AU5409801A - Spring silencer - Google Patents

Description

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ORIGINAL

Complete Specification too.

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Applicant: Inventor: William Mackie Douglas Park William Mackie Douglas Park Spring Silencer Title: Address for Service: LESICAR PERRIN, 49 Wright Street, Adelaide, South Australia 5000, Australia The following statement is a full description of this invention, including the best method of performing it known to melus: Spring Silencer The present invention relates to a spring silencer and in particular to a spring silencer that is used with leaf springs such as that commonly found on buses and trucks.

BACKGROUND OF THE INVENTION Heavy vehicles, such as buses and trucks generally use a leaf spring suspension system that supports the axle of the vehicle, each axle having at least two wheels one at either end thereof. Generally each wheel of the axle is attached through a leaf spring arrangement having a number of leaf springs (usually more than 3) that are mutually superposed. Inserts are provided between the ends of the leaf springs to prevent the springs from being in contact with each other and thus rub, this being undesirable for a number of reasons including wear and tear.

The difficulty with these types of arrangements is that the inserts themselves are caused to frictionally rub against the leaf springs and thus wear out requiring continual replacing. The wear rates are also at times uneven depending on the road conditions and the loading on the vehicle. It has actually been found that under extreme driving conditions the inserts may also fall out. Further, under hot and dry conditions, the frictional response is such so as to produce an undesirable and irritating noise.

Anumber of solutions have been proposed to overcome the above identified problems.

These have included adding various coatings and lubricants to the inserts themselves.

20 Whilst a short-term solution, the inserts still require maintenance and the above solutions add to the complexity and the cost.

It is therefore an object of the present invention to overcome at least some of the abovementioned problems or provide the public with an alternative insert to be used in leaf spring suspensions.

9 25 BRIEF SUMMARY OF THE INVENTION Therefore according to one aspect of the present invention there is provided a silencer for use in leaf spring suspensions having multiple longitudinal leaf springs arranged on top of each other, said silencer including: a base having an upper and a lower surface and a body there in-between; a projection extending from said base; at least one of said leaf spring having an aperture therein; said base positioned in-between two leaf springs such that said projection is adapted to engage said leaf spring aperture; wherein said silencer base is made from a material adaptable for a shear motion between said upper and lower surfaces in a direction generally parallel to the longitudinal direction of the leaf springs.

Preferably the silencer is so positioned that said projection extends generally downwardly and engages an aperture in a leaf spring below said base.

Advantageously the aperture is correspondingly shaped to said projection.

Preferably both said base and projection are made from an elastic material such as plastic or plastic compounds.

Preferably said base is of a wedge shape configuration that corresponds to the shape of the vertical gap between adjacent leaf springs.

In another form of the invention there is proposed a leaf suspension system including a plurality of superposed leaf springs, at least one leaf spring having an aperture therein, S" at least one silencer extending between adjacent leaf springs and adapted to engage said aperture, said silencer having a pre-determined height and being composed of a 20 material accommodating for shear motion through said height whereby during relative slidable motion of the two adjacent springs the interposed silencer remains in static S* contact with each of said springs but distorts to accommodate for the relative movements between said springs.

Other objections and advantages of the present invention will become apparent in view of the following detailed description and accompanying drawings.

S: BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the invention is described hereunder in some detail with reference to and as illustrated in the accompanying drawings, in which: Figure 1 is a partial perspective view illustrating a typical leaf spring suspension system; Figure 2 is a perspective view of a spring silencer according to the present invention; Figure 3 is an exploded perspective view showing the position of a number of silencers within a number of leaf springs; and Figure 4 is a cross sectional view of an insert positioned between two springs when the suspension is inactive; is a cross-sectional view as in but when a lower spring has moved to the left of the spring above; is a cross-sectional view as in but when a lower spring has moved to the right of the spring above.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Turning now to the figures in detail there is shown in Figure 1 a vehicle chassis supporting an axle 12 via leaf springs 14. The leaf springs are attached to said chassis via brackets 16 and 18. A shock absorber 20 extends between the chassis 10 and the axle 12 and is adapted to absorb sudden movement between the two. One skilled in the art will therefore appreciate that the leaf springs provide for greater load bearing.

Typically a plurality of leaf springs are arranged in a mutually superposed arrangement, 20 in this example there being three springs. The leaf springs are attached to the axle via bracket 22 and are also clamped together using brackets 24 and 26 at either end receptively. Located in-between and adjacent the ends of the leaf springs are inserts or silencers 28. The silencers serve to maintain a constant separation between the springs and also to provide for an intermediate surface and therefore prevent the leaf springs from rubbing directly against one another.

S.The typical construction of these silencers can be observed in Figures 2-4 where they include a base 30 and an extending projection 32 (downwardly when positioned in place) that engages a correspondingly shaped groove or aperture 34 in the leaf springs to thereby effectively lock the silencer into place. The shape of the projection and the aperture is generally rectangular with rounded ends. It is however to be understood that the invention is not to be limited to the shape and/or orientation of the projection and that it may very well be that in some circumstances the projection may be oriented upwardly. Of course, to ensure that the silencer remain at the same horizontal position to the leaf springs, it is preferred that the shape of the projection at least in part is the same as the aperture in the leaf spring.

The silencers are advantageously manufactured from a hard inelastic plastic that separates the springs. However in some cases if the silencers are made from a hard material they may be subject to significant rubbing action and may wear out at a quick rate. In addition, the silencers may produce audible noise when the springs move relative to them.

In a further embodiment of the invention it has been have discovered that the use of a relatively soft plastic solves the problems of both wear and noise. It has long been assumed that the use of soft plastics is not appropriate for silencers in-between leaf springs. It was thought that soft plastic would be compressed and would not provide the necessary separation between the springs. However, I have discovered that a satisfactory silencer may be made from a softer plastic that exhibits shear motion qualities. A softer plastic that can accommodate shear motion within the body is caused to experience a shear motion allowing the leaf springs to slide with respect to each other yet at the same time remain in generally firm contact with the silencer. Of course, 20 other materials may equally well be used provided that they allow for shear motion between the top and bottom surfaces of the silencer, that is, within the body.

Thus a further operation of the silencers according to the present invention can be more readily observed in Figure 4. It is to be understood that this Figure is presented for illustrative purposes only and it is not suggested that this is the exact configuration of the silencers in operation or the physical dimensions. The illustration exaggerates the actual shear motion that may be experienced by the silencer. It is however a good schematic representation where a representation of the physical motion is reproduced for illustrative purposes only.

Thus in Figure 4(a) when the leaf springs are static to each other the silencer simply fills the gap between the springs. When an upper spring 36 moves, say right, with respect to a lower one 38 as shown in Figure the silencer experiences a shear motion. That is, the top surfaces 40 of the silencer does not move with respect to the bottom surface 42 of the upper spring 36 whilst the bottom surface 44 of the silencer does not move with respect to the top surface 46 of the lower spring 38. This can happen because of the property of the material from which the silencer is made in that a shear 48 is allowed to occur within the material.

Similarly, when the upper spring 36 moves left with respect to the lower one (shown in Figure the silencer also experiences a shear in the opposition direction to that shown in Figure 4(b).

Further, the gap between the springs is greater at their ends than towards the centre, that is it is a wedge shape. The silencer is therefore appropriately of a wedge shape wherein the side 50 of the silencer that is located closer to the end of the leaf springs is thicker than the side 52 that is located further away from the end of the springs.

The person skilled in the art will appreciate that there are numerous materials that may exhibit relative shear motion and are generally not easily compressible. It will also be appreciates that the silencer is oriented so that the projection points downwardly. This orientation assists in ensuring that the silencer does not easily fall out from between the leaf springs.

Thus one can see that the present invention provides for and embodiment of a silencer S. wherein the material allows for a shear to occur. This greatly reduces the relative movement between the surfaces of the silencer and the springs that are in contact with each other thereby removing most of the abrading and noise generating action. The 20 substantial decrease in wear means that the silencers have a much greater life-time and do not require maintenance as is needed with conventional silencers. This invention is in contrast with conventional thought where any separation needs to be supported by the use of hard and resilient material that includes frictionless coatings.

S: 2 While the invention has been described in terms of a preferred embodiment, the person skilled in the art will appreciate the various modifications, changes and substitutions which may be made without departing from the scope of the invention and are not intended to be construed as limitations upon the scope of the invention.

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Claims (7)

1. A silencer for use in leaf spring suspensions having multiple longitudinal leaf springs arranged on top of each other, said silencer including: a base having an upper and a lower surface and a body there in-between; a projection extending from said base; at least one of said leaf spring having an aperture therein; said base positioned in-between two leaf springs such that said projection is adapted to engage said leaf spring aperture; wherein said silencer base is made from a material adaptable for a shear motion between said upper and lower surfaces in a direction generally parallel to the longitudinal direction of the leaf springs.

2. A silencer as in claim 1 wherein said silencer is so positioned that said projection extends generally downwardly and engages an aperture in a leaf spring below said base.

3. A silencer as in any one of the above claims wherein said aperture is correspondingly shaped to said projection.

4. A silencer as in any one of the above claims wherein both said base and projection S are made from an elastic material such as plastic or plastic compounds. g.

5. A silencer as in any one of the above claims where said base is preferably of a wedge shape configuration that corresponds to the shape of the vertical gap between adjacent leaf springs. oo

6. A leaf suspension system including a plurality of superposed leaf springs, at least one leaf spring having an aperture therein, at least one silencer extending between adjacent leaf springs and adapted to engage said aperture, said silencer having a pre- determined height and being composed of a material accommodating for shear motion through said height whereby during relative slidable motion of the two adjacent springs the interposed silencer remains in static contact with each of said springs but distorts to accommodate for the relative movements between said springs. 8

7. A silencer substantially as hereinbefore described and with reference to the accompanying drawings. Dated this 27th day of June 2001 WILLIAM MACKIE DOUGLAS PARK By his Patent Attorneys LESICAR PERRIN o* o *oo oo*** o* o. oo* f