EP2288886A1

EP2288886A1 - Method and apparatus for measuring temperatures in connection with manufacturing of a glue board or a corresponding product

Info

Publication number: EP2288886A1
Application number: EP08857777A
Authority: EP
Inventors: Sampsa HÄMÄLÄINEN; Petri HYVÖNEN
Original assignee: UPM Kymmene Oy
Current assignee: UPM Kymmene Oy
Priority date: 2007-12-03
Filing date: 2008-11-11
Publication date: 2011-03-02
Also published as: FI20075872A; WO2009071738A1; FI20075872A0; FI122590B; EP2288886A4

Abstract

The object of the invention is a method and an apparatus for measuring temperatures in connection with the manufacturing of glue board (10) or a corresponding product, wherein the glue board (10) is manufactured from wooden laths (2) that are placed adjacent to each other and glued together, in the gluing stage of which the wooden laths (2) and the glued joints are heated and pressed against each other with a press apparatus (7). According to the invention the temperature of at least the glued joints of the glue board (10) is measured after pressing by imaging the glue board with a thermographic camera (9).

Description

METHOD AND APPARATUS FOR MEASURING TEMPERATURES IN CONNECTION WITH MANUFACTURING OF A GLUE BOARD OR A CORRESPONDING PRODUCT

The present invention relates to a method as presented in the preamble of claim 1 and an apparatus as presented in the preamble of claim 9 for measuring temperatures in connection with the manufacturing of a glue board or a corresponding product.

One product manufactured in the sawmill industry is so-called glue board, which is manufactured from sawn timber pieces, such as e.g. wooden laths, glued together side-by-side. The applications of finished glue board are large board surfaces, such as e.g. tables, doors, cupboards and shelves. In these types of large board surfaces the living of the wood must be controlled so that the board does not warp e.g. owing to living of the wood caused by the ambient temperature and moisture. To prevent warping, the juxtaposed pieces of glue board manufactured from wooden laths are placed so that the heartwood is alternately on the top and on the bottom.

Glue board is manufactured such that the wooden laths are sawn to the desired dimensions before gluing and they are trimmed and their sides are planed straight. After this glue is spread on the sides of the laths and they are glued side- by-side to each other, after which the pieces that are glued together are fitted into a press, which is arranged to press the pieces together while the glue is drying. In connection with the presses used in the sawmill industry, means are also generally known by the aid of which the glued joints between glued pieces are heated to a suitable temperature, which improves the end result of the gluing and speeds up drying of the glue. To achieve a sufficient process speed in the pressing stage, e.g. so-called radio-frequency presses are generally used, for which the abbreviation RF press is also used. The advantage of these presses is the great speed because, in addition to pressing, RF presses in practice heat only the glued joints containing liquid with the thermal energy produced by an electromagnetic field. For the gluing to succeed as well as possible, the temperature should remain essentially the same in all the glued joints in the whole area of the glue board, which for its part requires that the electromagnetic field producing the thermal energy should be as homogeneous as possible. A homogeneous electrical field is, however, awkward to implement and often the temperature varies at different points of the glued joints of the glue board in the press. Large temperature variations in the glued joints can cause failure of the gluing. For this reason it would be good to monitor the temperatures during or after pressing so that large temperature deviations would be eliminated and any unsuccessfully glued glue boards could be directed from the press elsewhere than the glue boards in which the gluing succeeded.

It is known that the temperatures of glue boards have been monitored such that glue board coming from the press has been measured manually at a few points e.g. with a spot thermometer or with an infrared thermometer. It is in no way possible to measure temperatures at every point of the glue board with these types of measurements, however, but instead temperature values are obtained at only certain selected measurement points. For this reason a gluing error can easily remain undetected. This kind of measuring is not otherwise very practical because the measurements must be performed on- site on the line after the glue board has come out of the press.

The purpose of this invention is to eliminate the aforementioned drawbacks and to achieve a method and an apparatus that are as inexpensive and simple as possible for measuring temperatures in connection with the manufacturing of glue board or a corresponding product. Another purpose is that the temperatures of the glue board and of its glued joints can be observed in the whole area of the glue board throughout the glue pressing in real-time. The method according to the invention is characterized by what is disclosed in the characterization part of claim 1. Likewise the apparatus according to the invention is characterized by what is disclosed in the characterization part of claim 9. Other embodiments of the invention are characterized by what is disclosed in the other claims.

In the solution according to the invention the temperatures of the wooden laths and of the glued joints are verified digitally by imaging. In this case the temperature shown by each pixel of the image obtained can be obtained separately, in which case each pixel is in principle a separate thermometer. In this way essentially all the temperatures of the whole image area are seen on the screen at essentially the same time, for instance at a glance. The image area of the measuring point to be imaged can be very large, e.g. 6*2 m = 12 m², in which case it is important that the temperatures of the image area can be analyzed very quickly. One advantage of the solution according to the invention is also that it is possible by means of it to observe the temperatures of the glue board and of its glued joints during glue pressing or immediately after pressing for the whole area of the glue board. Another advantage is that the temperatures of the glue board do not need to be measured manually on-site but instead the measurement can take place automatically and the measurement results can be scrutinized in real-time e.g. from a monitor situated in the control room. Yet another advantage is that two prior-art techniques are combined in the solution, which have been in use earlier and they have been tested and developed, and they have been observed to be very effective. A further advantage is that the solution according to the invention is simple and inexpensive to implement. In the following, the invention will be described in more detail by the aid of two different examples of its embodiment with reference to the attached drawings, wherein

Fig. 1 presents a glue board manufacturing line, in which one embodiment of the solution according to the invention is used, as a block diagram

Fig. 2 presents a glue board manufacturing line, in which a second embodiment of the solution according to the invention is used, as a block diagram and

Fig. 3 presents an image taken with a thermographic camera of glue board that has come from the press .

Fig. 1 presents as an example a block diagram of a glue board manufacturing line, in which one embodiment of the solution according to the invention is used. The apparatus comprises a line 1 provided with at least one or more conveyors for conveying the raw materials of the glue board, such as wooden laths 2, and the manufactured glue board. At the forward end of the line 1 is an temperature measuring apparatus 3, such as a first thermographic camera operating in the infrared range that records an essentially continuous video image for a digital imaging sensor, to measure the temperature of the wooden laths to be taken into the line 1, which camera is connected to a control and recording apparatus 4 in the control room, such as a computer, which is further provided with a first screen 5a for showing the temperature of the wooden laths 2 in real-time. The line 1 comprises a return conveyor Ia after the first thermographic camera 3 for returning to a buffer storage those wooden laths 2a of which the temperature is not within the permitted range. These types of returnable wooden laths 2a are directed to the return conveyor Ia with means suited to the purpose either manually or automatically. The direction of travel of the return conveyor Ia is marked with arrows drawn with a dashed line.

After the first thermographic camera 3 the line 1 comprises a gluing station 6 and after this, in the direction of travel of the line, a press apparatus 7 for pressing the wooden laths 2 that are glued together against each other as well as for heating and drying the glued joints between them. The press apparatus 7 is e.g. a fast RF press, which in addition to pressing also heats the glued joints of the glue board by means of an electromagnetic field. The press apparatus 7 is also connected to the computer 4 that functions as a control and recording apparatus. After the press apparatus 7 in the direction of travel of the line 1 is a second measuring apparatus 9 that operates in the infrared range and is fitted to measure the temperatures of the glue board 10 just manufactured and in particular the temperatures of the glued joints, which similarly to the apparatus 3 that measures the temperatures of the wooden laths 2, is a thermographic camera that records an essentially continuous video image for a digital imaging sensor. The second thermographic camera 9 is connected to the computer that functions as a control and recording apparatus 4 in the control room, which computer is further provided with a second screen 5b for showing the temperatures of the manufactured glue board 10 and of its glued joints in essentially real-time. In addition the final end of the line 1 comprises a receiving station Ib for the manufactured glue boards 10.

The method according to the invention is fitted to function such that the raw materials of the glue board, which in this embodiment are pre-trimmed and pre-planed wooden laths 2, are initially directed from the buffer storage to the first measuring element 3, which in this embodiment refers to the thermographic camera 3 intended for imaging the object, fitted to the forward end of the line 1. Before being taken to the manufacturing process the wooden laths 2 are kept for some time at an essentially even temperature in the buffer storage to equalize their temperatures and bring their temperatures into the permitted range. The wooden laths 2, now at an essentially even temperature, at the forward end of the line 1 are fitted to travel below the thermographic camera 3 and the thermographic camera 3 is arranged to photograph an essentially real-time video image, in which the temperature of the upper surface of each wooden lath 2 at different points of the surface in the area of the whole surface is seen. Different temperatures are seen with a predetermined precision as pixels of different colors. The first thermographic camera 3 is connected to a computer 4 disposed e.g. in the control room or corresponding, to which the thermographic camera 3 is arranged to send a video image of its imaging. If the mutual temperature of the wooden laths 2 of a raw material batch is very different or the wooden laths are e.g. too cold for the gluing to succeed well, the wooden laths 2a that are too cold or that differ in their temperature from the defined ideal values are directed back to the buffer storage with the return conveyor Ia to reach the correct temperature. The wooden laths 2 that are within the correct temperature spread are directed to the assembly of the glue board, gluing, pressing and temperature measurement conveyed by the conveyors of the line 1.

A first screen 5a is connected to the computer 4, which screen is monitored by a person, who is assigned the task of inspecting the temperatures of the wooden laths 2 coming from the line. The temperature of the raw material affects, among other things, how the RF press 7 disposed downstream on the line 1 is adjusted to operate. For example, in winter the raw material can be frozen and, conversely, in summer it can be warm, so the temperature of the raw material can vary within the permitted limits very much in different seasons of the year. Also the RF press 7 is connected to the computer 4, by means of which the parameters of the press 7 are regulated on the basis of the temperature observations of the wooden laths 2 made with the first thermographic camera 3. This regulation can be performed manually or automatically, in which case the apparatus comprises means for performing the automatic regulation. Regulation of the heating energy is performed e.g. by adjusting the electromagnetic field by changing the anode current/cathode current.

The computer 4 also comprises means that are arranged to edit, if necessary, the image photographed by the thermographic camera 3 to a suitable format and to show e.g. the temperatures corresponding to the colors seen in the image and possibly to suggest how the press 7 should be adjusted at any given time.

From the first thermographic camera 3 the wooden laths 2 are directed onwards on the line 1 by means of the conveyor to the gluing point 6, in which glue is spread on the sides of the wooden laths 2 and the wooden laths 2 are placed together side-by-side. After this the wooden laths 2 that are glued together are directed to the RF press 1 , in which the wooden laths 2 that are glued together are pressed against each other. Heating means 8 are also disposed in connection with the press 7 , by the aid of which means the wooden laths 2 that are glued together as well as the glued joints between them are heated to a suitable temperature so that the gluing succeeds as well as possible. The heating means 8 are e.g. metal plates, by means of which an electromagnetic field is created, which produces thermal energy. When the wooden laths 2 that are glued together have been in the press 7 for the set time, they are directed to the second measuring element 9 disposed after the press 7 by means of a suitable conveyor of the line 1, where the wooden laths that are glued together, i.e. at this stage already glue board 10, are directed to travel under the second thermographic camera 9 and the glue board 10 is imaged with the second thermographic camera 9, i.e. a real-time video image of the glue board is photographed in which the temperatures are seen e.g. pixel- by-pixel over the whole area of the glue board 10 and its glued joints. The data imaged as a video image by the second thermographic camera 9 is sent in essentially real-time to the computer 4 and on the basis of the data the temperatures of the glue boards 10, and particularly of their glued joints, coming from the press 7 is analyzed. If the temperatures of all or also of only some of the glued joints of the glue board 10 differ by too much from the pre-defined limit values, the glue board is diverted from the line of glue boards going for actual sale. The analysis of the temperatures and the diversion can again be performed manually or automatically, whereby in the latter case the apparatus comprises means for performing the automatic diversion.

In manual supervision the second screen 5b is monitored by e.g. a person, who is assigned the task of inspecting the temperatures of the glue boards 10, and of their glued joints, coming from the press 7. If the temperatures of a glue board 10 or in particular of its glued joints differ from normal, the person monitoring the temperatures can take a still photo of the glue board 10 in question by pressing e.g. a button in the computer 4 intended for this purpose. Images taken of nonconforming glue boards can later be analyzed as to why the temperatures diverged from the normal and whether the gluing e.g. failed owing to the divergent temperatures. It can also easily be seen from the imaging results taken whether there was no glue at all in a joint or in a part of a joint or whether there was not enough glue in it. In this way the glue boards that have been unsuccessfully glued can be weeded out from those that have been successfully glued. The glue boards that have been successfully glued are directed to finishing after imaging and analysis of the glued joints.

As already mentioned above, the monitoring of the temperatures of the objects to be imaged, i.e. the wooden laths 2 that are the raw materials and the manufactured glue boards 10 as well as their glued joints, and the procedures to be performed on the basis of them, such as adjusting the heating powers of the press 7 as well taking still photos of nonconforming glue boards and weeding out failed glue boards, can also be performed fully automatically. In this case a separate person, who monitors the temperatures and based on temperature observations performs the necessary procedures manually, is not needed.

Fig. 2 presents as an example a block diagram of a glue board manufacturing line, in which a second embodiment of the solution according to the invention is used. In this solution the screens 5a and 5b are not connected to the computer 4, but instead they are connected directly to their own thermographic cameras, in which case the first screen₍ 5a is connected to the first thermographic camera 3 and the second screen 5b is connected to the second thermographic camera 9. The imaging data from the thermographic cameras 3 and 9 are led to a computer 4 in essentially the same manner as in the embodiment presented in Fig. 1. Likewise the connection between the computer 4 and the press apparatus 7 is essentially similar to that in the solution according to Fig. 1.

Fig. 3 presents a simplified view of a still photo of one glue board 10 taken from the imaging data of the second thermographic camera 9. In the figures the different temperatures are seen as different grayscale colors. In reality there are many more colors and the temperatures. The temperatures of the cooler parts, i.e. of the wooden laths 2, of the glue board 10 are shown as darker in Fig. 3 and the warmer temperatures of the glued joints 11 as lighter. At one point in the glue board is a colder area 12, in which the temperature of the glued joints differs from the temperature of the other glued joints 11. This difference is seen in the real-time video image, and in colors very clearly. Additionally, the lateral deviations 13 that can be caused e.g. by the non-homogeneity of the electrical field formed are seen in Fig. as border points. The goal is an electrical field that is as homogeneous as possible, so that in the case of Fig. 3 the press apparatus 7 needs new adjustments.

It is obvious to the person skilled in the art that the invention is not limited solely to the example described above, but that it may be varied within the scope of the claims presented below. Thus, for example, the line can be different than what is described above.

It is also obvious to the person skilled in the art that in place of thermographic cameras, the imaging means can also be some other solution than a digital video camera operating in the infrared range, e.g. a corresponding analog video camera.

It is further obvious to the person skilled in the art that instead of an RF press, some other apparatus suited to the purpose can be used as the press and heating apparatus of the glue board. For example, heat boards operating by means of hot oil or corresponding, which are however slower than an RF press .

It is also obvious to the person skilled in the art that the apparatus can be fitted to automatically record a thermal image and/or to give an alert if a temperature smaller than the pre-determimed limit value is detected in the object to be imaged. In this case the apparatus comprises means suited to the purpose and actuators for implementing the recording and for giving an alert .

Claims

1. Method for measuring temperatures in connection with the manufacturing of glue board (10) or a corresponding product, wherein the glue board (10) is manufactured from wooden laths (2) that are placed adjacent to each other and glued together, in the gluing stage of which the wooden laths (2) and the glued joints are heated and pressed with a press apparatus (7) against each other, characterized in that at least the temperature of the glued joints of the glue board (10) is measured after pressing by imaging the glue board (10) with a thermographic camera (9) or corresponding apparatus .

2. Method according to claim 1, characterized in that the imaging data of the thermographic camera (9) is led to a control and recording apparatus (4) for processing and analysis of the imaging data.

3. Method according to claim 1 or 2, characterized in that the imaging data produced by the thermographic camera (9) is shown on the screen (5b) as a video image in essentially real-time.

4. Method according to claim 1, 2 or 3, characterized in that the imaging data produced by the thermographic camera (9) is processed such that the different temperatures of the object imaged are shown as different colors.

5. Method according to any of the preceding claims, characterized in that on the basis of the imaging data produced by the thermographic camera (9) the production of the thermal energy of the press apparatus (7) is regulated.

6. Method according to any of the preceding claims, characterized in that the temperature of the wooden laths (2) taken to the line (1) for gluing is measured before gluing by imaging the wooden laths (2) with a first thermographic camera (3) , and in that the wooden laths (2a) outside the permitted temperature range are separated from the wooden laths (2) going to gluing and directed to a buffer storage.

7. Method according to claim β, characterized in that the imaging data produced by the first thermographic camera (3) is shown on the screen (5a) as a video image in essentially real-time.

8. Method according to claim 6 or 7 , characterized in that on the basis of the imaging data produced by the first thermographic camera (3) the production of the thermal energy of the press apparatus (7) is regulated according to the temperatures of the wooden laths (2) that are the raw material .

9. Apparatus for measuring temperatures in connection with the manufacturing of glue board (10) or a corresponding product, wherein the apparatus comprises a line (1) provided with at least one or more conveyors for conveying the raw materials of the glue board, such as the wooden laths (2) and the manufactured glue board (10), a gluing station (6), and a press apparatus (7) producing heating energy after the gluing station (6) in the conveying direction of the line (1), characterized in that after the press apparatus (7) the apparatus comprises at least one apparatus (9) for measuring the temperature of the manufactured glue board (10) and its glued joints, with which measuring apparatus measurement of the temperatures of the manufactured glue board (10) is arranged to be performed by imaging the glue board (10) .

10. Apparatus according to claim 9, characterized in that the temperature measuring apparatus (9) is a thermographic camera operating in the infrared range that records an essentially continuous video image for a digital imaging sensor.

11. Apparatus according to claim 9 or 10, characterized in that the apparatus comprises a computer (4) being as a control and recording apparatus, to which the thermographic camera (9) measuring the temperature of the manufactured glue board (10) is connected.

12. Apparatus according to any of claims 9-11, characterized in that the apparatus comprises at least a screen (5b) , which is arranged to show the imaging data produced by the thermographic camera (9) that measures the temperature of the glue board (10) as a video image in essentially real-time.

13. Apparatus according to any of claims 9-12, characterized in that the apparatus comprises means for showing as different colors the different temperatures of the objects imaged.

14. Apparatus according to any of claims 9-13, characterized in that the apparatus comprises means for regulating the production of thermal energy of the press apparatus (7) on the basis of the imaging data produced by the thermographic camera (9) that measures the temperature of the glue board (10) .

15. Apparatus according to any of claims 9-14, characterized in that before the gluing station (6) the apparatus comprises a measuring device, such as a thermographic camera (3) fitted to image, that measures the temperature of the wooden laths (2) to be taken for gluing, which thermographic camera (3) is connected to a computer (4) .

16. Apparatus according to claim 15, characterized in that the apparatus comprises a screen (5a) , which is arranged to show the imaging data produced by the thermographic camera (3) that measures the temperature of the wooden laths (2) as a video image in essentially real-time.

17. Apparatus according to claim 15 or 16, characterized in that the apparatus comprises means for regulating the production of thermal energy of the press apparatus (7) on the basis of the imaging data produced by the thermographic camera (3) that measures the temperature of the wooden laths

(2) .