Abstract:
A gasket, in particular a valve-cover or cylinder-head cover seal, for sealing a connection between a substantially thin-walled, molded part and an additional molded part. The gasket includes an elastic sealing lip which is disposed between the two molded parts, and the elastic sealing lip is molded onto the outer edge region of a dimensionally stable support frame.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation of international patent application no. PCT/EP2004/050120, filed Feb. 12, 2004, designating the United States of America, and published in German on Aug. 26, 2004 as WO 2004/072515, the entire disclosure of which is incorporated herein by reference. Priority is claimed based on Federal Republic of Germany patent application no. DE 103 06 211.4, filed Feb. 13, 2003. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The invention relates to a gasket, particularly a valve cover gasket, for sealing a connection between two molded parts having an elastic sealing lip disposed between the two molded parts.  
         [0003]     Thin-walled molded parts, such as valve covers or cylinder head covers for internal combustion engines, have elastic or resilient gaskets to provide a seal when they are connected with other molded parts. Published United Kingdom patent application no. GB 2,328,990 (=DE 197 38 275) discloses an elastic gasket for the static sealing of thin-walled covers of internal combustion engines. The thin-walled cover has a circumferential mounting flange with a circumferential groove intended to receive the elastic gasket. It is proposed to provide the elastic gasket with projections that encompass the outer rim of the mounting flange, such that hook-shaped collars reach behind the mounting flange. This achieves a positive clamping of the gasket on the cover. A drawback is the relatively complex construction of the gasket with the hook-shaped collar and the projections as well as the time-consuming mounting of the gasket to the thin-walled cover. The gasket, adapted to the shape of the cover, must be carefully fastened to the cover following the contour. To prevent leaks, it is necessary to ensure the encompassing of the flange at each point along the contour of the cover.  
         [0004]     Published German patent application no. DE 41 25 344 discloses a metal-reinforced molded rubber gasket for mutually sealing two molded parts that are pressed together by screw bolts. The gasket consists of a vulcanized sheet metal support, such that the vulcanized rubber layer has longitudinally extending sealing beads and sealing lips that circle the screw holes on one side traversing the gasket on the inside. Such metal-reinforced molded rubber gaskets are used, in particular, to sealingly mount sheet metal covers or similar molded castings. A drawback is the mixture of metal and plastic, especially since these gaskets are usually intended as replaceable gaskets and recovery or recycling is much more difficult as a result. The mixture of materials also has a negative impact on production and hence on the production costs.  
         [0005]     U.S. Pat. No. 4,819,953 (=DE 36 39 218) discloses a device in which thermally softened gasket material is injection molded onto the marginal portion of the valve cover to form the gasket with at least one coupling agent applied therebetween. After cooling, the gasket in its cooled form adheres to the marginal portion of the cover. The marginal portion of the valve cover simultaneously acts as one part of the die that is required to form the gasket. Although this gasket facilitates handling in connection with the valve cover because it requires no gasket to be inserted following a complex contour and held until the connection is established, but it has the significant drawback that when the two molded parts are separated, the reinsertion of a new, unused gasket is complicated and time-consuming. The old gasket must be removed from the valve cover without residue and a new gasket must again be injection molded in a heated state. This process is costly and time-consuming and requires a great deal of care when the gasket is replaced.  
       SUMMARY OF THE INVENTION  
       [0006]     It is therefore an object of the present invention to provide an improved gasket for sealing a connection between two molded parts.  
         [0007]     Another object of the invention is to provide a gasket that is easy to replace, simple and cost-effective to manufacture and has a better functionality.  
         [0008]     These and other objects are achieved in accordance with the present invention by providing a gasket for sealing a connection between a substantially thin-walled molded part and an additional molded part, said gasket having an elastic sealing lip disposed between the two molded parts, wherein said elastic sealing lip is injection molded onto an outer marginal portion of a stably-shaped support frame. Advantageous further refinements and preferred embodiments are described in more detail hereinafter.  
         [0009]     The gasket according to the invention serves to seal a joint between a substantially thin-walled molded part and another molded part. The gasket has an elastic sealing lip which is arranged between the two molded parts. Furthermore, the elastic sealing lip is injection molded onto the outer portion of a shape-stable support frame. A gasket of this type is suitable particularly for valve cover gaskets or cylinder head gaskets of an internal combustion engine. However, the gasket according to the invention can also be used wherever two parts must be sealingly connected with each other. The gasket according to the invention is especially advantageous when the two molded parts have complex contours because the elastic sealing lip conforms to the predefined shape of the molded parts since it is connected to the stably-shaped support frame and is therefore very easy and quick to apply.  
         [0010]     The sealing lip has a preferably oval shape tapering toward the faces which seat with the molded parts, but a round or angular basic form is also feasible. To enable the sealing lip to compress when the two molded parts are assembled, it is thicker than the shape-stable support frame. The deformation of the sealing lip when the two molded parts are assembled compensates for minor unevennesses in the sealing face of the molded parts and thus provides a tight fit over the entire area of the sealing faces of the two molded parts to ensure a reliable seal. The stably-shaped support frame is made of a firm, non-elastic dimensionally-stable material and thus holds the elastic sealing lip in a predetermined shape.  
         [0011]     To increase the stability between the longitudinal sides of the support frame, the support frame preferably has connecting segments that are made of the same material. These are optional, however, and are not absolutely necessary for the function of the gasket and the supporting aid provided by the support frame.  
         [0012]     The gasket design according to the invention facilitates the insertion of the gasket into the molded parts which correspond for this purpose, particularly since unlike in the prior art where a soft gasket must follow a partly complex contour of the sealing face of the molded parts, in the present invention the support frame has exactly the same contour, so that the elastic sealing lip can be inserted into the contour precisely and quickly. This also prevents any incorrect insertion or squashing of an imprecisely inserted gasket. The gasket according to the invention is therefore particularly suitable for valve cover gaskets and cylinder head cover gaskets. As described above, however, it may also be used, for example, for air filter housing covers or oil pan gaskets.  
         [0013]     In one preferred embodiment of the gasket according to the invention, the sealing lip is made of an elastomer and the support frame of a thermoplastic material. The elastomer portion may be a synthetic rubber and the thermoplastic portion a polyamide, for example. It is preferred to use materials known to those skilled in the art, which have a certain resistance to aggressive media, such as oils, greases or aerosols. Because of this material combination of the gasket, it is particularly easy to reproduce complex contours of the sealing face of the molded parts by injection molding using a suitable tool. In a first step, the stably-shaped thermoplastic support frame is injection molded in the mold, and in the second step the elastic sealing lip is then injection molded onto the outer portion of the frame. This provides a shape-stable and easily applied gasket with a soft, well-sealing outer circumferential sealing lip.  
         [0014]     In accordance with another advantageous embodiment of the gasket according to the invention, the support frame has means for the detachable corresponding connection of the gasket with one of the molded parts. The detachable corresponding connection can be realized by using a clip system, expansion pins or screws. A tool-less connection that requires no additional parts is preferred, however. To this end, openings may be provided to receive flexible hooks or the like which are formed in the molded part to correspond to the openings. When equipped in this manner, the gasket according to the invention is secured against falling out if it needs to be transported together with one of the molded parts to the assembly location where it is joined to the second molded part, or the joining of the two molded parts in an exposed position is simplified. Thus, in a difficult mounting position, for example, there is no need to take care that the gasket does not slip or fall out just before assembly.  
         [0015]     A special embodiment of the gasket according to the invention includes at least one indicator on the side of the sealing lip, which indicates that a seal is inserted between the two joined parts. The indicator extends substantially parallel to the parting plane between the two molded parts and preferably comprises a lateral extension of the sealing lip. However, it is also feasible to additionally injection mold an indicator onto the sealing lip.  
         [0016]     Since, in the prior art, the gasket is inserted into grooves made in the sealing face of the molded parts, there is no visible evidence after the two molded parts are assembled to indicate whether a gasket is inserted between the molded parts. An inadvertent omission of a gasket may result in serious engine damage, which can be prevented by the indicator proposed here. With the indicator it is possible to determine from the outside beyond any doubt whether there is a gasket inserted between the two molded parts even after the molded parts have been assembled. The indicator is guided outwardly through a corresponding opening in at least one of the molded parts to show visible evidence of the presence of a gasket.  
         [0017]     In accordance with another advantageous embodiment of the gasket according to the invention, at least one functional component is arranged on the support frame by means of at least one detachable connection. The presence of the support frame makes it possible to arrange functional components, such as oil traps for the removal of oil from aerosols, valves for the controlled opening of a passage or other means to integrate additional functions on the support frame. These functional components may be detachably connected with the support frame within the range of action of the sealing lips along the inner portion of the support frame. The connection may be effected with screws, clips, bayonet catches or other fastening means known in the art.  
         [0018]     In accordance with yet another embodiment of the gasket according to the invention, the at least one functional component is integrated directly into the support frame and is formed together with the support frame directly during the injection molding process. This may include, for example, plastic baffles or simple umbrella valves, which are not costly and can be disposed of when the gasket is replaced. Because the material is the same, recycling is not an issue. It is also possible to inject functional elements made of the same or a different material into the support frame or to attach them permanently to the support frame using a welding or adhesive bonding process.  
         [0019]     In accordance with yet another embodiment of the invention, the gasket is inserted between two molded parts, and the molded parts are correspondingly interconnected by screw connections. Thus, the seal surrounds the through-holes formed in the molded parts for the passage of the screws on all sides. In other words, gasket openings are provided in the gasket contour, which correspond to the openings in the molded parts for the screw bolts. This provides additional centering and securing of the gasket and an advantageous sealing of the connection.  
         [0020]     In another modification of the gasket according to the invention, the range of action of the gasket extends along the inside of the through-holes made for the screwed connections in the two molded parts. Thus, the sealing lip seals the volume between the two molded parts also relative to the through-holes that are provided for screwing the two parts together.  
         [0021]     In another variation of the gasket according to the invention, the range of action of the sealing lip runs past the through-holes on the outside so that the through-holes are included in the seal relative to the outside. Here, the bores of the through-holes are to be individually sealed in addition relative to the outside, so that no leaks can occur in this area.  
         [0022]     In a special embodiment of the invention, the support frame is substantially plate-shaped, such that the elastomer gasket is arranged along the margin and the support frame has at least one passage between the two molded parts. In special applications it is useful to limit the passage between the two molded parts. This makes it possible, for example, to inhibit the foaming of oil or escaping of a heavily oil-laden aerosol. With a corresponding configuration of the size and arrangement of the at least one passage in the support frame, such cases can be minimized or avoided entirely. To this end the plate-shaped part of the support frame can also be slit, perforated or provided with a three-dimensional contour, so that production in a standard injection mold is readily possible.  
         [0023]     These and other features of preferred embodiments of the invention, in addition to being set forth in the claims, are also disclosed in the specification and/or the drawings, and the individual features each may be implemented in embodiments of the invention either alone or in the form of subcombinations of two or more features and can be applied to other fields of use and may constitute advantageous, separately protectable constructions for which protection is also claimed.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]     The invention will be described in further detail hereinafter with reference to illustrative preferred embodiments shown in the accompanying drawing figures, in which:  
         [0025]      FIG. 1  is an isometric view of a gasket according to the invention;  
         [0026]      FIG. 2  is an enlarged cross-sectional detail view taken in the area of the sealing lip;  
         [0027]      FIG. 3  is an isometric view of the assembly of the gasket according to the invention with a thin-walled molded part, and  
         [0028]      FIG. 4  is a representation of a gasket according to the invention with integrated functional components. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0029]      FIG. 1  depicts an embodiment of the gasket  10  according to the invention with an elastic sealing lip  11 , which is injection molded onto a support frame  12 . The elastic sealing lip  11  has a specific outer contour, which is matched or adapted to the contour of the corresponding molded parts. In the interior portion of the gasket  10 , center segments  13  are formed in the support frame  12  to enhance the stability of the gasket  10  as a whole. The height of the sealing lip  11  starting from the gasket plane substantially exceeds the thickness of the support frame  12 . This ensures that when the two molded parts are assembled with the inserted gasket, the sealing lip can be compressed at each point of its contour. Along the outer circumference of the sealing lip  11 , an indicator  14  is arranged. This indicator  14  is injection molded onto the support frame  12  in the mold together with the sealing lip  11 . It does not interrupt the sealing lip, so that the sealing action is the same in this area as in any other area. Clip openings  15  are disposed on the opposite narrow sides of the support frame. These clip openings  15  in the form of a transverse slot each have a transverse segment  16 . These transverse segments  16  serve to receive a corresponding fastening means of one of the molded parts.  
         [0030]      FIG. 2  is a cross-sectional view of an enlarged detail of the gasket  10  according to the invention in its installed state. Components corresponding to those of  FIG. 1  are identified by the same reference numerals. The sealing lip  11  rests on a molded part  17 , such as a camshaft housing, for example, and is slightly compressed in the area of the seating face  18  on the molded part  17 . A cover  19  corresponding to the molded part  17  and having a groove  20  to receive the sealing lip  11  is mounted. In the area of the receiving groove  20 , the upper portion of the sealing lip  11  is enclosed by the receiving groove  20 . It is slightly compressed here, like in the area of the seating face  18 , and thereby connects the molded part  17  with the cover  19  so as to provide a seal. When the cover  19  and the molded part  17  are joined in the direction of the arrow, an outer leg  21  of the cover  19  pushes against the seating face  18  of the molded part  17 . This figure, too, shows the difference in the thickness between the sealing lip  11  and the support frame  12  relative to the plane of the gasket  10 .  
         [0031]      FIG. 3  shows the gasket according to the invention in the process of being connected to a cover. Components corresponding to those shown in  FIG. 1  are identified by the same reference numerals. The gasket corresponds to the gasket described with reference to  FIG. 1 . The contour of the gasket  10  correspondingly follows the contour of the cover  19 . To connect the cover  19  with the molded part  17  (not shown), a plurality of through-holes  22  are provided circumferentially in the outer portion. As may be seen, the sealing lip extends on one side past the inside of the through-holes  22 , such that a separate seal for the through-holes  22  is not required. A retaining pin  23  is arranged in the center region of the opposite margins of the narrow sides of the cover  19 . This retaining pin  23  is designed to correspond to the clip opening  15  of the gasket  10  according to the invention. When the gasket  10  is inserted into the cover  19  in the direction of the arrow, the retaining pin  23  pushes through the clip opening  15  and then hooks into the cross segment  16 . The cover  19  and the gasket  10  are thereby interconnected, and there is no risk that the gasket  10  will fall out during assembly of the cover  19  that includes the inserted gasket  10  with the molded part  17 , or that it will be damaged during assembly. If the gasket  10  needs to be replaced after use, the cover  19  including the inserted gasket  10  is unscrewed from the molded part  17 , and the gasket  10  can be detached from the cover  19  without destroying it by pushing the retaining pins  23  apart. The rear longitudinal portion of the circumferential outer leg  21  has an indicator opening  24 , which is designed to correspond to the indicator  14  arranged on the gasket  10 . Thus, after assembly, it is readily visible from the outside whether a gasket has been inserted. In this figure, the cover  19  is a flat cover used to cover a camshaft housing, for example, and is moreover provided with an oil-pouring hole  25 .  
         [0032]      FIG. 4  shows a variant of the gasket according to the invention with integrated functional elements. Components corresponding to those of  FIG. 1  are identified by the same reference numerals. In this figure, the cover  19  is already connected to the gasket  10 . To make the representation clearer, the cover  19  over the underlying parts is indicated by a phantom line. The contour of the gasket  10  again extends on one side past the through-holes  22  along the inside, so that no separate seal for the through-holes  22  is required. The longitudinal sides of the gasket  10  are connected not by cross segments  16  but by a continuous plate  26 . The plate  26  is made of the same material as the support frame  12  and is injection molded together with the support frame in a single process step. Along the outer ends of the gasket  10 , there are passages  27 , which admit a gas flow, e.g., of crankcase gases, into the volume enclosed by the cover  19 . The oil laden gases flowing through the passage  27  into the volume enclosed by the cover  19  flow through two air de-oiling elements  28 , such that the oil contained in the gas in the form of droplets is deposited along these air de-oiling elements  28  and flows back into the subjacent volume across the plates  26  and through the passage  27 . Thereafter, the gases leave the volume enclosed by the cover  19  through a ventilation port  29  and are fed, for example, into the intake system of the internal combustion engine. In this example, the air de-oiling elements  28  are thus functional components integrated into the gasket  10 , which have been injection molded together with the plate  26  directly when the support frame  12  was produced. The air de-oiling elements  28  should be understood as a kind of labyrinth for the gas flowing through, such that the oil droplets are deposited along the walls of the air de-oiling elements  28  that guide the gas. The plate  26  serves to separate the volume enclosed by the cover  19  from the volume underneath the plate  26  in the molded part  17  to calm the gas flowing through and to isolate it from any oil spatters that may occur in the lower volume of the molded part. This view actually shows two different functional components in the gasket  10 : the air de-oiling elements  28  on the one hand and the protective plates  26  on the other.  
         [0033]     The foregoing description and examples have been set forth merely to illustrate the invention and are not intended to be limiting. Since modifications of the described embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed broadly to include all variations within the scope of the appended claims and equivalents thereof.