CA1045780A - Pattern alignment or distortion preventing concept for use with lost foam molding process - Google Patents
Pattern alignment or distortion preventing concept for use with lost foam molding processInfo
- Publication number
- CA1045780A CA1045780A CA216,626A CA216626A CA1045780A CA 1045780 A CA1045780 A CA 1045780A CA 216626 A CA216626 A CA 216626A CA 1045780 A CA1045780 A CA 1045780A
- Authority
- CA
- Canada
- Prior art keywords
- patterns
- frame
- sand
- pattern
- flask
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
- B22C9/02—Sand moulds or like moulds for shaped castings
- B22C9/04—Use of lost patterns
- B22C9/046—Use of patterns which are eliminated by the liquid metal in the mould
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C7/00—Patterns; Manufacture thereof so far as not provided for in other classes
- B22C7/02—Lost patterns
- B22C7/023—Patterns made from expanded plastic materials
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Casting Devices For Molds (AREA)
- Molds, Cores, And Manufacturing Methods Thereof (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An apparatus and method is disclosed for casting parts by the cavityless molding method. A plurality of complex or difficult cored consumable patterns are stabilized on a heat resistant frame. Means is employed to prevent the transfer of heat between the molten charge (subplanting the patterns) and the stabilizing frame. The assembly is installed in a semi-filled flask or empty flask; fluidizing means is employed when a partly sand-filled flask is used and a deep pouring spout is used for an empty flask.
An apparatus and method is disclosed for casting parts by the cavityless molding method. A plurality of complex or difficult cored consumable patterns are stabilized on a heat resistant frame. Means is employed to prevent the transfer of heat between the molten charge (subplanting the patterns) and the stabilizing frame. The assembly is installed in a semi-filled flask or empty flask; fluidizing means is employed when a partly sand-filled flask is used and a deep pouring spout is used for an empty flask.
Description
1()457~0 The present invention is directed to a lost foam molding process.
Cavityless molding performed with consumable patterns have several distinct advantages, the chief of which is that the shape to be cast may take any configuration. Molding, itself, comprises ramming the sand or other suitable molding material around the pattern, without regard to a parting line or pattern draft. This allows for a considerable decrease in the cost of molding, particularly for parts where a single casting is required from a given pattern.
Typically, the expendable pattern may be made from an expanded plastic material, such as expanded polystyrene beads or polyethylene which, as is well known, is porous because it contains air voids in the expanded condition. The material is light weight, economical and easy to form into any desired shape. This pattern material is capable of being volatilized or burned, particularly in the absence of oxygen without appreci-able residue remaining. The method of casting conventionally employed by those skilled in the art, is to utilize the molten charge for combusting and destroying the pattern. Molten metal poured into a mold containing a polystyrene pattern consumes the pattern, fills the resultant cavity with molten metal, which later solidifies, leaving a casting having the exact contour of the original pattern.
This mode of casting has worked admirably well for parts which are relatively open and can be freely filled with sand during flask filling operations. That is to say, success has been achieved to date only with patterns that, when set with-in a flask, permit dry unbonded sand to be easily introduced and which will occupy all voids within and without the patterns.
~owever, when a multiple number of castings are attempted to i~, . :~ . .
1~)4~81D
be cast within a single flask and particularly from a common sprue, the feasibility of sand filling is considerably reduced.
In addition, when the parts to be cast are not necessarily of a simple type, but have small openings leading to cored parts which will not lend themselves to free sand filling, the concept of cavityless casting is hampered. One suggestion, according to this invention to overcome these problems, is to separately pre-fi11 the polystyrene patterns with loose unbonded sand and close the polystyrene pattern in some fashion to assure the retention of the closed parts. These relatively heavy filled parts must be stabilized in some manner during overall flask filling. Proper alignment of parts relative to each other, as well as to the placement of sprues and risers, is extremely important if efficiency in the casting process is to be maintained.
Accordingly, there is a need for a method which will allow complex and intricate polystyrene patterns to be used in multiple numbers ~ithin a single flask and which method lens itself to a high speed molding operation; the method may wor~
with conventional sand filling mechanisms, such as sand slingers or deep pouring spouts.
In accordance with one aspect of the present invention, there is provided an apparatus for making multiple castings from a single pouring thro~gh a common sprue in a body of sand, the apparatus comprising: (a) a plurality of consumable foam type patterns which are combustible substantially without residue on subjection to a molten casting chaxge, each of the pattexns having at least one-ear effective to serve as a stabilizer, (b) a rigid stabilizing frame supported against movement, the frame having at least one finger for each of the patterns, each finger providing a support upon which the ear of one of the patterns may be journalled, (c) independent sprue means for con-.~
~45'781) ducting a molten metallic charge to the combustible pattern forconsummation, and (d) means to prevent consummation of the frame during introduction of the molten charge. .
In accordance with another aspect of the present :
invention, there is provided a method for fabricating a plurality of castings from a single pouring through a common sprue in a body of sand, the method comprising: (a) preparing a skeleton stabilizing frame effective to be easily inserted into a fluid-ized sand medium, the frame having a plurality of fingers extend-ing inwardly thereof in a number of common planes generally equally spaced apart, (b) preparing a plurality of consumable foam patterns of the type which is combustible substantially without residue on subjection to a molten casting charge, ~
each pattern being provided with a plurality of foam ears extend- ~ .
ing generally away from the pattern to lay in one of the horizon- .
tal planes defined by the fingers of the frame, the patterns being joined together by a consumable sprue effective to be com- . .
busted without residue by the molten charge for defining a ;
channel to feed the patterns, (c) filling the flask with a body 20 of dry, loose unbonded sand, the sand being introduced to the flask by means effective to fluidly locate the sand progressively from the bottom upwardly through the flask, (d) pouring molten metal into the consumable sprue and pattern for combusting the foam material to occupy the void left by the foam, (e) stripping the patterns from the frame and fingers and from the sand, and then breaking off the cast ears from the casting, and ~f) re-installing the frame in a stripped flask and repeating steps (b) through ~e).
The present invention, therefore, provides a method and apparatus which will permit the casting of a plurality of complex parts or simple parts having small openings, within a .
.... .
~L~45'7~
single flask requiring precise alignment with appropriate sprues and risers by employing cavityless casting in which the pattern is consumed by contact with molten metal.
One of the key problems to be overcome by this in-vention is to permit the use of a multiple number of relatively complex shaped or narrowly cored consumable patterns to be used in a high production Fasting line.
The use of consumable patterns is relatively well known in the art. This known technique has had its greatest demonstrated feasibility in connection with open parts which will fill relative-ly easy with sand during flask filling. However, when a number of relatively complex parts are utilized or where openings in the outer configuration will not fill easily with sand, special measures must be undertaken particularly with respect to the necessity for special alignment and stabilization. Parts such as manifold intakes or heaters for cooling systems, hub-type rotors or disc brake castings, all are of complex configuration which will not fill easily with sand. Simple parts having small cored openin~s may comprise exhaust manifolds, water pumps, un-usually designed hollow section crank shafts, transmission oilpumps and disc brake calipers.
To overcome these problems, in the present invention consumable patterns are hung on a fixture which cooperates with air fluidization of mold sand or with special sand pouring spouts to facilitate proper flask filling.
The invention is described further, by way of illustration, with reference to the accompanying drawings, in which:
Figure 1 is an overall elevational view of a mechanism upon-~hich one or more flasks may be mounted for appropriate sand compacting and filling;
. .
:1~4578~
Figure 2 is an enlarged sectional view of a portion of Figure 1 showing the arrangement of the pattern stabilizing means within the flask;
Figure 3 is a greatly enlarged perspective view of the stabilizing means and patterns and consumable patterns mounted thereon; and Figure 4 is a highly enlarged exploded view o a portion of the pattern and stabilizing means of Figure 3.
Referring now to the drawings, consumable patterns 10 are provided with at least one preformed consumable ear 11 typically extending outwardly from one side wall 12 of the ;
pattern 10. Preferably, at least three of such ears 11 extend outwardly in equi-circumferentially spaced arrangement about the ~ -side wall of the pattern to lay in a common plane. Each of the ears is provided with an opening 13 to receive stabilizing means 14, the latter being re-useable in subsequent cycles of the ;
casting method. Each of the ears is provided with an annular groove 15 or recess at the juncture with the pattern wall 12 so that a weakness line is created. After the metal casting solidifies and replaces the consumable pattern, the metallic ear may be easily struck and removed from the completed part.
The stabilizing means 14 comprises a rigid stabilizing frame 15, which is preferably constructed of tubular heat resistant steel. The frame has an annular base 15a adapted to seat in a secure position on a horizontal wall of the molding flask. The frame has uprights 15b along at least two sides thereoE which connect with an upper annular ring 15c. At spaced elevations along the u~rights, fingers 16 extend inwardly toward the inner region of the frame wherein the patterns are hung.
Each finger has an upright pin 17 at its inner extremity effective to extend through the opening 13 in a mating ear of the pattern.
~,, , ' ' .
~ - 5 -~457~
Means 18 is provided to prevent the transfer of heat between the molten charge (displacing the pattern 10) and the ; supvorting or stabilizing frame 14. To this end, one mode may .
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.
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S7l~
comprise the use oE an annular ceramic insert 19 which is preiormed into the polystyrene ear; the insert may have a central opening 20 commensurate in size and shape to receive one of the pins 17 of said stabilizing frame. An annular groove 21 in the side wall l9a of the insert assures a good - interlock with the ear.
Another mode may comprise the use of a narrow gauge in the connection between the ear and frame; an extremely narrow or wire-like restriction can be provided in pin 17 as a substi~u~e for the separating ceramic insert 19. According-ly when the molten charge is applied, the narrow gauge of the supporting finger prevents undue transfer of heat there-along and can be easily replaced with low cost replacement for a subse~uent molding operation.
A preferred method mode would comprise:
(A) Prepare a skeleton stabilizing frame effective to be seated on a horizontal plane within a mol~ing flask; the frame should have a plurality of fingers extending inwardly of the frame to support a body in spaced vertical orientation, (B~ Prepare consumable foam-type patterns having configurations not easily filled internally with sand and may have cored parts. Each pattern should be prepared with a plurality of ears extending outwardly ln circumferentially spaced arrangement about the side walls of said patterns so as to mate with the fingers of said frame and be supported in a stabilizing manner, (C) Prepare a common sprue and risers for said consumable pattern, (D) Insert said supported stabilized patterns into a flask having sufficient space about the frame to introduce ~' .
- 6 - ~
~4S78C) sand to the bottom thereof; fluidize the sand by air pressure to assist in placement of the assembly of patterns, compact the introduced sand by vacuum or vibration, (E) Introduce molten metal to said sprue and patterns to displace same and form a solidified casting having ears as defined by said patterns, and (F) Strip the patterns from said sand and remove said frame therefrom for reuse of said sand. Re-install said frame work with a new set of patterns in a similar flask devoid of sand. Tap the ears of said castings for being strippe~ therefrom.
The consumable pattern is adapted to be displaced in a mold by the poured casting charge; it is converted sub-stantially ln its entirety to a gaseous state and permitted to escape from the mold through suitable vent provisions. To this end, any suitable material which is readily combustible substantially without residue upon subjec~ion to a molten casting charge can be used as pattern material. It should be sufficiently rigid to safely withstand the stresses induced by the customary ramming of molding sand thereagainst. A
suitable material for these purposes is an expanded poly-styrene. It has been found that polystyrene is well adapted for the intended purposes if it is expanded to a density sub-stantially but not more than 2 lbs./ft.2. If this material has substantially greater density, it will not readily burn ;~
away on sub jection to a molten casting charge. On the other hand there is a limit to the expansion of this material in order to be sultable for forms of this type, for if the density becomes too low, it may lack adequate strength to withstand ordinary molding pressures and other stresses, at ~4S'780 least in parts, to spoil a mold. It is comparat.ively easy to make a form of this material for the production of a casting of most any configuration. For the sake of illustration, the pattern is shown as a simple block having a plurality of ears extending from a continuous side wall thereof, the ears being circumferentially spaced thereabout.
A typical preferred apparatus useful in carrying out step (D) of the preferred method is illustrated in Figures 1 and 2. A carousel 30 is employed having a turn table 31 or disc mounted at its center upon a tubular support 32 which in turn is stabilized on a base plate 33. A
plurality of sand flasks 34 (for example, as many as eight) ;
may be carried at various stations about the periphery of the turn table. Each of the flasks 34 is mounted.on a pair of trunnions 35 at spaced locations along the turn table, the trunnions pexmitting the flask to be tilted for emptying of sand upon completion of the casting mode. To enable the carousel to be automated, an electric motor 36 and trans-mission 3 8 may be employed to drive the main bearing ring 37 of the turn table; another electric motor 39 may be employed to rotate the flasks about their trunnlons 34, the drive being through chains 40. :
. Each of the flasks 34 may be of one piece or non-separable construction in whi~h the mold is destroyed upon removal of the cast object and the pattern is destroyed ~ ,.
during the casting process. Each flask is preferably provided .~ :
with an air permeable wall 41 over at least the floor of the flask interior, space, the air permeable plate or wall being preferably formed of a sintered metal ~such as iron~. The .
permeable wall divldes the interior of the flask into a : -, . - . . ~ , .. . . . .. . . .
4S'~80 casting chamber 42 and a gas plenum chamber 43, the latter selectively comm~nicating by way of suitable ducts 44 with a suction source at one side and selectively communicating with a source 45 of fluid under pressure from the opposite side thereof. The communications may be respectively provide~ by the inlet duct 46 passing throuyh the right hand trunnion and the communication of suction provided by a conduit 44 having a high velocity jet 44 connected to a source of pressure in the interior of the support 32 of the carousel. The interior of the support may act as a com-pressed air storage tank or accumulator fed by a pump 50.
; In operation, the emptied upwardly oriented flask is halted at a first station of the carousel~ Sand (moldlng medium) of the dry unbonded type is introduced in a pre-determined quantity to the interior of the flask. This may be preferably accomplished by use of a deep penetrating pouring spout which would effectively fill chamber 42 in a -~
manner as water would fill a vessel. While sand is being introduced, air is fed through passage 46 from source 45 to the chambers 43 which will effectively fluidize sand in chamber 42 thereby enabling the frame 14 and patterns 10 to be inserted into the fiask. The fluidization of the sand is carried such that the motion of the particles is slightly turbulant and yet no substantial tendency to drive the particles out o the mold is maintained. Because of the fluidization of the molding medium, the patterns and frame can be easily seated in the molding chamber 42 without noticeable resistance.
The carousel may then be indexed to the next position where the compressed air is interrupted and _ g _ 1~5~
- vibrators 4~ are set in motion to compact the sand mass around the pattern. An air impermeable membrane 48 such as aluminum foil or polyester film is placed across the top of the sand body in the flask and may have an aperture for a casting funnel. The carousel is then indexed to a third position where suction is applied through the passage 44 and thus a differential pressure is applied between the membrane 48 and the floor 41 of the sand body. Suction may be created by use of a high velocity jet 49 in conduit 44.
The pouring of molten metal can be carried out at the third station and as the molten metal is introduced to the mold, the pattern is destroyed and the mold cavity is filled. Gas evolved by the destruction of the porous polystyrene pattern may be drawn off through the sand mass under suction. The carousel is indexed to a fourth station where the casting is permitted to cool, solidify. Upon advance of the carousel to a fifth station, tne cast body may be removed from the sand mass. In this station, the compressed air may be again supplied to the chamber 42 beneath the floor 41 to fluidize and loosen the sand to enable the cast bodies and frame to be drawn outward without effort. Finally, the carousel may be indexed to a sixth position where the flask is tilted and the sand medium is withdrawn.
.
,
Cavityless molding performed with consumable patterns have several distinct advantages, the chief of which is that the shape to be cast may take any configuration. Molding, itself, comprises ramming the sand or other suitable molding material around the pattern, without regard to a parting line or pattern draft. This allows for a considerable decrease in the cost of molding, particularly for parts where a single casting is required from a given pattern.
Typically, the expendable pattern may be made from an expanded plastic material, such as expanded polystyrene beads or polyethylene which, as is well known, is porous because it contains air voids in the expanded condition. The material is light weight, economical and easy to form into any desired shape. This pattern material is capable of being volatilized or burned, particularly in the absence of oxygen without appreci-able residue remaining. The method of casting conventionally employed by those skilled in the art, is to utilize the molten charge for combusting and destroying the pattern. Molten metal poured into a mold containing a polystyrene pattern consumes the pattern, fills the resultant cavity with molten metal, which later solidifies, leaving a casting having the exact contour of the original pattern.
This mode of casting has worked admirably well for parts which are relatively open and can be freely filled with sand during flask filling operations. That is to say, success has been achieved to date only with patterns that, when set with-in a flask, permit dry unbonded sand to be easily introduced and which will occupy all voids within and without the patterns.
~owever, when a multiple number of castings are attempted to i~, . :~ . .
1~)4~81D
be cast within a single flask and particularly from a common sprue, the feasibility of sand filling is considerably reduced.
In addition, when the parts to be cast are not necessarily of a simple type, but have small openings leading to cored parts which will not lend themselves to free sand filling, the concept of cavityless casting is hampered. One suggestion, according to this invention to overcome these problems, is to separately pre-fi11 the polystyrene patterns with loose unbonded sand and close the polystyrene pattern in some fashion to assure the retention of the closed parts. These relatively heavy filled parts must be stabilized in some manner during overall flask filling. Proper alignment of parts relative to each other, as well as to the placement of sprues and risers, is extremely important if efficiency in the casting process is to be maintained.
Accordingly, there is a need for a method which will allow complex and intricate polystyrene patterns to be used in multiple numbers ~ithin a single flask and which method lens itself to a high speed molding operation; the method may wor~
with conventional sand filling mechanisms, such as sand slingers or deep pouring spouts.
In accordance with one aspect of the present invention, there is provided an apparatus for making multiple castings from a single pouring thro~gh a common sprue in a body of sand, the apparatus comprising: (a) a plurality of consumable foam type patterns which are combustible substantially without residue on subjection to a molten casting chaxge, each of the pattexns having at least one-ear effective to serve as a stabilizer, (b) a rigid stabilizing frame supported against movement, the frame having at least one finger for each of the patterns, each finger providing a support upon which the ear of one of the patterns may be journalled, (c) independent sprue means for con-.~
~45'781) ducting a molten metallic charge to the combustible pattern forconsummation, and (d) means to prevent consummation of the frame during introduction of the molten charge. .
In accordance with another aspect of the present :
invention, there is provided a method for fabricating a plurality of castings from a single pouring through a common sprue in a body of sand, the method comprising: (a) preparing a skeleton stabilizing frame effective to be easily inserted into a fluid-ized sand medium, the frame having a plurality of fingers extend-ing inwardly thereof in a number of common planes generally equally spaced apart, (b) preparing a plurality of consumable foam patterns of the type which is combustible substantially without residue on subjection to a molten casting charge, ~
each pattern being provided with a plurality of foam ears extend- ~ .
ing generally away from the pattern to lay in one of the horizon- .
tal planes defined by the fingers of the frame, the patterns being joined together by a consumable sprue effective to be com- . .
busted without residue by the molten charge for defining a ;
channel to feed the patterns, (c) filling the flask with a body 20 of dry, loose unbonded sand, the sand being introduced to the flask by means effective to fluidly locate the sand progressively from the bottom upwardly through the flask, (d) pouring molten metal into the consumable sprue and pattern for combusting the foam material to occupy the void left by the foam, (e) stripping the patterns from the frame and fingers and from the sand, and then breaking off the cast ears from the casting, and ~f) re-installing the frame in a stripped flask and repeating steps (b) through ~e).
The present invention, therefore, provides a method and apparatus which will permit the casting of a plurality of complex parts or simple parts having small openings, within a .
.... .
~L~45'7~
single flask requiring precise alignment with appropriate sprues and risers by employing cavityless casting in which the pattern is consumed by contact with molten metal.
One of the key problems to be overcome by this in-vention is to permit the use of a multiple number of relatively complex shaped or narrowly cored consumable patterns to be used in a high production Fasting line.
The use of consumable patterns is relatively well known in the art. This known technique has had its greatest demonstrated feasibility in connection with open parts which will fill relative-ly easy with sand during flask filling. However, when a number of relatively complex parts are utilized or where openings in the outer configuration will not fill easily with sand, special measures must be undertaken particularly with respect to the necessity for special alignment and stabilization. Parts such as manifold intakes or heaters for cooling systems, hub-type rotors or disc brake castings, all are of complex configuration which will not fill easily with sand. Simple parts having small cored openin~s may comprise exhaust manifolds, water pumps, un-usually designed hollow section crank shafts, transmission oilpumps and disc brake calipers.
To overcome these problems, in the present invention consumable patterns are hung on a fixture which cooperates with air fluidization of mold sand or with special sand pouring spouts to facilitate proper flask filling.
The invention is described further, by way of illustration, with reference to the accompanying drawings, in which:
Figure 1 is an overall elevational view of a mechanism upon-~hich one or more flasks may be mounted for appropriate sand compacting and filling;
. .
:1~4578~
Figure 2 is an enlarged sectional view of a portion of Figure 1 showing the arrangement of the pattern stabilizing means within the flask;
Figure 3 is a greatly enlarged perspective view of the stabilizing means and patterns and consumable patterns mounted thereon; and Figure 4 is a highly enlarged exploded view o a portion of the pattern and stabilizing means of Figure 3.
Referring now to the drawings, consumable patterns 10 are provided with at least one preformed consumable ear 11 typically extending outwardly from one side wall 12 of the ;
pattern 10. Preferably, at least three of such ears 11 extend outwardly in equi-circumferentially spaced arrangement about the ~ -side wall of the pattern to lay in a common plane. Each of the ears is provided with an opening 13 to receive stabilizing means 14, the latter being re-useable in subsequent cycles of the ;
casting method. Each of the ears is provided with an annular groove 15 or recess at the juncture with the pattern wall 12 so that a weakness line is created. After the metal casting solidifies and replaces the consumable pattern, the metallic ear may be easily struck and removed from the completed part.
The stabilizing means 14 comprises a rigid stabilizing frame 15, which is preferably constructed of tubular heat resistant steel. The frame has an annular base 15a adapted to seat in a secure position on a horizontal wall of the molding flask. The frame has uprights 15b along at least two sides thereoE which connect with an upper annular ring 15c. At spaced elevations along the u~rights, fingers 16 extend inwardly toward the inner region of the frame wherein the patterns are hung.
Each finger has an upright pin 17 at its inner extremity effective to extend through the opening 13 in a mating ear of the pattern.
~,, , ' ' .
~ - 5 -~457~
Means 18 is provided to prevent the transfer of heat between the molten charge (displacing the pattern 10) and the ; supvorting or stabilizing frame 14. To this end, one mode may .
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.
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- 5a -~j, .
~ ,~
.~ ~ ..
S7l~
comprise the use oE an annular ceramic insert 19 which is preiormed into the polystyrene ear; the insert may have a central opening 20 commensurate in size and shape to receive one of the pins 17 of said stabilizing frame. An annular groove 21 in the side wall l9a of the insert assures a good - interlock with the ear.
Another mode may comprise the use of a narrow gauge in the connection between the ear and frame; an extremely narrow or wire-like restriction can be provided in pin 17 as a substi~u~e for the separating ceramic insert 19. According-ly when the molten charge is applied, the narrow gauge of the supporting finger prevents undue transfer of heat there-along and can be easily replaced with low cost replacement for a subse~uent molding operation.
A preferred method mode would comprise:
(A) Prepare a skeleton stabilizing frame effective to be seated on a horizontal plane within a mol~ing flask; the frame should have a plurality of fingers extending inwardly of the frame to support a body in spaced vertical orientation, (B~ Prepare consumable foam-type patterns having configurations not easily filled internally with sand and may have cored parts. Each pattern should be prepared with a plurality of ears extending outwardly ln circumferentially spaced arrangement about the side walls of said patterns so as to mate with the fingers of said frame and be supported in a stabilizing manner, (C) Prepare a common sprue and risers for said consumable pattern, (D) Insert said supported stabilized patterns into a flask having sufficient space about the frame to introduce ~' .
- 6 - ~
~4S78C) sand to the bottom thereof; fluidize the sand by air pressure to assist in placement of the assembly of patterns, compact the introduced sand by vacuum or vibration, (E) Introduce molten metal to said sprue and patterns to displace same and form a solidified casting having ears as defined by said patterns, and (F) Strip the patterns from said sand and remove said frame therefrom for reuse of said sand. Re-install said frame work with a new set of patterns in a similar flask devoid of sand. Tap the ears of said castings for being strippe~ therefrom.
The consumable pattern is adapted to be displaced in a mold by the poured casting charge; it is converted sub-stantially ln its entirety to a gaseous state and permitted to escape from the mold through suitable vent provisions. To this end, any suitable material which is readily combustible substantially without residue upon subjec~ion to a molten casting charge can be used as pattern material. It should be sufficiently rigid to safely withstand the stresses induced by the customary ramming of molding sand thereagainst. A
suitable material for these purposes is an expanded poly-styrene. It has been found that polystyrene is well adapted for the intended purposes if it is expanded to a density sub-stantially but not more than 2 lbs./ft.2. If this material has substantially greater density, it will not readily burn ;~
away on sub jection to a molten casting charge. On the other hand there is a limit to the expansion of this material in order to be sultable for forms of this type, for if the density becomes too low, it may lack adequate strength to withstand ordinary molding pressures and other stresses, at ~4S'780 least in parts, to spoil a mold. It is comparat.ively easy to make a form of this material for the production of a casting of most any configuration. For the sake of illustration, the pattern is shown as a simple block having a plurality of ears extending from a continuous side wall thereof, the ears being circumferentially spaced thereabout.
A typical preferred apparatus useful in carrying out step (D) of the preferred method is illustrated in Figures 1 and 2. A carousel 30 is employed having a turn table 31 or disc mounted at its center upon a tubular support 32 which in turn is stabilized on a base plate 33. A
plurality of sand flasks 34 (for example, as many as eight) ;
may be carried at various stations about the periphery of the turn table. Each of the flasks 34 is mounted.on a pair of trunnions 35 at spaced locations along the turn table, the trunnions pexmitting the flask to be tilted for emptying of sand upon completion of the casting mode. To enable the carousel to be automated, an electric motor 36 and trans-mission 3 8 may be employed to drive the main bearing ring 37 of the turn table; another electric motor 39 may be employed to rotate the flasks about their trunnlons 34, the drive being through chains 40. :
. Each of the flasks 34 may be of one piece or non-separable construction in whi~h the mold is destroyed upon removal of the cast object and the pattern is destroyed ~ ,.
during the casting process. Each flask is preferably provided .~ :
with an air permeable wall 41 over at least the floor of the flask interior, space, the air permeable plate or wall being preferably formed of a sintered metal ~such as iron~. The .
permeable wall divldes the interior of the flask into a : -, . - . . ~ , .. . . . .. . . .
4S'~80 casting chamber 42 and a gas plenum chamber 43, the latter selectively comm~nicating by way of suitable ducts 44 with a suction source at one side and selectively communicating with a source 45 of fluid under pressure from the opposite side thereof. The communications may be respectively provide~ by the inlet duct 46 passing throuyh the right hand trunnion and the communication of suction provided by a conduit 44 having a high velocity jet 44 connected to a source of pressure in the interior of the support 32 of the carousel. The interior of the support may act as a com-pressed air storage tank or accumulator fed by a pump 50.
; In operation, the emptied upwardly oriented flask is halted at a first station of the carousel~ Sand (moldlng medium) of the dry unbonded type is introduced in a pre-determined quantity to the interior of the flask. This may be preferably accomplished by use of a deep penetrating pouring spout which would effectively fill chamber 42 in a -~
manner as water would fill a vessel. While sand is being introduced, air is fed through passage 46 from source 45 to the chambers 43 which will effectively fluidize sand in chamber 42 thereby enabling the frame 14 and patterns 10 to be inserted into the fiask. The fluidization of the sand is carried such that the motion of the particles is slightly turbulant and yet no substantial tendency to drive the particles out o the mold is maintained. Because of the fluidization of the molding medium, the patterns and frame can be easily seated in the molding chamber 42 without noticeable resistance.
The carousel may then be indexed to the next position where the compressed air is interrupted and _ g _ 1~5~
- vibrators 4~ are set in motion to compact the sand mass around the pattern. An air impermeable membrane 48 such as aluminum foil or polyester film is placed across the top of the sand body in the flask and may have an aperture for a casting funnel. The carousel is then indexed to a third position where suction is applied through the passage 44 and thus a differential pressure is applied between the membrane 48 and the floor 41 of the sand body. Suction may be created by use of a high velocity jet 49 in conduit 44.
The pouring of molten metal can be carried out at the third station and as the molten metal is introduced to the mold, the pattern is destroyed and the mold cavity is filled. Gas evolved by the destruction of the porous polystyrene pattern may be drawn off through the sand mass under suction. The carousel is indexed to a fourth station where the casting is permitted to cool, solidify. Upon advance of the carousel to a fifth station, tne cast body may be removed from the sand mass. In this station, the compressed air may be again supplied to the chamber 42 beneath the floor 41 to fluidize and loosen the sand to enable the cast bodies and frame to be drawn outward without effort. Finally, the carousel may be indexed to a sixth position where the flask is tilted and the sand medium is withdrawn.
.
,
Claims (12)
1. An apparatus for making multiple castings from a single pouring through a common sprue in a body of sand, the apparatus comprising:
(a) a plurality of consumable foam type patterns which are combustible substantially without residue on subjection to a molten casting charge, each of said patterns having at least one ear effective to serve as a stabilizer, (b) a rigid stabilizing frame supported against move-ment, said frame having at least one finger for each of said patterns, each finger providing a support upon which said ear of one of said patterns may be journalled, (c) independent sprue means for conducting a molten metallic charge to said combustible pattern for consummation, and (d) means to prevent consummation of said frame during introduction of said molten charge.
(a) a plurality of consumable foam type patterns which are combustible substantially without residue on subjection to a molten casting charge, each of said patterns having at least one ear effective to serve as a stabilizer, (b) a rigid stabilizing frame supported against move-ment, said frame having at least one finger for each of said patterns, each finger providing a support upon which said ear of one of said patterns may be journalled, (c) independent sprue means for conducting a molten metallic charge to said combustible pattern for consummation, and (d) means to prevent consummation of said frame during introduction of said molten charge.
2. The apparatus of Claim 1, wherein said means to prevent consummation of said frame comprises a ceramic annular insert carried by said consumable foam pattern in the ear thereof, said insert having a central opening of a size effective to fit snugly about the finger of said stabilizing frame.
3. The apparatus of Claim 1, wherein said means to prevent consummation of said stabilizing frame comprises a narrow or wire like restriction in said finger so that the molten charge coming in contact therewith is ineffective to transmit damageable heat content to the remainder of said stabilizing frame.
4. The apparatus of Claim 1, wherein the patterns each have at least three ears extending away from said pattern in a horizon?al plane and spaced apart about said pattern to provide a secure horizontal support for said pattern, said stabilizing frame having a finger for each of said ears effective to secure said ears in said predetermined horizontal plane.
5. The apparatus of Claim 4, wherein the horizontal planes for each of said patterns are spaced apart generally equally with the patterns generally vertically aligned.
6. The apparatus of Claim 1, wherein said ears have an annular recess at the joint between said principal pattern and the ear whereby upon casting, the resulting casting ear may be easily severed by impact.
7. The apparatus of Claim 1, wherein said frame is formed of tubular heat-resistant steel, and said ear has a ceramic insert disposed to surround said finger for preventing transfer of heat therebetween.
8. A method for fabricating a plurality of castings from a single pouring through a common sprue in a body of sand, the method comprising:
(a) preparing a skeleton stabilizing frame effective to be easily inserted into a fluidized sand medium, said frame having a plurality of fingers extending inwardly thereof in a number of common planes generally equally spaced apart, (b) preparing a plurality of consumable foam patterns of the type which is combustible substantially without residue on subjection to a molten casting charge, each said pattern being provided with a plurality of foam ears extending generally away from said pattern to lay in one of said horizontal planes de-fined by the fingers of said frame, said patterns being joined together by a consumable sprue effective to be combusted without residue by said molten charge for defining a channel to feed said patterns, (c) filling said flask with a body of dry, loose unbonded sand, said sand being introduced to said flask by means effective to fluidly locate said sand progressively from the bottom upwardly through said flask, (d) pouring molten metal into said consumable sprue and pattern for combusting said foam material to occupy the void left by said foam, (e) stripping said patterns from said frame and fingers and from said sand, and then breaking off cast ears from said casting, and (f) re-installing said frame in a stripped flask and repeating steps (b) through (e).
(a) preparing a skeleton stabilizing frame effective to be easily inserted into a fluidized sand medium, said frame having a plurality of fingers extending inwardly thereof in a number of common planes generally equally spaced apart, (b) preparing a plurality of consumable foam patterns of the type which is combustible substantially without residue on subjection to a molten casting charge, each said pattern being provided with a plurality of foam ears extending generally away from said pattern to lay in one of said horizontal planes de-fined by the fingers of said frame, said patterns being joined together by a consumable sprue effective to be combusted without residue by said molten charge for defining a channel to feed said patterns, (c) filling said flask with a body of dry, loose unbonded sand, said sand being introduced to said flask by means effective to fluidly locate said sand progressively from the bottom upwardly through said flask, (d) pouring molten metal into said consumable sprue and pattern for combusting said foam material to occupy the void left by said foam, (e) stripping said patterns from said frame and fingers and from said sand, and then breaking off cast ears from said casting, and (f) re-installing said frame in a stripped flask and repeating steps (b) through (e).
9. The method of Claim 8, wherein said patterns are aligned and supported on said frame prior to assembly of said frame within said flask whereby damage due to handling of said patterns is prevented as well as distortion while packing with sand.
10. The method of Claim 8, wherein a pouring spout is utilized to direct filling sand first to the lower most regions of said flask.
11. The method of Claim 8, wherein air pressure is utilized to fluidize said sand while installing said frame and attached patterns in said flask.
12. The method of Claim 11, wherein vacuum is utilized to compact said fluidized sand after the patterns are installed in the flask.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US430972A US3868986A (en) | 1974-01-04 | 1974-01-04 | Pattern alignment means for use with lost foam molding process |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1045780A true CA1045780A (en) | 1979-01-09 |
Family
ID=23709887
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA216,626A Expired CA1045780A (en) | 1974-01-04 | 1974-12-16 | Pattern alignment or distortion preventing concept for use with lost foam molding process |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US3868986A (en) |
| CA (1) | CA1045780A (en) |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2519463A1 (en) * | 1975-05-02 | 1976-11-11 | Gruenzweig Hartmann Glasfaser | CASTING FORM AND METHOD FOR MANUFACTURING CASTINGS |
| US4003423A (en) * | 1975-06-09 | 1977-01-18 | Precision Metalsmiths, Inc. | Methods and means for making dental castings and the like |
| US4043379A (en) * | 1976-04-12 | 1977-08-23 | Trw Inc. | Method of making a mold |
| FR2540761A1 (en) * | 1983-02-15 | 1984-08-17 | Citroen Sa | INSTALLATION FOR MOLDING IN LOST MODEL |
| US4609028A (en) * | 1984-06-20 | 1986-09-02 | Outboard Marine Corporation | Evaporative pattern assembly for use in sand casting |
| US4724889A (en) * | 1987-04-27 | 1988-02-16 | Ford Motor Company | Degating technique for clustered castings made by ECP |
| FR2688720B1 (en) * | 1992-03-17 | 1994-06-17 | Pont A Mousson | LOST MODEL MOLDING PROCESS AND INSTALLATION AND USE OF THE INSTALLATION. |
| DE69920652T2 (en) * | 1999-02-26 | 2005-02-10 | Fata Aluminium S.P.A. | Apparatus for filling containers in a lost foam casting system |
| US6293968B1 (en) | 1999-09-02 | 2001-09-25 | Syde A. Taheri | Inflatable intraluminal vascular stent |
| US8240490B2 (en) * | 2006-01-11 | 2012-08-14 | Mohammad Ghassem Malekmadani | Anti-vibration rack, mount and feet for computer servers |
| US8025163B2 (en) * | 2008-12-22 | 2011-09-27 | Metal Masters Foodservice Equipment Co., Inc. | Wall mounted shelving |
| US10159339B1 (en) * | 2017-02-02 | 2018-12-25 | Metal Masters Foodservice Equipment Co., Inc. | Shelving bracket |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3374824A (en) * | 1965-07-13 | 1968-03-26 | Thomas E. Snelling | Displacement process for the casting of metals |
| CH502861A (en) * | 1968-02-03 | 1971-02-15 | Gruenzweig & Hartmann | Method and device for the production of castings |
-
1974
- 1974-01-04 US US430972A patent/US3868986A/en not_active Expired - Lifetime
- 1974-12-16 CA CA216,626A patent/CA1045780A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| US3868986A (en) | 1975-03-04 |
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