US3688830A - Method of making molds - Google Patents

Method of making molds Download PDF

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Publication number
US3688830A
US3688830A US853984A US3688830DA US3688830A US 3688830 A US3688830 A US 3688830A US 853984 A US853984 A US 853984A US 3688830D A US3688830D A US 3688830DA US 3688830 A US3688830 A US 3688830A
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United States
Prior art keywords
pattern
mold
sand
cavity
passage
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Expired - Lifetime
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US853984A
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English (en)
Inventor
Walter H Van Deberg
Earl A Thompson
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EARL A THOMPSON Manufacturing CO
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EARL A THOMPSON Manufacturing CO
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C23/00—Tools; Devices not mentioned before for moulding
    • B22C23/02—Devices for coating moulds or cores
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C15/00—Moulding machines characterised by the compacting mechanism; Accessories therefor
    • B22C15/23—Compacting by gas pressure or vacuum
    • B22C15/24—Compacting by gas pressure or vacuum involving blowing devices in which the mould material is supplied in the form of loose particles

Definitions

  • This invention relates to the making of molds, for example shell molds for making ferrous metal castings.
  • the invention is concerned with improvements in both the application of parting agent to permanent patterns and with the delivery of mold-forming material into the pattern cavity.
  • the walls of the cavity which determine and shape the mold are coated with a parting agent such as a silicon oil which may be applied before each mold is formed.
  • a parting agent such as a silicon oil which may be applied before each mold is formed.
  • the parting agent is sprayed on the exposed cavity surfaces of an open pattern with an air suspension or mist of the parting agent. But the parting agent also coats the surfaces of separation of the pattern. This retains particles of dust or fine sand which may dislodge from the finished molds. Such particles may prevent the subsequent precise mating of the mold halves and prevent precise closing of the pattern.
  • One of the objects of the invention is to increase the reliability and evenness of coating with parting agent.
  • Another object is to prevent application of parting agent to the parting surfaces of the pattern.
  • Another object is to provide an improved method for detecting minute separation of parts of a mold which is nominally and apparently closed but actually held slightly open by small obstacles such as grains of molding sand adhering to the surfaces of separation.
  • Another object is to prevent excessive build-up of parting agent in one part of the pattern.
  • Another object of the invention is to provide an improved, economical, efficient and rapid device for transferring measured amounts of sand from a storage place into a mold cavity and packing the sand in the cavity to form a precise mold.
  • Another object of the invention is to provide an improved method and means for maintaining, during the blowing operation, a body of sand having fluid characteristics so that the sand will flow accurately into the mold cavity and be firmly packed to provide a precise mold.
  • Another object is to provide an apparatus which can readily be moved against the pattern and away from the pattern to permit the coating of the pattern with a parting agent between intervals of blowing the sand into the mold.
  • FIG. I is a diagrammatic side elevation of a pattern for forming molds in accordance with this invention.
  • FIG. 2 is a diagrammatic plan of the pattern shown in FIG. 1 showing one form of blow-vent nozzle for coating the mold cavity with parting agent.
  • FIG. 3 is a view corresponding to FIG. 2 showing the blow-vent nozzle in a different position to perform another coating step.
  • FIG. 4 is a view corresponding to FIG. 2 showing schematically one form of nozzle for blowing molding sand into the pattern cavity.
  • FIG. 5 is a diagrammatic illustration of one form of device for detecting an inaccurately closed pattern.
  • FIG. 6 corresponds to FIG. 4 but shows a modified fonn of the sand nozzle.
  • FIG. '1 is a flow diagram illustrating successive steps in the making of a mold in accordance with my invention.
  • FIG. 8 is a partial structural elevation corresponding to FIG. 1 showing one form of apparatus for carrying out this invention with the blow-bent nozzle in the position indicated by FIG. 2.
  • FIG. 9 is an elevation like FIG. 8 showing the blowvent nozzle in a position corresponding to FIG. 3.
  • FIG. 10 is a partially schematic elevation taken from the right of FIG. 8 and 9 showing the movement of the blow-vent nozzle toward and away from the pattern.
  • FIG. 11 is a schematic elevation of another form of device for blowing sand into the pattern.
  • FIG. 12 is an enlarged structural section in the plane of the paper showing the lower portion of the sand blowing device illustrated in FIG. ll.
  • FIG. 13 is an enlarged elevation partly in section of the sand fluidizing nozzle shown in FIG. 12.
  • FIG. 14 is a perspective partly broken away of a modified form of fiuidizing nozzle.
  • pressure gas means any gas under pressure, including, without limitation air and superheated steam.
  • Sand means any granular mold-forming material adapted to be packed into a cavity and cured to form a mold.
  • 10 and I2 are the top and bottom halves of a permanent metal pattern which mate along a plane of separation indicated by the line 14.
  • the pattern has a series of cavities 16 connected by passages 18 as shown in dotted lines.
  • the bottom half 12 has, at the parting plane, grooves forming passages 20 and 22 from outside the pattern into the series of cavities, there being one passage connecting each end of the series of cavities with the atmosphere as shown in FIG. 2.
  • a gas suspension of parting agent is sprayed into one of the passages 20 or 22 while venting the other passage 22 or 20.
  • the spray can pass through the entire pattern and coat the walls of each of the four cavities.
  • a blow-vent nozzle 24 including a bar 26 carrying spray nozzle 28 and having spaced calibrated orifices 30 and 32 through the bar.
  • the size of the exit orifices 30 and 32 is so related to the size of the nozzle 28, to the blowing pressure and to the size of the passages that the suspension is somewhat retarded in being vented to the atmosphere to encourage even coating.
  • the pattern can be sprayed in the reverse direction as shown in FIG. 3 in which the blow-vent nozzle has been moved so that the nozzle 28 sprays into the pattern passage 20 and the passage 22 is vented through the orifice 32.
  • parting agent has various advantages. As parting agent is sprayed into one passage (e.g., 22) it tends to coat the early part of the passage through the pattern (including the cavities) more heavily than the later part of the passage near the exit 20. Not only does reverse blowing promote even coating, but this even coating tends to prevent excessive build-up of parting agent during the repetition of the process in making a large number of molds. Repeated removal of cured molds progressively removes or consumes the parting agent. If the parting agent were sprayed always from the same end, and sufficient agent were maintained at the other end, an undesirable quantity would build up near the apply end.
  • the invention includes spraying alternately from opposite ends of the pattern successively even when a single spray in one direction is enough to coat the pattern between making one mold and making the next.
  • the mold cavity may always be sprayed through passage 22 but may be sprayed, for example, every other time a mold is made, or every fourth time.
  • the mold cavity may be sprayed only through passage 20, but may be sprayed only in the intervals between spraying at station 1. This tends to even the consumption of the parting agent, even if every application, while sufficient, is not uniform.
  • parting agent Since the parting agent is applied only when the mold halves are accurately mated and since the passages and cavities of the pattern are exposed to the atmosphere through a vent which controls the pressure in the cavities and prevents the development of an excessive pressure, no parting agent reaches the surfaces of separation of the pattern.
  • the gas used for blowing the parting agent may be superheated steam. This appears to reduce the viscosity of some parting agents and to distribute them evenly. Also it tends to prevent cooling of the mold between curing operations which would otherwise occur with compressed air.
  • the pattern is ready to be filled with sand.
  • we pack the cavities by blowing sand into one of the passages, for example, 22, while closing or blocking the other passage 20.
  • This provides a single dead-end passage for delivering an air suspension of treated sand into the pattern.
  • the pattern is provided with small air vents, as is known in the art, to permit the escape of the air from the suspension of sand grains while preventing the escape of the sand and thus effect packing.
  • vents occur around ejection pins which have a carefully determined clearance between the pins and the holes in which they are mounted. This is customary molding practice and being well known is not illustrated here.
  • a sand blow nozzle as shown in FIG. 4, in which a bar 34 carries the nozzle 36 and is elongated to cover the passage 20 while the male 36 is opposite the passage 22. When the bar is clamped against the pattern this effectively closes the passage 20.
  • One very good way of preventing flow out of the passage 20 while blowing sand into the passage 22 is to blow sand into the mold cavity through both passages at the same time, for example with a twin sand blow nozzle as illustrated in FIG. 6. Sand is blown simultaneously into both passages 20 and 22 through two sand nozzles 36' and 36' in a manifold 38.
  • the process of making molds includes the following steps: close pattern, apply parting agent, blow sand, cure mold, open pattern and remove finished mold, close pattern, apply parting agent if necessary, blow sand, and repeat.
  • a passage 40 is provided through one of the pattern halves to the surface of separation as shown in FIG. 5.
  • a passage 40 is provided through one of the pattern halves to the surface of separation as shown in FIG. 5.
  • air is supplied from a pressure regulator 42 through a calibrated orifice 44 to a test line 46 from which it is delivered into the passage 40 through a pressure tight connection.
  • Pressure in the line 40 is measured by any suitable sensor 48, which may be a flexible diaphragm clamped between two halves of a chamber and carrying a rod which, when there is high pressure in line 46, holds open a switch 50 in an electric circuit.
  • An open switch indicates that the pattern is closed.
  • the electric circuit 52 may make a visual or audible signal or may reject the pattern so that the parting agent may not be applied or so that sand will not be blown in.
  • reject to include anything which prevents use of the pattern, for example physically removing the pattern from proximity to the blow-vent nozzle or from proximity to the sand blow nozzle, or activating mechanism to cause the pattern to pass by the nozzles while preventing operation of the nozzles.
  • the invention includes mounting a series of patterns on a transfer device such as a rotary indexing table 60, for example like that shown at 10 in the US. Re. Pat. No. 26,218 to Earl A. Thompson, June 6, I967, the disclosure of which is incorporated by reference herein.
  • the table is intermittently rotated, to present each mold successively to a series of stations in which the operations diagrammatically indicated in FIG. '7 may be performed.
  • the mold may be coated with parting agent sprayed in one direction as indicated in FIG. 2.
  • the pattern may be sprayed with parting agent in the reverse direction as indicated in FIG. 3.
  • the pattern may pass by station 2 depending on whether or not a reverse coating is required.
  • the pattern may be filled with sand either as indicated in FIG. 4 or as in FIG. 6.
  • the mold is cured in any well known manner.
  • the pattern is opened and the finished mold removed.
  • the mold is closed.
  • the mold is tested for precise closing as indicated in FIG. 5. If the mold is not closed it is rejected in any one of the ways indicated above.
  • the mold is not rejected it is coated with parting agent again, if this is necessary, and this may be done either in a single stage illustrated in FIG. 2 or in two stages as illustrated in FIG. 3. Then the cycle is repeated as described above.
  • patterns 10-12 are attached at intervals around the circumferencc of the table 60 corresponding to the positions of the fixtures 1 14 of the reissue patent.
  • the table is rotated step by step as disclosed therein, stopping with a pattern at each station.
  • Blow-vent nozzles 24 and sand blow nozzles 36 are placed at the various stations, corresponding to stations 14 in the reissue patent, to perform the operations described above whenever the table is at rest.
  • the parts 24, and 36 may be constructed as shown in FIGS. 10-14.
  • arm 62 carries the blow-vent nozzle 24 and is pivoted between the arms 64 of a pivoted yoke 65 by a shaft 66.
  • the rod can be rocked in the yoke to move the blow-vent nozzle between its FIG. 8 (or FIG. 2) position and its FIG. 9 (or FIG. 3) position by a piston rod 68 sliding in a double-acting cylinder 70 pivoted to the yoke.
  • the piston rod may be activated by suitable hydraulic apparatus like that shown in the reissue patent by having the cylinder form part of a hydraulic link such as a, c or e in FIG. 5 of that patent.
  • the pivoted yoke 65 is clamped to a shaft 72 (FIG. 10) journaled in a fixed support 74 so that the entire structure including blow-vent nozzle 24, arm 62, yoke 65, and cylinder can be rocked selectively to clamp the blow-vent nozzle against the pattern, as in full lines in FIG. 10, or move away from the pattern (dotted lines in FIG. 10) to let the table be moved.
  • This rocking is done by a piston rod 76 pivoted to the yoke 65 (FIG. 10) and sliding in a double-acting hydraulic cylinder 78 pivoted to the support 72.
  • the cylinder may be actuated as shown in the Reissue patent. In the position of FIG.
  • the central nozzle 28 discharges into the first passage 22 in the pattern and the passage 20 is vented through the control orifice 30.
  • the nozzle 28 is supplied with a suspension of parting agent by any suitable connection, not shown, connected to a timed control valve, not shown. In the position of FIG. 9 the nozzle 28 discharges into the passage 20 of the pattern while the control orifice or vent orifice 32 vents the passage 22.
  • FIGS. 11 and 12 show diagrammatically and structurally one form of device for blowing sand into the patterns.
  • a sand hopper including a discharge tube 92 is attached to the upper side of a sand blow box 94 which carries and communicates with a sand blow nozzle 36 which may have a seal 95 which can be pressed against the pattern 10-12.
  • the hopper and blow box together form a rigid structure which is rigidly supported on a bar 96 pivoted to a fixed support at 98 so that the bar can be swung up and down by a rod and piston 100 pivoted at 102 to a fixed support and sliding in a double acting hydraulic cylinder 104 pivoted at 106 to the bar 96 and supplied by a hydraulic lines 108 and 110.
  • Sand contained in the hopper 90 can drop into the blow box when a sand valve 112 opens downward at the bottom of the tube 92.
  • the valve is pivoted to a link 116 pivoted at its left end to the hopper at 118 and pivoted at its right end at 120 to a double acting hydraulic cylinder 122 having a piston and rod 124 pivoted to the bar 96 at 106 and supplied by hydraulic lines 126 and 128.
  • the valve 112 may be supported by a tube 114 pivoted at in the link 116. When there is higher hydraulic pressure in the line 126 this tends to lengthen the link formed by the cylinder, piston and rod, and this holds the valve closed. When there is higher pressure in the line 128 the valve is dropped to admit sand to the blow box.
  • Opposite ends of the cylinder 122 may be pressurized to open or close the valve by a hydraulic link corresponding to the link 3144 in the Reissue patent referred to.
  • a quantity of sand approximately equal to that required to fill the mold cavity will be dropped into the blow box.
  • the maximum quantity of sand in the blow box at this time will be about 25 percent more than required to fill the mold and will substantially fill the blow box, although it may be slightly less than the capacity of the blow box.
  • valve 112 With the blow box 94 held against the pattern -12 by the cylinder 104 the valve 112 is momentarily opened to deposit the desired quantity of sand. Then the valve 112 is closed and air under pressure is admitted by a valve 130 to the interior of the blow box to blow sand into the pattern until the cavity is tightly packed with sand, leaving some sand remaining in the blow box. Thereafter the valve 130 is closed, the blow box is vented to relieve pressure therein through vent line 152 and the entire apparatus is swung away from the pattern 10-12 to allow table 60 to be rotated.
  • the sand should be in a condition approximating that of a fluid and there should be a moving force on the top surface of the sand.
  • the first is achieved by blowing air under pressure into the body of the sand below its top surface and distributing this air throughout the sand to produce an airsand mixture which has fluid characteristics analogous to the properties of quick sand.
  • This fluid condition is achieved by the air nozzle 134 in FIGS. 12 and 13.
  • This is a hollow tube 154 having an interior passage which is an extension of the passage 132 and which is connected through radial passages 156 with exterior grooves 158 inside a screen 160 which surrounds the tube.
  • the nozzle 134 has a flange 162 by which it is attached to an adjustable plug 164 through which the passage 132 is formed. The plug can be adjusted in and out by screws 166 and springs 168.
  • the nozzle 134' shown in FIG. 14 can be formed as a hollow cylinder of porous sintered metal analogous to the metal used for porous self-lubricating bearings.
  • the nozzle extends substantially across the width of the blow box and is aligned with the blow nozzle 36 and extends close to a tapered opening 170 which matches the tapered opening 172 of the interior of the blow nozzle 36.
  • the air admitted through the nozzle 134 fluidizes the entire body of sand in the blow box.
  • the force which flows the sand into the pattern may be the force of air pressure on top of the sand in the blow box, plus the force of fluidizing air, the air being admitted through the passages 132 and 174, whenever the valve 130 is open.
  • the pressure on top of the sand should be equal to or preferably greater than the pressure of the air within the body of the sand in order to achieve satisfactory flow of sand and to prevent the air from the nozzle 134 causing a sand storm in the space above the sand above the blow box.
  • the pressure above the sand will be the pressure of the air supply while the pressure within the sand will be somewhat less due to the resistance to flow through the nozzle 134 and through the sand itself.
  • the required balance between air pressure on top of the sand and fluidity can be determined by proper adjustment of the plug 164 in or out and by proper proportion of the passages 156 and 158 and screen (or al ternatively the porousity of the nozzle 134').
  • a choke may be placed in the passage 132.
  • vent line 152 has a choke 176 to reduce the pressure slowly above the sand.
  • FIG. 12 shows the air supply and vent connection to the space above the sand and the blow box.
  • the wall of the blow box is provided with an opening 180 for connection to the line 174 and an opening 182 containing the suitable choke 176 for connection to the vent line 152.
  • a screen 184 may be placed over these openings.
  • the pressure from air above the sand in the blow box can be dispensed with and the sand flowed into the pattern centrifugally.
  • the vent line and the fluidizing line would be used and the entire structure would be revolved rapidly about an axis to the right of the blow box as seen in FIG. 12.
  • the L-shaped blow box illustrated would be changed to a straight cylindrical structure arranged radially between the axis of rotation and the patterns 10-12. The entire structure would be rotated or revolved at any suitable speed to provide the necessary force on the inter-face between the sand and the space in the box which force would be equal to or greater than the force exerted by the air pressure in the sand.
  • the table 60 is intermittently rotated. When the table is at rest the blow nozzles and sand nozzles are pressed against the patterns, then the appropriate blowing operations are performed, the air supply is shut off and the blow-vent nozzle and sand nozzles are swung away from the patterns. Then the table is advanced to the next position of rest. All of these movements are in timed coordination and can be effected by the actuation and control apparatus disclosed in said Reissue patent.
  • Each of the movements and each opening and closing of a valve to supply parting agent or sand may be performed by the appropriate cylinders shown herein or other cylinders, not shown, to operate the valves, all of which cylinders are connected to hydraulic links such as a, c, e, g, h disclosed in said Reissue patent. These are arranged to perform in order the steps illustrated in H0. 7.
  • the method of making a mold which includes using a pattern having a cavity for forming a mold and having a pair of passages from outside the pattern into the cavity, which includes flowing a gaseous suspension of parting agent in one direction through to one of the passages and into the cavity, then flowing a gaseous suspension of parting agent in the opposite direction through the other passage and into the cavity, then preventing flow from the pattern out of one of the passages while flowing a gaseous suspension of moldforming material through the remaining passage and while permitting escape through the pattern of the gas of the last named suspension to pack the cavity with mold-forming material.
  • the method of making molds in a pattern having a passage through the pattern including a cavity for forming a mold which method includes blowing a suspension of parting agent in one direction into the passage to coat the cavity, filling the cavity with mold-forming material and forming a mold, removing the mold, blowing a suspension of parting agent in the opposite direction through the cavity to coat the mold and again makiaigla mold in the cavity.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Casting Devices For Molds (AREA)
  • Mold Materials And Core Materials (AREA)
US853984A 1969-08-28 1969-08-28 Method of making molds Expired - Lifetime US3688830A (en)

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US85398469A 1969-08-28 1969-08-28

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US (1) US3688830A (de)
AU (1) AU1866970A (de)
DE (1) DE2042824A1 (de)
FR (1) FR2059729A1 (de)
GB (1) GB1326245A (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20050067128A1 (en) * 2003-09-27 2005-03-31 Korneff Neil Alex On-demand ejection for injection molds

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS55147462A (en) * 1979-05-08 1980-11-17 Sintokogio Ltd Molding method of lower mold and squeeze plate device

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE513378C (de) * 1930-11-26 Wilhelm Seidemann Sandschleuderformmaschine
US3001829A (en) * 1959-03-21 1961-09-26 Siderurgie Fse Inst Rech Arrangement for the automatic adjustment of a distributor of pulverulent material under pressure
US3121593A (en) * 1961-02-23 1964-02-18 Simpson Herbert Corp Pneumatic material handling apparatus
US3149884A (en) * 1963-01-07 1964-09-22 Magnet Cove Barium Corp Pneumatic conveyer
US3192580A (en) * 1962-11-14 1965-07-06 British Ind Corp Apparatus and method for continuously producing investment molds
US3269428A (en) * 1960-10-24 1966-08-30 St Regis Paper Co Method for packaging dry divided solid materials
US3360301A (en) * 1966-07-11 1967-12-26 Hughes Tool Co Loading apparatus for bulk transport systems
US3470938A (en) * 1966-09-28 1969-10-07 Sherwin Williams Co Mold and core blowing machine
US3540520A (en) * 1967-09-01 1970-11-17 Sherwin Williams Co Foundry molding machine with sand valve seal and diaphragm blow valve means

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE513378C (de) * 1930-11-26 Wilhelm Seidemann Sandschleuderformmaschine
US3001829A (en) * 1959-03-21 1961-09-26 Siderurgie Fse Inst Rech Arrangement for the automatic adjustment of a distributor of pulverulent material under pressure
US3269428A (en) * 1960-10-24 1966-08-30 St Regis Paper Co Method for packaging dry divided solid materials
US3121593A (en) * 1961-02-23 1964-02-18 Simpson Herbert Corp Pneumatic material handling apparatus
US3192580A (en) * 1962-11-14 1965-07-06 British Ind Corp Apparatus and method for continuously producing investment molds
US3149884A (en) * 1963-01-07 1964-09-22 Magnet Cove Barium Corp Pneumatic conveyer
US3360301A (en) * 1966-07-11 1967-12-26 Hughes Tool Co Loading apparatus for bulk transport systems
US3470938A (en) * 1966-09-28 1969-10-07 Sherwin Williams Co Mold and core blowing machine
US3540520A (en) * 1967-09-01 1970-11-17 Sherwin Williams Co Foundry molding machine with sand valve seal and diaphragm blow valve means

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20050067128A1 (en) * 2003-09-27 2005-03-31 Korneff Neil Alex On-demand ejection for injection molds

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DE2042824A1 (de) 1971-03-11
GB1326245A (en) 1973-08-08
FR2059729A1 (de) 1971-06-04
AU1866970A (en) 1972-02-17

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