Patent GB-910500-A (GB)
Title: Electrophotographic printing apparatus
IPC: G03G15/26
Filed: 1959-03-31
Abstract: 910,500. Electrophotographic printing apparatus. MAGNEFAX CORPORATION. March 31, 1959 [March 31, 1958], No. 10814/59. Class 98 (2). A charging, exposing and developing apparatus for use in electrophotographic printing comprises a light-tight housing, means for holding in fixed position therein a sheet coated with photo-conductive material at an exposure position, electrostatic charging means, means mounting said charging means for movement across the treated side of said sheet to charge the same, means for exposing said charged sheet to an original so as to form a latent image of said original on the charged side thereof, magnet means for forming a brush containing developing material and for applying the same to said side of the sheet on which is disposed said latent image, means mounting said magnet means for movement substantially parallel to the sheet between a rest position adjacent said sheet, across the sheet and backwardly to the rest position, said magnet means being arranged to operate subsequent to the operation of said exposing means, and means for imparting movement to said charging means and said magnet means. As shown (Fig. 2), the apparatus includes a light-tight housing 19 and an apertured focal plane support 23. Sheets 43 (Fig. 13) of copy material may be held in fixed position against this support 23 by means of a plate 27, hinged at 29 and urged against the support 23-when a door 21 is closed-by sprung parts 31 (cf. Fig. 14, not shown). A lens 35 is all that is shown of the exposure means. The charging means comprises a housing 57 which is guided for movement in a vertical plane by means of parts 63, 65 and rollers 61. A sliding contact member in engagement with an insulated vertical conducting rail 81 is provided for connecting corona discharge wires 47 to a source of high voltage. Movement of the charging means-from its rest position shown in Fig. 2 in full lines to its lowermost position shown in dotted lines-is controlled by means of a member 91, pivoted at 95 and having a portion 97 engaging a kidney-shaped control cam 99. A switch 114 is provided whereby the wires 47 are only connected to the high voltage source when the charging means has moved from its rest position. A further safety switch 37 operated by the door 21 is provided. The magnet developing means comprises a unit 49 (Fig. 13) containing permanent magnets 161 and an armature unit 51 containing two bars 163 and 165 of magnetic material and a spacer bar 117 of non-magnetic material. The unit 49 is mounted for movement in a vertical plane by means of tie-rods 151 sliding in a guide channel formed by vertical posts 157 (Fig. 9) and by means of gear-wheels 153 engaging vertical rack portions 155. End plate 145 of the unit 49 extends through the support 23 and is rigidly connected to a parallel plate 189 by means of a bar 187. The two plates 145 and 189 have slots 191 cut therein forming a lostmotion coupling with longitudinal extensions of the spacer bar 177, whereby the result is obtained that on movement of unit 49 in the upwards direction, first only this unit moves and then-when magnets 161 come level with armature bars 163-the two units 49 and 51 move together along with a brush of developing material and magnetic carrier powder picked up from receptacle 171, the ends 173 of which receptacle form (in the out position of the unit 49) a support for the unit 51. Movement of the magnet unit 49 is controlled by a member 131 which is pivoted at 135, carries a roller 139 in sliding contact with the under side of the unit 49 and has an end 137 in engagement with a control cam 129 mounted on the same shaft 101 as the cam 99. Operation of the apparatus is as follows. After a sheet of electrophotographic copy material has been placed in the apparatus with its coated side towards the support 23 and an exposure timer 195 has been set, a button 193 is pressed whereby an electric motor connected to shaft 101 is energized. After a small rotation of this shaft in the clockwise direction (Fig. 4) a cam pin 123 disengages from switch 125 whereby this switch is closed and pressure on button 193 may then be removed. A lamp 128 is arranged to light up when the switch 125 is closed. During the first 180 degrees rotation of the shaft 101, the cam 99 actuates the member 91 to lower and raise the charging means 45 for applying a uniform charge to the sheet 43. At the end of 180 degrees rotation, cam pin 123 actuates switch 127 to stop the motor driving shaft 101 and to start the exposure. After the exposure, the timing mechanism actuates a switch to restart the above referred to motor, whereby a further 180 degrees rotation of the shaft 101 is initiated. During this 180 degrees rotation, cam 99 is ineffective, but cam 129 actuates member 131 to raise and lower the magnet developer means 49, 51 whereby the latent electrostatic image formed on the sheet 43 during exposure is developed. On re-engagement of the cam pin 123 with switch 125, the shaft driving motor is stopped and the lamp 128 goes out, indicating that the charging, exposing and developing process has been completed. An electrical control circuit for ensuring the order of the above operation is described with respect to Fig. 15, not shown.