JPH10115580A - Method and apparatus for inspection of hollow body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably eliminate a delayed-fractured product as a defective product from a line by judging that a product is acceptable only when an internal pressure reaches a set pressure in a predetermined time and a differential value of the internal pressure when it drops does not exceed a set value. SOLUTION: If a hollow body W is delayed-fractured after an internal pressure reaches a set value, an inverse differential value of the internal pressure becomes extremely large. A second comparison means 9 issues an NG signal when an output from an inverse differentiation circuit 8 exceeds a set value. The NG signal is input via a self holding circuit 10 to a process controller 6 as a means for judging whether a product is acceptable. If the internal pressure of the hollow body W reaches a set pressure, only when an OK signal is input from a first comparison means 5 monitoring a rise in pressure and no NG signal is output from the self holding circuit 10, the product is judged to be acceptable. Therefore even if the OK signal is input from the first comparison means 5, if an NG signal is output from the second comparison means 9, the hollow body W is judged to be delayed-fractured, so that it is eliminated from a line as a defective product.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for water pressure inspection of a hollow body.

[0002]

2. Description of the Related Art A water pressure inspection method for a hollow body, in which cracks and other defects are inspected by applying a water pressure to a hollow body such as a suspension insulator for a predetermined time, has been widely used. In such a water pressure test of the hollow body, it is usual that a water pressure is applied to the inside of the hollow body for a predetermined time, and when the internal pressure does not reach the set pressure within the predetermined time, it is determined to be rejected.

FIG. 3 is a view for explaining a conventional water pressure inspection apparatus. Water in a water tank 1 is pressed into a hollow body W (suspension insulator) via a switching valve 3 by a pump 2 and the internal pressure is reduced. It is detected by the pressure gauge 4. Then, the comparing means 5 determines whether or not the internal pressure reaches a set pressure (product inspection pressure). When the internal pressure reaches the set pressure, an OK signal is output.

FIG. 4 is a pressure waveform diagram in the case where there is no defect in the hollow body.
Emits an OK signal, and the process controller 6
From the inspection head 7. Then, this hollow body W
Is transported as a non-defective product to a subsequent process. FIG. 5 is a pressure waveform diagram when the hollow body has a defect. The internal pressure is destroyed before reaching the set pressure, and does not reach the set pressure.
At this time, the OK signal is not output from the comparing means 5 within the signal monitoring time, and the hollow body W is removed from the line as a defective product.

However, depending on the condition of the defect, the internal pressure may be destroyed after reaching the set pressure as shown in FIG. In this case, since the comparison means 5 emits an OK signal at the same time as the set pressure is reached, the hollow body W is conveyed to the subsequent process as a good product despite being destroyed.
As a result, the debris may be conveyed to a subsequent process and damage the equipment, so that there is a problem that the entire line must be stopped to clean the debris.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems and reliably removes the hollow body from the line even if the hollow body is broken after the internal pressure reaches a set pressure. The present invention has been made in order to provide a method and an apparatus for inspecting the water pressure of a hollow body which can be performed.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a method for inspecting the water pressure of a hollow body according to the present invention is provided. The method is characterized in that a pass is determined only when the internal pressure reaches the set pressure within a predetermined time and the differential value of the internal pressure does not exceed the set value. Further, the water pressure inspection apparatus for a hollow body of the present invention includes an inspection head for applying a water pressure to the inside of the hollow body, a pressure gauge for detecting the internal pressure of the hollow body, and a pressure gauge when the detected internal pressure reaches a set pressure within a predetermined time. OK
First comparing means for outputting a signal, a differentiating circuit for calculating a differential value of the internal pressure, and comparing the differential value of the internal pressure at the time of pressure drop calculated by the differential circuit with a set value, and the differential value exceeds the set value. A second comparing means for outputting an NG signal when the signal is output, and a pass / fail determination means for determining a pass when the OK signal is output and the NG signal is not output.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below. In the embodiment of the present invention shown in FIG. 1 as well, water in a water tank 1 is pressed into a hollow body W (porcelain suspension insulator) by a pump 2 through a switching valve 3 and the internal pressure is measured by a pressure gauge 4. To detect. The first comparing means 5 determines whether or not the internal pressure of the hollow body W reaches a set pressure (product inspection pressure) within a predetermined time. When the internal pressure reaches the set pressure, the first comparing means 5 issues an OK signal. However, if the set pressure has not been reached, no OK signal is issued. Further, in the present invention, a differentiating circuit 8 is provided, and the internal pressure detected by the pressure gauge 4 is input to the differentiating circuit 8, and a differential value of the internal pressure is calculated.

The upper part of FIG. 2 shows the pressure waveform of the internal pressure of the hollow body W detected by the pressure gauge 4, and the lower part shows the inverted differential value obtained by inverting the differential value of the internal pressure. As shown in this figure, when the hollow body W has no defect, after the internal pressure of the hollow body W reaches the maximum pressure, the process controller 6
Is released from the inspection head 7, the pressure gradually decreases. Therefore, the inversion differential value of the internal pressure at the time of pressure drop is very small. Further, if the hollow body W is broken before the internal pressure reaches the set pressure, the internal pressure is released at the same time as the breakage, so that the inverted differential value of the internal pressure at the time of the pressure drop slightly increases. However, when the hollow body W is delayed and destroyed after the internal pressure reaches the set pressure, a sharp pressure drop occurs from a high pressure level as shown on the right side of FIG. The value will be very large. Therefore, the detection level of the inversion differential value of the internal pressure at the time of the pressure drop is set, and an NG signal is output in the second comparing means 9 when the output of the differentiating circuit 8 exceeds this set value. If it does not exceed the threshold, no NG signal is output.

The NG signal from the second comparing means 9 is input to the process controller 6 via the self-holding circuit 10. The process controller 6 has a function as a pass / fail determination means, and monitors a pressure increase.
Only when the OK signal is input from the comparing means 5 and the NG signal is not output from the self-holding circuit 10, it is determined to be acceptable. Therefore, when the OK signal is input from the first comparing means 5 and the NG signal is output from the second comparing means 9, it is determined that the hollow body W has been destroyed, and the hollow mechanism is removed by a removing mechanism (not shown). The body W is removed from the line as a defective product. As a result, even if the hollow body W is delayed and destroyed after the internal pressure reaches the set pressure, the broken product is not erroneously transported as a good product to the subsequent process as in the conventional case, and the fragments are transported to the subsequent process. This can eliminate the risk of damaging the device.

Although the above description has been made on the case where the hollow body W is a suspension insulator, the hollow body W is not limited to this, and a hollow body made of a brittle material which causes a rapid pressure drop at the time of breaking. Is widely applicable.

[0012]

As described above, according to the method and apparatus for testing the water pressure of a hollow body according to the present invention, the differential value of the internal pressure when the internal pressure reaches the set pressure within a predetermined time and the internal pressure decreases is obtained. Since the pass is determined only when the value does not exceed the set value, it is possible to reliably remove a delayed breakage product which was erroneously determined as a good product as a defective product from the line. For this reason, there is an advantage that there is no possibility that the fragments are conveyed to the subsequent process to damage the device as in the related art.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a graph showing a pressure waveform and an inverted differential waveform in the present invention.

FIG. 3 is a block diagram showing a conventional example.

FIG. 4 is a graph of a pressure waveform for a good product.

FIG. 5 is a graph of a pressure waveform for a defective product.

FIG. 6 is a graph of a pressure waveform for a delayed fracture product.

[Explanation of symbols]

W hollow body, 1 water tank, 2 pumps, 3 switching valves, 4 pressure gauges, 5 first comparing means, 6 process controller, 7 inspection head, 8 differentiating circuit, 9 second comparing means, 10 self-holding circuit

Claims (2)

[Claims] 1. A method for testing the water pressure of a hollow body in which the presence of a defect is checked by applying a water pressure to the inside of the hollow body, wherein the internal pressure reaches a set pressure within a predetermined time, and a differential value of the internal pressure does not exceed the set value. A method for testing the water pressure of a hollow body, wherein the method is determined to be acceptable only when the pressure is good. 2. A test head for applying a water pressure to the inside of a hollow body, a pressure gauge for detecting an internal pressure of the hollow body, and a first signal for outputting an OK signal when the detected internal pressure reaches a set pressure within a predetermined time. Comparing means, a differentiating circuit for calculating a differential value of the internal pressure,
A second comparing means for comparing a differential value of the internal pressure calculated by the differentiating circuit with a set value and outputting an NG signal when the differential value exceeds the set value; an OK signal and an NG signal; A water pressure inspection apparatus for a hollow body, comprising: a pass / fail determination means for determining a pass when no test is made.