JPH0431526Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a device that can measure the thickness of a sheet-like material such as paper online. The present invention relates to an apparatus for measuring the thickness of a sheet-like material that can prevent an accident of breakage of the sheet-like material caused by foreign matter contained in the sheet-like material colliding with a detection head facing the sheet-like material.

<Prior art> Fig. 4 shows an upper detection head floating above a sheet material with a small gap by air blowing, and a lower detection head having a sensor coil disposed below the sheet material. FIG.

In the figure, A is an upper detection head, and a tank cap 2 is attached to a base 1, and a diaphragm 5 is fixed to the periphery of an opening 3 provided in the base 1 via a retainer ring 4.

A conductor target 6 is attached to the center of the diaphragm, and has a chamber 6a inside and a plurality of air blowing holes 6b on its surface. 7 is a tube that guides air to the target 6.

A coil spring 8 is fixed to the diaphragm 5 on the opposite side of the target 6, and the other end of this spring is fixed to a support provided on the base 1 within the tank cap 2.

B is the lower detection head, with body 1 attached to base 9.
0 is attached and an opening 1 provided in the base 9
A diaphragm 12 is attached to the periphery of 1,
A sensor coil 13 is attached to the central opening of this diaphragm.

C is a sheet material sandwiched between these detection heads.

With such a configuration, the sheet-like material C is indicated by the arrow D1.
In the case of feeding in the direction, the upper detection head A and the lower detection head B are reciprocated in the width direction of the sheet material C (perpendicular to the plane of the paper) according to guides on the frame.

The thickness is measured using the detection head A of the sheet-like material C.
and B, increase the internal pressure of the tank cap 2 and body 10, and bring the target 6 and sensor coil 13 closer to the sheet material C.

At this time, air is being supplied to the target 6 through the tube 7, and as shown in FIG. is balanced, and the target 6 is levitated by a certain amount ε above the sheet material C.

A high frequency current is passed through the sensor coil 13 in the lower detection head B, and a magnetic flux is generated. The target 6 placed opposite the sensor coil 13 is a good conductor, and an eddy current is generated in this portion, and this eddy current causes the sensor coil 13 to
The magnetic flux of the coil decreases and the coil impedance changes. This change in impedance is proportional to the distance between the target 6 and the sensor coil 13, and this distance is also expressed as the sum of the thickness e of the sheet material C and the constant flying height ε. If detected using a bridge circuit or the like, the thickness e of the sheet material C can be measured online.

However, in such a device, as shown in FIG. 6, if foreign matter 14 is contained in the sheet-like material C which exceeds the gap ε between the target 6 and the sheet-like material C, the foreign matter 14 is not fed in the direction of the arrow E. As the sheet material C moves, it collides with the front end of the target 6.

The force F due to the collision is decomposed into a component f1 in a direction perpendicular to the sheet material C and a component f2 in a lateral direction. Since the front end of the target 6 has almost no slope, the lateral component f2 becomes large.

On the other hand, the target 6 is supported by the diaphragm 5, and has a structure in which it can move perpendicularly to the sheet material C, but can hardly move laterally.

For this reason, only the foreign matter 14 gets caught on the front end of the target 6 and is separated from the sheet-like material C, often causing an accident in which the sheet-like material C is broken.

<Problem to be solved by the invention> The technical problem to be solved by the invention is to measure the thickness of a sheet-like material such as paper by placing a small gap in the sheet-like material and placing a detection head close to it. In the apparatus, the object is to prevent an accident of breakage of the sheet-like material caused by foreign matter contained in the sheet-like material coming into contact with the detection head.

<Means for Solving the Problems> The configuration of the present invention is such that in the sheet-like material thickness measuring device, the surface of the target facing the upstream side of the sheet-like material is An inclined surface is provided that increases the distance between the target and the sheet material, and the air blowing holes are set so that the air blowing pressure on the upstream surface of the target is stronger than the air blowing pressure on the downstream surface of the target. By correcting the weakening of the levitation force due to the provision of the inclined surface, the levitation force on the upstream side and the downstream side of the target is balanced, and the foreign matter contained in the sheet-like material comes into contact with the inclined surface. At this time, the entire target was pushed up in a direction perpendicular to the sheet material to allow the foreign matter to pass under the target.

<Operation> The technical means described above operates as follows. That is,
When the foreign matter contained in the sheet-like material collides with the target, the force due to the collision is resolved into a vertical force and a lateral force by the inclined surface. The majority is converted into vertical force. This vertical force forces the entire target upward.

At this time, since the lateral force is not large enough to separate the foreign matter from the sheet-like material, the foreign matter moves together with the sheet-like material,
While pushing the target upward, it passes under the target. Furthermore, the number of air blowing holes provided on the surface of the target or the diameter of the holes are changed to balance the levitation force due to the air blowing on the upstream and downstream sides of the target, and the slope is provided. The inclination of the image was corrected to enable accurate thickness measurement.

<Examples> Examples of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a main part of an apparatus according to an embodiment of the present invention, and FIG. 2 is a plan view of the target 6 seen from the plane H--H in FIG. In these figures, the same elements as those in FIG. 4 are given the same reference numerals. The distance between the front end surface of the target 6 facing the upstream side of the sheet material C and the sheet material C increases toward the upstream side. An inclined surface 6c of about 11° to 15° is provided.

Further, among the plurality of air blowing holes 6b provided on the surface of the target 6, the holes located downstream from the center, for example, the portion surrounded by a dotted line are crushed.

With this configuration, as shown in Figure 3,
When a foreign object 14 whose size exceeds the gap ε between the target 6 and the sheet material C collides with the front end of the target 6 as the sheet material C is being fed, the force F' due to the collision is Due to the inclined surface 6c at the front end, the sheet material C is decomposed into a component f1' in the vertical direction and a component f2' in the lateral direction,
Most of it is converted into vertical force f1′. The entire target 6 is pushed up by this vertical force f1'.

At this time, since the lateral force f2' is not large enough to separate the foreign matter 14 from the sheet-like material C, the foreign matter 14 moves together with the sheet-like material C, pushing up the target 6 and pushing the target 6 upward.
It passes under the .

Incidentally, the detection heads A and B are also driven in the width direction of the sheet material C, but the inclined surface 6c is
It is provided only in the part facing the upstream side of the sheet-like material C. However, the feeding speed in the longitudinal direction of the sheet material C is overwhelmingly faster than the driving speed of these detection heads, and these detection heads follow a trajectory that moves in a zigzag manner in the upstream direction of the sheet material C. For this reason, the inclined surface is covered with sheet-like material C.
A sufficient effect can be obtained just by providing it on the part facing the upstream side.

By the way, the air outlet 6b of the target 6
Assuming that the target remains the same as before, the provision of the inclined surface 6c causes the air from the blowout hole 6b to escape from this part to the outside of the target 6, weakening the levitation force caused by the blowout, and causing the target 6 to become a sheet material C.
The slope tilts toward the upstream side, canceling out the effect of providing the slope.

In the device according to the embodiment of the present invention, in order to make the air blowing pressure on the upstream side surface of the target 6 stronger than the blowing pressure on the upstream side surface of the target 6, the hole on the downstream side of the target 6 is crushed, and the air blowing pressure on the upstream and downstream sides is Balance the levitation force and target 6
was able to float stably.

Incidentally, as a method of balancing the floating force due to the air blowing on the upstream side and the downstream side, the diameter of the hole on the downstream side of the center of the target 6 may be made smaller to weaken the blowing pressure on the downstream side.

<Effects of the invention> According to the invention, even if a foreign object contained in the sheet-like material collides with the target, the entire target is prevented from colliding with the sheet-like material by the inclined surface provided on the front end surface of the target. On the other hand, since the foreign matter is pushed up in the vertical direction, the foreign matter can easily pass through this portion, and the sheet-like material will not be broken by the foreign matter. Furthermore, the number of air blowing holes on the target surface and the diameter of the holes are adjusted to balance the levitation forces on the upstream and downstream sides of the target, so even if the slope is provided, the target surface will not tilt. There is no.

[Brief explanation of drawings]

Fig. 1 is a sectional view of the main parts of the device according to the present invention;
The figures are a plan view of the target 6 seen from the H-H plane in FIG. FIG. 6 is an explanatory diagram of the operation of the conventional device shown in FIG. A... Upper detection head, B... Lower detection head, C... Sheet-like material, 5... Diaphragm, 6... Target, 6b... Air outlet, 6c... Inclined surface, 8... coil spring,
13...Sensor coil, 14...Foreign object.

Claims (1)

[Scope of utility model registration request] A pair of detection heads are arranged opposite to each other with a sheet-like material in between, the lower detection head is provided with a sensor coil, and the upper detection head is provided with a conductive target having a plurality of air blowing holes on the surface of the sheet-like material. The target is elastically supported so as to be movable perpendicularly to the surface of the sheet-like material, and the levitation force caused by the air blowing of the target, the target's own weight, and the spring force of the elastic support means are balanced, and the target is kept at a constant distance from the surface of the sheet-like material. In the apparatus, the thickness of the sheet-like material is measured from a change in impedance of the sensor coil by levitating the sheet-like material. A slope is provided so that the distance between the target and the sheet-like material increases toward The hole is set to correct the weakening of the levitation force due to the provision of the inclined surface, to balance the levitation force on the upstream side and downstream side of the target, and to prevent foreign matter contained in the sheet material from falling on the inclined surface. An apparatus for measuring the thickness of a sheet-like material, characterized in that when it comes into contact with a surface, the entire target is pushed up in a direction perpendicular to the sheet-like material, so that the foreign object can pass under the target.