Electricity: measuring and testing – Magnetic – With means to create magnetic field to test material
Reexamination Certificate
1998-09-14
2001-01-16
Patidar, Jay (Department: 2862)
Electricity: measuring and testing
Magnetic
With means to create magnetic field to test material
C324S231000, C033S501030
Reexamination Certificate
active
06175235
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a thickness detector for detecting a thickness of a paper sheet or the like.
In a conventional thickness detector using a belt to convey a paper sheet a roller having a fixed shaft and a movable roller having a support structure are used. These rollers are movable vertically and are paired in opposition to each other. When a paper sheet or the like passes between the pair of rollers, a displacement amount of the movable roller is detected as a thickness of the object. In this case, a plurality of pairs of rollers are disposed to measure a thickness distribution of the object in the direction perpendicular to the conveyance direction of the object.
In a conventional apparatus using another detection method, optical range-meters are provided at predetermined intervals above and below an object to be measured, opposed to each other. The distance to the object is measured by each of the optical range-meters, to detect the thickness thereof.
In the above-described method of detecting a thickness by a displacement of a roller, the roller has a certain weight, and therefore, a paper sheet or the like sometimes jams into the roller. Also, this method achieves only a low response ability to a rapid change caused when the top end of an object running enters into between rollers, when the rear end of the object comes out from between the rollers, or when a surface onto which a tape is adhered passes. Therefore, the detection speed is limited. Consequently, there has been a demand for a detector capable of detecting the thickness of an object being conveyed at a high speed with high accuracy.
In case of detecting a thickness distribution in the widthwise direction by disposing pairs of rollers, the rollers cannot be provided tightly due to roller support members and the like. It is therefore difficult to raise the resolution in the widthwise direction. Further, there is a problem that a swing of an object may be measured as displacement of the roller so that the detection accuracy is deteriorated when an object swings in the thickness direction while running. From the view point of manufacture, the manufacturing cost is high since the processing accuracy of the rollers and roller support members must be raised to reduce rattling during rotation of the rollers.
In the above-described method of detecting a thickness using optical range-meters, the amount of reflection light changes depending on the coloring of an object to be measured, and therefore, errors are included in the thickness measurement results. An optical range-meter which is not influenced by the coloring of an object is expensive, and has a large outer size which restricts the space where the range finder can be installed. Therefore, there has been a demand for a low priced thickness detector, which is not influenced by the coloring of an object to be measured and which does not occupy a large installation space.
BRIEF SUMMARY OF THE INVENTION
The present invention therefore has an object of providing a thickness detector which achieves a high response ability to a rapid change of the thickness of an object to be measured and is capable of detecting the thickness of a paper sheet or the like running at a high speed.
The present invention has another object of providing a thickness detector in which a plurality of thickness detecting portions are provided to be close to each other in the widthwise direction of an object to be measured.
The present invention has another object of providing a thickness detector which is not influenced by a swing of an object to be measured, in the thickness direction of the object.
The present invention has yet another object of providing a thickness detector at a low price, which is not influenced by coloring of an object to be measure.
In order to achieve the above objects, according to an aspect of the present invention, there is provided a thickness detector comprising: a pair of elastic members opposed to each other so as to hold an object to be measured, and having top end portions which are brought into contact with both surfaces of the object, the top end portions being provided with coil, respectively; and measurement means for measuring a clearance between the top end portions of the pair of elastic members, as a thickness of the object, by using inductances of the coils respectively provided for the elastic members.
Each of the elastic members is constituted by two or more elastic films adhered to each other by an adhesive member which functions as a damping material. Each of the coils of the elastic members consists of printed coils provided respectively on both sides of one of the elastic films and connected to each other by a through-hole.
The mass of the top end portions of the elastic members which detect the thickness of an object to be measured is small, and a damping member is provided in each of the elastic members. It is therefore possible to provide a thickness detector which has an excellent response ability to a rapid change in the thickness of the object to be measured, is capable of detecting the thickness of a paper sheet or the like running at a high speed, and is not influenced by the switch of the object in the thickness direction thereof.
The coils provided at the top end portions of the elastic members are connected in series with each other, functioning as a detection coil, and the measurement means includes a bridge circuit consisting of a first resistor connected in series with the detection coil, a second resistor having a resistance equal to that of the first resistor, and a dummy coil connected in series with the second resistor and having an inductance which is equal to that of the detection coil. The measurement means further includes a differential amplifier having a first input connected to a connection point between the detection coil and the first resistor and a second input connected to a connection portion between the dummy coil and the second resistor, an oscillator for supplying a sine wave to the bridge circuit, and means for outputting a signal representing the thickness of the object, using an output of the differential amplifier. The measurement means is thus constituted by a simple electric circuit. It is therefore possible to provide a thickness detector at a low price, which is not influenced by coloring of an object to be measured.
A wear-resistance member is provided on a surface of each of the elastic members that is brought into contact with the object sliding thereon, and the wear-resistance member is made of ceramics or diamond like carbon film.
Since each of the elastic members can be easily constructed to have a small overall width, a plurality of pairs each consisting of the elastic members can be easily provided in a direction perpendicular to the conveyance direction in which the object to be measured is conveyed. It is therefore possible to provide a thickness detector capable of detecting a thickness distribution of an object in the widthwise direction thereof.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
REFERENCES:
patent: 4107606 (1978-08-01), Typpo et al.
patent: 4107847 (1978-08-01), Typpo et al.
patent: 9-46809 (1997-02-01), None
Obama Masao
Tsukahara Tadashi
Andersen Henry S.
Kabushiki Kaisha Toshiba
Patidar Jay
Pillsbury Madison & Sutro LLP
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