Abstract:
A chuck for detachably fixing an object to a rotatable base, the chuck comprising (a) a support detachably mountable to the base, (b) a clamp having opposite ends, the clamp being pivotally mounted to the support between the ends of the clamp, and (c) a resilient member connected to one end of the clamp, the resilient member being resiliently deformed when the support is mounted to the base, which applies a force to the one end of the clamp, thereby causing the other end of the clamp to pivot downward, and apply a pressing force against an object disposed between the base and the other end of the clamp, wherein when the base rotates, centrifugal force acts on the clamp and increases the pressing force against the object.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a fixing structure for detachably fixing an object to a base such as a rotational drum or the like. 
     2. Description of the Related Art 
     A photosensitive member, (referred to as a print plate hereinafter) which is formed such that a photosensitive layer is formed on a thin, sheet-shaped support which is made of aluminum, is used for printing. An image is recorded on the print plate in an exposure step and the exposed print plate is developed in a development step. Then, the resultant print plate is used as a machine plate for printing. A longitudinal dimension and a horizontal dimension of the print plate (machine plate) are different depending on sizes of printed matters. 
     As an image exposure device for a print plate, a device is known in which a print plate is wrapped around a rotational drum so as to be integrally held, the rotating drum is rotated at a high speed and a light beam in accordance with image data is irradiated onto the print plate, thus the print plate is scanned and exposed. 
     In this type of the image exposure device, as a structure for fixing a print plate to a rotating drum, a structure is known which clamps and fixes non-image portions of both ends of a print plate along the circumferential direction of the rotating drum with respect to an outer circumferential surface of the rotating drum. In the fixing structure, a clamp portion is urged to the rotating drum side by an urging force of an urging means, and the print plate is clamped and fixed between the clamp portion and the outer surface of the rotating drum. 
     However, in a case of this fixing structure, there is a structural drawback that when the rotating drum is rotated at a high speed, a centrifugal force acts on the clamp portion in a direction opposite a direction of clamping and fixing, thus a force of clamping and fixing is inevitably decreased. Further, there is a drawback that the print plate itself comes up off the drum due to an action of the centrifugal force so that deviation of print plates may be generated. These drawbacks cause image recording failures such as offset of positions of images, light beams being out of focus and torsion of images recorded on the print plate, and the like. As a result, the finish of printed matters may be poor. 
     Next, a description will be given of a chuck-type fixing structure which is similar to the above-described clamp-type fixing structure. The chuck-type fixing structure has a chuck. The chuck presses and fixes side edge portions of a print plate along the circumferential direction of a rotating drum to the outer surface of the rotating drum. A plurality of grooves, whose cross-sections are formed in an up-side-down T-shaped configuration and which extend in the circumferential direction of the rotating drum, are formed in parallel at the outer surface of the rotating drum so as to correspond to print plates of various sizes. It is structured such that a base portion of the chuck (so-called fixing piece) is mounted to one of the grooves and the chuck can be moved along (and fixed to) the groove. 
     FIG. 19 shows a relationship between the chuck of the above-described fixing structure and the groove. In FIG. 19, a groove  212  formed at a rotating drum  210  includes a narrow width portion at an entrance side and an enlarged width portion  214  whose cross-section is formed in a rectangular configuration at an inner side (center of drum side). 
     A chuck includes a thin and round bar-shaped supporting shaft  218 , a base portion  216 , i.e., a fixing piece  216  which is formed in a substantially rectangular shape such that longitudinal direction end portions are round. The longitudinal dimension of the fixing piece  216  is substantially the same as the width dimension of the enlarged width portion  214  of the groove  212 , and a length of the fixing piece  216  perpendicular to the longitudinal direction thereof is shorter than the width dimension of the narrow width portion of the groove  212 . 
     When the chuck is mounted and fixed to the drum, firstly, the fixing piece  216  of the chuck is inserted into the enlarged width portion  214  through the narrow width portion of the groove  212 . Then, the supporting shaft  218  is rotated about 90° about its axis. At this time, the fixing piece  216  is also rotated about 90° within the groove  212  (the enlarged width portion  214  of the groove  212 ). Therefore, the fixing piece  216  cannot be removed from the enlarged width portion  214  of the groove  212 . That is, the chuck (the fixing piece  216 ) is fixed to a rotating drum  210 . 
     The following drawbacks arise in the above-described fixing structure. That is, when the rotating drum  210  is rotated at a high speed in order to carry out exposure, a centrifugal force acts on the chuck (the fixing piece  216 ), and a force to bend the peripheral edge of the opening portion of the groove  212  is applied thereto. As the thickness of the peripheral edge of the opening portion is thin, the peripheral edge of the opening portion deforms upwards and the fixing piece  216  is removed from the groove. Further, if the peripheral edge of the opening portion is deformed, there may be an undesirable case in which adhering of the print plate to the outer circumferential surface of the rotating drum may be poor. 
     In order to avoid damage of the peripheral edge of the opening portion of the groove, the peripheral edge of the opening portion needs to be made thicker, however, in order to make the peripheral edge of the opening portion thicker, the thickness of the rotating drum needs to be thick. As a result, the weight of the rotating drum is inevitably increased. 
     SUMMARY OF THE INVENTION 
     The present invention provides a fixing structure which can solve the above-described drawbacks. Further, the present invention provides a fixing structure which can detachably fix an object to a base such as a rotating drum or the like without using a complicated mechanism. The present invention provides a fixing structure which, when a sheet material such as a print plate or the like (fixing member) is wrapped around the base, the sheet material can be securely fixed to the base. 
     An aspect of the present invention is a chuck for detachably fixing an object to a rotatable base, the chuck comprising, (a) a support detachably mountable to the base, (b) a clamp having opposite ends, the clamp being pivotally mounted to the support between the ends of the clamp, and (c) a resilient member connected to one end of the clamp, the resilient member being resiliently deformed when the support is mounted to the base, which applies a force to the one end of the clamp, thereby causing the other end of the clamp to pivot downward, and apply a pressing force against an object disposed between the base and the the other end of the clamp, wherein when the base rotates, centrifugal force acts on the clamp and increases the pressing force against the object. 
     Another aspect of the present invention is a fixing structure for detachable mounting, comprising, a base having a dovetail groove-type groove including a bottom and a top, formed along the base and whose cross-section is a substantially trapezoidal such that the groove has a width less than a width of the groove top, and an object having an end with a block integrally provided at the end of the object and the block being insertable into the groove, wherein the object is rotatable with the block about an axis of the object, and the block is structured such that when the object is positioned at a first rotation angle position around the axis of the object, the block can be inserted into the groove and when the block is rotated from the first rotation angle position to a second rotation angle position, the block engages with the groove and thus further rotation of the block is prevented and the block cannot be removed from the groove at the second rotation angle position. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic structural view of a first embodiment of an image exposure device relating to the present invention. 
     FIG. 2 is a schematic structural view of a recording section of the first embodiment. 
     FIG. 3 is a schematic perspective view showing an arrangement of a distal end chuck and a back end chuck with respect to a rotating drum. 
     FIG. 4 is a schematic perspective view of the distal end chuck. 
     FIG. 5 is an enlarged perspective view of a main portion of the distal end chuck. 
     FIG. 6 is an enlarged cross-sectional view of the distal end chuck seen from the longitudinal direction thereof. 
     FIG. 7 is a view of the distal end chuck seen from the longitudinal direction thereof, showing a centrifugal force generated at a clamp and a pressing force generated at a clamp portion when a rotating drum rotates. 
     FIG. 8 is a schematic perspective view of a back end chuck. 
     FIG. 9 is an enlarged perspective view of a main portion of the back end chuck. 
     FIG. 10 is a cross-sectional view of the back end chuck seen from the longitudinal direction thereof. 
     FIG. 11A is a view of the back end chuck seen from the longitudinal direction thereof, showing a centrifugal force generated at a clamp and a pressing force generated at the clamp portion when a rotating drum rotates. 
     FIG. 11B is a view of the back end chuck seen from the longitudinal direction thereof, for explaining a movement of a clamp by a centrifugal force. 
     FIG. 12 is an enlarged perspective view of a main portion of a back end chuck of a second embodiment. 
     FIG. 13 is an enlarged cross-sectional view of the back end chuck of FIG. 12, seen from the longitudinal direction thereof. 
     FIG. 14 is an exploded perspective view of a main portion of a fixing piece of a leg of the back end chuck. 
     FIG. 15 is a bottom view of the fixing piece. 
     FIG. 16 is a cross-sectional view, along an axis of the rotating drum, of a main portion of a mounting groove formed at the rotating drum. 
     FIGS. 17A through 17F are views showing rotation of the fixing piece in the mounting groove. FIG. 17A shows a state in which the fixing piece is inserted into the mounting groove. 
     FIG. 17B shows a state in which the fixing piece inserted into the mounting groove is in the process of being rotated. 
     FIG. 17C shows a state in which the fixing piece is mounted to the mounting groove. 
     FIG. 17D is a cross-sectional view, along the axis of the rotating drum, of a main portion of the mounting groove of FIG.  17 A. 
     FIG. 17E is a cross-sectional view, along the axis of the rotating drum, of a main portion of the mounting groove of FIG.  17 B. 
     FIG. 17F is a cross-sectional view, along the axis of the rotating drum, of a main portion of the mounting groove of FIG.  17 C. 
     FIG. 18A is a view of a modified example of the mounting groove for mounting the fixing piece, seen from the direction of groove. 
     FIG. 18B is a view showing another modified example of the mounting groove. 
     FIG. 18C is a view showing yet another modified example of the mounting groove. 
     FIG. 18D is a bottom view of a modified example of the mounting groove. 
     FIG. 19 is a perspective view of main portions of a conventional fixing piece and a conventional groove of a rotating drum. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the present invention will be described with reference to the drawings. 
     FIG. 1 shows a schematic structure of a first embodiment of an image exposure device relating to the present invention. In the image exposure device  10 , a photosensitive lithographic print plate, (which will be referred to as a “print plate  12 ” hereinafter) in which a photosensitive layer is formed on a thin rectangular plate-shaped support (for example, a thickness thereof is about 0.3 mm) formed of, for example, aluminum or the like, is used as a sheet, and a light beam which is modulated on the basis of image data is irradiated onto the print plate  12  so as to carry out scanning-and-exposing. The print plate  12  subjected to image exposure in the image exposure device  10  is subjected to development processings or the like by an automatic developing apparatus (not shown) or the like. 
     The image exposure device  10  is structured such that a cassette loading section  18 , a feed plate conveying section  20 , a recording section  22  and a discharge buffer section  24  and the like are disposed within a machine frame  14 . The cassette loading section  18  is disposed (at a lower right side in FIG. 1) within the machine frame  14 , and a plurality of cassettes  16  each of which accommodates a large number of print plates  12  are loaded while inclined at a predetermined angle. 
     In the image exposure device  10 , various sizes of print plates  12  whose longitudinal dimensions and lateral dimensions are different can be processed. The print plate  12  having any one of the various sizes is accommodated within the cassette  16  such that a photosensitive layer of the print plate  12  faces upwards and the print plate  12  is positioned such that one end thereof is at a predetermined position. A plurality of cassettes  16  is loaded into the cassette loading section  18  with a predetermined interval between each other such that respective ends of print plates  12  accommodated within the cassettes  16  are at the substantially same height. 
     The feed plate conveying section  20  is disposed above the cassette loading section  18 . The recording section  22  is disposed at a lower central portion of the device so as to be adjacent to the cassette loading portion  18 . The feed plate conveying section  20  is provided with a pair of side plates  26  (only one side plate is shown in FIG. 1) to which an inverting unit  28  and a sheet unit  30  are mounted. 
     The inverting unit  28  includes an inverting roller  32  having a predetermined outer diameter. A plurality of small rollers (in the first embodiment, for example, four small rollers  34 A,  34 B,  34 C and  34 D) are provided around the inverting roller  32 . The small rollers  34 A,  34 B,  34 C and  34 D are disposed from the cassette loading section  18  side to the recording section  22  side via the top of the inverting roller  32 . An endless conveying belt  36  is passed across the small rollers. Thus, the conveying belt  36  is entrained about the inverting roller  32  over about half the circumference thereof, by being extended between the small roller  34 A and the small roller  34 D. 
     The sheet unit  30  has a plurality of suckers  38  which suction an upper end portion of the print plate  12  within the cassette  16 . The suckers  38  move downwards so as to oppose an upper end portion of the print plate  12  within the cassette  16  loaded into the cassette loading section  18  and suction the print plate  12 . In the sheet unit  30 , the suckers  38  which suction the print plate  12  are moved substantially upward such that the print plate  12  is drawn from the cassette  16 , and a distal end of the drawn print plate  12  is inserted between the inverting roller  32  and the conveying belt  36 . In FIG. 1, an outline of the movement positions of the suckers  38  are shown by two-dot chain lines. 
     In the inverting unit  28 , the inverting roller  32  and the conveying belt  36  are rotated in a direction in which the print plate  12  is drawn from the cassette  16  (a direction shown by the arrow A in FIG.  1 ). Thus, the print plate  12  is nipped between the inverting roller  32  and the conveying belt  36  and drawn from the cassette  16 . At the same time, the print plate  12  is entrained about the circumferential surface of the inverting roller  32  so as to be conveyed in a curved manner and to be inverted. A radius of the inverting roller  32  is such that when the print plate  12  is curved, the print plate  12  is not folded or bent (for example, at least 100 mm). 
     As shown by solid lines and two-dot chain lines in FIG. 1, the side plate  26  is moved horizontally in accordance with the position of the cassette  16  from which the print plate  12  is taken. Thus, the suckers  38  of the sheet unit  30  face the print plate  12  within the selected cassette  16 . 
     The side plate  26  is provided with a guide  40  which is below the small roller  34 D. The print plate  12  which is inverted by the inverting roller  32  is, at the small roller  34 D side, fed from between the inverting drum  32  and the conveying belt  36  toward the guide  40 . A conveyer  42  is disposed above the recording section  22 . The print plate  12  fed from the inverting unit  28  is guided to the conveyer  42  by the guide  40 . 
     The guide  40  is swung in accordance with the movement of the side plates  26  such that a direction in which the print plate  12  is guided is always directed to the conveyer  42 . The small roller  34 D at the recording section  22  side is moved so as to change a direction in which the print plate  12  is fed from the inverting unit  28  in accordance with the movement of the side plates  26 . The small roller  34 C is moved so as to apply substantially constant tension to the conveying belt  36  when the small roller  34 D is moved. Accordingly, the print plate  12  fed from the inverting unit  28  is moderately curved by the guide  40  and is guided to the conveyer  42 . 
     In the conveyer  42 , a conveying belt  48  is entrained between a roller  44  at the feed plate conveying section  20  side and a roller  46  at the recording section  22  side, and the conveying belt  48  is inclined such that the recording section side thereof is directed downwards. The conveyer  42  is provided with a roller  50  so as to oppose the roller  46 . The print plate  12  which is fed on the conveyer  42  is conveyed on the conveying belt  48  and is nipped by the rollers  46  and  50 . 
     In the recording section  22 , a rotating drum  54  and a recording head portion  56  are mounted to a stand  52 . A puncher  58  is disposed above the rotating drum  54 . In the conveyer  42 , the print plate  12  is nipped by the rollers  46  and  50 , and the distal end of the print plate  12  is inserted into a holding opening of a gripper  60  and held. When the distal end of the print plate  12  is inserted into the holding opening of a gripper  60 , the puncher  58  punches a cutout for positioning at a predetermined position of the distal end of the print plate  12 . 
     When the cutout is punched on the print plate  12 , the conveyer  42 , together with the conveying belt  48 , drives the rollers  46  and  50  in reverse such that the distal end of the print plate  12  is drawn from the holding opening of a gripper  60  of the puncher  58 . Further, the conveyer  42  is provided with a swinging means (not shown). The roller  46  side of the conveyer  42  is moved downward by the swinging means with the roller  44  side thereof being an axis, so as to approach the rotating drum  54  of the recording section  22 . Thus, the end of the print plate  12  on the conveying belt  48  is directed to a predetermined position on the outer circumferential surface of the rotating drum  54 , and the print plate  12  is conveyed on the conveying belt  48  toward the rotating drum  54 . 
     The rotating drum  54  is rotated by a driving means (not shown) in a direction in which the print plate  12  is mounted and exposed (a direction shown by the arrow B in FIGS. 1 and 2) and in a direction in which the print plate  12  is removed, i.e., in a direction which is opposite the direction in which the print plate  12  is mounted and exposed (a direction shown by the arrow C in FIGS.  1  and  2 ). 
     As illustrated in FIG. 2, a distal end chuck  62  is mounted, as a fixing device, to the rotating drum provided in the recording section  22  at a predetermined position of the outer circumferential surface of the rotating drum  54 . When the print plate  12  is mounted to the rotating drum  54 , firstly, the distal end chuck  62  stops the rotating drum  54  at a position which opposes the distal end of the print plate  12  fed by the conveyer  42  (print plate mounting position). 
     The recording section  22  is provided with a mounting cam  64  which opposes the distal end chuck  62  at the print plate mounting position. The mounting cam  64  is pivoted to press one end side of the distal end chuck  62 , thereby the print plate  12  can be inserted between the circumferential surface of the rotating drum  54  and the distal end chuck  62 . In the recording section  22 , with the distal end of the print plate  12  being inserted between the distal end chuck  62  and the rotating drum  54 , if the mounting cam  64  is pivoted so as to release the pressing on the distal end chuck  62 , the distal end of the print plate  12  is nipped and held between the distal end chuck  62  and the circumferential surface of the rotating drum  54 . At this time, the print plate  12  is positioned relative to the rotating drum  54  by a positioning pin (not shown), which is protruded from the predetermined position on the circumferential surface of the rotating drum  54 , by being entered into the cutout punched by the puncher  58 . 
     In the recording section  22 , when the distal end of the print plate  12  is fixed to the rotating drum  54 , the rotating drum  54  is rotated in the direction in which the print plate  12  is mounted and exposed. Therefore, the print plate  12  fed from the conveyer  42  is wrapped around the circumferential surface of the rotating drum  54 . 
     A squeeze roller  66  is disposed near the circumferential surface of the rotating drum  54  at the downstream side with respect to the print plate mounting position in the direction in which the print plate is mounted and exposed. The squeeze roller  66  is moved toward the rotating drum  54  to press the print plate  12  which is wrapped around the rotating drum  54  toward the rotating drum  54  such that the print plate  12  is tightly adhered to the circumferential surface of the rotating drum  54 . 
     In the recording section  22 , a back end chuck mounting/dismounting unit  68  is provided near the rotating drum  54  at the upstream side with respect to the squeeze roller  66  in the direction in which the print plate is mounted and exposed. A removing cam  70  is disposed near the downstream side in the direction in which the print plate is mounted and exposed. In the back end mounting/dismounting unit  68 , a back end chuck  74  is mounted to a distal end of a shaft  72  which protrudes toward the rotating drum  54 . 
     In the recording section  22 , when the back end of the print plate  12  which is wrapped around the rotating drum  54  opposes the back end chuck mounting/dismounting unit  68 , the shaft  72  is protruded such that the back end chuck  74  is mounted at a predetermined position on the rotating drum  54 . Thus, the back end chuck  74  nips and holds the back end of the print plate  12  between the rotating drum  54  and the back end chuck  74 . 
     In the recording section  22 , when the distal end and the back end of the print plate  12  are held on the rotating drum  54 , the squeeze roller  66  is moved away from the rotating drum  54 . Thereafter, in the recording section  22 , while the rotating drum  54  is rotated at a predetermined high rotational speed, a light beam which is modulated based on image data from the recording head section  56  is irradiated, and is synchronized with rotation of the rotating drum  54 . As a result, the print plate  12  is scanned and exposed on the basis of the image data. 
     In the recording section  22 , when the scanning-and-exposing of the print plate  12  is finished, the back end chuck  74  which holds the back end of the print plate  12  temporarily stops the rotating drum  54  at a position in which the back end of the print plate  12  opposes the back end chuck mounting/dismounting unit  68 , and the print plate  12  is nipped between the rotating drum  54  and the squeeze roller  66 . When the back end chuck  74  opposes the back end of the print plate and the rotation of the rotating drum  54  is stopped, in the back end chuck mounting/dismounting unit  68 , the back end chuck  74  is removed from the rotating drum  54 . As a result, the back end of the print plate  12  is released. 
     In the recording section  22 , when the back end chuck  74  is removed from the rotating drum  54 , the rotating drum  54  is rotated in a direction in which the print plate  12  is removed. Thus, the print plate  12  is fed from its back end from between the squeeze roller  66  and the rotating drum  54 . 
     As illustrated in FIG. 1, the discharge buffer section  24  is disposed above the squeeze roller  66 . When the rotating drum  54  is rotated in a direction in which the print plate  12  is removed, the print plate  12  is fed from its back end toward the discharge buffer section  24 . The rotating drum  54  is rotated in a direction in which the print plate  12  is taken out and stops at the print plate removing position in which the distal end chuck  62  opposes the removing cam  70 . In the recording section  22 , the removing cam  70  is pivoted to press the distal end chuck  62 , and the distal end of the print plate  12  is released from being nipped between the distal end chuck  62  and the rotating drum  54 . In this way, the print plate  12  is removed from the rotating drum  54 . 
     The discharge buffer section  24  is provided at the inside of a discharge port  76  formed at the machine frame  14 , and includes a discharge roller  78 . A plurality of small rollers (for example, small rollers  80 A,  80 B,  80 C,  80 D and  80 E) are disposed around the discharge roller  78 , and an endless conveying belt  82  is passed across the small rollers  80 A,  80 B,  80 C,  80 D and  80 E. Thus, the conveying belt  82  is entrained about the discharge roller  78  in a range from ½ to ¾ of the circumference of the discharge roller  78  by being extended between the small rollers  80 A and  80 E. 
     The small roller  80 A is formed so as to protrude toward the squeeze roller  66  side in the recording section  22 , and a roller  84  is disposed to oppose the small roller  80 A. The print plate  12  fed from the recording section  22  is guided toward between the small roller  80 A and the roller  84  and is nipped therebetween. 
     In the discharge buffer section  24 , the discharge roller  78  is rotationally driven in a direction in which the print plate  12  is taken in (in a direction shown by the arrow D), and therefore the print plate  12  nipped by the small roller  80 A and  84  is drawn from the recording section  22  to be guided between the discharge roller  78  and the conveying belt  82 . Then, the print plate  12  is nipped by the discharge roller  78  and the conveying belt  82  to be entrained about the discharge roller  78 . In the discharge buffer section  24 , the distal end portion of the print plate  12  (the distal end chuck  62  side in the recording section  22 ) is nipped by the small roller  80 A and the roller  84  such that the print plate  12  entrained about the discharge roller  78  is temporarily held. 
     On the other hand, as shown by two-dot chain lines, in the discharge buffer section  24 , the small roller  80 A and the roller  84  move to a position in which the small roller  80 A and the roller  84  oppose the discharge port  76 . At this time, the small roller  80 A and the idle roller  84  are integrally rotated, and therefore the distal end of the print plate  12  is directed to the discharge port  76 . A small roller  80 B which is positioned above the small roller  80 A is moved following the movement of the small roller  80 A, and applies constant tension to the conveying belt  82 . 
     In the discharge buffer section  24 , when the distal end of the print plate  12  is directed to the discharge port  76 , the discharge roller  78  is rotationally driven in a direction in which the print plate  12  is fed out (a direction opposite a direction shown by the arrow D) at a rotational speed corresponding to a conveying speed of the print plate  12  in a processing device such as an automatic developing device or the like, which is disposed adjacently to the discharge port  76 . Thus, the print plate  12  is fed out from the discharge port  76 . 
     The distal end chuck  62  and the back end chuck  74  are provided at the rotating drum  54  as fixing devices which fix the print plate  12 . The distal end chuck  62  is mounted to the rotating drum  54  so as to fix the distal end of the print plate  12  to a predetermined position. The back end chuck  74  is mounted to the rotating drum  54  so as to oppose the back end of the print plate  12  wrapped round the rotating drum  54 . 
     As shown in FIGS. 3 and 4, the distal end chuck  62  is provided with a clamp  100  which is formed in a band plate shape having a predetermined length as a first clamp. The clamps  100  are disposed at predetermined intervals on the rotating drum  54  along an axial direction thereof. As shown in FIGS. 3 and 8, a clamp  140  formed in a band plate shape having a predetermined length is disposed around the rotating drum  54  as a second clamp. The clamps  140  are disposed at predetermined intervals on the rotating drum  54  along the axial direction thereof. 
     A description will be given of the distal end chuck  62  with reference to FIGS. 3 to  7 . 
     As illustrated in FIG. 3, the distal end chuck  62  includes a clamp  100  which is formed in a band plate shape and has a predetermined length. The clamps  100  are disposed at predetermined intervals on the rotating drum  54  in an axial direction thereof. 
     As shown in FIGS. 4 to  7 , the clamp  100  has a clamp portion  102  at one widthwise direction end which clamp portion is protruded towards a circumferential surface of the rotating drum. The clamp portion  102  presses the distal end of the print plate  12  with respect to an outer circumferential surface of the rotating drum  54  so as to fix the print plate  12  to the rotating drum  54 . 
     Substantially rectangular shaped recess portions  104  are formed at a plurality of positions on a surface of the clamp  100  which surface is on the opposite side of the clamp portion  102 . Each recess portion  104  is provided with a leg  106  as supporting means. 
     As shown in FIGS. 5 to  7 , each leg  106  has a rectangular block-shaped base portion  108 , a leg portion  110  and a supporting shaft  112  having a small diameter (see FIG.  6 ). 
     As illustrated in FIG. 6, a through hole  114  is formed at the recess portion  104  of the clamp  100 . The supporting shaft  112  of the leg  106  is inserted into the through hole  114 . The leg  106  is connected by the clamp  100  being nipped between a screw  116  which is screwed into the distal end of the supporting shaft  112  and the leg portion  110 . The distal end chuck  62  is mounted to the rotating drum  54  by the base portion  108  of the leg  106  being inserted further to the inner side than the circumferential surface of the rotating drum  54  and fixed thereto. Any method can be used for fixing the base portion  108  to the rotating drum  54 , and therefore detailed descriptions thereof will be omitted. 
     As shown in FIGS. 5 and 6, a seat plate  118  formed by a resilient body is interposed between the leg portion  110  of the leg  106  and the clamp  100 . A similar seat plate  118  and a retaining plate  120  which is formed by a flexible member in a substantially rectangular shape are interposed between the screw  116  and the clamp  100 . The inner diameter of the through hole  114  is slightly larger than the outer diameter of the supporting shaft  112  (see FIG.  6 ). 
     In the distal end chuck  62 , an end portion of the clamp  100  which is on the opposite side of the clamp portion  102  is pressed in a vertical direction (an up-down direction in FIGS. 5 and 6) such that the seat plate  118  is resiliently deformed and the retaining plate  120  is deflected. As a result, the distal end chuck  62  swings with a predetermined position of the supporting shaft  112  being its supporting point (supporting point P A  shown in FIG.  7 ). 
     The clamp  100  is provided with a pressing portion  122  which is at the side of the supporting shaft  112  opposite the side at which the clamp portion  102  is formed. The pressing portion  122  is provided with a plurality of urging legs  124  at the rotating drum  54  side of the pressing portion  122  (lower side in FIG.  6 ). Each urging leg  124  is disposed adjacently to each of the legs  106 . 
     Each urging leg  124  has a substantially disc-shaped wear plate  126  which opposes the circumferential surface of the rotating drum  54 . A shaft  128  which is integrally formed with the wear plate  126  is inserted into a through hole  130  (see FIG. 6) formed at the pressing portion  122  of the clamp  100 . 
     A flange portion  132  is formed at an axially intermediate portion of the shaft  128 . The through hole  130  communicates with an enlarged diameter portion  134  which is formed at a side of the clamp  100  opposite the side of the rotating drum  54 . The flange portion  132  enters within the enlarged diameter portion  134  so as to prevent the shaft  128  from slipping to the rotating drum  54  side. 
     As shown in FIG. 6, a coil spring  136  is disposed at the urging leg  124  between the wear plate  126  and the clamp  100 . The urging leg  124  is protruded towards the rotating drum  54  side by the urging force of the coil spring  136 . In FIG. 5, the coil spring  136  is not shown. Guide rings  138  are formed at the wear plate  126  and the clamp  100  so as to prevent the coil spring  136  from being shifted. 
     In the distal end chuck  62 , when the base portion  108  of the leg  106  is fixed to the rotating drum  54  at a predetermined position on the outer circumferential portion thereof, the wear plate  126  abuts the outer circumferential surface of the rotating drum  54 . Thus, the pressing portion  122  side of the clamp  100  is urged away from the circumferential surface of the rotating drum  54  by the urging force of the coil spring  136 , and the clamp  102  is urged toward the circumferential surface of the rotating drum  54 . As illustrated in FIG. 7, the distal end chuck  62  nips the print plate  12  between the clamp portion  102  and the circumferential surface of the rotating drum  54  by the urging force. 
     When the rotating drum  54  stops at the print plate mounting position or the print plate removing position, the pressing portion  122  of the clamp  100  opposes the mounting cam  64  or the removing cam  70 . If the pressing portion  122  is pressed by the mounting cam  64  or the removing cam  70  toward the circumferential surface of the rotating drum  54 , the clamp  100  swings against the urging force of the coil spring  136 . Thus, the clamp portion  102  is spaced apart from the circumferential surface of the rotating drum  54  such that the print plate  12  can be inserted between the clamp portion  102  and the circumferential surface of the rotating drum  54  or can be removed therefrom. 
     As shown in FIGS. 6 and 7, the position of the through hole  114  to which the leg  106  is connected deviates to the clamp portion  102  side with respect to the center of gravity G A  of the clamp  100 . Namely, the supporting point P A  when the clamp  100  swings, is more toward the clamp portion  102  side with respect to the center of gravity G A . 
     Therefore, the clamp  100  swings due to a centrifugal force which acts on the clamp  100  when the rotating drum  54  rotates, such that the clamp portion  102  thereof is directed toward the circumferential surface of the rotating drum  54 . 
     Namely, as shown in FIG. 7, a pressing force F 1  which is directed toward the center of rotation of the rotating drum  54  acts on the clamp portion  102  due to a centrifugal force F A  which acts on the clamp  100  when the rotating drum  54  rotates. Therefore, the print plate  12  is securely fixed to the circumferential surface of the rotating drum  54  not only by the urging force of the coil spring  136  but also by the nipping force of the pressing force F 1  corresponding to the centrifugal force F A . 
     Next, a description will be given of the back end chuck  74  with reference to FIGS. 8 to  10 ,  11 A and  11 B. As shown in FIG. 8, the back end chuck  74  has a clamp  140  which is formed in a band shape and has a predetermined length. The back end chuck  74  is disposed such that the longitudinal direction of the clamp  140  extends along the axial direction of the rotating drum  54 . A plurality of clamps  140  are disposed on the rotating drum  54  at predetermined intervals along the rotating drum  54  in the axial direction. 
     As shown in FIGS. 8 to  10 , a clamp portion  142  is formed at one widthwise direction end of the clamp  140 . The clamp portion  142  is protruded in a direction perpendicular to the widthwise direction of the clamp  140 . As shown in FIGS. 11A and 11B, a distal end portion of the clamp portion  142  is curved in an arc about a predetermined position P 1  so as to form an abutting portion  144 . 
     The back end chuck  74  is mounted to the rotating drum  54  with the abutting portion  144  being directed to the circumferential surface of the rotating drum  54 . Thus, the abutting portion  144  abuts the peripheral edge of the back end portion of the print plate  12  wrapped around the rotating drum  54  such that the print plate  12  is nipped and held between the clamp portion  142  and the rotating drum  54 . 
     As shown in FIG. 8, the clamp  140  is provided with a plurality of recess portions  146  at a surface of the clamp  140  which is opposite to the surface which opposes the rotating drum  54  (a surface on the front side of the paper surface in FIG.  8 ). The planar configuration of each recess portion  146  is a substantially T shape, and the recess portions  146  are formed at the clamp portion  142  side. As shown in FIGS. 9 and 10, in the back end chuck  74 , supporting members  148  are mounted to respective recess portions  146 . 
     As shown in FIG. 9, a base plate  152  is extended from an intermediate portion of the supporting member  148  along the axial direction of a shaft  150 . A leg  154  is mounted to the base plate  152 . 
     As shown in FIG. 3, a plurality of mounting grooves  90  are formed at the circumferential surface of the rotating drum  54  at predetermined intervals in an axial direction of the rotating drum  54 . The back end chuck  74  is mounted to the rotating drum  54  such that the supporting member  148  is inserted into the mounting groove  90  (a mounted state of the back end chuck  74  is not shown). In the first embodiment, for example, a pair of two mounting grooves  90  corresponds to one clamp  140 . The clamp  140  is provided with two supporting members  148 . 
     The mounting groove  90  is formed around substantially whole circumference of the rotating drum  54 . Thus, regardless of the size of the print plate  12 , the back end chuck  74  can be mounted to a position opposing the back end of the print plate  12 . 
     A groove  156  whose direction extends along the longitudinal direction of the clamp  140  is formed in the clamp  140  at the clamp portion  142  side of the recess portion  146 . A rectangular hole  158  is formed within the recess portion  146  so as to be adjacent to the groove  156 . The shaft  150  is fitted into the groove  156  and the base plate  152  is fitted into the rectangular hole  158 . Thereby, the supporting member  148  is mounted to the clamp  140  so as to be swingable about the shaft  150 . 
     That is, as shown in FIGS. 11A and 11B, the clamp  140  can swing with respect to the supporting member  148  with the shaft center of the shaft  150  (not shown in FIGS. 11A and 11B) being the supporting point P B . 
     As illustrated in FIGS. 9 and 10, the leg  154  includes a base portion  160  which is formed in a rectangular block shape, a leg portion  162  and a shaft  164  (see FIG.  10 ). The shaft  164  is inserted into a through hole (not shown) formed at the base plate  152  of the supporting member  148  and connected thereto. 
     As shown in FIG. 10, a seat plate  166  formed in a ring shape by a resilient body is interposed between the leg portion  162  and the base plate  152 . On the upper side of the base plate  152 , a wear plate  168  formed in a substantially rectangular shape by a flexible member is interposed between the seat plates  166 . The wear plate  168  and the seat plates  166  which nip the wear plate  168  are mounted by a screw  170  screwed into the shaft  164 . 
     The wear plate  168  is passed across from the shaft  150  side of the base plate  152  to the recess portion  146  of the clamp  140 . A step portion  172  is formed at an end portion of the base plate  152  which is opposite to the shaft  150 . A peripheral edge portion of the rectangular hole  158  of the clamp  140  is nipped between the step portion  172  and the wear plate  168 . 
     When the seat plates  166  are resiliently deformed and the wear plate  168  is deflected, the clamp  140  swings with respect to the supporting member  148  with its axis (supporting point P B ) being the shaft  150  of the supporting member  148 . 
     In the supporting member  148 , one end of a plate spring  174  is nipped between the leg portion  162  of the leg  154  and the base plate  152  of the supporting member  148  and mounted therebetween. The other end of the plate spring  174  is bent to the rotating drum  54  side. 
     If the base portion  160  of the leg  154  is fitted into a predetermined position on the rotating drum  54  with the abutting portion  144  of the clamp portion  142  opposing the back end portion of the print plate  12 , the back end chuck  74  is mounted to the rotating drum  54 . At this time, the plate spring  174  abuts the circumferential surface of the rotating drum  54  so as to be resiliently deformed. 
     The back end chuck  74  is urged by the urging force generated by the plate spring  174  being resiliently deformed so as to direct the abutting portion  144  of the clamp  142  to the circumferential surface of the rotating drum  54 . Thus, the print plate  12  is nipped between the abutting portion  144  and the rotating drum  54 . 
     The back end chuck  74  is mounted to the rotating drum  54  by using a plurality of mounting grooves  90  (see FIG. 3) which are formed at the circumferential surface of the rotating drum  54  at predetermined intervals. The interior of each mounting groove  90  is widened. The base portion  160  of the leg  154  is inserted into the mounting groove and the base portion  160  is rotated with the shaft  164 , thus the circumferential surface of the base portion  160  abuts the inner surface of the groove and is fixed thereto. Structure (not shown) may be used in place of the above-described structure. 
     As shown in FIGS. 10,  11 A and  11 B, the supporting point P B  in a case in which the clamp  140  swings with respect to the supporting member  148  is positioned at the clamp portion  142  side with respect to the center of gravity G B  of the clamp  140 . The supporting point P B  is positioned at the rotating drum  54  side with respect to the point P 1  which is the center of an arc of the abutting portion  144 . 
     When the rotating drum  54  rotates, a centrifugal force is generated at the clamp  140 . The centrifugal force F B  acts so as to rotate the clamp  140  about the supporting point P B  in a direction in which the center of gravity G B  is spaced apart from the rotating drum  54 . 
     Therefore, the clamp portion  142  is also rotated about the supporting point P B , the abutting position to the print plate  12  is shifted in a direction opposite the rotational direction, and the back end portion of the print plate  12  which abuts the abutting portion  144  is pulled in a direction in which the print plate  12  is pulled. Namely, the abutting portion  144  which abuts the print plate  12  is formed in a circular arc, and therefore a tensile force F 2  is generated at the abutting position S of the abutting portion  144  to the print plate  12  in a direction in which the print plate  12  is pulled due to the centrifugal force F B . 
     In the abutting portion  144  which abuts the print plate  12 , the point P 1  which is a center of a circular arc surface which opposes the print plate  12  is positioned at an outer side in a radial direction of the rotating drum  54  with respect to the supporting point P B . Thus, the distance r 1  from the supporting point P B  to the abutting position S 1  of the abutting portion  144  to the print plate  12  when the rotating drum  54  stops is shorter than the distance r 2  from the supporting point P B  to the abutting position S 2  (shown by two-dot chain lines in FIG. 11B) of the abutting portion  144  to the print plate  12  when the rotating drum  54  rotates (i.e., r 1 &lt;r 2 ). 
     When the clamp  140  rotates due to the centrifugal force F B , the pressing force F 3  of the clamp portion  142  on the print plate  12  becomes large and the tensile force F 2  is decreased. Further, rotation of the clamp  140  due to the centrifugal force F B  is suppressed by a drag against the pressing force F 3 . That is, a center of curvature of the abutting portion  144  (the point P 1 ) is positioned at the rotating drum  54  side with respect to the supporting point P B , and therefore pulling of the print plate  12  by the clamp  140  is restricted and the print plate  12  cannot be pulled out more than needed. 
     An operation of the first embodiment will be described hereinafter. 
     In the image exposure device  10 , image data for exposing the print plate  12  is inputted, the size of the print plate  12  to be subjected to image exposure and the number of the print plate  12  to be exposed are set. When the starting of image exposure is instructed, image exposure processing on the print plate  12  starts. The processing may be instructed by operating switches of an operation panel provided in the image exposure device  10 . Alternatively, the starting of processing of the image exposure device  10  may be instructed by a signal from an image processing device or the like which outputs image data to the image exposure device  10 . 
     In the image exposure device  10 , when the starting of processing is instructed, the sheet unit  30  is moved with the inverting unit  28  to a position corresponding to the cassette  16  which accommodates the print plate  12  with a designated size. The print plate  12  within the corresponding cassette  16  is suctioned by the suckers  38  and is removed from the cassette  16 . Then, the print plate  12  is fed between the inverting roller  32  and the conveying belt  36  in the inverting unit  28 . Thus, the print plate  12  is nipped and conveyed by the inverting roller  32  and the conveying belt  36  to be fed to the conveyer  42 . 
     The distal end of the print plate  12  is inserted into the holding opening of a gripper  60  by the conveyer  42 . The puncher  58  punches a cutout for positioning at a predetermined position on the print plate  12 . When the cutout is punched at the print plate  12 , the conveyer  42  draws the print plate  12  from the holding opening of a gripper  60  to feed the print plate  12  onto the circumferential surface of the rotating drum  54 . 
     In the recording section  22 , the distal end of the print plate  12  is held to the rotating drum  54  by the distal end chuck  62 , and the print plate  12  is wrapped around the rotating drum  54  while being squeezed by the squeeze roller  66 . The back end chuck  74  is mounted to the rotating drum  54  so as to correspond to the back end position of the print plate  12  wrapped around the rotating drum  54 , and therefore the back end portion of the print plate  12  is fixed to the rotating drum  54 . 
     Thereafter, a light beam based on image data is irradiated to the print plate  12  from the recording head portion  56  while the rotating drum  54  is rotated at a high speed, and thereby the print plate  12  is scanned and exposed. When the scan-exposure of the print plate  12  is finished, the back end chuck  74  is removed from the rotating drum  54  and the print plate  12  is fed out to the discharge buffer section  24 . 
     In the discharge buffer section  24 , the print plate  12  is nipped and conveyed by the small roller  80 A and the roller  84  so as to be entrained about the discharge roller  78 . Then, the small roller  80 A and the roller  84  oppose the discharge port  76  and the print plate  12  is fed out from the discharge port  76  at a predetermined conveying speed. 
     In the recording section  22 , the mounting cam  64  presses the pressing portion  122  downward against the urging force of the coil spring  136 , and the clamp portion  102  is thereby spaced apart from the circumferential surface of the rotating drum  54  such that the print plate  12  can be inserted. When downward pressing of the pressing portion  122  by the mounting cam  64  is released, the distal end chuck  62  nips the distal end of the print plate  12  between the clamp portion  102  and the rotating drum  54 . In this way, the distal end of the print plate  12  is fixed to the rotating drum  54 . 
     On the other hand, the back end chuck  74  is mounted to the rotating drum  54  at a position in which the back end of the print plate  12  opposes the clamp portion  142 . The back end chuck  74  is mounted to the rotating drum  54 , and the plate spring  174  abuts the circumferential surface of the rotating drum  54  and resiliently deforms. The back end portion of the print plate  12  is nipped between the clamp portion  142  and the rotating drum  54  and is fixed therebetween by the urging force generated by the plate spring  174  being resiliently deformed. 
     At this time, the back end chuck  74  is mounted to the rotating drum  54  such that the supporting member  148  is inserted into the mounting groove  90  which is formed at the outer circumferential portion of the rotating drum  54 . Since the mounting groove  90  is formed along the circumferential direction of the rotating drum  54 , the back end chuck  74  can be mounted to any position along the circumferential direction of the rotating drum  54 . As a result, regardless of the size of the print plate  12 , the distal end and the back end of the print plate  12  are reliably nipped between the distal end chuck  62  and the rotating drum  54  and between the back end chuck  74  and the rotating drum  54  so as to fix the print plate  12  to the rotating drum  54 . 
     The distal end portion and the back end portion of the print plate  12  wrapped around the rotating drum  54  are fixed to the distal end chuck  62  and the back end chuck  74 , respectively. 
     As shown in FIG. 7, when the rotating drum  54  rotates, the centrifugal force F A  acts on the clamp  100  of the distal end chuck  62 . A rotation moment with its center being the supporting point P A  is generated at the clamp  100  of the distal end chuck  62  by the centrifugal force F A . The pressing force F 1  which is directed to the circumferential surface of the rotational drum  54  is generated by the rotation moment. 
     Accordingly, the print plate  12  is securely fixed between the rotating drum  54  and the distal end chuck  62  by, in addition to the pressing force corresponding to the urging force of the coil spring  136 , the pressing force F 1  corresponding to the centrifugal force F A . Thus, the distal end chuck  62  can securely fix the distal end of the print plate  12  to a predetermined position on the rotating drum  54 . 
     On the other hand, as shown in FIG. 11A, due to rotation of the rotating drum  54 , the centrifugal force F B  acts on the clamp  140  of the back end chuck  74  which fixes the back end portion of the print plate  12  to the rotating drum  54 . The rotation moment with its axis being the shaft  150  of the supporting member  148  is generated by the centrifugal force F B . 
     The clamp portion  142  of the clamp  140  has the abutting portion  144  which abuts the print plate  12 . The abutting portion  14  is chamfered in a circular shape (see FIGS.  11 A and  11 B). At the abutting position S 1  at which the print plate  12  is pressed, a tensile force F 2  is generated in a tangential direction by the rotation moment caused by the centrifugal force F B . This tensile force F 2  is directed to the direction of the arrow C. 
     Thus, if the rotating drum  54  rotates, the back end portion of the print plate  12  is pulled by the back end chuck  74  in a direction in which the print plate  12  is pulled, and it is possible to prevent the print plate  12  from becoming slack when the rotating drum  54  rotates. Namely, if the print plate  12  is rotated integrally with the rotating drum  54 , the print plate  12  would come up from off the circumferential surface of the rotating drum  54  due to the centrifugal force generated at the print plate  12 . However, at this time, because the back end chuck  74  pulls the back end portion of the print plate  12  due to the tensile force F 2  based on the centrifugal force F B  generated at the clamp  140 , it is possible to ensure prevention of offset or coming up of the print plate  12  off the drum surface caused by the print plate  12  wrapped around the rotating drum  54  being spaced away from the circumferential surface of the rotating drum  54 . 
     As shown in FIG. 11B, the supporting point P B  of the back end chuck  74  is positioned at the circumferential surface of the rotating drum  54  side with respect to the point P 1  which is a center of a circular arc of the abutting portion  144  which abuts the print plate  12 . Thus, by the clamp portion  142  being rotated by the rotation moment, the abutting position at which the print plate  12  abuts is moved from the abutting position S 1  to the abutting position S 2 , and the distance between the supporting point P B  and the print plate  12  becomes long. Accordingly, the pressing force of the clamp portion  142  on the print plate  12  is large and the tensile force F 2  is small. 
     That is, in the back end chuck  74 , the centrifugal force F B  acts on the clamp  140  by rotation of the rotating drum  54  so as to rotate the clamp portion  142 . Thus, at first, the tensile force F 2  is generated together with the pressing force F 3 . Then, as the pressing force F 3  pressing the print plate  12  to the circumferential surface of the rotating drum  54  becomes gradually larger, the tensile force F 2  decreases. 
     Thus, rotation of the clamp portion  142  by the centrifugal force F B  is suppressed, and pulling of the print plate  12  by the clamp  140  is restricted. Accordingly, the print plate  12  cannot be pulled by the clamp  140  more than needed. 
     When the rotating drum  54  rotates at a high speed in order to scan and expose the print plate  12 , not only the print plate  12  cannot come up off the drum surface or be offset, but also mispositioning of the print plate  12  due to excess pulling thereof cannot be caused. As a result, an image can be recorded at an appropriate position on the print plate  12 . Further, images recorded on the print plate  12  will not be damaged. 
     The structure of the present invention is not limited to the above-described first embodiment. For example, in the first embodiment, the back end chuck  74  is inserted into the mounting groove  90  of the rotating drum  54  so as to be mounted to the rotating drum  54 . Thus the back end of the print plate  12  is held at any position along the circumferential direction of the rotating drum  54 . The back end chuck  74  may be movable within the mounting groove  90  along the circumferential direction of the rotating drum  54 . In this way, regardless of the size of the print plate  12 , the distal end and the back end of the print plate  12  can be reliably nipped and held between the distal end chuck  62  and the rotating drum  54  and between the back end chuck  74  and the rotating drum  54 . 
     In the first embodiment, the distal end chuck  62  is mounted to a predetermined position on the rotating drum  54 , and the back end chuck  74  is mounted to a position corresponding to the size of the print plate  12 . The distal end chuck  62  and the back end chuck  74  may be, however, detachable to positions corresponding to the size of the print plate  12 . 
     Second Embodiment 
     The first embodiment of the image exposure device relating to the present invention has been described. A second embodiment of the image exposure device of the present invention will be explained below. Descriptions of parts and portions, which are (may be) the same as in the above-described first embodiment, are appropriately omitted, and characteristic contents of the second embodiment will be described in detail. 
     As described above, a plurality of mounting grooves  90  are formed at the circumferential surface of the rotating drum  54  at predetermined spaces. The back end chuck  74  is mounted to the rotating drum  54  by each supporting member  148  being attached to each mounting groove  90 . In the second embodiment, as an example, a pair of two mounting grooves  90  corresponds to one clamp  140  of the back end chuck  74 . Two supporting members  148  are provided in one clamp  140 . 
     As shown in FIGS. 13 and 14, a leg  154  of the supporting member  148  includes a base portion  160  which is formed in a rectangular block shape (referred to as a fixing piece hereinafter), a leg portion  162  (referred to as a supporting shaft hereinafter) and a shaft  164  (referred to as a small diameter portion hereinafter) (see FIG.  14 ). The small diameter portion  164  is inserted into a through hole (not shown) formed at a base plate  152  of the supporting member  148 , and is connected thereto. 
     As shown in FIGS. 12 and 13, a wear plate  166  is interposed between a supporting shaft  162  and a base plate  152 . On the upper side of the base plate  152 , a handle plate  168  is disposed so as to be interposed between the wear plates  166 . The handle plate  168  and the wear plates  166  which nip the handle plate  168  are mounted by a screw  170  which is screwed into a shaft  164 . 
     As shown in FIG. 14, a cutout  164 A along the axial direction of the supporting shaft  162  is formed at the outer circumference portion of the small diameter portion  164  of the supporting shaft  162 . A through hole  168 A which corresponds to the outer configuration of the small diameter portion  164  is formed at the handle plate  168 , and the small diameter portion  164  is inserted into the through hole  168 A. Thus, the fixing piece  160  of the leg  154  rotates about the supporting shaft  162  integrally with the handle plate  168 . 
     As shown in FIGS. 12 and 13, the handle plate  168  is disposed within a recess portion  146  of the clamp  140 . In the back end chuck  74 , the fixing piece  160  is rotated by rotating the handle plate  168 . As shown in FIG. 13, a step portion  172  is formed at an end portion of the base plate  152  which is opposite to the shaft  150 . A peripheral edge portion of a rectangular hole  158  of the clamp  140  is nipped between the step portion  172  and the handle plate  168 . Thus, the clamp  140  cannot be unnecessarily swung with respect to the supporting member  148 . 
     As shown in FIGS. 12 and 13, one end of a plate spring  174  is nipped between the supporting shaft  162  of the leg  154  and the base plate  152  of the supporting member  148  such that the plate spring  174  is mounted to the supporting member  148 . The other end of the plate spring  174  is bent toward the rotating drum  54  side (downward in FIGS.  12  and  13 ). 
     If the back end chuck  74  is mounted to the rotating drum  54  with the clamp portion  142  opposing the back end portion of the print plate  12 , the plate spring  174  abuts the rotating drum  54  so as to be resiliently deformed. Then, a nipping force, by which the print plate  12  is nipped between the clamp portion  142  and the circumferential surface of the rotating drum  54 , is applied. 
     As shown in FIG. 14, the fixing piece  160  is formed in a rectangular block shape such that one side of the fixing piece  160  is longer than the other side thereof. Hereinafter, a direction in which a shorter side of the fixing piece  160  extends will be referred to as a widthwise direction, and a direction in which a longer side of the fixing piece  160  extends will be referred to as a longitudinal direction. 
     The supporting shaft  162  is provided such that a center of the fixing piece  160  in the widthwise direction and the longitudinal direction is a shaft center. 
     As shown in FIGS. 14 and 15, a circular arc shaped portion  176  and a linear portion  178  are formed at longitudinal direction end portions of the fixing piece  160 . As shown in FIG. 15, the circular arc shaped portion  176  is formed such that one widthwise direction end of the fixing piece  160  is curved about the supporting shaft  162  at a predetermined radius. The outer configuration of the fixing piece  160  is such that the portion from the widthwise direction intermediate point P 1  of the fixing piece  160  to the point P 2  in the longitudinal direction of the one widthwise direction end portion of the fixing piece  160  is formed in a circular arc. Further, the linear portions  178  are formed at the longitudinal direction end portions of the fixing piece  160  such that the portion from the intermediate point P 1  to the other widthwise direction end point P 3  is formed in a linear manner along the widthwise direction. 
     Thus, in the fixing piece  160 , the distance r 2  from the center Q to the point P 2 , the distance r 1  from the center Q to the intermediate point P 1  and the distance r 3  from the center Q to the point P 3  increase in that order (i.e., r 2 &lt;r 1 &lt;r 3 ). 
     As shown in FIG. 14, the fixing piece  160  is provided with inclined portions  180  at the longitudinal direction end portions thereof. Each inclined portion  180  is formed such that an upper portion of the fixing piece  160  is cutout at a predetermined angle. Thus, an inclined surface  182  which contours an inner surface of a mounting groove  90  to be described later is formed at the linear portion  178 . The inclined surface  182  at the circular arc shaped portion  176  side is formed in a circular arc with its center being Q. 
     FIG. 16 illustrates a cross-section of the vicinity of the mounting groove  90  along the axial direction of the rotating drum  54 . In the mounting groove  90 , a width W 1  of an opening near the surface of the rotating drum  54  is slightly larger than a size W 0  (see FIG. 15) in the widthwise direction of the fixing piece  160 . The width W 1  of the opening is narrower than a size L 0  (see FIG. 15) in the longitudinal direction of the fixing piece  160 . Therefore, the fixing piece  160  can be inserted into and removed from the mounting groove  90  only when the longitudinal direction of the fixing piece  160  aligns with the direction of grooves in the mounting groove  90 . 
     An enlarged width portion  92  is formed within the mounting groove  90  in the rotating drum  54 . The enlarged width portion  92  is formed such that widthwise direction inner surfaces of the mounting groove  90  (referred to as inclined surfaces  96  hereinafter) are inclined a predetermined angle θ with respect to a bottom surface  94  of the mounting groove  90 . The angle θ is in a range from at least 45° to less than 90°, and in the second embodiment, as an example, the angle θ is about 45°. 
     The inclined surfaces  96 , whose inclined angle is θ, are formed at the enlarged width portion  92 . Thereby the width of the opening of the mounting groove  90  is gradually widened toward the bottom surface  94 . Due to the enlarged width portion  92 , the mounting groove  90  is formed at the rotating drum  54  as an opening whose cross-section in the widthwise direction is a substantially trapezoidal configuration. 
     As shown in FIG. 14, the fixing piece  160  is inserted into the mounting groove  90  such that the widthwise direction of the fixing piece  160  aligns with the widthwise direction of the mounting groove  90 . Then, the fixing piece  160  is rotated from the circular arc shaped portion  176  side thereof in the direction of arrow E such that the longitudinal direction of the fixing piece  160  aligns with the widthwise direction of the mounting groove  90  (shown by two-dot chain lines in FIG.  14 ). 
     As shown in FIG. 15, the enlarged width portion  92  of the mounting groove  90  corresponds with the dimension L 0  along the longitudinal direction of the fixing piece  160  at a position at which inclined surfaces  96  are spaced apart at a predetermined interval. Thus, if the longitudinal direction of the fixing piece  160  inserted into the mounting groove  90  is aligned with the widthwise direction of the mounting groove  90 , the intermediate points P 1  of end portions of the fixing piece  160  abut the inclined surfaces  96 . As a result, the fixing piece  160  cannot be removed from the mounting groove  90 . 
     On the other hand, as shown in FIGS. 13 and 14, the leg  154  is provided with a torsion spring  184 . The torsion spring  184  is disposed around the supporting shaft  162 . One end of the torsion spring  182  is anchored to the fixing piece  160  and the other end thereof is anchored to the base plate  152  of the supporting member  148 . Thus, the fixing piece  160  is urged about the supporting shaft  162  in the direction of arrow E. 
     Anchoring means, such as a projection which anchors the handle plate  168  against the urging force of the torsion spring  184  such that the widthwise direction of the fixing piece  160  extends along the widthwise direction of the mounting groove  90 , is formed at the recess portion  146  of the clamp  140 . In the back end chuck  74 , if anchoring of the handle plate  168  by the anchoring means is released with the fixing piece  160  being inserted into the mounting groove  90 , the fixing piece  160  is rotated with the handle plate  168  by the urging force of the torsion spring  184  in the direction of arrow E. Therefore, the longitudinal direction end portions of the fixing piece  160  abut the inclined surfaces  96  of the mounting groove  90 . 
     Further, in the back end chuck  74 , if the handle plate  168  is rotated against the urging force of the torsion spring  184  to be anchored to the anchoring means (not shown), the fixing piece  160  can be removed from the mounting groove  90 , i.e., the fixing piece  160  can be removed from the rotating drum  54 . Any structure may be used as the back end chuck mounting/dismounting unit  68  which mounts the back end chuck  74  to the rotating drum  54  and dismounts it therefrom. 
     Movements of the back end chuck  74  when mounted to and dismounted from the rotating drum  54  will be described. 
     If the handle plate  168  is anchored to a predetermined position on the recess portion  146  of the clamp  140 , the back end chuck  74  is held with the fixing piece  160  of the leg opposing the mounting groove  90  of the rotating drum  54  and the widthwise direction of the fixing piece  160  being aligned with the widthwise direction of the mounting groove  90  against the urging force of the torsion spring  184 . 
     In the back end chuck mounting/dismounting unit  68 , when rotation of the rotating drum  54  temporarily stops at a position in which the back end of the print plate  12  wrapped around the rotating drum  54  opposes the back end chuck  74 , the back end chuck  74  is moved to the circumferential surface of the rotating drum  54 . Thereby the clamp portion  142  of the back end chuck  74  abuts the back end of the print plate  12 . Further, as shown in FIGS. 17A and 17D, the fixing piece  160  of the leg  154  is inserted into the mounting groove  90  formed at the circumferential surface of the rotating drum  54 . 
     At this time, the plate spring  174  provided at the back end chuck  74  abuts the circumferential surface of the rotating drum  54  so as to be resiliently deformed. By inserting the fixing piece  160  into the mounting groove  90  against the urging force generated by resilient deformation of the plate spring  174 , an urging force which nips the print plate  12  between the clamp portion  142  and the rotating drum  54  is applied. 
     When the fixing piece  160  is inserted into the mounting groove  90  of the rotating drum  54 , anchoring of the handle plate  168  by the anchoring means (not shown) is released by, for example, the handle plate  168  being rotated in the direction of arrow E. 
     In this way, the fixing piece  160  inserted into the mounting groove  90  is rotated in the direction of arrow E within the enlarged width portion  92  of the mounting groove  90  by the urging force of the torsion spring  184 . The fixing piece  160  is rotated in the direction of arrow E from the state in which the widthwise direction thereof aligns with the widthwise direction of the width of the mounting groove  90 . At first, as shown in FIGS. 17B and 17E, the circular arc shaped portion  176  side of the fixing piece  160  approaches the inclined surfaces  96  within the enlarged width portion  92 . At this time, since the longitudinal direction end portions of the fixing piece  160  are spaced from the inclined surfaces  96  of the enlarged width portion  92 , the fixing piece  160  is further rotated in the direction of arrow E by the urging force of the torsion spring  184 . 
     As shown in FIGS. 17C and 17F, the fixing piece  160  is rotated up to about 90° by the urging force of the torsion spring  184  from a state in which the fixing piece  160  is inserted into the mounting groove  90 , and its longitudinal end portions (intermediate points P 1 ) abut the inclined surfaces  96  of the enlarged width portion  92 . At this time, corner portions, which are formed at the fixing piece  160  and which are formed by the linear portion  178  and the inclined portion  180 , abut the inclined surfaces  96  of the enlarged width portion  92 , thus rotation of the fixing piece  160  by the urging force of the torsion spring  184  stops. 
     That is, the circular arc shaped portions  176  are formed at the longitudinal direction end portions, and therefore the fixing piece  160  is rotated by the urging force of the torsion spring  184  in the direction of arrow E until the intermediate points P 1  abut the inclined surface  96  of the enlarged width portion  92 . If the longitudinal direction end portions of the fixing piece  160  (intermediate points P 1 ) abut the inclined surfaces  96 , because portions of the fixing piece  160  opposite the direction of arrow E with respect to the intermediate point P 1  (point P 3  side) are spaced from the center Q, the fixing piece  160  cannot be rotated more than 90° is held by the urging force of the torsion spring  184 . 
     In this way, the back end chuck  74  with which the fixing piece  160  is provided can be attached to the rotating drum  54  together with the fixing piece  160  without using a mechanism for accurately rotating the fixing piece  160 . Since the fixing piece  160  is urged in the direction of arrow E by the urging force of the torsion spring  184 , it cannot be removed from the mounting groove  90 . 
     The fixing piece  160  which is attached to the rotating drum  54  is urged in a direction in which the fixing piece  160  is removed from the mounting groove  90  by the urging force of the plate spring  174  and the centrifugal force of the rotating drum  54  when the rotating drum  54  rotates. 
     At this time, since the longitudinal direction end portions of the fixing piece  160  abut the inclined surfaces  96 , the fixing piece  160  cannot be removed from the mounting groove  90  and is securely held. In the fixing piece  160 , the inclined surface  182  at the circular arc shaped portion  176  side is formed in a circular arc with its center being the supporting shaft  162 , and therefore even if the urging force of the torsion spring  184  does not appropriately act on the fixing piece  160  and the fixing piece  160  cannot rotate up to about 90°, when the circular arc shaped portion  176  opposes the inclined surface  96  of the mounting groove  90 , it is possible to ensure that the fixing piece  160  is prevented from being removed from the mounting groove  90 . 
     On the other hand, the fixing piece  160  abuts the inclined surfaces  96  such that the rotating drum  54  receives the urging force and the centrifugal force that the inclined surfaces  96  exert on the fixing piece  160 . At this time, the inclined surface  96  is inclined at a predetermined angle θ in a range from at least 45° to less than 90° with respect to the bottom surface  94  of the mounting groove  90 . As a result, the thickness of the mounting groove  90  at a position at which it abuts the fixing piece  160  can be made relatively thick. 
     That is, as shown in FIG. 19, the cross-section of the opening of the enlarged width portion  214  is conventionally formed in a substantially rectangular configuration, thus the thickness of the peripheral edge of the opening is thin, and this thin portion receives a force from the fixing piece  216 . In order to make the portion thick, the groove  212  needs to be made deep. Accordingly, the thickness of the outer circumferential portion of the rotating drum  210  needs to be made thick. 
     In contrast, in the mounting groove  90  of the rotating drum  54  used in the second embodiment, when the enlarged width portion  92  is formed, the inclined surfaces  96 , which are inclined at a relatively large angle θ, are formed, thereby the mounting groove  90  can receive a force from the fixing piece  160  at a position whose thickness is relatively thick. Thus, the outer circumferential portion of the rotating drum  54  needs not be made thick in order to strengthen the peripheral edge portion of the mounting groove  90 . 
     Because the thickness of the rotating drum  54  can be made relatively thin, a mechanism for supporting the rotating drum  54  can be made simple and light. As the inertial force of the rotating drum  54  is small, a driving force for driving the rotating drum  54  and a braking force can be relatively small. 
     On the other hand, the angle θ of the inclined surface  96  is from at least 45° to less than 90°. Thus a force that the inclined surfaces  96  receive from the fixing piece  160  in the widthwise direction of the groove becomes large. A force, in a direction in which the circumferential surface portion of the mounting groove  90  is rolled up, can be made small. In this way, it is possible to avoid deformation of the mounting groove  90  by the fixing piece  160  without making the thickness of the rotating drum  54  thick. 
     Because the mounting groove  90  is formed in a simple shape such that its cross-section is a substantially trapezoidal configuration, a process for forming the mounting groove  90  at the rotating drum  54  is easy. 
     In this way, in the second embodiment, by providing the inclined surfaces  96  which are inclined at a predetermined angle θ at the time of forming the mounting groove  90 , it is possible to avoid deformation of the peripheral edge of the opening of the mounting groove  90  without making the thickness of the rotating drum  54  thick. Further, it is possible to avoid the mounting failure of the print plate  12 , such as the print plate  12  coming up off the drum, caused by the deformation of the peripheral edge of the opening. 
     In the second embodiment, since the circular arc shaped portion  176  is formed at only one widthwise direction end side of the fixing piece  160 , the fixing piece  160  can be rotated to a predetermined direction by a simple mechanism. 
     The second embodiment described above is shown as an example of the present invention and does not limit the structure of the present invention. In the second embodiment, the cross-section of the mounting groove  90  is formed in a trapezoidal configuration, but the present invention is not limited to the trapezoidal configuration. Any configuration may be used so long as the inclined surface is formed so as to be inclined at a predetermined angle θ which is in a range from at least 45° to less than 90°. 
     For example, like a mounting groove  188  shown in FIG. 18A, the mounting groove may be formed such that standing walls  189  are formed at the opening side thereof, a width of an opening is constant to a predetermined depth and inclined surfaces  191  which are inclined at a predetermined angle θ are formed at a bottom surface  190  side of the rotating drum  54 . 
     Like a mounting groove  193  shown in FIG. 18B, the mounting groove may be formed such that standing walls  195  are provided at the bottom surface  194  side and inclined surfaces  196  which are inclined at a predetermined angle θ are formed at the rotating drum  54  between the standing walls  189  and  195 . In this case, a structure in which the longitudinal end surfaces of the fixing piece  160  (linear portions  178 ) abut the standing walls  195  at the bottom surface  194  side is preferable. 
     Although in the second embodiment, upper ends of the linear portions  178  of the fixing piece  160  abut the inclined surfaces  96  of the mounting groove  90 , the present invention is not limited to this case. It least suffices for one portion of the fixing piece  160  to abut the inclined surface formed within the mounting groove. That is, as shown in FIG. 18C, a mounting groove  200 , in which each standing wall  199  is provided at a bottom surface  198  side of the inclined surface  197 , may be formed at the rotating drum  54  and each upper end of the linear portions  178  of the fixing piece  160  inserted into the mounting groove  200  may abut an end portion of the inclined surface  197  at the standing wall  199  side or at a bent portion between the inclined surface  197  and the standing wall  199 . 
     Further, as shown in FIGS. 18A and 18B, the inclined surfaces  182  may abut the inclined surfaces  191  and  196  of the mounting grooves  188  and  193 . 
     In the second embodiment, the circular arc shaped portion  176  is formed from the widthwise direction intermediate point of the fixing piece  160  to one widthwise direction end side thereof. For example, as shown in FIG. 18D, a fixing piece  202  in which a circular arc shaped portion  204  which is curved in a circular arc from the other widthwise direction end side of the fixing piece to the one widthwise direction end side thereof is formed and an area of a linear portion  206  is narrower than the circular arc shaped portion  204  suffices. Any fixing piece will suffice so long as the circular arc shaped portion is formed at least at only one widthwise direction end side thereof. It is preferable that a linear portion, even if it is short, is formed at its shortest at the other widthwise direction end side thereof so as to be adjacent to the circular arc shaped portion. 
     The present invention has been described by taking an image exposure device which exposes a print plate as an example. The present invention may be used in various types of exposure devices which expose photosensitive materials including not only the print plate but also a photographic film, a printing paper and the like. The present invention may be used in any device in which a fixed member such as a back end chuck or the like is fixed to a fixing member such as a rotating drum or the like at an arbitrary position. 
     The present invention may be used for a fixing member which is formed in any shape such as a cylindrical shape, a columnar shape a plate shape, and the like and a member to be fixed such as a back end chuck whose shape corresponds to that of the fixing member.