Abstract: An operating unit for an industrial robot is provided with hand-sensing device arranged in such a way that, when an operator operates the robot with the aid of a joystick, the operator's hand rests on the hand-sensing device enabling the joystick to be operated with the fingers of the same hand. Suitably the hand-sensing device includes a plate and a transducer sensing the presence of the operator's hand when it rests on the plate. The transducer influences a control unit which only allows the joystick to influence the robot when a hand is sensed by the hand-sensing device when the hand rests on the plate.

Abstract: A DC arc furnace electrically conductive hearth brickwork wear lining has metal electrical conductors extending through it which are molten for their upper portions when working and by electromagnetic flowing can erode the bricks of the brickwork. To prevent this erosion resistant refractory shields are positioned so as to shield the bricks from such flows.

Abstract: An induction coil, preferably for an induction heater, comprises a working coil, an outer casing and an inner lead-through channel for the workpieces, such as rods or tubes, which are to be treated in the induction coil. The region of the outer casing closest to the working coil consists of a layer of a rubber-elastic compound outside which is arranged a concrete casing. Using a two-part outer casing of this kind avoids the use of asbestos which is increasingly suspect because of its health hazard.

Abstract: In a means for detecting the wear of a current interrupting contact (4) there is used a light conductor (12) as a connecting link between the contact (4) and a detector (20) arranged at ground potential. The light conductor is inserted into an aperture (11) provided from the rear side of the contact, the bottom of said aperture being positioned at the level corresponding to a worn out contact. When the wear has grown so great that the light conductor (12) is exposed, the light or heat of the breaking arc will generate or interrupt a light signal, which via the light conductor is transmitted to the detector.

Abstract: A spot welding gun adapted for use in robotic welding in which the electrode holding arms of the gun are each turnably journalled on an attachment means. One of the electrode holding arms or an operating lever thereof supports a cam member with a cam surface thereon. A pressure roller acts against said cam surface during transport of the welding gun between welding points and thereby holds each electrode holding arm in a respective fixed position relative to the attachment means.

Abstract: The invention relates to an optical transducer for measuring position, angle, and the time dependence of these quantities in one, two or three dimensions, with at least one fiber optical transducer having light-emitting means which feeds incident light to an object on which the measurement is to be effected, a photo-detector which senses light emanating from the object after said incident light has been influenced by the object and an electronic unit partly for controlling the light-emitting means, and partly for evaluating the output of the photo-detector, the output signal being dependent on the variations in light transmission, light absorption, light reflection and/or photo-luminescence of a pattern on the object.

Abstract: A fiber-optical measuring apparatus for measuring magnetic fields, current, position, and various mechanical quantities consists of a transducer connected to a measuring electronic unit via at least one optical fiber, and the transducer comprises a magneto-optical modulator with a domain-producing magnetic material. The transducer is provided with at least two optical filters, of which at least one filter is positioned in the ray path on one side of the magneto-optical modulator and at least one other filter is positioned in the ray path on the opposite side of the modulator.

Abstract: A method and a device for detecting ground faults in a network for distribution of electric power from a power station from which a number of lines, included in the network, emanate and where the ground fault current I.sub.J of each line is measured. According to this method, that line is selected (10) which shows the greatest active ground fault current I.sub.JR (8), alternatively the greatest ground fault current I.sub.J, or the greatest change in the ground fault current .DELTA.I.sub.J. Thereafter, the measured ground fault current, or the change thereof, in the selected line is compared (12) with at least one predetermined reference value (11). A fault indication is obtained (13) at a level exceeding the reference value.

Abstract: A metallurgical ladle furnace has a ladle for containing the melt, an arcing electrode positioned on the ladle's axis, and a melt electrode in the ladle's lower portion and substantially symmetric with respect to the arcing electrode. DC power applied to the electrodes results in an arc between the arcing electrode and the melt for heating the melt and incidentally causing the melt to stir in vertical directions, the melt moving downwardly in the middle below the arc, upwardly along the walls of the melt and inwardly towards the arc. A DC powered coil surrounds the ladle horizontally at half the ladle's height or higher, around the upper portions of the melt. The field of this coil in cooperation with a DC flow in the melt caused by the current flow between the electrodes, provides a substantially tangential stirring force on the melt which is in addition to the stirring force of the electrode current in the melt.

Abstract: The electrical conductivity of solid, impregnable materials, such as cellulose-based insulating materials, can be increased by supplying to the solid impregnable material a substance with the ability, during polymerization of a pyrrole compound comprising at least one of the substances pyrrole and N-methylpyrrole, to give a polymer with higher electrical conductivity than the solid impregnable material, as well as a pyrrole compound of the kind stated, whereafter the pyrrole compound is transformed into a polymer in the solid, impregnable material.

Abstract: A grinding unit especially adapted for use for grinding with a robot and in automatic machines. The unit is designed with a grinding wheel on an axially displaceable shaft, which is urged in a direction towards a surface to be ground by a spring. The grinding pressure is determined by this spring and the position of the grinding wheel is determined by the level of the grinding surface. The mass of the parts which are displaced under the influence of the grinding pressure can be made small. Only the grinding wheel, the shaft and a member, which is directly connected to said shaft, are displaced. Therefore, the grinding pressure is influenced only to an insignificant extent when changing the orientation of the grinding unit.

Abstract: In a DC power transmission system the rectifier and inverter stations are controlled by transmitting a signal representative of the voltage of the AC network in the inverter station, to the rectifier station and/or measuring the voltage in the AC network of the rectifier station and comparing it with the DC voltage on the transmission line. When the measured AC voltage exceeds the measured DC voltage, this indicates that the AC voltage of the inverter station has been reduced to such an extent that the rectifier station may receive a signal to this effect at the same time as the voltage reduction has been measured in the inverter station.

Abstract: A device for detecting undesired, light-producing events in a protected installation, for example arcing of electrical apparatus or the outbreak of fire in a building, comprises a detector for receiving light produced directly or indirectly by the undesired event and directing at least part thereof into the field of view of fiber optic means which transmits at least part of the received light to a monitoring unit. The detector is in the form of material applied to an end of the fiber optic means situated at the protected installation, the detector material being in the form of at least one light-transmitting body with a large number of light-refracting surfaces within the same which refract received light and conduct at least part of the refracted light into the field of view of the fiber optic means.

Abstract: A method for controlling the lateral displacement of a trolley supporting goods to be unloaded at an unloading location, the goods being releasably attached to the trolley by an elongated flexible member. The method is characterized in that the trolley, which supports the goods, via the elongated flexible member during a first phase of the unloading operation, is decelerated from a certain lateral displacement speed at which it approaches the unloading station and, at least after part of the unloading operation of the goods, is accelerated in the opposite direction, whereby the retardation phase and the acceleration phase are invidually carried out within less than one period of the pendulum motion of the elongated flexible member. The method can be used in cases where the length of the flexible member varies during the approach of the goods to the unloading location.

Abstract: A two-pole overcurrent protection device comprises an integrated circuit with a thyristor having an emitter layer and base layer which, on the cathode side, is connected to the emitter layer on the cathode side by means of a normally non-conducting MOS transistor. The on-state voltage across the thyristor is supplied to the control electrode of the transistor via a Schottky diode, whereby, at a certain thyristor current, the thyristor is made conducting and short-circuits the cathode-emitter junction. The edge of the Schottky diode is arranged adjacent to the cathode base layer and at such a distance therefrom that the barrier layer at the center junction of the thyristor penetrates into the diode and limits the voltage on the control means of the MOS transistor to a harmless value.

Abstract: Compensation for external and internal pressure variations in hermetically closed load cells is achieved using three parallel diaphragms vacuum-tightly attached between a force-transmitting member and a surrounding housing. An internal diaphragm is located adjacent the transducer space, a preferably equally large external diaphragm is located adjacent the atmospheric pressure, and an intermediate diaphragm is located therebetween, the intermediate diaphragm being considerably larger than the other two diaphragms. The space between the external diaphragm and the intermediate diaphragm is connected to the transducer space and the space between the internal diaphragm and the intermediate diaphragm is connected to the atmospheric pressure.

Abstract: A torque transducer comprises a sleeve of magnetic material, which is attached concentrically and rigidly to an axle, and at least two stationary windings for excitation of the axle and two windings for sensing the torque transmitted by the axle, as well as a magnetic housing concentrically surrounding the windings. The sleeve is formed with two parallel, annular zones, which are provided with slits having a substantially regular pitch and making an angle of .+-.45.degree. with a generatrix of the envelope surface of the sleeve. The excitation windings are series-connected and generate a magnetic flux in the axle surface. The measuring windings are connected in opposition, whereby the measuring signal is approximately zero in case of zero torque in the axle. When the axle is subjected to a torque, the bars between the slits in the annular zones will be subjected to tensile stress and compressive stress, respectively, in the direction of the flux.

Abstract: A handling robot for a current-consuming appliance (e.g. a welding head) comprises a pivotal stand with a first arm which is rotatably journalled in the stand and a second arm which is rotatably journalled in the first arm. The second arm has a sleeve which is journalled in the first arm. In said sleeve, a portion with a holder for the appliance is rotatably journalled. From a transformer, the supply current for the appliance is conducted to a rotatable contact device and to two preferably concentric tubular electrical conductors through the rotatable portion. The tubular conductors are utilized as conduits for cooling water.

Abstract: An electrical contact device for transmitting heavy currents between relatively rotatable parts, for example between a fixed welding transformer and a rotatable unit which supports a spot welding gun. The contact device comprises a spaced-apart pair of annular, axially fixed, contact segments on one unit and, between these, an axially displaceable pair of annular contact disks on another unit. The disks are urged towards each other by springs and are thereby centered by a centering device to provide a well-defined clearance between each contact disk and the confronting contact segment, and the disks are pressed outwardly against the co-acting contact segments, to eliminate said clearances when current is to flow therebetween, by an annular operating device. The contact device has particular utility in robotics and prevents wear at the contacting surfaces on the appearance of relative rotation therebetween.

Abstract: Disclosed is a method for manufacturing an object of silicon nitride. In the method, a body preformed from silicon nitride is surrounded with a casing which is permeable to gas. Upon heating, the casing is transformed into a layer which is impermeable to a pressure medium which is used during isostatic pressing of the preformed body while a pressure outside the casing is maintained which is at least as high as the pressure of the gas which is present in the pores of the preformed product. After the casing has been made impermeable to the pressure medium and the preformed body has been enclosed therein, the isostatic pressing is carried out while the body is simultaneously sintered.