Photography – Camera detail – Shutter
Reexamination Certificate
2002-01-28
2004-12-28
Adams, Russell (Department: 2851)
Photography
Camera detail
Shutter
C396S488000, C396S489000
Reexamination Certificate
active
06835009
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to shutter apparatus being suitably applicable to single-lens reflex cameras and of a so-called split blade type.
2. Related Background Art
Conventionally, the single-lens reflex cameras and others are often constructed using a focal plane shutter of a type in which groups of split light shielding blades are rotatably supported by parallel link mechanisms using two arm members.
The general mechanisms used in the focal plane shutters of this type are classified into a long arm type and a short arm type, depending upon the difference in a method of holding the light shielding blade groups by the arm members.
Described herein are so-called, vertically running focal plane shutters constructed to run the light shielding blade groups vertically.
First, the focal plane shutters of the long arm type are constructed in such structure that the light shielding blade groups are rotatably held on the arm members on the opposite side of the shutter aperture to the rotatable base ends of the arm members, as disclosed in Japanese Utility Model Publication No. 35-29651. For this reason, the arms become longer than the width of the shutter aperture.
Since this long arm type requires only small angles of rotation of the arm members for opening and closing of the shutter aperture by the light shielding blade groups, amounts of displacement become small in the direction perpendicular to the running direction of the light shielding blade groups during the opening and closing operation, which is advantageous to lateral downsizing of the shutter apparatus.
However, where the number of light shielding blades in each group that can be held by the two arm members was not less than 3, the long arm type had the drawback that the structure became complicated and the drawback that the inertia of the blade units became so large because of the long arms as to be disadvantageous to fast running. For this reason, the focal plane shutters of the long arm type unsuitable for increase of speed are not being used with increase in exposure time of the shutter and with increase in flash light synchronization time in recent years.
Thus the short arm type was devised in order to overcome the drawbacks of the long arm type and was substantiated in such structure that the two arm members rotatably held each group of many light shielding blades near the same side with respect to the shutter aperture as the side near the base ends of the arm members, without interposing the shutter aperture in between, though it was disadvantageous to the lateral downsizing of the shutter apparatus. In addition, in order to make the inertia smaller, it is desirable to minimize the lengths of the arms.
As an example of this short arm type, the structure and dimensional relation thereof are presented in
FIGS. 21 and 22
(wherein
FIG. 21
shows a running ready state and
FIG. 22
a running end state).
In this shutter apparatus (which will be referred to hereinafter as the first conventional example), a leading-curtain blade unit and a trailing-curtain blade unit are mounted on a base plate
101
(shutter ground board) having a shutter aperture
101
a.
The leading-curtain blade unit is composed of five blades. Each of first arm
106
and second arm
107
on the leading curtain side has a base end rotatably supported at a shaft
101
d,
101
e.
A slit forming blade
102
and covering blades
103
,
104
,
105
,
105
′ are rotatably coupled to the first arm
106
and the second arm
107
by blade caulking dowels
108
a,
108
b,
108
c,
108
d,
108
e,
109
a,
109
b,
109
c,
109
d
,
109
e,
and a parallel link is comprised of these two arms
106
,
107
, five blades, and base plate.
The trailing-curtain blade unit is composed of four blades. Each of first arm
114
and second arm
115
on the trailing curtain side has a base end rotatably supported at a shaft
101
f,
101
g.
A slit forming blade
110
and covering blades
111
,
112
,
113
are rotatably coupled to the first arm
114
and the second arm
115
by blade caulking dowels
116
a,
116
b
,
116
c,
116
d,
117
a,
117
b,
117
c,
117
d,
and a parallel link is comprised of these two arms
114
,
115
, four blades, and base plate.
In each of the leading curtain and the trailing curtain, the blade caulking dowels are successively arranged so as to draw a gentle arc and the first arm and the second arm are juxtaposed near to each other in a superimposed state in which the blade unit opens the shutter aperture.
In each of the leading curtain and the trailing curtain, neither of the blade
105
′,
113
with the smallest travel (moving distance) and the blade
105
,
112
with the second smallest travel (moving distance) is provided with a light shielding piece extending generally in the blade running direction, near the coupling portion to each arm.
For this reason, each of the blades
104
,
111
with the third smallest travel, and the blade
103
with the fourth smallest travel in the leading curtain is provided with a light shielding piece (
103
a,
104
a,
111
a
indicated by hatching in the drawings).
Further, in the superimposed state in which the blade group of the leading curtain or the trailing curtain opened the shutter aperture
101
a,
the light shielding piece of the blade
104
,
111
with the third smallest travel (
104
a,
111
a
indicated by hatching) was not located between the coupling portions
109
d,
109
e
;
117
c,
117
d
to the second arm, of the blade
105
′,
113
with the smallest travel and the blade
105
,
112
with the second smallest travel.
From the viewpoint that it was hard to achieve the downsizing by the parallel link mechanisms using two arms, the following was proposed as a shutter apparatus downsized by adding the third auxiliary arm.
The shutter apparatus disclosed in Japanese Utility Model Publication No. 6-26896 (which will be referred to hereinafter as the second conventional example) was constructed in such structure that in the blade superimposed state the coupling portions on the first and second arms for coupling and supporting the slit forming blade were accommodated in a storage region present between the finder and the aperture window and that the third arm supporting the other covering blades was located outside the region, thereby decreasing the lateral contour size of the shutter apparatus.
This apparatus is constructed in the structure in which each arm is made slim in order to place the three arms in the narrow space and, in the superimposed state in which the blade group opens the shutter aperture, the first arm and the third arm are arranged so that the center of rotation of the base end of the third arm is interposed between the center of rotation of the base end of the first arm and the caulking dowel of the third covering blade and so that the caulking dowel of the third covering blade on the first arm is interposed between the center of rotation of the base end of the third arm and the caulking dowel of the third covering blade.
Although not referred to in this official gazette, the light shielding piece projecting on the almost opposite side to the blade running direction is provided near the coupling portions to the first and second arms in the blade with the second smallest travel, as shown in the drawings of the official gazette.
However, the light shielding piece provided in the blade with the third smallest travel is not located between the coupling portions to the second arm of the blade with the smallest travel and the blade with the second smallest travel in the superimposed state in which the blade group opens the shutter aperture.
Further, Japanese Utility Model Publication No. 7-25787 discloses the shutter apparatus also having the third arm (which will be referred to hereinafter as the third conventional example) wherein, in order to prevent exposure unevenness caused when the parallel state of the slit forming blade is degraded by deflection, swingback, play, etc. of the slit forming blade, the parallel lin
Adams Russell
Canon Kabushiki Kaisha
Dalakis Michael
Fitzpatrick ,Cella, Harper & Scinto
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