Abstract:
The present invention provides an improved collapsible step assembly for recreational vehicles. The movable step apparatus comprises a mounting frame, at least one step mounted to the frame through a linkage assembly, and a pivot rod with a longitudinal axis of rotation. In use, the pivot rod is rotatably mounted to the frame and rotates the linkage assembly and the at least one step between an extended position and a retracted position. Rotating the pivot rod in a first direction moves the step to the extended position, and rotating the pivot rod in the opposite direction moves the step to the retracted position. The linkage assembly includes a link which is movable in the direction of the link toward extension of the step to contact a stop of the frame that reacts against a gravitational load acting on the step.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     FIELD OF THE INVENTION 
     The invention relates generally to movable step assemblies for recreational vehicles and in particular to an apparatus for extending and retracting a movable step assembly. 
     BACKGROUND OF THE INVENTION 
     Automatic step systems for recreational vehicles, motor homes, and the like are well known in the art. These systems are typically electrically-controlled and electrically-actuated to extend and retract an entryway step in response to a signal provided by an individual wishing to enter or exit the vehicle. One common system extends the step when the vehicle door is opened, and then retracts the step when the vehicle door is closed. Other systems offer a switch located just inside the vehicle door which controls the extension and retraction of the step. These systems also include a master power switch which can be used to lock the step in a given position. 
     Alternative systems incorporate a motor assembly for automatically-extending and retracting the step assembly. The motor rotates a pivot rod through a gear assembly which is coupled to the rod. The pivot rod moves a linkage assembly to extend and retract the steps. However, these systems can give the step a “spongy” or unstable feel. In addition, a load applied to the step tends to move the step towards the retracted position. Therefore, an improved mechanism for extending and retracting collapsible steps in recreational vehicles is needed. 
     SUMMARY OF THE INVENTION 
     The present invention provides an improved collapsible step assembly for recreational vehicles. In one aspect, the invention provides a movable step apparatus including a mounting frame, at least one step mounted to the frame through a linkage assembly with at least two non-parallel links and a pivot member having a longitudinal axis of rotation. A gravitational load on the step urges at least one of the links of the linkage assembly in the direction of rotation of the link toward extension of the step to press against a stop of the frame to react against the load. 
     In one aspect, the invention provides a movable step apparatus including a mounting frame, a motor mounted to the frame, at least one step mounted to the frame, a pivot member mounted to the frame, a linkage assembly, and a transmission assembly. The at least one step is mounted to the frame through the linkage assembly. 
     In use, the pivot member is rotatably mounted to the frame. The transmission assembly rotates the pivot member, the linkage assembly, and the at least one step between an extended position and a retracted position. Rotating the pivot member in a first direction moves the step to the extended position, and rotating the pivot member in an opposite direction moves the step to the retracted position. 
     Opposing ends of the pivot member are attached to the linkage assembly. The linkage assembly comprises a plurality of links pivotally connecting the frame to the at least one step. The linkage assembly also includes a link that is movable to contact a stop. When the at least one step is in the extended position, the link contacts the stop, and the stop reacts against the load applied to the at least one step. 
     The foregoing and other objects and advantages of the invention will appear in the detailed description which follows. In the description, reference is made to the accompanying drawings which illustrate a preferred embodiment of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side plan view of a step assembly of the invention in an extended position; 
         FIG. 2  is a front, top perspective view of the step assembly in the extended position; 
         FIG. 3  is a rear, bottom perspective view of the step assembly in the extended position; 
         FIG. 4  is a side plan view of the step assembly in a retracted position; 
         FIG. 5  is a detail view of the drive portion of the step assembly in the extended position circumscribed by line  5 - 5  in  FIG. 3 ; 
         FIG. 6  is a detail view of the drive portion of the step assembly of  FIG. 5  but in the retracted position; 
         FIG. 7  is a detail cross sectional view of the step assembly in the extended position along line  7 - 7  in  FIG. 3 ; and 
         FIG. 8  is a detail cross sectional view of the step assembly of  FIG. 7  in the retracted position. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The invention comprises a collapsible step assembly  10  for use with recreational vehicles. Referring to  FIGS. 1-4 , the assembly  10  comprises a generally rectangular and planar upper step  12 , a lower step  14 , and a frame  16 . The steps  12  and  14  move between an extended position ( FIGS. 1 ,  2  and  3 ) and a retracted position ( FIG. 4 ). 
     Each step  12  and  14  may be covered with a non-skid material (not shown) to increase the friction of their respective surfaces. The lengths of the steps  12  and  14  are approximately one-half of their respective widths. 
     Each step  12  and  14  also has arms  18 A and  18 B, respectively, which extend in a rearward direction from their outer edges. Arms  18 A and  18 B are symmetrically arrayed along each side of the assembly  10 . For simplicity, these components are only numbered on a single side of the assembly  10  in  FIGS. 2 and 3 . Arms  18 A and  18 B are approximately equal in length to the steps  12  and  14  and may be reinforced by pieces of angle bar stock welded to them as illustrated on arm  18 A. 
     The frame  16  is generally box-like in shape and has open front, rear and bottom sides. The frame  16  includes a top bracket  17  and side brackets  21 . Each side bracket  21  includes a stop  19 , which is a pin that is welded, screwed or secured with a nut or other suitable fastener to the side bracket  21 . The purpose of stops  19  is explained below. The plane of the top bracket  17  is generally horizontal when the assembly  10  is properly installed on a recreational vehicle on level ground. The steps  12  and  14  are located below the frame  16  in the retracted position as shown in  FIG. 4 . The frame  16  may also include a mounting assembly for attachment to a vehicle (not shown), or may be bolted, welded, or otherwise fixed to the vehicle. 
     As seen in  FIG. 1 , when the assembly  10  is in the extended position, the steps  12  and  14  are generally parallel relative to each other and the top bracket  17 . As seen in  FIG. 4 , when the assembly  10  is in the retracted position, the steps  12  and  14  are skewed rearward and downward at approximately 10 degrees and 15 degrees, respectively, relative to the top bracket  17 . 
     The steps  12  and  14  and the frame  16  are interconnected by a linkage assembly including three types of pivotable links; rearward links  20 , medial links  22 , and forward links  24 . The links  20 ,  22 , and  24  comprise straight, flat metal strips having two opposing lower and upper ends symmetrically arrayed along each side of the assembly  10 . For simplicity, these components are only numbered on a single side of the assembly  10  in  FIGS. 2 and 3 . The links  20 ,  22 , and  24  pivot around each point of attachment between the extended and retracted positions. Rectangular support bracket  64  is secured to the medial links  22  to reinforce the assembly  10  during use. The forward links  24  may also include a support bracket to reinforce the assembly during use. 
     The rearward links  20  connect the upper step  12  to the frame  16 . As most easily seen in  FIG. 1 , the upper ends of each rearward link  20  are pivotally mounted near the lower rearward corners of the side brackets  21 . The lower ends of each rearward link  20  are pivotally mounted near the rearward ends of the upper step arms  18 A. Each rearward link  20  also includes a tab  23  as most easily seen in  FIG. 3 . The purpose of the tab  23  is explained below. 
     As seen in  FIG. 1 , when the assembly  10  is in the extended position, the rearward links  20  are skewed downward and forward at approximately 15 degrees relative to the top bracket  17 . As seen in  FIG. 4 , when the assembly  10  is in the retracted position, the rearward links  20  are skewed rearward and downward at approximately 35 degrees relative to the top bracket  17 . 
     The medial links  22  have a dogleg shape and pivotally connect the lower step  14  to the frame  16  and have approximate midpoints pivotally connected to the upper step  12  near the point where the step  12  meets the upper step arm  18 A. Each medial link  22  is approximately three times as long as and slightly wider than the rearward links  20 . The upper ends of the medial links  22  are pivotally mounted to the upper forward corners of the side brackets  21 . The lower ends of the medial links  22  are pivotally mounted near the ends of the lower step arms  18 B. The pivot rod  26  connects to the upper ends of the medial links  22  at opposing ends of the rod  26 . 
     As seen in  FIG. 1 , when the assembly  10  is in the extended position, the medial links  22  are skewed forward and downward at approximately 70 degrees relative to the top bracket  17  and approximately straight down from step  12 . As seen in  FIG. 4 , when the assembly  10  is in the retracted position, the medial links  22  are skewed rearward and downward at approximately 35 degrees relative to the top bracket  17 . 
     The forward links  24  connect the lower step  14  to the upper step  12 . The forward links  24  are approximately twice as long as the rearward links  20  and approximately half the length of the medial links  22 . The upper ends of the forward links  24  are pivotally mounted near the forward corners of the upper step  12 . The lower ends of the forward links  24  are pivotally mounted to the lower step  14  near the point where the lower step arm  18 B extends from the lower step  14 . 
     As seen in  FIG. 1 , when the assembly  10  is in the extended position, the forward links  24  are skewed downward and slightly forward at approximately 85 degrees relative to the top bracket  17 . As seen in  FIG. 4 , when the assembly  10  is in the retracted position, the forward links  24  are skewed rearward and downward at approximately 25 degrees relative to the top bracket  17 . 
     Referring to  FIG. 3 , the assembly  10  also includes a pivot rod  26  extending transversely through the frame  16 . The longitudinal axis of the pivot rod  26  is generally perpendicular to the surface of the side brackets  21 . The pivot rod  26  connects to the upper ends of the medial links  22  at opposing ends of the rod  26 . As seen in  FIGS. 5-8 , the pivot rod  26  also includes a short finger assembly  36  rigidly mounted to the rod  26 . The finger assembly  36  extends radially away from the longitudinal axis of the rod  26 . A link arm  38  with a fixed length is connected to the finger assembly  36  with a universal joint  40 . The universal joint  40  allows the finger assembly  36  and link arm  38  to pivot about generally vertical (about pivot  41 ) and horizontal (about the axis of the pin  35  extending through the two arms  36 ) axes relative to the fingers  36 . 
     The link arm  38  is swivelly-mounted to a horizontal drive gear  42  by a ball joint  39  at the end of crank arm  44  which is fixed to gear  42 . The gear  42  has teeth (not shown) which extend circumferentially along an arcuate edge portion of the gear  42 . The gear  42  is centrally and pivotally mounted with a second pivot pin  48  to a motor mounting plate  50 . The motor mounting plate  50  is mounted to the frame  16 . The gear teeth (not shown) engage a second drive gear (not shown) within housing  52  which extends from a lower side of a motor  54 . The motor  54  is also mounted to the motor mounting plate  50 . 
     As shown in  FIGS. 5 and 7 , when the assembly  10  is in the extended position, the finger assembly  36  extends forward and downward relative to the pivot rod  26 , and the link arm  38  is horizontally rotated to a position below the pivot rod  26 . As shown in  FIGS. 6 and 8 , when the assembly is in the retracted position, the finger assembly  36  extends rearward and downward relative to the rod  26 , and the link arm  38  is rotated to a position below the drive gear  42 . 
     The motor  54  rotates the segment gear  42  approximately 90 degrees between the extended and retracted positions. The particular drive for driving the gear within housing  52  that meshes with segment gear  42  may be a worm gear drive, although any suitable drive could be used to rotate rod  26 . 
     In use, the frame  16  of the assembly  10  is mounted to the underside of a vehicle adjacent to the doorway (not shown). Prior to use, the assembly  10  is in the retracted position so that the upper and lower steps  12  and  14  are recessed beneath the frame  16 , as shown in  FIG. 4 . When the assembly  10  is actuated to move to the extended position, the motor  54  and associated drive train rotates the gear  42  clockwise approximately 90 degrees. As the gear  42  moves between these positions, the link arm  38  pushes the finger assembly  36  in a direction away from the gear  42  so that the rod  26  is rotated so as to extend the linkage assembly. This rotation causes the upper and lower steps  12  and  14  to move to the extended position. 
     When the step assembly  10  is in the extended position ( FIGS. 1 through 3 ), the tab  23  on the rearward link  20  engages the stop  19  on the side bracket  21  of the frame  16 . Applying a load to either step has a tendency to press the tab  23  on the rearward link  20  against the stop  19 , tending to rotate the link  20  further in the direction it rotates relative to the frame  16  when the step is extending, i.e., clockwise as viewed in  FIG. 3 . That is, the size and orientation of the links results in a gravitational load on either step holding the step assembly  10  in the extended position, with the link  20  pressing against the stop  19  so that the stop  19  reacts against the load. Additionally, the assembly  10  can still support the load if the motor/drive unit is removed. This is possible since the stop  19  completely resists the load applied on either step. In addition, the step assembly  10  does not need to be preloaded since the applied gravitational load does not tend to move the assembly to the retracted position. 
     When the step assembly  10  is extended, the arm  44  engages a stop  47 , as shown in  FIG. 5 . This stop  47  is engaged in addition to the tab  23  on the rearward link  20  engaging the stop  19 . The stop  47  is engaged after the tab  23  on the rearward link  20  engages the stop  19 . Therefore, play from the step assembly  10  is reduced since the arm  44  continues to move after the tab  23  on the rearward link  20  engages the stop  19 . 
     The stop  19  on the frame  16  may be a rotatable eccentric cam. If this is the case, rotating the stop  19  changes the extended position of the step assembly  10 . Dimensional uncertainties of the linkage assembly may cause the steps to be non-parallel or rotated at an angle with respect to the top bracket  17  of the frame  16 . The eccentric cam may be useful for making adjustments to ensure the steps are properly positioned if such problems occur. If the stop  19  is an eccentric cam, the stop  19  may also include a nut on the outer surface of the side bracket  21  for convenient adjustment of the stop  19 . 
     When the step assembly  10  is retracted, as shown in  FIG. 4 , the upper step  12  is preferably pulled against bumpers  53  on each side of the frame  16 . The lower step  14  is also pulled against bumpers  55  on the bottom of the upper step  12 . In addition, the arm  44  moves near, but does not normally engage, a stop  49 , as shown in  FIG. 6 . 
     Motion of the step assembly is preferably controlled by a current sensor. When the steps  12  and  14  contact bumpers  53  and  55  or the rearward link  20  contacts the stop  19  in the retracted or extended positions, respectively, the motor current will suddenly increase. The current sensor is capable of determining if a current threshold has been exceeded for the duration of a set time period. If such a current increase is sensed, the current sensor sends a signal to a controller to stop motion of the step assembly  10 . The current threshold and time period may be selected as appropriate for the current requirements of the motor  54 . 
     Of course, the description set out above is merely of an exemplary preferred version of the invention, and it is contemplated that numerous additions and modifications can be made. The example should not be construed as describing the only possible version of the invention, and the true scope of the invention will be defined by the claims.