JP4276191B2 - Sheet thickness measuring device - Google Patents

Description

  The present invention relates to a sheet thickness measuring apparatus for a resin film / sheet manufacturing machine, and more particularly to an apparatus for measuring an extremely thick sheet of about 2 mm to 20 mm formed by pressing a molten resin with a forming roll on the surface of the forming roll. .

  Conventional sheet thickness measuring devices are mainly measured in the state where the sheet is cooled and solidified in the latter half of the sheet forming apparatus, but the thickness profile is measured on the forming roll immediately after forming, minimizing the time delay, A method of measuring the thickness is disclosed in Patent Document 1. That is, in Patent Document 1, there is a method in which the sheet temperature at substantially the same position as the thickness sensor on the forming roll 2 is simultaneously measured to correct the thickness of the temperature contraction after cooling to increase the detection accuracy and detect the sheet thickness. It is disclosed.

  The method of measuring the thickness with the sheet in the latter half of the forming apparatus solidified is a method in which the sheet is projected from one surface with a light projecting element and received by a light receiving element provided on the opposite surface, that is, radiation (β-ray) ), Existing thickness gauges such as infrared rays can be used. In addition, the method disclosed in Patent Document 1 for measuring from one side of the sheet describes an infrared transmission absorption type, a laser front / back surface reflection type, an ultrasonic type, an optical type (scattering reflection type, regular reflection type), and a capacitance type.

Such a method is applicable when there is a space on both sides of the sheet, and is widely used in the industry.
JP-A-5-157522

  On the other hand, with a relatively thick sheet, the forming speed is slow, the time delay until the thickness unevenness is detected is large, and it takes time to adjust the forming conditions such as flow rate unevenness and thickness unevenness from the T-die, and the material during that time is wasted. become.

  In the method of Patent Document 1, since measurement is performed immediately after molding, there is no detection delay, but a specific sensor configuration is not described in the extremely thick sheet of about 10 mm targeted by the present invention. In addition, it is difficult to detect from both sides of the sheet and precisely detect the front and back in units of μm simultaneously from the viewpoint of the accuracy and measurement range of the sensor. Since the measurement range becomes wider as the thickness increases, the detection accuracy becomes worse.

  In addition, the still-hot semi-molten resin that has been formed into a sheet by a forming roll often peels off from the surface of the roll, covers the traversing sensor, entangles the resin sheet, or breaks the sensor at high temperatures. There is a case. In particular, as the thickness of the sheet increases, the amount of resin increases, and when the sensor collides with the resin that hangs down, the damage to the sensor increases. The prior detection and avoidance of damage to the apparatus after the resin collides with the sensor are important issues in practical use.

  Accordingly, an object of the present invention is to provide a sheet thickness measuring device capable of accurately measuring the thickness dimension profile (thickness distribution in the sheet width direction) of an extremely thick precision resin sheet from the outer peripheral surface of the forming roll.

  The sheet thickness measuring device of the present invention is a sheet thickness distribution in the width direction of a sheet formed by pouring molten resin extruded from a T-die into a nip portion of a rotating forming roll. In the sheet thickness measurement device that measures from the upper surface side of the forming roll while moving to the surface, the surface detection sensor that detects the surface position of the sheet and the back surface position of the sheet are detected on one traverse table that can move in the width direction of the sheet. The back surface detection sensor is mounted so that the relative position with respect to the thickness direction of the sheet can be adjusted, and at least the front surface detection sensor is an optical axis coincidence sensor in which the optical axes of light projection and reception are the same To do.

  As described above, since the sheet thickness measuring apparatus of the present invention has the sensor dedicated to the front surface and the sensor dedicated to the back surface of the sheet, a highly accurate sensor with a narrow measurement range can be used, and each sensor is 1 Since it is provided on one traverse table, the center roll of the forming roll and the vibration of the traverse table can be canceled, and the sheet thickness can be accurately measured. Furthermore, since the sheet thickness measuring device of the present invention can adjust the relative position of each sensor according to the sheet thickness, even a precision sensor with a narrow measurement range of each sensor can adjust the thickness of sheets of various thicknesses to the outer periphery of the forming roll. Precise measurement from the surface side.

  Further, the front surface detection sensor and the back surface detection sensor of the sheet thickness measuring apparatus of the present invention may be an optical axis coincidence type laser sensor or an optical axis coincidence type optical sensor. Thereby, thickness measurement with higher accuracy becomes possible.

  Further, the back surface detection sensor of the sheet thickness measuring device of the present invention may be an eddy current sensor. In this case, in addition to the transparent sheet, it is possible to measure the thickness of a colored sheet, a matte sheet, or an embossed sheet that has fine unevenness on the surface of the sheet and cannot transmit light to be measured to the back surface.

  Further, in the sheet thickness measuring apparatus of the present invention, the increase in detection distance ΔL from the forming roll of the back surface detection sensor to the front end portion of the back surface detection sensor is expressed as follows. Where n is ΔL = t−t / n.

The sheet thickness measuring device of the present invention is a sheet thickness distribution in the width direction of a sheet formed by pouring molten resin extruded from a T-die into a nip portion of a rotating forming roll. In the sheet thickness measuring device that measures from the upper surface side of the forming roll while moving to the surface, the surface detection sensor that detects the surface position of the sheet and the back surface detection sensor that detects the back surface position of the sheet are positioned relative to the sheet thickness direction. The traverse base, which is mounted so as to be adjustable in the width direction of the seat, has a safety detection sensor for detecting foreign matter before it collides with the foreign matter.

  In the case of an extremely thick sheet, the amount of resin and the amount of heat are particularly large, so damage to the front surface detection sensor and back surface detection sensor is great when it collides, but the sheet thickness measuring device of the present invention avoids collision with foreign matter. Since it has the safety detection sensor for doing, the collision with the sheet | seat which hangs down can be prevented beforehand.

  The sheet thickness measuring device of the present invention is a sheet thickness distribution in the width direction of a sheet formed by pouring molten resin extruded from a T-die into a nip portion of a rotating forming roll. In the sheet thickness measuring apparatus that measures from the upper surface side of the forming roll while moving to the front surface, a front surface detection sensor that detects the front surface position of the sheet, a rear surface detection sensor that detects the rear surface position of the sheet, And a collision detection sensor for detecting a collision when the bumper collides with a foreign object, and at the time of collision with the foreign object, the width of the sheet retracts and retracts to the roll end opposite to the direction in which the bumper collides with the foreign object. It is characterized by having a traverse table movable in the direction.

  If resin drooping has already occurred during measurement movement, the sheet thickness measuring device of the present invention is equipped with a bumper, so that the impact on the traverse table can be buffered, and the collision detection sensor Is detected, and the bumper is retracted and retracted to the roll end in the direction opposite to the direction in which the bumper collides with the foreign object, so that the damage caused by the collision can be reduced.

  In the sheet thickness measuring apparatus of the present invention, the traverse base is equipped with a front surface detection sensor and a back surface detection sensor so that the relative position with respect to the thickness direction of the sheet can be adjusted, and at least the front surface detection sensor is a light for receiving and receiving light. It may be an optical axis coincidence type sensor whose axes coincide.

  Further, the front surface detection sensor and the back surface detection sensor of the sheet thickness measuring apparatus of the present invention may be a laser sensor or an optical sensor.

  Further, the back surface detection sensor of the sheet thickness measuring device of the present invention may be an eddy current sensor.

  Further, in the sheet thickness measuring apparatus of the present invention, the increase in detection distance ΔL from the forming roll of the back surface detection sensor to the front end portion of the back surface detection sensor is expressed as follows. Where n is ΔL = t−t / n.

  In the sheet thickness measuring apparatus of the present invention, the front surface detection sensor and the back surface detection sensor may have heat resistance means, and the service life can be extended by taking measures against high temperatures.

  As described above, since the sheet thickness measuring device of the present invention has the sensor dedicated to the front surface and the sensor dedicated to the back surface of the sheet in one traverse table, the sheet thickness from the outer peripheral surface side of the forming roll is accurately measured. Measurement is possible.

Next, embodiments of the present invention will be described with reference to the drawings.
(Embodiment 1)
FIG. 1 is a schematic side view of a sheet forming apparatus provided with an extremely thick sheet thickness measuring apparatus according to Embodiment 1 of the present invention.

  The sheet forming apparatus according to the present embodiment has a plate-like melt in the roll gap 32 between the four forming rolls 1 to 4 and the forming rolls 1 and 2 that are arranged in parallel with each axis being balanced. A T die 5 for supplying the sheet 30 and a sheet thickness measuring device 34 installed on the traverse table 9 are provided below the forming roll 2.

  The plate-shaped molten sheet 30 supplied from the T-die 5 passes through the roll gap 32 that is the first nip portion 33a, moves along the winding side of the forming roll 2, and is molded in the same manner as the first nip portion 33a. The sheet is formed at the second nip portion 33b sandwiched between the rolls 2 and 3 and the third nip portion 33c sandwiched between the forming rolls 3 and 4 and cooled to be formed into a sheet 6 with good dimensional accuracy. Each roll is adjusted to a temperature lower than that of the sheet.

  After the forming roll 4, the sheet is gradually solidified, and in the case of a thick sheet, it is cut into a plate shape and manufactured as a sheet product.

  The first nip portion 33 a is formed with a “stack” of molten resin, that is, a bank 31. The size of the bank 31 is determined by the balance between the inflow of resin from the T-die 5 and the outflow as the sheet 6 from the roll gap 32, and the sheet is usually formed in a slightly raised state.

  In order to adjust the sheet thickness in the width direction, the molten sheet 30 extruded from the T-die 5 is performed by a die lip adjusting device 45 arranged in a large number in the width direction at a pitch of 25 mm to 30 mm. The die lip adjusting device 45 is mainly a heat bolt method, and adjusts the sheet exit slit width by pushing and pulling the flexible lip of the T die 5. Similarly, a choke bar 46 that adjusts the sheet thickness profile along the width direction of the flow path inside the T die 5 is also used.

Sheet thickness measuring device:
A sheet thickness measuring device 34 that measures the thickness of the sheet 6 that is molded into a semi-molten state is disposed below the forming roll 2. In the sheet thickness measuring device 34, the front surface detection sensor 7 and the back surface detection sensor 8 are mounted on one traverse base 9 so that the relative position with respect to the thickness direction of the sheet 6 can be adjusted.

  The sheet thickness is measured from the position difference from the surface detection sensor 7 that detects the sheet surface position and the back surface detection sensor 8 that detects the sheet back surface position.

  Referring to FIG. 2 viewed from the direction of arrow A in FIGS. 1 and 1, the front surface detection sensor 7 and the back surface detection sensor 8 are respectively a slider 39 (Y1 axis direction) and a slider 40 (Y2 axis) that are driven to move in the sheet thickness direction. The two sliders 39 and 40 are mounted on the common traverse table 9 as described above, and this traverse table 9 is in the roll longitudinal direction (X axis). It moves along the two traverse rails 38 in the direction. The movement of the sliders 39 and 40 in the Y1 and Y2 axis directions is electrically driven by a ball screw, and the front surface detection sensor 7 and the back surface detection sensor 8 can be positioned from the reference position. The moving range of the sliders 39 and 40 is from a forward position at which the front surface detection sensor 7 and the back surface detection sensor 8 can detect the roll surface position to a sufficiently backward position at which the sheet can be retracted while avoiding sheet sag.

  In the present embodiment, two sensors, a front surface detection sensor 7 dedicated to the front surface of the sheet and a back surface detection sensor 8 dedicated to the rear surface, are used, but since these are mounted on the common traverse base 9, molding is performed. Roll center runout and vibration of the traverse table 9 can be canceled, and the sheet thickness can be accurately measured.

  A traverse base 9 for moving the front surface detection sensor 7 and the back surface detection sensor 8 in the X-axis direction is electrically moved by being pushed and pulled by a toothed belt 43 (see FIG. 3), and the traverse base 9, that is, the front surface detection sensor 7 and the rear surface detection sensor. The X-axis position of 8 is detected by an encoder.

  Each of the front surface detection sensor 7 and the back surface detection sensor 8 is provided with a cover 36, which cools the sensor by air purging. In addition, air purge is performed from a hole formed at the optical axis position of the sensor lens surface so that dust and dust do not adhere to the lens surfaces of the front surface detection sensor 7 and the back surface detection sensor 8.

  The cable bear 41 connects the traverse base 9 and the X-axis frame 42 to guide wiring and air piping.

Collision avoidance sensor:
Three safety sensors 35 are installed in a range in which the front surface detection sensor 7 and the back surface detection sensor 8 on the lower surface of the molding roll 2 move on the X axis. The safety sensor 35 is a sensor that detects the presence of a foreign object or a sheet sag that is close to the roll surface and blocks light through the laser beam in the longitudinal direction of the roll. The safety sensor 35 serves as a collision avoidance sensor with the sheet thickness measuring device 34.

  The safety sensor 35 includes a light projecting element and a light receiving element disposed at both ends of the roll in the longitudinal direction. The light receiving element receives the light projected from the light projecting element and detects a foreign matter that blocks the light. One safety sensor 35 is installed on the side of the forming roll 2 below the first nip portion 33a, one on the front side of the front surface detection sensor 7 and the back surface detection sensor 8, and one on the second nip portion 33b. Yes.

  Further, the foreign object 100 may be detected by the configuration illustrated in FIG. That is, as collision avoidance sensors, light (laser) reflection type foreign matter detection sensors 54 and 55 (for example, at the positions of sensors 50 and 51 in FIG. 1) in the front and rear traveling direction of the traverse base 9, and reflection plates 56 and 57 of the fixed portion. May be provided in combination. Further, the positions of the reflectors 56 and 57 and the light (laser) reflective foreign matter detection sensors 54 and 55 can be changed. Moreover, it is good also as a system which senses the foreign material 100 with an ultrasonic sensor as a collision avoidance sensor.

Sheet thickness measuring device and foreign object collision detection means during traverse (movement):
FIG. 4 is a schematic view showing an example of the structure of the bumper of the present embodiment, FIG. 4 (a) is a schematic side view of a traverse table provided with a bumper, and FIG. 4 (b) is a support guide and a bumper. It is a partially enlarged view of an axis.

  Referring to FIGS. 1 and 4, bumpers 52 and 53 made of round bars are respectively provided on the traverse table 9 so as to be able to bend at the front and rear parts of the traverse table 9. Sensors 50 and 51 are provided for detecting when the bumpers 52 and 53 collide with a foreign object such as a sheet or tool and the apparatus. FIG. 4 shows only the bumper 52 side.

  The traverse base 9 is provided with a support guide 9a which is hollow and has a long hole 9a 'formed on the side surface. The bumper 52 is provided with a bumper shaft 52a to be inserted into the support guide 9a. The bumper shaft 52a has a stopper pin for restricting the movement of the bumper shaft 52a by a long hole 9a 'formed in the support guide 9a. 52b is attached. The spring 52c is disposed between the bumper 52 and the end surface of the support guide 9a through the bumper shaft 52a. Further, the traverse base 9 is provided with a limit switch type sensor 50 provided so as to be positioned between the bumper 52 and the traverse base 9.

  The bumper 52 is normally pushed in the axial direction of the support guide 9a and away from the traverse base 9 by the urging force of the spring 52c. When a foreign object collides with the bumper 52 (at the time of abnormality), the bumper shaft 52a is pushed into the support guide 9a by overcoming the biasing force of the spring 52c. As a result, the distance between the bumper 52 and the traverse base 9 is reduced, and the bumper 52 presses the sensor 50 to detect a collision. Note that the biasing force of the spring 52c is set weak so that the sensor 50 operates even with a small collision resistance.

  When the sheet hangs down, the safety sensor 35 operates to avoid a collision between the hanging sheet and the sheet thickness measuring device 34. However, when the sheet thickness measuring device 34 is already in operation, the tool or the like is on the X axis. The sensor 35 cannot detect it. In such a case, the bumper 52 can detect the foreign matter and avoid the collision between the foreign matter and the sheet thickness measuring device 34. That is, in this safety device including the bumpers 52 and 53 and the sensors 50 and 51, during the measurement traverse in the state where the resin sag has already occurred, the resin sag (resin sheet) causes the surface detection sensor 7 and the back surface detection sensor 8 and When a load is applied due to a collision with the traverse base 9, the collision detection sensors 50 and 51 are activated and detected by the deflection of the X-axis bumpers 52 and 53, and the traveling in the X-axis direction is stopped and moved backward. Thus, the sheet thickness measuring device 34 is retracted at the roll end to enhance safety.

  In addition to the safety sensor 35 and the sensors 50 and 51, the collision prevention sensors include reflection type optical sensors 54 and 55 as reflection avoidance sensors 56 and 57 as collision avoidance sensors in the X-axis traverse running as shown in FIG. You may install in traverse stand 9 in combination. The reflectors 56 and 57 may be provided on the traverse base 9. In addition, an ultrasonic sensor having a wide detection range may be applied as a collision prevention sensor.

Sensor position adjustment considering sheet material refractive index and thickness:
With reference to FIG. 5, the detection distance increase ΔL away from the roll surface when there is a back surface detection sensor 8 and a sheet will be described. The two sensors shown in FIG. 5 are both back surface detection sensors 8. In the figure, reference numeral 8 indicates the position of the back surface detection sensor 8 when the sheet 6 is on the surface of the forming roll 2. , 8 ′ indicates the position of the back surface detection sensor 8 when the sheet 6 is not present.

  In the case of this embodiment, when a laser sensor with coaxial light projection and reception is used for the front surface detection sensor 7 and the back surface detection sensor 8, the detection distance L is 30 mm, and the detection range ΔM is centered on that point. Narrow as ± 1 mm = 2 mm (see FIG. 5). In general, this type of distance measuring device has a high detection accuracy and therefore has a narrow detection range. In the present embodiment, in order to accurately measure the thickness of an extremely thick sheet having a sheet thickness of about 20 mm, a total of two front surface detection sensors 7 and a rear surface detection sensor 8 for the front surface and the rear surface are used.

  In this case, since the laser beam of the back surface sensor passes through the inside of the sheet, the sheet thickness is detected as being thinner than the actual thickness due to the influence of the refractive index. The sheet thickness of polycarbonate PC resin (refractive index n = 1.567) is about 1 / 1.567 times the actual sheet thickness t.

Therefore, as shown in FIG. 5, the set position of the back surface detection sensor 8 for the back surface also takes this refractive index into consideration, and the back surface detection sensor is encoded to about 1t- (1t / 1.567) times the actual sheet thickness t. It is preferable to set the distance from the position 8 ′ to the position 8 by increasing the detection distance ΔL, and to measure at approximately the center of the detection range. The detection distance increase ΔL is expressed by the following equation (1).
ΔL = t−t / n (1 formula)
Here, n in the formula is defined as a refractive index n = 1.567, but the constant related to the refractive index is correct, and is determined by the sheet material, the sheet temperature, the sensor device constant, etc., where n = refractive index for convenience. Defined.

When measuring the roll surface position in the air without a sheet, for example, when the PC (polycarbonate) material, the sheet thickness t = 10 mm, the detection distance is 30 mm, and the detection range is 2 mm (BB = 30 mm ± 1 mm: sensor position (here, sensor tip) and measurement distance BB (standoff) between roll surface),
Increase in detection distance ΔL = 10−10 / 1.567 = 3.62 mm
It becomes. Therefore, the detection distance on the back surface of the sheet is 30 mm + 3.62 mm = 33.62 mm. That is, the back surface detection sensor 8 for the back surface is placed away from the detection distance of 30 mm by 3.62 mm. When the sheet thickness is 20 mm, the detection distance increment ΔL is 7.2 mm, and thus the detection distance is 30 mm + 7.2 mm = 37.2 mm. If this operation is not performed, the detection range by the back surface detection sensor 8 for the back surface will be out of range. Note that ΔL may be set stepwise according to the sheet thickness. The level may be within a new detection range ΔM ′, and is usually adjusted when the sheet thickness changes in mm.

Regarding the calculation for obtaining the sheet thickness from the calculation data of the front surface detection sensor 7 and the back surface detection sensor 8:
First, with reference to FIG. 6, the adjustment of the sensor position in the case where the front surface detection sensor 7 and the rear surface detection sensor 8 for measuring the sheet thickness are laser-type sensors on which light projection and reception are coaxial will be described.

  The origins ref. Measures the common reference plane (roll surface) in advance and grasps the deviation.

The position set difference ΔY between the sensor heads of the front surface detection sensor 7 and the back surface detection sensor 8 is assumed to take into account the refractive index n of the resin sheet to be measured. That is, the laser from the surface detection sensor 7 for measuring the distance AA to the sheet surface passes only in the air and is therefore set at the normal position, but the back surface detection sensor 8 transmits the sheet of thickness t. Since the distance BB to the back surface of the sheet is measured, it is affected by the refractive index n of the resin sheet. Therefore, the position set difference ΔY between the sensor heads of the front surface detection sensor 7 and the back surface detection sensor 8 is determined in consideration of the refractive index n.
ΔY = t− (t−t / n) = t / n (2 formulas)
The front surface detection sensor 7 and the back surface detection sensor 8 are positioned.

  The sheet surface is measured along the X axis by the front surface detection sensor 7 and the back surface detection sensor 8 positioned as described above. Since the sheet thickness measuring device 34 of the present embodiment is configured to change the relative positions of the front surface detection sensor 7 and the back surface detection sensor 8 according to the sheet thickness, even a precision sensor with a narrow measurement range of each sensor has various thicknesses. The thickness of the sheet can be accurately measured.

  Further, the sheet thickness is calculated from the position from the origin of the two sliders and the measured value. Since the measured value has a short sampling time, it can sufficiently follow even if there is vibration of the machine, and accurate thickness data can be obtained.

The X axis position in the sheet width direction is shifted by ΔX between the front surface detection sensor 7 and the back surface detection sensor 8, but the front surface detection sensor 7 and the back surface detection sensor 8 of this embodiment are as close as possible to make ΔX as short as possible. The front surface detection sensor 7 and the back surface detection sensor 8 are at the same position, and the front surface detection sensor 7 is used as a reference. Since the two surface detection sensors 7 and the back surface detection sensor 8 are installed close to the common traverse table 9 and measured simultaneously, the roll surface length is long, the roll is bent due to its own weight, and the roll is bent due to a change in nip force. Even if there is, the sheet thickness measuring device 34 of this embodiment has high thickness detection accuracy.
Optical axis coincidence type laser sensor:
For the front surface detection sensor 7 and the back surface detection sensor 8, for example, an optical axis coincidence type laser sensor as shown in FIG. 7 is preferably used. The outline of the measurement principle of the laser sensor will be described below.

  The optical axis coincidence type laser sensor has a lens focal length vibration sound 7a, a CCD sensor camera 7b, a pinhole 7c, and a light receiving element 7d. The focal length of the laser can be varied by a lens, and the focal length is varied at high speed (sampling period of 1 millisecond or less). If there is a reflection surface (sheet back surface) within the measurement distance (distance B shown in FIG. 7 and detection range ΔM), reflection is increased on this surface, and the light from the light receiving element 7c passes through the pinhole 7d in the sensor. The lens focal length at this moment is read, and the distance of the sheet back surface position can be indirectly measured.

  As the optical axis coincidence type sensor, an optical sensor (white light) may be used in addition to the laser sensor of FIG. The outline of the measurement principle of the light (white light) sensor will be described below.

  White light is a mixture of seven or more colors, and the refractive indices of the light of the individual colors are different, so they are continuously arranged at the wavelength of the color at the focal length. Using this property, a pinhole is provided in the light path in the sensor as in the above laser sensor, and the frequency: spectrum: color of the light passing through the pinhole is measured, and conversely, it is sensitive to the spectrum. The position of the back side of the sheet, that is, the distance can be measured with the output of a simple element.

  In the case of the above-mentioned sensor of the light receiving / receiving optical axis coincidence type, even if the sheet surface is inclined, only the sensitivity is lowered and no large error occurs. On the other hand, in the case of the regular reflection laser surface detection sensor 70 as shown in FIG. 8, if the sheet surface is inclined or wavy, the measurement data is likely to be affected by these effects. That is, the regular reflection laser surface detection sensor 70 irradiates a laser beam with a certain incident angle with respect to the sheet, and the sensing CCD element 71 receives the laser beam reflected on the sheet surface and is reflected on the sheet back surface. Since the distance d between the light receiving positions is detected as the sheet thickness, if the sheet surface is tilted or wavy, the distance between the light receiving positions is tilted or wavy on the sheet surface. Therefore, an error occurs in the measured sheet thickness.

Therefore, the present invention is systemized as an apparatus for detecting extremely thick sheets of about 10 mm and 20 mm using a light receiving / receiving optical axis coincidence type sensor, and is used for a liquid crystal screen requiring precise dimensional accuracy of several μm. This is suitable for molding transparent resin sheets such as PC (polycarbonate) and PMMA (polymethyl methacrylate), and can measure a precise sheet with high accuracy.
Thickness profile adjustment:
The sheet thickness is measured by the front surface detection sensor 7 and the back surface detection sensor 8 to grasp the width direction distribution of the sheet thickness. Based on this, coarse adjustment is performed by the choke bar 46 of the T die 5, and then the existing automatic die lip. The lip opening is precisely adjusted with the adjusting device 45. The die lip adjustment device 45 is automatically controlled via the control device 44 based on the measurement data of the front surface detection sensor 7 and the back surface detection sensor 8. Note that the absolute value of the sheet thickness is refracted to match the absolute value of the sheet thickness at the time of final cooling (actually measured values such as dial gauge), including the typical temperature of the sheet, the thermal shrinkage rate and refractive index of the material. The rate (1.567 in the PC example) is corrected to increase the accuracy. These correction data improve the data accuracy from past operation results, and a thickness profile with high reproducibility can be obtained under almost the same operation conditions. In the case of this embodiment, even a semi-molten sheet can be measured, and the sheet thickness is measured below the forming roll 2, so that the forming conditions of the sheet forming apparatus can be adjusted without time delay.
Bank amount adjustment:
In order to increase or decrease the entire sheet width collectively, the roll speed and the clearance at the roll nip portion are adjusted. Further, the overall inclination of the bank in the left and right direction in the sheet width direction is performed by individually adjusting the roll gap at one end. Since the bank amount profile has a correlation with the sheet thickness profile, it becomes uniform by adjusting the thickness profile.

  An example is shown in FIG. In FIG. 9, the sheet thickness shows almost the same profile as the bank amount (refractive index: set to 1.567).

Next, specific means and other safety measures for avoiding a collision in the X-axis direction in the sheet thickness measuring device 34 of the present embodiment will be summarized.
Prior detection of collisions in the X-axis direction:
As described above, the safety sensor 35 shown in FIG. 1 prevents the front surface detection sensor 7 and the back surface detection sensor 8 from colliding with a foreign object when moving in the sheet width direction (X direction in FIG. 3). Also, a collision operation is detected and a retreat operation is performed. That is, the front surface detection sensor 7 and the back surface detection sensor 8 travel while confirming that there are no abnormalities in the three safety sensors 35 when traveling by measurement. When the resin sheet hangs down during traveling and the safety sensor 35 senses an abnormality, each of the front surface detection sensor 7 and the rear surface detection sensor 8 has its slider (Y axis) lowered to its lowest position and the traverse rail (X axis). Retreat to the end of the roll along.
Post-detection of collision in the X-axis direction:
Normally, when the sheet hangs down, the safety sensor 35 is activated to avoid a collision. However, if the sheet is already hanged when the thickness measuring device is in operation, or if the tool is on the X-axis, etc. 35 is not detectable. Since the sheet thickness measuring device 34 of the present embodiment has the bumpers 52 and 53 mounted on the traverse base 9 as described above, the post-collision detection is performed and the device is prevented from being damaged due to the collision with a foreign object. It has become. That is, when the resin heat hangs down during measurement traverse and the resin heat collides with the front surface detection sensor 7, the back surface detection sensor 8, and the traverse base 9 and a load is applied, the bumpers 52 and 53 before and after the X-axis traverse base 9 After the deflection and collision detection sensors 50 and 51 are activated and the traverse base 9 stops traveling in the X-axis direction, the safety of the apparatus is enhanced by retracting back to the roll end.

When measuring the thickness, if the sheet suddenly hangs down and covers the front surface detection sensor 7 and the back surface detection sensor 8, the sheet returns to the retracted position of the roll end (two locations on both ends of the roll) while the sheet is soft at high temperature, minimizing resin entanglement To. Further, the apparatus is prevented from being damaged by the heat of the sheet in a high temperature state.
Thermal protection:
As described above, the front surface detection sensor 7 and the back surface detection sensor 8 are individually covered with the cover 36 (see FIG. 1), the inside is air-cooled, and air is exhausted (air purge) from the laser projection light receiving hole of the sensor. Prevents dirt on the lens surface. The upper half of the cover is attached with a roll, a metal mirror surface that reflects the radiant heat from the sheet, or silver paper. The upper surface of the slider rail is also provided with a fixed cover. Although the cover 36 is provided for each sensor in FIGS. 1 and 2, the cover 36 may be configured to integrally cover both the front surface detection sensor 7 and the back surface detection sensor 8. In this case, a cover may be provided only on the front surface of the sensor that emits a large amount of heat. Thus, the sheet thickness measuring device 34 according to the present embodiment can extend the service life because it is covered with the heat insulating cover and measures against high temperatures are taken.

In addition, in this embodiment, although the horizontal arrangement | positioning 4 roll type | mold forming apparatus which consists of the forming rolls 1-4 was illustrated, a 2 roll type and a 3 roll type may be sufficient. Further, a stand-up arrangement or an oblique arrangement multi-stage roll type may be used.
(Embodiment 2)
The sheet thickness measuring apparatus of the present invention is characterized in that it can measure an extremely thick sheet with high accuracy and can adjust the molding conditions of the sheet molding apparatus without a time delay, but rather than reducing the time delay of the molding conditions. When it is desired to further improve the measurement accuracy, the configuration shown in this embodiment may be adopted.

  In the embodiment described above, as shown in FIG. 1, the sheet thickness measuring device 34 is installed below the forming roll 2, but may be installed downward at a position α above the forming roll 3. In this case, there is no sagging of the sheet, but care should be taken because foreign matter such as bolts may bite into the roll. Further, the measurement at this position passes through the first and second nips and the sheet dimensional accuracy is fixed, but the time delay is larger than in the above-described embodiment.

  In addition, the sheet thickness measuring device 34 may be installed at a position β below the forming roll 4. In this case, the time delay is larger than the position α above the forming roll 3, but the measurement accuracy is increased because the sheet size is substantially fixed through the roll nip three times.

Further, the sheet thickness measuring device 34 may be arranged at an angle with respect to the intermediate position of the roll.
(Embodiment 3)
The sheet thickness measuring apparatus of the present invention is capable of measuring an extremely thick sheet with high accuracy and can adjust the molding conditions of the sheet molding apparatus without time delay, but is a colored sheet, matte sheet, or sheet surface In the case of measuring the sheet thickness of an embossed sheet in which light is unevenly measured and light to be measured cannot be transmitted to the back surface, the configuration shown in the present embodiment may be adopted.

  The laser-type sheet back surface back surface detection sensor 8 of Embodiment 1 is suitable for a transparent sheet, but a colored sheet, a matte sheet, or an emboss that has fine irregularities on the surface of the sheet and cannot transmit light to the back surface. The sheet cannot be used because the laser beam does not reach the back of the sheet.

  FIG. 10 shows an example in which an eddy current sensor type capable of measuring the thickness of a colored sheet or an embossed sheet is used as a sensor for measuring the back side of the sheet. Since the configuration other than the eddy current type back surface detection sensor 8a is basically the same as the configuration described in the first embodiment, detailed description thereof is omitted. Further, the symbols used in the first embodiment are also used in the description of the present embodiment.

  When the eddy current type back surface detection sensor 8a is used as the sheet back surface sensor, the forming roll 2 is made of a metal roll surface. Usually, most metal rolls are used.

  The eddy current type back surface detection sensor 8a can naturally be used for a transparent sheet in addition to a colored sheet and an embossed sheet. Compared with the eddy current type back surface detection sensor 8a, the laser type sensor of the first embodiment has high measurement accuracy and can be easily downsized. However, in the case of the eddy current type back surface detection sensor 8a, the roll surface to be measured is the sheet surface. The measurement range B has a wide detection range on the roll surface, not a spot as in a laser type sensor. For this reason, there is little influence on the overall sheet thickness accuracy. Further, since the eddy current type back surface detection sensor 8a measures the distance BB to the surface of the metal forming roll 2, it is not affected by the sheet thickness, and it is not necessary to change the position even if the thickness changes. Is not particularly restricted.

  In addition, each numerical value, material, etc. in each said embodiment are examples, and this invention is not limited to these.

1 is a schematic side view of a sheet thickness measuring device and a sheet forming machine in Embodiment 1 of the present invention. It is a figure which shows schematic structure of the sheet | seat thickness measuring apparatus in Embodiment 1 of this invention seen from the arrow A shown in FIG. It is a figure explaining the foreign material detection by the sheet thickness measuring apparatus in Embodiment 1 of this invention. It is a figure which shows an example of the bumper with which the sheet | seat thickness measuring device in Embodiment 1 of this invention was mounted | worn. It is explanatory drawing of detection distance increase (DELTA) L in the positioning of the optical laser used for the sheet thickness measuring apparatus in Embodiment 1 of this invention. It is explanatory drawing regarding positioning of the optical laser used for the sheet thickness measuring apparatus in Embodiment 1 of this invention. It is a schematic block diagram of the optical axis coincidence type laser sensor applicable to this invention. It is a figure explaining the schematic structure and measurement principle of a regular reflection laser sensor. It is a graph which shows the relationship between bank amount and sheet thickness. It is a figure which shows the structure of the sensor part of the sheet thickness measuring apparatus using the eddy current sensor in Embodiment 3 of this invention.

Explanation of symbols

1, 2, 3, 4 Forming roll 5 T die 6 Sheet 7 Surface detection sensor 7a Lens focal length vibration sound 7b CCD sensor camera 7c Light receiving element 7d Pinhole 8, 8 'Back surface detection sensor 8a Eddy current type back surface detection sensor 9 Traverse base 9a Support guide 9a 'Slot 30 Melted sheet 31 Bank 32 Clearance 33a First nip portion 33b Second nip portion 33c Third nip portion 34 Sheet thickness measuring device 35 Safety sensor 36 Cover 38 Traverse rail (X axis)
39 Y1 slider (Y1 axis)
40 Y2 slider (Y2 axis)
41 Cable bearer 42 Frame 43 Toothed belt 44 Control device 45 Die lip adjustment device 46 Choke bar 50, 51 Sensor (for collision detection)
52, 53 Bumper 52a Bumper shaft 52b Stopper pin 52c Spring 54, 55 Sensor (light reflection type)
56, 57 Reflector

Claims (13)

The sheet thickness distribution in the width direction of the sheet (6) formed by pouring the molten resin extruded from the T die (5) into the nip part (33a) of the rotating forming rolls (1, 2). In the sheet thickness measuring device for measuring from the upper surface side of the forming roll (1, 2, 3, 4) while moving in the width direction of the sheet (6),
A surface detection sensor (7) for detecting the surface position of the sheet (6) and a back surface detection for detecting the position of the back surface of the sheet (6) on one traverse base (9) movable in the width direction of the sheet (6) The sensor (8) is mounted so that the relative position with respect to the thickness direction of the sheet (6) can be adjusted, and at least the surface detection sensor (7) has an optical axis coincidence type in which the optical axes of light projection and reception coincide with each other. A sheet thickness measuring device which is a sensor. The sheet thickness measuring device according to claim 1, wherein the front surface detection sensor (7) and the back surface detection sensor (8) are optical axis coincidence type laser sensors. The sheet thickness measuring device according to claim 1, wherein the front surface detection sensor (7) and the back surface detection sensor (8) are optical axis coincident optical sensors. The sheet thickness measuring device according to claim 1, wherein the back surface detection sensor (8) is an eddy current sensor. The detection distance increase ΔL from the forming roll (2) without the sheet (6) of the back surface detection sensor (8) to the leading end of the back surface detection sensor (8) is the approximate thickness of the sheet t. If the refractive index is n,
ΔL = t−t / n
The sheet thickness measuring device according to any one of claims 1 to 4, wherein The sheet thickness distribution in the width direction of the sheet (6) formed by pouring the molten resin extruded from the T die (5) into the nip part (33a) of the rotating forming rolls (1, 2). In the sheet thickness measuring device for measuring from the upper surface side of the forming roll (1, 2, 3, 4) while moving in the width direction of the sheet (6),
The relative position of the surface detection sensor (7) for detecting the surface position of the sheet (6) and the back surface detection sensor (8) for detecting the back surface position of the sheet (6) with respect to the thickness direction of the sheet (6) can be adjusted. The traverse base (9) movable in the width direction of the seat (6) has a safety detection sensor (35, 54) for detecting the foreign matter before colliding with the foreign matter. Thickness measuring device. The sheet thickness distribution in the width direction of the sheet (6) formed by pouring the molten resin extruded from the T die (5) into the nip part (33a) of the rotating forming rolls (1, 2). In the sheet thickness measuring device for measuring from the upper surface side of the forming roll (1, 2, 3, 4) while moving in the width direction of the sheet (6),
A front surface detection sensor (7) for detecting the front surface position of the sheet (6), a back surface detection sensor (8) for detecting the rear surface position of the sheet (6), and bumpers (52, 53) and The bumper (52, 53) has a collision detection sensor (50, 51) for detecting a collision when the bumper (52, 53) collides with a foreign object. When the bumper (52, 53) collides with the foreign object, the bumper (52, 53) collides with the foreign object. A sheet thickness measuring apparatus comprising a traverse base (9) that moves backward in the width direction of the sheet (6) and retracts at a roll end in a direction opposite to the roll direction. The traverse base (9) is mounted with the front surface detection sensor (7) and the rear surface detection sensor (8) so that the relative position with respect to the thickness direction of the sheet (6) can be adjusted, and at least the front surface detection sensor ( The sheet thickness measuring device according to claim 6 or 7, wherein 7) is an optical axis coincidence type sensor in which the optical axes of light projection and reception coincide with each other. The sheet thickness measuring device according to claim 8, wherein the front surface detection sensor (7) and the back surface detection sensor (8) are optical axis coincidence type laser sensors. The sheet thickness measuring device according to claim 8, wherein the front surface detection sensor (7) and the back surface detection sensor (8) are optical axis coincidence type optical sensors. The sheet thickness measuring device according to claim 8, wherein the back surface detection sensor (8) is an eddy current sensor. The detection distance increase ΔL from the forming roll (2) without the sheet (6) of the back surface detection sensor (8) to the leading end of the back surface detection sensor (8) is the approximate thickness of the sheet t. If the refractive index is n,
ΔL = t−t / n
The sheet thickness measuring device according to any one of claims 6 to 11, wherein The sheet thickness measuring device according to any one of claims 1 to 12, wherein the front surface detection sensor (7) and the back surface detection sensor (8) have heat resistance means.

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