Patent ID: 6145185
Filing Date: 2000-11-14
Classification: B21J,B21K,B23P,F16L,Y10T

Abstract:
A method for forming a pipe (10) comprising the steps of:providing a tubular workpiece (10A) having an upper portion and a lower portion;providing a female die (25) having a lower portion defining a passage (254) for receiving said workpiece (10A), an upper portion defining a cavity (251) having a diameter greater than that of said workpiece (10A), a space defined between said upper portion of said workpiece (10A) and the wall of said cavity (251) when said workpiece (10A) is inserted into said female die (25), and a flange (252) formed between said cavity (251) and said passage (254);providing a male die (20) to move relative to said female die (25), said male die (20) including an upper portion defining a first channel (200), and a lower portion (21) defining a second channel (212) having a diameter smaller than that of said first channel (200), thereby forming a stop (204) between said first channel (200) and said second channel (212), said lower portion (21) of said male die (20) having an abutting edge (22), and a tapered portion (23) formed on the underside of said abutting edge (22);providing a retaining axle (24) which can be moved with said male die (20) to be inserted into said workpiece (10A), said retaining axle (24) received in said second channel (212) and including an enlarged head (241) received in said first channel (200) and retained by said stop (204);providing a biasing member (242) received in said first channel (200) and urged on said enlarged head (241);inserting said workpiece within said female die (25);moving said male die (20) relative to said female die (25) to contact said tapered portion (23) and said abutting edge (22) of said male die (20) against said workpiece (10A), said tapered portion (23) contacting said workpiece (10A) to form a tapered hole (12) in an inner wall of said upper portion of said workpiece (10a), and said abutting edge (22) contacting said workpiece (10A) to form an annular shoulder (11) on an outer wall of said upper portion of said workpiece (10A) by means of a cold forging operation;providing a fastener member (80) securely clamping said upper portion of said workpiece (10A), said fastener member (80) including a positioning base (81) having a first portion defining a first chamber (811) and a second portion having an inner wall (813) defining a second chamber (815) in communication with said first chamber (811), a cone-shaped clamping member (84) received in said second chamber (815) of said inner wall (813) of said positioning base (81) and including three separate abutting pieces (840) each having a first side facing said first channel (811) and a second side having a flared inner wall (842) formed with a plurality of spaced stepwise urging portions (841) for clamping said upper portion of said workpiece (10A), a returning rod (83) slidably received in said first chamber (811) and having a first end portion abutting said first side of each of said three abutting pieces (840), and a biasing member (82) received in said first chamber (811) and pressing between a second end portion of said returning rod (83) and said positioning base (81);moving said upper portion of said workpiece (10A) toward said fastener member (80) and securely clamping said upper portion of said workpiece (10A) in said fastener member (80);forming a plurality of teeth (13) on an outer wall of said lower portion of said workpiece (10A) by means of a turning-machining operation, thereby forming said pipe (10) which includes said tapered hole (12), said annular shoulder (11) and said teeth (13); andreinforcing said pipe (10) by means of carburizing treatment.