Patent Application
20060146111
The present invention relates generally to an apparatus and method for thermally processing an imaging media, and more specifically to an apparatus and method for thermally developing an imaging media employing a replaceable sleeve positioned about a rotatable member.
Photothermographic film generally includes a base material, such as a thin polymer or paper, typically coated on one side with an emulsion of dry silver or other heat sensitive materials. Once the film has been subjected to photostimulation (exposed), for example, by light from a laser of a laser imaging system, the resulting latent image is developed through application of heat to the film. To produce a high quality image, controlling heat transfer to the photothermographic film during the development process is critical. If heat transfer is not uniform, visual artifacts such as non-uniform density and streaking may occur.
Several types of thermal processors have been developed in efforts to achieve optimal heat transfer to exposed photothermographic film during processing. One type employs a rotating heated drum having multiple pressure rollers positioned around a segment the drum's circumference to hold the film in contact with the heated drum during development. Another type of processor, commonly referred to as a flat-bed processor, employs multiple transport rollers spaced to form a generally horizontal transport path that moves the photothermographic film through an oven. Both the heated drum and the transport rollers of the flatbed processor have surfaces which may be coated with a thin polymer coating which contacts and assists in transporting the photothermographic film through the processor during development.
As the photothermographic is heated during development, some types of emulsions produce gases that include contaminants which can condense and become deposited on surfaces within the processor. Over time, these and other contaminants can accumulate on the polymer-coated surfaces of the drums and rollers and potentially cause visual defects in the developed image. Consequently, the processors require regular cleaning to remove such deposits from the surfaces of the drums and rollers.
During the cleaning process, a qualified technician generally applies solvents to the surfaces of the drums and rollers to dissolve and remove the deposits. However, due to inherent variations in such a procedure, one portion of the surface of a drum or roller may be more thoroughly cleaned than another portion of the surface during a single cleaning process, and the thoroughness of the cleaning may vary from one cleaning process to the next. Such variations in the cleaning process can result in inconsistencies in the quality of the images produced by the thermal processors. Such a cleaning process can be also be costly and result in processor downtime, and solvents employed in the cleaning process sometimes produce undesirable odors, resulting in complaints from customers and technicians alike. Furthermore, in situations where an entire drum is replaced, associated heaters must be recalibrated in order to operate properly.
It is evident that there is a need for improving thermal processors, particularly drum type processors, to reduce problems associated with routine maintenance.
In one embodiment, the present invention provides a thermal processor for thermally developing an image in an imaging material, the thermal processor including an oven and at least one rotatable member positioned within the oven. A sleeve is adapted to slidably fit over and selectively couple to at least a portion of the rotatable member, the sleeve having an exterior surface coated with a layer of polymer material. The sleeve is positioned such that the layer of polymer material contacts the imaging material and transports the imaging material through the oven as the at least one rotatable member rotates.
In one embodiment, the present invention provides a thermal processor including an enclosure forming an oven, a heated drum for thermally developing an image in an imaging media, wherein the heated drum positioned at least partially within the oven, and a drive system for rotating the heated drum. The thermal processor further includes a tubular sleeve adapted to slidably fit over and selectively couple to at least a portion of an outer surface of the heated drum. The tubular sleeve has an exterior surface substantially coated with a polymer material and is positioned such that the polymer material contacts and transports the imaging media through the oven as the heated drum rotates.
By providing a removable sleeve coated with a layer of polymer material, the layer of polymer material can be replaced upon becoming contaminated with byproducts released by the imaging media during development by installing a new sleeve. Installation of a new sleeve eliminates problems associated with cleaning the integral polymer surfaces of standard processing drums, such as image defects resulting from nearly inherent variations in the cleanliness of the polymer material after cleaning and undesirable odors associated with cleaning solvents. Furthermore, replacement of the sleeve can be completed more quickly than cleaning the integral polymer surfaces of standard processor drums, thereby reducing labor associated with maintenance and processor downtime. Also, since the drum is not being replaced, calibration of associated heaters is not required.
The foregoing and other objects, features, and advantages of the invention will be apparent from the following more particular description of the embodiments of the invention, as illustrated in the accompanying drawings. The elements of the drawings are not necessarily to scale relative to each other.
To provide sufficient heat transfer from circumferential heater 42 to polymer material layer 50, tubular sleeve 50 comprises a material having high thermal conductivity characteristics. In one embodiment, tubular sleeve 48 comprises a metallic material, such as nickel. In order to improve heat transfer from processor drum 44 to polymer material layer 50, the wall thickness 54 of tubular sleeve 48 should be as thin as possible. However, the wall thickness 54 of tubular sleeve 48 must also be able to provide structural stability to tubular sleeve 48 so that it can be handled and installed without damage. Thus, in one embodiment, tubular sleeve has a wall thickness 54 sufficiently thin to enable heat transfer from the heated drum 44 to polymer material layer 50 to develop imaging media and sufficiently thick to provide structural stability. In one embodiment, tubular sleeve 48 has wall thickness 54 of about 0.005 inches. Further embodiments of tubular sleeve 48 are described below by
Returning to
An upper condensation trap 82, lower condensation trap 84, and duct 86 form a portion of contaminant removal system 40. As illustrated by the dashed lines in
During operation, circumferential heater 42 heats drum 44 and tubular sleeve 48 to a temperature necessary to provide a uniform development temperature to the imaging media being developed. For photothermographic medical film, for example, drum 44 and tubular sleeve 48 operate at a temperature of approximately 122.5° C. Feed rollers 75 receive and feed a piece of exposed imaging media, such as imaging media 100, to media guide 76 which channels imaging media 100 to drum 44 and sleeve 48. As exposed imaging media 100 contacts polymer layer 50, the rotation of drum 44 and sleeve 48 draws exposed imaging media under pressure rollers 52 and transfers exposed imaging media 100 from entrance region 68 to exit region 74. As imaging media 100 reaches exit region 74, film diverter 78 directs imaging media 100 from polymer layer 50 to cooling region 36.
As imaging media 100 wraps around tubular sleeve 48 and is transported toward exit region 74, imaging media 100 begins to be heated to the desired development temperature. Photothermographic film, such as imaging media 100, generally comprises a base material, such as a thin polymer or paper, which is typically coated on one side with an emulsion of heat sensitive materials. To obtain a more uniform development temperature, the emulsion side of imaging media 100 is in contact with polymer layer 50 of tubular sleeve 48. As the emulsion is heated, it produces gasses containing contaminants, fatty acids (FAZ) in particular, which may subsequently condense and collect on surfaces within enclosure 56.
In efforts to remove these contaminants, vacuum system 90 draws air into oven 62 from entrance region 68 and produces upper and lower air streams 110 and 112 around drum 44 and tubular sleeve 48. Upper air stream 110 is drawn into upper condensation trap 82 via duct 86 and lower air stream 112 is drawn in lower condensation trap 84, wherein the gasses are mixed with ambient air and subsequently condense.
While contaminant removal system 40 is effective at removing contaminants, at least some of the contaminants produced by the emulsion during the development process remain within enclosure 48. Over time, these contaminants collect on surfaces within enclosure 64, particularly polymer layer 50 of tubular sleeve 48 which is in direct contact with the emulsion, and can result in damage to processor components and in visual defects in developed image of imaging media 100. Consequently, regular maintenance is required to remove accumulated contaminants from thermal processor 30.
Unlike standard thermal processors, however, which require a qualified technician to manually clean the integral polymer surfaces of standard processing drums, a technician maintaining thermal processor 30 according to the present invention simply removes and replaces a used tubular sleeve 48 with a new tubular sleeve 48. Thus, tubular sleeve 48 of thermal processor 30 in accordance with the present invention, substantially eliminates potential image defects resulting from variations in the cleaning process and reduces and/or eliminates the occurrence of undesirable side effects associated with use of cleaning solvents. Furthermore, replacement of tubular sleeve 48 can be completed more quickly than cleaning the integral polymer surfaces of standard processor drums, thereby reducing labor associated with maintenance and processor downtime. Also, since process drum 44 s not being replaced, calibration of associated heaters is not required.
In one embodiment tubular sleeve 46 comprises a material having a rate of thermal expansion lower than a rate of thermal expansion of processor drum 44. In one embodiment, tubular sleeve 46 comprises nickel. In one embodiment, tubular sleeve 46 comprises a polycarbonate material. In one embodiment processor drum 44 comprises aluminum. As such, during operation, as thermal processor 30 is heated to a desired processing temperature by circumferential heater 42, an exterior diameter processor drum 44 expands at a rate greater than an interior diameter of tubular sleeve 46. As the temperature of processor drum 44 and sleeve 46 approach the desired processing temperature, the exterior surface of processor drum 44 expands to a diameter such that processor drum 44 engages and “captures” tubular sleeve 48 by creating a pressure fitting between itself and tubular sleeve 48. Tubular sleeve 48 and processor drum 44 are then in “intimate” contact with one another such that tubular sleeve 48 is interlocked with and rotates with processor drum 44 as it is driven by drive system 34. As such, in the embodiment illustrated generally by
As illustrated by
As illustrated by
During operation, feed rollers 275a and 275b receive and feed a piece of exposed imaging media 300 to media guide 276. Media guide 276 in-turn channels exposed imaging media 300 into oven 262 via entrance 268. Polymer layer 250 contacts exposed imaging media, and the rotation 246 of rollers 244 and tubular sleeves 248 transport the exposed imaging media 300 through oven 262 along a sinusoidal-like transport path 280. As imaging media 300 travels along transport path 280 through oven 262, it is heated to the desired development temperature and, in the process, produces contaminants that over time can accumulate on surfaces within enclosure 256. In particular, these contaminants can accumulate on polymer layers 250 of tubular sleeves 248, which are in direct contact with imaging media 300. In a fashion similar to that described above by
By providing a removable sleeve coated with a layer of polymer material, the layer of polymer material can be replaced upon becoming contaminated with byproducts released by the imaging media during development by installing a new sleeve. Installation of a new sleeve eliminates problems associated with cleaning the integral polymer surfaces of standard processing drums, such as image defects resulting from nearly inherent variations in the cleanliness of the polymer material after cleaning and undesirable odors associated with cleaning solvents. Furthermore, replacement of the sleeve can be completed more quickly than cleaning the integral polymer surfaces of standard processor drums, thereby reducing labor associated with maintenance and processor downtime. Also, since the drum is not being replaced, calibration of associated heaters is not required.
All documents, patents, journal articles and other materials cited in the present application are hereby incorporated by reference.
The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.
