US3903953A

US3903953A - Investment casting apparatus on framework

Info

Publication number: US3903953A
Application number: US296291A
Authority: US
Inventors: Billy C Hudson
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-11-19
Filing date: 1972-10-10
Publication date: 1975-09-09
Anticipated expiration: 1992-09-09

Abstract

Apparatus and method for making investment, or lost-wax, castings. A mold cavity and an air passageway are formed in a mold of investment material, and a vacuum is applied to the air passageway to draw molten metal into the details of the cavity. The vacuum is provided by heating water to produce steam in an open chamber and then closing the chamber and condensing the steam.

Description

United States Patent [I91 *Sept. 9, 1975 Hudson INVESTMENT CASTING APPARATUS ON FRAIVIEWORK [76] inventor: Billy C. Hudson, 948 Coronado Way, Livermore Calif. 94550 Notice: The portion of the term of this patent subsequent to Oct. 17 1989, has been disclaimed.

[22] Filed: Oct. 10, 1972 [21] Appl. No.: 296,291

Related U.S. Application Data [63] Continuation-impart of Ser. No 878,111 Nov. 19

1969, Pat. No 3,698,468.

[52] US. Cl 164/255; 164/63 [51) Int. Cl 322d 27/16 [58] Field of Search t. 164/63, 65, 255, DIG 4 [56] References Cited UNITED STATES PATENTS 1,105,425 7/1914 Hart 164/D1G. 4

1,186.558 6/1916 Dunn 11 164/255 X 1,698,197 1/1929 bentz v. 164/D1G. 4 3353.219 11/1967 Synder 264/87 X 3,698 468 10/1972 Hudson 164/65 X FOREIGN PATENTS OR APPLICATIONS 16314 1910 United Kingdom 164/255 168684 9/1921 United Kingdom v. 164/65 Primary ExaminerRobert D. Baldwin Attorney, Agent, or Firm-Flehr, Hohbach, Test, Albritton & Herbert 10 Claims, 8 Drawing Figures PATENTED E 1975 SHEET 1 BF 3 4 .7 llllllld V PATENTEU SEP 9 I975 SHEET 2 o 3 PATENTEUSEP mm 3 903 953 sum 3 o 3 INVESTMENT CASTING APPARATUS ON FRAMEWORK CROSS REFERENCE TO RELATED APPLICATION This is a continuation-in-part of Ser. No. 878,111, filed Nov. 19, 1969, now US. Pat. No. 3,698,468, issued Oct. 17, 1972.

BACKGROUND OF THE INVENTION This invention pertains generally to casting processes and more particularly to a method and apparatus particularly suitable for investment, or lost-wax, casting.

The basic principles of investment, or lost-wax, casting were discovered and applied thousands of years ago in China, Egypt, and other parts of the world. The process has been used for hundreds of years for the casting of statues and other artistic works. More recently it has come into use by hobbyists for making small castings, such as jewelry.

The basic steps of the lost-wax casting process include making a wax pattern of the casting to be pro duced, assembling the wax pattern to a wax gating and sprue system, investing the wax pattern in an investment material to produce a mold, removing the wax material from the mold, pouring molten metal into the mold, removing the casting from the mold, and cleaning and polishing the casting.

There is a need for a new and improved method and apparatus which can be utilized by hobbyists in the investment, or lost-wax, casting process.

SUMMARY OF OBJECTS OF THE INVENTION In the method and apparatus of the invention, a pattern fabricated ofa meltable material is coated with investment material and placed in a cradle which is also fabricaated of a meltable material. The cradle is mounted on a mandrel having a flow passageway. A flask is placed over the pattern and mandrel and filled with investment material. The pattern and cradle are then removed from the investment material to form a mold cavity and air passageway. Molten metal is poured into the cavity, and a vacuum is applied to the air passageway to enhance the flow of metal into the details of the mold. The vacuum is produced by heating water to produce steam in an open chamber and hereafter closing the chamber and condensing the steam.

It is in general an object of the invention to provide a new and improved method and apparatus which can be utilized in the investment, or lost-wax, casting process.

Another object of the invention is to provide a method and apparatus of the above character which includes heater and tank means for heating water and condensing steam to produce a vacuum which is applied to the mold cavity to enhance the flow of casting material into the cavity.

Another object of the invention is to provide a method and apparatus of the above character which are particularly suitable for use by hobbyists.

Additional objects and features of the invention will be apparent from the following description in which the preferred embodiments are set forth in detail in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevational view of one embodiment of casting apparatus incorporating the present invention, with the investment mold in place.

FIG. 2 is a side elevational view of the embodiment shown in FIG. 1.

FIG. 3 is an enlarged sectional view of a portion of the apparatus shown in FIG. 1, illustrating the interior of the investment mold.

FIG. 4 is an exploded isometric view, illustrating the manner in which the investment mold is formed.

FIG. 5 is a front elevational view ofa second embodiment of casting apparatus incorporating the invention.

FIG. 6 is a front elevational view of a third embodiment of casting apparatus incorporating the invention.

FIG. 7 is a front elevational view of a fourth embodiment of casting apparatus incorporating the invention.

FIG. 8 is a front elevational view of a fifth embodiment of apparatus incorporating the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the embodiment illustrated in FIGS. 1-4, the casting apparatus comprises an investment mold 10, framework means ll adapted for removably holding the mold, crucible means 12 mounted on the framework means and adapted for holding and pouring molten metal, heating means 13 for melting the metal in the crucible means, and vacuum means 14 for drawing the molten metal into the mold.

The framework means 11 includes a horizontally disposed base member 16 and a platform member 17. These members are generally rectangular in shape and are conveniently fabricated of a metal such as steel plate. A plurality of mounting feet 18 are secured to the lower surface of the base member 16 and adapted for resting upon a suitable supporting surface such as a table top. The platform member 17 is generally parallel to and spaced above the base member 16. The platform member is supported by a plurality of spacer members 19 which extend between the base member and platform member and are attached thereto by conventional means such as welding or bolting.

A threaded elongate member 21 is mounted on the platform member 17 to provide means for supporting the crucible means 12. The threaded member 2| extends vertically through a mounting hole formed in the platform member 17 and is secured in place by nuts 22 and 23 which engage the upper and lower surfaces of the platform member, respectively. A yoke member 24 is mounted at the upper extremity of the threaded member 21 by means of nuts 26. A shaft 27 is pivotally mounted between the arms of the yoke 24, and a platform 28 is mounted on the shaft 27. In the preferred embodiment, the platform is secured to the shaft by means of rivets. The crucible means 12 is mounted on the platform 28 and is thereby adapted for movement between level and inclined positions. A vertically extending lip 28a is formed at the forward extremity of the platform 28, and a clamp screw 29 is carried by the platform. The lip and clamp screw cooperate to hold the crucible means on the platform.

The crucible means 12 includes a conventional crucible 31 having a wall 32 and a spigot 33. The spigot communicates with the well in such manner that when the crucible is in a level position, as illustrated in FIG.

1, molten metal can be retained in the well. When the crucible is in its inclined position, the molten metal is discharged through the spigot.

It should be noted that in addition to securing the threaded member 21 to the platform member 17, the nuts 22 and 23 provide means for adjusting the vertical position of the crucible means 12 above the mold 10.

In the preferred embodiment, the heating means 13 includes a source of combustible fluid, such as propane gas. As shown in the drawing, this source is provided by small propane torch of conventional design. This torch includes a tank 36 in which the gas is stored, a valve 37 for metering the flow of gas out of the tank, and a tip 38. The tip 38 is disposed in proximity to the crucible 31, and the tank 36 is mounted on the framework 11 in such a manner that the position of the tip 38 can be adjusted as desired. The tank 36 is clamped to a pair of parallel, spaced apart rod members 41 by means of resilient spring member 42. The rod members 41 are attached toward their lower extremities to a mounting yoke 43 by conventional means such as welding or riveting. The mounting yoke 43 is pivotally mounted on a shaft 44 carried by another yoke 46 which is attached to the rear portion of the platform member 17. End caps 47, fabricated of a material having a relatively high coefficient of friction, are provided at the upper and lower extremities of the rod members 41. The ends of the resilient spring member 42 are attached to the mounting yoke 43 and this spring member urges the tank 36 into engagement with the end caps 47.

Means is provided for adjusting the angle of inclination of the tank 36 relative to the platform member 17. This means includes an eyebolt mounting bracket 48 attached to the platform member 17 and turnbuckle means 49 pivotally connected to the bracket 48 and to the upper portion of one of the rod members 41. The position of the torch can also be adjusted by sliding the tank 36 axially of the rod members 41.

The vacuum means 14 includes a hermetically sealed vacuum chamber 51 formed within a spherical container 52. The container 52 is provided with threaded bushing 53 having a bore 54 communicating with the chamber 51. This bushing extends through an opening in the platform member 17, and a nut 56 is threadedly mounted thereon to secure the container 52 to the platform member. The bore 54 provides means for introducing water into the chamber 51, and a conically tapered plug 57 provides means for closing the bore 54. This plug also serves as a safety valve in the event the pressure within the chamber becomes excessively high.

Means is provided for heating water Within the chamber 51. This means includes a coventional source of hear 58 carried by the base member 16 and disposed vertically below the container 52. In the preferred embodiment, the source 58 comprises a container of combustible fuel in jellied form. A plurality of locating studs 59 are attached to the base member 16 to provide means for positioning the fuel supply 58.

A vacuum line 61 is provided for interconnecting the vacuum chamber 51 with the mold to provide communication between the chamber and the mold cavity. This line includes a first section 61a communicating with the chamber 51 and connected at one end to a fitting 62 mounted on the container 52. The outer end of the section 61a is connected to the inlet side of a valve 63. A seecond section 61b of the vacuum line extends between the discharge side of the valve and a T-fitting 64. The vacuum line 61 also includes an upper section 61c which extends from the upper side of the T-fitting 64 through an opening 66 in the platform 17. The upper end of the section 610 extends above the platform member and into a connector 67. The connector 67 is formed to include a passageway 68 to provide communication between the line 61 and the mold cavity. The outer contour of the connector includes a cylindrical lower section 69, a cylindrical upper section 71 of smaller diameter than the lower section, and a conically tapered shoulder 72 intermediate the upper and lower sections. In the preferred embodiment, the connector 67 is fabricated of metal and is attached to the line 61 by threads.

The vacuum line 61 is formed to include trap means for preventing foreign matter, such as molten metal and particles of the mold, from being drawn into the vacuum chamber 51. This trap means include a trap section 61d connected to the lower side of the T-fitting 64 and located below and in axial alignment with the passageway 68 in the connector 67. The cap 73 is removably attached to the lower end of the trap section to permit cleaning of this section.

The valve 63 provides means for controlling the communication between the vacuum chamber 51 and the mold cavity. In the preferred embodiment, this valve comprises a conventional stopcock having a butterfly member adapted for movement between open and closed positions through rotational movement on the order of Linkage means is provided for interconnecting the crucible means 12 and the valve 63 in such manner that the position of the crucible corresponds to the position of the butterfly member in the valve. This means includes a shaft 76 operably connected at one end to the butterfly member of the valve and pivotally supported toward its other end by a bracket 77 attached to the under surface of the platform member 17. An operating handle 78 is connected near the outer extremity of the shaft 76 to provide means for rotating the shaft. The linkage means also includes a crank 81 attached to the shaft 76 proximate to the handle 78, an elongate member 82 having its upper end pivotally connected to the rear portion of the crucible platform 28, and an adjustable clamp member 83 pivotally connecting the lower portion of the elongate member 82 to the crank 81. The clamp member 83 can be adjusted axially of the elongate member 82 to provide means for adjusting the length of the linkage and the relative positions of the crucible and valve. ln FIG. 1, the valve 63 is shown in its closed position, and the crucible is level. When the valve is opened by rotating the operating handle 78 in a clockwise direction, the crucible is moved to its inclined position.

The investment mold 10 is adapted to be removably mounted on the upper surface of the platform member 17, with the connector 67 extending into the lower portion of the mold. The mold includes a cylindrical sleeve or flask 86 which preferably has a substantially flat surface 86a at one end to provide a good sealing surface. A rubber gasket 87 is disposed between the surface 860 and the upper surface of the platform member 17 to insure a good seal during investment. This sleeve is adapted for holding a conventional investment material 83 which is formed to define a mold cavity 89, a funnelshaped sprue 91, and a gate 92 interconnecting the sprue and cavity. In addition, the investment material 88 is formed to define air passageways 93 which communicate with the cavity 89 through the porous investment material and which are adapted for communicating directly with the passageway 68 in the connector 67. Suitable investment materials include refractory material such as silica in the form of quartz or cristobalite, with a gypsum plaster binder.

Operation and use of the apparatus described above and therein the method of the invention can now be described briefly. Let it be assumed that the rubber gasket 87 has been placed over the connector 67 and is resting upon the upper surface of the platform member 17. Further let it be assumed that a pattern 101 fabricated of wax or another suitable material has been prepared in the conventional manner and that a wax column 102 has been attached to the pattern to provide means for forming the gate 92. A cradle 103 for the pattern is formed by bending columns of wax 104, commonly known as wax wires, or another suitable material, into a form generally corresponding to the contour of the pattern. The cradle is attached to the upper portion of the connector 67 by additional wax 106, and this cradle provides means for forming the air passageway 93. Preferably, the cradle and wax attaching it to the connector should seal the passageway 68 to prevent investment material from entering this passageway during formation of the mold.

A coating of investment material 107 is formed on the pattern, and the coated pattern is placed in the eradle, with the wax column for forming the gate extending in an upward direction. The coating can be conveniently formed by brushing successive layers of investment material in slurry form into the pattern. It is important that the coating have a sufficient thickness to prevent cave-ins between the cavity and the air pas sageways. A thickness on the order of Va inch has been found to give satisfactory results in casting pieces of jewelry, such as rings. Alternatively, if desired, the coating can be formed on the cradle instead of or in addition to the pattern.

After the pattern has been placed in the cradle, the sleeve 86 is placed over the pattern, with its lower surface 86a resting on the rubber washer 87. A slurry of investment material 88 is poured into the sleeve and allowed to harden.

After the investment material has hardened, the mold and rubber gasket are removed from the platform member 17, and the funnel-shaped sprue 69 is formed by cutting away a portion of the investment material.

The wax is removed from the hardened mold by conventional means, such as heating in an oven or furnace to a temperature on the order of l,000 to 1,200 F. Alternatively, the wax can be removed by means ofa solvent-vapor bath. such as trichloroethylene vapor. After the wax has been removed, the mold is maintained at a temperature on the order of 700 to 1,000F, the exact temperature depending upon the metal to be cast. Maintaining the mold at this temperature tends to vaporize and eliminate any wax which remains in the mold, and it facilitates the flow of metal in the mold during the casting process.

While the mold is being heated, a vacuum is formed in the vacuum chamber 51. For this purpose, the plug 57 is removed and water is introduced into the chamber through the opening 54. The water is then heated by means of heat source 58 until it vaporizes and there is a steady flow of steam from the opening 54. The heat source is then extinguished, the plug 57 is replaced and the chamber is allowed to cool. When chamber cools to room temperature, the steam will condense, producing a pressure on the order of 1/200 of an atmosphere in the chamber.

After the vacuum has been formed, the metal to be cast is placed in the crucible 31 and melted by means of the torch 13. When the metal is ready for casting, the heated mold 10 is replaced on the platform 17, with the connector 67 by engaging the investment material in a sealing relationship. The valve 63 is opened by rotating the handle 78 which causes the crucible means 12 to move to its inclined position, pouring the metal into the sprue 91. The molten metal flows downwardly through the gate 92 and into the cavity 89. The difference in pressure between the vacuum chamber 51 and the sprue 91 which is exposed to the atmosphere enhances the flow of metal into the details of the cavity. When the casting has cooled, it can be removed from the mold and finished in a conventional manner.

FIG. 5 illustrates a simplified embodiment of the invention which has an inverted U-shapcd framework 111 fabricated of a suitable material such as sheet metal. Mandral member 67 is mounted on the upper surface of the framework, and a vacuum tank 112 is mounted below the mandrel member. The tank has a removable stopper 113, and communication between the tank and mandrel member is controlled by a valve 114. Mold 10 is removably mounted on the framework over the mandrel member, as in the previous embodiment. Instead of using a separate crucible, a crucible well 116 is formed in the investment material in the upper portion of the mold. Metal placed in this well is melted by a hand-held torch 117. This torch can also be used for heating water in tank 112 or, if desired, the apparatus can be placed on a stove to heat the water.

Operation and use of the embodiment shown in FIG. 5 can be described briefly. The mold is formed as before, except that a crucible well 116 is formed in the upper portion of the investment material. The material to be cast is placed in this well and melted by torch 117. A vacuum is produced in tank 112 by boiling water with stopper 113 removed and then condensing the steam with the stopper in place. When the material in crucible well 116 is molten, valve 114 is opened to draw the material into the mold cavity.

The embodiment shown in FIG. 6 is generally similar to that shown in FIG. 5 except that it does not have a mandrel member. Instead, a flat plate 119 is mounted on the upper surface of the framework, and the mold rests on this plate during the casting process. If desired, a gasket similar to gasket 87 can be utilized between the mold and plate.

The embodiment shown in FIG. 7 also includes an in verted U-shaped framework within which a vacuum tank 122 having a removable stopper 123 is mounted. A mandrel member 67 is mounted on the upper surface of the framework, and a vacuum line 124 extends down from the mandrel member. This line is connected to the vacuum tank through a T-fitting 126 and a valve 127, the latter providing means for controlling communica tion between the tank and mold. A trap 128 is also connected to the T-fitting for preventing foreign matter, such as molten metal and particles of the mold from being drawn into the vacuum tank. Mold 10 is mounted over mandrel 67, as before, and it is formed to include a crucible well 116 in which material to be cast can be melted. A torch 13] mounted on an adjustable holder 132 provides means for melting the material in the crucible well. The operation and use of this embodiment are similar to the operation and use of the embodiment shown in FIG. 5.

FIG. 8 shows an embodiment of the invention which is particularly suitable for making larger castings. In this embodiment, the framework includes a support stand 136 having a base portion 1360, a pair of spaced apart upright members l36b and a stop 13642. A crucible 137, mold l0, and vacuum tank 138 are mounted on a pivot arm 139 to form a rigid assembly which is pivotally mounted on the support stand. A valve 141 controls communication between the vacuum tank and mandrel 67 in mold 10. This valve has a flow control member movable between open and closed positions in 90 of rotation. The valve member is rigidly affixed to the upright members of the support stand, and the valve serves as a pivot for the crucible, mold and tank assembly. The valve is closed when the assembly is in the horizontal position. and it is opened by rotating the assembly 90 in the clockwise direction to an upright position. A torch 142 is mounted on an adjustable holder 143 for heating material in the crucible. As illustrated, the torch holder is mounted on the pivot arm, and the torch moves with the rest of the assembly. Alternatively. if desired. the torch holder can be mounted on the support stand.

Operation and use of the embodiment shown in FIG. 8 can be described briefly. Mold 10 is prepared as before and placed over mandrel member 67. With the pivotally mounted assembly in its horizontal position. material to be cast is melted in crucible 137, and a vacuum is formed in tank 138. Thereafter. the assembly is swung to its upright position, pouring the material from the crucible into the mold. As the assembly swings, valve 14! opens, and the vacuum draws the material into the mold cavity.

The invention has a number of important features and advantages. It provides a casting method and apparatus which are easy to use and particularly suitable for use by hobbyists. While only certain presently pre ferred embodiments have been described herein. as will be apparent to those familiar with the art, certain changes and modifications can be made without departing from the scope of the invention as defined by the following claims.

I claim:

1. In casting apparatus, a mold comprising a body of investment material defining a mold cavity, a framework including a horizontally extending platform for supporting the mold in an upright position, tank means for heating water and condensing steam to form a vacuum, means mounting the tank means in a predetermined position beneath the platform and forming a vacuum passageway between the tank means and the mold cavity, a mandrel member carried by the framework and extending a substantial distance into the investment material, said mandrel member having a passageway communicating with the vacuum passageway, 5 one end of the mandrel passageway being in close proximity to the mold cavity, and valve means movable between open and closed positions for controlling communication between the tank means and the mold cavity.

2. Casting apparatus as in claim 1 wherein the vacuum passageway includes a trap for preventing foreign matter from being drawn into the tank means from the mold.

3. Casting apparatus as in claim 1 wherein the mold is removably mounted on the horizontally extending platform.

4. Casting apparatus as in claim 3 together with a gasket member disposed between the mold and the platform.

5. Casting apparatus as in claim 1 wherein the mold is formed to include a crucible well in which material to be cast can be heated and melted.

6. Casting apparatus as in claim 5 wherein the crucible well is formed in the upper portion of the investment material.

7. Casting apparatus as in claim 5 together with means carried by the framework for heating the material in the crucible well.

8. In casting apparatus, an inverted U-shaped framework having a generally planar base and a pair of depending legs at opposite sides of the base for supporting said base in a generally horizontal position, a mold comprising a body of investment material defining a mold cavity surmounted on the base, tank means mounted beneath the base and between the legs of the framework for heating water and condensing steam to form a vacuum, means including a vacuum passageway connected between the tank means and the mold cavity, a mandrel mounted on the base of the framework and having a passageway communicating with the vacuum passageway, said mandrel extending a substantial distance into the mold and into close proximity to the mold cavity, and valve means movable between open and closed positions for controlling communication between the tank means and the mold cavity.

9. The casting apparatus of claim 8 wherein the U- shaped framework is fabricated of sheet metal.

10. The casting apparatus of claim 8 wherein the mandrel includes a rigid body through which the passageway extends in an axial direction, said body having a cylindrical outer wall portion and a conically tapered portion adjacent to said cylindrical portion, said conically tapered portion engaging the investment material in the mold to form a vacuum, seal therewith.

* IF i

Claims

1. In casting apparatus, a mold comprising a body of investment material defining a mold cavity, a framework including a horizontally extending platform for supporting the mold in an upright position, tank means for heating water and condensing steam to form a vacuum, means mounting the tank means in a predetermined posiTion beneath the platform and forming a vacuum passageway between the tank means and the mold cavity, a mandrel member carried by the framework and extending a substantial distance into the investment material, said mandrel member having a passageway communicating with the vacuum passageway, one end of the mandrel passageway being in close proximity to the mold cavity, and valve means movable between open and closed positions for controlling communication between the tank means and the mold cavity.

9. The casting apparatus of claim 8 wherein the U-shaped framework is fabricated of sheet metal.