Patent Publication Number: US-2022226679-A1

Title: Expansion bolt and pivot and swivel mechanism therefor

Description:
RELATED APPLICATIONS 
     This is a continuation of application Ser. No. 17/082,465, filed Oct. 28, 2020, which is incorporated by reference herein in its entirety. 
    
    
     FIELD OF INVENTION 
     The present invention relates to an expansion bolt, particularly for engaging holes in structures, typically to provide an anchor point for tethering a worker to the structures, and a pivot and swivel mechanism that can be used in an expansion bolt but which can also be used in other applications as well. 
     BACKGROUND 
     An exemplary prior art expansion bolt is disclosed in U.S. Pat. No. 7,357,363.  FIGS. 1 and 2  are taken from that patent, showing an expansion bolt  10  for engaging cylindrical holes, typically though not necessarily drilled or bored into concrete or other construction substrate. Referring to  FIG. 1 , as is common in the art the expansion bolt  10  includes a cable  12  having a center chock  13  at a distal end thereof. The center chock has an outer surface  13   a  and a cooperating outer chocks  16  and  17  provided to engage the center chock and to accommodate linear movement of the cable  12  along a longitudinal axis “L.” 
     The outer chock assembly  15  may include the two outer chocks referenced as  16  and  17 . Each outer chock is preferably attached to a collar  20  through a respective elongate control cable or rod  22  that permits moving the outer chock along the longitudinal axis with respect to the inner chock by pushing on the collar  20 . 
     The outer chocks  16  and  17  have inner surfaces  16   a  and  17   a  against which the outer surface  13   a  of the center chock  13  slides as a result of relative linear movement of the cable with respect to the collar  20 . Particularly, when the collar  20  is pulled against the bias of a compression spring  32  along the axis “L” in the direction of the arrow with respect to the cable, the outer chocks can move radially inwardly, to provide a contracted configuration of the expansion bolt; and conversely, when the collar is pushed back by the spring  32  in the opposite direction the outer chocks are forced radially outwardly, to provide an expanded configuration of the expansion bolt. When introduced into a hole, the outward expansion of the outer chocks is resisted by the inner surface of the hole, anchoring the expansion bolt in the hole; whereas the contracted configuration permits removing the expansion bolt from the hole. 
       FIG. 2  shows the center and outer chocks wedged in a hole  61 . In this configuration, the chocks cannot be pulled out from the hole under an axial (i.e., directed along the longitudinal axis) load, such as may be imposed by a construction worker who is tethered to the expansion bolt and who has fallen. Expansion bolts are designed to support axial loads of at least 900 pounds for this purpose. 
       FIG. 2  also shows a “cleaning bushing”  62  that is used for removing the expansion bolt from the hole once the chocks have been wedged into the hole. A hammer (not shown) is used to hammer on a punch to provide an impact force to the cleaning bushing, that knocks the center chock  14  forward relative to the outer chocks  16  and  17 , thereby loosening the grip between the outer chocks and the interior surface  64  of the hole sufficient to allow a user to pull the expansion bolt out of the hole. 
     Returning to  FIG. 1 , a loop  30  is provided at a proximal end of the cable  12  providing a hand-hold for a user of the expansion bolt  10 , and a means for moving the cable with respect to the collar  20 . A compression spring  32  is provided between the loop  30  and the collar  20 , to bias the device into its expanded configuration. The compression spring is important. Its bias protects against small amounts of slippage out of the hole that may otherwise occur as a result of the surface of the hole crumbling or deforming in response to the load applied to the loop  30 . Even very small amounts of slippage may lead to a catastrophic loss of grip with potentially very serious consequences. It also allows for single-handed operation of the expansion bolt. With the spring  32  in place and the expansion bolt grasped in one hand like a syringe, e.g., the index and middle fingers are positioned on the collar  20 , at “A 1 ” and “A 2 ” respectively, and the thumb in the loop  30  at “B,” the collar can be pulled back against the spring bias for inserting the expansion bolt in to the hole and simply released for chocking the expansion bolt snugly into the hole. 
     The cable  12  extends out of the hole and supports the load. Because it is a cable, it is flexible and can twist and bend elastically when it is loaded, to convert bending stress into axial stress and thereby to minimize the effects of what is known in the art as a “cross-loading” condition in which the expansion bolt would otherwise be placed under significant bending stress. 
     It is possible to use a “concrete anchor” to provide the anchoring function of an expansion bolt.  FIG. 3  shows a typical concrete “sleeve anchor”  2 . The sleeve anchor is intended to be installed in a hole which has been drilled into a concrete structure, such as a concrete floor or wall of a building. 
     The sleeve anchor has a housing  4  and a threaded bolt  6 , the shank of which is coaxially disposed inside the housing and is able to turn relative to the housing. 
     The housing  4  has a plurality of leaves (leaves  4   a ,  4   b  are shown) which are azimuthally separated, relative to a longitudinal axis “L” of the sleeve anchor, by corresponding slots (slot  4   c  is shown). 
     The bolt  6  has a frustoconically shaped distal end  7 . The bolt end  7  is sized to provide for expanding the housing  4  at the leaves as the bolt end is drawn up into the housing, as a result of turning the bolt. 
     Due to the presence of the slots between the leaves, the leaves are individually cantilever supported by a contiguous base  5  of the housing, and bend to allow for the expansion. The bending of the leaves is permanent, and the original configuration of the housing is not recoverable. Concrete anchors are intended to remain permanently in the structures in which they have been installed. 
     Exemplary prior art pivot and swivel mechanisms are shown and described in applicant&#39;s U.S. Pat. No. 8,424,638. Those prior art pivot and swivel mechanisms are particularly adapted for use as dedicated anchor points; whereas itis an object of the present invention to provide such a mechanism that has more general application, such as being a part of an easily removable and reusable expansion bolt. 
     SUMMARY 
     An expansion bolt and pivot and swivel mechanism therefor is disclosed herein. 
     The expansion bolt may have a base and a plurality of radially spreadable elongate elastic members cantileveredly projecting from the base at respective points of joinder to the base and terminating in respective spoons at respective points of joinder of the spoons, wherein the elongate elastic members have respective radially defined thicknesses at the points of joinder to the base that are substantially less than the corresponding thicknesses of the base, and respective radially defined thicknesses at the points of joinder of the spoons that are substantially less than the corresponding thicknesses of the spoons. 
     In one embodiment, the expansion bolt comprises a housing member, a central shaft member, and a biasing member. 
     The housing member defines a longitudinal axis, which defines axial directions parallel thereto and radial directions perpendicular thereto. The housing member has a base and a plurality of radially spreadable elongate elastic members cantileveredly projecting distally from the base at respective points of joinder of the elongate elastic members to the base, the elongate elastic members distally terminating in respective spoons at respective points of joinder of the spoons to the elongate elastic members. 
     The central shaft member extends through the housing member, and terminates at a distal end thereof in a wedge member. The spoons define a cavity for receiving the wedge member. The elongate elastic members provide for increasing elastically recoverable radial expansion of the cavity as a consequence of increasing relative axial translation of the wedge member into the cavity. 
     The biasing member is for biasing the shaft member relative to the housing member in the direction of the increasing relative translation. 
     The elongate elastic members have respective radially defined thicknesses at the points of joinder of the elongate elastic members to the base that are substantially less than the corresponding thicknesses of the base, and the elongate elastic members have respective radially defined thicknesses at the points of joinder of the spoons to the elongate elastic members that are substantially less than the corresponding thicknesses of the spoons. 
     The expansion bolt may further comprise a ring element, a swivel housing element, and a capping element, the ring element defining a closed or closeable attachment aperture and attached to a proximal end of the central shaft member, the ring element including two spaced apart leg members, the leg members including foot portions that turn to extend toward each other, the foot portions having respective, spaced-apart relatively enlarged ends, the swivel housing element providing for receiving and at least partially containing the ends of the foot portions within the swivel housing element so that the ring element can be substantially freely rotated about a pivot axis, the swivel housing element having a first open end, and the capping element adapted for interlocking with the first open end of the swivel housing element, the capping element having a bottom surface portion of radial symmetry about a swivel axis that is distinct from the pivot axis. 
     The ring element may be pivotally attached to the central shaft member, to allow for pivoting the ring element about radial axis. 
     Alternatively or in combination, the ring element may be swivelly attached to the central shaft member, to allow for pivoting the ring element about a longitudinal axis. 
     The wedge element may be swivelly attached to the central shaft member, to allow for swiveling the wedge member about a longitudinal axis. 
     The housing member may be formed as a single piece of material, and the housing member and the wedge member may be integrally formed together as a single piece of material. 
     The biasing member may comprise a spring, so that the bias comprises a spring-bias. 
     The pivot and swivel mechanism may have a ring element that includes two spaced apart leg members having foot portions that turn to extend toward each other, the foot portions having respective, spaced-apart relatively enlarged ends; a swivel housing element having an open end for receiving and at least partially containing the ends of the foot portions so that the ring element can be substantially freely rotated about a pivot axis; and a capping element adapted for interlocking with the open end of the swivel housing element; the capping element having a bottom surface portion of radial symmetry about a swivel axis that is distinct from the pivot axis. 
     In one embodiment, the pivot and swivel mechanism comprises a ring element, a swivel housing element, and a capping element. 
     The ring element defines a closed or closeable attachment aperture and includes two spaced apart leg members, the leg members including foot portions that turn to extend toward each other, the foot portions having respective, spaced-apart relatively enlarged ends. 
     The swivel housing element has a first open end for receiving and at least partially containing the ends of the foot portions within the swivel housing element so that the ring element can be substantially freely rotated about a pivot axis. 
     The capping element is adapted for interlocking with the first open end of the swivel housing element, the capping element having a bottom surface portion of radial symmetry about a swivel axis that is distinct from the pivot axis. 
     The swivel axis may be substantially perpendicular to the pivot axis. 
     The swivel housing element may have a second open end opposite the first open end, wherein the capping element has a hole therethrough, and the mechanism may further comprise a shaft extending through the hole in the capping element and the first and second open ends of the swivel housing element. 
     The shaft may be threaded proximate the second open end of the swivel housing element, and the mechanism further comprising a nut threaded onto the threads of the shaft. 
     The shaft may have a ledge for receiving the capping element over the bottom surface portion thereof. 
     The mechanism may further comprise an annular element concentrically disposed around the shaft and supporting the capping element. 
     Such annular element may be a flat washer, which may comprise Teflon. 
     It is to be understood that this summary is provided as a means of generally determining what follows in the drawings and detailed description and is not intended to limit the scope of the invention. Objects, features and advantages of the invention will be readily understood upon consideration of the following detailed description taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a pictorial elevation view of an exemplary prior art expansion bolt. 
         FIG. 2  is a cross-section of a portion of the expansion bolt of  FIG. 1 , shown installed in a hole. 
         FIG. 3  is a sectional elevation view of a typical prior art concrete sleeve anchor. 
         FIG. 4  is an isometric view of a preferred expansion bolt according to the present invention. 
         FIG. 5  is an exploded isometric view of the expansion bolt of  FIG. 4 . 
         FIG. 6  is an exploded isometric view of a first alternative expansion bolt according to the invention. 
         FIG. 7  is an isometric view of a worker connected to the expansion bolt of  FIG. 4  and is thereby tethered to a structure according to the present invention. 
         FIG. 8  is a side elevation of the expansion bolt of  FIG. 4  in a state of manipulation by which the expansion bolt is configured for insertion into a hole. 
         FIG. 9  is a cross-section of the expansion bolt of  FIGS. 4 and 8  being inserted into a hole. 
         FIG. 10  is the same as  FIG. 9  but with the expansion bolt in an anchoring configuration, seated in the hole. 
         FIG. 10A  is a detail view of a region of the expansion bolt of  FIG. 10 , showing bending of a leaf portion thereof. 
         FIG. 11  is a broken side view of the expansion bolt as shown in  FIG. 8  in the anchoring configuration shown in  FIG. 10 . 
         FIG. 12  is a cross-section of the expansion bolt as shown in  FIG. 11  taken a long a line  12 - 12  thereof. 
         FIG. 13  is a cross-section of the expansion bolt as shown in  FIG. 11  taken a long a line  13 - 13  thereof. 
         FIG. 14  is an exploded isometric view of a second alternative expansion bolt according to the invention. 
         FIG. 15  is an exploded isometric view of a portion of a pivot and swivel mechanism according to the present invention. 
         FIG. 16  is a front broken cross-section of the pivot and swivel mechanism of  FIG. 15  as provided in the expansion bolt of  FIG. 5 , taken along a line  16 - 16  thereof. 
         FIG. 17  is a side broken cross-section of the pivot and swivel mechanism of  FIG. 15  as provided in the expansion bolt of  FIG. 5 , taken along a line  17 - 17  thereof. 
         FIG. 18  is an isometric cross-section of the expansion bolt of  FIGS. 4 and 5 . 
         FIG. 19  is a broken isometric cross-section of the expansion bolt of  FIG. 5 , viewed from a different direction than that of  FIG. 18 . 
         FIG. 20  is an isometric view of a third alternative expansion bolt according to the present invention. 
         FIG. 21  is a cross-sectional side elevation of the expansion bolt of  FIG. 20  installed in a hole. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Embodiments of the present invention may be used to provide for the advantages of a prior art expansion bolt such as that disclosed in the &#39;363 patent described above in a simplified and therefore cost-reduced configuration, and that does not require a tool for removal. In addition or in the alternative, embodiments of the present invention may be used to provide for the advantages of the more simply constructed prior art concrete anchor in a reusable configuration. Thus, embodiments of the present invention may be used either as expansion bolts or concrete anchors, and they may have other uses as well. Such uses may include, but are not limited to, supporting workers who are performing maintenance or construction work, and providing fall protection to such workers. 
       FIGS. 4 and 5  show a preferred expansion bolt  100  according to the invention that provides for all the aforementioned advantages over the prior art. 
     With particular reference to  FIG. 5 , the expansion bolt  100  includes a central shaft  112  terminating, at a proximal end “PE” of the central shaft, in a pivot and swivel mechanism  150 , and at a distal end, a wedge element  126 . The proximal end PE of the central shaft ultimately terminates in a capturing tip CT 1  which is not shown in  FIG. 5  but is discussed in connection with  FIG. 17 . 
     The central shaft  112  is coaxially received through a central hole  114   a  in a cap  114 , through a housing  116 . The central hole  114   a  is large enough to loosely or slidable receive a shank  112   b  of the central shaft  112 , but not so large as to allow passage of the wedge element  126 . 
     The housing  116  houses a spring  120  which biases the housing  116  relative to the central shaft  112  during use of the device as will be explained further below. The housing  116  is captured between the cap  114  and the wedge element  126 . The housing  116  has a base portion  116   a  and, as referenced in  FIG. 4 , a plurality of leaves “LV” (LVa, LVb are shown) depending from the base portion. The leaves are separated by first slots “SL 1 ,” (two of these first slots SL 1 a, SL 1 b are shown). The leaves project as cantilevers from the base portion at respective points of joinder “PJ LV-B ” (also referenced in  FIG. 9 ) of the leaves to the base portion, and the first slots are defined by and between the leaves. In the preferred embodiment there: are 3 leaves and 3 of the first slots SL 1  symmetrically radially disposed about a longitudinal axis “L 1 ” (referenced in  FIG. 8 ) of the expansion bolt  100 , i.e., a 3-fold symmetry in this particular embodiment. But the number and spacing of the leaves can be varied, and radial symmetry is not essential either. 
     The leaves are also preferably perforated, such as with second slots “SL 2 ” that, along with the first slots SL 1 , provide migration paths for dust particles when the expansion bolt is installed in a hole. 
     The leaves LV distally terminate in respective “spoons” “SP,” which are connected to the leaves at respective points of joinder “PJ LV-SP ” (also referenced in  FIG. 9 ) of the spoons to the leaves. The aforementioned second slots SL 2  may also be used to assist to provide bending flexibility to the leaves, which is also preferably otherwise provided by making them thinner than the spoons as discussed further below. 
       FIG. 6  shows a first alternative expansion bolt  200 , which is the same as the expansion bolt  100  except the housing  116  is replaced with a housing  216  that replaces the leaves LV of the embodiment  100  with an equivalent number of discrete elongate elastic members  225 . The discrete elongate elastic members  225  may be, without implying any material or shape limitation, rods, wires, or cables, any of which may be woven or non-woven. As for the embodiment  100 , in the preferred embodiment  200  there are three of the discrete members  225 , one for each of the three spoons SP. The spoons SP may be the same in the embodiment  200  as in the embodiment  100  but are preferably modified at the points of joinder connections with the elongate members  225  as shown. 
     For purposes herein, the term “elongate elastic member” is intended to be generic for both the leaves LV of the embodiment  100  and the members  225  of the embodiment  200 . The term “elastic” is intended herein to have its ordinary engineering meaning. 
     Returning to  FIG. 5 , expansion bolts according to the invention preferably include a tethering ring, here referenced as  140 , for connecting, to the expansion bolt, an additional article of hardware such as a carabiner, through a retaining aperture “A” defined by the tethering ring, such as shown in  FIG. 7 . The tethering ring may be provided in a standard form known in the fall-protection art as a “D-ring” but this is not essential. As shown, the aperture A would be circular over 360 degrees of arc; whereas in a D-ring, the aperture A would be circular over more than 180 degrees of arc, but less than 270 degrees of arc. Preferably, the radius of the circle defined by the aperture A is between 1.5 and 3.0 inches, more preferably between 2.0 and 2.5 inches, more preferably still between 2.20-2.30 inches, and most preferably 2.25 inches. 
     For connection security, the retaining aperture A should be “closed” or “closeable.” For purposes herein, an aperture is “closeable” when it can be placed in a closed configuration, and an aperture is in a closed configuration for purposes herein when it is contiguously surrounded (360 degrees) by structure, so that a ring (which by this same definition also has a closed aperture) encircling any portion of the structure and passing through the aperture could not be removed from the aperture without changing the configuration of the device. As shown in preferred embodiments, the retaining aperture A is permanently closed; whereas the corresponding apertures defined by the carabiners  42  and  46  shown in  FIG. 7  are closeable, and are shown in closed configurations. 
       FIG. 8  shows an example of how the expansion bolt  100  may be manipulated to place it in a minimum diameter configuration, measured radially of the longitudinal axis L 1 , so that it can be inserted into a hole with the assistance of the cap  114 . 
     Such a hole  9   a  in a structure  9  is shown in  FIGS. 9 and 10 , in which the embodiment  100  is shown. For reference in both  FIGS. 9 and 10 , the longitudinal axis L 1  of the expansion bolt  100  shown in  FIG. 8  is coincident with a longitudinal axis “L 2 ” of the hole  9   a.    
     The hole  9   a  may be adapted in advance for receiving the expansion bolt; or the expansion bolt nay be adapted in advance for use in an existing hole. Typically, the hole  9   a  is a drilled hole and is therefore substantially cylindrical. But the hole  9   a  could be a cast or existing hole, and the hole  9   a  need not be cylindrical; the expansion bolt could easily be adapted for use in a square (using four leaves) or triangular shaped hole, for example. In all cases, however, the hole will have a longitudinal axis L 2  which, in the case of a cylindrical hole, is the cylindrical axis of the hole. The longitudinal axis L 2  of the hole aligns substantially with the longitudinal axis L 1  of the expansion bolt as the expansion bolt  10  is inserted into the hole. 
     Returning to  FIG. 8 , the cap  114  has a flange portion  114   b  with an undersurface “US,” and a reduced diameter body portion  114   c , which is reduced in diameter relative to the flange portion, the diameters measured radial to the longitudinal axis L 1 . 
     In the example, a user&#39;s thumb may be positioned to press down on the top of the pivot and swivel mechanism  150 , and the user&#39;s index and middle fingers placed on an under-surface “US” of the flange portion  114   b  for pulling on the flange portion, against a spring bias provided by the spring  120 . 
       FIG. 9  shows the expansion bolt  100  partially inserted into the hole  9   a . The expansion bolt is held as shown in  FIG. 8 , and the spring  120  is compressed as a consequence of being captured between a ledge “LG 116 ” of the housing  116  and a bottom or distal portion of the pivot and swivel mechanism  150 . The expansion bolt is thus caused to adopt a contracted, minimal diameter configuration, measured radially from the longitudinal axis L 1 , so that the expansion bolt can be inserted into the hole  9   a  with the assistance of the cap  114 . 
       FIG. 10  shows the expansion bolt after it has been seated in the hole and the user has let go of it. The spring  120  is allowed to extend and thereby force the central shaft  112  upwardly relative to the housing  116 , drawing the wedge member  126  into a cavity “CVT” defined interiorly between the spoons SP of the housing, thereby radially spreading the spoons so as to produce a larger diameter, expanded configuration of the expansion bolt, which by forcing the spoons against the interior surface of the hole to anchor the expansion bolt in the hole defines an “anchoring configuration” of the expansion bolt in which the expansion bolt is both seated in the hole and expanded. 
     The spring  120  may be a coiled compression spring such as shown in, e.g.,  FIGS. 5 and 6 , but other spring configurations could be used to achieve the same results. 
       FIG. 10  also shows that in the anchoring configuration of the expansion bolt, the leaves LV are caused to bend into a slight “S” configuration by their reaction to the hole, in the region indicated at “S LV ” (see  FIG. 10A ) as a consequence of the spoons SP moving radially outwardly in response to receiving the wedge member  126 , closing the slight gap between the spoons and the surface of the hole  9   a  that can be seen in  FIG. 9 , and as a consequence of the fact that the outer surfaces of the spoons, “OS SP ” as referenced in  FIG. 9 , are substantially parallel to the surface of the hole, before being expanded against the surface of the hole as shown in  FIG. 10 . 
     The wedge element  126  is typically frustoconical, as defined by its outer surface  126   a . In that case, as suggested by comparison of  FIGS. 12 and 13 , the inside surfaces “IS SP ” of the spoons SP are preferably cylindrical (not tapered), with radial curvature that matches that of the wedge element  126  where the wedge element is widest, nearest the distal end “DE” of the central shaft  112  (see  FIG. 5 ), and which is therefore less than that of the wedge element where the wedge element is narrowest, farthest from the end DE. This provides for maximum surface contact between the spoons and the wedge element when the expansion bolt is anchored in the hole. 
     As can be seen in  FIGS. 9 and 10 , the cylindrical inner surfaces IS SP  identified in  FIGS. 12 and 13  are angled a small amount from the longitudinal axis L 1 , such as by about 3-5 degrees. 
     Staying with  FIG. 5 , the wedge element  126  need not be frustoconical. For example, it could be configured as a three-sided pyramid (or as another example, a two-sided wedge), for engaging three (or, in the case of a two-sided wedge, two) spoons having planar inner surfaces IS SP . The wedge element  126  may be integrally formed with the central shaft  112 , although this is not essential. 
     The tethering ring  140  is preferably connected to the central shaft  112  so as to allow the tethering ring to pivot about a pivot axis “PA” that is perpendicular to the longitudinal axis L 1  of the expansion bolt. Preferably, the tethering ring is enabled to substantially freely pivot about the pivot axis PA through a pivot angle of at least 90 degrees, more preferably at least 170 degrees, and most preferably at least 180 degrees. 
     It is also desirable to provide for swiveling the tethering ring  140  about the longitudinal axis L 1 . Providing for both pivoting and swivelling of the tethering ring is important for minimizing the effects of cross-loading conditions as noted previously. 
     One way to provide a swivelling feature in expansion bolts according to the invention is to employ a frustoconically shaped wedge member  126  that is a separate part from the central shaft  112 , such as in the embodiment  300  shown in  FIG. 14 . In the embodiment  300 , the capability to pivot the ring  140  about the pivot axis PA is provided by a connecting ring  112   a  at the proximal end “PE” of the central shaft  112 , and a pivot shaft  112   d  extending through the connecting ring and through corresponding holes at terminating ends  140   a  of the tethering ring  140 . The ends of the pivot shaft may be swaged to capture the ends  140   a  of the tethering ring. Of course, there are many other ways to provide for pivotally connecting the tethering to the central shaft  112 , as will be readily appreciated by persons of ordinary mechanical skill. 
     To provide for swivelling the tethering ring in the embodiment  300 , the wedge element  126  has a central hole  126   b  for loosely receiving the distal end DE of the central shaft  112  so that the wedge element can spin or swivel about the central shaft (axis L 1 ). For this purpose, the distal end DE of the central shaft may have a reduced-diameter portion  112   c , which is reduced in diameter relative to the diameter of the shank  112   b , the diameters measured radially, perpendicular to the longitudinal axis L 1 . 
     With the wedge element  126  in place, a capturing tip “CT 2 ” may be provided or formed at the distal end DE of the central shaft  112 , such as by swaging the end of the central shaft, in cases where the central shaft is formed of metal, or by an equivalent process in cases where the central shaft is formed of plastic, to produce in the capturing tip an outer diameter “D CT ” that is larger than the diameter of the central shaft, for capturing and retaining the wedge element at the distal end of the central shaft. Of course, there are many other ways the wedge element  126  could be captured to the central shaft  112 , as will be readily appreciated by persons of ordinary mechanical skill. 
     Another way to provide for swiveling the tethering ring  140  about the longitudinal axis L 1  is to incorporate a swivel mechanism on the central shaft  112 . Any known swivel mechanism could be used, but a preferred and novel mechanism  150  is shown employed in the embodiment  100  of  FIGS. 4 and 5  that provides for both pivoting and swivelling. Details of this pivot and swivel mechanism  150  are shown in  FIGS. 15-19 . 
     With particular reference to  FIG. 15 , the pivot and swivel mechanism  150  includes the aforedescribed ring  140  (see, e.g., the discussion of  FIGS. 4 and 5 ), a “swivel housing”  156 , and a “cap”  158 . The parts are shown exploded along a longitudinal axis “L 3 ” of the pivot and swivel mechanism, which is congruent with the axis “L 1 ” of the expansion bolt  100  when the pivot and swivel mechanism  150  is employed therein. 
     The ring  140  has a closed retaining aperture “RA,” but it could be merely closeable. The ring  140  also has two leg portions “ 140 L,” namely “ 140 L 1 ” and “ 140 L 2 ;” the leg portions  140 L each have corresponding inwardly turned foot portions “ 140 F,” namely “ 140 F 1 ” and “ 140 F 2 ;” and the foot portions each have enlarged, flanged ends “ 140 FE,” namely, “ 140 FE 1 ” and “ 140 FE 2 .” The foot portions and flanged ends are cylindrical to allow for pivoting the ring  140  about a pivot axis “PA,” and the leg portions define a clearance aperture “CA” therebetween in the ring  140  so that when the ring is pivoted about the pivot axis it can clear the swivel housing  156 . 
     The swivel housing  156  has two leg openings “LO” (only one is visible in  FIG. 15 ) for receiving the leg portions  140 L of the ring  140 . The width “W” of each leg opening LO is sufficient for receiving the corresponding leg portion  140 L, but smaller than the diameter of the flanged ends  140  FE to provide for partial capture of the flanged ends within the swivel housing  156 . Capture of these ends inside the swivel housing is completed by fitting the cap  158  to a base “B 156 ” of the swivel housing, to result in the configuration shown in  FIG. 4 . 
     As best seen in  FIG. 16 , with the cap  158  fitted to the swivel housing  156 , and with the flanged ends  140 F of the ring  140  captured therebetween, there remains space for the central shaft  112  about which (axis L 2 ) the ring  140  can swivel. The central shaft  112  may have a ledge “LG 112 ” on which the cap  158  may be seated (see also  FIG. 5 ). 
       FIG. 18  shows the pivot and swivel mechanism  150  as employed in the expansion bolt  100 , sectioned for clarity. This view shows the swivel housing  156  capped with the cap  158  as it appears in  FIG. 15 . With reference to the latter, the cap  158  has a proximally extending, annular cup portion “C 158 ” for interfacing with the base B 156  of the swivel housing. 
     It is an outstanding feature of this interface that the swivel housing  156  “interlocks” into the cup portion of the cap  158 , and consequently resists prying the swivel housing  156  apart from the cap  158 , such as where the ring  140  is loaded downwardly, perpendicular to the axis L 2 . 
     As best seen in  FIG. 17 , this interlocking feature may be provided by an interface between the base B 156  of the swivel housing and the cup portion C 158  of the cap that becomes progressively narrower in the radial dimension (see the angle θ) with increasing elevation in the direction in which the swivel housing would be extracted from the cap. This interlocking feature is generally defined for purposes herein as being complementary mating structures on the base and cap that provide resistance to pulling these two elements apart along the longitudinal axis L 3  ( FIG. 16 ). As will be readily appreciated by persons of ordinary mechanical skill, there are many other ways these two elements could be interlocked together, such as by providing complementary screw threads on the two elements, or by providing complementary “snap” fitting features on the two elements such as corresponding ribs and rib-receiving voids. 
     Returning to  FIG. 18 , the swivel housing  156  may be enabled to resist being pulled out of the cap  158  in response to a force or component of force that is applied to the ring  140  axially, i.e., parallel to the axis L 2 , by a nut  160  that is threaded onto the distal end of the central shaft  112 . With additional reference to  FIG. 17 , the nut  160  may be further captured by the capturing tip CT 1  that was mentioned briefly above in connection with its omission from  FIG. 5 , that may be formed in the same manner as the capturing tip “CT 2 ” described previously for capturing the wedge element  126  to the central shaft  112  in the embodiment  200  of the expansion bolt. Of course, there are many other ways the central shaft  112  could be adapted to resist thrust loads applied to the swivel housing, as will be readily appreciated by persons of ordinary mechanical skill. 
     With reference to  FIG. 16 , the cap  158  can be made radially symmetric about the axis L 3  where it contacts the ledge LG 112  to provide the desired swiveling capability; no additional structure is necessary. However, with additional reference to  FIG. 19 , it may facilitate this swiveling capability to provide a “Teflon” washer  165 , which may be but which need not necessarily be a flat washer, to provide a larger surface BS 158  to ride on, which may be but need not necessarily be supported by the spring  120 . This washer may also be used to keep the end of the spring  120  off the ledge LG 112 . 
     As noted previously in connection with  FIGS. 8-10 , the expansion bolt  100  may be manipulated to place it in a minimum diameter configuration so that it can be inserted into a hole  9   a  in a structure  9  with the assistance of the cap  114 . This will be explained further in the discussion to follow, with the understanding that this discussion applies equally as well to the embodiments  200  and  300 . 
     As indicated in  FIG. 5 , the cap  114  has a floor “FL;” and as indicated in  FIG. 10 , this floor has a top surface “TS 114 ” and a bottom surface “BS 114 .” In the embodiment shown, both of these surfaces are annular, but that is not essential. 
     Normally, the outer face  9   b  of the concrete structure in proximity to the hole is flat; so it is normally preferable to provide that the bottom surface BS 114  of the cap  114  is flat, for seating on this typically flat outer surface of the structure. But in any case, at least some portions of the bottom surface of the cap should extend radially outwardly of the longitudinal axis L 3  far enough, relative to the size of the hole  9   a , to rest on the outer face  9   b  of the structure  9 , as shown in  FIG. 16 . 
     Also as best seen in  FIG. 5 , the base portion  116   a  of the housing  116  has a flange “FL 116 ” at a proximal end thereof. With particular reference to  FIG. 10 , the flange. FL 116  has a bottom surface “BS FL-116   ”  that is adapted to rest on the top surface TS 114  of the cap  114 , as shown in both  FIGS. 9 and 10 . Contact between these surfaces is maintained by compression of the spring  120 . 
     In contrast to the prior art concrete anchor, the elongate elastic members of the housing  116  are adapted or configured to bend elastically in repeated normal use, so that the expansion bolt can be removed from the hole and reused if it has not been involved in arresting a fall; and the ends: of the leaves are adapted or configured to so that they will not crush if there is a fall. 
     As best seen in  FIG. 9 , these features may be facilitated by use of a configuration of the leaves according to which the leaves LV have a radial thickness “t 1 ” that is thinner than the minimum radial thickness “t 2 ” of the spoons SP. A relatively small thickness t 1  provides for greater bending elasticity, and a relatively large thickness t 2  provides for greater crush resistance. Normally the t 2  dimension is the same regardless of the t 1  dimension. Providing for both the desired bending elasticity and crush resistance using leaves of constant thickness is possible, but there are undesirable consequences such as a need to substantially increase the overall length of the leaves LV (distance “OL” in  FIG. 8 ). 
     Preferably, where such differential in thickness is provided, t 1  is no more than 90% of t 2 , and more preferably t 1  is no more than 70% of t 2 . Generally, increasing the dimension t 2  provides for greater crush resistance while decreasing the dimension t 1  provides for greater bending elasticity. Both greater crush resistance and greater bending elasticity reduce the possibility of permanent deformation and thus increase the effectiveness of the expansion bolt for reuse. 
     The same result could be provided in ways other than by use of different material thicknesses of the leg portions and the ends of the leaves. For example, the same or similar result could be provided by joining different materials; however, the use of leaves configured as shown with differential thicknesses allows for forming the leaves integrally or monolithically with the body, in a single piece of material, which provides manufacturing cost advantages over prior art expansion bolts. 
     Preferably, the spoons SP have sufficient crush resistance to provide that the expansion bolt can support an axial load, i.e., a load directed along the longitudinal axis L 1 , of at least 450 pounds, with substantially no plastic deformation, i.e., no plastic deformation that would render, to a person of ordinary skill, reuse of the expansion bolt for supporting the same load, imprudent. 
     It was noted previously that leaves LV with differential thicknesses can be formed integrally or monolithically with the body, in a single piece of material, which provides manufacturing cost advantages over prior art expansion bolts. The body can be formed of a metal, plastic, or composite material. 
     Likewise, the central shaft  112  can be formed as an integral or monolithic single piece of material, such as metal, plastic, or composite material, which likewise provides manufacturing cost advantages over prior art expansion bolts, which typically employ braided cables. 
     It is also advantageous to provide that the central shaft  112  is “rigid,” i.e., sufficient that a compression force applied to the central shaft, when it is otherwise unloaded, by pushing on the central shaft (such as by hammering on the capturing tip CT 1  of the tethering ring  140 ) in the load-releasing direction “LRD” shown in  FIG. 8 , will force the wedging member  126  out of the aformentioned cavity CVT, to loosen the hold or grip the expansion bolt has on the interior of the hole into which it is installed. This provides the outstanding advantage of allowing a user to remove the expansion bolt without need for the prior art “cleaning bushing”  62  ( FIG. 2 ) and punch, shown and described in the &#39;363 patent. 
     Achieving the desired rigidity in the central shaft  112  is facilitated by forming it as an integral, monolithic, or non-woven structure. Sufficient rigidity could be achieved with a central shaft  112  that is either partially or wholly in the form of a braided or woven cable, but cables by nature are less effective to resist compressive loads. So if the central shaft  112  were to be provided either partially or wholly in the form of a cable, that cable should be relatively thick, to compensate for its relative lack of resistance to buckling. 
       FIG. 7  shows the expansion bolt  100  installed in the structure  9 , and being used to tether a worker to the structure. A first carabiner  42  may be connected to the ring  140  of the cap  114  and one end of a lanyard  44 . The other end of the lanyard  44  may be connected by a second carabiner  46  to a D-ring  48  which in turn connects to a harness  50  worn by the worker. Other equivalent structures as known in either the recreational climbing or the industrial fall protection arts could be used for connecting the worker to the expansion bolt  100 . 
       FIGS. 20 and 21  show another alternative expansion bolt  400  that replaces the spring  120  of the embodiment  100  with an alternative biasing member which is a cam  402 . The cap  114  may be retained, or not, and the cam could be used in combination with the spring  120 . The cam may be set by hand in the direction of the arrow in  FIG. 21  to produce a bias equivalent to that of the spring  120 , for drawing the central shaft  112  upwardly relative to the spoons SP and thereby radially spreading the spoons against the inner surface of the hole; and/or it may be set or urged to stay in place by gravity. 
     It may be noted that the anchoring bolt in its unloaded anchoring configuration as shown in  FIG. 10  is only subject to whatever anchoring force can be developed by the spring  120 , but of course, the anchoring force will increase significantly if the worker falls. Although it may be possible to reuse the expansion bolt after such an event, this is not normally intended. 
     While expansion bolts according to the invention are typically used for installation in holes in concrete structures for the purpose of tethering a worker engaged in construction work on the structure, they could be used for other attachment or connecting purposes, in holes in other types of structures or substrates, man-made or natural. 
     It is to be understood that the pivot and swivel mechanism is not limited to use in expansion bolts generally or expansion bolts according to the present invention particularly. It may be used in any application in which a pivot and swivel mechanism or feature is desired. 
     It is to be understood that, while a specific expansion bolt and pivot and swivel mechanism therefor has been shown and described as being preferred, variations may be made, in addition to those already mentioned, without departing from the principles of the invention. 
     The terms and expressions which have been employed in the foregoing specification are used therein as terms of description and not of limitation, and there is no intention in the use of such terms and expressions to exclude equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims which follow.