Device for driving the claw shaft of a motion picture camera
AssigneeAaton
InventorJean-Pierre Beauviala
Life of this patent
Estimating the term…
Abstract
A device for driving the claw shaft of a motion picture camera, comprises an electric motor coupled to the claw shaft itself connected to said claw by a mechanism of the crank-connecting rod system type, for converting the movement of rotation of the electric motor into a movement of reciprocating translation. Means are provided for modulating the speed of rotation of the claw shaft as a function of the angle of rotation thereof with respect to a reference position, so that the speed of the claw at the moment of its engagement in a perforation of the film is as low as possible and that this speed then increases, during the descent of the film, according to a law such that the acceleration communicated to the film causes only a minimum stress exerted on said latter.
Claims12
A device for driving the claw shaft of a motion picture camera, said device comprising:
- a reciprocating claw engageable with a film perforation;
- a rotatable claw shaft;
- means connected between said claw shaft and said claw for converting the rotary motion of said claw shaft into reciprocating motion of said claw;
- an electric motor connected to said claw shaft;
- control means for said motor, said control means modulating the speed of rotation of the claw shaft as a function of the angle of rotation of said claw shaft with respect to a reference position, said control means including means for delivering a periodic reference signal whose frequency is modulated as a function of the angle of said claw shaft, said means for delivering including means for storing and selecting at least two types of reference signals, each of said at least two types of reference signals corresponding to an angle of obturation of the camera shutter.
A device for driving the claw shaft of a motion picture camera, said device comprising:
- a reciprocating claw engageable with a film perforation;
- a rotatable claw shaft;
- means connected between said claw shaft and said claw for converting the rotary motion of said claw shaft into reciprocating motion of said claw;
- an electric motor connected to said claw shaft;
- control means for said motor, said control means modulating the speed of rotation of the claw shaft as a function of the angle of rotation of said claw shaft with respect to a reference position, said control means comprising a function generator delivering a periodic reference signal whose frequency is modulated as a function of the angle of said claw shaft, a tachometric generator producing a measuring signal corresponding to the instantaneous value of the speed of rotating of said claw shaft, a comparator having said periodic reference signal and said measuring signal as its inputs and having as its output a control signal corresponding to the difference between said input signals, and means for adjusting the speed of rotation of said claw shaft as a function of said control signal so as to annul said control signal,
- whereby the speed of said claw may be minimized at the beginning and end of the reciprocation stroke.
A device for driving the claw shaft of a motion picture camera, said device comprising:
- a reciprocating claw engageable with a film perforation;
- a rotatable claw shaft;
- means connected between said claw shaft and said claw for converting the rotary motion of said claw shaft into reciprocating motion of said claw;
- an electric motor connected to said claw shaft;
- control means for said motor, said control means modulating the speed of rotation of the claw shaft as a function of the angle of rotation of said claw shaft with respect to a reference position, said control means comprising a tachometric wheel fixed to the shaft of said motor, said tachometric wheel including indices thereon at variable intervals corresponding to a function of the angle of rotation of said motor shaft, said control means further comprising a tachometric generator for detecting the passage of said indices and converting them into periodic reference signals, an oscillator emitting a constant frequency reference signal, a comparator providing an output and having said periodic reference signals and said constant frequency reference signals as its inputs, and an amplifier connected between said comparator output and said electric motor to control the speed of rotation of said claw shaft as a function of the output of said comparator.
A device for driving the claw shaft of a motion picture camera, said device comprising:
- a reciprocating claw engageable with a film perforation;
- a rotatable claw shaft;
- means connected between said claw shaft and said claw for converting the rotary motion of said claw shaft into reciprocating motion of said claw;
- an electric motor connected to said claw shaft;
- control means for said motor, said control means modulating the speed of rotation of the claw shaft as a function of the angle of rotation of said claw shaft with respect to a reference position, said control means comprising an independent motor for separately driving the shutter, a first pulse generator emitting a first pulse each time that the shutter passes in a predetermined position, a second pulse generator emitting a second pulse when a point of the plate of the crank-connecting rod system passes into a predetermined position, and a phase synchronization device with two inputs respectively connected to the first and second pulse generators and of which the output is connected to the independent electric motor driving the shutter.
Dependencies are inferred from the claim text.