WALL SUPPORT STRAP

Abstract

This invention relates to a wall support strap. According to one aspect of the present invention there is provided an elongated wall support strap comprising a plurality of tendons which extend for the full length of the strap and a plurality of transverse strap members which extend transversely to the 5 tendons and connect them to one another, opposite end regions of the support strap being narrower than a middle region thereof situated between tendons, the tendons in the middle region being held in spaced apart, generally parallel relationship by middle region strap members while outer tendons in the end regions converge on and are connected to at least one 10 inner tendon in the end regions by end region strap members.

Description

FIELD OF THE INVENTION

This invention relates to a wall support strap.

BACKGROUND TO THE INVENTION

One well-known wall support strap which is widely used in underground mining operations to provide localised or micro-support, typically for a hanging or side wall in a mine working, is the so-called “Oslo” strap. This has a number of round bar steel tendons which are held together in a spaced apart, parallel array by means of “pigtail” strap members. These are round steel bars which, at regular intervals, are bent to form loops or pigtails. The tendons pass through the loops and welds connect the tendons to the strap members at each loop.

Known wall support straps of this general type have a rectangular shape in which the tendons, defining the length of the strap, are equally spaced from one another throughout. The length of the strap, corresponding to the length of the tendons, may for example be 1.5 m to 2.5 m or more, and the width of the strap, corresponding to the length of the strap members, may for example be 300 mm to 500 mm.

In use, ends of the strap are fixed to the hanging or side wall to restrain the rock surface and hold back rock fragments which may have broken from the surface and could otherwise fall dangerously from the wall. The straps are usually fixed to the wall by means of rock bolts which are anchored in holes drilled into the face. In practice, roof bolt washers through which the roof bolts pass are opposition so as to overlap components of the strap and the rock bolts are tensioned so that the washers press the ends of the support strap against the face.

A problem with the conventional fixture system as described above is the fact that the roof bolt washers are typically arranged and are so dimensioned that they press only against a central region of the strap and do not act at all against side regions of the strap. As a result, the side regions of the strap which are not contacted by the washer are not directly supported against the hanging wall. This in turn means that the side regions have a reduced ability to restrain the rock surface and any loose fragments at the surface.

The present invention seeks inter alia to address this problem.

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided an elongated wall support strap comprising a plurality of tendons which extend for the full length of the strap and a plurality of transverse strap members which extend transversely to the tendons and connect them to one another, opposite end regions of the support strap being narrower than a middle region thereof situated between tendons, the tendons in the middle region being held in spaced apart, generally parallel relationship by middle region strap members while outer tendons in the end regions converge on and are connected to at least one inner tendon in the end regions by end region strap members.

At least some end region strap members comprise an elongate strip of material to which at least one inner tendon is secured, the strip having respective end sections at either end to which two or more tendons, including outer tendons are secured. In the preferred embodiment, the end sections of the end strap members are at least partially folded over to define pockets in each of which the tendons are secured. Where the tendons and the end strap members are made of steel the outer tendons may be welded to each end strap member in the pockets.

Each middle region strap member may comprise a generally flat, elongated strip formed with longitudinally extending slits at longitudinally spaced apart slit positions, strip material or one side of the slit being deform, in a direction transverse to the length of the strip relative to strip material on the other side of the slit so as to define openings in the strip through which the tendons pass. It is within the scope of the invention for end region strap members also to comprise strips formed with slits for the same purpose.

According to another aspect of the invention there is provided a wall support strap comprising a plurality of tendons which extend for the full length of the strap and a plurality of transverse strap members which extend transversely to the tendons and connect them to one another, each strap member including an elongate strip of material with end sections that are at least partially folded over to define pockets in each of which tendons are secured. Where the tendons and the end strap members are made of steel, the tendons may be secured in the pockets by welding.

The tendons may be straight. Alternatively, the tendons may have an undulating or zigzag shape at least for portions of their length.

Connection means in the form of triangular plates are used to ensure that outer tendons are securely connected to inner tendons.

There is further provided for the strap member to have alternating receiving formations.

The receiving formations alternate in that they alternatively face operatively upwards or operatively downwards.

A yet further feature of the invention provides for the strap members to include cut out sections for strengthening thereof.

There is still further provided for strap members to include receiving formations having openings smaller than a diameter of a tendon so that the receiving formations may be clipped over a tendon.

Still further features of the invention provide for the strap member to have crimp-on receiving formations for crimping the receiving formations on to tendons; for a c-shaped resilient clips to be locatable over a tendon and a receiving formation; and for a strap member to have a prop-receiving formation

There is provided for a prop-receiving formation to be a dome-shaped indent in a strap member.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the invention which are summarised above are now described in more detail by way of example only, with reference to the accompanying drawings in which:

FIG. 1 illustrates one end of the first embodiment of wall support strap according to the invention;

FIG. 2 illustrates one end of a second embodiment of wall support strap according to the invention;

FIG. 3 illustrates one end of a third embodiment of wall support strap according to the invention;

FIG. 4 illustrates a fourth embodiment of wall support strap according to the invention;

FIG. 5 shows a cross-section at the line 5-5 in FIG. 4;

FIG. 6 shows a perspective view of the connecting strap member seen in FIGS. 4 and 5; and

FIGS. 7 to 22 show further embodiments of a wall strap and of strap members;

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

FIGS. 1 to 3 illustrate three embodiments of a wall support strap 10 according to a first aspect of the present invention.

FIG. 1 shows an end of the elongate wall strap 10 according to the first embodiment of the invention. It may be assumed that the opposite end of the strap is similar to the illustrated end. The wall support strap includes four tendons 12 in the form of round section steel bars, typically a 5 mm diameter, which extend to the full length of the strap, typically 1.5 m to 2.5 m or more. It also includes transverses strap members 14 and 16. The tendons 12 can also be square or rectangular bar that may be stronger than round bars of similar size and which will provide a larger contact surface for a washer used together with a rock bolt to anchor the ends of the straps to a wall in a mine working such as a hanging wall.

The strap members 14 in the middle region 28 of the strap 10 are each provided by flat steel strip 18, in this case of 350 mm overall length. At regular intervals, in this case 100 mm intervals, slits 20 are formed at slit positions on the longitudinal centre line of each strip; for example by a punching operation. Strip material 22 on one side of each slit is deformed in one direction out of the general plane of the strip and strip material 24 on the other side of each slit is deformed in an opposite direction out of the general plane of the strip as is shown. The tendons 12 extend through openings 26 formed by the respective zones of deformed material 22 and 24.

Tack welds (not shown) may be used at each position where a tendon passes through an opening 26, or at least at some of these positions, to anchor the strap members and tendons to one another. The arrangement of tendons and strap members in the middle region 28 of the wall support strap 10 is such that the tendons are held in spaced apart parallel relationship with one another, as shown.

In the illustrated end region 36 of the strap 10, the two outer tendons 12 i.e. those tendons which are located furthest from the longitudinal centre line 32 of the strap, are bent inwardly so as to converge on the two neighbouring, inner tendons as indicated by the numerals 34.

An end region strap member 16 is provided at each end of the strap. Each of these strap members are provided by a steel strip 36 with end sections 38 that are partially folded over to define pockets 40 which embrace the ends of the convergent pairs of tendons. Welds 42 secure the ends of the tendons to the strap 16.

In the resulting wall support strap 10, as seen partially in FIG. 1, the end regions 30 are somewhat narrower than the middle region 28. The advantage of this is described below.

As indicated previously, the ends of the wall support strap are in use fixed to the hanging wall or side wall of a mine working to restrain the rock surface.

This is achieved by means of rock bolts which are anchored in holes drilled into the face. Roof bolt washers, through which the roof bolts pass, are positioned so as to press the ends of the support strap against the face. In a conventional case, the width of the support strap at its ends is too great for the washers to contact the strap across its full width, so the outer tendons, i.e. those which are not directly acted upon by the washers, have a limited support capability. However, in the illustrated case, the end region of the strap 10 is sufficiently narrow for a conventional washer to act directly on the ends of all four tendons.

Thus, the ends of all four tendons are pressed against the wall by the washer when the roof bolt is tensioned, and all four tendons are able to serve a proper load supporting function.

The embodiment of FIG. 2 differs from that of FIG. 1 primarily in that the strap 10 has five tendons 12 instead of four. However, as in the embodiment of FIG. 1, the outer tendons converge inwardly to the neighbouring tendons in the end regions. The ends of the tendons are secured relative to one another by an end region strap member 16. In this case it will be seen that the pockets 40 each embraced the ends of two tendons, while an opening 26, corresponding to the openings 26 formed in the middle region strap members in FIG. 1, receives the end of the central tendon. Welds are, once again, used to provide connections between the tendons and strap members.

The embodiment of FIG. 3 differs from those seen in FIGS. 1 and 2 in that the strap 10 has six tendons 12 instead of four or five. In this case there are to end regions in the region strap members 16.1 and 16.2, connected to the tendons in the illustrated manner.

In both FIGS. 2 and 3, the end regions of the strap 10 are again narrower than a middle region so the advantage of direct washer contact can again be achieved.

FIG. 4 illustrates a roof support strap 100 according to a second aspect of the invention. The strap has only two tendons 102. These are spaced apart from and connected to one another by strap members 104. The strap members 104, one of which is seen at a larger scale in FIGS. 5 and 6, are similar to the end region strap member 16 seen in FIG. 1. In this case, the flat steel strip 106 is formed with a dimple 108 in a central region to improve its bending strength. As shown, end sections of the strip are partially folded over to form pockets 110 in which the ends of the tendons 102 are received and fixed by welding 112. It will be understood that the end strap members 16 seen in FIGS. 1 to 3 could also have reinforcing dimples like the dimple 108.

The tendons 102 in FIG. 4 include regions 114 which they have undulating or zig zag profiles alternating with regions 116 where they are straight.

An advantage of the wall support strap 100 of FIG. 4 is the simple manner in which the strap members 104 enabled the tendons to be connected to and spaced apart from one another. Another advantage, attributable to the partially zig zag shape of the tendons, is the ability of the strap to provide yielding support to the wall to which it is fixed. In practice, where the strap 100 is fixed to the hanging wall of a mine working, and the mine working closes with time as the hanging wall descends towards the foot wall or floor, the tendons can stretch in length to accommodate this closure. It will be understood that this is permitted by the fact that the zig zag or undulating profiles of the regions 116 can straighten out if the tendon is under sufficient tension, thereby increasing the overall length of the strap.

Another advantage of the strap 100 is the fact that the undulating or zig zag profile of the tendons increases effective width of the strap, when compared to a strap which merely has straight tendons, thereby enabling the strap to serve a micro-wall support function over a greater area. The strap 100 may alternatively include straight round, square or rectangular bars instead of the zig zag tendons.

With reference to FIG. 7, triangular plates 203 are used to ensure that the outer tendons 12 are securely connected to the inner tendons by welding the plates along their edges to the tendons as well as to the connecting strap member 201 abutting the rectangular plates 203.

FIG. 8 shows a strap member in the form of a plate 204 which has tendon receiving formations along its outer edges. The plate 204 may be used with the connecting strap members 201.

The connecting strap member 205 of FIG. 9 has alternating receiving formations in the sense that they face in alternate 180° directions so that they locate alternatively underneath and on top of adjoining tendons 12.

FIGS. 10 to 13 show yet further embodiments of strap members 206 which may be used instead of strap member 205 or in combination with each other. Strengthening cut outs such as those indicated by the broken lines in Figures 11 to 13 may be included in the strap members to strengthen the strap members.

FIGS. 14 and 15 show clip on strap members. In this case, the receiving formations shaped to receive the tendons 12 have openings smaller than a diameter of the tendons 12 so that they must be forced open to clip onto the tendons 12. The strap members of FIGS. 14 and 15 are resiliently deformable to facilitate clipping onto the tendons 12.

FIGS. 16 and 17 show strap member 301 having opposite crimped ends 302 for receiving one or more tendons 12 therein. In this case, the opposite ends of the strap member 301 are substantially C-shaped in cross-section to receive a tendon or tendons therein. These C-shaped ends are then forced closed or crimped to secure the tendons therein.

FIGS. 18 and 19 show the use of strap members such as strap members 204, 205 and 206, which do not have clip on receiving formations. In this case a clip 310, which is substantially C-shaped in cross-section and made of a resilient material, have an open section that is smaller than the diameter of the tendon 12 together with the receiving formation of the strap member so that the clip may clip over the tendon 12 as well as the receiving formation of the strap member thereby securing the strap member to the tendon 12.

FIGS. 20, 21 and 22 show yet another alternative strap member similar to that of strap member 204 and are also referred to in these drawings as strap member 204. In this case the strap member 204 connects four tendons 12 at their ends and is in the form of a plate like strap member. A centrally located dome 320 is included in the strap member for receiving an upper end of pit prop 321 therein. The dome member 320 is located between the two inner receiving formations of the strap member 204.

Claims

1. An elongated wall support strap comprising a plurality of tendons which extend for the full length of the strap and a plurality of transverse strap members which extend transversely to the tendons and connect them to one another, opposite end regions of the support strap being narrower than a middle region thereof situated between tendons, the tendons in the middle region being held in spaced apart, generally parallel relationship by middle region strap members while outer tendons in the end regions converge on and are connected to at least one inner tendon in the end regions by end region strap members.

2. An elongated wall support strap as claimed in claim 1 in which an end region strap member has an elongated strip of material to which at least one inner tendon is secured, the strip having respective end sections at either end to which two of more tendons, including outer tendons are secured.

3. An elongated wall support strap as claimed in claim 2 in which the end sections of the end strap members are at least partially folded over to define pockets in each of which the tendons are secured.

4. An elongated wall support strap as claimed in claim 3 in which the tendons and the end strap members are made of steel and the outer tendons are welded to each end strap member in the pockets.

5. An elongated wall support strap as claimed in claim 1 in which each middle region strap member has a generally flat, elongated strip formed with longitudinally extending slits at longitudinal spaced apart slit positions, strip material on one side of the slit being deformed, in a direction transverse to the length of the strip relative to the strip material in the other side of the slit so as to define openings in the strip through which the tendons pass.

6. An elongated wall support strap as claimed in claim 1 in which each middle region strap member has a generally flat, elongated strip formed with longitudinally extending slits at longitudinal spaced apart slit positions, strip material on one side of the slit being deformed, in a direction transverse to the length of the strip relative to the strip material in the other side of the slit so as to define openings in the strip through which the tendons pass.

7. An elongated wall support strap as claimed in claim 1 in which the tendons are straight.

8. An elongated wall support strap as claimed in claim 1 in which the tendons have an undulating or zigzag shape for part of their length.

9. A wall support strap comprising a plurality of tendons which extend for the full length of the strap and a plurality of transverse strap member which extend transversely to the tendon and connect them to one another, each strap member including an elongate strip of material with end sections that are at least partially folded of the define pockets in each of which tendons are secured.

10. A wall support strap as claimed in claim 9 in which the tendons and the end strap members are made of steel and the tendons are secured in the pockets by welding.

11. An elongated wall support strap as claimed in claim 9 in which of the tendons are straight.

12. An elongated wall support strap as claimed in claim 9 in which the tendons have an undulating or zigzag shape for part of their length.

13. An elongated wall support strap as claimed in claim 9 in which outer ends of tendons are connected together.

14. An elongated wall support strap as claimed in claim 9 in which tendons are square or rectangular or round rods.

15. An elongated wall support strap as claimed in claim 9 in which strap members have prop receiving means.

16. An elongated wall support strap as claimed in claim 9 in which clips clip strap members to tendons.

17. An elongated wall support strap as claimed in claim 9 in which strap members have clip on receiving formations.

18. An elongated wall support strap as claimed in claim 9 in which strap members have crimp-on receiving formations.

19. An elongated wall support strap as claimed in claim 9 in which strap members have receiving formations that face in different directions.