JPH091787A - Printing apparatus - Google Patents

Abstract

PURPOSE: To keep ink ejected from an ink ejecting part to hit on a correct printing position by maintaining constant at all times the distance between the ink ejecting part of an ink head and the printing surface of a recording sheet irrespective of a cockling state in the print-finished part. CONSTITUTION: A pressing member 12 is provided for pressing the print-finished part of a recording sheet S to be set on the platen 5 only when the printing head 6 is carrying out printing operation. The pressing member 12 retreats upside of the platen 5 while the printing head 6 lies in a position of home position (b), and it comes down from the retreating position to press the print- finished part of the recording sheet S on the platen 5 when the printing head 6 starts to move in the direction of arrow X1 for printing. In this instance, a number of claws 12A press down rising parts SC on the platen 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet type printing apparatus for ejecting ink onto a printing surface of a fed recording sheet to perform predetermined printing.

[0002]

2. Description of the Related Art Since a recording sheet printed by an ink jet type printing apparatus absorbs ink, unevenness occurs on a printing surface. This is called cockling. This cockling amount increases in proportion to the ink absorption amount, but when it exceeds a predetermined amount, the distance between the ink ejection portion (nozzle surface) and the recording sheet surface (printing surface) is not constant, and therefore the ink is ejected from the nozzle. The ink landing position on the print surface is misaligned. As a result, problems such as uneven density, printing of a curved straight line, and a step at the connecting portion of the line occur. In addition, the nozzle may rub the printed surface, and in such a case, there is a problem that the rubbing marks stain the print surface.

In conventional ink jet type printers, cockling is dealt with by the following various methods. That is, (1) Press the printing surface with a large number of spurs, (2)
Use a spur to disperse the cockling below a predetermined size, (3) Heat the printing surface immediately after printing with a heater to dry the ink before the printing surface causes cockling, (4) Absorb the ink. However, a special paper that does not cause cockling is used as a recording sheet.

[0004]

However, the above (1),
With the method (2), it is difficult to cope with high-definition printing and color printing in recent years, and density unevenness, color tone unevenness, ruled line shift, and the like have occurred.

The method (3) requires a large amount of electric power, and the method (4) has a problem that plain paper cannot be used.

Therefore, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a printing apparatus capable of performing high-quality printing even in high-definition printing, color printing, or printing on plain paper. And

[0007]

According to the present invention, there is provided a printing table on which a recording sheet to be printed is placed, a recording sheet carrying means for carrying a predetermined amount of the recording sheet onto the printing table, and an upper part of the printing table. A print head that ejects ink onto a recording sheet surface set on the print table while moving in a direction orthogonal to the sheet conveying direction to perform predetermined printing.
The present invention relates to a printing device provided with.

In order to achieve the above object, the present invention presses the printed portion of the recording sheet set on the print table on the print table only while the print head is performing the printing operation. A recording sheet pressing means is provided.

[0009]

According to the printing apparatus of the present invention having the above-mentioned structure, the printed portion of the recording sheet set on the printing stand is the recording sheet pressing means while the printing head is performing the printing operation. It is held on the printing table by. Therefore, the distance between the ink ejection portion of the print head and the printing surface of the recording sheet is always kept constant regardless of the cockling state of the printed portion, and the landing position of the ink ejected from the ink ejection portion on the printing surface is displaced. Disappear.

As a result, even in the case of high-definition printing, color printing, or printing on plain paper, high-quality printing can be performed without density unevenness, color tone unevenness, ruled line deviation, and the like.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. <Embodiment 1> FIG. 1 shows the configuration of a printing apparatus according to Embodiment 1 of the present invention, FIG. 1 (a) is a vertical sectional side view showing the overall configuration, and FIG. FIG. 3 is a vertical sectional front view showing the configuration of the (invention part).

First, the overall structure of the printing apparatus 1A will be described along the flow of the recording sheets S fed from the paper feed tray 2.

The recording sheet S placed on the paper feed tray 2
Is sandwiched between a conveying roller (recording sheet conveying means) 3 and a pinch roller 4 which rotate in a clockwise direction in the figure, and is sent onto a platen (printing table) 5. And platen 5
The recording sheet S sent upward stops moving when the first printing position reaches a predetermined position on the platen 5.

Next, the carriage 7 carrying the print head 6 reciprocates along the guides 8 and 9 in the X1 and X2 directions (sheet width direction) orthogonal to the sheet conveying direction. During the forward movement of the carriage 7, the print head 6
Ejects ink from the nozzle 6A to form an ink image at the print position on the recording sheet S.

When the carriage 7 returns to the home position, the conveying roller 3 conveys the recording sheet S by a predetermined amount and sets the next printing position (row) at a predetermined position on the platen 5.

At this time, the leading edge of the recording sheet S enters the nip between the paper discharging roller (recording sheet carrying means) 10 and the spur 11 which rotate clockwise in the figure, and is also carried by the paper discharging roller 10. Like

In this case, since the peripheral speed of the discharge roller 10 is set to be higher than the peripheral speed of the transport roller 3, the recording sheet S is pulled between the transport roller 3 and the discharge roller 10. However, since the conveying force of the discharge roller 10 is set to be smaller than the conveying force of the conveying roller 3, the conveying accuracy of the recording sheet S is determined on the conveying roller 3 side.

Here, the spur 11 supported by the spring shaft 11A is brought into light contact with the recording sheet S so that the carrying force of the paper discharge roller 10 is smaller than the carrying force of the carrying roller 3.

When the setting of the recording sheet S is completed, the carriage 7 reciprocates again and the ink image is printed by the print head 6 at the next print position. By repeating such operations in sequence, the recording sheet S that has been printed at the final printing position is discharged by the discharge roller 10 to the outside of the apparatus.

In the printing apparatus 1A, the recording sheet S
When a printing operation is performed on the platen 5, that is, when the print head 6 reciprocates in the directions of arrows X1 and X2, the platen 5
Pressing member retracted above (recording sheet pressing means)
12 descends and presses the printed portion of the recording sheet S set on the platen 5. In this case, the pressing member 12S is a portion SC that is lifted from the platen 5 by the cock ring by the many claws 12A.
Will be pressed against the platen 5. A groove 5A is formed in a portion of the platen 5 corresponding to the claw 12A.

Next, referring to FIG. 1B, the pressing member 1
Operation 2 will be described.

FIG. 1B shows a state in which the print head 6 is located at the home position. The print head 6 reciprocates from this position on the platen 5 in the X1 and X2 directions, and ejects ink from the nozzles 6A during forward movement to form an ink image at the print position on the recording sheet S.

When the print head 6 starts moving in the X1 direction, the lock claw 7A of the carriage 7 is disengaged from the retracting lever 14. Then, the elevating member 13 that has been pulled in the direction of arrow a by the retracting lever 14 via the rope 16 guided by the pulleys 17 and 18 is pulled in the direction of arrow b by the retracting spring 19. Then, when the elevating member 13 moves in the direction of the arrow b, the pressing member 12 that has been lifted by the elevating cam portions 13A and 13B of the elevating member 13 descends and presses the recording sheet S on the platen 5. Become.

The portion SC of the recording sheet S that is lifted by the cockling extends to the portion where printing is to be performed, but by pressing the portion SC of each of the pawls 12A of the pressing member 12 that is lifted to the platen 5, it will be The part to be printed is adapted to the platen 5 and comes into close contact therewith.

In this way, when the pressing member 12 finishes pressing the printed portion of the recording sheet S on the platen, the arrow X
The print head 6 moving in one direction enters the print area of the recording sheet S and starts printing. The pressing member 12 continues to press the printed portion of the recording sheet S on the platen 5 until the print head 6 reciprocates in the X1 and X2 directions along the arrow and returns to the home position.

When the print head 6 moving in the direction of the arrow X2 on the return path reaches the home position, the retracting lever 14 which is pulled downward by the retracting spring 19 and pivoted downward is locked by the lock pawl 7A of the carriage 7. Lifted by. Then, the elevating member 13 moves in the direction of the arrow a against the spring force of the retracting release spring, and the elevating cam portions 13A and 13B of the elevating member 13 lift the pressing member 12. As a result, the pressing member 12 releases the recording sheet S on the platen 5 and retreats above the platen 5 (states of FIGS. 1A and 1B).

The auxiliary spring 15 shown in FIG. 1 (b) always biases the retracting lever 14 in the clockwise direction so that the rope 1
The slack in 6 does not occur. This auxiliary spring 1
The spring force of 5 is set to be smaller than the spring force of the retracting release spring 19.

In the printing apparatus 1A, the print head 6
During the printing operation, the pressing member 12 presses the printed portion of the recording sheet S on the platen 5 and presses the portion SC that is lifted up by the cock ring against the platen 5, so that The distance between the recording sheet surfaces is always kept constant regardless of the cockling state of the printed portion. Therefore, the landing position of the ink ejected from the ink ejection unit on the printing surface does not shift.

Further, since the pressing member 12 comes into contact with the recording sheet S via a plurality of claws 12A which make point contact or short line contact, the pressing trace of the pressing member 12 on the recording sheet S is inconspicuous. .

Further, since each claw 12A of the pressing member 12 contacts the printing surface of the recording sheet S only during printing, the amount of ink adhered to each claw 12A is small, and the ink adhered to each claw 12A is about to be printed. It is also not reversely transferred to the surface to be printed. <Embodiment 2> FIG. 2 shows the construction of a printing apparatus according to Embodiment 2 of the present invention, FIG. 2 (a) is a vertical sectional side view showing the overall construction, and FIG. FIG. 3 is a vertical sectional front view showing the configuration of the (invention part).

In describing the construction of the printing apparatus 1B, the same members as those of the printing apparatus 1A of the first embodiment are designated by the same reference numerals, and those which are structurally and mechanically unchanged are described. The description is omitted.

In the printing apparatus 1B, the print head 6
Printing is performed either when the printer moves on the forward path (moves in the arrow X1 direction) or when it moves on the return path (moves in the arrow X2 direction). Therefore, when the print head 6 finishes printing on the outward path, the recording sheet S is transported to the next printing position by the transport roller 3. Further, when the print head 6 finishes printing on the return path, the recording sheet S is transported to the next printing position by the transport roller 3.

The printing apparatus 1B has a platen 5 while the print head 6 is performing printing on the forward path and printing on the return path.
A pressing member 21 is provided that holds down the printed portion of the upper recording sheet S and releases the recording sheet S when the conveying roller 3 is conveying the recording sheet S to the next printing position. The pressing member 21 is provided with a plurality of claws 21A that press the portion SC of the recording sheet S that is lifted up by the cockling against the platen 5. In addition, the pressing member 21 includes a large number of spurs 11 and a spring shaft 11.
The support shaft 2 at the rear end with respect to the spur holder 20 supported by A
It is attached so as to be rotatable in the up and down directions around 1D.

Next, referring to FIG. 2B, the pressing member 2
1 will be described.

FIG. 2B shows a state in which the print head 6 is located at the home position. The print head 6 reciprocates from this position on the platen 5 in the directions of arrows X1 and X2, and ejects ink from the nozzle 6A during forward movement and backward movement to form an ink image at the printing position on the recording sheet S. .

When the print head 6 starts moving in the direction of arrow X1, the lift member 7B of the carriage 7 pushes the pressing member 21.
21C of the hook comes off. Then, the pressing member 21 retracted above the platen 5 descends due to its own weight, and the recording sheet S on the platen 5 as well as the pressing member 12 described above.
Will be able to press. In this case, the hook portion 21C slides on the inclined surface 22 of the lift claw 7B and gradually descends to land on the recording sheet surface.

In this way, the pressing member 21 becomes the platen 5.
When the printed portion of the upper recording sheet S has been pressed down, the print head 6 moving in the direction of the arrow X1 enters the print area of the recording sheet S and starts printing. When the print head 6 that is performing printing approaches the end point of the outward path, the lift claw 7B of the carriage picks up the hook portion 21B of the pressing member 21, and the print head 6 reaches the end point of the outward path and moves. When is stopped, the hook portion 21B scooped up by the lift claw 7 is held in a state of being lifted by the lift claw 7B. As a result, the pressing member 21 releases the recording sheet S and is retracted above the platen 5.

When the print head 6 reaches the end point of the forward path and stops moving, the carry roller 3 carries the recording sheet S to the next print position. After that, the print head 6 moves in the direction of the arrow X2 to perform printing on the return path.

When the print head 6 starts moving in the direction of the arrow X2, the lift member 7B of the carriage 7 presses the pressing member 21.
The hook portion 21B of is removed. Then, the pressing member 21 retracted above the platen 5 descends by its own weight, and presses the printed portion of the recording sheet S on the platen 5. In this case, the hook portion 21B slides on the inclined surface 23 of the lift claw 7B and gradually descends to land on the recording sheet surface.

In this way, the pressing member 21 becomes the platen 5.
When the printed portion of the upper recording sheet S is pressed down, the print head 6 moving in the direction of arrow X2 enters the print area of the recording sheet S and starts printing. Then, the print head 6 that is performing printing returns to the end point (home position) of the return path.
The lift pawl 7B of the carriage 7 approaches the pressing member 2
When the print head 6 reaches the end point of the return path and stops moving, the hook portion 21C picked up by the lift claws 7B is lifted by the lift claws 7B. Held in. This allows
The pressing member 21 releases the recording sheet S and is retracted above the platen 5.

The means for retracting and releasing the pressing members 12, 21 is not limited to the illustrated mechanism. For example,
It is also possible to use a solenoid, a motor, or the like.

[0042]

As described above, in the printing apparatus of the present invention, since the printed portion of the recording sheet being printed is pressed on the printing table, the printing is performed regardless of the cockling state of the printed portion. It is possible to always keep the distance between the ink ejection portion of the head and the printing surface of the recording sheet constant. Therefore, the landing position of the ink ejected from the ink ejection unit on the printing surface does not shift.

Therefore, even in high-definition printing, color printing, or printing on plain paper, high-quality printing without uneven density, uneven color tone, ruled line deviation, etc. can be performed.

[Brief description of the drawings]

FIG. 1 is a vertical sectional side view (FIG. 1A) and a vertical sectional front view (FIG. 1) showing a configuration of a printing apparatus according to a first embodiment of the invention.
(B)).

FIG. 2 is a vertical sectional side view (FIG. 2A) and a vertical sectional front view (FIG. 2) showing a configuration of a printing apparatus according to a second embodiment of the invention.
(B)).

[Explanation of symbols]

 3 Conveying Rollers (Recording Sheet Conveying Means) 5 Platen (Printing Platform) 6 Printing Heads 10 Discharging Rollers (Recording Sheet Conveying Means) 12, 21 Holding Members (Recording Sheet Holding Means) 12A, 21A Claws S Recording Sheets

Claims (5)

[Claims] 1. A printing table on which a printing sheet to be printed is placed, a printing sheet carrying means for carrying the printing sheet onto the printing table by a predetermined amount, and an upper side of the printing table orthogonal to the sheet carrying direction. A printing apparatus comprising: a print head that ejects ink onto a recording sheet surface set on the print table while moving in a predetermined direction to perform predetermined printing, and is set on the print table. A printing apparatus comprising a recording sheet pressing means for pressing the printed portion of the recording sheet on the printing table only while the print head is performing a printing operation. 2. The printing apparatus according to claim 1, wherein the recording sheet pressing means presses a printed portion of the recording sheet in the vicinity of the reciprocating print head. 3. The printing apparatus according to claim 1, wherein the recording sheet pressing means is provided with a large number of claws that make point contact or short line contact with the recording sheet. 4. The printer according to claim 3, wherein each of the claws presses a raised portion of the recording sheet. 5. The recording sheet pressing means retracts above the printing table when the print head is not performing a printing operation, and descends from the retracted position when the print head starts moving to perform printing. The printing device according to claim 1, wherein the printed portion of the recording sheet is pressed.