JP3886208B2 - Platen rotation drive structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rotational drive structure for a platen such as a printer.
For example, in an impact printer, in order to perform printing, a platen is arranged facing a print head and maintaining an interval corresponding to the thickness of a print medium (paper, ink ribbon, etc.).
[0002]
This platen is freely rotated along with the printing line feed of the paper so that the same position on the outer peripheral surface is not hit. If the platen rotates freely and has not stopped at the next printing, the paper will settle down. Worsens and adversely affects print quality. Therefore, there is a strong demand for a structure that immediately stops after rotating the platen.
[0003]
[Prior art]
As shown in the schematic perspective view of the main part of FIG. 3, the platen 12 in the conventional impact printer has a platen 12 disposed opposite to the print head 11 indicated by a two-dot chain line. A sheet and an ink ribbon (not shown) are horizontally passed between the platen 12 and printing. An arrow B indicates the paper feeding direction.
[0004]
The platen 12 is pivotally supported so as to rotate according to the print line feed of the paper so that the same position on the outer peripheral surface is not stamped for a long time. That is, the platen 12 is rotatably supported at both ends by a bearing (not shown) that is guided by a guide rail provided on a printer frame (not shown) and slides vertically.
[0005]
Further, after the platen 12 is separated from the print head 11 by the platen moving means 13, the platen 12 approaches again and is set at a predetermined print interval.
In this platen moving means 13, two eccentric cams 13b fixed on a cam shaft 13a pivotally attached to the printer frame in parallel with the platen 12 abut against a rotating roller (ball bearing) 12a fixed to the platen 12. The platen 12 is supported, and the camshaft 13a is rotated forward and backward by a pair of drive gears 13d and 13e provided between the camshaft 13a and a pulse motor 13c that can rotate forward and backward, and torque not shown in the gear 13d. It is configured with a limiter. Further, a light shielding plate 13f for detecting the reference position of the eccentric cam 13b by the light detecting element 13g is attached to one end of the cam shaft 13a.
[0006]
As shown in the schematic side view of FIG. 4, the outer peripheral surface of the eccentric cam 13 b is eccentric in a cochlear shape with a gradually increasing radius. If the eccentric cam 13 b rotates in the clockwise direction, the platen 12 is temporarily removed from the print head 11. When it is separated (outward) and rotated counterclockwise, it approaches the print head 11 (return).
[0007]
Next, automatic adjustment of the printing interval between the platen 12 and the print head 11 by the platen moving means 13 will be described with reference to FIGS.
When printing is started for the printer, automatic adjustment of the printing interval of the platen 12 is started. That is, when the pulse motor 13c is rotated reversely by a drive circuit (not shown), the light shielding plate 13f of the camshaft 13a rotates counterclockwise and the edge thereof is detected by the light detection element 13g, the pulse motor 13c is stopped. Thus, the eccentric cam 13b returns to the reference position. At this time, the platen 12 is also at the reference position.
[0008]
Next, the pulse motor 13 c rotates forward to rotate the eccentric cam 13 b in the clockwise direction, and moves the platen 12 toward the print head 11 to press the paper and the ink ribbon against the print head 11.
[0009]
Then, a torque limiter (not shown) is operated by the pressing force, and the pulse motor 13c is stopped by the output. Again, the pulse motor 13c is reversely rotated to return the eccentric cam 13b to the reference position.
[0010]
The moving distance of the return path of the platen 12 (the approach to the print head 11) is smaller than the reference distance from the reference position of the platen 12 to the print head 11 by a distance equal to the thickness of the paper 14 and the ink ribbon 15. Therefore, the eccentric cam is rotated by rotating the pulse motor 13c again in the forward direction so as to correspond to the moving distance obtained by subtracting the distance (corresponding to the predetermined printing interval) obtained by adding the predetermined gap to the distance (thickness) from the reference distance. When the 13b is rotated clockwise from the reference position, the platen 12 is automatically set apart from the print head 11 by a predetermined printing interval.
[0011]
The relationship between the rotation angle of the eccentric cam and the amount of movement of the platen is designed and assembled in advance so as to be a predetermined printing interval.
[0012]
[Problems to be solved by the invention]
However, according to the platen rotation drive structure as described above, the platen is automatically set apart from the print head by a predetermined printing interval, but can be freely rotated. However, if it still moves at the time of the next printing due to inertia, there is a problem that the settling of the paper after the line feed becomes worse and the printing quality is adversely affected.
[0013]
Therefore, it is conceivable to connect rotation drive means such as a pulse motor to the platen and rotate the platen in conjunction with the adjustment of the printing interval of the platen, but the problem is that the electrical control circuit and mechanical structure become complicated. There is.
[0014]
In view of the above problems, an object of the present invention is to provide a platen rotation drive structure in which the platen is not rotated in the paper feed direction after being rotated by a fixed rotation angle in conjunction with the adjustment of the printing interval with the print head. To do.
[0015]
[Means for Solving the Invention]
In order to achieve the above object, in the platen rotation drive structure of the present invention, in the platen rotation drive structure in which the platen is set at a print interval corresponding to the thickness of the print medium with respect to the print head, the platen is connected to the print head. A platen moving means for making the print head approach again after separation, first and second one-way clutches fixed to the platen with the same locking direction, and the first and second one-way clutches. The first and second pinion gears fixed to each of the first and second pinion gears, and the first and second pinion gears are rotated in opposite directions in conjunction with the movement of the platen by the platen moving means. configuring comprises first fixed to the mesh was in the printer frame, a platen rotating means consisting of a second rack, the Preferably, the platen moving means has a rotation driving means capable of rotating in the forward and reverse directions to rotate the eccentric cam in contact with the rotation roller fixed to the platen to move the platen relative to the print head. And configure.
[0016]
With this configuration, when the platen moves away from the print head when the printing interval is adjusted by the platen moving means, the first and second pinion gears rotate in opposite directions, and the rotation direction and the one-way clutch lock The first one-way clutch having the same direction rotates the platen, and the other second one-way clutch rotates idly with respect to the platen.
[0017]
Next, when the platen approaches the print head, the first and second pinion gears rotate in the opposite directions in the same manner, but this time the second one-way clutch that coincides with the opposite direction of the lock direction is moved to the platen. Are further rotated in the same direction, and the first one-way clutch is idled with respect to the platen.
[0018]
As a result, the platen can be rotated in one direction when being separated or approached (in a later-described embodiment, the platen is rotated in the direction opposite to the paper feed direction), and can be set at a position shifted from the original position.
[0019]
The first and second racks are engaged so that the first and second pinion gears of the first and second one-way clutches fixed to the platen with the same locking direction are rotated in opposite directions. Therefore, after the platen is set at the printing interval, it cannot be rotated in the paper feed direction.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the gist of the present invention will be described in detail based on the embodiments shown in the drawings. In addition, the part demonstrated in the prior art figure uses the same code | symbol, and abbreviate | omits the description.
[0021]
As shown in the schematic perspective view of the main part of FIG. 1, the platen moving means 13 for moving the platen 12 away from the print head 11 and then approaching it again is the same as the conventional structure. In addition, the printing interval is automatically set corresponding to the thickness of the ink ribbon.
[0022]
As shown in FIG. 1, the rotation driving structure of the platen of the present invention includes first and second one-way clutches 1a and 1b fixed on the platen 12 with the same locking direction, and the first and second one-way clutches. First and second pinion gears 1a-1 and 1b-1 (fixed to an outer ring (not shown) of the one-way clutch) and platen 12 fixed to the clutches 1a and 1b, respectively, in one direction, that is, the direction opposite to the sheet feeding direction The first and second pinion gears 1a-1 and 1b-1 are engaged with each other so as to rotate in opposite directions in conjunction with the movement of the platen 12 (movement when adjusting the printing interval). It differs from the conventional structure in that platen rotating means 1 including first and second racks 1a-2 and 1b-2 fixed to the printer frame is provided.
[0023]
The one-way clutch has a structure in which when an inner ring (not shown) fixed to the shaft portion of the platen is rotated in the direction of arrow A, an outer ring (not shown) is locked to the inner ring and can be driven, and when the inner ring is reversely rotated, it rotates idly. Yes.
[0024]
Next, the operation of the platen rotating means will be described with reference to FIG. 1 and using the diagram showing the relationship between the movement and rotation of the platen of FIG. 1 shown in FIG. In the figure, point P indicates the state of rotation of the platen.
[0025]
The first and second pinion gears 1a-1 and 1b-1 of the first and second one-way clutches 1a and 1b are engaged with the first and second racks 1a-2 and 1b-2, respectively. When the platen moving means 13 separates the platen 12 from the print head 11 to return to the reference position, the first and second pinion gears 1a-1 and 1b-1 are moved to the first and second racks 1a-2 and 1b. -2 rotate in opposite directions to each other, and the first one-way clutch 1a that coincides with the locking direction (clockwise direction of arrow A) rotates the platen 12 in the counterclockwise direction (the direction opposite to the paper feeding direction). The other second one-way clutch 1b idles with respect to the platen 12.
[0026]
Next, when the platen 12 approaches the print head 11 to press the paper and the ink ribbon, the first and second pinion gears 1a-1 and 1b-1 are similarly connected to the first and second racks. The second one-way clutch 1b whose locking direction coincides with the counterclockwise rotation further rotates the platen 12 further in the same counterclockwise direction, and the first one-way clutch 1a is rotated by 1a-2 and 1b-2. It idles with respect to the platen 12.
[0027]
Next, the platen 12 is further rotated in the same direction when the platen 12 is separated from the reference position again, and the platen 12 is further rotated in the same direction when set at a predetermined printing interval from the reference position. That is, since the platen 12 rotates by the rotation angle of four times for every two reciprocations, the platen 12 is set at a position shifted from the original position.
[0028]
Thus, the platen 12 set at a predetermined printing interval cannot be rotated in the paper feed direction via the first and second one-way clutches 1a and 1b.
Therefore, when the platen 12 is moved back and forth by the platen moving means 13 to adjust the printing interval, the platen 12 once separates from the print head 11 and approaches again to print media (paper and ink ribbon in the above embodiment). When the printing interval is set according to the thickness of the sheet, the platen rotating means 1 of the present invention causes the platen 12 to deviate from the original position by the rotation angle and cannot always rotate in the paper feeding direction. Settles quickly and does not adversely affect print quality.
[0029]
In the embodiment described above, the platen is rotated by two reciprocating movements by four rotation angles. However, the platen is temporarily returned to the reference position, and then the platen is pressed against the print medium and slightly retracted from the position. The rotation angle may be set to a predetermined printing interval, and the reciprocating movement may be rotated by two rotation angles (ignoring a slight backward movement).
[0030]
【The invention's effect】
As described above, according to the present invention, a simple mechanical platen rotating means that operates in conjunction with the reciprocating movement of the platen is provided without depending on a complicated electrical and mechanical configuration. The platen can be rotated by a certain rotation angle at the same time as adjusting the printing interval according to the thickness of the print medium, and after adjusting the printing interval of the platen, it cannot be rotated in the paper feed direction. It produces extremely useful effects in the industry such as calming and not deteriorating print quality.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view of a main part of an embodiment according to the present invention. FIG. 2 is a diagram showing a relationship between movement and rotation of a platen of FIG. Schematic side view of the eccentric cam in Fig. 3 [Explanation of symbols]
1: Platen rotating means 1a, 1b: One-way clutches 1a-1, 1b-1: First and second pinion gears 1a-2, 1b-2: First and second racks 11: Print head 12: Platen 13: Platen moving means

Claims (2)

In the platen rotation drive structure in which the platen is set at a print interval corresponding to the thickness of the print medium with respect to the print head,
A platen moving means for moving the platen away from the print head and then bringing the platen closer to the print head;
First and second one-way clutches fixed to the platen with the same locking direction; first and second pinion gears fixed to each of the first and second one-way clutches;
First and second fixed to the printer frame in mesh with the respective pinion gears so as to rotate the first and second pinion gears in opposite directions in conjunction with the movement of the platen by the platen moving means. Platen rotating means comprising a rack of
A platen rotation drive structure characterized by comprising: The platen moving means includes rotation driving means capable of rotating in the forward and reverse directions to rotate an eccentric cam that is in contact with a rotation roller to which the platen is fixed to move the platen relative to the print head. Item 2. A platen rotation drive structure according to Item 1.

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