Centrifugal apparatus with overspeed protection

• US 5,726,881 A
• Filed: 08/14/1995
• Issued: 03/10/1998
• Est. Priority Date: 08/17/1994
• Status: Expired due to Term

• Current Assignee: Hitachi KOKI Company Limited (Koki Holdings Co., Ltd.)
• Original Assignee: Hitachi KOKI Company Limited (Koki Holdings Co., Ltd.)
• Inventors: Kawanobe, Osamu, Watanabe, Shinji, Inaniwa, Masahiro, Niinai, Yoshitaka, Matsufuji, Noriyasu, Kido, Nobuharu
• Primary Examiner(s): Trammell, James P.
• Assistant Examiner(s): Wachsman, Hal D.
• Application Number:
  US08/514,814
• Time in Patent Office: 939 Days
• Field of Search: 318/462, 318/434, 318/439, 318/719, 318/799, 318/801, 318/254, 361/23, 361/51, 364/184, 364/132, 364/133, 364/187, 364/138, 364/141, 364/142, 364/174, 364/474.12, 364/474.3, 364/550, 364/551.01, 364/565, 364/566, 324/160-163, 324/167, 324/177, 73/335
• US Class Current: 700/79
• CPC Class Codes: B04B 13/003 Rotor identification systems
• CPC Class Codes: B04B 9/10 Control of the drive; Speed regulating for solid bowl screw centrifuges B04B1/2016
• CPC Class Codes: G05B 9/02 electric

Abstract

A centrifugal apparatus includes a rotor having a marker for generating an index signal, a motor for rotating the rotor, first and second detectors for detecting the index signal with rotation of the rotor to generate first and second detection signals, an input terminal for receiving supply power, a drive circuit for generating a drive signal from the supply power according to the first detection signal, and first and second switch circuits for controlling the supply of the drive signal to the motor. First and second judging portions are used to detect whether the first and second detection signals are respectfully generated within a given condition. The first judging portion operates the first switch circuit to stop the drive signal from being supplied to the motor when the first detection signal is not generated within the given condition, while said second judging portion operates the second switch circuit to stop the drive signal from being supplied to the motor when the second detection signal is not generated within the given condition. The first and second detectors, judging portions, and switch circuits, respectively, independently operate to provide double feedback loops, so that an overspeed or the like is prevented.

Claims

1. A centrifugal apparatus comprising:

rotor having marker means;

a motor operating responsive to a drive signal for rotating said rotor;

first detection means for detecting said marker means with rotation of said rotor and generating a first detection signal;

second detection means for detecting said marker means with said rotation of said rotor and generating a second detection signal;

an input terminal for receiving a supply power;

a drive circuit responsive to a command for generating said drive signal from said supply power in accordance with said first detection signal;

first and second switch circuits for controlling supply of said drive signal to said motor, said first and second switch circuits being provided in a route from said input terminal and said motor via said drive circuit;

first judging means for receiving said first detector signal and detecting whether said first detection signal is generated within a predetermined condition and for operating said first switch circuit to stop said drive signal from being supplied to said motor when said first detection signal is not generated within said predetermined condition; and

second judging means for receiving said second detection signal and detecting whether said second detection signal is generated within said predetermined condition and for operating said second switch circuit to stop said drive signal from being supplied to said motor when said second detection signal is not generated within said predetermined condition.

2. A centrifugal apparatus as claimed in claim 1, wherein said first and second judging means independently detect first and second rotation speeds from said first and second detection signals respectively, said first and second judging means independently detect whether said first rotation speed exceeds a predetermined value and whether said second rotation speed exceeds said predetermined value respectively, said first judging means controls said first switch to stop said drive signal from being supplied to said motor when said first rotation speed exceeds said predetermined value, and said second judging means controls said second switch to stop said drive signal from being supplied to said motor when said second rotation speed exceeds said predetermined value.

3. A centrifugal apparatus as claimed in claim 1, wherein said rotor is detachable from said motor and said marker means has information indicative of a kind of said rotor, said first and second judging means further detect said information from said first and second detection signals respectively and determine first and second maximum values in accordance with said detected information respectively, said first judging means operates said first switch to stop said drive signal from being supplied to said motor when said first rotation speed exceeds said first maximum value, and said second judging means operates said second switch to stop said drive signal from being supplied to said motor when said second rotation speed exceeds said second maximum value.

4. A centrifugal apparatus as claimed in claim 1, wherein said marker means comprises at least a magnet.

5. A centrifugal apparatus as claimed in claim 1, wherein said drive circuit comprises an inverter circuit for generating phase signals and a power bridge circuit for generating said drive signal from said phase signals and said first switch circuit is provided between said input terminal and said inverter circuit.

6. A centrifugal apparatus comprising:

rotor having marker means;

a motor operating responsive to a drive signal for rotating said rotor;

first detection means for detecting said marker means with rotation of said rotor and generating a first detection signal;

second detection means for detecting said marker means with said rotation of said rotor and generating a second detection signal;

an input terminal for receiving a supply power;

a drive circuit responsive to a command for generating said drive signal from said supply power in accordance with said first detection signal;

first and second switch circuits for controlling of supplying said drive signal to said motor, said first and second switch circuits being provided in a route from said input terminal and said motor via said drive circuit;

first judging means for receiving said first detector signal and detecting whether said first detection signal is generated within a predetermined condition and for operating said first switch circuit to stop said drive signal from being supplied to said motor when said first detection signal is not generated within said predetermined condition; and

second judging means for receiving said second detection signal and detecting whether said second detection signal is generated within said predetermined condition and for operating said second switch circuit to stop said drive signal from being supplied to said motor when said second detection signal is not generated within said predetermined condition;

wherein said drive circuit comprises an inverter circuit for generating phase signals and a power bridge circuit for generating said drive signal from said phase signals and said first switch circuit is provided between said input terminal and said inverter circuit; and

wherein said second switch circuit comprises photocouplers transmitting said phase signals to said power bridge circuit, a switch, and a power source for supplying a power to said photocouplers through said switch and said second judging means controls said second switch circuit to stop said drive signal from being supplied to said motor by controlling said switch when said second detection signal is not generated within said predetermined condition.

7. A centrifugal apparatus comprising:

rotor having marker means;

a motor operating responsive to a drive signal for rotating said rotor;

first detection means for detecting said marker means with rotation of said rotor and generating a first detection signal;

second detection means for detecting said marker means with said rotation of said rotor and generating a second detection signal;

an input terminal for receiving a supply power;

a drive circuit responsive to a command for generating said drive signal from said supply power in accordance with said first detection signal;

a first switch circuit for controlling supply of said supply power to said drive circuit;

a second switch circuit for controlling supply of said drive signal to said motor;

first judging means for receiving said first detector signal and detecting whether said first detection signal is generated within a predetermined condition and for operating said first switch circuit to stop said supply power from being supplied to said motor when said first detection signal is not generated within said predetermined condition; and

second judging means for receiving said second detection signal and detecting whether said second detection signal is generated within said predetermined condition and for operating said second switch circuit to stop said drive signal from being supplied to said motor when said second detection signal is not generated within said predetermined condition.

8. A centrifugal apparatus as claimed in claim 7, wherein said first and second judging means independently detect first and second rotation speeds from said first and second detection signals respectively, said first and second judging means independently detect whether said first rotation speed exceeds a predetermined value and whether said second rotation speed exceeds said predetermined value respectively, said first judging means controls said first switch to said supply power from being supplied to said drive circuit when said first rotation speed exceeds said predetermined value, and said second judging means controls said second switch to stop said drive signal from being supplied to said motor when said second rotation speed exceeds said predetermined value.