AU2013200159A1 - Vehicle Access System - Google Patents

Abstract

A vehicle access system and method with retractable access means (10) e.g. ladder or stairs and the retracting mechanism (25) therefor. Force applied to the access means is sufficient to retract the access means from a fully deployed position to a partially retracted position but not sufficient to be physically resisted by a user during at least part of the retraction. With the access means in a fully retracted position, force exerted on the retracted access means can be sufficient to hold the access means in a retracted position without the need for auxiliary restraining means.

Description

I FIELD OF THE INVENTION This invention relates to access systems for vehicles, specifically the access system for large earth moving equipment. 5 BACKGROUND OF THE INVENTION Access systems for large earth moving equipment often incorporate a set of deployable stairs so that the operator can climb up into the cab without climbing a vertical ladder that may have a negative inclination if the equipment is not parked on level ground. 10 Once the operator is on the machine the operator retracts the stairs so that they are not hanging down and the ground clearance of the machine is increased thus minimizing the probability of the stairs being damaged by contacting rocks when the machine is in motion. The stairs need to be retracted so that other personal cannot climb up onto 15 the machine with out the operator's knowledge. Should a person be on the stairs without the operator's knowledge then the possibilities for injury to that person are numerous. The possible injuries could range from overbalancing the person to crushing trapping the person between the moving parts of the equipment and the adjoining bodywork of the equipment. 20 The systems used for retracting the stairs can vary but generally they rely on either an electric or hydraulic system that is manually actuated by the operator. Should an emergency occur such as a fire it is necessary for the operator to activate a switch to lower the stairs to evacuate the machine or find an 25 alternative way off the machine or equipment. This can be a particular problem if there is a fire in the vicinity of the stair operating switch. Should the operator forget to retract the stairs and drive the machine off, it is possible to destroy the stairs, causing an expensive repair, downtime and generating safety issues, resulting from damage to an emergency exit. 30 Another known problem of prior art ladder retraction systems is that, when retracted, the ladder is either held retracted by hydraulic/pneumatic pressure, such as provided by the lifting cylinder, or once retracted a locking pin is used to 2 lock the ladder in place. The locking pin itself can be driven by a small hydraulic/pneumatic cylinder. Problems with such systems are typically associated with bounce. The ladder can bounce during movement of the vehicle, causing failure of the lifting 5 system. Also, damage caused to the locking pin by ladder bounce can result in failure of the locking pin mechanism. Where the vehicle has an interlock system, such as a proximity switch, connected to the ladder retraction mechanism or to the locking pin actuating mechanism to prevent movement or starting the vehicle until the interlock is 10 operated, ladder bounce can result in the switch operating thereby stopping or shutting down the vehicle unexpectedly. This results in excess downtime of the vehicle and loss of productivity. With the aforementioned in mind, it is an object of the present invention to provide a system for retracting a ladder that allows a user to physically halt initial 15 retraction but provides sufficient force to maintain the ladder retracted when retracted. SUMMARY OF THE INVENTION With this in view, there is provided A vehicle access system including an access means and a retracting mechanism for the access means, wherein a force 20 applied to the access means is sufficient to retract the access means from a fully deployed position to a partially retracted position but not sufficient to not be physically resisted by a user during at least part of the retraction. Thus, advantageously, an access system for a vehicle is provided that will allow a user to overcome the retraction forces during at least part of the retraction 25 process to thus prevent further retraction, and optionally commence re deployment of the stairs to alleviate risk of injury to the user. It will be appreciated that a user wishing to prevent retraction of the stairs will be able to safely apply sufficient force or weight to overcome retraction forces and thus halt or reverse the retraction process. 30 It will be appreciated that the term access means may encompass stairs, steps and ladders for accessing vehicles. A further aspect of the present invention provides a retractable access system for a vehicle including an access means and a retracting mechanism for 3 said access means, wherein an applied moving force is translated into a variable force for retracting the access means wherein torque generated to retract the access means exceeds torque required to retract the access means by an amount that is able to be resisted by a user for a portion of the retraction phase 5 and increases to a greater force for a latter portion of the retraction phase. Preferably, when the access means is fully retracted, a force may be exerted on the retracted access means sufficient to hold the access means in a retracted position without the need for auxiliary restraining means. Preferably torque provided to retract the access means may vary through 10 at least part of the retraction cycle. The torque generated may vary throughout the retraction cycle so that the torque provided to retract the access means from 0-70% of the retraction cycle just exceeds the required torque necessary to retract the access means, and between 70-100% of the retraction cycle the torque generated may increase such 15 that when the access means is fully retracted the torque applied to the access means is sufficient to hold the access means in the retracted position without the need for auxiliary restraining means. This provides the advantage that when the access means are within reach or use of ground personnel, the forces retracting the access means may be 20 countered by the user. When the access means are out of the reach of ground personnel, the force applied through the retraction mechanism increases so that the access means are firmly held in the retracted position. Preferably the retracting/deploying system may be connected into a hydraulic pilot control circuit and/ora hand brake hydraulic circuit of the vehicle. 25 This has the advantage that when the hand brake is released the access means are automatically retracted. When the park brake is applied or if there is a hydraulic failure the access means are deployed. The geometry of the parts of the linkage is configured to provide a required torque profile. 30 A further aspect of the present invention provides a method of retracting an access means including the steps of; 4 a) applying a first lifting force during an initial portion of a retraction phase of a deployed access means, the applied first lifting force being equal to or greater than a minimum force required lift the access means, and b) subsequently applying a second lifting force during a secondary 5 portion of the retraction phase of the deployed access means, the second lifting force being greater than the minimum required to lift the ladder. Preferably the first lifting force may be less than a manual effort required to retard retraction of the access means. Preferably the manual effort may be sufficient to reverse retraction of the access means and commence re 10 deployment thereof. Preferably the second lifting force (torque) may diverge (and increase) compared to the required lifting force during the secondary portion of the retraction phase. Preferably the initial portion of the retraction phase may be about two 15 thirds of the entire retraction phase from commencement to fully retracted. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a side view of an embodiment of the present invention showing the mechanical arrangement of the retracting mechanism. Figure 2 is a graph showing the torque required and the torque applied to 20 retract the stair from +450 to -900 according to an embodiment of the present invention. Figure 3 is a graph showing the torque required and the torque applied to retract the stair from +600 to -1200 according to an embodiment of the present invention. 25 Figure 4 shows a graph of excess lift torque for a ladder retracting through 9Q0 in accordance with an embodiment of the present invention. Figure 5 shows a graph of excess lift torque for a ladder retracting from 450 extended to -90o retracted, according to an embodiment of the present invention. Figures 6a to 6d show a series of images of a set of vehicle stairs being 30 retracted from a deployed position to a fully retracted position according to an embodiment of the present invention.

9 extension of the ladder. That is, for example, a graph of the difference between the dotted line and the solid line shown in each of figures 2 and 3. In the embodiment shown, excess lift torque is minimal for initial lift (retraction) (right hand portion of curve) and thereafter increases once the ladder 5 has retracted sufficiently that a user or personnel is either not in danger of injury, or the ladder is considered sufficiently retracted that the user has had sufficient warning of retraction or the ladder is out of reach. It may be appreciated that although ideally the excess lift torque would be linear or near linear i.e. a straight line prior to the increase portion of the graph, 10 physical, mechanical and force characteristics of the system approximate or approach the ideal, which is sufficient to provide an effective and efficient working system without requiring over-engineering or more complex configurations. Figure 5 shows an alternative excess lift torque curve being for a ladder retracting from 450 angle of extension (from the horizontal) to -90' retracted 15 (vertical). Again, ideally the right hand portion of the graph (before the steep sloped section) would be linear. It will be appreciated that the nearer the generated torque (solid line in Figures 2 and 3) is to the required lift torque in the right hand dise of each graph across the range of angles, the less manual force is required to halt retraction of 20 the ladder. Also, in the left hand (steep) section of the graph, the more the solid (applied force) line deviates away from and above the dotted line, the greater the force (torque) applied, and the greater the holding force can be when the ladder is fully retracted. Thus, for the first approximately two thirds of the retraction process, the difference between required and applied torque can be minimal, 26 though applied should not be less than the required torque, the easier a person can manually stopped retraction (lift) of the ladder. However, once the ladder has approximately one third retraction travel to go, lift force (torque) can be significantly increased, thus speeding up retraction and also providing sufficient force to maintain the laddr retracted without needing additional restraIning means 30 such as a locking pin mechanism (though such can be provided if required). Figures 6a to 6d show a series of steps in the retraction process. Figure Ga shows the steps 101 fully extended (approx 450 from horizontal). The upper end 102 would normally be mounted to a vehicle (not shown). The steps are 10 pivoted to a retracted position, with deployment being the reverse of retraction, though if required, the force curve for deployment may differ from the force curve for retraction. Figure 6b shows the steps approximately one third through the retraction process. The lower end 103 is almost horizontal with the upper end 5 102. It will be appreciated that the steps or ladders etc. may take various forms and arrangements e.g. pivoted in the middle so as to also collapse to a shorter retracted form. Also the steps or ladders may retract sideways e.g. pivot sideways. However, the force curve nature of retraction according to the present invention remains the same. 10 Lifting force is provided via an actuating cylinder 104 applying force between a linkage at the upper end of the steps and a connection 105 approximately halfway down the steps, It will be appreciated that the arrangement of actuators and linkages may vary depending on the form and application of the steps, though the present invention remains unchanged. 15 Figure 6c shows the steps at approximately two thirds retracted. Consequently, the steps are, in this embodiment, considered sufficiently retracted as to be generally out of reach of personnel on the ground or that personnel on the vehicle/steps have had sufficient time (warning) of retraction of the steps and therefore are deemed either clear of the steps or have had sufficient time to apply 20 force during the initial retraction phase to halt retraction or to manually cause the steps to re-deploy by overcoming the applied lift torque. Figure 6d shows the steps fully (vertically) retracted. Between phases 6c and 6d, torque applied to the steps increases, thereby diverging the applied lift torque curve away from the required lift torque curve. Force applied at the fully 25 retracted position is sufficient to prevent or mitigate ladder/step bounce, thereby reducing risk of damage, injury or vehicle failure (eg due to bounce causing a proximity switch to inadvertently operate). While the method and apparatus has been explained by illustrative examples it will be appreciated by those skilled in the art that varying 30 embodiments and applications are within the teaching and scope of the present invention. The examples presented here in are by way of example and should not be construed as lirniting the scope of the present invention.

Claims (6)

1. A vehicle access system including an access means and a retracting mechanism for the access means, wherein a force applied to the access means is sufficient to retract the access means from a fully deployed position to a partially retracted position but not sufficient to not be physically resisted by a user during at least part of the retraction.

2. A retractable access system for a vehicle including an access means and a retracting mechanism for said access means, wherein an applied moving force is translated into a variable force for retracting the access means wherein torque generated to retract the access means exceeds torque required to retract the access means by an amount that is able to be resisted by a user for a portion of the retraction phase and increases to a greater force for a latter portion of the retraction phase.

3. A vehicle access system as claimed in claim I or 2, wherein when the access means is fully retracted, force exerted on the retracted access means is sufficient to hold the stairs in a retracted position without the need for auxiliary restraining means.

4. A system as claimed in any one of the preceding claims, wherein torque provided to retract the access means varies through at least part of the retraction cycle.

5. A system as claimed in claim 4, wherein the torque provided to retract the access means from 0-70% of the retraction cycle exceeds the required torque necessary to retract the stairs, and wherein between

70-100% of the retraction cycle the torque generated is increased such that when the access means is fully retracted the torque applied to the access means is sufficient to hold the access means in the retracted position. 12 6. A system as claimed in any one of the preceding claims, wherein the retracting mechanism is connected to a hydraulic pilot control circuit or a hand brake hydraulic circuit of the vehicle. 7. A system as claimed in any one of the preceding claims, wherein geometry of parts of the retracting mechanism is configured to provide a required retraction torque profile. 8. A system as claimed in any one of the preceding claims, including an access means retracting and deploying mechanism. 9. A method of retracting an access means including the steps of; a) applying a first lifting force during an initial portion of a retraction phase of a deployed access means, the applied first lifting force being equal to or greater than a minimum force required lift the access means; b) subsequently applying a second lifting force during a secondary portion of the retraction phase of the deployed access means, the second lifting force being greater than the minimum required to lift the access means. 10. A method as claimed in claim 9, wherein the first lifting force is less than a manual effort required to retard retraction of the access means. 11. A method as claimed in claim 10, wherein the manual effort is sufficient to reverse retraction of the access means and commence re-deployment thereof. 12. A method as claimed in any one of claims 9 to 11, wherein the second lifting force diverges and increases compared to the required lifting force during the secondary portion of the retraction phase. 13. A method as claimed in any one of clairns 9 to 12, wherein the initial portion of the retraction phase is about two thirds of the entire retraction phase from commencement to fully retracted.