Optical: systems and elements – Lens – With variable magnification
Reexamination Certificate
1999-10-29
2001-02-27
Epps, Georgia (Department: 2873)
Optical: systems and elements
Lens
With variable magnification
C359S700000, C359S694000
Reexamination Certificate
active
06195212
ABSTRACT:
This application claims the benefit of Japanese Applications Nos.10-320913 and 10-320914 which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a variable focal length lens barrel.
2. Related Background Art
Japanese Patent Application Laid-Open Publication No.10-31150 discloses a lens group moving mechanism for a variable focal length lens in the prior art, which is constructed to attain a decrease in thickness of a camera by increasing a moving quantity for a collapsing operation without any rises both in length and diameter of a lens barrel. A configuration of this mechanism is that a width-enlarged portion with an enlarged width of a thread root is formed in a part of a female helicoid thread of a multi-streaks thread, and a dimension of length of the width-enlarged portion in a direction along the helix Is equalized to a length of crest of a male helicoid thread in the direction along. the helix, which meshes with the female helicoid thread. With this configuration, it is possible to obtain thread-fitting having a comparatively small lead at a portion with a non-enlarged width of the root of the thread, and a thread fitting having a comparatively large lead at the portion with the enlarged-width of the root. That is, a dimension in section right-angled to the helix with respect to the crest of the male helicoid thread is defined as a “width”, while a length in the direction along the helix is defined as a “length”. In this case, the male helicoid thread and the female helicoid thread mesh with each other over the “width” or the “length” thereof. Then, in the case of meshing over the “width”, there is acquired a thread fitting state having a comparatively small lead. In the case of meshing over the “length”, there is obtained a thread fitting state having a comparatively large lead. The complex lead threads having two leads different from each other can be obtained in the way described above.
Further, Japanese Patent Application Laid-Open Publication No.
3-209445
discloses a technology of reducing the number of parts of the helicoid thread and the cam for moving the lens groups. According to this technology, one single cam ring is formed with both a cam groove and a lead thread.
If the complex lead thread and the cam groove are formed in overlap in an internal peripheral surface of a cylindrical member of the single cam ring, the cam groove might extend across a portion where the lead changes, i.e., a bending portion of a root of the female helicoid thread. At this time, a side wall of the bending portion of the helicoid thread is separated by the cam groove, resulting in a deficient state.
When the crest of the male helicoid thread meshing over the “width” is on the verge of reaching the separated bending portion, with the bending portion being in the as-deficient state, the same crest advances rectilinearly without being changed to the state of meshing over the “length”, consequently comes off the root of the female helicoid thread, and drops down to the cam groove. As a result, a rotation of the cam ring is locked, and the variable focal length lens might be incapable of performing a zooming operation in some cases.
SUMAMRY OF THE INVENTION
It is a primary object of the present invention to provide a variable focal length lens barrel capable of providing a thread having a complex lead thread and a cam grove in overlap on one single cam barrel, and preventing a crest of a helicoid thread meshing with the complex lead thread from coming off a root of the complex lead thread.
To accomplish the above object, according to one aspect of the present invention, in the following description corresponding to the members in
FIG. 1
showing in development an internal peripheral surface of the variable focal length lens barren in one embodiment, a variable focal length lens barrel comprises a bottomed cam groove
3
d
2
having a first depth b, and a complex lead thread
3
f
1
structured so that a root of a first lead thread
3
b
1
having a first lead is connected via a bending portion
3
e
1
to a root of a second lead thread
3
c
1
having a second lead, this complex lead thread having a thread bottom of a second depth a shallower than the first depth b, wherein the cam groove and the complex lead thread are disposed in overlap on one single barrel. Then, the complex lead thread
3
f
1
and the cam groove
3
d
2
are disposed so as not to intersect each other at the bending portion
3
e
1
.
In the variable focal length lens barrel of the present invention, a plurality of cam grooves
3
d
1
-
3
d
3
are provided, the complex lead threads
3
f
1
-
3
f
6
are multi-streak threads having a plurality of streaks, and positions of disposing the plural streaks of complex lead threads
3
f
1
-
3
f
6
and the plurality of cam grooves
3
d
1
-
3
d
3
are determined so that the complex lead thread and the cam groove do not intersect each other at leastwise one bending portion among the bending portions
3
e
1
-
3
e
6
included respectively in the plural streaks of complex lead threads.
In the variable focal length lens barrel, the number of the plural streaks of complex lead threads
3
f
1
-
3
f
6
formed on the barrel is a multiple of integer that is equal to or more than twice the number of the cam grooves
3
d
1
-
3
d
3
formed on the barrel.
REFERENCES:
patent: 4069724 (1978-01-01), Sobotta
patent: 6002531 (1999-12-01), Nakashima et al.
Epps Georgia
Nikon Corporation
Thompson Tim
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