Abstract:
A radially expansible sleeve to provide part of a drop-in anchor for receipt in a bore formed in a concrete structure. The sleeve has arcuate protrusions with knife-like distal edges extending therearound. Upon radial expansion of the sleeve, the knife-like edges cut into the interior surface of the bore to anchor the sleeve in place.

Description:
[0001]    The present invention relates to a drop-in anchor for use in a cylindrical bore formed in a concrete structure and, more particularly, is concerned with an expansible sleeve for such an anchor which is provided with protrusions having knife-like edges which cut into the walls of the bore to secure the anchor in place. 
       BACKGROUND OF THE INVENTION  
       [0002]    Various types of drop-in anchors have been provided in the prior art. Typically, these are used to secure some type of an object, such as the base for a tilt-up brace, to a concrete wall or floor. These anchors are generally temporary. Once they have served their purpose, the part or parts of the anchor which extend from the surface of the concrete structure are removed. The bore may then be grouted over, or otherwise closed. 
         [0003]    Prior art anchors generally employ some type of an expansible sleeve which is inserted into a bore formed in the concrete structure, and then expanded to grip the wall of the bore. The sleeve serves as the part to which the bolt of the anchor may be secured. 
         [0004]    U.S. Pat. No. 6,666,636 discloses a drop-in anchor of the above described type. This anchor has components corresponding generally to those of the present invention, except for the provision of knife like protrusions on the expansible sleeve. U.S. Pat. No. 5,116,176 is of interest in that it discloses an expansion anchor having a sleeve which may be inserted into a bore formed in a concrete structure, wherein the sleeve carries rings which are expansible into biting engagement with the bore. This patent also shows a prior art device wherein the angular grooves are formed around a sleeve like anchor. 
         [0005]    Another example of a drop-in anchor is found in U.S. Pat. No. 4,690,597, wherein the anchor employs an expansible sleeve like element designed to engage an undercut formed in the bore of the member to which the anchor is secured. 
       SUMMARY OF THE INVENTION  
       [0006]    The present invention provides an apparatus and method employing a sleeve with knife-like arcuate protrusions extending therefrom for expansion into cutting engagement with the walls of a bore formed in the concrete member. The sleeve is co-axially insertable into the bore and has a diameter slightly less than that of the bore. Upon expansion of the sleeve within the bore, the protrusions cut into the bore and secure the sleeve in place. 
         [0007]    A principal object of the invention is to provide a drop-in anchor for secure engagement within a bore formed in a concrete structure. 
         [0008]    Another and more specific object of the invention is to provide such an anchor wherein knife-like protrusions forming part of the anchor are expanded into cutting engagement with the walls of the bore. 
         [0009]    Yet another object of the invention is to provide such an anchor wherein the anchoring function is not reliant solely upon frictional forces. 
         [0010]    A further object of the invention is to provide a drop-in anchor for use in a concrete structure which avoids frictional movement of the anchor relative to the structure and resultant fluidization of the concrete surface at the interface of the anchor and the concrete. 
         [0011]    Still another object of the invention is to provide such an anchor wherein which does require the formation of an undercut in the bore of the concrete member within which the anchor is received. 
         [0012]    The foregoing objects are not intended to be exhaustive of all of the benefits which flow from the present invention. Others will become apparent from the accompanying drawings and description of the preferred embodiment. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0013]      FIG. 1  is a cross-sectional elevational view of the anchor of the present invention, received within a bore formed in a concrete slab, as the anchor would appear after being set in place; 
           [0014]      FIG. 2  is an elevational view of the anchor sleeve; 
           [0015]      FIG. 3  is a bottom plan view of the anchor sleeve shown in  FIG. 2 ; 
           [0016]      FIG. 4  is an elevational view of the bolt of the anchor; 
           [0017]      FIG. 5  is a top plan view of the bolt; 
           [0018]      FIG. 6  is a perspective view, in cross-section, of a concrete slab having a bore formed therein for receipt of the anchor; 
           [0019]      FIG. 7  is a perspective view, similar to  FIG. 6 , showing the anchor of the present invention, with the bolt in place, in the process of being driven into the bore in the concrete slab; 
           [0020]      FIG. 8  is a perspective view, similar to  FIG. 7 , showing the expansion plug for the anchor sleeve in the process of being driven into place to expand the sleeve into engagement with the walls of the bore; 
           [0021]      FIG. 9  is a perspective view, similar to  FIG. 8 , showing the anchor sleeve fully expanded and the bolt in the process of being tightened to secure a plate to the surface of the concrete slab; 
           [0022]      FIG. 10  is a perspective view, similar to  FIG. 9 , showing the bolt of the anchor in the process of being removed, with the anchor sleeve remaining in place within the bore. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0023]    The concrete slab shown in  FIG. 1  is depicted by the letter C and shown as having a bore B therein. The bore is formed by drilling and terminates in a frusto-conical end E. 
         [0024]    As shown in  FIG. 1 , the anchor assembly of the present invention is fully in place within the bore B. The assembly comprises: a sleeve  10 ; a bolt  12  threably engaged in a screw threaded upper portion  14  of the sleeve; a frusto-conical plug  16  received within and extending through a complimental inwardly tapered portion  18  of the sleeve  10 ; and an activation rod  20  extending slidably through a passage  22  therefor in the bolt  12 . The upper end of the bolt has an integrally formed collar  24  and hex-head  26  (see  FIGS. 4 and 5 ). 
         [0025]    As shown in  FIG. 1 , a plate  28  having a slot  30  (see  FIG. 7 ) extending partially thereacross is secured beneath the collar  24 . The plate  24  has aligned apertured ears  32  extending upwardly therefrom. These ears may be used to attach any desired component to the plate  26 , e.g. a brace for a tilt-up slab. 
         [0026]    The sleeve  10  is shown, in detail, in  FIGS. 2 and 3 . It comprises: a cylindrical section  34 ; a reduced diameter split section  36  integrally formed with and extending from the cylindrical section, said split section having slots  38  extending longitudinally over its length to divide the section into four quadrants (see  FIG. 3 ); and, arcuate protrusions  40  extending radially from the split sections. The arcuate protrusions  40  provide three longitudinally spaced rings extending around the split section, each of which rings is interrupted by the slots  38 . 
         [0027]    As shown in  FIG. 2 , the sleeve  10  has a longitudinal axis  42 , a leading end  44  and a trailing end  46 . The protrusions  40  are disposed in planes extending normal to the longitudinal axis  42 . Each protrusion  40  has leading and trailing surfaces  48  and  50 , respectively, which converge to form knife-like edges  52 . 
         [0028]    The sleeve  10 , including the arcuate protrusions  40  extending around the split section  36 , has an outside diameter slightly less than that of the bore B, in order that the sleeve may be easily slipped into place within the bore. Placement is also facilitated by sloping the leading surfaces  48  of the protrusions so that they converge toward the leading end of the sleeve. 
         [0029]    In a typical embodiment, the sleeve  10  is formed of 4140 steel, with the following dimensions, in millimeters: 
         [0030]    overall length: 65.50/64.50 
         [0031]    slot length: 32.50/31.00 
         [0032]    cylindrical section length: 37.60/38.40 
         [0033]    screw threaded portion: 30.00/31.00 
         [0034]    outside diameter of cylindrical section: 22.98/22.85 
         [0035]    minimum diameter of tapered portion: 13.50/14.00 
         [0036]    maximum diameter of tapered portion: 15:80/15.50. 
         [0037]    With the above dimensions for the sleeve  10 , typical dimensions for the plug  16  would be: 
         [0038]    Length: 19.05 
         [0039]    minimum diameter: 14.47 
         [0040]    maximum diameter: 15.76. 
         [0041]    The leading edges of the sleeve  10  and plug  16  are chamfered, externally. The rearward edge of the sleeve  10  is inwardly chamfered. 
         [0042]    The bolt  12  is of a unitary construction and, as may be seen from  FIG. 4 , comprises: a screw threaded distal portion  56  for threaded engagement in the screw threaded portion  14  of the sleeve  10 ; a collar  58  to improve the bending characteristics of the bolt and assist in maintaining it in alignment with the bore B; and, a reduced diameter section  60  proportioned so that the key slot  30  of the plate  28  may be easily slid around the bolt. 
         [0043]      FIG. 7  shows the first step of placing the drop-in anchor. As there shown, the plug  16  is loosely received within the inwardly tapered portion  18  of the sleeve  10  and bolt  12  is threadably received within the screw threaded portion  14  of the sleeve. The assembled anchor is then slid into place within the bore B, with the plate  28  engaged beneath the flange  24  of the bolt. The outside diameter of the anchor assembly is slightly less than that of the bore, in order to assure that the assembly may be easily slid into place within the bore. A mallet M is used to tap the bolt fully into place within the bore. 
         [0044]      FIG. 8  shows the anchor assembly and place within the bore B, with the sleeve  10  in the process of being expanded into secure gripping engagement with the interior of the bore. As there shown, the rod  20  is slidably extended into the passage  22  and engaged with the top of the plug  16  (see  FIG. 1 ). The mallet M is used to drive the rod  20  downwardly, against the top of the plug  16 , thus moving the plug longitudinally and spreading the split section  36  to force the knife-like edges of the protrusions  40  into cutting engagement with the wall of the bore B. ( FIG. 1  shows the sleeve fully expanded, with the protrusions so engaged and cut into the walls of the bore.) 
         [0045]    The fully engaged condition of the sleeve  10  may also be seen from  FIG. 9 . As there shown, the plug  16  extends through the sleeve  10  and partially into the end E of the bore B.  FIG. 9  also shows that the rod  20  is so proportioned that when the top of the rod is flush with top of the bolt head  26 , the sleeve  10  is fully expanded. The flush interrelationship of the top of the rod and top of the bolt also indicates that the anchor is fully seated. 
         [0046]      FIG. 9  also shows a wrench W in the process of tightening the bolt  12 . Such tightening securely compresses the plate  28  between the flange  24  and the top surface of the concrete structure C, thus assuring that the plate cannot inadvertently move. 
         [0047]      FIG. 10  shows the final step of removing the reusable portions of the anchor assembly (the bolt  12  and rod  20 ) from the bore B. As there shown, the bolt  12  has been unscrewed from the sleeve  10  and the bolt and rod have been removed from the bore, leaving the sleeve  10  and plug  16  in place. The bore may then be grouted over, if desired. 
         [0048]      FIGS. 1 and 10  illustrate both how the protrusions  40  extend into cutting engagement with the walls of the bore and resist pullout of the sleeve, relative to the bore. Such resistance is maximized by locating the protrusions  40  in planes which extend normal to the axis  42  and forming the protrusions so that the trailing surfaces  50  thereof also extend normal to that axis. 
       CONCLUSION  
       [0049]    From the foregoing description and accompanying drawings, it will be apparent that the present invention provides an improved and more secure drop-in anchor. In particular, it provides an anchor which penetrates and securely engages the walls of a bore within which it received, without the requirement of pre-formed undercuts, or the possibility that relative frictional movement of the anchor sleeve within the bore may fluidize the concrete at the surface of the bore.