Wire rope flaw detection device

Patent metadata

Field	Value
Publication number	US-10514362-B2
Application number	US-201515766160-A
Country	US
Kind code	B2
Filing date	Nov 2, 2015
Priority date	Nov 2, 2015
Publication date	Dec 24, 2019
Grant date	Dec 24, 2019

Abstract

Provided is a wire rope flaw detector including a magnetizer configured to form a main magnetic flux in a part of a wire rope in a longitudinal direction thereof. A plurality of search coils are configured to detect a leakage flux that occurs from a damaged part of the wire rope in a segment in which the main magnetic flux is formed. A control unit is configured to detect induced voltages generated in the plurality of search coils. Further, the control unit is configured to superimpose voltage waveforms of the plurality of search coils on one another while shifting the voltage waveforms by a time calculated based on an interval between the plurality of search coils adjacent to each other and on a relative moving speed of the wire rope with respect to the magnetizer, to thereby amplify a peak of the induced voltage.

First claim

The invention claimed is:

1. A wire rope flaw detector, comprising:
a magnetizer, which is configured to form a main magnetic flux in a part of a wire rope in a longitudinal direction of the wire rope;
a plurality of search coils, which are arranged with an interval so as to be spaced apart from one another in the longitudinal direction of the wire rope, and are configured to detect a leakage flux that occurs from a damaged part of the wire rope in a segment in which the main magnetic flux is formed; and
a control unit, which is configured to detect induced voltages generated in the plurality of search coils, wherein:
the plurality of search coils are adjacent to each other with an interval of a half of a pitch between indentations of strands of the wire rope due to twisting of the strands; and
the control unit is configured to superimpose voltage waveforms of the plurality of search coils on one another while shifting the voltage waveforms by a time calculated based on the interval between the plurality of search coils adjacent to each other and on a relative moving speed of the wire rope with respect to the magnetizer, to thereby amplify a peak of the induced voltage.

2. The wire rope flaw detector according to claim 1 , wherein the control unit is configured to use, as an evaluation index S(t) of whether or not the damaged part exists, the following expression:

S
⁡

(
t
)

=

∑

k
=
1

m

⁢

V
k

(

t
-

P
v

⁢

(

m
-
k

)

)

where m being an integer equal to or larger than 2 represents a number of the plurality of search coils, P represents an installation interval of the plurality of search coils, ν represents the relative moving speed of the wire rope with respect to the magnetizer, and V 1 (t), . . ., V m (t) represent the induced voltages generated in the respective plurality of search coils in order from an upstream side of the wire rope in a moving direction of the wire rope.

3. The wire rope flaw detector according to claim 2 , wherein m is equal to 2.

4. A wire rope flaw detector comprising:
a magnetizer, which is configured to form a main magnetic flux in a part of a wire rope in a longitudinal direction of the wire rope;
a plurality of search coils, which are arranged with an interval so as to be spaced apart from one another in the longitudinal direction of the wire rope, and are configured to detect a leakage flux that occurs from a damaged part of the wire rope in a segment in which the main magnetic flux is formed; and
a control unit, which is configured to detect induced voltages generated in the plurality of search coils, wherein:
the control unit is configured to superimpose voltage waveforms of the plurality of search coils on one another while shifting the voltage waveforms by a time calculated based on the interval between the plurality of search coils adjacent to each other and on a relative moving speed of the wire rope with respect to the magnetizer, to thereby amplify a peak of the induced voltage;
the plurality of search coils are connected to one another in series in order in terms of a moving direction of the wire rope; and
the control unit is configured to store V(t) for a fixed time period, and to use, as an evaluation index S(t) of whether or not the damaged part exists, the following expression:

S
⁡

(
t
)

=

∑

k
=
1

m

⁢

V
(

t
-

P
v

⁢

(

k
-
1

)

)

where V(t) represents a voltage generated between terminals of ones of the plurality of search coils that are located at both ends of the wire rope in the moving direction, each of the terminals being not connected to an adjacent one of the plurality of search coils, m being an integer equal to or larger than 2 represents a number of the plurality of search coils, P represents an installation interval of the plurality of search coils, and ν represents the relative moving speed of the wire rope with respect to the magnetizer.

5. The wire rope flaw detector according to claim 4 , wherein:
the plurality of search coils are connected to one another in series in order in terms of the moving direction of the wire rope; and
the control unit is configured to cause an amplitude response of a frequency response to waveform processing performed with V(t) as input and S(t) as output to have a local minimum point within a frequency range expressed by the following expression:

v
P

⁢

(

1
m

+
α

)

±

v

4
⁢
P

where V(t) represents a voltage generated between terminals of ones of the plurality of search coils that are located at both ends of the wire rope in the moving direction, each of the terminals being not connected to an adjacent one of the plurality of search coils, m being an integer equal to or larger than 2 represents a number of the plurality of search coils, P represents an installation interval of the plurality of search coils, ν represents the relative moving speed of the wire rope with respect to the magnetizer, α represents an integer, and S(t) represents an evaluation index of whether or not the damaged part exists,
S(t) being a su

Assignees

• Mitsubishi Electric Corp

Inventors

• Yoshioka Takashi
• Kotera Takayuki
• Hirota Kazuaki
• Hoshinoo Tomokazu
• Takahashi Fumitake
• Akashi Masao
• Seki Tetsuro

Classifications

• G01N27/83 Primary

  by investigating stray magnetic fields · CPC title

• G01N27/87 Primary

  using probes · CPC title

• G01N27/82 Primary

  for investigating the presence of flaws · CPC title

• B66B7/1215

  specially adapted for ropes or cables · CPC title