Patent Publication Number: US-2022234271-A1

Title: Concrete dowel placement system and method of making the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable 
     STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT 
     Not Applicable 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates generally to a system for use in concrete construction and a method for making the system. More specifically, the present disclosure relates to a system for placing slip dowels into concrete slabs accurately and a method for making the system. 
     2. Description of the Related Art 
     In construction, a “cold joint” in concrete may refer to a weakened interface between two sections of concrete that harden at different times. Typically, a concrete slab is formed by pouring concrete into a form all at once, where the concrete is allowed to harden. Although, sometimes it is desirable to form a continuous section of concrete by pouring it piecewise in sections at different times, allowing each section to harden to some extent before the next adjacent section is poured and allowed to harden. The interface between a previously poured section of concrete and a more recently poured section is called a cold joint. 
     A cold joint in concrete is typically weaker under tension than concrete that has been allowed to dry without any cold joints, and this weakness at the cold joint may cause problems after the concrete hardens. Due to this weakness, cold joints often become uneven or buckled due to thermal expansion and contraction of the concrete. Compaction of the underlaying soil caused by improper substrate preparation before pouring the concrete can also cause buckling or cracking at the cold joint. Further, too much water moisture may accumulate on the end face of the first concrete section before the second concrete section is poured and hardens. If the water freezes, undesirable cracking in the concrete may occur due to ice expansion against the concrete. In terms of aesthetics, cold joints often form a visual line at the interface of the two concrete sections, which is often undesirable. 
     To resist buckling, bulging, or displacement of concrete at the cold joint, it is common to insert long steel rods, known as “slip dowels,” into the edge portions of adjoining concrete sections so that the concrete sections may slide freely along one or more of the slip dowels. This key feature, the ability to slide freely, may allow linear expansion and contraction of the concrete sections while substantially maintaining the concrete in a common plane, thus preventing undesirable buckling, bulging, or unevenness at the cold joint. 
     To function properly, it is typically important to properly position the slip dowels within adjoining concrete sections. For instance, most slip dowels are placed in substantially parallel alignment relative to each other to allow the concrete sections to slide along the slip dowels. Thus, the purpose of placing the slip dowels may be defeated when the dowels are not positioned in substantially parallel relation to each other because, in such a case, the concrete sections are not able to slide along the slip dowels. Further, nonparallel placement of slip dowels can cause cracking in the concrete as well as faulting, i.e., misalignment of the concrete sections at the cold joint. Thus, various systems, methods, and devices have been developed for installing slip dowels properly. 
     In the prior art, two methods of installing slip dowels have become widely used. According to the first method, concrete may be poured into a first form. After the first pour hardens sufficiently, an edge of the form, usually a wooden stud, may be removed. Next, a series of holes, arranged in a straight line, may be drilled into the first concrete slab along the exposed edge from which the form has been removed. The depth and diameter of the individual holes may vary depending on the purpose of the concrete slabs and the size of the concrete slabs to be supported. Generally, these holes are at least twelve inches deep and typically have a diameter of approximately five-eighths of an inch, which is complimentary to typical slip dowels having a diameter of five-eighths of an inch. 
     After the series of holes are drilled into the edge of the first portion of concrete, dowel rods may be inserted into each hole so that one end of each dowel rod is positioned within the first section of concrete. The remainder of each dowel extends into the adjacent area where the second slab of concrete is to be poured. Next, concrete may be poured into the adjacent area and is permitted to harden with the dowels inside. After the second section of concrete hardens, the dowels are held firmly within the second section, but are permitted to slide longitudinally within the drilled holes of the first section. This allows longitudinal expansion and contraction of the two concrete sections while at the same time preventing buckling or faulting at the cold joint. 
     The “drilling method” of placing slip dowels described above is very labor intensive. It can take about ten minutes to drill a five-eighths inch diameter by twelve inches long hole into the first concrete section. Additionally, the drilling equipment, bits, accessories, and associated setup time tends to be very expensive. Moreover, the construction workers who drill the holes and place the slip dowels must have sufficient training to ensure generally parallel arrangement of each dowel to the other dowels and to the underlying support surface. 
     A second widely-used method of placing slip dowels involves using wax-treated cardboard sleeves positioned over one end of each individual dowel. By this method, a series of holes may be drilled through one edge of a concrete form and smooth dowels may be inserted through each hole. Wax-treated cardboard sleeves may be placed over one end of each dowel and the first pour may be made within the form. After the first pour hardens, the previously-drilled form may be stripped away, leaving the individual dowels extending into the adjacent open space where the second pour is to be made. Subsequently, the second pour may be made and allowed to harden. As a result, the slip dowels are held firmly by the concrete of the second pour but are permitted to slide longitudinally against the inner surfaces of the wax-treated cardboard sleeves within the first concrete section. Thus, the waxed cardboard sleeves facilitate longitudinal slippage of the dowels, while at the same time holding the two concrete slabs in a common plane, preventing undesirable buckling or angular movement at the cold joint. 
     Although this second method is widely used, it is commonly associated with a variety of problems. For example, after the first pour is made, the free ends of the dowels are likely to project as much as eighteen inches through the forms and into the adjacent open space allowed for the second pour. Because the drilled section of the form must be slid over those exposed sections of the dowels to accomplish stripping or removal of the form, it is not uncommon for the exposed portions of the dowels to become bent, and thus, not substantially parallel. Also, the drilled section of the form may become damaged or broken during the removal process, thus preventing its reuse. 
     Unfortunately, both of the popular methods of placing slip dowels discussed above often cause the slip dowels to be positioned at various angles rather than in the desired aligned arrangement. When this occurs, the necessary slippage of the slip dowels is impeded or prevented and the likelihood of cracking and faulting in the concrete increases. 
     Alternative prior art dowel placement devices may comprise elongated, hollow tubes sized to receive portions of dowel rods. The tubes may be mounted to one edge of a concrete form in generally parallel relation to each other via integral base portions. Next a first concrete pour may be made over the tubes. After the first pour hardens, the edge of the concrete form to which the tubes are mounted may be stripped away from the first slab. Then, dowel rods may be inserted into the exposed open ends of the tubes embedded within the first slab. The portions of the dowel rods not inserted into the tubes extend into an adjacent area where a second pour of concrete may be made. Concrete poured into the adjacent area completely covers the outer surfaces of the dowel rods which are held firmly within the second slab formed when the second pour hardens. The dowels, though being held firmly within the second slab, are permitted to slide longitudinally within the tubes embedded in the first slab. 
     Even though these prior art placement devices have advantages over the previously described dowel placement methods, several disadvantages inhibit their usefulness. In particular, the attachment of the base portions of these prior art placement devices to a concrete form often requires the use of multiple fasteners, making the attachment process difficult and time-consuming. Additionally, in the prior art placement devices, both the tube and its integral base portion used to facilitate the connection of the tube to the concrete form are embedded in the first slab, thus necessitating that additional placement devices be attached to the concrete form prior to its reuse. Further, the prior art placement devices are generally only suited for attachment to a concrete form, and not to reinforcement materials, such as rebar or wire mesh. As such, these prior art placement devices do not lend themselves to use within the interior areas of a poured slab, but rather are limited to use along the periphery of the slab which is defined by the concrete form to which the placement devices must be attached. 
     Another problem with prior art concrete dowel placement devices is the high manufacturing cost. Prior art placement devices have been manufactured using injection molding. Injection molding can be cost prohibitive and have other problems innate with the method itself. Such problems include burning of the material being molded, thus weakening its final structure; flashing, i.e., excess molded material attached to the molded product which requires extra time and effort to remove; and short shotting, i.e., when a region of the mold lacks sufficient quantity of injected material, resulting in a physical deformity in the final molded product. 
     Accordingly, there remains a need in the art for methods and/or systems for facilitating the proper placement of slip dowels, and methods for manufacturing such placement systems, which overcome the previously described deficiencies associated with prior art placement devices and systems. 
     BRIEF SUMMARY 
     The present disclosure specifically addresses and alleviates the above-identified deficiencies in the art. In this regard, the disclosure is directed to a concrete dowel placement system and method of making the concrete dowel placement system. As will be discussed in more detail below, the method allows for cost-efficient manufacturing of the system. The concrete dowel placement system allows for easy and accurate placement of slip dowels into concrete. 
     According to one embodiment, a method of constructing a concrete dowel placement system includes the step of constructing a coupler. The step of constructing a coupler includes the step of extruding a polymer to form a first tubular element. The step of constructing a coupler also includes the step of extruding a polymer to form a second tubular element, the second tubular element having a dimensional size different from a dimensional size of the first tubular element. The step of constructing a coupler additionally includes the step of attaching an end portion of the second tubular element to an end portion of the first tubular element. Further, the method includes the step of extruding a polymer to form an elongated, tubular, dowel-receiving sheath, the sheath having at least one interior opening extending along the entire length of the sheath and the sheath being configured to be slidably extensible over the coupler to frictionally engage one of the first tubular element and the second tubular element. 
     It is contemplated that the method may also include the step of attaching an end cap to an end portion of the sheath to completely cover the at least one interior opening at the end of the sheath. 
     It is further contemplated that the step of extruding a polymer to form the first tubular element may include forming a body having a circular cross-sectional configuration along a longitudinal axis during extrusion of the polymer. The step of extruding a polymer to form the first tubular element may include forming the first tubular element to have an inner sleeve and a plurality of splines extending radially outward from the inner sleeve and longitudinally along the inner sleeve. The step of extruding a polymer to form the first tubular element may include forming the first tubular element to have a quadrangular configuration along a longitudinal axis during extrusion of the polymer. The first tubular element may define opposed first tubular element end portions having maximum outer diameters approximately equal to each other, and the second tubular element may define opposed tubular element end portions having maximum outer diameters approximately equal to each other. 
     The step of extruding a polymer to form the first tubular element may include forming at least one reinforcement wall between an inner sleeve and an outer sleeve during extrusion of the polymer. 
     The step of extruding a polymer to form a sheath may include forming at least one linear rib protrusion, raised helical element, helical groove element, or linear groove element along a longitudinal axis of the sheath on an outer surface of the sheath during extrusion of the polymer. Additionally, this step may include forming a sinusoidal outer surface or a helical uneven outer surface on the sheath during extrusion of the polymer. 
     Another embodiment of the disclosure relates to a concrete dowel placement system having a coupler. The coupler includes a first tubular element having an inner sleeve disposed about a central axis to define an aperture. An outer body is disposed radially outward of the inner sleeve. The coupler also includes a second tubular element having an inner sleeve disposed about a central axis to define an aperture. An outer body is disposed radially outward of the inner sleeve. The concrete dowel placement system also has a sheath having an interior opening extending along the entire length of the sheath and being slidably extensible over the coupler to frictionally engage one of the first tubular element and the second tubular element. 
     The concrete dowel placement system may also include an end cap attachable to the interior opening at the end of the sheath to completely cover the interior opening at the end of the sheath. 
     The outer body of the first tubular element may include a plurality of splines extending longitudinally along the inner sleeve. 
     Another embodiment of the disclosure relates to an additional method of making a concrete dowel placement system including the step of extruding a polymer to form a tubular element. The tubular element has at least one interior opening extending along the entire length of the tubular element. The method further includes the step of extruding a polymer to form a sheath. The method may also include the step of forming a coupler by removing some of the polymer from a first length portion of the tubular element so that the first length portion of the tubular element is of a different dimensional size than a second length portion of the tubular element. 
     The present disclosure is best understood by reference to the following detailed description when read in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages of the various embodiments disclosed herein will be better understood with respect to the following description and drawings, in which like numbers refer to like parts throughout, and in which; 
         FIG. 1  is an upper perspective view of an embodiment of a concrete dowel placement system; 
         FIG. 2  is a front cross-sectional view of an embodiment of a first tubular element having four reinforcement walls; 
         FIG. 3  is an upper perspective view of an extrusion die head having a first extrusion aperture; 
         FIG. 4  is an upper perspective view of an extrusion die head have a second extrusion aperture; 
         FIG. 5  is a side cross-sectional view of embodiments of a first tubular element and a second tubular element; 
         FIG. 6  is a side cross-sectional view of an embodiment of a coupler; 
         FIG. 7  is a front cross-sectional view of an embodiment of a sheath having rib protrusions on an outer surface of the sheath; 
         FIG. 8  is a perspective view of an embodiment of a sheath having a helical element on an outer surface of the sheath; 
         FIG. 9  is a front cross-sectional view of an embodiment of a coupler disposed within an embodiment of a sheath; 
         FIG. 10  is a side cross-sectional view of an embodiment of a tubular element; 
         FIG. 11  is a side cross-sectional view of an embodiment of a coupler; 
         FIG. 12  is a side cross-sectional exploded view of the concrete dowel placement system of  FIG. 1 ; 
         FIG. 13  is a side cross-sectional view of the concrete dowel placement system of  FIG. 1  employing a first orientation of a coupler having an outer sleeve of a first diameter at a distal end; 
         FIG. 14  is a side cross-sectional view of the concrete dowel placement system of  FIG. 1  employing a second orientation of a coupler having an outer sleeve of a second diameter at a distal end; 
         FIG. 15  is a side cross-sectional view of the concrete dowel placement system of  FIG. 13  disposed within a first concrete section; 
         FIG. 16  is a side cross-sectional view of the concrete dowel placement system of  FIG. 15  wherein a form section and the coupler have been removed; 
         FIG. 17  is a side cross-sectional view of the concrete dowel placement system of  FIG. 16  wherein a portion of a slip dowel is disposed within an interior opening of a sheath; 
         FIG. 18  is a side cross-sectional view of the concrete dowel placement system of  FIG. 17  wherein an exposed portion of the slip dowel is disposed within a second concrete section; 
         FIG. 19  is an elevational view of another embodiment of a tubular element and a screw adapted for use as part of a concrete dowel placement system; 
         FIG. 20  is a cross sectional view of the tubular element depicted in  FIG. 19 ; 
         FIG. 21  is a side, partial cross sectional view of a concrete dowel placement system including the tubular element depicted in  FIG. 19 ; and 
         FIG. 22  is another embodiment of a coupler adapted for use as part of a concrete dowel placement system. 
     
    
    
     Common reference numerals are used throughout the drawings and the detailed description to indicate the same elements. 
     DETAILED DESCRIPTION 
     The detailed description set forth below in connection with the appended drawings is intended as a description of some, but not all, of contemplated embodiments of the disclosure, and is not intended to represent the only form in which the present disclosure may be constructed or utilized. The description sets forth the functions and the sequence of steps for developing and operating the disclosure in connection with the illustrated embodiments. 
     It is to be understood, however, that the same or equivalent functions and sequences may be accomplished by different embodiments that are also intended to be encompassed within the spirit and scope of the disclosure. It is further understood that the use of relational terms such as first and second, top and bottom, and the like are used solely to distinguish one entity from another entity without necessarily requiring or implying any actual such relationship or order between such entities. 
     Referring to  FIG. 1 , a perspective view of an embodiment of a concrete dowel placement system  10  in accordance with an aspect of the present disclosure is illustrated. The concrete dowel placement system  10  generally includes a coupler  12 , a sheath  14 , and an end cap  20 . The concrete dowel placement system  10  may be used to form a concrete structure. 
     Now referring to  FIG. 2 , the coupler  12  includes a first tubular element  22  having an outer sleeve  24  and an inner sleeve  26  defining an aperture  28  extending along the entire length of the outer sleeve  24 . The first tubular element  22  further includes at least one reinforcement wall  30  between the outer sleeve  24  and the inner sleeve  26 . The reinforcement wall  30  secures the inner sleeve  26  to the outer sleeve  24  so that the inner sleeve  26  may receive a securing device  18 . By way of example and not limitation,  FIG. 2  shows a front cross-sectional view of a first tubular element  22  that includes four reinforcement walls  30 . However, it is also contemplated that the first tubular element  22  may include any number of reinforcement walls  30 . 
     Referring to  FIGS. 3 and 4 , the first tubular element  22  may be formed via extrusion, which may include extruding a material, such as a polymer, preferably a thermoplastic polymer, through a die head  32  to form the first tubular element  22 . The extrusion die head  32  may include an extrusion aperture  34 .  FIGS. 3 and 4  illustrate exemplary extrusion die heads  32  through which the extrusion of the material may be performed. Each extrusion die head  32  includes an extrusion aperture  34  through which a material is extruded. By way of example and not limitation,  FIGS. 3 and 4  show exemplary extrusion apertures  34   a  and  34   b  where the extrusion apertures  34 , in minor part, or substantially define the cross sectional shape of the first tubular element  22  formed during extrusion. Further, it is also contemplated that the material may be extruded by alternative methods other than through die heads  32  having extrusion apertures  34 . It is contemplated that the extrusion may occur through any shaped space such that the extruded material acquires a cross-sectional shape which is substantially the same as the shape of the shaped space during extrusion. 
     By way of example and not limitation, it is contemplated that the extruded material may alternatively be a thermosetting polymer or any other material that may be appreciated by one of ordinary skill of the art that does not depart from the spirit of the present disclosure. Further, the material may be any polymer that falls within the scope of the materials discussed above, that will not chemically react with concrete so as to substantially weaken the polymer or the concrete during the lifespan of the use of the polymer within the concrete. 
     The first tubular element  22  may be formed via extrusion to have a circular cross sectional configuration in a plane perpendicular to a longitudinal axis, so as to resemble a traditional pipe or tube. This circular configuration allows for less material to be used in order to manufacture the first tubular element  22 , thus reducing cost. Alternatively, the first tubular element  22  may be formed via extrusion to have a quadrangular configuration. 
     As shown in  FIG. 5 , the coupler  12  of the concrete dowel placement system  10  further includes a second tubular element  36  of a different dimensional size than the first tubular element  22 . The second tubular element  36  includes an outer sleeve  25  and an inner sleeve  27  defining an aperture  29  extending along the entire length of the outer sleeve  25 . The second tubular element  36  further includes at least one reinforcement wall between the inner sleeve  27  and the outer sleeve  25 . The second tubular element  36  may differ from the first tubular element  22  in size only, and thus, the cross-sectional configuration depicted in  FIG. 2  may also be representative of a cross-sectional view of an exemplary embodiment of the second tubular element  36 , albeit on a different scale. It is further contemplated that the second tubular element  36  may be formed via extrusion as described herein. More specifically, the second tubular element  36  may be formed via extrusion through an extrusion die head  32  or by any other form of extrusion that would be appreciated by a person of ordinary skill in the art. 
     With regard to the first tubular element  22  and second tubular element  36 , it is further contemplated that at least one of the first tubular element  22  and the second tubular element  36  may be formed to have a diameter of slightly less than five-eighths inches so that a slip dowel  56  with a diameter of about five-eighths inches may be used with the concrete dowel placement system  10  as will be discussed in further detail herein. Although, it is also contemplated that neither the first tubular element  22  nor the second tubular element  36  is about five-eighths inches, but rather is of some other dimensional size. Additionally, the second tubular element  36  may be formed to have the same configuration as the first tubular element  22 , but it is also contemplated that the configurations of the first tubular element  22  and the second tubular element  36  may be different. By way of example and not limitation, according to one embodiment, the first tubular element  22  is formed to have a circular configuration while the second tubular element  36  is formed to have a quadrangular configuration. Other alternative configurations are also contemplated, such as oval or rounded rectangle configurations. 
     By the embodiment of a coupler  12  shown in  FIG. 6 , an end portion of the outer sleeve  25  of the second tubular element  36  is attached to an end portion of the outer sleeve  24  of the first tubular element  22  to form the coupler  12 . The first tubular element  22  and second tubular element  36  may be attached at absolute ends, but it is also contemplated that attachment may be achieved by inserting an end portion of the first tubular element  22  into a hollow of an end portion of the second tubular element  36 . 
     The concrete dowel placement system  10  further includes an elongated, tubular, dowel-receiving sheath  14  (see  FIGS. 1 and 12 ) having at least one interior opening  38  extending along the entire length of the sheath  14 , the sheath  14  being slidably extensible over one of the first tubular element  22  and the second tubular element  36  to frictionally engage the sheath  14  to the coupler  12 . The sheath  14  having an empty and smooth interior opening  38  allows for the desired unrestricted slippage of the slip dowel  56  within the sheath  14  once the slip dowel  56  has been placed within a second concrete section  58 . Further, the sheath  14  may be formed to have a longitudinal length of about twelve inches so that a slip dowel  56  may be advanced twelve inches into a section of concrete as will be discussed in further detail herein, but it is alternatively contemplated that any other length sufficient for placing a slip dowel  56  may be used. 
     It is contemplated that the sheath  14 , similar to other components of the concrete dowel placement system  10 , may be formed via extrusion through an extrusion die head or any other process of extrusion that would be known by a person of ordinary skill in the art, such as the processes described above. Further, it is contemplated that the sheath  14  may be formed via extrusion to include a completely smooth outer surface  40 , but it is also contemplated that the outer surface  40  of the sheath  14  may be formed to be not completely smooth. For example, the sheath  14  may be formed via extrusion to include at least one or a plurality of elements on the outer surface  40  of the sheath  14  that extend along the longitudinal axis of the sheath  14 . Such elements may include linear rib protrusions  42  or linear grooves. The outer surface  40  of the sheath  14  may be formed to also include raised or grooved helical elements  44 .  FIG. 7  shows a cross-sectional view of an embodiment of a sheath  14  including rib protrusions  42  on the outer surface  40  of the sheath  14 . Additionally,  FIG. 8  is an upper perspective view of a sheath  14  that includes a raised helical element  44  on the outer surface  40  of the sheath  14 . In a similar vein, it is contemplated that the sheath  14  may be formed via extrusion to include a sinusoidal outer surface  40  on the sheath  14  or a helical uneven outer surface  40  on the sheath  14 . The external features formed on the outer surface of the sheath, e.g., ribs or raised elements, may mitigate cracks formation in the concrete. 
     The aforementioned elements and characteristic features that may be formed on the outer surface  40  of the sheath  14  allow for improved attachment between the concrete and the sheath  14 , as concrete is more prone to cracking when it is attached to completely smooth surfaces. A secure, crack-resistant attachment between the sheath  14  and the concrete is critical because the secure attachment allows the slip dowel  56  to slide within the sheath  14  without disrupting the functionality of the sheath  14  as will be discussed in more detail below. To clarify how the sheath  14  may engage the coupler  12 ,  FIG. 9  shows a front cross-sectional view of an embodiment of a concrete dowel placement system  10  where a sheath  14  has been slibably extended over a coupler  12 . 
     The concrete dowel placement system  10  may also include an end cap  20  attachable to an end portion of the sheath  14  to completely cover the interior opening  38  at the end of the sheath  14 . The end cap  20  helps prevent pourable concrete from entering the interior opening  38  of the sheath  14  while the concrete hardens. The end cap  20  may be a element of duct tape or construction tape, a cap, a plug, a element of film, or any blockade that is either permanently affixed or removably attached to the distal end of the sheath  14 . 
     An additional embodiment of the disclosure relates to another method of constructing a coupler  12 . Now referring to  FIGS. 10 and 11 , in this embodiment, the coupler  12  may be formed by first extruding a material, such as a polymer, to form a tubular element  46  having a first length portion  48  and a second length portion  50 . The tubular element  46  further includes at least one interior opening  38  extending along the entire length of the tubular element  46 . By way of example and not limitation,  FIG. 10  illustrates a cross-sectional view of an exemplary embodiment of a tubular element  46 . 
     Next, as  FIG. 11  shows, this method includes removing some of the material from the first length portion  48  of the tubular element  46  so that the first length portion  48  of the tubular element  46  is of a different dimensional size than the second length portion  50  of the tubular element  46 , thus ultimately forming a coupler  12 . 
     By way of example and not limitation, the step of removing some of the material from a first length portion  48  of the tubular element  46  may be by lathing, milling, or computer numerical control machining devices. 
     Now referring to  FIGS. 12 and 13 , the concrete dowel placement system  10  discussed above may be used to form a concrete structure, however, before any concrete is poured, at least one coupler  12  is affixed to a form section  16 . A form is used to define the shape of the concrete once it hardens. The coupler  12  may be affixed using a securing device  18 . The securing device  18  may be a nail, screw, or any other device similar in nature so that the coupler  12  may be securely affixed to the form section  16 . Alternatively, the coupler  12  may also be affixed to the form section  16  using adhesive placed on a proximal end of the coupler  12 , or any other appropriate method of attachment that would be appreciated by one of ordinary skill of the art. According to various aspects of the present disclosure, the configuration of the coupler  12  and the corresponding sheath  14  allows the coupler  12  to be formed without a flange at the end portion which abuts the form section  16 . Thus, the outer sleeve  24  of each tubular element of the coupler  12  may define the maximum outer diameter of the coupler  12 , and the tubular elements themselves are capable of withstanding the forces associated with pouring concrete around the sheath  14 . In a contemplated embodiment, to prepare to pour a large section of concrete, a plurality of couplers  12  is affixed to the form section  16  in a straight line; the line may run generally parallel to the underlying support surface  54 . 
     It is to be appreciated that the form section  16  to which the couplers  12  are attached is part of a complete form used to dictate the shape of the concrete once the concrete hardens. That is, the form section  16  is part of a complete form that forms a boundary for concrete that is poured within the boundary. 
     The form is arranged upon the underlying support surface  54  so that concrete remains within the boundary defined by the form when the concrete is poured within the form. The form may be made of wooden studs or planks, plastic slabs, or any supports that will not chemically react with the concrete in a way that adversely affects the shape or structural integrity of the concrete. 
     A sheath  14  is slidably disposed over each of the couplers  12  and may be held in place by friction or by other means of attachment, such as adhesives. One of ordinary skill in the art will appreciate that the fit between each coupler  12  and its corresponding sheath  14  is tight and sealed enough so that it is unlikely that pourable concrete can leak into the sheaths  14  when the concrete is poured. Concrete leaking into the interior of the sheaths  14  can negatively impact one of the functions of the concrete dowel placement system  10 , which is to allow slip dowels  56  to slide freely within the sheaths  14 . Further, regardless of the method used to secure the coupler  12  to the form section  16 , it is contemplated that the secure and sealed connection between the coupler  12  and the form section  16  can be maintained during the pouring of the concrete and until the concrete hardens. That is, the connection between the coupler  12  and sheath  14  is strong enough such that the pouring of the concrete does not break or disrupt the connection. 
     An attachable end cap  20  may be disposed on a distal end of the sheath  14  to completely cover the opening  38  at the end of the sheath  14  to prevent pourable concrete from leaking into the interior of the sheath  14  after the concrete is poured over the concrete dowel placement system  10 . 
     Now referring to the cross-sectional view of two different orientations of a concrete dowel placement system  10  of  FIGS. 13 and 14 , the coupler  12  may have at least two positional orientations. As shown in  FIG. 13 , in one orientation, the smaller end of the coupler  12  is affixed to the form section  16 . The smaller end may have a diameter or cross-sectional area that is smaller than the diameter or cross-sectional area of the bigger end. This permits a sheath  14  with an interior size similar to the bigger end of the coupler  12  to slidably engage the bigger end of the coupler  12 . Alternatively, as shown in  FIG. 14 , a bigger end portion of the coupler  12  may be affixed to the form section  16 . In this case, a sheath  14  with an interior size similar to the size of the smaller end of the coupler  12  may slidably engage the smaller end of the coupler  12 . Thus, the coupler  12  may have at least two different orientations upon the form section  16  to allow connectability with at least two different sheaths  14  having different dimensions. It is to be appreciated that regardless of the positional orientation of the coupler  12 , the connection between the coupler  12  and the sheath  14  is tight and sealed enough to prevent pourable concrete from substantially intruding into the interior of the sheath  14 . 
     Next, concrete may be poured within a first form. Now referring to  FIG. 15 , concrete is poured onto the underlaying support surface  54  and within the first form. The poured concrete makes contact with the sheath  14  and the end cap  20 . It is contemplated that the pourable concrete may completely cover the outer surfaces  40  of the sheath  14  and the end cap  20  that are exposed to the pourable concrete. Once the concrete hardens, this portion of concrete is a first concrete section  52 . The concrete of the hardened first concrete section  52  affixes to the sheath  14  to prevent movement between the sheath  14  and the hardened first concrete section  52 . As shown in  FIG. 15 , after the first concrete section  52  is established, the interior of the sheath  14  remains hollow except possibly for a portion of the end cap  20  which may be disposed within an end portion of the sheath  14  if the end cap  20  is in the form of, for example, a plug. The empty interior of the sheath  14  allows a slip dowel  56  to be inserted within the sheath  14  at a later time. 
     Referring to  FIGS. 16 and 17 , after the first concrete section  52  hardens, the form section  16  and coupler  12  are removed. The removal of the form section  16  and coupler  12  exposes an edge surface of the first concrete section  52 , the edge surface allowing access to the interior of the sheath  14 . Thus, a slip dowel  56  may be advanced into the sheath  14  as shown in  FIG. 17 . 
     The slip dowel  56  may be a smooth steel rod, but it is contemplated that the slip dowel  56  may be made of aluminum, iron, or any other suitable metal or metal alloy strong enough to endure longitudinal or vertical compression and expansion forces that may occur between sections of concrete without bending substantially. Further, the entire outer surface of the slip dowel  56  need not be smooth. For example, a length portion of the slip dowel  56  may include a ribbed outer surface, similar to the outer surface of typical re-bar, or include other features on the outer surface such that the slip dowel  56  is unsmooth. It is further contemplated that the edge surface of the first concrete section  52  allows access to a plurality of interior openings  38  of sheaths  14  aligned generally in parallel within the first concrete section  52 , thus allowing for a plurality of generally parallel-aligned slip dowels  56  to be inserted into sheaths  14 . 
     The slip dowel  56  may be fully advanced within the sheath  14  so as to make contact with the end cap  20 , but it is also contemplated that the slip dowel  56  may be only partially advanced within the sheath  14  to allow space between the inserted end of the slip dowel  56  and the end cap  20 . The space can help prevent undesirable pressure within the first concrete section  52  and the second concrete section  58  that may be caused by the slip dowel  56  pressing against the end cap  20  when the concrete expands. Such pressure can potentially expedite undesirable weakening of the concrete. 
     The slip dowel  56  projects into an area immediately adjacent to the first concrete section  52  to define an exposed segment, allowing for a second concrete section  58  to be poured over the exposed segment of the slip dowel  56 . 
     Now referring to  FIG. 18 , next, the second concrete section  58  may be formed. A second form is prepared and disposed upon the underlaying support surface  54 , bounding the area immediately adjacent to the first concrete section  52  and encompassing the exposed segments of the slip dowels  56 . Then, concrete is poured within the second form and the concrete is allowed to make contact with the exposed segments of the slip dowels  56 . The concrete may also completely cover the outer surfaces of the slip dowels  56 . After the concrete hardens, this portion of concrete is the second concrete section  58  and the form may be removed. 
     Since the edge surface of the second concrete section  58  that makes contact with the edge surface of the first concrete section  52  hardens at a different time than the edge surface of the first concrete section  52 , a cold joint  60  forms at the interface. 
     In contrast to the first concrete section  52 , which includes a sheath  14  and an end cap  20  disposed within, the second concrete section  58  has no portion of a concrete dowel placement system  10  disposed within, and thus makes contact with the slip dowels  56 . This contact with the slip dowels  56  allows the second concrete section  58  to adhere to the slip dowels  56 , thus prohibiting movement between the slip dowels  56  and the second concrete section  58 . This adhesion allows the slip dowels  56  to slide longitudinally within the sheaths  14  and across the cold joint  60 . As the first concrete section  52  and the second concrete section  58  expand and contract, the second concrete section  58  holds onto to the slip dowels  56  while the sheaths  14  disposed within the first concrete section  52  allow the slip dowels  56  to slide back and forth freely within the sheaths  14 . 
     The ability for the slip dowels  56  to slide freely within the sheaths  14  aids in preventing buckling and bulging of the concrete at the cold joint  60 . Buckling and bulging is often undesirable because it can result in cracks in the concrete, thus reducing the structural integrity of the concrete, and in the case of a pedestrian application, can pose a safety hazard by increasing the risk of people tripping on the cracks. Cracks and bulging in the concrete may also be considered aesthetically unappealing. 
     The ability for the slip dowels  56  to slide freely within the sheaths  14  also allows the interface between the first concrete section  52  and the second concrete section  58  to remain aligned, thus preventing faulting, i.e., undesirable skewing of the first concrete section  52  and the second concrete section  58  at the cold joint  60 . Skewing at the cold joint  60  may damage the concrete, weaken the concrete, or result in undesirable aesthetics. 
     Referring now to  FIGS. 19-21 , there is depicted yet another embodiment of a coupler  100  including a tubular element  102  including an inner sleeve  104  and a plurality of splines  106  extending along the inner sleeve  104 . Notably, the coupler in  FIGS. 19-21  does not include an outer sleeve coaxially disposed relative to the inner sleeve  104 . Rather, the splines  106  extend radially outward from the inner sleeve  104  to provide an outer engagement surface adapted to frictionally engage the sheath  108 . The use of splines  106 , rather than an outer sleeve, may allow the coupler  100  to be formed using less material, and thus, cost savings may be achieved. 
     The inner sleeve  104  depicted in  FIGS. 19-21  is a cylindrical tube disposed about a central axis  110 , and thus, includes an inner surface  112  defining an aperture  114  extending along the length of the inner sleeve  104 . The aperture  114  is sized and configured to receive a fastener  116 , such as a nail, screw, or the like for securing the coupler  100  to the concrete form  118 . The inner sleeve  104  includes a first end  120  and an opposing second end  122 , wherein the first end  120  is adapted to be disposed in abutting contact with the concrete form  118  when the coupler  100  is attached thereto. 
     The plurality of splines  106  are coupled to the inner sleeve  104 , with each spline  106  extending radially outward from an outer surface  124  of the inner sleeve  104 , so as to define a coupler outer diameter, D. The coupler  100  is configured such that the outer diameter D is sized and configured so as to enable the sheath  108  to be advanced over the coupler  100 , with an inner surface  126  of the sheath  108  frictionally engaging with the splines  106 . Each spline  106  also extends axially along the outer surface  124  of the inner sleeve  104  between the first and second ends  120 ,  122  thereof. In the exemplary embodiment, the coupler  100  includes eight splines  106  spaced evenly around the outer circumference of the inner sleeve  104 , e.g., the splines  106  are spaced apart by about 45 degrees. As shown in  FIGS. 19 and 21 , the splines  106  extend completely between the first and second ends  120 ,  122 , with the splines  106  having a beveled surface  128  adjacent the second end  122 . However, it is understood that in other implementations, the splines  106  may extend only partially between the first and second ends  120 ,  122 . 
     The coupler  100  may be formed via extrusion, wherein an extrusion die having an opening corresponding to the cross section depicted in  FIG. 20  is used to form the coupler  100 , as described in more detail above. Of course, other materials and manufacturing techniques may also be used without departing from the spirit and scope of the present disclosure. 
       FIGS. 19-21  show the coupler  100  being of a substantially uniform configuration between the first and second ends  120 ,  122  thereof. In this respect, the outer diameter D is substantially uniform along the length of the coupler  100 . Thus, the coupler  100  is adapted for use with a sheath  108  having an inner opening that is of a specific diameter, which corresponds to the outer diameter D of the coupler  100 . 
     However, referring now to  FIG. 22 , there is depicted another embodiment of a coupler  200  including a first tubular element  202  defining a first outer diameter, D 1 , and a second tubular element  204  defining a second outer diameter, D 2 , greater than the first outer diameter D 1 . The first and second tubular elements  202 ,  204  are coupled to each other at a joint  205 , either through the use of an adhesive, or other joining elements known in the art. The first tubular element  202  includes a first inner sleeve  206  and a plurality of first splines  208 , while the second tubular element  204  includes a second inner sleeve  210  and a plurality of second splines  212 . The plurality of first splines  208  define the first outer diameter D 1 , and the plurality of second splines  212 . define the second outer diameter D 2 . The first tubular element  202  defines a first abutment end  214 , while the second tubular element  204  defines a second abutment end  216 , with the first and second abutment ends  214 ,  216  each being adapted to be positioned in abutting contact with a concrete form  118 , depending on the intended use of the coupler  200 , e.g., whether the coupler  200  is to be used with a sheath adapted to frictionally engage the outer surface of the splines  208  on the first tubular element  202 , or the splines  212  on the second tubular element  204 . In particular, if the coupler  200  is to be used with a sheath which engages with splines  208  on the first tubular element  202 , the coupler  200  is attached to the form  118  with the second abutment end  216  coupled to the form, and the first tubular element  202  extending away from the form. Conversely, if the coupler  200  is to be used with a sheath which engages with splines  212  on the second tubular element  204 , the coupler  200  is attached to the form  118  with the first abutment end  214  coupled to the form, and the second tubular element  204  extending away from the form. 
     The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present disclosure only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present disclosure. In this regard, no attempt is made to show structural details of the present disclosure in more detail than is necessary for the fundamental understanding of the present disclosure, the description taken with the drawings making apparent to those skilled in the art how the several forms of the present disclosure may be embodied in practice.