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Патент USA US2388609

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_ Nov. 6, 1945.
Filed May 17, 1943
Patented Nov. 6, 1945
Arvid I. Ericsson, Chicago, Ill.‘
Application May 17, 1943, Serial No. ‘487,257
7 Claims. (CI. 95-64)
My invention relates to automatic camera
adjuster includes a photoelectric vcell, which is
diaphragm adjusters. That is, it relates to mech
mounted to be in?uenced by the same light con
anism for automatically varying the size of the ,
iris diaphragm opening of a camera in accord
ance with variations in light intensity so that
substantial uniformity of exposure may be se
the photoelectric cell in accordance with changes
in the intensity of light acting upon the cell, step
by-step mechanism for selectively actuating the
Although applicable to so-called. "still picture”
ditions as the camera lens or ?lm, a relay, pref
erably of the galvanometer type, controlled by
diaphragm so that its opening may be contracted
cameras, the invention is likely to have its great- or expanded as conditions require, and relays and
est utility in conjunction with moving picture 10 electrical circuits whereby the response of the
cameras, since in the operation of the latter, the
necessity for or desirability of continuity during
galvanometer to the varying intensity of light
example, during the "taking” of a parade in the
also be provided a manual adjustment whereby
the range of automatic expansion and contrac
tion of the diaphragm opening may be shifted to
accommodate the automatic movements of the
acting upon the photoelectric cell causes the step
the ?lming of some particular scene or occurrence
by-step mechanism to operate in one direction
may render impossible manual diaphragm ad
or the other, depending upon whether the light
justment for change of light intensity. Thus, for 15 diminishes or increases in intensity. There may
open air, the passage of clouds across the sun,
resulting in greater or lesser and possibly fre
quent increases and decreases in light intensity,
or desirable movement of- the camera, which may 20 diaphragm to different general conditions, such
result in shifting of background from light to
as the previously mentioned differences in film
dark objects and vice versa, makes one dia
emulsion speeds, etc.
phragm “setting" incapable of producing uni
. Referring now to the drawing, the size of the
form exposure; and of course, continuity is lost
iris or light opening of the camera may be
if the “taking” is interrupted in order to per 25 changed and governed by‘, the usual diaphragm
mit manual adjustment of the iris opening.
leaves 5 and-an actuating ring 6. In a manner
The principal object of my invention is to
well known in the art, and consequently which
provide a reliable automatic adjustment of dia
needs no illustration or explanation, the clock
phragm so that the iris opening is expanded and
wise and counterclockwise rotation of ring 8 ef
contracted as the light intensity decreases and 30 fects movements of the diaphragm leaves to con
tract or enlarge the central lens or iris opening
Another object is to provide an automatic ad
de?ned by them. Diaphragm ring 6 is provided
juster which can be easily and quickly adapted
with a gear sector l’, the teeth of which mesh with
to different ranges of diaphragm opening so as
the teeth of a pinion 8 so that rotation of the
to accommodate itself to different conditions of 35 pinion in one direction or the other causes the
operation, such as different ?lm-emulsion speeds,
diaphragm ring to move correspondingly, either
shifting between color and black and white pic
to enlarge or to contract the iris opening in the
tures, and differences in general or overall envi
ordinary manner. The shaft of pinion 8 has a
ronment, such for example as the marked con
ratchet wheel 9 rigidly secured thereto. This
trast between taking a picture in dense woods 40 ratchet wheel 9 may be engaged and rotated step
and of a snow scene on a generally sunny day.
by-step either clockwise or counterclockwise by
Another object is to provide automatic ad
pawls I0 and II, respectively. Pawls l0 and H
justment mechanism which, although controlled
are pivotally carried on bell crank armature le
by a photoelectric cell, derives the power for op
vers l2 and I3, respectively, which are mounted
45 upon ?xed pivots l4 and I5, and acted upon by
erating the diaphragm from a diiferent source.
A further object is to provide mechanism in
electromagnets l6 and II, respectively. A pin
corporating elements of currently available
[8, against which a tension spring l9 biases pawl
equipment, such as commercial photoelectric
l0, guides the movements of pawl l0; and in
cells, ordinary ?ashlight batteries and relays.
like manner a pin 20 against which a tensioning
Other objects and advantages will hereinafter 50 spring 2| biases pawl l I guides the movements
of pawl H. Compression springs 22 and 23 bias
The accompanying drawing shows, more or
armature levers I2 and I3, respectively, against
less diagrammatically, a typical embodiment of
the attraction of their respective electromagnets.
my invention.
When the electromagnets are deenergized, the
In general, the preferred embodiment of my 55 springs 22 and 23 retract the armature levers
against a stop 25, and in this condition the guide
pins I3 and 23 insure that both pawls are dis
engaged irom ratchet wheel 9 as shown in the
drawing. However, when either electromagnet
is energized, its armature lever and pawl causes
the ratchetwheel to move a step in a correspond
tact 15 or 11 to interrupt whatever circuit might
otherwise be completed therebetween. I have
found that suilicient power to energize the power
magnets and actuate the diaphragm of an ordi- .
nary amateur moving picture camera may be
ing direction. Thus, when electromagnet I6 is
had from two commercial ?ashlight batteries.
The two spaced galvanometer contacts 33 and
energized, it rotates armature lever I2 in a clock
31 are carried upon one arm of a bell crank lever
wise direction about its pivot I4, causing pawl III
33, which is mounted on a ?xed pivot 3|. The
to engage a tooth of ratchet wheel 9 and rotate 10 other arm of lever 30 has a projection 32 bearing
the ratchet wheel and pinion 3 one step in a
upon the peripheral surface of a cam disc 33
clockwise direction. And when electromagnet I1
which is frictionally retained upon the cylindrical
is energized, the reverse action takes place, viz.,
?ange 34 of diaphragm ring 3 by suitable means,
armature lever I3 is rocked counterclockwise and
such as a pipe clamp 33. As shown, a sector of
ratchet wheel 9 is moved one step in a counter
16 cam disc 33 is provided with an eccentric cam
clockwise direction.
surface 36 which gradually inclines away from
The energization of electromagnets I6 and I1
the axis so that as the cam disc move’; counter
is governed by the action of light upon a photo
clockwise. bell-crank 33 is rocked counterclockwise
electric cell 30 which is mounted adjacent the
about its pivot 3|, and vice versa. Thus depend
iris opening or lens of the camera in such a posi
nt upon the inclination of cam 33 and the location
tion that it is pointed in the same direction and
of projection 32 thereupon, changes may be made
in?uenced by the same light conditions as the
in the angular position of bell crank lever 33
camera lens. I have found that a Weston Pho
with a resultant change in the relation of the two
tronic (Central Scienti?c Co. No. 80915) cell,
galvanometer contacts "-31 with respect to the
which transforms light directly into electrical
of needle contact 35. A biasing spring
_ energy, gives satisfactory results. The terminals 25 31 insures that projection 32 always bears ?rmly
of photoelectric cell 30 are connected by wires 3|
upon cam surface 33 so that the bell crank lever
and 32 to the opposite terminals of the movable
rocks clockwise or counterclockwise as the cam
armature coil 33 of a sensitive galvanometer re
disc moves one way or the other, as will be pres- ’
lay 34. For this purpose, I have successfully
ently explained, in response to changes in light
used a Weston model 334 DC (Central Scienti?c 30 intensity.
Co. No. 80920) ‘galvanometer. The galvanometer
A worm 95 formed as a part oi’ adjusting stem
armature 33 carries a needle 35 which is posi
96 is journaled in a bracket 31 carried by dia
tioned between two ?xed contacts 36 and 31 and
phragm ring 6 and meshes with a gear segment 33
directionally biased by a small hair spring (not
formed in the periphery oi’ cam disc 33. Rotation
shown) toward contact 36. The voltage gen
of stem 96 enables relative movements in both
erated by the action of light on cell 33 is directly
clockwise and counterclockwise directions be
proportional to the intensity of the light and the
tween diaphragm ring 5 and cam disc 33. If de
de?ection of the armature of galvanometer 34
sired, vdiaphragm ring 3 may be provided with a
is directly proportional to the voltage impressed
40 pointer I33 movable over a scale calibrated to
thereon by cell 30. 'The spacing of contacts 33
the various iris openings, e. g., “F stops”; and like
and 31 is ?xed, but they are mounted so that
wise cam disc 33 may be equipped with a pointer
their relation to the movable contact or needle 35
IUI movable over a scale indicative, for example,
may be changed in a manner 'and for a purpose to
of emulsion speeds of ?lms. The adjusting stem
be later explained.
96 may, as desired, be located either inside the
The ?xed contacts 36 and 31 of galvanometer 45 camera casing or outside of it, depending upon
34 are connected by wires 45—46 and 41-43 re
whether it‘ is considered preferable to have the
spectively to one terminal of the winding of re
adjustment more or less accessible.
lays 49 and 53; the other terminals of the wind
In order to prevent inductive discharges, which
ings of these relays are connected by wires 5i
50 may be caused by the opening of the circuits of
52-53 and 54-—55—53, respectively, to one side
electromagnets 43 and 53, creating objectionable
of a battery 60. The other side of battery 60 is
sparking at the galvanometer contacts, the coils
connected through a switch 6i and wires 62—63
of these magnets may be bridged by small con
to the movable-needle contact 35 of galvanometer
densers I33 and I34. respectively.
34. Thus, with switch 6| closed, the movement 56 Switch iii, the closing of which initiates the
of needle 35 into engagement with contact 36 en
operation of the automatic iris-opening adjuster,
ergizes relay 49 over the circuit 63—6 I —62-63
is preferably of the push button type. It may, as
35-36-45-46-49-5l-52-53 back to bat
desired, be associated with the button which con
tery 63. And when the needle 35 engages con
trols the feeding of the ?lm and the action of
tact 31, the relay 50 is energized over the cir
the camera shutter so that both the camera and
cuit 60-6I-62_63-35—31-41—43-5Il-54the adjuster start functioning at the same time;
55-53 back to battery 60.
or this button may be independent of the camera
Upon energization, relay 49 closes its contacts
10-1I to complete a circuit for electromagnet I6
The operation will now be reviewed. If, upon
over the path from battery 63 through switch GI 65 the closing of switch 3 I, the effect of the light upon
and over the path 64-1I--'|0—12, the coil of
cell 30 is such that the voltage generated thereby
magnet l6, conductor 13, the contacts 14-15 of
is su?lcient to enable the galvanometer arma
magnet I3, wire 16 which interconnects contacts
ture to overcome the force exerted by its biasing
15 and 11 of magnets I6 and I1 respectively, and.
spring so as to move the needle 35 out of engage
wires 19-55-53 back to the battery. Contacts 70 ment with the contact 33, but insu?lcient to en
14 and 18 are related to the armatures of electro
a'ble the armature to move the needle into en
magnets I6 and I1, respectively, in such a way
gagement with contact 31, no energizing circuit
that when either electromagnet is energized, the _ will be completed and the apparatus will remain
armature l‘ever thereof causes the associated con
inactive. Under such conditions, the iris opening
tact 14 or 18 to separate from companion con 75 is proper for the intensity of light existent.
Assuming now that the light intensity for some
reason diminishes, for example, a cloud obscures
until the action of cam 66 is such that contact
the sun or the camera is moved to point toward a
which the galvanometer biasing spring can move
needle 35 against the counter armature turning
darker background. The diminished intensity ‘of
light causes the photoelectric cell to generate a
lower voltage with the result that the hair’ spring
acting upon' armature 33 rotates it to swing needle
35 against contact 36. As soon as needle 36 en
gages contact 36, a circuit is completed for relay
36 has been moved beyond the range through
force of the voltage generated by cell 30 under
a particular light intensity. Thereupon the sep
aration of needle 35 and contact 36 opens the en
ergizing circuit for relay 49 and the step-by
step_ diaphragm-opening movements cease be
46 from battery 60, switch 6|, conductors 62-63, 10 cause the opening corresponds to the existent light
needle 35, contact 36, conductors 45-46, the coil
of relay 49, and the conductors 5l-52 and 53 back
Ii’, on the other hand, the light intensity at
to the battery. Relay 6! is thereupon energized
any time increases, the higher voltage generated
and its contacts ‘Hi-1| close. The closure of
by photoelectric cell 38 causes the galvanometer
these contacts completes a power circuit for actu 15 needle 35 to engage contact 31. The engagement
ating magnet l6 over a circuit from the battery
of contacts 35-31 completes a circuit through
through switch 6|, conductor 64, contacts ‘II-10,
relay 50 over the circuit from battery 60, switch
conductor ‘I2, the coil of magnet l6, conductor ‘I3,
6|, conductor .62-63, needle 35, contact3‘l, con
contacts ‘ll-‘l5, conductors 16-19-55 and 53
ductors 41-46, the winding of relay 50 and con
back to the battery. The resultant energization 20 ductors 54-55-53 back to the battery, with the
of magnet l6 performs two functions in sequence.
result that its contacts Nil-I05 are closed. The
First, it causes its armature lever i2 and pawl ID
closing of relay contacts Ind-I05 completes a cir
to advance and rotate ratchet wheel 6 one clock
cult through power magnet I‘! over the path from
wise step. This clockwise advance of ratchet
battery through switch 6|, conductor 62, relay
wheel 9 causes pinion 8 and gear sector ‘I to 25 contacts IDS-I84, conductor I06, the winding of
rotate diaphragm ring 6 through 3. correspond
magnet ll, conductor I01, magnet contacts
ing arc in a counterclockwise direction, which
18-", and conductors 16-19-55-53 back to
opens the diaphragm a corresponding amount to
the battery.‘ The energization of power magnet
let more light go through the camera lens. Sec
i1 produces two effects in sequence, just as has
ond, it causes contacts 14-15 to separate to 30 been described in connection with magnet l6.
interrupt the circuit through magnet 16 even
First, it causes pawl H to rotate ratchet wheel 9
though the contacts 35-36 at the galvanometer
in a counterclockwise direction; and second, it
remain together and as a result relay 49 remains
effects the separation of its contacts ‘ll-18. The
energized. Thus, the magnet l6 effects its own de
rotation of ratchet wheel 9 in a counterclockwise
energization after it has caused the ratchet wheel 3. direction causes pinion 8 and gear segment ‘I to
to advance a step, whereby its pawl I0 is retracted
rotate diaphragm ring 6 and cam disc 83 through
preparatory to producing another step, and con
a small arc in a clockwise direction. This move
tinuance of step-by-step operation is insured until
ment of the diaphragm ring closes the iris open
the proper diaphragm adjustment is made. In
ing a corresponding amount and the movement
addition to the increment opening of the dia 40 of cam disc 83 causes a lower part of cam surface
phragm, the step of counterclockwise movement
86 to be presented in contact with projection
of the diaphragm ring 6 also causes cam disc 83
82. Therefore, biasing spring 81 moves bell crank
to move counterclockwise through a small arc
lever 60 to the right or in a clockwise direction,
with the result that projection 82 of bell crank
which tends to move contact 31 beyond the range
lever 80 contacts a higher portion of cam surface 45 of the deflection of needle 35 caused by the volt
86. The result is that bell crank lever 80 is rocked
age generated in cell 30 under the particular light
slightly in a counterclockwise direction to move
intensity then existent. Such increment closing
contact 36 slightly in the same direction as the
of the diaphragm opening continues until the re
galvanometer spring is tending to move the arma
lation of cam 86 and projection 82 are such that
ture and needle 35-i. e., to the left. And if this 50 contact 31 has been moved beyond the range
movement of contact 36 is sufficient to separate it
from needle 35, no further operation ensues, be
cause the diaphragm has been opened by the one
step an amount su?lcient to compensate for the
decrease inlight intnsity. However, if the light
intensity affecting cell 36 is so low that the voltage
generated therein is insu?lcient to balance the
action of the coil spring acting upon the arma
through which the photoelectric cell voltage cre
ated by the present light intensity can swing
needle 35, whereupon movement ceases, because
the diaphragm opening then corresponds to the
light intensity acting upon the photoelectric cell.
Thus, during the “taking” of a picture, the dia
phragm opening will expand and contract auto~
matically in accord with variations in light in
ture. and as a result needle 35 is swung to the
just as long as control switch 6! remains
left further than the ?rst step movement of cam 60 tensity
surface 86 has moved contact 36 in the same direc
Under some conditions, it may be desirable that
tion, then the engagement of needle 35 and con
tact 36 persists and relay 49 remains energized
the range of the expanding and contracting of
the diaphragm opening be shifted. In other
with its contacts ‘HI-‘II closed. Then, as soon
as spring 22 of power magnet I6 has retracted 65 words that, for example, the minimum opening
and also the maximum opening to which the auto
armature lever l 2 so that pawl ID has disengaged
matic adjuster can move the diaphragm leaves
ratchet wheel 9 and contacts 14-15 are again
be reduced in size. Such a change may be ad
engaged, the energizing circuit for magnet 16 is
visable to secure the best results if extremely high
re-established and thereby another step of dia
speed ?lm is substituted for much less sensitive
phragm opening is produced and cam 86 presents
?lm. Or if, for example, color ?lm is substituted
a still higher level to projection 82-the latter
for the more rapid black and white ?lm, a shift
condition resulting in contact 36 being moved an
in the opposite direction may be desirable to pro~
additional small increment to the left. Such
duce the most satisfactory pictures from an ex
step-by-step movements continue-the dia
posure standpoint. The desirable shift in the
phragm opening being enlarged more and more
75 range of iris operation may be brought about by
4 .
altering the relative positions of diaphragm ring
circuit individual to and closable by each relay;
6 and cam disc 83. Such alterations of relative.
an electromagnet in each power circuit; and dia
phragm actuating mechanism operable in one
direction by one electromagnet and in the oppo
position are e?ected by turning the adjusting
stem 86 in one direction or the other, depending
upon whether the shift is to be toward smaller
site direction by the other electromagnet, said
or larger diaphragm openings at opposite ends
diaphragm actuating mechanism including cam
of the automatic expansion and contraction.
means to actuate the contact mounting means to
of ggirse, similar results may be obtained by
move the pair of galvanometer contacts in the
the use or appropriate ?lters in lieu of such a
same direction as the de?ection of the galvanom
10 eter armature.
mechanical shift 01' range.
By the use of sensitive low power relays in the
3. In a camera having the usual adjustable
galvanometer circuits to control heavier duty
diaphragm to provide exposure openings of dif
magnets deriving power from batteries?such as
ierent sizes, the combination of step-by-step
ordinary ?ashlight batteries-it is unnecessary
mechanism for expanding and contracting the
to depend upon the photoelectric cell- to deliver 15 diaphragm opening, a photoelectric cell respon
more than very small currents. This is a matter
sive to the light conditions to which the camera
of importance with present day photoelectric cells
lens is subject, a galvanometer connected to the
of the voltage generating type because, as far as
cell so that the armature moves in accord with
I am aware, they are incapable of delivering much
voltage changes created in the cell by light in
power-enough satisfactorily to operate the usual 20 tensity changes, 'a contact carried by the gal
camera-diaphragm mechanism. A further ad
vanometer armature, a pair of spaced contacts,
vantage ?ows from the interposition of extrane
one on each side of the armature contact and
ously powered mechanism-especially step-by
selectively engageable thereby depending upon
step mechanism—between the photoelectric cell
whether the light intensity acting on the cell in
control and the diaphragm, via, a lessening of 25 creases or decreases, means mounting the pair of‘
the tendency for constant variation in iris open
spaced contacts, means movable with the camera
ing which might result in more or less fogging
diaphragm and by the step-by-step mechanism
of the negatives. Thus, although the apparatus
may be su?iciently sensitive to produce substan
for moving the contact mounting means in oppo
site directions, a relay connected to each of the
tially uniform exposure, it is not so supersensitive 30 spaced contacts, both being connected to the
as to be affected by light variations which are
armature ‘contact so that one or the other relay is
of no consequence as far as ?lm exposure is con
energized depending upon-Which of the spaced
contacts is engaged by the armature contact, a
The automattic adjuster mechanism which I
pair of operating electromagnets operatively as
have herein speci?cally described, lends itself 35 socaited with the step-by-step mechanism so as
readily to construction as an attachment for dia
to operate the same in opposite directions, and
phragm control of present day standard cameras,
a circuit between each relay and one of the op
or it may be built in‘ as an integral part of a
special camera.
erating electromagnets closable by the energize.
Letters Patent is as in?ows:
the diaphragm opening when moved in opposite
tion of the corresponding relay, and a source of
Having illustrated and explained the nature 4;) electrical power for said circuits.
and a typical embodiment of my invention, what
4. An automatic camera-diaphragm adjuster
I claim and desire to secure by United States
including a ratchet which expands or contracts
1. In a camera having the usual adjustable
directions; a pair of electromagnets, each oper
diaphragm to provide exposure openings of dif 45 ating a pawl which moves the ratchet in one of
ferent sizes, the combination of a photoelectric
its two directions of movement: a pair of relays,
cell responsive to the light conditions to which
each having contacts for closing a circuit for one
the camera lens is subject, a galvanometer con
of the electromagnets; a galvanometer having an
nected to the cell so as to de?ect in accord with
armature carrying a movable contact, and two
variations of voltage generated by the cell under 50 relatively ?xed contacts, one engageable by the
_ varying light intensities, step-by-step mechanism
movable contact upon de?ection of the armature
in opposite directions to close a circuit for one or
for actuating the camera diaphragm, said mech~
anism being responsive to de?ections of the gal
vanometer, a source of power for actuating the
step-by-step mechanism, cam means movable 65
with the camera diaphragm, and means actu
direction of armature de?ection; a photoelectric
cell subject to the same light conditions as the
ated by the cam means to cut off the source of
the galvanometer so as to effect de?ections there
power from the step-by-step mechanism when
the diaphragm opening is proper for the existing
of in accord with changes in light intensity; a
mounting for the two relatively ?xed contacts
movable to shift the contacts in either direction
relative to the armature contact; and means op
eratively connected with the contact mounting
light conditions.
2. In a camera having the usual adjustable dia
phragm to provide exposure openings of different
sizes, the combination of a photoelectric cell re
sponsive to light conditions to which the camera
lens is subject; a galvanometer having its arma
ture'connected to the cell so as to de?ect in ac
cord with variations in voltage induced by light
the other of the two relays depending upon the
camera lens and connected to the armature of
and with the ratchet to move the mounting in one
direction or the other so as to alter the relation
between the ?xed and movable contacts of the
5. In a camera having the usual adjustable
intensity variations acting on the cell, and hav
diaphragm to provide exposure openings of dif
ing a movable contact carried by the armature,
ferent sizes, the combination of an actuator mov
and a pair of ?xed contacts, one engageable by 70 able in opposite directions for operating the dia
the movable contact when the armature de?ects
phragm to change the size of the opening; a pair
in opposite directions; means mounting said ?xed
of electromagnets, one for moving the actuator in
contacts for movement together; a pair of relays,
each direction; a photoelectric cell subject to the
each in circuit with the movable contact and one
same light conditions as the camera lens; a gal
of the ?xed contacts of the galvanometer; a power
vanometer having a movable armature electrically
connected to the cell, a movable contact carried by
the armature, and a pair of relatively ?xed con
tacts, one located on each side oi! the movable
contact to be selectively engaged thereby depend
ing upon the direction of de?ection of the arma
ture; means interposed between the galvanometer
contacts and the electromagnets whereby de?ec
tions of the galvanometer armature in opposite
directions can selectively effect energization of
energization of one or the other oi.’ the electro
magnets; a mounting for the two ?xed galva
nometer contacts movable to shift their position
in either direction relative to the ?xed contact;
a cam movable with the diaphragm actuator and
operatively associated with said mounting to move
the latter in one direction or the other depend
ing upon the direction of movement of the actu
atm- and thereby causing the ?xed contacts of the
one or the other of the electromagnets; a mount 10 galvanometer to shift position relative to the mov
ing for the two ?xed galvanometer contacts mov
able contact: and means for altering the relation
able to shift their position in either direction
between the cam and the diaphragm actuator.
relative to the ?xed contact; and a cam movable
7. In a camera having the usual adjustable
with the diaphragm actuator and operatively as
diaphragm to provide exposure openings of dif
sociated with said mounting to move the latter in 15 ferent sizes, the combination of a photo-electric
one direction or the other depending upon the
cell responsive to light conditions to which the
direction of movement of the actuator so as to
camera lens is subject, a galvanometer including
alter the relation between the ?xed and movable
a pair of relatively fixed but movable contacts and
contacts of the galvanometer.
a movable contact, said galvanometer being con
6. In a camera having the usual adjustable 20 nected to the cell so as to de?ect in accord with
diaphragm to provide exposure openings of dif
variations in voltage induced by light changes
ferent sizes, the combination of an actuator mov
acting upon the cell, mechanism for actuating
able in opposite directions for operating the dia
the camera diaphragm to expand and contract
phragm to change the size of the opening; a pair
the opening therethrough, electric circuit means
of electromagnets, one for moving the actuator 25 including the ?xed and movable contacts selec
in each direction; a photoelectric cell subject to
tively responsive to de?ections in opposite direc
the same light conditions as the camera lens; a
tions of the galvanometer and being connected
galvanometer having a movable armature elec
to operate the diaphragm actuating mechanism,
trically connected to the cell, a movable contact
cam means movable with the camera diaphragm
carried by the armature, and a pair of relatively 30 and by the diaphragm actuating mechanism, and
?xed contacts, one located on each side of the
a cam follower connected to the relatively ?xed
movable contact to be selectively engaged thereby
contacts and actuated by the cam to maintain in
depending upon the direction of de?ection of the
open condition the electric circuit means when
armature; means interposed between the gal
the diaphragm opening is proper for the exist
vanometer contacts and the electromagnets
whereby de?ections of the galvanometer arma
ture in opposite directions can selectively e?ect
‘ ing light conditions.
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