LIFTING PIN ANCHOR WITH ANNULAR PLATE

Abstract

Al anchor is provided having a lifting pin, with a shaft, a head at an upper end of the shaft, and a foot at a lower end of the shaft, and the anchor further comprising an annular plate with an opening through the center, positioned with the shaft extending through the opening and the annular plate overlaying and supported by the foot. The annular plate has an area that is at least 80% of the area of a hypothetical circle circumscribing the annular plate.

Claims

1. An anchor for lifting precast concrete, comprising: (a) a lifting pin having a shaft, a head positioned at an upper end of the shaft, and a foot positioned at a lower end of the shaft, wherein the head is smaller than the foot; and (b) an annular ring having an opening in the center, and the annular ring overlays the foot of the pin, with the shaft extending through the opening, wherein the annular ring has an area that is at least 70% of an area of a hypothetical circle circumscribing the annular ring.

2. The anchor of claim 1, wherein the annular ring has a shape selected from the group consisting of circular, elliptical, pentagonal, hexagonal and heptagonal shapes.

3. The anchor of claim 2, wherein the annular ring has a circular or hexagonal shape.

4. The anchor of claim 1, wherein the annular ring is circular.

5. The anchor of claim 1, wherein the area of the annular ring is at least 75% of the area of the hypothetical circle.

6. The anchor of claim 1, wherein the area of the annular ring is at least 80% of the area of the hypothetical circle.

7. A precast concrete structure, comprising the anchor of claim 1, with the lower end of the shaft, the foot and the annular ring embedded in the concrete structure, and with the head of the anchor exposed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a side elevation view of the lifting pin anchor with annular plate of the present invention.

[0011] FIG. 2 is an upper perspective view of the anchor.

[0012] FIG. 3 is a schematic view of the face of an annular plate having an elliptical shape, and showing the annular plate with a circumscribed circle.

[0013] FIG. 4 is a schematic view of the face of an annular plate having a regular, hexagonal shape, and showing the annular plate with a circumscribed circle.

DETAILED DESCRIPTION OF THE INVENTION

[0014] Without intending to limit the scope of the invention, the preferred embodiments and features are hereinafter set forth. All of the United States patents and published applications cited in the specification are incorporated herein by reference.

[0015] Referring to FIGS. 1 and 2, anchor 1 has lifting pin 2 with shaft 3, head 4 at the upper end, and foot 5 at the lower end, opposite head 4. Annular ring 6 has opening 7 in the center, which is sufficiently sized relative to head 4, to allow annular ring 6 to pass over head 4, with shaft 3 extending through opening 7. Opening 7 is sized relative to foot 5, whereby annular ring 6 is too small to pass over foot 5, but rather rests on and is supported by foot 5, with the planar extent of annular ring 6 aligned perpendicular to shaft 3. Annular ring 6 may be welded to foot 5 by one or more spot welds 8, or a continuous weld (not shown). In the example illustrated, foot 5 has the general shape of the frustum of a cone.

[0016] In one embodiment of the invention, head 4 is cylindrical in shape, with a circular cross section, and the axis of the cylinder is aligned with shaft 3. Opening 7 may also be circular, and the diameter of opening 7 is greater than the diameter of head 4. It can be understood that it may be convenient to employ a head that is not cylindrical in shape, in order to engage a certain design of lifting eye. A feature of the invention, however, is that opening 7 of annular ring 6 is able to pass over head 4, even if one or both of the shapes of head 4 and opening 7 are irregular, and even if one must be rotated relative to the other, to allow annular ring 6 to pass over head 4.

[0017] The actual dimensions of anchor 1 may vary depending on the application. By way of example, a lift anchor rated for 4 tons (8,000 lbs.) with a 4 to 1 ultimate load of 16 tons, may have an overall length of 4 ½″, a head diameter of 1 7/16″, a shaft diameter of ¾″, and a foot diameter of 2″. The annular plate may have a diameter of 4″ and a thickness of ½″.

[0018] FIGS. 1 and 2 illustrate the anchor of the present invention with a circular annular plate. The annular plate may have an elliptical or polygonal shape, provided that the area of the plate, including the opening, is at least 70%, in particular at least 75%, or even more particularly at least 80% of the area of a hypothetical circle circumscribing the plate. By way of example, the shape of the annular plate may be circular, elliptical, oval, or ovate, or the shape of the annular plate may be a convex polygon having five or more sides, in particular, from five to twelve sides. By way of further example, the shape of the annular plate may be a regular polygon, such as a pentagon, hexagon, heptagon, octagon, nonagon, decagon, hendecagon or dodecagon.

[0019] It is believed that providing an annular plate with an area that is large relative to a circumscribing circle allows the pull out capacity of the anchor to be maximized for a given thickness of metal. In other words, the present invention allows users to achieve a desired pull out capacity, with a minimum thickness of metal.

[0020] Referring to FIG. 3, ellipse 10 has major axis 11 and minor axis 12, and ½ of the major axis is shown as distance “a” and ½ of the minor axis is shown as distance “b.” A circumscribing circle 13 has a radius of “a.” The area of an ellipse (A.sub.ellipse) is equal to πab, and the area of a circle (A.sub.circle) is αa.sup.2. Accordingly, when the value of “b” is at least 70% of the value of “a,” then the annular plate will have an area that is at least 70% of the circumscribing circle.

[0021] Referring to FIG. 4, hexagon 20 is circumscribed by circle 21 having radius “R.” The area of a hexagon (A.sub.hexagon) is 2.59808R.sup.2. The area of a circle (A.sub.circle) having a radius “R” is πR.sup.2. Accordingly, a regular hexagon has an area approximately 82.7% of a circumscribing circle.

[0022] In contrast, the area of a square plate, such as may be found in prior art anchors, has an area that is less than 64% of the area of a circle circumscribing the square plate.

[0023] Formulas for calculating the areas of regular polygons and conical sections, such as ellipses, may be found in the CRC Standard Mathematical Tables, CRC Press, Cleveland, Ohio, as well as other commonly available reference books.

[0024] The anchor is designed for use in precast concrete, whereby the lower portion of the shaft, foot and annular ring are embedded in the concrete. The head of the lifting pin component of the anchor is exposed, typically, by using a recess member aligned flush with the top of the concrete surface, as is well known to those skilled in the art. The anchor may be employed in a wide variety of precast concrete structures, including slabs, such as are used in the walls, floors and ceilings of buildings.

[0025] The anchor of the present invention may be used in precast concrete in conjunction with rebar or other steel bar, welded-wire mesh, pre-tensioned cables or post-tensioned cables, placed in proximity to the anchor.

[0026] There are, of course, many alternative embodiments and modifications of the invention, which are intended to be included in the following claims.