CA1153865A - Metal casting - Google Patents
Metal castingInfo
- Publication number
- CA1153865A CA1153865A CA000409359A CA409359A CA1153865A CA 1153865 A CA1153865 A CA 1153865A CA 000409359 A CA000409359 A CA 000409359A CA 409359 A CA409359 A CA 409359A CA 1153865 A CA1153865 A CA 1153865A
- Authority
- CA
- Canada
- Prior art keywords
- mold
- cavities
- spaced
- inches
- molten metal
- 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
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D18/00—Pressure casting; Vacuum casting
- B22D18/06—Vacuum casting, i.e. making use of vacuum to fill the mould
Abstract
ABSTRACT
A rigid, self supporting, gas permeable low temperature bonded sand grain mold is disclosed. The mold has side surfaces extending between vertical-ly spaced upper and lower surfaces. A plurality of horizontally spaced cavities for molding respective parts are spaced between the upper and lower surfaces.
The mold cavities have gate passages with portions having a maximum width of 0.75 inches extending from the cavities, with their lower open ends at the lower surface of the mold.
A rigid, self supporting, gas permeable low temperature bonded sand grain mold is disclosed. The mold has side surfaces extending between vertical-ly spaced upper and lower surfaces. A plurality of horizontally spaced cavities for molding respective parts are spaced between the upper and lower surfaces.
The mold cavities have gate passages with portions having a maximum width of 0.75 inches extending from the cavities, with their lower open ends at the lower surface of the mold.
Description
~1538~5 This application is a division of application 336,736 filed October 1, 1979.
This application relates to metal casting in gas permeable molds.
Although the techniques disclosed in United States Patent Nos.
3,863,706 and 3,900,064 have been in successful commercial use for several years, we have discovered the existence of certain problems in their use with gas permeable molds of the low temperature bonded sand grain type rather than the high temperature resistant ceramic type with which they were primarily intended to be used.
These problems occur because low temperature bonded sand grain shell molds, such as those of the Croning type, in which sand grains or similar particles are bonded together with a small proportion of an inorganic or organic plastic thermal or chemical setting resin or equivalent material, although much less expensive to produce than ceramic molds, have two major deficiencies as compared to ceramic molds, in that they have relatively soft interior mold cavity surfaces and also fail rapidly at high temperatures be-cause their low temperature bonding materials decompose at low temperatures so that the mold fails rapidly at temperatures lower than that of the molten casting metal, particularly with ferrous metals.
Insofar as the first deficiency is concerned, under the high vacuum required with the techniques of those patents in order to lift the molten metal up the single long vertical central riser from which it flows into the multiple mold cavities through vertically spaced gate passages, the molten metal frequently penetrates the soft mold surface of a low temperature bonded sand grain mold to the extent that casting quality is so reduced as to be unacceptable.
Insofar as the second deficiency is concerned, since the effective 115~
life before failure of a low temperature bonded sand grain mold is measured in seconds in the presence of molten ferrous metals, the time required to solidify the castings in the molds of those patents is frequently of such duration that the low temperature bonded sand grain mold fails before the molten metal in the mold cavities is sufficiently solidified.
Because of these problems, under many circumstances, particularly when casting parts of ferrous metals, Iow temperature bonded sand-grain molds ca~not be utilized with the techniques of those patents, so that the much more expensive ceramic shell molds must be substituted in order to provide acceptable castings.
According to the present invention there is provided a rigid self supporting gas permeable low temperature bonded sand grain mold havirlg side surfaces extending between vertically spaced upper and lower surfaces with a plurality of mold cavities spaced therebetween in a generally horizontal area and horizontally spaced from one another, said mold cavities having gate pass-ages with portions having a maximum width of 0.75 inches extending from said cavities with their lower open ends spaced from one another and t~rminating in a generally horizontal plane at the lower surface of said mold.
In use of the mold, the lower surface and the open end of the gate passages are submerged beneath an underlying surface of molten metal while the upper surface and at least a portion of the side surfaces are maintained thereabove. A reduced pressure is applied to the upper surface of the mold to fill the mold cavities with molten metal. The molds are unheated and at ambient room temperature, so that the thin sections of molten metal in the relatively narrow gate passage portions quickly solidify, but only for a short period of time before they remelt due to the heat provided by the underlying molten metal in the container. This brief period of gate passage solidifica-tion makes it possible quickly to move the mold vertically upwardly out of . 2 ' ' ~53t~6S
contact with the underlying surface of molten metal~ even though the molten metal in the mold cavities may not yet have entirely solidified, before the solidified metal in the narrow gate passage portions remelts and allows the molten metal in the mold cavities to drain back into the container of molten metal. Particularly with high melting point metals such as ferrous metals cast at temperatures of 2000 degrees ~ or higher, we have found that by quick-ly moving the mold out of contact with the underlying surface of molten metal, after the initial occurrence of solidification of metal in the narrow gate passage portions, further heat input into the mold is prevented and mold failure time is extended sufficiently for the castings in the mold cavities to solidify. It also makes possible an unusually short casting cycle time, which reduces production cost.
With molds having relatively small cavities, such as those having internal thicknesses of less than 0.50 inches, we have found that filling and solidification of the molten metal both in the mold cavity and the adja-cent narrow gate passage or portion thereof will occur rapidly enough so that the mold may be removed before it fails. With larger mold cavities, at least with metals which do not shrink upon solidification, more than a single narrow gate passage may be used for more rapid mold cavity filling so that the mold may be removed before it fails.
With metals which shrink upon solidification and with large mold cavities, such as those having internal thicknesses of greater than 0.50 inches which cannot be filled through the narrow gate passage portions of the in-vention before mold failure occurs, a blind riser may be used between one or re vertical gate passages and a mold cavity, so that at least a portion of the metal in the blind riser and in the mold cavity will remain in molten condition for flow into the mold cavity after removing the mold from contact ~153~6S
with the underlying surface of molten metal.
When using multiple cavity molds, since the lower open ends of the gate passages are spaced from one another, a plurality of unconnected cast metal parts or groups of parts are automatically provided.
With the conventional rigid, self supporting, low temperature bonded sand grain mold as used in the methods of the present invention, we have dis-covered that the maximum permissible submergence times, that is, maximum length of time that the mold may be in contact with the underlying surface of molten metal before the solidified metal in the narrow portions of the gate passages remelts or the mold begins to fail, is largely determined by the temperature at which the underlying molten metal must be maintained.
In the case of ferrous metal, such as cast iron and steel, which are cast at temperatures greater than 2000 degrees F, the time is relatively short, a maximum of about 30 seconds; so that submergence times of no more than about 5 to 15 seconds have been found to be desirable. Also, in order to prevent mold cavity surface penetration, reduced pressures of only about -1.0 to -3.0 psig (13.7 to 11.7 psia) should be used to raise the molten ferrous metal into mold cavities to a level no higher than about 6 to 8 inches above the surface of the molten metal in the container. With lower melting point metals, such as copper and alur.~inum and their alloys, longer times and higher mold cavity heights may be used.
Thc mold cavities may extend to or across a mold parting plane and may be arranged in a generally horizontal plane, preferably distributed both lengthwise and widthwise thereof, and horizontally spaced from one another.
The maximum width of each of the gate passage portions is prefer-ably no more than about 0.5 inches. With multiple cavity molds, the vertical portions of the gate passages are generally perpendicular to the parting plane ~ws~
and their open ends are spaced from one another and distributed in a horizontal plane.
For castings having wall thicknesses of less than about 0.50 inch, the narrow gate passage portions may be adja.cent the mold cavity, with a larger central vertical gate passage. For larger castings having greater wall thicknesses, more than one narrow gate passage portion may be used if shrink-age is not a problem; otherwise, a blind riser may be interposed between one or more gate passages having a narrow vertical portion and one or more part cavities.
The vacuum means for relatively varying the pressure within the chamber preferably provide the sole support for the mold against the chamber.
In the accompanying drawings, which illustrate exemplary embodiments of the present invention:
Figure 1 is a diagrammatic side view, partly in section, of a mold and apparatus according to the invention;
Figure 2 is a detail side cross-sectional view of the chamber por-tion of the apparatus of Figure l;
Figure 3 is a top view of the mold of Figure l;
Figure 4 is a detail side partial cross-sectional view of the mold of Figure 3;
Figure 5 is a detail side partial cross-sectional view of the mold of Figures 3 and 4 mounted on the chamber of the apparatus, with the lower surface of the mold submerged beneath the underlying surface of molten metal in the container;
Figure 6 is a cross-sectional side view of a molded metal part;
Figure 7 is a detail side partial cross-sectional view of a modifi-llS;~
cation of the mold of Figure l;
Figure 8 is a detail top partial cross-scctional view of the mold of Figure 7, taken along line 8-8 of Figure 7;
Figure 9 is a detail side partial cross-sectional view of another modification of the mold of Figure l; and Figure 10 is a detail side partial cross-sectional view of a further modification of the mold of Figure 1.
Referring to Figure 1, the apparatus in general includes a base 12 having mounted thereon a post 14 on which is mounted, for vertical sliding movement by power piston and cylinder 16, a horizontally extending arm 18.
Chamber 20, hereinafter more fully described, is mounted on support member 19 which extends downwardly from the free end of arm 18 above a container 22 for holding molten metal.
Referring to Figures 3 and 4, the rigid, self supporting, gas perm-eable, low temperature bonded sand grain mold, generally designated 30, commonly referred to as a Croning shell mold, is made by techniques and equip-ment well known in the art, of sand grains or equivalent particles and in-organic or organic thermal or chemical setting plastic or equivalent low temperature bonding material, with a minor percentage, usually about 5 %, of .
low temperature bonding material, by distributing the loose sand and bonding material mixture over heated metallic half patterns on a metal base plate which forms the parting plane, over which it hardens into a rigid, self supporting mold half shell which is then removed from the metallic half patterns and base plate for use.
- As shown in Figure 4, the mold 30 is constructed of two such half shells, upper and lower, which are then adhesively secured together along horizontal mold parting plane 29 to provide a unitary, disposable, rigid, self ~L153~6S
supporting mold 30. Mold 30 has peripherally extending side surfaces 32 extending vertically between vertically spaced upper surface 31 and lower sur-face 33 which are generally parallel to mold parting plane 29. Surfaces 31 and 33 are irregular and have a rough outer surface since they wereformed of generally uniform thickness on the irregular contour of the heated pattern.
To provide for the support of mold 30 and for the application of re-duced pressu~e to its upper surface 31, said upper surface is formed at its outer edge, as by pressing it while still in plastic condition, to form a con-tinuous peripheral horizontal flat sealing surface portion 38 suitable for sealing against chamber 20, as hereinafter more fully explained.
A plurality of single part mold cavities are provided spaced between the upper and lower surfaces, extending across mold parting plane 29, as shown in Figures 3 and 4, of which two are shown in Figure 4. Multiple part cavities may also be so provided, as explained in more detail hereinafter. In commercial practice, the number of such mold cavities would generally fall between six and twenty, seventeen being shown in Figure 3. Such single or multiple part mold cavities are distributed within the horizontal area within the periphery of mold 30, with a plurality thereof extending across the length and width of the mold 30 between its upper and lower surface 31 and 33. Cavities 34 are hori-zontally spaced from one another generally in a horizontal plane and extend across parting plane 29. Each mold cavityJ such as is shown in connection with cavities 34, has an individual vertical gate passage 35, generally perpendicular to parting plane 29, extending from its lower side, with the lower open ends of such vertical gate passages 35 being spaced from one another both widthwise and lengthwise and terminating in a generally horizontal plane parallel to parting plane 29 at the lower surface 33 of mold 30.
As explained above, at least a portion of each of gate passages 35 115~
should be relatively narrow in at least one dimension, at most not greater than 0.75 inch, and preferably not more than 0.5 inch. Conveniently, these narrow gate passages or portions thereof are vertical and of circular cross section, although other configurations may be used.
Referring to Figures 1, 2 and 5, chamber 20 provides the sole sup-port for holding mold 30 against chamber 20 and for applying reduced pressure from vacuum pump 24 through a suitable valve 26 and hose 28 to its upper sur-face 31. As seen in Figure 2, chamber upper wall 44 is connected to the lower end of support 19 and is provided with an access port 58 to which vacuum hose 28 is connected for applying a reduced pressure to the interior of cham-ber 20 and to the upper surface 31 of mold 30 when desired.
In addition, chamber 20 has a bottom opening defined by its down-wardly extending peripheral outer wall 40 which extends downwardly from the outer periphery of its upper wall 44 to define the interior of chamber 20.
As best seen in Figures 2, 4 and S, outer wall 40 may be provided about its lower end with a horizontal sealing surface 42 for sealing against the hori-zontal upper sealing surface 38 of mold 30 around the periphery thereof and generally coextensive with the horizontal area of mold 30 containing the mold cavities, with a portion of the peripheral side surface 32 and bottom surface 33 of mold 30 extending downwardly beyond chamber 20.
In operation, with chamber 20 in raised position as shown in Figure 1, mold 30 is manually or automatically positioned with its peripheral sealing surface 38 against sealing surface 42 of chamber 20. Valve 26 is then operated to provide the sole force to hold mold 30 into operating position against chamber 20 and to apply throughout upper surface 31 of mold 30 a reduced pres-sure, preferably only of about -1.0 to -3.0 psig (13.7 to 11.7 psia), through chamber port 58 to the interior of chamber 20 and the upper surface 31 of mold 1~S3~GS
30 within the periphery of sealing surface 38 and coextensive with the mold area containing the mold cavities.
Power piston and cylinder 16 are then operated to move chamber 20 carrying mold 30 therebeneath downwardly toward container 22 to lower the lower surface 33 of mold 30 with the lower open ends of all of the vertical gate passages beneath the surface 60 of molten metal in container 22.
The reduced pressure applied to the upper surface 31 of mold 30 causes molten metal to rise into the gate passages and fill all the mold cavi-tives simultaneously.
The power piston and cylinder 16 are operated shortly af*er sub-mergence, as soon as the mold cavities have been filled and molten metal extend-ing across at least a portion of each of the gate passages has solidified, to raise chamber 20 and mold 30, whereupon a portion of molten metal remaining in the gate passages adjacent their lower ends below the solidified portion drains back into container 22, leaving unconnected metal parts, such as shown in Figure 6, in mold 30.
After chamber 20 has been raised to its inoperative position, as shown in Figure 1, valve 26 may be operated to disconnect the vacuum pump 24 and to release mold 30 so that a new mold can be substituted.
The unconnected metal parts 62, Wit]l a short portion of gate passage metal 64 connected to them, as shown in Figure 6, may then be separated from the decomposed mold 30 in the usual manner.
In Figures 7 through 10 are shown molds having multi-part cavities and multiple vertical gate passages.
Thus, in Figures 7 and 8 is shown a portion of a multi-cavity mold, generally designated 65 and constructed as explained above, having spaced between its upper surface 67 and its lower surface 69 and inwardly of its peri-_ g ~s3a6~
pheral side surface 71, a plurality of multi-part mold cavities, of which one is shown in Figures 7 and 8.
Each multi-part mold cavity includes two part cavities 73 and 75 having horizontal riser ingate passages 77 and 79, respectively, both connect-ed to a central blind riser 78, which is in turn connected to a narrow vertical gate passage 80. The shape, quantity and size of the riser ingate passages 77 and 79 and of blind riser 78 may be varied to suit the particular castin~
shape and size. The transverse dimension of vertical gate passage 80 is about 0.25 to 0.50 inches in diameter. More than one such vertical gate passage may be needed in certain circumstances.
Molds of the type illustrated in Figures 7 and 8 are particularly useful when large parts, having mold cavity dimensions in excess of 0.50 inches, for example, are to be molded since otherwise there may be insuffi-cient time available to completely solidify the molten metal in the mold part cavities before mold failure occurs, particularly with ferrous metals. Also, with metals which shrink upon solidification, the blind riser acts as a source of supply of molten metal during solidification of the metal in the part cavities.
In operation, mold 65 is filled as described abave and the mold ~0 removed from contact with the molten metal in the container as soon as molten metal has filled mold cavities 73 and 75 and blind riser 78 and has solidified in vertical gate passage 80. However, the metal in blind riser 78 remains molten for a sufficieint period of time after the removal of mold 65 from contact with the molten metal in the container to continue to feed mold cavities 73 and 75 through their riser ingate passages 77 and 79 to compen-sate for shrinkage during solidification of the meta-l in the mold cavities 73 and 75. This arrangement allows the mold cycle time to be reduced so that 1153~65i premature mold failure is avoided. After solidification is complete, uncon-nected groups of metal parts, including their connecting riscr ingates and portions of the blind riser and the vertical gate, remain in the decomposed mold 65.
In Figllre 9 is shown a multi-cavity mold 81 having, between its upper surface 82 and lower surface 83, a plurality of mold cavities 84, of which two are shown in Figure 9, clustered around a central vertical gate passage 85 'naving narrow horizontal gate passage portions 86 according to the inventionconnecting the mold cavities 84 to vertical gate passage 85. This arrangement is satisfactory for casting parts having thicknesses of no more than about 0.5 inch, since solidification will immediately occur both in the mold cavities 84 and the narrow gate passage portions 86, with the molten metal draining ~rom vertical gate passage 85 upon removal of mold 81 from contact with the underlying surface of molten metal to provide unconnected cast parts.
In Figure 10 is shown a multi-cavity mold 90 having, between its upper surface 92 and its lower surface 94, a plurality of mold cavities 95, each having two vertical gate passages 97 and 98, for more rapid filling of the relatively large mold cavities 95 through narrow vertical gate passages in accordance with our invention in order to fill the mold cavities and remove the mold as soon as the metal in the vertical gate passages solidifies and before mold failure occurs. This type of mold is particularly useful when casting metals in which shrinkage compensation is not required, in molds having large part cavities which cannot be filled through a single narrow vertical gate passage before mold failure occurs.
This application relates to metal casting in gas permeable molds.
Although the techniques disclosed in United States Patent Nos.
3,863,706 and 3,900,064 have been in successful commercial use for several years, we have discovered the existence of certain problems in their use with gas permeable molds of the low temperature bonded sand grain type rather than the high temperature resistant ceramic type with which they were primarily intended to be used.
These problems occur because low temperature bonded sand grain shell molds, such as those of the Croning type, in which sand grains or similar particles are bonded together with a small proportion of an inorganic or organic plastic thermal or chemical setting resin or equivalent material, although much less expensive to produce than ceramic molds, have two major deficiencies as compared to ceramic molds, in that they have relatively soft interior mold cavity surfaces and also fail rapidly at high temperatures be-cause their low temperature bonding materials decompose at low temperatures so that the mold fails rapidly at temperatures lower than that of the molten casting metal, particularly with ferrous metals.
Insofar as the first deficiency is concerned, under the high vacuum required with the techniques of those patents in order to lift the molten metal up the single long vertical central riser from which it flows into the multiple mold cavities through vertically spaced gate passages, the molten metal frequently penetrates the soft mold surface of a low temperature bonded sand grain mold to the extent that casting quality is so reduced as to be unacceptable.
Insofar as the second deficiency is concerned, since the effective 115~
life before failure of a low temperature bonded sand grain mold is measured in seconds in the presence of molten ferrous metals, the time required to solidify the castings in the molds of those patents is frequently of such duration that the low temperature bonded sand grain mold fails before the molten metal in the mold cavities is sufficiently solidified.
Because of these problems, under many circumstances, particularly when casting parts of ferrous metals, Iow temperature bonded sand-grain molds ca~not be utilized with the techniques of those patents, so that the much more expensive ceramic shell molds must be substituted in order to provide acceptable castings.
According to the present invention there is provided a rigid self supporting gas permeable low temperature bonded sand grain mold havirlg side surfaces extending between vertically spaced upper and lower surfaces with a plurality of mold cavities spaced therebetween in a generally horizontal area and horizontally spaced from one another, said mold cavities having gate pass-ages with portions having a maximum width of 0.75 inches extending from said cavities with their lower open ends spaced from one another and t~rminating in a generally horizontal plane at the lower surface of said mold.
In use of the mold, the lower surface and the open end of the gate passages are submerged beneath an underlying surface of molten metal while the upper surface and at least a portion of the side surfaces are maintained thereabove. A reduced pressure is applied to the upper surface of the mold to fill the mold cavities with molten metal. The molds are unheated and at ambient room temperature, so that the thin sections of molten metal in the relatively narrow gate passage portions quickly solidify, but only for a short period of time before they remelt due to the heat provided by the underlying molten metal in the container. This brief period of gate passage solidifica-tion makes it possible quickly to move the mold vertically upwardly out of . 2 ' ' ~53t~6S
contact with the underlying surface of molten metal~ even though the molten metal in the mold cavities may not yet have entirely solidified, before the solidified metal in the narrow gate passage portions remelts and allows the molten metal in the mold cavities to drain back into the container of molten metal. Particularly with high melting point metals such as ferrous metals cast at temperatures of 2000 degrees ~ or higher, we have found that by quick-ly moving the mold out of contact with the underlying surface of molten metal, after the initial occurrence of solidification of metal in the narrow gate passage portions, further heat input into the mold is prevented and mold failure time is extended sufficiently for the castings in the mold cavities to solidify. It also makes possible an unusually short casting cycle time, which reduces production cost.
With molds having relatively small cavities, such as those having internal thicknesses of less than 0.50 inches, we have found that filling and solidification of the molten metal both in the mold cavity and the adja-cent narrow gate passage or portion thereof will occur rapidly enough so that the mold may be removed before it fails. With larger mold cavities, at least with metals which do not shrink upon solidification, more than a single narrow gate passage may be used for more rapid mold cavity filling so that the mold may be removed before it fails.
With metals which shrink upon solidification and with large mold cavities, such as those having internal thicknesses of greater than 0.50 inches which cannot be filled through the narrow gate passage portions of the in-vention before mold failure occurs, a blind riser may be used between one or re vertical gate passages and a mold cavity, so that at least a portion of the metal in the blind riser and in the mold cavity will remain in molten condition for flow into the mold cavity after removing the mold from contact ~153~6S
with the underlying surface of molten metal.
When using multiple cavity molds, since the lower open ends of the gate passages are spaced from one another, a plurality of unconnected cast metal parts or groups of parts are automatically provided.
With the conventional rigid, self supporting, low temperature bonded sand grain mold as used in the methods of the present invention, we have dis-covered that the maximum permissible submergence times, that is, maximum length of time that the mold may be in contact with the underlying surface of molten metal before the solidified metal in the narrow portions of the gate passages remelts or the mold begins to fail, is largely determined by the temperature at which the underlying molten metal must be maintained.
In the case of ferrous metal, such as cast iron and steel, which are cast at temperatures greater than 2000 degrees F, the time is relatively short, a maximum of about 30 seconds; so that submergence times of no more than about 5 to 15 seconds have been found to be desirable. Also, in order to prevent mold cavity surface penetration, reduced pressures of only about -1.0 to -3.0 psig (13.7 to 11.7 psia) should be used to raise the molten ferrous metal into mold cavities to a level no higher than about 6 to 8 inches above the surface of the molten metal in the container. With lower melting point metals, such as copper and alur.~inum and their alloys, longer times and higher mold cavity heights may be used.
Thc mold cavities may extend to or across a mold parting plane and may be arranged in a generally horizontal plane, preferably distributed both lengthwise and widthwise thereof, and horizontally spaced from one another.
The maximum width of each of the gate passage portions is prefer-ably no more than about 0.5 inches. With multiple cavity molds, the vertical portions of the gate passages are generally perpendicular to the parting plane ~ws~
and their open ends are spaced from one another and distributed in a horizontal plane.
For castings having wall thicknesses of less than about 0.50 inch, the narrow gate passage portions may be adja.cent the mold cavity, with a larger central vertical gate passage. For larger castings having greater wall thicknesses, more than one narrow gate passage portion may be used if shrink-age is not a problem; otherwise, a blind riser may be interposed between one or more gate passages having a narrow vertical portion and one or more part cavities.
The vacuum means for relatively varying the pressure within the chamber preferably provide the sole support for the mold against the chamber.
In the accompanying drawings, which illustrate exemplary embodiments of the present invention:
Figure 1 is a diagrammatic side view, partly in section, of a mold and apparatus according to the invention;
Figure 2 is a detail side cross-sectional view of the chamber por-tion of the apparatus of Figure l;
Figure 3 is a top view of the mold of Figure l;
Figure 4 is a detail side partial cross-sectional view of the mold of Figure 3;
Figure 5 is a detail side partial cross-sectional view of the mold of Figures 3 and 4 mounted on the chamber of the apparatus, with the lower surface of the mold submerged beneath the underlying surface of molten metal in the container;
Figure 6 is a cross-sectional side view of a molded metal part;
Figure 7 is a detail side partial cross-sectional view of a modifi-llS;~
cation of the mold of Figure l;
Figure 8 is a detail top partial cross-scctional view of the mold of Figure 7, taken along line 8-8 of Figure 7;
Figure 9 is a detail side partial cross-sectional view of another modification of the mold of Figure l; and Figure 10 is a detail side partial cross-sectional view of a further modification of the mold of Figure 1.
Referring to Figure 1, the apparatus in general includes a base 12 having mounted thereon a post 14 on which is mounted, for vertical sliding movement by power piston and cylinder 16, a horizontally extending arm 18.
Chamber 20, hereinafter more fully described, is mounted on support member 19 which extends downwardly from the free end of arm 18 above a container 22 for holding molten metal.
Referring to Figures 3 and 4, the rigid, self supporting, gas perm-eable, low temperature bonded sand grain mold, generally designated 30, commonly referred to as a Croning shell mold, is made by techniques and equip-ment well known in the art, of sand grains or equivalent particles and in-organic or organic thermal or chemical setting plastic or equivalent low temperature bonding material, with a minor percentage, usually about 5 %, of .
low temperature bonding material, by distributing the loose sand and bonding material mixture over heated metallic half patterns on a metal base plate which forms the parting plane, over which it hardens into a rigid, self supporting mold half shell which is then removed from the metallic half patterns and base plate for use.
- As shown in Figure 4, the mold 30 is constructed of two such half shells, upper and lower, which are then adhesively secured together along horizontal mold parting plane 29 to provide a unitary, disposable, rigid, self ~L153~6S
supporting mold 30. Mold 30 has peripherally extending side surfaces 32 extending vertically between vertically spaced upper surface 31 and lower sur-face 33 which are generally parallel to mold parting plane 29. Surfaces 31 and 33 are irregular and have a rough outer surface since they wereformed of generally uniform thickness on the irregular contour of the heated pattern.
To provide for the support of mold 30 and for the application of re-duced pressu~e to its upper surface 31, said upper surface is formed at its outer edge, as by pressing it while still in plastic condition, to form a con-tinuous peripheral horizontal flat sealing surface portion 38 suitable for sealing against chamber 20, as hereinafter more fully explained.
A plurality of single part mold cavities are provided spaced between the upper and lower surfaces, extending across mold parting plane 29, as shown in Figures 3 and 4, of which two are shown in Figure 4. Multiple part cavities may also be so provided, as explained in more detail hereinafter. In commercial practice, the number of such mold cavities would generally fall between six and twenty, seventeen being shown in Figure 3. Such single or multiple part mold cavities are distributed within the horizontal area within the periphery of mold 30, with a plurality thereof extending across the length and width of the mold 30 between its upper and lower surface 31 and 33. Cavities 34 are hori-zontally spaced from one another generally in a horizontal plane and extend across parting plane 29. Each mold cavityJ such as is shown in connection with cavities 34, has an individual vertical gate passage 35, generally perpendicular to parting plane 29, extending from its lower side, with the lower open ends of such vertical gate passages 35 being spaced from one another both widthwise and lengthwise and terminating in a generally horizontal plane parallel to parting plane 29 at the lower surface 33 of mold 30.
As explained above, at least a portion of each of gate passages 35 115~
should be relatively narrow in at least one dimension, at most not greater than 0.75 inch, and preferably not more than 0.5 inch. Conveniently, these narrow gate passages or portions thereof are vertical and of circular cross section, although other configurations may be used.
Referring to Figures 1, 2 and 5, chamber 20 provides the sole sup-port for holding mold 30 against chamber 20 and for applying reduced pressure from vacuum pump 24 through a suitable valve 26 and hose 28 to its upper sur-face 31. As seen in Figure 2, chamber upper wall 44 is connected to the lower end of support 19 and is provided with an access port 58 to which vacuum hose 28 is connected for applying a reduced pressure to the interior of cham-ber 20 and to the upper surface 31 of mold 30 when desired.
In addition, chamber 20 has a bottom opening defined by its down-wardly extending peripheral outer wall 40 which extends downwardly from the outer periphery of its upper wall 44 to define the interior of chamber 20.
As best seen in Figures 2, 4 and S, outer wall 40 may be provided about its lower end with a horizontal sealing surface 42 for sealing against the hori-zontal upper sealing surface 38 of mold 30 around the periphery thereof and generally coextensive with the horizontal area of mold 30 containing the mold cavities, with a portion of the peripheral side surface 32 and bottom surface 33 of mold 30 extending downwardly beyond chamber 20.
In operation, with chamber 20 in raised position as shown in Figure 1, mold 30 is manually or automatically positioned with its peripheral sealing surface 38 against sealing surface 42 of chamber 20. Valve 26 is then operated to provide the sole force to hold mold 30 into operating position against chamber 20 and to apply throughout upper surface 31 of mold 30 a reduced pres-sure, preferably only of about -1.0 to -3.0 psig (13.7 to 11.7 psia), through chamber port 58 to the interior of chamber 20 and the upper surface 31 of mold 1~S3~GS
30 within the periphery of sealing surface 38 and coextensive with the mold area containing the mold cavities.
Power piston and cylinder 16 are then operated to move chamber 20 carrying mold 30 therebeneath downwardly toward container 22 to lower the lower surface 33 of mold 30 with the lower open ends of all of the vertical gate passages beneath the surface 60 of molten metal in container 22.
The reduced pressure applied to the upper surface 31 of mold 30 causes molten metal to rise into the gate passages and fill all the mold cavi-tives simultaneously.
The power piston and cylinder 16 are operated shortly af*er sub-mergence, as soon as the mold cavities have been filled and molten metal extend-ing across at least a portion of each of the gate passages has solidified, to raise chamber 20 and mold 30, whereupon a portion of molten metal remaining in the gate passages adjacent their lower ends below the solidified portion drains back into container 22, leaving unconnected metal parts, such as shown in Figure 6, in mold 30.
After chamber 20 has been raised to its inoperative position, as shown in Figure 1, valve 26 may be operated to disconnect the vacuum pump 24 and to release mold 30 so that a new mold can be substituted.
The unconnected metal parts 62, Wit]l a short portion of gate passage metal 64 connected to them, as shown in Figure 6, may then be separated from the decomposed mold 30 in the usual manner.
In Figures 7 through 10 are shown molds having multi-part cavities and multiple vertical gate passages.
Thus, in Figures 7 and 8 is shown a portion of a multi-cavity mold, generally designated 65 and constructed as explained above, having spaced between its upper surface 67 and its lower surface 69 and inwardly of its peri-_ g ~s3a6~
pheral side surface 71, a plurality of multi-part mold cavities, of which one is shown in Figures 7 and 8.
Each multi-part mold cavity includes two part cavities 73 and 75 having horizontal riser ingate passages 77 and 79, respectively, both connect-ed to a central blind riser 78, which is in turn connected to a narrow vertical gate passage 80. The shape, quantity and size of the riser ingate passages 77 and 79 and of blind riser 78 may be varied to suit the particular castin~
shape and size. The transverse dimension of vertical gate passage 80 is about 0.25 to 0.50 inches in diameter. More than one such vertical gate passage may be needed in certain circumstances.
Molds of the type illustrated in Figures 7 and 8 are particularly useful when large parts, having mold cavity dimensions in excess of 0.50 inches, for example, are to be molded since otherwise there may be insuffi-cient time available to completely solidify the molten metal in the mold part cavities before mold failure occurs, particularly with ferrous metals. Also, with metals which shrink upon solidification, the blind riser acts as a source of supply of molten metal during solidification of the metal in the part cavities.
In operation, mold 65 is filled as described abave and the mold ~0 removed from contact with the molten metal in the container as soon as molten metal has filled mold cavities 73 and 75 and blind riser 78 and has solidified in vertical gate passage 80. However, the metal in blind riser 78 remains molten for a sufficieint period of time after the removal of mold 65 from contact with the molten metal in the container to continue to feed mold cavities 73 and 75 through their riser ingate passages 77 and 79 to compen-sate for shrinkage during solidification of the meta-l in the mold cavities 73 and 75. This arrangement allows the mold cycle time to be reduced so that 1153~65i premature mold failure is avoided. After solidification is complete, uncon-nected groups of metal parts, including their connecting riscr ingates and portions of the blind riser and the vertical gate, remain in the decomposed mold 65.
In Figllre 9 is shown a multi-cavity mold 81 having, between its upper surface 82 and lower surface 83, a plurality of mold cavities 84, of which two are shown in Figure 9, clustered around a central vertical gate passage 85 'naving narrow horizontal gate passage portions 86 according to the inventionconnecting the mold cavities 84 to vertical gate passage 85. This arrangement is satisfactory for casting parts having thicknesses of no more than about 0.5 inch, since solidification will immediately occur both in the mold cavities 84 and the narrow gate passage portions 86, with the molten metal draining ~rom vertical gate passage 85 upon removal of mold 81 from contact with the underlying surface of molten metal to provide unconnected cast parts.
In Figure 10 is shown a multi-cavity mold 90 having, between its upper surface 92 and its lower surface 94, a plurality of mold cavities 95, each having two vertical gate passages 97 and 98, for more rapid filling of the relatively large mold cavities 95 through narrow vertical gate passages in accordance with our invention in order to fill the mold cavities and remove the mold as soon as the metal in the vertical gate passages solidifies and before mold failure occurs. This type of mold is particularly useful when casting metals in which shrinkage compensation is not required, in molds having large part cavities which cannot be filled through a single narrow vertical gate passage before mold failure occurs.
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A rigid self supporting gas permeable low temperature bonded sand grain mold having side surfaces extending between vertically spaced upper and lower surfaces with a plurality of mold cavities spaced therebetween in a generally horizontal area and horizontally spaced from one another, said mold cavities having gate passages with portions having a maximum width of 0.75 inches extending from said cavities with their lower open ends spaced from one another and terminating in a generally horizontal plane at the lower surface of said mold.
2. A mold as claimed in claim 1, further having a horizontal parting plane between said upper and lower surfaces and wherein, portions of said gate passages extend generally perpendicular to said parting plane.
3. A mold as claimed in claim 2, wherein said mold cavities extend to said parting plane and are distributed both lengthwise and widthwise thereof.
4. A mold as claimed in claims 1, 2 or 3, wherein said mold cavities include a blind riser between a said gate passage and a part cavity.
5. A mold as claimed in claims 1, 2 or 3, wherein each said mold cavity has an internal dimension of greater than 0.50 inches.
6. A mold as claimed in claim 1, wherein said mold cavities include at least two part cavities and a blind riser connected between said part cavities and a said gate passage.
7. A mold as claimed in claim 6, wherein each said part cavity has an internal dimension of greater than 0.50 inches.
8. A mold as claimed in claims 1, 2 or 3, wherein said mold has a peripheral sealing surface extending around the upper surface of said mold.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US94762178A | 1978-10-02 | 1978-10-02 | |
| US947,621 | 1978-10-02 | ||
| US7516979A | 1979-09-12 | 1979-09-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1153865A true CA1153865A (en) | 1983-09-20 |
Family
ID=26756509
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000336736A Expired CA1146717A (en) | 1978-10-02 | 1979-10-01 | Metal casting |
| CA000409359A Expired CA1153865A (en) | 1978-10-02 | 1982-08-12 | Metal casting |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000336736A Expired CA1146717A (en) | 1978-10-02 | 1979-10-01 | Metal casting |
Country Status (11)
| Country | Link |
|---|---|
| AU (1) | AU527558B2 (en) |
| BR (1) | BR7906311A (en) |
| CA (2) | CA1146717A (en) |
| DE (1) | DE2939974A1 (en) |
| FI (1) | FI66551C (en) |
| FR (2) | FR2437901A1 (en) |
| GB (1) | GB2035165B (en) |
| IN (1) | IN155806B (en) |
| IT (1) | IT1119201B (en) |
| SE (1) | SE444124B (en) |
| YU (1) | YU42313B (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL7909293A (en) * | 1979-12-21 | 1981-07-16 | Wavin Bv | METHOD FOR APPLYING A SEALING BODY IN A GROOVE OF A SOCKET |
| GB8414129D0 (en) * | 1984-06-02 | 1984-07-04 | Cosworth Res & Dev Ltd | Casting of metal articles |
| GB2159445B (en) * | 1984-06-02 | 1988-07-06 | Cosworth Res & Dev Ltd | Casting of metal articles |
| US4532976A (en) * | 1984-06-13 | 1985-08-06 | Hitchiner Manufacturing Co., Inc. | Gas permeable metal casting mold having gas collection voids |
| FR2597770A1 (en) * | 1986-04-23 | 1987-10-30 | Pechiney Aluminium | DEVICE FOR MOLDING THIN PIECES AND LARGE DIMENSIONS OF ALUMINUM ALLOYS |
| FR2615768A1 (en) * | 1987-05-27 | 1988-12-02 | Centre Nat Rech Scient | METHOD FOR SHELL MOLDING, PARTICULARLY METALLIC, AND DEVICE AND SHELL THEREFOR |
| FR2635995B1 (en) * | 1988-09-02 | 1991-10-04 | Haehne Siefried | PROCESS FOR MOLDING OBJECTS, MEANS FOR CARRYING OUT SAID METHOD AND FACILITIES PROVIDED WITH SUCH MEANS |
| JP2541341B2 (en) * | 1990-05-15 | 1996-10-09 | 大同特殊鋼株式会社 | Precision casting method and precision casting apparatus for Ti and Ti alloy |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE466835C (en) * | 1928-10-12 | Carl Feldhaus Fa | Casting device for refractory metals such as aluminum, gunmetal and the like. Like., With suction device | |
| NL15051C (en) * | 1923-08-09 | |||
| FR1441165A (en) * | 1965-07-22 | 1966-06-03 | Vacuum casting process for light metal alloys | |
| CH490913A (en) * | 1968-05-03 | 1970-05-31 | Sulzer Ag | Method and device for casting objects, product and application of the method |
| CH503533A (en) * | 1968-05-03 | 1971-02-28 | Sulzer Ag | Device for casting objects |
| US3863706A (en) * | 1972-12-04 | 1975-02-04 | Hitchiner Manufacturing Co | Metal casting |
| US3900064A (en) * | 1972-12-04 | 1975-08-19 | Hitchiner Manufacturing Co | Metal casting |
| US3862656A (en) * | 1973-02-16 | 1975-01-28 | Aurora Metal Corp | Method and apparatus for vacuum casting of metal |
| DD119726A1 (en) * | 1975-06-02 | 1976-05-12 | ||
| US4112997A (en) * | 1977-02-28 | 1978-09-12 | Hitchiner Manufacturing Co., Inc. | Metal casting |
-
1979
- 1979-09-21 SE SE7907847A patent/SE444124B/en not_active IP Right Cessation
- 1979-09-27 GB GB7933618A patent/GB2035165B/en not_active Expired
- 1979-10-01 BR BR7906311A patent/BR7906311A/en not_active IP Right Cessation
- 1979-10-01 AU AU51337/79A patent/AU527558B2/en not_active Ceased
- 1979-10-01 FI FI793036A patent/FI66551C/en not_active IP Right Cessation
- 1979-10-01 YU YU2387/79A patent/YU42313B/en unknown
- 1979-10-01 IT IT68900/79A patent/IT1119201B/en active
- 1979-10-01 CA CA000336736A patent/CA1146717A/en not_active Expired
- 1979-10-02 FR FR7924551A patent/FR2437901A1/en active Granted
- 1979-10-02 DE DE19792939974 patent/DE2939974A1/en active Granted
-
1980
- 1980-03-21 FR FR8006427A patent/FR2452986A1/en active Granted
-
1982
- 1982-08-12 CA CA000409359A patent/CA1153865A/en not_active Expired
-
1983
- 1983-05-18 IN IN623/CAL/83A patent/IN155806B/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| FR2437901B1 (en) | 1983-12-02 |
| IT7968900A0 (en) | 1979-10-01 |
| GB2035165A (en) | 1980-06-18 |
| IT1119201B (en) | 1986-03-03 |
| FR2452986A1 (en) | 1980-10-31 |
| FI66551C (en) | 1984-11-12 |
| SE7907847L (en) | 1980-04-03 |
| FR2452986B1 (en) | 1983-05-13 |
| YU42313B (en) | 1988-08-31 |
| DE2939974A1 (en) | 1980-04-10 |
| SE444124B (en) | 1986-03-24 |
| BR7906311A (en) | 1980-05-27 |
| GB2035165B (en) | 1982-08-18 |
| CA1146717A (en) | 1983-05-24 |
| AU527558B2 (en) | 1983-03-10 |
| DE2939974C2 (en) | 1988-06-09 |
| FR2437901A1 (en) | 1980-04-30 |
| FI66551B (en) | 1984-07-31 |
| YU238779A (en) | 1984-08-31 |
| FI793036A (en) | 1980-04-13 |
| AU5133779A (en) | 1980-05-01 |
| IN155806B (en) | 1985-03-09 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4340108A (en) | Method of casting metal in sand mold using reduced pressure | |
| US4606396A (en) | Sand mold and apparatus for reduced pressure casting | |
| US8061409B2 (en) | Mold | |
| CA1153865A (en) | Metal casting | |
| EP0738192B1 (en) | Method and equipment for feeding shrinkage voids in metal castings | |
| US4993473A (en) | Differential pressure, countergravity casting using mold ingate chills | |
| US4862945A (en) | Vacuum countergravity casting apparatus and method with backflow valve | |
| US5355933A (en) | Method of squeeze casting metal articles using melt-out metal core | |
| CN1054086C (en) | Lost foam process for casting stainless steel | |
| US6845810B2 (en) | Lost-foam casting apparatus for improved recycling of sprue-metal | |
| US7360577B2 (en) | Process for lost-foam casting with chill | |
| CA2047545A1 (en) | Vacuum-assisted, countergravity casting apparatus and method | |
| US5088546A (en) | Vacuum-assisted counter gravity casting apparatus with valve to prevent flow of melt from mold | |
| JP2560356B2 (en) | Vacuum suction precision casting method | |
| JPS6123566A (en) | Mold and casting device | |
| JPH0241752A (en) | Device for casting wheel for vehicle and method for using device thereof | |
| JP4262416B2 (en) | Caliper body for disc brakes for vehicles | |
| CA1102995A (en) | Mould for casting at low pressure | |
| JPS59156560A (en) | Local pressurizing method for die casting | |
| JPS6415472A (en) | Abrasion-resistance pump part and manufacture thereof | |
| JPH0741400B2 (en) | Suction casting method in green casting | |
| JP2820882B2 (en) | Vacuum suction casting apparatus and method | |
| JP2585842Y2 (en) | Casting mold equipment | |
| JPS55109543A (en) | Casting method of nonferrous alloys and mold thereof | |
| JPS613647A (en) | Mold device |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |