GB2101237A

GB2101237A - Improvements to lipped seals for rotary members

Info

Publication number: GB2101237A
Application number: GB08217083A
Authority: GB
Inventors: Raymond Cadic
Original assignee: AMIOT EXPL PROCEDES FELIX SEPF
Current assignee: AMIOT EXPL PROCEDES FELIX SEPF
Priority date: 1981-06-26
Filing date: 1982-06-11
Publication date: 1983-01-12
Also published as: DE3222838A1; SE449652B; IT8248699A0; NL8202520A; NO822130L; GB2101237B; KR840000301A; JPS5850362A; SE8203950L; IT1148347B; FR2508585A1; SE8203950D0; FR2508585B1

Abstract

The invention relates to a lipped seal (1) for a rotary member (4), comprising at least one lip (2) having at least one sealing edge (3) for cooperating with the rotary member, a base (8) for cooperating with a fixed member (12) associated with said rotary member, and a sleeve (7) connecting said lip and base together and adapted to resiliently support the lip. The base has a back (9) and a front face (10) one at least of which is in the shape of a truncated cone, a cylindrical face (11) adapted to cooperate with the opposed face of said fixed member and at least one annular groove (15, 16, 17) provided in one at least of the back, the front face and the cylindrical faces, so that the base is, in cross section, substantially trapezoidal and possesses a resorption volume under longitudinal compression. <IMAGE>

Description

SPECIFICATION Improvements to lipped seals for rotary members The present invention relates to improvements to lipped seals for rotary members and more particularly to seals of this kind called "coreless", comprising at least one lip having at least one sealing edge for cooperating with the rotary member, a base with substantially trapezoidal cross section for cooperating with a fixed member associated with said rotary member, and a sleeve connecting said lip and base together and adapted to resiliently support the lip, the base having a back and a front face one at least of which is in the shape of a truncated cone and one cylindrical face adapted to cooperate with the opposite face of said fixed member.

Lipped coreless seals have, with respect to cored seals, the advantage of simpler and less expensive manufacture precisely because of the absence of a core.

However, coreless seals at present known have on the contrary considerable drawbacks: they must have relatively accurate dimensions which complicates the manufacture thereof; they have in general a complex shape which makes the mold more difficult to produce and so more expensive, and it is necessary to provide, for holding them in an operational position, parts for centering the different faces of the base (back, front face) which must themselves be produced with very close tolerances and have complex shapes making them particularly costly; finally, since these seals are obtained by molding synthetic elastomers which differ depending on the applications contemplated and which present respectively different shrinkage coefficients, it has been necessary up to the present time, because of the obligation of respecting tight tolerances, to provide several sets of molds each one adapted for molding a specific elastomer.

The aim of the invention is essentially to remedy, as much as possible, the abovementioned drawback and to propose improved seals which answer better than heretofore the different requirements of practice, particularly in so far as the simplicity of manufacture and fitting are concerned.

To these ends, in accordance with the invention, the base further comprises at least one annular groove provided in one at least of the back, front face and cylindrical face, whereby the base is provided with a resorption volume under longitudinal compression.

With this arrangement, the annular expansion groove(s) forming longitudinal compression resorption volumes, are adapted to resorb the deformations of the elastomer when the base is subjected to considerable axial crushing by the axial clamping members or "rammers". It follows from these possibilities of deformation of the elastomer that it is no longer necessary to allow for dimensions as accurate as before; the base may be clamped on all its faces while ensuring, during positioning of the seal, centering and recentering on the fixed member and gripping on the rotary member.

That results for the rammers in less severe tolerances, these parts being then able to be made inexpensively, for example on a simple conventional lathe.

Finally, the molding operation is made both simpler and less inexpensive since the same mold may serve whatever the shrinkage of the elastomer used on removal thereof from the mold.

According to the application contemplated for the seal, the back is substantially flat and extends substantially perpendicularly to the axis of the seal and the front face has the shape of a truncated cone; or else the back is in the shape of a truncated cone and the front face is substantially flat and extends substantially perpendicularly to the axis of the seal; or else, further, the back and the front face are in the shape of truncated cones.

In this case, there is associated with the seal a rammer cut straight on the side facing the flat back or flat front face and/or a rammer cut in the shape of a truncated cone on the side facing the truncated cone shaped back and/or front face.

Advantageously, the base is provided with at least three annular grooves formed respectively in the back, the front face and the cylinder face.

There may further be provided an annular groove in the internal face of the lip, this groove being adapted to receive an annular spring for resiliently applying the lip against the rotary member.

The invention will be better understood from reading the following detailed description of a preferred embodiment, given by way of illustration which is in no wise limiting, in which reference is made to the accompanying drawing where the single figure shows, in cross section, and in an operational position, a seal in accordance with the invention.

The seal 1 ,formed from a synthetic elastomer, for example nitrile or elastomer containing fluoride, has a lip 2 provided with a sealing edge 3 held sealingly against the surface of a rotary shaft 4 under the action of an annular spring 5 housed in an annular groove 6 formed in the outer face, or face opposite edge 3, of lip 2.

Lip 2 is carried by the free end of a sleeve 7 extending from a centering or anchoring base 8 of the seal. Base 8 has a back 9 substantially flat and substantially perpendicular to the axis of the seal, a front truncated cone shaped face 10 with conicity turned towards the back, and a cylindrical face 11 cooperating with the surface of a fixed member 12 such as a casing. In other words, the base presents, in cross section, a trapezoidal shape whose large base or maximum width coincides with the cylindrical surface 11.

The front face 10 forms with the back.an angle between about 250 and 350, preferably of the order of 30". Sleeve 7 forms, with the back 9 of the base, an angle between about 900 and 105 , for example 1000.

At the junction of the outer face 13 of sleeve 7 and the front face 10 of base 8 is located an annular groove 14 having possibly a semi-circular cross section.

Three grooves 15, 1 6 and 1 7 are provided respectively in back 9 and the cylindrical face 11 of the base, so as to resorb the deformations of the elastomer when the seal is clamped by crushing of the base between a front rammer 1 8, with truncated cone shaped face cooperating with the truncated cone shaped front face 10 of the base, and a rear rammer 19, with a straight face cooperating with the back 9 of the base (in the figure, the seal is shown in the operational position, but in the non crushed condition).

By way of example, grooves 1 5 and 1 7 formed in back 9 and cylindrical face 11 have, in cross section, a trapezoidal profile with rounded angles; groove 1 6 formed in the front face 10 has, in cross section, a triangular profile with rounded point.

Of course, the shape as well as the number of grooves formed in back 9, front face 10 and cylindrical face 12 are only given by way of example and may be adapted depending on requirements. Similarly, only one or two of these faces may be provided with a groove.

As is evident, and as it follows already moreover from what has gone before, the invention is in no wise limited to those of its modes of application and embodiments which have been more especially considered; it embraces, on the contrary, all variations thereof.

In particular, although the example described and shown relates to a seal with inner lip, for a rotary shaft, similar arrangements are transposable, without departing from the scope of the invention, for seals without lip, for a rotating case and a fixed shaft.

Similarly, a seal arranged in accordance with the invention may be equipped with a dust-proof lip or a leak-proof spring lip extending from the junction of the sleeve and the base.

Finally, the trapezoidal shape, in cross section, of base 8 may be obtained from different configurations of the back and the front face; the back may have a truncated cone shape and the front face may be flat and perpendicular to the axis of the seal, or else the back and the front face may both have the shape of a truncated cone. Of course, the rammers will have appropriate faces.

Claims

1. A lipped seal for a rotary member, comprising at least one lip having at least one sealing edge for cooperating with the rotary member, a base with substantially trapezoidal cross section for cooperating with a fixed member associated with said rotary member and a sleeve connecting said lip and base together and adapted to resiliently support the lip, the base having a back and a front face one at least of which is in the form of a truncated cone and a cylindrical face adapted to cooperate with the opposite face of said fixed member, characterized in that the base further comprises at least one annular groove provided in one at least of the back, the front face and the cylindrical face, whereby the base is provided with a resorption volume under longitudinal compression so as to be gripped on all its faces while ensuring, during positioning of the seal, centering and recentering on the fixed member and gripping on the rotary member.

2. The seal according to claim 1, characterized in that the back is substantially flat and extends substantially perpendicularly to the axis of the seal and in that the front face is in the shape of a truncated cone.

3. The seal according to claim 1, characterized in that the back is in the shape of a truncated cone and in that the front face is substantially flat and extends substantially perpendicularly to the axis of the seal.

4. The seal according to claim 1, characterized in that the back and the front face are in the shape of truncated cones.

5. The seal according to any one of the preceding claims, characterized in that the conicity of the back and/or of the front face is orientated so that the axial extent of the base is maximum at the level of the cylindrical surface.

6. The seal according to any one of the preceding claims, characterized in that the base is provided with at least three annular grooves formed respectively in the back, front face and the cylindrical face.

7. The seal as claimed in any one of the preceding claims, characterized in that an annular groove is further provided in the outer face of the lip, said groove being adapted so as to receive an annular spring.

8. The seal according to any one of the preceding claims, characterized in that yet another annular groove is provided at the junction of the front face of the base and the internal face of the sleeve.

9. The seal according to any one of the preceding claims, characterized in that the conicity of the front face is between about 250 and 350, and is preferably of the order of 300.

1 0. The seal according to any one of the preceding claims, characterized in that the sleeve forms, with the back, an angle between about 900 and 1050.