Abstract:
The invention relates to a seal ( 160 ) for sealing two opposite contact surfaces along a closed contour, comprising an elastic sealing element ( 210 ), which has two opposite sealing surfaces ( 240 ) to bear against the contact surfaces in the region of the contour, two spring elements ( 220, 230 ), each of which is associated with one of the sealing surfaces, and a supporting element ( 250 ) arranged between the spring elements, wherein each spring element comprises two limbs ( 260, 270 ), one limb pressing the sealing surface associated with the spring element against one of the contact surfaces and the other limb being supported on the supporting element.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a seal. In particular, the invention relates to a seal for sealing off two bearing faces lying opposite one another. 
     Sealing off bearing faces which lie opposite one another is necessary, for example, where slide valves are concerned. The planar surfaces of a valve body and of a sealing disk are mounted there parallel to one another with a clearance. An orifice in the valve body enables a fluid medium, for example a cooling liquid, to flow to the valve disk. The valve disk is arranged displaceably with respect to the valve body, for example linearly or rotatably, and has an orifice which is more or less in alignment with the orifice in the valve body, depending on the position of the valve disk. The orifices may, for example, have a round or elliptic cross section. Accordingly, a flow of a fluid medium through the valve disk is dependent upon its displacement position with respect to the valve body. 
     In order to prevent medium from flowing through the gap between the valve disk and the valve body, it is necessary to provide a seal in this region. Such a seal usually lies in the gap and is fastened non-displaceably on one side either to the valve disk or to the valve body. 
     The seal is arranged in such a way that it bears under a certain pressure against the two surfaces lying opposite one another and thereby ensures leaktightness with respect to the fluid. In some applications, a clearance between the two surfaces may be variable during operation, and under some circumstances the clearance is subject to a certain variance even at the time of installation. Leaktightness of the two surfaces may be dependent upon a clearance of the bearing faces, and the result of this may be that no leaking occurs in the region of the seal in specific operating situations, for example in the case of a fluid contaminated with pollutants or in the case of different thermally induced expansions of parts of the slide valve. 
     SUMMARY OF THE INVENTION 
     The object on which the invention is based, therefore, is to specify a reliable seal of two faces lying opposite one another. 
     A seal for sealing off two bearing faces lying opposite one another, along a closed contour, comprises an elastic sealing element which has two sealing faces lying opposite one another for bearing against the bearing faces in the region of the contour, two spring elements which are assigned in each case to one of the sealing faces, and a supporting element arranged between the spring elements, each spring element comprising two legs, of which in each case one leg presses the sealing face assigned to the spring element onto one of the bearing faces and in each case the other leg is supported on the supporting element. 
     Two spring elements are thereby connected in series in respect of the spring direction, so that a spring constant of the overall seal is lower than a spring constant of an individual spring element. Thus, operating, installation and manufacturing tolerances in the spring direction can be compensated, without major forces having to be exerted upon the sealing faces, which would result in making it more difficult for the bearing faces to be displaced with respect to the sealing faces. 
     The supporting element at the same time absorbs part of the shear forces which act in the lateral direction upon the seal during a displacement of a bearing face with respect to a sealing face, so that the seal is not appreciably deformed during displacement and leaktightness can be maintained. The spring elements can be designed to be integrated with the supporting element in the form of a wavy profile, with the result that the seal can be produced more easily. The wavy profile may have perforations in order to make it easier for the wavy profile to bend along the contour. 
     Each of the spring elements may comprise a U-shaped or V-shaped profile which runs along the contour. This simple embodiment is known from conventional seals and is tried and tested. Furthermore, in the event of a pressure drop between the inside and the outside of the contour, such a profile can be oriented such that the legs point in the direction of the high-pressure side. The pressure drop presses the legs of the spring element apart, with the result that the sealing action of the seal can be further improved. 
     The spring elements and the supporting element may be portions of a helical spring. This constitutes a further simple and cost-effective possibility for combining a low spring constant perpendicularly to the sealing faces with a good supporting action against shear forces running laterally with respect to the sealing faces. 
     The spring elements and the supporting element may alternatively also be portions of an elastic all-metal cushion made from knitted wire cloth, so that the seal also has a high thermal load-bearing capacity. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is described in more detail below by means of the accompanying drawings in which: 
         FIG. 1  illustrates a lateral sectional view of a rotary slide valve; 
         FIG. 2  a sectional view of a first embodiment of a seal for the valve from  FIG. 1 ; 
         FIG. 3  a sectional view of a second embodiment of a seal for the valve from  FIG. 1 ; 
         FIG. 4  a sectional view of a third embodiment of a seal for the valve from  FIG. 1 ; 
         FIG. 5  a sectional view of a fourth embodiment of a seal for the valve from  FIG. 1 ; 
         FIG. 6  a sectional view of a fifth embodiment of a seal for the valve from  FIG. 1 ; 
         FIG. 7  a side view of a sixth embodiment of a seal for the valve from  FIG. 1 ; 
         FIG. 8  a sectional view of a seventh embodiment of a seal for the valve from  FIG. 1 ; and 
         FIG. 9  a sectional view of an eighth embodiment of a seal for the valve from  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a sectional view of a rotary disk valve  100 . The rotary disk valve  100  comprises a valve housing  110 , a valve disk  120  with a circular orifice  130  and a hub  140 , a disk shaft  150  and two seals  160 . Bearing faces  170  for the seals  160  are formed on the valve disk  120  and on the valve body  110 . The bearing faces  170  may be composed, for example, of ceramic, hard metal, steel or plastic. A contour  180  runs circularly along the cylindrical connecting face which connects mutually opposite bearing faces  170  to one another. The contour  180  may, for example, be of annular, elliptic, polygonal or irregular form and run parallel between the bearing faces. The valve housing  110  has three inlets/outlets A, B and C. Although a seal  160  according to the invention is not restricted to use in the rotary disk valve  100  or in a valve at all, one possible area of intended use for the seal  160  will be described with reference to the rotary disk valve  100 . 
     The rotary disk valve  100  is designed to allow or prevent a liquid between inlets/outlets A and C or B and C selectively and proportionally. By means of the disk shaft  150 , the valve disk  120  is rotated such that the orifice  130  in the valve disk  120  is more or less in alignment with the inlet/outlet A or the inlet/outlet B, as required. In the position illustrated, the orifice  130  in the valve disk  120  is completely in alignment with the inlet/outlet A, so that it is possible for liquid to flow between the inlets/outlets A and C. At the same time, the valve disk  120  prevents liquid from flowing between the inlet/outlet B and one of the inlets/outlets A and C. 
     The seals  160  in the region of the inlets/outlets A and B have the task of counteracting an overflow of liquid between the inlets/outlets A and B and the valve disk  120 . The seals  160  must therefore maintain good upward contact at the bearing faces  170  with respect to the valve disk  120  and downward contact at the bearing faces  170  with respect to the valve housing  110  and at the same time be insensitive to movement of the valve disk  120 . In order to compensate operating and manufacturing tolerances in the clearance between the valve disk  120  and the valve housing  110  in the region of the seals  160 , the seals  160  have a low spring constant in the vertical direction. 
       FIG. 2  shows a sectional view of a first embodiment of a seal  160  for the valve  100  from  FIG. 1 . The seal  160  runs along the circular contour  180  (not depicted) which runs perpendicularly with respect to the drawing plane. For reasons of symmetry, only one sectional plane of the seal  160  is illustrated, and at the left margin of the drawing the bisecting line is depicted which at the same time forms a mid-axis of the contour  180 . 
     The seal  160  comprises a sealing element  210 , a first spring element  220  and a second spring element  230 . The sealing element  210  has at the top and bottom in each case a sealing face  240  for contact with a bearing face  170  (not depicted). Between the spring elements  220  and  230  the sealing element  210  comprises a web  250 . The sealing element  210  has at the top and bottom in each case a sealing lip, the removed boundary faces of which form the sealing faces  240 . In the region of the upper sealing lip, the first spring element  230  is arranged in the form of a U-shaped profile open toward the inside of the seal  160  or the contour  180 . 
     Each spring element  220 ,  230  comprises in each case an upper leg  260  and a lower leg  270 . The upper leg  260  of the first spring element  220  presses the sealing face  240  upward. Correspondingly, the second spring element  230  is located in the region of the lower sealing lip, the lower leg  270  of said second spring element pressing the lower sealing face  240  downward. The upper leg  260  of the second spring element  230  and the lower leg  270  of the first spring element  220  are supported against the web  250  from opposite directions. The web  250  is thicker than the portions between the sealing faces  240  and the assigned spring elements  220  and  230 , in order to increase the movability of the sealing faces  240  in the vertical direction and at the same time provide a good supporting action between the adjacent legs  260 ,  270  of the spring elements  220  and  230 . 
     The sealing element  210  surrounds the spring elements  220  and  230  on its outside (on the right). This version is especially advantageous in the event of a pressure drop from the inside of the sealing element  210  to its outside, because the pressure drop can then be utilized to press the sealing faces  240  more strongly onto the respective bearing faces  170 . 
     The sealing element  210  may be manufactured from any permanently elastic material, for example based on silicone, rubber or plastic. The spring elements  220 ,  230  are manufactured from a spring-elastic stainless sheet steel. 
     In contrast to a seal  160  with only one spring element, in the case of two spring elements  220 ,  230  with a corresponding spring constant it is possible to adapt to different clearances between the bearing faces  170  by means of a pressure force which varies by less than a factor 2. If, for example, the clearance is variable by +/−0.1 mm in the case of an individual spring constant of 60 N/mm, when only one spring element  220 ,  230  is used the pressure force varies by +/−12 N, whereas, when two series-connected spring elements  220 ,  230  are used, as shown, the pressure force varies by only +/−6 N. 
       FIG. 3  shows a sectional view of a second embodiment of a seal  160  for the valve  100  from  FIG. 1 . The embodiment illustrated corresponds to that from  FIG. 2 , the difference being that the legs  260 ,  270  of the U-shaped profiles of the spring elements  220  and  230  point outward and are covered inwardly by the sealing element  210 . This type of construction is recommended in the case of a pressure drop from the outside inward, in order to increase a pressing action of the sealing faces  240  to the corresponding press-on faces by means of the pressure drop. 
       FIG. 4  shows a sectional view of a third embodiment of a seal  160  for the valve  100  from  FIG. 1 . The seal illustrated is constructed in a similar way to the embodiment illustrated in  FIG. 3 , but, in contrast to the U-shaped spring elements  220  and  230  in  FIG. 3 , V-shaped spring elements  220 ,  230  composed of a V-shaped profile are used. These have a lower spring constant in the vertical direction than the spring elements  220 ,  230  composed of a U-shaped profile from  FIGS. 2 and 3  and thus ensure a lower spring constant of the overall seal  160  in the vertical direction between the sealing faces  240 . 
       FIG. 5  shows a sectional view of a fourth embodiment of a seal  160  for the valve  100  from  FIG. 1 . The embodiment illustrated corresponds to those of  FIGS. 3 and 4 , the difference being that spring elements  220 ,  230  with an O-shaped cross section are used. These may selectively be hollow profiles or profiles composed of solid material; where hollow profiles are concerned, these may be closed or, for example, open along a peripheral seam. A supporting action of the spring elements  220 ,  230  composed of an O-shaped profile in a vertical direction is greater than, for example, that of the spring elements  220 ,  230  in the embodiment of  FIG. 4 . Depending on how far inward or outward the spring elements  220 ,  230  are arranged on the sealing element  210 , they are at a greater or lesser distance from a connecting face between the sealing faces  240  and correspondingly bring about a weaker or stronger spring action in the vertical direction between the sealing faces  240 . If the spring elements  220 ,  230  are far removed from the connecting face, a considerable part of the spring constant of the seal  160  between the sealing faces  240  is brought about by the sealing element  210 . 
       FIG. 6  shows a sectional view of a fifth embodiment of a seal  160  for the valve  100  from  FIG. 1 . The embodiment illustrated corresponds essentially to that from  FIG. 3 , the difference being that the spring elements  220 ,  230  shown there and the web  250  are implemented by three portions  620 ,  630  and  640  of a one-piece spring element  610 . The first portion  620  and the third portion  640  correspond to the first spring element  220  and to the second spring element  230  respectively, and the second portion  630  corresponds to the web  250  in the embodiment illustrated in  FIG. 3 . 
       FIG. 7  shows a side view of a sixth embodiment of a seal  160  for the valve  100  from  FIG. 1 . The embodiment illustrated corresponds to the embodiment illustrated in  FIG. 6 , the difference being that the spring element  610  has a multiplicity of portions  710  composed of a U-shaped profile in the vertical direction. Moreover, cutouts  720  are made along a circumference of each of the portions  710 , in order to make it easier for the spring element  610  to bend along the circumference of the seal  160  during production. Clearances between the perforations may be variable and be low in the region of a narrow radius of the contour and high in the region of a large radius of the contour. 
       FIG. 8  shows a sectional view of a seventh embodiment of a seal  160  for the valve  100  from  FIG. 1 . This embodiment corresponds to that illustrated in  FIG. 6 , the difference being that, instead of the spring element  610 , a helical spring  810  which comprises a plurality of turns is arranged between the sealing faces  240 . The portions  620 ,  630  and  640  correspond in each case to portions  820  of the helical spring  810  which comprise at least one turn. 
       FIG. 9  shows a sectional view of an eighth embodiment of the seal  160  for the valve  100  from  FIG. 1 . The embodiment illustrated corresponds likewise to the embodiment illustrated in  FIG. 6 , the difference being that, instead of the spring element  610 , an all-metal cushion  910  is arranged between the sealing faces  240 . The all-metal cushion  910  is elastic and comprises a multiplicity of knitted wire cloths (not illustrated in detail), the portions  620 ,  630  and  640  from  FIG. 6  being replaced by any vertical portions of the all-metal cushion  910 .