AU8026087A

AU8026087A - Securing a sulcated spring to a suspension component

Info

Publication number: AU8026087A
Application number: AU80260/87A
Authority: AU
Inventors: Colin Edward Spedding
Original assignee: GKN Technology Ltd
Current assignee: GKN Technology Ltd
Priority date: 1986-10-08
Filing date: 1987-10-05
Publication date: 1988-05-06
Also published as: GB8624183D0; GB2196093B; GB8723361D0; WO1988002828A1; ZA877394B; GB2196093A

Description

SECURING A SULCATED SPRING TO A SUSPENSION COMPONENT

This invention relates broadly to springs of the kind which comprises a continuous strip of fibre- reinforced plastics material in the form of a zig-zag having a number of limbs joined by reflex portions, the longitudinal centre line of the strip lying substantially in a single plane. Such springs are disclosed in European Patent Application 0132048-A and are there called sulcated springs, which term will also be used herein for such springs. More particularly, the present invention relates to means by which a sulcated spring is secured to another component, preferably a suspension component for a vehicle. Sulcated springs are particularly useful in vehicle suspensions, where their configuration and properties enable weight and/or space savings.

Sulcated springs, being made of fibre-reinforced plastics material, are susceptible to damage if the continuity of their constituent fibres is interrupted. This causes a design problem in respect of whatever means is used to secure sulcated springs to other components, since expedients such as bolts or other fasteners penetrating parts of the spring cannot be used. The fibre disruption caused by drilling or otherwise providing a hole is the spring to receive a fastener will lead at least to a degradation of the properties, and ultimately possibly to failure, of the spring.

There is thus a requirement for connecting a sulcated spring to another component, particularly for use in vehicle suspension, which provides a secure connection and yet which does not risk damage to the spring. It is the object of the present invention to meet this requirement.

The invention provides apparatus for securing a sulcated spring to a component, comprising a support member having a flat support surface and connectable to the component, and an anchoring member having a flat anchoring surface, the support member and anchoring member having formations which are inter-engageable to interconnect the support member and anchoring member with the said support and anchoring surfaces parallel so as to grip therebetween a flat end limb of the sulcated spring parallel thereto, the inter-engagement of the formations being external of the said end limb.

The invention thus provides for the clamping of the end limb of the spring between flat surfaces of the support member and anchoring member without penetrating the limb. The use of flat surfaces has the advantage of avoiding pressure points, so that the clamping force is spread evenly over a substantial portion of the end limb.

The formations preferably extend generally normal to the plane of the corresponding support surface and anchoring surface.

Advantageously, the anchoring member is slidable relative to the support member in a direction parallel to the support surface thereof, and the formations afford cam surfaces which urge the anchoring surface towards the support surface during such sliding movement. In preferred embodiments, the support member and anchoring member are channel-shaped and nestable one with the other, the bases of the channels affording the support surface and the anchoring surface respectively and the side walls of the channels, which overlap in use, affording or being provided with said formations.

The cam surfaces are preferably constituted by edges of the side walls of one of the channel-shaped members and corresponding rails projecting from the other channel-shaped member, the said edges and/or the rails being inclined to the plane of the corresponding base to provide the camming action as the edges move along the corresponding rails during the sliding movement.

Such an arrangement of cam surfaces enables a clamping force sufficient for holding the spring limb to be produced by the sliding movement of the anchoring member relative to the support member. When the spring limb is satisfactorily clamped, the anchoring member can be fixed to the support member by any appropriate means, to prevent any possibility of slackening of the connection. In the embodiments described hereafter, such fixing is carried out by welding between the anchoring member and support member, which welding is carried out at a distance from the spring limb sufficient to prevent any possibility of damage to the latter due to heat.

In use of a sulcated spring, as it compresses and expands under changing loads in the direction lengthwise of the spring as a whole, the limbs of the spring change the angles at which they lie relative to one another. It has been found that the possibility of failure in the reflex portions of a sulcated spring adjacent an end limb can be reduced if the end limb of the spring is allowed to pivot about an axis normal to the general plane of the spring. This allows the end limb to assume an angle appropriate to the state of compression or extension of the spring, equalising stresses in the adjacent reflex portions of the spring. The present invention provides for this, in one of the embodiments described hereafte ,- by additionally providing an intermediate member which is pivotally connected to the support member to allow such pivotal movement of the support membe .

The invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, wherein:-

Figure 1 is a diagrammatic side view of a shock absorber strut for use in a vehicle suspension, provided with sulcated springs and to which the invention may be applied;

Figure 2 is a partially broken-away side view of part of the shock absorber strut, to which is secured a sulcated spring in accordance with the invention;

Figure 3 is a cross-section of part of the apparatus shown in Figure 2;

Figure 4 is a view as Figure 2 but of a second embodiment of the invention;

Figure 5 is a cross-section on the line 5-5 in Figure 4.

Referring firstly to Figure 1 of the drawings, this shows a shock absorber strut 10 of telescopic form. having relatively movable parts 14, 16. Such shock absorber struts are well known for connection between relatively movable parts of a vehicle suspension. The strut has associated therewith two sulcated springs 12, one disposed at each side of the strut. Each spring 12 comprises a strip of fibre-reinforced plastics material in the form of a zig-zag having limbs 11 interconnected by reflex portions 13. For each spring the longitudinal centre line of the strip of which it is made lies substantially in a single plane, and in the illustrated assembly of springs and strut such plane is common to the springs and also contains the axis of the strut along which the two parts 14, 16 thereof are relatively movable. The uppermost ends of the springs are connected to the part 14 of the strut, and the lowermost ends of the springs to the part 16 of the strut, in the manner described hereafter.

With reference now to Figures 2 and 3, showing a first embodiment of the invention, there is shown in greater detail the relatively axially slidable upper and lower parts 14, 16 of the shock absorber strut 10; and the fibre-reinforced plastics sulcated spring 12, of which a part has been omitted in Figure 2 for the sake of clarity. As shown in Figure 2, the sulcated spring 12 is fully compressed.

The upper and lower parts 14, 16 of the shock absorber strut 10 carry respective projecting arms 18, 20 which support opposite ends of the spring 12. These arms 18, 20, and the ends of the spring 12 to which they are secured, are identical except one is inverted relative to the other, and accordingly only the upper arm 18 and the upper end of the spring 12 will be described in detail. /02828

The arm 18 comprises a channel section member having a base 22 and two side walls 24. Projecting plates 26 are welded by spot welds 28 to ^"respective opposed inner surfaces of the side walls 24. Each projecting plate 26 has an upper edge 30 inclined at a small acute angle to the plane of the base 22, the edge constituting a rail for a purpose to be described below. The base 22 has a flat inner support surface 32 for supporting the flat end limb 34 of the sulcated spring 12.

A recess or aperture 38 in the support surface 32 is provided at the end remote from the shock absorber strut 10, for receiving a foot 36 at the free end of the end limb 34 of the sulcated spring 12, to locate the spring 12 relative to the projecting arm 18. The recess 38 is, in this example, in the form of a slot which constrains the spring 12 against movement towards and away from the shock absorber strut 10.

The end limb 34 of the spring 12 is clamped against the support surface 32 of the arm 18 by means of an anchoring member 40. The anchoring member 40 is of channel section, and nests wholly within the channel section of the arm 18. The base 46 of the channel section of the anchoring member 40 has a flat, external anchoring surface which engages the flat inner surface of the end limb 34 of the spring 12. As shown in Figure 3, the external width of the anchoring member 40 is slightly less than the internal width of the projecting arm 18 so that the anchoring member 40 is capable of sliding within the channel section of the arm 18, as indicated by the arrow X of Figure 2. The spring 12 has a width slightly less than the internal width of the anchoring member 40, and the side walls 24 of the arm 18 accommodate and protect an upper end portion of the spring 12; when the spring 12 is fully compressed, the upper half of the spring is accommodated within the projecting arm 18.

The side walls 42 of the anchoring member 40 have lower end edges 44 which are inclined at a small acute angle to the plane of the base 46, this angle, in this example, being equal to the angle of inclination of the rails 30 of the projecting plate 26. The projecting plates 26 are positioned at such a height and inclination that, as the anchoring member 40 is slid in the direction X, the edges 44 slide along the rails 30 with a camming action which urges the anchoring member 40 towards the base 22 of the projecting arm 18, to clamp the end limb 34 between the bases 22, 46 of the arm 18 and anchoring member 40 respectively.

The shock absorber is assembled by locating the end limb 34 in the projecting arm 18 with the foot 36 located in the slot 38. The anchoring member 40 is then slid in the direction X, the side walls 42 travelling in the spaces between the spring 12 and the side walls 24 of the projecting arm 18. With the anchoring member 40 in position as shown in Figure 2, it is then fixed by welds 48 through holes 50 in the side walls 24 of the arm 18, as shown in Figure 3.

It has been found that wear in the reflex portions of such a sulcated spring 12 can be reduced by allowing the end mounting to pivot in use about a pivot axis normal to the plane of the spring. This is achieved by a second embodiment of the invention, shown in Figures 4 and 5 of the drawings.

The shock absorber of Figures 4 and 5 is similar to that of Figures 2 and 3, and similar components are denoted by identical reference numerals. Again, since the upper part of the spring 12 is clamped in exactly the same way as the lower part, the only difference being inversion of the various components, only the upper part will be described in detail.

The upper limb 34 of the spring 12 is clamped between a channel-shaped support member 72, furnishing a flat inner support surface (comprising two spaced rectangular regions) , and a channel-section anchoring member 40 which nests slidably in the support member 72. A slot-shaped recess 86 in the support member 72 accommodates a foot 36 at the free end of the end limb 34 of the spring 12. Projecting plates 42 on the opposed inner faces of the side walls 74 of the support member 72 provide inclined rails 44, along which slide the lower edges 30 of the anchoring member 40 to provide the camming action which urges the anchoring member against the inner support surface of the support member 72. The anchoring member 40 is fixed in place by welds through apertures 75 in the side walls 74 of the support member 72.

An intermediate member in the form of projecting arm 66 carried by an upper part 14 of the shock absorber strut 10 is channel-shaped, having a base portion 104 and side walls 100 whose inner spacing is slightly larger than the external spacing of the side walls 74 of the support member 72. Thus, the anchoring member 40 nests within the support member 72 which in turn nests within the intermediate projecting arm 66.

The support member 72, anchoring member 40 and spring 12 are mounted pivotally on the projecting arm 66, to pivot about an axis normal to the plane of the spring 12 and parallel to the bases 46, 72 of the support member 72 and anchoring member 40. The base of the support member 72 has an outwardly convex, part-cylindrical surface 102 whose centre of curvature defines the pivot axis of the said pivotal mounting. (The corresponding inwardly concave surface 103 divides the support surface of the support member 72 into the two spaced rectangular regions mentioned above) . A bearing block 106 is fixed to the undersurface of the base 104 of the projecting arm 66, and has a concave, part-cylindrical bearing surface which is complementary to the convex surface 102 of the support member 72. Thus, the support member 72 is received in the bearing block 106 which allows a relative sliding movement over a predetermined angular range. In order to constrain the sliding movement to pivotal movement about a unique fixed pivot axis, a pair of pivots 96 project from the side walls 74 of the support member 72 and are constrained to slide vertically in corresponding slots 98 formed in the side walls 100 of the projecting arm 66. The assembly comprising the support member 72, spring 12 and anchoring member 40 is thus constrained to pivot about the pivots 96, which, in use, remain at the same extreme position in their slots 98. In this example, the bearing block 106 is of elastomeric material to provide a degree of resilience.

It will be appreciated that the principle of the invention as above exemplified is applicable to securing sulcated springs to components other than shock absorber struts. Sulcated springs are particularly useful for vehicle suspensions, to provide for springing between relatively movable components where hitherto other types of spring would have been used.

Claims

1. Apparatus for securing a sulcated spring to a component, comprising a support member having a flat support surface and connectable to the component, and an anchoring member having a flat anchoring surface, the support member and anchoring member having formations which are inter-engageable to interconnect the support member and anchoring member with the said support and anchoring surfaces parallel so as to grip therebetween a flat end limb of the sulcated spring parallel thereto, the inte -engagement of the formations being external of the space between said surfaces wherein said end limb is received.

2. Apparatus according to Claim 1, wherein the formations extend generally normal to the plane of the corresponding support surface and anchoring surface.

3. Apparatus according to Claim 1 or Claim 2, wherein the anchoring member is slidable relative to the support member in a direction parallel to the support surface thereof, and the formations afford cam surfaces which urge the anchoring surface towards the support surface during such sliding movement.

4. Apparatus according to any one of the preceding claims, wherein the support member and anchoring member are channel-shaped and nestable one with the other, the bases of the channels affording the support surface and the anchoring surface respectively and the side walls of the channels, which overlap in use, having the said formations.

5. Apparatus according to Claim 4 as appendant to Claim 3, wherein the cam surfaces are constituted by edges of the side walls of one of the channel-shaped members and corresponding rails projecting from the other channel-shaped member, the said edges and/or the rails being inclined to the plane of the corresponding base to provide the camming action as the edges move along the corresponding rails during the sliding movement.

6. Apparatus according to Claim 5, wherein the anchoring member nests wholly within the support member, its side walls being shorter than those of the support member, and the rails are provided on internal surfaces of the side walls of the support member.

7. Apparatus according to any one of the preceding claims, wherein the support surface has a recess for accommodating a foot provided at the free end of the end limb of the spring, to locate the end limb.

8. Apparatus according to any one of the preceding claims, further comprising an intermediate member which is connectable to the component, and means for pivotally connecting the support member to the intermediate member, the pivotally-connecting means allowing pivotal movement of the support surface relative to the component about a pivot axis parallel to the plane of the support surface and normal to the general plane of the spring.

9. Apparatus according to Claim 8, wherein the pivotally-connecting means comprises a bearing on the intermediate member having a concave part-cylindrical surface facing the support member, the support member having a complementary part-cylindrical surface resting /02828 PCT/GB87/00701

12

slidably in the bearing against the concave surface thereof.

10. A vehicle suspension including a sulcated spring secured to a suspension component by apparatus according to any one of Claims 1 to 9.

11. An assembly of a shock-absorber strut having relatively movable parts and at least one sulcated spring connected between said parts, the spring(s) being connected by apparatus according to any one of Claims 1 to 9 to components associated with said parts.