Abstract:
Objects of the invention are to provide an instant film unit advancing apparatus, used in camera or printer, of which size is reduced and to provide a film unit advancing apparatus which can avoid failure of discharging film unit out of camera or printer when a slip arises between a pair of spreading rollers and the film unit. To accomplish reduced size, the components to drive and support the pair of rollers and a picking claw for thrusting the film unit to a bite of the pair of roller by picking the edge thereof, and the picking claw itself are arrange to locate within the width of a film unit pack. The arrangements are realized by a spreading rollers supporting means which can support the spreading rollers on the surface unlike the normal bearings on the journal portion, a driving power source unit including motor and reducing gear train of which shafts are disposed parallel to the spreading rollers and a rotating cam shaft to move the picking claw which is also parallel to the spreading roller instead of a large cam plate used conventional apparatus. To avoid the failure of discharging, the cam shaft and a featured mechanism is used which is able to keep rotation of the spreading rollers independent from cam mechanism for moving the picking claw.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to a instant film unit advancing apparatus used for an instant camera or an instant printer to perform a diffusion transfer development while advancing the film unit.  
         BACKGROUND OF THE INVENTION  
         [0002]    Cameras or video printers using a mono-sheet type instant film unit as a recording media are equipped with a film unit advancing apparatus to thrust the film unit out of a film unit pack after exposing the film. The film unit advancing apparatus includes a picking claw to pick the film unit to thrust it out of the film unit pack through an exit slot, a pair of spreading rollers for spreading a developing liquid by pressing the film unit while advancing it to discharge from the camera or video printer and a driving mechanism therefor, which are driven by a common motor. Instant film unit is used for the camera or printer usually in the form of a film pack which holds a plurality of film units arranged in stacked relation therein. The camera or the printer has a film pack loading chamber around which a pair of spreading rollers, driving mechanism therefor and a picking claw driving mechanism are disposed. Japanese laid-open patent application 92/194832 (tokkai-hei 4-194832) shows an instant camera in which a pair of spreading rollers disposed above the film pack loading chamber and a spreading roller driving mechanism and a picking claw driving mechanism are disposed along the side of the chamber.  
           [0003]    Japanese laid-open patent application 95/24553 (tokkai-hei 7-248553) shows a picking claw moved by a cam plate to move which is rotated by a common motor to drive a pair of spreading rollers. The picking claw is supported by a slide plate having an integrally formed cam follower. The cam follower engages a periphery of the cam plate so that the picking claw is moved as the cam plate rotates. A predetermined stroke movement of the picking claw thrusts a film unit to a bite of the rotating spreading rollers. Then the film unit is further advanced by the pair of rotating spreading rollers while developing liquid in a container of the film unit is discharged and spread by the roller pressure. Meanwhile, the cam keeps on rotating to return the picking claw to its home position. One cycle of a sequential process that film unit is picked up at its trailing end by the picking claw, thrust out into the bite of a pair of spreading rollers, discharged out of camera and the picking claw is returned to the home position is made by one rotation of the cam plate. Upon detecting the one rotation, the motor is stopped.  
           [0004]    This mechanism requires relatively large cam plate because the difference between the largest diameter and the smallest diameter of the cam plate has to match the stroke of the picking claw, which makes it difficult to reduce the size of film unit advancing apparatus. The mechanism also requires an appropriate number of the spreading roller rotation during one rotation of the cam plate so as to discharge the film unit out of the camera or the printer, which may cause failure of discharging film unit if a slip arises between the spreading rollers and the film unit.  
           [0005]    The spreading roller has extended small diameter portions (journal portions) both at its end to be supported by bearings, which makes total length of the spreading rollers wider than the width of film pack. This is another cause of making it difficult to reduce the size of camera or printer using an instant film unit.  
         SUMMARY OF THE INVENTION  
         [0006]    An object of the invention is to provide an instant film unit advancing apparatus used in camera or printer of which size is reduced by designing new dispositions of a roller driving mechanism and/or a picking claw mechanism, particularly by improvements in terms of preventing components for the mechanism from being located beyond the width of the film unit pack.  
           [0007]    Another object of the invention is to provide a compact picking claw mechanism which does not use a large cam plate as in conventional technology to finish one cycle of picking claw sequence, i.e. from starting advancing a film unit by picking an trailing edge thereof through returning to home position. Further object of the invention is to provide a film unit advancing apparatus which can avoid failure of discharging film unit out of camera or printer when a slip arises between spreading rollers and the film unit.  
           [0008]    Yet further object of the invention is to provide a method for operating the improved film unit advancing apparatus.  
           [0009]    To accomplish those objects, the following each elements is used alone or in combination of some elements for the instant film unit advancing apparatus of the invention.  
           [0010]    1. One way transmission device for transmitting rotational force from a motor to a pair of spreading roller only when the motor rotates forwardly and not transmitting when the motor rotates reversely.  
           [0011]    2. Keep-positioning means for keeping the picking claw in the same position despite of rotation of the motor.  
           [0012]    3. Reciprocating means for reciprocating a picking claw between a home position and an advanced and waiting position, wherein the reciprocating means can return the picking claw from the advanced and waiting position to the home position by making use of reverse rotation of the motor.  
           [0013]    4. Each of a pair of spreading rollers is rotatably supported on its surface by roller supporting means.  
           [0014]    5. A driving power source unit for driving the pair of spreading rollers and picking claw constituted by the motor and the reducing gear train mounted on a plurality of shaft one of which is connected to a output shaft of the motor, wherein all the shafts of the driving power source unit is arranged parallel to the pair of spreading rollers.  
           [0015]    6. The picking claw is slidably mounted behind a rear plate of the base frame which is mounted inside the film unit loading chamber for positioning the film unit pack.  
           [0016]    7. Forward and reverse rotation to advance the film unit and return the picking claw is controlled by a timer.  
           [0017]    Preferred embodiments of the invention are as follows.  
           [0018]    An instant film unit advancing apparatus for advancing a film unit after exposure for developing and discharging outside, comprises a loading chamber for loading a film unit pack; a pair of spreading rollers driven by a motor for developing and advancing an exposed film unit; a picking claw for thrusting the exposed film unit to a bite of the pair of spreading roller (by picking a trailing edge of the exposed film unit); an one way transmission device for transmitting rotational force from the motor to the pair of spreading roller only when the motor rotates forwardly and not transmitting when the motor rotates reversely; and a reciprocating means for reciprocating the picking claw between a home position and an advanced and waiting position, wherein the reciprocating means includes a shifting means for shifting the picking claw between the home position and the advanced and waiting position and a keep-positioning means for keeping the picking claw in the same position despite of rotation of the motor. Preferably the shifting means includes a motor driven cam shaft having a spiral cam groove on the periphery and a interconnecting lever which has a cam follower on one end engaging the spiral cam groove so that the interconnecting lever can swing as the cam shaft rotates to shift the picking claw by a predetermined stroke.  
           [0019]    An instant film unit advancing apparatus for advancing a film unit after exposure for developing and discharging outside, comprises a loading chamber for loading a film unit pack; a pair of spreading rollers driven by a motor for developing and advancing an exposed film unit; a picking claw for thrusting the exposed film unit to a bite of the pair of spreading roller (by picking a trailing edge of the exposed film unit); and a reciprocating means for reciprocating the picking claw between a home position and an advanced and waiting position, wherein the reciprocating means can return the picking claw from the advanced and waiting position to the home position by making use of reverse rotation of the motor.  
           [0020]    An instant film unit advancing apparatus for advancing a film unit after exposure for developing and discharging outside, comprises a loading chamber for loading a film unit pack; a base frame mounted inside the loading chamber for positioning the film unit pack; a picking claw for thrusting the exposed film unit to a bite of the pair of spreading roller (by picking a trailing edge of the exposed film unit); and a pair of spreading rollers driven by a motor for developing and advancing an exposed film unit, wherein each of the pair of spreading rollers is rotatably supported on its surface by a roller supporting means.  
           [0021]    An instant film unit advancing apparatus for advancing a film unit after exposure for developing and discharging outside, comprises a loading chamber for loading a film unit pack; a base frame mounted inside the loading chamber for positioning the film unit pack; a picking claw for thrusting the exposed film unit to a bite of the pair of spreading roller; a pair of spreading rollers for developing and advancing an exposed film unit; and a driving power source unit for driving the pair of spreading rollers and picking claw constituted by the motor and the reducing gear train mounted on a plurality of shaft one of which is connected to a output shaft of the motor, wherein all the shafts of the driving power source unit is arranged parallel to the pair of spreading rollers. Preferably the picking claw is slidably mounted behind a rear plate of the base frame.  
           [0022]    An instant film unit advancing apparatus for advancing a film unit after exposure for developing and discharging outside, comprises a loading chamber for loading a film unit pack; a base frame mounted inside the loading chamber for positioning the film unit pack; a picking claw driven by a cam shaft for thrusting the exposed film unit to a bite of a pair of spreading roller; and a driving unit including a driving power source unit, a pair of spreading rollers, intermediate gears for transmitting a rotational force from the driving power source unit to the pair of spreading rollers and the cam shaft, wherein the driving unit is located within a space defined by a top wall of a cassette of the film unit pack where a film unit exit slot is formed and both side plates of the base frame.  
           [0023]    A method of advancing an instant film unit for developing and discharging outside, comprises steps of starting a motor rotating forwardly after a film unit is exposed in order to rotate a pair of rollers and a cam shaft to move a picking claw; starting timer system at the same time where a first predetermined time period is set, generating motor-stop signal when the first predetermined time period passes; starting the motor rotating reversely to return the picking claw to home position while keeping stopping the pair of rollers; starting timer system at the same time where a second predetermined time period is set; and generating motor-stop signal when the second predetermined time period passes.  
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0024]    [0024]FIG. 1 shows an external perspective view of an electronic still camera with a printer.  
         [0025]    [0025]FIG. 2 shows an exploded perspective view illustrating a main portion of a structure inside a film unit pack loading chamber.  
         [0026]    [0026]FIG. 3 shows across-sectional view of the film unit pack loading chamber where the pack is loaded.  
         [0027]    [0027]FIG. 4 shows an exploded perspective view of a pair of spreading rollers.  
         [0028]    [0028]FIG. 5 shows an explanatory diagram illustrating a main portion of a pair of spreading rollers.  
         [0029]    [0029]FIG. 6 shows an explanatory diagram illustrating a main portion of a pair of spreading rollers where an film unit is nipped.  
         [0030]    [0030]FIG. 7 shows a perspective view of a driving system including driving power source unit for a pair of spreading rollers.  
         [0031]    [0031]FIG. 8 shows an exploded perspective view of a structure of a film unit advancing apparatus.  
         [0032]    [0032]FIG. 9 shows a developed view of a cam groove and movement of a cam follower in association with rotational direction of motor.  
         [0033]    [0033]FIG. 10 is a front view in elevation showing layout of a driving unit and a film unit pack.  
         [0034]    [0034]FIG. 11 is a exploded perspective view illustrating a mechanical structure for moving a exposure head in both main and sub scanning direction.  
         [0035]    [0035]FIG. 12 is a block diagram illustrating a system of an electronic camera with printer using instant film unit.  
         [0036]    [0036]FIG. 13 is a sectional view of a one way clutch.  
         [0037]    [0037]FIG. 14 is an explanatory diagram illustrating a positional relation in a picking claw mechanism when the picking claw is in the home position  
         [0038]    [0038]FIG. 15 is an explanatory diagram illustrating a positional relation in a picking claw mechanism when the picking claw is in the advanced and waiting position.  
         [0039]    [0039]FIG. 16 shows a timing chart illustrating the timing of a motor, a pair of spreading rollers, a picking claw and a film unit in a cycle of operation.  
         [0040]    [0040]FIG. 17 is a sectional view of a frictional clutch. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0041]    [0041]FIG. 1 shows an electronic still camera with printer  10  using instant film unit. In the front side of a camera body  12  are disposed a taking lens  13 , a flash emitting window  14 , a film pack loading lid  22 , a loading lid opening button  15  and a shutter release button  17  located on a grip portion  16 . A film unit used for the camera with printer  10  is a well-known mono-sheet type instant film unit  19  which is stacked in a cassette of film pack  20 . The instant film unit  19  includes a photographic sheet, an image receiving sheet, a pod  19   a  containing developing liquid therein and a trap  19   b  disposed opposite end to the pod  19   a  for trapping excess developing liquid. After the photographic sheet is exposed, the pod  19   a  is ruptured by a pair of pressing spreading rollers to spread the developing liquid between the photographic sheet and the image receiving sheet to develop the image, and finally a visible image is formed on the image receiving sheet.  
         [0042]    The film pack  20  consists of a cassette and film units stacked therein. The film pack  20  is loaded in a film pack loading chamber  23  formed in the front side of the camera. A film pack loading lid  22  hinged  21  to the camera body is used for closing the loading chamber  23 . In the top side of the camera body  12  is formed an exit slot  24  through which the film unit  19  is discharged after being exposed in printing operation. A pair of spreading rollers are located behind the exit slot  24  which spreads a developing liquid before discharging the film unit  19  out of the camera body. On the back side of the camera body  12  (not shown) a LCD panel, print start switch and power switch are disposed. The LCD panel is a display monitor to display an image of photographic object through the lens and an image to be printed in printing operation.  
         [0043]    As shown in FIG. 2 and FIG. 3, a base frame  26  for positioning a film unit pack and for mounting a printing exposure unit is built-in inside the film unit pack loading chamber  23 . Loaded film pack  20  is pressed against a front plate  26   a  of the frame by a pressing member  27  mounted on the back of the loading lid  22 . A cassette of the film unit pack has an exposure aperture  28  to define an exposed image area in the front side of the cassette and an film unit exit slot  20   a  in the top wall of the cassette close to the spreading rollers. The front plate  26   a  has a front plate opening  29  facing the exposure aperture  28 . The front plate opening  29  is large enough to expose whole exposure aperture  29 . On the top edge and both side edge forming the front plate opening  29  are formed positioning ribs or positioning projections which fit in positioning members formed on the front side of the cassette of the film pack  20 .  
         [0044]    A driving unit  31 , comprising a motor  30 , a roller driving mechanism including gears, a pair of spreading rollers, and a part of a picking claw driving mechanism (a camshaft), is located immediately above the film unit exit slot  20   a  of the film unit pack  20  loaded in the loading chamber  23 . A base frame  26  includes a front plate  26   a,  a rear plate  26   d,  a left side plate  26   c  and a right side plate  26   b  which are formed by bending or folding a metal plate. Between the front plate  26   a  and the rear plate  26   d  is installed a printing exposure unit  32  which is movable in the film advancing direction when printing. A picking claw  33  as a part of the picking claw driving mechanism is slidably mounted behind the rear plate  26   d.    
         [0045]    As shown in FIG. 4, A pair of spreading rollers  36  as a part of the roller driving mechanism consists of a fixed roller  36  and a movable roller  38  which pressed against each other. Both the fixed roller  36  and the movable roller  38  have the same radius and roller gears  39  and  40  at their one ends respectively. Both rollers surfaces  37   a  and  38   a  have axial lengths L which barely cover a width of the film unit  19 . The two roller gears  39  and  40  are away from each other.  
         [0046]    The roller surface  37   a  of the fixed roller  37  is born at both end portions by fixed roller supporting units  41  and  42  each of which consists of a set of three wheels  43  and a wheel holding member  44 . Each of the fixed roller supporting unit  41  and  42  secured to the front plate  26   a  is positioned opposite to the movable roller  38  and the set of three wheels are arranged in arc by the wheel holding member  44  so that three wheels  43  can contact rotating roller surface  37   a.  Also the roller surface  38   a  of the movable roller  38  is born at both end portions by movable roller supporting units  47  and  48  each of which consists of a set of three wheels  49 . a movable wheel holding member  50  and a spring  51  to urge each of the movable roller supporting units toward the movable roller.  
         [0047]    The movable roller supporting units  47  and  48  is positioned opposite to the fixed roller  37  and the set of three wheels are arranged in arc by the movable wheel holding member  50  so that three wheels  49  can contact rotating roller surface  38   a.  Each set of three wheels  49  and  43  thus contacts, supports and presses the spreading roller surface at the position in the axial direction where the spreading rollers pressure is to be applied to the film unit  19 , i.e. within the width of the film unit.  
         [0048]    As shown in FIG. 5 and FIG. 6, the movable wheel holding member  50  has a wide-U or arc shape in the section open toward the movable roller  38 . The movable wheel holding member  50  is pivotally mounted to a wheel holding member supporting shaft  50   a  at one end portion of the wide-U shape and urged against the movable roller  38  so that the movable roller can be pressed against the fixed roller  37 . Each set of three wheels  49  and  43  is arranged so as to approximately face each other via a pair of spreading rollers to be able to resist mutual reaction and so as to be off the film unit advancing path H. As shown in FIG. 6, when the film unit is put into the bite of a pair of rollers, the movable roller  38  slightly rotates counterclockwise about an axis of the wheel holding member supporting shaft  50   a  to allow the film unit to pass through while being held by the movable roller supporting units  47  and  48 .  
         [0049]    Clutch gears  52  and  53 , which mesh with each other, are meshed with the gear  39  fixed to the fixed roller  37  and the gear  40  fixed to the movable roller  38  respectively. As shown in FIG. 7, a clutch gear  53  and the intermediate gear  54  are mounted on the same shaft side by side. The clutch gear  53  has a built-in one way clutch mechanism to transmit only a forward rotation by the motor  30  via a reducing gear train  55  to the shaft of the intermediate gear  54 . A reverse rotation of the motor  30  can not be transmitted to the gear  53 . Thus a pair of spreading rollers  36  can rotates in the film advancing direction to advance the film unit  19  toward the exit slot  24  only when the forward rotation is transmitted.  
         [0050]    The clutch gear  53  is rotatably mounted on the wheel holding member supporting shaft  50   a.  Therefore the mesh between the clutch gear  53  and the gear  40  which rotates together with the movable roller  38  is always kept when the wheel holding member  50  swings to allow the film unit to pass through or for some other reasons.  
         [0051]    [0051]FIG. 8 shows the intermediate gear  54  meshes with a gear  56  which meshes with a gear  57 . The gear  57  and a slipping gear  58  are mounted on the same shaft side by side to function as a friction clutch  59 . When the slipping gear  58  rotates, a cam shaft  60  which has specially designed cam groove  61  is rotated integrally. A cam follower  62   a  formed in one end portion of a swing lever  62  is engaged with the cam groove  61 . The swing lever  62  interconnects the cam shaft  60  and the picking claw member  33  to transform the movement of cam follower  62   a  into the movement of picking claw member. A picking claw engaging pin  62   b  formed in the other end is engaged with the picking claw member  33  via a slot formed therein. Thus, when the motor  30  rotates, the cam shaft rotates, which causes the swing lever  62  to swing (about an axis of hole  62   c  by a movement of the cam pin  62   a  according to the cam groove  61  and the picking claw is moved by a swing of the engaging pin  62   b.  Thus the cam shaft  60  and the swing lever  62  constituting a cam mechanism  63  can convert a rotational movement given by the motor  30  into a linear one in the film advancing direction.  
         [0052]    As mentioned before, FIG. 8 shows a structure of the film unit advancing apparatus  132  which includes a motor  30 , the spreading rollers driving mechanism  34  and the picking claw driving mechanism  63 . An rotary encoder  136  is mounted on an output shaft of the motor  30 , which consists of a slit disc  137  having a great number of slit in radial direction fixed on the output shaft  133   a  of the motor  30  and a photo sensor  138 . The rotary encoder  136  generates pulse signal the number of which corresponds to the number of slits of the slit disc  137  counted by the photo sensor  138 . A magnetic or brush-type rotary encoder can be substituted for the optical one.  
         [0053]    When the motor  30  rotates forwardly, the rotation of the motor  30  is transmitted to the spreading roller driving mechanism  134  and the picking claw driving mechanism  63  via the speed reducing mechanism (gear train)  55 . When the motor  30  rotates reversely, the rotation is not transmitted to the spreading rollers  36  due to one way clutch (explained later) but only to the picking claw mechanism. The spreading roller driving mechanism  134  transmits the rotation of the motor  30  to the spreading rollers  36  via gear train  54 ,  56 ,  53 ,  52 ,  40  and  39 .  
         [0054]    As shown in FIG. 13, one way clutch gear  53  is constituted by a ring  146  with an engaging recess  147  formed in periphery thereof and an engaging small shaft  148  therein. When the ring  146  rotates counterclockwise in the drawing due to the rotation of the gear  54  adjacent to the clutch gear  53 , the engaging small shaft  148  moves toward narrower space in the engaging recess  147  and finally stops relative movement between the inner wall of a ring gear  139   a  and the recess  147  of the ring  146  by a strengthened friction, which leads to rotation of the ring gear  139   a  (i.e., rotation of the clutch gear  53 ) together with the ring  146 . Rotation of the gear  53  rotates the spreading roller via gear  40  in the film unit advancing direction.  
         [0055]    [0055]FIG. 8 shows a picking claw mechanism  35  which includes gears  57  and  58 , a cam  61  formed on a cam shaft  60 , a swing lever  62  and a picking claw  33 . The picking claw member  33  formed by bending a metal plate comprises a claw portion  33   b  and a bracket portion  33   a.  The claw portion  33   b  moves through a slot  46  formed in the rear plate  26   b  of the base frame  26  and another slot formed in the cassette of the film pack  20  to pick up the trailing edge of the film unit  19 . The picking claw member  33  is mounted for sliding movement in the film advancing direction on the back side of the rear plate  26   b  of the base frame  26  by using mounting pins  159  through three guide slots  158  formed in the bracket portion  33   a.  The guide slots  158  and the mounting pins  159  functions as guide for the sliding movement. One of the mounting pins near the claw portion  33   b  wears a coil spring  160  between its head and the bracket portion  33   a  to bias the bracket portion  33   a  toward the film pack (more precisely to urge the claw portion  33   b  against the exposure side of the film unit  19 ) in order to ensure that the claw portion  33   b  picks up the trailing edge of the film unit  19 . The bracket portion  33   a  has an engaging slot  161  into which the engaging pin  62   b  formed on the swing lever  62  is put in.  
         [0056]    On the base frame  26  for swinging about a hole  62   c  is mounted the swing (interconnection) lever  62  which makes the picking claw member  33  move back and forth between a home position shown in FIG. 14 and an advanced and waiting position shown in FIG. 15 which predetermined stroke away from the home position. The lever  62  also has a cam follower  62   a  to engage the cam groove  61 . The cam follower  62   a  is spring-biased toward the right in the drawing by a spring  162 . A gear  58  is mounted on one end of a cam shaft  60  which is driven by a gear  57  to which driving force of the motor  30  is transmitted via gear train  55 . Thus the cam shaft  60  is driven by the motor  30 .  
         [0057]    On the periphery of the cam shaft  60  is formed the cam groove  61  which makes the swing lever  62  swing to move the picking claw member  33  back and forth between the home position and the advanced and waiting position. In this embodiment the cam follower  62   a  is moved by the rotation of the cam groove  61 , however FIG. 7 shows a relative position of the cam follower  62   a  to the cam groove assuming that the cam groove  61  stays still and the cam follower  62   a  relatively moves. In the drawing, when the motor rotates in the forward direction, i.e. the film unit is to be advanced, the cam follower  62   a  moves toward the right, and when the motor rotates in the reverse direction, the cam follower  62   a  moves toward the left. The cam groove  61  consists of a shifting portion  61   a  and a keep positioning (non-shifting) portion  61   b.  The shifting portion  61   a  has a spiral groove which is capable of moving the picking claw member  33  back and forth between the home position and the advanced and waiting position according to the direction of motor rotation.  
         [0058]    The keep-positioning portion  61   b  functions as a stopping cam for keeping a cam follower  62   a  staying in the same position and consists of a closed loop groove, continued to the end of the shifting portion  61   a,  formed in the plane perpendicular to the axis of the cam shaft  60 . While the motor  30  rotates in the forward direction, the cam follower  62   a  in the keep-positioning portion  61 a can not move into the shifting portion  61   a,  which keeps the picking claw member  33  staying at the advanced and waiting position. When the motor  30  rotates in the reverse direction, the cam follower  62   a  moves back to the shifting portion  61   a  with the help of spring  162  urging the cam follower  62   a  toward the shifting portion  61   a,  which makes the picking claw member  33  move back to the home position.  
         [0059]    [0059]FIG. 16 shows a timing chart indicating sequential actions of the main components of the film advancing apparatus at the film unit advancing stage. When printing the image on the instant film unit starts after photographing through the taking lens, first an exposure unit  64  exposes the film unit  19  and then the motor  30  starts to rotate in the forward direction. The rotation is transmitted to the spreading roller  36  and the cam shaft  60 . The rotation of the cam shaft  60  moves the cam follower  62   a  in the shifting portion  61   a,  which causes the swing lever  62  to swing so as to shift the picking claw member  33  from home position toward the advanced and waiting position. In this process, the claw portion  33   b  of the picking claw member  33  picks up the edge of the film unit  19  and advances it toward the spreading rollers  36 .  
         [0060]    When the picking claw member  33  reaches the advanced and waiting position illustrated in FIG. 15, the cam follower  62   a  also arrives at the keep-positioning portion  61   b,  which stops swinging of the swing lever  62 . Thus the picking claw member  33  is stopped there. By this point, the film unit  19  reaches the bite of a pair of spreading rollers  36  and the pod  19   b  of the film unit  19  is ruptured to discharge and spread the developing liquid inside the film unit.  
         [0061]    As the cam shaft  60  can keep rotating, i.e. a pair of spreading rollers  36  as well as the motor  30  can keep rotating, while the picking claw member is staying at the advanced and waiting position, the film unit  19  is certainly discharged out of the camera with completing spreading the liquid to develop even if the slip arises between the rollers  36  and the film unit  19 , which is impossible in the conventional way using one-turn cam plate sequential control.  
         [0062]    After completing spreading the developing liquid in the film unit  19 , the motor  30  stops and the spreading rollers  36  and other rollers including the cam shaft stop rotating. The time period of motor rotation from starting to stopping is set by a timer so as to have enough time to discharge the film unit  19  out of the pair of rollers  36 , which consists of some extra time T 2  in addition to normal time T 1  to discharge the film unit without any slip. In this embodiment, the time period T 1 +T 2  is stored in memory in advance and when the motor driving time after starting motor rotation, which is calculated by detecting the number of total motor rotation by a rotary encoder  136 , reaches T 1 +T 2 , the motor  30  is stopped.  
         [0063]    Then the motor  30  starts to rotate again in the reverse direction. In this stage, the spreading rollers  36  do not rotate because of the one way clutch  45  and only the cam shaft  60  rotates. Lack of reverse rotation of the spreading rollers  36  can reduce the battery energy consumption and may avoid the invasion of foreign matters stuck on the surface of the rollers into the inside of the camera body  12 .  
         [0064]    As the cam shaft  60  rotates in the reverse direction, the cam follower  62   a  of the swing lever  62  is shifted back into the shifting portion  61   a  due to biasing force by the spring  162 , which makes the picking claw member  33  move back toward the home position. After the picking claw member  33  arrived at the home position, the motor  30  is stopped. A time period T 3  of motor rotation is set by a timer so as to have enough time to return the home position. In this embodiment, when the motor driving time after starting reverse rotation of the motor  30 , which is calculated by detecting the number of total motor rotation by a rotary encoder  136 , reaches T 3 , the motor  30  is stopped. When the cam follower  62   a  reaches dead end of the cam groove which corresponds to the home position of the picking claw member  33  yet before the time T 3  does not pass, the cam shaft is forced to stop rotating, but the motor  30  is still rotating. The slipping gear  58  in FIG. 8 and FIG. 17 can absorb the rotating force by slipping to protect the motor from overload.  
         [0065]    As the invention explained above uses the cam shaft having the cam groove  61  with keep-positioning portion  61   a  to be able to keep the picking claw member  33  staying in the advanced and waiting position even while the motor rotates, it is no need to use a large cam plate for one-turn sequential control of shifting the picking claw member  33  in the conventional way, which can reduce the size of the film unit advancing apparatus  132 . Also it is avoided that the motor  30  stops in the middle of advancing the film unit.  
         [0066]    In the above embodiment, keep-positioning portion is used for keeping the picking claw member  33  staying the advanced and waiting position. Another way to perform the same function is, for example, to use a friction clutch such as disc clutch which is disposed between the gears  57  and  58 . As shown in FIG. 9, a disc clutch  70  consists of a friction surface  57   a  of the gear  57  and a friction surface  58   a  of the gear  58  which are urged against each other. The rotation of gear  57  is transmitted to the gear  58  to rotate the cam shaft  60  according to a friction force between the two surfaces. In the case where a dead end cam groove is used instead of the non-shifted portion of closed ring groove, when the cam follower  62   a  reaches dead end of the cam groove which corresponds to the advanced and waiting position of the picking claw member  33 , the cam shaft  60  is forced to stop rotating, but the motor  30  is still rotating. However, as the friction disc clutch  59  can absorb the rotating force by slipping, the picking claw member can stay in the same position without giving an overload to the motor  30  and the cam mechanism. A conical clutch or a drum clutch also can be used as a friction clutch.  
         [0067]    On the contrary, the keep-positioning portion of closed ring groove can be used for keeping the picking claw member  33  staying at the home position instead of using a slipping mechanism and the dead end cam groove. In this case, another cam follower shifting mechanism such as a coil spring, which pull the cam follower toward the shifting portion, may be necessary to shift the cam follower  62   a  into the shifting portion from the keep-positioning portion corresponding to the home position.  
         [0068]    How long the motor has been rotating is calculated by detecting the number of total motor rotation by a rotary encoder  136  in the above embodiment. Another ways without measuring time can be used, for example, that the motor is stopped when the completion of discharging the film unit out of the spreading rollers is determined by detecting its trailing end using a photo-sensor. For confirming the picking claw member reaches home position, a photo sensor can be used and upon confirming, reverse rotation of the motor is stopped. A micro-switch also can be substituted for the photo-sensor.  
         [0069]    As explained in conjunction with FIG. 7, a spreading roller driving mechanism includes a motor  30 , a gear train  55 , intermediate gears  52  and  53 , and the gears  39  and  40  of the spreading rollers. The picking claw driving mechanism includes the motor  30 , the gear train  55  and the clutch gear  54 , which are common in the spreading roller driving mechanism, in addition to those, the gears  56  and  57 , the slipping gear  58 , the cam shaft  60 , the swing lever  62  and the picking claw  33  as explained in association with FIG. 8. The components from the motor  30  through the cam shaft  52  are included in the power  31 . A driving power source unit is constituted by the motor  30  and the reducing gear train  55  mounted on a plurality of shaft one of which is connected to a output shaft of the motor  30  directly. All the shaft of the driving power source is arranged parallel to the pair of spreading rollers  36  and the entire length of the power source unit is less than the width of the film unit pack  20 . The gears, the spreading rollers and other rotating shafts are all disposed so that the rotational axes become perpendicular to the film unit advancing direction. As shown in FIG. 2 and FIG. 3, the pair of spreading rollers and the driving power source unit are supported by a base frame and so closely placed that an output of the driving power unit can be transmitted to the pair of rollers via only one or two intermediate gear.  
         [0070]    The surfaces of a pair of spreading rollers  37   a  and  38   a  are supported by the fixed roller supporting units  41  and  42  and the movable roller supporting units  47  and  48  at both end portions of the rollers, i.e. within the width of the film unit respectively as explained before, which leads to no need of anything disposed outside the both ends of the spreading rollers except thin gears on one side of each rollers. Thus whole width of the driving unit  31  can be less than inner width of the base frame  26 , namely the driving unit  31  can exist within the area of the base frame  26 *. Besides the picking claw member  33 * is located behind the rear plate  26   b  of the base frame  26 , which leads to no need of anything disposed outside the side plate of the base frame  26 . Consequently, the inner width of the base frame  26  can be substantially the same as a width of the film pack  20  as shown in FIG. 10. Nothing to advance the exposed film unit has to be placed outside the base frame area unlike the conventional instant film unit advancing apparatus. This makes it possible to reduce the size of camera or printer using instant film unit according to reduced size of the film pack loading chamber  23 .  
         [0071]    [0071]FIG. 11 shows a printing exposure unit  64  , for printing the image recorded by the electronic still camera on the film unit, comprising a exposure head  66  and a head moving mechanism  67  for scanning which are accommodated in a thin rectangular box  65  which has an opening  65   a  for the light emitted from the exposure head  66 . The exposure head  66  has a light emitting portion and an optical image focusing system built-in. The light emitting portion has a set of three minute white light emitting elements which are lined up in the sub-scanning direction (film unit advancing direction) each of which is covered by a R, G or B color filter respectively to emit the light of three colors. The optical image focusing system includes a CELFOC lens (“CELFOC” is the trademark for graded index type optical fiber which functions as a lens due to its refractive index distribution of the second order curve symmetrical about the axis) and a mirror to focus the three color lights emitted by the light emitting elements on the film unit.  
         [0072]    The head moving mechanism  67  consists of two mechanisms; a main scanning direction moving mechanism  67   b  and a sub-scanning direction moving mechanism  67   a  both of which are driven by a common single motor  69 . The main scanning direction moving mechanism  67   a  moves the head  66  reciprocally in a direction perpendicular to film unit advancing direction and the sub-scanning direction moving mechanism  67   a  moves the head  66  by one line of forming image per one reciprocal movement of the main moving mechanism  67   b.    
         [0073]    The sub-scanning direction moving mechanism  67   b  includes a gear train  68 , a pair of s gear  71  and  72  which are exposed outside the box  65 , and a pair of racks  73  and  74 . (See also FIG. 2) The gear train  68  transmits a reduced rotation of the motor  69  to a pair of pinion gears  71  and  72  which mesh a pair of rack  73  and  74  respectively. A pair of the racks  73  and  74  is formed on the edges of the left side plate  26   c  and the right side plate  26   d  in the sub-scanning direction. The box  65  is guided and properly positioned by making use of the rear plate  26   b  and both side plates  26   c  and  26   d  so as to avoid any deviation from the exact sub-scanning direction and backlash to mesh of the pinion and the rack when it moves.  
         [0074]    The main scanning direction moving mechanism  67   b  comprises the gear train  68 , a reciprocating cam shaft  75 , a bush with cam follower  76  secured to a exposure head  66  and a rotation stopper consisting of a slide rail  77  and a rail receiver  78 . The reciprocating cam shaft  75  is disposed parallel to the main scanning direction and rotated by a motor  69  via the gear train  68 . A reciprocating cam  75   a  is formed on the reciprocating shaft  75 . The bush with cam follower  76  is fit on the reciprocating cam  75   a  which is an endless circulating cam capable of reciprocating the exposure head  66  repeatedly in the main scanning direction. The slide rail  77  is placed parallel to the main scanning direction on the bottom of the box  65 . The rail receiver  78  formed in a lower portion of the exposure head  66  is slidably received by the slide rail  77 .  
         [0075]    The exposure head  66  exposes the instant film unit  19  with RGB three colors by one line of the image while traveling from one side (exposure head home position) to the other and shifts by one line in the sub-scanning direction while traveling back to the home position. In such serial printing, it is preferable to install one way clutch somewhere in the drive transmission mechanism, for example, in the middle of gear train, in order to avoid any movements of the exposure head  66  in the main scanning direction when the motor  69  rotates reversely to return the exposure head  66  to the original position for initiating the image printing. At the original position, the exposure head  66  is at its home position (in the main scanning position) and the exposure unit  64  is also at its home position (in the sub scanning direction).  
         [0076]    The box  65  is equipped with a photo sensor  80  to detect the home position for the exposure unit  64 . The photo sensor  80  generates a stopping signal to stop the motor  69  when detecting a light shielding plate  81  fixed on the rear plate  26   d  of the base frame  26  to indicate the home position.  
         [0077]    An rotary encoder  82  for detecting rotation angle is mounted on an output shaft of the motor  69  consisting of a slit disc  83  fixed on the output shaft of the motor  69  and a photo sensor  84 . The rotary encoder  82  generates pulse signal the number of which is corresponds to the number of slits of the slit disc  83  counted by the photo sensor  84 . A position of the exposure unit  64  in the sub-scanning direction is determined by counting the number of the pulse.  
         [0078]    As shown in FIG. 12, a camera  10  has a photographic section  85  including a CCD image sensor  86 , an A/D converter  87  and a image processor  88 . A subject image is focused on the CCD image sensor  86  through a taking lens  13 , the CCD image sensor transforms the optical image to an electronic image signal. The A/D converter  87  converts the electronic image data to the digital image data which is input into the image processor  88  sequentially which processes the digital image data for adjusting white balance and giving a γ correction.  
         [0079]    A controller  90  generates an image signal corresponding to a composite signal based on an image data processed by the image processor  88  to input a driver  93  via a D/A converter  91  and an amplifier  92 . The driver  93  drives a LCD panel  94  according to the image signal. Thus the image of the subject can be continuously displayed on the LCD panel  94 , which can function as an electronic view finder.  
         [0080]    The film unit advancing motor  30  is controlled by a driver  95 . The controller  90  actuates a first timer circuit  96  after the exposure by the exposure head  66  to count down according to a predetermined time period T 1 +T 2  for whole instant film unit  19  to emerge from the camera  10 , i.e. the trailing edge of the film unit  19  leaves the bite (nip) of the pair of spreading rollers  36 , while controlling the driver  95  to keep the motor  30  forwardly driving. When the predetermined time period T 1 +T 2  for the film unit emerging passes, i.e. count-down reaches zero, the controller  90  controls the driver  95  to start the motor  30  reversely while starting to actuate a second timer circuit  97  at the same time to count down according to the predetermined time period T 3  for the picking claw member  33  to return to its home position. When the predetermined time period for the picking claw returning passes, the driver  95  stops the motor  30 .  
         [0081]    The motor  69  for moving the exposure head is controlled by a driver  98  which the controller  90  controls based on a signal output from the photo sensor  80  and the encoder  82 . The controller  90  is also connected to a memory card drive  99  to which a memory card  100  is plugged in. Each of image data processed by the image processor  88  is recorded on the memory card. At printing, image data for each colors is read line by line from the memory card  100  to be stored in a line memory  101 . A driver  102  drives the exposure head  66  based on the image data stored in the line memory  101 . The exposure head  66  controls light intensity of each light emitting elements according to the image data.  
         [0082]    Sequential operations and processes of the camera with printer are as follows. First, the film pack loading lid  22  is opened by pressing the loading lid opening button  15  to load the film pack  20  in the film pack loading chamber  23 . The exposure aperture  28  of the film pack faces the front plate opening  29  of the base frame  26 . When the lid  22  is closed, the film pack  20  is pressed by the pressing member  27  against the base frame  26  so as to be set in a position for printing which is defined by the front plate  26   a  of the base frame  26 .  
         [0083]    When photographing, user depresses the shutter releasing button while monitoring the displayed image of the subject on the LCD panel  84 . The displayed image on the LCD at the shutter releasing is recorded in the memory card  100 .  
         [0084]    At printing, the images stored in the memory card  100  are to be displayed on the LCD panel  64 . When user selects one of the image on the display panel  64  and turns on a printing switch, the controller  90  makes three colored image data of the selected one be read from the memory card  100  sequentially line by line and transferred to the line memory  101 . During this process, the exposure head  66  starts an approach run above (in the sub scanning direction) an actual printing area (photosensitive area of the film unit) and reaches a starting line where the actual exposure for printing is to start after the running speed of the exposure head  66  becomes constant.  
         [0085]    When the head  66  reaches the starting line is detected by counting the number of pulse signal generated by the encoder  82 . When the exposure head  66  reaches the starting line, edge of the printing area, the controller  90  drives the exposure head  66  according to the image data of each colors by controlling the driver  102 . While the exposure head  66  moves, the controller  90  controls light emitting time or light intensity of the light emitting element in response to pulse signal from the encoder  82  to avoid unevenness of exposure, such as mottled density and/or color caused by moving speed fluctuation.  
         [0086]    The exposure head  66  exposes the instant film unit  19  with RGB three colors by first one line of the image while traveling from one side (exposure head home position) to the other and shifts by one line in the sub-scanning direction while traveling back to the home position. Before exposing for second line of the image, image data of three colors for second line are transferred from the memory card  100  to the line memory  101  and the second line of the image is printed in the same way as the first line. In this manner, the printer section of the camera  10  forms picture on the instant film unit  19  by serial recording method.  
         [0087]    The controller  90  can recognize by counting the number of pulse signal from the encoder  82  that the exposure head  66  reached the last line to be printed and reciprocated to make the last line exposure for the picture. Thus the latent full-color image of the user-selected one is completed on the photosensitive sheet of the film unit  19 . Then the controller  90  stops the forward rotation of motor  69 .  
         [0088]    Alternatively, a line-printing method can be substituted for the serial printing method mentioned above. The line-printing method uses line-type light emitting elements which holds a great number of light emitting elements side by side in line, which does not need to make movement in the main scanning direction as in the serial printing method.  
         [0089]    After finishing the exposure printing, the controller  90  returns the exposure head  66  to the original position by switching the rotation direction of the motor  69  from forward direction to reverse one. When the exposure head  66  reaches the original position, the photo-sensor  80  detects the light-shield plate  81  and generates stopping signal for the motor  69 . In succession, the controller  90  starts the motor  30  rotating forwardly for advancing and developing the film unit  19  and activates the first timer circuit  96  for count-down the time period for rotating the spreading rollers.  
         [0090]    A forward rotation of the motor  30  is transmitted to the pair of spreading rollers  36  via the gear train  55  and the clutch gear  54 , which advance the film unit  19  toward the exit slot  24 . The gear train  55  also transmits the rotation to the cam mechanism  63  via the slipping gear  58 . The cam mechanism  63  shifts the picking claw member  33  from the home position toward the advanced and waiting position by a predetermined stroke by using a rotation of the cam shaft  60  with cam groove and the swing lever  62  swung thereby. At the beginning of the shifting, the claw portion  33   b  slips into the slot formed in the cassette of the film pack  20  to pick up the trailing edge of the film unit  19  and advance it toward the spreading roller  36 . Then the film unit  19  is put into the bite of the pair of spreading roller  36  through the exit slot  20   a  (See FIG. 3). At this point, the movable roller  38  is pushed up by the edge of film unit  19  and turned together with the movable wheel holding member  50  counterclockwise about an axis  50   a  shown in FIG. 6 against biasing force of the spring  51  to allow the film unit  19  to pass through. The film unit  19  is further advanced by the pair of spreading rollers  36  toward the exit slot  24  while the pod  19   a  is ruptured by the nip of the rollers  36  and the developing liquid is being spread between the photosensitive sheet and the image receiving sheet so that the dye-image material is transferred to the receiving sheet to form the image thereon. The excess amount of the developing liquid is accommodated in the trap  19   b  formed in the trailing end portion of the film unit  19 .  
         [0091]    After the film unit  19  is discharged out of camera  10  through the exit slot  24 , the predetermined time period T 1 +T 2  set by the first timer circuit  96  elapses, which causes the controller  90  to generate a stopping signal to stop forward rotation of the motor  30 . A visible positive color image shows up on the image receiving sheet of the film unit discharged. After stopping the forward rotation, the controller  90  generates a starting signal to start reverse rotation of the motor  30  to return the picking claw member  33  to its home position. Upon starting reverse rotation, the predetermined time period T 3  set by the second timer circuit  97  counted down. The reverse rotation of the motor  30  is transmitted to the cam mechanism  63  to move back the picking claw member  33  toward the home position but not transmitted to the spreading roller  36  because of the one way clutch built-in the clutch gear  54 .  
         [0092]    When the picking claw member  33  reaches home position, the cam follower  62   a  reaches a dead end  61   c  of the shifting portion of the cam groove which corresponds to the home position of the picking claw member  55 , the cam shaft is forced to stop rotating, but the motor  33  is still rotating. The slipping gear  58  in FIG. 8 can absorb the rotating force by slipping to eliminate overload from the cam mechanism and the motor. Shortly after, count-down of the time period T 3  set in the second timer circuit  97  reaches zero, which makes the controller  90  generate a stopping signal to stop the reverse rotation of the motor  30 . Thus resetting the picking claw member is completed and the camera become ready to start next printing.  
         [0093]    Above described invention of film unit advancing apparatus can be applied not only to an electronic still camera with printer but also to a conventional instant film camera or a printer using an instant film unit. In the instant film unit advancing apparatus of the invention which has a driving unit for advancing exposed film unit and driving a picking claw member, all the components of the driving unit including the motor, the gear train, the spreading rollers and the cam shaft are located within the width of the instant film unit pack  20  and between the top wall of the cassette of the film pack and the top side of the camera or printer where a film unit exit slot is formed and also the picking claw member itself is disposed within the width. Those structures can give the camera a very compact size, specially in its width size. The cam mechanism and the controlling system given by the invention can eliminate use of a large cam plate used in a conventional apparatus and motor stop before discharging the film unit is completed if the slip arises.