Photography – Camera detail – Shutter
Reexamination Certificate
2000-03-30
2002-05-07
Gray, David M. (Department: 2851)
Photography
Camera detail
Shutter
C396S469000, C396S470000, C396S478000
Reexamination Certificate
active
06382848
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a shutter for a camera.
2. Description of the Related Art
Although a shutter for a camera is available in various styles and types, as one type there is a shutter for a camera provided such that an aperture of a lens is closed in a state in which a plurality of sheets of sectors are closed and a hole for exposure is opened at a central portion thereof by pivoting the sectors. According to opening and closing operation of the sectors, a base portion of each of the sectors is pivotably supported, a drive pin of a sector drive lever is engaged with a drive hole portion provided at a position apart from the support point by a predetermined distance and the sector can be opened by pivoting the lever and can return to an original position by spring force.
FIG. 8
shows the principle of a shutter drive apparatus for operating a shutter to open and close two sheets of sectors according to a conventional technology and a description of the shutter drive apparatus is as follows. Two sheets of sectors
83
are attached between a shutter base plate
81
and a rear plate
82
to thereby enable to open and close lens apertures
81
a
and
82
a
. The shutter base plate
81
and the rear plate
82
can be fixed to be apart from each other at an interval capable of installing the sectors pivotably by screws
84
, Respective elements of the shutter drive apparatus are provided on a front face (upper face of
FIG. 8
) of the shutter base plate
81
.
First, a sector drive lever
85
formed with projected portions on both sides of a plate-like member formed substantially in a heart-like shape, is provided at a vicinity of a central portion of the upper face of the shutter base plate
81
. According to the sector drive lever
85
, a bearing portion
85
a
provided to project at a pivotal center portion thereof is fitted to a support shaft portion
81
b
provided to project from the upper face of the shutter base plate
81
. A sector drive pin
85
b
is provided to hang down from a vicinity of a top portion of a lower face of the sector drive lever
85
and the pin passes through an arc groove portion
81
c
formed in the shutter base plate and is engaged with an oval groove portion
83
a
of the sector. Further, respective sectors constituting the sector
83
are pivotably supported by pivotal center holes
83
b
and support pins
81
d
provided to project from a rear face of the shutter base plate. The respective support pins
81
d
stably support respectively the sector
83
by being engaged with through holes
82
b provided at the rear plate
82
.
The sector drive lever
85
is biased in the counterclockwise direction by a spring
86
, thereby, the sector
83
is biased in a direction of closing the shutter
83
. A drive coil
87
constituted by winding a coil in a spiral shape and solidifying the coil in a doughnut-like shape, is fixedly attached to a rear face of an ear portion
85
c
formed on a side of the sector drive lever
85
opposed to a position attached with the spring
86
. One lead wire
87
a
of the coil
87
is connected to an outer peripheral portion of the coil and other lead wire
87
b
is connected to an inner peripheral portion thereof. When electricity is conducted from a drive circuit
88
to the coil
87
, there is produced magnetic flux an upper side of which constitutes an S pole and a lower side of which constitutes an N pole, for example. Conduction of electricity to the coil
87
can be controlled by the drive circuit
88
to thereby enable to arbitrarily open and close the shutter.
The drive coil
87
is also pivoted centering on the support shaft portion
81
b
by pivoting the sector drive lever
85
and a pair of permanent magnets
89
and
90
in a shape of a thin plate are provided on a pivotal locus of the center of the coil. These permanent magnets are fixedly attached onto the upper face of the shutter base plate
81
and the one magnet
89
is disposed on a forward side of the pivotal locus of the coil
87
in the clockwise direction at an initial position and is pasted such that an upper face thereof constitutes an N pole. In contrast thereto, the other permanent magnet
90
is disposed on a rearward side of the pivotal locus of the coil
87
and is pasted such that an upper face thereof constitutes an S pole.
Since the constitution is constructed in this way, when magnetic force with the S pole on a downward side is produced in the coil by conducting controlled electricity from the drive circuit
88
to the coil
87
, by the operation of the magnetic force, a suction force is operated between the drive coil
87
and the magnet
89
on the front side and a repulsion force is operated between the drive coil
87
and the magnet
90
on the rear side to thereby move the drive coil
87
in the clockwise direction and pivot the sector drive lever.
85
in the same direction. Thereby, the sector
83
is opened and an exposable state is brought about. Next, when electricity is made to stop conducting to the drive coil
87
, the magnetic force is extinguished, the sector drive lever
85
returns to the original position by the spring
86
and the shutter is closed.
According to the shutter drive apparatus of the conventional example, the sector drive lever
85
and the drive coil
87
are disposed on different planes and accordingly, there poses a problem in which areas on the planes become large. Further, in addition thereto, the sector drive lever
85
, the drive coil
87
and the permanent magnets
89
and
90
are provided at respectively different heights and accordingly, there poses a problem in which a thickness of the shutter becomes large by that amount. Further, the sector drive lever
85
is pivoted by pivoting the drive coil
87
per se and accordingly, there poses a problem in which large kinetic energy is needed and accordingly, power consumption is increased.
SUMMARY OF THE INVENTION
A supporting plate having an opening is integrated with magnetic field generating elements in the form of a fixed printed board having a plurality of coil patterns substantially disposed in a concentric shape relative to a center of an optical axis of the opening and a movable printed board opposed to (confronting) one face of the fixed printed board and having magnetic field generating elements in the form of a plurality of coil patterns in a similar manner, the movable printed board is made pivotable by conducting electricity to the respective coil patterns acting as electromagnets and the movable printed board is constituted to be capable of opening and closing a sector to thereby enable to realize thinned formation and downsized formation of the shutter.
Polarities of the two printed boards are made the same in directions in which the two printed boards are opposed to each other, further, initial positions of the movable coil patterns of the movable printed board are set to positions deviated from positions of the fixed coil patterns of the fixed printed board in an advancing direction by a predetermined angle, electromagnetic forces produced from the two coil patterns and produced by conducting electricity from a drive circuit repulse each other and the movable printed board is made pivotable in a direction of opening the sector.
The movable printed board is easily pivoted in the direction of opening the sector by providing a cam mechanism for making the movable printed board progress and regress in a direction of the optical axis on faces of the movable printed board and a shutter base plate opposed to each other.
When the sector is opened to an aperture having a size determined by a diaphragm value, the sector is set to stop driving, at this occasion, when electricity is made to stop conducting to the coil patterns by the drive circuit, the electromagnetic forces of the two printed boards are extinguished and a sector lever returns to an original position by biasing force of a spring to thereby close the shutter.
As an example of the cam mechanism, there is adopted a cam mechanis
Adams & Wilks
Gray David M.
Seiko Precision Inc.
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