JPS585362B2 - Method for detecting uneven thickness of insulating coating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thickness unevenness detection method for detecting uneven thickness of an insulating coating of a linear test object coated with a conductive material. .

For example, when the insulation coating of electric wires or the rubber lining of pipes, etc., the thickness of the coating is extremely thin, that is, if the thickness is uneven, it may cause the contents to deteriorate and rot, causing safety problems such as electrical dielectric strength. Invite the state.

Therefore, detecting this type of uneven thickness is important in the manufacturing process.

However, conventionally, two electrode plates are placed facing each other and the coated wire is sandwiched between them, and the capacitance formed between each electrode plate and the core wire is measured.

For this reason, it is not possible to measure the wall thickness around the entire circumference of the coated wire at once, and in order to find out the uneven thickness of the coat, another set of electrodes must be placed opposite the coated wire at right angles to the electrode plate mentioned above. There was a need.

Furthermore, it is necessary to readjust the spacing between the electrode plates to bring them into contact with coated wires having different external dimensions or diameters.

The present invention aims to provide a method for detecting uneven thickness that eliminates the above-mentioned drawbacks, and embodiments shown in the drawings will be described below.

Figure 1 shows a case where an object to be inspected, which is a metal tube 1 covered with a rubber coating 2, is inspected without grounding the tube 1.
4 is a closed loop electrode, and 4 is a roller electrode having preferably V-shaped grooves provided at intervals before and after the electrode 3.

The closed-loop electrode 3 has a number of electrode tentacles projecting inwardly of the closed loop, and these tentacles are in contact with the covering.

The roller electrode 4 functions as a counterpart electrode of the electrode 3, and an alternating current voltage, preferably a high frequency high voltage E, is applied between the electrode 3 and the electrode 4.

The electrical equivalent circuit at this time is shown in FIG.

In this figure, C1 is the capacitance generated between the inner metal tube 1 and the electrode 3, R is the electrical resistance of the metal tube 1, and C2 is the metal tube 1.
This is the capacitance generated between the electrode 4 and the electrode 4.

Reference numeral 6 denotes an amplifier, which produces an output when the terminal voltage of a resistor 5 inserted into the circuit becomes larger than a certain value, energizes a relay 7, and activates an alarm device and the like.

The operating input level of the amplifier 6 or the magnitude of the voltage E is determined by the third
As shown in the figure, the relay 7 is set to operate when the thickness of the coating 2 becomes thinner than the minimum allowable value t.

With this setting, the pipe that is the object to be inspected will be the first one.
As it is fed in the direction of the arrow P in the figure, if there is a part where the thickness of the coating 2 is thinner than the allowable value t, the value of the capacitance C1 increases, the circuit current increases, and the terminal voltage of the resistor 5 increases. It rises and relay 7 is activated.

Therefore, this uneven thickness location is reliably detected.

As described above, the method for detecting uneven thickness of an insulating coating of a linear test object according to the present invention involves preparing a closed loop electrode having a large number of electrode tentacles protruding inward of the closed loop, and A linear object to be inspected is passed through the linear object continuously in its axial direction, and at this time, a roller electrode provided on the front side or the rear side of the linear object in the insertion direction of the linear object with respect to the closed loop electrode is attached to the linear object to be inspected. A high frequency voltage is applied between the closed loop electrode and the roller electrode, and when the thickness of the coating is thinner than a permissible value, a change in the current flowing between the electrode and the content is detected. It is something to do.

Since the electrode 3 has a closed loop shape, it is possible to inspect the entire circumference of the coating at once for uneven thickness.

In addition, the electrode 3 has a large number of tentacles that protrude toward the inside of the loop and is in contact with the object to be inspected. It is possible to accurately detect uneven thickness of the coating along the line.

The detection method of the present invention is particularly advantageous for detecting uneven thickness of relatively long objects, such as electric wire cables made of aluminum tubes containing electric wires covered with polyethylene. By doing so, it is possible to detect uneven thickness in packages of ham, sausage, fish cakes, etc., as well as in containers containing conductive liquids, such as Ringer's solution bottles, injection ampoules, etc.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram illustrating the method of the present invention for inspecting uneven thickness of a long object to be inspected, Fig. 2 is an explanatory diagram showing the detection principle of the invention, and Fig. 3 is a coating of the object to be inspected in Fig. 1. FIG. 3 is a diagram illustrating an example of uneven thickness. 1...Metallic tube, 2...Coating, 3,
10,12゜16.17... Electrode, 4,9,1
5...roller electrode, 6...amplifier, 7
...Relay, 8...Object to be inspected.

Claims (1)

[Claims] 1. In a method for detecting uneven thickness of an insulating coating of a linear test object whose conductive content is coated with an insulating material, a closed loop electrode having a number of electrode tentacles protruding inward of the closed loop is prepared, A linear test object is continuously passed through the closed loop electrode in its axial direction, and at this time, a roller electrode provided on the front or rear side of the linear test object is inserted into the closed loop electrode. A high frequency voltage is applied between the closed-loop electrode and the roller electrode in contact with the object to be inspected, and when the thickness of the coating is thinner than an allowable value, a change in the current flowing between the electrode and the content is detected. A method for detecting uneven thickness of an insulating coating.