Abstract:
The invention relates to a ball valve having a housing made of plastic in which a carrier structure is disposed that is encased in plastic in which a valve ball having a through opening is pivotally supported between an opening and closing position, said carrier structure comprising two carrier rings positioned opposite each other, and a connecting element connecting said carrier rings. In order to create a ball valve made of plastic that is characterized by a simple construction and improved impermeability, the invention provides for the carrier structure to separate the valve ball completely from the plastic of the housing.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to a ball valve having a housing in which there is disposed a support structure which is encased by synthetic material and in which a valve ball having a through-opening is mounted so as to be able to rotate between an open position and a closed position. 
         [0002]    A ball valve made from synthetic material and a method for the production thereof are known from the European Patent EP 0 575 643 B1. The ball valve consists essentially of a housing, in which there is mounted a valve ball as a shut-off element. The housing comprises two pipe connection pieces which are connected to each other in a typical manner via the through-bore of the valve ball when the valve ball is in an open position and are separated from each other via the valve ball when the valve ball is in a closed position. The housing is produced in one piece in an injection-molding process and from polyethylene. In order to be able to be rotated from the open position to the closed position, the valve ball is mounted so as to be able to rotate about a substantially—as seen in the case of horizontally aligned pipe connection pieces—vertical axis and is connected to a switching shaft for actuating the valve ball. The valve ball is mounted via two bearing rings which are connected to each other via an annular inlay. The bearing rings comprise openings corresponding to the inner cross-section of the pipe connection pieces and adjoin the valve ball at the front and the rear as seen in the direction of flow of a fluid through the ball valve. When the valve ball is in the open position, its through-bore is aligned with the openings of the bearing rings. As seen in cross-section, the bearing rings are substantially triangular in formation and thus protrude over a portion of the outer peripheral surface of the valve ball. In this region which protrudes over the valve ball a respective sealing ring is provided in the bearing rings and is supported on the outer peripheral surface of the valve ball. Nitrile butyl rubber is preferably provided as the material for the sealing rings. The outer peripheral region of the bearing rings which is remote from the valve ball and is directed in the radial direction is ribbed in formation, wherein the ribs extend in parallel with the through-flow direction of the ball valve. The outer ends of the ribs of the two bearing rings are connected to each other via an annular inlay. The annular inlay is adhered or welded to the bearing rings. The two bearing rings with the sealing rings and the inlay thus form a type of support cage for the valve ball. The bearing rings, the valve ball and the inlay can be produced from bronze, brass, special steel or synthetic material, preferably glass fibre-reinforced synthetic material or polypropylene. In addition, the annular inlay is provided with through-openings, so that during the production process the injected synthetic material of the housing can penetrate through the through-openings in the direction of the valve ball and in the direction of the ribs. The housing synthetic material penetrates as far as to the surface of the valve ball. As a consequence, an intimate connection is established between-the material of the housing and the bearing rings and the inlay in the form of an embedded arrangement. The inlay has the task as a type of reinforcement to absorb the tensile, compressive and movement forces and the occurring turning moments within the ball valve. 
         [0003]    For the production of the ball valve, in one of the first operating steps the bearing rings together with the sealing rings are placed onto the opposite ends of the valve ball. Subsequently, the annular inlay is slid over the two bearing rings. Then, the annular inlay is connected at its ends to the two bearing rings by an adhesion or welding procedure. This support cage which consists of the valve ball, the bearing rings and the inlay is then inserted into an injection mold and subsequently the support cage is injection-molded around and penetrated by the housing material. In the case of this injection-molding procedure, the through-openings of the inlay have the task of separating the housing produced during the injection-molding procedure into an outer part and an inner part. As the housing produced in the injection-mold is cooled, a shrinking procedure of the two housing parts relative to each other is forced and any shrinkage of the housing in a radial manner inwards is prevented. This should prevent the valve ball from becoming jammed in the housing. In order to achieve some clearance between the valve ball and the synthetic material housing, the valve ball is heated prior to the injection-molding of the housing. 
         [0004]    Furthermore, a further shut-off valve made from synthetic material and a method for the production thereof are known from the European Patent 1 121 549 B1. In terms of its basic construction, this shut-off valve corresponds with the above-described ball valve apart from the inlay which connects the two bearing rings together. In accordance with this patent document, the inlay is produced in two steps as an injection-molded part. In a first step, a molded part is produced, which consists preferably of a thermoplastic synthetic material, in particular an adhesion copolymer, and is injection-molded. This molded part forms the outer shape of the inlay and thus also the inner shape of the housing subsequently sprayed from polyethylene. In a second production step, a synthetic material, preferably a glass fibre-reinforced synthetic material or polypropylene, is sprayed from the inside onto the molded part. As this synthetic material is sprayed onto the molded part, the molded part melts partially and a fusion-welded connection is formed between the molded part and the synthetic material introduced in the second method step. The inlay thus consists of a first outer layer of thermoplastic synthetic material, in particular an adhesion copolymer, and a second inner layer of a synthetic material, preferably a glass fibre-reinforced synthetic material or polypropylene. This inlay also comprises the above-described through-openings, so that during the last production step of the shut-off valve the injected polyethylene for the housing can pass through the through-openings of the inlay to the valve ball and, therefore, the inlay is embedded into the housing material. 
         [0005]    Furthermore, a ball valve having a valve ball and a bipartite housing is known from the European Patent EP 0 756 681 B1. The housing is divided centrally and—as seen in the through-flow direction—transversely in a plane which centrally bisects an adjusting spindle of the valve ball. The housing halves comprise a recess for receiving a ball valve insert. The ball valve insert is inserted into the bipartite housing during assembly and the two housing halves are clamped together by means of screws. Since the ball valve insert is oversized in comparison with the recess in the housing, sealing is effected by the pretensioning achieved. This ball valve insert consists essentially of the valve ball having a switching shaft and an opposite bearing spigot which on the whole are surrounded by a seamless lining which as seen in the through-flow direction has a flange at the front and rear. Since the lining of the ball valve insert is seamless and continuous from flange to flange and is produced from a fluoric synthetic material such as PFA, PTFE or FEP, the further parts of the ball valve insert do not have any medium contact and do not need to be produced from such high-quality materials. In order to dismantle the valve ball, the lining has to be divided and thus destroyed. The valve ball is rotatable within the lining and lies against the surface of the valve ball and partially against the bearing spigot and the switching shaft. Disposed on the outer side of the lining remote from the valve ball is a resilient inlay around which engages a further housing body of the ball valve insert. The resilient inlay has the task of sealing the lining with respect to the housing body. The housing body can be produced from metal or synthetic material and is then divided in half for assembly purposes. The housing body can also be produced in an undivided manner from injection-molded synthetic material. The processing temperature of the synthetic material of the housing body must then be less than that of the lining and of the resilient inlay. In addition, the lining and the housing body are connected mechanically, in a positive-locking manner or by adhesion by means of an adhesive agent. In order to seal the ball valve insert in the region of the switching shaft, the ball valve insert comprises in addition a pressure piece which is located on the resilient inlay and is pretensioned by a sleeve-shaped pressure flange, which surrounds the switching shaft concentrically, in the direction of the lining until the desired sealing tightness is achieved. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention provides a ball valve consisting essentially of synthetic material which is characterized by simple production and improved sealing tightness. 
         [0007]    In accordance with an aspect of the invention, a ball valve includes a housing consisting essentially of synthetic material, in which there is disposed a support structure which is encased or injection-molded around by the synthetic material of the housing and in which a valve ball having a through-opening is mounted so as to be able to rotate between an open position and a closed position. The support structure includes two opposite support rings, which receive the valve ball, and a connection element which connects these support rings. Simpler production and simplified assembly is achieved by virtue of the fact that the support structure separates the valve ball completely from the synthetic material of the housing. Therefore, a desired amount of clearance in the form of a gap can be adjusted between the outer surface of the valve ball and the inner surface of the support structure merely by virtue of the dimensioning of these components and is not changed during the creation of the housing of the ball valve in the injection-molding process. 
         [0008]    The support structure in accordance with the invention together with the valve ball already forms a functional, self-contained ball valve. In order to be able to connect the support structure in a convenient manner to existing pipeline networks which are typically made from polyethylene, the support structure may be injection-molded around with the housing from polyethylene which also forms the connection piece. In the ball valve, the shut-off function is assumed by the support structure with the valve ball and the connection function is assumed by the housing with the connection piece. Since the support structure is closed, it is not necessary for the valve ball to be heated during the injection-molding procedure of the housing. It is only necessary to ensure that the shrinkage force of the housing does not damage the support structure. 
         [0009]    When the valve ball is assembled into the support structure, an adjustment of the gap between the outer surface of the valve ball and the inner surface of the support structure may be facilitated by virtue of the fact that bearing surfaces are disposed on the connection element and bearing surfaces are disposed on the support rings such that after the support rings are connected by the connection element the support rings are at a preselected spaced interval with respect to each other, so that a small gap remains between the valve ball and the support rings. 
         [0010]    The support structure may be assembled in a convenient manner by virtue of the fact that the support rings inserted from opposite ends into the connection element and the support rings form on a step-like projection a bearing surface which lies against a bearing surface which is formed on a step-like extension of the connection element. 
         [0011]    In order to be able to introduce the forces, which act upon the valve ball during operation of the ball valve, in a reliable manner into the support rings, without changing the gap between the valve ball and the support rings significantly, the support rings are inserted into the sleeve-shaped connection element and are each held by a holding part in the inserted position. 
         [0012]    The holding part may be formed as a u-shaped clamp having a long limb and a short limb, the long limb being in contact with the support ring and the short limb is supported on the connection element. 
         [0013]    To facilitate assembly of the support structure, the annular holding part may be formed in two parts so that it can be opened via a hinge and can be closed via a latching connection. 
         [0014]    In order to improve the stability of the connection pieces, it is provided that the support rings on their sides remote from the valve ball may include a tubular connection part which is surrounded by the part of the synthetic material of the housing which forms a connection piece. 
         [0015]    The housing may be injection-molded from a thermoplastic synthetic material, in particular polyethylene, polyvinylchloride or an elastomer. The support structure which includes the support rings, the connection element and the holding parts may be injection-molded from a heat-resistant, high-performance, engineering synthetic material, in particular glass fibre-reinforced polyamide. The surfaces which are connected to the housing may be coated with a bonding layer as an adhesive agent and the surfaces of the support structure which are connected to the medium are coated with a medium-resistant protective layer. This support structure can reliably absorb the forces acting upon the valve ball and by reason of the small deformation of the valve ball even under pressure the sealing element remains securely in contact with the valve ball. In this case, the phrase “medium-resistant” is understood to mean that the synthetic materials are not attacked by the substances, such as gases, water, crude oils or chemical products which are carried in the pipelines and thus through the ball valves. 
         [0016]    The valve ball may be constructed in the manner of a composite component consisting essentially of a support element and a cover layer, the cover layer completely surrounding the support element and the support element being produced from a heat-resistant, high-performance, engineering synthetic material, in particular glass fibre-reinforced polyamide, and the cover layer being produced from a medium-resistant synthetic material, in particular fluoric synthetic material, polyethylene, polyoxymethylene or an elastomer. By virtue of the fact that the support structure is produced from a high-performance, engineering synthetic material and the valve ball is also very dimensionally stable, on the one hand the sealing tightness of the ball valve is increased and on the other hand neither the support structure nor the valve ball is deformed to an appreciable extent even under high pressures, so that the valve ball continues to be able to move freely in the support structure and therefore no high breakaway torques are required for the switching procedure of the ball valve. The required turning moment is also generally constant over the adjustment range of the valve ball. The composite construction of the valve ball results in a lightweight construction thereof, a reduction in weight and a reduction in materials. Moreover, the cover layers can be adapted in a simple manner to suit the requirements of the medium. 
         [0017]    In order to improve the sealing tightness of the ball valve, the contact region between the support rings and the connection element may be sealed or adhered. Therefore, a sealing element may also be disposed in each case between the valve ball and the support rings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The invention will be described in more detail hereinafter with reference to an exemplified embodiment illustrated in the drawing, in which 
           [0019]      FIG. 1  shows a longitudinal sectional view of a ball valve, 
           [0020]      FIG. 2  shows a detailed view of the valve body of the ball valve of  FIG. 1 , 
           [0021]      FIG. 3  shows a side view of the valve body of  FIG. 2 , and 
           [0022]      FIG. 4  shows an enlarged detailed view of a sealing element of the ball valve of  FIG. 1 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0023]      FIG. 1  illustrates a longitudinal sectional view of a ball valve  1  in accordance with an embodiment of the present invention. As seen from the inside outwards, the ball valve  1  includes a valve ball  2 , a support structure  3  and a housing  4 . 
         [0024]    Typically, the valve ball  2  which serves as the shut-off element in the ball valve  1  comprises a cylindrical through-opening  5  in the centre. In  FIG. 1 , the valve ball  2  is illustrated in its open position, in which the through-opening  5  connects together two aligned and mutually opposite connection pieces  4   a  which form part of the housing  4 , so that a fluid is able to flow through the ball valve  1 . In order to be able to move the valve ball  2  from its open position to its closed position, the valve ball is mounted in the support structure  3  in such a manner as to be able to rotate about—in the present case—a vertical axis A. For this purpose, the valve ball  2  includes in the region of its lower end a circular spigot  2   a,  whose longitudinal axis L extends in parallel with the axis A. The longitudinal axis L of the spigot  2   a  also extends at a right angle with respect to the through-flow direction D of the through-opening  5 . Provided at the upper end of the valve ball  2  opposite the spigot  2   a  is a recess  2   b,  into which an adjusting spindle  7  engages in a positive-locking manner. By means of this adjusting spindle  7 , the valve ball  2  can be moved from the outside from its open position to its closed position or vice versa. The positive-locking connection between the adjusting spindle  7  and the recess  2   b  can be formed, e.g., as a polygon or Torx-connection and also simply as a slot having a rectangular cross-section. 
         [0025]    The valve ball  2 , per se, is produced in a hybrid or composite construction. Located in the interior of the valve ball  2 , which as a result of the through-opening  5  is substantially sleeve-shaped, is a support element  2   c  which is produced from a heat-resistant, high-performance, engineering synthetic material, such as, e.g., glass fibre-reinforced polyamide. In order to achieve a lightweight construction of the valve ball  2 , this support element  2   c  comprises where possible enclosed cavities  8  as illustrated, e.g., in the Figure in the region of the spigot  2   a.  This support element  2   c  is encased in an injection-molding process with a media-resistant synthetic material in the form of a cover layer  2   d,  in order to achieve the final shape of the valve ball  2 . Possible synthetic materials for the cover layer  2 d include fluoric synthetic materials, polyethylene, polyoxymethylene (POM) or elastomers. Prior to spraying on the cover layer  2   d,  the surface of the support element  2   c  is prepared with an adhesive agent  2   e  or primer in the form of a bonding layer. The adhesive agent  2   e  can also be an injection-molded copolymer. The cover layer  2   d  surrounds the support element  2   c  completely, so that the support element  2   c  does not come into contact with the medium or fluid which is carried through the pipelines and thus through the ball valve  1 . A connection can also be established without the adhesive agent  2   e.  The cover layer  2   d  comprises approximately a thickness of 5 to 25 mm, preferably 8 to 10 mm and can be machined or processed in another suitable manner, in order to achieve the desired or required roundness of the valve ball  2 . The valve ball  2  formed in this manner is characterized by a small charge weight, high resistance with respect to aggressive media and a high degree of dimensional stability. The high degree of dimensional stability ensures that even when high pressure is present at the valve ball  2  in the closed state, breakaway torques produced by a deformation of the valve ball  2  do not make it more, difficult for the ball valve  1  to be opened. 
         [0026]    The above-described valve ball  2  is mounted in the support structure  3  so as to rotate about the axis A and is sealed with respect to the support structure  3  by a sealing element  9 . The support structure  3  is constructed from several components and in particular a first support ring  10   a,  a sleeve-shaped connection element  11  and a second support ring  10   b.  The first support ring  10   a,  the connection element  11  and the second support ring  10   b  are disposed one behind the other as seen in the through-flow direction D. In other words, the connection element  11  connects the first support ring  10   a  to the second support ring  10   b  which is spaced apart therefrom, in order to form the support structure  3  which surrounds the valve ball  2 . Each of the two support rings  10   a  and  10   b  comprise a connection part  10   c  which in each case is surrounded by the synthetic material of the connection piece  4   a  of the housing  4 , and a support part  10   d  which in each case surround in an annular manner the valve ball  2  from opposite ends in the region of their front and rear ends as seen in the through-flow direction D. Also, on their side facing the valve ball  2 , the support parts  10   d  each comprise a circular arc surface  10 e which follows the sealing surface  2   f  of the outer surface of the valve ball  2 . Moreover, the support rings  10   a  and  10   b  are provided in the region of their connection part  10   c  with openings  13  in a grid-like fashion, so that the synthetic material of the housing  4  introduced during the injection-molding process can penetrate the connection part  10   c  and therefore during its formation the connection piece  4   a  establishes an intimate connection with the connection part  10   c  of the support rings  10   a  and  10   b.    
         [0027]    Furthermore, in each of the support rings  10   a  and  10   b,  in the region of their circular arc surface  10   c  facing the valve ball  2 , there is provided a recess  12  which as seen in cross-section is triangular in formation, wherein the annular recess  12  comprises two bearing surfaces  12   a  and  12   b  for the sealing element  9  which are aligned with each other at right angles and which are aligned in each case in parallel with the through-flow direction D and perpendicular thereto. Received in this recess  12  is the sealing element  9  which seals the first support ring  10   a  or the second support ring  10   b  with respect to the sealing surface  2   f  of the valve ball  2 . 
         [0028]    On the whole, each of the two support rings  10   a  and  10   b  has a tubular configuration which is cylindrical and grid-like in formation in the region of the respective connection part  10   c  and in the subsequent support part  10   d  has an enlarged wall thickness for absorbing the forces acting upon the valve ball  2  during operation, and extends in the direction of the valve ball  2  with its circular arc surface  10   e.  It is apparent that as a result only a small gap  14  remains between the sealing surface  2   f  of the valve ball  2  and the circular arc surface  10   e  of the support rings  10   a  and  10   b  and therefore the ball valve  1  as a whole only has a small clearance volume, in the event that media should penetrate beyond the sealing element  9  in the direction of the valve ball  2  or the adjusting spindle  7 . The gap  14  has a width of 1/10 min to 5/10 mm. 
         [0029]    On the outer side  10 f remote from the valve ball  2 , the first support ring  10   a  and the second support ring  10   b  are substantially cylindrical in formation. However, on this outer side  10   f  which is remote from the valve ball  2 , there is provided on each of the support rings  10   a  and  10   b  a projection  10   g  which extends in a step-like manner outwards and thus forms a bearing surface  10   h  which is aligned substantially vertically with respect to the through-flow direction D. In order to form the support structure  3 , the first support ring  10   a  and the second support ring  10   b  are inserted from the ends into the substantially sleeve-shaped connection element  11  which comprises a cylindrical inner side  11   a.  On its two opposite ends on its inner surface  11   a,  the connection element  11  also comprises an outwardly directed, step-like extension  11   b  which forms a bearing surface  11   c  which is aligned substantially perpendicular to the through-flow direction D. The spaced interval a between the two bearing surfaces  11   c  thus determines the spacing between the two support rings  10   a  and  10   b  inserted into the connection element  11  and thus ultimately the extent of the gap  14  remaining between the circular arc surfaces  10   e  and the sealing surface  2   f  of the valve body  2 , and of the pretensioning of the sealing element  9  when the valve ball  2  is clamped into the support structure  3 . 
         [0030]    In order to hold the first support ring  10   a  and the second support ring  10   b  in each case in the opposite ends of the connection element  11 , two holding parts  15   a,    15   b  are provided which as seen in cross-section are formed in a u-shaped manner and with a long limb  15   c  and a short limb  15   d.  When the holding part  15   a,    15   b  is in the installed state, the long limb  15   c  lies in each case against a holding surface  10   i,  which is opposite the sealing element  9 , and is aligned at a right angle with respect to the through-flow direction D of the ball valve  1  and terminates in a flush manner with an outer surface  11   d  of the connection element  11 . The short limb  15   d  of the holding part  15   a,    15   b  lies against a counter surface  11   e  of the connection element  11 . This counter surface  11   e  is likewise aligned at a right angle with respect to the through-flow direction D of the ball valve  1 . The clamp-like holding part  15   a,    15   b  thus has the task in each case with its long limbs  15   c  to urge the first support ring  10   a  and the second support ring  10   b  from the outside into the open ends of the connection element  11  until their bearing surfaces  10   h  come to lie against the bearing surfaces  11   c  of the connection element. In order to be able to apply this holding force, the holding part  15   a,    15   b  is supported with its short limb  15   d  against a counter surface  11   e  of the connection element  11 . 
         [0031]    For assembly of the holding parts  15   a,    15   b,  provision is made to form them in two parts and to connect in each case one of the two ends together in an articulated manner and to close the other end by means of a type of latching or snap-action connection. In addition to this mechanical clamping of the two support rings  10   a  and  10   b  via the connection element  11  by means of the holding part  15   a,    15   b,  provision is made to additionally seal or adhere together the inner surface  11   a  of the connection element  2   a  and the outer side  10   f  of the two support rings  10   a  and  10   b.    
         [0032]    In addition, as seen in the through-flow direction D the connection element  11  comprises in the region of its centre a sleeve  11   f,  in which the adjusting spindle  7  is rotationally mounted and is sealed by sealing rings  16 . This sleeve  11   f  is aligned with its longitudinal extension at aright angle with respect to the through-flow direction D. 
         [0033]    The support structure  3  which is formed substantially from the first support ring  10   a,  the connection element  11 , the second support ring  10   b  and the two holding elements  15   a,    15   b  is produced essentially in the injection-molding process from so-called high-performance, engineering synthetic materials which are characterized by a high degree of strength and heat resistance at the same time. For example, reference is made here to glass fibre-reinforced polyamide. When using polyamide, the regions of the surfaces of the support structure  3  are coated with a protective layer  17  which can come into contact with the medium in the pipelines, not illustrated, and thus in the ball valve  1 . An adhesive agent or preferably an injection-molded copolymer can be used as the protective layer  17 . Moreover, all of the surfaces, preferably the outer surfaces of the support structure  3  are surrounded by an adhesive agent  18  or preferably an injection-molded copolymer as a bonding layer, in order to establish an intimate connection between the synthetic material of the housing  4  and the support structure  3 . 
         [0034]    Therefore, the adhesive agent  18  begins in the region of the outer side of the sleeve  11   f  and continues in the region of the outer surface  11   d  of the connection element  11 , then surrounds the short limb  15   d  of the holding part  15   a,    15   b  and then passes into the long limb  15   c  of the holding part  15   a,    15   b  where it impinges upon the connection part  10   c  of the support rings  10   a  and  10   b.    
         [0035]    It is evident that the support structure  3  and thus also the adhesive agent  18  surround the valve ball  2  completely and there are no openings, in which synthetic material of the housing  4  can penetrate in the direction of the valve ball  2  during the injection-molding procedure. The support structure  3  and the valve ball  2  thus already form a sealed and functional ball valve  1 . 
         [0036]    In the final production step of the ball valve  1 , the support structure  3  together with the valve ball  2  and the adjusting spindle  7 , which are surrounded by the adhesive agent  18 , are inserted into an injection-mold and the housing  4  is produced by injection-molding around the aforementioned parts with a thermoplastic resin, preferably polyethylene, polyvinylchloride or elastomers. The housing  4  has the task of protecting the support structure  3  against any mechanical and chemical loads, as the high-performance materials of the support structure  3  are generally not very resistant. In the present case, the connection pieces  4   a  comprise an opening  6 , whose opening cross-section corresponds to that of the through-opening  5  of the valve ball  2 . In the region of the connection pieces  4   a,  the thermoplastic resin used also renders it possible to weld and press the pipelines, which are to be connected and are not illustrated, or to connect threads which are to be cut in via the outer surfaces of the connection pieces  4   a.    
         [0037]    The term “adhesive agent” or “primer” refers to thin layers in the μm-range which are applied in the flame spraying process, plasma process, whirl sintering process from a suitable material, such as, e.g., synthetic material powder, synthetic material powder as an emulsion in a suitable solvent. The material of the adhesive agent generally consists of materials (synthetic materials) which are compatible with the materials which are to be bonded. Adhesive bonding is performed by effects such as adhesion, diffusion of the molecular structure and/or formation of hydrogen bonds. 
         [0038]      FIG. 2  illustrates a detailed view of the valve body  2  of the ball valve of  FIG. 1 , showing clearly the above-described division of the valve body  2  into a support element  2   c,  a bonding layer  2   e  and a cover layer  2   d.  In the region of the projection  2   a,  the frame-like support element  2   c  provides adequate stability so that in addition a weight reduction can be achieved via a cavity  8  within the support element  2   c.    
         [0039]      FIG. 3  illustrates a side view of  FIG. 2 . 
         [0040]    The embodiment of the synthetic material valve ball is considered as an independent inventive idea. Improved dimensional stability of a synthetic material valve ball of a ball valve, which has a through-opening and can be mounted in a housing of the ball valve so as to be able to rotate between an open and a closed position, may be achieved by constructing the valve ball in the manner of a composite component from a support element and a cover layer. As a consequence, it is possible in the valve ball to combine the characteristics of high dimensional stability provided by the support element and effective resistance against media provided by the cover layer. Effective dimensional stability ensures that the valve ball is deformed only slightly even under high operating pressures and can therefore also be rotated in an effective manner from the closed position to the open position within the housing of the ball valve, without having to overcome high breakaway torques in relation to the valve ball. The required turning moment is also constant over the adjustment range of the valve ball. The composite construction of the valve ball results in its lightweight construction, a weight reduction and a reduction in material. 
         [0041]    Valve balls having a large diameter can also be injection-molded. They do not have to be produced from an extruded semi-finished product. In order to achieve the effective resistance against media, the cover layer surrounds the support element completely. Moreover, the cover layers can be conveniently adapted to suit the requirements of the medium. In a particularly advantageous manner, it is provided that the support element is produced from a heat-resistant, high-performance, engineering synthetic material, in particular glass fibre-reinforced polyamide, and the cover layer is produced from a medium-resistant synthetic material, in particular fluoric synthetic material, polyethylene, polyoxymethylene, elastomer or synthetic thermosetting materials such as rubber and the surfaces of the support element connected to the cover layer are coated with a bonding layer as an adhesive agent. A lightweight construction of the valve ball is achieved by virtue of the fact that the support element comprises at least one enclosed cavity. In order to ensure that the valve ball is guided effectively and can be adjusted conveniently, a spigot which protrudes outwardly is disposed on one end and a recess for receiving an adjusting spindle is disposed on the opposite end of the valve ball. It is provided that a cavity may be disposed in the region of the spigot. 
         [0042]      FIG. 4  illustrates an enlarged detailed view of a sealing element  9  of the ball valve  1  as shown in  FIG. 1 .  FIG. 4  illustrates clearly the cross-section of the annular sealing element  9  in the form of a profile seal. The sealing element  9  is made up of two sealing bodies  9   a  which are connected to each other via a carrier element  9   b.  The sealing bodies  9   a  are each semi-circular as seen in cross-section, have the function of sealing lips or are comparable to O-rings, as their semi-circular outer contour is in contact with the sealing surface  2   f  of the valve ball  2 . As seen in the direction of action of the sealing element  9 —i.e., starting from the region of the ball valve  1 , which carries the medium, towards the adjusting spindle  7  of the ball valve  1 —the two sealing bodies  9   a  are disposed one behind the other and spaced apart from each other. As seen from the second support ring  10   b  in the direction of the sealing surface  2   f  of the valve ball  2 , the two sealing bodies  9   a  protrude from the carrier element  9   b,  so that a recess  20  is present between the sealing bodies  9   a.  Disposed centrally in this recess  20  between the two sealing bodies  9   a  is an annular storage element  19  which has a rectangular cross-section and is produced preferably from a polyamide fibre pad. Other synthetic materials can also be used. It is also feasible to form the storage element  19  as a brush or foam, e.g., consisting of bronze in order to dissipate static charges. The storage element  19  has the task of accommodating fine particles which have penetrated through underneath the first sealing body  9   a  and thus to protect the second sealing body  9   a  therefrom. This enhances the sealing tightness of the second sealing body  9   a.  Moreover, the storage element  19  which is formed as a fibre pad is impregnated or filled with a lubricant. Preferably, a fluorine-containing lubricant is used. Since the lubricant filling is protected by the two sealing bodies  9   a,  it is not carried off by the medium and therefore a ball valve can be put into operation again even after years of idleness without experiencing any adhesion effects. The lubricant also aids the reception and retention of the particles. 
         [0043]      FIG. 4  illustrates the sealing bodies  9   a  and the storage element  19  in each case in their unstressed form, in order to show their original form. Of course, the sealing bodies  9   a  and the storage element  19  are compressed in the installed state and lie against the sealing surface  2   f.    
         [0044]    As seen in cross-section, the sealing element  9  has essentially the shape of a right-angled triangle, wherein the sealing bodies  9   a  protrude in the region of the ends of the hypotenuse. The two catheters are in contact with the bearing surfaces  12   a,    12   b  of the recess  12  in the support ring  10   b.    
         [0045]    The two sealing bodies  9   a,  the carrier element  9   b  and the storage element  19  are formed in one piece in the illustrated embodiment. The sealing bodies  9   a  and the carrier element  9   b  are produced in an injection-molding process from an elastomer, in particular nitrile butyl rubber, wherein the storage element  19  is connected to the sealing bodies  9   a  and the carrier element  9   b  during the injection-molding process. 
         [0046]    In a further production step, the sealing element  9  is then inserted into the mold for the first or second support ring  10   a,    10   b  and is then injection-molded around by the synthetic material of the support rings  10   a,    10   b.    
         [0047]    The embodiment of the sealing elements is considered as an independent inventive idea. Simplified production and improved sealing tightness in the case of a ball valve having a housing consisting of synthetic material, in which a valve ball having a through-opening is mounted so as to be able to rotate between an open position and a closed position, wherein the valve ball is sealed with respect to the housing via annular sealing elements, can be achieved by ensuring that the sealing elements in each case comprise two sealing bodies which are in contact with the valve ball. The connection of the sealing bodies to the support ring is facilitated by virtue of the fact that the sealing bodies of a sealing element are connected to each other via a carrier element. An improvement in the sealing effect is achieved by virtue of the fact that the sealing bodies of a sealing element are disposed one behind the other and spaced apart from another as seen in the direction of action of the sealing element. The sealing effect is also aided by virtue of the fact that, as seen in cross-section and in the contact region with the valve body, the sealing bodies are formed in a semi-circular fashion in the manner of an O-ring. Impurities are removed from the medium, which has passed the first valve body, by virtue of the fact that between the sealing bodies of a sealing element there is disposed a storage element which is in contact with the valve body. Therefore, the action of the second sealing body is not impaired by the impurities. The storage element may be cuboidal in the form of a fibre pad consisting of polyamide. The housing may be provided with annular recesses, in which sealing elements are inserted, the recesses having two bearing surfaces disposed at right angles with respect to each other and, as seen in cross-section, the sealing elements having substantially the shape of a right-angled triangle. The sealing bodies may protrude from the housing in the direction of the valve body. Handling of the sealing element is facilitated by virtue of the fact that each sealing element is formed in one piece with the sealing bodies and is produced from an elastomer, in particular nitrile butyl rubber. It is provided that each sealing element is mounted in the housing via a support structure consisting of two opposite support rings which receive the valve ball. This support structure has a high degree of dimensional stability, so that the sealing element has to compensate for small deformations only. 
         [0048]    Changes and modifications in the specifically described embodiments can be carried our without departing from the principles of the present invention, which is intended to be limited only by the scope of the appended claims, as interpreted according to the principles of patent law including the doctrine of equivalents.