Abstract:
A method for fastening cementitious components together or for fastening a cementitious component to a non-cementitious component to form a structure. In a preferred embodiment, the apparatus is a screw having a hollow shaft from which threads protrude and a tip comprising a plurality of drilling teeth or a plurality of thread members that surround said central space, each of said thread members forming a two-dimensional spiral. In use, the invention is operated by screwing it into the cementitious components and then injecting an adhesive into the void created by the screwing step.

Description:
This application is a division of application Ser. No. 11/497,653 filed Jul. 31, 2006. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to an apparatus and method for fastening cementitious structural components, e.g., autoclaved aerated concrete or other cementitious components, together and for fastening other components to such cementitious structural components. In particular, the invention relates to a fastener for use in autoclaved aerated concrete and its use. 
     The background art is characterized by U.S. Pat. Nos. 86,935; 2,351,449; 2,603,319; 3,202,035; 3,361,481; 3,494,133; 4,092,814; 4,247,223; 4,696,354; 4,765,778; 5,002,435; 5,044,832; 5,085,026; 5,143,498; 5,531,553; 6,048,343; and 6,296,433; U.S. Patent Application No. 2002/0174606; 2004/0109738; and 2004/0161316; the disclosures of which patents and application are incorporated by reference as if fully set forth herein. The background art is also characterized by Japan Patent No. JP 2000-297588, German Patent No. DE 44 08 159, United Kingdom Patent No. GB 2 256 666 and Williamson, IBM Technical Disclosure Bulletin, February, 1962. 
     BRIEF SUMMARY OF THE INVENTION 
     One purpose of preferred embodiments of the invention is to allow the fastening of together of cementitious (e.g., autoclaved aerated concrete) structural components. Another purpose of preferred embodiments of the invention is to allow fastening other components to such cementitious structural components. One advantage of preferred embodiments of the invention is that it creates a void between the shaft of the screw and the wall of hole in the cementitious material into which it is being installed. Another advantage of preferred embodiments of the invention is that it allows the head of the screw to be countersunk. Another advantage of preferred embodiments of the invention is that it allows quick release of the component being fastened by the crane being used to lift the component into place. 
     One object of preferred embodiments of the invention is to facilitate the fastening together of autoclaved aerated concrete components. Another object of preferred embodiments of the invention is to fasten together two separate, distinct pieces of cementitious material to produce a monolithic, reinforced piece. Another object of preferred embodiments of the invention is to allow an adhesive to be used to hold the fastener in the hole it creates during the screwing step of the installation process. 
     The invention is a method for fastening cementitious components together or for fastening a cementitious component to a non-cementitious component to form a structure. The apparatus comprises a screw having a hollow shaft from which screw threads protrude, a screw tip comprising spiral tip threads and a head. In use, the invention is operated by screwing it into the cementitious components and then injecting an adhesive into the void created by the screwing step. 
     In a preferred embodiment, the fastener is for use in a cementitious material (e.g., autoclaved aerated concrete), said fastener comprising: a shaft comprising a first portion having a (preferably cylindrical) first shaft outer surface, a (preferably cylindrical) first shaft inner surface and a first shaft outside diameter and a second portion having a second shaft outer surface (preferably having a truncated conical shape), a second shaft inner surface (preferably having a truncated conical shape) and a second shaft outside diameter, said shaft having a longitudinal void therein; a longitudinal axis and two ends; a shaft thread that is attached to said first shaft outer surface and said second shaft outer surface, said shaft thread having a variable shaft thread outer diameter with a maximum extent; a tip that is attached to one end of said shaft, said tip having an upper tip outside diameter that is greater than said second shaft outside diameter, said tip comprising tip threads that are self-centering and self-setting, said tip threads comprising a plurality of thread members that are substantially triangular in cross section and that surround a substantially conical space that is in communication with said longitudinal void; and a head that is attached to the other end of said shaft. Preferably, said second shaft inner surface is rifled. Preferably, said head comprises grinding teeth and has a head outer diameter that is less than or equal to the maximum extent of said shaft thread outer diameter. Preferably, said shaft thread has holes therein that are aligned parallel with said longitudinal axis. Preferably, second shaft inner surface is provided with a plurality of spiraling ridges that extend from said second end to said first shaft inner surface. Preferably, said first portion has radial holes therein. Preferably, said first portion has radial holes therein. Preferably said head has a receiver for a bit, said receiver being in communication with said longitudinal void, said receiver having slots therein. 
     In yet another preferred embodiment, the fastener is for use in a cementitious material (e.g., autoclaved aerated concrete), said fastener comprising: a shaft comprising a first portion having a first shaft outer surface and a first shaft inner surface and a second portion having a second shaft outer surface and a second shaft inner surface, said shaft having a longitudinal void therein and two ends; a shaft thread that is attached to said first shaft outer surface and said second shaft outer surface; a tip that is attached to one end of said shaft, said tip comprising tip threads, said tip threads comprising a plurality of thread members that surround a space that is in communication with said longitudinal void; and a head that is attached to the other end of said shaft. 
     In a further embodiment, the fastener comprises a shaft having two ends, an outer surface and a longitudinal bore; a screw thread having a base that is attached to said outer surface along a curve traced on surface outer surface by its rotation past a point crossing a right section of said shaft at an oblique angle; a tip that is attached to one end of said shaft, said tip having a central space that is in communication with said longitudinal bore, said tip comprising a plurality of thread members that surround said central space, each of said thread members forming a two-dimensional spiral having a maximum outer diameter. Preferably, the fastener further comprises a head that is attached to the other end of said shaft. Preferably, said screw thread is perforated by a plurality of aligned holes. Preferably, said shaft comprises a first portion and a second portion, said first portion being cylindrical in shape and having a cylinder diameter and said second portion having the shape of a truncated cone with a base having a base diameter, and wherein said base diameter is greater than said cylinder diameter and approximately equal to said maximum outer diameter. Preferably, said longitudinal bore is rifled. Preferably, a plurality of holes extend from said longitudinal bore to said outer surface. Preferably, said head has a receiver that is capable of accepting a screwdriver or drill bit of polygonal cross section. Preferably, said head has a hole through which an adhesive is injectable. 
     In another preferred embodiment, the invention is a method for attaching a fastener to a cementitious material body (e.g., an autoclaved aerated concrete body), said method comprising: screwing the fastener into the body, the fastener being operative to penetrate a portion of the body and create a void therein by crushing the portion of the body into which it penetrates to produce crushed cementitious product, and moving said crushed cementitious product into a longitudinal void in the fastener; and when the fastener is seated in the autoclaved aerated concrete body, injecting a thermosetting plastic (e.g., epoxy) into said void through holes in the threads and head of the fastener. 
     In another preferred embodiment, the fastener comprises a shaft having two ends, an outer surface and a longitudinal bore; a screw thread having a base that is attached to said outer surface along a curve traced on said outer surface by its rotation past a point crossing a right section of said shaft at an oblique angle; a tip that is attached to one end of said shaft, said tip having a central space that is in communication with said longitudinal bore, said tip having a plurality of drilling teeth protruding from it that surround said central space, said tip having a maximum outer diameter. 
     In yet another preferred embodiment, the fastener joins two separate cementitious items without pre-drilling of a hole into the two separate cementitious items in which to insert the fastener, the fastener comprising: a shaft having two ends, an outer surface and a longitudinal bore; a screw thread having a base that is attached to said outer surface along a curve traced on said outer surface by its rotation past a point crossing a right section of said shaft at an oblique angle; and a tip that is attached to one end of said shaft, said tip having a central space that is in communication with said longitudinal bore, said tip comprising a plurality of thread members that surround said central space, each of said thread members forming a two-dimensional spiral having a maximum outer diameter; wherein said tip, said screw thread and said tip constitute a single component and said fastener is operative to join the two separate cementitious items to produce an adhered and reinforced single object. 
     In a further preferred embodiment, the invention is a method for fastening and adhering two cementitious material bodies to become one reinforced object without pre-drilling either of the cementitious material bodies, the method comprising: placing the cementitious material bodies adjacent to one another so that one of their surfaces abut; screwing a fastener having threads and a head into the cementitious material bodies, the fastener being operative to penetrate all of one of the cementitious material bodies and at least a portion of the other of the cementitious material bodies and create a void therein by crushing the portion of the cementitious material bodies into which it penetrates to produce crushed cementitious product, and moving said crushed cementitious product into a longitudinal void in the fastener; and when the fastener is seated in the cementitious material bodies, injecting a thermosetting plastic adhesive or a grout adhesive into said void through holes in the threads and head of the fastener; thereby fastening and adhering the two cementitious material bodies to become one reinforced object without pre-drilling by using only the fastener and the adhesive. 
     Further aspects of the invention will become apparent from consideration of the drawings and the ensuing description of preferred embodiments of the invention. A person skilled in the art will realize that other embodiments of the invention are possible and that the details of the invention can be modified in a number of respects, all without departing from the concept. Thus, the following drawings and description are to be regarded as illustrative in nature and not restrictive. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The features of the invention will be better understood by reference to the accompanying drawings which illustrate presently preferred embodiments of the invention. In the drawings: 
         FIG. 1  is a side view of a preferred embodiment of the invention. 
         FIG. 2  is a bottom plan view (looking up) of a preferred embodiment of the invention. 
         FIG. 3  is a bottom cross-sectional view (looking up) through section  3 - 3  on  FIG. 1 . 
         FIG. 4  is a top plan view of a preferred embodiment of the invention. 
         FIG. 5  is a cross-sectional view (looking up) through section  5 - 5  on  FIG. 1 . 
         FIG. 6  is side view of a preferred embodiment of the invention installed in cementitious material. In this view, the thread members are shown penetrating the cementitious material and the front half of the cementitious material (the half in front of a plane through the centerline of the invention) is removed for clarity. 
         FIG. 7  is a perspective view of a preferred embodiment of the invention of  FIG. 6  with a thermoset plastic being injected into the hole created by the invention. 
         FIG. 8  is a perspective view of an alternate embodiment of the invention having teeth along the bottom surface of the second portion. 
         FIG. 9  is a plan view (looking up) at the bottom of the alternate embodiment of  FIG. 7 . 
     
    
    
     The following reference numerals are used to indicate the parts and environment of the invention on the drawings:
           10  fastener, screw     12  shaft     14  helical rib, screw thread     16  tip     18  head     20  first portion     22  second portion     24  longitudinal void, longitudinal bore     26  first shaft outer surface     28  first shaft inner surface     32  second shaft outer surface     34  second shaft inner surface     38  spiraling ridges     40  thread members     42  space, central space     46  grinding teeth     48  longitudinal holes     50  radial holes     54  receiver     60  cementitious body, autoclaved aerated concrete body     62  parallel void     64  terminal slot     66  wall     70  rifling, spiral grooves     72  opening     74  drilling teeth     76  thermoset plastic, thermosetting plastic or grout     78  escaping air     80  bottom surface       

     DETAILED DESCRIPTION OF THE INVENTION 
     The disclosures of the following patent applications are incorporated by reference as if fully set forth herein: U.S. patent application Ser. No. 11/123,635, filed May 6, 2005, now pending; U.S. patent application Ser. No. 10/210,035, filed Jul. 23, 2003, now pending; U.S. patent application Ser. No. 09/784,848, filed Feb. 16, 2001, now abandoned; U.S. patent application Ser. No. 09/741,787, filed Dec. 21, 2000, now abandoned; and U.S. Provisional Patent Application No. 60/183,472, filed Feb. 18, 2000; the disclosures of which patent applications are incorporated by reference as if fully set forth herein. 
     Referring to  FIG. 1 , a preferred embodiment of fastener  10  is presented. In this embodiment, fastener  10  comprises shaft  12 , helical rib or screw thread  14  that projects from shaft  12 , tip  16  that is attached to a first end of shaft  12  and head  18  that is attached to a second end of shaft  12 . Shaft  12  preferably comprises first portion  20  and second portion  22  through which longitudinal void  24  extends, a shaft longitudinal axis and two ends. First portion  20  preferably has first shaft outer surface  26 , first shaft inner surface  28  and a first shaft outside diameter. 
     In a preferred embodiment, first portion  20  is cylindrical and screw thread  14  is attached at its base to outer surface  26  along a curve traced on outer surface  26  by its rotation past a point crossing a right section of first portion  20  at a (preferably constant) oblique angle. Preferably, screw thread  14  is self-starting and self-tapping in that the lower end of screw thread  14  extends outward from shaft  12  less far than the upper end of screw thread  14  does. In this embodiment, a line along the base of screw thread  14  forms a right-handed helix. Preferably, first shaft inner surface  28  is rifled (a plurality of spiral grooves  70  are provided) so that rotation of screw  10  urges cementation material crushed by the installation of screw  10  to move upward through longitudinal void  24 . 
     In a preferred embodiment, second portion  22  has a second shaft outer surface  32 , second shaft inner surface  34  (both of which preferably have the shape of a truncated cone) and a second shaft outside diameter. In a preferred embodiment, second shaft inner surface  34  is provided with a plurality of spiraling ridges  38  that extend from said second end to first shaft inner surface  28 . In a preferred embodiment, second portion  22  has radial holes  50  therein. In an alternative embodiment, first portion  20  has radial holes  50  therein. Radial holes  50  allow air to escape from longitudinal void  24  as it is filled with crushed cementitious material. 
     Screw thread  14  is attached to first shaft outer surface  26  and said second shaft outer surface. Preferably, screw thread  14  has a shaft thread outer diameter. In a preferred embodiment, shaft thread  14  is provided with holes  48  therein that are preferably aligned parallel with the shaft longitudinal axis. 
     Tip  16  has a tip upper outside diameter that is greater than the second shaft outside diameter. Tip  16  comprises tip threads  38  that are self-centering and self-setting, the tip threads  38  comprising a plurality of thread members  40  that are preferably substantially triangular in cross section and that surround space  42  that is in communication with longitudinal void  24 . In a preferred embodiment, space  42  is conical in shape and the bases of thread members  40  follow along a curve traced on the outer extent of space  42  by its rotation past a point crossing a right section of space  42  at a (preferably constant) oblique angle. In this embodiment, each of thread members  40  forms a conical helix, that is, a two-dimensional spiral on a conical surface, with the distance to the apex of the spiral an exponential function of the angle indicating direction from the axis of the spiral. In this embodiment, thread members  40  follow a curve which turns around a central axis, getting progressively closer to or farther from it, depending on which way one follows the curve. 
     Head  18  is preferably attached to the other end of shaft  12 . Head  18  preferably comprising grinding teeth  46  and has a head outer diameter that is less than of equal to the shaft thread outer diameter. Grinding teeth  46  are configured so that rotation of screw  10  during its installation grinds away the cementitious material beneath head  18 , thereby allowing head  18  to be countersunk. 
     Referring to  FIG. 2 , a bottom view of screw  10  is presented. Tip  16  is shown to comprise four tip threads  38 . One of the tip threads  38  preferably matches up with shaft thread  14 . 
     Referring to  FIG. 3 , a cross-sectional view through second portion  22  is presented at the section indicated on  FIG. 1 . In this view, the plurality of thread members  40  is visible. The plurality of thread members  40  move ACC material up and into longitudinal void  24 . In this preferred embodiment, the plurality of thread members  40  are closer together and narrower as they approach the mouth of longitudinal void  24 , thereby causing the pieces of ACC material created by screwing fastener  10  into ACC body  60  to be broken up into smaller pieces. 
     Referring to  FIG. 4 , a top view of a preferred embodiment of fastener  10  is presented. In this embodiment, head  18  has receiver  54  for accepting a bit (not shown). Preferably, receiver  54  is in communication with longitudinal void  24  and receiver  54  has slots  56  in its sides. Slots  56  allows air present in longitudinal void  24  to escape as crushed ACC material enters longitudinal void  24  during the screwing step of the installation process. 
     Referring to  FIG. 5 , a cross-sectional view through a preferred embodiment of head  18  is presented at the section indicated on  FIG. 1 . In this view, receiver  54  is shown in the center of head  18 . In this embodiment, longitudinal holes  48  are shown having a circular cross-sectional different shape. Opening  72  is also preferably provided in head  18 . Grinding teeth  46  are shown attached to head  18 . 
     Referring to  FIG. 6 , fastener  10  is shown installed in two cementitious material bodies  60 , preferably autoclaved aerated concrete (AAC) bodies  60 , that have been placed adjacent to one another so that one of their surfaces abut. Fastener  10  is screwed into AAC bodies  60  using a screw driver having a bit that fits in receiver  54 . Fastener  10  is operative to penetrate all of the first ACC body  60  and a portion of the other AAC body  60  and create parallel void  62  therein by crushing the portion of the AAC into which it penetrate to produce crushed cementitious product, and moving said crushed cementitious product into longitudinal void  24  in fastener  10 . When fastener  10  is seated in AAC bodies  60 , a thermosetting plastic (e.g., epoxy) or grout  76  is injected into parallel void  24  through longitudinal holes  48  in screw threads  14  and in head  18  of fastener  10  as illustrated in  FIG. 7 . During this operation, escaping air  78  discharges from opening  72 . 
     Injectors for thermoplastics and/or grouts having tubular nozzles that are capable of being inserted into holes, such as longitudinal holes  48 , are well known in the art. In this embodiment, excess thermosetting plastic or grout  76  discharges from opening  72  when parallel void  24  is full. In a preferred embodiment, after parallel void is full, the thermosetting plastic or grout is injected into parallel void during the removal of the tubular nozzles, thereby causing the excess thermosetting plastic or grout  76  that discharges from opening  72  to cover countersunk head  18 . The result is that, when installed, fastener  10  is hidden and a smooth finish is produced at the surface of ACC body  60 . 
     Parallel void  62  is created as fastener  10  is screwed into AAC body  60  because the outside diameter of second portion  22  is larger than the outer diameter of first portion  20 . Fastener  10  is preferably countersunk into ACC body  60 . This is preferably facilitated by providing grinding teeth  46  on the underside of head  18 . In preferred embodiments, head  18  is provided with terminal slot  64 , one surface of which is bound by screw thread  14 . In this embodiment, screw thread  14  terminates in head  18  by becoming horizontal, thereby rendering fastener  10  self-stopping during the screwing step of the installation process. 
     Screw threads  14  protrude into wall  66  of parallel void  62 , gripping ACC body  60  and holding fastener  10  in place until a thermosetting plastic or grout can be injected into parallel void  62 . This allows components of cementitious structures, such as AAC body  60 , to be held in place by a crane while fastener is screwed into AAC body  60 , and then released after the screwing step, because screw threads are configured to hold the components together until the thermosetting plastic or grout is injected at a later time, e.g., at the end of the day. In a preferred embodiment, thermosetting plastic or grout that has been injected into parallel void  62  hardens in longitudinal holes  48 , further anchoring fastener  10  in ACC body  60 . 
     Referring to  FIGS. 8 and 9 , an alternate embodiment of the invention is illustrated. In this embodiment, thread members  40  are not provided. Instead, drilling teeth  74  are provided along and protrude from bottom surface  80  of second portion  22 . Drilling teeth  74  serve to grind a hole in aerated autoclaved concrete body  60 . 
     Many variations of the invention will occur to those skilled in the art. Some variations do not include providing rifling  70  and radial holes  50 . Other variations do not call for providing thread members  40 . All such variations are intended to be within the scope and spirit of the invention. 
     Although some embodiments are shown to include certain features, the applicant specifically contemplate that any feature disclosed herein may be used together or in combination with any other feature on any embodiment of the invention. It is also contemplated that any feature may be specifically excluded from any embodiment of the invention.