Photography – Having variable focal length of camera objective – Power zoom
Reexamination Certificate
2000-06-21
2001-11-13
Gray, David M. (Department: 2851)
Photography
Having variable focal length of camera objective
Power zoom
C396S132000, C396S418000
Reexamination Certificate
active
06317564
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical apparatus capable of selectively supplying power from a drive source to a plurality of power transmission mechanisms.
2. Description of the Related Art
A conventional general planetary gear mechanism includes, as shown in FIGS.
32
(
a
) and
32
(
b
), a sun gear
101
which rotates by means of a certain power, an arm
102
which rotates about a shaft
108
common to the sun gear
101
independently of the sun gear
101
, and a planetary gear
103
, which is secured to the arm
102
by a shaft
107
for rotation with respect to the arm
102
against the resistance of a spring
106
and in mesh with the sun gear
101
.
In the shown mechanism, the planetary gear
103
can turn (revolve) about the sun gear
101
, and can also turn (rotate) on its axis.
Such a planetary gear mechanism is generally used for a switching mechanism for selectively transmitting power for winding or rewinding of film in a camera or the like. In the planetary gear mechanism, as shown in
FIG. 33
, the extent of revolution of the planetary gear
103
is not an angle of 360 degrees, and is limited by two gears: a gear
104
for transmitting power to a winding system and a gear
105
for transmitting power to a rewinding system. In practice, however, since the gears may bite into each other, the extent of revolution of the planetary gear
103
is limited by bringing the shaft
107
of the planetary gear
103
into abutment with a portion
109
or
110
. In this arrangement, if. the sun gear
101
rotates toward the left as viewed in
FIG. 33
, the planetary gear
103
meshes with the gear
105
to cause the gear
105
to rotate in the direction indicated by a solid arrow. If the sun gear
101
rotates toward the right, the planetary gear
103
meshes with the gear
104
to cause the gear
104
to rotate in the direction indicated by a dashed arrow. A number of states brought about by the above-described operation are enumerated below:
1) Whether power is switched to the gear
104
or
105
is determined only by whether the sun gear
101
rotates toward the right or the left.
2) Each of the gear
104
and the gear
105
to which power is transmitted rotates in one direction only. That is to say, two lines are available for force transmission.
3) During power transmission or if gear backlash occurs in the direction of power transmission, the abutment portion
109
is subjected to a force F-
109
from the shaft
107
. In the opposite case, the abutment portion
110
is subjected to a force F-
110
.
4) If the planetary gear
103
is switched from the gear
105
to the gear
104
while power is being transmitted to the gear
105
as shown in
FIG. 33
, the planetary gear
103
only makes rotation (left-handed rotation) immediately after the right-handed rotation of the sun gear
101
is started, until the backlash is removed and the force F-
109
disappears. Subsequently, the planetary gear
103
starts revolution.
The reasons why only two lines are only available for force transmission as described above in Paragraph 2) are:
a) Since the conventional planetary gear mechanism is arranged in such a manner that the extent of revolution of the planetary gear
103
is limited by the gear
104
and the gear
105
as shown in
FIG. 33
, it is impossible to mesh the planetary gear
103
with any gear other than the gear
104
and the gear
105
.
b) The direction of rotation of either one of the gears
104
and
105
is the direction of power transmission, while the direction of rotation of the other is the direction in which the planetary gear
103
is switched. As a result, either one of the gears
104
and
105
can transmit a force in one direction only.
For the above reasons, the number of transmission lines of force is two.
To realize the number of transmission lines of force which is greater than two, a planetary gear mechanism such as that shown in
FIG. 34
may also be considered. In the shown mechanism, a plurality of (four, in this example) gears
111
a
to
111
d
are disposed circumferentially, and the positional relation between each of the gears
111
a
to
111
d
, the sun gear
101
and the planetary gear
103
is selected so that they can be arranged in a straight line to prevent each of the gears
111
a
to
111
d
from hindering the planetary gear
103
. Stoppers
112
a
to
112
d
each of which prevents the left-handed revolution of the planetary gear
103
are disposed in the vicinity of the respective gears
111
a
to
111
d
for movement toward and away from the planetary gear
103
. In this arrangement, by causing the sun gear
101
to rotate toward the right, a gear with which the planetary gear
103
is to be meshed is selected from among the gears
111
a
to
111
d
, and by causing the sun gear
103
to rotate toward the left, the shaft
107
is brought into abutment with the associated one of the stoppers
112
a
to
112
d
so that force is transmitted to the selected one of the gears
111
a
to
111
d
. However, this arrangement merely solves the problem stated in paragraph a), and the problem of paragraph b) remains. The direction in which force can be transmitted to each of the gears
111
a
to
111
d
is limited to one direction only as shown in
FIG. 34
, and no force can be transmitted through rotation in the opposite direction.
However, the arrangement of
FIG. 34
which uses four gears
111
a
to
111
d
and four gear trains which can be coupled to the respective gears
111
a
to
111
d
has a problem: Since force can be transmitted in one direction only, it is difficult to use the arrangement as a mechanism which requires rotation in both right-handed and left-handed directions. If there is a planetary gear mechanism which can transmit force in both right-handed and left-handed direction by means of one gear train, it is possible to selectively transmit power from a single power source to a plurality of gear trains by causing a sun gear to rotate toward the right or the left.
FIG. 35
shows a model diagram of the basic concept of such a planetary gear mechanism.
In the arrangement shown in
FIG. 35
, the revolution of the planetary gear
103
is stopped by an arbitrary one of stoppers
113
a
to
113
d
and the adjacent one of stoppers
114
a
to
114
d
, whereby both the right-handed and left-handed revolutions of the planetary gear
103
are stopped and power can be transmitted to the desired one of the gears
111
a
to
111
d
in either direction of rotation thereof.
Consideration will be given below to a case where, in such an arrangement, an element to which power is to be transmitted is switched, for example, from the gear
111
a
which is presently in mesh with the planetary gear
103
to the gear
111
b
. It is assumed that the direction of rotation of the output gear
111
b
after switching is desired to be made left-handed (the direction of rotation of the sun gear
101
is also made left-handed).
In this case, the sun gear
101
is made to rotate toward the right to cause the planetary gear
103
to revolve toward the right and mesh with the gear
111
b
. However, since it is desired that the direction of rotation of the output gear
111
b
be made left-handed, it is necessary to cause the sun gear
101
to rotate in the opposite direction (toward the left) after the gears
103
and
111
b
have meshed with each other. This means that at the time when the gears
103
and
111
b
mesh with each other, a driving force is instantaneously transmitted to the gear
111
b
in the direction opposite to the desired direction. At this time, if the gear
111
b
is coupled to, for example, a power transmission mechanism for effecting zooming, the angle of view will shift in the direction opposite the desired direction and a photographer will have a sense of incompatibility.
To realize the above-described mechanism, the following problems must also be solved.
1) It is necessary to design a mechanism in which while the planetary gear
113
is revolving to mesh with any one of the gears
11
Fujihara Yuji
Hamada Yoshiaki
Ichino Kazushige
Kaneko Yoshiyuki
Suzuki Ryoichi
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Gray David M.
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