Abstract:
A component having at least one support member with a first connecting portion and at least one part with a second connecting portion is formed by activating the second connecting portion by plasma treatment and then combining the first and second connecting portions and securing their attachment to one another by a heat and pressure treatment.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The invention relates to a component comprised of at least one support member and at least one part connected thereto whereby at least the connecting portion of the part connected to the support member consists of poly fluorocarbon. The invention also relates to a method for manufacturing a connection between a support member and a part of such a component in which at least the connecting portion of the part connected to the support member consists of poly fluorocarbon.  
           [0002]    Support members in the form of support bodies are known for sealing rings having sealing elements consisting of poly fluorocarbon, especially of polytetrafluoroethylene. The sealing element is etched in the connecting area by liquid ammonia or a solution of polyanyl and alkali metals in ether. The etched sealing element is then placed into a mold into which the polymer material is filled that combines with the etched portion of the sealing element to form a sealing ring. This wet-chemical etching method is complicated and also causes considerable environmental problems.  
           [0003]    Sealing rings are known in which the surface of the sealing element consisting of polytetrafluoroethylene has introduced therein a small amount of the plastic material of the support body or a component that is compatible therewith. The chemical and material-bonded connection is then carried out by melting the pretreated sealing element to the support body during the injection molding process. The introduction of the plastic component into the surface of the sealing element is complicated and makes the manufacture of the sealing ring very expensive.  
           [0004]    It is therefore an object of the present invention of embody the component and the method of the aforementioned kind such that the component and the connection can be produced in a simple manner, inexpensively, and without causing environmental problems.  
         SUMMARY OF THE INVENTION  
         [0005]    The object in regard to the component of the aforementioned kind is inventively solved in that the connection between the support member and the part connected thereto, at least in the area of the connecting portion, is activated by plasma treatment. In the aforementioned method the object is inventively solved by activating at least the connecting portion of the part at its surface by plasma treatment and by fixedly connecting the activated surface of the connecting portion with pressure and/or heat treatment to the support member.  
           [0006]    At least the connecting portion of the part that is provided for fastening to the support member is treated by plasma treatment. This plasma treatment results in a micro-sandblasting effect (plasma etching) and/or in chemical changes in the micro area at the surface of the connecting portion of the part. The plasma-activated surface of the connecting portion ensures in a surprisingly simple manner that the part can be reliably and fixedly connected to the support member without requiring etching processes with solvents or solutions. The plasma treatment is environmentally friendly and requires no solutions or solvents that are difficult to discharge so that the otherwise required conventional methods for avoiding environmental problems are eliminated. The support member with the part attached thereto can be produced in a simple manner. It is possible to connect the plasma-treated part directly or with use of a bonding agent in the form of an intermediate layer to the support member. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    The object and advantages of the present invention will appear more clearly from the following specification in conjunction with the accompanying drawings in which:  
         [0008]    [0008]FIG. 1 shows an axial section one half of a support member with a part consisting of poly fluorocarbon attached thereto, whereby the support member and the part belong to a component that is inventively embodied as a sealing ring;  
         [0009]    [0009]FIG. 2 shows in a schematic representation a plasma device for treatment of parts of the component of FIG. 1;  
         [0010]    [0010]FIG. 3 shows a view of a second embodiment of the inventive component;  
         [0011]    [0011]FIG. 4 shows an enlarge detail of a section along the line IV-IV of FIG. 3. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0012]    The present invention will now described in detail with the aid of several specific embodiments utilizing FIGS. 1 through 4.  
         [0013]    With the aid of FIGS. 1 and 2 a sealing ring is disclosed as the inventive component. The support member and the part connected thereto can be embodied in any other suitable manner. For example, the component may be a bearing housing having glide surfaces comprised of poly fluorocarbon and having a housing mantle that is, for example, comprised of a thermoplastic material. It is only important in the context of the present invention that the part with its connecting portion is activated by plasma treatment in order to ensure the connection between it and the support member. The support member can be a unitary part made of plastic material such as a thermoplastic material, a thermosetting material or an elastomer. However, it is also possible to produce only the connecting portion for the poly fluorocarbon part to be attached to the support member from such a plastic material and to produce other portions of the support member of any other suitable material, for example, metal. It is also possible to produce the entire support member of metal.  
         [0014]    [0014]FIG. 1 shows only in a exemplary manner a sealing ring which comprises a cup-shaped support body  1  which is comprised of metallic material, of a hard plastic material etc. The cylindrical mantle  2  as well as the exterior side  3  of the bottom  4  of the support body  1  are partly covered by a cover or coating  5 . In the shown embodiment the cover  5  covers the entire exterior side of the cylindrical mantle  2  and also the exterior side of the bottom  4 . Depending on the application, it is, of course, also possible to cover only a part of the exterior side of the cylindrical mantle  2  and/or a part of the exterior side  3  of the bottom  4  with a cover or coating  5 . The cover  5  positioned on the exterior side of the cylindrical mantle  2  can also be separate from the cover provided at the exterior side  3  of the bottom  4 . The cover in the shown embodiment covers also the inner side of the cylindrical mantle  2  and of the bottom  4 . In this case it is also possible to cover with the cover  5  only a portion of the inner side of the cylindrical mantle and/or of the bottom  4 . The cover  5  is comprised of an elastomeric material.  
         [0015]    The sealing ring is provided with a sealing element  6  that is comprised of poly fluorocarbon. The poly fluorocarbons to be used in the context of the invention may be homo polymers, especially polytetrafluoroethylene but also poly vinylidene fluoride, poly vinyl fluoride etc. Poly fluorocarbon can also be used in the form of a copolymer, for example, poly fluoro ethylene-propylene, vinylidene fluoride-hexa fluoro propylene copolymer, ethylene-tetra fluoroethylenecopolymer, perfluoroalkoxyalkane copolymer etc. These poly fluorocarbon materials exhibit very high chemical resistance even at increased temperatures and are harmless with regard to physiological aspects, are not flammable or flame resistant and have excellent gliding and anti adhesion properties. Of the aforementioned homo polymers especially polytetrafluoroethylene is suitable as a sealing element  6  for the sealing ring.  
         [0016]    The sealing element  6  has a connecting portion  7  which in the shown embodiment is positioned radially relative to the axis of the shaft  8  to be sealed, but may be positioned at any suitable angle to the axis of the shaft. The radially inwardly positioned area of the disc-shaped sealing element  6  is bent and rests sealingly at the shaft  8 .  
         [0017]    As indicated by a dashed line in FIG. 1, the sealing element  6  can be provided with a dust lip  9  which is formed by radially slotting the radially inner area of the sealing element  6 . Of course, in this case the sealing element  6  is thicker than represented in FIG. 1.  
         [0018]    The connecting portion  7  is used to fixedly connect the sealing element  6  to the inner side of the bottom  4  of the support member  1 , i.e., to the part  10  of the cover  5 . This connection, as will be disclosed in the following in more detail, is achieved without use of wet-chemical etching of the connecting portion  7  of the sealing element  6 . The connection between the sealing element  6  consisting of poly fluorocarbon and the connecting portion of the cover  5  consisting of elastomer material is effected by a plasma treatment of the connecting portion  7  of the sealing element  6 . The plasma treatment activates the surface of the connecting portion  7  which abuts the cover portion  10  so that it can be fixedly connected to the elastomer material of the connecting portion  10  of the cover  5 . With the plasma activation it is also possible to connect the connecting portion  7  of the sealing element  6  with an adhesive to the connecting portion  10  of the cover  5  or directly to the support body  1 . It is no longer necessary to introduce into the upper side of the connecting portions  7  of the sealing element  6  such material parts which allow for a material-bonded connection to the elastomer material of the connecting portion  10  of the cover  5 . The plasma treatment eliminates the use of additives, respectively, the need for embedding of certain materials into the upper side of the connecting portion  7 .  
         [0019]    [0019]FIG. 2 shows in a schematic representation a plasma device in which the surface of the sealing element  6 , at least in the area of the connecting portion  7 , is surface-activated, whereby the sealing element  6  is comprised of poly fluorocarbon. The plasma device has a chamber  11  in which the plasma treatment of sealing elements  6  is carried out. In the interior of the chamber  11  vacuum is produced by a vacuum pump  12 . When a pressure of approximately 0.1 to 1 mbar is provided, a processing gas is introduced into the interior of the chamber  11 .  
         [0020]    A support  13  is positioned in the chamber  11  onto which the poly fluorocarbon sealing element  6  can be placed for plasma treatment. Above the support  13  and the sealing elements to be treated an antenna  14  is positioned within the chamber which is connected to a high frequency generator  15  positioned outside the chamber. The high frequency generator  15  supplies frequencies within the KHz and MHz range. The high frequency generator  15  and the antenna  14  ionize the process gas within the receiving chamber so that a plasma  16  results.  
         [0021]    The energy required for ionization of the process gas can also be introduced, alternatively or in addition, by microwave devices. The plasma device is then provided with a microwave power supply  17  that is positioned exterior to the chamber  11  and connected to the magnetron  18 . An antenna  19  is provided thereat and extends into a hollow guide  20 . The magnetron  18  is a diode oscillator which oscillates at a fixed frequency. The antenna  19  of the magnetron  18  is not positioned within the vacuum of the chamber  11 . A glass window  21  separates the chamber  11  from the magnetron  18  and the antenna  19  via which the microwave radiation is introduced into the chamber  11 .  
         [0022]    The high frequency generator  15  and the microwave power supply  17  are connected to a control unit  22  which also controls the supply of processing gases via line  23 , the supply of a flushing gas via line  24 , venting via line  25  as well as pressure measurement via line  26 .  
         [0023]    For the plasma treatment of poly fluorocarbon sealing elements  6 , which are positioned within the receiving chamber  11  on the support  13 , the vacuum is generated in the aforementioned manner by the vacuum pump  12 . As soon as the desired vacuum has been reached, the control unit  22  is activated, and via line  23  the process gas is introduced into the receiving chamber  11 . For producing the plasma  16  energy in the form of high frequency radiation is needed so that the process gas can be ionized. For this purpose, the high frequency generator  15  is controlled by the control unit  22  so that via the antenna  14  the high frequency radiation is introduced into the process gas.  
         [0024]    Pressure within the receiving chamber  11  can be measured via the line  26  by employing the control unit  22 . The energy-rich plasma activates the side of the sealing element  6  facing the antenna  14 . With a respective design of the support  13  and of the antenna  14  it is also possible to provide for a general activation of the sealing element  6 . The treatment period of the sealing element  6  is advantageously between one minute and approximately 30 minutes.  
         [0025]    A flushing gas is introduced via line  24  into the receiving chamber  11 . Upon completion of the plasma treatment of the sealing element  6  the line  25  can be used for venting the interior of the receiving chamber  11 .  
         [0026]    The process gases may be, for example, air, oxygen, argon, nitrogen, hydrogen, tetrafluoromethane or mixtures thereof.  
         [0027]    The thus plasma-treated sealing element  6  is then connected in a conventional manner in a vulcanization mold to the elastomer material of the cover  5 . Due to the plasma treatment a wet-chemical etching of the sealing element  6 , respectively, its connecting portions  7  is no longer required. This also eliminates the environmental problems resulting from chemical etching. Also, it is no longer necessary to introduce into the surface of the sealing element  6  or of the connecting portion  7  plastic components or materials which allow for a material-bonded connection between the cover  5  and the part.  
         [0028]    The plasma treatment of the sealing elements  6  can be controlled, in addition to selecting the type of process gas and the amount of vacuum generated, by the shape of the antenna  14  and/or its output.  
         [0029]    The sealing elements  6  contain in addition to the poly fluorocarbon compound, of course, further components or substrates such as, for example, fillers and additives as they are known in connection with sealing elements made of polytetrafluoroethylene.  
         [0030]    The sealing elements  6 , after pretreatment as disclosed, can be directly connected to the support member  1  when the support member is comprised of plastic material. For this purpose, the plastic body  1  can be connected permanently, for example, as a plastic melt, in the manufacturing process (injection molding) directly to the plasma activated poly fluorocarbon part  6 .  
         [0031]    The support  1  (FIG. 3 and  4  ) may also be a flange for sealing the crankshaft of an automobile. The flange  1  is comprised of a thermoplastic material, such as poly phenylene sulfide, and has a circular through opening  27  for the crankshaft. In this through opening  27  a sealing ring  28  consisting of poly fluorocarbon, especially polytetrafluoroethylene, is arranged which seals relative to the crankshaft. This sealing ring  28  is connected in the aforementioned manner by plasma treatment to the flange  1 . In order to combine with the flange  1  further sealing rings  29 ,  30  which are not comprised of poly fluorocarbon, the flange  1  is subjected to plasma treatment when it has anti-adhesive properties for the material of further (auxiliary) seals  29 ,  30 . They are comprised substantially of elastomeric material but can also be comprised of thermoplastic material. After plasma treatment the further seals  29 ,  30  are connected in a manner known per se to the flange  1 . The plasma treatment of the flange  1  no longer makes it necessary to employ bonding agents for connecting thereto the further sealing rings  29 ,  30 . Of course, it is possible to use a bonding agent. The further sealing  29  is an annular ring (O ring) which is fastened at the bottom  31  of a depression  32  at the end face of the flange  1  and extends with the sealing lip  33  inwardly into the through opening  27 . At the opposite end face  34  of the flange  1  an annular groove  35  positioned coaxially to the through opening  27  has connected thereto a static seal  30  which projects past the end face  34 . The seal  30  is effective after screwing the flange  1  to a housing part and provides a sealing action between the flange and the housing part.  
         [0032]    The specification incorporates by reference the disclosure of German priority document 197 34 330.9 of Aug. 8, 1997.  
         [0033]    The present invention is, of course, in no way restricted to the specific disclosure of the specification and drawings, but also encompasses any modifications within the scope of the appended claims.