Method of hydrostatic extrusion

Claim 1

Method of hydrostatic extrusion in a press comprising a yoke, a die support carried by the yoke, a pressure chamber formed by a high pressure cylinder axially movable in a press stand, a Die insertable in the cylinder and a pressure-generating punch which can be pushed into the cylinder at the end remote from the die to generate a pressure necessary for the extrusion in a pressure medium enclosed in the pressure chamber and surrounding a billet to be pressed, a billet holder axially movable in the cylinder which divides the pressure chamber into first and second spaces and includes valve means which, at a certain pressure difference between the spaces, permit pressure medium to pass from the first space between the punch and billet holder to the second space between the billet holder and the die, and at least one pressure medium source connectable to the first space, which comprises: a. placing a billet and a die between the yoke of the press and the high pressure cylinder, opposite its opening; b. moving the cylinder over the billet; c. furnishing to the first space from the source pressure medium having a pressure less than the pressure at which the valve means permits pressure medium to flow past the billet holder to the second space, whereupon the billet holder presses the billet and die against the die support; d. pushing the cylinder all the way in over the billet and die so that the second space is closed, while keeping the pressure in the first space substantially constant; e. increasing the pressure of the pressure medium in the first space to a level above the pressure at which the pressure medium flows from the first space to the second space so that the second space is filled with pressure medium under higher pressure; f. moving the punch into the cylinder, whereby the pressure in the pressure chamber is increased to the level necessary for extrusion.