US2720144A

US2720144A - Flashlight synchronizing device for photographic rotary shutters

Info

Publication number: US2720144A
Application number: US276490A
Authority: US
Inventors: Kaden Willy
Original assignee: Agfa Camera Werk AG
Current assignee: Agfa Gevaert NV
Priority date: 1951-03-31
Filing date: 1952-03-14
Publication date: 1955-10-11
Anticipated expiration: 1972-10-11
Also published as: GB708684A; FR1050554A

Description

Oct. 1l, 1955 w. KADEN 2,720,144

FLASHLIGHT SYNCHRONIZING DEVICE FOR PHOTOGRAPHIC ROTARY SHUTTERS Filed arch 14, 1952 INENTOR.

ATTORNEY United States Patent O FLASHLIGHT SYNCHRONIZING DEVICE FOR PHOTOGRAPHIC ROTARY SHUTTERS Willy Kaden, Munich, Germany, assignor, by mesne assignments, to Agfa Camera-Werk Aktiengesellschaft, a corporation of Germany Application March 14, 1952, Serial No. 276,490

Claims priority, application Germany March 31, 1951 Claims. (Cl. 95--11.5)

The present invention relates to a flashlight synchronizing device for photographic rotary shutters, of the type in which completion of the flashlight circuit is effected by means of a Contact pin attached to the shutter disc, which pin, on rotation of the shutter, comes into contact with a contact spring.

Previous devices of this type suffered in most cases from the disadvantage that they did not always make satisfactory contact, since either the springs used were subject to displacement by bending, or making of the contact took place over too short or too long a contact path so that the necessary ignition did not always take place at all or sometimes took place for too long a time.

An object of the present invention is to provide flash synchronizing means of simple construction which may be easily adjusted to control the point in the shutter actuation cycle at which the contacts of said means are closed.

A further object thereof is the provision of such means which may similarly easily control the length of time said contacts remain closed.

Another object is the provision of such means which are more reliable than present types.

Still another object is the provision of an improved synchronizing means which may be easily incorporated in shutters already on the market.

According to this invention, in a flashlight synchronizing device of the above type, means are provided for rendering adjustable the separating distance between the contact pin on the shutter disc and the circuit-making contact portion of the spring, without substantial variation of the separating distance between the said portion of the spring and the axis of rotation of the shutter disc. Thus the spring may be adjustably mounted so that the positions of adjustment of any part thereof are on an arc of a circle whose centre is on the said axis. This effect is attained by corresponding arrangement of the contact portion of the spring, the spring mounting and the portion of the spring adjustable within this mounting.

The spring may be of U-shape and may be adjustably mounted by one of the U-arms while making contact with the other, in which case it is preferably arranged so that, on exposure, the contact pin first makes contact with the free end of the contact arm of the U.

While the contact arm of the U needs to be sufficiently long to provide the required resilience, it may be too long for the whole of it to constitute the Contact path, for the reason that with flash bulbs it may happen that owing to incomplete melting of the fusible wire, with too long a contact path the ignition current circuit remains made, so that partial discharge of the battery takes place. This is particularly likely to happen with time exposures. Thus in order to interrupt the contact between the contact pin and the spring, in the case of time exposure of the shutter, after ignition of the flashlight, the contact arm of the U may be so shaped that contact is broken before the pin reaches the bend of the U. This may be effected be suitably cranking the contact arm.

Ffice The mounting arm of the U may be adapted to be fixed in a mount attached to the base plate of the shutter. Fixing may be by clamping between jaws or by means of a grub screw. With the provision of a shutter stop on the base plate, the mount for the spring may be on the shutter stop.

Other objects and a fuller understanding of the present invention may be had by referring to the following expanded description and claims, taken in conjunction with the accompanying drawing which illustrates a preferred embodiment thereof, it being understood that the foregoing statement of the objects of the subject invention and the summary thereof are intended to generally explain the same without limiting it in any manner.

The invention is illustrated diagrammatically in the accompanying drawing in which:

Fig. l is an elevation of the shutter components of a box camera with a synchronizing device, embodying the subject invention, arranged upon a base plate, shown before the flashlight circuit is made.

Fig. 2 is an elevation of the same arrangement at the moment of contact, and

Fig. 3 is a cross section through a stud on which the contact spring is mounted.

The shutter shown in Fig. 1 comprises the customary shutter disc 1 with the kidney shaped exposure window 3 and the lens Window 2. Upon the shutter disc 1 there is provide a pin 4 which, upon clockwise rotation of the shutter disc 1, approaches a U-shaped spring 5 and, by touching the contact arm 5a thereof, closes the circuit for the flashlight device. Spring 5 is mounted with its xed or non-contact-making other arm 5c in a stud 7 attached to the base plate 6. In order to guarantee effective contact between pin 4 and arm 5a, the latter is so constructed that it is substantially arcuate with respect to the axis of rotation of the shaft 8 of shutter disc 1, so that there is a long path of contact between pin 4 and contact arm Sa. In order to ensure maximum illumination of the subject by the flashlight while the shutter is fully open, which effect might be disturbed by inaccuracies in the assembly of the shutter, escpecially by small differences in length of contact arm 5a, the separating distance between contact pin 4 and the free end of arm 5a of said U-shaped spring 5 is adjustable. This adjustment need only be made once for each camera and it is effected by adjustable arrangement of xed arm 5c of spring 5 in stud 7. In this connection it is important that the mounting for fixed arm 5c of spring 5 in stud 7 and the portion of spring 5 which is adjustable in this mounting, shall be so shaped that the various positions of adjustment of the spring are on an are of a circle whose centre is on the axis of rotation of shaft 8 upon which shutter disc 1 is mounted, so that the same separating distance is always guaranteed between contact arm 5a of said spring and the said axis.

The securing of fixed arm 5c of spring 5 in stud 7 may be made by simple clamping between two jaws located on the stud 7.

The illustrated method of fixing the spring 5 in the required position is shown in Fig. 3. Stud 7 has an insert 9 of insulating material, within which spring 5 can be clamped by means of the likewise insulated grub screw 10. Stop pin 11, comprising with indentation 1b the lower stop for disc 1, may be used as a mounting for stud 7. Indentation 1a in shutter disc 1 coacts with pin 11 to provide the upper ston.

Contact arm 5a of spring 5 is cranked at 5b to form a retracted angular portion which occurs at a point in arm 5a which is reached by contact pin 4 when it has completely traversed the contact path required for ignition. When pin 4 arrives at cranked portion 5b, the position of which can be adjusted, contact between arm 5a of spring 5 and pin 4 is interrupted.

The device according to the present invention as illustrated, has the practical advantage that it can be associated at any time with the components already present in any box camera. All that is required is the attachment of the U-shaped spring to the normally present stop pin for the shutter disc.

Although the subject invention has been described with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example and that numerous additions and changes in the details of construction, combination and arrangement may be resorted to without transcending the scope of the invention as hereinafter claimed.

What is claimed is:

l. In a photographic rotary shutter having a base plate, a shutter disc rotatably mounted about an axis on said base plate, means for synchronizing said shutter with flash means comprising a protruding member mounted on said disc and electrically connected to a first terminal, support means mounted on said base plate, an electricallyconductive resilient U-shaped contact member electrically connected to a second terminal, the arms of said member being a support arm, adjustably mounted on said support means, and a contact arm, portions of said contact arm being maintained in the path of the protruding member so as to cause electrical contact between said protruding member and said contact arm to be made and broken during each of the rotation movements of said shutter disc for exposure and return to normal position, said portion of said contact arm being of arcuate configuration having a radius of curvature substantially equal to the distance between said protruding member and said axis, said support arm being of arcuate configuration, having a radius of curvature substantially equal to the distance between said support means and said axis whereby upon adjustment of said support arm the radial orientation of said contact arm to said axis is maintained substantially constant, but the separation distance of said protruding member and said Contact is varied so as to control the time of initiation of electrical contact therebetween.

2. A device as described in claim l, said contact member being so positioned relative to the path of said protruding member as to cause said protruding member to tirst contact the free end of said contact arm upon actuation of the shutter.

3. A device as described in claim l, said shutter having a shutter disc stop mounted on said base plate, said support means being axed to said base plate by being secured to said stop.

4. A device as described in claim l, said contact arm being depressed suiciently at a distance from the end of said arm, nearest said protruding means in the rest position thereof, as to cause contact to be broken between said protruding member and arm before the said protruding member fully traverses said arm.

5. In a photographic rotary shutter having a base plate, a shutter disc rotatably mounted about an axis on said base plate, means for synchronizing said shutter with flash means comprising a protruding member mounted on said disc and electrically connected to a rst terminal, support means mounted on said base plate, an electrically-conductive resilient U-shaped contact member electrically connected to a second terminal, the arms of said member being a support arm, adjustably mounted on said support means, and a contact arm, portions of said contact arm being maintained in the path of the protruding member so as to :ause electrical contact between said protruding member and said contact arm to be made and broken during each of the rotation movements of said shutter disc for exposure and return to normal position, said portion of said contact arm being of arcuate configuration having a radius of curvature substantially equal to the distance between said protruding member and said axis, said contact arm being depressed sufficiently at a distance from the end of said arm, nearest said protruding means in the rest position thereof, as to cause contact to be broken between said protruding member and arm before the said protruding member fully traverses said arm.

References Cited in the le of this patent UNITED STATES PATENTS