US1962456A - Casting apparatus - Google Patents

Description

June 12, 1934. R. E. MYERS 1,962,456

CASTING APPARATUS Filed July 19, 1930 3 Sheets-Sheet 1' June 12, 1934. R. E. MYERS CASTING APPARATUS 3 Sheets-Sheet 2 Filed July 19, 1930 M INVENTQR M ATTORNEY June 12, 1934. R. E. MYERS 1,962,456

CASTING APPARATUS Filed July 19, 1930 3 Sheets-Sheet 3 ZINVENTOR I /MM 4 ATTORNEY$ Patented June 12, 1934 UNITE STATES PATENT OFFICE 17 Claims.

The present invention relates to casting apparatus, one object thereof being to provide a device for casting metal under pressure and in such a way that castings of unusual shape or of a k character ordinarily difficult to cast may be successfully produced. Although the embodiment of my invention illustrated in connection with the following description is intended to be used more particularly in the production of so-called l0 dental castings, there is of course no reason to limit the use of the invention to this particular field and it is therefore contemplated that the principles involved in the illustrated embodiment of my invention may be applied with beneficial results to casting operations in fields other than that of dental casting.

Molders have long found difficulty in success fully producing castings of relatively extended areas in proportion to their thickness. In ordinary dental casting work, the failure of the castings is probably due to the congealing of the metal before it penetrates to the farthest recesses of the mold cavity. In many cases, it is possible to overcome this difficulty in some degree by supplying the molten metal through a number of sprues. It has also been suggested that the difficulty may be overcome by utilizing pressure in connection with the casting operation.

In dental work, it is common practice to form castings in a mold made of so-called investment material which has a certain porosity characteristic. Successful castings are made from time to time in this kind of a mold by the application of pressure to the top of the molten metal thus '35 forcing it through a sprue or sprues into the mold cavity.

For some types of castings, ordinary wellknown methods serve fairly well. However, for the casting of thin plates, discs and other small .40 castings of extensive area and of thin section, the

usual casting practice is not successful. In connection with this practice, I have found that the molten metal when subjected to pressure applied in the usual way does not spread throughout the mold cavity. In fact, in many instances it advances no farther than the end of the sprue even though considerable pressure may be exerted on its exposed surface within the flask.

While it is diflicult to ascertain the exact con- ."1 ditions prevailing during any casting operation, which by the way in dental practice takes place over a period measured in seconds, my theory is that, for some reason, the advancing portion of the molten metal in the sprue rebounds or is thrown back towards the sprue when the air pressure is applied suddenly or in excessive amount upon the upper surface of the molten metal in the flask. It may well be that this rebound is caused by the cushioning eifect of the air or other gas entrapped in the mold cavity 60. and which, when pressed suddenly, causes a reverse action after the maximum pressure is reached and an equalizing operation takes place or it may be that the metal actually rebounds after striking a portion of the mold cavity. Ac- 65. cording to the theory of operation of my invention, the initial advance of the metal into the mold cavity is preferably controlled so as to correspond at least approximately with the capacity of the investment material of the mold to ab- 70, sorb or carry away the gas or air entrapped in the sprue and mold cavity as it is displaced by the advancing molten metalr Then a greater pressure may be applied to the exposed surface of the molten metal in the flask to secure the chief benefits of pressure castings Accordingly, it is a further object of vmy in-. vention to provide casting apparatus whereby castings may be made under pressure so regulated that an initially low pressure is applied to prevent rebound of the metal in the sprue, after which gradually increased pressure is applied to complete the casting. The time interval between the application of the low pressure and the admission of increasing pressure will de- 5 pend upon the speed with which the molten metal moves toward the mold cavity. This in turn is a function of the porosity of the investment, the temperature of themold, the degree of pressure used and the character of the metal. Obviously, no hard and fast rule as to the time interval can be formulated to cover every case. However, for any given class of castings, it is possible to arrive at an arrangement or sequence of valve operation in a suitable machine which will automatically, in the greater number of cases, produce substantially perfect castings.

A preferred embodiment of my invention is described in the following specification and illustrated in the appended drawings, in which Figure 1 is a diagrammatic representation of a casting device for use more particularly in a dental laboratory 01' ofiice supplied with compressed air from a central system or the like;

Figure 2, a similar diagrammatic representation of a casting apparatus designed more particularly for use where no air line is available;

Figure 3, a diagrammatic representation of a modification in which gradually increasing pressure is supplied to the molding flask or metal confining means through a valve without an interposed expansion chamber;

Figure 4, a detail partly in section, of one form of a slow acting valve and its connection with an operating handle;

Figure 5, a modified device for casting with graduated air pressure; and

Figure 6, a further modification.

Referring to Figure 1 of the drawings, a casting machine embodying my invention is shown in a form which includes a tank or container 1 adapted to hold a supply of fluid under pressure, such for example as compressed air which may conveniently be supplied thereto through aconduit 2 connected with a reservoir or other source of air under pressure, not shown. A reducing valve 3 is interposed between conduit 2 and the interior of container 1 for the purpose of admitting thereto and maintaining therein under certain conditions a supply of air under a predetermined low pressure. In dental casting work, a great number of casting operations utilize a pressure of approximately 2% to 3 lbs. as an initial pressure in the container 1. Under these circumstances, the valve 3 is adapted to be adjusted to produce the required pressure in container 1, regardless of pressure variation in the air line or conduit 2. A flexible tube 4 connects the interior of container 1 with a hollow head 5 having a valve 6 to which is secured a lever '1. An operating handle or lever 8 is pivoted at 9 and is connected to the valve actuating lever '7 by means of a link 10.

The operating handle 8 also supports a flask sealing cap 11 through which the opening in head 5 extends to admit air under pressure into a flask 12 when cap 11 is in sealing contact therewith. A spring 13 interposed between cap 11 and the operating arm 8 permits a differenair under pressure from container 1 to the interior of said flask.

At this stage of the operation, it will be understood that flask 12 contains a mold usually of porous investment material 14 surrounding a cavity 15 which is connected by a sprue 16 to a cone-shaped upper or crucible surface adapted to hold a supply of metal 17. In practice a blow torch is used to fuse the metal and to heat the investment.

With the apparatus thus far described, and which is now known in the art, it is possible under some circumstances to make successful castings under pressure. But it is practically impossible to make an extended or thin casting such as a dental plate or the like by means of such a machine unless the operator has more than ordinary skill in casting practice.

To eliminate some of the factors which cause failures in casting with devices of the kind de- -7 scribed, I have provided means whereby an extension 18 of the conduit 2 by-passes the reducing valve 3 to admit high pressure into the interior of container 1 under controlled conditions, for example, as by a valve 19 interposed in conduit 18 and having a stem 20 with its upper exposed free end arranged in the path of and engaged by a portion of the operating arm 8 when the latter is deflected downwardly in the course of the normal operation of the casting machine. Suitable means, such as a spring 21, are provided to retain valve 19 normally in conduit closing position and to yield only when the operating arm is depressed to the proper extent.

In normal casting practice, with my improved apparatus, the parts are so positioned and proportioned that the opening of valve 19 takes place at a predetermined time interval subsequent to the opening of valve 6. Thus, in effect, where a relatively low pressure, as three pounds for example, is normally maintained in container 1, the opening of valve 6 will admit said low pressure to the interior of the flask as previously described and, at a proper interval thereafter, continued downward movement of the operating arm 8 opens valve 19 whereupon high pressure is admitted to container 1 and is transmitted therefrom in a gradient through the conduit 4 and valve 6 to the interior of the flask, thereby effecting an increasing pressure therein. It is contemplated that the container 1 in this type of machine serves as a cushioning or expansion chamber forming part of conduit means by which air is supplied from the source to the interior of flask 12, first absorbing a portion of the high pressure and then transmitting the same gradually to the flask 12 or other metal confining device.

In the modified or hand pump form of apparatus illustrated in Figure 2, relatively high pressure is produced in a tank 30 by means of a pump 31. An adjustable reducing valve 32 is interposed in a conduit 33 connecting said tank 30 with a container 34 corresponding in function to the container 1 in Figure 1. A pressure gauge 35 communicates with the interior of tank 30 and a pressure gauge 36 communicates with the interior of container 34. A conduit 3'7 connects tank 30 with container 34. A valve 38 corresponding in function to valve 19 of Figure 1 is interposed in conduit 37 and operates in the same manner as valve 19.

The mode and sequence of operation of the parts shown in Figure 2 are the same as those of the corresponding elements embodied in the device illustrated in Figure 1.

In the modification shown in Figure 3, provi sion is made for securing a pressure gradient directly from the high pressure line after or during operation of the low pressure valve and without the aid of an expansion chamber. For

this purpose, a conduit 40 is connected at the outlet side of valve 41 permitting direct communication between conduit 18 and the hollow head 5. However, valve 41 is preferably designed to release the high pressure slowly or gradually from conduit 18 to conduit 40, as by retarding the opening of said valve compared to the speed with which operating handle 8 is depressed. Thus, in one form of valve, Figure 4, the valve stem 42 interposed between conduit 18 and conduit 40 has a plurality of air passages 43 of as the stem moves downwardly the pressure in x conduit 4, Figure 3.

conduit and consequently in flask 12 is gradually increased to the maximum desired amount. Where a more widely or carefully adjusted or controlled gradient is required, a regulating valve having a stem 56 and a thumb piece 57 is interposed between the inlet conduit 18 and the conduit 40, preferably as a part of a valve mechanism indicated generally at 41, The latter operates independently of reducing valve 3 which remains unchanged and undisturbed. This feature of my invention enables me to make a large number of castings with one setting of the reducing valve. Furthermore, it permits the use of a properly designed pressure gradient producing valve, thus avoiding the difficulties involved in attempting to combine the two in a single eiiiciently operating unit.

In some forms of apparatus, as those in which valve 6 closes before cap 11 is lifted to unseal the flask, a condition of high pressure remains in the system between the reducing valve 3 or 32 and the valve 6, so that except for equalization caused by leakage the apparatus would not be in proper condition for the next increment of normal cas ing operation. To bring about automatic resetting of the apparatus, or re-establishment of predetermined pressure conditions or relations therein, is a further object of my invention the attainment of which contributes to rapid and efficient operation. Thus, an adjustable maximum pressure or safety valve 49 of any suitable type is in communication with the interior of chamber 1 in the apparatus shown in Figure 1, with the interior of chamber 34, Figure 2, or with The outlet port of valve 49 is controlled by a valve 56 to which is secured a lever arm 51 connected by a link 52 with an extension 53 or the like of operating lever 8. The parts just described are so arranged and adjusted that, when operating lever 8 is in its up or inoperative position, valve 50 remains open. Any excess pressure behind valve 49 is thus exhausted before the next downward movement of operating lever 8. It will be suflicient if valve 50 closes simultaneously with or just prior to the opening of valve 6, or in such relation thereto that after the desired initial low pressure is released in the flask, the desired gradient of increased pressure follows in proper sequence.

In the modification shown in Figure 5, the handle or lever 8 and flask 12 with its cover 11 are mounted in effective operative relation to an air reservoir communicating through a valve 61 with an expansion chamber 62. A flexible conduit 63 affords communication means between the interior of the expansion chamber 62 and the hollow stem 64 which supports cover 11 on han dle 8.

In operation, handle 8 is depressed to flask closing position, whereupon further downward movement opens valve 61. The air under pressure in reservoir 60 expands into chamber 62 and thence through conduit 63 into the flask 12. In so doing, the pressure in the flask rises gradually from approximately atmospheric to any predetermined maximum, depending in part on the pressure in reservoir 60, the rate of increase being varied to accommodate different casting conditions. A convenient expedient for varying the pressure gradient is to vary the efiective capacity of the'expansion chamber 62, assuming that the pressure in reservoir 60 remains substantially constant. For this purpose, an end wall of chamber 62 is in the form of a piston head 65 which is advanced and retracted by any suitable means as a stem 66 in threaded engagement with fixed bearing or support 67. A handle '75 on stem 66 permits the stem to be rotated manually to effect any required adjustment of piston head 65. Obviously, a variety of expedients readily suggest themselves as alternatives for the gradient control and adjustment means hereinabove described. It will be apparent that when handle 8 is reversed or raised to inoperative position, its movement closes valve 61 and lifts cap 64, thus automatically restoring the pressure in expansion chamber 62 to normal or atmospheric pressure before the following casting operation.

Another form of apparatus suited to dental casting and other work is shown in Figure 6. Referring thereto, air under pressure is supplied to the flask through conduit 68 from any suitable source such as the reservoir 69 having an outlet valve 70, the operation of which is controlled by handle 8 as in previously described forms of apparatus. To effect the desired graduated eifect or pressure gradient in flask 12, a suitably restricted opening is provided between the valve 70 and said flask. In the illustrated embodiment the opening takes the form of a central longitudinal passageway '71 in a plug 72 inserted in nipple '73 forming part of the head or flask cover supporting stem. Where air pressure of approximately 15 to 20 pounds is available in reservoir 69 and the apparatus is'provided with air conduits and connections of sizes usual or common in known dental casting machines, good re-' sults are secured where the passageway '71 is of the diameter produced by a No. '70 drill. In operations where a more rapid pressure acceleration is desired, a plug having an opening or passageway of larger diameter is inserted in the opening of nipple 73. Similarly, a plug having a smaller opening is used where slower pressure acceleration is desired. a

From the foregoing description and the stated mode of operation of my improved casting apparatus, it will be apparent that my invention resides in the provision of novel means in pressure casting apparatus whereby the metal confined in a flask mold or the like is subjected to a gradually increasing pressure or to an initial relatively low pressure and thereafter to an increasing pressure by the cooperation of suitable and properly related parts of relatively simple construction. In the case of devices constructed according to Figures 1, 2 and 5 the efifective pressure gradient following the low pressure is secured by applying the high pressure through an expansion chamber, and in the case of devices of the type shown in Figure 3, by applying the high pressure through a suitably controlled pressure gradient producing valve or valves.

I claim as my invention:

1. Casting apparatus which comprises mean for confining a material to be cast in position to enter a mold cavity, a source of fluid under pressure, a container for a supply of fluid under pressure, an inlet valve for admitting thereto from said source fluid under a predetermined relatively low pressure, an outlet valve between said container and said material confining means, and a valve separate from said first mentioned inlet valve and said outlet valve and adapted to admit fluid from said source to said container under higher pressure than that of the fluid admitted through said first mentioned inlet valve.

2. Casting apparatus which comprises means for confining a material to be cast in position to enter a mold cavity, a source of fluid under pressure, a fluid container operatively interposed between said source and said material confining means, an adjustable reducing valve between the source and the container, a valve between the source and the confining means adapted to admit a predetermined pressure to said confining means, a separate valve adapted to admit a different pressure to said confining means, and means for actuating said two last mentioned valves at a; predetermined time interval.

3. Casting apparatus which comprises means for confining a material to be cast in position to enter a mold cavity, a source of fluid under pressure, a container for a supply of fluid under pressure, a reducing valve between said source and said container for admitting thereto fluid under a predetermined relatively low pressure, an outlet valve between said container and said material confining means, a valve separate from said reducing valve and said outlet valve and adapted to admit fluid to said container under a pressure greater than that of the fluid admitted through the reducing valve, an operating handle for open ing said outlet-valve and said separate valve when deflected in one direction, and means for automatically closing said valves when said handle is deflected in the opposite direction.

4. Casting apparatus which comprises means for confining a material to be cast in position to enter a mold cavity including a mold flask, a sealing cap therefor, and a cap supporting operating handle, a source of air under pressure, an eX- pansion chamber, a reducing valve between said source and said chamber adjusted to maintain a predetermined low pressure therein, a valve effectively positioned between said chamber and said sealing cap and adapted to be actuated by said handle to admit air from said chamber to said confining means, and a separate valve interposed 1 between said source and said confining means to admit relatively high pressure thereto.

5. In apparatus for casting under pressure, the combination of a mold flask having a cap mounted to be seated on and unseated from the flask, a

source of air under pressure, conduit means operatively arranged between said source and said flask to pass air from the source to the flask, valve means operatively arranged to control the passage of air through the conduit means from said source to said flask, an actuating member 013- eratively related to said cap and to said valve means and adapted to be moved manually in one direction to effect the seating of said cap and then the opening of said valve means, and pressure varying means operatively arranged in relation to said conduit means and said valve means and adapted to effect variation of air pressure in the flask during movement of said actuating member in said one direction whereby air is delivered into said flask from the conduit initially at relatively low pressure and thereafter at gradually increasing pressure.

6. In apparatus for casting under pressure, the combination of a mold flask having a cap mounted to be seated on, and unseated from the flask, 'a source of air under pressure, conduit means operatively arranged between said source and said flask to pass air from the source to the flask, valve means operatively arranged to control the passage of air through the conduit means from said source to said flask, an actuating member operatively related to said cap and to said valve means and adapted to be moved manually in one direction to effect the seating of said cap and then the opening of said valve means, and an expansion chamber operatively arranged between said source and the flask and adapted during movement of said actuating member in said one direction to receive air from the source and to deliver air to the flask initially at relatively low pressure and thereafter at gradually increasing pressure.

7. In apparatus for casting under pressure, the combination of a mold flask having a cap mounted to be seated on and unseated from the flask, a source of air under pressure, conduit means operatively arranged between said source and said flask to pass air from the source to the flask, valve means operatively arranged to control the passage of air through the conduit means from said source to said flask, an actuating member operatively related to said cap and to said valve means and adapted to be moved manually in one direction to effect the seating of said cap and then the opening of said valve means and in the opposite direction to close said valve means and to unseat said cap, means operatively arranged in relation to said conduit means and said valve means and adapted to effect variation of air pressure in the flask during movement of said actuating member in said one direction whereby air is delivered. into said flask from the conduit initially at relatively low pressure and thereafter at gradually increasing pressure, and means operatively arranged in relation to the conduit means and to said actuating member and adapted to discharge air from said conduit to atmosphere when the actuating member is moved in said opposite direction.

8. In apparatus for casing under pressure, the combination of a mold flask having a cap mounted to be seated on and unseated from the flask, a source of air under pressure, conduit means operatively arranged between said source and said flask to pass air from the source to the flask, valve means operatively arranged to control the passage of air through the conduit means from said source to said flask, an actuating member operatively related to said cap and to said valve means and adapted to be moved manually in one direction to effect the seating of said cap and then the opening of said valve means and in the opposite direction to close said valve means and to unseat said cap, an expansion chamber operatively arranged between said source and the flask and adapted, during movement of said actuating member in said one direction, to receive air from the source and to deliver air to the flask initially at relatively low pressure and thereafter at gradually increasing pressure, and means operatively arranged in relation to the expansion chamber and to said actuating member and adapted to discharge air from said expansion chamber to atmosphere when said actuating member is moved in said opposite direction.

9. In casting apparatus, the combination of a flask, a source of air under pressure, a conduit arranged to pass air from said source to said flask, a valve effectively arranged in relation to the conduit and to said flask and normally seated to prevent passage of air from said source to said flask, and air pressure varying means, operative when said valve is open, to supply air to said flask initially at low pressure and thereafter at gradually increasing pressure, and an operating lever movable in one direction to open said valve and in the opposite direction to close said valve.

10. Casting apparatus which comprises means for confining a material to be cast in position to enter a mold cavity, a source of air under pressure, a conduit arranged to pass air from said source to said confining means, an inlet valve for admitting air into said conduit from said source under a predetermined relatively low pressure, an outlet valve for discharging air from said conduit into said material confining means, and a valve separate from said inlet valve and said outlet valve and adapted to admit air from said source to said conduit under higher pressure than that of the air admitted through said inlet valve.

11. Casting apparatus which comprises means i or confining a material to be cast in position to enter a mold cavity, a source of air under pressure, a conduit arranged to pass air from said source to said material confining means, a reducing valve between the source and the conduit adapted to admit a predetermined pressure to said conduit, a separate valve adapted to admit a different pressure to said conduit, another valve adapted to release air from said conduit to said confining means, and means for actuating said last mentioned valves in sequence at a predetermined time interval.

12. Casting apparatus which comprises means for confining a material to be cast in position to enter a mold cavity, a source of air under pressure, an expansion chamber, a reducing valve operatively positioned between said source and said chamber and adapted to admit thereto air under a predetermined relatively low pressure, an outlet valve operatively positioned to discharge air from said chamber to said material confining means, a valve separate from said reducing valve and said outlet valve and adapted to admit air from said source to said chamber under a pressure greater than that of the air admitted thereto through the reducing valve, an operating handle for opening said outlet valve and said separate valve when moved in one direction, and means for automatically closing said valves when said handle is moved in the opposite direction.

13. Casting apparatus which comprises means for confining a material to be cast in position to enter a mold cavity, a source of air under pressure, a conduit arranged topass air from said source to said confining means and provided with a valve adapted to pass air at low pressure from the source to said confining means, a separate conduit operatively arranged to pass air from said source to said first mentioned conduit and provided with means adapted to pass air at gradually increasing pressure from the source to said confining means including a valve, an actuating member operatively arranged in relation to said valves and, when moved in one direction adapted to actuate said valves to initially admit low pressure and thereafter increasing pressure to said conduits through said valves, and means for automatically releasing excess pressure from said conduits to atmosphere upon return movement of said actuating member.

14. Casting apparatus which comprises means for confining a material to be cast in position to enter a mold cavity, a source of air under pressure, a conduit arranged to pass air from said source to said confining means, a valve operative independently of pressure in the source and positioned and adapted to be actuated to control the passage of air from said source to the confining means, and pressure varying means operatively interposed between the confining means and the valve whereby, when said valve is opened, the air pressure from said source effects gradually increasing pressure in the confining means.

15. Casting apparatus which comprises means for confining a material to be cast in position to enter a mold cavity, a source of air under pressure, a conduit arranged to pass air from said source to said confining means, a valve operatively positioned in relation to said conduit and adapted to control passage of air from the source to the confining means, pressure varying means operatively interposed between the confining means and the valve whereby, when said valve is opened, the air pressure from said source effects gradually increasing pressure in the confining means, and means cooperating with said last mentioned means and adapted to vary the rate at which said increase in pressure is effected in the confining means.

16. Casting apparatus which comprises means for confining a material to be cast in position to enter a mold cavity, a source of air under pres sure, a conduit arranged to pass air from said source to said confining means, a valve operatively positioned in relation to said conduit and adapted to control passage or" air from the conduit to the confining means, and an expansion chamber arranged between the confining means and the valve, whereby, when said valve is opened, the air passing into and through said chamber from said source through said valve effects a gradually increasing pressure in the confining means.

17. Casting apparatus which comprises means for confining a material to be cast in position to enter a mold cavity, a source of air under pressure, a conduit arranged to pass air from said source to said confining means, a valve operatively positioned in relation to said conduit and adapted to control passage of air from the conduit to the confining means, an expansion chamber arranged between the confining means and the valve whereby, when said valve is opened, air passing into and through said chamher from said source through said valve effects a gradually increasing pressure in the confining means, and means for varying the effective size of said chamber to control the rate of air pressure variation therein when said valve is opened.

RAYMOND E; MYERS.

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