Ribbon cassette

Abstract: The present invention provides a cassette (2) for a printer unit (1) comprising: an endless ribbon; means for transporting the ribbon; and means (7) causing the ribbon to move reciprocally comparatively slowly in a direction substantially transversely of the direction of movement of the ribbon. The moving means preferably comprise a (gradually) camming track (7), the driving (4,5,6) of which is coupled to the transporting means for the ribbon.

Description: Ribbon cassettes are used for printing characters using a printer unit such as a typewriter or a printer unit coupled to a (micro)computer, wherein the number of characters for printing with one cassette for the printer unit is of great importance. Such a cassette is a disposable product of plastic and therefor has an environmental impact. Although laserjet and inkjet printing becomes more fashionable, such printing is expensive and therefor a high demand remains for inexpensive printed (or typed) matter showing high quality. The present invention relates to a cassette for a printer unit provided with a printer head, a drive shaft and a contact surface, said cassette comprising: an endless ribbon to be transported in a first direction; transporting means for transporting the ribbon in said first direction; and pivot pins for pivotally mounting said cassette. Such a cassette is known from US-A-4,854,027 which shows a cassette for a printing unit provided with specially designed projecting means to be inserted into the cassette such as to operate certain mechanisms inside the cassette and operate a stepwise shifting mechanism for the ribbon of the cassette. The present invention has for its object to improve upon the cassette above mentioned and known from the prior art, so that the ribbon thereof is used as optimally as possible. The cassette according to the present invention is characterized in: a reducing transmission which is suitable for driving engagement with said drive shaft; a cam disc provided on said reducing transmission; arms provided with said cassette and extending beyond the printer head; and a swivel member located for oscillation between said arms, the arrangement being such that in operation said cam disc causes said cassette to pivot relatively slowly, while said swivel member continuously pushes against said contact surface and said relatively slow pivoting movement is in a plane perpendicular to said first direction. Due to the reciprocating movement of the cassette, i.e. the ribbon, this ribbon, and therefor the cassette, is used as optimally as possible and has a longer life span. The printer unit does not require any special provisions for this optimal use of the ribbon. Preferably the ribbon is of non-woven synthetic material, such as polyester, to which material the ink is coated. For improving printing quality matrix printing units make use of an increasing number of printing pins, viz. 24, 36 or even 48. Using such high number of pins the weaving structure of nylon ribbon becomes apparent on paper, which therefor has an adverse effect on such printing quality. More finely woven nylon ribbon is hard to find and very expensive. It is expected that a cassette with a ribbon 12 mm wide and 5 m of length will be able to print 2.5 million characters on paper with substantially constant darkness. Because of the reciprocal movement of the ribbon all characters maintain the same degree of darkness over the height thereof, even such characters as g,l,y etc which show a projection from the central part of the ribbon. For a 20 mm wide ribbon (length 5 m) the number of characters is expected to reach 3.5 million. According to the preferred embodiments of the cassette of the present invention - see subclaims 2, 4 and 5 - the construction is very compact, while it remains completely compatible with non-reciprocating or non-jogging cassettes. The printing unit remains unchanged while a higher umber of characters for each cassette is obtained. Further advantages, features and details of the present invention will become apparent in the light of a description of a preferred embodiment thereof with reference to the annexed drawing, in which: Fig. 1 shows a perspective, partially broken away view of a printer unit with a preferred embodiment of a cassette according to the present invention; fig. 2 is a side view of the cassette of fig. 1; and fig. 3 is a view in perspective and partly broken away of the cassette of fig. 1 (and 2). A printer unit 1 (fig. 1) is provided with a cassette 2 of which arms 23, 24 extend beyond a printing head 25. The cassette 2 (fig. 2) is driven by means of a shaft or pin 3 from the printer unit 1. Gear wheels 4, 5, 6 form a reducing transmission of the drive shaft 3 to the last mentioned gear wheel on which is arranged a cam disc or plate 7. The gear wheels 4, 5, 6 are arranged partly one above the other because of the limited space available in the embodiment shown according to the present invention. Cassette 2 is further provided with pivot pins 8, of which only one is visible in fig. 2, in addition to a swivel member 9 which is movable between the position drawn with full lines and the position drawn with broken lines. During this movement brought about by the curve track 7 the whole cassette 2 is moved around the pivot points 8 between the position drawn with full lines and the position drawn with broken lines. The swivel or pivoting member 9 herein pushes against a contact surface 10 forming part of the printer unit. In the view of the cassette shown in perspective in fig. 3 can further be seen a mask 11 received between the arms 23 and 24 which is provided with a relatively large window 12 in order to be able to accommodate the movement of cassette 2. The pivotally attached member 9 can be swivelled between the arms 23 and 24 and can thus be placed in a packaging that does not need to be any higher than the thickness of the cassette. The swivel member 9 is preferably held in its active position by means of a spring 13. A cassette according to the present invention is preferably used with a ribbon of so-called matrifilm or plastic carbon, wherein, in contrast to nylon ribbon, ink is not continually applied to the ribbon at each loop thereof. Tests with such ribbon in an ink cassette according to the present invention have demonstrated the probability that with the cassette according to the present invention 50% more characters can be printed without special provisions being required therefor in the printer unit. It is noted that the present invention is not limited to the embodiment shown and described. The curved track on the disc can e.g be provided with one or abrupt transitions in the curved surface. This feature is expected to further increase printing quality.

Claims: A cassette (2) for a printer unit (1) provided with a printer head (25), a drive shaft (3) and a contact surface (10), said cassette comprising: an endless ribbon to be transported in a first direction; transporting means for transporting the ribbon in said first direction; and pivot pins (8) for pivotally mounting said cassette, characterized by: a reducing transmission (4, 5, 6) which is suitable for driving engagement with said drive shaft (3); a cam disc (7) provided on said reducing transmission; arms (23, 24) provided with said cassette and extending beyond the printer head (25); and a swivel member (9) located for oscillation between said arms (23, 24), the arrangement being such that in operation said cam disc (7) causes said cassette (2) to pivot relatively slowly, while said swivel member (9) continuously pushes against said contact surface (10) and said relatively slow pivoting movement is in a plane perpendicular to said first direction. A cassette (2) according to claim 1, wherein said cam disc is formed as a camming track. A cassette (2) according to claim 1 or 2, wherein said endless ribbon comprises a non-woven plastic material. A cassette (2) according to claim 1, 2 or 3, further comprising a spring (13) for biasing said swivel member. A cassette according to any one of claim 1-4, further comprising: a mask (11) received between said arms; and a window (12) provided in said mask which has a sufficient width to accommodate the movement of said cassette about said pivot axis.

Inventors: RAAR HANS, RAAR, HANS
Applicants: MERLIN CTC PROD, MERLIN C.T.C. PRODUCTION DIVISION NEDERLAND B.V.
Application year: 1992
Main classification: B41J35
IPC codes: B41J35, B41J31, B41J32, B41J33