AU778699B2 - Vehicle axle - Google Patents

Description

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Name of Applicant Actual Inventor Address for Service:

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT The Boler Company.

Mr Phillip John Britton CULLEN CO Patent Trade Mark Attorneys, 239 George Street Brisbane QId 4000 Australian Vehicle Axle c Invention Title: Details of Associated Applications British Patent Application 0106331.2 filed on 15 March 2001 No.

The following statement is a full description of this invention, including the best method of performing it, known to us: 1. 1, -1la- VEHICLE AXLE This invention relates to vehicle axles, and is particularly concerned with fixed lorries and trailer vehicles provided with a supplementary suspension and axle system that is self-steering.

It is already known to provide a vehicle with a self-steering axle system, where the wheels are located on a pivotally mounted axle, such that the wheels can freely turn to follow the steered wheels of the vehicle as the vehicle, for example, progresses round a corner or bend in a road.

Such self-steering axle assemblies provide notable advantages over fixed axle systems, by avoiding excessive tyre wear or damage to tyres caused by a transverse shear load applied to a tyre as it slides or bounces whilst progressing round a corner or bend.

10 Existing constructions of self-steering axles are quite adequate for all occasions (save perhaps for high vehicle speeds) whilst the vehicle is travelling in a forward direction, but suffer serious operational problems when the vehicle is required to be reversed, so much so that selfsteering axles are frequently provided with a means of locking the axle against pivoting, when a reverse movement is needed, but with attendant wear on the tyres of the wheels on the self- 15 steering axle.

The cause of this stems from the setting of pivot for the axle at an appreciable castor angle, to provide a line of action that projects from the axis of pivot through the road wheel centre and to a point on the tyre surface in advance of the tyre road contact. By providing the axle with an appreciable amount of castor angle, there is the substantial guarantee that the road wheels of the self-steering axle will hold in a straight line when the vehicle is travelling in a forward direction and the self-steering axle will follow the steered axle when the vehicle is travelling in a forward direction around a corner or bend.

The object of the present invention is to provide a means of eliminating those operational problems attendant to known supplementary suspension and axle systems when the vehicle is being reversed.

According to the present invention, a vehicle axle comprises a stub axle assembly mounted by a first pivot on a support, and the support being mounted on a second pivot on an axle beam, said support being provided with a means of causing it to pivot between two operational positions, -2and to hold the support in a required operational position, and said first and second pivots being disposed at a convergent angle whereby to set the first pivot at a first castor angle in one operational position, and at an equal and opposite second castor angle in the other operational position.

The particular means of causing the support to pivot and to hold it in its required operational position is not critical, but can conveniently be chosen to suit the power supply on the vehicle.

Thus with vehicles with a compressed air system for such as the brakes, two air springs may be provided, one to either side of the support. With one air spring disconnected, the other can be activated to cause the support to pivot, and lock it in its required position. With vehicles having 10 hydraulic systems, hydraulic piston and cylinders can be provided, single or double acting, to cause the support to pivot and lock it in its required position.

.o *The invention will now be described briefly with reference to the accompanying drawings in which: So Figure 1 is a perspective view of a vehicle axle according to the invention; set for forward 15 travel; Figure 2 corresponds to Figure 1 but shows the axle set for reverse travel; Figures 3 and 4 are front elevations respectively of Figures 1 and 2; Figures 5 and 6 are plan views respectively of Figures 3 and 4; Figure 7 is rear elevation of Figure 1 with a wheel and tyre fitted in place; and Figures 8 and 9 are schematic representations of the axle systems set respectively for forward and reverse travel.

In the drawings, a stub axle 1 for a supplementary suspension and axle system has an attachment plate 2 to which a vehicle wheel (not shown) may be directly or indirectly attached, the axle 1 being secured to a first pivot 3 in bearings on a support 4 such that the axle can pivot freely about the support. The support may be of unitary construction, but conveniently it is formed by two cast, forged or machined components 5, 6 suitably secured together, the component 6 being formed with bearings for a second pivot 7 attaching the support to the vehicle frame or to an axle beam 8.

-3- The first and second pivots 3, 7 whilst lying in the same plane are angularly disposed with respect to each other at an angle that is downwardly convergent. It is also desirable as is indicated in Figure 7 that the angles of inclination 11 and 12 of the pivots 3 and 7 respectively are such that they are as closely coincident with each other and with the point of ground contact 13 of a tyre 14 on a wheel on the stub axle 1, as is practicable. This minimises actuating and locking forces transmitted through the tyre.

To each side of the support 4 is an attachment 9 for an air spring 10 whereby to cause the support arm to pivot from its position as shown in Figures 1, 3, 5 and 8 to its position as shown in Figures 2, 4, 6 and 9, and to lock the support in the one or the other of its operational positions.

10 As is indicated in Figure 8, and when the support is in its position for a forward movement S* of the vehicle, the pivot 3 for the axle is provided with a positive castor angle to provide a line of action through the vehicle wheel centre to a point on the wheel periphery in advance of the point of road contact in the forward direction of travel, and consequently there is the substantial guarantee that the self-steering axle wheels will follow the steered axle wheels during normal 15 forward travel in both a straight line, and when progressing around a corner or bend.

When the vehicle needs to be reversed, the air springs 10 can be operated to pivot the support 4 about the pivot 7 to its position shown in Figures 2, 4, 6 and 9, where again the support is locked in position. As is indicated by Figure 9, the pivot 3 for the axle is provided with a negative castor angle, again to provide a line of action through the vehicle wheel centre to a point on the wheel periphery in advance of the point of road contact in the reverse direction of travel, and consequently there is the substantial guarantee that the self-steering axle wheels will follow the steered axle wheels during normal reverse travel of the vehicle.

The positive and negative castor angles should be greater than 30, and preferably at or about 60 relative to the vertical plane containing the axle centre and the point of ground contact by the wheel.

Although not illustrated, it may be advisable to provide a means of locking the axle 1 against pivoting with respect to the support 4, when high speed forward travel is intended.

Claims (8)

1. A vehicle axle comprising a stub axle assembly mounted by a first pivot on a support, and the support being mounted on a second pivot on an axle beam, said support being provided with a means of causing it to pivot between two operational positions, and to hold the support in a required operational position, and said first and second pivots being disposed at a convergent angle whereby to set the first pivot at a first castor angle in one operational position, and at an equal and opposite second castor angle in the other operational position.

2. A vehicle axle as in Claim 1, wherein the particular means of causing the support to pivot and to hold it in its required operational position is such as to suit the power supply on the vehicle.

3. A vehicle axle as in Claim 2, wherein two air springs are provided, one to either side of the support.

4. A vehicle axle as in Claim 3, wherein one air spring is deactivatable and the other air spring activatable to cause the support to pivot and lock it in its required position.

5. A vehicle axle as in Claim 2, wherein at least one hydraulic piston and cylinder is provided to pivot the support and lock it in its required position.

6. A vehicle axle as in Claim 5, wherein two single acting piston and cylinders are provided one being deactivatable and the other activatable to cause the support to pivot and lock it .ooo S in its required position. 0

7. A vehicle axle as in Claim 5, wherein the or each hydraulic piston and cylinder is *O*i S double acting, and oppositely activatable to cause the support to pivot and lock it in its required position.

8. A vehicle axle as in any of Claims 1 to 7 wherein the angles of inclination of the first and second pivots in the transverse direction are such that their axes are substantially coincident with each other and with the point of ground contact of a wheel on the stub axle assembly. o• Dated this 2 1 st day of October 2004 The Boler Company By Its Patent Attorneys CULLEN CO.