Abstract:
A dot-matrix printer comprises a main frame, a first movable frame, and a second movable frame, wherein the main frame supports a printer head; the first movable frame supports a platen and a first paper feeding roller, and is pivotally connected to one end of the main frame via a first pivot shaft to permit itself to be opened or closed relative to the main frame; the second movable frame supports a second paper feeding roller, and is pivotally connected to the other end of the main frame via a second pivot shaft to permit itself to be opened or closed relative to the main frame; and wherein when the first movable frame and the second movable frame are closed relative to the main frame, the printer head is opposite to the platen to form a printing position; and the first paper feeding roller is tangent to the second paper feeding roller. The dot-matrix printer according to the present invention has two movable frames. The first paper feeding roller and the second paper feeding roller are provided in these two movable frames, respectively. The above movable frames can rotate about the main frame to be opened, avoiding the inconvenience of replacing the ink ribbon and cleaning the printer head in the prior art.

Description:
[0001]    The present application claims priority of a Chinese Patent No. 200810167483.9 filed with the Chinese Patent Office on Oct. 10, 2008, entitled “Dot-Matrix Printer”, the disclosure of which is hereby incorporated by reference herein in its entirety. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to a printer, in particular to a dot-matrix printer. 
       BACKGROUND OF THE INVENTION 
       [0003]    The dot-matrix printer is the earliest form of a printer. The dot-matrix printer has advantages of simple structure and low cost. What is more important is, the dot-matrix printer is characterized by printing in an impact manner. Such a characteristic is a second-to-none choice in various printing occasions such as department stores, supermarkets, etc, in which it is needed to provide duplications. 
         [0004]    The operation principle of the dot-matrix printer is that, a printer head drives its printer pins to impact an ink ribbon to bring the ink of the ink ribbon onto a printing medium, so as to form images and characters on the printing medium. In order to facilitate replacing the printing medium, the dot-matrix printing generally uses an “easy-paper-loading” structure. However, the “easy-paper-loading” mechanism provided in the prior art has some apparent drawbacks. 
         [0005]      FIG. 1  is a paper-rolling printer disclosed by Chinese Patent Document CN03148992. In said printer, a fixed frame  12  supports a printer head, a movable frame  13  supports a paper supporting member  55 , the movable frame  13  is hinged to the fixed frame  12  via a pivot shaft, and the movable frame  13  rotates about the pivot shaft to be opened or closed relative to the fixed frame  12 . When the movable frame  13  is closed relative to the fixed frame  12 , the printer head is opposite to the paper supporting member  55  to form a printing position. Along the paper-conveying direction, a first path  15  and a second path  36  are provided at downstream of the printing position, wherein the first path  15  is used for guiding printed paper  7   a  to be outputted from a paper exit of the printer, and the second path  36  is used for guiding an ink ribbon  9  to be conveniently placed at the printing position. In addition, said printer also comprises a pair of rollers, wherein one roller  25  is mounted in the movable frame  13 , and the other roller  26  is mounted between the first path  15  and the second path  36  for outputting the printed paper from the printer. In order to facilitate bringing the ink ribbon into the printing position, a first guiding surface  27   a  and a second guiding surface  41   a  are provided at two sides of the second path  36 . The disadvantage of the above invention is that, the roller  26  is provided between the first path  15  and the second path  36 , directly above the printer head. Such a configuration, on one hand, hinders the smooth entry of the ink ribbon into a printing position, resulting in difficulties in replacing the ink ribbon, and on the other hand, hides the printer head to bring trouble to the cleaning and maintenance of the printer head. 
       SUMMARY OF THE INVENTION 
       [0006]    With respect to the above defects, the present invention aims at providing a dot-matrix printer, which facilitates the replacement of the ink ribbon and the cleaning and maintenance of the printer head. 
         [0007]    The dot-matrix printer provided by the present invention comprises a main frame, a first movable frame, and a second movable frame, wherein the main frame supports a printer head; the first movable frame is used for supporting a platen and a first paper feeding roller, and is supported by the main frame and pivotally connected to one end of the main frame via a first pivot shaft to permit itself to be opened or closed relative to the main frame; the second movable frame is used for supporting a second paper feeding roller, and is supported by the main frame and pivotally connected to the other end of the main frame via a second pivot shaft to permit itself to be opened or closed relative to the main frame, and wherein when the first movable frame and the second movable frame are closed relative to the main frame, the printer head is opposite to the platen to form a printing position; and the first paper feeding roller is tangent to the second paper feeding roller. 
         [0008]    Preferably, a paper feeding mechanism, formed by the tangential cooperation of the first paper feeding roller and the second paper feeding roller, is provided downstream of the printing position. 
         [0009]    Preferably, at least one of the first paper feeding roller and the second paper feeding roller is provided in a floating manner to act as a floating rotation roller, and is supplied with a pressure by an elastic member in the direction toward a paper exit path. 
         [0010]    Preferably, the floating rotation roller is mounted in such a way: an elongated slot perpendicular to the direction of the paper exit path is provided in a bracket for supporting the floating rotation roller, and the two shaft ends of the floating rotation roller are supported by the elongated slot and are movable in the elongated slot, and the elastic member is provided between the floating rotation roller and the bracket. 
         [0011]    Preferably, the bracket supporting the floating rotation roller is formed integrally with the movable frame where it is located, or fixed, as an independent member, on the movable frame where it is located. 
         [0012]    Preferably, the printer also comprises an automatic paper cutting device located along the paper conveying direction and downstream of the paper feeding mechanism. 
         [0013]    Preferably, it further comprises a movable blade and a fixed blade, wherein the movable blade is mounted in one of the first movable frame and the second movable frame, and the fixed blade is mounted in the other one of the first movable frame and the second movable frame. 
         [0014]    Preferably, its paper cartridge is provided at one side of the main frame corresponding to the first movable frame or at one side of the main frame corresponding to the second movable frame; and the printer head and the ink ribbon cassette support are provided at one side of the main frame corresponding to the other movable frame. 
         [0015]    Preferably, the upper portion of the first movable frame and/or the second movable frame are in such a structure that it is partially open. 
         [0016]    Preferably, the first pivot shaft and/or the second pivot shaft are in pivotal connection in a detachable manner. 
         [0017]    Compared with the prior art, the dot-matrix printer provided by the present invention may have two movable frames. The first paper feeding roller and the second paper feeding roller are provided in these two movable frames, respectively. When needing to replace the paper and the ink ribbon and to clean a printer head, the above movable frames can rotate about the main frame to be opened so as to drive both the first paper feeding roller and the second paper feeding roller to move synchronizally, such that the upper side of the printer head is completely exposed, avoiding the inconvenience of replacing the ink ribbon and cleaning the printer head in the prior art. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a structural view of a dot-matrix printer provided in the prior art; 
           [0019]      FIG. 2  is a structural view of a dot-matrix printer in an operational condition according to the first embodiment of the present invention; 
           [0020]      FIG. 3  is a sectional view of a dot-matrix printer in an operational condition according to the first embodiment of the present invention; 
           [0021]      FIG. 4  is a structural view of a dot-matrix printer in an opened condition according to the first embodiment of the present invention; 
           [0022]      FIG. 5  is a structural view of an ink cassette of a dot-matrix printer according to the first embodiment of the present invention; 
           [0023]      FIG. 6  is a structural view for mounting a second paper feeding roller of a dot-matrix printer according to the first embodiment of the present invention; and 
           [0024]      FIG. 7  is a structural view of a dot-matrix printer according to the second embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0025]      FIG. 2  is a schematic view of a dot-matrix printer according to the first embodiment of the present invention. In said figure, the printer is in an operational state. 
         [0026]    As shown in  FIG. 2 , the printer mainly comprises a main frame  01 , a first movable frame  02 , and a second movable frame  03 . For the sake of convenience, a movable frame is used hereinafter as a general name for the first movable frame  02  and the second movable frame  03 . 
         [0027]    The main frame  01  supports a printer head  07 . 
         [0028]    The first movable frame  02  is supported by the main frame  01  wherein one end thereof is pivotally connected to one end of the main frame  01  in the length direction via a first pivot shaft  05  and the other end thereof is clamped into an intermediate part of the main frame  01  in a longitudinal direction via a detachable clamping structure. With the above structure, it is made opened or closed relative to the main frame  01 . In the figure, the first movable frame  02  is in the structure in which its upper portion is opened. In fact, it is also possible that a complete upper plate completely covers the upper portion of the printer on this position. 
         [0029]    The second movable frame  03  is supported by the main frame  01  and pivotally connected with the other end of the main frame  01  by a second pivot shaft  06 , and the other end thereof is clamped into an intermediate part of the main frame  01  in a longitudinal direction via a detachable clamping structure. With the above structure, it is made opened or closed relative to the main frame  01 . In this figure, the second movable frame  03  is in the structure in which its upper position is opened. In fact, it is possible that a complete upper plate completely covers the upper portion of the printer on this position. 
         [0030]    With the above structure, the first movable frame  02  is allowed to rotate about the first pivot shaft  05  to be opened towards one end of the main frame  01 , and the second movable frame  03  is allowed to rotate about the second pivot shaft  06  to be opened towards the other end of the main frame  01 . 
         [0031]    A paper cartridge  011  of the dot-matrix printer is provided on the main frame  01  and located below the first movable frame  02 . It can be seen from  FIG. 2  that, a downwardly dent arc shape is defined at the opening position on the main frame  01  corresponding to the upper portion of the first movable frame  02 . Such a position is used for the paper cartridge  011  for mounting a printing medium. The printing medium of the dot-matrix printer is generally tube-shaped printing paper. Due to the open upper portion, it is convenient to place a tube-shaped medium with a larger diameter. 
         [0032]    An ink cassette  08  of the dot-matrix printer is provided on the main frame  01  and located below the second movable frame  03 . It can be seen from  FIG. 2  that, the ink cassette  08  and the printer head  07  are mounted at the opening position on the main frame  01  corresponding to the upper portion of the second movable frame  03 , wherein the ink cassette  08  is provided near the position where the main frame  01  is pivotally connected to the second frame  03 , and the printer head  07  is provided at the position close to the first movable frame  02 . Particularly, the ink cassette  08  is provided at said position via the ink ribbon support  04 , and the ink cassette  08  can be conveniently detached from the ink ribbon support  04 , such that the replacement of the ink cassette  08  is very convenient. 
         [0033]    In the above the basic arrangement of the primary components of the dot-matrix printer is introduced. A paper feeding path of the dot-matrix printer is described hereinafter in combination with  FIG. 3 .  FIG. 3  is a sectional view of the dot-matrix printer as shown in  FIG. 2 . 
         [0034]    As shown in  FIG. 3 , an upper path plate  013  is provided at one end of the first movable frame  02  corresponding to the first pivot shaft  05 , and the upper path plate  013  is an irregular arc-shaped plate which is opening towards the first pivot shaft  05 . The upper path plate  013  comprises two parts, a paper pressing plate  013   a  and a platen  013   b.  The paper pressing plate  013   a  is a segment which, in operational position, is located at the lower portion and, against the main frame  01  and is close up to the bottom surface of the paper cartridge  011 . In operation, the external surface thereof facing outside and the upper surface of the bottom plate of the paper cartridge  011  form a prearranged gap therebetween, constituting a paper entry path. The platen  013   b  is a segment which, in an operational position, abuts against the printer head  07 . In operation, said position faces exactly a printing surface  07   a  of the printer head  07  to form the printing position. A first paper feeding roller  010  is mounted at the top of the platen  013   b  in said first frame  02 , correspondingly to which, a second paper feeding roller  09  is mounted in the second movable frame  03 . In the operational state, the above first paper feeding roller  010  is just in tangential cooperation with the second paper feeding roller  09 , to form a paper feeding mechanism. The printing surface  07   a  and the platen form a printing path therebetween. The first paper feeding roller  010  and the second paper feeding roller  09  form a paper exit path therebetween. The paper entry path, the printing path, and the paper exit path together form a paper feeding path of printing paper P. The printing paper P is outputted by the paper cartridge  011 , then passes sequentially through the paper entry path and the printing path, and finally is outputted from the paper exit path. 
         [0035]      FIG. 4  is a schematic view of the dot-matrix printer after the first movable frame  02  and the second movable frame  03  are opened. It can be seen from the figure that, both the first movable frame  02  and the second movable frame  03  can be completely opened to expose completely the top of the printer head  07 , such that it is convenient to replace the ink cassette  08  and to clean the printer head  07 . 
         [0036]    For easily understanding the above advantages of this embodiment, the structure and the mounting method of the ink cassette  08  are further described hereinafter. Referring to  FIG. 5 , said figure is a schematic view of the ink cassette  08 . As shown in  FIG. 5 , the ink cassette  08  comprises a case  081  and an ink ribbon  082 . The ink ribbon  082  is drawn out from one end of the case and enters the other end of the case. The surface of the ink ribbon  082  is covered by ink. When printing, the case  081  is supported by the ink ribbon support  04 . The ink ribbon  082  covers the surface of the printing end surface  07   a  of the printer head  07 . The printing pin (not shown in the figure) of the printer head  07  perpendicular to the ink ribbon  082  impacts the ink ribbon  82  to bring the ink thereof onto the printing paper P to form images and characters. The surface of the printing paper P facing away the printer head  07  is padded under the platen  013   b  of the upper path plate  013  of the first movable frame  02 . 
         [0037]    As mentioned in the above, said ink cassette  08  is mounted in a detachable manner on the main frame  01  via the ink ribbon support  04 . The ink cassette  08  needs to be replaced frequently in use. The process of mounting the ink cassette  08  in this embodiment is as follows: the second movable frame  03  is opened to completely expose the ink ribbon support  04 ; since the second paper feeding roller  09  rotates with the second movable frame  03  and there is no obstacle above the printer head  07 , the ink ribbon  082  enters the printing position under the guidance of the guiding surface  07   b  of the printer head  07 ; and then the second movable frame  03  is closed to accomplish the mounting of the ink cassette  08 . The guiding surface  07   b  of the printer head  07  is shown in  FIG. 3 . 
         [0038]    The process of mounting the printing paper P is as follows: the first movable frame  02  is opened to completely expose the paper cartridge  011 ; the printing paper P is put into the paper cartridge  011 ; next, the front end of the printing paper is drawn out and then the first movable frame  02  and the second movable frame  03  are closed; at this time, the printing paper P is held on the paper entry path and the printing position, and the front end thereof is clamped tightly by the first paper feeding roller  010  and the second paper feeding roller  09 . In this way, the rotation of the first paper feeding roller  010  and the second paper feeding roller  09  can drive the printing paper P to move in a paper conveying direction indicated by an arrow a as shown in  FIG. 3 . 
         [0039]      FIG. 6  is a structural schematic view for mounting the second paper feeding roller  09  of the present invention. As shown in the Figure, the second paper feeding roller  09  is fixed on the second movable frame  03  via a bracket  015 . The bracket  015  comprises a fixing surface  015 - 1  attached against the second movable frame  03  and is fixed to the second movable frame  03  through a through hole  015   b  of the fixing surface  015 - 1 . The left and right ends of said bracket  015  have protruding branch arms  015 - 2 . An elongate slot  015   a  is provided on the branch arms  015 - 2 . The second paper feeding roller  09  comprises a roller body  09   a  and a core shaft  09   b.  The shaft end of the core shaft  09   b  is inserted into the elongated slot  015   a  and is supported by the elongated slot  015   a,  and is movable in the elongated slot  015   a.  The roller body  09   a  comprises two segments of cylindrical bodies sleeved onto the surface of the core shaft  09   b  and having relatively great frictional force. An elastic member  014  is provided in the bracket  015 . Said elastic member  014  provides to the second paper feeding roller  09  an elastic force toward the front end. In this way, in an operational state, a certain pressing force is present between the first paper feeding roller  010  and the second paper feeding roller  09 , such that the two can clamp the paper tightly therebetween to ensure the synchronous movement of the printing paper with the first paper feeding roller  010  and the second paper feeding roller  09 . 
         [0040]    The mounting manner of the second paper feeding roller  09  can be also applied to the first paper feeding roller  010 , as long as one of the two uses the above movable mounting manner and the elastic member is used for providing to the one a pressing force toward the paper exit path. Of course, it is possible that the two use simultaneously the above mounting manner. 
         [0041]    When printing, the printing paper P moves in a paper conveying direction indicated by the arrow a. The printing paper P passes through the paper entry path and enters the printing position. The printer pin of the printer head  07  impacts the ink ribbon  082  to bring the ink thereof onto the printing paper P to form images and characters. The printed printing paper P is outputted from the printer under the driving of the first paper feeding roller  10  and the second paper feeding roller  9 . 
         [0042]    What needs to be explained is that, the bracket  015  can be an independent member which is mounted on the second movable frame  03 , as shown in the embodiment of  FIG. 6 . In addition, the bracket  015  can be formed integrally with the second movable frame  03 , viz. the branch arms  015 - 2  supporting the second paper feeding roller  09  are directly provided on the second movable frame  03 . 
         [0043]      FIG. 7  is a schematic diagram of the printer according to the second embodiment of the present invention. The difference between the present embodiment and the first embodiment of the present invention is that the printer further comprises an automatic paper cutting device  016 . Along the paper conveying direction, the automatic paper cutting device  016  is located downstream of the paper conveying mechanism. The automatic paper cutting device  016  comprises a movable blade  016   a  and a fixed blade  016   b.  As shown in this figure, the movable blade  16   a  is provided above the first paper feeding roller  010  of the first movable frame  02  and the fixed blade  016   b  is provided above the second paper feeding roller  09  of the second movable frame  03 . When the printer is in an operational state, the movable blade  016   a  and the fixed blade  016   b  cooperate with each other. When the first movable frame  2  and the second movable frame  3  are opened relative to the main frame  01 , the movable blade  016   a  rotates with the first movable frame  02 . The fixed blade  016   b  can rotate with the second movable frame  03 . Said printer may cut automatically the printed paper. 
         [0044]    In the above second embodiment, the mounting positions of the movable blade  016   a  and the fixed blade  016   b  can be exchanged, viz. the movable blade  16   a  is provided above the second paper feeding roller  09  of the second movable frame  03 , and the fixed blade  016   b  is provided above the first paper feeding roller  010  of the first movable frame  02 . 
         [0045]    Further improvement can be made on the above two embodiments. For example, the first pivot shaft  05  and the second pivot shaft  06  is in the form of a detachable pivot shaft to allow the first movable frame  02  and the second movable frame  03  to be completely detached from the main frame  01 . With such a structure, the printer can have more flexibility. 
         [0046]    The description above is given merely for preferable embodiments of the present invention. It shall be pointed out that, for the person skilled in the art, any improvements and modifications can be made without departing from the principles of the present invention. The improvements and modifications can be deemed as being covered by the scope of protection of the present invention.