1. Field of the Invention
The present invention relates to self-drilling anchors. In particular, it relates to a self-drilling anchor assembly and system for suspending a member from a hollow wall.
2. Description of the Related Art
Conventional hollow wall anchors are well known in the art. These anchors have evolved along a common conception in the design of anchoring members to a hollow wall. One such design is the toggle bolt anchor, exemplified by the TOGGLER® anchor, which when positioned, expands behind the inner surface of a wall, to spread the holding load against a greater surface of the wall. In this manner, the toggle bolt anchor provides an ability to support a heavy load. However, this type of anchor requires pre-drilled holes for installation and often damage to the wall, upon removal. Self-drilling anchors are also well known. These anchors generally include a plastic tapered body having external helical threads with a contiguous driving end for taping into a hollow wall without the need for a predrilled aperture in the wall. Up until now, a few such examples of self drilling anchors exist.
One such example, U.S. Pat. No. 6,196,780 to Wakai et al., discloses a threaded anchor having a hollow shank. The shank has a head at one end, an integral blade portion at the other end, and is formed with external threads on the outer periphery. Cuts are formed in a peripheral wall for the shank to define a bendable portion. The bendable portion is adapted to bend when pushed out by a mounting screw driven into the hollow shank. The blade portion is semicylindrical with side edges defining cutting edges. Tips for inclining the mounting screw are formed on the inner surfaces of the blade portion and the hollow shaft, respectively. When a mounting screw is driven through the article into the anchor to fix an article to the board, the mounting screw is inclined relative to the anchor, so that the bendable portion is pushed out, thus preventing the anchor form rotating together with the screw.
Another example, U.S. Pat. No. 7,144,212 to Kaye et al., discloses a self-drilling hollow wall anchor. The anchor has a self drilling threaded installation body adapted to be broken, after positioning, by inserting a screw into expandable anchoring elements. The anchoring elements are designed to engage internally formed cams and the distal surface of the wall into which the anchor is deployed. The anchoring elements are made of a plastic which is designed as a compromise such that it is sufficiently ridged in order to effect a threaded insertion and also to be broken apart. The anchor also includes anti-rotation elements to retard over-tightening and anchor removal prior to screw removal.
While the foregoing examples offer some utility, a major disadvantage in each lies in the fact that, while they do provide for a self drilling anchor, they do not provide the high load bearing capacity of a toggle bolt anchor, and their one piece plastic design is inherently compromised in providing a drilling tip strength but are made of sufficient flexibility so as to allow for expansion of the internal anchoring members. The foregoing examples are also difficult to remove and are limited in application for use in the anchoring of members which can be suspended through the head of a screw. Thus, it is desirable to provide a self-drilling anchor which is designed to provide the high load bearing capacity in conjunction with a hardened pin-point drilling tip for accurate placement, but which is also easily removed without damage to the wall and which is capable of suspending members other than through the head of a screw. The present invention satisfies these needs.