AU612663B2 - Casting method and apparatus therefor - Google Patents

Description

JU-T.' I'- S F Ref: 64048 FORM COMMONWEALTH OF AUSTRALIA PATENTS7 ACT 1952 1 COMPLETE SPECIFICATIC 6

(ORIGINAL)

FOR OFFICE USE: Class Int Class 9 9 .e.

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*9 0 Sft .9 Complete Specification Lodged: Accepted: Published: Priority: Related Art: of Applicant: Address for Service: Morikawa Sangyo Kabushiki Kaisha 150, Oaza Imojiya Kohshoku-shi Nagano-*ken

JAPAN

Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia *9 0 009 S Complete Specification for the inventon entitled: Casting )4ethod and Apparat .is Therefor The following statement is a full description of this invention, includirg the best method of performing it kncwn to me/us 5845/3 TITLE OF THE INVENTION CASTINC METHOD AND APPARATUS THEREFOR BACKGROUND OF THE INVENTION 1. Field of the Invention: The present invention relates to a method of manufacturing castings and an apparatus therefor. More specifically, it pertains to a casting method which employs a melting pattern and a casting apparatus for carrying out this A method.

0* 2. Description of the Prior Art: TI The present inventor has made a patent application of *apparatus, a large number of flasks which are made of metal o and have a box-like shape are movable provided, and each of 00 the flasks is filled with noncombustile filling material such as sand. Embedded in the filling material is a melting patteri which is made of polystyrene foam and which is coated with a layer formed of mineral particles and a binder. A runner which has a sprue is connected to the melting pattern, and a hollow combustion suction device which has vent holes on its side wall forming a gas collecting chamber and a burner at the upper portion thereof is provided in such a manner that it is in contact with the layer of filling material. The flasks are vibrated by a vibrating device so i R- I as to closely pack the filling material. Thereafter, a molten metal is poured from the sprue. The molten metal gasifies the melting pattern and fill.- the cavity which has been formed by the melting of the melting pattern. The generated gas flows through the interstices of the particles of the filling material, and enters the combustion suction device from the vent holes. It fills the gas collecting chamber, and moves upwar' to the burner, at which it is ignited by an ignition uevice provided in such a manner as to face the burner, and is burned. Thereafter, the flask where the above-described operation is conducted is moved away for another process. Upward movement of the burned gas decreases the pressure within the combustion suction device, by which *suction of the gas through the vent holes is conducted.

9 9 Unlike the known casting apparatus which employs a pump a to Luck the gas, the disclosed method and apparatus can omit the use of pump. Further, suction force can be varied to a suitable value as a series of operations are carried out including starting of generation of the gas, increase and decrease in the amount of gas generated, and completion of generation of the gas. Also, generation of gas can be automatically started and completed. These enable manufacture of a sound casting which cannot be obtained by an apparatus employing a pump.

However, such apparatus and method have following 2 3 disadvantages: in the above-described method, the flasks are vibrated by the vibrating device so as to closely pack the filling material accommodated in each of the flasks and to thereby hold the melting pattern firmly during casting and prevent collapsing of the filling material into a cavity formed by the dissipation of the melting pattern. However, if the flask has four right-angled corners, the flask has four square corners, the filling material cannot be closely packed uniformly when it is vibrated. Further, after the burner has been ignited, that flask is moved away from the ignition device to a position at which another process is carried out so as to enable a casting operation to be conducted continuously. This makes flow of the gas filling in the filling material into the combustion suction device discontinuous, and the burning at the .0 burner and hence the suction are interrupted.

OBJECT AND SUMMARY OF THE INVENTION It is the object of the present invention to overcome or substantially ameliorate the above disadvantages.

There is disclosed herein a casting method comprising the steps of: providing a noncombustible filling material within a flask, the flask having obtuse-angled or arcuate corner portions provided therein at its inne" periphery, said flask being provided in such a manner as to be movable by a moving device; embedding in said fillng material a melting pattern coated with a gas permeable layer formed of mineral particles and a binder; providing a runner having a sprue in such a manner that it is in contact with said melting pattern; providing a hollow combustion suction device having vent holes on its side wall forming a gas collecting chamber as well as a burner at its upper portion in such a manner that it is in con'tact with said layer of filling material and that said burner projects from the upper surface of said layer of filling material; vibrating said flask by a vibrating device so as to pack said fitt-g.

material densely; pouring a molten metal from a furnace through said sprue so as to gasify said melting pattern by said molten metal and replace said pattern with a product; igniting and burning at said burner by an ignition device the gas which enters said gas collecting chamber of said combustion suction device S-though said vent holes after it has passed through the interstices in said -H 381 -4 filling material so as to cause it to rise, such that the pressure in said gas collecting chamber decreases by upward movement of said gas so as to enable suction of the gas through said vent holes to be conducted; and moving said flask and then providing said burner with another ignition device after the movement of said flask has taken place.

There is further disclosed herein a casting manufacturing apparatus comprising: a plurality of flasks provided in such a manner as to b? movable by a moving device, each of said flasks having obtuse-angled or arcuate corner portions provided therein at its inner periphery; a vibrating device adapted to act on the flasks so as 'to densely pack a noncombustible filling material in each of said flasks; a melting pattern within each flask and adapted to be embedded in 5 said filling materip.l for generating combustible gas when heated; a aas permioable coating formed on the outside of said pattern, said coating being formed of mineral particles and a binder; a runner within each flask and adapted to pass through the filling material and having a sprue, said runner being provided in such a manner 2, that 'it is in contact with said pattern; a hollow combustion suction device provided within each flask and adapted to contact said filling material, said combustion suction device having vent holes on a side wall thereof forming a gas collecting chamber and a burner at an upper portion thereof; a plurality of ignition devices adjacent to and for igniting each of et: sai.d burners; and mea1 t for supplying a molten metal to said sprue.

BRIEF DESCRIPTION OF THE DRAWINGS A preferred form of the present invention will now be described by way of example with reference to the accompanying drawings, wherein: Fig. 1 is a cross-sectional view of an apparatus embodying this invention, showing one of the steps of a method embodying this invention; Fig. 2 is a cross-sectional view of the apparatus of Fig, 1, showing anothe step of the method of the present invention; Fig. 3 is a schematic perspective view of 'the casting manufacturing apparatus; Fig. 4 is a plan view of a flask; Fig. 5 is a plan view of another example of the flask; Fig. 6 is a plan view of the flask employed in the apparatus of the

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same type which has been disclosed by the present inventor; Fig. 7 is a side elevational views of part of the casting manufacturing apparatus according to the present invention; Fig. 8 is a perspective cross-sectional view of part of the casting manufacturing apparatus of the present invention; Fig. 9 is a plan view of part of the apparatus of the p,'esent invention; and 9.

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Fig. 10 is a plan view of part of the apparatus of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to Figs. 4 and 5, a flask 3 has obtuse-angled or arcwise portions 1 at its inner periphery. In this case, the obtuse-angled portion means a portion made up of straight lines, as the corner portion 1 shown in Fig. 5, or a portion made up of a straight line and a curve, as shown in Fig. 4.

In Figs. 1 to 3, a moving device 2 includes rollers 24, shafts 25, bearings 26, a base 27 for supporting the bearings 26, and urging members 28 which are hydraulic cylinders. As shown in Fig. 3, a plurality of flasks 3 can be continuously pivoted in an endless fashion by the four urging members 28 of the moving device 2. A vertically moving roller 29 shown in Figs. 3 and 7 whose detailed description is omitted moves ,h flasks 3 up and down, by which the flasks 3 are located above a vibrating device 15 having a spring 30 and are loaded on toe vibrating device. Each of the flasks 3 is made of iron or other metal which is in the form of a container. The flask 3 is filled with a noncombustible filling material 4 such as molding sand. A melting pattern 6 which generates combustible gas when heated is embedded in the filling material 4. The pattern may be formed from a polystyrene foam. Although it may also be formed from other synthetic resin foams, polystyrene foam is preferable. A gas permeable 6 MNEI Nlayer 5 mainly made of mineral particles is provided on the pattern 6. The coated layer 5 may be formed by coating on the pattern 6 a liquid which contains silica or other mineral particles dissolved in a binder such as molasses, and then by drying it. A known coated layer 5 including an imported product may be employed. A sprue 7 may be a ceramic molded product, and a runner 8 may be a shell molded product. The sprue 7 and the runner 8 may also be made of the same material as that from which the pattern 6 is formed. A ;o combustion suction device 13 may be of a cylindrical shape S• and made of metal. The device 13 has vent holes 11 on a side wall 10 thereof. The vent holes 11 are so small as to inhibit entrance of the sand. As shown in Fig. 8, the C' combustion suction device 13 may comprise a spiral pipe filter 32 and a pipe 33 having the same diameter as that of the spiral pipe filter 32, the pipe 33 being welded to the spixal pipe filter 3 The spiral pipe filter 32 may be 4: .formed of steel having the continuously formed vent holes 11.

Therefore, it can withstand a high external pressure. The vent holes 11 have a width which is largest at the inner surface and which gradually decreases as it approaches the outer surface. In consequence, the vent holes 11 are prevented from being clogged with the filling material 4, that is, cleaning of the vent holes is easy. The combustion suction device 13 also includes a reinforcing nat- 34, 'Al

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.j Ionsi y ^nak and a protector 22 made of a bar steel. The protector prevents damage to the vent holes 11 which would be caused by the contact of a product 18 shown in Fig. 2 with the vent holes 11 which would occur when the product 18 is taken out.

The protector 22 also makes the fixing of the filter 32 to the pipe 33 firm.

The combustioon suction device 13 may be fixed to a f bottom of the flask 3 by bolts 36. Alternatively, it may be fixed to a guide rail (not shown) provided on the bottom of the flask 3 at any desired position. In this way, the combustion suction device 13 can be moved to a suitable position, depending on the size and length of the melting pattern 6. The combustion suction device 13 may aloo be made of any of various kinds of material having a multiplicity of openings, such as a wire net, a punched metal or steel wool.

An ignition device 19 may be of any type which is capable of igniting the combustible gas, such as a burner which is fired with town or propane gas. As shown in Figs. 3 and 10, a plurality of ignition devices 19 are provided along a passage 20 of the flasks 3 as an ignition device set 21.

Since a plurality of iginition devices 19 are provided, even if the flow of gas into the combustion suction device 13 becomes irregular or discontinuous, the gas is kept burning, thereby keeping the suction substantially continuous and constant. The reference numeral 37 denotes a valve.

L G iv r Next, the corner portions 1 of the flask 3 are reshaped in an obtuse angled or arcwise form, as shown in Figs. 4 and They are so formed because it was found out in the experiments that, when the corner portions 1 were formed at a right angle, as shown in Fig. 6, the filling material 4 was packed in a region 38 at a different density from that at which it was packed in any of regions 39. More specifically, the filling material was packed at a high density in the region 38, whereas the packing density of the material at the regions 39 was low. This occurs when the filling material 4 c* is shaken by the vibrating device shown in Fig. 7 and 3 so S: that it is densely packed. If this happens, it is difficult for the filling material 4 to hol3 the melting pattern 6 stationarily. Further, there is a possibility of the filling material ccllapsing into a cavity formed by the melting of the melting pattern 6. These problems can be prevented if the bent portions 1 are shaped in an obtuse angled or an S arcuate form. With the bent portions thus shaped, the filling material 4 could be packed substantially uniformly over the entirety of the flask when it was shaken in experiments conducted by us, and the above-described problems were therefore solved. This phenomenon can be surely reproduced in an experiment.

Reference numeral 40 denotes a hook. The apparatus of this embodiment is moved a distance equivalent to one 4yj n~ I 1 flask 3 in the direction indicated by th'i arrows A28 by the urging members 28. While it is being pivoted on the plane, a series of casting operations, including pc:ring of the molten metal, ignition of the generated gas, combustion of the gas, continuation of ignition, cooling of a molded product, removal of the molded product, supply of the filling material 4, embedding of the pattern 4, and shaking of the filling material by the vibrating device 15, are carried out in 0* that order. When the gas is burned at a burner portion *12, it rises from the lower portion of the combustion suction device, making the pressure in that portion lower and thereby making suction of the gas possible.

In the present invention arranged in the abo'e-described manner, suction of the gas is conducted by the combustion O* suction device. Therefore, timing of the suction operation I including generation of the gas, increases and decreases in the amount of gas generated and completion of the generation, as well as the suction force, can be automatically adjusted, unlike the case in which a pump is employed for suction, and well-molded products can thereby be easily manufactured.

When the flasks are moved after the gas has been burned, the burner of each of the flasks is provided with another ignition device. In consequence, even if the flow of gas into the combustion suction device becomes irregular and discontinuous, the gqs is ignited every time burning of the I-n

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gas is interrupted, and the suction can be thereby -onducted continuously.

Further, since the bent portions of the flask have an obtuse-angled or arcuate shape, the filling material in the flask can be closely packed substantially uniformly over the entirety of the flask. In consequence, the melting pattern can be held firmly, and the possibility of the filling material collapsing into the cavity formed by the decomposition of the pattern can be eliminated. In addition, the provision of protectors in the combustion suction device enables damage to the vent holes thereof which would be otherwise caused by the product to be prevented.

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Claims (4)

1. A casting method comprising the steps of: roviding a noncombustible filling material within a flask, the flask haviny obtuse-angled or arcuate corner portions provided therein at its inner periphery, said flask being provided in such a manner as to be movable by a moving device; embedding in said filling material a melting pattern coated with a gas permeable layer formed of mineral particles and a binder; providinr a runner having a sprue in such a manner that it is in contact with said melting pattern; providing a hollow combustion suction device having vent hoT., on its side wall forming a gas collecting chamber as well as a burner at its upper portion in such a manner that it is in contact with said layer of filling material and that said burner projects from the upper surface of said layer S of filling material; vibrating said flask by a vibrating device -o as to pack said i-t-t- qg- material densely; pouring a molten metal from a furnace through raid sprue so as to gasify said melting pattern by said molten metal and replace said pattern with a product; igniting and burning at said burnter by an ignition device the gas which enters said gas collecting chamber of said combustion suction device through said vent holes after it has passed through the interstices in said filling miaterial so as to cause it to rise, such that the pressure in said gas collecting chamber decreases by upward movement of said gas so as to enable suction of the gas through said vent holes to be conducted; and SImoving said flask and then providing said burner with another ignition device after the movement of said flask has taken place.

A casting manufacturing apparatus comprising: a plurality of flasks provided in such a manner as to be movable by a moving device, each of said flasks having obtuse-angled or arcuate corner portions provided therein at its inner periphery; a vibrating device adapted to act on the flasks so as to densely pack a noncoibustible filling material in each of saia flasks; a melting pattern wit'in each flask and adapted to be embedded in said filling material for generating combustible gas when heated; a gas permeable coating formed on the outside of said pattern, said coating being formed of mineral particles and a binder; JLH/'7381 0 1 ILo 1 13 a runner within each flask and adapted to pass through the filling material and having a sprue, said runner being provided in such a manner that it is in contact with said pattern; a hollow combustion suction device provided within each flask and adapted to contact said filling material, said combustion suction dev'ce having vent holes on a side wall thereof forming a gas collecting chamber and a burner at an upper portion thereof; a plurality of ignition devices adjacent to and for igniting each of said burners; and 0- -furnacs- meanwkfor supplying a molten metal to said sprue.

3. A casting manufacturing apparatus according to claim 2, wherein said combustion suction device has a longitudinal protector on the outside thereof which runs in the axial direction thereof,

4. A casting method substantially as hereinbefore described with reference to the accompanying drawings. A casting manufacturing apparatus substantially as hereinbefore described with reference to the accompanying drawings. DATED this EIGHTH day of APRIL 1991 Morikawa Sangyo Kabushiki Kaisha Patent Attorneys for the Applicant SPRUSON FERGUSON U NVI -4 LH... JLH/27381 L