Method for producing a bellows with oval cross section and apparatus for carrying out the method

Claim 1

A method for producing a bellows with an oval cross section comprising the steps of bulging a metallic cylindrical tube to form a bellows with a circular cross section and ovalizing the bellows with the circular cross section to form the bellows with the oval cross section, said ovalizing step comprising an upsetting of the bellows with the circular cross section by using a pair of dies for applying upsetting forces to the circular bellows in a radial direction of the bellows, and applying hydraulic pressure inside of the circular bellows during said upsetting.

Claim 2

A method for producing a bellows with an oval cross section comprising the steps of bulging a metallic cylindrical tube to form a bellows with a circular cross section and ovalizing the bellows with the circular cross section to form the bellows with the oval cross section, said ovalizing step comprising an upsetting of the bellows with the circular cross section by using a pair of dies for applying upsetting forces to the circular bellows in a radial direction of the bellows, and applying hydraulic pressure inside of the circular bellows during said upsetting.

Claim 8

A method as claimed in claim I, wherein ovalizing is conducted by means of stretching dies which have a same external form as an internal form at ends on the major axis of the oval of the bellows with the oval cross section to be formed and provide corrugations capable of being fitted to ridges and grooves of the bellows with the circular cross section.

Claim 9

An apparatus for producing a bellows with an oval cross section which comprises a frame; a first supporting mechanism having a pair of first supporting parts, the first supporting mechanism being mounted on the frame in such a manner that the pair of first supporting parts are opposed to each other in a first direction and are capable of approaching each other and moving away from each other so as to be able to support both ends of a metallic tubular body in a liquid-tight manner; a second supporting mechanism having a pair of second supporting parts, the second supporting mechanism being mounted on the frame in such a manner that the pair of second supporting parts are capable of approaching each other and moving away from each other in a second direction orthogonal to the first direction; two sets of sectional dies supported by the second supporting parts so that the sectional dies can be brought into contact with opposed side walls of the metallic tube when the second supporting parts are moved so as to approach each other; a hydraulic pressure introducing means for introducing hydraulic pressure into the metallic tube through at least one of the first supporting parts to conduct bulging of the metallic cylindrical tube while both ends of the metallic cylindrical tube are supported by the first supporting parts in the liquid-tight manner and the opposed side walls of the metallic cylindrical tube are kept in contact with the two sets of sectional dies, the sectional dies in each set being kept away from each other in the first direction; and a third supporting mechanism having a pair of third supporting parts, the third supporting mechanism being mounted on the frame in such a manner that the pair of third supporting parts are capable of approaching each other and moving away from each other in the third direction orthogonal to the first and second directions and adapted to ensure that the cross-sectional shape of a bellow with circular shape formed by the bulging is changed into a bellows with an oval shape by deforming opposed side walls of the bellows when the third supporting parts are caused to approach each other, the third supporting parts of the third supporting mechanism having upsetting parts adapted to change the cross-sectional shape of the bellows from the circular shape into a oval shape by applying upsetting forces to the opposed side walls of the bellows when the third supporting parts are caused to approach each other; wherein the first supporting parts are operative to support both ends of the circular bellows in the liquid-tight manner during the upsetting by the upsetting parts and hydraulic pressure is applied to the inside of the circular bellows by means of the hydraulic pressure introducing mechanism during the upsetting.

Claim 10

An apparatus for producing a bellows with an oval cross section which comprises a frame; a first supporting mechanism having a pair of first supporting parts, the first supporting mechanism being mounted on the frame in such a manner that the pair of first supporting parts are opposed to each other in a first direction and are capable of approaching each other and moving away from each other so as to be able to support both ends of a metallic tubular body in a liquid-tight manner; a second supporting mechanism having a pair of second supporting parts, the second supporting mechanism being mounted on the frame in such a manner that the pair of second supporting parts are capable of approaching each other and moving away from each other in a second direction orthogonal to the first direction; two sets of sectional dies supported by the second supporting parts so that the sectional dies can be brought into contact with opposed side walls of the metallic tube when the second supporting parts are moved so as to approach each other; a hydraulic pressure introducing means for introducing hydraulic pressure into the metallic tube through at least one of the first supporting parts to conduct bulging of the metallic cylindrical tube while both ends of the metallic cylindrical tube are supported by the first supporting parts in the liquid-tight manner and the opposed side walls of the metallic cylindrical tube are kept in contact with the two sets of sectional dies, the sectional dies in each set being kept away from each other in the first direction; and a third supporting mechanism having a pair of third supporting parts, the third supporting mechanism being mounted on the frame in such a manner that the pair of third supporting parts are capable of approaching each other and moving away from each other in the third direction orthogonal to the first and second directions and adapted to ensure that the cross-sectional shape of a bellow with circular shape formed by the bulging is changed into a bellows with an oval shape by deforming opposed side walls of the bellows when the third supporting parts are caused to approach each other, the third supporting parts of the third supporting mechanism having upsetting parts adapted to change the cross-sectional shape of the bellows from the circular shape into a oval shape by applying upsetting forces to the opposed side walls of the bellows when the third supporting parts are caused to approach each other; wherein the first supporting parts are operative to support both ends of the circular bellows in the liquid-tight manner during the upsetting by the upsetting parts and hydraulic pressure is applied to the inside of the circular bellows by means of the hydraulic pressure introducing mechanism during the upsetting.