Patent Publication Number: US-6663316-B1

Title: Support for concrete reinforcing members

Description:
This application claims priority to provisional patent application No. 60/285,531 filed Apr. 20, 2001, now abandoned. 
    
    
     TECHNICAL FIELD 
     The present invention is generally directed to structures for supporting concrete reinforcing members. More particularly, the invention is directed to a chair for supporting two reinforcing bars in an orthogonal relationship as concrete is poured to form a concrete slab. 
     BACKGROUND OF THE INVENTION 
     Steel reinforcement bars are typically used in concrete slabs and other concrete structures to provide structural support to the concrete. In slab applications, the bars are usually arranged in a rectangular lattice which is supported some distance above the ground or other surface on which the slab is to be poured. In this manner, the concrete may flow under and around the lattice, thereby encapsulating the lattice when the concrete hardens. 
     Prior structures for supporting the lattice above the ground, also referred to as chairs, have been lacking in several respects. Prior chairs have not provided stable support and have not effectively captured the reinforcing members to adequately keep them in the proper position as the concrete is poured. Also, some prior chairs have been difficult to use in that multiple pieces are required to capture the reinforcement bars. Further, many prior chair designs have been difficult to fabricate, which increases their cost. 
     What is needed, therefore, is an easy-to-use, low-cost structure for providing stable support for reinforcement bars in concrete slabs. 
     SUMMARY OF THE INVENTION 
     The foregoing and other needs are met by an apparatus for supporting reinforcement bars in a concrete structure. The apparatus includes a base member having a lower surface and an opposing upper surface, a pair of opposing first leg members extending upward from the upper surface of the base member, and a pair of opposing second leg members extending upward from the upper surface of the base member, where the second leg members are alternatingly disposed between the first leg members. An upper cradle is attached to the first leg members for receiving an upper reinforcement bar, and a lower cradle is attached to the second leg members for receiving a lower reinforcement bar. 
     The upper cradle comprises a first upper bar-support member and a second upper bar-support member. The first upper bar-support member has a pair of opposing first upper sidewalls separated by an upper channel, and the second upper bar-support member has a pair of opposing second upper sidewalls also separated by the upper channel. 
     The lower cradle comprises a first lower bar-support member and a second lower bar-support member. The first lower bar-support member has a pair of opposing first lower sidewalls separated by a lower-channel. One of the first lower sidewalls is attached to an adjacent one of the first upper sidewalls at an angle of about 90 degrees. Another of the first lower sidewalls is attached to an adjacent one of the second upper sidewalls at an angle of about 90 degrees. The second lower bar-support member has a pair of opposing second lower sidewalls separated by the lower channel. One of the second lower sidewalls is attached to an adjacent one of the first upper sidewalls at an angle of about 90 degrees. Another of the second lower sidewalls is attached to an adjacent one of the second upper sidewalls at an angle of about 90 degrees. 
     In a preferred embodiment, the apparatus includes upper retaining members protruding inwardly from the opposing first upper sidewalls and the opposing second upper sidewalls to retain the upper reinforcement bar within the upper cradle. These preferred embodiments also include lower retaining members protruding inwardly from the opposing first lower sidewalls and the opposing second lower sidewalls to retain the lower reinforcement bar within the lower cradle. 
     Preferably, the base member, first and second leg members, upper cradle, and lower cradle comprise a unitary structural element, such as a continuous piece of thermoplastic material formed by injection molding. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further advantages of the invention will become apparent by reference to the detailed description of preferred embodiments when considered in conjunction with the drawings, which are not to scale, wherein like reference characters designate like or similar elements throughout the several drawings as follows: 
     FIG. 1 is a perspective view of a structure for supporting concrete reinforcement bars according to a preferred embodiment of the invention; 
     FIG. 2 is a first side view of a structure for supporting concrete reinforcement bars according to a preferred embodiment of the invention; 
     FIG. 3 is a second side view of a structure for supporting concrete reinforcement bars according to a preferred embodiment of the invention; 
     FIG. 4 is a top view of a structure for supporting concrete reinforcement bars according to a preferred embodiment of the invention; and 
     FIG. 5 is a perspective view of a structure that is supporting concrete reinforcement bars according to a preferred embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Depicted in FIGS. 1-5 is a structure  10  for supporting concrete reinforcement bars, also referred to herein as a re-bar chair. As shown in FIG. 5, the chair  10  may be used to hold two concrete reinforcement bars B 1  and B 2  in a substantially orthogonal relationship as concrete is poured around the chair  10  and the bars B 1  and B 2  to form a concrete structure. As one skilled in the art will appreciate, many such chairs  10  may be used to support a rectangular lattice of reinforcement bars in a concrete slab. 
     The chair  10  includes a base member  12 , which is preferably square, but which also could be circular, octagonal, or other shape. Within the base member  12 , there is preferably an opening  14 . Situated around the opening  14  are a set of leg members, including opposing long leg members  16   a  and  16   b  and opposing short leg members  18   a  and  18   b . The leg members  16   a-b  and  18   a-b  are attached at their lower extremities to the base member  12  and extend upward therefrom. The leg members  16   a-b  and  18   a-b  of the preferred embodiment are rectangular in cross-section, and, as shown most clearly in FIGS. 2 and 3, are somewhat thicker at their lower extremities than at their upper extremities. 
     Attached to the upper extremity of the long leg member  16   a  is an upper bar-support member  20   a , and attached to the upper extremity of the long leg member  16   b  is an upper bar-support member  20   b . As shown most clearly in FIGS. 1 and 3, the upper bar-support member  20   a  includes opposing sidewalls  24   a  and  26   a , which together form a channel C 1  therebetween. Similarly, the upper bar-support member  20 b includes opposing sidewalls  24   b  and  26   b.    
     Attached to the upper extremity of the short leg member  18   a  is a lower bar-support member  22   a , and attached to the upper extremity of the short leg member  18   b  is a lower bar-support member  22   b . As shown most clearly in FIGS. 1 and 2, the lower bar-support member  22   a  includes opposing sidewalls  28   a  and  30   a , which together form a channel C 2  therebetween. Similarly, the lower bar-support member  22   b  includes opposing sidewalls  28   b  and  30   b.    
     The sidewall  26   a  of the upper bar-support member  20   a  is attached to the sidewall  28   a  of the lower bar-support member  22   a , and the sidewall  24   a  of the upper bar-support member  20   a  is attached to the sidewall  28   b  of the lower bar-support member  22   b . Similarly, the sidewall  26   b  of the upper bar-support member  20   b  is attached to the sidewall  30   a  of the lower bar-support member  22   a , and the sidewall  24   b  of the upper bar-support member  20   b  is attached to the sidewall  30   b  of the lower bar-support member  22   b . Based on this arrangement, the lower bar-support members  22   a  and  22   b  form a lower cradle  22  for receiving a lower reinforcement bar (such as the bar B 1  in FIG.  5 ), and the upper bar-support members  20   a  and  20   b  form an upper cradle  20  for receiving an upper reinforcement bar (such as the bar B 2  in FIG.  5 ). 
     To prevent the reinforcement bars from lifting out of the cradles  20  and  22 , on the inner surfaces of the opposing sidewalls  24   a - 26   a ,  24   b - 26   b ,  28   a - 30   a , and  28   b - 30   b  are retaining members  32 . As shown most clearly in FIGS. 2 and 3, the retaining members  32  extend slightly over the channels C 1  and C 2  to prevent the reinforcement bars from moving upward and out of the channels C 1  and C 2 . As the FIGURES indicate, the upper surfaces of the retaining members  32  are beveled, sloped, or curved slightly downward so that when the bars are pressed downward toward the channels C 1  and C 2 , force is transferred outward to cause the sidewalls  24   a-b ,  26   a-b ,  28   a-b , and  30   a-b  to flex outward and allow the reinforcement bars to snap into the channels C 1  and C 2 . The lower surfaces of the retaining members  32  are preferably not beveled, but rather have a square or barbed comers for effectively capturing the reinforcement bars within the channels C 1  and C 2 . Compared to prior chair designs that have used opposing tapered slots in a conical or cylindrical wall, the opposing sidewalls and retaining members of the present invention provide a significantly improved retention mechanism. 
     In the preferred embodiment of the invention, all of the components of the chair  10  are formed from one continuous piece of thermoplastic, such as polypropylene, which, though rigid enough to support the weight of the reinforcement bars, is flexible enough to allow the sidewalls  24   a-b ,  26   a-b ,  28   a-b , and  30   a-b  to flex outward to receive the reinforcement bars as described above. Thus, when a reinforcement bar is laid across the cradle  20  on top of the retaining members  32 , and is pressed downward, the sidewalls  24   a-b  and  26   a-b  may flex outward to allow the reinforcement bar to slide past the retaining members  32  and snap into place in the channel C 1 . Similarly, when a reinforcement bar is laid across the cradle  22  on top of the retaining members  32 , and is pressed downward, the sidewalls  28   a-b  and  30   a-b  may flex outward to allow the reinforcement bar to slide past the retaining members  32  and snap into place in the channel C 2 . Of course, if the chair  10  is used to support two orthogonal reinforcement bars, the lowermost bar must be snapped into the lower cradle  22  first, and then the uppermost bar may be snapped into the upper cradle  20 . 
     In the preferred embodiment of the invention, the height of the lower cradle  22  above the base  12  is about three to four inches, which would place the reinforcement bars at about the center of a six to eight inch concrete slab. However, one skilled in the art will appreciate that with appropriate scaling of the base  12  and the leg members  16   a-b  and  18   a-b , the height of the lower cradle  22  above the base  12  could be practically any desired value. Thus, the present invention is not limited to any particular height of the cradles  20  and  22  above the base  12 . 
     As one skilled in the art will appreciate, the chair  10  as depicted in the FIGURES is designed to be formed using an injection molding process in a two-piece injection mold. For compatibility with a two-piece mold, the leg members  16   a-b  and  18   a-b  preferably lean slightly inward and have cross-sections which are preferably tapered from thicker to thinner from the lower to the upper extremities. 
     The foregoing description of preferred embodiments for this invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiments are chosen and described in an effort to provide the best illustrations of the principles of the invention and its practical application, and to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as is suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.