Shutter for camara

A shutter for a camera having leading and trailing blade groups movably interposed in between a plurality of plate-shaped members each of which having a shutter aperture, each of the blade groups including a plurality of divided blades, is provided with a protruding part which is formed along the edge of the shutter aperture in a slanting and outwardly protruding manner. This protruding part prevents the blade groups from being damaged by the impact of collision of them with the edge of the shutter aperture even when they travel in a state of being warped to the outside of a normal blade moving area by an external force.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a shutter for a camera having a plurality of 
divided blades and more particularly to a structural arrangement of the 
shutter which prevents the shutter blades from being damaged by their 
collision against the edge of a shutter aperture provided in a shutter 
base plate, etc. when an external force is exerted on the shutter blades 
while they are operated. 
2. Description of the Related Art 
A desire to enlarge the range of photographable objects for a camera has 
recently resulted in the increase of the maximum and flash-synchronizing 
speeds of shutters. The increase in speed necessitates an increased 
driving force on the shutter blades and a decreased weight of shutter 
blades. Hence, the thickness of the shutter blades has become thinner for 
reduction in weight. 
However, as shown in FIG. 11 of the accompanying drawings which shows an 
example of the prior art, a travelling space for shutter blades is 
provided jointly by a shutter base plate 1 (positioned on the front side 
of the shutter or the mirror box side of the camera), a separating plate 
5, a cover plate 2, etc. These plates generally require no special 
arrangement in connection with the reduction in thickness of shutter 
blades. Therefore, no change has been made in the form of these plates. 
For example, the shutter base plate 1 is provided simply with a tapered 
face lh along the edge of a shutter aperture 1a located in the traveling 
direction of shutter blades. 
Further, referring to FIGS. 11 to 15 which show the prior art example, the 
conventional shutter arrangement includes a leading blade group 3; a 
trailing blade group 4; a shutter aperture la provided in the shutter base 
plate 1; a shutter aperture 2a which is provided in the cover plate 2; a 
shutter aperture 5a provided in the separating plate 5; blade arms 6 and 
7; and blade dowels 8. 
The structural arrangement of the conventional shutter, however, has the 
following drawback: The shutter blades having their rigidity lowered by 
the above stated reduction in thickness would be greatly warped if the 
shutter is operated while the shutter blades are under an external force 
which is exerted on them from behind (from the back cover side of the 
camera) in cases, for example, where the shutter is inadvertently operated 
with the leader part of a loaded roll of film riding on the shutter blades 
or with the shutter blades under air pressure while the inside of the back 
cover of camera is being cleaned by means of a spray. Under such a 
condition, a slit forming part 4a of the trailing blade group 4 comes to 
collide with an aperture edge 1c of the shutter base plate 1 which is 
confronting it and thus would be damaged as shown in FIGS. 12 to 14. More 
specifically, in the case of a vertical-travel blade type shutter having 
shutter blades arranged to travel downward from above, the slit forming 
part 4a of the trailing blade group 4 comes to collide with the aperture 
edge 1c of the shutter base plate 1 when the shutter blades are traveling, 
or another part of the trailing blade group 4, such as a part 4b as shown 
in FIG. 15, comes to collide with another aperture edge of the shutter 
base plate 1 when the shutter blades are being set for a travel preparing 
position to cause the shutter blades to be thus damaged there. In the case 
that the shutter blades are arranged to travel upward from below, a slit 
forming part of the leading blade group 3 comes to collide with an 
aperture edge of the shutter base plate 1 when the shutter blades are 
being set for a travel preparing position or another part of the leading 
blade group 3 similar to the above stated part 4b comes to collide with an 
aperture edge of the shutter base plate 1 to damage the shutter when the 
blades are on their travel. 
SUMMARY OF THE INVENTION 
One aspect of this invention is the provision of a camera shutter wherein 
the shutter aperture edge part of a shutter base plate or that of a cover 
plate is arranged to solely protrude outward in such a way as to prevent 
shutter blades from being damaged. 
Another aspect of the invention is the provision of a camera shutter 
wherein the shutter aperture edge part of a shutter base plate or that of 
a cover plate is provided with an elastic member which absorbs the impact 
of contact with shutter blades to prevent the shutter blades from being 
damaged. 
The above and other aspects and features of the invention will become 
apparent from the following detailed description of embodiments thereof 
taken in connection with the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A first embodiment of this invention is arranged as shown in FIGS. 1 to 7, 
wherein: FIG. 1 is an oblique view showing in outline a whole shutter 
arranged as the first embodiment. FIGS. 2 and 3 are longitudinal sectional 
views taken across the middle of a shutter aperture part both showing 
shutter blades as under an external pressure exerted from behind them, 
FIG. 2 showing them as in a travel preparing state and FIG. 3 showing them 
as in a state of being set. FIG. 4 is an oblique view showing the shutter 
blades as in a traveling state while being warped by an external force 
exerted from behind them. FIG. 5 is an enlarged partial section view taken 
across the middle of the shutter aperture part showing the shutter as in 
the same state as the state shown in FIG. 4. FIG. 6 is an oblique view 
showing the shutter blades as in a state of having completed their travel 
while being warped by the external force exerted from behind them. FIG. 7 
is an enlarged partial sectional view also taken across the middle of the 
shutter aperture part showing the shutter as in the same state as the 
state shown in FIG. 6. 
Referring to these drawings, a shutter base plate 1 has a shutter aperture 
la formed in the middle of the base plate 1. The base plate 1 is provided 
with shutter aperture bent edge parts 1b and 1e. The bent edge parts 1b 
and 1e represent an essential feature of this embodiment. They are 
arranged to have end parts 1c and 1f bent and extended toward the front of 
the shutter (on the side of the lens and the mirror box of the camera) to 
an extent of not causing any adverse effect on a film exposure and on the 
action of a movable mirror system, which is not shown. The shutter 
aperture 1a is further provided with smooth slanting faces 1d and 1g. 
Further, the above stated bent edge parts 1b and 1e are formed on the edge 
parts of the shutter aperture 1a on the sides thereof located in the 
travelling directions of a trailing blade group 4 which is moving as will 
be described later. The bent edge parts lb and le protrude outward or 
toward the front of the shutter from the shutter aperture edge sides 
located perpendicularly to the moving directions of the trailing blade 
group 4. A cover plate 2 is opposed to the shutter base plate 1 at an 
unvarying distance away from the base plate 1. The cover plate 2 is also 
provided with a shutter aperture 2a which is in a position corresponding 
to the above stated shutter aperture 1a. A leading blade group 3 and the 
above stated trailing blade group 4 are interposed in between the shutter 
base plate 1 and the cover plate 2 across a separating plate 5. The 
separating plate 5 is also provided with an aperture 5a which is located 
in a position corresponding to the aperture 1a. Blade arms 6 and 7 (blade 
arms for the leading blade group 3 are not shown) are arranged in 
combination with a known link device to open and close (blocking and 
unblocking light) the shutter apertures 1a and 2a. Blade dowels 8 are 
arranged to turnably connect the shutter blades to the blade arms. The 
trailing blade group 4 is provided with a slit forming part 4a. The 
leading and trailing blade groups 3 and 4 are arranged similarly to each 
other as blade units. A leading blade driving lever 9 is coupled to the 
blade arms by a pin 9a and is arranged to drive the leading blade group 3 
to open and close by pivoting on a shaft P. A trailing blade driving lever 
10 is coupled to the blade arms by a pin 10a and is arranged to drive the 
trailing blade group 4 to open and close by pivoting on a shaft Q. A 
leading blade driving spring 11 and a trailing blade driving spring 12 are 
respectively arranged to cause their arms 11a and 12a to abut on a pin 9b 
of the leading blade driving lever 9 and a pin 10b of the trailing blade 
driving lever 10. The spring forces of the springs 11 and 12 are exerted 
to turn the driving levers 9 and 10 clockwise on the shafts P and Q. A 
ratchet 13 is provided for adjusting the leading blade driving spring 
force and another ratchet 14 for adjusting the trailing blade driving 
spring force. The stationary arms (not shown) of the driving springs are 
carried by these ratchets. The spring forces are adjusted by turning these 
ratchets round in such a way as to obtain a given shutter curtain speed. 
The positions of these ratchets are arranged to be fixed by means of pawls 
which are not shown. The leading blade driving lever 9 and the trailing 
blade driving lever 10 are arranged to be turned round counterclockwise on 
their shafts P and Q by means of a charging device which is not shown. 
Each of these blade driving levers 9 and 10 is thus shifted from a travel 
completed position shown in FIG. 1 to a travel preparing position and is 
locked in that position by means of a clamping device which is not shown. 
A shutter control device 15 comprises magnets (not shown), etc. which are 
arranged to operate the above stated clamping devices. The device 15 thus 
controls the travel timing of the shutter blades to define an exposure 
time thereby. 
The first embodiment which is arranged in this manner operated as follows: 
When an action start signal is applied to a leading blade controlling 
magnet among shutter time controlling magnets under a condition in which 
the shutter blades are shifted from the travel completed state of FIG. 1 
to the travel preparing state by the charging device (not shown), the 
magnet renders a leading blade clamping lever which is not shown 
operative. This unlocks the leading blade driving lever 9. The leading 
blade driving lever 9 is then caused by the urging force of the leading 
blade driving spring 11 to open the leading blade group 3 by turning round 
clockwise on the shaft P. Then, after the lapse of a given period of time, 
when an action start signal is applied to a trailing blade control magnet 
which is not shown, the trailing blade group 4 begins its closing action 
through a process similar to the process for the leading blade group 3. 
Then an exposure comes to an end with the shutter blades having completed 
their travel. Whereas, in case that the shutter is operated in a state of 
having an external force thereon due to the leader part of the film or air 
pressure exerted on the shutter blades from behind them, the shutter 
blades which have their rigidity lowered by reduction in thickness is 
greatly warped by the external force during the process of the shutter 
operation. However, as shown in FIG. 2, the relation of the warping 
direction of the leading blade group 3 to the overlapped arrangement of 
the blades saves a blade 3d which is located most leeward among the blades 
from completely falling into the inside of the aperture part 5a of the 
separating plate 5. It enables the leading blades to uphold and guide one 
another from the one located leeward. Therefore, the leading blade group 3 
can be operated without any problem even under the above stated condition. 
In the case of the trailing blade group 4, however, a blade which is 
located most leeward and has the slit forming part 4a among the trailing 
blades as shown in FIG. 3 comes to completely fall into the inside of the 
shutter aperture 1a of the shutter base plate 1. Then, the shutter is 
operated with the middle part 4s of the slit forming part 4a and the end 
part 4b of the intermediate blade in a state of somewhat protruding from 
the front surface of the shutter base plate 1. If the shutter is arranged 
like the conventional shutter, the edge of the shutter aperture of the 
shutter base plate 1 would damage the shutter by colliding with the middle 
part 4s when the shutter blades are traveling and with the end part 4b 
when the shutter blades are being set. Whereas, this embodiment is 
arranged to solve this problem as follows. Since the embodiment acts in 
the same manner both when the shutter blades are traveling and when the 
shutter blades are being set in respect to the effect attainable according 
to the invention, the following description covers only the action to be 
performed when the blades are travelling. The middle part 4s is in a state 
of protruding forward somewhat further than the front surface of the 
shutter base plate 1 in this instance as mentioned above. This state is as 
shown in FIGS. 4 and 5. FIG. 5 is an enlarged section taken across the 
middle of the shutter aperture part showing the embodiment as in the same 
state as shown in FIG. 4. Then, the slit forming part 4a of the trailing 
blade group 4 eventually comes to pass near the end part 1c of the bent 
edge part 1b. The end part 1c which virtually serves as one side of the 
shutter aperture 1a in this case is located further forward from the front 
surface of the shutter base plate 1 than the middle part 4s of the slit 
forming part 4a. This arrangement thus prevents the slit forming part 4a 
from colliding with the end part 1c serving as one side of the shutter 
aperture la. Referring to FIG. 6 and FIG. 7 which is an enlarged sectional 
view taken across the middle of the shutter aperture part showing the 
shutter as in the same state as shown in FIG. 6, with the collision thus 
prevented, the shutter blades are allowed to smoothly complete their 
travel being guided by the smooth slanting face 1d of the bent edge part 
1b provided on the shutter base plate 1. 
A second embodiment of the invention is arranged as shown in FIGS. 8 to 10, 
wherein FIG. 8 is an oblique view showing in outline the whole shutter of 
the second embodiment. FIG. 9 is an enlarged partial sectional view taken 
across the middle of a shutter aperture part showing the shutter blades as 
in a state of travelling while being warped by an external force exerted 
from behind. FIG. 10 is another enlarged partial section across the middle 
of the shutter aperture part showing the shutter blades as in a state of 
having completed their travel while being warped by an external force 
which is applied from behind. 
In these drawings, the parts performing the same actions as those of the 
first embodiment described in the foregoing are denoted by the same 
reference numerals. Slanting guide pieces 16 and 17 which represent an 
essential feature of the second embodiment are provided for shutter blades 
and arranged along the upper and lower side ends of the shutter aperture 
1a. Each of the slanting guide pieces 16 and 17 is made of a flexible, 
highly resilient material such as a leaf spring material or a polyester 
sheet material. The guide pieces 16 and 17 have end parts 16a and 17a 
which are located in front of the shutter (on the side of a mirror box of 
the camera) in such a position as to have no adverse effect on a film 
exposing action and on the action of the movable mirror system. The guide 
pieces 16 and 17 also have smooth slanting faces 16b and 17b and are 
secured to the shutter base plate 1 on the side of the blade travelling 
space by means of an adhesive or the like. With the exception of this, the 
rest of the arrangement of the second embodiment is exactly the same as in 
the first embodiment. 
The second embodiment which is arranged in this manner operates as follows: 
Since the essential action of the embodiment is performed in the same 
manner both during the travel of the shutter blades and during the blade 
setting process, the following description covers only the operation to be 
performed while the shutter blades are travelling. Since the second 
embodiment differs from the first embodiment in the state obtained 
immediately before the end of the travel of the trailing shutter blades, 
this part will solely be described here. Like in the case of the first 
embodiment, the shutter blades are assumed to be greatly warped by an 
external force exerted from behind. The trailing blade group 4 is assumed 
to travel then in a state of having the middle part 4s of its slit forming 
part 4a protruded forward slightly further than the front surface of the 
shutter base plate 1. This state is as shown in FIG. 9. The slit forming 
part 4a of the trailing blade group 4 then comes to pass near the shutter 
aperture end part 17a. In this instance, the shutter aperture end part 17a 
is located further forward away from the front surface of the shutter base 
plate 1 than the middle part 4s of the slit forming part 4a of the 
trailing blade group 4. Therefore, the slit forming part 4a never comes to 
collide with the shutter aperture end part 17a and smoothly complete its 
travel along the smooth slanting face 17b of the slanting guide piece 17. 
In this instance, as shown by a two-dot-chain line in FIG. 10, the 
slanting guide piece 17 suitably flexes away from its original position in 
accordance with the movement of the slit forming part 4a in such a way as 
to absorb the impact of contact with the shutter blade. 
In the first and second embodiments described, protruding parts are formed 
along the two edges of the shutter aperture la located in the moving 
directions of the trailing shutter blade group 4. These protruding parts 
are arranged as the bent edge parts 1b and 1e or as the slanting guide 
pieces 16 and 17. The provision of these two protrudent parts, instead of 
one protrudent part, further enhances the safety of the shutter. However, 
the travel of the trailing blade group 4 from the travel preparing 
position (see FIG. 2) to the travel completed position (see FIG. 1) is a 
sole high speed motion that otherwise has the possibility of damaging the 
shutter blade. In actuality, therefore, an adequate result is attainable 
by singly providing the bent end part 1b or the slanting guide piece 17 
solely in the above stated travelling direction of the shutter blades. 
Further, in each of the embodiments described, the bent edge parts 1b and 
1e or the end parts 16a and 17a of the slanting guide pieces 16 and 17 of 
the shutter aperture 1a are arranged to give about the same opening area 
as that of other shutter apertures 2a and 5a. This arrangement, therefore, 
precludes the possibility of causing any undesired eclipse of light coming 
from an object to be photographed. 
In the first and second embodiments described, the slit forming part 4a of 
the trailing blade group 4 is arranged to be located further toward the 
travelling direction than the basic point (cardinal point) of the 
capability of the shutter will be not much impaired. 
Further, in the first and second embodiments, the bent edge parts 1b handle 
or the slanting guide pieces 16 and 17 of the shutter aperture 1a are 
formed to protrude from edges which are located on the sides extending 
perpendicularly to the moving directions of the trailing blade group 4 
(laterally extending without any reference numerals as viewed on FIG. 4). 
In other words, slanting faces 1d and 1g or 16b and 17b are obtained by 
protruding only the edges located in the moving directions of the trailing 
blade group 4. Therefore, each blade of the trailing blade group 4 has its 
longitudinal side spaces always restricted by the above stated 
perpendicular side edges of the shutter aperture. The travelling space of 
the trailing blade group 4 available in the direction of an optical axis 
never widens. The travel of the trailing blade group 4 and its position 
after completion of the travel are thus adequately restricted to preclude 
any problem in terms of the light shielding (light leak preventing) 
capability of the shutter. 
Further, in the first and second embodiments, the bent edge parts lb and le 
or the slanting guide pieces 16 and 17 are provided as the protruding 
parts of the shutter aperture 1a of the shutter base plate 1. In cases 
where the relative positions of the shutter base plate 1 and the cover 
plate 2 are conversely arranged or where an external force is expected to 
be exerted from the lens side of the camera, protruding parts which are 
similar to the bent edge parts 1b and 1e are of course formed at the 
shutter aperture 2a of the cover plate 2. 
As described in the foregoing, in the case of the first or second 
embodiment, this invention is applied to a camera shutter having a leading 
blade group and a trailing blade group, each consisting of divided blades 
which are movably arranged. The invention provides the shutter with a 
structural arrangement whereby the parts protruding from the edges of a 
shutter aperture provided in the shutter base plate or in the cover plate 
effectively prevents the blades from being damaged by colliding against an 
edge part of the shutter aperture even when an external force is applied 
to the shutter blades while the shutter is operating. 
A third embodiment of the invention is arranged as shown in FIGS. 16 to 23, 
wherein: FIG. 16 is an oblique view showing in outline a whole shutter. 
FIGS. 17 and 18 are longitudinal sections taken across the middle of a 
shutter aperture part showing shutter blades as under an external force 
exerted from behind while they are in a state of being prepared for 
travelling in the case of FIG. 17 and in the process of being set in the 
case of FIG. 18. FIG. 19 is a partial oblique view showing the blades as 
in a state of travelling while being warped by the external force exerted 
from behind. FIG. 20 is an enlarged partial section taken across the 
middle of the shutter aperture part showing the shutter as in the same 
state as the state shown in FIG. 19. FIG. 21 is a partial oblique view 
showing the shutter blades as in a state of having completed their travel 
under the external force exerted from behind. FIG. 22 is an enlarged 
partial section taken across the middle of the shutter aperture part 
showing the shutter as in the same state as the state shown in FIG. 21. 
FIG. 23 shows the shutter blades as in a state of having been relieved 
from the external force exerted from behind and resumed its normal 
condition after completion of their travel. 
The following description of the third embodiment is limited to the 
difference thereof from the first embodiment: Referring to FIGS. 16 to 23, 
a shutter base plate 101 is provided with a shutter aperture 101a in about 
the middle part thereof. A shock absorbing elastic member 101b is provided 
along one side edge of the shutter aperture 101a located in the moving 
direction of shutter blades. The elastic member 101b is made of a highly 
flexible, resilient material such as a soft rubber material, Moltoprene or 
the like. An end part 101c of the member 101b forms one side of the 
shutter aperture while a bottom 101d of the member 101b is secured by 
means of an adhesive to one side face of the aperture. A bent edge part 
101e is formed along an edge of the shutter aperture on a side opposite to 
the above stated elastic member 101b. The bent edge part 101e extends 
outward, or toward the front of the shutter (on the side of the lens and 
mirror box of the camera) to have an end part 101f thereof in a position 
not to affect a film exposure to light and the operation of the moving 
mirror system of the camera. The bent edge part 101e has a smooth slanting 
face 101g. 
The third embodiment operates as follows: With the shutter shifted from the 
travel completed position of FIG. 16 and set in a travel preparing 
position by means of a charging device which is not shown, when an 
operation start signal is applied to a leading blade control magnet among 
magnets provided for shutter time control, a leading blade clamp lever 
which is not shown is operated by the magnet to unlock a leading blade 
driving lever 9. This allows the urging force of a leading blade driving 
spring 11 to turn the lever 9 round on a shaft P to open the leading blade 
group 3. 
Then, when an operation start signal is applied to a trailing blade control 
magnet (not shown) after the lapse of a given period of time, the trailing 
blade group 4 begins to perform a closing action through the same process 
as the leading blade group 3. This brings an exposure to an end. The 
travel of the shutter blades comes to an end. However, in case that the 
shutter is operated while an external force is applied to the shutter 
blades from behind the shutter by the leader part of film or some air 
pressure or the like, the shutter blades which have a low degree of 
rigidity due to their reduced thickness come to be greatly warped by the 
external force before the end of the operation. Then, as shown in FIG. 17, 
the relation of the warping direction of the leading blade group to the 
overlapped state of the blades prevents a blade 3d which is located most 
leeward from completely falling into the aperture part 5a of a separating 
plate 5. Among the leading blade group 3, blades uphold one another with 
each leeward blade carrying another blade located right above while they 
are being guided. Therefore, the leading blade group 3 can be operated 
without difficulty. In the case of the trailing blade group 4, a blade 
which is located most leeward among them and has a slit forming part 4a 
comes to fall completely into the shutter aperture 101a as shown in FIG. 
18. The middle part 4s of the slit forming part 4a and the end part 4b of 
a blade intermediately located among the group 4 protrude forward a little 
further than the front surface of the shutter base plate 101 while the 
shutter is in operation. Under such a condition, the conventional shutter 
has been damaged as the edge of the shutter aperture has the middle part 
4s come to collide therewith if the shutter blades are travelling or has 
the end part 4b come to collide therewith if the shutter blades are being 
set. This problem is solved by this embodiment. FIG. 19 shows the shutter 
blades as in a state of travelling with the middle part 4s caused to 
protrude a little further than the front surface of the shutter base plate 
101 under the external force. FIG. 20 is an enlarged sectional view taken 
across the middle of the shutter aperture part showing the shutter as in 
the same state as the state shown in FIG. 19. Referring to FIGS. 19 and 
20, when the slit forming part 4a of the trailing blade group 4 reaches 
the position of the end part 101c, the shock absorbing elastic member 101b 
which is made of a material sufficiently softer than the material of the 
blade is pushed and begins to be deformed. The elastic member 101b is 
further deformed to absorb the impact of the blade until it becomes as 
shown in FIGS. 21 and 22. This allows the trailing blade group 4 to 
complete its travel without damaging the slit forming part 4a. When the 
external force which is exerted from behind disappears, the trailing blade 
group 4 settles in its normal position as shown in FIG. 23. This allows 
the elastic member 101b to come back to its initial state. 
A fourth embodiment of the invention is as shown in FIGS. 24 to 26, 
wherein: FIG. 24 is an oblique view showing in outline a whole shutter. 
FIG. 25 is an enlarged partial section taken across the middle of a 
shutter aperture part showing shutter blades as in a traveling state while 
being warped by an external force exerted from behind. FIG. 26 is a like 
sectional view showing the shutter blades as in a state of having 
completed their travel while being warped by an external force. 
In FIGS. 24 to 26, the parts acting in the same manner as those of the 
third embodiment are indicated by the same reference numerals. The shutter 
is provided with slanting guide pieces 116 and 117, which represent an 
essential feature of the fourth embodiment. The slanting guide pieces 116 
and 117 are provided at the upper and lower sides of a shutter aperture 
101a for guiding shutter blades. These pieces 116 and 117 are made of a 
flexible, highly resilient material such as a leaf spring material, a 
polyester sheet material or the like. They are allowed to extend toward 
the front of the shutter (on the side of the mirror box of the camera 
which is not shown) to have their end parts 116a and 117a located in 
positions not to affect an exposure of film to light and the operation of 
the moving mirror system of the camera. They are provided with smooth 
slanting faces 116b and 117b and are secured to a shutter base plate 101 
by means of an adhesive or the like. The rest of the arrangement of the 
shutter is the same as the third embodiment. 
The fourth embodiment which is arranged in this manner operates as follows: 
The advantageous effect of the embodiment is likewise attained both in 
cases where the shutter blades are travelling and where they are being 
set. Therefore, the following description is limited to the operation of 
the embodiment performed when the shutter blades are travelling. Further, 
since the fourth embodiment differs from the third embodiment only in the 
state obtained immediately before the end of the travel of the trailing 
blade group 4, that part of the operation alone will be described. Like in 
the case of the third embodiment, an external force is assumed to be 
exerted on the shutter blades from behind the shutter. Under this 
condition, the trailing blade group 4 travels in a state of being greatly 
warped to have the middle part 4s of the slit forming part 4a thereof 
protruding a little further than the front surface of the shutter base 
plate 101. This state is as shown in FIG. 25. The slit forming part 4a of 
the trailing blade group 4 comes to pass near the position of the end part 
117a of the slanting guide piece 117. In this instance, the end part 117a 
is arranged to be further forward away from the front surface of the 
shutter base plate 101 than the middle part 4s of the slit forming part 
4a. This enables the trailing blade slit forming part 4a to smoothly move 
along the smooth slanting face 117b of the slanting guide piece 117 and 
comes to complete its travel without colliding with the end part 117a of 
the slanting guide piece 117. At that time, as shown in FIG. 26, the 
slanting guide piece 117 suitably flexes according to the movement of the 
slit forming part 4a to absorb the impact of contact with the shutter 
blade. When the external force applied from behind the shutter disappears, 
the trailing blade group 4 settles in its normal position. As a result, 
the slanting guide piece 117 also comes to resume its initial position as 
shown in FIG. 25 or as shown by a two-dot-chain line in FIG. 26. 
In the third and fourth embodiments described, the end part 101c of the 
elastic member 101b or the end parts 116a and 117a of the slanting guide 
pieces 116 and 117 of the shutter aperture 101a are arranged to let the 
aperture 101a have about the same area as other shutter apertures 2a and 
5a which are provided in the cover plate 2 and the separating plate 5. 
This arrangement, therefore, prevents the object's light from being unduly 
eclipsed by these aperture defining parts. 
Further, the third and fourth embodiments are arranged to provide the 
shutter aperture 101a of the shutter base plate 101 with the shock 
absorbing elastic member 101b or the slanting guide pieces 116 and 117. 
However, in cases where the positional relation between the shutter base 
plate 101 and the cover plate 2 is reversed or where the external force is 
expected to be exerted from the lens side, instead of from behind the 
shutter, the shutter aperture 2a of the cover plate 2 is of course 
provided with a shock absorbing member that is similar to the elastic 
member 101b or the like. 
As described in the foregoing, in the case of the third and fourth 
embodiments, the camera shutter having leading and trailing blade groups, 
each consisting of divided blades which are arranged to be movable is 
capable of preventing the shutter blades from being damaged by colliding 
with an edge part of the shutter aperture even when an external force is 
applied to the shutter blade while the shutter is operating. This 
advantageous feature of these embodiments is attained by virtue of the 
shock absorbing elastic member which is provided at the edge part of the 
shutter aperture formed in the shutter base plate or in the cover plate of 
the shutter.