Shutter device

Details Shutter device Shutter device

2001-04-17

2003-10-28

Gray, David (Department: 2851)

Photography

Camera detail

Shutter

C396S489000

Reexamination Certificate

active

06637955

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a shutter device for a camera, an image display apparatus or the like.
2. Description of Related Art
A focal plane shutter of the kind having a plurality of divided blade groups swingably held by parallel link mechanisms each of which consists of two arms is popularly used for a camera or the like. The parallel link mechanisms used for focal plane shutters can be divided into a long arm type and a short arm type. In the long arm type, the base end parts of the arms are swingably mounted on one of two sides of a shutter aperture formed in a shutter base plate. The arms straddle the shutter aperture. The blade groups are interlinked by the fore end parts of the arms on the other side of the shutter aperture. In the short arm type, the base end parts of the arms are swingably mounted on one of two sides of the shutter aperture. The arms interlink the blade groups by their fore end parts on the same one side of the shutter aperture without straddling the shutter aperture.
Among the known focal plane shutters, so-called vertical travel focal plane shutters are most popularly used. Of the vertical travel focal plane shutters, the long arm type focal plane shutter is arranged, as disclosed in Japanese Laid-Open Utility Model Publication No. Sho 35-29651, to swingably hold the blade groups by the arms on the opposite side across the shutter aperture with respect to the base end parts of the arms. Because of this arrangement, the arms become longer than the width of the shutter aperture.
In the long arm type, the arm swinging angle required for opening and closing the shutter aperture with the.blade groups is small. Therefore, the amount of displacement of the blade groups in the direction of orthogonally intersecting the traveling direction of the blade groups for opening or closing the shutter aperture, i.e., in the direction of width, becomes small. The small amount of displacement is advantageous for reduction in size of the shutter. However, in a case where the number of blades to be held by the two arms is arranged to be three or more, the arrangement results in a complex structure. Besides, the use of long arms increases the inertia of the shutter blade unit consisting of the blade groups and the arms. The large inertia is a disadvantage for a high speed travel of the shutter blades.
Therefore, as a result of the recent trend of increasing a shutter speed for an exposure and making flash light emission synchronizing time shorter, the long arm type focal plane shutter has come to be seldom used.
On the other hand, the short arm type focal plane shutter has come to be more popularly used. Although it is more disadvantageous than the long arm type in respect of reduction in width, the short arm type is advantageous in the following points. The two arms are arranged not to straddle the shutter aperture and to be able to swingably hold many blades on the side of the shutter aperture located close to their base end parts. Besides, the inertia of the shutter blade unit can be minimized by arranging the arms to be as short as possible.
FIGS. 19 and 20
show the arrangement and dimensions of the parts of a short arm type focal plane shutter.
FIG. 19
shows the short arm type focal plane shutter as in a state of having completed preparation for a travel.
FIG. 20
shows it as in a state obtained upon completion of the travel. In the case of this shutter device, the base end part of a first leading-curtain arm
106
and that of a second leading-curtain arm
107
are swingably mounted on shafts
101
d
and
101
e
which are provided on a shutter base plate
101
having a shutter opening
101
a
. These two leading-curtain arms
106
and
107
interlink and carry in a swingable manner a slit forming blade
102
and four cover blades
103
,
104
,
105
and
105
′ which jointly form a leading curtain consisting of five blades. These blades are interlinked to form a parallel link by using blade caulking dowels
108
a
to
108
e
and
109
a
to
109
e
. The base end part of a first trailing-curtain arm
114
and that of a second trailing-curtain arm
115
are swingably mounted on shafts
101
f
and
101
g
on the shutter base plate
101
. The trailing-curtain arms
106
and
107
swingably interlink and carry a slit forming blade
110
and three cover blades
111
,
112
and
113
which jointly form a trailing curtain consisting of four blades. These blades are interlinked to form a parallel link by using blade caulking dowels
116
a
to
116
d
and
117
a
to
117
d.
On each of the leading- and trailing-curtain sides, the blade caulking dowels are simply allocated in a moderately arcuate line. The first and second arms are arranged to come close to each other side by side when the leading and training curtains are in a state of overlapping each other. The shutter device described above is hereinafter called a first example of prior art.
A shutter device disclosed in Japanese Laid-Open Utility Model Publication No. Hei 6-26896 is arranged to permit reduction in size by adding a third auxiliary arm (and may be a fourth auxiliary arm) to the two arms in view of that a parallel link consisting of the two arms does not easily permit reduction in size. The shutter device is arranged such that, when the shutter blades are overlapping, support parts of the first and second arms where the slit forming blades are carried by these arms are located within a stowing area between a viewfinder and an aperture window, while the third arm which carries other covering blades is arranged to be located outside of the stowing area, so that an outside lateral dimension of the shutter device can be lessened.
To have three arms within a small space, each arm is arrange to be thin, this shutter device is arranged as follows. In the blade overlapping state, the center of swing of the base end part of a third arm enters in between the center of swing of the base end part of a first arm and the caulking dowel of a third cover blade, and the caulking dowel of the third cover blade on the first arm enters in between the center of swing of the base end part of the first arm and the third cover blade. That shutter device is called a second example of prior art.
Japanese Laid-Open Utility Model Publication No. Hei 6-26897 disclosed another shutter device. The shutter device is arranged to permit reduction in size and to increase the durability thereof. For this purpose, one of two main arms is connected to one of the pivotal support parts of each blade on the other main arm while the other pivotal support part is connected to the other main arm and also to an auxiliary arm. The shutter device is called a third example of prior art.
Japanese Utility Model Registration No. 2501747 disclosed a shutter device. The shutter device consists of slit forming blades arranged to be driven by a first parallel link, cover blades arranged to be driven by a second parallel link. An interlinking distance on the slit forming blade of the first parallel link is arranged to be longer than an interlinking distance on the cover blades of the second parallel link in such a way as to keep the parallelism of the slit forming blades and yet to reduce a space from the shutter aperture to the base end part of each parallel link. The shutter device is called a fourth example of prior art.
Japanese Laid-Open Patent Application No. Sho 53-143314 disclosed a shutter device arranged to reduce the size of a long arm type shutter by reducing a space for stowing shutter blade groups in an overlapped state. For this purpose, arm blades are arranged to function both as arms of a parallel link and as cover blades for blocking light from a shutter aperture. The arm blades are arranged to carry slit blades (slit forming blades) in conjunction with arms and also to cover spaces between other cover blades. The shutter device is called a fifth example of prior art.
Generally, it is advantageous for reduction in size (particularly in width) of a shutter device (focal plane sh

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