Abstract:
A slab bolster upper for supporting rebar in a reinforced concrete structure while the concrete is poured and thereafter cures, is of molded plastic construction and is formed with horizontal and vertical voids that facilitate concrete placement and break up potential shear planes. Opposite ends of each unit are provided with complementary buckles to interconnect with like units to form a continuous support of desired length.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    In reinforced concrete construction, it is necessary to support the reinforcing bars (“rebars”) in their designated locations during placement of the concrete and thereafter as it cures. This is accomplished in its most rudimentary form by simply resting the rebar on pieces of concrete placed on the form surface. Obviously, this approach may be unsatisfactory for many reasons, such as the lack of any means for fixing the rebar at their designed positions, as a result of which the rebar may be displaced as the concrete is poured.  
           [0002]    In response to the shortcomings of this method of supporting rebar, welded wire supports have been developed and are used extensively in the reinforced concrete construction industry. For example, U.S. Pat. No. 4,689,867 is directed to a welded wire rebar of one type, while U.S. Pat. No. 4,996,816 describes another welded wire rebar support design. With metal supports, however, there is a potential problem of corrosion. Coating the wire with epoxy is a method of dealing with this problem, but coating is expensive, and if the coating is damaged, corrosion may still occur.  
           [0003]    Plastic supports are generally non-corrodible and therefore overcome the problems noted above with welded wire supports, but they usually lack the open construction provided by wire supports that permits full flow of concrete through and around the support during concrete placement. While U.S. Pat. Nos. 5,729,949 and 6,089,522 disclose supports that may be formed of plastic and have openings formed in them to facilitate concrete placement, the supports shown in these patents are individual units as opposed to supports that may extend for several spans. U.S. Pat. No. 5,664,390 discloses a plastic bolster that may extend across several spans and uses a pair of spaced legs and a control body that resists deformation through the use of pin-like projections that bite into the underlying surface.  
         SUMMARY OF THE INVENTION  
         [0004]    The above-noted problems associated with prior art bolsters are obviated by the bolster of the present invention. Specifically, the bolster of the present invention is preferably molded of non-corrodible plastic, is of inverted T-shape for greater stability, and provides an open construction that facilitates distribution of concrete during placement through and around the bolster.  
           [0005]    The base of the bolster of the present invention may be molded integrally with the rebar support section that projects substantially perpendicularly away from an upper surface of the base and terminates in a rebar-engaging cap that extends in generally parallel relationship to the base. Both the base and the support section may be of truss-like construction, which results in a high weight-to-strength ratio, with a major portion of the base and web being occupied by voids, thereby enhancing concrete flow through and around the bolster.  
           [0006]    In another preferred embodiment of the invention, the base may be molded with a series of posts spaced along and projecting from an upper surface and a rebar-engaging cap molded separately and mechanically interconnected to outer ends of the posts by means of joint elements molded in the posts and the cap. The latter may also be provided with transverse ridges on its outer rebar-engaging surface to break up shear planes. Additionally, the junctures of the posts and the base are strengthened by gussets that project upwardly from the base and extend both longitudinally and laterally of the base upper surface. To further strengthen the bolster, opposite longitudinal edges of the base are provided with continuous upstanding ribs, and the ribs and gussets further serve to break up shear planes.  
           [0007]    The post construction of this embodiment is conducive to flexible injection mold tolling that can mold a wide range of sizes without the need for different molds for each size. The portions of the mold that forms the posts are simply adjusted.  
           [0008]    The bolster of the present invention may be utilized separately, or in a preferred form of the invention, may be provided with complementary buckles at opposite ends to permit connection with like units to form a continuous bolster of desired length. In this regard, both the base and the rebar support section are each provided with complementary buckles so that the units, when interconnected, are joined at both their upper and lower extremities, thereby enhancing the strength and stability of the composite bolster.  
           [0009]    In either case, that is, whether formed as discrete units or with interconnecting buckles, the bolsters are formed of a convenient length, e.g., about 2.5 feet in length. The inverted T-shape of the units, which permits the units to be nested, and the convenient unit length, greatly facilitate packaging the units for shipment.  
           [0010]    The bolsters of the present invention may be formed from a variety of plastics, such as polycarbonate/ABS, polyproylene, nylon, or ABS. Additionally, the plastic may be reinforced with a variety of fibers, such as fiberglass, Kevlar, carbon fibers, or metal fibers.  
           [0011]    These and other features and advantages of the bolster of the present invention will become more apparent from the following description. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the invention.  
         [0013]    [0013]FIG. 1 is a perspective view of a slab bolster upper in accordance with the present invention;  
         [0014]    [0014]FIG. 2 is a perspective view of a plurality of slab bolster uppers nested for shipping;  
         [0015]    [0015]FIG. 3 is a view similar to FIG. 1 of a second preferred embodiment of the invention;  
         [0016]    [0016]FIG. 4 is an exploded perspective view of another preferred embodiment of the invention;  
         [0017]    [0017]FIG. 5 is a perspective view of the embodiment of FIG. 4 showing the slab bolster upper assembled;  
         [0018]    [0018]FIG. 6 is a perspective view of two units of the type shown in FIG. 5 interconnected by complementary buckles;  
         [0019]    [0019]FIG. 7 is an enlarged perspective view showing the buckle construction at one end of the slab bolster upper;  
         [0020]    [0020]FIG. 8 is a view similar to FIG. 7, but showing the buckle construction at the opposite end of a slab bolster upper;  
         [0021]    [0021]FIG. 9 is a view similar to FIG. 6, but showing a second preferred embodiment of buckle;  
         [0022]    [0022]FIG. 10 is an enlarged perspective view showing the complementary buckle of FIG. 9 with the components disengaged;  
         [0023]    [0023]FIG. 11 is a view similar to FIG. 10, but showing the complementary buckle components engaged;  
         [0024]    [0024]FIG. 12 shows the slab bolster upper of FIG. 5 embedded in a reinforced concrete structure; and  
         [0025]    [0025]FIG. 13 is a view taken on line  13 - 13  of FIG. 12. 
     
    
     DETAILED DESCRIPTION  
       [0026]    With reference to FIG. 1 of the drawings, a slab bolster upper  10  in accordance with the first preferred embodiment of the invention comprises an elongated base  12  having upper and lower surfaces  14  and  16 , respectively and an elongated rebar support section  18  connected to and projecting from the upper surface of the base for engaging and supporting reinforcing bars. As will readily be seen from FIG. 1, the base  12  has a truss-like construction comprising a series of struts  20  extending between spaced parallel outer edges  22  and a medial portion  24 . Upstanding ribs  26  extend longitudinally of said base at said outer edges  22  and project substantially perpendicularly upwardly from the upper surface  14  of the base  12 . The rebar support section  18  is formed as a substantially planar web projecting substantially perpendicularly from the upper surface  14  of the base  12  substantially medially thereof. Similarly to the base  12 , the rebar support section  18  comprises a series of struts  30  to provide a strong, yet open, truss-like configuration extending from a bottom, longitudinally extending lower rib  32  to a corresponding upper rib  34 . Attached to the upper rib and extending substantially parallel to the base  12  is a rebar-engaging cap  36 .  
         [0027]    The slab bolster upper as shown in FIG. 1 may be injection molded from a suitable plastic such as polycarbonate, polypropylene, and nylon and may be reinforced from various fibers, such as fiberglass, carbon fiber, and metal fibers. Additionally, it will be noted that with the truss-like construction of both the base and the rebar support section, the voids  40  and  42  through the base  12  and support section  18 , respectively, comprise a major portion of the base and support section, whereby concrete, during placement, may flow freely through and around the base and the support section. Preferably, the openings  40  and  42  are made sufficiently large to permit the flow of sizable aggregate of up to 1.5 inches through the base and support section.  
         [0028]    Turning to FIG. 2 of the drawings, a plurality of the slab bolster uppers  10  of FIG. 1 are shown nested in a compact configuration to facilitate shipment. Thus, the inverted T-shape of the slab bolster uppers permits them to be assembled in nested relation as shown in FIG. 2, and that, together with a convenient length of the units, for example on the order of 2.5 feet each, render the slab bolster uppers of the present invention readily adapted for shipment.  
         [0029]    [0029]FIG. 3 of the drawings shows a second preferred embodiment  50  of the present invention, including a base  52  having a lower surface  54  and an upper surface  56  from which projects upwardly a rebar support section  58 . The base  52  has upstanding ribs  60  projecting substantially perpendicularly from the upper surface  56  and extending along opposite edges  52 . The rebar support section  58  has a substantially planar web  62  and a longitudinally extending cap  64  which extends in substantially parallel relationship to the base  52 . Both the base and the rebar support section are provided with large voids,  66  in the base and  68  in the rebar support section, which, as seen in FIG. 3, comprise a major portion of the base and the rebar support section, and as in the embodiment of FIG. 1, facilitate flow of concrete through and around the bolster  50 .  
         [0030]    [0030]FIG. 4 is an exploded perspective view of another embodiment  70  of the present invention. As seen in FIG. 4, a slab bolster upper  70  comprises a base  72  having a lower surface  74  and an upper surface  76 , from which project a series of regularly spaced posts  78  having sockets  80  in their outer ends adapted to receive pins  82  formed integrally on short cap members  84  molded integrally with a central rib  86  formed on a rebar engaging cap  88 . The latter, it will be noted, is provided with a series of regularly spaced transverse ridges  90 . The posts  78  and a cap  88  with their associated, integrally molded joint element  80 ,  82  and  84 , comprise a rebar support section  91  when assembled as seen in FIG. 5 of the drawings.  
         [0031]    As shown in both FIGS. 4 and 5 of the drawings, at the juncture of each post  78  with the upper surface  76  of the base  72 , longitudinally extending gussets  92  and transversely extending gussets  94  project upwardly from the upper surface  76  of the base  72 . Along opposite side edges of the base  72  are a pair of longitudinally extending ribs  96 , while medially thereof a third rib  98  extends parallel to the ribs  96 . It will also be seen from FIG. 5 of the drawings that a series of voids  100  are formed through the base  72  while the spacing of the posts  78  provides further voids  102  defined by the posts, the upper surface of the base, and the cap  88 , which voids comprise a major portion of the base and support section, respectively.  
         [0032]    In all three embodiments of the invention thus described, it will be noted that the large voids, both horizontally and vertically, break up shear planes that would be created in the structure in which the bolster is embedded and contribute to cracking and weakness. The same function is also served by the longitudinally extending ribs with which all three embodiments are provided and the ridges  90  on the cap  88 , which, although shown only in the embodiment of FIG. 5 of the drawings, are also applicable to the embodiments shown in FIGS. 1 and 3. While the embodiment of FIG. 5 is preferably of injection molded construction of various plastic material as noted above with respective to FIG. 1, the embodiments of FIGS. 1 and 3 may be extruded and all embodiments may be reinforced with a variety of fibers as also discussed above.  
         [0033]    Up to this point, the slab bolster uppers of the present invention have been described as discrete units that would usually be used alone. However, in accordance with the present invention, any of the three embodiments discussed so far may be provided with complementary buckles on opposite ends to permit them to be joined with like units. For purposes of illustration, buckle construction will be described in conjunction with an embodiment similar to that of FIG. 5, although it will be apparent that the same buckle construction is equally applicable to the embodiments of FIGS. 1 and 3.  
         [0034]    With reference, therefore, to FIG. 6 of the drawings, it will be seen that multiple slab bolster uppers  100  in accordance with the present invention are joined end to end with complementary buckle constructions  102 ,  104 ,  106  and  108 . With reference also to FIGS. 7 and 8 of the drawings, it will be seen that the left end of each unit  100  is provided with upper and lower hasps, the upper hasp  110  being molded integrally with the cap  112 , while the lower hasp  114  is molded integrally with the base  116 . On the opposite end of each unit  100  are sockets  115  and  1   16 , which are complementary with and receive the upper and lower hasps  110  and  114 . As will be apparent from an inspection of FIGS.  6 - 8 , as the hasps  110  and  114  are inserted into the sockets  115  and  116 , the projections  118  on the upper hasp  110  and  120  on the lower hasp  114  lock the hasps in place in their complementary sockets.  
         [0035]    FIGS.  9 - 11  show a further form of complementary buckles for joining successive units of slab bolster uppers of the present invention. As seen in FIGS.  9 - 11 , the complementary buckles  112  and  124  comprise a projecting member  126  receivable in the socket  128  on the opposite end of a like unit. A stabilizing portion  130  projects from the buckle  124  and is received in overlying relationship to the base of the slab bolster upper for stabilizing effect.  
         [0036]    [0036]FIGS. 12 and 13 depict a slab bolster upper in a reinforced concrete structure. For purposes of illustration, the embodiment of FIG. 5 of the invention is depicted in FIGS. 12 and 13, although it will be apparent that any of the embodiments thus far described would perform nearly identically. A reinforced concrete structure  150 , including concrete  152  containing aggregate  154  and reinforced with rebars  156  is shown in conjunction with a slab bolster upper  70 . A plurality of posts  78  carry the rebar engaging cap  88  upon which the rebars  156  are positioned. Additionally, a lower surface of the base,  72  in FIGS. 12 and 13 is provided with projections  158  extending from the lower surface of the base  72  to space the base slightly above the surface of the underlying form. As seen in FIGS. 12 and 13, this permits the concrete to spread beneath the lower surface of the base  70 . Although the embodiment of FIG. 5 of the drawings is depicted for purposes of illustrating the projections  158 , it will be apparent that any of the embodiments of the present invention may be provided with similar projections for the same purpose.  
         [0037]    While the present invention has been illustrated by the description of an embodiment thereof, and while the embodiment has been described in considerable detail, it is not intended to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and method and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the scope or spirit of applicant&#39;s general inventive concept.