Incremental printing of symbolic information – Thermal marking apparatus or processes – Ink cassette or cartridge
Reexamination Certificate
1999-01-29
2001-02-27
Tran, Huan (Department: 2861)
Incremental printing of symbolic information
Thermal marking apparatus or processes
Ink cassette or cartridge
C400S207000, C400S208000, C400S208100, C400S249000
Reexamination Certificate
active
06195111
ABSTRACT:
This invention relates to thermal transfer printing and more particularly to a cassette casing for holding the thermal ribbon during storage and when in use in a thermal printer.
Thermal transfer printing is a generic term for processes in which one or more thermally transferable dyes are caused to transfer from a dye sheet to a receiver sheet in response to thermal stimuli. Using a dye sheet comprising a thin substrate supporting a dye coat containing one or more such dyes uniformly spread over an entire printing area of the dye sheet, printing can be effected by heating selected discrete areas of the dye sheet whilst the dye coat is pressed against a receiver sheet. The shape of the pattern transferred is determined by the number and location of the discrete areas which are subject to heating. Complex images can be built up from large numbers of very small pixels placed close together, the resolution of the final image being determined by the number, size and spacing of such pixels. Full colour prints can be produced by printing with different coloured dye coats sequentially in like manner. Usually, the dye sheet is in the form of a ribbon with the different coloured dye coats being in the form of discrete stripes transverse to the axis of the ribbon in a repeated sequence along the ribbon, printing of the three colours being effected by moving the dye ribbon, in a printer, axially relative to the receiver sheet and whatever means are used to generate the thermal stimuli such as a print head consisting of a plurality of tiny heaters or a laser beam.
Conventionally, the ribbon is rolled up and stored in a cassette which consists essentially of a pair of spools and a moulded casing in which the spools are rotatably mounted in parallel and spaced apart positions. Each spool has end portions, by means of which the spool is mounted in the casing and a bobbin portion on which the ink ribbon is wound, one of the spools acting as a feed spool and the other acting as a take-up spool.
Cassette casings typically comprise two parallel, hemi-cylindrical spool housings having end portions interconnected by bridge members such that the housing and bridge members together define an open access port through which the ink ribbon is exposed to the thermal stimuli as it extends from one spool to the other.
Such a cassette has the drawback that no information is provided to the printer about the type and/or characteristics of the ink ribbon contained therein, for example whether the ribbon is mono or polychromatic or about the heat sensitivity of the specific dyes in the ribbon.
It is known to provide an information mark on the outside of the cassette which can be read by a sensor in the printer on insertion of the cassette. However, the amount of information that can be made available is limited in dependence on the amount of movement of the cassette past the sensor unless the sensor itself is capable of movement, which arrangement would unnecessarily complicate the printer.
U.S. Pat. No. 5,385,416 discloses a way of solving this problem by providing the information mark on the peripheral surface of the feed spool. On insertion of the cassette into the printer, the feed spool is rotated sot hat the information mark passes by a sensor. The amount of information that can be made available is thus independent of the way in which the cassette is inserted.
As pointed out in U.S. Pat. No. 5,290,114, this arrangement has the disadvantage that a portion of the ribbon is of necessity unwound during the information reading operation and either this portion is wasted or must be rewound before printing can start.
According to U.S. Pat. No. 5,290,114, this disadvantage may be overcome by providing the feed spool with a coaxial shaft portion and mounting a ring bearing the information mark on said shaft portion so that it can be rotated independently of the feed spool itself by drive means located in the printer.
The cassette body may be designed so that it can be reloaded with dye ribbon by the end-user, thus saving on the usage of raw materials and providing both cost and environmental benefits.
However, the arrangement of U.S. Pat. No. 5,290,114 results in a complex spool manufacturing process and, if the cassette is of the reloadable type, excessive wastage of raw materials required for a code wheel on each feed spool.
According to the present invention there is provided a dye ribbon cassette for thermal transfer printing comprising a casing containing bearing means having rotatably mounted thereon a cylindrical member having on tis periphery a mark carrying information capable of being detected by a sensor on rotation of the member and means operatively engageable with a drive source which is disposed outside of said casing to cause rotation of the member.
The arrangement according to the invention has several advantages over the arrangement of U.S. Pat. No. 5,290,114. In U.S. Pat. No. 5,290,114, each assembly of dye ribbon and feed and take-up spools requires its own cylindrical information carrying member whereas in the arrangement of the invention only one per casing is needed giving a reduction in materials usage and costs. There is also the risk of the information carrying member of U.S. Pat. No. 5,290,114 being damaged by clumsy handling during loading of a dye ribbon into the casing which risk is obviated in the arrangement of the invention. Also, in the arrangement of the invention, the assembly of the dye ribbon on to the feed and take-up spools is simplified and there is less chance of errors occurring.
Clearly, the positional relationship of the information carrying member to the drive means and the sensor, which are located in the printer, is critical for correct operation. In the invention, the information carrying member is fixed in position during manufacture of the casing whereas in U.S. Pat. No. 5,290,114 reliance is placed the feed spool being correctly positioned during reloading by the user. As a consequence, to reduce the possibility of incorrect positioning, the feed spool must be manufactured to exact dimensions whereas wider tolerances are possible with the arrangement of the invention.
The arrangement of the invention allows the feed and take-up spools to be identical which means that the spent feed spool can be used as a take-up spool. This is not possible with the arrangement of U.S. Pat. No. 5,385,414 and in the case of U.S. Pat. No. 5,290,114 either feed and take-up spools must be supplied or the additional step of removing the information carrying member from the spent feed spool is necessary making it difficult for the end user to reload the cassette body with fresh dyesheet.
The information carrying member may be mounted so as to be co-axial with the feed spool. Alternatively, it may be offset which has the advantage that different positioning of the sensor and the drive means can be accommodated.
According to a preferred aspect of the invention, a pair of identical, spaced apart shafts are rigidly mounted at one end of the casing the cylindrical member being mounted on one of said shafts so as to be rotatable thereon, the shaft protruding therethrough and forming a mounting point for a feed spool.
Each shaft preferably has an axial bore therein through which passes a rod, a spring being positioned between the rod and an endwall of the casing so that the rod is capable of axial movement against the tension of the spring.
According to a further aspect of the invention, there is provided a cassette for thermal transfer printing comprising a casing comprising two parallel, hemi-cylindrical spool housings having end portions interconnected by bridge members, the housings and bridge members together defining an open access port, a feed spool and a take-up spool located in said housings with a dye ribbon extending therebetween so as to extend across the port, a pair of identical shafts rigidly mounted on one of the bridge members so as to extend along the axes of the spool housings, each shaft having an axial bore therein through which passes a spring-loaded, axially movable r
Burch Terence J
Hann Richard A
Nelson Anthony J
Orton Jeffrey B
Imperial Chemical Industries plc
Pillsbury Madison & Sutro LLP
Tran Huan
LandOfFree
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