Patent ID: 6397449
Filing Date: 2002-06-04
Classification: B21D,Y10T

Abstract:
A method of forming a tubular member comprising:(a) providing a die having therein a cavity having a cross section corresponding to a configuration of a desired final tubular member; (b) providing a tubular blank having thereon an end portion; (c) engaging the end portion of said tubular blank with a clamp member; (d) confining said tubular blank in said cavity; (e) sealing said blank by applying a sealing member to said end portion; (f) pressurizing the blank internally to cause it to define the shape of the cavity; and (g) releasing the pressure, removing the sealing member and withdrawing the blank from the die; wherein in said step of providing a die, said die comprises die sections moving through open, intermediate and closed positions, each die section having a die cavity portion and a mating surface portion, which die sections in the closed position have the mating surface portion of each section in mating engagement with the mating surface portion of each adjacent section on the die cavity portions defining said cavity, and said step of engaging said end portion of said tubular blank with said clamp member comprising placing the blank between the die sections in the open position, and partially closing the die sections to said intermediate position to engage said end portion by said clamp member and by a portion adjacent to a die section, and wherein said sealing member is inserted into said end portion after the end portion is engaged by the clamp member and before the blank is confined in the die by moving said die sections to the closed position; and wherein, in said step of providing a die, at least one die section has said clamp member connected thereon through a lost motion linkage, said clamp member defining with at least ore other die section a throat, said clamp member being biased toward said other die section and clamping said end portion of the blank on movement of the said one die section from the open to said intermediate position, and retracting relative to said one die section and remaining substantially stationary relative to said other die section on movement of said die section from the intermediate to the closed position.