Metal founding – Process – Shaping a forming surface
Patent
1991-03-29
1992-11-10
Batten, Jr., J. Reed
Metal founding
Process
Shaping a forming surface
164 38, 1641601, 164195, B22C 1524, B22C 1528
Patent
active
051616033
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to foundry practice and, more particularly, to a method for the production of single-use foundry molds, and an apparatus for realization thereof.
PRIOR ART
Known in the prior art is a method for the production of single-use foundry molds (US, A 4313486), comprising the delivery of the sand mixture by the stream of air into the molding chamber accommodating a pattern plate, in the direction parallel to the pattern plate. Concurrently with its delivery, said mixture is preliminarily compacted by the stream of compressed air in the direction perpendicular to the pattern plate. The molding chamber being filled, the mixture is compacted by pressing.
This method is realized in the known apparatus (U.S. Pat. No. 4,313,486), comprising a molding chamber formed by plates arranged in pairs, viz., upper and bottom plates, side plates, pattern plate and pressing plate, a compressed air source and a means for its delivery into the molding chamber. The pattern and pressing plates have cavities and channels for the passage of air through said cavities. The upper plate has a channel for the delivery of sand mixture into the molding chamber, said mixture being delivered by the air stream in the direction parallel to the pattern plate. Concurrently, the compressed air is delivered by the molding chamber air supply unit from the compressed air source into the pressing plate cavity wherefrom it flows through pressing plate channels into the molding chamber.
Due to a pressure differential, the air is removed into the atmosphere from the molding chamber through channels of the pattern, upper and bottom plates. As a result, the air streams created in the molding chamber flow both in the vertical and horizontal directions. The horizontal streams entrain the particles of sand mixture and carry them towards the pattern plate, filling the deep hollows in the patterns.
However, said horizontal streams of air directed towards the pattern plate, perpendicularly thereto, are created by only a part of compressed air delivered through the channels of the pressing plate, the pressure of this compressed air being equal to, or somewhat lower than, the pressure of the air which forces the sand mixture into the molding chamber so that the power of the horizontal air streams is insufficient for efficient filling of narrow and deep hollows in the patterns with sand mixture and for compacting said mixture therein.
Owing to the action of the created air streams on the sand mixture, the density of said mixture is distributed irregularly throughout the volume of the molding chamber: the mixture layers adjoining the pattern plate have a maximum density while near the pressing plate the mixture has a minimum density and this leads to creation of voids in the foundry mold opposite the air channels in the pressing plate because the compressed air jets discharged from the channels interfere with the filling of these mold zones with sand mixture.
Subsequent pressing of the sand mixture by moving the pressing plate towards the pattern plate compacts the sand mixture in the layers adjoining the pressing plate; however, complete elimination of irregular distribution of mixture density throughout the volume of the mold and voids in the compressed air supply zones proves impossible.
Besides, the produced mold is difficult to extract from the molding chamber without breaking the thin protruding parts of the mold, formed by narrow and deep hollows in the pattern since the pattern plate is fixed immovably and cannot move the mold out of the molding chamber.
Thus, the known method for the production of foundry molds and the apparatus for realization thereof fail to ensure making high-quality molds of a complex configuration.
There is another method for the production of single-use foundry molds (SU, A, 1060299), consisting in that the molding chamber incorporating a pattern plate is filled with sand mixture delivered by the air stream in the direction parallel to the pattern plate. Then, on expiration of time equal
REFERENCES:
patent: 3293703 (1966-12-01), Taccone
patent: 3880223 (1975-04-01), Gunnergaard
patent: 4313486 (1982-02-01), Kondo et al.
patent: 4620584 (1986-11-01), Witt
patent: 4750540 (1988-06-01), Boenisch
patent: 4791974 (1988-12-01), Larsen
Bekh Nikolai I.
Blagonravov Boris P.
Bobryakov Gennady I.
Chernyshev Nikolai K.
Garibian Garegin S.
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