Abstract: Digital circuitry and microprocessor techniques are used to monitor the quality of toner operations in a copier and take appropriate corrective action based upon the monitoring results. Patch sensing is used. Reflectivity signals from the patch and from clean photoconductor are analog-to-digital converted and a plurality of these signals taken over discrete time periods of a sample are stored. The stored signals are averaged for use in determining appropriate toner replenishment responses and/or machine failure indicators and controls.

Abstract: A flexible, closed loop belt having a photoconductive surface is mounted internally to a xerographic-type copier. The belt mounting frame or guide, is arranged to include a series of interconnected courses defining a supporting path for the belt. One or more portions of the guide surface are formed as peripheral segments of a cylinder. Various courses are interconnected in a generally continuous closed loop path for the belt.

Abstract: Lateral force is applied to a web material by an air bearing for the purpose of guiding the web against a fixed reference edge. A bearing surface over which the web is movable includes an arrangement of holes for establishing a differential flow across the bearing surface to produce a lateral force on the web in the direction of the reference edge. The holes are arranged asymmetrically relative to the center line of the bearing surface but typically are parallel to the reference edge. The differential air flow is established by controlled sizes of apertures through the bearing plate, variable air permeability of the material forming the bearing surface or the like. A common source of pressurized air is coupled to all of the bearing surface holes.

Abstract: A precision-surface is constructed to support magnetic tape on a dynamically-stiff air film above the surface. The precision-surface is achieved by using relatively thick stock material for the bearing. The bearing may be ground to the precise contour and dimensions for the desired tape path. A thin stiff air film between the bearing surface and the tape is provided by deep pools in the bearing surface. The bottom of each pool contains a single small hole in the order of 0.010 inch (0.254 mm.) in diameter for supplying air under pressure to the pool. The small holes are placed in the bottom of the pools preferably by using a thin foil with the holes etched therein and bonding the foil inside the rigid bearing so that the foil becomes the bottom of the pools. The total cross-sectional area of pools on the bearing surface is limited to a small percentage of the area of the bearing surface as the compressibility of the air in the pools can affect the stiffness of the air film.