GB2030267A

GB2030267A - Leaf-spring assembly

Info

Publication number: GB2030267A
Application number: GB7932305A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-09-21
Filing date: 1979-09-18
Publication date: 1980-04-02
Also published as: AU5087079A

Abstract

A horizontal leaf-spring suspension assembly, fitted with a beam axle 11 and suitable for reducing sway in vehicles, such as towed vehicles, comprises a leaf- spring 12, one end of which is pivotally connected to the chassis by a connecting means comprising plates 41, 42 and three pivots 43, 44, 45, the pivot 43 connecting the plates 41, 42 to a hanger 2 of a chassis 1, the pivot 44 connecting an eye 16 of the leaf spring 12 to the plates 41, 42 and the pivot 45 connecting the plates 41, 42 to a shackle 46 connected to a plate 14 to which the axle 11 is attached, the other end of the spring being free to slide in a support 3 such that, on deflection of the spring, both ends of the spring travel through a substantially equal distance. <IMAGE>

Description

SPECIFICATION Leaf-spring assembly FIELD OF THE INVENTION This invention relates to leaf-spring suspensions, and particularly but not exclusively to leaf-spring suspensions for use in caravans and other towed vehicles to reduce the sway in such vehicles.

Many vehicles, and particularly towed vehicles such as caravans and trailers, are fitted with beam axle, longitudinal leaf-spring suspensions. When one wheel of a towed vehicle encounters an obstacle, the spring on that side is compressed.

Compression of the spring causes it to elongate towards the shackle, usually rearwardly. The axle moves slightly backward on that side, and, in the case ot a prolonged compression of the spring on one side of the vehicle, this results in a swaying movement of the vehicle itself. On an undulating road, this swaying motion is difficult to control, and the vehicle may in fact become dangerous.

It appears that where swaying in vehicles, including towed vehicles, occurs as a result of spring deflection, it is caused by deviation of one end of the axle from a pre-deflection axis, which pre-deflection axis is perpendicuiar to the longitudinal axis of the vehicle. A towed vehicle in such a situation will tend to follow a longitudinal axis created by the disaligned axie along a periodically swaying path.

DESCRIPTION OF THE PRIOR ART One solution to the problem is the installation of independent suspensions, which are effective in the reduction of swaying. However, independent suspensions are expensive to make and install.

There is a need to provide a leaf-spring suspension assembly which can be installed in new vehicles, or used to modify existing leafspring suspensions, and which will also be effective in the reduction of swaying.

BRIEF SUMMARY OF THE iNVENTION An object of this invention is to provide a leafspring suspension assembly which can reduce the swaying movement of a vehicle.

A further object is to provide a means of preventing one end of an axle in a leaf-spring suspension assembly from deviating substantially from an axis perpendicular to the longitudinal axis of a vehicle.

Accordingly, this invention provides a horizontal leaf-spring suspension assembiy for a vehicle fitted with a beam axle, the assembly comprising a ieaf-spring fitted to an axle and a connecting means, wherein a first end of the leaf-spring is movably attached to a vehicle chassis so that it can freely elongate in a longitudinal direction on deflection of the leaf-spring, and a second end of the leaf-spring is supported by the connecting means relative to the vehicle chassis, whereby when the leaf-spring is deflected, the first end of the leaf-spring elongates at its attachment to the vehicle chassis, and the connecting means is such that the second end of the leaf-spring elongates through a substantially equal distance, and whereby the position of the axle does not deviate substantially from its pre-deflection vertical axis perpendicular to the vehicle chassis.

In a preferred embodiment, this invention provides a horizontal leaf-spring suspension assembly for a vehicle fitted with a beam axle, the assembly comprising a leaf-spring fitted to an axle and a connecting means, wherein a first end of the leaf-spring is movably attached to a vehicle chassis so that it can freely elongate in a longitudinal direction on deflection of the leafspring, the connecting means has at least three points of attachment, a second end of the leafspring is pivotally attached to one point of attachment of the connecting member, a second point of attachment of the connecting means being pivotally attached to the vehicle chassis, and an at least third point of attachment of the connecting means being connected in relation to the spring between the second end of the leafspring and the axle in such a way that, when the spring is deflected, the first end elongates at its attachment to the vehicle chassis, and the action of the spring on the at least third point of attachment of the connecting means causes the second point of attachment of the connecting means to pivot and enable the second end of the leaf-spring to elongate so that both ends of the leaf-spring move through a substantially equal distance, and the position of the axle does not deviate substantially from its pre-deflection vertical axis perpendicular to the vehicle chassis.

Preferably, the area described by the points of attachment of the connecting means is triangular, or has the shape of a truncated triangle.

BRIEF DESCRIPTION OF THE DRAWINGS The invention wili now be explained in more detail by reference to the accompanying drawings which illustrate preferred embodiments of the invention, wherein: Figure 1 is a side perspective view partially broken away for clarity; Figure 2 is a side perspective view of the embodiment illustrated in Figure 1, again partially broken away for clarity; Figure 3 is a side view partiaily in section of an embodiment which is a modification of the embodiment illustrated in Figures 1 and 2; Figure 4 is a side view partially in section, of another preferred embodiment; Figure 5 is a side view partially in section, of a further preferred embodiment; and Figure 6 is a side view partially in section, of the same preferred embodiment illustrated in Figure 5.

DETAILED DESCRIPTION OF THE INVENTION Figure 1 and Figure 2 show chassis 1 with hanger 2 and slipper enclosure 3. Axle 1 1 is attached to a leaf-spring 12, comprising a plurality of single-leaf elements, by U- bolts 13 fastened to plate 14. The individual leaves of leaf-spring 12 are held together by spring clip 15. Leaf-spring 12 has eye 16 and slipper 1 7.

Connecting plate 41 (shown partially in dotted lines for clarity) and connecting plate 42 are pivotally attached to hanger 2 by pivot 43, and to the eye 16 of leaf-spring 12 by pivot 44.

Connecting plates 41 and 42 are pivotally attached to one end of shackle members 46 by pivot 45. The lower end of shackle members 46 are pivotally attached to projections 47 (other side not shown) which rigidly project from plate 14.

In operation, as spring 12 is deflected, it moves upwards through distance D (shown in Figure 2), carrying axle 11 with it. As spring 1 2 is deflected, slipper end 1 7 elongates within enclosure 3 by distance E.

The upward movement of spring 12 through distance D, exerts, by means of projections 47 extending from plate 14, an upward force on shackle members 46 which, in turn, exert an upward pressure on plates 41 and 42 through pivotal attachment 45. This causes plates 41 and 42 to turn in an anti-clockwise direction about pivot 43, and thereby translates the upward force exerted through shackle member 46 into substantially horizontal movement. This substantially horizontal movement of plates 41 and 42 causes eye of spring 1 6 through its pivotal attachment to pivot 44 to elongate through distance E.

As spring 12 rebounds, thereby moving downward through distance D, slipper end 1 7 travels back distance E through slipper enclosure 3, and eye end 16 also travels back through the same distance E. This movement of eye 1 6 is controlled by the response of plates 41 and 42 to downward force exerted by shackle members 46 through pivot 45 which causes plates 41 and 42 to turn in a clockwise direction about pivot 43.

This turning of plates 41 and 42 is such that, through the attachment of eye 1 6 to pivot 44, travel of eye 1 6 toward axle 11 is brought about.

In practice, the extent of substantially horizontal movement of eye 16 in response to rebound of spring 12 is determined by the configuration of plates 41 and 42. Where the axle is placed approximately equidistantly from each end of the spring, so that it is desirable to have both eye end 1 6 and slipper end 17 travel through and equal distance, it has been observed in this particular embodiment that the distance through which eye 1 6 will elongate is governed by the distance between pivots 43 and 44. This distance should, therefore, correspond to the natural elongation properties of the particular leaf-spring during deflection. Generally, it has been found that the distance between pivots 43 and 44 will be approximately equal to one third of the distance between pivot 43 and the centre of the axle attached to the leaf-spring.

It is to be understood that the distances between the points of attachment on the plates may be adjusted in accordance with the natural elongation and deflection characteristics of a leafspring.

It is also to be understood that eye 1 6 and slipper 1 7 move through approximately equal distances E at different rates. Eye 1 6 moves at a rate substantially constant with each added unit of deflection of the spring. Slipper 1 7 moves at a rate diminishing with each added unit of deflection.

Therefore, these two rates of movement must be accommodated by such measurements between the points of attachment on the plates as will prevent any substantial deviation of the axle upon deflection of the spring.

Figure 3 iilustrates a preferred embodiment which is a modification of the embodiment illustrated in Figures 1 and 2. Chassis 1 has hanger 2 and slipper enclosure 3. Axle 11 is attached to leaf-spring 12 by means of a pair of U bolts 13 which are secured to plate 14. The individual leaves of leaf -spring 12 are held together by spring clip 1 5. Slipper 17 is held in place by slipper enclosure 3. Connecting plate 42 (the corresponding plate is not shown for clarity) is pivotally and rotatably attached to hanger 2 by pivot 43, and eye 1 6 is pivotally attached to plate 42 by pivot 44. Bar 45 rides within an elongate slot at the end of the plate 42. Bar 45 is attached to support member 46 which is angularly inclined and fastened between the spring 12 and axle 11 by U-bolts 13.

In operation, when the leaf-spring 12 is deflected, it moves, together with axle 11 through distance D. This movement of spring 1 2 causes support member 46 and bar 45 to act within the elongate slot forcing plate 42 upward and tuming plate 42 anti-clockwise about pivot 43. This causes pivot 44 and eye of spring 1 6 to move through distance E with the movement of plate 42. On deflection of spring 12, slipper end 17 travels by distance E within slipper enclosure 3.

When spring 12 rebounds, thereby moving downward through distance D, slipper end 1 7 travels back by distance E within slipper enclosure 3. The downward motion of spring 12 exerts a downward force on support member 46 and bar 45, which acts within the elongate slot forcing plate 42 downward. This downward force causes plate 42 to turn clockwise about pivot 43, which causes pivot 44 and eye 16 to travel towards the axle through distance E.

The embodiment illustrated in Figure 4 is a further preferred embodiment in which chassis 1 has slipper enclosure 3 and hanger 2. Axle 11 is fixed to spring 12 by U-bolt 13 and plate 14.

Individual spring elements are held together by spring clips 1 5. Connecting plate 42 is pivotally attached to hanger 2 by pivot 43 and pivotally attached to eye 1 6 by pivot 44. Plate 42 is fixed in relation to spring 12 by pins 45' and 46'.

Upon deflection, spring 12 and axle 14 move upward through distance D. This upward movement causes slipper 1 7 to travel within slipper enclosure 3 by distance E. The progress of eye 1 6 along distance E resulting from tuming of plates 42 during deflection of spring 12 is controlled by the interaction of pins 45' and 46' with the adjacent region of the spring.

When spring 1 2 rebounds through distance D, the movement of spring 1 2 downward through distance D causes slipper 1 7 to travel back within slipper enclosure 3 by distance E, and also causes eye 16 and pivot 44 to travel back through distance E. This movement of eye 1 6 and pivot 44 is controlled by the interaction between pins 45' and 46' and the adjacent section of spring 12.

Figures 5 and 6 illustrate a further preferred embodiment, which is a variation of the embodiment illustrated in Figure 4 and is an embodiment suitable for light duty suspensions.

Figures 5 and 6 show chassis 1, hanger 2, and slipper enclosure 3. Spring 12 is fixed to axle 11 by U-bolts 13 and plate 14. Spring 12 has eye 1 6 and slipper 1 7. Eye 16 is fixed to plate 42 by pivot 44. Connecting plates 41 and 42 (shown in Figure 6) are pivotally attached to hanger 2 by pivot 43. Plates 41 and 42 are fixed to spring 12 by rollers 45' and 46'.

When spring 1 2 is deflected, it moves with axle 11 upward through distance D. This upward movement of spring 1 2 causes slipper 1 7 to travel within slipper enclosure 3 by distance E. Again, as in the previous embodiment, the progress of eye 1 6 along distance E resulting from tuming of plates 41 and 42 during deflection of spring 1 2 is controlled by the interaction of rollers 45' and 46' w;th the adjacent region of the spring 1 2.

When spring 1 2 rebounds through distance D, slipper 1 7 travels back within slipper enclosure 3 by distance E. The downward movement of spring 12 also interacts with rollers 45' and 46' to control the travel of eye 1 6 and pivot 44 through the turning of plates 41 and 42 about pivot 43.

It is believed that arrangement of the leafspring assembly of the invention with the free end mounted towards the direction of travel (i.e.

towards the front of the vehicle) actually assists in conversion of some portion of the horizontal force of impact on the wheel into a vertical upward force, adding to the deflection of the spring. For this reason, it is preferred that the free end of the spring be mounted towards the direction of travel.

It will readily be understood that, although the free end in the embodiments described is a slipper, the free end may be an eye, provided that the attachment means permits unimpeded movement on deflection of the spring. Preferably, the attachment means of the free end is a conventional compensating shackle or compensating enclosure.

The leaf-spring assembly of the present invention can be installed on both single and multiple axle vehicles. Where the leaf-spring assembly is installed on a multiple axle vehicle, the hanger may incorporate a rocker to at least one end of which the connecting plates of a spring assembly is pivotally attached.

One connecting plate may be used, but it is preferred that the spring be enclosed within a pair of plates.

These and other modifications may be made without departing from the ambit of the invention, the nature of which is to be determined from the foregoing description, and it will be appreciated that the invention is not restricted to the embodiments herein described. It is to be understood that the invention includes any modifications or embodiments shown or implied which would be apparent to a person skilled in the field of this invention.

Claims

1. A horizontal leaf-spring suspension assembly for a vehicle fitted with a beam axle, the assembly comprising a ieaf-spring fitted to an axle and a connecting means, wherein a first end of the leafspring is movably attached to a vehicle chassis so that it can freely elongate in a longitudinal direction on deflection of the leaf-spring, and a second end of the leaf-spring is supported by the connecting means relative to the vehicle chassis, whereby when the leaf-spring is deflected, the first end of the leaf-spring elongates at its attachment to the vehicle chassis, and the connecting means is such that the second end of the leaf-spring elongates through a substantially equal distance, and whereby the position of the axle does not deviate substantially from its pre-deflection vertical axis perpendicular to the vehicle chassis.

2. An assembly according to claim 1, wherein the connecting means has at least three points of attachment, one point of attachment being attached to the second end of the leaf-spring, a second point of attachment being attached to the vehicle chassis and an at least third point of attachment is attached in relation to the spring.

3. An assembly according to claim 2, wherein the at least third point of attachment is attached above or below the spring adjacent the axle.

4. An assembly according to claim 2, wherein the at least third point of attachment is attached above or below the spring in the region of the spring between the axle and the second end.

5. A horizontal leaf-spring suspension assembly for a vehicle fitted with a beam axle, the assembly comprising a leaf-spring fitted to an axle and a connecting means, wherein a first end of the leafspring is movably attached to a vehicle chassis so that it can freely elongate in a longitudinal direction on deflection of the leaf-spring, the connecting means has at least three points of attachment, a second end of the leaf-spring is pivotally attached to one point of attachment of the connecting member, a second point of attachment of the connecting means being pivotally attached to the vehicle chassis, and an at least third point of attachment of the connecting means being connected in relation to the spring between the second end of the leaf-spring and the axle in such a way that, when the spring is deflected, the first end elongates at its attachment to the vehicle chassis, and the action of the spring on the at least third point of attachment of the connecting means causes the second point of attachment of the connecting means to pivot and enable the second end of the leaf-spring to elongate so that both ends of the leaf-spring move through a substantially equal distance, and the position of the axle does not deviate substantially from its pre-deflection vertical axis perpendicular to the vehicle chassis.

6. An assembly according to claim 5, wherein connection of the connecting means in relation to the spring is by a support means fixed above or below the spring adjacent the axle.

7. An assembly according to claim 6, wherein the area described by the points of attachment on the connecting means is triangular in shape.

8. As assembly according to claim 5, wherein connection of the connecting means in relation to the spring is by any suitable means above and below the spring.

9. An assembly according to claim 8, wherein the area described by the points of attachment on the connecting member is a truncated triangle in shape, the top of the truncated triangle being connected above and below the spring.

10. An assembly according to claim 5, wherein the first end of the spring is a slipper.

11. An assembly according to claim 5, wherein the first end of the spring is an eye.

12. An assembly according to claim 5, wherein the second end of the spring is an eye.

13. An assembly according to claim 5, wherein the first end of the spring is mounted towards the direction of travel.

14. An assembly according to claim 1 substantially as hereinbefore described with reference to the accompanying drawings.

1 5. An assembly according to claim 5 substantially as hereinbefore described with reference to the accompanying drawings.