GB2216202A

GB2216202A - Seals

Info

Publication number: GB2216202A
Application number: GB8903886A
Authority: GB
Inventors: Heinz Strathmann
Original assignee: Gelenkwellenbau GmbH
Current assignee: Gelenkwellenbau GmbH
Priority date: 1988-02-22
Filing date: 1989-02-21
Publication date: 1989-10-04
Also published as: IT1233461B; DE3805443A1; FR2628814A1; IT8905118A0; DE3805443C2; GB8903886D0

Abstract

A seal for sealing between outer and inner parts, having a fixing portion and a sealing portion with at least one sealing lip, has its fixing portion and/or its sealing portion provided with a magnetised material so as to be magnetically attracted to the part it engages. Preferred embodiments are main seals 20 or secondary seals 19 for the journals and bearing cups of Hookes universal joints. <IMAGE>

Description

2216202 GMD/88012GB1 SEALS - This invention relates to seals which are

generally of annular form for sealing between an outer part and an inner part supported within the outer part, a seal comprising a fixing portion adapted to be fixed to one of said parts and a flexible sealing portion having at least one sealing lip adapted sealingly to engage the other part.

In one known type of such seal, there is provided in the region of the sealing lip a spring, e.g. a spiral spring extending circumferentially around the sealing lip, to ensure that the sealing lip engages the inner part, e.g. a rotary shaft, with the required force to ensure effective sealing throughout the service life of the seal. Seals are also known where the maintenance of an effective seal depends on the shape and/or nature of the material from which the seal is made.

It is one object of the present invention to provide a seal with another means for ensuring that the sealing lip engages the part, outer or inner, with which it is to engage, under the required force. Alternatively or in addition, the invention is applicable to the means whereby the fixing portion of the seal is adapted to be fixed to the other one of the outer and inner parts.

Accordingly, the invention provides that at least one of said portions of the seal is provided with a magnetised material whereby said at least one portion of the seal is able to be magnetically attracted to the part it engages.

2 In a seal according to the invention, if the magnetised material is provided in the region of the sealing portion, particularly the sealing lip or lips, of the seal, provided the part which the sealing portion engages in use is of a material which is magnetically attracted, the sealing portion engages the part with a force depending on the strength of the magnetism of the material. Such magnetic strength can be made higher or lower, up to the limit of magnetic saturation of the material, according to the application where the seal is to be used. Mechanical tensioning means for the sealing portion of the seal becomes superfluous or at least of reduced significance. Furthermore, if the magnetic material is also arranged in the region of the fixing portion of the seal then it may fix or assist in fixing the seal, provided the part to which it is to be fixed is magnetically attracted.

The magnetised material may be embedded in the seal, e.g. in the course of production of the seal from a plastics or rubber material by a moulding process. The material may comprise a metal or ceramic powder. Alternatively the magnetised material may comprise a ring or portions of a ring made of a wire of magnetised material. An alternative is to provide a coating of the magnetised material, again for example a metal or ceramic powder, on the surface of the seal, particularly in the region of the lip or lips of the sealing portion thereof.

Yet a further alternative is.that it is possible to embed a number of bar magnet elements in a circumferential distribution about the seal, such members possibly being of cylindrical shape.

3 c The material may be permanently magnetised before it is introduced to the seal, or may be permanently magnetised after it has been introduced or applied to the seal.

One particularly advantageous application of a seal according to the present invention is as a secondary seal for a Hookes universal joint, where each journal of the cross-member of the joint is supported in a respective bearing bush.

In this case, the fixing portion of the seal is adapted to fit on the journal of the cross-member and the sealing portion of the seal is adapted to engage an end surface of the bearing bush.

In the type of Hookes universal joint most commonly used for automotive applications, it is usual to provide pre-assembled bearing units each comprising a bearing bush in the form of a cup containing needle roller bearings and having main and secondary seals. Each yoke of the joint is fitted to the joint cross-member by arranging the cross-member with its opposed journals extending into bores in the limbs of the yoke, and then the pre-assembled bearing units are fitted from the outside into the bores in the yoke limbs and onto the journals of the cross-member. By providing the secondary seal with magnetic means which holds it to its bearing cup, assembly of the joint is facilitated since there is no need for any special mechanical measure to hold the secondary.seal inrelation to the bearing cup. The secondary seal is held to the bearing cup in the correct position to be pushed onto the journal of the cross-member as the bearing unit is fitted into the bore in the yoke limb.

4 Furthermore, if the magnetic means of the secondary seal is also provided in the region of the fixing portion thereof, it assists the seal to remain firmly held to the journal of the cross-member in use.

The invention may also apply to a seal which is intended for use as the main seal between a bearing bush of a Hookes universal joint and an journal of the joint cross-member, wherein the fixing portion of the seal is adapted to be fixed within the bearing bush and the sealing portion of the seal has its at least one sealing lip adapted to engage the journal of the cross-member. In such a seal, the sealing lip or lips has the magnetised material.

The invention also provides a Hookes universal joint in which the secondary and/or main seals are seals according to the invention as above set forth.

The invention will now be described by way of example with reference to the accompanying drawings, of which:- Figure 1 is an elevation, partly in section, of a universally jointed shaft which may incorporate seals according to the invention; Figure 2 is a view, partly in section, of a cross member of a Hookes universal joint, and associated bearing assemblies provided with seals; Figure 3 is a section through a bearing assembly having seals according to the invention; Figure 4 is a section as Figure 3 through a bearing assembly with a further embodiment of seal according to the invention; Figure 5 is a section as Figure 3 through a bearing assembly with yet a further embodiment of seal according to the invention; Figure 6 is a section through another bearing assembly, with a final embodiment of seal according to the invention.

In the following description, seals according to the invention are described with particular reference to the seals incorporated in Hookes universal joints for sealing between the journals of the joint cross-member and the bearing assemblies of the joint, However, it is to be appreciated that the invention is more widely applicable to seals of other configuration and for other purposes. Such seals may be, for example, of the annular cup-seal type, or rings of U- or V- shaped cross- section.

Referring firstly to Figure 1 of the drawings, there is shown a universally jointed shaft such as is typically provided as the propeller shaft in a motor vehicle. The shaft, indicated generally at 1, comprises two Hookes universal joints 2, 3 at its ends, connected to each other by an intermediate shaft 4. Each of the universal joints 2, 3 comprises a first yoke 8 provided with a flange for bolted connection to a-driving element, and a second yoke 9 which is connected to the intermediate shaft 4. As is well known, the yokes 8, 9 of each joint are connected to one another for torque transmission and universal articulation by way of a cross-member 5 whose 6 journals are received in bearing assemblies 6 held in bores 7 in spaced limbs of the yokes.

The intermediate shaft 4 incorporates a sliding splined joint for torque transmission whilst accommodating relative axial movement between the two universal joints 2, 3 which occurs in service in a typical automotive installation. The yoke 9 of joint 2 is welded to a tubular element 12 provided in its interior with longitudinally extending splines. A shaft element 11 with external splines 13 engages in the tubular element 12, the shaft element 11 being welded to a tubular element 10 which in turn is welded to the yoke 9 of the other joint 3.

Figure 2 shows, partly in section, the cross-member 5 of one of the universal joints and its associated bearing assemblies, the cross-member having four journals 14. Each journal 14 is received in a respective bearing bush in the form of a cup 6, and in the bearing cup 6 which is sectioned in Figure 2 it will be seen that a plurality of needle roller bearings 17 are interposed between a cylindrical outer surface 15 of the journal 14 and a cylindrical internal surface 16 of the bearing cup 6. An end surface 18 of the journal 14 engages a surface at the closed end of the bearing cup 6. Two seals are provided for sealing the bearing cup assembly, namely a main seal 20 which fits within the bearing cup at the ends of the needle rollers 17 therein and engages a circumferential surface of the journal 14 adjacent its cylindrical surface 15, and a secondary seal 19 which is received on the journal 14 of the cross-member at its route and engages the bearing cup 6 at its open end.

7 The main seal 20 has the primary function of retaining lubricant in the region of the needle roller bearings 17 within the bearing cup 6. The secondary seal 19 has the primary function of preventing external dirt from penetrating to the region of the main seal 20.

Possible configurations of the main seal 20 and the secondary seal 19 will now be described with reference to Figures 3 to 6. In each of these figures there is shown the bearing cup 6 with the needle roller bearings 17 inside it. The journal of the cross-member is omitted.

In Figure 3, the main seal 20 has a fixing portion 21b which is secured to a metal carrier ring 24 by being moulded thereinto. Where the seal is of a rubber material, it may be vulcanised to its carrier ring 24.

The carrier ring 24 fits closely within the internal cylindrical surface 16 of the bearing cup, and has a portion which extends radially outwardly into an annular groove 25 inside the bearing cup to hold the seal firmly therein. The main seal 20 further comprises two radially inwardly extending sealing lips 27 for engaging the journal, not shown in Figure 3, of the joint cross-member. The lips 27 are inclined towards the open end of the bearing cup.

The secondary seal 19 comprises a fixing portion 21a which is so dimensioned as to be a firm fit on a circumferential surface at the root of the journal 14 of the joint cross-member. The secondary seal 19 further comprises a sealing portion 22a with a sealing lip 26 engageable with a frustoconical surface at the open end of the bearing cup. In cross-section, the seal 19 is generally U- or V- shaped.

8 Both the main seal 20 and secondary seal 19 are seals according to the invention. The main seal 20 has its sealing lips 23 provided with embedded particles 23 of powder of a permanently magnetised material (e.g. a suitable metal or ceramic material), so that the lips 27 are kept in contact with the surface of the cross-member journal under a predetermined force in accordance with the strength of magnetism of the particles of magnetic powder (provided, of course, that the journal is of a material which is attracted by a magnet). This ensures that even if wear occurs beyond a calculated service life, a good sealing contact will prevail.

The secondary seal 19 has particles of permanently magnetised powder 23 embedded therein throughout the seal, both in its fixing portion 21a and sealing portion 22a. On the one hand, this ensures that the sealing lip 26 engages the surface 28 under a predetermined force to ensure effective sealing. On the other hand, in the region of the fixing portion 21a of the seal the magnetised particles therein ensure that the seal is held on the journal of the cross-member of the joint so as not to rotate thereon. For this purpose, the fixing portion 21a of the seal may contain a higher concentration of magnetised powder than the rest of the seal.

Incorporation of the magnetised material in the secondary seal 19 also has the benefit that the seal is held to the bearing cup 6 during assembly of the joint.

The preassembled unit comprising the bearing bush 6, needle roller bearings 17, main seal 20 and secondary seal 19 can readily be inserted into its respective bore 17 in its joint yoke 8 or 9, with the secondary seal 19 held in the correct orientation and position.

9 The particles of magnetised powder 23 may be introduced into the material of the main and secondary seals 20, 19 in the course of production thereof by a moulding process. The powder 23 may be magnetised before it-is introduced, or magnetised by suitable exposure of the seal to a magnetising field after moulding of the seal.

Referring now to Figure 4 of the drawings, this shows an assembly as Figure 3 with the difference that the main seal 20 incorporates no magnetised material.

The secondary seal 19 incorporates magnetised material only in the region of its sealing portion 22a, in the form of a coating 123. Such a coating may be produced, for example, by spraying or by extrusion of the coating material, which again may be for example a metal or ceramic powder, onto the seal.

Referring now to Figure 5, this shows an embodiment wherein, as Figure 4, the main seal 20 incorporates no magnetised material. The secondary seal 19, however, in its sealing portion 22a incorporates a ring 223 of wire of magnetised material. Instead of a ring 223, a number of part-annular elements could be incorporated. Such a ring or number of separate elements are effective to hold the sealing portion 22a of the seal in engagement with the surface 28 of the bearing cup, to hold the seal for assembly purposes and assist the sealing effectiveness thereof. The ring 223 or elements thereof may be magnetised before or after they are embedded in the seal.

Referring finally now to Figure 6, this shows an assembly wherein the secondary seal 19 has its fixing portion 21a provided with a number of circumferentially spaced bar magnet elements 323. Such elements hold the k seal to the bearing cup during assembly, and also are effective to assist fixing of the seal to the journal of the joint cross-member.

5.

p 11 1

Claims

1. A seal for sealing between an outer part and an inner part supported within the outer part, the seal comprising a fixing portion adapted to be fixed to one of said parts and a flexible sealing portion having at least one sealing lip adapted sealingly to engage the other of said parts, wherein at least one of said portions of the seal is provided with a magnetised material whereby said at least one portion of the seal is able to be magnetically attracted to the part it engages.

2. A seal according to Claim 1, wherein the magnetised material comprises a metal or ceramic powder embedded in the seal.

3. A seal according to Claim 1, wherein the magnetised material comprises an applied coating thereof.

4. A seal according to Claim 1, wherein the magnetised material comprises at least portions of a ring of magnetised wire, embedded in the seal.

5. A seal according to Claim 1, wherein the magnetised material comprises a number of circumferentially spaced bar magnet elements, embedded in the seal.

6. A seal according to any one of Claims 2, 4 or 5, wherein said material is magnetised before having been applied to the seal.

7. A seal according to any one of Claims 1 to 5, wherein said material is magnetised after having been applied to the seal.

Ik 12

8. A seal according to any one of the preceding claims, for use as a secondary seal between a bearing bush of a Hookes universal joint and a journal of the joint cross-member, the fixing portion of the seal being adapted to fit on the journal of the cross-member and the sealing portion thereof being adapted to engage an end surface of the bearing bush.

9. A seal according to any one of Claims 1 to 7, for use as the main seal between a bearing bush of a Hookes universal joint and an journal of the joint cross-member, the fixing portion of the seal being adapted to be fixed within the bearing bush, and the sealing portion of the seal having at least one sealing lip adapted to engage the journal of the cross-member.

10. A Hookes universal joint comprising seals according to Claim 8 and/or seals according to Claim 9.

11. A seal substantially as hereinbefore described with reference to the accompanying drawings.

12. A Hookes universal joint comprising seals according to Claim 11.

Published 1989 at The Patent Office, State House, 88 71 High Holbora, LondonWClR 47?. Further copies maybe obtained from The Patent Ofnce Sales Branch, St Mary Cray, Orpington, Kent BR,5 3RD. Printed by Multiplex techniques It4, St Mary Cray, Kent, Con. 1/87