Photography – With film drive – Double exposure prevention
Reexamination Certificate
1999-11-19
2001-11-20
Perkey, W. B. (Department: 2851)
Photography
With film drive
Double exposure prevention
C396S536000
Reexamination Certificate
active
06321042
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a camera having a manual film winding apparatus.
2. Description of the Related Art
In a conventional manual film winding apparatus, a film is wound by one frame by rotating a film winding lever. When the film wind lever is rotated to a winding operation completion position and is thereafter returned to its initial position, the film wind lever is locked by a double winding prevention device so as not to rotate in the film winding direction, so that no double winding occurs. The film wind lever is unlocked in association with a shutter which is moved by depressing a release button. Thus, the film wind lever is unlocked when the shutter movement is completed. Namely, in general, a conventional manual film winding apparatus is provided with a double winding prevention device which prevents the rotation of the film wind lever so long as the shutter is not released.
However, the amount of film to be wound varies depending on the operation state of the camera, such as indexing of the first frame of the film, or the film winding. Moreover, in case of a Brownie film camera, different kinds of films having different numbers of frames, with or without a backing paper, or different lengths of leader, such as a 120 film or 220 film can be used. For any given film, the film winding device winds the film by the same amount, and hence the position of the first frame of the film is different, thus resulting in imprecise indexing of the first frame.
In order to overcome all of these problems by mechanical device, for example, if an attempt is made to mechanically achieve the indexing operation of the first frame or film feed operation different from the normal film winding operation for each frame, the structure will become complex, require an extremely high machining precision, and the number of the components will be increased, thus resulting in an increase in the manufacturing cost.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an apparatus for manually winding a film in a camera having a double winding prevention mechanism, wherein the operation state of the camera is detected so that the locking operation of the double winding prevention device can be released under desired conditions.
To achieve the object mentioned above, according to the present invention, a camera is provided having a manual film winding apparatus in which a film is wound in association with the rotation of a wind lever from a start position to an end position, including: a double wind prevention device which prevents the wind lever from rotating from the start position toward the end position when the wind lever is returned to a predetermined position beyond the start position after the wind lever has been rotated to the end position from the start position; and a double wind prevention releasing device for electrically releasing the double wind prevention of the double wind prevention device, in accordance with an operation state of the camera.
Preferably, the double wind prevention releasing device carries out a release operation of the double wind prevention when a rear cover of the camera is open.
Preferably, the double wind prevention releasing device maintains the release operation of the double wind prevention thereof until a first frame of a film is moved to an exposure position in an first frame indexing operation.
Preferably, the double wind prevention releasing device carries out the release operation when the wind lever is returned from the end position to the predetermined position before the first frame of the film is moved to the exposure position in the first frame indexing operation, and wherein the double wind prevention releasing device does not carry out the release operation when wind lever is returned from the end position to the predetermined position after the first frame has been moved to the exposure position.
Preferably, the double wind prevention releasing device carries out the release operation when it is detected that a releasing operation of a shutter has been completed.
Preferably, the double wind prevention releasing device maintains the release operation until it is at least detected that the film is entirely wound onto a spool after a shutter releasing operation of the last frame of the film.
Preferably, a feed amount detection device is included for detecting an amount of the film to be wound by the rotation of the wind lever, wherein the double wind prevention releasing device maintains the release function until it is detected by the feed amount detection device that a predetermined amount of the film has been wound.
Preferably, upon indexing the first frame, the double wind prevention releasing device maintains the release operation of the double wind prevention before it is detected by the feed amount detection device that a predetermined amount of the film is wound, wherein the first frame is moved to the exposure position.
Preferably, the predetermined feed amount is set in accordance with the type of the film to be used.
Preferably, the feed amount detection device includes a film feed amount detector which detects the amount of the film via an output of a photo-interrupter having a roller which comes into contact with the film and is rotated in association with the movement of the film and an encoder which is rotated in association with the roller, and wherein the camera includes a friction clutch device which connects or disconnects the wind lever to, or from, the spool; and a film engagement device which causes the friction clutch device to slip to thereby stop the rotation of the spool when the film feed amount detector detects that a predetermined amount of film has been wound.
Preferably, the double wind prevention device prevents the wind lever from rotating from the start position to the end position when the wind lever is returned to the start position after the wind lever has been rotated from a predetermined position to a wind end position.
Preferably, a ratchet device is further included, which prevents the wind lever from rotating between the start position to the end position in a direction toward the predetermined position, the ratchet device being provided with a ratchet wheel which rotates together with the wind lever and a pawl which engages with a plurality of teeth of the ratchet wheel to thereby restrict the rotation of the ratchet wheel, the pawl being inclined in a first direction to prevent reverse rotation of the ratchet wheel when the wind lever is rotated from the start position toward the end position and being inclined in a second direction opposite to the first direction to permit the ratchet wheel to rotate toward the start position and prevent the ratchet wheel reversing when the wind lever reaches the wind end position. The double wind prevention device is provided with a lock lever which prevents the pawl from being inclined in the first direction to thereby prevent the wind lever from rotating in a direction toward the wind end position when the wind lever is returned to the predetermined position. The double wind prevention releasing device includes an electromagnetic actuator which releases the prevention of the inclination of the pawl by the lock lever in the first direction.
The present disclosure relates to subject matter contained in Japanese Patent Application No. 10-334627 (filed on Nov. 25, 1998) which is expressly incorporated herein by reference in its entirety.
REFERENCES:
patent: 5903784 (1999-05-01), Hori
patent: 6126333 (2000-10-01), Hori
patent: 19728982 (1998-01-01), None
patent: 10-20375 (1998-01-01), None
Asahi Kogaku Kogyo Kabushiki Kaisha
Greenblum & Bernstein P.L.C.
Perkey W. B.
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