Device for coupling a lens barrel and a camera body

A device for electrically connecting a lens barrel and a camera body includes a connector provided integrally with the fixed cylinder of the lens barrel along the cylindrical surface of the fixed cylinder. The connector has a movable contact resiliently displaceable in the diametral direction of the cylinder. The movable contact is urged against a contact piece provided on the camera body upon completion of the mounting of the lens barrel to the camera body. The camera body is provided with an inclined surface for displacing the movable contact in the diametral direction against the resilient force during the mounting operation of the lens barrel to the camera body.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a device for coupling the lens barrel and camera 
body of a camera having an interchangeable picture-taking lens, and more 
particularly to a device for enabling the connection between the 
electrical device of the lens barrel and the electrical device of the 
camera body to result from the mounting of the lens barrel to the camera 
body. 
2. Description of the Prior Art 
With the advance of electronic technology, it has become introduced into 
exposure adjustment, distance adjustment, etc. in both still cameras and 
cinecameras and connector devices of various constructions have recently 
been proposed for connecting the electrical device of the lens barrel and 
the electrical device of the camera body. These proposed connector devices 
may generally be grouped into two types, namely, a type which has a fixed 
contact on the lens barrel side and a movable contact on the camera body 
side and a type which has a movable contact on the lens barrel side and a 
fixed contact on the camera body side. The former type is simple in 
construction of the lens barrel side but complex in construction of the 
camera body side and it involves an extreme difficulty to provide a 
connector having such a movable contact within a camera body side mount 
which does not have a sufficient space. Also, in the latter type, the 
movable contact of known construction is provided on the end surface of 
the lens barrel opposed to the mount portion of the camera body which is 
perpendicular to the optical axis while being biased by a spring and is 
constructed so as to be displaceable in the direction of the optical axis. 
In the conventional connector device so constructed, particularly in the 
case of a lens barrel having a large exit pupil diameter, a sufficient 
space cannot be secured on the end surface on which the movable contact is 
provided and therefore, it has been difficult to provide a number of 
contacts. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide an improved device for 
electrically connecting a lens barrel and a camera body with the mounting 
of the lens barrel to the camera body. 
The device of the present invention includes a connector provided 
integrally with the fixed cylinder of the lens barrel along the 
cylindrical surface of the fixed cylinder, and the connector has a movable 
contact resiliently displaceable in the diametral direction of the 
cylinder. The movable contact is urged against a contact piece provided on 
the camera body upon completion of the mounting of the lens barrel to the 
camera body. 
In a preferred embodiment of the present invention, the camera body is 
provided with an inclined surface for displacing the movable contact in 
the diametral direction against the resilient force during the mounting 
operation of the lens barrel to the camera body. Thereby, the displacement 
of the movable contact associated with the mounting operation achieved by 
moving the lens barrel relative to the camera body in the direction of the 
optical axis and/or about the optical axis is made possible. 
The invention will become more fully apparent from the following detailed 
description thereof taken in conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows an embodiment in which the present invention is applied to an 
autofocus single lens reflex camera. An interchangeable lens barrel 10 is 
removably mounted to a camera body 50. Part of a light beam passed through 
a picture-taking lens system 3 is reflected by a movable mirror 51 having 
a semi-transmittal portion and enters a viewfinder optical system, and 
then arrives at the photographer's eye via a focus screen 52, a condenser 
lens 53, a pentaprism 54 and an eyepiece 55. The remainder of the light 
beam passes through the semi-transmittal portion of the mirror 51 and 
enters a light-receiving element 58 via a reflecting mirror 56 and a lens 
57, and judgment of in-focus is effected in a focus detecting circuit 59 
by the output of the light-receiving element 58. All this is a known 
technique and need not be described any further. 
As shown in FIGS. 2 and 3, the lens barrel 10 is provided with a fixed 
barrel 11 having a bayonet mount 12 to be coupled to the camera body, and 
a distance adjusting ring 13 and an aperture adjusting ring 14 are 
rotatably provided on the barrel 11. When the distance adjusting ring 13 
is rotated, a movable lens barrel 16 holding a movable lens 15 is moved in 
the direction of the optical axis, thus accomplishing focus adjustment. A 
fixed lens protecting cylinder 17 is formed between the movable lens 
barrel 16 and the bayonet mount 12, and a portion thereof projects from 
the end surface of the bayonet mount to form a projected portion 18. A 
contact holding member 20 of non-conducting material is inserted in a 
cut-way 19 formed in the projected portion 18 and is fixed to the inner 
surface of the bayonet mount 12 by small screws. A movable contact piece 
21 of good electrical conducting material and having resiliency is secured 
to the contact holding member 20 and connected by a cord 22 to a drive 
circuit 23 which controls the rotation of a motor for moving the lens. A 
semi-spherical contact 30 of very low electrical resistance is welded to 
the free end of the movable contact piece 21. The contact holding member 
20 and the movable contact piece 21 having a contact 30 are made into a 
unit which forms a connector. On the other hand, a contact piece holding 
member 70 of insulative material holding a contact piece 71 of conducting 
material is provided in a mount 60 on the camera body side and connected 
to the focus detecting circuit 59 by a cord 72 connected to the contact 
piece 71. 
When the lens barrel and the camera body are coupled together through the 
bayonet mounts 12 and 60 as shown in FIG. 3, the contact 30 and the 
contact piece 71 are brought into contact with each other with a 
predetermined contact pressure by the radial resiliency of the movable 
contact piece 21 centered at the optical axis, whereby there is brought 
about a conductive state. In this embodiment, the contact holding member 
20 is fixed to the inner surface of the bayonet mount 12, but 
alternatively, the contact holding member 20 may be provided on the outer 
surface of the lens protecting cylinder 17 integral with the fixed barrel. 
Plural sets of movable contact pieces 21 and contacts 30 are disposed in 
accordance with the quantity of the signal transmitted between the camera 
body and the lens barrel. The lens barrel of FIG. 2 has a connector in 
which three contacts are disposed, and the lens barrel shown in FIG. 4 has 
a connector in which five contacts 130 are disposed. 
The construction of the connector made into a unit will hereinafter be 
described in detail with respect to some embodiments thereof. In the 
connector shown in FIG. 5, five movable contact pieces 121 each formed in 
the shape of a crank are parallel-disposed on a holding member 120 so that 
the free ends thereof having contacts 130 are bent in the opposite 
direction from the fixed ends 131 with respect to the direction of 
mounting rotation indicated by arrow. Therefore, in this embodiment, 
during the rotative mounting of the lens barrel onto the camera, the 
influence of the torsion of each contact piece is reduced, whereby the 
connection with the contact piece 71 on the camera body side is 
accomplished smoothly and reliably. 
The connector shown in FIG. 6 includes a holding member 220 in which are 
disposed five movable contact pieces 221 obliquely juxtaposed and having 
contacts 230, and this makes the working easier. 
Another modification will be described with respect to the arrangement of a 
plurality of contacts. The contacts 330 shown in FIG. 7A are arranged on a 
circumference inclined by a predetermined angle relative to the optical 
axis O, the contacts 430 shown in FIG. 7B are separately arranged on two 
circumferences perpendicular to the optical axis O, and the contacts 530 
shown in FIG. 7C are staggered on two circumferences perpendicular to the 
optical axis. That is, the contacts 130 and 230 of FIGS. 5 and 6 are 
arranged in a row in the rotational direction (arrow) and therefore, the 
contact lying at the right end may contact the five contact pieces on the 
camera body side in succession with the rotation thereof and thus may be 
abraded. In contrast, if the contacts are arranged with an interval d in 
the direction perpendicular to the rotational direction (arrow) as are the 
contacts 330 of FIG. 7A, the above-mentioned disadvantage will not occur. 
Also, if the contacts are arranged as shown in FIG. 7C, the abrasion of 
the numerous contacts will be reduced to one half as compared with the 
case of FIG. 5. 
Referring to FIG. 8, there are shown modifications of the construction of 
the contact portion of the connector. The connector shown in FIG. 8A has a 
holding member 620 provided with a cleaning hole 622 used when dust or the 
like enters from a hole 621 through which a contact 630 extends. The 
connectors of FIGS. 8B and 8C have contacts 730, 830 formed separately 
from a movable contact piece to prevent entry of dust or the like, the 
outer periphery of the contact 730, 830 being slidable in the through-hole 
721, 821 of holding member 720, 820. 
Description will now be made in detail of the construction of the contact 
pieces of the camera body which make contact with the contact of the 
above-described lens barrel. As shown in FIG. 9, a holding member 70 
having contact pieces 71 is fixed along the inner periphery of the lens 
mounting opening of the camera body. The holding member 70 is of an 
arcuate shape and a cam surface 73 gradually changing in diameter in the 
circumferential direction is formed on one end of the holding member 70. A 
suitable number of contact pieces 71 connected to the focus detecting 
circuit of FIG. 1 are embedded in the inner peripheral surface of the 
holding member 70, and the surface thereof is smoothly formed relative to 
the surface 74 of the holding member 70. 
When a lens barrel 110 as shown in FIG. 4 is to be mounted to the camera 
body 50, it is inserted from a rotated position about the optical axis so 
that none of the movable contacts 130 of the lens barrel 110 contacts the 
holding member 70. Thereafter, when the lens barrel 110 is leftwardly 
turned by an angle .theta. about the optical axis O, the contact 130a 
comes into contact with the cam surface 73 of the holding member 70 in 
that process and is radially inwardly displaced against the resiliency of 
a movable contact piece 121 and rides onto the surface 74. Accordingly, 
upon completion of the rotation of the lens barrel 110 through the angle 
.theta., the contact 130a moves to a position 130a' and contacts a contact 
piece 71a. At this point of time, all contacts 130 come into contact with 
all contact pieces 71 and accordingly, the focus detecting circuit 59 and 
the lens driving circuit 23 conduct and movement of the picture-taking 
lens 3 becomes possible depending on the in-focus. 
The holding member 170 of the camera body shown in FIG. 10 comprises a 
first area in which contact pieces 171 are disposed and a second area 
extending from the first area in the circumferential direction to support 
the contact 130 of the lens barrel on the surface of the holding member. A 
cam surface 175 inclined in the direction of the optical axis and provided 
in opposed relationship with the picture-taking lens, instead of the cam 
surface 73 of FIG. 9, is formed in the second area substantially over the 
entire region thereof. Accordingly, when the lens barrel as shown in FIG. 
4 is made to bear against the camera body in the direction of the optical 
axis so that all contacts 130 are in contact with the cam surface 173, the 
contacts 130 ride onto the surface 174 of the holding member while being 
guided by the cam surface, as shown in FIG. 11. When the lens barrel is 
leftwardly turned from this position by an angle .theta. about the optical 
axis, the contact 130a of the lens comes into contact with the contact 
piece 171a of the camera body, thus completing the mounting. 
Where it is necessary to increase the width of the aforementioned first 
area because the number of the contacts of the lens barrel and of the 
contact pieces of the camera body is great, design may be made as shown in 
FIG. 12. That is, a holding member 270 is provided with both a cam surface 
273 similar to the cam surface 73 of FIG. 9 and a cam surface 275 similar 
to the cam surface 175 of FIG. 10. Accordingly, when the lens barrel is 
made to bear against the camera body in the direction of the optical axis, 
contacts 130a and 130b are guided by the cam surface 275 and ride onto the 
surface of the holding member 270 and, when the lens barrel is rotated 
from this position by an angle .theta. about the optical axis, the 
remaining contacts are successively caused to ride onto the surface of the 
holding member 270 by the cam surface 273 and the contact 130a comes into 
contact with the contact piece 271a, thus completing the mounting. 
Where the contacts of the lens barrel are arranged as shown in FIGS. 7A to 
7B, it is necessary that the contact pieces of the camera body be provided 
at positions corresponding thereto. In that case, for example, if the 
contact pieces are arranged in the same manner as the contacts 430 of FIG. 
7B, a holding member 370 as shown in FIG. 13 wherein cam surfaces 373a and 
373b are separately formed for each group may be prepared. 
The movable contact provided on the lens barrel need not always be an 
electrical contact, but may be one used for other purposes. For example, 
the movable contact can be used also as a click stop for determining the 
rotation terminating position of the lens mount or for the purpose of 
producing a contact pressure for pressing the mounting reference surface 
on the camera body side and the mounting reference surface on the lens 
barrel side during the mounting.