1. Field of the Invention
The present invention relates to a roll paper holding mechanism which rotatably holds a roll paper at a predetermined position, the roll paper being rotated by pulling out a leading portion of the paper, and more particularly to a roll paper holding mechanism having a structure which presses a side face of a roll paper. The invention relates also to a printer including such a roll paper holding mechanism.
2. Description of the Related Art
In small printers and the like, such a roll paper is often used. The roll paper is rotatably held by a structure of the drop-in type in which the roll paper is dropped in a housing space, or of the shaft-supporting type in which a core member is supported by a shaft, and then the paper is pulled out by a motor to be subjected to a printing process. When the paper is pulled out in order to conduct a printing process, the roll paper is rotated. Even when the printing process is ended, however, there is a case where an inertia force corresponding to the weight acts on the roll paper, and the rotation of the roll paper is not stopped simultaneously with the end of the printing process, so that overrun in which the rotation is continued by a certain degree occurs. The overrun causes slack in an outer circumferential portion of the roll paper. Such slack may produce wrinkles or a bend in the paper. Therefore, a structure which is provided with an elastic member that always presses a side face of a roll paper to restrict overrun has been proposed (for example, see JP-A-8-217294 (Abstract,
As disclosed in JP-A-8-217294, when the side face of the roll paper is pressed by the elastic member, it is certainly possible to prevent overrun from occurring. In this case, however, the elastic member exhibits a constant elasticity, and hence the pressing force by which the side face of the roll paper is pressed is always constant. By contrast, as the roll paper is further consumed, the outer diameter becomes smaller, and the weight is further reduced. Therefore, the following disadvantages may occur.
In order to pull out the paper of the roll paper to which a constant load (pressing force) is applied by the elastic member, a driving force that must be large as the diameter of the roll paper is reduced must be applied. This phenomenon is caused because, as the distance between the rotation center of the roll paper and the outermost portion from which the paper is pulled out is longer, the force required for pulling out can be further reduced by the function of a moment force. When the diameter of the roll paper is considerably reduced, therefore, the load of the motor for pulling out the paper is excessively increased, thereby causing a possibility that a failure such as step out occurs. In order to prevent such a failure from occurring, a motor of a large driving force may be disposed. In this case, however, the production cost is increased.
In the case of the drop-in type (as disclosed in JP-A-8-217294), the roll paper which is in an initial use condition and hence heavy is always settled by its own weight in a bottom portion of a housing space. When consumption of the paper is advanced and the weight of the roll paper is reduced, however, the whole roll paper is pulled by the operation of pulling out the paper to be raised, and the raised state is held by the elastic member, so that the roll paper is hardly returned by its own weight to the bottom portion of the housing space. When the paper is pulled out in this state and a printing process is conducted while the roll paper is rotated, the print surface of the paper is rubbed, or wrinkles or a bend is produced in the paper. In the case where a sensor which detects that the paper amount is reduced and informs of the reduction in order to promote replacement of the paper is disposed on the side face of the roll paper, the sensor may malfunction because the roll paper does not exist at a predetermined position.
Therefore, it is an object of the invention to provide a roll paper holding mechanism in which over run can be effectively prevented from occurring, the paper can be pulled out by a driving force that is constant or substantially constant irrespective of the outer diameter and weight of the roll paper that vary in accordance with consumption, so that a driving unit such as a motor for pulling out the paper can stably operate, and the production cost does not become disadvantageous, and also a printer including such a roll paper holding mechanism.
A roll paper holding mechanism according to the invention is characterized in that the roll paper holding mechanism includes: a holding unit which rotatably holds a roll paper; a driving unit which pulls out a leading portion of the roll paper held by the holding unit; and a pressing unit which presses a side face of the roll paper held by the holding unit, wherein the pressing unit includes a pressing force adjusting section for gradually reducing a pressing force in accordance with reduction of a diameter of the roll paper.
According to the roll paper holding mechanism of the invention, the roll paper is rotatably held by the holding unit. The holding unit may be of the drop-in type or the shaft-supporting type. The leading portion of the roll paper held by the holding unit is pulled out by the driving unit, and, in accordance with the pulling out, the roll paper is rotated. Even when the pulling operation is stopped, overrun which is caused to occur by an inertia force can be restricted because the side face of the roll paper is pressed by the pressing unit.
In the invention, the pressing force of the pressing unit is gradually reduced in accordance with reduction of the diameter of the roll paper. This change of the pressing force is realized by the pressing force adjusting section. The leading portion of the roll paper is pulled out by the driving unit configured by a motor and the like. As described above, in a state where a load is applied by the pressing unit, a driving force required for pulling out the paper must be large as the diameter of the roll paper is reduced.
In the invention, however, unlike the conventional art, the load which is applied to the roll paper by the pressing unit is not constant, but is gradually reduced in accordance with reduction of the diameter of the roll paper. Specifically, in “state where the roll paper has a large diameter and the driving force for pulling out can be reduced,” the pressing unit exerts a large pressing force, and, in “state where the roll paper has a small diameter and the driving force for pulling out must be large,” the pressing force of the pressing unit is reduced. Therefore, the driving force required for pulling out the paper (this force matches the load applied to the driving unit) may be constant or substantially constant irrespective of the outer diameter and weight of the roll paper. As a result, even when the diameter of the roll paper is reduced, an excessive load is not applied to the driving unit, and a stable operation of pulling the roll paper can be attained. Moreover, it is possible to avoid a cost for enabling the driving unit to cope with an excessive load.
In the case where the holding unit for roll paper is of the drop-in type, when the diameter of the roll paper is reduced and also the weight is reduced, there may arise a failure that, as described above, the roll paper is raised by the operation of pulling out the paper and the raised state is held by the pressing unit. In the invention, however, the pressing force which is applied to the roll paper by the pressing unit is gradually reduced in accordance with reduction of the diameter of the roll paper. Even when the roll paper is reduced in diameter and weight, therefore, the own weight of the roll paper overcomes the pressing force of the pressing unit, and hence the roll paper can be returned to the bottom portion of the housing space. Consequently, the failure due to the state where the roll paper remains to be raised can be prevented from occurring.
More specific modes of the roll paper holding mechanism of the invention are as follows.
The pressing force adjusting section includes a plurality of elastic members which are arranged substantially along a direction of reducing the diameter of the roll paper, and in a sequence in which an elasticity is further reduced as advancing in the diameter reducing direction.
The pressing unit includes a pressing member which butts against the side face of the roll paper, and the pressing force adjusting section includes a swinging mechanism which gradually swings the pressing member in one direction in accordance with reduction of the diameter of the roll paper.
The pressing unit includes a pressing member which butts against the side face of the roll paper, and the pressing force adjusting section includes a link mechanism which urges the pressing member by a pressure corresponding to an own weight of the roll paper.
The invention is characterized in that the pressing force of the pressing unit which presses the side face of roll paper held by the holding unit is gradually reduced by the pressing force adjusting section in accordance with reduction of the diameter of the roll paper. According to the configuration, first, overrun of the roll paper by an inertia force can be effectively prevented by the pressing unit from occurring. Moreover, irrespective of the outer diameter and weight of the roll paper which vary in accordance with consumption, paper can be pulled out by a driving force that is constant or substantially constant. As a result, the driving unit can stably operate, and increase of the cost of the driving unit can be avoided.
FIGS. 4(a) to 4(d) are plan sectional views showing the configuration and function of a pressing unit in the first embodiment;
FIGS. 5(a) to 5(d) are plan sectional views showing the configuration and function of a pressing unit in a second embodiment of the invention;
Hereinafter, embodiments of the invention will be described with reference to the accompanying drawings.
As shown in FIGS. 1 to 3, the outer case 10 has a box-like shape including a bottom plate 11, a pair of right and left side plates 12, a front plate 13, and a back plate 14. A roll paper holder unit (holding unit) 15 which has a substantially semi cylindrical shape is formed in rear of the case. The roll paper holder unit 15 is of the drop-in type in which a roll paper 30 is dropped to be loaded, and formed by: right and left rear plates 16 which have a substantially sector shape, and which are formed in rear of the side plates 12 (the rear side in
As shown in
As shown in FIGS. 1 to 3, the cover 20 is formed into a substantially semi cylindrical shape which is similar to the roll paper holder unit 15, and which is slightly larger than the roll paper holder unit 15. The cover is mounted so as to, in an opened state, cover the outer side of the roll paper holder unit 15. Specifically, the cover 20 includes: a pair of right and left side plates 21 having a substantially sector shape; and a curved plate 22 which connects together arcuate peripheral edges of the side plates 21. In each of the side plates 21, a portion corresponding to the axis of the curved plate 22 is supported swingably and coaxially via a cover shaft 23 by the corresponding rear plate 16 of the roll paper holder unit 15.
When the cover 20 is rearward swung, the cover 20 is opened along the outer side of the roll paper holder unit 15, so that, as shown in
As shown in
When the cover 20 is closed, the platen roller 51 is opposed to the print head 52, and the print head 52 is elastically brought into press contact with the platen roller 51 by the elasticity of the coil spring 54. The paper 31 pulled out from the roll paper 30 is interposed between the platen roller 51 and the print head 52, and then further pulled out by rotation of the platen roller 51. When the paper 31 is pulled out, the roll paper 30 is rotated.
As shown in
The cutter mechanism 60 is disposed immediately downstream (the upper side in
A pair of guide plates 46, 47 which guide the paper 31 to the printing mechanism 50 are disposed upstream from the printing mechanism 50. The one guide plate 46 is disposed on the outer case 10, and the other guide plate 47 on the tip end portion of the cover 20. In a state where the cover 20 is closed, the paper transport path which is narrow, and which guides a leading portion of the paper 31 toward the printing mechanism 50 is formed between the guide plates 46, 47. A tension roller 44 which pushes up the paper 31 to apply tension to the paper is disposed upstream from the guide plate 46 on the side of the outer case 10. The tension roller 44 is upward urged by a plate spring 45 disposed on the outer case 10.
As shown in
The basic operations of the printer 1 in a process from printing to cutting of paper will be described. The printer 1 is caused to automatically operate by a control unit which is disposed in, for example, the outer case 10.
In the state where the cover 20 is opened, first, the user pulls out a leading portion of the paper 31 from the roll paper 30 loaded in the roll paper holder unit 15, to the outside of the outer case 10, and then closes the cover 20. When the cover 20 is closed, the paper 31 pulled out from the roll paper 30 is interposed, as advancing from the upstream side, between the guide plate 46 and the guide plate 47, the platen roller 51 and the print head 52, the stationary blade 61 and the movable blade 63, and an opening edge of the outer case 10 and a tip end edge of the cover 20.
Thereafter, the cutter mechanism 60 operates so that the movable blade 63 of the movable blade unit 62 reciprocates to cut the leading portion of the paper 31, and the printer then enters a print waiting state. Although the leading portion of the cut paper 31 is interposed between the opening edge of the outer case 10 and the tip end edge of the cover 20, the leading portion can be removed away by pulling out the paper to the outside.
The printing process is started by supplying a printing command to the print head 52 and the transportation motor. Specifically, the printing process is conducted by repeating a printing operation by the print head 52, and an operation of transporting the paper 31 by rotation of the platen roller 51. In accordance with the transportation of the paper 31, the paper 31 is transported to the paper stocker 24 while being guided by the guide plate 26.
When the printing process is ended, the platen roller 51 is rotated by a degree corresponding to a predetermined length to transport the paper 31 so as not to cut a printed portion. Thereafter, the cutter mechanism 60 operates to cut the paper 31. The cut paper 31 is stored on the paper stocker 24.
In the roll paper holder unit 15 of the printer 1, disposed is a pressing unit 70 which presses the side faces of the roll paper 30 loaded in the roll paper holder unit 15. This pressing unit 70 will be described in detail.
As shown in
Each of the pressing plates 72 is an elongated plate member having a U-like sectional shape, and has a pressing face 72a which is inward directed. As shown in
The spring seat plate 75 extends between edges of the inner plate 27 and the curved plate 17, and is fixed thereto. The pressing plate 72 is movable in lateral directions (vertical directions in
As shown in
As shown in
The two coil springs 76, 77 which are longitudinally arranged at an adequate interval have different elasticity, or the coil spring 77 in the rear side (the side of the outer circumference of the roll paper 30) exhibits an elasticity which is larger than that of the coil spring 76 in the front side (the side of the inner circumference of the roll paper 30). As shown in
As shown in
As seen from the above-described operations, in the pressing unit 70, the pressing force which is applied to the side faces of the roll paper 30 by the pressing plates 72 is gradually reduced in accordance with reduction of the diameter of the roll paper 30. According to the pressing unit 70, the side faces of the roll paper 30 are pressed by the pressing plates 72, and hence overrun in which the roll paper 30 is caused to continue the rotation by an inertia force generated in the roll paper 30 when the printing process is stopped is restricted. Therefore, slack in the paper 31 due to overrun, and wrinkles or a bend in the paper 31 caused by the slack are prevented from occurring.
When the roll paper 30 is reduced in diameter and weight, the pressing force which is applied to the side faces of the roll paper 30 by the pressing unit 70 is gradually reduced in accordance with the reduction of the diameter of the roll paper 30. Therefore, the own weight of the roll paper 30 overcomes the pressing force of the pressing unit 70, so that the roll paper can be returned to the bottom portion of the roll paper holder unit 15. As a result, failures such as rubbing of the print surface, and wrinkles or a bend in the paper 31 which may be caused when a printing process is conducted in a state where the roll paper 30 is raised do not occur. In the case where a sensor which detects that the amount of the paper 31 is reduced and informs of the reduction in order to promote replacement of the paper 31 is disposed, the sensor can surely operate because the roll paper 30 always exists at the predetermined position in the roll paper holder unit 15.
The paper 31 is pulled out from the roll paper 30 by the function of rotation of the platen roller 51 which is rotated by the transportation motor. In the roll paper 30 in which a load is applied to the side faces in order to prevent overrun from occurring, a larger driving force for pulling out the paper 31 must be applied as the diameter of the roll paper 30 becomes smaller. In the embodiment, however, the load which is applied to the roll paper 30 by the pressing unit 70 is not constant. Namely, in “state where the roll paper 30 has a large diameter and the driving force for pulling out can be reduced,” the pressing unit 70 exerts a large pressing force, and, in “state where the roll paper 30 has a small diameter and the driving force for pulling out must be large,” the pressing force of the pressing unit 70 is reduced.
Therefore, the driving force which is to be produced by the transportation motor in order to pull out the paper 31 can be constant or substantially constant irrespective of the outer diameter and weight of the roll paper 30. As a result, even when the diameter of the roll paper 30 is reduced, an excessive load is not applied to the driving unit configured by the transportation motor and the reduction gear, and a stable operation of pulling the roll paper 30 can be attained. Moreover, it is possible to avoid a cost for enabling the driving unit to cope with an excessive load.
Next, a pressing unit 80 in a second embodiment which is another mode of the pressing unit 70 in the first embodiment will be described with reference to FIGS. 5(a) to 5(d).
In
In the plate spring 83, a front-end portion which is an end portion in the direction of the length is cantilevered to the outer face of the inner plate 27 which is more forward than the cutaway 71. The plate spring can be elastically deformed about the cantilevered portion in the directions of the arrows A-B in
In the pressing unit 80 in the second embodiment, as shown in
As shown in
As described above, according to the pressing unit 80 in the second embodiment, the elasticity of the plate springs 83 is gradually reduced in accordance with reduction of the diameter of the roll paper 30, and hence also the pressing force which is applied to the side faces of the roll paper 30 by the pressing plates 82 is similarly reduced. In the same manner as the first embodiment, therefore, overrun of the roll paper 30 can be prevented from occurring, and moreover it is possible to attain various effects due to functions such as that, even when the roll paper 30 is reduced in diameter and weight, the roll paper is not kept to be raised, but is returned by its own weight to the predetermined position, and that the paper 31 can be pulled out by a constant driving force.
FIGS. 6, 7(a) and 7(b) are diagrams schematically showing a third embodiment in which the side faces of the roll paper 30 are pressed with using the own weight of the roll paper 30. In the embodiment, a roll paper holder unit (holding unit) 90 is of the drop-in type, and configured by a pair of right and left pressing plates (pressing members) 92. The pressing plates 92 have a rectangular shape which is longer than the maximum diameter of the roll paper 30, and are incorporated so as to, in a state where the roll paper 30 is loaded, vertically extend and oppose each other in parallel so as to hold the roll paper 30 therebetween.
In each of the pressing plates 92, a bearing 92a is formed on the outer face of an end portion (the lower portion in FIGS. 6, 7(a) and 7(b)), and a support shaft 93 which horizontally elongates is passed through the bearing 92a. The support shafts 93 are fixed to the frame (not shown) or the like of the printer so as to be parallel to each other, thereby enabling the pressing plates 92 to be swingable via the support shafts 93 in the directions of the arrows D-E in
In the roll paper holding mechanism, the roll paper 30 is placed on the right and left rollers 94. Then, the pressing plates 92 are swung about the support shafts 93 in the directions of the arrows D in
FIGS. 8, 9(a) and 9(b) are diagrams schematically showing a roll paper holding mechanism in which the side faces of the roll paper 30 are pressed with using the own weight of the roll paper 30 in a similar manner as the third embodiment. In the embodiment, a roll paper holder unit (holding unit) 100 is of the shaft-supporting type in which the roll paper 30 is rotatably supported by a pair of right and left rollers 101 that are inserted into the core member 32. The rollers 101 are rotatably supported by a pair of right and left pressing plates (pressing members) 102, respectively. The pressing plates 102 are similar to the pressing plates 92 in the third embodiment, and have a bearing 102a in respective lower end portions. The pressing plates are swingable in the directions of the arrows F-G in
In the roll paper holding mechanism, the right and left rollers 101 are inserted into the core member 32, and the roll paper 30 is rotatably supported in a state where the roll paper hangs from the rollers 101. In this state, the right and left pressing plates 102 are swung about the support shafts 103 in the directions of the arrows F in
In the roll paper holding mechanisms of the third and fourth embodiments, the side faces of the roll paper 30 are pressed by the pressing plates 92 or 102 by the own weight of the roll paper, and, in accordance that the roll paper 30 is consumed and the diameter is reduced, the pressing force applied by the pressing plates 92 or 102 is gradually reduced. Also in the embodiments, in the same manner as the first and second embodiments, therefore, it is possible to attain the effects due to functions such as that overrun of the roll paper 30 can be prevented from occurring, and that the paper can be pulled out by a constant driving force. In the third embodiment which is of the drop-in type, moreover, the failure due to the state where the roll paper 30 remains to be raised can be prevented from occurring.
Number | Date | Country | Kind |
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2004-123691 | Apr 2004 | JP | national |