Abstract: The structure comprises at least a first and a second element connected together in correspondence with respective flat walls by a connection unit consisting essentially of a screw and a pair of plates each of which comprises a bore in a central position and at least two parallel projections defining opposing bearing surfaces. One plate is mounted between the head of the screw and the flat wall of the first structural element, and the other plate rests on the flat wall of the second structural element and cooperates with the end of the shank of the screw in such a manner as to lock said walls tightly together. The plates are positioned such that the respective opposing projections define two parallel planes.

Abstract: The assembly comprises a frame, a pair of body sides, a front panel, a rear panel and a roof, and is characterized in that said parts are connected together by threaded connection means.

Abstract: The inner ring of a rolling bearing is mounted on one end of a rotary shaft where the shaft is of reduced diameter. The inner ring of the bearing bears on the larger diameter part of the shaft but projects beyond this part to define an annular space with the reduced diameter part of the shaft. A circular-sectioned ring of elastomeric material is located in this annular space. This ring is pressed into the annular space by a washer of smaller diameter than the internal diameter of the bearing, which is mounted on the end of the shaft and is locked against the ring by screw means engaging the end of the shaft.

Abstract: A Roots-type rotary volumetric compressor with two double-lobed rotors in which, for each of the four quadrants defined by the major and minor axes of the rotor, each rotor has a particular profile constituted by seven arcs of circles which extend from the point of intersection with the minor axis to the point of intersection with the major axis. The coordinates of the respective centers of curvature (C.sub.1 to C.sub.7) of the arcs in a frame of reference having its origin at the center of the rotor and its axes of the asbcissae (X) and ordinates (Y) coincident with the minor and major axes of the rotor, and the values of the respective radii of curvature (R.sub.1 to R.sub.7), are given. The arcs have respective angular extents (A.sub.1 to A.sub.7) of substantially 12.degree., 40.degree., 1.degree., 29.degree., 88.degree., 13.degree. and 6.degree..