CA1228216A - Bonded sand sprue cup - Google Patents
Bonded sand sprue cupInfo
- Publication number
- CA1228216A CA1228216A CA000483722A CA483722A CA1228216A CA 1228216 A CA1228216 A CA 1228216A CA 000483722 A CA000483722 A CA 000483722A CA 483722 A CA483722 A CA 483722A CA 1228216 A CA1228216 A CA 1228216A
- Authority
- CA
- Canada
- Prior art keywords
- sprue
- cup
- neck portion
- sand
- sprue cup
- 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
- B22C9/08—Features with respect to supply of molten metal, e.g. ingates, circular gates, skim gates
- B22C9/082—Sprues, pouring cups
Abstract
ABSTRACT OF THE INVENTION
A disposable sprue cup for use in a metal casting process using a mold pattern embedded in unbound process sand having a grain size, the disposable sprue cup being made of bonded sand having a grain size substantially equal to the grain size of the process sand and having a binder that breaks down under the heat of resident metal remaining in the cup after the casting process is completed.
A disposable sprue cup for use in a metal casting process using a mold pattern embedded in unbound process sand having a grain size, the disposable sprue cup being made of bonded sand having a grain size substantially equal to the grain size of the process sand and having a binder that breaks down under the heat of resident metal remaining in the cup after the casting process is completed.
Description
~2,~
BOND~D SAND SPRUE CUP
BACKGROUND OF_THE INVENTION
The invention relates to sprue cups used in metal casting processes, and, more particularly, to such sprue cups that are disposable.
Sprue cups used in metal casting processes can be either permanent, i.e., made of metal, or disposable. Permanent or metal sprue cups last indefinitely, but they have several disadvantages. Because they are permanent, they must be retrieved for reuse after each casting process is complsted. Because they are made of metal, they absorb a great deal of heat, and therefore the molten metal poured into the sprue cup must be heated to a higher temperature than would be necessary if the sprue cup were made of a non-metal. Furthermore, metal sprue cups must be kept coated with a refractory coating, and this necessitates frequent recoating of the sprue cup. Finally, permanent sprue cups require general maintenance so that they are in a suitahle condition for use.
Disposable sprue cups, on the other hand, do not have these disadvantages. Disposable sprue cups are typically made of a ceramic material or a fibrous refractory material. Disposable sprue cups generally last ~hrough only one casting process and therefore need not be retrieved, recoated, or maintained for reuse. ~dditionally, ceramic and fibrous refractory materials absorb relatively lit~l~
heat, so that the molten metal need not be heated higher than is necessary to pour the casting.
~zz~
The major disadvantage of known disposable sprue cups is that they break down into the process sand of the casting process. As a result, the process sand must be screened out in order to remove either refractory fibers or pieces of ceramic material. Otherwise. the process sand would become contamina~ed and would not produce satisfactory castings.
Attention is directed to the following U.S. patent6:
Zoda Patent No. 1.657,9'~, issued January 31, 1928;
Gans, Jr. Patent No. 2,784,467, issued March 12, 1957:
Hoefer Patent No. Z,835,007, issued May 20, 195~;
Snelling Patent No. 3,526,266, issued ~eptember 1, 1970:
Larsen et al. Patent No. 3,841,846. issued October 15. 1974; and Yamasaki Patent No. 4,154,285, issued May 15, 1979.
SUMMARY OF THE INVENTION
The invention provides a disposable sprue cup for use in a metal casting process. the process using a mold pattern embedded in unbound proces~ sand having a grai~ size and the process including ~he pouring of molten metal into the sprue cup, the disposable sprue cup comprising bonded sand including unbound sand having a grain ~ize substantially egual to ~he grain size of the process sand and a binder that remains intact until after the pouring is completed and the~ breaks down under the heat received during the casting process.
The invention also provides a disposable sprue cup for use in a metal casting process, the process using a mold pattern embedded in unbound process sand having a grain size and the process including the pouring of molten metal into the sprue cup, the disposable sprue cup having walls of a predetermined thickness and comprising bonded sand including unbound sand having a grain size substantially equal to the grain size of the process sand and a binder that forms a prede~ermined percentage of the bonded sand. The wall thickness and the binder percentage are such that the bonded sand remains intact until after the pouring is completed and then breaks down under the heat received during the casting process, thereby leaving essentially unbound sand that does not contaminate the unbound process sand.
In one embodiment, the cup comprises an enlarged cup portion adapted to receive molten metal, and an elongated neck portion extending downwardly from the cup portion when the sprue cup is oriented for casting and adapted to be attached to the sprue o~ a mold pattern such that molten metal received in the cup portion flows within the neck portion to ~he sprue of the mold pattern.
In one embodiment, the neck portion has a cross-sectional area, and the cup portion includes a main portion having a cross-sectional area substantially greater than the cross-sectional area of the neck portion and a tapered portion inte~rally connected between the main portion and the neck por~ion.
~Z'Z8~6 In one embodiment. the elongated nack portion includes a lower end and is adapted to be attached to the sprue of a foam mold pattern by extending the sprue through the lower end into the neck portion.
In one embodiment, the metal casting process includes the pouring of molten metal into the sprue cup, and the binder remains intact until after the pour is complete.
In one embodiment, the neck portion has a length such that, when metal is poured into the speue cup and the foam of the sprue melts beneath the lower end of the neck portion, ths flow of metal adjacent the unbound proces& sand is laminar.
The invention also provides a casting process comprising the steps of fabricating a disposable 6prue cup made of bonded sand including a binder and unbound sand having a grain size, the sprue cup including an enlarged cup portion adapted to receive molten metal and an elongated neck portion extending downwardly from the cup portion when the sprue cup is oriented ~or casting, attaching the sprue cup to a foam mold pattern having a sprue by extending the sprue into the neck portion of the sprue cup, e~bedding the foam mold pattern and a portion o~ the attached sprue cup in unbound process sand, and pouring molten metal into the sprue cup so that the molten metal received in the cup portion ~lows within the neck portion to the sprue of the mold pattern, whereby, after completion o~ the pouring ~tep, the binder of the sprue cup disintegrates in response to heat received during the casting process, thereby leaving essentially unbound sand that does not contaminate the unbound proces&
sand~
i In one embodiment, the pouring step includes pouring at a predetermined rate molten metal having a predetermined temperature into the sprue cup so that the metal ~lowing within the neck portion melts the sprue of the mold pattern, the attaching step includes extending a predetermined length of the sprue into the neck portion of the sprue cup, and the fabricating step includes fabeicating the sprue cup such that the neck portion has a length. The length of the neck portion, the length of ~he sprue ex~ended into the neck portion, and ~he temperature and pouring rate of the metal are such that, when the foam of the sp~ue melts beneath the lower end of the neck portion in response to the pouring step, the flow of metal adjacent the unbound process sand is laminar.
A principal feature of the invention is to provide a disposable sprue cup made of bonded sand having a grain size substantially equal to the grain size of the process sand and having a binder that breaks down under the heat of resident metal remaining in the cup after the casting procesfi is completed. Because the bonded sand has a grain size sub~tantially equal to the grain size of the process sand, when the sprue cup breaks down, the unbou~d sand that remains mixe~ with the unbound process sand and does not contaminate the process sand.
Another principal feature of the invention is that the breaking down of the bonded sand sprue cup of the invention helps to replace the process sand that is normally lost during the casting process, especially during removal of the casting feom the sand.
~Z28216 Other features and advantages of the invention will become apparent to those skilled in the art upon ~eview of the following detailed description, drawings, and claims.
DESCRIPTION OF THE DXA~INGS
Figure 1 illustrates a casting process using a disposable ~prue cup embodying the invention.
Figure 2 i6 an enlarged cro6s-sectional view of a disposable ~prue cup embodying the invention.
Before explaining one embodiment of the invention in detail, it is ~o be understood that the invention is not limited in its application to the details of construction and the arrangements of components set forth in ~he following description or illustrated in the drawings. ~he invention is capable of other embodiment~ and of being practiced or being carried out in vacious ways. Also, it is to be understood that the phraseology and terminology used herein i8 for the purpose of description and should not be regarded a~ limiting.
D~SCRIPTION OF THE PREFER~ED EMBODIMæNT
Illustrated in Figure 1 is a mold flask 10 containing a foa~ mold pattern 12 and a sprue cup 14 embedded in compacted unbound process ~and 16.
The sprue cup 14 is attached to the sprue 1~ of the mold pattern 12. Also illustrated in Figure 1 is molten metal being poured into the sprue cup 14.
As best shown in Figure 2, the sprue cup 14 comprises an enlarged cup portion 20 adapted ~8~
to receiYe molten metal and an elongatad neck portion 22 ex~ending downwardly from the cup portion 20 and adapted to be attached to the sprue 18 of the mold pattern 12, as illustrated. The enlarged cup portion 20 include~ a main portion 24 having an in6ide diameter subatantially greater than the in6ide diameter of the neck portion 22 and a tapered portion 26 integrally connected between the main portion 24 and the neck portion 22.
The sprue cup 14 is attached to the sprue 18 o~ the mold pattern 12 by extending the speue 18 through the lower end of the neck poLtion 22 into the neck portion 22, as shown in Figure 2. In the illustrated construction, the sprue 18 is cylindrical and fits snuggly into the neck portion 22 of the sprue cup 14.
In a casting process utilizing the sprue cup 14, after the mold pattern 12 and attached sprue cup 14 are surroundad by compac~ed process sand 16 as shown in Fisure 1, molten matal is poured into the cup portion 20 of the sprue cup 14, as also shown in Figure 1. The molten metal flows through the tapered portion 26 of the sprue cup 14 into the neck portion 22 where it contacts the serue 18 of the mold pattern 12. The molten metal then melts the foam sprue 18, causing the foam to evaporate, and flows downwardly into the cavity within the compacted procesa sand 16 aa it melts the foam of the ~old pa~tern 12. Eventually, molten metal fills the entire cavity that was once filled by the foam mold pattern 12, and this metal will harden to form the deaired casting. When the pouring of the molten metal is completed, molten ~etal should also fill the neck portion 22 of the sprue cup 14. This increases Z~6 the pres~ure in the metal filling tha cavity for a better casting.
The prue cup 14 has wall6 of a certain thickness and is made of bonded ~and compri~ins unbound sand ha~ing a grain ~ize 6ub~tantialIy equal to the gcain si2e of the process sand 16 and a binder that forms a certain percentage of the bonded ~and.
A typical binder percentage is 3 percent by weight.
Factors that must be considered in choosing the binder percentage include the temperature and density of the molten metal being poured, the wall thickness o~ the sprue cup 14, and how long the sprue cup 1~ is to remain intact (or how long the pour will take).
The wall thickness of the sprue cup 14 and the binder percentage are cho~en, considering the temperatuce and density of the metal to be poured, so that the bonded sand of at least the neck portion 22 of the sprue cup 14 breaks down under the heat of metal flowing through the cup 14 and resident metal remaining in the cup 14 after the casting proces~ is completed, thereby leaving essentially unbound sand that does not contaminate the unbound proces~ sand 16.
If the binder percentage is too low, the sprue cup ~4 will break down before the pour is completed, and ~and from the broken down sprue cup 14 will bacome mixed in the casting. If the binder percentage is too high, the ~prue cup 1~ will not break down at all.
The dimen~ions of ~he spcue cup 14, other ~han the wall thickness. are deter~ined by, among other thing5, the volume of th~ mold pa~tern 12 and the diametec of the sprue 18 of the mold pattern 12. The inside diameter of the neck poction 22 must .~ .
~22~3Zl~
g be substantially equal to the diameter of the sprue 18, so that the sprue 18 fits snuggly into the neck portion 22. The shape of the main and tapered portions 24 and 26 of the cup portion 20 are not important, except that the volume of molten metal ~hat can be contained by the cup portion 20 of the sprue cup 14 must be enough so that the sprue cup 14 does not run dry during the pouring of the molten metal. If the sprue cup 14 runs dry during the pouring of the metal, 50 that the level of the metal is below the cup 14 and a portion of the cavity once filled with foam is empty, the unsupported unbound process sand surrounding that portion of the cavity can callapse and ruin the castin~.
A sprue cup 14 having a volume equal to 15 percent of the volume of the mold pattern 12 is usally sufficient for preventing the cup from running dry. When molten metal is poured into the sprue cup 14 at ~he proper rate (this can be done, for example, manually or by a proyrammable ladler), the sprue cup 14 is filled with molten metal and then maintained substantially full during most of the pour. However, at a point near the end of the pour. there can be a surge in the flow of metal from the sprue cup 1~ into the mold pattern 12. If the sprue cup 14 is not substantially full when this surge takes place, the sprue cup 14 will run dry and the ca6~ing will be lost. Therefore, the volume of the sprue cup 14 should be such ~hat~ when the surge takes place, and if the sprue cup 14 is subs~antially full. the volume of molten metal in the sprue cup 14 will be enough so that the s~rue cup 14 will not run dry. For this reason, the volume of the cu~ portion 20 of ths sprue cup 14 is also referred ~o as ~he surge volume.
~28~
The other important dimension of the sprue cup 14 is the length of the neck portion 22.
The neck portion 22 should be long enough so that the flow of the metal adjacent the unbound proces~ sand 16 beneath the cup 14 is laminar when the foam of the sprue 18 melts beneath the lower end of the neck portion 22. This is because if the flow of metal adjacent the unbound process sand 16 is turbul~nt, the turbulent metal will dislodge the compacted unbound process sand 16 and the d;slodged sand will be included in the casting. In order to prevent this, by providing laminar flow when the foam melts beneath the lower end of the neck portion 22, the neck portion 22 ~hould be long enough 80 that a sufficient pressure head builds up in the metal before the foam melts beneath the lower end of the neck portion 22. Factors to be considered in determining a suf~icient neck portion length include .
the temperature and pouring rate of the metal and the length of the sprue 18 extending into the neck portion 22.
A ca~ting process utilizing the sprue cup 14 of the invention and carrying out the method of the invention i~ performed as follows. After the mold pattern lZ and attached sprue cup 14 are surrounded by unbound proces~ sand 16, molten metal i~ poured in~o the sprue cup 14. The metal will begin to melt the foam of the sprue 18 while the sprue cup 14 fills with molten metal. If the neck portion 22 is long enough, by the time the foam sprue 18 melts beneath the lower end of ~he neck portion 22, a sufficient pres~ure head will have buil~ up in the molten metal so that the flow of the metal adjacent the unbound process sand beneath the neck portion 22 is laminar. The metal is continuously poured ~hroughout the process at a rate sufficient to keep the sprue cup 14 substantially full. The metal continues to melt and evaporate the foam of the sprue 18 and mold pattern 12 until the cavity once occupied by the foam mold pattern 12 is occupied by molten metal. At some point near the end of the pour, a surge in the flow of molten metal into the mold pattern 12 will take place, and the sprue cup 14 will be partially bu~ not completely emptied, assuming the surge volume of the sprue cup 14 is sufficiently great. ~hen the pour is completed~ the neck portion 22 of the sprue cup 14 will be substantially filled with molten metal.
Throughout the pouring of the molten metal, the ~inder in the bonded sand of the sprue cup 14 begins to break down under the heat of the molten metal flowinq through the sprue cup 14. However, if the binder percentage is great enough in light of the density and termperature of the metal and the length of the pour, the binder will remain intact until the pour is completed. Afterward, due to the heat received during the cas~ing process, the binder in the neck portion 22 and possibly other portions of the sprue cup 14 breaks down, thereby leaving essentially unbound sand that mixes with the unbound process sand 16 without contamination.
Any portion of the sprue cup 14 that does not break down can be removed from the process sand 16 during the normal culling process. The sand from the sprue cup 14 that does mi~ with the process sand 16 helps to offset the natural loss of process sand tha~ occurs during other casting steps, especially during the step of removing the casting from the mold flask 10.
~Z'Z~6 Variou~ of the featu~es of the invention are ~e~ fo~th in the following claim~.
BOND~D SAND SPRUE CUP
BACKGROUND OF_THE INVENTION
The invention relates to sprue cups used in metal casting processes, and, more particularly, to such sprue cups that are disposable.
Sprue cups used in metal casting processes can be either permanent, i.e., made of metal, or disposable. Permanent or metal sprue cups last indefinitely, but they have several disadvantages. Because they are permanent, they must be retrieved for reuse after each casting process is complsted. Because they are made of metal, they absorb a great deal of heat, and therefore the molten metal poured into the sprue cup must be heated to a higher temperature than would be necessary if the sprue cup were made of a non-metal. Furthermore, metal sprue cups must be kept coated with a refractory coating, and this necessitates frequent recoating of the sprue cup. Finally, permanent sprue cups require general maintenance so that they are in a suitahle condition for use.
Disposable sprue cups, on the other hand, do not have these disadvantages. Disposable sprue cups are typically made of a ceramic material or a fibrous refractory material. Disposable sprue cups generally last ~hrough only one casting process and therefore need not be retrieved, recoated, or maintained for reuse. ~dditionally, ceramic and fibrous refractory materials absorb relatively lit~l~
heat, so that the molten metal need not be heated higher than is necessary to pour the casting.
~zz~
The major disadvantage of known disposable sprue cups is that they break down into the process sand of the casting process. As a result, the process sand must be screened out in order to remove either refractory fibers or pieces of ceramic material. Otherwise. the process sand would become contamina~ed and would not produce satisfactory castings.
Attention is directed to the following U.S. patent6:
Zoda Patent No. 1.657,9'~, issued January 31, 1928;
Gans, Jr. Patent No. 2,784,467, issued March 12, 1957:
Hoefer Patent No. Z,835,007, issued May 20, 195~;
Snelling Patent No. 3,526,266, issued ~eptember 1, 1970:
Larsen et al. Patent No. 3,841,846. issued October 15. 1974; and Yamasaki Patent No. 4,154,285, issued May 15, 1979.
SUMMARY OF THE INVENTION
The invention provides a disposable sprue cup for use in a metal casting process. the process using a mold pattern embedded in unbound proces~ sand having a grai~ size and the process including ~he pouring of molten metal into the sprue cup, the disposable sprue cup comprising bonded sand including unbound sand having a grain ~ize substantially egual to ~he grain size of the process sand and a binder that remains intact until after the pouring is completed and the~ breaks down under the heat received during the casting process.
The invention also provides a disposable sprue cup for use in a metal casting process, the process using a mold pattern embedded in unbound process sand having a grain size and the process including the pouring of molten metal into the sprue cup, the disposable sprue cup having walls of a predetermined thickness and comprising bonded sand including unbound sand having a grain size substantially equal to the grain size of the process sand and a binder that forms a prede~ermined percentage of the bonded sand. The wall thickness and the binder percentage are such that the bonded sand remains intact until after the pouring is completed and then breaks down under the heat received during the casting process, thereby leaving essentially unbound sand that does not contaminate the unbound process sand.
In one embodiment, the cup comprises an enlarged cup portion adapted to receive molten metal, and an elongated neck portion extending downwardly from the cup portion when the sprue cup is oriented for casting and adapted to be attached to the sprue o~ a mold pattern such that molten metal received in the cup portion flows within the neck portion to ~he sprue of the mold pattern.
In one embodiment, the neck portion has a cross-sectional area, and the cup portion includes a main portion having a cross-sectional area substantially greater than the cross-sectional area of the neck portion and a tapered portion inte~rally connected between the main portion and the neck por~ion.
~Z'Z8~6 In one embodiment. the elongated nack portion includes a lower end and is adapted to be attached to the sprue of a foam mold pattern by extending the sprue through the lower end into the neck portion.
In one embodiment, the metal casting process includes the pouring of molten metal into the sprue cup, and the binder remains intact until after the pour is complete.
In one embodiment, the neck portion has a length such that, when metal is poured into the speue cup and the foam of the sprue melts beneath the lower end of the neck portion, ths flow of metal adjacent the unbound proces& sand is laminar.
The invention also provides a casting process comprising the steps of fabricating a disposable 6prue cup made of bonded sand including a binder and unbound sand having a grain size, the sprue cup including an enlarged cup portion adapted to receive molten metal and an elongated neck portion extending downwardly from the cup portion when the sprue cup is oriented ~or casting, attaching the sprue cup to a foam mold pattern having a sprue by extending the sprue into the neck portion of the sprue cup, e~bedding the foam mold pattern and a portion o~ the attached sprue cup in unbound process sand, and pouring molten metal into the sprue cup so that the molten metal received in the cup portion ~lows within the neck portion to the sprue of the mold pattern, whereby, after completion o~ the pouring ~tep, the binder of the sprue cup disintegrates in response to heat received during the casting process, thereby leaving essentially unbound sand that does not contaminate the unbound proces&
sand~
i In one embodiment, the pouring step includes pouring at a predetermined rate molten metal having a predetermined temperature into the sprue cup so that the metal ~lowing within the neck portion melts the sprue of the mold pattern, the attaching step includes extending a predetermined length of the sprue into the neck portion of the sprue cup, and the fabricating step includes fabeicating the sprue cup such that the neck portion has a length. The length of the neck portion, the length of ~he sprue ex~ended into the neck portion, and ~he temperature and pouring rate of the metal are such that, when the foam of the sp~ue melts beneath the lower end of the neck portion in response to the pouring step, the flow of metal adjacent the unbound process sand is laminar.
A principal feature of the invention is to provide a disposable sprue cup made of bonded sand having a grain size substantially equal to the grain size of the process sand and having a binder that breaks down under the heat of resident metal remaining in the cup after the casting procesfi is completed. Because the bonded sand has a grain size sub~tantially equal to the grain size of the process sand, when the sprue cup breaks down, the unbou~d sand that remains mixe~ with the unbound process sand and does not contaminate the process sand.
Another principal feature of the invention is that the breaking down of the bonded sand sprue cup of the invention helps to replace the process sand that is normally lost during the casting process, especially during removal of the casting feom the sand.
~Z28216 Other features and advantages of the invention will become apparent to those skilled in the art upon ~eview of the following detailed description, drawings, and claims.
DESCRIPTION OF THE DXA~INGS
Figure 1 illustrates a casting process using a disposable ~prue cup embodying the invention.
Figure 2 i6 an enlarged cro6s-sectional view of a disposable ~prue cup embodying the invention.
Before explaining one embodiment of the invention in detail, it is ~o be understood that the invention is not limited in its application to the details of construction and the arrangements of components set forth in ~he following description or illustrated in the drawings. ~he invention is capable of other embodiment~ and of being practiced or being carried out in vacious ways. Also, it is to be understood that the phraseology and terminology used herein i8 for the purpose of description and should not be regarded a~ limiting.
D~SCRIPTION OF THE PREFER~ED EMBODIMæNT
Illustrated in Figure 1 is a mold flask 10 containing a foa~ mold pattern 12 and a sprue cup 14 embedded in compacted unbound process ~and 16.
The sprue cup 14 is attached to the sprue 1~ of the mold pattern 12. Also illustrated in Figure 1 is molten metal being poured into the sprue cup 14.
As best shown in Figure 2, the sprue cup 14 comprises an enlarged cup portion 20 adapted ~8~
to receiYe molten metal and an elongatad neck portion 22 ex~ending downwardly from the cup portion 20 and adapted to be attached to the sprue 18 of the mold pattern 12, as illustrated. The enlarged cup portion 20 include~ a main portion 24 having an in6ide diameter subatantially greater than the in6ide diameter of the neck portion 22 and a tapered portion 26 integrally connected between the main portion 24 and the neck portion 22.
The sprue cup 14 is attached to the sprue 18 o~ the mold pattern 12 by extending the speue 18 through the lower end of the neck poLtion 22 into the neck portion 22, as shown in Figure 2. In the illustrated construction, the sprue 18 is cylindrical and fits snuggly into the neck portion 22 of the sprue cup 14.
In a casting process utilizing the sprue cup 14, after the mold pattern 12 and attached sprue cup 14 are surroundad by compac~ed process sand 16 as shown in Fisure 1, molten matal is poured into the cup portion 20 of the sprue cup 14, as also shown in Figure 1. The molten metal flows through the tapered portion 26 of the sprue cup 14 into the neck portion 22 where it contacts the serue 18 of the mold pattern 12. The molten metal then melts the foam sprue 18, causing the foam to evaporate, and flows downwardly into the cavity within the compacted procesa sand 16 aa it melts the foam of the ~old pa~tern 12. Eventually, molten metal fills the entire cavity that was once filled by the foam mold pattern 12, and this metal will harden to form the deaired casting. When the pouring of the molten metal is completed, molten ~etal should also fill the neck portion 22 of the sprue cup 14. This increases Z~6 the pres~ure in the metal filling tha cavity for a better casting.
The prue cup 14 has wall6 of a certain thickness and is made of bonded ~and compri~ins unbound sand ha~ing a grain ~ize 6ub~tantialIy equal to the gcain si2e of the process sand 16 and a binder that forms a certain percentage of the bonded ~and.
A typical binder percentage is 3 percent by weight.
Factors that must be considered in choosing the binder percentage include the temperature and density of the molten metal being poured, the wall thickness o~ the sprue cup 14, and how long the sprue cup 1~ is to remain intact (or how long the pour will take).
The wall thickness of the sprue cup 14 and the binder percentage are cho~en, considering the temperatuce and density of the metal to be poured, so that the bonded sand of at least the neck portion 22 of the sprue cup 14 breaks down under the heat of metal flowing through the cup 14 and resident metal remaining in the cup 14 after the casting proces~ is completed, thereby leaving essentially unbound sand that does not contaminate the unbound proces~ sand 16.
If the binder percentage is too low, the sprue cup ~4 will break down before the pour is completed, and ~and from the broken down sprue cup 14 will bacome mixed in the casting. If the binder percentage is too high, the ~prue cup 1~ will not break down at all.
The dimen~ions of ~he spcue cup 14, other ~han the wall thickness. are deter~ined by, among other thing5, the volume of th~ mold pa~tern 12 and the diametec of the sprue 18 of the mold pattern 12. The inside diameter of the neck poction 22 must .~ .
~22~3Zl~
g be substantially equal to the diameter of the sprue 18, so that the sprue 18 fits snuggly into the neck portion 22. The shape of the main and tapered portions 24 and 26 of the cup portion 20 are not important, except that the volume of molten metal ~hat can be contained by the cup portion 20 of the sprue cup 14 must be enough so that the sprue cup 14 does not run dry during the pouring of the molten metal. If the sprue cup 14 runs dry during the pouring of the metal, 50 that the level of the metal is below the cup 14 and a portion of the cavity once filled with foam is empty, the unsupported unbound process sand surrounding that portion of the cavity can callapse and ruin the castin~.
A sprue cup 14 having a volume equal to 15 percent of the volume of the mold pattern 12 is usally sufficient for preventing the cup from running dry. When molten metal is poured into the sprue cup 14 at ~he proper rate (this can be done, for example, manually or by a proyrammable ladler), the sprue cup 14 is filled with molten metal and then maintained substantially full during most of the pour. However, at a point near the end of the pour. there can be a surge in the flow of metal from the sprue cup 1~ into the mold pattern 12. If the sprue cup 14 is not substantially full when this surge takes place, the sprue cup 14 will run dry and the ca6~ing will be lost. Therefore, the volume of the sprue cup 14 should be such ~hat~ when the surge takes place, and if the sprue cup 14 is subs~antially full. the volume of molten metal in the sprue cup 14 will be enough so that the s~rue cup 14 will not run dry. For this reason, the volume of the cu~ portion 20 of ths sprue cup 14 is also referred ~o as ~he surge volume.
~28~
The other important dimension of the sprue cup 14 is the length of the neck portion 22.
The neck portion 22 should be long enough so that the flow of the metal adjacent the unbound proces~ sand 16 beneath the cup 14 is laminar when the foam of the sprue 18 melts beneath the lower end of the neck portion 22. This is because if the flow of metal adjacent the unbound process sand 16 is turbul~nt, the turbulent metal will dislodge the compacted unbound process sand 16 and the d;slodged sand will be included in the casting. In order to prevent this, by providing laminar flow when the foam melts beneath the lower end of the neck portion 22, the neck portion 22 ~hould be long enough 80 that a sufficient pressure head builds up in the metal before the foam melts beneath the lower end of the neck portion 22. Factors to be considered in determining a suf~icient neck portion length include .
the temperature and pouring rate of the metal and the length of the sprue 18 extending into the neck portion 22.
A ca~ting process utilizing the sprue cup 14 of the invention and carrying out the method of the invention i~ performed as follows. After the mold pattern lZ and attached sprue cup 14 are surrounded by unbound proces~ sand 16, molten metal i~ poured in~o the sprue cup 14. The metal will begin to melt the foam of the sprue 18 while the sprue cup 14 fills with molten metal. If the neck portion 22 is long enough, by the time the foam sprue 18 melts beneath the lower end of ~he neck portion 22, a sufficient pres~ure head will have buil~ up in the molten metal so that the flow of the metal adjacent the unbound process sand beneath the neck portion 22 is laminar. The metal is continuously poured ~hroughout the process at a rate sufficient to keep the sprue cup 14 substantially full. The metal continues to melt and evaporate the foam of the sprue 18 and mold pattern 12 until the cavity once occupied by the foam mold pattern 12 is occupied by molten metal. At some point near the end of the pour, a surge in the flow of molten metal into the mold pattern 12 will take place, and the sprue cup 14 will be partially bu~ not completely emptied, assuming the surge volume of the sprue cup 14 is sufficiently great. ~hen the pour is completed~ the neck portion 22 of the sprue cup 14 will be substantially filled with molten metal.
Throughout the pouring of the molten metal, the ~inder in the bonded sand of the sprue cup 14 begins to break down under the heat of the molten metal flowinq through the sprue cup 14. However, if the binder percentage is great enough in light of the density and termperature of the metal and the length of the pour, the binder will remain intact until the pour is completed. Afterward, due to the heat received during the cas~ing process, the binder in the neck portion 22 and possibly other portions of the sprue cup 14 breaks down, thereby leaving essentially unbound sand that mixes with the unbound process sand 16 without contamination.
Any portion of the sprue cup 14 that does not break down can be removed from the process sand 16 during the normal culling process. The sand from the sprue cup 14 that does mi~ with the process sand 16 helps to offset the natural loss of process sand tha~ occurs during other casting steps, especially during the step of removing the casting from the mold flask 10.
~Z'Z~6 Variou~ of the featu~es of the invention are ~e~ fo~th in the following claim~.
Claims (12)
1. A disposable sprue cup for use in a metal casting process, the process using a mold pattern embedded in unbound process sand having a grain size and the process including the step of pouring molten metal into the sprue cup, the disposable sprue cup comprising bonded sand including unbound sand having a grain size substantially equal to the grain size of the process sand and a binder that remains intact until after the pouring is completed and then breaks down under the heat received during the casting process.
2. A disposable sprue cup in accordance with Claim 1 wherein said cup comprises an enlarged cup portion adapted to receive molten metal, and an elongated neck portion extending downwardly from said cup portion when said sprue cup is oriented for casting and adapted to be attached to the sprue of a mold pattern such that molten metal received in said cup portion flows within said neck portion to the sprue of the mold pattern.
3. A disposable sprue cup in accordance with Claim 2 wherein said neck portion has a cross-sectional area, and wherein said cup portion includes a main portion having a cross-sectional area substantially greater than the cross-sectional area of said neck portion and a tapered portion integrally connected between said main portion and said neck portion.
4. A disposable sprue cup in accordance with Claim 2 wherein said elongated neck portion includes a lower end and is adapted to be attached to the sprue of a foam mold pattern by extending the sprue through said lower end into said neck portion.
5. A disposable sprue cup in accordance with Claim 4 wherein said neck portion has a length, said length of said neck portion being such that, when metal is poured into said sprue cup and the foam of the sprue melts beneath said lower end of said neck portion, the flow of metal adjacent the unbound process sand is laminar.
6. A disposable sprue cup for use in a metal casting process, the process using a mold pattern embedded in unbound process sand having a grain size and the process including the step of pouring molten metal into the sprue cup, the disposable sprue cup having walls of a predetermined thickness and comprising bonded sand including unbound sand having a grain size substantially equal to the grain size of the process and and a binder that forms a predetermined percentage of said bonded sand, said wall thickness and said binder percentage being such that said bonded sand remains intact until after the pouring is completed and then breaks down under the heat received during the casting process, thereby leaving essentially unbound sand that does not contaminate the unbound process sand.
7. A disposable sprue cup in accordance with Claim 6 wherein said cup comprises an enlarged cup portion adapted to receive molten metal, and an elongated neck portion extending downwardly from said cup portion when said sprue cup is oriented for casting and adapted to be attached to the sprue of a mold pattern such that molten metal received in said cup portion flows within said neck portion to the sprue of the mold pattern.
8. A disposable sprue cup in accordance with Claim 7 wherein said neck portion has a cross-sectional area, and wherein said cup portion includes a main portion having a cross-sectional area substantially greater than the cross-sectional area of said neck portion and a tapered portion integrally connected between said main portion and said neck portion.
9. A disposable sprue cup in accordance with Claim 7 wherein said elongated neck portion includes a lower end and is adapted to be attached to the sprue of a foam mold pattern by extending the sprue through said lower end into said neck portion.
10. A disposable sprue cup in accordance with Claim 9 wherein said neck portion has a length, said length of said neck portion being such that, when metal is poured into said sprue cup and the foam of the sprue melts beneath said lower end of said neck portion, the flow of metal adjacent the unbound process sand is laminar.
11. A casting process comprising the steps of fabricating a disposable sprue cup made of bonded sand including a binder and unbound sand having a grain size, the sprue cup including an enlarged cup portion adapted to receive molten metal and an elongated neck portion extending downwardly from the cup portion when the sprue cup is oriented for casting, attaching the sprue cup to a foam mold pattern having a sprue by extending the sprue into the neck portion of the sprue cup, embedding the foam mold pattern and a portion of the attached sprue cup in unbound process sand, and pouring molten metal into the sprue cup so that the molten metal received in the cup portion flows within the neck portion to the sprue of the mold pattern, whereby, after completion of said pouring step, the binder of the sprue cup disintegrates in response to heat received during the casting process, thereby leaving essentially unbound sand that does not contaminate the unbound process sand.
12. A process in accordance with Claim 11 wherein said pouring step includes pouring at a predetermined rate molten metal having a predetermined temperature into the sprue cup so that the molten metal flowing within the neck portion melts the sprue of the mold pattern, wherein said attaching step includes extending a predetermined length of the sprue into the neck portion of the sprue cup, and wherein said fabricating step includes fabricating the sprue cup such that the neck portion has a length, the length of the neck portion, the length of the sprue extended into the neck portion, and the temperature and pouring rate of the metal
12. A process in accordance with Claim 11 wherein said pouring step includes pouring at a predetermined rate molten metal having a predetermined temperature into the sprue cup so that the molten metal flowing within the neck portion melts the sprue of the mold pattern, wherein said attaching step includes extending a predetermined length of the sprue into the neck portion of the sprue cup, and wherein said fabricating step includes fabricating the sprue cup such that the neck portion has a length, the length of the neck portion, the length of the sprue extended into the neck portion, and the temperature and pouring rate of the metal
Claim 12 (continued) being such that, when the foam of the sprue melts beneath the lower end of the neck portion in response to said pouring step, the flow of metal adjacent the unbound process sand is laminar.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/634,599 US4598757A (en) | 1984-07-26 | 1984-07-26 | Bonded sand sprue cup |
| US634,599 | 1990-12-27 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1228216A true CA1228216A (en) | 1987-10-20 |
Family
ID=24544462
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000483722A Expired CA1228216A (en) | 1984-07-26 | 1985-06-12 | Bonded sand sprue cup |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US4598757A (en) |
| CA (1) | CA1228216A (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4854369A (en) * | 1988-03-22 | 1989-08-08 | Outboard Marine Corporation | Apparatus for surrounding a foam pattern cluster with sand |
| US5054537A (en) * | 1988-06-03 | 1991-10-08 | Outboard Marine Corporation | Lost foam pattern assembly for V-block engine |
| US4981166A (en) * | 1989-06-27 | 1991-01-01 | Brown Foundry Systems, Inc. | Foundry paper riser and system therefor |
| US5205340A (en) * | 1989-06-27 | 1993-04-27 | Brown Foundry System, Inc. | Insulated paper sleeve for casting metal articles in sand molds |
| DE102007034426B3 (en) * | 2007-07-20 | 2008-12-04 | HAGENBURGER Feuerfeste Produkte für Gießereien und Stahlwerke KG | Component of a casting system through which a molten metal can flow |
| CN103418748A (en) * | 2012-05-18 | 2013-12-04 | 无锡蠡湖叶轮制造有限公司 | Manufacturing method of sprue for metal mould gravity casting |
| CN103878319A (en) * | 2012-12-21 | 2014-06-25 | 南通太和机械集团有限公司 | Inverted A-shaped casting mould |
| CN109047666B (en) * | 2018-07-27 | 2020-06-05 | 宁夏共享能源有限公司 | Paper pouring gate pipe for casting and preparation method thereof |
| CN111250661A (en) * | 2020-03-23 | 2020-06-09 | 共享智能铸造产业创新中心有限公司 | Pouring basin |
Family Cites Families (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1657952A (en) * | 1926-04-14 | 1928-01-31 | Zoda Salvatore | Skim gate |
| US2198498A (en) * | 1938-06-11 | 1940-04-23 | Castings Patent Corp | Apparatus for forming sprue tube sockets |
| US2269455A (en) * | 1940-02-17 | 1942-01-13 | Castings Patent Corp | Mold and sprue sleeve therefor |
| US2845669A (en) * | 1953-10-12 | 1958-08-05 | Gen Motors Corp | Method of casting in shell molds |
| US2835007A (en) * | 1954-03-12 | 1958-05-20 | William F Hoefer | Screen for molding flasks |
| US2784467A (en) * | 1956-04-20 | 1957-03-12 | United States Steel Corp | Mold appliance |
| US3526266A (en) * | 1965-07-13 | 1970-09-01 | Thomas E Snelling | Mold for the casting of metals |
| US3841846A (en) * | 1970-01-25 | 1974-10-15 | Mallory & Co Inc P R | Liquid phase sintered molybdenum base alloys having additives and shaping members made therefrom |
| US3844337A (en) * | 1972-12-18 | 1974-10-29 | Packaging Corp America | Pouring sprue |
| JPS5360820A (en) * | 1976-11-12 | 1978-05-31 | Koujirou Yamazaki | Method to degas for casting metal mould |
| US4506813A (en) * | 1979-12-15 | 1985-03-26 | Dughan Terence G | Tubular assembly, method of preparing the assembly, apparatus for uphill teeming which incorporates the assembly and method of casting metal |
-
1984
- 1984-07-26 US US06/634,599 patent/US4598757A/en not_active Expired - Fee Related
-
1985
- 1985-06-12 CA CA000483722A patent/CA1228216A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| US4598757A (en) | 1986-07-08 |
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