GB2077371A

GB2077371A - Rotating shaft seal

Info

Publication number: GB2077371A
Application number: GB8117142A
Authority: GB
Original assignee: IAO Industrie Riunite SpA
Current assignee: IAO Industrie Riunite SpA
Priority date: 1980-06-04
Filing date: 1981-06-04
Publication date: 1981-12-16
Also published as: IT8053271V0; DE3120795A1; FR2484043A1; FR2484043B3

Abstract

A sealing device comprising a diaphragm 18 (A-A'') carrying a lipped sealing ring 20 and having a skirt 18A, and a cap 26 which is rotatable with a shaft 10. The lips 22 and 24 of sealing ring 20 seal against hub portion 26B of cap 26 and serve to prevent leakage of lubricant and ingress of moisture and dirt, respectively. An annular packing 33 of a porous filtering material, which may be saturated with a lubricating oil, is arranged between the cap and the diaphragm to prevent the ingress of moisture and dirt to the vicinity of lip 24. Stop means, such as lugs 18A'', may be provided to prevent separation of the cap 26 from the diaphragm. In use with a shaft 10 the packing 33 is compressed and there exists an axial interference between it and the cap and diaphragm. One or both of the lips may seal against the radially extending wall of the cap. <IMAGE>

Description

SPECIFICATION Rotating shaft seal The present invention relates to a rotating shaft seal of the type comprising a rigid annular diaphragm an outer circumferential face of which forms an axially directed cylindrical fixing skirt, a lipped sealing ring of flexible polymeric material moulded onto an inner circumferential edge of the diaphragm, and a centrifuging annular cap in sealing contact with the lips of the sealing ring, which cap includes an annular disc part and cylindrical tubular hub part which extends axially from the inner circumference of the said disc part in the opposite direction to the said skirt, the free edge of the skirt having stop means projecting radially inwardly, either at separate points or over the whole of its circumference, and intended to prevent the separation of the cap from the diaphragm.

The term "rotating shaft" is intended herein not only to indicate a shaft as such, but also any member whatsoever which is rotatable in an aperture of a fixed member in which the seal in question is disposed. Thus, for the purpose of the present invention, the term "rotating shaft" also includes, for example, the inner ring of a rolling element bearing, the outer ring of which then constitutes the above mentioned fixed member.

A seal of the type indicated above is disclosed in our co-pending Application No. 7920683 (Serial No. 2030236).

The present invention aims to further improve the operation of the seal of our co-pending application and, in particular, to effectively prevent the penetration of extraneous particles such as water, dust or mud into the region of the sealing lips during use of the seal.

According to the present invention there is provided a rotating shaft seal comprising a rigid annular diaphragm, an outer circumferential face of which forms an axially directed cylindrical fixing skirt, a lipped sealing ring of flexible polymeric material moulded onto an inner circumferential edge of the diaphragm, and a centrifuging annular cap in sealing contact with the lipped sealing ring, which cap includes an annular disc part and a cylindrical tubular hub part which extends axially from the inner circumference of the said disc part in the opposite direction to the said skirt, the free edge of the skirt having stop means projecting radially inwardly, either at separate points or over the whole of the circumference, and intended to prevent separation of the cap from the diaphragm, and wherein between the rigid annular diaphragm and the centrifuging annular cap there is interposed an annular packing of porous filtering material mounted with axial interference with respect to the annular diaphragm and the disc part of the centrifuging annular cap.

Preferably the porous filtering material of the annular packing is an elastically compressible material, for example open cell expanded polyurethane, or felt.

The annular packing of porous filtering material can be saturated with a liquid lubricant or impregnated with a semi-solid lubricant.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 illustrates in partial section a first embodiment of seal according to the present invention mounted in position on an associated shaft; Fig. 2 illustrates a second embodiment of the seal in a free (unmounted) condition; Fig. 3 illustrates the embodiment of Fig. 2 mounted in position on a shaft; Fig. 4 illustrates a third embodiment in a free condition; Fig. 5 illustrates the embodiment of Fig. 4 mounted in position; Fig. 6 illustrates a fourth embodiment of seal, and Fig. 7 illustrates a fifth embodiment of seal.

Referring to Fig. 1, there is shown a rotating shaft 10 mounted in a fixed support 12 by means of a ball bearing 14. A seal according to the present invention is generally indicated 1 6. In the following description there will be described in detail only those parts of the seal 1 6 necessary for an understanding of the present invention, whilst for a more complete treatment of the other parts of the device reference can be made to our copending application mentioned above.

The seal device 1 6 comprises a rigid annular diaphragm 18 integrally moulded with a cylindrical circumferential skirt 1 8A. In use the skirt 1 8A is sealingly forced into bore 12" in the support 1 2 in such a way that free edge 1 8A' of the skirt faces outwardly and is, preferably, flush with face 12' of the support 12. On the inner circumferential edge of the diaphragm 1 8 there is moulded, in a manner known per se, a sealing ring 20 of rubber having a sealing lip 22 facing obliquely in a direction generally opposite that of the skirt 18, whilst a sealing lip 24 faces obliquely in generally the same direction as the skirt 1 8A.

The seal device 1 6 further comprises a cap 26 of pressed sheet steel comprising an annular disc part 26A and a tubular cylindrical hub part 26B. In the illustrated position of use, the hub 26B is sealingly forced onto the shaft 10 in such a way that the outer front face of the disc 26A is flush with the face 12' of the support 12. During rotation of the shaft 10, foreign material which might adhere to the cap tends to be thrown off by centrifugal force.

An outer circumferential zone 26C of the disc 26A is re-entrant and is joined to a cylindrical ring 26D facing towards the diaphragm 18 and forming a radial clearance 28 with the skirt 18A.

As can be seen in Fig. 1, the lips 22, 24 are both located in sealing relation with the outer cylindrical surface of the hub 26B. The radial clearance 28 is sufficiently small to prevent excessive deformation of the lips 22, 24 due to possible radial displacement of the cap 26. Axial separation of the cap 26 with respect to the annular diaphragm 1 8 is prevented by a series of axial stops in the form of bent over tabs 1 8A" which are punched radially inwardly from the free edge 18A' of the skirt 1 8A.In the shown mounted condition, the ring 26D is in an intermediate position between the diaphragm 1 8 and the bent over tabs 1 8A", with axial clearances 30, 32 with respect to these members, such clearances being necessary to permit the rotation of the cap 26 together with the shaft 1 0. Not withstanding the fact that the dimensions of these axial clearances 30, 32 are rather limited, there is the possible risk of penetration of extraneous material, such as, water, dust or mud, from the outside into the interior of the device 16, with the consequent possible interruption of the sealing contact between the two lips 22 and 24 and the outer cylindrical surface of the hub 26B.To avoid this risk, and to ensure perfect operation of the seal in any operating conditions whatsoever, according to the present invention there is interposed between the rigid annular diaphragm 18 and the annular cap 26 an annular packing 33 of porous filtering material. As can be clearly seen in the drawing, the annular packing 33 has, in transverse section, a shape complementary to that of the region which it occupies in the space between the annular diaphragm 18 and the cap 26.The packing 33 is made of an elastically compressible porous filtering material, for example open cell expanded polyurethane or felt and has, in its nondeformed condition, that is to say before being mounted, a thickness slightly greater than the distance between the diaphragm 18 8 and the surface of the cap 26 facing it across the region occupied by the packing 33 when it is mounted in position. In this way, when the annular packing 33 is mounted in position, it becomes slightly axially compressed between the annular diaphragm 18 and the cap 26, which is to say that between the front surfaces of the annular packing 33 and the corresponding surfaces of the diaphragm 18 and the cap 26 which face it, there exists an axial interference.Moreover, the greater part of the outer circumferential surface of the annular packing 33 interferes radially with the inner surface of the outer cylindrical ring 26D of the cap 26. In this way the remaining part of the outer circumferential surface of the annular packing 33 penetrates slightly into the axial clearance 30 lying between the ring 26D and the diaphragm 18.

For the purpose of reducing the sliding friction between the outer surface of the annular packing 33 and the corresponding surfaces of the diaphragm 18 and/or of the cap 26, and moreover for improving the filtering capacity of the material constituting the packing 33, this packing 33 is preferably saturated with a lubricating oil or else impregnated with a semi-solid lubricant, for example, a graphited lubricating grease.

In operation the escape of lubricant into the interior of the support 1 2 is prevented by the sealing contact of the lip 22 ("inner sealing lip") with hub 26B, whilst the penetration of water or of other materials from outside is prevented both by sealing contact of the lip 24 ("outer sealing lip") with the hub 26B itself and by the presence of the annular packing 33.

In Figs. 2 and 3, the parts corresponding to those already described in relation to Fig. 1 have been indicated with the same reference numerals increased by 200. In this embodiment the inner sealing lip 222 is still located in sealing relation with the outer cylindrical surface of the hub 226B, as in Fig. 1, whilst on the other hand the outer sealing lip 224 is moulded in the form of a cupshape lip for establishing frontal sealing contact with the inner front face (smooth and polished) of the disc part 226A of the cap 226.The annular packing 233 of porous filtering material is substantially similar to that described in relation to Fig. 1, and has in this case a further supplementary function in the free condition before the device is mounted on a shaft, of preventing the lip 224 being subjected to excessive crushing by the disc 226A when the device is handled. In the mounted condition illustrated in Fig. 3 the annular packing 233 is slightly axially compressed in the same way as in the preceding case.

In Figs. 4 and 5 the parts corresponding to those already described in referring to Fig. 1 are indicated with the same reference numerals increased by 400. In this embodiment, both the lips 422, 424 are so arranged as to form a seal against the front inner face of the disc part 426A of the cap 426. Again, in this case the thickness of the annular packing 433 is such as to be able to stop the cap 426 from undergoing excessive displacements so that the lips 422 and 424 are not subjected to excessive deformations by reason of displacements of the disc 426A when the device is handled in its free or unmounted condition as illustrated in Fig. 4.

In Fig. 6 the parts corresponding to those already described with reference to Fig. 1 are indicated with the same reference numerals increased by 600. In this embodiment the "shaft" component is represented by the inner ring 610 of a ball bearing, whilst the fixed member is represented by the outer ring 61 2 of the same bearing, and the seal according to the present invention has the purpose of ensuring sealing between the said two rings. The lips 622 and 624 are arranged in a frontal sealing configuration as in Figs. 4 and 5. As distinct from the preceding embodiments, however, the re-entrant part 626C of the cap 626 ends with a radially directed circumferential edge 626C'. Moreover, in place ot' the stop tabs 18A" of Fig. 1 there is used a stop ring 40 received in a circumferential inner groove of the skirt 61 8A of the diaphragm 618.

In this case the annular packing 633 of porous filtering material is interposed with axial interference between the annular diaphragm 618 and the circumferential edge 626C' of the annular cap 626, and its outer circumferential surface presses radially against the circumferential skirt 61 8A of the diaphragm 618.

In Fig. 7 the parts corresponding to those already described with reference to Fig. 1 are indicated with the same reference numerals increased by 700. As opposed to the preceding embodiments, the cap 726 is not provided with an axially re-entrant part in the space surrounding the skirt 718A. The lips 722 and 724 are maintained in radial sealing contact with the surface of the hub 726B by means of a toroidally disposed helical spring 42. Moreover, in this embodiment the annular packing 733 of porous filtering material interferes axially with the annular diaphragm 71 8 and with the disc 726A of the cap 726, whilst its outer circumferential surface presses radially against the cylindrical skirt 71 8A of the annular diaphragm 718.

Claims

1. A rotating shaft seal comprising a rigid annular diaphragm, an outer circumferential face of which forms an axially directed cylindrical fixing skirt, a lipped sealing ring of flexible polymeric material moulded onto an inner circumferential edge of the diaphragm, and a centrifuging annular cap in sealing contact with the lipped sealing ring, which cap includes an annular disc part and a cylindrical tubular hub part which extends axially from the inner circumference of the said disc part in the opposite direction to the said skirt, the free edge of the skirt having stop means projecting radially inwardly, either at separate points or over the whole of the circumference, and intended to prevent separation of the cap from the diaphragm, and wherein between the rigid annular diaphragm and the centrifuging annular cap there is interposed an annular packing of porous filtering material mounted with axial interference with respect to the annular diaphragm and the disc part of the centrifuging annular cap.

2. A seal as claimed in claim 1, wherein the cap includes a cylindrical ring which extends from the outer circumference of the annular disc part in the opposite direction to the skirt, which cylindrical ring penetrates axially into the space surrounded by the skirt with radial clearance with respect to the skirt, and wherein the outer circumferential surface of the annular packing of porous filtering material presses radially against the said cylindrical ring.

3. A seal as claimed in claim 1, wherein the outer circumferential surface of the annular packing of porous filtering material presses radially against the cylindrical fixing skirt of the rigid annular diaphragm.

4. A seal as claimed in claim 1, wherein the porous filtering material of the annular packing is an elastically compressible material.

5. A seal as claimed in claim 4, wherein the porous filtering material of the annular packing is open cell expanded polyurethane.

6. A seal as claimed in claim 4, wherein the porous filtering material of the-annular packing is felt.

7. A seal as claimed in any one of the preceding claims, wherein the annular packing of porous filtering material is saturated with a lubricating liquid.

8. A seal as claimed in any one of claims 1 to 6, wherein the annular packing of porous filtering material is impregnated with a semi-solid lubricant.

9. A seal as claimed in claim 8, wherein the semi-solid lubricant is a graphited lubricating grease.

1 0. A rotating shaft seal substantially as herein described with reference to and as illustrated in Fig. 1, Figs. 2 and 3, Figs. 4 and 5, Fig. 6 or Fig. 7 of the accompanying drawings.

11. A unit having a rotary shaft in a support and sealed by a seal as claimed in any one of the preceding claims.