Method for detecting metallic foreign matter and system for detecting metallic foreign matter

• US 6,958,603 B2
• Filed: 09/19/2002
• Issued: 10/25/2005
• Est. Priority Date: 09/21/2001
• Status: Expired due to Fees

• Current Assignee: TOK Engineering Co., Ltd. (Tokyo OHKA Kogyo Company Limited)
• Original Assignee: TOK Engineering Co., Ltd. (Tokyo OHKA Kogyo Company Limited)
• Inventors: Kondo, Nobukazu
• Primary Examiner(s): Ledynh, Bot
• Assistant Examiner(s): Whittington, Kenneth
• Application Number:
  US10/250,582
• Publication Number:
  US 20040046550A1
• Time in Patent Office: 1,132 Days
• Field of Search: 324/239, 324/233, 324/228, 324/234, 324/236, 324/243, 324/225
• US Class Current: 324/239
• CPC Class Codes: G01N 27/82 for investigating the presence of flaws
• CPC Class Codes: G01V 3/104 using several coupled or uncoupled coils G01V3/101 takes precedence

Abstract

A metallic contaminant detecting method and apparatus according to the present invention detect metallic contaminants mixed in objects under inspection, such as food products, pharmaceuticals, and materials for industrial use, which are wrapped in electrically conductive packaging materials, e.g. aluminum. A small magnetic field is generated by applying a voltage to coils (10, 11) or supplying an electric current to the coils. A detection magnetic field generated from a metallic contaminant in response to the small magnetic field is detected as a detection voltage or a detection current of the coils (10, 11), and a detection signal is output. The detection signal is analyzed to detect the metallic contaminant. The small magnetic field is created by applying a small voltage or supplying a small electric current to the coils (10, 11) and using a non-linear portion of the magnetic field characteristics of cores constituting the coils (10, 11).

Claims

1. A metallic contaminant detecting method comprising the steps of:

conveying an inspection object contained in a package along a conveyance path to detect a metallic contaminant accidentally mixed in said inspection object during a manufacturing process; and

detecting step of detecting the metallic contaminant mixed in said inspection object by generating a magnetic field from a detecting element provided in an intermediate portion of said conveyance path, said detecting element having a coil comprising a core and a conductor wound around said core;

generating a small magnetic field by applying a voltage to said coil or supplying an electric current to said coil, and detecting a detection magnetic field generated from said metallic contaminant in response to said small magnetic field as a detection voltage or a detection current of said coil, and then outputting a detection signal;

analyzing said detection signal to identify said metallic contaminant, wherein said small magnetic field is created by applying a small voltage to said coil or supplying a small electric current to said coil and using a non-linear portion of magnetic field characteristics of said core constituting said coil; and

magnetizing said metallic contaminant in said conveyance path by a magnet booster comprising magnet elements before said metallic contaminant detecting step,

wherein said magnet booster comprises at least two constituent parts disposed at respective positions facing each other across said conveyance path, and

wherein said magnet elements forming said two constituent parts are disposed in such a manner that like magnetic poles thereof face toward said conveyance path.

2. The metallic contaminant detecting method according to claim 1, wherein said detecting element outputs said detection signal when said metallic contaminant affects said detection magnetic field to change a condition of said coil.

3. A metallic contaminant detecting apparatus comprising:

conveying means having a conveyance path for conveying an inspection object contained in a package to detect a metallic contaminant accidentally mixed in said inspection object during a manufacturing process;

metallic contaminant detecting means for detecting the metallic contaminant mixed in said inspection object by generating a magnetic field from a detecting element, provided in an intermediate portion of said conveyance path, said detecting element having a coil comprising a core and a conductor wound around said core;

detection signal outputting means for generating a small magnetic field by applying a voltage to said coil or supplying an electric current to said coil, and for detecting a detection magnetic field generated from said metallic contaminant in response to said small magnetic field as a detection voltage or a detection current of said coil and outputting a detection signal; and

a signal analyzing means for analyzing said detection signal to identify said metallic contaminant, wherein said small magnetic field is created by applying a small voltage to said coil or supplying a small electric current to said coil and using a non-linear portion of magnetic field characteristics of said core constituting said coil;

a magnet booster disposed in said conveyance path upstream of said metallic contaminant detecting means, said magnet booster comprising magnet elements,

wherein said magnet booster comprises at least two constituent parts disposed at respective positions facing each other across said conveyance path, and

wherein said magnet elements forming said two constituent parts are disposed in such a manner that like magnetic poles thereof face toward said conveyance oath.

4. The metallic contaminant detecting apparatus according to claim 3, wherein said detecting element outputs said detection signal when said metallic contaminant affects said detection magnetic field to change a condition of said coil.