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This application is a continuation-in-part of patent application Ser. No. 10/126,823 filed Apr. 19, 2002 now U.S. Pat. No. 6,663,316. 

   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, concrete foundations, 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 foundation applications, the bars are usually arranged parallel to the walls of the foundation, and supported above the ground or other surface. In this manner, the concrete may flow under and around the bars, thereby encapsulating the bars when the concrete hardens. 
   Prior structures for supporting the reinforcement bars 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, foundations, and other concrete structures. 
   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 plurality of pairs of opposing first leg members extend upward from the upper surface of the base member. Each of the first leg members have a lower end connected to the base member and an upper end distally disposed from the lower end. The apparatus includes a plurality of cradles for receiving the reinforcement bars, where each cradle is attached to the upper ends of a corresponding pair of the opposing first leg members. In a preferred embodiment, the apparatus includes horizontal support members disposed between and connecting the cradles. 
   Preferably, the base member, opposing leg members, cradles, and horizontal support members 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; 
       FIG. 5  is a perspective view of a structure that is supporting concrete reinforcement bars according to a preferred embodiment of the invention; 
       FIG. 6  is a perspective view of a structure for supporting concrete reinforcement bars according to an alternative embodiment of the invention; 
       FIG. 7  is a side view of a structure for supporting concrete reinforcement bars according to an alternative embodiment of the invention; 
       FIG. 8  is an end view of a structure for supporting concrete reinforcement bars according to an alternative embodiment of the invention; and 
       FIG. 9  is a perspective view of a structure that is supporting concrete reinforcement bars according to an alternative 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 reinforcement 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 square or barbed corners 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. 
   Depicted in  FIGS. 6–9  is an alternative embodiment of a structure  100  for supporting concrete reinforcement bars, also referred to herein as a re-bar chair. As shown in  FIG. 9 , the a preferred embodiment of the chair  100  may be used to hold three concrete reinforcement bars B 1 , B 2 , and B 3  in a substantially parallel relationship as concrete is poured around the chair  100  and the bars B 1 , B 2 , and B 3  to form a concrete structure, such as a foundation or footer. As one skilled in the art will appreciate, many such chairs  100  may be used to support several reinforcement bars in a concrete foundation. 
   The chair  100  includes a base member  102 , which is preferably rectangular, but which also could be oval, elliptical, or other shape. Within the base member  102 , there is preferably an opening  104 . Situated around the opening  104  are a set of leg members  106  and  108 . The leg members  106  and  108  are attached at their lower extremities to the base member  102  and extend upward there from. The leg members  106  and  108  of the preferred embodiment are rectangular in cross-section, and are somewhat thicker at their lower extremities than at their upper extremities. 
   Attached to the upper extremity of each pair of leg members  106  is a cradle  120 . Each cradle  120  preferably includes opposing sidewalls  124  and  126  which form a channel C 1  in which a reinforcement bar (such as the bar B 1  in  FIG. 9 ) is received. Preferably the sidewalls  124  and  126  of the cradles  120  include a gap  136 , as depicted in  FIGS. 6 and 8 . However, in an alternative embodiment, the sidewalls  124  and  126  have no gap. One advantage of the embodiment with the gap  136  is that the sidewalls  124  and  126  are easier to flex outward to allow insertion of the reinforcement bars into the channel C 1 . 
   To prevent the reinforcement bars from lifting out of the cradles  120 , on the inner surfaces of the opposing sidewalls  124  and  126  are retaining members  132 . As shown most clearly in  FIGS. 6 and 7 , the retaining members  132  extend slightly over the channel C 1  to prevent the reinforcement bars from moving upward and out of the channel C 1 . As the Figures indicate, the upper surfaces of the retaining members  132  are preferably beveled, sloped, or curved slightly downward so that when the reinforcement bars are pressed downward toward the channel C 1 , force is transferred outward to cause the sidewalls  124  and  126  to flex outward and allow the reinforcement bars to snap into the channel C 1 . The lower surfaces of the retaining members  132  are preferably not beveled, but rather have square or barbed corners for effectively capturing the reinforcement bars within the channel C 1 . 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. 
   The preferred embodiment of the chair  100  includes three cradles  120  for holding three reinforcement bars. However, one skilled in the art will appreciate that the chair  100  may include any number of cradles  120  to hold any number of reinforcement bars in a parallel arrangement in a concrete foundation or footer. 
   As shown in  FIGS. 6 and 7 , horizontal support members  134  are preferably provided between adjacent cradles  120  to provide lateral support. 
   In the preferred embodiment of the invention, all of the components of the chair  102  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  124  and  126  to flex outward to receive the reinforcement bars as described above. Thus, when a reinforcement bar is laid across the cradle  120  on top of the retaining members  132 , and is pressed downward, the sidewalls  124  and  126  may flex outward to allow the reinforcement bar to slide past the retaining members  132  and snap into place in the channel C 1 . 
   In the preferred embodiment of the invention depicted in  FIGS. 6–9 , the height of the cradles  120  above the base  102  is about 3 to 4 inches, which would place the reinforcement bars at about the center of a 6 to 8 inch concrete foundation. However, one skilled in the art will appreciate that with appropriate scaling of the base  102  and the leg members  106  and  108 , the height of the cradles  120  above the base  102  could be practically any desired value. Thus, the present invention is not limited to any particular height of the cradles  120  above the base  102 . 
   The spacing between adjacent cradles  120  is about five inches in the preferred embodiment that has three cradles. This provides for a spacing of about ten inches between the outer two cradles  120 , which is an optimum arrangement for 12-inch wide footers. However, it will be appreciated that the invention is not limited to any particular spacing between adjacent cradles  120 . 
   As one skilled in the art will appreciate, the chair  100  as depicted in  FIGS. 6–9  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  106  and  108  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.

Summary:
A structure is described for supporting concrete reinforcement bars in a concrete structure, such as a footer or foundation. The structure includes a base member having a lower surface and an opposing upper surface. A plurality of pairs of opposing first leg members extend upward from the upper surface of the base member. Each of the first leg members have a lower end connected to the base member and an upper end distally disposed from the lower end. The structure includes a plurality of cradles for receiving the reinforcement bars, where each cradle is attached to the upper ends of a corresponding pair of the opposing first leg members. In a preferred embodiment, the structure includes horizontal support members disposed between and connecting the cradles. To retain the reinforcement bars within the cradles, preferred embodiments of the structure include retaining members that protrude inward from the inner surfaces of the opposing sidewalls. These retaining members offer interference to any upward movement of the reinforcement bars. Preferably, the base member, opposing leg members, cradles, retaining members, and horizontal support members comprise a unitary structural element, such as a continuous piece of thermoplastic material formed by injection molding.