GB2100822A - Expansion anchor - Google Patents

Abstract

The expansion cone 10 of an anchor has an axial extension 15 in threaded engagement with the end 24 of a shank 12 of approximately the same diameter as that of the unexpanded shell. The opposite end of the shank has a threaded portion normally projecting above the surface of the material in which the hole is drilled to engage a nut. In use the shank is rotated relative to the cone to cause axial movement of the cone. The shank may be of reduced hardness relative to the cone. The cone may have a ridge 16 which engages a slot in the shell to prevent rotation of the cone. The use of a separate shank allows it to be removed from the hole e.g. to allow the structure secured to the wall by the anchor bolt to be moved. <IMAGE>

Description

SPECIFICATION Expansion anchor This invention relates generally to expansion anchors for installation in holes drilled in rock, concrete or similar materials.

Expansion anchors are bolt-like device inserted in holes drilled in rock, concrete, or similar materials, and then manipulated to expand a portion of the device solidly into engagement with the wall of the hole to hold the anchor in position.

Such devices are commonly used to secure machines in position on a concrete floor, or to secure equipment in place on a rock surface. A number of forms of this general type of device are currently available, and they are used in vast quantities. The most common form is based upon a shank that has a conical surface machined integrally in one end, with the small end of a cone facing the opposite end of the device. This conical surface is surrounded by an expansible shell. The opposite end of the shank has a threaded portion that should project above the surface of the material in which the hole is drilled, and in which the device is being installed. The unit is "set" by tightening a nut on this outer portion against the surface of whatever is interposed between the nut and the surface at the edge of the hole.

The problems that are commonly encountered in the use of these devices begin with the continued projection of the threaded end of the anchor above the rock or concrete after installation. This condition dictates that the machine or other structure to be secured must be vertically lowered into engagement with the projections, or the anchors can alternatively be installed in holes drilled through the openings in the base of the machine or structure after it is in position. Subsequent lateral movement of the machine is, of course, impossible without first lifting it over the projections. Some current forms of the device can conceivably be removed by tapping the outer end of the anchor to relieve the expansion pressure, but this cannot be counted on to permit full withdrawal of the anchor from the drilled hole.Often, it is simply not convenient to lift the structure or machine enough to clear it for lateral movement.

Another problem in the common form of expansion anchor is the cost of a one-piece unit incorporating both the shank and the cone. The shank should preferably occupy substantially the full diameter of the drilled hole, with just enough clearance for insertion. This results in the junction of the cone and the shank having a much smaller diameter, through which all of the tension forces must pass. If the unit is made of a material strong enough to tolerate the necessary stresses at this point, a considerable quantity of material is obviously wasted in the shank. A third problem is related to this same one-piece construction, which is that a one-piece expansion shell cannot be installed initially on the cone portion of the anchor without first over-expanding the shell to the point that it is difficult to return it to its original diameter small enough to enter the hole.The present invention is directed at an extremely simple modification of the standard construction which completely eiiminates these problems, and provides a different installation procedure.

The present invention is directed to an expansion anchor including a cone portion, an expansible shell surrounding said cone portion, and a shank extending from said cone portion, said shank having a threaded portion at the end opposite from said cone portion, said anchor being characterized in that a separate member provides said cone portion, said member having an axial threaded extension, and said shank having an internally threaded end portion receiving said threaded extension is threaded interengagement.

The present invention also relates to a method of anchoring a structure to a support, including the steps of drilling a hole in said support, installing an expansible shell around a cone member having a large end, a small end, a conical surface between said ends, and a threaded extension from said small end, installing a shank in axial threaded engagement with said extension, and inserting the assembly of said cone member, shell, and shank into said hole to a depth leaving a portion of said shank projecting out of said hole, and rotating said shank to induce relative rotation between said shank and said cone member to expand said shell.

Features and advantages of this invention will become more apparent from the following description of a preferred embodiment of the invention taken together with the accompanying drawings wherein: Figure 1 is a perspective view of a completely assembled expansion anchor, prior to installation; Figure 2 is a side elevation, partially in section, of the shank of the assembly shown in Figure 1; Figure 3 is an end view of the shank shown in Figure 2; Figure 4 is a side elevation of the cone unit incorporated in the Figure 1 assembly; Figure 5 is an end view with respect to Figure 4; Figure 6 is a side elevation of the un-expanded shell of the Figure 1 assembly; Figure 7 is an end view with respect to Figure 6; Figure 8 is an axial section on the plane 8-8 of Figure 7;; Figure 9 illustrates the first step in the installation of the assembly shown in Figure 1 into a hole drilled in a material such as concrete; and Figure 10 shows the final stage in the installation of the expansion anchor.

The anchor assembly illustrated in the drawings includes the cone member 10, the expansion shell 1, the shank 12, and the standard nut 13.

Referring particularly to Figure 4, the cone member 10 has a conical surface 14, and the threaded extension 1 5 integral with the small end of the conical configuration. A ridge 1 6 extends along the conical surface 14 parallel to a geometrical element of the conical surface. The entire cone member 10 is manufactured of a high tensile steel, preferably by a cold-heading process which provides the simplest procedure for producing the optional ridge 1 6 when it is used.

The expansible shell 11 has an internal conical surface indicated at 1 7 which rides on the exterior conical surface 14. The shell member 1 1 is peripherally discontinuous at the full-length slot 18, and at the shorter slots 1 9-21 which extend over only a major portion of the length of the shell from the end 22, which faces the large end of the cone member 10. The full-length slot 1 8 is interengaged with the ridge 16, if it is used, to provide a non-rotative relationship between the shell and the cone member. The height of the optional ridge 16 should not extend radially beyond the outside diameter of the unexpanded shell 11.

The end 23 of the shell bears against the end 24 of the shank 12. The axial internal threading 25 is interengaged with the threaded extension 1 5 of the cone member, and relative rotation between the cone member and the shank 12 causes the shell to be entrapped between the conical surface 14 and the end 24 of the shank. Continued relative rotation of the interengaged threads induces the expansion of the shell 11. The opposite (outer) end 26 of the shank 12 is threaded with the standard thread system associated with the nut 13, and normally extends over the surface of the rock or concrete in which the hole is drilled for the installation of the anchor.

This installation proceeds as shown in Figures 9 and 10. The hole 27 is first drilled in the concrete (or rock, or other material) 28 of a diameter just slightly greater than the outside diameter of the shank 12. This is approximately the same as the expanded diameter of the shell 11. The assembly shown in Figure 1 is then interengaged with the setting tool 29, which has an internal thread capable of mating with the threading 26 at the outer end of the shank 12. A ball 30 is positioned as an abutment at the inner extremity of the internal threading of the tool 29 to provide a central bearing against the end of the shank to minimize the torque necessary to unscrew the tool from the shank after the installation has been completed.When the assembly has been inserted to approximately the depth shown in Figure 10, the tool 29 is rotated to produce relative rotation between the shank and the cone member 10, and thus induce the expansion of the shell 11 solidly against the wall of the hole 27. When this has been accomplished, the installation has been completed, and the tool 29 can be back-rotated to remove it from the assembly. If convenient, this installation procedure can take place through the hole 31 in a base foot 32 associated with a machine or some other structure which the anchor assembly is intended to secure in position. After the removal of the tool 29, the nut 1 3 is installed.

Whenever it becomes necessary later to move the machine laterally, the nut 13 can usually be loosened slightly, and an added similar nut tightened down on top of it to provide a point for the application of wrench torque sufficient to back-rotate the shank in its threaded engagement with the cone member 10. If the oppositely set nuts do not provide a sufficient torque resistance, the nut 1 3 can be removed, and a convenient clamping device applied directly to the end of the shank. This is usually not preferred, as it tends to distort the exterior threading. Once the shank 12 has been back-rotated from the cone member, it may be removed from the hole 27 so that the machine can be moved laterally directly across the surface 33 of the material in which the hole 27 has been drilled. The cone member 10 and the shell 11 remain solidly engaged against the wall of the hole 27, and the shank 12 may be re-inserted whenever convenient, and re-engaged with the threaded extension 1 5 of the cone member.

Claims (7)

1. An expansion anchor including a cone portion of expansible shell surrounding said cone portion, and a shank extending from said cone portion, said shank having a threaded portion at the end opposite from said cone portion, said anchor being characterized in that a separate member provides said cone portion, said member having an axial threaded extension, and said shank having an internally threaded end portion receiving said threaded extension in threaded interengagement.

2. The anchor of Claim 1, wherein said separate member is of a material having substantially greater strength than that of the material of said shank.

3. The anchor of Claim 1 or 2, wherein said separate member has a conical surface interrupted by a ridge extending parallel to an element of said conical surface, and said shell has a discontinuity engaged by said ridge.

4. A method of anchoring a structure to a support, including the steps of drilling a hole in said support, installing an expansible shell around a cone member having a large end, a small end, a conical surface between said ends, a a threaded extension from said small end, installing a shank in axial threaded engagement with said extension, and inserting the assembly of said cone member, shell, and shank into said hole to a depth leaving a portion of said shank projecting out of said hole, and rotating said shank to induce relative rotation between said shank and said cone member to expand said shell.

5. The method of Claim 4, including the step of rotating said shank to disconnect it from said cone member and to permit removal of said shank from said hole without disturbing the engagement of said cone and shell in said hole.

6. An expansion anchor constructed substantially as herein described with reference to the accompanying drawings.

7. The method of anchoring a structure to a support substantially as herein described.