Abstract:
The seal arrangement ( 1 ) for piston compressors comprises a deformable ring support ( 2 ) and a first and a second endless sealing ring ( 3   a,    3   b ), wherein the ring support ( 2 ) has a longitudinal axis (L) which extends perpendicularly with respect to its circumferential direction, and wherein the ring support ( 2 ) has a gap ( 2   i ) with play in its circumferential direction, and wherein each sealing ring (3 a,    3   b ) has a longitudinal axis ( 3   c,    3   d ) which extends perpendicularly with respect to its circumferential direction, and wherein the sealing rings ( 3   a,    3   b ) are arranged in such a way that the ring support ( 2 ) encloses them from the outside, and wherein the two sealing rings ( 3   a,    3   b ) are arranged next to one another in the direction of extent of the longitudinal axis (L), and wherein the ring support ( 2 ) and the sealing rings ( 3   a,    3   b ) are designed to be adapted to one another in such a way that the first sealing ring ( 3   a ) bears on one side against a first side wall ( 2   d ) of the ring support ( 2 ) and forms a first gap (S 1 ) to the ring support ( 2 ) on the opposite side with regard to the longitudinal axis ( 3   c ) of the first sealing ring ( 3   a ), and wherein the second sealing ring ( 3   b ) bears in a diametrically opposed manner on one side against a second side wall ( 2   l ) of the ring support ( 2 ) and forms a second gap (S 2 ) to the ring support ( 2 ) on the opposite side with regard to the longitudinal axis ( 3   d ) of the second sealing ring ( 3   b ), wherein the first and second side walls ( 2   d,    2   l ) are arranged so as to lie opposite one another with regard to the longitudinal axis (L), with the result that the ring support ( 2 ) can in each case bring about a prestressing force ( 5   a,    5   b ) on the first and second sealing rings ( 3   a,    3   b ) respectively via the first and second side walls ( 2   d,    2   l ) respectively, wherein the prestressing forces ( 5   a,    5   b ) extend in an opposed manner.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a National Phase Application of PCT International Application No. PCT/EP2011/065054, International Filing Date Aug. 31, 2011, claiming priority of European Patent Application No. 10174738.4, filed Aug. 31, 2010, which is hereby incorporated by reference. 
     FIELD OF THE INVENTION 
     The invention relates to a seal arrangement for piston compressors. 
     BACKGROUND OF THE INVENTION 
     It is known to seal the piston rod of crosshead piston compressors movably supported in an oscillating manner with the aid of dry-running or lubricated friction sealing elements. The seal along the piston rod takes place via so-called packings which are usually structured in the form of a serial connection of single-part or multipart sealing elements. 
     The different variants of packings with seal arrangements can roughly be divided into seal arrangements with single-part sealing rings and with multipart sealing rings. 
     Document WO 97/00397 discloses a multipart sealing ring which comprises three segments. These segments are subject to wear during operation, with the segmentation of the sealing ring having the consequence that the contact pressure of the segments on the piston rod, and thus the sealing effect, is maintained up to a predefined wear limit despite the wear thanks to a self-adjustment of the segments. Such a multipart sealing ring thus has a wear compensation in that the segments are automatically displaced in dependence on the wear. 
     Document WO 97/00396 discloses a single-part sealing ring which is suitable as a piston rod seal arrangement. This sealing ring includes an individual single-part ring having a ring gap. With this sealing ring, the wear compensation takes place by an elastic and/or plastic deformation of the sealing ring. 
     The sealing rings of a piston rod packing are pressed toward the piston rod by a coil spring, for example, in the unloaded state. An additional pressing of the sealing ring toward the piston rod takes place by the differential pressure applied to the sealing ring during the operation of the compressor. In particular with segmented sealing rings, but also with single-part sealing rings with a ring gap, the changing pressure engaging at the sealing ring effects an elastic and/or plastic deformation of the sealing ring or of the individual segments, which has the consequence, among other things, of an unequal material removal along the periphery of the sealing ring. These effects in particular occur with seal arrangements arranged directly toward the sealing space since these seal arrangements are usually loaded with a pressure difference fluctuating over time. The load has the consequence that this seal arrangement has a rapidly decreasing sealing effect and that a flow or a break failure of the seal arrangement respectively occurs in dependence on the material used for the sealing rings. 
     Known seal arrangements thus have the disadvantage that they may have a rapidly decreasing sealing effect or a relatively high wear under certain circumstances. 
     SUMMARY OF THE INVENTION 
     It is the object of the invention to form an economically more advantageous seal arrangement. 
     This object is satisfied by a seal arrangement having the features of the claims that follow. 
     The object is in particular satisfied by a seal arrangement comprising a deformable ring carrier as well as comprising a first and a second continuous sealing ring, wherein the ring carrier has a longitudinal axis extending perpendicular to its peripheral direction, and wherein the ring carrier has a gap with clearance in its peripheral direction, and wherein each sealing ring has a longitudinal axis extending perpendicular to its peripheral direction, and wherein the sealing rings are arranged such that the ring carrier surrounds them from the outside, and wherein the two sealing rings are arranged next to one another in the direction of extent of the longitudinal axis, and wherein the ring carrier and the sealing rings are designed mutually adapted such that the first sealing ring contacts a first side wall of the ring carrier at the one side and forms a first gap toward the ring carrier at the side disposed opposite with respect to the longitudinal axis of the first sealing ring, and wherein the second sealing ring contacts a second side wall of the ring carrier at the one side in mirror inversion and forms a second gap toward the ring carrier on the side disposed opposite with respect to the longitudinal axis of the second sealing ring, wherein the first and second side walls are arranged disposed opposite with respect to the longitudinal axis so that the ring carrier can effect a respective preload force on the first or second sealing ring respectively via the first or second side walls respectively, wherein the preload forces extend in an opposite manner, in particular in the direction of extent of the incision. 
     The object is further in particular satisfied by a seal arrangement for piston compressors comprising a deformable ring carrier as well as a continuous first sealing ring, wherein the ring carrier has a longitudinal axis L extending perpendicular to its peripheral direction, and wherein the ring carrier has a gap with clearance in its peripheral direction, and wherein the ring carrier is designed in L shape with a side part extending perpendicular to the longitudinal axis and a surrounding part extending in the direction of the longitudinal axis L, wherein the first sealing ring has a longitudinal axis extending perpendicular to its peripheral direction, and wherein the first sealing ring is arranged in the ring carrier such that the surrounding part surrounds the first sealing ring from the outside, and wherein the first sealing ring is arranged next to the side part and contacting it in the direction of extent of the longitudinal axis, and wherein the ring carrier and the first sealing ring are designed mutually adapted such that when they contact a piston rod, the first sealing ring contacts a first side wall of the ring carrier at the one side and forms a first gap toward the ring carrier at the side disposed opposite with respect to the longitudinal axis of the first sealing ring, wherein the ring carrier has a second side wall which is arranged disposed opposite the first side wall with respect to the longitudinal axis L so that the ring carrier can effect a preload force on the first sealing aligned toward the longitudinal axis L via the first side wall, and wherein a clamping ring surrounds the ring carrier from the outside in the peripheral direction. 
     It was recognized that the ring gaps required for wear compensation in known seal arrangements have the consequence of instability under the load caused by pressure changes and pressure differences, which has the consequence of an increased wear at the sealing ring and at the total seal arrangement. The seal arrangement in accordance with the invention has the advantage that the actual sealing rings no longer have any ring gaps in that the sealing rings are designed as continuous sealing rings. That is, the sealing ring extends over 360° and does not have any gap or ring gap, but is rather designed in a throughgoing manner over a full circle of 360°. The seal arrangement in accordance with the invention with sealing rings without ring gaps thus has the advantage that the pressure changes and pressure differences engaging at the sealing ring have the consequence of no instability, or only a very small stability, of the sealing ring so that the sealing ring has substantially smaller wear in comparison with known seal arrangements. 
     To achieve a sealing effect comparable with known friction seal arrangements, the seal arrangement in accordance with the invention for sealing a piston rod of a piston compressor has two continuous sealing rings, with these two sealing rings being arranged next to one another in the direction of extent of the piston rod and being held in a common ring carrier, and with the two sealing rings as well as the ring carrier being designed mutually adapted such that the two sealing rings are supported displaceably in opposite directions in the ruing carrier for wear compensation. The seal arrangement in accordance with the invention thus makes it possible to use two continuous sealing rings for rubbing sealing, with these two sealing rings having war during operation and the ring carrier therefore being designed such that it can carry out wear compensation. In a preferred embodiment, the ring carrier is designed such that it surrounds the two sealing rings such that the two sealing rings are displaceably supported in opposite directions. In a preferred embodiment, the ring carrier has a gap in the peripheral direction, with the ring carrier being formed from a deformable material and being designed as elastically or plastically deformable, which has the consequence that the ring carrier can change its diameter in the radial direction and can thereby effect a force or a displacement on the two sealing rings. In a preferred embodiment, the seal arrangement includes a coil spring or a clamping ring which surrounds the ring carrier at its periphery to effect a force on the sealing rings at least in the unloaded state and thus to ensure that they also remain in contact with the piston rod in the unloaded state. 
     In an advantageous embodiment, the ring carrier has a ring gap, with the sealing rings being arranged in the ring carrier and being held mutually displaceably such that the direction of displacement of the two sealing rings is aligned orthogonally or perpendicular to the direction of extent of the ring gap. 
     The contact of the two sealing rings to the movable piston rod as well as the wear compensations of the seal arrangement in accordance with the invention required due to the wear of the sealing rings in which the two sealing rings are displaced in opposite directions has the consequence that each sealing ring only has a rubbing contact with the piston rod over an angle of 180 degrees or substantially 180 degrees and thus only contacts the piston rod periphery along this angle. An asymmetrical material removal thus takes place at each of the two sealing rings, which has the consequence that they move toward tone another during operation or during wear. The ring carrier and the two sealing rings are designed mutually adapted in a particularly advantageous embodiment such that the maximum permitted wear path of the sealing rings is limited, which is possible, for example, by grooves eccentrically worked in the ring carrier. As soon as the point of the maximum permitted wear path has been reached, the ring carrier no longer exerts the forces on the sealing rings acting in opposite directions. As soon as the maximum permitted wear path of the sealing rings has been reached, the sealing function of the seal arrangement thus changes from a friction seal into a gap seal, preferably into a contact-free gap seal. 
     The seal arrangement in accordance with the invention has, among other things, the advantage that the sealing rings are designed as continuous, that is the sealing rings have no incision or gap, so that the sealing rings have a high stiffness so that the compression forces engaging at the sealing ring effect a smaller deformation, which in turn has the consequence that the wear reduces. In addition, the sealing rings also do not require any elastic or plastic deformability for wear compensation as was required with previously known sealing rings. This allows a seal arrangement with small wear. In the seal arrangement in accordance with the invention, the wear direction of the two sealing rings is predefined by the ring carrier, for example by eccentrically designed grooves which hold the sealing rings so that no security against rotation by a fixing pin is required in the seal arrangement so that the seal arrangement can be designed favorably and reliably. 
     In a further advantageous embodiment, the ring carrier of the seal arrangement is configured such that the two sealing rings are held in a mutually spaced apart position by the ring carrier in the axial direction in that the ring carrier has a spacer ring which is arranged between the sealing rings. In a particularly advantageous embodiment, the spacer ring is designed such that its inner side comes to lie close to the piston rod or contacts the piston rod and thus likewise exerts a sealing function. If the spacer ring contacts the piston rod, a rubbing contact results along the piston rod in that the first sealing ring has a 180 degree contact to the piston rod, then the spacer ring has a rubbing contact to the piston rod and then the second sealing ring has a 180 degree contact to the piston rod. In this embodiment, the ring carrier has a pressure-relieving function for the sealing rings. In addition, the sealing rings are guided in a lateral direction by the spacer ring. 
     The sealing rings are preferably produced from dry-running materials such as filled PTFE or polymer blends modified specifically for dry running or high-temperature polymers such as PEEK or PI as well as special sintered bronze. For use in oil-free piston compressors, the sealing rings comprise, for example, filled plastics and composites or also metals such as lead bronze or tin bronze. The ring carrier is preferably produced from a plastic such as PEEK. If the ring carrier has a contact with the piston rod, a modified plastic containing solid lubricants such as graphite or PTFE is preferably suitable. 
     The invention will be explained in detail in the following with reference to embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings used to illustrate the embodiments show: 
         FIG. 1  a front view of a seal arrangement; 
         FIG. 2  a section of  FIG. 1  along the line A-A: 
         FIG. 3  a sealing ring; 
         FIG. 4  a side view of the sealing ring in accordance with  FIG. 3 ; 
         FIG. 5  a clamping ring; 
         FIG. 6  a seal arrangement arranged at a piston rod; 
         FIG. 7  a section through a piston rod with a sealing ring arranged thereat along the line B-B; 
         FIG. 8  a section through a piston rod, with the sealing rings having wear; 
         FIG. 9  a section through  FIG. 8  along the line C-C; 
         FIG. 10  a section through a further seal arrangement; 
         FIG. 11  a section through a ring carrier along the line D-D; 
         FIG. 12  a front view of the ring carrier shown in  FIG. 11 ; 
         FIG. 13  a front view of a further ring carrier; 
         FIG. 14  a sealing ring for the ring carrier shown in  FIG. 13 ; 
         FIG. 15  a front view of a further seal arrangement; 
         FIG. 16  a section through a further seal arrangement; 
         FIG. 17  a section through a piston rod and through a further embodiment of a seal arrangement; 
         FIG. 18  a sealing ring for the seal arrangement shown in  FIG. 17 ; 
         FIG. 19  a section along the line F-F through the ring carrier shown in  FIG. 20 ; 
         FIG. 20  a front view of the ring carrier shown in  FIG. 19 ; 
         FIG. 21  a front view of a further ring carrier; and 
         FIG. 22  a section along the line G-G through the ring carrier shown in  FIG. 21 . 
     
    
    
     Generally, the same parts are provided with the same reference numerals in the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a seal arrangement  1  in a plan view and in a section along the line A-A in  FIG. 2  comprising an elastically or plastically deformable ring carrier  2  and a first and a second sealing ring  3   a ,  3   b  which are arranged in the ring carrier  2 . A continuous sealing ring is understood as a ring extending over 360° which thus has not gap or no ring gap site respectively. The ring carrier  2  has a longitudinal axis L extending perpendicular to its peripheral direction. The ring carrier  2  additionally has a gap  2   i  with clearance T in its peripheral direction. Each sealing ring  3   a ,  3   b  has a longitudinal axis  3   c ,  3   d  extending perpendicular to its peripheral direction. The sealing rings  3   a ,  3   b  are arranged such that the ring carrier  2  surrounds them from the outside, with the two sealing rings  3   a ,  3   b  being arranged lying directly next to one another in the direction of extent of the longitudinal axis L, as can be seen from  FIG. 2 . The ring carriers  2  and the sealing rings  3   a ,  3   b  are in a new state, that is are designed mutually adapted without any wear or only with little wear and contacting a piston rod  6  such that the first sealing ring  3   a  contacts a first side wall  2   d  of the ring carrier  2  at the one side and forms a first gap Si toward the ring carrier  2  at the side disposed opposite with respect to the longitudinal axis  3   c  of the first sealing ring  3   a  and such that the second sealing ring  3   b  contacts a second side wall  21  of the ring carrier  2  in mirror inversion at the one side and forms a second gap S 2  toward the ring carrier  2  at the side disposed opposite with respect to the longitudinal axis  3   d  of the second sealing ring  3   b , wherein the first and second side walls  2   d ,  21  are arranged disposed opposite with respect to the longitudinal axis L so that the ring carrier  2  can effect a respective preload force  5   a ,  5   b  on the first or second sealing ring  3   a ,  3   b  respectively via the first or second side walls  2   d ,  21 , wherein the preload forces  5   a ,  5   b  extend in opposite directions in the direction of extent of the section A shown in  FIG. 2 . The previously described arrangement of the ring carrier  2  and of the two sealing rings  3   a ,  3   b  in particular applies in the new state and as long as the sealing rings  3   a ,  3   b  have no wear or only small wear. In the new state, the sealing rings  3   a ,  3   b  are arranged in a starting position along a piston rod  6 , with the two sealing rings  3   a ,  3   b  preferably being arranged contacting the piston rod  6  such that the longitudinal axes  3   c ,  3   c  extend identically. In the embodiment shown, the ring carrier  2  has a cut-out  2   f  in which a clamping ring  4  is arranged and which surrounds the ring carrier  2 . The ring carrier  2  has a web  2   h  to prevent a rotation of the clamping ring  4  with respect to the ring carrier  2 . 
     The seal arrangement  1  shown in  FIGS. 1 and 2  shows the ring carrier  2  designed as a ring shaped body with a gap  2   i . The view in accordance with  FIG. 1  in particular shows the second sealing ring  3   b  and the ring carrier  2  surrounding it, with the second sealing ring  3   b  having an inner radius R and an outer radius R 1 . The ring carrier  2  has side walls at its inner side which are designed such that they effect the oppositely acting preload forces  5   a ,  5   b  on the first or second sealing ring  3   a ,  3   b  respectively, with the clamping ring  4  exerting a preload force on the ring carrier  2 . In the view shown in accordance with  FIG. 1 , the ring carrier  2  has, on the inner side shown at the left, a second side wall  21  extending in a semicircular manner and having a center Z 1  and a radius R 2 . In addition, the ring carrier  2  has, at the inner side shown at the right, a second spaced apart side wall  2   m  extending in a semicircular manner and having a center Z 2  and a radius R 3 , with the radii R 2  and R 3  being identical in the embodiment shown. The two centers Z 1  and Z 2  are mutually spaced apart by a distance Z, with the distance Z being able to have a value between 0.1 and 10 mm depending on the embodiment of the ring carrier  2  or depending on the maximum permitted wear of the sealing rings  3   a ,  3   b . To hold the first sealing ring  3   a  arranged at the rear from the view in accordance with  FIG. 1 , the ring carrier  2  has, as can be seen from  FIGS. 1 and 2 , a first side wall  2   d  designed in mirror inversion with respect to the second side wall  21  and the second spaced apart side wall  2   m  and a first spaced apart side wall  2   e  such that the first side wall  2   d  is of semicircular design and has a center Z 1  and a radius R 2  and such that the first spaced apart side wall  2   e  is of semicircular design and has a center Z 3  and a radius R 3 , with the radii R 2  and R 3  again being identical in the embodiment shown. The two centers Z 1  and Z 3  are in turn mutually spaced apart by the distance Z. The continuous sealing ring  3   a ,  3   b  has an inner radius R. 
       FIG. 3  shows in a plan view the continuous sealing ring  3   a  or  3   b  with a center axis  3   c ,  3   d , an inner radius R, an outer radius R 1  and a ring width  3   k .  FIG. 4  shows the continuous sealing ring  3   a ,  3   b  with a width  3   g  in a side view. 
       FIG. 5  shows the clamping ring  4  with a gap  4   a  and a gap width  4   b  in a plan view. 
       FIG. 6  shows a piston rod  6  movable in a direction of movement v and having a longitudinal axis M. In addition,  FIG. 6  shows the left half of a seal arrangement  1  in a part longitudinal section, said seal arrangement being arranged in a chamber ring  8  having a sealing chamber  7 , with P 1  representing the side with higher pressure and P 2  the side with lower pressure.  FIG. 6  shows a similar seal arrangement  1  as shown in  FIGS. 1 and 2 , with the seal arrangement  1  shown in  FIG. 6  likewise being in a new state. The design and the operation of this seal arrangement  1  was has already been described with the aid of  FIG. 2 . 
       FIG. 7  shows a section through a piston rod  6 , for example along the line B-B in accordance with  FIG. 6 , with a sealing ring  3   b  in the new state contacting the piston rod  6 . The longitudinal axis M of the piston rod  6  extends identically or almost identically with the center axis  3   d  of the sealing ring  3   b . The inner radius R of the sealing ring  3   b  is larger than or equal to the radius R 5  of the piston rod. 
       FIG. 8  shows the view shown in  FIG. 7  after a certain operating time during which the sealing rings  3   a ,  3   b  are subject to wear. The preload force  5   b  acting on the second sealing ring  3   b  has the consequence that the second sealing ring  3   b  wears at the inner surface of the left side in the representation in accordance with  FIG. 8 , with this inner surface contacting the surface of the piston rod  6  so that a gap S 6  is formed on the right side between the piston rod  6  and the second sealing ring  3   b . The first sealing ring  3   a  undergoes wear in mirror inversion with respect to the second sealing ring  3   b , for example, and therefore carries out a movement in mirror inversion in the direction of the preload force  5   a  so that a gap S 3  is formed between the piston rod  6  and the first sealing ring  3   a .  FIG. 9  shows a section along the line C-C shown in  FIG. 8 , with in addition in  FIG. 9  the ring carrier  2  being shown which surrounds the first and second sealing rings  3   a ,  3   b . The wear of the first and second sealing rings  3   a ,  3   b  has the consequence that the gaps S 3 , S 4 , S 5  and S 6  are formed, with the seal arrangement  1 , as can be seen from  FIG. 9 , having an excellent sealing effect despite these gaps S 3 , S 4 , S 5  and S 6  in the longitudinal direction M of the piston rod  6 . In  FIG. 9 , the first and second sealing rings  3   a ,  3   b  have reached the maximum wear path, which can be recognized from the fact that the first sealing ring  3   a  contacts the ring carrier  2  at the left in the shown view and thus can no longer be displaced further to the left. In mirror inversion to this, the second sealing ring  3   b  contacts the ring carrier  2  at the right and can thus also no longer be displaced further to the right. As soon as the sealing rings  3   a ,  3   b  have reached the maximum possible wear path, the sealing function of the seal arrangement  1  changes from a friction sealing into a gap seal, preferably into a contact-free gap seal. 
       FIG. 10  shows a further embodiment of a seal arrangement  1  in a section. Unlike the seal arrangement  1  shown in  FIG. 2 , the seal arrangement  1  in accordance with  FIG. 10  has a ring carrier  2  with a ring part  2   k  which is designed as an intermediate wall and which the two sealing rings  3   a ,  3   b  contact so that the two sealing rings  3   a ,  3   b  are arranged mutually spaced apart in the direction of the longitudinal axis L. The ring part  2   k  is also called a spacer ring  2   k.    
       FIG. 12  shows a plan view of a similar ring carrier  2  to that shown in  FIG. 10 .  FIG. 11  shows a section along the line D-D in accordance with  FIG. 12 . The ring carrier  2  has a cut-out  2   a  for the first sealing ring  3   a  as well as a cut-out  2   b  for the second sealing ring  3   b . The ring carrier  2  in addition has a ring gap  2   k  or an intermediate web  2   k  having a cut-out  2   c  for the piston rod  6 , with the cut-out as shown preferably having a surface aligned toward the piston rod  6 , with the ring part  2   k  preferably being designed such that a gap forms between the ring part  2   k  and the piston rod  6  so that a gap seal is formed. In a preferred embodiment, the intermediate web  2   k  has an inner diameter R 4  which substantially corresponds to the inner diameter R of the first and second sealing rings  3   a ,  3   b . The extent of the grooves for receiving the first and second sealing rings  3   a ,  3   b  is designed identical to that shown in  FIG. 1  in that the cut-out  2   b  for the second sealing ring  3   b  has a second side wall  21  which extends in a semicircular manner and has a radius of curvature R 2  and a center Z 1  as well as a spaced apart side wall  2   m  extending in a semicircular manner and having a radius of curvature R 3  and a center Z 2 . The cut-out  2   a  for the first sealing ring  3   a  is designed in mirror inversion to this and has a first side wall  2   d  extending in a semicircular manner and having a radius of curvature R 2  and a center Z 1  as well as a side wall  2   e  spaced apart and extending in a semicircular manner and having a radius of curvature R 3  and a center Z 3 , with the centers Z 3  and Z 2  having the same spacing with respect to the center Z 1 . Due to this arrangement of the sealing rings  3   a ,  3   b  in the ring carrier  2 , as described in  FIGS. 1 and 2 , a preload force  5   a ,  5   b  on the sealing rings  3   a ,  3   b  is effected so that the sealing rings  3   a ,  3   b  move relative to the ring carrier  2  due to the wear occurring over time, as shown in  FIGS. 8 and 9 . The ring part  2   k  inter alia has the advantage that it forms as supporting side surface for the sealing ring  3   a ,  3   b  so that it is guided better on engaging changing loads. 
     In addition, the ring part  2   k  can form a gap seal together with the piston rod  6  in the longitudinal direction L. 
       FIG. 13  shows a further embodiment of a ring carrier  2  with a ring part  2   k  with an inner diameter R 4 .  FIG. 14  shows a second sealing ring  3   b  adapted to this ring carrier  2  and having an inner radius R. Unlike the embodiment shown in  FIG. 12 , the ring carrier  2  shown in  FIG. 13  has a cut-out  2   b  with a circular side wall with a center Z 1  and a radius R 2  so that the second side wall  21  and the spaced apart side wall  2   m  extend in a circular manner with the same center Z 1 . So that the second sealing ring  3   b  can nevertheless be displaced in the cut-out  2   b  of the ring carrier  2 , as described in  FIGS. 1 and 2 , the second sealing ring  3   b  is designed as shown in  FIG. 14 . The second sealing ring  3   b  has a first, semicircular outer surface  3   h  with a center Z 1  and a radius R 1 . The second sealing ring  3   b  in addition has a second, semicircular outer surface  3   i  with a center Z 3  and a radius R 1 . The two centers Z 1  and Z 3  are mutually spaced apart by the distance Z. The second sealing ring  3   b  thus has a smaller width on the right side in  FIG. 14 , which has the consequence that this sealing ring  3   b , arranged in the cut-out  2   b  of the ring carrier  2  shown in  FIG. 13 , has a gap S 2  in the new state between the spaced apart side wall  2   m  of the ring carrier  2  and the second semicircular outer surface  3   i . The first sealing ring  3   a  is of exactly the same design as the second sealing ring  3   b  shown in  FIG. 14 , with the first sealing ring  3   a  being arranged in mirror inversion to the second sealing ring  3   b  in the ring carrier  2  shown in  FIG. 13  such that in the new state as shown in  FIG. 2 , for example, a gap S 1  forms on the left side. 
     The ring carrier  2  and/or the sealing ring  3   a ,  3   b  in the embodiment shown in  FIGS. 13 and 14  advantageously has/have a security against rotation  10 , for example a pin, to fix the position of the sealing ring  3   a ,  3   b  with respect to the ring carrier such that no mutual rotation occurs. Further embodiments of securities against rotation  10  are shown in  FIG. 15 . 
       FIGS. 12 and 13  each show a ring carrier  2  with a ring part  2   k  or an intermediate web  2   k . The ring carrier  2  shown in  FIG. 13  could, however, also be designed without an intermediate web  2   k  so that two sealing rings  3   b ,  3   a  designed in accordance with  FIG. 14  could be held in the ring carrier  2  in manner similar to that shown in  FIG. 2 . 
     The side walls  21 ,  2   m  of the cut-outs  2   a ,  2   b  in the ring carrier  2  intended to receive the first and second sealing rings  3   a ,  3   b  and the outer surface  3   h ,  3   i  of the sealing rings  3   a ,  3   b  can be designed mutually adapted in a plurality of possibilities such that the sealing ring  3   a ,  3   b  is displaceably supported in the ring carrier  2  in the direction of extent of the engaging preload force  5   a ,  5   b . The side walls  21 ,  2   m  and/or the outer surface  3   h ,  3   i  can also be designed as a frequency polygon or as a polygon, for example, or could also extend in an oval manner, for example. 
     The ring carrier  2  and the sealing rings  3   a ,  3   b  are preferably designed mutually adapted such that the first and/or the second gap S 1 , S 2  has/have a maximum width in the new state in the range from 0.1 mm to 10 mm, and preferably a maximum width in the range from 1 mm to 2 mm. 
     The sealing rings  3   a ,  3   b  are preferably composed of a wearable material, in particular of a metal such as bronze, gray cast iron or sintered iron or of a plastic such as PEEK, filled PTFE or hollow temperature polymers such as PEEK, PI or epoxy. The ring carrier  2  is composed of a metal, in particular of steel, stainless steel, bronze or gray cast iron or of a plastic, in particular PEEK, filled PTFE or high-temperature polymers such as PEEK, PI or epoxy. 
     A plurality of seal arrangements  1  can be arranged lying behind one another in the direction of extent of seal arrangements  1 . 
       FIG. 15  shows a further seal arrangement  1  which is designed the same per se as the seal arrangement shown in  FIG. 1  with the exception that the seal arrangement  1  in accordance with  FIG. 15  has a security against rotation  10  which is designed such that it prevents a rotation of the first sealing ring  3   a  and/or of the second sealing ring  3   b  with respect to the ring carrier  2 . The section along the line E-E is identical to the section shown in  FIG. 2 . The security against rotation  10  can be designed in different embodiments. In an embodiment shown in  FIG. 15 , the security against rotation  10  is configured such that the first sealing ring  3   a  and/or the second sealing ring  3   b  has/have a projecting nose  31  and such that the nose  31  is designed as so wide in the peripheral direction of the sealing ring  3   a ,  3   b  that the nose  31  has room in the gap  2   i  of the ring carrier  2  so that the nose  31  together with the gap  2   i  formed by the ring carrier  2  forms the security against rotation  10  to prevent a rotation of the first and/or second sealing rings  3   a ,  3   b  with respect to the ring carrier  2 . The view shown in  FIG. 15  shows only the second sealing ring  3   b . In a preferred embodiment, the first sealing ring  3   a  could likewise have a nose  31  which projects into the gap  2   i  to effect a security against rotation  10 .  FIG. 15  additionally shows a further embodiment of a security against rotation  10 , with it including a pin  10   a  as well as a bore  10   b  in the ring carrier  2  and a bore  10   c  in the first sealing ring  3   a  and/or in the second sealing ring  3   b . The bore  10   b ,  10   c  and the pin  10   a  introduced into the bores  10   b ,  10   c  are designed mutually adapted such that a mutual rotation of the ring carrier  2  with respect to the first sealing ring  3   a  and/or the second sealing ring  3   b  is prevented. 
       FIG. 16  shows a section through a further seal arrangement  1  which has a similar design to the seal arrangement  1  shown in  FIG. 10 . Unlike the seal arrangement  1  shown in  FIG. 10 , the first and the second sealing rings  3   a ,  3   b  project beyond the ring carrier  2  in the direction of the longitudinal axis L in the seal arrangement  1  shown in  FIG. 16 . The first and/or second sealing rings  3   a ,  3   b  can equally also be designed so wide that they project beyond the ring carrier  2  in the direction of the longitudinal axis L. In a particularly advantageous embodiment, the sealing rings  3   a ,  3   b  are not, as shown in  FIG. 16 , designed wider, but the ring carrier  2  shown in  FIG. 9  or  10  is rather designed narrower in the direction of the longitudinal axis L and the width of the sealing rings  3   a ,  3   b  is maintained so that it is possible to form a very narrow ring carrier  2 . 
       FIG. 17  shows a further embodiment of a seal arrangement  1  in a longitudinal section. This seal arrangement  1  includes a first sealing ring  3   a  as well as a ring carrier  2 , with the piston rod  6  additionally being shown in section in  FIG. 17 . A clamping ring  4  surrounds the ring carrier  2  at least in part.  FIG. 18  shows a side view of the sealing ring  3   a  with an inner radius R and an outer radius R 1 , with the sealing ring  3   a  additionally having a radially projecting nose  31  in the embodiment shown.  FIG. 19  shows the ring carrier  2  in a section which is identical to the section shown in  FIG. 17 . The ring carrier  2  shown in  FIG. 19  has an L-shaped section with a side part  2   n  extending in the radial direction and a surrounding part  2   m  extending in the direction of the longitudinal axis L. The side part  2   n  has a sealing surface  2   c  which extends in circular form and is aligned toward the piston rod  6 . The ring carrier  2  has a cut-out  2   a  on the one side for receiving the sealing ring  3   a . The cut-out  2   a  includes a first side wall  2   d  and a spaced apart side wall  2   e  disposed opposite with respect to the longitudinal axis L.  FIG. 20  shows a plan view of the ring carrier  2 , with  FIG. 19  showing a section along the line F-F. The ring carrier  2  has a gap  2   i  extending in the peripheral direction. The ring carrier  2  additionally has a web  2   h . The ring carrier  2  includes a first center Z 1 , with a semicircle with a radius R 2  defining the first side wall  2   d . The ring carrier  2  includes a second center Z 2  which is spaced apart by the distance Z with respect to the first center Z 1 . A semicircle about the second rotational center Z 2  with a radius R 3  defines the spaced apart side wall  2   e . The ring carrier  2  additionally includes an outwardly peripheral cut-out  2   f  for a clamping ring  4  which could be designed as shown in  FIG. 5 , for example. This clamping ring  4  effects a force extending in the peripheral direction, with the ring carrier  2  being designed as deformable, in particular elastically deformable, so that the ring carrier  2 , as shown in  FIG. 17 , contacts the piston rod  6  in the peripheral direction. The spaced apart side wall  2   e  is designed such that a first gap S 1  arises between the sealing ring  3   a  and the spaced apart side wall  2   e  at least with a new, not yet worn seal arrangement  1 . The width of the gap S 1  reduces as the wear of the sealing ring  3   a  and/or of the ring carrier  2  increases. 
       FIG. 21  shows a plan view of a further embodiment of a ring carrier  2 . Unlike the ring carrier  2  shown in  FIG. 20 , the ring carrier  2  shown in  FIG. 21  has backflow grooves  2   o . In the embodiment shown, three backflow grooves  2   o  are arranged spaced apart in the peripheral direction.  FIG. 22  shows a section through the ring carrier  2  shown in  FIG. 21  along the line G-G. The backflow grooves  2   o  are designed as recesses in the ring carrier  2  to allow a backflow of a fluid. 
     In an advantageous embodiment, the first and the second side walls  2   d ,  2   e  have the same radius of curvature R 2 , R 3 . In an advantageous embodiment, the distance between the first and the second centers Z 1 , Z 2  has a value in the range between 0.1 and 10 mm. In an advantageous embodiment, the first gap S 1  has an axial width in the range from 0.1 mm to 10 mm. In an advantageous embodiment, the sealing ring  3   a ,  3   b  is composed of a wearable material, in particular of a metal such as bronze, gray cast iron or sintered iron or of a plastic such as PEEK, filled PTFE or hollow temperature polymers such as PEEK, PI or epoxy. In an advantageous embodiment, the first side wall  2   d  extends over an angle of 180 degrees or approximately 180 degrees and the first gap S 1  extends over an angle of 180 degrees or approximately 180 degrees. In an advantageous embodiment, the sealing ring  3   a  has an inner radius R which is larger than or equal to the outer radius R 5  of a piston rod  6 . In an advantageous embodiment, the ring carrier  2  is composed of a metal, in particular of steel, stainless steel, bronze or gray cast iron or of a plastic, in particular PEEK, filled PTFE or high-temperature polymers such as PEEK, PI or epoxy.