Anchor bolt

An anchor bolt is provided which includes a head, a drill portion, and an intermediate shank portion. The intermediate shank portion has a longitudinal cavity formed therein for receiving a mounting set screw. An external thread is formed on the shank portion for threading the anchor bolt into the wall. The shank portion is divided by a slit into at least one portion and the external thread on the shank portion is divided into a plurality of discrete thread segments by the slit. The drill portion has a cutting edge and at least one flute formed therein which also extends to a drill tip and to a sharpened point. The anchor bolt is driven into the wall portion with a screwdriver, and then a mounting set screw is inserted into the longitudinal cavity. When the mounting set screw is inserted into the cavity, the set screw causes a portion of the shank portion to separate from the shank portion to engage with the wall.

FIELD OF THE INVENTION
 The present invention relates generally to self-drilling threaded inserts.
 More particularly, it pertains to a threaded insert structure which when
 installed into a wall is adapted to receive a threaded fastener therein,
 where the threaded insert structure provides an anchor in drywall or
 sheetrock.
 BACKGROUND OF THE INVENTION
 When objects or fixtures are to be mounted on a wall, the installer
 searches for a stud into which a screw or nail can be inserted. However, a
 stud is not always available or in a convenient place. Where an object is
 to be mounted in hollow wall construction such as plasterboard, sheetrock,
 fiberboard or any other material employed in hollow wall construction, the
 common practice is to use a hollow anchor for this purpose. The
 conventional hollow anchor is formed of metal such as zinc or of plastic
 such as PVC, which when hammered into a hole pre-drilled into the wall, is
 then adapted to receive a threaded fastener or mounting screw that goes
 through the mounting hole in the object and turns into the hollow of the
 anchor.
 The installation of a conventional anchor entails three distinct
 operations: 1) drilling a hole, 2) hammering the anchor into the hole, and
 3) inserting a threaded fastener into the anchor. The first and most
 critical step is the drilling of a hole in the wall which must be
 appropriate to that of the anchor. Should an oversize hole be drilled,
 then in the next step when the anchor is hammered into the hole, the
 anchor will not wedge firmly therein. As a consequence, it will not be
 possible to carry out the third step. In the third step, a threaded
 fastener is inserted into the hollow portion of the anchor. But if the
 anchor is loose in the wall hole, this will cause the anchor to turn as
 the fastener is turned, and the fastener will not be able to thread its
 way into the anchor.
 The installation of a convention hollow anchor typically requires several
 tools including a drill provided with a drill bit having a diameter
 appropriate to that of the anchor, a hammer to drive the anchor in the
 hole drilled in the wall, and a screwdriver to turn the threaded fastener
 into the anchor or to later remove it from the anchor.
 Though hollow wall anchors are used on a large scale by installers, the
 need to drill holes and then hammer the anchors into the holes is a
 practical drawback, for these operations are time consuming and impose
 distinct limits on the number of anchors that can be installed in a given
 period. In addition, if anchors of different sizes must be installed, then
 the installer must change the drill bit when switching from one anchor
 size to another, which, consumes time and reduces the productivity of the
 installer. Furthermore, when a wall anchor is hammered into a wall, the
 rear surface of the wall board is often destroyed, thereby minimizing the
 anchor strength of the wall anchor.
 One approach to the above is a self-threading anchor with spreadable distal
 leg portions joined by a frangible drill end portion described in U.S.
 Pat. No. 5,692,864 to Powell on Dec. 2, 1997. In the '864 Patent, Powell
 teaches a spade-shaped drill end portion with a frangible web portion
 which holds the drill end portion together during drilling while allowing
 the drill end portion to split apart to accommodate the spreading of the
 leg portions. Other self drilling and self tapping anchors are described
 in U.S. Pat. No. 5,536,121 to McSherry on Jul. 16, 1996. However, the
 cutting portions of these anchors create rough cutting surfaces which
 decrease the strength of the engagement of any external threads. In
 addition, the rough cutting creates an unsightly appearance after the
 anchor is installed.
 Accordingly, what is needed is an improved anchor bolt which requires a
 minimum number of tools to install. What is further needed is an anchor
 bolt which is aesthetically pleasing once installed, and is not unduly
 disruptive to a mounting surface. What is also needed is an anchor bolt
 which is securely mounted within a wall for attaching objects thereto.
 SUMMARY OF THE INVENTION
 An improved self-drilling plastic anchor bolt is provided which is
 installable in a wall with a screwdriver. The anchor bolt is adapted to
 receive a threaded fastener that holds a fixture or other object against
 the wall, where the anchor bolt dispenses with the need for a drill, a
 hammer, or any tool other than a screwdriver to install the anchor bolt.
 The self-tapping anchor bolt has a head with a through-hole opening for
 receiving a screwdriver. In one embodiment, the through-hole is adapted to
 receive a Phillips screwdriver. The head is coupled with a shank at a
 first end of the shank, where a second end of the shank is coupled with a
 drill portion. The shank has a longitudinal cavity therein which is
 adapted to receive a set screw. In addition, the shank includes points of
 weakness therethrough to accommodate expansion of a portion of the shank
 after insertion of the set screw. The points of weakness allow for a
 portion of the shank to deflect away proximate the head. In another
 embodiment, the points of weakness allow for a portion of the shank to
 deflect away from the bolt proximate an intermediate portion of the bolt.
 An external helical thread on the shank portion is coiled about the
 external surface of the shank and extends between the head and the drill
 portion. The drill portion includes a cutting edge and at least one
 helical flute for carrying away the material during installation of the
 anchor bolt.
 In another embodiment, the self-tapping anchor bolt has a head with a
 through-hole opening for receiving a screwdriver. The head is coupled with
 a shank at a first end of the shank portion, where a second end of the
 shank is coupled with a drill portion. The shank has a longitudinal cavity
 therein which is adapted to receive a set screw. The longitudinal cavity,
 in one embodiment, is tapered. In addition, the shank includes slits
 therethrough to accommodate expansion of the shank after insertion of the
 set screw. In one embodiment, the points of weakness comprise slits. At
 least one portion of the shank is adapted to expand outwardly and is
 separable from the shank proximate the head. The portion of the shank,
 when partially severed from the shank upon insertion of the set screw,
 secures the anchor bolt within the wall. In one embodiment, an external
 helical thread on the shank portion is coiled about the external surface
 of the shank portion and extends between the head and the drill portion.
 The external thread allows for the anchor bolt to engage with the mounting
 surface before the set screw is installed. In another embodiment, the
 drill portion includes a cutting edge and at least one helical flute for
 carrying away the material during installation of the anchor bolt.
 To install the anchor bolt, first a sharpened point on the drill tip is
 used to pierce the mounting surface. A screwdriver is then used to drill
 the anchor bolt into the wall. After the anchor bolt is inserted into the
 wall such that the head abuts an outer surface of the wall, a mounting set
 screw is inserted into the longitudinal cavity of the shank portion. A
 screwdriver is then used to concurrently apply an axial force while
 rotating the mounting set screw. As the mounting set screw is further
 installed into the anchor bolt, the set screw places an outward force on
 the shank, to thereby separate at least one portion of the shank. The at
 least one portion of the shank expands away to engage firmly into the
 wall. As the portion of the shank is wedged radially outwardly from the
 shank portion, the anchor bolt is held firmly within the wall.
 Since the anchor bolt can be fabricated from high strength material, the
 anchor bolt can be manufactured at a relatively low cost. The anchor bolt
 is held in the wall by the resistance of the external threads on the
 anchor bolt which engages with the wall, in addition to the engaging
 member which is radially spreadable upon insertion of the fastener into
 the anchor bolt to provide a secure device on or to which structure can be
 securely mounted.
 These and other embodiments, aspects, advantages, and features of the
 present invention will be set forth in part in the description which
 follows, and in part will become apparent to those skilled in the art by
 reference to the following description of the invention and referenced
 drawings or by practice of the invention. The aspects, advantages, and
 features of the invention are realized and attained by means of the
 instrumentalities, procedures, and combinations particularly pointed out
 in the appended claims.

DESCRIPTION OF THE EMBODIMENTS
 In the following detailed description, reference is made to the
 accompanying drawings which form a part hereof, and in which is shown by
 way of illustration specific embodiments in which the invention may be
 practiced. These embodiments are described in sufficient detail to enable
 those skilled in the art to practice the invention, and it is to be
 understood that other embodiments may be utilized and that structural
 changes may be made without departing from the scope of the present
 invention. Therefore, the following detailed description is not to be
 taken in a limiting sense, and the scope of the present invention is
 defined by the appended claims.
 FIG. 1A illustrates one embodiment of an anchor bolt 100. The anchor bolt
 100 generally comprises a head 112, a shank 110, and a drill portion 120.
 The head 112 generally comprises, in one embodiment, a circular flange
 which extends outward from a radial axis 109 of the shank 110.
 Alternatively, the head 112 can have other shapes, such as square,
 rectangular, or square shapes, or can be tapered toward the shank 110. The
 head 112 can be formed with a flat outer surface 113 such that the anchor
 bolt 100, if no longer needed, can be plastered over to provide a smooth
 surface to the mounting surface.
 FIG. 2 illustrates an end view of the head 112. The head 112 has a
 through-hole 114 therein for receiving a set screw therethrough. The
 through-hole 114, in one embodiment is adapted to receive a screwdriver
 therein. The opening 114 can be aligned with the radial axis 109 of the
 shank 110 such that axial force directed thereon can be efficiently
 transmitted to the drill tip, as will be further discussed below. In one
 embodiment, the through-hole 114 is adapted to receive a Phillips head
 screwdriver therein. Alternatively, other shapes, for example a flathead
 opening, can be incorporated and are considered within the scope of the
 present invention.
 Referring to FIG. 3, the shank 110 comprises a generally elongate
 cylindrical structure which is coupled with the head 112. The shank
 portion 110, in one embodiment, has external threads 116 which helically
 coil about the exterior of the shank 110. The external threads 116 assist
 in tapping and securing the anchor bolt 100 within a wall, as will be
 further described below. In one embodiment, the shank 110 has at least one
 point of weakness 123. The points of weakness 123 can be formed in the
 shank 110 in a variety of manners resulting in several different
 structures. For instance, the points of weakness 123 can be formed by
 providing a thinner wall structure for a portion of the shank 110. The
 shank 110 has, in another embodiment, a plurality of slits 122 therein.
 Alternatively, at least one slit 122 can be used in the present invention
 and formed in many different configurations as will be further described
 below. In one embodiment, the slits 122 extend longitudinally down the
 shank 110 and divide the external threads 116 into a plurality of discrete
 segments. The slits 112, in another embodiment, extend through the shank
 portion such that the slits 112 are substantially parallel with the radial
 axis of the shank 110. The purpose of the slits 112 and the points of
 weakness 123 are to weaken a connection of at least one portion 146 of the
 shank 110 so that the portion 146 of the shank 110 can separate upon
 insertion of a threaded fastener. Either the slits 112 or the points of
 weakness 123, or a combination of them can be used within the present
 invention.
 The shank 110, in one embodiment, extends from a first end 111 proximate
 the head 112 to a second end 113 proximate the drill portion 120. The at
 least one portion 146 of the shank 110 is defined in part by the points of
 weakness 123 or the slits 122 and the head 112. Upon insertion of a
 fastener, at least one portion 146 of the shank will separate from head
 112 and the shank 110, and at least one portion of the shank 110 will
 remain connected with the head 112. Alternatively, in another embodiment,
 a plurality of portions 146 of the shank 110 can separate from the shank
 110 and the head 112 and still be considered within the scope of the
 invention. The at least one portion 146 of the shank disengages from the
 shank 110 upon the insertion of the mounting set screw. As the set screw
 is inserted through the hole 114 and into the longitudinal cavity 142, the
 at least one portion 146 of the shank pivots away from the first end 130
 of the shank 110 at pivot point 148. Alternatively, in another embodiment,
 the at least one portion 146 bends outward from the shank 110. In yet
 another configuration, the at least one portion 146 curls outward from the
 shank 110.
 FIG. 1B illustrates another embodiment illustrating an area of weakness
 123. The area of weakness 123 comprises a slot 107 which includes a first
 portion 106 and a second portion 104. The first portion 106 extends
 longitudinally along the shank 110 and is coupled with the second portion
 104. In one embodiment, the first portion 106 extends from proximate the
 head 112 to an intermediate portion 102 of the anchor bolt 100, where a
 hinge point 103 is formed proximate to the intermediate portion 102. The
 second portion 104, in one embodiment, is disposed perpendicular to the
 first portion 106. In another embodiment, the shank 110 includes two slots
 107.
 Referring again to FIG. 3, the shank portion 110 also has a longitudinal
 cavity 142 therein. In one embodiment, the longitudinal cavity 142 is
 connected with the through-hole 114. The longitudinal cavity 142 is
 adapted to receive a mounting set screw 144 therein, as will be further
 discussed below. The longitudinal cavity 142, in one embodiment, is
 generally aligned with the radial axis of the shank portion 110. In
 another embodiment, the longitudinal cavity 142 is aligned with the slits
 122. The width and the depth of the longitudinal cavity 142 can be
 modified to accommodate a wide variety of threaded fasteners therein.
 The anchor bolt 100 extends from a first end 130 to a second end 132.
 Proximate to the first end 130 is the shank 110, and proximate the second
 end 132 is the drill portion 120. The drill portion 120 has, in one
 embodiment, a smaller diameter than the shank 110. The drill portion 120,
 in another embodiment, comprises a drill bit. The drill portion 120
 extends from proximate the shank 110 to a drill tip 124. The drill tip
 124, in one embodiment, is sharpened to a point 126. The point 126 of the
 drill tip 124 is sharpened to assist in the installation process. In
 another embodiment, as illustrated in FIG. 1B, the drill tip 124 has a
 sharpened projection 125 in combination with extended cutting features 127
 of the drill portion 120. The sharpened projection, in one embodiment, is
 aligned with the radial axis 109 of the anchor bolt 100. The extended
 cutting features 127 extend from the drill portion to a point 129. The
 extended cutting features 127 allow for the anchor bolt 100 to self-tap
 into a wall, and eliminate the need for extra tools, such as a drill, when
 installing the anchor bolt. The sharpened projection 125 assists in
 centering the anchor bolt 100 as the extended cutting features 127 engage
 with the wall. In addition, the sharpened projection 125 prevents the
 anchor bolt 100 from wandering during installation of the anchor bolt 100
 into the wall.
 In another embodiment, the drill portion 120 has substantially the same
 length as the shank 110. The drill portion 120 has cutting edges 136
 formed at the periphery of the cylindrical drill portion 120. The cutting
 edges 136 define a portion of helical flutes 134 which are formed in the
 drill portion 120. The flutes 134 allow for the release of material as the
 drill portion 120 is drilled into a wall.
 FIG. 4 illustrates installation of the anchor bolt 100 into a wall 152. The
 point 126 of the drill portion 120 is used to pierce an outer surface of
 the wall 152. A screwdriver 150 is then used to rotate the anchor bolt 100
 and simultaneously place an axial force on the anchor bolt 100. As the
 anchor bolt 100 is turned, and the axial force is applied, the cutting
 edges 136 of the drill portion 120 cut into the wall 152 forming a bore
 therein. Material from cutting of the wall is transferred away from the
 cutting edges 136 by the flutes 134, thereby providing a clean cut in the
 wall 152. As the anchor bolt 100 is further inserted into the wall 152,
 the external threads 116 of the shank portion 110 cut a helical thread
 into the wall 152 and secure the anchor 100 within the wall 152.
 Installation of the anchor bolt 100 into the wall 152 is complete when the
 head 112 abuts or is proximately disposed to the outer surface of the wall
 152, as shown in FIG. 4.
 FIGS. 5 and 6 illustrate installation of the mounting set screw 144. After
 the anchor bolt 100 is inserted into the wall 152 such that the head 112
 abuts an outer surface of the wall 152, the mounting set screw 144 is
 inserted through the hole 114 and into the longitudinal cavity 142 of the
 shank 110. A screwdriver 150 is then used to apply an axial force and
 rotate the mounting set screw 144. As the mounting set screw 144 is
 further installed into the anchor bolt 100, the set screw 144 places an
 outward force on the shank portion 110. The force from the set screw 144
 causes a crack to initiate in the shank portion 110 causing the at least
 one portion 146 of the shank 110 to split away from the shank 110
 proximate to the point of weakness or the slits 122. The at least one
 portion 146 of the shank 110 is no longer coupled with the head 112 and is
 expanded away from the shank 110 to engage firmly into the wall 152. As
 the at least one portion 146 of the shank 110 is wedged radially outwardly
 from the shank 110, the anchor bolt 100 is held firmly within the wall
 152.
 FIGS. 7A and 7B illustrate another embodiment of an anchor bolt 200. The
 anchor bolt 200 generally includes a head 212, a shank 210, and a drill
 portion 214, as discussed in the earlier embodiments, and also include the
 variations discussed above. The anchor bolt 200 extends from a first end
 202, proximate to the head 212, to a second end 204, proximate to the
 distal end of the drill portion 214, and includes an intermediate portion
 203 disposed in between the first end 202 and the second end 204. In one
 embodiment, the intermediate portion 203 is disposed between the shank 210
 and the drill portion 214.
 An area of weakness 220 is formed in the anchor bolt 200, and in one
 embodiment, extends from the first end 202 to the intermediate portion
 203. The area of weakness 220 allows for at least one deflecting portion
 222 to bend outward at a hinge point 224 proximate the head 212. The
 deflecting portion 222 includes a distal end 226 which is adapted to
 engage with the wall 228, as shown in FIG. 8 and retain the anchor bolt
 200 within the wall 228. The distal end 226 of the deflecting portion 222,
 before it is expanded by a set screw, is disposed at the intermediate
 portion 203 of the anchor bolt 200. In one embodiment, the area of
 weakness comprises a slot 230.
 The slot 230, in another embodiment, is comprised of a first portion 232
 coupled with a second portion 234, and in one embodiment, the first
 portion 232 is perpendicularly disposed to the second portion 234. The
 first portion 232 is disposed longitudinally along the anchor bolt 200,
 and in one embodiment, is disposed completely through the anchor bolt 200.
 The second portion 234, in another embodiment, extends from the first
 portion 232 and is disposed at least partially through the intermediate
 portion 203 of the anchor bolt 200, where a tab 236 of material remains.
 As a set screw is inserted into the anchor bolt 200, the tab 236 is
 severed, as shown in FIG. 8, by the force of the inserted set screw.
 FIG. 9 illustrates yet another embodiment of an anchor bolt 300. The anchor
 bolt 300 includes similar features as discussed above, where the anchor
 bolt 300 is adapted to deflect at an intermediate portion 303. In
 addition, the shank portion 310 has a longitudinal cavity 342 therein. The
 longitudinal cavity 342 is adapted to receive a mounting set screw
 therein, as discussed above. The longitudinal cavity 342, in one
 embodiment, is generally aligned with the radial axis of the shank portion
 310, and extends from the first portion 302 to the intermediate portion
 303. In another embodiment, the longitudinal cavity 342 has an internal
 surface 344 which is tapered toward the radial axis of the anchor bolt 300
 from the first portion 302 toward the intermediate portion 303. In an
 alternative embodiment, the tapered internal surface 344 is tapered toward
 an area of weakness 330. It should be noted, however, that the width and
 the depth of the longitudinal cavity 342 can be modified to accommodate a
 wide variety of threaded fasteners therein. The tapered surface of the
 longitudinal cavity 342 can also be incorporated with other embodiments
 discussed herein.
 FIG. 10 illustrates another embodiment of an anchor bolt 400, which
 generally includes a head 412, a shank 410, and a drill portion 414, as
 discussed in the earlier embodiments, and also include the variations
 discussed above. The anchor bolt 400 extends from a first end 402,
 proximate to the head 412, to a second end 404, proximate to the distal
 end of the drill portion 414, and includes an intermediate portion 403
 disposed in between the first end 402 and the second end 404. In one
 embodiment, the intermediate portion 403 is disposed between the shank 410
 and the drill portion 414.
 An area of weakness 420 is formed in the anchor bolt 400, and in one
 embodiment, extends from the first end 402 to the intermediate portion
 403. The area of weakness 420 allows for a plurality of deflecting members
 422 to bend outward at a respective hinge point 424 proximate the head
 412. The deflecting members 422 each include a distal end 426 which is
 adapted to engage with the wall to retain the anchor bolt 400 within the
 wall. The distal end 426 of the deflecting members 422, before it is
 expanded by a set screw, is disposed at the intermediate portion 403 of
 the anchor bolt 400. In one embodiment, the area of weakness 420 comprises
 a slot 430.
 The slot 430 is comprised of a first portion 432 coupled with a second
 portion 434, and in one embodiment, the first portion 432 is
 perpendicularly disposed to the second portion 434, and the first portion
 432 relative to the second portion form a T-shape. The first portion 432
 is disposed longitudinally along the anchor bolt 400, and in one
 embodiment, is disposed completely through the anchor bolt 400. The second
 portion 434, in another embodiment, extends from the first portion 432 and
 is disposed at least partially through the intermediate portion 403 of the
 anchor bolt 400, where a tab 436 of material remains. As a set screw is
 inserted into the anchor bolt 400, the tabs 436 are severed, as shown in
 FIG. 11, by the force of the inserted set screw. When the tabs 436 are
 severed, the shank 410 is separated from the drill portion 414.
 Advantageously, an improved self-drilling plastic anchor bolt is provided
 which is installable in a wall with a screwdriver. The anchor bolt is
 adapted to receive a threaded fastener that holds a fixture or other
 object against the wall, where the anchor bolt dispenses with the need for
 a drill, a hammer, or any tool other than a screwdriver to install the
 anchor bolt. The same screwdriver can be used to install the shank and
 drill portion as the mounting set screw. The anchor bolt can be fabricated
 from high strength material, such as a thermoplastic material, which can
 be manufactured at a relatively low cost. Alternatively, the anchor bolt
 can be fabricated from other high strength materials, such as a metal. The
 anchor bolt is held in the wall by the resistance of the external threads
 on the anchor bolt which engages with the wall, in addition to the
 engaging member which is radially spreadable upon insertion of the
 fastener into the anchor bolt.
 It is to be understood that the above description is intended to be
 illustrative, and not restrictive. Many other embodiments will be apparent
 to those of skill in the art upon reviewing the above description. For
 example, the helix angles of the flutes may vary. The scope of the
 invention should, therefore, be determined with reference to the appended
 claims, along with the full scope of equivalents to which such claims are
 entitled.