Focal plane shutter and optical device

This application is a continuation of and claims priority to International Patent Application No. PCT/JP2011/050134 filed on Jan. 6, 2011, which claims priority to Japanese Patent Application No. 2010-035703 filed on Feb. 22, 2010, 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 device.

(ii) Related Art

Japanese Unexamined Patent Application Publication No. 8-334808 discloses a focal plane shutter. In the focal plane shutter, a drive pin provided in a drive lever engages a drive arm connected to a blade, thereby driving the blade.

The drive arm and the drive pin are engaged with each other, causing at least one of them to be chipped. This might generate dusts. Such dusts might influence on image quality.

It is therefore an object of the present invention to provide a focal plane shutter and an optical device that prevent dusts from generating.

According to an aspect of the present invention, there is provided a focal plane shutter including: a board including an opening; a blade movable between a position where the blade recedes from the opening and a position where the blade covers at least part of the opening; a drive arm connected to the blade, the drive arm including an engagement hole; a drive lever including a drive pin engaging the engagement hole; and a restriction portion provided in the drive arm, the restriction portion abutting the drive pin and being thicker than the drive arm, wherein the engagement hole includes a first edge positioned at a start side where the drive pin moves in a predetermined direction and a second edge positioned at a terminal side where the drive pin moves in the predetermined direction, and the restriction portion allows an abutment of the second edge with the drive pin, and abuts the drive pin to restrict an abutment of the first edge with the drive pin.

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

FIG. 2 is an explanatory view of an operation of the focal plane shutter;

FIG. 3 is an explanatory view of the operation of the focal plane shutter;

FIG. 4 is a sectional view of a structure around a trailing blades-drive lever;

FIG. 5 is a perspective view of a structure around the drive pin;

FIG. 6 is an explanatory view of a restriction portion;

FIG. 7 is an explanatory view of the restriction portion; and

FIG. 8 is an explanatory view of a variation of the restriction portion.

An embodiment will be described with reference to the drawings as follows. In the present embodiment, a focal plane shutter will be described as an example of a blade drive device. FIG. 1 is front view of a focal plane shutter according to the present embodiment. As illustrated in FIG. 1 , the focal plane shutter 1 includes: a board 10 ; blades 21 a to 24 a and 21 b to 24 b ; drive arms 31 a , 32 a , 31 b and 32 b ; and electromagnets 70 A and 70 B. The board 10 is made of a synthetic resin, and includes an opening 11 with a rectangular shape. Each of the blades 21 a to 24 a and 21 b to 24 b is made of a synthetic resin and is thinly formed. Also, each of the drive arms 31 a , 32 a , 31 b and 32 b is made of a metal sheet to retain its strength. Each of the blades 21 a to 24 a and 21 b to 24 b move between a position of receding from the opening 11 and a position of covering at least part of the opening 11 .

Four blades 21 a to 24 a configure leading blades 20 A. Four blades 21 b to 24 b configure trailing blades 20 B. FIG. 1 illustrates the leading blades 20 A in an overlapped state and the trailing blades 20 B in a expanded state. In FIG. 1 , the leading blades 20 A recedes from the opening 11 and the trailing blades 20 B close the opening 11 .

The leading blades 20 A are connected to the drive arms 31 a and 32 a . The trailing blades 20 B are connected to the drive arms 31 b and 32 b . These drive arms 31 a , 32 a , 31 b and 32 b are swingably supported by the board 10 .

A leading blades-drive lever 40 A for driving the drive arm 31 a and a trailing blades-drive lever 40 B for driving the drive arm 32 b are provided in the board 10 . The leading blades-drive lever 40 A and the trailing blades-drive lever 40 B are supported by the board 10 to be swingable in a predetermined range. Specifically, the leading blades-drive lever 40 A is supported to swing about a spindle provided in the board 10 . The swinging range of the leading blades-drive lever 40 A is limited by a rubber, mentioned later, provided at an end portion of a slot formed in the board 10 . This is applicable to the trailing blades driving lever 40 B. The leading blades-drive lever 40 A and the trailing blades-drive lever 40 B are each made of a synthetic resin.

The drive arm 31 a is connected to the leading blades-drive lever 40 A. The drive arm 32 b is connected to the trailing blades-drive lever 40 B. The swinging of the leading blades-drive lever 40 A causes the drive arm 31 a to swing, thereby moving the leading blades 20 A. Likewise, the swinging of the trailing blades-drive lever 40 B causes the drive arm 32 b to swing, thereby moving the trailing blades 20 B.

The leading blades-drive lever 40 A and the trailing blades-drive lever 40 B each holds an iron piece which does not have a reference numeral. The leading blades-drive lever 40 A can swing between the position where the iron piece abuts the electromagnet 70 A and the position where the iron piece recedes from the electromagnet 70 A. This is applicable to the trailing blades-drive lever 40 B.

Also, the leading blades-drive lever 40 A is biased by a spring, not illustrated, in such a direction as to move away from the electromagnet 70 A. Likewise, the trailing blades-drive lever 40 B is biased by a spring, not illustrated, in such a direction as to move away from the electromagnet 70 B.

Ratchet wheels 50 A and 50 B engage the leading blades-drive lever 40 A and the trailing blades-drive lever 40 B, respectively, through the springs mentioned above. One end of the spring, which biases the leading blades-drive lever 40 A in such a direction as to move away from the electromagnet 70 A, engages the ratchet wheel 50 A. The other end of the spring engages the leading blades-drive lever 40 A. The rotational amount of the ratchet wheel 50 A is adjusted, thereby adjusting the biasing force of the spring. The ratchet wheel 508 also has a function similar to that of the ratchet wheel 50 A.

The electromagnet 70 A is energized, thereby adsorbing the iron piece of the leading blades-drive lever 40 A. Likewise, the electromagnet 70 B is energized, thereby adsorbing the iron piece of the trailing blades-drive lever 40 B.

Next, the operation of the focal plane shutter 1 will be described. FIGS. 1 to 3 are explanatory views of the operation of the focal plane shutter 1 . Here, FIG. 2 illustrates the focal plane shutter 1 in an initial state. In this initial state, a set lever not illustrated is secured to an initial position, the leading blades 20 A are expanded to close the opening 11 , and the trailing blades 20 B are overlapped each other to recede from the opening 11 . In this initial state, the iron pieces of the leading blades-drive lever 40 A and the trailing blades-drive lever 40 B abut the electromagnets 70 A and 70 B respectively, and are set in such an initial position as to be adsorbed to them respectively.

In shooting, a release button of the camera is pushed to energize coils of the electromagnets 70 A and 70 B, whereby the iron piece of the leading blades-drive lever 40 A is adsorbed to the electromagnet 70 A and the iron piece of the trailing blades-drive lever 40 B is adsorbed to the electromagnet 70 B. After that, the set lever moves away from the leading blades-drive lever 40 A and the trailing blades-drive lever 40 B. At this time, the leading blades drive lever 40 A and the trailing blades-drive lever 40 B remain adsorbed to the electromagnets 70 A and 70 B, respectively.

Afterward, the energization of the coil of the electromagnet 70 A is cut, thereby rotating the leading blades-drive lever 40 A in a clockwise direction by the biasing force of the spring as illustrated in FIG. 3 . Therefore, the leading blades 20 A move away from the opening 11 to be in the overlapped state. Also, the energization of the coil of the electromagnet 70 B remains for a predetermined period, whereas the trailing blades 20 B remain away from the opening 11 . This causes the opening 11 to be in an opened state. FIG. 3 illustrates an exposed state.

After a predetermined period lapses from a time when the release button is pushed, the energization of the coil of the electromagnet 70 B is cut, and then the trailing blades-drive lever 40 B rotates clockwise by the biasing force of the spring. Therefore, the trailing blades 20 B are expanded to close the opening 11 . The trailing blades-drive lever 40 B abuts a rubber, as will be mentioned later, for preventing bound, provided at an end of the slot formed in the board 10 . FIG. 1 illustrates the state just after the exposure operation is finished. In such a way, one cycle of shooting is finished.

Next, the leading blades-drive lever 40 A and the trailing blades-drive lever 40 B are rotated counterclockwise by a set lever not illustrated. Therefore, the leading blades 20 A are expanded to close the opening 11 and the trailing blades 20 B are overlapped each other to recede from the opening 11 , whereby the state is returned to the initial state illustrated in FIG. 2 .

Next, the structure around the drive lever will be described below. Although the leading blades-drive lever 40 A and the trailing blades-drive lever 40 B differ in shape from each other, they have substantially the same configuration and the same parts. The following description will be given of only the trailing blades-drive lever 40 B. FIG. 4 is a sectional view of the structure around the trailing blades-drive lever 40 B.

The trailing blades-drive lever 40 B includes: a board-shaped base portion 41 b , a cylindrical portion 41 b 1 and a drive pin 41 b 8 standing on the base portion 41 b . Around the cylindrical portion 41 b 1 , there are provided the ratchet wheel 50 B and a spring 54 B for giving the trailing blades-drive lever 40 B a biasing force. One end of the spring 54 B is secured to the trailing blades-drive lever 40 B side, and the other end of the spring 54 B is secured to the ratchet wheel 50 B side. The rotational amount of the ratchet wheel 50 B is adjusted, thereby adjusting the biasing force of the spring 54 B. The spring 54 B biases the trailing blades-drive lever 40 B in such a direction as to move away from the electromagnet 70 B.

A spindle 11 b 1 provided in the board 10 is fitted into the cylindrical portion 41 b 1 . The trailing blades-drive lever 40 B rotates about the spindle 11 b 1 in a predetermined range. An end of the spindle 11 b 1 is attached to a printed circuit board 100 by a pin 110 . The printed circuit board 100 controls the energization of the electromagnets 70 A and 70 B.

The drive pin 41 b 8 extends downwardly from the base portion 41 b . The drive pin 41 b 8 is fitted onto the drive arm 32 b . Further, an escape hole 13 b for escaping the drive pin 41 b 8 is formed in the board 10 . A spindle 11 b 2 is coaxially formed with the spindle 11 b 1 in the board 10 . The drive arm 32 b rotatably fits onto the spindle 11 b 2 . The drive arm 32 b rotates about the spindle 11 b 2 in a predetermined range.

A back board 18 is arranged to face the board 10 . The drive arm 32 b , the trailing blades 20 B, and the like are housed between the board 10 and the back board 18 . As illustrated in FIG. 4 , the drive arm 32 b is provided with a restriction portion 35 b . The restriction portion 35 b is configured with a pin 35 b 1 and an elastic portion 35 b 2 . They will be described later in detail. In the back board 18 , there are provided an escape hole 18 b 8 for escaping the drive pin 41 b 8 and the restriction portion 35 b , and an escape hole 18 b 2 for escaping the spindle 11 b 2 .

FIG. 5 is a perspective view of the structure around the drive pin 41 b 8 . FIG. 5 is a perspective view around the drive pin 41 b 8 in a state where the set operation illustrated in FIG. 2 is accomplished. Additionally, the blades except for the blade 21 b are omitted in FIG. 5 . As illustrated in FIG. 5 , the escape hole 13 b has an arc shape with a pivot serving as a rotation center of the trailing blades-drive lever 40 B. The drive pin 41 b 8 moves within the escape hole 13 b . A rubber 13 b 1 for preventing the bound of the drive pin 41 b 8 is secured at the end of the escape hole 13 b.

After the set operation is accomplished, the energization of the electromagnet 70 A is cut to drive the leading blades-drive lever 40 A at first. Then, after a predetermined period, the energization of the electromagnet 70 B is cut to drive the trailing blades-drive lever 40 B. A movement direction D 1 illustrated in FIG. 5 is one of movements of the drive pin 41 b 8 when the energization of the electromagnet 70 B is cut to cause the trailing blades-drive lever 40 B in the set state to be driven according to the biasing force of the spring 54 B. Thus, the drive pin 41 b 8 moves in the movement direction D 1 to abut the rubber 13 b 1 at the terminal end of the movable range, and then stops.

Additionally, when the state illustrated in

FIG. 1 is shifted to the state illustrated in FIG. 2 , the drive pin 41 b 8 is moved in the opposite direction of the movement direction D 1 by the set lever not illustrated. The speed of the drive pin 41 b 8 moved in the movement direction D 1 by the biasing force of the spring is faster than that of the drive pin 41 b 8 moved in the opposite direction of the movement direction D 1 by the set lever.

Next, the restriction portion 35 b will be described. FIGS. 6 and 7 are explanatory views of the restriction portion 35 b . FIG. 6 is the view of the restriction portion 35 b when viewed from its top, and FIG. 7 is the sectional view taken along line A-A. The drive arm 32 b is formed with an engagement hole 34 b into which the drive pin 41 b 8 fits. The pin 35 b 1 is secured to the drive arm 32 b by caulking and is made of a synthetic resin. The pin 35 b 1 fits into the elastic portion 35 b 2 . The elastic portion 35 b 2 has a ring shape, and is made of a rubber which is elastically deformable. The elastic portion 35 b 2 abuts the drive pin 41 b 8 . The restriction portion 35 b is thicker than the drive arm 32 b.

The engagement hole 34 b has a first edge 34 b 1 positioned at the start side of the movable range in the movement direction D 1 and a second edge 34 b 2 positioned at the terminal side of the movable range in the movement direction D 1 . The first edge 34 b 1 and the second edge 34 b 2 face each other through the drive pin 41 b 8 . The restriction portion 35 b and the drive pin 41 b 8 are arranged in the movement direction D 1 in this order.

The restriction portion 35 b restricts the abutment of the drive pin 41 b 8 with the first edge 34 b 1 . However, the abutment of the drive pin 41 b 8 with the second edge 34 b 2 is permitted. As illustrated in FIGS. 6 and 7 , a predetermined clearance is formed between the drive pin 41 b 8 and the first edge 34 b 1 . The restriction portion 35 b abuts the drive pin 41 b 8 to remain such a state.

Next, a function of the restriction portion 35 b will be described. When the trailing blades-drive lever 40 B drives and the drive pin 41 b 8 moves in the movement direction D 1 , the drive pin 41 b 8 pushes the second edge 34 b 2 to drive the drive arm 32 b . This drives the trailing blades 20 B. When the trailing blades-drive lever 40 B moves in a predetermined range, the drive pin 41 b 8 abuts the rubber 13 b 1 illustrated in

FIG. 5 , and then the drive lever 40 B stops. When the drive pin 41 b 8 stops, the drive arm 32 b intends to cause the drive pin 41 b 8 to abut the first edge 34 b 1 by a inertia force of the drive arm 32 b and the like. However, the restriction portion 35 b restricts the abutment of the drive pin 41 b 8 with the first edge 34 b 1 . For this reason, even when the drive pin 41 b 8 stops in the movable state, the drive pin 41 b 8 does not abut the first edge 34 b 1 .

If the restriction portion 35 b is not provided, the drive pin 41 b 8 abuts the first edge 34 b 1 according to the inertial force of the drive arm 32 b and the like at the time when the drive pin 41 b 8 stops in the movable state. Especially, when the trailing blades-drive lever 40 B moves at a high speed or repeats reciprocation for a short period, at least one of the drive pin 41 b 8 and the first edge 34 b 1 might be chipped. This might generate dusts. When the dusts disperse and reach the opening 11 side, the image quality might be affected. However, in this embodiment, since the restriction portion 35 b restricts the abutment of the drive pin 41 b 8 with the first edge 34 b 1 , the above problem can be prevented.

Also, the elastic portion 35 b 2 is elastically deformed to absorb the inertia force of the drive arm 32 b and the like, thereby reducing the load applied on the drive arm 32 b at the time when the elastic portion 35 b 2 abuts the drive pin 41 b 8 . This can prevent the damage of the drive arm 32 b.

The restriction portion 35 b restricts the abutment of the first edge 34 b 1 with the drive pin 41 b 8 , but allows the abutment of the second edge 34 b 2 with the drive pin 41 b 8 . If the second edge 34 b 2 surrounds the entire outer periphery of the drive pin 41 b 8 to restrict the abutment of the second edge 34 b 2 with the drive pin 41 b 8 , the following problem might occur. The elastic portion 35 b 2 is elastically deformable as mentioned above. For this reason, if the drive pin 41 b 8 abuts the elastic portion 35 b 2 at the time when the drive pin 41 b 8 starts moving in the movement direction D 1 , the elastic portion 35 b 2 is elastically deformed and the timing when the drive arm 32 b starts moving might be delayed from the timing when the drive pin 41 b 8 starts moving. For this reason, the timing when the trailing blades 20 B start moving might be delayed.

However, the restriction portion 35 b permits the abutment of the drive pin 41 b 8 with the second edge 34 b 2 in the present embodiment. This prevents the timing when the trailing blades 20 B start moving from being delayed.

Next, a variation of the restriction portion will be described. FIG. 8 is an explanatory view of the variation of the restriction portion. FIG. 8 corresponds to FIG. 7 . A restriction portion 36 b is made of a synthetic resin. The restriction portion 36 b is secured to the drive arm 32 b by caulking. Even if such a configuration is employed, the abutment of the first edge 34 b 1 with the drive pin 41 b 8 can be restricted. Additionally, the restriction portion 36 b is thicker than drive arm 32 b , as illustrated in FIG. 8 . For this reason, the area of the abutment of the drive pin 41 b 8 with the restriction portion 36 b is comparatively large. Thus, there is little possibility that the drive pin 41 b 8 or the restriction portion 36 b is chipped due to the abutment of the drive pin 41 b 8 with the restriction portion 36 b.

In addition, the restriction portion 36 b may be integrally formed with the drive arm 32 b.

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.

The focal plane shutter according to the present embodiment can be employed in an optical device such as a still camera or a digital camera.

The restriction portion may be provided in the drive arm 31 a connected to the leading blades-drive lever 40 A.

Although the blade having a thin shape and made of a synthetic resin has been described in the present embodiment, the blade having the thin shape may be made of a metal. Also, the drive arm 32 b may be made of a synthetic resin and the drive pin 41 b 8 may be made of a metal, and both may be made of synthetic resins.

Finally, several aspects of the present invention are summarized as follows.

According to an aspect of the present invention, there is provided a focal plane shutter including: a board including an opening; a blade movable between a position where the blade recedes from the opening and a position where the blade covers at least part of the opening; a drive arm connected to the blade, the drive arm including an engagement hole; a drive lever including a drive pin engaging the engagement hole; and a restriction portion provided in the drive arm, the restriction portion abutting the drive pin and being thicker than the drive arm, wherein the engagement hole includes a first edge positioned at a start side where the drive pin moves in a predetermined direction and a second edge positioned at a terminal side where the drive pin moves in the predetermined direction, and the restriction portion allows an abutment of the second edge with the drive pin, and abuts the drive pin to restrict an abutment of the first edge with the drive pin.

When the drive pin moves in a predetermined direction and stops, the first edge intends to abut the drive pin by an inertial force of the drive arm. For this reason, at least one of the drive arm and the drive pin is chipped, whereby dusts might be generated. However, the restriction portion provided in the drive arm restricts the abutment of the first edge with the drive pin. This can prevent dusts from generating.

According to another aspect of the present invention, there is provided an optical device including the above focal plane shutter.