Abstract:
The present disclosure relates to a telescoping step system which has at least one stringer assembly having telescopically coupled first and second tubular components. The second tubular component is telescopically extendable relative to the first tubular component. The stringer assembly is operably associated with a structure. The system further has at least one step assembly associated with one of the first and second tubular components. The stringer assembly is telescopically collapsible into a retracted position to form a compact assembly either adjacent to or within a portion of the structure, and extendable into an extended position extending outwardly from the structure. In the extended position the stringer assembly presents the step assembly as a platform which a user is able to step on to, and thus aids the user with ingress into and egress from the structure.

Description:
FIELD 
     The present invention relates generally to assist steps used with vehicles, and more particularly to a telescoping step system having pivotally mounted steps which pivot between stowed and deployed positions as stringers supporting the steps move telescopically between retracted and extended positions. 
     BACKGROUND 
     It is known to provide a step assist platform or bar to promote ingress and egress of a vehicle. Typically, most present day step assist platforms are fixedly mounted relative to a frame portion of the vehicle and thus do not articulate. Furthermore, the single, fixedly mounted step assist platform is often disposed at a height that is not practical for all users. Moreover, present day step assist platforms can be subject to high capacity load resulting in deflection or possibly even failure. 
     Present day articulating step systems are also known and typically employ some type of four bar linkage arrangement. The four bar linkage arrangement is used to deploy and retract a single step bar. The step bar is typically retracted under a rocker panel area of the vehicle, and when deployed extends out from the rocker panel area adjacent a vehicle door. However, such systems typically only make use of a single step, which does not necessarily provide an optimal and comfortable means of ingress and egress relative to an interior area of the vehicle. With modern day vehicles such as vans, pickup trucks and SUVs, RV&#39;s, buses, trains, planes, heavy equipment and other vessels requiring ingress and egress of occupant(s), often it would be more comfortable for occupants to be able to use two or more steps when entering or exiting a vehicle. This is so for people of smaller stature, and especially so for small children. 
     Therefore, it is desirable to provide a telescopic step assist system that supports a relatively high capacity load. It is also desirable to provide a telescoping step assist system that affords the user with two or more steps, such that a smaller step height for each step can be implemented, to thus significantly ease ingress into and egress from a vehicle. Such a step system would also need to be relatively compact when in its stowed or fully retracted orientation, would need to be easily mounted to some suitable portion or substructure of a vehicle (such as to a frame portion of the vehicle), but not necessarily limited to only frame mounting. 
     Other objects, features and advantages of the present invention will be readily appreciated, as the same becomes better understood, after reading the subsequent description taken in conjunction with the accompanying drawings. 
     SUMMARY 
     In one aspect the present disclosure relates to a telescoping step system comprising at least one stringer assembly having at least first and second tubular components. The second tubular component is telescopically extendable relative to the first tubular component. The at least one stringer assembly is operably associated with a structure. The system further may comprise at least one step assembly associated with one of the first and second tubular components. The at least one stringer assembly is telescopically collapsible into a retracted position to form a compact assembly at least one of adjacent to the structure or within a portion of the structure, and telescopically extendable into an extended position extending outwardly from the structure. In the extended position the at least one stringer assembly presents the at least one step assembly in an orientation which is easily accessible as a platform on which a user is able to step on to, and thus aids the user with ingress into and egress from the structure. 
     In another aspect the present disclosure relates to a telescoping step system. The system may comprise at least one stringer assembly having at least first and second tubular components, where the second tubular component is telescopically extendable relative to the first tubular component, and where the at least one stringer assembly is operably associated with a structure to allow easier ingress to and egress from the structure. The system may also include a first actuator subsystem for causing telescopic movement of the at least one stringer assembly between extended and retracted positions. At least one step assembly may also be included which is associated with one of the first and second tubular components. The at least one step assembly may be pivotally operatively coupled to the at least one stringer assembly and movable from a stowed position to an operative position. A second actuator subsystem may be included for causing pivoting motion of the at least one step assembly between the stowed position and the operative position. The at least one stringer assembly may be positioned to be telescopically collapsible into the retracted position to form a compact assembly at least one of adjacent to the structure or within a portion of the structure, and telescopically extendable into the extended position extending outwardly from the structure to present the at least one step assembly in an orientation which is easily accessible as a platform on which a user is able to step on to. In this manner the step assembly aids the user with ingress into and egress from the structure. The at least one step assembly is pivotally movable in response to control by the second actuator subsystem, to position the at least one step assembly in either the stowed or operative positions when the at least one stringer assembly is telescopically moved into the retracted or extended positions, respectively. 
     In still another aspect the present disclosure relates to a method for controlling motion of a movable step associated with a fixed structure. The method may comprise supporting at least one stringer assembly having at least first and second tubular components from the structure, where the second tubular component is telescopically extendable relative to the first tubular component. The method may also involve supporting at least one step assembly from one of the first and second tubular components so that the at least one step assembly is pivotally movable from a stowed position to an operative position, and wherein in the operative position the at least one step assembly forms a platform on which a user may step. The method may also involve using a first actuator subsystem to cause telescopic motion of the at least one stringer assembly between extended and retracted positions, and using a second actuator subsystem to cause pivotal movement of the at least one step assembly between stowed and operative positions. When the at least one stringer assembly is moved telescopically into the extended position the at least one step assembly will be pivotally moved into the operative position to form the platform upon which the user is able to step. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG. 1  shows a perspective view of one embodiment of a telescoping step assist system in accordance with the present disclosure secured to a frame portion of a motor vehicle, with the system shown in an extended or deployed position; 
         FIG. 1 a    shows the telescoping step assist system of  FIG. 1  with additional components being visible which are used to secure the system to the frame portion of the vehicle shown in  FIG. 1 ; 
         FIG. 2  is another perspective view of the telescoping step assist system of  FIG. 1  showing the system in a retracted position; 
         FIG. 3  is a perspective view of the system similar to that shown in  FIG. 1 , but from an inboard perspective to illustrate various additional components of the system; 
         FIG. 4  is an outboard perspective view of one of the telescoping stringer assemblies used with the system showing the telescoping stringer assembly in an extended orientation; 
         FIG. 5  is a plan view of the telescoping step assist system of  FIG. 1 ; 
         FIG. 6  is a front elevational view of the telescoping step assist system of  FIG. 1 ; 
         FIG. 7  is an end view of the telescoping step assist system of  FIG. 1 ; 
         FIG. 8  is an exploded perspective view of just one step assembly of the system of  FIG. 1 ; 
         FIG. 9  is a perspective view showing just the three step assemblies of the telescoping step assist system of  FIG. 1 ; 
         FIG. 10  is a typical section through a D-shaft hinge pin of the telescoping step assist system of  FIG. 1 ; 
         FIG. 11  is another exploded perspective view of a portion of the telescoping step assist system of  FIG. 1 ; 
         FIG. 12  is another perspective view of a representative portion of the telescoping step assist system of  FIG. 1 , used with one of the stringers, without the tube sections of the stringer being illustrated; 
         FIG. 12 a    is another perspective view of just the dual action hydraulic cylinders of the telescopic assist system of  FIG. 12  and their associated actuator rods; 
         FIG. 13  a high level block diagram showing how one spool is coupled to a pair of multistrand cables to allow rotation of the spool in either rotational direction, depending on how the multistrand cables are actuated; 
         FIG. 14  is an elevation view of one of the spools illustrating the two grooved surfaces which allow a pair of the multistrand cables to be secured thereto in 180 degree opposite orientations; 
         FIG. 15  is a high level block diagram showing another embodiment of the system which makes use a reversible electric DC motor and dual linear actuators for enabling the pivoting motion of the step assemblies and the telescoping movement of the stringers, respectively; and 
         FIG. 16  shows another embodiment of the system of the present disclosure being employed as a step assembly on the rear of a pickup truck. 
     
    
    
     DETAILED DESCRIPTION 
     To achieve one or more of the foregoing objects, the present disclosure provides a telescoping step assist system and method. One embodiment of the telescoping step assist system includes a plurality of steps. Each of the telescoping sections has a portion of each rotating step attached to it. The telescoping step assist system is stowed underneath or inside the vehicle and includes either a hydraulic drive mechanism or an electric drive mechanism that extends and retracts the steps of the system adjacent a lower area of the vehicle. The telescoping step assist system may also include a dual action hydraulic drive mechanism, or an all-electric drive system, for extending and retracting the telescoping sections each at approximately the same rate of speed, or at different speeds. The telescoping step assist system may also include either a hydraulic drive system or an electric drive system that rotates each step from a stowed vertical position into a usable horizontal position. The steps may be rotated substantially simultaneously at the same rotational speeds, or they may be rotated at different time intervals and/or at different rotational speeds. 
     One advantage of the disclosed system and method is that a new telescoping step assist system is provided to support a relatively high capacity load, but is yet a highly compact system when in its stowed orientation. Another advantage of the disclosed is that it allows even more comfortable and convenient ingress and egress relative to the interior area of a vehicle. Yet another advantage of the present invention is that it does not introduce significant added weight to a vehicle with which it is used, and does not require modification of the frame structure of the vehicle. As such, the system disclosed herein can be installed on vehicles as they are manufactured or may be retrofitted onto existing vehicles without significant modification to the frame structure of most existing vehicles. 
     Referring now to the drawings, and in particular  FIGS. 1, 1   a  and  2 , one embodiment of a telescoping step assist system  10  (hereinafter simply “system  10 ”) according to the present disclosure, is shown for use with a vehicle  12 . It will be appreciated that while the vehicle  12  is shown in  FIG. 1  as an SUV, that the system is also expected to find use on a wide variety of other vehicles or structures where a user needs to step up one or more steps for ingress or egress to the structure, and where it is desirable to retract the steps before operation of the vehicle or structure. As such, the system  10  may find utility with motor homes, aircraft or rotorcraft, trains, heavy equipment (e.g., earth moving equipment), farm equipment such as tractors, combines, etc., and even watercraft. The system  10  may also find utility with fixed structures such loading docks at warehouses where it would be convenient to provide a telescopically retractable step system to augment use of the loading dock. It will be appreciated, then, that the system  10  is not limited to use with any one single type of vehicle or structure. 
     Referring to  FIGS. 1, 1   a  and  2 , the system  10  in this example includes a pair (plurality) of identical mounting mechanisms, each indicated at  14 , for rigidly mounting the system  10  to a suitable portion of a mounting surface of a structure. Of course, in some applications only one such mounting system may be required. In other applications it may be desirable to provide more than two mounting systems  14 . In one implementation the support surface may be portions of a frame of the vehicle  12 . The mounting mechanisms  14  each include mounting plates  16 . The mounting plates  16  in this example are planar and preferably made of a structurally strong material such as metal. The mounting plates  16  are each secured to a suitable mounting surface (e.g., portion of a frame of the vehicle  12  or other structure) by suitable fasteners (not shown) extending through the mounting plates  16 . A vanity plate  17  may be included to provide a pleasing appearance and to help block portions of the mechanical components from view when the system  10  is in its extended (deployed) orientation. The system  10  is shown in  FIGS. 1 and 1   a  in its extended or deployed position, and in  FIG. 2  in its retracted or stowed position. It will also be appreciated that the system  10  may be mounted so as to be positioned within a portion of a structure, and does not necessarily need to be mounted to an external surface of the structure. The only requirement is that the mounting is such that the system  10  can operate to telescopically extend and retract without interference from any portion of the structure (i.e., any portion of the vehicle or fixed structure). 
     Referring to  FIG. 3 , the mounting plates  16  may contain a plurality of ball bearing carriage assemblies  18  made of steel and secured to the support surface by suitable fasteners extending through the ball bearing carriage assemblies  18  and threaded into the mounting plates  16 . The ball bearing carriage assemblies  18  provide precision motion along the Y-axis (i.e., cross car). Linear guide rails  20  are contained within the ball bearing carriage assemblies  18 . The linear guide rails  20  in this example are made of steel and are planar. It should be appreciated that in the embodiment illustrated in the figures, the ball bearing carriage assemblies  18  allow the system  10  to provide precision, low-friction, quiet, linear motion in the cross-car direction. A pair of actuators  21 , which may each be an hydraulically driven actuator or an electrically driven linear actuator, or even pneumatically driven (i.e., air driven) actuators, is provided for providing linear translating movement of a portion of the system  10  outwardly (away from the rocker panel area of the vehicle  12 ), as well as inwardly (toward the rocker panel area). This operation will be described more fully in the following paragraphs. It will be appreciated however, that the system  10  may be used without the linear translating movement provided by actuators  21 . 
     Linear guide rails  20  are secured to angle plates  22  by suitable fasteners extending through the linear guide rails  20  and threaded into the angle plates  22 . Angle plates  22  are generally 90 degree sections made of steel. Tube extenders  24  are generally rectangular box sections. Tube extenders  24  are secured to angle plates  22  by suitable threaded fasteners  26  extending through the angled plates  22  and the tube extenders  24 , and retained with threaded nuts  28 . 
     With further reference to  FIGS. 1, 1   a  and  2 , the system  10  can be seen to also include a pair of stringer assemblies  30  and a plurality of step assemblies  32   a - 32   c . While three step assemblies  32   a - 32   c  are shown, it will be appreciated that the system  10  could use one, two, four or more such step assemblies, and therefore is not limited to using only three such assemblies. However, it is anticipated that for most passenger vehicle applications involving cars and trucks, three independent step assemblies will be optimal for providing comfortable ingress to, and egress from, the vehicle&#39;s interior. For large industrial equipment it may be desirable to use more than three such step assemblies, depending largely on the height of the cabin of the vehicle above the ground surface.  FIG. 2  particularly shows that the step assemblies  32   a - 32   c  form a highly compact assembly when in the retracted (stowed) orientation. 
     Referring to  FIG. 4 , one of the stringer assemblies  30  can be seen in greater detail. Each stringer assembly  30  includes an outer tube  34 , one of the tube extenders  24 , a mid tube  36  telescopically mounted to the outer tube  34 , and an inner tube  38  telescopically mounted to the mid tube  36 . The tube extender  24  is fixedly secured to the outer tube  34  such as be welding or possibly by a suitable plurality of threaded fasteners. The outer tube  34  also includes a pair of longitudinally aligned standoffs  40  which are threaded into threaded openings in the outer tube. Similarly, the mid tube  36  includes a separate pair of fixedly secured, longitudinally aligned standoffs  42  threaded mounted on the mid tube, and the inner tube  38  includes its own pair of fixedly secured, longitudinally aligned standoffs  44  threaded mounted on the inner tube. The stringer assemblies  30  can also be seen in  FIGS. 5-7 . 
     Referring briefly to  FIGS. 12 and 12   a , the system  10  also includes a telescopic drive mechanism, generally indicated at  50 , to extend and retract each stringer assembly  30 . The telescoping drive mechanism  50  consists of two opposing dual action hydraulic cylinders  52   a  and  52   b  securely mounted to the mid tube  36  of the stringer assembly  30  by suitable fasteners. The dual action hydraulic cylinders  52   a / 52   b  make use of a drive mechanism which is formed in part by inboard and outboard articulating rods  54   a  and  54   b , respectively. It should be appreciated that the dual action hydraulic cylinders  52   a / 52   b  are conventional and well known in the art. It should also be appreciated that each stringer assembly  30  contains the pair of dual action hydraulic cylinders  52   a / 52   b , opposed, and mounted to function as an integral, single subsystem as shown in  FIG. 12 a   . An inboard end  56  of an articulating dual action hydraulic cylinder rod  54   a  is attached to a mount  34   a  associated fixedly with the outer tube  34 . An outboard end  58  of an articulating dual action hydraulic cylinder rod  54   b  is attached fixedly to the inner tube  38  via a mount  38   a . Threaded fasteners  39 , visible in  FIG. 7 , are received in threaded bores in the mount  38   a  and enable the mount to be secured to the inner tube  38 . In this example, the drive action of each dual action hydraulic cylinder  52   a  and  52   b  transfers fluid volumes within the closed system of the cylinders&#39; chambers, thereby extending and/or retracting the outer tube  34  and inner tube  38  in a constant manner as related to the mid tube  36 . Since the two dual action hydraulic cylinders  52   a / 52   b  are mounted within the mid tube  36 , when the cylinder rods  54   a  and  54   b  are simultaneously extended, this causes simultaneously extending movement of the mid tube  36  relative to the outer tube  34 , and of the inner tube  38  relative to the mid tube  36 , which makes for extremely rapid deployment of the stringer assemblies  30  into their fully extended positions. Likewise, when the cylinder rods  54   a  and  54   b  are simultaneously retracted, this causes retracting movement of the mid tube  36  relative to the outer tube  34 , as well as simultaneous retracting movement of the inner tube  38  relative to the mid tube  36 , which makes for a rapid retracting motion of the stringer assemblies  30  into their stowed positions. 
     With reference to  FIGS. 1 a    and  7 , the outer tube  34  can be seen to support the step assembly  32   a , the mid tube  36  can be seen to support the mid tube  32   b , and the inner tube  38  can be seen to support the step assembly  32   c . With reference to  FIGS. 4 and 8 , the pairs of standoffs  40 ,  42  and  44  provide smooth inner bearing surfaces through which D-shaft hinge pins  60  are inserted and rotate. As shown in  FIG. 8 , one pair of D-shaft hinge pins  60  functions as a pivoting axis by which step assembly  32   c  is rotated generally 90 degrees from a vertical (i.e., retracted or stowed) position to a horizontal (i.e., extended or deployed) position, and vice-versa. The D-shaft hinge pins  60  associated with step assemblies  32   a  and  32   b  function in identical fashion to that described for step assembly  32   c.    
     With reference to  FIG. 8 , step assembly  32   c  can also be seen to include a pair of step ends  62   a  and  62  having through bores  64  for receiving the D-shaft hinge pins  60 . With brief reference to  FIG. 10 , the D-shaft hinge pins  60  are each secured for non-rotational movement by a pair of shouldered fastener hinge pins  60   a  extending through keyway features of each of the D-shaft hinge pins, and threaded into the step ends  62   a  and  62   b . Referring further to  FIG. 8 , a central step member  70  is positioned between the step ends  62   a  and  62   b  receives neck portions  72  of each step end  62   a  and  62   b . Threaded screws  74  are used to secure the step ends  62   a  and  62   b  to opposing ends of the central step member  70 . The construction of step assemblies  32   b  and  32   a  are identical to that described above for step assembly  32   c.    
     With reference to  FIG. 10 , one end of step assembly  32   c  can be seen in greater detail. It will be appreciated that the opposite end of step assembly  32   c  with step end  62   b  has the identical construction.  FIG. 10  shows that an additional bearing  76  is used to help support and provide a low friction rotation of the step end  62   a  during extending or retracting rotational movement of the step assembly  32   c . The spool  66  can also be seen housed within an interior area of the inner tube  38  with the assistance of the standoffs  44 .  FIG. 9  shows the step assemblies  32   a ,  32   b  and  32   c  without the tubes  34 ,  36  and  38  to illustrate that the spool  66  of each step assembly is aligned along a common linear plane to permit a cable assembly to simultaneously rotate the step assemblies  32   a - 32   c  during when extending or retracting the step assemblies. It will be appreciated that the system shown in the art merely represents one drive method for rotating the step assemblies. Other embodiments may include using a rack and pinion configuration, worm gear and/or hydraulic/pneumatic rotary actuation to rotate the step assemblies  32   a - 32   c . As such, it will be appreciated that the system  10  is not limited to only one specific type of subsystem for providing the rotation of the step assemblies  32   a - 32   c.    
     As shown in  FIGS. 3 and 11 , in one embodiment a hydraulic drive mechanism  78  is used to provide rotational actuation of the step assemblies  32   a - 32   c . The drive mechanism includes a hydraulic cylinder  80 . The fluid lines to the hydraulic cylinder  80  have been omitted for clarity. A cable lever  82  is attached to a clevis of an articulating rod  84  of the hydraulic cylinder  80  via pin  81 . Multistrand cables (not shown), mounted to upper portion  82   a  and lower portion  82   b  of the cable lever  82  are routed through a rear tube  86  of the system  10 . Rear tube  86  is also visible in  FIG. 3 . The rear tube  86  has tube extenders  24  attached to its opposite ends via threaded screws  88  and nuts  90  as shown in  FIG. 3 . The rear tube  86  is secured to the angle plates  22 . In this manner, the actuators  21  can be used to translate the rear tube  86 , and thus the stringers  30  and steps  32   a - 32   c , outwardly and inwardly a small distance relative to the vehicle  12 . The distance is in accordance with the degree of linear travel of the actuators  21 , but in one embodiment of the system  10  is about four to eight inches. Obviously, this distance may be modified by selecting actuators having a different maximum length of travel. 
     With further reference to  FIG. 11 , the cable lever  82  is supported for pivotal movement and secured to the rear tube  86  by a threaded screw  92  and nut  94 . A pair of thrust washers  96  (only one being partially visible) and a pair of sleeve bushings  98  may also be used to help provide smooth pivoting motion of the cable lever  82 . An end portion  100  of the hydraulic cylinder  80  is fixedly secured to arm portions  102 , which are in turn fixedly secured to the rear rube  86 , via a pin  104 . 
     With further reference to  FIG. 12 , one of a pair of multistrand cables  106  is shown along with cable brackets  108 ,  110  and  112 . It will be appreciated that each spool  66  has two separate multistrand cables  106  secured to it in a manner such that rotational movement in a first direction causes one of the cables  106  to be taken up on the spool while simultaneously the other cable  106  is being unspooled. Since each spool  66  has two multistrand cables  106  attached to it, a total of six multistrand cables will extend through each stringer  30  (i.e., twelve total multistrand cables thus being used). As will be described further in the following paragraphs, this enables the step assemblies  32   a - 32   c  to all be rotated from their retracted (vertical) orientation into their extended (horizontal) orientation virtually simultaneously. The multistrand cables  106  are all hidden from view by being routed internally through the tubes  34 - 38  of each stringer assembly  30 . 
     With brief reference to  FIGS. 13 and 14 , the coupling of a pair of multistrand cables  106  to one spool  66  is shown. Conduits  107  in  FIG. 13  may be fixedly disposed within each stringer assembly  30  to help guide movement of the multistrand cables  106 . Cable tensioners  119  may also be included to provide tension and prevent slack from developing in the multistrand cables  106  as they are spool or unspooled from the spool  66 . Ball ends  66   a  on an end of each multistrand cable enable the cable to be retained in keyed openings in the spool  66 . From  FIGS. 13 and 14 , it will be apparent that when one of the multistrand cables is unspooled from the spool  66  the other will be simultaneously spooled onto the spool  66 . Thus, pivoting movement of the lever  82  works to implement somewhat of a “push/pull” operation on the multistrand cables  106 , to thus cause either clockwise or counterclockwise rotational movement of the spool  66 . 
     Cable bracket  108  is operably associated with spool  66  of step assembly  32   c , while cable bracket  110  is operably associated with spool  66  of step assembly  32   b , and cable bracket  112  is operably associated with spool  66  of step assembly  32   a . Each cable bracket  108 - 112  is pivotally mounted on its associated D-shaft hinge pin  60  and thus is free to pivot. The cable bracket  108  is also visible in  FIG. 10 . 
     With further reference to  FIG. 11 , each multistrand cable  106  is coupled at the upper and lower ends of the cable lever  82 . In this manner, when the cable lever  82  pivots in a first rotational direction, the cables  106  each work to rotate the step assemblies  32   a - 32   c  in somewhat of a “push-pull” fashion, and when pivoted in the opposite direction, the multistrand cables  106  operate to rotate the step assemblies substantially simultaneously, but in the opposite rotational direction, using the same “push-pull” action. Thus, pivoting the cable lever  82  in one direction causes the step assemblies  32   a - 32   c  to all be simultaneously pivoted into their extended (i.e., horizontal) orientations, while pivoting the cable lever  82  in the opposite direction causes all of the step assemblies  32   a - 32   c  to be pivoted into their retracted (i.e., vertical) orientations. It will also be noted in  FIG. 12  that each multistrand cable  106  extends through one of a pair of openings  112  in each cable bracket  108 - 112 , and thus is contained within the stringer assembly  30  and the rear tube  86 . 
     In operation, the system  10  receives suitable control signals to the dual action hydraulic cylinders  52   a / 52   b , the hydraulic cylinder  80  and the actuator  21  which cause either an extending (deploying) movement or a retracting movement (i.e., movement into the stowed position). As noted above, the lateral translating movement provided by the actuators  21  is optional, but it is believed that this feature will even further enhance positioning of the step assemblies  32   a - 32   c  when the system  10  is used on various vehicles and structures, and therefore will be desirable in most applications. The following description of operation assumes that the actuators  21  are being employed with the system  10 . For example, when the system  10  is in its retracted position and control signals are received to initiate deployment of the system  10 , the actuator  21  operates first to move the assembly of stringer assemblies  30  and step assemblies  32   a - 32   c  laterally outwardly away from the vehicle  12  a small distance (e.g., four to 8 inches). Next, the control signals causes the During the extending motion the tubes  34 - 38  telescopically extend while the step assemblies  32   a - 32   c  are simultaneously being rotated from their stowed to their extending (deployed) orientations by the hydraulic cylinder  80  acting on the multistrand cables  106 . Thus, the step assemblies  32   a - 32   c  are moved into horizontally extending positions at about the time that the tubes  34 - 38  become fully telescopically extended. Of course this sequence could be modified slightly such that the step assemblies  32   a - 32   c  are deployed fully either before or after the tubes  34 - 38  are fully telescopically extended. Conversely, during retracting movement the step assemblies  32   a - 32   c  are pivoted into vertical orientations simultaneously with retracting telescopic movement of the tubes  34 - 38  of the stringer assemblies  30 . It will also be appreciated then that the system  10  is not limited to having the step assemblies  32   a - 32   c  pivot while the stringers  30  are being telescopically extended or retracted. Pivotal motion of the step assemblies  32   a - 32   c  may instead be initiated as soon as the actuator  21  begins to move the stringer assemblies  30  laterally outwardly away from the vehicle  12  or towards the vehicle, or alternatively after the lateral movement by the actuator  21  has been completed. As such, the system  10  is not limited to any specific sequence of lateral movement, telescopic movement and pivotal movement, when deploying or retracting step assemblies  32   a - 32   c.    
     In another embodiment  200  of the system shown in  FIG. 15 , which is even more suited to passenger cars and trucks, an all-electric drive system is used which includes electrically powered linear actuators  202 , a reversible DC electric motor  204 , and linear actuators  206 . The linear actuators  202 , the electric motor  204 , and linear actuators  206  may receive signals from a vehicle wiring harness when a key FOB is actuated to unlock a vehicle door, indicating that the occupant is approaching the vehicle and will be entering the vehicle cabin. Likewise, electrical signals are received from the vehicle wiring harness to indicate when the door of the vehicle is opened from the inside by an occupant who is leaving the cabin of the vehicle. In both instances the linear actuators  202 , the electric motor  204  and the linear actuators  206  may perform functions that are essentially equivalent to the dual action hydraulic cylinders  52   a / 52   b , the hydraulic cylinder  80 , and the actuators  21 , respectively, to provide the retracting and extending movements of the stringers  30 , the pivoting movements of the step assemblies  32   a - 32   c , and the extending/retracting movement of the rear rube  86 . 
     Referring to  FIG. 16 , a system  300  in accordance with another embodiment of the present disclosure is shown in which is especially well suited for use with passenger vehicles such as pickup trucks. The system  300  may be constructed substantially identically to the system  10 , but as is apparent the system  300  includes only a single stringer  302 . The stringer  30  includes tubes  304 ,  306  and  308  which support pivotal step assemblies  310   a ,  310   b  and  310   c . Extending and retracting movement of the system  300  may be initiated via a user control, such as a pushbutton, mounted in any convenient location on the system  300  or a convenient location on the vehicle  12 . Extending and retracting movement could also be via a key FOB command initiated by the user. Still further, extending and retracting movement could be initiated by a sensor that senses opening and closing of a tailgate  12   a  of the vehicle. As noted earlier, however, it will be appreciated that the system  10  or  300  could be employed on virtually any other type of vehicle or structure where one needs to step up into an elevated cabin or work area, and where there is a need to be able to retract the system  10  or  300  when it is not needed. 
     With the foregoing embodiments, while a plurality of steps has been shown with each embodiment, it will also be appreciated that the various embodiments described herein could just as readily be constructed with only a single step assembly. Still further, while the various embodiments described herein provide for rotational movement of each of the step assemblies  32   a - 32   c , it will also be appreciated that one or more, or all, of the step assembly(s) could be fixedly secured to the stringer(s) so that there is no rotation of the step assembly(s) during extending or retracting movement of the stringer. 
     It will also be appreciated that the vehicle with which the system  10  is being used could include a “car wash” mode that allows the user to lock the system with the step assemblies  32   a - 32   c  in their fully deployed positions, to thus allow easy and convenient washing of the step assemblies. This may be accomplished by a control input provided inside the vehicle, for example somewhere on the dashboard or possibly in the footwell area of the cabin of the vehicle, or possibly even from a command generated from a key FOB. Alternatively such a feature could be implemented on the system  10  itself by the inclusion of a user accessible switch and a microcontroller mounted somewhere on the system  10 . 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.