| 摘要 |
1400874 Extruding; drawing WESTERN ELECTRIC CO Inc 17 Nov 1972 [17 Nov 1971] 53178/72 Heading B3P An apparatus for the continuous extrusion of an elongated workpiece 2 through a die 12, Fig. 10, comprises sets of segmented gripping jaws 4 which move in endless paths 6 and co-operate on the innermost part of their paths to feed the workpiece to the die and effect the extrusion. The workpiece 2 is coated with a shear transmitting medium such as beeswax or polyethylene wax in two chambers 82, 83, Fig. 4, before reaching the feeding jaws. A sizing die 73 is provided between the chambers and a wiper 79 removes dirt from the workpiece before coating and a wiper 71 determines the thickness of the coating. The coating acts as a lubricant for both the sizing die and the extrusion die and is progressively pressurized by the jaws to beyond the yield strength of the workpiece. The gripping jaws are moved in the feed direction by staggered pinions 5a-5d, 25a- 25d, Fig. 5, which engage teeth on the outside of the jaws. The pinions are housed in a gear block 14 provided with gears trains and fluid driven motors for the pinions, Fig. 3 (not shown). The gear block 14 has a bore 16 to guide the jaws aligned with the bore of a pressure cylinder 11 and the bore of a further gear block 15 downstream of the extrusion die. The gear block 15 also has pinions 27a-27d engaged with the jaws but these pinions drive fluid pumps so that the jaw feed is retarded by the pinions to keep the jaws closely adjacent. The pressure cylinder 11 is internally lined by a sleeve (34), Fig. 8 (not shown), and a segmented sleeve (38a)-(38d), Fig. 9 (not shown). The segments define bores 40 for electrical heaters and supports guiding bars (42) for the jaws. The jaws are urged inwards by fluid pressure to sets of chambers (52a)-(52d), behind the jaws to pressurize the shear transmitting medium. A set of pressure reducing valves (53a)-(53d), (54a)-(54d), (55a)-(55d), Fig. 8 (not shown), ensure that the pressure in the sets chambers behind the jaws is progressively greater in the workpiece feed direction. The jaws are guided in the curved and straight return paths 7, 8, Fig. 5, by segment cross-section passages in guide blocks, Figs. 6 and 7 (not shown). In operation the jaws 4 closely contact the entire perimetric surface of a length of shear transmitting medium coating on the workpiece 2. The feed of the jaws provide a motive force along the surface of the coating and thereby produce a shear force in the coating medium which is applied as viscous drag to propel the workpiece to the die. The viscous drag produces axial compressive stress in the workpiece. The coating medium cannot escape between the jaws and must pass through the extrusion die. The medium accumulates at the entrance of the die and produces normal compressive stress in the workpiece upstream of the die. The difference between the axial and normal stress is arranged to not exceed the yield strength of the workpiece which may be copper or aluminium. |
