GB2402445A

GB2402445A - A bladder system for lining a bore formed in a spherical bearing

Info

Publication number: GB2402445A
Application number: GB0311453A
Authority: GB
Inventors: Allen Christopher Clarke; Jamie Back; Clive Harrie Boshier
Original assignee: Minebea Co Ltd
Current assignee: Minebea Co Ltd
Priority date: 2003-05-19
Filing date: 2003-05-19
Publication date: 2004-12-08
Anticipated expiration: 2023-05-19
Also published as: GB2402445B; GB0311453D0

Abstract

A bladder system for facilitating a bond between a liner 4 and a bore 3 formed in a spherical bearing 2. The bladder system comprises a bladder 14 having an outer diameter which is adjustable to expand from a first diameter which is smaller than the internal diameter of the bore to a second diameter which is greater than the internal diameter of the bore 3. The bladder system 14 preferably comprises a bladder 14 in the form of an elastomeric rubber ring sandwiched between a pair of plates 11,13 which are movable towards one another to compress the bladder 14 and thereby increase the outer diameter of the bladder 14. A threaded shaft may run between the plates 11,13 and a nut 17 maybe rotatable on the shaft 5 to urge the plates 11,13 together. As an alternative the bladder system may comprise a bladder 14 with a hollow portion in communication with a supply of fluid under pressure, so that expansion of the bladder 14 can be controlled by regulation of the fluid pressure within the bladder 14.

Description

PATENTS ACT 1977 Agent's Ref: P17503GB-LH/mf

A BLADDER SYSTEM

This invention relates to a bladder system and more particularly to a bladder system for facilitating a bond between a liner system and a bore of a bearing. The invention also relates to a method of facilitating a bond between a liner system and a bore of a bearing.

It is common in the field of spherical bearings to incorporate a central bore running through a spherical ball so that the internal bore acts as a bush within the ball. It is also common to line the internal bore or at least regions thereof with a liner system. The liner usually comprises a mesh or weave construction of metal, a composite such as Kevlar (_3 or a thermoplastic material such as a nylon-based thermoplastic. The mesh or weave construction is impregnated with a polymer such as PTFE or the like. Typically, the liner system is bonded to the internal bore of the ball. To ensure a satisfactory bond between the liner system and the bore, pressure is normally used so that the liner system is pressed against the internal bore until the adhesive used is totally or at least partially cured.

There are two conventional techniques used to apply the pressure in the bore of the ball. In the first technique, a mandrel comprising a solid cylindrical rod is artificially cooled so as to contract in size and then inserted in the internal bore of the ball. At ambient temperature, the diameter of the mandrel is slightly greater than the internal diameter of the bore but when significantly cooled, the outer diameter of the mandrel is smaller than the internal diameter of the ball so that the mandrel fits within the internal bore as a clearance fit. As the mandrel returns to ambient temperature it expands, sandwiching the liner between the ball and the mandrel, thereby applying pressure to the bond between the liner system and the ball. The pressure is applied evenly around the diameter of the internal bore using this technique. The mandrel is then knocked out from the bore.

The second technique uses an interference fit mandrel which is very slightly tapered having a diameter at one end which is slightly smaller than the internal diameter of the bore and a diameter at the other end which is slightly greater than the internal diameter of the ball. The interference fit mandrel can be inserted gently into the internal bore with the liner system fitted thereby pressing the liner system against the internal bore and facilitating the bond until such time as the adhesive is totally cured or at least partially cured. The interference fit mandrel can then be pushed out from the internal bore in the opposite direction.

The above two techniques have some disadvantages in that if either mandrel is attempted to be removed before the liner system has totally cured, then there can be some slippage of the liner system within the internal bore. It the ball is formed from a single material, then the above two techniques provide a satisfactory solution to the problem of facilitating the bond between the liner system and the bore. However, the ball may be formed with a coating of another material over the primary material of the ball.

In the case of an aluminium ball which is coated with a hard coating of chromium plate, then any expansion of the aluminium caused by the uncontrolled thermal expansion of the mandrel, or sudden uncontrolled mechanical expansion caused by the interference fit mandrel can crack the l chromium plate. Therefore, the use of temperature to bond the liner in place or the use of an interference fit mandrel can only be applied with great care and are normally excluded from use.

It is an object of the present invention to provide a method of facilitating a bond between a liner system and an internal bore of a bearing which does not suffer from the above-mentioned drawbacks.

Accordingly, one aspect of the present invention provides a bladder system for facilitating a bond between a liner and a ball in a bearing having an internal bore, the system comprising a bladder having an outer diameter which is adjustable to expand from a first diameter which is smaller than the internal diameter of the bore to a second diameter which is greater than the internal diameter of the bore.

Another aspect of the present invention provides a method of facilitating a bond between a liner system and a bore of a bearing, the bore of the bearing having an internal diameter and the method comprising the steps of: applying a liner on an interior surface of a bore of a bearing with an adhesive, providing a bladder having an outer diameter which is adjustable to expand from a first diameter which is smaller than the internal diameter to a second diameter which is greater than the internal diameter; inserting the bladder into the bore to sandwich the liner between the bore and the bladder; and expanding the outer diameter of the bladder to put the liner under compression between the bladder and the interior surface of the bearing.

In order that the present invention may be more readily understood, embodiments thereof will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a partial cross-section through a spherical ball fitted with two bladder systems embodying the present invention; Figure 2 is a cross section of a bladder system embodying the present invention in an uncompressed state; Figure 3 is a cross-section of the bladder system of Figure 2 in a compressed state; and Figure 4 is a cross-section of another bladder system embodying the present invention in an inflated state.

Referring to Figure 1, a spherical 1 for use in a spherical bearing assembly comprises an aluminium ball 2 formed with an internal bore 3. The internal bore 3 is cylindrical and runs centrally through the ball 2. A liner system comprising a liner 4 in the form of an annular band is fixed to each end of the internal bore 3, preferably using an adhesive applied to both the internal bore and an outer surface of the liner 4. Preferably, the liner 4 is provided as a strip of liner material. Most preferably, the liner is a self-lubricating liner comprising a metal mesh infused with a polymer such as PTFE or Teflon (a).

A bladder system 10 embodying the present invention is fitted in both ends of the bore 3 as shown in Figure 1. The bladder system 10 is shown in more detail in Figures 2 and 3, to which reference is now made. In the example of Figure 1, two bladder systems 10 are employed and are spaced apart by a predetermined distance by a connecting mandrel 5.

Referring to Figure 2, each bladder system 10 comprises a circular base plate 11 formed with an upstanding centrally mounted threaded shaft 12 upon which another circular plate 12 is slidably mounted through a central bore. An annular rubber ring 14 having an outer diameter substantially greater than the diameter of the circular plates 11, 13 and an inner diameter less than the diameter of the circular plates 11, 13 is sandwiched between the circular plates 11, 13. Preferably, the rims of the rubber ring are bonded to the circular plates 11,13. The inside surface 15 of the rubber ring 14 is concave and the outside surface of the rubber ring 14 is also concave, although it does have rounded convex edges where the rims of the ring 14 join with the respective circular plates, 11,13. Figure 2 shows the rubber ring 14 in an uncompressed state.

A butterfly or wing nut 17 is threadedly mounted on the threaded shaft 12 and is wound down until contact is made with the circular plate 13 slidably mounted on the threaded shaft 12.

Referring now to Figure 3, the rubber ring 14 can be compressed in a controlled manner by tightening the butterfly nut 17 down onto the slidable circular plate 13. As the rubber ring 14 is compressed between the circular plates 11,13, the rubber ring bows out around its waist so that the previously concave outer surface 16 becomes flat. It is also possible for the concave surface 16 to become convex. The effect of this is that the outer diameter of the rubber ring 14 effectively increases as the compression applied to the rubber ring 14 increases. It should be noted that the pressure applied by the increasing diameter of the rubber ring 14 can be closely controlled by adjustment of the butterfly nut 17 and can be measured with reference to the torque applied to the butterfly nut 17. Indeed, an end stop 18 can be provided on the threaded shaft 12 to prevent over-tightening of the butterfly nut 17. The end stop 18 comprises a projection from the threaded shaft 12, preferably in the form of an 1 r annular lip as shown in Figure 3. The end stop is absent from the variant of the bladder system shown in Figure 2.

The outer diameter of the rubber ring 14 is carefully chosen to be smaller than the internal diameter of the internal bore 3 within which the bladder system is to be used when in an uncompressed state as shown in Figure 2.

However, when compressed, as shown in Figure 3, the outer diameter of the rubber ring 14 should be greater than the diameter of the internal bore 3.

Accordingly, compression of the rubber ring 14 by the controlled tightening of lo the butterfly nut 17 provides pressure to the liner system 4, against the internal bore 3 when the bladder system 10 is inserted in the internal bore 3.

Importantly, the pressure applied to the liner can be accurately controlled by tightening of the butterfly nut 17. The pressure applied to the liner 4 can be derived empirically from the torque applied to the butterfly nut 17 for a known bladder system, ring outer diameter and internal bore diameter.

Referring again to Figure 1, the connecting mandrel 5 comprises, at its opposite extremities, the threaded shaft 12.

In operation, a bond between a liner system and a bore of a bearing is facilitated by use of the bladder system 10. The liner is applied to the interior surface of the bore of the bearing with an adhesive. The adhesive or bonding medium used should be a cold-setting type of adhesive, such as Araldite (Registered Trade Mark) 4076.

The bladder system 10 is inserted in the bore with the outer surface 16 of the rubber ring 14 adjacent the liner 4. Preferably, the rubber ring 14 is wider than the liner 4 so that consistent uniform pressure is applied around the liner 4. With the bladder system 10 inserted in the internal bore 3, the butterfly 1 ' nut 17 is tightened until the desired pressure is achieved. A torque wrench can be used to tighten the butterfly nut 17 to a pre-determined threshhold torque indicative of the correct pressure being applied to the liner 4. After application of the controlled pressure for a pre-determined amount of time dictated by the curing of the adhesive, the butterfly nut 17 is released and the bladder system removed from the internal bore 3.

The screw mechanism is tightened until movement is detected on the outside diameter. The torque required up to this point is recorded for future use. The resulting bore size is also critical, therefore the rubber ring has to be of specific initial size to result in the correct final size at the required torque level. The required torque level and correct final size is determined by experiment for each internal bore size.

As shown in Figure 1, a pair of liners 4 are provided one at each end of the internal bore 3 and a pair of bladder systems 10 are spaced apart by the connecting mandrel 5. The bladder systems 10 are preferably used simultaneously upon each end of the internal bore 3 as shown in Figure l. er Less preferably, bladder systems 10 which are not connected to one another or, indeed, the same bladder system 10 can be used at the ends of the bore 3, for example, when the adhesive in one liner has cured, the same bladder system 10 can be moved from one end of the internal bore 3 and inserted in the other end to apply pressure to the other liner.

Referring now to Figure 4, the mechanical application of pressure to the rubber ring 14 by compressing the rubber ring between the circular discs 11, 13, can also be achieved by means other than the combination of the threaded shaft and butterfly nut. In the example shown in Figure 4, in which like numerals are used to denote like parts from Figure 2, the circular plates 11, 13, are spaced apart by a pre-determined distance and secured to one another by an axially mounted spacer 20. The structure of the rubber ring 14 is the same as the bladder system shown in Figures 2 and 3, but the rubber ring 14 is sealingly bonded at least around its rims to the respective circular plates 11, 13. A port 21, preferably fitted with a valve passes through the circular plate 13 and into the interior toroidal volume defined between the rubber ring 14, the spacer 20 and the circular plate 11, 13. Compressed air or another suitable fluid under pressure can be used to increase the pressure within the interior volume thereby expanding the rubber ring 14 as shown in Figure 4. When the pressure within the interior volume is returned to ambient by venting the port 21, the rubber ring 14 returns to its deflated state, equivalent to the uncompressed state shown in Figure 2. Controlled regulation of the pressure within the rubber ring 14 determines the amount of pressure applied by the rubber ring 14 to the liner within the internal bore 3.

The rubber ring 14 illustrated in the Figures has a comparatively thin wall, certainly the thickness of the wall of the rubber ring 14 is less than the width from rim to rim of the rubber ring 14 itself - i.e. the distance between the circular plates 11,13.

The profiling of the interior and exterior surfaces 15, 16 of the rubber ring 14 with respective concave profiles in their uncompressed or deflated states is not essential but simply preferable since the profile of the rubber ring 14 when in the compressed or inflated state, determines the amount of pressure applied to respective parts of the liner. Preferably, uniform pressure is applied to the liner across its width and around the internal bore. This is most readily achieved by adopting at least a concave or straight section of the exterior surface 16 of the rubber ring 14 when in an uncompressed or deflated state.

Although rubber is described as the preferred material for the ring 14, any other elastomeric material may also be used, the essential property being that under compression or when inflated, the material is elastic enough to cause a corresponding or related increase in diameter of the outer diameter of the ring 14. It is also envisaged that a solid block of rubber may be used instead of a rubber ring 14 for the compression variant of the bladder system 10 shown in Figures 2 and 3.

In the present specification "comprises" means "includes or consists of" and "comprising" means "including or consisting of".

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

CLAIMS: 1. A bladder system for facilitating a bond between a liner and a

ball in a bearing having an internal bore, the system comprising a bladder having an outer diameter which is adjustable to expand from a first diameter which is smaller than the internal diameter of the bore to a second diameter which is greater than the internal diameter of the bore.
2. A bladder system according to Claim 1, wherein the bladder comprises an elastomeric ring sandwiched between a pair of plates, which plates are movable towards one another to compress the ring and thereby increase the outer diameter of the ring.
3. A bladder system according to Claim 2, wherein a threaded shaft extends from one plate through the other plate and wherein a nut is rotatable on the shaft to urge the two plates together.
4. A bladder system according to any preceding claim, wherein the bladder is an elastomeric block.
5. A bladder system according to Claim 4, wherein the block has a hollow section.
6. A bladder system according to Claim 1, wherein the bladder has a hollow portion in communication with a supply of fluid under pressure, expansion of the bladder being controlled by regulation of the fluid pressure within the bladder.
7. A bladder system according to any preceding claim, wherein the bladder has a concave outer surface when not under compression or when not inflated and a flattened or convex outer surface when under compression or inflated.
8. A method of facilitating a bond between a liner system and a bore of a bearing, the bore of the bearing having an internal diameter and the method comprising the steps of: applying a liner on an interior surface of a bore of a bearing with an adhesive; providing a bladder having an outer diameter which is adjustable to expand from a first diameter which is smaller than the internal diameter to a second diameter which is greater than the internal diameter; inserting the bladder into the bore to sandwich the liner between the bore and the bladder; and expanding the outer diameter of the bladder to put the liner under compression between the bladder and the interior surface of the bearing.
9. A method according to Claim 8, wherein the bladder maintains the liner under compression between the bladder and the interior surface of the bearing for a predetermined time period.
10. A method according to Claim 8 or 9, comprising the step of allowing the bladder to contract, thereby reducing the outer diameter thereof until the outer diameter is less than the internal diameter of the bearing and removing the bladder from the bore.
11. A method according to any one of Claims 8 to 10, wherein the outer surface of the bladder is wider than the liner.
12. A bladder system substantially as hereinbefore described with reference to and as shown in the accompanying drawings.
13. A method of facilitating a bond between a liner system and a bore of a bearing substantially as hereinbefore described with reference to and as shown..

I

in the accompanying drawings. . . À À À Àe À .. À. À Àe Àe À À. Ace Àe

13. A bladder system according to any preceding claim spaced apart from another bladder system according to any preceding claim by a connecting mandrel.

14. A method of facilitating a bond between a liner system and a bore of a bearing substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

IS. Any novel feature or combination of features disclosed herein.

Amendments to the claims have been filed as follows CLAIMS: 1. A controllable expansion system for facilitating a bond between a liner and a ball in a bearing, the ball having an internal bore, the system comprising an elastomeric ring or block having an outer diameter, which is adjustable to expand from a first diameter, which is smaller than the internal diameter of the bore, to a second diameter which is greater than the internal diameter of the bore, to exert a predetermined pressure on the liner.

2. A controllable expansion system according to Claim 1, wherein the elastomeric ring or block is sandwiched between a pair of plates, which plates À-e are movable towards one another to compress the elastomeric ring or block and.

thereby increase the outer diameter of the elastomeric ring or block. I:::

3. A controllable expansion system according to Claim 2, wherein a threaded shaft extends from one plate through the other plate and wherein a nut is rotatable on the shaft to urge the two plates together.

4. A controllable expansion system according to Claim 1, wherein the elastomeric ring or block has a hollow portion in communication with a supply of fluid under pressure, expansion of the elastomeric ring or block being controlled by regulation of the fluid pressure within the elastomeric ring or block.

5. A controllable expansion system according to Claim 1, wherein the elastomeric block has a hollow section.

6. A controllable expansion system according to any preceding claim, wherein the elastomeric ring or block has a concave outer surface when not under compression or when not inflated and a flattened or convex outer surface when under compression or inflated.

7. A controllable expansion system according to any preceding claim spaced apart from another controllable expansion system according to any preceding claim by a connecting mandrel.

8. A method of facilitating a bond between a liner system and a bore of a bearing, the bore of the bearing having an internal diameter and the method. . comprising the steps of: . applying a liner on an interior surface of a bore of a bearing with an adhesive, À.

providing an elastomeric ring or block having an outer diameter which is adjustable to expand from a first diameter which is smaller than the.

internal diameter to a second diameter which is greater than the internal.

diameter; inserting the elastomeric ring or block into the bore to sandwich the liner between the bore and the elastomeric ring or block; and controllably expanding the outer diameter of the elastomeric ring or block to put the liner under compression between the elastomeric ring or block and the interior surface ofthe bearing.

9. A method according to Claim 8, wherein the elastomeric ring or block maintains the liner under compression between the elastomeric ring or block and the interior surface of the bearing for a predetermined time period.

10. A method according to Claim 8 or 9, comprising the step of allowing the elastomeric ring or block to contract, thereby reducing the outer diameter thereof until the outer diameter is less than the internal diameter of the bearing and removing the elastomeric ring or block from the bore.

11. A method according to any one of Claims 8 to 10, wherein the outer liner contacting surface of the elastomeric ring or block is wider than the liner.

12. A controllable expansion system substantially as hereinbefore described with reference to and as shown in the accompanying drawings.