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Hybrid eccentric wedge anchor

Hybrid eccentric wedge anchor includes a cylindrical anchor body, an eccentric wedge unit, and cylindrical leading end. The eccentric wedge unit includes a tapered body, a shoulder between the tapered body and the anchor body, and a crescent shaped clip rotatably positioned around the tapered body.

The longitudinal axis of the tapered body is different from the longitudinal axis of the anchor body. The shoulder varies in width around the circumference of the anchor body. As the crescent shaped clip rotates around the tapered body, its outer circumference varies from being flush with the outer circumference of the cylindrical anchor body to extending beyond the outer circumference of the cylindrical anchor body.The hybrid eccentric wedge anchor can be configured in many useful anchor forms having the eccentric wedge unit. Examples include, but are not limited to, expansion bolt or drop-in configurations.

The purpose of this invention is to produce a medium to heavy-duty mechanical anchor which is easy to install, is less sensitive to hole diameter, is not hole depth dependent, is less sensitive to voids in the concrete, has superior holding capacities, remains flush with (or below) the surface level of the concrete, and is less expensive to produce.

Two similar embodiments satisfy these criteria: The basic embodiment and the preferred embodiment. The basic embodiment includes a cylindrical anchor body, an eccentric unit, and a crescent shaped clip. The eccentric unit consists of a cylindrical section which has a different longitudinal axis from that of the anchor body and upper and lower shoulders which vary in width around the circumference of the anchor body. The crescent shaped clip fits within the eccentric unit and is free to rotate about the cylindrical section. Since the longitudinal axis of the eccentric unit is different from the longitudinal axis of the anchor body, the eccentric unit acts as a cam upon the crescent shaped clip. As the anchor body rotates, the outer circumference of the anchor body at the eccentric unit ranges from near-flush to far-from-flush. The total diameter of the anchor, measured at the eccentric unit, ranges from near the anchor body diameter to far-from-near the anchor diameter.

To install the anchor, the crescent shaped clip is positioned so that the eccentric unit is near flush with the outer circumference of the anchor body. It is then installed into a pre-drilled hole is slightly larger than the anchor diameter and then rotated. Since the crescent shaped clip remains stationary, when the anchor body is turned the eccentric unit acts as a cam and forces the crescent shaped clip to expand the circumference of the anchor body. The increase in circumference causes the anchor body to wedge into the concrete. Friction between the crescent shaped clip and the concrete supports the loads applied to the anchor.

Because simply rotating the anchor body sets the anchor, this embodiment has the advantage of being easily installed. In addition, the anchor can easily be removed by simply rotating the anchor body counter-clockwise.

The hybrid embodiment (or the preferred embodiment), which may be called a hybrid eccentric wedge, also consists of the cylindrical anchor body, an eccentric unit, and a crescent shaped clip. The eccentric unit, however, consists of a tapered wedge rather than a cylindrical body, which has a longitudinal axis different from the longitudinal axis of the anchor body. There is an upper shoulder of the tapered wedge which varies in width around the circumference of the anchor body. Since the eccentric unit is tapered, there is no lower shoulder as in the basic embodiment. The crescent shaped clip fits within the eccentric unit and is free to rotate. It is, however, tapered to match, or nearly match, the taper of the eccentric unit. Since the longitudinal axis of the eccentric unit is different from the longitudinal axis of the anchor body, the eccentric unit acts as a cam upon the crescent shaped clip. As the clip rotates around the circumference of the eccentric unit, the outer circumference of the anchor body at the eccentric unit ravages from near flush to far-from-flush.

To install the anchor, the crescent shaped clip is positioned so that the eccentric unit is near flush with the outer circumference of the anchor body. It is generally inserted with a nut and washer into a pre-drilled hole slightly larger than the anchor diameter until the nut and washer touch the concrete The anchor body is then rotated. Since the crescent shaped clip remains stationary, when the anchor body is turned the eccentric unit acts as a cam and forces the crescent shape clip to expand the circumference of the anchor body. Upon turning, tightening of the anchor by rotating the nut clockwise draws the anchor away from the bottom of the hole. As the anchor draws up, the wedging element engages into the sides of the concrete hole causing a wedging action. The wedging action supports the load applied to the anchor.

The hybrid (or preferred) embodiment has several advantages over the prior art. First, the anchor is less sensitive to hole diameter. Because a typical expansion anchor cannot be adjusted prior to engagement of the wedging mechanism, it is very sensitive to hole size. However, because the initial turning of the anchor body of this invention produces a clamping effect caused by the cam action of the crescent shaped clip against the eccentric unit, the expansion mechanism (crescent shaped clip) has the ability to adjust for different hole Diameters. Second, it is easier to install than a conventional drop-in. A conventional drop-in requires excessive, labor intensive pounding to drive the expansion plug through the expansion wedge. Frequently this pounding is done with a heavy sledge in overhead installations. An installation tool, however, could provide a simpler method of installing the hybrid embodiment without this pounding. Third, superior holding capacities are possible. The crescent shaped clip performs holding values that are similar to, or exceed, performance of acts similar to the expansion elements of a typical torque controlled expansion anchor. Finally, the hybrid embodiment is less expensive to produce than a conventional drop-in. Because the production of drop-ins requires the labor intensive step of cutting the expansion wedges longitudinally into sections, they are extremely expensive. Because the hybrid embodiment eliminates this manufacturing step, it would be less expensive to produce.

Both of these embodiments, the basic embodiment and the hybrid embodiment, could be utilized in either the conventional male threaded anchor or the conventional female threaded drop-in. The female-threaded embodiments have the added advantage of remaining flush or near flush, with the concrete.

Consequently, this invention satisfies the need for a medium to heavy-duty mechanical wedge anchor which is easy to install, is less sensitive to hole diameter, is not hole depth dependent, is less sensitive to voids in the concrete, has superior holding capacities, remains flush with (or below) the level of the concrete, and is less expensive to produce.

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