Abstract:
A method for attaching an article to a hardened concrete body includes a tool that has a slotted base plate and a downwardly depending slotted guide cylinder having at the lower end thereof a circular end plate which has a central aperture, insertable into a bore hole to support a rotatably driven shaft disposed through the slot, guide cylinder, and central aperture through said end plate and having at its lower end a cutting head, the shaft being pushed downwardly into the bore and rocked back and forth in the slot, causing the cutting head to form an oval enlargement at the base of the bore hole. An anchor bolt fastener according to the invention is then inserted into the bore hole, the fastener including an elongated shank which has a central shaft bore slidably holding a shaft having at its lower end an expander wedge forcible upwards into a slot extending into a lower end face of the shank to thus expand bolt legs on opposite sides of the slot into the oval bore hole enlargement.

Description:
BACKGROUND OF THE INVENTION 
     A. Field of the Invention 
     The present invention relates to fasteners for anchoring objects to concrete bodies such as pediments and precast concrete walls. More particularly, the invention relates to a novel anchor bolt fastener for installation in precast and poured concrete structures, a novel tool and method for cutting a specially shaped hole in hardened concrete which is adapted to receive the novel fastener and a method for installing the fastener in the hole. 
     B. Description of Background Art 
     there are a wide variety of applications in which it is necessary to install a fastener in a concrete structure after the concrete has been poured and hardened. For example bolts or threaded studs protruding perpendicularly from a concrete pediment, base or wall are installed to support vertically disposed street light standards, power poles or the like, or horizontally disposed structures such as floor beams or posts. 
     Typical prior art fasteners used for installation in concrete bodies such as a pre-cast pediment or wall are expansion-type fasteners which-include an elongated tubular sleeve that has longitudinally disposed slots which extend upwardly from the lower annular end wall of the sleeve, the slots forming therebetween circumferentially spaced apart, longitudinally disposed legs. The shank of an inverted externally threaded stud or bolt which has a rounded head of larger diameter than a bore disposed longitudinally through the sleeve extends upwardly through the bore and protrudes outwardly from the upper annular end wall of the sleeve. The upper threaded end of the stud or bolt shank also protrudes through a circular washer and is threadably received in a hexagonal nut. 
     Expansion-type concrete anchor bolt fastener of the type described are installed in a concrete body by first boring perpendicularly into an outer face of the body a circular cross-section hole which has a diameter slightly greater than the head of the stud or bolt located at the lower end of the sleeve. The anchor bolt is inserted into the hole bored into the concrete body with the lower surface of a bearing washer seated on the outer flat surface of the concrete body. The hex nut is then tightened onto the threaded shank of the stud or bolt, thus drawing the head at the bottom of the bolt upwards. Upward tension exerted on the bolt shank causes the rounded bolt head to press upwardly against and enter the lower entrance opening of the sleeve bore, causing lower ends of longitudinally disposed legs of the sleeve to expand radially outward and thus exert radially outwardly directed frictional gripping forces on the inner circumferential wall surface of the concrete bore hole. When the hex nut on the upper end of the bolt shank is tightened sufficiently, a substantial frictional force is exerted on the concrete bore wall by the expanded sleeve legs. Thus, the sleeve and bolt are anchored against being withdrawn from the concrete bore hole by substantial frictional forces exerted by the outer surfaces of the sleeve legs on the concrete bore hole wall surface. 
     Although prior art expansion type concrete anchor bolt fasteners of the type described above are reasonably effective, the uniform diameter of a concrete bore hole in which the anchor bolt sleeve is installed does not have any abutting surfaces which positively resist tensional forces exerted on the upper end of the bolt that could pull the bolt upwards in the bore hole. Therefore, such prior art concrete anchor bolts can and sometimes do work free from their anchored location in a concrete support structure, and are therefor problematic. The present invention was motivated in part by the desire to provide a more securely retainable concrete anchor bolt fastener. 
     OBJECTS OF THE INVENTION 
     An object of the present invention is to provide improved concrete anchor bolt fasteners, and a tool and method for installing the improved fasteners in hardened concrete. 
     Another object of the invention is to provide a tool and method for forming at the base of a circular cross-section bore hole in a concrete body an enlarged lower base portion which has an oval cross-section adapted to receive expandable lower portions of the body of an elongated tubular fastener. 
     Another object of the invention is to provide a tool and method for forming at the base of an elongated circular cross-section bore hole in hardened concrete an enlarged generally oval-shaped cross-section lower base section which is adapted to receive outwardly expandable parts of a tubular fastener member. 
     Another object of the invention is to provide a tool and method for forming at the base of an elongated circular cross-section bore hole in hardened concrete at least a first radially outwardly disposed enlarged, oval portion of larger diameter than the upper circular cross-section portion of the bore hole, thus giving the bore in a medial vertical sectional view thereof the shape of a generally frusto-conically shaped base section which is truncated at an upper transverse end thereof by a coaxially aligned, elongated upwardly extending circular cross-section cylindrical bore hole section. 
     Another object of the invention is to provide a tool for forming in the base of an elongated circular cross-section bore hole in a hardened concrete body an oval cross-section enlargement having a major axis larger than the diameter of the circular cross-section bore hole, the tool including a flat fixture base plate for placement on a concrete body, the fixture base plate having through its thickness dimension a transversely disposed, generally rectangularly-shaped guide slot and a longitudinally disposed guide cylinder which protrudes perpendicularly downwardly from the bottom of the fixture base plate, the guide cylinder having front and rear wall sections adjacent to front and rear laterally disposed edges of the guide slot, the bottom end of the guide cylinder supporting a transversely disposed circular end plate having through its thickness dimension a central circular perforation coaxially aligned with the slot in the fixture base plate, and a rotary cutting tool having an elongated straight drive shaft which is disposed vertically through the slot and perforation, the cutting tool having at a lower end thereof a rotary cutting head, the drive shaft having a lower stop collar located above the cutting head, and an upper stop collar affixed to the drive shaft above the fixture base plate, the drive shaft being rotatable and longitudinally movable to thus enable the shaft to be pivoted between opposite ends of the slot, to thereby enable the shaft and rotary cutting head to be rotated, moved longitudinally downwards in said slot and said aperture, and rocked back and forth between lateral edges of the slot to thus form an oval enlargement of the base of the concrete bore hole, the oval enlargement having a major axis aligned with the axis of the slot. 
     Another object of the invention is to provide a tool and method for forming in hardened concrete at the base an elongated circular cross-section bore hole at least a first radially outwardly tapered, generally oval-shaped base enlargement of larger diameter than the upper circular cross-section portion of the bore hole, thus giving the bore hole in a medial vertical sectional view thereof the shape of a generally frusto-conically shaped base section which is truncated at an upper transverse end thereof by a coaxially aligned, upwardly extending elongated circular cross-section cylindrical section, and a fastener for installation in the bore hole, the fastener including an elongated tubular bolt which has disposed through its length a central longitudinally disposed coaxial shaft bore which communicates at the lower end thereof with a longitudinally disposed slot that penetrates the lower transverse end wall of the bolt and extends upwardly from the lower end wall, the slot forming on opposite sides thereof a pair of longitudinally downwardly disposed legs which are expandable into the enlarged oval base portion of the bore hole to anchor the fastener in the bore hole. 
     Another object of the invention is to provide a tool and method for forming in hardened concrete at the base an elongated circular cross-section bore hole at least a first outwardly tapered, oval base enlargement of larger diameter than an upper circular cross-section portion of the bore hole, thus giving the bore hole in a medial vertical sectional view thereof the shape of a generally frusto-conically shaped base section which is truncated at an upper transverse end thereof by a coaxially aligned, upwardly extending elongated circular cross-section cylindrical section, and a fastener for installation in the bore hole, the fastener including an elongated tubular bolt which has disposed through its length a longitudinally disposed central coaxial shaft bore which communicates at the lower end thereof with a longitudinally disposed, vertically elongated slot that penetrates the lower transverse end wall of the bolt and extends upwardly from a chamfered wedge shaped entrance opening in the lower end wall, the slot forming on opposite sides thereof a pair of longitudinally disposed, vertically elongated legs which are expandable into the enlarged oval base portion of the bore hole to anchor the fastener in the bore hole, the fastener including an expander member which has an elongated cylindrical shaft longitudinally movable within the central coaxial shaft bore of the bolt, the expander member having at the lower end of the shaft an enlarged flat sided wedge-shaped head that has a cross-sectional shape similar to that of the chamfered lower entrance opening of the slot, the fastener including forcing members adapted to forcibly wedge the wedge-shaped expander member head of the expander member into the entrance opening of the slot at the lower end of the bolt and thus expand the bolt legs into the oval space of the bore hole base. 
     Another object of the invention is to provide a tool and method for forming in hardened concrete at the base of an elongated circular cross-section bore hole at least a first outwardly tapered, oval base enlargement of larger diameter than the upper circular cross-section portion of the bore hole, thus giving the bore hole in a medial vertical sectional view thereof the shape of a generally frusto-conically shaped base section which is truncated at an upper transverse end thereof by a coaxially aligned, upwardly extending elongated circular cross-section cylindrical section, and a fastener for installation in the bore hole, the fastener including an elongated tubular bolt which has disposed through its length a coaxial shaft bore communicating at a lower end thereof with a longitudinally disposed slot that penetrates the lower transverse end wall of the bolt and extends upwardly from the lower end wall of the bolt, the slot forming on opposite sides thereof a pair of longitudinally downwardly disposed legs which are expandable into the enlarged oval base portion of the bore hole to anchor the fastener in the bore hole, the fastener including an expander member which has an elongated cylindrical shaft longitudinally movable within the shaft bore of the bolt, the expander member shaft having at the lower end thereof an enlarged flat sided wedge-shaped head that has a cross-sectional shape similar to that of a tapered lower entrance opening to the slot located in a base of the bolt, the fastener including forcing members adapted to forcibly wedge the wedge-shaped expander member head into the slot at the lower end of the bolt and thus expand the bolt legs into the oval enlargement of the bore hole base, the forcing members consisting of an impact bushing which is seated on an upper annular end wall of the bolt, and receives upwardly through a central hole in the bushing the upper end of the expander member shaft, and a cylindrical impact collar which has a central blind bore extending upwards from a lower surface thereof to receive the upwardly protruding expander member shaft, and an upper flat surface for receiving hammer blows to drive the bolt body downwards relative to the expander member shaft. 
     Another object of the invention is to provide a tool and method for forming in hardened concrete at the base of an elongated circular cross-section bore hole which has at a lower base end thereof at least a first outwardly tapered, oval base enlargement of larger diameter than the upper circular cross-section portion, thus giving the bore hole in a medial vertical sectional view thereof the shape of a generally frusto-conically shaped base section which is truncated at an upper transverse end thereof by a coaxially aligned, upwardly extending elongated circular cross-section cylindrical section, and a fastener for installation in the bore hole, the fastener including an elongated tubular bolt which has disposed through its length a coaxial shaft bore which communicates at a lower end thereof with a longitudinally disposed slot that penetrates the lower transverse end wall of the bolt and extends upwardly from the lower end wall of the bolt, the slot forming on opposite sides thereof longitudinally downwardly disposed legs which are expandable into the enlarged oval base portion of the bore hole to anchor the fastener in the bore hole, the fastener including an expander member which has an elongated cylindrical shaft longitudinally movable within the shaft bore of the bolt, the expander member shaft having at the lower end thereof an enlarged, wedge-shaped flat sided head having a cross-sectional shape similar to that of a tapered wedge-shaped lower entrance opening to the slot located in the lower end wall of the bolt, the fastener including forcing members adapted to pull the enlarged wedge-shaped head into the wedge-shaped opening of the slot and thus expand the bolt legs into the oval space of the bore hole base, the forcing members consisting of a bearing collar which is seated on the upper annular end wall of the bolt which receives through the center hole of the bearing collar the protruding externally threaded upper end of the shaft, and a nut threadably tightenable onto the threaded shaft to thus exert a downwardly compressive force on the upper surface of the bearing collar and hence an upwardly directed tensioning force on the shaft which forces the wedge-shaped expander member head to splay the bolt legs apart and into the oval base of the bore hole, thus securing the bolt and expander member from both rotation and longitudinal movement within the bore hole. 
     Various other objects and advantages of the present invention, and its most novel features, will become apparent to those skilled in the art by perusing the accompanying specification, drawings and claims. 
     It is to be understood that although the invention disclosed herein is fully capable of achieving the objects and providing the advantages described, the characteristics of the invention described herein are merely illustrative of the preferred embodiments. Accordingly, I do not intend that the scope of my exclusive rights and privileges in the invention be limited to details of the embodiments described. I do intend that equivalents, adaptations and modifications of the invention reasonably inferable from the description contained herein be included within the scope of the invention as defined by the appended claims. 
     SUMMARY OF THE INVENTION 
     Briefly stated, the present invention comprehends a novel concrete anchor bolt fastener for anchoring objects to hardened concrete bodies and structures such as pediments or bases for supporting electrical power transmission or lighting pole standards, pre-cast concrete walls and floors and the like, and a novel tool and method for installing the fasteners Preferred embodiments of the novel fasteners according to the present invention may be used as replacements for prior art concrete bolt anchors and thus include an externally threaded bolt shank or stud which protrudes perpendicularly from a concrete structure in which the novel fastener is installed. Objects such as standards of power poles or street lamps which are to be fastened to the concrete structure are thus fastenable by conventional means as for example by receiving the protruding threaded shanks of four fasteners arranged in a square through holes of a power pole base plate and securing the base plate in place by installing nuts on the threaded shanks and tightening the nuts down against the outer surface of the base plate. 
     According to one aspect of the invention, a hole is bored perpendicularly into a hardened concrete body, the hole having an elongated upper section which has a conventional uniform circular cross-section. Then, according to the invention, a conventional uniform circular cross-section bore hole for receiving an anchor bolt is modified by forming at the bottom end of the cylindrically-shaped anchor bolt bore hole an elongated, generally, oval-shaped base enlargement or extension which has a minor axis of approximately the same length as the diameter of the circular upper part of the bore hole, and a major axis of greater length than the diameter of the circular upper part of the bore hole. Preferably, the elongated enlarged diameter oval part of the bore hole base extension lies symmetrically on a diameter of the circular upper part of the bore hole, and extends equal distances radially outwards of opposite diametrically opposed sides of the upper circular portion of the bore hole. Within this construction, the modified anchor bolt bore hole according to the present invention has in a vertical medial sectional view a shape approximating that of the frustum of a cone which is terminated at an upper transverse end thereof by a coaxially aligned, perpendicularly upstanding circular cylinder which has the same diameter as the upper diameter of the truncated cone. 
     According to another aspect of the invention, a tool for forming the novel tapered anchor bolt bore hole described above is provided. 
     A tool according to the invention for forming the base of a cylindrically-shaped concrete anchor bolt fastener bore hole in a concrete body includes a jig or fixture for placement on the surface of a concrete body in which a conventionally shaped uniform circular cross-section bore hole has previously been made. The fixture for making an enlarged oval base in a bore hole according to the present invention includes a flat metal base plate. The base plate has protruding perpendicularly downwardly from the center thereof a tubular circular cross-section guide cylinder which has an outer diameter equal to that of a previously formed bore hole, and a pre-determined length slightly less than the depth of the bore hole, so that the guide cylinder can be inserted into the bore hole with the lower surface of the base plate seated on the outer surface of the concrete body in which the bore hole is formed. The guide cylinder has at the lower end thereof a circular end plate which has through its thickness dimension a coaxially centered circular clearance hole for receiving the rotating shaft of a rotary cutting tool, the inner circumferential wall of the circular clearance hole forming a fulcrum or pivot surface for the rotating shaft. 
     The base plate of the fixture for modifying a cylindrical bore hole to have a radially outwardly tapered lower end portion having an oval cross-section, enlarged diameter base includes a rectangular perforation or slot through the base plate, which is centered between and disposed perpendicularly to front and rear long edges of the base plate. The slot has the same width as the diameter of the tool shaft guide hole through the bottom end plate of the guide tube cylinder, and has a length slightly larger than the diameter of the concrete bore hole. 
     The guide cylinder has through front and rear wall surfaces thereof longitudinally disposed vertical slots which are vertically aligned with front and rear sides of the base plate slot, but are of slightly greater width. The front and rear longitudinally disposed vertical guide cylinder slots extend from the upper surface of the bottom end cap of the guide cylinder, and through the upper annular end wall of the guide cylinder, to the lower surface of the fixture base plate. 
     The tapered anchor bore hole forming tool according to the present invention includes a cutting tool which has a rotary cutting head and an elongated drive shaft which extends perpendicularly upwards form the center of the cutting head. The cutting head is located below the bottom circular end plate of the fixture guide cylinder, at the lower end of the drive shaft, which extends upwardly through the circular guide hole through the circular end plate, and upwardly through the rectangular guide slot through the fixture base plate. That portion of the cutting tool drive shaft which protrudes above the fixture base plate has attached to it outer circumferential wall an upper stop collar of larger outer diameter than the width of the slot through the fixture base plate. Contact of the lower surface of the upper stop collar with the upper surface of the fixture base plate limits downward motion of the tool drive shaft and hence the depth of a modified bore hole which may be made using the fixture and rotary power source turning the drive shaft of the cutting tool. Preferably, the cutting tool drive shaft also has a lower collar on the upper surface of the cutting head to limit upward movement of the cutting head so that it does not contact the guide cylinder. 
     The base plate of the fixture according to the present invention preferably has at least one and most preferably two indexing guides spaced apart from the center of the base plate. The purpose of the indexing guides is to enable the base plate to be oriented and secured to concrete surfaces in a known direction, so that the orientation of the major axis of an oval enlargement of a bore hole made using the tool can be readily determined. 
     The bore enlarging tool according to the present invention is used by retracting the rotary cutting tool shaft fully upwards until the cutting head abuts the lower surface of the fixture guide cylinder bottom end plate. The guide cylinder and cutting tool are then inserted as a unit into a previously formed, cylindrical bore hole. Rotary drive power is then applied to the upper end of the cutting tool drive shaft, by an electric power drill, for example. The shaft is then pushed downwardly with the shaft angled so that it presses against a front or rear edge of the rectangular guide slot in the base plate of the fixture, clearance for that part of the cutting tool drive shaft below the base plate being provided by the front and rear vertical guide cylinder slots. Downward boring motion is continued until the stop collar limits further downward movement of the cutter head. As a result of the foregoing actions, a radially outwardly tapered, oval enlargement is formed at the base of the originally formed, uniform circular cross-section bore hole. The enlargement has an oval shape, the major axis of which is aligned with the rectangular slot through the base plate of the fixture. The drive shaft and cutting tool are then retracted from the hole to their upward movement limits, the drive shaft is then angled to impact the opposite, e.g., rear edge of the guide plate, and the downward boring step repeated, thus forming an oval bore enlargement which extends equal radial distances from the bore center line. 
     According to the present invention, two related embodiments of a novel fastener are provided for installation in a concrete anchor bolt bore hole modified by the method and tool described above. One embodiment of a novel fastener according the present invention includes an elongated tubular bolt which has at the lower end thereof a longitudinally disposed slot that penetrates the lower end wall of the bolt and extends upwardly from the lower end wall of the bolt, the slot forming on opposite sides therein longitudinally a pair of downwardly disposed legs which are expandable into the enlarged oval base portion of the bore hole to anchor the fastener in the bore hole, the fastener including within the bore of the bolt an expander member including an elongated cylindrical shaft which has at the lower end thereof an enlarged flat sided wedge-shaped head which has a cross-sectional shape similar to that of the tapered lower base portion of the bore hole, the fastener including forcing members adapted to force the wedge-shaped head into the slot of the bolt and thus expand the bolt legs into the oval space of the bore hole base, the forcing members consisting of an impact bushing which is seated on an upper annular end wall of the sleeve, and receives upwardly through a central hole in the bushing the upper end of the expander member shaft, and a cylindrical impact collar which has a central blind bore extending upwards from a lower surface thereof to receive the upwardly protruding shaft, and an upper flat surface for receiving hammer blows to drive the sleeve body downwards relative to the expander member shaft. 
     A second embodiment of a novel fastener according to the present invention includes an elongated tubular bolt which has at the lower end thereof a longitudinally disposed slot which penetrates the lower end wall of the bolt wall and extends upwardly from the lower end wall of the bolt, the slot forming on opposite sides thereof a pair of longitudinally downwardly disposed legs which are expandable into the enlarged oval base portion of the bore hole to anchor the fastener in the bore hole, the fastener including within the bore of the bolt an expander member including an elongated cylindrical shaft which has at the lower end thereof an enlarged, wedge-shaped flat sided head having a cross-sectional shape similar to that of the tapered lower base portion of the bore hole, the fastener including forcing members adapted to force the enlarged wedge-shaped head into the slot of the bolt and thus expand the bolt legs into the oval space of the bore hole base, the forcing members including a milled polygonal cross-section bearing collar head fixed to the upper annular end wall of the bolt which receives through a center hole of the collar head the protruding externally threaded upper end of the shaft, and a nut threadably tightenable onto the threaded shaft to thus exert a downwardly compressive force on the upper surface of the bearing collar, and hence an upwardly directed tensioning force on the shaft. Preferably, the bearing collar head is a milled, integral part of the fastener bolt body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a prior art expansion-type concrete bolt fastener. 
         FIG. 2  is a view similar to  FIG. 1 , but showing the bolt tensioned to radially expand lower leg segments of the fastener sleeve. 
         FIG. 3  is a sectional view showing a hole being bored in a concrete structure for receiving the fastener of  FIG. 1 . 
         FIG. 4  is a sectional view showing the fastener of  FIG. 1  inserted into a bore hole formed as shown in  FIG. 3 . 
         FIG. 5  is a sectional view showing a nut of the fastener of  FIG. 4  tightened onto the protruding threaded shank of an anchor bolt of the fastener to radially expand lower leg segments of the fastener sleeve into anchoring contact with the inner circumferential wall surface of the bore hole. 
         FIG. 6  is a perspective view of an impact installable concrete anchor bolt fastener according to the present invention, showing an impact anvil collar tool useable to install the fastener. 
         FIG. 6A  is a fragmentary vertical medial sectional view of the fastener of  FIG. 6 . 
         FIG. 7  is a view similar to  FIG. 6 , but showing a tubular bolt part of the fastener driven downwardly on a central expander shaft of the fastener and showing a nut tightened on the threaded shank of the expander shaft which protrudes upwardly through the impact bushing of the fastener. 
         FIG. 8  is an upper plan view of the fastener of  FIG. 7 . 
         FIG. 9  is a lower plan view of the fasten er of  FIG. 7 . 
         FIG. 10A  is a perspective view of a novel concrete bore hole enlargement tool for use with the fastener of  FIGS. 6-9 . 
         FIG. 10B  is a transverse sectional view of the tool of  FIG. 10A , taken in the direction of line  10 B- 10 B. 
         FIG. 10C  is a transverse sectional view of a first modification of the tool of  FIG. 10B . 
         FIG. 10D  is a transverse section view of a second modification of the tool of  FIG. 10B . 
         FIG. 11  is a perspective view of a carbide drill bit for use with the hole forming tool of  FIG. 10A . 
         FIG. 12  is an upper plan view of the tool of  FIG. 10A . 
         FIG. 13  is a vertical medial sectional view of the tool of  FIG. 12 , taken in the direction of the line  13 - 13 . 
         FIG. 14  is another vertical medial sectional view of the tool of  FIG. 12 , taken in the direction of the line  14 - 14 . 
         FIG. 15  is a vertical medial sectional view of the tool of  FIGS. 12 and 13 , showing the tool positioned above a straight, uniform circular cross-section bore hole formed in a concrete structure. 
         FIG. 16  is a view similar to  FIG. 15 , showing the tool installed in the bore hole. 
         FIG. 17  is a view similar to  FIG. 16 , showing a base plate of the tool being used as a template to drill a first tool positioning hole in a concrete structure. 
         FIG. 18  is a view similar to  FIG. 17 , showing the base plate orbited 180° and a securing pin inserted into the pre-drilled hole. 
         FIG. 19  is a perspective view showing a guide slot of the base plate template of the tool of  FIG. 12  being used to guide the shaft of a rotary cutting wheel in forming a leftward angled expansion of the lower base end of a cylindrical bore hole made in a concrete structure. 
         FIG. 20  is a view similar to  FIG. 19 , showing the tool used to guide formation of a rightward angled expansion of the lower end of the bore. 
         FIG. 21  is a sectional view similar to  FIG. 19  but showing the shaft of the cutting wheel tool extended downwardly to its lower collar-limited depth to finish formation of the tapered bore expansion of the lower end of the bore hole. 
         FIG. 22  is a sectional view showing the fastener of  FIGS. 6 and 7  positioned above the tapered bore hole formed as shown in  FIG. 21 , preparatory to installing the fastener in the tapered bore hole. 
         FIG. 23  is a view similar to  FIG. 22 , but showing the fastener inserted into the tapered bore hole and an impact anvil collar positioned at the upper end of the fastener preparatory to striking the upper end face of the impact anvil collar to thus drive the fastener bolt downwards relative to a central expander shaft and wedge of the fastener bolt. 
         FIG. 24  is a lower horizontal sectional view of the arrangement of  FIG. 23 . 
         FIG. 25  is a view similar to  FIG. 23 , but showing the bolt of the fastener having been driven by impact to the bottom of the tapered bore hole, and the base plate of an object fastened to the bolt. 
         FIG. 26  is a lower horizontal sectional view of the arrangement of  FIG. 25 , showing the expanded legs of the tubular fastener bolt. 
         FIG. 27  is a perspective view of an alternate embodiment of the fastener of  FIG. 6 , which is expanded by torque. 
         FIG. 28  is a view similar to  FIG. 27 , showing a lower slotted end of the fastener fully expanded. 
         FIG. 29  is an upper plan view of the arrangement of  FIG. 28 . 
         FIG. 30  is a lower plan view of the arrangement of  FIG. 28 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIGS. 1-5  illustrate the construction and function of an expansion type prior art concrete anchor bolt fastener. 
       FIGS. 6-30  illustrate to construction and function of a novel concrete anchor bolt fastener, and a novel tool and method for installing the fastener according to the present invention. 
       FIG. 1  shows a prior art expansion-type concrete anchor bolt fastener A that includes an elongated thin-wall tubular metal sleeve B which has a circular cross-section. Sleeve B has extending longitudinally upwards from the lower transverse annular end wall C thereof a plurality of circumferentially spaced apart slots D which form therebetween longitudinally downwardly disposed legs E. The slots have widened upper ends F, thus narrowing the upper portions G of the legs. A stud or bolt H which has an externally threaded shank I is insertably received into the lower opening J of a longitudinally disposed bore K through sleeve B. Bolt H has a rounded doughnut-shaped head L which has a larger diameter than bore K, and thus limits upward motion of shank I in bore K of sleeve B. Fastener A includes a flat annular ring-shaped bearing washer M of larger outer diameter than sleeve B, which is seated on the upper transverse annular end wall of the sleeve, and a hex nut O which is seated on the upper surface of the bearing washer and is threadably tightenable on the upwardly protruding shank I of bolt H. As shown in  FIGS. 1 and 2 , fastener A may have friction enhancing rectangular bosses P which protrude outwardly from the outer wall surfaces Q of legs E. 
       FIGS. 3-5  show how prior art concrete anchor bolt fastener A is installed in a concrete body R, such as a pediment or base for the standard of a street light, sign, electrical power distribution pole, telephone pole or the like. As shown in  FIG. 3 , a bore hole T is bored perpendicularly inwards from the surface S of concrete body T into the body to a depth slightly greater than the length of fastener sleeve B. Bore hole T has a uniform diameter slightly larger than the outer diameter of sleeve B, and is formed using a suitable drill bit U powered by a rotary power tool V such as an electric drill. 
     Next, as shown in  FIG. 4 , a prior art fastener A is inserted into bore hole T, the lower surface of a bearing washer M seating on surface S of concrete body R. Finally, as shown in  FIG. 5 , hex nut O is tightened on shank I of bolt H. As may be understood by referring to  FIG. 2  in addition to  FIG. 5 , tightening nut O on shank I of bolt H draws doughnut-shaped enlarged head L of bolt H upwardly into compressive contact with lower entrance opening J of bore K through the sleeve, thus causing head L to enter bore K and force sleeve legs E radially outwards into frictionally gripping contact with the inner circumferential wall surface W of bore hole T, thus retaining the fastener frictionally within the bore hole. 
       FIGS. 6-9  illustrate a basic impact-type embodiment of a novel concrete anchor bolt fastener according to the present invention, which is described immediately below, while  FIGS. 26-29  illustrate a torque-type embodiment of the invention, which is described further below. 
     As shown in  FIG. 6 , an impact-type embodiment  50  of a novel concrete anchor bolt fastener according to the present invention includes a longitudinally elongated tubular metal body  51 , which preferably is fabricated from the shank of a steel bolt. Body  51  has a lower expandable slotted section  52  which has smooth or preferably ridged outer walls  53 . As shown in  FIGS. 6 and 9 , lower slotted section  52  of fastener body  51  has a uniform diameter circular cross-section and a uniform diameter, circular bore  54  which extends through the entire length of the body. As shown in  FIG. 6 , body  51  of fastener  50  has an upper externally helically threaded section  55  which is axially aligned with lower section  52 . Upper threaded section  55  of body  51  is a coaxially aligned extension of lower section  51 , and has an upper transverse annular end wall  56  which is coextensive with upper end wall of body  51 . 
     As shown in  FIGS. 6 and 9 , lower expandable slotted section  52  of fastener  50  has at least one pair of vertically elongated, rectangularly-shaped slots  57 A,  57 B which penetrate the cylindrical wall  58  of fastener body  51  at diametrically opposed locations, e.g., front and rear or left and right sides of the wall. As shown in  FIG. 6 , slots  57 A,  57 B penetrate and extend perpendicularly upwards from the lower transverse annular end wall  59  of body  51 , and form therebetween outwardly convex, arcuately curved longitudinally disposed diametrically opposed legs,  60 A,  60 B, e.g., left and right or front and rear legs. Preferably, legs  60 A,  60 B have on outer surfaces thereof a series of longitudinally spaced apart ring-shaped gripping ridges  58 A. 
     Referring to  FIGS. 6 ,  8  and  9 , it may be seen that impact-type concrete anchor bolt fastener  50  includes a longitudinally disposed expander member  61  which extends axially through bore  54  of fastener body  51 . As shown in the figures, expander member  61  includes an elongated cylindrical shaft  62  which has an upper section  63  that has external helical threads. As shown in  FIGS. 6 and 8 , the externally threaded upper section  63  of expander member shaft  62  is received through a central clearance hole  64  of a circular ring-shaped flat washer or bushing  65  which seats on upper transverse end wall  56  of fastener body  51 . Alternately and preferably, ring-shaped flat washer  65  is replaced by a similarly-shaped, milled upper end portion of body  51 . 
     Referring to  FIGS. 6 ,  6 A,  7  and  9 , it may be seen that expander member  61  has located at the lower end thereof an axially centered expander head  66 . As shown in the lower end view of  FIG. 9 , expander head  66  has the shape of a prism having flat and parallel front and rear surfaces  67 ,  68 , which are spaced equidistant from the axis of expander member shaft  62 . As shown in  FIG. 6 , expander head  66  has in front elevation view the shape of a regular trapezoidal body, including a flat, rectangularly-shaped horizontally disposed long lower base  69 , left and right sides  70 ,  71 , which are of equal length and angle upwardly and inwardly at equal angles from the base, and a rectangular horizontally disposed short upper base  72  which conformally joins the lower end of expander member shaft  62 . 
     As may be envisioned by referring to  FIGS. 6 and 7 , if the base  69  of expander head  66  is fixed against downward vertical movement, as for example by resting on the bottom of a concrete bore hole, as shown in  FIG. 23 , driving body  51  of fastener  50  downwards relative to expander member shaft  62  and expander head  66  causes the sloping, wedge-shaped sides  70 ,  72  of the expander head to forcibly enter slots  57 A and  57 B at the lower entrance opening  78  of bore  56  disposed coaxially through fastener body  51 . Wedging entry of expander head  66  into bore  54  of body  51  in turn forces left and right legs  60 A,  60 B to splay outwards, as shown in  FIG. 7 . 
       FIG. 6  illustrates an impact collar  79  which may be used to facilitate driving fastener body downwards relative to expander member head  66  to splay legs  60 A,  60 B outwards as shown in  FIG. 7 . As shown in  FIG. 6 , impact collar  79  consists essentially of a cylindrical body  80  which is made of a durable, impact resistant material such as steel. Body  80  has extending longitudinally inwards from lower face  81  thereof a coaxially located blind smooth bore  82  of somewhat larger diameter than upper externally threaded section  63  of expander member shaft  62 . 
     As shown in  FIG. 6 , impact collar  79  is used by placing lower annular face  81  of the collar on the upper face  83  of impact washer  65 , with the upper threaded end  63  of expander member shaft  62  received in blind bore  82  of the impact collar. The upper flat surface  84  of impact collar  79  is then struck with a hammer to drive body  51  of fastener  50  downwards relative to expander member shaft  62  and expander head  66 , thus causing the expander head to spread legs  60 A,  60 B outwardly apart, as shown in  FIG. 7 . Impact washer  65  may then be removed, or optionally, as shown in  FIG. 7 , secured in place by tightening a hex nut  85  onto threaded section  63  of the expander member shaft. 
     In a preferred embodiment, in which washer  65  is a milled part of fastener body  52 , the expander head  66  is secured in place by tightening a hex nut  85  and a lock washer  85 A onto threaded section  63  of the expander member shaft  62  thus fixing the location of expander head  66 , and fixing the expanded legs  60 A and  60 B in place so that they cannot return to their original configuration. 
     As shown in  FIGS. 6 and 7 , tubular bolt  50  preferably is provided with a hexagonal main ring nut  86  which is threaded onto the externally threaded upper section  55  of body  51 , the lower surface of the ring nut  86  abutting the upper surface  150  of an object  140  to be secured on the upper surface  120  of a concrete body  119 , as shown in  FIG. 25 . At this point by tightening nut  86  compressive forces are placed on the top surface of legs  60 A and  60 B against the top surface of the tapered elongated oval formed hole. The legs  60 A and  60 B are prevented from returning to their original position due to hexagonal nut  85 . As nut  86  is tightened, the body  51  of fastener  50  tends to retract itself from the bored hole. This is prevented due to the fact that the wedge  66  is secured in place by expansion member shaft  62  and nut  85 , thus creating a united fastener that would have to retract in its entirety from the hole. This is not possible due to the fact that the lower portion of the united fastener is bigger than the diameter of the hole. 
     Preferably, as shown in  FIGS. 6 and 8 , the upper face  83  of milled section  65  of body  51  has marked or engraved thereon centered index lines  90 A and  90 B of which are parallel and directly in line above slots  57 A and  57 B. Wedge  66  is manufactured and installed in place along top flat portion of wedge inserted in slots  57 A and  57 B. When fastener  50  is inserted into bore hole, the index lines  90 A and  90 B signify that the legs  60 A and  60 B are oriented to expand left to right in the elongated oval formed hole. 
       FIGS. 10A-14  illustrate a novel tool  91  according to the present invention for forming an oval elongated enlargement in the base section of a concrete bore hole. As shown in  FIGS. 10A and 11 , tool  91  includes a rotary cutting tool  94  adapted to cutting concrete, the tool having an elongated straight cylindrically-shaped steel shaft  93  that has at the lower end thereof a transversely disposed cutting head  94  centered on the shaft. As shown in  FIG. 10A , cutting head  94  has the shape of a circular cutting wheel. Alternatively, as shown in  FIG. 11 , a carbide drill bit  95  may be fitted to the shaft  93 . As shown in  FIG. 10A , shaft  93  has attached coaxially to the outer circumferential surface  96  thereof an upper stop collar  97  which, as will be explained below, limits the downward vertical travel of the cutting tool  92  to a pre-determined depth, and a lower stop collar  97 A to limit upward vertical travel of cutting tool  94 . 
     Concrete bore hole shaping tool  91  according to the present invention also includes a jig or fixture component  101  which functions as a guide for positioning rotary cutting tool in the formation of an elongated, generally oval-shaped enlargement at the base section of a concrete bore hole. As shown in  FIGS. 10 ,  12  and  13 , cutting tool guide fixture  101  includes a flat, laterally elongated generally rectangular-shaped metal base plate  102  which preferably has rounded, arcuately curved left and right sides  103 ,  104 . Base plate  102  has a flat and parallel upper and lower surfaces  105 ,  106 , and straight and parallel front and rear edges  107 ,  108 . 
     As shown in  FIGS. 10A and 12 , base plate  102  of fixture  101  has cut through its thickness dimension a rectangularly-shaped cutting tool shaft guide slot  109  which lies along a fore-and-aft center line of the base plate which is located equidistant between left and right edges  103 ,  104  of the base plate. As shown in  FIG. 12 , guide slot  109  has straight and parallel left and right long edges  110 ,  111  which are disposed in a fore-and-aft direction, perpendicularly to front and rear edges  107 ,  108  of the base plate. As shown in  FIG. 12 , cutting tool guide slot  109  has front and rear inwardly concave, arcuately curved or radiused front and rear transversely disposed edges  112 ,  113  which are located equal distances from front and rear edges  107 ,  108 , respectively, of base plate  102 . As shown in  FIG. 14 , the spacing between front and rear guide slot edges  112 ,  113  is slightly larger than the diameter of guide cylinder  114  and bore hole into which it is to be inserted. 
     As shown in  FIG. 10A , cutting tool shaft guide slot  109  has a width equal to the diameter of rotary cutting tool shaft  93 , and a length which enables substantial fore-and-aft movement of the shaft within the guide slot. 
     As shown in  FIGS. 10A ,  10 B and  13 , fixture  101  of bore hole shaping tool  91  according to the present invention includes a tubular cutting tool shaft guide cylinder  114  which is vertically aligned with the center of guide slot  109  and extends perpendicularly downwards from the lower surface  106  of base plate  102 . As shown in  FIGS. 10A and 10B , cutting tool shaft guide cylinder  114  has disposed longitudinally therethrough a circular cross-section bore  115  that has a diameter equal to the long, fore-and-aft length dimension of guide slot  109 . Also, guide cylinder  114  has at the lower end thereof a circular bottom end plate  116  which has through its thickness dimension a coaxially centered circular clearance hole  117  of the same diameter as that of rotary cutting tool shaft  93 , enabling the shaft to freely rotate and move up and down within the clearance hole. 
     As shown in  FIG. 16 , guide cylinder  114  has a diameter equal to that of a bore hole  118  which extends perpendicularly inwards from the surface  120  of a concrete body  119  into the body, and a length less than the depth of the bore hole, so that the guide cylinder  114  may be easily inserted into the bore hole, with the lower surface  106  of the base plate  102  of fixture  101  resting on the upper surface  120  of the concrete structure. 
     Optionally, as shown in  FIG. 10C , the semi-cylindrical walls  114 A,  114 B of guide cylinder  114  may be replaced by a pair of vertically elongated, rectangular plates  114 L,  114 R, or, as shown in  FIG. 10D , by semi-cylindrically-shaped plates  114 LC,  114 RC. Plates  114 L,  114 R,  114 LC,  144 RC preferably are sufficiently wide for outer longitudinal edges thereof to contact the inner wall surface of a bore hole into which guide cylinder  144  is to be inserted, thus constraining the guide cylinder to be coaxially aligned with the bore hole. 
     Referring again to  FIGS. 10A and 10B , it may be seen that guide cylinder  114  has a pair of longitudinally disposed, vertically oriented rectangular front and rear cutting tool shaft clearance slots  121 ,  122  which penetrate the cylindrical wall  123  of the guide cylinder. The slots  121 ,  122  extend from the upper surface  123  of bottom end plate  116  to the open upper end  124  of guide cylinder  114 . Front and rear clearance slots  121 ,  122  are vertically aligned with front and rear edges  112 ,  113  of fore-and-aft guide slot  109  in base plate  102 , but are slightly wider. 
     Referring to  FIGS. 10A ,  12 ,  13  and  14 , it may be seen that base plate  102  of cutting tool guide fixture  101  has through its thickness an indexing hole  125  and a setting pin hole  124  for aligning the fixture at a particular orientation on the surface of concrete body in which a conventually shaped straight cylindrical bore hole has been previously formed. As shown in  FIG. 12 , indexing hole  125  and setting pin hole  124  lie on a laterally disposed line centered between front and rear edges  107 ,  108  of base plate  102 , and are laterally spaced equidistant from the center of the base plate. As shown in  FIGS. 12 and 13 , tool guide fixture  101  is optionally provided with one or more ferrules  126  which are insertable into indexing hole  125 . The function of indexing hole  125  and setting pin hole  124  are described below. 
       FIGS. 15-21  illustrate how concrete bore hole shaping-tool  91  according to the present invention is used. First, as shown in  FIG. 15 , tool  91  is positioned above a concrete body  120  which has extending perpendicularly into an outer surface  119  thereof an elongated, cylindrically-shaped, uniform circular cross-section bore hole  118  which has been previously bored to a pre-determined depth by conventional means. Next, as shown in  FIGS. 15  and  16 , cutting tool guide cylinder  114  is inserted downwardly into the bore hole  118  until the lower surface  106  of the tool base plate  102  rests on the upper surface  120  of concrete body  119 . Then, as shown in  FIG. 17 , a first shallow fixture pinning hole  121  is bored into the surface  120  of concrete body  119  by inserting the rotating drill bit  130  of an electric drill  129  perpendicularly downwards into one of the two indexing holes in base plate  102 , e.g., right-hand indexing hole  125 . Then, base plate  102  is turned 180 degrees and pin  127  is then inserted through indexing hole  125  to retain base plate  102  in place on the surface  102  of concrete body  120 , and secure base plate  102  from rotating. Base plate  102  is secured against rotation by physically pressing down on surface  105  of tool  91  either with a user&#39;s hand or foot, or mechanically fastening the plate by hole  125  and through-pin  126 . 
     Cutting tool shaft  92  is first pulled up so that collar  97 A rests on the bottom surface of circular plate  116 . While holding shaft  92  in a raised position while the shaft  92  is rotating, the shaft is first gently rocked to the forward section of slot  109  beginning to bore a tapered hole at just under the location of circular plate  116 , while still rotating, the shaft  92  and cutting end  94  are gently moved slowly downward in the direction of the pivoted shaft  92  allowing for cutting end  94  to cut a tapered hole until it is restricted from going any further into hole  118  by collar  97 . At this point one half of an elongated oval enlargement of the base of the concrete bore hole has been formed. 
     Now, once again, shaft  92  is pulled up so that collar  97 A rests on the bottom surface of circular plate  116 . Then, once again, while holding shaft  92  in a raised position and shaft  92  is rotating, the shaft is first gently rocked to the back section of slot  109 , thus beginning the boring of a tapered hole just under the location of circular plate  116 . While still rotating, the shaft  92  and cutting end  94  are gently moved slowly downward in the direction of the pivoted shaft  92  allowing cutting end  94  to cut a tapered hole until it is restricted from going any further into hole  118  by collar  97 . At this point, a complete generally oval-shaped elongated section of the hole along the major “X:” axis has been formed symmetrically with respect to the center line of the concrete bore hole. 
     The combination of fore-and-aft and vertically downward motions of rotary cutting head  94  forms at the lower end of base wall  134  of cylindrical bore hole  118  a radially outwardly tapered generally oval cross-sectional base enlargement  135  or bore  118 , along the “X” axis, as shown in  FIGS. 21 and 25 . As shown in  FIG. 21 , base enlargement  135  has in vertical medial sectional view the approximate shape of a frustum of a cone, which has radially inwardly tapered side walls  136 ,  137  that angle inward from the base  138  of the cone to terminate at the upper ends thereof in the straight vertical wall of the originally formed cylindrical bore hole. As shown in  FIG. 21 , the base  138  has an upwardly concave surface which has a depth measured from the surface  120  of concrete  119  that is limited by stop collar  92  on the shaft  93  or rotary tool  91 . Also, as previously mentioned and shown in  FIG. 25 , the base  137  of base enlargement  134  has a generally oval rather than a circular transverse cross-sectional shape. 
     The generally oval shape of the elongated concrete bore hole enlargement has the following advantage. When nut  86  is tightened, rotational forces are exerted along interior surface of the elongated bore hole enlargement. Due to the generally oval shape of bore hole enlargement, the fastener can not rotate within that enlargement. 
     For explanation purposes only, if it were desired to drill a full bell-shaped, enlargement at the bottom of a concrete bore hole, the tool could be rotated 90 degrees and the steps above repeated, thus elongating the bottom of the hole along the “Y” axis. 
       FIG. 25  illustrates how a perforated base plate of an object such as a lamp standard  140  is attached to the protruding externally threaded shank  55  of fastener  50 , using a hexagonal nut  86 . 
       FIGS. 27-30  illustrate an alternate embodiment  150  of a concrete anchor bolt fastener which is a modification of the impact installable fastener  50  shown in  FIGS. 6-9  and described above. Modified concrete anchor bolt fastener  150  is similar to impact installable fastener  50 , but is installed by exerting torque on fastener components, rather than exerting impact forces. Thus, as shown in  FIG. 28 , fastener  150  has an expander head  166  which is tensioned upwardly to thus wedge outwardly against and thus deform outwardly bolt legs  160 A,  160 B. This tensioning is effected by using a wrench to tighten a hex nut  185  downwardly onto the upper surface of a milled polygonal cross-section bearing collar head  165  located at the upper end of fastener  150  and thus onto the upper annular end wall  156  of an upper externally threaded section  155  of fastener body  151 . This tightening action in turn exerts an upward tensional force directed on the threaded upper end  163  of expander shaft  162 , thus drawing expander head  166  upwardly into bore  154  of the fastener bolt and thereby causing the expander head to wedge legs  160 A,  160 B radially outwards, as shown in  FIG. 22 . 
     As shown in  FIG. 28 , upper integral milled bearing collar head  165  of fastener  50  is, in embodiment  150 , modified to have a hexagonal external cross-section, which may be engaged by a wrench W2 while torque is applied to nut  185  by a wrench W1, as shown in  FIG. 27 . Wrench W2 is used to keep bearing collar head  165  irrotatably fixed with respect to the bore hole, thus preventing the tubular body of fastener bolt  150  from rotating in the bore hole and thereby preventing misalignment of expander head  166  and legs  160 A,  160  B with the oval enlargement of the base of the bore hole.