Patent Publication Number: US-8109682-B2

Title: Printer for a plurality of layered sheets

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a printer, and more particularly, to a printer for processing a recording medium formed of a plurality of laminated sheets. 
     2. Description of the Related Art 
     A printer is known that transports a recording medium, which is formed of a plurality of laminated sheets, along a predetermined transport path and performs various processes, including printing, in the middle of the path. If there is a curved portion in the transport path, differences are caused in feed rate between sheets outside and inside of the curved portion. If the sheets continue to be transported in this state, a printing shear or paper jam may be caused. In consideration of these circumstances, there is used a method in which a transport path is set in a straight line or a method in which adhesion between a plurality of sheets is improved. As described in Jpn. Pat. Appln. KOKAI Publication No. 5-38855, moreover, a technique is provided in which a bail roller is disposed extending near and along the outer peripheral surface of a platen roller that constitutes a curved portion of a transport path. According to this technique, the position of the bail roller is moved for adjustment such that sheets can be reversely transported in a curve at the same rate with the curved portion on the downstream side of the curved portion. 
     However, the above-described transport system has the following problems. If the transport path is restricted in configuration, then substantial limitations will be placed on the design and usability of the printer. Further, the improvement of the adhesion requires use of an expensive adhesive agent. Furthermore, a complicated mechanism must be used for the method in which the bail roller is moved based on the curved portion. 
     Accordingly, the object of the present invention is to provide a printer with a simple construction capable of preventing sheets of a recording medium from being deviated from one another. 
     BRIEF SUMMARY OF THE INVENTION 
     A printer according to an aspect of the present invention is a printer which transports a recording medium, provided with a plurality of laminated sheets, along a predetermined transport path including a curved portion, and comprises a dot head for printing the recording medium, a platen roller which faces the dot head with the recording medium therebetween, and a feed guide which is located on the downstream side of the dot head and the platen roller with respect to the direction of transport and guides the recording medium in a manner such that the recording medium is bent in the direction opposite to that in which the curved portion is bent. 
     A printer according to another aspect of the invention is a printer which transports a recording medium, provided with a plurality of sheets, along a predetermined transport path including a curved portion, and comprises a dot head for printing the recording medium, a platen roller which faces the dot head with the recording medium therebetween, a first feed roller which is located on the downstream side of the dot head and the platen roller with respect to the direction of transport and contacts a sheet or sheets inside the curved portion as the recording medium passes the curved portion, and a second feed roller which contacts a sheet or sheets outside the curved portion and holds and transports the recording medium in conjunction with the first feed roller, the feed rate of the first feed roller being higher than that of the second feed roller. 
     Objects and advantages of the invention will become apparent from the description which follows, or may be learned by practice of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       The accompanying drawings illustrate embodiments of the invention, and together with the general description given above and the detailed description given below, serve to explain the principles of the invention. 
         FIG. 1  is a side view showing principal parts of a dot printer according to a first embodiment of the invention; 
         FIG. 2  is a side view illustrating a transporting operation of the dot printer; 
         FIG. 3  is a side view illustrating the transporting operation of the dot printer; 
         FIG. 4  is a side view showing principal parts of a dot printer according to a second embodiment of the invention; 
         FIG. 5  is a side view illustrating a transporting operation of the dot printer; 
         FIG. 6  is a side view illustrating a transporting operation of a dot printer according to a third embodiment of the invention; 
         FIG. 7  is a side view illustrating a transporting operation of a dot printer according to a fourth embodiment of the invention; and 
         FIG. 8  is a side view illustrating a transporting operation of a dot printer according to a fifth embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     First Embodiment 
     A printer  10  according to a first embodiment of the present invention will now be described with reference to  FIGS. 1 to 3 . 
       FIG. 1  schematically shows the interior of the printer  10 . The printer  10  is a wire dot printer in which a recording paper P as a recording medium, such as a continuous slip or a simple slip formed of a plurality of laminated sheets, is transported along a predetermined transport path and subjected to processing such as printing. 
     A push tractor  11  is provided on one end side (or left-hand side in  FIG. 1 ) of the printer  10 . The recording paper P as a set object to be processed is guided into the printer  10  through an inlet  12  of the push tractor  11  and transported along a predetermined transport path A indicated by broken line in  FIG. 1 . The inlet  12  forms an upstream end of the transport path, while an outlet  72  that is situated at the upper part of the printer  10  forms a downstream end of the transport path A. 
     A platen roller  15  is disposed in the central part of the printer  10 . The platen roller  15  is integrally mounted on a rotatable platen shaft  16  that extends horizontally (or depthwise perpendicular to the drawing plane). The roller  15  is in the form of a horizontally extending column, which can rotate integrally with the platen shaft  16 . The roller  15  is formed of an elastic material such as nitrile-butadiene rubber (NBR). The platen roller  15  is located opposite a dot head  41  (mentioned later) with the recording paper P between them. 
     Two pinch rollers  20  and  21  are arranged along the outer periphery of the platen roller  15 . The rollers  20  and  21  are individually located opposite the platen roller  15  with the recording paper P between them. 
     A dot head unit  30  is disposed along the outer periphery of the platen roller  15 . The head unit  30  is provided with the dot head  41  that is pressed and urged toward the roller  15 . 
     The transport path A includes a first curved portion A 1 , which is curved forward and upward from the lower end part of the platen roller  15  along a front half (or right-hand half in  FIG. 1 ) of the outer periphery of the platen roller  15  and further to the upper rear side. 
     The recording paper P is held between the pinch rollers  20  and  21 , dot head  41 , and platen roller  15 . As the rollers  20 ,  21  and  15  rotate, the paper P is transported along the transport path A that includes the first curved portion A 1 . The direction of this transport is counterclockwise around the central shaft C 1  of the platen roller  15 . 
     The dot head  41  is located in a longitudinal (or substantially vertical) rear-facing orientation. The head  41  is disposed so as to contact a thermosensitive layer of the recording paper P and face the platen roller  15  with the paper P therebetween. 
     A first exit roller  51  is provided over the dot head  41  and the platen roller  15 . The roller  51  is located over the platen roller  15  and at the back (or on the left-hand side in  FIG. 1 ) of the dot head  41 . Thus, the transport path A is additionally curved so as to return from the first curved portion A 1  to the inlet  12 . 
     An openable cover member  60  is provided over the first exit roller  51 . The recording paper P is transported between the cover member  60  and the first exit roller  51 . The cover member  60  can be opened and closed for the supply of the paper P, paper jam removal, etc., and protects the interior when it is closed. The distal end portion of the cover member  60  forms the outlet  72 . 
     Further disposed on the downstream side of the first exit roller  51  is an exit guide (feed guide)  70  that extends to the outside of the printer  10  beyond the cover member  60 . The guide  70  extends curved rearward and upward at the back (or on the left-hand side in  FIG. 1 ) of the first exit roller  51 . In this section, the recording paper P is transported clockwise around the center of curvature of a curved surface  71  of the exit guide  70 . 
     Specifically, the transport path A includes a second curved portion A 2 , which is curved opposite to the first curved portion A 1  that is formed in the right-hand curve of the platen roller  15 , thus constituting an S-shaped configuration. This second curved portion A 2  on the downstream side is formed near and outside the outlet  72 . The second curved portion A 2 , which is curved reversely to the first curved portion A 1 , is configured so that there is a difference between sheet feed rates inside and outside the curve, as in the first curved portion A 1 . For example, the curvature of the curved surface  71  may be set equal to that of the outer peripheral surface of the platen roller  15 . 
     As the platen roller  15 , pinch rollers  20  and  21 , and first exit roller  51  are driven at a predetermined feed rate by a motor (not shown), the recording paper P is fed along the transport path A from the inlet  12  toward the outlet  72 . 
     The following is a description of the operation of the printer  10  according to the present embodiment. 
     The recording paper P is set in the push tractor and fed obliquely downward and forward (or downward to the right in  FIG. 1 ) through the inlet  12 . The paper P that is carried into the printer  10  passes through the spaces between the platen roller  15  and the pinch rollers  20  and  21  and is transported in a curve along the outer periphery of the roller  15  and the first curved portion A 1 . 
     Then, the recording paper P is printed as it passes between the platen roller  15  and the dot head  41  at the outer periphery of the roller  15  and is fed upward and rearward (or to the left in  FIG. 1 ). Further, the paper P advances rearward (or to the left in  FIG. 1 ) between the first exit roller  51  and the cover member  60 . Finally, the paper P is guided along the curved surface  71  of the exit guide  70  between the cover member  60  and the guide  70 , transported along the second curved portion A 2  that is curved opposite to the first curved portion A 1 , and discharged through the outlet  72 . 
     Referring to  FIGS. 2 and 3 , there will be described an operation in which a plurality of sheets P 1  to P 4  (four sheets in the illustrated case) that constitute the recording paper P are fed along the transport path A of the printer  10  of the present embodiment.  FIG. 2  shows a state immediately after the first curved portion A 1  is passed, and  FIG. 3  shows a state immediately after the second curved portion A 2  is passed. After having passed the first curved portion A 1 , as shown in  FIG. 2 , sheets P 1  to P 4  are fed in a manner such that sheets P 3  and P 4  on the outer side of the curve are fed farther than sheets P 1  and P 2  on the inner side. Accordingly, the inner sheets are subject to deflections in regions ahead of the platen roller  15 . 
     Since the second curved portion A 2  is curved in the direction opposite to that in which the first curved portion A 1  is curved, as shown in  FIG. 3 , sheets P 1  and P 2  and the like that are situated inside at the first curved portion A 1  are situated outside at the second curved portion A 2 . Thus, sheets P 1  and P 2  and the like are fed farther than sheets P 3  and P 4 . After the second curved portion A 2  is passed, therefore, a deviation caused at the first curved portion A 1  is eliminated. 
     The printer  10  according to the present embodiment has the following effects. The outlet  72  is provided with the curved exit guide  70  so as to form the curved portion A 2  that is curved opposite to the first curved portion A 1  of the transport path A. Therefore, differences between the respective feed rates of the inner and outer sheets P 1  to P 4  for the case where the transport path A is curved can be adjusted with a simple configuration without adjusting the feed rates of the rollers. Since the exit guide  70  is located outside the printer  10 , moreover, the degree of freedom in the design of the internal structure of the printer  10  itself can be ensured. 
     Second Embodiment 
     A dot printer  120  according to a second embodiment of the present invention will now be described with reference to  FIGS. 4 and 5 . Since the components other than a second exit roller  52  have the same configurations as those of their counterparts in the first embodiment, like numbers are used to designate those components, and a description thereof is omitted. 
     As shown in  FIG. 4 , an outlet  72  is provided with the second exit roller  52  that faces a first exit roller  51  with a recording paper P between them. Further, an exit guide  70  is not curved, so that a curved portion A 2  is not formed. 
     The feed rate of the first exit roller  51  is made higher than that of the second exit roller  52  by adjusting the output of a motor. In this case, the rotational speed of the first exit roller  51  is set to be higher than that of the second exit roller  52 . Thus, in the present embodiment, differences between the respective feed rates of inner and outer sheets caused by a first curved portion A 1  can be canceled by varying the motor output to adjust the respective feed rates of the first and second exit rollers  51  and  52 . 
     In the dot printer  120 , as shown in  FIG. 4 , the individual sheets are deviated from one another at the first curved portion A 1 . Since the rotational speed of the first exit roller  51  is higher than that of the second exit roller  52 , however, the inner sheets are fed farther between the exit rollers than the outer sheets by the exit rollers, so that the deviation is eliminated. 
     Referring to  FIGS. 2 and 5 , there will be described an operation in which a plurality of sheets P 1  to P 4  (four sheets in the illustrated case) that constitute the recording paper P are fed along a transport path A of the printer  120  of the present embodiment. A state shown in  FIG. 2  is established immediately after the first curved portion A 1  is passed, as in the case of the first embodiment. 
     After sheets P 1  to P 4  have passed between the first and second exit rollers  51  and  52 , as shown in  FIG. 5 , the rotational speed of the first exit roller  51  is high. Thus, sheets P 1  and P 2  and the like on the inner side of the first curved portion A 1  are fed farther than sheets P 3  and P 4  on the outer side, so that a deviation caused at the first curved portion A 1  is eliminated. 
     The dot printer  120  can also produce the same effects of the first embodiment. Further, the shape of the exit guide  70  can be simplified. 
     Third Embodiment 
     A dot printer  130  according to a third embodiment of the present invention will now be described with reference to  FIGS. 4 and 6 . Since the components other than a second exit roller  53  have the same configurations as those of their counterparts in the first and second embodiments, like numbers are used to designate those components, and a description thereof is omitted. 
     As shown in  FIG. 4 , an outlet  72  is provided with the second exit roller  53  that faces a first exit roller  51  with a recording paper P between them. Further, an exit guide  70  is not curved, so that a curved portion A 2  is not formed. 
     The feed rate of the first exit roller  51  is made higher than that of the second exit roller  53 . In this case, as shown in  FIG. 6 , the outside diameter of the first exit roller  51  is set to be larger than that of the second exit roller  53 . Thus, in the present embodiment, differences between the respective feed rates of inner and outer sheets caused by a first curved portion A 1  can be canceled by differentiating the respective outside diameters of the first and second exit rollers  51  and  52  to adjust the feed rates thereof. 
     In the dot printer  130 , as shown in  FIG. 2 , the individual sheets are deviated from one another at the first curved portion A 1 . Since the outside diameter of the first exit roller  51  is larger than that of the second exit roller  53 , as shown in  FIG. 6 , the inner sheets P 1  and P 2  are fed farther between the first and second exit rollers  51  and  53  than the outer sheets P 3  and P 4 , so that a deviation caused at the first curved portion A 1  is eliminated. 
     The dot printer  130  can also produce the same effects of the dot printers  10  and  120  of the first and second embodiments. Further, the shape of the exit guide  70  can be simplified. Since the motor output need not be varied for the two exit rollers  51  and  53 , moreover, the motor drive is simple. 
     Fourth Embodiment 
     A dot printer  140  according to a fourth embodiment of the present invention will now be described with reference to  FIGS. 4 and 7 . Since the components other than a second exit roller  54  have the same configurations as those of their counterparts in the first and second embodiments, like numbers are used to designate those components, and a description thereof is omitted. 
     As shown in  FIG. 4 , an outlet  72  is provided with the second exit roller  54  that faces a first exit roller  51  with a recording paper P between them. Further, an exit guide  70  is not curved, so that a curved portion A 2  is not formed. 
     The feed rate of the first exit roller  51  is made higher than that of the second exit roller  54 . In this case, a material that constitutes the outer surface of the first exit roller  51  is formed of ethylene-propylene rubber (EPDM) or nitrile-butadiene rubber (NBR), while a material that constitutes the outer surface of the second exit roller  54  is formed of polyacetal (POM) or the like. Accordingly, the two exit rollers are different in frictional force such that the friction coefficient of the outer surface of the first exit roller  51  is higher than that of the outer surface of the second exit roller  54 . Thus, the feed rate on the first exit roller  51  side is so high that differences between the respective feed rates of inner and outer sheets caused by a first curved portion A 1  can be canceled by adjusting the respective feed rates of the first and second exit rollers  51  and  52 . 
     In the dot printer  140 , as shown in  FIG. 2 , the individual sheets are deviated from one another immediately after the first curved portion A 1  is passed. Since the frictional force and feed rate of the first exit roller  51  are greater or higher than those of the second exit roller  54 , the inner sheets P 1  and P 2  are fed farther than the outer sheets P 3  and P 4  when the recording paper P is fed between the first and second exit rollers  51  and  54 , as shown in  FIG. 7 . Thus, a deviation caused at the first curved portion A 1  is eliminated. 
     The same effects of the first to third embodiments can also be obtained from the present embodiment. Further, the shape of the exit guide  70  can be simplified. Since the two exit rollers  51  and  54  can have the same outside diameter and be subjected to the same motor driving force, moreover, the driving force can be adjusted with ease, and the design is subject to few restrictions. 
     Fifth Embodiment 
     A dot printer  150  according to a fifth embodiment of the present invention will now be described with reference to  FIGS. 4 and 8 . Since the components other than a second exit roller  55  have the same configurations as those of their counterparts in the first embodiment, like numbers are used to designate those components, and a description thereof is omitted. 
     As shown in  FIG. 4 , an outlet  72  is provided with the second exit roller  55  that faces a first exit roller  51  with a recording paper P between them. Further, an exit guide  70  is not curved, so that a curved portion A 2  is not formed. 
     Further, the dot printer  150  is provided with a sheet number detection section  75 , space adjusting means  80 , and feed rate adjusting means  90 . The sheet number detection section  75  receives or detects the number of sheets or thickness of the recording paper P as an input. The space adjusting means  80  adjusts the space between a dot head  41  and a platen roller  15  based on the result of the detection or input. The feed rate adjusting means  90  adjusts the respective feed rates of outside and inside feed rollers based on the number of sheets or thickness of the recording paper P. The feed rate adjusting means  90  serves to adjust the driving force of a motor and rotational speed. 
     If the recording paper P is formed of a plurality of sheets, for example, the rotational speed of the first exit roller  51  is adjusted to be higher than that of the second exit roller  55 , whereupon the feed rate of the first exit roller  51  is higher than that of the second exit roller  55 . 
     If the recording paper P is formed of a single sheet, on the other hand, the feed rate of the first exit roller  51  is adjusted to be equal to that of the second exit roller  55 . 
     Thus, in the dot printer  150 , differences between the respective feed rates of inner and outer sheets caused by a first curved portion A 1  can be canceled by adjusting the respective feed rates of the first and second exit rollers  51  and  52 . 
     In the dot printer  150 , as shown in  FIG. 8 , the individual sheets are deviated from one another at the first curved portion A 1 . Since the rotational speed of the first exit roller  51  is higher than that of the second exit roller  55 , however, the inner sheets P 1  and P 2  are fed farther between the exit rollers than the outer sheets P 3  and P 4 , so that a deviation is eliminated. 
     The dot printer  150  can also produce the same effects of the second embodiment. Further, the shape of the exit guide  70  can be simplified. Besides, the recording paper P can be suitably transported according to the number of sheets included therein. Furthermore, the it is easily applicable to an apparatus that has a function to adjust the space between the dot head  41  and the platen roller  15  depending on the number of sheets, since the apparatus requires only few configurations anew. 
     The present invention is not limited to the embodiments described herein. It is to be understood, in carrying out the invention, that the components of the invention may be variously modified without departing from the spirit or scope of the invention. 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the inventive as defined by the appended claims and equivalents thereof.