X-ray or gamma ray systems or devices – Photographic detector support – For movable film or plate
Patent
1989-11-08
1991-12-17
Westin, Edward P.
X-ray or gamma ray systems or devices
Photographic detector support
For movable film or plate
378182, G03B 4202
Patent
active
050739166
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to apparatus for unloading and loading X-ray cassettes of the type having upper and lower parts for enclosing the film, which parts are moved apart to open position for unloading and loading film. More particularly, the invention relates to a novel method and apparatus for determining the loaded/unloaded condition of the cassette and the location of a film therein, as regards whether it is in the upper or lower part of the cassette, and whether a film of proper size is in the cassette. The novel apparatus in a preferred embodiment is mounted on parallelly movable guide members which engage the lateral edges of the cassette to position it, and which guide members also carry means for holding the cassette parts in open position, and air jet means for separating film from the upper cassette part.
Film location and presence or absence of film are determined by directing into each cassette part, when open, radiation harmless to the film that is, having no adverse effect on the film, such as a physical or chemical reaction, infrared radiation being preferred. The radiation is differentially reflected according to the presence or absence of film in that cassette part. Comparison of the radiation reflected from the respective cassette parts then indicates the presence or absence and location of film in the cassette.
BACKGROUND ART
An apparatus is known (DE-OS 33 06 720, U.S. Pat. No. 4,541,173) in which an X-ray film cassette is positioned between two parallelly guided bars pulled together by a tension spring and is transported by means of motor-driven rollers on a receiving plate towards an end abutment in a cassette unloading and reloading station. The bars have vertically shiftable claws at their free ends located in the area of the end abutment, said claws serving to open the locking means of the upper cassette portion, when the receiving plate and thus the X-ray film cassette are moved to an inclined position, as well as to hold down the lower cassette portion on said receiving plate.
An infrared-light sensor with an associated light-receiving element is arranged above the front area of the X-ray film cassette when said cassette is in its functional position, the infrared light rays of that sensor sensing a point on the inner surface of the lower cassette portion when the upper cassette portion is pivoted to its open position in order to ascertain whether a film sheet is present or not. If there is no film sheet present, the X-ray film cassette is fed out of the apparatus in its open condition.
This known apparatus is disadvantageous in that when the upper cassette portion is pivoted to its open position, the film sheet adheres to the inner surface of the upper cassette portion owing to static charges of the film sheet in surface-to-surface contact with the inner surface of the plastic lining of the upper cassette portion. The film sheet is only released after a period of time and then drops back into the lower cassette portion. If during the adherence of the film sheet to the upper cassette portion in its open position, the lower cassette portion is sensed by infrared light, no film sheet is detected in the lower cassette portion so that the X-ray film cassette in its open position along with the film sheet adhering to the upper cassette portion may be erroneously fed out. If several sensing operations were performed at intervals, with the last one ascertaining that a film sheet was present, having been released from the upper cassette portion in the meantime and dropped back into the lower cassette portion, this operation would take much too long.
If a film sheet of small size is erroneously loaded in an X-ray film cassette of large size the film sheet will be detected even if only one single point in the lower cassette portion is sensed. However the detection does not reveal whether it is of a size suitable for the X-ray film cassette.
Finally, the infrared-light sensor is arranged at a great distance above the X-ray film cassette. This remote arrangement of the i
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Baumann Kurt
Killguss Heinz
Mirlieb Bernd
Childress G. Herman
Chu Kim-Kwok
Eastman Kodak Company
Westin Edward P.
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