Abstract: A document feeder for moving documents across an upwardly facing imaging platen of a copying machine includes a stacking tray disposed above the platen and in substantially parallel relationship therewith. A first guide element guides documents moving off the imaging platen at one edge thereof along an upwardly extending curved path and discharges the documents at one end of the stacking tray along an upwardly directed trajectory. A second guide element intercepts documents discharged along the upwardly directed trajectory at a location above the top of the tray and guides the documents downwardly into the stacking tray, thus obviating interference between a document moving into the tray and a bent or curled document already in the tray.

Abstract: An automatic background brightness control for document copiers of the type using automatic feeders for advancing original documents along a transport path to an imaging platen at which the documents are copied. As the feeder advances a document to the imaging platen, one or more light sources disposed at spaced locations across the transport path direct scanning beams onto the indicia-bearing side of the document. Photodetectors sense the light reflected from the scanned portions of the document to provide signals indicating the reflectance of the scanned portions. A signal-processing circuit responsive to the reflectance signals generates a background brightness control signal representing the maximum reflectance sensed by any of the detectors. The background brightness control signal regulates the intensity of the exposure lamp of the copier when the document reaches the imaging platen.

Abstract: A semi-automatic document feeder for use with a photocopying machine in which each of a plurality of parallel spaced belts supported by first and secondary pulley assemblies has a lower traverse running across the machine imaging platen. Documents which are introduced to the feeder through an entrance port located near the top of one of said pulley assemblies, are guided around said pulley assembly onto a lower transport path defined by the plurality of belts and the imaging platen, and are stopped for copying by a gate located on the opposite edge of the machine platen and arranged to be moved into and out of the path of a document.

Abstract: A toner concentration detecting and toner replenishing system for use in an electrostatic copier having a magnetic brush which carries dry developer comprising a mixture of ferromagnetic carrier particles and toner particles into contact with the surface of a photoconductor upon which a latent electrostatic image has been formed, in which system a quantity of developer is removed from the magnetic brush after development of the image and the brush leaves the surface. The removed developer is directed into a dielectric tube having a restricted outlet which inhibits unstable flow through the tube so that developer in the tube determines the inductance of a coil surrounding the tube. The coil is one element of the tuned circuit of a sensing oscillator, the output frequency of which is compared with that of a tunable reference oscillator to provide a frequency difference signal which is a measure of the relative proportion of toner to carrier in the developer.

Abstract: An electrophotographic liquid developing system for overcoming the effect of photoconductor background potential in which during the passage of the image area through the developer unit a constant current source supplies a small current to the development electrode to raise the electrode to a potential of the same polarity as and of a magnitude greater by predetermined amount than that of the average background potential of the image area. In a preferred embodiment the constant current source is provided by a small plate mounted in and insulated from the transfer corona housing and having such dimensions as to provide the required current. Preferably, the output of the constant current source is controlled in response to a measurement of the conductivity of the developer.

Abstract: A toner concentration detecting and toner replenishing system for use in an electrostatic copier having a magnetic brush which carries dry developer comprising a mixture of ferromagnetic carrier particles and toner particles into contact with the surface of a photoconductor upon which a latent electrostatic image has been formed, in which system a quantity of developer is removed from the magnetic brush after development of the image and the brush leaves the surface. The removed developer is directed into a dielectric tube having a restricted outlet which inhibits unstable flow through the tube so that developer in the tube determines the inductance of a coil surrounding the tube. The coil is one element of the tuned circuit of a sensing oscillator, the output frequency of which is compared with that of a tunable reference oscillator to provide a frequency difference signal which is a measure of the relative proportion of toner to carrier in the developer.

Abstract: A self-cleaning developer applicator system for applying liquid developer to a latent electrostatic image carried by an organic photoconductor supported on a conductive substrate which moves relative to a developer station in which a biasing potential is applied between the substrate and a conductive developer applicator electrode to reduce the effect of the background potential of the latent image while adequately developing desired image areas together with means for cleaning the applicator electrode continuously during operation of the system to remove toner particles which collect thereon under the influence of the biasing potential. In a preferred embodiment the applicator is arranged to flow a film of developer liquid at the speed of movement of the photoconductive surface over a relatively extended area of the image during development thereof.

Abstract: Our invention contemplates a liquid developer which carries a toner which is tacky. This tackiness, however, is a transient one. After the latent electrostatic image is developed by our tacky toner, that is one that has adhesive properties, the developed image with the toner in tacky state is contacted with sheet material such as paper. The developed tacky toner image has greater affinity for the paper than it does for the photoconductive surface. We insure this by using a photoconductive surface which has less affinity for the tacky toner than the sheet material to which the image is to be transferred. After the image is transferred to the sheet material the toner quickly loses its tackiness and dries to a hard scuff-resistant surface.Our invention also contemplates a developer liquid which contains a toner which is non-sticky when first deposited then becomes sticky or tacky so that it can be transferred while tacky and loses its tackiness and remains firmly bonded to the surface to which it is transferred.