Patent GB-808036-A (GB)
Title: Improvements in intermittent electro-photographic recorder
IPC: G01D15/14
Filed: 1956-12-31
Abstract: 808,036. Printing processes. HORIZONS Inc. Dec. 31, 1956 [July 3, 1956], No. 39631/56. Class 100(2) In a xerographic apparatus, the photosensitive element is selectively caused to move intermittently or to remain at rest, and there are provided means for imparting a uniform electrostatic charge to the photoconductive coating while the element is moving, means for exposing the element to information in the form of a light pattern while the element is stationary, means for developing the latent image while the element is moving, means for transferring the visible image to a continuously moving permanent record medium while the element is stationary, and means for cleaning the element while it is moving, to prepare it for a repetition of the process. The xerographic drum 100 comprises a conductive support 104 and a photoconductive layer 108, preferably of amorphous selenium, having a resistivity in the dark of at least 10<12> ohm cms., decreasing to below 10<10> when it receives the information. The charge is applied to the drum by charging rollers 122 having conductive cores and covers 126 of neoprene. The rollers are driven by friction when forced against the drum by springs 129 Potentials of 600-2,000 volts D.C. are suitable for imparting the charge. The layer 108 is then exposed while at rest at the point E to information (such as radar) portrayed as a single horizontal line of light modulated along its length, derived from a film illuminated by a slit of light or from a cathode ray tube scanned in a single direction. The information is conveyed by a lens 142 and a mirror 144. The latent image thus formed is moved past a roller 162 provided with a liquid developer from a pump through a conduit 174 and a manifold 176 having four needle valves 178 through which the liquid is dripped, excess liquid returning through a tank 164 to the pump. The developer may be a suspension of a talcum powder, magnesium oxide, carbon black or certain pigments, in petrol, kerosine, turpentine, benzol or carbon tetrachloride. The visible image is then brought to rest below a printing head 188 which presses against it a web of permanent record medium 181 fed by pin wheels 186, 186<1> at 2 feet per hour. The web is moved against the drum under the action of a cam 192 co-operating with a carriage 182 pivoted at 184. The remains of the image is moved past a cleaning roller 193 of gelatin, to which is supplied by a manifold 196 cleaning liquid which may be any of the hydrocarbons used for the developer. The arrangement is such that while the drum is rotating, part of it is charged while another part is developed and a further part cleaned, and when it is at rest part is printed from while latent images are formed on a further part. One cycle of operation may take 3 seconds, which includes one period of movement and one of rest, each operation taking place once on different parts of the layer 108. Printing takes place 30 seconds after the corresponding information is received. In operation, the pumps for the developer and cleaning liquid and the record medium feed are continuously operated, while the drum, information receiving device, printing head and charging rollers are controlled by an electric motor through a magnetic clutch associated with a brake. The sequence of operations in a cycle is controlled by two micro-switches actuated in succession by a cam follower co-operating with a cam rotating with the drum drive shaft 102, the cam having two adjacent low portions to actuate the switches. When the follower reaches the first low portion, the first switch is opened, to release the clutch and remove the charging voltage. The shaft rotates through inertia as far as the second low portion, when the second switch is closed, to actuate a first timing means, which initiates the operation of the source of information, and also actuates a second timing means. The second timing means causes the movementment of the printing head towards and away from the drum. The first timing means then actuates a third timing means which moves the follower away from the. cam, thereby opening the second switch to inactivate the source of information and reset the first and second timing means, and closing the first switch to release the brake and engage the clutch, and restore the charging voltage. The third timing means then returns the follower into engagement with the cam before the first low portion is again reached, and the cycle is repeated. The photoconductive material may be any of those referred to in Specification 672,767.