Patent GB-819481-A (GB)
Title: Electrophotographic printer
IPC: G03G15/30
Filed: 1955-12-19
Abstract: 819,481. Printing processes. INTERNATIONAL BUSINESS MACHINES CORPORATION. Dec. 19, 1955 [Dec. 24. 1954]. No. 36310/55. Class 100(2) [Also in Group XX] An electrophotographic printer includes an electrophotoplate which carries a first latent electrostatic image which is developed and fixed so as to remain thereon and a second latent electrostatic image which is developed but not fixed so that for each revolution of a drum carrying the plate the design of the first image remains the same whilst the design of the second image is continually changed. As shown records cards 10 bearing a "heading" are stacked in a hopper 11 and fed, one by one, by a picker mechanism, through an optical scanning system 22 to a collector 12. The image of each card is projected by a light source 24 on to the surface of the electrophotoplate 29 on a xerographic drum 23. The cylinder 33 of the drum 23 is mounted on a shaft 28 which is earthed, and has secured thereto the plate 29 which consists of a photoconductive insulating layer 31, e.g. of amorphous selenium, and a backing layer 32 of aluminium. A format record 34 is fed, during the first cycle of the machine from station 36, passed a gate 53, which is raised to allow passage of the record 34 by the action of a cam 49 on a cam-follower 51 as the drum rotates, and between the plate 29 and a transparent belt 38. During the first cycle of the machine the record card 10 is fed from the hopper 11 so that as the format 34 moving with the plate 29 is exposed to the light source 24 via mirror 46 and lens 47 a latent electrostatic image is formed on the plate corresponding to the design on the format 34. Further rotation of the drum 23 causes the format 34 to be discharged on to a receiver 37 and causes the plate 29 to be moved into a developing chamber 56 wherein xerographic toner is cascaded on to the plate so as to adhere to the charged image thereon. Further rotation of the drum 23 brings the developed image to a fixing station 57 including a reservoir of solvent 65 such as methylene chloride which is sprayed on to the plate 29 via a heated element 61 which vaporizes the solvent. The solvent vapour causes the xerographic toner to be fixed to the plate so as to provide a permanent design image layer of insulating material which is secured to the plate 29. Further rotation of the drum carries the plate 29 passed a positively charged roller 64 over which runs a web 66 which is to be printed. This is moved into operative relation with the plate 29 by means of a solenoid 67. During the first cycle of the machine the solenoid 67 remains deenergized so that no printing takes place. As the drum rotates further excess tone powder is brushed off by a brush 71 and the plate travels passed pads 77 adapted to carry solvent 81 which serve, when a solenoid 74 is energized, to remove the fixed image of the format 34. The solenoid 74 is, however, de-energized so long as record cards 10 remain in hopper 11. During the second cycle the plate 29 passes under an ion-source charging unit 48 and the charged plate is subjected to light from the source 24 through a card 10 which has been fed in timed relation to the station 22. The plate now bears a composite image consisting of the format design area. which is not discharged by light owing to the insulating fixing layer which has been applied thereto, and the design area of the card 10. As the drum rotates the image is developed in the developer 56, and the design printed on the web 66, the solenoid 67 being operative, and the fixing station 57 inoperative during the second cycle. The excess toner is brushed off the plate by the brush 71, the plate recharged at station 48, and the cycle of events repeated, a new heading image being developed on the plate at each rotation of the drum until the record cards 10 are exhausted. In the cycle succeeding the feeding of the last record card 10 the apparatus at wiping station 73 is rendered operative by energization of the solenoid 74 so that the fixed design image of the format 34 is removed from the plate and the machine is stopped ready for a complete new operation. An electrical circuit is described suitable for controlling the operations of the various parts of the machine at the proper time. The circuit further includes means whereby the machine may be operated as a duplicating machine, a counter being provided for preventing the machine from stopping when the last card is fed from hopper 11 until a predetermined number of prints with the same heading design have been taken. Instead of projecting the image records cards 10 by a light a cathode ray tube on the face of which characters representing the image are formed may be employed. Specifications 766,426, 768,020, and U.S.A. Specifications 2,357,809 and 2,576,047 are referred to.