Patent Publication Number: US-9849664-B2

Title: Thermal stencil making unit

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to a thermal stencil making unit that makes a stencil of a perforated image on a thermal gauze by a thermal print head while relatively moving the thermal gauze tightly stretched in a gauze frame and the thermal print head, and that includes a head protecting member for protecting the thermal print head when the gauze frame is set. 
     2. Related Art 
     Generally, because of having a simple structure and allowing a simple stencil making operation, there is widely used a thermal stencil making unit that makes a screen stencil by heating and perforating image information in a heat-sensitive film of a thermal gauze through the use of a plurality of heat elements provided in the thermal print head by relatively moving: the thermal gauze in which the thermal film is stuck with an adhesive agent onto the gauze tightly stretched in the gauze frame and having a plurality of meshes by weaving warps and woofs; and the thermal print head having, on its surface, a plurality of the heat elements for heating and perforating this thermal gauze. 
     In addition, an image is screen-printed on a sheet or a T-shirt by dropping ink onto the screen plate on which a stencil is made by the thermal stencil making unit. 
     As an example of this type of the thermal stencil making unit, there is known a thermal stencil making unit using a thermal print head in which a surface portion of the thermal print head can be protected by a head protective plate when the gauze frame is replaced (for example, refer to Patent Document 1). 
     In the thermal stencil making unit using the thermal print head disclosed in Patent Document 1, the gauze frame in which the thermal gauze is tightly stretched is detachably fixed to a stencil making unit body, although not shown here. 
     Furthermore, a platen roller is provided below the thermal gauze in the stencil making unit body. On the other hand, above the stencil making unit body, a thermal print head portion in which the thermal print head is mounted on a thermal print head supporting member is openably and closably mounted above the thermal gauze. 
     At this time, the platen roller and the thermal print head portion are movably provided by being guided by a pair of guide rails. 
     In addition, when a stencil is made, the platen roller and the thermal print head are moved while the thermal gauze is sandwiched between the platen roller and the thermal print head in a pressure-contact manner, and thereby a stencil of the perforated image is made on the thermal gauze. 
     Furthermore, a pair of plate supporting members that support the head protective plate for protecting the surface portion of the thermal print head are rotatably mounted on the thermal print head supporting member of the thermal print head portion. 
     The pair of these plate supporting members also have a function as an operation lever of the head protective plate and is constituted so as to selectively open/close the surface portion of the thermal print head by rotating the head protective plate via the pair of plate supporting members. 
     With the configuration described above, when the thermal print head is to be used with the thermal print head portion being closed, the head protective plate is rotated in an opening direction and is separated from the surface portion of the thermal print head. On the other hand, it is described that when the thermal print head portion is opened for replacement of the gauze frame, the head protective plate is rotated in a closing direction to thereby protect the surface portion of the thermal print head, whereby damage on the thermal print head can be prevented. 
     PRIOR ART DOCUMENT 
     Patent Document 
     Patent Document 1: Japanese Patent Application Laid-Open Publication No. 10-138534 
     SUMMARY 
     Problems to be Solved by the Invention 
     Incidentally, in the thermal stencil making unit using the thermal print head described in Patent Document 1, since the head protective plate is rotated in the closing direction via the pair of thermal print head supporting members manually by the operator after the thermal print head portion is opened in replacement of the gauze frame as described above, the surface portion of the thermal print head can be protected by the head protective plate. 
     However, since the gauze frame is detachably fixed to the stencil making unit body, while the thermal print head is openably and closably mounted on the openable and closable thermal print head portion, the thermal print head is not disposed on a side where the gauze frame is set. 
     Accordingly, if an operator forgets an opening/closing operation of the head protective plate due to a human error, the surface portion of the thermal print head is damaged when the gauze frame is replaced in a state where the head protective plate remains opened. On the other hand, if the thermal print head portion is closed in a state where the head protective plate remains closed, there is generated a problem such as damages or the like of the thermal gauze or the platen roller. 
     The present invention has been made in view of the above problem, and an object of the present invention is to provide a thermal stencil making unit which can safely protect the thermal print head without causing a human error by disposing the thermal print head on a side where the gauze frame is set when protecting the thermal print head by the head-protecting member in setting of the gauze frame. 
     Means to Solve the Invention 
     A first invention is a thermal stencil making unit that makes a stencil of a perforated image on a thermal gauze by selectively heating and driving a plurality of heat elements in accordance with image information while moving a thermal print head having the plurality of heat elements relative to the thermal gauze tightly stretched in a gauze frame detachably set in a unit housing, the thermal stencil making unit including 
     a head-protecting member that moves between a protection position where the thermal print head is protected and a protection release position where a protective state is released, while being urged to a side of the protection position via urging means, 
     wherein the thermal stencil making unit: 
     moves the head-protecting member to the protection position by the urging means, when the gauze frame is not set in the unit housing; and 
     moves the head-protecting member against the urging means from the protection position to the protection release position, in conjunction with an operation of setting the gauze frame in the unit housing. 
     In addition, a second invention is a thermal stencil making unit, wherein, in the thermal stencil making unit in the first invention described above: 
     the head-protecting member is a head-protecting cover that protects the plurality of heat elements at the protection position; 
     the head-protecting cover is integrally provided with a pressing member; and 
     when the thermal print head and the head-protecting cover are provided in the unit housing and the gauze frame is set in the unit housing, the pressing member presses the head-protecting cover from the protection position toward the protection release position by one end portion of the gauze frame in a setting direction. 
     Furthermore, a third invention is a thermal stencil making unit, wherein, in the thermal stencil making unit in the second invention described above: 
     when a platen portion that supports a platen roller capable of being pressed on a side of the thermal print head via the thermal gauze is provided in the unit housing, capable of being opened and closed, the pressing member is provided at least on one end portion side of both end portion sides in a direction orthogonal to the setting direction of the gauze frame on the head-protecting cover. 
     Moreover, a fourth invention is a thermal stencil making unit, wherein, in the thermal stencil making unit in the second or third invention described above: 
     the head-protecting cover is provided with a head cleaning material on a surface facing the plurality of heat elements. 
     In addition, a fifth invention is a thermal stencil making unit, wherein, in the thermal stencil making unit in the first invention described above: 
     the head-protecting member is a head periphery-protecting cover that has an opening portion through which the plurality of heat elements advances and retreats and that protects the thermal print head at the protection position in a periphery of the plurality of heat elements on an advance direction side of the gauze frame; and wherein 
     when the gauze frame is set in the unit housing, the gauze frame is pressed, while resisting an urging force of the urging means, against the head periphery-protecting cover having reached the protection position, and the head periphery-protecting cover is moved from the protection position to the protection release position. 
     Furthermore, a sixth invention is a thermal stencil making unit, wherein, in the thermal stencil making unit in the fifth invention described above: 
     the head periphery-protecting cover is rotatably provided between the protection position and the protection release position, and a cylindrical pipe for introducing setting of the gauze frame to an upstream side facing the setting direction of the gauze frame is mounted along a direction orthogonal to the setting direction of the gauze frame; 
     the plurality of heat elements is rotated by the urging force of the urging means to the protection position while facing an inside of the opening portion and waits for the setting of the gauze frame; and 
     the plurality of heat elements is pushed in by the gauze frame while resisting the urging force of the urging means in the setting of the gauze frame and is rotated to the protection release position where the plurality of heat elements protrudes upward from the inside of the opening portion. 
     Moreover, a seventh invention is a thermal stencil making unit, wherein, in the thermal stencil making unit in the fifth invention described above: 
     the head periphery-protecting cover is movably provided in a vertical direction between the protection position and the protection release position; 
     the plurality of heat elements is moved by the urging force of the urging means to the protection position while facing the inside of the opening portion and waits for the setting of the gauze frame; and 
     the plurality of heat elements is pushed in by the gauze frame while resisting the urging force of the urging means in the setting of the gauze frame and is moved to the protection release position where the plurality of heat elements protrudes upward from the inside of the opening portion. 
     In addition, an eighth invention is a thermal stencil making unit, in the thermal stencil making unit in any of the first to seventh invention described above, further includes: 
     a first detection sensor configured to detect that the gauze frame is set by the head-protecting member when the head-protecting member has moved from the protection position to the protection release position; and 
     a second detection sensor configured to detect the presence or absence of the thermal gauze when the gauze frame is set in the unit housing. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The invention will now be described with reference to the accompanying drawings wherein: 
         FIG. 1  is a perspective view illustrating a thermal stencil making unit according to a first embodiment of the present invention; 
         FIG. 2  is a side view illustrating the thermal stencil making unit according to the first embodiment of the present invention, in a partial cross-section; 
         FIG. 3  is a perspective view illustrating a head-protecting cover and a pressing/positioning member mounted on an upper surface of this head-protecting cover, in the thermal stencil making unit according to the first embodiment of the present invention; 
         FIG. 4  is a plan view illustrating the thermal stencil making unit according to the first embodiment of the present invention; 
         FIG. 5A  is an operation diagram for explaining an operation of the thermal stencil making unit according to the first embodiment of the present invention and is a view illustrating a setting start state of a gauze frame; 
         FIG. 5B  is an operation diagram for explaining an operation of the thermal stencil making unit according to the first embodiment of the present invention and is a view illustrating a middle state of the setting of the gauze frame; 
         FIG. 5C  is an operation diagram for explaining an operation of the thermal stencil making unit according to the first embodiment of the present invention and is a view illustrating a setting end state of a gauze frame; 
         FIG. 6  is a perspective view illustrating a head-protecting cover and a pressing/positioning member mounted on an upper surface of this head-protecting cover, in a first modification obtained by partially modifying the thermal stencil making unit according to the first embodiment of the present invention; 
         FIG. 7  is a plan view illustrating the first modification obtained by partially modifying the thermal stencil making unit according to the first embodiment of the present invention; 
         FIG. 8  is a perspective view illustrating the head-protecting cover and the pressing/positioning member mounted on an upper surface of a link arm, in a second modification obtained by partially modifying the thermal stencil making unit according to the first embodiment of the present invention; 
         FIG. 9  is a plan view illustrating the second modification obtained by partially modifying the thermal stencil making unit according to the first embodiment of the present invention; 
         FIG. 10  is a perspective view illustrating a head portion and a platen portion in the thermal stencil making unit according to a second embodiment of the present invention; 
         FIG. 11A  is a top view illustrating the head portion in the thermal stencil making unit according to the second embodiment of the present invention; 
         FIG. 11B  is a side view illustrating the head portion in the thermal stencil making unit according to the second embodiment of the present invention; 
         FIG. 12A  is a view perspectively illustrating a head periphery-protecting cover and a pair of right and left brackets in an exploded manner, in the thermal stencil making unit according to the second embodiment of the present invention; 
         FIG. 12B  is a partially cross-sectional view of a spot of an arm member of the head periphery-protecting cover illustrated in  FIG. 12A ; 
         FIG. 13A  is a perspective view illustrating a state where the head periphery protective cover is rotatably supported by the pair of right and left brackets in the thermal stencil making unit according to the second embodiment of the present invention; 
         FIG. 13B  is a front view illustrating a state where the head periphery-protecting cover is rotatably supported by the pair of right and left brackets in the thermal stencil making unit according to the second embodiment of the present invention; 
         FIG. 13C  is a side view illustrating a state where the head periphery-protecting cover is rotatably supported by the pair of right and left brackets in the thermal stencil making unit according to the second embodiment of the present invention; 
         FIG. 13D  is an XIIID-XIIID line cross-sectional view illustrating a state where the head periphery-protecting cover is rotatably supported by the pair of right and left brackets in the thermal stencil making unit according to the second embodiment of the present invention; 
         FIG. 14  is a first operation diagram illustrating an operation of the thermal stencil making unit according to the second embodiment of the present invention; 
         FIG. 15  is a second operation diagram illustrating the operation of the thermal stencil making unit according to the second embodiment of the present invention; 
         FIG. 16  is a third operation diagram illustrating the operation of the thermal stencil making unit according to the second embodiment of the present invention: 
         FIG. 17A  is a top view illustrating the head portion in the first modification obtained by partially modifying the thermal stencil making unit according to the second embodiment of the present invention; 
         FIG. 17B  is a side view illustrating the head portion in the first modification obtained by partially modifying the thermal stencil making unit according to the second embodiment of the present invention; 
         FIG. 18  is a first operation diagram illustrating an operation of the first modification obtained by partially modifying the thermal stencil making unit according to the second embodiment of the present invention; 
         FIG. 19  is a second operation diagram illustrating the operation of the first modification obtained by partially modifying the thermal stencil making unit according to the second embodiment of the present invention; 
         FIG. 20  is a third operation diagram illustrating the operation of the first modification obtained by partially modifying the thermal stencil making unit according to the second embodiment of the present invention; 
         FIG. 21  is a flowchart illustrating a detection operation of the gauze frame and a detection operation of the thermal gauze, in the first modification obtained by partially modifying the thermal stencil making unit according to the second embodiment of the present invention; 
         FIG. 22  is a perspective view illustrating the second modification obtained by partially modifying the thermal stencil making unit according to the second embodiment of the present invention; 
         FIG. 23  is a first operation diagram illustrating an operation of the second modification obtained by partially modifying the thermal stencil making unit according to the second embodiment of the present invention; 
         FIG. 24  is a second operation diagram illustrating the operation of the second modification obtained by partially modifying the thermal stencil making unit according to the second embodiment of the present invention; and 
         FIG. 25  is a third operation diagram illustrating the operation of the second modification obtained by partially modifying the thermal stencil making unit according to the second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments for putting a thermal stencil making unit according to the present invention into practice will be described below in detail in the order of a first embodiment and a second embodiment by referring to  FIGS. 1 to 25 . 
     First Embodiment 
       FIG. 1  perspectively illustrates a thermal stencil making unit according to a first embodiment of the present invention. In addition,  FIG. 2  illustrates the thermal stencil making unit according to the first embodiment of the present invention seen from a side surface side, in a partial cross-section. 
     As illustrated in  FIGS. 1 and 2 , in the thermal stencil making unit  10 A according to the first embodiment of the present invention, a unit housing  11  is formed in a box shape. 
     An opening portion  11   b  (illustrated only in  FIG. 1 ) is formed by being largely opened in a rectangular shape, on an upper surface  11   a  of the unit housing  11  described above. A gauze frame  21  formed in a rectangular shape is disposed above the opening portion  11   b  formed in the upper surface  11   a  of the unit housing  11  and at a substantially same position as that of the upper surface  11   a.    
     At this time, the gauze frame  21  is mounted on a pressing/positioning member  34  on a head-protecting member  33  that will be described later and that is provided so as to be capable of reciprocating in an arrow X-direction and on a movable positioning member  14  movable in accordance with a length size of the gauze frame  21 , in the opening portion  11   b  formed in the upper surface  11   a  of the unit housing  11 . Note that, although the head-protecting member  33  moves, the pressing/positioning member  34  described above has a function of a fixed positioning member fixed and placed on this head-protecting member  33 . 
     In addition, a thermal gauze  22  is tightly stretched on a lower part in the gauze frame  21 , and this thermal gauze  22  is formed in a rectangular shape in a state where a heat-melting film is stuck with an adhesive agent onto a gauze having a plurality of meshes by weaving warps and woofs. 
     Furthermore, in the opening portion  11   b  formed in the upper surface  11   a  of the unit housing  11 , a head portion  30  is placed so as to face the thermal gauze  22  below the thermal gauze  22  tightly stretched in the gauze frame  21 . 
     The head portion  30  described above includes a head base  31  and a thermal print head  32  having a plurality of heat elements  32   a . In addition, the thermal print head  32  in which the plurality of heat elements  32   a  is aligned in a Y-direction which is a main scanning direction is mounted on the head base  31  and attached so that the plurality of heat elements  32   a  comes into contact with the thermal gauze  22 . 
     Moreover, the head base  31  on which the thermal print head  32  is mounted is mounted on a pair of right and left movable plates  12  and  12  reciprocating in an arrow X-direction while facing each other at intervals in the arrow Y-direction by sandwiching the gauze frame  21 . 
     At this time, the pair of right and left movable plates  12  and  12  are provided in parallel with each other at intervals in the arrow Y-direction in the unit housing  11  and is movable along a pair of right and left guide shafts  13  and  13  provided lengthily along the arrow X-direction. 
     In addition, upper portions  12   a  and  12   a  of the pair of right and left movable plates  12  and  12  protrude upward from an inside of the opening portion  11   b  formed in the upper surface  11   a  of the unit housing  11 . 
     Furthermore, in the unit housing  11 , the head-protecting member  33  that protects this thermal print head  32  is provided facing the thermal print head  32 , so as to be capable of reciprocating between a protection position P 1  and a protection release position P 2  where the protection state is released. 
     The head-protecting member  33  described above is a head-protecting cover that protects (covers) the plurality of heat elements  32   a  provided in the thermal print head  32  at the protection position P 1  (covering position) and is provided so as to go away from the plurality of heat elements  32   a  at the protection release position P 2  (covering release position). 
     Moreover, the head-protecting member  33  (hereinafter, referred to as a head-protecting cover) is movable from the protection position P 1  to the protection release position P 2  in conjunction with an operation of setting the gauze frame  21  to the unit housing  11  as will be described later. 
     Moreover, as illustrated in  FIGS. 3 and 4 , a gauze frame mounting portion  33   a   1  on which a front end portion  21   a  (one end portion) side of the gauze frame  21  in a setting direction SD is mounted is formed on an upper surface  33   a  of the head-protecting cover  33 , on a front side facing the setting direction SD of the gauze frame  21 . In addition, the pressing/positioning member  34  is placed upright on the upper surface  33   a  of the head-protecting cover  33  and at the rear of the gauze frame mounting portion  33   a   1  formed on the front side of this upper surface  33   a.    
     The pressing/positioning member  34  described above has a function of positioning the front end portion  21   a  of the gauze frame  21  when the front end portion  21   a  of the gauze frame  21  is pressed approachably and separably and the gauze frame  21  is to be set in the unit housing  11 . 
     At this time, when a platen portion  40  which will be described later is opened and the gauze frame  21  is not set in the unit housing  11 , the head-protecting cover  33  has reached the protection position P 1  (covering position) of a high height position indicated by a two-dot chain line in  FIG. 2 . 
     On the other hand, when an operator opens the platen portion  40  which will be described later to thereby set the gauze frame  21  in the unit housing  11 , the front end portion  21   a  of the gauze frame  21  is pressed onto the pressing/positioning member  34 , and thus the head-protecting cover  33  is pushed from the protection position P 1  (covering position) described above to the lower protection release position P 2  (covering release position) indicated by a solid line in  FIG. 2 . 
     The head-protecting cover  33  described above and the pressing/positioning member  34  mounted on the upper surface  33   a  of this head-protecting cover  33  constitute an essential part of this first embodiment and will be described later in detail. 
     Returning to  FIGS. 1 and 2 , in the unit housing  11 , the movable positioning member  14  on which a rear end portion  21   b  (the other end portion) side of the gauze frame  21  opposite to the setting direction SD is mounted is provided movably back and forth in the arrow X-direction, when the gauze frame  21  is set on the upper surface  11   a  side of the unit housing  11 . A U-shaped portion  14   a  is formed so as to follow a U-shape of a rear portion of the gauze frame  21 , on an upper part of this movable positioning member  14 . 
     In addition, there is formed, in the U-shaped portion  14   a  of the movable positioning member  14 , a gauze frame mounting portion  14   al  on which the rear end portion  21   b  of the gauze frame  21  is mounted. 
     At this time, each of right and left end portions of the U-shaped portion  14   a  of the movable positioning member  14  is connected to a pair of right and left sliders  15  and  15  which advances from above into the opening portion  11   b  formed in the upper surface  11   a  of the unit housing  11  and is movable back and forth along the pair of right and left guide shafts  13  and  13 . 
     The movable positioning member  14  retreats to the rear in the unit housing  11  when the gauze frame  21  is not set, whereas when the gauze frame  21  is set, the movable positioning member  14  moves to the front in accordance with the length size of the gauze frame  21  and causes the gauze frame mounting portion  14   al  formed on the U-shaped portion  14   a  to abut against the rear end portion  21   b  side of the gauze frame  21  while positioning, and allows the rear end portion  21   b  side of this gauze frame  21  to be mounted. 
     Accordingly, the movable positioning member  14  is fixed to a pair of right and left guide rails  17 L and  17 R by using a fixing means, not shown, at a position according to the length size of the gauze frame  21 . 
     On the other hand, above the unit housing  11 , the platen portion  40  is mounted capable of being opened and closed around a pair of right and left rotating shafts  16  and  16  on each of upper parts  12   a  and  12   a  of the pair of right and left movable plates  12  and  12  movable in the arrow X-direction. 
     The platen portion  40  described above includes, as illustrated in  FIG. 2 , a platen cover  41 , a platen roller  42 , and a compression spring  43  for pressing. In addition, in the platen cover  41  opened and closed around the rotating shaft  16 , the platen roller  42  formed lengthily along the arrow Y-direction is rotatably provided via a platen roller driving source not shown. Furthermore, both end portion sides of a rotating shaft  42   a  of the platen roller  42  are pressed and urged toward the thermal print head  32  side in a lower position by the pair of right and left compression springs  43  and  43  for pressing. 
     Therefore, the thermal print head  32  provided in the head portion  30  and the platen roller  42  provided in the platen portion  40  are capable of integral movement in the arrow X-direction by facing each other via the pair of right and left movable plates  12  and  12 . 
     When the thermal stencil making unit  10 A is constituted as above, the plurality of heat elements  32   a  provided in the thermal print head  32  is brought into contact with the thermal gauze  22  tightly stretched in the gauze frame  21 . Moreover, the platen roller  42  is pressed onto the thermal print head  32  side via the thermal gauze  22  by the compression springs  43  for pressing, from above the thermal gauze  22 . 
     Then, while the thermal print head  32  and the platen roller  42  are moved in the arrow X 1 -direction that is a sub-scanning direction, the plurality of heat elements  32   a  aligned in the arrow Y-direction which is the main scanning direction is selectively heated and driven in accordance with the image information, whereby a stencil of a perforated image is made on the heat-melting film of the thermal gauze  22 . 
     Here, there will be described, by the use of  FIGS. 3 to 4 , the head-protecting cover  33  and the pressing/positioning member  34  mounted on the upper surface  33   a  of this head-protecting cover  33  which serve as the essential part of this first embodiment. 
       FIG. 3  perspectively illustrates the head-protecting cover and the pressing/positioning member mounted on the upper surface of this head-protecting cover in the thermal stencil making unit according to the first embodiment of the present invention. In addition,  FIG. 4  planarly illustrates the thermal stencil making unit according to the first embodiment of the present invention. 
     As illustrated in  FIGS. 3 and 4 , the head-protecting cover  33  has a pair of right and left side surfaces  33   b  and  33   b  formed by bending downward both end parts of the upper surface  33   a  in the arrow Y-direction by the use of a plate material. 
     In addition, two guide pins  35  and  35  are laterally provided, respectively, on outer sides of the pair of right and left side surfaces  33   b  and  33   b  formed on the head-protecting cover  33 . 
     These two guide pins  35  and  35  are fitted into a pair of right and left guide grooves  17   a  and  17   a  formed in a pair of right and left frames  17  and  17  placed to face each other at intervals with the thermal print head  32  sandwiched in the unit housing  11 . 
     At this time, in the guide grooves  17   a  formed in the frame  17 , a first horizontal guide groove  17   al  whose height is great, an inclined guide groove  17   a   2 , and a second horizontal guide groove  17   a   3  whose height is small are connected in a stepped form, from an upstream side toward a downstream side in the setting direction SD of the gauze frame  21 . 
     In addition, each of one end portions of a pair of right and left tension springs  36  and  36  (urging means) urging this head-protecting cover  33  to the protection position P 1  side (arrow X 1 -direction side) is hooked on the pair of right and left side surfaces  33   b  and  33   b  of the head-protecting cover  33 , while each of the other end portions of the pair of right and left tension springs  36  and  36  is hooked to the pair of right and left frames  17  and  17 . 
     Furthermore, at the rear of the gauze frame mounting portion  33   a   1  on the upper surface  33   a  of the head-protecting cover  33 , the pressing/positioning member  34  described above by using  FIG. 2  is fixed in a state of being formed in a plate shape with a predetermined height upward along a direction (arrow Y-direction) orthogonal to the setting direction SD of the gauze frame  21 . 
     Moreover, in the pressing/positioning member  34 , a pair of right and left protruding portions  34   a  and  34   a  are formed protrusively upward by a slight height, on both end portion sides of the direction (arrow Y-direction) orthogonal to the setting direction SD of the gauze frame  21 . 
     In addition, when the head-protecting cover  33  has reached the protection position P 1  in a state where the gauze frame  21  is not set and the platen cover  41  of the platen portion  40  is closed, the rotating shaft  42   a  of the platen roller  42  illustrated in  FIG. 2  is lifted upward against the pair of right and left compression springs  43  and  43  for pressing, by the pair of right and left protruding portions  34   a  and  34   a  formed protrusively on the both end portion sides of the pressing/positioning member  34 . Accordingly, the pressing/positioning member  34  does not damage the surface of the platen roller  42 . 
     The pressing/positioning member  34  described above pushes the head-protecting cover  33  in an arrow X 2 -direction in conjunction with the setting operation of the gauze frame  21  as described above, and positions the front end portion  21   a  of this gauze frame  21  when the setting of the gauze frame  21  is completed. 
     Furthermore, a head cleaning material  37  using a felt or the like is fixed to a lower surface  33   c  of the head-protecting cover  33  facing the plurality of heat elements  32   a  provided in the thermal print head  32 . This head cleaning material  37  can clean the plurality of heat elements  32   a  provided in the thermal print head  32  when the head-protecting cover  33  has reached the protection position P 1 , and thus a stencil of the perforated image can be favorably made on the thermal gauze  22 . 
     Then, the head-protecting cover  33  is positioned at the protection position P 1 , when the head-protecting cover  33  has moved in the arrow X 1 -direction by the urging force of the tension spring  36  and has reached the first horizontal guide groove  17   al  whose height is great in the guide grooves  17   a.    
     On the other hand, when the pressing/positioning member  34  on the head-protecting cover  33  has been pressed by this front end portion  21   a  in conjunction with the setting operation of the gauze frame  21 , and thereby when the head-protecting cover  33  has moved while being pushed in the arrow X 2 -direction resisting the urging force of the tension spring  36  and has reached the second horizontal guide groove  17   a   3  whose height is small via the inclined guide groove  17   a   2  in the guide grooves  17   a , the head-protecting cover  33  is located at the protection release position P 2 . 
     At this time, a controller  39  can detect that the head-protecting cover  33  has reached the protection release position P 2 , by pushing the micro switch  38  or the like by the head-protecting cover  33 . 
     When the pressing/positioning member  34  is placed upright on the upper surface  33   a  of the head-protecting cover  33  as described above, an operation of the thermal stencil making unit  10 A according to the first embodiment of the present invention will be described by the use of  FIGS. 5A, 5B, and 5C . 
       FIGS. 5A, 5B, and 5C  are operation diagrams for explaining the operation of the thermal stencil making unit according to the first embodiment of the present invention.  FIG. 5A  illustrates a setting start state of the gauze frame,  FIG. 5B  illustrates a middle state of the setting of the gauze frame, and  FIG. 5C  illustrates a setting end state of the gauze frame. Note that, in  FIGS. 5A, 5B, and 5C , only a right side surface side of the unit is described in illustration, and description for a left side surface side symmetric to the right side surface side will be omitted. 
     First, as illustrated in  FIG. 5A , in the thermal stencil making unit  10 A according to the first embodiment of the present invention, when the operator starts setting of the gauze frame  21  in which the thermal gauze  22  is tightly stretched in the unit housing  11 , the platen cover  41  of the platen portion  40  mounted on the movable plates  12  moving along the guide shafts  13  is rotated in a clockwise direction around the rotating shaft  16  and opened. Accordingly, the platen roller  42  provided in the platen cover  41  of the platen portion  40  is separated from the thermal print head  32  provided in the head portion  30 . 
     On the other hand, the thermal print head  32  mounted on the movable plates  12  via the head base  31  is stopped at an initial position set on the right (arrow X 2 -direction side) in the unit housing  11 . 
     In addition, in the head-protecting cover  33 , the two guide pins  35  laterally provided on the side surface  33   b  of the head-protecting cover  33  are fitted by the urging force of the tension spring  36  into the first horizontal guide groove  17   al  whose height is great in the guide grooves  17   a  formed in the frame  17 . 
     Accordingly, the head-protecting cover  33  has reached the protection position P 1  (covering position) whose height is great in order to protect (cover) the plurality of heat elements  32   a  by facing the plurality of heat elements  32   a  provided in the thermal print head  32 . At this time, the head cleaning material  37  mounted on the lower surface  33   c  of the head-protecting cover  33  is in contact with the plurality of heat elements  32   a.    
     Then, when the head-protecting cover  33  has reached the protection position P 1  in a state where the platen cover  41  of the platen portion  40  is closed, the rotating shaft  42   a  of the platen roller  42  is lifted upward by the pair of right and left protruding portions  34   a  and  34   a  formed protrusively on the both end portion sides of the pressing/positioning member  34  mounted on the upper surface  33   a  of the head-protecting cover  33 , and thus no trouble is caused. 
     Therefore, when the gauze frame  21  is not set in the unit housing  11 , the head-protecting cover  33  has been moved to the protection position P 1 . It is needless  15  to say that, when the gauze frame  21  is not set in the unit housing  11 , the head-protecting cover  33  is automatically returned by the urging force of the tension spring  36  from the protection release position P 2  to the protection position P 1 . 
     Moreover, the movable positioning member  14  obtained by forming, on the U-shaped portion  14   a , the gauze frame mounting portion  14   a   1  on which the rear end portion  21   b  side of the gauze frame  21  is mounted and positioned retreats to the rear of the unit housing  11  (arrow X 1 -direction side) via the slider  15  moving along the guide shafts  13 . 
     Here, when the operator starts the setting operation by directing the gauze frame  21  toward the setting direction SD of the gauze frame  21  with the front end portion  21   a  side of this gauze frame  21  at the head while grasping the gauze frame  21 , the front end portion  21   a  side of the gauze frame  21  is mounted on the gauze frame mounting portion  33   a   1  formed on the upper surface  33   a  of the head-protecting cover  33 , and at the same time, the front end portion  21   a  of the gauze frame  21  comes into contact with the pressing/positioning member  34  placed upright at the rear of the gauze frame mounting portion  33   al.    
     After that, as illustrated in  FIG. 5B , when the operator pushes the pressing/positioning member  34  toward the setting direction SD of the gauze frame  21  by the front end portion  21   a  of this gauze frame  21 , the head-protecting cover  33  is pushed into the arrow X 2 -direction while resisting the urging force of the tension spring  36  and is separated from the protection position P 1 . At this time, the two guide pins  35  laterally provided on the side surface  33   b  of the head-protecting cover  33  goes from the first horizontal guide groove  17   al  whose height is great in the guide grooves  17   a  formed in the frame  17  toward the inclined guide groove  17   a   2 . 
     Furthermore, after that, as illustrated in  FIG. 5C , when the operator further pushes the pressing/positioning member  34  by the front end portion  21   a  of the gauze frame  21 , the two guide pins  35  laterally provided on the side surface  33   b  of the head-protecting cover  33  are fitted into the second horizontal guide groove  17   a   3  whose height is small in the guide grooves  17   a  formed in the frame  17 . Accordingly, since the head-protecting cover  33  reaches the protection release position P 2  (covering release position) whose height is small, there can be prevented collision of this platen portion  40  against the head-protecting cover  33  when the platen portion  40  is closed. 
     Then, the pressing/positioning member  34  on the head-protecting cover  33  which has reached the protection release position P 2  positions the front end portion  21   a  of the gauze frame  21 . 
     After that, the operator moves the movable positioning member  14  to the front (arrow X 2 -direction side) of the unit housing  11  via the slider  15  moving along the guide shafts  13 . In addition, the gauze frame mounting portion  14   a   1  formed on the U-shaped portion  14   a  of the movable positioning member  14  abuts while being positioned against the rear end portion  21   b  side of the gauze frame  21  and thus the rear end portion  21   b  side of this gauze frame  21  is mounted, and the setting operation of the gauze frame  21  in the unit housing  11  is completed. At this time, the plurality of heat elements  32   a  provided in the thermal print head  32  is in contact with the thermal gauze  22  tightly stretched in the gauze frame  21 . 
     Then, after the setting operation of the gauze frame  21  is completed, although illustration here is omitted, the platen portion  40  is closed, and the thermal print head  32  and the platen roller  42  are moved integrally to the arrow X 1 -direction while the platen roller  42  is pressed toward the thermal print head  32  side via the thermal gauze  22  by  10  the urging force of the compression spring  43  for pressing, and a stencil of the perforated image is made on the thermal gauze  22  by the plurality of heat elements  32   a.    
     The thermal stencil making unit  10 A according to the first embodiment of the present invention described above in detail includes the head-protecting cover  33  moving while being urged to the protection position P 1  side via the tension spring  36  between the protection position P 1  where the plurality of heat elements  32   a  provided in the thermal print head  32  is protected and the protection release position P 2  where the protection state is released; and the head-protecting cover  33  is moved from the protection position P 1  to the protection release position P 2  against the tension spring  36  in conjunction with the operation of setting the gauze frame  21  in the unit housing  11 , while the head-protecting cover  33  is moved to the protection position P 1  by the tension spring  36  when the gauze frame  21  is not set in the unit housing  11 . 
     As a result, a human error caused by the operator does not occur in setting of the gauze frame  21 , the plurality of heat elements  32   a  provided in the thermal print head  32  can be reliably protected by the head-protecting cover  33  that has reached the protection position P 1 , and the head-protecting cover  33  can be reliably moved from the protection position P 1  to the protection release position P 2  against the tension spring  36  in conjunction with the setting operation of the gauze frame  21 . It is needless to say that, when the gauze frame  21  is not set in the unit housing  11 , the head-protecting cover  33  can be automatically returned from the protection release position P 2  to the protection position P 1  by the tension spring  36 . 
     At this time, when the gauze frame  21  is to be set in the unit housing  11 , the pressing member  34  pressing the head-protecting cover  33  from the protection position P 1  toward the protection release position P 2  by the front end portion  21   a  (one end portion) of the gauze frame  21  is provided integrally on the head-protecting cover  33 , and thus the thermal print head protection structure is simple, and the operator can easily move the head-protecting cover  33  from the protection position P 1  to the protection release position P 2 . 
     First Modification of First Embodiment 
     Subsequently, a first modification obtained by partially modifying the thermal stencil making unit  10 A according to the first embodiment of the present invention will be described by the use of  FIGS. 6 and 7 . 
       FIG. 6  perspectively illustrates the head-protecting cover and the pressing/positioning member mounted on the upper surface of this head-protecting cover in the first modification obtained by partially modifying the thermal stencil making unit according to the first embodiment of the present invention. In addition,  FIG. 7  planarly illustrates the first modification obtained by partially modifying the thermal stencil making unit according to the first embodiment of the present invention. 
     The first modification obtained by partially modifying the thermal stencil making unit according to the first embodiment of the present invention illustrated in  FIGS. 6 and 7  is different from the first embodiment only in terms of two pressing/positioning members  50  and  50  mounted on the upper surface  33   a  of the head-protecting cover  33 , and thus the same reference numerals are attached to the same constituent members as those in the first embodiment in illustration, and detailed description will be omitted, and points different from the first embodiment will be mainly described below. 
     Namely, as illustrated in  FIGS. 6 and 7 , in the first modification obtained by partially modifying the thermal stencil making unit according to the first embodiment of the present invention, instead of the pressing/positioning member  34  illustrated in  FIGS. 3 and 4 , the two pressing/positioning members  50  and  50  are provided upright on the upper surface  33   a  of the head-protecting cover  33  and also at the rear of the gauze frame mounting portion  33   al  formed on the front side of this upper surface  33   a , and on both end portion sides of the direction (arrow Y-direction) orthogonal to the setting direction SD of the gauze frame  21 , respectively. 
     The above-described two pressing/positioning members  50  and  50  are fixed in a state of being formed as rod-shaped members having predetermined heights upward from the upper surface  33   a  of the head-protecting cover  33 . 
     Then, when the head-protecting cover  33  has reached the protection position P 1  in a state where the platen cover  41  of the platen portion  40  is closed, the rotating shaft  42   a  of the platen roller  42  illustrated in  FIG. 2  is lifted upward by the two pressing/positioning members  50  and  50  against the pair of right and left compression springs  43  and  43  for pressing. Accordingly, the pressing/positioning member  50  does not damage the surface of the platen roller  42 . 
     Note that the pressing/positioning member  50  in the first modification only needs to be provided on at least one end portion side of the both end portion sides in the direction orthogonal to the setting direction SD of the gauze frame  21  on the upper surface  33   a  of the head-protecting cover  33 . 
     As in the first embodiment, the above-described pressing/positioning members  50  also pushes the head-protecting cover  33  in the arrow X 2 -direction from the protection position P 1  (covering position) to the protection release position P 2  (covering release position) in conjunction with the setting operation of the gauze frame  21 , and positions the front end portion  21   a  (one end portion) of this gauze frame  21  when the setting of the gauze frame  21  is completed. 
     Accordingly, in a state where the head-protecting cover  33  has reached the protection position P 1  (covering position) where the plurality of heat elements  32   a  provided in the thermal print head  32  is protected (covered), when the operator erroneously closes the platen portion  40 , a part of this platen portion  40  comes into contact with the two pressing/positioning members  50  and  50 , and thus the platen roller  42  in the platen portion  40  or the thermal gauze  22  in the gauze frame  21  is not damaged, which can contribute to safety of the thermal stencil making unit  10 A. 
     Second Modification of First Embodiment 
     Subsequently, a second modification obtained by partially modifying the thermal stencil making unit  10 A according to the first embodiment of the present invention will be described by the use of  FIGS. 8 and 9 . 
       FIG. 8  perspectively illustrates the head-protecting cover and the pressing/positioning member mounted on a link arm, in a second modification obtained by partially modifying the thermal stencil making unit according to the first embodiment of the present invention. In addition,  FIG. 9  planarly illustrates the second modification obtained by partially modifying the thermal stencil making unit according to the first embodiment of the present invention. 
     In the second modification obtained by partially modifying the thermal stencil making unit according to the first embodiment of the present invention illustrated in  FIGS. 8 and 9 , only the head-protecting member  60  (hereinafter, referred to as a head-protecting cover) and a pressing/positioning member  67  mounted on the link arm  65  are different from those of the first embodiment, and thus the same reference numerals are attached to the same constituent members as those in the first embodiment in illustration, and detailed description will be omitted, and points different from the first embodiment will be mainly described below. 
     Namely, as illustrated in  FIGS. 8 and 9 , in the second modification obtained by partially modifying the thermal stencil making unit according to the first embodiment of the present invention, instead of the head-protecting cover  33  in the first embodiment, a head-protecting cover  60  opposable to the thermal print head  32  is movably provided between the protection position P 1  (covering position) where the plurality of heat elements  32   a  is protected (covered) and the protection release position P 2  (covering release position) where the protection state (covering state) is released. 
     This head-protecting cover  60  is also movable from the protection position P 1  to the protection release position P 2  in conjunction with the setting operation of the gauze frame  21  in the unit housing  11 , as in the first embodiment. 
     The above-described head-protecting cover  60  is formed on the front side where a gauze frame mounting portion  60   al  on which the front end portion  21   a  side of the gauze frame  21  is mounted on this upper surface  60   a  faces the setting direction SD of the gauze frame  21 . 
     In addition, at the rear of the gauze frame mounting portion  60   al  on the upper surface  60   a  of the head-protecting cover  60 , a long hole  60   a   2  is penetratingly formed along the arrow Y-direction orthogonal to the setting direction SD of the gauze frame  21 , and two guide pins  61  and  61  are laterally provided on outer sides of a pair of right and left side surfaces  60   b  and  60   b , respectively. 
     These two guide pins  61  and  61  are fitted into a pair of right and left horizontal guide grooves  62   b   1  and  62   b   1  formed in a pair of right and left side surfaces  62   b  and  62   b  obtained by bending downward both end sides of an upper surface  62   a  in the arrow Y-direction, of an arm support body  62  placed in the unit housing  11 . 
     Additionally, each of one end portions of a pair of right and left tension springs  63  and  63  that urge this head-protecting cover  60  to the protection position P 1  side (arrow X 1 -direction side) is hooked to the pair of right and left side surfaces  60   b  and  60   b  of the head-protecting cover  60 , whereas each of the other end portions of the pair of right and left tension springs  63  and  63  is hooked to the pair of right and left side surfaces  62   b  and  62   b  formed on the arm support body  62 . 
     Furthermore, the head cleaning material  37  using a felt or the like is fixed onto the lower surface  60   c  of the head-protecting cover  60  facing the plurality of heat elements  32   a  provided in the thermal print head  32 . 
     Moreover, one end portion side of the link arm  65  is rotatably supported by a rotating shaft  64  placed upright on a back side of the upper surface  62   a  of the arm support body  62  and on the side surface  62   b  side on a lower side in the illustration. This link arm  65  is mounted inclined by only a predetermined angle α toward an inner side with respect to the arrow X-direction by a stopper material  66  at the time of an initial state. 
     Moreover, the pressing/positioning member  67  is fixed to an intermediate portion on the upper surface  65   a  of the link arm  65 , in a state of being formed as a rod-shaped member having a predetermined height upward. 
     As in the first embodiment, the pressing/positioning member  67  described above also pushes the head-protecting cover  60  into the arrow X 2 -direction from the protection position P 1  toward the protection release position P 2  in conjunction with the setting operation of the gauze frame  21 , and positions the front end portion  21   a  of this gauze frame  21  when the setting of the gauze frame  21  is completed. 
     Moreover, an engagement pin  68  having a low height is fixed to the other end portion side on the upper surface  65   a  of the link arm  65 , and this engagement pin  68  is fitted into the long hole  60   a   2  penetratingly formed in this upper surface  60   a  from the back surface side of the head-protecting cover  60 . 
     In addition, when the head-protecting cover  60  is moving in the arrow X 1 -direction by the urging force of a tension spring  63 , the head-protecting cover  60  is located at the protection position P 1 . 
     At this time, when the head-protecting cover  60  has reached the protection position P 1  in a state where the platen cover  41  of the platen portion  40  is closed, the upper surface  60   a  of the head-protecting cover  60  is formed flat and thus, even if the upper surface  60   a  of the head-protecting cover  60  faces the platen roller  42 , the surface of this platen roller  42  is not damaged. 
     On the other hand, when the pressing/positioning member  67  on the link arm  65  is pushed by this front end portion  21   a  in conjunction with the setting operation of the gauze frame  21 , the link arm  65  is rotated in the clockwise direction around the rotating shaft  64 . 
     Note that, when the pressing/positioning member  67  on the link arm  65  is pushed by the front end portion  21   a  of the gauze frame  21 , since the link arm  65  is mounted inclined by only a predetermined angle α toward the inner side with respect to the arrow X-direction, the link arm  65  is deviated from a dead point direction in parallel with the arrow X-direction and can be easily rotated. 
     In addition, along with the rotation of the link arm  65 , the engagement pin  68  on the link arm  65  moves toward the inner side in the long hole  60   a   2  formed in the upper surface  60   a  of the head-protecting cover  60 , and thus the head-protecting cover  60  is pushed in the arrow X 2 -direction against the urging force of the tension spring  63  and is located at the protection release position P 2 . 
     At this time, the controller  39  can detect that the head-protecting cover  60  has reached the protection release position P 2 , by pushing the micro switch  38  or the like by the head-protecting cover  60 . 
     Note that, in this second modification, since the pair of right and left horizontal guide grooves  62   b   1  and  62   b   1  formed in the pair of right and left side surfaces  62   b  and  62   b  of the arm support body  62  are linearly formed unlike the first embodiment, no trouble is caused in the head-protecting cover  60  even though the protection position P 1  and the protection release position P 2  have the same height. 
     Moreover, instead of the pair of right and left horizontal guide grooves  62   b   1  and  62   b   1  formed in the pair of right and left side surfaces  62   b  and  62   b  of the arm support body  62 , a pair of right and left inclined guide grooves (not shown) whose height is gradually lowered from the protection position P 1  toward the protection release position P 2  can be provided. 
     Therefore, also in the second modification, as in the first embodiment, the head-protecting cover  60  moving between the protection position P 1  where the plurality of heat elements  32   a  provided in the thermal print head  32  is protected and the protection release position P 2  where the protection state is released is included, and the head-protecting cover  60  has been moved to the protection position P 1  when the gauze frame  21  is not set in the unit housing  11 , while the head-protecting cover  60  is moved from the protection position P 1  to the protection release position P 2  in conjunction with the operation of setting the gauze frame  21  in the unit housing  11 . 
     As a result, a human error caused by the operator does not occur at the time of setting of the gauze frame  21 , the plurality of heat elements  32   a  provided in the thermal print head  32  can be reliably protected by the head-protecting cover  60  which has reached the protection position P 1 , and the head-protecting cover  60  can be reliably moved from the protection position P 1  to the protection release position P 2  in conjunction with the setting operation of the gauze frame  21 . 
     Note that, in the first embodiment (or the first and second modifications of the first embodiment) described above in detail, the example in which the front end portion  21   a  (one end portion) of the gauze frame  21  is mounted on the head-protecting cover  33  or  60 , whereas the rear end portion  21   b  (the other end portion) of the gauze frame  21  is mounted on the U-shaped portion  14   a  of the movable positioning member  14  is described, but this is not limiting, and the gauze frame  21  can be mounted on the upper surface  11   a  of the unit housing  11 . 
     Namely, when the gauze frame  21  is mounted on the upper surface  11   a  of the unit housing  11 , although not shown here, a pair of right and left escape holes in which the pair of right and left movable plates  12  and  12  and the movable positioning member  14  can reciprocate are formed lengthily and at small widths along the arrow X-direction on right and left side surface sides in the upper surface  11   a  of the unit housing  11 . Furthermore, an opening portion is largely opened in a rectangular shape in an upper surface portion of the gauze frame  21  facing the thermal gauze  22  tightly stretched in this gauze frame  21  excluding the portion of the gauze frame  21  between the pair of right and left escape holes formed in the upper surface  11   a  of the unit housing  11 . Accordingly, the gauze frame  21  can be mounted on the upper surface  11   a  formed between the pair of right and left escape holes and the opening portion. 
     Second Embodiment 
       FIG. 10  perspectively illustrates the head portion and the platen portion in the thermal stencil making unit according to a second embodiment of the present invention. In addition,  FIGS. 11A and 11B  illustrate the thermal stencil making unit according to the second embodiment of the present invention, with the head portion viewed from an upper surface and a side surface, respectively. 
     The thermal stencil making unit  10 B according to the second embodiment of the present invention illustrated in  FIG. 10  has a structure partially different from the thermal stencil making unit  10 A according to the first embodiment of the present invention described previously by the use of  FIGS. 1 and 2 , and the same reference numerals are attached to the same constituent members as those in the first embodiment, and detailed description will be omitted, while new reference numerals are given to constituent members different from those in the first embodiment and thus different points will be mainly described below. 
     As illustrated in  FIGS. 10, 11A, and 11B , the thermal stencil making unit  10 B according to the second embodiment of the present invention is different from that in the first embodiment, in terms of a head-protecting member  72  for protecting the thermal print head  32  mounted on an upper surface  71   a  of a head base  71  in a head portion  70 . 
     In this second embodiment, the head-protecting member  72  is a head-periphery-protecting member that has an opening portion  72   k  through which the plurality of heat elements  32   a  provided in the thermal print head  32  advances and retreats and that protects the plurality of heat elements  32   a  at the protection position P 1  where the thermal print head  32  is protected in a periphery on an advance direction side of the gauze frame  21 . At this time, the periphery on the advance direction side of the gauze frame  21  is a periphery other than the opening portion  72   k  of the head periphery-protecting cover  72 . 
     Then, when the head-protecting member  72  (hereinafter, referred to as a head periphery-protecting cover) has reached the protection position P 1 , unlike the first embodiment, the plurality of heat elements  32   a  provided in the thermal print head  32  can be visually recognized without being hidden by the opening portion  72   k  formed in the head periphery-protecting cover  72 , and improvement is made such that the thermal print head  32  is protected when the gauze frame  21  is set, by protection (covering) of the periphery other than the plurality of heat elements  32   a  by the periphery other than the opening portion  72   k  of the head periphery-protecting cover  72 . 
     The head periphery-protecting cover  72  described above is rotatably provided in a vertical direction (up-and-down direction) between the protection position P 1  and the protection release position P 2  around a pair of right and left rotating shafts  73  and  73  provided across the longitudinal direction (arrow Y-direction) of the thermal print head  32  and in the vicinity of right and left sides on one end side of the thermal print head  32  on the upper surface  71   a  of the head base  71 . 
     Then, the head base  71  obtained by mounting the thermal print head  32  and the head periphery-protecting cover  72  is mounted on the pair of right and left movable plates  12  and  12  reciprocating in the arrow X-direction while facing each other at intervals in the arrow Y-direction which is the main scanning direction of the thermal print head  32 , as in the first embodiment. 
     In addition, the platen portion  40  is mounted on an upper part of the pair of right and left movable plates  12  and  12 , capable of being opened and closed, by facing the head portion  70 , as in the first embodiment. 
     Additionally, a platen opening/closing frame  44  provided along the inner side of the platen cover  41  of the platen portion  40  is supported capable of being opened and closed integrally with the platen cover  41  around the rotating shaft  16  illustrated in  FIGS. 14 to 16 , in a state where the platen roller  42  is mounted. 
     Furthermore, in the platen opening/closing frame  44 , a pair of right and left locking claws  45  and  45  are rotatably mounted in the vicinity of right and left ends in the longitudinal direction of the platen roller  42 . The pair of these right and left locking claws  45  and  45  are locked to a pair of right and left locking pins  18  and  18  laterally provided on each of the inner sides of the pair of right and left movable plates  12  and  12  when the platen opening/closing frame  44  is closed. 
     Moreover, on the platen opening/closing frame  44 , a pair of right and left pressing pieces  46  and  46  are mounted on each of outer sides of the pair of right and left  5  locking claws  45  and  45 . The pair of these right and left pressing pieces  46  and  46  are constituted to press the head periphery-protecting cover  72  downward when the platen opening/closing frame  44  is closed, which will be described later by the use of  FIG. 16 . 
     Here, the head periphery-protecting cover  72  serving as an essential part of the second embodiment will be described by the use of  FIGS. 12A, 12B, 13A, 13B, 13C, and 13D . 
       FIG. 12A  is a view perspectively illustrating the head periphery-protecting cover and a pair of right and left brackets in an exploded manner in the thermal stencil making unit according to the second embodiment of the present invention.  FIG. 12B  is a partially cross-sectional view of a position of an arm member of the head periphery-protecting cover illustrated in  FIG. 12A . In addition,  FIGS. 13A, 13B, 13C , and  13 D illustrate states where the head periphery-protecting cover is rotatably supported by the pair of right and left brackets, and  FIGS. 13A, 13B, 13C, and 13D  are a perspective view, a front view, a side view, and an XIIID-XIIID line cross-sectional view, respectively, in the thermal stencil making unit according to the second embodiment of the present invention. 
     As illustrated in  FIG. 12A , the head periphery-protecting cover  72  (head-protecting member) serving as the essential part of the second embodiment is integrally formed by a cylindrical pipe  72 A formed lengthily along the arrow Y-direction that is the main scanning direction of the thermal print head  32  and a pair of right and left arm members  72 B and  72 B fastened on slightly inner sides from right and left end portions of this cylindrical pipe  72 A. 
     In the head periphery-protecting cover  72  described above, the cylindrical pipe  72 A for guiding setting of the gauze frame  21  to an upstream side facing the setting direction SD of the gauze frame  21  is mounted along a direction orthogonal to the setting direction SD of the gauze frame  21 , and a downstream side of the setting direction SD of the gauze frame from the cylindrical pipe  72 A is pivotally supported rotatably via the pair of right and left rotating shafts  73  and  73 . 
     Furthermore, the opening portion  72   k  facing the plurality of heat elements  32   a  provided in the thermal print head  32  is opened largely in an inner side surrounded by the cylindrical pipe  72 A and the pair of right and left arm members  72 B and  72 B. 
     At this time, the cylindrical pipe  72 A described above is formed to be lightweight by the use of, for example, a stainless pipe having rigidity and abrasion resistance. In addition, as will be described later, when the gauze frame  21  is to be set from the setting direction SD in a state where the head periphery-protecting cover  72  has risen to the protection position P 1 , the setting of the gauze frame  21  is guided by the cylindrical pipe  72 A so that the setting can be smoothly carried out without the front end portion  21   a  of the gauze frame  21  being hooked by the head periphery-protecting cover  72 . 
     On the other hand, the arm member  72 B described above is formed by downward bending of a front surface  72 Ba directed to the setting direction SD of the gauze frame  21  and right and left side surfaces  72 Bc and  72 Bd consecutively connected to right and left of an upper surface  72 Bb, by the use of a sheet metal material. 
     In addition, as illustrated in  FIG. 12B , when the head periphery-protecting cover  72  is formed, a female screw member  72 C is fitted into the cylindrical pipe  72 A, and subsequently this cylindrical pipe  72 A is brought into contact with the front surface  72 Ba of the arm member  72 B and fastened by a male screw  72 D from a back surface side of the front surface  72 Ba of this arm member  72 B. 
     Returning to  FIG. 12A , a pair of right and left brackets  74  and  74  are prepared by facing the arm members  72 B, respectively, below each of the pair of right and left arm members  72 B and  72 B of the head periphery-protecting cover  72 . 
     The pair of these right and left brackets  74  and  74  are formed by bending of a sheet metal material into an upward U-shape. 
     In addition, after each of the brackets  74  is fitted in an inner side between the right and left side surfaces  72 Bc and  72 Bd on a rear side opposite to the front surface  72 Ba of each of the arm members  72 B, each of the arm members  72 B and each of the brackets  74  are rotatably connected via each of the rotating shafts  73 . 
     Furthermore, when each of the arm members  72 B and each of the brackets  74  are to be connected, each of torsion springs  75  is fitted into each of the rotating shafts  73 , and an urging force of each of the torsion springs  75  urges the head periphery-protecting cover  72  upward via each of the rotating shafts  73 . 
     Moreover, an escape hole  72 Bh through which a screw, not shown, for mounting each of the brackets  74  on the upper surface  71   a  of the head base  71  is inserted is penetratingly formed in the upper surface  72 Bb of each of the arm members  72 B. 
     Therefore, the states illustrated in  FIGS. 13A, 13B, 13C, and 13D  are obtained when the head periphery-protecting cover  72  is supported by the pair of right and left brackets  74  and  74  via the pair of right and left rotating shafts  73  and  73 . 
     After the head periphery-protecting cover  72  is supported by the pair of right and left brackets  74  and  74  via the pair of right and left rotating shafts  73  and  73 , the pair of right and left brackets  74  and  74  are mounted onto the upper surface  71   a  of the head base  71 . 
     Here, there will be described, by the use of  FIGS. 14 to 16 , an operation of the thermal stencil making unit  10 B according to the second embodiment of the present invention when the head periphery-protecting cover  72  is rotatably supported on the head base  71  across the longitudinal direction of the thermal print head  32 , as described above. 
       FIGS. 14 to 16  schematically illustrate first to third operations for describing the operation of the thermal stencil making unit according to the second embodiment of the present invention. 
     Note that, in  FIGS. 14 to 16 , only a right side surface side of the unit is described in illustration, and description for a left side surface side symmetric to the right side surface side will be omitted. 
     Furthermore, in  FIGS. 14 to 16 , on a front of the head portion  70  in the second embodiment, unlike the first embodiment, a positioning member  19  for causing the front end portion  21   a  side of the gauze frame  21  to abut while positioning and mounting it is assumed to be fixed and placed on the upper surface  11   a  of the unit housing  11 . 
     First, in the first operation in the second embodiment illustrated in  FIG. 14 , the platen opening/closing frame  44  in the platen portion  40  is in an open state around the rotating shaft  16 . In this state, the head periphery-protecting cover  72  mounted, via the bracket  74 , on the upper surface  71   a  of the head base  71  provided in the head portion  70  via the bracket  74  is raised while rotating in the clockwise direction around the rotating shaft  73  by the urging force of the torsion spring  75  fitted into the rotating shaft  73 , and has reached the protection position P 1  where the thermal print head  32  is protected. 
     At this time, since a rear-end lower surface  72 Be of the arm member  72 B of the head periphery-protecting cover  72  comes into contact on the upper surface  71   a  of the head base  71 , the height of the head periphery-protecting cover  72  at the protection position P 1  is regulated. 
     Then, when the head periphery-protecting cover  72  has reached the protection position P 1 , the operator starts the setting operation by directing the gauze frame  21  toward the setting direction SD of the gauze frame  21  with the front end portion  21   a  side of this gauze frame  21  at the head while grasping the gauze frame  21  in which the thermal gauze  22  is tightly stretched, from above the head periphery-protecting cover  72 . 
     At this time, since the cylindrical pipe  72 A of the head periphery-protecting cover  72  is directed to the setting direction SD of the gauze frame  21  and guides the setting of the gauze frame  21 , the setting operation can be smoothly carried out even if the front end portion  21   a  of the gauze frame  21  comes into contact with the cylindrical pipe  72 A of the head periphery-protecting cover  72 . 
     In addition, when the head periphery-protecting cover  72  has reached the protection position P 1 , the plurality of heat elements  32   a  provided in the thermal print head  32  faces the inside of the opening portion  72   k  formed in this head periphery-protecting cover  72  without protruding from the upper surface  72 Bb of the arm member  72 B. 
     Furthermore, when the head periphery-protecting cover  72  has reached the protection position P 1 , the outer peripheral surface other than the opening portion  72   k  by the cylindrical pipe  72 A and the arm member  72 B of the head periphery-protecting cover  72  protects the periphery other than the plurality of heat elements  32   a  provided in the thermal print head  32 . 
     From the above, when the head periphery-protecting cover  72  has reached the protection position P 1 , the operator can observe the state of the plurality of heat elements  32   a  provided in the thermal print head  32  through the opening portion  72   k  from above the head periphery-protecting cover  72 . 
     Accordingly, a harmful stain such as deposits deposited on the plurality of heat elements  32   a  in the previous stencil making of the thermal gauze  22  can be visually checked, and the harmful stain can be cleaned before stencil making this time, and thus a stencil making operation onto the thermal gauze  22  can be favorably carried out in the stencil making this time. 
     Subsequently, in the second operation in the second embodiment illustrated in  FIG. 15 , while the cylindrical pipe  72 A of the head periphery-protecting cover  72  provided in the head portion  70  is pressed downward by the gauze frame  21  in a state where the platen opening/closing frame  44  in the platen portion  40  is kept open, the  15  front end portion  21   a  of this gauze frame  21  is mounted abutting while being positioned against the positioning member  19  fixed and placed on the upper surface  11   a  of the unit housing  11 . Moreover, the movable positioning member  14  movable in accordance with the length size of the gauze frame  21  is caused to abut against the rear end portion  21   b  of the gauze frame  21  while being positioned and allows the rear end portion  21   b  side of this gauze frame  21  to be mounted. 
     Here, when the operator presses the cylindrical pipe  72 A of the head periphery-protecting cover  72  downward by this gauze frame  21  while grasping the gauze frame  21 , the head periphery-protecting cover  72  is pushed in while resisting the urging force of the torsion spring  75  and rotated in a counterclockwise direction around the rotating shaft  73  and lowered. 
     At this time, the plurality of heat elements  32   a  provided in the thermal print head  32  advances into the opening portion  72   k  of the head periphery-protecting cover  72  and approaches the thermal gauze  22  tightly stretched in the gauze frame  21 . 
     Next, in the third operation in the second embodiment illustrated in  FIG. 16 , the platen opening/closing frame  44  in the platen portion  40  is closed, and the head periphery-protecting cover  72  is further lowered by the pressing piece  46  provided in this platen opening/closing frame  44 . 
     Here, when the operator closes the platen opening/closing frame  44  of the platen portion  40 , the platen roller  42  mounted on this platen opening/closing frame  44  comes into contact with the thermal gauze  22  tightly stretched in the gauze frame  21 , and the locking claw  45  provided in the platen opening/closing frame  44  is locked to the locking pin  18  laterally provided on the inner side of the movable plate  12 . 
     Furthermore, when the platen opening/closing frame  44  in the platen portion  40  is closed, the pressing piece  46  provided in this platen opening/closing frame  44  presses downward the cylindrical pipe  72 A of the head periphery-protecting cover  72 , and thus the head periphery-protecting cover  72  is further pushed in while resisting the urging force of the torsion spring  75  and is rotated around the rotating shaft  73  in the counterclockwise direction, and is further lowered from the position illustrated in  FIG. 15  and reaches the protection release position P 2 . 
     Then, the plurality of heat elements  32   a  provided in the thermal print head  32  protrudes upward from the inside of the opening portion  72   k  of the head periphery-protecting cover  72  and comes into contact with the thermal gauze  22  tightly stretched in the gauze frame  21 , and thus the thermal gauze  22  is sandwiched between the plurality of heat elements  32   a  and the platen roller  42 . 
     After that, stencil making on the thermal gauze  22  can be carried out by moving the thermal print head  32  and the platen roller  42  in the sub-scanning direction of the thermal print head  32  integrally with the movable plate  12 . 
     It is needless to say that, when the gauze frame  21  is not set in the unit housing  11 , the head periphery-protecting cover  72  is automatically returned from the protection release position P 2  to the protection position P 1  by the urging force of the torsion spring  75 . 
     First Modification of Second Embodiment 
     Subsequently, there will be described a first modification obtained by partially modifying the thermal stencil making unit  10 B according to the second embodiment of the present invention. 
       FIGS. 17A and 17B  illustrate the head portion seen from an upper surface and a side surface, respectively, in the first modification obtained by partially modifying the thermal stencil making unit according to the second embodiment of the present invention. 
     The first modification obtained by partially modifying the thermal stencil making unit according to the second embodiment of the present invention illustrated in  FIGS. 17A and 17B  is different from the second embodiment only in that a detection operation of the gauze frame  21  and a detection operation of the thermal gauze  22  are constituted to be carried out when the gauze frame  21  in which the thermal gauze  22  is tightly stretched is to be set in the unit housing  11  and when stencil making is to be carried out on the thermal gauze  22 , and thus points different from the second embodiment will be mainly described below. 
     Namely, as illustrated in  FIGS. 17A and 17B , in the first modification obtained by partially modifying the thermal stencil making unit according to the second embodiment of the present invention, a gauze frame detection sensor  76  serving as a first detection sensor is mounted on a lower part on a back surface of the right arm member  72 B of the pair of right and left arm members  72 B and  72 B of the head periphery-protecting cover  72  (head-protecting member), on the upper surface  71   a  of the head base  71  in the head portion  70 . 
     Note that the gauze frame detection sensor  76  (first detection sensor) may be mounted at the lower part on the back surface of either one arm member  72 B of the pair of right and left arm members  72 B and  72 B on the upper surface  71   a  of the head base  71 . 
     The gauze frame detection sensor  76  described above detects whether or not the gauze frame  21  in which the thermal gauze  22  is tightly stretched is set in the unit housing  11 , in other words, detects the presence or absence of the gauze frame  21 . In addition, the gauze frame detection sensor  76  detects whether or not the head periphery-protecting cover  72  has moved from the protection position P 1  where the thermal print head  32  is protected and has reached the protection release position P 2 . 
     Furthermore, a thermal gauze detection sensor  78  serving as a second detection sensor is mounted via a bracket  77  having a predetermined height, at substantially the center portion in the longitudinal direction (arrow Y-direction) on the upper surface  71   a  of the head base  71 . 
     The thermal gauze detection sensor  78  (second detection sensor) described above detects whether or not the thermal gauze  22  is tightly stretched on a lower surface of the gauze frame  21  when the gauze frame  21  is regularly set in the unit housing  11  or in other words, detects the presence or absence of the thermal gauze  22 . 
     At this time, the gauze frame detection sensor  76  and the thermal gauze detection sensor  78  both use a known reflection-type optical sensor and a detection distance of this reflection-type optical sensor is approximately 5 mm and a detection range is set to approximately ±2 mm around that point. 
     Along with the above, in the gauze frame detection sensor  76  and the thermal gauze detection sensor  78 , mounting heights of the gauze frame detection sensor  76  and the thermal gauze detection sensor  78  are adjusted by using the bracket  77  or the like so that a reflection surface to be detected is located within a detection range of 3 to 7 mm from distal ends of the gauze frame detection sensor  76  and the thermal gauze detection sensor  78 . 
     In addition, in a case where the thermal gauze  22  tightly stretched on the lower surface of the gauze frame  21  is regularly set in the unit housing  11  when the gauze frame detection sensor  76  and the thermal gauze detection sensor  78  both having characteristics described above are used, the thermal gauze  22  is located within the detection range (5 mm+2 mm) of the thermal gauze detection sensor  78 , and thereby the presence or absence of the thermal gauze  22  can be detected by the thermal gauze detection sensor  78 . 
     On the other hand, in a case where the user erroneously sets the gauze frame  21  upside down in the unit housing  11 , since a height H of the gauze frame  21  is generally 20 mm or more, the thermal gauze  22  is located upward by the height H from the regular position, and thereby this thermal gauze  22  cannot be detected by the thermal gauze detection sensor  78 . 
     Therefore, the thermal gauze detection sensor  78  is also capable of up-and-down inversion detection of the gauze frame other than detection of the presence or absence of the thermal gauze  22  regularly set to the gauze frame  21 . 
     Here, there will be described, by the use of  FIGS. 18 to 21 , the operation of the first modification obtained by partially modifying the thermal stencil making unit  10 B according to the second embodiment of the present invention constituted by mounting the gauze frame detection sensor  76  and the thermal gauze detection sensor  78  on the head base  71  as above. 
       FIGS. 18 to 20  schematically illustrate first to third operations for describing the operation of the first modification obtained by partially modifying the thermal stencil making unit according to the second embodiment of the present invention. 
     Note that, in  FIGS. 18 to 20 , only a right side surface side of the unit is described in illustration, and description for a left side surface side symmetric to the right side surface side will be omitted. 
     First, in the first operation in the first modification of the second embodiment illustrated in  FIG. 18 , the platen opening/closing frame  44  in the platen portion  40  is in the open state around the rotating shaft  16 . In this state, the head periphery-protecting cover  72  mounted, via the bracket  74 , on the upper surface  71   a  of the head base  71  provided in the head portion  70  is raised while rotating in the clockwise direction around the rotating shaft  73  by the urging force of the torsion spring  75  fitted in the rotating shaft  73  and has reached the protection position P 1  where the thermal print head  32  is protected. 
     Then, when the head periphery-protecting cover  72  has reached the protection position P 1 , the operator starts the setting operation by directing the gauze frame  21  toward the setting direction SD of the gauze frame  21  with the front end portion  21   a  side of this gauze frame  21  at the head while grasping the gauze frame  21  in which the thermal gauze  22  is tightly stretched, from above the head periphery-protecting cover  72 . 
     In addition, when the head periphery-protecting cover  72  has reached the protection position P 1 , the plurality of heat elements  32   a  provided in the thermal print head  32  faces the inside of the opening portion  72   k  formed in this head periphery-protecting cover  72  without protruding from the upper surface  72 Bb of the arm member  72 B. 
     Furthermore, when the head periphery-protecting cover  72  has reached the protection position P 1 , the outer peripheral surface other than the opening portion  72   k  by the cylindrical pipe  72 A and the arm member  72 B of the head periphery-protecting cover  72  protects the periphery other than the plurality of heat elements  32   a  provided in the thermal print head  32 . 
     Moreover, in this first operation, the gauze frame detection sensor  76  mounted on the upper surface  71   a  of the head base  71  is largely separated from the back surface of the right-side arm member  72 B of the head periphery-protecting cover  72  which has risen to the protection position P 1 . Therefore, the controller  39  detects according to the detection result from the gauze frame detection sensor  76  that “there is no gauze frame” and “the head periphery-protecting cover has not reached the protection release position P 2 ”. 
     On the other hand, the thermal gauze detection sensor  78  mounted on the upper surface  71   a  of the head base  71  via the bracket  77  is largely separated from the thermal gauze  22  tightly stretched on the lower surface of the gauze frame  21  during the gauze frame setting operation. Therefore, the controller  39  detects according to the detection result from the thermal gauze detection sensor  78  that “there is no thermal gauze”. 
     Subsequently, in the second operation in the first modification of the second embodiment illustrated in  FIG. 19 , while the cylindrical pipe  72 A of the head periphery-protecting cover  72  provided in the head portion  70  is pressed downward by the gauze frame  21  in a state where the platen opening/closing frame  44  in the platen portion  40  is kept open, the front end portion  21   a  of this gauze frame  21  is mounted abutting against the positioning member  19  and being positioned on this positioning member  19 , fixed and placed on the upper surface  11   a  of the unit housing  11 . 
     After that, the user causes the movable positioning member  14  movable in accordance with the length size of the gauze frame  21  to abut against the rear end portion  21   b  of the gauze frame  21  while positioning the movable positioning member  14 , to thereby mount the rear end portion  21   b  of this gauze frame  21 , and then fixes the movable positioning member  14  by a fixing means not shown. 
     Here, when the operator presses downward the cylindrical pipe  72 A of the head periphery-protecting cover  72  by this gauze frame  21  while grasping the gauze frame  21 , the head periphery-protecting cover  72  is pushed in against the urging force of the torsion spring  75  and rotated around the rotating shaft  73  in the counterclockwise direction and lowered. 
     At this time, the plurality of heat elements  32   a  provided in the thermal print head  32  advances into the opening portion  72   k  of the head periphery-protecting cover  72  and approaches the thermal gauze  22  tightly stretched in the gauze frame  21 . 
     In addition, in this second operation, the gauze frame detection sensor  76  mounted on the upper surface  71   a  of the head base  71  approaches the back surface of the right-side arm member  72 B of the lowered head periphery-protecting cover  72 . 
     At this time, the position of the back surface of the right-side arm member  72 B of the head periphery-protecting cover  72  has not yet reached within the detection range (5 mm±2 mm) of the gauze frame detection sensor  76 . Therefore, the controller  39  detects according to the detection result from the gauze frame detection sensor  76  that “there is no gauze frame” and “the head periphery-protecting cover has not reached the protection release position P 2 ”. 
     On the other hand, the thermal gauze detection sensor  78  mounted on the upper surface  71   a  of the head base  71  via the bracket  77  approaches the thermal gauze  22  tightly stretched on the lower surface of the gauze frame  21  regularly mounted on the movable positioning member  14  and the positioning member  19 . 
     At this time, the position of the thermal gauze  22  has reached within the detection range (5 mm+2 mm) of the thermal gauze detection sensor  78 . Therefore, the controller  39  detects according to the detection result from the thermal gauze detection sensor  78  that “there is thermal gauze”. 
     Next, in the third operation in the first modification of the second embodiment illustrated in  FIG. 20 , the platen opening/closing frame  44  in the platen portion  40  is closed, and the head periphery-protecting cover  72  is further lowered by the pressing piece  46  provided in this platen opening/closing frame  44 . 
     Here, when the operator closes the platen opening/closing frame  44  of the platen portion  40 , the platen roller  42  mounted on this platen opening/closing frame  44  comes into contact with the thermal gauze  22  tightly stretched in the gauze frame  21 , and the locking claw  45  provided in the platen opening/closing frame  44  is locked to the locking pin  18  laterally provided on the inner side of the movable plate  12 . 
     Furthermore, when the platen opening/closing frame  44  in the platen portion  40  is closed, the pressing piece  46  provided in this platen opening/closing frame  44  presses downward the cylindrical pipe  72 A of the head periphery-protecting cover  72 , and thus the head periphery-protecting cover  72  is further pushed in while resisting the urging force of the torsion spring  75  and is rotated around the rotating shaft  73  in the counterclockwise direction, and is further lowered from the position illustrated in  FIG. 15  and reaches the protection release position P 2 . 
     Moreover, in this third operation, the gauze frame detection sensor  76  mounted on the upper surface  71   a  of the head base  71  approaches the back surface of the right-side arm member  72 B of the head periphery-protecting cover  72  pressed by the pressing piece  46  provided in the platen opening/closing frame  44 . 
     At this time, the position of the back surface of the right-side arm member  72 B of the head periphery-protecting cover  72  has reached within the detection range (5 mm±2 mm) of the gauze frame detection sensor  76 . Therefore, the controller  39  detects according to the detection result from the gauze frame detection sensor  76  that “there is gauze frame” and “the head periphery-protecting cover has reached the protection release position P 2 ”. 
     On the other hand, the thermal gauze detection sensor  78  mounted on the upper surface  71   a  of the head base  71  via the bracket  77  further approaches the thermal gauze  22  more than in the second operation, but as in the case of the second operation, the controller  39  detects according to the detection result from the thermal gauze detection sensor  78  that “there is thermal gauze”. 
     After that, stencil making on the thermal gauze  22  can be carried out by moving the thermal print head  32  and the platen roller  42  in the sub-scanning direction of the thermal print head  32  integrally with the movable plate  12 . 
     As described above, in the first modification of the second embodiment, there are provided the gauze frame detection sensor  76  (first detection sensor) detecting that the gauze frame  21  is set by the head periphery-protecting cover  72  when the head periphery-protecting cover  72  (head-protecting member) has moved from the protection position P 1  to the protection release position P 2 , and the thermal gauze detection sensor  78  (second detection sensor) detecting the presence or absence of the thermal gauze  22  when the gauze frame  21  is set in the unit housing  11 . 
     Accordingly, since detection of the presence or absence of the gauze frame  21  formed in a general shape and detection of the presence or absence of the thermal gauze  22  become possible without the use of a gauze frame exclusively for a device specially formed, damage of various constituent members can be previously prevented by grasping an abnormal state in the thermal stencil making unit  10 B, and since stencil making on the thermal gauze  22  can be reliably carried out, and thereby a contribution can be made to enhancement of reliability of the thermal stencil making unit  10 B. 
     Incidentally, in the first to third operations in the first modification of the second embodiment illustrated in  FIGS. 18 to 20 , the operation of detecting the presence or absence of the gauze frame  21  and the presence or absence of the thermal gauze  22  when the gauze frame  21  is to be set in the unit housing  11  is described, but in the first modification of this second embodiment, the presence or absence of the gauze frame  21  and the presence or absence of the thermal gauze  22  are detected also in the middle of making a stencil on th the thermal gauze  22 . 
     The reason for that is that, when the gauze frame  21  is to be mounted on the movable positioning member  14  and the positioning member  19  in the unit housing  11 , as described above, the user causes the front end portion  21   a  side of the gauze frame  21  to abut against the positioning member  19  and to be mounted, causes the movable positioning member  14  movable in accordance with the length size of the gauze frame  21  to abut against the rear end portion  21   b  side of the gauze frame  21  while positioning the movable positioning member  14  to thereby mount the rear end portion  21   b  of this gauze frame  21 , and fixes the movable positioning member  14  by the fixing means not shown. 
     However, because of carelessness of the user, if the user starts stencil making on the thermal gauze  22  while forgetting to fix the movable positioning member  14  movable in accordance with the length size of the gauze frame  21 , there is generated an abnormal situation in which the movable positioning member  14  moves in the middle of stencil making on the thermal gauze  22 , and the gauze frame  21  drops from the movable positioning member  14  or the gauze frame  21  moves forward and backward, and a stencil cannot made onto the thermal gauze  22  normally. 
     Accordingly, in order to previously avoid the abnormal situation by detecting the abnormal stencil making state as above, in the first modification of this second embodiment, the presence or absence detection of the gauze frame  21  and the presence or absence detection of the thermal gauze  22  are carried out via the controller  39  in the setting of the gauze frame and in stencil making on the thermal gauze as illustrated in  FIG. 21  below. 
       FIG. 21  illustrates the gauze frame detection operation and the thermal gauze detection operation in the first modification obtained by partially modifying the thermal stencil making unit according to the second embodiment of the present invention. Note that, in a flow illustrated in  FIG. 21 , determination processing to the gauze frame detection sensor  76  and the thermal gauze detection sensor  78  is carried out in the controller  39 , but illustration of the gauze frame detection sensor  76  and the thermal gauze detection sensor  78  is omitted in the description. 
     As illustrated in  FIG. 21 , after power not shown is turned on, when the gauze frame  21  is to be set in the unit housing  11 , first, whether or not there is the gauze frame is asked at Step S 11 . 
     If a detection result of the gauze frame detection sensor  76  at this Step S 11  is “OFF”, the gauze frame  21  is in a NO state of not being set in the unit housing  11 , and thus the process proceeds to Step S 11  again. 
     On the other hand, if the detection result of the gauze frame detection sensor  76  is “ON” at Step S 11 , the gauze frame  21  is in a YES state of being set in the unit housing  11 , and thus process proceeds to Step S 12 . 
     Subsequently, at Step S 12 , whether or not there is the thermal gauze is asked. 
     If the detection result of the thermal gauze detection sensor  78  is “OFF” at this Step S 12 , the thermal frame  22  is in a NO state of not being tightly stretched in the gauze frame  21 , and thus process proceeds to Step S 13 . 
     Subsequently, at Step S 13 , whether or not there is the thermal gauze is asked again after a certain time has elapsed, with the time when the presence of the gauze frame is detected at Step S 11  as a calculation start point. The reason why whether or not there is the thermal gauze is asked again after the certain time has elapsed from the point of time when the presence of the gauze frame is detected at this Step S 13  is that, in some cases, only the gauze frame  21  is detected while the thermal gauze  22  is not detected, if the gauze frame  21  is not set from the perpendicular direction, or for example, if the gauze frame  21  is set from an oblique direction. 
     In addition, if the detection result of the thermal gauze detection sensor  78  is still “OFF” at Step S 13  even after the certain time has elapsed, the thermal gauze  22  is in a NO state of not being tightly stretched in the gauze frame  21 , and thus “alarm of no thermal gauze is displayed” to the user at Step S 14 . 
     On the other hand, if the detection result of the thermal gauze detection sensor  78  is “ON” at Step S 12  or Step S 13 , the thermal gauze  22  is in a YES state of being tightly stretched in the gauze frame  21 , and thus process proceeds to Step S 15 . 
     Subsequently, whether or not there is an instruction of stencil making to the thermal gauze  22  is asked at Step S 15 . If there is no stencil making instruction at this Step S 15  (in the case of NO), the process returns to Step S 11 . On the other hand, if there is a stencil making instruction at Step S 15  (in the case of YES), the stencil making instruction is made at Step S 16 , and stencil making on the thermal gauze  22  is started. 
     After that, the presence or absence detection of the gauze frame  21  and presence or absence detection of the thermal gauze  22  are carried out during the stencil making on the thermal gauze  22 . 
     Namely, in the thermal gauze stencil-making when the stencil is made on the thermal gauze  22 , whether or not there is the gauze frame is asked at Step S 21 . 
     In a case where it is determined at this Step S 21  from the detection result of the gauze frame detection sensor  76  that there is no gauze frame  21  (in the case of NO), an error display is made at Step S 22 , whereas in a case where it is determined that there is the gauze frame  21  (in the case of YES), whether or not there is the thermal gauze is asked at Step S 23 . 
     In a case where it is determined at this Step S 23  from the detection result of the  10  thermal gauze detection sensor  78  that there is no thermal gauze  22  (in the case of NO), an error display is made at Step S 22 , whereas in a case where it is determined that there is the thermal gauze  22  (in the case of YES), whether or not the stencil making is finished is asked at Step S 24 . 
     In a case where it is determined at this Step S 24  that the stencil making is not finished (in the case of NO), the routine returns to Step S 21 , whereas in a case where it is determined that the stencil making is finished (in the case of YES), this flow is completed by finishing the stencil making on the thermal gauze  22  at Step S 25 . 
     From the above, according to the first modification of the second embodiment, the presence or absence detection of the gauze frame  21  and the presence or absence detection of the thermal gauze  22  are carried out at Steps S 11  to S 15  in the setting of the gauze frame and at Steps S 21  to S 24  in the thermal gauze stencil-making. 
     At this time, particularly, when the user makes a stencil on the thermal gauze  22  while the user forgets to fix the movable positioning member  14  on which the rear end portion  21   b  side of the gauze frame  21  is mounted, there can be detected an abnormal situation in which the movable positioning member  14  moves in the middle of stencil making on the thermal gauze  22  and thus the gauze frame  21  drops from the movable positioning member  14 , or the gauze frame  21  moves back and forth, with the result that a contribution can be made to enhancement of reliability of the first modification of the second embodiment. 
     Note that, although not shown here, in the first embodiment of the present invention described by the use of  FIGS. 1 to 9  and also in the first and second modifications obtained by partially modifying this first embodiment, when the thermal gauze detection sensor (second detection sensor) is mounted on the head base  71  of the head portion  30 , whether or not the head periphery-protecting cover  33  or  60  (head-protecting member) has moved from the protection position P 1  where the thermal print head  32  is protected and has reached the protection release position P 2  is detected by the micro switch  38  (first detection sensor) via the controller  39 , and thereby the flow illustrated in  FIG. 21  can be executed similarly to the first modification of the second embodiment. 
     Second Modification of Second Embodiment 
     Subsequently, there will be described, by the use of  FIG. 22 , a second modification obtained by partially modifying the thermal stencil making unit  10 B according to the second embodiment of the present invention. 
       FIG. 22  perspectively illustrates the second modification obtained by partially modifying the thermal stencil making unit according to the second embodiment of the present invention. 
     In the second modification obtained by partially modifying the thermal stencil making unit according to the second embodiment of the present invention illustrated in  FIG. 22 , only a head-protecting member  82  provided on a head base  81  in a head portion  80  is different from the head-protecting member  72  illustrated in  FIGS. 10 to 16  described above. 
     Namely, as illustrated in  FIG. 22 , the second modification of the second embodiment is different from the second embodiment in that the head-protecting member  82  movable in the vertical direction between the protection position P 1  and the protection release position P 2  is used instead of the rotatable head-protecting member  72  in the second embodiment and the first modification of the second embodiment. 
     In the second modification of this second embodiment, the head-protecting member  82  is a head-periphery-protecting member that has an opening portion  82   k  through which the plurality of heat elements  32   a  provided in the thermal print head  32  advances and retreats and that protects the plurality of heat elements  32   a  at the protection position P 1  where the thermal print head  32  is protected in a periphery on an advance direction side of the gauze frame  21 . At this time, the periphery on the advance direction side of the gauze frame  21  is a periphery other than the opening portion  82   k  of the head periphery-protecting cover  82 . 
     Then, when the head-protecting member  82  (hereinafter, referred to as a head periphery-protecting cover) has reached the protection position P 1 , unlike the first embodiment, the plurality of heat elements  32   a  provided in the thermal print head  32  can be visually recognized without being hidden by the opening portion  82   k  formed in the head periphery-protecting cover  82 , and improvement is made such that the thermal print head  32  is protected when the gauze frame  21  is set, by protection (covering) of the periphery other than the plurality of heat elements  32   a  by the periphery other than the opening portion  82   k  of the head periphery-protecting cover  82 . 
     The head periphery-protecting cover  82  described above is movably provided in a vertical direction (up-and-down direction) between the protection position P 1  and the protection release position P 2  around a pair of right and left rotating shafts  83  and  83  provided across the longitudinal direction (arrow Y-direction) of the thermal print head  32  and in the vicinity of right and left sides on one end side of the thermal print head  32  on the upper surface  81   a  of the head base  81 . 
     Then, the head base  81  obtained by mounting the thermal print head  32  and the head periphery-protecting cover  82  is mounted on the pair of right and left movable plates  12  and  12  reciprocating in the arrow X-direction while facing each other at intervals in the arrow Y-direction which is the main scanning direction of the thermal print head  32 , as in the second embodiment. 
     Here, the head periphery-protecting cover  82  (head-protecting member) serving as an essential part of the second modification of the second embodiment is formed to be lightweight by the use of, for example, a resin material having rigidity and abrasion resistance. 
     In addition, as will be described later, when the gauze frame  21  is to be set from the setting direction SD in a state where the head periphery-protecting cover  82  has risen to the protection position P 1 , an R portion  82   r  is formed on one end side of the flat upper surface  82   a  toward the setting direction SD of the gauze frame  21  and this R portion  82   r  guides the setting of the gauze frame  21  so that the setting can be smoothly carried out without the front end portion  21   a  of the gauze frame  21  being hooked by the head periphery-protecting cover  82 . 
     Furthermore, the opening portion  82   k  that faces the plurality of heat elements  32   a  provided in the thermal print head  32  is largely opened in the upper surface  82   a  of the head periphery-protecting cover  82 . 
     Moreover, a pair of right and left boss portions  82   b  and  82   b  are formed downward on the back surface of the upper surface  82   a  of the head periphery-protecting cover  82  and on an outer side from the right and left side surfaces of the gauze frame  21 , the pair of right and left shafts with screws  83  and  83  are inserted from the upper surface  82   a  side into boss holes not shown, formed in the pair of right and left boss portions  82   b  and  82   b , and male screw portions  83   s  and  83   s  formed below the pair of right and left shafts with screws  83  and  83  are screwed with a pair of right and left female screw portions  81   b  and  81   b  formed in the head base  81 . 
     In addition, a pair of right and left compression springs  84  and  84  are fitted into the pair of right and left boss portions  82   b  and  82   b  provided in the back surface of the upper surface  82   a  of the head periphery-protecting cover  82 , and the pair of these right and left compression springs  84  and  84  are locked between the upper surface  81   a  of the head base  81  and the back surface of the upper surface  82   a  of the head periphery-protecting cover  82 . 
     Accordingly, the head periphery-protecting cover  82  is urged upward by the pair of right and left compression springs  84  and  84  and the height at the protection position P 1  is regulated by head portions  83   a  and  83   a  of the pair of right and left shafts with screws  83  and  83 . 
     Here, there will be described, by the use of  FIGS. 23 to 25 , the operation of the second modification of the second embodiment when the head periphery-protecting cover  82  is supported capable of vertical movement (up-and-down movement) on the head base  81  across the longitudinal direction of the thermal print head  32 , as described above. 
       FIGS. 23 to 25  schematically illustrate first to third operations for describing the operation of the second modification of the second embodiment. 
     Note that, in  FIGS. 23 to 25 , only a right side surface side of the unit is described in illustration, and description for a left side surface side symmetric to the right side surface side will be omitted. 
     Moreover, in  FIGS. 23 to 25 , on a front of the head portion  80  in the second modification of the second embodiment, unlike the first embodiment, the positioning member  19  that positions the front end portion  21   a  side of the gauze frame  21  and causes the front end portion  21   a  side of the gauze frame  21  to be mounted is assumed to be fixed and placed on the upper surface  11   a  of the unit housing  11 . 
     First, in the first operation in the second modification of the second embodiment illustrated in  FIG. 23 , the platen opening/closing frame  44  in the platen portion  40  is in the open state around the rotating shaft  16 . In this state, the head periphery-protecting cover  82  mounted, via the shaft with screw  83 , on the upper surface  81   a  of the head base  81  provided in the head portion  80  is raised in the vertical direction by the urging force of the compression spring  84  fitted into the boss portion  82   b  and has reached the protection position P 1  where the thermal print head  32  is protected. 
     At this time, since the head portion  83   a  of the shaft with screw  83  comes into contact with the upper surface  82   a  of the head periphery-protecting cover  82 , the height of the head periphery-protecting cover  82  at the protection position P 1  is regulated. 
     Then, when the head periphery-protecting cover  82  has reached the protection position P 1 , the operator starts the setting operation by directing the gauze frame  21  toward the setting direction SD of the gauze frame  21  with the front end portion  21   a  side of this gauze frame  21  at the head while grasping the gauze frame  21  in which the thermal gauze  22  is tightly stretched, from above the head periphery-protecting cover  82 . 
     At this time, since the R portion  82   r  of the head periphery-protecting cover  82  is directed to the setting direction SD of the gauze frame  21  and guides the setting of the gauze frame  21 , the setting operation can be smoothly carried out even if the front end portion  21   a  of the gauze frame  21  comes into contact with the R portion  82   r  of the head periphery-protecting cover  82 . 
     In addition, when the head periphery-protecting cover  82  has reached the protection position P 1 , the plurality of heat elements  32   a  provided in the thermal print head  32  is faced with an inside of the opening portion  82   k  formed in this head periphery-protecting cover  82  without protruding from the upper surface  82   a  of the head periphery-protecting cover  82 . 
     Moreover, when the head periphery-protecting cover  82  has reached the protection position P 1 , the outer peripheral surface other than the opening portion  82   k  of the head periphery-protecting cover  82  protects the periphery other than the plurality of heat elements  32   a  provided in the thermal print head  32 . 
     From the above, when the head periphery-protecting cover  82  has reached the protection position P 1 , the operator can observe the state of the plurality of heat elements  32   a  provided in the thermal print head  32  through the opening portion  82   k  from above the head periphery-protecting cover  82 . 
     Accordingly, a harmful stain such as deposits deposited on the plurality of heat elements  32   a  in the previous stencil making of the thermal gauze  22  can be visually checked, and the harmful stain can be cleaned before stencil making this time, and thus a stencil making operation onto the thermal gauze  22  can be favorably carried out in the stencil making this time. 
     Subsequently, in the second operation in the second modification of the second embodiment illustrated in  FIG. 24 , while the upper surface  82   a  of the head periphery-protecting cover  82  provided in the head portion  80  is pressed downward by the gauze frame  21  in a state where the platen opening/closing frame  44  in the platen portion  40  is kept open, the front end portion  21   a  of this gauze frame  21  is mounted abutting while being positioned against the positioning member  19  fixed and placed on the upper surface  11   a  of the unit housing  11 . Moreover, the movable positioning member  14  movable in accordance with the length size of the gauze frame  21  is caused to abut against the rear end portion  21   b  of the gauze frame  21  while being positioned and allows the rear end portion  21   b  side of this gauze frame  21  to be mounted. 
     Here, when the operator presses the head periphery-protecting cover  82  downward by this gauze frame  21  while grasping the gauze frame  21 , the head periphery-protecting cover  82  is pushed in while resisting the urging force of the compression spring  84  and lowered in the vertical direction. 
     At this time, the plurality of heat elements  32   a  provided in the thermal print head  32  advances into the opening portion  82   k  of the head periphery-protecting cover  82  and approaches the thermal gauze  22  tightly stretched in the gauze frame  21 . 
     Next, i in the third operation in the second modification of the second embodiment illustrated in  FIG. 25 , the platen opening/closing frame  44  in the platen portion  40  is closed, and the head periphery-protecting cover  82  is further lowered by  15  the pressing piece  46  provided in this platen opening/closing frame  44 . 
     Here, when the operator closes the platen opening/closing frame  44  of the platen portion  40 , the platen roller  42  mounted on this platen opening/closing frame  44  comes into contact with the thermal gauze  22  tightly stretched in the gauze frame  21 , and the locking claw  45  provided in the platen opening/closing frame  44  is locked to the locking pin  18  laterally provided on the inner side of the movable plate  12 . 
     When the platen opening/closing frame  44  in the platen portion  40  is closed, the pressing piece  46  provided in this platen opening/closing frame  44  presses the head periphery-protecting cover  82  downward and thus, the head periphery-protecting cover  82  is further pushed in while resisting the urging force of the compression spring  84  and is further lowered in the vertical direction from the position illustrated in  FIG. 24  and reaches the protection release position P 2 . 
     Then, the plurality of heat elements  32   a  provided in the thermal print head  32  protrudes upward from the inside of the opening portion  82   k  of the head periphery-protecting cover  82  and comes into contact with the thermal gauze  22  tightly stretched in the gauze frame  21 , and thus the thermal gauze  22  is sandwiched between the plurality of heat elements  32   a  and the platen roller  42 . 
     After that, stencil making on the thermal gauze  22  can be carried out by moving the thermal print head  32  and the platen roller  42  in the sub-scanning direction of the thermal print head  32  integrally with the movable plate  12 . 
     It is needless to say that, when the gauze frame  21  is not set in the unit housing  11 , the head periphery-protecting cover  82  is automatically returned from the protection release position P 2  to the protection position P 1  by the urging force of the compression spring  84 . 
     Moreover, also in the second modification of the second embodiment, the gauze frame detection sensor (first detection sensor) and the thermal gauze detection sensor (second detection sensor), not shown, are mounted on the head base  81  in the head portion  80 , and thereby the flow illustrated in  FIG. 21  can be executed similarly to the first modification of the second embodiment. 
     In the first and second embodiments described above, there is adopted a structural form in which the thermal gauze  22  tightly stretched in the gauze frame  21  is fixed and the thermal print head  32  and the platen roller  42  are moved in the sub-scanning direction, but this is not limiting, and there can also be adopted a structural form in which the thermal print head  32  is fixed and the gauze frame  21  is moved integrally with the thermal gauze  22  in the sub-scanning direction. 
     Moreover, although not shown here, there can also be adopted a structural form in which, without provision of the platen roller, only the thermal print head is brought into contact with the thermal gauze for stencil making, tightly stretched by application of a gauze-strained tension in the gauze frame. 
     Therefore, the thermal stencil making units  10 A and  10 B according to the first and second embodiments of the present invention may have a structural form in which, while the thermal gauze  22  tightly stretched in the gauze frame  21  detachably set in the unit housing  11  and the thermal print head  32  having the plurality of heat elements  32   a  are relatively moved, the plurality of heat elements  32   a  is selectively heated and driven in accordance with the image information to thereby make a stencil of a perforated image on the thermal gauze  22 . 
     At this time, the thermal print head  32  and the head-protecting cover  33  are provided on the side where the gauze frame  21  is set in order to move each of the head-protecting members  33 ,  60 ,  72 , and  82  from the protection position P 1  to the protection release position P 2  in conjunction with the setting operation of the gauze frame  21 . 
     Furthermore, in the first and second embodiments, although not shown here, a configuration can also be such that, for example, when the user starts the setting of the gauze frame, this gauze frame is detected by a proximity sensor placed in the unit or the like and the head-protecting member in the first and second embodiments is automatically moved by an actuator from the protection position P 1  to the protection release position P 2 . 
     The above-described embodiments of the present invention are only exemplifications described in order to facilitate understanding of the present invention, and the present invention is not limited to the embodiment. A technical scope of the present invention is not limited to specific technical matters disclosed in the embodiments but also includes various modifications, changes, alternative technologies and the like which can be easily derived from there. 
     The present application claims priority based on Japanese Patent Application No. 2016-059631 filed on Mar. 24, 2016 and priority based on Japanese Patent Application No. 2016-145340 filed on Jul. 25, 2016 and the entire content of these applications is incorporated herein by reference. 
     INDUSTRIAL APPLICABILITY 
     According to the present invention, without generation of a human error by the operator in the setting of the gauze frame, the thermal print head can be reliably protected by the head-protecting member that has reached the protection position, and furthermore, the head-protecting member can be reliably moved from the protection position to the protection release position against the urging means in conjunction with the setting operation of the gauze frame. Moreover, when the gauze frame is not set in the unit housing, the head-protecting cover can be automatically returned from the protection release position to the protection position by the urging means.