Abstract: Fluorine content of tantalum and niobium hydroxides is reduced to under 0.5 weight % by washing such hydroxide precipitates (as obtained by HF digestion and solvent extraction) with dilute ammonia (1 to 10%) and then water in two washing stages. The first washing stage includes a partial neutralization and the used wash water of the second stage is advantageously recycled, after adjustment of its ammonia concentration, for use as the first stage washing liquid.

Abstract: Process for the preparation of 1,4-butanediol or tetrahydrofuran or both by the catalytic hydrogenation of maleic anhydride, succinic anhydride, maleic acid, succinic acid, fumaric acid, or the alkyl esters of these acids at temperatures of from 100.degree. C. to 350.degree. C. and pressures of from 50 bar to 350 bar over a catalyst containing cobalt as the active metal and one or both of the elements copper and phosphorus, if necessary in the presence of an aliphatic alcohol.

Abstract: A non-contacting sealing arrangement for sealing two counter-rotating shafts with the aid of a housing having a tire-casing-like shape which surrounds at least one centrifugal disk connected for rotation in unison with one rotatable shaft and laterally surrounded by the casing-like part with a narrow gap; the casing-like part is arranged eccentrically to the axis of the shaft on which the centrifugal disk is mounted in order to thus assure a return feed for the liquid sealing medium, such as oil, to bearing places. The invention enables alternate pressure loads and is particularly suited in applications between at least two bearing chambers of aircraft propulsion units.

Abstract: A non-contacting seal between a rotating part to be sealed and a stationary part, in which the rotating part includes a coaxial disk which is surrounded by a stationary collecting channel axially closely adjoining the disk but without contacting it. The collecting channel forms a spirally shaped hollow space in the circumferential direction of the rotating part, with a sealing medium return line connected to the hollow space within the area of enlargement of the hollow space. A seal, however, may also be installed between the rotating part and the fixed part.

Abstract: A method of manufacturing a tube bend of a metal comprises positioning a base ring in the range of the welding device, using the welding device to deposit a first section of metal on the ring, moving the ring and the welding device through an arc relatively to each other by substantially the thickness of the first section of metal and thereafter depositing a subsequent section over the first section and repeating the moving and the depositing until the desired section thickness is formed into a wall. The device includes means for mounting a plate for pivotal movement and a base ring mounted on the plate for movement therewith below a welding device arranged so that the welding device and the plate remove relatively through an arcuate path so that a series of sections of metal may be built up into a tube bend wall. The welding device advantageously includes an electrode feeder and the apparatus preferably includes a welding device to provide a plating along the side of the wall section which is built up.

Abstract: A control arrangement for a static converter of the type which supplies a DC machine. A pilot signal is produced, the pilot signal being responsive to the actual speed value and the desired current value of the DC machine. The pilot signal is then combined with a control signal of the converter so as to improve the dynamic characteristic of the control arrangement.

Abstract: A device for feeding welding wire in a submerged arc welding operation in which there is a narrow gap between workpieces which are to be welded together comprises a guide support having a plurality of spaced apart welding wire straightening roller assemblies mounted thereon which are in a position at selected angles relative to each other around and in engagement with the welding wire and which define a feed guide path for the passage of the welding wire between the rollers of each assembly. A welding head is pivotally mounted on a support for pivotal movement transverse to the welding direction and the head includes a welding guide and a carrying guide which together define tongs of the head which are mounted on the support for pivotal movement toward and away from each other. Tongs carry a plurality of guide shoes which define a continuing guide path for the welding wire received from the welding wire feed guide and deliver it to the welding zone between the workpieces.