Abstract:
A safety stilt for users requiring extended access to overhead or elevated surfaces has two slidably mated shells able to be adjusted to a variety of heights. Foot attachment means are attached to a top surface on the upper shell and a base defines a greater surface area than the surface area defined by the top surface.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to improved vertically adjustable safety stilts used to increase the height of wearers working in an overhead environment such as drywalling, painting, and electrical work. The stilt has a stable base and a safety release foot attachment mechanism that will release in the event of a fall, greatly improving a user&#39;s chance of landing safely. 
       BACKGROUND 
       [0002]    Workers in such occupations as drywall, painting, texturing or electrical work frequently must work in an overhead or ceiling environment that is, for most workers, far above the head and out of arm&#39;s reach. Several types of stilts have been previously developed in an effort to assist overhead workers. U.S. Pat. No. 5,645,515 to Armstrong et al. describes a spring loaded parallelogram stilt having foot straps and leg straps attached to a raised leg which attaches below the wearer&#39;s knee. A different concept is described by Hale in U.S. Pat. No. 5,593,373 wherein a shoe like device is provided with straps for attaching a human foot as well as a second strap, which extends below a user&#39;s foot to attach to an inverted bucket. An adjustable leg for stilts is described in U.S. Pat. No. 4,569,516 to Masterson wherein vertically slidable upper and lower struts are interfitted and provided with foot and leg straps. U.S. Pat. No. 3,595,339 to Ballard et al. describes a pair of spring loaded, adjustable stilt boots. Vertically configured sliding adjustable riser halves having non-breakaway foot straps are described in U.S. Pat. Des. No. 217,371, to Clark. U.S. Pat. No. 2,832,079 to Bailey describes a stilt device which features a foot plate with straps for foot attachment with a pair of tubular risers extending downward to a tread-plate approximately the same size as the foot plate. In all cases, the foot plate is no larger than the portion of the stilt contacting the floor, resulting in a less stable device. Also in all cases, attachment means used to secure the user&#39;s foot to the stilt device are firmly attached to the stilt and therefore unable to break away in the event of a fall. Thus, what is clearly needed is an improved safety stilt device which offers improved stability. Such a device combined with a safety release foot attachment that allows the user&#39;s foot to release from the stilt device in the event that the user falls during use, allowing a greatly reduced chance of falling safely, would be even more desirable. 
       SUMMARY 
       [0003]    In one aspect the invention comprises a safety stilt having a first shell which defines a vertical axis and a horizontal axis, a top surface and a base. The top surface has a lesser surface area than the area defined by the base. A second shell defines a vertical axis and a horizontal axis, a top surface and a base, with the top surface having a lesser surface area than the area defined by the base. The top surface of the second shell is sized and shaped to be slidably received within the base of the first shell, allowing the second shell to move along the vertical axis of the first shell. Additionally, the safety stilt has height adjustment means allowing the relative position between the first shell and the second shell along the vertical axis to be securely adjusted. Releasable foot attachment means allow a user&#39;s foot to be secured to the top surface, which will release from the safety stilt if the user falls. 
         [0004]    In another aspect the invention comprises a safety stilt having a first shell which defines a vertical axis and a horizontal axis, a top surface and a base. The top surface has a lesser surface area than the area defined by the base, and a wall extends between and connects the top surface and the base. A second shell defines a vertical axis and a horizontal axis, a top surface and a base, with the top surface having a lesser surface area than the area defined by the base. A wall extends between and connects the top surface and the base. The second shell is sized and shaped to be slidably received within the base of the first shell, which allows the top surface of the second shell to move along the vertical axis of the first shell. A rib is configured into the first shell, defines an outer surface and extends from the wall of the first shell. A rib is similarly configured into the second shell, defines an outer surface, and extends from the wall of the second shell. The rib of the first shell further defines an inner surface corresponding with the outer surface of the rib such that the outer surface of the rib of the second shell slidably mates with the inner surface of the rib of the first shell. Height adjustment means are provided which allow the relative position between the first shell and the second shell along the vertical axes to be securely adjusted. Releasable foot attachment means allowing a user&#39;s foot to be secured to the top surface are attached to the first shell, which will release from the safety stilt if the user falls. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a perspective view of the first shell. 
           [0006]      FIG. 2  is a first side view of the first shell. 
           [0007]      FIG. 2A  is a cross section taken through the lines  2 A- 2 A as shown in  FIG. 2 . 
           [0008]      FIG. 2B  is a cross section taken through the lines  2 B- 2 B as shown in  FIG. 2 . 
           [0009]      FIG. 3  is a second side view of the first shell. 
           [0010]      FIG. 4  is a top view of the first shell. 
           [0011]      FIG. 5  is a bottom end view of the first shell. 
           [0012]      FIG. 6  is a perspective view of the second shell. 
           [0013]      FIG. 7  is a first side view of the second shell. 
           [0014]      FIG. 7A  is a cross section taken through the lines  7 A- 7 A as shown in  FIG. 7 . 
           [0015]      FIG. 7B  is a cross section taken through the lines  7 B- 7 B as shown in  FIG. 7 . 
           [0016]      FIG. 8  is a second side view of the second shell. 
           [0017]      FIG. 9  is a bottom end view of the second shell. 
           [0018]      FIG. 10  is a top view of the second shell. 
           [0019]      FIG. 11  is a perspective view of the first and second shells fitted together and assembled to form the present invention. 
           [0020]      FIG. 12  is a side view of the present invention with the first and second shells attached to each other to form a stilt having a relatively tall configuration. 
           [0021]      FIG. 13  is a side view of the present invention with the first and second shells attached together to form a stilt having a relatively short configuration. 
           [0022]      FIG. 14  is a side view of the first shell. 
           [0023]      FIG. 15  is a top view of the top surface. 
           [0024]      FIG. 16  is a side view of an embodiment of a release fastener. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    The particulars shown herein are by way of example and for purposes of illustrative discussion of the invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for the fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. 
       Nomenclature 
       [0000]    
       
           10  First Shell 
           12  Vertical Axis 
           14  Horizontal Axis 
           16  Top Surface 
           18  Wall 
           20  Base 
           21  Lip 
           22  Rib 
           24  Hollow Space 
           26  Raised Ridge 
           28  Heel End 
           30  Toe End 
           40  Height Adjustment Aperture 
           42  Foot Strap Aperture 
           50  Foot Strap Assembly 
           50   a  Foot Strap Half (Outside) 
           50   b  Foot Strap Half (Inside) 
           52  Release Fastener 
           54   a  Bolt 
           54   b  Nut 
           70  Second Shell 
           72  Vertical Axis 
           74  Horizontal Axis 
           76  Top Surface 
           78  Wall 
           80  Base 
           81  Lip 
           82  Rib 
           84  Hollow Space 
           86  Raised Ridge 
           88  Heel End 
           90  Toe End 
           100  Safety Stilt 
       
     
       Construction 
       [0059]      FIG. 1  shows a perspective view of the first shell  10  of the safety stilt  100  of the present invention. It is seen that the first shell  10  defines a vertical axis  12  and a horizontal axis  14  as well as a top surface  16  for receiving a user&#39;s foot and a wall  18  which supports and vertically separates the top surface  16  from the base  20 . In one embodiment, the top surface  16  defines a plane that is substantially parallel with a plane defined by the perimeter of the base  20 . In other embodiments (not shown) the plane defined by the top surface  16  may be at an angle to the plane defined by the perimeter of the base  20 , for reasons of comfort or safety. A raised ridge  26  extends above and at least partially surrounds the perimeter of the top surface  16 . As shown in  FIG. 1 , a heel end  28  is surrounded by the ridge  26  whereas a toe end  30  is not surrounded. The purpose of the ridge  26  is to enhance the security and safety of the safety stilt  100  while in use, by providing a tactile guide to when the proper position of the user&#39;s foot on the top surface  16  has been located. 
         [0060]    The surface area defined by the base  20  is greater than the surface area defined by the top surface  16 , which allows a second shell  70  to be slid into the open base  20  of first shell  10 , as explained in more detail below. In one embodiment (not shown), a single rib  22  substantially the length of the vertical axis  12  extends in a substantially tapered manner from the base  20  along the wall  18  to the top surface  16  and runs substantially parallel with the vertical axis  12 . In other embodiments, as shown in  FIGS. 1-2B ,  4 - 5 , and  11 - 15 , a plurality of ribs  22  is provided to enhance the overall strength and assembled rigidity of the safety stilt  100 , without substantially increasing the weight of the safety stilt  100 .  FIGS. 2A-2B  are cross sections taken through the lines  2 A- 2 A and  2 B- 2 B of  FIG. 2  respectively and show that a hollow space  24  is formed behind and corresponds in position with the rib  22  which extends from and is part of the wall  18 . It is also understood and therefore within the scope of the invention, that in one embodiment (not shown) the safety stilt will also work without any ribs configured into the wall  18 .  FIG. 2  shows a first side view (from the wider side—unnumbered) of the first shell  10 .  FIG. 3  shows a second side view (from the narrower or end side—unnumbered) of the first shell  10 . While no ribs are shown on the end (unnumbered) shown in  FIG. 3 , it is contemplated by and therefore within the scope of the invention to have a rib  22  or ribs  22  on this end also. 
         [0061]    In one embodiment, as shown in  FIGS. 1-2  and  5 , the base  20  is provided with a widened lip  21  surrounding its perimeter which strengthens the base  20  extending its useful life.  FIG. 4  shows a top view of the first shell  10  including the top surface  16  to which a human foot can be attached prior to using the safety stilts  100 . As best shown in  FIG. 15 , the top surface  16  may be optionally configured to have a textured surface (unnumbered) which enhances safety by improving the grip between the top surface  16  and a user&#39;s foot.  FIG. 5  shows a bottom view of the first shell  10  including the perimeter of the base  20 , which also shows that the base  20  is open and contains no restrictions to entry. As seen in  FIGS. 11-13 , at least one foot strap assembly  50 , which includes an outside foot strap half  50   a  and inside foot strap half  50   b , is attached proximate the top surface  16  to attach a user&#39;s foot to the first shell  10 . In one embodiment, the foot strap assembly  50  is attached to the first shell  10  through an appropriately located aperture  42  by a release fastener  52  such as a bumper fascia retainer, part number 12571, manufactured by AV-EE-Co, Cold Springs, Ky., (as shown in  FIG. 16 ) commonly used in the automotive industry to attach door panels. Other fasteners would also work such as which will pull out when a sudden breakaway force between approximately 15-30 pounds is applied to the safety stilt  100  in the event of a fall are also contemplated by and therefore within the scope of the invention. The release fastener  52  releases the user&#39;s foot from the safety stilt  100 , giving the user a greatly increased chance of landing safely on his/her feet as opposed to falling down from an elevated height with the stilts firmly and unreleasably attached. The foot strap assembly  50  is provided with fastening means (not shown) for attaching the outside foot strap half  50   a  and inside foot strap half  50   b  to each other to adjustably accommodate various sized feet. Suitable fastening mechanisms include but are not limited to hook and loop fastening material, buckles, snaps, and laces. In the embodiment where hook and loop fastener is used, a breakaway force of approximately 35 to 40 pounds per square inch is sufficient. It should be mentioned that the first shell  10  can be used by itself in instances where the extra height provided by the first shell  10  alone is sufficient and no variable height adjustment is needed. 
         [0062]      FIG. 6  shows a perspective view of the second shell  70  of the safety stilt  100  of the present invention. It is seen that the second shell  70  defines a vertical axis  72  and a horizontal axis  74  as well as a top surface  76  and a wall  78  which supports and vertically separates the top surface  76  from a base  80 . The top surface  76  defines a plane that is substantially parallel with a plane defined by the perimeter of the base  80  as it contacts the floor or other supporting surface. The surface area defined and enclosed by the base  80  is greater than the surface area dimension defined by the top surface  76 , which enables the second shell  70  to slidably fit into upwardly tapering first shell  10 . In one embodiment (not shown), a rib  82  substantially the length of the vertical axis  72  extends in a substantially tapered manner from the base  80  to the top surface  76  and runs parallel with the vertical axis  72 . In other embodiments, as shown in  FIGS. 6-8 , and  10 - 14 , a plurality of ribs  82  is provided to enhance the overall strength and assembled rigidity of the safety stilt  100 , without substantially increasing the weight of the safety stilt  100 .  FIGS. 7A-7B  are cross sections taken through the lines  7 A- 7 A and  7 B- 7 B of  FIG. 7  respectively and show that a hollow space  84  is formed behind and corresponds in position with the rib  82  which extends from and is part of the wall  78 . The hollow space  84  of the second shell  70  is sized and located to slidably receive the rib  22  of the first shell  10 , thereby providing enhanced stability and rigidity to the assembled stilt  100 . It is understood and therefore within the scope of the invention, that in another embodiment (not shown) the safety stilt will also work without any ribs configured into the wall  78 .  FIG. 7  shows a first side view (from the wider side—unnumbered) of the second shell  70 .  FIG. 8  shows a second side view (from the narrower or end side—unnumbered) of the second shell  70 . In one embodiment, as shown in  FIGS. 6 and 7 , the base  80  is provided with a widened lip  81  surrounding its perimeter which strengthens the base  80 , contacts the floor or support surface and adds extra stability due to an increased perimeter defined by the base  80 . While no ribs (not shown this view) are shown on the end (unnumbered) shown in  FIG. 8 , it is contemplated by and therefore within the scope of the invention to have a rib  82  or ribs  82  on this end also.  FIG. 9  shows a top view of the second shell  70  including the top surface  76 .  FIG. 10  shows a bottom view of the second shell  70  including the perimeter of the base  80  which contacts the floor or other surface while the safety stilt  100  is being used. 
         [0063]    An advantage of the stilts  100  of the present invention is that the first shell  10  and second shell  70  are substantially identical prior to attachment of the foot strap assembly  50  and can thus be made from the same mold. Injection molds are extremely expensive to have built, in some cases costing several hundred thousand dollars each, which facilitates a great manufacturing cost savings. As shown in  FIGS. 11-13 , the first shell  10  is slidably fitted over the second shell  70  to create the safety stilt  100  of the present invention. 
         [0064]    Materials used to construct the first  10  and second  70  shells include, but are not limited to high density polyethylene such as that sold under the trade name of Fortiflex® and manufactured by Ineos Polyolefins. Other plastic materials would work equally well and are therefore within the scope of the invention. A wall  18 ,  78  thickness range of ⅛″ to ¼ inch is sufficiently strong to be able to support a worker&#39;s weight of at least 250 lbs without adding unnecessary weight. In one embodiment, the shells  10 ,  70  are made by injection molding, followed by trimming and creation of a plurality of at least one column of height adjustment apertures  40  parallel with the vertical axes  12 ,  72 , however, the height adjustment apertures  40  and foot strap apertures  42  can also be formed as part of the molding process. Foot strap apertures  42  are located proximate the top surface  16  of the first shell  10  and can be created by a cutting or drilling process or as part of the molding process. It should be mentioned that in one embodiment as shown in  FIG. 15 , four foot strap apertures  42  are provided to allow attachment of two foot strap assemblies  50  (front and back) should the user desire additional foot securement. The release fasteners  52  attaching the foot strap assembly  50  to the first shell  10  can be made of nylon or other plastic materials. The foot strap assembly  50  can be made of nylon backed hook and loop fastening material or leather backed hook and loop fastening material. The bolt  54   a  and nut  54   b  that are used to attach the first shell  10  to the second shell  70  and adjust their relative position, can be made of suitable non-conductive materials such as nylon or other plastics. In one embodiment, the height adjustment apertures  40  are configured to be square to be able to accommodate the square configured underside of the head of a carriage bolt (not shown), which as the advantage of not requiring an additional wrench to tighten the nut  54   b  on the other side. 
       Use 
       [0065]    Using the safety stilt  100  involves first determining the height of the surface to be worked on (the workspace). The workspace height is factored with the height and working preferences of the user to determine the degree of height adjustment of the safety stilt  100 . Presumably two safety stilts will be used (one for each foot of the user). The desired height is set by inserting a bolt  54   a  through the appropriate height adjustment aperture  40  followed by securing the bolt  54   a  with a non-insulating nut  54   b  on the inside of the safety stilt  100 . Depending on the particular configuration of the first  10  and second  70  shells, a plurality of bolts  54   a  and nuts  54   b  may be used to set the desired height of the safety stilt  100 . Because of the taper between the top surface  16 ,  76  and base  20 ,  80 , the top surface  76  of the second shell  70  is able to slide within the open base  20  of the first shell  10  to create a variety of possible adjustment heights. In one embodiment, the first  10  and second  70  shells are approximately 31 inches high, between the base  20 ,  80  and the top surface  16 ,  76  respectively. Height adjustment apertures  40  can be located at any interval and in one embodiment are spaced about three inches apart. 
         [0066]    Upon properly adjusting the height of the individual safety stilts  100  the user steps on to the top surface  16  and after ensuring that the user&#39;s heel is proximate the heel end  28  of the raised ridge  26 , securely fastens the foot strap assemblies  50   a ,  50   b  together to stably attach the user&#39;s foot to the safety stilt  100 . Should the user fall during use, one or more release fastener  42  attaching the foot strap assembly  50  to the first shell  10  will pull out, allowing the user to safely land on his/her feet as opposed to falling from the height of the still attached stilts  100 . In the event that the safety stilt  100  releases during use, a new release fastener  42  should be used to reattach the foot strap assembly  50  to the first shell  10 . This is because the original release fastener  42  may have become damaged as a result of releasing under force and could be unable to provide the specified amount of release force required for additional releases.