EP0234254B1

EP0234254B1 - Inked ribbon cartridge equipped with a ribbon end detecting mechanism

Info

Publication number: EP0234254B1
Application number: EP19870100657
Authority: EP
Inventors: Shigeru C/O Nec Corporation Kikkawa
Original assignee: NEC Corp
Current assignee: NEC Corp
Priority date: 1986-01-21
Filing date: 1987-01-20
Publication date: 1990-10-31
Also published as: EP0234254A1; DE3765790D1

Description

BACKGROUND OF THE INVENTION

The present invention relates to an inked ribbon cartridge for use in a serial printer, and more particularly to a ribbon end detecting mechanism for an inked ribbon cartridge.
An inked ribbon cartridge of this kind is attached to a carrier unit of a serial printer which includes a print head so that an inked ribbon of the cartridge is supplied to the print head for purpose of printing. The inked ribbon cartridge has a supply spool around which the inked ribbon not yet used is wound and a take-up spool for taking up the inked ribbon from the supply spool such that the inked ribbon passes in front of the print head. Since the printer cannot help stopping the printing operation when all of the inked ribbon of the supply spool has been taken up to the take-up spool, it is necessary to detect a ribbon end of the inked ribbon.
The conventional ribbon end detecting mechanism is disclosed in U.S. Pat. No. 4,115,013, wherein an optical sensor is provided for detecting the ribbon end by sensing a reflective material attached thereto. In this mechanism, the extra manufacturing process is required to attach the reflective material to the ribbon end, with the result that the manufacturing cost of the inked ribbon cartridge is increased. Further, since the optical sensor is employed, the output thereof is disturbed by the dust arising from the inked ribbon and adhering to the optical sensor and the reflective material.
The other ribbon end detecting mechanism is disclosed in Japanese Patent Disclosure No. Sho 56(1981 )-77181. This mechanism has a detecting lever which is urged to an outer circumferential surface of the inked ribbon wound around the supply spool. The detecting lever rotates in response to the decrease of the diameter of the inked ribbon around the supply spool, and then actuates a ribbon end switch to turn on when the diameter becomes smaller than a predetermined length. Since the detecting lever always presses the supply spool via the wound inked ribbon, this mechanism has a shortcoming that the supply spool is deflected with respect to a supply spool supporting member by the detecting lever. Accordingly, the supply spool is subject to an excess friction from the spool supporting member, and its rotational stability is degraded. As a result, an irregular and excess tension arises in the inked ribbon fed by the take-up spool so that the irregular and excess tension often cuts the inked ribbon.
Similar disadvantages shows the mechanism according to Patent Abstracts of Japan, Vol. 4, No. 41 (M-5) (523) (JP-A 5 511 805) which relates to a converting system of ink ribbon winding direction. To convert the winding direction, an ink ribbon winding device comprises near-end detecting levers which always contact the outside of the ribbon wound on the ribbon spools of said ink ribbon winding device. The levers are urged against the outside of the ink ribbon by the action of a respective spring. When the amount of the ribbon remaining on either of the ribbon spools becomes little, the near-end detecting levers operate microswitches linked with these levers and stop the motion of the driving ribbon spool, and start driving the other spool. No stopper means are provided for holding the lever, so that the lever which is urged by a spring always presses against the ribbon spool via the wound inked ribbon.
EP-A-2 0 008 279 relates to a removable cartridge for typewriter inked ribbon and the relative typewriter, wherein said cartridge encloses two superimposed or juxtaposed step by step rotating spools for unwinding from a spool and rewinding to the other spool an inked ribbon. This cartridge comprises a follower resting on an outer circumferential surface of the wound inked ribbon. As the diameter of the wound ribbon increases, the follower rotates around an axis until to a specific point where the follower snaps to the other side. By this action, the winding direction of the ribbon is converted. One of the levers is always urged to the outer circumferential surface of said wound inked ribbon since no stopper means is provided.
It is an object of the present invention to provide an inked ribbon cartridge equipped with a ribbon end detecting mechanism capable of detecting an ribbon end of an inked ribbon with high reliability and capable of feeding the inked ribbon without damaging it.
This object is solved with the features of claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a plan view of an inked ribbon cartridge to a first embodiment of the present invention;
Fig. 2 is a plan view of the inked ribbon cartridge shown in Fig. 1 with a cover opened;
Figs. 3, 4 and 5 are sectional side views of the inked ribbon cartridge shown in Fig. 1 take along the lines III-III, IV-IV and V-V of the Fig. 1, respectively;
Fig. 6 is a perspective view showing a ribbon end detecting mechanism used in the inked ribbon cartridge shown in Fig. 1;
Figs. 7 and 8 are perspective views showing a tension mechanism used in the inked ribbon cartridge shown in Fig. 1;
Figs. 9A and 9B are perspective views of the inked ribbon cartridge shown in Fig. 1 attached on a carrier unit;
Fig. 10 is a plan view of an inked ribbon cartridge according to a second embodiment of the present invention;
Fig. 11 is a plan view of the inked ribbon cartridge shown in Fig. 10 with a cover opened; and
Figs. 12, 13 and 14 are sectional side views of the inked ribbon cartridge shown in Fig. 10 taken along the lines XII-XII, XIII-XIII and XIV-XIV of Fig. 10, respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to Figs. 1 and 2, an inked ribbon cartridge 100 of a first embodiment comprises a base housing 1 having a base plate 1a and side walls 1 b rectangularly extending from the outline of the base plate 1a. A cover plate 2 covers over the base housing 1. Two arm portions 3s and 3t extend upward in the figures to guide a film inked ribbon 4 to a printing position 4p. A feed pulley 5 and a pulley portion 6a of a take-up spool 6 project out of the cover plate 2, which are connected in rotation by a feed belt 7. A rotary shaft 5a of the feed pulley 5 extends in the housing 1 and integrally provided with a drive roller 8. The rotary shaft 5a is connected to a motor M provided on a carrier unit 101 on which the ribbon cartridge 100 is attached to receive a rotary force thereof as shown in Fig. 9A.
An idle roller 10 is rotatably supported by a roller holder 9 via an rotary shaft 10a. The roller holder 9 is supported by a guide member 11 and a guide hole 12 to slide thereon. The guide member 11 is integrally formed with the base housing 1 and the guide hole 12 is penetrated through the cover plate 2. The idle roller 10 is urged to the drive roller 8 by means of a spring 13 via the roller holder 9 so that it rotates together with the drive roller 8.
As also shown in Fig. 3, a separating plate 14 is located in the housing 1 by stads 15a and 15b to form upper and lower linked ribbon spaces 16u and 16£ separated thereby. The upper space 16u is used for storing used inked ribbon 4b wound around the take-up spool 6 and the lower space 162 is for the inked ribbon 4a not yet used wound around a supply spool 17. Further, the inside of the inked ribbon cartridge 100 is divided into an upper stage portion U and a lower stage portion L. The supply spool 17 is rotatably supported by an outer circumference of a hollow rotary shaft 18 standing on the substantially central portion of the base plate 1a of the housing 1. The take-up spool 6 has a shaft portion 6b extending to the base plate 1a for rotatably engaging an inside of the hollow shaft 18. Thus, the rotary axis A of the supply spool 17 is the same as that of the take-up spool 6. The diameters of the supply spool 17 and the take-up spool 6 are 20 mm and 18 mm, respectively. As well known, terminal ends of the inked ribbon are secured to the supply spool 17 and the take-up spool 6.
The inked ribbon 4a not yet used is led to an tension mechanism which comprises a tension roller 18, a tension lever 19 and a tension spring 20 as also shown in Fig. 7. The tension lever 19 is rotatably supported by a rotary shaft 19a integrally formed on the base plate 1a. A free end of the tension lever 19 is rotatably provided with the tension roller 18 around which the inked ribbon 4a engages. The tension spring 20 is wound around the shaft 19a and secured to the side wall 1 b and the tension lever 19 at its ends, respectively, to supply rotary force to the tension lever 19 in the clockwise direction in Fig. 2. As shown in Fig. 8, a brake shoe 19b may be provided to press the inked ribbon 4a onto the roller 18.
The inked ribbon 4a from the supply side engages the tension roller 18 and is bent toward the arm portion 3s. As also shown in Fig. 4, guide protuberances 21 s are formed on the base plate 1a to guide the inked ribbon 4a so as to gradually run apart from the base plate 1 a. That is, the inked ribbon 4a is guided upward and leftward in Fig. 4 from the lower stage portion L to the upper stage portion U by the guide protuberances 21 s, and then runs out of an opening of the arm portion 3s to reach the printing position 4p.
Subsequently, the inked ribbon 4b used at the printing position 4p enters through an opening of the arm portion 3t. The inked ribbon 4b is guided to run in the upper stage portion U by guide protuberances 21t. Next, the inked ribbon 4b engages a first guide post 22 and a second guide post 23 and passes between the drive roller 8 and the idle roller 10 both having notches therearound. Then, the inked ribbon 4b further engages a third guide post 24 and reaches to the take-up spool 6.
When the rotary force is supplied to the drive roller 8, the drive roller 8 rotates in the counterclockwise direction in Fig. 2 to feed the inked ribbon 4 from the supply spool 17 to the take-up spool 6. The take-up spool 6 is also rotated in the counterclockwise direction via the feed pulley 5, the feed belt 7 and the pulley portion 6a to wind the inked ribbon 4b therearound. Owing to the tension lever 19, the adequate and regular tension is applied to the inked ribbon 4 in a ribbon feed path.
A ribbon end detecting mechanism will be now described in reference further to Figs. 5 and 6. The ribbon end detecting mechanism includes a detect lever 25 provided with a detect roller 26 at one end of the upper stage portion U. The detect lever 25 is rotatably provided around a shaft 25a which stands on the base plate 1 a. The other end 25b of the detect lever 25 contacts one end 27b of a actuating lever 27 which is rotatably supported by a rotatry shaft 27a formed on the side wall 1 b. The actuating lever 27 engages one end of a spring 28 the other end of which is connected to a protuberance 29 of the base plate 1a so that the spring 28 supplies a rotary force to the actuating lever 27 in the counterclockwise direction in Fig. 5. The rotary force of the spring 28 is also applied to the detect lever 25 via the end 27b of the actuating lever 27. A stopper 30 is provided to stop the rotation of the detect lever 25 in the clockwise direction in Fig. 2. The actuating lever 27 further has an actuating tip 27c to actuate a switch SW of the carrier unit 101 when the detect lever 25 is moved in the counterclockwise direction in Fig. 2 to turn the actuating lever 27 in the clockwise direction in Fig. 5. A window 31 is formed on the base plate 1a to permit the projection of the actuating tip 27c out of the inked ribbon cartridge 100.
Referring back to Fig. 2, the radius Rs of the wound inked ribbon 4a around the supply spool 17 from the rotary axis A is 38 mm in the initial state. The detect lever 25 is stopped by the stopper 30 such that the distance R_r between the rotary axis A and the outer circumferential surface of the detect roller 26 is set by 36 mm. Thus, the detect roller 26 does not contact the outer circumferential surface of the inked ribbon 4b wound around the take-up spool 6 when a radius R_t of the wound inked ribbon 4b around the take-up spool 6 is smaller than 36 mm. When the radius R_t is greater than 36 mm, the outer surface of the wound inked ribbon 4b comes to contact with the detect roller 26 and enables the detect lever 25 to rotate around the shaft 25a in the counterclockwise direction in Fig. 2 in accordance with the increase of the radius Rt. The detect lever 25 moves the actuating lever 27 in the clockwise direction in Fig. 5. When the radius R_t becomes more than 38 mm, the actuating tip 27c of the lever 27 makes the switch SW turn on to inform that almost all of the inked ribbon 4 is taken up by the take-up spool 6 as shown in Fig. 9B. It is noted that a predetermined amount of the inked ribbon 4a not yet used is left in the supply side in this state so that the printing operation can be continued at least for one line or one page.
Since the detect lever 25 and roller 26 do not press the supply spool 17 for detecting the ribbon end, the supply spool 17 does not subject to an excess friction from the rotary shaft 18, and thus can rotate smoothly. As a result, the inked ribbon 4 is prevented from cutting off. Further, the detect roller 26 does not contact the outer surface of the wound inked ribbon 4b around the take-up spool 6 until the radius R_t of the inked ribbon 4b becomes a predetermined amount (36 mm). Accordingly, the take-up spool 6 does not subject to a excess pressure, which makes the friction between the shaft portion 6b and the rotary shaft 18 increase, while the radius Rt is smaller than the predetermined amount. Consequently, the take-up roller 6 rotates without deflecting and the inked ribbon 4b can regularly be wound around the take-up spool 6.
Figs. 10 to 14 illustrate a second embodiment of the present invention in which the same elements in these figures bear the same reference numerals as in Figs. 1 to 9 and explanation thereof is omitted. The inked ribbon 4 is much wound around the take-up spool 6 than the supply spool 17. In this embodiment, the ribbon end detecting mechanism includes a detect lever 35 rotatably supported around a shaft 35a and provided with a detect roller 36. The detect lever 35 is located near the idle roller 10 and has a actuating tip 35c engageable to the switch SW by the rotation in the clockwise direction in Fig. 11. A window 41 is provided on the side wall 1b for permitting the projection of the actuating tip 35c. The detect lever 35 is supplied with a rotary force in the counterclockwise direction by a spring 38. The detect lever 35 is prevented from rotating in the counterclockwise direction by a stopper portion 40 of the side wall 1 where the window 41 is formed. When the detent lever 35 engages the stopper portion 40, the distance R_r' between the detent roller 36 and the rotatary axis A is the same as the first embodiment, i.e., 36 mm. When the radius R_t of the wound inked ribbon 4b becomes 38 mm, the switch SW is turned on. In this embodiment, since the detent lever 35 directly actuates the switch SW, the acuating lever 27 of the first embodiment can be omitted.
Further in the second embodiment, the take-up spool 6 has a disk member 6c integrally formed therewith to guide winding of the inked ribbon 4b around the take-up spool 6, instead of the separating plate 14 of the first embodiment.
As described above, according to the present invention, the reliable detection of the ribbon end can be carried out without disturbing the ribbon feeding operation.

Claims

1. An inked ribbon cartridge (100) having a ribbon end detecting mechanism (25, 26, 27; 35, 36) including a movable member (25, 26; 35, 36) engageable to an outer circumferential surface of a wound inked ribbon (4), around a take-up spool (6) and actuating a ribbon end detecting switch (SW) when a radius (Rt) of the wound inked ribbon is greater than a first value, characterized by stopper means (30; 40) for holding said movable member in a position apart said take-up spool, so that said movable member (25, 26; 35, 36) engages said outer surface of said wound inked ribbon (4) after said radius (Rt) is greater than a second value (Rr), which is slightly smaller than said first value.

2. An inked ribbon cartridge (100) according to claim 1 to be mounted on a carrier unit (101) of a serial printer, comprising supply and take-up spools (17 and 6) rotatably supported by a housing (1), wherein said inked ribbon (4) is wound around said supply and take-up spools and terminal ends of said inked ribbon are secured to said supply and take-up spools; drive means (8) to be coupled with a motor means (M) provided on said carrier unit to receive a rotary force therefrom for feeding said inked ribbon from said supply spool to said take-up spool, said drive means engaging said take-up spool to transmit said rotary force thereto to enable said take-up spool to wind said inked ribbon fed by said drive means whereby said radius (R_t) of the wound inked ribbon around said take-up spool is gradually increased; wherein said ribbon end detecting mechanism (25, 26; 35, 36) is disposed on an outer circumference of said take-up spool so as to move in response to a change of said radius.

3. The inked ribbon cartridge as claimed in claim 2, wherein said supply and take-up spool (17 and 6) is rotatably supported by said housing (1) around the same rotary axis (A).

4. The inked ribbon cartridge as claimed in claim 2 or 3, wherein said housing includes an upper stage 'portion (U) where said take-up spool is provided and a lower stage portion (L) where said supply spool is provided.

5. The inked ribbon cartridge as claimed in claim 4, wherein said housing (1) further includes guide protuberances (21) for guiding said inked ribbon from said lower stage portion (L) to said upper stage portion (U).

6. The inked ribbon cartridge as claimed in any of claims 2 to 5, wherein said housing (1) is provided with a tension mechanism (18, 19, 20) for applying a tension to said inked ribbon between said supply spool and said take-up spool.