Copy magnification change apparatus in magnetic copying machine

Claim 1

A copy magnification change apparatus in a magnetic copying machine in which light from a document is converted into an electrical video signal by photoelectric converting means, said video signal being supplied to a magnetic head, which is moved along the axial direction of a magnetic recording drum to form a magnetic latent image on said magnetic recording drum, said copy magnification change apparatus comprising: (a) a first clock pulse generating means for generating in accordance with the rotation of said magnetic recording drum, an index pulse representing one revolution of said magnetic recording drum, a first train of clock pulses for an actual size copy operation, each representing a position of the periphery of said magnetic recording drum during one revolution of said magnetic recording drum, and a second train of clock pulses each representing a position of the periphery of said magnetic recording drum during one revolution of said recording drum, the pulse interval of said second train of clock pulses being longer than that of said first train of clock pulses, and a third train of clock pulses each representing a position of the periphery of said magnetic recording drum during one revolution of said recording drum, the pulse interval of said third train of clock pulses being shorter than that of said first train of clock pulses; (b) said photoelectric converting means being coupled to one of said first, second and third trains of clock pulses to read out said electrical video signal; (c) a second clock pulse generating means for generating, on the basis of said index pulse, a fourth train of clock pulses having a pulse number for actual size copy operating to control a movement length of said magnetic head, a fifth train of clock pulses whose pulse number is larger than that of said fourth train of clock pulses, a sixth train of clock pulses whose pulse number is smaller than that of said fourth train of clock pulses; (d) a drive source for moving said magnetic head along the axial direction of said magnetic recording drum for every one line read-out of said photoelectric converting means and for controlling the movement length of said magnetic head on the basis of pulse number; (e) a selecting means for selectively outputting said first train of clock pulses from said first clock pulse generating means and said fourth train of clock pulses from said second clock pulse generating means in actual-size copy operation, said second train of clock pulses from said first clock pulse generating means and said fifth train of clock pulses from said second clock pulse generating means in enlargement copy operations and said third train of clock pulses from said first clock pulse generating means and said sixth train of clock pulses from said second clock pulse generating means in reduction copy operation.