JPH08183215A - Method and structure for adjusting automatically paper thickness for printer - Google Patents

Abstract

PURPOSE: To adjust automatically and correctly a space between a platen roller and a print head by pressing a printing paper sheet on the print head and adjusting the space as prescribed by moving the platen roller backward by a given distance. CONSTITUTION: An automatic paper thickness adjustment structure is composed of a tractor 2 for transporting printing sheets 1, a print head 3 for printing, a platen roller 4 facing the print head 3, a platen rotating motor 5, a cam 6 for moving the platen roller 4 toward/away from the print head 3, and a cam driving motor 7. In the cylindrical platen roller 4, the shaft protruding from both ends of the roller is supported on bearings attached to right and left frames with the roller shaft center pivoted in parallel with a print head 3 surface. The bearings are engaged slidably with elliptic holes 8 formed in the right and left frames to move vertically to the print head 3 surface. In this way, a space between the platen roller 4 and the print head 3 can be adjusted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printer device,
Particularly, it relates to a structure for automatically adjusting the facing distance between the print head and the platen roller according to the thickness of the printing paper.

For example, in a dot printer device,
Since printing is performed by passing the printing paper between the print head and the platen roller, it is necessary to make the interval a minute dimension that matches the thickness of the printing paper. From the viewpoint of operability and print quality, the interval is required. There is a demand for automatic and accurate adjustment according to changes in the thickness of printing paper.

[0003]

2. Description of the Related Art Conventionally, in a dot printer, for example, a print head and a cylindrical platen roller are opposed to each other, and the distance between the print head and the platen roller is manually set on the print head side (or platen roller side) with respect to the other surface. The structure is designed to move in parallel, and the operator sees the print while printing and adjusts it manually.

Alternatively, a thickness detector such as a potentiometer for directly detecting the thickness of the set printing paper is provided at the printing position, and either the print head side or the platen roller side is fixed and the other is fixed. It is arranged so that it can be moved forward and backward by a motor with respect to the mating surface, and the forward and backward movement is performed by driving and controlling the motor. For example, pinch the printing paper between the platen roller and the print head, and press it once,
After the paper thickness is detected by the thickness detector, the distance between the platen roller surface and the print head surface is automatically adjusted by retracting the paper based on the electrical output of the thickness detector.

[0005]

However, according to such a structure as described above, in the case of manual adjustment, the operator's operation is increased when the thickness of the printing paper is different, so that the operation time increases and the apparatus malfunctions due to an operation error. There is a problem that is easy to invite. Also, in the case of automatic adjustment, if the printing paper between the platen roller and the print head is in a loose state,
The gap between the platen roller surface and the print head surface is affected by the partial deformation of the platen roller surface caused by wrinkles and the impact of the print pin caused by the slack in the print paper when the print head (or platen roller) is pressed against the print paper. However, there is a problem in that it cannot be accurately adjusted to a predetermined interval.

In view of the above problems, the present invention accurately and automatically adjusts the distance between the platen roller surface and the print head surface without being affected by wrinkles due to slack of the printing paper and partial deformation of the platen roller surface due to hitting of the printing pin. An object is to provide an adjustable printer device.

[0007]

In order to achieve the above object, in the automatic paper thickness adjusting method for a printer according to the present invention, a platen roller and a print head are sandwiched by a print paper which is engaged with a tractor and conveyed. Are arranged so as to face each other, and the platen roller is brought into contact with the print sheet and moved toward the print head while rotating in a direction opposite to the conveying direction, and the print sheet is reversed by contact friction with the tractor as a fulcrum. After being pulled in the direction and stopped at a new striking surface position, the printing paper is sandwiched and pressed against the print head, and then the platen roller is retracted by a predetermined distance and adjusted to a predetermined facing interval.

Further, an automatic paper thickness adjusting structure for realizing this method is provided with a print head arranged at a print position in front of a tractor for conveying print paper, and a spring in a direction facing the print head and away from the print head. A platen roller that is urged and rotatably supported, a platen rotation motor that drives the platen roller to rotate in a direction opposite to the printing paper conveyance direction, and a cam that moves the platen roller forward and backward with respect to the print head. It is composed of a cam having a surface and a cam drive motor that drives the cam to rotate forward and backward through a torque limiter.

[0009]

With this structure, the platen roller can be moved forward to the printing position by the cam while being rotated by the platen rotation motor. When the platen roller is moved forward, the platen roller is brought into contact with the printing paper and the printing paper is conveyed in the conveying direction. Since the print paper can be stretched around the tractor as a fulcrum by rotating the print paper in the reverse direction to pull back, it is possible to prevent wrinkles from being generated in the print paper when the print paper is pressed against the print head.

Further, since the platen roller rotates and stops at the new striking surface position, the printing paper is sandwiched and pressed against the printing head, so that the paper thickness can be adjusted accurately without being affected by the partial deformation of the platen roller surface. Further, since the printing can be performed at the new striking surface position as it is, the printing quality can be improved.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The gist of the present invention will be described below in detail based on an embodiment of the dot printer shown in the drawings.

As shown in the schematic side view of FIG. 1, the automatic paper thickness adjusting structure of the dot printer has a tractor 2 for conveying the print paper 1, a print head 3 for printing, and a platen facing the print head 3. A roller 4; a platen rotation motor 5 for rotating the platen roller 4; a cam 6 for moving the platen roller 4 forward and backward with respect to the print head 3;
And a cam drive motor 7 that rotates. FIG.
Indicates a state in which the platen roller 4 has been moved to a position where printing is possible and set, and an ink ribbon (not shown) is arranged between the printing paper 1 and the printing head 3.

The tractor 2 is arranged vertically and horizontally between the left and right frames (not shown) of the printer device, and the left and right feed holes of the printing paper 1 are engaged with the pin belts 2a to print the printing paper 1.
Is conveyed upward. The tractor 2 is driven by a paper transport motor (not shown).

The print head 3 has the upper tractor 2, that is, the print head 3.
Before 2-1 is fixed between left and right frames, and printing pins (not shown) are arranged along the printing line for the number of printing digits. The print pin is magnetically driven by a drive circuit (not shown).

The platen roller 4 is a cylindrical roller in which a synthetic rubber is concentrically fixed to a metal shaft, and shafts projecting at both ends are mounted on bearings (not shown) provided on the left and right frames, and the roller shaft center is on the print head surface. Pivot and support in parallel with each other. This bearing is slidably fitted in the oval holes 8 provided in the left and right frames so as to move forward and backward in the direction perpendicular to the print head surface (the direction facing the print head). Thereby, the facing distance between the platen roller 4 and the print head 3 can be adjusted.

Further, the platen roller 4 is provided in the print head 3
In the direction away from, the print head 3 is urged in a vertical direction by a tension spring 9 having one end fixed to the frame. The figure is slightly skewed for clarity.

Further, the both end shafts of the platen roller 4 are fitted with a disc 10 which is received by a cam surface described later. The platen roller 4, which is pressed against the disk 10 by spring pressure, holds the facing interval of the print head 3 in parallel.

The platen roller 4 is in the opposite direction (clockwise direction) to the conveying direction of the printing paper 1 during the paper thickness adjustment movement.
Then, it contacts the printing paper 1 and rotates, and stops during the printing operation. The platen rotation motor 5 is a stepping motor whose rotation angle can be easily controlled, is arranged apart from the platen roller 4, and is driven via the timing belt 11. The timing belt 11 is provided with an idle pulley (not shown) that maintains tension so that the platen roller 4 does not loosen even when moving. Be careful that there is no backlash in power transmission.

The cam 6 is driven to rotate in the forward and reverse directions to move the platen roller 4 forward or backward with respect to the print head 3.
The shape of the cam 6 is a cochlear eccentric cam, and the cam surface receives the disk 10 fitted on both end shafts of the platen roller 4. The correlation between the rotation angle of the cam 6 and the displacement of the cam surface is determined in advance, and the cam shape is configured so that the platen roller 4 is displaced substantially linearly (advance and retreat) toward the print head 3 with respect to the rotation angle of the cam 6. To design.

When the platen roller 4 is moved forward by the cam 6, the position where the platen roller 4 contacts the print head 3 is set to the top dead center so that excessive pressure is not applied to the print head 3. Excise at that position.

When the printing paper 1 is set, the platen roller 4 is sufficiently separated from the print head 3 so that the printing paper 1 can be set easily, and the platen roller 4 is returned by a predetermined rotation angle from the top dead center for assembly.
The cam drive motor 7 is a stepping motor whose rotation angle is easy to control, and a torque limiter 12 is mounted on the rotation shaft. The drive side of the torque limiter 12 is fixed to the rotating shaft, and the driven side thereof is directly connected to the cam shaft. For the sake of clarity, the figure is shown by connecting and disconnecting with a one-dot chain line.

The cam drive motor 7 drives the cam 6 through the torque limiter 12 in the forward and reverse directions. The torque limiter 12 uses a mechanical friction clutch and is set in advance to a limiting torque, that is, a torque that allows the platen roller 4 to smoothly advance until the printing paper 1 presses the printing head 3 and load torque beyond that. That is, the print head 3 with the printing paper 1 sandwiched therebetween
When it comes into contact with, it will rub and slip.

The cam drive motor 7 and the torque limiter
Although 12 is directly connected to the platen roller 4 on one axis shown by the one-dot chain line, other power transmission mechanisms such as gears and belts may be used as long as they perform the same function instead of on one axis, but there is no backlash. It needs to be noted.

Next, the sheet thickness adjusting operation of the platen roller will be described with reference to the schematic side view of the essential portions showing the operating state of the platen roller of FIG. 2 and the time chart thereof shown in FIG. When starting printing, set the printing paper 1 on the lower tractor 2-2. When the print start switch is pressed, the automatic paper loading means (not shown) is activated and the printing paper 1 is conveyed to the upper tractor 2-1 and stopped at a predetermined position.

At this time, the automatic paper thickness adjusting signal A is issued to activate the platen rotation motor 5 and the cam drive motor 7. The cam 6 and the platen roller 4 start rotating separately. By the normal rotation (counterclockwise) of the cam 6, the platen roller 4 moves forward toward the print head 3 against the urging force of the tension spring 9, and the printing paper 1 is conveyed in the transport direction with the upper tractor 2-1 as the fulcrum. The print paper 1 is pressed against the print head 3 while sandwiching the print paper 1 in the opposite direction by contact friction. At that time, instead of measuring the thickness of the sandwiched printing paper 1 dimensionally, the platen roller 4 is prevented from advancing at a position corresponding to the thickness.

The cam drive motor 7 for rotating the platen roller 4 is designed in advance so that the rotation angle of the cam 6 and the displacement of the cam surface are correlated with each other as described above. The number S _{1 of} driving steps until the printing paper 1 is abutted, which corresponds to the distance L (between the roller surface and the print head surface in FIG. 2) that is pressed against the print head 3, and
After hitting, the torque limiter 12 is overloaded and starts slipping to drive the sum (S ₁ + S ₂ ) of the number of S ₂ drive steps that slips once or twice.

On the other hand, the platen roller 4 is the print head 3
While it is moving forward toward, it contacts the printing paper 1 and rotates,
When the torque limiter 12 receives a repulsion from the print head 3 and makes an integer rotation before it starts slipping, it returns to the origin and is further rotated slightly from the previous striking position by the printing height to make a new striking surface position and then stop. . Therefore, the platen rotation motor 5 correlates with the S ₁ drive step number of the cam drive motor 7, and gives the S ₃ drive step number for rotating the platen roller 4 just before the contact position (corresponding to L ₁ in FIG. 2). And the number of S ₄ drive steps that give rotation that shifts by the print height from the previous striking position ((corresponding to L ₂ in FIG. 2)
And sum (S ₃ + S ₄ ) is driven.

Alternatively, in order to bring out a new striking surface of the platen roller, an encoder having an index divided into one round is attached to the platen roller (or platen rotation motor shaft) without correlation, and the index on the encoder is counted by the sensor. Alternatively, until the forward movement of the platen roller stops, the platen roller may be rotated by an integral number to return to the origin (return to the position where it was hit last time), and may be stopped by rotating the origin by the index number for shifting to the new hitting surface. In this case, it is not necessary to correlate the number of drive steps of the platen rotation motor and the number of drive steps of the cam drive motor.

Next, after the cam drive motor 7 is stopped, a timer circuit (not shown) delays the cam drive motor 7 for a predetermined time t seconds, and again, the cam drive motor 7 is again driven clockwise by the S ₅ driving step number (the striking stroke of the printing pin). Based on, for example, 0.1 m
Only m) is started in reverse. The cam 6 reverses in the clockwise direction, and causes the platen roller 4 which has stopped contacting to follow the cam surface by the urging force of the tension spring 9. That is, the print head 3
In order that the printing paper 1 sandwiched between the platen roller 4 and the platen roller 4 can pass through without any trouble and perform proper printing, the thickness of the sandwiched printing paper is adjusted to a predetermined distance by adding a predetermined distance of 0.1 mm. This ends the paper thickness adjustment operation.

As a result, the platen roller 4 is held at a predetermined printing interval with the printing paper 1 sandwiched between the printing head 3 and a new striking surface during the printing operation. When the printing operation is completed, the cam drive motor 7 rotates by (S ₁ + S ₂ ) drive steps and returns the platen roller 4 to the original position.
In the above description, the thickness of the ink ribbon placed between the printing paper 1 and the print head 3 is ignored, but it goes without saying that the thickness of the ink ribbon is also taken into consideration.

As described above, in the process of moving the platen roller while rotating it in the reverse direction to sandwich the print sheet with the print head, tension is applied to the print sheet, and the platen roller moves the print sheet to the print head with a new surface. Since it is pressed against, the wrinkles due to the looseness of the printing paper and the partial deformation of the platen roller surface due to the printing impact do not affect the paper thickness, and the facing distance between the platen roller and the print head changes according to the change in the printing paper thickness Can be adjusted automatically and accurately.

Therefore, printing is started (printing paper is loaded)
Since the sheet thickness is adjusted every time and the platen roller is always set on a new surface, the print quality can be stabilized and greatly improved.

[0033]

As described in detail above, according to the present invention,
The platen roller eliminates the slack of the printing paper that is engaged with the tractor and is conveyed by the reverse movement operation, and the printing paper is stretched and the printing paper is sandwiched by the new striking surface to adjust the paper thickness. It is possible to automatically and accurately adjust the facing interval between and according to the change in the thickness of the printing paper. In addition, the paper thickness is adjusted every time printing is started, and printing can be performed on a new striking surface of the platen roller, so that a very high printing quality can be stably maintained, which is an extremely useful effect in the industry.

[Brief description of drawings]

FIG. 1 is a schematic side view of an embodiment according to the present invention.

FIG. 2 is a schematic side view of essential parts showing an operating state of the platen roller of FIG.

FIG. 3 is a time chart of FIG.

[Explanation of symbols]

 1 Printing paper 2, (2-1), 2-2 Tractor 3 Print head 4 Platen roller 5 Platen rotation motor 6 Cam 7 Cam drive motor 8 Torque limiter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Teruhito Kushida 35, Saho, Shrine Town, Kato-gun, Hyogo Prefecture (no address) Inside Fujitsu Peripheral Machines (72) Inventor Kaoru Hama 35, Saho, Kato County, Hyogo Prefecture (No address) Inside Fujitsu Peripherals Co., Ltd.

Claims (2)

[Claims] 1. A platen roller and a print head are arranged so as to face each other with a print sheet conveyed by engaging with a tractor being sandwiched therebetween,
The platen roller is brought into contact with the printing paper and moved toward the printing head while rotating in the direction opposite to the conveying direction, and the printing paper is pulled in the opposite direction by contact friction with the tractor as a fulcrum and a new striking surface is obtained. An automatic paper thickness adjusting method for a printer device, comprising: stopping at a position and pressing a print paper against the print head; and then retracting the platen roller by a predetermined distance to adjust to a predetermined facing distance. 2. A print head disposed at a print position in front of a tractor that conveys print paper, and a platen that is movably and pivotally mounted so as to face the print head and be urged by a spring in a direction away from the print head. A roller, a platen rotation motor that rotationally drives the platen roller in a direction opposite to the printing paper conveyance direction, a cam having a cam surface that moves the platen roller forward and backward with respect to the print head, and a torque limiter for the cam. And a cam drive motor that is driven to rotate forward and backward through the platen roller, while moving toward the print head while rotating the platen roller in contact with the printing paper,
Performing a printing operation by pulling the printing paper in a direction opposite to the conveying direction and pressing the printing paper while sandwiching the printing paper against the print head while stopping at a new striking surface position, and retracting the platen roller a predetermined distance. An automatic paper thickness adjustment structure for printers.