Apparatus for printing successive sheets

Claim 1

SPOT PRINTING APPARATUS OF THE CLASS DESCRIBED COMPRISING A CONVEYOR FOR MOVING SHEETS TO BE PRINTED UPON BENEATH A PRINTING CYLINDER, A PRINTING CYLINDER POSITIONED OVER THE CONVEYOR FOR PRINTING ON SHEETS BEING SO TRANSPORTED BY THE CONVEYOR, DRIVING MEANS FOR THE CONVEYOR, MEANS CONNECTED WITH THE CONVEYOR FOR DRIVING THE PRINTING CYLINDER TO CO-RELATE THE PERIPHERAL SPEED OF THE PRINTING CYLINDER TO THE LINEAR SPEED OF THE SHEETS BEING TRANSPORTED BY THE CONVEYOR, A COMBINED ELECTROMAGNETICALLY-OPERATED CLUTCH AND BRAKE MECHANISM OPERATIVELY INTERPOSED BETWEEN THE PRINTING CYLINDER AND ITS DRIVING MEANS FOR HOLDING THE CYLINDER FROM ROTATION AND HOLDING THE CLUTCH DISENGAGED AND OPERATIVE TO ENGAGE THE CLUTCH AND RELEASE THE BRAKE TO CAUSE THE CYLINDER TO BE ROTATED, AN ELECTRIC CIRCUIT FOR THE ELECTROMAGNETICALLY-OPERATED CLUTCH AND BRAKE MECHANISM INCLUDING AN ELECTROMAGNETICALLY-OPERATED SWITCH HAVING TWO POSITIONS, IN THE FIRST OF WHICH IT EFFECTS THE RELEASE OF THE BRAKE AND ENGAGEMENT OF THE CLUTCH TO ROTATE THE DRUM AND IN THE OTHER OF WHICH IT EFFECTS SETTING OF THE BRAKE AND DISENGAGEMENT OF THE CLUTCH, MEANS CONTROLLED BY ROTATION OF THE CYLINDER EFFECTIVE TO MOVE THE SWITCH TO THE SECOND POSITION AFTER A SINGLE ROTATION OF THE CYLINDER, AND MEASURING MEANS DRIVEN BY THE CONVEYOR AND RESPONSIVE TO ANY SPEED VARIATION THEREOF CONTROLLED BY THE MOVEMENT OF THE SHEET TO BE PRINTED UPON EFFECTIVE FOR MOVING THE SWITCH TO THE FIRST POSITION, SAID LAST-NAMED MEANS COMPRISING A SENSING HEAD RESPONSIVE TO THE PASSAGE OF THE LEADING EDGE OF A SHEET TO BE PRINTED UPON AND A SELECTIVELY ADJUSTABLE ELECTRONIC IMPULSE COUNTER WHICH IS ENERGIZED BY THE PASSAGE OF THE LEADING EDGE OF A SHEET PAST THE SENSING MEANS, AN IMPULSE GENERATOR DRIVEN BY THE CONVEYOR FOR GENERATING IMPULSES THAT ARE REGISTERED BY THE COUNTER ONLY WHEN IT IS SO ENERGIZED, SAID COUNTER BEING CONNECTED WITH SAID SWITCH TO MOVE IT TO THE FIRST POSITION AFTER A SELECTED NUMBER OF IMPULSES HAS BEEN COUNTED, AND MEANS FOR DE-ENERGIZING THE COUNTER WHEN THE SWITCH IS SO MOVED WHEREBY THE PRINTING CYLINDER IS REVOLVED BUT ONCE FOR EACH SHEET.