Abstract:
A valve mechanism having at least one movable valve member for sealing of a valve opening in a housing. Movements of the individual movable valve members are accomplished essentially parallelly to, and perpendicularly to, the seat surface of the valve during the opening and closing of the valve. In order to achieve high forces and low wear in the movement carried out with aid of a slot guide which guide serves to transmit forces during, and in the direction of, the opening and closing, the slot guide comprises slots which are formed in a drive plate, which slots cooperate with and overlap complementary slots in the movable valve members.

Description:
FIELD OF THE INVENTION 
   The invention relates to a valve mechanism for a vacuum valve, and more particularly to a mechanism to apply a high sealing pressure through the use of two mutually movable elements. 
   DISCUSSION OF PRIOR ART 
   Vacuum valves are preferred for closing of throughgoing openings in vacuum equipment. Valve mechanisms of the type described may also be used for other valves in which forced guidance is advantageous, for example, shutoff elements in pipes or the like wherein liquids are transported. 
   A known valve mechanism is disclosed by the present Applicant in EP 0662575 B1. According to that publication, a movable valve member is rolled on fixed mounted support shafts. The costs of realizing such a solution are high, and the support shafts disclosed cannot bear as much stress as free guided roll members guided in suitable guide means without bearings. 
   An example of bearing-free guided shafts, referred to hereinbelow as “roll bodies” in roll or cylindrical roller form, is disclosed in JP 2001-090849 A1. In this known valve mechanism, three circular plates which are mutually translatably movable are provided, and between them free guided spheres are disposed which spheres serve as roll bodies. Upwardly inclined grooves are distributed over the periphery of a first plate which is rotationally driven, and the spheres are translationally guidably disposed in the grooves. These spheres engage corresponding, opposite, grooves of a second, middle plate. On the opposite side of said middle plate, additional grooves are provided wherein spheres arc translatably guided which spheres engage corresponding grooves in a third plate. This third plate is the valve plate (movable valve member) which, depending on the rotational position of the other two plates, is moved against the throughgoing opening in the housing or is moved away from that opening. 
   These guide means have major drawbacks. They have an open structure, such that the spheres can fall out any time the accommodating plates are not adequately pressed together, for example, on the occasion of a disturbance, vibration, impact, malfunction, spring breakage, or the like. This problem will occur if the plates cease to be pressed together for even a very short period of time, sufficient for the weight of the spheres to allow them to fall out of their designated grooves and positions. 
   Ordinarily, quite large forces are employed for closing such valves, in order to achieve sufficient pressing of the seal against the valve seat. Whereas a pressure difference across the valve can act on the movable valve member in such a way as to add to the achievable sealing forces, it is also true that that such a pressure difference can act in the opposite sense, to hold the movable valve member closed. Thus the system overall will be useless. Valve components become disengaged, the movable valve member tends to break, and substantial damage can result. 
   The above-cited EP 0662575 B1 discloses guides with closed grooves, but bolts travel in the grooves which are supported on only one side. Because of space considerations, these support means must be kept relatively small, so that they are operating close to their stress tolerance limits. 
   SUMMARY OF THE INVENTION 
   A feature of the invention is that only as few as two pieces are provided which are translationally movable with respect to each other, one such piece being the drive plate and the other being the movable valve member. At least one slot is formed in the drive plate which slot cooperates with and overlaps a complementary slot in the neighboring movable valve member. A roll body, having a cylindrical or drum or roller shape is disposed in the overlap region between the drive plate slot and the complementary (valve member) slot. 
   This structure affords the important advantage that for the first time it is possible, with the use of two mutually movable pieces, to admit a high pressing force for sealing purposes, and with the same force to bring about opening of the valve, without the risk that the roll body becomes undesirably displaced in its accommodating structure or becomes completely lost. 
   Another advantage of the present invention is that the cooperating slots in the one piece and the neighboring piece are both closed, so that the roll bodies are secured against undesirable displacement (or dislodgment) upward or downward or otherwise. The closed slots limit engagement of the roll bodies to the axial longitudinal direction. 
   The roll bodies disclosed here are not self-supported bearings, such as ball bearings with inner and outer races, but are free guided roll bodies without the use of additional mechanical elements. Accordingly, for a given external diameter they have appreciably higher load bearing capability. This leads to the advantage that a closed slot in accordance with the invention has equal force transmission capability and equal force sustaining capability, in both the closing and the opening operations. This enables the invention to have very high sealing forces and very high releasing forces. Such releasing forces may also be required if, after a very long period of being closed, the seal, which generally will be an elastomeric seal, has developed substantial adhesion forces which must be overcome in the opening operation. 
   A particular advantage of the invention is that in the simplest case no tensile return springs are needed, because the roll bodies are completely forced and guided, and enclosed, in associated accommodating configurations between the slots, and are forcibly guided in the valve-sealing direction and in the opposite direction. 
   The embodiments of the invention are not limited to a configuration in which the roll bodies are in the form of rolls or the like extending entirely from one side of the device to the other. According to another embodiment of the invention it may be provided that the roll bodies are only present in the form of segments of rolls or the like and, for example, do not extend over the entire width of the valve from one side of the valve to the other, and are not interconnected by a connecting member. 
   The embodiments of the invention are not limited to the use of roll bodies in the form of cylindrical rolls. Other shapes may be employed, such as, in particular, triangular bodies which enable direct rolling movement with rounded spherical surfaces. 
   Because the forces on the roll bodies are substantially smaller than the forces employed previously in related valve structures, it is sufficient for the roll bodies to be comprised of a commercially widely available and relatively inexpensive metallic material. Similarly, it is unnecessary for the guide slots for the roll bodies to have specially hardened support surfaces. 
   As a supporting element for the slots according to the invention, preferably a carriage is employed which is driven in the horizontal direction. Suitable drive means are known in the art and are not specifically described herein. 
   It is not essential to the embodiments of the invention that the carriage have four supporting wheels. Other types of support elements may be utilized, such as convex roller bearings or the like. 
   The term “carriage” is referred to herein as the “drive plate,” because it is in the form of a plate-shaped body borne by rollers which body is driven in translational movement on a support surface in a housing. 
   In this connection the movable valve member borne by the carriage is longitudinally guided by a guide slot (guideway) which at its end forces the movable valve member to move upward toward the sealing seat. Instead of such a guideway for the movable valve member, other means of forcing and guiding mechanisms for lifting may be used such as, for example, a rocker arm or the like. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     The objects, advantages, and features of the invention will be more clearly perceived from the following detailed description, when read in conjunction with the accompanying drawing, wherein: 
       FIG. 1  is a cross section through a first embodiment of the invention of a valve mechanism in a vacuum valve; 
       FIG. 2  is a plan view of the guideway slot in the  FIG. 1  embodiment for forcible guiding of the movable valve member; 
       FIG. 3  is a cross section through line III-III of  FIG. 1 ; 
       FIG. 4  is an enlarged cross sectional view through a detail of the guide means for the roll body in the slot of  FIG. 1 ; 
       FIG. 5  is a cross section through a second exemplary embodiment of the valve mechanism of the invention, with a movable valve member and a counter-disc; 
       FIG. 6  is a cross section through line VI-VI of  FIG. 5 ; 
       FIGS. 7A-7E  show several exemplary embodiments of the complementary slots in accordance with the invention; 
       FIGS. 8A-8F  show the course of movement when complementary slots in accordance with the invention are moved with respect to each other; 
       FIG. 9  is a perspective, expanded view of the disc with the roll bodies in accordance with the invention; and 
       FIG. 10  is an enlarged view of a portion of  FIG. 9 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  is a general view of a valve mechanism of the invention in a vacuum valve, wherewith throughgoing valve opening  2  is disposed in housing  1 . The valve opening can be closed off by movable valve member  4  with the aid of sealing element  8 . 
   The traveling element (carriage) illustrated in  FIGS. 1 and 3  is essentially comprised of drive plate  14  which is drivable back and forth in the direction of arrow  22  (see also  FIG. 6 ); 
   The excursion of movable valve member  4  is effected with the aid of guideway slot  3  which is bent at its end, as shown in  FIGS. 1-3 , which slot  3  is formed in the two sides of the housing  1 . Guideway slot  3  is engaged on both sides by rollable suspension means (wheel or roller)  9 . 
   Guideway slot  3  and its function are illustrated more clearly in  FIG. 2 . Wheel  9  moves exclusively along axis  10 , which axis has at its front end a part  11  which extends perpendicularly to its main direction. Between the two parts a gradual transition or radius  12  is provided to ensure a smooth transition of the movement. It is understood that a small amount of air reaches this wheel traveling in the guideway slot, to enable the bearing to roll on the running surface of the guideway slot. The wheel is connected to the movable valve member  4  via the arm  13  which is integral to or fixed to said valve member  4 . 
   Wheel  9  has exclusively guiding functions, and in particular is not subjected to stresses of the sealing or release of the valve closure. It bears only the weight of the parts suspended on it, such as movable valve member  4 . 
   Drive plate  14  has a plurality of suspension means  15  which are movable in the drive plane along the axis or in direction of arrow  22  but are not movable along any other axis. In the embodiment shown, the suspension means are wheels  15  which roll on corresponding support surfaces  24  disposed in the interior of the housing. The actual support surface for wheels  15  is either the lower support surface  24  or the opposite support surface  24 ′, depending on the installed orientation of the overall housing  1 . 
   In order to bring about the rise of the valve member  4  in the direction of arrow  33  in  FIG. 1  toward the sealing seat, forceful guide elements are provided in the form of roll bodies  16 . Roll bodies  16  are in the form of throughgoing profiled rolls, shafts, or pins (see  FIG. 3 ). The outer end of each roll body  16  engages a corresponding control slot  23  in the region of the drive plate  14 . In this way, a form-interlocking (configurationally engaging) connection between the two slots ( 6 ,  23 ) is provided, via the respective engaging gudgeon ends of the roll bodies  16 . 
   It was mentioned in the Summary hereinabove that it is not critical to the invention that the roll body  16  extend over the entire width of the valve member. The support member embodied as the roll body  16  may be comprised of two aligned roll bodies which are not joined. Thus, roll body  16  may have a break in its center, to form two roll body parts which are held in alignment in movable valve member  4 . Such a configuration with divided roll bodies  16  is particularly preferred for vacuum valves of large operating width. 
   The shapes of the slots  6  and  7  ( FIG. 5 ) are preferably arcuate curves. However, other shapes may be chosen, such as:
         inclined straight lines at a constant angle;   straight lines with two angles (a reverse bend) and an arcuate transition between them; or   a configuration with a straight inclined region in the region of high force, and possibly with a small indentation at each end position for catching the end position.       

     FIGS. 7A-7E  show examples of various slot shapes meeting this description, The slots are surrounded by walls which limit movement in the direction perpendicular to their longitudinal extent. Such limiting is also present on the ends of the slots (the upper and lower ends). Thus a roll body can enter into engagement with a control slot only in a plane perpendicular to the plane of the longitudinal extent of the control slot. 
   It may be seen from  FIGS. 7A-7E  that the coordinated complementary slots  6  and  23  have overlapping end regions. In particular, it may be seen from  FIGS. 8A-8F  that the control slot  23  in drive plate  14  has an end region  29  which forms one side of an accommodating opening  32 , whereas the other side of the accommodating opening  32  is formed by the end region  30  of the complementarily disposed slot  6  in the movable valve member  4 . In this way, a complete accommodating opening  32  which surrounds roll body  16  is formed, in which opening  32  the roll body is held without appreciable play. 
   The various slot embodiments illustrated in  FIGS. 7A-7E  demonstrate that the shape of the slots is not confined to simple arcuate curves but may have angular bends, or slots  6  and  23  may be substantially comprised of respective straight inclined regions ( FIG. 7B ). Thus it is possible to provide a constant deflection over the extent of the slot. In any event, it is important that slots  23  on both sides of drive plate  14  have the same shape (but rotated 180° to result in a complementary shape). 
   If the slots had different slot shapes, this would be attended by different characteristics of the rolling contact and rolling wear which, while tolerable, would not be desirable, because then the frictional angles between roll body  16  and its support surface  34  would cause a certain amount of play whereas, in contrast, with geometrically congruent but oppositely disposed slots  6  and  23 , the traveling contact points on support surfaces  31  and  34  will be fundamentally diametrically oppositely disposed on the outer circumference of roll body  16 . Thus the roll body will essentially continuously move exactly between two parallel surfaces, even when the paths of these surfaces are curved. This will provide optimal stress transmission between the roll bodies and the associated contact points, in the region of support surfaces  31 ,  34 . 
   For the exemplary embodiments of  FIGS. 8A-8F , illustrating the contact points during the opening of the valve, the analogous considerations apply to those which apply for the valve-closing process, except that the contact points on the respective support surfaces  31  and  34  are reversed. 
   As described above in connection with  FIG. 3 , the two parallel roll bodies  16  disposed a distance apart are positioned in parallel slots  6  disposed a distance apart in movable valve member  4 . 
   According to a refinement of the invention, it is provided that the movement of the parallel roll bodies  16  disposed a distance apart is synchronized. For this purpose, synchronization plate  36  ( FIG. 10 ) is employed which is shown disposed on one side of movable valve member  4  in the intermediate space between the outer side surface of the movable valve member and the opposing surface of drive plate  14 . As seen in  FIG. 3 , a gap is provided there (gap  35  in  FIGS. 9 and 10 ), in which gap the synchronization plate  36  is disposed with some space to spare, allowing plate  36  to operate with some play. Only one such gap  35  and plate  36  is shown, but it is preferable that there be a plate  36  on each side valve member  4 . The end of each roll body  16  extends through and engages a synchronization plate  36 , so that the synchronization plate accommodates and guides the ends of the roll bodies on both sides of movable valve member  4 . This achieves absolute parallel guiding of the two roll bodies  16  on each side of the movable valve member  4 . 
   This synchronization means, employing synchronization plates, applies analogously for the embodiment according to  FIG. 5 , which (as shown) has twice as many roll bodies. Also for this case, it is provided that the laterally disposed roll bodies extend through and engage the synchronization plate on the front and rear sides, so that here, in the embodiment shown, the front and rear roll bodies are moved in continuous synchrony, via the synchronization plate(s) disposed between said roll bodies. 
     FIG. 4  illustrates another embodiment of the above-described roll body. This roll body  17  may have a groove  25  at one or more locations which groove receives a spring-loading element, such as O-ring  18 . At the corresponding location on drive plate  14 , recess  19  is provided, the resulting configuration being that O-ring  18  is pressed (lightly) on only one side, namely, that of the support surface  26 . 
   Such a mechanism ensures that that roll body  17  is always urged in one lateral direction, even in the presence of tolerances which may be necessary for manufacturing engineering reasons and which cause a slight play. The arrangement with the O-ring according to  FIG. 4  may optionally (but not necessarily) be provided in the embodiment according to  FIGS. 5 and 6 . Spring element  20  is provided in that embodiment which, when slightly pre-stressed, urges roll bodies  16  against the corresponding surfaces in slots  6  and  7 . 
   Also in  FIGS. 5 and 6  spring element  20  is employed as a detent means  21  for the forward position. As illustrated, the spring element may be in the form of a sheet spring, but other types of spring elements may used, for example, helical springs, plate springs, or ring-shaped plate springs, which also urge the movable valve member  4  against the second movable valve member  5 , or against the drive plate  14 . The use of a second (cooperating) movable valve member  5  has the advantage that when the valve is closed not only is the upper valve opening  2  closed via the seal element  8  but the lower valve opening is also closed via the valve member  5 . 
   In the embodiments shown, the drive means and its associated components are not illustrated because the features of the drive means are not material to the present invention. It is merely specified that forces are applied to the drive plate  14  in the direction of arrow  22  and in the opposite direction in a known manner. 
     FIGS. 8A-8F  illustrate in more detail the course of the movement of the two cooperatively (and oppositely) moved slots  6  and  23 . It is seen from  FIG. 8A  that in the rest position an accommodation opening  32  is formed by the mutually complementary cooperating slots  6 ,  23 . This overlap region was described above as being formed from the adjacent end regions  29 ,  30  of the respective slots  6 ,  23 . 
   As soon as a translational displacement force is applied to control slot  23  in the direction of arrow  22  ( FIG. 3 ), slot  23  is moved rightward, until wheel  9  ( FIGS. 1-3 ) passes through the curved region  12  of the guideway slot  3  and into region  11 , whereby movable valve member  4  is raised in the direction of arrow  33 . Meanwhile, slot  6  stays unmoved, because the movable valve member  4  can only move upward, in the direction of arrow  33 , while roll body  16  also moves upward in the region of slot  6  and downward in the region of control slot  23 . 
   This is illustrated in the in  FIGS. 8B and 8C . Control slot  23  has been moved rightward through distance  22 ′ (which may be, for example, about 6 mm), during a period when slot  6  has not been moved in the horizontal direction. However, slot  6  has been moved vertically upward by the distance  33 ′. In the rest position ( FIG. 8A ) and in the final position ( FIG. 8F ), the accommodation opening  32  takes on a circular shape for accommodating roll body  16  or  17 . 
   In the intermediate positions, the accommodation opening expands to an ovaloid shape. In the final position ( FIG. 8F ), control slot  23  has been moved completely rightward, again while slot  6  has remained unmoved in the horizontal direction. This process describes the maximum possible vertical or upward excursion of the roll body in the direction of arrow  33  as the roll body is accommodated under the constraints of the accommodation opening. 
   In the final position, movable valve member  4  has thus undergone its maximum possible upward lifting movement to come to press against the sealing seat, in that roll body  16  is now at the end of the support surface  34  of slot  6 . The progression of views of the movement in  FIGS. 8A-8F  also shows clearly how the reverse progression, that is, movement of the control slot leftward from the  FIG. 8F  position, leads to movement of the movable valve member  4 ,  5  away from the respective sealing seat. Because the roll bodies are constantly surrounded on all sides in accommodation opening  32 , and are guided by configurational engagement, this movement away from the sealing seat is a continuously forced movement which occurs without play (as was the case with the upward movement in the direction of arrow  33 ). 
   For the sake of easy comprehensibility, in the exemplary embodiment according to  FIGS. 5 and 6 , slot  6  in cooperating movable valve member  5  is shown as a slot  7  which has the same function as slot  6  in movable valve member  4 . In this exemplary embodiment, when movable valve member  4  is moved toward the sealing seat of valve opening  2 , gap  27  is formed between movable valve member  4  and cooperating movable valve member  5 . 
   The return to the rest position illustrated in  FIG. 5  occurs in the reverse sequence, with the aid of the spring element  20 . The spring element serves only to compensate for the necessary play. 
   The exemplary embodiment according to  FIGS. 5 and 6  shows that one does not need a slot having a part  11  which serves as a detent, but rather spring element  20  can serve as detent  21 . 
   Roll bodies  16  and  17  are protected against falling out in their longitudinal directions by means of external detents  28  which are disposed on drive plate  14 . 
   It is important that the interrelationships of the roll bodies and slots  6 ,  23  according to  FIG. 8A  (rest position) are preserved over the entire course of movement, and that drive plate  14 , with its support rolls  9 , is out of engagement with the part  11  of guideway slot  3  but is instead in the region of axis  10 . During this longitudinal movement, roll bodies  16  and  17  are arranged stablely in the rest position according to  FIG. 8A . 
   The invention affords the advantage that the connection between drive plate  14  and movable valve member  4  (also cooperating movable valve member  5 ) is controlled via two cooperating control slots  6 ,  23  which have mutually complementary configurations, and via the supporting ends (gudgeon ends) of roll bodies  16  and  17 , so as to achieve a guiding configurational engagement between drive plate  14  and movable valve member  4 ,  5 . In this connection, it is advantageous that the slots are all closed laterally, that is, such that roll bodies  16  and  17  cannot exit from the slots, which represents an improvement over the state of the art. 
     FIG. 9  is a perspective view of movable valve member  4  with roll bodies  16  which undergo rolling in slots  23  of drive plate  14 . 
   For the sake of clarity, the two beam-like parallel parts of drive plate  14  have been moved farther apart, whereby movable valve member  4  disposed in the space between the parallel parts can be depicted more clearly. In an actual embodiment, parts  4  and  14  will be closer together and gap  35  will be much smaller. 
     FIG. 10  illustrates an enlarged detail of  FIG. 9 , wherewith synchronizing plate  36  has been added which has two bores  37  which are engaged by roll bodies  16  with a certain support play. The synchronization plate  36  serves to synchronize the movement of parallel roll bodies  16  disposed a mutual distance apart. If and when the position of the frontmost roll body (in the direction of travel)  16  in slots  6  and  23  is changed, rear roll body  16  is carried along, by the intermediary of the synchronization plate  36 .