Abstract:
An anchoring assembly and method adapted to secure a screw fastener at a pre-drilled hole in a concrete, brick or masonry building material with an elongated engagement cavity between the screw and the pre-drilled hole radially offset to one side of and extending axially along the depth of the hole, an elongated anchor strip axially adjacent the screw including an elongated malleable and non-resilient anchor member adapted to frictionally engage both the helical threads and the building material and to frictionally engage the threads to the building material radially opposite to the engagement cavity, the malleable anchor member having at least one transverse dimension which is substantially greater than the transverse radial dimension of the axial engagement cavity.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to concrete and masonry anchors and methods of securely and removeably fastening construction materials to concrete slabs, concrete bodies, masonry blocks, and the like. 
       BACKGROUND 
       [0002]    A screw is a fastener is a type of fastener characterized by a helical ridge, known as an external thread or thread, wrapped around a cylinder designed to cut a helical groove in a softer material as the screw is inserted. Commonly screws are used to hold objects together and to position objects. A screw has a head by which it is turned and thereby driven into the objects. 
         [0003]    By contrast, a nail is a type of fastener which is driven into the objects by an axial blow or series of axial blows. 
         [0004]    Concrete is a common construction material which is widely used for a variety of purposes including structural members, walls, floors, beams and the like. Concrete is a hard composite material including coarse granular components embedded in a hard matrix being the cement that fills the space among the aggregate particles and glues them together. Concrete is not malleable, ductile or resilient and is not known to permit plastic deformation of any kind once hardened. Similar to masonry and brick, concrete is considerably harder than most materials used for typical fasteners and is cut, drilled or threaded by vary hard abrasives or destructive impact tools. As such, concrete has a degree of non-uniformity which makes it difficult to precisely re-form, as by cutting and drilling, particularly on modern construction sites. This is particularly so when other building materials are to be attached or secured to a concrete member on site. Most often a pilot hole is required which would necessarily be irregular by reason of manual high-speed drilling tools such as a hammer drill or masonry bit. Such a pilot hole would have a nominal diameter and internal irregularities, which would include loose, partially detached and fully detached elements which could reduce or increase the nominal diameter. 
         [0005]    The very hardness of concrete members and a high resistance to compressive forces makes on site attachment of other objects a common task which remains a time consuming, expensive and risk prone construction activity. This requires skilled labor and care in relation to supply of parts and their installation, both in relation to the object attached to the concrete, and the concrete itself. 
       PRIOR ART 
       [0006]    Many solutions to this attachment task have been proposed, most of which are referred to as concrete or masonry anchors. The most common of these is referred to the Tapcon. This concrete screw is turned into a pre-drilled and cleaned hole of a specific size where its hardened and specialized threads cut radially into the concrete itself, creating a mating female thread pattern as the screw is advanced. Such concrete screws are commonplace and are often required by specification for economical construction which meets modern needs for high-speed installation with an extremely secure result. 
         [0007]    In others attachment instances, radial deformation spreading in a soft material, such as lead, is used. An annular anchor expands its circumference as a result of expansion of an inner diameter caused by the action of an advancing screw or other means. 
         [0008]    Such attachments are meant to be permanent and to resist variations in methods, tensile and vibration forces, corrosion and the like. Unfortunately, each of these solutions requires a specific size of anchor, screw, hole. Often these are inconsistent with the placement requirements for the objects being attached and they do not readily permit relocation or reuse should construction requirements change. 
         [0009]    Attempts to provide a more economical, faster and equally secure means of attachment have been sought but are not widely adopted. 
         [0010]    The patent prior art shows several separate classes of construction anchor, firstly the use of screw enveloping plugs, and, secondly, helical coils which can be placed in a receiving hole to provide provide a laterally expansible engaging thread which is then expanded by insertion of a threaded fastener. 
         [0011]    An example of the first class is shown in U.S. Pat. No. 1,248,008 issued Nov. 27, 1917 to Pleister. A lead plug with a central open shaft is expanded by the insertion of an oversized screw so as to interact with pilot hole walls. 
         [0012]    A simple example of the 2nd class is shown in U.S. Pat. No. 2,520,232 issued Aug. 29, 1950 to Bereza. That patent describes use of an expansible helical coil for fastening to a wood substrate. The screw is wound with the coil and then turned into the pre-prepared hole. Engagement in the reverse direction is asserted to occur by unwinding of the coil against the hole. 
         [0013]    In U.S. Pat. No. 4,309,135 issued Jan. 5, 1982 to Gutshall it is asserted that it is well known to use an expandable helical coil for concrete fasteners where the coil is expanded into contact with the hole by a wedging action of a bolt or screw. Gutshall addresses this problem by providing a 2-part system comprising a speciality bolt and a specially formed coil which interact to complete an improved concrete anchor. 
         [0014]    U.S. Pat. No. 4,536,115 issued Aug. 20, 1985 to Helderman describes a more complex helical coil structure which is inserted into a pre-drilled hole to a prescribed depth and then expanded radially over its circumference to embed into the wall of the hole (col 2, line 28). At col 2 line 52 the device is identified as being made of metal, plastic coated metal or other suitable material but the only coatings are referred to as frangible upon use in situ. The coil is further described as molded of plastic or die cast from metal. The main features are seen to be radial expansion so as to embed into the concrete. 
         [0015]    Other examples appear in U.S. Pat. No. 5,006,023 issued Apr. 9, 1991 to Kaplan; U.S. Pat. No. 5,366,328 issued Nov. 22, 1994 to Helderman; U.S. Pat. No. 5,636,549 issued Jun. 10, 1997 to Devenyi; U.S. Pat. No. 6,835,036 issued Dec. 28, 2004 to Sigismund. Development in this area seems to continue as shown in USPPA 2003/0086772 published May 8, 2003 by Giannakakos; USPPA 2008/0025810 published Jan. 31, 2008 by Grubert; USPPA 2010/0221087 published Sept. 2, 2010 by Gillis; and USPPA 2012/0315107 published Dec. 13, 2012 by Grubert. 
         [0016]    An example of yet another class is the fastener shown in U.S. Pat. No. 4,973,210 issued Nov. 27, 1990 to Osborne et al. In this it appears that the fastener threads include cutting teeth which seek to form female corresponding threads in the pre-drilled concrete pilot hole. It is noted that a locking key is required to prevent loosening of the connector. Other examples of cutting threads include U.S. Pat. No. 8,360,702 issued Jan. 29, 2013 to Yu. 
         [0017]    Other examples are shown in U.S. Pat. No. 5,749,688 issued May 12, 1998 and U.S. Pat. No. 6,196,778 issued Mar. 6, 2001 to Wakai. These seek to provide a concrete plug with a first part having an axial bore to receive a screw and a second part having a pair of legs formed of a flexible plastic material. These legs form a irregular hole bounded by a single flexible plastic material. As shown in  FIGS. 2A and 2B  a starter hole is formed in the concrete or other building material sufficiently wide for insertion of the Wakai plug and a screw is passed through the axial bore and then is driven by twisting into the irregular hole. The plastic material is asserted to be deformed sufficiently by the screw threads to form flexible retaining female threads in the plastic material and the screw shank itself is driven laterally so that its hardened threads cut corresponding female threads in to the concrete building material. As noted at page 6, column 3, lines 50 to 67, two separate areas are said to provide both strong resistance to a pulling force and resilient absorption of vibrations for long-lasting pulling forces. These characteristics are asserted to provide a secure and long-lasting fastening system. The system is complex, uses speciality materials including hardened screws and requires a carefully matched pair of fasteners, the screw and the plug, each matched to the finished size of the receiving hole and the material being secured. It is not only expensive but prone to error in stocking and in use, particularly as it is difficult in an ordinary construction site to ensure perfectly drilled receiving holes and availability of matched parts of different sizes. The Wakai references are not known to be in common use or to be especially effective, as asserted. 
         [0018]    It is apparent from these examples that the progress of the development in this art is provided by extensive efforts to maximize embedding of screw threads within the walls of the pre-drilled concrete pilot hole, or, alternatively, by expanding a circumferential plug to fill the void between threads and the pilot hole wall. In every case, a speciality part or parts are required, each of which is specifically sized to correspond with a particular use. 
         [0019]    In modern construction none of the previously noted types of anchor are most common. Modern concrete anchors also include self threading anchors, bolts or screws, examples of which are supplied under the name Tapcon, a trade mark attributed to Illinois Tool Works Inc. With such screws a receiving hole is drilled into the concrete base to a full service depth. The self-threading screw anchors are screwed into the hole by passing through the part to be attached. Since the screws are hardened they are adapted to cut holding threads into the concrete wall material as by configuration and thread hardening. Necessarily the tolerances are low as even with a hardened or specially shaped cutting thread the hard and abrasive concrete of the hole wall must be overcome, firstly, to cut the thread in a single pass, and, then, to accommodate the sliding action of following threads and accumulating debris. All of the forces required to carry out this action must be transmitted down the shank of the anchor from its head. The actual cutting thread must maintain its shape and outer diameter throughout the process to achieve adequate holding power. In such instances there is often a need to pass the drill in/out of the pilot hole 2 to 4 times to clear debris. Unfortunately, too little means leftover debris in the hole and the hole is likely too narrow. Too many times and the hole is slightly too large or an irregular shape or both. 
         [0020]    Removal of the concrete drilling debris to accommodate the action of such a bolt dictates a need to blow out the hole to remove concrete dust and drilling particles. This adds an additional installation step and additional equipment to the installation process, plus an additional power line for powered operation. 
         [0021]    Concrete is a non-uniform and abrasive material into which it is difficult to drill a cylindrical hole with precision, especially on a modern work site with highly powered but yet hand held drilling devices. 
         [0022]    If the hole is not the perfect size and shape, there is a need to screw-in and unscrew the bolt a few times to get the anchor all the way in, otherwise it may become wedged due to additional abraded material and can break off. Hardness of the material of the anchor and the concrete provide an ideal condition where torque loading requirements precipitously increase when a jam occurs. A jam leads to an unpredictable failure profile for the anchor, especially if the hole is slightly undersized in whole or in part as may arise with hand held drilling. 
         [0023]    On the other hand, if the hole is slightly too big, these anchors will not work at all as they act as stripped thread. 
         [0024]    As a result, self-threading anchors are often as much as 10 times the price of regular screws, require care in installation and are not reusable. In use, ease of use does not always occur as they often get stripped, wedged or broken off. Broken anchors at individually located drill sites themselves cannot be reused without significant remedial work or at all. In most circumstances if an anchor gets stuck or breaks off the project will require that the entire position of the material being fastened or the location of that fastening will need to be moved as you cannot typically drill out a wedged or broken anchor. Even cleared of a broken anchor and debris the resulting hole will be too big to reuse. Moving the fastening point may require changing the position or fastening location of the attached materials or equipment and will leave a weakness in the concrete. These result in significant incremental costs of the materials successfully used and the overall work project, effectively increasing the real cost of the ones that work. 
         [0025]    Even so, these anchors are are not forgiving, especially in the hands of even skilled trades under pressure to complete work as quickly as possible. The margin for error is small with regards to hole vs thread. Further, they need special bits, such as hex-head or large philips. 
         [0026]    In the result, operating with these anchors requires a large inventory as much as doubling the job-site-available inventory of screws, typically in the range of 1″ to 4″ which adds greatly to the fastening costs of any project. 
         [0027]    Other solutions are not known to be as widely adopted in the trades, such as use of a pair of standard construction nails and twisted concrete nails with and without a filler. 
       OBJECTS OF THE INVENTION 
       [0028]    It is an object of the invention to provide a simple concrete anchor which is economical, faster to install, and an equally secure means of attachment using commonly available screws. 
         [0029]    Further objects of the present invention include providing:
       a single pass drilling operation without a need to drill back and forth,to avoid a need to blow out the drilled hole,   avoiding backing out the screw so that the screw goes in on the first attempt,   a more forgiving anchor with a large margin of error for size of hole,   for the use of regular screws in a manner where most are reusable,   minimal breakage or stripping of the pilot hole,   minimizing actual and incremental costs,   for re-use same hole in the event of failure,   accommodation for oversize holes,   an easy means to remove the screw and try again while maintaining position,   for use standard tool bits, such as a regular square or Phillips tips, and,   for use of standard concrete drill bits to prepare anchoring holes.       
 
       THE INVENTION 
       [0041]    The invention provides an anchoring assembly and method adapted to secure a screw fastener in a material engaging position at a pre-drilled hole in a concrete, brick or masonry building material, with an elongated screw with a threaded portion including a cylindrical shank and laterally extending helical cutting threads with an overall outside diameter less than the nominal diameter of a pre-drilled hole so as to provide an elongated engagement cavity between said screw and said pre-drilled hole, wherein said engagement cavity is radially offset from the axis of the screw to one side of the pre-drilled hole and extends axially along a substantial portion of the depth of the said pre-drilled hole, and an elongated anchor strip axially adjacent the screw including an elongated malleable and non-resilient anchor member adapted to frictionally engage both the helical threads and the building material in the engagement cavity and to frictionally engage the threads to the building material radially opposite to the engagement cavity, wherein said malleable anchor member has at least one transverse dimension which is substantially greater than the transverse radial dimension of the axial engagement cavity. 
         [0042]    The invention also provides an anchor and method with at least one transverse dimension greater than the transverse dimension of the axial engagement cavity plus the difference between the radius of the shank and the radius of the helical cutting threads. 
         [0043]    Further, the invention provides an anchor and method which is substantially non-resilient and preferably selected from the group of copper, aluminium or soft malleable steel, malleable under the stresses applied in manual drilling of concrete or masonry. 
         [0044]    Further, the invention provides an anchor and method wherein the malleable core is plastically deformed within the engagement cavity by the threads and the pre-drilled hole and, also, by the screw shank, upon axial rotation of the screw. 
         [0045]    Further, the invention provides an anchoring assembly with plastic deformation including both helical deformation of the elongated anchor strip and axial continuity of the strip along the engagement cavity and means to resist rolling of the strip about its own axis. 
         [0046]    Further, the invention provides an anchoring assembly with an anchor strip including a resilient and malleable outer sheath member, preferably of nylon or PVC. 
     
    
     
       THE DRAWINGS 
         [0047]      FIG. 1  is a partial perspective end view of a preferred embodiment of the anchor invention in a pre-achoring condition. 
           [0048]      FIG. 2  is a partial perspective top view of the embodiment of  FIG. 1  in an engaged anchoring state showing an enlarged pre-drilled hole diameter for illustration purposes. 
           [0049]      FIG. 3  is a partial perspective end view of the anchor of  FIG. 1  engaging a composite building structure to a masonry block also showing an enlarged pre-drilled hole diameter for illustration purposes. 
           [0050]      FIG. 4  is an illustrative vertical section of the installed anchor of  FIG. 2  of the preferred embodiment. 
           [0051]      FIG. 4   a  is a further illustrative vertical section of the installed anchor of  FIG. 4  of the preferred embodiment shown without a outer resilient sheath. 
           [0052]      FIG. 4   b  is a further illustrative vertical section of the installed anchor of  FIG. 4   a  of the preferred embodiment shown with the added outer resilient sheath. 
           [0053]      FIGS. 5 through 9  show a sequence of pictorial views of a screw and anchor combination which has been installed and then removed from engagement by reversal of the driver and reverse axial rotation. In each successive case the screw remains unmoved and the anchor is incrementally rotated about its long axis. 
           [0054]      FIG. 10  is an expanded pictorial view of the anchor of  FIGS. 5 through 9  wherein the rupture in the resilient sheath is opened to illustrate the deformations. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0055]    A preferred embodiment of the concrete and masonry anchor of the invention is shown in  FIG. 1 .  FIG. 1  is shown partially exploded for ease of reference in that the material being secured is separated from a the concrete base. 
         [0056]    The anchor  1  is shown in the form of a cylindrical sheathed copper wire in conjunction with a coarse thread screw  2  and a construction material  3  with a thickness  12 , such as plywood, being secured to a concrete or masonry base  4 . For attachment, a pilot hole  6  is drilled through material  3  and well in to the base  4  to a depth  7 , as at pre-drilled hole  5 . 
         [0057]    Anchor  1  as shown in this preferred embodiment is uniform in section over its length  8  and substantially smaller than hole  5 . Anchor  1  is inserted in to pre-drilled hole  5  to a depth  17  forming its working length  17  and providing an axial elongated cavity inside hole  5 . Working length  17  may or may not be the same as the depth  7  as the anchor need not extend through all of hole depth  7 . As shown, anchor  1  extends beyond base  4  and hole  5  and through pilot hole  6  by its residual length  9 . The exposed portion of anchor  9  adjacent lengths  14  and  15  may be used as a place holder since the anchor  1  may be gripped and held in place as by pliers (not shown). 
         [0058]    Once material  3  is in place screw  2  is inserted into the axial elongated cavity provided by pilot hole  6  adjacent anchor  1  and turned axially by its head end  13  to engage its threaded portion  11  between anchor  1  and material  3 . Preferably, screw  2  will preferably readily advance into pilot hole  6  a length  16  and through material  3  without significant resistance. In some cases, it will be understood, pilot hole  6  may be undersized or material  3  may be non-resilient as would be the case with attachment of metal or concrete parts. 
         [0059]    Further axial rotation of screw  2  will cause it to advance into pre-drilled hole  5 , preferably until threaded portion  11  with length  15  and  16  is completely engaged in pre-drilled hole  5  between concrete base  4  and anchor  1  over the whole of length  17 . Most preferably, screw  2  will advance until it head end  13  engages fully with material  3  and draws it in to full engagement with the concrete base  4  with unthreaded portion  10  passing through material  3 . 
         [0060]    Preferably screw length  10  is chosen so that its unthreaded body portion  10  has a length  14  which corresponds to material depth  12 . 
         [0061]    The preferred embodiment of  FIG. 1  is shown in a partially engaged position in a perspective overall view from the top surface of material  3 . Pre-drilled hole  5  is shown with an expanding and over-sized diameter for ease of illustration of the anchor  1  and its method of installation. 
         [0062]    Anchor  1  preferably includes a central cylindrical copper core  23  and an enveloping resilient sheath  22  of, preferably, nylon or PVC. Hole  5  may accumulate debris  21  from the drilling process and/or by the installation of anchor  1 . As screw tip  20  advances in to hole  5  anchor  1  becomes compressively engaged between hole  5  and screw  2  by its threaded portion  11  and its main screw body. Rotation of screw  2  drives anchor  1  in to a long helical shape  24  whose lead is much greater than the lead of screw  2 . Preferably helical shape  24  is no longer a regular cylinder. 
         [0063]    In  FIG. 3  anchor  1  and screw  2  of  FIGS. 1 and 2  are shown engaging a composite building structure to a masonry block. In  FIG. 3  the pre-drilled hole  33  corresponding to pre-drilled hole  5  in  FIGS. 1 and 2  is shown with an enlarged diameter for illustration purposes. Construction material  31  and metal strapping  35  are both to be engaged to hollow masonry block  32  which would include regular cavities  39 . For installation, anchor  1  is fed in to and through pilot hole  36  and pre-drilled hole  33  so a to preferably extend somewhat into cavity  39  as at  34 . Anchor  1  may then be bent over as at  38  so as to hold it in position against falling through or, in the case of an overhead installation, falling out of pre-drilled hole  33 . Turning screw  2  axially advances threaded portion  37  through strapping  35  and material  35  into engagement between anchor  1  and the masonry wall of pre-drilled hole  33  until its head draws the strapping  35  fully tight against the masonry block  32 . 
         [0064]      FIG. 4  is an illustrative vertical section of an embodiment of the anchor of  FIG. 2  also with an expanded horizontal diameter of pre-drilled hole  5 . To the right of screw axis A-A material  3  is shown thin as at  55  and fully engaged to concrete  4  as at  56 . To the left of screw axis A-A material  3 ′ is shown as thicker, as at  54 , to demonstrate engagement between screw head  41  and surface  53  and drawing down of material  3  into tight engagement with concrete  4  as at  56 ′. 
         [0065]    Anchor  1  is shown with a central axis D-D fully extended into a pre-drilled hole  5  with a nominal diameter  52  as shown. Such pre-drilled holes  5  are known to be somewhat irregular due to the hardness of the concrete itself and the usual procedures for on-site drilling. Anchor diameter in its uncompressed state  57  includes a cylindrical malleable core element  23 , preferably formed of copper or aluminium or other substantially non-resilient material, with a nominal diameter  50  surrounded by a sheath of resilient material  22  with lateral extremities  22   a  and  22   b.    
         [0066]    In  FIG. 4  screw threaded portion  11  and screw axis A-A are offset from the central axis of hole  5  so as to have direct engagement between thread teeth  49  and concrete  4  opposite anchor  1  as the anchor is driven laterally. For ease of illustration, a small gap is shown in  FIG. 4  between teeth  49  and concrete  4  as the wall of hole  5  on a construction site may include irregularities which do not conform to the shape of threaded portion  11 . 
         [0067]    Overall, hole diameter  52  is significantly greater than the outside diameter of threaded portion  11 . The lateral extremity  22   b  of sheath  22  engages material  3  as at B and is compressed, preferably out of round. Pilot hole  6  may be slightly larger than pre-drilled hole  5  but these are shown with the same diameter in this Figure for ease of illustration. Most preferably, pilot hole  6  and pre-drilled hole  5  are drilled at the same time on site using a standard size concrete drill, such as 3/16 inch. 
         [0068]    The nominal outside diameter  57  of anchor  1  is compressed against the concrete  4  by an amount  42 , leaving, in one embodiment, a remaining nominal diameter  44  and residual amount of sheath material as at  43  between the core and the wall C. Sheath amounts  42  and  43  may vary due to irregularities in the hole wall C and by the amount of compression applied by the advancement of screw  2 . Preferably, as with a number ten 3 ½ inch screw residual sheath amount  43  may be reduced to zero or near zero as the core  23  is driven laterally towards and to the side C of hole  5  and its shape is deformed circumferentially of hole  5 . Most preferably, residual amount  43  is zero through the larger portion of hole  5  as the core  23  is driven laterally completely through the outer sheath  23  of anchor  1  along a substantial portion of its length. Core  23  may engage wall C axially of the hole  5  or, most preferably, in an elongated helical form as shown in  FIG. 2  where the lead  24  of the core helix is more than, and preferably 3-6 or more times more than, the lead of screw  2 . 
         [0069]    Since elongated cavity  5   a  is narrower than the hole diameter  52  less anchor diameter  57 , male screw threads  11  cut corresponding female threads in to and, preferably, through sheath  22   a  within the elongated cavity as shown in  FIG. 4 . Thread outside diameter  59  is significantly greater than the diameter  52  of the hole  5  less the nominal anchor outside diameter  57  and, preferably, less the compression amount  42 . As shown in  FIG. 4  threads cut into core  23  by an depth  46  leaving a radial space of depth  47  between the unthreaded core  58  of screw  2  (diameter  51 ) and the internal edge of core  23 . Further, resilient sheath  22   a  will be axially compressed and, preferably, axially ruptured as its remaining diameter ( 57  less  42 ) is greater than the radial width of hole  5 , namely less than diameter  52  less screw diameter  59 . 
         [0070]    Most preferably, anchor diameter  57  is equal to or greater than the space  45  between the hole wall C and the unthreaded body cylinder of screw  2  resulting in significant circumferential deformation of anchor core  23  and rupturing of sheath  22  both between the screw  2  and the core  23  and between the core  23  and the wall C. Ruptured sheath material is driven into remaining spaces in the elongated cavity  5   a.    
         [0071]    In  FIG. 4   a  the preferred embodiment is shown without any sheath on anchor  1 , namely as a malleable non-resilient core  23  of copper, aluminium or like metal or equivalent. In this Figure anchor core  23  is shown in vertical section as being radially compressed at  550  in an cumulative fashion. Core  23  is compressed to wall C in a radial dimension as at  551 . Core  23  is also compressed to the screw  2  in a radial dimension as at  553  and around threads  11  as at  552  so as to maintain an axial core body of radial width  554 . As can been seen in  FIG. 4   a  core  23  is molded circumferentially, axially and radially to fill and overfill the spaces between screw unthreaded cylinder body of screw  2  resulting in an circumferential increase in the dimension of core  23  and full contact between core  23  and all surfaces of screw threaded portion  11 . 
         [0072]    In  FIG. 4   b  the preferred embodiment of the anchor  1  including a resilient sheath  22  is a further illustrated in vertical section. Compression of the core  23  ruptures resilient sheath  22  along both sides in an axial fashion, preferably including long helical contacts between the core  23  and the remaining sheath  23  and each of screw  2  and wall C. Resilient sheath  22  is deformed in to remaining elongated cavities on both sides of core  23  in full contact between the screw  2 , the wall C and the core  22 . 
         [0073]      FIGS. 5 through 9  show a sequence of plan views of a single screw (# 12 ) and anchor pair of the preferred embodiment. In each of these Figures the anchor and screw have been installed in concrete and then removed by reversal of turn about the screw axis and simple withdrawal from pre-drilled hole  5 . In each successive Figure anchor  1  is rotated axially about its length as at  601 . 
         [0074]    In  FIG. 5  anchor  1  is shown with an overall length  501 . Anchor  1  includes an area of full interaction with screw  2  over ruptured distance  502  plus a compressed length  504  and a relatively intact length  503 . The threaded length  11  of screw  2  corresponds to both ruptured length  502  and compressed length  504 . 
         [0075]    As screw point  513  engages with the elongated cavity  5   a  thread teeth  49  cut into and deform resilient sheath  22  circumferentially expanding the resilient material into the elongated space  5   a  while reducing its radial dimension as shown at  506  in comparison with relatively unchanged portion  505 . Advancement of the screw  2  cuts a series of lateral cuts  508  transverse to the screw axis and generally parallel to the angle of the screw thread. As advancement continues sheath  22  is ruptured between the core  23  and the screw  2  as shown at  512 . The anchor is twisted about its length into an expanded long lead helical shape as at  507  several to many times the lead length of threaded portion  11 . As screw  2  nears the bottom of pre-drilled hole  5  and the distal end  515  of anchor  1  its point  513  compresses the anchor less and less as in length  514  and rupturing deformations  509  gradually cease as at  511 . 
         [0076]    In  FIG. 6  anchor  1  is rotated by about 35 degrees axially from  FIG. 5 . Rupturing of sheath  22  has exposed core  23  to a combination of axial, lateral and circumferential deformation as at  507  to form a series of cut grooves  509  separating a series of lands  510  each of which is a general trapezoidal shape with a curved interior surface. 
         [0077]    A further rotation of anchor  1  by about 35 degrees is shown in  FIG. 7 . Anchor core  23  has been compressed entirely through resilient outer sheath  22  so as to come in direct contact with wall C under compression from screw  2  in the form of an elongated helical contact shape  701 . 
         [0078]    A still further rotation of anchor  1  is shown in  FIG. 8  wherein helical contact shape  701  is shown to extend over a substantial length of anchor  1  as at  801  while resilient outer sheath remains intact as at  802  at least insofar as the compressive side of the twisting. 
         [0079]    A yet further rotation of anchor  1  is shown in  FIG. 9  where helical contact shape  701  is shown to extend in the preferred embodiment to about a full rotation of screw  2  as by distance  901 . 
         [0080]    Variations of the above described anchor and anchoring system, method, structures and components will be apparent to those skilled in the art and such variations are considered to be within the scope of the present invention. Thus, modifications and alterations can be used in the system and method of the present invention without departing from the scope of the invention.