GB2057598A

GB2057598A - Shaft Sealing Rings

Info

Publication number: GB2057598A
Application number: GB8026879A
Authority: GB
Original assignee: Carl Freudenberg KG
Current assignee: Carl Freudenberg KG
Priority date: 1979-08-22
Filing date: 1980-08-18
Publication date: 1981-04-01
Also published as: GB2057598B

Abstract

A shaft sealing ring consisting of a supporting ring 1 with an angular cross section, and a lip ring 3, the lip ring having a sealing lip 8, and being connected to the supporting ring by an intermediate ring 5 formed like a membrane, resilient pressing of the sealing lip against the surface of a sealed shaft 9 being provided by an extension 2 of the supporting ring, which reaches into the intermediate ring, the axial extent of the extension within the intermediate portion being between 40 and 80% of the axial extent of the intermediate ring. <IMAGE>

Description

SPECIFICATION Shaft Sealing Rings The invention relates to shaft sealing rings consisting of a supporting ring with an angular cross section, and a lip ring, the lip ring having a sealing lip, and being connected to the supporting ring by an intermediate ring formed like a membrane, wherein a resilient pressing element is provided for resilient pressing of the sealing lip against the surface of a sealed shaft.

A shaft sealing ring as described above is known from German Patent Specification 10 07 130. The lip ring has also a groove in the outer circumference, in which a coil spring is seated in the immediate region of the sealing lip. However, manufacture and incorporation of this coil spring increase the cost of the shaft sealing ring in an undesired manner, and it is often difficult to produce a uniform pressing force on the entire circumference. This is true especially with small nominal diameters, where the stiffening produced by the pushing of the two ends of the coil spring into one another spreads over a zone, which occupies in percentage a substantial part of the entire circumference.

A shaft sealing ring is known from U.S. Patent Specification 2 267 930, in which the pressing element extends into the interior of the lip ring, and indeed even into the immediate region of the sealing lip. However, the properties of this sealing ring in use were also not satisfactory, and good sealing results could for example only be achieved if true running of the shaft to be sealed were ensured, as well as a very precise adherence to the predetermined external diameter of the shaft to be sealed. Both requirements cannot be satisfied when having regard to the usual tolerances in manufacture.

The object underlying the invention is to develop a shaft seal which, while keeping usual constructional tolerances, ensures a good sealing result, which is cheap in manufacture, and which in mass production shows a highest possible consistency in the quality characteristics of each unit.

This object is solved according to the invention in a shaft sealing ring of the kind mentioned initially, wherein resilient pressing of the sealing lip against the surface of a sealed shaft is provided by an extension of the supporting ring, which reaches into the intermediate ring, the axial extent of the extension within the intermediate portion being between 40 and 80% of the axial extent of the intermediate ring.

The supporting ring of a shaft sealing ring according to the invention preferably consists of a deep-drawn steel sheet, and the deep-drawing operation employed for its manufacture makes possible, at the same time as the general deformation, the formation of the extension on the limb directed radially inwards. Thus the manufacture of the reinforcing ring for a shaft sealing ring according to the invention does not fundamentally involve additional costs as compared with conventional constructions.

The axial extent of the intermediate ring is determined as in German Patent Specification 10 07 130 or the DIN 3760, selection sheet 1, May 1972, price group 4 conceived in accordance with it. The lip ring is then bounded in the axial direction by a plane extending perpendicularly to the axis of rotation. The ratio required according to the invention is related to the distance between this plane, facing towards the supporting ring, and the surface facing towards the lip ring of the radially inwardly extending limb of the supporting ring.

The lip ring of a shaft sealing ring according to the invention no longer has in the external circumference the groove hitherto necessary for reception of the coil spring. From the omission of the flank surfaces needed for the formation of the groove, there results a saving as regards the necessary elastomeric material and also, considered in total, a reduction of the mass of those components which during operation always follow the movements of the sealed shaft. It is assumed that the exceptional sealing results are to be attributed to this and to the relatively increased flexibility of the lip ring.

For improvement of the elastic properties of the extension towards its terminal edge, the extension may have a lessee thickness near the terminal edge than near the supporting ring.

Furthermore, the extension may be sub-divided into individual segments by notches distributed uniformly around the circumference. In connection with or independently of the tapering of the extension towards the terminal edge, described above, particularly good results are often achieved if the segments taper in width towards the terminal edge. A particularly suitable average width of the individual segments, with shaft diameters of 20 to 100 mm, is 2 to 10 mm.

The resiliently elastic behaviour of the extension acting in the radial direction is influenced to a substantial extent by the angle at which the extension is arranged to the axis of the shaft to be sealed. Particularly advantageous are angles between 1 5 and 40 , preferably in the order of magnitude of 25 . In contrast, angles of 0 or negative angles have acted adversely in some cases on the vibration behaviour of the sealing lip in operation, and thus on the dynamic sealing.

All these preferred features assist the improvement of the elastic properties of the annular extension of the supporting ring, and their employment becomes the more important, the further the extension reaches into the intermediate ring. In embodiments in which the extension reaches into the intermediate ring by only a little more than 40% of the axial extent of the intermediate ring, such additional measures can be redundant.

The accompanying drawing shows an example of a shaft sealing ring embodying the invention. In these drawings:- Figure 1 is a perspective view of the sealing ring on a shaft, with part of the sealing ring broken away; and Figure 2 is a radial section of half of the ring.

The sealing ring comprises a supporting ring 1 of metal with an angular cross section. An annular lip ring 3 of elastomeric material is connected by an intermediate ring 5, formed like a membrane, to an inwardly directed limb 6 of the supporting ring 1. In fact the elastomeric material is moulded around the inwardly directed limb 6.

The lip ring 3 has a sealing lip 8 which makes sealing engagement with a rotating shaft 9.

The radially inwardly directed limb 6 is deformed into an extension 2. The extension 2 is totally embedded in the intermediate ring 5.

In Figure 2 the axial extent of the extension 2 is indicated at x1, while the axial extent of the intermediate ring 5 is indicated at x2.

The resilient pressing force of the sealing lip 8 on the surface of the shaft 9 to be sealed is particularly determined from the material properties and the dimensions of the extension 2 and of the lip ring 3. Both parameters can be very precisely controlled and continuously ensured, without particular difficulties, in continuous manufacture. A modification of the elastic properties can moreover be additionally made possible through an additional projection 4 of defined length, extending in the axial direction from the lip ring 3. It is then of particular advantage that the length of the projection 4 can also if necessary subsequently be reduced by a mechanical treatment, without the surface of the lip ring in the functionally important region of the sealing lip 8 being affected.

The properties in use of shaft sealing rings according to the invention are at least equivalent to those of a construction according to DIN 2760.

At the same time the simplicity of manufacture, and also the exceptional consistency of all properties of the individual units in a comparison with the usual units, is a notable advantage.

Claims

1. A shaft sealing ring consisting of a supporting ring with an angular cross section, and a lip ring, the lip ring having a sealing lip, and being connected to the supporting ring by an intermediate ring formed like a membrane, resilient pressing of the sealing lip against the surface of a sealed shaft being provided by an extension of the supporting ring, which reaches into the intermediate ring, the axial extent of the extension within the intermediate portion being between 40 and 80% of the axial extent of the intermediate ring.

2. A shaft sealing ring according to claim 1, in which the extension has a lesser thickness near the terminal edge of the extension than near the supporting ring.

3. A shaft sealing ring according to claim 1 or claim 2, in which the inner surface of the extension includes with the axis of the sealing ring an angle of 15 to 400, preferably an angle of 250.

4. A shaft sealing ring according to any of claims 1 to 3, in which the extension is subdivided into individual segments by notches distributed uniformly around the circumference.

5. A shaft sealing ring according to claim 4, in which the individual segments have a lesser width near the terminal edge of the extension than near the radially inwardly directed limb of the supporting ring.

6. A shaft sealing ring according to claim 1, substantially as described with reference to the accompanying drawings.