JPH02303872A - Automatic sheet thickness detection mechanism - Google Patents

Abstract

PURPOSE:To provide an automatic sheet thickness detection mechanism having improved reliability by providing an arrangement including a first lever to move a press roller relative to a feed roller depending on the thickness of record sheets passing therethrough. CONSTITUTION:In a printer, a first automatic sheet thickness detection mechanism is provided on one side of platen, while a second one on the other side thereof, whereby, when a cutform 1a, as a record sheet, is supplied from F side, it is conveyed, being held between a feed roller 4a and a press roller 5a, whereby a first lever 6a for supporting the roller 5a pivots on its axis counterclockwise through an angle corresponding to the thickness of the sheet 1a so that the gap between the rollers 5a and 4a is adjusted depending on the thickness of the cutform 1a. And then, a second lever 8a pivots on its axis to depress a fixed axis 3a provided at the center of the platen 3, thereby causing the platen 3 to be automatically pressed down over a distance corresponding to the thickness of the cutform 1a, so that the gap between the print surface of a print head 2 and the record surface of cutform 1a can always be kept by the stable action, effecting printing actions at uniform density. As a result, an automatic sheet thickness detection mechanism having improved reliability can be provided.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a printing device capable of recording on recording paper of different thicknesses, and in particular, to a printing device that automatically sets the gap between the print head and one latin. Related to automatic paper thickness detection mechanism.

[Conventional technology]

In a printing device using a wire dot print head,
It is necessary to maintain a constant gap between the printing surface of the recording paper and the recording surface of the print head so that printing can be done with uniform density.For example, it is necessary to keep the gap between the printing surface of the recording paper and the recording surface of the print head constant, so that it can be printed with uniform density. When printing, the platen or print head is moved up and down by the thickness of the recording paper each time to maintain a constant gap.

Conventionally, in this type of mechanism, for example, in the method of moving the platen up and down, the platen does not operate by itself, so some kind of drive source is always required. The camshaft is connected to the camshaft by a gear, or the camshaft is connected to the camshaft by a toothed belt.

Furthermore, a pair of rollers for detecting paper thickness is provided near the platen, and changes in the thickness of the recording paper pinched by the rollers are made to face an optical sensor fixed to the platen side via a lever. As a shielding plate, the output of the optical sensor (for example, when the lever moves slightly due to fluctuations in paper thickness, the "bright"
to "dark"), the head gap setting value is determined.

Assuming that the output of the optical sensor indicates a "dark" state under operating conditions and the gap between the print head and platen is within the set value, the shielding plate that moves slightly due to changes in the thickness of the recording paper will Move away from the center of the optical sensor, and the output will recognize the "bright" state. Here, the motor is driven by a control unit that controls the drive source, and the camshaft is rotated to move the platen up and down to find the position where the optical sensor is in the "dark" state.

Additionally, the paper thickness detection mechanism is generally provided at a location on the recording paper insertion side of the apparatus, that is, in front of the platen.

[Problem to be solved by the invention]

With the above-mentioned structure, operational variations such as motor stopping position accuracy, gear backlash, toothed belt elongation, and cam accuracy are likely to occur, which requires manpower and time for adjustment during assembly. In addition, it also requires an amplifier circuit for the optical sensor and a drive circuit for the motor, resulting in an overall increase in the number of parts and an increase in cost.

SUMMARY OF THE INVENTION An object of the present invention is to provide an automatic paper thickness detection device that solves the above problems.

[Means to solve the problem]

In order to achieve the above object, the automatic paper thickness detection mechanism according to the present invention includes a platen for supporting recording paper whose relative position changes with respect to the print head, a feeding roller that feeds the recording paper, and a recording paper on the feeding roller. a pressure roller that presses the paper; a first lever that pivotally supports the pressure roller and displaces the pressure roller relative to the feeding roller according to the paper thickness of the recording paper that passes between the feeding roller and the pressure roller;
a second lever that moves the platen parallel to the print surface with respect to the print head while being driven by the first lever; and a second lever that applies a pressure contact force to the pressure roller with respect to the pressure roller, and causes the print head to print on the platen. It has a pressurizing means that applies a force that withstands the pressure.

[Effect]

The automatic paper thickness detection mechanism for printing on recording paper of different thickness according to the present invention always presses the pressure roller against the feeding roller by a predetermined uniform tension from a tensioned spring in the initial state, and also presses the pressure roller against the feeding roller. It is also applied upwardly as a force to withstand the printing pressure of the print head.

When recording paper is inserted from the front or rear of the platen in this state, the thickness of the recording paper rotates the first lever that supports the pressure roller, transmits the amount of rotation to the second lever, and rotates the platen. It moves in parallel to a predetermined position with high precision.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic side view showing an automatic paper thickness detection mechanism according to the present invention, and the process mechanism section of the entire printing apparatus is omitted.

In Fig. 1, la and lb are recording sheets, 1a shows the case when they are inserted from the front of the platen (hereinafter referred to as FIII!I), and 1b shows the case when they are inserted from the rear of the platen (hereinafter called the R side). There is.

In the figure, the present invention is directed to a printing device that allows recording paper to be conveyed from the front or rear of the device, and a first automatic paper thickness detection mechanism is provided on one side centering on the position of the platen 3. The other side is equipped with a second automatic paper thickness detection mechanism.

The first and second automatic paper thickness detection mechanisms are connected to the print head 2.
A platen 3 for supporting recording paper is displaceable in the vertical direction relative to
feeding rollers 4a, 4b that feed the recording sheets 1a, lb; pressure rollers 5a, 5b that press the recording sheets 1a, lb against the feeding rollers 4a, 4b; and pressure rollers 5a, 5b.
The pressure roller 5a rotates angularly around the support shaft, depending on the paper thickness of the recording paper 1a, lb that passes between the feeding rollers 4a, 4b and the pressure rollers 5a, 5b.
, 5b relative to the feed-out rollers 4a, 4b, and a first lever 6a, 6b connected to the first lever 6a, 6b via a link 7.7 and engaged with the fixed shaft 3a of the platen 3. second levers 8a and 8b that move the platen 3 parallel to the printing surface relative to the print head 2 while being driven by the first levers 6a and 6b; It rotates around the support shaft in response to the force, supports the platen 3 with the force that withstands the printing pressure from the print head 2, and both levers 6a, 6
b, 8a, 8b and the pressure roller 5a via the link 7,
5b is a feeding roller 4a.

It has a pressurizing lever 9 that applies a pressing force to 4b.

The operation of the above configuration will be explained.

In FIG. 1, if a cut sheet 1a is inserted as a recording sheet from the F side, the cut sheet 1a will be moved to the feeding roller 4a.
The first lever 6a, which supports the pressure roller 5a, moves counterclockwise around the supporting shaft by the thickness of the cut sheet 1a. The pressure roller 5a and the feeding roller 4 rotate.
Adjust the gap between the cut sheet 1a and the sheet 1a according to the paper thickness of the cut sheet 1a.

As a result, the second lever 8a becomes the first lever 6a.
It is pulled in the direction of arrow A by a link 7 that fits and connects to a pivot provided at the lower end of the .

Therefore, the second lever 8a rotates about the support shaft,
By pushing down the fixed shaft 3a provided at the center of the platen 3 and automatically pushing down the platen 3 by the thickness of the above-mentioned cut sheet 1a, the print surface of the printing pad 2 and the cut sheet 1a are separated.
The gap between the recording surface and the recording surface can be maintained at all times through stable operation, and printing operation with uniform density is possible.

By the way, it goes without saying that the position of the platen 3 must be guaranteed for accuracy during the printing operation after automatic paper thickness detection. In order to maintain the force, the pressure rollers 5a and 5b are pressed as described above using the spring 1G and the pressure lever 9 used as the pressure means, and a predetermined uniform tension is always applied to the platen 3. giving direction.

Next, from Rrllll: For example, when a continuous form 1b is inserted, automatic paper thickness detection is performed by the mechanism shown on the left side of the platen 3 in FIG.

The operation is symmetrical to the above-described embodiment in which the cut sheet 1a is inserted from the F side, and the continuous I! 1 vote
b is conveyed, and the first lever 6b, which supports the pressure roller 5b, is moved clockwise about the supporting shaft by the thickness of the continuous form 1b by being pinched between the feed roller 4b and the pressure roller 5b. Rotate.

Thereby, the second lever 8b becomes the first lever 6b.
It is pulled in the direction of arrow B by a link 7 that fits and connects to a pivot provided at the lower end of the .

Since the subsequent operation is the same as that described in the embodiment on the F side, a detailed explanation of the operation will be omitted.

In the F-side and F-side paper thickness detection mechanisms shown in FIG. The springs 10) are provided on the left and right sides of a side frame (not shown) with respect to a specific printing device width.

Although the illustrated embodiment is applied to a printing device that switches between single sheet and continuous form recording paper, it is not limited to this type of printing device. Although automatic paper thickness detection mechanisms are provided before and after the platen, it is also possible to use only one automatic paper thickness detection mechanism depending on the case.

〔Effect of the invention〕

As explained above, according to the automatic paper thickness detection mechanism according to the present invention, (1) the II structure can be simplified, so reliability is improved;

(2) Since there is no need to have a separate drive system such as a motor, costs can be reduced.

(3) It is not necessary to detect the thickness every time the recording paper is conveyed to the printing position, and the processing speed of the printing apparatus can be improved.

(4) Manual adjustment and time during assembly can be saved.

It has the following effects.

[Brief explanation of drawings]

FIG. 1 is a schematic side view showing an automatic paper thickness detection mechanism according to an embodiment of the present invention. la, lb...recording paper 2...print head 3...
-Platen 4a, 4b...Feeding rollers 5a, 5b...Pressure rollers 6a, 6b...First lever 7...Links 8a, 8b...Second lever 9...Pressure lever 10- ...Spring patent applicant NEC Corporation Shinko Seisakusho Co., Ltd. Representative Patent attorney Naka Kanno/a,
fb: # for R@ 6a, 6b: 'U lever: To print/end 7: Link 3 nib platen δY, 8b: Coil 2 lever ° -4a, 4b: Closing roller 9: Pressure lever 5α, 5b: Pressure Lola 10: Human link Figure 1

Claims (1)

[Claims] (1) A platen for supporting recording paper whose relative position changes with respect to the print head, a feeding roller that feeds the recording paper, a pressure roller that presses the recording paper against the feeding roller, and a pivoting support for the pressure roller. a first lever that displaces the pressure roller relative to the feeding roller in accordance with the paper thickness of the recording paper passing between the feeding roller and the pressure roller;
a second lever that moves the platen parallel to the print surface with respect to the print head while being driven by the first lever; and a second lever that applies a pressure contact force to the pressure roller with respect to the pressure roller, and causes the print head to print on the platen. An automatic paper thickness detection mechanism characterized by having a pressure means that applies a force that withstands pressure.