GB2129030A

GB2129030A - Mine roof support clamp

Info

Publication number: GB2129030A
Application number: GB08327166A
Authority: GB
Inventors: Dr Manfred Frohlke; Helmut Grub; Kurt Bernhofer; Otto Wilden
Original assignee: Arbed SA
Current assignee: Arcelor Luxembourg SA
Priority date: 1982-10-23
Filing date: 1983-10-11
Publication date: 1984-05-10
Also published as: FR2534965B1; DE3239343C2; DE3239343A1; GB2129030B; FR2534965A1; BE898064A; GB8327166D0

Abstract

A tension connector to surround and secure together channel-shaped sections 3, 4 for mining supports. The connector comprises a resilient top member 5 and a bottom member 6 which is also of resilient construction. The top member has a pair of screw- threaded spindles 8 at its ends which pass through corresponding holes 13 in the bottom member 6. The two parts of the connector are then secured together under tension by lock nuts 17. <IMAGE>

Description

SPECIFICATION A tension connection for interfitting slidable channel sections for mining supports This invention relates to a tension connection for interfitting slidable channel sections for mining supports, in which the resilient top member is screwed to the bottom member.

The main feature of flexible mining supports is that the channel-section segments making up the multi-element arches which form the supports overlap at their connecting points, said sections being disposed co-directionally one inside the other, and can then slide inside one another if the rock pressure exceeds the frictional resistance produced by the predetermined clamping tension at the connecting points.

Resilient dynamic tension connections are known (DAS 27 26 455, DOS 28 54 457). They have the disadvantages that they are expensive to produce and are complex to fit in underground workings. Individual prestressing is impossible, and the same applies to post-tensioning.

Known tension connections consisting of top and bottom members are connected by two screws. The resulting box-shaped saddle has high flexural rigidity, but is not particularly suitable for taking impacts from the rock. This tension connection has substantially no resilient properties of the kind increasingly required.

The object of this invention is to provide a tension connection of the kind referred to hereinbefore, which is simple and cheap to make, easily installed, and ensures reliable bracing of the channel sections in response to variations in rock pressure.

To this end, according to the invention, the top member has screw spindles at both ends and the bottom member is also of resilient construction.

According to one aspect of the invention, the bottom member is V-shaped, has a constant wall thickness and outwardly curved flanges, and the bottom member is so shaped that it contacts only the bottom edge of the flange of the outer channel section, said bottom edge being in the form of a nose.

According to another aspect of the invention, the flanges of the bottom member are bent down from the horizontal.

The particular advantages of the invention are that uniform sliding of the channel sections is possible in response to variations in the rock pressure, because the entire tension connection can behave elastically. The tension connection according to the invention can also be prestressed within a wide range. Also, it is easily fitted and removed in underground workings.

Fig. 1 illustrates two channel sections 3 and 4, at the free ends of which are disposed a main saddle 1 and a guide saddle 2. These tension connections consist of top members 5 and bottom members 6, which are bolted together by means of lock nuts 1 7. The top members 5 have screw spindles 8 for this purpose. Top member 5 of the main saddle 1 has two claws 10 to ensure that the main saddle 1 is also moved on insertion of the channel section 3, the same effect being achieved for the guide saddle 2 by means of claws 16.

Fig. 2 is a cross-section of a tension connection. The channel sections are denoted by references 3 and 4. The resilient top members 5 are of M-shaped construction and in the zone 7 where they are tensioned against the flange 1 5 of the inner section 3, they have a parallel flat with semi-circular edges in the direction of insertion.

Their free ends extending perpendicularly to the direction of insertion are cylindrical, however, and have screw spindles 8 for tensioning with the bottom member 6.

The middle part 9 of the top member 5 is of such a configuration according to the invention as to form a kind of handle to facilitate handling during transport and assembly.

The top member 5 is additionally provided with a claw 10 at each of the convex arcuate sections at the main saddle, and this claw engages behind the flange 1 5 of the inner section 3. This ensures that the main saddles 1 also move on insertion of the channel section 3.

The bottom member 6 is of V-shaped crosssection with outwardly curved flanks 11 each terminating in flanges 12 via an arc and being bent downwards from the horizontal. The flanges 12 have oval holes 1 3 through which the screw spindles 8 of the top member 5 are passed after the bottom member has been so fitted against the ends of the interfitting channel sections 3 and 4 as to engage from below around the outer channel section 4. In these conditions it bears only against the bottom nosing 14 of the flange 1 5.

The centres of the holes 1 3 in the bottom member 6 of the main saddles 1 are on the transverse axis of symmetry of the bottom member 6. On the other hand, the centres of the holes 13 in the bottom member 6 in the guide saddles 2 are offset eccentrically in relation to the member edge situated opposite the free end of the outer channel section 4 in the overlap zone. Thus when the guide saddle 2 is tensioned a force is built up to counteract the tipping force occurring on insertion of the channel sections 3 and 4.

Movement of the guide saddle 2 during the insertion movement is ensured by the fact that the bottom member 6 has two claws 1 6 symmetrically to the centre axis at its edge associated with the end of the outer channel section 4, said claws engaging behind said end.

The necessary pre-stressing is obtained by screwing the top member 5 to the bottom member 6, lock nuts 1 7 preferably being used.

The longitudinal force produced in the flanges 1 2 of the bottom members 6 by the tightening of the lock nuts 17 produces a bending moment about the contact area 1 8 between the top flange curvature of the bottom member 6 and the nose 14 of the flange 1 5 of the outer section 4. The antipole of this pressure area 1 8 is the area 19 between the inner arc of the top member 5 which, at this point, is in the form of a parallel flat with semicircular edges, and the spine 20 of the flange 1 5 of the inner section 3. This results in substantially ideal tensioning of the interfitting channel sections 3 and 4 with the contact pressures being extensively transmitted to the slideways defined by the flange construction.

The screw tensioning between the screw spindle 8 and the flange 12 provides a resilient suspension in response to impacts followed by immediate closure of the screw connection so that only low pressure amplitudes occur at relatively high frequency.

During prestressing, the outwardly curved flanks 11 of the bottom member 6 are bent away from the outer channel section 4 as a result of the bending moment occurring at the contact area 18, so that there is no risk of any rubbing, which would have a very adverse effect on the sliding movement, or even any risk of seizing, at the flanges of the channel sections 3 and 4 in the overlap zone.

The provision of semi-circular edges on the bottom member 6, which is in any case formed as a parallel flat, and on the top member 5 which is also in the form of a parallel flat in the contact area 1 9 is intended for the same purpose.

Claims

1. A tension connection for interfitting slidable channel sections for mining supports, comprising a resilient top member screwed to a bottom member, wherein the top member has screw spindles at both its ends and the bottom member is also of resilient construction.

2. A tension connection according to Claim 1, wherein the bottom member is V-shaped, has a constant wall thickness and outwardly curved flanks, and the bottom member is so shaped that it contacts only the bottom edge of the flange of the outer channel section, said bottom edge being in the form of a nose.

3. A tension connection according to Claim 1 or Claim 2, wherein the flanges of the bottom member are bent down from the horizontal.

4. A tension connection according to any preceding claim wherein the flanges of the bottom member have oval holes.

5. A tension connection according to any preceding claim wherein the top member where it contacts a channel section under pressure is in the form of a parallel flat with semi-circular edges and has a gradual transition to the circular crosssection of its middle part.

6. A tension connection according to any preceding claim wherein the top members of the main saddles and the bottom members of the guide saddles have claws and respectively.

7. A tension connection substantially as herein described with reference to and as illustrated in the accompanying drawings.