JPH08197799A - Paper pressing mechanism for image forming apparatus - Google Patents

Abstract

PURPOSE: To prevent paper slippage at print time by a simple mechanism. CONSTITUTION: Paper pressing members 20a, 22a which are made of a flexible resin sheet are fitted to the sides of a platen 12, a clearance through which the paper 24 is inserted is formed between the paper pressing members 20a, 22a and the paper supporting face of the platen 12, the lateral end of the paper 24 is inserted in the clearance, both sides of the paper 24 are pressed by the paper pressing members 20a, 22a. To print on the paper 24, a serial contact type printing head 10 is moved onto the paper 24 from the side of the platen 12 in a lifted state, when the printing head 10 moves onto the paper pressing member 20a, the print head 10 is lowered and presses the paper 24 from the top of the paper pressing member 20a. The printing head 10 moves in the direction of printing while pressing the paper pressing member 20a, comes down further when leaving the paper pressing member 20a and reaching the face of the paper 24, touches the paper 24, moves in the direction of printing while pressing the paper 24 and prints characters on the paper 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention conveys a sheet onto a platen, and a serial contact type print head is brought into contact with the sheet on the platen, and the print head is moved across the sheet to print on the sheet. The present invention relates to a paper pressing mechanism in an image forming apparatus such as a shuttle type thermal plotter.

[0002]

2. Description of the Related Art JP-A-3-212336 and JP-A-3-212336
JP-A-274174 discloses a paper pressing mechanism for pressing the left and right ends of a paper with a leaf spring in an image forming apparatus.

[0003]

In the case of an image forming apparatus using a serial contact type print head such as a shuttle type thermal plotter, the print head 2 is mounted on the platen 4 as shown in FIG. Contacting the sheet 6 and moving it across the sheet 6 while applying pressure. In this method, when the print head 2 enters on the paper 6,
May shift in the direction of the arrow. To prevent this,
If the spring pressing mechanism of the conventional example is adopted and the spring pressure is increased in order to prevent paper misalignment, the plate spring acts as a brake for the paper, making it difficult to carry the paper. Further, if the spring pressure is weakened, it becomes impossible to prevent paper misalignment. The present invention aims to solve the above problems.

[0004]

In order to achieve the above object, the present invention arranges a sheet-shaped sheet pressing member at a side end of a platen with a slight gap between the platen and a sheet supporting surface of the platen. , A side end portion of the paper is inserted into the gap to convey the paper onto the paper supporting surface of the platen, and a serial contact type print head is lowered on the paper pressing member. After that, the print head is moved in the print direction to print on the paper.

[0005]

When the print head presses the paper from above the paper pressing member and moves in the printing direction, air is released between the paper pressing member and the platen due to the pressing force of the print head, so that the space between the paper pressing member and the platen is increased. A sheet holding force is generated, and this holding force prevents the sheet from being displaced when the print head comes into contact with the sheet and pressurizes it to move in the printing direction.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described below in detail with reference to the embodiments shown in the accompanying drawings. An image forming apparatus 8 such as a shuttle type thermal plotter includes a platen (paper mounting member) 12 and a serial contact type print head 10.
And a controller (not shown) for controlling the input signal to the print head 10 and the drive signal to the drive mechanism of the print head 10, the lifting mechanism, and the drive unit of the paper transport mechanism 14. It is the main component.

A guide rail (not shown) is provided on the platen 12 in the Y-axis direction so as to support the sheet supporting surface 1 of the platen 12.
The print head 10 is attached to a carrier (not shown) that is movably attached to the guide rail and that is erected parallel to 2a. The paper transport mechanism 14 includes a driving roller 16 and a pressing roller 18, and is arranged in front of the platen 12.

Numerals 20 and 22 denote sheet retainers arranged on both sides of the platen 12, and the sheet retainers 20 and 22 are thin sheet-like members having a strong stiffness and elasticity and smooth sheets. A resin sheet made of a material having a static elimination effect so that it can be transported, for example, a product name “Lumirror” manufactured by Toray is used. The paper pressing members 20 and 22 include belt-shaped paper pressing members 20a and 22a and a vertical member 2 perpendicular to the belt pressing members 20a and 22a.
0b, 22b, and the paper pressing members 20a, 2
The paper retainer 2 is arranged so that the lower surface of the paper 2a faces the paper supporting surface 12a in parallel with a slight gap for inserting the paper.
The vertical members 20b and 22b of 0 and 22 are fixed to both side surfaces of the platen 12 with a space slightly wider than the lateral width of the paper 24.

A taper piece 26, which is inclined upward, is provided at the paper insertion opening of each paper pressing member 20a, 22a of the paper pressing member 20, 22 on the side facing the paper conveying mechanism 14.
28 are formed. Head cleaning members 30 and 32 such as sandpaper are removably adhered to the upper surfaces of the pressing members 20a and 22a of the paper pressing members 20 and 22, respectively.

In this embodiment, a plate-shaped paper support surface 12 is used.
Although a fixed base platen having a is used, a rotatable roller platen may be used. In this case, the paper retainers 20 and 22 may be provided on the roller support portion at the end of the platen so as not to rotate with the platen roller.

Next, the operation of this embodiment will be described. A long sheet of paper 24 with a specified width, such as roll paper,
The sheet is conveyed in the arrow direction in FIG. 1 by the sheet conveying mechanism 14,
It is supplied onto the sheet support surface 12a of the platen 12. When the front edge of the paper 24 enters the platen 12, the paper 2
As shown in FIG. 2, the front end of the sheet 4 has sheet retainers 20, 22.
The taper pieces 26 and 28 are guided to the lower side of the pressing members 20a and 22a of the paper pressing members 20 and 22, respectively. Further, when the paper 24 is driven in the carrying direction by the paper carrying mechanism 14, the paper 24 is transferred to the paper supporting surface 1 of the platen 12.
2a, and the paper 24 on the paper support surface 12a has predetermined regions on both sides thereof located below the pressing members 20a and 22a of the paper pressing members 20 and 22, respectively.
It is in a state of being slidably held by a and 22a.

When the printing operation is started, the print head 10 moves upward from the side of the platen 12 onto the paper 24. When the print head 10 moves on the paper pressing member 20, the print head 10 descends under the control of the controller, and the print head 10 comes into pressure contact with the paper pressing member 20a.
As a result, the print head 10 presses the paper 24 from above the paper pressing member 20a, and the paper 24 is sandwiched between the paper pressing member 20a and the paper support surface 12a of the platen 12, as shown in FIG.

Next, the print head 10 pressurizes the pressing member 20a of the paper pressing member 20 and presses the paper 24 in the arrow direction in FIG.
Move to the position where it comes into contact with the surface. At this time, due to the pressing force of the print head 10, the paper holding surface 20 of the paper pressing member 20a and the platen 12 at the portion where the print head 10 has moved.
Air between the sheet holding member 20a and the platen 12 at the portion where the air escapes is generated.

At this time, since the print head 10 on the paper pressing member 20a does not directly contact the paper 24, the pressure in the direction in which the paper 24 is displaced is extremely weak, and the paper 24 is
It does not shift due to the pressure movement of the print head 10.
The print head 10 includes a paper pressing member 20 in the arrow direction in FIG.
When the sheet a is moved while being pressed, and is separated from the end of the sheet pressing member 20a, the print head 10 is further lowered to come into contact with the sheet 24 to start printing.

As shown in FIG. 3, a non-printing area A is generated in the portion of the paper 24 covered by the paper pressing member 20a, but in order to prevent the paper misalignment even in the normal case where the paper pressing is not used. Since the non-printing area cannot be printed from the edge of the paper and the non-printing area is formed in this embodiment, the non-printing area can be made smaller than the normal case. The non-printing area A of the portion covered by the member 20a does not cause any particular problem.

When the print head 10 reciprocates along the Y-axis and prints in the return movement, the print head 10 presses on the other paper retainer 22 in the same manner as above. Take action. When the print head 10 prints only when moving in one direction and does not print when reciprocating, the other paper retainer 22 need not be provided.

[0017]

Since the present invention is configured as described above, it is possible to press the paper with a simple mechanism and prevent paper misalignment or printing misalignment. Further, since the edge portion of the paper is pressed, it is possible to prevent the paper jam caused by the floating of the paper. Further, there is an effect that the print head can be cleaned by using the cleaning member.

[Brief description of drawings]

FIG. 1 is an overall schematic view of an image forming apparatus.

FIG. 2 is a side view of a main part of the present invention.

FIG. 3 is a front view of a main part of the present invention.

FIG. 4 is an explanatory diagram.

[Explanation of symbols]

 2 print head 4 platen 6 paper 8 image forming apparatus 10 print head 12 platen 14 paper transport mechanism 16 drive roller 18 presser roller 20 paper presser 22 paper presser 24 paper 26 taper piece 28 taper piece 30 head cleaning member 32 head cleaning member

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B41J 13/10 29/17 B41J 29/00 M

Claims (3)

[Claims] 1. A sheet-shaped sheet pressing member is arranged at a side end of a platen with a slight gap between the platen and a sheet supporting surface of the platen, and a side end of the sheet is inserted into the gap. To convey the sheet onto the sheet supporting surface of the platen, and the serial contact type print head is lowered on the sheet pressing member, and then the print head is moved in the printing direction. A sheet pressing mechanism in an image forming apparatus, which is characterized in that printing is performed on the sheet. 2. The paper pressing mechanism for an image forming apparatus according to claim 1, wherein a cleaning member for the print head is provided on an upper surface of the paper pressing member. 3. A sheet inserting port of the sheet pressing member is provided with a taper piece inclined upward to facilitate insertion of a sheet into a gap between the sheet pressing member and the platen. A paper pressing mechanism in the image forming apparatus described in 1 or 2.