JPH0518714B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to a head gap adjustment device for a printer.

Prior Art First, a conventional example will be explained based on FIGS. 4 to 6. A platen 2 and a support shaft 3 are installed on opposing side plates 1, and a drive shaft 5 and a cam shaft 6, which are connected to a motor (not shown) and rotate integrally with a feed roller 4, are supported respectively. ing. Further, both sides of paper guide plates 7, which are vertically opposed to each other, are fixed to the side plate 1. A pair of left and right lift arms 10 connected by two guide shafts 8 and 9 are held on the support shaft 3 so as to be movable up and down.
A dot printer head 12, which is a printing head, is attached to these lift arms 10 via a guide shaft 8 and a carrier 11. carrier 11
is slidably held on the guide shaft 8. Further, a pinch roller 14 is rotatably held on a roller shaft 13 installed on the left and right lift arms 10. A lever 16 having a leg 15 that abuts the lower part of the shaft 9 is held on the support shaft 3 so as to be rotatable while being biased clockwise.
a first cam 18 having a pressing surface 17 that presses 6;
is fixed. Further, on the inner surface of the side plate 1, a spring 2 is provided that urges the lift arm 10 toward the platen 2.
5 is retained.

Therefore, as shown in FIG.
is released from the cam 18, the lift arm 10 rotates downward by the force of the spring 25 about the support shaft 3, and the pinch roller 14 presses the paper 19 against the feed roller 4. The lift arm 10 is stable in this position and the gap between the paper 19 and the dot printer head 12 is defined.

When the number of sheets 19 increases or the thickness of the sheets 19 increases, the pinch roller 14 receives resistance from the sheets 19, so the lift arm 10 rises by the thickness of the sheets 19, as shown in FIG. Therefore, the gap between the surface of the paper 19 and the tip of the dot printer head 12 is automatically adjusted.

When not in use, the cam shaft 6 is rotated 180 degrees together with the cam 18 as shown in FIG. Rotate the lift arm 10 upward about the shaft 3,
The pinch roller 14 is separated from the feed roller 4.

Problems to be Solved by the Invention However, when not in use, the lever 16 and the lift arm 10 are subject to the force of the cam 18 while being subjected to the resistance of the spring 25 for a long period of time, so that they are easily permanently deformed. Particularly when molded from synthetic resin, it becomes easily deformed. In addition, the spring 25 fatigues quickly.

Measures to solve the problem: The print head is fixedly attached to a lift arm that is movable so as to move toward and away from a fixed platen, and a pinch roller is attached to the lift arm, which contacts a feed roller that rotates at a fixed position. a first cam that is rotatably mounted, has a spring that urges the lift arm toward the platen and the feed roller, and has a pressing surface that directly or indirectly presses the lift arm in a direction away from the platen; and a second cam having a pressing surface that presses the spring to increase the amount of deflection.

Therefore, when in use, the lift arm is released from the first cam, the pressing surface of the second cam presses the spring, the pressure of this spring presses the lift arm toward the platen, and the pinch roller pulls the paper out. A gap is established between the platen and the print head at the position where the print head is pressed against the feed roller, and when not in use, the spring is released from the second cam and restored to its free state. In this state, the lift arm is separated from the platen by the first cam. to separate the pinch roller from the feed roller.

Embodiment An embodiment of the present invention will be described based on FIGS. 1 to 3. Components that are the same as those described in FIGS. 4 to 6 are designated by the same reference numerals, and description thereof will be omitted. A holding member 21 that holds one end of a plate spring 20, which is a spring, is fixed to the side plate 1, and a cam shaft 22 connected to a motor (not shown) is rotatably supported on the left and right side plates 1. This camshaft 22
There are pressing surfaces 23 near both ends of which press the plate springs 20.
A pair of left and right second cams 24 are fixed.

In such a configuration, when in use, the lever 16 is released from the first cam 18 and the pressing surface 23 of the second cam 24 presses the plate spring 20, as shown in FIG. In this state, lift arm 1
0 is rotated downward by the force of the plate spring 20 about the support shaft 3, and the pinch roller 14 presses the paper 19 against the feed roller 4. The lift arm 10 is stable in this position and the gap between the paper 19 and the dot printer head 12 is defined.

When the number of sheets 19 increases or the thickness of the sheets 19 increases, the pinch roller 14 receives resistance from the sheets 19, so that the lift arm 10 rises by the thickness of the sheets 19, as shown in FIG. Therefore, the gap between the surface of the paper 19 and the tip of the dot printer head 12 is automatically adjusted.

When not in use, as shown in Figure 3,
The cam shaft 22 is rotated 180 degrees, the second cam 24 is separated from the plate spring 20, the plate spring 20 is restored to its free state by its own elasticity, the cam shaft 6 is rotated 180 degrees, and the first cam 18 is rotated 180 degrees. The lever 16 is pressed clockwise by the pressing surface 17 of the lever 16, the shaft 9 is pushed up by the leg 15 of the lever 16, the lift arm 10 is rotated upward about the support shaft 3, and the pinch roller 14
is separated from the feed roller 4.

In the state when not in use as shown in FIG.
The lift arm 10 receives pressure from the first cam 18 but does not receive any resistance from the plate spring 20.
Therefore, permanent deformation of the lift arm 10, lever 16, plate spring 20, etc. can be prevented.

Effects of the Invention Since this invention is configured as described above, when in use, the lift arm is released from the first cam, the pressing surface of the second cam presses the spring, and the pressure of the spring moves the lift arm toward the platen. Press to
A gap between the platen and print head is established at the position where the paper is pressed against the feed roller by the pinch roller, and when not in use, the first cam moves the lift arm away from the platen and the pinch roller moves away from the feed roller, but the second cam can be released from the cam and restored to its free state,
Therefore, the lift arm is not subjected to resistance from the spring when not in use, which has the effect of preventing permanent deformation of the lift arm, the spring, etc.

[Brief explanation of drawings]

Figures 1 to 3 show an embodiment of the present invention, with Figure 1 being a longitudinal side view showing the state in which printing is performed on a single sheet of paper, and Figure 2 showing the state in which printing is performed on multiple sheets of paper. Figure 3 is a vertical side view showing the state when not in use, Figures 4 to 6 show conventional examples, and Figure 4 is a vertical side view showing the state of printing on a single sheet of paper. FIG. 5 is a longitudinal sectional side view showing a state in which printing is performed on a plurality of sheets of paper, and FIG. 6 is a longitudinal sectional side view showing a state when not in use. 2...Platen, 4...Feed roller, 10
... Lift arm, 12 ... Dot printer head (printing head), 14 ... Pinch roller, 17
... Pressing surface, 18 ... First cam, 20 ... Plate spring (spring), 23 ... Pressing surface, 24 ... Second cam.

Claims (1)

[Claims] 1. A print head is fixedly attached to a lift arm that is displaceable so as to approach and move away from a fixed platen, and a pinch roller that contacts a feed roller that rotates at a fixed position is rotatably attached to the lift arm. A first cam is provided with a spring that urges the arm toward the platen and the feed roller, and has a pressing surface that directly or indirectly presses the lift arm in a direction away from the platen, and a first cam that presses the spring. 1. A head gap adjustment device for a printer, characterized in that a second cam having a pressing surface that increases the amount of deflection is rotatably provided.