Abstract:
A clip for use in a cable system for stretching a sheet across a surface and maintaining it under tension, the clip comprising a base plate and a top plate. The base plate has a pair of opposing retaining arms extending from the top surface and a recessed area defined in the base plate. The top plate has a hook protruding from the top surface having a channel defined therein. The top plate slides between the arms of the base plate and is removably retained therein and the plates engage the edge of a sheet. The hook removably engages a cable and the sheet is stretched when the cable is tensioned. The clip can be retained on the cable when a sheet is to be replaced by partially separating the two plates.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This patent application is a continuation-in-part of U.S. patent application Ser. No. 12/246,167, filed Oct. 6, 2008 now U.S. Pat. No. 8,020,260, which is a continuation-in-part of U.S. patent application Ser. No. 12/104,257, filed Apr. 16, 2008 now U.S. Pat. No. 7,836,562, which claims the benefit of U.S. Provisional Patent Application No. 60/912,058, filed Apr. 16, 2007, the disclosures of which are incorporated herein by reference in their entirety. This patent application is a continuation-in-part of U.S. patent application Ser. No. 12/246,167, filed Oct. 6, 2008, which is also a continuation-in-part of U.S. patent application Ser. No. 12/174,449, filed Jul. 16, 2008 now U.S. Pat. No. 8,042,292, which claims the benefit of U.S. Provisional Patent Application No. 60/950,025, filed Jul. 16, 2007, the disclosures of which are incorporated herein by reference in their entirety. 
    
    
     FIELD 
     The present disclosure relates to locking clips for holding and maintaining a generally flat sheet of material in a tensioned or stretched condition on a billboard or similar flat backing surface. 
     BACKGROUND 
     Large printed vinyl sheets have generally replaced pasted paper signs in the outdoor advertising industry. Installation of large printed vinyl display sheets requires two or more workers who push light weight fiberglass or similar non-conductive rods through pockets heat-sealed in each of the four end surfaces of a sheet, which forms the advertising or display face of a billboard. 
     The vinyl sheets typically have to be hung from the top of a billboard after the top rods are secured to the billboard frame and then pulled or tensioned horizontally and vertically across the metal backing of the billboard. Various tensioning devices have been used. Generally the installation process requires at least two workers who take on average approximately 20 to 30 minutes or more to complete an installation. 
     The industry recently developed light weight vinyl or polyethylene display sheets, which can be recycled and cost less but are not as strong as the vinyl in predominate use today. Its lighter weight and lesser strength make the light weight vinyl or polyethylene display sheets unsuitable for heat-sealing pockets and more subject to tearing from excess tensioning and repeated installations and removals. Display sheets are frequently moved from one billboard location to another to save on printing and material costs. 
     U.S. Pat. No. 6,789,295 discloses a clamp apparatus for application to a plate, sheet, fabric or thin film by gripping two opposite sides of the object. A rope or cord is inserted into holes in the top and bottom units comprising the clamp apparatus. The rope or cord is secured to a stationary object. There is no accommodation for attachment to a cable, although each individual rope or cord could be tied to a cable. However, uniform tension to the display sheet can only be realized if the length of each piece of rope or cord running from each clamp apparatus around the perimeter of the display is identical. If the clamp apparatus is attached directly to the cable with the cable running through the holes in the top and bottom units, the clamp apparatus would be turned approximately 90 degrees to the face of the billboard or display surface, resulting in undesirable twists, folds, and wrinkles in the display sheet. 
     International Patent Publication No. WO 03/098055 issued to Gunnarsson discloses a clamp apparatus closely similar to the apparatus disclosed in U.S. Pat. No. 6,789,295. The clamp apparatus disclosed in the International Publication has the same deficiencies of U.S. Pat. No. 6,789,295 described above. 
     U.S. Pat. No. 4,686,748 issued to Kaivanto discloses an attachment device for gripping the edge of a sheet, but does not disclose a mechanism for removably attaching the device directly to a portion of a cable while the cable is under tension. The clamping mechanism squeezes the edge of a sheet or fabric between the curved edges of one unit and the tapered length of a second unit resulting in distortion, folding, or creasing of the sheet or fabric. This is an undesirable result for a billboard or other application where a flat display sheet is preferred. Additionally, the eyelet/rope combination of this attachment device would permit the display sheet to twist. As noted above, unless uniform lengths of rope or cord were used to attach the several clamps to a tension cable, uneven force would be applied to the display sheet resulting in folds, wrinkles, or other distortions of the display sheet. 
     It would be desirable to have a clip which could attach to a cable running horizontally and vertically along the perimeter of a billboard or display surface, which will minimize or eliminate twisting and wrinkling of the display sheet. It would be further desirable to have a clip which would allow application to a cable running parallel to the face of the clip and which clip would remain attached to the cable while one display sheet is removed and another installed in its place. It would be further desirable to have a clip that could be retained on the cable when a sheet is being dismounted, remounted or when the clip is not in use so that the clip is not dropped or lost. It would be further desirable to have a two-piece clip which will allow for limited movement of the two pieces with respect to each other when a sheet is detached from the clip yet prevent complete separation of the two pieces. 
     Kaivanto and Gunnersson disclose clips which require removal from the cable in order to become disengaged from the display sheet. To remove the sheet you have to remove the pressure. With Kaivanto, the bottom plate would fall off. It would be desirable to have a clip which could be retained on the cable during sheet changeout. 
     SUMMARY 
     The present disclosure provides a clip for use in a cable tensioning system. One aspect of the present disclosure provides a clip for use in a cable tensioning system comprising (a) a base plate comprising a generally flat base member having a front portion with a gripping surface, a middle portion containing a recess, and a rear portion with a pair of opposing retaining arms extending upward from the top surface, each arm having an angled portion angled toward the other arm, the retaining arms capable of engaging the top plate, a bottom surface, a front edge and a rear edge, and at least one slot formed in the base member; and, (b) a top plate comprising a top surface having a hook extending upward therefrom, the hook and the top surface defining a channel capable of receiving a portion of a cable, a bottom surface, and, a front portion and front edge and a rear portion and rear edge, the rear portion being wider than the front portion, wherein the top plate is adapted to secure an edge of a substantially flat medium between the base plate and the top plate when the top plate and the bottom plate are in an engaged relationship, wherein the channel can receive a portion of a cable, and the clip remains attached to the cable. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present disclosure are illustrated in the drawings in which like reference characters designate the same or similar parts throughout the figures of which: 
         FIG. 1  is a schematic perspective view of the clip apparatus installed on a cable and holding a vinyl sheet in conjunction with a billboard, also showing a guide clip. 
         FIG. 2  is a perspective view of a top and bottom plate of the embodiment of  FIG. 1 . 
         FIG. 3  is a perspective view of a top plate according to one exemplary embodiment. 
         FIG. 4  is a rear elevation view of the top plate of  FIG. 2 . 
         FIG. 5  is a left side elevation view of the top plate of  FIG. 2 . 
         FIG. 6  is a top plan view of the top plate of  FIG. 2 . 
         FIG. 7  is a perspective view of a first alternative embodiment of the top plate. 
         FIG. 8  is a bottom perspective view of a second alternative embodiment of the top plate. 
         FIG. 9  is a left side elevation view of the top plate of  FIG. 2 . 
         FIG. 10  is a bottom perspective view of a third alternative embodiment of the top plate. 
         FIG. 11  is a perspective view of a fourth alternative embodiment of the top plate. 
         FIG. 12  is a perspective view of the base plate according to one exemplary embodiment. 
         FIG. 13  is a left side view of the base plate of  FIG. 2 . 
         FIG. 14  is a front elevation view of the base plate of  FIG. 2 . 
         FIG. 15  is perspective view of the top plate partially inserted into the recessed area in the base plate. 
         FIG. 16  is a perspective view of the top plate inserted into the base plate and including a cable engaged by the hook. 
         FIG. 17  is a perspective view of the top plate fully inserted into the base plate. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure relates generally to a locking clip for a cable tensioning system. In a typical installation, a cable is hung on slides along the four corners and four sides of a billboard face, hidden from view by the face frame. A number of clips are attached to the display sheet, typically polyethylene or light weight vinyl, at selected intervals, commonly approximately 2-3 feet apart. Each clip releasably holds a portion of the sheet under tension. The clip has a hook with a channel or guideway through which a portion of the cable passes. For the purposes of the present disclosure the cable may refer to a portion of the cable, as the context reflects. As tension is increased on the cable by means of a spring-loaded single arm locking mechanism or other tensioning mechanism known to those skilled in the art, the tension on the display sheet is increased resulting in an overall flat, undistorted display sheet. When the display sheet is subsequently removed or replaced with another display sheet, the clips remain attached to the cable, facilitating installation of a new display sheet and preventing the disengagement of one or both clip plates from the cable. An example of a cable tensioning system is disclosed in co-pending U.S. patent application Ser. No. 12/174,449, PCT Patent Application No. PCT/US2008/070197, commonly assigned to the assignee of the present application. 
       FIG. 1  illustrates one exemplary embodiment of the present disclosure and shows an assembled clip  10  engaging a sheet  12  and a cable  15 . The cable  15  generally surrounds a billboard frame  16 . The clip  10  generally comprises a top plate  20  and a base plate member  50 . The clip parts may be made of a composite nylon material which provides the strength required to sustain constant tensioning pressure and withstand long-term outdoor exposure to heat, cold, sun, rain, and non-atmospheric conditions such as excessive installation pressure, tensioning pressure, and corrosive elements. Alternatively, the clip may be made of other suitable polymers, plastic, metal, alloy, ceramic, wood, combinations and mixtures thereof, and the like. The top plate  20  and base plate  50  may be made of the same or different materials. 
     As shown in  FIGS. 2-6 , the top plate  20  has a hook  22  having corners  23  and an interior recess portion or channel  46  (which preferably is rounded) through which a cable  15  passes and can be retained. The top plate  20  has a front edge  28 , rear edge  30 , first side  32 , second side  34 , bottom surface  36 , and top surface  38 . As shown in  FIG. 2 , the thickness of the top plate  20  preferably tapers toward the front edge  28  from the rear edge  30 . The tapering may be from edge to edge, or, alternatively, the tapering can be a portion of the distance from edge to edge. The tapering allows the cable  15  to slide within the hook  22  and facilitates the insertion, gripping and locking functions when the top plate  20  is engaged with the base plate  50 . Alternatively, rather than a straight taper, the top plate  20  may have a curved portion. Free or substantially unimpeded lateral movement of the cable  15  within the channel  46  is preferable for smooth operation of the cable tensioning system. Alternatively, for certain applications the hook  22  and channel  46  may form a snug fit over the cable  15 . Optionally, the top plate  20  may have one or more open or reduced thickness areas  49 A and  49 B proximate to the rear edge  30  and a slot  40  between the front edge  28  and the rear edge  30  which reduce the amount of material needed and the weight of the part. The areas  49 A and  49 B may be recessed areas extending from the top surface partially toward the bottom surface, or, may be from one surface through to the other surface. 
     In a variation of this embodiment (shown in  FIG. 7 ) the corners  23  may be angled or beveled, preferably at about 45 degrees (although other angles are usable), to facilitate the attachment of the assembled clip apparatus  10  to the cable  15 . In another variation of this embodiment (shown in  FIGS. 8-10 ), the hook  22  may have at least one lip ( FIGS. 8 and 9 ), nub, rib, tooth ( FIG. 10 ) or other protrusion  41  along the bottom of the leading edge  29  of the hook  22 , which protrusions assist in preventing the top plate  20  from becoming disengaged from the cable  15 . The length and height of the hook  22  and/or the shape of the channel  46  can be modified to accommodate different diameter or shape cable or other article. 
     In an alternative embodiment, shown in  FIG. 11 , the hook  22  can comprise a plurality of spaced apart narrower fingers  40 A,  4013 , each finger generally shaped like the hook  22  (though narrower in width). While two such fingers  40 A,  40 B are shown, more fingers may be used. 
     As shown in  FIGS. 3 and 5 , the thickness of the top plate  20  preferably tapers from the front portion  28  toward the rear portion  30 . The tapering may be from the rear edge  30  to the front edge  28 , or, alternatively, the tapering can be a portion of the distance from front edge to rear edge. The tapering allows the cable  15  to slide within the hook  40  and facilitates the insertion, gripping and locking functions when the top plate  20  is engaged with the base plate  50 . Alternatively, rather than a straight taper, the top plate  20  may have a curved portion. Free or substantially unimpeded lateral movement of the cable  15  within the channel  46  is preferable for smooth operation of the cable tensioning system. 
       FIGS. 12-14  show the base plate  50  having a top surface  52  and two retaining arms  54 ,  56  extending upward from the base plate  50  and facing each other. Each retaining arm has a side face  57  and a top face  55 . The retaining arms  54 ,  56  provide a friction fit with the top surface  38  of the top member  20 . The bottom edge  59  of each retaining arm  54 ,  56  may be angled to facilitate insertion of the top plate  20  into the base plate  50 , and to apply consistent pressure upon the tapered top surface  38  of the top plate  20 . The base plate  50  has a bottom surface  58  and sides  60 ,  62 . A portion of the top surface  52  (proximate to the front edge  64 ) preferably has a gripping surface, comprising a series of surface irregularities, such as protrusions  66  extending from the first side  60  to the second side  62  (or at least a portion thereof) to provide a friction fit against a portion of the bottom surface  36  of the top member  20  and to prevent premature separation of the top plate  20  from the base plate  50 , yet still permit separation by manually pushing or pulling the two parts apart. The protrusions  66  can be teeth, protrusions, bumps, ribs, ridges, spikes, or the like. Alternatively, the surface irregularities can be grooves, indentations, channels, detents, divots, or the like. Preferably, the protrusions  66  have a relatively sharp end ( FIG. 14 ) to engage a sheet  12  (described hereinbelow in greater detail). In the middle of the base plate  50  between the two tension arms  54 ,  56  is recessed area  67  extending generally parallel to the front  64  and rear edges  70 . A beveled or curved edge  68  of the recessed area closest to the front edge  64  of the base plate allows display sheets with differing edge thickness to be captured between the top and base plate. The recessed area  67  may extend partially or fully from the top surface  52  to the bottom surface  58 . A beveled or curved edge  69  of the recessed area portion proximate to the rear edge  70  of the base plate  50  facilitates both insertion of the top plate  20  into the base plate  50  and removal of the display sheet  12  upon partial disengagement of the top plate  20  from the base plate  50 . 
     The top surface  52  of the base plate  50  may taper or angle downward at a portion extending from the front edge  64  toward the rear edge  70  to increase the amount of pressure between the top member  20  and the base plate  50  when pressed together. 
     In assembly and operation (see  FIGS. 15-17 ), the front edge  28  of the top plate  20  is inserted over the front edge  64  forward and between the arms  54 ,  56  with the edge of a display sheet  12  positioned between the top plate  20  bottom surface  36  and the protrusions  66  of the base plate  50  top surface  52  (see  FIGS. 1 and 15 ). Hand pressure is generally applied to the rear edge  30  of the top plate  20  and the rear edge  70  of the base plate  50  sufficient to guide the front edge  28  into a portion (i.e., partially or fully into) of the recessed area  67  and then between the arms  54 ,  56  until the tapered portion of the top plate  20  is partially wedged within the arms  54 ,  56 . The cable  15  is inserted in the channel  46  ( FIG. 16 ) and around the arms  54 ,  56  with the cable  15  being on the side faces  57  of the arms  54 ,  56 . At this time the sheet  12  can be inserted or removed from the clip  10  while the clip  10  is loosely maintained on the cable  15 . To fully grasp the sheet  12 , the top plate  20  is more fully inserted through the retaining arms  54 ,  56  until snug, as shown in  FIG. 1 . When tension is applied to the cable, the display sheet  12  is stretched on the face  80  of a billboard along the billboard frame edge  16 .  FIG. 1  also shows a conventional guide clip  90 , known to those skilled in the art, which may be used to retain the cable  15  in its preferred location on the billboard. 
     A single worker can install a display sheet  12  using a cable tensioning system. This is in comparison to conventional systems, which require several workers. The reduction in time to install the display sheet represents a significant time and expense savings to the installation company. 
     The assembled clip, engaged with the stretched sheet  12  and the cable  15  is shown in  FIG. 1  which also shows a conventional guide clip  90  and a billboard frame  16 , known to those skilled in the art. A number of clips  10  are assembled around the periphery of the billboard frame  16  retaining the cable  15  around the periphery with the display sheet  12  attached to the clips  10 . As tension is applied to the cable  15  the display sheet  12  is stretched across the face of the billboard frame  16  holding the display sheet  12  flat with minimal or no twisting, wrinkling, or other distortion. 
     The clip  10  provides the operator the option of attaching the clips  10  to a display sheet  12  off-site in a weather-protected facility. After attaching the clips  10  to the display sheet  12 , the worker can transport the sheet  12  to the installation site where the clips  10  are attached to the cable  15  using the hooks  22 . Once a clip  10  is attached to the cable  15  using the hook  22 , the base plate  50  and the top plate  20  remain attached together as a result of the cable  15  running through the channel  46  of the hook  22  and resting on the side faces  57  of the arms  54 ,  56 . When required, the untensioned cable  15  can be disengaged from the clip  10  by pulling the cable  15  from under the hook  22 . 
     When an operator needs to replace the display sheet  12 , the clip  10  parts are loosened by sliding the front edge  28  of the top plate  20  toward the main part of the sheet  12 , which “unwedges” the top plate  20  from between the retaining arms  54 ,  56  and allows the operator to remove the sheet  12 . The cable  15  running through the hook  22  and on the side faces  57  of the retaining arms  54 ,  56  prevents detachment from the cable  15  as well as separation of the base plate  50  from the top plate  20 . The clip  10  remains attached to the cable  15  and the operator can attach a replacement display sheet  12  to the clip  10  without concern that the clip  10  or either of the plates  20 ,  50  will disengage and fall off the cable  15   
     It is to be understood that the locking clip of the present disclosure can be used or adapted to be used with other types of systems or be used to grip any suitable type of surface, such as, but not limited to, tent fabric, paper, film, cotton, wood, ceramic, composite or other natural or synthetic fiber (woven or nonwoven material), combinations of the foregoing and the like. The clip of the present invention can be adapted to secure relatively inflexible surfaces (such as, but not limited to, metal sheeting, glass, plastic, wood, composites, ceramic, combinations of the foregoing, and the like), such as, for example, by incorporating a rubberized, nonslip, tacky or other friction-type surface on or as part of the engaging surfaces  36  and  52 . 
     In addition, configuration of the top plate and the retaining arms  54 ,  56  can be modified for different applications, such as for use with thicker cable or different cross-sectional shape cable, where the cable is instead a rod or pipe, or the like. 
     Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims. 
     All patents, patent applications and publications referred to herein are incorporated by reference in their entirety.