Vehicle access system

Abstract

A vehicle access system and method with retractable access means, e.g., ladder or stairs and a retracting mechanism 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 not 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.

What is claimed is: 
     
         1 . A vehicle access apparatus comprising:
 an access device including a ladder or stairs configured and arranged to, when mounted to a vehicle, rotate about a pivot axis relative to the vehicle; and   a retraction mechanism configured and arranged to retract the access device from a deployed position to a final retracted position, the retraction mechanism including an actuator and a linkage, the actuator being connected to and configured and arranged to operate the linkage, the linkage being connected to the access device and configured and arranged to, using a linear force provided by the actuator and a geometry of the linkage, rotate the access device about the pivot axis by applying a rotational force to the access device that is sufficient to retract the access device from a fully deployed position to a partially retracted position, and by increasing the applied rotational force during retraction between the partially retracted position and the final retracted position.   
     
     
         2 . A method of retracting an access device about an axis of rotation from a deployed position to a final retracted position, the method including the steps of:
 a) applying a first torque to the access device through a linkage arrangement between an actuator applying a linear force and the access device during an initial portion of a retraction phase of said access device to rotate the access device about the axis of rotation from a fully deployed position to a partially retracted position, the applied first torque being equal to or greater than a minimum force required to rotate the access device toward the final retracted position;   b) subsequently applying a second torque to the access device through the linkage arrangement during a secondary portion of the retraction phase after the initial portion of the retraction phase of the access device, the second torque being greater than the first torque; and   c) wherein applying the first torque and applying the second torque includes translating the applied linear force to become the first torque and the second torque, utilizing the geometry of the linkage arrangement to provide the second torque as being greater than the first torque.