The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Oct. 22, 1991
Filed:
Jul. 10, 1990
Michel Garat, Voiron, FR;
Aluminium Pechiney, Paris, FR;
Abstract
An improvement in the lost foam casting process in which a foam pattern of a part to be cast is immersed in a dry sand mold and the mold is filled with molten metal in order to burn the pattern. According to the improvement, after filling but before the solidified fraction of metal exceeds 40% by weight, an isostatic gas pressure which increases at a predetermined and substantially constant rate to a predetermined maximum value is applied to the mold and maintained at the maximum value until solidification occurs. The rate of increase of pressure is determined as a function of the granulometry of the sand and depth of immersion of the pattern, to cause due to a temporary lag in pressure transmittal through the sand, a rapid and temporary overpressure of the molten metal relative to the sand at the sand/metal interface. The overpressure reaches a maximum value of 0.001 to 0.030 MPa at the beginning of the pressure application and declines as the applied pressure further increases. The invention is especially useful in the production of cast aluminum alloy parts having an improved level of compactness and a surface which is free from blowholes and carbon inclusions.