US3526183A

US3526183A - Variable time delay mechanism for controlling release of a cocked photographic shutter

Info

Publication number: US3526183A
Application number: US714237A
Authority: US
Inventors: Karl Hartl
Original assignee: Compur Werk GmbH and Co
Current assignee: Compur Werk GmbH and Co
Priority date: 1967-03-22
Filing date: 1968-03-19
Publication date: 1970-09-01
Anticipated expiration: 1987-09-01

Description

United States Patent [72] Inventor Karl Hart] Munich, Germany [21 AppLNo. 714,237

March 19, 1968 Sept. 1, 1970 Compur-Werk Gesellschaft mit beschrankter Haftung & Co. Munich, Germany a firm of Germany [22] Filed [45] Patented [73] Assignee [32] Priority March 22, 1967 Germany [31] N0.C4l827 [54] VARIABLE TIME DELAY MECHANISM FOR CONTROLLING RELEASE OF A COCKED Primary ExaminerNort0n Ansher Assistant Examiner-Richard L. Moses Attorney- Charles Shepard and Stonebraker and Shepard ABSTRACT: A photographic shutter with an electronically controlled mechanism operatively interposed between the trip or trigger which initiates operation of the shutter, and the latch which releases the tensioned or cocked master member for starting its running down movement to open and close the shutter blades. This mechanism can be set for various periods of delay, e.g., a relatively long delay of about l0' seconds, to give time for the operator to place himself in front of the camera after he has actuated the trigger, or a relatively short delay ofabout 20 milliseconds to compensate for the illumination peak lag of certain types of flash bulbs. This delay mechanism, which is independent of other delay mechanism optionally used for determining the speed or duration of the exposure, comprises a main lever with two supplementary levers pivoted for limited lost motion with respect to the main lever. When the main lever is moved, under the influence ofa spring, from a tensioned position to an actuated position, it engages the latch ofthe master member and releases the latch so that the master member can start its running down movement. The first supplementary lever has an armature held by an electromagnet so long as current is flowing through the electromagnet, in a position preventing the main lever from moving to its actuated position to release the master member latch. The second supplementary lever is engaged by the master member during its tensioning movement from run down position to tensioned position, and serves to restore the main lever to its tensioned position. An electronic circuit including a Schmitt trigger causes current to flow through the electromagnet at the appropriatetime and to cut off the flow of current at the desired interval after the trigger is actuated, so that the armature can then pull away from the electromagnet and the main lever can release the latch of the master member. The parts are so arranged that they are very small and compact, to flt within the limited space available in a small photographic shutter, and so that current flows through the electromagnet only during a portion of the running down movement of the shutter parts, thus avoiding drain on the electric battery at other times.

Patented Sept. 1, 1970 Sheet Patented Sept. 1, 1970 3,526,183

Sheet 2.

l fi Q \W .21

BACKGROUND OF THE INVENTION In modern photographic shutters, particularly those designed for small hand-held cameras for amateur use, it is desirable to have two different delaying or retarding mechanisms, one for variably delaying the running down motion of the so-called master member which serves to open and close the shutter blades, to provide variable control for the length or duration of the exposure (usually called the shutter speed), and the other to provide an initial delay between the time that the shutter trigger is actuated to start the exposure cycle, and the time that the master member begins to operate to open the blades. The purpose of this initial delay is sometimes to compensate for the well known time lag required for certain types of flash bulb to reach peak illumination, usually about 20 milliseconds in typical conventional flash bulbs, and sometimes to provide the time required for the photographer, after tripping the shutter, to place himself in front of the camera so that he will be included in the picture, this time being usually about seconds. The present invention deals only with delaying mechanism of the second kind mentioned; that is, mechanism to provide the initial delay between the time the shutter trigger is tripped and the time the blades begin their opening movement. It is not concerned with the other delaying mechanism which determines the duration or speed of the exposure, and any conventional kind of such delaying mechanism for determining shutter speed may be used in conjunction with the present invention,

Various forms of mechanism for delaying the beginning of the exposure are already known in the art. The object of the present invention is the provision of generally improved and more satisfactory mechanism of this kind.

Another object is the provision of such mechanism so designed that it will operate with great accuracy, while at the same time the mechanism is extremely small and compact and is sturdy and reliable, and can be built into the very limited space available in a modern small shutter intended for a small hand camera.

Still another object is the provision of initial delaying mechanism controlled by a reliable electronic circuit which is so designed that current flows only during a portion of each operating cycle after the trigger is tripped, to avoid unnecessary drain on the battery at other times.

-A further object is the provision of delaying mechanism so designed that it may be adjusted to provide a delay as great as, for example, 10 seconds, and as small as, for example, milliseconds, and can also be adjusted to provide various intermediate delaying times if desired, although ordinarily no other delaying intervals are required other than the above mentioned long delay to enable self-portraiture and the short delay for use with flash bulbs having a short lag interval.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings, which are incorporated herein by reference and constitute a material part of the disclosure, and which illustrate an exemplary embodiment ofthe invention: v

FIG. 1 is an enlarged front view of a shutter in accordance with a preferred embodiment of the invention, with parts not essential to an understanding of the present invention removed, and with some parts shown schematically, the shutter being shown in tensioned or cocked position ready for the making of an exposure;

FIG. 2 is a view similar to a fragment of FIG. I with the parts in an intermediate position during the tensioning or cocking operation after completion of one exposure and being made ready for the next exposure;

FIG. 3 is a view similar to FIG. 2, showing the same parts during the progress of making an exposure, with the shutter blades open;

FIG. 4 is an edge view or side view of the shutter in approximately its full actual size; and

FIG. 5 is a circuit diagram of the electronic control arrangement included in the shutter housing.

DESCRIPTION OF THE PREFERRED EMBODIMENT The preferred embodiment of the invention comprises the usual conventional shutter housing or casing indicated in general at 10, of annular form, having a central circular flange or lens tube 10a defining the exposure aperture, the optical axis extending centrally through the lens tube, as usual, Any desired number of conventional shutter blades 12 are provided, five of such blades being here shown. They are pivotally connected in the conventional manner to a blade ring partially shown at 14, of conventional kind, and are arranged to be swung from the closed position shown in FIG. 1 to an open position when the blade ring is rotated in a counterclockwise direction, and to be closed again when the blade ring rotates back again in a clockwise direction. The rotation of the blade ring to open and close the blades is accomplished by a conventional main operating member or master member 16, secured to and rotatable with a tensioning shaft 16a which extends out through the back of the shutter housing in order to be operated in the usual way by mechanism mounted in the camera body.

The master member 16 is powered by a main spring or master spring I8 wrapped around the shaft 16a, one end of which spring engages a pin 16b on the master member, while the other end is anchored to a fixed member 20. The spring tends to turn the master member in a counterclockwise direction, when viewed from the front as in FIG. 1. When the master member is turned clockwise (by appropriate force applied to the shaft 16a) to the cocked or tensioned position shown in FIG. I, it is held in tensioned position by the latch 22 mounted on the pivot 22a. When the latch is released, the master member may perform its running down motion in a counterclockwise direction under the power of the spring 18. During such running down motion, it turns the blade ring 14 first in a counterclockwise direction to open the blades 12, and then in a clockwise direction to close the blades. The operating connection between the master member 16 and the blade ring 14 is not here shown, as it is a conventional connection, the details of which are not important for purposes of the present invention. The connection preferably comprises the usual push-pull pawl well known in the art.

The parts thus far described are all of conventional form, the details of which are not important for purposes of the present invention, and may be widely varied without departing from the invention.

In many photographic shutters, the latch of the master member (corresponding functionally to the present latch 22, although not necessarily of the same shape) .is arranged to be directly operated by hand, and constitutes the trigger or trip which is manually operated to start the exposure cycle. In the present shutter, however, the manually operated trigger or trip is separate from the latch 22 (being shown at 44, as further described below) and the delaying mechanism of the present invention is operatively interposed between the trigger and the latch 22, to provide an interval of delay between the operation of the trigger and the release of the master member, for the purposes already mentioned. This delaying mechanism, while very sturdy and reliable, is nevertheless of such small and compact form that it can be built into the limited available space in a modern photographic shutter of substantially the actual size illustrated in FIG. 4 (original application drawing, not the reduced reproduction appearing in this patent), thus being suitable for use on a modern small hand-held camera for amateur use.

The intermediate mechanism operatively interposed between the trigger 44 and the master member latch 22, for releasing the latch at an appropriate delayed interval after the operation of the trigger, comprises a double-armed main lever 24 pivotally mounted within the shutter housing or casing 10 on the pivot 24a, and biased in a clockwise direction by a spring 26 which may be appropriately called a stripper spring, since it serves to strip an armature away from an electromagnet (as further described below) when no current is flowing through the electromagnet, and to cause the main lever 24 to engage the tail of the latch 22 to release this latch. The stripper spring 26 is wound around the pivot 24a, has one end bearing against the lens tube a, and at its other end bears against a pin 24b on the lever 24.

The lever 24 has one arm 24c which extends in a general direction toward the master member latch 22, in position to engage the tail of this latch and release the latch when the lever 24 is turned slightly in a clockwise direction from-its position illustrated in FIG. 1. The second arm of the lever 24, extending in the opposite direction, is indicated at 24d, and this end cooperates with a locking lever 28 mounted in the shutter housing on a fixed pivot 28a and having a downturned end 28b which extends out through a small arcuate slot 10b in the back wall of the shutter housing. A restoring spring 30 wound around the pivot 28a has one end engaged with the lens tube 10:: and the other end engaged with the locking lever 28 to tend to move it in a counterclockwise direction. The range of movement of the lever is determined by engagement of the downturned ear 2811 with the ends of the slot 10b. When the locking lever 28 is in its maximum counterclockwise direction as illustrated in FIG. 1, it lies in the path ofthe end 240' of the main lever 24 and prevents this lever from turning in a clockwise direction from the position shown in FIG. 1, thereby preventing it from engaging the latch 22 to release the same. When the locking lever 28 is moved clockwise to the other end of its range, to the position illustrated in FIG. 3, it no longer obstructs the end 24a of the lever 24, and unless the lever is otherwise restrained (as for example by the electromagnet further described below) it can then move clockwise to actuate and release the latch 22 of the master member 16.

Two

supplementary levers

32 and 36 are pivotally associated with the main lever 24, each having only a limited degree of lost motion with respect to the main lever 24. The first supplementary lever 32, which may also be called a rocker lever, is mounted for free rotation around the pivot pin 24a of the main lever 24, and is biased in a counterclockwise direction with respect to the main lever by a coupling spring 34 which engages around the pivot pin 24a and has one end engaged with a pin 32a on the lever 32, and the other end engaged with an appropriate part. This tends to bring the pin 32a on the lever 32 up against the abutment edge or driving edge 24f of the lever 24. The free end of the rocker lever 32 has pivotally connected to it a metallic armature 35a cooperating with an electromagnet 35 stationarily mounted within the shutter housing or casing, this electromagnet 35 being connected in an electronic delay circuit as further described below. So long as current is flowing in the electromagnet 35, the armature 35a will be held firmly against the electromagnet, so that the lever 32 cannot turn in a clockwise direction, and therefore the main lever 24 cannot turn clockwise from the position shown in FIG. 1 (even if released from the locking lever 28) except to a very limited extent until the edge 24f comes in contact with the pin 32, this limited amount of movement being insufficient to release the master member latch 22. When current ceases to flow in the electromagnet 35, however, then (assuming that the locking lever 28 has meanwhile moved to a non-obstructing position with respect to the lever 24) the armature 350 can pull away from the electromagnet and the stripping spring 26 can turn the main lever 24 far enough so that the arm 24c thereof will move the latch 22 to an unlatched position, releasing the master member 16 for its running down movement.

The second supplementary lever associated with the main lever 24 is the lever 36, in the form ofa bellcrank pivoted on a pivot pin 24g on the main lever 24 and having only a limited range of rotation on the pivot 24g, the range being defined by engagement of the pin 24/1 on the lever 24 with one side or the other of a slot 36a in the bellcrank lever 36. Spring means is provided, biasing the lever 36 in a counterclockwise direction on its pivot 24g. Preferably this spring action is provided by the same spring 34a which also biases the lever 32 with respect to the main lever 24, one end of this spring engaging a small upstanding ear on the bellcrank lever 36, as seen in FIG. 1. The long arm 36b of the bellcrank lever projects into the vicinity of the master member 16, overlying the latter in such "'position that it lies in the path of travel of the pin 16b of the master member 16 when the latter runs down from its tensioned or cocked position to its fully run down position.

The shutter is provided with a release ring 38 rotatable concentrically with the optical axis. For convenience of schematic illustration, the ring 38 is shown in FIGS. 1 and 3 as rotatable around the exterior of the casing or housing 10. However, in the actual shutter it may be in any convenient location, usually near the rear of the shutter, and either inside or outside the housing. A spring 40 tends to move the ring 38 in a clockwise direction around the optical axis. When the shutter is used with a conventional single lens mirror reflex camera, the release ring 38 is preferably coupled to the mirror actuating device of the camera, to synchronize the functions of the camera body parts with those of the shutter, and consequently is made subservient to the operation of the film feed mechanism of the camera, so as to turn the ring 38 in a counterclockwise tensioning direction when the film is fed forwardly to bring a fresh exposure area or frame of film into the exposure position within the camera.

To this end there may be, for example, gear teeth 38a on the release ring 38, engaged by gear teeth on a pinion 42a mounted on a shaft 42 which extends into the camera body and is turned in known manner by the film feeding mechanism. Thus when the film is wound, the shaft 42 and pinion 42a are operated to move the release ring 38 in a counterclockwise direction from its run down position to its tensioned or cocked position where it is latched by the trigger latch 44, and simultaneously therewith the shaft 16a of the master member 16 is turned in a clockwise direction by the film feeding mechanism to move the master member from its run down position to its tensioned or cocked position wherein it is latched by the latch 22. Both the master member 16 and the release ring 38 are shown in their respective tensioned positions, in FIG. I. The details of the mechanism for turning the

shafts

16a and 42 from the film feeding mechanism are unimportant for purposes of the present invention, and may be of any known form conventional in the art.

The release ring 38 carries a nose or projection or arm 38b which, during the clockwise running down movement of the ring 38 (after the trigger latch 44 is operated to release the ring) will engage the ear 28b on the locking lever 28 and move it from the locking position shown in FIG. 1 to the unlocked position shown in FIG. 3. This occurs just at the end of the clockwise running down movement of the release ring 38. The release ring also carries a cam portion 38c which cooperates with a switch 46 forming part of the electronic circuit further described below, to hold the switch 46 closed while the ring 38 is in its tensioned position and during most of its running down movement. Near the end of the running down movement of the ring 38, the trailing end of the cam portion 38c passes beyond the cooperating part of the switch 46, and allows the switch 46 to open, as it is resiliently biased toward open position. In addition to the switch 46, there is a second switch 48 also constituting part of the electronic control circuit, this switch 48 being positioned to be normally open and to be closed by movement of the trigger member 44 to its released position, and it stays closed during the entire running down movement of the release ring 38 and until the release ring is moved again to its cocked or tensioned position, since the cam portion 38c is so shaped as to hold the trigger lever 44 in its actuated position, once the ring 38 has started to run down, until the ring reaches fully tensioned position once more.

The electronic control arrangement for the holding magnet 35 is illustrated diagrammatically in FIG. 5. It forms a Schmitt trigger circuit with two feed-

back transistors

50 and 52, and with a resistance-capacitor or R-C portion formed by the capacitor 54 and a plurality of resistances 56, of different resistance values, selectively connected into the circuit by a selector switch orslider 58, selectively settable manually from the exterior of the shutter housing by means of an accessible finger piece 58a (FIG. 4) set in conjunction with scale or reference markings 60. It is usually sufficient to have two separate resistances 56, one of them (marked V) being of suchresistance value as to give a time delay of about seconds, to enable the photographer to place himself in front of the camera so that he will appear in the picture, the other (marked M) having a resistance value such as to give a time delay of about 20 milliseconds, to make the shutter useable with flash bulbs of a well known type having a time lag of about 20 milliseconds from the time that the electric circuit to the flash bulb is closed, to the time that the bulb reaches peak- I appropriate time during the operation of the shutter, e.g., at

the completion of the running down movement of the release ring 38, which is when the electronic delay mechanism begins to operate effectively. Of course other resistances 56 may be used in addition to or instead of the above described resistances V and M, if it is desired to produce other delays than the preliminary self-portrait delay and the flash time-lag delay above mentioned.

The holding magnet 35, and the

switches

46 and 48, are connected into the system with a source of current such as'a battery 61, and a limit resistance 62, a protective resistance 64, and a collector resistance 66, and with a setting potentiometer 68, in the manner indicated in FIG. 5, the connections being clearly understood from FIG. 5 by those skilled in the electronic transistor art, without the need for further detailed explanation. The setting potentiometer 68 is used for calibration and trimming adjustment of the control circuit.

It has previously been mentioned that the delay mechanism of the present invention relates to an initial delay between the time that the shutter trigger is operated and the time that the master member is unlatched to start its running down movement to open and close the shutter blades, and does not relate to the conventional delay mechanism which operates during the running down movement of the master member, in order to determine or control the duration of the exposure, com monly referred to as the shutter speed. The delay mechanism of the latter kind, determining the shutter speed, may be of any conventional construction; for example, there may be a blocking or retaining member 70, shown in broken lines in FIG. 1, which temporarily stops the running down movement of the master member 16 at an intermediate point when the shutter blades are fully open, and which can be set to determine specific delay intervals, controlled either mechanically (e.g., by clockwork gearing) or electronically, and which, after the appropriate interval for which it is set, willmove aside and allow the master member 16 to complete its running down movement and close the shutter blades. Such delaying mechanism for determining the length of exposure may take many possible forms, all well known in the art, the details of which are not important for purposes of the present invention and therefore need not be specifically described. The setting of this speed control delaying mechanism is accomplished usually by turning a conventional speed control ring 72 (FIG. 4) rotatably mounted on the front of the shutter for turning movement about the optical axis, and carrying a reference mark 72a which is set in conjunction with a shutter speed scale 74 marked on the casing or housing. The particular setting illustrated as an example in FIG. 4 shows that the shutter is set for a speed of 60, meaning an exposure of l/th of a second.

It is believed that the operation of the shutter may be sufficiently understood from the preceding part of the description, but it may be summarized as follows:

The desired interval of delay between the tripping of the shutter trigger and the release of the master member is set by moving the finger piece 58a (FIG. 4) with respect to the scale or marking 60, and is here illustrated as being set in position M, for a delay of 20 milliseconds. The shutter speed or exposure time is set by turning the ring 72 to bring the mark 72a opposite the desired graduation of the scale 74, and is here illustrated as being set for an exposure of 1/60th of a second. Either before or after these settings are made, the conventional film feed mechanism on the camera body is operated, and through conventional mechanism this turns the master member shaft 16a and the pinion shaft 42, to turn the master member 16 clockwise to its fully tensioned or cocked position illustrated in FIG. 1 (where it is held by the latch 22) and to turn the release ring 38 counterclockwise to its fully tensioned or cocked position also illustrated in FIG. 1 (where it is held by the trigger 44). In this tensioned position of the parts, the switch 48 is open and the switch 46 is closed. No matter how long the parts are kept in this position, there is no drain on the battery 61, because the switch 48 is open.

During the tensioning movement of the master member 16 in the clockwise direction, the pin 16b thereof makes temporary contact with the arm 36b of the bellcrank lever or second supplementary lever 36, and moves this lever 36 counterclockwise on its pivot 24g until it can turn no farther because of the limit pin 24h so that further movement of the lever 36 in the same direction will swing the main lever 24 also counterclockwise on its pivot 24a, thereby tensioning or loading the stripper spring 26. In the course of this movement of the main lever 24, the supplementary locking lever 32 also turns with it in a counterclockwise direction, under the action of the spring 34, until the armature 35a bears against the holding magnet 35. After the armature makes contact with the magnet, the lever 32 can turn no farther in a counterclockwise direction, but the main lever 24 turns a little farther (separating the edge 24ffrom the pin 32a as seen in FIGS. 1 and 2) and the nose 24d moves out of the way of the locking lever 28 so that the latter may now move counterclockwise to its locking position under the influence ofits spring 30. This position of the parts, during the tensioning movement of the master member 16, is best illustrated in FIG. 2.

As the tensioning movement of the master member continues, the pin 16b passes beyond the end 361) of the lever 36, thus releasing the tensioning force applied to the main lever 24, and the main lever tries to move clockwise under the influence of the stripping spring 26, but can move only to a very slight extent until the nose 24d comes in contact with the ear 28b of the locking lever 28, which holds the lever 24 in its tensioned position shown in FIG. 1. When the master member 16 continues its clockwise tensioning movement and reaches the end of such movement, it becomes latched in tensioned position by the master member latch 22, which now assumes the position shown in FIG. 1. The slight clockwise movement of the main lever 24 (from the position of FIG. 2, held by the pin 16b to the position of FIG. I, held by the locking lever 28) brings the lever 36b to a position in the path of travel of the pin 16b during the subsequent running down movement of the master member. Although the magnet 35 is not energized at this time, the armature 35a nevertheless stays in contact with the magnet because of the action of the spring 34 tending to swing the lever 32 in a counterclockwise direction.

When the user is ready to make the exposure, he trips the trigger or trip lever 44, turning it slightly in a clockwise direction from the latching position shown in FIG. 1. This permits the release ring 38 to begin its clockwise running down movement under the influence of the spring 40, and simultaneously therewith closes the switch 48 so that the battery 61 is now operatively connected into the electronic circuit. The emitter leads of both

transistors

50 and 52 are thus connected to the battery 61. Since the base of the transistor 50 is at a potential less than its emitter potential, as determined by the transistor 52, it is completely blocked at the moment that the switch 48 is closed, so that the base of the transistor 52 is connected via resistance 66 to the battery 61. The collector current then flowing through the transistor 52 energizes the holding magnet 35, so that the armature 35a is held by the full retentive power of the magnet 35, from a moment shortly after the closing of the switch 48, which closing occurs, as above stated, at the time that the trigger 44 is tripped to start the cycle.

When the trigger 44 is tripped, the release ring 38 starts to run down in a clockwise direction. The switch 46 continues to be held closed by the cam 38c on the ring 38, during most of the running down movement of the ring, thus giving enough time, e.g., for preliminary run down ofa fully open diaphragm to a pre-selected diaphragm aperture position, if the camera is of the type employing such a run down ofa diaphragm. Thus the electronic arrangement has not been brought into operation during this phase of the running down of the release ring 38, so long as the switch 46 remains closed, since the closing of this switch short circuits the R-C time delay portion of the electronic circuit. Only when the trailing end of the cam 38c passes beyond the arm of the switch 46, can the latter open under its intrinsic resilience or spring effect and thus remove the short circuit of the time-determining capacitor 54. This opening of the switch 46 occurs approximately simultaneously with and actually a very slight interval after the arm 38b of the ring 38 engages the lug 28b of the locking lever 28 to move the latter toward unlocked position. Just as this lever 28 reaches its fully unlocked position, the switch 46 opens and the electronic timing circuit begins to function to determine the delaying time interval for which it has been set. Simultaneously therewith the circuit to the flash lamp (not shown) is closed.

When the locking lever 28 is moved to its unlocked position at the end of the running down movement of the ring 38, the main lever 24 can now move in a clockwise direction under the influence ofthe stripper spring 26, but only to a very slight extent, until the edge 24fof the main lever 24 comes into contact with the pin 32a of the lever 32, and further movement is stopped thereby because the lever 32 is still held stationary by the attraction of the armature 35a to the magnet 35, which is now being energized by flow of current. The attraction of the energized electromagnet 35 for the armature 35a is stronger than the force of the stripper spring 26 tending at this time to separate the armature from the magnet.

When the switch 46 is opened substantially at the end ofthe running down movement of the release ring 38, however, charging current begins to flow into the capacitor 54 through the time-determining resistance 56 and this flow continues until the base of the transistor 50 is raised to a potential exceeding the emitter potential of this transistor. The transistor 50 then begins to conduct from this moment, and there is a slight voltage drop at the resistance 66. As a result, the conductivity of the transistor 52 falls a little, and the voltage drop at the potentiometer 68 is also reduced in consequence, because the current ofthe input transistor 50 is less by the amplification factor of the two transistors and first has no effect on the potentiometer 68. Thus the emitter voltage of the transistor 50 is in consequence reduced, and the potential difference between the base and the emitter of the transistor 50 increases, especially as the voltage further increases at the capacitor 54 in the meantime. The now increased current flow at the transistor 50 is effective through the feedback coupling as described above, whereby the current in the transistor 50 increases abruptly while it drops just as suddenly in the transistor 52. Thus the transistor 50 becomes conductive and the transistor 52 becomes blocked.

As soon as the current flow through the transistor 52 ceases, after the lapse of time determined by the R-C member, the winding of the holding magnet 35 is no longer supplied with current, and becomes de-energized. The stripper spring 26 can now move the two

levers

24 and 32 in a clockwise direction, stripping the armature 35a from the holding magnet 35, which is now dead. In so doing, the arm 24c of the main lever 24 engages the master member latch 22 and turns the latch in a counterclockwise direction, thereby unlatching it and releasing the master member 16 so that it can make its running down movement, to open and subsequently to close the shutter blades. Thus there is a time interval or period of time between the moment when the trigger 44 is tripped or operated, and the moment when the latch 22 releases the master driving member 16, and this period of time corresponds to the delay period which has been preselected and set at 58a, 60. In the case illustrated it is assumed as amounting to only about 20 milliseconds, but as already pointed out it can be set to as much as 10 seconds, to enable taking a self portrait. If need be, still other resistances can be supplied in the group 56, for selective inclusion in the circuit if other time intervals are wanted.

The master member or main driving member 16, when released by the latch 22, runs down in a counterclockwise direction, the shutter blades 12 being opened in the familiar way, and the running down motion of the master member being interrupted temporarily by the conventional delaying mechanism 70 in order to make the exposure of the length or speed selected by the setting 72a 74. When the delaying mechanism 70 has performed its function, the master member 16 becomes free again, and is able to continue its running down movement to its rest position, during which running down movement the blades 12 are closed.

During this running down movement of the master member, the pin 16b thereon temporarily strikes the arm 36b of the bellcrank lever 36, but this results only in a small deflection of the lever 36 relative to the lever 24, through the lost motion between the

levers

36 and 24. As soon as the pin 16b slides past the arm 36b after slightly deflecting it, the arm 36b snaps behind the pin 16b again and reinstates the positive coupling between the parts 36a and 2411, so that the parts will be in readiness for tensioning the main lever 24 whenever the master member 16 performs its tensioning motion.

All of the parts operatively interposed between the trigger 44 and the master member latch 22 may be collectively referred to as a mechanism train or gear train. This includes, for example, the control member 38, the intermediate member 24, the blocking member 28, the rocking lever 32, the bellcrank lever 36, and their respective springs, as well as the electromagnet 35 and armature 35a. The mechanism train, broadly considered, also includes the entire electronic circuit, including the

switches

46 and 48, which are under the control of the control member 38 as above explained.

It is to be understood that the disclosure is given by way of illustrative example only, rather than by way of limitation, and that without departing from the invention, the details may be varied within the scope of the appended claims.

1 claim:

1. A photographic shutter having a master member mounted for tensioning movement in one direction from a run-down position to a tensioned position to prepare the master member for an exposure, and for running down movement in an opposite direction from tensioned position to rundown position to make an exposure during such running down movement, a releasable latch for holding said master member in tensioned position, a trigger operable to initiate an exposure cycle, and a mechanism train operatively interposed between said trigger and said releasable latch for releasing said latch at i an interval after operation of said trigger, characterized by the fact that said mechanism train includes:

a. an intermediate member movable from a first position to a second position and effective upon reaching its second position to release said releasable latch of said master member;

b. a spring tending to move said intermediate member from its first position to its second position;

c. an electromagnet effective, when energized, to hold said intermediate member against movement to its second position;

d. a part connected to said intermediate member and positioned to be engaged and displaced by said master member during tensioning movement thereof, to move said intermediate member toward its said first position and thereby to tension said spring;

e. a releasable blocking member for blocking movement of said intermediate member from its first position to its second position, independently of said electromagnet;

. electronic circuit means for energizing said electromagnet; and

g. a control member movable in response to operation of said trigger and effective upon such movement to release said blocking member and concomitantly to activate said electronic circuit means to energize said electromagnet to hold said intermediate member against movement to its second position notwithstanding release of said blocking member, during a predetermined time interval controlled by said electronic circuit means.

2. A construction as defined in claim 1, wherein said control member is a rotatable ring, and further including a spring tending to rotate said ring in one direction, said trigger serving to hold said ring against rotation in said direction until said trigger is operated.

3. A construction as defined in claim 2, further including a portion on said rotatable ring for engaging said releasable blocking member and moving said blocking member to a released position during movement of said rotatable ring in said one direction.

4. A construction as defined in claim 1, wherein said intermediate member is a double armed pivoted lever, said part connected to said intermediate member is a bellcrank lever pivotally mounted on said intermediate member, and wherein there is a rocking lever coupled to said intermediate member, and an armature carried by said rocking lever and cooperating with said electromagnet.

5. A construction as defined in claim 1, further including a projecting part on said master-member, a bellcrank lever rotatably mounted on said intermediate member, a pin and slot connection between said bellcrank lever and said intermediate member to define a limited range of'rotation of said bellcrank lever relative to said intermediate member, and a spring tending to turn said bellcrank lever to one end of its said range, said bellcrank lever having an arm which, when at said one end of its range and when said intermediate member is in its said second position, lies in the path of travel of said projecting part on said master member during tensioning movement thereof, the parts being so arranged that during tensioning movement of said master member, said projecting part thereon will engage said arm of said bellcrank lever and move said bellcrank lever to cause said bellcrank lever to move said intermediate member from its second position to its first position, thereby to tension said spring of said intermediate member.

6. A construction as defined in claim I, further including a releasable blocking member 28 for blocking movement of said intermediate member from its first position to its second position, said intermediate member being in the form of a pivoted lever 24 having a first arm 240 for cooperating with said releasable latch 22 and a second arm 24d for cooperating with said blocking member 28.

7. A photographic shutter having a master member mounted for tensioning movement in one direction from a run-down position to a tensioned position to prepare the master member for an exposure, and for running down movement in an opposite direction from tensioned position to rundown position to make an exposure during such running down movement, a releasable latch for holding said master member in tensioned position, a trigger operable to initiate an exposure cycle, and a mechanism train operatively interposed between said trigger and said releasable latch for releasing said latch at an interval after operation of said trigger, characterized by the fact that said mechanism train includes:

a. an intermediate member movable from a first position to a second position and effective upon reaching its second position to release said releasable latch of said master member, said intermediate member being a pivoted lever 24 mounted for turning movement about an axis 24a; b. a spring tending to move said intermediate member from its first position to its second position;

d. a rocking lever 32 mounted for rotation about said axis 24a and having a driving member 320 coacting with a driving edge 24f of said intermediate member; and

e. an armature 35a mounted on said rocking lever for cooperating with said electromagnet.

8. A photographic shutter having a master member mounted for tensioning movement in one direction from a run-down position to a tensioned position to prepare the master member for an exposure, and for running down movement in an opposite direction from tensioned position to rundown position to make an exposure during such running down movement, a releasable latch for holding said master member in tensioned position, a trigger operable to initiate an exposure cycle, and a mechanism train operatively interposed between said trigger and said releasable latch for releasing said latch at an interval after operation of said trigger, characterized by the fact that said mechanism train includes:

d. a control member movable in response to operation of said trigger; and

e. means effective upon operation of said trigger and movement of said control member for energizing said electromagnet and keeping it energized for a limited predetermined time.

9. A construction as define in claim 8, wherein said shutter includes a housing encircling an optical axis, and wherein said control member is a ring rotatably mounted on said housing for rotation concentrically with said optical axis.

10. A construction as defined in claim 8, wherein said mechanism train further includes:

f. a releasable blocking member for blocking movement of said intermediate member from its first position to said second position, independently of said electromagnet; and

g. a part on said control member for engaging and releasing said blocking member during movement of said control member in response to operation of said trigger.

11. A construction as defined in claim 8, wherein said means for energizing said magnet and keeping it energized includes a first electric switch normally open and closed by operation of said trigger, a second electric switch normally closed and opened only upon movement of said control member in response to operation of said trigger, and means on said control member for keeping said first switch closed, after initial closing thereof by operation of said trigger, at least until said second switch has opened.

12. A construction as defined in claim 1, further including an electronic circuit for energizing said electromagnet, said circuit comprising a Schmitt trigger portion, a resistancecapacitor portion, and a battery.

13. A construction as defined in claim 12, further including a switch for connecting said battery to said Schmitt trigger portion, said switch being associated with said trigger operable to initiate an exposure cycle.