HIGH PRESSURE CONTAINERS FOR CYCLICALLY VARYING PRESSURES

1,201,464. Extruding. NATIONAL RESEARCH DEVELOPMENT CORP. 14 Aug., 1967 [15 Aug., 1966], No. 36455/66. Heading B3P. A high-pressure container 1, particularly for a hydrostatic extrusion apparatus, has an inner pressure chamber 2 and an outer chamber 6 which is subjected to fluid pressure less than but proportional to that in the chamber 2 for reducing the hoop stress in the cylinder wall. Hydrostatic pressure is produced in chamber 2 by a plunger 18 to extrude a billet 16 through die orifice 15 in an axially movable member 9 with differential upper and lower surface areas. The member encloses an annular fluid chamber L communicating through passages 19 with the outer chamber 6 which is surrounded by an outer cylinder 5. A further outer cylinder 20 may be used to define a further outer pressure chamber F. Seals S1-S8 are provided. In another embodiment, Fig. 2 (not shown), the inner cylinder (21) is itself axially movable within the outer cylinder. In another embodiment, Fig. 3, a continuous billet 44 is indirectly extruded through die 42 carried by the movable plunger 41. During extrusion the billet 44 is clamped by pairs of jaws 45 actuated by radial plungers 46 subjected to the fluid pressure in chamber L. The inner cylinder may be formed of ceramic/ metallic components and may include an electrical resistance heating element. Reference is made to the extrusion of alloy steel. A specific relationship is established for the fluid pressures in chambers 1, 6 and their diameters in order to eliminate hoop stress.