GB2298010A

GB2298010A - Sealing devices for shafts

Info

Publication number: GB2298010A
Application number: GB9601485A
Authority: GB
Inventors: Joachim Meyer; Angela Vollmer
Original assignee: Renk GmbH
Current assignee: Renk GmbH
Priority date: 1995-02-17
Filing date: 1996-01-25
Publication date: 1996-08-21
Anticipated expiration: 2016-01-25
Also published as: DE19505405B4; GB9601485D0; GB2298010B; DE19505405A1

Description

2298010 SEALING DEVICES FOR SHAFTS This invention relates to sealing

devices for shaf ts, comprising at least one sealing ring which has an inner end face, an outer end face, an outer periphery and an inner periphery, at least one annular outer peripheral rib on the outer periphery for the axial positioning of the sealing ring in a seal carrier, a plurality of annular sealing ribs at the inner periphery, which are arranged spaced from each other in the axial direction and which define annular collecting grooves therebetween, flow return means for liquid provided at the lowermost portion of said collecting grooves and through which liquid can flow out from the sealing ring from the collecting grooves in the direction towards the inner end face.

The invention is concerned particularly with a socalled "floating knifeedge seal" and its use in bearings, particularly in sliding bearings. Such sealing devices and bearings are utilisable for shafts of many types of machine, particularly for electrical machines, fans and compressors. The sealing ring of such a sealing device preferably comprises two semicircular seal halves, which are movably mounted in a seal carrier which can be the housing of the relevant machine or of the relevant bearing. The two halves are preferably held together by means of a tension spring whose ends are turned in towards each other or are hooked to each other. The radial moveability of the sealing ring in the seal carrier preferably amounts to approximately 1mm. By this means one prevents the sealing ribs or the sealing knife edges of the sealing ring being damaged by the shaft due to manufacturing inaccuracies or during the assembly. The sealing ring can be made of a material which is particularly insensitive to temperature, radiation and chemicals, for example of high-strength polyamide which is stable at high temperatures. This also has excellent sliding properties. Additions such as for example PTFE and glass fibres can be incorporated.

Between the sealing ribs, or in the case of knifeedge seals between the sealing knife-edges, and a shaft extending therethrough, leak oil can travel from the inner end face of the sealing ring into oil collecting grooves which are formed between the sealing ribs or sealing knife-edges in the sealing ring. With a large flow of leak oil it is important that the leak oil can run away without hindrance from the oil collecting grooves into an oil sump. Due to the rotation of the shaft which extends through the sealing ring, this shaft forces oil by centrifugal action into the bearing housing or machine housing, which oil should be fed back as quickly as possible and without hindrance into the oil sump without it becoming heated to any substantial degree.

It is an object of the present invention to create a sealing device of the type first referred to above in which oil centrifuged by the shaft is collected and directed into an oil sump without it falling back on the shaft.

It is a further object of the invention to ensure that leak oil is directed from the oil collecting grooves of the sealing ring rapidly and without hindrance into the oil sump before it can become heated in the oil collecting grooves. Consequently, it is overall the intention of the invention to ensure that oil flowing away from a shaft is directed along a short path and rapidly into a collecting chamber, without the oil being heated by the shaft to any substantial degree, after the oil has fulfilled its lubricating effect. Instead of oil, with this sealing device on a shaft, other types of liquid could also be sealed, for example water.

These objects are achieved, in accordance with the invention, by a sealing device in accordance with claim 1.

The subsidiary claims refer to improvement features and preferred uses of the sealing device. The invention will now be described in more detail with reference to the drawings and to a preferred embodiment which is given by way of example. The various Figures of the drawings are drawn to different scales. In the drawings:

Fig. 1 is a side view of the sealing device according to the invention for a shaft; Fig. 2 is an end view taken in the direction of the arrow II in Fig. 1; Fig. 3 is an axial section through the sealing device shown in Figs. 1 and 2; Fig. 4 is a section, on an enlarged scale, of the upper part of the sealing device of Fig. 3, turned through 1800 and set in a seal carrier; Fig. 5 is a section, on an enlarged scale, of the lower part of the sealing device of Fig. 3, turned through 1800 and set in a seal carrier; Fig. 6 is an axial section through a radial bearing having two sealing devices of the type shown in Figs. 1 to 5 arranged in opposition to each other on respective sides of a bearing shell; Fig. 7 is a cross-sectional view of the bearing of Fig. 6 taken from the plane VII, viewed on the inner end face of one sealing device and without the shaft which is shown in Fig. 6; and Fig. 8 is a perspective view of the sealing device.of Fig. 1.

The sealing device for shafts according to the invention, shown in the drawings, consists essentially of a sealing ring 2 which is composed of a semicircular upper ring half 2.1 and a semi- circular lower ring half 2.2 on each side of a dividing plane 4, as well as a tension spring 6. The tension spring 6 is mounted in a peripheral groove 8 which encircles the sealing ring 2 on its outer periphery 22. The tension spring has its ends connected together. The outer peripheral groove 8 is formed in an outer peripheral rib 10 which projects radially outwards from the outer periphery of the sealing ring 2. The outer peripheral rib 10 serves for the axial positioning of the sealing ring 2 in an inner peripheral groove 12 of a seal carrier 14. As shown in Figs. 6 and 7, the seal carrier 14 can be a bearing housing or some other machine housing or a retaining ring. The outer peripheral rib 10 has radial play within the inner peripheral groove 12.

The sealing ring 2 has an inner end face 18 which delimits the inner chamber 16 of the housing, an outer end face 20 which is spaced from the inner end face, the outer periphery 22 and an inner periphery 24. The inner end face 18 is the sealing side at which one finds the liquid whose leakage is to be prevented.

At the inner periphery 24 there are a plurality of annular sealing ribs or sealing knife-edges 26 which are arranged axially one behind the other with reference to the central axis of the sealing ring 2, which is at the same time the bearing axis 30. These ribs or knife-edges 26 define annular oil collecting grooves 32 between themselves. At the lowermost zone of the ring there is an oil return slot 34 in the inner end face 18 which extends below the sealing ribs 26, adjacent to the lowermost ring zone of the oil collecting grooves 32, from the inner end face 18 to bridge all oil collecting grooves 32 in the direction from the inner end face 18 to the closed end of the slot, thereby crossing the groove bottom of the oil collecting grooves 32. The oil collecting grooves 32 are connected with the oil return slot 34 for liquid flow at their lowest peripheral region by way of holes 33. The length of the oil return slot 34 in the circumferential direction is a multiple, at least twice the width of the oil return slot 34 in the radial direction, at least at the inner end face 18, but preferably over the whole depth of the slot. The cross section of the oil return slot 34 must be so largeat all positions that the oil which enters into it from the oil collecting grooves 32 can flow out without any real throttling effect from the sealing ring 2 at its inner end face 18 into a sump 36 in the internal chamber 16 of the housing. It is particularly advantageous if the radially outer slot wall surface 38 is angled downwards and outwards, with the result that it diverges away from the radially inner slot wall surface 40 and consequently also from the sealing ring axis and bearing axis 30 at a specific angle 42, such that the radial width and consequently also the aperture cross-section of the oil return slot 34, viewed in the axial section of the sealing ring, is radially larger as it extends outwardly, in the form of a wedge from the oil collecting groove 32 which lies deepest in the oil return slot 34 up to the inner end face 18. By using this special form of oil return slot 34 one achieves two real advantages. Even with an inclined setting for the sealing ring 2, particularly when used on a ship, oil return from the oil collecting grooves 32 through the oil return slot into the inner chamber 16 of the housing is guaranteed; also, the oil flow at the sealing ribs 26 whichserve as sealing knife-edges and also at the oil collecting grooves 32 is improved, since the aperture cross-section of the oil return slot 34 is greater from the inside outwards, corresponding to the increasingly greater quantity of oil which flows from oil collecting groove to oil collecting groove 32 and from sealing rib to sealing rib 26 in the direction towards the inner end face 18. By the use of an oil return slot 34 extending in the circumferential direction, instead of using return bores for the individual oil collecting grooves 32, one still achieves a substantially greater oil flow cross section even if the oil return slot 34 is of constant size in the flow direction, instead of using the wedge shaped, larger cross-section in the flow direction as is in the illustrated embodiment.

At the outer periphery 22 of the sealing ring 2, between its outer peripheral rib and its inner end face 18, there is an annular collecting funnel 44 extending through 3600 of the outer periphery and which, viewed in axial section, has the form of an oil collecting nose. The oil collecting funnel 44 collects the oil which is thrown out centrifugally by rotation of a shaft 47, and permits it to flow downwards in both peripheral directions and drop off at an edge 46 of the funnel or nose at the inner end face 18. The shaft 47 is rotatably mounted in the bearing housing 14 in a pivotally arranged bearing shell 48, and on both sides of the bearing shell 48, axially spaced from it, it is sealed off by respective sealing rings 2 which are non rotatably arranged within the bearing housing 14 and which are in sealing contact via the sealing ribs 26 with the shaft 47.

The oil collecting funnel 44, on the outer periphery of the sealing ring 2, has a grooved shape whose ring diameter increases regularly in a frusto- is conical manner from the outer peripheral rib 10 up to the edge 46 of the funnel at the inner end face 18, with the result that oil collected by the oil collecting funnel 44 can drop off at its lowest peripheral region at the inner end face 18.

In Figs. 6 and 7 it is indicated by arrows 52 how oil is thrown out centrifugally by the shaft 47 and from the bearing shell 48 into the inner chamber 16 of the housing, and is collected by the oil collecting funnel 44 which directs the oil back to the oil sump 36 along the path prescribed for it without the oil falling back onto the shaft 47 or onto the bearing shell 48.

The sealing ring 2, starting from its outer peripheral rib 10, and going towards its inner end face 18, has a different length as compared with its length in the direction towards its outer end face 20. Also, its outer peripheral surface is formed differently on the two sides of the outer peripheral rib 10. By this unsymmetrical formation, the sealing ring 2 can only be inserted in one particular direction into the seal carrier, in the present case the housing 14. As shown in Fig. 6, two sealing rings 2 are arranged to be set at 1800 to one another. In order to ensure that the sealing ring 2 is always introduced in the same angular position into the housing 14 in the circumferential direction, the lower ring half 2.2 is provided with a locating nose 54 which is arranged in the dividing plane 4 and engages in a locating groove 55 of the bearing housing 14 which is provided there. The bearing housing 14 is divided at the dividing plane 4 into an upper housing part 14.1 and a lower housing part 14.2. The locating groove 55 is located on the -dividing plane 4 in the lower housing part 14.2. The dividing plane 4 extends in a plane in which the bearing axis 30 is located.

The following summarises the real advantages of the sealing device formed as a floating knife-edge seal. The sealing ring 2 is constructed unsymmetrically, so that errors of assembly are excluded. An oil return slot 34 replaces the conventionally used oil return bores, from which only an insufficient amount of oil could flow. The oil return slot 34 has a radially outwardly extending inclination corresponding to the angle of inclination 42 of for example 7.50, so that even with an inclined position of the sealing ring 2, for example when used on ships, an oil return from the sealing ring into the bearing housing 14 is ensured. By the slope of the is radially outer slot wall 38 of the oil return slot 34, the unhindered flow of the oil is also improved. By extending the seal seats 10 and 12 in the radial direction, an inversion of the sealing ring 2 by the oil to be sealed is better prevented. obviously, the sealing device can be used not only for the sealing of oil, but also for the sealing of other liquids. The edges of the outer peripheral rib 10 are chamfered, in order to facilitate the insertion of the sealing ring into the seal carrier 14. The end face 18 which is shown on the inside is characterised by the oil collecting nose or funnel 44. This prevents sprayed oil from the outer edge of the seal dropping again onto the shaft 47 and reaching the sealing gap between the sealing ring 2 and the shaft 47. The sprayed oil is directed back into the oil collecting funnel 44 around the sealing ring. The locating nose 54 for the prevention of rotation of the seal ring 2 is located on the dividing plane 4 in order to make it possible more easily to orientate and assemble the device. The number of knife-edges or sealing ribs 26 has been is -g- increased from the previous 5 to 6. By this means the sealing effect of the knife-edge seal is substantially improved.

Claims

CLAIMS:

1. A sealing device for shafts, comprising at least one sealing ring which has an inner end face, an outer end face, an outer periphery and an inner periphery, at least one annular outer peripheral rib on the outer periphery for the axial positioning of the sealing ring in a seal carrier, a plurality of annular sealing ribs at the inner periphery which are arranged spaced from each other in the axial direction and which define annular collecting grooves therebetween, flow return means for liquid provided at the lowermost portion of said collecting grooves and through which liquid can flow out from the sealing ring from the collecting grooves in the direction towards the inner end face, wherein at the outer periphery of the sealing ring, between the outer peripheral rib and the inner end face, there is at least one annular liquid collecting funnel in which liquid which is thrown out centrifugally by rotation of a supported shaft is collected and then can flow downwards in both circumferential directions.

2. A sealing device according to claim 1, in which the collecting funnel has a bottom surface whose diameter increases in a frusto-conical manner from the outer peripheral rib towards the inner end face, such that liquid collected by the funnel is directed in the lower ring half axially in the direction towards the inner end face and then drops off at the funnel edge which is at the inner end face.

3. A sealing device according to claim 1 or 2, wherein the flow return means comprises at least one return slot which is formed in the inner end face and extends below the sealing ribs, at the lowermost ring -zone of the collecting grooves, from the inner end face in the direction to embrace all collecting channels and is open at the bottom of these collecting channels into these collecting channels, wherein the length of the return slot in the circumferential direction is at least twice its width in the radial direction, measured at the inner end face, and wherein the radially outer slot wall surface diverges away from the radially inner slot wall surface and from the central axis of the sealing ring such that the radial width and consequently also the aperture cross-section of the return slot, viewed in the axial section of the sealing ring, becomes greater in the manner of a wedge, from the collecting groove located deepest within the return slot up to the inner end face.

4. A sealing device according to any preceding claim, in which the sealing ring, or its parts in the case of a multi-part sealing ring, is unsymmetrical so that it cannot be inserted into the seal carrier when turned through 1800 with reference to its two end faces.

5. A sealing device according to any preceding claim, in which the sealing ring comprises a locating nose for setting it into a locating recess or groove which is located on a dividing plane of the seal carrier in order to ensure correct circumferential positioning of the sealing ring within the seal carrier.

6. A sealing device according to any preceding claim, in which the sealing ring comprises two semicircular ring halves.

7. A sealing device according to any preceding claim, in which the sealing ribs are formed as sealing knife-edges.

8. A bearing comprising at least one sealing -device as claimed in any of the preceding claims.

9. A bearing according to claim 8, having two sealing devices according to any of the preceding claims, spaced axially from one another and set in opposition in a bearing housing on respective opposite sides of a bearing shell which is arranged within the bearing housing.

9. A bearing according to claim 8, having two 0 sealing devices according to any of the preceding claims, spaced axially from one another and set in opposition in a bearing housing on respective opposite sides of a bearing shell which is arranged within the bearing housing.

10. A sealing device as claimed in claim 1 substantially as hereinbefore described with reference to the accompanying drawings.

1 Amendments to the claims have l-eer-f-iled as follows 13) 1. A sealing device for shafts, comprising at least one sealing ring which has an inner end face, an outer end face, an outer periphery and an inner periphery, at least one annular outer peripheral rib on the outer periphery for the axial positioning of the sealing ring in a seal carrier, a plurality of annular sealing ribs at the inner periphery which are arranged spaced from each other in the axial direction and which define annular collecting grooves therebetween, flow return means for liquid provided at the lowermost portion of said collecting grooves and through which liquid can flow out from the sealing ring from the collecting grooves in the direction towards the inner end face, wherein at the outer periphery of the sealing ring, between the outer peripheral rib and the inner end face, there is at least one annular liquid collecting funnel in which liquid which is thrown out centrifugally by rotation of a supported shaft is collected and then can flow downwards in both circumferential directions.

3. A sealing device according to claim 1 or 2, wherein the flow return means comprises at least one return slot which is formed in the inner end face and extends below the sealing ribs, at the lowermost ring zone of the collecting grooves, from the inner end face in the direction to embrace all collecting channels and li is is open at the bottom of these collecting channels into these collecting channels, wherein the length of the return slot in the circumferential direction is at least twice its width in the radial direction, measured at the inner end face, and wherein the radially outer slot wall surface diverges away from the radially inner slot wall surface and from the central axis of the sealing ring such that the radial width and consequently also the aperture cross-section of the return slot, viewed in the axial section of the sealing ring, becomes greater in the manner of a wedge, from the collecting groove located deepest within the return slot up to the inner end face.

5. A sealing device according to any preceding claim, in which the sealing ring comprises a locating nose for setting it into a locating recess or groove which is located on a dividing plane of the seal carrier in order to ensure correct circumferential positioning of the sealing ring within the seal carrier - 6. A sealing device according to any preceding claim, in which the sealing ring comprises two semicircular ring halves.

8. A bearing comprising at least one sealing device as claimed in any of the preceding claims.