Patent ID: 6029737
Filing Date: 2000-02-29
Classification: B22D

Abstract:
A hot chamber injection apparatus for corrosive alloys including a body which, when operating, is immersed in a molten alloy contained in a crucible, wherein the body forms a chamber above an injection cavity and includes an injection piston reciprocally sliding vertically therein, an upper portion of the chamber being in communication with the crucible through a plurality of first ducts, the cavity being in fluid communication with the crucible and with a mold via a plurality of second ducts and sealing/guiding means for the piston extending between the upper portion and the cavity, wherein the sealing/guiding means includes:first and second centering members mounted in the chamber, wherein the first centering member forms an upper surface of revolution and the second centering member forms a lower surface of revolution; anda bush having an outer diameter smaller than an inner diameter of the chamber, the bush being interposed between the first and second centering members so that the upper and lower surfaces of revolution maintain the bush coaxial with the chamber, the upper surface of revolution forming a pressure-tight sealing against an upper side of the bush and the first centering member forming a pressure-tight sealing against the sidewall of the chamber, wherein an outer lateral surface of the bush is in fluid communication with the injection cavity through a channel in the second centering member, the upper side of the bush being immersed in the crucible to a depth which, when measured from a lowest level reachable by a surface of the molten alloy, is greater than a maximum travel of the piston, and wherein an inner surface of the bush is a surface of revolution with a diameter slightly larger than an outer diameter of the piston.