US3581802A

US3581802A - Method for making castings

Info

Publication number: US3581802A
Application number: US795570*A
Authority: US
Inventors: Erich Krzyzanowski
Original assignee: Gruenzweig und Hartmann AG
Current assignee: Saint Gobain Isover G+H AG
Priority date: 1968-02-03
Filing date: 1969-01-31
Publication date: 1971-06-01
Anticipated expiration: 1988-06-01
Also published as: GB1254592A; SE343493B; DK124460B; CH502861A; FR2001291A1

Abstract

A method and apparatus for making castings. A body of granular material is confined in a container and a stream of gaseous fluid is introduced into the bottom of the container to impart to the granular material a state at least approaching fluidization. Into the thus agitated granular material a form is introduced consisting of a material which is subject to consumption on contact with a molten metal. Admission of gaseous fluid is terminated to permit settling and compacting of the granular material about the form. Molten metal is introduced into the form to assume the configuration of the same while simultaneously consuming the form. Gaseous fluid is then again admitted into the container to agitate the granular material for facilitating removal of the finished casting therefrom.

Description

United States Patent Inventor Appl. No.

Filed Patented Assignee Priority METHOD FOR MAKING CASTINGS 7 Claims, 1 Drawing Fig.

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References Cited UNITED STATES PATENTS 2,660,770 12/1953 Davis Primary Examiner.l. Spencer Overholser Assistant Examiner-V. K. Rising Attorney-Michael S. Striker ABSTRACT: A method and apparatus for making castings. A body of granular material is confined in a container and a stream of gaseous fluid is introduced into the bottom of the container to impart to the granular material a state at least approaching fluidization. Into the thus agitated granular material a form is introduced consisting of a material which is subject to consumption on contact with a molten metal. Admission of gaseous fluid is terminated to permit settling and compacting of the granular material about the form. Molten metal is introduced into the form to assume the configuration of the same while simultaneously consuming the form. Gaseous fluid is then again admitted into the container to agitate the granular material for facilitating removal of the finished casting therefrom.

PATENTED JUN I an v INVENTOR sum KRZYIMMMI 14'! 1 ATTORNEY METHOD FOR MAKING CASTINGS BACKGROUND OF THE INVENTION The present invention relates generally to casting of materials, and more particularly to a method of making castings. The invention so relates to an apparatus for carrying out the method.

This invention is particularly concerned with the type of casting method wherein a casting mold or casting form is used consisting of a material which will be consumed by contact with the molten metal. Such casting forms may be made of relatively inexpensive material and/or of material which is quite thin and therefore not in itself very resistant, because they are embedded in sand or other granular material and thereby reinforced. To obtain exact replicas, that is articles which have exactly the configuration and dimensions dictated by the form, it is necessary that the granular material in which the latter is embedded be compacted rather solidly about the form or to provide the granular material with binders of known type so as to prevent breakout of the molten material beyond the outline of the form when the latter is consumed.

It has been generally preferred to use binders because mechanical compacting of the granular material by shaking, pounding or the like, can easily lead to damaging of the form which, as mentioned before, consists of material which is not very resistant to mechanical stresses.

The approaches which are known in this field have suffered from various disadvantages, among these the fact that they have not been found suitable for mass production. While it is possible to economically produce the individual forms, it has never been economically feasible to carry out the additional steps required namely, the embedding of the form in the sand, the compacting of the sand with or without the use of binding agents, and the various other required manipulations.

SUMMARY OF THE INVENTION It is a general object of the present invention to overcome these disadvantages.

A more particular object of the invention is to provide a casting method of the general type outlined above which is extremely simple and economical and which eliminates manual operations to a very significant extent.

A further object of the invention is to provide such a method which, despite all of its advantages, permits the use of consumable forms despite their low mechanical strength.

An additional object of the invention is to provide an apparatus carrying out the novel method.

In pursuance of the above objects, and others which will become apparent hereafter, one feature of my invention resides in the provision of a method for making castings according to which I confine a body of granular material in a container and thereupon admit into a bottom region of the container a stream of gaseous fluid requisite for agitating the granular material and for imparting the body a state at least approaching fluidization. Thereupon I introduce into the thus agitated granular material a casting form consisting of a material subject to consumption on contact with a molten metal, for instance a foam plastic of suitable type. Admission of the gaseous fluid is now terminated whereby the granular material settles about and into contact with the form, becoming compacted by such settling and tightly embedding the form. The molten metal is now introduced into the form and fills the same, assuming the configuration of the form while simultaneously consuming the latter. On completion of the casting, the gaseous fluid is again admitted into the bottom region of the container whereby the granular material is again agitated to facilitate removal of the finished casting from the body of granular material.

Referring to my novel method, I make possible series casting and mass production in a most simple and highly economical manner, as well as the casting of individual pieces. My novel method for the first time permits the embedding of consumable forms of very highly complicated outline in the granular material without having to make allowance for the low mechanical resistance of lightweight, thin and otherwise readily damaged molds and cast articles. Furthermore, it is no longer necessary to resort to manual operations for improving the surface of the cast article, as was heretofore necessary.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The single FIG. is a diagrammatic illustration of an apparatus for carrying out my novel method.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Discussing the drawing in detail, it will be seen that reference numeral 1 identifies a container which may be entirely of conventional construction, but which is provided, in accordance with the present invention, with a gas-permeable bottom wall 2. Below the bottom wall 2, wall means provides a pressure equalization chamber 3 with which the container 1 is rigidly connected via flanges 4. The purpose of the chamber 3 is to distribute the incoming gaseous fluid before it can enter through the gas-permeable bottom wall 2 into the interior of the container 1. I

An outer shield 8 surrounds the container 1 and the chamber 3 and is configurated to catch any granular material which may be expelled from the container 1 on undergoing agitation as a result of admission of gaseous fluid. The outer shield actually consists of a socket 7 and an upper portion 8, the latter being seated on the socket 7 and being provided .with suitable handles 9 whereby it can be lifted off from the socket 7.

A source of gaseous fluid is provided, identified in the drawing diagrammatically and with a legend, and it is connected with a conduit 5a to a conduit 5 which in turn communicates with the interior of the chamber 3. A suitable valve is interposed between the

conduits

5 and 5a and can be opened and closed depending on whether gaseous fluid is to be admitted into the chamber 3 whether such admission is to be terminated.

In the illustrated embodiment, I additionally provide a source of vacuum, also diagrammatically illustrated and provided with a legend, and also communicating with a conduit 5a which in turn communicates with a conduit 5. In the illustrated embodiment I provide further, because of the presence of sources of gaseous fluid and vacuum, both, a three-way valve 6 of known construction which is operable in suitable manner, for instance via a foot pedal 6a, so as to selectively connect the conduit 5 with one of the conduits 5a, either the one leading to the source of vacuum or the source of gaseous fluid, the selection being determined by pressure on the foot pedal 6a and this determination in turn being made by an operator. The purpose of providing a source of gaseous fluid and a source of vacuum will be discussed subsequently.

The consumable mold is identified with reference numeral CF shown outside the container 1 ready to be introduced thereinto. This consumable mold is of any type already well known in the art. A casting means CM is provided for introducing molten metal into the consumable mold when the same is introduced into the container 1 and embedded therein into the body of granular material which is contained in the container 1 but not illustrated except for the dotted indication of granular material.

Operation of my novel apparatus to carry out my novel method will beobvious from the drawing and from what I have set forth already.

Contrary to conventional casting operations, the body of granular material which may be sand or a high-heat-resistant granular material such as zirconium dioxide or an analogous material, or which may be sand mixed with zirconium dioxide or a similar material, is introduced first into the container 1. A binder material may or may not be added but will advantageously be present in the case of large castings or castings which are tall. The casting form CF may consist, as already pointed out, of a material which is consumed on contact with the molten metal, for instance foamed polystyrol, and will contain all of the features necessary for casting and well known to those skilled in the art. By operation of the foot pedal 6a, the conduit 5 is connected with the conduit 5a leading to the source of gaseous fluid such as compressed air. Introduction of the gaseous fluid through the gas-permeable bottom wall 2 of the container 1, results in strong agitation of the granular material therein, approaching or even reaching a state of fluidization. As soon as the desired agitation is obtained, the casting form CF is slowly introduced into the thus agitated granular material until it reaches the desired position. This requires only a slight pressure upon the casting form CF and thus eliminates the possibility of damage to the same. The agitated granular material swirls around the casting form CF as would a liquid, but despite this the casting form is not lifted if it is properly handled.

When the casting form CF is in its proper location, the admission of gaseous fluid is discontinued, preferably slowly and in stages to thereby obtain settling and compacting of the granular material about the casting form CF. The form is now tightly and completely embedded in the material which surrounds it on all sides in firm engagement.

Now the molten metal is introduced via the casting means CM and this is not illustrated in detail because it is entirely conventional and well known to those skilled in the art. As the molten metal enters the casting form CF, it consumes the material thereof in known manner. Thus, if the form consists of foamed or expanded polystyrol, the polystyrol will collapse. As soon as the molten metal has solidified so that a solid casting is obtained, gaseous fluid is again admitted into the container 1 through the bottom wall 2 thereof, again placing the granular material into a state of near or complete fluidization and making it possible to readily and without any difficulty remove the cast article.

I have found it to be particularly advantageous that the casting process can be repeated any desired number of times without any necessity for changing the granular material. This means that my present method is particularly advantageous for continuous casting with the time intervals between each casting occurrence being determined only by the period required for cooling of the molten metal and solidification. If the casting form CF consists of a synthetic foam plastic material, then the time required for the granular material to cool must be taken into account because casting forms made from foamed plastic materials should not be used at temperatures in excess of approximately 80 C. However, it is emphasized that by properly selecting the weight relationships of granular material and of the cast article, a relationship which can be readily determined by those skilled in the art through simple experimentation, it is possible to achieve a median temperature as a result of the agitation of the granular material which makes it possible to carry out successive casting operations at short time intervals.

Where large quantities of articles of identical type are to be produced, for instance brake drums for automobiles or the like, the present invention is very well suited for mechanization of the casting procedure. The valve 6 is operated, as already shown in the drawing, with a foot pedal, although a different type of operation is possible. The foot pedal operation is preferred because this leaves both hands of the operator free and makes it possible for him to service several apparatuses at the same time, thereby again increasing the economic feasibility of the method.

It has already been suggested that loose forming or casting sand may be used as the granular material in the container 1. This is generally preferable particularly where small and medium size workpieces are to be cast. However, highly heat and combustion-resistant materials, such as zirconium dioxide materials or the like or a loose casting sand mixed therewith, may be used where necessary or desired and particularly good results are then obtained. lt is emphasized that where these basically much more expensive materials are employed, the novel method and apparatus are still economical because the granular material can be used over and over again without having to go through any preparatory or recovery operations. lf zirconium dioxide is used, or a granular material in admixture therewith, the danger of penetration is eliminated which has always presented a very significant casting processes.

In the event of casting of articles having relatively great height, that is a height on the order of 300 millimeters or more, I have found it advantageous to assist the settling and compacting of the granular material prior to introduction of the molten metal into the form, by applying an underpressure to the interior of the container. This is the reason for the provision of the source of vacuum shown in the F10. and it will be appreciated that the use of the three-way valve 6 makes it possible to switch from a connection between the chamber 3 and the source of gaseous fluid to a connection between the interior of the chamber 3 and the source of vacuum which then results in further compacting of the granular material in the interior of the container 1. Under certain circumstances, it may be necessary to further assist the vacuum by using a conventional shaking device for a short period of time. It will be appreciated that the use of vacuum for further compacting the granular material in the container 1 additionally increases the value of the present method for mass production purposes.

It is evident that the elimination of blackwash which has been made possible with the present invention, greatly facilitates the simplicity of the casting process. It is also evident that auxiliary components, such as casting funnels of consumable material for introducing the molten metal into the casting form, may also be embedded in the granular material in the same manner as the casting form, with requisite portions of such auxiliary elements being exposed, such as the inlet ofa casting funnel.

Finally, 1 wish to point out that l have found it advantageous to construct the bottom wall 2 of the container 1 from a highly heat-resistant material, advantageously a sinter material having requisite porosity to obtain the necessary gas permeability. It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of applications differing from the types described above.

While the invention has been illustrated and described as embodied in the casting of molten materials, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit ofthe present invention.

What I claim as new and desired to be protected by Letters Patent is set forth in the appended claims.

1. A method of making castings, comprising the steps of confining a body of granular material in a container; initially admitting into a bottom region of said container a stream of gaseous fluid requisite for agitating said granular material and for imparting to said body a state at least approaching fluidization; introducing into the thus agitated granular material a form consisting of a material subject to consumption on contact with a molten metal; terminating admission of said gaseous fluid to thereby permit settling of the granular material about and into contact with said form; admitting molten metal into said form whereby the metal assumes the configuration of the same while simultaneously consuming the form; and again admitting gaseous fluid into said bottom region of said container to agitate said granular material for facilitating removal of the finished casting therefrom.

2. A method as defined in claim 1, the steps of initially and again admitting gaseous fluid comprising admitting such gaseous fluid in such a manner as to fluidize said granular material.

5. A method as defined in claim I, being highly resistant to combustion.

6. A method as defined in claim 5, said granular material being ZrO 7. A method as defined in claim 5, said granular material consisting of a mixture of sand and ZrO said granular material

Claims

3. A method as defined in claim 1, the step of terminating admission of said gaseous fluid comprising gradually terminating such admission.

4. A method as defined in claim 1; and further comprising the step of subjecting the interior of said container to underpressure subsequent to terminating admission of said gaseous fluid, whereby to facilitate settling and compacting of said granular material.

5. A method as defined in claim 1, said granular material being highly resistant to combustion.

6. A method as defined in claim 5, said granular material being ZrO 2.

7. A method as defined in claim 5, said granular material consisting of a mixture of sand and ZrO 2.