Photography – With object illumination for exposure – Having exposure synchronizer
Reexamination Certificate
2001-05-14
2002-12-03
Perkey, W. B. (Department: 2851)
Photography
With object illumination for exposure
Having exposure synchronizer
C396S195000
Reexamination Certificate
active
06490416
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a shutter for use in a camera and, more particularly, to a camera shutter having exposure control means that performs an opening operation by an opening sector and a closing operation by a closing sector.
2. Description of the Related Art
A shutter that controls exposure by an opening sector and a closing sector has opening and closing levers for performing opening and closing operations, respectively. The opening and closing levers are spring-biased in opening and closing directions and are held in their charged condition by electromagnets. The electromagnets are deenergized whereby the opening and closing levers are driven by the stored spring forces to perform opening and closing operations. Exposure is controlled by varying the timing at which the opening and closing electromagnets are deenergized. A synchronous contact member for producing a trigger signal for a strobe is mounted near the position at which the operation of the opening lever ends. The opening lever fully opens the opening sector and simultaneously therewith, the synchronous contact member is energized to produce the trigger signal to cause the strobe to flash.
One known structure is shown in
FIG. 6
, where a shutter base plate
1
is provided with a shutter opening
1
c
. An opening lever
21
is rotatably fitted over a shaft
1
a
standing on the shutter base plate
1
. The opening lever
21
is biased in a counterclockwise direction by an opening spring (not shown). Similarly, a closing lever
22
is rotatably fitted over a shaft
1
b
on the shutter base plate
1
, and the closing lever
22
is biased in a counterclockwise direction by a closing spring (not shown). The opening lever
21
and the closing lever
22
have protrusions
21
b
and
22
b
at their respective front ends. The protrusions
21
b
and
22
b
pass through arc-shaped holes
1
e
and
1
f
, respectively, formed in the shutter base plate
1
, and the protrusions protrude below the shutter base plate
1
. An opening sector and a closing sector (neither of which is shown) are driven by the opening lever
21
and the closing lever
22
, respectively, to open and close the shutter opening
1
c.
A charge lever
30
is rotatably fitted over a shaft
1
d
on the shutter base plate
1
. The opening lever
21
and the closing lever
22
are placed into a charged position by the charge lever
30
. The motion of the opening lever
21
and the closing lever
22
is controlled by an opening electromagnet
41
and a closing electromagnet
42
under control of a CPU (not shown) incorporated in the camera. A printed circuit board
60
is supported on the top ends of the shafts
1
a
and
1
b
standing on the shutter base plate
1
. The opening electromagnet
41
and the closing electromagnet
42
are soldered to circuits on the printed circuit board
60
and electrically connected with these circuits. opening contact members
151
a
,
151
b
and closing contact members
152
a
,
152
b
are crimped to the printed circuit board
60
.
FIG. 5
shows portions for activating and deactivating the opening contact members
151
a
and
151
b
of a shutter similar to the shutter of FIG.
6
. Note that elements or components performing like functions are indicated by like reference numerals in both
FIGS. 5 and 6
. Each of the opening contact members
151
a
and
151
b
is fabricated by bending a metal leaf spring in a complex manner to crease the spring. In the state of
FIG. 5
, the opening sector has been displaced into the charged position, thus closing the shutter opening
1
c
. Under this condition, the opening sector is attracted and held by the opening electromagnet
41
. At this time, the opening contact members
151
a
and
151
b
are opened. When the shutter opening
1
c
is opened, the opening lever
21
is released from the opening electromagnet
41
and rotated by the opening spring in a counterclockwise direction. A pin
21
a
mounted on the opening lever
21
is pushed against the opening contact member
151
a
near the position at which the counterclockwise travel of the opening lever
21
ends. The opening contact member
151
a
is thereby pushed against the opening contact member
151
b
, closing both contact members. Thus, both contact members are electrically connected with each other. In this structure, if the shutter opening
1
c
is not fully opened by the opening sector, an opening signal indicating opening of the contact members is produced. If the shutter opening is fully opened by the opening sector, a closure signal is produced. Since the closing contact members
152
a
and
152
b
are substantially identical in structure with the opening contact members
151
a
and
151
b
, a description thereof has been omitted.
In this way, in the prior art structure, when the shutter opening
1
c
is opened by the opening sector, the opening contact members
151
a
and
151
b
are closed and electrically connected together. When the shutter opening
1
c
is closed by the closing sector, the closing contact members
152
a
and
152
b
are closed and electrically connected. Therefore, immediately after the contact members are closed, chattering tends to occur because of the resilience of the contact members. In the case where the opening contact members
151
a
and
151
b
are fabricated as synchronous contact members and an electric signal is used to trigger flash of the strobe, the chattering may produce a false trigger signal for flash of the strobe. As a result, the strobe may erroneously flash. Furthermore, each of the contact members
151
a
,
151
b
,
152
a
, and
152
b
is fabricated by bending a metal leaf spring in a complex manner to crease the spring, which increases the fabrication cost. Another problem is that there are a large number of input and output terminals between the CPU in the camera and the driver circuit of the shutter, which complicates assembly.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a focal plane shutter which uses a synchronous contact member thereby resulting in a decreased amount of chattering.
Another object of the present invention is to provide a focal plane shutter having a synchronous contact member which is easy and inexpensive to fabricate and assemble in the shutter.
A further object of the present invention is to provide a focal plane shutter having a synchronous contact member and which has a reduced number of input and output terminals.
Another object of the present invention is to provide a focal plane shutter having a synchronous contact member which produces an output signal used as a trigger signal for flashing a strobe thereby securing generality of use and design.
A focal plane shutter in accordance with the present invention has a shutter base plate provided with a shutter opening, an opening sector for opening the shutter opening, a closing sector for closing the shutter opening, and a normally closed synchronous contact member linking the opening sector and an output circuit. When the shutter opening is opened, the synchronous contact member is opened. The output circuit produces an opening signal when the synchronous contact member is closed. When the synchronous contact member is opened, the output circuit produces a given output signal different from the opening signal. Since the synchronous contact member, which is normally closed, is opened when the shutter opening is opened, the amount of chattering is reduced. The shutter can be assembled and inspected in a shorter time. Misflash of the strobe can be prevented. Furthermore, because an opening signal is produced when the synchronous contact member is closed, and because a given signal different from the opening signal is produced when the synchronous contact member is opened, a signal corresponding to the degree to which the shutter opening is opened by the opening sector can be obtained thereby securing generality of design.
In accordance with the invention, the focal plane shutter includes a
Ito Akira
Nakano Yoichi
Nemoto Chiaki
Tanikawa Miyoshi
Adams & Wilks
Perkey W. B.
Seiko Precision Inc.
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