The present invention relates to a method for the deformation of plate material.

The bending of a plate into a defined profile is effected in practice by placing it between a template conforming to the desired profile and a counter-template and by subsequently moving the two templates towards each other at a defined force and speed. The result of such machine-working is then a plate having the profile in question. Practice has shown that the final shape of the product which is thus formed depends upon the material thickness, the material properties of the plate material and upon the deformation speed and contact pressure. Especially where large batches of profiles are produced according to this method, it is important in order to obtain a uniform series of products that the material thickness and/or other material properties of the plate material should be at least substantially constant. If, for example, in a batch of plates to be worked, the thickness of such plates were to vary considerably, then in principle, for each new plate to be worked, a different template and counter-template would have to be placed in the machine-working appliance so that, following the working operation, the desired profile is again obtained. It is self-evident that when a profile in plate material is shaped in this way each desired profile requires its own template and counter-template, whilst the number of different templates and counter-templates, where there is a wide divergence in the properties of the plates to be worked, needs to be greater still, which is not only expensive but also slows down the production cycle as a result of the respective changing of the templates.

The object of the invention is to provide a method for the deformation of plate material, which method does not possess the aforementioned drawbacks.

This object is achieved by a method for the deformation of plate material, comprising the steps of: placing a plate of the plate material against a

supporting surface of resilient material; applying a sweeping member against that side of the plate material facing away from the supporting surface; pressing the sweeping member and the plate material located between the sweeping member and the supporting surface to a predefined depth of impression in the supporting surface; following a path over the plate material, substantially parallel to the supporting surface, the said supporting surface being impressed with the sweeping member; and removing the plate material from the supporting surface.

With the method according to the invention, it is no longer necessary to constantly change components of a bending machine when shaping repeatedly differing profiles and where there is possible divergence present in the material properties and material thicknesses of the plate material to be bent, but it can in principle be sufficient - whether or not in a programmed manner - to match the adjustment of the depth of impression in the supporting surface and the path to be described by the sweeping means to the changes in the profile to be shaped and in (the properties of) the plate material to be worked. Some favourable embodiments of the method according to the invention are described in claims 2 - 8.

The invention further relates to a device which is designed to implement the method for the deformation of plate material, which device is characterized by: - a sweeping table which is designed to support plate material to be worked and is provided with a supporting surface of resilient material; a sweeping member; displacement means for displacing a sweeping member and the sweeping table in relation to each other; control means for commanding the displacement means and for adjusting the depth of impression to be realized with a sweeping member, via the plate material to be worked, in the resilient supporting surface.

Some favourable embodiments of the device according to the invention are described in claims 10 - 18.

The invention shall be explained in greater detail below with reference to the appended drawing, in which: Fig. 1 is an illustration showing the principle of the method and device according to the invention; Fig. 2 is a graphic representation of the relationship between the impression of the supporting surface and the radius of curvature to be acquired with the working operation as a function of the thickness and hardness of the material of the supporting surface; Fig. 3 shows an embodiment of the device according to the invention; Fig. 4 shows an embodiment of the pressure and displace¬ ment means in the embodiment of the device accor¬ ding to Fig. 3; Fig. 5 shows an alternative favourable embodiment of the device according to the invention; and Fig. 6 is an illustration showing an embodiment of the principle of the method and device according to the invention, which embodiment is altered in relation to Fig. 1.

Fig. 1 shows the principle of the method according to the invention. Prior to the execution of the bending operation, there is laid on a table 1, which table is represented diagrammatically, a plate 2 of the plate material to be worked, made, for example, from aluminium. The supporting leaf 3 of the table 1 is provided on the side upon which the plate material 2 rests with a layer 4 of a resilient material of predetermined thickness. The layer of resilient material 4 can be fixedly connected to the supporting leaf 3 but can likewise by means of an appropriate connection be detachably applied to the supporting leaf 3.

A sweeping member 5 - which in this basic example is elongated and extends perpendicularly to the surface of the figure - is subsequently pressed with means (not represented) appropriate to this purpose, with the plate 2

to be worked, over a certain distance, the depth of impression, into the resilient layer 4. Hereafter the sweeping member 5 is slid substantially parallel to the supporting leaf 3 over the plate 2 in the direction of the arrow PI, the resilient layer 4 being continuously impressed.

As a result of the impression of the resilient layer 4 with the sweeping member 5 and the plate 2, reaction forces are induced in the zone of impression of the resilient layer 4, which reaction forces are directed towards the sweeping member 5 and deform the plate material 2 close to the zone of impression of the resilient layer 4.

By meanwhile moving the sweeping member 5 con¬ tinuously over the plate 2, that portion of the plate 2 which has already been swept will begin to display a curvature of a certain radius R. If now the entire plate 2 is swept, a constant depth of impression being maintained in the resilient layer 4, the result of the working operation will be a curved plate which assumes the shape of an arc of a circle of constant radius R, presupposing that the material properties of the plate material, in the direction of the sweeping motion, exhibit no great variances.

By now varying, during the sweeping cycle, the depth of impression in the resilient layer 4, it is possible to vary the radius of curvature R locally and a defined profile can be bestowed upon the plate.

It is apparent that the greater the choice of impression of the layer of resilient material 4, the greater is the curvature effect which is realized, i.e. the lesser becomes the acquired radius R.

Fig. 2 illustrates in graphical representation the relationship between the impression (in mm) of the layer 4 of resilient material and the obtained radius R. It is evident from this array of graphs that, in the case of one type of plate 2 to be worked, the resulting radius R, apart from the extent of impression of the resilient layer 4, is likewise dependent upon the thickness of the resilient layer 4 and the hardness of the material of the resilient

layer 4. It is evident from the graphical drawing that where the impression value is fixed, in one type of plate material the radius R which results after the working operation will increase as the thickness of the resilient layer 4 is increased, but also as the hardness of this layer 4 is reduced.

On the basis of the above-described principle of the bending of plate material and of a device intended for this purpose, a large number of devices can be conceived for the bending of plates in this way.

Fig. 3 now shows an embodiment of a device according to the invention having two sweeping members, which, in this illustrative embodiment, are likewise elongated and with which, either simultaneously or not, two sweeping motions are able to be performed, and which embodiment is especially suitable for the (in relation to an axis extending parallel to the sweeping members) symmetrical deformation of the plate material.

The bending device 6 comprises a table 7 which is composed of two table parts 7a and 7b respectively, which can be swung aside about hinge points 8a and 8b.

The device 6 is provided moreover with two sweeping arms 9a and 9b, which can be operated independently of each other and which, in a manner to be described later, are driven by one or more motors (here indicated diagrammati- cally by reference numeral 13) .

The working of this bending device 6 will be described presently. Before a plate 2 to be worked can be laid upon the resilient layer 10a, 10b of the table parts 7a and 7b respectively, the table parts have to be brought into a position in which the resilient layers 10a and 10b respectively lie at least substantially in one plane. This can be realized using the - likewise controllable - hydraulic cylinders 11a and lib respectively, which are connected to the table parts 7a, 7b. In addition, the sweeping arms 9a and 9b have to be brought into such a position that there is sufficient space to lay a plate to be worked on the table 7.

Once a plate 2 has been laid on the table 7, two

pressure bars 12a and 12b which are present on both sides of the plate 2 and interact with each other are moved towards each other with the aim of holding the plate 2 to be worked such that it is fixed substantially immovably on the table 7 between the pressure bars 12a and 12b.

Hereafter the sweeping arms 9a and 9b are positioned such that their "sweeping points" 14 in question rest upon the outermost margins of the plate 2. Subsequently the sweeping points 14 will be brought to a depth of impression in the resilient layers 10a and 10b respectively which is appropriate to the desired profile, whereafter both sweeping arms 9a and 9b are moved towards each other, the depth of impression applied with the sweeping points 14 in question being either maintained or varied. The plate 2 is thus provided with a profile which is either symmetrical or not, having two plate margins which are oppositely situated and are bent over towards each other.

Just before the sweeping arms 9a and 9b, close to the middle of the device, reach a position in which the plate 2 is no longer supported by the resilient layer 10a or 10b, the motion of both sweeping arms is halted.

Depending upon the final profile which is desired, the plate 2 can now be removed or subjected to subsequent working. Where, for example, a V-shape is desired in the cross-sectional profile to be made of the plate 2, then the device according to the invention can continue the working operation as follows:

The sweeping arms 9a and 9b are returned to a starting position, free from the worked plate 2, whilst the plate continues constantly to be held in place by the pressure bars 12a and 12b. Subsequently the supporting surface, i.e. the table parts 7a and 7b, is removed by means of the cylinders 11a and lib from beneath the worked plate 2 by being swivelled away. By now, in this position, moving the sweeping arms 9a and 9b such that their respective sweeping points make a substantially vertical motion downwards along the pressure bars 12a and 12b and over the plate surface, the plate 2 is provided with a V- shaped profile. Following the completion of this, the

worked plate has a symmetrical profile which is curved in relation to the V, presupposing that the same impression in the plate 2 has previously been made by the two sweeping arms 9a and 9b. If the bending device 6 is of the stand-alone type, i.e. where it does not form part of a series of successive automatic machine-working appliances, then in principle, after the sweeping arms 9a and 9b have been returned to a starting position, free from the worked plate 2, the latter can subsequently be manually removed and replaced by a plate which is newly to be worked.

Where the bending device 6 does form part of a series of successive automatic machine-working appliances, then a grab member 23, which is represented diagrammatically in Fig. 3, can grip the plate 2 and the said plate, once the sweeping arms 9a and 9b have been pulled back and the fixation by the pressure bars 12a and 12b has been lifted, is able to be taken up and introduced to a following machine-working appliance. Fig. 4 represents diagrammatically a possible embodiment of the control system of the sweeping arms, this figure illustrating, for the sake of simplicity, only the left half of the sweeping device shown in Figure 3.

The bending device 6 shown in Fig. 4 comprises, for the driving of the sweeping arm 9a and for the pressing of the sweeping point 14 over a certain distance, the depth of impression, into the resilient layer 10a, two motors 15 and 16 respectively, which can be commanded independently from each other. The motor 15 is hingingly connected at a point 18, by means of a spindle 17 or the like, to a stand 20, which is tiltable about a hinge point 19. If the motor 15 is driven such that, via the spindle 17, the tiltable stand 20 is moved from the table part 7a, then, provided the motor 16 is not being driven, the sweeping arm 9a will likewise perform a tilting motion, the sweeping point 14 rotating about the point 19 and detaching itself from the plate 2.

The driving of the motor 16 drives a spindle 21, which is connected to the sweeping arm 9a and causes the

latter to pivot, when the motor 15 is not being driven, at the point 22 where the sweeping arm 9a is connected to the tiltable stand 20. Using the motor 16, it is thus possible to adjust and vary the position of the sweeping point 14 in relation to the plate 2.

By driving the motors 15 and 16 simultaneously, the sweeping arm 9a, once this has been placed with its sweeping point 14 on the plate 2 , can be swept over the plate 2. The vertical position of a sweeping point 14 in relation to the plate 2 and hence also the depth of impression in the plate 2 is particularly defined, whilst following the predetermined path of the sweeping point, by the motor 16.

The control of the two motors 15, 16 should preferably be programmed. Any changes to the composition or thickness of a plate 2, after having being introduced to the control unit (not represented and not specified here in any greater detail) , can be processed in a programmed manner, whereafter such plates are also able to be provided with the desired profile.

Fig. 5, finally, shows a different favourable embodiment of the device according to the invention. This device 24 is similar to that of Fig. 3 and those components which conform to the components from the device 6 of Fig. 3 have one and the same reference numeral.

The device 24 is arranged moreover such that, during a sweeping operation by the sweeping arms 9a and 9b, the surface of a plate 2 to be worked is protected against damage such as scratches and the like by virtue of the plate 2 being covered during sweeping with a foil 25, preferably made from a strong plastic material.

To this end, the device 24 is provided with supply rollers 26 holding the foil 25 of a width which is at least as large as the longitudinal dimension of the elongated sweeping point. The foil is led via a conducting member 27, such as a roller, about the sweeping point 14 towards a collecting member 28, which collects foil 25 which has been used once. During the sweeping motion with the sweeping arm 9a, 9b, the foil 25 is arrested by the supply roller 26 and

the foil is unrolled under tension from the collecting member 28, so that the foil 25 slides underneath the sweeping point 14 but does not move over the plate surface, which once again reduces the occurrence of scratches. Following the execution of a sweeping operation on a plate 2, the supply roller 26 is unrolled to some extent so that, in the following working operation, the foil surface which has previously been swept with the sweeping point 14 is not swept again in full. The extent of unrolling, i.e. the number of times which a foil surface can be swept, is primarily determined by the strength of the foil 25.

A device 24 of this type is particularly favourable in the machine-working of high-gloss plate material, as is used in fluorescent-light fittings. In the template method according to the prior art, it has hitherto been usual to use plate material which was already lined with a protective foil, which then, following the working operation, was able to be removed with great difficulty, this giving rise to a considerable expense. With the device 24 according to Fig. 5 this action may be omitted, thereby producing a saving in both time and cost.

Fig. 6 shows an embodiment of the general prin¬ ciple, shown in Fig. 1, of the method and device according to the invention, which embodiment is to some extent altered, those components conforming to the components from Fig. 1 having the same reference numerals.

Fig. 6 shows the situation in which a spring-steel foil 29 is fitted between the plate 2 to be worked and the layer 4 of resilient material. This form of execution of the method according to the invention has the surprising effect that, in plates 2 provided with punch holes, the appearance of visual stress phenomena around the contours of the punch holes is considerably reduced. The abovemen- tioned phenomenon can prove a nuisance, particularly in respect of the plate material used in fluorescent-light fittings.

The spring-steel foil 29 is preferably laminated in structure and not bonded to the layer 4 of spring material.

The thickness of the foil 29 should be matched to the material to be bent and measures, for example, between 0.05 and 0.7 mm.

Although reference has been made above to sweeping points 14, these should be taken to mean that part of a sweeping body which is in contact with the plate material to be bent. The sweeping body can be, for example, an elon¬ gated, substantially rectangular body, having a margin which is rounded to some extent towards the plate 2 to be worked. However, the sweeping body can also be constructed as an elongated roller body of small radius, whilst deformation operations according to the present invention can also be executed, furthermore, with non-elongated sweeping bodies. It is self-evident that the construction of a bending device according to the invention has to be very solid with a view to obtaining a depth of impression in the resilient supporting surface which is as adjustable and reproducible as possible. Although, in the embodiments represented above, the sweeping motion is performed by the sweeping arms/blades in relation to an immovable plate, the reverse is likewise possible in principle, namely a fixed arrangement of one or more sweeping bodies with a sweeping table which is mobile in relation thereto and on which the plate to be worked is fastened.