Abstract:
An auxiliary pullout step for a vehicle having a yieldingly resilient mechanism for urging the step into the extended step position thereof and resisting movement of the step into a retracted position thereof and an indexing mechanism for selectively restraining the step in the retracted position thereof and selectively releasing the step from the restrained position thereof to allow the yieldingly resilient mechanism to move the step into the extended step position/

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation in part of my co-pending application Ser. No. 12/660,864, filed Mar. 6, 2010 and the teaching and technology thereof are incorporated by reference herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates to the auxiliary vehicle step art and more particularly to an auxiliary step arrangement that may be bolted to the underside of a vehicle and which auxiliary step arrangement has a step therein movable from a first, retracted position to a second, step position and in which the step is sequentially and automatically locked when in the retracted position and automatically un-locked with each movement between the retracted position and the step position. 
         [0004]    2. Description of the Prior Art 
         [0005]    In many vehicle applications it is desirable to provide a step on the vehicle to allow a person to step thereon in order to facilitate reaching various portions of the vehicle. There have hereto fore been proposed various step arrangements that may be mounted on a vehicle to provide the convenient access to the desired portion of the vehicle. Some of these prior movable, auxiliary step arrangements have provided a step that may be connected to the vehicle and may be positionable under the vehicle, if desired, while the vehicle is being driven and extendable from the vehicle when it is desired to use the step. Many of these movable, auxiliary step arrangements have incorporated complex mechanical systems that increased the cost thereof sand/or have required extensive modifications to the vehicles in order to install them. Other step devices have shown systems that, in practice, have not proven to be reliable over long periods of time thereby often resulting in frequent repair or replacement. Still other of such movable steps have not been rugged enough to withstand the heavy use thereof often required in many applications. 
         [0006]    In utilization of such auxiliary steps, it is desirable to have the step locked when in the retracted position so as to avoid undesirable opening of the step when the step is not in use and also easily unlocked to be moved from the retracted position to the step position and retained in the step position to prevent inadvertent retraction of the step when it is desired to utilize the step. 
         [0007]    Accordingly, it has long been desired to provide a rugged, movable step that is conveniently attachable to a vehicle. Such step should have the mechanism for easily locking the step in the retracted position as well as easily or automatically restraining the step in the step position to prevent inadvertent retraction thereof. It is also desired that such step is comparatively inexpensive to fabricate and is free of complex mechanical components. 
         [0008]    It is an object of the present invention to provide a step arrangement that may be fastened to a vehicle and in which the step arrangement is movable between a retracted position in which the step is moved inwardly with respect to vehicle and a step position wherein the step is extended outwardly from the vehicle. 
         [0009]    It is another object of the present invention to provide a step arrangement that may be fastened to a vehicle and in which the step arrangement is movable between a retracted position in which the step is moved inwardly with respect to vehicle and a step position wherein the step is extended outwardly from the vehicle and in which the step is selectively and sequentially moved from a locked condition in the retracted position to a restrained condition in the step position thereof. 
         [0010]    It is another object of the present invention to provide a step arrangement that may be fastened to a vehicle in which the step may be easily moved between a locked, retracted condition to a restrained step condition. 
         [0011]    It is another object of the present invention to provide a step arrangement that may be fastened to a vehicle in which the step may be easily moved from a locked, retracted condition to a restrained step condition and in which the components of the step assembly arrangement are rugged construction and free of overly complex mechanical components and which will last for comparatively long times in use. 
       SUMMARY OF THE INVENTION 
       [0012]    The above and other objects of the present invention are achieved, in a preferred embodiment of an auxiliary step for attachment to a vehicle by providing a frame that is attachable to the underside of a vehicle such as a pickup truck or other vehicle. Such vehicles often require access to either the storage bed of the truck, the roof of the truck or other portions and the access thereto is facilitated by having a step upon which a person may stand to reach the desired portions. However, the step is preferably positioned and retained under the vehicle in a restrained or retracted position when not in use and movable outwardly with respect to the vehicle into a step position when it is desired to utilize the step and the step is yieldingly restrained from moving from the step position to the restrained position. 
         [0013]    A step with a tread member is provided and the step with the tread member is connected to a pair of rails which are operatively mounted on the frame and the step is movable relative to the frame in reciprocal directions with respect to the frame and to the vehicle such that in a retracted or restrained position of the step and tread, the step and tread are retained to be substantially under the vehicle and restrained in this position and in a step position the step and tread are extended outwardly from the vehicle. 
         [0014]    A yieldingly resilient mechanism is provided to yieldingly restrain the step and tread in the step position of the step. The yieldingly resilient mechanism may be, for example, a coil spring for yieldingly urging the tread into the step position from the restrained position and yieldingly resisting movement of the tread from the step position to the retracted or restrained position. In another preferred embodiment of the present invention the yieldingly resilient mechanism is provided by a conventional gas spring cylinder of the type often utilized on hoods, hatch backs and similar components of vehicles. The gas spring cylinder urges the step outwardly from the retracted or restrained position to the step position and yieldingly resists motion of the step from the step position to the retracted position. 
         [0015]    An indexing mechanism is provided which is operatively connected to the step and to the frame. The indexing mechanism locks the step in the retracted or restrained position against the force of the resilient mechanism and is movable from the locked condition in the retracted or restrained position to a release position wherein the step is moved from the locked, retracted or restrained position to the step position under the force of the resilient mechanism. 
         [0016]    In a first preferred embodiment of the present invention, the indexing mechanism has a slotted track member which is attached to the frame. A guide pin is resiliently and pivotally mounted on the step and the guide pin moves in the track of the slotted track member during movement of the step between the step position and the retracted or restrained position. An elongated spring like member which may be a length of spring steel has a first end mounted on the step for limited lateral pivotal movement and the spring like member urges the pin downward into contact with the slots in the slotted track member and resists movement of the pin upward from the slotted track member. The track is configured to have a first portion of a slot defining restraining portion for restraining the pin and thereby restraining the step in the retracted or restrained position. The track also has a second portion of the slot for guiding the pin to a release position wherein the guide pin then moves in a third portion of the slot from the release position to the extended position wherein the step is in the step position. The track has a fourth portion of the slot wherein the guide pin moves from the extended position to the restraining position. 
         [0017]    In another embodiment of the present invention, the indexing mechanism is provided by a multi-part telescoping tube arrangement. The multi-part telescoping indexing mechanism has an outer tube with a flanged first end fixedly coupled to the step and the outer tube moves with the step as the step moves between the step position and the retracted or restrained position. An intermediate tube is slidably mounted in the outer tube for axially reciprocating motion with respect to the outer tube. A plurality of tracks extend axially on the inside surface of the outer tube and the tracks have a an inwardly directed tab at the inner end of the outer tube which engage grooves or slots on the outer surface of the intermediate tube to prevent relative rotational movement of the intermediate tube with respect to the outer tube. The grooves or slots on the outer surface of the intermediate tube extend from the inner end of the intermediate tube to a stop located a spaced a preselected distance from the outer end of the intermediate tube to prevent the intermediate tube from axial movement which would allow the intermediate tube to extend axially past the inner end of the outer tube when the step is moved to the step position. Thus, at least a portion of the intermediate tube is always restrained in the outer tube. 
         [0018]    An inner tube is mounted in the intermediate tube. Both the inner end of the intermediate tube and the inner end of the inner tube are provided with a disc like plate to close the ends of the tubes and the disc like plates have a central aperture extending therethrough. A bolt having a bolt head is positioned in the inner tube and the bolt extends through the apertures in the disc like plates and through an aperture in the frame. A nut fastens the bolt as well as the inner tube and intermediate tube to the frame. A spring is provided between the bolt head and the inside surface of the disc like plate in the inner tube to yieldingly restrain the nut in engagement with the frame. The inner tube and the intermediate tube move together in axial directions in the outer tube in movement between the step position and the retracted or restrained position. 
         [0019]    The inner end of the tracks on the inside surface of the outer tube have the tabs extending inwardly to project into the slots on the outer surface of the intermediate tube to engage the stop portion on the outer surface of the intermediate tube at the outer end of the slots so as to limit the travel of the intermediate tube relative to the outer tube when the step is in the step position thereof and also to prevent relative rotation of the intermediate tube relative to the outer tube 
         [0020]    The outer end of the inner tube has a shoulder and a ring gear is slidably mounted on the outer surface of the inner tube and abuts against the shoulder. The outer end of the intermediate tube has a plurality of teeth thereon. The ring gear has two sets of teeth thereon. A first of the sets of teeth on the ring gear are equally spaced on the outer peripheral surface and the second set of teeth on the ring gear are equally spaced on the inner end surface of the ring gear. The second set of teeth on the ring gear are adapted to selectively engage the teeth on the end surface of the intermediate tube. 
         [0021]    The tracks on the inside surface of the outer tube have a plurality of teeth thereon spaced from the outer end of the outer tube. The number of tracks and consequently the number of teeth on the outer end of the tracks correspond to the number of the second set of teeth on the inner surface of the ring gear. The second set of teeth on the inner surface of the ring gear are adapted to operatively engage the teeth on the outer ends of the tracks on the inside surface of the outer tube. The first set of teeth on the outer peripheral surface of the ring gear are adapted to operatively engage the plurality of teeth on the outer end of the intermediate tube. The spacing between the first set of teeth on the outer peripheral surface of the ring gear allows the ring gear to selectively slide past the teeth on the outer end of the tracks and slide along the tracks without relative rotary motion between the ring gear and the outer tube as the intermediate tube and the inner tube travel between the step position and the retracted position. 
         [0022]    For the condition of the auxiliary step in the retracted position, the selective engage of the various teeth on the indexing mechanism provides a locked condition under the force exerted thereon by the yieldingly resilient mechanism to prevent relative movement of the auxiliary step from the retracted position. When it is desired to move the auxiliary step to the step position, a slight inward movement of the step against the force of the yieldingly resilient mechanism towards the vehicle releases the engagement of the teeth and allows the yieldingly resilient mechanism to extend the step to the step position. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0023]    The above and other embodiments of the present invention my be more fully understood from the following detailed description taken together with the accompanying drawing wherein similar reference characters refer to similar elements throughout and in which: 
           [0024]      FIG. 1  is a perspective view of a vehicle showing two of the steps of the present invention installed thereon and the steps in the step position thereof; 
           [0025]      FIG. 2  is a partial perspective view of a vehicle similar to the vehicle of  FIG. 1  showing a step in the retracted position; 
           [0026]      FIG. 3  is a partial perspective view of the vehicle of  FIG. 2  showing the step in the step position thereof; 
           [0027]      FIG. 3A  is a partial perspective view similar to  FIG. 2  showing an exploded view of the step of the present invention as installed on a vehicle; 
           [0028]      FIG. 4  is perspective view of one embodiment of the present invention in the step position; 
           [0029]      FIG. 5  is a perspective view of the embodiment shown in  FIG. 4  in the retracted position thereof; 
           [0030]      FIG. 6  is a perspective view of a frame useful in the practice of the present invention; 
           [0031]      FIG. 7  is a perspective view of a stationary channel useful in the practice of the present invention 
           [0032]      FIG. 9  is a perspective view of a tread useful in the practice of the present invention; 
           [0033]      FIG. 10  is a top plan view of a guide plate useful in the indexing mechanism of the embodiment shown in  FIG. 4 ; 
           [0034]      FIG. 11  illustrates a spring loaded guide pin for the indexing mechanism of the embodiment shown in  FIG. 1 ; 
           [0035]      FIG. 12  is a perspective view of a gas spring cylinder useful in the practice of the present invention; 
           [0036]      FIG. 13  is a perspective view of another embodiment of the present invention in the step position thereof; 
           [0037]      FIG. 14  is a perspective view of the embodiment shown in  FIG. 13  in the retracted position thereof; 
           [0038]      FIG. 15  is a perspective view taken along the line  15 - 15  of  FIG. 14 ; 
           [0039]      FIG. 16  is an exploded perspective view of an indexing mechanism useful in the embodiment shown in  FIG. 13 ; 
           [0040]      FIGS. 18 through 22  illustrate the indexing mechanism of  FIG. 16  in various operational positions thereof. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0041]    Referring now to the drawing, there is shown on  FIG. 1  a perspective view of a vehicle  9  of the type having a storage bed  11 . Access to the storage bed  11  from the sides of the vehicle such as side  13  is often hindered in such vehicles by the height of the side above the ground level. In order to provide convenient access to the bed  11 , steps of a preferred embodiment  10  of the present invention as indicated at  12  and  14  are installed on the underside  15  of the vehicle  9 . While two installations are shown on  FIG. 1 , many vehicles are of a size such that only one step may be required. The step of the present invention may be installed on one side of the vehicle  9  or on both sides of the vehicle as desired for particular applications, or installed on one or more than one location as may be required or desired in other applications. 
         [0042]      FIG. 2  illustrates a vehicle  9 ′ in which the step  14  is installed to allow access to the roof  9 ′ a  of the vehicle  9 ′. In  FIG. 2  the step  14  is shown in the retracted position and for the installation in a vehicle such as vehicle  9 ′, a pair of support straps  16  may be installed to provide additional support for the step  14 .  FIG. 3  shows the step  14  as installed on the vehicle  9 ′ in the step position thereof As shown there is a tread  20  that is reciprocatingly movable between the retracted position shown in  FIG. 2  and the step position as shown in  FIG. 3 . 
         [0043]      FIG. 3A  shows the step  14  as installed in the vehicle  9 ′ in an exploded perspective view of the step  14 . As shown thereon, the tread  20  is mounted on a frame  18  which is bolted by bolts  22  and nuts and washers  24  to an underside  15 ′ of the truck  9 ′ which also connect the support straps  16  for the additional support as may be required in some applications. There may also be provided bolts  23  and nuts and washers  25  for additional support extending through the support straps  16 . The tread  20  is reciprocatingly movable in the directions of the double ended arrow  29  with respect to the frame  18 , as well as the vehicle  9 ′, on which the tread  20  is mounted. 
         [0044]      FIG. 4  illustrates an exploded view of a step arrangement  30  of an embodiment  32  having a frame  18  on which a tread  20  is movably mounted for reciprocating motion with respect to the frame  18  in the directions of the arrow  34  from the step position thereof to the retracted position thereof as shown in  FIG. 5  and in the direction of the arrow  36  from the retracted position thereof as shown in  FIG. 5  to the step position thereof as shown in  FIG. 4 . 
         [0045]    The embodiment  32  has a yieldingly resilient mechanism which, in the embodiment  32 , is a gas spring cylinder  38  which resists movement of the tread  20  in the direction of the arrow  34  and urges the tread  20  in the direction of the arrow  36 . The gas spring cylinder may be of the type presently available as utilized on, for example, hoods, hatch backs and the likes of many vehicles. The gas spring cylinder is illustrated in  FIG. 12  and has a first end  38   a  which is attached to the inner end  40  of the frame  18  and an second end  38   b  which is attached to the outer wall  20   a  of the tread  20 . Other types of resilient mechanisms such as a coil spring, leaf spring or the like could be utilized to provide the function of the gas spring cylinder  38 . 
         [0046]      FIG. 6  shows a perspective view of the frame  18 . The frame  18  has a base plate  26 . The base plate  26  has the outer wall  20   a , an inner edge  30 . The base plate  26  is substantially planar. A pair of spaced apart side walls  18   b  and  18   c  are connected to and upstanding from the base plate  26 . Each of the side walls  18   a  and  18   b  have a flange member  18   d  and  18   e , respectively connected thereto. The flange members  18   d  and  18   e  extend outwardly from side walls  18   a  and  18   b , respectively, in a direction away from the base plate  26 . The flange members  18   d  and  18   e  are substantially coplanar and in a plane substantially parallel to the plane of the base plate  26 . 
         [0047]    A pair of guides  48  and  50  are mounted on the base plate  26  and the guide  48  is in regions adjacent the side edge  18   c  and the guide  50  is in regions adjacent the side edge  18   b  of the base plate  26 . The guides  48  and  50  are substantially parallel to each other and to the side walls  18   b  and  18   c .  FIG. 7  shows a perspective view of the guide rail  48 , the guide rail  50  being substantially identical thereto. As shown thereon, the guide rail  50  is substantially “box shaped” guides and the base  50   a  of the box shaped guides is affixed to the base plate  26 . 
         [0048]    A pair of rails  52  and  54  are connected to the tread  26  and mounted in the guides  48  and  50  for movement with the tread  20  In the preferred embodiment of the present invention the rail  52  is mounted in the box shaped guide  48  and the rail  54  is mounted in the box shaped guide  50 . A mounting flange  41  is attached to the base plate  26  as shown on  FIG. 6  and has an aperture  43  therein. A pin or bolt  91  ( FIG. 13 ) may extend through the aperture  43  and ride in slot  47  The pin  91  tends to help maintain the alignment of the rail  54  in the guide  50 . 
         [0049]      FIG. 9  illustrates the tread  20  of the step  14 . As shown thereon, the tread  20  has an outer edge  20   a  to which the rails  52  and  54  as well as the gas spring cylinder are attached. The upper surface  20 ′ of the tread  20  may be textured as shown in conventional patterns for added stability during use. 
         [0050]    The step  14  of the embodiment  32  is provided with an indexing mechanism generally indicated at  70  ( FIG. 4 ) having a guide plate  72  and a spring loaded engagement pin  74 . The guide plate  72  is attached to the base plate  26  and has a plurality of pin accepting slot paths therein. A top plan view of the guide plate  70  is shown in  FIG. 10 . A first slot path  74  extends from an outer end  76  which is at a base, lower level indicted at  76 ′ bounded by the upstanding walls  80  and  82 , upwardly to a second level indicated at  78 ′ spaced higher from the base plate  26  to an inner end  78 . The inner end  78  ends at a wall  84  bounding a second slot path  86  which ends in an inner wall  88  bounding a retention surface  90  at a lower level than the second slot path  86 . A central wall member  92  is provided and has a first wall  96  bounding the first slot path  74  and a retention wall  94  bounding the retention surface  90 . The retention surface  90  has a wall  100  forming a wall bounding a third slot path  102  which is lower than the retention surface  90 . The inner end  104  of the third slot path  102  may be at the same level as the base level  78 ′ and slopes upwardly to a second end  106  bounded by wall  108 . The second end  106  is spaced a greater distance from the base plate  26  than the base level  76 ′. 
         [0051]      FIG. 11  illustrates the engagement pin  74 . The engagement pin  74  has a body  115  which is preferably fabricated of spring steel and has a mounting end  110  connected by bolt  112  to angle flange  114  that is fastened to the outer wall  20   a  of the tread  20 . The connection of the connection end of the body  115  to the angle flange  114  allows for limited pivotal movement into and out of the plane of the paper as indicated by the double ended arrow  120  on  FIG. 4  The engagement pin has a pin end  116  in which a pin  118  is attached. The body  115  of the engagement pin  74  urges the pin  118  in the direction of the arrow  122 . The pin  118  has an outer end  121  which is adapted to slide in the slots of the guide plate  72 . 
         [0052]    The operation of the indexing mechanism  70  starting from the step position shown on FIG.  4  and moving against the force of the resilient mechanism to the retracted position shown in  FIG. 5 , the pin  118  slides from the level indicated at  76 ′ in the first slot at  76  up to the wall  84 . Upon reaching the wall  84 , the outer end  121  of the pin drops to the level of the second slot path  86  and contacts the wall  123  in the end wall  125  of the guide  72 . Releasing the force moving the tread allows the pin  118  to slide into the retention slot  150  in the wall  92 . The force of the resilient mechanism keeps the pin  118  in this position. 
         [0053]    When it is desired to move the tread from the retracted position of  FIG. 4  to the step position of  FIG. 5 , the tread is moved slightly towards the inner end of the frame  18  which forces the pin  118  against the wall  123  and drops down to the level of the third slot path  102 . The force of the resilient mechanism moves the tread outwardly with the pin  118  moving in the third slot path  102  upwardly to the wall  108  where it drops into the level  76 ′. The wall  108  prevents the pin  118  from moving into the third slot path  102  and guides the pin  118  to engagement with the wall  141  of the central wall member which guides the pin into the first slot path  74  to move the tread to the retracted position. 
         [0054]      FIGS. 13 to 22  illustrate another embodiment  160  of the present invention. The embodiment  160  is generally similar to the embodiment  32  described above except that there is provided an indexing mechanism  162  which differs from the indexing mechanism described above.  FIG. 13  illustrates the embodiment  160  in the step position thereof wherein the tread  20  is extended outwardly from the frame  18 .  FIG. 14  illustrates the embodiment  160  in the retracted position thereof and  FIG. 15  illustrates the embodiment  160  taken along the line  15 - 15  of  FIG. 13 .  FIG. 15A  illustrates a detail if the embodiment  160 .  FIG. 13  shows the bolt  45  in the flange  41  as 
         [0055]      FIGS. 16 through 22  illustrate details of the indexing mechanism  160 . As shown on  FIG. 16 , the indexing mechanism  160  has four basic components: an outer tube  180 , an intermediate tube  182  slidingly mounted in the outer tube for primarily axial sliding motion therein, an inner tube  184  mounted in the intermediate tube  182  for sliding motion therewith as the intermediate tube  182  moves in the outer tube  180 . The outer tube  180  has a flange end  188  which has a mounting flange  190  and the mounting flange  190  is bolted or otherwise secured to the end wall  18   a  of the frame  18 . The outer tube  118  has an inside surface  192  and a plurality of tracks  194  which in embodiment  162  is four are on the inner surface  192  and the tracks  192  have flange end teeth  195 , shown in more detail on  FIG. 17  as discussed below, and at an inner end  197  of the outer tube  180  the four tracks  194  have a tab  196  projecting radially inwardly. The flange end teeth  195  are spaced axially from the outer surface  201  of the flange  190 . 
         [0056]    The intermediate tube  182  has a plurality of slots  202  on the outer surface  205  and the number of slots  202  is the same as the number of tracks  195  on the outer tube  180 . The intermediate tube  182  has an outer end  207  and an inner end  203  and the outer end  207  has a plurality of teeth  210  on the annular outer end  207 . The slots  202  have an end  211  which are adapted to engage the tabs  196  so as to align the outer tube  180  and intermediate tube  182  when the step  160  is in the step position as shown on  FIG. 13 . The intermediate tube  182  has a plate  213  covering the inner end  203  and the plate  213  has an aperture  215  therethrough concentric with the axis  161  about which the outer tube  180 , the intermediate tube  182  and the inner tube  184  are concentric. 
         [0057]    The inner tube  184  and the ring gear  186  are mounted in the intermediate tube  182  and are shown spaced therefrom in  FIG. 16  for clarity of description. The inner tube  184  has an outer end  220  with a shoulder  222  on the outer surface  223 . The inner tube  184  has a plate  225  closing the inner end  229  and the plate  225  has an aperture  227  there through which is concentric to the axis  161  and aligned with the aperture  217  in the plate  213  of the intermediate tube  182 . The outer surface of the plate  225  abuts the inner surface of the plate  113  in the intermediate tube  182 . 
         [0058]    The ring gear  186  is slidingly mounted on the outside surface  223  of the inner tube  184  and has an outer end surface  230  which abuts the shoulder  222  of the inner tube  186  and an inner end surface  232 . The ring gear  186  has an outer cylindrical surface  234 , and two sets of teeth. The details of the teeth are shown on  FIG. 16A . A first outer set of teeth  240  is on the outer cylindrical surface  234  of the ring gear  186  and has twice the number of the slots  202  of the intermediate tube  182 . The first outer set of teeth  240  extend from the outer end surface  230  towards the inner end surface  232  and has a slant edge  240   a . The second inner set of teeth  250  extend from the inner end surface  230  of the ring gear  186 . 
         [0059]      FIGS. 17 and 18  show the indexing mechanism  162  in the locked position thereof which is the condition of the step embodiment  160  is in the retracted position thereof as shown on  FIG. 14 . As shown on  FIGS. 17 and 18 , four of the eight ring gear outer teeth  240  have the edge  240   a  engaged with the four flange end teeth of the  195  of the tracks  194 . As shown on  FIGS. 17 and 18 , the flange end teeth  195  have a “saw tooth” configuration and the ring gear outer teeth  240  are operatively engaged therein. The intermediate tube  182  is spaced slightly axially inwardly from the ring gear inner teeth  250 . The resilient mechanism  38  maintains the force on the indexing mechanism  162  to hold the components in the locked position thereof as shown on  FIGS. 17  and  18 . The four ring gear inner teeth are positioned separated from and half way across the intermediate gear teeth  210 . 
         [0060]    When it is desired to move the step  160  from the locked, retracted position shown in  FIGS. 14 and 16  and as detailed on  FIGS. 17 ,  17 A,  18  and  18 A to the unlocked position wherein the tread  20  is extended outwardly as shown on  FIGS. 13 and 15  and as detailed in  FIGS. 19 ,  19 A,  20  an inward pressure is placed on the tread  22  to move the tread  22  inwardly against the force of the resilient mechanism  38 .  FIGS. 19 and 20  illustrate the position of the indexing mechanism  162  of the step  160  when it is first moved from the locked position. As shown thereon the intermediate tube teeth  210  push against the ring gear inner teeth  250 . Such action lifts the gear outer teeth  240  above the flange end teeth  195 . The ring gear inner teeth  250  slide down intermediate tube teeth  210  and such action causes the ring gear outer teeth to slide down the outer portion  195   a  of the flange end teeth  195 . In this position, the indexing mechanism  162  is unlocked and under the force of the resilient mechanism  38 , the inner tube  184 , the ring gear  186  and the intermediate tube  182  move axially in the outer tube  180  to the position shown on  FIGS. 21 and 22  under the influence of the resilient mechanism  38 . Such axial movement continues until the end  211  of the slots  202  engage the stop  196  on the inside of the outer tube  180 . 
         [0061]      FIGS. 22 ,  22 A and  22 B illustrate the position of the indexing mechanism  162  for the condition of the step  132  fully extended outwardly. As shown in  FIG. 22B , there is provided a bolt  299  with a bolt head  304  inside the inner tube  184  at the inner end  184   a  and the bolt extends through the plate  225  of the inner tube  184 , through the plate  213  of the intermediate tube  182 , through the wall  18   a  of the frame  18  and is held in place by nut  300 . A spring  306  is provided between the bolt head  304  and the washer  302  bearing against the inside surface of the plate  225  of the inner tube  184 . 
         [0062]    While particular embodiments and applications of the present invention have been above described an illustrated, the present invention is not limited to the precise construction and arrangements disclosed. Those persons knowledgeable in the art may conceive of certain modifications, changes and variations in the detailed embodiments disclosed above as illustrative, to suit particular circumstances or products to be formed. The invention is therefore not intended to be limited to the preferred embodiments depicted, but only by the scope of the appended claims and the reasonably equivalent apparatus and methods to those defined therein.