Patent Application
20130125498
1. Field of the Invention
This invention relates in general to rebar chairs for supporting reinforcement bars at a pre-selected elevated position above a bearing surface during the formation of a concrete slab or foundation.
2. Prior Art
Concrete and many plastic compositions have a relative weak tensile strength. When used to form a slab these compositions will be placed in tensile stress from imposed loads, thermally induced changes or solidification upon setting. To increase the tensile strength of the slab, rebar rods are used to form a grid that acts as skeletal reinforcing members.
It is generally the practice to form a frame around the site that a foundation is to be formed, then to form a rigid rebar grid within the frame, and then to place and level the wet concrete over the grid. Upon the setting of the concrete a slab construction is completed. One problem with this practice is forming the rebar grid within the frame whereby the grid is properly positioned within the slab. For best results, the grid should be positioned where the greatest protection from stress is needed. This is generally close to the surface of the concrete. In many cases attaching the prior art rebar chairs to the rebar is difficult or once attached the rebar chairs become loose as other rebar chairs are being attached. Another problem results when the concrete is placed over the rebar grid and leveled.
It is often the practice in such constructions to position a grid a few inches above the ground by resting the grid upon rigid supports or chairs. However, in actual practice the grids do not remain in their initially arranged pre-selected positions. For example, workers often walk upon the grid during the placing operation. These actions in many cases results in rebar chairs becoming partially or completely detached from the rebar or rotated or twisted causing the rebar to shift to an undesirable level that defeats the strengthening function of the grid. To combat this problem many of the prior art rebar chairs are designed to affix to the grid at the points of intersection. However, in these designs it becomes more difficult, more time consuming, and more cost prohibitive to attach the rebar chairs to the grid.
Still another problem with many prior art rebar chair constructions results when the person who is shoveling or leveling the wet concrete in the frame backs into or missteps on the rigid rebar chair causing them to trip and injure themselves or to cause the concrete to be misplaced or misshaped.
Therefore, one object of this invention is to provide an improved rebar chair for use to position a rebar formed grid at the desired height from the base surface that is easy and quick to attach to the rebar used in forming the grid.
Another object of this invention is to provide an improved rebar chair that can serve as a stable support for a rebar formed grid during the positioning of the grid and during the concrete pouring for forming the foundation or other structure being constructed.
Still another object of this invention is to provide a rebar chair that avoids twisting or angular deflection, sometimes referred to as racking, and does not tip over during the concrete pouring for a foundation or other similar concrete structure.
A further object of this invention is provide a rebar chair that is easy and quick to attach to the intersecting rebar members forming the grid in a manner that permits the grid to be constructed and then transported to the concrete pouring site.
A still further object of this invention is provide an improved process for forming a concrete foundation utilizing a rebar grid that can be foamed and then transported to the framed foundation pouring site.
Other objects and advantages of this invention shall become apparent from the ensuing descriptions of the invention.
Accordingly, an improved rebar chair for supporting a rebar formed grid at a pre-selected elevated position above a bearing surface during formation of a concrete slab or other structure is constructed having a base member shaped to rest on the bearing surface, a support structure having a lower section affixed to the base member and an upper section affixed to a rebar retention member shaped to attach to and support the rebar grid at one of its intersections so as to position the rebar grid at the desired elevated position. The base member is preferably constructed in the shape of a ring having a generally flat bottom surface positioned on the bearing surface wherein the ring has a shoulder member extending vertically around the inner perimeter of the ring. The support structure includes at least three legs, preferably four legs, equally spaced about and extending upward from the ring at an inward angle to attach to the rebar retention member. The rebar retention member includes a floor, preferably with intersecting reinforcing braces extending from one perimeter section to an opposing perimeter section of the floor. The rebar retention member further includes one or more walls extending upward from the floor and to which the support structure legs are affixed. The walls are constructed to form four slots that are equal distant from one another to form a first pair of opposing slots and a second pair of opposing slots. Each slot in the first pair is formed in one of the side walls beginning at the upper edge of the side wall and terminating near the floor. Each slot of the first pair has a receiving section formed by inwardly sloping edges to form a gap less than the diameter of the rebar and a retention section extending from and below the gap having a cross-section sufficiently large for the rebar to extend through the retention section. The wall is constructed from a flexible plastic or other material that permits the rebar to be pushed through the gap and into the retention section, but of sufficient rigidity to prevent the rebar from passing back through the gap under the normal forces exerted during the positioning of the grid and the placement of the concrete over the rebar chair. The second pair of opposing slots is similarly formed but with the slots terminating at a position at or above the lower portion of the gaps of the first pair of opposing slots to accommodate the intersecting rebar members that overlay one another. In a preferred embodiment each leg of the support structure is constructed from material that retains its shape when concrete is placed over the rebar chair, but which further provides sufficient elasticity to the leg to bend under the force from the weight of a person stepping on the rebar chair and to return to its original shape when that force is removed.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention.
The accompanying drawings illustrate a preferred embodiment of this invention. However, it is to be understood that this embodiment is not intended to be exhaustive, nor limiting of the invention. They are but examples of some of the forms in which the invention may be practiced.
Without any intent to limit the scope of this invention, reference is made to the figures in describing the preferred embodiments of the invention.
As seen in
The support structure 3 is formed from equally spaced apart four legs 11A-11D affixed at their lower sections 12A-12D, respectively, to circular member 6. Each leg 11A-11D is shaped to extend inward of shoulder member 10 and over central opening 5, and is provided with a connecting section 13A-13D, respectively, that is affixed to the retention member 4. Legs 11A-11D must be constructed to have sufficient rigidity and strength to support the rebar grid 14 constructed of intersecting lower rebar member 15 and upper rebar member 16, and to prevent a change in the height of the rebar grid 14 from the bearing surface 7 during installation and placement of the concrete over the rebar chair 1 and rebar grid 14. At the same time legs 11A-11D must have sufficient resiliency to bend when receiving the force from the weight of a person stepping on the rebar chair 1 and to return to its original shape when the force is removed from the rebar chair 1.
The retention member 4 is constructed from one or more walls 17 extending above a floor 18 and to which is affixed leg connecting sections 13A-13D. In a preferred embodiment the floor 18 is circular with a single wall 17 affixed at its lower edge 19 to floor 18 and extending upward to its top edge 20 a distance, preferably, at least three times the diameter of rebar members 15 and 16. Wall 17 is provided with a first pair of opposing slots 21A, 21B and a second pair of opposing slots 21C, 21D wherein each slot 21A-21D is preferably equally spaced from its adjacent slots. Each of slots 21A-21D extend from the wall top edge 20 toward retention member floor 19 and have a receiving section 22A-22D, respectively, formed of inwardly sloped wall edges 23A-23D, 24A-24D, respectively, to form a gap 25A-25D, respectively, less than the diameter of rebar members 15 and 16 that leads to a retention section 26A-26D, respectively, shaped to permit one of rebar members 15, 16 to pass through the retention section 26A-26D, respectively. The retention sections 26A and 26B of the first pair of slots 21A, 21B, respectively, are positioned to be adjacent floor 18. The retention sections 26C and 26D of the second pair of slots 21C, 21D, respectively, are positioned to be above gaps 25A and 25B to permit the lower and upper rebar members 15 and 16 to be positioned in the first and second pair of slots 21A, 21B and 21C, 21D, respectively.
The retention member wall 17 is constructed of material having sufficient flexibility to allow a person to manually push the lower and upper rebar members 15 and 16 through gaps 25A, 25B and 25C, 25D, respectively, but sufficiently rigid to prevent the forces against rebar members 15 and 16 and chair 1 during installation and the placing of concrete from dislodging rebar members 15 and 16 from retention sections 26A, 26B and 26C, 26D, respectively. If desired retention sections 26A-26D can be sized to hold more than one rebar member 15 or 16. This will be particularly useful if it is desired to utilize L-shaped rebar members 15 or 16 to provide additional strength to the cured concrete foundation.
In construction of a concrete foundation slab a frame is formed, typically with 2×6 or 2×12 lumber planks, that defines the outer perimeter of the concrete slab to be formed. Once the frame has been formed then a rebar grid 14 is formed. A partially constructed grid 14 is illustrated in
Once grid 14 has been formed it is sufficiently rigid to be carried and placed within the frame. Once grid 14 has been positioned within the frame concrete may be placed in and over grid 14 and leveled by traditional methods. In a preferred embodiment chair floor 18 is provided with one or more openings 30 sized to permit wet concrete to flow through openings 30 to better insure there will be no voids formed around or in retention member 4.
Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
