Abstract: A method, a device, and a computer program product for determining a refractive error of an eye of a user are disclosed, as well as a method for producing a spectacle lens. The method for determining includes: displaying an image with a spatial modulation to the user; optionally, recording a reaction of the user to a variation of the spatial modulation over time; detecting a point in time at which a perception threshold of the user is reached; and determining the refractive error of the user from the spatial modulation, wherein the image contains a source image with several picture elements, wherein values for an image parameter are assigned to the picture elements, and wherein the spatial modulation is generated such that the values of the image parameter determine the values of a modulation parameter of the spatial modulation in the image.

Abstract: A method and apparatus for grinding fresh stock, comprising comminuting the fresh stock in a first roller press roller gap into ground grinding stock, dividing the ground grinding stock via an adjustable divider into a first and second part stream in a variably adjustable ratio and comminuting the ground grinding stock of the first part stream in a second roller press. The adjustable divider divides ground grinding stock into an intermediate stream comprising ground grinding stock issuing from an intermediate roller gap region, and into two peripheral streams each comprising ground grinding stock issuing from one of the two roller gap peripheral regions. The two peripheral streams are combined to form the first part stream and the intermediate stream forms the second part stream. The second part stream is conveyed from the divider into a bypass line, passing the second roller press.

Abstract: A plant for producing cement, having a first stage for crushing raw material to form raw powder, a second stage for calcination and sintering of the raw powder to form cement clinker, a third stage for cooling the sintered cement clinker, and a fourth stage for crushing the sintered cement clinker to form cement. The first stage for crushing raw material to form raw powder and the fourth stage for crushing the sintered cement clinker to form cement are structurally combined. In this way, during servicing or repair of one crushing stage, the plant need not be shut down because, y variable circuitry switching, the crushing stages permit plant operation with reduced production output.

Abstract: A closed-circuit grinding installation for comminuting material to be ground, the grinding installation having at least one high-pressure roller press, at least one apparatus for sifting out fine material from the material to be ground which is situated within the closed circuit and at least two apparatuses for conveying the material to be ground. The at least one high-pressure roller press is arranged at a spatial distance from and approximately at the same height as the at least one apparatus for sifting out fine material from the material to be ground, wherein the at least two apparatuses for conveying the material to be ground, when viewed from the side, intersect approximately in the center of the spatial distance, wherein the spatial distance is at least between five and twenty times the width or length of the high-pressure roller press.

Abstract: A plant for producing cement, having a first stage for crushing raw material to form raw powder, a second stage for calcination and sintering of the raw powder to form cement clinker, a third stage for cooling the sintered cement clinker, and a fourth stage for crushing the sintered cement clinker to form cement. The first stage for crushing raw material to form raw powder and the fourth stage for crushing the sintered cement clinker to form cement are structurally combined. In this way, during servicing or repair of one crushing stage, the plant need not be shut down because, y variable circuitry switching, the crushing stages permit plant operation with reduced production output.

Abstract: A closed-circuit grinding plant for comminuting material to be ground, in which at least one comminution apparatus and at least one apparatus for separating comminuted material are connected to each other and keep the brittle material to be ground in the grinding circuit until it is removed from the grinding circuit by the separating device on account of the level of comminution, wherein a control loop controls the feed of fresh material to be ground into the circuit, and also relates to a corresponding method for operating such a closed-circuit grinding plant. A buffer for the material to be ground is present in the grinding circuit. The integration of the buffer enables a reduced overall height of the closed-circuit grinding plant, which saves energy costs. The filling level of the integrated buffer is suitable for controlling the closed-circuit grinding plant.

Abstract: A recirculating grinding mill, including at least two rolling presses for comminuting the material to be ground, at least two first classifiers for classifying a coarse-grain fraction, at least one second classifier for classifying a fine-grain fraction and a medium-grain fraction from the fractions classified in the at least two first classifiers. The feedstock is fed into the recirculating grinding mill passing the at least two rolling presses and the at least two first classifiers and then the at least one second classifier and the medium-grain fraction and the coarse fraction of the at least two first classifiers being fed once again to the rolling presses, and the at least two first classifiers being arranged underneath the at least two rolling presses. The rolling presses are placed between at least two risers for transporting the circulating material being ground.

Abstract: In a screening device for sorting granular material with at least one rotatable rod basket and a downstream fine material separator a cyclone-type eddy separator is attached with the smaller diameter of its housing cone in order to draw off the screening gas flow charged with fine material and flowing out due to twisting energy in such a way that the rod basket screening device and the separator form a compact unit. A submerged pipe is located in the center of the cyclone-type eddy separator for drawing off the screening gas flow freed of fine material. At least one opening is provided for discharging the fine material at the periphery of the eddy separator housing.

Abstract: A recirculating grinding mill, including at least two rolling presses for comminuting the material to be ground, at least two first classifiers for classifying a coarse-grain fraction, at least one second classifier for classifying a fine-grain fraction and a medium-grain fraction from the fractions classified in the at least two first classifiers. The feedstock is fed into the recirculating grinding mill passing the at least two rolling presses and the at least two first classifiers and then the at least one second classifier and the medium-grain fraction and the coarse fraction of the at least two first classifiers being fed once again to the rolling presses, and the at least two first classifiers being arranged underneath the at least two rolling presses. The rolling presses are placed between at least two risers for transporting the circulating material being ground.

Abstract: A roller press which is used, in particular, for material bed comminution and into the material feed hopper of which both coarse-grained material, such as, for example, fresh material, and fine-grained material, such as, for example, recirculated grits from a downstream sifter and/or, for example, fly ash, are introduced, wherein the stability of the material bed or grinding bed and therefore a high grinding efficiency are ensured despite the considerably different grain size and grain distribution in the two material flows to be drawn into the roller nip. A pressure screw which conveys the fine material under pressure is inserted into the material feed hopper through at least one fine-grain inlet opening in the hopper, a nozzle-like outlet, in particular a flat nozzle, of the pressure screw extending into a central region of a material draw-in of the press roller nip.

Abstract: In a screening device for sorting granular material with at least one rotatable rod basket and a downstream fine material separator a cyclone-type eddy separator is attached with the smaller diameter of its housing cone in order to draw off the screening gas flow charged with fine material and flowing out due to twisting energy in such a way that the rod basket screening device and the separator form a compact unit. A submerged pipe is located in the center of the cyclone-type eddy separator for drawing off the screening gas flow freed of fine material. At least one opening is provided for discharging the fine material at the periphery of the eddy separator housing.

Abstract: In the production of meal-fine products by a milling process the milling material generated in a comminuting device is ordinarily separated at the desired grain size in a downstream sifter and the fine material (meal-fine product) obtained here is then separated in the fine material separating device from the sifting air. According to the invention it is proposed to construct the sifter as a V-sifter and to connect this latter, without interposition of the otherwise ordinarily used pipelines, directly with the fine material separating device, preferably an electro-filter.

Abstract: Two-stage classification of a granular material, in particular a cement grinding feed, is accomplished in two classifiers connected in series in such a way that the separative behavior or the separative action and thus the particle-size distribution of the undersized or finished material coming from the second classifier can be modified with simple resources. Part or all of the oversized material of the second classifier is recycled to the second classifier.

Abstract: In order to create a sifting device with integrated static sifter member and dynamic sifter member having at least one rotatably disposed rod basket such that the two sifter members are optimally coordinated so as to operate efficiently, particularly with moist sifting material to be dried, it is proposed in accordance with the invention to have a bypass line leave from the intermediate area between the static member and the dynamic member of the sifting device for drawing off a partial flow of the sifting air flow/sifting gas flow and to supply only the remaining outgoing sifting air of the static sifter member (static cascade sifter or V-sifter) to the dynamic sifter member with the at least one rotatably disposed rod basket.

Abstract: To construct a tube mill such that a simple and compact circulation grinding system can be created therewith, with little outlay in terms of machinery, that can also manage higher stock circulation rates without high operating costs, a tube mill is disclosed whose drop-delivery housing consists of two spaced stationary non-rotating side faces, between which a rotatably mounted material conveyor ring is arranged, which can be rotated; whereby a sifting space with a dynamic sifter and/or a static sifter is integrated in this so constructed drop-delivery housing.

Abstract: Two-stage classification of a granular material, in particular a cement grinding feed, is accomplished in two classifiers connected in series in such a way that the separative behavior or the separative action and thus the particle-size distribution of the undersized or finished material coming from the second classifier can be modified with simple resources. Part or all of the oversized material of the second classifier is recycled to the second classifier.

Abstract: A compact circuit grinding apparatus wherein two press rolls are housed in one housing, comprising of two stationary lateral end walls, between which is arranged a material conveyor ring, which is rotatably seated and can be set into rotation, for an internal material circulation. The inflow of material takes place through one or more openings in one or both housing end walls and the outflow of material likewise takes place laterally through one or more openings in the housing end wall. A sifter is arranged underneath the nip of the two rolls in the housing. The sifter can comprise a static or dynamic sifter and a flow of air through the sifter removes the fines from the crushed granular material.

Abstract: A product bed comminution high-pressure roller press wherein the problem of great recirculations of product material or, respectively, high product circulation rates caused, for example, because of reduced roller press pressures is solved employing little machine outlay. Two rollers (10, 11) are surrounded by a housing composed of two stationary lateral end walls (12, 13) between which a rotatably seated material conveying ring (16) that can be rotated is arranged for an internal product material circulation. The product material is admitted from the side through one or more openings (22) in one or in both housing end walls (12, 13) and the product material is discharged laterally through one or more openings (24) in the housing end walls (12, 13) via a discharge element (25) and/or via one or more discharge elbows (27).

Abstract: In two-roll machines for high-pressure disintegration of granular material, in which typically only one of the two rolls is motor driven, while the other roll is driven by means of friction via the granular material pressed in the roll gap, and thus operates as a drag roll, it is proposed to equip the drag roll with a separate, smaller drive mechanism including a separate smaller drive motor. This drive is thereby dimensioned in such a way that the startup of the drag roll is ensured and a drop in revolutions per minute of the drag roll is avoided. Alternatively, this separate drive is enlarged in such a way that it can transmit 10% to 40%, preferably 20%, of the total required drive power.

Abstract: In order to assure that an adequately small delivery granulation is offered to the nip of a two-roller machine, preferably a high-pressure roller press for interparticle crushing, namely for an optimum draw-in of the granular material, it is inventively proposed that a sieve means to be arranged in the product delivery shaft of the two-roller machine and that the oversized sieve particles be comminuted with a crushing roller that is likewise arranged in the product delivery shaft and that the comminuted particles then be presented to the high pressure nip for further interparticle crushing.