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.
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.
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.
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°.
The chair of this embodiment is shown in
As viewed in cross-section (see
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
The distal ends of the legs 16 are formed by extensions 30 of the web portions 22 (see
The cradle defined between the ears 12 extends transversely across the table 10 so that a rebar R (see
This embodiment is shown in
Table 10a
Ears 12a
Cradle 14a
Legs 16a
Outer surface portions 20a
Reinforcing web portions 22a
Central portion 24a
Extensions 30a
Serrations 32a
Inclined surfaces 34a
As may be seen from
The second embodiment operates in the same manner as the first embodiment in that the cradle 14a extends transversely of the table 10a between a pair of legs 20a 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.
The bearing plate shown in
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, 30a, and 30b 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
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.
The chair of this embodiment is shown in
The chair of this embodiment is shown in
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 10b
Ears 12b
Cradle 14b
Legs 16b
Outer surface portions 20b
Reinforcing web portions 22b
Central portion 24b
Extensions 30b
Serrations 32b
Inclined surfaces 34b
Shoulder 38b
The fourth embodiment also differs from the second embodiment in that it is provided with additional reinforcing webs 52 integrally formed with the table 10b and merging with the reinforcing web portions 22b (see
The crossed-shaped configuration of the table 10b also differs from that of the tables 10 and 10a in that it is not of a planar configuration. Rather, it is of a generally concave configuration at the portion thereof defining the cradle 14b. The ears 12b are of a concave arcuate configuration which merge with the cradle 14b, as may best be seen from
The cross-shaped table 10b has inwardly scalloped edges between the legs 16b (see
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.
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Number | Date | Country | |
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20050210816 A1 | Sep 2005 | US |