Patent Application
20070186492
The present invention relates generally to a lifting fixture for concrete structures, and more particularly to an anchor secured to reinforcing wires embedded within a concrete structure.
Concrete structures are used extensively in the construction industry. For example, concrete pipes are commonly installed underground and used to transport liquid and waste materials. Because of their durability and strength, concrete pipes typically require minimal upkeep and retain their serviceability for many years. Such pipes are also very versatile in the sense that they can be easily and economically formed with the necessary shape, size, and strength to suit a particular application.
Two of the most common processes for forming concrete pipes are dry casting and wet casting. Dry casting typically involves supplying a dry cast concrete mix, or “no-slump” mix, to a mold having an annular cavity between an inner form and outer form. The mix is densely compacted within the mold using specialized consolidation techniques, such as spinning, vibration, packing and/or “slinging” the concrete mix into the mold. After the pipe has been produced, the mold may be immediately removed and used to create another structure. Wet casting typically involves supplying a relatively wet concrete mix to the annular cavity of a mold. The concrete mix is cured within the cavity before the mold is removed. In order to increase the strength of both wet-cast and dry-cast pipe, reinforcing wires or bars are typically placed in the annular cavity of the mold prior to supplying the concrete mix so that the wires ultimately become embedded within the final concrete structure.
Although these manufacturing processes produce long-lasting, serviceable concrete pipes, one of the challenges associated with such pipes is the ability to transport them between various locations at a particular job site. The pipes are typically too heavy to be lifted by hand and must instead be moved with the assistance of a hoisting device. To facilitate lifting with a hoisting device, a hole may be cast in the concrete for receiving a conventional lifting hook. Alternatively, holes may be formed through the concrete after casting. While the holes may facilitate lifting, they must be patched once the pipes are installed in order to meet hydrostatic testing requirements. If a hole is not patched correctly, the patch may fail and may even fall out after the pipe has been installed. This is particularly problematic for pipes installed underground where soil and other materials may enter the pipe through a failed patch. This displacement of soil often creates a sinkhole at the grade level, which can become especially undesirable if the pipe is installed beneath a roadway or the like.
For all these reasons, several attempts have been made to provide concrete structures with a suitable anchor for engaging the lifting hook of a hoist device. More specifically, several attempts have been made to provide recessed anchors in the outer surfaces of concrete pipes. The recessed arrangement of the anchor eliminates the need for a subsequent cutting operation to remove any portion of the anchor that projects beyond the outer surface after installation. For example, U.S. Pat. No. 6,082,700, issued to Lancelot, III et al., discloses a removable anchor-positioning insert, or “void,” for forming a recess in the outer surface of a concrete structure. The insert is bolted to the outer form of a mold and includes an anchor placement channel for receiving the apex of a U-shaped or V-shaped anchor. The anchor placement channel is shaped to cooperate with the anchor so as to prevent the anchor from moving relative to the insert when concrete is supplied to the mold. Thus, after the concrete structure is formed, the mold and positioning insert are separated from the concrete pipe to expose the recess with the apex of the anchor positioned therein.
While bolting an anchor-positioning insert to the mold may suffice for some operations, Applicant has found that occasionally during the molding process, the anchor is pulled out of the insert when a no-slump concrete mix is “slung” into the mold. Supplying heavier wet-cast concrete mix may also cause the anchor to shift relative to the insert during molding. Thus, there is a need for a lifting fixture that does not require support from the mold during the formation of the concrete structure.
The present invention provides a lifting fixture for concrete structures having reinforcing wires embedded therein. The lifting fixture generally comprises an anchor having a first end adapted to be operatively coupled to the lifting hardware of a hoist and a second end configured to be securely embedded within the concrete structure. At least one clip member is coupled to the anchor for securing the lifting fixture to the reinforcing wires. The clip member also positions the first end of the anchor relative to a recess to be formed in the outer surface of the concrete structure, thereby providing easy access to the anchor.
The lifting fixture may further comprise a cover member, or “void former,” for forming the recess in the outer surface. The cover member is adapted to cover at least a portion of the first end of the anchor when secured thereto, and may be removed from the first end after the concrete structure has been formed. Removing the cover thus exposes the recess with the first end of the anchor positioned therein.
In one aspect of the invention, each clip member comprises a body, a first clasp positioned on the body and sized to operatively engage a first reinforcing wire, and a second clasp positioned on the body and sized to operatively engage a second reinforcing wire. The second clasp is spaced apart from said first clap by a distance corresponding to the spacing of the reinforcing wires. Thus, the first and second clasps secure the anchor while the concrete structure is formed in a mold. Additional attachments to secure the anchor to the mold are not required, but may be provided if desired.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the general description of the invention given above, and the detailed description given below, serve to explain the principles of the invention.
Referring to
The lifting fixture 10 is generally positioned in a recess 14 formed in an outer surface 16 of the concrete structure 12. More specifically, the lifting fixture 10 includes an anchor 20 having a first end 22 extending into the recess 14, and a second end 24 securely embedded within the concrete structure 12. At least one clip member 30 is coupled to the anchor 20 to secure the lifting fixture 10 to reinforcing wires 32 that are also embedded within the concrete structure 12, as best seen in
In order to properly position the first end 22 of anchor 10 relative to the recess 14 and outer surface 16 of the concrete structure 12, pairs of clip members 30 are secured to the anchor 20 at a desired location along the first and second legs 42, 44. Each clip member 30 generally comprises a body 54, a first clasp 56 positioned on the body 54 and sized to operatively engage a first reinforcing wire 32a, and a second clasp 58 positioned on the body 54 and sized to operatively engage a second reinforcing wire 32b. The first and second clasps 56, 58 are spaced apart from each other by a distance corresponding to the spacing of the first and second reinforcing wires 32a, 32b. While a pair of clip members is shown for securing anchor 20 to the reinforcing wires 32a, 32b, it will be recognized that a single clip member, or more than two clip members may alternatively be used to secure an anchor to the reinforcing wires.
In the embodiment shown, each clip member 30 is constructed from a metal rod that has been bent into the appropriate shape to form the body 54, first clasp 56, and second clasp 58. In this embodiment, the body 54 may be welded to the anchor 20 and the first and second clasps 56, 58 resemble hooks that are configured to wrap around respective portions of the first and second reinforcing wires 32a, 32b. The second clasp 58 includes a guide portion 60 that facilitates securely engaging the second clasp 58 to the second reinforcing wire 32b by providing a small amount of interference between the parts in an installed position. In the embodiment shown, guide portion 60 comprises a length of rod that is bent downwardly and outwardly relative to the body 54. Thus, the lifting fixture 10 may be secured to the reinforcing wires 32 by “hooking” the first clasp 56 onto the first reinforcing wire 32a, and then applying a sufficient force to overcome the interference of the guide portion 60 and “snap-fit” the second clasp 58 onto the second reinforcing wire 32b.
The simple and economical configuration of the exemplary fixture 10 makes it feasible to produce the lifting fixture 10 according to a concrete manufacturer's specifications. For example, concrete pipes are typically produced with a particular diameter and wall thickness. The shape and size of the anchor 20 may generally be determined from this information. The clip members 30, on the other hand, are designed with reference to the gage and spacing of the reinforcing wires 32, 32a, 32b. Wire sizes in large concrete pipes typically vary from 10 gage (0.135 inch diameter) to 2 gage (0.331 inch diameter), and spacing arrangements between intersecting wires typically range from 2 inch ×2 inch to 3 inch ×8 inch.
As shown in
In the embodiment shown in
A method of forming the concrete structure 12 will now be described. The concrete structure 12 is formed in a mold, which is not shown in the figures for the sake of clarity. As discussed in the background section, the mold for a concrete pipe typically includes an inner form and outer form. After positioning the reinforcing wires 32 in the mold, between the inner and outer forms, one or more anchors 20 may be secured to the reinforcing wires 32, 32a, 32b using the clip members 30. The removable cover 70 is then positioned over the first end 22 of the anchor 20 in the manner described above, with the outer surface 72 of the cover member 70 generally bearing against the outer form of the mold. Alternatively, cover member 70 may be secured to the first end 22 of anchor 20 and the anchor secured to the reinforcing wires 32, 32a, 32b prior to positioning the wires in the mold.
Once the lifting fixture 10 is appropriately secured and positioned within the mold, concrete may be supplied to the mold to form the concrete structure 12. Even if a no-slump concrete mix is slung into the mold in a dry-cast operation, or even if a heavier concrete mix is supplied to the mold for the purposes of a wet-cast operation, the secure attachment between the clip members 30 and the reinforcing wires 32 helps ensure that the anchor 20 remains in the desired position. Thus, the lifting fixture 10 may be advantageously used for both wet-cast and dry-cast operations.
Concrete mix is added until it fills the mold and surrounds any portion of the lifting fixture 10 that is not covered by the cover member 70. As shown in
As shown in
Thus, whenever the concrete structure 12 needs to be transported between various locations, installed at a job site, or otherwise moved, the hook 90 may be used to engage the first end 22 of the anchor 20 and apply a sufficient force to lift the concrete structure 12. The rigidity and strength of the concrete ensures that the second end 24 of the anchor 20 remains embedded therein so that the concrete structure 12 moves with the anchor 20. Additionally, the first and second flanges 46, 48 further extend within the concrete structure 12 to provide additional resistance to the lifting force and thus assist retaining the second end 24 within the concrete structure 12.
As a result of such an arrangement, the first end 22 of the anchor 20 must have sufficient strength to support the weight of the concrete structure 12. In other words, the first end 22 must not break or substantially deform when the lifting force is applied thereto. In one embodiment, the anchor is formed from low carbon steel.
After the concrete structure 12 has been moved to its intended location, the hook 90 may simply be disengaged from the first end 22. There is no need to complete a subsequent patching operation because the recess 14 does not extend through the concrete structure 12. If desired, however, mortar may be packed into the recess 14 to provide a clean appearance and give the pipe a uniform thickness.
The clip members 130, on the other hand, differ in several respects from the clip members 30. In the embodiment shown in
The clip members 130 are also adapted to accommodate a wide variety of wire sizes. More specifically, the first clasp 156 includes threaded aperture 166 adapted to receive a fastener 168, such as a screw or bolt. When the first reinforcing wire 132a is received in the first clasp 156, the fastener 168 is tightened to secure the reinforcing wire 132a within the clasp 156. Thus, even if a reinforcing wire is too small to frictionally engage the first clasp 156, the wire may be secured therein by the fastener 168.
Instead of being welded to the anchor 120, the clip members 130 are removably and adjustably secured thereto. To this end, each clip member 130 further includes a receiving member 174 positioned on the body 154 and adapted to receive a portion of the anchor 120. Like the first clasp 156, the receiving member 174 resembles a slot defined by opposing, spaced surfaces and includes a threaded aperture 176 for receiving a fastener 178. Thus, when a first leg 142 or second leg 144 of the anchor 120 is received in the slot, the fastener 178 may be tightened to secure the clip member 130 to the anchor 120.
The ability to adjust the position of each clip member 130 before tightening the fastener 178 enables the lifting fixture 110 to be used for many different sizes of concrete structures. More specifically, the position of each clip member 130 may be adjusted for different wall thicknesses of the concrete structure to ensure that the first end 122 of the anchor 120 is positioned at a desired location within the recess to be formed in the outer surface of the concrete structure. For relatively thick concrete structures, the receiving member 174 of each clip member 130 may further include an offset portion 184 (
In the various embodiments described above, the anchors and clip members have been shown in configurations wherein the legs 42, 44, 142, 144 of the anchors 20, 120 extend generally through a plane that includes the reinforcing wires 32, 32a, 32b. Such configurations are typical when the reinforcing wires 32, 32a 32b are substantially centered within the thickness of the concrete section 12. In some applications, however, the reinforcement wires 32, 32a, 32b may be arranged so that they lie relatively deep within the thickness of the concrete section 12, such that the reinforcement wires 32, 32a, 32b are closer to an inner surface of the concrete structure 12 compared to the distance of the wires 32, 32a, 32b from a surface where the anchor will be positioned.
A fourth leg 230 of the clip member 202 is spaced from the closed end 206 of the body 204 and extends upwardly from the second leg 210. An arm 232 extends from the fourth leg 230 in a direction substantially parallel to the second leg 210 and has a bent distal end 234 with a bend radius sized to receive one of the legs of the anchor member 120. When two such clip members 202 are secured to the reinforcing wires 32a, 32b and an anchor member 120 is secured within the bent distal ends 234 of the arms 232, the first and second clip members 202 are able to support the anchor member 120 such that it is spaced from the plane of the reinforcing wires 32, 32a, 32b, as best depicted in
While the invention has been illustrated by the description of one or more embodiments thereof, and while the embodiments have been described in considerable detail, they are not intended to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and methods and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the scope or spirit of Applicant's general inventive concept.
