US20130125498A1

US20130125498A1 - Rebar chair

Info

Publication number: US20130125498A1
Application number: US13/300,225
Authority: US
Inventors: Clayton W. Lowery
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-11-18
Filing date: 2011-11-18
Publication date: 2013-05-23

Abstract

A chair for supporting a rebar grid formed from intersecting lower and upper rebar members at a predetermined height above a bearing surface is constructed having a base member, a support structure having three or more equally spaced apart legs affixed to the base member, and a retention member constructed whose walls have four equally spaced apart slots extending downward from the walls upper edges, a first and second opposing pairs of the slots each having an upper receiving section formed by inwardly sloped wall edges to form a gap less than the diameter of the rebar members and having a retention section formed below the gap of sufficient size to permit one of the rebar members to extend through the retention section, wherein the retention section of the second opposing pair is formed below the retention section of the first opposing pair.

Description

BACKGROUND OF THE INVENTION

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.

OBJECTS AND SUMMARY OF THE INVENTION

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.

BRIEF DESCRIPTION OF THE DRAWINGS

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.

FIG. 1 is a perspective view of a rebar grid utilizing a preferred embodiment of the rebar chair of this invention to connect the rebar members at their intersections for positioning a desired distance above the foundation bearing surface.

FIG. 2 is a three-quarter perspective view of a preferred embodiment of the rebar chair of this invention.

FIG. 3 is a front view of the rebar chair of FIG. 2.

FIG. 4 is a side view of the rebar chair of FIG. 2.

FIG. 5 is a top view of the rebar chair of FIG. 2.

FIG. 6 is a bottom view of the rebar chair of FIG. 2.

PREFERRED EMBODIMENTS OF THE INVENTION

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 FIGS. 2-6, the rebar chair 1 contains three basic elements. They are the base member 2, the support structure 3 and the retention member 4. In the preferred embodiment shown base member 2 is ring-shaped having a central opening 5 forming a solid circular member 6 having a width “w” less than 20% of the diameter of opening 5. Other shapes, such as rectangular or other multi-sided polygons, could be utilized in the construction of base member 2. In selection of the design to be utilized the solid portion of the base member 2 that is to contact the load bearing surface 7 should be sufficiently wide to support the rebar members in a stable position when the grid is positioned for use. In a preferred embodiment the bottom surface 8 of circular member 6 will be substantially flat to allow it to sit evenly on the bearing surface 7 where concrete will be placed to form the foundation or other structure. Positioned about the perimeter 9 of opening 5 is a raised shoulder member 10.
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 FIG. 1. Although the most common grid 14 is rectangular in shape, grid 14 can be formed in other shapes by either cutting one or more of the end sections 27 of the rebar members 15 and/or 16 or by using different length rebar members 15 and/or 16 to achieve the desired shape. Grid 14 includes lower rebar members 15 and upper rebar members 16 that are positioned perpendicular to one another. Grid 14 further includes rebar chairs 1 preferably positioned at each intersection formed by upper and lower rebar members 15 and 16, respectively. Each rebar chair 1 is attached to one lower rebar member 15 and to one upper rebar member 16. In a preferred embodiment of this invention grid 14 is first formed outside of the frame and then carried to and positioned within the frame. This procedure has several advantages. First, the layout of the rebar chairs 1 can be done on a flat hard surface which makes the approximate positioning of the rebar chairs 1 easier and quicker. Second, the persons assembling grid 14 are not constricted by having to maneuver within the frame, again making the construction of grid 14 easier and quicker. The distance separating rebar chairs 1 in grid 14 is dependent on the size of the rebar and the amount of deflection allowed after placement. For a #5 rebar member it is preferred that the center of rebar chair floors 18 be separated approximately 26 inches. Once the rebar chairs 1 have been positioned to form rows 28 and columns 29, then each lower rebar member 15 is attached to the rebar chairs 1 in one of the parallel rows 28. This is continued until there is a lower rebar member 15 attached to the rebar chairs 1 in each of the parallel rows 28. Next, each upper rebar member 16 is attached to the rebar chairs 1 forming a column 29 that is perpendicular to the lower rebar members 15. This is continued until there is an upper rebar member 16 attached to the rebar chairs 1 in each of the parallel columns 29. The attachment of each lower rebar member 15 to a rebar chair 1 is accomplished by placing the lower rebar member 15 across slots 21A and 21B and pressing down until lower rebar member 15 passes through gaps 25A and 25B, respectively, and then into retention sections 26A and 26B, respectively. Similarly, the attachment of each upper rebar member 16 to a rebar chair is accomplished by placing the upper rebar member 16 across slots 21C and 21D and pressing down until upper rebar member 16 passes through gaps 25C and 25D, respectively, and then into retention sections 26C and 26D, respectively.
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.

Claims

1. A chair for supporting a rebar grid formed from intersecting lower and upper rebar members at a predetermined height above a bearing surface comprising:

a. a base member provided with a central opening formed by an opening perimeter, wherein the base member is ring-shaped and has a width less than about 20% of the central opening;

b. a support structure having three or more equally spaced apart legs, each leg having a lower section affixed to the base member adjacent the opening perimeter and shaped to extend over the central opening and having a connecting section; and

c. a retention member constructed having a floor and one or more walls to which the connecting member of each leg is affixed, each of the one or more walls having a lower end affixed to the floor and an upper edge extending vertically from the floor, the one or more walls having four equally spaced apart slots extending downward from the upper edge of the one or more vertically extending walls, a first opposing pair of the slots having an upper receiving section formed by inwardly sloped wall edges to form a gap less than the diameter of the rebar members and having a retention section formed below the gap of sufficient size to permit one of the rebar members to extend through the retention section, and a second opposing pair of the slots having an upper receiving section formed by inwardly sloped wall edges to form a gap less than the diameter of the rebar members and having a retention section formed below the gap of the second opposing pair of the slots but at a height from the floor above the gap of the first opposing pair of the slots.

2. (canceled)

3. A rebar chair according to claim 1 wherein:

a. each leg is constructed having sufficient rigidity and strength to support the rebar grid at the predetermined height, and

b. each leg is constructed having sufficient resiliency to bend when receiving a force from the weight of a person stepping on the rebar chair and to return to its original shape when the force is removed from the rebar chair.

4. A rebar chair according to claim 1 wherein the one or more walls are constructed having sufficient flexibility to manually push a rebar member through one or more of the gaps.

5. A rebar chair according to claim 1 wherein the floor has one or more openings sized to permit wet concrete to flow through the openings.

6. A method of forming a rebar grid comprising a series of lower parallel rebar members and upper parallel rebar members perpendicularly intersecting one another at intervals and fixed in position to one another by one or more rebar chairs, comprising the steps of:

a. determining the shape of the rebar grid to be formed;

b. determining the distance between each of the intervals to be formed by the

c. intersecting lower and upper rebar members; the intervals forming columns and rows;

d. positioning at each of the intervals a rebar chair to form columns and rows of rebar chairs; the rebar chair comprising:

i. a base member provided with a central opening formed by an opening perimeter, wherein the base member is ring-shaped and has a width less than about 20% of the central opening;

ii. a support structure having three or more equally spaced apart legs, each leg having a lower section affixed to the base member adjacent the opening perimeter and shaped to extend over the central opening and having a connecting section; and

iii. a retention member constructed having a floor and one or more walls vertically extending above the floor to which the connecting member of each leg is affixed, each of the one or more walls having four equally spaced apart slots extending downward from an upper edge of the one or more vertically extending walls, a lower first opposing pair of the slots having a first receiving section to receive a first rebar member and formed by inwardly sloped wall edges to form a first gap less than the diameter of the rebar member and having a first retention section formed below the first gap of sufficient size to permit the rebar member to extend through the first retention section, and an upper second opposing pair of the slots having a second receiving section to receive a second rebar member and formed by inwardly sloped wall edges to form a second gap less than the diameter of the second rebar member and having a second retention section formed below the second gap of the second opposing pair of the slots but at a height from the floor above the first gap of the first opposing pair of the slots.

e. attaching a lower rebar member to each of rows of rebar chairs by pushing the lower rebar member into the first retention section of each of the rebar chairs in one of the rows of rebar chairs; and

f. attaching an upper rebar member to each of the columns of rebar chairs by pushing the upper rebar member into the second retention section of each of the rebar chairs in one of the columns of rebar chairs.

7. The method of forming a rebar grid according to claim 6 wherein the floor has one or more openings sized to permit wet concrete to flow through the openings.

8. A chair for supporting a rebar grid formed from intersecting lower and upper rebar members at a predetermined height above a bearing surface comprising:

a. a base member provided with a central opening formed by an opening perimeter, the base member is ring-shaped and has a width less than about 20% of the central opening;

c. a retention member constructed having a floor and one or more walls to which the connecting member of each leg is affixed, each of the one or more walls having a lower end affixed to the floor and an upper edge extending vertically from the floor, the one or more walls having a retention section of sufficient size to permit one of the rebar members to extend through the retention section.

9. A rebar chair according to claim 8 wherein the floor has one or more openings sized to permit wet concrete to flow through the openings.

10. A rebar chair according to claim 8 wherein each leg is constructed having sufficient resiliency to bend when receiving a force from the weight of a person stepping on the rebar chair and to return to its original shape when the force is removed from the rebar chair.