Abstract:
The space required in the vicinity of a shutter aperture can be reduced to achieve an overall reduction in size of a device by providing a diaphragm mechanism for covering the shutter aperture formed of a plurality of members cooperating with each other to cover the shutter aperture. By cooperation of a small-diaphragm plate having a diaphragm aperture formed therethrough smaller in diameter than the shutter aperture and an auxiliary plate, for example, a space reduction is facilitated. The small-diaphragm plate is pivotably mounted adjacent one side of the shutter aperture. The auxiliary plate has a shape that cooperates with the convex-arcuate portion to cover the shutter aperture. When the small-diaphragm plate and the auxiliary plate are driven by the diaphragm actuating member and moved to a first position covering the shutter aperture, the two plate cooperate to fully cover the shutter aperture. In a second position retracted from the shutter aperture, the space around the shutter aperture is reduced because the small-diaphragm plate is small in size.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a diaphragm device for changing a shutter aperture diameter in a step-wise manner. 
     2. Description of the Related Art 
     A known diaphragm device is described in Japanese Patent Laid-open No. 79541/1993 by the present assignee. This known diaphragm device will be explained with reference to FIG.  8 . 
     In FIG. 8, a rotor  10  formed by a permanent magnet, a rotor actuated lever  11 , a diaphragm actuating member  12  and a small-diaphragm plate  73  are pivotably supported on a main plate (not-shown) through a rotor shaft  10   a , a shaft  12   a  and a shaft  4 . The small-diaphragm plate  73  has a sufficient overall size to cover the shutter aperture  2  and has a small-diameter diaphragm aperture  73   a . The small-diaphragm is pivotably supported by the shaft  4  to move between a first position A fully covering the shutter aperture  2  and a second position B fully retracted from the aperture  2 . Also, the small-diaphragm plate  73  is urged in a clockwise direction in the drawing by a spring  73   c  and abutted against and rested on a positioning pin  5 . 
     The diaphragm actuating member  12  is latched and biased in a counterclockwise direction in the drawing by a spring  13 , and is abutted against an engagement pin  14 . 
     When a coil L is energized to excite the stator  9 , the rotor  10  rotates in a counterclockwise direction and the rotor actuated lever  11  fixed on the rotor shaft  10   a  also rotates in a counterclockwise direction. This rotation causes the diaphragm actuating member  12  to rotate in a clockwise direction through a rotor actuated lever pin  11   a . Through a protrusion  12   b  of the diaphragm actuating member  12 , the small-diaphragm plate  73  is rotated counterclockwise about the shaft  4  from the second position B to the first position A where it goes into abutment against a positioning pin  15 . Consequently, the shutter aperture  2  is restricted by a diaphragm aperture  73   a . At this time, a pin  73   b  fixed on the small-diaphragm plate  73  moves a movable iron piece  18  along an attraction surface of an iron core  17   a . At a time that the small-diaphragm plate  73  reaches the first position A, an electromagnet  17   b  is excited to attract and hold the movable iron piece  18 , maintaining the small-diameter diaphragm aperture  73   a.    
     In this related-art diaphragm device, the small-diaphragm plate  73  is structured by one plate and has a sufficient size to fully cover the shutter aperture  2 . Because the small-diaphragm plate  73  has a size large enough to cover the shutter aperture  2  when in the first position A, it must be moved by a large amount to the second position B to be fully retracted from the shutter aperture  2 . This requires the small-diaphragm plate  73  to be dimensioned to provide a large space for retraction, resulting in an increased size in the vicinity of the shutter aperture  2 . 
     SUMMARY OF THE INVENTION 
     In order to solve the above problem, a small-diaphragm plate is provided with a diaphragm aperture smaller in diameter than a shutter aperture and an auxiliary plate so that when the small-diaphragm plate is selected, the small-diaphragm plate and the auxiliary plate cooperate to cover the shutter aperture. Since the small-diaphragm plate is provided in a divided manner to cooperate with the auxiliary plate, the small-diaphragm plate can be made smaller in area than in the conventional device, making it possible to reduce the size of the diaphragm device. 
     A diaphragm device according to one aspect of the present invention comprises a small-diaphragm plate having a diaphragm aperture smaller in diameter than a shutter aperture and being movable between a first position at which the diaphragm aperture is positioned in the shutter aperture and a second position at which the diaphragm aperture is retracted from the shutter aperture, an auxiliary plate cooperating with the small-diaphragm plate to cover the shutter aperture, and a diaphragm actuating member for actuating the small-diaphragm plate or the auxiliary plate, wherein actuation of the diaphragm actuating member causes the small-diaphragm plate to be moved to the first position and the auxiliary plate to be moved to a first position covering the shutter aperture, and actuation of the diaphragm actuating member in the other direction causes the small-diaphragm plate to be moved to a the second position and the auxiliary plate to be moved to a second position retracted from the shutter aperture. Because the shutter aperture is covered by cooperation of the small-diaphragm plate and the auxiliary plate, the small-diaphragm plate can be made smaller than in the related device, making possible to reduce the dimensions in the periphery of a shutter. 
     The auxiliary plate may be positioned on a side opposite to or the same side of the shutter aperture as the small-diaphragm plate when the small-diaphragm plate is positioned in the second position. This structure improves the freedom in arrangement of parts around the periphery of the shutter. 
     Actuation of the diaphragm actuating member in one direction may be conveyed through the small-diaphragm plate to the auxiliary plate to move both in unison or may be conveyed through the auxiliary plate to the small-diaphragm plate to move both in unison. This structure improves the shape and freedom of the arrangement of parts. Also, the diaphragm actuating member if driven by a motor will achieve automation of the diaphragm device. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front view showing an initial state prior to actuation of the shutter to which is applied a diaphragm device showing one embodiment of the present invention; 
     FIG. 2 is a front view of sectors and associated members therewith in the initial state of the shutter; 
     FIG. 3 is a control block diagram of the diaphragm device shown in FIG.  1  and FIG. 2; 
     FIG. 4 is an Ev value diagram showing first and second programs; 
     FIG. 5A is a time chart showing operation of each member in the case the first program is selected, and 
     FIG. 5B is a time chart showing operation of each member in the case the second program is selected; 
     FIG. 6 is a front view showing an initial state prior to actuation of the shutter to which is applied a diaphragm device showing another embodiment of the invention; 
     FIG. 7 is a front view showing an initial state prior to actuation of the shutter to which is applied a diaphragm device showing still another embodiment of the invention; and 
     FIG. 8 is a front view showing an initial state prior to actuation of the shutter in a related art. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the present invention will be explained with reference to the attached drawings. In the explanation, the same or similar parts as those of the related structure explained in FIG. 8 are denoted by the same reference numerals. 
     In FIG. 1, a stator  9 , a rotor  10  and a coil L constitute a swing motor M. On the stator  9 , an N pole and an S pole are generated by energizing to the coil L having magnetic pole portions  9   a ,  9   b . This enables the rotor  10  to rotate in both forward and reverse directions. 
     Sectors  23 ,  24 , which are to be driven by rotation of the swing motor M and open and close a shutter aperture  2 , are arranged symmetric about the shutter aperture  2  as shown in FIG.  2 . The sector  24  is pivotably supported about a shaft  25  protruding on a not-shown main plate. The sector  23  is pivotably supported about a shaft  22  protruding on the main plate. On an upper surface of the sector  23 , a sector open-close lever  20  is pivotably supported about the shaft  22 . The sector open-close lever  20  has an arm  20   b  in engagement with an engagement pin  21  provided on the main plate. A sector open-close lever pin  20   a  of the sector open-close lever  20  is shaft-fixed to the sector  23  and in engagement with a groove  24   a  of the sector  24  to drive the sectors  23 ,  24 . The sector open-close lever  20  is urged at all times in a clockwise direction by a spring  20   d.    
     On a rotor shaft  10   a  of the rotor  10  shown in FIG. 1, a rotor-actuated lever  11  is press-fitted so that the rotor-actuated lever  11  rotates in unison with the rotor  10 . A rotor-actuated lever pin  11   a  provided on the rotor-actuated lever  11  is in pivotable engagement about a shaft  12   a  projecting on the main plate. A diaphragm actuating member  12  is in rotatable abutment against a small diaphragm plate  3 , hereinafter described, through a protrusion  12   b  and urged at all times in a counterclockwise direction by a spring  13 . 
     In addition, an engagement pin  14  is provided on the main plate to prevent the diaphragm actuating member  12  from rotating in the counterclockwise direction when the rotor-actuated lever  11  rotates in the clockwise direction. 
     Furthermore, a rotor-actuation lever pin lib provided on the rotor-actuated lever  11  shown in FIG. 2 is allowed to abut against the sector open-close lever  20 . By rotating the rotor-actuated lever  11  clockwise, the sector open-close lever  20  is rotated counterclockwise so that the sector open-close lever  20  can actuate the sectors  23 ,  24 . 
     The small-diaphragm plate  3  has a diaphragm aperture  3 a smaller in diameter than the shutter aperture  2  in order to swiftly restrict an accurate diaphragm aperture for picture taking, and is pivotably supported about the shaft  4  protruding from the main plate. The small-diaphragm plate  3  has a shape that an outer peripheral shape distant from the shutter aperture  2  is arcuate somewhat greater than an arcuate of the shutter aperture  2  and an outer peripheral shape close to the shutter aperture  2  that is a concave arcuate portion  3   d  extending along the arcuate of the shutter aperture  2 . A pin  3   b  provided standing on the small-diaphragm plate  3  is in engagement with a movable iron piece  18 . The small-diaphragm plate  3  is urged clockwise at all times by a spring  3   c  and in abutment against a positioning pin  5  protruding from the main plate thus being kept in position. 
     The movable iron piece  18  is attracted to and released from an iron core  17   a  by tuning ON and OFF of an input signal to the coil  17   b  by an electromagnet unit  17 . When the movable iron piece  18  is released from the iron core  17   a  without attraction to it, the small-diaphragm plate  3  is allowed to move to a first position A where the diaphragm aperture  3   a  comes in the shutter aperture  2 . By attracting the movable iron piece  18  in this position to the iron core  17   a , the small-diaphragm plate  3  is held not retractable from the shutter aperture  2 . When the movable iron piece  18  is released from the attraction of the iron core  17   a , movement is possible to a second position B where abutment is made against the positioning pin  5  by the spring  3   c.    
     Because the small-diaphragm plate  3  in the first position A covering over the shutter aperture  2  does not entirely cover the shutter aperture  2  due to the concave-arcuate portion  3   d , an auxiliary plate  28  is provided to cover this portion. 
     The auxiliary plate  28  is pivotably supported about the shaft  12   a . The auxiliary plate  28  has a shape that cooperates with the small-diaphragm plate  3  to fully cover over the shutter aperture  2  and slightly overlaps the concave arcuate portion  3   d  of the small-diaphragm plate  3 , and is positioned on an opposite side of the small-diaphragm plate  3  with respect to the shutter aperture  2 . The auxiliary plate  28  is urged counterclockwise about the shaft  12   a  by a spring  28   a . When the diaphragm actuating member  12  moves the small-diaphragm plate  3  to the first position A through a reception portion  3   f  by the protruding portion  12   b , the pin  3   e  of the small-diaphragm plate  3  pushes a protruding portion  28   b  of the auxiliary plate  28  thereby causing the auxiliary plate  28  to follow the rotation of the small-diaphragm plate  3 . When moving from the second position B shown by the solid line to the first position A shown by the two-dot-chain line, the small-diaphragm plate  3  and the auxiliary plate  28  can cooperate to cover over the entire shutter aperture  2 . 
     The operation of the diaphragm device thus constructed will next be explained. 
     FIG.  1  and FIG. 2 show a state before operating the shutter. In this state, the electromagnet unit  17  is OFF, but the small-diaphragm plate  3  is restricted in rotation due to the clockwise bias force applied by the spring  3   c  and positioned by the positioning pin  5  and held in the second position B. 
     An explanation will be made of a case when a subject to be photographed is bright, so that a first program (shown by the broken line in FIG. 4) is selected for use whereby the shutter aperture  2  is limited to the smaller-diaphragm aperture  3   a . The first program is selected by program select means  1  shown in FIG.  3 . 
     At first, when a camera release button  6  shown in FIG. 3 is pressed, a control circuit  7  energizes the coil L shown in FIG. 1 in a reverse direction through a motor driving section  8 . By energizing the coil L, an S pole is first generated in the magnetic pole portion  9   a  of the stator  9  and an N pole is generated in the magnetic pole portion  9   b  to rotate the rotor  10  in a counterclockwise direction. Because this causes the rotor-actuated lever  11  press-fitted on the rotor shaft  10   a  of the rotor  10  to be rotated in the counterclockwise direction, the small-diaphragm plate  3  also rotates in a counterclockwise direction through the diaphragm actuating member  12  engaging the rotor-actuated lever pin  11   a  of the rotor-actuated lever  11 , and moves to a position A shown by the two-dot-chain line in FIG. 1 into abutment against the positioning pin  15 . Also, a pin  3   e  of the small-diaphragm plate  3  pushes the protruding portion  28   b  of the auxiliary plate  28  and moves the auxiliary plate  28  to a position A shown by the two-dot-chain line in FIG.  1 . The shutter aperture  2  is placed in a small-diameter state by cooperation of the small-diaphragm plate  3  and the auxiliary plate  28 . In this state, the electromagnet unit  17  turns from OFF to ON, and the iron core  17   a  attracts and fixes the movable iron piece  18 , holding the small-diaphragm plate  3  and auxiliary plate  28  in the first position A. 
     Next, the coil L is energized in a forward direction to cause the rotor  10  and the rotor-actuated lever  11  to begin rotating clockwise. However, the small-diaphragm plate  3  and the auxiliary plate  28  are kept in the state of the first position A because the pin  3   b  engages the movable iron piece  18 . 
     When the rotor  10  continues to rotate clockwise, as shown in FIG. 2 the rotor-actuated lever pin  11   b  provided on the rotor-actuated lever  11  rotates clockwise and thereby begins abutting against the sector open-close lever  20 , thereby rotating the sector open-close lever  20  in a counterclockwise direction. Due to this, the two sectors  23 ,  24  rotate oppositely to each other through the sector open-close lever pin  20   a  provided on the sector open-close lever  20 , thereby staring exposure. 
     The sectors  23 ,  24  operate only for an exposure time determined by subject brightness information from a photometric section  26  shown in FIG. 3, aperture-sop information, film-sensitivity ISO information, etc. in the control circuit  7 . Thereafter, the coil L is reverse energized, and the rotor-actuated lever  20  is rotated in a counterclockwise direction and returned to the state illustrated in FIG.  2 . 
     Thereafter, the electromagnet unit  17  turns from ON to OFF. Due to this, the movable iron piece  18  is released, and the small-diaphragm plate  3  and the auxiliary plate  28  return from the first position A to the second position B by a force of the spring  3   c , ending the exposure operation. 
     The above operation, if represented as a time chart separately for the sectors  23 ,  24 , the electromagnet unit  17 , the small-diaphragm plate  3  and the coil L, is as shown in FIG.  5 ( a ). 
     Next, a description will be provided of a case in which the subject to be photographed is dark, so that a second program (shown by the solid line in FIG. 4) is selected for use whereby the shutter aperture is opened fully. the second program is selected by the program select means  1  shown in FIG.  3 . 
     When the camera release button  6  is pressed, the control circuit  7  forwardly energizes the coil L shown in FIG.  1  through the motor driving section  8 . By this energization, an N pole is generated in the magnetic pole portion  9   a  of the stator  9  and an S pole is generated in the magnetic pole portion  9   b  to rotate the rotor  10  in a clockwise direction. Due to this, because the rotor-actuated lever pin  11   a  and the diaphragm actuating member  12  are out of abutment and the diaphragm actuating member  12  remains in abutment against the engagement pin  14 , the small-diaphragm plate  3  is kept in a waiting state in the second a position B due to a force of the spring  13 . Also, the electromagnet unit  17  remains in the OFF state. 
     The sectors  23 ,  24  rotate to an exposure position as determined by the brightness information, etc. Thereafter, the coil L is reverse energized to rotate the rotor  10  in a reverse direction (counterclockwise) returning to the state of FIG.  2 . 
     The above operation, if represented as a time chart separately for the sectors  23 ,  24 , the electromagnet unit  17 , the small-diaphragm plate  3  and the coil L, is as shown in FIG.  5 ( b ). 
     Incidentally, in the above example, because the auxiliary plate  28  is positioned on a side of the shutter aperture  2  opposite the side on which the small-diaphragm plate  3  is positioned, the auxiliary plate  28  structurally moves to the first position A covering the shutter aperture  2  from the opposite side with respect to the small-diaphragm plate  3 . However, the structure may be modified to provide for movement from the same direction without limitation to the foregoing example. This example will be next described based on FIG.  6  and FIG.  7 . 
     First, in the embodiment of FIG. 6, on one side (right-hand side in the drawing) of an outer peripheral portion of the shutter aperture  2 , a small-diaphragm plate  33  having a small diameter diaphragm aperture  33   a  and an auxiliary plate  38  are both pivotably supported on the same shaft  34 . The small-diaphragm plate  33  is urged clockwise by a spring  3   c . A protruding portion  12   b  of the diaphragm actuating member  12  first contacts a reception portion  38   f  of the auxiliary plate  38  and pushes it so that the auxiliary plate  38  is rotated in a counterclockwise direction and then contacts a reception portion  33   f  of the small-diaphragm plate  33  to rotate the small-diaphragm plate  33  in the counterclockwise direction. Then, the small-diaphragm plate  33  and the auxiliary plate  38  are simultaneously pushed and moved to a first position A shown by the two-dot-chain line. Other structural parts and methods of operation the same or similar to those of FIG. 1 are denoted by the same reference numerals. 
     In the embodiment shown in FIG. 7, on one side (right-hand side in the drawing) outer peripheral portion of a shutter aperture  2 , a small-diaphragm plate  43  having a small-diameter aperture  43   a  and an auxiliary plate  48  are both pivotably supported by the same shaft  44 . The small-diaphragm plate  43  is urged clockwise by a spring  3   c . The small-diaphragm plate  43  has a shape such that an outer peripheral portion on a side close to the shutter aperture  2  has an arcuate form with a diameter somewhat greater than an arc of the shutter aperture  2  and an outer peripheral portion distant from the shutter aperture  2  is formed as a cut-out outer peripheral portion  43   d . The auxiliary plate  48  is nearly in a bow-like shape which is a shape for cooperating with the outer peripheral portion  43   d  to cover over the shutter aperture  2 . Accordingly, a protruding portion  12   b  of the diaphragm actuating member  12  first contacts a reception portion  43   f  of the small-diaphragm plate  43  and pushes it to pivot in the counterclockwise direction, and contacts a reception portion  48   f  of the auxiliary plate  48  with a slight delay of time. Thereafter, the small-diaphragm plate  43  and the auxiliary plate  48  are simultaneously pushed and pivoted in the counterclockwise direction to a first position A shown by the two-dot-chain line. Other structural parts and operation methods the same or similar to those shown in of FIG. 1 are denoted by the same reference numerals. 
     Although the above embodiments are provided to illustrate the example, the invention is not limited thereby and many modifications or changes may be made without departing from the scope of the invention. For instance, although the diaphragm actuating member is moved by a motor in the foregoing embodiments, the invention is not so limited and manual operation may be used. In addition, the diaphragm device of the invention is usable not only for a photographic camera using a film or charge coupled device but also for a video camera or the like. 
     Because the shutter aperture can be changed over between the large-diameter aperture and the small-diaphragm aperture and the switching is structurally performed by the cooperation of the two or more members, i.e. the small-diaphragm plate and the auxiliary plate, the small-diaphragm plate can be made smaller than in the related device. It is possible to reduce the space around the shutter aperture where the small-diaphragm plate retracts from the shutter aperture and to achieve a size reduction in the device. Also, the freedom of part shape or arrangement is improved.