JPH0623738B2 - Device for detecting defective adhesion of wood laminates - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting defective adhesion of a wooden laminate.

In this specification, "latent" with respect to defective adhesion means that there is a defective adhesion part, but the defective adhesion part cannot be detected even by simply inspecting with an ultrasonic inspection device, In addition, "revealing" means that even if the defective adhesion portion is apparently unknown, it can be detected by an ultrasonic inspection apparatus.

Conventional technology Plywood, which is used in large quantities for construction and furniture,
There is a problem of defective adhesion between laminated veneers, which is inevitable in manufacturing. Conventionally, in order to determine the adhesive strength of plywood, a so-called sampling test has been generally performed in which a fixed number of plywood produced in one lot are extracted and a strength test is performed.

Problems to be Solved by the Invention According to the conventional sampling test method, when a defective adhesion product is present in the plywood subjected to the sampling test in a ratio equal to or higher than a predetermined ratio, one lot is rejected, and in other cases. It has been passed. However, since it is a sampling test, there is a drawback that defective adhesion products may be present in the lots judged to be acceptable. As a result, in the sampling test, adhesion failure was found after use even in plywood which was judged to be non-defective in the test results, causing various troubles. The cause lies in the following facts. That is, at the time of manufacturing a plywood, there are some adhesion defective portions such that an air layer is formed between the laminated veneers, but these are found by visual inspection, and the number thereof is small. However, the heat and pressure applied to the plywood after manufacturing,
In the secondary processing stage where chemical coating, cutting, drying, etc. are performed to obtain a flooring material or a wall material from plywood, the potential that was not detected because the air layer did not occur to the extent that the adhesive strength was weak during plywood manufacturing As a result of the above-described processing, a defective adhesion portion is found when the surface of the plywood floats or delamination occurs and the adhesion failure becomes apparent. Furthermore, 1 to 2 months after construction as a floor or wall material, it may be affected by the weather, absorb moisture from the concrete, and in the case of floor materials, the furniture and the load from walking may add a potential bond as above. The defective part is revealed and discovered. Thus, even if the adhesion is poor, it is in a latent state at the time of plywood production, but most of it is manifested by external influences after plywood production. In order to detect defective adhesion of plywood, there is a proposal to use ultrasonic waves in addition to the above-mentioned sampling test method (Japanese Patent Publication No. 45-18635, Japanese Patent Publication No. 49-5186 and Japanese Patent Publication No. 51-186). 19105), since these are for inspecting whether or not there is an air layer due to defective adhesion in the plywood after manufacturing, such an intrinsic defective adhesion product can be detected.
It was not possible to detect a latent defective product.

It is an object of the present invention to provide an apparatus capable of detecting any existing internal or latent adhesion failure immediately after the production of the wooden laminate.

Means for Solving the Problems In order to achieve the above object, a device for detecting defective adhesion of a wooden laminate according to the present invention is latent by applying a predetermined bending load to a conveying device and a wooden laminate that is being conveyed. It consists of a bending device that makes the adhesion failure point visible, and an ultrasonic inspection device that detects the adhesion failure point that was revealed after the bending load was removed from the wooden laminate and the original adhesion failure point.
The wave transmitter and the wave receiver of the ultrasonic detecting device are arranged so as to face each other with a space that allows the wooden laminated plate to pass therethrough in a non-contact state.

A specific example of a wood laminated board which is a target of use of the detection device according to the present invention is mainly a plywood, but other so-called LVL and LVL in which fiber directions are laminated in parallel with each other.
In the composition of (1), a material including an adhesive layer such as one in which the fiber direction of one veneer is orthogonal to the other, one in which a peeling board and plywood are bonded, and one in which a medium specific gravity fiber board and plywood are bonded Can be raised.

Operation A defective adhesion product of a wooden laminated board according to the present invention comprises a conveying device, a bending device for applying a predetermined bending load to a wooden laminated board in the middle of conveyance to reveal a potential defective adhesion portion, and a wooden laminated board. Since it consists of an ultrasonic inspection device that detects the defective adhesion part that has become apparent after the bending load is removed from the original and the original defective adhesion part, whether the adhesion defect is intrinsic or latent All can be detected immediately after the production of wood laminates.

In addition, since the wave transmitter and the wave receiver of the ultrasonic wave detecting device are arranged so as to face each other with a space through which the wooden laminated plates can pass in a non-contact state with each other, the wave transmitter and the wave receiver. Is not damaged by the wooden laminated board, and conversely, the front surface or the back surface of the wooden laminated board is not damaged by the wave transmitter and the wave receiver. When ultrasonic vibration is contact-transmitted and inspected, there is not only the above-mentioned problem of damage, but if the wooden laminate has uneven thickness or distortion, the vibration is transmitted to the transmitter and receiver. Since the wave transmitter and the wave receiver fluctuate up and down irregularly, the transmission of ultrasonic vibration becomes unstable, causing a problem in inspection accuracy.

Embodiments Embodiments of the present invention will be described below with reference to the drawings. The front and rear sides are based on the conveying direction of the wooden laminate, and the forward side is the front and the opposite side is the rear.

The device for detecting defective adhesion of the wooden laminate shown in the figure is a conveyor device.
(1) and a bending device that exposes potential adhesion failure points by applying a predetermined bending load to the wooden laminate (2) in transit
(3), and an ultrasonic inspection device (4) for detecting a defective adhesion portion that has become apparent after the bending load is removed from the wooden laminate (2) and an inherent defective adhesion portion.

The transport device (1) is composed of several sets of driving pinch rollers (5) arranged at a predetermined interval in the front-rear direction. Bending device
(3) is an upward pressure roller (6) arranged between the lower rollers of the adjacent pinch rollers (5) and the roller shaft (7) at approximately the center of the length of the transport device (1). Pillow block (8) receiving both ends of the pillow block (8)
A pedestal installed via a spacer (9) that is replaceably placed underneath and a pedestal (13) for placing the spacer (9)
(14) Consists of the load cell (10) above. Ultrasonic inspection device
(4) detects whether there is a defective adhesion part by transmitting an ultrasonic pulse through the wooden laminate (2) and utilizing the fact that the propagation time of the sound waves changes depending on the internal state of the wooden laminate (2). The wave transmitters (11) and wave receivers (12) that compose them are placed facing each other with an interval that allows the wooden laminate (2) to pass through them in a non-contact state. ing. Ultrasonic inspection equipment (4)
Has a transmission / reception unit (not shown), and the transmission unit includes an oscillation circuit that generates a transmission pulse and a timing circuit that generates a control pulse. The transmission pulse is power-amplified and then the wave transmitter (11). It is emitted as an ultrasonic pulse. The receiver detects the ultrasonic pulse transmitted through the wooden laminated board (2) at the receiver (12), passes the RF amplification circuit, the detection amplification circuit, and the level discrimination circuit to detect the propagation time, and propagates it. It converts time into an analog voltage output. Then, a signal having a propagation time equal to or greater than the set value is taken out as an output signal. A plurality of pairs of the wave transmitter (11) and the wave receiver (12) are arranged at predetermined intervals in the width direction of the wooden laminated board (2). Of course, the greater the number of this pair, the higher the inspection accuracy. When the wood laminated board (2) is a plywood having a width of 300 mm, the distance may be 80 to 100 mm. The measurement cycle is a wooden laminated board
It can be determined based on the transport speed in (2) and the required measurement accuracy. For example, when the conveyance speed is 50 m / min and the inspection range is a circle having a diameter of 50 mm, the inspection can be continuously performed according to the conveyance of the wooden laminated board (2) if the measurement cycle is 60 msec. If the measurement cycle is 30 msec, the inspection accuracy is improved because the inspections are sequentially overlapped by half.

In the bending device (3), when the spacer (9) is removed, the upper end of the pressure roller (6) is at the same level as the upper end of the lower roller of the pinch roller (5). Load·
By placing a spacer (9) of an appropriate thickness between the cell (10) and the pillow block (8), a wooden laminate (2)
A bending load is applied from the bottom to the load cell. This load is measured by a load cell (10), and a spacer (9) having an appropriate thickness is selected so that an appropriate bending load can be applied according to the measured value. How much bending load is appropriate can be calculated based on the material, thickness, width, etc. of the wooden laminate, but the physical strength such as the bending strength of the wooden laminate itself decreases by applying the bending load. Since this should not be the case, the stress generated in the wooden laminate by the bending load should be below the bending proportional limit stress.
For example, in the case of a 5-ply plywood having a thickness of 12 mm and a width of 300 mm, a bending stress of 150 to 250 kg / cm ² is suitable.

In this embodiment, the bending device (3) incorporates the load cell (10), which may or may not be included.
Although (3) is arranged on the lower side of the wooden laminated board, it may be arranged on the upper side. Further, the bending load can be adjusted by a fluid pressure cylinder, a pinion rack mechanism with a handle, or the like.

It is potentially possible to place another bending device outside the illustrated bending device (3) close to the ultrasonic inspection device (4) of the embodiment which is arranged in front of the transport device (1). It is preferable in that the state in which the adhesion failure is actualized is secured. In this case, the latter bending load may be much smaller than the former.

The conveying device is not limited to the one including a pinch roller group, but may be a belt conveyor, a chain conveyor, or the like.
It is necessary to be able to apply a bending load to the transported wooden laminate and to hold down the wooden laminate so that it does not rise above the conveyor.

Experimental example Ultrasonic frequency: 40 KHZ, detection hole diameter of transmitter and receiver: 50 mm, distance between them: 60 mm, measurement cycle: 2
The following experiment was conducted using an ultrasonic inspection device of 0 to 60 msec (variable).

A normal plywood having a thickness of 12 mm, a width of 310 mm and a length of 1820 mm, and an intrinsically defective adhesive plywood of the same size with delamination due to defective adhesion were prepared for each 10 sheets, and 75 points were inspected for each. The results shown in Table 1 were obtained.

Based on the above facts, in the case of plywood with a thickness of 12 mm, if the propagation time is less than 1.20 msec, it is normal plywood, 1.20 msec.
The above values are abnormal values, and those having a longer propagation time are determined to be poorly adhered plywood.

Now, using lauan veneer, 1.5m each for 1st and 5th layers
m, 3 layers and 4 layers 3.0 mm each, 2 layers only 3.
0 mm, 2.6 mm, and 3.0 mm three veneers are laterally scooped to form a layer with uneven thickness, and each layer is thermocompressively integrated using a known adhesive for plywood, and has a thickness of 12 mm and a width. Six 5-ply plywood sheets having a length of 310 mm and a length of 1820 mm and having uneven thickness at the same position were obtained. Of the six sheets, one sheet was not subjected to bending load (Sample No. 1), and the remaining five sheets were subjected to predetermined bending load (Sample Nos. 2 to 6). Also, instead of using a single plate with uneven thickness as the second layer, a plywood adhesive is applied to the second layer of the single plate.
After applying 0g / m ₂ , especially 200mm × 20 on this
A 0 mm blotter paper was placed to absorb a portion of the adhesive. From the weight calculation of the blotter paper, it was found that the residual adhesive amount was 40 g / m ₂ . The amount of adhesive applied to the other veneers was 120 g / m _2, and _two plywood of the same size as the above plywood were obtained. No bending load was applied to one of the two (Sample No.
7), bending load was applied to the remaining one (Sample No.
8). The result of inspecting these with an ultrasonic inspection device is the second
It is as shown in the table.

2 to 7, · indicates a normal value and × indicates an abnormal value.

As is clear from Table 2, in plywood No. 1 and No. 7 which did not use the apparatus of the present invention, all showed normal values, and latent adhesion defects remained as they were and could not be detected at all by inspection. On the contrary, plywood Nos. 4 to 6 and No. 8 using the device of the present invention showed abnormal values.
As a result of cutting the portion showing the abnormal value and examining the inside, it was found that the portion where the abnormal value is concentrated at two or more locations is a clearly defective adhesion portion. Therefore, No. 4 to No. 6
The plywood of No. 8 and No. 8 showed latent adhesion failure due to the application of appropriate bending load.
Since No. 2 and No. 3 do not have sufficient bending load, it can be said that latent adhesion failure has not been satisfactorily manifested.

In addition, when using the device of the present invention, not only can the above-described exposed adhesive failure points be detected, but also the internal adhesive points can be detected. Those with cracks, cracks, etc. on the board,
It is possible to detect even if the cut surface is too rough.

The device of the present invention is not limited to the detection of defective adhesion products immediately after the production of plywood, but the plywood can be processed into a floor material, a wall material, or the like and used before shipment.

EFFECT OF THE INVENTION According to the device for detecting defective adhesion of the wood laminate according to the present invention,
Poorly adhered products can be eliminated, as any imperfect or imperfect bond can be detected immediately after the wood laminate is manufactured, thus
There is no fear that a potentially existing adhesion defect will become apparent during the production of the flooring material or the wall material and further after the flooring material or the wall material is applied, causing trouble.

Also, in the work of detecting defective adhesion of the wooden laminated board, the wave transmitter and the wave receiver are in non-contact with the wooden laminated board, so the wave transmitter and the wave receiver may be damaged by the wooden laminated board. The ultrasonic detection device has good durability, the wooden laminate itself is not damaged, and even if the wooden laminate has uneven thickness or distortion, the inspection accuracy is not affected.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an embodiment of the present invention, and FIGS. 2 to 6 are plan views of plywood showing the results of inspection after revealing potential adhesion defects using the apparatus of the present invention. FIG. 7 and FIG. 7 are plan views of the plywood showing a state in which the latent adhesion failure remains as it is because the apparatus of the present invention is not used and it cannot be detected by the inspection. (1) …… Conveyor, (2) …… Wood laminate, (3) …… Bending device, (4) …… Ultrasonic inspection device.

Claims (1)

[Claims] 1. A transfer device (1) and a wooden laminated board during transfer
A bending device (3) that applies a predetermined bending load to (2) to make latent adhesive failure spots visible, and an adhesive failure spot that became apparent after the bending load was removed from the wooden laminate (2). It consists of an ultrasonic inspection device (4) that detects the inherent defective adhesion part, and it is a transmitter (11) and a receiver (12) of the ultrasonic detection device (4).
Is a device for detecting defective adhesion of a wooden laminated plate, in which the wooden laminated plates (2) are arranged so as to face each other with an interval so that they can pass in a non-contact state with each other.