Abstract:
An extendible leg device for use in supporting a portion of a platform assembly above a floor surface. The extendible leg device has a leg tube that slidably receives a foot tube which is moved relative to the leg tube via selective rotation of an axle. The axle has a first link pivotally connected to a first end of a second link which second link is further pivotally connected at its second end to the foot tube.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention generally relates to leg devices for load carrying platforms, such as in portable staging and seating equipment. More particularly, the invention relates to an extendible leg device for use in supporting a portion of a platform assembly above a floor surface.  
           [0003]    2. Discussion of the Prior Art  
           [0004]    Platform assemblies are widely used in staging and seating equipment for auditoriums, gymnasiums, and event halls to accommodate performers or spectators. Depending on the intended use, a facility may require such equipment to be moved between use and storage positions on a repeated basis. To accommodate such repeated movement of the equipment, manufacturers may incorporate wheels, such as of the caster type. However, straight legs significantly out perform caster wheels with respect to platform stability and load carrying capacity. Hence, it is desirable to have an extendible leg device which permits transportation of a load carrying platform assembly on caster wheels while also offering the advantage of removing the load from the wheels, in whole or in part, so as to “park” the equipment once it has reached its intended location for use or storage. Such parking enhances platform stability and load carrying capacity. Transportation and parking may be accomplished in at least two ways. The assembly could have attached wheels for floor engagement during transportation and then extendible legs having foot pads, where such legs extend to lift the assembly to remove at least a portion of the load from the wheels for parking. Alternatively, the assembly could have fixed legs for parking and extendible legs having wheels, where the legs having wheels extend to lift the assembly onto the wheels for use in transporting the assembly on a floor surface.  
           [0005]    The extendible leg device of the present invention could be adapted for use with a platform assembly or the like in a side to side format or front to rear. Given that, in a position for use or storage, there may be obstructions, such as a side wall when using a side to side format, it is desirable to be able to access and control the raising or lowering of an extendible leg device from either end of the device.  
           [0006]    It is further advantageous to conceal components of the extendible leg device within the structural components of the platform assembly, such as within commonly used tubular frame members, to protect such components from potential damage and to reduce undesirable pinch points.  
           [0007]    It is also advantageous to achieve simple operation of such an extendible leg device, to enhance reliability and serviceability and so that it may be operated by unskilled individuals, with only a simple hand tool, such as a crank handle.  
           [0008]    The present invention overcomes disadvantages of the prior art, while providing the above mentioned desirable features in an extendible leg device.  
         SUMMARY OF THE INVENTION  
         [0009]    The purpose and advantages of the invention will be set forth in and apparent from the description and drawings that follow, as well as will be learned by practice of the invention.  
           [0010]    The present invention is generally embodied in an extendible leg device for use with load carrying platforms, such as in staging or seating equipment. In a first aspect, the invention provides an extendible leg device having a plurality of substantially upright leg tubes, where each leg tube has a side wall, and a plurality of foot tubes, where each foot tube slidably engages a respective leg tube. The device further comprises an axle extending through the side wall of each leg tube and having a plurality of first links fixedly connected to the axle. A plurality of second links is provided with each second link pivotally connected at a first end to a first link and pivotally connected at a second end to a foot tube, wherein rotation of the axle causes slidable displacement of the foot tubes relative to the leg tubes.  
           [0011]    In another aspect, the invention provides an extendible leg device having at least an extended position and a retracted position. The device comprises at least one substantially upright leg tube having a side wall and at least one foot tube slidably received in the at least one leg tube. An axle extends through the side wall of the leg tube and at least one first link is fixedly connected to the axle. At least one second link is pivotally connected at a first end to the at least one first link and pivotally connected at a second end to the at least one foot tube.  
           [0012]    In still a further aspect, the present invention provides an extendible leg device having a plurality of substantially upright leg tubes, with each leg tube having a side wall. Also provided is a plurality of foot tubes, with each foot tube slidably engaging a respective leg tube. The device further comprises a substantially horizontal tube having a first end connected to a first upright leg tube and a second end connected to a second upright leg tube. An axle extends through the side wall of each leg tube and the substantially horizontal tube, and a plurality of first links is fixedly connected to the axle and disposed in the upright leg tubes. The device further comprises a plurality of second links, each second link being pivotally connected at a first end to a first link and pivotally connected at a second end to a foot tube, where rotation of the axle causes slidable displacement of the foot tubes relative to the leg tubes.  
           [0013]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and provided for purposes of explanation only, and are not restrictive of the invention, as claimed. Further features and objects of the present invention will become more fully apparent in the following description of the preferred embodiment and from the appended claims.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    In describing the preferred embodiment, reference is made to the accompanying drawing figures wherein like parts have like reference numerals, and wherein:  
         [0015]    [0015]FIG. 1 is a front perspective view of an embodiment of a leg assembly of a platform assembly having a pair of caster wheels and employing an extendible leg device.  
         [0016]    [0016]FIG. 2 is an expanded perspective view of a portion of the leg assembly in accordance with FIG. 1.  
         [0017]    [0017]FIG. 3 is a front perspective view of a foot assembly and portions of an embodiment of an axle assembly as may be used in the device of FIGS. 1 and 2.  
         [0018]    FIGS.  4 A- 4 C are end views of three positions of the foot assembly in combination with the axle assembly of FIG. 3, as they are moved within the leg tube of FIG. 2. 
     
    
       [0019]    It should be understood that the drawings are not to scale and that certain aspects are illustrated in phantom views. While considerable mechanical details of an extendible leg device, including details of fastening means and other plan and section views of the particular embodiment depicting the invention have been omitted, such detail is not per se part of the present invention and is considered well within the comprehension of those skilled in the art in light of the present disclosure. It also should be understood that the present invention is not limited to the preferred embodiment illustrated.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0020]    Referring generally to FIGS.  1 - 3  and  4 A- 4 C, it will be appreciated that the extendible leg device  10  of the present invention generally may be embodied within numerous configurations of a leg assembly  12  for a load carrying platform assembly. Ideally, the extendible leg device  10  is to be used with portable platform assemblies that have wheels  14  mounted to a leg assembly  12 , which may run side to side or front to rear relative to the platform assembly. This is shown, for instance, in FIG. 1 where a pair of caster wheels  14  are mounted to a substantially horizontal member  16 . Wheels  14  may be mounted to member  16  in any number of ways and in FIG. 2, a flange of caster wheel  14  is fastened to a flange attached to but spaced from the bottom of member  16 . It will be appreciated that the extendible leg device  10  alternatively may be used to provide adjustment between two platform heights for platform assemblies that do not have wheels.  
         [0021]    As shown in FIGS. 1 and 2, fixedly attached to each end of substantially horizontal member  16  is an upright leg tube  18 . Leg tube  18  may have a mounting plate  20  at its upper end for connection to the remainder of the platform assembly. This configuration allows a common leg assembly  12  to be mounted to platforms of varying heights. Alternatively, leg tube  18  may extend further upward to be directly incorporated into the remainder of the platform structure. Each leg tube  18  is open at its lower end to receive a foot assembly  20 , shown in FIG. 3. It will be appreciated that each upright leg tube  18  and member  16  need not be, but preferably is constructed from thin wall steel tube, preferably rectangular tube, where rectangular tube is understood to include square tube.  
         [0022]    The foot assembly  20  of FIG. 3 includes an upright foot tube  22 . A foot pad  24  is fixedly attached to the lower end of foot tube  22 , such as by welding. As shown in FIG. 4A, foot pad  24  preferably carries a covering  26  to protect floor surfaces. The covering  26  may, for instance, be a detachable rubber cover or the foot pad  24  may be dipped in a plasticized rubber coating material or the like. One of skill in the art will appreciate that wheels  14  may be adapted for mounting to upright leg tubes  18  instead of member  16 , which would still facilitate parking the platform assembly by extending foot tubes  22  relative to leg tubes  18 . Further, as at least one alternative to the embodiment of FIG. 1, fixed legs could be used in place of the wheels shown, and wheels  14  could replace foot pads  24  at the bottom of foot tubes  22 . This would facilitate parking the device when the foot tubes  22  with wheels are retracted, and transportation of the assembly when the foot tubes  22  are extended. It will further be appreciated that the wheels  14  need not necessarily be inboard of the legs.  
         [0023]    In the preferred embodiment shown in FIG. 3, fixedly attached to the exterior four corners of upright foot tube  22  are right angle vertical guides  28 . Guides  28  help prevent binding when a foot tube  22  slides within a leg tube  18 . It will be appreciated that guides  28  may not be necessary or guides of different shape may be necessary depending on the sizes and shapes of leg tubes  18  and foot tubes  22 .  
         [0024]    Foot tube  22  also receives through its side walls a pivot  30 . A cam link  32  is pivotally connected to pivot  30 , and has an aperture proximate its distal end. It will be appreciated that one or more cam links  32  could be employed, and that cam link  32  may be of an alternative construction, such as a single piece having a plurality of projecting flanges.  
         [0025]    The extendible leg device  10  also includes an axle assembly  40  having an axle  42  which preferably is constructed of circular steel tube to facilitate bearing surfaces for rotation of axle  42 , and to reduce weight and inherent deflection associated with the weight of axle  42 . Fixedly attached to and proximate each end of axle  42  is a pair of crank links  44 . Each crank link  44  includes an aperture proximate its distal end to removably receive a pivot  46 . It will be appreciated that a single crank link  44  may be employed, and that crank links  44  may be of an alternative construction, such as a single piece having a plurality of projecting flanges. Similarly, pivot  46  may be provided in any one of many ways available to one of skill in the art, and is shown in FIG. 3 as a shouldered bolt.  
         [0026]    Also fastened to axle  42 , proximate its mid-point and relatively opposite the distal end of crank links  44 , is a lobe  48  preferably formed from round bar stock of a plastic material such as Delron™ or Nylon™. Lobe  48  may be of alternative constructions and may consist of a plurality of spaced apart or adjacent pieces attached to axle  42  in various ways. Lobe  48  is shown in FIG. 3 as attached to axle  42  using countersunk fasteners, such as machine screws. In the embodiment shown, each end of axle  42  has a slot  50  for engagement with a crank handle to achieve clock-wise and counter-clockwise rotation to axle  42 . It will be appreciated that various alternative structures and tools may be employed to facilitate such rotation of axle  42 .  
         [0027]    Each leg tube  18  has openings in its side wall. Substantially horizontal member  16  need not be a tube. However, to conceal the axle assembly  40 , member  16  is preferably a tube. In the preferred embodiment, the opening in leg tubes  18  are aligned with the interior of tube  16  to permit access to the interior of tube  16 . Accordingly, the axle assembly  40  is received through the openings in the side wall of upright leg tubes  18  and through the interior of tube  16 .  
         [0028]    Each foot assembly  20  is received in the lower end of a leg tube  18 . With the axle assembly  40  and foot assembly  20  in position, pivot  46  may be installed to pivotally connect crank links  44  to cam link  32 . An axle retaining plate  60 , having an axle receiving aperture, is removably mounted to each leg tube  18  to provide a bearing surface for axle  42  and to permit an end of axle  42  to project therethrough. Alternative constructions may be employed to retain axle  42 , as well as to provide separate bearings for axle  42 .  
         [0029]    With the axle assembly  40  and foot assemblies  20  pivotally connected, axle  42  may be rotated to move foot tube  22  between a retracted position and an extended position. This is shown in FIGS.  4 A- 4 C. In the preferred embodiment shown in FIG. 4A, the lobe  48  is trapped in the lower right-hand corner of the square tube  16 . This effectively locks the extendible leg device  10  in a retracted position due to the generally downward deflection present in the center of axle  42 , as depicted by  42 ′.  
         [0030]    From the retracted position shown in FIG. 4A, if enough torque is applied via slot  50 , axle  42  may be rotated counter-clockwise, as shown in FIG. 4B, forcing lobe  48  to run into the right-hand interior side wall of tube  16 . Given that lobe  48  is mounted proximate the midpoint of elongated axle  42 , this forces axle  42  to deflect or bend throughout its length, as depicted by the horizontally offset position  42 ′ of the center of axle  42  in FIG. 4B. In light of the intended interference between lobe  48  and the interior wall of tube  16 , it is desirable that lobe  48  be made of a plastic material to prevent binding and wear on the inside of tube  16 . As axle  42  is rotated counter-clockwise from the retracted position, crank links  44  drive cam link  32  and foot tube  22  downward.  
         [0031]    Axle  42  may continue to be rotated counter-clockwise until foot tube  22  goes slightly beyond full extension from leg tube  18 , and crank links  44  contact the right-hand interior side wall of tube  16 . In this extended leg position, lobe  48  becomes trapped against the interior top wall of tube  16 , causing some generally downward deflection in the center of the axle as depicted by  42 ′, and effectively locking the device  10  in the extended leg position shown in FIG. 4C. In the embodiment shown, due to the deflection of axle  42  and the positioning of lobe  48  within tube  16 , some torque must be applied via the axle slot  50  to rotate axle  42  clockwise to unlock and begin retracting foot tube  22 .  
         [0032]    Alternative constructions of member  16 , such as a circular tube will provide slightly different operation of device  10 . For instance, lobe  48  would then preferably be adapted to be in constant contact with tube  16  to prevent foot tube  22  from inadvertently lowering when in the retracted position. Similarly, axle assembly  40  could be configured so as not to be concealed within member  16 , and therefore member  16  may be, but need not be tubular. If axle assembly  40  does not extend through member  16 , then lobe  48  on axle  42  could be made to contact an exterior surface of member  16  when axle  42  is in selected rotational positions.  
         [0033]    It will be appreciated that platform assemblies are load bearing structures that may carry people and equipment, such as with portable staging and seating equipment. Therefore, extendible leg device  10  should be suitably constructed. For instance, the structural members of the device  10  preferably are constructed of thin wall tubing, straight bar stock, right angle bar stock, and plate of suitable materials, for instance, steel, alloy, aluminum or high strength plastics. Components may be joined in any number of conventional manners, such as by use of welding or with suitable fasteners.  
         [0034]    It also should be understood that while a preferred embodiment has been described herein, any of a variety of fastening means and suitable materials of construction and dimensions may be used to satisfy the particular needs and requirements of the end user. It will be apparent to those skilled in the art that various modifications and variations can be made in the design and construction of an extendible leg device without departing from the scope or spirit of the present invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein.