WO2004083017A1

WO2004083017A1 - Steering mechanism

Info

Publication number: WO2004083017A1
Application number: PCT/AU2004/000324
Authority: WO
Inventors: Steve Corboy; Aaron Anthony Arnold
Original assignee: STERILINE RACING Pty Ltd
Current assignee: STERILINE RACING Pty Ltd
Priority date: 2003-03-18
Filing date: 2004-03-18
Publication date: 2004-09-30
Anticipated expiration: 2005-09-18
Also published as: EP1611000A4; AU2003901217A0; EP1611000A1

Abstract

A steering system wherein there are one or more sets of wheels having a common steered axle (8) associated with a bell-crank, each bell-crank having a body having at least two spaced pivot points (9), a steering crank assembly with a pivot point located intermediate the pair of bell cranks having four spaced pivot points (10), the steered axle (8) associated with each bell crank and at least four pushrods (3, 3a), each pivotally attached at one end to a bell crank pivot point (9), there being two pushrods (3, 3a) for each bell crank, and the other end of pushrod (3a) being pivotally attached to their other end the predetermined distance from the steering crank pivot point on the steering crank assembly.

Description

STEERING MECHANISM

This invention relates to steering mechanisms and in particular steering mechanisms for use with a racing starting gate.

BACKGROUND

A conventional means of implementing a steering mechanism for a pair of steerable single axle wheels is to use a tie rod arm projecting out of each axle and a rod called a pushrod connected between the two tie rod arms. The pair of wheels can then be moved in unison when the single pushrod is moved laterally between the wheels because the lateral movement of the ends of the tie rod arm rotates the wheel axle and thence the wheel to which it is attached.

Racing starting gates, in this example for horse racing, are a large and typically cumbersome transportable framework, partitioned to create a plurality (typically 4- 20) of individual enclosures called stalls that each accommodates a horse and its rider. The front and rear of each stall has a gate to allow egress and access respectively. Once all the horses and their riders are in place and settled, the front gate(s) of each stall are arranged to simultaneously open to commence a race.

The framework is typically heavy because it needs to be self-supporting over its length between wheels located at its ends. It is desirable that there are no wheels or wheel housings immediately adjacent any of the enclosures located between the ends of the framework.

Wheels are needed on the starting gate framework so that it can be moved to an ever changing starting line position on the race track because the length of any particular race demands a particular starting point with respect to a permanently located finish line. In some cases the large structure needs to be moved out of the way of horses running more than one lap of the course and in other situations the starting gate needs to be located to a new starting position in a short amount of time before the next race. It is preferable for the steering mechanism used on the assembly to be as agile as possible, so as to facilitate ease and accuracy of movement sometimes within the confines of a race track that is narrow with respect to the length of the starting gate framework.

The tie rod steering system described above is used for most starting gate arrangements, and works adequately for steering angles that are less than approximately 70 degrees from the straight-ahead position. However, for larger steering angles, the reduction in the effective arm length of the tie rod arm means that the torque available to steer the wheels reduces sharply, becoming zero as the steering angle passes through 90 degrees even if the tie rod was configured not to interfere with the wheel or the wheel assembly.

Typically, before the 90 degree angle is achieved the tie rod and the steered axle can hit one another restricting any further movement to achieve a tighter steering angle. For most practical purposes, the maximum useable steering angle is 70 degrees. This necessitates multiple manoeuvres to direct the starting gate out of position or into a new position, when in many cases an increased steering capability would enable a single movement to achieve the desired result.

Being able to steer with an increased angle, say of 90 degrees, can facilitate rapid movement of the starting gate assembly out of the way laterally across the racetrack and in any event allows more accurate and rapid removal and re-positioning of the starting gate.

Thus steering systems (not only those fitted to starting gate assemblies) would benefit if they had a greater steering angle, and therefore require something different to the tie rod steering system described. In one example of an alternative, a chain drive mechanism can replace a tie rod system. Each axle of each wheel to be steered is fitted with a sprocket in a horizontal plane. Rotation of the sprocket causes rotation of the steered axle. Rotation of both sprockets is achieved using a continuous loop of chain joining them. The loop of chain is moved by a lever mechanism located along its length intermediate the wheels. Such a system is conceptually simple, but requires significant maintenance and has been found to be difficult to implement reliably.

The steering mechanism described herein retains the desirable features of conventional tie rod steering systems (forces applied through rigid articulated elements, minimum number of pivoting joints in system) but uses particular arrangements to permit rotation of the wheels to at least 90 degrees.

Throughout this specification unless the context requires otherwise, the words 'comprise' and 'include' and variations such as 'comprising' and 'including' will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. Further, the use of particular examples of alternatives is not an indication or admission that those examples are part of the common knowledge of those skilled in the art.

BRIEF DESCRIPTION OF THE INVENΗON

In a broad aspect of the invention a steering system includes: at least a pair of opposed bellcranks each having a body having at least two spaced pivot points thereon that are a predetermined distance from a steered axle pivot point wherein the lines between said steered axle pivot point on said bellcrank and said spaced pivot points of each bellcrank is an angle other than 180 degrees, a steering crank assembly with a pivot point located intermediate a said pair of bellcranks having four spaced pivot points, a steered axle associated with each bellcrank, and at least four pushrods, each pivotally attached at one end to a bellcrank pivot point, there being two pushrods for each bellcrank, and the other end of a said pushrod being pivotally attached at their other end said predetermined distance from the steering crank pivot point on the steering crank assembly and lines between two of said pivot points on said steering crank assembly and said steering crank pivot point having an angle to each other the same as said angle.

In an aspect of the invention a steering system includes: a steering crank assembly having a point about which parts of the assembly pivot horizontally and at least four pivot points a predetermined distance and orientation from the point about which the parts of the assembly pivot, at least two opposed bellcranks having said steering crank intermediate said bellcranks and each bellcrank having a body with at least two spaced pivot points thereon said predetermined distance and said orientation from a steered axle pivot point about which the bellcranks pivot horizontally, wherein lines between said steered axle pivot point on said bellcrank and said spaced pivot points of each bellcrank is an angle other than 180 degrees, and pushrods pivotally attached to the spaced pivot points of a bellcrank remain substantially parallel while their other ends are pivotally connected to respective pivot points on said steering crank when said steering crank is turned about said horizontal pivots.

In an aspect of the invention there are one or more wheels having a common steered axle associated with each bellcrank and each wheel is steered using said pair of pushrods to activate a respective bellcrank, such that as the transference of turning force to a bellcrank pivot point by a respective pushrod is becoming less effective to turn said bellcrank, the transference of turning force to the other bellcrank pivot point of the same bellcrank by a respective other pushrod is becoming more effective to turn said bellcrank and thus steer a respective steered axle.

Specific embodiments of the invention will now be described in some further detail with reference to and as illustrated in the accompanying figures. These embodiments are illustrative, and not meant to be restrictive of the scope of the invention. Suggestions and descriptions of other embodiments may be included within the scope of the invention but they may not be illustrated in the accompanying figures or alternatively features of the invention may be shown in the figures but not described in the specification.

BRIEF DESCRIPTION OF THE FIGURES

Fig 1 depicts an underside view of an embodiment of the steering mechanism providing wheel axis alignment at zero degrees adjustment;

Fig 2 depicts the embodiment of Fig 1 with the steering mechanism providing wheel axis alignment at Forty-Five degrees adjustment;

Fig 3 depicts the embodiment of Fig 1 with the steering mechanism providing wheel axis alignment at approximately Seventy-Five degrees adjustment; Fig 4 depicts the embodiment of Fig 1 with the steering mechanism providing wheel axis alignment at Ninety degrees adjustment;

Fig 5 depicts a perspective view of the embodiment of Fig 1 with the steering mechanism fitted to the underside of a framework;

Fig 6 depicts a top view of the embodiment of Fig 5; Fig 7 depicts a side view of the embodiment of Fig 5;

Fig 8 depicts a front view of the embodiment of Fig 5;

Fig 9 depicts a horse racing starting gate assembly;

Fig 10 depicts a further steering assembly;

Fig 11 depicts the generic steering assembly at a zero angle of steer; Fig 12 depicts the generic steering assembly at a Forty Five angle of steer; and Fig 13 depicts the generic steering assembly at a Ninety degree angle of steer.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

Nomenclature used in Fig 1 is maintained throughout all the Figs 1 to 9 for the same or like elements.

In Fig 1 is a plan view of a drawbar (1) attached to a towing vehicle (not shown) at its free end and an embodiment of a steering mechanism (20) according to the invention is depicted at the other. Attachment of the drawbar to the steering system is via an articulated joint (7) having in use a horizontal axis. The articulated joint allows the towing arm to be moved upward and downward pivoting about the joint to permit hitching and unhitching of the free end of the drawbar to a towing vehicle coupling that may be at varying heights due to uneven ground. The articulated joint does not permit lateral movement and hence, by the action of the steering mechanism yet to be explained in detail, the wheels (not shown) located on axles (11) are steered through at least 90 degrees as the drawbar is moved laterally through up to 90 degrees with respect to the axis of the wheel axles (11).

Moving the towing vehicle end of the drawbar laterally when manoeuvring the starting gate, rotates a central steering crank assembly (2) that is fixedly connected to the articulated joint (7). The steering crank assembly rotates about a pivot (6) that is fixed to the starting gate framework (not shown in Fig 1 but shown in Fig 5). Rotation of the steering crank assembly produces rotational forces that translate an arm (3a) and a respective pushrod (3) formed, in this embodiment, with a unitary bent element. There are four bent elements of arms and pushrods that are so shaped so as to avoid mechanical interference with the wheel or its axle. It is not absolutely necessary for the pushrods (3 and 3a) to be bent. In this embodiment the pushrods have been bent so they can clear the steered axle. However, it is possible to design a system where the pushrods act at the top of the steered axle, and so they pass over the top of the steered axle and do not need to be bent to clear the axle. Another approach would be to configure the included angle of the bellcranks to face inwards towards the steering crank and also configure the steering crank to allow pushrods connected between it and the bellcranks to not interfere with each other. Fig 10 depicts an example of such a configuration showing the steering crank configured as two parts, both parts pivoting about the same axes but connected to the same drawbar.

The four unitary bent elements (3 and 3a) mimic the function of a tie rod in a conventional steering system as they directly rotate each wheel axle (11) about the steered axle pivot point (8). In Fig 1 the wheel axle axis is shown (dotted line) at right angles to the drawbar (1). This means that the wheels are pointed in the same direction as the drawbar is pointed. As the steering mechanism (20) is typically located at the end of a long frame containing a plurality of gates the steering position depicted in Fig 1 would allow the starting gate assembly to be towed lengthways. Fig 5 depicts the typical configuration of the steering mechanism below a framework and an outline of two wheel axles (11) is shown for illustrative purposes.

The unitary bent elements (3 and 3a) are rotatably attached to the steering crank assembly (2) at the inboard end and also to the bellcranks (4) at the outboard end on both sides of a line between the steering crank pivot point and each bellcrank pivot point at the outboard end of the bent elements. There is a required geometric relationship between the steering crank assembly pivot point (6) and inboard pushrod attachment point (10), and the steered axle pivot point (8) and the outboard pushrod attachment point (9). A line drawn through each pair of points (9-10) and (6-8) are parallel, and the distance between each pair of points (9-10) on one side of said line must be the same at all times during the rotation of the steering crank and bellcranks about their respective pivot points. In the mechanism depicted, the steered angle is changed by the action of the drawbar (1) and directly follows its direction. However, in the alternative the steering force may be imparted at any point in the steering system described such as for example, directly upon the steering crank, either bellcrank or any of the arms (3a) or pushrods (3).

In one embodiment, power steering is provided by the operation of hydraulic rams (5) that are pictured in Fig 1 only. An operator can then modify the steering angle by operating the hydraulic rams.

There are other possible power steering options that are an alternative to the use of hydraulic rams. For example, hydraulic rotary actuators (rotary output, connected directly to points 6 or 8 in the system), electric rotary actuators (an electric motor with gearbox, also connected to points 6 or 8), or electric linear actuators connected to similar points in the system as hydraulic rams.

Power assisted steering is likely to be used on the non-towed end of a racing starting gate frame so as to negate reliance on the need to have workers at the non- towed end using a drawbar to steer. However, it is possible for the non-towed end to be manually steered by workers while the whole racing starting gate frame is being moved about by the towing vehicle.

One or more rams, levers or mechanical equivalents can apply load to a selected part of the steering mechanism to modify the steering angle at almost any point in the system, some examples of which are described herein.

It is also preferable for the steering system to have readily adjustable steering arrangements. One arrangement allows the steering system to be locked at the non-towed end so the wheels at the non-towed end are orientated to allow the attached gates to be towed lengthways behind the towing vehicle which is attached to the steered and towed end.

Preferably, changing from variable steering to a fixed steering system should be possible using no special tools and in quick time as is sometimes necessary in preparation for a race or shortly thereafter. This can be achieved using simple couplings and /or pre-fitted power assisting devices such as hydraulic rams or easily operated levers.

One such simple coupling arrangement is illustrated by way of the mechanism (40) shown in Fig 6 which is achieved by dropping a rod end into a hole in the central steering crank (2) from the frame (30). A simple T-shaped handle (41) to the rod is depicted in the top view of the rod in Fig 5. This simple coupling arrangement allows the wheel orientation to be fixed with respect to the structure and in this embodiment, the wheels at the non-towed end to be orientated to allow the structure (starting gates) to be towed lengthways behind the towing vehicle.

It is also possible to remove the drawbar from the central location depicted and reinstall it on either of the steered axles at either side of the system. This permits one steered axle to be steered directly by the drawbar, and the other steered axle to be steered by the movement transmitted through the steering mechanism. That mechanism comprises the operation of one bellcrank (4) applying force through the pushrods (3), the steering crank assembly (2) and the other pushrods, through to the second bellcrank and second steered axle.

Alternatively, it is possible to use a drawbar that is not straight. If the drawbar is shaped appropriately, it will permit the steering mechanism to be steered to at least 90 degrees without the drawbar striking the wheels. As an example of such an arrangement the drawbar can be bent in the vertical and/or the horizontal plane to clear the wheel assembly. When bent in the horizontal plane, greater than 90 degree steering can be achieved in one direction while restricting the angle of steering in the other direction. It is possible then for the drawbar to be joined to the steering mechanism by 180 degrees of freedom pivot that with appropriate manipulation allows the drawbar to be rotated to thus provide unhindered movement in the now opposite direction since the bend in the drawbar will avoid contact with the opposite wheel assembly.

In the embodiment depicted in Figs 1 to 6, the pushrods are shaped to clear the steered axle. It can be seen, that in the diagram corresponding to the 90 degrees steering angle, if there was not a bend in the pushrod, the pushrod would strike the steered axle. Alternative embodiments some of which are depicted in Figs 10 to 13, may use straight pushrods but the bellcranks will need to be located above the steered axle assembly or inwards of the wheels. Such arrangements are shown in their generic form in Figs 10 to 13.

As for all the embodiments, the purpose of using two pushrods per side is that while one pushrod becomes ineffective as its turning torque reduces to zero, the other pushrod takes over and becomes effective in providing the torque required to continue turning the steered axle.

Figs 2 to 4 and Figs 11 to 13 show the progressive movement of the steering mechanism as the steering of the wheels moves from zero degrees to 90 degrees and further depicts the maintenance of the relationships between the elements of the steering system previously described.

Fig 5 depicts the mounting of the steering mechanism to the underside of a structure, which in this embodiment is the end frame of a horse racing starting gate assembly shown by way of example in Fig 9. Only the lower portion of the framework is shown along with the wheel axles, there being two each side that are shown in phantom. Two wheels are typical per side as the total weight of the horse racing starting gates need to be distributed over the ground in a manner that minir ises damage to the race track surface. It is an important beneficial feature of such apparatus that it can be readily manoeuvred into position while causing minimum impact on the race track surface.

Figs 6 to 8 depict different views of the embodiment depicted in Fig 5. A padded division panel (21) is shown on the side of the frame opposite the drawbar (1) that forms part of the sidewall of an enclosure for a horse and its rider. Below the division panel is a standing platform (22) for assistants to the jockey and horses within the enclosure.

Fig 9 depicts a full sized horse racing starting gate that is illustrated by way of an example of the described steering mechanism. It will be apparent that the large size of the starting gate and the relatively narrow width of some racetracks make it advantageous to have a steering capability that matches that described herein. The steering mechanism is preferably fitted to both ends of the starting gate assembly so as to allow flexibility in steering and towing the gate from either end and to assist in the manoeuvrability of the structure. The starting gate may need to be towed from either end as the need arises and fixing of the wheel orientation may need to be achieved at either end as required.

The preceding description is of a particular embodiment of a steering mechanism used for a horse racing starting gate. The following description provided a more general arrangement of the steering mechanism that could be used for a horse racing starting gate and many other apparatus.

Fig 10 depicts the pair of bellcranks having arms and the arms are orientated at approximately a right angle to each other. Of course the arms could be arranged to have an included angle of anything other than 180 degrees. If, however, the pivot points on the bellcrank had an included angle of 180 degrees, it would act the same as a conventional tie rod system. Fig 10 has been described previously and is an example of the use of straight pushrods and bellcranks orientated inward towards the steering crank. The simplicity of having the bellcranks above and inward of the wheels is offset by the need for some complexity in the arrangement of the steering crank as shown in Figure 10 which has previously been described.

Figs 11 to 13 show a simplistic straight pushrod arrangement but various configurations of the location of pivots for the pushrods on the bellcranks and steering crank will address the issue of interference between the pushrods. It is preferred that the bellcrank has two arms at the ends of which are located the pushrod pivot points and that the two arms are at 90 degrees to each other because the transference of turning forces to the wheels by the pushrods is optimised by such a configuration.

Fig 11 shows the arrangement with the steering angle being zero (0) degrees, while Fig 12 shows the steering angle of forty five (45) degrees and Fig 13 shows the steering angle being ninety (90) degrees. The pushrods are shown as lines to indicate the linkages rather than being a true representation of their shape as this is a generalised illustration of the arrangement.

There are at least four pushrods pivotally attached at one end a predetermined distance and orientation from the steered axle pivot point along an arm of a respective bellcrank, there being two pushrods for each bellcrank. Each pushrod being pivotally attached at their other end the same predetermined distance and orientation from the steering crank pivot point on the steering crank assembly. In the figure this is shown and simply replicated by noting that the shape, size and orientation of each steered bellcrank is the same as the shape, size and orientation of the steering crank.

As explained previously the forces exerted by opposed pushrods are at their maximum and minimum at the same time such that overall an adequate steering force is applied to the steered wheel axles throughout the whole steering action.

The orientation of the bellcranks with the steering angle at zero degrees depicted in Fig 11 can be adjusted to suit specific steering layouts. Some bellcrank orientations, such as that illustrated in Figs 1 to 9 may require bent pushrods, and result in a wider steering system, but do not require pushrods to overlap vertically or cross pivot points. Other bellcrank orientations are possible to suit external space constraints. For example, those illustrated in Figs 11 to 13 are potentially more compact and can be implemented with straight pushrods, but require pivot point or bellcrank designs that prevent pushrods overlapping or passing through pivot axes.

The external shape of the bellcranks illustrated in this specification appears to incorporate the right angle of the generic shape but the external shape does not contribute to its function. It is the relative position of the steered axle pivot and the pushrod pivots that matter and the shape about them is not always critical.

It will be appreciated by those skilled in the art that the invention is not restricted in its use to the particular application described. Neither is the present invention restricted in its preferred embodiment with regard to the particular elements and /or features described or depicted herein. It will be appreciated that various modifications can be made without departing from the principles of the invention. Therefore, the invention should be understood to include all such modifications within its scope.

Claims

THE CLAIMS DEFINING THE INVENπON ARE AS FOLLOWS:

1. A steering system including: at least a pair of opposed bellcranks each having a body having at least two spaced pivot points thereon that are a predetermined distance from a steered axle pivot point wherein the lines between said steered axle pivot point on said bellcrank and said spaced pivot points of each bellcrank is an angle other than 180 degrees, a steering crank assembly with a pivot point located intermediate a said pair of bellcranks having four spaced pivot points, a steered axle associated with each bellcrank, and at least four pushrods, each pivotally attached at one end to a bellcrank pivot point, there being two pushrods for each bellcrank, and the other end of a said pushrod being pivotally attached at their other end said predetermined distance from the steering crank pivot point on the steering crank assembly and lines between two of said pivot points on said steering crank assembly and said steering crank pivot point having an angle to each other the same as said angle.

2. A steering system according to claim 1 wherein there are one or more wheels having a common steered axle associated with each bellcrank and each wheel is steered using said pair of pushrods to activate a respective bellcrank, such that as the transference of turning force to a bellcrank pivot point by a respective pushrod is becoming less effective to turn said bellcrank, the transference of turning force to the other bellcrank pivot point of the same bellcrank by a respective other pushrod is becoming more effective to turn said bellcrank and thus steer a respective steered axle.

3. A steering system according to claim 1 wherein each bellcrank includes two arms at substantially 90 degrees to each other, the arms having a common steered axle pivot point and near the end of each said arm a said spaced pivot point to which is connected a respective pushrod.

4. A steering system according to any preceding claim wherein said steering crank assembly has a drawbar attached such that when the free end of said drawbar is moved laterally of said assembly said steering crank rotates about said steering crank assembly pivot point and transfers forces to said pushrods to effect transference of turning force to a bellcrank pivot point by a respective pushrod.

5. A steering system according to claims 1, 2 and 3 further including a steering member connected to one or other of said steering crank or said bellcranks arranged so that movement of said steering member rotates a said connected crank.

6. A steering system including a steering crank assembly having a point about which parts of the assembly pivot horizontally and at least four pivot points a predetermined distance and orientation from the point about which the parts of the assembly pivot, at least two opposed bellcranks having said steering crank intermediate said bellcranks and each bellcrank having a body with at least two spaced pivot points thereon said predetermined distance and said orientation from a steered axle pivot point about which the bellcranks pivot horizontally, wherein lines between said steered axle pivot point on said bellcrank and said spaced pivot points of each bellcrank is an angle other than 180 degrees, and pushrods pivotally attached to the spaced pivot points of a bellcrank remain parallel while their other ends are pivotally connected to respective pivot points on said steering crank when said steering crank is turned about said horizontal pivots.

7. A steering system according to claim 6 wherein there are one or more wheels having a common steered axle associated with each bellcrank and each wheel is steered using said pair of pushrods to activate a respective bellcrank, such that as the transference of turning force to a bellcrank pivot point by a respective pushrod is becoming less effective to turn said bellcrank, the transference of turning force to the other bellcrank pivot point of the same bellcrank by a respective other pushrod is becoming more effective to turn said bellcrank and thus steer a respective steered axle.

8. A steering system according to claims 6 or 7 further including a steering member connected to one or other of said steering crank or said bellcranks arranged so that movement of said steering member rotates a said connected crank.

9. A steering system according to claims 6, 7 or 8 wherein each bellcrank includes two arms at substantially 90 degrees to each other, the arms having a common steered axle pivot point and near the end of each said arm a said spaced pivot point to which is connected a respective pushrod.

10. A steering system including: a structure; at least a pair of steerable assemblies depending from said structure, each assembly having an axle, a rotatable bellcrank associated with said axle and at least one ground engaging rotatable member arranged about said axle; a steering crank pivotally mounted to said structure at a position intermediate said bellcranks; and a pair of pushrods per steerable assembly, said pushrods connecting respective steering assemblies to said steering crank, wherein said pushrod pairs are connected such that one or other of said pushrods of each pair transmit torque to said bellcrank irrespective of the angle of said axle to said structure so as to effect rotation of each said bellcrank through at least 180 degrees so as to steer said structure.

11. A steering system according to claim 9 further including a steering member connected to one or other of said steering crank or said bellcranks arranged so that movement of said steering member rotates a said connected crank.

12. A steering system according to claim 10 or 11 wherein each bellcrank includes two arms at substantially 90 degrees to each other, the arms having a common steered axle pivot point and near the end of each said arm a said spaced pivot point to which is connected a respective pushrod.

13. A steerable racing starting gate including: a structure including a plurality if simultaneously openable enclosures; and a steering system according to any preceding claim for steering rotatable ground engaging means positioned at least as each end of said structure.