Lens barrel

A lens barrel includes a vibratory-wave motor whose stator is in frictional contact with its rotor and which has a hollow core to admit passage of a light beam, a lens group held by an axially movable lens holder, a drive mechanism for axially moving the lens holder, a rotatable manual ring, and a clutch for selecting either one of the rotor and the manual ring to transmit its rotation to the drive mechanism, the clutch having a plurality of axially movable members arranged upon movement in a direction to establish a transmission for the rotation of the rotor to the drive mechanism or upon movement to the opposite direction to establish a transmission for the rotation of the manual ring to the drive mechanism.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a lens barrel in which a lens is driven by a 
vibratory-wave motor. 
2. Description of the Related Art 
Various proposals for using a vibratory-wave motor as a drive source for 
driving the lens have already been made (in, for example, U.S. Pat. No. 
4,793,685 and U.S. Patent Application Serial No. 261,265 filed on Oct. 24, 
1988; 103,303 filed on Oct. 1, 1987; U.S. Pat. No. 4,660,933, for 
example). 
In a lens barrel of this kind, for driving the lens, if the vibratory-wave 
drive device using an electrostrictive element is utilized, a 
simplification of the structure of construction, a minimization of the 
size, etc. can be achieved on one hand and such a problem as follows 
arises on the other hand. That is, the vibratory-wave drive device has a 
stator in the form of a vibrator and a rotor which are pressed against 
each other to exert a frictional force which is made use of as the drive 
transmission source. In the manual mode (focusing manually), therefore, a 
large force is required for moving the rotor against the frictional force. 
In other words, the conventional lens drive device when switched to the 
manual mode necessitates a torque which overcomes the aforesaid frictional 
force. For this reason, there has been a requirement for reducing it to 
improve the manageability. 
Therefore, many improved techniques have been proposed. For example, in 
U.S. Pat. No. 4,864,344 the rotation of the manual ring is electrically 
detected, and the amount of rotation of this ring is translated to the 
time for which the vibratory-wave drive device is driven. 
Another method of reducing the frictional torque is to cause the vibrator 
in the form of a vibrating ring of the stator to vibrate in a stationary 
wave, which allows for reduction of the contact area of the rotary ring 
for the rotor with the vibration ring for the stator. However, in both 
methods, even in the manual mode, the electrostrictive element has to be 
energized. This leads to an increase in the consumption of electric power. 
Therefore, the camera must accommodate an electric power source of 
increased capacity. 
Meanwhile, it has been proposed in U.S. Pat. No. 4,660,933 to make use of a 
simple clutch mechanism arranged so that when switching the camera to the 
manual mode, the vibration ring for the stator and the rotation ring for 
the rotor are taken out of frictional contact with each other. The use of 
this technique, however, makes it difficult to re-establish the constant 
frictional force between the stator and the rotor when the camera is 
switched to the automatic mode. In the vibratory wave drive device, the 
instability of the frictional force between the stator and the rotor gives 
cause for lowering the drive efficiency and for generating noise during 
operation. 
SUMMARY OF THE INVENTION 
One aspect of the invention is to provide a lens barrel in which use is 
made of a clutch for cutting off the operative connection between the 
rotor and the lens drive mechanism without causing a change of the 
frictional contact between the stator and the rotor, and further, this 
clutch is mounted on a ring member which rotates at the same speed as that 
of rotation of the rotor, thereby making it possible to perform manual 
driving of the lens, while nevertheless preserving the efficiency of the 
vibratory-wave motor from changing and also permitting smooth management 
of the actuator to be achieved.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 in sectional view shows an embodiment of the lens barrel according 
to the invention. 
In FIG. 1, a lens barrel main body 1 is secured to a fixed tube 2 by a 
screw fastener. A bayonet mount 3 and a cover ring 4 are also secured in 
unified form to the fixed tube 2 by screw fasteners, or the like. A manual 
operating ring 5 is rotatably, axially movably fitted on the front end 
portion of the lens barrel main body 1. A click spring 6 extends from the 
inner radial wall of the ring 5 rearward. When the click spring 6 engages 
in a front click groove 1a or a rear click groove 1b, the manual operating 
ring 5 is restrained from axial movement. The inner peripheral surface of 
the lens barrel main body 1 has a screw-threaded portion 1c to which a 
rotary helicoid 7 is in helicoid connection. 
A plurality of interlocking pins 8 are inserted along the axial direction 
into the rotary helicoid 7 in equally spaced relation over the 
circumferential length thereof. The interlocking pins 8 are urged normally 
axially rearward (to the right as viewed in the figure) by the respective 
compressed coil springs 9. In the manual focusing position shown in the 
figure, by this springing force, the head portion 8a of the interlocking 
pin 8 and the manual operating ring 5 are brought into pressure contact 
with each other. 
The interlocking pin 8 has a 2-cheeked portion 8b at the center of the 
axial length thereof as shown in FIG. 2. This 2-cheeked portion 8b is 
fitted in a letter "U" shaped cutout 10a of a rotation restraining plate 
10 which is fixedly secured to the rotary helicoid 7 by screw fasteners, 
so that the interlocking pin 8 is restrained from rotation about its own 
axis. 
The rotary helicoid 7 has a helicoid screw 7a in the inner diameter portion 
and is in helicoid connection with a helicoid portion 11a of a lens 
holding tube 11 holding a plurality of lenses. The lens holding tube 11 
has one or more key groove or grooves 11b formed in the outer peripheral 
end portion thereof along the axial direction. A straight key 12 whose 
rear end is fixedly secured to the fixed tube 2 is inserted into the key 
groove 11b, so that a straight axial movement of the lens holding tube 11 
is assured. 
Meanwhile, an annular ball race 13 is fixedly mounted to the inner 
peripheral portion of the lens barrel main body 1 so as to rotatably hold 
a rotary ring 15 through a plurality of steel balls 14. The rotary ring 15 
has a large number of holes 15a formed in the front end portion (the left 
end portion as viewed in the figure) thereof along the circumferential 
direction as shown in FIG. 4 and arranged so that the rear end portion of 
the interlocking pin 8 fits in one of them. 
A rotor carrier 16 is fixedly secured to the rotary ring 15 by screw 
fasteners. A rotor 18 of the vibratory-wave motor is fitted in the rotor 
carrier 16 through a vibration-proof rubber 17. A stator 19 of the 
vibratory-wave motor is urged axially forward by a dish spring 22 whose 
rear end abuts on the fixed tube 2 through a felt 20 and a felt base plate 
21 and is arranged so that the rotor 18 and the stator 19 are brought into 
pressure contact with each other by a set frictional force. 
The foregoing relates to the construction and arrangement of the elements 
of the present embodiment. Next, the operation of the manual focusing mode 
is described. 
When the manual operating ring 5 is rotated in the state of FIG. 1, the 
rotating force is transmitted through the interlocking pin 8 to the rotary 
helicoid 7 by the frictional engagement of the manual operating ring 5 
with the head 8a of the interlocking pin 8 which is brought into pressure 
contact with a portion of the manual operating ring 5 by the action of the 
compressed coil spring 9. Incidentally, at this time, the interlocking pin 
8 is non-rotated by the rotation restraining plate 10. By the rotation of 
the rotary helicoid 7 and the action of the straight key 12, the lens 
holding tube 11 is non-rotated, but is axially moved by the sum of the 
screw lead of the helicoid portion 11a and the helicoid portion 7a so that 
the focus optical system moves. 
Meanwhile, to change over from this manual focus state to an operation of 
the auto-focus time, the user slides the manual operating ring 5 axially 
rearward (to the right as viewed in the figure) by as large a force as to 
disengage the click spring 6 from the front click groove 1a, until the 
click spring 6 engages in the rear click groove 1b. 
FIG. 3 shows the changed-over state to the auto-focus side, wherein the 
manual operating ring 5 is held in restrained relation from axial movement 
by the click spring 6 and the rear click groove lb of the lens barrel main 
body 1. Though, up to now, the interlocking pin 8 has been in pressure 
contact with the manual operating ring 5 by the action of the compressed 
coil spring 9, when the user slides the operating ring 5, the interlocking 
pin 8 moves axially rearward (to the right in the figure) by the force of 
the compressed coil spring 9 and the rear end portion of the interlocking 
pin 8 enters the hole 15a of the rotary ring 15. In a case where the phase 
angles of interlocking pin 8 and the hole 15a are not in coincidence, 
after the current supply to the vibratory-wave motor, the rotary ring 15 
rotates in vain. When the coincidence in the phase angle position occurs, 
the rear end portion of the interlocking pin 8 fits in the hole 15a. 
In this state, the rotary ring 15 and the rotary helicoid 7 are connected 
to each other by the interlocking pin 8, while the pressure contact of the 
manual operating ring 5 with the interlocking pin 8 is being cut off. 
Therefore, even if the user carelessly turns the manual operating ring 5, 
the optical system does not move. 
That is, the member to be driven, namely, the rotary helicoid 7 is brought 
into operative connection with either one of the manual operating ring 5 
and the rotary ring 15 fixedly mounted on the rotor 18 of the 
vibratory-wave motor by the axial movement of the manual operating ring 5. 
Hence, according to the present embodiment, a relatively small part called 
the interlocking pin 8 suffices for changing over between the manual 
operation and the auto-focus driving. Due to this and also to the light 
load, the changing over goes smoothly and opportunties for damage are few. 
Also, since the interlocking pin 8 is provided at a plurality of places, 
all the interlocking pins do not necessarily change over at once, and 
their change-over timings may slightly shift from each other. Therefore, 
the changing over is reliably performed for a high reliability. 
Further, since the load torque is dispersed to a plurality of points, even 
a good rigidity of structure is advantageously obtained. 
Due to the small size of the interlocking pin 8, the space efficiency is 
improved, so that the lens barrel can be minimized in bulk and size. 
Also, in view of the constructional feature, the required parts are few in 
number, making it easy to assemble them. Thus, the production cost is 
inexpensive. 
Further, the manual operating ring also serves as the auto-manual selector. 
Therefore, the changing over between the auto and manual modes can be 
performed quickly. It becomes possible to provide an interchangeable lens 
of very good manageability. 
Since the clutch is located in such a position as not to decelerate the 
speed of rotation of the rotor, the mechanism required for a change over 
can be simplified in structure. 
Also, since the clutch is arranged to selectively set the rotor or the 
manual operating ring in operative connection to the rotary helicoid which 
constitutes part of the drive mechanism for driving the lens, no excessive 
load is produced. 
Though, in the illustrated embodiment, the vibratory-wave motor has been 
used as the drive source for focusing, modifications may be made by using 
the vibratory-wave motor as the drive source for zooming, or by 
selectively carrying out focusing and zooming by one vibratory-wave motor.