Printer with a print head urged to come into contact with a platen roller

The invention provides a printer in which a lock lever comes into contact with a roller shaft of a platen roller in upper open grooves disposed in a frame and controls the position of the upper portion of the upper open grooves so that the platen roller is supported in a predetermined position of the frame and reliably comes into contact with a thermal head disposed to be opposite to the platen roller, and a lock lever member disposed so as to position a joint member for joining the upper open grooves and close to a bottom plate of the frame in a print portion in which the platen roller and a thermal head come into pressure contact with each other.

This application claims the benefit of priority under 35 U.S.C. §119 to Japanese Patent Application No. 2006-206301, filed Jul. 28, 2006, which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a printer, and particularly to the printer including a device in which a print head supports a platen which is detachable so that the print head can come into pressure contact with the platen.

2. Description of the Related Art

The known printer in which a platen roller is detachable, print paper can be easily loaded, and the like has been used.

For example, in the printer disclosed in JP-A-2000-318260, the platen roller has a roller shaft and is retained in U-shaped grooves (hereinafter, referred to as upper open grooves) which is formed in a pair of lateral plates formed in the right and left of a frame and of which the upper portion is open. In addition, the roller shaft is controlled in the right, left, and lower directions in position by the upper open grooves and controlled in the upper direction in position by a lock lever disposed in both the lateral plates of the frame.

The lock levers are lever members disposed to be rotatable around the rotation point of the frame and are together joined by the joint member with a plate shape to constitute the lock lever member. The lock lever member is disposed in the frame so as to allow the joint member to be positioned in the opposite side of the platen roller of a thermal head, which is the print head disposed to come into contact with the platen roller. In addition, a spring member urging the thermal head retention plate and the joint member to move away is mounted between thermal head retention plates which bear the joint member and the thermal head.

The spring member applies an urging force for locking a roller shaft of the platen roller between the lock lever and the upper open groove of the frame. In addition, the spring member also applies the urging force for bringing the thermal head into pressure contact with the platen roller in a state where the roller shaft of the platen roller is locked between the upper open groove of the frame and the lock lever.

As described above, the lock lever member is disposed in the frame so that the joint member is positioned in the opposite side of the platen roller of the thermal head. Such a configuration does not meet the recent requirement of a decrease in size.

In addition, one spring member allows the lock lever to lock the roller shaft and urges the thermal head to come into pressure contact with the platen roller. Consequently, the one spring member cannot adjust only the spring load required to lock the lock lever and in the roller shaft for itself, for example.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a printer capable of independently adjusting a lock force of a lock lever for a roller shaft and a pressure contact force of a thermal head for a platen roller as well as providing a miniaturized printer.

According to an aspect of the invention, there is provided a printer including a print head; a platen roller with which the print head is urged to come into pressure contact by a first spring member and which has a roller shaft; a motor capable of rotating the platen roller; a frame in which upper open grooves that support the platen roller are disposed on a pair of lateral plates thereof opposite to each other; and a lock lever member in which a pair of lock levers that controls a position of an open side of the roller shaft urged by a second spring member to be normally present in the upper open grooves and to be supported in the upper open grooves is joined to a joint member, and which is rotatably supported by a rotation shaft axially supported by an shaft hole disposed in the pair of lateral plates of the frame; wherein the lock lever member is disposed so as to position the joint member close to a bottom plate of the frame in a print portion in which the platen roller and a thermal head come into pressure contact with each other.

In this manner, it is possible to reduce a printer in size by disposing the lock lever member so as to position the joint member close to the bottom plate of the frame in the print portion in which the platen roller and the thermal head come into pressure contact with each other. In addition, it is possible to independently adjust a lock force of the lock lever for the roller shaft and a pressure contact force of the thermal head for the platen roller.

The joint member may be a longitudinal plate shaped member and a reinforcing rib that extends in a longitudinal direction may be disposed in the center in the width direction of the joint member.

In this manner, it is possible to increase strength of the joint member constituted by the plate-shaped member so as to suppress bending deformation by forming the reinforcing rib in a longitudinal direction of the joint member. Consequently, it is possible to reliably lock the roller shaft of the platen roller.

In a printer according to the invention, it is possible to independently adjust a lock force of a lock lever for a roller shaft and a pressure contact force of a thermal head for a platen roller as well as realizing a miniaturized printer. Consequently, it is possible to surely support the platen roller in a predetermined position of a frame and to satisfactorily bring the platen roller into contact with a thermal head disposed to be opposite to the platen roller.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A printer according to an embodiment includes a feeding portion which is made of a resin material and feeds print paper, an ejecting portion which ejects print paper, a printer chassis (not shown) in which a wiring board is disposed and an opening is formed. In addition, a terminal for supplying an electric power to a motor, a control board, and the like described below and inputting input print data is formed in the wiring board.

A platen roller, a lock lever member, a head retention member, a thermal head which is a kind of a print head, a deceleration device, a frame which movably supports the head retention member and rotatably supports a roller shaft of the platen roller, a motor which has a drive shaft and rotatably drives the platen roller with the deceleration device interposed therebetween, and a print paper guide are generally disposed in the printer chassis.

FIG. 1is an exploded perspective view showing each member of the frame of the printer according to the embodiment.FIG. 2is a perspective view showing the frame of the assembled printer.

A frame1disposed within the printer chassis has a bottom plate3of which an opening portion2with a rectangular shape is formed at the center. A pair of lateral plates4aand4bopposite to each other is formed in the right and left of the bottom plate3. In each substantial center of the upper end portions of the pair of the lateral plates4aand4b, -shaped notches (hereinafter, referred to as -shaped notches)5aand5bare formed. In positions adjacent to the -shaped notches5aand5b, U-shaped grooves6aand6b(hereinafter referred to as upper open grooves) of which the upper portions are open are formed. In addition, in the lower portions of the -shaped notches6aand6bof the pair of the lateral plates4aand4b, shaft holes7aand7bin which a rotation shaft14is axially supported to rotate the lock lever member and the head retention plate26described below are formed.

In the upper open grooves6aand6b, roller shafts9aand9bof the platen roller9disposed in a concentric shape in both ends of a roller body9care each retained, so that the platen roller9is axially supported between the lateral plates4aand4bso as to be rotatable.

In the printer according to the embodiment, a pair of lock levers10aand10bwhich prevent the roller shafts9aand9bsupported in the upper open grooves6aand6bfrom coming out are joined to a joint member11cwith a plate shape to be incorporated into a lock lever member10, which is disposed within the pair of the lateral plates4aand4bof the frame1.

According to the embodiment, the pair of the lock levers10aand10bwith a substantially right triangle shape are formed. In addition, each substantially right-angled corner portion is positioned below the platen roller9in each of the lock levers10aand10b, so that each bottom side constituted by each corner portion is joined to the joint member10cin a long plate shape. In addition, according to the embodiment, a reinforcing rib10dfor preventing the lock lever member10from being deformed extends in a longitudinal direction to be formed in the center of the width direction of the joint member10c.

In the upper end portions of each the lock levers10aand10b, locking projections15aand15bfor locking the platen roller9in the roller shafts9aand9bare formed.

The locking projections15aand15baccording to the embodiment have a slope guiding portion15cfor guiding the roller shafts9aand9bso as to be slid into upper open grooves6aand6b, and a slope locking portion15dfor locking the outer periphery of the roller shafts9aand9b.

In the corner portions of the lock levers10aand10b, which are positioned in the opposite side of the platen roller, shaft holes13aand13bin which the lock levers10aand10bare rotatable are formed. In a state where the joint member10cis positioned within the opening portion2formed in the bottom plate3of the frame1and the extension portion12extends in a direction of the upper open grooves6aand6b, the lock lever member10is axially supported to be rotated by the rotation shaft14so that the shaft holes13aand13bare matched in position with the shaft holes7aand7bformed in each lateral plates4aand4bof the frame1. That is, the lock lever member10is disposed so that the joint member10cis positioned on the bottom plate3of the frame1in a print portion in which the platen roller9comes into pressure contact with a thermal head24described below.

In the center of the opposite side of the platen roller of the lock lever10a, a lock piece10ein which the some end portion of the bottom plate3of the frame1is bent to be inclined inwardly to the frame1and which locks some end portion of the lock spring18, which is a second spring member, disposed between the a spring bearing portion3aand the some end portion is formed. As shown inFIG. 3, the lock spring18is a wound coil spring. One locking end portion19with a substantially straight line-shape is fixed to the lock piece10ein a state where the rotation shaft14penetrates through the wound coil spring. The other locking end portion20comes into contact with the spring bearing3eso that the tension for urging the lock lever member10to the platen roller9is applied.

That is, the lock lever member10is urged to the platen roller9by the lock spring18disposed in a state where spring bearing3aand the lock piece10eare under the influence of the tension. The locking projections15aand15bcome into contact with the upper open grooves6aand6bso as to be locked in the roller shafts9aand9b.

In the-shaped notches5aand5b, slide shafts26aand26bof a head retention plate26supporting the thermal head25, where a plurality of heater elements24is disposed in a longitudinal direction as shown inFIG. 4, is born to be slid. In addition, the slide shafts26aand26bare disposed to bring the heater elements24into pressure contact with the outer periphery of the roller body9cof the platen roller9.

Specifically, the head retention plate26is a plate-shaped member extending in the arrangement direction of the heater elements24of the thermal head25. The thermal head25is disposed in the front surface of the head retention plate26with adhesive seal material29, which is capable of adhering both sides, interposed therebetween, and a spring pressure plate27is disposed in the back surface. A flexible wiring board28for connecting a drive control unit or a power supply (not shown) is connected to the thermal head25.

In the lower portion of the lateral plates30aand30bof the head retention plate26, the shaft holes31aand31bin which the rotation shaft14for rotating the upper portion of the head retention plate26is axially supported are formed. The head retention plate26is axially supported within the lock lever member10so as to be rotated by the rotation shaft14by matching the shaft holes31aand31b, the shaft holes7aand7bformed in each of the lateral plates4aand4bof the frame1, and the shaft holes13aand13bof the lock lever member10in position.

In the back surface of the spring pressure plate27, two head fitting portions27cwith a convex shape for fitting each one end of two compressed coil springs32described below, which are first spring members, are formed. In addition, in an end plate4cof the frame1formed to be opposite to the back surface of the spring pressure plate27, two wall fitting portions4dwith a convex shape for fitting the other end of the compressed coil spring32are formed. The two coil springs32for applying tension between the head fitting portions27cand the wall fitting portions4dto the rotation shaft14axially supported in the shaft holes31aand31bso as to normally rotate the upper portion of the thermal head retention plate26toward the platen roller9are disposed.

The head retention plate26is urged toward the platen roller9by the compressed coil springs32so that each heater element24of the thermal head25comes into pressure contact with the platen roller9. Consequently, a pressure contact force of the thermal head25for the platen roller9can be simply adjusted by changing the spring pressure of the compressed coil springs32. When the thermal head25comes into pressure contact with the platen roller9, the slide shafts26aand26bslide in each of the-shaped notches5aand5b. A position in which each heater element24of the thermal head25and the platen roller9come into pressure contact with each other is the print portion of the printer.

In the lateral plate4a, a gear box40housing a deceleration device is fixed by screw cramps.

On the back surface of the bottom plate3of the frame1, the drive shaft34aprojects from an opening40ato the inside of the gear box40so that a motor34with the drive shaft34afor rotatably driving the platen roller9is disposed. Within the gear box40, a drive gear37is retained in the drive shaft34aof the motor34and an intermediate gear group38, which is the deceleration device, engages with the drive gear37. A platen gear39retained in the roller shaft23of the platen roller22engages with the intermediate gear group38. In addition, when the motor is rotatably driven, the drive gear37and the intermediate gear group38rotate, and then the platen gear39rotates. In the end, the platen roller9rotates.

In one side in which the end plate4cof the bottom plate3of the frame1is formed and in the opposite side, a paper guide member42for guiding a conveyance path of print paper (not shown) fed in a printing process and for keeping a paper detection sensor41detecting print paper is disposed.

The thermal head25and the platen roller9can print images such as characters on the print paper (not shown) conveyed to the print portion in which the thermal head25and the platen roller9come into pressure contact with each other.

In the rear of the head retention plate26, a cam member (not shown) capable of releasing the pressure contact of the platen roller9and the thermal head25is disposed. An operation member capable of operating the cam member is connected to the cam member. By rotating the operation member, the thermal head25can be detached from the platen roller9against the urging force of the compressed coil springs32.

In such a printer, for example, when print paper is set and the platen roller9is separated from the printer, the platen roller9can be extracted while being raised. In this case, the roller shafts9aand9bof the platen roller9come into contact with the locking projections15aand15band rotate the lock levers10aand10bon the shaft holes13aand13b, which are rotation points, in a clockwise direction inFIG. 3and in a counterclockwise direction inFIG. 4.

According to the embodiment, since the pair of the lock levers10aand10bis incorporated into the joint portion10C, both of the lock levers10aand10bfurther press the lock spring18disposed under the influence of tension. Consequently, the lock levers10aand10brotate against a repulsive force of the lock spring18.

In this manner, the platen roller9is separated from the frame of the printer by releasing the engagement of the locking projections15aand15bof the lock lever10from the roller shafts9aand9band opening the upper portions of the roller shafts9aand9bin the upper open grooves6aand6b.

After the platen roller9is separated from the frame, the lock lever member10is rotated by the urging force of the lock spring18in the clockwise direction inFIG. 3and in the counterclockwise direction inFIG. 4so that the locking projections15aand15bare positioned in the upper open grooves6aand6b.

When the platen roller9is mounted in the printer, the roller shafts9aand9bcome into contact with the slope guiding portions15cof the locking projections15aand15bpresent in the upper open grooves6aand6b, and is slid in the back direction of the upper open grooves6aand6b. In this manner, while the lock lever member10further presses the lock spring18disposed under the influence of the tension against the repulsive force of the lock spring18, the lock levers10aand10brotate on the shaft holes13aand13bin the clockwise direction inFIG. 3and in the counterclockwise direction inFIG. 4and open the upper portions of the upper open grooves6aand6b. Consequently, the roller shafts9aand9bare axially supported in the upper open grooves6aand6band the slope locking portions15dare locked in the roller shafts9aand9b.

In the printer according to the embodiment, the urging force of the lock spring18and the urging force of the compressed coil spring32can be each adjusted by using the individual spring member. Consequently, it is possible to individually adjust the lock force of the lock levers10aand10bfor the rollers shafts9aand9band the pressure contact force of the thermal head24for the platen roller9.

Consequently, it is possible to reliably support the platen roller9in a predetermined position of the frame1and to simply detach the platen roller9by adjusting the urging force of the lock spring18. In addition, it is possible to satisfactorily bring the platen roller9into contact with the thermal head24by adjusting the urging force of the compressed coil spring32.

Since the joint member10cof the lock lever member10is positioned on the bottom plate3of the frame1in the print portion in which the platen roller9and the thermal head25come into contact with each other, it is possible to reduce the printer in size.

The invention is not limited to the embodiment, but can be modified into various forms, if necessary.