GB2080363A - Articulate Structures - Google Patents

Abstract

The invention provides an articulated structure comprising two angularly disposed trough section beams 1 a & 2 located in one plane and coupled together by a pair of fishplates 4, 5, the fishplates being secured each to a separate one of the beams by bolts in apertures 6 & 7 so as to overlap and nestle in the trough of the other, aligned apertures 8 being provided in the fishplates for receiving a bolt or pin between the two sections, said bolt or pin being laterally movable in one or both of said apertures whereby to permit a limited degree of articulation between the two sections. <IMAGE>

Description

SPECIFICATION Articulated Structures This invention relates to articulated structures and more particularly relates to load bearing structures such as mine roof supports.

'Roadway' arches frequently comprise channelsection beams secured together in a variety of ways including the common fishplate which may be curved or chevron-shaped as appropriate.

The assembly into place of fixed arches however presents difficulties in so far as one current practice is to assemble the arch, e.g. on the floor, lightly secure the fishplate bolts and then pivot it upwardly into place by a machine and secure the bolts. With a relatively inflexible assembly of this nature difficulty is encountered since the roof, and more particularly the walls, present obstructions to such movement and even the preceding arches erected can foul the side legs of the newly assembled arch as it is pivotted into place.

It is an object of this invention to mitigate this problem.

From one aspect, the present invention provides an articulated structure comprising two angularly disposed beam sections located in one plane and coupled together by a pair of fishplates, each secured to one of the beams and overlapping and nestling in the trough of the other, aligned apertures being provided in the fishplates for receiving a bolt between the two sections which is laterally movable in one or both of said apertures whereby to permit a limited degree of articulation between the two sections.

The reference above to angular disposition includes curved arrangements, i.e. it refers to the tangents to those curved beams where this is the case.

Preferably the aperture in each of the fishplates is elongated to enable the bolt to be laterally movable in both. The ends of the beams may be designed to abut one another, e.g. by mitring, to reduce the load on the fishplate with loads applied at the joint in which case they are cutaway to accommodate the bolt - or (preferably) they are cropped at right angles to their lenghh such that the bolt passes between them.

The fishplates may be chevron-shaped to suit the design of the arch and each may be cut away slightly at its apex to ensure that undue pressure is not exerted on the upper flange before the lower forward end of the fishplate is in firm contact with the lower flange. This lower forward end or toe is in turn måde to protrude as far as is practicable along the flange so as to ensure that the maximum point of pressure is as far away as possible from the joint.

Articulated structures in accordance with this invention are readily capable of being assembled on, e.g., a mine roadway floor, and then lifted into place; an articulation of between 12" and 150 is readily obtainable in the loosely bolted condition without sacrificing strength beyond acceptable limits. Further, an additional advantage of an articulated structure of this nature is that it will accommodate limited movements of the tunnel walls occasioned for example by expansion of the tunnel wall stratum. Under these circumstances the legs will move inwards rather than deflect into a (possibly) unstable position in response to these pressures.

In order that the invention may be fully understood one embodiment thereof will now be described, by way of example, with reference to the accompanying drawings in which Figure 1 is a side elevation of an articulated arch according to this invention, and Figure 2 is a detailed side elevation of the fishplate coupling.

Referring now to Figure 1 the typical mine arch shown comprises three rolled steel joist sections namely two upstanding curved leg beams 1 a and 1 b and a roof beam or crown 2. These sections are coupled together by two pairs of chevronshaped fishplates 3 permitting a measure of articulation as depicted by the chain-dotted outline of the legs 1a and 1 b.

Referring now to Figure 2 the couplings are shown in more detail. In particular, the flanged Hbeam sections 1 a and 2 have cropped ends and roughly abut one another at their inner corners only. Bolted to these sections on opposite sides thereof are a pair of fishplates 4,5 the bolts (not shown) being secured through aligned apertures 6 in the fishplate 4 and the beam 1 a and apertures 7 in the fishplate 5 and the cross beam 2. Centrally disposed between the beam ends are two aligned elongated apertures 8 in each of the fishplates 4,5 through which a bolt (not shown) extends, from which it can be seen that a measure of articulation is permitted between the two beam sections within the limits defined by the permitted movement about the bolt in these apertures.

The design profile of the fishplates is such that, under conditions of maximum stress, pressures are not exerted on the extremities of the upper flange 9 before the lower toe 10 of these plates is in firm contact with the lower flange 11. Should this happen the plates will exert pressure on the upper flanges only which is likely to cause fractures along the web roots. To avoid this therefore, the area 12 around the apex of each plate is cut away or inset and this is carefully dimensioned in order that the converse should not occur, that is, pressure exerted on the lower flange only.

Tests which have been conducted on this joint w h RSJ's of 127x1 14 mm, fishplates of nominally 90x20 mm and a 30 mm diameter centre bolt resulted in failure only at vertical loads of the order of 20 tons or more which adequately meets the requisite safety standards for a variety of applications.

Although this invention has been described with reference to the particular embodiment illustrated it is to be understood that various modifications may readily be introduced without depàlting from the scope of this invention. For example, marginally stronger joints may be formed by mitring the ends of the beam sections so that they abut along their whole length but in this instance 'half' slots must be cut into each exposed end of the beam. The non-standard manufacturing process and the added length of the beam also adds to costs.

The thickness, width, length and quality of the steel used will clearly vary with the expected demand on the joint and it is not essential of course to have elongated apertures 8 in each fishplate-only one fishplate need have an elongated aperture but the drawback here is that only half the movement permitted with both apertures elongated would then be possible.

Claims (9)

Claims

1. An articulated structure comprising two angularly disposed trough section beams located in one plane and coupled together by a pair of fishplates, the fishplates being secured each to a separate one of the beams so as to overlap and nestle in the trough of the other, aligned apertures being provided in the fishplates for receiving a bolt or pin between the two beams, said bolt or pin being laterally movable in one or both of said apertures whereby to permit a limited degree of articulation between the two beams.

2. A structure according to Claim 1 wherein the aperture in each of the fishplates is elongated to enable the bolt to be laterally movable in both.

3. A structure according to Claim 1 or 2 wherein the ends of the beams at the coupling are shaped to abut one another across the beam ends, and are provided with slots or notches from the ends thereof to accommodate the pin or bolt.

4. A structure according to Claim 1 or 2 wherein the ends of the beams are cropped at right angles to their length.

5. A structure according to any one of the preceding claims wherein each of the fishplates is chevron-shaped in plan view, one side arm thereof being secured to a beam.

6. A structure according to Claim 5 wherein each of the fishplates is reduced in width, in plan view, at and adjacent to the apex thereof.

7. A structure according to claim 5 or 6 wherein the end of each fishplate remote from secured arm thereof is provided with an extended toe on that side of the fishplate containing the included angle.

8. An articulated underground roadway arch comprising a structure according to any one of the preceding claims.

9. An articulated arch substantially as shown in and as hereinbefore described with reference to the accompanying drawings.