INK RIBBON CASSETTE

Abstract: An ink ribbon cassette includes a case, supply side core rotatably held by the case and having an uneven portion in a portion thereof, an ink ribbon wound on the core, a take-up side core rotatably held by the case to take up the ink ribbon, and a spring resiliently engaged with the uneven portion of the supply side core and resiliently pressing the outer periphery of the ink ribbon wound on the supply side core.

Description: This invention relates to an ink ribbon cassette as specified in the preamble of claim 1 , for example as disclosed in US-A-4 422 592. This document discloses a braking means which brakes the ink ribbon in accordance with the diameter of the supply spool. This breaking means is adjustable and, corresponding to this purpose, has a plurality of components. Thus, the construction of this braking means is to be considered as relatively complicated. In contrast thereto, the invention has the underlying object to create a braking means according to the preamble of patent claim 1, which is constructed as simple as possible and which has a low number of components so that the assembly is simple and the production costs are low. As a matter of fact, the quality that the ink ribbon on the supply spool is steadily wound off via a constant force shall be retained. This object is solved by the features indicated in the characterizing part of patent claim 1. According to the invention, the plurality of components is substantially replaced by a single component, namely the hairpin spring. Figure 1 is a perspective view of a printer in which is mounted an ink ribbon cassette according to an embodiment of the present invention. Figure 2 is an illustration of a partly broken-away plane of the ink ribbon cassette according to an embodiment of the present invention. Figure 3 is a cross-sectional view of a supply side ribbon spool. A printer in which is mounted an ink ribbon cassette 7 according to an embodiment of the present invention is comprised of an operating unit 1 and a printing mechanism unit 2, as shown in Figure 1. The printing mechanism unit 2 comprises a platen 3, a printing carriage 5 and a driving portion 6 therefor. A character wheel 8, a printing hammer 9 and the ink ribbon cassette 7 for supplying ink are mounted on the printing carriage 5. Figure 2 shows the details of the ink ribbon cassette. The cassette is divided into a take-up side A engaged with the printing carriage to take up the ink ribbon and a supply side B for supplying the ink ribbon so as not to interfere with the taking-up and printing operations. The cassette is comprised of a lower case 11 and an upper case 12, and various portions to be described are contained in the space therebetween. A central supply side core 14 is rotatably fitted in a rotating boss 13 provided in the lower case 11, and the ink ribbon 15 is wound on the supply side core 14 to thereby form a supply spool 16. The peripheral surface of that portion of the supply side core 14 which is lower than the portion thereof on which the ink ribbon is wound is formed with a knurled uneven portion 14a for controlling the amount of unwinding of the supply spool 16. A first arm 17a of a detent spring 17 fixed to the lower case 11 by the restraining portion 11a thereof is resiliently engaged with the knurled uneven portion 14a, and a second arm 17b of the detent spring 17 is resiliently urged against the outermost periphery of the supply spool 16. The ink ribbon 15 drawn out through such a detent mechanism is further biased by the arm 18a of a tension spring 18 for eliminating any slack of the ink ribbon, and is taken up by a take-up core 21 via guides 19 and 20. The take-up core 21 is rotatably provided on the tip end of a take-up lever 23 pivotable about a shaft 22. The take-up lever 23 is biased by a plate spring 24 toward ribbon feeding teeth 25 rotatably held between the upper case 12 and the lower case 11. Minute needles project around the ribbon feeding teeth 25 and penetrate into the take-up core 21 or the ink ribbon wound on the core 21 and thus, it becomes possible to take up the ink ribbon onto the take-up core 21 by rotating a manually operated knob 26 in the direction of arrow D, the knob 26 being fixed coaxially with the ribbon feeding teeth 25 and partly exposed from the upper case 12. As the ribbon is taken up onto the core 21, the winding diameter of the take up spool is increased. Figure 3 shows a cross-section of the supply spool. As can be seen in this Figure, the knurled uneven portion 14a of the supply side core 14 at the lower end thereof is greater in diameter than the portion of the central core on which is the ribbon is wound and accordingly, the ribbon winding position becomes stable when the ribbon is wound onto this supply side core 14. In the above-described embodiment, the first arm 17a of the detent spring 17 is engaged with the knurled uneven portion 14a of the supply side core 14 to impart back tension to the ribbon, and further the second arm 17b presses the peripheral surface of the supply spool 16 to impart back tension so as to ensure the supply spool 16 to be drawn out with the same torque. Also, back tension is further imparted to the ink ribbon by the tension spring 18. The present invention is not restricted to the above-described embodiment, but for example, the tension spring 18 may be eliminated. Also, the ink ribbon drawn out toward the guide 19 may be passed over the second arm 17b of the detent spring, and the second arm 17b may be caused to perform the function of the arm 18a of the tension spring 18. Thereby, the number of parts is reduced. In the present invention, as described above, not only a detent force is imparted to the central core of the supply spool by the detent spring, but also a pressure force is imparted to the peripheral surface of the supply spool, whereby back tension can be effectively imparted to the supply spool by a small number of parts, thus stabilizing the draw-out of the ribbon.

Claims: An ink ribbon cassette, comprising an ink ribbon braking means (17) in the form of a two-arm lever, the one arm of which is operatively connected to a supply side core (14) and the other arm of which contacts the outer edge of an ink ribbon (15) wound on a supply spool (16) characterized in that said two-arm lever is formed by a hairpin spring (17a, 17b), the first arm (17a) of which engages in a knurled uneven portion (14a) of said supply side core (14) and the second arm (17b) of which presses against the outer peripheral surface of said ink ribbon (15) wound on said supply spool (16). An ink ribbon cassette according to claim 1, wherein said cassette has a lower case (11) and an upper case (12). An ink ribbon cassette according to claim 2, wherein the moving range of said first arm (17a) of said hairpin spring (17a, 17b) is limited by a locking portion (11a) provided on said lower case (11). An ink ribbon cassette according to one of the claims 1 to 3, wherein said knurled uneven portion (14a) is provided on a lower circumference of said supply side core (14). An ink ribbon cassette according to one of the claims 1 to 4, wherein said ink ribbon is wound onto a winding core (21), said taken out from said supply spool (16) and wound onto a winding core (21) is biased by an arm portion (18a) of a tension spring (18) to remove the slack in a course from said supply spool (16) to said winding core (21). An ink ribbon cassette according to one of the claims 2 to 5, wherein said ink ribbon is wound onto a winding core (21) by manually rotating a manually-operated nob (26) partially exposed from said upper case (12). An ink ribbon cassette according to one of the claims 1 to 6, wherein said supply spool (16) is formed by winding said ink ribbon onto a supply side core (14). An ink ribbon cassette according to one of the claims 2 to 7, wherein said supply spool (16) is formed by inserting said supply side core (14) into a boss provided on said lower case (11) winding said ink ribbon onto said supply side core (14). A printer for recording on a recording medium comprising: a mounting section (5) for mounting thereon an ink ribbon cassette (7) having ink ribbon braking means in the form of a two-arm lever, the one arm of which is operatively connected to a supply side core (14) and the other arm of which contacts the outer edge of an ink ribbon (15) wound on a supply spool (16), said two-arm lever being formed by a hairpin spring (17a, 17b) and the first arm (17a) thereof engaging in a knurled uneven portion (14a) of said supply side core (14) and the second arm (17b) thereof pressing against the outer peripheral surface of said ink ribbon (15) wound on said supply spool (16); and recording means (5, 6) for effecting said ink ribbon (15) of said ink ribbon cassette (7) mounted on said mounting section (5) to record on a recording medium. A printer according to claim 9, wherein said recording means has a character wheel (8) and a printing hammer (9). A printer according to claim 9, wherein said mounting section has a printing carriage (5) and said printing carriage is movable by a driving portion (6).

Inventors: SHIMOYAMA, NOBORU
Applicants: CANON KABUSHIKI KAISHA
Application year: 1986
Main classification: B41J33
IPC codes: B41J33, B41J32