The present invention relates to concrete poles, and, in particular, to an attachment mechanism for a concrete pole which permits items to be bolted to the pole.
In the prior art, the most common way to attach structural appurtenances to a centrifugally cast concrete pole is to pass bolts completely through the pole and connect nuts to the bolts on the opposite side of the pole. This requires casting or drilling holes through the pole, which is labor intensive. Even more importantly, this means that, in order to attach anything near the base of the pole, which can have a very large diameter, very long bolts are required. These long bolts are very expensive, and, in order to be able to attach to the pole at a variety of different heights on a tapered pole, a variety of different length bolts must be stocked, which is also very expensive.
Also, since the centrifugally cast concrete poles are hollow and relatively thin-walled, the bolts are not very well supported by the pole and therefore cannot support much attachment load.
U.S. Pat. No. 5,761,875, Reinforced Concrete Pole with Attachment Mechanism, issued Jun. 9, 1998, which hereby incorporated by reference, discloses an improved attachment mechanism which introduces the use of shorter, standard size bolts, as well as material and labor cost savings, and improves the versatility of the concrete poles. However, as is discussed in more detail in the specification, this improvement has weaknesses, including a cantilevered load on the nuts and bolts securing the attachment to the pole.
The present invention provides an attachment mechanism which does not require drilling through the concrete pole in order to attach items to the pole, thereby saving labor. Also, the present invention provides an attachment mechanism which permits a single length bolt to be used to attach items to the pole at any elevation on the pole, even though the thickness of the concrete may vary and the diameter of the pole may vary with elevation, thereby permitting the use of less expensive bolts and permitting the stocking of only a single length bolt, which saves considerable cost.
The present invention also provides an attachment mechanism which provides excellent support to anything that is bolted onto the attachment mechanism, allowing heavier loads to be attached to the pole or providing better support for the same load than prior designs. Furthermore, the bolts are not supporting a cantilevered load, but are instead supported the length of the bolt by the concrete pole.
As seen in
As shown in
The attachment mechanism 30 of
The base plate 32 and the reinforcing bars 34 of the attachment mechanism 30 preferably are placed inside the spiral reinforcing wire 54, as shown here. The reinforcing bars 34 of the attachment mechanism may be tied to the spiral reinforcing wire 54. The base plate 32 preferably is welded to the reinforcing bars 34, as well as to the insert fasteners 38, before the attachment mechanism 30 is inserted inside the cage, and the base plate 32 is located so that the fastener inserts 38 project beyond the cage in order for their first ends 40 to be flush with the finished outer surface of the pole 10. Then the concrete is cast around the rods 50, the spiral wire 54, the reinforcing rods 34, the base plate 32, and the fastener inserts 38, preferably by spin casting. Several of the attachment mechanisms 30 of
In order to attach an arm 12 or any other attachment 12 to the pole 10, bolts 56 are inserted through upper and lower holes 56A in the attachment 12 and are threaded into the internal threads 38A of the respective fastener inserts 38. The holes 56A in the attachment 12 have the same spacing as the holes 36 in the base plate 32, so they align directly with each other for bolting the attachment 12 to the pole 10.
The bolts 56 are very well supported by the structure of the pole 10 for several reasons. First, the base plate 32, on which the fastener insert 38 is fixed, is very well supported. The base plate 32 is prevented from moving in any direction by the concrete 58 that surrounds it and by the reinforcing rods 34, the vertical rods 50, the spiral wire cage 54, and the concrete 58 surrounding them. Furthermore, not only is the fastener insert 38 fully welded to the base plate 32, but the outer shoulder 44 on the fastener insert 38 abuts the inside surface 32A of the base plate 32, providing an even stronger joint which is unlikely to pull out of the pole 10. Since the bolts 56 are threaded into the fastener inserts 38 substantially over the entire length of the bolts 56, and preferably up to the finished outer surface of the pole 10, the bolts 56 are supported along their length, experiencing no cantilevered load, and making the attachment 12 stronger and less likely to fail.
The ends of the pipe 60 fit axially over the second ends 42 of the opposed fastener inserts 38. The pipe 60 slides over the second ends 42 of the fastener inserts 38 until the ends of the pipe 60 abut the inner shoulders 46 of the fastener inserts 38. The pipe 60 is then fixed, as by welding, to the respective fastener inserts 38. As shown in
Not only does this second embodiment provide a second attachment site for an arm 12, but the pipe 60 also provides additional strength to the attachment mechanism 30A. In a typical installation involving two bolts 56 affixing an arm 12, the upper bolt 56 is in tension as the weight of the arm 12 tries to pull it away from the pole 10, while the lower bolt 56 is under compression as the arm pushes in against the side of the pole 10. The pipe 60 helps transfer some of the tensile and compressive forces across from one side of the pole 10 to other side. Furthermore, if another arm 12 is mounted to the other side of the pole 10 (as shown in the bottom embodiment of
Thus, the present invention provides a concrete pole with an attachment mechanism that is functionally far superior to the prior art. It will be obvious to those skilled in the art that modifications may be made to the embodiments described above without departing from the scope of the present invention.
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Number | Date | Country | |
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20060086060 A1 | Apr 2006 | US |