JPS6342883A - Head gap adjustor for printer - Google Patents

Abstract

PURPOSE:To prevent a permanent set of a lift arm, a spring or the like from being generated, by providing a first cam for pressing the lift arm away from a platen and a second cam for pressing the spring to increase the deflection quantity of the spring, in rotatable conditions. CONSTITUTION:When in use, a lever 16 is released from a first cam 18, and a leaf spring 20 is pressed by a second cam 24. Under this condition, a lift arm 10 is turned downward with a support shat 3 as a fulcrum by the force of the spring 20, and a pinch roller 14 presses a paper 19 against a feeding roller 4. The lift arm 10 is stabilized at this position, and a gap between the paper 19 and a dot printer head 12 is determined. When not in use, a cam shaft 22 is rotated 180 deg., the leaf spring 20 is restored to a free condition under its own elasticity, and a cam shaft 6 is rotated 180 deg., whereby the lever 16 is pressed clockwise by the first cam 18, a shaft 9 is pushed upward by a base 15 of the lever 16, and the lift arm 10 is turned upward with the support shaft 3 as a fulcrum, thereby separating the pinch roller 14 from the feeding roller 4.

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 are supported, respectively, which are connected to a motor (not shown) and rotate integrally with a feed roller 4. has been done. Further, both sides of paper guide plates 7, which are vertically opposed to each other, are fixed to the side plate 1. Support shaft 3
A pair of left and right lift arms 10 connected by two guide shafts 8 and a shaft 9 are held so as to be vertically movable. A dot printer head 12 is installed. The 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 contacts the lower part of the shaft 9 is supported on the support shaft 3 so as to be rotatable while being biased clockwise, and the cam shaft 6 has a pressing surface 17 that presses the lever 16. A first cam 18 is fixed.

Furthermore, a spring 25 for biasing the lift arm 10 toward the platen 2 is held on the inner surface of the side plate l.

Therefore, as shown in FIG.
8, the lift arm 10 is attached to the support shaft 3.
The paper 19 is rotated downward by the force of the spring 25 using the paper 19 as a fulcrum, 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. The lift arm 10 is rotated upward about the support shaft 3, and 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 resistance from 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.

Means to Solve the Problem The print head is fixedly attached to a lift arm that is movable to approach and move away from a fixed platen, and a pinch roller that contacts a rotating feed roller at a fixed position. is rotatably mounted, is provided with 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. A cam and a second cam having a pressing surface that presses the spring to increase the amount of deflection are rotatably provided.

Therefore, 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 this spring presses the lift arm toward the platen,
A gap between the platen and the 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 spring is released from the second cam and restored to its free state, and in this state it is lifted by the first cam. Move the arm away from the platen and move the pinch roller away from the feed roller.

Embodiment An embodiment of the present invention will be described with reference to 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. Near both ends of this camshaft 22 are pressing surfaces 23 that press the plate spring 23.
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 temporary spring 20 is pressed by the pressing surface 23 of the second cam 2/l, as shown in FIG.

In this state, the lift arm 10 rotates downward by the force of the plate rays 20 using the support IM3 as a fulcrum, and the pinch roller 1
4 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 I9 and the tip of the dot printer head 12 is automatically adjusted.

When not in use, the camshaft 2
2 is rotated 180°, the second cam 24 is separated from the plate spring 20, the plate spring 2Q is restored to its free state by its own elasticity, the cam shaft 6 is rotated 180°, and the first cam 1 is rotated 180°.
Press the lever 16 clockwise with the pressing surface 17 of 8,
1tIllI9 is pushed up by F#15 of 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 shown in FIG. 3 when not in use, the lever 16 and lift arm 10 receive pressure from the first cam 18 but do not receive any resistance from the plate spring 20.

Therefore, the lift arm 10, the lever 16, the plate spring 2
Permanent deformation such as 0 can be prevented.

Effects of the Invention Since this invention is constructed as described above, when in use, the lift arm is released from the first cam, the spring is pressed by the pressing surface of the second cam, and the lift arm is moved toward the platen by the pressure of this spring. The gap between the platen and the print head is determined at the position where the paper is pressed against the feed roller by the pinch roller, and when not in use, the lift arm is moved away from the platen by the first cam, and the pinch roller is moved away from the feed roller. However, the spring can be released from the second cam and restored to its free state, thus
The lift arm does not receive resistance from the spring when not in use, and 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.

Claims (1)

[Claims] 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. A head gap adjustment device for a printer, characterized in that a head gap adjustment device for a printer is rotatably provided with a second cam having a pressing surface that increases the amount of deflection.