AU614013B2

AU614013B2 - An assembly for a shaft seal, particularly at a stern tube of a ship

Info

Publication number: AU614013B2
Application number: AU28429/89A
Authority: AU
Inventors: Gunter Mewes; Gunter Pietsch; Ernst-Peter Von Bergen
Original assignee: Blohm and Voss GmbH
Current assignee: SKF Marine GmbH
Priority date: 1988-01-13
Filing date: 1989-01-12
Publication date: 1991-08-15
Anticipated expiration: 2009-01-12
Also published as: JPH01210665A; DE3800706C2; GB2213882B; GB8900034D0; NL8803059A; AU2842989A; KR960014628B1; NL193288C; CN1011159B; DE3800706A1; CN1034986A; SE8900088D0; JPH086817B2; SE467841B; ID873B; NL193288B; SE8900088L; KR890012098A; GB2213882A

Description

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FORM COMMONWEALTH OF AUSTRALI PATENTS ACT 1952 COMPLETE SPECIFICATION S F Ref: 80138

A

(ORIGINAL)

FOR OFFICE USE: Class Int Class Complete Specification Lodged: Accepted: Published: Priority: Related Art: Name and Address of Applicant: Blohm Voss AG Hermann-Blohm-Strasse 3 2000 Hamburg 11 FEDERAL REPUBLIC OF GERMANY Address for Service: Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia Complete Specification for the invention entitled: An Assembly for a Shaft Seal, Particularly at a Stern Tube of a Ship The following statement is a full description of this invention, including the best method of performing it known to me/us 5845/3 2 TECHNICAL FIELD The invention relates to an assembly for a shaft seal, particularly at a stern tube of a ship, with the features recited in the precharacterising part of Claim 1.

BACKGROUND OF THE INVENTION -During installation work on assemblies of this type (German Patent 26 09 414), the sealing ring must be pushed with its back into a cavity formed by a collar and a groove. Since in these known assemblies, the groove of the first support ring extends from the collar to the articulation-like intermediate portion (membrane) of the sealing ring and therefore is provided with a peripheral extension in the region close to the shaft, the entire back of the sealing ring is embraced in a pliers-like fashion.

Particularly in the case of large shaft diameters, there result problems insofar as when the sealing ring is being inserted, it readily tilts and therefore a tight contact of its back with the internal wall of the cavity is not obtained. This shortcoming is not overcome by subsequently clamping the sealing ring by means of the tensioning ridge of the second ring, so that tilting of the sealing edge may cause a pumping action and, hence, leakage during operation. These problems are amplified in that, since the second portion of the sealing ring is relatively short in the axial direction, the rear of the sealing ring forms an inflexible member opposed to being locked in the locking enclosure. Further, the cited enclosure of the sealing ring prevents free movement of the articulation-like intermediate portion of the sealing lip so that, due to lack of resilience of the sealing lip portion, the above-mentioned tilting of the sealing ring is facilitated during installation work. Besides that, the lack of resilience may result in leakage, in the case of vibrations of the shaft.

SUMMARY OF THE INVENTION According to the invention, there is provided a shaft seal assembly, comprising a first support ring fixable relative to a housing and a second support ring fixable relative to the housing and a sealing ring of rubber elastic material clampable between the two support rings, the sealing ring comprising a clamping part and a hinge-like intermediate part which adjoins the clamping part and carries a sealing lip, the first support ring having a hollow cavity matched to the clamping part of the sealing ring into which _I I1 I~II-~LI1-r~llY_ ~I~LL-Pjl.

2A the clamping part of the sealing ring can be pushed, and wherein the second support ring has an axially projecting clamping web with which it clamps the clamping part, wherein: the hollow cavity has two ring-shaped undercuts which broaden the base of the cavity, the clamping part is provided with two conical broadened portions in such a way that it latches into the undercuts on being pushed into the hollow cavity, at least one groove is provided in the rear part of the clamping part in such a way that they make it possible for the conically broadened portions to compress resiliently on being pushed through the hollow cavity, the hollow cavity is provided with a shaft side ring wall so shaped that the hinge-like intermediate part of the sealing lip extends from this ring wall in a contact-free manner.

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-3- In principle, the cited measures have been proposed for shaft seals which in their generic aspects deviate more or less from the shaft seal configuration under conside,ation, namely there were suggested: measure a) by German Patent Application 24 59 732 Laid Open for Public Inspection, Figure 4; measures b) and c) by US Patent 4,526,385; and measure d) by US Patent 3,871,666, Figure 2. Yet this is irrelevant for the present invention because the solution to the problem considered is satisfactorily obtained only by the simultaneous implementation of all the measures a) through and, hence, it is irrelevant whether one or the other of the measures of the combination has been known per se, or whether one or the other subcombination of these measures has been known.

o By combining the four characterising design features, the following is accomplished: The sealing ring can be moved toward the cavity of the first support ring without any friction because the usual chamfers are provided at the cone-like protrusions, the diameter being smaller than the diameter of the S: cavity. When during the further movement into the annular cylindrical part of the cavity, the cone-like protrusions of the sealing ring bounce back because of the grooves provided on the back of the tensioning member and, S hence, facilitate forward movement under application of a relatively small C force. Finally, the cone-like protrusions lock in undercuts of th3 first support ring so that the sealing ring is positively fixed in this position and tilting is precluded. Further, since during the entire entry movement, the articulation-like intermediate portion (membrane) of the sealing lip is spaced from the inner ring wall of the first support ring, no tilting of the sealing ring from that side occurs.

BRIEF DESCRIPTION OF THE DRAWINGS

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In what follows, the invention is described with reference to the embodiment shown in the drawing. There is shown: in Figure 1, an assembly before its installation; in Figure, the assembly mounted at a shaft seal, with three seals axially arranged in side-by-side relationship.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Figure 1 shows the three rings of the assembly, namely first support ring 1, second support ring 2, and sealing ring 6, in spaced relationship 4to clearly illustrate form and shape of the various rings. In their operation, support rings 1 and 2 are connected with each other and with the stern post, they have a fixed position in the housing, whereas sealing ring 6 is clamped between the two support rings.

First support ring 1, which in the present case is far from the medium to be sealed off (sea water), is provided with a peripheral cavity 3 on the side facing the sealing ring. That region of cavity 3, which faces sealing ring 6, has the form of an annular cylinder but has peripheral undercuts 4, 4' flaring toward the bottom of the cavity.

Furthermore, in the embodiment under consideration, cavity's 3 annular wall 5 on the side of the shaft is inclined on the inside, with the angle of the inclination 5' exceeding the ascending angle 8' of the articulation-like intermediate portion so that, after installation, this part extends without contact from inclination 5' of annular wall Sealing ring 6 is made of a rubber-elastic material and is composed of three parts, namely sealing lip 7, articulation-like intermediate portion 8, and clamping portion 9. Sealing lip 7 is in conventional fashion provided with an edge which rests on the shaft to be sealed or on a shaft bushing.

Articulation-like intermediate portion 8 connects sealing lip 7 with clamping portion 9 and facilitates an articulation-like yielding of sealing a lip 7 vis-a-vis clamping portion 9. The clamping portion matches cavity 3 of first support ring 1, in the region far from support ring 1, the clamping portion has the form of an annular cylinder and, in the region facing support ring 1, is provided with cone-like protrusions 10, In the latter region, sealing ring 6 is provided with grooves 11, 11' dimensioned so that when clamping portion 9 is moved through the annularo cylindrical region of cavity 3, the cone-like protrusions 10, 10' deform elastically and therefore facilitate initiation of the insertion operation without application of an important force. In order to facilitate the insertion, the cone-like protrusions are provided with conventional chamfers 12.

Shortly before the insertion operation is completed, the cone-like protrusions 10, 10' of sealing ring 6 lock into undercuts 4, 4' of support ring l and in this way safeguard termination of the insertion operation with ensuing tight contact of clamping portion 9 with the bottom of cavity 3.

5 Second support ring 2 is provided with axially protruding annularcylindrical tensioning ridge 13 which, in operation, rests with its side facing sealing ring 6 on clamping portion 9, compressing the same and effecting in this way the clamping of sealing ring 6 between the two support rings. Figure 2 shows the assembly in the mounted state for which there was chosen a sealing arrangement in which three lip seals in axial side-by-side relationship act on the shaft, with two lip seals 6, 6' facing the medium to be sealed off (sea water) and one lip seal 6" directed in the opposite direction. In this conventional sealing arrangement, support ring 1 acts not only as a first support ring for lip seal 6 but also as a second support ring for lip seal and support ring 2 acts not only as the second support ring of lip seal 6 but also as a first support ring of lip seal whereas a separate second support ring 2' is required for lip seal 6' and a separate first support ring 1" is required for lip seal with peripheral undercuts 4, 4" disposed in the annular-cylindrical region in the case of support ring 1".

Claims

1. A shaft seal assembly, comprising a first support ring fixable relative to a housing and a second support ring fixable relative to the housing and a sealing ring of rubber elastic material clampable between the two support rings, the sealing ring comprising a clamping part and a hinge-like intermediate part which adjoins the clamping part and carries a sealing lip, the first support ring having a hollow cavity matched to the clamping part of the sealing ring into which the clamping part of the sealing ring can be pushed, and wherein the second support ring has an axially projecting clamping web with which it clamps the clamping part, wherein: the hollow cavity has two ring-shaped undercuts which broaden the base of the cavity, the clamping part is provided with two conical broadened portions in such a way that it latches into the undercuts on being pushed into the hollow cavity, at least one groove is provided in the rear part of the clamping part in such a way that they make it possible for the conically broadened portions to compress resiliently on being pushed through the hollow cavity, the hollow cavity is provided with a shaft side ring wall so shaped that the hinge-like intermediate part of the sealing lip extends from this ring wall in a contact-free manner.

2. A shaft seal device comprising two or more of the assemblies of claim 1 arranged axially alongside one another, wherein a support ring which is located between two adjacent sealing rings is so shaped that it acts as a support ring for two adjacent sealing rings.

3. A shaft seal assembly substantially as herein described with reference to the accompanying drawings. DATED this TWELFTH day of FEBRUARY 1991 Blohm Voss AG Patent Attorneys for the Applicant SPRUSON FERGUSON 1 J