Description:
1. Field of the Invention
The present invention relates to devices for supporting and securing reinforcing bars for concrete construction. More specifically, the present invention relates to a device and method for supporting and securing rebar upon a form tie within a wall form.
2. Related Art
Reinforced concrete is one of the most common and time-tested materials in modern building construction. The placement of ductile steel reinforcing bars (“rebar”) within a concrete mass gives the resulting structure the combined benefits of concrete's high compressive strength and steel's high tensile strength and ductility. Additionally, cast-in-place concrete can be formed into almost any shape, allowing the creation of beams, columns, arches, and other shapes in almost any desired form.
It is well known that the strength and suitability of a reinforced concrete structure depends in part upon the quantity and location of the reinforcing steel. Considerable effort is expended in the design of reinforced concrete structures to determine and specify the optimum amount and location of rebar. Consequently, one persistent challenge in the subsequent construction of the structure is the proper placement of metal reinforcement within the concrete forms and keeping the reinforcement properly aligned (so as to provide adequate and consistent reinforcement) and with proper clearance from outer surfaces of the finished structure (so as to protect the reinforcement from exposure to the environment). If the steel is not placed according to the design, the resulting structure may not have the desired structural characteristics, and/or may be subject to premature degradation from environmental factors and age.
Rebar ties, chairs, and supports of various designs have been produced to help guide the placement of metal reinforcement. Unfortunately, forces created by the flow of wet concrete during placement can shift and move rebar from its intended position even when rebar fixing device are used properly, and this can easily go undetected by workers, even if they are paying close attention. Furthermore, many devices for supporting and securing rebar are inadequate for their purpose, either because of design aspects or difficulty of use. Some of these devices require significant skill and care by their user to avoid improper or inadequate rebar placement.
Unfortunately, in the construction industry, economic pressures constantly work against the effort to apply proper skill and attention to a given job. Placing additional chairs and ties within a form in order to better secure the rebar in the proper place takes time and money. Since the position of rebar within a concrete structure is generally not visible after the concrete is placed, shoddy work can easily go undetected during construction, and will generally not be noticed soon afterward except in extreme cases. Such flaws are frequently only discoverable many years after construction, when warranties have expired and there is little chance of holding the builder accountable. Furthermore, low wage, low skill laborers (as are frequently employed in the construction industry) may not possess the skill, knowledge or care needed to properly use devices that do exist to help with rebar placement, especially where such devices are cumbersome or difficult to use.
It has been recognized that it would be desirable to have an apparatus and method for placing rebar within concrete forms that encourages proper placement of the rebar and helps secure it better.
It has also be recognized that it would be desirable to have an apparatus and method for encouraging proper rebar placement that is inexpensive and simple to use.
In accordance with one embodiment thereof, the invention provides a device for supporting reinforcing bars within a form for a concrete wall having transverse form ties. The device includes a non-metal body, configured to attach to a form tie in a fixed orientation. The body includes at least one aperture, configured to receive an elongate reinforcing bar, so as to substantially fix the position of the reinforcing bar with respect to the form tie.
In accordance with another embodiment thereof, the invention provides a concrete form system, comprising a wall form having transverse ties, and a non-metal rebar spacer, attached to a transverse tie in a fixed orientation within the wall form. The rebar spacer has at least one aperture, configured to receive an elongate reinforcing bar, and to substantially fix the position of the reinforcing bar with respect to the form tie.
In accordance with another aspect thereof, the invention provides a method for supporting horizontal reinforcement within a concrete wall form. The method includes the steps of connecting a form tie between opposing vertical walls of the wall form, attaching a non-metal rebar spacer to the form tie between the form walls in a fixed orientation, and transversely inserting an elongate reinforcing bar into at least one aperture disposed in the rebar spacer, so as to substantially fix the position of the reinforcing bar with respect to the form tie.
Additional features and advantages of the invention will be apparent from the detailed description which follows, taken in conjunction with the accompanying drawings, which together illustrate, by way of example, features of the invention, and wherein:
FIG. 1 provides a front view of one embodiment of a rebar spacer
FIG. 2 is a side, cross-sectional view of a concrete wall form, showing the rebar spacer of FIG. 1 attached to a bar-type form tie;
FIG. 3 is a top view of the rebar spacer of FIG. 1;
FIG. 4 is a partial side, cross-sectional view of the rebar spacer of FIG. 1.
FIG. 5 is a side, cross-sectional view of a concrete wall form, showing another embodiment of a rebar spacer attached to a wire-type form tie;
FIG. 6 is a side, cross-sectional view of the rebar spacer of FIG. 5;
FIG. 7 is a front view of an embodiment of a rebar spacer configured to support rebar both above and below a form tie; and
FIG. 8 is a front view of an embodiment of a rebar spacer having a branched configuration.
A front view of one embodiment of a rebar spacer 10 in accordance with the present invention is provided in FIG. 1, and a top view of the same is shown in FIG. 3. Shown in FIG. 2 is a cross-sectional view of opposing concrete forms 12 with a flat bar-type form tie 14 extending therebetween, and a rebar spacer disposed upon it. One piece of rebar 16 is shown in cross-section, disposed in one of the top slots 18 of the rebar spacer.
The rebar spacer 10 generally comprises a flat body 20 of non-metal material with a variety of openings formed in it. In the embodiment of FIG. 1, the top of the body includes several rebar apertures 18 that are open rounded slots designed to receive and support rebar 16 (shown in hidden lines in cross-section in FIG. 1) that is oriented substantially transverse to the body of the rebar spacer. Other openings 22 are also formed in the body. These openings perform several functions. They allow liquid concrete to flow through the body, so that the rebar spacer does not hinder concrete placement, and also operate to provide a mechanical interconnection with the concrete that helps to anchor the rebar spacer and the form tie within the wall when the concrete has cured. Additionally, these openings reduce the total quantity and weight of material in the rebar spacer, which can help reduce manufacturing and shipping costs.
The rebar slots or apertures 18 are generally U-shaped, and have a total width or maximum diameter that is large enough to accommodate rebar up to a certain intended size, taking into account the surface deformations of the bar. The upper opening or mouth 24 of the slots include lips 26 that protrude inwardly on each side of the opening. These lips are closer together than the minimum diameter of the bar 16 for which the particular slot is intended, so that a user is required to press the bar into the slot, after which the lips hold the bar in the slot in a press fit. This helps prevent the bar form unintentionally coming out of the slot during placement of other rebar, or during placement of the concrete in the form.
The lips 26 of the rebar apertures 18 also allow the rebar spacer 10 to support rebar 16 that is inserted from below. As shown in FIG. 2, the rebar spacer can be attached to the form tie 14 in an inverted orientation (shown in dashed lines 28), so as to extend down form the form tie, to support and hold rebar that is below the form tie. The lips of the rebar apertures allow the rebar, so long as it is of sufficient size, to be inserted upward and held in the rebar aperture. This feature of the rebar spacer allows great flexibility of use, allowing the rebar spacer to support rebar above or below a form tie.
The rebar slots or apertures 18 can be of a variety of sizes, so as to accommodate rebar of different sizes. For example, different rebar spacers can be configured for supporting #4 bars (i.e. ½″ diameter), #5 bars ( 5/8″ diameter), etc., for all of the different standard rebar sizes, depending upon the size to be used in a given location. Thus, where several different sizes of rebar are to be used in a given project, rebar spacers configured for each size of rebar can be provided. Alternatively, a single rebar spacer can include apertures of different sizes. For example, as shown in FIG. 2, the rebar spacer 10 can include one or more apertures 18a configured to receive a bar of one size (e.g. a #4 bar), and one or more other apertures 18b configured to receive and hold a bar of a different size (e.g. a #5 bar). Additionally, it will be apparent that rebar of a smaller size can always be supported in a larger slot when the rebar spacer is in the upright orientation, though such a use may not provide quite as tight a fit. Nevertheless, where a wall includes both #4 and #5 bars, for example, a rebar spacer that is configured with apertures sized to support #5 bars can be used throughout.
The bottom region 29 of the body 20 includes two open elongate slots 30 that are configured to fit over the flat bar-type concrete form tie 14 and allow the bottom of the device to be attached thereto. The slots are disposed so as to provide a center tab region 32 and two outer tab regions 34. As shown in FIG. 2, the spacer body is attached to the form tie by deflecting the center tab region out of the plane of the body in one direction, while the two outer tab regions are deflected out of the plane of the body in the opposite direction. The body is then pressed down over the top edge 36 of the form tie, so that the center tab is on one side of the bar, while the outer tab regions are on the other side of the flat bar.
A pair of deformable locking buttons 38 protrude from the plane of the body 20 upon one side of each of the outer tab regions 34. A side cross-sectional view of one of these buttons is shown in FIG. 4. The locking buttons comprise a pair of opposing tabs 40 with oppositely oriented wedge-shaped lips 42 disposed on their extreme ends. The wedge shape of the lips causes the tabs to deflect toward each other when the button is pushed into a slot 44 on the form tie 14. Once the tabs are pushed sufficiently far into the slot that the wedges emerge upon the other side of the bar, the tabs snap back into position, and the wedges lock the button in place in the slot, and thus hold the rebar spacer to the form tie.
The locking buttons 38 have an elongate shape that matches the shape of the slots 44 on the form tie, and thus helps to fix the orientation of the body 20 of the rebar spacer 10 upon the form tie 14. That is, the elongate shape resists rotation of the rebar spacer relative to the form tie, in addition to simply supporting the form tie. Additionally, because there are two locking buttons that are spaced a distance apart, this provides additional stability to the position of the rebar spacer when attached to the form tie. With the locking buttons press-fit into the slots on the form tie, the rebar spacer is thus attached to the form tie in a substantially fixed orientation.
Naturally, the size of the rebar spacer 10 will vary depending upon various factors, including the size of the wall and the size (diameter) of the rebar it is designed to support. In the embodiment shown in FIGS. 1 and 2, the device is designed to support ½″ diameter (#4) bars, and is approximately 5.5 inches long, 2.5 inches high, and 3/16 inches thick. Other sizes and configurations are also possible. For example, the rebar spacer can be configured to support and hold various numbers of bars in almost any desired arrangement, and the height of the spacer—and hence the distance from the form tie at which the bars are held—can vary as desired.
Shown in FIG. 5 is a front view of another embodiment of a rebar spacer 50 configured to mount upon a wire-type form tie 52, rather than a flat bar-type form tie. A side, cross-sectional view of this embodiment is provided in FIG. 6. This embodiment is much like the above-described embodiment, with slots 54 in the top for supporting rebar 16, and other apertures 56 in the body for allowing flow of wet concrete, etc. However, on the bottom edge 62, rather than open slots for sliding over an edge of a flat bar, this embodiment includes a pair of gripping feet 58 for gripping the wire-type form tie 52.
Wire-type form ties are widely used, especially in commercial construction. These ties have a generally circular cross-section. However, as seen in FIG. 6, each tie includes a region 60 that is partially flattened (i.e. a region not having a circular cross-section) toward each end of the tie. This flattened region provides a structural discontinuity that allows the tie to be twisted and broken off at that point after the concrete has at least partially cured and the form walls have been removed. The gripping feet 58 of the embodiment of FIGS. 5-6 extend along a portion of the bottom edge 62 of each lateral side of the rebar spacer 50, and are configured to press onto and resiliently grip the flattened region of the wire tie to support the rebar spacer.
As shown in the side, cross-sectional view of FIG. 6, the gripping feet 58 include resilient forward and rearward portions 64, 66, that are configured to wrap around the flattened region 60 the form tie 52. The opening 68 between the forward and rearward portions is smaller than the corresponding dimension of the wire tie, so that the gripping feet must be pressed onto the wire in a press fit. Additionally, the interior region between the forward and rearward portions of the gripping feet includes at least one flattened or faceted inner surface 70 that is configured to mate with a flat surface 72 of the flattened region of the form tie, so as to fix the orientation of the rebar spacer 50 with respect to the form tie. That is, when the gripping feet are pressed onto the flattened region of the form tie, their resilient nature holds the flat surface of the gripping feet against the flat surface of the form tie, so that rotation of the rebar spacer upon the form tie is prevented. With two gripping feet spaced apart and the gripping feet including flattened or faceted surfaces, this embodiment of the rebar spacer thus also effectively attaches to the wire-type form tie in a substantially fixed orientation.
Rebar spacers in a variety of other configurations can also be made in accordance with the present invention. It was noted above that a rebar spacer such as that shown in FIG. 1 can be attached to a form tie in an upright orientation, so as to support rebar above the form tie, or can be attached in a downward orientation, so as to hold rebar below the form tie. As another embodiment, shown in FIG. 7, a rebar spacer 80 according to the present invention can be configured to support rebar 16 both above and below a form tie. As shown, this embodiment includes a lower portion 82 that is effectively an extension of the center tab 84 of the rebar spacer. Both the lower portion and the upper portion 86 include rebar apertures 88, the resilient lips 90 of the lower apertures operating to hold the rebar therein in the manner discussed above.
Other configurations are also possible. For example, as shown in FIG. 8, a rebar spacer 100 according to the present invention can be provided with a branched configuration. In this embodiment, the lower portion 102 of the rebar spacer is configured to attach to the form tie 104 in the manner described above. However, the upper portion 106 of the rebar spacer includes a first branch 108 and a second branch 110, each branch extending toward opposing side walls 112 of the form. Each branch includes one or more rebar apertures 114, and operates to hold rebar near to the opposing sides of the form. The branched configuration can be used in situations where two layers of rebar on opposing sides of a wall are desired. It will be apparent that the geometry and dimensions of the branched rebar spacer can be selected to correspond to the total thickness of the wall, so that neither the rebar nor the rebar spacer itself is placed too close to the outer surface of the finished concrete.
Rebar spacers according to the present invention can be made of a variety of materials, including polymers such as polypropylene, polyethylene, nylon, etc. The body of the spacer can be injection molded, machined, or formed in any other manner that is suitable for the type of material. The use of non-metal materials helps prevent corrosion that can degrade a concrete structure. As is well known, corrosion of metal reinforcement within a concrete mass not only gradually destroys the reinforcing properties of the rebar, but also cracks and breaks up the concrete because of the very high expansive forces created by the corrosion process. Thus, if the rebar spacer were of a metal material, because it is in contact with the form tie and the metal rebar, corrosion of the exposed form tie end could result in corrosion of the rebar spacer and the rebar through cathodic action, and thence of any other electrically conductive material in contact therewith.
It is also desirable that the rebar spacer be somewhat flexible, though suitable materials can have a wide range of flexibility. In order to fit over a bar-type form tie, as shown in FIG. 2, where the body of the spacer is substantially planar, it must be able to flex to allow the center tab and outward portions to slide over opposing sides of the form tie. Additionally, a certain degree of flexibility and resilience are needed to allow the resilient lips of the rebar apertures to effectively receive and hold the rebar therein, and some flexibility and resilience are needed for the locking buttons and gripping feet.
At the same time, a large degree of flexibility is not necessarily required. For example, for an embodiment like that of FIG. 1, the body of the rebar spacer need not be planar, but can be molded or otherwise formed in a non-planar configuration that is adapted to slide over the form tie with portions abutting opposing sides of the form. Such a configuration can be of a more rigid material than may be desired for the embodiment of FIGS. 1-2. Those skilled in the art will recognize that the polymer materials mentioned above, and others not mentioned, can be adapted to provide the needed flexibility for the various embodiments disclosed herein and modifications of them.
While a variety of configurations for the rebar spacer have been shown and described, it will be apparent that other configurations and combinations of elements shown can also be provided. For example, any of the various rebar spacer embodiments shown herein can include gripping feet for use with wire-type form ties, or locking buttons for attachment to bar-type form ties. Rebar apertures of different sizes and in different positions can also be provided, and any number of rebar apertures can be included on a single rebar spacer, though practical limitations of space and proper rebar spacing will likely affect the number and position of the apertures. Additionally, different combinations and arrangements of branches, etc. can also be used.
In its various embodiments, the invention provides a simple and inexpensive system and method for assisting accurate and consistent placement of rebar in a concrete form. The rebar spacer helps ensure proper alignment of rebar in spite of worker inexperience or carelessness, and helps prevent displacement of the rebar during placement of concrete. Additionally, because the device is simple, inexpensive, and easy to use, its use will not add significantly to the cost of construction.
While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.
Want more information on concrete rebar spacers? Click the link below to contact us.