In the manufacture of sheet products comprising patterns, such as protru- sions and/or recesses, a larger blank sheet is divided into smaller sheet products e. g. by sawing in relation to the patterns. A typical product of this type is a pre-formed door skin. Typically, the manufacturing process of this type of products involves inaccuracies, with the result that the blank sheet cannot be positioned and sawed with respect to the edge of a master sheet.

In prior-art solutions, the blank sheet, i. e. the so-called master sheet, is pro- vided with at least one positioning groove formed during the pressing stage, and this groove is used for guiding the sheet by means of mechanical guides so that the sheet can be sawn with respect to the patterns. These require complicated arrangements. Prior-art systems are quite slow and, moreover, there are problems with their accuracy. To be able to work reliably, the guide elements require a large space, so the master sheets must also comprise plenty of excess material for the guide elements. Therefore, a lot of waste material is produced.

The object of the present invention is to achieve a completely new type of method and apparatus in which, among other things, the drawbacks of prior- art systems are avoided.

The invention is characterised by what is presented in the claims.

The method and apparatus of the invention have numerous significant ad- vantages. The method allows very fast and accurate positioning. The system is highly reliable in operation. The system of the invention makes it possible to use a smaller master sheet because it does not involve the use of guides placed upon the sheet. Therefore, a significant saving in material consump- tion is achieved.

In the following, the invention will be described in detail by the aid of an ex-

ample with reference to the attached drawings, wherein Fig. 1 presents a simplified illustration of the method of the invention, Fig. 2 illustrates a sheet-like object before its division, Fig. 3.1 presents an apparatus applying the method of the invention, in top view, Fig. 3.2 presents the apparatus in Fig. 3.1 as seen from direction A, Fig. 3.3 presents the apparatus in Fig. 3.1 as seen from direction B, Fig. 4 illustrates a production line applying the invention.

Fig. 1 is a schematic illustration of an arrangement according to the inven- tion. In this arrangement, a sheet-like object 1 with patterns 2, such as pro- trusions or recesses, has been brought to a positioning station. A typical ob- ject is a pressed door skin made of fibrous material, e. g. MDF material. In the positioning station, the object 1 is adjusted to the correct position relative to the patterns 2, whereupon the object is moved from the positioning station to a division stage, such as a sawing station 8, while substantially maintain- ing its position. The location of at least one register point 6 formed in the ob- ject 1 is detected using at least one optic detector means 7 and, based on this detection data, the position of the sheet-like object in the positioning sta- tion, the division apparatus 8 or both are influenced so that the sheet is di- vided along a predetermined line 9 with respect to the patterns. In the figure, the predetermined division lines 9, along which the sheet-like object is di- vided into smaller objects, are indicated by broken lines.

The register point 6 formed in the object is e. g. a groove or a protuberance.

The essential thing about the nature of the register point 6 is that it can be identified from a distance, preferably using an optic detector means 7. In this case, the register point formed in the object may also be a line or hole in the sheet 1.

The object is preferably provided with at least two register points 6 formed in

it. The register points 6 are located at a distance from each other. Thus, the position of the sheet-like object can be adjusted with respect to the patterns.

The register points 6 are preferably formed in the blank sheet 1 in conjunc- tion with the formation of the patterns 2. They can be formed beforehand in the patterning means, for instance in a press mould, thus ensuring that their location in relation to the patterns always remains correct.

The register point 6 may also consist of a single continuous line, groove or embossment, whose location is detected by a detector means 7 at least from two points of observation.

The object 1 is illuminated at least in the area of the register point 6, thus rendering the register point different from the surrounding material e. g. in re- spect of contrast or brightness, and this difference is detected optically by a detector means 7, such as an opto-electric camera. The detection signal is transmitted from the detector means 7 to a control device, which gives the required control commands to positioning means used to position the object.

The positioning means are e. g. grippers that engage the object, e. g. by its edge. The control device may be e. g. a computer or programmable logic.

The detector means 7, the object 1 being treated or both can be moved dur- ing detection. The directions of movement of the object are indicated by ar- rows in the figure. It is to be noted that the object can also be turned about an axis perpendicular to the plane of the object.

Fig. 2 presents a sheet-like object, i. e. a master sheet, before the division stage. The parting lines are indicated by broken lines 9,9'. The object is in- tended to be treated in two stages. First, it is positioned in accordance with a first pair of register points 6'and sawed in a first sawing operation along lines 9, the edges at the long sides of the object being thus evened out. After this, the treatment of the object is continued in the manner illustrated in Fig. 1. It is obvious that the object illustrated in Fig. 2 is only presented as an example of how the invention can be applied.

The apparatus of the invention for positioning a sheet-like object provided with patterns, such as protrusions or recesses, into a desired position in rela- tion to the patterns comprises a base 11 onto which the sheet-like object is brought, means for moving the sheet-like object on the base, and means 13

for moving the sheet-like object from the base to a further treatment stage in a substantially predetermined position. The means for moving the object are e. g. grippers which move the sheet-like object by gripping it by its edge.

The positioning station is provided with at least one detector means 7 and the sheet-like object is provided with at least one register point 6,6'. Based on the information obtained from the detector means, the control device (not shown) controls the positioning means. There are preferably at least two register points 6,6'. The register point is e. g. a groove, hole or embossment formed in the sheet. Typically, the register point may consist of a spot, e. g. a steam groove, created during an operation, such as moulding, for the forma- tion of the patterns 2.

The example presented in the figure comprises two detector means 7. The detector means are e. g. opto-electric cameras known in themselves, which are used to detect a difference caused by the register point, e. g. a difference in contrast or brightness, in relation to the surrounding material. Typically, the camera is a so-called matrix camera, which takes a picture ("photograph") of the register point and processes it digitally, typically searching e. g. for grey- ness differences between the pixels in the image area.

The detector means 7 are preferably disposed on a movable frame 10. This makes it possible to bring the object 1 under treatment close to the detection area, whereupon the detectors in the detector means detect the register point and transmit a signal to the control device. The control device issues a control command to a sheet moving device, which then moves the sheet on the basis of information obtained from the detector means 7.

Figures 3.1,3.2 and 3.3 present a typical positioning station employing a solution according to the invention. The apparatus comprises a base 11 onto which the sheet-like object is brought on a conveying means, e. g. a roller conveyor, from direction S in Fig. 3.1. The detector means 7 in the posi- tioning station is a camera, and the register point on the sheet-like object is brought to the detection area of the the camera. The detection area is illu- minated by means of an illuminator 20. In this case, the detector means 7 has been arranged to observe the sheet-like object from below. The posi- tioning station comprises means 13 for moving the sheet-like object and po-

sitioning it on the base to the correct position on the basis of the information obtained from the detector means. In the case of Fig. 3.1,3.2 and 3.3, the moving means are gripping elements 13 arranged to be movable along guide rails 21. In addition, the moving means can be used to turn the sheet-like object about an axis perpendicular to the plane of the sheet-like object. After the positioning, these means 13 are used to move the sheet-like object in the desired position from the base 11 to a further treatment stage away from the positioning station. The exit direction is indicated in Fig. 3.1 by arrow U and is, in the case of the example, a direction substantially transverse to the feed direction.

In a typical case, where master sheets are sawn in two crosswise directions, a sawing line is used which comprises a first positioning station 15 followed by a first sawing station 16 and a second positioning station 17 followed by a second sawing station 18. Fig. 4 presents a solution like this. The sheet feed directions are indicated by arrows in the figure. The positioning stations 15, 17 also function as feeding stations for the sawing stations 16,18. The base in the positioning station is typically a conveyor, for instance a roller con- veyor, along which the sheets are brought to the positioning station. The feed movement into the sawing station is generated by using a feeder which moves e. g. along a guide rail.

With the solution of the invention, very fast and accurate positioning is achieved, allowing the speed of the sawing line to be increased as compared with prior-art positioning systems.

It is obvious to a person skilled in the art that the invention is not restricted to the embodiments described above, but that it can be varied within the scope of the claims presented below.