High speed capacitance apparatus for classifying pharmaceutical capsules
First Claim
1. Apparatus for checking the relative masses of a plurality of capsules or the like comprising a capacitance-sensing transducer including a pair of spaced capacitor plates, and pneumatic means for individually moving said capsules one at a time between said plates.
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Abstract
A dielectric tube, such as glass or plastic, having a square cross section extends between the two plates of a capacitance-sensing transducer. The opposite sides of the tube have a spacing only slightly greater than the diameter of the capsules to be checked. The capsules to be classified are oriented prior to their introduction into the tube so that they enter in an end-to-end relationship. The requisite spacing between the capsules is accomplished by an air jet device that rapidly accelerates the leading capsule as it enters the tube to such a velocity that it leaves the transducer before the next capsule enters, thereby assuring that only one capsule is in the transducer at any given moment. The capacitance-sensing transducer is repeatedly charged and discharged by means of a high frequency oscillator circuit. Capacitance variations from capsule to capsule are measured on a continuous analog basis and logic signals derived from such analog signals are used to determine whether a given capsule should be accepted or rejected. A reject mechanism diverts each bad capsule from the stream of acceptable or good capsules.
88 Citations
25 Claims
- 1. Apparatus for checking the relative masses of a plurality of capsules or the like comprising a capacitance-sensing transducer including a pair of spaced capacitor plates, and pneumatic means for individually moving said capsules one at a time between said plates.
- 7. Apparatus for checking the relative weights of a plurality of capsules comprising a capacitance-sensing transducer including a pair of spaced plates, a tube of dielectric material extending between said plates, means for feeding said capsules in an end-to-end relation into one end of said tube, and means for propelling said capsules one at a time through said tube so that only one capsule is between said plates at any given moment.
- 15. Apparatus for checking the relative weights of elongated capsules comprising a capacitor including a pair of spaced plates, means for charging and discharging said capacitor, means for advancing each capsule between said plates in an end-to-end and sufficiently separated relation so that only a single capsule is between said plates at any given movment, means connected to said plates for providing an electrical analog signal representative of the capacitance of each capsule as it is advanced between said plates, comparator means controlled by portions of said analog signal for providing output signals representative of those capsules which are unacceptable, and means controlled by the output signals from said comparator means for rejecting said unacceptable capsules.
- 19. Apparatus for checking the relative weights of capsules comprising a capacitive transducer through which said capsules are successively passed, means providing analog signals representative of changes in the capacitance of said capsules and hence changes in the weight thereof, first, second and third comparators each having first and second input terminals and an output terminal, said first input terminals being connected to said analog signal providing means, first, second and third potentiometers, said first potentiometer being connected to the second input terminal of said first comparator for providing a relatively low set point value, said second potentiometer being connected to the second input terminal of said second comparator for providing an intermediate set point value, said third potentiometer being connected to the second input terminal of said third comparator for providing a relatively high set point value, first, second and third AND logic elements each having first, second and third input terminals and an output terminal, said first input terminals of said AND logic elements being connected to the output terminal of said first comparator, a first inverter connected between the output terminal of said second comparator and the second input terminal of said first AND logic element, a second inverter connected between the output terminal of said third comparator and the third input terminal of said first AND logic element, said output terminal of said second comparator also being connected to the second input terminals of said second and third AND logic elements, said third input terminal of said second AND logic element connected to said second inverter between said second inverter and the third input terminal of said first AND logic element, said output terminal of said third comparator also being connected to the third input terminal of said third AND logic element, whereby an output signal appears at the output terminal of said first AND logic element when said analog signal reaches said relatively low set point value, whereby an output signal appears at the output terminal of said second AND logic element when said analog signal reaches said intermediate set point value, and whereby an output signal appears at the output terminal of said third AND logic element when said analog signal reaches said relatively high set point value, and means connected to the output terminals of said first and third AND logic elements for rejecting a capsule as a result of signals appearing on either of the output terminals of said first and third AND logic elements.
Specification