Patent Publication Number: US-7593027-B2

Title: Image generating apparatus

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an image generating apparatus. 
   2. Description of the Background Art 
   An image generating apparatus comprising various rotating shafts are known in general, as disclosed in each of Japanese Patent Laying-Open Nos. 2005-219310, 2004-114588, 2001-271826, 06-317975 (1994) and 08-225182 (1996), for example. 
   The aforementioned Japanese Patent Laying-Open No. 2005-219310 discloses a thermal transfer sheet cassette (ink sheet cartridge) comprising a columnar take-up core for taking up a thermal transfer sheet (ink sheet) and a take-up core holding portion. In the thermal transfer sheet cassette described in Japanese Patent Laying-Open No. 2005-219310, two cylindrical members are inserted into both ends of the take-up core, while a coil spring is set in the cylindrical member provided on one of the ends of the take-up core. The coil spring and the two cylindrical members keep the position of the take-up core. 
   The aforementioned Japanese Patent Laying-Open No. 2004-114588 discloses a thermal printer (image generating apparatus) comprising a thermal head for printing images on papers, a shaft (shaft portion) for rotatably mounting the thermal head on the printer body and a fixture for keeping the position of the shaft. In the thermal printer described in Japanese Patent Laying-Open No. 2004-114588, the shaft is inserted into axial holes provided on both ends of the thermal head respectively to pass through the same. At this time, the fixture is mounted from outside one of the axial holes of the thermal head to block up this axial hole, so that an end of the shaft passing through the axial holes comes into contact with the fixture. Thus, the fixture comes into contact with the shaft, thereby keeping the position of the shaft in the thermal head. 
   The aforementioned Japanese Patent Laying-Open No. 2001-271826 discloses an image generating apparatus comprising a paper feed support shaft including a paper feed roller for feeding recording sheets (printing papers) to the body of the apparatus and two bearing set portions including bearings for supporting the paper feed support shaft respectively. In the image generating apparatus described in Japanese Patent Laying-Open No. 2001-271826, the paper feed support shaft is inserted into holes provided in the bearings of the bearing set portions while two clasps are arranged on the paper feed support shaft to hold one of the bearings therebetween, thereby keeping the position of the paper feed support shaft on the bearing set portions. 
   The aforementioned Japanese Patent Laying-Open No. 06-317975 discloses an image generating apparatus comprising a roller shaft of metal, a slide bearing for rotatably supporting the roller shaft and a bearing slide guide pawl for holding the slide bearing. In the image generating apparatus described in Japanese Patent Laying-Open No. 06-317975, the slide bearing includes a hole for receiving the roller shaft, while the hole has a stopper for preventing the roller shaft from slipping off the hole. The bearing slide guide pawl formed on the body of the image generating apparatus holds the slide bearing, thereby fixing the same. 
   The aforementioned Japanese Patent Laying-Open No. 08-225182 discloses an image generating apparatus comprising a chassis so formed as to cover the body of the apparatus, a transport roller for transporting sheets (papers) to the body of the apparatus, two plastic bearings having holes and an L-shaped wire spring. In the image generating apparatus described in Japanese Patent Laying-Open No. 08-225182, the bearings are mounted by fitting both side ends of the transport roller into the holes of the bearings respectively, and thereafter fitting the portions of the bearings mounted on the transport roller into holes of the chassis. The center of the L-shaped wire spring is engaged with a groove provided in one of the bearings while both ends of the L-shaped wire spring are urged against the chassis respectively, thereby keeping the position of the transport roller on the chassis. 
   In the thermal transfer sheet cassette described in the aforementioned Japanese Patent Laying-Open No. 2005-219310, however, the coil spring and the two cylindrical members must be separately provided in order to keep the position of the take-up core, whereby the number of components is disadvantageously increased. 
   In the thermal printer described in the aforementioned Japanese Patent Laying-Open No. 2004-114588, the fixture must be separately provided in order to keep the position of the shaft, whereby the number of components is disadvantageously increased. 
   In the image generating apparatus described in the aforementioned Japanese Patent Laying-Open No. 2001-271826, the two clasps must be separately provided in order to keep the position of the paper feed support shaft, whereby the number of components is disadvantageously increased. 
   In the image generating apparatus described in the aforementioned Japanese Patent Laying-Open No. 06-317975, the slide bearing must be separated in order to support the roller shaft, whereby the number of components is disadvantageously increased. 
   In the image generating apparatus described in the aforementioned Japanese Patent Laying-Open No. 08-225182, the two bearings and the wire spring must be separately provided respectively in order to keep the position of the transport roller, whereby the number of components is disadvantageously increased. 
   SUMMARY OF THE INVENTION 
   The present invention has been proposed in order to solve the aforementioned problems, and an object of the present invention is to provide an image generating apparatus capable of keeping the position of a shaft without increasing the number of components. 
   An image generating apparatus according to a first aspect of the present invention comprises a chassis detachably mounted with an ink sheet cartridge storing an ink sheet and integrally provided with a first bearing, a print head rotatably mounted on the chassis, a print head pressing member, including a shaft held by the first bearing, pressing the print head, a cartridge stop member provided on a first side surface of the chassis for engaging with the ink sheet cartridge thereby preventing the ink sheet cartridge from slipping off the chassis and a side plate, provided on a second side surface of the chassis, integrally including at least a second bearing of a paper feed roller, while the cartridge stop member provided on the first side surface of the chassis integrally includes a first shaft stop portion coming into contact with a first end surface of the shaft of the print head pressing member, and the side plate provided on the second side surface of the chassis integrally includes a second shaft stop portion coming into contact with a second end surface of the shaft of the print head pressing member. 
   In the image generating apparatus according to the first aspect, as hereinabove described, the first bearing is integrally provided on the chassis while the cartridge stop member integrally including the first shaft stop portion is provided on the first side surface of the chassis and the side plate integrally including the second shaft stop portion is provided on the second side surface of the chassis so that the first and second shaft stop portions for holding the shaft of the print head pressing member are integrally included in the cartridge stop member and the side plate respectively and the first bearing is integrally provided on the chassis, whereby no member may be separately provided for holding the shaft of the print head pressing member on the chassis. Therefore, increase in the number of components can be suppressed. Further, both end surfaces of the shaft of the print head pressing member are brought into contact with the first shaft stop portion of the cartridge stop member and the second shaft stop portion of the side plate respectively and supported by the first bearing of the chassis, whereby the shaft of the print head printing member can be held without newly providing a separate member. 
   In the aforementioned image generating apparatus according to the first aspect, the second shaft stop portion preferably includes a shaft pressing portion elastically deformable in a first direction intersecting with the axis of the shaft and pressed in the first direction by a peripheral surface of the shaft close to a second end thereof when the shaft is mounted on the first bearing of the chassis. According to this structure, the shaft can be easily mounted on the first bearing of the chassis by pressing the elastically deformable shaft pressing portion of the second shaft stop portion with the peripheral surface of the shaft close to the second end thereof. 
   In the aforementioned image generating apparatus according to the first aspect, the second shaft stop portion is preferably provided with a contact portion, coming into contact with the second end surface of the shaft, on a position separated from a side surface of the shaft pressing portion closer to the shaft by a prescribed length outwardly from the shaft to be continuous with the shaft pressing portion. According to this structure, the second end surface of the shaft can be brought into contact with the contact portion, whereby the shaft can be inhibited from slipping off the body of the image generating apparatus. Therefore, the position of the shaft can be reliably kept. 
   In the aforementioned image generating apparatus according to the first aspect, the thickness of the contact portion in the first direction intersecting with the axis of the shaft is preferably larger than the corresponding thickness of the second shaft stop portion. According to this structure, the contact area between the contact portion and the second end surface of the shaft of the print head pressing portion can be so increased that the shaft can be reliably inhibited from slipping off the first bearing. 
   In the aforementioned image generating apparatus according to the first aspect, the second shaft stop portion is preferably so formed that the width in the axial direction of the shaft is larger than the thickness in the direction intersecting with the axis of the shaft. According to this structure, the second shaft stop portion can be inhibited from deformation in the axial direction of the shaft, whereby the shaft can be inhibited from slipping off the first bearing in the axial direction. Consequently, the shaft can be reliably held. 
   In the aforementioned image generating apparatus according to the first aspect, the first bearing preferably includes an L-shaped notch having a vertically extending first portion and a second portion horizontally extending from the first portion, for holding the shaft in the vicinity of the forward end of the second portion of the L-shaped notch. According to this structure, the horizontally provided second portion regulates vertical movement of the shaft, whereby the shaft can be reliably held. 
   The aforementioned image generating apparatus according to the first aspect preferably further comprises a platen roller opposed to the print head and a heat radiating member mounted on the print head for radiating heat generated in the print head, while the heat radiating member is preferably integrally provided with a push-up portion pushed up by the print head pressing member upon rotation of the print head pressing member, and the print head pressing member preferably so pushes up the push-up portion of the heat radiating member upon rotation of the print head pressing member as to move the heat radiating member and the print head in a direction for separating from the platen roller. According to this structure, the print head pressing member pushes up the push-up portion by the rotational force upon rotation thereof, whereby the heat radiating member and the print head can be easily rotated in the direction for separating from the platen roller with no requirement for a transmission mechanism so provided as to transmit the rotational force of the print head pressing member to the heat radiating member and the print head. Consequently, increase in the number of components can be further suppressed. 
   In this case, the print head pressing member preferably presses the print head toward the platen roller in printing, and the heat radiating member preferably includes a deviation preventing portion preventing the print head pressing member from deviating in the rotational direction when the print head pressing member presses the print head toward the platen roller in printing. According to this structure, the print head pressing member does not deviate in the rotational direction in printing, thereby reliably pressing the print head toward the platen roller. 
   In the aforementioned image generating apparatus according to the first aspect, the body of the print head pressing member is preferably made of resin. According to this structure, noise caused in the print head pressing member when sliding with the shaft of metal upon rotation can be suppressed as compared with a case where the print head pressing member is made of metal. 
   An image generating apparatus according to a second aspect of the present invention comprises a chassis detachably mounted with an ink sheet cartridge storing an ink sheet, a print head rotatably mounted on the chassis, a first bearing, integrally provided on the chassis, constituted of an L-shaped notch, a print head pressing member, including a shaft held by the first bearing, pressing the print head, a cartridge stop member provided on a first side surface of the chassis for engaging with the ink sheet cartridge thereby preventing the ink sheet cartridge from slipping off the chassis and a side plate, provided on a second side surface of the chassis, integrally including at least a second bearing of a paper feed roller, while the cartridge stop member provided on the first side surface of the chassis integrally includes a first shaft stop portion coming into contact with a first end surface of the shaft of the print head pressing member, the side plate provided on the second side surface of the chassis integrally includes a second shaft stop portion coming into contact with a second end surface of the shaft of the print head pressing member, the second shaft stop portion includes a shaft pressing portion elastically deformable in a first direction intersecting with the axis of the shaft and pressed in the first direction by a peripheral surface of the shaft close to a second end thereof when the shaft is mounted on the first bearing of the chassis, the second shaft stop portion of the side plate further includes a contact portion provided on a position separated from a side surface of the shaft pressing portion closer to the shaft by a prescribed length outwardly from the shaft to be continuous with the shaft pressing portion for coming into contact with the second end surface of the shaft, and the thickness of the contact portion of the second shaft stop portion in the first direction intersecting with the axis of the shaft is larger than the corresponding thickness of the second shaft stop portion. 
   In the image generating apparatus according to the second aspect, as hereinabove described, the first bearing is integrally provided on the chassis while the cartridge stop member integrally including the first shaft stop portion is provided on the first side surface of the chassis and the side plate integrally including the second shaft stop portion is provided on the second side surface of the chassis so that the first and second shaft stop portions for holding the shaft of the print head pressing member are integrally included in the cartridge stop member and the side plate respectively and the first bearing is integrally provided on the chassis, whereby no member may be separately provided for holding the shaft of the print head pressing member on the chassis. Therefore, increase in the number of components can be suppressed. Further, both end surfaces of the shaft of the print head pressing member are brought into contact with the first shaft stop portion of the cartridge stop member and the second shaft stop portion of the side plate respectively and supported by the first bearing of the chassis, whereby the shaft of the print head printing member can be held without newly providing a separate member. 
   In the image generating apparatus according to the second aspect, further, the second shaft stop portion includes the shaft pressing portion elastically deformable in the first direction intersecting with the axis of the shaft and pressed in the first direction by the peripheral surface of the shaft close to the second end thereof when the shaft is mounted on the first bearing of the chassis, whereby the shaft can be easily mounted on the first bearing of the chassis by pressing the elastically deformable shaft pressing portion of the second shaft stop portion with the peripheral surface of the shaft close to the second end thereof. In addition, the second shaft stop portion is provided with the contact portion, coming into contact with the second surface of the shaft, on the position separated from the side surface of the shaft pressing portion closer to the shaft by the prescribed length outwardly from the shaft to be continuous with the shaft pressing portion so that the second end surface of the shaft can be brought into contact with the contact portion, whereby the shaft can be inhibited from slipping off the body of the image generating apparatus. Therefore, the position of the shaft can be reliably kept. Further, the thickness of the contact portion in the first direction intersecting with the axis of the shaft is larger than the corresponding thickness of the second shaft stop portion, whereby the contact area between the contact portion and the second end surface of the shaft of the print head pressing portion can be so increased that the shaft can be reliably inhibited from slipping off the first bearing. 
   In the aforementioned image generating apparatus according to the second aspect, the second shaft stop portion is preferably so formed that the width in the axial direction of the shaft is larger than the width in the first direction intersecting with the axis of the shaft. According to this structure, the second shaft stop portion can be inhibited from deformation in the axial direction of the shaft, whereby the shaft can be inhibited from slipping off the first bearing in the axial direction. Consequently, the shaft can be reliably held. 
   In the aforementioned image generating apparatus according to the second aspect, the first bearing preferably includes the L-shaped notch having a vertically extending first portion and a second portion horizontally extending from the first portion, for holding the shaft in the vicinity of the forward end of the second portion of the L-shaped notch. According to this structure, the horizontally provided second portion regulates vertical movement of the shaft, whereby the shaft can be reliably held. 
   The aforementioned image generating apparatus according to the second aspect preferably further comprises a platen roller opposed to the print head and a heat radiating member mounted on the print head for radiating heat generated in the print head, while the heat radiating member is preferably integrally provided with a push-up portion pushed up by the print head pressing member upon rotation of the print head pressing member, and the print head pressing member preferably so pushes up the push-up portion of the heat radiating member upon rotation of the print head pressing member as to move the heat radiating member and the print head in a direction for separating from the platen roller. According to this structure, the print head pressing member pushes up the push-up portion by the rotational force upon rotation thereof, whereby the heat radiating member and the print head can be easily rotated in the direction for separating from the platen roller with no requirement for a transmission mechanism so provided as to transmit the rotational force of the print head pressing member to the heat radiating member and the print head. Consequently, increase in the number of components can be further suppressed. 
   In this case, the print head pressing member preferably presses the print head toward the platen roller in printing, and the heat radiating member preferably includes a deviation preventing portion preventing the print head pressing member from deviating in the rotational direction when the print head pressing member presses the print head toward the platen roller in printing. According to this structure, the print head pressing member does not deviate in the rotational direction in printing, thereby reliably pressing the print head toward the platen roller. 
   In the aforementioned image generating apparatus according to the second aspect, the body of the print head pressing member is preferably made of resin. According to this structure, noise caused in the print head pressing member when sliding with the shaft of metal upon rotation can be suppressed as compared with a case where the print head pressing member is made of metal. 
   The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view showing the overall structure of a sublimatic printer according to a first embodiment of the present invention; 
       FIG. 2  is an exploded perspective view showing the overall structure of the sublimatic printer according to the first embodiment of the present invention shown in  FIG. 1 ; 
       FIG. 3  is a perspective view of the sublimatic printer according to the first embodiment of the present invention shown in  FIG. 1 ; 
       FIG. 4  is a plan view of the sublimatic printer according to the first embodiment of the present invention shown in  FIG. 1 ; 
       FIG. 5  is a sectional view of the sublimatic printer according to the first embodiment of the present invention shown in  FIG. 1 ; 
       FIG. 6  illustrates the arrangement of gears in the sublimatic printer according to the first embodiment of the present invention shown in  FIG. 1 ; 
       FIG. 7  is an enlarged perspective view showing a side plate mounted on a first side surface of the sublimatic printer according to the first embodiment of the present invention shown in  FIG. 1 ; 
       FIGS. 8 and 9  are entire perspective views of the side plate mounted on the first side surface of the sublimatic printer according to the first embodiment of the present invention shown in  FIG. 1 ; 
       FIG. 10  is an entire perspective view showing another side plate mounted on a second side surface of the sublimatic printer according to the first embodiment of the present invention shown in  FIG. 1 ; 
       FIG. 11  is a plan view showing a second shaft stop portion provided on the side plate shown in  FIG. 10 ; 
       FIG. 12  is a side elevational view showing the second shaft stop portion provided on the side plate shown in  FIG. 10 ; 
       FIG. 13  is a perspective view of a print head pressing member mounted on the sublimatic printer according to the first embodiment of the present invention shown in  FIG. 1 ; 
       FIG. 14  is an exploded perspective view of the print head pressing member mounted on the sublimatic printer according to the first embodiment of the present invention shown in  FIG. 1 ; 
       FIG. 15  is a perspective view for illustrating a method of mounting the print head pressing member on the sublimatic printer according to the first embodiment of the present invention shown in  FIG. 1 ; 
       FIG. 16  is a sectional view for illustrating the method of mounting the print head pressing member on the sublimatic printer according to the first embodiment of the present invention shown in  FIG. 1 ; 
       FIG. 17  is a perspective view for illustrating the method of mounting the print head pressing member on the sublimatic printer according to the first embodiment of the present invention shown in  FIG. 1 ; 
       FIG. 18  is a sectional view for illustrating the method of mounting the print head pressing member on the sublimatic printer according to the first embodiment of the present invention shown in  FIG. 1 ; 
       FIG. 19  is a perspective view for illustrating the method of mounting the print head pressing member on the sublimatic printer according to the first embodiment of the present invention shown in  FIG. 1 ; 
       FIG. 20  is a sectional view for illustrating the method of mounting the print head pressing member on the sublimatic printer according to the first embodiment of the present invention shown in  FIG. 1 ; 
       FIGS. 21 and 22  are perspective views for illustrating the method of mounting the print head pressing member on the sublimatic printer according to the first embodiment of the present invention shown in  FIG. 1 ; 
       FIG. 23  is a diagram for illustrating an operation of the sublimatic printer according to the first embodiment of the present invention shown in  FIG. 1 ; 
       FIG. 24  is a perspective view showing the overall structure of a sublimatic printer according to a second embodiment of the present invention; 
       FIGS. 25 and 26  are perspective views for illustrating a print head pressing member of the sublimatic printer according to the second embodiment of the present invention shown in  FIG. 24 ; and 
       FIGS. 27 to 29  are sectional views of the sublimatic printer according to the second embodiment of the present invention shown in  FIG. 24 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Embodiments of the present invention are now described with reference to the drawings. 
   First Embodiment 
   First, the structure of a sublimatic printer  90  according to a first embodiment of the present invention is described with reference to  FIGS. 1 to 22 . According to the first embodiment, the present invention is applied to the sublimatic printer  90  employed as an exemplary image generating apparatus. 
   As shown in  FIG. 1 , the sublimatic printer  90  according to the first embodiment of the present invention comprises a chassis  1  of metal (sheet metal), a print head  2  for printing images, a platen roller  3  (see  FIG. 5 ) opposed to the print head  2 , a feed roller  4  (see  FIG. 5 ) of metal, a press roller  5  (see  FIG. 5 ) of metal pressing the feed roller  4  with prescribed pressing force, a print head pressing member  6 , including a shaft  6   a , pressing the print head  2 , a driving gear  7  (see  FIG. 4 ) of resin constituted of a small-diametral gear  7   a  and a large-diametral gear  7   b , a feed roller gear  8  (see  FIGS. 2 and 6 ), a lower paper guide  9   a  of resin, an upper paper guide  9   b  (see  FIG. 5 ) of resin, a paper feed roller  10  of rubber, a paper feed roller gear  11  (see  FIGS. 2 and 6 ), a paper discharge roller  12  of rubber, a paper discharge roller gear  13  (see  FIGS. 2 and 6 ) and a take-up reel  14  (see  FIG. 2 ). 
   The sublimatic printer  90  further comprises a motor bracket  15  (see  FIG. 2 ) of sheet metal, a stepping motor  16  (see  FIG. 2 ) for transporting papers  60 , another stepping motor  17  (see  FIG. 2 ) serving as the driving source for rotating the print head  2 , a swingable swing gear  18  (see  FIGS. 2 and 6 ), a plurality of intermediate gears  19  to  22  (see  FIGS. 2 and 6 ), a cartridge support portion  23  supporting an ink sheet cartridge  50  storing an ink sheet  51 , a top plate  24  and a housing  80  (see  FIG. 3 ) storing the chassis  1  therein. The ink sheet cartridge  50  and a paper feed cassette case  70  for storing the papers  60  supplied to the sublimatic printer  90  are detachably mounted on the sublimatic printer  90  according to the first embodiment. 
   As shown in  FIG. 1 , the chassis  1  has a first side surface  1   a  and a second side surface  1   b  opposed to each other and a bottom surface  1   c . The first side surface  1   a  of the chassis  1  is provided with a cartridge receiving hole  1   d  for receiving the ink sheet cartridge  50  and a support hole  1   e  (see  FIG. 2 ) supporting a first end of the shaft  6   a  of the print head pressing member  6 . 
   According to the first embodiment, the second side surface  1   b  of the chassis  1  is integrally provided with an L-shaped bearing if formed by notching the second side surface  1   b  in an L-shaped manner, in order to support a second end (along arrow Z in  FIG. 2 ) of the shaft  6   a  of the print head pressing member  6 , as shown in  FIG. 2 . The L-shaped bearing if is constituted of a vertical portion extending in the vertical direction (along arrow X 1 ) and a horizontal portion extending in the horizontal direction (perpendicular to the direction along arrow X 1 ). The L-shaped bearing  1   f  is an example of the “first bearing” in the present invention. 
   According to the first embodiment, a side plate  26  of resin integrally provided with a cartridge stop member  25  (see  FIGS. 1 and 3 ) engaging with the ink sheet cartridge  50  thereby preventing the ink sheet cartridge  50  from slipping off the chassis  1  is mounted on the first side surface  1   a  of the chassis  1 , as shown in  FIG. 1 . The side plate  26  is further integrally provided with a platen roller bearing  26   a  and a feed roller bearing  26   b  (see  FIGS. 8 and 9 ) extending toward the inner side of the chassis  1  respectively, for supporting first ends (along arrow Y in  FIG. 2 ) of the platen roller  3  and the feed roller  4  through holes (not shown) provided in the chassis  1  respectively, as shown in  FIG. 2 . Another side plate  27  of resin integrally including a platen roller bearing  27   a  supporting a second end (along arrow Z in  FIG. 2 ) of the platen roller  3 , a feed roller bearing  27   b  supporting the feed roller  4 , a paper feed roller gear bearing  27   c  supporting the paper feed roller gear  11 , a paper discharge roller gear bearing  27   d  supporting the paper discharge roller gear  13  and intermediate gear bearings  27   e  to  27   h  supporting the intermediate gears  19  to  22  respectively is mounted on the second side surface  1   b  of the chassis  1 . 
   According to the first embodiment, the cartridge stop member  25  integrally provided on the side plate  26  mounted on the first side surface  1   a  of the chassis  1  integrally includes a first shaft stop portion  25   a  coming into contact with a first end surface of the shaft  6   a  of the print head pressing member  6 , as shown in  FIGS. 7 to 9 . 
   According to the first embodiment, the side plate  27  integrally provided with the platen roller bearing  27   a  supporting the second end of the platen roller  3  and the like integrally includes a second shaft stop portion  27   i , as shown in  FIGS. 2 and 10 . 
   According to the first embodiment, the second shaft stop portion  27   i  of the side plate  27  includes a shaft pressing portion  27   j  and a contact portion  27   k , as shown in  FIGS. 10 and 11 . The shaft pressing portion  27   j  of the second shaft stop portion  27   i  is elastically deformable in a direction (along arrow X 1  in  FIG. 10 ) perpendicular to the shaft  6   a  of the print head pressing member  6 , and pressed by a peripheral surface of the shaft  6   a  of the print head pressing member  6  close to the second end (along arrow Z in  FIG. 2 ) thereof along arrow X 1  when the shaft  6   a  is mounted on the L-shaped bearing  1   f  of the chassis  1 . The contact portion  27   k  of the second shaft stop portion  27   i  is provided on a position separated from the side of the shaft pressing portion  27   j  closer to the shaft  6   a  of the print head pressing member  6  by a prescribed length (length L in  FIG. 11 ) outward from the shaft  6   a  to be continuous with the shaft pressing portion  27   j  as shown in  FIG. 11 , to come into contact with a second end surface of the shaft  6   a.    
   According to the first embodiment, the thickness t 1  of the contact portion  27   k  of the second shaft stop portion  27   i  in a direction (along arrow X 1 ) intersecting with the axis of the shaft  6   a  of the print head pressing member  6  is larger than the corresponding thickness t 2  of the second shaft stop portion  27   i , as shown in  FIG. 12 . The second shaft stop portion  27   i  is so formed that the width W in the axial direction (along arrow Z) of the shaft  6   a  is larger than the thicknesses (t 1  and t 2  in  FIG. 12 ) along arrow X 1  as shown in  FIG. 11 , to be hardly elastically deformable in the axial direction (along arrow Z) of the shaft  6   a.    
   As shown in  FIGS. 13 and 14 , the print head pressing member  6  mounted on the chassis  1  is constituted of the shaft  6   a  of metal, a rotational portion  6   b  of metal and a pressing portion  6   c  of resin. The rotational portion  6   b  of metal is formed by performing sheet metal working on a plate member, and provided with receiving holes  6   d  for receiving the shaft  6   a  on both ends thereof respectively. A threaded hole  6   e  for mounting the pressing portion  6   c  with a screw  28  is provided on the side of the rotational portion  6   b  opposed to the first side surface  1   a  of the chassis  1 . The pressing portion  6   c  is fixed to the rotational portion  6   b  by meshing the screw  28  with the threaded hole  6   e  of the rotational portion  6   b  through another threaded hole  6   f  of the pressing portion  6   c . A gear portion  6   g  is provided on the side opposed to the second side surface  1   b  of the chassis  1 . The pressing portion  6   c  is provided with a boss-shaped engaging portion  6   h  engaging with a notch  2   e  of the print head  2  described later in a projecting manner. 
   As shown in  FIGS. 4 and 7  to  9 , the cartridge stop member  25  integrally provided on the side plate  26  is provided with the aforementioned first shaft stop portion  25   a , a support shaft  25   b  rotatably supporting the cartridge stop member  25 , an engaging pawl  25   c  engaging with an engaging portion  53   e  (see  FIGS. 1 and 3 ) of the ink sheet cartridge  50  described later, a grasp portion  25   d  employed by the user for lifting the cartridge stop member  25  upward (along arrow B 1  in  FIG. 7 ) with his/her finger and a spring portion  25   e  applying urging force for rotating the engaging pawl  25   c  of the cartridge stop member  25  downward (along arrow C 1  in  FIG. 7 ) when the user lifts up the grasp portion  25   d . When the user lifts up the grasp portion  25   d  of the cartridge stop member  25 , the cartridge stop member  25  slides upward along a hole  1   g  (see  FIGS. 1 and 3 ) of the first side surface  1   a  of the chassis  1 . When the cartridge stop member  25  slides upward, the cartridge stop member  25  is released from the state engaging with the ink sheet cartridge  50 , so that the ink sheet cartridge  50  can be drawn out in a take-out direction (along arrow A 1  in  FIG. 1 ). 
   As shown in  FIG. 1 , two pairs of mounting portions  1   h  for mounting the top plate  24  are formed on the upper ends of the first and second side surfaces  1   a  and  1   b  of the chassis  1  respectively. The four mounting portions  1   h  of the chassis  1  are provided with threaded holes  1   i  for fixing the top plate  24  to the chassis  1  with screws  29  inserted into four holes  24   a  provided in the top plate  24  respectively. Paper sensors  30   a  and  30   b  for detecting front and rear ends of each paper  60  in printing are provided on the bottom surface  1   c  of the chassis  1 , as shown in  FIG. 5 . 
   As shown in  FIG. 2 , the feed roller bearings  26   b  and  27   b  integrally provided on the side plates  26  and  27  respectively rotatably support the platen roller  3  and the feed roller  4 . The feed roller bearing  26   b  of the side plate  26  supports the feed roller  4  through a hole (not shown) of the chassis  1 , similarly to the platen roller bearing  26   a . A press roller bearing  5   a  rotatably supports the press roller  5 . The feed roller  4  and the press roller  5  rotate while holding each paper  60  therebetween, thereby transporting the paper  60  in a paper feed direction (along arrow T 1 ) or a paper discharge direction (along arrow U 1 ), as shown in  FIG. 5 . The paper feed roller  10  transports the papers  60  stored in the paper feed cassette case  70  (see  FIG. 1 ) into the chassis  1 . 
   As shown in  FIG. 5 , the print head  2  includes a pair of support shafts  2   a , a head portion  2   b  opposed to the platen roller  3  (see  FIG. 2 ), a pair of arm portions  2   c  coupling the support shafts  2   a  and the head portion  2   b  with each other and a heat radiating member  2   d  of aluminum for radiating heat generated in the head portion  2   b , and is vertically rotatable around the support shafts  2   a  mounted on the inner sides of the first and second side surfaces  1   a  and  1   b  of the chassis  1  respectively. The notch  2   e  engaging with the engaging portion  6   h  (see  FIGS. 13 and 14 ) of the print head pressing member  6  is integrally formed on the central portion of the heat radiating member  2   d  by uprighting. When the print head pressing member  6  is rotated upward, therefore, the engaging portion  6   h  of the print head pressing member  6  and the notch  2   e  of the print head  2  engage with each other, whereby the head portion  2   b  is also rotated upward and the head portion  2   b  pressed by the platen roller  3  is separated from the platen roller  3 . 
   As shown in  FIGS. 2 and 4 , the driving gear  7  constituted of the small-diametral gear  7   a  and the large-diametral gear  7   b  and the intermediate gear  31  constituted of a small-diametral gear  31   a  and a large-diametral gear  31   b  are so provided as to rotate the pressing portion  6   c  by transmitting the driving force of the stepping motor  17  to the pressing portion  6   c  of the print head pressing member  6 . The driving gear  7  is mounted on the inner side of the second side surface  1   b  of the chassis  1 . The intermediate gear  31  and the stepping motor  17  are mounted on the outer side of the second side surface  1   b  of the chassis  1  through the motor bracket  15 . The small- and large-diametral portions  7   a  and  7   b  of the driving gear  7  mesh with the gear portion  6   g  (see  FIGS. 13 and 14 ) of the print head pressing member  6  and the small-diametral gear  31   a  of the intermediate gear  31  respectively. The large-diametral gear portion  7   b  of the driving gear  7  meshes with a motor gear  17   a  of the stepping motor  17 . Thus, the driving force of the stepping motor  17  is transmitted to the pressing portion  6   c  via the rotational portion  6   b  through the intermediate gear  31  and the driving gear  7 . 
   As shown in  FIG. 2 , the side plate  27  is fixed by clamping two screws  32  into threaded holes  1   j  provided in the second side surface  1   b  of the chassis  1  through two holes  27   l  provided in the side plate  27 , as shown in  FIG. 2 . The side plate  27  integrally includes a positioning portion  27   m  for positioning the motor bracket  15  mounted thereon. 
   As shown in  FIG. 2 , a motor gear  16   a  is mounted on the shaft of the stepping motor  16  mounted on the motor bracket  15 . The stepping motor  16  functions as a driving source for driving a gear portion  14   a  of the take-up reel  14 , the paper feed roller gear  11 , the paper discharge roller gear  13  and the feed roller gear  8 , as shown in  FIG. 6 . 
   The take-up reel  14  engages with a take-up bobbin  52   b  (see  FIG. 1 ) arranged in a take-up bobbin storage portion  53   b  of the ink sheet cartridge  50  described later, thereby taking up the ink sheet  51  wound on the take-up bobbin  52   b . The gear portion  14   a  of the take-up reel  14  meshes with the swing gear  18  upon swinging thereof, as shown in  FIG. 6 . 
   The lower paper guide  9   a  is set in the vicinity of the feed roller  4  and the press roller  5 , as shown in  FIG. 5 . The upper paper guide  9   b  is mounted on the upper portion of the lower paper guide  9   a . The upper paper guide  9   b  has a function of guiding each paper  60  to a paper feed path to a printing portion through the lower surface thereof in paper feeding while guiding each paper  60  to a paper discharge path through the upper surface thereof in paper discharge. 
   As shown in  FIG. 3 , the housing  80  includes a paper feed cassette receiving portion (not shown) receiving the paper feed cassette case  70  (see  FIG. 1 ), a receiving hole  81  for receiving the ink sheet cartridge  50 , a slot  82  passing each paper  60  therethrough in a reciprocative manner in printing and a heat discharge hole  83  for discharging heat generated in the print head  2  from the sublimatic printer  90 . 
   As shown in  FIG. 1 , the ink sheet cartridge  50  includes a supply bobbin  52   a  for supplying the ink sheet  51  and the take-up bobbin  52   b  for taking up the supplied ink sheet  51 . A cartridge case  53  constituting the ink sheet cartridge  50  is constituted of a supply bobbin storage portion  53   a  rotatably storing the supply bobbin  52   a , the take-up bobbin storage portion  53   b  rotatably storing the take-up bobbin  52   b  and a pair of coupling portions  53   c  and  53   d  coupling the supply bobbin storage portion  53   a  and the take-up bobbin storage portion  53   b  with each other at a prescribed distance. When the supply bobbin storage portion  53   a  and the take-up bobbin storage portion  53   b  store the supply bobbin  52   a  and the take-up bobbin  52   b  respectively, therefore, the ink sheet  51  wound on the supply bobbin  52   a  and the take-up bobbin  52   b  is exposed on the space of the prescribed distance between the supply bobbin storage portion  53   a  and the take-up bobbin storage portion  53   b . The coupling portion  53   d  is provided with the engaging portion  53   e  engaging with the cartridge stop member  25  (see  FIGS. 1 and 3 ) of the side plate  26  provided on the first side surface  1   a  of the chassis  1 . Helical compression springs (not shown) are provided in the supply bobbin storage portion  53   a  and the take-up bobbin storage portion  53   b  of the ink sheet cartridge  50  respectively. These helical compression springs regularly urge the ink sheet cartridge  50  mounted on the sublimatic printer  90  in the take-up direction (along arrow A 1  in  FIG. 1 ) for the ink sheet cartridge  50 . 
   A method of mounting the print head pressing member  6  on the chassis  1  is now described. First, the first end (along arrow Y) of the shaft  6   a  of the print head pressing member  6  is inserted into the support hole  1   e  of the chassis  1 , as shown in  FIG. 2 . At this time, the shaft  6   a  comes into contact with the first shaft stop portion  25   a  provided on the cartridge stop member  25  of the side plate  26  through the support hole  1   e  of the chassis  1  so that movement along arrow Y (see  FIG. 4 ) is regulated, as shown in  FIGS. 4 and 7  to  9 . Therefore, the shaft  6   a  is inhibited from slipping off the chassis  1  along arrow Y. Then, the second end (along arrow Z in  FIG. 2 ) of the shaft  6   a  is inserted along arrow X 1  (vertical direction) with respect to the L-shaped bearing if of the chassis  1 , as shown in  FIGS. 15 and 16 . At this time, the shaft  6   a  inserted along arrow X comes into contact with the shaft pressing portion  27   j  of the second shaft stop portion  27   i  provided on the side plate  27  without reaching the L-shaped bearing if, as shown in  FIGS. 17 and 18 . When the shaft  6   a  presses the shaft pressing portion  27   j  along arrow X 1 , the second shaft stop portion  27   i  is so deflected along arrow X 1  that the shaft  6   a  reaches the bottom (horizontal portion) of the L-shaped bearing if, as shown in  FIGS. 19 and 20 . In this state, the shaft  6   a  so slides along arrow X 2  as to reach a position (close to the forward end of the horizontal portion) of the L-shaped bearing if for holding the shaft  6   a  while the second shaft stop portion  27   i  is released from the pressing force of the shaft  6   a  along arrow X 1 , to be restored from the deflected state by restoring force along arrow X 3 , as shown in  FIGS. 21 and 22 . At this time, the second end (along arrow Z in  FIG. 2 ) of the shaft  6   a  comes into contact with the contact portion  27   k  of the restored second shaft stop portion  27   i  so that movement along arrow Z (see  FIG. 2 ) is regulated, as shown in  FIG. 22 . Thus, the shaft portion  6   a  is inhibited from slipping off the chassis  1  along arrow Z (see  FIG. 2 ). Thus, the shaft  6   a  is supported by the support hole  1   e  and the L-shaped bearing  1   f  (see  FIG. 1 ) of the chassis  1  and inhibited from slipping off the chassis  1  and the side plates  26  and  27  by the first shaft stop portion  25   a  and the contact portion  27   k  (see  FIGS. 9 and 10 ) of the second shaft stop portion  27   i , to be kept at the proper position. 
   A printing operation of the sublimatic printer  90  according to the first embodiment of the present invention is now described with reference to  FIGS. 6 and 20 . 
   First, the stepping motor  16  is so driven as to rotate the motor gear  16   a  mounted thereon along arrow C 3  and to rotate the feed roller gear  8  along arrow C 1  through the intermediate gears  21  and  22 , as shown in  FIG. 6 . Thus, the feed roller  4  is rotated along arrow C 1  in  FIG. 6 . Further, the paper feed roller gear  11  and the paper feed roller  10  are rotated along arrow C 4  in  FIG. 23  through the intermediate gears  19  and  20 . Thus, each paper  60  is transported in the paper feed direction (along arrow T 1  in  FIG. 23 ). At this time, the swingable swing gear  18  and the gear portion  14   a  of the take-up reel  14  are out of mesh, and the gear portion  14   a  of the take-up reel  14  remains unrotated. Thus, the ink sheet  51  wound on the supply bobbin  52   a  and the take-up bobbin  52   b  is not taken up in paper feeding. 
   As shown in  FIG. 23 , the paper sensors  30   a  and  30   b  detect the front and rear ends of the paper  60  respectively, thereby determining whether or not the paper  60  has been transported to a printing start position. When the paper  60  reaches the printing start position, the print head  2  lowers to the printing position and starts printing. 
   As shown in  FIG. 23 , further, the stepping motor  16  (see  FIG. 6 ) is so driven as to rotate the motor gear  16   a  mounted thereon along arrow D 3  in  FIG. 6  and to rotate the feed roller gear  8  along arrow D 1  in  FIG. 6  through the intermediate gears  21  and  22 . Thus, the feed roller  4  is rotated along arrow D 1  in  FIG. 23 , and the press roller  5  is rotated along arrow B in  FIG. 23  following the rotation of the feed roller  4 . Further, the paper discharge roller gear  13  and the paper discharge roller  12  are rotated along arrow D 5  in  FIGS. 6 and 23  through the intermediate gears  19  and  20  and the paper feed roller  10 . Thus, the paper  60  is transported in the paper discharge direction (along arrow U 1  in  FIG. 23 ) corresponding to the printing direction. At this time, the swingable swing gear  18  (see  FIG. 6 ) meshes with the gear portion  14   a  of the take-up reel  14 , so that the ink sheet  51  wound on the supply bobbin  52   a  and the take-up bobbin  52   b  engaging with the take-up reel  14  is taken up on the take-up bobbin  52   b.    
   After the paper  60  is printed, the printed paper  60  is discharged. At this time, the printed paper  60  is transported along arrow U 1  in  FIG. 23 , similarly to the operation for printing images on the paper  60 . The printed paper  60  is transported on the upper side of the upper paper guide  9   b , and discharged by the paper discharge roller  12  rotated along arrow D 5  in  FIG. 23 . 
   According to the first embodiment, as hereinabove described, the chassis  1  is integrally provided with the first bearing if while the cartridge stop member  25  integrally including the first shaft stop portion  25   a  is provided on the first side surface  1   a  of the chassis  1  and the side plate  27  integrally including the second shaft stop portion  27   i  is provided on the second side surface  1   b  of the chassis  1  so that the first and second shaft stop portions  25   a  and  27   i  for holding the shaft  6   a  of the print head pressing member  6  are integrally included in the cartridge stop member  25  and the side plate  27  respectively and the first bearing  1   f  is integrally provided on the chassis  1 , whereby no member may be separately provided for holding the shaft  6   a  of the print head pressing member  6  on the chassis  1 . Therefore, increase in the number of components can be suppressed. Further, both end surfaces of the shaft  6   a  of the print head pressing member  6  are brought into contact with the first and second shaft stop portions  25   a  and  27   i  of the cartridge stop member  25  and the side plate  27  respectively and supported by the first bearing  1   f  of the chassis  1 , whereby the shaft  6   a  of the print head pressing member  6  can be held without newly providing a separate member. 
   According to the first embodiment, the second shaft stop portion  27   i  includes the shaft pressing portion  27   j  elastically deformable along arrow X 1  (see  FIG. 12 ) perpendicularly to the axis of the shaft  6   a  and pressed by the peripheral surface of the shaft  6   a  close to the second end (along arrow Z in  FIG. 1 ) thereof along arrow X 1  (see  FIG. 12 ) when the shaft  6   a  is mounted on the L-shaped bearing if of the chassis  1 , whereby the shaft  6   a  can be easily mounted on the L-shaped bearing if of the chassis  1  by pressing the elastically deformable shaft pressing portion  27   j  of the second shaft stop portion  27   i  with the peripheral surface of the shaft  6   a  close to the second end (along arrow Z in  FIG. 1 ) thereof. 
   According to the first embodiment, the second shaft stop portion  27   i  is provided with the contact portion  27   k  coming into contact with the second end surface (along arrow Z) of the shaft  6   a  on the position separated from the side surface of the shaft pressing portion  27   j  closer to the shaft  6   a  by the length L (see  FIG. 11 ) outward from the shaft  6   a  to be continuous with the shaft pressing portion  27   j  so that the second end surface (along arrow Z in  FIG. 1 ) of the shaft  6   a  can be brought into contact with the contact portion  27   k , whereby the shaft  6   a  can be inhibited from slipping off the chassis  1 . Therefore, the position of the shaft  6   a  can be reliably kept. 
   According to the first embodiment, the thickness of the contact portion  27   k  along arrow X 1  (see  FIG. 12 ) perpendicular to the axis of the shaft  6   a  is larger than the corresponding thickness of the second shaft stop portion  27   i  so that the contact area between the contact portion  27   k  and the second end surface (along arrow Z in  FIG. 1 ) of the shaft  6   a  of the print head pressing member  6  can be increased, whereby the shaft  6   a  can be reliably inhibited from slipping off the chassis  1 . 
   According to the first embodiment, the width W of the second shaft stop portion  27   i  in the axial direction (along arrow Z) of the shaft  6   a  is larger than the thicknesses (t 1  and t 2  in  FIG. 12 ) along arrow X 1  so that the second shaft stop portion  27   i  can be inhibited from deformation in the axial direction of the shaft  6   a , whereby the shaft  6   a  can be inhibited from slipping off the chassis  1  in the axial direction, and can be reliably held as a result. 
   Second Embodiment 
   The structure of a sublimatic printer  100  according to a second embodiment of the present invention is described with reference to  FIGS. 24 to 29 . In the sublimatic printer  100  according to the second embodiment, a rotational portion  102  of a print head pressing member  101  is made of not metal but resin, dissimilarly to the sublimatic printer  90  according to the aforementioned first embodiment. 
   The sublimatic printer  100  according to the second embodiment comprises the print head pressing member  101 , including a shaft  6   a , pressing a print head  2 , as shown in  FIG. 24 . 
   The print head  2  includes a heat radiating member  103  for radiating heat from a head portion  2   b , as shown in  FIG. 24 . 
   According to the second embodiment, the print head pressing member  101  is constituted of the shaft  6   a  of metal and the rotational portion  102  of resin, as shown in  FIGS. 24 and 25 . A pressing portion  102   a  and a sectorial gear portion  102   b  are integrally provided on longitudinal ends of the rotational portion  102  respectively. The print head pressing member  101  is so arranged above the print head  2  that the pressing portion  102   a  presses a substantially central portion of the print head  2  in the cross direction (along arrows Y and Z). Receiving holes  102   c  for receiving the shaft  6   a  are provided on both ends of the rotational portion  102  of resin respectively. The rotational portion  102  is rotatable around the shaft  6   a  received in the receiving holes  102   c . As shown in  FIG. 26 , the receiving holes  102   c  are so formed that the distance h 1  between the upper surface of the print head  2  and the receiving holes  102   c  is larger than the distance h 2  between the upper surface of the print head  2  and support holes  1   e  and if for the shaft  6   a  provided on first and second side surfaces  1   a  and  1   b  of a chassis  1  respectively when the pressing portion  102   a  is in contact with the upper surface of the print head  2  in printing. Thus, the shaft  6   a  is so deflected as to protrude the axial center thereof upward when the pressing portion  102   a  is in contact with the upper surface of the print head  2  in printing, thereby pressing the print head  2  downward from above with downward restoring force of the shaft  6   a  through the pressing portion  102   a . Consequently, the print head  2  is pressed toward the platen roller  3  in printing. 
   According to the second embodiment, a push-up portion  103   a  pushed up by a protrusion  102   d  provided on the rotational portion  102  upon upward rotation of the rotational portion  102  is integrally formed at the center of the heat radiating member  103  by uprighting. Thus, the push-up portion  103   a  of the heat radiating member  103  is pushed up by the protrusion  102   d  of the rotational portion  102  upon upward rotation of the rotational portion  102  thereby rotating the print head  2  in a direction for separating from the platen roller  3 , as shown in  FIG. 27 . 
   An edge  103   b  of an opening resulting from the uprighting for forming the push-up portion  103   a  is smoothly inclined in the vertical direction. Thus, the pressing portion  102   a  of the rotational portion  102  smoothly slides along the edge  103   b  upon downward rotation of the rotational portion  102  as shown in  FIGS. 28 and 29 , whereby the pressing portion  102   a  can easily move to the upper surface of the heat radiating member  103 . 
   As shown in  FIG. 29 , a deviation preventing portion  103   c  is integrally formed on an end of the upper surface of the heat radiating member  103 , in order to prevent the rotational portion  102  so rotated that the pressing portion  102   a  reaches the upper surface of the heat radiating member  103  from deviating in the rotational direction (along arrow F). 
   The remaining structure of the sublimatic printer  100  according to the second embodiment is similar to that of the aforementioned first embodiment. 
   According to the second embodiment, as hereinabove described, the sublimatic printer  100  is provided with the platen roller  3  opposed to the print head  2  and the heat radiating member  103  mounted on the print head  2  for radiating heat generated in the print head  2  while the heat radiating member  103  is integrally provided with the push-up portion  103   a  pushed up by the rotational portion  102  upon rotation of the rotational portion  102  and the rotational portion  102  pushes up the push-up portion  103   a  of the heat radiating member  103  upon rotation for moving the heat radiating member  103  and the print head  2  in the direction for separating from the platen roller  3  so that the rotational portion  102  pushes up the push-up portion  103   a  upon rotation thereof, whereby the heat radiating member  103  and the print head  2  can be easily rotated in the direction for separating from the platen roller  3  with no requirement for a transmission mechanism so provided as to transmit the rotational force of the rotational portion  102  to the heat radiating member  103  and the print head  2 . Consequently, increase in the number of components can be further suppressed. 
   According to the second embodiment, the rotational portion  102  presses the print head  2  toward the platen roller  3  in printing while the heat radiating member  103  is provided with the deviation preventing portion  103   c  preventing the rotational portion  102  from deviating in the rotational direction when the rotational portion  102  presses the print head  2  toward the platen roller  3  in printing so that the rotational portion  102  does not deviate in the rotational direction in printing, thereby reliably pressing the print head  2  toward the platen roller  3 . 
   According to the second embodiment, the body of the rotational portion  102  is made of resin, whereby noise caused in the rotational portion  102  when sliding with the shaft  6   a  of metal upon rotation can be suppressed as compared with a case where the rotational portion  102  is made of metal. 
   The remaining effects of the second embodiment are similar to those of the aforementioned first embodiment. 
   Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims. 
   For example, while each of the aforementioned first and second embodiments is applied to the sublimatic printer employed as an exemplary image generating apparatus, the present invention is not restricted to this but is also applicable to an image generating apparatus other than the sublimatic printer, so far as the same has a print head pressing member pressing a print head. 
   While the thickness t 1  of the contact portion of the second shaft stop portion along arrow X 1  (see  FIG. 12 ) is larger than the corresponding thickness t 2  (see  FIG. 12 ) of the second shaft stop portion in each of the aforementioned first and second embodiments, the present invention is not restricted but the thickness (t 1  in  FIG. 12 ) of the contact portion and the corresponding thickness (t 2  in  FIG. 12 ) of the second shaft stop portion may alternatively be equalized to each other so far as the shaft pressing portion of the shaft stop portion is elastically deformable along arrow X 1 .