GB1572738A

GB1572738A - Bearings

Info

Publication number: GB1572738A
Application number: GB1812/77A
Authority: GB
Original assignee: Ransome Hoffmann Pollard Ltd
Current assignee: Pilgrim House Group Ltd
Priority date: 1978-04-17
Filing date: 1978-04-17
Publication date: 1980-08-06

Description

(54) BEARINGS (71) We, RANSOME HOFFMANN POLLARD LIMITED, a British Company of New Street, Chelmsford, Essex, CMi lPU, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates in general to spherical bearings and, more particularly, to methods of making such bearings.

Spherical bearings consist of spherical element surrounded by an outer ring. It is common to provide the spherical element with a central bore which receives a rod or similar component in the application to which the bearing is put. The contact between the spherical element and the ring may be a metal-to-metal contact but lowfriction surface layers or linings are often incorporated between the ring and the spherical element. Such spherical bearings are usually designed to cope with high radial and axial loads as well as with misalignment, oscillation and rotation of associated parts.

Spherical bearings are used extensively in the aircraft industry as rod-end bearings for air frame and control linkages and otherwise in a variety of industrial, mining and control equipment. Spherical bearings are also used extensively in the suspension and steering mechanisms of vehicles.

Hitherto, various methods have been employed in manufacturing spherical bearings. In one common method, a ring is separately fabricated to possess a spherical bore designed to accommodate the associated spherical element. One slot, or preferably two, diametrically-opposed slots, are then machined in the ring to permit the ring to expand to allow spherical elements to be fitted into the bore of the ring. Although this method is relatively simple it does suffer from one major disadvantage in that the slot or slots in the ring reduce the contact area between the spherical element and the ring and weaken the ring. In order to overcome this disadvantage other methods of manufacture involve deformation of spherical element or ring. In one such method, a ring is again fabricated to possess a spherical bore but with sufficient clearance to permit the spherical element to be easily received therein. The clearance is then reduced by compression of the ring radially, e.g., by the use of a die or dies, or by expanding the spherical element. In another method the ring has a simple cylindrical bore which again easily receives the spherical element and the ring is deformed by pressure applied radially by means of dies to shape the bore to conform with the spherical element therein.

A general object of this invention is to provide an improved method of making a spherical bearing.

The present invention is based upon the concept of shaping the ring in a manner such that essentially axial pressure exerted on its radial side faces will cause the cylindrical bore of the ring to assume the desired spherical shape to conform with the spherical element therein.

A method of making a spherical bearing in accordance with the invention may comprise pre-shaping a ring to provide shaped radial side faces and a cylindrical bore, placing a spherical bearing element in the bore of the ring and subjecting the side face to pressure to deform the ring so as to re-shape the side faces and cause the bore to adopt a spherical profile about the spherical element.

A method of making a spherical bearing in accordance with the invention may also comprise pre-shaping a ring to provide a continuous outer peripheral surface, tapered plane radial side faces which converge towards the outer peripheral surface and an internal cylindrical bore, placing a spherical bearing e element in the bore of the ring and subjecting the tapered side faces of the ring to direct pressure to deform the ring so as to re-shape the side faces and cause the bore to adopt a spherical profile about the spherical element.

The spherical shape of the bore of the ring need not be a continuous profile and only separate-spaced surfaces of the bore need contact the spherical element and lie on the surface of the sphere described by the element.

In known manner a low-friction lining material or layer can be introduced into the cylindrical bore prior to the deformation.

Various examples of lining materials and structures are described in detail hereinafter.

The pre-shaped side faces of the ring may assume a frusto-conical shape and preferably these faces may coincide with the surfaces of imaginary cones coaxial with the bore, the cones opening towards one another and having half-angles within the range of from 50 to 700. Although the entire pre-shaped side faces may be planar to assume the shape specified it is possible to impart a slight concave or convex shape to one or both sides faces. It is also possible to provide one or more grooves or other recesses in one or both side faces or to adopt other special shaping techniques in relation to the side faces to control the direction of deformation.

In effecting the deformation of the ring, the side faces may be engaged by a pair of substantially flat, i.e., planar, pressureapplying surfaces which are relatively movable. These pressure-applying surfaces may lie in planes perpendicular to the axis of the bore of the ring although a slight inclination of these surfaces can produce advantageous results as described hereinafter. As with the side faces of the ring, it is also possible to provide slightly concave or convex pressure-applying surface or surfaces with an axis or axes of symmetry coaxial with the bore of the ring.

The pressure-applying surfaces can engage the side faces of the ring simultaneously over continuous circumferential regions thereof and can move relative to one another in a direction solely axially of the bore. It is however possible to provide an additional orbital motion to one or both pressureapplying surfaces and in this case the pressure is applied to the side faces over different successive portions of their circumferential regions.

In carrying out the invention it may be preferred to constrain the ring by contact with its outer periphery radially-outwards from the bore. Such constraint may then substantially flatten the outer peripheral surface of the ring. The re-shaping of the side faces of the ring during deformation can also result in substantially flat near-radial side faces and in many applications no additional operations, other than possibly a finishing operation, are required.

The invention may be understood more readily and various other features of the invention may become apparent from consideration of the following description.

Methods of making self-aligning spherical bearings, in accordance with the invention, will now be described, by way of examples, with reference to the drawings accompanying the provisional specification, wherein: Figure 1 illustrates schematically an arrangement for performing a first method in accordance with the invention; Figure 2 depicts an arrangement for performing a second method in accordance with the invention; Figure 3 depicts a spherical bearing made in accordance with the invention; Figure 4 is an enlarged sectional view of part of a spherical bearing produced by the first method (Figure 1); Figure 5 is an enlarged sectional view of part of a spherical bearing produced by the second method (Figure 2) and Figure 6, 6a, and 6b collectively depict an arrangement for performing a third method in accordance with the invention.

For convenience like reference numerals are used throughout the drawings to designate like parts.

Figure 3 depicts a typical self-aligning spherical bearing made in accordance with the invention. The bearing is composed of a spherical inner element 20, an outer ring 1 and a liner 21, conveniently made of synthetic plastics, between the ring 1 and the spherical element. The presence of the liner 21 is not essential however and depending upon the materials used the spherical element 20 may contact the ring 1 directly.

Where a liner 21 is employed it is preferably installed in the ring 1 prior to assembly with the spherical element and is preferably a millimetre or less in thickness. A variety of lining materials or structures can be adopted but a preferred liner consists of, or includes, p.t.f.e. The p.t.f.e., may be in the form of fibres woven, with cellulosic or glass fibres as a reinforcement, into a compcsste mat with a thickness in the order of 0.2 mm. Proprietary lining materials of this type are marketed under the trade names "Fiberglide", "Fiberslip" (RTM) "Ampex X-1" and "Airflow". Other composite liners can be formed from p.t.f.e. fibres woven with metallic, e.g., copper or stainless steel wires, to produce a mat with the p.t.f.e.

predominantly on one side (directed towards the spherical element) and the metal wires predominantly on the other side to facilitate bonding to the ring. A proprietary lining material of the latter type is marketed under the trade name "Pydane". Instead of a woven mat, the p.t.f.e. fibres may be held in a vinyl phenolic resin which may be additionally reinforced with other materials.

Alternatively p.t.f.e. particles may be carried by a metal or metal alloy, such as sintered bronze in mixture with lead powder for example, conveniently mounted to a steel backing or support. A proprietary material of this type is marketed under the trade name "Glacier DU". The p.t.f.e. particles can also be used to impregnate a wire mesh such as a woven phosphor bronze wire mesh. A further type of liner is produced by taking an abrasion resistant p.t.f.e. tape and by sintering a woven and fused phosphor bronze wire mesh into the tape to act as a carrier and reinforcement. A proprietary material of this type is marketed under the trade name "Metaloplast" (RTM). Although it is preferred to utilize p.t.f.e. in the liner other materials can be employed. The liner can for example take the form of a synthetic resin impregnating a porous bronze material and supported by a steel or aluminium backing.

The backing can be perforated and can store additional low-friction materials which can "feed" the impregnated base material.

Where the finished bearing is only subjected to relatively dynamic forces the liner can be a simple thermoplastic substance, such as a polyacetal or a polyamide, possibly impregnated with a lubricant which can diffuse to the surface in contact with the spherical element.

In carrying out the invention the ring 1 is pre-shaped and is then deformed about the spherical element 21 in situ.

Referring now to Figure 1 of the drawings, the pre-shaped ring 1, made for example, from a sintered carbide equivalent of EN3 1, is shown in its initial state prior to deformation. For convenience, the spherical element, which is arranged within the cylindrical bore 4 of the ring 1, is omitted from Figure 1. If it is desired to incorporate a liner between the ring 1 and the spherical element the liner is preferably bonded with adhesive to the cylindrical inner bore 4 of the ring 1. The adhesive can be set by heating before or after the deformation of the ring 1.

The ring 1 has radial side faces 2, 3 which are of frusto-conical shape. More particularly, the surfaces 2,3, coincide with the surfaces of imaginary cones which are coaxial with the axis of the bore 4, which open towards each other and which each have a half-angle of 60". Thus, each face 2, 3 is inclined to an angle of 30 to a radial plane perpendicular to the axis of the ring 1. The outer circumferentially-extending surface 5 of the ring 1 is like the bore 4, cylindrical.

The ring 1 is disposed axially between a pair of pressure-applying surfaces 24, 25.

These pressure-applying surfaces 24, 25 are formed by two rigid members, namely a plate 6 and a cylindrical tube 7. The plate 6 has a recess or boring (not shown) over a central region aligned with the interior of the tube 7 to accommodate therewith the spherical element of the bearing. In this arrangement the plate 6 is fixed and supported on a bed 30 while the tube 7 is axially displaceable and driven by power means (not shown) such as a hydraulic ram. The application of pressure to the faces 2, 3 of the ring 1 deforms the latter about the spherical element so that the bore 4 (with the liner if provided) assumes a curvilinear shape corresponding to the curvature of the spherical element. Graphite flakes can be used as a lubricant for the deformation process. The force which causes the application of deformation pressure to the ring 1 occurs in a direction substantially parallel to the axis of the bore 4. Since the pressure applying surfaces 24, 25 are flat and normal to the axis of the bore 4 no forces are actually applied to the ring 1 in a radial direction. The pre-shaping of the ring 1 providing the surfaces 2, 3 ensures that during deformation the ring material is effectively moved from the faces 2, 3 to a bore 4. The resultant curvilinear shape of the bore 4 need only be approximately spherical and the spherical profile may be defined by separate non-continuous surfaces as shown in Figure 4. In Figure 4, the final shape of the ring 1 after deformation produces end surfaces 4c, 4a of the bore 4 conforming to the peripheral contour 9 of the spherical bearing element. The central region 4b of the bore 4 deviates from the contour 9. The separate surfaces 4c, 4a are found to provide adequate contact with the spherical bearing element especially where the bearing is only subjected to thrust loads during use. As can also be seen in Figure 4, the outer peripheral surface 5 of the ring is slightly curved and, if desired, this surface 5 can be made flat by machining. In contrast to their initial shape after deformation the faces 2, 3 are only inclined at a very small angle to a radial plane perpendicular to the axis of the ring and again, if desired, the faces 2, 3 can be made radially flat by machining.

In one specific example of a bearing made in accordance with the invention (Figure 3 and 4) the spherical element has a diameter of about 34 mm., the bore 4 of the ring 1 is 36 mm. in diameter and about 19 mm. in axial length and the peripheral surface 5 of the ring 1 has a diameter of about 45 mm. In forming the ring 9 for this bearing in the manner described a load in the order of 50 tons equivalent weight is applied to the member 7.

Referring now to Figure 2, in a second method of making a spherical bearing, which here incorporates a liner 21 between the ring 1 and the spherical element 20, the ring 1 is constrained by constraining means in the form of a cylinder 10 engaging and supporting the peripheral exterior surface 5 of the ring 1.

The pressure-applying surfaces 24, 25 which engage the faces 2,3 of the ring 1 are in this arrangement formed by the inner end faces, of a pair of opposed tubular members 6', 7'. The opposite outer end faces of the members 6', 7' are closed and the members 6', 7' are arranged within the cylinder 10.

One or both members 6', 7' may slide within the cylinder 10 in the manner of a piston. The ring 1 is pre-formed to the shape described above in connection with Figure 1 and the ring 1 containing the spherical element is placed inside the cylinder 10 as shown. Force is applied to one or both the members 6', 7' to bring the flat pressureapplying surfaces 24, 25 of the members 6', 7' into contact with the faces 2, 3. As before, axial force applied to the ring 1 deforms the latter to bring the lined bore into approximately spherical form. The radiallyoutward constraint of the ring 1 by the cylinder 10 is useful in extending the separate surfaces of the bore 4 which lie on the desired spherical contour. Figure 5 represents the ring 1 after deformation by the arrangement and method shown in Figure 2 and as shown in surfaces 4a, 4c are extended in relation to Figure 4. The constraint of the ring 1 is also useful in providing or maintaining a substantially flat outer peripheral surface 5 as also shown in Figure 5. Hence after deformation, the surface 5 may not need to be machined at all and a simple finishing process may be all that is necessary. The method represented in Figure 2 may be carried out so as to leave chamfered corners 11, between the faces 2, 3 and the surface 5 as shown in Figure 5.

As mentioned, the faces 2,3 of the ring 1 after deformation can be machined to adopt a flat profile vis a viz a respective radial plane. The flat pressure-applying surfaces of the members 7,6 (Figure 1) or the members 6', 7' (Figure 2) will not, in general deform the faces 2, 3 to a precisely flat profile mainly because of the inherent resilience of the ring material.

In a modified arrangement however the faces 2, 3 can be brought into a substantially flat profile vis a viz a respective radial plane by a compensatory counter inclination imparted to the pressure-applying surfaces 24, 25. In one example of this modified arrangement the pressure applying surface 24, 25 of the members 7,6 (Figure 14 or 6', 7' (Figure 2) are given a shallow frusto-conical shape coinciding with the surface of imaginary cones with half angles exceeding 85" (preferably 87" or 88 ) and opening away from one another. These modified inclined pressure-applying surfaces 24, 25 will have an axis of symmetry parallel to the axis of the ring and the force applied will still be axial with respect to the ring 1.

Referring now to figures 6, 6a and 6b, in a third method of making a spherical bearing, the ring 1 is radially outwardly constrained by a recessed portion 31 of the cylinder 7".

The recessed portion 31 of the cylinder 7" has a shoulder which conveniently forms the pressure-applying surface 25 which engages the face 2 of the ring 1. The other pressureapplying surface 24 engaging the face 3 of the ring 1 is formed by a tubular member 6". In contrast to the other methods described, the member 6" is able to perform an orbital motion with its line of action or axis 15 eccentric or canting with respect to the axis 14 of the ring 1. The member 6" is connected to a body 12 which preferably provides both drive, i.e., thrust, force and the orbital motion for the member 6". The other pressure-applying surface 25, i.e., the shoulder of the recessed portion 31 of the cylinder 7" may be static but it is preferred to load the cylinder 7" with an axial force indicated by arrows at the bottom of Figure 6, for example with the aid of a hydraulic ram. The drive force for the body 12 may also be provided by a hydraulic ram. In contrast to the other methods described where pressure is applied uniformly and simultaneously to the faces 2, 3 over their entire circumferential contact with the pressure-applying surfaces during deformation, the orbital motion of the member 6" causes pressure to be applied to different portions of the faces 2, 3 in succession as can be appreciated from Figure 6. Figures 6a and 6b are sections taken perpendicular to the axis 14 of the ring 1 and describe by loci suitable paths which may be performed by the axis 15 of the member 6" during one cycle of movement. Other orbital paths can be envisaged however. Normally the maximum angle between the axes 14, 15 would not exceed 4" and is preferably in the region of 1-2". In carrying out the method represented by the arrangement of Figure 6, the ring 1 is pre-formed. e.g., to the shape described in connection with Figure 1, and placed in position with the spherical element 20 as shown in Figure 6. he pressureapplying surfaces 24, 25 r,:. be flat or parallel to radial planes of ht ring 1 - with the axes 14, 15 in alignmpl - or inclined as described to produce neai- aptness for the surfaces 2, 3 after deformatien. The ring is then deformed in successive stages by the orbital motion of the member 6". The ring after deformation may take the form shown in Figure 5.

One advantage of applying the shaping force in successive stages, as in the manner described in connection with Figure 6, is that less overall drive force is needed. Thus, for example, is forming the bearing of the dimension specified above it will be recalled that a force equivalent to about 50 tons weight is required. In the case of the arrangement shown in Figure 6 a load of only about 2 tons in weight needs to be applied to the body 12.

Another advantage of the method represented in Figure 6 is that by successive deformation of the ring in definite stages there can be better control and the faces 2, 3 and the surface 5 may finish up as substantially-flat radial and axial surfaces, respectively, just requiring a simple finishing treatment.

WHAT WE CLAIM IS: 1. A method of making a spherical bearing, said method comprising pre-shaping a ring to provide shaped radial side faces and a cylindrical bore, placing a spherical bearing element in the bore of the ring and subjecting the side faces to pressure to deform the ring so as to re-shape the side faces and cause the bore to adopt a spherical profile about the spherical element.

2. A method of making a spherical bearing, said method comprising pre-shaping a ring to provide a continuous outer peripheral surface, tapered plane radial side faces which converge towards the outer peripheral surface and an internal cylindrical bore, placing a spherical bearing element in the bore of the ring and subjecting the tapered side faces of the ring to direct pressure to deform the ring so as to re-shape the side faces and cause the bore to adopt a spherical profile about the spherical element.

3. A method according to Claim 1, wherein the side faces of the ring are each pre-shaped to assume a frusto-conical shape.

4. A method according to Claim 2 or 3, wherein the side faces of the ring are preshaped to coincide with the surfaces of imaginary cones coaxial with the bore; the cones opening towards one another and having half-angles within the range of from 50O to 70".

5. A method according to any one of Claims 1 to 4, wherein the force producing the pressure on the side faces is directed solely axially of the bore of the ring.

6. A method according to any one of Claims 1 to 5, wherein the side faces are engaged by a pair of pressure-applying surfaces which directly subject the faces to said pressure.

7. A method according to Claim 6, wherein the pressure-applying surfaces are flat and extend in planes perpendicular to the axis of the bore of the ring.

8. A method according to Claim 6, wherein the pressure-applying surfaces are flat and extend in planes slightly inclined to the axis of the bore of the ring.

9. A method according to Claim 8, wherein the pressure-applying surfaces coincide with the surfaces of imaginary cones which open towards one another and which have half-angles within the range 85" to 900.

10. A method according to claim 6, 7, 8 or 9, wherein the pressure-applying surfaces engage the side faces and apply pressure thereto over substantially continuous circumferential regions thereof.

11. A method according to claim 6, 7, 8, or 9, wherein the pressure-applying surfaces engage the side faces and apply pressure thereto over successive portions of circumferential regions thereof.

12. A method according to any one of claims 6 to 11 wherein one pressure-applying surface is static and the other pressureapplying surface is movable.

13. A method according to any one of claims 6 to 11, wherein both pressureapplying surfaces are movable.

14. A method according to any one of claims 1 to 13, and further comprising constraining the ring radially-outwardly of the bore.

15. A method according to, any one of claims 1 to 14, wherein the spherical profile of the bore of the ring is defined by separate surfaces of the bore.

16. A method according to claim 15, wherein said separate surfaces are adjacent the side faces of the ring.

17. A method according to any one of claims 1 to 16, and further comprising introducing a low-friction lining material or layer into the bore of the ring prior to deformation.

18. A method of making a spherical bearing substantially as hereinbefore described with reference to any one or more of the Figures of the drawing accompanying the provisional specification.

19. A spherical bearing when made by the method according to any one of the preceding claims.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. dimension specified above it will be recalled that a force equivalent to about 50 tons weight is required. In the case of the arrangement shown in Figure 6 a load of only about 2 tons in weight needs to be applied to the body 12. Another advantage of the method represented in Figure 6 is that by successive deformation of the ring in definite stages there can be better control and the faces 2, 3 and the surface 5 may finish up as substantially-flat radial and axial surfaces, respectively, just requiring a simple finishing treatment. WHAT WE CLAIM IS:

1. A method of making a spherical bearing, said method comprising pre-shaping a ring to provide shaped radial side faces and a cylindrical bore, placing a spherical bearing element in the bore of the ring and subjecting the side faces to pressure to deform the ring so as to re-shape the side faces and cause the bore to adopt a spherical profile about the spherical element.