Abstract: A screw rotor tooth profile which comprises a pair of male and female rotor tooth profiles engaging each other. The screw rotor tooth profile is configured such that at least one of the male and female rotor tooth profiles has a point of minimum pressure angle or an engaging tooth surface concurring with those of a theoretical tooth profile and is deviated from the theoretical tooth profile such that the amount of deviation increases as going from the point of minimum pressure angle or the engaging tooth surface toward the tooth top side and the tooth bottom side. The screw rotor tooth profile, even in case of the presence of machining and/or assembling errors in the profiles, are capable of assuring excellent mutual tooth engagement therebetween and almost not susceptible to that or those errors, that is, insensitive to manufacturing precision.

Abstract: In a heat transfer surface having cavity groups and restricted opening groups in an outer surface region, the cavity groups are composed of a plurality of rows of void strip members. The cavity strip members are arranged in parallel on a base member of the heat transfer surface and are laminated in one or more layers. Each strip member has a number of elongate cavities laterally arranged in parallel. The elongate cavities are closed at upper surfaces and have at both ends openings. The adjacent cavities in the same layer are communicated with each other by communicating portions each provided between the cavity strip members and by the openings. The restricted opening groups are formed on the upper surfaces of the communicating portions. The restricted opening groups render the communicating portions in one layer, the communicating portions in another layer and the outside to communicate with each another. The method of manufacturing such a heat transfer surface is also disclosed.

Abstract: Rotor tooth forms for a pair of screw rotors in the form of a female rotor and a male rotor, wherein the female rotor has a rotor tooth form including a flank of a surface of advance constituted by an arc and a second order curve, and a flank of a surface of retrocession constituted by a curve generated by an arc of a forward end portion of a lobe on the male rotor and an arc, and the male rotor has a rotor tooth form essentially formed by generating loci of the flank of the surface of advance of the female rotor and the flank of the surface of retrocession thereof.

Abstract: A screw compressor including a female rotor and a male rotor rotating while meshing with each other, with the rotor tooth form of one of the female and male rotors meshing with each other without any clearance therebetween in normal temperature condition being used as a basic tooth form for obtaining a rotor tooth form produced by deformation on account of thermal expansion during operation. The basic tooth form and the tooth form thus obtained are employed in the assembled compressor. The rotors with these teeth form, when brought together in meshing engagement, have a clearance at start-up which allows for their expansion. This clearance is maintained at a minimum during operation of the compressor.

Abstract: In a screw rotor including a female rotor member and a male rotor member rotatable about parallel shafts and respectively while meshing with each other, the forward face flank of the female rotor member is composed of a first flank of the forward face formed by a parabolic curve, and a second flank of the forward face formed by a circular arc of a radius R.sub.2, and the backward face flank of the female rotor member is composed of a first flank of the backward face generated by the backward face tooth top flank of the male rotor member having a radius R.sub.5, and a second flank of the backward face formed by a circular arc of a radius R.sub.3 which is smaller than the radius R.sub.2 of the second flank of the forward face flank. The tooth profile of the male rotor member is essentially formed by the forward face flank and the backward face flank of the female rotor member.

Abstract: An oil-cooled type screw rotor assembly having a female rotor and a male rotor adapted to rotate around parallel axes in meshing relation to each other. The leading side flank of the female rotor is constituted by a first leading side flank formed by an arc of a radius R.sub.1 and a second leading side flank formed by an arc of a radius R.sub.2. Also, the trailing side flank of the female rotor is constituted by a first trailing side flank formed by an arc of the tooth ends of the male rotor having a radius R.sub.5 and a second trailing side flank formed by an arc of a radius R.sub.3 which is smaller than the radius R.sub.2 of the second leading side flank. The configuration of the teeth of the male rotor is materially formed by arcs of the leading and trailing side flanks of the female rotor.