| 摘要 |
PCT No. PCT/GB96/00648 Sec. 371 Date Nov. 18, 1996 Sec. 102(e) Date Nov. 18, 1996 PCT Filed Mar. 15, 1996 PCT Pub. No. WO96/29162 PCT Pub. Date Sep. 26, 1996A die top assembly engaging with a rotating wheel (not shown) of a continuous extrusion apparatus includes a die top (22) formed with a part cylindrical face (34) coacting with the wheel cylindrical surface and is positioned in a shoe held in contact with the wheel. The die top (22), which is required to resist the very high extrusion pressure forces, is carried on a support block (30) and, at the face remote from the part cylindrical face (34), is formed with a recess (50) accommodating a die support ring (54) and spacer (52). Ports (28) registering with circumferential grooves in the rotating wheel extend from the part cylindrical face (34) to a semitoroidal channel (44) and extrudate supply chamber (46) extending around a central boss (80). A central mandrel die piece (72) is secured in position by means of a bolt (76) threaded into a blind bore (78) in the boss (80) and coacts with a cylindrical die (56) to form an extrusion orifice (86). By securing the die piece (72) by means of the bolt (76) threaded into the blind bore (78), the dimension radially of the die top (22) may be reduced to a minimum by virtue of avoidance of weakening penetrations other than the ports (28) in the portion of the die top (22) adjoining the rotating wheel. This has the benefit that the axial extent of the ports (28) may be reduced to a minimum, thereby reducing to a minimum the frictional losses imposed on feed material extruded through the ports, an important consideration particularly when extruding copper.
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