GB1571575A

GB1571575A - Methods for obtainig pivoting resilient joints and joints thus obtained

Info

Publication number: GB1571575A
Application number: GB35767/77A
Authority: GB
Original assignee: Paulstra SNC
Current assignee: Paulstra SNC
Priority date: 1976-08-25
Filing date: 1977-08-25
Publication date: 1980-07-16
Also published as: NL183781B; FR2363024A1; ZA775150B; DE2737898B2; DE2737898C3; FR2363024B1; NL7709127A; IT1116689B; ES461852A1; DE2737898A1; RO78736A; NL183781C

Description

(54) IMPROVEMENTS MADE TO METHODS FOR OBTAINING PIVOTING RESILIENT JOINTS AND JOINTS THUS OBTAINED (71) We. PAULSTRA, a French Society Anonyme. of 61 Avenue Marius Auflin. 92305 Levallois-Perret, France, do herebv declare the invention, for which we prav that a patent may be granted to us, and the method by which it is to be performed, to be particularlv described in and by the folloing statement: - The present invention concerns a method of making a resilient bushing for use in mounting a member on a pivot.

One example of such a resilient bushing comprises an assembly of two hollow sleeves engaged one within the other, the external sleeve being of elastomer and the internal sleeve of thermo-plastic material, said internal sleeve being provided on its interior surface with holes or protrusions allowing greasing of the pivot on which the assembly is mounted, the said holes and protrusions being formed at the time of the injection under pressure of the elastomer forming the external sleeve.

Various solutions have already been proposed for the construction of these bushings.

In particular. a method of obtaining such a bushing is already known, consisting of effecting the deformation of an internal sleeve around a grooved core under the combined effects of the pressure and heat resulting from the injection, around the internal sleeve, of the elastomer constituting the external sleeve. the elastomer being injected into a mould having a form corresponding to that of the said external sleeve.

However. in this known method, the deformation of the internal sleeve is produced only under a high pressure for the injection of elastomer, and only in the situation where the thickness of this internal sleeve is small.

The invention has the object of correcting the drawbacks of this known method, simplifying the moulding operations, and allowing the manufacture with greater precision, of resilient bushings in which the sleeve does not necessarily have a small thickness.

According to the invention there is provided a method of making a resilient bushing comprising arrangement of a hollow sleeve of extruded synthetic plastics material onto- a grooved former, injection of an elastomer into a mould bounded in part by the sleeve, said injection being performed at a temperature below that temperature corresponding to complete curing of the sleeve and at a pressure sufficient to effect plastic deformation of the surface of the sleeve into grooves in the former, and subsequent curing of the sleeve.

It is advantageous if the opposed surfaces of the sleeves are treated chemically so as to ensure adherence.

The invention will be described by way of example with reference to the accompanying drawings.

Figure 1 of these drawings shows in axial section, a pivoting joint in a part of the suspension of a vehicle, this joint being constructed according to the invention, Figure 2 shows, in axial section, on a larger scale, a mould intended for the manufacture of such a joint, Figures 3 and 4 show, in transverse section and in axial section, respectively, another type of pivoting joint capable of being obtained according to the method of the invention.

Finally, Figures 5 and 6 similarly illustrate another type of joint obtained according to the method of the invention.

In Figure 1, a pivoting joint between two units one within the other is represented - in particular, a pivot A belonging, for example, to a stub axle 1 or a support for a vehicle-wheel and a sleeve B mounted, for example, on the end of one or several arms 2 belonging to a suspension - of the type concerned in the invention.

This joint is essentially constituted by the assembly: - of an external sleeve 3 of elastomer offering a certain elasticity, this sleeve being suitable for being connected in a - fixed manner, by a method of adherence of the usual kind, to the surface of a rigid tubular unit 4, metal, for example, itself fixed, at the time of mounting, to the exterior piece B (Figure 1 and 2), although fixing could be equally well provided directly to the piece B, without, therefore, resort to the unit 4, as provided in Figures 3 and 4, - of a sleeve 5 of elastomeric material and harder thermoplastic, for example of polyurethane, suitable for being fixed to the interior of the sleeve 3, this sleeve 5 ensuring, by its interior surface, relative rotation around the pivot A, or, for preference, around a rigid sleeve 6 mounted on this pivot.

- the whole in combination with an appropriate lubrication between sleeve 5 and pivot or sleeve 6, a lubrication made possible by the presence of means, such as a series of protrusions and grooves, provided in the interior surface of the sleeve 5, these means contributing to the formation of preferential friction areas and delimiting cavities filled with lubricant.

These last means, represented at 7 on the various figures. can be of different kinds, comprising, for example: - either flanges and longitudinal grooves, as visible in Figure 1, - or flanges and transverse helicoid grooves, as visible in Figures 3 and 4, - or flanges in two directions at the same time, - or any other holes and protrusions.

Arrangements for axial staying are of course provided at the ends to hold the assembly in functioning position after mounting. these being arrangements such as washers 8, 9, in combination with a nut 10 screwed on a threaded end 11 of the pivot A. These arrangements also allow the avoidance of lubricant leak and penetration of impurities. Any other arrangements could be provided to the same end.

The construction of the joint is carried out in the following way, illustrated in Figure 2.

Resort is made to a mould in the centre of which a central core 12 is set up, carried by the base 13 of the said mould, this core comprising systems of flanges and grooves 14 in the likeness of the above-mentioned flanges and grooves f7;ted 7, - on this core is fitted a polyurethane blank 51, intended for the obtaining of the sleeve 5, this blank being smooth-walled and obtained for example by cutting from a tube of extruded and only partially vulcanized polyurethane, and its diameter being adapted to the diameter of the exterior dimension of the flanges and grooves 14 of the core 12, - and, having put in place, in the body of the mould 15, the rigid exterior sleeve 4 (when it exists), and closed the mould at 16, one proceeds to the moulding under pressure of the elastomer intended to form the sleeve 3, by the ram 17 of a press 18, the elastomer being driven in under pressure through the feeder channels 19 to fill the cylindrical space remaining free and submit the blank 5, to pressure.

Under the effect of this pressure, the surface of the polyurethane, only partially cured of the blank 51 is impressed on the flanges and grooves 14 of the core 12.

A further heating, at a suitable temperature and of a suitable duration, ensures the final curing, giving the required properties to the elastomer of the sleeve 3, as well as the desired rigidity for the sleeve 5.

Moreover, adherence can be advantageously realised between, on the one hand, the exterior unit 4 and the elastomer and, on the other hand, between this last and the interior sleeve 5, the surfaces opposite units 4 and 5 having been previously treated chemically to ensure adherence.

After moulding and curing, the mould is opened and the core 12 withdrawn from the sleeve 5. This last extraction operation does not cause any difficulty, even when the grooves and protrusions are transverse, thanks to the fact that the sleeve 5 still retains a certain elasticity.

In what precedes, it has been supposed, with reference to Figures 1 and 2, that recourse is made to a rigid exterior unit 4, of metal or other material.

But this unit can be omitted, as shown in Figures 3 to 6.

In this case, the exterior sleeve of elastomer 3 can be mounted directly in the piece intended to receive it, preferably with a slight tightening.

To facilitate introduction into the said piece, a transversely or longitudinally channelled shape can be provided on the exterior surface of the sleeve 3.

By way of example, it can be seen in Figures 5 and 6 that the said exterior surface comprises, on the one hand, transverse protrusions 20 and, on the other hand, small longitudinal flanges 21 on these protrusions.

For the moulding of a joint of this type, the procedure will be as represented in Figure 2, where there has been shown in dotted lines at 22 surfaces intended to ensure the formation of chamfers 23, visible in Figure 4.

In Figures 3 to 6, it has been supposed that the internal flanges and protrusions 7 of the sleeve 5 are transverse.

Pivoting joints of this type offer numerous advantages over those already existing especially: - that of being obtained with great precision, - and that of giving rise to extremely simple moulding operations.

WHAT WE CLAIM IS: 1. A method of making a resilient bushing comprising arrangement of a hollow sleeve of extruded synthetic plastics material onto a grooved former, injection of an elastomer into a mould bounded in part by.

the sleeve, said injection being performed at a temperature below that temperature corresponding to complete curing of the sleeve and at a pressure sufficient to effect plastic deformation of the surface of the sleeve into grooves in the former, and subsequent curing of the sleeve.

2. A method as claimed in claim 1, wherein the opposed surfaces of the sleeve and the elastomer are treated chemically in a manner to ensure adherence.

3. Resilient pivoting joints made by the method of claims 1 or 2.

4. Resilient pivoting joints substantially as described with reference to the accompanying drawings.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the procedure will be as represented in Figure 2, where there has been shown in dotted lines at 22 surfaces intended to ensure the formation of chamfers 23, visible in Figure 4. In Figures 3 to 6, it has been supposed that the internal flanges and protrusions 7 of the sleeve 5 are transverse. Pivoting joints of this type offer numerous advantages over those already existing especially: - that of being obtained with great precision, - and that of giving rise to extremely simple moulding operations. WHAT WE CLAIM IS:

1. A method of making a resilient bushing comprising arrangement of a hollow sleeve of extruded synthetic plastics material onto a grooved former, injection of an elastomer into a mould bounded in part by.

3. Resilient pivoting joints made by the method of claims 1 or 2.