1. Field of the Invention
The present invention relates to a thermal printer unit and a thermal printer, and, in particular, to a thermal printer unit and a thermal printer applied to a portable terminal apparatus and a POS (Point Of Service) apparatus, and employing rolled paper.
For a printer of a portable terminal apparatus or a POS apparatus, increase in printing speed and easy exchange of printing paper are demanded. In order to deal with these requests, a line thermal printer employing rolled paper as printing paper is used.
2. Description of the Related Art
FIG. 1 shows a line thermal printer 10 in the related art. FIG. 2 shows a general configuration of the line thermal printer 10 shown in FIG. 1. FIGS. 3A, 3B and 3C illustrate operation of a platen roller and a thermal head of the line thermal printer 10 shown in FIG. 1.
The line thermal printer 10 is of a clam-shell-type, and has a body 11 and a cover 13 supported by a shaft 12 on the body 11. The body 11 has a paper roll containing part 11a in which a paper roll is contained, and, also, has the thermal head 15 incorporated therein together with a head pressing spring 14. The platen roller 16 is supported on an extending end of the cover 13. In the body 11, grooves 18 in which a shaft 17 of the platen roller 16 is fitted are formed. Each of these grooves 18 has a shape of a vertically extended straight line and has an opening 18a at the top thereof, as shown in FIG. 3A.
The line thermal printer 10 enters a condition, shown in FIGS. 2 and 3C, such that the printer 10 can perform printing as a result of: the cover 13 being opened; the paper roll 20 having a paper end 21 thereof unwound partially being contained in the paper roll containing part 11a; the unwound paper end 21 being drawn out so as to pass in front of the thermal head 15; and the cover 13 being closed. That is, at the last stage of closing the cover 13, the platen roller 16 comes into contact with the thermal head 15 and pushes it out, the shaft 17 enters the grooves 18, and, the platen roller 16 reaches a position shown in FIGS. 2 and 3C, as shown in FIGS. 3A and 3B. In this condition, the head pressing spring 14 presses the thermal head 15 onto the platen roller 16 by a force F1 (functioning as a head pressure), and the paper end 21 is sandwiched between the thermal head 15 and platen roller 16, as shown in FIG. 2. Further, the platen roller 16 and cover 13 are locked together in a condition in which the shaft 17 of the platen roller 16 is fitted into the grooves 18 and are pressed onto the bottoms of the grooves 18 by the above-mentioned force F1.
As the necessity arises, the paper roll 20 is exchanged after the cover 13 is opened as a result of the end of the cover on the side of the platen roller 16 being pulled up with a strong force.
In this line thermal printer 10, when the cover 13 is opened, a wide space is formed between the thermal head 15 and platen roller 16, and, thereby, exchange of the paper roll 20 can be easily performed. Further, the cover 13 is locked through the operation of closing the cover 13, and the lock is released as a result of the cover 13 being pulled up. Accordingly, any other special locking operation or lock releasing operation is needed to be performed. Accordingly, the printer 10 is convenient in operation thereof.
There is a possibility that a portable terminal apparatus is knocked or dropped by accident during handling thereof. Accordingly, the line thermal printer which is incorporated in the portable terminal apparatus is required to have a strong locking mechanism such that the cover 13 is prevented from being opened by accident, even when the portable terminal apparatus is knocked or dropped.
As shown in FIG. 3C, in the above-mentioned line thermal printer 10, the cover 13 is locked or prevented from opening by the force F1. Accordingly, in order to achieve the stronger locking mechanism as mentioned above, it is necessary to increase the force F1 applied by means of the head pressing spring 14.
However, when the force F1 is increased, the head pressure may become larger than a proper head pressure. Thereby, the printing quality may be degraded, the thermal head 15 may be easily worn so as to have a shorter life, and so forth.
In contrast to this, when it is demanded that the locking of the cover be easily released, the above-mentioned force F1 applied by the head pressing spring 14 is to be decreased. However, when the force F1 is decreased, the head pressure may become lower than the proper one, and, as a result, the print becomes faint.
Further, the thermal head 15 is inclined in the direction of the grooves 18 as shown in FIG. 2 so that the force F1 is directed obliquely downward. Thereby, at the last stage of closing the cover 13, the platen roller 16 may come into contact with a top corner 15a of the thermal head 15 strongly, as shown in FIG. 3A. Thereby, the platen roller 16 may be harmed.
FIG. 11 shows a line thermal printer unit 130 incorporated in another clam-shell-type line thermal printer in the related art. In the line thermal printer unit 130, a thermal head assembly 132 is incorporated into a frame 131, and, also, a platen roller assembly 133 is incorporated into the frame 131 detachably.
On the bottom of the frame 131, a photosensor 134 for detecting roll paper is mounted, and, also, a mechanical switch 135 for detecting that the platen roller assembly is mounted at a proper position is mounted on a side wall of the frame 131. A detecting knob part 135a of the mechanical switch 135 projects into a depressed receiving part 138 of the frame 131 used for mounting the platen roller assembly 133 therein. A flexible cable 136 extends from the photosensor 134, while a normal covered cable 137 extends from the mechanical switch 137.
In this thermal printer unit 130, because the frame 131 has not an enough space therein, the mechanical switch 135 is mounted on the outer wall of the frame 131. Accordingly, the substantial lateral length of the line thermal printer unit 130 becomes larger by the mechanical switch 135 than that of the frame 131 itself.
Further, as the photosensor 134 and mechanical switch 135 are components different in type therebetween, the manufacturing costs thereof are high.
Further, works of wiring the flexible cable 136 and covered cable 137, which are different in type therebetween, are troublesome, accordingly.
An object of the present invention is to provide a thermal printer unit and a thermal printer in which the above-described problems are solved.
A thermal printer unit according to the present invention comprises:
a thermal head assembly; and
a platen roller,
wherein:
the thermal head assembly comprises:
a frame having platen roller receiving parts receiving both ends of the platen roller, respectively;
a thermal head mounted on the frame; and
a spring member mounted on the frame and applying a head pressure to the thermal head,
wherein each platen roller receiving part comprises:
a vertical groove part having an opening at the top thereof;
a horizontal groove part extending from the bottom of the vertical groove part in a direction such as to be away from the thermal head; and
a projection part formed relatively by the vertical groove part and horizontal groove part, located above the horizontal groove part, and projecting from a depth part of the horizontal groove part toward the thermal head, and
wherein both ends of the platen roller are inserted into the horizontal groove parts of said platen roller receiving parts, respectively, and, also, are pressed by the spring member via the thermal head into the depth parts thereof, respectively.
In this configuration, both ends of the platen roller are loaded into the depth parts of the horizontal groove parts of the platen roller receiving parts in a condition in which the ends of the platen roller being pressed toward the depth parts of the horizontal groove parts by the spring member. Thus, the platen roller is locked into the platen roller receiving parts. In this configuration, by adjusting the dimension and shape of the projection parts, it is possible to control the strength of locking of the platen roller into the platen roller receiving parts without changing the head pressure applied to the thermal head by the spring member. Accordingly, it is possible to achieve an appropriate strength of the locking of the platen roller while maintaining the printing quality.
The platen roller may comprise bearing members at both ends thereof; and
the bearing members rotatably support the both ends of the platen roller in the horizontal groove parts, respectively.
Thereby, as the outer shell of the bearing members do not rotate while the platen roller rotates, a force for causing the platen roller to be removed from the platen roller receiving parts is prevented from being generated during the printing operation. Accordingly, it is possible to maintain a stable locked condition of the platen roller.
A member may be provided for covering the top end of the thermal head so as to prevent the platen roller from directly coming into contact with the top end of the thermal head.
Thereby, when the platen roller is being fitted into the platen roller receiving parts, the platen roller can be prevented from coming into contact with the top end of the thermal head directly. Accordingly, it is possible to prevent the platen roller from being harmed.
A thermal printer according to the present invention comprises:
a body comprising a paper roll containing part for holding a paper roll;
a thermal head assembly mounted on the body, and comprising: a frame having platen roller receiving parts receiving both ends of a platen roller, respectively; a thermal head mounted on the frame; and a spring member mounted on the frame and applying a head pressure to the thermal head; and
a cover rotatably supported on the body, supporting the platen roller, and covering an opening of the paper roll containing part,
wherein, in a condition in which the opening of the paper roll containing part is covered by the cover, the platen roller is pressed onto the thermal head, and the platen roller is fitted into the platen roller receiving parts so that the cover is maintained in the condition in which the opening is covered by the cover, and
wherein each platen roller receiving part comprises:
a vertical groove part having an opening at the top thereof;
a horizontal groove part extending from the bottom of the vertical groove part in a direction such as to be away from the thermal head; and
a projection part formed relatively by the vertical groove part and horizontal groove part, located above the horizontal groove part, and projecting from a depth part of the horizontal groove part toward the thermal head, and
wherein, in the condition in which the cover covers the opening of the paper roll containing part, both ends of the platen roller are inserted into the horizontal groove parts of the platen roller receiving parts, respectively, and, also, are pressed by the spring member through the thermal head into the depth parts thereof, respectively.
In this configuration, both ends of the platen roller are loaded into the recess parts of the horizontal groove parts of the platen roller receiving parts in a condition in which the ends of the platen roller being pressed toward the depth parts of the horizontal groove parts by the spring member. Thus, the platen roller is locked into the platen roller receiving parts. In this configuration, by adjusting the dimension and shape of the projection parts, it is possible to control the strength of locking of the platen roller into the platen roller receiving parts without changing the head pressure applied to the thermal head by the spring member. Accordingly, it is possible to achieve an appropriate strength of the locking of the platen roller while maintaining the printing quality.
The platen roller may comprise bearing members at both ends thereof; and
the bearing members rotatably support the both ends of the platen roller in the horizontal groove parts, respectively.
Thereby, as the outer shell of the bearing members do not rotate while the platen roller rotates, a force for causing the platen roller to be removed from the platen roller receiving parts is prevented from being generated during printing operation. Accordingly, it is possible to maintain a stable locked condition of the platen roller.
A member may be provided for covering the top end of the thermal head so as to prevent the platen roller from directly coming into contact with the top end of the thermal head.
Thereby, when the platen roller is being fitted into the platen roller receiving parts, the platen roller can be prevented from coming into contact with the top end of the thermal head directly. Accordingly, it is possible to prevent the platen roller from being harmed.
A position on an outline of the platen roller at which the thermal head comes into contact with the platen roller loaded into the horizontal groove parts may be different in a direction reverse to a direction in which the platen roller rotates during feeding the paper from a position on the side of the thermal head at which the outline of the platen roller is intersected by a straight line passing through both the rotational axis of the cover and the center of the platen roller loaded into the horizontal groove part.
Thereby, the angle of inclination of the thermal head with respect to a bottom surface of the frame becomes nearly 90 degrees, and a dimension the top end of the thermal head projects toward the platen roller is short, so that a hit of the platen roller by the top end of the thermal head becomes a weaker one, and, thus, the platen roller is prevented from being harmed thereby.
A thermal printer unit according to another aspect of the present invention comprises:
a thermal head assembly; and
a platen roller,
wherein:
the thermal head assembly comprises:
a frame having a platen roller receiving part receiving the platen roller;
a thermal head mounted on the frame; and
a spring member mounted on the frame and applying a head pressure to the thermal head,
wherein:
the thermal head assembly further comprises photosensors provided on the rear side of the platen roller receiving part so as to face the platen roller; and
the photosensors are used for detecting, through a combination of outputs thereof, any of a condition in which printing operation of the printer unit can be properly performed, a condition in which paper for the printing is nearly run out, a condition in which the paper for the printing is run out, and a condition in which the platen roller is removed from the platen roller receiving part.
As the photosensors are disposed on the rear side of the platen roller receiving part, the lateral dimension of the thermal printer unit is prevented from increasing much although the photosensors are provided for detecting various conditions of the printer unit. Further, because the same type of sensors are used, it is possible to prevent the costs thereof from increasing much, in comparison to a case where different types of sensors are used for the same purpose.
A thermal printer unit according to another aspect of the present invention comprises:
a thermal head assembly; and
a platen roller,
wherein:
the thermal head assembly comprises:
a frame having a platen roller receiving part receiving the platen roller;
a thermal head mounted on the frame;
a radiator plate, supported by the frame and having the thermal head fixed thereto, for radiating heat generated by the thermal head; and
a spring member applying a head pressure to the thermal head, and
wherein the radiator plate and the spring member are formed integrally.
In this configuration, as the radiator plate and spring member are formed integrally, it is possible to omit provision of any separate member in particular for the purpose of pressing the thermal head other than the radiator plate. Accordingly, it is possible to reduce the number of necessary components, and to reduce the costs of the printer unit.