Lens barrel

Details Lens barrel Lens barrel

2003-02-25

2004-11-02

Mack, Ricky (Department: 2873)

Optical: systems and elements

Lens

With variable magnification

C359S699000

Reexamination Certificate

active

06813093

ABSTRACT:

This application claims benefit of Japanese Application No. 2002-51812 filed on Feb. 27, 2002, in Japan, and No. 2002-51813 filed on Feb. 27, 2002, in Japan, the entire contents of both of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lens barrel.
2. Description of the Related Art
A conventional lens barrel shown in a vertical sectional view in
FIG. 10
has been known as a lens barrel having a cam frame which can be rotationally and linearly moved, and a lens frame which can be linearly driven by the cam frame. A conventional lens barrel
50
comprises, a fixed frame
51
, a cam frame
52
, a first group frame (described hereafter as the first group frame)
53
holding first group lenses
65
, a second group frame (described hereafter as the second group frame)
54
which slidably supports a lens frame
59
holding second group lenses
66
, a third group frame (described hereafter as the third group frame)
55
holding third group lenses
67
, and a straight float key
56
.
Note that, with the second group frame
54
, shutter blades
68
are mounted thereto, and a blade suppressor
58
, which is a suppression member for the shutter blades
68
, is mounted thereto. A compression spring
57
is inserted between the blade suppressor
58
and the third group frame
55
for preventing linear movement play.
With the cam frame
52
, a male helicoid
52
a,
which spirally meshes with a female helicoid
51
a
of the fixed frame
51
, is provided on the outer circumference of the back end thereof, and furthermore, the female helicoid
52
b
and two pairs of cam grooves
52
c
and
52
d
are provided at the inner circumference portion thereof, and a bayonet groove
52
h,
which is an inner groove for holding the straight float key
56
, are provided on the back end of the inner circumference portion thereof. Note that the female helicoid
52
b
and two pairs of the cam grooves
52
c
and
52
d
are disposed such that the helicoid and the cam grooves cross one another as shown in a development of the inner circumferential face of the cam frame in
FIG. 11
which will be described later.
With the first group frame
53
, a male helicoid
53
a
which spirally meshes with the female helicoid
52
b
of the cam frame
52
is provided on the outer circumference portion of the back end thereof. With the second group frame
54
, a cam follower
62
, which is freely slidably fitted into the cam groove
52
d
of the cam frame
52
, is implanted (supported in a fixed manner) on the outer circumference portion thereof. With the third group frame
55
, a cam follower
61
which is freely slidably fitted into the cam groove
52
c
of the cam frame
52
is implanted (supported in a fixed manner) on the outer circumference thereof. With the straight float key
56
, a protruding straight key
56
b
which is freely slidably fitted into a straight guide groove
51
b
of the fixed frame
51
, and a bayonet tab
56
a
which is freely slidably fitted into the bayonet groove
52
h
of the cam frame
52
, are provided.
With the lens barrel
50
having a linear driving mechanism described above, upon the cam frame
52
being rotationally driven by the lens barrel linear driving unit, the cam frame
52
is linearly moved while rotating. The straight float key
56
is linearly moved along the direction of the optical axis O along with the rotationally moving cam frame
52
without rotational movement. The first group frame
53
, the second group frame
54
, and the third group frame
55
are linearly driven, respectively, according to the rotational movement and linear movement of the cam frame
52
with the rotational movement being restricted by the straight float key
56
.
Detailed description will be further made regarding the configuration of the inner circumference portion of the cam frame
52
with reference to FIG.
11
through FIG.
13
.
FIG. 11
is a development which illustrates an inner circumference face of the cam frame,
FIG. 12
is a sectional view taken along line XII—XII of
FIG. 11
, and
FIG. 13
is a diagram which illustrates the bayonet tab of the cam frame
52
and the insertion portion for the cam follower, as viewed from the back end side.
As shown in
FIG. 11
, with the inner circumference face of the cam frame
52
, the female helicoid
52
b
with a predetermined lead, and three pairs of the cam grooves
52
c
and
52
d
are provided, and a bayonet groove
52
h
is provided at the back end face side. Furthermore, six notch-shaped inserting portions
52
e
for inserting the bayonet tab
56
a,
and three notch-shaped inserting portions
52
f
and
52
g
for inserting the cam followers
61
and
62
, are provided on a ring-shaped back end wall portion
52
j
on the back end face where the bayonet groove
52
h
of the cam frame
52
is provided, respectively, as shown in FIG.
13
. The cam followers
61
and
62
are fitted into the cam grooves
52
c
and
52
d
through the inserting portions
52
f
and
52
g.
The bayonet tab
56
a
is fitted into the bayonet groove
52
h
through the inserting portion
52
e.
Note that the inner diameter of the inner circumference face
52
i
(see
FIG. 13
) of the cam frame
52
is the same as the inner diameter of the back end wall portion
52
j.
The female helicoid
52
b
of the cam frame
52
has a thread height (depth) H0 from the inner circumference face
52
i.
The male helicoid
53
a
of the first group frame
53
which spirally meshes with the female helicoid
52
b
also has the same thread height (depth) H0. The cam grooves
52
c
and
52
d
of the cam frame
52
have a groove depth C0 from the inner circumference face
52
i.
The minimal wall thickness of the circumference portion of the cam frame
52
is represented by t0. The thickness d0 from the outer circumference face up to the inner circumference face
52
i
where the cam grooves are provided is C0+t0.
The total wall thickness (required frame thickness) T0 of the cam frame
52
in the radial direction is a thickness wherein the thread height H0 of the female helicoid
52
b
and the thickness d0 from the outer circumference face up to the inner circumference face
52
i
of the cam groove are added. That is to say, the total wall thickness T0 in the radial direction T0 is represented by
T
0=
H
0+
d
0.
Substituting the above-described d0=C0+t0, the following expression is obtained.
T
0=
H
0+
C
0+
t
0  (1)
Note that a zoom lens barrel according to conventional art has been disclosed in Japanese Unexamined Patent Application Publication No. 6-67076, which employs a linear driving mechanism wherein the helicoid and the cam groove are disposed on the inner circumference face of the cam frame so as to cross one another, as with the conventional lens barrel shown in
FIG. 10
described above.
With the above-described conventional lens barrel
50
shown in
FIG. 10
, while the cam grooves
52
c
and
52
d,
and the female helicoid
52
b
are disposed so as to cross one another, these are disposed in a pattern separated one from another. Accordingly, the total wall thickness (required frame thickness) T0 in the radial direction of the cam frame
52
with the minimal wall thickness t0 is obtained by simply adding the thread height H0 and the thickness d0 up to the outer face from the inner face.
SUMMARY OF THE INVENTION
A lens barrel according to the present invention comprises a first frame and a second frame. With the first frame, a first female helicoid is formed on the first region on the inner circumference face thereof, and a second female helicoid is formed with the same lead as the first female helicoid and a different groove depth from that of the first female helicoid on the second region in the inner circumference face thereof. The second frame is disposed inside of the first frame, and a first male helicoid which spirally meshes with the first female helicoid, and a second male helicoid which spirally meshes with the second female helicoids, are

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