GB2316462A - Deformable spacer - Google Patents

Abstract

The spacer for compensating axial play between machine components has a deformation area (14) arranged between its axial end portions (10, 12) and comprising at least one radial bulge of predetermined wall thickness. In order to achieve a more even characteristic force/deformation curve, provision is made for the wall thickness to vary constantly in the axial direction at least over the majority of the deformation area (14), the difference between the smallest and largest wall thicknesses amounting to at least 20 % of the smallest wall thickness and at least one thicker area being located between two thin areas.

Description

1 2316462 Spacer The invention relates to a spacer for compensating axial

play between machine components, which spacer has, between its axial end portions, a deformation area with at least one radial bulge of predetermined wall thickness.

Such spacers, also known as distance sleeves, are preferably used between rolling bearings arranged in pairs, especially tapered roller bearings and angular contact ball bearings with adjustable bearing clearance. Their manner of operation and advantages are described by R. HUbener in the paper "Verformbare DistanzhUlsen fdr paarweise angeordnete einstellbare W.flzlager" ("Deformable distance sleeves for adjustable rolling bearings arranged in pairs") in the journal 'Tonstruktion", 16th volume (1964), No. 4, pp. 143 - 145.

The quality of a spacer is expressed in its force/deformation diagram. With increasing axial compression of a tubular spacer, the force curve initially rises sharply and then falls away again under increasingly extensive radial bulging when a maximum is exceeded. As flat as possible a drop is desired, i.e. as uniform as possible a force over a certain deformation area of, for example, approximately 1 - 1.5 mm in length. This target has hitherto basically been approached by plastic deformation effected during manufacture, in which a bulge was preformed on the spacer by radial or axial pressure.

At present two types of spacer are in use. The more economical, which is less favourable, however, from the point of view of the force/deformation characteristic, consists of a tube portion with a bulge in the middle caused by radial pressure. Better results are achieved with preformed spacers 2 which, starting with a tubular starting material, are firstly turned between end portions to a certain uniform wall thickness and are then given radial convexity in a second step by axial compression. In both cases, relatively large differences in quality, i.e. wide variations in the individual force/deformation diagrams, arise within one production run when the bulge is produced by plastic deformation.

The problem on which the invention is based is that of providing a spacer of the above-mentioned type which provides a more uniform force curve over a given deformation area and may be produced more economically with less significant variations in quality than the known spacers manufactured by turning and compression.

The above problem is solved according to the invention by a spacer in which the wall thickness varies constantly in the axial direction at least over the majority of the deformation area, the difference between the smallest and largest wall thicknesses amounting to at least 20 % of the smallest wall thickness and at least one thicker area being located between two thin areas.

The more even deformation force in the load area of the novel spacer must be the result of the fact that the thinner wall areas ease somewhat the initial radially outward bulging, but then the thicker zones in the deformation area resist further deformation more strongly, i.e. produce a flatter drop in the force curve than is the case with a spacer comprising the same wall thickness throughout the deformation area.

The variation in wall thickness in the deformation area is preferably constant, but may be provided by one or more stepped changes in diameter or, for example, by obtuse-angled edges surrounding the circumferential surface.

3 A substantial advantage of the new spacer is thus the greater variety of possibilities for influencing the force/deformation characteristic. This is important, because spacers are not generally standard elements but rather are developed and specially designed for specific uses. The length and diameter are generally predetermined. Therefore, the range of influence was hitherto restricted to the choice of material and a particular wall thickness as well as the extent of plastic predeformation. In all instances, however, there was a relatively steep drop in the tension force curve plotted over the deformation area after the maximum force is exceeded. In the case of the spacer according to the invention, the drop is not only flatter but may also be better tailored in its elastic and plastic deformation properties because, in addition to the above-mentioned influencing factors, the variation in wall thickness in the deformation area theoretically offers infinite variation possibilities for influencing the force/deformation diagram of a spacer of a certain diameter and a certain length.

The spacer according to the invention also exhibits advantages if it is firstly conventionally machined and then plastically deformed to a certain degree by axial compression or optionally by radial compression. Through the proposed variation in wall thickness in the deformation area, at least a flatter drop in the axial force needed for deformation and better adaptation to specific conditions may be achieved in individual cases even with otherwise conventional manufacture. The range of variation in the results within a production run may be improved by a lower plastic deformation level. However, experience so far has shown that the best results may be achieved if, in a preferred embodiment of the invention, the external shape of the spacer is generated merely by machining.

The omission of plastic pre-deformation basically rules out all unevennesses caused thereby, which may arise in particular because unevennesses in the material have very varied effects 4 when subjected to strong plastic deformation. Moreover, there is a considerable cost advantage over spacers hitherto preformed firstly by machining and then without cutting by plastic deformation owing to the elimination of the latter step.

The results achieved with the novel spacers are surprising to the extent that, as previous tests had shown, spacers which were produced merely by machining with a bulge of uniform wall thickness exhibited a steeper drop in the force/deformation characteristic than those which had been preformed by plastic deformation.

Further tests have shown that the outer shape of the spacer according to the invention may also be produced by sintering, extrusion, forging or casting as well, optionally, as similar shaping processes, without subsequent plastic deformation. However, since quite specially shaped spacers are used for virtually all applications, the machining processes of turning and grinding generally exhibit cost advantages over noncutting processes, which incur high forming tool costs. It should also be taken into account that the optimum shape for a spacer for a special application has generally to be determined empirically by tests. The changes necessary therefor in order to reach the optimum shape may be effected very quickly and simply on a lathe or grinding machine, while alterations to forming tools are considerably more complex.

In the case of spacers in the diametrical and length ranges most commonly used, just as in the case of known spacers produced by turning and compression, a single bulge is generally provided in the middle between the axial end portions of the spacer, the overall shape being symmetrical with respect to a central transverse plane. As a rule, the spacer according to the invention differs in this case from the conventional in that the wall thickness in the zones of the deformation area adjoining the axial end portions is slightly thinner and then increases constantly from both sides towards the middle of the bulge, such that in the middle of the deformation area the wall thickness is markedly greater than in the case of a conventional spacer used for the same purpose. The difference between the smallest and largest wall thicknesses is at most approximately 30 % of the smallest wall thickness.

For cost reasons also, it is recommended, in the case of machining of the spacer according to the invention, to start with a tubular starting material, from which as little as possible need be turned or ground off both inside and out. It is then often possible to dispense with machining of the outer circumferential surfaces of the axial end portions. Thus, as a rule spacers are provided which lie straight with parallel longitudinal central axes when their circumferential surfaces are positioned on a flat base, while, in the case of conventional, plastically predeformed spacers, the bulge generally projects radially beyond the outer circumference of the axial end portions, such that the spacers, if lain on their circumferential surface, tilt and remain lying in an inclined position, which may necessitate special measures in conveying and feed apparatuses in automatic packing and assembling machines.

From the above explanations it may be seen that the subject matter of the invention is both a new spacer and a new method for its production, wherein, starting with a tubular starting material, the outer shape, i.e. both the radially inner and the radially outer contours, is generated by machining alone. The spacer may in individual cases also be heat-treated after this shaping.

An exemplary embodiment of the invention is described below in more detail with the aid of the attached drawings, in which:

Fig. 1 is a longitudinal section through a spacer; 6 Fig. 2 shows the profile of the spacer according to Fig. 1 on an enlarged scale with dimensions given by way of example for the constantly changing wall thickness; 5 Fig. 3 is a force/deformation diagram, in which the characteristic of a spacer with a wall thickness varying over the deformation area is compared with the characteristic of a comparable conventional spacer.

The spacer illustrated in Figs. 1 and 2 consists of steel, but could also be made of another metal, a metal alloy or optionally even a non-metallic material, such as plastics for example. The shape illustrated, i.e. the contours of the radially inner and the radially outer circumferential surfaces, is generated by turning alone, in the example from an ST 35 BK tube with a 35.4 mm external diameter. Plastic deformation by axial compression is not effected. The spacer is fitted in the form shown with the dimensions indicated, e.g. for spacing tapered roller bearings arranged in pairs.

The spacer shown consists of two axial end portions 10, 12 and a deformation area 14 arranged therebetween. The axial end portions have a uniform wall thickness, which results from the dimensions indicated in the drawings. They do not need to be machined on their outer circumferential surfaces, such that turning and/or grinding machining is restricted to the inner circumferential surface and radially outwardly only the deformation area 14.

According to Fig. 2, encircling, rounded indentations 16 and 18 respectively adjoin the end portions 10 and 12 radially outwardly, while the cylindrical inner circumferential walls of the end portions 10 and 12 extend further with unchanged diameter beyond the end portions towards the axial centre of the spacer, such that, as a result of the outer, rounded 7 indentations 16, 18, the wall thickness is reduced to a specific minimum, which is a consequence of the dimensions illustrated in Fig. 2.

Continuing axially from the ends towards the middle of the spacer, there follows on each side, after the above-mentioned indentations 16, 18, a radial bulge 20 which, however, does not extend beyond the external diameter of the axial end portions 10, 12. The bulge in the outer contour is accompanied by an indentation 22 or concave radial bulge of the inner circumferential surface of the spacer. In longitudinal section, the outer indentations 16, 18 and the outer bulge 20 are formed by radii whose arcs merge constantly with each other at points of inflection. The inner indentation 22 also merges constantly via points of inflection and connecting radii with the cylindrical circumferential surfaces of the end portions 10, 12. The outer bulge 20 and the inner indentation 22 are each mainly produced by a single radius. The centres of both arcs lie in the same transverse plane (indicated in Fig.

2 by a dash-dotted line) in the middle between the axial ends of the spacer. As indicated, the radius generating the outer bulge 20 is substantially smaller than the radius defining the inner indentation 22. In this way, there is provided a constant increase in the wall thickness of the spacer from the points of minimum wall thickness in the outer indentations 16, 18 towards the axial centre of the bulge 20.

In the diagram according to Fig. 3, the reduction in length of the spacer is plotted in millimetres on the abscissa and the axial load in KN is plotted on the ordinate. The hatched area is a tolerance area provided for a specific application, in which the characteristic curves of the measured spacers lie. The curve designated A characterises a spacer produced in the conventional manner by turning and axial compression, while the curve designated B represents the force behaviour, plotted over the linear deformation, of a spacer according to the invention provided for the same application, said spacer 8 having a wall thickness variable over the area of deformation. Although both curves lie in the hatched tolerance field permitted in the Example, it may be seen that the drop in force after the maximum is exceeded is substantially flatter as the deformation increases in the case of the spacer according to the invention, i.e. the force is correspondingly more uniform than is the case with the conventional spacer. Since the reproducibility of the result within a production run of spacers according to the invention is also better as a result of the omission of the plastic predeformation process, in future the hatched tolerance area may be reduced, and indeed even with a simultaneous reduction in production costs.

9

Claims (14)

CLAIMS:

1. A spacer for compensating axial play between machine components, which spacer has, between its axial end portions, a deformation area with at least one radial bulge of predetermined wall thickness, wherein the wall thickness varies constantly in the axial direction at least over the majority of the deformation area, the difference between the smallest and largest wall thicknesses amounting to at least 20% of the smallest wall thickness and at least one thicker area being located between two thin areas.

2. A spacer according to claim 1, wherein its outer shape is generated by machining alone.

3. A spacer according to claim 1, wherein its outer shape is generated by sintering, extrusion, forging or casting.

4. A spacer according to any one of claims 1 to 3, wherein the difference between the smallest and largest wall thicknesses amounts to approximately 3050% of the smallest wall thickness.

5. A spacer according to any one of claims I to 4, wherein it consists of metal, especially steel.

6. A spacer according to any one of claims 1 to 5, wherein a thin area adjoins each end portion and in that a bulge- forming area becoming thicker towards the middle is located therebetween.

7. A spacer according to any one of claims 1 to 6, wherein it has a cross-section symmetrical with respect to a central transverse plane.

8. A spacer according to any one of claims 1 to 7, wherein the wall thickness of the axial end portions is larger than the thinnest wall thickness.

9. A spacer according to any one of claims 1 to 8, wherein the largest external diameter of the bulge is approximately as large as the external diameter of the end portions.

10. A spacer according to any one of claims I to 9, wherein the bulge is formed in axial longitudinal section by an outer arc with a relatively smaller radius and an inner arc with a relatively larger radius, the centres lying on the same transverse line.

11. A method of producing a spacer according to claim 1, wherein starting with a tubular starting material, the outer shape is generated by machining alone.

12. A method according to claim 11, wherein the spacer is heat-treated after shaping.

13. A spacer substantially as hereinbefore described with reference to the accompanying drawings.

14. A method of producing a spacer, substantially as hereinbefore described with reference to the accompanying drawings.