GB2296951A - Anchoring device - Google Patents

Abstract

An anchor (10) for a bolt and the like includes a expandable sleeve (12) including a plurality of pressed metal segments (26) defining axially extending windows (28), a thin-walled ferrule (14) and an elongate member (16), for extending through the expandable sleeve (12) and the ferrule (14). The elongate member (16) has a tapered expander member (18) mounted on an inner end thereof and a threaded free end for extending from the ferrule (14) and engaging a nut. The ferrule (14) serves to space the expandable sleeve (12) from the free end of the elongate member (16), and the free ends of the segments (26) are received in the end of the ferrule (14). The segments (26) are pressed from sheet metal, e.g. aluminium alloy.

Description

ANCHORING DEVICE This invention relates to an anchoring device, and in particular to a device for use in anchoring a bolt or the like in a hole which has been drilled in brick work, masonry, concrete or the like.

A typical bolt anchor comprises a number of segments which together define an expandable tubular sleeve and are pivotally located at one end by a tubular end piece or ferrule. The segments are usually held in the tubular configuration by a spring clip located in a circumferential groove formed in the outer surface of the segments. An expander, typically in the form of a nut or bolt head, is provided at the other end of the sleeve and is arranged to be drawn into the sleeve to bear on the inner faces of the segments and expand the sleeve, such that the sleeve becomes wedged or clamped in a hole.

The segments may be cast or pressed steel, and the end piece in the form of a pressed steel cap.

The most expensive element of an anchor tends to be the segments, due to the relatively large amount of material necessary to form a segment and the difficulties in forming the irregular segment shapes.

Accordingly, it is an object of one aspect of the present invention to provide a bolt anchor in which the segments may be produced more economically, thus reducing the cost of the anchor.

According to the present invention there is provided an anchor comprising a tubular expandable portion including a plurality of segments, a thin-walled sleeve, and an elongate member for extending through the expandable portion and the sleeve, having an expander member mounted on an inner end thereof and a free end for extending from the sleeve, the sleeve serving to space the expandable portion from the free end of the elongate member.

The sleeve permits provision of a relatively short expandable portion, with a corresponding reduction in manufacturing costs. The provision of the thin-walled sleeve, in the absence of a relatively thick-walled end sleeve, precludes the anchor from use in high shear applications, but is satisfactory for low shear, tensile applications.

Preferably, the segments and the sleeve are of generally similar length.

Preferably also, the segments are pressings formed from metal sheet, the relatively short length of the segments simplifying the forming operation and reducing tooling costs. Most preferably four segments are provided, allowing for relatively straightforward forming and assembly. Only three segments may be utilised, though this would increase tooling and forming costs. Providing a larger number of segments would facilitate forming but increase assembly costs. Alternatively, the segments may be formed by pressing or cutting a single sheet and rolling the sheet to define the tubular form. It would also be possible to cast the segments individually, as is the case in the majority of existing anchors, or as a single piece as described in EP-A-0154466.

Preferably also, the sleeve serves to contain the outer end of the expandable portion, and thus holds the segments together. Conveniently, the sleeve is a metal pressing.

Preferably also, the segments include axially extending windows. These reduce the mass of material required to form the segments, and also provide for location of the expander member as it is drawn into the expandable portion on setting the anchor.

Preferably also, the segments are of aluminium alloy, which reduces the weight and cost of the anchor relative to anchors having steel segments.

According to another aspect of the present invention there is provided an anchor including an expandable portion formed of a plurality of segments, the segments including axially extending windows therein.

According to a still further aspect of the present invention there is provided a method of forming the segments of the expandable portion of an anchor including pressing the segments from metal sheet, the segments including apertures therethrough.

These and other aspects of the present invention, will now be described, by way of example, with the reference to the accompanying drawings, in which: Figure 1 is an exploded perspective view of an anchor in accordance with a preferred embodiment of the present invention; Figure 2 is a plan view from below of a segment of the anchor of Figure 1; Figure 3 is a sectional view on line 3 - 3 of Figure 2; Figure 4 is an end view of the segment of Figure 2; and Figure 5 is a sectional view of the ferrule of the anchor of Figure 1 (on same sheet as Figure 1).

Reference is first made to Figure 1 of the drawings, which illustrates a preferred embodiment of the present invention in the form of a bolt anchor 10 such as would be utilised to secure a bolt in a hole in brickwork, masonry, concrete or the like. The anchor includes a tubular expandable portion in the form of an expansion sleeve 12 and a thin-walled sleeve in the form of a ferrule 14. An elongate member in the form of a taper bolt 16 extends through the sleeve and ferrule 12, 14 and has a expander member in the form of a tapered head 18 for location at the inner end of the anchor 10, and a threaded free end (not shown) for engaging a nut 20 which is spaced from the end of the ferrule by a washer 22. In other embodiments the taper bolt and nut 16, 20 may be replaced with a conventional bolt (not shown), the threaded end of which engages a taper nut 24.

The expansion sleeve 12 is formed of four similar segments 26, one of which is illustrated in Figures 2 to 4 of the drawings. In this particular example the segments 26 are formed of aluminium alloy pressings. Each segment 26 defines an axially extending aperture in the form of a window 28, the provision of which reduces the weight of the material required to form each segment 26, facilitates pressing of the segment 26, and also assists in guiding and locating the head of the taper bolt 18 within the sleeve 12. The outer end of each segment 30 is adapted to be located within the inner end of the ferrule 14 and is provided with a 20 taper 32 to facilitate location within the ferrule. In addition, a circumferential groove 34 is formed in the segment end 30 to facilitate pivoting of the segment 26 relative to the ferrule 14 as the sleeve 12 is expanded. A further circumferential groove 36 is formed towards the inner end of each segment 26, to locate a spring retaining clip 38 (see Figure 1). The clip 38 is spaced from the inner end of the sleeve such that it does not interfere with the gripping action of the expanded sleeve 12.

The inner end of each segment 40 is provided with an internal 12 flat taper 42 for co-operating with a respective face of the taper bolt head 18. The use of a flat taper, as opposed to a conical taper, provides for a more reliable contact with the taper bolt head and minimises the energy that is lost in deforming metal as the bolt 16 is tightened.

Reference is now made to Figure 5 of the drawings which illustrates the ferrule 14, which in this example is formed of deep drawn mild steel which has been zinc plated.

The inner end of the ferrule 44 is formed to define an inwardly and rearwardly projecting lip 46 to centralise the outer end of the ferrule 14 on the bolt 16, and also to provide a reinforced bearing surface for contact with the washer 22.

It will be evident to those of skill in the art that the ferrule 14 is relatively long in comparison with the ferrules of conventional bolt anchors, in which the ferrules serve solely to locate the outer ends of the segments. Surprisingly, it has been found that the bolt anchor 10 as described above performs in a similar manner to conventional anchors in which the expansion sleeve and segments are of a length substantially similar to the combined lengths of the sleeve and ferrule 12, 14 described above. As the ferrule 14 is a relatively low cost item, the anchor 10 is thus less expensive to manufacture than comparable existing anchors.The relatively short length of the segments 26, and the provision of the windows 28, further reduce forming and material costs, and it is estimated that the manufacturing costs of the anchor 10 described above will be at least 308 less than corresponding conventional anchors.

By way of example, Tables 1 and 2 below indicate the relative dimensions of the sleeves and ferrules that would be utilised in producing anchors of the widely used sizes M6, M8, M10, M12, M16 and M20.

TABLE 1 - (SEGMENT - see Figures 2- 4) all dimensions in mm SIZE R1 R2 L1 L2 L3 L4 W M6 3.05 4.9 20 5 11 2.5 2.80 M8 4.10 5.9 20 5 11 2.5 3.00 M10 5.10 7.4 25 5 15 2.5 4.00 M12 6.15 8.9 35 7.5 22 3.0 6.00 M16 8.15 11.8 50 10 35 4.0 7.5 TABLE 2 (FERRULE - see Figure 5) SIZE D1 D2 L1 L2 T R M6 11.60 6.75 20 18 0.27 0.50 M6 11.50 6.50 20 18 0.27 0.50 M8 13.58 8.75 30 28 0.27 0.50 M8 13.48 8.50 30 28 0.27 0.50 M10 15.52 10.75 40 38 0.27 0.50 M10 15.39 10.50 40 38 0.27 0.50 M12 9.53 12.95 40 38 0.27 0.50 M12 19.41 12.70 40 38 0.27 0.50 M16 23.53 16.95 45 43 0.37 0.50 M16 23.40 16.70 45 43 0.37 0.50 It will be clear to those of skill in the art that the above-described embodiment is merely exemplary of the present invention, and that modifications and improvements may be made thereto without departing from the scope of the invention.

Claims (10)

1. An anchor including a tubular expandable portion including a plurality of segments, a thin-walled sleeve, and an elongate member, for extending through the expandable portion and the sleeve, having an expander member mounted on an inner end thereof and a free end for extending from the sleeve, the sleeve serving to space the expandable portion from the free end of the elongate member.

2. The anchor of claim 1 wherein the segments are metal pressings.

3. The anchor of claim 1 or 2, wherein four segments are provided.

4. The anchor of claim 1, 2 or 3, wherein the sleeve serves to contain an outer end of the expandable portion, and thus holds the segments together.

5. The anchor of any preceding claim wherein the segments include axially extending windows.

6. The anchor of anlpreceding claim wherein the segments are of aluminium alloy.

7. The anchor of any of the preceding claims wherein the segments and the sleeve are of generally similar length.

8. An anchor including an expandable portion formed of a plurality of segments, the segments including axially extending windows therein.

9. A method of forming the segments of the expandable portion of an anchor including pressing the segments from metal sheet, the segments including apertures therethrough.

10. The anchor substantially as described herein and as illustrated in the accompanying drawings.