US3762296A

US3762296A - Photographic shutter with electronic timing circuit

Info

Publication number: US3762296A
Application number: US00219952A
Authority: US
Inventors: W Rentschler
Original assignee: Prontor Werk Alfred Gauthier GmbH
Current assignee: Hittech Prontor GmbH
Priority date: 1971-01-23
Filing date: 1972-01-24
Publication date: 1973-10-02
Anticipated expiration: 1990-10-02
Also published as: DE2103148B2; FR2122850A5; GB1361880A; DE2103148C3; DE2103148A1

Abstract

The shutter comprises shutter blades of relatively large mass which are displaceable, in the opening direction, by means of a driving force which is weak with respect to the inertia of the shutter blades, and which are displaceable, in the closing direction, by a relatively strong driving force. The edges of the shutter blades are formed to produce a diaphragm aperture such that there is an exposure time-aperture value corresponding to each instant of time following beginning of the displacement in the opening direction. The position of the shutter blades at any instant during the displacement in the opening direction defines a predetermined aperture, and the exposure time-aperture value has a graduation which is uniform with respect to exposure. The driving means are springs, acting on levers and the like, for displacing the shutter blades. The driving force for displacing the shutter blades in the opening direction may be derived from two springs, with the first spring being stronger than the second and put out of action after an initial movement of the blades so that further movement of the blades is due to the kinetic energy imparted to the blades and the force of the second and weaker spring. A magnetic lock is provided under the control of the timing circuit to lock a displaceable part which is released by triggering of the shutter, and the magnetic lock releases this part after a time interval determined by the electronic timing circuit.

Description

United States Patent 11 1 Rentschler 1 PI-IOTOGRAPIIIC SHUTTER WITH ELECTRONIC TIMING CIRCUIT Waldemar T. Rent'schler, Calmbach/Schwarzwald, Germany 22 Filed: Jan. 24, 1972 211' Appl. No.: 219,952

[75] Inventor:

[30] Foreign Application Priority Data .Ian. 23, 1971 Germany P 21 03 148.1

[52] US. Cl. 95/53 EB, 95/10 CT, 95/63 [51] Int. Cl. G03b 9/14 [58] Field of Search 95/10 C, 10 CT, 10 CE, 95/10 CD, 53 R, 53 BA, 53 EB, 58, 59,60, 63, 62

[56] References Cited UNITED STATES PATENTS 3,358,575 12/1967 Kitai 95/63 3,661,066 5/1972 Ettischer et a1... 95/53 EB 3,459,112 8/1969 Starp et al. 95/60 3,662,664 5/1972 Goshima.... 95/63 3,375,769 4/1968 Kiper 95/63 3,482,501 12/1969 Helber et al. 95/63 Primary Examiner-Joseph F. Peters, Jr. Attorney-Arthur A. March [57] ABSTRACT The shutter comprises shutter blades of relatively large mass which are displaceable, in the opening direction, by means of a driving force which is weak with respect to the inertia of the shutter blades, and which are displaceable, in the closing direction, by a relatively strong driving force. The edges of the shutter blades are formed to produce a diaphragm aperture such that there is an exposure time-aperture value corresponding to each instant of time following beginning of the dis placement in the opening direction. The position of the shutter blades at any instant during the displacement in the opening direction defines a predetermined aperture, and the exposure time-aperture value has a graduation which is uniform with respect to exposure. The driving means are springs, acting on levers and the like, for displacing the shutter blades. The driving force for displacing the shutter blades in the opening direction may be derived from two springs, with the first spring being stronger than the second and put out of action after an initial movement of the blades so that further movement of the blades is due to the kinetic energy imparted to the blades and the force of the second and weaker spring. A magnetic lock is provided under the control of the timing circuit to lock a displaceable part which is released by triggering of the shutter, and the magnetic lock releases this part after a time interval determined by the electronic timing circuit.

7 Claims, l 2 llirawing Figures PATENTEDIBI 21915 SHEET 2 [IF 3 PIIO'IOGRAPIIIC SHUTTER WITH ELECTRONIC TIMING CIRCUIT The present invention concerns a bladed shutter with electronic exposure timing, the blades effecting not only the opening and closing of the lens passage, but also acting as a diaphragm.

Diaphragm shutters of this type with electronic exposure timing are already known. One of their essential advantages resides in the guaranteeing of accurate exposure over a wide range of light values. These diaphragm shutters which have an electronic timing device are not provided with a separate diaphragm system, the diaphragm aperture being formed by the shutter blades which normally cover the lens opening, and have opening drive and, in the case of a reciprocating shutter blade system, also a closing drive.

A characteristic of these conventional diaphragm shutters with electronic exposure timing is the relatively long opening time of the shutter blade system. Whereas, in the case of photographic shutters which, in addition to the shutter blade system, are also provided with a diaphragm, the shutter opening time amounts to only a few milliseconds (m.s.) usually a maximum of 5 ms. with diaphragm shutters, opening times of 40 60 ms. are usual, which means that the full opening of the shutter takes place only after an extended time interval. If, however, shorter time intervals are called for by the electronic timing circuit of such shutters, the opening movement of the shutter blade system is prematurely concluded and this in turn means that the shutter system opens up only to a correspondingly smaller aperture value. In this manner an exposure time-aperture programme extending for example over a range of l/500th sec at F16 to l/30th sec at F4, may be covered. The relatively long opening time is achieved in conventional diaphragm shutters in that the movement of the opening drive is suitably retarded by a mechanical timing system as in shutters having a mechanical device for time regulation.

It is a disadvantage of these conventional diaphragm shutters that mechanical timing systems to extend the aperturctime interval involves not only considerable additional expense, but also correspondingly increased space. Thus, in many cases it is impossible or only just possible to accommodate all the units, such as the electronic circuit, the electromagnetic lock and a timing mechanism used for the operation of the shutter, in the housing of such camera shutters, particularly in the housing of a compact camera (camera having relatively small dimensions). From the point of view of operation, there is the fact that the mechanical retarding mechanism used for extending the opening time of a diaphragm shutter involves precisely the same disadvantage which it is intended to avoid by eliminating the mechanical exposure time retarding mechanism and replacing it by an electronic time control circuit.

The object of the present invention is to provide a programmed shutter of the above-mentioned type which is of simple and economical design and is free from the above-mentioned disadvantages.

According to the present invention there is provided a photographic diaphragm shutter with an electronic exposure timing circuit comprising shutter blades of relatively large mass which are displaceable in the opening direction by means of a driving force which is weak with respect to the shutter inertia, and in the closing direction by a relatively strong driving force, the edges of the shutter blades being formed to produce a diaphragm aperture such that there is an exposure time-aperture value corresponding to each moment of time after the beginning of the shutter opening, the position of the shutter blades at any such time defining a predetermined aperture, the said value having a uniform exposure graduation. A shutter according to this construction has, in the same manner as the already known electronic diaphragm shutters, a relatively long opening movement time. However, this is not achieved by means of a mechanical retarding mechanism, but in a more simple, compact and economical manner by using shutter blades which have a relatively large mass in conjunction with a relatively low driving force for opening the blades. This gives a diaphragm shutter a long shutter opening time.

Since the values for the mass and driving force of the shutter blades are pre-determined, the exposure time becomes the independent parameter of the timeaperture programme, the diaphragm aperture as a dependent parameter being produced by a suitable selection of the formation of the edges of the shutter blades. The present invention can be applied to any conventional type -of lens shutter and especially to shutters having reciprocating blades and to shutters which use separate shutter systems for opening and for shutting the lens opening.

The present invention is now described in detail with reference to two embodiments having reciprocating shutter blades and illustrated in the accompanying drawings, in which:

FIG. I shows a diaphragm shutter including a cocking, driving and electromagnetic locking system,

FIG. 2 shows the shutter blades, including the driving levers, in the inoperative position,

FIG. 3 shows the electromagnetic lock of the shutter in the operative position,

FIG. 4 is a perspective view of the lever system which is used for the drive of a part associated with the lock, and of the shutter blades, the particular bearing point of the individual levers being indicated by chain-dotted lines; the movement of the individual levers out of the illustrated basic position, is indicated by arrows;

FIG. 5 is a cross-section through the lever system shown in FIG. 4;

FIG. 6 is another shutter embodiment differing from that of FIG. 3, the shutter blade driving lever being driven by means of two springs of different strength, both springs being jointly effective at first and after a certain amount of movement, only one is effective,

FIG. 7 is a partial view of the shutter blade driving lever of FIG. 6 in the first movement phase in which the two springs are operative,

FIG. 8 shows the same shutter blade drive lever in the second movement phase in which only the weaker spring of the two is in action,

FIG. 9 is another embodiment of a diaphragm shutter which, as well as the actual shutter blade system, has an additional cover blade assembly, one cover blade of which forms part of the electromagnetic locking sys' tem,

FIG. llll is the basic circuit of the electronic timing device,

FIG. 11 is a graph showing how the exposure time aperture programme is effected, and

FIG. 12 is a selector ring for setting the working range, including the flash contact switch of the shutter, viewed from the rear of the shutter.

A capsule-like housing of a diaphragm shutter designed as a self-cocking shutter, is indicated in the drawings by the reference numeral 1. This housing has a cylindrical outer casing 1a, a base 1b and a center lens socket 1c provided with an opening. A cocking and release lever 2 (FIG. 1) is rotatably journalled on the upper surface (in the direction of vision) of the base lb, the lever being displaceable in a slot provided in the housing wall 1a. Instead of this lever, a cocking member driven from the film feed mechanism, could be used. The cocking and release lever 2 is engaged by a spring 3 which always tends to keep the lever in a starting position defined by a stationary pin 4. A drive pawl 7 is mounted to rotate on the lever 2 and is kept in contact with a pin 6, also located on the lever, by means of a spring 5. The pawl co-operates with one end of a double-armed intermediate lever 9 displaceable out of a normal position against the action of a return spring 8. At the other end, a one-armed lever 12 pivotable about a pin 11 is associated with the intermediate lever 9 which rotates about a stationary pin 10. The lever 12 is displaceable by the lever 9 out of its normal position determined by a pin 13, against the action of a spring 14. The rotary movement of the lever 12 is effected after the cocking and release lever 2 is first moved in the direction of the arrow in FIG. 1; when the intermediate lever 9 has been turned in a clockwise direction about its axis by lever 2, the end of the intermediate lever 9 facing the lever 12 slides along a rejecting catch 12a provided on the lever 12. This catch rises slantingly in the direction of movement of the lever 9, and the lever finally drops below the catch. Immediately thereafter, the drive pawl 7 becomes disengaged from the other end of the intermediate lever 9, the result of which is that, under the influence of the spring 8 engaging thereon, and acting as an energy storer, the lever 12 pivots at first anticlockwise about its bearing pin 1 1. In the course of this rotation, the end of the intermediate lever 9 finally becomes disengaged from the bottom of rejecting catch 12a in order immediately afterwards to act on a lug 12c formed on the lever 12. This operation causes the intermediate lever 9 to move the lever 12 in a direction opposed to the previous direction of rotation, provided it is not temporarily prevented from doing so by a magnetic lock described in greater detail hereinafter.

FIGS. 1, 3 and 5 show that the lever 12 located on the base lb of the housing, is associated with a crescentshaped lever 15 mounted under the base and located to rotate on a stationary pin 16. The lever 12 and crescent-shaped lever 15 are coupled together. For this purpose the lever 12 is provided with a laterally extending pin 17 passing both through an arcuate recess 1d formed in the base 1b of the housing, and through a slot 15a provided on the crescent-shaped lever 15 itself. The free end of the crescent-shaped lever 15 pivoting about the lens socket 1c co-operates, as shown more particularly in FIG. 3, with the above-mentioned magnetic lock. This lock, controllable by an electronic timing mechanism to be described in greater detail hereinafter, comprises an electromagnet 18, an armature 19 and a

lever assembly

20, 21 carrying the armature. This assembly is acted upon by the lever 2 and forms as a link; the lever 20, biased by a return spring 22, is journalled to rotate on a fixed pin 24 and is displaceable by means of a pin 25 secured to the release lever 2. The lever 21, positively coupled by a link device 26 to the lever 20, is journalled on a stationary pin 27. The arrangement of these two levers, held in their normal position against a pin 28, is such that, when the cocking and release lever 2 is actuated, the drive pin 25 acts on the lever 20 so that the assembly applies the armature 19 to the magnet 18 and brings a retaining pawl 30, pivoted on the lever 21, into a position in which the pawl is able to intercept the free end of the crescent-shaped lever 15 which always executes a reciprocating movement with the lever 12, due to its positive connection, at the moment the movement is reversed, as shown in FIG. 3. The retaining pawl 30, pivoted on the pin 27 on which the lever 21 also pivots, is kept in contact with the stop 32 by spring 31 so that at first it is deflected away from the crescent-shaped lever 15, but encounters it in the end phase of its deflecting movement in order, after sliding over the lever 15, as shown in FIG. 3, to place itself in the return path thereof. The other end of the pawl spring 31 rests against a pin 33 which carries the armature l9, and is displaceably mounted in a guide slot 34 of the lever 21.

As may be seen more particularly from FIGS. 4 and 5, a pin 36, provided with a drive disc 35, co-operates with the drive pin 17 which is secured to the lever 12. The pin 36 is fastened to the side of a lever 37 and is mounted by a pivot pin 38 on an auxiliary plate 39 spaced slightly from the base lb. Te one-armed lever 37, biased by a spring 40 (FIG. 2), is in driving engagement with the

shutter blades

41 and 42 which are formed as vanes, for which purpose the pin 36 extends through

longitudinal slots

41a and 42a provided in the shutter blade system. The linkage of the driving lever 37 to the lever 12 is such that the pin 36 driving the

shutter blades

41, 42, follows the drive pin 17, retarded to a certain extent, as soon as the lever 12 and the crescent-shaped lever 15 have left their starting positions. The form of linkage between the two

levers

12 and 37 serves to effect various functions, the first of which, as already described above, is a locking function. Under the bias of the spring 14, which is stronger than spring 40, the lever 12, in its basic position, keeps the

shutter blades

41 and 42 closed, as may be seen from FIGS. 1 and 2. However, as soon as the lever 12 begins to move in an anti-clockwise direction, the

shutter blades

41, 42 also begin to leave their closed positions. The anticlockwise movement of the lever 12, is derived from the intermediate lever 9, the relatively strong driving spring 8 of which ensures that the lever 12 rapidly reaches a position corresponding to the open position of the

shutter blades

41 and 42. In this position, as may be seen from FIG. 3, the lever 12 is held by the magnetic lock 18 32 through the crescent-shaped lever 15 and pawl 30. The time the crescent-shaped lever 15 remains locked is dependent on the operation of an electronic time-control circuit which is shown in FIG. 10. The timing mechanism includes a relaxation oscillator and is actuated from a voltage source E. In addition to transistors T1 and T2, there is a capacitor C which is charged either by way of a photo-resistor P or a fixed resistor F; during the charging of the capacitor, the electro-magnet 18 continuously retains the armature 19, and releases it at the end of the said time.

A switch S in the circuit is actuated by a lug 2a provided on the cocking and release lever 2, the control circuit being connected to the battery as soon as the lever 2 leaves its normal position. The lever 12 has a pin 12b at its free end, which acts on a contact Spring 45 when the lever is in the starting position. The spring 45, together with

stationary contacts

46 and 47 together form switches S and S The switch S is a charging start contact for the electronic timing mechanism, whilst, closure of the switch S establishes a parallel connection with switch S,. This switch S maintains the current supply even if, after the shutter is released, the cocking and release lever 2 is immediately released, at a moment whilst the electronic timing is still not concluded. A switch S switches in either a photo-resistor P for the purpose of exposure-dependent timing, or a fixed resistor F for taking flash-light photographs with a specific exposure time of for example l/30th sec. Ac-

tuation of this switch is effected by means of a setting ring 48 serving also to pre-select an aperture value, as shown in FIG. 12. This, in the setting auto of the ring, the photo-resistor P is included in the control circuit, whereas, in the setting range defined by the aperture scale 48a (manual range) the fixed resistor F is placed in the control circuit.

The mode of operation of the above-described shutter and the co-operation of the

lever system

12, 15, the magnetic lock 18 32 and the drive lever 37 following said system and transferring the

shutter blades

41, 42 first to the open and second to the closed position, is described hereinafter.

If the cocking and release lever 2 is actuated, energy is stored in the drive spring 8 engaging on the intermediate lever 9 so that the spring 8 drives the lever 12 with relatively great acceleration after the intermediate lever drops behind the rejecting catch 12a and subsequent disengagement of the pawl 7. The armature 19 already placed in contact with the electro-magnet 18 during the movement of the lever 2, is retained by the magnet due to the fact that the magnet is energised by closure of the switch 8,, during the actuation of the cocking and release lever 2. Contact 40 actuated by the lever 12 changes over switches S and S as the lever leaves its starting position, whilst the disconnection of contact 45 from contact 46 starts the timing operation of the electronic control circuit, and the transfer of contact 45 to contact 47 results in a parallel connection with the switch 5,. Whilst the outer end of the crescentshaped lever 15, participating in the rapid movement of the lever 12, springs towards the pawl 30 of the magnetic lock 18 32, the drive lever 37 carrying pin 36, is delayedby the bias of the relatively weak spring 40 engaging thereon. Due to the use of shutter blades of comparatively large mass, and a relatively weak spring 40' acting on the drive lever 37, the lever 37 lags progressively behind the lever 12.

The conditions under which the movements of the lever 12 and drive lever 37 are carried out are clearly shown by the time and motion diagram in FIG. 11. With reference to the curve A which shows the movement of the reciprocating lever 12, it is clear that it has already covered its path after 5 m.s. by the time it reaches the reversing point U, whilst the time required by the

shutter blade system

41, 42 until complete opening is about 45 m.s according to the curve B. If the lever 12, including the crescent-shaped lever 15, returns immediately to its starting position after reaching the reversing point U, uninfluenced by the magnetic lock 18 32, the lever, as may also be seen from curve A, re-

turns thereto after approximately 10 m.s. If the crescent-shaped lever 15 is intercepted by the pawl 30 before the return movement starts, and is held by the magnetic lock 11% 32, the return movement of the lever 12 is delayed during the time interval which the electronic timing mechanism requires to release the armature 119 from the electro-magnet 118. In the time and motion diagram shown in FIG. Ill, time units are recorded on the abscissa in m.s, and the ordinate shows aperture values and percentages of the full lens aperture, produced by the

shutter blades

41, 42 for the various opening positions. The exposure values formed by the time and aperture product are shown in the diagram as BLW. Depending on the time at which the magnetic lock 18 32 releases the lever 15, and conse quently the lever 112, for its return, the opening movement of the drive lever 37 and the

shutter blades

41 and 42 is concluded sooner or later by the lever 12, driven by the intermediate lever 9. If the lighting conditions shown in FIG. lll produce an exposure value 10', the

shutter blades

41 and 42 are able to swing out to their full opening width, due to the retarded release of the levers l2 and along the opening curve B shown in the diagram, whereupon the blades return to their starting position along the closing curve A 13' upon reaching the reversing point U at BLW 10. At this time, the release of the levers 112 and I5 coincides with the time at which the

shutter blades

41, 42 have reached the full opening width corresponding to aperture value F4. If the lighting conditions produce an exposure value 1 1 due to more intensive light action on the photo-resistor P, the drive lever 37 moving the

shutter blades

41 and 42 to the open position along the opening curve B, is caused to return by the levers I2 and I5 released by the magnetic lock 13 32, as shown by the curves A", B" in the diagram, this corresponding to an exposure of approximately 1/60th sec. and an aperture of

F

5,6. If there are illumination conditions which produce an exposure value 17 due to even higher light intensity, this permits the lever 12 to return immediately to its starting position after reaching the reversing point U along the curve A, without the lever being delayed by the magnetic lock I3 32. The drive lever 37 moves the

shutter blades

41, 42 to the open position from which they are returned after approximately 10 m.s by the action of the pin 17 on the lever 12. In this case the

shutter blades

41, 42 open to an aperture F16 with an exposure time of l/500th sec. However, exposure conditions of such a low light intensity may occur that the release of the levers l2, 15 is delayed by the electronically controlled magnetic lock I3 32 far beyond the time interval which the drive lever 37 requires for transferring the

shutter blades

41, 42 to the open position along the rising curve B. In this case the spring 44 acting on the drive lever 37 retains the shutter blades 411, 42 fully open until the magnetic lock 118 32 releases the levers under control of the electronic timing mechanism, which in turn moves the shutter blades in a movement parallel to the curve A B to the closed position. At the other extreme, the levers 112, 115, as already described above, are not locked at all, or only for a very short time, and are thus caused to return immediately. The levers 112, 115 encounter the

shutter blades

41, 42 at a point shortly after they begin to open. This produces a pair of values corresponding to an extremely small aperture and an extremely short exposure time. The weaker the intensity of illumination, the

greater are the values of aperture and exposure time as determined by the electronic timing circuit. From FIG. 11 it is clear that, during the entire opening time of the shutter, exposure values of 17" (1/500 sec. and aperture F16) to "(1/60 sec. and aperture F4) can be catered for. Again, by retaining aperture F4, long exposure times may be formed corresponding to exposure values less than 10. In order to ensure that the apertures formed by the

shutter blades

41 and 42, together with the exposure times formed by the electronic time control circuit, produce an exposure value corresponding to the illumination of the photo-resistor P, the edges of the blades forming the light passage opening or aperture are formed as shown in FIGS. 1 3.

It canbe seen from the above that the advantages of the programmed shutter proposed are considerable. Both as regards parts and space the device of the invention shows no increase over a shutter having a fixed diaphragm and electronic timing mechanism. Furthermore, due to the simple design and the aperture-time combination derived from the power of the drive spring 8 in conjunction with the configuration of the edges of the

shutter blades

41, 42, a very high degree of functional reliability is achieved.

In order to achieve a long opening time of the shutter by means of accurate dimensioning of the weak driving force for the

shutter blades

41, 42, two

springs

50 and 51 having different ratings may be used to drive them, as shown in FIGS. 6 8. Here the spring 50, together with the spring 51 act on the lever 37, which in turn act on the

shutter blades

41, 42, but only over certain portions of movement. Thus spring 50 acts over the first third of this movement, as shown in FIG. 7, on the lever 37 by contact with a lug 37b. When this phase of the movement is exceeded, during which the lever 37 has covered approximately a third of its entire path, the end of the spring 50 which previously drove the lever 37, encounters a stationary pin 52, which stops the spring from acting on the lever. The weaker spring 51 then remains effective during the remainder of the lever movement, by acting on a lug 370 of the lever 37. This means that the lever 37 and the

shutter blades

41, 42 cover the last part of their movement under the kinetic energy imparted to them by the spring 50 and under the additional influence of the weaker spring 51, until the blades are fully open. The tension of the weaker spring 51 is such that the

shutter blades

41, 42 open according to the curve S in the diagram shown in FIG. 11, unless motion is reversed to a starting position by the lever 12. The advantage of this double spring drive resides in the feature that the time interval from the triggering of the shutter blade movement until a certain shutter blade opening is achieved remains substantially constant, since the spring 50 is sufficiently strong to overcome any initial friction effects which could lead to considerable variations in exposure values. Thus, even in the case of shutter blades with considerable inertia, very exact results can be achieved even with exposure values needing a small diaphragm aperture and a short exposure time. On the other hand, by selecting the position of the pin 52, the influence of the spring 50 can be interrupted sufficiently early for the opening characteristic not to be steeper in the initial range than the characteristic produced by only one spring acting on the drive lever of the shutter blades, as in the embodiment shown in FIGS. 1 3. Another advantage of the double spring arrangement resides in the feature that the opening time can be made longer than in the case of the single spring. This is achieved, by so dimensioning the weaker spring 51, that in conjunction with the kinetic energy inherent in the shutter blade system after parting from spring 50, the opening characteristic follows an exponential curve extending in the shape of an S, which at the end is almost asymptotic. In the time and motion diagram shown in FIG. 11, this curve is indicated by S. Thus the part of the time and aperture curve before full opening can be extended.

FIG. 9 shows an alternative embodiment of the above-described diaphragm shutter. In this case two cover blades 56 and 57 are associated with the lever 12. co-operating with the intermediate lever 9, the blades being coupled by a pin 17 to the lever 12' which is biased by a spring 14'. As in the embodiment shown in FIGS. 1 3, the lever 12' also carries a contact pin 12b serving to actuate the switches 47, S and S Whilst, in FIG. 9, these switches are not shown for the sake of clarity, the magnetic lock 18 32 is indicated in chain-dotted lines in order to show the co-operation of one shutter blade 57 with the retaining pawl 30'. In the starting or rest position of the lever 12', the cover blades 56 and 57 completely cover the lens opening in addition to the

shutter blades

41 and 42, whilst in the position of the lever 12', corresponding to the opening position of the shutter blades, a shown in FIG. 9, they completely uncover the lens opening. As may also be seen from this illustration, the cover blade 57 cooperates with the magnetic lock 18 32 in the same manner as the crescent-shaped lever 15 in the embodiment according to FIGS. 1 3. The advantage of the above-described cover blade system is that no great attention need be paid to making the

shutter blade system

41, 42 completely light-tight. This is of importance if the

shutter blades

41, 42 are made of a thick material in order to achieve a large mass. It is also not necessary to ensure complete flatness of the blade material, a feature which keeps the manufacturing costs of the shutter low.

For those shutter arrangements which have separate shutter blades for opening and closing respectively, the same conditions apply with regard to the opening movement of the shutter as in the case of a shutter having a reciprocating shutter blade system of the type described. Furthermore, the mode of operation and the drive of the closing blades are important. Provided that the driving force closing the blades is always greater than that for opening the blades, such shutter arrangements using a rapid lever system co-operating with a magnetic lock, and a relatively weak lever system serving to drive the blades open, achieve the same effects as depicted in FIG. 11 as in the case of the above described embodiments.

FIG. 12 shows a selector for the above described diaphragm shutter by means of which the shutter is set to two operating ranges. One range is indicated by auto" and corresponds to the mode of operation apparent from the previous description. The other operating range is a manual range in which a manual aperture setting is possible on the basis of a pre-selected exposure time, for example, 1/30 sec. In particular, this manual range may also serve as a range for flash exposures. In this case the photo-resistor P is switched off by changing over to the manual range and actuating the switch S and, in its place, the fixed resistor F is switched in by which an exposure time suitable for flashlight photos is set by the time control circuit.

In the case of photos with electronic flash, it is important that the flash takes place to coincide with the full opening of the shutter. This may be achieved with a diaphragm shutter of the above-described kind, by designing parts of the setting mechanism intended for manual diaphragm setting as flash contact switches. For this purpose a control cam 60 connected to the selector 48, and the lever 37 moving the

shutter blades

41, 42 are insulated from each other. In the embodiment shown the selector 48 is a ring of synthetic material, and a metal control cam member 60 is mounted thereon. An electrical connection is established between the control cam member 60 and a conventional flashlight attachment provided on the shutter housing by means of an insulated sliding contact 61, the other part of the flash contact switch being formed by the driving lever 37 the end of which, cranked for cooperating with the diaphragm control cam 60a, carries a metal contact member 37a.

When the selector 48, as shown in FIG. 12, is set to the position auto, a recess 60b allows the driving lever 37 to swing out to its fullest extent. If, however, the selector 48 is set to the manual range, i.e. if an aperture value scale on the control cam 60a is placed opposite a fixed mark 62, the driving lever 37 is able to swing out in the course of movement only so far as permitted by the step of the control cam 60a associated with the particular aperture value. At the time, the arrangement is such that, the movement of the setter 48, automatically actuates the switch S which switches on the fixed resistor F into the control circuit of the electronic timing mechanism. This provides a fixed exposure time, for example an exposure time of l/30th sec. suitable for flashlight photos.

Finally, it may be pointed out that the relatively weak driving force for the shutter blades need not be supplied by one or more initially tensioned springs, but that other known means such as electro-magnets may be used as the driving member. In particular, with the use of an electro-magnet in which the armature has to traverse a certain path before it comes into contact with the core, a relatively long opening time may be achieved by providing a spring which by progressively increasing its tension counteracts the armature pull over the last part of its movement, wherein the space between the armature and core is rapidly diminishing. The last portion of the armature movement is thus greatly slowed up. However, a spring is preferred as a driving member for the shutter blades, since it is simple, cheap and small.

What is claimed is:

l. A photographic diaphragm shutter, with an electronic timing circuit, comprising, in combination, shutter blades having a relatively large mass mounted for displacement in the opening and closing directions; first driving means having a driving force which is weak relative to the shutter blade inertia, operable to displace said blades in the opening direction; and second driving means, having a relatively strong driving force, operable to displace said blades in the closing direction; said first driving means comprising a spring having a force which is a fraction of the driving force of said second driving means; said blades having aperture delltll fining edges operable to provide a diaphragm aperture such that there is an exposure time-aperture value corresponding to each instant of time following beginning of such displacement in the opening direction; the position of said blades at any such instant defining a respec tive predetermined aperture; said exposure timeaperture value having a graduation which is uniform with respect to exposure.

2. A photographic diaphragm shutter, as claimed in claim 11, wherein said first driving means comprises first and second springs, said first spring being stronger than said second spring; and means operable to deactivate said first spring after an initial opening movement of said shutter blades; said shutter blades then being moved further under the influence of the kinetic energy imparted thereto by said first driving means, and under the influence of said second spring; said second spring having a driving force sufficient to move said shutter blades to a completely open position and to retain the same in said completely open position.

3. A photographic diaphragm shutter, as claimed in claim 2, in which said shutter blades are oscillatable to open and close a lens opening; means operable to trigger said shutter; an oscillatable part released by operation of said triggering means to oscillate; said first spring being operable to displace said oscillatable part; said oscillatable part being cooperable with said shutter blades to serve as a lock therefor; a magnetic lock operable at the end of the oscillating movement of said oscillatable part to lock said oscillatable part; and circuit means connecting said magnetic lock to said electronic timing circuit; said magnetic lock being released at the end of a time interval determined by said electronic timing circuit to release said oscillatable part for a return movement; said shutter blades, responsive to release of said oscillatable part, moving from the open to the closed position.

4. A photographic diaphragm shutter, as claimed in claim 3, in which said oscillatable part comprises one blade of a cover blade system acting as an additional light safeguard.

5. A photographic diaphragm shutter, as claimed in claim 1, including separate shutter blades for effecting opening and closing of a lens opening, respectively; a locking mechanism operable to lock the closing blades; and circuit means connecting said locking mechanism to said electronic timing circuit; said electronic timing circuit releasing said locking mechanism at the end of a predetermined time interval; said first driving means being operatively associated with the opening of said blades and said second driving means being operatively associated with the closing of said blades.

6. A photographic diaphragm shutter, as claimed in claim 1, including a selector operable to set said shutter to an auto range or to a manual range, of the diaphragm aperture; a control cam connected to said selector and operable, in the manual range, to determine the value of the diaphragm aperture; and a driving lever operable to displace said shutter blades and engaged with said control cam.

7. A photographic diaphragm shutter, as claimed in claim 6, in which said control cam and said driving 1evers are electrically insulated from each other and constitute a switch for a flash circuit.

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Claims

1. A photographic diaphragm shutter, with an electronic timing circuit, comprising, in combination, shutter blades having a relatively large mass mounted for displacement in the opening and closing directions; first driving means having a driving force which is weak relative to the shutter blade inertia, operable to displace said blades in the opening direction; and second driving means, having a relatively strong driving force, operable to displace said blades in the closing direction; said first driving means comprising a spring having a force which is a fraction of the driving force of said second driving means; said blades having aperture defining edges operable to provide a diaphragm aperture such that there is an exposure time-aperture value corresponding to each instant of time following beginning of such displacement in the opening direction; the position of said blades at any such instant defining a respective predetermined aperture; said exposure time-aperture value having a graduation which is uniform with respect to exposure.

2. A photographic diaphragm shutter, as claimed in claim 1, wherein said first driving means comprises first and second springs, said first spring being stronger than said second spring; and means operable to deactivate said first spring after an initial opening movement of said shutter blades; said shutter blades then being moved further under the influence of the kinetic energy imparted thereto by said first driving means, and under the influence of said second spring; said second spring having a driving force sufficient to move said shutter blades to a completely open position and to retain the same in said completely open position.

6. A photographic diaphragm shutter, as claimed in claim 1, including a selector operable to set said shutter to an ''''auto'''' range or to a ''''manual'''' range, of the diaphragm aperture; a control cam connected to said selector and operable, in the ''''manual'''' range, to determine the value of the diaphragm aperture; and a driving lever operable to displace said shutter blades and engaged with said control cam.

7. A photographic diaphragm shutter, as claimed in claim 6, in which said control cam and said driving levers are electrically insulated from each other and constitute a switch for a ''''flash'''' circuit.