Photography – With exposure objective focusing means – focusing aid – or... – Dual purpose motor
Reexamination Certificate
2002-03-28
2003-04-29
Perkey, W. B. (Department: 2101)
Photography
With exposure objective focusing means, focusing aid, or...
Dual purpose motor
C396S505000
Reexamination Certificate
active
06556789
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a diaphragm switching apparatus for switching a diaphragm by utilizing a driving force of a focus motor used for driving a focus lens.
BACKGROUND OF THE INVENTION
For switching a diaphragm in a camera or the like, an actuator such as a plunger has conventionally been employed. However, in order to reduce the size, weight, and cost of cameras, other driving sources mounted in a camera, such as a focus motor for driving a focus lens, for example, may be used for switching the diaphragm with a driving force of the focus motor.
Specifically, a diaphragm switching apparatus
100
shown in
FIG. 8
maybe considered. This diaphragm switching apparatus
100
comprises a gear
101
adapted to rotate in response to a driving force of a focus motor; a shaft
102
rotatably supporting the gear
101
; a diaphragm switching member
103
secured to the axis
102
and adapted to rotate together with the shaft
102
; a compression spring
106
for urging the gear
101
away from the diaphragm switching member
103
by way of a washer
105
by receiving a reaction force from the diaphragm switching member
103
by way of a washer
104
; and an E ring
108
, fitted onto the shaft
102
, for receiving the gear
101
urged by the compression spring
106
by way of a washer
107
.
The diaphragm switching member
103
comprises a cylindrical barrel
103
a
in which the shaft
102
is press-fitted, and a lug-shaped protrusion
103
b
extending from the barrel
103
a
toward a diaphragm switching lever which is not depicted. The protrusion
103
b
engages the diaphragm switching lever. The diaphragm switching lever rotates within a predetermined angle range, and switches the diaphragm in two stages of open and stop-down by back-and-force actions of the angular switching.
First, in the diaphragm switching caused by the diaphragm switching apparatus
100
, the gear
101
rotates in response to the driving force of the focus motor at the time of focusing. Since the gear
101
is urged by the compression spring
106
so as to be pressed against the E ring
108
, the shaft
102
rotates due to a frictional force, and the diaphragm switching member
103
rotates together with the shaft
102
. Here, the diaphragm switching member
103
causes the diaphragm switching lever engaged with the protrusion
103
b
to rotate by a predetermined angle, thereby switching the diaphragm. Then, while the diaphragm switching member
103
and shaft
102
stop rotating at the same time when the diaphragm switching lever stops, the gear
101
rotates in response to the driving force of the focus motor until the driving of the focus lens ends. During this time, the gear
101
idles, thus attaining a slipping rotation state.
SUMMARY OF THE INVENTION
In the above-mentioned diaphragm switching apparatus
100
, however, not only the gear
101
but also the washers
104
,
105
,
107
and compression spring
106
are rotatably supported by the shaft
102
. Therefore, when the gear
101
attains a slipping rotation state as the diaphragm switching member
103
and shaft
102
stop rotating upon switching the diaphragm, members attaining a slipping rotation state do not become stable. For example, the washers
105
,
107
may rotate together with the gear
101
, thereby attaining a slipping rotation state, or the compression spring
106
may also rotate together and attain a slipping rotation state. In particular, when the direction of rotation changes, the site of slippage may change, whereby the load imparted on the driving of the focus motor fluctuates in the slipping rotation state. Since the E ring
108
is press-fitted in a groove formed in the shaft
102
, it is not always placed at right angles. When the E ring
108
is inserted obliquely, for example, the washer
107
may tilt and thereby fail to receive the gear
101
in a stable state, i.e., at right angles with respect to the shaft
102
, whereby the slipping state becomes unstable.
As a consequence, a large fluctuation may occur in the load applied to the focus motor in the slipping rotation state, which may apply a heavy load to the focus motor, whereby the focus motor may cause malfunctions. For preventing the focus motor from malfunctioning, the torque of focus motor must be set while assuming the highest load, which leads the focus motor to enhance its size, power consumption, and the like, thus opposing the tendency of cameras to reduce their size, weight, and cost.
In view of such circumstances, it is an object of the present invention to provide a diaphragm switching apparatus which can stably switch a diaphragm by using a driving force of a focus motor.
Namely, the diaphragm switching apparatus in accordance with one aspect of the present invention comprises a gear adapted to rotate in response to a driving force of a focus motor used for driving a focus lens; a shaft for rotatably supporting the gear; diaphragm switching means, secured to the shaft and adapted to rotate together with the axis, for switching a diaphragm as the shaft rotates; an intermediate member, attached to the shaft so as to be axially slidable, engaging the diaphragm switching means so as to rotate together with the shaft; urging means for urging the gear away from the diaphragm switching means by way of the intermediate member by receiving a reaction force from the diaphragm switching means; and a holding part for receiving the gear urged by the urging means.
According to this aspect of the present invention, the intermediate member engages the diaphragm switching means, whereas the urging means is placed in contact with the diaphragm switching means and the intermediate member. Therefore, when the diaphragm switching means and shaft stop rotating upon switching the diaphragm, the intermediate member and urging means also stop rotating, thus leaving only the gear to be maintained in a rotating state with respect to the intermediate member and the brim in response to the driving force of the focus motor until the driving of the focus motor ends. Therefore, fluctuations in the load applied to the focus motor in the slipping rotation state can be reduced, whereby the focus lens can be prevented from malfunctioning due to a heavy load applied to the focus motor. Also, since fluctuations in the load applied to the focus motor in the slipping rotation state are small, the torque of focus motor can be set low, whereby the focus motor can reduce its size, weight, and power consumption.
The diaphragm switching apparatus in accordance with another aspect of the present invention is characterized in that the holding part is a brim projecting from the outer periphery of the shaft.
According to this aspect of the present invention, the brim yields neither rattling nor tilting with respect to the shaft, thus being able to receive the gear urged by the urging means in a stable state. As a consequence, fluctuations in the load applied to the focus motor when the gear rotates in a slipping fashion can further be reduced.
The diaphragm switching apparatus in accordance with still another aspect of the present invention is characterized in that a low-friction member is disposed between the intermediate member and the gear and/or between the holding part and the gear.
According to this aspect of the present invention, since a low-friction member is disposed, the frictional force of the gear with respect to the intermediate member and holding part can be reduced when the gear rotates in a slipping fashion, whereby the load applied to the focus motor can be lowered. Therefore, the torque of focus motor can be set lower, whereby the focus motor can further reduce its size, weight, and power consumption.
The diaphragm switching apparatus in accordance with still another aspect of the present invention is characterized in that the urging means is an elastic member such as a compression spring or rubber material, and that the urging force of the urging means is made adjustable by changing the distance between the diaphragm switching means and the holding part.
Fuji Photo Optical Co., Ltd.
Leydig , Voit & Mayer, Ltd.
Perkey W. B.
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