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:
Jun. 04, 1991
Filed:
Oct. 24, 1989
Norbert Damm, Karlsdorf-Neuthard, DE;
Thomas Parr, Karlsruhe, DE;
BMD Badische Maschinenfabrik Durlach GmbH, Karlsruhe, DE;
Abstract
To improve the accuracy of making a casting pattern from a casting model or mold (2, 2') in a molding material (M) retained in a foundry form, a single pressure pulse (P) is applied to the molding material which, however, has two phases of pressure gradient, namely a first or initial phase (1) of low pressure gradient extending up to about 1 to 3 bar during between about 10-100 m/sec, for example about 50 m/sec, to initiate fluidization of the molding material. The then fluidized and still fluidized molding material is compacted by raising the pressure from the initial low pressure pulse abruptly at a second and much higher pressure gradient to the customary compaction pressure of between 3 to 6 bar. The two-phase pressure pulse can be applied, selectively, only in a region above the model or throughout the entire mold. The pressure pulse can be generated by applying the pulse but controlling a gas admission valve (11) for an initial slow valve-opening movement, for example by throttling hydraulic counterpressure (35, 36), and then permitting rapid opening movement of the valve (11) by inhibiting the throttling; or (FIG. 4) by applying the full pressure pulse from the valve and interposing a throttle (41) in the path of the air flow from a compressed air chamber (5) to the mold box (3, 4), for example by a relatively shiftable apertured plate operable above a similarly apertured counter plate for selective alignment and misalignment of the respective apertures.