Lens barrel structure for waterproof camera

A lens barrel for a waterproof or dustproof camera which can assure maintenance of a reliable liquid-tight or airtight condition between a movable lens barrel member and a fixed lens barrel member with a structure of a comparatively small size. The lens barrel comprises a fixed lens barrel member provided on a camera body, a movable lens barrel member mounted for movement on the fixed member between a position advanced outwardly from the camera body and another position retracted in the camera body, and a bellows member secured at an end thereof to an inner periphery of a rear portion of the movable member and at the other thereof to an inner periphery of a rear portion of the fixed member. The bellows member is folded back at an intermediate portion thereof between the movable member and the fixed member in such a manner as to surround a rear end of the movable member, and the folded back portion moves as the movable member is moved between the retracted position and the advanced position.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a waterproof structure of a lens barrel of a 
camera wherein a movable lens barrel member is designed to move forwardly 
and backwardly over a comparatively large distance such as a lens barrel 
of a two-focal length change-over lens, a zoom lens or a collapsible mount 
type lens. 
2. Description of the Prior Art 
A waterproof camera conventionally employs, as a waterproof or dustproof 
structure of a movable lens barrel, an O-ring or a fold type bellows. 
An exemplary one of conventional waterproof structures which employ an 
O-ring is shown in FIGS. 10 and 11. Referring to FIGS. 10 and 11, a fixed 
lens barrel member 1 is secured to a body of a camera not shown, and a 
movable lens barrel member 4 having a main lens 5 carried therein is 
disposed in the fixed lens barrel member 1 for sliding movement in the 
direction of an optical axis of the main lens 5. 
A pair of O-rings 2 and 3 are mounted on front and rear faces of an annular 
rib 1a formed on an inner face at a front end portion of the fixed lens 
barrel member 1. In a condition shown in FIG. 10 wherein the movable lens 
barrel member 4 is accommodated in the fixed lens barrel member 1, that 
is, in a wide angle photographing or collapsed condition, the O-ring 2 on 
the front face of the annular rib 1a of the fixed lens barrel member 1 
contacts with an annular rib or flange 4a formed at the front end of the 
movable lens barrel member 4 to establish a liquid-tight condition. To the 
contrary, in another condition shown in FIG. 11 wherein the movable lens 
barrel member 4 is advanced or projected forwardly from the fixed lens 
barrel member 1, that is, in a tele-photographing or non-collapsed 
condition, the other O-ring 3 on the rear face of the annular rib 1a of 
the fixed lens barrel member 1 contacts with another annular rib or flange 
4b formed at the rear end of the movable lens barrel member 1 to establish 
a liquid-tight condition. 
An exemplary one of conventional waterproof structures which employ a fold 
type bellows is shown in FIGS. 12 and 13. Referring to FIGS. 12 and 13, a 
fold type bellows 12 made of a material which can maintain a liquid-tight 
condition such as rubber or rubber-coated cloth is connected at a rear end 
thereof to an annular rib 11a formed at a rear end portion of a fixed lens 
barrel member 11 and at the other front end thereof to an annular rib or 
flange 14a formed at the front end of a movable lens barrel member 14. 
When the movable lens barrel member 14 is retracted to a wide angle 
photographing or collapsed position as shown in FIG. 12, the fold type 
bellows 12 is accommodated in a folded condition in a spacing formed by 
and between the annular rib 11a at the rear portion of the fixed lens 
barrel member 11 and the annular flange 14a at the front end of the 
movable lens barrel member 14 as seen in FIG. 12. To the contrary, when 
the movable lens barrel member 14 is projected to a tele-photographing or 
non-collapsed position as shown in FIG. 13, the fold type bellows 12 is 
extended following the movement of the movable lens barrel member 14. The 
fold type bellows 12 thus maintains the liquid-tight condition between the 
fixed lens barrel member 11 and the movable lens barrel member 14 in this 
manner. 
The former conventional waterproof structure which employs an O-ring has a 
drawback that, when the movable lens barrel member is at an intermediate 
position between the fully retracted position and the fully advanced 
position, the liquid-tight condition thereof cannot be maintained because 
the O-rings do not contact sufficiently with the movable lens barrel 
member. 
It may seem recommendable, in order to maintain the liquid-tight condition 
at any intermediate position of the movable lens barrel member of the 
waterproof structure, to continuously apply a pressure so as to normally 
contact an outer periphery of the movable lens barrel member 4 with an 
inner periphery of the fixed lens barrel member 1. In this instance, 
however, such pressure makes a high load to the movable lens barrel member 
4 when the movable lens barrel member 4 moves forwardly or backwardly. 
Accordingly, there is a drawback that a motor of large size and a power 
source of a large capacity are required, which will lead to an increase in 
overall size of the camera. 
To the contrary, the latter conventional waterproof structure which employs 
a fold type bellows requires, between the movable lens barrel member 14 
and the fixed lens barrel member 11, a spacing for accommodating the 
folded bellows 12 therein. Accordingly, there is a drawback that the fixed 
lens barrel member 11 is required to have an increased size, which also 
leads to an increase in overall size of the camera. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a lens barrel for a 
waterproof or dustproof camera which can assure maintenance of a reliable 
liquid-tight or airtight condition between a movable lens barrel member 
and a fixed lens barrel member. 
It is another object of the present invention to provide a lens barrel for 
a waterproof or dustproof camera wherein a liquid-tight or airtight 
condition can be attained with a structure of a comparatively small size. 
In order to attain the objects, according to the present invention, there 
is provided a lens barrel for a camera which comprises a fixed member 
provided on a body of the camera, a movable member having at least a part 
of an optical system of the camera carried thereon and mounted for 
movement on and with respect to the fixed member between a first position 
advanced outwardly from the camera body and a second position retracted in 
the camera body, and a bellows member secured at an end thereof to an 
inner periphery of a rear portion of the movable member and at the other 
thereof to an inner periphery of a rear portion of the fixed member, the 
bellows member being folded back at an intermediate portion thereof 
between the movable member and the fixed member in such a manner as to 
surround a rear end of the movable member. 
With the above-mentioned structure, when the movable member is at the 
second or retracted position, the bellows member serving as a watertight 
means has the intermediate folded back portion thereof positioned around 
the rear end of the movable member near a position at which the bellows 
member is mounted on the movable member. Then, as the movable member is 
moved from the retracted position to the first or advanced position, the 
folded back portion of the bellows member gradually moves to a position at 
which the bellows member is mounted on the fixed member, and the bellows 
member is positioned in a spacing from which the movable member has 
advanced. When the movable member is moved reversely from the advanced 
position to the retracted position, the bellows member moves in the 
reverse operation. In this manner, the watertight means requires no 
special or additional spacing for disposition thereof and assures smooth 
movement of the movable member between the advanced and retracted 
positions while maintaining a reliable watertight or airtight condition. 
Besides, the watertight means does not apply such a high load to the 
movable member upon movement between the advanced and retracted positions 
that may be applied in a conventional lens barrel wherein an O-ring is 
employed as a watertight means, and accordingly, the power required for 
movement of the movable member between the advanced and retracted 
positions can be reduced and the lens barrel can be reduced in overall 
size. 
The above and other objects, features and advantages of the present 
invention will become apparent from the following description and the 
appended claims, taken in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring first to FIGS. 1 and 2, there is shown a waterproof camera in 
which a lens barrel according to the present invention is incorporated. 
The waterproof camera is of the type having a two-focal length change-over 
lens wherein the focal length range can be changed over between a wide 
angle photographing range and a tele-photographing range. The lens barrel 
of the camera shown includes such a fold back type bellows 22 as 
particularly shown in FIGS. 3 to 5. In FIG. 3, the bellows 22 is shown in 
perspective view in an extended condition before it is secured to a fixed 
lens barrel member side and a movable lens barrel member side of the 
waterproof camera. In the condition shown in FIG. 3, the bellows 22 is not 
folded back at an intermediate portion thereof. To the contrary, in FIGS. 
4 and 5, the bellows 22 is shown in different conditions when the fixed 
lens barrel member side and the movable lens barrel member side to which 
the bellows 22 is secured are positioned at different positions relative 
to each other and the bellows 22 is folded back at an intermediate portion 
thereof. 
In particular, referring to FIGS. 1 and 2, the bellows 22 has an end 
portion 22a secured to an inner periphery 21a of a rear portion of a fixed 
lens barrel member 21 of the camera and the other end portion 22b secured 
to an inner periphery 24a of a rear portion of a movable lens barrel 
member 24 of the camera in which a main lens 25 is supported. The bellows 
22 is folded back at an intermediate portion 22c (specifically denoted at 
22c1 and 22c2 in FIGS. 1 and 4 and in FIGS. 2 and 5, respectively) thereof 
between the inner periphery 21a of the rear portion of the fixed lens 
barrel member 21 and the inner periphery 24a of the rear portion of the 
movable lens barrel member 24. The folded back portion 22c of the bellows 
22 varies in accordance with a position of the movable lens barrel member 
24 relative to the fixed lens barrel member 21. When the movable lens 
barrel member 24 is positioned at a wide angle photographing position at 
which the movable lens barrel member 24 is retracted in the fixed lens 
barrel member 21 as shown in FIG. 1, the folded portion 22c1 of the 
bellows 22 is positioned in contact with a rear end portion 24b of the 
movable lens barrel member 24. As the movable lens barrel member 24 is 
advanced or projected outwardly from the wide angle photographing position 
in the the fixed lens barrel member 21 to a tele-photographing position 
thereof shown in FIG. 2, the folded back portion 22c of the bellows 22 is 
gradually spaced from the rear end portion 24b of the movable lens barrel 
member 24 and moves toward the inner periphery 21a of the rear portion of 
the fixed lens barrel member 21 at which the end portion 22a of the 
bellows 22 is secured to the fixed lens barrel member 21. Thus, the folded 
back portion 22c of the bellows 22 finally comes to a position near the 
end portion 22a of the bellows 22 as seen in FIGS. 2 and 5. 
Referring to FIGS. 6 and 7, the bellows 22 extending between the fixed lens 
barrel member 21 and the movable lens barrel member 24 is shown in an 
enlarged scale when the movable lens barrel member 24 is at the wide angle 
photographing position and the telephotographing position shown in FIGS. 1 
and 2, respectively. 
In order to secure the rear end portion 22a of the bellows 22 to the fixed 
lens barrel member 21, such an annular bellows securing member 26 as shown 
in FIG. 8 is used. The annular bellows securing member 26 has a major 
cylindrical portion 26b adapted to be inserted into the inner periphery of 
the rear end portion 21a of the fixed lens barrel member 21 and cooperate, 
in its fully inserted position, with the rear end portion 21a of the 
fixed lens barrel member 21 to hold the end portion 22a of the bellows 22 
therebetween. The bellows securing member 26 further has a plurality of, 
say, 3 or 4, pawls 26a formed rearwardly on the cylindrical portion 26b 
thereof. The pawls 26a of the bellows securing member 26 are bent rather 
radially outwardly as seen in FIG. 8. The pawls 26a of the annular bellows 
securing member 26 are fitted individually in a plurality of recesses 21b 
formed in an inner circumferential wall near the rear end of the fixed 
lens barrel member 21 to prevent the bellows securing member 26 from 
coming off in the rearward direction from the fixed lens barrel member 21. 
In assembly, the end portion 22a of the bellows 22 is wrapped around the 
cylindrical portion 26b of the bellows securing member 26, and then the 
bellows securing member 26 is inserted into the inner periphery of the 
rear end portion 21a of the fixed lens barrel member 21 from the rear side 
whereupon the pawls 26a thereon are resiliently yielded and fitted into 
the recesses 21b of the fixed lens barrel member 21 to restore its 
original configuration. In this condition, the end portion 22a of the 
bellows 22 is securely retained in position due to a resilient pressure 
holding function of the cylindrical portion 26b of the bellows securing 
member 26 and also to a coming off preventing function of the recesses 21b 
of the fixed lens barrel member 21 cooperating with the pawls 26a of the 
bellows securing member 26. 
An annular lip packing 27 and a teremp or plush packing 28 are provided at 
a forward end portion of the fixed lens barrel member 21 for preventing 
sand, dust or some other foreign articles than water from entering the 
inside of the camera by way of a gap between the fixed lens barrel member 
21 and an outer periphery of the movable lens barrel member 24. 
The lip packing 27 is fitted in an annular groove 21c formed on an inner 
wall of the front end portion of the fixed lens barrel member 21. The lip 
packing 27 has a resilient tongue-like projection 27a formed thereon and 
extending to the outer periphery of the movable lens barrel member 21. The 
resilient tongue-like projection 27a of the lip packing 27 has an inner 
diameter a little smaller than the outer diameter of the movable lens 
barrel member 24 so that the inner end thereof may be held in normal 
sliding contact with the outer periphery of the movable fixed barrel 
member 24 when the movable lens barrel member 24 is advanced out of or 
retracted into the fixed lens barrel member 21. The lip packing 27 can 
prevent comparatively large sands or the like from entering the inside of 
the camera. In this instance, an additional lip packing may be provided. 
The teremp packing 28 is provided on the inner periphery of the fixed lens 
barrel member 21 adjacent the lip packing 27 and has a large number of 
fine projections or fibers provided in a juxtaposed relationship as in a 
flocked fabric so that it can prevent entry of comparatively small dust or 
the like which has passed the lip packing 27. 
An annular limiting projection or rib 21d is formed on the inner periphery 
of the front end portion of the fixed lens barrel member 21 adjacent the 
teremp packing 28 such that it may engage with three positioning 
projections 24c shown in FIG. 9 formed on the outer periphery of the rear 
end of the movable lens barrel member 24 to limit the forwardly advanced 
position of the movable lens barrel member 24. Each of the positioning 
projections 24c is rounded at a front face 24c1 thereof at which it 
contacts with the limiting projection 21d of the fixed lens barrier member 
21 in order to minimize the contacting area thereof with the limiting 
projection 21d. Such minimization of the contacting area is effective to 
reduce the possibility that dust or the like which should enter the inside 
of the camera without being successfully prevented by either of the 
packing members 27 and 28 may stick to the contacting faces 24c1 of the 
movable lens barrel member 24 to deteriorate the accuracy of the advanced 
position of the movable lens barrel member 24. 
Meanwhile, where the bellows 22 has a smaller thickness at an intermediate 
portion thereof than at the opposite secured end portions thereof so that 
they may be accommodated to a change in pressure in a spacing defined by 
the fixed lens barrel member 21, the movable lens barrel member 24 and the 
bellows 22, a change in volume of the inside of the camera can be 
compensated for by elongation or contraction of the bellows 22. 
As described above, according to the embodiment of the present invention, 
the lens barrel for a camera comprises the fixed member 21 provided on the 
body of the camera, the movable member 24 having at least part 25 of an 
optical system of the camera carried thereon and mounted for movement on 
and with respect to the fixed member 21 between a first position advanced 
outwardly from the camera body and a second position retracted in the 
camera body, and the bellows member 22 secured at the end thereof to the 
inner periphery 24a of the rear portion of the movable member 24 and at 
the other thereof to the inner periphery 21a of the rear portion of the 
fixed member 21, the bellows member 22 being folded back at an 
intermediate portion 22c thereof between the movable member 24 and the 
fixed member 21 in such a manner as to surround the rear end 24b of the 
movable member 24. With the lens barrel, the movable member can make 
smooth movement from the retracted position to the advanced position or 
reversely from the advanced position to the retracted position, and the 
bellows member serving as a watertight means can maintain a reliable 
liquid-tight condition thereof without requiring a specific or additional 
spacing therefor. 
It is to be noted that, while the camera in the embodiment described 
hereinabove is a waterproof camera and the bellows has a watertight 
performance, it may otherwise be a dust-proof camera, and in such an 
instance, the bellows is only required to prevent entry of dust into the 
inside of the camera. Meanwhile, if such bellows is formed from a light 
intercepting material, stray light which may otherwise enter the inside of 
the camera can be eliminated without the necessity of employment of a 
complicated light intercepting structure. 
Having now fully described the invention, it will be apparent to one of 
ordinary skill in the art that many changes and modifications can be made 
thereto without departing from the spirit and scope of the invention as 
set forth herein.