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Publication numberUS3693310 A
Publication typeGrant
Publication dateSep 26, 1972
Filing dateNov 9, 1970
Priority dateNov 9, 1970
Also published asCA947529A1
Publication numberUS 3693310 A, US 3693310A, US-A-3693310, US3693310 A, US3693310A
InventorsMiddleton Thomas E
Original AssigneePre Stress Concrete
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Support for elongated reinforcing members in concrete structures
US 3693310 A
Abstract
A support for reinforcing members used in fabricating concrete structures including a base and an upright portion which is formed to receive and support two intersecting reinforcing members in a concrete structure at the point where the members intersect. The support holds the reinforcing members during the pouring of concrete to maintain the reinforcing members at a predetermined position with reference to the ground or the outer surface of the concrete structure.
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Description  (OCR text may contain errors)

United States Patent 1151 3,693,310 Middleton 1 1 Sept. 26, 1972 [54] SUPPORT FOR ELONGATED 3,360,898 1/1968 Beckman ..52/684 REINFORCING MEMBERS IN 3,368,320 2/1968 Lowery ..52/686 CONCRETE STRUCTURES FOREIGN PATENTS OR APPLICATIONS [72] 23 Middlemn' 1,484,976 2/1969 Germany ..52/684 1,029,643 5/1966 Great Britain ..52/686 [73] Assignee: Pre-Stress Concrete, Inc., Houston, 1,142,886 2/1969 Great Britain ..685/ Tex. 211,591 8/1966 Sweden ..52/685 [22] Filed: Nov. 9, 1970 Appl. No.: 87,924

Primary Examiner1-1enry C. Sutherland Alt0rney-Arnold, White & Durkee, Bill Durkec, Frank S. Vaden, 111, Louis T. Pirkey and Stanley A. Becker [57] ABSTRACT A support for reinforcing members used in fabricating concrete structures including a base and an upright portion which is formed to receive and support two intersecting reinforcing members in a concrete structure at the point where the members intersect. The support holds the reinforcing members during the pouring of concrete to maintain the reinforcing members at a predetermined position with reference to the ground or the outer surface of the concrete structure.

2 Claims, 8 Drawing Figures PATENIEIJ 26 I972 3.693.310

sum 1 or 2 17 FIG. 3

i i 4 1w 2 3 I 7' I Mm Thomas EMidd/eton 74x 3' INVENTOR A T TORNE VS PATENTEDSEP 2 an 3.693.310

SHEU 2 0F 2 FIGS /72 Thomas E, Middleton INVENTOR ll/uwedwliiie & Uwvfiee ATTORNEYS SUPPORT FOR ELONGATED REINFORCING MEMBERS IN CONCRETE STRUCTURES BACKGROUND OF THE INVENTION In using concrete as a building material, it is often necessary to reinforce the concrete by using reinforcing bars, wire, mesh, cable, or strand, or by prestressing the concrete structures. A concrete structure is ordinarily pre-stressed by using pretensioning or post-tensioning techniques. In pretensioning, steel bars, wires or cables are stretched between the end points of a concrete form and tension is applied thereto. Then concrete is poured into the forms and allowed to set to form a concrete structure. When the concrete sets, the tension on the cables is relieved thereby inducing compressive stresses in the concrete to pre-stress the concrete structure.

In post-tensioning, the cables are similarly positioned, but have little or no tensile forces applied thereto until after the concrete is poured and sets. Then, the cables are tensioned using hydraulic jacks or the like. The ends of the tensioned cables are then anchored to the concrete structure to pre-stress the structure. To prevent the cable from bonding to the concrete, so that there can be relative movement therebetween to accomplish the pre-stressing, a sheathed cable is used.

In using any technique of pre-stressing, however, it is desirable that the bars or cables be positioned within the concrete structure near the center thereof to provide uniform strength thereto. Consequently, it is necessary to support the cables and hold them in the desired position during the pouring of the concrete, otherwise the cables will sag or otherwise be improperly positioned, thereby weakening the structure.

Heretofore, support members which are capable of holding only a single strand or cable have been used to support the cable at various positions within the form. When using such support members, it has been necessary to tie the cables together with wire at the points where the cables intersect one another in order to keep all of the reinforcing cable in substantially the same plane. Unless the reinforcing cables are tied at the intersecting points, they tend to snake either before or during the pouring of the concrete structure, resulting in an improperly reinforced structure. It can be ap preciated that a considerable amount of time and effort is utilized in the positioning of the support members and in the individual wire tying together of every intersectin g point of each cable.

The subject device not only eliminates the wire material necessary for tying intersecting cables together, but also reduces considerably the labor time required in fabricating a reinforced concrete structure.

SUMMARY OF THE INVENTION The subject support member or slab chair is capable of holding two intersecting cables at the point where they intersect and supporting them relative to the ground or to the bottom of a wood form so that the desired spacing between the ground and the plane in which the strands lie is maintained. The subject device includes a base portion having a supporting portion which extends substantially perpendicularly from the base portion. Slots or spaces are formed in or near the top of the supporting portion for receiving and holding two cables at the intersection thereof. Since the two cables are securely held together at the intersecting point, there is no need to tie wire the cables together. Holes are generally provided in the upright support portion to permit concrete to enter and thus solidly hold the slab chair in the concrete structure. Use of the slab chairs at the intersecting points of the cables adequately supports the cables during the pouring of the concrete.

While the slab chair is described herein for use primarily in horizontal slabs or applications, it is also applicable for use in vertical concrete structures such as retaining walls. In these applications, the slab chairs could, for example, be nailed to a wood form in order to hold vertically positioned reinforcing members in the proper position spaced from the walls of the form.

The subject device eliminates the need for any wire tying at the intersections of reinforcing members, and reduces the amount of materials and labor required in fabricating a concrete structure. Other advantages of the present invention will be apparent from the following detailed description when considered in conjunction with the following detailed drawings. It is apparent that many alternative embodiments may be fabricated for supporting two intersecting cables at a predetermined distance from the ground in accordance with the principles of this invention. It is to be noted, however, that the drawings illustrate only typical embodiments of the invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally efi'ective embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial perspective view of a typical concrete form having reinforcing members which are supported by slab chairs embodying the principles of this invention.

FIG. 2 is a perspective view of a slab chair embodying the principles of this invention.

FIG. 3 is a perspective view of the slab chair shown in FIG. 2 supporting two intersecting reinforcing members.

FIG. 4 is a top view of the slab chair shown in FIG. 3 further illustrating the manner in which the intersecting reinforcing members are held.

FIG. 5 is a cross-sectional view of the slab chair taken along line 5-5 from FIG. 2.

FIG. 6 is an alternative embodiment of the present invention including a substantially U-shaped member for supporting the intersecting reinforcing members.

FIG. 7 is another alternative embodiment of the present invention illustrating a slab chair having a substantially square or rectangular cross-section.

FIG. 8 is still another alternative embodiment of the present invention illustrating a slab chair having a substantially circular cross-section.

DESCRIPTION OF THE INVENTION Referring to FIG. I, there is shown a portion of a typical assembly from which a concrete slab can be fabricated. The assembly includes a concrete form illustrated by boards 11 and 12 which are usually adequately supported in a vertical position by braces and stakes which are not shown. Immediately above the ground a moisture barrier 13, commonly a sheet of plastic such as polyethylene, is placed to prevent moisture from seeping into the concrete structure from the ground. A plurality of reinforcing members 14 and which can be reinforcing bar, cables, strand, wires, or the like, are positioned in intersecting relationship at equal points along the boards 11 and 12. Supporting the reinforcing members are a plurality of slab chairs 16 which are positioned at each intersection of the reinforcing members 14 and 15 to receive and support the members at the intersections thereof.

As shown in FIGS. 2 through 6, the slab chair 16 generally includes a rounded base 17. While bases of any shape may be utilized, it is desirable that the base not have any sharp corners so as to preclude piercing of the plastic sheet 13 which acts as a moisture barrier. The slab chair 16 includes a tubular portion 18 which extends upwardly from the base 17. While the tubular portion is shown as having a circular cross-section, it may be formed to have a square or other shaped crosssection as well. The tubular portion 18 is desirably hollow so as to permit concrete to flow through the open end 19 and also through holes 21 which are provided in the sides of the tubular portion 18. Thus, when concrete is poured, there will be no voids in the concrete structure which may tend to weaken the structure, and also the slab chair 16 will be securely held in the concrete structure after the concrete sets. Four vertical arms 23, 24, 25, and 26 are provided for holding the intersecting cables 14 and 15 as shown in FIG. 3. Typically, the cables 14 and 15 are assembled with all of the first group of parallel cables, such as 14, being installed first, and then all of the second group of parallel cables, such as 15, being installed afterwards and being positioned substantially perpendicular to and on top of the first group of cables 14. Thus, the first group of cables 14 will lie in a slightly lower plane than the second group of cables 15. Nevertheless, both planes desirably will be near the middle of the concrete structure.

The upper part of each of the arms 23, 24, 25, and 26 have inwardly projecting portions 31, 32, 33, and 34, respectively. The space between adjacent inwardly projection portions, such as 31 and 32, is less than the diameter of a cable 14 or 15. Likewise, the same is true of the spacing between the other adjacent inwardly projecting portions. The space provided between the inwardly projecting portions, such as 31, and the top 30 of the tubular portion 18 is approximately equal to the sum of the diameters of the cables 14 and 15. In other words, the space between the projection 31 and the top of the tubular portion 18 is sufficient to accommodate and hold the two intersecting cables.

To install the slab chair 16, one of the cables 14 is first pressed into the openings between opposing pairs of arms, such as the arms and 26 on one side, and arms 23 and 24 on the other side as shown in FIG. 3. As the cable 14 is pressed downwardly, the opposing arms 25 and 26 are urged apart from on another and the arms 23 and 24 are likewise urged apart to permit the cable 14 to move down between the arms and rest on the top 30 of the tubular portion 18. The intersecting cable 15 is then similarly positioned between arms 23 and 26 on one side and arms 24 and 25 on the other side and is pressed downwardly to force the arms apart until cable 15 is resting on top of cable 14. The arms spring back after the cable 15 is in its proper position on top of cable 14 and the projections 31, 32, 33, and 34 extend partially over the cable 15 and serve to hold both the cables 14 and 15 secure and properly spaced from the ground. The distance that the projections 31, 32, 33, and 34 extend over the cables 14 and 15 can most easily be seen in FIG. 4. The arms 23, 24, 25, and 26 are advantageously made relatively thin so that they are easily flexed when the cables are installed therein. It has been found advantageous to have the slab chair 16 integrally molded in one piece out of a plastic such as polypropylene. However, numerous other materials can be used as well as plastic, and likewise, the device can be built in separate pieces and, for example, welded or glued together if so desired.

FIG. 5 is a cross-section of the slab chair 16 more clearly illustrating the tubular portion 18, which may be tapered as shown, the base 17, and arms 23, 24, and 25. Base 17 has a central aperture 20 which further facilitates the securing of the slab chair 16 in the concrete structure by permitting the concrete to flow thereinto. The other openings 21 in the tubular portion 18 serves a similar purpose, as stated previously.

Referring now to FIG. 6, there is shown an alternative embodiment of a slab chair which is generally designated as 41 and has a U-shaped cross-section. A base 42 supports the U-shaped structure which consists of a central wall 43 and two opposite side walls 44 and 45. A vertical slot 49 is formed in the central wall 43 to receive and support the lower cable 14. An elongated horizontal slot 47 is formed in side wall 44 and a similar slot 48 is formed in side wall 45 for receiving and supporting the upper cable 15. The dimensions of the side walls 44 and 45 are such that the slots 47 and 48 are positioned substantially near the top of the side walls so that the upper portions of the side walls are formed into relatively thin tabs 50 and 60. These tabs 50 and 60 may be bent downwardly as shown by the dotted lines around cable 15 to securely grip the cable if desired. The lower cable 14 is supported by the bottom of slot 49 and is prevented from inadvertently coming out of the slot 49 by the upper cable 15 which lies on top of it. If desired, the sharpened corners where the side walls 44 and 45 meet the base 42 may be rounded off to prevent accidental piercing of the moisture barrier 13. While the slab chair 41 preferably leads itself to being made out of metal, it may, of course, be made out of plastic or other materials if so desired. The tabs 50 and 60 may then not be bendable, but they can be suffciently resilient to hold the cables securely within the slots.

Referring now to FIG. 7, there is shown another embodiment of a slab chair generally designated as 51 which has either a square or a rectangular cross-section. The slab chair 51 includes a base 52 and four vertical side walls 53, 54, 55, and 56. The opposing side walls 54 and 56 each have deep slots 61 and 62 formed therein for receiving the lower cable 14 and supporting it. The other side walls 53 and 55 have shallower slots 63 and 64 formed therein for receiving and supporting the upper cable 15. The slab chair 51 may have holes formed in the lower portions of the side walls if desired, to permit concrete to easily flow thereinto. However, in

view of the large open top area, this is not deemed necessary.

Referring to FIG. 8, there is shown still another embodiment of a slab chair generally designated as 71, having a substantially circular cross-section. The slab chair 71 includes a base 72 having a cylindrical vertical portion 73 mounted thereto. Deep slots 76 and 77 are formed vertically in the cylindrical portion 73 to receive the lower cable 14. Shallower slots 78 and 79 are formed equidistantly from the slots 76 and 77 to receive the upper cable 15. The width of the slots 76, 77, 78, and 79 are desirably made slightly smaller than the diamerter of the cables 14 and so that the cables are tightly gripped when inserted into the slots. Openings 81 are provided near the bottom of the tubular portion 73 to permit concrete to enter through the sides as well as the top to fill the void inside the slab chair 71 as previously described.

In use, after the moisture barrier 13 is put in place and the reinforcing members 14 and 15 are laid out, a worker will take a quantity of slab chairs such as 16 and go to each cable intersection attaching the intersecting cables 14 and 15 to the slab chair 16 by pressing each between the upstanding arms or into the appropriate slots as previously described. The subject slab chairs support the cables 14 and 15 the desired distance above the ground and securely hold them in place while concrete is poured and while the concrete sets. Slab chairs of different heights may, of course, be used for different applications. The use of the subject slab chairs eliminates the necessity of wiring the intersecting cables together and saves both time and materials in the fabrication of a concrete structure. The holes provided in the lower portion of the slab chair 16 permits concrete to fill in the voids and thus solidly hold the chair in the concrete structure.

It is to be understood that the above described embodiments are merely illustrative of an application of the principles of this invention, and that numerous other arrangements and modifications may be made within the spirit and scope of the invention.

What is claimed is:

l. A slab chair integrally formed of a plastic material for supporting elongated reinforcing members at a desired position in a concrete structure comprising a circular planar base,

a tubular support member extending centrally from said base for supporting two intersecting elongated reinforcing members a predetermined distance from said base, said tubular support member having openings therethrough permitting concrete to enter the interior thereof,

four equidistantly spaced radially disposed arms projecting from said base along the length of said hollow support member and extending above the top of said support member for receiving and providing lateral support for said two intersecting elongated reinforcing members, said extending arms having inwardly projecting portions at the tips thereof for retaining said elongated members between said arms, the spacing between the top surface of said support member and the inwardly projecting portions at the tips of said extending arms being substantially equal to the sum of the diameters of said two elongated reinforcing members, the spacing between the inwardly projecting portions of adj cent arms b ei g less than the diameter of san e ongated rem orcing members,

said arms being capable of flexing to receive said reinforcing members therebetween.

2. A slab chair as described in claim 1, wherein said base, extending arms and hollow support member are integrally formed of synthetic resinous material.

* II i l i

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Classifications
U.S. Classification52/685, 52/689
International ClassificationE04C5/16
Cooperative ClassificationE04C5/168
European ClassificationE04C5/16C