WO1987003238A1

WO1987003238A1 - Process and device for identifying and/or controlling the abrasive removal of taping paper and taping paper residue from veneered surfaces

Info

Publication number: WO1987003238A1
Application number: PCT/EP1986/000672
Authority: WO
Inventors: Wilhelm Hoffmann
Original assignee: Karl Heesemann Maschinenfabrik Gmbh & Co. Kg
Priority date: 1985-11-21
Filing date: 1986-11-21
Publication date: 1987-06-04
Also published as: EP0245408A1

Abstract

In order to be able better identify taping paper (F) or residues thereof on veneered surfaces of a workpiece (19) and to be able, if necessary, to remove by abrasion automatically such taping paper (F) from veneered surfaces it is envisaged that the taping paper (F) or its adhesive layer is replaced by luminescent, preferably fluorescent substances, and that this taping paper (F) affixed to the veneered surfaces is irradiated by a suitable electromagnetic source, particularly an ultraviolet source.

Description

Method and device for recognizing and / or controlling a grinding process of joint paper and joint paper residues on veneered surfaces

The invention relates to a method and a device for detecting and / or controlling the grinding process of joint paper or. Joint paper residues on veneered surfaces.

Sanding flat, veneered surfaces is crucial for the later surface quality. With box furniture, tables, panels, room doors, etc. it decides on the so-called Finish. For series production, even with smaller lot sizes, the so-called Grinding machines enforced, as are known for example from DE-GM 82 23 923. This known belt grinding machine comprises a pressure beam with a large number of pressure shoes arranged next to one another, each

Pressure shoe in the inlet area is assigned a switch that is actuated when the workpiece is advanced over this point of the inlet area. The switches received or actuated by the workpiece provide information that the pressure shoe assigned to the switch is in its position

Active position must be lowered. The electromagnets of the pressure shoes are switched on late via a delay circuit in order to ensure that the pressure shoe is only pressed down into an active position when the corresponding workpiece shape has reached its position under the respective pressure shoe. The top of the electromagnet is supported on a pressure hose, which in turn is supported on its top in a stationary manner. By adjusting the pneumatic pressure in the pressure hose accordingly, the pressing force of the

Pressure bar can be adjusted and regulated.

On the underside, a soft layer, for example made of felt, can initially be provided, over which a wear-resistant graphite impregnated overall

Sliding surface is tensioned. Finally, the sanding belt runs over this with at least one drive roller.

With such a belt sander, the veneered surface is in accordance with the set pressure values in

Dependence on the workpiece shape ground. Although the sanding of flat veneered surfaces with today's belt sanding units can also be carried out largely satisfactorily automatically, problems arise when adhesive paper, so-called. Grout paper has been used, each on the

Veneer strips lying parallel to one another are glued over in order to fix them in a parallel position. It also happens that occasionally two paper thicknesses lie one above the other. The use of such joint papers is still considered today, particularly in the case of expensive veneers, in which it is worthwhile to pull together small shrinkage cracks, hold looseness together, patch out wormholes or even cross-tap with paper. The glued joint paper must be sanded down before further processing.

Even if the machines can at least sometimes be set so precisely and precisely in mass production that the mentioned joint papers are also completely and securely sanded during veneer sanding, this is always a problem in the case of order-specific one-off production, be it that very thin, e.g. B. 0.5 mm thick fine veneer is used, or be it that the formats to be sanded fluctuate very strongly. In this case, the setting parameters would have to be chosen very carefully to avoid grinding through. Because with fluctuating width utilization, differently blunted abrasive paper can intervene.

The cost of such a sanding can be extremely high, especially in the case of precious woods, so that several DM 100 costs can easily be caused by a single sanding. So far, the problem has been solved in that joint paper residues that have not been completely sanded are reworked in an additional work step, for example with a hand belt sanding machine. In addition, a careful final inspection is necessary, which is not always easy, since the joint paper that has not been completely sanded or only sanded usually has only a very slight contrast to the surrounding veneer surface and is difficult to see.

The object of the present invention is therefore to develop a method or. to create a device for recognizing and / or controlling the abrasion process of joint paper or joint paper residues on veneered surfaces, in particular flat surfaces, without problems with regard to an optical inspection or during automatic abrasion.

The object is achieved according to the invention with respect to the method according to the features specified in the characterizing part of claim 1 and with respect to the device according to the features specified in the characterizing part of claim 10. Advantageous embodiments of the invention are specified in the subclaims.

The process according to the invention is essentially based on the fact that the joint paper, the adhesive layer of the joint paper and / or the adhesive for the joint paper, which may have been applied only during processing, is mixed with an aluminizing substance. If it is irradiated with suitable electromagnetic radiation, especially ultraviolet light, it lights up clearly. Fluorescent substances in particular are particularly suitable, since these cease to shine immediately after the irradiation process when the radiation source, especially the UV light source, is switched off. This has advantages in use.

If afterglow substances are used for longer, one speaks of phosphorescence.

This so-called cold lights are generated by excitation of the electrons on the outermost electron shell of an atom or. generated by molecules. The fabric then shines with a different wavelength than the illuminated one.

Preference is given to substances which are irradiated with a narrow-band spectrum with an average wavelength of, for example, 360 nm and which emit almost white light, that is to say a broad spectrum. This enables further advantages, particularly in practical use.

According to the invention, commercially available joint paper can be used. In a preferred embodiment of the invention, the fluorescent substances can be provided in the adhesive layer itself or can be supplied with the adhesive layer. The incorporation of the luminous, preferably fluorescent, substances with the dampening liquid for activating the adhesive layer has proven to be particularly advantageous. This means that even the finest remnants of the adhesive, which can sit in the unfavorable pores of the wood, can be made visible.

With the method according to the invention, a hitherto unproblematic final inspection of the Presence of joint paper or. Carry out grouting paper residues. This method can also be used to further control the grinding process, namely when the emitted radiation is detected by sensors and the pressure shoes are controlled via this. When emitted radiation occurs, the pressure shoe can be switched on at all with a presettable force or, depending on the light intensity emitted, can be controlled in accordance with an increasing characteristic curve.

Further advantages can be achieved if, for the sanding of the joint paper, not separate pressure shoes or. a separate sanding unit, but the pressure shoes required for the veneer sanding process can also be used and controlled accordingly.

The device according to the invention as a control device comprises a suitable electromagnetic emitter, preferably in the form of a UV fluorescent tube, which is provided with a cover housing in such a way that only the veneered surface, possibly with a joint paper, is irradiated. With strong contrast, the human eye can easily recognize any joint paper that is still present, such as the remainder of the joint paper.

In the context of an automatic control, the sensors can also be provided under the common cover housing, with which the sensors reflecting or reflecting from the joint paper can also be provided. emitted radiation is collected and converted into corresponding control signals for controlling the pressure shoes. If the corresponding device is arranged in the feed direction of the workpiece in front of the pressure shoes, it is possible to use corresponding control units or. Delay elements the pressure shoes can be controlled specifically for sanding the joint paper. Corresponding devices behind the pressure shoes can also be provided for a final inspection.

Particularly precise and sensitive control can be achieved if the pressure force control of the pressure shoes is carried out in accordance with the intensity of the radiation emitted by the fluorescent substances.

Although the device according to the invention can be used as a separate belt sanding device only for sanding joint paper and in connection with a conventional belt sanding device for sanding the veneer surface, it has proven to be advantageous and advantageous to use the device provided in a belt sanding device. see pressure shoes u. a. can also be controlled directly via the sensors mentioned, and this may be preset or depending on u. a. Modify the pressure force signal determined and controlled by the workpiece shape for the pressure shoes accordingly.

Further advantages, details and features of the invention result below from the exemplary embodiments illustrated with the aid of drawings. The individual show:

Figure 1: a veneered workpiece with glued joint paper; -8th-

FIG. 2: a schematic side view of a belt grinding device with the device according to the invention for the detection of joint paper;

FIG. 3: a modification to FIG. 2, in which the pressure shoes of the belt grinding device are also controlled via the scanner that detects a workpiece shape;

FIG. 4: a schematic circuit diagram for operating the device according to FIG. 3;

FIG. 5: a typical pressure curve over the time axis with different joint papers located on the veneered wooden surface;

Figure 6: an explanatory example for the detection of a

Joint paper and for controlling the abrasion process.

Figures 7 and 8: modification to Figure 6.

A veneered workpiece is schematically shown in FIG. 1, on the surface of which a glue paper F running in the transverse direction and several in the longitudinal direction are glued.

Such joint papers are known and can also be provided with perforations. -9-

As a rule, the joint papers are provided with an adhesive layer that is damp or damp. Liquid can be activated. If, for example, the dampening liquid is mixed with fluorescent, especially fluorescent, substances, the phosphors are also included when the joint paper F is moistened. The thicker the joint paper, the more liquid and the more luminescent or. fluorescent substances can be included. This has the consequence that the - which will be discussed later - luminescent or. fluorescent radiation with the thickness of the joint paper or. the residue of grouting increases.

In the case of other joint papers, it could also be considered to provide the actual paper layer directly with an adhesion-promoting layer in which the fluorescent or. Luminescent substances are directly incorporated.

Generally speaking, the joint paper and / or its adhesive layer can be provided with the phosphors in all conceivable types, for example by impregnation, printing, spraying, impregnation, etc.

In Figure 2 is a schematic side view of a recognition device 1 for recognizing joint paper or. Residue paper residues on flat veneered surfaces with a shield housing 3 with a UV lamp 5 arranged transversely to the feed direction and several sensors 7 arranged next to one another and parallel to the UV lamp 5 in the form of photo cells. -10-

The belt sanding unit comprises a sanding belt 11 which rotates around three rollers 9 and has a large number of pressure shoes 13 arranged next to one another, which are firmly supported upwards in the housing and act downwards on a pressure hose 15 which is grinded by a sanding protection 17 Workpiece 19 is separated. A workpiece 19 is advanced in each case in the direction of arrow 21 via a conveyor belt, not shown in detail.

As they pass through the workpiece, they recognize them from photocells

7 existing sensors and any existing joint papers or. Groove paper residues, since the reflected light from the UV lamp gives a clearly evaluable light signal. A valve, preferably a proportional valve, is actuated via a delay element 23, so that the pressure prevailing in the compressed pressure hose 15 is transferred to the workpiece at precisely those points at which the joint paper is seated, via a cylinder 25. The residues of the workpiece that are free of joint paper, which appear darker in the detection device 1, have no influence and keep the other pressure shoes in a pressure-free position.

As can be seen from this simple exemplary embodiment, such an additional “joint paper sanding belt unit with detection device” can be used at any time separately or as an additional unit for conventional belt sanding machines. It is also possible to use the detection device 1 with the UV lamp in a completely isolated manner for an optical check, in particular a final check for manual post-processing. A further detection device 1 described could also be used behind a grinding unit without sensors 7 for the final inspection. -11-

The device 1 explained above can also be used as an additional unit in a conventional belt grinding machine, so that no additional grinding unit is required.

For this purpose, reference is made to FIGS. 3 and 4, in which a belt grinding machine 8 for grinding a veneer surface of a workpiece 19 is shown. The same reference numerals correspond to the exemplary embodiment according to FIG. 2.

The workpiece shape to be ground is usually detected by sensors 27 in the form of mechanical sensors or switches. For this purpose, a plurality of sensors 27 are again arranged transversely to the feed direction. A pressure shoe can be assigned to each sensor 27. As soon as the individual sensors 27 are actuated in accordance with the shape of the workpiece, the individual double-acting pneumatic cylinders 25 are pressurized via a delay element 29. Instead of the delay element, information that is dependent on the conveyor belt can, of course, also be used as a trigger signal (electronic point-to-point control or route control in woodworking machines). The joint papers glued to the veneer surface via the photocells 7 of the recognition device 1 trigger a signal in the photocells 7, which in turn signals the aforementioned delay element 23 and then via a summation point 33 via an amplifier stage 31 the proportional valve for triggering and controlling the type - Pressing force of the pressure shoe is supplied. -12-

The mechanical sensor thus scans the front and rear edge of the workpiece, the optical button 7 scanning the joint paper. Each signal passes through a delay element corresponding to the distance to the grinding unit. Both signals go to a summation point 33

The result is applied to the proportional valve of the cylinder via an amplifier. The signal from the mechanical sensor 27 is constant and results in the constant grinding pressure required for surface grinding. Superimposed on this is a time-varying pressure for the

Sand the joint paper. This fluctuating pressure is proportional to the brightness of the joint paper.

The brightness can be proportional to the amount of joint paper to be sanded or its adhesive. Then only the joint paper and no longer be ground off by this device. An interposed network would also have to take into account a non-linear course between the brightness and the quantity to be ground off.

A typical pressure curve over time is shown in FIG. 5. At a the workpiece 19 runs under the grinding unit. The grinding pressure increases to the value P- according to the transition function that characterizes the system.

At b comes a piece of joint paper, then a remainder c and then a double point d, where two joint papers can be glued on top of each other. Then only the surface veneer of the workpiece follows to the end. -13-

In deviation from the previous explanation, the arrangement can also be such that when only a single button or. Sensors 27 and. 7 not only a downstream, but optionally three, five or seven pneumatic cylinders can be operated. A button thus drags one, two or three neighboring cylinders with it. The drag that is actually to be selected depends on the construction of the grinding unit and is determined empirically.

Reference is also made to FIG. 6, in which an extensive circuit diagram with a corresponding arrangement of the sensors 7 is shown. Is by a suitable arrangement of the sensors 7 z. B. by f one-part division or by evaluating the signals of several sensors 7 the exact

Position y and z and the width b of the joint paper F can be determined using a suitable signal processing unit X and by simultaneously applying several cylinders 25 lying next to one another with different input signals to limit the grinding pressure to the surfaces covered with joint paper F.

It is shown in Figure 6 for a sensor 7 or. 27 a delay element 23 or. 29 downstream, the determined signals for controlling the respective pressure cylinders 25 converging at respective summation points 33. To evaluate the signals from the sensors 7 in accordance with the mode of operation explained in the preceding paragraph, the output signals of the optical sensors 7 are simultaneously also fed to the signal processing unit X, the output signals of which are also fed to the summation points 33 for modified control of the cylinders 25. -14-

In a departure from the illustration in FIG. 6, the delay elements 23 and 29 of the optical or mechanical sensors 7 or. 27 and the respective downstream wiring to the summation point 33 are dispensed with if all signals from the optical and mechanical sensors 7 and 27 are fed to the signal processing unit X, via which the cylinders 25 are then ultimately controlled. The switching principle of FIG. 6 can thus also be implemented by the modification according to FIGS. 7 and 8, in which only one optical sensor 7 and one mechanical button 27 and an associated pressure cylinder 25 are shown for simplification. In the modification according to FIG. 7, the output signals of the optical sensors 7 are only processed via the signal processing unit X, the output signals of the signal processing unit X being fed to the various summation points 33 at which the signals from the mechanical buttons 27 are also fed queue.

In the exemplary embodiment according to FIG. 8, the signals of the optical sensors 7 as well as of the mechanical buttons 27 are processed solely via the signal processing unit X, via which the several pressure cylinders arranged next to one another are then controlled.

With the aid of the same arrangement and signal processing X according to FIGS. 6 to 8, the grinding pressure can be limited to the workpiece surface if instead of the signals from the optical sensors 7 the signals from the mechanical buttons 27 are processed. The round grinding of edges can thus be avoided. -15-

The signal processing unit X can process both the data of the mechanical buttons 27 and the optical sensors 7 together.

It is also noted that the sensors 27 can not necessarily consist of mechanical buttons, but also of optical sensors. It is also conceivable that only a number of optical sensors arranged next to one another is provided, via which the tasks of the "sensors 27" for recognizing the workpiece shape and at the same time for recognizing the joint paper F are initially carried out. This can be achieved, for example, by the signal processing unit X in that, in the absence of a workpiece, there is practically no reflection of light rays on the conveyor belt, and when the workpiece shape is continuous there is little normal reflection without luminance or fluorescence radiation, whereas in the presence of Fugenpa¬ pier the luminance or. Fluorescence radiation occurs and. the intensity, as shown in FIG. 5, rises again. The corresponding control can thus be carried out by means of a corresponding detection circuit.

As already stated, all luminous or fluorescent substances are suitable for the present invention. The use of fluorescent liquids to prove the joint paper or. to be able to soak the adhesive layer. Solutions of uranyl salts and some rare earths fluoresce under the fluids of inorganic substances, but also very many -16-

organic substances such as benzene, naphthalene, anthracene and their derivatives, solutions of sulfuric acid quinine, aesculin, and numerous dyes such as eosin and fluorescein, which therefore bears his name, as well as turmeric tincture.

Claims

- π method and device for recognizing and / or controlling a grinding process of joint paper and joint paper residues on veneered surfaces

1. Method for recognizing and / or controlling a grinding process of joint paper (F) or. Joint paper residues on veneered surfaces, characterized in that the joint paper (F) and / or the adhesive of the joint paper (F) is provided with luminescent substances, and that the joint paper (F) is used for education by means of electromagnetic waves is irradiated with emission radiation. -] <?

2. The method according to claim 1, characterized in that the joint paper and / or the adhesive of the joint paper (F) is provided with fluorescent substances, and that the joint paper (F) is irradiated by means of a UV lamp (5).

3. The method according to claim 1 or 2, characterized gekennzeich¬ net that radiant phosphors are used ver¬ in the visible range.

4. The method according to any one of claims 1 to 3, characterized in that the joint papers (F) are irradiated by means of ultravio¬ letter radiation.

5. The method according to any one of claims 1 to 4, characterized in that the luminescent substances of the humidifying liquid for activating the adhesive of the Fugen¬ paper (F) are added.

6. The method according to any one of claims 1 to 5, characterized in that the luminescent substances the Fugen¬ paper (F) during the moistening process of the Fugen¬ paper (F) or. whose adhesive layer are added to activate them.

7. The method according to any one of claims 1 to 8, characterized in that the during a abrasion process of veneered surfaces of the thereon provided with luminescent substances joint paper (F) after the excitation by an electromagnetic radiator (UV lamp 5) emitted rays can be detected by sensors (7) for controlling the grinding process. / 9 -

8. The method according to any one of claims 1 to 7, characterized in that, depending on the presence of jets emitted by the joint paper (F), the pressure of pressure shoes of a belt sanding unit is changed or. is controlled.

9. The method according to any one of claims 1 to 8, characterized in that the pressure of the pressure shoes of a belt sanding unit changes or changes depending on the intensity of the rays reflected from the joint paper (F). is controlled.

10. The device, in particular for performing the procedural method according to one of claims 1 to 9, characterized by an electromagnetic radiator (5), in particular

UV lamp for generating luminescent radiation on joint paper (F) provided with luminescent materials and glued to veneered surfaces.

11. The device according to claim 10, characterized in that the electromagnetic radiator (5) with a Abschirm¬ housing (3) is provided with an exit opening only directed to the grinding surface Fur¬ nier.

12. The apparatus of claim 10 or 11, characterized gekenn¬ characterized in that adjacent to the electromagnetic radiator (5) optical sensors (7) are arranged for detecting the reflected by the Fu¬ gene paper (F) / emitted beams.

13. Device according to one of claims 10 to 12, characterized in that the electromagnetic radiator (5) and the optical sensors (7) are arranged under a common shielding housing (3) in alignment with the workpiece (19) to be treated.

14. Device according to one of claims 10 to 13, characterized in that a detection device (1) with the electromagnetic radiator (5) and preferably the optical sensors (7) in front of and / or behind a belt grinding machine (8) is.

15. The apparatus according to claim 14, characterized in that by the belt grinding unit downstream Erken¬ identification device (1) a workpiece transport switch for Aus¬ segregation of not completely free of joint paper veneered surfaces can be controlled.

16. Device according to one of claims 10 to 15, characterized in that the optical sensor output signal of the optical sensors (7) in particular via a summation point (33) ascertained or depending on the workpiece shape. the set pressure force signal for controlling the respectively assigned pressure shoe (13) is superimposed, whereby in each case several pressure shoes (13) are arranged in a belt grinding machine (8) transversely to the feed direction of a workpiece, forming a pressure bar.

17. Device according to one of claims 10 to 15, characterized in that the pressure force of the pressure device (13) by means of a signal processing which takes account of the light intensity reflected / emitted by the joint paper (F) and preferably the workpiece shape ¬ tion unit is controlled.

- 2nd

18. Device according to one of claims 10 to 17, characterized in that the pressure shoes (13) are formed as proportional actuators with preferably a linear characteristic.

19. Device according to one of claims 10 to 18, characterized in that the optical sensors (7) each have a delay element (23) connected downstream.