Abstract:
A swivel anchor point for fall protection. The swivel anchor point includes a ring element and a housing element. The ring element defines a closed attachment aperture. The housing element is adapted to receive and retain the ring element such that the ring element can be freely rotated through a swivel angle of at least 180 degrees about a swivel axis, and freely rotated through a pivot angle of at least 90 degrees about a pivot axis that is perpendicular to the swivel axis and that substantially intersects the swivel axis. The ring element includes two spaced apart leg members, the leg members having foot portions extending inwardly, toward the swivel axis. The foot portions have respective, spaced apart relatively enlarged ends. The housing element includes apertures corresponding to these ends, the apertures being suitably sized, closer to the swivel axis, for pivotally receiving the ends, while being of a sufficiently smaller size, farther from the swivel axis, to prevent passage of the ends therethrough.

Description:
FIELD OF THE INVENTION 
     The present invention relates to anchor points, for attaching a lanyard, strap or cable, to provide fall protection for a worker. 
     BACKGROUND 
     In construction, there is a need to tether construction workers to the structure being constructed, so that if the worker falls, the fall is short rather than deadly. What are known as “anchor points” have been provided in the prior art to help serve this purpose. Anchor points attach to the structure, e.g., the floor, wall, roof, or other structural element, and typically have a ring or through-hole to which a lanyard, strap or cable can be attached. That part of the anchor point that mounts to the structure can vary considerably; however, anchor points having rings generally share the characteristic that the ring is either fixedly disposed, or if it pivots, it does so such that the plane of the ring sweeps through a range of angles (e.g., 0-180 degrees) relative to the plane defining the surface to which the anchor point is mounted. 
       FIG. 1  illustrates the described pivoting. An anchor point  2  comprises a ring  4  and a strap  5  which mounts the ring to a structure  8  defining a mounting surface  6 . A Cartesian coordinate system is also shown for reference. The x and y axes of the coordinate system are aligned with the mounting surface  6 . The ring defines a plane “P” that pivots about a line “A” which is aligned with the x-axis. A line “B” is chosen that both lies in the plane P and is perpendicular to the line A, and the ring can pivot such that the angle δ defined between the line B and the mounting surface  6  varies between 0 and 180 degrees. Such anchor points will be referred to herein as pivot anchor points. 
     The pivot anchor point allows for pivoting that tracks a worker&#39;s movements in a plane aligned with the y and z axes. However, the present inventor has recognized that there is a need for an anchor point that provides for pivoting about the z axis, to track the worker&#39;s movements in a plane aligned with the x and y axes. 
     SUMMARY 
     A swivel anchor point for fall protection is disclosed herein. The swivel anchor point includes a ring element and a housing element. The ring element defines a closed attachment aperture, for connecting thereto a caribiner or the like. The housing element is adapted to receive and retain the ring element such that the ring element can be freely rotated through a swivel angle of at least 180 degrees about a swivel axis, and freely rotated through a pivot angle of at least 90 degrees about a pivot axis that is perpendicular to the swivel axis and that substantially intersects the swivel axis. The ring element further includes two spaced apart leg members, the leg members having foot portions extending inwardly, toward the swivel axis. The foot portions in turn have respective, spaced apart relatively enlarged ends. The housing element further includes apertures corresponding to these ends, the apertures being suitably sized, closer to the swivel axis, for pivotally receiving the ends, while being of a sufficiently smaller size, farther from the swivel axis, to prevent passage of the ends therethrough. The apertures are thereby adapted to capture the ends within the housing element for securing the ring element. 
     Preferably, the swivel anchor point further includes a cap and baseplate, for capturing the housing element therebetween. The cap and baseplate are separable elements. 
     More preferably, the cap and baseplate include corresponding portions that abut one another so as to space the cap and baseplate apart by an amount greater than that required to clamp the housing element and prevent rotation thereof about the swivel axis. 
     Still more preferably, one of the portions of the cap and baseplate is adapted to be captured by the other so that the portions resist displacing one of the cap and baseplate relative to the other in response to forces applied perpendicular to said swivel axis. 
     Yet more preferably, one of the portions is adapted to be seated in the other. 
     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 THE DRAWINGS 
         FIG. 1  is an isometric view of a prior art anchor point, illustrating a pivoting capability. 
         FIG. 2  is an isometric view of a swivel anchor point according to the present invention. 
         FIG. 3  is an exploded isometric view of the swivel anchor point of  FIG. 2 . 
         FIG. 4  is an elevation view of the anchor point of  FIG. 2  mounted to a structure, illustrating a pivoting capability. 
         FIG. 5  is a top plan view of the anchor point of Figure, illustrating a swivelling capability. 
         FIG. 6  is an isometric view of a first alternative embodiment of a swivel anchor point according to the invention. 
         FIG. 7  is an isometric view of a second alternative embodiment of a swivel anchor point according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 2  shows a preferred swivel anchor point  10  according to the invention, and  FIG. 3  shows the anchor point  10  exploded. The anchor point provides for the same pivoting provided by the pivot anchor point described above in connection with  FIG. 1 , as indicated in  FIG. 4 , but also provides for swiveling azimuthally, about a central or swivel axis “L I ” corresponding to the aforementioned z axis, as indicated in  FIG. 5  (angle φ). In these respects, it may be noted that the anchor point  10  provides the same freedom of movement that has been provided in prior art “hoist rings.” However, the anchor point  10  provides at least three important structural points of departure, in addition to having a different use. 
     Referring particularly to  FIG. 3 , the anchor point  10  includes a “base plate”  12 , a “ring”  14 , a “swivel house”  16 , and a “cap”  18 . The parts are shown exploded along the axis L I . 
     The ring  14  has a ring portion  14   a  defining an attachment aperture  14   a A, for receiving a caribiner or the like, and a swivel house clearance portion  14   b  defining a clearance aperture  14   b A. As shown, the overall shape of the ring  14  resembles a “D” and so it may be referred to as a “D ring.” 
     The ring portion  14   a  of the ring  14  is “closed,” meaning that over the entire 360 degrees of its circumference there are no gaps, the purpose being to prevent the caribiner or other attachment hardware from finding a passage through the ring portion so as to become unintentionally removed therefrom. The ring portion is also preferably annular over at least the radially outermost 180 degrees of its circumference (“C”) so that the caribiner slides equally well over this range which, because the anchor point  10  can swivel as well as pivot, is sufficient to allow the user to move anywhere within a given radius of the anchor point  10 . 
     By contrast to the ring portion  14   a , the clearance portion  14   b  is “open,” meaning that there is a gap in the aperture, here referenced as “G.” 
     The swivel house clearance portion  14   b  of the ring  14  has two spaced apart, parallel legs  14   b L, namely  14   b L, and  14   b L 2 , each leg having a corresponding inwardly turned foot portion  14   b F, namely  14   b F, and  14   b F 2 . The foot portions  14   b F have enlarged, flanged ends  14   b FE, namely,  14   b FE, and  14   b FE 2 . The flanged ends  14   b FE are spaced apart to create the gap G. 
     The foot portions  14   b F are cylindrical with diameters D 1 , and the flanged ends  14   b FE are cylindrical with enlarged diameters “D 2 .” 
     Reference is next made to the swivel house  16 , which has a cylindrical exterior face  16   a , a plane circular base plate-facing side  16   b , and an opposed, plane circular cap-facing side  16   c  (not visible in  FIG. 3 , but indicated in  FIG. 2 ). A circular central aperture  16   d  extends through the sides  16   b  and  16   c  centered on the axis L I , and a pair of stepped apertures  16   e , comprising apertures  16   e , and  16   e   2 , extend through the side  16   a  along a perpendicular axis L 2  that intersects the axis L I . The apertures  16   e  are open to the base plate-facing side  16   b , but preferably do not extend to the cap-facing side  16   c.    
     The apertures  16   e  have a width w 1  at the face  16   a , and the width is increased, preferably step-wise, to w 2  nearer the central aperture  16   d.    
     The dimension w 1  is selected to receive the foot portions  14   b F, i.e., the diameter D 1 , and the dimension w 2  is selected to receive the flanged ends  14   b FE of the foot portions, i.e., the diameter D 2 . 
     The base plate-facing side  16   b  of the swivel house  16  is essentially “capped” by abutting the side  16   b  to the base plate  12 , particularly to a circular recessed portion  12   a  described below, which thereby confines the flanged ends  14   b FE in a cavity defined between the increased width portions of the apertures  16   e  of the swivel house and the base plate  12 . The narrower width of the radially outermost portions of the apertures  16   e  provides the important advantage of retaining the flanged ends in the cavity against laterally outwardly directed forces, particularly tensile forces applied to the D ring  14  such as by, e.g., an attached lanyard, in directions perpendicular to the axis L I . 
     The cavity defined by the apertures  16   e  and the base plate  12  is suitably large, relative to the feet  14   b F and flanged ends  14   b FE, to allow for substantially free, pivoting rotation about the axis L 2 . 
     Reference is next made to the base plate  12 , which as mentioned above includes a circular, recessed surface  12   a  for receiving the side  16   a  of the swivel house. The recessed surface  12   a  provides the advantage of seating the swivel house and retaining it against laterally directed forces. 
     The base plate  12  further includes a circular through-hole  12   b  centered on the axis L I , and has a cylindrical inside surface  12   b   1 . 
     The base plate still further includes a planar mounting surface  12   c . This surface is adapted to mount to the structural member to which the anchor point is attached; particularly in this embodiment the planar surface portion  6  as described above in connection with  FIG. 1 . 
     Reference is next made to the cap  18 , which has three cylindrical, stepped diameter portions, a base plate-facing portion  18   a , a middle portion  18   b , and a swivel house-facing portion  18   c . The base plate-facing portion  18   a  has an interior surface  18   a , which defines a through-hole centered on the axis L 1  that extends through the anchor point  10  for receiving a fastener “F” (see  FIGS. 2 and 4 ), as well as an outer cylindrical surface of diameter D 3  sized to fit snugly into the through hole  12   b  of the base plate; the middle portion  18   b  has a cylindrical exterior surface  18   b , having a diameter that is sized to be slidably received within the hole  16   c  through the swivel house, as well as a supporting surface  18   b   2 ; and the outermost portion  18   c  has a capping surface  18   c   1 , that abuts the cap-facing surface  16   b  of the swivel house, to secure the cap to the swivel house when the cap is inserted through the hole  16   c  thereof, as well as a mounting surface  18   c   2  (see also  FIG. 2 ). 
     The through-hole defined by the base plate-facing portion  18   a  as described above is preferably over-sized relative to the fastener F, providing the advantage that the fastener F may be easily removed and replaced with a fastener of a different type or even size, so that the anchor point  10  can be mounted to various sizes, forms, and configurations of structural members. 
     The fastener is preferably tightened down on the anchor point  10 , the tightening force being resisted by the base plate  12  and cap  18 , leaving the swivel house stress free for free rotation about the axis L 1 , carrying the ring  14  (and axis L 2 ) with it. On the other hand, the cap  18  and the base plate  12  are stationary as a result of frictional forces developed between these parts, the structure, and the head of the fastener, as a result of tightening the fastener. More specifically, the head of the fastener frictionally engages the mounting surface  18   c   2  of the cap; the supporting surface  18   b   2  of the cap frictionally engages the recessed surface  12   a  of the base plate, and the outer cylindrical surface of the base plate-facing portion  18   a  of the cap frictionally engages the inside cylindrical surface  12   b , of the through hole of the base plate; and the mounting surface  12   c  of the base plate frictionally engages the surface  6  of the structure. 
     To ensure that the cap bears the tightening force rather than the swivel house, the height “H 18 ” ( FIG. 3 ) of the middle portion  18   b  of the cap is provided to be sufficiently greater than the height “H 16 ” of the swivel house to allow for a slight clearance remaining between these parts when the cap compresses in response to the tightening force. Accordingly, the capping surface  18   c   1  of the cap is spaced away from the cap-facing side  16   c  of the swivel house  16  so that there is substantially no frictional engagement between these surfaces. 
     As one alternative,  FIG. 6  shows a minimal embodiment  20  of an anchor point according to the invention, that includes only the swivel house  16  and ring  14 , with the base plate-facing surface  16   a  of the swivel house abutting the surface  6  of the structural member. Without suitable adaptation, tightening the fastener will clamp the swivel house to the surface  6 , and thereby hinder or completely prevent rotation of the swivel house. However, the head “H” of the fastener may be spaced above the surface  6 , such as by use of a tubular washer or stand-off (not shown), to avoid this problem. Preferably, a washer  21  would be used between the head H and the cap-facing surface  16   b  of the swivel house to mediate the otherwise inevitable contact between the fastener head H and the swivel house. 
       FIG. 7  shows another alternative anchor point  30  according to the invention, having a base plate  12 ′ and cap  18 ′ that are modified versions, respectively, of the base plate  12  and cap  18 . The base plate  12 ′ includes a stand-off portion  12 ′ a  having a distal end  12 ′ b.    
     The cap  18 ′ is, essentially, a washer having an internal diameter D 4  and an external diameter D 5 . The annulus thus defined seats on a distal end  12 ′ b  of the stand-off portion  12 ′ a  of the base plate  12 ′, so that the swivel house is captured between the base plate  12 ′ and the cap  18 ′ as in the embodiment  10 . The stand-off portion  12 ′ a  of the base plate  12 ′ a  projects above the floor of the baseplate by an amount H 12 ′ that is greater than the height H 16  of the swivel house  16 , so that the swivel house can freely swivel about the stand-off portion  12 ′ a.    
     As described, the embodiment  30  does not provide for centering the cap  18 ′ relative to the stand-off portion  12 ′ a  of the base plate  12 ′. By contrast, the embodiment  10  does provide for centering the cap  18  relative to the base plate  12 , by virtue of the portion  18   a  of the cap fitting into the hole  12   b  of the base plate. This functionality is not essential; however, it will be readily appreciated that it is desirable and can easily be provided in the embodiment  30  in like manner. 
     Anchor points according to the invention preferably provide at least over 90 degrees of pivot angle θ; more preferably at least over 150 degrees of pivot angle; and still more preferably at least over 175 degrees of pivot angle, with at least 180 degrees of pivot angle being optimum. As an independent consideration, anchor points according to the invention preferably provide at least up to 180 degrees of swivel angle φ; more preferably at least 350 degrees of pivot angle; and still more preferably at least 360 degrees of pivot angle, with over 360 degrees being optimum. 
     It should be noted that the preferred anchor point utilizes, as described and shown, circular and cylindrical surfaces and holes, to best facilitate relative rotation of the various parts as described. However, it should be understood that this is not a requirement. For example, the foot portions  14   b F of the ring will still be able to turn within the stepped apertures  16   d  of the swivel house even if the foot portions are not cylindrical, and even if they are not smooth or continuously curved, e.g., they could be hexagonal. 
     Moreover, the preferred anchor point uses planar abutting and mutually facing surfaces as described and shown; however, where abutting surfaces provide for frictional engagement as described, and may be replaced by non-planar surfaces providing for either frictional or specific mechanical engagement due to have complementary mating features (such as pins and holes). Also, mutually facing surfaces that are spaced apart from one another need not be planar either. 
     Anchor points, including anchor points according to the present invention, must be capable, when mounted to a structure, of withstanding a 5,000 pound force applied to the ring in any direction, without breaking. 
     It is to be understood that, while a specific swivel anchor point has been shown and described as preferred, other configurations could be utilized, 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.