AU602809B2

AU602809B2 - Improved method and apparatus for producing expanded products

Info

Publication number: AU602809B2
Application number: AU31258/89A
Authority: AU
Inventors: Neil Harvey Willox
Original assignee: Expamet Pty Ltd
Current assignee: Expamet Pty Ltd
Priority date: 1988-03-16
Filing date: 1989-03-13
Publication date: 1990-10-25
Anticipated expiration: 2009-03-13
Also published as: AU3125889A

Description

COMMONWEALTH OF AUSTRALIA FORM PATENTS ACT 1952 (C 0M PT F T S P E C "F ICA T IO N C FOR OFFICE USE: Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Class Int.Class 6028 SPriority: Related Art: This document contains the amendments made under Section 49 and is correct for printing SName of Applicant: Address of Applicant: Actual Inventor: EXPAMET PTY. LIMITED 42 Fitzpatrick Street, Revesby, New South Wales 2212, Australia Neil Harvey Willox i Address for Service: SHELSTON WATERS, 55 Clarence Street, Sydney Complete Specification for the Invention entitled: "IMPROVED METHOD AND APPARATUS FOR PRODUCING EXPANDED PRODUCTS" The following statement is a full description of this invention, including the best method of performing it known to us:i, 1 Complete of PJ 3097 dated 16th March, 1988 (NT Or RECEIPT o6 i 07 -:3/03/8 o, o 0 o +I

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0s r *s I 0P 0P. PP 0 0 This invention relates to the production of expanded products such as expanded metal mesh and in particular to an improvement in the invention disclosed in our Australian Patent No. 580714.

Although the invention will be described hereinafter with reference to expanded mesh it will be appreciated that the invention is not limited to this particular product but may be applied to any expanded product, such as plastics screens or metal ballustrading.

Expanded metal mesh is well known and there have been many previously known methods of producing it. One such method is described in Australian Patent specification 434,936 where an extruded flanged metal sheet is pre-formed to define laterally staggered parallel overlapping slots separated by bridges of metal left in the web portions between the co-linear slots. The sides of the sheet are then clamped securely and moved apart t,, expand the sheet into its final form.

Problems are encountered with this method because the sheet tends to distort unevenly during the forming process. Stress concentration at the end of the slots adjacent the bridges also causes the ends to split, so care must be taken to avoid sharp corners in the slot ends such as would be formed by square or pointed milling or punching methods.

In International Application PCT/AU84/00249 it has also been proposed to expand a pre-formed sheet by means of a lattice arrangement supporting a plurality of la i c "1 _i OR oo o ."'10 o*o o 0 60 0 9 0 e 9 o 04 j 0 0 0 on o 0 0 o 0 re o6 0000 00 0 0 0 Q0 e 0 o 0 00 0 0 00 0 0 S 0 e0 00 *0* 00 0 2.0 0 0

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melao ec expander bars. The expander bars lie along the entire length of the sheet between adjacent flanges and move apart to expand the sheet. However, this method can apply expanding forces unevenly to the sheet, which may still distort unevenly during the forming process. It also requires the presence of a plurality of parallel flanges across the sheet and so cannot be applied to planar sheets.

Our Australian Patent No. 580714 disclosed an improvement to previously known devices to reduce at least some of the problems of the prior art by providing an expanding method and apparatus to expand the sheet more accurately and evenly across its area, preferably producing less distortion and being less susceptible to the effect of stress concentration at the ends of the slots.

According to one aspect of our earlier invention there was provided apparatus for expanding a pre-formed metal sheet in which the sheet includes a plurality of laterally staggered parallel overlapping slots, the slots being separated by bridges of metal left between co-linear slots, the apparatus including an expandable lattice array in which a plurality of bridge engagement means are each pivotably mounted in spaced array across the lattice for individually engaging selected bridges on the sheet and applying expanding force directly to the bridges.

In another aspect, the earlier invention provided a method for expanding a pre-formed metal sheet by applying the sheet to an expandible lattice array, individually 14, 2 "5ku ft 1 a *i 4 OI it

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engaging a plurality of selected bridges by corresponding bridge engagement means each pivotably mounted in spaced array across the lattice and then expanding the lattice to form the expanded sheet.

Tests conducted with our earlier invention have demonstrated the viability of the lattice array and the plurality of bridge engagement means for individually engaging the sheet. At the same time they have led to a number of improvements to this basic concept. In particular it has been found that improved geometric accuracy can be achieved across an entire sheet by adopting a lattice formed by a plurality of individual links rather than by spacing pivot points and bridge engagement means along continuous rigid lattice arms.

The use of long continuous arms can produce geometric disconformity between the sheet and the lattice which accumulates towards the extremities of the sheet.

Depending on the size, shape and required configuration of the sheet this may not be significant, particularly where the bridge engagement means are arranged to engage the bridges loosely (in the sense of non-rigidly) and thereby allow for lost motion and relative movement as mentioned on page 4 of our earlier application.

However, for some configurations the disconformity may become important and the present invention was developed to extend the operation of the earlier invention to a wider range of applications.

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t~t 3 ci- 1 4 According to one aspect of the present invention there is provided apparatus for expanding a pre-formed metal sheet in which the sheet includes a plurality of laterally staggered parallel overlapping slots, the slots being separated by bridges of metal left between co-linear slots, said apparatus including an expandable lattice array defined by a plurality of pivot blocks interconnected by a plurality of links pivoted at each end oO 1 to a respective pivot block, selected ones of said pivot a 60 T1Q blocks supporting bridge engagement means for individually 0 engaging selected bridges on the sheet and for applying expanding force directly to said bridges.

oo 0* e *In another aspect the present invention provides a method for expanding a pre-formed metal sheet in which the sheet includes a plurality of laterally staggered parallel overlapping slots, the slots being separated by bridges of 000 0- metal left between co-linear slots, by applying the sheet to an expandable lattice array, individually engaging a plurality of selected bridges on the sheet by S, corresponding bridge engagement means each pivotably o 1 mounted in spaced array across the lattice and then 19 expanding the lattice to form the expanded sheet, said lattice being defined by a plurality of pivot blocks interconnected by a plurality of links pivoted at each end to a respective pivot block, selected ones of said pivot blocks supporting said bridge engagement means.

It is not necessary to engage every bridge in the sheet. In one simplified form of the invention the 0 1cL "I'P 4a bridges along one or both longitudinal edges are engaged by a 'mini' lattice with no engagement of the intermediary bridges. In this form of the invention the other edges of 00P Pt P- 64 -0 o P P 0 046 P 89 P P

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t I 4 I the sheet may be engaged by sliding blocks not fixed to the lattice but merely restraining the sheet during the expansion process. The transverse edges may also be engaged by the mini lattice if desired.

Depending upon the particular application, satisfactory results can be obtained by engaging preselected bridges such as every second, third, fourth, fifth or higher number spaced longitudinally and transversely across the sheet. Preferably however, each bridge or corresponding position is engaged along the opposite longitudinal edges of the sheet.

The sheet is preferably flanged such that the slots and bridges are formed in the web portions of the sheet bet-ween adjacent flanges. The bridge engagement means can then act directly on the flanges. However, the invention may also be applied to flat sheets where the bridges are engaged loosely at their edges or by secure clamping force applied transversely of the bridge and/or normally of the sheet if required.

The bridge engagement means may be secured at any suitably spaced locations on the lattice but are preferably all located on respective pivot blocks. They may clamp the bridges tightly, or less firmly to allow for some relative movement during forming. Preferably the sheet is securely entrapped by the lattice such that there is no relative movement between the sheet and the engagement means during expansion. The forming process is then totally controlled by the lattice geometry and the final product is uniform across its entire area.

4 1 C' I7 A preferred embodiment of the invention will now be described by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic plan view showing part of an extruded and slotted sheet before and after expansion.

Figure 2 is a section of the unexpanded sheet, taken on line 2-2 of Figure 1.

Figure 3 is an end elevation of an expanding machine according to the invention, the machine being Shown in its open position with the lattice closed, ready to receive an unexpanded sheet.

Figure 4 is a plan view of the lattice assembly in its expanded configuration but omitting the sheet.

Figure 5 is an enlarged plan view of part of the lattice assembly indicated in Figure 4, showing the sheet dotted but omitting the guide bars.

Figure 6 is a further enlarged sectional view taken generally on line 6-6 of Figure Figure 7 is a similar view to that of Figure 5 but tt 0 showing the simplified form of the lattice assembly.

Referring to the drawings, Figures 1 and 2 illustrate one example of a pre-formed metal sheet. This particular sheet 1 is formed of extruded aluminium and includes parallel flange portions 2 separated by webs 3. A plurality of slots 4 are formed in the webs 3 by any suitable and well known means, such as punching by reciprocating or rotating dies, cutting or slotting. The slcts are arranged in laterally staggered parallel -e a

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lC o 0 o a a or a o overlqpping relationship and are separated by bridges of metal 5 left between co-linear slots, as shown in the lower portion A of Figure i. Portion B illustrates the final form of the sheet after it has been expanded laterally by the machine described below.

Referring now to Figure 3, the expanding machine 6 is shown in its open position, ready to receive a preformled unexpanded sheet as shown in portion A of Figure 1. The machine includes a fabricated steel bottom frame 7 and a corresponding top frame 8 hinged to the bottom frame for rotation about hinge axis 9. The top frame can be raised or lowered by a double acting hydraulic cylinder 10 to permit the sheet 1 to be inserted and removed from the expanding lattice assembly The machine may incorporate a rack stabiliser 12.

The lattice assembly 11 includes an expanding lattice array 13 defined by a plurality of pivot blocks 14 interconnected by a plurality of links 15 pivoted at each end 16 to a respective pivot block 14. The main lattice pivot blocks 14 are each slidably mounted to spaced parallel guide bars 17.

The lattice array 13 extends within a frame comprising fixed and moving opposed parallel longitudinal members 18 and 19 respectively, slidably interconnected by corner slide blocks 20 with opposed parallel transverse members 21 of which only one is shown.

Marginal lattice pivot blocks 22 are connected to adjacent frame members by slider units 23 incorporating suitable bearings 24.

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*49O An hydraulic cylinder and ram assembly 25 connected to the movable longitudinal frame member 19 expands and contracts the lattice to effect the forming process. The transverse members 21 are outwardly biased by counterweights, springs or hydraulic means (not shown) to facilitate closing of the lattice. During expansion and contraction, the lattice moves between a bottom plate 26 on the bottom frame 7 and a corresponding removable top cover plate 27 forming part of the top frame 8. Each pivot block 14 includes a spring-loaded downwardly directed sliding pad 28 for engaging the bottom plate 26 and supporting the lattice assembly.

Selected pivot blocks support bridge engagement means 29 in the form of upwardly directed forks able to receive the bridges 5. Each bridge engagement means 29 is preferably removable but in use is rigidly connected to its respective pivot block and is able accurately to guide and form the sheet during the expanding process. The lattice applies individual forming forces, in this example applied to each third bridge spaced evenly across the sheet.

In cases such as this where not every bridge or bridge position is engaged, it is desirable to incorporate side lattice assemblies 30 and 31 along Opposite longitudinal sides of the lattice. It can be seen that the pitch of the side lattice assemblies corresponds to that of the sheet such that edge engagement means 32 can 8 i .?i i o o o o a 0 0 0 o or 4 o o 00 4 0 00 00 0 4 40 00 0 act simultaneously on each free bridge position 5A along the opposite longitudinal edges of the sheet. The side lattice assemblies are essentially identical to the main lattice but on a suitably reduced scale with intermediate pivot blocks 34 interconnected by links 35 but without engaging parallel guide bars.

Preferably, means are provided for engaging a; constraining the transverse ends of the sheet. As shown in Figures 5 and 6 this means comprises a yoke 37 which accepts and holds the final cut bridge portion 36 ensuring that the sheet ends will move in conformity with the lattice. The yokes 37 are mounted on transverse marginal pivot blocks 22 in the same way as the bridge engaging forks 29. The yoke formation provides an abutment for applying inwardly directed force to the sheet as the lattice expands. The yokes may be replaced with releasable clamps for rigidly holding the sheet ends.

Depending upon requirements, each free bridge portion 36 may be engaged across the entire transverse width of the sheet or selected ones as shown.

Referring to Figure 7 a simplified form of the lattice assembly is shown. This assembly employs only the side lattice assembly 30. The components of such assembly have been described hereinbefore. In this form of the invention one or both of the longitudinal edges of the sheet are engaged by a side lattice assembly 30 or assemblies and the sheet 1 expanded by use of these assemblies without the need for the major lattice array 1~ 9 1 a

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13. The transverse edges of the sheet 1 may be restrained by yokes 37 in a similar fashion to that described in respect of Figure 5, however, the blocks mounting these yokes need not be coupled to the side lattices 30. If only one longitudinal side lattice array 30 is employed the other longitudinal edge of the sheet 1 may be restrained in a similar fashion to the transverse edges.

The selective spaced engagement provided by the present invention also makes it particularly suitable for producing patterned mesh, where repeated but internally irregular patterns may be spaced across the sheet.

Although the invention has been described with reference to a specific example, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.

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Claims

1. Apparatus for expanding a pre-formed metal sheet in which the sheet includes a plurality of laterally staggered parallel overlapping slots, the slots being separated by bridges of metal left between co-linear slots, said apparatus including an expandable lattice array defined by a plurality of pivot blocks interconnected by a plurality of links pivoted at each end to a respective pivot block, selected ones of said pivot blocks supporting bridge engagement means for individually engaging selected bridges on the sheet and for applying expanding force directly to said bridges.

2. Apparatus according to Claim 1 including a plurality of narallel guide bars spaced across said lattice and along which said pivot blocks are constrained to move as said lattice expands.

3. Apparatus according to Claim 2 wherein said lattice array extends within a frame comprising fixed and moving opposed parallel longitudinal members slidably interconnected at frame corners with opposed parallel transverse members, marginal lattice pivot blocks being connected to adjacent frame members by slider units.

4. Apparatus according to Claim 3 wherein said parallel guide bars extend parallel with said longitudinal frame members and engage slider units mounted to said transverse members. Apparatus according to anyone of claims 1 to 4 wherein said selected pivot blocks lie along one longitudinal edge of said sheet.

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6. Apparatus according to claim 5 wherein said pivot blocks further lie along at least one transverse edge of said sheet.

7. Apparatus according to any one of the preceding claims wherein means are provided for engaging and constraining the transverse ends of said sheet.

8. Apparatus according to Claim 7 wherein each of said means is located on one of said pivot blocks.

9. Apparatus according to Claim 7 or Claim 8 wherein o° said means includes an abutment for applying inwardly r, o 4 directed force to said transverse ends of said sheet in a 0..o direction transverse to the expansion direction as said o o lattice expands.

Apparatus according to Claim 7 or Claim 8 wherein o" said means comprises a releasable clamp for rigidly 0 0 holding said ends.

11. Apparatus according to any one of Claims 7 to wherein said means engages said sheet at each bridge or corresponding bridge position across the entire Stransverse width of said sheet.

12. Apparatus according to Claim 1 including means for engaging each bridge or corresponding bridge position along the entire opposite longitudinal edges of said sheet.

13. Apparatus according to Claim 12 wherein said edge engagement means are located on pivot blocks of opposite side lattice assemblies where the pitch of said side lattice assemblies corresponds to that of said sheet. 12 N 1k It 1 It 1~. 0 0 0 o ttt .4 00.-i St I 0. 0.0.10. 0 0. 0 1 0. 0. 0. t 0- 0. 0. 0.t 1~0. I 13

14. Apparatus according to any one of the preceding claims including a single horizontally disposed lattice and wherein each pivot block includes a spring-loaded downwardly directed sliding pad for engaging a horizontal bottom plate across which said lattice expands.

Apparatus according to Claim 14 incluo-ing a removable top plate for covering the lattice and sheet during expansion.

16. Apparatus according to Claim 15 wherein said bottom plate and said lattice are supported by a bottom frame and said top plate is supported by a top frame hingedly mounted for rotation with respect to said bottom frame to permit placement and removal of said sheet.

17. Apparatus according to any one of the preceding claims wherein said bridge engagement means loosely engage said bridges.

18. Apparatus according to any one of Claims 1 to 16 wherein said bridge engagement means angage said bridges by positive clamping engagement.

19. Apparatus according to any one of the preceding claims wherein said bridge engagement means comprise upwardly directed forks.

Apparatus according to Claim 3 wherein said transverse members are biased outwardly.

21. A method for expanding a pre-formed metal sheet in which the sheet includes a plurality of laterally staggered parallel overlapping slots, the slots being separated by bridges of metal left between co-linear I W 7 oI I o 0 0 0 0 ,,t 0 40 00 0 4 14$ i II 4 It~ 14 slots, by applying the sheet to an expandable lattice array, individually engaging a plurality of selected bridges on the sheet by corresponding bridge engagement means each pivotably mounted in spaced array across the lattice and then expanding the lattice to form the expanded sheet, said lattice being defined by a plurality of pivot blocks interconnected by a plurality of links pivoted at each end to a respective pivot block, selected ones of said pivot blocks supporting said bridge engagement means.

22. A method according to claim 21 wherein said selected pivot blocks lie along one longitudinal edge of said sheet.

23. A method according to claim 22 wherein said pivot blocks further lie along at least one transverse edge of said sheet.

24. An expanded metal sheet formed by the method of anyone of Claims 21 to 23.

25. Apparatus for expanding a pre-formed metal sheet substantially as herein described with reference to the accompanying drawings.

26. A method for expanding a pre-formed metal sheet substantially as herein described with reference to the accompanying drawings. DATED this 26th Day of July, 1990 EXPAMET PTY. LIMITED Attorney: PETER HEATHCOTE Fellow Institute of Patent Attorneys of Australia of SHELSTON WATERS i I