JPH0214197B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an impact printer.

BACKGROUND ART This type of impact printer has the advantage of being low-priced, highly reliable, has low running costs, and prints reliably, and is widely used as a peripheral device for word processors, personal computers, etc. .

In this impact type printer, in order to maintain uniform print quality, it is necessary to keep the gap between the paper surface and the print head, or in other words, the gap between the platen and the print head, accurate and constant.

However, in conventional printers of this type, two guide shafts and a platen are directly attached to the frame provided on the base plate.
A printing device having a printing head is supported on a book guide shaft via a head carriage. Therefore, the gap between the platen and the print head is determined depending on the mounting accuracy of the guide shaft and platen to the frame. Therefore, if you want to create the gap accurately, it is necessary to It was necessary to precisely align the parts and attach them to the frame. As a result, positioning and setting the gap between the platen and print head has become extremely difficult and cumbersome. Furthermore, since the individual members are directly aligned and assembled to the frame, the assembly is complicated and difficult.

DISCLOSURE OF THE INVENTION This invention allows the gap between the platen and the print head to be easily set with high precision, and also allows the gap between the print head and the platen to be adjusted to different spacings at both ends of the platen, thereby keeping the gap between the two ends constant. The purpose is to provide a printer with a structure that can be modified.

In order to achieve the above object, the present invention has a side frame swingably attached to both ends of one of two guide shafts supported between base frames, and a receiver formed on the pair of side frames. The shaft end of the platen is rotatably supported in the groove, eccentric cams are attached to both ends of the other guide shaft, and the eccentric cams are fitted into cam receiving grooves formed in the side frame for eccentric rotation. It has the following characteristics.

According to this invention, the left and right side frames are swung around one guide shaft by the rotation of the eccentric cam, and the platen, whose both ends are supported by the side frames, is moved toward or away from the print head. This makes it easy to adjust the gap between the platen and print head to suit the thickness of the paper, etc.
Moreover, it can be set with high precision. Furthermore, according to the present invention, the positions of both ends of the platen are regulated by the left and right eccentric cams via the side frames, so that by adjusting the left and right eccentric cams, the printing head and the platen at both ends of the platen can be adjusted. The gap can be set with different travel amounts and intervals. Therefore, according to the present invention, not only can the gap be easily adjusted, but even if the gap between the platen and the print head becomes different at both ends of the platen for some reason, for example, the gap can be adjusted easily. The difference in the gap at both ends can be easily corrected to a constant value.

Furthermore, assembly is extremely simple, as all the members need to be assembled one after another with the guide shaft as a reference.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

1 and 2 show the main parts of a printer according to the present invention, in which a pair of base frames 11, 11 are erected in parallel on a base plate 10 with an interval therebetween. Two parallel guide shafts 12 and 13 are supported between the base frames 11 and 11.

A head carriage 14 constituting a printing mechanism is inserted into and supported by the guide shafts 12 and 13 so as to be movable within a certain range in the axial direction. The head carriage 14 is integrally provided with a printing device 16 having a plurality of printing heads 15 in the printing line direction.

A side frame 17 is provided outside the base frames 11, 11. side frame 1
7 and 17 are the base frames 11 and 11 of the guide shaft 12 located in the middle on one side (the front side in the figure).
It is fitted and supported by the shaft end protruding from the shaft. Furthermore,
A cam groove 171 into which the eccentric cam 18 provided at the shaft end of the guide shaft 13 is fitted is formed at one end of the side frames 17, 17.

A platen 20 is supported on the side frames 17, 17. That is, side frame 1
A receiving groove 172 is formed in the upper part of one side of the platen 7, 17, and the shaft ends of the central shaft 21 protruding from both sides of the platen 20 are rotatably fitted and supported in the receiving groove 172, 172. As a result, the platen 20 is mounted on the guide shafts 12, 13 via the side frames 17, 17 in a state facing the print head 15.

Reference numeral 22 denotes a paper guide installed between the base frames 11 and 11, which has a certain clearance between it and the platen 20 and guides the fed paper, which is a print medium, along the circumferential surface of the platen 20. It's becoming like that. A plurality of openings 23 are provided in the bottom of the paper guide 22 in the longitudinal direction, and the pressure rollers 24 sandwich and press the paper against the platen 20 through the openings 23. The pressure rollers 24 are arranged along the longitudinal direction of the leaf spring body 25, and shaft portions 241 protruding on both sides thereof are rotatably supported in recesses 251 formed in the leaf spring body 25. One side of the leaf spring body 25 is placed on a wall 26 erected on the base plate 10 and is held on the wall 26 through engagement between the mounting hole 252 and the support piece 261. Further, the other sides are supported on a notch 27 formed in the circumferential surface of the guide shaft 12. The leaf spring body 25 is rotated by appropriately rotating the guide shaft 12 by external operation.
The pressure roller 24 swings up and down using one side as a fulcrum at an angle corresponding to the level difference between its peripheral surface and the notch 27.
... are pressed against the platen 20 while sandwiching the paper, and are separated from the platen 20. The paper is inserted between the platen 20 and the paper guide 22 from the rear side in FIG. It is guided by a guide 22 and sent sequentially to the front side. A printing hammer (not shown) is provided on the front side of the printing head 15 of the printing device 16.
is provided to strike the back of the selected print head to print on the paper on the platen 20.

When assembling the printer configured as described above, first, the printing device 1 is attached to the guide shaft 13.
Support frames 141, 141 which insert and support the head carriage 14 equipped with a
is inserted and supported into the guide shaft 12 avoiding the notch 27. Next, the guide shafts 12 and 13 are supported between the base frames 11 and 11, and the side frames 17 and 17 are attached to their shaft ends as described above. Thereafter, the leaf spring body 25 to which the pressure roller 24 is attached is installed between the guide shaft 12 and the wall portion 26, and the paper guide 22 is fitted between the base frames 11 from above. Next, if the platen 20 is attached to the upper part of the side frames 11, 11 via the receiving groove 172,
The printer is assembled as shown in FIGS. 1 and 3. According to this, the printer can be assembled by sequentially stacking each component around the guide shafts 12 and 13, which makes assembly easy and allows automation of assembly using an automatic assembly machine or the like.
Mechanization can also be easily achieved. Further, since the platen 20 is attached to the guide shafts 12 and 13 via the side frames 11 and 11, positioning of the platen 20 with respect to the print head 15 and setting of the gap 100 are performed by the guide shafts 12 and 13.
This can be done using only 13 as a reference. Therefore, positioning between the platen 20 and the print head 15 can be easily and accurately performed. Therefore, the gap 100 between the platen 20 and the print head 15 can be easily obtained with higher precision than in the past. Moreover, guide shaft 1
Attach the side frames 17, 17 to 2, 13,
Since it is only necessary to attach the platen 20 to the upper part of the side frames 14, 14, the structure is simple and the manufacturing cost can be reduced. Further, it is easy to assemble and can be easily performed.

Then, when the guide shaft 13 is externally operated via an adjustment lever or the like and rotated by a required angle, the left and right eccentric cams 18, 18 eccentrically rotate within the cam grooves 171 of the left and right side frames 17, 17, The side frames 17, 17 swing upward or downward about the guide shaft 12 in accordance with the amount of eccentricity of the eccentric cam 18, and the platen 20 approaches or moves away from the print head 15 and the gap 100 is closed. Change. As a result, the gap 100 between the paper mounted on the platen 20 and the print head 15 is
can be adjusted appropriately according to the thickness of the paper, etc.

Furthermore, since the positions of both ends of the platen 20 are regulated by the left and right eccentric cams 18, 18 via the side frames, adjusting the eccentric cams will change the gap between the print head and the platen at both ends of the platen. Can be set at intervals. Therefore,
For example, even if the gap between the print head and the platen becomes different on both ends of the platen for some reason, the position of the platen relative to the print head can be adjusted by adjusting the left and right eccentric cams, and the gap between the two can be adjusted. can be fixed to a certain degree.

The present invention is applicable not only to line printers shown in the embodiments, but also to serial type printers, and not only to printers whose paper feeding method uses a friction feed method using a pressure roller, but also to other types of printers. Of course, the present invention can also be applied to pin feed and tractor feed type printers.

[Brief explanation of drawings]

FIG. 1 is a perspective view of essential parts of a printer according to the present invention;
FIG. 2 is an exploded perspective view thereof, and FIG. 3 is a side view of FIG. 1. 11, 11... base frame, 12, 13...
...Guide shaft, 15...Print head, 16...
...Printing device, 14...Head carriage, 17,
17...side frame, 20...platen.

Claims (1)

[Claims] 1. A printing device equipped with a printing head is movably mounted on two parallel guide shafts supported between a pair of base frames, a platen is rotatably supported opposite the printing head, and a platen is rotatably supported on its circumferential surface. In a printer that prints on paper that is fed by the impact of a printing head, side frames are swingably attached to both ends of the one guide shaft, and the shaft of the platen is inserted into receiving grooves formed in the pair of side frames. an eccentric cam is attached to both ends of the other guide shaft, and the eccentric cam is eccentrically rotatably fitted into a cam receiving groove formed in the pair of side frames;
A printer characterized in that the position of both ends of the platen is regulated by the eccentric cam.