BACKGROUND For several decades, roll-forming has been used for producing different profiles of above all sheet metal. Upon employment of the rollforming technique, a sheet is fed through a roll former having a number of upper and lower forming tools cooperating to gradually form profile folds in the sheet when it passes between them. Thus, a profile having more or less complicated shape along its length is obtained when the sheet has passed the roll former.

By means of this technique products having a wide range of different profiles can be produced, all from simple angle profiles and plates having regular, evenly distributed corrugations to complicated and even closed profiles. However, a clear limitation associated with this technique is that it, as was mentioned above, practically only allows producing products having a profile that is unchanged along their length. By the manufacturing of products having a profile with varying cross-section along their length, supplementary processing is normally required, which makes the manufacturing more complicated and expensive.

Examples of this problem and of how other types of products may be produced by supple- mentary processing of a rollformed product may for instance be found in our International Patent Application PCT/SE01/01253. Although this patent application particularly concerns the production of closed profiles through rollforming, it also provides examples of how e. g. profiled, generally conical sheet metal products may be produced by first roll forming a sheet metal plate in the conventional way to form a regular, as viewed in the forming direction, profile shape. Then, the profile is closed in a tube or pipe mill that is a specific type of roll former for producing tube-shaped profiles. When the long sides of the tube profile have been interconnected, a pressure is applied inside the profile and against selected portions thereof, whereby a practically conical tube can be formed. Finally, the conical tube can be split and unfolded to obtain optional sections of generally conical profiled sheets for various fields of application that are not further specified. Although the described prior art in itself constitutes a great advance within this field by enabling flexible manufacturing of special products, it involves additional process steps and accompanied costs.

Accordingly, there is a great need within this field for a simple and non-expensive solution to the problem of providing a flexible manufacturing of roll formed products having specific shapes adapted to various specific fields of application.

SUMMARY OF THE INVENTION The present invention eliminates the above drawbacks in an efficient and appropriate way.

A general object of the invention is to provide an inexpensive and practical manufacturing of products or semimanufactures of sheet-like workpieces, having a specific, more or less irregular shape along their length.

More specifically, a basic object of the invention is to find a simple and appropriate method of forming sheet-like workpieces to a shape that is irregular in at least one plane. According to the invention this is achieved by forming the workpiece in a rollforming machine having several subsequently arranged stations with upper and lower forming tools, and in particular by intentionally interrupting the forming of the workpiece during its passage through the machine. More specifically, in a manner that is absolutely unique for this technical field and that contradicts the basic features of conventional rollforming, forming is thus interrupted intentionally before the entire workpiece has passed all forming stations. This makes it possible to form products having an irregular shape, as viewed in the forming direction, in one and the same process step and at a relatively low cost.

According to an embodiment of the invention, forming is interrupted at a point of time when a front edge of the workpiece engages a last forming station in the roll-forming machine. With such a technique, it is possible to manufacture products that have a generally conical shape at least in the front end with regard to the forming direction.

In an alternative embodiment, the forming process is interrupted at a point of time when a front edge of the workpiece has passed a last forming station in the roll-forming machine.

With such a technique, it is possible to manufacture products that at least in the front end, with regard to the forming direction, are provided with a portion having a shape differing from the generally conical shape.

According to another embodiment of the invention, the forming process is interrupted when a rear edge of the workpiece has passed a first forming station. Hereby, a product may be given the generally conical shape all the way up to the rear edge thereof.

According to a further embodiment of the invention, forming is interrupted before a rear edge of the workpiece has passed a first station. In this way, the rear end of the manufactured product remains unworked and has the shape of the initial material.

According to an embodiment of the invention, the workpiece is fed through the rollforming machine by driven forming tools and the forming is interrupted by bringing the drive of these forming tools to a standstill. According to further embodiments of the invention, the forming process is interrupted by separating the forming tools that engage the workpiece and that cooperate in the respective station. This separation of the forming tools is performed separately or alternatively in combination with stopping the driven forming tools. Thereby, are offered practically feasible solutions for interrupting the forming. In further alternative embodiments, the separation of the tools may be accomplished by raising the respective upper tools, by lowering the respective lower tools or by a combination thereof.

According to other practically feasible embodiments of the invention it is suggested that the respective upper and/or lower tools are raised and/or lowered as a single unit; that said tools are divided into groups and are raised and lowered, respectively, as a single unit in each group; or that said tools are individually raised and lowered, respectively.

According to a variant of the invention it is suggested that in the two last-mentioned embodiments the tools or groups of tools are selectively raised and lowered, respectively, and in particular that the individually movable tools or groups of tools are raised and lowered, respectively, with a time delay or time shift. Hereby, roll forming is interrupted in a number steps, whereby it becomes possible to manufacture products having a shape that changes in different steps along their length.

When the forming process has been interrupted, the workpiece is removed from the roll forming machine, and in one embodiment this is performed by pulling out the formed workpiece from the machine when the tools have been brought apart. In another embodiment, all upper or lower tools are arranged in a common frame. When forming is completed this frame is removed from the area above and below, respectively, the corresponding lower and upper tools, respectively, in order to expose the formed product for removal thereof.

These and other objects of the present invention are achieved by the invention as defined by the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS Further objects, specific features and advantages of the invention, as well as further embodiments thereof, are specified in the patent claims and in the following detailed description taken together with the accompanying drawings, in which: Fig. 1A is a schematic partial plan view from above of an embodiment of a roll forming machine that may be used when practicing the invention; Fig. 1B is a likewise schematic partial side view of the roll-forming machine of fig. 1A ; Fig. 1C is a partial view of a forming station in the roll-forming machine of fig. 1A, as seen in the rollforming direction; Fig. 2A illustrates a plan view from above and two end views, respectively, of a first example of a product manufactured according to the principles of the invention; Fig. 2B is a plan view from the side of the first example of the product of fig. 2A; Fig. 2C is a schematic partial side view of a roll forming machine and illustrates forming of the product of fig. 2A-B; Fig. 3A illustrates a plan view from above and two end views, respectively, of a second example of a product manufactured according to the principles of the invention; Fig. 3B is a plan view from the side of the second example of the product, illustrated in fig.

3A; Fig. 3C is a schematic partial side view of a roll forming machine, and illustrates forming of the product of fig. 3A-B; Fig. 4A illustrates a plan view from above and two end views, respectively, of a third example of a product manufactured according to the principles of the invention; Fig. 4B is a plan view from the side of the third example of the product, illustrated in fig.

4A; Fig. 4C is a schematic partial side view of a roll forming machine, and illustrates forming of the product of fig. 4A-B; Fig. 5A illustrates a plan view from above and two end views, respectively, of a fourth example of a product manufactured according to the principles of the invention; Fig. 5B is a plan view from the side of the fourth example of the product, illustrated in fig.

5A ; Fig. 5C is a schematic partial side view of a roll forming machine, and illustrates forming of the product of fig. 5A-B ; Fig. 6 is a schematic illustration of an embodiment comprising different steps for interrupting the forming procedure of a product manufactured according to the principles of the invention; Fig. 7A is a schematic illustration of a first embodiment of a principle for uncovering the product after forming of a product manufactured according to the principles of the invention; Fig. 7B is a schematic illustration of a second embodiment of a principle for exposing the product after forming a product manufactured according to the principles of the invention, and; Fig. 8A-B is an end view and a partial side view, respectively, of an example of a roll forming stand for use in the roll forming machine of fig. lA-C.

DESCRIPTION OF EXAMPLARY EMBODIMENTS With reference to the drawings, the basic principles of the invention will now be described by means of embodiments thereof, and thereby the differences compared to the technique employed in the prior art will also be clarified.

In the below description, references like the first, last, etc. are used to indicate specific forming stations, forming tools etc. in a roll-forming machine. To begin with, it shall be emphasized that these references at each occasion relate to the last, first etc. forming stations, forming tools, etc. that participate in the forming of the particular product. Irrespective of these references, the employed roll forming machine may therefore in itself contain a large number of stations or tools so that it may be easily adapted to a new product, whereby only some of these stations and tools are used when forming the majority of products.

The technique upon which the invention is based will now be described with reference to the partially schematic illustrations of figure lA-C. In these drawings, a basic example of a roll forming machine or mill 2 is shown, the machine being of the kind that may advantageously be used when practicing the method proposed according to the invention for forming a product that is preferably made of sheet metal. This roll forming machine 2 consists of a number of, in the illustrated example seven, forming stations 3A-3G arranged one after the other in a forming direction F. In fig. 1A and 1B a first 3A, a middle 3D and a final 3G forming station are marked with solid lines, whereas the intermediate stations 3B-C and 3E-F are just outlined with dashed-dotted lines.

Each forming station 3A-G comprises a roll-forming stand 4 carrying a pair of cooperating upper and lower forming tools 5 and 6, respectively. The forming tools 5,6 are in the illustrated embodiment constituted of forming rolls 7 and 8, respectively, supported on an upper 9 and lower 10 shaft, respectively. The number and shape of the rolls 7,8 corresponds to the shape of the product P1-P4 (see fig. 2A-C, 3A-C, 4A-C and 5A-C, respectively) to be manufactured.

Normally, the rolls 7,8 are firmly supported on the respective shaft 9,10, whereas the shafts are rotatably journalled in their stand 4. One of the shafts 9,10, typically the lower one, is driven for feeding the workpiece 1 through the machine 2. A practical example of such a roll forming stand 4 having a driven lower shaft 10 is shown in detail in fig. 8A-B and will be described below with reference to these drawings. However, it shall be emphasized at this early stage that the principal structure of the roll forming stands and their respective forming tools do not constitute any part of the invention. Thus, they may be varied and modified within the scope of the invention, by employing other designs that are known within this technical field.

Thus, fig. 8A-B illustrates a detailed example of a basically conventional roll-forming stand 4 that may be employed for the method of the invention. The stand 4 comprises two shafts 9,10, arranged vertically on top of each other, the ends of the two upper and lower shafts 9 and 10, respectively, being mounted in upper and lower frames 4A and 4B, respectively. The two shafts 9,10 carry the upper and lower forming rolls 7 and 8, respectively. The rolls 7, 8 are typically fixed to the shafts 9,10, which in turn are rotatably journalled in the frames 4A, 4B.

However, there are also designs where the rolls on one shaft, more specifically a non-driven shaft, are rotatably journalled thereon. In the illustrated example, a drive unit (not shown) drives the lower shaft 10, through a drive wheel 12 attached to one end of the shaft 10.

The frames 4A, 4B and thus the shafts 9,10 are vertically adjustable with regard to each other for changing the mutual positions of the upper and lower forming tools, i. e. the rolls 7,8. More specifically, in the example the upper frames 4A with the upper shaft 9 are vertically adjustable upwardly and downwardly, respectively. According to the invention this adjustability may be employed for providing the separation of the forming rolls 7,8 as described below. In the way indicated from the figures, such a separation may be achieved by connecting an appropriate drive 13 for synchronized driving of the two upper frames 4A of each roll forming stand 4, of some or all of them. In the drawings, this drive 13 is indicated by symbolically drawn drive wheels 14,15 and a transmission 16 interconnecting them.

By conventional roll forming of sheet metal plate, where a workpiece is provided with several parallel longitudinal profile folds, a single profile fold is normally formed in the first stand or station, whereafter the forming of additional profile folds begins in separate subsequent stations. Such a design of the roll-forming machine may very well be employed to practice the method of this invention by the manufacturing of products with specific shapes. However, in the currently preferred and herein described embodiments, a roll forming machine is employed that is unique in the sense that it presents the same number of forming rolls in all stations. Through the described design, all profile folds of the workpiece and product, respectively, are at least partially formed in each station.

The method proposed according to the invention for forming a sheet-like workpiece in a roll forming machine will now be described with reference first to figs. 1A and 2A-C. Initially, the front edge 1A of a workpiece 1, preferably of sheet metal, in inserted into the"nip"between the forming tools 5,6, i. e. the rolls 7,8 in the illustrated example, in the first forming station 3A. The front portion of the workpiece 1 is drawn in the forming direction F, see fig. 2C, through the first forming station 3A by the driven forming tool, in the example of fig. 8A-B the lower tool 6.

Then, the profile folds or corrugations K are formed in the workpiece 1, or more correctly in the product P1 of the first embodiment. Starting at the front edge 1A/PA of the workpiece/product 1/P, the profile folds K are gradually formed in the subsequent stations 3B-3E. In the present example, where the product PI is provided with simple corrugations K, the main task is to gradually increase their depth (see for example fig. 2B and the end views in fig. 2A) in the subsequent stations 3A-3E, but other embodiments, not illustrated herein, may concern other more or less complicated profile folds. Due to this continuing forming of the profile folds K, the width of the workpiece/product will also gradually decrease such that the long sides obtain a generally tapering, in fig. 2A conical, course.

As mentioned above, the invention is based on the recognition that it is possible to achieve a flexible manufacturing of products having an irregular shape along their length by, as opposed to the method of all conventional roll forming, deliberately interrupting the forming process before the workpiece/product 1/P1 has passed all forming stations 3A-3E. In the example illustrated in fig. 2A-C, the forming is interrupted essentially at the point of time when the front edge 1A/PA of the workpiece/product 1/Pl is in the middle of the"nip"between the tools 5,6 of the last forming station 3E, and the rear edge 1B/PB of the workpiece/product 1/P1 is in the middle of the"nip"between the tools 5,6 of the first forming station 3A, i. e. in this case the upper and lower rolls 7 and 8. Using this method, a product P1 is obtained having a generally conical shape, both with regard to the side edges, fig. 2A, and to the"peaks"and "valleys"of the corrugations K, , see fig. 2B and the end views in fig. 2A. Such a product PI may for instance be used as a filter section within the pulp industry or as a part of a heat exchanger.

The forming is interrupted either by first stopping the driving, described in connection with fig. 8A-B, of the shaft 9 or 10 of one of the forming tools 5 or 6, while the tools 5,6 are still in the closed position C, and then separating the tools 5,6 to the open position D; or alternatively by first separating the tools 5,6, whereupon the driving is stopped. Naturally, it is also possible to stop the driving and to separate the tools practically at the same time. In the example of fig. 2C, the forming tools 5,6 are opened into the position D by raising the upper tools 5 of all forming stations 3A-E in a first opening direction S1. Then, the product PI can be pulled out of the machine 2 in or opposite the forming direction F as a final product or a semimanufactured product to be further worked. Finally, the upper tools 5 of all forming stations 3A-E are lowered to the closed position C and the machine is ready for a new forming process.

From the above description it is evident that the solution proposed according to the invention results in a flexible and comparatively simple and time-saving production of a sheet-like product having an irregular shape along its length. More specifically, the now presented example enables manufacturing of a"fan-shaped"product in one single process step, i. e. in one single passage through the roll forming machine.

Figs. 3A-C, 4A-C and 5A-C illustrate examples of products having a slightly modified shape, which may be manufactured in the corresponding way, with certain modifications of the method.

Fig. 3A shows an example of a modification that involves the use of a slightly differently dimensioned roll forming machine 2 for producing a product P2 having a slightly different shape by means of a practically identical method. More specifically, forming is again interrupted when the front edge 1A or PA of the workpiece or product 1 or P2 is positioned in the middle of the"nip"between the tools 5,6 of the last forming station 3E, whereby the main portion of the product P2 obtains a generally tapered shape. However, in this case the workpiece 1 is longer than the distance between the"nips"between the tools 5,6 of the first and last forming station 3A and 3E, respectively, whereby forming is interrupted before the rear edge 1B/PB of the workpiece/product 1/P2 has reached the"nip"between the tools 5,6 of the first forming station 3A. Thus, in the rear area of the product P2 the corrugations K become more and more shallow up to a completely unprocessed area close to the rear edge PB.

The example of fig. 4A-C corresponds to the one in fig. 3A-C in that the workpiece/product 1/P3 is longer than the distance between the"nips"between the tools 5,6 of the first and last forming station 3A and 3D, respectively. However, in this case forming is again interrupted when the rear edge 1B/PB of the workpiece/product 1/P3 has reached the"nip"between the tools 5,6 of the first forming station 3A. At this point of time, the front edge 1A/PA of the workpiece/product 1/P3 has passed the"nip"between the tools 5,6 of the last forming station 3D, whereby the front portion of the product obtains a shape of constant width having corrugations K of constant depth. On the other hand, like before, the main portion of the product P3 obtains a generally tapered shape. Furthermore, fig. 4C schematically illustrates an embodiment where the separation of the forming tools is performed by raising the upper tools 5 of all forming stations 3A-E in a first opening direction Sl like before, but by simultaneously lowering the lower tools 6 of all forming stations in a second opening direction S2.

Finally, figs. 5A-C illustrate an embodiment of a product P4 that is a combination of the above described products P2 and P3 according to fig. 3A-C and fig. 4A-C and that consequently has a front portion of constant width and with corrugations K of constant depth up to the front edge PA, as well as a rear portion where the corrugations K become more and more shallow up to a completely unworked area closest to the rear edge PB. Between the front and rear portions, there is a generally tapered portion like before. This product P4 is produced by interrupting the forming at a point of time when the front edge lA/PA of the workpiece/product 1/P4 has passed the"nip"between the tools 5,6 of the last forming station 3F, but before the rear edge 1B/PB of the workpiece/product 1/P4 has reached the"nip"between the tools 5,6 of the first forming station 3A. Thus, the workpiece 1 is in this case much longer than the distance between the"nips"between the tools 5,6 of the first and last forming station 3A and 3F, respectively. In this case is also illustrated an embodiment where forming is interrupted by performing the separation of the forming tools such that the lower tools 6 of all forming stations 3A-F are lowered in the second opening direction S2.

By the above-described opening movements Sl and S2, respectively, the upper and lower shafts 9,10 are moved apart by the drives 13, mentioned above with reference to fig. 8, that are arranged adjacent to the roll forming stands 4 and that for example comprise drive wheels 14,15 and transmission means 16 transferring a synchronized driving movement to the forming tools 5,6, i. e. typically to their shafts 9,10, from a common drive unit.

In fig. 6 is shown an alternative embodiment of the actual procedure for interrupting the forming. In this example, the upper forming tools 5 of the different forming stations are divided into different groups 25-28. More specifically, the upper forming tools 5 of the first two stations 3A and 3B are arranged in a first group 25, to be moved together, as indicated by the connection 25A. In a similar way, the upper forming tools 5 of the next two stations 3C and 3D are arranged in a second group 26, to be moved together, as indicated by the connection 26A. In each of the two last stations 3E and 3F, the separate upper tools 5 form a group of their own 27 and 28, respectively. With this configuration, forming can be selectively interrupted in different steps, with a time delay between the steps, and with the division for instance into the steps M1-M2-M3-M4 shown in the example.

In the illustrated example, forming is briefly interrupted in the way described below. In the uppermost illustration I, the first phase or the first step M1 begins by raising the group 28, i. e. the upper tools of the last forming station 3F, in such way that the forming in this station is interrupted, while the forming in other stations continues. In the next illustration II, the second step M2 is performed by raising the group 27, i. e. the upper tools of the penultimate forming station 3E, whereby forming is interrupted in this station as well. Then, in illustration m the third step M3 is performed by raising the group 26, i. e. the upper tools 5 of the forming stations 3C and 3D, whereafter forming only takes place in the first two stations 3A and 3B. In the lowermost illustration IV, the fourth and last step M4 is at finally performed by raising the group 25, i. e. the upper tools of the first two forming stations 3A and 3B, to finally interrupt forming. Then, the product is removed from the roll-forming machine in the above-described manner or according to fig. 7A-B below. The illustrated example is not to be regarded as limiting, but the division of the tools into the different groups as well as, to some extent, the sequential order for activating the different steps may be varied to suit the product to be manufactured.

Figs. 7A and 7B very schematically illustrate two alternative procedures for further facilitating removal of a formed product from a roll forming machine when practicing the method of the invention. In fig. 7A, the upper tools 5 of all forming stations 3A-F are mounted in a common frame 30, whereby the separation of the upper 5 and lower 6 tools for interrupting the forming may be performed by raising the entire frame in a first opening movement 01. This replaces the above-described movement of the tools in the first opening direction Sl. Then, the frame 30 is swung up to expose the formed product, which is illustrated in two further steps 02 and 03 of the opening movement. Naturally, this process may also include separation of individual tools or groups of tools in accordance with the above description, i. e. the raising of the frame 30 may take place after interrupting the forming.

The variant according to fig. 7B corresponds to the one according to fig. 7A, except for the fact that after the initial opening movement 01 the frame 40 is displaced sideways in a second opening movement 04 to expose the formed product. The examples of figs. 7A and 7B in both cases show that the upper forming tools 5 are arranged in a frame 30 and 40, respectively, that is raised for the opening movement 01, but the invention naturally also covers the alternative that the lower tools 6 are arranged in a corresponding frame that is lowered from the upper tools 5 for the opening movement. Moreover, for both these embodiments according to fig. 7A and 7B specific roll forming stands, not shown herein, have to be used, allowing the upper and lower tools to be completely separated from each other.

Although the invention has been described above with reference to the specific embodiments illustrated in the drawings, it should be emphasized that it also comprises other variants employing the basic principles of the invention. Hence, it also lies within the scope of the invention to employ the described method for forming products that are either simpler or more complicated than the ones that have been disclosed herein. As was mentioned above, the invention is for instance not restricted to forming products having the described shapes, where all profile folds are formed in all stations, but may also be practiced using a more conventional type of roll-forming machine, i. e. where new profile folds are formed in different stations. This may for example be appropriate when forming products that shall have different numbers of profile folds along their length. Since the roll forming is interrupted in the above-described manner, with or without division into several steps, before the workpiece has passed stations having additional forming rolls or the like different profile folds can be formed only in limited areas of the workpiece. In the embodiments shown and described herein, the products also have mutually uniform indentations or corrugations, i. e. the forming rolls on each upper and lower shaft, respectively, are identical. However, the invention is not limited thereto, but also covers the use of its principles for forming products having profiles with mutually different shape, depth and/or width, for example in accordance with the description of our international patent application PCT/SE01/01253, which was mentioned above.

In the above description, sheet metal plate has been mentioned as a suitable choice of material for practicing the invention. Irrespective of this, it should be emphasized that the invention is in no way is limited to such a material, but can be employed for workpieces of different materials. More specifically, the invention may come to use for forming products of plates or sheets made of other materials, such as other metals or plastic materials, suitable for the roll forming technique.

A man skilled in the art recognizes that various modifications and changes can be made to the present invention without departing from the scope thereof, as defined by the appended claims.