Abstract: Powder particles blemishing the background of a powder image formed by attraction of toner particles to an electrostatic charge pattern on a photoconductive support surface are removed selectively without loss of the image by subjecting the image bearing surface to a limited electric field generated from a wall defining a suction mouth through which the powder particles attracted by this field from the support are sucked away. In an embodiment involving transfer of the powder image, the suction mouth serves also as a protective device for removing all powder particles from the support surface if a receiving material is not in position at the transfer station to receive the image, for which purpose a high voltage is applied at the suction mouth and/or the support surface is treated ahead of the suction mouth to diminish its charges attracting the image particles.

Abstract: A pressure roller for applying pressure to a sheet-like material passing between the pressure roller and an application roller for applying a layer of liquid to the material, as in the development of diazotype copies, comprises a plurality of relatively short constituent rollers connected to one another by connecting means which permit radial displacement of the adjacent constituent rollers relative to each other and wherein each constituent roller is urged toward the application roller by at least one resilient spring-like element. The pressure roller thus enables contact between it and the application roller with an even pressure, without significant sagging along its length, while allowing uneven areas of the sheet-like material to pass therebetween without affecting the force exerted over the entire nip between the rollers. Improved development of diazotype copies can thus be obtained.

Abstract: High operating speeds of the powder brush of a rotating magnetic brush developing apparatus are made feasible, in order to improve the quality of developed images without causing contamination by powder escaping from the brush, by locating an air deflecting partition, for instance in the form of a plate arranged tangentially relative to the rotating sleeve of the apparatus, so that the partition will guide away an air stream entrained by the moving powder brush before it reaches the location where powder is supplied to the brush. The partition advantageously delimits a chamber formed over a sector of the powder brush, from which air carried past the partition in the powder brush and then expelled from it will escape in a controlled manner enabling recapture of the powder particles carried by such air before the air is discharged.

Abstract: An apparatus for developing electrostatic charge images on a moving support, e.g. on a photoconductive belt, by a developing powder composed of toner particles and magnetizable carrier particles, which powder is transported by a rotating magnetic roller from a reservoir through a developing zone where a magnetic roller from a reservoir through a developing zone where a magnetic brush is formed between the roller and the support, is provided with means for preventing variations of the quality of the developed images by supplying more developing powder to the brush than the roller transports through the developing zone. The excess powder flows away over a partition into a trough containing a rotor, to be remixed with powder from the reservoir and propelled by the rotor into a narrowing passage defined between the partition and the side of the magnetic roller that moves toward the support.

Abstract: An exposure system for electrophotographic copiers, by which large originals such as engineering drawings can be exposed at high light intensity yet with the space requirement held to a minimum. The exposure is obtained by the provision of at least one tubular light source disposed parallel to a slit exposure zone at the side of that zone facing away from the image projection (optical) system and, at the side thereof facing toward the optical system, of tubular light sources disposed parallel to said zone in two equal groups arranged opposite to one another and adjacent to the reflection object space of the exposure system. The lamps of each of the two groups are closely spaced and have disposed closely about them a diffusely reflecting wall of a form generated by a straight line moving parallel to the lamps.

Abstract: An electrophotographic copying apparatus employing a moving endless photoconductive belt for image formation and image transfer is provided with a control system whereby images are formed on the belt at fixed locations relative to at least one marking on the belt, without need to make the belt precisely to a certain length or to provide more than a single marking which, if the belt is made endless by a seam, can be located near the seam to enable skipping of the seam in the imaging operations.

Abstract: A circuit for controlling the power transmitted from an a.c. voltage source by a switching element, particularly a triac, connected in series with a power element, e.g. with the heating element of an image fixing device in an electro(photo)graphic copier, is safeguarded against errant operation by the provision of a checking circuit which comprises means for blocking periodically the transmission of power by the switching element under its normal control and means effective in intervals of the interruption of said transmission by the blocking means for detecting whether power is then being transmitted to the power element and, if it then is, producing a corrective control signal.

Abstract: Polyethylene having an average molecular weight of at least 1,500, a crystallinity of at least 75% and a density of at least 0.93 has been found advantageous as a base material for making pressure-fixable toner powder for developing electrostatic images. The toner powder can be fixed satisfactorily to image substrates by the pressure of fixing rollers of conventional electrophotographic copying apparatus, yet it can be produced readily by grinding a suitable composition based on the polyethylene. The polyethylene preferably has an average weight of between 2,000 and 10,000, a crystallinity of at least 80% and a density of at least 0.94. Especially advantageous pressure-fixable, electrically conductive toner powders are obtained from pigmented masses of the polyethylene in which 3 to 20% of the weight consists of carbon black having a specific surface of at least 750 m.sup.2 /g, preferably of about 1,000 m.sup.2 /g, and an oil absorption of between 250 and 400 ml/g.

Abstract: A process and apparatus for developing an electrostatic latent image on a surface of a strip-type photoconductor. A working supply of developer material, held readily available for application to the photoconductor, is carried from a holding device to the photoconductor by means of a rotatable applicator. A magnet, magnetically coupled to the applicator, brings the developer material on the applicator into sufficient contact with the photoconductor to cause the developer material to brush the image bearing surface of the photoconductor, thereby developing the latent image on the same. The developer material is collected before being returned to the working supply, and fed to the middle of the working supply to facilitate mixture and blending therewith.

Abstract: In electrographic copying apparatus of the type in which a powder image is transferred from a moving surface to a surface moving in pressing contact with it and then is transferred from the latter surface to a sheet of copy paper, pollution of the transfer station by powder is avoided by providing one of the two surfaces with at least one receding surface portion which recedes away from the other surface so as not to make contact with it, and causing a receding surface portion to be positioned opposite to the other surface so that the two surfaces are not in contact when no image transfer is being effected, such, for instance, as when powder images are not being formed or when a copy sheet is not being supplied so as to receive an image formed.

Abstract: Edge shadow effects on copies obtained by episcopic exposure of an original lying on a transparent exposure plate are prevented by directing light toward at least one side edge of the original from a surface laterally adjacent thereto of a light transmitting means disposed on the exposure plate. Each light transmitting means is constituted by a transparent plate member having its surfaces made diffusely reflecting, except a transparent surface directed toward the original and a transparent surface disposed in a path of illumination from a light source. Such a plate member extending along a margin of the exposure plate in electrophotographic copying apparatus serves the dual function of guiding the laying of an original onto the exposure plate and preventing edge shadow effects which otherwise result from a narrow slit or cavity that usually occurs between an edge of the original and the guide member usually provided on the exposure plate.

Abstract: Development of a charged photoconductive medium in xerographic copying apparatus is prevented when a properly formed charge image is missing as a result of insufficient imagewise exposure, by a system in which the intensity of the exposing illumination is sensed by a detector such as a photoelectric cell or a phototransistor, and when the illumination is below a level sufficient to form a proper charge image a signal emitted by a detector causes a discharging device such as an A.C. corona or a lamp to discharge the charged medium at a location between the exposure station and the developing station of the apparatus. Means also are provided whereby said signal causes interruption of the feeding of copy material to receive an image, and whereby it causes the execution of a preset copy program to be blocked until the exposing illumination is restored to a proper level of intensity.

Abstract: In electrophotographic copying apparatus utilizing a photoconductive belt having markings regularly spaced apart on its back side for control of the copying operations by moving past a detector comprising a light source and a photoelement to generate signal pulses, the detector is made to perform reliably notwithstanding variations of the sensitivity of the photoelement, or of the light emission, by the provision of a circuit for emitting a detector signal proportional to the amount of light sensed by the photoelement together with a signal modifying circuit that maintains an output signal level corresponding to the average value of the detector signal and a control circuit responsive to the output signal level for controlling the intensity of the light source.

Abstract: In a process and apparatus for fixing thermoplastic image material onto paper, wherein the image material in thermally softened condition is transported through a pressure zone while being pressed between and in contact with the paper and belt moving together through said zone, and upon leaving said zone the paper and belt are separated from each other by forced movement of the belt along a path curved away from the paper, the fixing of the image material to the paper is achieved reliably in a simple manner, with little sensitivity to variations of temperature or of the character of the belt surface, by maintaining the thickness of the belt, the speed of movement of the belt and the radius of curvature of said path in a relationship defined by the formula: (D .times. V/R).gtoreq. 0.05, in which D represents said thickness (in meters), V represents said speed (in meters per second), and R represents said radius (in meters).

Abstract: A collating apparatus is mounted above a copying machine and includes a housing frame enclosing a conveying mechanism for conveying sheets from the copy-ejection part of the copying machine along a vertical path alongside of which are positioned horizontal trays for receiving the copy sheets as collated. The trays have associated therewith guide elements which are balanced in equilibrium in a first position in which they project into the conveying path to guide sheets into their corresponding trays and which are activated by the receipt of a sheet in the tray to a second position in which they are moved out of the path. The guide elements are locked in this second position by pawl-like locking elements until all locking elements are released by an unlocking means activated by the copy machine start button.

Abstract: A photocopying material is provided having a light-sensitive layer comprising an oleophilic resin and a resinous diazonium compound, which both are soluble in an organic solvent but substantially insoluble in water, in admixture with a surface active agent which, after imagewise exposure, renders the layer developable with plain water such as ordinary tap water so as to yield an excellent photocopy and in particular a printing form from which many thousands of fine prints can be made on an offset machine.

Abstract: In an electrophotographic copying apparatus in which an imagewise exposed photoconductive plate moving to a developing station passes a light source and a light shield which are arranged for selectively exposing parts of the photoconductive plate outside the area of the copy image, the light shield is made slightly light transmitting, such as by making it of a glass or plastic having a light transmittance of 2.5 to 25%, so that the light source and shield serve the dual functions of fully exposing nonimage parts of the plate and weakly exposing its image area, thus improving the contrast and tone reproduction in the developed image.

Abstract: In transferring powder images from a moving photoconductive support to a receiving material such as copy paper passing in contact with the support over a transfer roller, while both applying a direct current potential to effect image transfer and brushing the surface of the transfer roller to remove powder particles attracted to it from parts of the support. A potential effective for transferring the image is applied without hampering the cleaning action of the brush or brushes by maintaining between the support and the transfer roller a pulsating direct current which, for instance, has a frequency of 60 Herz or 50 Herz and preferably is generated by single phase rectification of a current formed by superimposing a sinusoidal alternating current and a direct current.

Abstract: In copying apparatus utilizing an endless belt to hold electrostatic or powder images and carry them through a station for transfer to a receiving surface, the belt is arranged for movement through a path containing turns where it is engaged by rollers, with some of these rollers contacting its image bearing side, and each roller so contacting the belt is constituted by freely rotatable narrow roller members which contact it only in narrow margins along its opposite edges, so outside the surface regions that usually carry the images. A considerable length of the belt can be held in a close undulating path, as in a compact magazine, by a series of rollers arranged in parallel rows with each roller in one of these rows constituted by such narrow roller members engaging the image bearing side of the belt.

Abstract: Toner powders for developing electrostatic images are provided which contain in epoxy resin organic dye that, although in itself insoluble in the resin, is solubilized therein by one or more substances selected from the group consisting of complete esters and alkyl and aryl amides of o- and m-phthalic acid, carbonic acid, phosphoric acid, benzoic acid and benzenesulfonic acids and condensation products of formaldehyde with alkyl and aryl amides of benzenesulfonic acids.