BACKGROUND OF THE INVENTION

( 1 ) Field of the Invention

This invention relates to improvements in annular seal assemblies .

( 2 ) Prior Art

A known type of seal assembly, sold under the trade mark "DUO-CONE", is illustrated in the specific¬ ation of our Australian Patent No. 539,123, and consists of a pair of oppositely arranged but otherwise similar metal rings of angled or more or less L-shaped cross- section, corresponding and adjacent outwardly extending flanges of the two rings being coned or otuwardly con¬ vergent to contact at or near their extremities, the corresponding other two flanges having coned or oblique surfaces between which, and the similarly coned or oblique surfaces of the parts of the apparatus to be sealed, resilient sealing rings are compressed. As one part of the apparatus is rotated relative to the other, the metal rings, urged by the resilient rings into firm contact only at or near the outermost parts of their convergent flanges, seal the junction of the parts of the apparatus.

Seal assemblies of this type are effective in including abrasive particles from bearings when there is a relatively low rubbing speed, or speed of rotation of one metal ring relative to the other; but it has been found that when the rubbing speed is high, the seals are subject to excessive wear and must be replaced at frequent intervals, involving unacceptable down-time of the appar¬ atus to which the seals are fitted.

SUMMARY OF THE PRESENT INVENTION The present invention has been devised with the general object of overcoming this disadvantage by provid- ing seal assemblies which are characterized by high

durability under high rubbing speed and the press¬ ures likely to be found in under-water equipment.

With the foregoing and other objects in view, the invention resides broadly in a sealing assembly of the type including two rings with means for urging them into annular line contact, wherein the contact surface of at least one of the two rings is of or coated with a ceramic material. The contact surface of one of the rings may be planar, the other coned for line contact, particularly where there is minimal oscillation of the rotating part or parts of the apparatus. Other features of the invention will become apparent from the following description. BRIEF DESCRIPTION OF THE DRAWINGS In order that the invention may be readily understood and carried into practical effect, reference is now made to the accompanying drawings, wherein:

FIG. 1 is a sectional view of apparatus incor¬ porating sealing assemblies according to the invention, FIG. 2 is a sectional view to larger scale of a part of the sealing assembly shown in FIG. 1 , FIG. 3 is a view, similar to FIG. 2, of a modification of the invention,

FIG. 4 is a sectional view of a part of a sealing assembly according to an alternative embodi¬ ment of the invention, _. and

FIG. 5 is a view similar to FIG. 4 of a modification.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The apparatus of which part is shown in FIG. 1 is a pump drive bearing assembly for a dredge, and it includes a body 10 within which is a housing 11 for the anti-friction bearings 12 for a shaft 13- A pair of clamp rings 14 are engaged in sealed manner on the shaft to either side of and spaced from, the body 10. To

prevent ingress of abrasive particles to the bearings 12 there are provided, between each of the clamp rings 14 and a side of the body 10, a sealing assembly indicated generally at 15 and illustrated particularly in FIG. 2.

Annular recesses coaxial with the shaft 13 are formed in each clamp ring and a side of the body 10, as indicated at 16 and 17 respectively, the peri¬ pheries 18 of these recesses being oppositely coned or substantially frusto-conical surfaces. At each side of the body 10 -a pair of similar .but oppositely arranged metal rings 19, generally of "DUO-CONE" type are disposed coaxially about and spaced from the shaft 10 , their annular base flanges 20 extending into the annular recesses 16 and 17. The coned or frusto- conical contact flanges 21 of the two rings 19 make an annular line contact near to their outermost parts, being urged into firm inter-engagement by a pair of resiliently deformable rings 22 compressed between the coned surfaces 18 of the clamp ring 14 and body 10 and the oblique or coned outer surfaces 23 of the sealing ring base flanges 20.

According to the invention, the coned adjacent faces of the contact flanges 21 of the two rings 19 are coated, as indicated at 24, with a hardwearing, non-corrosive and shock resistant material such as chromium oxide ceramic or aluminium oxide ceramic or tungsten carbide ceramic. The ceramic coating or facing is applied in any suitable known manner and is ground and radiused about its peripheries by grinding tech¬ niques of any appropriate type.

It will be found that a sealing assembly according to the invention will outlast by several times an assembly of convention "DUO-CONE" type, particularly when high rubbing speed is involved.

In the modified embodiment shown in FIG. 3, only one of the metal sealing rings 19 has its contact flange 21 coated with a ceramic facing 24, the other ring being untreated in this manner. This form of the invention has been found satisfact¬ ory in applications where the vibration or rubbing speed of the rings is not unduly high.

In the embodiment of FIG. 4, only one of the sealing rings 19 is used, its ceramic coned surface 24 making annular line contact with a planar annulus 25 of the ceramic material seated in a shallow annular recess 26. Such a seal is found to be satisfactory where there is no undue oscillation of the shaft 13. It will be apparent that as in this embodiment there is no necessity for the body 10 to be formed with the fairly deep recess 17 shown in FIG. 2, the apparatus may be of more compact and economical character.

In the modification of FIG. 5, the planar annulus of FIG. 4 is replaced by a machined hard stainless steel annulus 27.

It will be understood, of course, that the invention is applicable to a very wide range of apparatus and devices, and that the particular embodiments of the invention herein described and illustrated by way of example only may be subject to many modifications of constructional detail and design, which will be readily apparent to skilled persons, may be made within the ambit of the invention hereinafter claimed.