Focal-plane shutter and optical device

This application is a continuation of and claims priority to International Patent Application No. PCT/JP2013/078868 filed on Oct. 24, 2013, which claims priority to Japanese Patent Application No. 2012-241981 filed on Nov. 1, 2012, subject matter of these patent documents is incorporated by reference herein in its entirety.

(i) Technical Field

The present invention relates to focal-plane shutters and optical devices.

(ii) Related Art

Japanese Unexamined Patent Application Publication No. 09-179167 discloses a focal-plane shutter driving a blade by two arms.

To improve the shutter speed, it is contemplated that two arms are made of synthetic resins for reduced weight. In this case, the rigidity of the arms are reduced, so that the arms might flap in the optical axis direction when the blade stops after moving from a state of closing an opening to a state of opening the opening. This might damage the arms.

According to an aspect of the present invention, there is provided a focal-plane shutter including: first, second, and third boards each including an opening and arranged in an optical axis direction passing through the openings; a first blade arranged between the first and second boards and capable of opening and closing the openings; a second blade arranged between the second and third boards and capable of opening and closing the openings; first and second arms arranged between the second and third boards, connected to the second blade, made of synthetic resins, and capable of rotating about respective different fulcrums; a drive member connected to the first arm and driving the first arm; and a support member provided within a working region of the first arm when viewed in the optical axis direction or in a position close to the first arm and distant from the second arm in an opened state where the second blade opens the openings, the support member being provided in the first board side and supporting the second board.

FIG. 1 is a front view of inner structure of a focal-plane shutter according to the present embodiment;

FIG. 2 is an external perspective view of the focal-plane shutter; and

FIG. 3 is a sectional view around a support member.

FIG. 1 is a front view of inner structure of a focal-plane shutter 1 according to the present embodiment. FIG. 2 is an external perspective view of the focal-plane shutter 1 . The focal-plane shutter 1 is employed in an optical instrument such as a digital camera or a still camera. The focal-plane shutter 1 includes a board 10 , a leading blade 20 A, a trailing blade 20 B, arms 31 a , 32 a , 31 b , and 32 b , drive members 40 a and 40 b , output members 50 a and 50 b , and rotors 72 a and 72 b . Additionally, the rotors 72 a and 72 b , and the output members 50 a and 50 b are omitted in FIG. 1 . The board 10 includes an opening 11 . The leading blade 20 A and the trailing blade 20 B open and close the opening 11 . The rotor 72 a is included in an actuator for driving the leading blade 20 A. The rotor 72 b is included in an actuator for driving the trailing blade 20 B. Each actuator includes a stator around which a coil is wound, and is omitted in FIGS. 1 and 2 .

The leading blade 20 A includes plural blades 21 a to 23 a . The trailing blade 20 B also includes plural blades. Each of the leading blade 20 A and the trailing blade 20 B can shift between an overlapped state where the plural blades overlap one another and an expanded state where the plural blades are expanded. These plural blades recede from the opening 11 in the overlapped state to bring the opening 11 into a fully opened state. These plural blades close the opening 11 in the expanded state to bring the opening 11 into a fully closed state. FIGS. 1 and 2 illustrate the state where the expanded leading blade 20 A closes the opening 11 and the trailing blade 20 B recedes from the opening 11 .

The leading blade 20 A is connected to the arms 31 a and 32 a . The trailing blade 20 B is connected to the arms 31 b and 32 b . As illustrated in FIG. 1 , the arms 31 a , 32 a , 31 b , and 32 b are rotatably supported by spindles 14 a , 15 a , 14 b , and 15 b provided in the board 10 , respectively.

The drive members 40 a and 40 b drive the arms 31 a and 31 b , respectively. The drive members 40 a and 40 b are provided with drive pins 43 a and 43 b connected to the arms 31 a and 31 b , respectively. The board 10 is formed with escape slots 13 a and 13 b for permitting the movement of the drive pins 43 a and 43 b , respectively. The drive members 40 a and 40 b will be described later in detail. The rotors 72 a and 72 b are respectively connected to the output members 50 a and 50 b . The rotation of the rotors 72 a and 72 b rotates the output members 50 a and 50 b , so the drive members 40 a and 40 b rotates, which drives the leading blade 20 A and the trailing blade 20 B, respectively. The positions of rotational axes of the output members 50 a and 50 b and the drive members 40 a and 40 b are different from one another.

The output members 50 a and 50 b and the drive members 40 a and 40 b are respectively formed with gear portions 55 a , 55 b , 45 a , and 45 b . The gear portions 55 a and 45 a mesh with each other, and the gear portions 55 b and 45 b mesh with each other, so that the rotation of the output members 50 a and 50 b respectively rotate the drive members 40 a and 40 b . The arms 31 a and 31 b are partially attached with reinforcement members 31 A and 31 B. The arms 31 a and 31 b and the reinforcement members 31 A and 31 B are made of synthetic resin, and each thereof has a thin plate shape.

As illustrated FIG. 2 , the board 10 is formed with a positioning portion 19 a near one end of the escape slot 13 a . Likewise, a positioning portion 19 b is formed near one end of the escape slot 13 b . The other ends of the escape slots 13 a and 13 b are provided with rubbers Ga and Gb for absorbing the impact of the drive members 40 a and 40 b , respectively. In addition, the board 10 is assembled with a holder holding the above actuators not illustrated.

As illustrated in FIG. 1 , the board 10 is secured with a support member GS. The support member GS is separate from the board 10 . Further, the board 10 is provided with plural support projections is to 4 s . The support member GS and the support projections is to 4 s will be described later. Furthermore, in FIG. 1 , working regions R 1 and R 2 of the arms 31 b and 32 b are depicted by dotted lines.

FIG. 3 is a sectional view around the support member GS. Additionally, FIG. 3 is the sectional view taken along line passing through the support member GS, the drive pin 43 b , and the spindle 14 b in FIG. 1 . As illustrated in FIG. 3 , the focal-plane shutter 1 includes boards 10 A and 10 B besides the board 10 . The boards 10 to 10 B are arranged in this order in the optical axis direction. That is, the board 10 A is provided between the boards 10 and 10 B. Like the opening 11 provided in the board 10 , an opening is provided in each of the boards 10 A and 10 B. The leading blade 20 A and the arms 31 a and 32 a are arranged between the boards 10 and 10 A. The trailing blade 20 B and the arms 31 b and 32 b are arranged between the boards 10 A and 10 B. The board 10 A prevents the interference of the leading blade 20 A with the trailing blade 20 B and the interference of the arm 31 a with the arm 31 b . The board 10 is an example of a first board. The board 10 A is an example of a second board. The board 10 B is an example of a third board. The leading blade 20 A is an example of a first blade. The trailing blade 20 B is an example of a second blade.

A holder 80 assembled on the board 10 holds the actuators not illustrated. The actuator includes the rotor 72 a , the stator, and the coil. The holder 80 is assembled on the board 10 . A spindle 84 b of the holder 80 is fitted into a support hole 42 b of the drive member 40 b for rotation. Therefore, the drive member 40 b is rotatably supported. The drive pin 43 b extends in a predetermined direction and is connected to the arm 31 b arranged between the boards 10 A and 10 B. As mentioned above, the arm 31 b is connected to the trailing blade 20 B. The arm 31 b is an example of a first arm. The arm 32 b not connected to the drive pin 43 b but to the trailing blade 20 B is an example of a second arm. Additionally, the board 10 A is provided with an escape slot for receiving the drive pin 43 b . The board 10 B is provided with an escape slot 13 b B.

The support member GS is secured to a surface, of the board 10 , facing the board 10 A, and supports the board 10 A from the board 10 side. The support member GS is made of a rubber. In particular, the support member GS is a foamed rubber forming bubbles, but not limited to this. For example, the support member GS may be made of a synthetic resin having no elasticity or may be a rubber, a leaf spring, a coil spring, or the like having elasticity. The support member GS may be integrally formed in the board 10 . In an inner peripheral edge of the board 10 , a receiving portion 18 protrudes inwardly from the inner peripheral edge. The receiving portion 18 supports the board 10 A from the board 10 B side. In other words, the receiving portion 18 receives the board 10 A serving as the second board between the receiving portion 18 and the support member GS from the board 10 B side serving as the third board. Herein, the support member GS is secured near the receiving portion 18 , and an end portion of the board 10 A is sandwiched between the support member GS and the receiving portion 18 . Further, the support projections is to 4 s formed in the board 10 also support the board 10 A from the board 10 side.

Next, the position of the support member GS will be described. As illustrated in FIG. 1 , the support member GS is provided at a position close to the arm 31 b and distant from the arm 32 b in the state where the trailing blade 20 B opens the opening 11 . That is, it is provided near the arm 31 b.

For example, the rotor 72 b causes the output member 50 b and the drive member 40 b to rotate from the state where the trailing blade 20 B closes the opening 11 . Thus, the drive pin 43 b of the drive member 40 b moves within the escape slot 13 b and abuts the positioning portion 19 b . At this time, the impact is applied to the drive member 40 b , so the arm 31 b might flap in the optical axis direction. When the arm 31 b flaps in the optical axis direction, the load is applied to the arm 31 b , so the arm 31 b might be damaged. In particular, since the arm 31 b engages with the drive pin 43 b , the area of the arm 31 b is formed to be greater than that of the arm 32 b . In addition, the reinforcement member 31 B is also attached to the arm 31 b . Thus, the arm 31 b is formed to be heavier than the arm 32 b . For this reason, the arm 31 b tends to flap. Further, in the opened state where the opening 11 is opened, the blades of the trailing blade 20 B are brought into the overlapped state. Therefore, the trailing blade 20 B further tends to flap in the optical axis direction, and the arm 31 b tends to flap.

In the present embodiment, the support member GS is provided near the arm 31 b in the opened state of the trailing blade 20 B. The support member GS presses the board 10 A, whereby the board 10 A suppresses the arm 31 b from flapping. This can prevent the damage to the arm 31 b . Further, since the support member GS has elasticity, it is possible to absorb the impact generated from the arm 31 b . Furthermore, as illustrated in FIG. 1 , the support member GS overlaps the arm 31 b when viewed in the optical axis direction. Accordingly, the flapping of the arm 31 b can be effectively suppressed thereby absorbing the impact.

Further, like the support member GS, the receiving portion 18 is formed at a position close to the arm 31 b and distant from the arm 32 b in the opened state where the trailing blade 20 B opens the opening 11 . That is, it is formed near the arm 31 b . Since it is formed near the arm 31 b when viewed in the optical axis direction in the opened state of the trailing blade 20 B, the board 10 A can be stably held between the receiving portion 18 and the support member GS. It is thus possible to suppress the flapping of the arm 31 b.

Also, since the flapping of the arm 31 b is suppressed, it is also possible to suppress the flapping of the arm 32 b . Therefore, the arm 32 b is prevented from being damaged.

In addition, the support member GS may be provided within the working region R 1 when viewed in the optical axis direction. Moreover, the support member GS may be provided at a position closer to the arm 32 b than to the arm 31 b in the opened state.

As illustrated in FIG. 1 , the support projections 3 s and 4 s integrally formed in the board 10 and supporting the board 10 A are provided within the working region R 1 of the arm 31 b when viewed in the optical axis direction. It is thus possible to press the flapping of the arm 31 b in the optical axis direction in cooperation with the support member GS. Further, the support projection may be provided not only within the working region R 1 but also within the working region R 2 . It is also possible to suppress the flapping of the arm 32 b in the optical axis direction.

Furthermore, the support projections is and 2 s are formed at positions to overlap the trailing blade 20 B in the optical axis direction in the opened state. This suppresses the trailing blade 20 B from flapping through the board 10 A.

In this way, the arm 31 b is suppressed from flapping, thereby suppressing the trailing blade 20 B from flapping. Accordingly, the operation noise of the focal-plane shutter can be reduced.

While the exemplary embodiments of the present invention have been illustrated in detail, the present invention is not limited to the above-mentioned embodiments, and other embodiments, variations and modifications may be made without departing from the scope of the present invention.

In the present embodiment, the leading blade 20 A and the trailing blade 20 B are driven by use of the actuators. However, the present invention is not limited to this. For example, the operation of an electromagnet and a spring may drive the blade through the drive member. Further, in the present embodiment, in order to suppress the flapping of the arm 31 b driving the trailing blade 20 B, the support member GS is provided in the board 10 at the arm 31 b side. However, in order to suppress the flapping of the arm 31 a driving the leading blade 20 A, such a support member may be provided in the board 10 B at the arm 31 a side.