US3648762A

US3648762A - Centrifugal casting machine

Info

Publication number: US3648762A
Application number: US841303A
Authority: US
Inventors: William J Hill
Original assignee: INT DEV CORP
Current assignee: International Development Corp; INT DEV CORP
Priority date: 1969-07-14
Filing date: 1969-07-14
Publication date: 1972-03-14
Anticipated expiration: 1989-03-14

Abstract

A portable, centrifugal casting machine has a drive motor and shaft that rotates a generally T-shaped rotor, the head of which is inclined relative to the stem with the trailing end of the head radially outward of the leading end thereof. A mold supporting cradle is mounted on the trailing end portion of the rotor head and a crucible, with a metal discharging outlet in the end thereof toward the cradle, is mounted for limited sliding movement along a path lengthwise of the head of the T-shaped rotor. A counterweight is mounted on the opposite end of the stem of the rotor from its head. When the motor is energized, the starting torque of the rotor drives a charge of molten metal in the crucible, by a combination of acceleration, inertia and centrifugal force, through the crucible outlet and into a mold cavity in a mold mounted on the cradle, where the metal is retained under centrifugal pressure until its sets.

Description

Hill

[54] CIEWTWKWUGAL CASTIINC MACHWE [72] Inventor: William .11. lilill, San Diego, Calif.

[73] Assignee: international Development Corporation,

San Diego, Calif.

[22] Filed: July 141, 1969 211 App]. No.: 841,303

[51] int. Cl ..lB22d 13/116 {58] lField at Search ..164/114, 286, 287, 289, 292, 164/293, 298

[56] References Cited UNITED STATES PATENTS 1,280,289 10/1918 Perry 164/287 1,331,660 2/1920 Mortonson et al.. 164/287 1,767,036 6/1930 Andresen et al.... ...;.164/289 2,265,043 12/1941 Moore 164/287 2,749,585 6/1956 Prosen ..l64/287 X 3,371,705 3/1968 Ghiorzo et al. ..164/298 X FORElGN PATENTS OR APPLICATIONS Primary Examinerl Spencer Overholser Assistant Examiner-John E. Roethel Att0mey-Carl R. Brown [57] AlBS'lTCT A portable, centrifugal casting machine has a drive motor and shaft that rotates a generally T-shaped rotor, the head of which is inclined relative to the stem with the'trailing end of the head radially outward of the leading end thereof. A mold supporting cradle is mounted on the trailing end portion of the rotor head and a crucible, with a metal discharging outlet in the end thereof toward the cradle, is mounted for limited sliding movement along a path lengthwise of the head of the T shaped rotor. A counterweight is mounted on the opposite end of the stem of the rotor from its head. When the motor is energized, the starting torque of the rotor drives a charge of molten metal in the crucible, by a combination of acceleration, inertia and centrifugal force, through the crucible outlet and into a mold cavity in a mold mounted on the cradle, where the metal is retained under centrifugal pressure until its sets.

8 Claims, 6 wing Figures PATENTEDMAR 14 I972 3, 648,762

SHEET 1 BF 2 I3 FIG. I

INVENTOR. WILLIAM J, HILL BY M ATTORNEY PAIENTEDMAR 14 I972 3, 648 7'62 SHEET 2 [IF 2 FIG.6

INVENTOR. WILLIAM J. HILL ATTORNEY C lENTlItllFlUG AL CASTING MA Cll-llllNlE BACKGROUND OF THE INVENTION In the past, centrifugal casting machines have been devised for use by dentists, jewelers, artists and the like, wherein a quantity of molten metal is poured into a mold cavity that is swung in a circular orbit to generate centrifugal force that causes the molten metal to fill the mold cavity. Most of such prior art casting mechanisms do not become effective until sufficient orbital speed has been attained to provide adequate centrifugal force. This time-delay often lessens the likelihood of effective insertion of the molten metal into the cavity, thus making it difficult to continuously obtain optimum castings and causing loss of the expensive molten metal. These difficulties are increased by the gradual buildup in speed of the rotating mechanism, and as a result most existing machines must be accelerated extremely rapidly and in a very short time interval that of necessity requires the mechanisms to be strong, power ful and bolted to a heavy base. This makes such existing mechanisms expensive, complicated, heavy, not portable, and expensive to use.

SUMMARY OF THE INVENTION It is a general objective of this invention to provide improvements in the structural and operational characteristics of a portable centrifugal casting machine, and more particularly to provide such a machine that employs the inertia of a mass of molten metal, in combination with the starting accelerative movement of a mold mounted on a rotor, to propel the molten metal rapidly and completely into a mold cavity in the mold and to thereafter maintain pressure on the metal in the mold by means of centrifugal force until the metal has cooled below its melting point to provide a fine grained, detailed and unflawed casting.

The foregoing objectives and advantages of the invention will be apparent from the following description and the accompanying drawings, wherein:

FIG. I is a perspective view of a portable centrifugal casting machine embodying the invention.

FIG. 2 is an enlarged top plan view of the machine shown in FIG. 1, with both the cradles and the small flask being shown in section and a corner of the base being broken away.

FIG. 3 is an end view of the head of the rotor looking in the direction of the arrows 33 of FIG. 2, the crucible, large cradle and flask being mounted thereon.

FIG. 4 is an enlarged, sectional view taken along lines 44 of FIG. 2, the small cradle and flask being removed, and the large flask, with a mold therein, being mounted in its cradle and a torch being shown in the act of melting metal in the crucible.

FIG. 5 is a fragmentary perspective view showing the head and a fragment of the stem of the T-shaped rotor with the small flask mounted in its cradle as shown in FIG. 2, the crucible being removed.

FIG. 6 is a longitudinal, vertical, sectional view of the small cradle and flask assembly of FIG. 5, with a fragment of the rotor head being shown.

Referring to the drawings in detail, a portable, centrifugal casting machine A embodying the invention comprises a base It) having a horizontal, rectangular bottom plate 11 with rubber support pads I2 and four upright corner posts 113. An upper plate 14, shaped similarly to the bottom plate II, is secured across the tops of the corner posts I3, and an upright motor support plate I5 extends from the lower plate II to the upper plate I4 and is secured to both plates.

A drive motor l7, which is a well known type of controlled speed, gear reduction, electrical motor, is secured to the motor support plate IS with its driven shaft I3 upright and extending through a hole 19 provided therefor in the upper base plate I4. The motor 117 preferably is controlled to rotate the shaft 113 at a speed of the order of 250-300 r.p.m.

An enlarged head portion 20 is provided on the upper end of the motor driven shaft 18, its upper end being generally flat and normal to the axis of rotation on the shaft. A flat, slanted T-shaped rotor 211 has a square hole 22, see FIG. 2, in the stern thereof which is fitted onto a correspondingly shaped projection of the shaft 118. The rotor is fixedly secured to the shaft by a cap screw 23. The head 24 of the T'shaped rotor is inclined with its center line at an angle of approximately 60/ to the center line of the rotor stem 25, the larger angle being between the trailing side of the stem 25 and the trailing portion of the head 24, relative to the direction of rotor rotation.

A cradle 27 for supporting a mold flask 28, herein referred to as the large cradle and flask, is mounted on the radially outward or trailing end portion of the rotor head 24. The cradle 27 comprises a cylindrically curved plate 29 and a metal end disk 30 secured coaxially thereto. The cradle 27 is secured to the upper surface of the rotor head 24 with its axis of curvature parallel to and directly above the longitudinal center line of the rotor head 24. The large flask 28 comprises a short length of cylindrical metal tubing of a diameter to fit snugly into the cradle 27 when laid thereon as shown in FIGS. I and 3.

A hole is provided in the cradle end disk 30 to receive a threaded stud 311, see FIGS. 2 and 6, which stud extends endwise from the end disk 32 of a smaller cradle 33, herein referred to as the small cradle. A wing nut 31a is provided for the stud 311 to anchor the small cradle 33 in position in the large cradle as best shown in FIGS. 2 and 6. Except for its size, the mounting stud 31 and an arched cylindrical band portion 34 adjacent its end disk 32, the small cradle 33 is generally similar to the large cradle 27. A small cylindrical molding flask 26 is provided of a size to fit snugly into the small cradle as shown in FIGS. 2, 5, and 6.

Mounted for limited slidable movement along a path on the head of the T-shaped rotor 21 ahead of the large cradle 27 in the direction of rotor rotation, is a channel shaped crucible support member 35. The latter has two threaded

studs

37 and 38 extending downwardly therefrom. These studs are fitted for guided, slidable movement in a guide slot 39, see FIG. 4, which slot extends lengthwise along the center line of the rotor head 24. The slot 39 is of sufficient length to permit a crucible 4t), clamped in adjusted but slidable position on its support member 35, to move in guide slot 39 from a position wherein the crucible is spaced inwardly from a mold 41 supported in the large cradle 27, as shown in solid lines in FIG. 4, to the position thereof shown in broken lines the same figure. This places the discharge outlet 43 of the crucible 40 closely adjacent and in line with the sprue opening of a mold 41 in the large flask 28 mounted in the large cradle 27. Wing nuts 42 are provided on the

studs

37 and 38 for securing the crucible support member 35 in fixed position on the rotor when desired, as for packing and shipping.

A pair of

wing screws

43 and 44 are provided, one in each side flange of the crucible support member 35, for gripping therebetween the narrower lower portion of the crucible 40 when the latter is mounted on the channel shaped support member 35.

The crucible 40 is of suitable heat resistant material, such as is commonly used for such purposes and for example fire clay, porcelain, graphite, or other suitable: materials, and has a curved or concave recess 45 for melting metal and holding the molten metal prior to casting. A hooded end portion 47 is provided on the crucible 4-0, with its inner surface converging funnellike toward a discharge outlet 43 in an end of the crucible 40.

A cylindrical counterweight 49 has an axial bore therethrough that fits over an upright pin 50 that is secured to the end of the stem 25 of the T-shaped rotor opposite the head 24. The counterweight 49 is secured in position by a set screw SI having a lock nut 52 thereon. The weight of the counter weight is between that required to balance the rotor when set up for casting with the large cradle and flask, and that required when set up with the small cradle and flask. Exact counterbalancing is not considered essential, since the speed of the rotor is only of the order of 250-300 rpm, and the base is strong and rigid. However, it would be a simple matter, well within the capabilities of a routine worker, to provide either two separate counterweights, or an adjustable counterweight if more exact counterbalancing were desired.

For preparing a mold 41 in the large flask 28 as shown in FIGS. 1 and 4, a conventional wax pattern, not shown, but similar to the mold cavity 53 in the mold 41 of FIG. 4, having a usual sprue attached thereto, is set in upright position on the large end of its sprue on a usual molding board, also not shown, with the large flask 28 in axially upright position around it. The sprue is so positioned, relative to the flask 28, that the sprue will align with the discharge outlet 48 of the crucible 40 when the parts are assembled for casting on the rotor head 24 as shown in FIGS. 1 and 4. The mold 41 is prepared in a conventional manner using any desired or conventional molding material such as plaster of Paris, plaster and brick, dust, or other suitable materials, to invest the pattern and sprue therein. The flask 28, with the pattern invested therein, is then baked in a usual manner, gate down, in accordance with the well known lost wax procedure, leaving the mold 41 with its cavity 53 ready for casting.

The mold 41, thus prepared in the large flask 28, is placed in its cradle 27 as shown in FIGS. 1 and 4. The crucible support member 35, with the crucible 40 mounted in adjusted position thereon and secured by the wing screws 43 and 44, is moved slidably inwardly away from the mold 41. The wing nuts 42 are freed sufficiently to permit easy slidable movement of the crucible 40 support along its path determined by the

studs

37 and 38 riding in the slot 39. A required amount of casting metal is then placed in the crucible 40 and is heated by any suitable means, such as a brazing or welding torch 54, see FIG.

4, until the metal 55 is melted and has attained a required temperature as determined by any suitable means, such as a pyrometer, not shown. The motor 17 is then energized by means of a starting switch 57 and starts the rotor 21 to rotate in the direction of the curved arrow in FIG. 2. The cradle and mold assembly moves with the rotor. However, the inertia of the crucible support member 35 with the crucible 40 secured thereon, tends to restrain these two members which are cammed outwardly by the slot 39, moving outwardly along their path on the rotor head 24 defined by the slot 39 until the stud 37 contacts the trailing end of the slot 39. This arrests further movement of the crucible support member 35 and the crucible 40 relative to the rotor head 24, and these two members are then suddenly driven to rotate with the speed of rotor 21. At this point, the molten metal 55 in the crucible 40, which metal is still not moving with the rotor, carries the metal forcibly toward and out through the crucible outlet 48 and through the sprue opening aligned therewith and into the mold terstices of the mold cavity 53, and maintains the required pressure on the metal during the time interval required for the molten metal to set and harden. This produces a high grade, fine grained, detailed casting without voids or shrinkage defects.

For making very small castings, the small cradle 33 is used. The cradle 33 is held in position by inserting the stud 31 on the end disk 32 of the small cradle 33 in the hole provided therefor in the end disk 30 of the large cradle 27 and securing it in position by means of the wing nut 31a, see FIGS. 2 and 6,

For using the casting machine A with the small flask 26, the flask 26 has a mold prepared therein using a wax pattern in the manner previously described herein for the large flask. The small flask 26 with a mold thus prepared therein is then seated in the small cradle 33 as shown in FIGS. 2, 5 and 6. The

remainder of the casting procedure is the same as that described previously herein for the large cradle 27 and flask 28.

The invention provides a simple, relatively inexpensive, and highly effective portable centrifugal casting machine, and one which produces uniform high grade castings with a minimum amount of skill required on the part of the operator.

Having described my invention, 1 now claim.

1. A centrifugal casting machine comprising:

a rotor mounted for rotation in a plane about an upright axis; power means operatively connected to rotatably drive said rotor in one direction about its axis of rotation;

a crucible for holding molten metal and having its inner surface sloping funnellike toward a discharge outlet in an end of said crucible;

means for mounting said crucible on said rotor with said discharge outlet directed outwardly for permitting limited guided movement of said crucible relative to said rotor along a path in response to rotation of said motor;

said path being fixed at an angle and intersecting a radius of said axis of rotation;

and mold support means fixedly mounted on said rotor outwardly of the outer limit of movement of said crucible along said path to support a mold with its sprue opening aligned with and closely adjacent said crucible discharge outlet when said crucible is at its outward limit of movement along said path;

whereby, after the initiation of rotation of said rotor said crucible moves outwardly on said slot until it reaches the terminal portion of said slot arresting further movement of said crucible and causing molten metal in said crucible to move forcibly out of said crucible and into said mold.

2. A casting machine as claimed in claim 1 in which, I

the path of the crucible is fixed at an angle of the order of about to a radius from the axis of rotor rotation as measured on the rearward, inward side of the intersection of the path with such radius.

3. A casting machine as claimed in claim 2 wherein,

a mold flask is provided in the form of a tube, open at both ends, and of a size and shape to conform with the cradle for stable support thereby when placed therein.

4. A casting machine as claimed in claim 1 wherein,

the mold support means is in the form of a cradle with a member across its outward end to retain a mold placed therein against outward displacement by centrifugal force generated by rotation of the rotor.

5. A casting machine as claimed in claim 1 wherein,

the means mounting the crucible on the rotor comprise a crucible support member with means for fixedly clamping the crucible thereon, said support member having means for engaging an elongated guide element provided therefore on the rotor for guiding the crucible, fixedly clamped in its support, along said path.

6. A casting machine as claimed in claim 5 wherein,

Y the elongated guide element on the rotor is the wall of an elongated slot in the rotor.

7. A casting machine as claimed in claim 5 wherein,

the crucible support member is channel shaped, is mounted with its flanges upward, and the cruciblehas a lower portion narrower than its upper portion and of a size to fit between the flanges of the support member.

8. A portable, centrifugal casting machine comprising:

a base;

a shaft rotatably mounted in axially upright position on said base;

power means for rotatably driving said shaft in one said head of said rotor being fixed before and during rota tion at an angle to said stem of approximately 60l20 with the larger angle defined by the trailing side of said stem and the trailing portion of said head of said T-shaped rotor;

means for supporting a mold having a sprue opening in an end thereof on said rotor head with said sprue opening directed inwardly along said rotor head;

and a crucible mounted on said rotor head ahead of and inwardly of said mold supporting means for limited guided movement along a path extending lengthwise of said rotor head, the crucible having a discharge opening in the end

Claims

1. A centrifugal casting machine comprising: a rotor mounted for rotation in a plane about an upright axis; power means operatively connected to rotatably drive said rotor in one direction about its axis of rotation; a crucible for holding molten metal and having its inner surface sloping funnel-like toward a discharge outlet in an end of said crucible; means for mounting said crucible on said rotor with said discharge outlet directed outwardly for permitting limited guided movement of said crucible relative to said rotor along a path in response to rotation of said motor; said path being fixed at an angle and intersecting a radius of said axis of rotation; and mold support means fixedly mounted on said rotor outwardly of the outer limit of movement of said crucible along said path to support a mold with its sprue opening aligned with and closely adjacent said crucible discharge outlet when said crucible is at its outward limit of movement along said path; whereby, after the initiation of rotation of said rotor said crucible moves outwardly on said slot until it reaches the terminal portion of said slot arresting further movement of said crucible and causing molten metal in said crucible to move forcibly out of said crucible and into said mold.

2. A casting machine as claimed in claim 1 in which, the path of the crucible is fixed at an angle of the order of about 120* to a radius from the axis of rotor rotation as measured on the rearward, inward side of the intersection of the path with such radius.

3. A casting machine as claimed in claim 2 wherein, a mold flask is provided in the form of a tube, open at both ends, and of a size and shape to conform with the cradle for stable support thereby when placed therein.

4. A casting machine as claimed in claim 1 wherein, the mold support means is in the form of a cradle with a member across its outward end to retain a mold placed therein against outward displacement by centrifugal force generated by rotation of the rotor.

5. A casting machine as claimed in claim 1 wherein, the means mounting the crucible on the rotor comprise a crucible support member with means for fixedly clamping the crucible thereon, said support member having means for engaging an elongated guide element provided therefore on the rotor for guiding the crucible, fixedly clamped in its support, along said path.

6. A casting machine as claimed in claim 5 wherein, the elongated guide element on the rotor is the wall of an elongated slot in the rotor.

7. A casting machine as claimed in claim 5 wherein, the crucible support member is channel shaped, is mounted with its flanges upward, and the crucible has a lower portion narrower than its upper portion and of a size to fit between the flanges of the support member.

8. A portable, centrifugal casting machine comprising: a base; a shaft rotatably mounted in axially upright position on said base; power means for rotatably driving said shaft in one direction; a generally T-shaped rotor comprising a stem portion and a head portion with said stem portion mounted on said shaft to rotate said rotor with said shaft in a plane normal to the axis of shaft rotation; said head of said rotor being fixed before and during rotation at an angle to said stem of approximately 60*-120* with the larger angle defined by the trailing side of said stem and the trailing portion of said head of said T-shaped rotor; means for supporting a mold having a sprue opening in an end thereof on said rotor head with said sprue opening directed inwardly along said rotor head; and a crucible mounted on said rotor head ahead of and inwardly of said mold supporting means for limited guided movement along a path extending lengthwise of said rotor head, the crucible having a discharge opening in the end thereof directed rearwardly and outwardly along said rotor head for alignment of the latter opening with said sprue opening in a mold mounted on said mold supporting means when said crucible is at its outward limit of movement; whereby, after the initiation of rotation of said rotor said crucible moves outwardly on said slot until it reaches the terminal portion of said slot arresting further movement of said crucible and causing molten metal in said crucible to move forcibly out of said crucible and into said mold.