Interchangeable objective for cameras

An interchangeable objective for a camera to provide diaphragm control. The objective has an objective tube and a lens mounting axially movable in the tube. A bayonet ring is provided for connecting the objective tube to a camera. Further means are provided for axially moving said objective tube within the bayonet ring to bring said tube into and out of the camera housing and for engaging said tube into the bayonet ring in the position ready for exposure. A diaphragm adjustment ring is rotatably mounted on the bayonet ring, and a diaphragm control ring rotatably disposed on the lens mounting transmits the adjustment of the adjustment ring upon the diaphragm. A coupling element on the adjustment ring is disengageable from and capable of being engaged into the diaphragm control ring.

BACKGROUND OF THE INVENTION 
The present invention relates to interchangeable objectives for cameras of 
the type having an objective tube and a lens mounting axially displaceable 
thereon so that the diaphragm may be adjusted after the objective has been 
inserted. 
Objectives for cameras of the type referred to above are known. These known 
objectives are focussed by axial displacement of the lens in the objective 
tube. A knurled ring is arranged at the objective tube for turning, and a 
worm gear translates the turning motion into an axial displacement of the 
lens mounting in the objective tube. The objective may be focussed and the 
diaphragm may be adjusted, e.g. by means of a diaphragm adjustment ring, 
even when the objective has been removed from the camera. Also, the 
objective tube carrying the lens with the diaphragm, the knurled ring and 
the diaphragm adjustment ring may be moved at will within the bayonet ring 
of the objective regardless of whether the objective is mounted at the 
camera bayonet mounting or not. 
Cameras are known having an exposure metering or exposure control system 
which require coupling with the objective diaphragm. In this case, it is 
conventional practice to provide the diaphragm adjustment ring with a 
plunger extending from the objective in direction to the camera or with a 
pin which can be swivelled. Such a plunger or pin engage a coupling 
element in the camera to couple the diaphragm with the exposure metering 
or control system when the objective is introduced and locked to the 
camera. The coupling must be coordinated with the introduction or removal 
of the objective that the coupling elements and plungers or pins clearly 
cooperate in a form-locking and positive-drive position. 
SUMMARY OF THE INVENTION 
It is accordingly an object of the present invention to provide a reliable 
connection or coupling of an interchangeable objective to a camera. 
It is another object of the present invention to improve interchangeable 
objectives having a tube for holding the objective proper, a diaphragm and 
a bayonet connection. 
It is a particular object of the present invention to improve the 
construction of interchangeable objectives not only having a lens which 
moves axially for focusing - inclusively its diaphragm - but being also 
displaceable with its objective tube over a larger distance without 
requiring long and complicated transmission devices or rods. 
In accordance with the present invention, a diaphragm adjustment ring is 
rotatably mounted on the bayonet ring of the objective. The adjustment 
ring carries a coupling element which may be disengaged from or engaged 
with a diaphragm control ring being rotatably mounted on a lens mounting 
of the objective. The diaphragm control ring adjusts the diaphragm. Hence, 
the diaphragm adjustment ring is spatially fixedly mounted with respect to 
the objective bayonet ring. Therefore, the known simple coupling with the 
coupling portions of the camera for transmitting or controlling the 
diaphragm may be retained. 
Preferably, the coupling element is comprised of a lever that turns about a 
tangential axis at the diaphragm adjustment ring. The lever may be 
selectively turned into the path of an axial projection of the diaphragm 
control ring or be moved into a cutout of the objective bayonet ring. 
Further in accordance with the invention, an opening may be provided at the 
objective tube for this lever which is so limited in its axial direction 
that it permits passage of the lever only in the exposure position of the 
objective tube. When the objective tube is introduced it displaces the 
lever outwardly and hence locks the diaphragm adjustment ring at the 
objective bayonet ring. Accordingly, the diaphragm adjustment ring will 
function for adjustment of the diaphragm only when the tube has been 
pulled out. Vice versa, removal of the objective from the camera is 
possible only when the objective tube has been pushed in. Furthermore, the 
diaphragm adjustment ring has a double function in that it serves on the 
one hand as diaphragm adjustment ring proper, and on the other hand as 
actuating ring or handle for connecting the objective to the camera or 
removing it therefrom. 
According to a further extension of the invention, the cutout of the 
objective bayonet ring is correlated to a predetermined position of the 
diaphragm adjustment ring, preferably corresponding to the largest opening 
of the objective diaphragm in such a manner that the lever may drop into 
the cutout only in this position. Thus, the diaphragm adjustment ring and 
diaphragm control ring may disengage only then, and the coupling of 
diaphragm adjustment ring with the bayonet ring and the introduction of 
the objective tube into the camera housing is likewise possible only in 
this position.

Referring now to the drawings, there is illustrated an objective tube 1 
having a frontal flange with a knurled ring 2 which serves as a handle. 
Tube 1 is axially slidably mounted in an objective bayonet ring 3. The 
objective bayonet ring 3 can be inserted into bayonet mounting 4 shown in 
FIG. 3, mounting 4 pertaining to the camera housing. The tube 1 carries 
also a bayonet ring 5 which faces the camera and serves as an axial stop. 
When the tube is in the pulled out position and ready for exposure, 
bayonet ring 5 can be inserted and locked into the objective bayonet ring 
3. The objective tube 1 is locked in the position ready for exposure as 
shown in FIG. 3. 
A lens mounting 6 with a lens system 7 and a diaphragm of iris 8 is 
provided in tube 1. A worm gear that is disposed in a sleeve 9 having 
inner and outer threads guides the lens mount. The adjustment knurled ring 
10 of the sleeve 9 is turned to move the lens 7 in an axial direction for 
purposes of focussing. Turning of ring 10 or of the sleeve 9 is limited to 
an adjustment range by a pin 11 mounted on the knurled ring 2 of the tube 
1 and by an arcuate slot 12 of the adjustment knurled ring 10. 
The diaphragm 8 is arranged within the lens system in a known manner. The 
blade or lamella drive ring 13 is adjusted by a follower lever 13' being 
connected thereto. Lever 13' is controlled by a diaphragm control ring 14 
by means of its radial cam track 15. The diaphragm control ring 14 is 
rotatably mounted on the lens mounting 6. A diaphragm adjustment ring 20 
is, in turn, rotatably mounted between the objective bayonet ring 3 and a 
bayonet ring housing 18, the latter being connected with the objective 
bayonet ring 3 by screws 27 and 28. 
Ring 20 is connected to knurled ring 19 by a screw 26. This knurled ring 19 
will be gripped by the user for manipulating ring 20. Ring 19 covers 
partially the diaphragm scale 19' disposed at the upper portion of the 
objective bayonet ring 3. A lever 21 is mounted at the diaphragm 
adjustment ring 20 for turning about a tangential axis 17. The objective 
bayonet ring 3 is provided with an axial cutout 22 into which the lever 21 
may be pushed as shown in dotted lines at 21'. This requires, of course, 
that lever 21 and cutout 22 are in alignment with each other. On the other 
hand, an opening 23 is provided in the tube 1 and is traversed by the 
lever 21, whereby the lever 21 projects into the interior of the tube. 
Insertion of lever 21 into cutout 22 occurs when tube 1 is pushed into the 
camera. As lever 21 is inserted in cutout 22, the diaphragm adjustment 
ring 20, or respectively the knurled ring 19, is locked to the objective 
bayonet ring 3. This opening 23 extends over that portion of the 
circumference of the tube which corresponds to the region of adjustment of 
the diaphragm. The axial length of the opening 23 is selected, at least in 
one place, so that lever 21 can only pass through this opening when the 
tube has been pulled out or extended. 
The cutout 22 of the objective bayonet ring 3 and the position of the tube 
opening 23 having the greates axial length for the insertion of the lever 
21, are arranged so that they permit the introduction of the lever only 
for one very particular position of the diaphragm adjustment ring 
corresponding to a particular predetermined position of the diaphragm; 
this corresponds preferably to the largest adjustable diaphragm opening. 
The diaphragm control ring 14 carries an axial extension 24 which, for 
example, is constructed to have the configuration of a fork into which the 
lever 21 may move through the opening 23 of the tube 1 due to the action 
of a spring not illustrated. The diaphragm adjustment ring 20 and the 
diaphragm control ring 14 are coupled in this manner. The axial length of 
the extension 24 depends upon the greatest axial movement of the lens 
mounting 6 during focussing. 
Since the extension 24 is constructed as a fork, lever 21 provides a rigid 
coupling between the diaphragm 8 and the diaphragm adjustment ring 20 or 
its knurled ring 19. By means of a tappet 25 which extends rearwardly from 
the diaphragm adjustment ring 20 through the arcuate slot 25', a rigid 
connection is provided to the exposure and diaphragm control at the camera 
in the conventional manner. 
For cameras having a measurement with open diaphragm and wherein the 
diaphragm is closed only and moved to the correct aperture value when the 
shutter is released, the extension 24 is preferably not arranged as a fork 
but should be provided as a simple stop. As the shutter is released in 
this case the diaphragm 8 is closed in the known manner by means of a 
diaphragm plunger 16 and against the action of a spring or under the 
action of a spring; that is the diaphragm control ring 14 is turned until 
closure movement of the diaphragm is stopped by the stop 24 intercepting 
lever 21. In this known camera the diaphragm is again fully opened after 
exposure, independently of the diaphragm value previously adjusted on the 
scale 19'. In this case, the most favorable solution for the position of 
the cutout 22 for the lever 21 for the adjustment of the diaphragm 
adjustment ring 19 corresponds to the largest opening of the diaphragm at 
scale 19'. 
The position of the objective as illustrated in FIG. 3 shows the objective 
attached to the camera and ready for exposure; focussing is accomplished 
by turning the knurled ring 10, while the diaphragm is adjusted by turning 
the ring 19. After adjustment of the diaphragm to the above mentioned, 
predetermined aperture value, the tube 1 may be disengaged by means of the 
handle 2 at the bayonet ring 3 and may be pushed into the camera housing. 
While the tube is pushed in, the lever 21 is displaced into the cutout 22 
of the bayonet ring 3. Thus, the diaphragm adjustment ring 20 is now 
locked to the objective bayonet ring 3 so that the objective can be 
disengaged by means of the knurled handle 19 from the camera bayonet ring 
4 and removed from the camera. 
In the opposite case, when the objective has been removed from the camera 
or the tube had been pushed in the camera housing, adjustment of the 
diaphragm is not possible. The diaphragm 8 or the diaphragm blade drive 13 
is disengaged from the diaphragm adjustment ring when the objective tube 
is pushed in. However, the diaphragm retains this position without the 
necessity of an additional locking device because an adjustment of the 
diaphragm is not possible without engaging the interior of the objective. 
The only possibility is to manually operate the plunger 16. This, however, 
will not result in any damage because the plunger is returned to its rest 
position by the action of a spring. 
The invention is not limited to the embodiments described above but all 
changes and modifications thereof not constituting departures from the 
spirit and scope of the invention are intended to be included.