Film metering apparatus and method with drive speed reduction
AssigneeEastman Kodak Company
InventorsConrad Diehl, David C. Smart, Wayne E. Stiehler
Life of this patent
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Abstract
A film metering mechanism has parallel pawl and blade elements with apertures that align in the beam of an infrared detector to slow down a camera drive motor when a pawl tooth senses a perforation during film advance, prior to reaching a drive motor stopping point. The pawl has a cutout with upper longitudinal and ramp surfaces that engage a fixed pin. The blade has a stepped surface that shifts contact between two pawl pins in correspondence with the relative location of the cutout surfaces and the fixed pin.
Claims18
In a camera having a housing, means defining an exposure plane within said housing, and means for advancing a strip of film in a frame-to-frame advance direction along said exposure plane, said film having a plurality of perforations located at predetermined frame metering intervals along said film, frame metering apparatus comprising:
- first and second guide pins fixedly located on said housing;
- an elongated pawl including a film perforation sensing tooth and first and second lift pins;
- said pawl being formed with an elongated slot and integral adjacent longitudinal and ramp surfaces;
- and said pawl being mounted for rotational and longitudinal movement relative to said housing, with said first guide pin engaging said slot and said second guide pin proximate said straight and ramp surfaces;
- means biasing said pawl in a longitudinal direction, with said ramp surface being urged away from said second guide pin;
- means biasing said pawl in a rotational direction about said first guide pin, with said tooth being urged toward said exposure plane and said longitudinal surface being urged toward said second guide pin;
- an elongated blade disposed generally parallel to said pawl in engagement for rotation about said second guide pin;
- said blade being formed with a stepped surface having a first section proximate said first lift pin and having a second section proximate said second lift pin;
- means biasing said blade in a rotational direction about said second guide pin, with said stepped surface being urged into contract with said first and second lift pins;
- and
- means for detecting when said second section is in contact with said second lift pin;
- said pawl, blade and biasing means being relatively dimensioned, configured and adapted so that said tooth is urged to engage in a perforation, with said longitudinal surface in contact with said second guide pin and said second section in contact with said second lift pin, when said film is moved in said advancement direction toward a position approaching registration of a next available exposure frame;
- so that said second section contact with said second lift pin is terminated and said first section is brought into contact with said first lift pin when said film reaches said position of registration;
- and so that said ramp surface is brought into engagement with said second guide pin against the bias of said longitudinal direction biasing means to disengage said tooth from said perforation in response to movement of said tooth with said film, when said film is moved beyond said registration position further in said advancement direction.
In a camera having a housing, means defining an exposure plane within said housing, and means including a drive motor for advancing a strip of film in a frame-to-frame advance direction along said exposure film, said film having a plurality of perforations located at predetermined frame metering intervals along said film, frame metering apparatus comprising:
- a pawl, including a film perforation sensing tooth;
- a blade;
- means biasing said pawl with said tooth urged toward said exposure plane;
- mechanical means mounting said pawl for movement in said housing so that said tooth is located to engage with a perforation under urging of said biasing means when said film is moved in said direction to advance a next available exposure frame to a first tooth engagement position, and so that said pawl tooth is caused to travel with said film by engagement of said tooth with said perforation as said film is further moved in said direction from said first position through a second intermediate position, to a third registration position;
- means mounting said blade for movement in said housing, including mechanical means coupling said pawl and said blade so that said blade is moved relative to said pawl when said tooth is moved with said film from said first to said second position;
- means for detecting said relative blade and pawl movement and for generating an electrical signal in response to said detection;
- and
- means for controlling said drive motor to slow the advance of said film in response to said signal when said film reaches said second position.
A method for metering the exposure frames of a strip of film in a camera having a housing, means defining an exposure plane within said housing, and means, including a drive motor, for advancing said film in a direction along said exposure plane, said film having a plurality of perforations located at predetermined frame metering intervals along said film, said method comprising the steps of:
- providing a pawl movably mounted on said housing, and a blade movably mounted on said housing, said pawl including a perforation sensing tooth and being mechanically coupled with said blade;
- biasing said pawl with said tooth being urged toward said exposure plane and against said film;
- moving said film in said advancement direction to a first position using said motor, so that said tooth automatically engages in a perforation due to said pawl biasing;
- moving said film further in said advancement direction to a second position using said motor, so that said tooth travels with said perforation and film to automatically move said blade relative to said pawl when said film is moved to said second position;
- detecting said relative movement of said blade and pawl and generating an electrical signal in response thereto;
- and
- controlling said motor in response to said signal to slow the advance of said film when said film reaches said second position.
Dependencies are inferred from the claim text.