WO2003024635A1

WO2003024635A1 - Roller bearing assembly

Info

Publication number: WO2003024635A1
Application number: PCT/GB2002/004300
Authority: WO
Inventors: Mark DOLBY; Peter David Spooner
Original assignee: Shape Technology Limited
Priority date: 2001-09-21
Filing date: 2002-09-20
Publication date: 2003-03-27
Also published as: GB0122795D0

Abstract

A roller air bearing assembly (1) for measuring flatness defects in a continuously running web comprises an array of annular rotors (2) mounted coaxially on a central tubular arbor (4). The arbor (4) comprises a closed end (5) and is formed with a series of radially extending fluid ports (6) that perforate the tubular wall of the arbor (4). In use compressed air is supplied to the inner region (8) of the arbor (4) via a compressed air pipe (not shown). The compressed air is exhausted from the region (8) via the ports (6). The exhausted air forms a film bearing between a radially outermost surface of the arbor and radially innermost surfaces of the respective rotors (2). In use the air film holds the rotors (2) spaced from the arbor (4) and forms a radial pneumatic bearing on which the rotors (2) may rotate about a common axis (10). The arbor (4) also comprises a series of pressure sensors (not shown) for detecting the differential pressure of the air film between the upper and lower regions of the pneumatic bearing supporting each rotor (2).

Description

ROLLER BEARING ASSEMBLY

The present invention relates to a roller bearing assembly and in particular to a roller fluid bearing assembly for measuring the flatness of a web running against the roller fluid bearing assembly.

A known roller air bearing assembly for measuring flatness defects in a continuously running web comprises an array of annular rotors mounted coaxially on a central stationary arbor. The central arbor is formed with a series of radially extending fluid ports, which provide the array of annular rotors with an air film. In use the air film holds the rotors spaced from the arbor and forms a radial pneumatic bearing on which the rotors rotate. The arrangement of the rotors is such that there may be a radial air gap between neighbouring rotors. The web material, typically a thin sheet metal, is passed over and supported by the rotors such that any transverse strain variation in the web material produces a variation of forces on the individual rotors. The force on each rotor is detected by a set of sensors that measure the differential pressure of the air film between the top and the bottom of the air bearing supporting the rotor. The sensors are disposed at the surface of the arbor. Such a device is presently manufactured by Shape Technology Ltd and is known as an air bearing shapemeter.

We have found that with some applications of the air bearing shapemeter individual rotors can experience a degree of tilt from the axis of rotation of the arbor due to uneven forces on the rotors induced by strain variations in the web. The tilt of a rotor will cause the air gap between the rotor and the arbor to be reduced. In some circumstances the tilt is such that the air gap may be closed causing the rotor and the arbor to touch. This problem is exaggerated when the longitudinal widths of the rotors are reduced. At present with the current designs of roller air bearing assemblies the width of each rotor must be greater than 40mm. This minimum width requirement is in order to provide adequate tilt stability and thereby prevent the rotors touching each other, or the arbor, at speed and causing damage. However, there is a desire to have rotors having widths less than 40mm in width. This desire is so that strain measurement can be provided at reduced intervals.

According to a first aspect of the present invention there is provided a roller bearing assembly comprising an array of rotors rotatably mounted on a central arbor, the arbor being formed with fluid channels for providing the rotors with radial pneumatic bearing means, and fluid means for exerting an axial force on at least one rotor disposed at one end of the array of rotors.

The fluid means for exerting an axial force is preferably pneumatic means comprising a manifold formed with a plurality of ports through which a gas may pass, the manifold being disposed adjacent to a rotor at one end of the array of rotors and being distant therefrom, the arrangement being such that in use an axial force is applied to the array of rotors via a flow of gas from the ports into the gap between the manifold and the adjacent rotor.

It is most convenient to use air as the gas to pressurise the gap between the manifold and the adjacent rotor. However, it should be appreciated that any other suitable fluid may be used such as, but not limited to, a nitrogen gas or a liquid such as water.

The manifold is preferably capable of movement in an axial direction substantially parallel to the axis of the array of rotors. The manifold is preferably capable of axial movement relative to the arbor.

Preferably, the roller bearing assembly comprises means for maintaining substantially constant, when in use, the axial force applied to the array of rotors.

The means for maintaining the substantially constant axial force on the array of rotors preferably comprises means for applying a force to the manifold, the arrangement being such that in use the axial force being applied to manifold is transferred to the array of rotors via the flow of gas from the ports into the gap between the manifold and the adjacent rotor.

The force applied to the manifold is preferably a substantially constant axial force.

The means for applying a constant axial force on the manifold preferably comprises hydraulic means.

In an alternative arrangement the means for applying a constant axial force to the manifold preferably comprises pneumatic means.

In a further alternative arrangement the means for applying a constant axial force to the manifold preferably comprises mechanical means.

Preferably, the means for applying a constant axial force to the manifold comprises a mechanism fixed to the arbor. Preferably, the means for applying a constant axial force to the manifold comprises a mechanism fixed to the arbor, the arrangement being such that in use the axial force applied to the manifold is transferred to the array of rotors by the manifold.

Preferably, the fluid channels formed in the arbor provide the manifold with radial pneumatic bearing means.

The roller bearing assembly preferably comprises an array of sensors that are used for measuring the flatness of a web material being carried by the roller bearing assembly.

It is preferable that the axial force applied to the rotors by the manifold is such that the rotors can still move independently.

The manifold is preferably annular and is preferably disposed coaxially on the arbor.

The manifold is preferably formed with an internal annular chamber.

The plurality of ports preferably each extend from the annular chamber perforating a wall section of the manifold.

In one alternative embodiment of the present invention the manifold is formed with radial ports that extend through a radially inner wall section, the arrangement being such that in use the radial ports provide the manifold with radial pneumatic bearing means.

The rotors are preferably an annular shape.

The longitudinal width of a rotor is preferably 50mm or less. The longitudinal width of a rotor is preferably within the range 10mm to 50mm.

Alternatively the longitudinal width of a rotor is 10mm.

We have found that the problems of rotor tilt may be reduced by applying an axial force to the array of rotors such that they are held in compression.

Preferably, the roller bearing assembly comprises fluid means for exerting a compressive axial force on the array of rotors, the fluid means being disposed at each end of the array of rotors.

The fluid means for exerting an axial force preferably comprises two manifolds each formed with a plurality of ports through which a fluid may pass, each manifold being disposed adjacent a rotor at one end of the array of rotors and being distant therefrom, the arrangement being such that in use a compressive axial force is applied to the array of rotors by a flow of fluid from the ports into the respective gaps between each manifold and the respective adjacent rotor.

The roller bearing assembly preferably comprises means for applying a force to the second manifold.

The arrangement of the second manifold is preferably substantially the same as the manifold of the roller bearing assembly herein before described.

The means for applying a force to the second manifold is preferably substantially the same as the means for applying a force to the manifold herein before described. It will be appreciated that the fluid means for exerting an axial force on at least one rotor disposed at one end of the array of rotors operates substantially as a fluid thrust bearing.

According to a second aspect of the present invention there is provided a method of stabilising an array of rotors of a roller bearing assembly, the rotors being rotatably mounted on an arbor comprising fluid bearing means, the method comprising applying an axial force to the array of rotors.

Preferably the method of stabilising an array of rotors comprises applying a constant axial force to the array of rotors.

Preferably the method of stabilising an array of rotors comprises applying a constant compressive axial force to the array of rotors.

The present invention may include any combination of the features or limitations referred to herein.

The present invention may be carried into practice in various ways, but embodiments will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 is a partial cross-section view of an end of a first embodiment of a roller bearing assembly;

Figure 2 is a partial cross-section view of an end of a second embodiment of a roller bearing assembly; and Figure 3 is an isometric view of a roller bearing assembly as shown in either Figure 1 or Figure 2 and shows a web of material passing there over.

Referring to the Figure 1 , a roller air bearing assembly 1 for measuring flatness defects in a continuously running web comprises an array of annular rotors 2 mounted coaxially on a central tubular arbor 4. The arbor 4 comprises a closed end 5 and is formed with a series of radially extending fluid ports 6 that perforate the tubular wall of the arbor 4. In use compressed air is supplied to the inner region 8 of the arbor 4 via a compressed air pipe (not shown) . The compressed air is exhausted from the region 8 via the ports 6. The exhausted air forms a film bearing between a radially outermost surface of the arbor and radially innermost surfaces of the respective rotors 2. In use the air film holds the rotors 2 spaced from the arbor 4 and forms a radial pneumatic bearing on which the rotors 2 may rotate about a common axis 10. The arbor 4 also comprises a series of pressure sensors (not shown) for detecting the differential pressure of the air film between the upper and lower regions of the pneumatic bearing supporting each rotor 2. The rotors 2 may have an axial width of less than 50mm. If desirable the axial width may be reduced to 10mm in order to reduce the intervals between neighbouring pairs of sensors.

The arrangement of the rotors 2 is such that there maybe a radial air gap between neighbouring rotors 2.

Disposed at one end of the arbor 4 within a stepped region 1 1 is an annular manifold 12. The manifold 12 is disposed adjacent a rotor 2' at one end of the array of annular rotors 2. The annular manifold 12 comprises an annular internal chamber 14 and is formed with a plurality of ports 16 that perforate a side wall of the manifold 12. The ports 16 are disposed substantially equally around the side wall of the manifold 12. The internal chamber 14 is supplied with compressed air via an air hose (not shown) . The compressed air within the chamber 14 is exhausted therefrom via the ports 16. In use the exhausted air from the manifold 12 forms a film bearing within the gap between the side wall of the manifold 12 and the adjacent side wall of the rotor 2' . The exhausted air from the manifold 12 produces an axial force on the side wall of the rotor 2' in the direction 18. It will be appreciated by the skilled in the art that the manifold 12 forms a thrust bearing that provides an axially compressive force to the array of rotors 2. The manifold 12 is provided with a radial pneumatic bearing by a set of ports 6 that perforate the arbor 4 and are adjacent to the radially innermost surface of the manifold 12. The manifold 12 is capable of movement in the direction of the axis 10. However, the manifold 12 is prevented from rotational movement about the axis 10 by a key way arrangement (not shown) .

A locking ring 17 is secured to the end of the arbor 4. The locking ring 17 comprises means 20 for applying s constant force to the manifold 12. The manifold 12 is freely able to move axially relative to the locking ring 17 such that the force applied by the means 20 is transferred to the array of rotors 2 via the manifold 12. Such a movement could be caused by an expansion of the overall, or part of, longitudinal length of the array of rotors 2. Such a movement could also be caused by an increase in the pressure of the air in the manifold 12. It is important to ensure that the force applied by the means 20 is kept substantially constant. It will be appreciated that means 20 and the manifold 12 operate as an auto- adjustable fluid thrust bearing arrangement. The means 20 for applying the axial force to the manifold 12 preferably comprises a pneumatic assembly. Alternatively, the means 20 may comprise a mechanical means, such as but not limited to, a spring assembly. In a further alternative the means 20 may comprise hydraulic means. The skilled person will appreciate that any suitable means for applying an axial force to the manifold 12 may be used.

The opposite end of the roller air bearing assembly 1 (not shown) may comprise the same arrangement as the end shown in Figure 1.

The present invention enables the use of narrow rotors 2, typically having a width of less than 50mm, without the risk of the rotors touching the arbor. The invention provides an arrangement that provides axial support to the array of rotors 2. Due to the compressive axial force applied to the array of rotors 2 each rotor 2 may have slight contact with the neighbouring rotors. However, it is known for the radial side surfaces of each of the rotors to comprise low friction pads and these will help to reduce the effect of any contact. With present roller bearing arrangements the rotors do not have support from adjacent rotors and therefore the tilt stiffness is only provided by the radial air film.

The present invention provides an axial thrust bearing in the form of the manifold 12 that maintains a constant small force on the array of rotors 2. The force is low enough to ensure that the rotors 2 can still move independently. This inter-rotor force assists the radial air bearing to support the rotors 2 and help prevent the rotors 2 tilting and touching the stationary arbor 4.

To maintain the constant force it is important that the thrust bearing manifold 12 is able to move laterally but should not be allowed to tilt. This may be achieved by incorporating a radial air bearing journal to each thrust bearing manifold 30 as shown in Figure 2. The thrust bearing manifold 30 shown in Figure 2 is formed with a plurality of ports 32 that perforate radially through the radially innermost wall 34. In this embodiment of the present invention the radial air bearing film for the manifold 30 is provided by air exhausting from the internal chamber 16 of the manifold 30.

Figure 3 shows a roller bearing assembly 1 according to the present invention and a continuous web 40 being passed over the rotors 2 and supported by the rotors 2 of the assembly 1.

Claims

1 . A roller bearing assembly (1) comprising an array of rotors (2) rotatably mounted on a central arbor (4), the arbor (4) being formed with fluid channels (6) for providing the rotors with radial pneumatic bearing means, and fluid means for exerting an axial force on at least one rotor (2') disposed at one end of the array of rotors (2) .

2. The roller bearing assembly (1) of claim 1 wherein the fluid means for exerting an axial force is pneumatic means comprising a manifold (12) formed with a plurality of ports (16) through which a gas may pass, the manifold (12) being disposed adjacent to a rotor (2') at one end of the array of rotors (2) and being distant therefrom, the arrangement being such that in use an axial force is applied to the array of rotors (2) via a flow of gas from the ports (16) into the gap between the manifold (12) and the adjacent rotor (2') .

3. The roller bearing assembly (1) of claim 2 wherein air is used as the gas to pressurise the gap between the manifold (12) and the adjacent rotor (2') .

4. The roller bearing assembly (1) of claim 2 or claim 3 wherein the manifold (12) is capable of movement in an axial direction substantially parallel to the axis of the array of rotors (2) .

5. The roller bearing assembly (1) of any one of claims 2 to 4 wherein the manifold (12) is capable of axial movement relative to the arbor (4).

6. The roller bearing assembly (1) of any one of the preceding claims comprising means for maintaining substantially constant, when in use, the axial force applied to the array of rotors (2) .

7. The roller bearing assembly (1) of claim 6 wherein the means for maintaining the substantially constant axial force on the array of rotors

(2) comprises means (20) for applying a force to the manifold (12), the arrangement being such that in use the axial force being applied to manifold (12) is transferred to the array of rotors (2) via the flow of gas from the ports (16) into the gap between the manifold (12) and the adjacent rotor (2') .

8. The roller bearing assembly (1) of claim 7 wherein the force applied to the manifold (12) is a substantially constant axial force.

9. The roller bearing assembly (1) of claim 8 wherein the means (20) for applying a constant axial force on the manifold (12) comprises hydraulic means.

10. The roller bearing assembly (1) of claim 8 wherein the means (20) for applying a constant axial force to the manifold (12) comprises pneumatic means.

11. The roller bearing assembly (1) of claim 8 wherein the means (20) for applying a constant axial force to the manifold (12) comprises mechanical means.

12. The roller bearing assembly (1) of any one of claims 8 to 11 wherein the means (20) for applying a constant axial force to the manifold (12) comprises a mechanism fixed to the arbor (4).

13. The roller bearing assembly (1) of claim 12 wherein the means (20) for applying a constant axial force to the manifold (12) comprises a mechanism fixed to the arbor (4) , the arrangement being such that in use the axial force applied to the manifold (12) is transferred to the array of rotors (2) by the manifold (12) .

14. The roller bearing assembly (1) of any one of claims 1 to 13 wherein the fluid channels (6) formed in the arbor (4) provide the manifold (12) with radial pneumatic bearing means.

15. The roller bearing assembly (1) of any one of the preceding claims comprising an array of sensors that are used for measuring the flatness of a web material being carried by the roller bearing assembly (1) .

16. The roller bearing assembly (1) of any one of claims 7 to 15 wherein the axial force applied to the rotors (2) by the manifold (12) is such that the rotors (2) can still move independently.

17. The roller bearing assembly (1) of any one of the preceding claims wherein the manifold (12) is annular and is disposed coaxially on the arbor (4).

18. The roller bearing assembly (1) of any one of the preceding claims wherein the manifold (12) is formed with an internal annular chamber (14) .

19. The roller bearing assembly (1) of claim 18 as dependent on claim 2 wherein the plurality of ports (16) each extend from the annular chamber (14) perforating a wall section of the manifold (12) .

20. The roller bearing assembly (1) of any one of claims 2 to 17 wherein the manifold (12) is formed with radial ports (16) that extend through a radially inner wall section, the arrangement being such that in use the radial ports (16) provide the manifold (12) with radial pneumatic bearing means.

21. The roller bearing assembly (1) of any one of claims 1 to 20 wherein the rotors (2) are an annular shape.

22. The roller bearing assembly (1) of any one of claims 1 to 21 wherein the longitudinal width of a rotor (2) is 50mm or less.

23. The roller bearing assembly (1) of any one of claims 1 to 22 wherein the longitudinal width of a rotor (2) is within the range 10mm to 50mm.

24. The roller bearing assembly (1) of any one of claims 1 to 23 wherein the longitudinal width of a rotor (2) is 10mm.

25. The roller bearing assembly (1) of any one of the preceding claims wherein the roller bearing assembly (1) comprises fluid means for exerting a compressive axial force on the array of rotors (2) , the fluid means being disposed at each end of the array of rotors (2) .

26. The roller bearing assembly (1) of claim 25 wherein the fluid means for exerting an axial force comprises two manifolds (30) each formed with a plurality of ports (32) through which a fluid may pass, each manifold (30) being disposed adjacent a rotor (2) at one end of the array of rotors (2) and being distant therefrom, the arrangement being such that in use a compressive axial force is applied to the array of rotors (2) by a flow of fluid from the ports (32) into the respective gaps between each manifold (30) and the respective adjacent rotor (2) .

27. The roller bearing assembly (1) of claim 26 comprising means for applying a force to the second manifold (30) .

28. The roller bearing assembly (1) of claim 26 or 27 wherein the arrangement of the second manifold (30) is substantially the same as the manifold (12) of the roller bearing assembly (1) of claims 2 to 24.

29. The roller bearing assembly (1) of claims 26, 27 or 28 wherein the means for applying a force to the second manifold (30) is substantially the same as the means (20) for applying a force to the manifold (12) of the roller bearing assembly (1) of claims 2 to 24.

30. The roller bearing assembly (1) of any one of the preceding claims wherein the fluid means for exerting an axial force on at least one rotor (2) disposed at one end of the array of rotors (2) operates substantially as a fluid thrust bearing.

31. A method of stabilising an array of rotors (2) of a roller bearing assembly (1) , the rotors (2) being rotatably mounted on an arbor (4) comprising fluid bearing means, the method comprising applying an axial force to the array of rotors (2) .

32. The method of claim 31 comprising applying a constant axial force to the array of rotors (2) .

33. The method of claim 32 comprising applying a constant compressive axial force to the array of rotors (2) .