GB2218162A

GB2218162A - Rotating shaft seal

Info

Publication number: GB2218162A
Application number: GB8910555A
Authority: GB
Inventors: Gunter Pietsch
Original assignee: Blohm and Voss GmbH
Current assignee: Blohm and Voss GmbH
Priority date: 1988-05-07
Filing date: 1989-05-08
Publication date: 1989-11-08
Anticipated expiration: 2009-05-08
Also published as: GB8910555D0; NL193842C; JPH086818B2; NL193842B; SE8901613D0; DE3815655A1; JPH0211969A; CN1015401B; NL8901132A; SE501939C2; DE3815655C2; CN1041030A; SE8901613L; GB2218162B

Description

1 n r%l 22 A. 1,.8 16 2 Seal for rotatinq shafts,,in particular a stern

tube seal The invention relates to a seal for rotating shafts, in particular to a stern tube seal for a ship having the features set forth in the preamble of claim 1.

In the known seals of this kind (DE-PS 2028 427) the engagement or spacing of the sealing strip takes place either in that the carrier which holds all the radial lip seals, i.e. also the reserve radial lip seals, is displaceable axially relative to the axially non-displaceable shaft or shaft sleeve, or in such a way that with an axially non-displaceable carrier the shaft or the sleeve is axially displaceable, wherein in both cases the reserve radial lip seal comes free from the shaft or sleeve surface in the one end position of the axial movement and contacts the shaft or sleeve in the other end position.

It is self-evident that a construction of this kind involves considerable constructional and design complexity, a disadvantage which in many cases exceeds the advantage of greater operating reliability which can be achieved with the reserve radial lip seal. It is thus the object of the invention to overcome this disadvantage and accordingly to set forth a solution which makes it possible to use reserve radial lip seals with relatively small cost and complexity.

This object is satisfied in that at least one hollow ring radial lip seal is used as a reserve radial lip seal for the sealing of a shaft or of a shaft sleeve, with the hollow ring radial lip seal being 1 pressurisable via a pressure line with a pressure medium, preferably air, by which the hollow ring radial lip seal is elastically deformable in such a way that its sealing strip adopts a sealing position relative to the shaft or shaft sleeve in the one operating state, and a position spaced from the shaft or shaft sleeve in the other operating state.

Hollow ring radial lip seals for shafts or shaft sleeves are admittedly known per se (DE-OS 2606813, FR-OS 2315045). However, these known seals are not reserve radial lip seals for main radial lip seals but are instead main radial lip seals for devices or systems which only require temporary shaft sealing.

The fact that hollow ring radial lip seals require relatively little constructional complexity is evident since they consist solely of an elastically def ormable hollow ring which is connected via a pressure line and a control member to a pressure source.

In accordance with an embodiment of the subject of the invention provision is made that in an arrangement in which a stern tube is sealed against the external water and in which three main radial lip seals are arranged alongside one another, of which the two outer lip seals face the external water and the inner lip seal faces a chamber containing liquid lubricant, preferably lubricating oil, the reserve radial lip seal is arranged in front of the inner main radial lip seal in the direction towards the lubricant chamber (claim 2). In this way, in addition to the named effect of reducing complexity and cost, the escape of lubricant into the external water on eventual failure of the main radial lip seal which faces the chamber containing lubricant is avoided in a simple manner, and can thus also satisfy strict environmental protection t 1 k_ requirements.

In accordance with a further embodiment provision is made that in an arrangement in which a liquid medium is sealed relative to a gaseous medium, preferably air, and in which two main radial lip seals are present which are arranged alongside one another and which face the liquid medium, the reserve radial lip seal is arranged in front of the main radial lip seal at the liquid side in the direction towards the liquid medium (claim 3). In'-this arrangement the reserve radial lip seal is pressurised with water under pressure as the pressure medium and is provided with a plurality of bores which are distributed in the circumferential direction closely adjacent the sealing strip of the reserve radial lip seal, and which open out of the hollow space of the reserve radial lip seal at the gas chamber side (claim 4).

In this embodiment it is advantageous when grooves are present in the circumferential direction in the region of the opening orifices of the bores of the outer surface of the reserve radial lip seal, with these grooves generating hydrodynamic effects such that they convey the liquid which emerges from the bores in the direction towards the sealing strip (claim 5). Through this measure the lubrication of the hollow ring radial lip seal by means of.pressurised water is ensured or improved while consciously tolerating a small leakage. It also possible to provide slide ring seals in place of the radial lip seals.

In the drawing the subject of the invention is schematically illustrated with respect to two embodiments. The drawing shows:

Fig. 1 a reserve radial lip seal in conjunction with a customary shaft seal at a stern tube, Fig. 2 a reserve radial lip seal in conjunction with a shaft seal for sealing a liquid medium relative a gaseous medium, Fig. 3 the reserve radial lip seal of figure 2 to an enlarged scale In the seal illustrated in figure 1 a running sleeve 2 is located on the propeller shaft 1. The shaft 1 is journalled in a non-illustrated bearing sleeve which is carried by a stern boss 3. A sealing housing 4 is also secured to be stern boss 3 and comprises five housing rings 4.1, 4.2, 4.3, 4.4, 4.5, which are arranged flush alongside one another and three radial lip seals 5.1, 5.2, 5.3 and 6 which are each inserted between two housing rings.

The radial lip seals 5.1 and 5.2 face the external water A whereas the radial lip seal 5.3 faces a lubricant chamber S. In front of this seal in the direction towards the lubricant chamber S there is located a further radial lip seal 6 which faces the lubricant chamber S. The radial lip seals 5.1, 5.2 and 5.3 are formed in the customary manner as full ring seals and act as main seals, whereas the radial lip seal-6 is formed as a hollow ring seal and has to be addressed as the reserve seal. The hollow chamber 7 of the seal 6 is connected via a line indicated in broken lines, in which a non-illustrated stop member or control member is inserted, with a pressure source which is likewise not shown but which delivers pressurised air.

z o I,- The hollow ring seal 6 is elastically deformable and so laid out that when the pressure medium is switched off it is located, as a result of its elastic resetting force, with its sealing strip or edge 61 at a small distance from the surface of the running sleeve 2. This operating state is recorded in figure 2. on being pressurised with the pressure medium the hollow ring seal deforms such that its sealing strip 61 rests on the surface of the running sleeve 2, with the desired contact pressure being adjustable in simple manner by appropriate metering of the pressure medium.

The hollow ring seal 6 is located during normal operation, i.e. with correct functioning of the full ring seal 5.3 which faces the lubricant chamber 5, in its spaced position. If a failure of the named full ring seal occurs, or if it becomes leaky, then the hollow ring seal 6 is switched over into its operating position with the aid of a nonillustrated sensor system or indicated system and then enters into operation as a full value substitute seal.

In figure 2 there is shown a shaft seal in which a running sleeve 2 is drawn onto the shaft 1. The shaft 1 is journalled in a non-illustrated bearing which is carried by a boss 3. A sealing housing 4 is secured to the boss 3 and comprises four housing rings 4.1, 4.2, 4.3 and 4.4, which are arranged axially flush alongside one another, and three radial lip seals 5.1, 5.2 and 6 which are each inserted between two housing rings.

Here all the radial lip seals are aligned in the same manner and indeed face the chamber W which is filled in the present embodiment with water.

-6 The radial lip seals 5.1 and 5.2 are formed in the customary manner as full ring seals and act as main seals, while the radial lip seal 6 is laid out as a hollow ring seal and has to be addressed as the reserve seal. The hollow chamber 7 of this seal 6 is connected via a line 8 which is indicated in broken lines with a pressure source which is not illustrated but which,in this case supplies water. The wall of the hollow ring seal 6 is provided closely adjacent the sealing strip or edge 61 with a ring of fine bores 9 which extend in the circumferential direction and which are so dimensioned and arranged that they make available a water film which is adequate for the lubrication of the sealing strip 61 of the hollow ring seal 6.

- i in the variant illustrated in figure 3 grooves 10 are present in the circumferential direction in addition to the named fine bores 9, with the grooves being so shaped that they act hydrodynanically and convey the water film which emerges from the bores 9 in the direction towards the sealing strip 61, and thus assist the lubrication.

C -1

Claims

Patent Claims

1. Seal for rotating shafts comprising at least one main radial lip seal which sealingly contacts the _shaft or a shaft sleave,and at least one reserve radial lip seal having a sealing strip which is spaced from the shaft or shaft sleeve in normal operation and can be brought into sealing contact with the shaft or shaft sleeve on failure of one or more main radial lip seals, characterised by the use as a reserve radial seal of at least one hollow ring radial lip seal for the sealing of a shaft or of a shaft sleeve, with the hollow ring radial lip seal being pressurisable via a pressure line with a pressure medium, preferably air, by which the hollow radial lip seal is elastically deformable in such a way that its sealing strip adopts a sealing position relative to the shaft or shaft sleeve in the one operating state, and a position spaced from the shaft or shaft sleeve in the other operating state.

2. Seal in accordance with claim 1, characterised in that, in an arrangement in which a stern tube of a ship is sealed against the external water (A) and in which three main radial lip seals (5.1-5.3) are arranged alongside one another, of which the two outer seals (5.l., 5.2) face the external water (A) and the inner seal (5.3) faces a chamber (S) containing a liquid lubricant, preferably lubricating oil, the reserve radial lip seal (6) is arranged in front of the inner main radial lip seal (5.3) in the direction towards the lubricant chamber (S) (Fig. 1).

Seal in accordance with claim 1, characterised in that, in an arrangement in which a liquid medium (W), preferably water, is sealed against a gaseuos medium (L), preferably air, and in which two main radial lip seals (5.1, 5.2) are present which are arranged alongside one another and face the liquid medium (W), the reserve radial lip seal (6) is arranged in front of the main radial lip seal (5.2) at the liquid seal in the direction towards the liquid medium (W) (Fig. 2).---

4. Seal in accordance with claim 3, characterised in that the reserve radial lip seal (6) is pressurised with water under pressure as the pressure medium and is provided with a plurality of bores (9) which are distributed in the circumferential direction closely adjacent the sealing strip (61) of the reserve radial lip seal (6),and which open out of the hollow chamber (7) of the reserve radial lip seal (6) at the gas-space side (Fig. 2.).

5. Seal in accordance with claim 4, characterised in that grooves (10) are provided in the circumferential direction in the region of the outlet orifices of the bores (9) at the outer surface of the reserve radial lip seal (6) and generate hydrodynamic effects such that they conve the liquid emerging from the bores (9) in the direction towards the sealing strip (61).

6. Seal in accordance with claim 1, characterised in that a hollow ring reserve cuff is provided for each active radial lip seal.

1 i 1 1 7e- o 1

7. Seal in accordance with the claims 1 and 2, characterised in that the contact pressure of the hollow ring radial lip seal can be regulated (feed-back control).

8. Seal substantially as herein described and -illustrated with respect to any one of the accompanying Figures.

Published 1989 at The Patent ffice,S e House. 66"? 1 High Holborn, London WClR 4TP. Further copies maybe obtained from The Patent Office. Sales Branch, St Mary Cray, Orpington, Kent BR5 3ELD. Printed by Multiplex techniques ltd, St Mary Cray. Kent. Con. 1/87