Abstract:
A method of sealing at least a first seal surface to a second seal surface comprises the steps of placing a flexible ring member between the first and second seal surfaces and juxtaposing the first and second seal surfaces. The flexible ring member is compressed between the first and second seal surfaces. Thereafter, the flexible ring member is expanded into at least one of a first recessed area in the first seal surface and a second recessed area in the second seal surface, with at least one of the first and second recessed areas having a plurality of spaced apart pressure points that contact the ring member. This method of sealing assures that when the O-ring (flexible ring) permanently sets over time, it takes the shape that makes the seal effective for a long time under high temperature, high pressure.

Description:
BACKGROUND OF THE INVENTION 
     The present invention generally relates to apparatus and methods of sealing surfaces to one another. More particularly, the present invention relates to apparatus and methods that allow for the use of standard O-rings that can seal static surfaces under changing conditions such as high temperature and pressure exposure. 
     In a variety of environments, two static surfaces oftentimes need to be sealed to one another. For example, compressors in vapor cycle systems of environmental control systems need to be hermetically sealed to prevent the escape of refrigerants. Currently, elastomer O-rings provide hermetic seals but they permanently set after exposure to high temperature and clamp load during operation. Consequently, refrigerant leakage occurs after a relatively short period of time. Leakage is aggravated by the movement of mating sealing surfaces when the compressor is under temperature and pressure. Of course, leakage leads to less than optimal performance. And the need to change O-rings leads to higher maintenance costs. 
     Numerous efforts have been made to improve sealing between static surfaces and between dynamic surfaces. One example of an effort to seal pipes inserted into holes in members such as manholes is found in U.S. Pat. No. 4,199,157. To prevent seal blowout, a two part sleeve gasket fits between the pipe and the hole. A first part of the gasket includes a tubular body portion that contacts the pipe and an outwardly curved flange radially spaced from the body portion and that contacts the hole. The second part of the gasket includes an O-ring that surrounds the body portion in the radial space defined by the flange. The cross-section of the O-ring is greater than the free radial space between the flange and the body portion so that the flange and body portion are expanded into engagement with the pipe and hole. A disadvantage to this design is its complexity, as well as the need for multiple parts. This design requires a specially shaped component that will be more expensive to fabricate compared to a standard O-ring seal. Also, this design will eventually leak when the elastomeric component permanently sets under pressure and/or temperature over time. 
     Another example of attempting to prevent seal blowout in the context of sealing a cylinder within a bore is found in U.S. Pat. No. 5,603,511. A seal element is moved from one axial position, up a ramp, and to a second axial position. In the second position, the seal assembly expands to contact the inside of the bore. An anti-extrusion element also contacts the inside of the bore and the seal element to prevent blowout of the seal element. The complex design of having to move the seal, however, presents a disadvantage and would not be practical to employ in varying applications. Specially designed components and complexity of assembly also make this design expensive and cumbersome to use, especially if the part needs to be reworked and the seal replaced. 
     In U.S. Pat. No. 4,614,348, a two component seal is provided for a fluid coupling in a pressurized fluid system having male and female parts. The male part includes a recess having a somewhat rectangular configuration. One part of the seal is an annular body having a U-shaped cross-section that defines a recess. The annular body fits within the recess of the male part such that the two extended portions of the annular body face towards the male part. The second part of the seal is an O-ring that fits within the recess of the annular body. Thereby, the O-ring sealingly engages the recess of the male part. Again, a disadvantage to this design is its complexity, the need for multiple parts, and the absence of addressing the effects of seal permanent set. Also, multiple parts and the use of specially shaped components make this part expensive. 
     FIG. 1 depicts a prior art design found, for example, in a compressor  10 . For purposes of illustration, the compressor  10  may include a first component  11  and a second component  12  that interface one another. The first component  11  includes a first seal surface  13  and the second component  12  includes a second seal surface  14 . With the first and second components juxtaposed to one another, a leakage inlet  15  may allow pressure to pass between the components  11 ,  12  and exit through a leakage outlet  16 . To prevent such leakage, the first component  11  has a recess  17  with a substantially rectangular cross section. Accordingly, each of the walls of the recess  17  is substantially planar. An O-ring  18  is disposed in the recess to block the flow of pressure from the leakage inlet  15  and to the leakage outlet  16 . As described above, however, this design is susceptible to pressure leakage over time, particularly when the compressor  10  is subject to high pressure, high temperature, and movement of the first and second seal surfaces  13 ,  14 . 
     A variation of the design in FIG. 1 is shown in U.S. Pat. No. 4,477,223 for a rotating shaft within a bore of a compressor. A non-rotating ring is disposed between the shaft and bore. An annular recess in the ring has an arcuate cross section. The annular recess interfaces a recess in the bore and has a rectangular cross section. An O-ring is held between the two recesses where one of the recesses is offset to deform the ring causing it to exert an axial force on a non-rotating cylinder against a rotating ring. This seal arrangement uses the O-ring to force a stationary part against a rotating part to effect the seal between the stationary and rotating parts. Furthermore, it does not take into consideration the eventual setting of the O-ring which will eventually render the seal ineffective. 
     As can be seen, there is a need for an improved apparatus and method of sealing surfaces together. A further need is for an apparatus and method that not only provides sealing but is simple in design and minimizes manufacturing costs. Yet another need is for an apparatus and method that can be implemented into existing components with limited changes to the design of such components. A still further need is for an improved method and apparatus that prevents leakage between mating surfaces over extended periods of time. An apparatus and method are needed that can block leakage between mating surfaces under conditions of high pressure, high temperature and movement of the mating surfaces. 
     SUMMARY OF THE INVENTION 
     In one aspect of the present invention, a method of sealing at least a first seal surface to a second seal surface comprises the steps of placing a flexible ring member between the first and second seal surfaces; juxtaposing the first and second seal surfaces; and creating a plurality of spaced apart pressure points in the first and second seal surfaces such that the pressure points contact the ring member. 
     In another aspect of the present invention, a seal surface for interfacing a flexible ring member comprises a recessed area having a plurality of recesses into which the ring member can expand; and a plurality of spaced apart pressure points in said recesses that contact the ring member. 
     These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of a prior art design of using an O-ring between mating surfaces; 
     FIG. 2 a  is a cross-sectional view of two embodiments of the present invention in the context of a compressor; 
     FIG. 2 b  is a cross-sectional view of a first embodiment of the present invention shown in FIG. 2 a;    
     FIG. 2 c  is a cross-sectional view of a second embodiment of the present invention shown in FIG. 2 a;    
     FIG. 3 is a cross-sectional view of a third embodiment of the present invention; 
     FIG. 4 is a graph of leak rate versus time for the prior art design of FIG.  1  and the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     While the present invention is described in the context of a compressor, the invention is not intended to be so limited. Rather, the present invention may be useful in the general context of two or more seal surfaces. Typically, the seal surfaces will be static. For example, the apparatus and method of the present invention may be used in pressurized vessels to prevent the escape of pressure or in components/systems containing two or more separate fluids/mediums to prevent them from mixing together. 
     FIG. 2 a  depicts a cross-sectional view of a portion of a device or compressor  30 . For purposes of illustration, the compressor  30  includes a first component  37 , a second component  38 , a third component  39 , and fourth component  40 , all of which are juxtaposed to one another at various seal surfaces. The first component  37  includes a seal surface  31  subtended by a wall surface  31   a;  the second component  38  includes seal surfaces  32 ,  33 ; the third component  39  includes a wall surface  44 , and the fourth component  40  includes a seal surface  34 . The seal surface  31  mates to the seal surface  32 . The seal surface  33  mates to the seal surface  34 . 
     With the first, second, third, and fourth components  37 - 40  juxtaposed, and again for purposes of illustration, leakage inlets  35  and  36  are respectively created between second and third components  38 ,  39  and between first and third components  37 ,  39 . A pressurized fluid from within the compressor  30  may enter the leakage inlets  35  and  36 , and then exit the compressor  30  through a leakage outlet  42 . A leakage inlet  41  between the second and fourth components  38 ,  40  can allow pressure leakage out of a leakage outlet  43 . 
     In still referring to FIG. 2 a,  pressure leakage out of the leakage outlet  42  is prevented, in part, by a flexible ring member or O-ring  49 . The O-ring  49  is disposed in a recessed area described below to block the flow/pressure escape from the leakage inlets  35  and  36  to the leakage outlet  42 . The O-ring  49  is of any well known, simple design and can be made of flexible materials such as neoprene, nitrile, viton or rubber. Likewise, leakage out of the leakage outlet  43  is prevented, in part, by a flexible ring member or O-ring  50 . 
     As better seen in FIG. 2 b,  and in one embodiment of the present invention, the seal surface  31  of the first component  37 , the seal surface  32  of the second component  38 , the wall  31   a  subtending the seal surface  31 , and the external wall surface  44  of the third component  39  surround the O-ring  49 . In contrast to the prior art which has one recess area and one planar seal surface, the first component  37  comprises a recessed area  51  having a plurality of recesses or recessed sections  55 ,  56 , together with a divided seal surface  31  (i.e., divided by recess  56 ). In other words, the recesses  55 ,  56  are within a larger recess  51 . The recess  55  has a substantially rectangular cross-section in this embodiment and is characterized by a cross-sectional recess dimension d 55  that is less than the cross-sectional dimension of the O-ring  49 . The recess  56  has a partially arcuate cross-section in this embodiment and is characterized by a cross-sectional recess dimension d 56  that is less than the cross-sectional dimension of the O-ring  49 . 
     In still referring to FIG. 2 b,  it can be seen that the creation of the recessed area  51  provides a plurality of spaced apart pressure points  63  that contact the O-ring  49 . This is in contrast to the prior art which provided an expanded surface area that was typically planar or, in other words, contiguous pressure points that contacted an O-ring. The pressure points  63  are spaced apart so that the O-ring  49  can expand between the points  63  and, thereby, create specific points at which pressure leakage is blocked. For example, the O-ring  49  may expand into the recessed section  56  and specifically between the pressure points  63  when the seal  49  is compressed by seal surfaces  31 ,  32 . 
     Similarly, the seal surface  32  of the second component  38  is configured with a recessed area  52 . However, unlike the recessed area  51 , the recessed area  52  only includes a single recess or recessed section  58  that is of a configuration similar to the recess  56 . The recessed section  58  is characterized by a cross-sectional recess dimension d 58  that is less than the cross-sectional dimension of the O-ring  49 . The recessed section  58  provides a plurality of spaced apart pressure points  64  that function in a fashion similar to the pressure points  63 . Recessed section  58  functions in conjunction with recessed section  56 . 
     In contrast to the seal surfaces  31 ,  32 , it can be seen in FIG. 2 b  that the external wall surface  44  is not configured with a recessed area. However, the present invention contemplates that the wall surface  44  can include a recessed area. Therefore, and in accordance with the present invention, not all of the surfaces that contact the O-ring need to have recessed areas. The total volume created by recessed areas  51 ,  52  is equal to the volume of the current standard O-ring groove configuration. 
     FIG. 2 c  depicts a second embodiment of the present invention wherein the seal surface  33  of the second component  38 , the sidewalls  33   a,    33   b  subtending the seal surface  33 , and the seal surface  34  of the fourth component  40  surround the O-ring  50 . Again in contrast to the prior art having one recess area with one planar seal surface, the second component  38  comprises a recessed area  53  having a plurality of recesses or recessed sections  59 ,  60 , together with a divided seal surface  33  (i.e., divided by recess  60 ). The recess  59  has a substantially rectangular cross-section and a cross-sectional dimension that is less than the cross-sectional dimension of the O-ring  50 . The recess  60  is configured and dimensioned similar to the recess  56 , although the configurations and dimensions between the recesses  56 ,  60  can be different. As with the above embodiment, the recessed area  53  provides a plurality of spaced apart pressure points  65  that contact the O-ring  50 . 
     In this second embodiment, the seal surface  34  of the fourth component  40  is configured with a recessed area  54  having a single recess or recessed section  62 . The recessed section  62  is configured and dimensioned similar to the recessed section  60 . However, different configurations and dimensions can be used for the recessed section  60 ,  62 . The recessed area  54  further includes a plurality of spaced apart pressure points  66 . 
     A third embodiment of the present invention is shown in FIG. 3 which is similar to the second embodiment but with a different configuration for the recessed areas. The second component  38  is juxtaposed to the fourth component  40  to create the leakage inlet  41  and the leakage outlet  43 . The seal surface  33  of the second component  38  provides a recessed area  47  having a plurality of recesses or recessed sections  47   a,    47   b.  The recesses  47   a, b  are rectangular in configuration and each has a cross-sectional dimension that is less than the cross-sectional dimension of the O-ring  50 . The recessed area  47  further includes a plurality of separated pressure points  47   c.  Similarly, the seal surface  34  of the fourth component  40  provides a recessed area  48  having plurality of recesses or recessed sections  48   a,    48   b,  and a plurality of pressure points  48   c.    
     While the above describes certain embodiments of the present invention, it should be understood that the scope of the invention is not so limited. For example, the seal surfaces ( 33  or  34 ) may include more than two recesses with spaced apart pressure points. The recesses ( 55 - 62 ) may have the same or dissimilar configurations, as well as configurations other than rectangular or partially arcuate, such as triangular or irregularly shaped polygon. The number of pressure points ( 63 - 66 ) can also vary, as well as the distance between them. The pressure points are preferably not sharp and may either be broken edge/champered or rounded corner. 
     In view of the above, it can also be seen that the present invention involves a method of sealing at least two seal surfaces together. An O-ring ( 49 ,  50 ) is placed between a first seal surface ( 31 ,  33 ) and a second seal surface ( 32 ,  34 ). The first and second seal surfaces ( 31 - 34 ) are then juxtaposed to one another. The O-ring ( 49 ,  50 ) is compressed in recess areas  55 ,  59 ,  47   b  and  48   b,  and then allowed to expand into at least one of the smaller recessed areas ( 56 ,  58 ,  60 ,  62 ,  47   a,    48   a ) provided by the first and second seal surfaces ( 31 - 34 ). More specifically, the O-ring expands into at least one recess ( 56 ,  58 ,  60 ,  62 ,  47   a,    48   a ) within the recessed areas. Further, the O-ring ( 49 ,  50 ) expands between separated pressure points ( 63 - 66 ) and contacts the O-ring. By such contact, the O-ring ( 49 ,  50 ) is retained within the recesses ( 55 - 62 ). 
     EXAMPLES 
     FIG. 4 depicts the performance of the present invention as compared to a prior art design. The embodiments shown in FIGS. 2 b,    2   c  and  3  were compared to the design shown in FIG.  1 . The present invention and the prior art design were subjected to pressures at 115 and 150 psi. FIG. 4 indicates that the prior art design had much greater leak than the present invention after 25 hours at pressure, and the present invention continued to have no leak after over 150 hours (with the graph lines for the present invention overlaying one another). 
     As can be appreciated by those skilled in the art, the present invention provides an apparatus and method that not only provides sealing but is simple in design and minimizes manufacturing costs. The present invention can be implemented into existing components with limited changes to the design of such components. It also prevents leakage between mating surfaces over extended periods of time. The present invention can also block leakage between mating surfaces under conditions of high pressure, high temperature and movement of the mating surfaces. 
     It should be understood, of course, that the foregoing relates to preferred embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.