Overspeed control for centrifuge

Claim 2

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.

Claim 3

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

Claim 4

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.

Claim 5

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.

Claim 6

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.

Claim 7

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.

Claim 8

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.

Claim 9

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.

Claim 10

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

Claim 11

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

Claim 12

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.

Claim 13

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

Claim 14

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.

Claim 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 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.

Claim 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 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.

Claim 17

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.

Claim 18

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.

Claim 19

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.

Claim 20

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.