Patent GB-1450080-A (GB)
Title: Electrostatic photographic copying apparatus
IPC: G03G15/30
Filed: 1973-11-28
Abstract: 1450080 Electro-photographic copying machine MITA INDUSTRIAL CO Ltd 28 Nov 1973 [30 Nov 1972] 55238/73 Heading G2H In an electro-photographic copying machine having a movable drum 6 carrying a sensitive surface 5 through image-forming and image transferring zones 8 and 9 respectively the drum is arranged to make two revolutions for each copying cycle so that the maximum length of a copy is not restricted to the length of the surface of the drum between the downstream end of the transfer zone 9 and the starting position of the drum, measured in the direction of drum rotation, for a copy cycle. Thus if the copying cycle starts at position Po, Fig. 2-A, (when the leading edge of the imaging surface 5 is at Po) the rear end F of the imaging surface is situated at a position between the position Po and the downstream end P 1  of the transfer zone regarded in the direction of drum rotation. P 7  is the upstream end of the image-forming zone. Any portion of the image not transferred during the first of the drum rotations is transferred during the second. The machine is equipped with an initial charging station 10, a light image exposure station 11, a developing station 13 (the last two stations constituting the image-forming zone), and a transfer station 37, a copy stripping station 38, an overall light exposure station CL and a brush cleaning  station 42. Copy paper is fed either from a roll b to a cutter 32 (which is arranged to cut a length corresponding to the length of the original) or from a sheet input slot 52 to the transfer zone 9 and thence on a suction belt 46 to a fixing zone 47 comprising heaters 48. Exposure station The original a to be copied is supported on a reciprocable frame 3 which is moved in synchronism with drum 6 past an exposure slit 17 by a drive mechanism comprising a wire which is reciprocated by a winding drum and clutch arrangement Figs. 11-A and 11-B (not shown). The optical system comprises a lamp 18, a series of mirrors 20, 21 and 22 and a transparent plate 19. The mirror 22 contains a lens. The system is airtight to prevent intrusion of toner powder. A blower is arranged to direct air through the exposure station to prevent toner contamination of the surface 5 being exposed. Developing station The magnetic brush developing station, Fig. 8, comprises magnets 70 supported within a rotary sleeve 68. A shield 72 prevents the magnetic field retaining developer outside the development zone. A stripper 74 (which is adjustable) controls the height of the brush. Toner is added to the developer from a replaceable cartridge (81), Fig. 7 (not shown) via a metering roller (88). Fixing station A heated roller fixing unit Fig. 9 (not shown) may be employed in place of the unit of Fig. 1. Sensitive element holding device To enable replacement of the element 5 this element is held on the drum 6 by clamping its leading ends between a jaw 204, Fig. 10, and a jaw 213 and engaging holes provided in its trailing end with hooks 231. Both the jaws and the hooks are arranged to be operated from a cam 220 through followers 219 and 237 such that an element fed to the drum by rollers 246 and 246' is clamped by its leading edge, is smoothed on to the surface by roller 247 carried on pivotal arm 249 and is engaged at its trailing edge by hooks 231. A solenoid operated release 260 for both the jaws and hooks is provided so that the element may be removed when required. Copy paper feed  To enable the length of paper cut from roll b' by cutters 32 to equal the length of the original a the drum 9 is arranged to operate the cutters by means of a switch S11, the position of which switch around the drum periphery is adjustable by means of a wire 97 connected to an indicator 93 adjacent the exposure frame 3. The pointer is manually adjusted in accordance with the length of the original on the frame. Timing control The various operations of the machine are controlled in accordance with the position of drum 6 by two cams M1 and M2 see also Figs. 5- A and 5-B (not shown) driven from the drum and arranged to operate a series of switches (S 1 -S 5 ) which initiate and terminate the operations. Image transfer The developer image is transferred to the copy sheet by a corona discharge device 37. In an alternative embodiment (not exemplified) the image transferred may be a latent electrostatic image which is then developed on the copy sheet.