Abstract: An oil-free scroll compressor used for compression of air or the like, comprises an orbiting scroll having a spiral-shaped lap or laps formed on one or both sides of an end plate, and a stationary scroll having a lap or laps adapted to mate with the orbiting scroll to define a compression chamber or chambers.Grooves are formed on tips of the respective scroll laps, and elastic tip seals are fitted into the grooves in order to prevent leakage of compressed gas from between the laps and the end plates. Those surfaces of the orbiting scroll and of the stationary scroll or scrolls, which define the compression chamber or chambers, are subjected to surface treatment in order to prevent seizure or the like caused by sliding of the tip seals and the laps. The stationary scroll or scrolls are subjected to an anodizing coating treatment while the orbiting scroll is subjected to Ni--P--B treatment.

Abstract: A method of producing an oil-free screw compressor has the following steps: preparing a semi-finished metallic female rotor which has a spiral profile, and a semi-finished metallic male rotor which has a spiral profile; forming a metallic coating film containing particles of grinding material on the surface of the semi-finished female rotor; forming, on the surface of the semi-finished male rotor, a coating film of a material softer than the metallic coating film on the female rotor; grinding the surfaces of the semi-finished rotors into predetermined configurations; mounting the ground rotors on bearings so that the rotors are assembled in a rotor casing with a substantially constant spacing held between the axes of the semi-finished rotors; mounting timing gears on the rotors so as to drivingly connect the rotors each other; and driving the rotors by driving means while restraining the back lash in the rotating direction by means of the timing gears and applying a compression load to the rotors so that the

Abstract: A screw-type rotary fluid machine such as a compressor or a vacuum pump has male and female rotors which rotate within a casing, with or without mutual contact. At least one of the male and female rotors being surface-treated to have a treated surface structure. The treated surface structure is a multi-layered structures composed of a plurality of layers including a non-electrolytic Ni plating layer and at least one covering layer of organic resin. The organic resin may be one or more kinds selected from a group of engineering plastics, so as to improve mechanical strength.

Abstract: A method treating a surface of rotors in a screw-type rotary fluid machine, with the method comprising the steps of: conducting a non-electrolytic Ni plating on the surface of each rotor so as to form a first layer of non-electrolytic Ni plating layer; heating the rotor having the first layer at a temperature not lower than 500.degree. C.; and forming, at least, a second layer of an organic resin so as to cover the first layer.

Abstract: A mixture of ceramic particles (such as SiC particles) with metallic powder (such as iron-base particles, e.g., stainless steel particles) is placed in a predetermined position of an internal wall of a mold and a molten metal (e.g., molten iron-base metal, particularly molten cast iron) is poured into the mold. In this manner a wear-resistant layer is formed in a necessary portion on a surface of the casting at the same time when casting is conducted.

Abstract: A magnet pump has a magnet coupling for magnetically coupling an inner ring yoke and an outer ring yoke so as to magnetically transmit a torque from driving part to driven part of the pump to rotate the driven part. The magnet pump comprises magnetized magnet pieces bonded to the outer peripheral surface of the inner ring yoke and magnetized magnet pieces bonded to the inner peripheral surface of the outer ring yoke; non-magnetic cylindrical covers covering the surface of the inner ring yoke carrying the magnet pieces and the surface of the outer ring yoke carrying the magnet pieces, respectively; and mold resin parts filling the gap between the surface of the inner ring yoke and the associated non-magnetic cylindrical cover and the gap between the surface of the outer yoke ring and the associated non-magnetic cylindrical cover.

Abstract: In a method for forming a cast article by slip casting through casting of a slip of powders of ceramics, etc. as disporsed in a solvent such as water, etc. into a solvent-absorbable, porous casting mold of gypsum, etc., the casting mold as made is heated to considerably lower the strength of the casting mold in a shape-maintainable range, the slip is cast into the cavity of the casting mold and after solidification of the slip into a green body the casting mold is removed to obtain a defect-free green body. The casting mold can be removed with much ease.

Abstract: In a casting method comprising casting a slip containing water or an organic solvent as the medium into a mold and removing the mold after solidification of the slip, use of a mold formed with an organic binder soluble in the medium of the slip allows the slip to quickly solidify and afford a green body due to absorption of the medium in the slip by the mold. In this case, the mold softens with loss of the binding power thereof simultaneously with the absorption of the medium. Therefore, no cracks appear at all in the green body, and removal of the mold is very easy.

Abstract: A cast article having a complicated shape of the appearance and the hollow can be obtained by forming a coating film on the surface of a pattern from a solvent-insoluble material to prepare a mold pattern, filling and hardening a molding material around the mold pattern, dissolving the pattern with a solvent, and removing the residue of dissolution and the coating film outside the mold.

Abstract: A mold forming method in which a pattern is made of an organic material such as foamed polystyrene and at least a portion of the outer or inner surface of the mold pattern is covered by a thin coating, and surrounded with a mold material. The pattern is then dissolved by a solvent, leaving the coating undissolved. The coating is finally removed by a solvent contained in a slip which is poured into the cavity provided with the coating.

Abstract: In a forming method and a mold wherein a slip is cast into the mold and wherein the mold is removed after hardening of the slip, the mold is patterned by the use of a water-soluble binder. The mold absorbs a water content in the slip to soften and to become easy of removal, while the slip has the water content absorbed to harden promptly. Therefore, the forming method and the mold are especially suited to produce a cast article of complicated shape.

Abstract: A slip casting mold consisting essentially of a gypsum mold, which contains a water-insoluble organic material, more particularly, a water-insoluble vegetable material such as cellulose, or which further contains glue in addition to the water-insoluble organic material. Since the strength of the casting mold is reduced markedly by heating, a cast article requiring a core (or master mold) having complex shape can be obtained extremely easily.

Abstract: A method of producing a heat exchanger in which a fin block of porous metal and fin plates connected to the fin block are unitarily secured to a serpentine heat-transmitting pipe. A plurality of fin molds produced with the use of plastic patterns formed therein with continuous, three-dimensional cavities are assembled with the heat-transmitting pipe shaped beforehand into a serpentine form in such a manner that the fin molds enclose the heat-transmitting pipe with suitable spacing intervals defined between the fin molds themselves and between the fin molds and the heat-transmitting pipe. Molten metal of high thermal conductivity is cast into continuous cavities in the fin molds and into the spacing intervals, and the material of the fin molds is removed after the molten metal has solidified.

Abstract: A three-dimensional network porous metallic structure is formed by filling the internal cavity of a mold, which has been prepared by making use of a three-dimensional network resin pattern, through driving the molten metal into the cavity by a pressure or through sucking the molten metal into the cavity by reducing the pressure in the cavity. The porous metallic structure thus obtained is characterized by a large specific surface area, as well as a reduced pressure drop of fluid passing through this structure, and, therefore, is fit for various uses such as the material of fins of heat exchangers, various filters and so forth.