Patent Application
20160017549
Not Applicable.
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Not Applicable.
1. Field of the Invention
The present invention pertains to jointed concrete. More particularly, the present invention pertains to the use of hollow carbon steel dowels in jointed concrete pavement and methods of forming such dowels.
2. General Background
To prevent concrete pavement from cracking along random fracture lines, it is common to partially cut through new pavement to create intentional fracture lines. However, creating near planar fractures in pavement prevents the concrete from transferring any appreciable out of plane shear loads across such joints. Thus, to prevent adjacent sections of concrete from shifting out of plane relative to each other, dowels running parallel to the pavement are often positioned within the concrete across such joint lines before the concrete cures. Once the concrete fractures along the joint, the dowels transfer the shear loads between adjacent sections of concrete to thereby prevent relative transverse movement between such sections of concrete.
Most concrete pavement dowels are solid carbon steel cylindrical rods. Such dowels are fairly inexpensive and are cut from longer lengths of rod. Typically, long rods of carbon steel are shipped to a processing center or to a job site, where they are then batch cut to length for use as dowels. The batch cutting typically involves placing a plurality of rods (20 or more) in a basket or cradle stye holder and thereafter cross-cutting the plurality of rods to length via a band saw. To reduce corrosion, carbon steel dowels may be galvanized or epoxy coated.
In rare situations requiring extremely long life pavement or involving pavement in abnormally corrosive environments, stainless steel dowels are used. In view of the relatively high cost of stainless steel compared to carbon steel, such stainless dowels are typically welded tube rather than solid rod. The added cost of forming the welded stainless tube is justified by the lower total material cost of the dowels. However, like the standard carbon steel rods, stainless steel tube dowels are typically batch cut from long cylindrical tubes of stainless steel that are shipped to a processing center or to a job site. In view of the inherent corrosion resistance of stainless steel, coating such stainless steel tube dowels with epoxy or otherwise coating such dowels is not necessary. It should be appreciated however that stainless steel tube dowels are significantly more expensive compared to carbon steel rod dowels.
Concrete pavement dowels can be place in concrete several ways. Prior to pouring the concrete, the dowels may be placed on baskets or cradles. The concrete can then be poured over the dowels, with the baskets or cradles holding the dowels near the center of the pavement thickness. Alternatively, it has been increasingly common to place the dowels into poured uncured concrete, thereby eliminating the need for baskets or cradles. The dowels can be placed in the uncured concrete by hand or in an automated manner via a concrete paving machine.
Although the use of carbon steel rod dowels is not seen as problematic, the inventor has conceived of using carbon steel tube dowels in lieu of rod dowels. Although others have assumed that the carbon steel tube dowels would be more costly than carbon steel rod dowels, the inventor has conceived of a manner of producing carbon steel tube dowels that renders such carbon steel tube dowels fifteen or more percent less expensive to produce as compared to current carbon steel rod dowels.
One aspect of the invention pertains to a method of forming jointed concrete dowels. The method comprises unspooling a coil of carbon steel strip and directing the uncoiled strip along a path. The uncoiled strip has opposite side edges that extend along the path. The method further comprises bending the strip into a hollow tube in a manner such that the side edges are adjacent to each other, and thereafter electric resistance welding the side edges of the strip to each other such that the hollow tube has a closed transverse cross-section. Still further, the method comprises transversely cutting the welded hollow tube into a plurality of jointed concrete dowels. The steps of unspooling the coil, bending the strip, and electric resistance welding the side edges of the strip occurs continuously as the strip is uncoiled and travels along the path, and the step of transversely cutting the hollow tube occurs as the hollow tube travels along the path.
Another aspect of the invention pertains to a method of forming jointed concrete pavement. The method comprises positioning a dowel in a location that will become pavement. The dowel comprises a carbon steel welded seam hollow tube and a pair of end caps. The caps are attached to opposite axial ends of the hollow tube. The method further comprises allowing concrete to cure around the dowel to thereby transform the concrete into pavement. Still further, the method comprises cutting a top surface of the pavement over the dowel.
In still another aspect of the invention, jointed concrete pavement comprises concrete cured around a dowel. The dowel comprises a welded seam carbon steel hollow tube and a pair of end caps. The end caps are attached to opposite axial ends of the hollow tube. The pavement comprising a fracture groove over the dowel.
Further features and advantages of the present invention, as well as the operation of the invention, are described in detail below with reference to the accompanying drawings.
Reference numerals in the written specification and in the drawing figures indicate corresponding items.
A carbon steel tube dowel assembly 10 in accordance with the invention is depicted in
The tube 12 is preferably generally cylindrical and is formed from carbon steel strip stock (e.g., four and a half inches by one-eighth inch grade 60 carbon steel strip). As shown schematically in
Following the formation of the now seam welded tube 28, several optional processes may be performed on the tube prior to cutting the tube into lengths of individual dowel tubes 12. For example, the exterior of the welded tube 28 may be cleaned and dried at a cleaning station 32 in preparation for painting and thereafter spray painted or dipped at a coating station 34 while still continuously moving along the path. In addition or alternatively, the welded tube 28 may be epoxy coated at the coating station 34.
Following any optional in-line cleaning and/or coating processes, the welded tube 28 is transversely cut into length of individual dowel tubes 12. This occurs as the welded tube 28 continuously moves along the path. Thus, the cutting station 36 comprises a cutting tool, such as a laser or traditional toothed saw that linearly reciprocates along the production path. When moving in the direction of the welded tube 28, the cutting tool moves along the path at the same speed so that it can transversely cut the welded tube. Of course, when moving in the opposite direction, the cutting tool can move at any speed necessary. In this manner, the cutting tool of the cutting station 36 can continuously transversely cut dowels tubes 12 from the recently formed welded tube 28 without pausing the unspooling of the strip stock 16 from the strip stock spool 18 or the forming and welding processes.
Following the cutting of the individual dowels tubes 12 from the welded tube 28, the dowel tubes can undergo several other optional processes via either automated or manual operations. For example, to the extent that the welded tube 28 was not earlier coated, the dowel tubes 12 may be cleaned and dried and thereafter coated as desired. If the strip stock 16 was originally galvanized, the dowel tubes 12 may be re-galvanized to galvanize the seam welds of the dowel tubes.
The actual dimensions of the dowel tubes 12 will likely be driven by various state requirements. For example, the diameter of the dowel tubes 12 may be required to be a particular nominal diameter that is anywhere from one-half of an inch to two inches. Likewise, the wall thickness of the dowel tubes 12 may be required to be a particular nominal thickness that is anywhere from 0.065″ to 0.1875″. Still further, the length may be dictated by state regulations and may be anywhere from one to two feet. Of course, if state regulations require dimensions outside of the ranges, the dowel tubes 12 can be manufactured to such dimensions as needed. Thus, these dimensions are merely suggestive of the dimensions of the actual dowel tubes 12.
Once the dowel tubes 12 are themselves complete, the end caps 14 can be inserted into or onto the axial ends of the dowel tubes 12. The end caps 14 are preferably made of relatively resilient polymeric material and are preferably simply press-fit into or onto the dowel tubes 12. If desired however, the end caps 14 may be epoxied or otherwise adhered to the dowel tubes 12. The completed dowel assemblies 10 are thereafter group and packaged for shipping.
As an additional option, a chemically active material may be used in with the dowel tubes 12 to provide cathodic protection for the dowel. For instance, a washer 39 made from zinc may be inserted between the axial end of the dowel tubes 12 and the end caps to act as a sacrificial anode. Other chemically active materials may also be used. The washer may provide additional cathodic corrosion resistance to the ends of the dowel tubes. The washer may be stamped from flat rolled material or formed from wire. The washer may be the same diameter and thickness as the tube. The washer may be located an insertion diameter of the end cap. The use of the washer and the material of the washer may be dictated by state regulations. The washer may retard corrosion on the edge/end of the dowel tubes.
As shown in
In view of the foregoing, it should be appreciated that the invention has several advantages over the prior art.
As various modifications could be made in the constructions and methods herein described and illustrated without departing from the scope of the invention, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative rather than limiting. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims appended hereto and their equivalents.
It should also be understood that when introducing elements of the present invention in the claims or in the above description of exemplary embodiments of the invention, the terms “comprising,” “including,” and “having” are intended to be open- ended and mean that there may be additional elements other than the listed elements. Additionally, the term “portion” should be construed as meaning some or all of the item or element that it qualifies. Moreover, use of identifiers such as first, second, and third should not be construed in a manner imposing any relative position or time sequence between limitations. Still further, the order in which the steps of any method claim that follows are presented should not be construed in a manner limiting the order in which such steps must be performed, unless such an order is inherent or explicit.
