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In existing systems, oil is doctored onto the width of the roll but this invention enables active control over the oil film thickness and the area to be coated meaning less waste.
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Summary This invention relates to the problem of dispensing a thin film of a release agent in liquid (oil) form to certain rotating rolls in electrophotographic copiers or printers. It consists of an integrated oil dispenser system with a pouch in which the oil is stored and a dispersing mechanism, controlled by an electrostatic transducer. An important feature of this dispersing system is a wiper blade with integral electrodes, permitting active control of the oil film that is applied to the roller. The entire dispensing system is conveniently fabricated from a single piece of flexible plastic film. The unit is disposable and can be replaced periodically as the oil in the pouch is depleted. Current electrophotographic printers and copiers generally use a doctor blade to apply a very thin layer of film to the transfer and/or fuser rollers in order to aid in toner release. The doctor blade is adjusted during initial assembly and then periodically by a service representative. There is no provision for active control of the blade to either maintain the correct film thickness or to image-wise selectively deposit the oil on the rolls. When the film is too thick it causes machine maintenance problems and also adversely affects the quality of prints. In this invention, electrodes are deposited on opposite sides of the pouch and then coated by appropriate plastic for protection and electrical isolation. When voltage is applied to these electrodes, the pouch is pinched, releasing the oil. Along one edge of the pouch, there are constricted flow passages that further control the oil flow by applying voltages to their respective electrodes. The dispensing wiper blade is mechanically held against the roller and contains an electrode on its back side running the length of the roller. When voltage is applied to this electrode, it forces the wiper tightly against the roller and allows control of the thickness of the oil film. Either DC or AC or a combination of both can be used in this system. This is useful since it helps prevent static charge buildup on the plastic wiper blade, thereby improving the metering control.