Patent Publication Number: US-2004046329-A1

Title: Sealing ring

Description:
[0001] This application claims the benefit of U.S. Provisional Application No. 60/408,426 filed Sep. 5, 2002 which is incorporated by reference herein for all purposes as if fuly set forth. 
    
    
     
       BACKGROUND OF THE INVENTION  
       [0002] 1. Field of the Invention  
       [0003] This invention relates to a sealing ring, and more particularly to an expandable sealing ring made of a synthetic material.  
       [0004] 2. Description of the Related Art  
       [0005] Sealing rings are used in mechanical devices for creating a seal between a shaft or rod and a bore, as for example in compressors, automatic transmissions, and power steering devices. A seal ring is generally of an open annular shape and is mounted on a circumferential groove of a shaft or rod that is situated within a cylindrical housing. The function of the seal ring is normally to control the leakage of fluid from one side of the ring to the other side while allowing the shaft or rod to turn or pulsate within the cylindrical housing.  
       [0006] Seal rings have been made with joints that allow the rings to expand or contract with expansion or contraction of the shaft or rod on which the seal ring is mounted, as occurs for example during thermal expansion or contraction of the shaft. The joints of such expandable seal rings have been made with various geometrical configurations according to which the open gap between ends of the ring is minimized when operating in the housing. Existing joint arrangements for seal rings include butt joints, scarf joints and step joints. International patent publication no. WO 96/21116 discloses a plastic sealing ring with a separating cut configured as a step-shaped overlap in which the mutually overlapping ring ends lie against each other along a sliding surface. Such overlapping sealing ring ends result in rings with relatively constant gaps that, for a given temperature range, are more or less independent of the coefficients of thermal expansion of the shaft, the housing and the sealing ring.  
       [0007] When existing expandable sealing rings expand, the overlapping ends tend to bow outward which causes the ends of the ring to press against the bore. This results in uneven wear on the rings, making more frequent replacement of the rings necessary. This increases down time as well as maintenance and material costs. Accordingly, there is a need for an expandable sealing ring with overlapping ends that maintains a round shape upon expansion and contraction. There is a further need for such expandable sealing rings that do not bow out upon expansion or contraction, especially where the ring is made of a synthetic polymer material such as plastic.  
       SUMMARY OF THE INVENTION  
       [0008] The present invention relates to a synthetic annular sealing ring. The ring has a break therein with first and second complementary ends defining opposite sides of the break. An internally directed annular section of the ring has a first internal tongue protruding from the first ring end and a first internal slot formed in the internally directed section at the first ring end. The internally directed annular section has a second internal tongue protruding from the second ring end and a second internal slot formed in the internally directed section at the second ring end. The first internal tongue is aligned to fit into the second internal slot, and the second internal tongue is aligned to fit into said first internal slot. An externally directed annular section of the ring has a first external tongue abutting the first internal tongue and protruding from the first ring end, and a first external slot formed in the externally directed annular section at the first ring end and abutting the first internal slot. The externally directed annular section also has a second external tongue abutting said second internal tongue and protruding from the second ring end, and a second external slot formed in the externally directed annular section at the second ring end and abutting the second internal slot. The first external tongue is aligned to fit into the second external slot, and the second external tongue is aligned to fit into the first external slot. The first and second internal tongues are each longer than both of the first and second external tongues in the annular direction of the ring. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0009]FIG. 1 is a perspective view of the sealing ring of the invention as viewed from a point in front of and above the sealing ring;  
     [0010]FIG. 2 is a perspective view of the sealing ring shown in FIG. 1 as viewed from a point in front of and below the sealing ring;  
     [0011] FIGS.  3 A- 3 C are each a detailed perspective view of the locking portion of the sealing ring shown in FIGS. 1 and 2, as viewed from the bottom of the ring. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0012] A sealing ring according to the present invention is illustrated in FIG. 1. The sealing ring  10  is shown mounted on a cylinder C. The sealing ring  10  is preferably comprised of a synthetic material such as a polymer resin. Sealing ring  10  has an internally directed annular section  12  surrounded by an externally directed annular section  14 . The sealing ring  10  has a break  16  defined by a first end  18  and a second end  20 . According to the preferred embodiment of the invention, ring ends  18  and  20  are generally complementary ends that define opposite sides of the break  16 .  
     [0013] In the embodiment of the invention shown in FIGS.  1 - 3 , the internally directed annular section  12  has a first internal tongue  22  protruding from the first ring end  18  and a first internal slot  24  formed in said internally directed section at said first ring end. The internally directed annular section also has a second internal tongue  26  protruding from the second ring end  20  and a second internal slot  28  formed in the internally directed section at said second ring end. The first internal tongue  22  is aligned to fit into said second internal slot  28 , and the second internal tongue  26  is aligned to fit into said first internal slot  24 .  
     [0014] In the embodiment of the invention shown in FIGS.  1 - 3 , the externally directed annular section  14  of the sealing ring  10  has a first external tongue  30  abutting said first internal tongue  22  and protruding from said first ring end  18 , a first external slot  32  formed in the externally directed annular section  14  at the first ring end  18  and abutting the first internal slot  24 . A second external tongue  34  abuts the second internal tongue  26  and protrudes from said second ring end  20 . A second external slot  36  is formed in the externally directed annular section  14  at the second ring end  20  and abutting the second internal slot  28 . The first external tongue  30  is aligned to fit into the second external slot  36 , and the second external tongue  34  is aligned to fit into said first external slot  32 .  
     [0015] In accordance with the invention, the first and second internal tongues are each longer than both of said first and second external tongues in the annular direction of the ring. In the embodiment of the invention shown in FIGS.  1 - 3 , the first and second internal tongues  22  and  26  are each longer than both of said first and second external tongues  30  and  34  in the annular direction of the ring  10 . As used herein, the length of a tongue is the length that the thinner portion of the tongue extends in the annular direction from where thinner portion of the tongue begins. As illustrated in FIG. 3A, the length of the first internal tongue  22  is the length “A” and the length of the second internal tongue  26  is the length “C”. Similarly, the length of the first external tongue  30  is the length “B” shown in FIG. 3A, and the length of the second external tongue  34  is the length “D” shown in FIG. 3A.  
     [0016] According to a preferred embodiment of the invention, the first internal tongue and the second internal slot are complementary, and the second internal tongue and said first internal slot are complementary. In the embodiment of the invention shown in FIGS.  1 - 3 , the first internal tongue  22  and the second internal slot  28  are complementary, and the second internal tongue  26  and said first internal slot  24  are complementary. It is further preferred that the first external tongue and the second external slot be complementary, and that the second external tongue and the first external slot be complementary. In the embodiment of the invention shown in FIGS.  1 - 3 , the first external tongue  30  and the second external slot  36  are complementary, and the second external tongue  34  and the first external slot  32  are complementary. According to a preferred embodiment of the invention, the first internal tongue forms a surface of said first internal slot, and the second internal tongue forms a surface of said second internal slot. In the embodiment of the invention shown in FIGS.  1 - 3 , the first internal tongue  22  forms a surface of said first internal slot  24 , and the second internal tongue  26  forms a surface of said second internal slot  28 . In a similar manner, the first external tongue  30  forms a surface of said first external slot  32 , and the second external tongue  34  forms a surface of said second external slot  36 .  
     [0017] According to one embodiment of the invention, the first and second internal tongues are each at least 20% longer than both of said first and second external tongues in the annular direction of the ring. The first and second internal tongues may be more than 50% longer than both of said first and second external tongues in the annular direction of the ring. In the embodiment of the invention shown in FIGS.  1 - 3 , the first and second internal tongues are about three times as long as said first and second external tongues in the annular direction of the ring.  
     [0018] Preferably, the first and second internal tongues have substantially the same dimensions, and the first and second external tongues have substantially the same dimensions. In the embodiment of the invention shown in FIGS.  1 - 3 , the first and second internal tongues  22  and  26  are of substantially the same length, width and height, and the first and second external tongues  30  and  34  are of substantially the same length, width and height. Likewise, the second internal slot  28  preferably has a length, width and height that are just a fraction larger than the complementary first internal tongue  22 , and the first internal slot  24  preferably has a length, width and height that are just a fraction larger than the complementary second internal tongue  26 . Similarly, the second external slot  36  preferably has a length, width and height that are just a fraction larger than the complementary first external tongue  30 , and the first external slot  32  preferably has a length, width and height that are just a fraction larger than the complementary second external tongue  34 . As used herein, the length of a slot is the length that the open space of the slot extends in the annular direction from where the open slot begins. As illustrated in FIG. 3A, the length of the first internal slot  24  is the length “A” and the length of the second internal slot  28  is the length “C”. Similarly, the length of the first external slot  32  is the length “B” shown in FIG. 3A, and the length of the second external slot  36  is the length “D” shown in FIG. 3A.  
     [0019] According to a preferred embodiment of the invention, the first and second internal tongues, the first and second internal slots, the first and second external tongues, and the first and second external slots each have substantially rectangular cross sections. More preferably, the first and second internal tongues, the first and second internal slots, the first and second external tongues, and the first and second external slots each have square cross sections as shown in FIGS.  1 - 3 . It is further preferred that the synthetic annular ring have an internally directed surface that is substantially concentric with an externally directed surface of the synthetic annular ring. In the embodiment of the invention shown in FIGS. 1 and 2, the internal surface of the internal annular section  12  is concentric with the external surface of the external annular section  14 . It is further preferred that the sealing ring have a substantially rectangular cross section, and still further preferred that the sealing ring have a square cross section.  
     [0020] According to the preferred embodiment of the invention, the sealing ring is comprised of a high performance polymer. It is further preferred that the sealing ring is comprised of a synthetic polymer that is resistant to high temperature, has a high melting point, has high compressive strength, and is not brittle. It is further preferred that the sealing ring be comprised of a material that has a low coefficient of thermal expansion and a low coefficient of friction. Preferred polymers include one or more polymers selected from the group of polyimide, Poly-ether-etherketon (“PEEK”), Poly-amide-imide (“PAI”), poly-ether-keton-keton (“PEKK”), Poly-ether-keton (“PEK”), Thermoplastic-polyimide (“TPI”), fluoropolymers such as polytetrafluorethylene (“PTFE”) or perfluoroalkoxy (“PFA”), polyetherimide (“PEI”), polyphenylene sulfide (“PPS”), polysulfones, polyether sulfones (“PES”), and liquid crystal polymer (“LCP”). More preferably, the sealing ring is comprised of a polyimide such as a Vespel® thermoplastic material sold by E.I. du Pont de Nemours and Company of Wilmington, Del. Preferably, the sealing ring of the invention is produced by injection molding, but it may alternatively be produced by other know methods.  
     [0021] The sealing ring of the invention that has been described above has the advantage that the two seal ring ends lock with each other in a manner that allows the ring to maintain the preferred ideal circular shape when the two ends of the ring are locked and overlapped so as to achieve the sealing function. With the sealing ring of the invention, the ideal circular shape is maintained independent of radial loading.