US2597896A - Casting core removal - Google Patents

Description

May 27, 1952 T. H. OSTER CASTING CORE REMOVAL Filed March 17, 1949 wil THOMAS H 0875? INVENTOR.

' ATTORNEYS Patented May 27.1952 2,597,896

UNITED. STATES PATENT OFFICE Thomas H; Oster, Romulus,- Mich., assignor to Ford Motor Company, Dearborn, Mich., a corporation of Michigan App licat i on ar h 17, 1949', Serial No. 81,990

This invention is concerned with foundry procedure and more specificallywith a rapid and economical method of removing cores from eastings. The removal of complex cores from castings has long been an expensive and time consuming foundry operation. The foundryman has been confronted with the fact that if cores were made sufliciently robust to be self supporting without resorting to the use of core wires or other bracing means, such cores remained suficiently strong after the casting was poured to resist ordinary core removal methods such as the shake out. This often necessitates the use of a relatively weak core material which is then supported by core wires; After the casting is poured the core material issufiicently weak to be readily shaken out, but the core wires must be removed by hand. i

Requirements other than strength may dictate the choice of a core material which will not readily shake out. For example Where very fine finishes or dimensional exactitude is required resort is often hadto sand plaster cores in which plaster is substituted for the usual drying oil or resin bonding materials. This type of-material has been particularly troublesome to remove from castings. To avoid such core removal difiiculties, the instant invention has been perfected.

This invention is probably best understood from a study of the appended drawing which depicts a cross section of one form of apparatus suitable for the'practice of said invention.

The invention contemplates the removal of cores from castings by exposing the castings to a steam ambient under high pressure and suddenly releasing this high pressure so that the steam pressure upon the casting drops almost instantaneously to atmospheric pressure. In most instances it is preferred to first soak the core carrying casting with water so that the interstices of the core material become filled with water. The casting should be completely cooled in any event before being subjected to the action of the steam.

When the relatively cold' casting is exposed to steam under high pressure and at high temperature this steam penetrates throughout the core material and heats the core material to the prevailing steam temperature. In this heating process, steam is condensed throughout the casting so that when the casting and core have become uniformly heated, the core contains very hot liquid water dispersed throughout its structure. This dispersed liquid water is of course in "5Claims. (Cl.13417) z I V Y equilibrium with steam at the prevailing temperatures. The soaking of the core and casting prior to the exposure to steam serves to increase the water content of the core after the core has become thoroughly heated and is in equilibrium with the steam ambient.

When the pressure of the steam surrounding the castings and core is suddenly reduced to atmospheric pressure, the water within the core tends to flash instantly to steam. This internal generation of steam serves to disintegrate the core material and to discharge it forcibly from the casting. I

The figure of the drawing illustrates a device which has been employed to clean castings in accordance with this invention. In the drawing It! indicates a heavy cylindrical steel shell adapted to withstand the heavy steam pressures employed. This shell may or may not be lagged as individual circumstances dictate. Steam is introduced into shell in through pipe II which is fitted with valve I2. Cover I3 is securely bolted to shell ID.

The lower end of shell I0 is in the form of a truncated cone and is closed by poppet valve l4. Poppet valve I4 is biased into the closed position by spring I5 and is opened by piston It which is operated by a fluid introduced through conduit I1. O-fltake I8 is provided to carry off waste steam and the dislodged core material when the pressure is released.

As typical of the working of the instant invention the following run is cited. The shell was loaded with castings designed for use in automotive torque convertors. The shell was first loaded with 2 reactor castings. On top of these reactors was placed a turbine castings which had been cut in two pieces on a plane coincident with the axis of the turbine. The cutting of the turbine was necessary inasmuch as its external diameter was greater than the interior diameter of the shell Hi. Each of these castings had been immersed in water for five minutes prior to being loaded in the shell. The pressure was raised by use of saturated steam to 500 pounds per square inch and held at that value for five minutes. The steam supply was then cut off and valve M was opened and the pressure almost instantly dropped to atmospheric. Thereafter the pressure-"was raised to 500 pounds per square inch and immediately released through four cycles. Upon inspection,-the gypsum sand core material was found to have been substantially completely removed despite the complex configuration of the castings. If a somewhat less thorough cleaning can be tolerated the entire cleaning operation can be performed in the initial explosion without resort to the subsequent pressure treatments.

The exact pressures and times employed must be adjusted to suit the requirements of the individual casting. Such pressures and times are in fluenced by the water content of the core, the composition of the core and the degree of cleaning desired. It is often expedient to use steam conditions only sufiiciently drastic to thoroughly break up the core without dislodging it from the casting. In such condition the core can readily be removed on a standard shake-out machine and the core material recovered for reuse.

It has been noticed in the development of this process that the more completelyicore material is confined, the easier it is to dislodge by steam treatment. Accordingly, it may be expedient. in certain cases to apply a temporary fixture to castings in which a large percentage of the core surface is exposed. Such a fixture should be a made to more completely enclose the core and facilitate its removal.

While steam is preierred as a working fluid because of its cheapness and ready availability, it is. to be understood that any other elastic fluid capable of filling the core interstices with the same or another expansible fluid under pressure can be substituted. The effectiveness. oi the action of any given steam pressure can be increased by exhausting the shell into a partial vacuum. Ordinary saturated steam will usually be employed. .However, under some circumstances it may be desirable to employ superheated steam. This has the effect of cooking and embrittling certain organic core binding materials such as drying oils, resins or cereals to expedite the destruction of the core. The upper limit of steam pressure is limited only by possible mechanical damage to, or chemical reaction with the castings. With a sharp explosion and exhaust into a sub-atmospheric, pressure good results can be obtained with quite low steam pressures.

Cold water may be injected into the. shell to increase the sharpness of the pressure drop when the shell is opened, or a less complicated overall mechanism may be employed if; the injection of water is relied upon. entirely to reduce .the.pressure by suddenly condensing the steam.

.For a detailed disclosure ofv many mechanisms suitable for this process, reference is made to the prolific. patent and general literature concerned with. cereal mining and wood disintegration I claim invention:

1. The method of removing cores fromcastings comprising enclosing the castings and cores in a substantially steam tight vessel, introducing steam into said vessel until the pressure within the vessel reaches a predetermined, superatmospheric value, maintaining this superatmospheric steam pressure until the castings and cores have been heated to the desired extent, suddenly reducing the steampressure upon the castings-to substantially atmospheric pressure, and repeatedly repressurizing and suddenly depressurizing the steam tight vessel until the'desired degree of disintegration and removal of the cores from the castings has been attained.

2. The method of. removing cores fromcastings comprising adding moisture to the cores, enclosing the castings containing the moistened cores in a substantially steam tight vessel, in-

sel with said steam While retaining the castings within the container.

The method of removing cores from eastings comprising enclosing the castings contain- .ing the cores iniasubstantially steam tight ves- SeLintroducingsteam into said vessel until the pressure within the vessel and upon the castings reaches a predetermined superatmospheric value at least sufficient to cause disintegration of the cores upon being decreased suddenly to substantially atmospheric value, causing thissuperatmospheric pressure within the vessel to suddenly decrease to substantially atmospheric pressure and permitting the. core material to escape from the vessel with said steam while retaining the castings within thecontainer.

'4. Themethod or removing. cores from eastings comprising enclosing the. castings containing the. cores in a substantially steam tight vessel, introducing steam into said vessel until the pressure within the vessel. and upon the castings reachesa predetermined superatmospheric value at least sufficient to cause disintegration of the .cores upon being decreased suddenly to substantially atmospheric value, causing this superatmospheric. pressure within the vessel to collapse suddenly and, permitting the core material to escape from the vessel with said steam while retaining the castings within. the container.

5. The method of removing .cores from castings comprising enclosing the castings and cores in .asubstantially steam tight vessel, in-

troducing. steaminto said vessel until the pressurev reaches .a predetermined, superatmospheric value atleast. sufficient to cause disintegration of the coresuponbeing.decreasedsuddenly to substantiallyv atmospheric value, maintaining this superatmospheric steam. pressure until. the castings and cores have been heated to the desired extent, causing thesteampressuretosuddenly collapse whereby thecores aredi'sintegrated and removed iromthe. castings.

' THOMAS H. .OS'IER.

' REFERENCES CITED The. following; references areof record in. the file of this patent:

- UNITED STATES PATENTS

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