JPS61215074A - Thermal transfer printer or thermal printer - Google Patents

Abstract

PURPOSE:To obtain certain paper feed capacity by small paper feed force, by forming a paper feed roller by using a material having friction coefficient larger than that of the material forming the flat part of a flat platen. CONSTITUTION:A flat platen 62 having a flat surface is integrally attached to a platen support plate 61. A surfaces 61a, 61b having radius of curvature corresponding to the parts above and below the flat platen 62 are provided to the platen support plate 61. The flat platen 62 is constituted so that the corner parts of the flat platen are not contacted with transfer paper 13 when the transfer paper 13 is wound around the flat platen 62. A paper feed exclusive roller 63 as the paper feed drive source of the transfer paper 13 and a press roller 64 for pressing the transfer paper 13 to the paper feed exclusive roller 63 are provided to the lower part of the platen support plate 61. The materials of the flat platen 62 and the paper feed exclusive roller 63 are set so that the friction coefficient mu2 between the paper feed exclusive roller 63 and the transfer paper 13 is made larger than the friction coefficient mu1 between the flat platen 62 and the transfer paper 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a paper feeding mechanism suitable for a thermal transfer printer or a thermal printer that uses a platen having a flat surface as a platen against which a thermal head is pressed.

[Background of the invention]

Conventionally, the cylindrical platen used in thermal transfer printers or thermal printers has a large outer diameter, and a flat part must be formed in the contact area with the thermal head for printing by elastic deformation. Pressing a large amount of pressure against the thermal head has disadvantages such as applying force. On the other hand, if a flat platen with a flat surface is used from the beginning, there is no need to elastically deform the platen, and the pressing force of the thermal head against the platen can be extremely small, making the entire printer device much more compact. becomes possible. However, the biggest problem in realizing the flat platen method is the paper feeding structure. In contrast to the conventional cylindrical platen, which has the function of forming a flat surface for printing and the function of feeding paper for line feed after one line of printing is completed, a flat platen has the function of forming a flat surface for printing. There is no paper feeding function. Therefore, it is necessary to separately provide a roller for paper feeding. The problem here is that when the paper moves over the surface of the flat platen, which is stationary, the frictional resistance generated between the flat platen and the paper to be transferred is large, making it difficult to feed the paper properly. Otherwise, a large paper transport force is required and the paper transport mechanism becomes large. In order to solve this problem, an example is known in which a Teflon sheet is wrapped around the surface of a flat platen to reduce the frictional resistance during paper feeding, as described in Japanese Patent Application Laid-Open No. 59-201879. However, this example increases the manufacturing process and the number of parts, and is also unfavorable from the viewpoint of reliability.

[Purpose of the invention]

An object of the present invention is to provide a thermal transfer or thermal printer that achieves reliable paper feeding performance with a small paper feeding force compared to a thermal transfer printer or a thermal printer using a flat platen.

[Summary of the invention]

During paper feeding in a flat platen type thermal transfer or thermal printer, the largest paper feeding load resistance is the frictional resistance due to the relative movement between the surface of the flat platen and the transfer paper. When the thermal head is pressed against the flat platen,
In order to make even surface contact between the print surface and the thermal head surface, the head is relatively easy to deform elastically even with a small pressing force.
It is common to use rubber with low hardness. However, on the other hand, low hardness rubber has a large coefficient of friction and causes a large load resistance when conveying the transfer paper. On the other hand, from the viewpoint of paper feeding force, the larger the friction coefficient of the paper feeding roller as the drive source for paper feeding is, the greater the paper feeding force can be obtained with a small pressing force of the paper feeding roller. The present invention focuses on the fact that the coefficient of friction varies depending on the hardness of the rubber, and sets the relationship between the material used for the flat platen and the material used for the paper feed roller to be optimal. Furthermore, when the sheet is wrapped around the flat platen during sheet feeding, if the corners are small, the corners of the flat platen will locally come into contact with the transferred paper, resulting in a large sheet feeding load resistance. This situation is shown in FIG. In this figure, part 0 is in local contact. For this reason, when wrapping the transfer paper around the flat platen, the corners must be made large to some extent. Therefore, in the present invention, in order to obtain an optimal configuration, members with large curvature are integrally formed above and below the member supporting the flat platen to prevent local contact.

[Embodiments of the invention]

An embodiment of the present invention will be described below. The overall configuration and operation of a thermal transfer printer to which the present invention is applied will be described with reference to FIG. A shaft 38 and a stay 34 are fixed between the side plates 24 and 40. Further, a carriage 32 is arranged to be slidable on a shaft 38 and a stay 34, a ribbon cassette 30 and a thermal head 1 are mounted on the carriage 32, and an ink ribbon 5 is stored in the ribbon cassette 30. ing. The carriage 32 is configured to be movable to the right in the figure by a carriage motor 26 via a timing belt 44. Further, the line feed motor 20 transmits driving force to the gear 18 fastened to the shaft of the paper transport roller 63 to feed the transfer paper 13. The transfer paper 13 runs between the paper feeding roller 63 and the press roller 64゛Φ, passes through the platen support plate 61,
It is configured to enter between the platen 62 and the ink ribbon 5. Paper can also be fed in the same way by rotating the paper feeding roller knob 22 by hand. 42 is a paper guide. Furthermore, by moving the release lever 16 in the front-back direction, the paper pressing roller 14, which is slidably disposed on the shaft 15, is pressed onto or separated from the paper surface.

36 is the home position sensor, 28 is the thermal head 1
This is a flat cable for energizing. This printer is a printer of a type in which the ink ribbon 5 is wound up when the carriage 32 moves to the right, but it is not wound up when the carriage 32 moves to the left. Further, the carriage motor 26. Line feed motor 20
, the thermal head 1, the home position sensor 36, etc.
It is controlled by the CPU 80. In addition, in the above thermal transfer printer, if the ribbon cassette 30 is removed and thermal paper is used instead of the transfer paper 13, it can be used as a thermal printer.

Next, the flat platen section and paper feeding section, which are the subject matter of the present invention, will be explained with reference to FIG.

A flat platen 62 having a flat surface on which the thermal head 1 is pressed to perform printing is integrally attached to the platen support plate 61 by gluing or vapor deposition. This platen support plate 61 has surfaces 6 having curvature at the top and bottom of the flat platen 62.
1a and 61b are provided. The configuration is such that when the transfer paper 13 is wound around the flat platen 62, the corners of the platen do not come into contact with the transfer paper. Further, at the lower part of the platen support plate 61, there is provided a pressing roller 64 which acts as a paper feeding drive source for the transfer paper 13 and presses it against the paper-dedicated roller 63. Here, the friction coefficient μ between the flat platen 62 and the transfer paper 13 is greater than the friction coefficient μ between the paper feeding roller 63 and the transfer paper 13.
flat platen 62 so that the friction coefficient μ2 between
and the material of the paper feed roller 63 is set. In general,
Rubber is usually used as the material for the flat platen 62 and the paper feeding roller 63. In this case, the paper feed roller 63
The rubber hardness of the flat platen 62 may be set to be smaller than that of the flat platen 62. In other words, as a basic property of rubber, the friction coefficient decreases as the rubber hardness increases, so rubber with high hardness is used for the flat platen 62, and rubber with low hardness is used for the paper feeding roller 63. Therefore, the relationship μ2>μm can be established.

According to experiments, the rubber hardness of the flat platen is Hs60″ or higher.
The rubber hardness of the paper feed roller is preferably set to Hs60' or less.

The above content can be applied not only to the paper feed roller 63 but also to the press roller 64 and the paper press roller 14.

With the above configuration, the flat platen 62 and the transfer paper 13
Only a small frictional resistance acts between them, and a large paper transport force can be obtained by simply applying a small pressing force to the paper transport roller 64, so that reliable paper transport is possible. Further, the curved surfaces 61a and 61b of the flat platen support plate 61 prevent the angle 2 of the flat platen 62 from coming into contact with the transfer paper 13, so that no conveyance load resistance occurs due to local contact. This allows for smooth paper feeding. Further, the curved surfaces 61a and 61b also serve as paper feeding guides, and can also be used as pressing surfaces by the paper pressing roller.

〔Effect of the invention〕

From the above description of the embodiments, etc., according to the present invention, the frictional resistance generated between the flat platen and the transfer paper can be greatly reduced, and smooth paper feeding becomes possible. Furthermore, not only the paper transport driving motor can be made smaller, but also the transport mechanism can be simplified and made smaller. Furthermore, by using a flat platen, a compact thermal transfer printer can be obtained.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the flat platen section and paper feeding section of the present invention;
The figure is an explanatory diagram of a flat platen section and paper feeding section of a conventional product, and FIG. 3 is a configuration diagram of a printer adopting the present invention. 1... Thermal head, 5... Ink ribbon, 13...
・Transfer paper, 14...Paper pressing roller, 15...Shaft, 16...Release lever, 18...Gear, 201
6. Line feed motor, 22... Roller knob for paper feeding, 24... Side plate, 26... Carriage motor, 28... Flat cable, 30... Ribbon cassette, 32... Carriage, 34...・Stay, 36
...Home position sensor, 38...Axis, 40
... Side plate, 42 ... Paper guide, 44 ... Timing belt, 61 ... Platen support plate, 62 ... Flat platen, 63 ... Paper feeding roller, 64 ... Holding roller, 61a... platen support plate upper curvature portion, 61b
. . . Platen support plate upper curvature portion, 70 . . . Platen support plate, 80 . . . CPU.

Claims (1)

[Scope of Claims] 1. Consisting of a thermal head, a platen having a flat surface against which the thermal head is pressed, a carriage on which the thermal head is mounted and moves it in a traverse motion, a paper feeding mechanism for feeding the transfer paper, etc. 1. A thermal transfer printer or thermal printer characterized in that a paper feed roller is formed using a material having a coefficient of friction greater than that of a material forming a flat portion of a flat platen. 2. The thermal transfer printer or thermal printer according to claim 1, characterized in that the hardness of the rubber forming the paper feed roller is smaller than the hardness of the rubber forming the flat platen. 3. A thermal transfer printer or thermal printer according to claim 1, characterized in that the upper and lower parts of the member supporting the flat platen are made of members having curvature. 4. In claim 1, the rubber hardness of the flat platen is Hs60° or more, and the rubber hardness of the paper feed roller is Hs6.
A thermal transfer printer or a thermal printer characterized in that the temperature is set to 0° or less.