GB2054769A

GB2054769A - Sliding face seal

Info

Publication number: GB2054769A
Application number: GB8020111A
Authority: GB
Original assignee: IAO Industrie Riunite SpA
Current assignee: IAO Industrie Riunite SpA
Priority date: 1979-06-26
Filing date: 1980-06-19
Publication date: 1981-02-18
Also published as: FR2459927A1; ES251661U; DE3021542A1; IT1119008B; IT7968358A0

Abstract

A sliding face seal, for use in a motor vehicle engine water pump, has a cylindrical housing 10 with an open end and an annular bottom 12 at the other end. A rigid graphite ring 14 is located within the open end of the housing and is movable axially but not rotatably therein. Between the ring 14 and the annular bottom 12 of the housing 10 there is a circular bell spring of elastomeric material, the base of the bell spring being in contact with the ring 14 and the free edge of the bell spring closely fitting into the housing 10 adjacent the annular bottom 12. A helical spring 18 compresses the base of the bell spring against the ring 14. In use, pressure from the impellor against the front face 14' of the ring causes increased sealing pressure between the base of tile bell spring and the rear face 14'' of the ring and also axial compression of the bell spring, resulting in increased sealing at 16A between the bell spring and the housing. <IMAGE>

Description

SPECIFICATION Sliding face seal This invention relates to a sliding face seal, of the type comprising a cylindrical housing of sheet steel with an open end and with an annular bottom at the other end, a rigid ring (for example of graphite) forming the sliding face seal, which is movable axially but not rotatably, in the said housing in a position adjacent the said open end, an annular hollow element of elastomeric material forming a seal between the said ring and the bottom of the housing, and a helical spring coaxial with the ring and with the said annular element, disposed in the housing for pressing the ring elastically towards the said open end.

Seals of the above specified type are particularly applied between the casing and the hub of the impellor in circulation pumps for cooling water in motor vehicles. In this case the seal surrounds the shaft of the impellor and the ring is in sealing contact with a front surface of the hub under the pressure of the said helical spring.

In known seals of the above specified type the annular element of elastomeric material has the form of a circular bellows with inwardly flanged edges, and the helical spring is enclosed in the bellows for reacting against the said flanged edges. For this reason both the pressing of the annular elastomeric element and the assembly of the seal are difficult and delicate. Moreover, very often it is necessary for the bellows to have internal reinforcement elements, such as, for example, steel cups telescopically interengaging with one another, and this again makes the manufacture both difficult and expensive.

According to the present invention there is provided a sliding face seal comprising a cylindrical housing with an open end and an annular bottom at the opposite end, a rigid sliding face seal ring movable axially but not rotatably in the housing in a position adjacent to the open end, a hollow annular element of elastomeric material forming a seal between the ring and the bottom of the housing, and a helical spring coaxial with the ring and with the annular element disposed in the housing to press the ring resiliently towards the open end, the annular element of elastomeric material being constituted by a bell spring having no undercut portions and working under axial compression between the said ring and the bottom of the housing, the free edge of the bell spring being in circumferential sealing contact with the region of connection between the bottom and the lateral wall of the bell, the bell wall of the bell spring being convex towards the lateral wall of the housing in such a way that the area of sealing contact with the lateral wall of the housing increases progressively with compression of the bell spring.

Since the bell spring is devoid of undercut parts, its pressing is simple and its sealing surfaces do not suffer from the risk of being damaged during formation. Moreover, assembly of the seal does not present further difficulty or risk of damage to the component. Further, and in contradistinction with the simple bellows, the bell spring is robust and does not require added reinforcement and centering members. Further again, when the seal is mounted, for example, in a circulation pump, the pressure of the hub against the ring axially compresses the bell thus automatically increasing the sealing contact between the bell and the housing of the seal.

Further characteristics and advantages of the seal according to the invention will become apparent from the following description with reference to the attached drawings, provided by way of example, in which: Fig. 1 is an axial section of an embodiment of the seal; Fig. 2 is a plan view according to the line Il-Il of Fig. 1, and Fig. 3 illustrates the seal in a position mounted in a water pump.

In the drawings, there is indicated a cylindrical circular housing 10 of steel having an annular bottom 12 the inner edge of which forms an inwardly turned lip 12' directed towards the interior of the housing. The face sealing ring, indicated 14, of material suitable for forming a sliding seal, for example graphite, is disposed in the housing 10 close to the open end of the latter.

The ring 14 has, in a known way, a polished front sliding seal face 14' and a polished rear face 14" parallel to the face 14'. The ring 14 has, moreover, in its periphery three notches 1 4a at 1 20O to one another, in which engage three impressions 1 OA formed in the later wall 10' of the housing, in such a way that the ring 14 is axially slidable in the housing but is prevented from rotating with respect to this, in conformity with known prlor art.

A circular bell spring 16, of rubber or other suitable elastomeric material, is interposed between the ring 14 and the bottom 1 2 of the housing, with the hollow interior facing towards the bottom. The bell spring comprises a bell wall 1 6A having no undercut parts, extending from an annular base 1 6B adjacent to the ring 14. The face of the base 1 6B in contact with the ring has a plurality of concentric ribs 16' which, in use, are in sealing contact with the face 1411 of the ring.

Alternatively, if desired, the base 1 6B of the bell spring could be glued or vulcanised to the ring, es convenient. The maximum diameter of the bell wall 1 6A corresponds substantially to the inner diameter of the housing i 18, and therefore the bell spring is centered in the housing by the fact that its free edge 1 6" engages, when mounted, in the region 12" of connection between the bottom 12 and the lateral wall 1 0' of the housing. Preferably, the said edge 1 6' is rounded in transverse section and has within it a reinforcing bead wire 17 constituted, for example, by a ring of steel wire.

The bell wall 1 6A has a slight convexity towards the lateral wall 10' of the housing and its thickness is calculated in such a way (known per se) that it works under axial compression, in contradistinction with a bellows the walls of which work under flexion. Between the base 1 EB of the bell spring and the bottom 12 is interposed a helical spring 18, maintained centred by the lip 12'.

In the assembled condition, illustrated in Figure 1 , the ring 14 is retained in the housing 10 by three tabs 20 punched from the free edge of the housing, which retain the ring at a level such that both the bell spring 1 6 and the helical spring 1 8 are lightly precompressed by the ring 14 against the bottom 12 of the housing. This establishes an initial sealing contact both between the ribs 16' and the ring 14, and between the edge 1 6" of the bell wall 1 6A and the housing 10, in such a way that possible subsequent penetration bv foreign particles into the interior of the housing cannot prejudice the seal formed in use.

In Figure 3 there is indicated the impellor 22 of a circulation pump, having a hub 24 and a drive shaft 26. This latter extends towards the outside through a circular bore 28 in the casing 30'of the pump and is supported in a known way by a bearing (not illustrated) mounted in the said bore.

The bore 28 is enlarged on the side facing the impellor to form a circular seat 28A into which is sealingly forced the housing 10 of the seal according to Figure 1. The hub 24 has, facing the seal, a polished annular face 24' which, in the working conditions illustrated, is in sliding sealing contact with the face 14' of the ring 14. When, upon assembly, the shaft 26 is inserted through the seal (towards the bottom in Figure 3) to assume its final illustrated position, the face 24' of the hub 24 presses the ring 14 towards the interior of the housing 10, thus producing an axial compression of the helical spring 1 8 and of the bell wall 1 6A of the bell spring 16. Upon further compression, the bell wall 1 6A swells and progressively enlarges so that the circumferential area of sealing contact of this wall with the part 10' of the housing 10 progressively increases to the desired degree. Preferably, in the bottom 12 of the housing 10 there is impressed an internal circumferential rib 1 2A, which closely engages the inside of the edge 16" of the bell wall 1 6A to improve the seal in the connection region 12" just mentioned.

Claims

CLAIMS:

1. A sliding face seal comprising a cylindrical housing with an open end and an annular bottom at the opposite end, a rigid sliding face seal ring movable axially but not rotatably in the housing in a position adjacent to the open end, a hollow annular element of elastomeric material forming a seal between the ring and the bottom of the housing, and a helical spring coaxial with the ring and with the annular element disposed in the housing to press the ring resiliently towards the open end, the annular element of elastomeric material being constituted by a bell spring having no undercut portions and working under axial compression between the said ring and the bottom of the housing, the free edge of the bell spring being in circumferential sealing contact with the region of connection between the bottom and the lateral wall of the bell, the bell wail of the bell spring being convex towards the lateral wall of the housing in such a way that the area of sealing contact with the laterial wall of the housing increases progressively with compression of the bell spring.

2. A seal according to claim 1, in which the bell spring is partially precompressed in the said housing.

3. A seal according to claims 1 or 2, in which the free edge of the bell has a rounded transverse section.

4. A seal according to claims 1, 2 or 3, in which the inner edge of the bottom of the housing has a lip turned inwardly towards the interior of the housing, which serves as a centering memberfor the helical spring.

5. A seal according to any of the preceding claims, in which the bottom of the housing has an inner rib which closely engages within the inside of the free edge of the bell.

6. A seal substantially as described and illustrated in the accompanying drawings.