INK CASSETTE AND INK TRANSFER ROLL THEREFOR

Abstract: In a cassette (3) for a printer unit, comprising an endless ribbon (9) to be provided with ink, means are provided for intermittently applying ink to said ribbon (9). These means for applying ink comprise a freely movable wheel (22) enclosed between the ink source (20) and the ribbon (9) and between connecting elements of housing and/or cover of the cassette.

Description: Printer apparatus is used more and more, as the use of (personal) computers has increased constantly over the past years. More and more development is aimed at obtaining ink cassettes which have a long and lasting life cycle, viz. are capable of printing more and more characters, and which are also easy to construct preferably with standardly available components. The present invention provides a cassette for a printer unit comprising: an endless ribbon to be provided with ink; at least one transporting member for transporting said ribbon and which is to be driven by said printer unit; ink applying means for applying ink onto said ribbon which ink applying means comprise one wheel which is rotatable by said ribbon. Such a cassette is known from US patent US-A-4.091.914 in which an intermediate wheel provided with a bearing is shown, which is suited for delayed replanishment of marking fluid to a ribbon. It is an object of the present invention to provide a cassette for printing many characters, at the same time preventing excessive local accumulation of ink on the ribbon which represents itself as a so-called hot spot on the paper. The cassette according to the present invention is characterized by an intermediate wheel which is enclosed between a housing and a cover of said cassette and which is freely moveable in a space defined by the outer periphery of said wheel and two or more connections extending between said housing and said cover. The ink cassette according to the present invention is capable of printing more than five million characters on paper without the blackness or reflection value on the paper falling to below 50% of the initial value. From US-A-4.493.572 a cassette is known, which is provided with an intermediate wheel which is rotatably mounted on one end of a lever, said lever being able to pivot about the other end of the lever against spring tension. Preferred embodiments according to the ink cassette according to the present invention are described in the sub-claims and relate e.g. to the relatively small rotation movement with which such cassette can be driven. Further advantages, features and details will be elucidated with reference to a drawing, in which: Fig. 1 shows a schematic, perspective view of a printer unit provided with a cassette according to a preferred embodiment of the present invention; fig. 2 is a partly broken away, enlarged top view of detail II from fig. 1; and fig. 3 is a perspective, partly broken away view of detail III from fig. 2. A printer unit 1, connected in a manner not shown to a computer, for example via cable 2, requires a cassette 3 provided with an ink ribbon, for example 13 mm in height, in order to enable a matrix head or other head of the printer unit to print particular characters on paper in ink. A cassette 3 (fig. 2) has a form dictated by the type of printer unit and comprises a housing- or bottom plate 4 usually of injection moulded plastic and provided with standing inner and outer edges 5 and 6 respectively. Fitting onto the housing 4 is a cover 7, likewise usually of injection moulded plastic; cover 7 is provided with co-moulded pins which fit into bushes 8 co-moulded with housing 4. A woven ribbon 9 made endless by means of a seam is moved along in the direction of arrow A by a transporting member which is for coupling to a drive member in the printer unit and which is formed by a toothed wheel 11, this wheel 11 being in engagement with a second toothed wheel 12. The second gear wheel 12 is pressed by means of a pin-like spring 10 against toothed wheel 11. After the ribbon 9 has passed through between the toothed wheels 11 and 12 it comes into the storage chamber 13 which in the present case makes up substantially half of the volume of the cassette, so as to be able to contain as much coiled and winding ribbon as possible. Clamped onto the ribbon at the exit to the ribbon chamber 13 is a leaf spring 14. The ribbon 9 is further trained along the small rollers 15 and 16 as well as along pins 17 and 18 and is turned over under a partition member 19, a so-called Möbius turn, in order to use the ribbon as long and as efficiently as possible. A roll 20 consisting of polyurethane foam (PUR) is mounted for rotation about a pin 21, is saturated with ink and forms an ink buffer for the purpose of applying ink to the ribbon in sufficient but not excessive measure during the printing of five million characters. If tension is exerted on the ribbon 9 in the direction of arrow A, that is, when the toothed wheel 11 exercises a force on the ribbon, a freely movable roll 22 is pressed against the ink roll 20; during transport of the ribbon 9 the intermediate roll 22, because of its rough surface, turns with the movement of the ribbon and likewise sets the ink roll 20 into motion. During this rotary movement ink transfer from ink roll 20 to intermediate roll 22 takes place. The intermediate roll 22 is preferably made of plastic and ribbed in the direction perpendicular to fig. 2. The ribbing on intermediate roll 22 preferably takes a slightly hook-shaped or asymmetrical form in order to bring about a (still) better gripping on the ribbon during transport of this ribbon in the direction of arrow A. Through intermediate roll 22 is prevented that when ribbon 9 is at standstill, that is when printing onto the paper is taking place, too much ink is applied locally to the ribbon, which after further transport will result in smudgy print work. The intermediate roll 22 only takes up ink from the ink wheel when the ribbon is being transported, while the ink roll thereby also rotates, so that there takes place an immediate and uniform transfer from ink roll 20 to intermediate roll 22 and therefore to ribbon 9. In the case of the preferred embodiment of the ink cassette according to the present invention shown in fig. 2 and 3, transport of the ribbon 9 is performed lightly and using simple means. The pin-like spring 10 is fixed in position in the housing between a protrusion 30 in the bottom of the housing and a standing portion 31, is bent over a protrusion 32 on the inner edge 5 and clamped against a bearing 33 on the second toothed wheel 12. The latter is furnished on its end with pins 34, one of which is shown, which are received into slots 35 in both the bottom and the cover 7 of the housing, the slot in a cover being visible in fig. 3. The spring 10 in co-action with the slots 35 and the second toothed wheel 12 in this way provides a constant press-on force on the first gear wheel 11. This toothed wheel 11 is provided with a ribbed control knob 36 for manual operation of this toothed wheel. Arranged for toothed wheel 11 on the underside of the cassette is a drive opening for engagement to a drive member of the printer unit. The toothed wheel is driven at the moment that the matrix head carries ink over onto the paper so that at the time the matrix head is not applying ink to the paper the ink is being transported out of the storage area 13 in the vicinity of the leaf spring 14. Since the ribbon is pressed firmly between the first and second gear wheels 11 and 12, ribbon transport is carried out precisely and the first gear wheel need be driven only with small turning moment, for instance 180 cNcm - the inner diameter of the first gear wheel amounts for example to 1.5 cm. Furthermore the press-on force of the intermediate roll 22 on the PUR roll 20 is determined by the tension in the ribbon, which results in this press-on force not becoming subject to wear of the ink roll 20 and intermediate roll 22. It should be apparent that the shown preferred embodiment according to the present invention not only enables printing onto paper of a large number of characters with sufficient blackness, but also effects this with extremely simple and economically realisable means.

Claims: 1. A cassette (3) for a printer unit (1) comprising: an endless ribbon (9) to be provided with ink; at least one transporting member (11, 12) for transporting said ribbon and which is to be driven by said printer unit, ink applying means (22) for applying ink onto said ribbon which ink applying means comprise one wheel (20) which is rotatable by said ribbon, characterized by an intermediate wheel (22) which is enclosed between a housing (4) and a cover (7) of said cassette and which is freely moveable in a space defined by the outer periphery of said wheel (20) and two or more connections (8, 16) extending between said housing (4) and said cover (7). 2. A cassette (3) according to claim 1, provided with two toothed wheels (11, 12) contacting each other, and between which the ribbon is transported, wherein one toothed wheel (11) is driveable from the printer unit and in which a spring (10) exerts a substantial constant force on a moveable second toothed wheel (12) in contact with the toothed wheel (11) driveable from the printer unit. 3. A cassette (3) according to claim 1 or 2, provided with a partition member (19) for turning over the ribbon (9). 4. A cassette (3) according to claims 1, 2 or 3, wherein the intermediate wheel (22) is ribbed. 5. A cassette according to any of the claims 1-4, provided with an infeed compartment in which the wheel (20) of the ink applying means and the intermediate wheel (22) are provided.

Inventors: RAAR, HANS
Applicants: MERLIN C.T.C. PRODUCTION DIVISION NEDERLAND B.V.
Application year: 1988
Main classification: B41J31
IPC codes: B41J31