Photography – Camera detail – Shutter
Reexamination Certificate
2002-02-20
2003-03-11
Mathews, Alan A. (Department: 2851)
Photography
Camera detail
Shutter
C396S484000
Reexamination Certificate
active
06530703
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to focal-plane shutters, and more particularly to focal-plane shutters having resilient stopping members for absorbing shutter blade impact forces without causing undue wear of the shutter blade connector portions.
2. Description of the Related Art
Japanese Utility Model Publication No. 34892/1981 discloses a known focal-plane shutter in which at least one stopping portion is mounted to a base plate to bring at least some of the closing blades and/or closure-assisting members to a stop. As shown in
FIG. 5
, a base plate
9
of this structure has bent portions forming stopping portions
9
b
,
9
b
which are brought into resilient contact with the front-end surface of a leading blade
6
a
of a set of closing blades
6
a
-
6
e
via resilient members
10
,
10
. Although the stopping portions
9
b
,
9
b
are shown to be two in number, at least one stopping portion is provided.
In this known structure, there are provided two stopping portions
9
b
,
9
b
in the case shown in FIG.
5
. The two stopping portions
9
b
,
9
b
are mounted to one side (i.e., the right side) of pivotal portions
7
b
and
8
b
which connect the leading blade
6
a
with closure-assisting members
7
,
8
for driving the blade
6
a
. Therefore, when the leading blade
6
a
of the set of closing blades
6
a
-
6
e
is moved by the spring force of a spring (not shown) and collides against the stopping portions
9
b
,
9
b
to close the shutter opening
2
, the resulting impact forces exert a counterclockwise force on the pivotal portions
7
b
and
8
b
. Since this action is repeated each time the shutter is used, eccentric wear occurs on the pivotal portions
7
b
,
8
b
, producing rattling between the blade
6
a
and the pivotal portions
7
b
,
8
b
. This makes it impossible to hold the blade
6
a
stably and, consequently, the exposure accuracy deteriorates.
Furthermore, since the end surface of the blade
6
a
making resilient contact with the stopping portions
9
b
,
9
b
is an end surface that passes over the shutter opening
2
and forms the slit, wear is produced on the end surface that makes resilient contact with the stopping portions
9
b
,
9
b
as a result of repeated resilient contacts. As a result, a problem occurs in that the amount of exposure differs between the portions of the end surface of the blade
6
a
on which wear has occurred and the other non-worn portions, resulting in so-called image nonuniformity.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a focal-plane shutter which overcomes the aforementioned drawbacks of prior art shutters.
Another object of the present invention is to provide a focal-plane shutter that prevents the application of unwanted forces to the connector portions connecting the shutter blades to the arms, thereby stabilizing the amount of exposure and improving the durability of the shutter.
A focal-plane shutter according to one embodiment of the present invention comprises a shutter plate having a shutter opening, a set of opening blades for opening and closing the shutter opening, and arms connected via connector portions to the opening blades for driving the opening blades parallel to the shutter opening. Resilient stopping members are provided for making resilient contact with the opening blades at opening positions where the opening blades are in a retracted state and open the shutter opening. The resilient stopping members are plural in number and make resilient contact with the opening blades on opposite sides of the connector portions.
A focal-plane shutter according to another embodiment of the present invention comprises a shutter plate having a shutter opening, a set of closing blades for opening and closing the shutter opening, and arms connected via connector portions to the closing blades for driving the closing blades parallel to the shutter opening. Resilient stopping members are provided for making resilient contact with the closing blades at closing positions where the closing blades close the shutter opening. The resilient stopping members are plural in number and make resilient contact with the closing blades on opposite sides of the connector portions. Since the resilient stopping members make resilient contact with the blades on opposite sides of the connector portions that connect the blades with the arms, impact forces produced when the blades collide against the resilient stopping members cancel out each other at the connector portions. Therefore no extra force acts on the connector portions, thereby enhancing the durability of the shutter.
According to another aspect of the present invention, the set of closing blades makes resilient contact with the resilient stopping members at portions thereof that do not traverse the shutter opening. This prevents damage to the end surface of the slit-forming blade that traverses the shutter opening and forms the slit. Thus the amount of exposure is not altered because of damage to the end surface of the slit-forming blade, even if the closing blades repeatedly collide against the resilient stopping members, thereby maintaining exposure accuracy and improving durability.
REFERENCES:
patent: 4692009 (1987-09-01), Toyoda et al.
patent: 4847649 (1989-07-01), Toyoda et al.
patent: 4975722 (1990-12-01), Suzuki et al.
patent: 5034765 (1991-07-01), Nemoto et al.
patent: 5594521 (1997-01-01), Hasuda et al.
patent: 5664247 (1997-09-01), Hasuda et al.
Nakano Yoichi
Takahashi Hiroshi
Adams & Wilks
Mathews Alan A.
Seiko Precision Inc.
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