Abstract:
An apparatus and method for temporarily anchoring a horizontal lifeline to existing rebar extending from concrete. Preferably, two triangular frames are temporarily secured to vertically extending rebar by eight sets of J-bolts and speed nuts. The frames are preferably made of tubular steel, and may be attached to the vertically extending rebar by one workman. Two or more rebar lifeline anchors may be used in combination to secure the ends of a horizontal lifeline. Three or more anchors can be used to secure two or more lifeline that are perpendicular to each other, such as along the outer, leading edges of a construction site.

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to apparatuses and methods for anchoring a horizontal lifeline and, more particularly, relates to apparatuses and methods for anchoring a horizontal lifeline to rebar. 
     BACKGROUND OF THE INVENTION 
     Reinforcing bar or “rebar” is typically used in concrete construction to reinforce a concrete structure by forming a web which is completely encased within the concrete. A raised pattern on the surface of the steel bar forms gripping surfaces around which the concrete hardens. Once the concrete hardens, shifting of the concrete is prevented by the outwardly protruding pattern on the bar. 
     When pouring the concrete for large elevated structures, such as sports stadiums, a horizontal lifeline may be employed to prevent workers on the leading edge, or at the forefront, of the structure under construction from falling from an elevated height and injuring themselves. A safety harness or line can be attached to the horizontal lifeline and may allow user movement in one or more directions while limiting user movement in the vertical or other direction (i.e.: prevent falling). The ends of the horizontal lifeline are typically anchored to the base of the concrete structure, or some other non-moveable object, to secure the lifeline. Previously, either no fall protection has been used or these lifelines have been secured to rebar by wrapping a cable around the vertical column. Since this method is quite variable and therefore not very reliable, let alone being subject to test, it could easily result in a system failure and user injury. 
     It would be desirable, therefore, to develop an apparatus and method for attaching a horizontal lifeline to rebar that did not present the disadvantages and shortcomings discussed above. 
     SUMMARY OF THE INVENTION 
     Generally, the present invention comprises an apparatus and method for anchoring a horizontal lifeline to existing rebar. Particularly, as a concrete structure is being constructed, it is often the case that vertically extending columns or rods of rebar stick up out of the previously poured section of concrete. This rebar is firmly anchored to the poured concrete, and hence, firmly anchored to the base or foundation of the structure. The apparatus of the present invention may be more easily and quickly attached and removed from the rebar than by conventional anchoring methods. Moreover, the horizontal lifeline anchoring apparatus of the present invention may be attached and removed by a single construction worker. 
     Preferably the anchoring apparatus of the present invention includes a pair of “L-shaped” or triangular brackets or anchor frames, oriented perpendicular to each other, that can be easily and quickly attached to the vertical rebar columns, preferably with J-bolts and speed nuts. A lifeline may then be strung from the attachment eye or connecting device that is preferably mounted on the top of the anchor frame. Two separate anchoring devices can be secured to two separate groups of extending rebar, and a lifeline can then be strung between the two anchors. A single user is thus able to more quickly and easily attach the horizontal lifeline to the vertical rebar than by conventional methods. 
     Other details, objects and advantages of the present invention will be more readily apparent from the following description of the presently preferred embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention and its presently preferred embodiments will be better understood by reference to the detailed disclosure hereinafter and to the accompanying drawings, wherein: 
     FIG. 1 is a front view of a horizontal lifeline connected between a rebar anchorage system of the present invention; 
     FIG. 2 shows typical diameters used for rebar; 
     FIG. 3 is a top view of a rebar anchorage system without the horizontal lifeline and the concrete column; 
     FIG. 4 shows a J-bolt that can be used with a rebar anchorage system of the present invention; 
     FIGS. 5A (top view) and  5 B (front view) show a speed nut used with a rebar anchorage system of the present invention; and 
     FIG. 6 shows four rebar anchors attached to four groups of rebar with an exploded view of one rebar anchor with two lifelines attached thereto. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 generally shows a front view of one preferred embodiment of the present invention, in which two rebar lifeline anchors are used in a horizontal lifeline system. A horizontal lifeline  10  is stretched between two rebar lifeline anchors  12  that secure horizontal lifeline  10  to rebar  15  extending from the top of a concrete column  17  or other reinforced structure. Each rebar lifeline anchor  12  generally is comprised of two triangular frames or brackets  20  and  32 , oriented generally perpendicular to each other (see FIG.  3 ), a plurality of J-bolts  27  and speed nuts  33  (see FIG.  3 ), and a connector or attachment eye  37  that allows a lifeline  10  to be hooked thereto. 
     FIG. 2 shows a conventional assortment of size diameters for rebar  15  used in making reinforced concrete structures. Typically, textured elongated rods of steel rebar  15  will be formed into a web-like arrangement to reinforce concrete poured into a frame placed over the top of rebar  15 . Rebar  15  strengthens a column of poured concrete  17  (FIG. 1) and helps to prevent shifting and cracking of the concrete over time. As concrete column  17  is poured, there is typically a group of vertical rods or columns of rebar  15  extending out of the top of the previously poured column of concrete. In connection with at least one presently preferred embodiment of the present invention, it is recognized that these vertically extending rebar rods  15  can provide a convenient anchorage location from which to mount a safety line  10  (FIG.  1 ) for workers who need to work at dangerous heights to prepare the structure for the next section of concrete to be poured. 
     FIG. 1 shows the front half of two rebar lifeline anchors  12 . Each rebar lifeline anchor  12  is preferably comprised of a triangular-shaped frame  20  having three members  21 ,  23  and  25  preferably made from hollow, square metal tubes. A base member  21  can run generally parallel to the ground, a vertical member  23  can run generally parallel to vertically extending rebar  15 , and a diagonal support member  25  can connect the ends of these two members  21  and  23  together for support. Triangular frame  20  is typically made of steel and is preferably welded together into a one piece unit before being attached to the rebar  15 . Frame  20  may also be made of aluminum or some other strong material. Using materials other than steel may make frame  20  lighter (allowing easier one-man mounting/dismounting) but may also increase the cost of the rebar anchorage system. It is also possible for these three frame members  21 ,  23  and  25  to be three separate pieces which are connected together during installation for ease of transportation of frame  20 . 
     FIG. 3 shows a plan view (from above) of a rebar anchorage system of the present invention without the horizontal lifeline and the concrete column. In FIG. 3, a top view of the triangular frame  20  (shown in FIG.  1  and described above) is shown oriented generally perpendicular to a second triangular frame  32  (described below). FIG. 3 shows columns or rods of rebar  15  extending vertically out of a formed concrete column (not shown). Base  21  and diagonal members  25  of a rebar triangular frame  20  may be attached to these rods of rebar  15  by J-bolts  27 . Specifically, a base member  21  and diagonal member  25  are typically provided with a plurality of holes  28  drilled therethrough along the horizontal side (see FIG.  1 ). Frame members  21  and  25  may be held against the outside of the group of vertical rebar  15 , and a plurality of J-bolts  27  may be inserted through the members  21  and  25 , with the hook of the J-bolt  27  being looped around one or more vertically extending portions of rebar  15  (see FIG.  3 ). 
     A J-bolt  27  for use with the present invention is shown in FIG. 4, but any number of similar attachment devices, as would be obvious to one skilled in the art, such as a flexible coupling, could be substituted for J-bolt  27  while still being within the scope of the present invention. The shorter end  29  of the J-bolt  27  is inserted into one of the holes  28  drilled through the base member  21  and diagonal member  25  of the frame  20  (and frame  32  described below) and extends into the middle of these hollow members. The longer end  31  of the J-bolt  27  is preferably threaded over a length  38  and is inserted all the way through both walls of the members  21  and  25 . The longer threaded end  31  typically protrudes outside the wall of the members  21  and  25  of the frame  20 . A speed nut  33  is then preferably threaded onto the threaded end  31  of the J-bolt  27  and tightened to secure the frame  20  to one or more vertically extending rebar rods  15 . A typical example of such a speed nut  33  is depicted in FIG. 5 with detailed top ( 5 A) and front ( 5 B) views. 
     A plurality of J-bolts  27  and speed nuts  33  can be used in tandem, as shown in FIG. 3, to secure the frame  20  to rebar columns  15 . Typically, four J-bolts  27  and speed nuts  33  (two for the base member  21  and two for the diagonal member  25 ) are used in a preferred embodiment of the present invention. Once the speed nuts  33  are tightened, the frame  20  resists sliding up or down the rebar  15 , and is thereby securely fixed with respect to the concrete  17 . The J-bolt  27  and speed nut  33  combination allows a single worker to securely attach one or more anchor frames  20  to rebar  15 . 
     As briefly mentioned above, preferably, a second frame  32  is attached to vertical rebar  15  adjacent to the first frame  20 . As seen in FIG. 3, this second frame  32  may preferably be attached perpendicular to first frame  20 . Although two separate reference numbers are shown for clarity, these two frames  20  and  32  may be identical in actual practice. This second frame  32  is preferably attached to the vertically extending rebar  15  in the same way as first frame  20 . Again, four J-bolts  27  used with four speed nuts  33  are sufficient for stability. 
     Although the frames  20  and  32  have been described above with respect to hollow, square tubes  21 ,  23  and  25  attached to rebar  15  with a plurality of J-bolts  27  and speed nuts  33 , one may replace one or more of these parts with alternate parts that function similarly. For example, one may use rods, hollow rods or angular bars instead of hollow bars. Similarly, one may use a square frame or other shaped frame instead of the triangular frame described herein. 
     Returning to FIG. 1, there are two frame connection tabs  35  that extend outward from the frame  20 , with a hole or slot extending therethrough in the vertical direction. These frame connection tabs  35  can be simple planar pieces of metal that are welded to vertical member  23  of the frame  20  (and the second frame  32 ). When viewed from above (see FIG.  3 ), a slot or hole extends therethrough. These frame connection tabs  35  are constructed so that when frames  20  and  32  are both attached to the vertically extending rebar  15 , and vertical members  23  of the frames  20  and  32  are oriented adjacent to each other, the two respective pairs of slots or holes through the frame connection tabs  35  line up vertically. Therefore, a pin  40  (see FIG. 3) can be inserted through the holes in frame connection tabs  35  to connect the two frames  20  and  32  together. In this way, frames  20  and  32  may be attached not only to the vertical rebar  15 , but also to each other, which increases the strength of rebar anchor  12  as a whole. 
     At the top of vertical member  23  of frame  20  (and frame  32 ) is a connector such as attachment loop  37  that allows a horizontal lifeline  10  or other safety device to be attached to frame  20  and, therefore, to the vertical rebar  15 . A horizontal lifeline  10  can be attached to eye  37 , and the lifeline  10  may be pulled in a variety of directions while remaining anchored to vertical rebar  15  through the rebar anchor  12 . 
     The above discussion detailed the structure and attachment methods of one embodiment of a rebar anchorage system of the present invention. Preferably two rebar lifeline anchors  12  are used with a horizontal lifeline system, with one at each end of the lifeline. FIG. 1 shows two rebar lifeline anchors  12  as used in a presently preferred embodiment of a present invention. To aid in clarity, the second frame  32  is not shown. The two anchors  12  are mounted on adjacent or parallel groups of rebar  15 , with the lifeline connectors, in this case loops  37 , lining up in the same plane. In this example, a horizontal lifeline  10 , such as the Horizon™ Horizontal Lifeline manufactured by the Rose Manufacturing Company, is connected between the two rebar anchors  12 . Generally, the ends of horizontal lifeline  10  are attached to loops  37  by way of a wedge socket on the free end  41 , with lifeline  10  having some small amount of slack. Then, lifeline  10  is tightened by way of a turnbuckle  39  at the jaw end or according to some conventional practice. The result is a horizontal lifeline cable  10  that is firmly attached to at least two sets of vertical rebar  15  extending from the top of a concrete column  17 . 
     The present rebar anchorage system may be more easily and more quickly attached to rebar  15  than by conventional methods and apparatuses. A single worker can attach, detach or adjust the anchorage of horizontal lifeline  10  with a decreased amount of effort in a decreased amount of time compared to conventional methods and devices. 
     In another embodiment, if one end of horizontal lifeline  10  is secured to the building foundation by some other arrangement, such as for example to an I-beam by means of a clamp such as the Versatile BeamGrip manufactured by the Rose Manufacturing Company, the present invention can be used with only one rebar lifeline anchor  12 . Such a method can be used in a system where one end of lifeline  10  remains fixed while the other end of lifeline  10  may be moved. The fixed end of lifeline  10  may be mounted to the building foundation while the moveable end of lifeline  10  may be mounted to various vertically extending rebar  15  as the construction proceeds. 
     In another preferred embodiment of the present invention, a third rebar lifeline anchor  12  may be attached to a third group of vertically extending rebar  15 . A second horizontal lifeline  10  may then be strung between the third anchor  12  and one of the first two anchors  12 . Preferably, this second horizontal lifeline  10  is strung perpendicular to the first horizontal lifeline  10 . Because each anchor  12  is secured to rebar  15  by two substantially perpendicular frames  20  and  32 , one anchor  12  is capable of supporting more than one horizontal lifeline  10  at the same time. The user merely has to connect one end of each horizontal lifeline  10  to each of loops  37  at the top of frames  20  and  32 . 
     For example, FIG. 6 shows four rebar lifeline anchors  12  attached to four groups of vertical rebar  12 . Preferably, there are three lifelines  10  attached between the four rebar lifeline anchors  12 . FIG. 6 shows the three lifelines  10  oriented generally perpendicular to each other and forming a safety system that runs along the outside of the vertically extending rebar  15 . The exploded view in the center of FIG. 6 details the connections at the top of rebar lifeline anchor  12 . Two loops  37  are attached to the top of frames  20  and  32  respectively. Because the frames  20  and  32  are oriented generally perpendicular with respect to each other, the loops  37  are likewise oriented generally perpendicular to each other. Therefore, two lifelines  10  can be connected to a single rebar lifeline anchor  12  perpendicular to each other. In this way, four rebar lifeline anchors  12  can be used to connect three or more lifelines  10  generally around the outside of four or more groups of extending rebar  15  (as in FIG.  6 ). 
     Also, more than one horizontal lifeline  10  may be strung parallel to each other from two or more rebar lifeline anchors  12 . Additional lifelines  10  may be strung for further safety support, or, for example, one lifeline  10  may extend further than another lifeline, allowing different users a greater or lesser amount of mobility depending on the intended application and safety requirements. 
     When horizontal lifeline  10  needs to be shifted, moved, or disassembled, a reverse process is employed. Horizontal lifelines  10  are disconnected, speed nuts  33  or other attachment devices are loosened, J-bolts  27  are removed, and frames  20  and  32  are removed. Frame  20  is then ready to be remounted in a different location. 
     Rebar lifeline anchors  12  according to the present invention may also be adjustable so that one or more anchors  12  can be moved without completely disassembling the entire horizontal lifeline system. In one presently preferred method, speed nuts  33  can merely be loosened, rather than removed, so that the J-bolt  27  and speed nut  33  combinations remain attached to frames  20  and  32 . Frames  20  and  32  can then be slid up or down the vertical rebar, or can be moved to an entirely new location. Once in a new location, speed nuts  33  can again be tightened, pulling the J-bolts  27  securely against the vertically extending rebar  15 . In this way, a reduced amount of time and effort can be expended to relocate or adjust the rebar anchorage system of the present invention. 
     Although the invention has been described with respect to attaching a horizontal lifeline onto vertically extending columns or rods of rebar, the present invention can also be used with other directional orientations. Because the anchor frames are fixedly attached to the rebar (not relying on gravity) a horizontal or otherwise oriented lifeline may be attached to rebar or other rods, textured or otherwise, that extend in any direction from concrete or some other material. Any orientations presented in the preceding disclosure were by way of example only and should not be construed to limit the present invention in any way. 
     Although the invention has been described above in terms of particular embodiments, one of ordinary skill in the art, in light of the teachings herein, can generate additional embodiments and modifications without departing from the spirit of, or exceeding the scope of, the claimed invention. Accordingly, it is to be understood that the drawings and the descriptions herein are proffered by way of example only to facilitate comprehension of the invention and should not be construed to limit the scope thereof.