Abstract: An exhaust manifold in which a plurality of branch tubes at an inlet side are connected to a collecting tube at an outlet side, and in which the fluid flows from the branch tubes to the collecting tube, wherein a volumetric chamber is provided between at least a pair of the branch tubes in communication with the branch tubes, with the volumetric chamber being gradually increased in its cross-sectional area in a fluid flowing direction. An exhaust manifold formed of upper and lower members comprises a branch tube having a bend. The upper lower members are interconnected by joining flanges having a broader width in the vicinity of the bend than other joining flange portions.

Abstract: A method of applying a synthetic resin layer to an outer surface of a metal part, comprising heating the metal part to a temperature higher than a melting point of a synthetic resin, embedding the heated metal part within a powdered mass of the synthetic resin, thereby melting a portion of the powdered mass surrounding the outer surface of the heated melt part, holding the heated metal part within the powdered mass for a time period sufficient to permit the molten portion of the powdered mass to be coated on the outer surface of the heated metal part as the synthetic resin layer, removing the metal part coated with the synthetic resin layer from the powdered mass, and maintaining the removed metal part at a temperature higher than the melting point and lower than a thermal decomposition point of the synthetic resin, to hold the deposited resin layer in a molten state for a suitable length of time, in order to allow the escape of possibly entrapped air from the resin layer.

Abstract: A broaching method for finishing an outer peripheral surface of a resin layer of a resin-coated lobe-type rotor for a rotary fluid machine of a Roots type, which includes the steps of forming, with a leading grooving cutter, at least one chip-breaker groove in the outer peripheral surface of the resin layer, such that the chip-breaker groove extends in a broaching direction parallel to an axis of rotation of the rotor. The method further includes the steps of finishing at least a portion of the outer peripheral surface of the resin layer with a trailing finish cutter having a cutting edge contour corresponding to the portion of the outer peripheral surface of the resin layer, which is finished by the finish cutter after the chip-breaker groove is formed therein by the grooving cutter. A composite broach or formed broach having the grooving and finish cutters is fed such that the grooving cutter leads the finish cutter in the broaching direction.

Abstract: A method of applying a synthetic resin layer to an outer surface of a metal part while the metal part is positioned within a powdered mass of a thermally fusible synthetic resin. The metal part within the powdered mass is induction-heated to a temperature between a melting point and a thermal decomposition point of the synthetic resin, to melt a portion of the powdered mass surrounding the outer surface of the heated metal part, and to deposit the molten portion of the powdered mass on the outer surface of the heated metal part, as the synthetic resin. The metal part is pushed down by a predetermined distance within the powdered mass, at least once at a point of time after the metal part has been positioned in the powdered mass, and before the induction-heating step has been completed.

Abstract: A method and apparatus for applying a synthetic resin layer to an outer surface of a metal part while the metal part is placed within a powdered mass of a thermally fusible synthetic resin. The metal part within the powdered mass is induction-heated to a temperature higher than a melting point and lower than a thermal decomposition point of the synthetic resin, in order to melt a portion of the powdered mass surrounding the heated metal part, and thereby permit the molten portion of the powdered mass to be deposited as the synthetic resin layer on the outer surface of the heated metal part. To facilitate the placement of the metal part in the powdered mass, air may be blown into the powdered mass to keep the mass in a fluid state.

Abstract: A Roots type pump comprising a pair of mating lobed rotors which are supported by rotor shafts, respectively. Each rotor is fixed to the corresponding rotor shaft by a pin forcibly inserted in a through hole provided through the rotor and rotor shaft. The outer surface of each rotor is surrounded by a coating layer of plastic material, at which the through hole has end openings having cross sectional dimensions greater than that of the substantial part of the through hole.

Abstract: A Roots pump having a plurality of rotor assemblies each including a light-alloy rotor, a steel shaft press-fitted in a bore of the rotor and a lock pin which is inserted through the rotor and the shaft to prevent removal of the shaft from the rotor. The lock pin is located substantially at an axial center of a press-fitted portion of the shaft accommodated the axial bore. The shaft has a timing gear at one end thereof for meshing with a timing gear of the shaft of the adjacent rotor assembly. The shaft further has a plurality of engagement teeth provided at one of opposite ends of the press-fitted portion on the side of the timing gear. The engagement teeth are at least partially embedded in an inner surface defining the axial bore of the rotor, upon press-fitting of the press-fitted portion in the axis bore, to thereby prevent a rotational movement of the shaft relative to the rotor.

Abstract: A Roots-type rotary fluid machine having resin-coated rotors fluid-tightly accomodated in a chamber formed in a housing structure which consists of a generally cup-shaped main housing body having a bore closed at its one end and open the other end, and a covering member which closes the open end of the bore in the housing body. The housing body includes a fillet portion which bridges an inner flat surface defining the bottom of the bore and facing one end face of each rotor, and an inner peripheral surface defining the periphery of the bore and facing the outer peripheral surface of each rotor. The fillet portion is formed along a line of intersection of extensions of the inner flat surface and the inner peripheral surface of the housing body, and inwardly into the bore from this line of intersection. The fillet portion has a generally triangular shape in cross section taken in a direction perpendicular to the above line of intersection.

Abstract: A broaching method for finishing an outer peripheral surface of a resin layer of a resin-coated lobe-type rotor for a rotary fluid machine of a Roots type, which includes the steps of forming, with a leading grooving cutter, at least one chip-breaker groove in the outer peripheral surface of the resin layer, such that the chip-breaker groove extends in a broaching direction parallel to an axis of rotation of the rotor. The method further includes the steps of finishing at least a portion of the outer peripheral surface of the resin layer with a trailing finish cutter having a cutting edge contour corresponding to the portion of the outer peripheral surface of the resin layer, which is finished by the finish cutter after the chip-breaker groove is formed therein by the grooving cutter. A composite broach or formed broach having the grooving and finish cutters is fed such that the grooving cutter leads the finish cutter in the broaching direction.