US2745154A - Improvements relating to the moulding of foundry casting, particularly for light alloys - Google Patents

Description

May 15, 1956 R. LUCIEN ET AL 2,745,154

IMPROVEMENTS RELATING TO THE MOULDING OF FOUNDRY CASTING, PARTICULARLY FOR LIGHT ALLoYs Filed Jan. 4, 1951 NYVE/ITORK YED/c150; A.

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United States Patent IMPROVEMENTS RELATING TO THE MOULDING OF FOUNDRY CASTING, PARTICULARLY FOR LIGHT ALLOYS Application January 4, 1951, Serial No. 204,318 Claims priority, applicationFrance May 2, 1950 3 Claims. (Cl. 22-134 The invention relates to a process of casting which is known in metallurgy as bottom-casting, according to which a metal enters a mould from the lower part thereof and then rises slowly therein under the inclosed gases and impurities.

In the accompanying drawing:

Figure 1 is a diagrammatic sectional view of a mould prepared for bottom-casting in known manner.

Figures 2 and 3 are enlarged sectional views of two examples of elements provided for use in such a mould in accordance with the present invention.

With reference to Figure 1 it is to be noted that in the bottom-casting process there is utilised a moulding box a comprising a runner cup b by which metal is poured into a down runner c, which is substantially vertical, to a feed runner d arranged in the lower part of the moulding box. At the gate e of this runner, the desired upward entry of the metal to the casting space P occurs.

It is known that, for the casting of light alloys that are very susceptible to oxidation, the foundryman generally uses bottom casting because it is the least disturbing casting process and because it ofiers known advantages relative to other casting processes.

It is known, on the other hand, that for the casting of metals having a substantial liquid shrinkage, it is common to arrange, over the work to be fed, one or several air holes 1, that, on the cooling of the work, continue protecting risers allowing the gases to escape and forming stores of liquid metal that feed the casting during its liquid shrinkage to allow the obtaining of sound castings.

It is also known that, while it is possible to determine with a sufficiently close approximation the volume of liquid metal necessary for feeding a casting P, having a given volume, it is, very difficult to control the cooling of the risers 1 during the duration of the liquid cooling of the casting. Now, at the instant when bottom casting is stopped, the metal is much hotter in the lower part of the casting than in the risers. Accordingly, in order that the risers assume their function of feeding, it is necessary to delay as much as possible the cooling thereof.

An object of the invention is therefore to provide for insulating the risers from the sand which surrounds them by means such as a sheath made in the form of a double envelope filled with an appropriate insulating material, for example glass wool or the like.

In Figures 2 and 3 are respectively shown, in cross section, two insulating sheaths for foundry risers according to the invention and as shown by the member g in Fig. 1.

The sheath is constituted by a double envelope, 1-2, the inner volume 3 of which is filled with insulating material. The internal space 4, which is reserved for the riser can advantageously be in the form of a truncated cone, the larger base of which is arranged at the bottom of the riser whereas the outer envelope 2, also has the shape of a truncated cone, the larger base of which is arranged at the top of the riser.

Patented May 15, 1956 This heat-insulated envelope can also be easily removed from the mould after the liquid shrinkage of the casting is completed, by lifting the handle 5, leaving thus full latitude for the casting to make its solid contraction without fear of the formation of flaws. The trimming of the casting is moreover greatly facilitated.

In the embodiment shown in Figure 2', the sheath is open to the atmosphere at 6 whereas, in the embodiment of Figure 3,- the sheath only has a narrow orifice 7 for the escaping of the gases.

' The volume of the insulating mass 3 and more partic- "ice ularly its mean thickness are determined in accordance with the conductibility of the insulating material chosen, in order to assure a time of solidification of the metal in the riser which is greater than the time of solidification of the material of the casting contained in the mould.

' Moreover, the volume of the riser, that is to say, of the space4, will be determined in accordance with the volume of the casting to be fed during its solidification.

In order to reduce to a minimum the volume of the riser, the heat sheath can advantageously be provided, without departing from the scope of the invention, with means for heating it, for example electrically, by means of a resistance arranged in the insulating material 3.

The invention can be put into practice in the casting shop by means of a series of heat insulated sheaths of suitable number and dimensions, formed as a standard stock of tools, which can be conveniently taken up in to be poured and taking account of the need which exists for the feeding of each piece. The sheaths are arranged in the sand of the moulding box and about the orifice provided for the riser.

By the application of the process according to the invention and of the above described stock of tools, one

can obtain in particular in the moulding of castings in light metals and of high mechanical resistance, characteristics entirely comparable with those which are obtained, by the employment in current technology, of much more bulky risers.

We are aware that it already has been proposed to provide with a heat insulated sheath the cups used in drop casting.

In said drop casting, substantially different from bottom casting as it consists of feeding the work by the upper part of the moulding box, the riser for feeding the shrinkage of the work to be moulded is usually and preferably formed by the runner cup itself. Now, said runner cup being filled last, that is at the end of the pouring, and consequently containing the hottest part of the metal, normally is in good condition for feeding with liquid metal the work during its cooling. The provision of a heat insulated sheath is practically useless in this instance.

On the contrary, in the process of bottom casting, the heat insulated sheath arranged in the risers is essential for the upper parts of the work to be constantly fed by liquid metal maintained at a suitable temperature. Moreover, the provision of heat insulated sheaths on the runner cups used in drop casting would be of no interest.

These differences, on the one hand in the location of the sheaths and on the other hand in the casting processes to which they are respectively applied, dillierentiate in its principle the present invention from the previous process.

We claim:

1. In combination with a bottom casting mould having an outer sand box with an outwardly flared vent therein, a heat-insulating sheath positioned in the vent and comprising a pair of hollow frusto-conical members positioned one inside the other defining an inner space for the escape of gases from the inside of the mould and the formation of a riser and an intermediate space between the two members, the outer one of said members flaring upwardly and the inner one downwardly, and a mass of insulating material in said intermediate space having a greater heat resistance than the sand in the box surrounding the vent, the hollow frusto-conical members constituting an integral unit adapted to be readily removed from the vent.

2. A heat-insulating sheath according to claim 1, wherein the upper, smaller end of the inner one of said members is entirely open.

3. A heat-insulating sheath according to claim 1 wherein the upper, smaller end of the inner one of said members is shaped to define a narrow, gas escape hole, and wherein said insulating material extends across said end around said hole.

References Cited in the file of this patent UNITED STATES PATENTS 1,218,438 McNaughton Mar. 6, 1917 Carroll Feb. 25, 1902 20 4 Brunner Sept. 16, 1919 Durville May 4, 1926 Trembour Jan. 1, 1929 Gathmann Dec. 10, 1929 Williams et al Nov. 27, 1934 Lewis Dec. 8, 1936 Seaver July 11, 1939 Lindemuth Dec. 19, 1939 McWane Jan. 9, 1940 Johnston Jan. 21, 1941 McDonald Feb. 11, 1941 Dornduf Feb. 9, 1943 FOREIGN PATENTS Great Britain Feb. 26, 1931 Great Britain May 31, 1934 Great Britain July 28, 1947 Great Britain Nov. 22, 1950 OTHER REFERENCES

Claims (1)

1. IN COMBINATION WITH A BOTTOM CASTING MOULD HAVING AN OUTER SAND BOX WITH AN OUTWARDLY FLARED VENT THEREIN, A HEAT-INSULATING SHEATH POSITIONED IN THE VENT AND COMPRISING A PAIR OF HOLLOW FRUSTO-CONICAL MEMBERS POSITIONED ONE INSIDE THE OTHER DEFINING AN INNER SPACE FOR THE ESCAPE OF GASES FROM THE INSIDE OF THE MOULD AND THE FORMATION OF A RISER AND AN INTERMEDIATE SPACE BETWEEN THE TWO MEMBERS, THE OUTER ONE OF SAID MEMBERS FLARING UPWARDLY AND THE INNER ONE DOWNWARDLY, AND A MASS OF INSULATING MATERIAL IN SAID INTERMEDIATE SPACE HAVING A GREATER HEAT RESISTANCE THAN THE SAND IN THE BOX SURROUNDING THE VENT, THE HOLLOW FRUSTO-CONICAL MEMBERS CONSTITUTING AN INTEGRAL UNIT ADAPTED TO BE READILY REMOVED FROM THE VENT.

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