Paper guide mechanism for serial printer

Abstract: A paper guide mechanism for a serial printer wherein print paper can be prevented from being soiled by contact thereof with an ink ribbon or an ink ribbon guide plate while also leaping out of the ink ribbon through a printing hole of the ink ribbon guide plate is prevented. A paper guide plate (2) is disposed in such a manner as to assure a gap from a print head (4) so that the ink ribbon (5) may not leap out readily from the printing hole (14) of the ink ribbon guide plate (3) mounted on the paper guide plate (2). The paper guide plate (2) is so shaped that, when the ink ribbon guide plate (3) is mounted on the paper guide plate (2), the ink ribbon guide plate (3) presents a concave configuration toward the platen (1) so as to prevent contact between the ink ribbon guide plate (3) and print paper as far as possible.

Description: This invention relates to a paper guide mechanism for a serial printer including an ink ribbon guide plate and a paper guide plate by which print paper is kept from being soiled by an ink ribbon. Conventionally, a paper guide plate and an ink ribbon guide plate mounted on the paper guide plate are generally flat in sectional view. The ink ribbon guide plate is set in a gap between a platen and a print head. If the gap between the print head and the ink ribbon guide plate is made comparatively large, the ink ribbon guide plate is displaced toward the platen. Consequently, the entire faces of the ink ribbon guide plate and the paper guide plate are liable to come into contact with print paper on the platen. On the contrary, if one decreases the gap between the ink ribbon guide plate and the platen, then the gap between the print head and the ink ribbon guide plate is narrow so that the ink ribbon becomes liable to leap out from a printing hole which is formed in the ink ribbon guide plate thereby allowing the print head to contact therethrough with the print paper on the platen with the ink ribbon interposed therebetween. Since the sectional shape of the conventional paper guide plate on which the ink ribbon guide plate is mounted is generally flat and, depending upon the position of the ink ribbon guide plate set in the gap between the platen and the print head, either the entire faces of the ink ribbon guide plate and the paper guide plate are brought into contact with the paper so that the print paper is soiled by the ink ribbon or the ink ribbon leaps out from the ink ribbon guide plate. As a result the positioning operation to set the ink ribbon guide plate in position in the gap between the platen and the print head is quite difficult. JP-A- 60-244 584 shows a paper guide mechanism comprising a paper guide plate and an ink ribbon guide plate mounted on the paper guide plate. The ink ribbon guide plate is shaped with a concave configuration towards the paper guide plate. It is an object of the present invention to provide a paper guide mechanism for a serial printer wherein print paper is prevented from being soiled by contact with an ink ribbon or with an ink ribbon guide plate while preventing the leaping out or disengagement of the ink ribbon from the ink ribbon guide plate. This object is achieved with a paper guide mechanism according to claim 1. According to the present invention, there is provided a paper guide mechanism for a serial printer in which print paper is fed from a paper introducing mechanism to a paper discharging mechanism along a paper path extending along a print face of a platen and is printed by a print head with an ink ribbon interposed therebetween. The mechanism comprises a paper guide plate for guiding print paper along the paper path and pressing the print paper for feeding movement against the platen, and an ink ribbon guide plate mounted on the paper guide plate for supporting an ink ribbon for feeding movement thereon. The ink ribbon guide plate has a printing hole formed therein for allowing printing on the print paper by means of the print head therethrough. The paper guide plate is so shaped that, when the ink ribbon guide plate is mounted on the paper guide plate, the ink ribbon guide plate presents a convex configuration in relation to the axis of the platen in order to assure a gap between the print head and the ink ribbon guide plate so as to prevent the ink ribbon positioned between the ink ribbon guide plate and the print head from leaping out readily through the printing hole of the ink ribbon guide plate and to minimize contact between the ink ribbon guide plate and the print paper. With the paper guide mechanism for a serial printer, since the paper guide plate is so shaped that, when the ink ribbon guide plate is mounted on the paper guide plate, the ink ribbon guide plate presents a convex configuration in relation to the axis of the platen in order to assure a gap between the print head and the ink ribbon guide plate so as to prevent the ink ribbon positioned between the ink ribbon guide plate and the print head from leaping out readily through the printing hole of the ink ribbon guide plate and to minimize contact between the ink ribbon guide plate and the print paper, the paper guide mechanism is advantageous in that print paper can be prevented from being soiled by contact thereof with the ink ribbon or the ink ribbon guide plate while also leaping out of the ink ribbon through the printing hole of the ink ribbon guide plate is prevented. The above and other objects, features and advantages of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings. FIG. 1(a) is a front elevational view showing a paper guide plate to which the present invention is applied; FIG. 1(b) is a right-hand side elevational view of the paper guide plate of FIG. 1(a); FIG. 1(c) is a sectional view taken along line A-A of FIG. 1(a); FIG. 2(a) is a sectional view of a paper guide mechanism for a serial printer taken along line B-B of FIG. 2(b) showing a preferred embodiment of the present invention; and FIG. 2(b) is a side elevational view of the paper guide mechanism shown in FIG. 2(a). A paper guide plate to which the present invention is applied is shown in FIGS. 1(a) to 1(c), and a paper guide mechanism for a serial printer to which the paper guide plate shown in FIGS. 1(a) to 1(c) according to the present invention is shown in FIGS. 2(a) and 2(b). Referring to FIGS. 2(a) and 2(b), a paper guide plate 2, a print head 4 and an ink ribbon 5 are carried at individual predetermined positions on a carrier 6 which is moved back and forth along a guide rod 7 mounted in parallel to a platen 1 which defines a print plane. An ink ribbon guide plate 3 is adhered to a face of the paper guide plate 2 in an opposing relationship to the platen 1. The ink ribbon 5 is fed along a fixed route in a fixed direction each time the carrier 6 makes a back and forth movement, and though not shown, a mechanism for feeding the ink ribbon 5 is carried on the carrier 6. Print paper 13 is guided by a paper holding plate 9 mounted on a paper holding plate holder 8 and a paper guide portion 10, passes through a gap between the platen 1 and the paper guide plate 2 and ink ribbon guide plate 3 and is discharged, after being printed by the print heat 4 and the ink ribbon 5, by a discharging roller 12 and an auxiliary discharging roller 11. The paper guide plate 2 is made greater in thickness at a central portion than a peripheral portion thereof on the face thereof on which the ink ribbon guide plate 3 is mounted such that, when the ink ribbon guide plate 3 is mounted on the paper guide plate 2, the ink ribbon guide plate 3 presents a convex configuration toward the platen 1 in order to assure a gap between the print head 4 and the ink ribbon guide plate 3 so as to prevent the ink ribbon 5 positioned between the ink ribbon guide plate 3 and the print head 4 from leaping out from a printing hole 14, which is formed in the ink ribbon guide plate 3 so as to allow the print head 4 to contact therethrough with the print paper 13 on the platen 1 with the ink ribbon 5 interposed therebetween. A recessed area 16 is formed on the front face of the paper guide plate 2 with the ink ribbon guide plate 3 secured to the recessed area 16 such that the front face of the ink ribbon guide plate 3 does not project from the front face of the paper guide plate 2 toward the platen 1, thereby minimizing contact between the ink ribbon guide plate 3 and the print paper 13. Also, a window 15 is formed in the paper guide plate 2 in order to assure a gap between the print head 4 and the ink ribbon guide plate 3, and the ink ribbon 5 is guided in the window 15 by the rear face of the ink ribbon guide plate 3. Here, preferably the ink ribbon guide plate 3 projects at the central portion by 0.2 to 0.3 mm with respect to the peripheral portion thereof to assure a gap of 0.05 mm or more between the ink ribbon guide plate 3 and the print paper 13 in FIG. 2(a) and another gap of a magnitude greater by 0.05 mm or more than the thickness of the ink ribbon 5 between the ink ribbon guide plate 3 and the print head 4.

Claims: A paper guide mechanism for a serial printer in which print paper (13) is fed from a paper introducing mechanism to a paper discharging mechanism along a paper path extending along a print face of a platen (1) and is printed by a print head (4) with an ink ribbon (5) interposed therebetween, said guide mechanism comprising a paper guide plate (2) for guiding print paper (13) along said paper path and pressing the print paper (13) for feeding movement against said platen (1), and an ink ribbon guide plate (3) mounted on said paper guide plate (2) for supporting said ink ribbon (5) for feeding movement thereon and having a printing hole (14) formed therein for allowing printing on said print paper (13) by means of said print head (14) therethrough, characterized in that said paper guide plate (2) is so shaped that, when said ink ribbon guide plate (3) is mounted on said paper guide plate (2), said ink ribbon guide plate (3) presents a convex configuration in relation to the axis of said platen (1) in order to assure a gap between said print head (4) and said ink ribbon guide plate (3) so as to hold said ink ribbon (5) in place and to minimize contact between said ink ribbon guide plate (3) and said print paper (13).

Inventors: KUSUMI TATSUYA, KUSUMI, TATSUYA, KUSUMI, TATSUYA C/O NEC CORPORATION
Applicants: NIPPON ELECTRIC CO, NEC CORPORATION
Application year: 1992
Main classification: B41J13
IPC codes: B41J13, B41J31, B41J11