Abstract: A casting apparatus for low-pressure or counterpressure casting of nonferrous metals comprises a casting mold which is fed with the melt by a siphon tube opening upwardly into the mold and communicating with an intermediate crucible for molten metal. The siphon tube has an elbow lying above the level of the molten metal in the intermediate crucible which is connected to a main crucible by a conduit whose inlet into the intermediate crucible can be blocked by a bell. Gas from an inert-gas supply can be applied under pressure to the crucible and the elbow.

Abstract: An improved technique of pulsed-arc welding is described for applying, to a consumable welding electrode, a DC welding current on which is superimposed a cyclic, high-amplitude pulse component. The pulse-generating circuit includes a capacitor chargeable during the existence of the arc, such capacitor having a normally disabled discharge path including a first thyristor. Such thyristor is energized at a rate of 200-1,000 Hz from a trigger generator, which in turn is energized during the existence of the arc. The discharge pulses from the capacitor are coupled to the welding electrode via a pulse transformer whose secondary winding is isolated from the DC source via a blocking diode. The pulse-generating circuit is so designed that the pulses have a duration in the range of 0.5 .times. 10.sup.-.sup.4 to 5 .times. 10.sup.-.sup.4 sec., a front edge steepness greater than 8 .times. 10.sup.6 amps/sec.

Abstract: A method of controlling the rate of filling of a casting mold wherein a pressure P.sub.1 is applied to a chamber containing a crucible holding the molten material to be cast, a pressure P.sub.2 is provided in a chamber containing the mold, the mold is connected with the crucible by a tube conveying the molten material to the mold, and the molten material is displaced through the tube by a pressure differential .DELTA.p equal to P.sub.1 -P.sub.2, which comprises detecting the time derivatives dP.sub.2 /dt and d.DELTA.P/dt of the pressure in the chamber containing the mold and the pressure differential, respectively. The rate of variation of the pressure in the chamber of the mold is monitored to regulate the process while one of the other derivatives is compared with a set point value to control one of the pressures as a function of time to vary the rate of filling of the mold in accordance with a predetermined program.

Abstract: A method of and apparatus for the molding of foamed thermoplastic bodies with integral skins wherein, for each mold operation after the first, a portion of previously foamed material produced by expansion in the mold cavity, is temporarily accumulated behind a body of unfoamed thermoplastic and the foamed and unfoamed material are then forced into the mold cavity and permitted to expand therein.