US2999445A - Photographic shutter - Google Patents

Description

Sept 12 1961 P. FAHLENBERG 2,999,445

PHOTOGRAPHIC SHUTTER Filed June 9, 1960 2 Sheets-Sheet 1 6 I+ M4-Hb L l Y. l 1l Z l l 8- Fig. Z

Sept. 12, 1961 P. FAHLENBERG PHOTOGRAPHIC SHUTTER 2 Sheets-Sheet 2 Filed June 9, 1960 United States Patent 2,999,445 PHOTOGRAPHIC SHUTTER Paul Fahlenberg, Baierbrunn, near Munich, Germany, as-

signor to Comput-Werk Friedrich Deckel OHG, Mu-

nich, Germany, a rm of Germany Filed June 9, 1960, Ser. No. 35,070 Claims priority, application Germany June 19, 1959 8 Claims. (Cl. 95-63) The present invention relates'to a photographic shutter and, more particularly, to an electrical timing mechanism for controlling the interval between the opening and closing of the shutter blades. Y

An object of the invention is to provide a generally improvedand more satisfactory photographic shutter of the objective type having a Wide range of shutter speeds which may be timed.

' Another object is the provision of a new and improved photographic shutter arranged to have an electrical timing device for controlling accurately a plurality of shutter speeds.

Still another object of the invention is to provide a shutter timing device for a photographic shutter employing a delay circuit comprising a capacitor and resistor in serres.

A further object is the provision of a photographic shutter having a timing device of the foregoing kind and wherein the timing device acts upon a magnet system for releasing a shutter blade actuating member at the end of a preset 'period of time.

These and other desirable objects may be attained in the manner disclosed as an illustrative embodiment of the invention in the following description and in the accompanying drawings forming a part hereof, in which:

FIG. 1 is a schematic wiring diagram of a circuit for the shutter timing device according tothe invention;

FIG. 2 is a schematic illustration of a magnet system associated with the timing device of FIG. 1;

FIG. 3 is a modification of the circuit shown in FIG. l;

FIG. 4 is a front view of a photographic shutter equipped with the timing device according to the invention, portions being broken away to show interior detail; and

FiG. 5 is a fragmentary axial cross-section taken radially approximately on a line A-A of FIG. 4.

The same reference numerals throughout the several views indicate the same parts.

Referring more particularly to the drawings in FIG. l, a time delay circuit and an associating compensating circuit are connected with a source of potential 2 through a mast-er Switch 4 and a change-over switch 6. The time delay circuit includes a capacitor 8 in series with a variable resistor 10. Shunted across the capacitor 8 are an inductor coil 12 and also a resistor 14 through which the capacitor discharges when its plates are short-circuited by the change-over switch 6. The voltage applied to the compensating circuit comprising a second inductance 16 in series with a variable resistor 18 may be adjusted by appropriately setting the tap of a potentiometer 20.

As shown in FIG. 2, the inductance coils 12 and 16 are wound in opposite directions on the pole pieces 22 of a permanent magnet 24, in such a way that a current iiowing through winding 12 will generate a magnetic iield opposing the iield of the permanent magnet, whereas a current passing through winding 16 will generate a magnetic field in the same direction as that of the permanent magnet. An armature 26 which cooperates with this magnet is biased by a spring 28 away from the pole pieces 22 -to oppose the magnetic attraction between the magnet and armature, and normally retains the armature 26 at a distance from the pole pieces 22. g

Prior to the performance of a timing operation, an arrangement to be described later in connection with FIG. 4

'2,999,445 Patented Sept. 12, 1961 ice 2. places the armature 26 into contact with the pole pieces 22 and is magnetically held in place because the force of the permanent magnet exceeds the restoring force of the spring 28. Change-over switch 6 is at the same time moved to connect the time delay circuit with the source of potential 2, as shown in FIG. l. Conveniently, the switch 6 is mechanically coupled with the armature 26 in a manner to be explained later. In this position, the delay circuit including the capacitor 8, the resistor 10, and the inductance 12, and the compensating circuit including the inductance 416, the resistor 18, and the potentiometer 20, are connected with one contact of the master switch 4. While the two-way switch 6 was in its former position, the capacitor 8 discharged completely through the resistor 14.

Upon the closing of the switch 4, the inductance 16 is energized and the substantially constant magnetic linx produced thereby supports or adds to the effect of the magnetic flux of the permanent magnet 24. The magnitude of the additional magnetic ilux contributed by the inductance 16 may be controlled by adjustment of the potentiometer 20 and of the variable resistor 18. At the same time, the capacitor 8 begins to accumulate charge at a rate determined by the magnitude of the resistance of the variable resistor 10. The ow of current through the inductance 12 commences to generate a magnetic ux which opposes the magnetic flux of the magnet 24 and the inductance 16. The opposing flux yrises as charge of the capacitor 8 increases, the magnetic force of attraction which retains the armature 26 decreasing by a corresponding amount. At the end of a predetermined time interval determined by the position of the tap of the potentiometer 20 and the adjustment of the two resistors 10 and 1S, the magnetic force of attraction falls below the level of the mechanical pull of spring 2S. At the instant that this occurs, the armature 26 is released from the pole pieces 22. In order to have the rate of change of the magnetic ilux as high as possible, the circuit is designed so that the armature will be released in the first part of the exponential charging characteristic of the capacitor. It will be recalled that the armature 26 is coupled with the change-over switch 6, so that release of the armature also actuates the change-Over switch 6 to short-circuit the capacitor `8 through the resistor "14, allowing the capacitor to discharge.

The circuit shown 4in FIG. 3 is avmodiication of the circuit shown in FiG. l. It comprises the same components as FIG. l excepting that theL inductor coil 12 is connected in series with the resistor 10 and the capacitor 8. For this circuit, the coils 12 and 16 are wound on the pole pieces 2 2 of the magnet so that the constant magnetic flux generated when the coil 16 is energized, opposes the flux of the permanent magnet, whereas the variable iiux generated by the coil 12 is in the same direction as that of the permanent magnet. The functioning of the circuit of FIG. 3 is similar to the circuit of FIG. l, `and further explanation is not required.

In both of the described circuits, the timed interval between the closing of the switch 4 and the release of the armature 26 is unaffected by the operational voltage of the source of potential 2 if the armature is released at the precise instant the resultant magnetic ux becomes zero, and if the further condition is satisfied that the resistances are proportional to the relative number of turns. The former condition can not be strictly fulfilled because the spring 28 is required to provide a given bias, but by suitable designing the dimensions of the mechanical parts which the spring is required to move (see FIG. 4), optimum conditions can be at least approximately established.

The practical application of the timing device de- E, scribed in FIG. 1 to a photographic shutter is illustrated in FIGS. 4 and 5. For the sake of clarity, the drawing is largely confined to showing the components associated with the mechanical operations, The elements of the electrical circuit are shown in FIG. 4 only to the extentv needed to convey a clear understanding of their cooperation with the mechanical movements.

The shutter is housed in an annular casing 30 having a rearwardly extending externally threaded tubev32 for securing the shutter to the body of a camera. An annular baseplate 34 is secured within the casing by screw fasteners, the center line of one being indicated at 36. An adjustable iris diaphragm is provided, including a plurality of diaphragm leaves 38 pivoted to a stationary blade-bearing ring 40, and adapted to be actuated by a ring 42 mounted to rotate about the optional axis. The ring 40 is secured to the casing 30 as at 44, representing the center line of a screw. The leaves of the diaphragm are pivotally mounted on pivot pins 46 on the ring 40, while the diaphragm leaves themselves carry other movable pivot pins 48, each engaged in a cam slot 50 in the actuating ring 42. In the well known manner, rotation of the ring 42 swings each diaphragm leaf 38 about its respective stationary pivot 46, to change the aperture of the diaphragm.

Secured to the baseplate 34 fis a forwardly projecting lens tube S2 which is centrally mounted and secured in a suitable manner not here shown. The shutter blade actuating mechanism is mounted on the baseplate 34 within the annular lens tube 52 and the outer wall of the casing 30. Although other types may be used, the shutter actuating mechanism may take the form disclosed in Patents 2,900,885 and 2,900,886 to K. Gebele, issued August 25, 1959. A plurality of shutter blades 54 are provided and are coupled for operation with a blade actuating ring 56 mounted for rotation about the optical axis, and also with a blade-bearing ring S which differs from the conventional form of construction in that it is likewise arranged to be rotatable about the optical axis. These two rings 56 and 58 bear radially on centering anges on the lens tube 52. The ring 56 is axially secured between the lens tube 52 and the baseplate 34, while the ring 58 is axially secured between the baseplate 34 and a separate retaining plate 62 disposed to the rear of the base plate and secured thereto by screws indicated by center line 60.

The shutter blades 54 pivot on pins 64 xed to the shutter blade-bearing ring 58 and are provided with elongated slots 66 engaged by driving pins 70 on the blade-actuating ring 56. The driving pins 70 extend through apertures 68 in the baseplate. The shutter blade mechanism is therefore so arranged that common rotation of the actuating and bearing rings 56 and 58 will not cause the blades 54 to swing on their pivots 64, whereas relative motion between the two rings will cause the blades to swing on their pivot pins 64. For the purpose of rotating the blade-actuating ring 56, referring to FiG. 4, the ring 56 is provided with a radial arm 72 having a pin 74, and also with another radial arm 76 to which is secured a tension spring 7S and a switch operating pin 77 made of insulating material. The other end of the tension spring 78 is attached to an eye on a lug 80 slidably mounted on the baseplate 34 and screwed down at a selected position of adjustment, Upon clockwise displacement of the arm 76 from the position shown in FIG. 4 and back again against the stop 81, a leaf spring 79 secured to the baseplate serves to absorb the momentum of the ring 56 and to prevent rebound upon striking stop pin 81.

The pin 74 on the arm 72 is actuated by the working edge 82 of a cam 34 which is fixed to a rotatable tensioning shaft 86 extending through casing 30 parallel with the optical axis. The cam 84 is urged to an inoperative position against the wallA of the casing by a return spring 8S. The springy 88 bears against a lpin on 4, the cam 82 and likewise against the wall of the casing. Tensioning shaft-86 is preferably coupled in a suitable manner with the film winding mechanism yin the camera body, not shown in the drawing, so that the shaft is turned clockwise through an appropriate fraction of a revolution, each time that the film is wound or advanced, and then is restored by the spring 88 to its normal rest position.

The blade-bearing rin-g 5S has a radial projection or abutment 90 to enable it to be entrained by a pin 70a on the blade-actuating ring 56 upon rotation of the ring 56 in a counter-clockwise direction. A radial arm 92 on the blade-bearing ring 58 is fastened to one end of a tension spring 28. The spring 28 and also the armature 26 of the magnet are secured to a pin 94 which extends from arm 92 perpendicular to the plane of the ring 58 and passes through a guide slot 96 in the baseplate 34. The other end of the tension spring 28 is fastened to an eye in a lug 98 slidably mounted on the baseplate 34 for adjustment and held in a desired position by screws. Another radial arm 100 of the bladebearing ring 58 carries a switch operating pin 102 which likewise extends perpendicular to the plane of the ring 58 and projects through a slot 104 in the base plate 34.

The master switch 4 takes the form of a leaf spring fastened at one end to the baseplate 34 and bearing at its other end a contact 4a to be detiected away from the baseplate 34 into engagement with another contact located forwardly of it perpendicular to the plane of the paper. In similar fashion, the change-over switch 6 is provided by a deilectable leaf spring having at its end a contact 6a, which may be engaged with another con ltact located forwardly of it. The master switch Itis' deflected forwardly by the switch operating pin 77 which slides across a sloping ramp 4b at the under side of the leaf spring. The master switch 4 is thus opened, and is closed when the leaf spring is in its normal unexed position. ln the case of the changeover switch 6, lthe switch operating pin 102 slidably engages the under side of the leaf spring and pushes it forwardly intoengagernent with the cooperating contact of the discharge resistor 14, whereas in the normal position of the leaf spring, the contact makes connection with a source of potential 2'.

Baseplate 34 also supports the permanent magnet with pole pieces 22 about which are wound coils 12 and 16. A shutter release pin extends through baseplate 34 to be slidably movable parallel to the optical axis. The release pin 110 is loaded by a weak spring not shown in the drawing, Vthereby to be urged into contact with the arm 76 when the shutter is untensioned, as illustrated in FIG. 4, but rises further from the baseplate 34 for engagement with the rear edge 76a of arm 76 when the shutter is tensioned and the arm 76 is moved counter-clockwise against the stop pin 112. The with drawal of the release pin 110 to trip the shutter and hence release arm 76 is effected by mechanism incorporated in the camera and well known to the art, so that further description is unecessary as regards the present invention. So far as the present invention is concerned, it is sufficient to say simply that the latching pin l110 is withdrawn in a rearward direction when an exposure is to be made.

For the operation of the photographic shutter of FIGS. 4 and 5, the tensioning shaft 86 is initially rotated in a clockwise direction so that the working edge 82 of cam 84 entrains pin 74 and moves it in the path illustrated by the dotted arrow into the position indicated by a dotted circle. The blade actuating ring S6 is thus rotated counter-clockwise about the optical axis against theresistance of spring 78 until the radial arm 76 engages lirnit pin 1112. The release pin 110 is biased forwardly and retains the blade actuating ring 56 in this tensionedpositiQn,Whereas cam 84 is restored to its rest position by` the retaining spring 88,

As the ring 56 is moved toits tensioned position,.the pin 70u engages the abutment 9,0`and entrains the bladebearing ring 58 for rotation in the4 same direction so that no relative motion` between/ the two rings occurs and the `shutter bladesV 54l therefore remain in closed position.

As lthe blade-bearing ring' 58 is rotated, the spring 28 is energized and armature 26 Vmoves-into contact with the pole pieces 22 of the permanent magnet. When the two rings `56 and 58 are in flly tensioned position, the permanent magnet attracts and retains the armature 26, while there is a slight separation of arm 76 from abutment 90. Theresultant slight relative motion between the two blade rings 56 and 58 is compensated by allowing suiiicient overlap between the individual shutter blades 54 so that no light will enter the camera. Toward the end of the tensioning movement, the master switch 4 is engaged by thepin 77 txed tothe ring S6, and moved to open position. Immediately afterward, the switch operating pin 102 carried by the rin-g 58 causes connection to be made with the source of potential 2.

Upon the completion of the above-'described mechanical movements, the shutter is cocked or tensioned and the electrical timing device laccording to the invention is ready to be operated for controlling the duration of the shutter opening. The resistors and 18 and the potentiometer 2t) may now -be adjusted to determine the desired exposure time, although it will be understood that these adjustments may be made before the shutter is tensioned.

Upon operating the shutter release to retract the release pin 110, the blade actuating ring 56 is rotated clockwise by the energy stored in the spring 78 to return it to its rest position. It will be recalled that the blade-bearing ring 58 is magnetically held in its tensioned position, sovthat this rotation of the ring 56 in clockwise direction causes the blades 54 to swing on their pivot pins `64 to open the shutter. At the same time, the switch actuating pin 77 slides olf of the sloping ramp `4b of `the Imaster switch 4 and allows the leaf spring to deflect down to close the switch. The electrical timing device will therefore now begin to function in the manner previously described with regard to FIGS. 1 and 2. The momentum of impact by the return of arm 76 against stop pin 81 is absorbed by the friction betweenV the leat` spring 79 and the pin 77,

As soon as the armature 26 is released from the pole pieces 22 of the magnet at the end of the pre-set time, the spring 28 pulls thev armature 26 away and at the saine time returns the blade bearing ring 58 clockwise back` to its rest position. The resultant relative motion between the ring 58 is opposite to .that of the preceding relative motion, and the blades 54 are swung back into a closed position covering the camera opening. The actuating pin 102 on the blade-bearing ring 58 lslides underneath the leaf spring of the change-over switch 6 and thus .causes the electrical connection of the timing device with the vsource of potential to be interrupted, and the capacitor S to be Short-circuited. The shutter has now been restored to its initial rest position and is ready for another operation Kby actuation of tensioning shaft 86.

A distinct advantage of the electrical shutter timing device according to the invention is its substantial independence in operation from the voltage of the source of supply. Consequently, fluctuations in the supply voltage have little or no cliect on the operation of the timing device. Moreover, a very small current is required to operate the timing device, because the opposing magnetic field need not be more powerful than is necessary for compensating the difference between the magnetic attraction and the pull of the bias spring. This latter feature affords the additional advantage of permitting the time of exposure to be controlled extremely accurately. At the same time, the exposure time may be varied within very wide limits. The necessary adjustments for setting the shutter speeds are few in number, and, in the case of the variable resistors, they may even be zero if the resistors are embodied in photosensitive elements. This possibility is of importance should it be desired to control shutter speeds automatically. Finally, in the construction of photographic apparatus, the use of the proposed timing device greatly reduces the difhcult problem of accommodating the necessary retarding mechanism within the restricted available space. The construction is quite suitable for a compact and light-weight hand camera, as a small and light dry cell (e.g., a small flashlight battery) is suiiicient for furnishingthe electrical power needed for operation.

It is seen from the foregoing disclosure that the above mentioned objects of the invention are well fulfilled. It is to be understood that the foregoing 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.

For a person who has difficulties to read an electrical circuit diagram it is explained supplementary to FIG. l;

If-the capacitor 8 being dischargedwthe switch 4 is closed and thus the arrangement is connected to the source of potential 2, four ways are open for the current. The first two ways are given at the one hand by the potentiometer 20 and at the other hand by the winding 16, the variable resistor 18 and the potentiometer 20. Since with the help of the control members 18 and 20 the drop of potential has been regulated in advance in the winding 16, there iiows an exactly controlled current of constant power in the winding 16. Thus a constant magnet iield is generated which is rectified to that of the permanent magnet 24 and thus increases the magnetic force of attraction of the latter by a constant amount.

The other two ways lead either through the winding l2 and the variable resistor 10 or via the capacitor Sand this resistor. The tiow of current in these branches of the current circuit is variable. The discharged capacitor 8 attracts the liow of current so that in the beginning there does not flow any current through the winding 12. While the charge of the capacitor increases the charging speed being regulated in advance by means of the resistor 10 the capacitor becomes a resistor of automatically increasing resistance. Consequently, the flow of current through the winding 12 and thus the magnetic eld around this winding increases during the charging of the capacitor 8. This magnetic field, however, opposes, as described above, that of the permanent magnet 24 and that generated by the flow of current in the winding 16. Therefore the resulting magnetic force of attraction of the magnet combination consisting of the permanent magnet 24 and the winding 16 and 12' decreases so that the armature 26 is released from the pole pieces 22. The duration of the whole process depends on the variable (resistor 18 and potentiometer 20) magnitude of the magnetic force of attraction and the variable (resistor 10) expense of time for the annihilation of thisV force of attraction.

The understanding of the electrical circuit diagram shown in FIG. 3 results from the description above. The variant according to FIG. 3 distinguishes itself by the fact that it contains only one switch 7 which has the functions of the switches 6 and 4 in FIG. 1. The switch 7 is mechanically cou-pled with the release button (not shown) in such a way that the position of the switch 7 as shown in the drawing corresponds to the rest position of the release button.

What is claimed is:

1. An electrical timing device for photographic cameras comprising a delay circuit means including a capacitor and resistor in series and also a first inductance coil, a source of potential for said circuit means, and compensating circuit means including a second inductance coil con` nected through a potentiometer with said sourcev of potential, characterized by a permanent magnet with which said first and second coils are magnetically coupled, an armature cooperating with said magnetV and, biased by a spring which opposes the magnetic force of attraction, the first of said coils producing a constantmagnetic ux while the second of said coils produces an oppositely directed flux which changes in magnitude dependingv on the changing capacitor charge so that the total iiux acting on the armature varies as a function of time.

2. A construction as defined in claim l wherein said irst inductance coil in said delay circuit means is in series withv said capacitor.

3. A construction as defined in claim l wherein said iirst inductance coil in said delay circuit means is in parallel With said capacitor.

4. A construction as deiined in claim 1 including a discharge resistor in parallel with said capacitor and a switch for simultaneously disconnecting said source of potential and coupling said capacitor to be discharged through said discharge resistor. f

5. A photographic shutter comprising lmovable blades,

- means for moving said blades to an open position to make an exposure, spring means tending to close said blades, a permanent magnet tending to hold said blades in open position against the force of said spring means, a magnetizing coil and a demagnetizing coil both in operative position with respect to said permanent magnet and operative, when current flows through'them, respectively to increase and to decrease the magnetic force tending to hold said blades in open position, a capacitor operatively connected to one of said coils to control the rate of ow of current therethrough, said permanent magnet serving to hold said blades in open position until the total magnetic attraction produced by said permanent magnet increased by the magnetic force of said magnetizing coil and decreased by the magnetic force of said demagnetizing coil falls below the force of said spring means, whereupon said spring means will close said blades, a source of electric current, and means effective concomitantly with movement of said blades to open position for connecting both of said coils simultaneously to said source of current, to minimize the eiect of variations in potential of said current upon the time interval from the opening of said blades to the closing thereof.

6. A construction as dened in claim 5, further including switch means operative upon closing said blades for discharging any charge remaining in said capacitor.

7. A photographic shutter comprising movableblades, a irst blade ring and a second blade ring separately movable and both pivotally connected to said blades, separate spring means tending to move each of said blade rings from a tensioned position to a rest position, said blades remaining closed when both of said rings are in their respective rest positions and when both of them are in their respective tensioned positions and being opened by movement of the iirst blade ring from tensioned position to rest position `While the second blade ring remains in tensioned position and being subsequently closed by movement of the second blade ring from tensioned position to rest position while the first` blade ring remains in rest position, magnetic means of variable force for holding said second blade ring in its tensioned position against the force of its spring means as long asI the force of said magnetic means exceeds the force of said last named spring means, said magnetic means including two electromagnet coils whose respective magnetic forces oppose each other, a source of electric current, switch means for operatively connecting both of said coils simultaneously to said source of current at the beginning of an exposure, electric capacitor means Ifor varying the flow of current through one of said coils as a function of time, and adjustable means for controlling the ow of current through one of said coils to vary the duration of an exposure, the simultaneous connection of both of said opposing coils to said source of current serving to minimize unwanted variations in duration of exposure which would otherwise occur V,as a result of variations in the electrical potential of said source of current.

8. A photographic shutter comprising movable blades, a rst blade ring and a second blade ring separately movable and both pivotally connected to said blades, separate spring means tending to move each of said blade rings from a tensioned position to a rest position, said blades remaining closed when both of said rings are in their respective rest positions and when both of them are in their respective tensioned positions` and being opened by movement of the first blade ring from tensioned position to rest position while the second blade ring remains in tensioned position and being subsequently closed by movement of the second blade ring from tensioned position to rest position while the rst blade ring remains in rest position, magnetic means of Variable force for holding said second blade ring in its tensioned position against the forceof its spring means as long as the force of said magnetic means exceeds the force of said last named spring means, said magnetic means including two electromagnet coils Whose respective magnetic forces oppose each other, a source of electric current, switch means operated by movement of said rst blade ring from tensioned position to rest position for operatively connecting both of said coils simultaneously to said source of current at the beginning of an exposure, electric capacitor means for varying the flow of current through one of said coils asa function of time, adjustable means for controlling the iiow of current through one of said coils to vary the duration of an exposure, the simultaneous connection of both of said opposing coils to said source of current serving to minimize unwanted variations in duration of exposure which would otherwise occur as a result of variations in the electrical potential of said source of current, and switch means operated by movement of said second blade ring from tensioned position to rest position for discharging any `charge remaining in said capacitor means.

References Cited in the tile of this patent UNITED STATES PATENTS

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