Belleville Spring

TECHNICAL FIELD

This invention relates to belleville springs and in particular to belleville springs of the type having an elastomeric coating. The invention also relates to mechanical assemblies incorporating belleville springs.

BACKGROUND OF THE INVENTION

A belleville spring is a spring configured as a dished washer. It is common for such springs to comprise an internal spring structure known as a barespring and an elastomeric coating on the barespring. The elastomeric coating provides a seal at the interface between the belleville spring and machine elements against which the belleville spring acts.

One application of a coated belleville spring is in a mechanical seal of the type disclosed in Australian Patent No. 597879. The coated belleville spring acts between a sleeve fitted onto a shaft and a housing which is mounted on the sleeve for rotation therewith while being movable axially with respect to the shaft. The belleville spring is accommodated in circumferential recesses within the housing and the sleeve and biases the housing in one direction of such axial movement.

The mechanical seal is installed such that there is a prescribed preload on the belleville spring. It has been found that when the coated belleville spring is installed with the prescribed preload, the elastomeric coating is squeezed or otherwise distorted radially, the result of which is that stresses are induced in the coating. These stresses have an influence on the extent of preload exerted by the belleville spring. The preload has two components, one being the force exerted by the barespring and the other being the force exerted by stresses induced in the elastomeric coating. This is undesirable as there is relaxation in the elastomeric material over a period of time, with the result that there is a loss in the preload.

It would be advantageous to provide an arrangement where the spring load provided by a coated belleville spring corresponds to the spring load of the barespring encapsulated therein. This could possibly be accomplished by an arrangement in which there is no radial squeezing or distortion of the coated belleville spring, but there are situations where radial squeezing or other distortion is necessary for sealing at the interface between the coated belleville spring and a machine element against which the spring acts.

SUMMARY OF THE INVENTION

The invention provides a mechanical assembly comprising a coated belleville spring having a barespring encapsulated in an elastomeric coating, and an element having a recess for receiving the coated belleville spring, characterised in that there is provided means for accommodating distortion of the elastomeric material of the coated belleville spring while under load.

By accommodating the distortion of the elastomeric coating there is less stress induced in the coating.

The means for accommodating distortion of the elastomeric material may comprise a cavity.

The cavity provided to accommodate distortion of the elastomeric material may be provided in the coated belleville spring or in the recess of the element.

There may be a plurality of the cavities. At least one of such cavities may be in the coated belleville spring and at least one other of the cavities may be in the element.

Where the cavity, or at least one of the cavities, is in the element, it may comprise a circumferential groove formed in the element. The groove may be formed in the element in the region thereof adjacent either the outer or the inner periphery of the belleville spring. Indeed, there may be two grooves, one adjacent the inner periphery and the other adjacent the outer periphery.

Where there are a plurality of cavities in the element, they may in another arrangement comprise depressions disposed in spaced apart relationship.

Where the cavity is in the coated belleville spring, it may be internally within the spring or it may open onto the exterior thereof.

Where the cavity, or at least one of the cavities, is in the coating, it may comprise a circumferential groove formed in the coating. The groove may be formed in either the outer or the inner periphery of the coating. Indeed, there may be two grooves, one formed in the inner periphery and the other formed in the outer periphery.

Where there are a plurality of cavities in the coating, they may in another arrangement comprise depressions disposed in spaced apart relationship.

The element may comprise part of a mechanical seal.

The invention also provides a belleville spring having an elastomeric coating, the coating being provided with at least one cavity to accommodate distortion of the elastomeric material. The cavity may be of any suitable form.

There may be a single cavity or a plurality of the cavities.

The cavity may exist internally within the coated belleville spring in which case it may comprise an internal void, or it may open onto the exterior thereof, or there may be a combination of internal and external cavities.

In one arrangement, the cavity may comprise a circumferential groove formed in the elastomeric coating of the spring. Conveniently, the circumferential groove may be provided at the outer and or inner periphery of the spring.

Where the cavity is an internal cavity, it may be provided within the ₍ encapsulated barespring.

The invention still further provides a mechanical assembly fitted with a belleville spring as set forth hereinbefore.

The invention still further provides a mechanical assembly comprising a belleville spring and an element having a recess in which the spring is received, the coated belleville spring comprising a barespring encapsulated in an

elastomeric coating, and a cavity being provided to accommodate distortion of the elastomeric material under load.

The invention still further provides a machine element having a recess to receive a belleville spring having an elastomeric coating, the recess being configured to accommodate distortion of the elastomeric material upon loading of the spring.

The configuration of the recess may include at least one cavity in the face of the recess which confronts the spring. The cavity may comprise a circumferential recess in the groove.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood by reference to the following description of several specific embodiments thereof as shown in the accompanying drawings in which:

Fig. 1 is a fragmentary sectional view of part of a mechanical seal fitted with a coated belleville spring; Fig. 2 is a sectional perspective view of the belleville spring;

Fig. 3 is a schematic fragmentary view of the coated belleville spring in position between a sleeve and a housing both of which form part of the mechanical seal, the arrangement being shown prior to loading of the spring; Fig. 4 is a view similar to Fig. 3 with the exception that the arrangement is shown in the condition where the spring is loaded such that the elastomeric material is distorted;

Fig. 5 is a schematic fragmentary view of a belleville spring according to a second embodiment; Fig. 6 is an elevational view of a mechanical seal according to a third embodiment;

Fig. 7 is a cross-sectional view of the belleville spring of Fig. 6;

Fig. 8 is an elevational view of a belleville spring according to a fourth embodiment; Fig. 9 is a cross-sectional view of the spring of Fig. 8;

Fig. 10 is an elevational view of a sleeve forming part of a mechanical seal according to a fifth embodiment; and

Fig. 11 is an elevational view of a sleeve forming part of a mechanical seal according to a sixth embodiment.

DESCRIPTION OF PREFERRED EMBODIMENTS 5

Referring now to Figs. 1 to 4, there is shown part of a mechanical seal 11 comprising a sleeve 13 adapted to be mounted onto a shaft (not shown) of a pump and to be secured thereon. A housing 15 is located about the sleeve. While not shown in the drawings, the housing 15 is connected to the sleeve 13 10 so as to undergo rotation with the sleeve and to also be capable of limited axial movement relative to the sleeve. The housing supports a sealing element 17.

A biasing means in the form of a coated belleville spring 21 operates between the housing 15 and the sleeve 13. The spring 21 serves to bias the housing 15 15 in a direction which maintains the sealing element 17 in sealing engagement with a further sealing element (not shown).

The belleville spring 21 is of annular configuration and comprises a barespring 23 configured as a dished washer so as to be of conventional form. The 20 barespring 23 is encapsulated in a coating 25 of elastomeric material such as Neoprene or Viton. The coating is provided with a thickened face section 26.

The belleville spring 21 has a radially inner end 27 which is received in an outwardly facing circumferential recess 29 in the sleeve 13. The radially outer 25 end 31 of the belleville spring 21 is received within an inwardly facing circumferential recess 33 formed in the housing 15.

A cavity 35 in the form of a circumferential groove is provided within the circumferential recess 29. Similarly, a cavity 37 in the form of a circumferential

30. groove is provided within the circumferential recess 33. The grooves 35 and 37 respectively are arranged to accommodate distortion of the elastomeric material as it squeezed when the belleville spring is under load. The grooves provide space into which part of the elastomeric material can move when distorting under load. This reduces the amount of stress induced in the elastomeric

35 material and so allows the preload to be more accurately determined. Figs. 3 and 4 of the drawings illustrates part of the elastomeric coating 25 occupying spaces provided by the grooves 35, 37.

As an alternative to providing space within the structures surrounding the belleville spring 21 to accommodate distorting elastomeric material, it is possible to provide one or more cavities in the belleville spring itself. One such arrangement is illustrated in Fig. 5 of the drawings where the belleville spring 21 is provided with a circumferential groove 41 on the radially outer periphery thereof and a circumferential groove 42 on the radially inner periphery thereof. The grooves 41 and 42 provides a space which accepts distorting elastomeric material when under load thereby reducing stresses induced in the elastomeric material.

Figs. 6 and 7 of the drawings illustrates an arrangement where the radially inner periphery of the belleville seal is provided with cavities in the form of a plurality of circumferentially spaced recesses 43 which provide space for accommodating distortion.of the elastomeric material.

Figs. 8 and 9 of the drawings illustrate a further embodiment, which is somewhat similar to the embodiment shown in Figs. 6 and 7, except for the configuration of the recesses 43.

In the first embodiment, the cavity 35 in the sleeve 13 for accommodating distorting elastomeric material is provided by the circumferential groove. Fig. 10 illustrates an alternative embodiment in which such cavities are provided by a plurality of circumferentially spaced depressions 45 provided in the recess.

Fig. 11 illustrates an embodiment similar to Fig. 10 with the exception that the depressions 45 are of a different configuration.

It should be appreciated that the scope of the invention is not limited to the scope of the various embodiments described. In particular, it should be understood that the invention may have various applications apart from mechanical seals. Indeed, the invention may have application in any mechanical assembly which utilises belleville springs having an elastomeric coating.