US3568586A

US3568586A - Photographic shutter with reciprocating sectors and electronic exposure timing device

Info

Publication number: US3568586A
Application number: US745229A
Authority: US
Inventors: Waldemar T Rentschler
Original assignee: Prontor Werk Alfred Gauthier GmbH
Current assignee: Hittech Prontor GmbH
Priority date: 1967-07-21
Filing date: 1968-07-16
Publication date: 1971-03-09
Anticipated expiration: 1988-03-09
Also published as: DE1282441B; GB1184758A

Abstract

A device for obtaining constancy in the movement of a photographic shutter at even the shortest exposure time having a spring mechanism located between the magnet armature and the member locking the blade driving part. The spring mechanism is releasable by the magnet armature to actuate the member locking the blade driving part. The spring mechanism is so formed that the time interval from the beginning of the actuation of the member locking the blade driving part to its disengagement from the blade driving part is substantially independent of the member locking the blade driving part, and approaches a zero value.

Description

United'States Patent i 72 Inventor Waldemar T.Rentschl er [56] References Cited Black Forest, Germany UNITED STATES PATENTS P 745,229 3,376,801 4/1968 Fahlenberg 95/53 221 Filed J ly 1 1968 3 400 645 9/1968 K rper 95153.3(X) [45] Patented Mar.9, 1971 e 3 425 328 2/1969 I ChljO 95/53(X) [73] Assrgnee Prontor-WerkAl'redGauthier G.m.b.l-l. 3 448 672 6/1969 Si 95/530) Calmbach/Bhckhm, Gem! nger [3 2] P i i J l 21, 1967 Primary ExaminerJohn M. l-loran [33] m Assistant Examiner-Robert P. Greiner 31] P 41 45 Attorney-March, Gillette and Wyatt ABSTRACT: A device for obtaining constancy in the move- [54] P mw ONIC ment of a photographic shutter at even the shortest exposure 2 8 RETXMgG DEVICE m time having a spring mechanism located between the magnet Po U armature and the member locking the blade drivin part. The 6 c s on in 8 hm i spring mechanism is releasable by the magnet armature to ac- [52] US. Cl 95/53, tuate'the member locking the blade driving part. The spring 95/533, 95/63 mechanism is so formed that the time interval from the [51] Int. Cl..., G03b 9/58, beginning of the actuation of the member locking the blade 60% 9/62 driving part to its disengagement from the blade driving part is [50] Field of Search ..95/53,53.3, substantially independent of the member locking the blade 63, 10 (inquired) driving part, and approaches a zero value.

2 Sheets-Sheet 1 INVE N TOR Waldemar 7IRenisch/er BY March Gillei te & Wyatt AT TORNEYS Patented March 9, 1971 2 Sheets-Sheet 2 IN VE N TOR Waldemar IRentschLer March, Gillette &WyaH

ATTORNEYS PHOTOGRAPHIC SHUTTER WITH RECIPROCATING SECTQBfi AND ELECTRONIC EXPOSURE TIMING DEVICE duration of the timing, the shutter drive having a device associated therewith to delay the shutter opening movement to compensate the various time lags of the mechanical locking catch of the shutter.

In shutters of the above kind having a driving spring causing the opening and closing movement of the shutter blades, timing is effected by locking the shutter drive in a position corresponding to the open position of the blades by means of an electromagnetically releasable-stop, and the latter is released again after an electronically controlled time interval, whereupon the driving spring closes the blades again. The stop is preferably so fashioned that the shutter drive is not held by the magnetic armature itself, but by a separate catch which in turn is actuated by the released magnetic armature after the magnet coil is deenergized. The magnetic armature is subject to the action of a return spring urging it in the direction of release, the spring being weaker than the holding force of the magnet, so that when the magnet coil is energized the armature is retained against the action of the spring in abutment against the magnet core. With this method of operation the stop cannot be released immediately at the instant at which the magnet is deenergized, but only after the lapse of some milliseconds. The reason for this is that the magnet armature and the catch have to move certain distances before the latter v is disengaged from the locked shutter driving part, which may be the blade driving ring.

In order to obtain a shutter timing independent of the aforesaid time interval existing between the deenergizing of the magnet and the stop becoming ineffective, and as determined by a photoresistor, it has already been proposed to provide a device serving to compensate the said time lags of the mechanical stop. This compensating device produces at the shortest exposure time, e.g., one five-hundredth sec. which is only dependent on the mechanical shutter drive, a shutter drive action completely unaffected by the stop, since the start contact initiating the timing, due to the retarding effect of the compensation mechanism, is closed so early with reference to the fully open position of the shutter, that when the blades are fully open, the magnet armature has already left the electromagnet and hence prevents the catch from engaging the shutter drive.

It has, however, been found that even when using a compensating mechanism of the kind referred to above, the object aimed at, namely to ensure continuous shutter timing over the whole range, could not be attained, more particularly at the fastest shutter speed, i.e., one five-hundredth sec., where despite the automatic control a certain instability occurs in this time range; it was found that not an intermediate speed, for instance a time value between one five-hundredth and one two hundred and fiftieth sec. but alternatively either one fivehundredth sec. or one two hundred and fiftieth see. was obtained. Investigation of this phenomenon showed the occurrence of certain deviations in the movement time of the stop mechanism consisting essentially of the magnet armature and catch, depending upon whether before releasing the drive stop the catch is biased or unbiased by the shutter drive. it has been found that if the catch is biased by the shutter drive the return movement of the stop member, from the instant of deenergization of the armature, occupies more time than in the case in which the parts can move without prior biasing by the driving force. This is because if the stop is in the biased state it has to be released against the frictional force or the prevailing surface pressure existing between shutter drive and the catch.

The present invention resides in means for obtaining constancy in the movement of the device serving the exposure timing even at the shortest exposure time, without any significant additional structural-complexity in the shutter systems of the kind referred to.

The invention consists in that between the magnet armature and the catch locking the blade driving part a spring relay is located which is releasable by the magnet armature to actuate the catch and is so formed that the time interval from the beginning of the actuation of the catch to its disengagement from the blade driving part is substantially independent of the catch loading, and approaches a zero value. In this way the period necessary for disengagement of the catch biased or unbiased, by the shutter drive is substantially constant, so that from the shortest to the longest exposure time of the shutter the timing takes a continuous course.

In a simple embodiment of a spring relay readily adaptable to the structural conditions of a shutter with electronic timing, there is a rotatably mounted two-armed actuating lever subject to the action of a relatively powerful spring, one lever arm of which is adapted to be locked by means of a pawl movable by the armature lever from the catch position, and the other lever arm of which cooperates with the catch. This arrangement may be simplified by mounting the two-armed actuating lever on the same pivot as the armature lever.

To ensureas simple as possible an operation of a shutter equipped with a spring relay and having an electronic timing device, according to a feature of the invention a cocking arm is moved during the cocking process of the'shutter, by means of which arm the actuating lever is brought into the cocking position and the magnet armature caused to abut against its magnet. To ensure an action unaffected by manufacturing inaccuracies, the cocking arm is formed by two levers mounted on the same pivot and positively supported against one another, one lever of which cooperates with a movable part of the shutter drive mechanism and the other with the actuating lever of the spring relay and the armature lever.

Reference should now be made to the accompanying drawings, in which:

FIG. I is an electronic shutter with its compensation mechanismin the cocked position;

FIG. 2 is a fragmentary view of the shutter shown in FIG. I with the shutter blades in the open position and the locking mechanism still in the stop position;

FIG. 3 is a further fragmentary view of the shutter blade drive mechanism, in which the locking mechanism has just released the return movement to transfer the blades into the closing position;

FIG. 4 is a diagram of the time interval divisions which occur between the deenergizing of themagnet of the timing device and the disengagement of the catch of the locking mechanism; and

FIG. 5 is a fragmentary section through the electronic shutter on the line V-V of FIG. 2.

The numeral 1 in the drawings denotes the base plate of a photographic shutter which is arranged in a shutter housing 2 and provided with a lens socket la. The base plate 1 serves to mount the shutter drive mechanism, which comprises a cocking and driving shaft 4, a driving disc 5 fixed thereto, a driving spring 6 acting thereon and a drive pawl 7 connected to the driving disc, the free end of the pawl cooperating so with the driving ring 8 of the shutter blades 9 through a lug 8a so that when the driving disc 5 rotates in the direction of the arrow, the driving ring 8 and the blades 9 execute a reciprocating movement. To lock the driving disc 5 in the cocked position shown in FIG. 1 a two-armed stop lever 10 is used, one lever arm of which is engaged by that of a further two-armed release lever 11 only part of which is shown in FIG. 1, the other part being indicated by a chain-dotted line. This lever is actuated by means of the camera release 12, also only part shown in FIG. 1, which is in operational engagement with the lever ill via suitable intermediate members which in the drawings are shown only by a chain-dotted line.

To hold the blades SI of the shutter open for a duration determined by an electronic switching device to be described in detail hereinafier, the driving ring 8 has a further lug 8b projecting through a slot in the base plate 1, which lug is locked by a spring-loaded catch 14, when the shutter blades are in an open position as shown in FIGS. 2 and 5. This catch as shown in FIG. is provided for this purpose with an engaging pin 14a and a laterally projecting lug 14b, which by means of a spring 15 acting on the catch is adapted to be moved into the movement range of the lug 8b provided on the driving ring 8 and to be moved out of the stop position by means of an actuating lever 17 rotatably mounted on the base plate 1, this lever 17 being acted upon by a relatively powerful spring 16. The actuating lever 17 is mounted on a pin 13 and has two

arms

17a and 17b and is adapted to be locked in a cooked position by a pawl 18. Mounted coaxially with the actuating lever 17 formed as a spring relay on the pin 13 there is a one-armed lever 19, at the free end of which an armature 20 is hinged. An electromagnet 21 connected in circuit with an electronic timing device acts on the armature 29. The timing device has a delay circuit 23 of known type and not shown in further detail in the drawings. This circuit is preferably formed as a trigger circuit comprising several transistors with a feedback path.

' The time determining members comprising the photoresistor R and capacitor C are located in thecircuit with a bat tery B adjacent to the electromagnet 21 and the electronic delay circuit 23. Apart from this RC network there is a main switch S actuable by the release mechanism 11 of the shutter, a start contact S, initiating charging of the capacitor C, and a switch 8, which changes over the photoresistor R at the beginning of the starting movement of the driving ring 8 from a moving coil meter 1 to the circuit of the timing device. The load start switch S, normally short circuits the capacitor C shown in FIG. 1, whilst the moving blade of the switch S establishes an electric connection between photoresistor R and the moving coil meter J. The starting movement of the driving ring 8, causes the pins 8c and 8d to transfer the two moving blades away from these previously made contacts; the switch S, changes over the photoresistor R to the circuit of the electronic timing device, and the switch S removes the short circuit on the capacitor C and hence initiates shutter timing. The pawl 18 is provided to lock the

spring relay

16, 17 and biased by a spring 25, is so formed that it constantly participatesin the movement of the armature lever 19, the latter being provided with an engaging pin 27 acting as support of the pawl. A device for compensating the time constant of the aforesaid mechanical catch and which is formed by a brake lever 29 subject to the action of a spring 28 and a rotatably mounted heavy disc 30 operationally connected therewith, cooperates with the driving ring 8.

Referring to the aforesaid spring relay consisting of spring 16 and actuating lever 17 in connection with the aforesaid compensation mechanism 28 to 30, the object of these devices is to obtain a range of continuous shutter speeds, all of which, even to the fastest speeds, remain constant, independently of whether the driving ring 8 has been locked in the shutter open position or not. Thus, catch 14 is no longer released as hitherto directly by the magnet armature, but by the

spring relay

16, 17 located between the latter and the catch 14 acting on the driving ring 8. This spring relay on release actuates the catch 14 with considerable force to reducethemovement time for this catch, up to the instant of disengagement at the lug 8b of the driving ring 8, to as near zero as possible. The time required for the movement of the catch 14 from a stop position is substantially the same, whether it is loaded or not. The driving force of the

spring relay

16, 17 is made as great as possible for this purpose. Apart from a certain maximum cocking pressure, the driving force of the

spring relay

16, 17 is indirectly limited by the holding force of the electromagnet 21. The latter has always to be greater than the return force of the return spring 31 acting on the armature lever 19. On the other hand, the return force of this spring must be great enough to cancel the latching of the

spring relay

16, 17 by the pawl 18 without appreciable loss of time.

On the presumption that the movement time of the catch M both in the loaded and unloaded state is substantially uniform, as shown by FIG. 4, the whole time interval T occurring between the deenergizing of the electromagnet 21 and the disengagement of the catch from the driving ring 8 can be compensated by the compensating mechanism 28 to 30. This time interval T is divided into the following time sections:

t movement time of the magnet armature 20 from leaving the electromagnet 21 to the release of the

spring relay

16, 17 by the pawl 18;

t starting time of the

spring relay

16, 17 to contact with the catch 14; and

t movement time of the catch 14 to the disengagement of the lug 8b of the driving ring 8.

From this diagram it is evident that the time sections t, and t, are completely independent of whether the catch 14 is loaded or not. They may thus be completely compensated for all shutter timings by means of the compensating mechanism 28 to 80. The only difference between the timing of the loaded and unloaded catch 14 exists only with regard to the time section i The

spring relay

16, 17 which by means of a relatively powerful spring causes this time section to approximate to zero, thus greatly reduces timing variations regardless of whether the catch 14 is to be moved loaded or unloaded from the stop position. Hence the time section t may also be taken into consideration by means of the compensating

mechanism

28, 30, whereby an effective compensation of the entire time interval T consisting of the aforesaid three time sections 1, to may be obtained.

In order to enable both the

spring relay

16, 17 and the armature lever 19 to be moved dependent upon the cocking operation into their positions assumed before the shutter action, against the action of the

springs

16 or 31 engaging these parts, a cocking arm rotatably mounted on an axis 34 is provided, formed by two coaxially mounted

levers

35 and 36. These levers in turn are positively held against one another by an excess tension spring 37 and a laterally bent over lug 35a. To move the cocking arm 35 to 37, the driving disc 5 has a laterally extending actuating pin 5a which is so arranged that during the cocking operation of the shutter, pressure is exerted on the free end of the cocking arm, which pressure is transmitted via a pin 35b provided on the lever both to the actuating lever 17 and the armature lever 19.

The method of operation of the shutter system described above is as follows:

Depressing the camera release 12 causes the release lever 11 and the catch lever 10 to move therewith, the result of which is that the main switch S is closed and the shutter drive is released for action. On closure of switch S, the electromagnet 21 is connected to the battery voltage, and the blades 9 are opened after the delay of the opening movement of the drive ring 8 caused by the compensating mechanism 28 to 30, the switches S and S being simultaneously actuated. On reaching the shutter open position the catch 14 as shown in FIG. 2 drops into position in front of the lug 8b of the driving ring 8 and hence locks the whole driving system. This condition persists until the timing device cancels the magnetic field of the electromagnet 21 and consequently releases armature 20. The armature lever 19 under the influence of the spring 31 is set in motion and thus by engaging the pin 27, disengages the pawl 18 from the

spring relay

16, 17. The actuating lever 17 thus released, rotates in a clockwise direction on its bearing pin 13 under the influence of the relatively powerful spring 16, striking with the arm 17b against the pin 14a arranged on the catch 14 with the result that the catch is rapidly moved out of the locking position. Consequently, as shown in HO. 3, the driving system is again able to move and to transfer the blades 9 into the closed position.

The

spring relay

16, 17 described above and located between the magnet armature 20 and catch M, in combination with the compensating mechanism 28 to 30, is not limited to specific use in electronic shutters having a shutter blade system comprising several blades. This combination may be part of which executes a reciprocating movement for opening and closing the lens aperture. ,Thus, the spring relay l6, 17

spring relay consists of a rotatably mounted two-armed actuat- 7 could also be installed in an electronic shutter the blade system of which had only a single segment. The essential feamechanical locking means of the shutter, electronic timing means controlling an electromagnetic armature biased by a return spring, a mechanical locking means including a catch actuated by the armature, said catch acting to lock said driving part for the duration of the. timing, spring relay means acting on said catch, said spring relay means being between said electromagnetic armature and said catch locking the driving part, said spring relay means being releasable by said armature and actuating said catch so that the time interval from the vbeginning of the actuation of said catch to its disengagement from said driving part approaches a zero value.

2. Ashutter according to claim l wherein the spring means ture is that the blade driving part executes an oscillating movecomprise a spring relay.

3. A photographic shutter according to claim 1, wherein the ing lever which is subject to the action of a spring, one lever arm of which can be locked by means of a pawl which can be moved out of the stop position by the armature lever, the

other lever arm cooperating with the catch.

lever carrying the electromagnet armature.

5. A photographic shutter according to claim 3 having a cocking arm which is moved during the cocking of the shutter, the movement of the cocking arm bringing the actuating lever into the cocking position and the electromagnet armature into contact with its electromagnet.

6. A photographic shutter according to claim.5 wherein the cocking arm is formed by two levers mounted on the same pivot and positively held against one another by means of an excess tension spring, one lever of which cooperates with a movable part of the shutter driving mechanism and the other with the actuating lever of the'spring' relay and the annature lever.

Claims

1. A photographic shutter having a reciprocating driving part acting on the shutter blades, said driving part having a retarding means associated therewith delaying the opening movement and serving to compensate time lags of the mechanical locking means of the shutter, electronic timing means controlling an electromagnetic armature biased by a return spring, a mechanical locking means including a catch actuated by the armature, said catch acting to lock said driving part for the duration of the timing, spring relay means acting on said catch, said spring relay means being between said electromagnetic armature and said catch locking the driving part, said spring relay means being releasable by said armature and actuating said catch so that the time interval from the beginning of the actuation of said catch to its disengagement from said driving part approaches a zero value.

2. A shutter according to claim 1 wherein the spring means comprise a spring relay.

3. A photographic shutter according to claim 1, wherein the spring relay consists of a rotatably mounted two-armed actuating lever which is subject to the action of a spring, one lever arm of which can be locked by means of a paWl which can be moved out of the stop position by the armature lever, the other lever arm cooperating with the catch.

4. A photographic shutter according to claim 3, wherein the two-armed actuating lever is mounted on the same pivot as a lever carrying the electromagnet armature.

6. A photographic shutter according to claim 5 wherein the cocking arm is formed by two levers mounted on the same pivot and positively held against one another by means of an excess tension spring, one lever of which cooperates with a movable part of the shutter driving mechanism and the other with the actuating lever of the spring relay and the armature lever.