Method of centrifugally casting plural layered cylinders and forming longitudinally spaced annular reinforcements and helical reinforcements therein

Claim 2

A PROCESS FOR OBTAINING A HOLLOW CYCLINDRICAL BODY HAVING A SUPPORT STRUCTURE OF REINFORCED THERMOSETTING RESIN, USING A MOLD HAVING A HORIZONTAL AXIS AND KEPT ROTATING AT A SPEED WHICH CREATES A CENTRIFUGAL ACCELERATION GREATER THAN THE ACCELERATION DUE TO GRAVITY, SAID PROCESS COMPRISING THE FOLLOWING STAGES: A. SIMULTANEOUSLY FEEDING INTO SAID MOLD, AND WITH PROGRESSION IN THE AXIAL DIRECTION OF THE MOLD A RESIN AND A FIBROUS MATERIAL AND PARTICULATE FILLERS TO FORM AT LEAST A FIRST CYCLINDRICAL WALL COAXIAL WITH SAID MOLD AND WHICH WILL CONSTITUTE THE OUTER WALL OF A FINAL HOLLOW CYCLINDRICAL BODY; B. POLYMERIZING SAID RESIN IN THE ROTATING MOLD; C. FEEDING INTO SAID MOLD, AND WITH PROGESSION IN THE AXIAL DIRECTION OF THE MOLD, AN EXPANDABLE RESINOUS MATERIAL COMPATIBLE WITH THE RESIN OF SAID FIRST MOLD, AND BONDING SAME TO SAID FIRST WALL TO FORM A LAYER OF SUBSTANTIALLY CONSTANT THICKNESS; D. FORMING, IN SAID LAYER OF SUBSTANTIALLY CONSTANT THICKNESS, CIRCUMFERENTIAL GROOVES THROUGH SUBSTANTIALLY THE ENTIRE THICKNESS OF SAID LAYER, SO AS TO EXPOSE PORTIONS OF THE INNER SURFACE OF SAID FIRST WALL; E. GIVING SAID GROOVES A CROSS SECTION SUBSTANTIALLY OF ISOSCELES TRAPEZIUM FORM WITH ITS MAJOR BASE EMERGING AT THE INNER SURFACE OF SAID LAYER; F. UNIFORMLY FILLING SAID GROOVES WITH A FIBROUS MATERIAL, PARTICULATE FILLERS AND A THERMOSETTING RESIN COMPATIBLE WITH THE RESINS OF SAID FIRST WALL AND IN SAID LAYER OF IMPROVING ITS MECHANICAL PROPERTIES; G. FEEDING INTO SAID MOLD, AND PROGESSIVELY IN THE AXIAL DIRECTION OF SAID MOLD, A RESIN AND SIMULTANEOUSLY A FIBROUS MATERIAL AND PARTICULATE FILLERS TO FORM AT LEAST A SECOND CYCLINDRICAL WALL COAXIAL TO SAID MOLD, BONDED TO SAID LAYER AND BONDED TO SAID FIRST WALL BY THE RSIN, FIBROUS MATERIAL AND PARTICULATE FILLERS WHICH FILL SAID CIRCUMFERANTIAL GROOVES, SAID SECOND WALL CONSTITUTING AN INNER SUPPORTING WALL OF THE FINAL HOLLOW CYLINDRICAL BODY, AND, POLYMERIZING SAID RESIN IN SAID GROOVES, AND THE RESIN OF SAID SECOND WALL IN THE ROTATING MOLD; H. THEN HALTING SAID MOLD AND EXTRACTING THE HOLLOW CYLINDRICAL BODY SO OBTAINED.

Claim 3

A process as claimed in claim 1, in which said grooves are of continuous helical extension of a predetermined constant pitch.

Claim 4

A process as claimed in claim 1 in which in said layer of expanded material is formed a plurality of annular parallel grooves regularly spaced by a predetermined constant distance.

Claim 5

The process of claim 1 in which the walls of said grooves have rounded inner edge portions.

Claim 6

A process as claimed in claim 1, in which said first wall, which constitutes the outer wall of the hollow cylindrical body obtained, comprises reinforced thermosetting resin and said process further comprising forming a support layer, of resin and inert materials, for said first wall.

Claim 7

A process as claimed in claim 5 in which said first and second walls, which constitute the outer wall and inner wall of the hollow cylindrical body obtained, each comprise a reinforced thermosetting resin and said process further comprising forming support layers of resin and inert materials for said first and second walls, said support layers having a modulus of elasticity less than the modulus of elasticity of said reinforced thermosetting resin in each of said first and second walls.

Claim 8

A process for obtaining a hollow cylindrical body having a supporting structure of reinforced thermosetting resin, using a mold having a horizontal axis and kept rotating at a speed which creates a centrifugal acceleration greater than the acceleration due to gravity, said process comprising the following stages: a. feeding into said mold, and with progression in the axial direction of the mold, a reinforced thermosetting resin to form at least a first cylindrical wall coaxial with said mold and which will constitute the outer wall of a final hollow cylindrical body; b. polymerizing said resin in the rotating mold; c. feeding into said mold, and with progression in the axial direction of the mold, an expandible resinous material, and expanding same, said resinous material being compatible with the material of said first wall thereby binding said material to said first wall to form a layer of substantially constant thickness; d. forming, in said layer of substantially constant thickness, circumferential grooves through substantially the entire thickness of said layer, so as to expose of the inner surface of said first wall; e. giving said grooves a cross section substantially of isosceles trapezium form with its major base emerging at the inner surface of said layer; f. uniformly filling said grooves with a thermosetting resin compatible with the resin of said first wall and a fibrous material and particular fillers foR improving its mechanical properties; g. feeding into said mold, and progressively in the axial direction of said mold, a reinforced thermosetting resin compatible with the resin in said grooves and in said layer to form at least a second cylindrical wall coaxial to said mold, bonded to said layer and bonded to said first wall by the resin, fibrous material and particulate fillers which fill said circumferential grooves, said second wall constituting an inner supporting wall of the final hollow cylindrical body, and polymerizing the resin in said grooves and the resin forming said second wall in the rotating mold; h. halting said mold and extracting the hollow cylindrical body so obtained.

Claim 9

A process for obtaining a hollow cylindrical body having a supporting structure of reinforced thermosetting resin, using a mold having a horizontal axis and kept rotating at a speed which creates a centrifugal acceleration greater than the acceleration due to gravity, said process comprising the following stages: a. feeding into said mold, and with progression in the axial direction of the mold, a reinforced thermosetting resin to form at least a first cylindrical wall coaxial with said mold and which will constitute the outer wall of a final hollow cylindrical body; b. polymerizing said resin in the rotating mold; c. feeding into said mold, and with progression in the axial direction of the mold, an expandible resinous material, and expanding same, said resinous material being compatible with the material of said first wall thereby binding said material to said first wall to form a layer of substantially constant thickness; d. forming, in said layer of substantially constant thickness, circumferential grooves through substantially the entire thickness of said layer, so as to expose of the inner surface of said first wall; e. giving said grooves a cross section substantially of isosceles trapezium form with its major base emerging at the inner surface of said layer; f. uniformly filling said grooves with a thermosetting resin compatible with the resin of said first wall and a fibrous material and particular fillers foR improving its mechanical properties; g. feeding into said mold, and progressively in the axial direction of said mold, a reinforced thermosetting resin compatible with the resin in said grooves and in said layer to form at least a second cylindrical wall coaxial to said mold, bonded to said layer and bonded to said first wall by the resin, fibrous material and particulate fillers which fill said circumferential grooves, said second wall constituting an inner supporting wall of the final hollow cylindrical body, and polymerizing the resin in said grooves and the resin forming said second wall in the rotating mold; h. halting said mold and extracting the hollow cylindrical body so obtained.