OVERSPEED CONTROL FOR CENTRIFUGE

• US 3,582,699 A
• Filed: 06/12/1969
• Issued: 06/01/1971
• Est. Priority Date: 06/12/1969
• Status: Expired due to Term

• Current Assignee: Rosario S. Badessa, Santis Italo J De
• Original Assignee: Rosario S. Badessa, Santis Italo J De
• Inventors: Badessa, Rosario S., SANTIS ITALO J DE
• Application Number:
  US04/832,776
• Time in Patent Office: 719 Days
• US Class Current: 388/809
• CPC Class Codes: B04B 13/003 Rotor identification systems
• CPC Class Codes: H02H 7/09 against over-voltage; against reduction of voltage; against phase interruption
• CPC Class Codes: H02H 7/093 against increase beyond, or decrease below, a predetermined level of rotational speed centrifugal switches H01H35/10
• CPC Class Codes: Y10S 388/903 Protective, e.g. voltage or current limit
• CPC Class Codes: Y10S 388/916 Threshold circuit
• CPC Class Codes: Y10S 388/93 Load or torque
• CPC Class Codes: Y10S 388/933 Radiant energy responsive device

Abstract

The centrifuge overspeed control disclosed herein facilitates the use of different rotors having different maximum speeds and automatically limits the rotational speed of the centrifuge to an appropriate level. As the rotor rotates, an optical pickup derives timing signals from first and second indicia carried by the rotor and deenergizes the centrifuge if the interval between successive timing signals drops below a predetermined value.

Claims

1. In a centrifuge adapted to employ different rotors having respective predetermined maximum speeds and having a drive means which is energized to rotate a selected one of said rotors, apparatus for limiting the rotational speed of the centrifuge comprising:

a respective means associated with each rotor carrying at least first and second indicia, the angular separation between the first and the second being substantially proportional to the predetermined maximum speed for the corresponding rotor;

sensing means for providing a pulse signal each time one of said indicia passes a preselected angular position as the rotor rotates;

means for generating a timing signal of predetermined duration in response to each of said pulse signals; and

means for deenergizing said drive means to stop the centrifuge rotor is pulse signals generated by the second of said indicia occur within the duration of timing signals initiated by the first of said indicia.

2. Apparatus as set forth in claim 1 wherein said sensing means comprises an optical pickup including a lamp and a photodetector.

3. Apparatus as set forth in claim 2 wherein said first and second indicia are carried by a disc which rotates with the respective rotor and which is adapted to direct light from said lamp to said photodetector except when one of said indicia passes the pickup.

4. Apparatus as set forth in claim 3 wherein said disc has a substantially reflective surface and said indicia are slots which interrupt said surface and break the light path between said lamp and said photodetector.

5. Apparatus as set forth in claim 3 including means for stopping the centrifuge if the average light level sensed by said photodetector falls below a preselected level.

6. Apparatus as set forth in claim 3 wherein said means for providing a pulse signal includes a trigger circuit having an operating threshold which varies in response to variations in the amplitude of the signal provided by said photodetector.

7. Apparatus as set forth in claim 1 wherein said means for generating a timing signal includes a monostable multivibrator which is triggered by said pulse signals.

8. Apparatus as set forth in claim 7 wherein said means for providing a pulse signal includes a monostable multivibrator having an operating period which is relatively short with respect to the predetermined duration of the timing signal provided by the first said multivibrator.

9. Apparatus as set forth in claim 1 including means for stopping the centrifuge if said pulse signal is not provided repetitively.

10. Apparatus as set forth in claim 1 wherein said means for deenergizing said drive means operates to stop the centrifuge.

11. Apparatus as set forth in claim 1 wherein said means for deenergizing said drive means comprises a gate for combining said pulse signals and said timing signals to generate an overspeed pulse signal when one of the first said pulse signals occurs within the duration of a previously initiated timing signal.

12. Apparatus as set forth in claim 11 including means for stopping the centrifuge if said overspeed pulses are generated repetitively.

13. Apparatus as set forth in claim 1 including means for dividing said pulse signal by a number equal to the number of indicia on each rotor thereby to provide a signal having a frequency equal to the rotational speed of the rotor.

14. In a centrifuge adapted to employ different rotors having respective predetermined maximum speeds and having a drive means which is energized to rotate a selected one of said rotors, apparatus for limiting the rotational speed of the centrifuge comprising:

a respective means associated with each rotor carrying at least first and second indicia, the angular separation between the first and the second being substantially proportional to the predetermined maximum speed for the corresponding rotor;

means, including a first one-shot multivibrator, for providing a pulse signal of predetermined duration each time one of said indicia passes a preselected angular position as the rotor rotates;

means, including a second one-shot multivibrator, for generating a timing signal of predetermined duration in response to each of said pulse signals; and

means, including an AND gate for combining said pulse and timing signals, for deenergizing said drive means to stop the centrifuge Rotor if pulse signals generated by the second of said indicia occur within the duration of timing signals initiated by the first of said indicia.

15. In a centrifuge adapted to employ different rotors having respective predetermined maximum speeds and having a drive means which is energized to rotate a selected one of said rotors, apparatus for limiting the rotational speed of the centrifuge comprising:

a light source;

a photodetector;

a respective means associated with each rotor carrying at least first and second indicia, the angular separation between the first and the second indicia being substantially proportional to the predetermined maximum speed for the corresponding rotor, said indicia carrying means being adapted to pass light from said source to said photodetector except when one of said indicia passes a predetermined angular position;

means controlled by said photodetector for providing a pulse signal each time one of said indicia passes said predetermined angular position as the rotor rotates;

means for generating a timing signal of predetermined duration in response to each of said pulse signals;

means for preventing operation of the centrifuge if the average amount of light reaching said photodetector is below a predetermined level; and

means for deenergizing said drive means to stop the centrifuge rotor if pulse signals generated by the second of said indicia occur within the duration of timing signals initiated by the first of said indicia.

16. In a centrifuge adapted to employ different rotors having respective predetermined maximum speeds and having a drive means which is energized to rotate a selected one of said rotors, apparatus for limiting the rotational speed of the centrifuge comprising:

a light source;

a photodetector;

a respective means associated with each rotor carrying at least first and second indicia, the angular separation between the first and the second indicia being substantially proportional to the predetermined maximum speed for the corresponding rotor, said indicia carrying means being adapted to pass light from said source to said photodetector except when one of said indicia passes a predetermined angular position;

means controlled by said photodetector for providing a pulse signal of predetermined duration each time one of said indicia passes said predetermined angular position as the rotor rotates;

means for generating a timing signal of predetermined duration in response to the trailing edge of each of said pulse signals; and

means for deenergizing said drive means to stop the centrifuge rotor if pulse signals generated by the second of said indicia occur within the duration of timing signals initiated by the first of said indicia.