Safety lid interlock circuit for centrifuges
AssigneeAmerican Home Products Corporation
InventorsGustavus W. Shaw, Raymond P. Walker
Life of this patent
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Abstract
The disclosure is directed to a lid latch concealed in a tamper-proof enclosure and a centrifuge interlock circuit which prevents the opening of the lid latch until the rotor has come to a full stop, and which requires electrical power to release the latch. Rotation is detected by a low level direct current applied through a sensing resistor to the brushes of the drive motor, after drive power to the motor has been cut off. Any rotation will cause rapid modulations of the current through the sensing resistor, which develop a corresponding signal voltage across the resistor. The signal voltage is amplified and applied to trigger a clamp circuit, which overrides a lid latch release device until rotary motion has ceased.
Claims5
In a centrifuge of the type having a housing retaining a lid in a closed position and an armature having brushes operatively connected to the rotating portions of the centrifuge, the improved combination comprising:
- a. a latch mounted on the housing;
- b. an enclosure mounted on the housing and adapted to surround the latch and render it tamper-proof in the closed position;
- c. a solenoid mounted on the housing and having a plunger and a spring to push said plunger into engagement with said latch when said solenoid is not actuated thereby preventing opening of said lid;
- d. means to actuate said solenoid thereby moving said plunger out of engagement with said latch and permitting opening of said lid;
- e. means to supply a current through the brushes of the armature;
- f. means to detect a signal and a signal so detected proportional to variations in the current flow through said brushes caused by rotation of the armature;
- g. a clamp circuit responsive to said signal to inactivate said solenoid actuating means thereby preventing opening of the lid when the armature is rotating,
- whereby the lid may not be opened when the armature is rotating regardless of whether the power is on or off.
In a safety device for a centrifuge of the type having a housing retaining a lid in a closed position and an armature having brushes operatively connected to the rotating portions of the centrifuge, the improved combination comprising:
- a. a first current source adapted to supply a current through the brushes of the armature;
- b. means to detect a signal so detected proportional to variations in the flow of current through the brushes;
- c. a second current source;
- d. a clamp circuit adapted to be triggered by said detected signal and to cut off the output of said second current source while said signal is being detected;
- e. a latch mounted on the housing;
- f. an enclosure mounted on the housing and adapted to surround the latch and render it tamper-proof in the closed position;
- g. a solenoid mounted on the housing and having a plunger urged into a first position in engagement with said latch, said solenoid being actuated by said second current source to move said plunger into a second position out of engagement with said latch when no signal is being detected whereby the lid can be opened when the armature is not rotating regardless of whether the power is on or off.
Dependencies are inferred from the claim text.