GB2143477A

GB2143477A - A sheet guide for a printer

Info

Publication number: GB2143477A
Application number: GB08414985A
Authority: GB
Inventors: Tadao Tumukai
Original assignee: Alps Electric Co Ltd
Current assignee: Alps Alpine Co Ltd
Priority date: 1983-06-14
Filing date: 1984-06-12
Publication date: 1985-02-13
Also published as: JPS59230779A; DE3421936C2; DE3421936A1; KR850000304A; GB2143477B; GB8414985D0

Abstract

A sheet guide device for a printer has a rotatable platen (1) onto which a record medium (S) is wound, a carriage (6) movable in the axial direction of the platen (1), a printing member (P) mounted on the carriage (6), a pair of lead-in guides (11) placed in opposition to the platen (1) with a gap therebetween and extending in the roll-in direction of the record medium (S), and a pressing guide (12) provided in opposition to an end portion of each of the lead-in guides (11) for separating the record medium (S) wound on the platen (1) from the lead-in guides (11) and pressing the record medium in a backward direction to roll the record medium (S) over the platen (1). When a wider width of record sheet (S) is used, (1), a second lead-in guide (13) can be mounted on the carriage (6) in opposition to the platen (1) with a gap therebetween and extending in the roll-in direction of the record medium (S), and a driving mechanism can displace the carriage (6) during positioning of the record medium (S) so as to set the second lead-in guide (13) at a substantially axial middle portion of the platen (1). <IMAGE>

Description

SPECIFICATION A guide device for a printer The present invention generally relates to a printer of the type in which a printing member is disposed in opposition to a rotary platen, and more particularly to a guide device for guiding a record sheet to be rolled over a platen.

Figure 1 is a perspective view showing the outline of the conventional pen type printer.

In a printer of this type, a record sheet S is mounted from the lower side of a rotary platen 1 and rolled thereover. The record sheet S is sandwiched between a roller 2 and the platen 1 at the lower side of the platen 1 and pressed at the upper side of the platen 1 by a pressing roller 4 provided on a sheet pressing rod 3. The platen 1 is driven by a stepping motor 5 so that the record sheet S may be reciprocated in the X-direction by the revolution of the platen in the forward/reverse direction.

A pen P which is a printing member is held on a carriage 6. The carriage 6 is arranged to be movable in the axial direction of the platen 1. A wire 7 is connected to the carriage 6 and put over a pulley 8 which is driven by a stepping motor 9. The rotation of the stepping motor 9 drives the carriage 6 to reciprocate in the Y-direction. The pen P on the carriage 6 is driven by a hammer mechanism (not shown) so that the tip end of the pen P is brought into contact with the record sheet S. By controlling the above-mentioned operations in the X- and Y-directions, characters, figures, or the like are drawn on the record sheet S by the pen P.

In such a conventional printer, when a record sheet S is mounted onto the platen 1, the sheet pressing rod 3 is separated from the platen 1 at first, and then the record sheet S is inserted from the under side of the platen 1. Then, the record sheet S is sandwiched between the platen 1 and the roller 2 and the forward end of the record sheet S is guided upward (Figure 2A). Next, the sheet pressing rod 3 is brought down toward the platen 1 so that the record sheet S is pressed against the platen 1 by pressing roller 4 (Figure 2B).

In such a conventional printer, however, there is a drawback that the operation is troublesome when a record sheet S is mounted on the platen 1 because it is necessary to separate the sheet pressing rod 4 from the platen 1 and to bring the same to the platen 1. Further, when a record sheet S is inserted from the lower side of the platen 1 with the sheet pressing rod 3 separated from the platen 1, as shown in Figure 2A, sometimes the forward end of the record sheet S may hit against the sheet pressing rod 3 or comes outside the sheet pressing rod 3.

The present invention is directed to eliminate such drawbacks in the prior art printer as described above and an object of the present invention is to provide a guide device for a printer in which the mounting of a record sheet can be smoothly performed through a simple operation without requiring the operation of a sheet pressing rod or the like.

According to an aspect of the present invention, the sheet guide device for a printer comprises: a rotatable platen onto which a record medium is to be rolled; a carriage movable in the axial direction of the platen; a printing member mounted on the carriage in opposition to the platen; a pair of lead-in guides placed in opposition to the platen with a gap therebetween at a side of the platen opposed to the printing member, the lead-in guides extending in a roll-in direction of the record medium; and a pressing guide provided in opposition to an end portion of each of the lead-in guides for separating the record medium attached to the platen from the leadin guides and pressing the record medium in the direction to roll the record medium over the platen.

According to another aspect of the present invention, the sheet guide device for a printer comprises: a rotary platen onto which a record medium is to be rolled; a carriage movable in the axial direction of the platen; a printing member mounted on the carriage in opposition to the platen; a pair of first lead-in guides placed in opposition to the platen with a gap therebetween at a side of the platen opposed to the printing member and at the opposite end portions of the platen which are out of a travelling range of the printing member, the first lead-in guides extending in the roll-in direction of the record medium; a second lead-in guide provided on a front face of the carriage opposed to the platen and placed in opposition to the platen with a gap therebetween, the second lead-in guide extending in the roll-in direction of the record medium; a pressing guide provided in opposition to an end portion of each of the first and second lead-in guides for separating the record medium attached to the platen from the first and second lead-in guides and pressing the record medium in the direction to roll the record medium over the platen; and driving means for displacing the carriage in mounting the record medium to set the second lead-in guide at a substantially axially middle portion of the platen.

A guide device for a printer will now be described, by way of example, with reference to the accompanying diagrammatic drawings in which: Figure 1 is a perspective view showing a conventional guide device for a printer; Figures 2A and 2B are side views showing the operation of the guide device of Figure 1; Figures 3A to 3D are side views showing the operation of a guide device according to an embodiment of the present invention; and Figure 4 is a perspective view showing another embodiment of a guide device according to the present invention.

Figures 3A to 3D are diagrams showing the operation of a guide device for a printer in accordance with the invention.

In the drawings, roller 2 is pressingly brought into contact with the platen 1. Similar to the case shown in Figure 1, platen 1 is driven by a stepping motor (not shown). Pen P is a printing member mounted on a carriage 6 and disposed to be in opposition to the platen 1. Similar to that shown in Figure 1, this carriage 6 is also driven by a stepping motor (not shown) to reciprocate in the axial direction of the platen 1.

Reference numeral 11 designates a pair of lead-in guides which are disposed at a side of the platen opposed to the printing member and at the opposite end portions of the platen 1 which are out of the travelling range of the carriage 6. Each lead-in guide 11 is formed by thin plate working or the like and shaped such that its upper half portion 11 a is curved along the platen 1 with a predetermined gap therebetween, while its lower half portion 11 b extends generally vertically. The lower half portion 11 b extends down enough so that it is in contact with the forward end Sa of a record sheet S when it is advanced between the platen 1 and the roller 2 toward the lead-in guides 11. A pressing guide 1 2 is provided at a portion in opposition to the upper end of each of the lead-in guides 11.The pressing guide 1 2 is formed of a thin plate, a transparent plastic plate, or the like. The forward end 1 2a of the pressing guide 1 2 is shaped to be bent slightly upward. The positional relation between the pressing guide 1 2 and the leadin guides 11 is such that, as shown in Figure 3D, the record sheet S is separated from the lead-in guides 11 to be completely rolled over the platen 1 when the record sheet S is in contact with the forward end 1 2a of the pressing guide 12.

The pressing guide 1 2 may be arranged such that it extends to cover the entire axial length of the platen 1, and the forward end thereof may be shaped to be sharp to be used as a paper cutter for a roll of paper. Alternatively, the pressing guide 1 2 may be divided into a plurality of sections provided side by side in the axial direction of the platen 1.

Alternatively, a pair of similar pressing guides 12 may be provided with the pair of lead-in guides 11 respectively at the axially opposite end portions of the platen 1 in the case where a record sheet S having a small width is used.

Further, alternatively, a shaft may be disposed in parallel with the platen 1 in place of the pressing guide 1 2 with a plate fixedly attached to the shaft and slanted similarly as the upper half portion 1 2a of the pressing guide 12.

The record sheet guiding operation by the guide device for the printer described above will now be described.

The record sheet S is inserted from the lower side of the platen 1 so as to be sandwiched between the platen 1 and the roller 2 (Figure 3B). Then, when the stepping motor is started so that the platen 1 is rotated, the forward end Sa of the record sheet S comes in contact with the lower half portion 11 b of each of the lead-in guides 11. When the record sheet S is further fed, the forward end Sa slides along the inner surface of each of the lead-in guides 11 to be rolled gradually over the platen 1.When the record sheet S is further advanced, the forward end Sa thereof comes off from the upper half portion 11 a of each of the lead-in guides 11 (Figure 3C) and comes into contact with the inner surface of the forward end 1 2a of the pressing guide 1 2. Thereafter, if the record sheet S is further advanced, the forward end Sa thereof slides along the forward end 1 2a of the pressing guide 1 2 and the record sheet S comes off from the lead-in guides 11. Then, if the forward end Sa separates from the pressing guide 1 2 and goes backward as shown in Figure 3D, the record sheet S is completely rolled over the platen 1.

In a recording operation, the stepping motor 5 is rotated to cause the platen 1 to reciprocate. Thus, a transportation force is exerted on the record sheet S sandwiched between the platen 1 and the roller 2 so that the sheet S is caused to reciprocate in the Xdirection (refer to Figure 1). At this time, the record sheet S slides against the pressing guide 1 2 and the record sheet S is transported as it is in close contact with the platen 1.

The carriage 6 is reciprocated in the Y-direction by the stepping motor 9 (refer to Figure 1). The pen P is pushed out toward the record sheet S by a hammer mechanism so as to draw characters, figures, or the like on the record sheet S in accordance with the X-Y operations.

Figure 4 shows another embodiment of the printer guide device. This embodiment is particularly suitable for a printer in which a record sheet having a large width is used.

In Figure 4, lead-in guides 11 are the same as those shown in Figures 3A to 3D and disposed at the axially opposite end portions of the platen 1 (only one lead-in guide at one end portion is shown in the drawing). Another lead-in guide 1 3 is fixedly provided on the carriage 6 on the side thereof opposed to the platen 1. This lead-in guide 1 3 has a longitudinal cross-section approximately equal to that of the lead-in guide 11 and has a slot 1 3a at about the central portion thereof. The tip of the pen P mounted on the carriage 6 is positioned opposite to the platen 1 through the slot 1 3a. This opposing positional relation is the same as that shown in Figures 3A et seq. A wire 7 puiling the carriage 6 is put over a pulley 8 which is driven by a stepping motor 9.

The carriage driving mechanism is constituted by this stepping motor 9 and a control circuit (not shown). The control circuit is arranged such that upon turning-on of a power source for the printer, the carriage 6 is displaced to the axially central portion of the platen 1. If a record-sheet S is inserted under this condition, the transversely opposite end portions of the record sheet S are guided by the lead-in guides 11 provided at the axially opposite end portions of the platen 1, the central portion of the record sheet S is guided by the lead-in guide 1 3 fixed onto the carriage 6, and the entire area of the record sheet S is surely guided by the pressing guide 1 2. In this manner, the record sheet S can be smoothly positioned even if it has a large width.Upon the detection of the completion of positioning of the record sheet S, the carriage 6 is moved to the print starting position.

It will be understood of course that the same effect can be obtained by using another printing member such as a wire dot head, a thermal head, or the like, other than the pen P.

As described above, according to the present invention, various meritorious effects can be obtained, as follovis: (1) Since a record sheet is led in by two guide members without using any conventionally used pressing rod, the operation to move such a pressing rod in positioning a record sheet becomes unnecessary so that a record sheet can be easily positioned; (2) Since a pressing guide is disposed at a position opposed to lead-in guides so that a record sheet is pressed against a platen by this pressing guide, the record sheet is surely rolled over the platen and there is no risk of creating wrinkles on the record sheet in printing by the printing member; ; (3) In the case where a lead-in guide is fixedly attached onto a carriage and the carriage is driven so as to be placed at the axially central portion of the platen when a record sheet S is positioned, as described above, the record sheet can be surely guided at its forward end central portion by the pressing guide so that the record sheet can be smoothly positioned even if it has a large width; and (4) In the case where a lead-in guide is fixedly attached on a carriage so that the leadin guide moves together with the carriage, the pressing guide operates to separate the record sheet from the lead-in guide so that the moving lead-in guide does not slide against the record sheet and there is no risk of damage of the record sheet.

Claims

1. A sheet guide device for a printer, comprising: a rotatable platen onto which a record medium is to be wound; a carriage movable in an axial direction of said platen; a printing member mounted on said carriage in opposition to said platen; a pair of lead-in guides placed in opposition to said platen with a gap therebetween at a side of said platen opposed to said printing member, said lead-in guides extending in a roll-in direction of the record medium; and a pressing guide provided in opposition to an end portion of said lead-in guide for separating the record medium wound on said platen from said lead-in guide and pressing the record medium in a backward direction so as to roll said record medium back over said platen.

2. A sheet guide device according to claim 1, in which the upper end of each of said iead-in guides is curved along said platen.

3. A sheet guide device according to claim 1, in which the upper end of each of said lead-in guides is provided out of a travelling range of said printing member.

4. A sheet guide device according to claim 1, in which a forward end of said pressing guide is bent upward in a direction to guide said record medium over said platen.

5. A sheet guide device for a printer, comprising: a rotary platen onto which a record medium is to be wound; a carriage movable in an axial direction of said platen; a printing member mounted on said carriage in opposition to said platen; a pair of first lead-in guides placed in opposition to said platen with a gap therebetween at a side of said platen opposed to said printing member and located respectively at the opposite end portions of said platen which are out of a travelling range of said printing member, said first lead-in guides extending in a roll-in direction of the record medium; a second lead-in guide provided on a front face of said carriage placed in opposition to said platen with a gap therebetween, said second lead-in guide extending in the roll-in direction of the record medium; a pressing guide provided in opposition to an end portion of each of said first and second lead-in guides for separating the record medium wound on said platen from said first and second lead-in guides and pressing the record medium in the direction to roll said record medium over said platen; and driving means for displacing said carriage during positioning of the record medium so as to set said second lead-in guide at a substantially axially middle portion of said platen.

6. A sheet guide device according to claim 5, in which the upper end of each of said first and second lead-in guides is curved along said platen.

7. A sheet guide device according to claim 5, in which a forward end of said pressing guide is bent upward in a direction to guide said record medium over said platen.

8. A guide device for a printer substantially as hereinbefore described with reference to Figures 3 and 4 of the accompanying drawings.