CA1049744A - Dry sand core for use with lost foam molding process - Google Patents
Dry sand core for use with lost foam molding processInfo
- Publication number
- CA1049744A CA1049744A CA217,434A CA217434A CA1049744A CA 1049744 A CA1049744 A CA 1049744A CA 217434 A CA217434 A CA 217434A CA 1049744 A CA1049744 A CA 1049744A
- Authority
- CA
- Canada
- Prior art keywords
- pattern
- sand
- filling
- molten metal
- cavity
- 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
- 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
- B22C7/026—Patterns made from expanded plastic materials by assembling preformed parts
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Casting Devices For Molds (AREA)
Abstract
DRY SAND CORE FOR USE WITH LOST
FOAM MOLDING PROCESS
ABSTRACT OF THE DISCLOSURE
A method of extending the cavityless molding technique to intricately cored objects to be cast is disclosed. Expanded consumable patterns are prepared in distinct parts capable of being locked together to form a completed assembly by use of integrally formed male and female elements. Openings to the interior of the pattern assembly are closed by pyrolyzible thin materials, such as tape, and one remaining passage is made available for filling the interior of the pattern with sand utilizing the pattern as a core box. The cored pattern is then located in a conventional flask or suitable holding means, filled with molding sand, followed by conventional casting techniques.
FOAM MOLDING PROCESS
ABSTRACT OF THE DISCLOSURE
A method of extending the cavityless molding technique to intricately cored objects to be cast is disclosed. Expanded consumable patterns are prepared in distinct parts capable of being locked together to form a completed assembly by use of integrally formed male and female elements. Openings to the interior of the pattern assembly are closed by pyrolyzible thin materials, such as tape, and one remaining passage is made available for filling the interior of the pattern with sand utilizing the pattern as a core box. The cored pattern is then located in a conventional flask or suitable holding means, filled with molding sand, followed by conventional casting techniques.
Description
The present invention relates to cavityless molding.
Cavityless molding is a method whereby consumable patterns, such as polystyrene foam plastic, are coated with a permeable refractory wash and then embedded in foundry sand to be eventually replaced by molten metal. The molten metal vaporizes the foam-type pattern and a metal duplicate of the pattern is the result. The cavityless feature is derived from the fact that the pattern is not removed from the mold, but rather it is replaced by the molten metal so that the mold is always full of material at any one time. In all other casting processes, a cavity must be provided before the metal can be poured. An important feature of the cavityless method is the fact that unbonded sand can be used which opens up an entirely new field for foundry development.
To this date, the cavityless method has shown good results when concerned only with patterns of a generally uncored configuration or of a cored configuration which is simple and has relatively large openings so that normal sand filling about the pattern will simultaneously fill the interior spaces of the pattern. Little attempt has been made to provide patterns in other than a single unitary form. In those instances where the prior art has attempted to provide a pattern with an interior void, to be filled with sand, pivotal problems of ade~uate compaction of the filled material has arisen.
The present invention is directed to an improved cavity-less casting method whereby intricatPly cored parts requiring special interior configurations may be formed. ~ pattern with a remote internal cavity is first prepared from material which is combustible substantially without residue upon contact with molten metal and a plurality of openings passing through the walls of the pattern communicating with the cavity are closed
Cavityless molding is a method whereby consumable patterns, such as polystyrene foam plastic, are coated with a permeable refractory wash and then embedded in foundry sand to be eventually replaced by molten metal. The molten metal vaporizes the foam-type pattern and a metal duplicate of the pattern is the result. The cavityless feature is derived from the fact that the pattern is not removed from the mold, but rather it is replaced by the molten metal so that the mold is always full of material at any one time. In all other casting processes, a cavity must be provided before the metal can be poured. An important feature of the cavityless method is the fact that unbonded sand can be used which opens up an entirely new field for foundry development.
To this date, the cavityless method has shown good results when concerned only with patterns of a generally uncored configuration or of a cored configuration which is simple and has relatively large openings so that normal sand filling about the pattern will simultaneously fill the interior spaces of the pattern. Little attempt has been made to provide patterns in other than a single unitary form. In those instances where the prior art has attempted to provide a pattern with an interior void, to be filled with sand, pivotal problems of ade~uate compaction of the filled material has arisen.
The present invention is directed to an improved cavity-less casting method whereby intricatPly cored parts requiring special interior configurations may be formed. ~ pattern with a remote internal cavity is first prepared from material which is combustible substantially without residue upon contact with molten metal and a plurality of openings passing through the walls of the pattern communicating with the cavity are closed
- 2 - ~
.:
, . . . :
. . . :
10497~
off except for one. The pattern is filled with unbonded sand through the one opening and compacted to ensure that all voids are occupied by densified sand. After positioning the pattern in a molding apparatus, molten metal is introduced to the pattern to displace the combustible material.
The invention is described further, by way of illustration, with reference to the accompanying drawings, in which:
Figure 1 is a central sectional elevational view of a consumable type pattern part in the unassembled condition and having separately prepared coring sand therein, the pattern assembly being ready for insertion into a molding flask;
Figure 2 is an isometric view of the part of Figure 1 mated to a complimentary part to form a pattern asembly;
Figure 3 is a central sectional elevational view of another pattern part illustrating a different embodiment; the pattern part has at least one passage therein pre-filled with sand;
Figure 4 is an isometric view of the part of Figure
.:
, . . . :
. . . :
10497~
off except for one. The pattern is filled with unbonded sand through the one opening and compacted to ensure that all voids are occupied by densified sand. After positioning the pattern in a molding apparatus, molten metal is introduced to the pattern to displace the combustible material.
The invention is described further, by way of illustration, with reference to the accompanying drawings, in which:
Figure 1 is a central sectional elevational view of a consumable type pattern part in the unassembled condition and having separately prepared coring sand therein, the pattern assembly being ready for insertion into a molding flask;
Figure 2 is an isometric view of the part of Figure 1 mated to a complimentary part to form a pattern asembly;
Figure 3 is a central sectional elevational view of another pattern part illustrating a different embodiment; the pattern part has at least one passage therein pre-filled with sand;
Figure 4 is an isometric view of the part of Figure
3 mated to a complimentary part to form a completed pattern assembly; and Figure 5 is yet still another pattern embodiment shown as a central sectional elevational view.
The cavityless casting method has been applied to the production of castings which either do not have Lnternal passages or which have internal passages largely opened or exposed which will easily ~ill with dry unbonded sand during the flask filling and compacting process.
The purpose of this invention is to provide a unique approach to pattern preparation of the consumable type wherein the pattern assembly may constitute the core box for the coring ,, 10497~4 sand. The pattern may be simultaneously filled with sand to define such cored body at the same time the pattern assembly is enveloped by sand within a flask. Alternatively, the internal passages of the patterns may be filled with dry unbonded ~and, compacted sufficiently to achieve good castings, all prior to the introduction of the filled pattern assembly into the flask or molding be~.
As shown in Figure 1, a transmission case pattern 10 is ilIustrated which has a large internal cavity inter-connected with smaller cavities 12 and 13 by openings 14 and 15 respectively. Cavity 11 has a wide mouth lla open-ing the upper wall of the case and has opening 16 communicat- -ing with the cavity 11 and passing through the bottom wall 17 of the case. The smaller cavities are shaped as cones 12a and 13a and each have a smaller cylindrical opening 18 and 19 passing through a hub 20 and 21 respectively. The pattern assembly will be defined by pattern parts which here are conveniently split across a parting line conforming to the section plane of Figure 2.
A preferred method of forming the metallic casting of Figure 2 by way of the pattern of Figure 1 would comprise the following:
(a) Prepare a plurality of consumable pattern parts (such as lOa) from material which is substantially combustible without residue upon contact with molten metal.
A preferred material is expanded polystyrene beads. The parts should cooperatively define at least one cavity (such -as 11) within a single pattern 10 when assembled together.
Male and female means 23 and 24 are respecti~ely located on said parts, formed integrally of the same material, and are useful in promoting a press lock therebetween when the parts .
.
.. :
are mated, (b) Assemble said parts (such as lOa and lOb) together with said male and female means interlocked to define said predetermined pattern and cavity therein; restrict all the openings through said pattern walls (such as 19, 18 and 16) except for one passage lla. A rigid refractory plug 25 may be used to close openings 18 and 19; a thin membrane 26, such as impregnated paper tape, may be used to close opening 16, (c) Fill said pattern with sand through said passage lla, while agitating said pattern to compact the filled sand therein to a density of at least 50 ~ 70% and to add greater strength to the pattern assembly, (d) Adjust the assembled pattern to return to its original predetermined configuration if distorted by the filling operation, and (e) Locate said filled pattern within a molding apparatus, such as flask 27, and introduce sand about the exterior thereof. Sprues 28 and risers 29 are located in appropriate alignment in said flask and are arranged to provide for bottom pouring or filling of the consumable pattern. The gating of said system is designed to limit the rush of molten metal to the pattern so as to prevent a torrent of metal within the pattern which might wash away some of the cored sand.
Alternatively, the pattern assembly may be filled simultaneously with the filling of the flask. To facilitate this, a special internal passage or pouring spout may be used to deliver the free-flowing dry unbonded sand to the interior of the pattern. Finally subject said sprues and consumable pattern to the molten charge to displace the same . . .
' ~049744 for defining a completed casting.
Other alternative embodiments may be designed in as many pieces as required to define internal passage shapes.
The pattern pieces would be assembled into a unit pattern using snap together joints or press-fit type male and female elements. The complete pattern assembly will be filled with dry molding sand and, depending on the shape and intricacies of the internal passages, a simultaneous vibration and/or light vacuum would be applied. To facilitate vacuum com-paction, a thin membrane may be placed across each exposedinterior of the separated pattern part; the membrane should be of the consumable type. Then suction can be applied through one of the openings to allow exterior pressure on the membrane to compact the sand in the part. The sand or molding medium contained within the pattern cavity serves to rigidify the assembly during subsequent movement and handling in or out of the flask. Containment can be provided by a removable cover, such as tape or snap-on cover or in special cases, by a rigid refractory based plug which is driven into the opening and extends beyond the pattern itself. The type or degree of containment re-quired would depend on the configuration of the part and the degree of exposure to the final flask filling and com-pacting. Should the filling or drive plug insertion cause distortion, the initial shape of the foam pattern may be adjusted to compensate. The pre-filled pattern ha= in-creased rigidity and particularly in the case of long slender patterns. Thus the potential distortion due to sand compaction in the filled flask is decreased.
In Figures 3 and 4, another embodiment is illustrated wherein an auxiliary intricate cavity 30 must 104974~
be filled as a core. Opening 31 through the wall 32 of the pattern part 33 is closed by a membrane 34. Opening 36 is retained open for filling of cavity 30. The other opening 35 in the part is so large that it can be filled by sand during normal flask filling in accordance with prior art techniques. The pattern has complimentary part 37 which is lockingly mated at parting line 38 by means of tape 39.
Still another embodiment is shown in section in Figure 5. Here part 40 has an intricate cavity 41 in communication with three passages or openings 42, 43 and 45. Opening 43 extends through the bottom of the part 40 and is closed by a rigid refractory plug 46 driven into the opening 43. Opening 45 is closed by a thin consumable membrane 47. Opening 42 is retained open for filling of cavity 41.
The cavityless casting method has been applied to the production of castings which either do not have Lnternal passages or which have internal passages largely opened or exposed which will easily ~ill with dry unbonded sand during the flask filling and compacting process.
The purpose of this invention is to provide a unique approach to pattern preparation of the consumable type wherein the pattern assembly may constitute the core box for the coring ,, 10497~4 sand. The pattern may be simultaneously filled with sand to define such cored body at the same time the pattern assembly is enveloped by sand within a flask. Alternatively, the internal passages of the patterns may be filled with dry unbonded ~and, compacted sufficiently to achieve good castings, all prior to the introduction of the filled pattern assembly into the flask or molding be~.
As shown in Figure 1, a transmission case pattern 10 is ilIustrated which has a large internal cavity inter-connected with smaller cavities 12 and 13 by openings 14 and 15 respectively. Cavity 11 has a wide mouth lla open-ing the upper wall of the case and has opening 16 communicat- -ing with the cavity 11 and passing through the bottom wall 17 of the case. The smaller cavities are shaped as cones 12a and 13a and each have a smaller cylindrical opening 18 and 19 passing through a hub 20 and 21 respectively. The pattern assembly will be defined by pattern parts which here are conveniently split across a parting line conforming to the section plane of Figure 2.
A preferred method of forming the metallic casting of Figure 2 by way of the pattern of Figure 1 would comprise the following:
(a) Prepare a plurality of consumable pattern parts (such as lOa) from material which is substantially combustible without residue upon contact with molten metal.
A preferred material is expanded polystyrene beads. The parts should cooperatively define at least one cavity (such -as 11) within a single pattern 10 when assembled together.
Male and female means 23 and 24 are respecti~ely located on said parts, formed integrally of the same material, and are useful in promoting a press lock therebetween when the parts .
.
.. :
are mated, (b) Assemble said parts (such as lOa and lOb) together with said male and female means interlocked to define said predetermined pattern and cavity therein; restrict all the openings through said pattern walls (such as 19, 18 and 16) except for one passage lla. A rigid refractory plug 25 may be used to close openings 18 and 19; a thin membrane 26, such as impregnated paper tape, may be used to close opening 16, (c) Fill said pattern with sand through said passage lla, while agitating said pattern to compact the filled sand therein to a density of at least 50 ~ 70% and to add greater strength to the pattern assembly, (d) Adjust the assembled pattern to return to its original predetermined configuration if distorted by the filling operation, and (e) Locate said filled pattern within a molding apparatus, such as flask 27, and introduce sand about the exterior thereof. Sprues 28 and risers 29 are located in appropriate alignment in said flask and are arranged to provide for bottom pouring or filling of the consumable pattern. The gating of said system is designed to limit the rush of molten metal to the pattern so as to prevent a torrent of metal within the pattern which might wash away some of the cored sand.
Alternatively, the pattern assembly may be filled simultaneously with the filling of the flask. To facilitate this, a special internal passage or pouring spout may be used to deliver the free-flowing dry unbonded sand to the interior of the pattern. Finally subject said sprues and consumable pattern to the molten charge to displace the same . . .
' ~049744 for defining a completed casting.
Other alternative embodiments may be designed in as many pieces as required to define internal passage shapes.
The pattern pieces would be assembled into a unit pattern using snap together joints or press-fit type male and female elements. The complete pattern assembly will be filled with dry molding sand and, depending on the shape and intricacies of the internal passages, a simultaneous vibration and/or light vacuum would be applied. To facilitate vacuum com-paction, a thin membrane may be placed across each exposedinterior of the separated pattern part; the membrane should be of the consumable type. Then suction can be applied through one of the openings to allow exterior pressure on the membrane to compact the sand in the part. The sand or molding medium contained within the pattern cavity serves to rigidify the assembly during subsequent movement and handling in or out of the flask. Containment can be provided by a removable cover, such as tape or snap-on cover or in special cases, by a rigid refractory based plug which is driven into the opening and extends beyond the pattern itself. The type or degree of containment re-quired would depend on the configuration of the part and the degree of exposure to the final flask filling and com-pacting. Should the filling or drive plug insertion cause distortion, the initial shape of the foam pattern may be adjusted to compensate. The pre-filled pattern ha= in-creased rigidity and particularly in the case of long slender patterns. Thus the potential distortion due to sand compaction in the filled flask is decreased.
In Figures 3 and 4, another embodiment is illustrated wherein an auxiliary intricate cavity 30 must 104974~
be filled as a core. Opening 31 through the wall 32 of the pattern part 33 is closed by a membrane 34. Opening 36 is retained open for filling of cavity 30. The other opening 35 in the part is so large that it can be filled by sand during normal flask filling in accordance with prior art techniques. The pattern has complimentary part 37 which is lockingly mated at parting line 38 by means of tape 39.
Still another embodiment is shown in section in Figure 5. Here part 40 has an intricate cavity 41 in communication with three passages or openings 42, 43 and 45. Opening 43 extends through the bottom of the part 40 and is closed by a rigid refractory plug 46 driven into the opening 43. Opening 45 is closed by a thin consumable membrane 47. Opening 42 is retained open for filling of cavity 41.
Claims (10)
1. A method of forming metallic castings, comprising:
(a) preparing a pattern from material which is combust-ible substantially without residue upon contact with molten metal, defining said pattern with a remote internal cavity and a plurality of openings passing through the walls of said pattern to communi-cate with said cavity, (b) closing off all except one of said openings sub-stantially with refractory material either in the rigid form or loose particulate form supported by a thin consumable membrane, (c) locating said pattern in a molding apparatus, (d) filling said pattern with dry unbonded sand through said opening either simultaneously with filling of said apparatus with dry unbonded sand or prior to the filling of said apparatus with dry unbonded sand, compacting said sand both within and about said pattern to achieve a density of at least 50-70%, and (e) introduce molten metal to pattern to displace said material.
(a) preparing a pattern from material which is combust-ible substantially without residue upon contact with molten metal, defining said pattern with a remote internal cavity and a plurality of openings passing through the walls of said pattern to communi-cate with said cavity, (b) closing off all except one of said openings sub-stantially with refractory material either in the rigid form or loose particulate form supported by a thin consumable membrane, (c) locating said pattern in a molding apparatus, (d) filling said pattern with dry unbonded sand through said opening either simultaneously with filling of said apparatus with dry unbonded sand or prior to the filling of said apparatus with dry unbonded sand, compacting said sand both within and about said pattern to achieve a density of at least 50-70%, and (e) introduce molten metal to pattern to displace said material.
2. A method of forming metallic castings, comprising:
(a) preparing a plurality of consumable pattern parts substantially combustible without residue upon contact with molten metal, said parts cooperatively defining at least one cavity within a single pattern when assembled together, male and female means being respectively located on said parts effective to promote a press lock therebetween when mated, said single pattern having a plurality of openings passing through the walls thereof to communicate with said cavity, (b) assembling said parts together with said male and female means interlocked so as to define said predetermined pattern and cavity therein, and restricting all said openings through said pattern except for one passage, (c) filling said pattern with dry unbonded sand through said one passage, compacting said sand to form a core within the pattern while insuring a full filling of all voids therein, (d) adjusting the assembled pattern to return into its original predetermined configuration if distorted by filling, (e) locating said filled pattern within a molding flask, introducing sand about the exterior of said pattern while arranging sprues and risers in appropriate alignment therewith, and (f) subjecting said sprues and pattern to a molten charge to displace said pattern for defining a completed casting.
(a) preparing a plurality of consumable pattern parts substantially combustible without residue upon contact with molten metal, said parts cooperatively defining at least one cavity within a single pattern when assembled together, male and female means being respectively located on said parts effective to promote a press lock therebetween when mated, said single pattern having a plurality of openings passing through the walls thereof to communicate with said cavity, (b) assembling said parts together with said male and female means interlocked so as to define said predetermined pattern and cavity therein, and restricting all said openings through said pattern except for one passage, (c) filling said pattern with dry unbonded sand through said one passage, compacting said sand to form a core within the pattern while insuring a full filling of all voids therein, (d) adjusting the assembled pattern to return into its original predetermined configuration if distorted by filling, (e) locating said filled pattern within a molding flask, introducing sand about the exterior of said pattern while arranging sprues and risers in appropriate alignment therewith, and (f) subjecting said sprues and pattern to a molten charge to displace said pattern for defining a completed casting.
3. The method as in Claim 2, in which said parts for said pattern are defined so as to render access for conveniently shaping the interior thereof and so that all internal surfaces are fully exposed when viewed from the internal side of said parts.
4. The method as in Claim 2, in which said male and female means are each formed from the same material as said pattern parts, all of said parts being constituted of expandable polystyrene having a density no greater than 2 lbs./ft.3.
5. The method as in Claim 2, in which the openings through said pattern except for said limited passage are closed by a thin membrane subject to being consumed upon contact with said molten metal without substantial residue.
6. The method as in Claim 1, in which said thin membrane is comprised of an adhesive paper tape.
7. The method as in Claim 2, in which said gating system defined by the sprues leading to said pattern are sized to prevent a torrent of molten metal consuming said pattern to wash away sand constituting said core.
8. The method as in Claim 2, in which the sand used to fill said pattern is comprised of irregular particles effective to obtain an interlock therebetween with a green strength to sustain said sand body if lifted.
9. The method as in Claim 2, in which said sprue and riser is effective to introduce molten metal to said pattern through the bottom thereof.
10. A method of forming a metallic casting, which comprises:
(a) preparing a pattern from material which is com-bustible substantially without residue upon contact with molten metal, said pattern being defined with a remote internal cavity and a plurality of openings passing through the walls of said pattern to communicate with said cavity, (b) closing off all except one of said openings, (c) filling said pattern with dry unbonded sand through the one opening and compacting the sand, (d) positioning said pattern in a molding apparatus, and (e) introducing molten metal to said pattern to displace said combustible material.
(a) preparing a pattern from material which is com-bustible substantially without residue upon contact with molten metal, said pattern being defined with a remote internal cavity and a plurality of openings passing through the walls of said pattern to communicate with said cavity, (b) closing off all except one of said openings, (c) filling said pattern with dry unbonded sand through the one opening and compacting the sand, (d) positioning said pattern in a molding apparatus, and (e) introducing molten metal to said pattern to displace said combustible material.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US430973A US3889737A (en) | 1974-01-04 | 1974-01-04 | Dry sand core process for use with lost foam molding process |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1049744A true CA1049744A (en) | 1979-03-06 |
Family
ID=23709891
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA217,434A Expired CA1049744A (en) | 1974-01-04 | 1975-01-03 | Dry sand core for use with lost foam molding process |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US3889737A (en) |
| CA (1) | CA1049744A (en) |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1979000795A1 (en) * | 1978-03-20 | 1979-10-18 | Caterpillar Tractor Co | Aperture forming member for gasifiable patterns |
| US4640333A (en) * | 1985-09-05 | 1987-02-03 | Ford Motor Company | Foam pattern assembly for use in evaporative casting process |
| US4736786A (en) * | 1985-12-31 | 1988-04-12 | Deere & Company | Method for improving stength of gasifiable patterns |
| FR2615425B1 (en) * | 1987-05-21 | 1990-11-16 | Peugeot | MODEL FOR LOSS FOAM MOLDING PROCESS |
| GB8804794D0 (en) * | 1988-03-01 | 1988-03-30 | Concentric Pumps Ltd | Pump impeller |
| US5054537A (en) * | 1988-06-03 | 1991-10-08 | Outboard Marine Corporation | Lost foam pattern assembly for V-block engine |
| FR2685230B1 (en) * | 1991-12-24 | 1995-04-28 | Peugeot | CLUSTER ASSEMBLY OF MODELS FOR LOST MODEL MOLDING OF PARTS, AND METHOD OF CLUSTER ASSEMBLY OF SUCH MODELS. |
| CA2087763C (en) * | 1992-02-11 | 2002-07-02 | Jimmy Cochimin | Stator frame for dynamoelectric machine and method for making same |
| GB9820073D0 (en) * | 1998-09-16 | 1998-11-11 | Rover Group | Casting die pattern |
| US6305458B1 (en) | 1999-03-17 | 2001-10-23 | Baker Hughes Incorporated | Lost foam and sand cores stage manufacturing technology |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2148223A (en) * | 1937-06-15 | 1939-02-21 | Edward Amacher | Apparatus for forming seamless milk can covers |
| US2793412A (en) * | 1950-12-15 | 1957-05-28 | Gen Motors Corp | Blade investment casting process |
| US2857641A (en) * | 1955-09-16 | 1958-10-28 | Mercast Corp | Disposable mercury alloy pattern and method of making the same |
| US3259949A (en) * | 1964-01-16 | 1966-07-12 | Meehanite Metal Corp | Casting method |
| US3707029A (en) * | 1970-09-25 | 1972-12-26 | John T Parsons | Superimposed modular construction of vaporizable patterns |
-
1974
- 1974-01-04 US US430973A patent/US3889737A/en not_active Expired - Lifetime
-
1975
- 1975-01-03 CA CA217,434A patent/CA1049744A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| US3889737A (en) | 1975-06-17 |
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