Lens barrier mechanism for use in a camera

Two barrier blades, a barrier interlocking plate and a barrier driver plate are arranged on a base to overlap one another. A first spring is arranged between the barrier interlocking plate and the barrier driver plate. By over-charging the first spring, the barrier blades are tightly closed. A second spring is provided between the barrier driver plate and the base to push both of the two barrier blades through the barrier interlocking plate 2. A through hole and a cutout are formed in the barrier driver plate at positions which do not interfere with the opening and closing loci of the barrier blades. The first and second springs are arranged in the through hole and the cutout, respectively.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a lens barrier mechanism for use in a 
camera, openably and closably attached at a front side of a taking lens 
for protecting the taking lens. 
2. Description of the Prior Art 
A lens barrier mechanism of this type is disclosed by the present applicant 
in Japanese Laid-open Patent Application No. H4-34709. In this prior art 
lens barrier mechanism, as shown in FIG. 1, two barrier blades 3' arranged 
on the same level and a driver ring 4' for driving the blades 3' are 
arranged to overlap each other on a substantially disk-shaped base member 
1' having an aperture 10' at its center. The barrier blades 3' and the 
driver ring 4' are held between a lens barrel (not shown) and the base 
member 1'. 
A first spring 5' is arranged between the driver ring 4' and each of the 
barrier blades 3'. The driver ring 4' is rotated until the first springs 
5' are overcharged so that the two barrier blades 3' are pressed against 
each other, thereby closing the barrier blades 3' tight enough to 
substantially completely prevent dust from coming into the lens barrel at 
a collapsed position. 
To prevent the aperture 10' of the base member 1' from being inadvertently 
closed during photographing, a second spring 6' is arranged between the 
driver ring 4' and the base member 1' to always push the driver ring 4' in 
a direction to open the barrier blades 3'. 
Moreover, in another prior art, a presser plate is provided as a means for 
holding the two barrier blades 3' and the driver ring 4' to overlap each 
other. The barrier blades 3' and the driver ring 4' are held between the 
presser plate and the base member 1'. 
In the above-described prior art lens barrier mechanisms, however, since 
the two barriers 3' are separately driven by receiving a rotation force 
from the driver ring 4', the first spring 5' should be provided between 
the driver ring 4' and each of the blades 3'. Thus, in the prior art 
mechanisms, two first springs 5' arranged between the driver ring 4 and 
the barrier blades 3' and one second spring 6, i.e. a total of three 
springs are required. 
In addition, since these springs have to be extension springs, under 
present circumstances, it cannot be helped to use coiled springs occupying 
considerable space. For this reason, the prior art mechanisms in which the 
coiled springs are incorporated to lie on the base member 1' is inevitably 
large in dimension along the optical axis, which makes it impossible to 
reduce the size of the barrier mechanism. A mechanism requiring the 
presser plate like the latter prior art mechanism is of great bulk with a 
greater thickness because of the thickness of the presser plate. 
SUMMARY OF THE INVENTION 
An object of the present invention is to reduce the thickness of a lens 
barrier mechanism by reducing the number of springs from the conventional 
number three to two and by decreasing the dimension of the lens barrier 
mechanism along the optical axis by efficiently arranging the springs. 
To achieve the above-mentioned object, a lens barrier mechanism of the 
present invention is provided with a barrier blade arranged in front of a 
lens for opening and closing a photographic optical path, a barrier driver 
plate for driving said barrier blade, a spring for pushing said barrier 
blade in a predetermined direction. In said barrier driver plate, a space 
constituted by a cutout or a through hole is formed at a position which 
does not interfere with an opening and closing locus of said barrier blade 
and wherein said spring is arranged in the space.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Hereinafter, an embodiment of the present invention will be described with 
reference to the drawings. FIG. 2 show each part of a lens barrier 
mechanism according to the embodiment in a disassembled condition. The 
lens barrier mechanism of FIG. 2 includes a base 1, a barrier interlocking 
plate 2, a pair of barrier blades 3, a barrier driver plate 4, and first 
and second springs 5 and 6 which are coiled extension springs. 
FIG. 3 shows an external barrel 7 and an inner barrel 8 engaging with the 
external barrel 7 slidably along the optical axis. The external and 
internal barrels 7 and 8 constitute a lens barrel for a taking lens to 
which the lens barrier of the present embodiment is attached. In FIG. 3, 
to show relevant elements of the external and internal barrels 7 and 8, 
they are turned about the optical axis at 180.degree. to the lens barrier 
mechanism of FIG. 2. 
The base 1 is constituted by a disk-shaped front plate 11 having an 
aperture 10 at its center and a peripheral wall 12 formed integrally with 
the plate 11 to protrude rearward from the periphery thereof. On the 
peripheral wall 12, two engagement claws 13 are formed with a necessary 
distance between. On the external barrel 7 of the lens barrel, claw 
catchers 71 are formed on the periphery of its front plate 70. 
In the lens barrier mechanism of the above-described structure, the barrier 
blades 3, the barrier interlocking plate 2 and the barrier driver plate 4 
are arranged to overlap one another in this order on the base 1, and the 
first and second springs 5 and 6 are arranged at subsequently-described 
predetermined positions, respectively. By engaging the claws 13 of the 
base 1 with the claw catchers 72 under this condition, the lens barrier 
mechanism is attached to a front end of the external barrel 7 while its 
separation therefrom is prevented. 
The barrier interlocking plate 2 is formed to be of a flat annular shape 
having an aperture 20 at its center so that the aperture 10 of the base 1 
is not interfered with. By engaging peripheral surfaces 2a constituting 
most of its periphery with an inner periphery of the peripheral wall 12 of 
the base 1, the barrier interlocking plate 2 is held rotatively about the 
optical axis. 
The two barrier blades 3 have the same dimensions and are made by using 
molding parts of the same configuration. Each has a boss hole 31 at the 
base of a blade member 30. An arm 32 extends from the boss hole 31 at a 
predetermined angle to the blade member 30. 
The barrier blades 3 are arranged on the same level. The boss holes 31 are 
pivotally engaged with cylindrical bosses 14 protruding from the rear 
surface of the front plate 11 of the base 1, and protrusions 33 provided 
at the front ends of the arm 32 are engaged with U-shaped cutouts 21 
formed to be opposite to each other with respect to the optical axis of 
the barrier interlocking plate 2. Thereby, the barrier blades 3 pivot 
about the cylindrical boss 14 of the base 1 in accordance with the 
rotation of the barrier interlocking plate 2 between a closed position 
where the opposing fringes 35 of the blades 30 are brought into contact 
with each other to close the aperture 10 of the base 1 from the opened 
position where the blades 30 are retreated from the aperture 10. 
The barrier driver plate 4 is formed to be substantially disk-shaped with 
an aperture 40 of a configuration similar to that of the aperture 10 of 
the base 1 at its center. At portions of the barrier driver plate 4 which 
are opposite to each other with respect to the optical axis and that do 
not interfere with the opening and closing loci of the barrier blades 3, a 
through hole 41 formed to be substantially fan-shaped along the periphery 
and a cutout 42 opening the periphery are provided. At an end surface of 
the through hole 41 along the diameter and at an end surface of the cutout 
42, a spring holder 43 and an abutment member 44 which also serves as a 
spring holder are respectively provided to protrude forward while being 
bent. 
The first spring 5 is arranged between the spring holder 43 provided at the 
through hole 41 and a spring holder 22 provided to protrude rearward to 
oppose the spring holder 43, thereby connecting the barrier interlocking 
plate 2 and the barrier driver plate 4 through the first spring 5. Under 
this connection condition, an end surface of a cutout 23 formed in the 
barrier interlocking plate 2 is pushed by the first spring 5 in a 
direction to abut the abutment member 44 of the barrier driver plate 4. 
At two positions on the periphery of the barrier driver plate 4, engagement 
cutouts 45 are formed. At the peripheral wall 12 of the base 1, bayonet 
claws 15 are formed to protrude rearward. By engaging the engagement 
cutouts 45 of the barrier driver plate 4 with the bayonet claws 15, the 
barrier driver plate 4 is held by the base 1 to be slidingly rotatable 
about the optical axis while being prevented from falling off in a 
direction along the optical axis. 
The second spring 6 is arranged between the abutment member 44 of the 
barrier driver plate 4 and a spring holder 16 provided on the periphery of 
the base 1 to protrude rearward to oppose the abutment member 44. The 
barrier driver plate 4 is pushed by the second spring 6 to rotate 
clockwise in FIG. 2. Thus, the cutout 23 receives a pushing force from the 
abutment member 44 so that the barrier interlocking plate 2 is pushed to 
rotate clockwise, thereby pushing the barrier blades 3 to retreat from the 
aperture 10 of the base 1 to the opened position. 
In the lens barrier mechanism thus assembled, the first spring 5 is 
arranged in a space formed by the through hole 41 of the barrier driver 
plate 4 as shown in FIG. 4, and the second spring 6 is arranged in a space 
formed by the cutout 42 of the barrier driver plate 4 as shown in FIG. 5. 
As a result, the first and second springs 5 and 6 are substantially neatly 
incorporated in the overlapping structure of the base 1, the barrier 
interlocking plate 2, the barrier blades 3 and the barrier driver plate 4. 
Thus, different from the conventional structures where the springs are 
arranged to lie on the base, the reduction in thickness of the lens 
barrier mechanism is achieved efficiently. 
At a portion on the periphery of the barrier driver plate 4 in the vicinity 
of the through hole 41, a cam follower 46 is formed to protrude rearward. 
On the periphery of an annular base plate 80 of the internal barrel 8 
shown in FIG. 3, three sliding guide members 81 are provided to be spaced 
substantially equally. One of the sliding guide members 81 has an 
inclining cam surface 82 formed by cutting a part of a corner thereof. On 
the periphery of the front plate 70 of the external barrel 7, an arc hole 
72 into which the cam follower 46 of the barrier driver plate 4 is 
inserted is formed. 
When the lens barrier mechanism is attached to the front end of the lens 
barrel, the cam follower 46 is inserted through the hole 72 of the 
external barrel 7 so that its tip is slidingly in contact with the 
inclining cam surface 82 of the internal barrel 8 inserted in the external 
barrel 7. 
FIGS. 6 to 8 show operation conditions of the lens barrier mechanism of the 
above-described structure. FIG. 6 shows the opened condition. FIG. 7 shows 
the condition of the moment the barrier blades 3 are closed. FIG. 8 show 
an overcharged condition. The base 1 is not shown in these figures. When 
the lens barrel is projecting, for example, when the focal length is 
shortest, the internal barrel is at a retreated position, and the 
inclining cam surface 82 thereof has no effect on the cam follower 46. 
Under this condition, as shown in FIG. 6, the clockwise pushing force of 
the second spring 6 working on the barrier driver plate 4 is transmitted 
to the barrier interlocking plate 2 by the abutment of the abutment member 
44 on the end surface of the cutout 23 to push the barrier interlocking 
plate 2 to rotate clockwise, thereby forcibly placing the barrier blades 3 
at the opened position where the blades 3 are retreated from the aperture 
10 of the base 1. 
When this condition is changed to the collapsed condition where the camera 
is not used, for example, by turning on the main switch of the camera, the 
degree of engagement between the external and internal barrels 7 and 8 
along the optical axis increases. Since the inclining cam surface 82 of 
the external barrel 8 pushes the cam follower 46 of the barrier driver 
plate 4 to move along the optical axis as the degree of engagement 
increases, the barrier driver plate 4 is rotated counterclockwise against 
the pushing force of the second spring 6, and in response to the rotation, 
the barrier interlocking plate 2 connected with the barrier driver plate 4 
by the first spring 5 rotates counterclockwise, thereby rotating the 
barrier blades 3 about the cylindrical boss 14 toward the closed position. 
Then, as shown in FIG. 7, when the opposing sides of the barrier blades 3 
come into contact with each other, the rotations of the barrier blades 3 
and the barrier interlocking plate 2 are stopped. However, the retraction 
of the external and internal barriers 7 and 8 into the camera body is 
continued thereafter, and the inclining cam surface 82 further rotates the 
cam follower 46 so that only the barrier driver plate 4 is rotated until 
it is slightly separated from the end surface of the cutout 23 of the 
barrier interlocking plate 2 while over-charging the first spring 5. 
Finally, a closed condition is maintained where the barrier blades 3 are 
pressed hard against each other as shown in FIG. 8. 
As described above, in the collapsed condition where the camera is not 
used, the barrier blades 3 are always maintained in the closed condition. 
Thereby, the front lens is covered with the barrier blades 3. As a result, 
the intrusion of dust is prevented without failure. Even if an external 
force is applied to rotate the barrier driver plate 4 from the closed 
condition of the barrier blades 3, it only stretches the first spring 5; 
no excessive force is applied directly to the barrier blades 3. 
Conversely, even if a force to forcibly open the closed barrier blades 3 
is applied to the barrier blades 3, since the force is absorbed by the 
first spring 5, no excessive force is applied to the barrier blades 3 and 
other parts. 
When the lens barrel is projected from the collapsed position, since the 
inclining cam surface 82 is relatively retreated from the cam follower 46, 
the force is removed which works to keep the barrier driver plate 4 at the 
closed position of the barrier blades 3. Therefore, the barrier driver 
plate 4 is rotated counterclockwise by the pushing force of the second 
spring 6. At this time, the end surface of the cutout 23 is pushed by the 
abutment member 44 to forcibly rotate the barrier interlocking 2, whereby 
the barrier blades 3 are opened and kept opened by the pushing force of 
the second spring 6. 
In the lens barrier mechanism of the above structure, there is a 
possibility that a gap is generated between the abutting opposing sides of 
the barrier blades 3 due to the influences of a configuration error of the 
barrier blades 3 or a relative position error of the cylindrical boss 14 
of the base 1 pivotally supporting the barrier blades 3 or a relative 
position error of the position of the engagement between the protrusion 33 
and the cutout 21 of the barrier interlocking plate 2. 
To prevent this, in this embodiment, a slit 34 opened at its end is formed 
in the arm 32 of each barrier blade 3 along the length of the arm 32. 
Because of the presence of the slit 34, the arm 32 is bent so that the 
remaining both sides thereof are in contact with each other by the strong 
pushing force generated when the first spring 5 is overcharged, thereby 
absorbing the above-mentioned various error elements to prevent the 
generation of the gap between the abutting opposing sides of the barrier 
blades 3. 
As described above, according to the lens barrier mechanism of the present 
invention, the barrier blades are opened and closed by transmitting the 
drive of the barrier driver plate to the barrier blades through the 
barrier interlocking plate, and the first spring overcharged to secure the 
closed condition of the barrier blades is arranged between the barrier 
interlocking plate and the barrier driver plate and the pushing force of 
the spring is applied to the two barrier blades through the barrier 
interlocking plate. Therefore, different from the conventional mechanisms 
where the first spring is arranged between the driver ring corresponding 
to the barrier driver plate and each barrier blade, by arranging only one 
spring between the barrier interlocking plate and the barrier driver 
plate, the pushing force of the spring generated by the charge of the 
spring is caused to act on the barrier blades. 
Since the number of necessary springs is reduced by one from the 
conventional number three, i.e. only one first spring and one second 
spring are necessary, not only the number of parts is reduced but also, 
and more importantly, spaces for arranging the springs are secured by 
providing a cutout or a through hole in the barrier driver plate. In the 
present invention, since the springs are arranged in corresponding spaces, 
the springs are substantially neatly incorporated in the overlapping 
structure of the base, the barrier interlocking plate, the barrier blades 
and the barrier driver plate. As a result, the thickness of the lens 
barrier mechanism is reduced efficiently. 
The lens barrier mechanism is unnecessary optically. However, since it is 
unnecessary to increase the amount of collapse of the lens barrel from 
that necessitated by the optical parts because of the reduction in 
thickness of the lens barrier mechanism, the amount of collapse of the 
lens barrel is reduced to the minimum. 
Further, since the aperture of the substrate can be arranged close to the 
lens because of the reduction in thickness of the barrier mechanism, the 
barrier mechanism can be employed for a relatively wide angle lens even if 
the diameter of aperture when the barrier blades are opened is small, 
thereby reducing the external diameter of the lens barrier mechanism. 
Obviously, many modifications and variations of the present invention are 
possible in light of the above teachings. It is therefore to be understood 
that within the scope of the appended claims, the invention may be 
practiced other than as specifically described.