Abstract:
A concrete dowel device including a sleeve and plate in which the sleeve includes break-away alignment tabs at the opening of the sleeve to ensure proper alignment of the plate within the sleeve during field installation. The tabs are positioned at the sleeve opening, rather than along the length of the socket, to avoid misalignment of the plate in the sleeve, simplify use and reduce manufacturing costs of the product. The sleeve and plate may include additional alignment surfaces on the plate, at the rear corners, or along the rear side of the plate and sleeve. To facilitate manufacturing, the break-away alignment tabs may be formed as molded components rotated and snapped into position. Alternatively, the break-away alignment tabs may be formed as part of an insert plate manufactured apart from and attached to the flange of the sleeve.

Description:
TECHNICAL FIELD 
     The present invention relates to concrete dowel devices and, more particularly, to a plate and a sleeve concrete dowel device with break-away alignment tabs. 
     BACKGROUND 
     Concrete dowels are embedded into joints between adjacent slabs of concrete to prevent vertical displacement between the slabs to maintain a smooth pavement surface and increase the strength of the concrete in the region of the joint. While the dowels are provided to prevent excessive vertical displacement between the slabs, they are typically designed to allow a small amount of horizontal separation and lateral displacement between the slabs to relieve internal stress to accommodate drying shrinkage and thermal expansion and contraction of the slabs. This permits a normal amount of slab movement to prevent excessive cracking while still maintaining a smooth top surface of the pavement. 
     Traditionally, two foot lengths of rebar rods were used as the concrete dowels. But rod dowels tend to cause cracking in the concrete due to concentration of the stress on the relatively small surface area of the rods. Concrete dowels configured as larger bars and load plates were therefore developed to reduce cracking by increasing the surface area of the dowel. In comparison to rebar rods historically used as concrete dowels, larger dowel bars and plates provide a flat and significantly increased dowel surface area to improve the dowel&#39;s load transfer capability and reduce the tendency of cracking to form at the dowel location. U.S. Pat. No. 6,354,760 and U.S. patent application Ser. No. 11/109,781 describe examples and the benefits of this approach. 
     To assist in embedding the dowels within adjacent slabs of concrete while the concrete is being poured, dowel devices including dowel bars (or plates) and sleeves have been developed. U.S. Pat. No. 6,145,262 describes this approach. The sleeved dowel bar has the benefit of permitting the bar to slide within the sleeve to accommodate a small amount of horizontal separation between the slabs to relieve internal stress. To accommodate lateral displacement between the slabs the sleeve is a little bit wider than the bar, which allows the bar to move laterally within the sleeve after the concrete slabs have cured. But simply making the sleeve wider than the bar removes positive registration between the bar and sleeve making it difficult to determine when the bar has been properly centered within the sleeve. As a result, construction workers have to install the bars carefully to ensure the proper spacing on either side of the plate within the sleeve, which can be a lot to ask of construction workers in some setting. To solve this problem, the sleeve described in U.S. Pat. No. 6,145,262 contains fins along the side walls of the sleeve to help align the dowel bar within the sleeve. 
     However, providing dowel sleeves with elongated fins along the interior side walls is an expensive solution. Including the fins along the internal surfaces of the sleeve complicates the manufacturing process and can require multiple molds to create the sleeve. Although a structure containing the fins may be manufactured separately and inserted into to the sleeve after the sleeve has been molded, this significantly complicates the manufacturing process and increases the cost of the dowel. For example, manual assembly steps may be required to insert and secure the fins within the sleeve. 
     In addition, even when fins are included, it is still possible with prior sleeved dowel devices to install the bar on a slant deflecting the fins prior to pouring the concrete slabs, which can reduce or eliminate the effectiveness of the fins. A plate installed on an angle within the sleeve with the fins deflected before the concrete is poured reduces or eliminates the lateral play that the dowel was designed to allow. With this system, it can also be difficult for the construction workers in the field to see whether the fins have been deflected when the plate is inserted, leading to some portion of the plates being installed without proper alignment within the sleeves. 
     As a result, there is a persistent need for a lower cost and more reliable concrete dowel solution and, more particularly, a need for a concrete dowel device to ensure proper registration of the plates within the sleeves without requiring cumbersome manufacturing or assembly procedures. 
     SUMMARY OF THE INVENTION 
     The present invention meets the needs described above in a concrete dowel device including a sleeve and plate in which the sleeve includes break-away alignment tabs at the opening of the socket to ensure proper alignment of the plate within the sleeve during field installation. The tabs are positioned at the sleeve opening, rather than along the length of the socket, to avoid misalignment of the plate within the sleeve, simplify use and reduce the manufacturing costs of the product. The plate may have a tiered structure to enhance registration between the place and sleeve. Alternatively or additionally, the sleeve and plate may include additional alignment surfaces at the rear corners or along the rear side of the plate and sleeve. For example, slanted corners and/or a “V” shaped groove can be provided to assist in properly aligning the plate within the sleeve. 
     To facilitate manufacturing, the break-away alignment tabs may be formed as molded components of the sleeve, which are rotated and snapped into position after the sleeve has been molded. Alternatively, the break-away alignment tabs may be formed as part of an insert plate that is molded separately and attached to the flange of the sleeve after the sleeve has been molded. Both approaches allow the sleeve (without the insert plate) to be molded as a single part without the need to insert fins or another alignment structure along the side walls of the sleeve. 
     In view of the foregoing, it will be appreciated that the present invention provides an improved plate and a sleeve concrete dowel device with break-away alignment tabs. The specific structures and techniques for accomplishing the advantages described above will become apparent from the following detailed description of the embodiments and the appended drawings and claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a top view of a plate and sleeve concrete dowel device with the plate positioned outside the sleeve. 
         FIG. 1B  is a front view of the sleeve showing the break-away alignment tabs before insertion of the plate into the sleeve. 
         FIG. 2A  is a top view of a plate and sleeve concrete dowel device with the plate inserted within the sleeve. 
         FIG. 2B  is a front view of the sleeve showing the break-away alignment tabs with the plate inserted within the sleeve. 
         FIG. 3A  is a plan view of the sleeve nailed to a concrete form before pouring of a first concrete slab over the sleeve. 
         FIG. 3B  is a cross-section plan view of the sleeve nailed to a concrete form after the first concrete slab has been poured over the sleeve. 
         FIG. 3C  is a cross-section plan view of the sleeve embedded within the first concrete slab after the first slab has set and the form has been removed. 
         FIG. 3D  is a cross-section plan view of the sleeve embedded within the first concrete slab after the plate has been inserted into the sleeve. 
         FIG. 3E  is a cross-section plan view of the dowel formed by the sleeve and plate embedded at the joint between the first and second concrete slabs. 
         FIG. 4A  is a top view of a first alternative concrete dowel device with the plate located outside the sleeve. 
         FIG. 4B  is a top view of the first alternative concrete dowel device with the plate inserted within the sleeve. 
         FIG. 4C  is a top view illustrating a waste-free approach for stamping the plated for the first alternative concrete dowel device from sheet stock material. 
         FIG. 5  is a top view of a second alternative concrete dowel device with the plate located outside the sleeve. 
         FIG. 6  is a top view of a third alternative concrete dowel device with the plate located outside the sleeve. 
         FIG. 7  is a top view of a sleeve for the concrete dowel device with break-away alignment tabs formed as molded components rotated and snapped into position. 
         FIG. 8A  is a top assembly view of an alternative sleeve design utilizing a plate insert for the break-away tabs. 
         FIG. 8B  is a front assembly view of the alternative sleeve design utilizing the plate insert for the break-away tabs. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The present invention may be embodied in a concrete dowel device, a method for constructing concrete structures using the concrete dowel devices, and concrete structures that include embedded concrete dowel devices. The innovative concrete dowel represents a significant improvement over the concrete dowel approaches shown in U.S. Pat. No. 6,354,760; U.S. Pat. No. 6,145,262; U.S. Pat. No. 4,733,515 and U.S. Pat. No. 8,454,265, which are incorporated by reference. 
     The concrete dowel device includes a sleeve and plate configured for use with a concrete form typically constructed with wooden boards. The dowels are embedded at the joints between adjacent concrete slabs to provide vertical support to keep the surface of the concrete level while allowing a small amount of horizontal and lateral movement to accommodate thermal expansion of the slabs while curing and during normal use, vibration, and other normal types of movement between adjacent concrete slabs. Providing for this type of relative movement between the slabs relieves stress to prevent or reduce cracking in the concrete during normal use while maintaining a smooth top surface of the pavement at the joints. 
     The concrete dowel accommodates a small amount of movement of the slabs away and towards each other transverse to the joint as well as lateral displacement between the slabs in the direction of the joint, while preventing substantial vertical movement to maintain a smooth, level surface at the joint between the concrete slabs. An improvement resides in the break-away tabs positioned at the opening of the sleeve to guide insertion of the plate into the sleeve during construction without inhibiting normal lateral movement between the slabs after they have cured. Additional guide structures, such as slanted corners ore a “V” groove in the sleeve and corresponding “V” groove guide surface in the plate may provide additional guide structures to ensure proper registration of the plate within the sleeve. 
     The sleeve is designed to be nailed to a wooden form defining the edge of the first slab (one side of the joint between adjacent slabs) where a dowel is desired prior to pouring the first slab. The first slab is then poured with the sleeve held in place by the form, which embeds the sleeve within the first slab. Once the first slab has set sufficiently, the form is removed and the plate is inserted into the sleeve so that about half the plate extends into the sleeve and half extends into the area where the second concrete slab is to be poured. The second slab is then poured with the plate held in place by the sleeve. Once the second slab sets, the dowel formed by the sleeve and plate is embedded into the joint between the slabs, while the plate can slide a small amount within the sleeve to accommodate horizontal separation and lateral displacement between the slabs while maintaining the slabs in vertical alignment. 
     The present invention includes break-away alignment tabs positioned at opposing sides of the opening to the socket of the sleeve. The alignment tabs remain in place during slab construction to guide proper alignment of the plate with the sleeve. The tabs are configured to break away as forced by relative movement of the concrete slabs after the concrete has cured to allow a small amount of displacement between adjacent slabs. Various embodiments include additional alignment mechanism, such as angled corners and a “V” groove along the rear side of the sleeve, with corresponding guide surfaces in the plate, to facilitate proper registration between the sleeve and the plate. 
     Turning now to the figures,  FIG. 1A  is a top view of a plate  10  and sleeve  12  forming a concrete dowel device with the plate positioned outside the sleeve. The sleeve  12  includes a socket  13  configured to snugly receive the plate  10  and typically includes ridges, dimples or other internal surface features to ensure a snug interference fit between the plat and the socket. The sleeve  12  also includes a flange  14  at the opening of the socket  13  that includes two nail guides  16   a - b  that typically support two pre-installed nails  18   a - b  positioned ready for nailing into a wooden form. 
       FIG. 1B  is a front view of the sleeve  12  showing the flange  14  defining a plate opening  20  flanked by two break-away alignment tabs  22   a - b  before insertion of the plate into the sleeve.  FIG. 2A  is a top view of a plate and sleeve concrete dowel device with the plate  10  inserted within the sleeve  12 .  FIG. 2B  is a front view of the sleeve  12  showing the break-away alignment tabs  22   a - b  with the plate inserted within the opening  20  of the sleeve, as guided by the alignment tabs to center the plate within the sleeve. The socket of the sleeve is a bit wider than the plate to accommodate some lateral movement of the plate within the sleeve after the concrete slabs have set, and the break-away alignment tabs are provided to facilitate proper centering of plate within the sleeve during construction of the concrete slabs. For example, the plate may be about eight inches wide and the socket in the range of about nine inches wide. The break-away alignment tabs are attached sufficient strongly to the flange to remain in place during construction, but are thinner than the rest of the sleeve, have thinner seams, are scored or interference fit in place to break away after the concrete has set to accommodate lateral movement between the concrete slabs joined by the dowel. The interference fit between the plate and the sleeve accommodates a bit of horizontal separation between the concrete slabs as wells as lateral displacement while maintaining smooth vertical alignment of the top surface of the slabs. 
       FIGS. 3A-E  illustrate use of the dowel during construction of the concrete structure, such as a pavement. Many dowels are used in a typical pavement project and the figures depict a representative dowel.  FIG. 3A  is a plan view of the sleeve  12  nailed to a concrete form  30  before pouring of a first concrete slab over the sleeve. The nail  18   a  is typically pre-installed allowing the construction worker to easily nail the sleeve to the form in the desired position with a few hammer strikes. As shown in  FIG. 3B , once the dowel has been nailed in place on the form, the first slab  32  is poured, which embeds the sleeve  12  within the first slab  32 . Once the first slab has set, the form  30  is removed as shown in  FIG. 3C . This exposes the socket opening of the sleeve at the edge of the first concrete slab. A construction worker then inserts the plate  10  into the sleeve  12  as shown in  FIG. 3D . It is at this point when the alignment tabs assist the construction worker to properly align the plate  10  within the sleeve  12  to ensure that the dowel accommodates the desired amount of lateral movement. It will be appreciated that dowel will not function as designed if the plate is not aligned properly in the center of the sleeve and construction worker are prone to work hastily with variable levels of attention. The alignment tabs do a good job of squaring the plate within the sleeve when the plate is jammed into the sleeve, for example when a worker pushes or hits the plate with a board, hammer, hand or foot. The second slab  34  is then poured as shown in  FIG. 3E  leaving the dowel formed by the sleeve and plate embedded at the joint between the first and second slabs. 
     It will be appreciated that ensuring proper registration between the plate and sleeve is of primary importance when installing the dowels. Several alternatives may be utilized to further ensure proper registration and, once these techniques are understood, other variations will become apparent to those skilled in the art.  FIGS. 4A-C  show a first alternative designed to ensure proper registration, which includes a plate  40  that has a wider portion  42  designed to remain outside the sleeve and a narrower portion  44  designed to be fully inserted into the sleeve. When the plate is fully inserted into the sleeve, transition edges  46   a - b  between the wider and narrower portions are designed to bottom out against the flange  14  providing a visual and physical indication of positive registration of the plate in the sleeve. Basically, this allows the construction worker to hand push, kick, or hit the plate with a board or hammer until the transition edges  46   a - b  of the plate are flush against the flange  14 . A quick visual inspection will confirm that all of the plates are properly installed. As shown in  FIG. 4C , the wider and narrower portions  42 ,  44  can have the same depth so that the plates can be formed (typically stamped) from sheet stock without waste. 
       FIG. 5  illustrates a second alternative to ensure proper registration of the plate  50  within the sleeve  52 . This alternative includes beveled corners  54   a - b  on the plate  50  configured to mate against beveled corners  56   a - b  one the sleeve  52 . The beveled corners cause the plate  50  to square up as the plate  50  is forced into the sleeve  52 .  FIG. 6  illustrates a variation on this theme, which utilizes mating “V” groove  66  in the sleeve  62  and “V” groove guide surface  64  in the plate  60  serving the same purpose. The various registration techniques may be employed individually or combined, as desired. For example, the “V” groove alternative shown in  FIG. 6  also includes the two-tiered plate configuration shown in  FIGS. 4A-C . 
     Ease and efficiency of manufacturing is another aspect of the present invention. The undercut nature of the alignment tabs over the side portions of the socket of the sleeve could prevent the sleeve from being molded as a single part due the undercut nature of the tabs preventing easy extraction of the sleeve from the mold. To alleviate this problem, the sleeve may be configured for injection molding as a single structure with the alignment tabs pointed away from the opening of the socket with a thin, flexible seam at the junction between the tab and sleeve body and small interference structures on the tabs or sleeve body. After molding, the tabs can then be rotated and snapped into position with an interference fit as shown in  FIG. 7 . Small taps, grooves or ridges may be provided as interference structures to ensure a positive interference fit when the tabs are rotated and snapped into place. 
     Another alternative is shown in  FIGS. 8A-B , in which the alignment tabs are formed as part of an insert plate  80  that is molded separately from the sleeve  12 . The insert plate  80  defines the plate opening  20  flanked by the break-away alignment tabs  22   a - b  and fits within an inset area  82  in the flange  14  of the sleeve. The insert plate  80  can be secured within the inset area  82  using an interference fit, adhesive, heat seal or any other suitable attachment technique. 
     Although the terms “horizontal” and “vertical” have been used to describe use of the dowel in the context of a horizontal pavement, it will be appreciated that the dowel is well adapted for but not limited to the pavement application and can be used for any concrete joint of sufficient size regardless of its orientation. For example, the invention is equally applicable to joints in concrete walls, ceilings, abutments and other structures Those skilled in the art will appreciate that the foregoing describes preferred embodiments of the invention and that many adjustments and alterations will be apparent to those skilled in the art within the spirit and scope of the invention as defined by the appended claims.