Metal founding – Process – Shaping a forming surface
Patent
1989-03-06
1990-07-10
Godici, Nicholas P.
Metal founding
Process
Shaping a forming surface
1641602, B22C 902, B22C 2102
Patent
active
049400711
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a device for fabricating foundry moulds from granular material and the method of implementation.
The fabrication of foundry moulds, in particular from siliceous sand by shaping a volume of sand is well known.
A gas-tight sheet such as a plastic film is placed on a form called a model, itself placed on a support allowing thermoforming of the plastic film by suction; above this is placed a frame called "chassis" equipped with air suction devices and filters designed to hold the sand; the volume thus determined is filled with granular material which can be compacted by vibration; above this is placed another plastic film, then, through the chassis, the air caught between the two plastic films in the chassis is drawn out which has the effect of causing cohesion of the grains.
The first half of the print is then made; the same process is used to make the second half and obtain a mould ready for casting. Once casting is completed and after solidification of the cast material, the vacuum is removed. The sand is recycled and the cycle is repeated.
French patent application 2 156 138 describing a device for obtaining molten metal casting moulds can be mentioned to illustrate such a method.
In this case, the chassis consists of two identical parts, one upper and one lower, each including air evacuation tubes connected to a manifold itself connected to a vacuum pump.
The tubes are distributed regularly so as to cover a large surface.
French patent application 2 307 596 concerns a foundry mould chassis in which is provided a means for introducing and recovering the granular material used. This means consists of a volume roughly shaped like a truncated cone, whose small base is provided with a flap through which can be inserted the filling tube. This flap is air-tight and remains closed while the chassis is being used. After moulding, the vacuum is unloaded, with the chassis overturned, the flap opens and allows the material to flow out by gravity.
Such methods and devices allow molding to proceed only at a slow rate since many operations are necessary.
Furthermore, casting is carried out with the mold made by assembling the two chassis, which immobilises two costly chassis to obtain a single mould. Also, it is necessary to perform the shaping operation twice to obtain the upper and lower parts of the mould, as only this double operation leads to obtaining a complete mould. Two separate plastic films are positioned vertically on two model plates which are themselves held vertically.
Mention can also be made of the methods described in German patents DE-A-2.305.229 (SINTOKOGIO) and DE-B-2.407.878 (WAGNER). The armature used in the first method is complex with its double internal wall and the two membranes surrounding it. As the air is drawn only through the lateral faces, the depression is not applied homogeneously to all the granular material, considering the leakage which occurs. The absence of armatures in the second method means that the suction, relatively localised on one or two sides of the block, is very heterogeneous and that handling of such blocks is very delicate.
The present invention concerns a method and device which remedy these drawbacks. The device uses a model plate support, a polymer envelope, an armature with air suction and filtering devices in a known way to retain the granular material which can be connected to a vacuum source. It is characterised by the fact that it includes at least two model plates placed in supports and that the armature has at most three faces.
The device is also remarkable in that the model plate supports are hinged to at least one lower closing plate with a device to supplement the clamping and in that the armature includes two faces interconnected by a device ensuring the rigidity of the assembly and at least part of the air suction and filtering.
The device provides for the use of a preformed envelope.
The process essentially consists of using two model plates to simultaneously make two prints for the same mold and, for this purpose, includ
Batten, Jr. J. Reed
Godici Nicholas P.
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