JPH0696298B2 - Printer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a platen mechanism, and more particularly to a platen mechanism in an impact printer which is suitable for printing passbooks and cut sheets.

[Background of the Invention]

An impact printing apparatus such as a printing apparatus having a wire matrix type print head is often used to print on a passbook or a single slip. In this case, since the thickness of these print media changes depending on the number of pages of the passbook and the number of cut sheets, it is important to keep the distance between the print head and the print medium constant even if the thickness changes. As a conventional technique of this type,
There is known a so-called platen retraction technique as disclosed in Japanese Patent Laid-Open No. 62106.

Furthermore, recently, it has been proposed to drive the platen by a solenoid. That is, the solenoid is operated to drive the platen, and the print medium is pushed from the back surface of the print medium to hold the print medium between the reference guide and the platen.

However, the solenoid conventionally used is a DC solenoid, and this DC solenoid generally has a suction force characteristic as shown in FIG. That is, the suction force decreases as the stroke increases. Therefore, when such a DC solenoid is used as the platen driving means, when the print medium is thin, the stroke of the DC solenoid is small, so that the platen has a large force (that is, a clamping force) for pressing the print medium against the reference guide. Become. On the contrary, when the print medium is thick, the clamping force becomes small. For this reason, when a multi-part pressure-sensitive paper having a small thickness is used, the clamping force is too large at the time of clamping and a line remains as a shadow at a position where it is pressed against the reference guide. On the contrary, when the printing paper is thick for the passbook, the clamping force is insufficient and the platen is pushed down by the printing power of the printing head, the gap of the printing paper of the printing head expands, and printing failure occurs. Also,
When printing near the folds of a passbook, if the clamping force is insufficient, the folds cannot be pressed down and the clamps are pushed down by the folds, resulting in defective printing.

[Object of the Invention]

An object of the present invention is to provide a platen mechanism that can obtain an appropriate platen clamping force against changes in the thickness of a print medium.

[Outline of Invention]

According to the present invention, the characteristic of the clamping force is small when the thickness of the print medium is thin, and when the thickness is large like a passbook, for example, it needs to be a constant clamp value necessary to crush the folds of the passbook. Pay attention to that. Therefore, the present inventors have found that a linear solenoid is appropriate as a driving means for the platen. That is, in the attraction force characteristic of the linear solenoid, the peak value of the attraction force is at a certain stroke. In other words, as the stroke increases, the suction force also increases and reaches the peak value, and when the stroke further increases, the suction force decreases.

In the present invention, a plurality of linear solenoids are arranged so that the attraction force characteristics of the linear solenoids are displaced, and the platen is driven by the plurality of linear solenoids. A suction force characteristic can be obtained in which the suction force rises in proportion to the stroke in a constant range, and when the suction force reaches a predetermined value, the suction force becomes a predetermined suction force in a constant stroke range thereafter.

By using a plurality of linear solenoids in the platen clamp mechanism by shifting the attraction force characteristic in this way, when printing on thin print media, the clamp force is reduced to leave a trace of the clamp on the pressure-sensitive paper. It is possible to obtain a sufficient clamping force to crush the folds when printing on a thick print medium such as a passbook.

Example of Invention

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. 1 is a front view and FIG. 2 is a left side view of FIG.

Multiple linear solenoids to drive the platen 3
71, 72 are provided. When the linear solenoids 71, 72 are energized, the plungers 91, 92 of the linear solenoids 71, 72 are attracted in the arrow x direction. Plungers 91 and 92 are levers 41,
The levers 41 and 42 are connected to the platen 42, and the levers 41 and 42 rotate about the shafts 61 and 62.
Raises 1,82. The levers 41 and 42 are joined by the link 5 so that the forces applied to the pins 81 and 82 are made uniform. Thus, the printing paper 2 is pressed against the paper guide 1 by the platen 3, and impact printing is performed by the printing head 10.

The attraction force characteristic of each linear solenoid 71, 72 is as shown in FIG. 3, which is different from the characteristic of the conventional DC solenoid (FIG. 5). In particular, the attraction force characteristic of the solenoid 71 is a in FIG. 4, and the attraction force characteristic of the linear solenoid 72 is b in FIG. The linear solenoids 71 and 72 have a suction force characteristic that is displaced by the stroke S, and the combined suction force characteristic of the two solenoids is the characteristic shown by the solid line c in FIG. According to this characteristic c, the suction force increases as the stroke increases, and the suction force characteristic having the range 1 in which the suction force is constant over a certain stroke is obtained.
In the attraction force characteristic of this characteristic c, the platen 3
By clamping the sheet, the clamping force increases as the sheet thickness increases with a small clamping force when the sheet thickness is thin, and a predetermined clamping force can be obtained for each page of the passbook during passbook printing, for example.

As described above, according to the present embodiment, since the clamping force can be properly obtained with respect to the paper thickness, a printing device suitable for both single-cut and passbook can be obtained.

For the features, structures, and principles of DC solenoids and linear solenoids, refer to the product catalog “DC Silent Actuator Solac SOLAC” of Act Giken Co., Ltd., which is a publication distributed before the application of this application. It is described in detail as a product (DC solenoid) and a sorac type (linear solenoid).

〔The invention's effect〕

According to the present invention, when printing on a thin print medium, the clamping force is small, the clamping force increases as the medium thickness increases, and a constant clamping force is obtained when the medium thickness exceeds a certain thickness. Obtainable. For example, even when using thin pressure-sensitive paper, there is no trace of platen clamps, and for example, when printing passbooks, sufficient clamping force to hold folds can be obtained, and the same clamping force can be obtained without excessive clamping force. The device enables good printing on cut sheets and passbooks.

[Brief description of drawings]

FIG. 1 is a front view showing a platen mechanism in a printing apparatus according to an embodiment of the present invention, FIG. 2 is a left side view of FIG.
FIG. 3 is a diagram showing a suction force characteristic with respect to a stroke of a single linear solenoid used in one embodiment of the present invention,
FIG. 4 is a diagram showing the attraction force characteristic by a plurality of linear solenoids, and FIG. 5 is a diagram showing the attraction force characteristic with respect to the stroke of a single DC solenoid according to the prior art. 1 ... Paper guide, 2 ... Paper, 3 ... Platen, 41, 42 ... Lever, 5 ... Link, 61, 62 ... Shaft, 71, 72 ... Linear solenoid, 81, 82 ... Pin, 91, 92 ... Plunger, 10 ... Print head

Claims (1)

[Claims] 1. A printing apparatus for driving a platen to press and hold a print medium having an arbitrary thickness against a paper guide and performing impact printing on the print medium, wherein a plurality of linear solenoids for driving the platen are provided. When the distance between the paper guide and the platen is small, the clamping force with which the platen presses the print medium increases in proportion to the spread of the distance, and the plurality of linear solenoids have a predetermined width. The printing apparatus is characterized in that the suction force characteristics are deviated so that the suction force characteristics become substantially the same for a certain period even if the distance increases thereafter.