  FIG. 4  in the opened state of the vacuum valve (with the bellows sealing the valve rod from the valve housing being omitted for reasons of simplicity); 
         FIG. 8  is a cross-section similar to  FIG. 7  in an interim position of the closure device; 
         FIG. 9  is an enlarged detail from  FIG. 8 ; 
         FIGS. 10   a .  11  are the closure device in a front view and a side view; 
         FIGS. 12 ,  13 ,  14  are cross-sections along the lines  12 - 12 ,  13 - 13 , and  14 - 14  of  FIG. 10 ; 
         FIG. 15  is the closure device in a perspective view, the counter plate being omitted; 
         FIGS. 16   a .  17  are exploded views of the closure device from different angles of view. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An exemplary embodiment of a vacuum valve according to the invention is shown in  FIGS. 1 to 7 . The vacuum valve comprises a valve housing  1  with a passage  2  having an axis  3 . In order to connect to other parts of the vacuum arrangement, for example a (respective) vacuum chamber and/or pipelines, the valve housing  1  comprises first and second flanges  4 ,  5  forming the inlet and outlet opening of the passage  2 . The exterior surfaces of the flanges  4 ,  5  are positioned perpendicular in reference to the axis  3  of the passage  2 . 
     The passage  2  penetrates window recesses in plate-shaped sections  6 ,  7  of the valve housing  1 . At the side facing the plate-shaped section  7 , the plate-shaped section  6  forms a seat  8  in the passage  2  and/or the window opening in the area surrounding the plate-shaped section  6  for a closure plate  10  of a closing arrangement  12 . The side of the plate-shaped section  7  facing the plate-shaped section  6  forms a counter seat  9  for the counter plate  11  of the closure device  12  in the passage  2  and/or the window opening in the area surrounding the plate-shaped section  7 . 
     The plate-shaped sections  6 ,  7  are aligned at an angle in reference to each other so that the seat  8  and the counter seat  9  are located in first and second planes  13 ,  14 , which are wedge-shaped in reference to each other and each form an angle to the axis  3  of the passage  2 . The first and second planes  13 ,  14  are here inclined by alignments located by opposite, equally sized angles in reference to an alignment that is perpendicular in reference to the axis  3 . The incline in reference to this right-angled alignment occurs here about an axis, which is aligned perpendicular in reference to the longitudinal axis  26  of the valve rod  23  described in the following. 
     Preferably the angle  15  formed by the first and second planes  13 ,  14  ranges from 5° to 20°, for example amounts to a value of about 10°. 
     The closure plate  10  of the closure device  12  is located parallel in reference to a first plane  13 . The counter plate  11  of the closure device  12  is located parallel in reference to a second plane  14 . 
     The closure device  12  further comprises a wedge-shaped spreading unit  16  located between the closure plate  10  and the counter plate  11 . The spreading unit  16  has a first spreading surface  17  positioned parallel in reference to the first plane  13  and cooperating with the closure plate  10 , as well as a second spreading surface  18  positioned parallel in reference to the second plane  14  and cooperating with the counter plate  11 . In the exemplary embodiment shown the first spreading surface  17  is formed by the surfaces of gliding inserts  19 , which are arranged in the recesses of a basic body  21  of the closure device  12 , with the side of the basic body  21  being provided therewith, facing the closure plate  10 . The second spreading surface  18  is formed by surfaces of gliding inserts  20 , which are arranged in the recesses of the basic body  21 , with the side of the basic body  21  being provided therewith facing the counter plate  11 . 
     The gliding inserts  19 ,  20  are made from a suitable gliding material, for example Teflon. Other gliding materials, preferably comprising plastic, may also be used. 
     The spreading unit  16  is fastened at the end of a valve rod  23 , located at the front in reference to the closing direction  22 . For this purpose, in the exemplary embodiment shown the valve rod  23  is screwed to a connector part  24  of the spreading unit  16 , which in turn is screwed to the basic body  21  of the spreading unit  16 . 
     The valve rod  23  is arranged perpendicular in reference to the axis  3  of the passage  2 . The first and second planes  13 ,  14  are inclined by opposite, equivalent angles in reference to an alignment parallel reference to the longitudinal axis  26  of the valve rod  23 , namely by an axis aligned perpendicular in reference to the longitudinal axis  26  of the valve rod  23  and perpendicular in reference to the axis  3  of the passage  2 . 
     The valve rod  23  is sealed via a bellows  51  (which may be formed, e.g., as a folded bellows or a diaphragm bellows or a Teflon bellows) from the valve housing  1  (which is only drawn in  FIGS. 4 and 5 ). Other seals of the valve rod  23  in reference to the valve housing  1  are also possible, for example by an O-ring arranged between the valve rod  23  and the passage in the valve housing  1  penetrated by the valve rod  23  (=slide passage). 
     A valve drive  25  serves to open and close the vacuum valve, e.g., for adjusting the closure device  12  between its open position and its closed position, which in the exemplary embodiment shown is formed by a piston-cylinder unit, with the valve rod  23  representing the piston rod of this piston-cylinder unit. The valve rod  23  can be displaced by the valve drive  25  in the direction of its longitudinal axis  26  in order to close the vacuum valve in the closing direction  22 , and to open the vacuum valve opposite the closing direction  22 . 
     Two spring elements  27  serve to pull the closure plate  10  and the counter plate  11  against the first and second spreading surface  17 ,  18  of the spreading unit  16  and hold them in contact thereby, which are arranged in reference to a direction perpendicular to the longitudinal axis  26  of the valve rod  23  and perpendicular to an axis  3  of the passage  2  at both sides of the spreading unit  16 . Each of the spring elements  27  comprises a first arm  28  embodied as a flat spring, which is fastened at the closure plate  10 , for example by way of welding, and a second arm  29  embodied as a flat spring fastened at the counter plate  11 , for example by way of welding. The first and second arms  28 ,  29  are connected to each other at the frontal end sections in reference to the closing direction  22 , for example by screw connections. The first and second arms  28 ,  29  then extend wedge-shaped away from each other at their connection section. 
     Instead of the two spring elements  27  shown, more or less spring elements may be provided, in order to pull the closure plate  10  and the counter plate  11  against the spreading unit  16  and they may also be formed in a different manner. 
     In order to additionally stabilize the mutual position of the closure plate  10  and the counter plate  11  on one side of the spreading unit  16 , a connection part  30  is screwed to the closure plate  10  and an equally embodied connection part  31  is screwed to the counter plate  11  at the opposite side of the spreading unit  16 . The connection parts  30 ,  31  each have a keyhole-shaped recess  32 , with a pin  33  engaging the narrower section, fastened at the other of the two plates  10 ,  11 , which has a mushroom shaped head. The dimensions of the connection parts  30 ,  31  and the pin  33  are such that a clear space develops between the head of the respective pin  33  and the recess  32 , which allows a spreading apart of the closure plate  10  and the counter plate  11  during the closing of the vacuum valve described in the following. 
     When assembling the closure device first the heads of the pins  33  are inserted into the enlarged sections of the recesses  32  and then displaced into the sections of the recesses  32  with the narrower width of the slit, with the width of these slits being smaller than the diameter of the head of the pin  33 , and subsequently the first and second arms  28 ,  29  of the spring elements  27  are screwed to each other. 
     The closure plate  10  and the counter plate  11  are supported by a support part  34  of the closure device  12 , which is guided in a displaceable fashion in reference to the spreading unit  16  in the direction of the longitudinal axis  26  of the valve rod  23 . For this purpose, the support part  34  is arranged in a first recess  35  of the basic body  21  of the spreading unit  16 , and is penetrated by a guiding pin  36  fixed at the basic body  21 . At the one side, a spring  37  is arranged on the guiding pin  36 , supported at the one side at the support part  34  and at the other side at the basic body  21 , pre-stressing the support part  34  in reference to the basic body  21  into a normal position limited by contacting the basic body  21 . The support part  34  can be displaced in reference to the basic body  21  against the force of the spring  37  opposite the closing direction  22 . 
     The closing plate  10  and the counter plate  11  are connected to the support part  34  in such a manner that they cannot be displaced in the closing direction  22  or opposite thereto. Here, connection elements  38 ,  39  serve for this purpose, preferably bendable in a spring-elastic fashion. They are connected to the basic body  21  of the spreading unit  16  in a form-fitting manner by latches  40 ,  41  of the basic body engaging recesses of the connection elements  38 ,  39 . 
     The spring-elastic arms of the connection elements  38 ,  39 , projecting from the basic body  21  at both sides of the form-fitting connection, show bore holes  42 ,  43  with pegs engaging them, arranged at the closure plate  10  and/or the counter plate  11 . 
     In the open state of the vacuum valve the closure device  12  is situated in an open position, in which it releases the passage  2 , and the valve rod  23  is situated in a first position (cf.  FIGS. 6 and 7 ). 
     In order to close the vacuum valve the valve rod  23  is displaced parallel in reference to its longitudinal axis  26  in the closing direction  22 . Here, the closure device  12  is inserted into the passage  2  until it assumes an intermediate position in a second position of the valve rod  23  (cf.  FIGS. 8 and 9 ). In this intermediate position the closure plate  10  and the counter plate  11  cover the passage  2 , seen in the direction of the axis  3  of the passage  2 , however they are still spaced apart from the seat  8  and the counter seat  9 . In this second position of the valve rod  23 , stops  46  formed by the ends of the spring element  27  located in the front in reference to the closing direction  22 , approach the counter stops  47  fixed at the valve housing. In the exemplary embodiment shown these counter stops  47  are formed by sections of a connection section connecting the plate-shaped sections  6 ,  7  (the stops  46  are drawn in FIGS.  7  and  12 - 15 , the reference character  47  is shown in  FIG. 7  for the counter stops). 
     For example, the stops  46  can also be formed by, in reference to the closing direction  22 , frontal ends of the closure plate  10  and the counter plate  11 . 
     From its second position the valve rod  23  is displaced further in the closing direction  22  with any additional displacement of the closure plate  10  and the counter plate  11  in the closing direction  22  now being blocked. This way, the spreading unit  16  is displaced in reference to the closing plate  10  and the counter plate  11  in the closing direction  22 , spreading apart the closure plate  10  and the counter plate  11  such that they are pressed against the seat  8  and the counter seat  9 . Here, the elastic annular seal  48 , arranged at the closure plate  10 , is pressed to the sealing surface of the seat  8 , hereby sealing the closure plate  10  in reference to the seat  8 . Further, the elastic contact ring  49  arranged at the counter plate  11  is pressed to the contact surface of the counter seat  9 . 
     The elastic contact ring  49  may comprise the same material as the seal  48 , for example Viton. 
     In order to achieve a defined pressure status between the closure plate  10  and the counter plate  11 , the counter plate  11  is provided with at least one penetrating opening  50 . 
     In the closed state of the vacuum valve the closure device  12  assumes its closing position and the closure plate  10  seals the passage  2  (cf.  FIGS. 1 to 5 ). 
     By the connection of the closure plate  10  and the counter plate  11  to the support part  34 , fixed in reference to the direction of the longitudinal axis  26  of the valve rod  23 , the support part  34  is displaced during the displacement of the valve rod  23  from its second position into its third position in reference to the spreading unit  16 . While the spreading unit  16  moves further in the closing direction  22  the motion of the support part  34  is blocked in the closing direction  22 . The displacement of the support part  34  in reference to the spreading unit  16  occurs here against the force of the spring  37 . 
     When the vacuum valve is opened again by the valve rod  23  being displaced, starting at its third position against the closing direction  22 , the spring  37  keeps at least one stop  46  pressed to at least one counter stop  47  and the spring elements  27  pull back the closure plate  10  and the counter plate  11  from the seat  8  and the counter seat  9  until the closure device  12  once more assumes the intermediate position shown in  FIGS. 8 and 9 . In a further displacement of the valve rod  23  from its second position into the first position, the closure plate  10  and the counter plate  11  are moved by the spreading unit  16  and the valve rod  23  against the closing direction  22  until the open position of the closure device  12  is reached. 
     In many applications the vacuum valve is only allowed to be opened when at both sides of the closure device  12  no or only little differential pressure is given. The force applied by the spring elements  27  can then be selected appropriately low. 
     It may also be provided in the closed position of the closure device  12  for the counter plate  11  to be pressed against the counter seat  9  in a sealing fashion with the counter plate  11  being embodied without any penetrating opening  50 . The space between the closure plate  10  and the counter plate  11  could then be provided with an intermediate suction, with the line by which said suction occurs can be closed by a valve. Further, the space between the closure plate  10  and the counter plate  11  may additionally be connected via a valve, which can be blocked, to a vacuum area located at one of the two sides of the closure device in order to allow pressure compensation. 
     Different modifications of the exemplary embodiment of the present invention shown are possible without departing from the scope of the invention. For example, the support part  34  could be connected fixed in reference to the closing direction  22  only to either the closure plate  10  or the counter plate  11  and the fixed connection to the other of these two plates may be created by the mutual connection of these two plates  10 ,  11 . Separate support parts  34  for the closure plate  10  and the counter plate  11  are also possible. In a further modified embodiment the closure plate  10  and/or the counter plate  11  could be connected via a support part to the spreading unit  16 , which in reference to the closure device  22  is connected fixed to the spreading unit  16  and displaceably to the closure plate  10  and/or counter plate  11 . 
     The spring  37  could also be omitted and, when opening the vacuum valve, the stop  46  could be held over the stroke of the valve rod from its third position into its second position or at least over a portion of this path by at least one spring element  27  being connected to the wedge-shaped arrangement of spreading surfaces  17 ,  18  and the closure plate  10  and the counter plate  11  contacting the counter stop  47 . 
     The seal  48  could also be arranged at the seat  8  and the closure plate  10  may be provided with a sealing surface cooperating therewith. 
     The elastic contact ring  49  could also be arranged at the counter seat  9  and a contact surface cooperating with it could be arranged at the counter plate  11 . 
     In the exemplary embodiment shown, the closure plate  10  and the counter plate  11  are embodied annularly. Other embodiments are also possible, for example rectangular embodiments. 
     The gliding inserts  19 ,  20  of the closure plate  10  and/or the counter plate  11  could also be omitted and the spreading surfaces  17 ,  18  could be formed directly by the surfaces of the basic body  21 . Preferably, in this case gliding inserts may be arranged in the closure plate  10  and/or the counter plate  11 , with their surfaces forming contact surfaces or compression surfaces, cooperating with the spreading surfaces  17 ,  18 . In case of the embodiment of the spreading unit  16  with gliding inserts  19 ,  20 , the closure plates  10  and/or counter plates  11  may also be provided with gliding inserts. 
     Transfer elements may also be arranged between the first spreading surface  17  and the closure plate  10  and/or between the second spreading surface  18  and the counter plate  11  in order to transfer the force applied by the spreading unit  16  upon the closure plate  10  and/or the counter plate  11 , by which the closure plate  10  and/or the counter plate  11  are guided parallel in reference to the first spreading surface  17  and/or the second spreading surface  18 . Such roller bodies, for example in the form of rolls or spheres, may be arranged in appropriate roller body cages. Any respective roller body cage could be held at a spreading unit  16  or at a closure plate  10  and/or a counter plate  11 . 
     The vacuum valve according to the invention is characterized in a relatively low production of particles when closing and opening the vacuum valve. Long life spans can be achieved in the vacuum valve according to the invention before any service is required, such as the exchange of the seal  48 . 
     LEGEND CONCERNING THE REFERENCE CHARACTERS 
     
         
         
           
               1  valve housing 
               2  passage 
               3  axis 
               4  flange 
               5  flange 
               6  plate-shaped section 
               7  plate-shaped section 
               8  seat 
               9  counter seat 
               10  closure plate 
               11  counter plate 
               12  closure device 
               13  first plane 
               14  second plane 
               15  angle 
               16  spreading unit 
               17  first spreading surface 
               18  second spreading surface 
               19  gliding insert 
               20  gliding insert 
               21  basic body 
               22  closing direction 
               23  valve rod 
               24  connection part 
               25  valve drive 
               26  longitudinal axis 
               27  spring element 
               28  first arm 
               29  second arm 
               30  connection part 
               31  connection part 
               32  recess 
               33  pin 
               34  support part 
               35  recess 
               36  guide pin 
               37  spring 
               38  connection element 
               39  connection element 
               40  latch 
               41  latch 
               42  bore hole 
               43  bore hole 
               44  peg 
               45  peg 
               46  stop 
               47  counter stop 
               48  seal 
               49  elastic contact ring 
               50  penetrating opening 
               51  bellows