Patent Abstract:
The present invention relates to a thread clamping device including a plurality of movable nut segments around a threaded rod, and spring members flexibly holding the segments against the rod. The thread clamping device has a structure adapted to accommodate substantially planar outer surfaces of the segments engaging planar surfaces of the end housing of the device, leading to a more robust device and improved performance. Such a thread clamping device can advantageously be used as a component of a self-adjusting shrinkage compensation device, a coupler for threaded rods, hold-downs, among other uses. Various embodiments of the thread clamping device include a multi nut configuration, a quick release, and including mechanical or magnetic clip attachments.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from provisional patent application Ser. No. 60/629,664 filed Nov. 19, 2004 and provisional patent application Ser. No. 60/724,173 filed Oct. 6, 2005 pursuant to one or more of 35 U.S.C. §119, §120, §365. The entire contents of both cited provisional patent applications is incorporated herein by reference for all purposes. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     (none) 
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     This invention relates generally to the field of fastening devices and methods of use, more particularly, to threaded fasteners and thread clamping devices, and most particularly to thread clamping devices typically in combination with a bearing plate and other components as a self-adjusting shrinkage compensation device. 
     2. Description of the Prior Art 
     Wood is a major construction material in many places throughout the world. Wooden structures frequently use “tie-downs” to secure the wooden structure to its foundation, typically a concrete foundation. The function of tie-downs is thus to secure the wooden structure to its foundation in the presence of forces (perhaps substantial forces) tending to separate the structure from its foundation, such as high winds, seismic events or general shifting and settling of the surrounding earth. However, the wood typically used for construction often has considerable water content when initially installed and with time, the water evaporates and the wood dries out. In the process of drying out, the wood dimensionally shrinks. Approximately 4% shrinkage in the first year following construction of a wooden structure is not uncommon. This shrinkage commonly causes tie-downs to loosen, thereby making the structure more susceptible to damaging displacements in the presence of high winds, earthquakes among other external forces. Catastrophic damage may result. 
     A common method for implementing a tie-down is by imbedding a vertical threaded rod into the concrete of the foundation at the location where the wooden structure is to be joined to the foundation. The threaded rod generally resides within the walls of a single or multilevel structure as it passes from the concrete foundation up through each floor of the structure. Each floor is typically attached to the threaded rod by a separate tie-down. The primary fastener presently used to implement a tie-down is a standard “hex” nut. 
     If a standard nut is used, a space will typically develop under the standard nut and above the wood as the wood shrinks in dimension due to loss of water as described above. This space allows the tie-down (and structure) to move vertically when an overturning moment is applied to the structure as might occur, for example, during a seismic event, wind loading, among other circumstances. This motion of the structure with respect to the foundation, in turn, allows for deformation of the structural walls and may produce substantial damage that the tie-down is designed to prevent when functioning properly, that is when holding the structure securely in place on the foundation. Thus, a need exists in the art for a tie-down that is self-compensating, that is, a tie-down that maintains secure attachment of the structure to the foundation despite shrinkage of the wood. 
     As described in detail below, various embodiments of the present invention relate to thread clamping devices that include movable segments or “nut segments.” Some distinguishing characteristics of some embodiments of the present invention relate to flat (or planar) surfaces on the nut segments contacting flat surfaces on the top and/or end housings of the thread clamping device. Other shrinkage compensation devices having moveable segments include those of Sasaki (U.S. Pat. No. 5,081,811) and Taneichi (U.S. Pat. No. 6,007,284). Related art includes the following U.S. Pat. Nos. 3,695,139; 4,378,187; 4,974,888; 5,324,150; 5,427,488; 5,733,084; 5,988,965; 6,361,260; 6,406,240. However, these devices use frustoconical surfaces to support the nut segments. That is, the surfaces of the nut segment and the surface(s) of the housing that the nut segment is matched against are both conical. This is a disadvantageous structure since (among other reasons) two conical surfaces only match exactly at a single position and at any other position the two surfaces contact only at lines and points. This typically causes high stress concentrations along the lines and points of contact. Also, as the two non-planar surfaces slide relative to one another in a radial direction, the two surfaces are forced apart. This causes non-linear motion of the segments and can cause the segments to jam within the supporting top and bottom structures if insufficient clearance is not allowed. The flat surfaces employed on various embodiments of the present invention reduce or avoid these problems by employing flat surfaces and a structure such that no conical surfaces engage one another. These flat surfaces allow linear segment motion and are easily guided as they move between minimum and maximum radial positions. Also, the use of flat surfaces causes the stress loads to be distributed over the entire flat surface area and thus the local stresses remain relatively low within the thread clamping device pursuant to various embodiments of the present invention. This is true even when sufficient forces are applied so as to force the rod engaged by the thread clamping device to fail in tension. 
     In addition, a major construction cost is often the cost of labor. Therefore, installation of tie-downs in a manner that reduces labor costs is advantageous. For example, one common requirement when installing tie-downs is that threaded rods be connected together end to end. This is generally accomplished with a machined component having internal threads matching the threaded rod. Often, the threaded rod that comes out of the foundation of the structure is of very short length and another threaded rod is connected to this short rod using a connector. The connector is first turned and threaded onto the projecting end of rod protruding from the foundation and a second rod joined to the first by means of the connector. This requirement to connect two threaded rods is fairly common worldwide, and not specific to the construction industry. This process of connecting two rods, most often performed manually, is time consuming and labor intensive. Thus, a need exists in the art for devices and procedures for the efficient and rapid connection of threaded rods. 
     SUMMARY OF THE INVENTION 
     Accordingly and advantageously the present invention relates to thread clamping devices including as a component thereof nut segments having flat surfaces that engage corresponding surfaces of the devices end housing and top housing. This flat-against-flat structure provides advantages in strength, stability and durability among other advantages. Such thread clamping devices can be combined with other structures to provide a self-adjusting shrinkage compensation device, couplers for threaded rods, among other devices. Methods of employing such thread clamping devices are also described. 
     In view of the foregoing, in accordance with the various embodiments of the present invention, there is provided a Thread Clamping Device (“TCD”) which may be advantageously configured pursuant to some embodiments of the present invention to move axially along a threaded rod in one direction without rotation, and further, will not move axially in the opposite direction without rotation. Indeed, in one embodiment, the TCD when combined with a bracket or bearing plate may become a “tie-down” for use in construction or for other purposes. 
     A bearing plate to distribute the load and to prevent medium crushing is typically attached to the shrinking medium (such as wood) using any convenient attaching means such as traditional screws, nails, rivets, adhesives, among others. The bearing plate is typically sandwiched between the TCD and the shrinking medium. That is, the bearing plate is located between the TCD and the shrinking medium. For typical wooden construction, a threaded rod protrudes vertically from a concrete foundation and upwards through components of the wooden structure such as a wooden wall top plate for single level construction or floor plate for the above floors in multilevel construction. Thus, the TCD is “on” the rod above the bearing plate (where “on” denotes having the rod passing through the TCD and engaging therewith substantially as depicted in  FIG. 1 ). In this manner, as shrinkage of the wood occurs, the screws typically attaching the TCD to the top plate or floor plate would pull the TCD downward with respect to the threaded rod. Each time the TCD moves at least one half (½) thread downward, the TCD pursuant to some embodiments of the present invention has a structure that permits the TCD to internally ratchet and lock in place, thus preventing the TCD from moving upward with respect to the threaded rod (where the threaded rod itself cannot move as one end is buried in concrete during the construction process). Thus, the TCD maintains a tight tie-down despite shrinkage. 
     Additionally, in some embodiments of the present invention, a coupler comprising two TCDs is incorporated into a single package, back to back, to couple ends of two opposing threaded rods. Moreover, in yet other embodiments of the present invention, a quick release mechanism is included within the TCD which allows for fast and convenient release of TCD engagement from the threaded rod. Additionally, further embodiments of the present invention relate to methods of attachment of a TCD to commercially available “hold-downs”. Hold-downs attach to the shrinking medium (such as wood) and provide substantially the same load distribution function as a bearing plate. Mechanical and magnetic attachment methods of TCD to hold-downs are described. 
     Additionally, another advantage of the TCD over a traditional hex nut is that the TCD is capable of successfully engaging a damaged threaded rod, even when a substantial portion of the threads of the rod have been deformed or contaminated with material (such as concrete) to the point where the standard hex nut will jam. 
     These and other features and advantages of the present invention will be understood upon consideration of the following detailed description of the invention and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. The drawings herein are schematic, not to scale and the relative dimensions of various elements in the drawings are not to scale. 
       Some of the drawings depict threaded structures having internal threads, external threads or both. An artifact in the drawing program produces threads whose depiction in the figures may appear as lacking the true spiral structure of actual threads, although the thread profile is properly depicted. However, the threads are depicted herein for purposes of explaining various structures, embodiments and/or other features or uses in connection with the present invention, and the possible apparent absence of spirals in the depiction does not affect the description of the invention. 
       The techniques of the present invention can readily be understood by considering the following detailed description in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a typical threaded clamping device (TCD) and threaded rod. 
         FIG. 2  is a top view of a typical TCD. 
         FIG. 3  is a first side view of a typical TCD. 
         FIG. 4  is a second side view of a typical TCD. 
         FIG. 5  is a top perspective three dimensional view of a typical TCD disassembled. 
         FIG. 6  is a top view of a typical end housing. 
         FIG. 7  is a vertical sectional view of the end housing taken substantially along line  7 - 7  of  FIG. 6 . 
         FIG. 8  is a three dimensional top perspective view of a typical end housing depicting segments in different positions. 
         FIG. 9  is a three dimensional top perspective view of a typical end housing and four segments in the engaged position. 
         FIG. 10  is a three dimensional top perspective view of a typical end housing and four segments in the disengaged position. 
         FIG. 11  is a three dimensional top perspective view of a typical end housing and four segments. 
         FIG. 12  is a three dimensional top perspective view of a typical end housing and four segments of identical threaded phase. 
         FIG. 13  is a bottom perspective view of a typical TCD with top housing partially removed to reveal internal components. 
         FIG. 14  is a top perspective view of a typical TCD with top housing partially removed substantially along line  14 ,  18 - 14 ,  18  of  FIG. 2  to reveal internal components. 
         FIG. 15  is a three dimensional top perspective view of four nut segments, coil springs and a threaded rod. 
         FIG. 16  is an expanded outer perspective view of a single nut segment. 
         FIG. 17  is an expanded inner perspective view of a single nut segment. 
         FIG. 18  is a vertical cross sectional view of a typical TCD taken substantially along line  14 ,  18 - 14 ,  18  of  FIG. 2 , and threaded rod depicting motion direction. 
         FIG. 19  is a perspective view of a typical assembly of TCD, screws and bearing plate. 
         FIG. 20  is a top perspective view of a typical TCD and bearing plate installed on a structure. 
         FIG. 21  depicts a partial stud structure and foundation with TCD, bearing plate installed onto a threaded rod. 
         FIG. 22  is a top three dimensional perspective view of a coupler assembly and two threaded rods disengaged. 
         FIG. 23  is a top three dimensional perspective view of a coupler assembly engaged with two threaded rods in the installed position. 
         FIG. 23A  is a top view of a typical coupler. 
         FIG. 24  is a cut-away cross sectional top perspective view taken substantially along line  24 ,  25 - 24 ,  25  of  FIG. 23A , of a coupler assembly and internal components. 
         FIG. 25  is a cross sectional view taken substantially along line  24 ,  25 - 24 ,  25  of  FIG. 23A , of a coupler and engaged threaded rods. Also motion directions are shown. 
         FIG. 26  is a three dimensional exploded top perspective view of a TCD and components. 
         FIG. 27  is an outside perspective side view of a single nut segment. 
         FIG. 28  is an inside perspective side view of a single nut segment. 
         FIG. 29  is a three dimensional top perspective view of a typical multi-nut segment TCD. 
         FIG. 30  is a three dimensional exploded top perspective view of a multi-nut segment TCD and components. 
         FIG. 30A  is a top view of a typical multi-nut segment TCD. 
         FIG. 31  is a three dimensional top perspective view of a multi-nut segment TCD with housing partially removed substantially along line  31 ,  32 - 31 ,  32  of  FIG. 30A  to reveal internal components. 
         FIG. 32  is a cross sectional view taken substantially along line  31 ,  32 - 31 ,  32  of  FIG. 30A , of a typical multi-nut segment TCD also showing motion directions. 
         FIG. 33  is a three dimensional top perspective view of a typical TCD with quick release mechanism in the unreleased position. 
         FIG. 34  is a three dimensional top perspective view of a typical TCD with quick release mechanism in the released position. 
         FIG. 35  is a three dimensional exploded perspective view of a typical TCD and internal components. 
         FIG. 36  is a top view of a TCD with release mechanism showing the wire posts in the unreleased position. 
         FIG. 37  is a top view of a TCD with release mechanism showing the wire posts in the released position. 
         FIG. 38  is a bottom perspective view of TCD release mechanism where the housing and segments have been removed and the end housing is depicted in cross section. 
         FIG. 39  is a top three dimensional perspective view of TCD, connector clip, coupler, threaded rod, sheet metal hold-down and the wood structure before assembly. 
         FIG. 40  is a top three dimensional expanded perspective view of a typical TCD attached to a sheet metal hold-down. 
         FIG. 41  is a top perspective view of a TCD, wire clip, and cross sectional depiction of a magnetic bracket assembly. 
         FIG. 42  is a top three dimensional expanded perspective view of a typical TCD, wire clip, and magnetic bracket attached to a sheet metal hold-down. 
         FIG. 43  is a top three dimensional perspective view of a typical TCD, wire clip, magnetic bracket, studs, and tube connector with a portion thereof removed to show cross bolts and threaded rod. 
         FIG. 44  is a perspective view of another TCD embodiment and threaded rod. 
         FIG. 45  is a top view of a typical TCD. 
         FIG. 46  is a first side view of a typical TCD. 
         FIG. 47  is a second side view of a TCD. 
         FIG. 48  is a top perspective three dimensional view of a TCD disassembled. 
         FIG. 49  is a top view of an end housing. 
         FIG. 50  is a vertical sectioned view of the end housing taken substantially along line  50 - 50  of  FIG. 49 . 
         FIG. 51  is a three dimensional top perspective view of a typical end housing depicting segments in different positions. 
         FIG. 52  is a three dimensional top perspective view of a typical end housing and four segments having identical threaded phase. 
         FIG. 53  is a bottom perspective view of a typical TCD with top housing partially removed to reveal internal components. 
         FIG. 54  is a top perspective view of four nut segments, coil springs and a threaded rod. 
         FIG. 55  is an expanded outer perspective view of a single nut segment. 
         FIG. 56  is an expanded inner perspective view of a single nut segment. 
         FIG. 57  is a vertical cross sectional view taken substantially along line  57 - 57  of  FIG. 45 , of a typical TCD and threaded rod depicting motion direction. 
         FIG. 58  is a perspective view of a typical assembly of TCD, fasteners and bearing plate. 
         FIG. 59  is an expanded perspective view of a typical TCD and bearing plate installed on a structure. 
     
    
    
     DETAILED DESCRIPTION 
     After considering the following description, those skilled in the art will clearly realize that the teachings of the invention can be readily utilized in the construction of fasteners, thread clamping devices, self-adjusting shrinkage compensation devices, among other structures and devices. 
       FIG. 1  depicts, in perspective view, a typical thread clamping device (“TCD”)  10  engaged with a threaded rod  11  in accordance with some embodiments of the present invention.  FIGS. 2 ,  3  and  4  show top view, first side view and second side view respectively of TCD  10 .  FIG. 5  depicts a typical TCD  10  including a bottom end housing  12  (in short, “end housing”), nut segments  16 A,  16 B,  16 C and  16 D supported by end housing  12 , and a top end housing  14  (in short, “top housing”) engaging end housing  12  with one or more fasteners  22 . For economy of language, “nut segments” are also referred to as “segments.” Nut segments  16 A,  16 B,  16 C and  16 D are contained within top housing  14 . 
     To be concrete in our descriptions, we describe herein the typical case in which four nut segments are used. However, this is not an essential limitation of the present invention as a different number of segments can be used. At least two segments are needed to enable the segments to move radially with respect to the threaded rod. An even number of segments is advantageous in that segments are thus positioned diametrically opposed across the threaded rod, loading the rod symmetrically with the opposing segments tending to be loaded equally. This is advantageous from the standpoint of stress distribution. But odd numbers of segments are not inherently excluded. Using a larger number of segments is disadvantageous in that the manufacturing cost of the TCD is likely to be increased, but also included within the scope of the present invention. Four segments are considered to be most advantageous from considerations of functionality, manufacturability and assembly. 
     Two coil springs  18  and  20  are shown surrounding nut segments  16 A,  16 B,  16 C and  16 D. At least one spring (or equivalent means) is needed for compressing the nut segments against the threaded rod. While one or two is an advantageous number pursuant to some embodiments of the present invention, it is not an essential limitation and more can be used. 
     Fastener holes  24  are shown in the top view of  FIG. 2 . Mounting fasteners  26  are shown in  FIG. 19 . Mounting fastener  26  passing through fastener hole  24  and plate fastener hole  30  attaches TCD  10  to the shrinking medium  32  (typically wood) shown in  FIG. 20 . Upon installation of mounting fastener  26 , bearing plate  28  is also attached in that bearing plate  28  is sandwiched between TCD  10  and the shrinking medium  32 . 
     While the top housing  14  is typically shown with substantially cylindrical side surfaces, within the scope of the present invention, the top housing  14  of the TCD  10  also includes hexagonal, cubic, square or other substantially tubular configurations capable of accommodating threaded rod  11 , and which is capable of including the components and features of the TCD  10  as described herein. 
       FIG. 5  illustrates a complete TCD  10  with various parts depicted in exploded view. While  FIG. 5  shows two housing fasteners  22  (typically screws) to be mounted to end housing  12  so as to couple end housing  12  to top housing  14 , a larger or smaller number of fasteners  22  can also be used (depending in part upon the shape of TCD  10 ), within the scope of the present invention. Above end housing  12  is shown the lower coil spring  18  and above spring  18  is upper coil spring  20 . 
     Referring to  FIG. 5 , directly above spring  20  are shown nut segments  16 A,  16 B,  16 C and  16 D. Above segments  16 A,  16 B,  16 C and  16 D is shown top housing  14 . The parts depicted in  FIG. 5 , when assembled, comprise a complete TCD  10  pursuant to some embodiments of the present invention. 
     Also shown in  FIG. 5  are slots  38 , right inner bearing surfaces  40  and left inner bearing surfaces  41  in end housing  12 . There are, in this example, four slots  38 , four right inner bearing surfaces  40  and four left inner bearing surfaces  41  arranged in a substantially equidistant polar array relative to central axis  8  (see  FIG. 7 ). In TCD  10 , central axis  8  is substantially coincident with the axis of threaded rod  11 . 
     Inner bearing surfaces  40 ,  41  and slot  38  are defined as a “feature set”. Also slot  38 , right inner bearing surface  40  and left inner bearing surface  41  typically have an orientation of substantially 30 degrees relative to central axis  8 .  FIG. 5  also shows nut segment ribs  46 , segment upper spring groove  42 , segment lower spring groove  44 , left outer segment surface  48  and right outer segment surface  50 . There is generally one nut segment rib  46 , one segment upper spring groove  42 , one segment lower spring groove  44 , one inner sloping surface  36 , one left outer segment surface  48  and one right outer segment surface  50  for each segment  16 A,  16 B,  16 C and  16 D. In the following descriptions various configurations of nut segment assemblies will be described. For economy of language, we define segments  16 A,  16 B,  16 C and  16 D as shown in  FIG. 5  as Nut Segment Assembly I or “NSA-I.” 
       FIG. 6  is a top view of end housing  12 . Shown in top view are right inner bearing surface  40 , left inner bearing surface  41  and slot  38 . 
       FIG. 7  shows slot  38  and surfaces  40  and  41  as substantially parallel and at substantially a 30 degree angle relative to central axis  8 . In an assembled configuration (as depicted, for example, in  FIG. 5 ), segment surfaces  48  and  50  bear against end housing surfaces  40  and end housing surface  41  respectively for each of the four segments  16 A,  16 B,  16 C,  16 D. 
     In an assembled configuration as depicted in  FIG. 5  for example, left and right outer segment surfaces  48  and  50  respectively bear against right and left inner bearing surfaces  40  and  41  respectively for each of the four nut segments  16 A,  16 B,  16 C and  16 D. 
     To be precise in our language we intend “outer segment surface” to denote the outermost surface (s) on the lower portion of each segment (in the orientation of  FIG. 5 ), e.g.,  48  and  50  in  FIG. 5 . The phrase “outer segment surface” does not include any surface of any raised portion or “segment rib” such as denoted by  46  in  FIG. 5 . 
     Further, we intend “inner bearing surface” to denote the innermost surface (s) on the tapering, inner portion of the end housing  12 , e.g.,  40  and  41  in  FIG. 5 . The phrase “inner bearing surface” does not include any surface of any depressed portion or “slot” such as denoted by  38  in  FIG. 5 . 
     As discussed in detail elsewhere herein, an important feature of some embodiments of the present invention relates to the use of planar surfaces as both outer segment surfaces and inner bearing surfaces, in contrast to the prior art in which frusto-conical surfaces are used in comparable locations. Thus, comparisons of the present invention with prior art should focus on the inner bearing surfaces and the outer segment surfaces. Structure of any segment rib(s) and slot(s) are not relevant to this comparison. 
     For economy of language, we refer to nut segments  16 A- 16 D as “segments,” inner bearing surfaces  40  and  41  as “end housing surfaces,” and left and right outer segment surfaces  48  and  50  as “segment surfaces.” 
     The end housing surfaces  40  and  41  lie in a single plane separated into two (left and right) surfaces by slot  38 . Similarly, segment surfaces  48  and  50  lie in a single plane separated by nut segment rib  46 . 
       FIG. 8  is a three dimensional top perspective view of end housing  12  depicting only two nut segments  16 B and  16 C. Segment  16 C is shown in an engaged position and segment  16 B is shown in an extreme disengaged position. It can also be observed that nut segment rib  46  resides substantially within slot  38 . All nut segment ribs  46  reside in their respective slots  38 . 
       FIG. 9  is a three dimensional top perspective view of end housing  12  with all four nut segments  16 A,  16 B,  16 C and  16 D in the engaged position. In some embodiments of the present invention, nut segments  16 A,  16 B,  16 C and  16 D are comprised of four individual, substantially equal sized segments (defined as Nut Segment Assembly I, or NSA-I) held by one or more springs  20  and  18  such that each of the four individual segments engage to substantially the same axial position on threaded rod  11 . In this embodiment, the segments are not geometrically identical. The segments in this assembly are physically different in that different segments have different thread phase. Since a thread advances axially one thread pitch for each revolution of the thread, (that is, the thread follows a spiral path), each segment must have its respective thread at a different axial position than any of the other three segments. Each of the four segments has its thread phase one quarter of a thread pitch in difference than an adjoining segment. In these embodiments, segments  16 A,  16 B,  16 C and  16 D ratchet approximately at the same moment each time the rod  11  moves one thread pitch in the ratcheting direction with respect to TCD  10 . It should also be noted that by changing the sequence of the segments radially around threaded rod  11  the motion of the segments change relative to one another whereas the ratcheting of the segments will not occur at the same moment each time the rod  11  moves one thread pitch. 
     The effect of thread phase can most easily be understood by considering a standard hex nut cut along the central (thread) axis into 4 substantially equal pieces. Each piece contains a quarter a full revolution and, hence, a quarter of a thread phase different from the adjoining pieces. If the pieces were to be rejoined, they would screw down a threaded rod just as they did before the hex nut was cut so long as they are rejoined in the same sequence as before separation. However if you exchange any two of the pieces before rejoining (that is, alter the circumferential sequence, “scrambling” the sequence) the resulting assembly will jam when an attempt is made to screw this scrambled assembly down a threaded rod because the scrambled pieces are out of correct thread phase position. If one examines the inside thread spiral it will not be a uniform continuous thread spiral but will have discontinuous jumps at the rejoined boundaries. 
     However, in contrast interchanging the position of nut segments in a TCD allows different ratcheting options and, because the TCD segments move independently, the TCD will successfully screw and unscrew correctly when engaging a threaded rod of matching pitch diameter and thread pitch. 
       FIG. 10  is a three dimensional top perspective view of end housing  12  with all four nut segments  16 A,  16 B,  16 C and  16 D in the disengaged position. 
       FIG. 11  is a three dimensional top perspective view of end housing  12  and all four nut segments  16 A,  16 B,  16 C and  16 D with the positions of segments  16 B and  16 D exchanged from that depicted in  FIG. 10 . When viewed from the top (see  FIG. 2 ) and counting in a counter clockwise polar direction starting with segment  16 A, the sequence of  FIG. 11  is thus is  16 A,  16 D,  16 C and  16 B. This is identified as “Nut Segment Assembly II” or “NSA-II”. Unless otherwise noted, when describing any nut segment assembly, the sequence is presumed to be viewed from the top and enumerated in a counter clockwise direction. NSA-II is distinct from that depicted in  FIG. 9  (for example) which is  16 A,  16 B,  16 C,  16 D and denoted herein as “Nut Segment Assembly I” or “NSA-I.” 
       FIG. 12  is a three dimensional top perspective view of end housing  12 . Four nut segments are shown. In this configuration all segments are the same and denoted as  16 A. When viewed from top and counting in a counter clockwise polar direction starting with segment  16 A the sequence is  16 A,  16 A,  16 A and  16 A or NSA-III. This is different from nut segment assembly NSA-I where the sequence is  16 A,  16 B,  16 C and  16 D. NSA-III denotes an assembly of segments that are geometrically identical ( 16 A for example, but any of the other segments suffice for NSA-III), and also have the same thread phase. In the NSA-III configuration, the segments do not move in and out (towards and away from threaded rod  11 ) in unison. Thus, while the segments of NSA-I move in and out in unison, those of NSA-III do not, but both function as a TCD within the scope of the present invention. 
       FIG. 13  is a three dimensional bottom perspective view of a TCD with a portion of end housing  12  removed and portions of top housing  14  removed. Also nut segments  16 A and  16 C are depicted as having been sliced in half and one half removed for clarity. Also nut segment  16 D has been removed to reveal internal ramps  34  (“ramps”). Eight ramps are typically present in top housing  14  although not all are depicted in  FIG. 13 . However there could be more or less ramps depending on the size of the TCD among other factors. The ramps  34  are part of top housing  14  and are substantially parallel to end housing surfaces  40  and  41  shown in  FIG. 6  respectively. The ramps  34  are advantageously configured in pairs. Each ramp pair engages the inner sloping surface  36  of a single nut segment. There are typically four slots  38  in end housing  12 . Each ramp pair is typically arranged in a quadrature polar array about central axis  8  (that is, every 90 deg. about central axis  8 ). 
       FIG. 14  is a three dimensional top perspective view of a typical TCD with half of top housing  14  removed to reveal the internal components (except for segment  16 D which has also been removed). As can be seen, nut segments  16 A,  16 B,  16 C with upper coil spring  20  and lower coil spring  18  are located substantially within top housing  14  and end housing  12  of TCD  10 . Also shown in  FIG. 14  are inner sloping surfaces  36  bearing against ramps  34 . The surfaces of ramps  34  are in edge view in  FIG. 14 . 
       FIG. 15  is a three dimensional perspective view of nut segments encircled by lower and upper coil springs  18  and  20  respectively (referred to collectively as “coil springs”) and engaged to threaded rod  11 . As shown, coil springs  18  and  20  reside in grooves  44  and  42  respectively in each segment  16 A,  16 B,  16 C and  16 D in the assembled configuration. The segments are shown in  FIG. 9  in the same position with respect to threaded rod  11  as they are in  FIG. 15 . 
       FIG. 16  is an expanded three dimensional outer perspective view of one nut segment of TCD  10  in accordance with one embodiment of the present invention.  FIG. 16  depicts segment upper spring groove  42 , segment lower spring groove  44 , left outer segment surface  48 , right outer segment surface  50  and nut segment rib  46 . 
       FIG. 17  is an expanded three dimensional inner perspective view of one segment, such as  16 A,  16 B,  16 C or  16 D, of nut assembly NSA-I of TCD  10 . Also depicted in  FIG. 17  are inner sloping surface  36 , segment upper spring groove  42 , segment lower spring groove  44  and segment thread  52 . 
       FIG. 18  is a cross sectional view of a TCD engaged with threaded rod  11  in accordance with one embodiment of the present invention. Also shown in cross section in  FIG. 18  are any two opposing nut segments (such as  16 A and  16 C), lower coil spring  18 , upper coil spring  20 , end housing  12  and top housing  14 . Also shown are directions of motion  56  and  58 . 
       FIG. 19  is a top perspective exploded view of a typical assembly of TCD  10 , mounting fasteners  26 , fastener holes  24  and bearing plate  28 . Also shown is plate fastener hole  30  in bearing plate  28 . 
       FIG. 20  is a top perspective view of TCD  10 , mounting fasteners  26  and bearing plate  28  shown installed to the shrinking medium  32  and engaged to threaded rod  11 . This combination of TCD  10 , mounting fasteners  26  and bearing plate  28  comprise one embodiment of a self-adjusting shrinkage compensation device. 
       FIG. 21  depicts a partial stud structure including TCD  10  in the installed configuration.  FIG. 21  depicts a typical configuration of foundation  54 , threaded rod  11 , TCD  10  and bearing plate  28  shown installed to the shrinking medium  32  with screws or other mounting fasteners (not visible in  FIG. 21 ) and engaged to threaded rod  11 . 
       FIG. 44  is a perspective view of another embodiment of TCD  222  engaged to a threaded rod  11  in accordance with other embodiments of the present invention.  FIGS. 45 ,  46  and  47  show top view, first side view and second side view respectively of TCD  222 .  FIG. 48  depicts a disassembled view of TCD  222  including an end housing  210 , nut segments  214  supported by end housing  210 , and a top housing  212  engaging end housing  210  with one or more tabs  218 . Nut segments  214  are contained within top housing  212 . Surrounding nut segments  214  is a coil spring  20 . For embodiments only having a single coil spring such as that depicted in  FIG. 48 , we omit the distinction of upper coil spring and lower coil spring. TCD  222  is depicted as having four identical nut segments  24  and therefore has the ratcheting properties described above for NSA-III. 
       FIG. 45  also shows fastener holes  220 .  FIG. 58  shows mounting fasteners  224 . Mounting fastener  224  passing through fastener holes  220  and plate fastener holes  228  attaches TCD  222  to the shrinking medium  230  (typically wood) as shown in a typical configuration in  FIG. 59 . 
     Upon installation of mounting fastener  224 , bearing plate  226  is also attached in that bearing plate  226  is sandwiched between TCD  222  and the shrinking medium  230 . 
     To be concrete in our depictions, top housing  212  is shown with substantially cylindrical side surfaces, but this is not an essential limitation of the present invention. Within the scope of the present invention, top housing  212  of the TCD  222  can include hexagonal, cubic, square or any other substantially tubular configuration capable of accommodating threaded rod  11 , and which is capable of including the components and features of the TCD  222  or other embodiments. 
       FIG. 48  depicts TCD  222  with all parts shown in exploded view. To be concrete in our depiction, but not restrictive, four tabs  218  are shown on end housing  210  and four tab holes  216  are shown in top housing  212  that are used to couple top housing  212  to end housing  210 . There is generally one tab hole  216  for each tab  218 . However, within the scope of the present invention, depending upon the shape of TCD  222 , less or more tabs  218  and tab hole  216  pairs may be used. 
     Above end housing  210  is shown a coil spring  20 .  FIG. 48  shows nut segments  214  directly above coil spring  20 . Top housing  212  is shown above nut segments  214 . The parts depicted in  FIG. 48 , when assembled, comprise a complete TCD  222 . 
     Also shown in  FIG. 48  are slots  244 , right inner bearing surfaces  246  and left inner bearing surfaces  248  in end housing  210 . There are, in this example, four slots  244 , four right inner bearing surfaces  246  and four left inner bearing surfaces  248  arranged in an equidistant polar array relative to central axis  8  (see  FIG. 50 ) in TCD  222  in end housing  210 . TCD  222  has central axis  8  substantially coincident with the axis of threaded rod  11 . Inner bearing surfaces  246 ,  248  and slots  244  are defined as a feature set. Also slot  244 , right inner bearing surface  246  and left inner bearing surface  248  have an orientation of substantially  30  degrees relative to central axis  8 . 
       FIG. 48  also shows nut segment ribs  240 , segment spring groove  242 , left outer segment surface  238  and right outer segment surface  236 . There is one nut segment rib  240 , one segment spring groove  242 , one left outer segment surface  238  and one right outer segment surface  236  for each nut segment  214 . Various configurations of nut segment assemblies can be used within the scope of various embodiments of the present invention. 
       FIG. 49  is a top view of end housing  210 . Shown in top view are right and left inner bearing surfaces  246  and  248  and slot  244 . 
       FIG. 50  shows slot  244  and inner bearing surfaces  246  and  248  as substantially parallel and at substantially a 30 degree angle to central axis  8 . As depicted in  FIG. 48 , right and left outer segment surfaces  236  and  238  bear against right inner bearing surface  246  and left inner bearing surface  248  respectively for each of the four nut segments  214 . Inner bearing surfaces  246  and  248  lie in a single plane separated into two surfaces by slot  244 . Similarly, outer segment surfaces  236  and  238  lie in a single plane separated by nut segment rib  240 . 
       FIG. 51  is an upper perspective view of end housing  210  in which only two nut segments are shown,  214 A and  241 B. Segment  214 A is shown in an engaged position and segment  214 B is shown in an extreme disengaged position. It can also be observed that nut segment rib  240  resides substantially within slot  244 . All nut segment ribs  240  reside in their respective slots  244 . 
       FIG. 53  is a three dimensional bottom perspective view of a TCD with a portion of end housing  210  removed and portions of top housing  212  removed. Also one nut segment  214  has been removed for clarity revealing internal ramps  252  (right ramp),  253  (left ramp), and center rib  254 . Four right ramps  252 , four left ramps  253  and four center ribs  254  are depicted. However, this number is not an essential limitation of the present invention and there could be more or less depending on the size of the TCD and other factors. 
     The ramps  252  and  253  and center ribs  254  are part of top housing  212  and are parallel to respective end housing  210 , inner bearing surfaces  246  and  248 . The ramps  252  and  253  are typically configured in pairs. Each ramp pair engages a single nut segment top surface  234  (left top surface) and  235  (right top surface). Each ramp pair is arranged in a quadrature polar array about axis  8 . Also shown are four tabs  218  extending outwardly from end housing  210 . 
       FIG. 54  is a three dimensional perspective view of four nut segments  214  encircled by coil spring  20  comprising NSA-IV and engaged to threaded rod  11 . It is shown that spring  20  resides in groove  242  in each segment  214  respectively in the assembled configuration. The segments are shown in  FIG. 52  in the same position with respect to threaded rod  11  as in  FIG. 54 . 
       FIG. 55  is a three dimensional outer perspective view of one nut segment  214  in accordance with some embodiments of the present invention.  FIG. 55  depicts spring groove  242 , left outer segment surface  238 , right outer segment surface  236  and rib  240 .  FIG. 56  is a three dimensional inner perspective view of segment  214  of NSA-IV of TCD  222 . Also shown are nut segment top surfaces  234  and  235 , groove  242 , segment slot (or slot)  232  and segment thread  258 . 
       FIG. 57  is a cross sectional view of TCD  222  engaged with threaded rod  11  in accordance with some embodiments of the present invention. Also shown in cross section are any two opposing nut segments  214 , coil spring  20 , end housing  210  and top housing  212 . Also shown are motion directions  260  and  262 . Other features shown are tabs  218  and tab holes  216 . 
       FIG. 58  is a top perspective exploded view of TCD  222 , mounting fasteners  224  and bearing plate  226 . Also shown is plate fastener hole  228  in bearing plate  226  above shrinking medium  230 . 
       FIG. 59  is a top perspective view of TCD  222 , mounting fasteners  224  and bearing plate  226  shown installed to the shrinking medium  230  and engaged to threaded rod  11 . This combination of TCD  222 , fasteners  224  and bearing plate  226  comprise a self-adjusting shrinkage compensation device. 
     Referring to  FIG. 44  TCD  222  may be configured to move along threaded rod  11  in one direction without rotation of TCD  222 , and to not move in the opposite direction without rotation. The direction of motion whereby the TCD moves along threaded rod  11  without rotation shall be defined as the “ratcheting direction” and the opposite direction of motion as the “non-ratcheting direction”. In particular, in accordance with some embodiments of the present invention, the TCD may be configured to be engaged to threaded rod  11  such that a single downward hand movement of the TCD down the length of threaded rod  11  will correspondingly move TCD  222  in the ratcheting direction to a predetermined position on threaded rod  11 . Once in place, an upward hand movement of the TCD along the length of threaded rod  11  will be met with an opposing force such that the TCD will not move in the non-ratcheting direction. Rather, in order to move the TCD in the non-ratcheting direction of threaded rod  11  (typically the upward direction when used in wooden structures), the TCD is rotated along the threads of threaded rod  11 . The most common configuration with respect to a TCD engaged to a vertical threaded rod  11  is where (when viewed from above) a clockwise rotation of the TCD will advance the TCD downward with respect to threaded rod  11  and a counter-clock wise rotation of the TCD will advance the TCD upward with respect to threaded rod  11 . 
     It should be noted that while the above description is discussed with respect to upward and downward movements of the TCD along the length of threaded rod  11 , the direction of the movements of the TCD may be arbitrary depending upon, for example, the position of threaded rod  11  to which the TCD is engaged. However, if the TCD is only to be used in a vertical position, the weight of the segments, as directed along the surfaces of the housing, is typically sufficient to maintain adequate contact with the threaded rod. That is, for vertical operation the springs holding the nut segments against the threaded rod can become optional and can be omitted in some embodiments of the present invention. 
     In one embodiment, the TCD will ratchet whenever the TCD is moved along threaded rod  11  a minimum of one quarter (¼) of a thread pitch in the ratcheting direction. That is, when the TCD moves one quarter of a thread pitch one of the segment pairs will ratchet such that if forces try to move the nut assembly in the opposite non-ratcheting direction, a minimum of one nut segment will lock up and prevent motion in the opposite direction with respect to threaded rod  11 . To implement ¼ thread ratcheting four identical nut segments are arranged in all four positions (for example, nut segments  214  in NSA-III shown in  FIG. 52 ). 
     We describe detailed functioning of a TCD by reference to  FIG. 53 ,  FIG. 54 ,  FIG. 55 ,  FIG. 56  and  FIG. 57 . However, this is by way of illustration and not limitation as other TCD embodiments function in a similar manner. Differences in mode of operation for different TCD embodiments will be noted when present. 
     Referring to  FIGS. 52-57 , each of the four nut segments are driven upwards and outward at a 30 degree angle relative to central axis  8  as a result of nut segment top right and left surfaces  234  and  235  contacting ramps  252  and  253  as threaded rod  11  is pushed upward, for example, by seismic movement or wind that cause building overturning moments. Overturning moments typically cause a structure to move up and down with respect to its foundation. In this case with enough linear segment movement in directions  260  and/or movement  262  ( FIG. 57 ) nut segments  214  will completely disengage threaded rod  11  threads, and re-engage when the next rod thread moves into position to allow the four segments  214  to move toward rod  11  center and re-engage the threads of threaded rod  11 . 
     On the other hand, if the forces reverse in direction and threaded rod  11  is driven down (or TCD  222  driven up), nut segments  214  will be driven toward threaded rod  11 , and the threads will stay engaged as long as the downward force exists because of the inward radial force pushing segments  214  toward threaded rod  11 . The inward radial force is generated by (see  FIGS. 48 ,  49  and  50 ) the inner bearing surfaces  246  and  248  of end housing  210  contacting outer segment surfaces  238  and  236  respectively of a segment. Also to be considered is the outward radial force caused by the interaction of thread flanks of rod  11  against the flanks of segment thread  258 , the upper thread flank  258 A and lower thread flank  258 B, as depicted in  FIG. 56  for example. The inward radial force relative to axis  8  on segments  214  overcomes the outward radial force on segments  214  as long as the thread flanks  258 A and  258 B included angle remains 60 degrees (the standard flank angle for American Standard and Metric threads) and the angle of surfaces  246 ,  248 ,  238  and  236  remain substantially 30 degrees relative to axis  8  and the forces pulling rod  11  downward relative to TCD  222  (“reversing forces”) are in effect. The resultant inward forward force keeps the segments  214  engaged with threaded rod  11 . 
     Moreover, in one embodiment of the present invention, the material for nut segments  214  is advantageously chosen so as to have a yield point greater than or equal to that of the material of threaded rod  11 . Even when the yield points are similar for the materials of threaded rod  11  and segments  214 , and one segment  214  begins plastic deformation, as soon as threaded rod  11  moves, other segments  214  engage threaded rod  11  to overcome the strength of threaded rod  11 . 
     Alternatively, the material for nut segments  214 , may have a yield point substantially lower than that for threaded rod  11 , in which case threaded rod  11  will still fail (i.e., give way or break) before TCD  222  is compromised if there is sufficient length of thread engagement. 
     Moreover, coil spring  20  in some embodiments of the present invention is chosen so as to have sufficient tension to cause nut segments  214  to close around threaded rod  11  even in the case where the gravitational force is pulling nut segments  214  away from threaded rod  11  (for example, in the case where TCD  222  is inverted). 
     Referring to  FIG. 57 , the directional arrows  260  and  262  illustrate the manner in which nut segments  214  are configured to move when the TCD moves in the ratcheting direction with respect to threaded rod  11 . 
     Referring to  FIG. 48 ,  FIG. 49 , and  FIG. 51 , segments  214 , the engagement of ribs  240  and slots  244  provide linear guidance and transfer torque to nut segments  214 . The ribs  240  and slots  244  are advantageously configured to engage one another. Ribs  240  are on segments  214 . The matching slots  244  are on end housing  210 . When torque is applied to end housing  210  this torque is transmitted to segments  214  through slot  244  engaging rib  240 . Additionally, the ribs and slots also guide the radial motion engagement of TCD  222  to threaded rod  11 . Torque may be applied to end housing  210  through top housing  212 . 
     Referring to  FIGS. 46-53  and  FIG. 57  torque is transmitted from the top housing  212  to end housing  210  through tab holes  216  on top housing  212  engaging tabs  218  on end housing  210 . Torque is also transmitted directly from top housing to segments by center rib  254  ( FIG. 53 ) engaging segment slot  232 . The tab holes  216  and tabs  218  also perform a fastening function and facilitate automatic assembly of the top housing  212  to the end housing  210 . During final assembly the top housing tab holes  216  are aligned over the end housing tabs  218  and then the top housing  212  is pushed down over the end housing  210 . The tabs  218  force the top housing  210  wall outward over the tabs  218  until the downward motion of the top housing  210  allows the tabs  218  to snap into the tab holes  216 . The top housing  212  now cannot be removed from the end housing  210  without damage to the top housing  212 . This accomplishes the final assembly of the TCD  222  without the use of other fasteners. 
     Referring to  FIGS. 50 and 53  a conical lead-in  256  is advantageously used to guide the TCD  222  over the threaded rod  11  upon initial engagement of TCD  222  to the end of threaded rod  11 . The conical lead-in  256  causes the installation of TCD  222  to be quick and easy as the conical lead-in  256  guides the end of threaded rod  11  to the center of TCD  222  and to the bottom of nut segments  214 . The nut segments  214  then move as depicted  FIG. 57  as previously described. 
     With respect to top housing  212 , it should be noted that some embodiments of this invention call for torque to be applied to housing  212  to tighten or loosen TCD  222  with respect to threaded rod  11 . Application of torque is typically applied with a wrench engaging exterior surfaces of a housing equivalent to top housing  212 , optionally with the addition of exterior “flats” to facilitate gripping by a wrench or other device. The use of exterior flats is included within the scope of some embodiments of the present invention. 
     While the previous description related chiefly to TCD  222 , a similar description applies to TCD  10 . 
     Referring to  FIG. 1  TCD  10  may be configured to move along threaded rod  11  in one direction without rotation of TCD  10  (the ratcheting direction), and to not move in the opposite direction without rotation (the non-ratcheting direction). In particular, in accordance with some embodiments of the present invention, TCD  10  is configured to be engaged to threaded rod  11  such that a single downward hand movement of TCD  10  down the length of threaded rod  11  will correspondingly move TCD  10  in the ratcheting direction, to a predetermined position on threaded rod  11 . Once in place, an upward hand movement of TCD  10  along the length of threaded rod  11  will be met with an equal and opposite force such that TCD  10  will not move in the non-ratcheting direction. Rather, in order to move TCD  10  in the upward direction of threaded rod  11 , TCD  10  is rotated along the threads of threaded rod  11 . The most common configuration with respect to TCD  10  engaged to a vertical threaded rod  11  is where a clockwise rotation of TCD  10  will advance TCD  10  downward with respect to threaded rod  11  and a counter-clock wise rotation of TCD will advance TCD upward with respect to threaded rod  11 . 
     It should be noted that while the above description is discussed with respect to upward and downward hand movements of TCD  10  along the length of threaded rod  11 , the direction of the movements of TCD  10  may be arbitrary depending upon, for example, the position of threaded rod  11  to which TCD is engaged. 
     In one embodiment, TCD  10  will ratchet whenever TCD  10  is moved along threaded rod  11  a minimum of one half (½) of a thread pitch in the ratcheting direction. That is, when TCD  10  moves one half of a thread pitch one of the segment pairs will ratchet such that if forces try to move the nut assembly in the opposite non-ratcheting direction, one nut segment pair will lock up and prevent motion in the opposite direction with respect to threaded rod  11 . To implement ½ thread ratcheting segments  16 A,  16 B,  16 C and  16 D are arranged so that two opposing nut segments have threads that are 180 degrees out of thread phase from the remaining two opposing nut segments. Referring to  FIG. 11  it is shown this is accomplished by exchanging the position in nut segment assembly of any two non-adjoining nut segments, but two and only two can be exchanged in any one 4 segment assembly. (Thus  16 A and  16 C could be exchanged or  16 B and  16 D could be exchanged). In this configuration one or the other of the nut segment pairs  16 A and  16 C or  16 B and  16 D will ratchet each time the rod  11  moves one half a thread pitch in the ratcheting direction with respect to TCD  10 . 
     In particular, with respect to  FIG. 13  through  FIG. 18 , each of the four segments  16 A,  16 B,  16 C and  16 D are driven upwards and outward at a 30 degree angle relative to central axis  8  as a result of surface  36  ( FIGS. 13 and 14  show the edge of ramp  34 ) contacting ramp  34  as threaded rod  11  is pushed upward (for example, by seismic movement or wind that cause building overturning moments. Overturning moments cause a structure to move up and down with respect to its foundation.) In this case with enough linear segment movement  56  and/or movement  58  ( FIG. 18 ) segments  16 A,  16 B,  16 C and  16 D will completely disengage threaded rod  11  threads, and re-engage when the next rod thread moves into position to allow the four segments  16 A,  16 B,  16 C and  16 D to move toward rod  11  center and re-engage the threads of threaded rod  11 . 
     On the other hand, if the forces reverse in direction and threaded rod  11  is driven down (or TCD  10  driven up), nut segments  16 A,  16 B,  16 C and  16 D will be driven toward threaded rod  11 , and the threads will stay engaged as long as the downward force exists because of the inward radial force pushing segment  16 A,  16 B,  16 C and  16 D toward threaded rod  11 . The inward radial force is generated by (see  FIGS. 5 ,  6  and  7 ) surfaces  40  and  41  contacting surfaces  48  and  50  of end housing  12 . Also to be considered is the outward radial force caused by the interaction of thread flanks of rod  11  against segment thread  52  flank. The inward radial force relative to axis  8  on segments  16 A,  16 B,  16 C and  16 D overcomes the outward radial force on segments  16 A,  16 B,  16 C and  16 D as long as the thread flank included angle remains 60 degrees (the standard flank angle for American Standard and Metric threads) and the angle of surfaces  40 ,  41 ,  48  and  50  remain substantially 30 degrees relative to axis  8  and the reversing forces are in effect. The resultant inward forward force keeps the segments  16 A,  16 B,  16 C and  16 D engaged with threaded rod  11 . 
     Moreover, in some embodiments of the present invention, the material for nut segments  16 A,  16 B,  16 C and  16 D is chosen so as to have a yield point greater than or equal to the material for threaded rod  11 . Even when the yield points are similar between the materials for threaded rod  11  and segments  16 A,  16 B,  16 C and  16 D, and one of segment  16 A,  16 B,  16 C and  16 D start plastic deformation, as soon as threaded rod  11  moves, other segments  16 A,  16 B,  16 C and  16 D will start to engage to overcome the strength of threaded rod  11 . 
     Alternatively, the material for nut segments  16 A,  16 B,  16 C and  16 D, may have a yield point substantially lower than that for threaded rod  11 , in which case threaded rod  11  will still fail (i.e., give way or break off) before TCD  10  is compromised if there is sufficient length of thread engagement. 
     Moreover, coil springs  20  and  18  in one embodiment are configured to have sufficient tension to cause nut segments  16 A,  16 B,  16 C and  16 D to close around threaded rod  11  even in the case where the gravitational force is pulling nut segments  16 A,  16 B,  16 C and  16 D away from threaded rod  11  (for example, in the case where TCD  10  is inverted). Indeed, if nut segments  16 A,  16 B,  16 C and  16 D are not driven to threaded rod  11  center by coil springs  20  and  18  force, nut segments  16 A,  16 B,  16 C and  16 D, may move to the outside top housing  14  wall and remain in that position resulting in TCD  10  not engaging with threaded rod  11 . 
     The example shown in  FIG. 9  depicts that nut segments  16 A,  16 B,  16 C and  16 D are comprised of four individual, substantially equal sized segments (defined as nut segment assembly NSA-I) held together by coil spring  20  and  18  such that each of the four individual segments engage to substantially the same axial position on threaded rod  11 . In this embodiment each segment is not geometrically equal to the other. All four segments in this assembly are physically different in thread phase. Since a thread advances axially one thread pitch for each revolution of the thread, each segment must have its respective thread at a different axial position than any of the other three segments. Each segment has its thread phase one quarter of a thread pitch in difference than an adjoining segment. In this embodiment segments  16 A,  16 B,  16 C and  16 D will ratchet approximately at the same moment each time the rod  11  moves one thread pitch in the ratcheting direction with respect to TCD  10 . 
     Referring to the  FIG. 11 , the directional arrows  56  and  58  shown in  FIG. 18  illustrate the manner in which nut segments  16 A,  16 B,  16 C and  16 D are configured to move when TCD  10  moves in the ratcheting direction with respect to threaded rod  11 . 
     Referring to  FIG. 5  through  FIG. 10 ,  FIG. 15  and  FIG. 16  segments  16 A,  16 B,  16 C and  16 D, the engagement of ribs  46  and slots  38  provide linear guidance and torque to nut segments  16 A,  16 B,  16 C and  16 D. The ribs  46  and slots  38  are configured to engage each other. Ribs  46  are on segments  16 A,  16 B,  16 C and  16 D. The matching slots  38  are on end housing  12 . When torque is applied to end housing  12 , this torque is transmitted to segments  16 A,  16 B,  16 C and  16 D through slot  38  engaging rib  46 . Additionally, the ribs and slots also guide the radial motion engagement of TCD  10  to threaded rod  11 . Torque may be applied to end housing  12  through top housing  14  and fasteners  22 . 
     With respect to top housing  14 , it should be noted that some embodiments of this invention call for torque to be applied to housing  14  to tighten or loosen TCD  10  with respect to threaded rod  11 . Application of torque is typically applied with a wrench or other tool engaging exterior surfaces of a housing equivalent to top housing  14 , optionally with the addition of exterior flats. 
     The TCDs pursuant to some embodiments of the present invention can be used as the basis for a coupler, multi nut TCD, quick release TCD, TCD with mechanical clip attachment, TCD with magnetic attachment as described in the following. To be concrete in our description, we describe these structures and uses in connection chiefly with TCD  10 . But this is by way of illustration and not limitation as other embodiments of TCDs as described herein can also be used in connection with such devices. 
     Coupler. 
       FIGS. 22-28  depict embodiments of the present invention including an optional coupler or coupler assembly. 
       FIG. 22  is a top perspective view of coupler  60  with top threaded rod  76  and bottom threaded rod  74  depicted without the rods inserted into coupler  60 . 
       FIG. 23  is a top perspective view of coupler  60  with top threaded rod  76  and bottom threaded rod  74  depicted with rods  76  and  74  inserted into coupler  60 . 
       FIG. 24  is a sliced cross section view of the coupler assembly in accordance with some embodiments of the present invention. A housing body (or housing)  62  is engaged at each end portion to a respective end housing  64 . Each of the two end housings  64  are engaged to the respective ends of the housing body  62  by attachment fasteners  68  such as those described above. Additionally, also shown in the  FIG. 24  is pin  66  mounted through the housing body  62  and center plug  86  of the coupler  60 . Also shown are segments  72 A,  72 B and  72 C resting against the surfaces of end housing  64  and under surfaces of center plug  86 . A full complement of nut segments  72 A,  72 B,  72 C and  72 D plus springs  18  and  20  are defined as segment assembly NSA-V. Coil springs  18  and  20  are shown residing in segments  72 A,  72 B and  73 C. The coupler assembly is symmetrical about a plane that is perpendicular to the axis of threaded rods  74  and  76  ( FIG. 23 ) and bisects pin  66 . That is, if the rod axis is the y-axis of a normal right-handed coordinate system, the symmetry plane is the (x,z) plane. Segments  88 A,  88 B,  88 C and  88 D plus springs  18  and  20  are defined as assembly NSA-VI and are mirror images of segment assembly NSA-V in the coupler assembly  60 . See also  FIG. 26 . Segments  88  are physically the same as segments  72 . All features described above in the lower half of coupler  60  appear in the upper half as mirror images in coupler  60 . Also shown in  FIG. 24  is a center plug  86  which is configured to receive threaded rod  74  and rod  76  into hole  120 . Holes  120  in center plug  86  are advantageously slightly smaller in diameter than the outer diameter of the threaded rods. 
       FIG. 25  is a cross sectional view of the coupler assembly engaged with two threaded rods depicting movements of segments  72 A,  72 B,  72 C and  72 D and segments  88 A,  88 B,  88 C and  88 D and threaded rod movements pursuant to some embodiments of the present invention. Referring to the Figure, the directional arrows as shown illustrate the directional movements of the various components of the coupler  60 . 
       FIG. 26  is a three dimensional perspective view of the components of the coupler assembly and pin  66  exploded or disassembled. This illustration shows that the coupler is comprised of two sets of nut segments  72 A,  72 B,  72 C and  72 D and segments  88 A,  88 B,  88 C and  88 D, assembled back to back in housing  62 . Nut segments  72 A,  72 B,  72 C and  72 D comprise Nut Segment Assembly V (NSA-V) and are shown also exploded radially. Nut segments  88 A,  88 B,  88 C and  88 D comprise Nut Segment Assembly VI (NSA-VI) and are shown in their operating configuration. Nut segment assemblies V and VI are separated by center plug  86 . Center plug  86  is retained in housing body  62  by pin  66  which passes through hole  96  and hole  97 . At each end of plug  86  are bearing surfaces  104  and  106  separated by rib  80 . Surfaces  104 ,  106  and rib  80  comprise a feature set. There are eight sets of surfaces  104  and  106  and rib  80 . Four sets are at one end and four sets at the opposite end of plug  86 . The feature sets are geometrically arranged similarly as slot  38 , surface  40  and  41  shown in  FIG. 6  if viewed from the end of plug  86 . At each end of housing  62  end housings  64  are shown attachment fasteners  68 , clearance holes  94  and threaded hole  98  in housing  62 . 
       FIG. 27  is a three dimensional outer perspective view of one segment of segments  72 A,  72 B,  72 C and  72 D (NSA-V) and segments  88 A,  88 B,  88 C and  88 D (NSA-VI) shown in coupler  60 , quick release TCD  122  and multi nut TCD  100 . The “quick release” TCD and the “multi nut” “multi-nut segment” TCD are described in detail elsewhere herein. Shown in this illustration are upper spring groove  114 , lower spring groove  116 , left bearing surface  108 , right bearing surface  110 , rib  112  and slot  102 . 
       FIG. 28  is a three dimensional inner perspective view of one of the segments  72 A,  72 B,  72 C or  72 D or segments  88 A,  88 B,  88 C or  88 D as in coupler  60 , quick release TCD  122  or multi nut TCD  100 . Also shown are surface  90 , surface  92 , slot  102 , upper spring groove  114 , lower spring groove  116 , optional spring groove  118  and segment thread  52 . 
     Referring to  FIG. 23  and  FIG. 24 , coupler  60  can have a configuration so as to engage one or two threaded rods  74  and/or  76 . As with TCD  10 , coupler  60  may move along threaded rod  74  and/or  76  in one direction without rotation of coupler  60 , and not move in the opposite direction without rotation. For the purposes of describing coupler  60  and other embodiments the direction of motion whereby coupler moves along threaded rods  74  and/or  76  without rotation shall be defined as the ratcheting direction and the opposite direction of motion as the non-ratcheting direction. Threaded rod  74  and/or  76  may be inserted into opening  126  at either end of coupler  60 . The insertion may continue until rod  74  and/or  76  fills hole  120  in center plug  86 . Verification of sufficient insertion of rod  74  and/or  76  may be observed through inspections holes  140  and  141  see  FIGS. 22 ,  23 ,  24  and  26 ). Inspection holes  140  and  141  are aligned to allow viewing through housing body  62  and center plug  86 . Now referring to  FIG. 24 , hole  120  is advantageously taken to be slightly smaller than rod  74  and/or  76  in outside diameter to provide locking friction between center plug  86  and rods  74  and/or  76 . The housing body (or body)  62  is typically constructed of steel as is rod  74  and/or  76 . The center plug  86  is typically constructed of a polymer such as nylon so as to deform under the force of rod insertion and provide a locking friction to rod  74  and/or  76 . 
     In these embodiments, coupler  60  will typically ratchet whenever rod  74  and/or  76  is moved along a minimum of one (1) thread pitch in the ratcheting direction until rod  74  and/or  76  bottoms in hole  120 . More specifically referring to  FIG. 25 , the vertical arrows  78  and  84  illustrate the movement of threaded rod  74  and rod  76 , while the angled arrows  82  illustrate the movement of nut segments  72 A,  72 B,  72 C and  72 D and segments  88 A,  88 B,  88 C and  88 D inward and outward, respectively relative to the movement of the threaded rod  74  and rod  76 . 
     Comparing  FIG. 27  and  FIG. 16 , the similarities between segments  72 A,  72 B,  72 C,  72 D, segments  88 A,  88 B,  88 C and  88 D and segments  16 A,  16 B,  16 C and  16 D are shown as follows: In  FIG. 16  left outer segment surface  48 , right outer segment surface  50 , nut segment rib  46 , segment lower spring groove  44  and segment upper spring groove  42  are equivalent and identical in function to (now refer to  FIG. 27 ) surface  108 , surface  110 , rib  112 , lower spring groove  116  and upper spring groove  114 . 
     Comparing  FIG. 28  and to  FIG. 17 , the similarities between segments  72 A,  72 B,  72 C,  72 D, segments  88 A,  88 B,  88 C and  88 D and segments  16 A,  16 B,  16 C and  16 D are shown as follows: In  FIG. 17  inner sloping surface  36  is equivalent and identical in function to (now refer to  FIG. 28 ) surface  90  and surface  92 . Surfaces  90  and  92  are in the same plane separated by slot  102 . 
     The difference between segments  16 A,  16 B,  16 C and  16 D and segments  72 A,  72 B,  72 C,  72 D, segments  88 A,  88 B,  88 C,  88 D is that there is no slot  102  on surface  36  (see  FIG. 15 ). Segments  16 A,  16 B,  16 C and  16 D are not stackable (stackable means one can nest on top of the other), segments  72 A,  72 B,  72 C,  72 D, segments  88 A,  88 B,  88 C,  88 D are stackable. 
     In particular with respect to  FIGS. 24 ,  25  and  26 , each of the segments  72 A,  72 B,  72 C,  72 D, segments  88 A,  88 B,  88 C,  88 D are driven towards coupler  60  midpoint and outward at a 30 degree angle relative to central axis  8  as a result of surface  90  and  92  ( FIGS. 26 and 28 ) contacting surface  106  and  104  ( FIG. 26 ) as threaded rod  74  and/or  76  is pushed inward as shown in  FIG. 25  by arrows  78  and  84 . In this case with enough linear segment movement  82  ( FIG. 25 ) segments  72 A,  72 B,  72 C,  72 D, segments  88 A,  88 B,  88 C,  88 D will completely disengage threaded rod  74  and/or  76  threads, and re-engage when the next rod thread moves into position to allow segments  72 A,  72 B,  72 C,  72 D, segments  88 A,  88 B,  88 C,  88 D to move toward rod  74  and/or  76  center and re-engage the threads of threaded rod  74  and/or  76 . 
     On the other hand, if the forces reverse in direction and threaded rod  74  and/or  76  is axially pulled outward with respect to coupler  60 , segments  72 A,  72 B,  72 C,  72 D, segments  88 A,  88 B,  88 C,  88 D will be driven toward threaded rod  74  and/or  76  axis  8 , and the threads will stay engaged as long as the axial outward force exists because of the inward radial force pushing segments  72 A,  72 B,  72 C,  72 D, segments  88 A,  88 B,  88 C,  88 D toward threaded rod  74  and/or  76 . The inward radial force is generated by (see  FIGS. 26 and 27 ) surfaces  108  and  110  contacting surfaces  130  and  128  of end housing  64 . Also present is the outward radial force caused by the interaction of thread flanks of rod  74  and/or  76  against segment thread flank  52  ( FIG. 28 ). The inward radial force relative to axis  8  segments  72 A,  72 B,  72 C,  72 D, segments  88 A,  88 B,  88 C,  88 D overcomes the outward radial force on segments  72 A,  72 B,  72 C,  72 D, segments  88 A,  88 B,  88 C,  88 D as long as the thread-included flank angle remains approximately 60 degrees (the standard flank angle for American Standard and Metric threads) and the angle of surfaces  90 ,  92 ,  104 ,  106 ,  108 , 110 ,  128  and  130  remain substantially 30 degrees relative to axis  8  and the reversing forces are in effect. The resultant inward forward force keeps segments  72 A,  72 B,  72 C,  72 D, segments  88 A,  88 B,  88 C,  88 D engaged against threaded rod  74  and/or  76 . Referring to  FIG. 26  when torque is applied to end housing  64  this torque is transmitted to segments  72 A,  72 B,  72 C,  72 D and  88 A,  88 B,  88 C,  88 D through slot  132  engaging rib  112  ( FIG. 28 ) Additionally, the ribs and slots also guide the radial motion engagement of segments contained within coupler  60  to threaded rod  74  and/or  76 . 
     Multi Nut TCD. 
       FIG. 29  illustrates a perspective view of a multi-nut TCD  100  engaged to threaded rod  11  in accordance with some embodiments of the present invention. There is a housing body  136 , engaged at the upper end to top housing  138  and at the lower end to an end housing  134 . Each of the two housings  134  and  136  are attached to the respective ends of the housing body  136  by attachment fasteners  68  typically of the type as previously described. 
       FIG. 30  is a three dimensional perspective view of the components of TCD  100  assembly exploded or disassembled. This illustration shows TCD  100  comprised of two sets of nut segments  72 A,  72 B,  72 C and  72 D one on top (nested) of the other in housing  136 . The bottom nut segment assembly is defined as assembly  73  and the upper nut segment assembly is defined as assembly  75 . (Also referred to herein as “segment assemblies,” “nut assemblies” or “assemblies.”) Both nut segment assemblies  73  and  75  are supported at the bottom by end housing  134 . Each nut segment assembly  73  and  75  is encircled by springs  18  and  20  (not shown in  FIG. 30 ). Also a retaining ring  142  resides in a groove  148  (see  FIG. 32 ) in end housing  134 . 
       FIG. 31  is a sliced cross section view of TCD  100  in accordance with some embodiments of the present invention. Housing body  136  (depicted as sliced in half) is engaged at each end portion to end housing  134  (depicted as sliced in half) and at the other end a top housing  138  (depicted as sliced in half). End housing  134  and top housing  138  are attached to housing body  136  by attachment fasteners  68  such as those described above. Also shown are segment assemblies  73  and  75 . The segment assemblies are nested one on top of the other. The lower segment assembly  73  is supported by end housing  134  and the upper segment assembly  75  is supported by the upper surfaces of assembly  73 . Coil spring  20  is shown residing in segments  72 A,  72 B and  73 C. Coil spring  18  is also present as shown in  FIG. 15 , but cannot be seen in this  FIG. 31 . 
       FIG. 32  is a cross sectional view of TCD  100  engaged with threaded rod  11  illustrating movements of segments  72 A,  72 B,  72 C and  72 D, upper assembly  75  and lower assembly  73 , and threaded rod movements, in accordance with some embodiments of the present invention. Directional arrows  144  and  146  illustrate the directional movements of the various segments of TCD  100 . More specifically, the vertical arrow  146  illustrates the movement of the threaded rod  11 , while the angled arrows illustrate the movement of nut segments  72 A,  72 B,  72 C and  72 D and segments  88 A,  88 B,  88 C and  88 D inward and outward, respectively relative to the movement of the threaded rod  11 . 
     TCD  100  typically has a configuration so as to move along threaded rod  11  in one direction without rotation of TCD  100 , and to not move in the opposite direction without rotation. For the purposes of describing TCD  100  and related embodiments, the direction of motion whereby TCD moves along threaded rod  11  without rotation shall be defined as the ratcheting direction and the opposite direction of motion as the non-ratcheting direction. In particular, in accordance with some embodiments of the present invention, TCD  100  may be configured to be engaged to threaded rod  11  such that a single downward hand movement of TCD  100  down the length of threaded rod  11  will correspondingly move TCD  100  in the ratcheting direction to a predetermined position on threaded rod  11 . Once in place, an upward hand movement of TCD  100  along the length of threaded rod  11  will be met with an equal and opposite force such that TCD  100  will not move in the non-ratcheting direction. Rather, in order to move TCD  100  in the upward direction of threaded rod  11 , TCD  100  is rotated along the threads of threaded rod  11 . The most common configuration with respect to TCD  100  engaged to a vertical threaded rod  11  is that in which a clockwise rotation of TCD  100  will advance TCD  100  downward with respect to threaded rod  11  and a counter-clock wise rotation of TCD will advance TCD upward with respect to threaded rod  11 . 
     The segment assemblies  73  and  75  within TCD  100  operate with rod  11  in the same manner as NSA-II in TCD  10  described previously. TCD  10  is a single nut segment assembly NSA-II ( FIG. 15 ) where TCD  100  has two segment assemblies  73  and  75  ( FIG. 30 ) stacked or nested one on top of the other. Because assemblies  73  and  75  are stacked the top surfaces of each segment has a slot  102  ( FIGS. 27 and 28 ) in the top surfaces  90  and  92  to interface with rib  112 . The ability to stack the segment assemblies offers the ability to strengthen thread engagement and to offer more thread phasing options with respect to rod  11  engagement. By altering the thread phasing within a segment assembly and between segment assemblies in a stack one can cause the TCD to ratchet with less motion along the rod  11 . Although only two nut segment assemblies are shown stacked ( FIGS. 30 and 31 ), this is by way of illustration and not limitation as several such assemblies can be stacked within the scope of the present invention. 
     Quick Release TCD. 
       FIGS. 33-35  depict a typical TCD with quick release mechanism in accordance with some embodiments of the present invention. A TCD with release mechanism, denoted by  122 , includes a top cap (or cap)  162  mounted to the modified top housing (or top housing)  156  and secured by a crescent ring  160 . The top housing  156  is attached to housing body (or housing)  154  with fasteners  68 . Also shown is end housing  152  attached to the opposite end of housing body  154  with fasteners  68 . TCD  122  is similar to TCD  100  with the following modifications. Wire posts  164 A,  164 B,  164 C,  164 D have been added. The top cap  162  has been added above the top housing  156  and top housing  156  has been modified with a post, or top housing post,  124  such that cap  162  can rotate about the top housing post  124  and cause the wire posts  164 A,  164 B,  164 C,  164 D to rotate 90 degrees upon a rotation of the cap  162  by approximately 25 degrees. 
       FIG. 34  is a three dimensional perspective view of TCD  122  with release mechanism in the released position.  FIG. 35  is a three dimensional perspective view of the components of TCD  122  assembly exploded or disassembled. This illustration shows that TCD  122  is typically comprised of two sets of nut segments, one on top (nested) of the other in housing  154 . Both nut segment assemblies  73  and  75  are supported at the bottom by end housing  152 . Each segment assembly  73 ,  75  is encircled by springs  18  and  20  (not shown). Also a retaining ring  158  resides in groove  168  in top housing  156 . More specifically, in the unreleased (i.e., normal) position, the wavy portion of the wire posts  164 A,  164 B,  164 C,  164 D reside between nut segments  72 A,  72 B,  72 C and  72 D as shown in  FIG. 36 .  FIG. 36  is a top view of TCD with release mechanism in normal (unreleased) position.  FIG. 37  is a top view of TCD  122  with release mechanism in the release position. Referring to  FIGS. 36 and 37 , the four wire posts  164  A-D are positioned relatively equidistant around upper nut assembly  75 . 
     In the manner described above, in accordance with some embodiments of the present invention, by incorporating wire posts between upper and lower nut segment assemblies  73  and  75  of TCD  122 , TCD  122  may be configured for quick release from its engaged position. More specifically, pursuant to some embodiments, upper and lower nut segments  72 A,  72 B,  72 C and  72 D segment assemblies  73 ,  75  of TCD  122  are configured so that the space between the individual nut segments making up the nut segment assemblies,  72 A- 72 D in  FIG. 36 , is wide enough to accommodate the wire posts. Further, a top housing post  124  is included in top housing  156 , while holes are present in top housing  156  to accommodate wire posts. Similarly, in some embodiments, holes are also present in end housing  152  to provide a bearing for the other end of the wire posts  164 A- 164 D. 
       FIG. 38  illustrates how wire posts  164 A,  164 B,  164 C and  164 D are typically retained by top cap  162  and end housing  152 .  FIG. 38  is a bottom perspective view of TCD  122  with top housing  156 , housing  154  and nut segment assemblies  75  and  73  removed to clearly show the under side of cap  162  and specifically pocket  172 A,  172 B,  172 C and  172 D and pocket hole  174 B. Only pocket hole  174 B is visible in the figure along with wire post  164 B entering pocket hole  174 B. However each pocket has a corresponding pocket hole. Also shown is end housing.  152  sliced in half revealing post end bearings (“bearings”)  176 A,  176 C, and  176 D. In the fully assembled TCD  122  bearings  176 A,  176 B,  176 C and  176 D reside in holes  170 A,  170 B,  170 C and  170 D respectively. 
     Referring to  FIGS. 36 ,  37 ,  38 , as nut segments  72 A,  72 B,  72 C and  72 D move in and out due to the ratcheting operation described previously, the space between nut segments  72 A,  72 B,  72 C and  72 D gets larger and smaller. With the rotation of top cap  162  by approximately 25 degrees, the wire posts  164 A,  164 B,  164 C,  164 D in turn are configured to rotate through a rotation angle of approximately 90 degrees. In this case, the wavy portion of the wire posts  164 A,  164 B,  164 C,  164 D occupy approximately twice the space and prevent nut segments  72 A,  72 B,  72 C and  72 D from closing (i.e., returning to the center position and engaging rod  11 ) after they open during the normal TCD operation described above. Once open, the nut segments remain open and TCD  122  (with the release mechanism) may be readily removed from threaded rod  11 . 
     In the manner described above, in accordance with some embodiments of the present invention, by incorporating wire posts between upper and lower nut segment assemblies  73  and  75  of TCD  122 , TCD  122  may be configured for quick release from its engaged position. More specifically, in some embodiments, upper and lower nut segments  72 A,  72 B,  72 C and  72 D of TCD  122  have a configuration so that the space between nut segments becomes wide slot  178  shown in  FIG. 37  to accommodate the wire posts  164 A,  164 B,  164 C,  164 D, and further, a post  124  is present in top housing  156 , while holes  166 A,  166 B,  166 C,  166 D are present in top housing  156  to accommodate wire posts  164 A,  164 B,  164 C,  164 D. Similarly referring to  FIG. 38 , in some embodiments, holes  170 A,  170 B,  170 C,  170 D are present in end housing  152  to provide a support for post end bearing  176 A,  176 B,  176 C,  176 D. 
     TCD with Mechanical Clip Attachment. 
       FIG. 39  is a top perspective view of TCD  100  and coupler  60  in the pre-installed configuration (that is, the components are in the act of being installed). Shown in this illustration is a shrinking medium (typically a wood structure)  32 , a typical sheet metal commercial hold-down  186 , hold-down bolts (“bolts”)  188 , connector clip (“clip”)  184  and bottom and top threaded rods  74  and  76 . 
       FIG. 40  is a top perspective close up view of TCD  100 , clip  184  and hold-down  186  in the installed configuration. Also shown is end housing groove  190 . 
       FIG. 39  shows the installation of TCD  100 , connector clip  184  and coupler  60 . In this configuration coupler  60  engages rod  74  and rod  76  providing a solid connection between the rods. Hold-down  186  has already been installed to wood  32  with bolts  188 . Rod  76  is fed through hold-down hole  208  as it is installed in coupler  60 . TCD  100  is then slid down rod  76  until TCD  100  engages hold-down  186 . 
     Now referring to  FIG. 40 , clip  184  is then installed into end housing groove (“groove”)  190  in TCD end housing  134  shown in  FIG. 29  and under hold-down  186 . TCD  100  is now coupled to wood  32  through hold-down  186 . This combination of TCD  100 , hold-down  186 , clip  184  and threaded rods  74  and  76  comprise a self-adjusting shrinkage compensation device. 
     TCD with Magnetic Attachment. 
       FIG. 41  is a top perspective close up view of TCD  100 , wire clip  196 , groove  190 , and sliced one half view of magnet bracket (“bracket”)  194  and ring magnet  192 . Also shown is bracket slot (“slot”)  198 . Bracket assembly  200  is comprised of bracket  194  and ring magnet  192  bonded to the internal diameter of bracket  194 . 
       FIG. 42  is a top perspective close up view of TCD  100 , wire clip  196 , slot  198 , bracket assembly (or “magnetic bracket assembly”)  200 , hold-down  186  and threaded rod  76 .  FIG. 43  is a top perspective view of TCD  60 ,  100 , magnetic bracket assembly  200  and attaching wire clip  196 , steel tube (or other magnetic material) hold-down  206 , end plate  204 , cross bolts (“bolts”)  202  through wood  32 . Also shown is threaded rod  76 . 
       FIG. 43  is similar to the functionally shown in  FIG. 42 , except the sheet metal hold-down  186  shown in  FIG. 42  is changed to a commercially available steel tube  206  with welded end plate  204 . Tube  206  and end plate  204  are shown with a pie shaped slice removed to reveal attaching cross bolts  202 . 
       FIG. 41  shows TCD  100  and a sliced magnetic bracket assembly  200 . Bracket  194  also has a slot  198  through which wire clip  196  will pass when attaching assembly  200  to TCD  100 . 
       FIG. 42  shows TCD  100  after it has been installed to hold-down  186  by clip  196  passing through slot  198  except, instead of a clip  184  making the connection, there is a magnetic assembly  200  attached to TCD  100 . This combination of TCD  100 , hold-down  186 , clip  196 , bracket assembly  200  and threaded rods  74  and  76  comprise a self-adjusting shrinkage compensation device. 
       FIG. 43  shows TCD  100  after it has been installed to steel tube hold-down  204 / 206  by clip  196  passing through slot  198  except, instead of a clip  184  making the connection, there is a magnetic assembly  200  attached to TCD  100 .  FIG. 43  is similar to  FIG. 42  except that in  FIG. 42  the commercial hold-down is a steel tube with a welded end plate attached to wood  32  with bolts  202 . This combination of TCD  100 , hold-down  204 / 206 , clip  196 , bracket assembly  200  and threaded rods  74  and  76  comprise a self-adjusting shrinkage compensation device. 
     Various other modifications and alterations in the structure and method of operation of this invention will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Although the invention has been described in connection with specific embodiments, it should be understood that the invention should not be unduly limited to such specific embodiments. 
     Although various embodiments which incorporate the teachings of the present invention have been shown and described in detail herein, those skilled in the art can readily devise many other varied embodiments that still incorporate these teachings.

Technology Classification (CPC): 5