Patent Publication Number: US-2021164570-A1

Title: Sealing apparatus and gasket

Description:
TECHNICAL FIELD 
     The present invention relates to a sealing apparatus and a gasket and, in particular, to a sealing apparatus and a gasket that do not affect sealing properties, and facilitate removal of the gasket from an inside of an attachment recessed part. 
     BACKGROUND ART 
     What uses a gasket integrally having a pair of seal beads that are positioned at both the ends of a gasket main body in the axial direction and are oriented in directions facing away from each other in the axial direction has been known as a sealing apparatus that seals the intermediation between connection portions and the like of a housing (Patent Literature 1). 
     As illustrated in  FIG. 12 , the gasket  100  of this sealing apparatus has a structure where a gasket main body  102  made of a rubber-like elastic material (a rubber material or a synthetic resin material having rubber-like elasticity) is integrally formed with a reinforcing ring  101  made of metal. On the gasket main body  102 , a pair of seal beads  102   a  and  102   b  that are positioned at both the ends thereof in the axial direction and are oriented on an inner periphery side and in directions facing away from each other in the axial direction are integrally formed. 
     This gasket  100  is disposed in an attachment recessed part  201  formed at an opening end portion of a housing  200  forming a sealing target space S. By being compressed in the axial direction between a bottom surface  201   a  of this attachment recessed part  201  and an end surface  300   a  of a cover  300 , a gap δ between the housing  200  and the cover  300  is sealed. 
     DOCUMENT LIST 
     Patent Literature 
     Patent Literature 1: WO2015/137491 
     SUMMARY OF INVENTION 
     Technical Problem 
     As for the conventional sealing apparatus described in Patent Literature 1, when the gasket  100  is replaced, the cover  300  is removed from the housing  200  and the gasket  100  is removed from the inside of the attachment recessed part  201 . At this time, according to the conventional sealing apparatus, a substantial entirety of the gasket  100  is positioned in the attachment recessed part  201 , and a substantial entirety of the outer peripheral surface  102   c  of the gasket  100  is hidden by the inner peripheral surface of the attachment recessed part  201 , and any site that can be supported by a driver or the like is not on the outer peripheral surface  102   c  of the gasket  100 . Accordingly, it is significantly difficult to remove the gasket  100  from the inside of the attachment recessed part  201 . 
     The gasket  100  receives, on the inner peripheral surface  102   d,  a pressure toward the outer periphery in a usage state. Accordingly, at a time for replacement, a seal bead  102   b  and the outer peripheral surface  102   c  are sometimes adhered on the bottom surface  201   a  and the inner peripheral surface of the attachment recessed part  201 . It is thus still difficult to remove the gasket  100  from the attachment recessed part  201  while holding the gasket  100  on the inner peripheral surface  102   d.  This is because if the gasket  100  is held on the inner peripheral surface  102   d,  the seal bead  102   b  and the outer peripheral surface  102   c  are pressed against the bottom surface  201   a  and the inner peripheral surface of the attachment recessed part  201 . 
     It is not preferable to form a support portion by changing the seal bead  102   a  of the gasket  100  to have a shape that can be easily supported, because there is a possibility of reducing the sealing properties of the seal bead  102   a.    
     Accordingly, the present invention has an object to provide a sealing apparatus and a gasket that do not affect the sealing properties and facilitate removal of the gasket from the inside of the attachment recessed part. 
     Another object of the present invention is identified by the following description. 
     Solution to Problem 
     The problem described above is solved by each of the following inventions. 
     1. A sealing apparatus using a gasket in which a gasket main body is integrally formed with a reinforcing ring, the gasket main body having a one-end-side seal bead and an other-end-side seal bead which are positioned on one end side and another end side of the reinforcing ring in an axial direction and are oriented in directions facing away from each other in the axial direction, the one-end-side seal bead being closely contacted on a bottom surface of an attachment recessed part formed in a housing, and the other-end-side seal bead being closely contacted on a cover which closes the attachment recessed part of the housing, characterized in that, in a state of being attached in the attachment recessed part with the cover removed from the housing, at least a part of an outer peripheral portion of the gasket serves as a supportable portion by providing a flange consecutively provided on an outer periphery side of the reinforcing ring. 
     2. The sealing apparatus according to the 1, characterized in that a gap with an inner peripheral surface of the attachment recessed part is formed in at least a part of the flange. 
     3. A gasket in which a gasket main body is integrally formed with a reinforcing ring, the gasket main body having a one-end-side seal bead and an other-end-side seal bead which are positioned on one end side and another end side of the reinforcing ring in an axial direction and are oriented in directions facing away from each other in the axial direction, the one-end-side seal bead being closely contacted on a bottom surface of an attachment recessed part formed in a housing, and the other-end-side seal bead being closely contacted on a cover which closes the attachment recessed part of the housing, 
     characterized in that, in a state of being attached in the attachment recessed part with the cover removed from the housing, at least a part of an outer peripheral portion of the gasket serves as a supportable portion by providing a flange consecutively provided on an outer periphery side of the reinforcing ring. 
     4. The gasket according to the 3, characterized in that a gap with an inner peripheral surface of the attachment recessed part is formed in at least a part of the flange. 
     5. The gasket according to the 3 or 4, characterized in that a consecutive link portion between the reinforcing ring and the flange is a curved surface. 
     6. A sealing apparatus using a gasket in which a gasket main body is integrally formed with a reinforcing ring, the gasket main body having a one-end-side seal bead and an other-end-side seal bead which are positioned on one end side and another end side of the reinforcing ring in an axial direction and are oriented in directions facing away from each other in the axial direction, the one-end-side seal bead being closely contacted on a bottom surface of an attachment recessed part formed in a housing, and the other-end-side seal bead being closely contacted on an end surface of a cover which closes the attachment recessed part of the housing, 
     characterized in that, in a state where the gasket is attached in the attachment recessed part with the cover attached, by forming a gap with the end surface of the cover in at least a part of an outer peripheral portion of the attachment recessed part of the housing, at least the part of the outer peripheral portion of the gasket serves as a supportable portion facing an outside, in a state where the cover is removed. 
     7. The sealing apparatus according to the 6, characterized in that the gap is intermittently formed at an equal angle interval on the outer peripheral portion of the attachment recessed part. 
     8. The sealing apparatus according to the 6, characterized in that the gap is formed consecutively over an entire periphery of the outer peripheral portion of the attachment recessed part. 
     Effects of Invention 
     According to the present invention, a sealing apparatus and a gasket that do not affect the sealing properties and facilitate removal of the gasket from the inside of the attachment recessed part can be provided. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  A perspective view (a) and a plan view (b) of a gasket according to a first embodiment of the present invention. 
         FIG. 2  A longitudinal sectional view of a sealing apparatus according to the first embodiment of the present invention. 
         FIG. 3  A longitudinal sectional view of comparing the sealing apparatus according to the first embodiment of the present invention with a conventional sealing apparatus. 
         FIG. 4  A longitudinal sectional view of a sealing apparatus according to a second embodiment of the present invention. 
         FIG. 5  A longitudinal sectional view of a sealing apparatus according to another embodiment of the present invention. 
         FIG. 6  A perspective view (a) (with a cover being removed), a plan view (b) (with the cover being removed) and a longitudinal sectional view (c) taken along line A-A of (b) (with the cover being attached) of a sealing apparatus according to a third embodiment of the present invention. 
         FIG. 7  A perspective view (a) (with a cover being removed), a plan view (b) (with the cover being removed) and a longitudinal sectional view (c) taken along line B-B of (b) (with the cover being attached) of a sealing apparatus according to a fourth embodiment of the present invention. 
         FIG. 8  A perspective view (a) (with a cover being removed), a plan view (b) (with the cover being removed) and a longitudinal sectional view (c) taken along line C-C of (b) (with the cover being attached) of a sealing apparatus according to a fifth embodiment of the present invention. 
         FIG. 9  A perspective view (a) (with a cover and a gasket being removed) and a longitudinal sectional view (b) taken along the center line (with the cover and the gasket being attached) of a sealing apparatus according to a sixth embodiment of the present invention. 
         FIG. 10  An exploded perspective view (a) (with a gasket being removed) and a longitudinal sectional view (b) taken along the center line (with a cover and the gasket being attached) of a sealing apparatus according to a seventh embodiment of the present invention. 
         FIG. 11  An exploded perspective view (a) and a longitudinal sectional view (b) taken along line A-A (with a cover being attached) of a sealing apparatus according to the third embodiment of the present invention in a mode where gaps are filled with bulging portions for the gaps. 
         FIG. 12  A longitudinal sectional view of a conventional gasket. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, sealing apparatus and gaskets according to preferable embodiments of the present invention will be described with reference to the drawings. 
     First Embodiment 
       FIG. 1  is a perspective view (a) and a plan view (b) of a gasket according to a first embodiment of the present invention. 
       FIG. 2  is a longitudinal sectional view of a sealing apparatus according to the first embodiment of the present invention. 
     This sealing apparatus is used as, for example, sealing means for a joint portion between an AT housing in an automatic transmission (AT) and a clutch housing of an automobile, and includes a gasket  1 , a housing  2  and a cover  3  as shown in  FIG. 2 . 
     As shown in  FIG. 2 , in the gasket  1 , a gasket main body  12  is formed integrally with a reinforcing ring  11 . The reinforcing ring  11  is provided for supplying the gasket  1  with strength and is formed to have a cylindrical shape appropriately using a metal, such as low-carbon free cutting steel, for example. 
     The length of the reinforcing ring  11  in the axial direction (the vertical direction in  FIG. 2 ) is smaller than the depth of an attachment recessed part  21 . 
     The gasket main body  12  is made of a rubber-like elastic material (a rubber material or a synthetic resin material having rubber-like elasticity) and is formed integrally with the inner peripheral surface and the outer peripheral surface of the reinforcing ring  11 . 
     The gasket main body  12  includes: a base portion  121  in which the reinforcing ring  11  is embedded; and a one-end-side seal bead  122  and an other-end-side seal bead  123  that are consecutive with the base portion  121 , are positioned at both the ends of the reinforcing ring  11  in the axial direction, and are oriented on the inner periphery side and in the directions facing away from each other in the axial direction. The one-end-side seal bead  122  is closely contacted on a bottom surface  21   a  of the attachment recessed part  21 . The other-end-side seal bead  123  is closely contacted on an end surface  3   a  of the cover  3 . 
     The base portion  121  of the gasket main body  12  is formed from the inner peripheral surface to the outer peripheral surface of the reinforcing ring  11 . Another end  11   b  of the reinforcing ring  11  in the axial direction is covered with the thinned gasket main body  12 . One end  11   a  of the reinforcing ring  11  in the axial direction protrudes from an outer peripheral portion of the one-end-side seal bead  122  in this embodiment, and may be covered with the gasket main body  12 . 
     The one-end-side seal bead  122  is formed to have a thinner wall and a smaller volume in comparison with the other-end-side seal bead  123 . Accordingly, the rigidity is lower than that of the other-end-side seal bead  123 . In other words, the other-end-side seal bead  123  is formed to have a thicker wall and a larger volume in comparison with the one-end-side seal bead  122 , thereby achieving a higher rigidity than that of the one-end-side seal bead  122 . Accordingly, when the gasket main body  12  receives a compression force in the axial direction, the amount of deformation of the one-end-side seal bead  122  is larger than the amount of deformation of the other-end-side seal bead  123 . 
     The gasket main body  12  is formed to have an outer diameter smaller than the inner diameter of the attachment recessed part  21 . A flange  14  is consecutively provided for the reinforcing ring  11  on its outer periphery side. The flange  14  is provided such that a part of the reinforcing ring  11  adjacent to its other end  11   b  in the axial direction nearer to the cover  3  is bent toward the outer periphery side. The outer periphery side of the flange  14  protrudes from the gasket main body  12  on the outer periphery side. The flange  14  is formed to have an outer diameter substantially equal to the inner diameter of the attachment recessed part  21 . Accordingly, in the gasket  1 , an inner peripheral surface  21   c  of the attachment recessed part  21  serves as a positioning surface, which can maintain the concentricity with respect to gasket  1  and attached recessed part  21 . 
     In a state where the gasket  1  is attached in the attachment recessed part  21  with the cover  3  being removed from the housing  2 , at least parts of the outer peripheral portion serve as supportable portions  13  owing to the flange  14  being formed. The supportable portions  13  are sites that can be supported at the outer peripheral portion of the gasket  1  by a jig, such as a driver, or fingers, when the cover  3  is removed from the housing  2  and the gasket  1  is removed from the inside of the attachment recessed part  21  and replaced. 
     Gaps with the inner peripheral surface  21   c  of the attachment recessed part  21  are formed at the outer peripheral portion of the flange  14  according to this embodiment. The gaps are formed by providing recessed portions  15  for the outer peripheral portion of the flange  14 . At the parts of the recessed portions  15 , the gaps with the inner peripheral surface  21   c  are formed. In this embodiment, the recessed portions  15  are provided at four sites on the outer periphery of the flange  14  at 90° intervals. 
     The supportable portions  13  according to this embodiment are the outer peripheral portion or a lower surface (a surface nearer to the bottom surface  21   a ) of the flange  14 . An outer peripheral surface portion  12   a  of the gasket main body  12  other than the flange  14  can also be used as the supportable portions  13 . By inserting a jig into the gap between the flange  14  and the inner peripheral surface  21   c  and supporting the supportable portions  13 , the gasket  1  can be easily removed from the inside of the attachment recessed part  21 . By forming the gap, the gasket  1  can be easily removed from the inside of the attachment recessed part  21  without using the jig. 
     In the sealing apparatus, it is significantly easy to remove the gasket  1  from the inside of the attachment recessed part  21  owing to the supportable portions  13 . Even when the supportable portions  13  are supported, the seal beads  122  and  123  and the outer peripheral surface of the gasket main body  12  are not pressed against the bottom surface  21   a  and the inner peripheral surface  21   c  of the attachment recessed part  21 . Accordingly, even when the seal bead  122  and the outer peripheral surface adhere to the bottom surface  21   a  and the inner peripheral surface  21   c,  it is easy to remove the gasket  1  from the inside of the attachment recessed part  21 . 
     The seal beads  122  and  123  of the gasket  1  are not changed to have easily supportable shapes. Accordingly, favorable sealing properties can be maintained. 
     It is preferable that a consecutive link portion  14   a  between the reinforcing ring  11  and the flange  14  have a curved surface. Accordingly, when a deformation force to the outer periphery side due to a fluid pressure is applied to the other-end-side seal bead  123 , it can prevent stress from being concentrated against the inner peripheral edge of the reinforcing ring  11  and can effectively prevent peeling of adhesion and a crack from occurring. 
     Next, operation when the gasket  1  is attached in the attachment recessed part  21  will be described. 
     The gasket  1  is disposed in the attachment recessed part  21  formed in the housing  2 . In  FIG. 3 , the one-end-side seal bead  122  is nearer to the bottom surface  21   a  of the attachment recessed part  21 . However, the assembling direction is not limited. 
     When the gasket  1  is disposed in the attachment recessed part  21 , and the housing  2  and the cover  3  are clamped with bolts or the like, not shown, the gasket  1  is pressed by the cover  3 , and the one-end-side and other-end-side seal beads  122  and  123  receive the compression force in the axial direction. At this time, the other-end-side seal bead  123  has a thick wall, a large volume and a high rigidity, while the one-end-side seal bead  122  has a low rigidity and tends to be deformed. Accordingly, the one-end-side seal bead  122  is preferentially deformed and collapses toward the inner periphery side. As a result, the gasket  1  is set in the attachment recessed part  21  so as to be on the one-end-side seal bead  122  side, that is, in a state of residing unevenly closer to the bottom surface  21   a  of the attachment recessed part  21 . 
     In this set state, the gasket  1  is in a state where the one end  11   a  of the reinforcing ring  11  in the axial direction is contacted on the bottom surface  21   a  of the attachment recessed part  21  or is close to the bottom surface  21   a.  Accordingly, the one-end-side seal bead  122  does not further collapse toward the inner periphery side. 
     Subsequently, after clamping of the housing  2  and the cover  3  is completed, the compression force in the axial direction is absorbed by the other-end-side seal bead  123  collapsing toward the inner periphery side or being compressed. This is because the other-end-side seal bead  123  has a sufficient interference with the end surface  3   a  of the cover  3  even if the one-end-side seal bead  122  has completely collapsed and the one end  11   a  of the reinforcing ring  11  in the axial direction is in the state of being contacted on the bottom surface  21   a  of the attachment recessed part  21 . Accordingly, as for the gasket  1 , the one-end-side seal bead  122  is contacted closely on the bottom surface  21   a  of the attachment recessed part  21 , and the other-end-side seal bead  123  is contacted closely on the end surface  3   a  of the cover  3 , thus sealing the sealing target space S. 
     When a fluid pressure that is a high pressure is present on the inner periphery side of the gasket  1  in this attached state, the fluid pressure is applied on each of the one-end side and other-end-side seal beads  122  and  123 . At this time, the one-end-side seal bead  122  having a low rigidity is backed up from the outer periphery side by the one end  11   a  of the reinforcing ring  11  in the axial direction residing at the position contacted on or close to the bottom surface  21   a  of the attachment recessed part  21 . Accordingly, deformation of the one-end-side seal bead  122  toward the outer periphery side is suppressed, and there is no possibility of sticking out to the outer periphery side, thus maintaining excellent sealing properties. 
     The gasket  1  in the attached state is pressed against the bottom surface  21   a  of the attachment recessed part  21  and resides unevenly closer to the bottom surface  21   a  of the attachment recessed part  21 , and the one end  11   a  of the reinforcing ring  11  in the axial direction is contacted on the bottom surface  21   a  to prevent further movement. Accordingly, there is substantially no movement in the axial direction. Consequently, even if the fluid pressure is intermittently and repetitively applied, there is no possibility of causing an abrasion or the like due to repetitive movement of the gasket  1  in the axial direction with a large stroke. 
     When the other-end-side seal bead  123  having a relatively high rigidity receives a fluid pressure, a force of deformation to the outer periphery side is applied. However, this bead has a thicker wall and a larger volume than the one-end-side seal bead  122 , and is contacted closely on the end surface  3   a  of the cover  3  with a sufficient interference. Consequently, large collapse of the other-end-side seal bead  123  to the outer periphery side does not occur. Accordingly, the other-end-side seal bead  123  is contacted further closely on the end surface  3   a,  which can improve the sealing properties. Accordingly, the gasket  1  exert excellent sealing properties also on the other-end-side seal bead  123 . 
     Furthermore, the other end  11   b  of the reinforcing ring  11  in the axial direction is disposed in the gasket main body  12  adjacent to the other-end-side seal bead  123 . Consequently, the other end  11   b  side of the reinforcing ring  11  in the axial direction functions to prevent the other-end-side seal bead  123  from collapsing to the outer periphery side. Accordingly, the other-end-side seal bead  123  does not stick out to the gap  8 . 
     It is preferable that a chamfer  11   c  be formed on one end inner peripheral edge of the reinforcing ring  11  as illustrated. Accordingly, when a deformation force to the outer periphery side due to a fluid pressure is applied to the one-end-side seal bead  122 , it can prevent stress from being concentrated against the inner peripheral edge of the reinforcing ring  11  and can effectively prevent peeling of adhesion and a crack from occurring. 
       FIG. 3  is a longitudinal sectional view of comparing the sealing apparatus according to the first embodiment of the present invention with a conventional sealing apparatus. 
     As shown in  FIG. 3 , as to the gasket  1  of the embodiment and the conventional gasket, a strain distribution in the gasket main body  12  was analyzed. As for the analysis of the strain distribution, the internal stress without an applied pressure and that with an applied pressure in a state of the maximum interference and in a state of the minimum interference were analyzed. 
     In the gasket  1  of the embodiment, the consecutive link portion  14   a  between the reinforcing ring  11  and the flange  14  is a curved surface. Accordingly, it was found that in comparison with the conventional gasket without a flange, the internal stress in proximity to the consecutive link portion  14   a  was reduced, and peeling of adhesion and a crack are prevented at this site. That is, in the state of the maximum interference, the concentration of stress, which was large even without an applied pressure in the conventional gasket, was small even with an applied pressure according to the gasket  1  of the embodiment. 
     Second Embodiment 
       FIG. 4  is a longitudinal sectional view of a sealing apparatus according to a second embodiment of the present invention. 
     In this sealing apparatus, the flange  14  of the gasket  1  may include a cover portion  124  consecutively provided integrally from the gasket main body  12 , as shown in  FIG. 4 . The cover portion  124  serves as an upper surface portion (a surface nearer to the cover  3 ) and an outer peripheral surface portion of the flange  14 . 
     In this embodiment, the supportable portions  13  are the cover portion  124  or a lower surface (a surface nearer to the bottom surface  21   a ) of the flange  14  serving as the outer peripheral surface portion of the flange  14 . That is, in a state where the gasket  1  is attached in the attachment recessed part  21  and the cover  3  is removed from the housing  2 , the cover portion  124  which is at least a part of the outer peripheral portion of the gasket  1  and serves as the outer peripheral surface portion of the flange  14 , or the lower surface (the surface nearer to the bottom surface  21   a ) of the flange  14 , serves as supportable portions  13  facing the outside. An outer peripheral surface portion  12   a  of the gasket main body  12  other than the flange  14  can also be used as the supportable portions  13 . 
     If the flange  14  is provided with recessed portions  15 , the recessed portions  15  are formed at the cover portion  124  of the flange  14 . In this case, the recessed portions  15  may have a depth (width) reaching a metal portion in the cover portion  124 , or have a depth (width) not reaching the metal portion and being formed only at the cover portion  124 . By the recessed portions  15 , a gap with the inner peripheral surface  21   c  of the attachment recessed part  21  is formed. In a state where the gasket  1  is attached in the attachment recessed part  21  and the cover  3  is removed from the housing  2 , at least a part of the outer peripheral portion of the gasket  1  (parts corresponding to the recessed portions  15 , the lower surface of the flange  14  (the surface nearer to the bottom surface  21   a ) or the outer peripheral surface portion  12   a  that is of the gasket main body  12  and is other than the flange  14 ) can serve as supportable portions  13  facing the outside. 
     The supportable portions  13  are sites that can be supported at the outer peripheral portion of the gasket  1 , when the cover  3  is removed from the housing  2  and the gasket  1  is removed from the inside of the attachment recessed part  21  and replaced. It is significantly easy to remove the gasket  1  from the inside of the attachment recessed part  21  owing to the supportable portions  13 . Even when the supportable portions  13  are supported, the seal beads  122  and  123  and the outer peripheral surface of the gasket main body  12  are not pressed against the bottom surface  21   a  and the inner peripheral surface  21   c  of the attachment recessed part  21 . Accordingly, even when the seal bead  122  and the outer peripheral surface adhere to the bottom surface  21   a  and the inner peripheral surface  21   c,  it is easy to remove the gasket  1  from the inside of the attachment recessed part  21 . 
     The seal beads  122  and  123  of the gasket  1  are not changed to have easily supportable shapes. Accordingly, favorable sealing properties can be maintained. 
     In this sealing apparatus, the gap formed between the outer peripheral portion of the flange  14  and the inner peripheral surface  21   c  of the attachment recessed part  21  is not limited to that in the embodiment described above, and may be over the entire periphery of the flange  14 , or may be present only at any one site. The gap is not necessarily the recessed portions  15  described above, and may be formed by providing projections at the outer peripheral portion of the flange  14 . If the protrusions are provided, the gap is formed at a part other than the protrusions. 
     According to any of the embodiments, in a state where the gasket  1  is attached in the attachment recessed part  21  and the cover  3  is removed from the housing  2 , at least a part of the outer peripheral portion of the gasket  1  (the outer peripheral portion or the lower surface of the flange  14  (the surface nearer to the bottom surface  21   a ) or the outer peripheral surface portion  12   a  that is of the gasket main body  12  and is other than the flange  14 ) can serve as supportable portions  13  facing the outside. 
     This sealing apparatus is not limited to that having a configuration where the gap is formed between the outer peripheral portion of the flange  14  and the inner peripheral surface  21   c  of the attachment recessed part  21 . 
       FIG. 5  is a longitudinal sectional view of the sealing apparatus according to another embodiment of the sealing apparatus according to the embodiment of the present invention described above. 
     If any gap is not formed between the outer peripheral portion of the flange  14  and the inner peripheral surface  21   c  of the attachment recessed part  21 , for example, as shown in  FIG. 5 , by providing the upper surface portion (the surface nearer to the cover  3 ) of the flange  14  with cut-and-raised nails  14   b,  the lower surfaces of the cut-and-raised nails  14   b  are allowed to serve as the supportable portions  13 . 
     Third Embodiment 
       FIG. 6  is a perspective view (a) (with a cover being removed), a plan view (b) (with the cover being removed) and a longitudinal sectional view (c) taken along line A-A of (b) (with the cover being attached) of a sealing apparatus according to a third embodiment of the present invention. 
     As shown in  FIG. 6( c ) , in a gasket  410 , a gasket main body  412  is configured by being formed integrally with a reinforcing ring  411 . The reinforcing ring  411  is provided for supplying the gasket  410  with strength and is formed to have a cylindrical shape appropriately using a metal, such as low-carbon free cutting steel, for example. 
     The length of the reinforcing ring  411  in the axial direction (the vertical direction in  FIG. 6 ) is smaller than the depth of an attachment recessed part  421 . 
     The gasket main body  412  is made of a rubber-like elastic material (a rubber material or a synthetic resin material having rubber-like elasticity) and is formed integrally with the inner peripheral surface and the outer peripheral surface of the reinforcing ring  411 . 
     The gasket main body  412  includes: a base portion  4121  in which the reinforcing ring  411  is embedded; and a one-end-side seal bead  4122  and an other-end-side seal bead  4123  that are consecutive with the base portion  4121 , are positioned at both the ends of the reinforcing ring  411  in the axial direction, and are oriented on the inner periphery side and in the directions facing away from each other in the axial direction. The one-end-side seal bead  4122  is closely contacted with a bottom surface  421   a  of the attachment recessed part  421 . The other-end-side seal bead  4123  is closely contacted on an end surface  430   a  of a cover  430 . 
     The base portion  4121  of the gasket main body  412  is formed from the inner peripheral surface to the outer peripheral surface of the reinforcing ring  411 . Another end  411   b  of the reinforcing ring  411  in the axial direction is covered with the thin-walled gasket main body  412 . One end  411   a  of the reinforcing ring  411  in the axial direction protrudes from an outer peripheral portion of the one-end-side seal bead  4122  in this embodiment, and may be covered with the gasket main body  412 . 
     The one-end-side seal bead  4122  is formed to have a thinner wall and a smaller volume in comparison with the other-end-side seal bead  4123 . Accordingly, the rigidity is lower than that of the other-end-side seal bead  4123 . In other words, the other-end-side seal bead  4123  is formed to have a thicker wall and a larger volume in comparison with the one-end-side seal bead  4122 , thereby achieving a higher rigidity than that of the one-end-side seal bead  4122 . Accordingly, when the gasket main body  412  receives a compression force in the axial direction, the amount of deformation of the one-end-side seal bead  4122  is larger than the amount of deformation of the other-end-side seal bead  4123 . 
     The gasket main body  412  is formed to have an outer diameter substantially equal to the inner diameter of the attachment recessed part  421 . Accordingly, in the gasket  410 , an inner peripheral surface  421   b  of the attachment recessed part  421  serves as a positioning surface, which can maintain the concentricity for the attachment recessed part  421 . 
     According to a housing  420 , in a state where the gasket  410  is attached in the attachment recessed part  421  and the cover  430  is attached, gaps  422  with the end surface  430   a  of the cover  430  are formed in at least parts of the outer peripheral portion of the attachment recessed part  421 . In this embodiment, the gaps  422  are intermittently formed at the outer peripheral portion of the attachment recessed part  421  at an equal angle interval. In this embodiment, the gaps  422  are formed at four sites on the outer peripheral portion of the attachment recessed part  421  at 90° intervals. Each gap  422  is formed to have a semicircular column shape whose axial direction is parallel to that of the gasket  410 , and have a shape open to the gasket  410 . 
     Owing to the gaps  422  being formed, in a state where the gasket  410  is attached in the attachment recessed part  421  with the cover  430  being removed from the housing  420 , at least parts (parts corresponding to the gaps  422 ) of the outer peripheral portion of the gasket  410  serve as supportable portions  413  facing the outside. 
     The supportable portions  413  are sites that can be supported at the outer peripheral surface of the gasket  410  by a jig, such as a driver, or fingers, when the cover  430  is removed from the housing  420  and the gasket  410  is removed from the inside of the attachment recessed part  421  and replaced. The supportable portions  413  are at least parts of the outer peripheral surface portion of the gasket main body  412 . By inserting a jig into the gaps  422  and supporting the supportable portions  413 , the gasket  410  can be easily removed from the inside of the attachment recessed part  421 . By forming the gaps  422 , the gasket  410  can be easily removed from the inside of the attachment recessed part  421  without using the jig. 
     In the sealing apparatus, it is significantly easy to remove the gasket  410  from the inside of the attachment recessed part  421  owing to the supportable portions  413 . Even when the supportable portions  413  are supported, the seal beads  4122  and  4123  and the outer peripheral surface of the gasket main body  412  are not pressed against the bottom surface  421   a  and the inner peripheral surface  421   b  of the attachment recessed part  421 . Accordingly, even when the seal bead  4122  and the outer peripheral surface adhere to the bottom surface  421   a  and the inner peripheral surface  421   b,  it is easy to remove the gasket  410  from the inside of the attachment recessed part  421 . 
     The seal bead  4123  of the gasket  410  is not changed to have an easily supportable shape. Accordingly, favorable sealing properties can be maintained. 
     Next, operation when the gasket  410  is attached in the attachment recessed part  421  will be described. 
     The gasket  410  is disposed in the attachment recessed part  421  formed in the housing  420 . In  FIG. 6 , the one-end-side seal bead  4122  is nearer to the bottom surface  421   a  of the attachment recessed part  421 . However, the assembling direction is not limited. 
     When the gasket  410  is disposed in the attachment recessed part  421 , and the housing  420  and the cover  430  are clamped with bolts or the like, not shown, the gasket  410  is pressed by the cover  430 , and the one-end-side and other-end-side seal beads  4122  and  4123  receive the compression force in the axial direction. At this time, the other-end-side seal bead  4123  have a thick wall, a large volume and a high rigidity, while the one-end-side seal bead  4122  has a low rigidity and tends to be deformed. Accordingly, the one-end-side seal bead  4122  is preferentially deformed and collapses toward the inner periphery side. As a result, the gasket  410  is set in the attachment recessed part  421  so as to be on the one-end-side seal bead  4122  side, that is, in a state of residing unevenly closer to the bottom surface  421   a  of the attachment recessed part  421 . 
     In this set state, the gasket  410  is in a state where the one end  411   a  of the reinforcing ring  411  in the axial direction is contacted on the bottom surface  421   a  of the attachment recessed part  421  or is close to the bottom surface  421   a.  Accordingly, the one-end-side seal bead  4122  does not further collapse toward the inner periphery side. 
     Subsequently, after clamping of the housing  420  and the cover  430  is completed, the compression force in the axial direction is absorbed by the other-end-side seal bead  4123  collapsing toward the inner periphery side or being compressed. This is because the other-end-side seal bead  4123  has a sufficient interference with the end surface  430   a  of the cover  430  even if the one-end-side seal bead  4122  has completely collapsed and the one end  411   a  of the reinforcing ring  411  in the axial direction is in the state of being contacted on the bottom surface  421   a  of the attachment recessed part  421 . Accordingly, as for the gasket  410 , the one-end-side seal bead  4122  is contacted closely on the bottom surface  421   a  of the attachment recessed part  421 , and the other-end-side seal bead  4123  is contacted closely on the end surface  430   a  of the cover  430 , thus sealing the sealing target space S. 
     When a fluid pressure that is a high pressure is present on the inner periphery side of the gasket  410  in this attached state, the fluid pressure is applied on each of the one-end-side and other-end-side seal beads  4122  and  4123 . At this time, the one-end-side seal bead  4122  having a low rigidity is backed up from the outer periphery side by the one end  411   a  of the reinforcing ring  411  in the axial direction residing at the position contacted on or close to the bottom surface  421   a  of the attachment recessed part  421 . Accordingly, deformation the one-end-side seal bead  4122  toward the outer periphery side is suppressed, and there is no possibility of sticking out to the outer periphery side, thus maintaining excellent sealing properties. 
     The gasket  410  in the attached state is pressed against the bottom surface  421   a  of the attachment recessed part  421  and resides unevenly closer to the bottom surface  421   a  of the attachment recessed part  421 , and the one end  411   a  of the reinforcing ring  411  in the axial direction is contacted on the bottom surface  421   a  to prevent further movement. Accordingly, there is substantially no movement of the gasket  410  in the axial direction. Consequently, even if the fluid pressure is intermittently and repetitively applied, there is no possibility of causing an abrasion or the like due to repetitive movement of the gasket  410  in the axial direction with a large stroke. 
     When the other-end-side seal bead  4123  having a relatively high rigidity receives a fluid pressure, a force of deformation to the outer periphery side is applied. However, this bead has a thicker wall and a larger volume than the one-end-side seal bead  4122 , and is contacted closely on the end surface  430   a  of the cover  430  with a sufficient interference. Consequently, large collapse of the other-end-side seal bead  4123  to the outer periphery side does not occur. Accordingly, the other-end-side seal bead  4123  is contacted further closely on the end surface  430   a,  which can improve the sealing properties. Accordingly, the gasket  410  exerts excellent sealing properties also on the other-end-side seal bead  4123 . 
     Furthermore, the other end  411   b  of the reinforcing ring  411  in the axial direction is disposed in the gasket main body  412  adjacent to the other-end-side seal bead  4123 . Consequently, the other end  411   b  side of the reinforcing ring  411  in the axial direction functions to prevent the other-end-side seal bead  4123  from collapsing to the outer periphery side. Accordingly, the other-end-side seal bead  4123  does not stick out to the gap  8 . 
     It is preferable that chamfers  411   c  be formed on inner peripheral edges of both ends of the reinforcing ring  411  (see  FIG. 7( c )  described later). Accordingly, when a deformation force to the outer periphery side due to a fluid pressure is applied to the one-end-side and other-end-side seal beads  4122  and  4123 , it can prevent stress from being concentrated against the inner peripheral edges of both ends of the reinforcing ring  411  and can effectively prevent peeling of adhesion and a crack from occurring. 
     Fourth Embodiment 
       FIG. 7  is a perspective view (a) (with a cover being removed), a plan view (b) (with the cover being removed) and a longitudinal sectional view (c) taken along line B-B of (b) (with the cover being attached) of a sealing apparatus according to a fourth embodiment of the present invention. 
     In this sealing apparatus, the gaps  422  between the housing  420  and the end surface  430   a  of the cover  430  may be formed to be in a state of being consecutive to each other on the outer periphery side of the housing  420 , as shown in  FIG. 7 . In this embodiment, the gaps  422  are formed at three sites at 120° intervals on the outer peripheral portion of the attachment recessed part  421 , and are consecutive to each other on the outer periphery side of the housing  420 . That is, in the housing  420  of this embodiment, wall parts (parts between the gaps  422 ) remain at three sites by 120° intervals on the outer peripheral portion of the attachment recessed part  421 , and parts other than these wall parts are apart from the end surface  430   a  of the cover  430  consecutively from the attachment recessed part  421  to the outer peripheral edge of the housing  420 . The housing  420  and the cover  430  may have matching surfaces at sites which are not shown. 
     Owing to the gaps  422  being formed, in a state where the gasket  410  is attached in the attachment recessed part  421  with the cover  430  being removed from the housing  420 , at least parts (parts corresponding to the gaps  422 ) of the outer peripheral portion of the gasket  410  serve as supportable portions  413  facing the outside. 
     The supportable portions  413  are sites that can be supported at the outer peripheral surface of the gasket  410  by a jig, such as a driver, or fingers, when the cover  430  is removed from the housing  420  and the gasket  410  is removed from the inside of the attachment recessed part  421  and replaced. It is significantly easy to remove the gasket  410  from the inside of the attachment recessed part  421  owing to the supportable portions  413 . Even when the supportable portions  413  are supported, the seal bead  4122  and the outer peripheral surface of the gasket main body  412  are not pressed against the bottom surface  421   a  and the inner peripheral surface  421   b  of the attachment recessed part  421 . Accordingly, even when the seal bead  4122  and the outer peripheral surface adhere to the bottom surface  421   a  and the inner peripheral surface  421   b,  it is easy to remove the gasket  410  from the inside of the attachment recessed part  421 . 
     The seal bead  4123  of the gasket  410  is not changed to have an easily supportable shape. Accordingly, favorable sealing properties can be maintained. 
     Fifth Embodiment 
       FIG. 8  is a perspective view (a) (with a cover being removed), a plan view (b) (with the cover being removed) and a longitudinal sectional view (c) taken along line C-C of (b) (with the cover being attached) of a sealing apparatus according to a fifth embodiment of the present invention. 
     In this sealing apparatus, the gaps  422  between the housing  420  and the end surface  430   a  of the cover  430  may be formed to be in a state of being consecutive to each other on the outer periphery side of the housing  420 , as shown in  FIG. 8 . In this embodiment, the gaps  422  are formed at three sites at 120° intervals on the outer peripheral portion of the attachment recessed part  421 , and are consecutive to each other on the outer periphery side of the housing  420 . That is, in the housing  420  of this embodiment, round rod portions (parts between the gaps  422 ) remain at three sites by 120° intervals on the outer peripheral portion of the attachment recessed part  421 , and parts other than these round rod portions are apart from the end surface  430   a  of the cover  430  consecutively from the attachment recessed part  421  to the outer peripheral edge of the housing  420 . Note that as shown in  FIG. 8( c ) , the round rod portions may be separated round rod members planted in the housing  420 . The housing  420  and the cover  430  may have matching surfaces at sites which are not shown. 
     Owing to the gaps  422  being formed, in a state where the gasket  410  is attached in the attachment recessed part  421  with the cover  430  being removed from the housing  420 , at least parts (parts corresponding to the gaps  422 ) of the outer peripheral portion of the gasket  410  serve as supportable portions  413  facing the outside. 
     The supportable portions  413  are sites that can be supported at the outer peripheral surface of the gasket  410  by a jig, such as a driver, or fingers, when the cover  430  is removed from the housing  420  and the gasket  410  is removed from the inside of the attachment recessed part  421  and replaced. It is significantly easy to remove the gasket  410  from the inside of the attachment recessed part  421  owing to the supportable portions  413 . Even when the supportable portions  413  are supported, the seal bead  4122  and the outer peripheral surface of the gasket main body  412  are not pressed against the bottom surface  421   a  and the inner peripheral surface  421   b  of the attachment recessed part  421 . Accordingly, even when the seal bead  4122  and the outer peripheral surface adhere to the bottom surface  421   a  and the inner peripheral surface  421   b,  it is easy to remove the gasket  410  from the inside of the attachment recessed part  421 . 
     The seal bead  4123  of the gasket  410  is not changed to have an easily supportable shape. Accordingly, favorable sealing properties can be maintained. 
     Sixth Embodiment 
       FIG. 9  is a perspective view (a) (with a cover and a gasket being removed) and a longitudinal sectional view (b) taken along the center line (with the cover and the gasket being attached) of a sealing apparatus according to a sixth embodiment of the present invention. 
     In this sealing apparatus, the gaps  422  between the housing  420  and the end surface  430   a  of the cover  430  may be formed consecutively over the entire periphery of the outer peripheral portion of the attachment recessed part  421 , as shown in  FIG. 9 . 
     In this embodiment, the gap  422  is consecutively formed over the entire periphery of the outer peripheral portion of the attachment recessed part  421 . The depth (the distance from the end surface  430   a  of the cover  430  to the bottom surface of the gap  422 ) is shallower than that of the attachment recessed part  421 . That is, the housing  420  of this embodiment is in a state where the outer peripheral portion of the attachment recessed part  421  is enlarged in diameter on the cover  430  side. In the shown example, the gap  422  is consecutively formed over the entire periphery of the outer peripheral portion of the attachment recessed part  421 . However, not limited thereto, the gap  422  may be provided at one site or intermittently. It is preferable that the depth of the gap  422  be deeper than the position of the other end  411   b  of the reinforcing ring  411  in the axial direction. 
     Owing to the gap  422  being formed, in a state where the gasket  410  is attached in the attachment recessed part  421  with the cover  430  being removed from the housing  420 , the outer peripheral portion of the gasket  410  serves, over the entire periphery, as a supportable portion  413  facing the outside. 
     The supportable portions  413  is sites that can be supported at the outer peripheral surface of the gasket  410  by a jig, such as a driver, or fingers, when the cover  430  is removed from the housing  420  and the gasket  410  is removed from the inside of the attachment recessed part  421  and replaced. It is significantly easy to remove the gasket  410  from the inside of the attachment recessed part  421  owing to the supportable portion  413 . Even when the supportable portion  413  is supported, the seal bead  4122  and the outer peripheral surface of the gasket main body  412  are not pressed against the bottom surface  421   a  and the inner peripheral surface  421   b  of the attachment recessed part  421 . Accordingly, even when the seal bead  4122  and the outer peripheral surface adhere to the bottom surface  421   a  and the inner peripheral surface  421   b,  it is easy to remove the gasket  410  from the inside of the attachment recessed part  421 . 
     The seal bead  4123  of the gasket  410  is not changed to have an easily supportable shape. Accordingly, favorable sealing properties can be maintained. 
     Seventh Embodiment 
       FIG. 10  is an exploded perspective view (a) (with a gasket being removed) and a longitudinal sectional view (b) taken along the center line (with a cover and the gasket being attached) of a sealing apparatus according to a seventh embodiment of the present invention. 
     In the case where the gap  422  between the housing  420  and the end surface  430   a  of the cover  430  is formed consecutively over the entire periphery of the outer peripheral portion of the attachment recessed part  421  (sixth embodiment), the gap  422  may be formed over the inner peripheral edge of the housing  420  as shown in  FIG. 10 . The depth of the gap  422  (the distance from the end surface  430   a  of the cover  430  to the bottom surface of the gap  422 ) is shallower than that of the attachment recessed part  421 . That is, as for the housing  420  of this embodiment, the entire outer periphery side of the attachment recessed part  421  in the sixth embodiment is removed and an end surface  423  facing the cover  430  side is made flat, and an annular protruding portion  431  protruding from the end surface  430   a  of the cover  430  toward the housing  420  is formed on the outer peripheral portion at a portion of the cover  430  that faces the end surface  423  of the housing  420 . Accordingly, the housing  420  is in a state where the housing  420  is apart from the end surface  430   a  of the cover  430 . In the state where the cover  430  is attached to the housing  420 , the outer peripheral portion of the gasket  410  is disposed on the inner periphery side of the protruding portion  431 , and the gap  422  is formed by the end portion  430   a  of the cover  430 , the protruding portion  431  and the end surface  423  of the housing  420 . In the state where the cover  430  is attached to the housing  420 , it is preferable that the depth of the gap  422  be deeper than the position of the other end  411   b  of the reinforcing ring  411  in the axial direction. 
     Owing to the gap  422  being formed, in a state where the gasket  410  is attached in the attachment recessed part  421  with the cover  430  being removed from the housing  420 , the outer peripheral portion of the gasket  410  serves, over the entire periphery, as a supportable portion  413  facing the outside. 
     The supportable portion  413  is sites that can be supported at the outer peripheral surface of the gasket  410  by a jig, such as a driver, or fingers, when the cover  430  is removed from the housing  420  and the gasket  410  is removed from the inside of the attachment recessed part  421  and replaced. It is significantly easy to remove the gasket  410  from the inside of the attachment recessed part  421  owing to the supportable portion  413 . Even when the supportable portion  413  is supported, the seal bead  4122  and the outer peripheral surface of the gasket main body  412  are not pressed against the bottom surface  421   a  and the inner peripheral surface  421   b  of the attachment recessed part  421 . Accordingly, even when the seal bead  4122  and the outer peripheral surface adhere to the bottom surface  421   a  and the inner peripheral surface  421   b,  it is easy to remove the gasket  410  from the inside of the attachment recessed part  421 . 
     The seal bead  4123  of the gasket  410  is not changed to have an easily supportable shape. Accordingly, favorable sealing properties can be maintained. 
     Note that in each embodiment described above, bulging portions for the gaps may be provided for the end surface  430   a  of the cover  430 , and the gaps  422  may be filled with the bulging portions for the gaps. 
       FIG. 11  is an exploded perspective view (a) and a longitudinal sectional view (b) taken along line A-A of (a) (with a cover being attached) of a sealing apparatus according to the third embodiment of the present invention in a mode where gaps are filled with bulging portions for the gaps. 
     In the third embodiment, as shown in  FIG. 11 , the bulging portions for the gaps  430   c  corresponding to the shapes of the gaps  422  may be provided on the outer periphery side with respect to the position where the other-end-side seal bead  4123  is closely contacted on the end surface  430   a  of the cover  430 , and when the cover  430  is attached, the bulging portions for the gaps  430   c  may enter the gaps  422  to fill the gaps  422 . The bulging portions for the gaps  430   c  may be formed integrally with the cover  430 , or may be configured by attaching separate members to the cover  430 . This is also applicable to the other embodiments. 
     LIST OF REFERENCE SIGNS 
     
         
           1  Gasket, 
           11  Reinforcing ring, 
           11   a  One end in axial direction, 
           11   b  Another end in axial direction, 
           11   c  Chamfer, 
           12 : Gasket main body, 
           12   a  Outer peripheral surface portion, 
           121  Base portion, 
           122  One-end-side seal bead, 
           123  Other-end-side seal bead, 
           124  Cover portion, 
           13  Supportable portion, 
           14  Flange, 
           14   a  Consecutive link portion, 
           14   b  Cut-and-raised nail, 
           15  Recessed portion, 
           2  Housing, 
           21  Attachment recessed part, 
           21   a  Bottom surface, 
           21   b  Opening edge, 
           21   c  Inner peripheral surface, 
           3  Cover, 
           3   a  End surface, 
         S Sealing target space, 
         δ Gap, 
           410  Gasket, 
           411  Reinforcing ring, 
           411   a  One end in axial direction, 
           411   b  Another end in axial direction, 
           411   c  Chamfer, 
           412  Gasket main body, 
           4121  Base portion, 
           4122  One-end-side seal bead, 
           4123  Other-end-side seal bead, 
           413  Supportable portion, 
           420  Housing, 
           421  Attachment recessed part, 
           421   a  Bottom surface, 
           421   b  Inner peripheral surface, 
           422  Gap, 
           430  Cover, 
           430   a  End surface, 
           430   c  Bulging portion for gap