US2563643A - Process for making cores - Google Patents

Description

g- 1951 J. P. DE RANEK PROCESS FOR MAKING CORES Fil'ed June 9, 1948 FIG. 2.

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II U ..K REr ON MA m. M H D| E S 0 .IV

Y B I A lllll ATTORNEYS.

Patented Aug. 7, 1951 s'rA'rEs PATENT OFFICE 2 Claims.-

This invention pertains to a process for making sand cores, such as are used in molding various metals in the usual foundry practice.

When sand cores are made by the blowing process, the core sand is projected into the core box on a blast ofair. As the air thus-entering the'box must be allowed to escape, various means for venting the box to permit such escape have been used. However, as the pressure in the box is usually above atmospheric pressure, and also possibly on account of uncontrolled currents of'a'ir in the box seeking exit, it has been found that often the sand does not pack tight at all points, and the formed cores have parts in which the sand is loose or excessively porous, or even'voids or'air pockets have formed.

One the objects'of this invention, therefore, is to provide a process for making such cores by which these diiiiculties may be overcome.

Another 'objeot is toprovide such a process whereby the excess air may be positively removed from the pores of the packed sand, so that tight packing is promoted during the forming of the core.

Further objects will" appear from the followingdescription, taken in connection with the accompanying drawings, in which will be set forth an illustrative embodiment of this invention. It -is understood, however, that this invention is susceptible of various embodiments, within the scope'of the appended claims, without departing from the principle or spirit of I this invention.

In accordance with the process of this invention, generally stated, the air in the core box in which the core is formed, is evacuated by suction means so that a negative pressure (below atmospheric pressure), is produced in the core box. The core sand is then fed into the box, through a suitable opening, on a current of air entering the box by such opening. The positive pressure by which the air and sand are carried into the box may be simply atmospheric pressure, or a higher pressure supplied by suitable air-compression means.

Apparatus suitable for carrying out the process of this invention is illustrated in the accompanying drawings, in which:

Figure l is a vertical sectional view of a core forming apparatus, embodying this invention, and adapted for carrying out the method thereof, and

Figures 2 and 3 are similar views, showing other embodiments of this invention.

Referringto the drawing, l designates a core box of any suitable type'whose interior is, of course, shaped to the shapeof the core to be formed. The boxl is provided with one or more air outlet passages 2, each having mounted therein a screen 3 adapted to prevent the pas sage of sand throughthe opening, while permitting the passage of air. The under-face '01 the bottom wall of the box I may be recessed as indicated at l to provide an' air-circulating passage. The box I rests on a supporting plate provided with one'or -more air openings'fi, communicating with a suction duct"! leading to the edge of the plate here it may be connected as by a pipe 8 to a suitable suction means represented by the 'suctio'npump 9.

Mounted on a suitable support, 'as'at 50, is a sand supply container [0, closed at the bottom by a blowplate Il, provided with one or more blowholes 12. The container [0 may be open at the top to atmospheric pressure. Under some conditions, however, it may be desirable to provide a positive pressure higher than atmospheric pressure. In such cases the top of the container may be closed, as 'bya plate 13, and its interior connected as by a conduit [4 with a source of pressure, represented by the pump l5. The box I and the plate 5 may be supported by the usual lifting table [6, which may be raised by pneumatic pressure to hold the box I against the blowplate l'l duringthe core rorming operation. In the embodiment shown, the table [6 slides on a support 5|, provided with a duct 52 communicating thereabove' and connected to a fluid pressurepipe 53.

In operation, the suction means/9 is operated to reduce the pressure in the core box I to below atmospheric pressure. The core sand from the container l0 feeds through the blowholes [2, being carried on a current of air forced through said holes by the positive pressure in the container [8, which may be at or above atmospheric pressure. The negative pressure produced in the box I by the means 9 is however maintained during the operation. The sand thus carried into the core box is deposited on the bottom and along the sides thereof, and builds up progressively until the core box is full. The sand enters the box I with a velocity depending on the pressure set up, so that its impact on the sand already placeo tends to pack it tightly. When the air-outlet openings have been covered by sand, the air, passing out at said openings, is drawn from the pores of the deposited sand. This removes all air which may tend to form voids, and the movement of air through the sand under negative pressure tends to draw the sand particles closer together, and thus pack it tighter.

In the embodiment of Figure 2, the air-outlet openings 20 provided with screens 3 are in the blowplate II, and communicate with one or more exhaust ducts 10, to which the suction pipes 8 are connected. In Figure 3, the airoutlet opening 22 is in the side wall of the box- I. It will be understood that the air outlets may be in the bottom, sides and top of the core box.

While the operation of the various embodiments is generally along the same principle, the following distinctions will be noted: I

In Figure 1, the air is evacuated from the core box at the bottom, so that while the sand-is fed into the core box its body builds up under atmos pheric pressure or super-atmospheric pressure, while the air is being evacuatedfrom the sand body as it 'buildsup in the bottom of the core box. In the embodiment shown inFigure 2, theair is again evacuated from the core box, and flows upwardly therein through the openings 20, while the sand again builds up in the core box. In this case again the air is not only evacuated fromthe core box itself, but from between the sand particles asthey build up. In the embodimentshown in Figure'3, the air is evacuated at the side of the core box, flowing from the interior to. the outlet; again, however, as the sand builds up in the .core box, the air is evacuated from the sand body. In all embodiments, therefore, the core box is not only evacuated so that pockets are avoidedat'corners and recesses in the core box, but the sand body itself is evacuated of air, sothat it can build up into a solid mass.

, It will be seen, therefore, that this invention provides a process and apparatus whereby sand cores may be made with assurance that they will be free from voids, of uniform texture, and tightly packed throughout. It will accordingly be seen that by the method and apparatus herein described and claimed, not only are pockets avoided, but the sand body itself is thoroughly evacuated ofair, sov that these particles will fit together without interference of porous spaces. By this method, therefore, the amount of binder which isreq'uiredwill be reduced to a minimum. However, the core is still sufliciently vented where such requirement is necessary in the making of castingsfrom ,the cores In the accompanying drawings, only so much oiiv theapparatus has been illustrated to facilitate disclosure of the fundamentals and principles of the process and apparatus embodying this invention. The usual supports may be provided; thus, as usual, the core box may be supported on a table [6 with a support 5|. As usual, moreover, the sand container or supply I0 is mounted on a support 50, so as to be positioned above the table. The core box can therefore, as usual, he placed on the table and brought up against the bottom of the container. The bottom and top of the core box may of course be suitably machined toirest firmly upon the table, in Figure 1 to make air-tight connections with the bottom of the sand container and with the plate 5; in Figure 2 to make air-tight connections between the blowplate I I and the core box and the sand container; and in Figure 3 'to make an air-tight connection with the bottom of the sand container.

Having thus described the invention, what is claimed and desired to besecured by Letters Patent is:

1. In the art of making cores of sand, the process comprising, feeding'core sand with attendant air under at-least atmospheric pressure into a core box provided with vents in order to deposit the sand in the box and simultaneously withdrawing air from the box through the vents by applying thereto a pressure below atmospheric pressure.

2. In the art of making cores of sand, the process comprising, blowing core sandwith air under at-1east atmospheric pressure into a core box provided with vents in order to deposit the sand in the box and simultaneously withdrawing air from the box through the vents by applying thereto a pressure below atmospheric pressure.

JOSEPH P. DE RANEK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS

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