Device for locking the operation ring of photographing lens

In a photographing lens barrel having a manual operation ring and a stationary ring, a device for locking said manual operation ring is provided. The locking device includes a lock member projecting from one of said two rings, a lock part formed on the other ring to engage with said lock member, and a lock-operating member movable between a lock position and an unlock position. The lock operating member is biased toward said locking position by spring means and is held in said unlock position by limiting means.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a device for locking the manual operation 
ring for exposure control on a photographing lens. More particularly, the 
present invention is directed to such locking device capable of locking 
the manual operation ring at a determined position for the change-over 
between manual control mode and automatic control mode. 
2. Related Background Art 
In a known photographing lens provided with a manual operation ring, the 
exposure control mode is changed over from manual mode to automatic mode 
when the manual operation ring is moved to a certain determined position. 
At this particular set position, a locking device is actuated to lock the 
manual operation ring against further rotation. In the art, there have 
been known various locking means for this purpose. 
In a typical example of the photographing lens with an aperture-presetting 
ring, a locking device is provided on a stationary ring opposed to the 
aperture-presetting ring. In the automatic aperture control mode including 
shutter time priority automatic exposure control mode, programmed 
automatic exposure control mode etc., the operator presets the 
aperture-presetting ring in the position for minimum aperture value. The 
locking device locks the presetting ring against any accidental rotation 
of the presetting ring. 
In a known construction, the locking device is so formed that it can be 
actuated automatically when the aperture-presetting ring has just been 
rotated to a predetermined lock position indicated by a mark. The lock 
position mark is at a point a little forward beyond the minimum aperture 
value position of the presetting ring. This known construction has some 
drawbacks. Firstly, a particular mark indicating the minimum aperture 
value position for aperture control mode is needed in addition to the mark 
indicating the lock position. Secondly, the aperture-presetting ring has 
to be moved over a larger rotational angle which is inconvenient to the 
user of the camera. 
In another known photographing lens, the locking device is so formed that 
it can be actuated automatically at once when the aperture-presetting ring 
reaches the position for minimum aperture value. However, the use of the 
known locking means limits the freedom of aperture selection in other 
exposure control modes than the automatic aperture control mode. For 
example, in the manual exposure control mode in which the operator can 
manually set the aperture to any desired value, or in the aperture 
priority automatic exposure control mode, there may occur such case where 
the operator wishes to change the aperture from minimum aperture value to 
another value. But, the known locking device inhibits such a selection of 
aperture value because the aperture-presetting ring has already been 
locked in the position for the minimum aperture value in this case. 
To overcome the drawback of the known locking means as mentioned above, a 
solution has been proposed, for example, by the invention of U.S. Pat. No. 
4,341,450 (patented on July 27, 1982). According to the known solution, a 
slidable lock member with a projection is provided on any one of the 
stationary ring and the aperture-presetting ring. The lock member is 
mounted for manual slide-movement in the direction along the optical axis. 
In a predetermined position on the other ring, there is formed a recess in 
which the above-mentioned projection is engageable. The 
aperture-presetting ring can be locked only when the projection gets in 
engagement with the recess by the operator's moving the lock member. The 
important disadvantage of this known solution is found in that the manual 
operation required for locking is complicate and takes a long time. The 
reason for this is that the operator has to rotate at first the preset 
ring up to the position in which the projection and the recess are opposed 
to each other, and then to move the lock member in the direction along the 
optical axis in order to establish the locking engagement. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to solve the problems 
involved in the prior art devices as mentioned above and to provide a 
locking device which is able to automatically lock the operation ring of a 
photographing lens at a predetermined position when the locking is 
desired. 
It is another object of the invention to provide a locking device which is 
simple in construction and reliable in operation and with which the 
locking and unlocking of the operation ring can be performed promptly 
without failure. 
To attain the objects, the present invention provides a photographing lens 
with an improved locking device comprising locking means and 
lock-operating means. 
The photographing lens according to the invention has a manual operation 
ring mounted for rotation about the optical axis of the lens and a 
stationary ring adjacent to the operation ring and fixed with the center 
of the ring on the optical axis of the lens. A lock member is provided on 
one of the two rings, that is, on the manual operation ring or on the 
stationary ring. The lock member projects toward the other ring and is 
mounted radially movable for engagement with a corresponding locking part 
formed on the other ring. Furthermore, a lock operation member is provided 
on the same ring as the lock member is provided. The lock operation member 
passes through the ring radially and is connectable with the lock member 
for rotation with the latter. The lock operation member is movable between 
locking and unlocking positions. In the locking position, the lock 
operation member allows the lock member to come into engagement with the 
locking part on the other ring. In the unlocking position, the lock 
operation member disengages the lock member from the locking part. The 
lock operation member is normally biased, together with the lock member, 
toward the locking position by spring means. The direction in which the 
lock operation member can be moved is limited by limiting means which 
serves to hold the lock operation member in the unlocking position. 
With the above construction according to the present invention, a person 
can easily select any desired one of automatic lock and non-automatic 
lock. When the automatic lock is selected, the manual operation member is 
automatically locked in the above-mentioned particular position. On the 
contrary, when the non-automatic lock is selected, the manual operation 
member can not automatically be locked. In the non-automatic lock 
position, that is, in the unlocking position of the lock operation member, 
the operation of the manual operation member is limited to prevent it from 
being carelessly operated. Therefore, there is no fear that the locking 
device may unintentionally be actuated thereby losing a good shutter 
chance. 
The locking device according to the present invention may be incorporated 
into an ordinary photographing lens with aperture-presetting means as 
later shown in a preferred embodiment of the invention, bringing forth the 
following advantages over the prior art ones: 
It is no longer necessary to particularly provide a set position for 
minimum aperture value to be used for aperture control. 
The locking mechanism can be automatically effective at the position for 
minimum aperture value. Therefore, the members otherwise required for it 
can be omitted. 
Since the aperture-presetting ring can not always be locked automatically 
at the position for minimum aperture value, the locking device never 
interferes with the operation for setting the aperture to any desired 
value from the minimum aperture value. 
Other and further objects, features and advantages of the invention will 
appear more fully from the following description taken in connection with 
the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring first to FIG. 1 there is shown a photographing objective lens as 
an embodiment of the present invention. The photographing lens is an 
interchangeable lens having two adjacent rings 10 and 40 on the 
circumferential surface. The ring 10 is a stationary ring fixed on the 
circumferential surface. The ring 40 is an aperture-presetting ring 
mounted for rotation about the optical axis of the lens. 
The stationary ring 10 has a lock holder 11 for holding an operation button 
20 and a lock plate 30 as shown in FIG. 2. The operation button 20 and the 
lock plate 30 constitute a locking mechanism. The lock plate functions as 
a leaf spring and one end of the lock plate is fixed by a washer 50 and a 
screw 60. At the other end, the locking plate 30 is connected to the 
operation button. As seen best in FIG. 3, the locking plate 30 has a lock 
portion 31 projecting toward the aperture-presetting ring 40 from the 
stationary ring 10. The stationary ring 10 has a mark 12 in opposition to 
a scale of aperture values on the presetting ring 40. 
To receive the lock portion 31 of the lock plate 30 the aperture-presetting 
ring 40 has a groove 43 formed on the inside surface of the ring. 
The structure of the lock holder part 11 of the stationary ring 10 is shown 
in detail in FIGS. 4 and 5. FIG. 4 is a plan view thereof and FIG. 5 is a 
sectional view taken along V--V. 
Referring to FIGS. 4 and 5, the lock holder 11 has a first through-hole 13 
and a second through-hole 14 with a stepped portion 15 therebetween. The 
first through-hole 13 is cylindrical. The second through-hole 14 is 
composed of a semicylindrical surface 14a and a semicircular hole 14b. The 
diameter of the semicylindrical surface 14a is smaller than that of the 
through-hole 13 whereas the diameter of the semicircular hole 14b is equal 
to that of the through-hole 13. The operation button 20 (see FIG. 6) can 
be inserted into the through-holes 13 and 14 and can be rotated therein. A 
segment groove 16 is formed on the inner wall of the through-hole 14. To 
indicate the angular positions for locking and for unlocking of the 
operation button 20, a lock position mark 17 and an unlock position mark 
18 are provided on the lock holder 11. 
As shown in FIG. 6, the operation button 20 has a first shank portion 21 to 
be fitted in the through-hole 13, a second shank portion 22 to be fitted 
in the semicircular hole part 14b and an engaging portion 23 to be engaged 
in a groove-like cutout 32 formed in the free end of the lock plate 30. 
Furthermore, the operation button 20 has two rotation-limiting portions 24 
and 25 and a lock plate-holding portion 26. The rotation-limiting portion 
24 is formed under the first shank portion 21 to limit the rotation angle 
of the operation button 20. The rotation-limiting portion 24 is in the 
form of a sector of an angle of 90 degrees and fitted to the 
semicylindrical surface 14a of the through-hole 14. The second 
rotation-limiting portion 25 is under the second shank portion 22 and is 
in the form of a semicylinder of 180 degrees corresponding to the 
semicircular hole 14b of the through-hole 14b. The rotation-limiting 
portion 25 has a pawl-like projection 27 which can engage in the groove 16 
on the lock holder 11. 
On the head of the button 20, a series of ridges are formed to prevent the 
slip of the operator's finger from the button. Also, on the button head, 
there is an alignment mark 29 to be aligned to the above-mentioned lock 
mark 17 or unlock mark 18 on the holder part 11. 
Between the first shank portion 21 and the rotation-limiting portion 25 
there is provided a cutout portion which allows the rotation of the 
operation button 20. 
As previously shown in FIG. 2, the operation button is inserted into the 
through-holes 13 and 14 of the lock holder 11 and then used in the 
following manner: 
Normally, the operation button 20 is in the position for inhibiting any 
unintentional actuation of the locking mechanism on the stationary ring 10 
during the rotation of the aperture-presetting ring 40. To this end, the 
operator at first depresses the operation button 20 down against the 
spring force of the lock plate 30 and then rotates the button until the 
mark 20 is aligned with the unlock mark 18 on the stationary ring 10 as 
shown in FIG. 7B. 
In this position, as seen in FIG. 7B, the bottom of the first shank portion 
21 (FIG. 6A) is in contact with the stepped portion 15 of the first 
through-hole 13 (FIG. 5). The rotation-limiting portion 24 is abutting on 
the side wall 19 of the second through-hole 14. Thus, no further rotation 
of the operation button is allowed. Under the spring force of the lock 
plate 30, the pawl-like projection 27 engages in the groove 16 to hold the 
operation button in the position. In this position, since the lock plate 
30 has been pushed down against its spring force by the operation button, 
the lock portion 31 projecting in the direction along the optical axis 
from the stationary ring 10 can not engage in the lock groove 43 even when 
the aperture-presetting ring 40 is rotated to a desired aperture value. 
Thus, in this position, the aperture-presetting ring 40 can not be locked 
by the locking mechanism. 
When the aperture control mode is selected, the operator has to set the 
aperture-presetting ring 40 to the position for minimum aperture value and 
then hold the ring in the position. Therefore, it is necessary to turn the 
lock plate 30 to the lock position from the above-mentioned unlock 
position. 
To this end, the operator rotates the operation button 20 clockwisely from 
the position previously shown in FIG. 7B to the lock position as shown in 
FIG. 7A in which the mark 29 on the button head is in alignment with the 
lock position mark 17. However, in the unlock position shown in FIG. 7B, 
it is not possible at once to rotate the operation button 20 clockwisely 
to the lock position because the pawl-like projection 27 is in engagement 
with the groove 16 under the spring force of the lock plate 30 as 
previously mentioned. 
Therefore, the operator at first pushes down the operation button 20 to 
disengage the pawl-like projection 27 from the groove 16 on the stationary 
ring 10. Thereafter, the operator rotates the operation button clockwisely 
from the unlock position mark 18 to the lock position mark 17. In the 
position shown in FIG. 7A in which the mark 29 on the button is in 
alignment with the lock position mark 17 on the holder, the 
rotation-limiting portion 25 of the button 20 is in the through-hole 14 
and, therefore, the operation button is allowed to be pushed up by the 
spring force of the lock plate 30. 
Thus, the operation button is returned to the position shown in FIG. 2. In 
this position, the lock portion 31 is in contact with the inside surface 
42 of the aperture-presetting ring 40. When the aperture-presetting ring 
is rotated by the operator, the lock portion 31 is slided on the inside 
surface 42 of the ring 40. When the ring 40 reaches just the position for 
minimum aperture value, the lock portion 31 engages in the groove 43 under 
the spring force of the lock plate 30. In this manner, the 
aperture-presetting ring 40 is locked in the minimum aperture value 
position. 
As will be understood from the foregoing, so long as the operation button 
20 is in the unlock position by depression, the lock portion 31 never 
engages in the groove 43. Therefore, the aperture-presetting ring 40 can 
be rotated freely to any desired aperture value. In this position, the 
engagement of the pawl-like projection 27 in the groove-like cutout 16 
prevents any unintentional rotation of the operation button from the 
unlock position to the lock position. 
The locking mechanism can be actuated only when the operation button is in 
the lock position. 
In the lock position, the lock portion 31 is urged into contact with the 
inside surface 42 of the ring 40 by the spring force of lock plate. As 
soon as the ring 40 has been rotated to the position for minimum aperture 
value, the lock portion 31 falls in the groove 43 to lock the ring 40 in 
the position. 
In the above embodiment, the mark indicating the minimum aperture value on 
the aperture-presetting ring 40 is commonly used to the indications of the 
minimum aperture value in the manual exposure control mode and of the set 
position in the aperture control, automatic exposure control mode. 
Therefore, it is no longer necessary to provide a particular mark 
indicating the set position for minimum aperture value in the automatic 
aperture control mode on the aperture-presetting ring. In the automatic 
aperture control mode, the locking of the aperture-presetting ring can be 
selected at one's will in a simple manner by changing over the operation 
position of the lock operation button. This construction according to the 
present invention brings about many advantages. A smaller rotation angle 
is required for the aperture-presetting ring. The size of the cam required 
for the aperture-presetting ring can be reduced accordingly. A further 
simplification of the internal structure of the lens tube can be realized. 
While the invention has been particularly shown and described with 
reference to a preferred embodiment thereof, it will be understood that 
various modifications may be made therein without departing from the sprit 
and scope of the invention. 
For example, while the groove 43 has been formed on the aperture-presetting 
ring and the holder 11, the operation 20 and the lock plate 30 have been 
provided on the stationary ring in the above embodiment, it is also 
possible to provide the lock operation button and the lock plate on the 
aperture-presetting ring while providing the lock groove in the stationary 
ring.