Abstract:
A polymeric chair having a rebar cradle and legs of a T-shaped cross-section diverging downwardly from the cradle. The outer surface portions of the legs are arcuate and define segments of a cone. Inwardly extending web portions reinforce the legs and provide feet at the distal ends of the legs disposed to the inside of the outer surface portions. A flat sand plate for the chair has radially extending slots formed therethrough which are proportioned for snug engagement with side surfaces of the feet. The slots are elongate to accommodate different sized chairs having feet spaced at varying radial dimensions. The web portions taper to optimize their reinforcing function and conserve material. In one embodiment, a ring is formed integrally with the legs intermediate the table and the distal ends of the legs. The chair is of a unitary construction and may have an integrally formed strap for extension over the cradle to secure a rebar in place.

Description:
The present invention relates to a chair for supporting rebars in spaced relationship above a surface over which poured concrete is formed. It is particularly concerned with a unitary chair fabricated of polymeric material wherein the legs of the chair present smooth outer surfaces and are internally formed with reinforcing webs which terminate in distal feet. In its more specific aspects, the invention is concerned with such a chair which may be injection molded and is of a very strong and stable construction. The invention also provides a bearing plate to support the chair against tipping or penetration relative to a soft earthen bed upon which the chair is supported. 
     The rebar chair of the invention may also be referred to as a pedestal. While the invention is described with reference to rebar, it may also be used to support other internal reinforcements for poured concrete, such as post tensioned cables or welded wire mesh. 
     BACKGROUND OF THE INVENTION 
     Chairs or pedestals for supporting rebar in spaced relationship to a surface over which poured concrete is formed are well known in the prior art. Some comprise no more than small concrete blocks provided with wire to secure the blocks to the rebar. Others are fabricated of bent wire. More recently, a number have been made of polymeric material. The devices of U.S. Pat. Nos. 4,682,461; 4,756,641; and 5,555,693 are typical of the later type. 
     While polymeric chairs have the advantage that they are relatively inexpensive and do not corrode, they have been problematic insofar as their strength and stability is concerned. Also, they have met with resistance in the trade because of the difficulty of securing the chairs to the rebar being supported. The later problem has been exacerbated by the provision of internal structure between the legs of the chairs, which structure has restricted free access between the legs. Such restricted access makes it difficult to extend ties through the chairs and also impedes stackability of the chairs during storage and transport. 
     Another problem with prior art polymeric chairs is that their relatively complicated construction has made it difficult and expensive to manufacture the chairs by injection molding. 
     SUMMARY OF THE INVENTION 
     The principal elements of the chair of the present invention comprise a cradle for supporting engagement with a rebar and legs fixed to and extending downwardly from the cradle at annularly spaced locations. The legs diverge outwardly from the cradle and are formed with arcuate outer surface portions which define a smooth interrupted cone. Web portions extend inwardly of the outer portions over the length of the legs and terminate in distal ends which provide feet to the interior of the outer portions. The feet are formed with irregular bottom surfaces to enhance traction. The cradle is provided by a table having diametrically opposed ears extending upwardly therefrom; which ears may be located so as to be intermediate the legs, or in alignment with the legs. 
     In one embodiment, a ring is integrally formed with and extends between the legs to reinforce the legs against spreading. The ring is located at a level between the cradle and the distal ends of the legs and is of an arcuate configuration which merges with the outer portions of the legs to continue the interrupted conical surface defined by the legs. 
     Another embodiment has a strap integrally formed with the chair for select extension over the cradle to secure a rebar within the cradle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a first embodiment of the inventive chair wherein a ring is formed integrally with the legs; 
         FIG. 2  is a elevational view of the first embodiment chair, with a part thereof broken away to show the internal construction of the chair; 
         FIG. 3  is a plan view of the first embodiment chair; 
         FIG. 4  is a bottom view of the first embodiment chair; 
         FIGS. 5 and 6  are cross-sectional views taken on the planes designated by lines  5 - 5  and  6 - 6 , respectively, of  FIG. 1 ; 
         FIG. 7  is a perspective view of a second embodiment of the inventive chair, wherein no ring is provided between the legs of the chair; 
         FIG. 8  is an elevational view of the second embodiment chair; 
         FIG. 9  is a plan view of the second embodiment chair; 
         FIG. 10  is a bottom view of the second embodiment chair; 
         FIG. 11  is a cross-sectional view taken on the plane designated by line  11 - 11  of  FIG. 7 ; 
         FIG. 12  is a plan view of the bearing plate of the present invention; 
         FIG. 13  is a cross-sectional view of the bearing plate, taken on the plane designated by line  13 - 13  of  FIG. 12 ; 
         FIG. 14  is a perspective view of the  FIG. 12  bearing plate; 
         FIG. 15  is a perspective view of the first embodiment chair of  FIG. 1 , shown supported on the bearing plate of  FIG. 12 ; 
         FIG. 16  is a cross-sectional elevational view taken on the plane designated by line  16 - 16  of  FIG. 15 ; 
         FIG. 17  is an elevational view of a third embodiment of the inventive chair, similar to that of  FIGS. 1 to 6 , except that it is additionally provided with an integrally formed strap and securing means therefore; 
         FIG. 18  is a perspective view of a fourth embodiment of the inventive chair, viewed from toward the top, wherein no ring is provided between the legs of the chair and the table of the chair of a generally X-shaped configuration; 
         FIG. 19  is a plan view of the fourth embodiment chair; 
         FIG. 20  is a bottom view of the fourth embodiment chair; 
         FIG. 21  is an elevational view of the fourth embodiment chair; and 
         FIG. 22  is a perspective view of the fourth embodiment chair, viewed toward the bottom. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     All embodiments of the inventive chair are injection molded from polymeric material. A preferred material has been found to be a derivative of recycled polypropylene known as “PRE-TUF” by PrePlastics of Auburn, Calif. Other suitable materials are polycarbonate/ABS alloy, polypropylene, polyethylene, polystyrene, glass filled polystyrene, glass filled nylon, and polyvinyl chloride. 
     The dimensions of the chair may vary, depending on the thickness of the concrete slab being formed. Typical chair heights range from one and one-quarter inch to ten inches, in one-quarter inch increments. The angle at which the legs diverge from the supporting table of the chair is chosen for optimum strength and stability, with the preferred range being 94° to 104°. 
     First Embodiment Chair 
     The chair of this embodiment is shown in  FIGS. 1 to 6  and designated in its entirety by the letter C 1 . It comprises a horizontal table  10  of a generally circular configuration having ears  12  extending upwardly from diametrically opposite sides thereof to define a rebar receiving cradle  14 ; legs  16  integrally formed with the table  10  and diverging downwardly and outwardly therefrom; and a ring  18  formed integrally with the legs  16  at a location intermediate the table  10  and distal ends of the legs  16 . As shown, four legs  16  are provided and extend downwardly from the table  10  at equally spaced annular locations around the table. The ears are located so as to be between the legs, thus providing a stable arrangement where two legs are disposed to either side of a rebar received in the cradle between the ears. 
     As viewed in cross-section (see  FIG. 6 ), the legs are of a generally T-shaped cross-section and each comprise an outer surface portion  20  and an inwardly extending reinforcing web portion  22 . The outer surface portions define as interrupted frusto conical cone diverging downwardly from the table  10 . The web portions  22  taper from either end of the legs so as to have an increased depth portion approximately mid-length of the legs (see  FIG. 2 ). The later construction provides a truss-like reinforcement for the legs which renders them very rigid. From  FIG. 2  it will also be seen that the web portions of oppositely disposed legs include a central portion  24  integrally formed with and extending beneath the table  10 . The merger between the reinforcing web portions  22  and central portion  24  has a relatively large radius, thus adding to the overall rigidity of the chair. The central portions  24  meet at the center of the table  10  (see  FIG. 4 ) to add even more to this rigidity. 
     The ring  18  merges with the outer surface portions  20  of the legs so as to form a smooth outer surface continuing the interrupted conical configuration defined by the outer surface portions. At the lower edge of the merger between the ring  18  and the outer surface portions  16 , the ring is arched so as to provide radius portions  26  which increase the area of merger between the ring and the legs and serve to expand the reinforcement to the legs provided by the ring. As viewed in cross-section, the ring  18  tapers in thickness from its upper edge  28  to its lower edge  29  (see  FIG. 5 ). This configuration ideally suits the chair for injection molding with a core of simple construction which may be readily removed. 
     The distal ends of the legs  16  are formed by extensions  30  of the web portions  22  (see  FIG. 2 ). These extensions are disposed inwardly on the outer surfaces of the portions  20  and provide a foot including, traction means in the form of serrations  32 , formed on the under-surface of the extensions. The serrations  32 , as may be seen from  FIG. 4 , extend transversely of the web portions  22 . The outer surface portions  20  converge towards the extensions  30  through inclined surfaces  34  proximal to the distal ends of the legs. These inclined surfaces provide space proximal to the distal ends of the legs  16  into which fluid concrete formed around the legs may flow, thus avoiding the creation of voids in the concrete. Such voids are also avoided through the use of rounded radiuses  36  at the merger of the web portions  22  and the extensions  32 . 
     The cradle defined between the ears  12  extends transversely across the table  10  so that a rebar R (see  FIG. 2 ) supported on the table is disposed between the legs  16 . As the result of this arrangement, with a four-legged chair, two legs are disposed symmetrically to either side of the rebar. 
     Second Embodiment Chair 
     This embodiment is shown in  FIGS. 7 to 11  and designated, in its entirety, by the reference C 2 . It differs from the first embodiment primarily in that it is not provided with a ring, such as the ring  18 , and in that the web portions converge uniformly towards the distal ends of the legs. Parts of the second embodiment corresponding to those of the first embodiment are designated by like numerals, followed by the reference “a”, as follows: 
     Table  10   a    
     Ears  12   a    
     Cradle  14   a    
     Legs  16   a    
     Outer surface portions  20   a    
     Reinforcing web portions  22   a    
     Central portion  24   a    
     Extensions  30   a    
     Serrations  32   a    
     Inclined surfaces  34   a    
     As may be seen from  FIG. 8 , the web portions  22   a  converge uniformly in a generally straight line from the central portion  24   a  to the extensions  30   a . Another difference between the first and second embodiments is that in the second embodiment a shoulder  38  is formed between the inclined surfaces  34   a  and the extensions  30   a.    
     The second embodiment operates in the same manner as the first embodiment in that the cradle  14   a  extends transversely of the table  10   a  between a pair of legs  20   a  to either side thereof. 
     While the first and second embodiments function in the same way, the first embodiment is especially designed for relatively high chairs where the legs  16  are quite long and the added reinforcement provided by the ring  18  and the truss-like reinforcing of portions  22  greatly enhances the rigidity of the chair structure. The second embodiment is a simplified construction ideally suited for use in relatively short chairs. 
     Bearing Plate 
     The bearing plate shown in  FIGS. 12 to 16  is designated in its entirety by the reference B and is for purposes of supporting the chair of the invention against uneven penetration into soft soil. Such plates are also known in the trade as “sand plates.” 
     In the illustrated embodiment, the body of plate B is fabricated of a polymer material similar to that of the chair. It is designed to universally accommodate chairs of different heights and may be used to support any of the embodiments of the chairs herein disclosed. A typical plate would measure 4½ by 4½ inches and have a thickness of one-quarter inch. 
     The plate B is formed with generally triangular lightening holes  40  and a central hole  42 . These holes are intended primarily to conserve material and lighten the weight of the plate. Diagonally extending slots  44  extend radially relative to the central hole  42  for alignment with and complimental receipt of the extensions  30 ,  30   a , and  30   b  of the chairs. These slots have a transverse dimension slightly less than that of the extensions, so that the opposed side surfaces of the slots, designated  46 ,  48  (see  FIG. 13 ) snuggly receive and frictionally engage opposite sides of the extensions. 
       FIGS. 15 and 16  show the chair C 1  of the first embodiment with the extensions  30  thereof snuggly received within the slots  44 . As there seen, it will be appreciated that the extensions  30  are disposed intermediate the radially spaced inner and outer extremities of the slots  44 . This demonstrates how a particular bearing plate B may accommodate chairs of different sizes. For smaller chairs, the extensions  30 ,  30   a  would be closer to the center of the plate. 
     The flat planar top surface of the plate B facilitates the formation of concrete around the assembled plate and chair, without creating voids. This contrasts to prior art plates wherein upperwardly extending structure on the plates may create such voids. 
     Third Embodiment Chair 
     The chair of this embodiment is shown in  FIG. 17 . It differs from the first embodiment chair in that it is provided with a strap S and retaining tab T therefor. The strap S is integrally formed with the chair C 1  to the outside of an in alignment with one of the ears  12 . The tab T is integrally formed with the chair C 1  in alignment with and extending downwardly from the other of the ears  12 . The thickness of the strap S is such that the strap is relatively flexible. Generally rectangular openings  50  are formed through the strap S at spaced intervals for select engagement over the tab T. The phantom line illustration in  FIG. 17  illustrates the condition which the strap would assume when engaged over the tab T. As so engaged, the strap would extend over and retain a rebar supported on the cradle of the chair. The alignment of the strap S with the ears  12  assures that such engagement is secure. 
     Fourth Embodiment Chair 
     The chair of this embodiment is shown in  FIGS. 18 to 22  and is designated, in its entirety, by reference C 4 . It differs from the second embodiment primarily in that: 
     1) the table is of a cross-shaped planar configuration; 
     2) additional reinforcements are provided beneath the table; and 
     3) the ears are aligned with oppositely disposed legs of the chair. Parts of the fourth embodiment corresponding to those of the second embodiment are designated by like numerals, followed by the reference “b,” as follows: 
     Table  10   b    
     Ears  12   b    
     Cradle  14   b    
     Legs  16   b    
     Outer surface portions  20   b    
     Reinforcing web portions  22   b    
     Central portion  24   b    
     Extensions  30   b    
     Serrations  32   b    
     Inclined surfaces  34   b    
     Shoulder  38   b    
     The fourth embodiment also differs from the second embodiment in that it is provided with additional reinforcing webs  52  integrally formed with the table  10   b  and merging with the reinforcing web portions  22   b  (see  FIG. 20 ). The reinforcing webs  52  function to further rigidify the legs  16   b  and to provide additional support for the table  10   b.    
     The crossed-shaped configuration of the table  10   b  also differs from that of the tables  10  and  10   a  in that it is not of a planar configuration. Rather, it is of a generally concave configuration at the portion thereof defining the cradle  14   b . The ears  12   b  are of a concave arcuate configuration which merge with the cradle  14   b , as may best be seen from  FIG. 21 . 
     The cross-shaped table  10   b  has inwardly scalloped edges between the legs  16   b  (see  FIG. 18 ). As compared to the circular tables of the first, second and third embodiments, the scalloped configuration has the advantage that it provides open space between the legs which facilitates extending a tie element beneath the table and over a rebar supported thereon. 
     CONCLUSION 
     From the foregoing description and accompanying drawings, it is believed apparent that the present invention enables the attainment of the objects initially set forth herein. In particular, it provides an improved rebar chair and sand plate of a strong and stable construction which is ideally suited for fabrication by injection molding. It should be appreciated, however, that the invention is not intended to be limited to the details of the illustrated embodiments, but rather is defined by the accompanying claims.