Patent Publication Number: US-6660206-B1

Title: Method of manufacturing a sealing device

Description:
This application is a division of prior U.S. patent application Ser. No. 08/379,599 filed Mar. 7, 1995, now U.S. Pat. No. 6,182,975 which is a 371 of PCT/JP94/00905 filed Jun. 3, 1994. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to a sealing device, and more particularly, to a compound-type sealing device having a combination of seal lips, wherein a first seal lip is formed of a rubber-like elastic material and a second seal lip is formed of a resin material, and to a method of manufacturing such a compound-type sealing device. 
     BACKGROUND OF THE INVENTION 
     It is well known in the art of sealing devices which have seal lips, to provide a sealing device which utilizes a seal lip formed of a rubber-like elastic material or a resin material such as PTFE (polytetrafluoroethylene). In a conventional sealing device where a seal lip formed only of a rubber-like elastic material is used, the seal lip may be damaged by contact with the fluid which is to be sealed, such as, oil or other chemicals. This may be very inconvenient. On the other hand, where a seal lip is used that is formed only of a resin material, the seal lip has the problem that the seal lip does not suitably follow-up the operation of a rotational shaft to be sealed due to a lack of elasticity of the resin of the seal lip and due to a leakage of fluid such as oil from a small gap. 
     The prior art has attempted to solve the aforementioned problems by providing a sealing device  100 , as shown in FIG. 10, having only a resin seal lip  101 , in which the elasticity of the resin seal lip  101  is improved. 
     In such a sealing device  100 , the resin seal lip  101  has outer diameter side end portions  102  which are nip-supported by a pair of reinforcing rings  103  and  104 . In order to improve the follow-up performance of the resin seal lip  101  to the rotation of the shaft and to prevent an oil leakage through the small gap, grooves  107  and  108  are formed so as to provide a bellows shape on the peripheral surfaces of the resin seal lip  101  on a side of the resin seal lip opposite the fluid to be sealed and on a side of the resin seal lip opposite a fluid side not to be sealed. These grooves  107  and  108  are formed by an upper die  111  and a lower die  112 , as shown in FIG. 11, and are provided with mutually opposing projections  109  and  110  on the die&#39;s pressing surfaces so as to provide grooves  107  and  108  on the upper and lower surfaces of the seal lip  101  as shown in FIG.  12 . 
     Although the resin seal lip  101  of the conventional sealing device  100  has improved elasticity, the improvement in the elasticity is limited. The resin seal lip  101  still does not have as much elasticity as that of the seal lip formed of the rubber-like elastic material. 
     Furthermore, a sealing device  400 , such as is shown in FIG. 13, is also well known. The conventional sealing device  400  includes a resin liner  407  which is bonded on a sliding surface  405  of a seal lip  402  formed of a rubber-like elastic material extending from a seal body  401  to the side of the seal lip opposite the fluid side to be sealed. The sealing device  400  thereby provides the elasticity of the rubber-like elastic material and improves durability of the sliding surface. The liner  407  has a sliding surface  403  on which is formed a helical groove  403  having a pumping function. 
     In such a conventional sealing device  400 , however, the unsolved problem is that oil leaks through the small gap between the resin liner  407  and the rotation shaft  406 . 
     In order to prevent the problems encountered in both the above-described conventional sealing devices, there have been further proposed various sealing devices of a compound type. Compound type sealing devices have a combination of a seal lip formed of a rubber-like material reinforcing ring  205  and the back-up ring  207 . 
     FIG. 16 illustrates manufacturing processes of the aforementioned integral-compound type sealing device. 
     That is, a resin material  204 A for forming a resin seal lip  204  is disposed in a mold cavity  507  of a rubber formation mold  506  constructed by upper first and second mold parts  501  and  502  and lower first, second and third mold parts  503 ,  504  and  505 . The reinforcing ring  205  having the perforations  206  is disposed on the resin material  204 A so as to abut against it, and under this state, a rubber material is vulcanized for forming the seal lip  203  of the rubber-like elastic material. Simultaneously with the formation of the rubber seal lip  203 , the rubber material is baked integrally with a portion of the resin material  204 A intruded into the cavity  507  and bonded thereto (refer to FIG.  16 ( a )). 
     Thereafter, as shown in FIG.  16 ( b ), the upper first and second mold parts  501  and  502  are opened (in the direction of the arrow) to open the mold  506 , and as shown in FIG.  16 ( c ), the lower mold part  503  is pushed up in the direction of the arrow to form a lip front end portion. Then, as shown in FIG.  16 ( d ), the lower second mold part  504 , against which are resin material  204 A abuts, is pushed up in the direction of the arrow, thereby separating the mold product from the mold  506 . 
     However, even in the conventional compound type sealing device described above, a side of the lip facing radially inwardly, facing the shaft and the resin lip  204  of the seal lip  203  formed of the rubber-like elastic material is disposed adjacent to the resin seal lip  204 , so that the resin seal lip  204  interferes with the rubber seal lip  203 , thus providing the problem of poor follow-up performance with respect to the rotation shaft  202 . 
     Furthermore, countermeasures for preventing the rubber material from rotating during manufacturing as well as the problems of dimensional performance in the formation of the resin seal lip  204  should be considered. 
     An object of the present invention is to solve the problems encountered in the prior art described above. A further object of the present invention is to provide a sealing device of a compound type having a combination of a seal lip formed of a rubber-like elastic material and a resin seal lip. A further object of the present invention is to provide a method of manufacturing the compound type sealing device capable of preventing the resin seal lip from interfering with the rubber seal lip. A further object of the present invention is to effectively prevent the rubber material from intruding during the manufacturing process. A further object of the present invention is to make the thickness of the resin seal lip relatively thin in order to improve the follow-up performance of the resin seal lip. A further object of the present invention is to reduce heat generation. A further object of the invention is to form the resin seal lip simultaneously with the rubber seal lip molding process. 
     SUMMARY OF THE INVENTION 
     The present invention provides a sealing device for sealing two members which are disposed to be relatively rotated mutually concentrically, the sealing device being provided with a first seal member having a seal lip formed of a rubber-like elastic material and a second seal member having a seal lip formed of a resin material to be assembled integrally with the first seal member, and characterized in that an annular space is formed between the rubber seal lip and the resin seal lip so as to prevent the resin seal lip from interfering with the rubber seal lip. 
     Accordingly, the resin seal lip becomes flexible following up the operation of a shaft without interfering with the rubber seal lip, thus improving the sealing performance. 
     It is characterized in that the annular space is formed between the resin seal lip and a side of the lip facing radially inward, facing the shaft and the resin seal lip of the rubber seal lip. This is because, in a conventional product, the side of the lip facing radially inward, facing the shaft and facing the resin seal lip of the rubber seal lip is most interfered with. 
     It is characterized in that an annular groove is formed to a side surface on the side of said annular space of the resin seal lip. 
     It is characterized in that a plurality of the annular grooves are formed in an axial direction. 
     The annular groove maybe formed continuous or partially discontinuous on an entire peripheral surface of the resin seal lip. 
     According to the formation of these annular grooves, the resin seal lip is liable to be flexed and hence the follow-up performance can be improved. 
     On the other hand, a helical groove is formed on a side surface opposite to the side of the annular gap of the resin seal lip to improve the sealing performance of the resin seal lip. 
     It is characterized in that the first seal member is provided with a reinforcing ring to which the rubber seal lip is integrally bonded. 
     It is characterized in that a film formed of a rubber-like elastic material is formed on the side surface of the gap side of the resin seal lip so that the rubber film is branched from a base portion of the rubber seal lip of the first seal member continuously therefrom. 
     Furthermore, a method of manufacturing a sealing device is characterized by the steps of: 
     preparing a mold for molding a rubber-like elastic material and a resin material having a flat washer shape; 
     inserting an outer diameter portion of the resin material into a mold cavity, and adhesively baking the rubber-like elastic material to the outer diameter portion of the resin material together with the molding of the rubber-like elastic material; 
     pressing an inner diameter portion of the flat washer shape resin material by a mold part adjacent to the mold cavity in utilization of a mold clamping pressure; and 
     bending the pressed inner diameter portion of the resin material under high temperature condition when a mold product is separated from the mold thereby to form a resin seal lip. 
     An annular projection is formed to an upper mold part to be pressed to form an annular groove to the upper surface of the resin material at a time when the inner diameter portion of the flat washer shape resin material is pressed to prevent the intrusion of the rubber material. Accordingly, it is not necessary to make thick the resin material as in the conventional technique to seal the surface contacting the mold and it becomes possible to reduce the thickness of the resin material to decrease tension force thereby to prevent heat generation from increasing. 
     Furthermore, it is characterized in that a helical projection is formed to a lower mold part to be pressed to form a helical groove to the lower surface of the resin material at a time when the inner diameter portion of the flat washer shape resin material is pressed. 
     It is characterized in that a part of the rubber-like elastic material is moved toward the upper surface side of the inner diameter portion of the resin material pressed from the inside of the mold cavity to form a rubber film thereon. 
     As described above, by moving a part of the rubber-like elastic material, the rubber-like elastic material easily flows in the mold cavity preventing formation of a defective product of the rubber-like elastic material. 
     In a case where a part of the rubber-like elastic material is intruded from the inner diameter side of the resin material to the lower surface side thereof through the inner diameter side end thereof, the intruded portion will be cut at the finishing process. However, the sealing device may be used with this intruded portion of the rubber-like elastic material if this portion does not affect on the sealing performance. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG.  1 (A) is an elevational section view of a sealing device according to a first embodiment of the present invention and FIG.  1 (B) is an elevational section view of an essential portion of a resin seal lip of FIG.  1 (A). 
     FIGS. 2 to  7  illustrate manufacturing processes in a compression formation of the sealing device of FIG. 1, in which: 
     FIG. 2 is a sectional view in which respective parts are set in a lower mold part of a formation mold; 
     FIG. 3 is an elevational section view showing a vulcanizing process; 
     FIG. 4 is an elevational section view showing a mold opening process of an upper mold part; 
     FIG. 5 is an elevational section view showing a process for forming a resin seal lip through bending working of an inner diameter side half portion of a resin material; and 
     FIGS. 6 and 7 are each elevational section views showing a mold releasing process of a mold product. 
     FIG. 8 is an elevational section view of a formation mold in a case where the sealing device of FIG. 1 is injection-molded or transfer-molded. 
     FIG.  9 (A) is an elevational section view of a sealing device according to a second embodiment of the present invention and FIGS.  9 (B) and  9 (C) are elevational section views showing essential portions of the resin seal of FIG.  9 (A). 
     FIG. 10 is prior art showing a state in which a rubber is moved on an upper surface of a resin sheet in a pressurizing and heating process. 
     FIGS. 11 to  16  are views showing structures of various sealing devices of a conventional type. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will be described hereunder with reference to the illustrated embodiments. 
     Referring to FIG. 1 showing a sealing device according to a first embodiment of the present invention, reference numeral  1  denotes a sealing device. This sealing device  1  is essentially comprises, between a housing  2  and a rotation shaft  3 , of an annular first seal member  4  formed with a seal lip  41  of rubber-like elastic material and an annular second seal member  5  formed with a seal lip  51  made of resin material such as PTFE (polytetrafluoroethylene) and disposed on the back surface side of the rubber seal lip  41 . An annular space  7  is formed between a bonded base portion  43  of the rubber seal lip  41  and the resin seal lip  51  so that interference of the resin seal lip  51  with the rubber seal lip  41  is prevented. 
     The first seal member  4  is an annular member having approximately a V-shaped cross section opened to a fluid side  0  to be sealed and is formed of a rubber-like elastic material. An outer one side portion of this V-shape of the first seal member  4  is formed as an outer peripheral seal portion  42  fitted and fixed to an inner periphery of a fitting hole  21  of the housing  2 , and an inner one side portion thereof is formed as the rubber seal lip  41  having a lip front end  44  contacting the outer surface of the rotation shaft  3  to be slidable in a fluid-tight condition. A helical groove  46  is formed in the sliding surface of the lip front end  44  for performing a pumping function. 
     A reinforcing ring  6  made of metal is embedded in the first seal member  4 . The reinforcing ring  6  is an annular member having approximately an L-shaped cross section and is composed of a cylindrical portion  61  and an inward flange portion  62  extending radially inward from this cylindrical portion  61 . The cylindrical portion  61  is embedded into the outer peripheral seal portion  42  to increase the rigidity thereof, and the inward flange portion  62  is disposed so as to support an atmospheric side surface of a base portion  43  to which the outer peripheral seal portion  42  and the rubber seal lip  41  are bonded. 
     The second seal member  5  is composed of the resin seal lip  51  having a conical trapezoidal shape surrounding the rotation shaft  3  and a fixed flange portion  56  extending radially inward from a base portion of the resin seal lip  51 . 
     A helical groove  53  is formed in an inner peripheral surface  52  of the resin seal lip  51  entirely from the lip front end to the base portion, and a plurality of annular small grooves  55  are cut-formed to the outer peripheral surface  54  facing the space  7  defined between the rubber seal lip  41  of the first seal member  4  and the resin seal lip  51  in an axially separated manner in parallel with each other (see FIG.  1 (B)). Further, it is not always necessary to form the parallel annular groove  55  entirely in the peripheral surface of the resin seal lip  51 , as they may be formed discontinuously or may not be formed as occasion demands. 
     The space  7  defined between the rubber seal lip  41  and the resin seal lip  51  is kept in a non-contacting state to the rubber seal lip  41  throughout the entire length of the resin seal lip  51 . 
     The resin seal lip  51  is disposed with a conical inclination so as to be reduced gradually in its diameter form the inner diameter end of the fixed flange portion  56  to the axial fluid seal side  0  and is bent to the inner side, i.e., the rotation shaft side. The curvature of this bent shape of the resin seal lip  51  is made largest at a bonded base portion  43  thereof and the resin seal lip  51  extends substantially linearly from the bonded base portion  43  towards the front end thereof. 
     On the other hand, the rubber seal lip  41  is disposed with a conical inclination so as to be reduced gradually in its diameter from the bonded base portion  43  towards the axial fluid seal side, but on the contrary to the case of the resin seal lip  51 , the rubber seal lip  41  is bent entirely outward, i.e., in a direction apart from the rotation shaft  3 . The inner periphery of the rubber seal lip  41  has a shape extending, at the root portion with the bonded portion  43 , towards the axial fluid seal side  0  substantially parallel to the rotation shaft  3 , inclining conically towards the lip front end  44  from the way of the extension and projecting inward at the lip front end  44  abutting against the rotation shaft  3  thereby to form a large space between the rotation shaft  3  and the rubber seal lip  41 . 
     As described above, according to this embodiment, since the resin seal lip  51  is bent entirely inward and the rubber seal lip  41  is bent outward, the annular space  7  is formed widely. Particularly, the inner peripheral portion of the rubber seal lip  41  facing the annular space  7  has a shape extending, at its root portion, substantially parallel to the rotation shaft  3 , and on the other hand, the root portion of the rubber seal lip  51  is largely bent inward thereby to provide a wide space between the resin seal lip  51  and the bonded base portion  43  of the rubber seal lip  41 . Furthermore, since the lip front end  44  of the rubber seal lip  41  projects inward to form a large space between it and the rotation shaft  3 , interference of the resin seal lip  51  with the rubber seal lip  41  can be surely avoided. 
     Further, as described hereinbefore, the flange portion  56  of the second seal member  5  is nip-fixed between the inward flange portion  62  of the reinforcing ring  6  and the bonded base portion  43  of the first seal member  4 , and the outer diameter side end surface of the flange portion  56  abuts against the inner peripheral surface of the cylindrical portion  62  of the reinforcing ring  6 . The flange portion  56  and the bonded base portion  43  of the first seal member  4  entirely contact each other and this contact surface entirely constitutes a bonded surface  22 , at which the rubber-like elastic material is baked and bonded to a resin surface at the molding time of the first seal member  4  as described hereinafter. A bonding agent may be utilized for such surface bonding or the resin material and the rubber material may be bonded without any bonding agent. 
     Furthermore, the fixed flange portion  56  of the second seal member  5  and the inward flange portion  62  of the reinforcing ring  6  also entirely contact each other, and this contact surface  9  may be glued or bonded, or may merely abut. 
     Still furthermore, a dust seal fixing member  45 , projecting axially on the atmosphere side and made of a rubber-like elastic material, is provided to an entirely outer peripheral surface of an outer corner side of the cylindrical portion  61  of the reinforcing ring  6  and the inward flange portion  62 . A washer-like dust seal  8  is fixed to the inner periphery of the dust seal fixing member  45 , and the inner diameter side of the dust seal  8  slidably contacts, in a sealed manner, the outer peripheral surface of the rotation shaft  3 . The dust seal  8  is formed of a felt material as an annular member rectangular in section, and the dust seal  8  maybe otherwise formed of another seal member such as lip-shaped seal member. 
     In the sealing device of the structure described above, since the annular space  7  is defined between the rubber seal lip  41  and the resin seal lip  51 , the resin seal lip  51  does not interfere with the rubber seal lip  4  thereby to smoothly follow up the operation of the rotation shaft  3 , thus improving the follow-up performance. 
     Furthermore, since the annular groove  54  is formed in the outer peripheral surface of the resin seal lip  51  and the helical groove  52  is formed in the inner peripheral surface thereof, the resin seal lip  51  is easily flexed, thus further improving the follow-up performance. In addition, a helical screw groove  53  is formed to the inner peripheral surface, and the sealing property can be improved by the screw pumping function. 
     Still furthermore, during manufacturing, as described hereinafter, the intrusion of the rubber-like elastic material can be also prevented by the formation of the annular groove  54 . 
     Still furthermore, since interference of the rubber seal lip  41  can be prevented, the resin seal lip  51  is made stable in dimension and the stable sealing performance can be maintained. 
     The manufacturing method of the sealing device  1  of the characters described above will be described hereunder with reference to FIGS. 2-7. 
     The mold  26  is first referred to, and the mold  26  includes a lower mold half  26 A of the stationary side and an upper mold half  26 B of the movable side. 
     The lower mold half  26 A includes a lower first mold part  20  provided with a stepped portion  20 A on which rubber material  4 A as a rubber-like elastic material is placed, a lower second mold part  21  to which the reinforcing ring  6  is disposed and a lower third mold part  22  for forming a helical groove by pressing the outer diameter side half portion of a flat washer-shaped sheet  5   a  made of a resin material such as PTFE. The lower third mold part  22  has an upper surface to which a helical projection  22 A for forming the helical groove is formed. 
     The upper mold half  26 B includes an upper first mold part for vulcanizing the rubber material  4 A and an upper second mold part  24  for pressing the outer diameter side of the resin sheet  5 A in association with the lower third mold part  22  thereby forming the annular grooves to the resin sheet  5 A. The upper second mold part  24  has a lower surface to which a plurality of projections  24 A for forming the plural annular grooves  55  are concentrically formed. A plate spring  25  is interposed as an urging member between the stepped portions  23 A and  24 A of the upper first and second mold parts  23  and  24  for urging the upper first and second mold parts  23  and  24  to separate them in the axial direction. 
     Through the mold clamping process to the upper and lower mold halves  26 B and  26 A, a mold cavity  27  is formed (see FIG.  3 ). 
     In the molding process of the sealing device  1 , as first shown in FIG. 2, the rubber material  4 A is placed on the stepped portion  20 A of the lower first mold part  20  of the lower mold half  26 A now opened, and the reinforcing ring  6  is placed on the upper surface of the lower second mold part  21  with the inward flange portion  62  being directed downward. 
     Next, the outer diameter side half portion of the preliminarily formed flat washer-shaped resin sheet  5 A as resin material is close contacted to the flange surface  63  of the inward flange portion  62  with the inner peripheral surface of the cylindrical portion  61  of the reinforcing ring  6  being a guide for this contacting, and also, the inner diameter side half portion thereof is placed so as to abut against the upper surface of the lower third mold part  22  adjacent to the mold cavity  27 , particularly, against the helical projection  22 A (see FIG.  2 ). 
     Under such setting condition of the reinforcing ring  6  and the resin sheet  5 A, the upper and lower mold halves  26 B and  26 A are clamped by a pressing machine, not shown, and then the rubber material  4 A in the mold cavity  27  is heated and pressurized, Although the molding conditions are optionally set in accordance with the dimension of the mold, it will be preferred that the rubber material  4 A is pressed by a pressure of about 5-10 tons at a temperature of about 180°-200° C. 
     Through the processes mentioned above, the fluidized rubber material fills with substantially no gap in the mold cavity  27 , and then, the first seal member  4  including the rubber seal lip  41  is molded. At the same time, the rubber material is baked and bonded to the bonding surface  57  of the outer diameter side half portion of the resin sheet  5 A. Further, the outer diameter side half portion of the resin sheet  5 A is pressed against the inward flange portion  62  of the reinforcing ring  6  through the molding pressure of the rubber material, thereby preventing the intrusion of the rubber material into the lower surface side of the resin sheet  5 A. 
     Furthermore, through the processes mentioned above, the helical screw groove  53  is formed by the helical projection  22 A of the lower third mold part  22  to the lower surface of the inner diameter side half portion of the resin sheet  5 A by the clamping pressure to the upper second mold part  24  and the lower third mold part  22 , and a plurality of small annular grooves  55  parallel with each other are formed in the upper surface of the inner diameter side half portion of the resin sheet  5 A by the annular projections  24 A formed to the lower surface of the upper second mold part  24 . These annular grooves  55  are formed each with a depth of 0.2-0.3 mm (see FIG.  3 ). 
     In this time, since the resin sheet  5 A is pressed by the annular projection  24 A, the intrusion of the rubber material in the mold cavity  27  to the upper surface side of the resin sheet  5 A can be prevented. In the described manner, after the completion of the vulcanizing process of the first seal member  4 , the upper mold half  26 B is released to open the mold as shown in FIG.  4 . 
     Next, as shown in FIG. 5, the inner diameter side half portion of the resin sheet  5 A is bent through the push-up motion of the lower third mold part  22  of the lower mold  26 A, thus forming the resin seal lip  5 . At this time, since the process is performed under the high temperature condition (180-200° C. in this embodiment), the resin sheet  5 A can be easily bent. 
     Then, as shown in FIG. 6, the lower second mold part  21  of the lower mold half  26 A is pushed up to discharge a product body (see FIG.  6 ). Thereafter, as shown in FIG. 7, only the lower third mold part  22  is pulled downward, thereby completing the mold separation. 
     Finally, the bars of rubber material  4 A of the thus molded product body are removed, and then, the sealing device  1  is completed by fixing the dust seal member  8  to the inner periphery of the dust seal fixing portion  45  of the rubber seal lip  4 . 
     According to the sealing device  1  manufacturing method described above, since the resin sheet  5 A in the form of the flat-washer shape is pressed against the reinforcing ring  6  at the same time of the vulcanization formation of the first seal member  4 , the thickness of the resin seal lip  5  can be made thin, and in the thus manufactured product, the intrusion of the rubber material can be prevented and the generation of high heat, which is a defect of the conventional resin seal lip having a large thickness, can also be prevented by making stable the dimension thereof. 
     FIG. 8 is an illustration representing an injection- or transfer-molding method in place of the compression molding shown in FIGS. 2-7. That is, an upper mold half  30  includes an upper first mold part  31  having a passage  31 A for flowing the fluidized material  4 A into the mold cavity  27 , an upper second mold part  32  having a gate  32 A communicated with the passage  31 A, and an upper third mold part  33  for forming a plurality of annular grooves  55  parallel to one another to the resin sheet  5 A. The lower mold half  26 A includes substantially the same mold parts as those of the former embodiment, so that the same reference numerals are added to the corresponding portions and the explanation thereof is omitted here. 
     FIG. 9 shows a sealing device according to a second embodiment of the present invention. 
     As this embodiment is basically identical to that of the first embodiment, the same reference numerals are added to the corresponding portions and the explanation thereof is omitted here, and only the structures different from those of the first embodiment will be explained hereunder. 
     In the second embodiment, as constructed in the first embodiment, the interference between the resin seal lip  51  and the rubber seal lip  41  are prevented by defining the annular space  7 , and the helical groove  53  is formed in the inner periphery of the resin seal lip  51  and the plurality of annular grooves  55  are also formed in the outer periphery in parallel with one another. However, this second embodiment is different from the first embodiment in that the rubber material is supplied to the side surface facing the annular space  7  of the resin seal lip  51  to cover the same with a thin rubber film  59 . This rubber film  59  extends continuously from the bonded base portion  43  of the first seal member  4 . 
     A plurality of small annular grooves  55  are formed in parallel with each other to this side surface of the resin seal lip  51  to be covered with the rubber film  59  as in the first embodiment and the rubber film  59  is covered on the annular grooves  55 . 
     In this second embodiment, it may be possible to make flat the upper surface of the resin sheet  4 A without forming such a plurality of annular grooves  55  and to supply the rubber material thereon. According to this embodiment, contrary to the prior art on which the resin sheet  4 A is made thick to prevent the intrusion of the rubber material, the rubber material is positively supplied on the upper surface of the resin sheet  4 A, so that the resin sheet  4 A can be made relatively thin. 
     The manufacturing method of the sealing device  1  of the second embodiment is substantially the same as that of the present invention described with reference to FIGS. 2-8, but is different in a process in which a clearance between the lower third mold half part  22  and the upper second mold part  24  for pressing the resin sheet  4 A is formed so that the rubber material intrudes a gap between the upper surface of the resin sheet  4 A and the lower surface of the lower second mold part  24 . Although in the first embodiment, the upper and lower surfaces of the resin sheet  4 A are pressed in close contact between the second upper mold part  24  and the lower third mold part  22 , in the second embodiment, a gap is formed. 
     In the manner described above, the rubber material is supplied on the upper surface of the inner diameter half portion of the resin sheet  4 A and a plurality of annular grooves  55  are pressurized and formed in the upper surface thereof. 
     As described above, since the space in which the rubber material flows can be made wide also together with the mold cavity  27  by forming such a gap, the flow of the rubber material can be rectified and hence stabilized. 
     On the other hand, as shown in FIG.  10 (C), in a case where the rubber material  59   a  is moved from the inner diameter side end of the resin sheet  4 A towards the helical groove  53  on the lower surface side, the thus moved rubber material portion at the front end of the resin seal lip  51  is cut in the finishing process after the mold separation, whereby a suitable resin seal lip  51  can be obtained. This cutting can be made obliquely as shown by an arrow in FIG.  10 (C), but the cutting may be done in a right angle and, otherwise, the moved rubber material portion may be left as it is in a case where that portion does not affect the sealing performance. 
     Possibility of Industrial Usage 
     According to the present invention, since the rubber seal lip and the resin seal lip are separated by a space so as not to interfere with each other, the resin seal lip can follow up the rotation of the rotation shaft with substantially no stress and the sealing performance can be hence stabilized. Accordingly, the sealing device can be utilized for sealing a portion to which a stable sealing performance is required for a long term under a severe condition. 
     Particularly, the follow-up performance can be remarkably improved by the groove formation to the resin seal lip. 
     Furthermore, since the resin seal lip can be made thin, tension force is reduced and heat generation can be hence lowered. 
     According to the manufacturing method of the present invention, in the molding process of the first seal member for a compound type sealing device, the integral bonding working of the second seal member and the bending working of the resin seal lip can be performed in the same process at the same time, thus realizing the extremely improved productivity of the sealing device. 
     Furthermore, since a portion to be formed as a flat washer shaped resin seal lip is disposed outside of the mold cavity and formed there, the dimensions of the rubber seal lip and the resin seal lip can be made stable. 
     Still furthermore, it becomes possible to prevent the rubber material at the resin seal member bonded portion from intruding toward the upper surfaces of the upper and lower mold halves adjacent to the mold cavity.