JPH0632967B2 - Head gap automatic setting mechanism - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanism for automatically setting a gap between a print head and a platen in a printer of an electronic computer according to the thickness of paper.

<< Prior Art >> In a printer that performs print processing by inserting a print sheet between the print head and the platen, a means for setting the head gap according to the thickness of the print sheet is provided in order to perform accurate and beautiful printing. is necessary. As this setting means, various mechanisms have been proposed for sandwiching a sheet between a print head and a platen to detect the sheet thickness, and then retracting the print head or the platen by a predetermined amount to automatically set the head gap.

The first one of the mechanisms is disclosed in Japanese Patent Application Laid-Open No. 50-53123, in which a print head and a platen are pressed against each other at a constant pressure to sandwich a sheet, and the print head is moved by a predetermined amount from the pressed position. It is a structure in which the head gap is set by retreating. As a modification of this first structure, Japanese Patent Laid-Open No. 62-187
According to the technique disclosed in Japanese Patent No. 064, the carriage on which the print head is mounted is supported by an eccentric guide shaft, and the shaft is urged by a spring in the advancing side rotation direction to press the print head against the paper on the platen. A structure is adopted in which a head contact is set and a head gap is set by rotating the shaft in a reverse direction by a predetermined amount via a drive system including a clutch.

The second one is disclosed in Japanese Patent Application Laid-Open No. 61-199969, in which a print head provided to be retractable and biased to its advanced position, a platen movable forward and backward, and a predetermined retracted position of the print head are provided. A sensor for detecting is provided, the platen is advanced toward the print head with the printing paper sandwiched, and the platen is retracted by a predetermined amount with the detection position of the sensor as the origin to set the head gap.

The third one is disclosed in Japanese Patent Laid-Open No. 61-262161, and is provided with a stepping motor for advancing and retracting a carriage having a print head toward a platen and a feedback pulse generator for detecting movement of the carriage. , The contact between the print head and the paper is detected by comparing the motor drive pulse and the feedback pulse when the carriage is advanced, and the absolute thickness of the paper is detected by the number of feedback pulses to the contact position.
After that, the carriage is retracted to an optimum position according to the sheet thickness to set the head gap.

<Problems to be Solved by the Invention> The first one has an advantage that the structure is simple, but holds the print head biased in the platen direction by a spring at a predetermined position by a holding current of a stepping motor or the like. Further, since the head gap is maintained, the tip of the print head is elastically pressed by the platen when the power is off, and there is a problem in that work is hindered when the ribbon is replaced.

Contrary to the first one, the second one does not have a problem such as an obstacle at the time of ribbon replacement, but has a problem that the structure is complicated, and the position where the head gap can be set is detected by the print head. There is a problem that it is limited to the position where the sensor for use is provided.

In principle, the third type performs positioning by stepping out of the stepping motor, so an error of the number of pulses for one cycle of excitation of the stepping motor (for example, 8 pulses for 1-2 phase excitation) Since the detent torque of the pulse motor is amplified and becomes large when a large reduction ratio is adopted to suppress this effect, an indentation is generated on the copy paper when the print head collides with the platen when the head gap is set. There is a problem such as doing. As a result, there is a problem that the detection accuracy of the paper thickness becomes poor, or an apparatus for increasing the detection accuracy becomes expensive and the operating speed also decreases.

An object of the present invention is to solve the above problems of the conventional apparatus, and in the case where the power is down in the head gap automatic setting mechanism of the structure in which the paper is sandwiched between the print head and the platen to detect the paper thickness. An automatic head gap setting mechanism that satisfies all the requirements that the set head gap be retained, that the structure is simple, and that the paper thickness can be detected with high accuracy with a simple structure. The challenge is to get it.

<Means for Solving the Problem> The head gap automatic setting mechanism of the present invention basically causes the print head 1 to advance and pinch the paper 3 between its tip and the platen 2 and then retract the print head by a predetermined amount. It has a structure to set the head zip. In the structure of the present invention, the carriage 4 on which the print head 1 is mounted is engaged with the first guide shaft 5 mounted at a fixed position of the frame 8 so as to be rotatable and axially movable, and parallel to the first guide shaft. It is engaged with the second guide shaft 6 so as to be movable in the axial direction. Second
The guide shaft 6 can be moved in the turning direction around the first guide shaft 5 (left and right direction in FIG. 1) by the reciprocating driving device 9, and the movement causes the print head 1 to advance and retract.

According to the first structure of the present invention, the engaging portion between the second guide shaft 6 and the carriage 4 is provided with the regulating member 12 that defines the mutual positional relationship between the second guide shaft 6 and the carriage 4. An elastic pressure member 14 that absorbs the advance of the second guide shaft 6 and urges the second guide shaft 6 toward the regulating member is provided so as to face the regulating member. A sensor 16 for detecting a predetermined amount of relative movement of the second guide shaft 6 and the carriage 4 in the engaging portion in the turning direction is provided.

In the second structure of the present invention, the regulating member 24, the elastic pressure member 22 and the sensor 16 are provided on the support portion of the second guide shaft 6. The restriction member 24 defines the positional relationship between the second guide shaft 6 and the frame 8, and the elastic pressure member 22 is
The second guide shaft 6 movable in the turning direction is attached to the regulating member 2
The sensor 16 is biased toward the second guide shaft 6
The relative movement between the frame and the frame 8 is detected.

<< Operation >> In the apparatus of the present invention, the second guide shaft 6 is moved in the advancing direction, and the paper 3 inserted by the print head 1 and the platen 2 is inserted.
The elastic guide members 14, 22 absorb the excessive advance of the second guide shaft 6 that further advances after that, and the relative movement between the members caused by the absorbing action is detected by the sensor 16. From the detection position of this sensor, The head cap is set by retracting the second guide shaft 6. When the head gap is set, the second guide shaft 6 is pressed against the regulating members 12 and 24 by the urging force of the elastic pressure members 14 and 22,
Since the urging forces of the elastic pressure members 14 and 22 are received by the regulating members 12 and 24, the set head gap is retained even after all the operating force is released.

<< First Embodiment >> FIGS. 1 to 5 and 10 show a first embodiment of the present invention. 1 is a print head, 2 is a platen, 3 is printing paper, and 4 is a print head. The carriage 5 is a first guide shaft that supports the carriage 4 so as to be rotatable about its axis and slidable in the axial direction, and 6 is a second guide shaft that is parallel to the first guide shaft. The second guide shaft 6 is axially supported by the frame 8 by eccentric end shafts 7 at both ends thereof, and a drive device 9 for rotating the second guide shaft 6 around the end shaft 7 is provided. As shown in FIG. 10, the rotation of the drive unit 9 includes a gear 25 fixed to the output shaft thereof, an intermediate gear 26 arranged immediately below the end shaft 7, and a gear 27 fixed to the end shaft 7. It is transmitted to the end shaft 7 via. Since the end shaft 7 is provided at the eccentric position of the second guide shaft 6, when the second guide shaft 6 rotates around the end shaft 7, the second guide shaft 6 is rotated.
Moves in the turning direction around the first guide shaft 5 (the tenth position).
In the figure, Δ).

10 and 11 are pins set up on the upper end of the carriage 4, 1
Reference numeral 2 denotes a roller which is pivotally attached to the pin 10 and faces the second guide shaft 6, 13 denotes an arm swingable around the pin 11, 14
Is a roller that is axially attached to the tip of the arm 13 and faces the roller 12 with the second guide shaft 6 interposed therebetween, and 15 is the arm 13
Is a winding spring that urges the roller 12 toward the opposing roller 12,
The second guide shaft 6 is sandwiched between the rollers 12 and 14 by the biasing force of the winding spring 15.

Reference numeral 16 is a photoelectric sensor fixed to the upper end of the carriage 4 via a bracket 17, and 18 is a shield plate fixed to the arm 13, which shields the rollers 12 and 14 with the second guide shaft 6 sandwiched therebetween. The tip of the plate 18 is located in the detection slit 19 of the photoelectric sensor 16 and blocks the light detected by the photoelectric sensor 16.

The head gap setting operation of the first embodiment will be described with reference to FIGS.

When inserting the paper 3, the second guide shaft 6 is rotated in the head retreating direction to separate the tip of the print head from the platen 2 (see FIG. 3), the paper 3 is inserted, and then the second guide shaft 6 is moved. Rotate the head in the forward direction. With the rotation of the second guide shaft 6, the front end of the print head 1 advances toward the platen 2 and contacts the paper 3 (FIG. 4). Then second
Although the guide shaft 6 continues to rotate, the carriage 4 cannot rotate any more due to the collision between the print head 1 and the paper 3, so that the second guide shaft 6 can be advanced by the rotation. Is absorbed by rotating around the pin 11 and retracting. As the arm 13 retreats, the shield plate 1
8 also retreats, and its tip is separated from the detection slit 19 of the photoelectric sensor 16. This detachment timing is the photoelectric sensor 1
6, the gap L formed between the roller 12 and the second guide shaft 6 at this time is always constant (fifth
Figure). The second guide shaft 6 is stopped by the detection signal,
Next, the gap L and the setting gap M set in the controller are set.
Move backward by an amount equivalent to the amount added. As a result, the gap between the tip of the print head 1 and the paper 3 is always set to a constant value. At this time, the fixed roller 12 and the second guide shaft 6 are in contact with each other (Fig. 1).

<< Second Embodiment >> FIGS. 6 to 9 are views showing a second embodiment of the present invention, and only differences from the first embodiment will be described below. The second guide shaft 6 is rotatably supported by eccentric end shafts 7 at both ends thereof being slidably fitted in the horizontal elongated holes 21 of the frame 8 in the left and right directions of FIGS. 7 to 9, And this on the right side of the figure (direction in which the print head 1 approaches the platen 2)
A tension spring 22 for urging the spring is provided. End shaft 7
In the same manner as in the first embodiment, the drive device 9 is linked to the shaft, and a shield disk 23 concentric with the end shaft 7 is provided. Since the amount of movement of the end shaft 7 along the elongated hole 21 is small, even if the end shaft 7 moves, the gears 26 and 27 shown in FIG. The rotation transmission of 9 will not be hindered.

The carriage 4 is sandwiched by rollers 12 and 14 which are axially attached to pins 10 and 11 which are planted at the upper end of the carriage 4. If necessary, one of the rollers is urged toward the other to roll the roller 1.
No clearance is formed between the second guide shaft 6 and the second guide shaft 6.

The photoelectric sensor 16 is fixed to the frame 8, and the detection slit 19 thereof faces the peripheral edge of the shielding disk 23. The peripheral edge of the shielding disk 23 blocks the optical path of the photoelectric sensor 16 when the end shaft 7 is in contact with the right end 24 of the elongated hole 21.

The head gap setting operation of the second embodiment will be described below.

When inserting the paper 3, the second guide shaft 6 is rotated in the head retreating direction to separate the tip of the print head from the platen 2 (see FIG. 7), the paper 3 is inserted, and then the second guide shaft 6 is moved. Rotate the head in the forward direction. With the rotation of the second guide shaft 6, the tip of the print head 1 advances toward the platen 2 and contacts the paper 3 (FIG. 8). Then second
Although the guide shaft 6 continues to rotate, the carriage 4 cannot rotate any more due to the collision between the print head 1 and the paper 3, so that the advance of the second guide shaft 6 by the rotation is an end shaft. 7 is absorbed by retreating along the slot 21 to the left in the figure. As the end shaft 7 retracts, the shield disk 2
3 also retreats, and its peripheral edge is separated from the detection slit 19 of the photoelectric sensor 16. This detachment timing is the photoelectric sensor 1
6, the gap L formed between the end shaft 7 and the right end 24 of the slot 21 at this time is always constant (FIG. 9). The second guide shaft 6 is stopped by the detection signal and then retracts by an amount corresponding to the amount of the gap L and the setting gap M set in the controller. As a result, the gap between the tip of the print head 1 and the paper 3 is always set to a constant value. At this time, the end shaft 7 is located at the right end of the elongated hole 21.

<< Advantages of the Invention >> According to the above-described configuration of the present invention, when the head gap is set, the fixed roller 12 is used in the first embodiment.
Between the second guide shaft 6 and the second guide shaft 6, and in the second embodiment, the end shaft 7 of the second guide shaft and the right end 24 of the slot 21.
Since the biasing forces of the springs 15 and 22 are received by the contact with the print head 1 and the printing head 1 does not move due to the biasing forces of these springs 15 and 22, the head gap once set does not have power down or the like. Even if it occurs, it will not go mad. Further, since the second guide shaft 6 is moved so that the carriage 4 is rotated around the first guide shaft 5 to move the print head 1 forward and backward, the structure is simple and the maintenance is easy. Further, since the reference position for setting the head gap can be detected with high accuracy by the sensor 16, the setting accuracy of the head gap can be made extremely high.

[Brief description of drawings]

1 to 5 show a first embodiment of the present invention. FIG. 1 is a side view of a printer when a head gap is set, FIG. 2 is a plan view of the same, and FIGS. [Fig. 8] is a side view showing a head gap setting operation. 6 to 9 show a second embodiment of the present invention. FIG. 6 is a plan view of the printer, FIGS. 7 to 9 are side views showing the head gap setting operation, and FIG. FIG. 6 is an enlarged side view showing a reciprocating drive mechanism of a second guide shaft. In the drawing, 1: print head 2: platen 3: printing paper 4: carriage 5: first guide shaft 6, second guide shaft 8: frame, 9: drive device 12: roller (regulating member), 14: Roller (pressurizing member) 16: Photoelectric sensor 22: Extension spring (pressurizing member) 24: Right end of elongated hole (regulating member)

Claims (2)

[Claims] 1. A head gap automatic setting mechanism for setting a head gap by retracting the print head by a predetermined amount after the print head (1) is advanced and the paper (3) is sandwiched between the tip of the print head (1) and the platen (2). A second guide parallel to the first guide shaft while a carriage (4) carrying the print head (1) is rotatably and axially movably engaged with a first guide shaft (5) mounted at a fixed position. The second guide shaft (6) is provided with a reciprocating drive device (9) that is engaged with the guide shaft (6) so as to be movable in the axial direction and moves the second guide shaft (6) in the turning direction around the first guide shaft (5). At the engaging portion between the carriage (4) and the carriage (4), the regulation member (12) that regulates the mutual positional relationship and the second guide shaft (6) after the print head (1) comes into contact with the paper (3) ) Is provided and a pair of elastic pressure members (14) for urging the elastic force toward the restricting member are provided, and the pair of elastic members is provided in front of the second guide shaft (6) and the carriage (4). An automatic head gap setting mechanism, characterized in that a sensor (16) for detecting a predetermined amount of relative movement in the turning direction is provided. 2. An automatic head gap setting mechanism for setting a head gap by retracting the print head by a predetermined amount after advancing the print head (1) and sandwiching the paper (3) between the tip of the print head (1) and the platen (2). A second guide parallel to the first guide shaft while a carriage (4) carrying the print head (1) is rotatably and axially movably engaged with a first guide shaft (5) mounted at a fixed position. The second guide shaft (6) is provided with a reciprocating drive device (9) that is engaged with the guide shaft (6) so as to be movable in the axial direction and moves the second guide shaft (6) in the turning direction around the first guide shaft (5). The support portion of (6) is provided with a regulating member (24) that regulates the positional relationship with the frame (8) and the second member after the print head (1) comes into contact with the paper (3).
A pair of the elastic member (22) for absorbing the advance of the guide shaft (6) and biasing the guide shaft (6) toward the restricting member is provided, and the turning of the second guide shaft (6) and the frame (8) is performed. A head gap automatic setting mechanism, characterized in that a sensor (16) for detecting a predetermined amount of relative movement in the direction is provided.