Abstract:
A print head assembly and a printer using the same are disclosed. The print head assembly includes: a bracket, a print head and an elastic element. The bracket includes a first bracket body having a cavity and a lid covered on the opening of the cavity. A window is opened on the first bracket body. The print head is accommodated in the cavity of the first bracket body and hinged to the first bracket body via a first rotary shaft. The surface of a heating element of the print head is matched with the window and faces an outside paper pressing roller. The elastic element biases towards the print head so as to make the surface of the heating element of the print head have a tendency to extend outside the window. The print head assembly is capable of being detached as a whole, thus the requirements of performing single-sided printing and duplex printing in the same printer is achieved.

Description:
This application claims priority of the Chinese invention patent application No. 201010551490.6, entitled “Print head assembly and printer using the same”, filed with State Intellectual Property Office of China on Nov. 19, 2010, and all contents thereof are incorporated by reference. 
     TECHNICAL FIELD OF THE INVENTION 
     The disclosure relates to the field of printer, and in particular to a print head assembly and a printer using the same. 
     BACKGROUND OF THE INVENTION 
     The application of duplex printer which prints simultaneously on front and back sides of printing paper is becoming increasingly wider. A U.S. Pat. No. 6,784,906 discloses a duplex thermal printer, as shown in  FIG. 1 , which includes a first print head  150  and a first platen  170  which are supported on a first arm  130 , and a second platen  180  opposite to the first print head  150  and a second print head  160  opposite to the first platen  170  which are supported on a second arm  140 . Thermal paper  10  with thermal coating on both sides passes between the first print head  150  and the second platen  180 , and between the second print head  160  and the first platen  170  along a paper conveying direction; the first print head  150  faces the front side  3  of the thermal paper  10  while the second print head  160  faces the back side  4  of the thermal paper  10 ; when both the first print head  150  and the second print head  160  generate heat under control respectively, preset images or characters are printed out on the front and back sides of the thermal paper  10 . 
     Since the print head is an expensive component for constructing a printer, a duplex thermal printer is more expensive than a single-sided thermal printer. Therefore, on one hand, when the user, who needs single-sided printing only at present but probably needs duplex printing in the future, purchases a duplex thermal printer at the earlier stage, the initial cost of purchasing apparatus is increased and the utilization of the apparatus is not high at the earlier stage; on the other hand, when the user, who has purchased a single-sided thermal printer at the beginning, purchases a duplex thermal printer again when needing duplex printing, it not only needs to spend money on purchasing apparatus again, but also causes the wasting of apparatus because the single-sided printer already purchased is left unused. 
     SUMMARY OF THE INVENTION 
     The purpose of the disclosure is to provide a print head assembly and a printer using the same, which can easily convert a single-sided printer into a duplex printer, so as to avoid the wasting of purchasing cost and apparatus. 
     Therefore, the disclosure provides a print head assembly, which includes: a bracket, which is detachably connected with an outside frame, comprises a first bracket body having a cavity and a lid covered on the opening of the cavity of the first bracket body, wherein on the first bracket body a window is opened; a print head, which is accommodated in the cavity of the first bracket body and hinged to the first bracket body via a first rotary shaft, wherein the surface of a heating element of the print head is matched with the window and faces an outside paper pressing roller; and an elastic element, which biases towards the print head so as to make the surface of the heating element of the print head have a tendency to extend outside the window. 
     Further, the print head assembly according to the disclosure further includes a transition socket arranged on the bracket and pluggably matched with an outside plug, wherein the print head is electrically connected to corresponding pins of the transition socket. 
     Further, the print head assembly according to the disclosure further includes a sensor arranged on the first bracket body for detecting printing paper, wherein the sensor is electrically connected to corresponding pins of the transition socket. 
     Further, the lid includes a second bracket body and a third bracket body; the transition socket is arranged on a convert board, and the convert board is fixedly connected to the second bracket body; one end of the elastic element presses against the third bracket body, while the other end presses against the print head. 
     Further, the print head assembly according to the disclosure further includes a print head lifting mechanism, wherein the print head lifting mechanism includes a driving element arranged inside the bracket and an adjusting element driven by the driving element; the print head is fixedly connected with a press rod and the press rod pressing against the adjusting element. 
     Furthermore, the adjusting element is a cam, and the driving element is a motor. 
     Further, two ends of the first rotary shaft extend outside the first bracket body to form a locating portion for matching with the outside frame. 
     According to another aspect of the disclosure, a printer is provided, the printer includes: a fixed frame, which has a paper holder for accommodating printing paper; a moveable frame, which is hinged with the fixed frame and could be opened or closed relative to the fixed frame; and a first side printing mechanism and a second side printing mechanism, which are arranged along a paper passage to respectively print on the front side and back side of paper, wherein the first side printing mechanism includes a first paper pressing roller arranged on the fixed frame and a first print head assembly arranged on the moveable frame; and the second side printing mechanism includes a second print head assembly arranged on the fixed frame and a second paper pressing roller arranged on the moveable frame; wherein at least one of the first print head assembly and the second print head assembly is the print head assembly described above, which is capable of being detached as a whole. 
     Further, the first print head assembly is capable of being detached as a whole. 
     Further, the second paper pressing roller on the moveable frame is located at the outside of the first print head assembly. 
     Further, the second print head assembly includes a print head pivotally connected with the fixed frame through a second rotary shaft and an elastic element biasing the print head towards the second paper pressing roller. 
     Further, two sides of the first bracket body are provided with a locating protrusion; a locating groove clamped with the locating protrusion is arranged on the moveable frame; and a locating groove clamped with the locating protrusion is also arranged on the fixed frame. 
     Further, the locating protrusions are formed by shaft ends of the first rotary shaft extending outside two sides of the first bracket body. 
     The disclosure also provides a printer, which includes the print head assembly described above, wherein the print head assembly is arranged on a frame. 
     In this disclosure, a print head assembly capable of being detached as a whole is provided, thus the printer can be configured flexibly according to the requirements of users so as to avoid the wasting of purchasing cost and apparatus. For example, mounting a print head assembly capable of being detached as a whole in a single-sided printer can convert the single-sided printer into a duplex printer conveniently, or demounting a set of print head assembly from a duplex printer can convert the duplex printer into a single-sided printer conveniently. Thus, the requirement of performing single-sided printing and duplex printing in the same printer is achieved. Moreover, by arranging a transition socket on the print head assembly, the print head assembly can be connected to or detached from the printer conveniently, thus, the replacement and maintenance of the print head assembly become convenient. 
     Besides the purpose, characteristics and advantages described above, other purposes, characteristics and advantages of the disclosure will be described in further detail in conjunction with the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Attached drawings constituting one part of the specification and used for further illustrating the disclosure are provided below to show the preferred embodiments of the disclosure and to describe the principle of the disclosure in conjunction with the specification. In the drawings: 
         FIG. 1  shows a diagram of a conventional duplex thermal printer; 
         FIG. 2  shows an axonometric view of a first embodiment of a printer according to the disclosure, in which a moveable frame of the printer is opened relative to a fixed frame; 
         FIG. 3  shows a longitudinal sectional view of the first embodiment of the printer according to the disclosure, in which the moveable frame of the printer is closed relative to the fixed frame; 
         FIG. 4  shows an axonometric view of a first print head assembly according to the first embodiment of the disclosure; 
         FIG. 5  shows a horizontal sectional view of the first print head assembly according to the first embodiment of the disclosure; 
         FIG. 6  shows a horizontal sectional view of the first print head assembly according to a second embodiment of the disclosure; 
         FIG. 7  shows a horizontal sectional view of the first print head assembly according to a third embodiment of the disclosure; 
         FIG. 8  shows an explosive view of the first print head assembly according to the third embodiment of the disclosure; and 
         FIG. 9  shows a diagram illustrating the assembly relationship between the first print head assembly and the moveable frame according to the disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The embodiment of the disclosure is described below in further detail in conjunction with the drawings; however, the disclosure can be implemented by a plurality of different ways limited and covered by claims. 
       FIG. 2  shows an axonometric view of a first embodiment of a printer according to the disclosure; and  FIG. 3  shows a longitudinal sectional view of the first embodiment of the printer according to the disclosure. As shown in  FIG. 2  and  FIG. 3 , the printer includes a moveable frame  1 , a fixed frame  2 , a first printing mechanism  3 , a second printing mechanism  4  and a control device  5 . 
     The first printing mechanism  3  is configured to print on one side of printing paper, while the second printing mechanism  4  is configured to print on the other side of the printing paper; the control device  5  is connected with the fixed frame  2  to control the operation of the first printing mechanism  3  and the second printing mechanism  4 . 
     The control device  5  includes a central processing unit  51  and a communication interface  52 , wherein the communication interface  52  is connected with an outside control device (such as computer) to receive printing data or instruction; the central processing unit  51  controls the operation of the first printing mechanism  3  and the second printing mechanism  4  according to the received data or instruction. 
     The moveable frame  1  is hinged with the fixed frame  2  and could be opened or closed relative to the fixed frame  2 . When the moveable frame  1  is opened relative to the fixed frame  2 , a top of a paper holder  21  formed in the fixed frame  2  is opened, rolled paper P used for printing can be replaced, wherein the rolled paper P could be duplex thermal paper of which both front side and back side are provided with thermal coating, or could be single-side thermal paper of which only one side is provided with thermal coating. 
     The first printing mechanism  3  includes a first print head assembly  31  and a first paper pressing roller  32 , wherein the first print head assembly  31  is arranged on the moveable frame  1  and the first paper pressing roller  32  is arranged on the fixed frame  2 ; the second printing mechanism  4  includes a second print head assembly  41  and a second paper pressing roller  42 , wherein the second print head assembly  41  is arranged on the fixed frame  2  and the second paper pressing roller  42  is arranged on the moveable frame  1 . 
     When the moveable frame  1  is closed relative to the fixed frame  2 , the first print head assembly  31  and the first paper pressing roller  32  cooperate correspondingly, and the second print head assembly  41  and the second paper pressing roller  42  cooperate correspondingly. 
     At least one of the first print head assembly  31  and the second print head assembly  41  is the one capable of being detached as a whole, and can be detachably connected with the frame on which it is provided. In this embodiment, the first print head assembly is the print head assembly capable of being detached as a whole. 
     The second print head assembly  41  includes a second print head  411 , a second rotary shaft  412  and a second elastic element  413 . The second print head  411  is hinged with the fixed frame  2  through the second rotary shaft  412 , and could rotate around the second rotary shaft  412 . The second elastic element  413  is arranged between the second print head  411  and the fixed frame  2  so as to push one side of the second print head  411  provided with a heating element towards the second paper pressing roller  42  by means of some preload force. The second print head  411  is electrically connected with the control device  5  directly through a connection cable (not shown in figures). 
       FIG. 4  shows an axonometric view of a first print head assembly according to the first embodiment of the disclosure; and  FIG. 5  shows a horizontal sectional view of the first print head assembly according to the first embodiment of the disclosure. Hereinafter, the specific implementation of the first print head assembly is described in conjunction with  FIG. 4  and  FIG. 5 . As shown in  FIG. 4  and  FIG. 5 , the first print head assembly  31  includes a bracket  11 , a print head module  12  and a convert component  13 , wherein the print head module  12  and the convert component  13  are arranged inside the bracket  11 . 
     The bracket  11  includes a first bracket body  111 , a second bracket body  112  and a third bracket body  113 , wherein the first bracket body  111  has a cavity, the opening of the cavity of the first bracket body is covered by the second bracket body  112  and the third bracket body  113  which are fixedly connected with the first bracket body  111  respectively, an internal space is formed by all three. The first bracket body  111  is provided with a mounting portion, wherein the mounting portion could be a mounting hole or a hook for connecting with the frame to which the first bracket body is attached. In this embodiment, the mounting portion could be of four mounting holes  141  arranged on four corners of the bracket  11 . Preferably, the first print head assembly  31  further includes a locating portion  16  which is matched with a corresponding position on the frame to which the first print head assembly  31  is attached, so as to accurately limit the fixing position on the frame to which the bracket  11  is attached. Specifically, locating portions  16  are arranged on two sides of the first bracket body  111  vertically, and could be a shaft or a rod. 
     The print head module  12  includes a first print head  121 , a first elastic element  122  and a first rotary shaft  123 . The first print head  121  is hinged with the first bracket body  111  through the first rotary shaft  123 , and could rotate around the first rotary shaft  123 . One end of the first print head  121  provided with a socket  121   a  is extended into the first bracket body  111 , and one end of the first print head  121  provided with a heating element  121   b  is matched with a window  111   a  arranged on the surface of the first bracket body  111  (refer to  FIG. 8 ), so that the surface of the heating element  121   b  of the first print head  121  is exposed outside the closed space which is formed by the first bracket body  111 , the second bracket body  112  and the third bracket body  113  and could be tangent with the first paper pressing roller. One end of the first elastic element  122  is located between the first print head  121  and the third bracket body  113  above the first print head  121  so as to push one side of the first printing head  121  provided with a heating element to the first paper pressing roller by means of some preload force. 
     Preferably, the first rotary shaft  123  and the locating portion  16  are of the same element; specifically, two ends of the first rotary shaft  123  vertically extend outside two sides of the first bracket body  111  respectively to match with a corresponding position on the frame of the printer, so as to accurately limit the fixing position of the bracket  11  on the frame of the printer. This setting mode enables the first rotary shaft to have a dual function of supporting the print head and locating the print head assembly, and reduce the number of elements. 
     The convert component  13  includes a convert board  131 , a print head connecting socket  132 , a transition socket  133  and a print head cable  134 . The convert board  131  is fixedly connected with the second bracket body  112 ; the print head connecting socket  132  and the transition socket  133  are welded with the convert board  131 ; and the transition socket  133  is provided with pins which are connected with each pin of the print head connecting socket  132  correspondingly. The transition socket  133  is matched with an opening  112   a  (shown in  FIG. 4 ) provided on the surface of the second bracket body  112 , and exposes outside the closed space formed by the first bracket body  111 , the second bracket body  112  and the third bracket body  113  so as to be interconnected with outside. One end of the print head cable  134  is connected with the print head socket  121   a , while the other end thereof is connected with the print head connecting socket  132 . It should be noted that the print head connecting socket  132  and the transition socket  133  might be a pin or a jack. 
     It should be noted that, in other embodiments of the disclosure, the convert board  131 , the print head connecting socket  132  and the transition socket  133  might not be provided, and the print head cable  134  could be connected with outside through the opening on the surface of the second bracket body  112 . 
       FIG. 6  shows a horizontal sectional view of the first print head assembly according to a second embodiment of the disclosure. The difference between this embodiment and the first embodiment lies in that: the first print head assembly further includes a sensor  17  which is configured to detect the existence state of printing paper or the mark on the surface of the printing paper. Correspondingly, the convert component  13  further includes a sensor socket  135  and a sensor cable  17   a , wherein the sensor socket  135  is welded with the convert board  131 , and the transition socket  133  is provided with pins which are connected with each pin of the sensor socket  135  correspondingly. The sensor cable  17   a  of the sensor  17  is connected with the sensor socket  135 . 
     It should be noted that, in the condition of not providing a convert board in other embodiments of the disclosure, the sensor cable  17   a  could be connected with outside through the opening on the surface of the second bracket body  112 . 
       FIG. 7  shows a horizontal sectional view of the first print head assembly according to a third embodiment of the disclosure; and  FIG. 8  shows an explosive view of the first print head assembly according to the third embodiment of the disclosure. The difference between this embodiment and the second embodiment lies in that: the first print head assembly  31  further includes a print head lifting mechanism  15  which is configured to lift or release the first print head, so that the first print head could be separated from or matched with the first paper pressing roller  32  opposite to the first print head. 
     The print head lifting mechanism  15  includes a driving element  151  and an adjusting element  152 , wherein the driving element  151  is fixedly connected with the bracket  11 ; specifically, the driving element  151  could be fixedly connected with one of the first bracket body  111 , the second bracket body  112  and the third bracket body  113 ; in this embodiment, the driving element  151  is fixedly connected with the second bracket body  112 . 
     The adjusting element  152  is fixedly connected with a driving shaft of the driving element  151  and is connected with a brace  121   c  of the print head  121 . When the driving element  151  drives the adjusting element  152  to rotate to a first position (as shown in  FIG. 7 ), the first print head  121  is located at a working position, where the first print head  121  is pressed against the first paper pressing roller  32 , under the elastic force of the first elastic element  122 ; when the driving element  151  drives the adjusting element  152  to rotate to a second position, the first print head  121  is located at a non-working position, where the first print head  121  is separated from the first paper pressing roller  32 , by overcoming the elastic force of the first elastic element  122 . 
     When the first print head  121  does not need to work, the driving element  151  of the print head lifting mechanism is controlled to drive the print head to rotate in the direction away from the first paper pressing roller  32 , so that the print head is located at a non-working position; thus, there is no force exerted between the print head and the thermal paper so that the abrasion of the print head caused by the paper is reduced and the load for conveying paper is reduced. 
     It should be noted that the driving element  151  could be an electrical component, such as motor, or could be a manual spanner. The adjusting element  151  could be a cam, an eccentric wheel or a press rod; in this embodiment, the driving element  151  is a motor and the adjusting element  152  is a cam. Correspondingly, the convert component  13  further includes a motor socket  137 , wherein the motor socket  137  is welded with the convert board  131 ; and the transition socket  133  is further provided with pins which are connected with each pin of the motor socket  137  correspondingly. The connection cable of the motor is connected with the motor socket  137 . 
     It should be noted that the purpose of providing the convert component  13  is to intensively output pins of the connection cable of the electrical components in the first print head assembly, such as print head, sensor, motor and so on, through the transition socket  133  of the convert component  13 , so that the control device  5  of the printer could be connected conveniently. 
     It should be noted that, in other embodiments, the second bracket body and the third bracket body can be substituted by an integrated lid. 
       FIG. 9  shows a diagram illustrating the assembly relationship between the first print head assembly and the moveable frame according to the disclosure. Hereinafter, the connection relationship between the first print head assembly and the moveable frame will be described in conjunction with  FIG. 1  and  FIG. 9 . As shown in  FIG. 1  and  FIG. 9 , a connection portion  1   c  (shown in  FIG. 9 ) matched with the mounting portion of the first print head assembly  31  is arranged on the moveable frame  1 , wherein the connection portion could be a mounting hole or a clamp groove. The first print head assembly  31  is detachably connected with the connection portion of the moveable frame  21  through the mounting portion. 
     The moveable frame  1  is further provided with a first locating groove  1   a  corresponding to the locating portion  16  of the first print head assembly  31 ; when the first print head assembly  31  is mounted on the moveable frame  1 , the locating portion  16  is clamped with the first locating groove  1   a , so that the fixing position of the first print head assembly  31  on the moveable frame  1  is accurate. Correspondingly, the fixed frame  2  is also provided with a second locating groove  22  corresponding to the locating portion  16  of the first print head assembly  31 ; when the moveable frame  1  is closed relative to the fixed frame  2 , the locating portion  16  is clamped with the second locating groove  22 , so that the fitting position between the print head and the first paper pressing roller can be accurate in the first printing mechanism  3 . 
     The moveable frame  1  is provided with an extension plug  1   b  matched with the transition socket  133  of the first print head assembly  31 ; after the first print head assembly  31  is fixedly connected with the moveable frame  1 , the transition socket  133  is plugged with the extension plug  1   b . The extension plug  1   b  is connected with the control device  5  through a connection cable (not shown in figures); therefore, electrical components in the first printing mechanism  31 , such as first print head, sensor or motor etc, are electrically connected with the control device  5  through the extension plug  1   b ; wherein the control device  5  can control the operation of each device of the first print head assembly  31  according to requirements. Therefore, by providing an extension plug  1   b  connected with the transition socket  133  of the first print head assembly  31  in the printer, convenience of the connection between the electrical component in the first print head assembly and the control device  5  of the printer is enhanced. 
     In the printer according to the disclosure, by providing a connection portion and an extension plug which are matched with a detachable print head assembly (that is, the first print head assembly in the above embodiments), a single-sided printer can be converted into a duplex printer conveniently. When the user who needs single-sided printing only at present but probably needs duplex printing in the future purchases a printer, it would be unnecessary to purchase the print head assembly, that is, unnecessary to install the print head assembly; therefore, the initial cost of purchasing apparatus is not increased. When duplex printing is needed, only a detachable print head assembly is purchased and is connected with the extension plug of the printer without reinstalling the connection cable and changing the control device, thus the single-sided printer could be converted into a duplex printer. When the printing requirement of a user is changed, the printer provided by the disclosure will not increase the initial cost of purchasing apparatus and waste the apparatus purchased. 
     It should be noted that, in other embodiments of the disclosure, the second print head assembly also could be a print head assembly detachably connected with the fixed frame  2 . When the second print head assembly is a print head assembly capable of being detached as a whole, the specific implementation thereof is the same as that of the first print head assembly  1 , not tired in words here. When both the first print head assembly and the second print head assembly are a print head assembly capable of being detached as a whole, besides that the printer could be conveniently converted from a duplex printer into a single-side printer, or from a single-sided printer into a duplex printer, a user could separate the print head assembly from the frame (that is, the moveable frame and the fixed frame) of the printer easily according to requirements so as to facilitate the replacement and maintenance of the print head assembly. 
     The above are only the preferred embodiments of the disclosure and not intended to limit the disclosure. For those skilled in the art, various modifications and changes can be made to the disclosure. Any modification, equivalent substitute and improvement made within the spirit and principle of the disclosure are deemed to be included within the scope of protection of the disclosure.