JP2752660B2 - Printing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing apparatus, and more particularly to a printing apparatus having a platen that moves according to the thickness of a printing medium.

[Conventional technology]

Conventional printing devices with a platen that changes the distance from the print head in accordance with the thickness of the print medium to be printed,
The apparatus has a measuring member whose position changes in accordance with the thickness of the print medium, and controls to change the position of the platen with respect to the print head using the position of the measuring member as an index.

[Problems to be Solved by the Invention] The conventional printing apparatus as described above has no means for confirming whether or not the thickness of the printing medium detected by the measuring member is accurate. In the case of the booklet, if a foreign object is caught in the detection location, or if the print medium has wrinkles or breaks at the detection location, it is detected as being thicker than the correct thickness of the print medium, and the platen is misaligned and printed. Has the disadvantage that it becomes unclear.

[Means for solving the problem]

SUMMARY OF THE INVENTION In order to solve the above-mentioned drawbacks of the conventional printing apparatus, the present invention provides a sensor, a detecting mechanism for changing a position of the printing medium in response to a change in thickness of the printing medium, a member to be detected by the sensor, and a print head. And a card holder having a pressure sensor for sensing a contact pressure with the print medium.

That is, the printing apparatus of the present invention includes two pairs of transport rollers that transport the print medium in the horizontal direction, an upper roller disposed in front of a transport roller on the near side of the two pairs of transport rollers, A lower roller facing the upper roller and disposed below the lower roller, a carrier supporting the lower roller, a shaft guiding the vertical movement of the carrier, a bracket supporting the shaft, and the bracket and the carrier. A spring mounted between the springs, for pressing the carrier upward, an optical sensor fixed to the carrier, and a card holder disposed above the print medium between the two pairs of transport rollers and disposed at a leading end thereof A pressure sensor mounted on the card holder, and a pressure sensor disposed below and opposed to the print head in the vertical direction. Comprises a linearly movable platen, and a plate to block the optical path of the optical sensor is fixed to the platen by the vertical motion of the platen.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

 FIG. 1 is a front view showing an embodiment of the present invention.

In FIG. 1, the mechanism for detecting the thickness of the print medium 8 includes a carrier 3 on which an optical sensor 1 and a lower roller 2 are mounted, and an upper roller 4 provided to face the lower roller 2. The carrier 3 is vertically slidable along a shaft 6 vertically supported by a bracket 5, and the lower roller 2 is pressed against the upper roller 4 by a spring 7. When the print medium 8 is transported between the upper roller 4 and the lower roller 2, the print medium 8 is sandwiched between the upper roller 4 and the lower roller 2. The platen mechanism includes a plate 9 to be detected by the optical sensor 1 and a platen 10 to which the plate 9 is attached. The platen 10 is provided to face the print head 11. And move in the printing direction. At the tip of the print head 11, a card holder 13 incorporating a pressure sensor 12 is mounted. The transport rollers 14a and 14b and 15a and 15b transport the print medium 8 therebetween. A sensor 16 provided between the card holder 13 and the transport roller 15a is a sensor for determining a stop position of the print medium 8.

Next, the operation of the above embodiment will be described with reference to FIG.

FIG. 2A shows a state in which the print medium 8 has been conveyed in the direction of arrow A, and the leading end thereof has been detected by the positioning sensor 16 and stopped. At this time, the platen 10 is moved downward and retracted to make it easier for the print medium 8 to be conveyed below the print head 11, and the carrier 3 corresponds to the thickness of the print medium 8. And is pushed down in the direction of arrow B.

FIG. 2B shows a state in which the platen 10 is driven in the direction of arrow C and the printing medium 8 is pressed against the card holder 13 in which the pressure sensor 12 is incorporated. At this time, the plate 9 on the platen 10 completely shields the optical sensor 1 on the carrier 3 from light.

FIG. 2 (C) shows that the pressure sensor 12 detects that the print medium 8 has been pressed against the card holder 13 by the platen 10, whereby the platen 10 descends in the direction of arrow D and the plate 9 It is in a state where it stops at the position where the light shielding is released. At this time, it is checked whether or not the amount of movement from when the platen 10 presses the print medium 8 to the card holder 13 until the platen 10 descends and stops again falls within a certain standard value range. At a position where the thickness of the print medium 8 is detected, that is, at a position sandwiched between the upper roller 4 and the lower roller 2,
When foreign matter is attached or wrinkled, the carrier 3 moves lower than the normal thickness of the printing medium. Therefore, when the movement of the platen 10 is controlled based on the sensor 1, the printing is performed with the platen 10. The gap with the head 11 increases. Therefore, once the platen 10 is raised until it comes into contact with the card holder 13 and then lowered, monitoring the amount of descent at that time makes it possible to determine whether or not the thickness of the print medium has been accurately measured, and to detect an erroneous detection. Can be prevented.

〔The invention's effect〕

As described above, when the printing apparatus of the present invention detects the thickness of the printing medium and controls the position of the platen, the platen is moved to the uppermost position, then lowered again, and moved to the predetermined position. By monitoring the amount of movement at that time, there is an effect that it is possible to prevent erroneous detection of the thickness of the print medium, so that a precise gap between the platen and the print head is always secured to ensure a clear image. There is an effect that printing can be performed.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of the present invention, and FIG.
FIGS. 1 to 3C are front views showing different operation states of the embodiment of FIG. 1 ... optical sensor, 2 ... lower roller, 3 ... carrier,
4 Upper roller, 5 Bracket, 6 Shaft, 7 Spring, 8 Print medium, 9 Plate, 10 Platen, 11 Print head, 12 Pressure sensor, 13 … Card holder, 14a ・ 14b ・ 15a ・ 15b…
… Transport roller, 16… Sensor.

Claims (1)

(57) [Claims] 1. A pair of transport rollers for transporting a print medium in a horizontal direction, an upper roller disposed in front of a transport roller on the near side of the two pairs of transport rollers, and an upper roller facing the upper roller. A lower roller disposed below the lower roller, a carrier for supporting the lower roller, a shaft for guiding the vertical movement of the carrier, a bracket for supporting the shaft, and a mounting between the bracket and the carrier. A print head disposed above the print medium between the two pairs of transport rollers and having a card holder at a leading end thereof, a spring for pressing the carrier upward, a light sensor fixed to the carrier, and a card holder. A pressure sensor mounted on the card holder, and a pressure sensor disposed below and opposed to the print head and capable of linearly moving in a vertical direction. Ten and printing apparatus characterized by comprising a plate to block the optical path of the optical sensor is fixed to the platen by the vertical motion of the platen.