HK1057513B - Printer - Google Patents

Description

Printer with a movable platen

Technical Field

The present invention relates to a printer, and more particularly, to a printer for positioning a platen on a cover with respect to a printhead on a frame when the cover is in a closed position.

Background

In the prior art, there is a printer that stores therein a continuous sheet such as roll paper, and pushes out the continuous sheet while printing. In this type of printer, if successive sheets are to be replaced, it is necessary to manually pull out the successive sheets and take out the successive sheets along a predetermined path. For this purpose, a platen for opening and closing the continuous sheet exchange port is provided on a side of the printer cover at a position opposite to the print head, so that the sheet path can be opened by opening the cover.

When the print head is a click type or ink jet type printer, a predetermined interval (platen interval) is left between the print head and the platen while the platen is disposed in parallel with the print line of the print head to ensure print quality.

However, the related art printer performs positioning by a combined action of a lock lever provided rotatably on the cover and a lock pin provided on the chassis. Thus, the positioning accuracy of the platen may be degraded by the influence of the loose coupling of the cover to the chassis.

Disclosure of Invention

It is an object of the present invention to provide a printer in which a platen placed on a cover can be positioned with high accuracy with respect to a print head placed on a carriage when the cover is closed. The above-described high accuracy can be achieved by employing the print head which eliminates the influence of the looseness of the connection of the cover body with respect to the chassis, so that a predetermined interval can be maintained between the print head and the platen, and the platen can be disposed in parallel with the print line of the print head, so that the print quality can be improved.

In order to achieve the above object, the present invention provides a printer comprising: the printing head is arranged on the rack; a cover body disposed on the frame to freely perform opening and closing operations; a platen provided on the cover body and spaced apart from the print head by a predetermined interval when the cover body is closed; a first positioning mechanism for positioning the platen with respect to the print head when the cover is closed, and for restricting a change in position of the platen rotating about the first positioning fulcrum; and a second positioning mechanism for positioning the platen with respect to the print head when the cover is closed, and for restricting rotation of the platen around the first positioning fulcrum by butting it onto the second positioning fulcrum.

In addition, the first positioning fulcrum is preferably disposed on a first imaginary line passing through the printing position of the print head as viewed from the lateral direction and substantially perpendicular to a surface of the platen which is spaced apart from the print head by a predetermined distance when the cover is closed.

In short, the plane defined by the print line and the first positioning fulcrum intersects at right angles the surface of the print platen, which is spaced from the print head by a predetermined distance when the cover is closed.

In this case, the amount of change in the platen gap caused by the rotation of the platen is minimized. As a result, the accuracy of platen spacing is enhanced to improve print quality.

In addition, in a preferred mode, the first positioning mechanism comprises a locking pin which is arranged on the frame and used as a first positioning fulcrum; a lock lever rotatably disposed on the platen or the cover body by a lock lever shaft and cooperating with the lock pin to lock opening and closing operations of the cover body when the cover body is closed; a lock lever shaft provided on one of the platen and the cover and serving as a second positioning fulcrum; and a first positioning groove provided on the platen or the cover for limiting a positional change of the platen around the locking pin in only rotation along an outer periphery of the locking pin when the cover is closed. In this case, the first positioning mechanism can be formed by adding a modification of the first positioning groove to the locking lever mechanism in the related art. Thus, the number of parts is reduced, and the structure of the printer is simplified.

In addition, in a preferred mode, the second positioning mechanism includes a second positioning groove provided on the frame, which restricts rotation of the platen winding locking pin by abutting the locking lever shaft on an inner edge portion of the groove when the cover is closed. In this example, the second positioning mechanism is formed by using a lock lever shaft. Accordingly, the number of parts is reduced, and the structure thereof is simplified. In addition, the distance between the first positioning fulcrum and the second positioning fulcrum is kept constant by the locking rod. Thus, the positioning accuracy of the platen is further improved.

Further, the printer preferably includes: a paper feeding roller disposed on one of the frame and the cover; and a paper pressing roller wheel which is arranged on the other one of the frame and the cover body and is butted on the paper feeding roller wheel when the cover body is closed; wherein the first positioning fulcrum is located at a position shifted by a certain amount from a second imaginary line passing through the paper feed roller and the paper pressing roller as viewed from the side. In other words, the first positioning fulcrum is disposed outside a plane defined by the axes of the paper feed roller and the platen roller.

In this case, momentum in a constant direction around the first positioning fulcrum is applied to the platen by a reaction force acting on the sheet feeding roller. In this way, the abutting position of the second positioning fulcrum and the second positioning groove can be determined to further improve the positioning accuracy of the platen.

In addition, the printer preferably includes a spring for biasing the platen roller toward the feed roller. In this example, a constant reaction force (spring force) acts on the platen roller. In this way, momentum in a constant direction can be stably applied to the platen.

Drawings

Fig. 1 is a perspective view showing a closed state of a cover of a printer assembly according to a first embodiment of the present invention.

Fig. 2 is a perspective view showing the printer assembly of fig. 1 with the cover in an open state (half-open state).

Fig. 3 is a perspective view showing the printer assembly of fig. 1 with the cover in an open state (fully open state).

Fig. 4 is a perspective view of the cover in the printer assembly shown in fig. 1 in a closed state showing the main components thereof.

Fig. 5 is a perspective view of the printer assembly shown in fig. 1 with the cover in an open state showing the major components thereof.

Fig. 6 is an exploded perspective view showing a cover in the printer assembly shown in fig. 1.

FIG. 7 is a longitudinal cross-sectional view of the printer assembly shown in FIG. 1 showing the major components thereof during closing of the cover.

Fig. 8 is a longitudinal sectional view showing the main components of the printer assembly shown in fig. 1 in a state before the cover is closed.

Fig. 9 is a longitudinal sectional view of the printer assembly shown in fig. 1 with the cover in a closed state showing the major components thereof.

Fig. 10 is a perspective view showing the platen of the printer assembly of fig. 1 from the rear.

FIG. 11 is a longitudinal cross-sectional view of the cover of the printer assembly showing the major components thereof in a closed position in accordance with another embodiment of the present invention.

Detailed Description

Embodiments of the present invention will be described below with reference to the accompanying drawings. Fig. 1 is a perspective view showing a closed state of a cover of a printer assembly according to a first embodiment of the present invention. Fig. 2 is a perspective view showing the printer assembly of fig. 1 with the cover in an open state (half-open state). Fig. 3 is a perspective view showing the printer assembly of fig. 1 with the cover in an open state (fully open state). The printer assembly 10 shown in the above figures is incorporated into a predetermined housing to form a printer. The printer assembly 10 includes a housing 11 for storing therein a rolled continuous sheet of paper, and one end of the continuous sheet of paper P rotatably secured in the housing 11 is withdrawn from an upper end portion of the printer assembly 10 via a paper path 12. The sheet path 12 is provided with a sheet feeding roller 13 for conveying the continuous sheet P, a platen roller 14 for pressing the continuous sheet P against the sheet feeding roller 13, a dot-and-click type print head 15 for performing a printing operation on the continuous sheet P, and a platen 16 for fixing the reverse side of the continuous sheet P at a position opposite to the print head 15.

The print head 15 is provided on a carriage 17 for reciprocating movement in the transverse direction (the width direction of the sheet path 12). Ink ribbon is fed from the ribbon cassette 18 to the moving area of the print head 15. The impact tip of the print head 15 protrudes outward and forms a state in which the ink ribbon is interposed between the print head 15 and the continuous sheet P. In this way, the printer can perform dot-matrix printing on the continuous sheet P.

The casing 11 is provided with an opening 19 for replacing the continuous sheet P. Side frames 20a constituting a part of the frame 20 stand on left and right sides of the housing 11, and the opening 19 is opened and closed by a cover 21 movably supported on a rear portion of the side frames 20 a. The cover 21 houses or accommodates the platen 16 and the platen roller 14 at its distal end portion position. When the cover 21 is opened, the platen 16 and the platen roller 14 are retracted, thereby opening the sheet path 12. In other words, when the continuous paper sheet P needs to be replaced, the cover 21 is opened to store the continuous paper sheet P in the casing 11 and to draw out one end of the continuous paper sheet P out of the casing. Then, the cover 21 is closed, so that the continuous sheet P is set to move along the sheet path 12. A motor 30 for driving the paper feed roller 13 is fixed to the outside of one of the side frames 20 a. A gear train 31 for transmitting the power of the motor 30 to the paper feed roller 13 is provided outside the same side frame 20 a.

FIG. 4 is a perspective view of the cover of the printer assembly of FIG. 1 in a closed position showing the major components thereof; FIG. 5 is a perspective view of the cover of the printer assembly of FIG. 1 with its major components shown in an open position; fig. 6 is an exploded perspective view showing a cover of the printer assembly in fig. 1.

As shown in the above drawings, the platen 16 includes a joining surface 16a integrally joined with the lower surface on the distal end side of the cover 21, a downstream end guide surface 16b for guiding the continuous sheet at the downstream end of the print head 15, a print head opposing surface (platen acting surface) 16c opposing the print head 15 and separated by a predetermined interval, and an upstream end guide surface 16d for guiding the continuous sheet at the upstream end of the print head 15. The platen roller 14 is rotatably fixed to the reverse side of the platen 16. The platen roller 14, which protrudes from a roller protrusion hole 16e formed in the upstream end guide surface 16d, abuts on the paper feed roller 13. When the cover body 21 is closed, the head-opposing surface 16c and the print head 15 are kept at a predetermined interval from each other and fixed in a state of being parallel to the print line of the print head 15. The first positioning mechanism 22 and the second positioning mechanism 23 for positioning the platen 16 with respect to the print head 15 will be described below.

FIG. 7 is a longitudinal cross-sectional view of the printer assembly of FIG. 1 showing the major components thereof during use in closing the cover; FIG. 8 is a longitudinal cross-sectional view of the printer assembly of FIG. 1 showing the major components thereof in a state prior to closure of the cover; fig. 9 is a longitudinal sectional view of the printer assembly shown in fig. 1 with the cover in a closed state showing the major components thereof. As shown in the above drawings, the first positioning mechanism 22 includes a pair of left and right lock pins (first positioning fulcrums) 24 protruding from the inner surface of the side frame 20a, a lock lever shaft 25 rotatably fixed to the side plate portion 16f of the platen 16, a pair of left and right lock levers 26 rotatably supported on the lock lever shaft 25, and a pair of left and right first positioning grooves 16g formed on the left and right side plate portions of the platen 16.

As shown in fig. 6, the left and right locking levers 26 are integrally connected by a connecting portion 26a and biased in the backward direction by a spring 27 interposed between the connecting portion 26a and the platen roller 14 in a compressor state. A coupling hook groove 26b and a conical portion 26c are formed at the distal end portion of the locking lever 26. When the cover 21 is closed, the conical portion 26c contacts the lock pin 24 before the cover 21 reaches the closed position. The locking pin 24 guides the conical portion 26c so that the locking lever 26 is rotated forward when the cover body 21 is in the closed state (see fig. 8). As shown in fig. 9, when the cover body 21 reaches the closed position, the conical portion 26c goes over the lock pin 24, so that the lock lever 26 is rotated rearward (rotated in the arrow a direction in fig. 9) by the energizing action of the spring 27. At this time, the coupling hook groove 26b is coupled with the locking pin 24 to lock the operation of opening and closing the cover body 21. The lock release lever 28 is rotatably supported on one end portion of the lock lever shaft 25. When the operator rotates the lock release lever 28 rearward, the lock lever 26 rotates forward (in the direction indicated by the arrow B in fig. 9), thus releasing the lock of the opening and closing operation of the lid body 21.

The first positioning groove 16g is formed in the lower end portion of the side plate portion 16f such that the lower end portion thereof forms a fan-shaped opening. As shown in fig. 8, when the cover body 21 is in the closed state, one of the groove inner edges of the first positioning groove 16g comes into contact with the lock pin 24, thereby positioning and guiding the platen 16. In addition, as shown in fig. 9, when the cover body 21 reaches the closed position, the slot upper end 16h of the first positioning slot 16g comes into contact with the lock pin 24, thereby positioning the platen 16. This state is secured by the combined action of the locking pin 24 and the locking lever 26. The groove upper end 16h of the first positioning groove 16g and the engaging hook groove 26b of the locking lever 26 are formed in an arc shape along the outer circumferential edge of the locking pin 24. In the fully closed state, the slot upper end 16h of the first positioning slot 16g and the engagement hook slot 26b of the lock lever 26 are engaged with the lock pin 24, and at this time, the position of the platen 16 can be changed only by rotating it around the lock pin 24.

As shown in fig. 9, the locking pin 24 serving as the positioning fulcrum of the first positioning mechanism 22 is placed on an imaginary line L1 viewed from the side upward. The first imaginary line L1 passes through the positioning position 15a of the print head 15 and is almost perpendicular to the print head opposing surface 16c of the platen 16 as viewed from the side. The locking pin 24 is disposed on the first imaginary line L1, and the amount of change in the platen gap during rotation of the platen 16 can be minimized.

The print head 15 described in the above embodiment is used for a click type printer such that nine wires are arranged in the sheet conveying direction. In this embodiment, in order to define the position of the first imaginary line L1, it is assumed that the printing position 15a is the center position between the upper and lower conductive lines.

The second positioning mechanism 23 includes a lock lever shaft (second positioning fulcrum) 25 and a pair of left and right second positioning grooves 20b formed on the left and right side frames 20 a. A second positioning groove 20b is formed at the upper end of the side frame 20a such that a fan-shaped opening is formed at the upper end thereof. When the cover body 21 is closed as shown in fig. 8, both left and right ends of the lock lever shaft 25 contact one of the inner edges of the second positioning grooves 20b, thereby positioning and guiding the platen 16. As shown in fig. 9, when the cover reaches the closed position, both ends of the lock lever shaft 25 enter the narrow portions 20c of the second positioning grooves 20 b. The narrowed portion 20c is sized slightly smaller than the diameter of the locking lever shaft 25. In the state where the lock lever shaft 25 is positioned, it abuts against the groove inner edge of the second positioning groove 20b, so that the platen 16 is restricted from rotating about the lock pin 24.

As shown in fig. 10, a roller holder 29 for supporting the platen roller 14 and the spring 27 is disposed on the back side of the platen 16. The roller holder 29 is combined with the lock lever shaft 25 and the roller protrusion hole 16e so that it is integrally fixed with the platen 16. The roller holder 29 is provided with a roller supporting groove 29a for rotatably supporting the platen roller shaft 14a and a protrusion 29b for supporting the spring 27. The roller supporting groove 29a is groove-shaped, and not only rotatably supports the platen roller shaft 14a, but also slidably supports the platen roller shaft 14a in the direction of a broken line L2 passing through the centers of the paper feed roller 13 and the platen roller 14. The projection 29b is a bent portion bent in the transverse direction, to which the spring 27 is connected from one end thereof. The spring 27 applies an energizing force to the lock lever 26 to make it rearward as described above, and further applies a force to make it downward to the platen roller shaft 14a, so that the platen roller 14 is protruded from the roller protrusion hole 16e by the energizing force of the spring 27. In a state where the platen roller 14 is positioned away from the paper feed roller 13, that is, in a state where the cover 21 is opened, both ends of the platen roller shaft 14a under the excitation of the spring 27 abut against the reverse surface of the platen 16, thus restricting further protrusion of the platen roller 14. On the other hand, in a state where the cover 21 is closed, the platen roller 14 abuts on the paper feed roller 13 and is retracted to the opposite side of the platen 16. At this time, the platen roller 14 is pressed against the paper feed roller 13 with a constant urging force (an urging force of the spring 27). Accordingly, the paper feed roller 13 applies a constant reaction force (excitation force corresponding to the spring 27) to the platen roller 14.

As shown in fig. 9, as seen from the side, the locking pin 24 serving as the first positioning fulcrum is disposed at a position offset from the second imaginary line L2 by a predetermined amount. Therefore, a constant directional momentum around the lock pin 24 is applied to the platen 16 by the reaction force acting on the platen roller 14. In other words, momentum acts on the platen 16 such that the platen 16 rotates in a constant direction about the locking pins 24 as a fulcrum. This makes it possible to determine the abutting position of the locking lever fulcrum 25 and the second positioning groove 20b, thereby increasing the positioning accuracy of the second positioning mechanism 23.

FIG. 11 is a longitudinal cross-sectional view of the cover of the printer assembly showing the major components thereof in a closed condition in accordance with another embodiment of the present invention. The same reference numerals in fig. 11 as those in fig. 1 to 10 denote the same components, and a detailed description thereof will be omitted.

In the embodiment shown in fig. 1 to 10, the paper feed roller 13 and the platen roller 14 are provided at the upstream end of the print head 15 in the paper path 12, and in the present embodiment, these are provided at the downstream end of the print head 15. Specifically, the roller protrusion hole 16e is placed on the downstream end guide surface 16b of the platen 16, and the sheet feed roller 13 protrudes therefrom. The platen roller 14 is partially rotatably supported at the upper end of the side frame 20a and is brought into contact with the paper feed roller 13 protruding from the roller protruding hole 16e by pressure when the cover 21 is closed. Specifically, in the embodiment shown in fig. 1 to 10, the continuous paper sheet P is pushed from the upstream end and delivered to the printing position 15a, whereas in the present embodiment, the continuous paper sheet P is pushed from the downstream end and delivered to the printing position 15 a.

In the embodiment shown in fig. 1 to 10, the paper feed roller 13 is disposed on the side of the frame 20 and the platen roller 14 is disposed on the side of the cover 21, whereas in the present embodiment, the paper feed roller 13 is disposed on the side of the cover 21 and the platen roller 14 is disposed on the side of the frame 20. Therefore, a gear (not shown) is provided at one of the axial ends of the paper feed roller 13, and engages with the gear train 31 when the cover 21 is in the closed state, thereby transmitting the power of the motor 30 to the paper feed roller 13.

Further, in the embodiment shown in fig. 1 to 10, when the spring 27 applies a backward energizing force to the lock lever 26, the platen roller 14 is biased toward the paper feed roller 13 by the energizing force, and in the present embodiment, the platen roller 14 is biased toward the paper feed roller 13 by the energizing force of the leaf spring 271, and the coil spring 272 applies a backward energizing force to the lock lever 26.

In the same manner as shown in fig. 9, in the embodiment shown in fig. 11, as seen from the side direction, the lock pin 24 serving as the first positioning fulcrum is disposed at a position shifted by a predetermined amount from the second imaginary line L2 passing through the center positions of the platen roller wheel 14 and the paper feed roller wheel 13. Therefore, a constant directional momentum around the lock pin 24 is applied to the platen 16 by the reaction force acting on the platen roller 14. In this way, the positioning accuracy of the second positioning mechanism 23 can be enhanced.

As described above, according to the embodiments of the present invention, the present invention provides a printer assembly 10 including: a print head 15 disposed on the frame 20; a cover 21 provided on the frame 20 to freely perform opening and closing operations; a platen 16 disposed on the cover 21 and spaced apart from the print head 15 by a predetermined interval when the cover 21 is closed; a first positioning mechanism 22 for positioning the platen 16 with respect to the print head 15 when the cover 21 is closed, and for restricting a change in position of the platen 16 so that it can only rotate about a first positioning fulcrum (locking pin 24); and a second positioning mechanism 23 for positioning the platen 16 with respect to the print head 15 when the cover 21 is closed, and for restricting rotation of the platen 16 about the first positioning fulcrum by abutting on a second positioning fulcrum (lock lever shaft 25). In other words, the platen 16 is restricted to rotate only by the first positioning fulcrum to change the position, and such rotation is restricted by the second positioning mechanism 23. This allows for highly accurate positioning of the platen 16 relative to the print head 15 without loosing the connection of the cover 21 relative to the frame 20. As a result, it is possible to maintain a predetermined interval between the print head 15 and the platen 16 and make the platen 16 parallel to the print line of the print head 15, so that the print quality can be improved.

Further, as seen from the side direction, the first positioning fulcrum (locking pin 24) is located at a first imaginary line L1 passing through the printing position 15a of the print head 15 and almost perpendicular to the head opposing surface 16c of the platen 16. In this way, the amount of change in platen gap during rotation of the platen 16 is minimized. As a result, the accuracy of the platen can be increased, thereby improving the print quality.

Further, the first positioning mechanism 22 includes: a locking pin 24 provided on the frame 20 and serving as a first positioning fulcrum; a lock lever 26 rotatably supported on the platen 16 by a lock lever shaft 25 and engaged with the lock pin 24 to lock an operation of opening the cover body 21 when the cover body 21 is closed; and a first positioning groove 16g provided in the platen 16 and restricting a positional change of the platen 16 about the lock pin 24 and along an outer peripheral edge of the lock pin 24 when the cover 21 is closed. Thus, the first positioning mechanism 22 can be formed by adding a simple modification of the first positioning groove 16g to the locking lever mechanism in the related art. As a result, the number of parts can be reduced and the printer structure can be simplified.

In addition, the second positioning mechanism 23 includes: a lock lever shaft 25 provided on the platen 16 and serving as a second positioning fulcrum; and a second positioning groove 20b provided in the frame 20 for restricting the rotation of the platen 16 about the locking pin 24 by abutting the locking lever shaft 25 against an inner edge of the groove when the cover 20 is closed. Thus, the second positioning mechanism 23 can be constituted by using the lock lever shaft 25. As a result, the number of parts can be reduced and the structure thereof can be simplified. Further, by using the lock lever 26, the distance between the first positioning fulcrum and the second positioning fulcrum can be kept constant. In this way, the positioning accuracy of the platen 16 can be enhanced.

In addition, the present invention is also provided with a paper feeding roller 13 positioned on the frame 20 and a paper pressing roller 14 positioned on the cover body 21 and butted against the paper feeding roller 13 when the cover body 21 is closed. The lock pin 24 (first positioning fulcrum) is provided at a position shifted by a certain amount from a second imaginary line L2 passing through the center positions of the paper feed roller 13 and the platen roller 14 as viewed from the side. Thus, momentum in a constant direction around the lock pin 24 is applied to the platen 16 by the reaction force acting on the platen roller 14. As a result, the abutting position of the lock lever shaft 25 (second positioning fulcrum) and the second positioning groove 20B can be determined. Thus, the positioning accuracy of the platen 16 can be further enhanced.

In addition, the present invention is also provided with an energizing member or a biasing member such as springs 27, 271 for biasing the platen roller 14 toward the paper feed roller 13. Thus, a constant reaction force (spring force) can be applied to the sheet feeding roller 14. As a result, momentum can be stably applied to the platen 16 in a constant direction, so that the positioning accuracy of the second positioning mechanism 23 can be enhanced.

Although the present invention has been described in connection with the embodiments with reference to the accompanying drawings, the present invention is not limited to the embodiments described above, and those skilled in the art can make various changes and applications of the present invention based on the scope of the claims, the detailed description of the present invention, and the known technology.

As described above, in the present invention, the platen provided on the cover is positioned with respect to the print head placed on the frame when the cover is closed, so that it can be positioned with high accuracy with respect to the print head without being loosened by the attachment of the cover to the frame. As a result, a predetermined interval can be maintained between the print head and the platen, and the platen is made parallel to the print line of the print head, so that the print quality can be improved.

Claims (8)

1. A printer, comprising:

the printing device comprises a rack and a printing head arranged on the rack;

a cover body disposed on the frame to freely perform opening and closing operations;

a platen provided on the cover body and spaced apart from the print head by a predetermined interval when the cover body is closed;

the first positioning mechanism is used for positioning the stamping disc relative to the printing head when the cover body is closed and limiting the position change of the stamping disc rotating around the first positioning fulcrum; and

and the second positioning mechanism is used for positioning the stamping disc relative to the printing head when the cover body is closed, and limits the rotation of the stamping disc around the first positioning fulcrum by butting the stamping disc to the second positioning fulcrum.

2. The printer of claim 1, wherein:

the first positioning fulcrum is disposed on a first imaginary line passing through a printing position of the print head and substantially perpendicular to a surface of the platen that is spaced apart from the cover by a predetermined distance when the cover is closed.

3. The printer of claim 1, wherein said first positioning mechanism comprises:

a locking pin arranged on the frame and used as a first positioning fulcrum;

a lock lever rotatably disposed on the platen and the cover body by a lock lever shaft and cooperating with the lock pin to lock opening and closing operations of the cover body when the cover body is closed;

and a first positioning groove provided on one of the platen and the cover for limiting a change in a position of the platen around the locking pin to rotate along an outer periphery of the locking pin when the cover is closed.

4. A printer according to claim 3, wherein:

the locking lever shaft is arranged on one of the platen and the cover body and is used as a second positioning fulcrum; and

the second positioning mechanism includes a second positioning groove provided on the frame, and the second positioning groove restricts the rotation of the platen coil locking pin by abutting the locking lever shaft against the groove inner edge portion when the cover is closed.

5. The printer of claim 1, further comprising:

a paper feeding roller disposed on one of the frame and the cover; and

a paper pressing roller wheel which is arranged on the other one of the frame and the cover body and is butted on the paper feeding roller wheel when the cover body is closed;

wherein the first positioning fulcrum is disposed at a position shifted by a certain amount from a second imaginary line passing through the paper feed roller and the platen roller.

6. The printer of claim 5, further comprising a spring for biasing the platen roller toward the feed roller.

7. The printer of claim 1, further comprising a carriage that holds the printhead and moves along a print line parallel to the platen,

wherein a plane defined by the print line and the first location pivot intersects substantially at right angles a surface of the platen that is spaced a predetermined distance from the print head when the cover is closed.

8. The printer of claim 1, further comprising:

a paper feeding roller disposed on one of the frame and the cover; and

a paper pressing roller wheel which is arranged on the other one of the frame and the cover body and is butted on the paper feeding roller wheel when the cover body is closed;

wherein the first positioning fulcrum is disposed outside a plane defined by an axis of the paper feed roller and an axis of the paper press roller.