US2245065A - Dental casting machine - Google Patents

Description

June10, 1941. BERGER 2,245,065

DENTAL CASTING MACHINE Filed Sept. 28, 1938 2 Sheets-Sheet 1 when R Berger.

June 10, 1941. R ER 1 2,245,065

DENTAL CASTING MACHINE Filed Sept. 2a, 1938 2 sheets-sheet 2 Herbert 1?. Berger- Patented June 10, 1941 UNITED STATES LPATENT OFFICE I DENTAL CASIING MACHINE Herbert R. Berger, Brooklyn, N. .Y., asslxnor to J. F. Jelenko & 00., Inc., New York, N. Y.

Application September 28, 1938, Serial No. 232,207

The present invention relates to improvements 4 7 Claims.

in casting apparatus of the type capable of use in dental and'jewelry work, or similar work.

In the casting of metals for dental work, jewelry, and other fine work by the usual centrifugal methods in which visual inspection is relied. upon to determine the proper time for molding, many defects are often present in the finished castvision of an apparatus of this character which may be manufactured as a complete unit or as an attachment to be applied to centrifugal machines now in use.

Other objects and advantages of the invention will b apparent during the course of the following description.

In the accompanying drawings, which form,a part of this specification and wherein like characters of reference denote like parts throughout,

Figure 1 is an elevation of a casting apparatus embodying the present invention and of the type capable of use with centrifugal apparatus now in use,

Figure 2 is a top plan view thereof,

Figure 3 is a vertical sectional view taken on the line 3-3 of Figure 1,

Figure 4 is a front elevation of the electrical melting furnace,

Figure 5 is a diagrammatic representation of the electrical circuits employed,

Figure 6 is a longitudinal sectional view on an enlarged scale of the furnace side of th apparatus, and,

Figure 7 is a side elevation of a complete casting apparatus embodying the present invention.

In the drawings, wherein for the purpose of illustration is shown a preferred embodiment of i the invention, the numeral l0 designates the base of a centrifugal casting machine of the type now in use in which a central vertical shaft H projects above the casing and is connected to a spring motor or other source of power within the casing which is adapted to rotate the shaft H at high speed. Casings and shafts of this type are in common use with various types of centrlfugal casting machines. A horizontal bar I2 is removably secured to the upper end of shaft l I to rotate therewith.

A furnace or oven l3 isrigidly secured to the bar 12 by means of a pair of clamping members l4 removably bolted at IE to the bar I! at a point between the shaft and one end of the bar l2. The furnace is supported above the bar, and when it is desired to remove the furnace, bolts l5 are removed and the furnace and clamp slid from. the bar longitudinally thereof. In order to insure proper location of the furnace, bolts l5 extend through suitable openings in the bar. The upper ends of clamp members H ar removably secured to the outer casing of the furnace by means of bolts l6. Clamp members [4 are provided with a pair of arms ll which extend below bar l2 oneon each side thereof. A panel or contact block i8 is removably secured between arms I)! by means of suitable bolts 19.

The furnace or oven 13 has an outer metal casing 20 which is cylindrical in shape and closed by end walls 28. A cylindrical refractory muille 22 is embedded in the end walls of the furnace and is spaced a substantial distance from the side walls of casing 20. Electrical resistance windings 23 encircle the outer periphery of the muflie 22 and are covered by some suitable insulating material such as alundum cement 24 which may in turn be surrounded by magnesia,

26 and 27! are disposed in a vertical row adjacent the inner edge of contact block it, projecting a short distance laterally beyond the panel or contact block.

A sliding contact holder comprises a bifurcated holder block 28 removably secured to the top of casing ID by means of lateral brackets 29 detachably bolted to the casing top. The lower portion of holder block 28 is shaped to conform to the top of the casing and is secured to brackets 29 by means of suitable bolts 30. A sliding contact plate 31 is slidably disposed in the bifurcated portion'of the-holder block and may be moved outwardly against the tension of a coil spring 32 by means of a finger piece or lug 33 extending through an elongated horizontal slot in the holder block. A cover cap 34 closes the top of ries wires connected to the contact strips 35 and terminates in a pronged plug 81, the prongs of' which vary in diameter to insure the proper electrical connections for the winding 23 and-thermocouple 25.

The contact carrying plate 8| is usually-in the retracted position indicated in Figures land 6. When the bar I2 is revolved towind up the spring in casing l0, plate 31 is moved outwardly against the tension of spring 32 to place contact strips 35 in the path of contact block l8 and contacts 26 and 21. The pressure of bar [2 and the casing spring will hold the plate 3i in extended position and prevent rotation of bar i2. When it is desired to release bar l2 for rotation, it is moved away from plate 3| against the tension of the casing spring, allowing spring 32 to retract plate 3|. Bar l2 may then be released to rotate with shaft ll. It will be seen that holder block 28 and sliding contact plate 3| may be readily attached to bases now in use, by means of the bolts on brackets 29.

By reference to Figure 6 it will be front end of the furnace casing is provided with a circular opening 38 which coincides with the inner periphery of the muilie 22. A smaller opening 39 is disposed in the rear wall of the furnace casing in concentric relation with the muiile. A door 40 fits in opening 38 and is pivoted at ti adjacent the top of the furnace casing. A transparent window 4} may be arranged in the center of the door ill.

A crucible 43 is cylindrical in shape and may be of carbon, alundum or other suitable material. Carbon makes an advantageous crucible for precious metals because of the reducing atmosphere.

The crucible d3 fits within the mufiie 22 and has a sprue M which extends through the opening 39 to the gate of the mold G5. The crucible t3 and door dd are held in place by centrifugal force when the bar I2 is rotated. The inner walls of the crucible taper at their ends to the opening in sprue M. The end of'the crucible opposite the sprue has an opening at therein of substantially less width than the inner periphery of the crucible and concentric therewith. A slot 61 is The contact strips 35 are spaced to engage the contacts 26 and 21. A flexible cable 38 Cal".

seen that the preferably arranged in the top of the crucible to register with the thermocoupla25.

A flask holder 58 is frusto-conical in shape and has a depending leg provided with a slot 59 to slidably receive the bar I2. A removable pin 50 in'the end of the bar it normally prevents removal of the holder d8. A flask or mold 65 is arranged between the furnace 2t and the frusto= conical portion of the holder d8. A cradle 5! is provided with a pair'of depending legs 52 adapted to straddle the bar i2,'and supports mold 65 in position to be engaged by flask holder 38. The

cradle 5! may be lifted vertically from bar i2 for removal, and may be adjusted longitudinally along the bar. Various size cradles are provided to accommodate different molds.

A clamping bolt 53 extends through the bottom of flask holder 58 into slot 69 and is provided with a handle 5% for easy operation. In operation, mold 45 is placed in cradle 5! in engagement with sprue 4B, and flask holder #38 is moved into clamping engagement therewith. Bolt 53 is then tightened to lock holder 43 on bar l2. The frusto-conical shape of the holder 38 assures proper centering of the mold 45. In order to produce a clamping action on the mold when bolt 511s tightened, slot 45 is disposed at a slight angle to a horizontal plane, as indicated in Figure 6, so that tightening of bolt 53 will tilt the holder and move the top of holder 48 towards the furnace 20 and firmly clamp the mold, as seen in Figure 1. v

. A cylindrical counterweight 55 is provided with a longitudinal slot to slidably receive the bar l2 on the side ofshaft H opposite the furnace. A plate 56 is bolted to the lower side of the weight 55 to close the bottom of the slot therein. A handle member 5'! extends above the weight 55 and has a reduced removable shank 58 extending through a vertical bore into the slot. The lower end or head of shank 58 is adapted to be received in one of a series of spaced openings 60 in the top of bar l2. A coil spring 59 surrounds the shank within the weight slot and, engages the head of the shank to normally force the shank into the openings 60. When it is desired to change the position of weight 55, shank 58 is released from openings 60 by raising handle 51 against tension of spring 59. The weight handle 51 is also used to rotate the bar l2 and shaft H, as when winding up the spring motor in casing I 0. A removable, supplementary weight 6! has a slot to receive the bar 52 and a horizontal pin 62 adapted to extend into an opening in weight 55 to interlock the two weights. Pins 63 on bar l2 limit movement of the weights 6i and 55 and may be detachably secured to the bar.

In Figures 1 to 6,the arm I2 is shown as attached to the usual base ea. In Figure 7 it is shown applied to a base ill which is designed to fit the new arm and furnace. .The base I0 is formed with a flat top to provide a more comother figures.

In Figure 5 a diagram of the electric circuits employed is illustrated. A pyrometer P is shown in circuit with thermocouple 25 through contacts 35 and 26 while an ammeter A, switch 66 and rheostat or other current controlling device 67 are included in the circuit to the heating coil 23 through contacts 35' and 27. Obviously, additional circuits may be added, by merely increasing the number of contacts.

In operation, the handle 57 is graspedand the bar 82 rotated to wind up the spring motor in casing id or i02 The slidable contact plate Si is then moved out into the path of contact block l8 against the tension of the spring 32. The pressure of the spring motor forces contact block firmly against plate 35 and retains it in extended position. The circuits to the heating coil and thermocouple are connected through contacts 35, 26 and 27 in this position of plate 3!. The mold 65 is then clamped in position, metal is placed in the crucible and the current turned on. When the desired temperature is reached, as determined by reference to the pyrometer, handle 51 is grasped and bar, i2 moved to separate contact 45 under the action of centrifugal force. By the use of thermocouple 25 and pyrometer P the desired temperature may be obtained before rotating arm l2, without relying upon visual inspection, and castings of a fine, uniform character may be obtained. The crucible "Imay be removed for cooling by opening door 40 and lifting out the crucible with a pair of tongs. l

The flask holder 48 may be adjusted to clamp molds of various sizes while the counterweights may be adjusted to properly balance the bar i2. The inclined slot 49 insures a lflrm clamping of to without departing from the spirit of the inven-" tion or the scope of the subjoined claims.

Having thus described my invention, what I claim and desire to protect by Letters Patent is:

' being an elongated slot in the upper wall of the crucible to connect the exterior of the crucible with the interior thereof.

4. In a centrifugal casting machine, means I forming a cylindrical heating chamber and comprising opposite end walls provided with a charging opening and a discharging opening, respectively, said heating chamber being mounted for rotation about an axis at right angles to the cylinder axis, a cylindrical refractory crucible positioned in said heating chamber coaxially therewith and provided with opposite end portions adjacent said end walls, respectively, one of said end portions having an opening registering with said charging opening, the other of said end portions having an end surface engaging the inner surface of said end wall which is provided with said discharging opening and having an axially extending part of reduced diameter proecting through said discharging opening outwardly beyond said last mentioned end wall and having a sprue opening, and a closure movably 1. In a centrifugal casting machine, a rotary furnace, a muffle disposed within said furnace,

an electrical heating element surrounding said muiile, said furnace having-a sprue opening on one side and a door on the opposite side thereof communicating with the muflle, a thermocouple disposed in theupper portion of said muflle, a removable crucible adapted to fit within said muille and having a sprue adapted to extend into the sprue opening of the furnace, and said crucible having an elongated slot in its upper portion adapted to register with the thermocouple in the muffle, said thermocouple being positioned externally of the crucible chamber.

2. In a centrifugal casting machine, a heating chamber having a cylindrical muilie, there being a sprue opening in one end of the furnace and a door in the other end thereof, and a crucible adapted to fit within the mufile, said crucible being of generally cylindrical shape and having a sprue of reduced size adapted to extend into the furnace sprue opening, the inner walls of said crucible tapering to said sprue, and said crucible having an opening in its end opposite the sprue, said opening being of less diameter than the inner periphery of the crucible whereby a circumferential flange is formed at the end of the crucible, and athermocouple in the upper portion of the muflle, said crucible being insertable in and. removable from said muflle while said thermocouple is in position in said muifle, there being a slot in the upper wall of the crucible communicating with the interior of the crucible and adapted to register with the thermocouple in the muffle.

3. In a centrifugal casting apparatus, a heating chamber, and a removable crucible adapted to be received in said heating chamber, said crucible having a sprueof reduced size at one end thereof, the inner walls of said crucible tapering to said sprue, saidsprue projecting outwardly of said heating chamber for engagement with a mold, said-crucible having an opening in its other end opposite the sprue, said opening being of substantial size and of less magnitude than the inner periphery of the crucible whereby a peripheral flange is formed at the end of the crucible by the end wall defining the crucible opening, and there secured at the charging end of said chamber for closing said charging opening and the adjacent opening of said crucible.

. 5. In a centrifugal casting machine, means forming a. cylindrical heating chamber and comprising opposite end walls provided with a charg ing opening and a discharging opening, respectively, said heating chamber being mounted for rotation about an axis at right angles to the cylinder axis, a cylindrical refractory crucible wardly beyond said last mentioned and wall andv having a sprue opening, and a closure movably secured at the charging end of said chamber for closing said charging opening and the adjacent opening of said crucible, said crucible being insertable in and removable from said heating chamber through said opening in the charging end of said chamber.

6. In a centrifugal casting machine, means forming a cylindrical heating chamber and comprising opposite end walls provided with a charging opening and a discharging opening, respectively, said heating chamber being mounted for rotation about an axis at right angles to the cylinder axis, a cylindrical refractory crucible positioned in said heating chamber coaxially therewith, and provided with opposite end portions adjacent said end walls, respectively, one of said end portions having an opening registering with said charging opening, said crucible having an inwardly projecting peripheral flange at said end portion thereof which is provided with said opening, the other of said end portions having an end surface engaging the inner surface of said end wall which is provided with said discharging opening and having an axially extending part of reduced diameter projecting through said discharging opening outwardly beyond said last mentioned end wall and having a sprue opening,

and a closure movably secured at the charging end of said chamber for closing said charging 4 aesaoee opening and the adjacent opening of said crucihie 7 In a centrifugal casting machine, means forming a cylindrical heating chamber and comprising opposite end walls provided witha charg 'ing opening and a discharging opening, respectively, said heating chamber being mounted for rotation about an axis at right angles to the cylinder axis, a cylindrical refractory crucible positioned in said heating chamber coaxiaily 1o therewith and provided with opposite endv portions adjacent said end walls, respectively, one of said end portions having an opening registering with said charging opening. said crucible having an inwardly projecting peripheral flange at 15 said end portion thereof which is provided with said opening, the other of said end portions having an end surface engaging the inner surface of said end wall which is provided with said dischar-opening and having an axially extending part of reduced diameter projecting through said discharging opening outwardly'beyond said last mentioned end wall and having a sprue openmg, and a closure movably secured at the charging end oi said chamber for closing said charging

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