GB2262577A

GB2262577A - Shaft sealing ring

Info

Publication number: GB2262577A
Application number: GB9225823A
Authority: GB
Inventors: Norbert Jung
Original assignee: Goetze GmbH
Current assignee: Goetze GmbH
Priority date: 1991-12-12
Filing date: 1992-12-10
Publication date: 1993-06-23
Anticipated expiration: 2012-12-10
Also published as: GB9225823D0; DE4140951A1; GB2262577B

Description

2262577 SHAF'T SEALING RING This invention relates to a shaft sealing ring

for sealing rotating shafts, with a sealing washer of polytetrafluoroethylene or a related kind of material gripped in a housing, the web of the washerbeing bent over at the inner periphery into a sealing lip bearing in sealing manner on the rotating shaft.

Lip sealing rings for scaling rotating shafts or reciprocating rods, with a sealing washer of polytetrafluoroethylene, whose webs are bent over at the inner periphery on to the shaft or rod and whose webs form the retaining part at the outer periphery and are gripped between the radial web of a housing ring and a clamping ring are known, for example from US-PS 3 984 113. The clamping ring has, as a junk ring, a rectangular cross-section and in order to obtain the desired pressure of application, it is fitted with its axially-aligned edge crimped in the axially-aligned web of the housing ring, at the end.

A disadvantage with polytetrafluoroethylene and with related kinds of materials is their tendency to creep or their plastic flow under pressure loading.

The rigidly clamped retaining part of the scaling washer is deformed by the clamping force under operating conditions by plastic flow, especially after thermal expansion, the sealing washer gradually comes loose in its seat, the sealing of the static seal part loses it tightness and finally becomes completely inoperative.

As a remedy, in US-PS 3 984 113 the sealing washer is clamped together with an elastomer washer; however the clamped elastomer washer is not compressible and is in any case only slightly deformable, elastically, so that this seal also gradually loses its tightness and becomes inoperative.

According to DE-PS 3 519 966 for example, a solid sealing ring of polytetrafluoroethylene is used and is fitted loose, directly in the housing groove of the receiving machinepart, without pressure loading. Such sealing rings are however only suitable for particular applications and solid sealing rings of polytetrafluoroethylene, free in the housing, are in particular costly and thus uneconomical to manufacture.

According to DE-PS 3 309 538 the sealing washers are gripped andlor vulcanised in the housing ring without the use of clamping rings. Adhesive bonds between polytetrafluoroethylene and the housing ring are however expensive to make, on account of the known poor adhesion of polytetrafluoroethylene, and such adhesive bonds remain a problem and prone to damage.

The present invention is therefore based on the object of providing a shaft sealing ring of the kind according to the pre-characterizing part of the main claim which remains sealed and functional over the longest possible lifetime. The sealing ring has to be capable of as economical manufacture as possible and suitable for many applications.

According to the invention, this object is met by a shaft sealing ring whose sealing washer is of polytetrafluoroethylene or a related kind of material is clamped at its retaining part on to the radial web of the housing ring, together with an elastomer washer, by means of a resiliently elastic clamping ring.

Preferably the resiliently elastic clamping ring is a Belleville spring of ordinary steel with a somewhat frustoconical cross-section. Its outer diameter is somewhat greater than the inner diameter of the axially-aligned web, so that, during assembly, it can be pressed with deformation on to the retaining part of the sealing washer and the elastomer washer and be gripped in the axially- aligned web of the housing ring. In addition the inner periphery of the axially-aligned web of the housing ring can be provided with grooves of sawtooth profile, in which the Belleville spring can engage with its outer peripheral surface, sharpened if desired.

In test runs with the temperature stresses experienced under operating conditions, the shaft sealing ring according to the invention proved to be statically sealed and fully functional even over long operating periods. Moreover the thermal expansion of the sealing washer in operation now leads to predominantly elastic deformation of the of the elastomer washer and the clamping ring, which is then restored elastically on cooling, in contrast to the known solutions with rigid clamping of -the sealing washer. Excessive pressure loading of the sealing washer is prevented, even with thermal expansion, and possible plastic flow of the sealing washer material is compensated for by the elastic restoring force of the elastomer washer and of the clamping ring. The seal itself remains in the static sealing region tight and functional, with substantially improved lifetime.

The seal according to the invention can be made with relatively simple 11 W 1 means and thus economically. Within the scope of the invention, the sealing washer can even be clamped together with the elastomer washer and the clamping ling in housing grooves without the use of housing rings. Areas of ap lication are Z5 I p especially housing closure caps for shaft through bearings, for example in closure caps for crankshaft through bearings.

In order that the elastomer washer shall be able to deform elastically as freely as possible under loading, it preferably has a round to oval, if desired profiled cross-section. The dimensions of the elastomer washer and the clamping ring are determined to suit the application and are so designed that the necessary clamping forces and deforming forces act on the gripped sealing washer. Together with the sealing washer of polytetrafluoroethylene or a related kind of material, further washers of preferably an elastomer, a felt material or even polytetrafluoroethylene are gripped therewith in the housing ring. The washers bearing on the shaft with their inner periphery are preferably on the air side of the sealing washer proper and act as dirt lips for the sealing lip proper. The frustoconical clamping ring acting as a Belleville spring preferably consists of steel and it has been found that ordinary tool steel is adequate as the steel, this being economical to work by stamping and drawing with sufficient elasticity.

The invention will be explained in more detail by means of the drawing, which is a cross-section through a preferred shaft sealing ring according to the invention.

In the drawing 1 is the shaft sealing ring with the metal housing ring 2 with (3) a radially-aligned webend an axially-aligned web 4 on the inner periphery. The sealing washer 5 bears with dynamic sealing action on the rotating shaft 7 at the inner periphery bent over to the sealing lip 6. In the retaining part 8 at the outer periphery, the sealing washer 5 together with a felt washer 14, an elastomer washer 9 and a clamping ring 10 are gripped against the radial web 3 of the housing ring 2.

The clamping ring 10 is a Belleville spring with an approximately frustoconical cross-section, which is pushed into the axially-aligned web 4 in assembly, with elastic deformation, as an interference fit. The outer periphery of the Belleville spring 10 is sharpened and engages with its sharp edge 11 for locking in the sawtooth profile 12 of the axially-aligned housing ring web 4.

Through the elastic tightening of the sealing washer 5 of polytetrafluoroethylene at the retaining part 8 between the elastically deformed elastomer washer 9 and the clamping ring 10, the plastic flow of the polytetrafluoroethylene, especially with thermal loading is restricted to a minimum and loosening of the seat is avoided, and the sealing ring 1 remains functional with improved life. The felt washer 14 on the air side of the sealing washer 5 bears with its inner periphery on the shaft 7 and serves as a protective lip and so as to keep out dirt. The axially-aligned web of the housing ring 13 at the outer periphery of the housing ring 2 is coated with a sealing and anti-corrosion lacquer, which facilitates good seating on pressing the sealing ring 1 into the receiving machine part housing groove.

2 -:i

Claims

1. A shaft sealing ring for sealing rotating shafts, with a sealing washer of polytetrafluoroethylene or a related kind of material gripped in a housing, the web of the washer bent over at the inner periphery into a scaling lip bearing on the rotating shaft, characterized in that the scaling washer is clamped at its retaining part together with an elastomer washer by a resiliently elastic clamping ring on to a radial web of the housing ring.

2. A shaft sealing ring according to claim 1, characterized in that the resiliently elastic clamping ring is a Belleville spring of steel with an approximately frustoconical cross-section.

3. A shaft sealing ring according to claim 1 or 2, characterized in that the outer diameter of the Belleville spring is somewhat greater than the inner diameter of the axially-aligned web, so that it can be inserted as an interference fit in the axiallyaligned web during assembly, with elastic deformation.

4. A shaft sealing ring according to any of claims 1 to 3, characterized in that the sealing washer is gripped together with one or more washers of polymer or felt material, which serve as protective lips on the air side of the sealing washer against the penetration of dirt from the outside.

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4. A shaft sealing ring according to any of claims 1 to 3, characterized in that annular, circumferential grooves are located on the inner periphery of the axiallyaligned web, with a somewhat sawtooth crosssection, and in that the outer periphery of the Belleville spring is sharpened, so that, on insertion, the Belleville spring locks with its sharpened periphery in the annular grooves of the axiallyaligned web of the housing ring.

5. A shaft sealing ring according to any of claims 1 to 4, characterized in that the elastomer washer has a circular to round, if desired profiled, cross-section.

6. A shaft scaling ring according to any of claims 1 to 5, characterized in that the scaling washer is gripped together with one or more washers of polymer or felt material, which serve as protective lips on the air side of the sealing washer against the penetration of dirt from the outside.

- c - Amendments to the claims have been filed as follows 1. A shaft sealing ring for sealing rotating shafts, with a sealing washer of polytetrafluorethylene or a related kind of material gripped in a housing, the web of the washer being bent over at the inner periphery into a sealing lip bearing on the rotating shaft, and the sealing washer being clamped at its retaining part together with an elastomer washer by a resiliently elastic clamping ring on to a radial web of the housing ring, wherein the resiliently elastic clamping ring is a Belleville spring of steel with an approximately frustoconical cross-section and the outer diameter of the Belleville spring is somewhat greater than the inner diameter of the axially-aligned web, so that it can be inserted as an interference fit in the axially-aligned web during assembly, with elastic deformation.

2. A shaft sealing ring according to claim 1, characterized in that annular, circumferential grooves are located on the inner periphery of the axially-aligned web, with a somewhat sawtooth cross-section, and in that the outer periphery of the Belleville spring is sharpened, so that, on insertion, the Belleville spring locks with its sharpened periphery in the annular grooves of the axially-aligned web of the housing ring.

3. A shaft sealing ring according to claim 1 or 2, characterized in that the elastomer washer has a circular to round, if desired profiled,--cosssection.