CA1205613A - Method for production of hollow (shell) foundry cores - Google Patents
Method for production of hollow (shell) foundry coresInfo
- Publication number
- CA1205613A CA1205613A CA000450083A CA450083A CA1205613A CA 1205613 A CA1205613 A CA 1205613A CA 000450083 A CA000450083 A CA 000450083A CA 450083 A CA450083 A CA 450083A CA 1205613 A CA1205613 A CA 1205613A
- Authority
- CA
- Canada
- Prior art keywords
- sand
- core
- binder coated
- coated sand
- hollow
- 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
- B22C9/10—Cores; Manufacture or installation of cores
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C13/00—Moulding machines for making moulds or cores of particular shapes
- B22C13/08—Moulding machines for making moulds or cores of particular shapes for shell moulds or shell cores
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
- B22C9/12—Treating moulds or cores, e.g. drying, hardening
- B22C9/123—Gas-hardening
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Molds, Cores, And Manufacturing Methods Thereof (AREA)
- Casting Devices For Molds (AREA)
Abstract
ABSTRACT
A method for the production of hollow foundry sand cores in which binder coated sand is cured in the core pattern cavity of a core box using an amine catalyst gas to form a hollow sand core, and uncured binder coated sand is discharged and recovered from the cavity of the hollow sand core. Fresh binder coated sand and recovered binder coated sand are volumetrically metered alternately to a blow head so that at no time is there a mixture of the two sands in the blow head.
The metered binder coated sand in the blow head is blown by compressed air through an investment aperture in the top of the core box into the core pattern cavity.
After gassing, an uncured binder coated sand is discharged and recovered from hollow sand cores while fresh binder coated sand is being metered to the blow head. Metering of fresh binder coated sand is discontinued after a predetermined period of time equivalent to about 1/10 to about 1/3 of the bench life of the binder coated sand. At this point, metering of recovered binder coated sand to the blow head is commenced and continued until essentially all of the sand is consumed in hollow core formation.
The metering of fresh binder coated sand is then recommenced and the procedure repeated.
A method for the production of hollow foundry sand cores in which binder coated sand is cured in the core pattern cavity of a core box using an amine catalyst gas to form a hollow sand core, and uncured binder coated sand is discharged and recovered from the cavity of the hollow sand core. Fresh binder coated sand and recovered binder coated sand are volumetrically metered alternately to a blow head so that at no time is there a mixture of the two sands in the blow head.
The metered binder coated sand in the blow head is blown by compressed air through an investment aperture in the top of the core box into the core pattern cavity.
After gassing, an uncured binder coated sand is discharged and recovered from hollow sand cores while fresh binder coated sand is being metered to the blow head. Metering of fresh binder coated sand is discontinued after a predetermined period of time equivalent to about 1/10 to about 1/3 of the bench life of the binder coated sand. At this point, metering of recovered binder coated sand to the blow head is commenced and continued until essentially all of the sand is consumed in hollow core formation.
The metering of fresh binder coated sand is then recommenced and the procedure repeated.
Description
~2~;)S6~L3 MF~TTTOD F()R T~IF' PRODUCTIOM
OF HO~I,OW FOUNDRY CORES
The present invention relates generally to the ~oundry fleld. More parti.cularly, the present invention relates to a method Eor the production of foundrv sand cores, and still more part.icularly~
relates to a method for the production of hollow foundry sand cores.
In the cold box process for making solid foundry 10sand cores as described in U.S. Patent 3,409,579, a charge of a mixture of sand and a binder comprising a phenolic resin and a polvisocyanate is shaped in the pattern cavity of a core hox. The resultant shaped sand mass is then subiected at room temperature to the action of a tertiarY amine catalyst introduced under sufficient pressure to penetrate the sand mass, wherebv an instantaneous cure of the binder is effected and a solid sand core Lormed. In practice, the process is conducted as a highlv automated procedure in which binder coated sand is invested from a blow head into a core box enclosing a core pattPrn through which the amine gas is passed, and the resultant cured solid sand core then removed from the opened core box.
25Notwithstanding the acceptance of the cold box process by the foundx~ industry and notwithstanding the commercial success that it has enjoyed in most o:f the industrlalized countries of the world over the past several years, there are certain disadvantages to the process. The most apparent disadvantage is that the coxes produced by the process are solid ~.
:~ 5 5 weighing as much as three or four times similar hollow cores produced by the well known Croning shell process. Raw material costs for the cold box process are, accordinq]y, correspondingly greater than for the shell pxocess, and handling of the cores produced by the process is more difficult because of their greater weight. Solid sand cores, moreover, inherently lack the permeahility and collapsibility properties of hollow sand cores that are so important ln in metal casting.
As currently practiced, the shell process for producing hollow sand cores, involves sub~ecting a mixture of sand coated with a hexamethylenetetramine-containing phenolformaldehyde ~5 resin to the curing action of heat in the range of 400-480F for a iime sufficient to effect a cure of the resin. Unfortunately, there are also disadvantages associated with ihe shell process most of which ar~ related to the high temperature curing step. Among these may be mentioned the need for excessive cure times, high fuel costs, the need for heat reslstant core boxes, as well as less than desirable foundry working conditions.
More recent]y, it has heen proposed to use the cold box concept to form hollow sand cores in an effort to gain the advantages of both procedures without suf~ering their respective disadvantages. As disclosed in II.S. Patent ~,232,726 issued in the name of Anatol Michelson, the resultant cold hollow core forming procedure comprises investing, or charging, a binder coated sand to the cavity of a gas perl~eable core pattern surrounded by a gas impermeable core ~2~ 3 box~ ~he charged sand mass is then cured by introducing a gaseous amine catalyst at ambient temperature and under pressure into the space enclosed by the gas permeable gas pattern and the gas impermeable core box. ~he amine ca~alvst penetrates the core pattern throughout itfi entire contour and enters the sand mass to a distance determined hv the equilibrium condition eventually reached between the pressure o-F the gaseou~ amine and of the air in the sand mass of the core pattern cavity. Curing of the binder occurs as the sand mass is penetrated by the amine gas r the extent of peneiration determining the depth of cure. Once pressure equilibrium is reached, residual gaseous amine is evacuated from the core lS box, uncured binder coated sana removed from the cavity of the hollow sand core, and the core box opened to effect separation of the hollow sand core from the core pattern.
Disclosed in U.S. Patent 4,291,740 also issued in the name of Anatol Michelson, is a process and apparatus for conducting the cold hollow core forming procedure disclosed in U.S. Patent 4,2,2,726 in a continuously automated manner. ~s described therein, the cold hollow core forming process comprises a plurallty of basic steps conducted in sequence includincJ (a) transferring ~inder coated sand from an upper feed hopper to a blow head, and from the latter to the cavity of a core pattern through an investment aperture in the core box top, wherebv a charge of 3n sancl i5 shaped in the core pattern cavity; (b) sealing the core bo~ and core pattern; (c) gassing the shaped sand mass bv introducing an amine catalyst 56~L3 at amhient temperature and under pressure lnto the enclosed space formed between the core pattern and the core hox to cure the binder and form a hollow core; (d) rotating the core box through 180 and discharging uncured binder coated sand, by means of gravity and compressed air, from the cavitv of the hollow core into a lower feed hopper ~or recycle, (e) again rotating the core box, this time through 90, to permit extraction of the hollow core ~rom the pattern, as by means shown in U.S. Patent 4,204,569 issued in the name of the inventor hereof; ancl (f) closing the core box and rotating it another 90~ to its original position for the start of another production cycle. A complete produc-tion cvcle conducted in accordance with the described process requires about 30 seconds.
While clearly providing advantages over existing sand core forming procedures, the described cold hollow core process is sub~ect to its own disadvantages. One such disadvantage, Eor instance, concerns the vaporization of the solvent used for the two component binder system. To the extent that the solvent is lost by vaporization, the binder coated sand becomes correspondingly less useable, until a degree of solvent loss can occur ~Ihlch can render the binder coated sand totally unuseable~ When practicing the described cold hollow core process, it has been the practice to charge binder coated sand to the blow head in a quantity several times greater in volume 3~ than the volume oE the core pattern cavity. Since only the equivalent of sand coxresponding to the volume of the core pattern cavity ls invested from ~z~
the hlow head into the cavitv in each core production evcle, a substantia] quantity o~ binder coated sand remains in the blow head to be exposed to the compressed air used in investing, as sand i9 charged to the pattern cavity during successive production cycles. The consequence of this e~osure to pressuri~ed air is compounded, moreover, as recovered uncured binder coated sand is recycled, mixed with fresh sand, returned to the blow head and sub~ected to repeated exposures to the investing compressed air during successive production cycles.
Another disadvantage to the described cold hollow core process lies in the faet that no physical means are pr~vided in the investment aperture, either during investing of sand or during gassing of the sand, for defining the top of the sand ~ass charged to the core pattern cavity. ~s a resu]t, when the core box is sealed and gassed, the gas will penetrate at random around and under the base of the investment sleeve into the investment aperture causing the ormation of a core top, or '7print", as the ease may be, that is rough, uneven and of uncertain configuration.
Finally, it should he noted that the eold hollow 25 core process described in U.S. Patent 4,191,170 calls for discharging uncured binder eoated sand from the cavity of the formed hollow eore through the investment aperture for recycle to the upper feed hopper. To aecomplish this, the core box i9 rotated through 1~0 thereby permitting the uncured binder coated sand to discharge. The means necessarily required to carry out sand discharge in this manner 56~3 are very complex and costly since they mus-t i.nclude a "cradle" or "cag~" in which to mount the core box for rotation, mechanism for ef~ecting rotation, conveyors for the recovered sand, and the like.
There has remained, therefore, a need for improving the above described cold hollow core forming process. Tt is a principal object of thls inventlon to fulfill this nee~.. It is a further object of this invention to provide a p.rocess for advancing, or conducting, binder coated sand through the various mechanical elements employed in conducting the process, in an effective manner. It is still a further ob~ect of this invention to minimize exposure o~ hinder coated sand to the solvent vaporizing effect of pressurized air used in the cold hollow core process thereby reducing the waste of sand. Still another object of this invention, in one form thereof, is to conduct the process so as to produce a hollow core whose top or "print", as the case may be, is smooth, even and of predetermined and final dimensions.
The invention is a method for forming hollow sand cores which comprises investing a charge of binder coated sand into the cavity o~ a gas permeable ~5 core pattern surrounded by a gas impermeable core box as conventionally done. Unlike previous practice, however, in which a quantity o~ sand equivalent to several times the volume o~ the core pattern cavity is charged to the blow head, a quantity o~ bi.nder coated sand is metered to the blow head, in accordance with the pre.sent invention, which is no greater than that which is essentially e~uivalent to ~2~S6~
the volume of the core pattern cavit,v. From the blow head, the binder coated sand is invested in the cavity of the core pattern through an investment aperture in the core hox top Eormed bv an investment 5 sleeve. Unlike previous practice, the protrusion, if any, of sand into the investment aperture and, accordingly, the definite, predetermined configuration of the top or "print", as the case may be, of the resultant hollow core is established by the positioning of the blow plate of the blow head in the investment aperture~
Once the sand has been char~ed to the core pattern cavity, the core box is sealed bv a seal head placed in the investment aperture at the sand level predetermined by earlier placement of the blow plate during sand investment. The core box is then yassed by introducing amine catalyst at amhient temperature and under pressure into the enclosed space between the core pattern and the core box the air from which ~ space has been evacuated. After curing of the binder coated sand to a selected depth in the core pattern, the core box is unsealed and, without rotation of the core box, uncured binder coated sand is removed from the hollow core cavity through ~he investment aperture, and the hollow core then separated from the opened core box.
Successive hollow core production cvcles are conducted in the same manner usln~ fresh binder coated sand, uncured binder coated sand beincJ
3~ recovered from the cavity of the hollow core produced in each cvcle. At a selected point in time in the hollow core production procedure, usuallv governed by ~\
~20~6: L~
the bench liEe of the sand coated binder or by the cap~cit~ of the equipment for storing and rec~c]ing uncured binder coated sand, the metering of fresh bincler coated sand to the blow head is discontinued~
A~ this selected point in time, the metering of recovered uncured binder coated sand to the blow head is commenced and successive hollow core production cycles are conducted in the same manner as done heretofore with fresh binder coated sand, uncured 1~ binder coated sand beinq recovered from the cavity of the hollow core produced in each cvcle. Recovered uncured bincler coated sand is recycled and metered to the blow hea~1 until insufficient sand is recovered to produce a ho~low core. At this point, fresh binder coated sand is again metered to the blow head and successive production cycles conducted as heretofore, the alternating use of rresh hinder coated sand and recovered uncured binder coated sand being observed so long as the production procedure is conducted~ At no time during the production procedure are fresh binder coated sand and recovered uncured binder coated sand metered to the blow head simultaneousl,v.
In the drawings, which illustrate that which is presently regarded as the preferred mode of carrying out the invention:
Fig. 1 is a schematic of a cold hollow core box assembly for use in the method for producing hollow foundry cores according to this invention.
Fig. 2 illustrates an embodiment for metering blnder coated sand to a blow head~
Fig. 3 illustrates the blow head in investing relationship with the core box for investing binder ~21~5;6.~3 coated sand into the cavity of the core pattern through the core box investment aperture.
Yiq. 4 illustrates the core box sealed by appropriate sealing means and the core hox ready for gassing wlth amine catalyst.
Figs. 5 and 6 illustrate an e~hodiment for recovering uncured hinder coated sand from the cavity of a hollow core formed in the core box without rotation of the core bo~ through 180.
Turning now to ~ig. 1 of the drawings, reference numeral 10 indicates a core box for use in the production of hollow foundry sand cores in accordance with the method of the present invention. Core box 10 comprises a pair of gas impermeable sections 11, 12 supporting gas permeable core patter sections 13, 14. When brought together along parting line 15, core pattern sections 13, 14 form core pattern 16 definirly a core pattern cavity 17 which communicates with the exterior of core box 10 through an investment aperture 18 defined bY investment sleeve 19. Also formed by the assemblage of core pattern sections 13, 14 is an enclosed flow space 20 situated between core box 10 and core pattern 16. Core box 10 is provided with a pair of ports 21, 22 in its wall which communicate with flow space 20. Port 21 is connected through suitable valve means 23 to an exhaust fan or scruhber means in one position of the valve, and with ihe atmosphere in another position of the valve. Port 22 is connected through similar valve means 24 with a source of compressed air in one position of the val~e, and with a source of amine catalyst gas in another position of the valve.
~Z05~:31 3 -ln-~ n the production method of the present invention, a meterea quantity of binder coated sand is charged by means of compressed air throuqh investment aperture 18 into core pattern cavity 17 as 5 air is exhausted from the core box through flow space 20 and port 21. When sand investment is completed, core box 10 is sealed and gaseous amine catalyst introduced at ambient temperature and under pressure through port 22 into flow space 20. The amine gas lo penetrates the gas permeable walls 13, 14 of core pattern 16 and the binder coated sand in core pattern cavity 17, thereby catalvzing the cure of hinder with which it comes in contact, the depth of cure in core pattern cavity 17 being governed by the equalization of the pressures of the amine gas and the air in the sand in core pattern cavity 17. Upon completion of curing, core box 10 is purged of residual amine gas through flow space 20, port 21 and valve means 22, and core box 10 unsealed. Without rotating core box 2n 10, uncured binaer coated sand is then recovered from the cavity of the hollow core, and core box 10 then opened to permit extraction o-f the hollow core.
~ s earlier described, one of the disaavantages to the cold hollow core process arises from the practice o-f charging binder coated sand so as to fill the entire volume of the blow head, i.e. several times the volume oE the core pattern cavity.
Inasmuch as each investment of sand into the core pattern cavity from the blow head is essentially no greater than the volume of the core pattern cavity, it necessarily follows that a considerable quantity of sand remains in the blow head to be subjected to Si6~3 the deleterious effect of the compressed air used in successive sand investments -to the core pattern cavity. Since recovered uncured binder coated sand is recycled to the blow head in admixture with resh binder coated sand, the exposure of any particular increment of sand to the compressed air used in the blow head can be considerable. As a consequence, sand can become unuseable because of vaporization of its solvent content through exposure to the compressed air and, accordinqlv, must be discarded.
In accordance with the present invention, the exposure of sand to compressed air in the blow head is minimized and the waste of sand reduced, by metering to the blow head only so much fresh binder coated sand as is essentiall~r eauivalent in volume to the volume of the core pattern cavity. The metered volume of sand is then invested in the core pattern cavity and a hollow core formed~ ~ncured binder coated sand is recovered and collected without mixing it with fresh sand. Successive production cycles are conducted in the same manner using only fresh binder coated sand, the uncured binder coated sand from each cycle being recovered and collected. At a selected point in the procedure, -the metering of fresh sand to the blow head is discontinued. This point will be governed either by the bench life of the recovered uncured binder coated sand, or by the size of the system for collectinq recovered sand. The bench life o~ the binder coated sand is that length of time required for the binder to sufficiently cure in the absence of anline catalyzation so as to render it unuseable in the production of hollow cores. The :~2~5~3 point at which the metering of fresh binder coated sand to the blow head is discontinued should preferably be about 1/10 to 1/3 of the bench time.
If the capacity of the system used in practice oE the procedure to collect recovered uncured hinder coated sand is less than that capable of accepting the quantity of sand recovered in that length of time, then the length of time should be adjusted to accommodate the collection system capacity.
n Preferahly, of course, the collection system capacity should be designed to complement the 1/10 to 1/3 of the bench life period of time.
When the metering of fresh binder coated sand to the blow heaa is discontinued at the point referred to above, the metering of the recovered uncured binder coated sand to the blow head is commenced in the same manner. As before, uncured binder coated sand is recovered from each production cycle~
collectea ana recycled for metering to the blow head.
~0 Only when the quantity of recovered binder coated sand is no longer sufficient to form a hollow core, is the metering of recovered sand discontinued to the blow head and the metering of fresh binder coated sand recommenced. The procedure of alternately metering fresh and recovered sand to the blow head is then repeated. At no time in the practice of the process are fresh and recovered sand mixed and metered to the blow head.
In accordance with the practice of the process o~ this invention, there-Eore, it can be readily recognized that the disadvantage of the cold hollow core process described above is substantially 31 z~563L~
minimized, if not totally eliminated. Since the charging of b.inder coatecl sand to the blow head is precisely metered in accordance with the volume of the core pattern cavity, only a single volume of sand is sub~ected to the investing compressed air during each investment of the core pattern cavity. Moreover, slnce there is no mixing of fresh sand and recovered sand r and since ~resh sand and recovered sand are alternately metered to the blow head, the period of 1~ time that any particular increment of sand remains in the system in which the procedure is conducted, is reduced to a preferred and acceptahle level.
Referring to Fig. 2, there is shown a meterin~
device 30 for charging a volumetrically measured quantity o~ binder coated sand to blow head 40 comprising a metering drum 31 having a chamber 32 defined by the drum ends, longitudinal wall members 33 and bottom plate 3~. Adjusting means 35 for modifying the position of bottom plate 34 ancl
OF HO~I,OW FOUNDRY CORES
The present invention relates generally to the ~oundry fleld. More parti.cularly, the present invention relates to a method Eor the production of foundrv sand cores, and still more part.icularly~
relates to a method for the production of hollow foundry sand cores.
In the cold box process for making solid foundry 10sand cores as described in U.S. Patent 3,409,579, a charge of a mixture of sand and a binder comprising a phenolic resin and a polvisocyanate is shaped in the pattern cavity of a core hox. The resultant shaped sand mass is then subiected at room temperature to the action of a tertiarY amine catalyst introduced under sufficient pressure to penetrate the sand mass, wherebv an instantaneous cure of the binder is effected and a solid sand core Lormed. In practice, the process is conducted as a highlv automated procedure in which binder coated sand is invested from a blow head into a core box enclosing a core pattPrn through which the amine gas is passed, and the resultant cured solid sand core then removed from the opened core box.
25Notwithstanding the acceptance of the cold box process by the foundx~ industry and notwithstanding the commercial success that it has enjoyed in most o:f the industrlalized countries of the world over the past several years, there are certain disadvantages to the process. The most apparent disadvantage is that the coxes produced by the process are solid ~.
:~ 5 5 weighing as much as three or four times similar hollow cores produced by the well known Croning shell process. Raw material costs for the cold box process are, accordinq]y, correspondingly greater than for the shell pxocess, and handling of the cores produced by the process is more difficult because of their greater weight. Solid sand cores, moreover, inherently lack the permeahility and collapsibility properties of hollow sand cores that are so important ln in metal casting.
As currently practiced, the shell process for producing hollow sand cores, involves sub~ecting a mixture of sand coated with a hexamethylenetetramine-containing phenolformaldehyde ~5 resin to the curing action of heat in the range of 400-480F for a iime sufficient to effect a cure of the resin. Unfortunately, there are also disadvantages associated with ihe shell process most of which ar~ related to the high temperature curing step. Among these may be mentioned the need for excessive cure times, high fuel costs, the need for heat reslstant core boxes, as well as less than desirable foundry working conditions.
More recent]y, it has heen proposed to use the cold box concept to form hollow sand cores in an effort to gain the advantages of both procedures without suf~ering their respective disadvantages. As disclosed in II.S. Patent ~,232,726 issued in the name of Anatol Michelson, the resultant cold hollow core forming procedure comprises investing, or charging, a binder coated sand to the cavity of a gas perl~eable core pattern surrounded by a gas impermeable core ~2~ 3 box~ ~he charged sand mass is then cured by introducing a gaseous amine catalyst at ambient temperature and under pressure into the space enclosed by the gas permeable gas pattern and the gas impermeable core box. ~he amine ca~alvst penetrates the core pattern throughout itfi entire contour and enters the sand mass to a distance determined hv the equilibrium condition eventually reached between the pressure o-F the gaseou~ amine and of the air in the sand mass of the core pattern cavity. Curing of the binder occurs as the sand mass is penetrated by the amine gas r the extent of peneiration determining the depth of cure. Once pressure equilibrium is reached, residual gaseous amine is evacuated from the core lS box, uncured binder coated sana removed from the cavity of the hollow sand core, and the core box opened to effect separation of the hollow sand core from the core pattern.
Disclosed in U.S. Patent 4,291,740 also issued in the name of Anatol Michelson, is a process and apparatus for conducting the cold hollow core forming procedure disclosed in U.S. Patent 4,2,2,726 in a continuously automated manner. ~s described therein, the cold hollow core forming process comprises a plurallty of basic steps conducted in sequence includincJ (a) transferring ~inder coated sand from an upper feed hopper to a blow head, and from the latter to the cavity of a core pattern through an investment aperture in the core box top, wherebv a charge of 3n sancl i5 shaped in the core pattern cavity; (b) sealing the core bo~ and core pattern; (c) gassing the shaped sand mass bv introducing an amine catalyst 56~L3 at amhient temperature and under pressure lnto the enclosed space formed between the core pattern and the core hox to cure the binder and form a hollow core; (d) rotating the core box through 180 and discharging uncured binder coated sand, by means of gravity and compressed air, from the cavitv of the hollow core into a lower feed hopper ~or recycle, (e) again rotating the core box, this time through 90, to permit extraction of the hollow core ~rom the pattern, as by means shown in U.S. Patent 4,204,569 issued in the name of the inventor hereof; ancl (f) closing the core box and rotating it another 90~ to its original position for the start of another production cycle. A complete produc-tion cvcle conducted in accordance with the described process requires about 30 seconds.
While clearly providing advantages over existing sand core forming procedures, the described cold hollow core process is sub~ect to its own disadvantages. One such disadvantage, Eor instance, concerns the vaporization of the solvent used for the two component binder system. To the extent that the solvent is lost by vaporization, the binder coated sand becomes correspondingly less useable, until a degree of solvent loss can occur ~Ihlch can render the binder coated sand totally unuseable~ When practicing the described cold hollow core process, it has been the practice to charge binder coated sand to the blow head in a quantity several times greater in volume 3~ than the volume oE the core pattern cavity. Since only the equivalent of sand coxresponding to the volume of the core pattern cavity ls invested from ~z~
the hlow head into the cavitv in each core production evcle, a substantia] quantity o~ binder coated sand remains in the blow head to be exposed to the compressed air used in investing, as sand i9 charged to the pattern cavity during successive production cycles. The consequence of this e~osure to pressuri~ed air is compounded, moreover, as recovered uncured binder coated sand is recycled, mixed with fresh sand, returned to the blow head and sub~ected to repeated exposures to the investing compressed air during successive production cycles.
Another disadvantage to the described cold hollow core process lies in the faet that no physical means are pr~vided in the investment aperture, either during investing of sand or during gassing of the sand, for defining the top of the sand ~ass charged to the core pattern cavity. ~s a resu]t, when the core box is sealed and gassed, the gas will penetrate at random around and under the base of the investment sleeve into the investment aperture causing the ormation of a core top, or '7print", as the ease may be, that is rough, uneven and of uncertain configuration.
Finally, it should he noted that the eold hollow 25 core process described in U.S. Patent 4,191,170 calls for discharging uncured binder eoated sand from the cavity of the formed hollow eore through the investment aperture for recycle to the upper feed hopper. To aecomplish this, the core box i9 rotated through 1~0 thereby permitting the uncured binder coated sand to discharge. The means necessarily required to carry out sand discharge in this manner 56~3 are very complex and costly since they mus-t i.nclude a "cradle" or "cag~" in which to mount the core box for rotation, mechanism for ef~ecting rotation, conveyors for the recovered sand, and the like.
There has remained, therefore, a need for improving the above described cold hollow core forming process. Tt is a principal object of thls inventlon to fulfill this nee~.. It is a further object of this invention to provide a p.rocess for advancing, or conducting, binder coated sand through the various mechanical elements employed in conducting the process, in an effective manner. It is still a further ob~ect of this invention to minimize exposure o~ hinder coated sand to the solvent vaporizing effect of pressurized air used in the cold hollow core process thereby reducing the waste of sand. Still another object of this invention, in one form thereof, is to conduct the process so as to produce a hollow core whose top or "print", as the case may be, is smooth, even and of predetermined and final dimensions.
The invention is a method for forming hollow sand cores which comprises investing a charge of binder coated sand into the cavity o~ a gas permeable ~5 core pattern surrounded by a gas impermeable core box as conventionally done. Unlike previous practice, however, in which a quantity o~ sand equivalent to several times the volume o~ the core pattern cavity is charged to the blow head, a quantity o~ bi.nder coated sand is metered to the blow head, in accordance with the pre.sent invention, which is no greater than that which is essentially e~uivalent to ~2~S6~
the volume of the core pattern cavit,v. From the blow head, the binder coated sand is invested in the cavity of the core pattern through an investment aperture in the core hox top Eormed bv an investment 5 sleeve. Unlike previous practice, the protrusion, if any, of sand into the investment aperture and, accordingly, the definite, predetermined configuration of the top or "print", as the case may be, of the resultant hollow core is established by the positioning of the blow plate of the blow head in the investment aperture~
Once the sand has been char~ed to the core pattern cavity, the core box is sealed bv a seal head placed in the investment aperture at the sand level predetermined by earlier placement of the blow plate during sand investment. The core box is then yassed by introducing amine catalyst at amhient temperature and under pressure into the enclosed space between the core pattern and the core box the air from which ~ space has been evacuated. After curing of the binder coated sand to a selected depth in the core pattern, the core box is unsealed and, without rotation of the core box, uncured binder coated sand is removed from the hollow core cavity through ~he investment aperture, and the hollow core then separated from the opened core box.
Successive hollow core production cvcles are conducted in the same manner usln~ fresh binder coated sand, uncured binder coated sand beincJ
3~ recovered from the cavity of the hollow core produced in each cvcle. At a selected point in time in the hollow core production procedure, usuallv governed by ~\
~20~6: L~
the bench liEe of the sand coated binder or by the cap~cit~ of the equipment for storing and rec~c]ing uncured binder coated sand, the metering of fresh bincler coated sand to the blow head is discontinued~
A~ this selected point in time, the metering of recovered uncured binder coated sand to the blow head is commenced and successive hollow core production cycles are conducted in the same manner as done heretofore with fresh binder coated sand, uncured 1~ binder coated sand beinq recovered from the cavity of the hollow core produced in each cvcle. Recovered uncured bincler coated sand is recycled and metered to the blow hea~1 until insufficient sand is recovered to produce a ho~low core. At this point, fresh binder coated sand is again metered to the blow head and successive production cycles conducted as heretofore, the alternating use of rresh hinder coated sand and recovered uncured binder coated sand being observed so long as the production procedure is conducted~ At no time during the production procedure are fresh binder coated sand and recovered uncured binder coated sand metered to the blow head simultaneousl,v.
In the drawings, which illustrate that which is presently regarded as the preferred mode of carrying out the invention:
Fig. 1 is a schematic of a cold hollow core box assembly for use in the method for producing hollow foundry cores according to this invention.
Fig. 2 illustrates an embodiment for metering blnder coated sand to a blow head~
Fig. 3 illustrates the blow head in investing relationship with the core box for investing binder ~21~5;6.~3 coated sand into the cavity of the core pattern through the core box investment aperture.
Yiq. 4 illustrates the core box sealed by appropriate sealing means and the core hox ready for gassing wlth amine catalyst.
Figs. 5 and 6 illustrate an e~hodiment for recovering uncured hinder coated sand from the cavity of a hollow core formed in the core box without rotation of the core bo~ through 180.
Turning now to ~ig. 1 of the drawings, reference numeral 10 indicates a core box for use in the production of hollow foundry sand cores in accordance with the method of the present invention. Core box 10 comprises a pair of gas impermeable sections 11, 12 supporting gas permeable core patter sections 13, 14. When brought together along parting line 15, core pattern sections 13, 14 form core pattern 16 definirly a core pattern cavity 17 which communicates with the exterior of core box 10 through an investment aperture 18 defined bY investment sleeve 19. Also formed by the assemblage of core pattern sections 13, 14 is an enclosed flow space 20 situated between core box 10 and core pattern 16. Core box 10 is provided with a pair of ports 21, 22 in its wall which communicate with flow space 20. Port 21 is connected through suitable valve means 23 to an exhaust fan or scruhber means in one position of the valve, and with ihe atmosphere in another position of the valve. Port 22 is connected through similar valve means 24 with a source of compressed air in one position of the val~e, and with a source of amine catalyst gas in another position of the valve.
~Z05~:31 3 -ln-~ n the production method of the present invention, a meterea quantity of binder coated sand is charged by means of compressed air throuqh investment aperture 18 into core pattern cavity 17 as 5 air is exhausted from the core box through flow space 20 and port 21. When sand investment is completed, core box 10 is sealed and gaseous amine catalyst introduced at ambient temperature and under pressure through port 22 into flow space 20. The amine gas lo penetrates the gas permeable walls 13, 14 of core pattern 16 and the binder coated sand in core pattern cavity 17, thereby catalvzing the cure of hinder with which it comes in contact, the depth of cure in core pattern cavity 17 being governed by the equalization of the pressures of the amine gas and the air in the sand in core pattern cavity 17. Upon completion of curing, core box 10 is purged of residual amine gas through flow space 20, port 21 and valve means 22, and core box 10 unsealed. Without rotating core box 2n 10, uncured binaer coated sand is then recovered from the cavity of the hollow core, and core box 10 then opened to permit extraction o-f the hollow core.
~ s earlier described, one of the disaavantages to the cold hollow core process arises from the practice o-f charging binder coated sand so as to fill the entire volume of the blow head, i.e. several times the volume oE the core pattern cavity.
Inasmuch as each investment of sand into the core pattern cavity from the blow head is essentially no greater than the volume of the core pattern cavity, it necessarily follows that a considerable quantity of sand remains in the blow head to be subjected to Si6~3 the deleterious effect of the compressed air used in successive sand investments -to the core pattern cavity. Since recovered uncured binder coated sand is recycled to the blow head in admixture with resh binder coated sand, the exposure of any particular increment of sand to the compressed air used in the blow head can be considerable. As a consequence, sand can become unuseable because of vaporization of its solvent content through exposure to the compressed air and, accordinqlv, must be discarded.
In accordance with the present invention, the exposure of sand to compressed air in the blow head is minimized and the waste of sand reduced, by metering to the blow head only so much fresh binder coated sand as is essentiall~r eauivalent in volume to the volume of the core pattern cavity. The metered volume of sand is then invested in the core pattern cavity and a hollow core formed~ ~ncured binder coated sand is recovered and collected without mixing it with fresh sand. Successive production cycles are conducted in the same manner using only fresh binder coated sand, the uncured binder coated sand from each cycle being recovered and collected. At a selected point in the procedure, -the metering of fresh sand to the blow head is discontinued. This point will be governed either by the bench life of the recovered uncured binder coated sand, or by the size of the system for collectinq recovered sand. The bench life o~ the binder coated sand is that length of time required for the binder to sufficiently cure in the absence of anline catalyzation so as to render it unuseable in the production of hollow cores. The :~2~5~3 point at which the metering of fresh binder coated sand to the blow head is discontinued should preferably be about 1/10 to 1/3 of the bench time.
If the capacity of the system used in practice oE the procedure to collect recovered uncured hinder coated sand is less than that capable of accepting the quantity of sand recovered in that length of time, then the length of time should be adjusted to accommodate the collection system capacity.
n Preferahly, of course, the collection system capacity should be designed to complement the 1/10 to 1/3 of the bench life period of time.
When the metering of fresh binder coated sand to the blow heaa is discontinued at the point referred to above, the metering of the recovered uncured binder coated sand to the blow head is commenced in the same manner. As before, uncured binder coated sand is recovered from each production cycle~
collectea ana recycled for metering to the blow head.
~0 Only when the quantity of recovered binder coated sand is no longer sufficient to form a hollow core, is the metering of recovered sand discontinued to the blow head and the metering of fresh binder coated sand recommenced. The procedure of alternately metering fresh and recovered sand to the blow head is then repeated. At no time in the practice of the process are fresh and recovered sand mixed and metered to the blow head.
In accordance with the practice of the process o~ this invention, there-Eore, it can be readily recognized that the disadvantage of the cold hollow core process described above is substantially 31 z~563L~
minimized, if not totally eliminated. Since the charging of b.inder coatecl sand to the blow head is precisely metered in accordance with the volume of the core pattern cavity, only a single volume of sand is sub~ected to the investing compressed air during each investment of the core pattern cavity. Moreover, slnce there is no mixing of fresh sand and recovered sand r and since ~resh sand and recovered sand are alternately metered to the blow head, the period of 1~ time that any particular increment of sand remains in the system in which the procedure is conducted, is reduced to a preferred and acceptahle level.
Referring to Fig. 2, there is shown a meterin~
device 30 for charging a volumetrically measured quantity o~ binder coated sand to blow head 40 comprising a metering drum 31 having a chamber 32 defined by the drum ends, longitudinal wall members 33 and bottom plate 3~. Adjusting means 35 for modifying the position of bottom plate 34 ancl
2~ consecIuentlv varying the volume of chamber 32 are provided to accommodate varying sizes of core patterns 16 that may be used in core box 10.
Metering drum 31 is mounted for rotation on axle 36, which supports member 37 Tn operation, meterincJ
device 30 is fed with binder coated sand from feed hopper 38 to fill chamber 32, drum 31 then being rotated clock~lise so as to place chamber 32 over the top of blow head 40. As metering device 31 is rotated, its sand content is confined in chamber 32 by means of stationary cylinder wall 39 until chamber 32 is properly positioned over the top of blow head 40, at which time the volumetrically measured ~L2~5~1 3 quantity of binder coated sand is discharged from chamher 32 into blow h~ad 40.
The volumetrically measured auantity of binder received by blow head 40 is then transferred to core 5 pattern cavity 17 by being blown be compressed air through investment aperture 18. This trans-fer is accomplished by movinq and stationing blow head 40, bv means not shown, under air cup 41 shown in Fig. 3.
Air cup 41 which is connected to a pneumatic cvlinder, see Fig. 5, then engages blow head 40 moving it downwardly in axial alignment with core box 10 along its axis 15 and ln sealed relationship with the top thereof by means of sealing element 42. The charge of binder coated sand is then blown from hlow head 40 through investment aperture 18 into core pattern cavity 17. If there is to be no core print on the hollow core, then blow plate 4~ will be made precise in its length to that of investment sleeve 19 so that there will be no protrusion of sand into investment aperture 18. On the other hand, if there is to be a core print, then the length of blow plate 4~ is correspondingly reduced to conform to the desired length of print. In either event, the placement of blow plate 44 within aperture sleeve 1~, coupled with the placement of a gas permeable disk within aperture sleeve 19 during gassing, as will be subsequently discuss~d, will assure a definite and predetermined configuration to the hollow core at the point of aperture 18.
On completion o the investment of sand and removal of blow head 40 from core box l0, the same cup 41 with its cylinder 78, as shown in Fig. 5, ~1L2~S~i~3 brings sealing means 50 provided with sealing head 51, as shown in Fig. 4, into alignment with a~is 15 of core box 10. ~ealing head 51 is provided with a gas permeable disk 52 which, by virtue of the action 5 of cup 41, ls caused to contact the upper surface of the binder coated sand charge in core pattern cavity 17, rather than the top o aperture sleeve 19 as previously practiced. Sealing head 51 is tiyhtly sealed against the top surface of core hox 10 by means of sealing element 54.
Gas permeable disk 52 holds the sand in core pattern cavity 17 down against the force of the catalyst gas pressure which otherwise would tend to throw sand out of cavity 17 into investment aperture 18. Accordingly, disk 52 serves to provide a hollow core whose configuration in the area of its aperture will be definite and predetermined. Disk 52, moreover, cooperates with escape space 57 in sealing head 51 by permitting air contained in the sand to retreat, or escape, into space 57 when amine catalyst is introduced under pressure into flow space 2n forcing air in the sand away from core pattern sections 13, lA. In this respect, escape space 57 can he varied in sl~e as, for example, by the placement therein of spacer rings or fillers, whereb~
the thickness of the hollow core can be correspondingly varied. Finally, gas permeable disk 52 also serves to allow compressed air to enter core pattern cavity 17 during the exhausting of core box 10.
As shown in Fig. 4, sealing head 51 is also provided with means 56 co ni cating with a source of ~OS613 -lfi-negative pressure applied to core pattern cavity 17 durin~ amine gassing. Sealiny head 51 is further provided w;th means 55 communicatin~ with a source of compressed air for facilitating the purging of core box 10 of residual amine after gassing.
As earlier discussed herein, another principal disadvantage to the cold hollow core process as described is the necessity to rotate the core box through 1~0 in order to discharge uncured binder coated sand from the cavity of the hollow core through the investment aperturef a procedure that involves complex and costly equipment to effect. In accordance with the present invention, this disadvantage is eliminated by effecting the discharge of uncured binder coated sand through the investment aperture of the core box while the core box is in a non-rotatedr i.e., up right, position by causing the uncured binder coatea sand to travel a path under the force o~ compressed alr upwardly and away from the investment aperture to a point at which it can flow freely under the force of gravity to a sand separation and collection means. In order to minimize the exposure time of the binder coated sand to the effect of the compressed air, the path of travel of the sand while under the influence of the compressed air is as short as possible and, accordingly, will preferably take the form of a curved or bent course the direction of which is essentially reversed from the point of discharge from the investment aperture to the point of deposit in the separation and collection means.
~0~
Turning now to Figs. 5 and 6, there i9 shown an embodiment for conducting the discharge of uncured binder coated sand in accor~ance with this invention comprising a sand discharge tube 60 adapted to be sealably engaged about lnvestment aperture 18 of core box 10 by means of sealing member 61 located in sand discharge head 62. Dlscharge head 62 i9 connected ~o three guide rods 63 which slide in two supporting plates 64, 73, both of which are attached to discharge tube 60. Under the force of springs 72, plate 76, which is attached to the upper ends of rods 63, is normally pushed upwardly, thus disengaging discharge head 62 from core box 10. ~hen air cup 41 presses plate 76 downwardly, it causes discharge head 62 to seal core box 10 with sealing member 61. The top of discharge head 62 can freely slide inside the end of discharge tube 60. A sand separator is rigidly mounted beneath the outside end of discharge tube 60 and comprises a housing 68, a pivotally mounted screen 69, a fine sand discharge duct 70 and lump sand discharge duct 71.
After gassing of core box 10 is complete and core box 10 is unsealed by removal of sealing head 51, sand discharge tube 60 is rotated by cylinder 67 and connecting means 66 so as to position discharge head 62 under air cup 41 which urges it toward core box 10 against the tensi.on of spring means 72 to sealably secure it to core box lO around investment aperture 18 by means of sealing element 61.
Compressed air is then introduced into flow space 20 by means of valve 24 and port 22 under suffici.ent pressure to convey uncured binder coated sand from - - ~
56~3 the cavity of the hollow core in core pattern cavity 17 through investment aperture 18 and along the bent or curved path provided by discharge tube 60 and deposit it ln the upper chamher 6R of the vibrating screen separator. Fine sand passes through screen 69 and ine discharge 70 into fine sand collector 74.
After separation of all fine sand is completed, screen 69 is pivoted to discharge lump sand through l~mp discharge duct 71 and into lump sand collector ln 75. The vibrating sand separator is provided with a deflector 77 to direct fine sand away from lump discharge duct 71 and into fine discharge duct 70.
In practicing the method oI producing hollow foundry sand cores in accordance with this invention, a charge of bindPr coated sand equivalent to essentially one volume of the core pattern cavity is metered into the blow head. The blow head is then brought into sealed relationship with the core hox ana the metered volume of sand blown into the core pattern cavity through the investment aperture, the hlow plate being positioned within the investment sleeve at su~h point as will produce the desired configuration at the aperture of the hollow core, which configuration may, if required, be in the form of a core print. The core box is then sealed with a gas permeable disk in contact with the sand in the core pattern cavity and the sand gassed with an amine catalyst to cure the binder. ~he depth of cure within the core pattern cavity will be d~termined by the equilibrium pressure reached between the amine gas and the air in the sand, which equilibrium pressure may he varied by applying a negative ~2C~S613 pressure to the core pattern cavity. After curing is complete, the core box is purged of residual amine gas and uncured binder coated sand recovered by causing it to flow upwardly under the force o~
compressed air through the investment aperture, and then to follow a hent or curved path thereafter to be deposited in a screen separator and collected. The hollow core thus formed is then removed from the core box.
The above procedure is repeatea in successive core production cycles using fresh binder coated sand in each cycle until a period of time has elapsed equivalent to about 1/10 to 1/3 the bench time of the binder coated sand. At that point in time, the metering of fresh sand to the blow head is discontinued, the metering of recovered sand to the blow head commenced, and the production procedure conducted in the same manner as before. Recovered sand is continually metered to the blow head in a quantity equivalent to about the volume of the core pattern cavity for each production cycle until essentially all of the sand lntroduced during the time period equivalent to 1/10 to 1/3 of the bench life of the binder coated sand is consumed in hollow core production. Only at this point, is fresh binder coated sand again metered to the blow head for the commencement of the production of hollow cores as before. The alternating use of fresh and recovered binder coated sand in the method of this invention
Metering drum 31 is mounted for rotation on axle 36, which supports member 37 Tn operation, meterincJ
device 30 is fed with binder coated sand from feed hopper 38 to fill chamber 32, drum 31 then being rotated clock~lise so as to place chamber 32 over the top of blow head 40. As metering device 31 is rotated, its sand content is confined in chamber 32 by means of stationary cylinder wall 39 until chamber 32 is properly positioned over the top of blow head 40, at which time the volumetrically measured ~L2~5~1 3 quantity of binder coated sand is discharged from chamher 32 into blow h~ad 40.
The volumetrically measured auantity of binder received by blow head 40 is then transferred to core 5 pattern cavity 17 by being blown be compressed air through investment aperture 18. This trans-fer is accomplished by movinq and stationing blow head 40, bv means not shown, under air cup 41 shown in Fig. 3.
Air cup 41 which is connected to a pneumatic cvlinder, see Fig. 5, then engages blow head 40 moving it downwardly in axial alignment with core box 10 along its axis 15 and ln sealed relationship with the top thereof by means of sealing element 42. The charge of binder coated sand is then blown from hlow head 40 through investment aperture 18 into core pattern cavity 17. If there is to be no core print on the hollow core, then blow plate 4~ will be made precise in its length to that of investment sleeve 19 so that there will be no protrusion of sand into investment aperture 18. On the other hand, if there is to be a core print, then the length of blow plate 4~ is correspondingly reduced to conform to the desired length of print. In either event, the placement of blow plate 44 within aperture sleeve 1~, coupled with the placement of a gas permeable disk within aperture sleeve 19 during gassing, as will be subsequently discuss~d, will assure a definite and predetermined configuration to the hollow core at the point of aperture 18.
On completion o the investment of sand and removal of blow head 40 from core box l0, the same cup 41 with its cylinder 78, as shown in Fig. 5, ~1L2~S~i~3 brings sealing means 50 provided with sealing head 51, as shown in Fig. 4, into alignment with a~is 15 of core box 10. ~ealing head 51 is provided with a gas permeable disk 52 which, by virtue of the action 5 of cup 41, ls caused to contact the upper surface of the binder coated sand charge in core pattern cavity 17, rather than the top o aperture sleeve 19 as previously practiced. Sealing head 51 is tiyhtly sealed against the top surface of core hox 10 by means of sealing element 54.
Gas permeable disk 52 holds the sand in core pattern cavity 17 down against the force of the catalyst gas pressure which otherwise would tend to throw sand out of cavity 17 into investment aperture 18. Accordingly, disk 52 serves to provide a hollow core whose configuration in the area of its aperture will be definite and predetermined. Disk 52, moreover, cooperates with escape space 57 in sealing head 51 by permitting air contained in the sand to retreat, or escape, into space 57 when amine catalyst is introduced under pressure into flow space 2n forcing air in the sand away from core pattern sections 13, lA. In this respect, escape space 57 can he varied in sl~e as, for example, by the placement therein of spacer rings or fillers, whereb~
the thickness of the hollow core can be correspondingly varied. Finally, gas permeable disk 52 also serves to allow compressed air to enter core pattern cavity 17 during the exhausting of core box 10.
As shown in Fig. 4, sealing head 51 is also provided with means 56 co ni cating with a source of ~OS613 -lfi-negative pressure applied to core pattern cavity 17 durin~ amine gassing. Sealiny head 51 is further provided w;th means 55 communicatin~ with a source of compressed air for facilitating the purging of core box 10 of residual amine after gassing.
As earlier discussed herein, another principal disadvantage to the cold hollow core process as described is the necessity to rotate the core box through 1~0 in order to discharge uncured binder coated sand from the cavity of the hollow core through the investment aperturef a procedure that involves complex and costly equipment to effect. In accordance with the present invention, this disadvantage is eliminated by effecting the discharge of uncured binder coated sand through the investment aperture of the core box while the core box is in a non-rotatedr i.e., up right, position by causing the uncured binder coatea sand to travel a path under the force o~ compressed alr upwardly and away from the investment aperture to a point at which it can flow freely under the force of gravity to a sand separation and collection means. In order to minimize the exposure time of the binder coated sand to the effect of the compressed air, the path of travel of the sand while under the influence of the compressed air is as short as possible and, accordingly, will preferably take the form of a curved or bent course the direction of which is essentially reversed from the point of discharge from the investment aperture to the point of deposit in the separation and collection means.
~0~
Turning now to Figs. 5 and 6, there i9 shown an embodiment for conducting the discharge of uncured binder coated sand in accor~ance with this invention comprising a sand discharge tube 60 adapted to be sealably engaged about lnvestment aperture 18 of core box 10 by means of sealing member 61 located in sand discharge head 62. Dlscharge head 62 i9 connected ~o three guide rods 63 which slide in two supporting plates 64, 73, both of which are attached to discharge tube 60. Under the force of springs 72, plate 76, which is attached to the upper ends of rods 63, is normally pushed upwardly, thus disengaging discharge head 62 from core box 10. ~hen air cup 41 presses plate 76 downwardly, it causes discharge head 62 to seal core box 10 with sealing member 61. The top of discharge head 62 can freely slide inside the end of discharge tube 60. A sand separator is rigidly mounted beneath the outside end of discharge tube 60 and comprises a housing 68, a pivotally mounted screen 69, a fine sand discharge duct 70 and lump sand discharge duct 71.
After gassing of core box 10 is complete and core box 10 is unsealed by removal of sealing head 51, sand discharge tube 60 is rotated by cylinder 67 and connecting means 66 so as to position discharge head 62 under air cup 41 which urges it toward core box 10 against the tensi.on of spring means 72 to sealably secure it to core box lO around investment aperture 18 by means of sealing element 61.
Compressed air is then introduced into flow space 20 by means of valve 24 and port 22 under suffici.ent pressure to convey uncured binder coated sand from - - ~
56~3 the cavity of the hollow core in core pattern cavity 17 through investment aperture 18 and along the bent or curved path provided by discharge tube 60 and deposit it ln the upper chamher 6R of the vibrating screen separator. Fine sand passes through screen 69 and ine discharge 70 into fine sand collector 74.
After separation of all fine sand is completed, screen 69 is pivoted to discharge lump sand through l~mp discharge duct 71 and into lump sand collector ln 75. The vibrating sand separator is provided with a deflector 77 to direct fine sand away from lump discharge duct 71 and into fine discharge duct 70.
In practicing the method oI producing hollow foundry sand cores in accordance with this invention, a charge of bindPr coated sand equivalent to essentially one volume of the core pattern cavity is metered into the blow head. The blow head is then brought into sealed relationship with the core hox ana the metered volume of sand blown into the core pattern cavity through the investment aperture, the hlow plate being positioned within the investment sleeve at su~h point as will produce the desired configuration at the aperture of the hollow core, which configuration may, if required, be in the form of a core print. The core box is then sealed with a gas permeable disk in contact with the sand in the core pattern cavity and the sand gassed with an amine catalyst to cure the binder. ~he depth of cure within the core pattern cavity will be d~termined by the equilibrium pressure reached between the amine gas and the air in the sand, which equilibrium pressure may he varied by applying a negative ~2C~S613 pressure to the core pattern cavity. After curing is complete, the core box is purged of residual amine gas and uncured binder coated sand recovered by causing it to flow upwardly under the force o~
compressed air through the investment aperture, and then to follow a hent or curved path thereafter to be deposited in a screen separator and collected. The hollow core thus formed is then removed from the core box.
The above procedure is repeatea in successive core production cycles using fresh binder coated sand in each cycle until a period of time has elapsed equivalent to about 1/10 to 1/3 the bench time of the binder coated sand. At that point in time, the metering of fresh sand to the blow head is discontinued, the metering of recovered sand to the blow head commenced, and the production procedure conducted in the same manner as before. Recovered sand is continually metered to the blow head in a quantity equivalent to about the volume of the core pattern cavity for each production cycle until essentially all of the sand lntroduced during the time period equivalent to 1/10 to 1/3 of the bench life of the binder coated sand is consumed in hollow core production. Only at this point, is fresh binder coated sand again metered to the blow head for the commencement of the production of hollow cores as before. The alternating use of fresh and recovered binder coated sand in the method of this invention
3~ is an essential feature thereof. At no ~ime are fresh and recovered binder coated sands admixed for charging to the blow head.
Claims (10)
1. A method for the production of hollow foundry sand cores in which binder coated sand is charged to a blow head and invested through an investment aperture of a core box into the core pattern cavity thereof, the sand in the core pattern cavity is gassed with a catalyst to cure the binder and form a hollow sand core, and uncured binder coated sand is discharged from the cavity of the hollow sand core and recovered, characterized by:
alternatively charging fresh hinder coated sand and recovered binder coated sand to the blow head for investment into the core pattern cavity whereby mixtures thereof in the blow head are avoided, the binder coated sand being charged to the blow head by volumetric metering; investing said volumetrically metered binder coated sand into the core pattern cavity through a blow plate extending into the investment aperture of the core box; inserting a gas seal in said investment aperture in contact with the sand in the core pattern cavity; providing an enclosed space outside of the core box communicating with the air contained in the sand in said core pattern cavity; and discharging uncured binder coated sand from the hollow sand core formed in said core pattern cavity through said investment aperture.
alternatively charging fresh hinder coated sand and recovered binder coated sand to the blow head for investment into the core pattern cavity whereby mixtures thereof in the blow head are avoided, the binder coated sand being charged to the blow head by volumetric metering; investing said volumetrically metered binder coated sand into the core pattern cavity through a blow plate extending into the investment aperture of the core box; inserting a gas seal in said investment aperture in contact with the sand in the core pattern cavity; providing an enclosed space outside of the core box communicating with the air contained in the sand in said core pattern cavity; and discharging uncured binder coated sand from the hollow sand core formed in said core pattern cavity through said investment aperture.
2. A method according to Claim 1 characterized in that the quantity of binder coated sand metered to said blow head is essentially equivalent to the volume of the core pattern cavity.
3. A method according to Claim 1 characterized in that the uncured binder coated sand from said hollow sand core is discharged upwardly through the investment aperture of said core box by compressed air.
4. A method according to Claim 1 characterized in that: the seal is gas permeable and compressed air is introduced through said permeable seal into said core box during exhausting thereof.
5. A method for the production of hollow foundry sand cores in which binder coated sand is charged to a blow head and invested through an investment aperture of a core box into the core pattern cavity thereof, the sand in said core pattern cavity is gassed with a catalyst to cure the binder and form a hollow sand core, and uncured binder coated sand is discharged from the cavity of said hollow sand core and recovered, characterized by:
volumetrically metering fresh binder coated sand to the blow head for investment into the core pattern cavity where the binder is cured to form a hollow sand core; discharging uncured binder coated sand from the cavity of said hollow sand core and recovering the same; forming additional hollow sand cores by metering only fresh binder coated sand to said blow head while recovering uncured binder coated sand discharged from the cavities of said cores;
discontinuing the metering of fresh binder coated sand to said blow head at a predetermined time;
commencing the volumetric metering of recovered binder coated sand to said blow head to form hollow sand cores while discharging and recovering uncured binder coated sand from the cavities of said cores;
continuing the metering of recovered binder coated sand to said blow head until said sand is essentially consumed in hollow core formation; and discontinuing the metering of recovered binder coated sand and recommencing the metering of fresh binder coated sand to said blow head, fresh and recovered binder coated sand at no time being simultaneously metered to said blow head.
volumetrically metering fresh binder coated sand to the blow head for investment into the core pattern cavity where the binder is cured to form a hollow sand core; discharging uncured binder coated sand from the cavity of said hollow sand core and recovering the same; forming additional hollow sand cores by metering only fresh binder coated sand to said blow head while recovering uncured binder coated sand discharged from the cavities of said cores;
discontinuing the metering of fresh binder coated sand to said blow head at a predetermined time;
commencing the volumetric metering of recovered binder coated sand to said blow head to form hollow sand cores while discharging and recovering uncured binder coated sand from the cavities of said cores;
continuing the metering of recovered binder coated sand to said blow head until said sand is essentially consumed in hollow core formation; and discontinuing the metering of recovered binder coated sand and recommencing the metering of fresh binder coated sand to said blow head, fresh and recovered binder coated sand at no time being simultaneously metered to said blow head.
6. A method according to Claim 5 characterized in that the quantity of binder coated sand metered to the blow head is essentially equivalent to the volume of the core pattern cavity.
7. A method according to Claim 5 characterized in that fresh binder coated sand is metered to said blow head for a time period equivalent to about 1/10 to about 1/3 of the bench life of said hinder coated sand.
8. A method according to Claim 5 characterized in that uncured binder coated sand is discharged from the hollow sand core through the aperture thereof while the core box is in the same position as during charging.
9. A method according to Claim 8 characterized in that the sand is discharged upwardly and is thereafter caused to follow a curved path.
10. A method according to Claim 9 characterized in that said curved path is greater than about 90°.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US46668083A | 1983-03-30 | 1983-03-30 | |
| US466,680 | 1983-03-30 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1205613A true CA1205613A (en) | 1986-06-10 |
Family
ID=23852693
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000450083A Expired CA1205613A (en) | 1983-03-30 | 1984-03-21 | Method for production of hollow (shell) foundry cores |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0126532A1 (en) |
| KR (1) | KR840007838A (en) |
| AU (1) | AU546308B2 (en) |
| BR (1) | BR8401558A (en) |
| CA (1) | CA1205613A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111699036A (en) * | 2018-02-15 | 2020-09-22 | 普莱克斯技术有限公司 | Excellent carbon adsorbent |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9629628B2 (en) | 2013-03-13 | 2017-04-25 | Covidien Lp | Surgical stapling apparatus |
| KR101280151B1 (en) * | 2013-03-15 | 2013-06-28 | 강성태 | Main control for hydraulic valve block casting sand-mold manufacturing method |
| CN103706765B (en) * | 2013-12-24 | 2016-01-27 | 上海爱仕达汽车零部件有限公司 | The casting method that a kind of thin-section casting is leakage-preventing |
| CN107470566A (en) * | 2017-09-25 | 2017-12-15 | 泰州康乾机械制造有限公司 | Reduce the method and sand core structure of permanent mold casting thin-wall case flange turning position gas hole defect |
| CN112264575B (en) * | 2020-10-20 | 2021-11-19 | 西安工程大学 | Hollow ceramic core adopting die swinging method and preparation method thereof |
| CN113523196A (en) * | 2021-06-05 | 2021-10-22 | 中国第一汽车股份有限公司 | Sand core structure for 3D printing |
| CN115625289A (en) * | 2022-10-19 | 2023-01-20 | 重庆长安汽车股份有限公司 | Manufacturing method of model component based on sand core additive manufacturing |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3429848A (en) * | 1966-08-01 | 1969-02-25 | Ashland Oil Inc | Foundry binder composition comprising benzylic ether resin,polyisocyanate,and tertiary amine |
| DE2557193C2 (en) * | 1975-12-18 | 1983-01-13 | Fomes S.A. Foundry and Metallurgical Supplies Corp., Chiasso | Device for the production of hollow casting cores |
| US4204569A (en) * | 1978-12-28 | 1980-05-27 | Anatol Michelson | Multi-core box apparatus for the manufacture of hollow mineral products, particularly foundry cores |
| US4232726A (en) * | 1979-03-20 | 1980-11-11 | Anatol Michelson | Process and core box assembly for heatless production of hollow items of mineral granular material |
| US4291740A (en) * | 1980-05-28 | 1981-09-29 | Anatol Michelson | Apparatus and method for heatless production of hollow items, for instance, foundry shell cores |
-
1984
- 1984-03-21 CA CA000450083A patent/CA1205613A/en not_active Expired
- 1984-03-26 AU AU26105/84A patent/AU546308B2/en not_active Ceased
- 1984-03-29 KR KR1019840001649A patent/KR840007838A/en not_active Application Discontinuation
- 1984-03-29 EP EP84302157A patent/EP0126532A1/en not_active Ceased
- 1984-03-30 BR BR8401558A patent/BR8401558A/en unknown
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111699036A (en) * | 2018-02-15 | 2020-09-22 | 普莱克斯技术有限公司 | Excellent carbon adsorbent |
Also Published As
| Publication number | Publication date |
|---|---|
| BR8401558A (en) | 1984-11-13 |
| AU546308B2 (en) | 1985-08-29 |
| EP0126532A1 (en) | 1984-11-28 |
| KR840007838A (en) | 1984-12-11 |
| AU2610584A (en) | 1984-10-11 |
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| MKEX | Expiry |