Patent Application
20140270949
This invention relates to a composite dowel basket for use generally in jointed plane concrete pavement applications and a method for making the same. More specifically, though not exclusively, the present invention relates to a composite dowel basket in which the dowels themselves are secured in place during the molding process such that no on-site assembly is required. Optionally, support frames may be molded separately from the dowels, wherein the dowel ends are slidably inserted into the support frame for assembly. The assembly is easy to use, lightweight and non-corrosive.
Currently, reinforced concrete employs a system of dowels which is supported by a wire support structure to elevate the dowels to a desired height within the poured concrete structure. For example, when roads are poured, a system of dowels and wire support structures work together to form what is typically known as a basket that allows the concrete to be poured over the dowels and its support structure. As discussed in U.S. Pat. No. 6,092,960, which is incorporated herein by reference, it is well-known that concrete has a high compressive strength with low tensile and shear strengths and that concrete expands and contracts due to changes in temperature. Previously, dowel bars have been incorporated into concrete structures to transfer shear loads at joints and allow the concrete blocks or slabs to expand in a desired direction. By controlling the direction of expansion of the slabs, engineers can minimize the likelihood that highways and other surfaces will become uneven.
As others have noted, steel dowels are typically used in current construction methods as it was considered a cost effective way to provide the necessary strength required by the application. Unfortunately, the steel in dowels has a tendency to corrode after years of use and this corrosion negates its beneficial incorporation.
To solve this problem, others have suggested using composite materials such as fiberglass dowel bars and fiber composite dowels to replace the steel dowel bars. While composite or fiberglass materials have been used to replace the steel dowels in the prior art, such incorporation also presents problems. For example, these fiberglass or composite materials can no longer be welded to their support structure. Thus, the prior art has developed numerous examples of securing apparatuses. For example, U.S. Pat. No. 6,092,960 to McCallion, describes a series of clips 30, 40 that may be used to secure the composite or fiberglass dowel to its underlying steel support structure. This requires extensive labor to assemble all of the components and ensure that the clips remain attached. Because the clips are not permanently secured, they may also cause problems during installation and pouring of concrete if things fall apart.
Others have attempted to support the existing rebar using plastic molded components. For example, U.S. Pat. No. 5,555,693 to Sorkin discloses a chair for use in construction that includes an indentation suitable for the receipt of rebar. A similar support structure is described in U.S. Patent Application Publication No. 2004/0261352 to Bennett et al. These structures are designed to hold rebar in place during pouring. Unfortunately, as these structures are separate from the rebar itself, they are prone to failure during the pouring process as they can easily be tipped over or separated from the rebar. To secure them to the rebar requires additional labor or materials. Also, these devices are designed for rebar, not the necessary dowels for joint load transfer.
It is therefore desirable to provide an improved road basket that requires no on-site assembly, uses no corrosive dowel or wire material and attempts to address some of the issues with the prior art.
A general feature of the present invention is an improved road basket and method of making same which addresses some of the issues with the prior art.
A further feature of the present invention is the provision of an improved road basket and method of making same which avoids the use of corrosive materials.
Another feature of the present invention is the provision of an improved road basket and method of making same which is easy to manufacture.
Still another feature of the present invention is the provision of an improved road basket and method of making same which is easy to install.
Another feature of the present invention is the provision of an improved road basket and method of making same which requires no on-site assembly.
Another feature of the present invention is the provision of an improved road basket and method of making same which is low cost to manufacture.
Still another feature of the present invention is the provision of an improved road basket and method of making same which is lightweight.
The present invention generally comprises an improved road basket including a non-metallic dowel having a dowel first end, a dowel second end, and a dowel intermediate portion, a first support frame including a first support frame first leg and a first support frame first cup moldably secured to the dowel first end, and a second support frame including a second support frame first leg and a second support frame first cup moldably secured to the dowel second end. Optionally, the support frames may be molded separately from the dowels, wherein after molding the dowel ends are slidably inserted into the frame cups. Multiple dowels can be secured in similar fashion to additional leg members of the frame. Preferably, the first support frame first leg and a first support frame second leg are connected by a base frame member. In addition, the first support frame first leg and the first support frame second leg may be connected by an intermediate frame member. The first support frame and the second support frame may be constructed of a single piece. The dowel is preferably made from fiberglass or glass fiber reinforced polymer and the frame is preferably high density polyethylene. Thus, the support frames and dowels should provide the ability to flex, while not compromising strength or durability.
During manufacturing, the dowels are protruded, depending on their construction, and cut to a desired length. Once cut to a desired length, at least a portion of each dowel is placed in an injection mold. The mold is then closed around at least a portion of the dowel and the frame is formed by injecting material into the mold. At least a portion of the frame is overmolded around the portion of the non-metallic dowel in the mold. Preferably, many dowels may be placed in the mold simultaneously and the frame members may be formed simultaneously such that when the frame and dowel structure is removed from the mold, the road basket is formed. Optionally, the frame may be formed in the mold separately from the dowels, wherein the dowels are added subsequently.
Preferably, the frame members are made from injection of a high density polyethylene or HDPE structural foam into the mold. During the cutting process, slight deformations of the dowel may occur. These deformations serve to reinforce the hold of the frame members on the dowel during the over-molding process.
Once formed, the complete road basket is transported to a work site. At the work site, the users may cut the road basket to a desired length using readily available cutting tools, including saws generally used to cut wood. If necessary, the road basket may be secured in a desired location on the work site by securing an anchor to the first support frame. These anchors may be U-shaped or any other shape of anchor which is capable of holding the road basket in place.
The present invention will be described as it applies to its preferred embodiment. It is not intended that the present invention be limited to the described embodiment. It is intended that the invention cover all modifications and alternatives, which may be included within the spirit and scope of the invention.
Referring to the drawings,
As shown in
A close-up of the connection point between the dowel 12 and the frame 14 is shown in
As shown in
During manufacturing, the dowels 12 are extruded or protruded, depending on their construction, and cut to a desired length. Preferably, an FRP pultrusion machine from Marine Products, Inc. or Liberty Pultrusions is used. Once cut to a desired length, at least a portion of each dowel 12 is placed in a structural foam injection molding machine, such as one from Uniloy Milacron using a mold, such as one from 20/20 Custom Molded Plastics. The mold may then be closed around at least a portion of the dowel 12, such as the dowel first end 16. After the dowel 12 sections 16, 18 have been placed in the mold, the mold is closed and the injection process begins. Initially, the injected material, preferably the HDPE structural foam, will be heated to a first formation temperature as needed to ensure the foam is generally in a liquid or flowing state. The heat and pressure from the HDPE structural foam will create a thermoset bond between the frame 14 and the dowel 12 as the HDPE structural foam cools to a second formation temperature in which the HDPE structural foam is generally in a solid state. The melting temperature or first formation temperature will vary by material and is typically specified by the material manufacturer.
When the overmolding occurs over a portion of the dowel 12, a bond is formed at the interface between the outer surface of the dowel 12 and the inner surface of the cup 28 as the cup 28 and interface are formed simultaneously. This bond at the interface can be broken by the forces of the expansion and contraction of the concrete, which is the design intent, which corresponds to current practice of welding every other end of steel dowel to wire frame. In this manner, the non-metallic road basket 10 of the present invention maintains the desired qualities of the prior steel dowels while providing additional benefits of non-corrosion and easy installation and manufacturing. Moreover, the present invention provides the added benefit of flexibility and self-adjustment as the dowels maintain the ability to slide inside the frame cups after the interface bond is broken.
During the molding process, the frame 14 is formed by injecting material into the mold. For example, as shown in
Once formed, the complete road basket 10 is transported to a work site. At the work site, the users may cut the road basket 10 to a desired length using readily available cutting tools, including saws generally used to cut wood. If necessary, the road basket 10 may be secured in a desired location on the work site by securing an anchor to the first support frame. These anchors may be U-shaped or any other shape of anchor which is capable of holding the road basket in place.
A general description of the present invention as well as a preferred embodiment of the present invention has been set forth above. Those skilled in the art to which the present invention pertains will recognize and be able to practice additional variations in the methods, systems and apparatuses described which fall within the teachings of this invention. Accordingly, all such modifications and additions are deemed to be within the scope of the invention which is to be limited only by the claimed appended hereto.
This application is a Continuation-in-Part of U.S. patent application Ser. No. 13/826,588 filed Mar. 14, 2013, herein incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13826588 | Mar 2013 | US |
| Child | 14103356 | US |
