Abstract: An apparatus for the manufacture, by the hydroforming process, of expansion bellows for pipelines or the like, the apparatus being of the type comprising, for contracting longitudinally a sleeve to be formed, an actuating chamber of annular configuration defined by a rigid sleeve associated with the sleeve to be formed, a cylindrical skirt, and two sealing rings, one of which constitutes one of the supports for the sleeve to be formed. The apparatus is characterized in that the annular chamber is arranged, not outside, but inside the rigid sleeve, in such a manner that the hydroforming circuit is completely separate from the actuating circuit.

Abstract: The manufacture of hydroforming of a deformable expansion bellows. A deformable sleeve is held on a support with an inner sleeve supported inside it to define a space into which is injected liquid under pressure. An axial force is applied to the sheath with the space pressurized to produce corrugation of the sheath so as to form a bellows.

Abstract: Large diameter expanding bellows is described for pipe systems produced by the invention from portable apparatus combining fixed and slidable rings, the former connected to an end of and the latter sealably mounted on a sleeve and a skirt slideable into sealing relationship with the former and connected to the slideable ring, pressure fluid admission means communicating with the annular space between the rings and an outlet for regulation of liquid flow therefrom; a sleeve 1 may be strengthened by a core 3 of cement and fitted with a dismountable ring 4 co-operative with a displaceable ring 6 connected to an upper skirt 8 defining a chamber in communication with a pump 15 for introducing fluid in hydroforming to lower fixed ring 4.