Abstract: Duplicating stencils of the kind used on typewriters and word-processors are given a much improved working life by providing the stencil sheet with flexible reinforcement at that part of the sheet which first contacts the sheet of paper which receives the duplicated image, and between the upper limit of the area of the sheet which is imaged and the adjacent edge.

Abstract: A duplicating stencil has its heading strip in the form of two separate regions separated by a perforation line.The holes on one region have a different arrangement from those on the other regions, so that tearing along the perforation line allows one region to be separated from the rest of the stencil and to leave the holes of the remaining region as the effective mounting holes.A single image field and a single top edge guide line apply for all of the heading strip regions.

Abstract: A multi-cylinder stencil duplicator includes ink-applying means in the form of a coating member offering a fixed nip between the coating member and a cylinder of the duplicator, ink being applied to one side of that nip and being held back as a wedge at the nip during rotation of the duplicator cylinder. The dispensing of ink to the wedge is controlled in response to variations in the capacitance between the coating member and the cylinder, so that when the ink wedge drops below a given threshold value further ink is dispensed.

Abstract: A phase locked loop control system, in particular for use for synchronizing the operation of a carriage drive motor and a main drive motor in a photocopier, uses a digital frequency- and phase-comparator and relies on the output pulses, used to power the slaved motor, being shaped so that each positive-going d.c. drive pulse is followed by a negative-going d.c. braking pulse of smaller amplitude, to provide positive registration of the slaved motor with the pulsed driving signal.

Abstract: A photocopier scanning system has a scanning member (which may be the scanning lamp, a scanning mirror, a scanning slit, or a document carrier) on a scanning system powered by a d.c. drive motor synchronized to the rotation of the a.c. main drive motor for the other components of the photocopier. A variable programmer using a phase locked loop control circuit including pulse encoders slaved to the motors maintains strict synchronization between the scanning drive motor and the main drive motor with an appropriate proportionality dependent upon the image magnification/reduction ratio of the photocopier. The optical system may include a movable zoom lens element which gives infinitely variable selection of the magnification/reduction ratio, and which can readily be connected to the programmer to achieve an infinitely variable proportionality between the speeds of the scanning drive motor and the main drive motor to suit any such magnification/reduction ratio.

Abstract: A magnetic brush developer unit has a toner sump below the level of the magnetic brush supporting roller-shell combination and a magnetic pump rotor rotatable in the bottom of the sump to agitate toner and to return toner to a location from which it is attracted onto the shell of the magnetic brush roller. A scraper blade is effective to remove substantially all the circulating brush-forming toner from the shell and to cause at least a part of the removed toner to fall into the sump to be pumped back up by the magnetic pump rotor. An optional second scraper blade, directed in the opposite direction from that of the first scraper blade, removes any lumps of agglomerated toner which may be moving countercurrent to the main magnetic brush-forming toner mass.

Abstract: A copying system and apparatus wherein a first electrostatic image of an original is formed and developed on a first photoconductive surface, and second electrostatic images of the developed image are repeatedly formed on a second photoconductive surface by illumination of the first surface. The second images, which can be formed at high speed, are developed and transferred to copy material.

Abstract: A magnetic brush monocomponent developer unit includes a doctor blade for rendering uniform the layer of toner magnetically attracted to the surface of a shell within which a rotating magnetic roller is positioned. A coil connected to the doctor blade receives an alternating magnetic field in response to rotation of the roller and the induced voltage fluctuations in that coil are sensed to determine when the voltage amplitude exceeds a given threshold value (indicative of a low amount of toner held back by the doctor blade) at which application of toner to the layer by way of a metering roller and sealing brushes is resumed.