Sept. 27, 1960
`
`Filed Jan. 23, 1958
`
`A. F. ARSON
`PHOTOGRAPHIC SHUTTER
`
`2,953,983
`
`7. Sheets-Sheet
`
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`Ex.1043 / Page 1 of 19
`TESLA, INC.
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`

`

`Sept. 27, 1960
`
`Filed Jan. 23, 1958
`
`A. F. Larson
`PHOTOGRAPHIC SHUTTER
`
`2,953,983
`
`7. Sheets-Sheet 2
`
`
`
`Ex.1043 / Page 2 of 19
`TESLA, INC.
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`

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`Sept. 27, 1960
`
`A. F. LARSON
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`2,953,983
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`
`
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`Ex.1043 / Page 3 of 19
`TESLA, INC.
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`

`

`Sept. 27, 1960
`
`Filed Jan. 23, 1958
`
`A. F. ARSON
`PHOTOGRAPHIC SHUTTER
`
`2,953,983
`
`7. Sheets-Sheet 4
`
`
`
`Ex.1043 / Page 4 of 19
`TESLA, INC.
`
`

`

`Sept. 27, 1960
`Sept. 27, 1960
`
`A. F. Larson
`A. F. LARSON
`PHO
`C SHUTTER
`
`2953,983
`2,953,983
`a
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`_Ex.1043 / Page 5 of 19
`TESLA,INC.
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`Ex.1043 / Page 5 of 19
`TESLA, INC.
`
`

`

`Sept. 27, 1960
`
`Filed Jan. 23, 1958
`
`A. F. LARSON
`PHOTOGRAPHIC SHUTTER
`
`2,953,983
`
`7. Sheets-Sheet 6
`
`
`
`Ex.1043 / Page 6 of 19
`TESLA, INC.
`
`

`

`Sept. 27, 1960
`
`Filed Jan. 23, 1958
`
`
`
`A. F. Larson
`PHOTOGRAPHIC SHUTTER
`
`2,953,983
`
`7 Sheets-Sheet 7
`
`Ex.1043 / Page 7 of 19
`TESLA, INC.
`
`

`

`United States Patent Office
`
`2,953,983
`Patented Sept. 27, 1930
`
`1.
`
`2,953,983
`PHOTOGRAPHC SHUTTER
`Alfred F. Larson, Halesite, N.Y., assignor to Systems
`Associates, Inc., Huntington Station, N.Y., a corpora
`tion of New York
`Filed Jan. 23, 1958, Ser. No. 710,698
`19 Claims. (C. 95-63)
`
`10
`
`15
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`2
`tached a small strip of material having magnetic proper
`ties, for example, iron or steel. This strip may be referred
`to as an armature.
`Each leaf is individually powered by its own individual
`spring.
`In one embodiment, each leaf is connected to the next
`leaf by a link, for the purpose of maintaining leaf-to-leaf
`position control. The forces applied to these links are
`determined by the difference in the forces applied by the
`individual springs to the individual leaves directly; that
`is, this arrangement is in this respect radically different
`from arrangements in which power from a single central
`source is applied through links to all the leaves. Because
`of the individual powering of the leaves in the arrange
`ment proposed, the links do not carry high forces, and
`they can be of much lighter weight than they would be
`if the arrangement just referred to were employed.
`Although in the past, individual springs for each leaf
`have been proposed, the latching and stopping arrange
`ment has commonly been of a mechanical type, and this
`has produced serious problems because of the need for
`simultaneous releasing of each leaf. If the release were
`not simultaneous, harmful reactions would occur between
`the leaf elements, because of the high stress and a general
`slowing down of the action.
`In the arrangement proposed in the present application,
`on the other hand, a magnetic latching or holding means
`is employed in combination with individual powering of
`the leaves. For this, there is provided in the plate, at
`locations opposed to the armatures carried by the leaves
`when the leaves are in the latched position, what is here
`referred to as a magnetic slot, including a magnetic pole
`piece, energized by an associated electromagnet. Thus, in
`the A blade system, for example, the leaf system is me
`chanically closed, and current is applied to the coils of the
`electromagnets which energize the magnetic latching slots.
`This causes the armature carried by each leaf to be at
`tracted to the plate by more than sufficient force to hold
`each leaf in position against the spring tending to pull
`this leaf open.
`An important feature is that this magnetic latch is ef
`fective over a large area, and this eliminates the need for
`close tolerances which would be required if the system
`were to be latched mechanically.
`To trip the leaf system, the circuits supplying current
`to the coils of the holding electromagnets are opened.
`This causes the magnets to release the armatures, thereby
`allowing the springs to move the leaves toward their other
`position.
`The spring system is arranged to preload all the leaves
`in their pivot bearings, and no backlash or lost motion ex
`ists in any part of the moving system.
`When the magnetic circuits are open, there is pro
`duced an exceptionally Smooth but fast simultaneous ac
`celeration of each leaf to high speed, without shock or
`noises.
`To brake the leaves to a complete, fast stop, simul
`taneously and without interaction of all the leaves in
`the system, there is provided a novel magnetic braking
`system. The armatures carried by each leaf encounter
`a second area of high magnetic flux just prior to the
`point where the leaves reach their desired end positions.
`The magnetic action forces the armature against the base
`plate, and produces a very high frictional force which
`brakes the motion of the leaf. This results in a very
`fast stopping of all the leaves in the desired position with
`out the application of high stress to any part of any leaf
`or other link system. The distribution of the braking
`over a wide area, and the individual braking of the
`leaves, provides a gentle but positive braking. This is
`far Superior to a central braking arrangement, the effect
`of which must be transmitted through links to the leaves.
`
`This invention relates to photographic shutters.
`It is particularly applicable to shutters of the type used
`with long focal length lenses with wide apertures, such
`as those used, for example, in aerial cameras.
`In one of its forms, the invention is applicable to a
`shutter mechanism of the type using two exposure control
`20
`leaf or blade systems, actuated sequentially. First, one
`leaf system uncovers the lens aperture; then, after the ap
`propriate exposure interval, the other leaf system closes
`the lens aperture.
`The first of these systems, for example, the one located
`toward the front of the camera, may conveniently be re
`ferred to as the A leaf or blade system, and the second
`as the B system.
`One problem of shutters heretofore existing is that they
`are complicated mechanisms, and to work properly, the
`various parts must be very accurately dimensioned, with
`tight tolerances. Because of the necessary tight toler
`ances, the adjustment of the shutter is difficult and time
`consuming. The adjustment should be such that the parts
`neither bind nor operate loosely, because looseness seems
`to be a main cause for destruction of or damage to the
`various parts, by the impact shocks which occur when the
`shutter. is operated. That is, very high forces have been
`required to produce fast action of the shutter, but these
`high forces have produced high impact shocks, which are
`accentuated by looseness in the parts of the shutter.
`The violent impact shocks existing in shutters hereto
`fore not only produced noise, but produced motion of the
`camera during exposure and tended dynamically to de
`grade the photographs.
`45
`Despite the need for faster exposure, and despite the
`desire to improve existing shutters, particularly to speed
`them up, improvements in the speed of operation have
`been relatively small for many years.
`An object of the present invention is to solve these and
`related problems by providing a shutter mechanism which
`is simple in structure, capable of faster operation than
`existing shutters, quiet, substantially shockless, efficient in
`operation, easy to assemble with minor adjustment, which
`does not require close tolerances, can readily use inter
`changeable parts, and which is less expensive than previ
`ous shutters.
`The shutter provided by the present invention represents
`a complete break-through in the art, is a radical departure
`from previous designs and produces a new and surprising
`type of operation.
`As contrasted with previous shutters, it contains only
`a small fraction of the number of moving parts which
`operate for the control of exposure.
`The invention is illustrated in an embodiment in which
`the shutter includes two apertured plates, each carrying
`a set of spring-actuated leaves or blades. The springs for
`one set of leaves bias the leaves toward an open position,
`and the springs for the other set of leaves bias the leaves
`toward a closed position.
`The individual leaves are preferably made of light
`weight material, for example, aluminum, to which is at
`
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`Ex.1043 / Page 8 of 19
`TESLA, INC.
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`20
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`3.
`The shutter of the present application provides many
`very important advantages, a number of which will be
`discussed at subsequent points in the description.
`In addition, there is also described in this application
`a novel system, including circuits, for controlling and
`actuating, in proper timed relation, the latching, releasing
`and braking of the two sets of leaves.
`Further objects, features, advantages and embodi
`ments of the invention will appear from the more de
`tailed description set forth by way of illustration, which
`will now be given in conjunction with the accompanying
`drawings, in which:
`Fig. 1 is a longitudinal sectional side view through the
`shutter, including an A leaf system toward the front of
`the camera (in the upper part of the figure), and a B
`leaf system (in the lower part of the figure). Certain
`parts are broken away for clarity,
`Fig. 2 is a view of the B leaf system in closed, tripped
`position, as seen from a position between the two sets of
`leaves. The point of view of Fig. 2 is indicated at 2-2
`in Fig. 1,
`Fig. 2A is an enlarged sectional view through a braking
`slot in the supporting plate for the B leaf system, the sec
`tional plane being shown at 2a-2a in Fig. 2,
`Fig. 3 is a view of the B leaf system, as seen from the
`rear, as indicated at 3-3 in Fig. 1, in closed, tripped
`position,
`Fig. 4 is a view of the B leaf system, in open, reset
`position, as seen from the same viewpoint as that of
`Fig. 2,
`Fig. 5 is a view of the A leaf system, in open, tripped
`position, as seen from the point of view indicated at
`5-5 in Fig. 1,
`Fig. 6 is a schematic diagram showing circuits and
`other components for controlling the resetting, tripping
`and braking of the two sets of leaves;
`Fig. 7 is a schematic circuit diagram used in explain
`ing how a single manual control can actuate and con
`trol, in proper timed relation, the tripping and braking
`of the two sets of leaves;
`Figure 7A is a schematic circuit diagram of one form
`of the timer shown in block diagram form in Figure 7;
`Figures 8 through 12 are fragmentary, partially dia
`grammatic views of representative leaves, as seen from
`the same viewpoint as that of Figure 4, together with
`associated components constructed in accordance with
`various other illustrative embodiments of the invention;
`Figures 13 and 14 are fragmentary, partially diagram
`matic views of certain alternative magnetic means in
`accordance with the invention, as seen from the same
`viewpoint as that of Figure 3; and
`Figure 15 is a view of a portion of a single leaf sys
`tem, as seen from the same viewpoint as the system
`shown in Figure 5.
`W
`m
`In the description of the embodiment illustrated in the
`drawings, the rear or B Set of leaves, and associated com
`ponents, will be described first, then the A set. There
`after, there will be described the apparatus for resetting
`and releasing the two sets of leaves.
`Both sets of leaves appear in Fig. 1, within a housing
`2, Schematically represented in broken lines. The front
`of the camera is toward the top of this figure. Conse
`quently, the A set of leaves is the top set, and the B
`set is the lower set, in this figure. Interposed between
`the two sets of leaves is an apertured plate 4.
`The B set of leaves
`As seen in Fig. 2, there is provided a base plate 10,
`of magnetic material, for example, steel, including an
`aperture 22, and five leaves 4, movable to an open posi
`tion, as shown in Fig. 4, and to a closed position, as
`shown in Fig. 2. When in the closed position, the
`leaves overlap with one another so as to close the aper
`ture. The main body portion of these leaves is of light
`weight material, for example, aluminum. This main
`
`2,953,983
`4.
`body portion thus need not be of magnetic material.
`On the other hand, it may in some embodiments be of
`magnetic material, for example, thin steel.
`The leaves 14 include bearings and are mounted for
`5 pivotal motion on pivots affixed to the plate 10. Each
`of these pivots terminates in an enlarged portion 20, for
`retaining the leaves.
`Coupling each of the leaves to the next one, there
`are provided links 22 rotatably affixed at their ends to
`10 the leaves, by pins 24 shaped to receive the links and
`having enlarged heads.
`The leaves are individually powered. That is, there
`is provided, for each individual leaf, a spring 28, ar
`ranged in this B. set of leaves, to urge the leaf toward
`l5 its closed position.
`Carried on the base plate 10, and arranged so that
`it may rotate a limited distance, there is provided a ring
`30, guided by ring bearings 32, which are rotatably
`mounted on pivots 34.
`.
`?
`?
`One end of each of the springs 28 is attached to its
`leaf at a pin 36. The other end is attached to the ring
`30 at a pin 38.
`The position of the ring 30 shown in Fig. 2 is its nor
`mal position. For resetting the set of leaves, means are
`25 provided for shifting the ring 30 in a counterclockwise
`direction. For this purpose, pivotally attached to the
`ring at one end there is provided a reset link 40. The
`other end of this link is pivotally carried on a crank pin
`42 which comprises a projection on a gear 44. The gear
`30 44 in turn is driven by a reset pinion gear 45.
`Affixed to each of the leaves, as an extension project
`ing outwardly, is an armature 46, of magnetic material,
`for example, steel.
`W
`To cooperate with each of the five armatures 46, there
`35 are provided in the base plate 10, latching magnetic
`slots 48, one for each of the leaves, positioned so that
`the armature 46 will be opposed to its slot 48 when the
`leaf is in its open position, as shown in Fig. 4. There
`are also provided a set of braking magnetic slots 50, one
`40 for each leaf, positioned so that the armature will be
`opposed to its slot 50 when the leaf is in its closed posi
`tion. The details of the construction of the magnetic
`slots, and their associated components, and the means for
`energizing and de-energizing them will be described in
`45 detail at a subsequent point.
`To reset the leaves, the reset pinion 45 is rotated in a
`counterclockwise direction, which then rotates the gear
`44 in a clockwise direction. As the gear 44 rotates
`through 180 degrees from approximately the starting
`50 point shown in Fig. 2, it acts through the link 40 to shift
`the ring 30 in a counterclockwise direction. In order
`that this motion of the ring may move the leaves to the
`open position, there are carried on the ring a set of arms
`55 52, one associated with each of the armatures 46. These
`arms 52 are of firm but resilient material, such as a strip.
`of steel, adapted to be resilient against bending. One
`end of each arm 52 is attached to the ring 30 at a pin
`54. There are also provided on the ring pins 56 located
`on either side of the arms 52 for bracing them. The
`60 arms each carry a small cylinder or button 57 on their
`inner end, for pushing against the opposed armature 46
`when resetting the leaves. When the ring is moved in a
`counterclockwise direction, the arms 52, acting through
`these cylinders 57, push the leaves open (counterclock
`65 wise) to the latched position. That is, each leaf of the
`B set of leaves will be thus pushed open to a position
`where its armature 46 is opposite its latching magnetic.
`slot 48.
`More particularly, the arms 52 push the armatures 46
`70 counterclockwise until this motion of the armatures is
`checked by stop pins 59. These stop pins are carried on
`the plate 10 at such positions that when the armatures.
`46 are pressed against them, the armatures will lie over
`the latching magnetic slots 48. The arms 52 being of
`75 firm but resilient material, the ring 30 provides sufficient
`
`// 1
`
`Ex.1043 / Page 9 of 19
`TESLA, INC.
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`5
`Övertravel to make certain that all the armatures definite
`62, 64 and 66 are of magnetic material. Details of a typi
`ly are brought to the correct latched position, over the
`cal slot, and an associated armature 46, are shown in
`latching magnetic slots.
`Fig. 2A. (Although the slot is in this figure a braking
`Because the latching and braking forces are applied
`slot, the construction is generally the same as for a latch
`through the armatures to the leaves, it is important that
`ing slot. At a later point there will be pointed out certain
`the armatures be firmly secured to the leaves. In one
`advantageous constructional features peculiarly applica
`arrangement, each armature is riveted to its leaf at four
`bles to the braking slots.) The end of the member 66,
`points. For example, these points may be in the regions
`which is sometimes referred to as a magnetic clutch pole
`near the pin 36, the pins 24, and surrounding the pivot
`piece, terminates in a region substantially flush with the
`20.
`surface of the base plate 10, on the side on which the
`The magnetic slots 48 then are energized, by means yet
`leaves are located. The width of the slot is somewhat
`to be described, and act to hold their associated arma
`wider than the width of the member 66, so as to provide a
`tures 46 and the leaves 14 in the open, latched position.
`gap in the magnetic path. This gap is, however, filled
`In one embodiment, the energizing of the latching mag
`with an epoxy-resin or other non-magnetic material 68.
`netic slots 48 is accomplished with the aid of a switch
`15
`The base plate is cut away in the region of the slot on its
`248, a portion of which is in position to be engaged by
`side opposite that on which the leaves are located in order
`one of the armatures when it has reached the latched
`to provide a high reluctance path in this region, thereby
`position, as may be seen in Fig. 4.
`forcing the magnetic flux to pass across the gap in a
`While the magnetic slots 48 are thus holding the leaves
`region closer to the leaves. The epoxy-resin prevents
`in the open position, the pinion 45 is rotated farther,
`stray particles, particularly partiles of magnetic metallic
`thereby rotating the gear 44 approximately another 180
`material, from entering the slot, and also gives the system
`degrees, so as to return that gear and the ring 30 to
`added mechanical strength.
`approximately the normal position of these elements.
`It will be understood that the pole piece 62, the mem
`The elements are now in the position shown in Fig. 4.
`bers 64 and 66, and the base plate 10 provide a magnetic
`Because of the relative position of the spring 28, as de
`flux path of relatively low reluctance, except in the region
`fined by its two end points at 36 and 38, with respect to
`of the resin-filled gap shown in Fig. 2A. When the mag
`the pivot 20 on which the leaves rotate, it may be seen
`met 58 is energized, and when the magnetic armature 46
`that the spring 28, under tension, applies a torque to the
`is covering the slot, the preferred path for the flux will
`leaves 14 in a clockwise direction, so as to urge them
`pass through the armature 46. The magnet pulls the
`toward the closed position.
`armature firmly against the plate.
`It will be understood from the previous description
`In the case of the latching slots, the action is that the
`that the general function of the B set of blades is to ter
`friction between the armature and the plate is great
`minate the exposure by closing the aperture quickly at
`enough so that when this magnet is energized, the springs
`the end of the required time. Thus whenever the mag
`are unable to shift the leaves from the latched position to
`netic latching slots 48 are simultaneously de-energized,
`the released position.
`35
`each of the springs 28, acting directly on its own asso
`In operation, the braking magnetic slots are energized
`ciated leaf 14, quickly rotates that leaf to the closed po
`before the latching magnetic slots are de-energized. Once
`sition.
`the latter are de-energized, the springs very quickly shift
`In this connection, it may be noted that there is no
`the leaves toward the released position. When the arma
`backlash in the system prior to the moment when the
`tures 46 approach the energized braking magnetic slots
`leaves begin to close, because the action of the springs
`50, these armatures will enter a region of high magnetic
`28 prestresses each individual leaf with a closing torque.
`flux, which will attract the armatures against the plate,
`As shown in Fig. 2, the links 22 are not the primary
`producing friction. This friction, together with the mag
`source of power for individual leaves; on the contrary, the
`netic field, brings the leaves firmly to a stop at the desired
`power is applied directly by the springs 28. The forces
`position where the leaves have closed the aperture, and the
`in the links 22 are second-order effects, produced by any
`armatures 46 are opposed to the braking slot as illustrated
`tendency toward minor differences in the closing motion
`in Fig. 2A.
`of the leaves. These links 22, because they do not carry
`The A set of leaves
`high forces, may be of much lighter material than would
`The B or rear set of leaves having been described above,
`be required if they transmitted primary power to the
`the A set or front set of leaves will now be described, in
`leaves. The links 22 serve to aid in maintaniing the
`connection with Fig. 5.
`leaves at their proper relative position to one another.
`In general, this set of leaves and its associated mecha
`They may, however, in some embodiments of the inven
`nism is the same as for the B set of leaves, except that
`tion, be eliminated. In embodiments in which they are
`the A set of leaves is closed when in the latched position,
`eliminated, the only parts of the apparatus which move,
`and the leaves are spring-biased so that, when released,
`when the leaves are moving from their latched to their
`they fly open. They are shown in the released, open posi
`tripped position, are the leaves, including their armature
`tion in Fig. 5. Magnetic latching and braking is em
`portions, and the springs.
`ployed, as has been described for the B set of leaves.
`As shown in Fig. 5, an apertured base plate 69, carries
`The magnetic slots
`leaves 70 pivotally mounted at 71. A ring 72, similar to
`Referring to Fig. 3, it may be seen that there are pro
`the previously-described ring 30 for the other set of leaves,
`vided, in this illustrative embodiment, ten electromagnets
`is also carried by the base plate 69. For each leaf there
`on the side of the base plate opposite the side on which
`is a spring 73, one end of which is attached to the leaf
`the leaves are located. Five of these magnets 58, con
`and the other end of which is attached to the ring 72.
`nected in parallel, are latching or holding magnets, asso
`The points of attachment of springs 73 to the ring 72 are
`ciated respectively with the latching magnetic slots 48.
`such that when the ring is in its normal position, and
`The other five magnets 60, connected in parallel, are brak
`when the leaves are in their closed or latched position, the
`ing magnets, associated with the braking magnetic slots
`springs apply to the leaves a torque in a direction to urge
`50. (For simplicity, most of the magnets are omitted in
`the leaves toward their open position.
`Fig. 1.) Each of the magnets comprises a coil through
`Affixed to each of the leaves, as an extension or crank,
`which an electric current is supplied when it is to be ener
`is an armature 74, of magnetic material, for example,
`gized. Extending through the coil is a core or pole piece
`steel. To cooperate with each of these armatures 74,
`62. Each of the magnets is attached to the plate 10 by
`there are provided in the base plate 69, latching magnetic
`a bracket 64. Connected to the member 62 and extend
`slots 75, one for each of the leaves, positioned so that the
`ing into the adjacent slot is a pole piece 66. The members
`armatures 74 will be opposed to their latching magnetic
`
`60
`
`65
`
`70
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`Ex.1043 / Page 10 of 19
`TESLA, INC.
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`2,958,988
`8
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`relay coil 100 so as to bring the projection 94 of the
`slots 75, respectively, when the leaf is in its closed position.
`armature into the path of the pin 90. When this condi
`There are also provided, in the base plate 69, a set of
`tion exists, the projection 94 prevents the collar 92 from
`braking magnetic slots 76, one for each leaf, positioned
`rotating, and the clutch is constructed and arranged so
`so that the armatures 74 will be opposed to their respec
`that power is not then transmitted from its input shaft
`tive braking slots when the leaves are in their open posi
`102 to its output shaft 104. The motor 84 is connected
`tion,
`through a shaft 106 and reduction gears (not shown) to
`Associated with the five latching magnetic slots, there
`the shaft 102. The output shaft 104 drives a pinion 110
`are five electromagnets 78, connected in parallel. Asso
`which in turn drives a gear 112. The gear 112, through
`ciated with the five braking magnetic slots, there are five
`a shaft 114, drives an A reset cam 116.
`electromagnets 80, respectively, connected in parallel.
`One terminal of the A clutch relay coil 100 is connected
`The general arrangement in this respect is similar to that
`to the grounded terminal of a source of D.-C. voltage.
`which has been illustrated for the other set of blades in
`Fig. 3. One of the latching or holding electromagnets 78.
`This terminal may, in this illustration, be assumed to be
`the negative terminal. The supply circuit to the other
`is shown in Fig. 1, the other four being omitted in this
`terminal of this coil may be traced from the positive ter
`drawing for clarity. The five braking electromagnets 80
`minal 120 of this voltage source, through a lead 122 to
`are also omitted in this drawing.
`a contact 126 of a relay 128. It may be assumed that
`Carried on the ring 72 there is a set of arms 81 of firm
`this relay is initially in a de-energized condition, because
`but resilient material, such as steel. These arms are
`the switch 188 is open. Consequently its armature 129,
`affixed to the ring at their outer ends, and carry at their
`spring-biased upward, is in engagement with the contact
`inner ends a small rotatable cylinder 83. When, in a man
`20
`126. Positive voltage from the terminal 120 is therefore
`ner to be described, the ring 72 is rotated in a clockwise
`applied from the contact 126 and the armature 129
`direction (from the viewpoint of Fig. 5), the ring, acting
`through a lead 130 to the upper contact 132 of the reset
`through the arms 81, causes the cylinders 83 to bear
`switch. It may therefore be seen that when the reset
`against the armatures 74 of the leaves 70, and thus to
`button 82 is depressed, this positive voltage is applied
`rotate the leaves on their pivots 71 clockwise from their
`from the contact 132 through the arm 134 and the lead
`open, released position shown in Fig. 5, to their closed,
`136 to the relay coil 100.
`latched position, where they overlap one another and close
`The depressing of the reset button 82 also brings its
`the aperture. In a manner to be described, power is then
`switch arm 138 into engagement with a contact 140.
`applied to the holding magnets for creating magnetic fields.
`(The button 82 is of insulating material, and hence it
`in the region of the latching slots 75. The ring 72 then
`does not itself provide an electrical connection between
`returns to its normal position and thereby applies tension
`the arm 134 and the arm 138.) Positive voltage from the
`?to the springs 73 so as to urge the leaves 70 toward the
`supply terminal 120 is applied to the switch arm 138, and
`open position. However, they are, for the present, held
`hence to the contact 140, and from this contact through
`in the closed, latched position because the magnetic action
`a lead 142 to the motor 84.
`of the holding magnets, acting through the slots 75, at
`35
`It may thus be seen that the depressing of the reset
`tracts the armatures 74 firmly against the plate 69. The
`button 82 energizes both the motor 84 and the clutch
`resulting friction, together with the magnetic force, thereby.
`relay 98. When this relay is energized, it pulls its arma
`restrains the leaves 70 from responding to the force of
`ture 96 downward, so as to remove the projection 94 from
`the springs until at a later moment the holding magnets
`the position where it can engage the pin 90. This allows:
`78 are released.
`the collar 92 to rotate, and shifts the clutch into such a
`Reference is now made to Fig. 6 for a description of
`condition that torque is transmitted from the input shaft
`the circuit for controlling the mechanism for resetting,
`102 to the output shaft 104. The reset cam 116 therefore
`releasing, and braking, the leaves.
`begins to rotate.
`It may be assumed initially that both sets of leaves
`Associated with the cam 116 there is a switch having
`have been tripped. That is, the front or A set of leaves
`contacts 146 and 148, and an arm 150 spring-biased
`is in the tripped position, as shown in Fig. 5, where the
`downwardly, toward the contact 148. Carried by this
`leaves are open; and the B set of leaves, at the rear, is
`arm is a projection 152, so positioned that a projection
`in the closed, tripped position, as shown in Fig. 2.
`154 on the cam 116 engages the projection 152 and tem
`In Fig. 6, there is represented one of the holding mag
`porarily lifts the arm 150 when the cam 116 rotates
`nets 78 for the A set of leaves, and one of the braking
`50
`through a predetermined position. It may be assumed
`magnets 80 for the A set of leaves. Also shown is a
`that, at the beginning of the operation to be described,
`holding magnet 58 and a braking magnet 60 for the B
`the arm 15 is in its lower position, as shown, in engage
`set of leaves. It will be understood that the other hold
`ment with the contact 148.
`ing magnets 78 for the A set of leaves are connected in
`Power from a positive voltage terminal 156 of the
`parallel with the one shown. Similarly, the magnet 58,
`voltage source is supplied through a lead to the arm 150,
`the magnet 69 and the magnet 80 each may in turn be
`and, when that arm is in engagement with the contact
`considered to represent schematically not just one but a
`148, through a lead 160 to the armature 96. When the
`group of parallel-connected magnets.
`relay 98 is energized by the depressing of the button 82,
`It will now be further described how all these magnets
`and the armature 96 consequently moves downwardly
`are energized and de-energized, how the shutter leaves are
`and engages its associated contact 162, the relay 98 be
`reset and released, and how these various actions are co
`comes locked in the energized condition, because the
`ordinated.
`power from the terminal 156 continues to be supplied
`through the arm 150, the lead 160 and the armature 96
`to the contact 162, which is connected to the coil 100.
`The result is that the power from the motor 84 con
`tinues to be transmitted through the clutch 86 to the cam
`116 until this cam rotates from its initial position to and
`through a position where its projection 154 lifts the arm
`150 away from engagement with the contact 148, thereby
`temporarily disconnecting the current supply circuit of
`the relay 98. This causes the upwardly spring-biased
`armature 96 to move upward so that its projection 94
`engages the pin 90, thereby shifting the clutch 86 to a
`condition where power is no longer transmitted to the
`75.
`' can 116,
`
`Resetting
`For controlling the reset operation, there is illustrated
`a reset switch including a manually operable reset lever
`or button 82 which, by an arrangement to be described,
`controls a motor 84 and two clutches 86 and 88.
`To reset the apparatus, the button 82 is depressed until
`both sets of leaves have been reset.
`The clutches in this illustration are of a spring type.
`Associated with the clutch 86 there is a pin or dog 90,
`carried on a rotatable collar 92. For cooperating with
`the pin 90, there is a projection 94 on an armature 96
`which forms part