Photo-copying device

A photo-copying device for regulating the displacement of the working member of a metal gas-cutting machine according to a contour being copied, said device comprising:

• a photoelectric transducer for the circular scanning of the line of the contour being copied by means of an optical scanning beam for the detection of points of intersection of said beam with said contour line;
• the path of said beam at the contour being a circumference of a circle a center lying at least approximately on the contour line being copied;
• said optical scanning beam moving along said path at a constant angular speed and intersecting said contour line at two points;
• the output signal of said photoelectric transducer during one scanning period being a short pulse generated when the contour line being copied is intersected at one of said points;
• mutually perpendicular guides for guiding displacement of said transducer;
• a reference signal source having two outputs at which are produced two reference signals in the form of sine and cosine voltages synchronized with said angular speed of movement of said scanning beam along said circumference, the initial phase of said sine voltage corresponding to the position of said scanning beam at the intercept of said scanning orbit with a positive X half-axis in a Cartesian coordinate system wherein the origin coincides with said center of said circumference, and whereof the X and Y axes run parallel to the mutually perpendicular guides for displacement of said photoelectric transducer along said line being copied;
• the initial phase of said cosine voltage corresponding to the position of said scanning beam on the positive Y half axis of said Cartesian coordinate system;
• said reference signals defining the coordinate components of the speed vector in displacement of said photoelectric transducer along said line being copied, the speed vector being directed from said center of the circumference toward the intercept of said beam with said line being copied;
• a first drive adapted to move said photoelectric transducer in said guides along the X axis;
• a second drive adapted to move said photoelectric transducer in said guides along the Y axis;
• machine guides for said working member;
• a third drive for shifting said working member along the machine guides corresponding to the X axis;
• a fourth drive for shifting said working member along the machine guides corresponding to the Y axis, and running perpendicular to said guides corresponding to the X axis;
• said third and fourth drives moving said working member along said guides of the machine with a predetermined proportionality factor with respect to similar displacement of said photoelectric transducer along said X and Y axes for obtaining a scale between the contour of a blank being cut out of a metal sheet by said working member and the contour being copied;
• a first converter for converting the instantaneous values of said cosine voltage of the reference signal, corresponding to the intercepts of said scanning optical beam with said line being copied, into a number of pulses delivered during each period of said circular scanning which determine the number of equal steps through which said first drive moves during each circular scanning period and define the scalar magnitude of said coordinate component in the speed vector of the displacement of said photoelectric transducer along the X axis, and also into a logic symbol defining the direction of displacement of said photoelectric transducer along said X axis, said first converter having a first input which is connected to one of the outputs of said reference signal source and which receives a cosine voltage therefrom, a second input coupled to the output of said photoelectric transducer, a frequency output giving out said pulses whose number during the circular scanning period is proportional to said instantaneous value of said cosine voltage, and two sign outputs a logic unity at one of which determines one of the two directions of displacement of the photoelectric transducer along the X asis;
• a second converter for converting the instantaneous values of said sine voltage generated at time moments when said scanning optical beam intersects said line being copied, into a number of pulses following during each period of said circular scanning which determine the number of equal steps made by the second drive during each circular scanning period and define the scalar magnitude of said coordinate component in the speed vector of the displacement of said photoelectric transducer along the Y axis, and also into a logic symbol designating the direction of movement of said photoelectric transducer along the Y axis;
• said second converter having a first input which is connected to another of the outputs of said reference voltage source and which receives a sine voltage therefrom, a second input coupled to the output of said photoelectric transducer, a frequency output producing said pulses which determine the number of equal steps of said second drive and whose number during the circular scanning period is proportional to said instantaneous value of said sine voltage, and two sign outputs a logic unity at one of which determines one of the two directions of displacement of said photoelectric transducer along the Y axis;
• each of said drives having a frequency input and two sign inputs;
• said frequency output of the second converter being connected to said frequency inputs of the second and fourth drives;
• said sign outputs of the second converter being connected to said sign inputs of the second and fourth drives;
• each of said converters comprising:
• a first shaper of unidirectional pulses in the form of rectified half-waves of said reference signal, having an input and an output;
• a second shaper of square pulses corresponding to the polarity of the half-wave voltages of said reference signal, having two inverted outputs;
• the inputs of said first and second shapers being interconnected to form said first converter input;
• a first gating circuit which has a signal input connected to said output of the first shaper, a gating input and an output;
• short pulses appearing at said output of the first gating circuit corresponding to the scalar magnitudes of said instantaneous values of the reference signal;
• a second gating curcuit having a signal input connected to one of said inverted outputs of the second shaper, a gating input and an output;
• a third gating circuit provided with a signal input coupled to the other said inverted output of the second shaper, a gating input and an output;
• said gating inputs of the first, second and third gating circuits being interconnected to form said second input of the converter;
• short pulses produced across any output of said second or third gating circuit defining the sign of said instantaneous values of the reference signal;
• a converter unit for converting the amplitudes of said output short pulses from said first gating circuit into a proportional number of pulses following at a frequency higher than the frequency of the reference signal;
• said unit having an input connected to said output of the first gating circuit and an output forming said frequency output of the converter;
• a memory store which has a unity input and a zero input;
• said zero input being connected to said output of the second gating circuit, said unity input being connected to said output of the third gating circuit, said zero and unity outputs forming said sign outputs of the converter.