Abstract:
A slotted insert based upon a non-metallic void former including a neck portion defining a longitudinally elongated slot, the neck portion having a first transverse width, and a channel portion defining a longitudinally elongated channel, the channel having a second transverse width substantially greater than the first transverse width. The insert includes a metal nut, captured within the channel, having an aperture and a third transverse width substantially greater than the first transverse width. The longitudinally elongated slot and longitudinally elongated channel are interconnected with the aperture of the captured metal nut accessible through the slot to provide an adjustable anchoring or connection point to other structural components. Various attachment features allow the insert to be positioned within formworks with or without direct attachment to the forming surface of a concrete form member.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to concrete forming systems, and more particularly to slotted inserts used to provide cast concrete elements with adjustable attachment points for wall panels, architectural panels, structural framing, decking, and other precast or premanufactured structural components. The slotted insert is embedded within a precast or site-cast concrete element, with the captured nut providing an adjustable, threaded-bolt-type connection for adjoining precast or premanufactured structural components. 
       BACKGROUND 
       [0002]    Slotted inserts are used in concrete construction, most typically in precast construction, to provide adjustable anchoring or connection points amongst precast and premanufactured structural components or between site-cast foundations or walls and such structural components. Such inserts typically have a metal body defining both a longitudinally elongated slot and a plurality of transversely projecting legs, such as in the P30 Corewall® Nut Type Slotted Insert (manufactured by Dayton Superior Corporation of Miamisburg, Ohio, USA). A metal nut is captured behind the elongated slot and within a housing defining elongated channel, with the captured nut being slidably positionable along the length of the slot and channel to provide a longitudinally-adjustable connection. The cap and elongated slot may face horizontally and extend vertically, e.g., be embedded within the face of a wall to provide a vertically adjustable connection point to a precast panel, or face vertically and run horizontally, e.g., be embedded within a floor to provide a horizontally adjustable connection point to a precast panel, however it will be appreciated that the insert may be molded in and/or ultimately positioned in any orientation, without limitation, as required by the intended connection. The insert may be attached to a concrete form so that the elongated slot is positioned against the inner face of the forming surface, or may be emplaced within a casting bed, with the cap and elongated slot facing upward and positioned proximate the free surface of the concrete, via attachment to a support member or even manual setting within the wet concrete. The captured nut is frequently protected from exposure to poured concrete by a removable cap positioned within the slot or could alternately be protected by a means for forming a seal against the inner face of the forming surface. Rebar is frequently clipped or tied to the transversely projecting legs of the steel body, between the legs and the inner face of the forming surface, to help to anchor the insert and resist pull-out from the surrounding concrete. 
         [0003]    Wet concrete is poured and cured within an assembled formwork around the attached insert. The formwork is subsequently stripped from the formed concrete and embedded insert, with the elongated slot of the insert ending up essentially flush with the surface of the formed concrete element. The removable cap, if present, is removed to expose the elongated slot and the captured nut, which remains longitudinally adjustable within the elongated slot but captured within the insert and the surrounding concrete. Precast or premanufactured structural components such as wall panels, structural framing, decking, and the like may be connected to the nut, insert, and surrounding concrete by a threaded bolt or by a threaded-bolt-type connection such as a threaded strap anchor. The resulting connection is both adjustable, to accommodate variation in the dimensions of other components and the positions of their connection points, and ductile, for use as a structural connection in seismically active regions. 
       SUMMARY 
       [0004]    The applicants have devised an improved slotted insert which functions similarly to known slotted inserts, but does not require a metal body like that used in existing inserts. Instead, the slotted insert uses a multi-part, non-metallic void former housing a metal nut. The void former defines an elongated slot with a first transverse width and a recessed, elongated channel with a second, substantially greater transverse width. In use, the metal nut, also having a transverse width substantially greater than the first transverse width, bears against concrete surrounding the void former rather than against a metal body member. Consequently, the void former or insert body may be manufactured entirely from molded plastics or other non-metallic materials. Thus construction reduces the weight of the resultant insert, the cost of manufacturing the insert, and the susceptibility of the insert to galvanic or oxidative corrosion. 
         [0005]    In a first aspect, a slotted insert comprises a non-metallic void former including a neck portion defining a longitudinally elongated slot, the neck portion having a first transverse width, and a channel portion defining a longitudinally elongated channel, the channel having a second transverse width substantially greater than the first transverse width. The insert further comprises a metal nut, captured within the channel, having an aperture and a third transverse width substantially greater than the first transverse width. The longitudinally elongated slot and longitudinally elongated channel are interconnected and mutually aligned such that the longitudinal axis of the slot and the longitudinal axis of the channel are parallel to each other, with the aperture of the captured metal nut accessible through the slot. 
         [0006]    In a second aspect, a formwork construction comprises an insert including a non-metallic neck portion defining a longitudinally elongated slot, the neck portion having a first transverse width, a non-metallic channel portion defining a longitudinally elongated channel, the channel having a second transverse width substantially greater than the first transverse width, a metal nut captured within the channel, the metal nut having an aperture and a third transverse width substantially greater than the first transverse width, and a removable cap portion configured to seal the longitudinally elongated slot opposite the longitudinally elongated channel. The longitudinally elongated slot and longitudinally elongated channel are interconnected and mutually aligned such that the longitudinal axis of the slot and the longitudinal axis of the channel are parallel to each other, with the aperture of the captured metal nut accessible through the slot upon removal of the removable cap portion. The formwork further comprises a pair of metal reinforcing bars, bracketing the void former proximate the longitudinally elongated channel and extending parallel to the longitudinal axis of the channel. The insert is preferably affixed to the metal reinforcing bars via a plurality of clips projecting outwardly from the void former channel portion. 
         [0007]    In a third aspect, a formwork construction comprises a an insert including a non-metallic neck portion defining a longitudinally elongated slot, the neck portion having a first transverse width, a non-metallic channel portion defining a longitudinally elongated channel, the channel having a second transverse width substantially greater than the first transverse width, and a metal nut, captured within the channel, having an aperture and a third transverse width substantially greater than the first transverse width. The longitudinally elongated slot and longitudinally elongated channel are interconnected and mutually aligned such that the longitudinal axis of the slot and the longitudinal axis of the slot are parallel to each other, with the aperture of the captured metal nut accessible through the slot. The formwork further comprises a support member, which may be a concrete form, wherein the neck portion is affixed to an inner surface of support member via a plurality of fasteners inserted through a projecting tab or flange and into the inner surface. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a perspective view of an embodiment of the void former. 
           [0009]      FIG. 2  is an exploded perspective of the embodiment of  FIG. 1  which further illustrates the longitudinally elongated slot, longitudinally elongated channel, and captured metal nut. 
           [0010]      FIG. 3  is a perspective view of a formwork assembly including metal reinforcing bars affixed to the void former. 
           [0011]      FIG. 4  is a perspective view of a formwork assembly including a void former affixed to the inner surface of a support member. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    As shown in  FIGS. 1 and 2 , an insert  100  comprises a non-metallic void former  110  including a neck portion  120  defining a longitudinally elongated slot  130  and a channel portion  140  defining a longitudinally elongated channel  150 . The insert  110  also includes a metal nut  160  captured within the channel  150 . The channel  150  is substantially wider than the neck portion  120 , with “substantially” meaning for the purposes of this application an average, along the respective longitudinally elongated structures, of ¼ inch wider or more on each side, so as to permit the metal nut  160  to bear against concrete surrounding the neck portion  120  of the void former  110 . As shown specifically in  FIG. 2 , the neck portion  120  may have a first transverse width  122 , the defined channel  150  a second transverse width  152  substantially greater than the first transverse width  122 , and the metal nut  160  a third transverse width  162  substantially greater than the first transverse width  122 . The third transverse width  162  is preferably, but not necessarily, essentially equal to the second transverse width  152 . The longitudinally elongated slot  130  and longitudinally elongated channel  150  (i.e., the voids, not the void-forming structures) are interconnected and mutually aligned such that the longitudinal axis of the slot and the longitudinal axis of the channel are parallel to each other. 
         [0013]    The neck portion  120  and the channel portion  140  are preferably separate portions of the insert  100  so that different neck portions  120  having different depths  124  may be affixed to the same channel portion  140  in order to provide an adjustable, threaded-bolt-type connection  164  at different depths from the surface of the concrete “S” (indicated in  FIG. 3 ). The portions  120 ,  140  may be releaseably interlocking with each other for interchangability. For example, a channel-facing end  126  of the neck portion  120  may include an outwardly-projecting peripheral flange  128 , and a neck-facing end  144  of the channel portion  140  may include an inwardly-open circumferential track  146  which engages the peripheral flange  128  to interlock the neck portion  120  and channel portion  140  together. It will be appreciated that the channel-facing end  126  of the neck portion  120  could include such a track, and the a neck-facing end  144  of the channel portion  140  include such a projecting peripheral flange, to provide the same functionality. The neck portion  120  may be flexible enough that the channel-facing end  126  and flange  128  may be compressed to fit within the circumferential track  146 . However, the channel portion  140  may comprise separable halves  140   a,    140   b  and be connectable by respective latching tabs  148   a  and ridged lands  149   a  (shown in  FIG. 2 ) or U-shapes latch arms  148   b  and locking ramps  149   b  (shown in  FIG. 4 ). This construction permits the channel portion halves  140   a,    140   b  to be snapped around the peripheral flange  128  of the neck portion  120 , and enables easy insertion of the metal nut  160  into the channel  150  formed by the halves during manufacturing or user assembly. Those of skill in the art will appreciate that the neck portion  120  and/or channel portion(s)  140  or  140   a  and  140   b  may be affixed to each other by solvent welding, ultrasonic welding, adhesives, and similar known means for joining materials so as to negate the need for one or more of the structures and features specifically described in this paragraph. 
         [0014]    In some embodiments, the insert portion  100  includes a removable cap portion  170  configured to seal the longitudinally elongated slot  130  opposite the longitudinally elongated channel  150 . The removable cap portion  170  may be a frangible part of the neck portion  120 , defined by a thinned web or line of perforation  172  (both indicated by the illustrated dashed line) proximate the periphery of the elongated longitudinal slot  130 . The cap portion  170  may be removed by puncturing the portion with a tool such as a screw driver and breaking the frangible web or line of perforation  172 . The removable cap portion  170  might include a pull-tab, e.g. a molded loop and stem attached to the cap portion via a living hinge, configured to enable tool-less removal. Alternately, the removable cap portion  170  might be a separate non-metallic or metallic cap which snap-fits into engagement with the neck portion  120  opposite the channel portion  140 . A separate, metallic removable cap  170 , such as a steel cap, could be detected by an appropriately calibrated metal detector and/or reused with other inserts  100  in subsequent forming activities. 
         [0015]    In some embodiments, the neck portion  120  includes a plurality of outwardly-projecting tabs  125  opposite the channel-facing end  126 . As shown, the tabs include reinforcing gussets  125   a  and project longitudinally from the neck portion  120 . However, it will be appreciated that gussets  125   a  are optional and that tabs  125  may project longitudinally from the neck portion  120 , transversely from the neck portion  120 , and/or at non-orthogonal angles with respect to the longitudinal axis of the elongated longitudinal slot  130 . The tabs  125  are illustrated as including apertures, but it will be appreciated that the apertures may instead be thin webs or even omitted, with fasteners such as nails serving to form their own aperture when used to secure the insert  100  against a concrete form via the tabs. In other embodiments, the neck portion  120  includes an outwardly-projecting peripheral flange, opposite the peripheral flange  128  at the channel-facing end  126 , which may include similar apertures or thin webs for receiving fasteners. For the purposes of the application and claims, this peripheral flange shall be considered a generic case which encompasses one or more outwardly-projecting tabs  125  of varying size. 
         [0016]    In some embodiments, the channel portion  140  includes a plurality of outwardly-projecting clips  145 . The clips may serve to affix the insert  100  to metal reinforcing bars or “rebar” positioned within the concrete form, removing the need to directly secure the insert  100  to a concrete form. It will be appreciated that the insert  100  may be positioned directly adjacent a concrete form, such as under a cap form or beside a wall form, through the clip-connection while not being directly secured to the form itself. In some embodiments (not shown), mutually opposing pairs of clips  145  may be disposed on the laterally outermost or longitudinally outermost sides of the channel portion  140 . In the illustrated embodiment, clips  145  are configured to receive metal reinforcing bars running parallel to the longitudinal axis of the channel  150 , and also to project across a longitudinally-running, laterally-projecting bearing surface  143  in the channel portion  140 . The bearing surface may further include a clip-opposing saddle  147  to maintain the metal reinforcing bar in position. As explained below, in this embodiment the metal nut  160  may bear against the reinforcing rod to resist pull-out of the nut from the insert  100  and surrounding concrete. 
         [0017]    The metal nut  160  is preferably a rectangular nut, but not necessarily a hyperrectangle or orthotope (i.e., not necessarily a strictly rectangular box). In some embodiments, metal nut  160  may be a rectangular nut with rounded edges, such as a conventional square nut. In other embodiments, the metal nut  160  may include a rectangular portion but also include an integral shaft structure, such as in a T-slot nut, to provide greater load capacity to the aperture  164  of the nut. The aperture  164  is typically threaded such that increasing the depth of the aperture will generally increase the load capacity of the metal nut  160 . In the illustrated embodiment, the metal nut  160  includes a pair of longitudinally-running, laterally-projecting wings  163  which generally conform to the longitudinally-running, laterally projecting bearing surfaces  143  in the channel portion  140 . Metal reinforcing bars positioned upon the bearing surfaces  143  of the channel portion will be disposed proximate the wings  163  of the nut  160 , and consequently the nut  160  will bear against those bars when a tensile load is applied to the aperture  162  by a threaded-bolt or threaded-bolt-type connection through the elongated longitudinal slot  130 . In each such embodiment, the aperture  162  is accessible through the longitudinally elongated slot  130  or becomes accessible through that slot upon removal of the removable cap portion  170 . In some embodiments, the metal nut  160  may include an elastomeric spacer  166 , e.g., a spacer formed from an elastomeric open-cell or closed-cell foam, adhered to one of the non-longitudinal sides of the nut. The elastomeric spacer  166  may be adhered to the nut using an adhesive, e.g., a pressure-sensitive adhesive, and serve to increase friction between the metal nut  160  and channel portion  140  in order to prevent unwanted sliding of the metal nut  160  within the channel  150 . In other embodiments, the a channel-facing end  126  of the neck portion  120  may include a plurality of elastic fingers  127  configured to project within the longitudinally elongated channel  150 . The elastic fingers  127  will interfere with movement of the metal nut  160  within the channel  150 , but deflect when force is applied to the nut to move it within the channel  150 , e.g., when a tool is used to positively manipulate the nut and/or an connected element is positioned prior to tensioning of the connection. In still other embodiments, a combination of such features can be used. The metal nut  160  may thus be manipulated to slide longitudinally within the channel  150 , but substantially prevented from sliding within the channel due to the force of gravity or minor manipulation of the insert  100  during installation. 
         [0018]    In use, an example of which is shown in  FIG. 3 , a formwork  200  may include the insert  100  and at least a pair of metal reinforcing bars  210  bracketing the void former  110  proximate the channel portion  140  and longitudinally elongated channel  150  (shown in  FIG. 2 ). At least those portions of the metal reinforcing bars  210  proximate the channel portion may be configured to extend parallel to the longitudinal axis of the longitudinally elongated channel  150 . In some embodiments, the insert  100  is affixed to the metal reinforcing bars  210  by wrapping the void former  110  and bracketing metal reinforcing bars  210  with wire (not shown), for example in an X-shaped pattern spanning the neck-facing end  144  and opposite end of the channel portion  140 , crossing itself midway along the longitudinally elongated channel  150  on the lateral sides of the channel portion  140 . Preferably, the metal reinforcing bars  210  are received within a plurality of clips  145  projecting outwardly from the channel portion  140 . Each metal reinforcing bar  210  is thus clipped between a bearing surface  143  in the channel portion  140  and one or more clips  145  on each side of the channel portion  210 . The metal reinforcing bars  210  may be positioned within surrounding concrete forms, e.g., opposing wall forms  220  (only one of which is shown), and with the channel  150  of the insert  100  at a depth “D” below the planned surface of the concrete—which may be formed by a cap form or, as indicated in the illustration, a free surface of the concrete “S”. The removable cap  170  ends up proximate the free surface of the concrete  230 , and may be located by identifying the edges of the neck portion  120  proximate the cap, by identifying the cap itself if visible, by striking the set concrete over the cap (which, being at most a thin layer over the non-metallic void former  120 , is likely to fracture and chip), or by locating upwardly projecting whiskers  176  located on or near the removable cap  170 . The removable cap  170  may subsequently be removed to expose the metal nut for connection to a threaded bolt or threaded-bolt-type connection. 
         [0019]    In another use, an example of which is shown in  FIG. 4 , a formwork  300  may include an insert  100  and at least one support member, such as the previously illustrated wall form  220  or the illustrated support member  230 . The insert  100  is secured directly to the member  230 , with the neck portion  120  opposite the channel portion  140  positioned against the forming surface. In one embodiment, the insert is secured directly to the member  230  using a plurality of fasteners  240  inserted through one or more outwardly-projecting tabs  125 , as described above. The elongated longitudinal slot  130  may be substantially sealed from exposure to concrete by the fit of the neck portion  120  against the member  230 , by a removable cap  170 , or by other means for forming a seal such as a gasket, a caulk, a putty, a highly viscous grease or gel, etc. As shown in  FIG. 3  and/or discussed above metal reinforcing bars  210  could also be secured to the insert  100  to reinforce the positioning of the insert and/or to position the metal reinforcing bars  210  at a definite location within the formwork  300 . The neck portion  120  opposite the channel portion  140  ends up proximate the formed surface of the concrete, and may be located by identifying the edges of the neck portion  120  and/or the elongated longitudinal slot  130  opening at the formed surface, by identifying any removable cap  170  provided, by striking any concrete skin formed upon the removable cap, etc. The slot opening to the metal nut  160  may then be used for connection to a threaded bolt or threaded-bolt-type connection. 
         [0020]    Having described the invention in detail and by reference to the preferred embodiments, it will be apparent that modifications and variations thereof are possible without departing from the scope of this disclosure.