AU2001285613A1 - Method and apparatus for the continuous press-forming of wide panels - Google Patents

Description

Method and apparatus for the continuous press-forming of wide panels

Field of the invention

This invention relates to the continuous or progressive press-forming of substantially flat strip material into wide panels of the kind having hollow ribs or like stiffening formations extending longitudinally of the panel. Typically, a panel of the kind in question has a cross- sectional profile displaying one or more half wave, full wave or wave-like shapes corresponding to the cross-sectional profiles of the respective stiffening formations, with or without intermediate or flanking straight-line portions corresponding to undeformed elongate zones oF the original workpiece. The terra "profile" as used hereinafter is to be construed in every instance as a reference to a "cross-sectional profile".

Background of the invention

An important class of wide panels of that kind are so-called corrugated panels wherein all, or at least a major part, of the profile is a continuous waveform displaying a constant pitch, shape, and amplitude, extending from or near one longitudinal edge of the panel to or near the other longitudinal edge. The present invention is well, but not exclusively adapted lo the production of such corrugated-panels.

The invention was devised primarily for use in the production of roof and wall cladding panels made of steel or other elastic materials exhibiting the property of an elastic limit and is described primarily in relation thereto herein. If such materials are stressed beyond their elastic limits they may be plastically deformed and, following relaxation of the stressing force, the material remains substantially in the deformed shape. If stressed to less than their elastic limits they revert to the unstressed shape following relaxation of the stressing force.

Although the invention was devised with the production of steel cladding panels in mind, it is also applicable to the production of wide panels for other purposes, or made from other sheet materials, including press-formable sheet material having little or no elasticity.

Broadly staled, progressive press-forming of wide panels of the kind in question amounts to plastically deforming narrow longitudinally extending zones of a transition zone of the workpiece strip, as the strip progresses .through the forming apparatus, to cause each said longitudinally extending zone to take on a profile corresponding to that of a stiffening formation or part thereof, and thereby building up the required profile for the panel as a whole.

Probably the best known and most widely used progressive press-forming process is so- called continuous roll-forming. In that instance the initially flat workpiece strip is passed through a sequence of spaced apart roll stands, each comprising a pair of co-acting forming rolls, which sequentially modify the profile of the workpiece in a series of stages, until the required profile is arrived at. Each roll may be referred to as a rotary "presser means" as that term is used hereinafter.

In conventional roll-forming of wide panels, the workpiece usually lies in a horizontal plane as it is presented to the first pair of rotary presser means. It then usually travels horizontally through the transition zone between the rotary presser means of successive stages of the roll-forming apparatus. The profile of the finished panel necessarily comprises parts that are above or below the initial straight-line profile or are inclined relative thereto. Thus, it is convenient when analysing or defining the progressive changes in shape of the profile to consider the workpiece deformation in terms of the elevation or depression of stream lines or stream ribbons, being lines traced out by points on the starting profile or ribbons traced out by short lengths of the starting profile as the workpiece moves through the transition zone, relative to a notional reference surface. hi aforesaid conventional roll-forming operations the reference surface is a plane surface which retains a straight-line reference surface profile throughout the transition zone. The profile of any notional reference surface is referred to as a "reference profile" hereinafter.

When a stream line or stream ribbon departs from the reference surface, it suffers longitudinal straining by comparison with adjacent lines or ribbons remaining in the reference surface. The degree of longitudinal strain is a direct function of the magnitude of the departure from the reference surface.

It is desirable to minimise that longitudinal strain and thus it is considered to be good practice in conventional roll-forming to arrange for the rotary presser means to both depress and elevate stream lines and stream ribbons relative to the planar reference surface, so that, for example, the reference surface is retained in a position midway between the planes in which the crests and troughs of a corrugated panel lie. More generally stated, if the workpiece profile at any stage is considered as if it were a longitudinal section of a beam extending from edge to edge of the workpiece, then the reference profile at the same stage is a straight line conforming to the neutral axis of the supposed beam.

That same relationship, between the position of the reference surface and the surfaces in which crests and troughs of a fully or partly formed workpiece may lie, is maintained in preferred embodiments of the present invention, although, as will be made clear below, the respective surfaces are not planar.

It will be apparent that if an originally planar stream ribbon is deformed so as to acquire a curved or angulated ribbon profile, then the overall, edge-to-edge width of the ribbon necessarily contracts. That contraction is of course reflected in a corresponding contraction of the edge-to-edge width of the workpiece.

Basically there are two operating techniques commonly used in conventional continuous press-forming processes to accommodate the contraction of the several stream ribbons and enable the workpiece to be fed from one presser means to the next as it proceeds through the transition zone, namely "pyramid forming" and "cross forming". hi pyramid forming one stream ribbon, usually the centre one, is fully deformed while the adjacent undeformed ribbons flanking it are allowed to draw together to accommodate that contraction. Then the two ribbons adjacent the deformed ribbon are simultaneously deformed while the ribbons flanking that trio are allowed to draw together; and so on until the required workpiece profile is attained. Thus, each stage of rotary presser means of a conventional pyramid roll-forming apparatus must be designed to operate only on one stream ribbon of the workpiece, or no more than two such ribbons, at a time so as to permit free lateral movement of adjacent ribbons.

The formation of even a relatively shallow corrugation may require passage of the corresponding stream ribbon through two or more pairs of rotary presser means in series so as to effect partial deformation of the ribbon by each of those pairs. This is to avoid excessive strain.

Therefore it will be apparent that conventional pyramid press-forming apparatus requires a considerable number of rotary presser means and a long transition zone.

In conventional cross forming, all of the ribbons to be deformed are worked upon simultaneously at each stage of the transition zone. However to enable acceptable workpiece feed from one stage to the next, the deformation of each ribbon at each stage has to be severely limited. Thus once again a considerable number of stages and rotary presser means are required along with a long transition zone.

The present invention is akin to the cross forming technique, in that all of the ribbons are worked on simultaneously, but is not subject to the feed problems referred to in that preceding paragraph.

To assist in providing an understanding of the invention, Figures 1 to 10 and Figures 8A, 9 A and 10A are annexed hereto and referred to below. All of the figures are diagrammatic cross-sections taken at various positions in the transition zones of press-forming operations. Figures 1 to 7 inclusive illustrate prior art, whereas Figures 8 to 10 and 8 A to 10A inclusive, illustrate an exemplary embodiment of the present invention. Figures 8 A to 10A are enlargements of the centre portions of figures 8 to 10 respectively.

For the sake of brevity, each of Figures 3 to 7 is a composite figure wherein the left hand and right hand halves respectively illustrate different tooling techniques commonly used in continuous press-forming operations, namely "full form tooling" and "air bending tooling". In figures 3 to 7 the workpiece is indicated by reference number 1 1 and the upper and lower rotary presser means by 12 and 13 respectively.

As an example of conventional pyramid forming, the successive profiles at each stage of the transition zone, during the formation of a sinusoidally corrugated wide panel by a plurality of rotary presser means, are shown one above the other in figure 1. It can be seen that the second presser means partly deforms a central ribbon into a crest and flanking troughs. The third presser means completes the deformation of the central ribbon. The fourth presser means commences the deformation of two ribbons one on each side of and adjacent the central ribbon, and so the work proceeds until the required workpiece profile is achieved. Figures 3 and 4 show a typical early stage and an intermediate stage of a pyramid forming operation respectively with the final stage shown in Figure 7. The stage shown in Figure 7 could be used towards the end of the roll former in either pyramid or cross formed tooling design. In the later stages rolls can be omitted from areas where forming is essentially completed. Figures 5 and 6 which show typical early and intermediate stages in a cross forming operation with the final stage shown in Figure 7 as mentioned earlier.

Rotary presser means are expensive items and a row of eight occupies considerable factory space. Therefore it would be desirable to reduce the number of presser means required without substantially increasing the straining imposed on the workpiece.

An earlier proposal to achieve that desirable objective comprised preforming an initially planar workpiece to impart it to the profile of a circular arc having a radius of curvature such that the accurate length equalled the total width of all of the ribbons to be deformed and the chorda! length equalled the edge to edge width of the finished corrugated panel. This enabled a sequence of presser means to be arranged so that simultaneous deformation of all of the ribbons could be effected. Instead of vertical elevation or depression of the stream lines relative to the straight-line reference profile of a planar reference surface, the deformation consisted in radially inward and outward displacement of the stream lines relative to the arcuate reference profile. Moreover each presser means was arranged to modify the reference profile so as to progressively increase its radius of curvature without affecting the chordal length. At the end of the transition zone the arc was reduced to a straight line coinciding with the chord and the straight-line reference profile of the finished product.

Figure 2 is a representation of the various stages of the formation of a corrugated panel according to the last mentioned prior art proposal. It will be noted that the number of complex presser means responsible for the corrugations are fewer in number but additional presser means are required for the pre-forming operation. The overall length of the production line is not greatly reduced by comparison with conventional planar roll-forming.

Brief description of the invention

A primary object of the present invention is to reduce unwanted strains and stresses in the workpiece during its passage through the transition zone, and thereby reduce prior occurring defects, such as oil-canning, splitting, edge wave and like malformations in the finished product. The invention achieves such a reduction in strains and stresses by causing the workpiece to conform to a converging curved reference surface as it travels through the transition zone. The length and convergence of the reference surface is chosen so that the progressive reduction in the arcuate length of the reference profile matches the reduction in length of the arcuate edge to edge width of the workpiece resulting from the progressive deformation of the several stream ribbons.

A secondary object that may be attained by at least preferred embodiments of the invention is to shorten the transition zone and reduce the number of presser means required, by comparison with the prior art.

The invention consists in a method of continuously press-forming panels having a profile which is not a straight line from a substantially planar strip of plastically deformable material comprising the steps of imparting a curved profile to a leading end of the strip, passing the strip between presser means arranged and adapted to cause stream lines of material to depart from a reference surface while ensuring that the reference surface conforms substantially to a converging curved surface, until a transversely curved version of the required panel having a curved reference profile is attained, and then allowing or causing that curved version to adopt the disposition of a finished panel having a substantially straight-line profile.

Preferably, the reference surface of the strip conforms substantially to a surface of a frustum of a converging cone as the strip passed between the presser means.

The present invention is a considerable improvement on prior art processes because in processes according to the invention the initial curvature is very much less than in the prior art. indeed the bowing of the leading end may be merely sufficient to effect entry of the strip into the presser means, which then take over to maintain the required curvature of the strip at entry and bring the strip into accurate conformity with the reference surface. Thereafter the presser means maintain the required conformity of the reference surface to that of a converging curve.

Normally the strip will be taken from an un-coiler and to reduce the bending implicit in bringing the flight of the strip from a planar profile as it leaves the un-coiler to the arcuate profile at entry to the presser means, that flight is preferably at least several metres long. In other embodiments, the strip may be fed in the form of a sheet. Also, in embodiments of the invention in which the reference surface of the strip is conformed substantially to the frustum of a converging cone, the apex angle of the cone is preferably chosen so as to be in the order of, say, about 15-20 degrees. Thus, the bending to which the strip is subjected at entry, to conform to the converging reference surface is accordingly preferably of the order of about 7.5 to 10 degrees. The particular angle used may vary from the above values and still fall within the scope of the present invention.

It will be appreciated that the traces of the ridges and troughs that are formed in producing the desired profile of the panel are maintained in their respective planes and thus all streamlines or traces of ridges and troughs are plane curves.

It will be appreciated that the curvature of the smaller end of the reference surface is such that the curved length of the fully shortened reference profile corresponds in length to the edge-to-edge distance of the finished panel.

It will also be appreciated that the regular reduction in the length of the reference profile as the workpiece passes through the transition zone matches the reduction in length of an arc subtending a constant angle ait the axis of the converging conical reference surface. As a result there is very little, if any, lateral straining of the workpiece and the length of the transition zone may be selected to limit the longitudinal straining to any safe value below the yield strength of the material, h practice this permits a considerable reduction in transition zone length by comparison with the minimum lengths attainable by the prior art processes. Furthermore, it is believed that the lateral strain imparted on the strip is less than the yield strain for most materials used in roll forming.

In the case of steel, the lateral straining of the workpiece occasioned by imparting the preparatory curvature to the workpiece to enable it to be taken in by the presser means and the ongoing further curvature required to keep the reference profile in conformity with the conical reference surface, fall well below the level of plastic straining. Thus a steel workpiece may be expected to resume an un-curved condition upon being released from the presser means.

Nevertheless it may be desirable to pass the workpiece through a single after stand of so- called sizing presser means, such as sizing rolls, to ensure that any residual curvature along with any adventitious inaccuracies in the emergent workpiece profile are eliminated. hi some embodiments of the invention the finished workpiece produced by the inventive method may be a precursor of the finished product having a simplified profile, conforming generally to the required finished profile, but lacking some details thereof. For example, it may be that small grooves in the finished product are required in the flanks of one or more half- waves corresponding to crests in the profile. Such grooves may be ornamental or may be needed for snap engagement of the panel by hold-down clips or for other purposes. In such instances it may be appropriate to produce a precursor devoid of such grooves and then form them in the precursor by or when passing it through an after stand.

When the required profile comprises or includes a curvilinear waveform, for example a sine wave or a waveform wherein each half-wave profile comprises or includes an arc of a circle, parabola or other smooth curve, it is necessary or at least desirable for the presser means to define every point on the profile to ensure it conforms to the required shape. This would indicate that rotary presser means having a well-defined nip between the respective rolls could be used. The present invention is applicable to such roll-forming processes utilising a plurality of spaced apart pairs of rotary presser means, provided the changes in shape imparted to the profile during each stage conform to the inventive concept detailed above.

However if the required profile comprises or includes an angulated waveform for example, saw tooth waves or trapezoidal waves, it is only strictly necessary to control the positions of the fold lines and allow the intervening ribbons to substantially retain their initial substantially straight line profile, albeit in an inclined disposition if they correspond to the flanks of a trapezoidal waveform.

Furthermore, in processes to the invention the stream lines coinciding with fold lines in angulated wave profiles lie in radial planes of the convergent curved reference surface. Thus those lines are plane curves and their projection onto a convergent curved surface, especially a surface of the frustum of a converging cone, are essentially straight, converging lines.

Thus linear presser means may be considered for use in some embodiments of methods according to the invention. Furthermore, such novel linear presser means may be arranged to impart a continuous modification to the profile as the workpiece progresses between them, instead of a stage-by-stage modification.

Thus according to a second aspect of the invention it consists in a linear presser means for use in continuous press-forming.

Such linear presser means may comprise a bar or blade supporting a plurality of small closely spaced rollers or wheels contacting the workpiece at closely spaced points along a linear track. However according to preferred embodiments of said second aspect of the invention, the linear presser means are translatory in a generally longitudinal direction and comprise a pliable, endless member having a smooth working surface and a support means for said pliable member permitting guided longitudinal movement of a flight of the pliable member while permitting the working surface of the flight to apply pressure to a workpiece strip.

Preferably the working surface of the pliable member has a profile that conforms to the desired profile of that part of the workpiece contacted by it.

Thus those preferred embodiments of linear translatory presser means resemble the well known bar and chain of a chain saw, but with chain links presenting a substantially continuous, smooth working surface to the workpiece instead of the projecting cutting teeth of the saw. hi some instances the linear presser means may be arranged in pairs with one unit of the pair bearing upon one surface of the workpiece sheet and the other unit bearing upon the opposite surface, with both units in register so as to provide a clamping effect upon the workpiece resisting lateral movement of the workpiece relative to the presser means. It will be appreciated that the elongate pliable members of linear translatory presser means are not necessarily chains. They may be an endless, pliable band, strap, thong or the like able to flex sufficiently to be able to be trained around spaced apart wheels or the like at opposite ends of a rigid elongate support. Alternatively they may of composite construction, namely a chain supporting and driving a plurality of discrete elements presenting a smooth, appropriately profiled, working surface to the workpiece.

Translatory movement of the operational flight of the pliable member may be provided by any appropriate drive mechanism, such as for example a powered rotation of a sprocket or the like engaged with an inoperative flight of the endless pliable member or a similar drive to one of the training wheels at the ends of the operative flight. It would generally not be necessary to drive all or any of the linear presser means. Some or all may simply move freely as a result of frictional contact with the moving workpiece, provided means are provided to ensure a satisfactory feed of the workpiece through the transition zone.

In a third aspect, the present invention provides an apparatus for press forming panels having a profile which is not a straight line from a strip of plastically deformable material including presser means for forming a desired profile in the strip by plastically deforming the strip to form stream lines of material that depart from a reference surface, characterised in that said presser means are arranged such that the reference surface of the strip is constrained to substantially conform to a converging curved surface as said strip passes through said presser means. Preferably, the presser means are arranged such that the reference surface of said strip is constrained to substantially conform to a surface of a converging frustum of a cone.

The apparatus may further comprise feeder means for feeding the strip to the presser means. The feeder means preferably imparts a curved profile to the strip that enters the presser means. The feeder means most preferably comprises an uncoiler for uncoiling the strip from a coil of strip and curved guide means through which the strip passes to thereby cause the strip to adopt a curved profile.

The apparatus may further comprise an after stand comprising one or more sizing presser means for eliminating any residual curvature in the reference surface of the strip and any inaccuracies in the panel. In some embodiments of the present invention, the presser means comprises a plurality of rolls, said plurality of rolls arranged to plastically deform said strip to form the streamlines and to constrain said strip such that the reference surface substantially conforms to a converging curved surface as the strip passes through the rolls. Preferably, the rolls are arranged in transversely spaced sets, with each set of rolls forming a streamline of the panel and the sets of rolls being arranged relative to each other such that the sets converge towards each other from an upstream end to a downstream end of the apparatus.

In other embodiments, the presser means comprises a plurality of linear presser means as described hereinabove. The linear presser means are preferably arranged relative to each other such that the linear presser means are laterally spaced from each other and converge towards each other from an upstream end to a downstream end of the apparatus.

Brief description of the drawings

Figure 1 is a diagrammatic cross-section representation of a profile of a strip taken al various stages of a prior art press-forming operation; Figure 2 is a diagrammatic representation in cross section of a profile of a strip at various stages of another prior art press-forming operation;

Figures 3 to 7 are diagrammatic cross-section representations of various stages of a prior art press-forming operation; Figures 8 to 10 are diagrammatic cross-section representations of various stages of a press-forming operation in accordance with the present invention;

Figures 8A, 9A and 10A are enlargements of Figures 8, 9 and 10 respectively;

Figure 11 is a schematic diagram showing the shape of the reference surface in the transition zone overlaid on the shape of a cone; Figure 12 shows a schematic side elevation of an apparatus in accordance with the present invention;

Figure 13 shows a plan view of the apparatus of Figure 12;

Figures 14 and 15 show end views of bridge gates that from part of the apparatus of the present invention; Figure 16 shows an end view of an entry guide for use in the present invention; and

Figure 17 shows a schematic diagram of a presser and roller in accordance with the present invention.

Detailed description of the drawings

By way of example, an embodiment of the invention is illustrated by figures 8, 9 and 10 and the respectively corresponding enlarged detail views 8 A, 9 A and 10A wherein a workpiece strip 14 is being formed into a panel having a trapezoidal wave shaped profile by a plurality of pairs of co-operating upper and lower presser means 15 and 16. Figures 8 and 8 A show the entry stage, figures 9 and 9 A show an intermediate stage and figures 10 and 10A show the exit stage of a single conical array of presser means defining the whole of the transition zone of a press-forming apparatus. The reference profile of the workpiece is indicated by the broken line 17. At the entry to the transition zone the reference profile 17 coincides with the workpiece profile 14. Comparison of the three sets of figures will show that the radius of curvature of the workpiece and the arcuate length of its reference profile are progressively shorter from figure to figure. This is compatible with the reference profiles being cross-sections of a converging conical surface.

Items 15 and 16 may each be conventional forming rolls, h that event there would be a sequence of roll pairs spaced apart in the axial direction of the transition zone to constitute a plurality of stages. The rolls of the respective stages would be aligned to track one behind the other. That is to say the stream ribbon leaving one pair of rolls would fee directly into the nip of the next met pair of rolls, so that each pair effects purely radial deflection of the ribbon concerned.

Alternatively each item 15 or 16 may be an operative flight of an endless linear translatory presser means as described above, h this event item 15 (or 16) is the cross-section of one and the same flight of a single linear translatory presser means.

It will also be noticed that the working surfaces of the respective flights of the linear translatory presser means correspond to the required profile of the workpiece ribbons contacted by the flights. This would appertain to other embodiments of the invention including those producing curvilinear waveforms in the workpiece profile.

Preferably the conical array of presser means is aligned so that the longitudinal centre line of the workpiece emerges horizontally from the exit end of the transition zone. Assuming the workpiece sheet is of steel or other elastic material and, in any particular instance concerned, the overall curvature of the exiting version of the workpiece does not strain it beyond the elastic limit, then the edges of the curved version will spring back and up once the restraint from the presser means is removed on exit from the transition zone. This should allow the emerging leading end of the workpiece to feed, or be fed, into the nip of a conventional after stand of sizing rolls spaced an appropriate distance from the end of the transition zone, whereby any residual curvature or other malformations may be corrected. In other instances, for example when working with non-elastic material, it may be necessary to follow the transition zone with a further array of presser means to bring the workpiece back to the required uncurved condition of the finished panel.

The shape of the reference surface of the strip of material as it passes through the transition zone where the presser means form the strip is best shown with reference to Figure 1 1. As shown in Figure 11, a cone 20 has a base 21 and an apex 22. The reference surface is shown by reference numeral 23 with the inlet to the transition zone being at end 24 and the outlet of the transition zone being at end 25. At the inlet end 24, the reference surface has relatively low curvature, or a relatively large radius of curvature. As the transition zone progresses towards the outlet 25, the curvature of the reference surface increases, or the radius of curvature decreases. Further, as the strip progresses through the transition zone, the height and depth of respective ridges and troughs formed in the strip by the presser means increases. As more material is moved into the ridges and troughs, the side edges of the strip move towarde each other. The shape of the reference surface in the transition zone effectively accommodates the apparent lessening in the overall width of the strip and as a result little or no lateral strain is placed on the strip.

Figures 12 to 15 show one embodiment of an apparatus for press forming panels in accordance with the present invention. The apparatus 30 comprises a support frame 31 having a plurality of legs 32. A plurality of vertical frame members 33,34,35 support respective bridge gates 36,37,38. Each bridge gate consists of two sets of cross bars arranged to form a space for a plurality of long bars (to be described hereunder).

As best shown in Figure 14, bridge gate 38 comprises an upper cross bar 39 and a lower cross bar 40 that are vertically spaced from each other. Cross bars 39, 40 are arcuate in shape and provide support for the long bars (not shown). Simarly, as shown in Figure 16, bridge gate 36 comprises upper cross bar 41 and lower cross bar 42. Cross bars 41,42 are also arcuate in shape. Although not shown in the drawings, middle bridge gate 37 is similar to bridge gates 36 and 38.

Arcuate cross bars 41,42 have a larger radius of curvature than the corresponding cross bars of middle bridge gate 37. Similarly, downstream end bridge gate 38 has cross members 39,40 that have a smaller radius of curvature than the corresponding cross bars of bridge gates 36,37. Thus, the cross members of the bridge gates have reducing radius of curvature in the downstream direction of the apparatus and help to define a reference surface for the strip in the transition zone that essentially comforms to the frustum of a converging cone.

The apparatus 30 further comprises a plurality of long bars, two of which are shown in

Figure 12. In particular, long bar 43 is mounted to an underside of the upper cross bars 39,41 . Long bar 44 is mounted to an upper side of lower cross bars 40,42. A plurality of such long bars are mounted in the apparatus such that they are in alignment with the rib traces 45, as shown in Figure 13. As can be seen from Figure 13, rib traces 45 converge in a downstream direction.

Returning to Figure 12, it can be seen that long bar 43 carries sprockets 46,47 near. the inlet end 24 of the transition zone. Long bar 43 also carries sprockets 48,49 near the outlet end of the transition zone. Sprockets 46,47,48,49 carry a linear presser means that comprises a chain or belt carrying a plurality of dies. The dies contact the surface of the strip and plastically deform the material to form a ridge or a trough in the panel. In this regard, the individual dies extend above or below the reference surface (as the dies must plastically deform the strip) but, taken collectively, the dies constrain the strip to a shape that has a reference surface that substantially follows a convergent curved surface. Long bar 44 similarly carries sprockets 50,51 ,52,53 that also carry a similar presser means. Suitable ones of the sprockets may be driven by any suitable drive means, such as an electric motor 75 driving an associated gearbox 76 and associated drive shafts, to drive the linear presser means in an endless fashion around the respective sprockets. In this way, the presser means plastically deform the material to form the desired profile of the panel.

In order to feed sheet with the desired curvature into the presser means, an entry guide such as that shown in Figure 16 may be used. The entry guide 60 comprises a mounting bar 61 carrying a first edge guide 62 and a second edge guide 63. Edge guide 62 has a slot for receiving an edge of the strip 14. A roller 64 is used to assist in smooth movement of the strip therethrough. Edge guide 65 also has a slot for receiving an edge of the strip and a roller 65 for assisting in smooth movement of the strip therethrough. The width between the edge guides 62 and 63 can be adjusted by adjusting the transverse position of edge guide 62. Width adjust screw 66 is provided for this purpose. The angle of edge guide 63 may also be adjusted by use of angle adjust screw 67. In this fashion the entry guide may be adjusted to accommodate a range of strip widths and desired curvature.

The long bars 43, 44 may also support chain bars (not shown) upon which the presser means travel when the presser means are in contact with the strip. The chain bars may have a curved supporting surface or they may have a straight upporting surface. Curved surfaces on the chain bars amy assist in minimising strain on the strip of material. A curved supporting surface may be achieved by placing suitable shime between the long bar and the chain bar. This also allows for adjustment of the curved surface of the chain bar, if desired. In order to achieve a more accurate final profile in the finished panel, especially where trapezoidal or rectangular profiles are formed in the panel, it may be appropriate to use one or more press wheels in engagement with a surface of the strip that is opposed to the presser means of the apparatus in accordance with the present invention. An example of this is shown in Figure 17. In Figure 17, a die element 70 mounted to a chain link 71 forms part of the presser means. The die element 70 and chain link 71 may be part of an endless presser means that travels around the sprockets shown in Figure 12. Die 70 contacts strip of material 72 to form a trapezoidal profile portion, hi order to ensure that the upper surface of the strip 72 is essentially flat and not curved, a press wheel 73 that has a suitable profile 74 contacts the upper surface of the strip 72.

The presser means shown in Figures 12-17 is an endless chain or belt type presser. However, the invention also encompasses the use of a number of small wheels or rollers mounted to a chain or belt or even to respective long bars. The invention also encompasses the use of discrete rolls or rollers as the presser means, provided that they are mounted in the required juxtaposition to achieve a reference surface that is curved and converges in a downstream direction.

The reference surface of the strip preferably is constrained to follow the frustum of a converging cone. However, a non-conical converging curved surface also falls within the scope of the present invention The method and apparatus of the present invention provides for press forming of panels from a strip of material, such as a steel strip, whilst minimising or avoiding lateral straining of the material in the strip. The present inventor has found that press forming can be achieved in a press forming apparatus that is of the order of 2 to 2.5 metres in length, compared to prior art press forming which typically requires a press forming apparatus of length in the range of 6 to 8 metresor even longer. In some embodiments of the present invention, the press forming operation is continuous in that the presser means are in continuous contact with the strip. The present invention also allows for the possibility of preparing panels with more complex shape by adding extra width to the apparatus. For example, a machine set up to make panels having one trough and two ridges could be converted to manufacturing panels having two troughs and three ridges by adding two further long bars to the apparatus shown in Figures 12 to 15. Prior art apparatus required that extra length be added in those circumstances. Those skilled in the art will appreciate that the present invention may be susceptible to variations and modifications other than those specificaly described. It is to be understood that the invention encompasses all such variations and modifications that fall within its spirit and scope.

Claims (30)

Claims

1. A method of continuously press-forming panels having a profile which is not a straight line from a substantially planar strip of plastically deformable material comprising the steps of imparting a curved profile to a leading end of the strip, passing the strip between presser means arranged and adapted to cause stream lines of material to depart from a reference surface while ensuring that the reference surface conforms substantially to a converging curved surface, until a transversely curved version of the required panel having a curved reference profile is attained, and then allowing or causing that curved version to adopt the disposition of a finished panel having a substantially straight-line reference profile.

2. A method according to claim 1 wherein the reference surface conforms substantially to a surface of a converging frustum of a cone.

3. A method according to claim 1 or claim 2 wherein the step of imparting a curved profile to the leading end of the strip is merely sufficient to effect entry of the strip into the presser means and the presser means thereafter maintain a required curvature of the strip al entry and bring the strip into conformity will the reference surface.

4. A method according to claim 2 wherein an angle of an apex of an imaginary cone extended from the reference surface falls within the range from about 15 to 20 degrees.

5. A method according to any one of claims 1 to 4 wherein a curvature applied to the strip to keep the strip in conformity with the reference surface does not cause plastic deformation and said panel adopts an essentially un-curved reference surface condition upon being released from said presser means.

6. A method as claimed in any one of claims 1 to 4 wherein said panel is passed through one or more sizing means after being released by said presser means to substantially eliminate curvature of the reference surface, and any inaccuracies in the profile.

7. A method as claimed in any one of claims 1 to 5 wherein said panel is passed through one or more sizing means after being released by said presser means to substantially eliminate any inaccuracies in the profile

8. A method as claimed in any one of the preceding claims wherein said panel emerging from said presser means comprises a precursor panel to a finished panel and the method further comprises passing said precursor panel through an after stand of forming means to form the finished panel.

9. Apparatus for use in continuous press forming characterised in that said apparatus includes linear presser means for forming a desired profile in a strip of material.

10. Apparatus according to claim 9 wherein said linear presser means comprises a bar or blade supporting a plurality of small closely spaced rollers or wheels contacting the workpiece at closely spaced parts along a linear track.

11. Apparatus according to claim 9 wherein the linear presser means are translatory and comprise a pliable, endless member having a smooth working surface and a support means for said pliable member permitting guided longitudinal movement of a flight of the pliable member while permitting the working surface of the flight to apply pressure to a workpiece strip.

12. Apparatus according to claim 11 wherein the working surface of the pliable member has a profile that conforms to the desired profile of that part of the workpiece contacted by it.

13. Apparatus as claimed in any one of claims 9 to 12 wherein the linear presser means are arranged in pairs with one unit of the pair bearing upon one surface of the workpiece sheet and the other unit bearing upon an opposite surface, with both units in register so as to provide a clamping effect upon the workpiece resisting lateral movement of the workpiece relative to the presser means.

14. Apparatus as claimed in claim 9 further comprising translatory drive means for providing translatory movement to the liner presser means.

15. An apparatus for press forming panels having a profile which is not a straight line from a strip of plastically deformable material including presser means for forming a desired profile in the strip by plastically deforming the strip to form stream lines of material that depart from a reference surface, characterised in that said presser means are arranged such that the reference surface of the strip is constrained to substantially conform to a converging curved surface as said strip passes through said presser means.

16. Apparatus as claimed in claim 15 wherein the presser means are arranged such that the reference surface of said strip is constrained to substantially conform to a surface of a converging frustum of a cone.

17. Apparatus as claimed in claim 15 or claim 16 further comprising feeder means for feeding the strip to the presser means.

18. Apparatus as claimed in claim 17 wherein the feeder means imparts a curved profile to the strip that enters the presser means.

19. Apparatus as claimed in claim 17 or claim 18 wherein the feeder means comprises an uncoiler for uncoiling the strip from a coil of strip and curved guide means through which the strip passes to thereby cause the strip to adopt a curved profile.

20. Apparatus as claimed in any one of claims 15 to 19 further comprising an after stand comprising one or more sizing presser means for eliminating any residual curvature in the reference surface of the strip, and any inaccuracies in the panel.

21. Apparatus as claimed in any one of claims 15 to 20 further comprising an after stand comprising one or more sizing presser means for eliminating any inaccuracies in the panel.

22. Apparatus as claimed in any one of claims 15 to 21 wherein the presser means comprises a plurality of rolls, said plurality of rolls arranged to plastically deform said strip to form the streamlines and to constrain said strip such that the reference surface substantially conforms to a converging curved surface as the strip passes through the rolls.

23. Apparatus as claimed in claim 22 wherein the rolls are arranged in transversely spaced sets, with each set of rolls forming a streamline of the panel and the sets of rolls being arranged relative to each other such that the sets converge towards each other from an upstream end to a downstream end of the apparatus.

24. Apparatus as claimed in any one of claims 15 to 21 wherein the presser means comprises a plurality of linear presser means.

25. Apparatus as claimed in claim 24 wherein the lineal" presser means are arranged relative to each other such that the linear presser means are laterally spaced from each other and converge towards each other from an upstream end to a downstream end of the apparatus.

26. Apparatus according to claim 24 or claim 25 wherein said linear presser means comprises a bar or blade supporting a plurality of small closely spaced rollers or wheels contacting the workpiece at closely spaced parts along a linear track.

27. Apparatus according to claim 24 or claim 25 wherein the linear presser means are translatory and comprise a pliable, endless member having a smooth working surface and a support means for said pliable member permitting guided longitudinal movement of a flight of the pliable member while permitting the working surface of the flight to apply pressure to a workpiece strip.

28. Apparatus according to claim 27 wherein the working surface of the pliable member has a profile that conforms to the desired profile of that part of the workpiece contacted by it.

29. Apparatus as claimed in any one of claims 24 to 28 wherein the linear presser means are arranged in pairs with one unit of the pair bearing upon one surface of the workpiece sheet and the other unit bearing upon an opposite surface, with both units in register so as to provide a clamping effect upon the workpiece resisting lateral movement of the workpiece relative to the presser means.

30. Apparatus as claimed in claim 24 further comprising translatory drive means for providing translatory movement to the linear presser means.