Photography – Camera detail – Shutter
Reexamination Certificate
2003-02-20
2004-08-17
Gray, David M. (Department: 2851)
Photography
Camera detail
Shutter
C396S487000
Reexamination Certificate
active
06776540
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a shutter device for use in a camera, an image display device and other devices.
2. Related Background Art
Many kinds of cameras and the like employ a focal plane shutter in which a blade group, which is divided to plural pieces by a parallel link mechanism constituted of two arms, is supported freely rotatably. As for the type of the parallel link mechanism used for such a focal plane shutter, according to a long-arm type, an arm proximal end is mounted freely rotatably on one portion of both side portions of a shutter opening in a shutter base plate, while a portion on the arm front end side is joined to the other side of the blade group (the arm being disposed such that it strides over from one side of the shutter opening to the other side), and according to a short-arm type, an arm proximal end is mounted freely rotatably on one portion of both side portions of the shutter opening in the shutter base plate while a portion on the arm front end side is joined to the one side of the blade group (the arm being disposed such that it does not stride over from one side of the shutter opening to the other side).
As the focal plane shutter, a so-called vertically-traveling type focal plane shutter in which the blade group travels vertically has been often used.
In the long-arm type of the vertically-traveling type focal plane shutter, as disclosed in Japanese Utility Model Publication No. 35-29651, the blade group is held freely rotatably on an opposite side to the arm proximal end across the shutter opening. For the reason, the arms are formed longer than the width of the shutter opening.
Because, in the long-arm type, a rotation angle of the arm necessary for opening/closing the shutter opening by means of the blade group may be small, a deflection amount in a direction (lateral direction) perpendicular to the traveling direction of the blade group upon opening/closing operation is small, which is advantageous for reduction of the lateral width of the shutter. If the number of the blades held by two arms is three or more, the structure becomes complicated and long arms need to be used. Thus, inertia of a blade unit comprised of the blade group and arms increases, which is disadvantageous for high-speed operation of the shutter.
For the reason, with increased speed in exposure second-basis time of a shutter and increased speed in flash light emission synchronous second-basis time in recent years, the long-arm type not suitable for high-speed operation has been refrained from use.
On the other hand, although the short-arm type is disadvantageous for reduction of the lateral width as compared to the long-arm type, its arms do not stride over the shutter opening and a plurality of blades are supported freely rotatably with two arms on a side near the arm proximal end. Further, to decrease inertia by the traveling of the blades, it is preferable that the arm length is as short as possible.
The structure and dimensions of respective components of the short-arm type focal plane shutter are shown in
FIGS. 22
to
24
(
FIG. 22
shows a traveling preparation completion state,
FIG. 23
shows a traveling completion state, and
FIG. 24
shows a state of blade movable end (over-charge max)).
In this shutter device, proximal ends of a first front curtain arm
106
and a second front curtain arm
107
are mounted freely rotatably around shafts
101
d
,
101
e
on a shutter base plate
101
having a shutter opening
101
a
. A slit forming blade
102
and four covering blades
103
,
104
,
105
,
105
′, which constitute the front curtain having five-blade structure are mounted freely rotatably on the two front curtain arms
106
,
107
through caulking dowels
108
a
to
108
e
and
109
a
to
109
e
so as to form parallel links.
Further, proximal ends of a first rear curtain arm
114
and a second rear curtain arm
115
are mounted freely rotatably around shafts
101
f
,
101
g
on the shutter base plate
101
. Then, a slit forming blade
110
and three covering blades
111
,
112
,
113
, which constitute the rear curtain having four-blade structure, are mounted freely rotatably on the two rear curtain arms
114
,
115
through caulking dowels
116
a
to
116
d
and
117
a
to
117
d
so as to form parallel links.
On the front curtain side and the rear curtain side, the blade caulking dowels are arranged such that they draw a smooth curve. The first arm and the second arm are disposed adjacent each other in a state in which the front curtain and the rear curtain overlap (hereinafter, this shutter device is called a first conventional example).
In addition, Japanese Utility Model Publication No. 6-26896 has disclosed a shutter device which adopts a third (further, a fourth) auxiliary arm to achieve miniaturization for a reason that the miniaturization is impossible with the parallel link composed of two arms. In this shutter device, when blades are overlapped, first and second arm supporting portions for supporting the slit forming blades are accommodated in an accommodating region existing between a finder and an opening window and the third arm for supporting other covering blades is located out of the region, thereby reducing the external shape dimensions in the horizontal direction of the shutter device.
Because in this shutter device, three arms are disposed in a small space, each arm is formed narrow and the rotation center of the proximal end of the third arm exists between the proximal end rotation center of the first arm and the caulking dowel of the third covering blade when blades are overlapped, while the caulking dowel of the third covering blade on the first arm exists between the proximal end rotation center of the third arm and the caulking dowel of the third covering blade (hereinafter, this shutter device is called a second conventional example).
Moreover, a shutter device (hereinafter this is called a third conventional example) disclosed by Japanese Utility Model No. 2501747 is provided with a slit forming blade driven by a first parallel link mechanism and covering blades driven by a second parallel link mechanism. A joining distance of the first parallel link on the slit forming blade is made longer than the joining distance of the second parallel link on the covering blade so as to maintain parallelism of the slit forming blades and reduce space from the shutter opening to the proximal end side of each parallel link.
On the other hand, Japanese Utility Model Publication No. 59-28414 has disclosed a focal plane shutter in which at least the slit forming blades in opening/closing blade groups divided to plural pieces are driven vertically by a parallel crank mechanism below a finder disposed on the top of a camera main body. Of both blade groups in this device, the degree of dividing of a blade group folded upward is made higher than the degree of dividing of a lower blade group, and of the upper blade group, at least pairing components constituting the parallel crank mechanism on the slit forming blade are located out of a region restricted in a vertical direction of the finder portion. Further, a top portion of the pairing portion is located above the lower edge of the finder portion so as to prolong the length of a section in the vertical direction. Consequently, a slit width upon exposure operation is stabilized and the top end of the shutter located at the top of the shutter opening is brought near the shutter opening without affecting exposure badly so as to set the finder position near the opening, thereby reducing the camera size (hereinafter this is called a fourth conventional example).
Generally, if the reduction in shutter size, particularly the lateral width, is achieved, the number of joint sections between the arm and the blade decreases as the number of divided blades decreases. Thus, area occupied by the joint sections decreases, which is advantageous for reduction of the lateral size.
In contrast, if the number of the blades is decreased, the overlapping amount
Canon Kabushiki Kaisha
Gray David M.
Robin Blecker & Daley
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