AU639135B2

AU639135B2 - Expanded metal mesh

Info

Publication number: AU639135B2
Application number: AU83787/91A
Authority: AU
Inventors: Van Tai Lam
Original assignee: John Lysaght Australia Pty Ltd
Current assignee: John Lysaght Australia Pty Ltd
Priority date: 1990-09-14
Filing date: 1991-09-10
Publication date: 1993-07-15
Anticipated expiration: 2011-09-10
Also published as: AU8378791A

Description

Il~l~i P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: EXPANDED METAL MESH The following statement is a full description of this invention, including the best method of performing it known to the Applicant:- This invention relates to the manufacture of expanded metal mesh.

The primary object of the invention is to provide an expanded metal mesh particularly suited for use as fence panels in high security fences. The invention achieves that object by providing an expanded metal mesh wherein the lower side of each aperture in the mesh is defined in part by at least one upwardly extending sharp edged protrusion. Thus fences incorporating mesh panels according to the invention cannot be climbed by a person with bare hands without his or her fingers being badly and painfully cut.

I -T I- -;II 2 The invention not only consists in mesh with protrusions as aforesaid, but also in apparatus for the manufacture of such mesh.

Figure 1 of the drawings herewith is a diagrammatic front elevation of a prior art shearing and pressing apparatus fitted with conventional shear blades for the manufacture of conventional expanded metal mesh.

Figure 2 is a scrap section taken on line 2-2 of figure 1.

e ee As may be seen from figures 1 and 2 conventional expanded metal mesh 5 is customarily made by means of a shearing and pressing S 1 0 apparatus comprising a fixed shear blade 6 with a straight cutting edge and a co-acting reciprocating shear blade 7 presenting a plurality of spaced apart V-shaped cutting teeth. The reciprocating blade may be a single, suitably profiled blade or a linear assembly of separate, Vshaped tooth elements.

o .15 It is usual for the fixed blade to extend horizontally and for the reciprocating blade to rise and fall in the vertical plane. That configuration is not essential but it is convenient, and for descriptive convenience is assuned to be the case hereinafter.

According to conventional practice, a work piece in the form of a solid metal sheet or plate 8, referred to hereinafter as the sheet, is advanced incrementally over the fixed blade 6 and each time the sheet 8 halts, with a margin projecting horizontally beyond the fixed blade 6, the reciprocating blade 7 moves downwardly through an ii operating stroke to shear spaced apart portions of that margin from the sheet 8 and simultaneously press those portions downwardly from the 3 plane of the sheet 8 into a V-shaped configuration. The relatively short parts of the margin intermediate the said portions, to which the portions remain attached and which are not sheared from the sheet 8 until the next operating stroke, are referred to as junctions hereinafter. The reciprocating blade 7 then rises through a return stroke to retract from the sheet 8 to enable it to be advanced by another increment..

As well as reciprocating through operating and return strokes (as indicated by the pairs of vertical arrows in the figures), the reciprocating blade 7 oscillates to and fro in its longitudinal direction (as indicated by the pairs of horizontal arrows in figure The oscillations are in timed 0 1000 relationship with the blade's reciprocating movement, so that a to or fro oscillatory stroke occurs prior to each operating stroke. Tiie magnitude 00.0 of the oscillatory movement is such that the margin portions sheared from the sheet 8 during each operating stroke of the reciprocatin~g blade 7 are fully staggered, in the longitudinal direction of the margin, in relation to those sheared during the preceding operating stroke. That is to ay hecentre of each sheared off portion of one margin is in alignment with, and indeed joined to, a junction of the previously sheared margin. Therefore, as each sheared off portion is pressed from the plane of the sheet 8, it carries a junction of the previously worked -margin with it. The net result is the formation of an expanded mesh sheet 5, referred to as the mesh hereinafter, wherein a regular array of columns of more or less diamond or lozenge shaped openings are each sheared off sheet margin, extending between junctions at the top, bottom and each end of the opening.

4 Expanded metal mesh is a well known and widely used product and its production, as briefly described above, and the apparatus used therefor, are similarly well known.

In accordance with the second aspect of the invention, the conventional apparatus for making the mesh described above is modified by the provision of at least one recess in the cutting and pressing edge of each of the teeth of the reciprocating shear blade.

This slightly delays the shearing off of elements of the sheet margin at the locations of the respective recesses, relative to the margin immediately adjacent those elements. It also delays the displacement of the elements from the plane of the sheet, which in turn causes plastic stretching of each of the elements in the direction of margin g 4: C displacement. Once the elements have been severed from the sheet, they remain as sharp edged protrusions extending upwardly into the mesh apertures. The protrusions are formed with a sharp edge because the stretching and displacement results in the upper front surface of the protrusion (form-erly an upper surface of the sheet) being inclined in the cc to finished mesh, so as to meet the back surface of the protrusion (a surface produced by the shearing cut) at an acute angle.

Two preferred embodiments of the invention are respectively illustrated by figures 3 and 4 of the drawings herewith. Each of those figures is a front elevation of portion of the movable shear blade of apparatus according to the invention and the mesh produced when the shear blade is substituted for the blade 7 of the prior art apparatus.

According to the figure 3 embodiment of the invention a sharp ed ,-Ied protrusion 31 as aforesaid extends from each junction 32 in the mesh 34. That mesh is produced from a work piece sheet 35 by the 59 provision of a reciprocating and oscillating shear blade 36, in apparatus of the kind described with reference to figures 1 and 2, in substitution of the blade 7 thereof. To that end the blade 36 has a single, centrally placed recess 37 of inverted V-shape in each of its teeth 38, that is to say a recess is formed in what would, in the absence of the recess, have been the lowest tip area of a conventional V-shaped tooth. Thus, each recessed tooth 38 has two symmetrically positioned tips. For preference those twvo tips are spaced apart by an amount substantially equal to the length of each junction 32, whereby each protrusion 31 in 1: 0 the finished 34 mesh is, at its base, as long as the junction from which it projects.

t C According to the figure 4 embodiment of the invention a plurality of sharp edged protrusions 41 are provided along the strands 49, as well as one at each junction 42, of a mesh 44 produced from a work piece sheet 45 by a reciprocating and oscillating blade 46 having a correspondingly positioned plurality of recesses 47 formed in the edges of its teeth 48.

It is known to vary the shape of the teeth of the reciprocating4 blades to produce what may be seen as more ornamental or unusual patterns of mesh. The present invention extends to all such variations from the regular pattern of lozenge-shaped openings described above, provided they display the characteristic sharp-edged protrusions of the invention.

Claims

1. An expanded metal mesh of the kind wherein each of a plurality of apertures is defined by strands of metal extending between junctions with others of said strands, characterised in that the lower side of each aperture is defined in part by at least one upwardly extending sharp edged protrusion.

2. An expanded metal mesh according to claim 1 having a said protrusion at each said junction.

3. An expanded metal mesh according to claim 2 wherein the said protrusion at each said junction is substantially as long at its base as the junction.

4. An expanded metal mesh substantially as described herein with reference to figure 3 or figure 4 of the accompanying drawings.

Shearing and pressing apparatus for making expanded metal mesh of the kind comprising a fixed shear blade with a straight It' i cutting edge, a co-acting movable shear blade with a plurality of spaced :t apart cutting and pressing teeth, means to reciprocate said movable ti I iblade through operating and return strokes, means to oscillate said movable blade longitudinally of itself in synchronism with its reciprocation and means to advance a work piece sheet incrementally across the fixed blade in synchronism with the said reciprocation, Icharacterised in that each of said teeth has at least one recess in its r t !-i cutting and pressing edge whereby an upwardly extending sharp-edged %tt protrusion is formed in the finished mesh. t o tit t Jo4" I. xw~P~ -Y^.LI

6. Apparatus according to claim 5 wherein each of said teeth is V shaped but for a said recess at the tip of the V.

7. Apparatus according to claim 5 wherein there are a plurality of said recesses in each of said teeth and wherein the recesses are substantially equally spaced apart.

8. Apparatus for making expanded metal mesh substantially as described herein with reference to figures 1 and 2 of the accompanying drawings when characterised by the inclusion of movable shear blades substantially as described herein with reference to figure 3 or figure 4 of the accompanying drawings. t i Applicant JOHN LYSAGHT (AUSTRALIA) LIMITED Date 10 September 1991 of CARTER SMITH BEADLE i i L i '-~w~PL~rrr?~ ABSTRACT An expanded metal mesh (34) (44) suitable for use as security fence panels is rendered unscaleable by virtue of sharp edged protrusions (31) (41) projecting upwardly into the mesh apertures. Apparatus for making the mesh from a work piece sheet is also disclosed of the kind comprising a fixed shear blade a co-acting reciprocating and longitudinally oscillating shear blade and means to advance a work piece sheet incrementally across the fixed blade, wherein the cutting and pressing edge of the movable blade (36) (46) has a recess or recesses in it for the formation of the mesh protrusions. Figure 3. I

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