Optical: systems and elements – Lens – With variable magnification
Reexamination Certificate
2001-11-19
2004-11-23
Mai, Huy (Department: 2873)
Optical: systems and elements
Lens
With variable magnification
C359S824000
Reexamination Certificate
active
06822809
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a drive transmission device, a lens unit using the drive transmission device, an optical apparatus that includes an imaging unit to which the lens unit is detachably mounted, and an optical-apparatus driving unit that is mounted to the lens unit using the drive transmission device.
2. Description of the Related Art
FIG. 9
shows the structure of a manually-operated part and an electrically-operated system of a conventional optical apparatus, such as that used for television shooting.
An operating ring
103
is rotatably disposed on the outer periphery of an apparatus body
101
. An optical adjusting means, such as a movable lens group, not shown, that is disposed inside the apparatus body
101
can be driven by manual operation of the operating ring
103
or by electric operation from a drive unit mounted in the apparatus body
101
.
A motor
105
and a control circuit used to electrically drive the operating ring
103
are housed in the drive unit. The motor
105
can be activated by operating an electric operation switch, or the like, that is disposed on the outer surface of the drive unit, and the optical adjusting means can be driven through the operating ring
103
.
In the optical apparatus capable of manually and electrically driving the movable lens group, switching between manual drive and electric drive is carried out in most cases by manually operating a clutch mechanism provided with a switching lever.
In this clutch mechanism, an idler gear
123
slidable in the axial direction of a shaft
124
by the operation of the switching lever, not shown, is provided between an operating gear
104
formed on the operating ring
103
and an output gear
122
of the motor
105
.
When electrically driven, the idler gear
123
is slid by the manual operation of the switching lever to a position where the idler gear
123
is engaged with the operating gear
104
and with the output gear
122
, thereby transmitting the driving force of the motor
105
to the operating ring
103
through the idler gear
123
.
When manually driven, the idler gear
123
is slid by the manual operation of the switching lever to a position where the idler gear
123
is disengaged from the output gear
122
.
The switching between manual drive and electric drive is conventionally carried out such that a driving-force transmission path from the motor
105
to the operating ring
103
is turned on or off by manually operating the clutch mechanism, as described above.
However, in the optical apparatus in which the transmission path of motor power is turned on or off by operating the switching lever so as to achieve the switching between manual drive and electric drive as described above, the switching lever must be operated whenever the switching therebetween is carried out. Therefore, there is a problem in that operations become complex, and thus quick switching between manual drive and electric drive is made difficult.
Additionally, if the idler gear
123
and the output gear
122
are different in phase from each other when switched from manual drive to electric drive, the idler gear
123
is first pressed against the side surface of the output gear
122
by the urging force of the spring
125
, and is caught there. Thereafter, when the output gear
122
begins to be driven by the motor
105
, and the phase of the output gear
122
coincides with that of the idler gear
123
, the gears mesh with each other, and the idler gear
123
is moved to a contact position with a stopper
126
by the urging force of the spring
125
. As a result, switching to a proper electric-drive state is completed.
However, a problem resides in that an impulse sound occurs at this time because the idler gear
123
collides with the stopper
126
owing to the urging force of the spring
125
.
Further, in actual shooting, there is a case in which, while being electrically driven, a cameraman attempts to forcibly stop the electric drive through the manual operation of the operating ring
103
, or attempts to perform the manual operation in a direction opposite to the electric-drive direction, or attempts to increase or decrease the electric-drive speed.
However, a problem resides in that the aforementioned clutch mechanism has difficulty in the manual operation while being electrically driven.
As consideration, use can be made of an electromagnetic clutch in which the electricity supply to a coil is turned on or off so as to turn on or off the transmission path of the motor power, which is different from the clutch mechanism in which the switching is carried out through the lever operation.
FIG. 8
shows the inner structure of the electromagnetic clutch. (a) of
FIG. 8
shows the electromagnetic clutch in which the electricity supply to a coil
217
is in an off-state. At this time, an armature
215
connected to the operating ring
103
through a gear train, not shown, is drawn by the urging force of a leaf spring
222
in a direction opposite to a rotor
214
to which a driving force is input from a motor not shown so that the frictional surface
216
of the rotor
214
and the frictional surface
216
of the armature
215
do not come in contact with each other.
(b) of
FIG. 8
shows the electromagnetic clutch in which the electricity supply to the coil
217
is in an on-state. At this time, a magnetic circuit is produced inside the electromagnetic clutch, and the armature
215
is drawn to the rotor
214
against the urging force of the leaf spring
222
and is brought into pressed contact with the rotor
214
. Thereafter, engagement torque is generated in the electromagnetic clutch by the frictional force of the frictional surface
216
, and the driving force of the motor can be transmitted to the operating ring
103
.
However, if the electromagnetic clutch constructed as shown in
FIG. 8
is used, the armature
215
moves in response to the switching between the ON and the OFF of the electricity supply to the coil
217
and collides with the rotor
214
or with the striking surface of the output shaft, and therefore a noise occurs.
Additionally, an electromagnetic force (i.e., coil voltage) that prevails against the urging force of the spring
222
is required in order for the armature
215
to come in contact with the rotor
214
by attraction. Therefore, delay arises during the period from the start of a command signal for performing the electric drive to the occurrence of the engagement torque resulting from the attractive contact of the armature
215
with the rotor
214
.
Additionally, the coil voltage required to cause the armature
215
to come in contact with the rotor
214
by attraction is inconstant because, for example, of the individual differences of the electromagnetic clutch.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a drive transmission device capable of preventing a sound from occurring when switched between the ON and OFF of the electricity supply, and capable of eliminating delay caused during the period from the beginning of the electricity supply to the engagement between an input member and an output member.
It is another object of the present invention to provide an optical apparatus or an optical-apparatus driving unit capable of easily, promptly, and quietly performing the switching between manual drive and electric drive by use of the aforementioned drive transmission device, and capable of smoothly performing the manual drive while being electrically driven.
In order to achieve the objects, according to the present invention, a drive transmission device for transmitting the drive of an actuator to a driven member comprises an input member which is driven by the actuator, an output member for transmitting the drive of the input member and driving the driven member, and a state switching unit for performing switching between a first state to transmit drive and a second state so as not to transmit drive in the input member and the output member, in which the input member and t
Canon Kabushiki Kaisha
Mai Huy
Morgan & Finnegan , LLP
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