SHAFT SEAL FOR A COMPRESSOR

Abstract: A shaft seal (3) for a compressor. The shaft seal (3) comprises a single integral plastics body having a flexible lip portion (31) and a relatively large holding portion (32).

Description: SHAFT SEAL FOR A COMPRESSOR This invention relates to a shaft seal for a compressor of the kind which is used in a refrigeration circuit. A typical shaft seal assembly for forming a seal around a rotary shaft projecting from a boss portion of a casing of an open type compressor is shown in Japaflese Publication No. 58-10586. This construction of shaft seal has the drawback of being very complicated. On the other hand, a seal assembly incorporating a lip seal, and of the kind which has been used as an oil seal, has recently been used as a shaft seal for such a compressor. Figure 1 of the accompanying drawings shows one example of such an assembly. Thus the assembly 10 includes a lip element 11, which is a ring made from a thin body of flexible material, and two annular casings 12, 13 which have L-shaped cross-sections. An inner lip portion of the lip element 11 bears against the outer surface of a rotary shaft 2. The lip element 11 and an O-ring 16 are supported between the casings 12 and 13 and the O-ring 16 forms a seal between casings 12, 13 and lip element 11. The seal assembly 10 is inserted into the bore of a boss 1 and is held against a shoulder 17 in the bore through an O-ring 14 and a snap ring 15. When such a construction of oil seal is used as a shaft seal for an open type compressor, an O-ring 16 is needed to seal between casings 12, 13 and lip 11 because a large pressure difference exists between the inside and the outside of the compressor housing. Thus, because the number of parts is large in this type of seal assembly efficient assembly, miniaturization, low cost and high reliability cannot be achieved. It is an overall object of the present invention to provide a shaft seal for an open type compressor which is easy to assemble and economical to manufacture. It is another object of the present invention to provide such a shaft seal which can be miniaturized and is highly reliable in operation. The present invention is directed to a shaft seal for an open type compressor. The seal element forms a seal about a rotary shaft which extends in the direction of its rotary axis from the inside of the housing of the compressor into a hole in a boss outside the housing. A pressure difference exists, in use, on opposite sides of the seal element. The seal element comprises an integral body of plastics material. The body includes at least one flexible lip portion for sealingly contacting fully around an outer surface of the rotary shaft, and a holding portion from which the flexible lip extends. The holding portion has an axial dimension larger the thickness of the lip portion to form an extended axial support surface around the outer circumference of the holding portion. The invention will be explained more fully by reference to the accompanying drawings, in which: Figure 1 is an axial sectional view of a seal assembly currently in use; and, Figures 2 to 6 are similar axial sectional views, each illustrating a different example of a seal assembly with a shaft seal constructed in accordance with the present invention. Figure 1 shows a lip seal element 3, which comprises of a lip portion 31 and a holding portion 32 formed from a single integral piece of resilient plastics material. The element 3 forms a seal about a rotary drive shaft 2 of an open type compressor. The shaft 2 extends from the inside of a compressor housing, shown diagrammatically in dash-line as 5, to within a hole 6 in a boss 1 which is outside the compressor housing 5. During operation of the compressor, a large pressure difference exists between the area inside the compressor housing 5 and the area outside the housing 5. The holding portion 32 is formed as a sufficiently large body or mass to function as a stable support for the lip portion 31 without the need for the supplemental supporting structures to support the seal assembly such as are illustrated in Figure 1. The axial length 1 (dimension in the direction of the rotary axis of shaft 2) of the holding portion 32 is thus substantially greater, for example, at least seven times greater, than the thickness t of the lip portion 31. Also, the holding portion 32 has a relatively large radial dimension. The relatively large axial dimension of the holding portion 32 results in an extended axial support surface, around the outer circumference of the holding portion 32, which faces the inside of an enlarged diameter bore 7 of the hole 6, within which the holding portion 32 is received. The outside axial end of the holding portion 32 abuts a shoulder formed at the end of the bore 7, and is held therein by an O-ring 4 carried in a groove 9 in the exterior surface (the extended axial support surface) of the holding portion 32. The radial thickness of the holding portion 32 is greater than the depth of the shoulder. Because of the relatively large size of holding portion 32, i.e., its axial and radial dimensions, particularly its large axial dimension, the seal element 3 can be held within the bore 7 of the boss 1 by the O-ring 4 without the need of additional support parts. The lip portion 31 and holding portion 32 are formed as a single integral body of one plastics material. The lip portion 31 thus bears flexibly and with equal force around, and thus sealingly contacts, the full periphery of the outer surface of the rotary shaft 2. The lip portion 31 is formed at the end of the holding portion 32 which faces the inside of the housing 5; and the end of the lip portion 31 extends in the direction towards the inside of the housing 5. In each of the views, the right hand side of the element 3 is the inside of compressor housing 5 and the left side is the outside of the compressor housing 5. Because the element 3 is formed as a single integral body, and is held in the bore 7 by the O-ring 4, its construction is simple and it is easy to assemble. Furthermore, the element 3 effectively seals between the inside and the outside of the compressor. Other different examples are shown in Figure 3 to 6, with various components indicated by numerals followed by the suffixes A, B, C and D. Referring to Figure 3, the lip seal element 3A comprises a lip portion 31A and a holding portion 32A, again formed as a single integral plastics body. The lip portion 31A is formed at the end of the holding portion 32A, which is located facing the outside of the housing 5A. The end of lip portion 31A, however, bends back and extends in the direction towards the inside of the housing 5A, and sealingly contacts the entire outer surface of the rotary shaft 2A. Referring to Figure 4, the lip seal element 3B comprises lip portions 31B, 33B and a holding portion 32B, formed as a single integral plastics body. The lip portions 31B, 33B both bear flexibly, and each with equal force about, and thus sealing contact, the entire outer surface of the rotary shaft 2B. The lip portion 31B is located at the axial end of holding portion 32B facing the outside of the housing SB; and the lip portion 33B is located at the opposite axial end of the holding portion 32B facing the inside of the housing 5B. The end of the lip portion 31B extends in the direction towards the outside of the housing 5B and the end of the lip portion 33B extends in the direction towards the inside of housing 5B. Referring to Figure 5, the lip seal element 3C comprises lip portions 31C, 33C and a holding portion 32C, formed as a single integral plastics body. The lip portions 31C, 33C bear flexibly and with equal force about, and thus sealing contact, the entire outer surface of the rotary shaft 2C. Both the lip portions 31C and 33C are formed at the end of the holding portion 32C facing the outside of the housing 5C. The end of the lip portion 31C extends in the direction towards the outside of the housing 5C; and the end of the lip portion 33C extends in the direction towards the inside of the housing 5C. Referring to Figure 6, the lip seal element 3D comprises lip portions 31D, 33D and a holding portion 32D, formed as a single integral plastics body. The lip portion 31D bears flexibly and with equal force about, and thus sealingly contacts, the entire outer surface of the rotary shaft 2D; and the lip portion 33D bears flexibly and with equal force about the entire outer surface of the lip portion 31D to increase the contact sealing force of the lip portion 31D on the shaft 2D. The lip portion 31D is formed at the end of the holding portion 32D facing the outside of the housing 5D and the lip portion 33D is formed inwardly of the lip portion 31D close to the axial centre of the holding portion 32D. The ends both of the lip portions 31D, 33D extend in the direction towards the inside of the housing 5D.

Claims: CLAIMS 1. A shaft seal element (3) for forming a seal about a rotary shaft (2) which extends from the inside of a housing (5) of an open type compressor into a hole (6) in a boss (1) outside the housing; the seal element (3) comprising an integral annular body of plastics material which provides at least one flexible lip portion (31,33) for sealingly contacting fully around the rotary shaft, and a holding portion (32) from which the lip portion extends, the holding portion having an axial dimension larger than the thickness of the lip portion to form an axially extending support surface around the outer periphery of the holding portion for use in mounting the seal element in the hole (6) in the boss (1). 2. A shaft seal element according to claim 1, wherein the support surface includes a groove (9) for holding an O-ring (4) for engaging an inner peripheral surface (7) of the hole (6) in the boss (1) to hold the element in the boss. 3. A shaft seal element according to claim 1 or claim 2, wherein the lip portion (31,73) is formed at an axial end of the holding portion (32). 4. A shaft seal element according to any one of the preceding claims, wherein there are two of the lip portions (31B,33B) each extending from a respective axial end of the holding portion (32B), the ends of the lip portions extending in opposite axial directions. 5. A shaft seal according to any one of claims 1 to 3, wherein there are two of the lip portions (31C,33C) both extending from one axial end of the holding portion (32C) the ends of the lip portions extending in opposite axial directions. 6. A shaft seal element according to claim 4 or claim 5, wherein the ends of the lip portions (31B,33Bt 31C,33C) extend away from one another. 7. A shaft seal according to any one of claims 1 to 3, wherein there are two of the lip portions (31D,33D) extending at axially spaced locations from the holding portion (32D), the ends of both of the lip portions extending in the same axial direction. 8. A shaft seal according to claim 7, wherein one of the lip portions (33D) overlies and contacts a radially outer surface of the other lip portion (31D). 9. An open type compressor comprising a housing (5), a rotary shaft (2) which extends out of the housing into a hole (6) in a boss (1) outside the housing, and a shaft seal element (3) according to any one of the preceding claims mounted in the hole in the boss with its lip portion (31,33) sealing against the shaft. 10. A compressor according to claim 9, wherein the shaft seal element (3) is held in position by means of an O-ring (4) which is interposed betwen the support surface of the element and an inner peripheral surface (7) of the hole (6) in the boss (1). 11. A compressor according to claim 9 or claim 10, wherein the, or at least one of the, lip portions (31,33), extends axially towards the interior of the housing.

Inventors: TERAUCHI, KIYOSHI
Applicants: SANDEN CORPORATION
Application year: 1985
Main classification: F16J15
IPC codes: F16J15, F04B39