Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Lumped type parameters
Reexamination Certificate
2000-09-01
2003-01-07
Le, N. (Department: 2858)
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Lumped type parameters
C324S658000
Reexamination Certificate
active
06504387
ABSTRACT:
TECHNICAL FIELD
This invention relates to an arrangement for detecting/inspecting items prior to them being packaged, and has particular application to pharmaceutical items, such as tablets, pills, capsules and the like.
BACKGROUND OF THE INVENTION
Item inspection arrangements, for example for inspecting tablets to establish if they are whole or broken to some degree, are known which utilise the passage of the tablets between two plates of a single capacitor. This results in a change of capacitance and a corresponding signal which is processed to provide an indication of the result of each inspection.
It has however been established that an item
1
having a rectangular plan, when disposed between parallel capacitor plates
2
,
3
, produces a varying increase in capacitance as it is rotated about a vertical axis (FIG.
1
). Since the orientation of the item in space is random, there is a large error resulting from orientation. A secondary further effect disrupting the inspection is the ‘end’ effect, which reduces field density at the mid-point between the capacitor plates, compared to that nearer each plate. Accordingly the sensitivity to an item varies as the item is moved along a line perpendicular to the plates.
SUMMARY OF THE INVENTION
An object is to minimise or obviate these disadvantages by providing an improved detection/inspection arrangement.
An item detection/inspection arrangement of the invention comprises at least four capacitor plates arranged together in at least two pairs of opposing or generally opposing plates to provide, in use, at least two intersecting electric fields, items passing through said fields, in use, producing respective signals/pulses dependent on the changes of capacitance for the pairs of plates, and processing means for producing from said signals/pulses, detection/inspection data for said items.
As used herein, the reference to electric(al) fields ‘intersecting’ includes actual intersection i.e. by two or more fields which are together simultaneously in existence, and also spacial intersection, i.e. where the fields do not exist together at any time but, when they exist separately, are positioned in space (within the transducer) so that they would intersect if they did exist simultaneously. Accordingly it will be appreciated that the invention relates not only to the spacial intersections of the second embodiment described, where the plates are sequentially pulsed, but also to actual intersecting electric(al) fields as is the case with the first embodiment where the two pairs of plates are driven not in phase.
REFERENCES:
patent: 3965416 (1976-06-01), Friedman
patent: 4223751 (1980-09-01), Ayers et al.
patent: 4461363 (1984-07-01), Loy
patent: 4710757 (1987-12-01), Haase
patent: 5461319 (1995-10-01), Peters
patent: 5602486 (1997-02-01), Novak
patent: 5668309 (1997-09-01), Codina et al.
patent: 0 643 281 (1994-08-01), None
Motion of Charged particles in a Uniform electric Fields, p. 643, Physics for Scientist and Engineers, Third Edition.
Shail Kenneth Victor
Tolputt Stephen Adrian
Le N.
Nguyen Vincent Q.
Sparc Systems Limited
Wells St. John P.S.
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