GB2236813A

GB2236813A - Non-contact seal

Info

Publication number: GB2236813A
Application number: GB9019837A
Authority: GB
Inventors: Wolfgang Biesold; Sebastian Merz
Original assignee: SKF GmbH
Current assignee: SKF GmbH
Priority date: 1989-09-11
Filing date: 1990-09-11
Publication date: 1991-04-17
Anticipated expiration: 2010-09-11
Also published as: GB9019837D0; GB2236813B; DE3930280A1; DE3930280C2

Abstract

A non-contact seal (4) for forming a seal between a stationary machine pan (3) and a rotatable machine part (1) comprising a slinger ring (5) which is mounted on the rotatable machine part (1) with an annular gap (21) formed between the ring and the stationary part (6) of the seal (4). In order that no liquid media may be able to penetrate into the bearing (2) even with a high-speed spindle (1) or the like, the slinger ring (5) forms with the stationary part (6) of the seal (4) a sealing gap (21) which is preferably radially directed and an annular chamber (A) which is connected, through a narrow extending circumferentially gap (22), to at least one further annular chamber (B), and the chamber (B) is substantially bounded by stationary parts (6,7) of the seal (4), one of the parts (7) of the seal comprising a collecting channel (31) for collecting and drawing oft liquid which has penetrated the seal. <IMAGE>

Description

J i t 1 1 1 NON-CONTACr SEAL The invention relates to a non-contact seal

for forming a seal between a stationary machine part and a rotatable machine part.

A non-contact seal comprising a slinger ring which is mounted on the rotatable machine part and forms an annular gap with a stationary part of the seal is already known from CH-PS 61 581. This known seal is, however, inadequate, for example for machine tools with high-speed spindles, since the cooling liquid can easily penetrate into the bearing.

It is an object of the present invention to provide a non-contact seal for high-speed spindles or the like which consists of easily manufactured parts and prevents liquid media from being able to enter the bearing.

According to the present invention there is provided a non-contact seal for forming a seal between a stationary machine part and a rotatable machine part, the seal comprising a slinger ring which is mounted on the rotatable machine part with an annular gap formed between the ring and a stationary part of the seal, characterised in that there is formed between the slinger ring and the stationary part of the seal a sealing gap, which is preferably radially directed, and an annular chamber (A), the chamber (A) is connected, through a narrow circumferentially extending gap. to at least one further annular chamber (B), and the chamber (B) is substantially bounded by stationary parts, one of the parts comprising a collecting channel for collecting and carrying away liquid which has penetrated into the seal.

An excellent sealing effect which also permits use under water is achieved by this formation of the seal.

K Further developments of the invention are described in the sub-claims.

The invention will now be described, by way of example, with reference to the accompanying drawing, which is an axial section of an embodiment of the invention.

In the drawing, a spindle 1 carrying a tool is mounted in a housing 3 (only shown by way of indication) via rolling bearings 2. The space between the housing 3 and the spindle 1 is closed by a non-contact seal 4 which forms an effective seal against liquid media, dust and the like. The seal consists of a slinger ring 5, a covering ring 6 and an L-shaped intercepting ring 7, the latter being disposed in a housing ring 8. The covering ring 6 and the intercepting ring 7 as well as the housing ring 8 form the stationary part of the seal which is secured to the housing 3 by screws. The slinger ring 5 mounted on a step 9 of the spindle 1 comprises a slinger disc 10 which is directed radially outwards and which has an inclined surface 11 on the outside to spray off liquids. The inner surface 12 of the slinger disc 10 extends in the radial direction and bears with play against a corresponding radial surface 13 of the covering ring 6. Provided on the circumferential surface 14 of the slinger ring 5 is a radially directed, encircling projection 15 with lateral surfaces 16, 17 and a circumferential surface 18. The radially directed inner surface 12 of the slinger disc 10, the circumferential surface 14 and the one lateral surface 16 of the projection 15 form, with a bore surface 19 and a radial surface 20 of the covering ring 6, a chamber A in which the liquid penetrating through the radial gap 21 is collected. The chamber A is connected to the chamber B through a narrow 1 i axial gap 22 which is bounded by the circumferential surface 18 of the projection 15 and a bore surface 23 of a radially inwardly directed projection 24 of the covering ring 6.

The projection 15 is made wider than the projection 24 so that liquids which have penetrated can be sprayed off to the outside. A reduction in pressure of the penetrating liquid is achieved by a throttle effect through the narrow axial gap 22 extending all round. The chamber B is formed by the lateral surface 25 and bore surface 26 of the covering ring 6 and by the circumferential surfaces 27, 28 and lateral surfaces 29 of the L-shaped intercepting ring 7. The intercepting ring 7 and the covering ring 6 are disposed in the bore 30 of the housing ring 8, the intercepting ring 7 being located in the axial direction by the covering ring 6. The intercepting ring 7 comprises a collecting channel 31 to collect and draw off the liquid which has penetrated. Since the chamber B is not bounded by rotating parts, no turbulence can occur in it. In addition, there is a very uniform distribution of pressure in the chamber B. The chamber C is bounded by the intercepting ring 7, a second L-shaped intercepting ring 32, for example made intergral with the housing ring, and the housing ring 8. The intercepting ring 7 bears with axial play with an end face 33 against the lateral surface 17 of the projection 15 and with radial play against the circumferential surface 14 of the slinger ring 5. The intercepting ring 32 provided with a collecting channel 34 bears with axial play with an end face 35 against the end face 36 of the slinger ring 5 and with radial play against a distance sleeve 37. The chamber C is likewise not bounded by rotating parts so that laminar flow conditions and a uniform distribution of pressure prevail in this chamber. The chamber C is provided with a supply of compressed air (not shown) so that liquids which have penetrated are urged outwards. This supply of compressed air is only necessary up to 800 r.p.m. At speeds above 800 r.p. m., air is, of course, drawn in by the pressure developing in the radial sealing gaps. The housing ring 8 is provided with drainage bores 38, 39 in the lower region so that liquids can flow out of the collecting channels 31, 34 into the drainage bores 38, 39.

The seal according to the invention works in the following manner: On rotation of the spindle 1, the slinger ring 5 is set in rotation so that some of the liquid impinging from the outside is slung radially outwards by the slinger disc 10. Furthermore, an axially directed shoulder 40 of the covering ring 6 prevents liquids from being able to splash directly into the gap 21. Some of the liquid penetrating into the gap 21 is slung out again by the suction directed radially outwards and developing in the gap 21 when the slinger disc 10 is rotating. The liquid remaining in the chamber A then passes through the axial gap 22 into the chamber B and into the collecting channel 31 of the intercepting ring 7, some of the liquid dripping into the drainage bore 38. If liquids should pass through the axial and radial gap between the intercepting ring 7 and the slinger ring 5. they are collected in a collecting channel 41 of the slinger ring 5 and pass, via an inclined surface 42 of the slinger ring 5, which reaches as far as the circumferential surface 43 of the circumferential ring 32, into the n collecting channel 34 and then into the drainage bore 39. Normally, however, the liquids only advance as far as the chamber B where they are stopped by the compressed air or the suction developing. The seal 4 is so formed that the arrangement can also be used under water.

This form of embodiment described only represents one example of a seal according to the invention. Variations in the construction of the individual components are easily possible within the scope of the invention. Thus, for example, one or both of the end faces bounding the radial gap may be provided with conveying grooves, for example spiral grooves.

CLAM 1. A non-contact seal for forming a seal between a stationary machine part and a rotatable machine part, the seal comprising a slinger ring which is mounted on the rotatable machine part with an annular gap formed between the ring and a stationary part of the seal, characterised in that there is formed between the slinger ring (5) and the stationary part (6) of the seal (4) a sealing gap (21), which is preferably radially directed, and an annular chamber (A), the chamber (A) is connected, through a narrow circumferentially extending gap (22), to at least one further annualar chamber (B), and the chamber (B) is substantially bounded by stationary parts (6,7), one of the parts (7) comprising a collecting channel (31) for collecting and carrying away liquid which has penetrated into the seal (4).

Claims

2. A non-contact seal according to Claim 1, characterised in that the

stationary part of the seal (4) comprises a housing ring (8), a covering ring (6) and at least one L-shaped intercepting ring (7), the covering ring (6) and the intercepting ring (7) being disposed in a bore (30) of the housing ring (8).

3. A non-contact seal according to Claim 1 or Claim 2, characterised in that an inner surface (12) of the slinger ring (5), a circumferentially extending surface (14) and a lateral surface (16) of a projection (15) on the slinger ring together with a bore surface (19) and a radial surface (20) of the covering ring 6 form the annular chamber (A).

7 - 4. A non-contact seal according to any one of Claims 1 to 3, characterised in that the further annular chamber (B) is bounded by a lateral surface (25) and a bore surface (26) of the covering ring (6) and by circumferential surfaces (27, 28) and a lateral surface (29) of the Lshaped intercepting ring (7).

5. A non-contact seal according to any one of Claims 1 to 4, characterised in that a third chamber (C) is provided, the chamber (C) being bounded by the intercepting ring (7), a second intercepting ring (32) which is, for example made integral with the housing ring (8), and the housing ring (8).

6. A non-contact seal according to Claim 5, characterised in that the chamber (C) is provided with a supply of compressed air.

7. A non-contact seal according to any one of Claims 1 to 6, characterised in that the intercepting ring (7) is arranged with an end face (33) thereof bearing with axial play against a lateral surface (17) of a projection (15) and with radial play against a circumferential surface (14) of the slinger ring (5).

8. A non-contact seal according to any one of Claims 1 to 7, characterised in that the intercepting ring (32) is arranged with an end face (35) thereof bearing with axial play against an end face (36) of the slinger ring (5) and with radial play against a distance sleeve (37).

1,k 9. A non-contact seal according to any one Claims 1 to 8, characterised in that the housing ring (8) is provided with drainage bores (38.39) which communicate with the collecting channels (31,34).

4; 10. A non-contact seal according to any one of Claims 1 to 9, characterised in that the covering ring (6) comprises an axially directed shoulder (40).

11. A non-contact seal according to any one of Claims 1 to 10, characterised in that the slinger disc (10) is made narrower at a free end thereof.

12. A non-contact seal according to any one Claims 1 to 11, characterised in that the slinger ring (5) is provided with a collecting channel (41).

13. A non-contact seal according to any one of Claims 1 to 12, characterised in that the slinger ring (5) has an inclined surface (42) which extends as far as a circumferential surface (43) of the intercepting ring (32).

14. A non-contact seal constructed. arranged and adapted to operate substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawing.

Published 1991 at 7be Patent Office. State House. 66/71 High Bolborn. LDndonWCIR47?. Further copies may be obtained from Sales Branch, Unit 6. Nine Mile point, Cwmfelinfach. Cross Keys. Newport. NPI 7HZ. Printed by Multiplex techniques lid, St Mary Cray, Kent.