JPH0263782A - Printing head position adjustment mechanism - Google Patents

Abstract

PURPOSE:To automatically adjust the distance between a platen and a printing head according to the thickness of paper to be supplied and thereby allow constantly optimal printing operation by providing a sensor which detects the displacement of the first linkage mechanism moving in an opposite direction to the platen in accordance with the thickness of paper and adjusting the position of the printing head according to the thickness of the paper to be supplied. CONSTITUTION:If paper 12 is supplied to a position immediately before a printing position, a stepping motor rotates an eccentric shaft 22 to move a carriage 20 downward from an initial position above where it is positioned in advance. Subsequently, a shaft 22 pushes a photosensor arm 30 downward around a pin 32, resisting the elastic force of a spring 36. The rotation of the stepping motor responds to the action of a photosensor 34, and allows the carriage 20 to move downward while the photosensor 34 is blocked from light by a sensor blocking plate 40. However, the rotation stops, if the carriage 20 arrives at a broken line position where the light is not blocked below the sensor blocking plate 40. In addition, the carriage 20 stops its descent, synchronized to the stop of the motor, and at the same time, the printing head 18 stops at an appropriate position where an optimal printing is ensured.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to printers, and more particularly to a print head position adjustment mechanism for a printer that detects the thickness of paper to be printed and adjusts the print head to an optimal position in response to the detected thickness. .

An example of a known printer print head position adjustment mechanism is one shown in FIG. 2, for example. In this mechanism, an eccentric shaft 1 is rotated by a stamping motor or the like to move a carriage 2 up and down along a support shaft 3, and at the same time, a print head 4 attached to the carriage 2 can be adjusted up and down. The paper 6 is sandwiched between the print head 4 and the platen 5, and after the motor has stepped out and the distance between the paper 6 and the head 4 is set to O, the distance between the paper 6 and the platen 4 is set to the proper distance for printing. Printing was performed after the eccentric shaft 1 was rotated in the opposite direction so as to be separated by a certain distance.

Another means is shown in FIG. In this known structure, a paper thickness detection lever 7, a CCD shielding plate 8, and a CCD element 9 are provided in order to automate the mechanism shown in FIG. When the paper 6 is fed between the paper thickness detection lever 7 and the table 10, the lever 7 rotates up and down around a pivot shaft. The CCD shielding plate 8 moves up and down in conjunction with the lever 7.

The amount of movement of this CCD shielding plate is read by a CCD element, and the data is sent to the CPU to drive the print head adjustment motor and adjust the print head 4 to the proper printing position.

The mechanism shown in Fig. 2 is cheap and simple, but it opens a gap between the head 4 and the platen 5 before the paper 6 reaches the printing position.
This function prevents thick paper from getting caught in the head, etc., and also lowers the head position after the paper reaches the printing position, and raises the head again to the optimal position after the motor is out of step. It was necessary to start printing after that. For that reason,
It took time to detect the paper thickness and adjust the print position, slowing down the overall printer processing speed. In addition, since this method causes the motor to step out, it is not possible to recognize the absolute value of the paper thickness, and it is not possible to determine the paper type based on the difference in paper thickness (for example, sheet or multi-copy paper). It was not possible to make adjustments, etc.

These problems have been solved to some extent by the mechanism shown in FIG. In other words, in the structure shown in Figure 3, the CCD element determines the paper thickness before the paper reaches the printing position, so the process of lowering the head and raising the head can be omitted, increasing the overall processing speed of the printer. Furthermore, since the paper thickness is known as an absolute value, it is possible to determine the paper type based on the paper thickness, and the problems of the apparatus shown in FIG. 2 can be solved. However, since the apparatus shown in FIG. 3 uses a CCD element having a resolution in the μm unit, the cost of the element itself is high, and therefore the overall cost is high.

The present invention provides a mechanism that achieves the same effect as using an expensive CCD element without using it.

In order to solve the above-mentioned problem, the present invention for increasing the amount of paper includes: a first link mechanism that moves in a direction opposite to the platen in response to the thickness of the paper; a sensor that detects at least the movement of the link mechanism; A second link mechanism that supports the acid sensor and moves the head in a direction opposite to the platen is provided, and accurate head position adjustment is made possible by adjusting the lever ratio of the levers that make up each link mechanism.

A sensor is provided to detect the displacement of a first link mechanism that moves in a direction opposite to the platen in response to the thickness of the paper being printed, and the head position is adjusted by a second link mechanism.

Figure 1 shows an embodiment of the present invention, in which a platen 16 is held on a side body, such as a table 14, that supports paper 12. A print head 18 is arranged in a direction facing the platen 16 (in the embodiment above the platen). The print head 18 is secured to a generally L-shaped carriage 20. The carriage 20 is pivoted to a shaft, preferably an eccentric shaft 22, mounted to the frame. This eccentric shaft 22 is connected to the output shaft of a motor (not shown) and is moved by the motor. The end of the carriage 20 has a groove shape in which a support shaft 24 fixed to the frame is held.

A first arm, ie, a photosensor arm 30, is arranged at a position on the paper exit side and between the lower side of the eccentric shaft 22 and the upper side of the paper. One end of the arm 30 is pivoted to the frame by a pin 32. The arm 30
The upper surface of the intermediate portion of is in contact with the eccentric shaft 22. Further, a photosensor 34 is fixed to the other end of the arm 30. The arm 30 is in elastic contact with the eccentric shaft 22 by a spring 36 attached to the frame at one end so as to be in forced contact with the eccentric shaft 22 at all times.

At the initial position, the shaft 22 is eccentric upward, and the carriage 20 and photosensor arm 30 are maintained at the uppermost position.

A second arm or sensor shielding plate 40 is disposed on the paper inlet side and above the paper.

One end of the sensor light shielding plate 40 is disposed to face the photosensor 34 fixed to the photosensor arm 30 and cooperates with the photosensor 34 . The other end of the sensor light shielding plate 40 is pivoted to a pin 42 fixed to the frame. Furthermore, a roller 44 is pivotally supported below the middle of the sensor light shielding plate 40. This roller 44 is
It is in contact with the paper 12 being fed onto the table 14.

One end of the sensor light-shielding plate 40 is brought into elastic contact with the table 14 by a spring 46 attached to the frame so that the roller 44 is always in contact with the paper.

In the apparatus of the present invention shown in FIG. 1, when paper 12 is fed onto table 14, spring 4 responds to the thickness of paper 12.
The roller 44 is moved upward against the elastic force of the pin 42, thereby causing the sensor light shielding plate 40 to move upward around the pin 42.

When the paper 12 is fed to just before the printing position, a stepping motor (not shown) is then activated. This stepping motor rotates the eccentric shaft 22 to move the carriage 20, which was pre-swaged and located at the initial position upward, downward. Along with this, the shaft 22 pushes the photosensor arm 30 downward around the pin 32 against the elastic force of the spring 36. The rotation of the stepping motor is responsive to the operation of the photosensor 34, and while the photosensor 34 is shielded from light by the sensor light shielding plate 40, the carriage 20
The stepping motor rotates in the direction of moving the sensor downward, but when the photosensor 34 reaches a position below the sensor light-shielding plate 40 and the sensor 34 is not shielded from light (the position shown by the broken line in FIG. 1), the stepping motor stops its rotation. do. The carriage 20, which has descended as the stepping motor rotates, stops descending in synchronization with the stop of the motor. The print head 18, which has lowered in response to the lowering of the carriage 20, also stops at the position. This position defines the optimum printing position for the supplied paper. Therefore, if printing is performed after the print head 18 has stopped at the optimum printing position, optimum printing can be performed on the supplied paper.

In the present invention, each member is adjusted such that the amount of movement of the roller 44, which rises in response to the thickness of the supplied paper, the amount of movement of the eccentric shaft 22, the amount of movement of the sensor light shielding plate 40, the amount of movement of the sensor 34, etc. Set the length. That is, pin 42
The distance from the pin 42 to the rotation axis of the roller 44 is a, the distance from the pin 42 to the lower edge of the sensor light shielding plate 40 where the sensor 34 is sensitive is b, and the distance from the pin 32 to the point where the eccentric roller 22 contacts the photosensor arm 30 is When the distance is C and the distance from the pin 32 to the point where the photosensor 34 detects the sensor light shielding plate 40 is d, the ratio of [a:b:l is (c
:d], even if the paper thickness changes, the print head 18 is fixed to the carriage 20, so the distance between the print head 18 and the platen 16 will always be the same as the supplied paper. 12, a position where optimal printing is possible is defined.

Accordingly, after the printing pressure is adjusted using the first sheet of the predetermined number of sheets according to the above procedure, the printing operation for the sheet of the predetermined loft can be completed under optimal conditions. When printing the next rond, the carriage 20 is lifted to the initial position again, and the printing pressure is adjusted in the same manner as described above, and then the printing operation is performed. Note that the photosensor 34 and the sensor light shielding plate 40 can also be attached to the other arm.

The optical plate automatically adjusts the distance between the platen and the print head in response to the thickness of the paper being fed, allowing for optimal printing at all times. Since the automatic adjustment device can be achieved with two arms, a sensor, and a motor drive shaft, the structure is simple and inexpensive.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the present invention, and FIGS. 2 and 3 show a known device. Explanation of symbols 12: Paper 14: Table 16: Platen 18; Print head 20: Carriage 2
2: Eccentric shaft support shaft pin spring pin spring.

Claims (1)

[Claims] a first arm that is in elastic contact with a shaft that is moved by a motor drive and is pivotable about one end; a second arm that is pivotable about one end in response to the thickness of the paper being fed; It consists of a rigid body that supports paper between the arms, a platen, a print head that is opposed to the platen, and a carriage that can be moved in a direction opposite to the platen by movement of the shaft, and the print head is It is attached to the carriage and can move together with the carriage in a direction opposite to the platen, and a photosensor is attached to the other end of the first or second arm to detect the other end of the second or first arm. a printhead, wherein the photosensor senses the other end of the second or first arm to stop movement of the shaft, thereby adjusting the position of the printhead relative to the platen in response to paper thickness. Position adjustment mechanism.