Claims
- 1. Apparatus for extruding an elongated member such as tubing and for enhancing extrusion initiation, said tubing having an O.D., an I.D. and a wall thickness, comprising:
- an annular extrusion die having a die surface defined by a forward truncated conical inner surface having a first predetermined included angle and a cylindrical rearward inner surface of constant diameter substantially equal to the tubing O.D.;
- a mandrel having a forward portion defined by a truncated conical outer surface having a second predetermined included angle smaller than said first predetermined angle, said mandrel truncated conical outer surface positioned opposite said forward truncated conical inner surface of said annular die to provide a die gap therebetween which decreases inwardly to enhance extrusion initiation, said mandrel provided with a centrally formed axial bore extending therethrough;
- a pilot rod residing in said axial bore for relative reciprocal sliding movement with respect to the mandrel, said pilot rod provided with a cylindrical outer surface of constant diameter substantially equal to said tubing I.D. and smaller than the constant diameter of the rearward surface of said annular extrusion die by an amount substantially equal to said tubing wall thickness;
- means for retracting the pilot rod from said extrusion die during extrusion start-up and for extending the pilot rod a predetermined distance into the rearward portion of said annular extrusion die during extrusion to extrude said tubing with said wall thickness.
- 2. Apparatus for providing a variable die gap for extruding an elongated member such as tubing, comprising:
- a mandrel having a forward portion defined by a truncated conical outer surface extending into the outer surface of a mandrel pilot rod, said conical outer surface having a first predetermined included angle;
- a composite annular extrusion die including an outer annular extrusion die having a passageway extending therethrough and an inner annular extrusion die mounted reciprocably in said passageway, said inner and outer annular extrusion dies each having a die surface defined by a truncated conical inner surface having a second predetermined included angle, said composite annular extrusion die positioned opposite and spaced from said forward portion of said mandrel and said variable die gap defined by the generally annular distance between the inner surfaces of said outer and inner annular extrusion dies and said outer surfaces of said mandrel and mandrel pilot rod;
- means for retracting said inner annular extrusion die a predetermined distance into said passageway to increase the size of said variable die gap and for extending said extrusion die a predetermined distance into said passageway to align the inner surfaces of said inner and outer annular extrusion dies.
- 3. Apparatus according to claim 2 wherein said first predetermined included angle and said second predetermined included angle are equal whereby upon said inner surface of said inner annular extrusion dies being aligned the width of said variable die gap is uniform.
- 4. Apparatus according to claim 2 wherein said second predetermined included angle is larger than said first predetermined included angle whereby upon said inner surface of said inner and outer annular extrusion dies being aligned the width of said variable die gap decreases inwardly.
- 5. Apparatus according to claim 2 wherein the outer surface of said mandrel pilot rod is cylindrical and wherein said inner annular extrusion die has a cylindrical passageway extending therethrough whereby upon said inner surfaces of said inner and annular extrusion dies being aligned said mandrel pilot rod extends into said cylindrical passageway to provide a portion of said variable die gap which portion is of uniform width.
- 6. Apparatus according to claim 2 wherein the outer surface of said mandrel pilot rod is a truncated conical surface and wherein said inner annular extrusion die has a cylindrical passageway extending therethrough whereby upon said inner surfaces of said inner and annular extrusion dies being aligned said mandrel pilot rod extends into said cylindrical passageway to provide a portion of said variable die gap which portion increases inwardly.
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of U.S. patent application Ser. No. 449,562, filed Dec. 13, 1982 in the name of Francis J. Fuchs, Jr. for METHODS AND APPARATUS FOR INITIATING TUBULAR EXTRUSION, now abandoned.
US Referenced Citations (6)
Foreign Referenced Citations (1)
Number |
Date |
Country |
406594 |
Nov 1973 |
SUX |
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
449562 |
Dec 1982 |
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