US2405254A - Mold core - Google Patents

Description

Aug. 6, 1946.

R. K. HOPKINS MOLD CORE Filed Marqh '2, 1943 INVENTOR Wk. BY

- ATTORNEY Patented Aug. 6, 1946 MOLD CORE Robert KHopkins, New York, N. Y., assignor to The M. W.

Kellogg Company,

New York, N. Y

a corporation of Delaware Application March 2, 1943, Serial No. 477,738 4 Claims. (01. 22 17c) The present invention relates to molds, and more particularly to cores for shaping the interior of hollow castings.

In castin hollow objects the use of a metal core is often desirable, particularly because of its durability. However, shrinkage of the cast metal makes removal of the core diiiicult, and will usually produce suflicient strain in said core to permanently deform it and render it unserviceable for further use.

One object of the present invention is to provide a new and improved metal core which can be easily removed from a casting, and which will not be permanently upset or deformed by the shrinkage pressure of the casting thereon.

As a feature of the present invention, the core is of sectional construction and is collapsible into a smaller cross-section upon application of shrinkage pressure thereon.

As a further feature, the sections of the core are automatically restored to expanded condition when the shrinkage pressure is removed.

As another feature, the different sections of the core are hollowed to permit circulation of a cooling liquid therethrough.

Various other objects, features and advantages of the invention will be apparent from the following particular description, and from an inspection of the accompanyin drawing, in which Fig. 1 is a vertical section, somewhat diagrammatic, through a casting apparatus containing a core which embodies one form of the present inventicn;

Fig. 2 is a transverse section of the core taken on line 2-2 of Fig. 1; and

Fig. 3 is a transverse section of another form of core embodying the present invention.

Referring to Figs. 1 and 2 of the drawing, the core Iii comprises a series of similar segments H, three being shown, separated by wedges 12. These core sections I l and 42 are desirably made of metal having high heat conductivity such as copper. Each of the core segments H ha an outer circular conformation i3 and an inner chordal surface it intersecting said circular conformation and slidably seating the wedges l2. The wedges [2 are approximately trapezoidal in cross-sectional outline with respective outer cir cular conformation l5 forming continuations of the segment conformations l3 in expanded condition of the core shown in Fig. 2. Each wedge l2 has a base it extending between the two chordal surfaces M of respective flanking segments l l, and opposed inclined plane surfaces l7 slidably engaging said chordal surfaces respec- 2 tively. The angle betwe n these inclined wedge surfaces l1 and the coeficient of friction between the contacting surfaces of the wedges I2 and the segments H are such that upon application of radially inward pressure on the segments H resulting from shrink pressure the wedges l2 slip radially inwardly along the inner surfaces [4 of said segments. This radially inward sliding of the wedges l2 causes collapsible approachment of the segments H, and resultant reduction in the diameter of the core I 0.

The core sections I I and I2 are normally maintained in expanded position shown in Fig. 2 by resilient means comprising radially extending coil springs 29, retained at their inner ends in respective recesses 2| of a block 22 which is set in the interior of the core l0, and which may be of metal as shown or of suitable refractory material. The outer ends of these coil springs 20 bear against the bases it of the wedges [2 to urge these wedges radially outwardly. Three of these springs 28 are arranged in the upper part of the core Hi and three in the lower part.

The internal hollow defined conjointly by the core sections H and I2, has an equilateral hexagonal cross-section, and the block 22 has a smaller equilateral hexagonal cross-section separated from the walls of said hollow by an intervening border gap 23 affording the necessary space for the collapse or contraction of the core It.

To hold the core sections H and 12 in assembled position shown in Fig. 2, there is provided at one end of the core li! a core retaining head plate 25 shown in Fig. 1 having a circular or hexagonal face groove 26. the core sections l l and I2 have flanges 21 extending in the plate groove 26 and abutting the outer peripheral wall of said groove in limiting expanded position of these core sections. The groove 26 is wide enough to permit radially inward collapse of the core Ill.

At its lower end, the core It seats on a retaining base member 28 shown in the form of a mold stool having a circular recess 30 for receiving the lower end of saidcore. The outer peripheral wall of the recess 39 by its engagement with the outer peripheries of the core sections II and I2, limits radially outward movement of these sec: tions to the position shown in Fig. 2, while permitting limited radially inward collapsing movement of said sections under shrink pressure.

The metal core sections ill and l I are respece tively'hollowed and provided with .end walls to The upper ends of stool 28 which also serves to seat the sectional core 18 centrally in the interior of the mold. The a core l defines with the outer mold 35 an annular mold chamber 38 of circular or any desired cross-sectional configuration. e

The deposition of molten metal in the mold chamber 38 may be effected by any suitable manner, thus molten metal may be poured in the conventional way from a ladle or other molten metal source or the metal may be produced directly in mold chamber 38. For instance, a series of circumferentially spaced consumable electrodes 45 may extend into the mold chamber 38 and be submerged in a blanket of floating flux 48 with the lower ends of said electrodes spaced from the deposited molten metal 4'1 by a gap. Current is discharged through the electrodes 45 and the metal 41 and across the intervening gap to progressively fuse the lower nds of said electrodes and produce the metal 41. Other ingredients to impart to the metal 41 the desiredanalysis may be delivered to the fusing zone of the mold chamber 38. The electrodes 45 are fed and the current supply adjusted so as to maintain a current discharg across the gap of substantially constant characteristics.

,During the fusing operations described, the mold is rotated slowly to distribute evenly the metal 41 deposited in the mold chamber 38 and to assure that the whole surface of the deposited metal is kept molten. This rotation of the mold may be effected in any suitable manner. For example, in the specific form shown, there is provided a turntable 58 seating the mold stool 28 and carrying on its lower face a crown gear Meshing with this crown gear 5! is a bevel gear 52 driven from any suitable source of power. This turntable 50 is supported by means of thrust bearings 53 on a bearing post 55 extending upw wardly from a fixed base 56. A shaft 51 depending from and rigid with the turntable 59 is journalled in the post 55.

The core block 22 may extend downwardly through an opening in the mold stool 28 and seat on the turntable 58 for rotation therewith.

The body of metal 41 is grounded or otherwise connected to the current discharge circuit of the electrodes 45. This electrical connection may be effected, for example, by means of a conductor ring or flange 68 rigid with and depending from the turntable 50 and partially submerged in an annular mercury well 6|. This mercury well 61 is fixed to the post 55 and connected to a lead 62 in the circuit of the electrodes 45. The stool 28 and turntable 50 being of metal or other suitable electrical conductive material, the body of molten metal 41 will be connected to the current discharge circuit of the electrodes 45.

The means for circulating a suitable cooling medium, as for example water, through various parts of the mold apparatus including the mold core ID, desirably comprises an inlet pipe 65 leading into the base 56 and connected to 'an annular recess 66 in a fixed distributing head 61. An outlet pipe 68 is connected to an annular recess I8 in the distributing head 61, and extends outwardly through the base 56. The shaft 51 has a central inlet duct 12 offset at its lower end for communication with the recess 66 and an outlet duct 13 offset at its lower end for communication with the recess '18. At its upper end, the inlet duct 12 extends through the turntable 58 and connects to the lower end of a pipe 15 passing through the core block 22 and the upper core retaining head plate 25. The upper end of this pipe 15 is connected to a header 16 above the core [0. The cooling liquid is distributed from this header I6 to the core sections H and I2 by respective pipes 11. Since the core sections H and I2 are moved radially inwardly by the shrink pressure of the cooling cast metal in the mold chamber 38, the pipes 11 and 18 are desirably made of suitable yieldable material to permit this collapsing movement of the core sections.

The turntable 56 has an annular chamber 82 communicating by ducts with the pipes 18 and also with theupper end of the outlet shaft duct 13.

The distributing system described can also be employed to circulate cooling liquid through the stool 28 and the. outer mold 35. For that purpose, the turntable 58 has a radial duct 85 connected at its inner end to the turntable duct 12 and at its outer end to one end of a pipe 86. The other end of this pipe 86 leads into the upper inlet end of the mold 35. The lower discharge end of the mold 35 is connected to one end of a pipe 81, the other end of which joins into the outer end of a radial duct 88 in the turntable 50. The inner end of this radial duct 88 connects with the annular chamber 82 in the turntable 56.

Although one inlet pipe 86 and one discharge pipe 81. are shown for the mold 35, it must be understood that any number of these pipes may be employed suitably distributed and arranged to obtain the most effective cooling of said mold.

To circulate cooling liquid through the turntable 58, said turntable has a hollow 90 with one or more inlet connections 9i leading from the duct 85, and one or more outlet connections 92 joined to pipe or pipes 81.

In the operation ofthe mold apparatus described, as the deposited metal 4'! solidifies and cools, the resultant shrinkage of said metal causes compression of the core segments I l in a radially inward direction. This shrinkage pressure causes the core wedges 12 to slide radially inwardly against the resisting action of the springs 28, so that the core segments H are moved radially inwardly and closer together. This collapse of the core In permits it to be easily removed from the cooled cast metal and to be reused for subsequent casting operations. When the core i8 is removed from the casting, the various sections thereof will be restored to expanded condition under the biasing action of the springs 28.

Although the core 10 of Fig. 2 has been shown in Fig. 1 as applied to a specific mold apparatus, it must be understood that as far as certain aspects of the invention are concerned, this core l8 maybe employed in connection with any other suitable mold apparatus.

In Fig. 3 is shown another form of collapsible mold core embodying the present invention. In this form, four main core sections Ha are quadrantly arranged and separated by wedge sections 12a. Each of these main core sections Ha has an outer circular conformation 13a and a pair of inner converging plane surfaces Ma On which slide the wedges l2a. The core sections Ha and I211 are hollowed to permit circulation of cooling liquid therethrough, and are shaped to conjointly define a continuous outer cylindrical surface in expanded position of said sections shown in Fig. 3, and a central hollow of substantially square cross-section. Extending in this core hollow is a block 22a of substantially square cross-section smaller in size than said hollow to define with the inner walls of the core section a marginal gap 23a affording the necessary space for the collapsing movement of the core sections I la and I2a. Springs 20a have one end retained in respective recesses 2| a of the core block 22a and the other end bearing against the bases of the wedges l2a to urge these wedges radially outwardly. These springs 20a are provided at the upper and lower sections of the core block 22a to afford the necessary equilibrium. The recesses Zla are desirably arranged with each pair of opposed recesses in a different plane from the other adjacent pair of opposed recesses, so that the corners of the block 22a where these recesses are disposed are not unduly weakened.

The core of Fig. 3 can be arranged in a mold as indicated in connection with the core [0 of Fig. 1 to shape the hollow of a casting. As the core sections Ila are pressed radially inwardly by the shrink pressure of the cooling casting, the wedges l2a are forced radially inwardly to cause approachment of the main core sections lZa and collapse of the core against the resisting action of the springs 20a.

As many changes can be made in the above apparatus, and many apparently widely difierent embodiments of this invention can be made without departing from the scope of the claims, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. A mold core comprising a plurality of sections having outer circular surfaces of the same radius, wedges spacing said sections and automatically slidable radially inwardly upon the application of shrinkage pressure of the cast material on the outer surfaces of said sections, a block in the interior of said core, and spring means bearing on said block and urging said wedges radially outwardly.

2. A collapsible mold core comprising three similar substantially segmental circumferentially 6 arranged sections having outer circular surfaces and inner plane substantially chordal surfaces, and a wedge between each adjoining pair of segmental sections having inclined plane surfaces seated on the inner chordal surfaces of said pair of adjoining segmental sections and slidable therealong to permit said sections to move radially, the inclination of said wedge surfaces being such as to allow said wedges and said sections to move radially inwardly out of molding position upon application of compressive pressure by shrinking cast metal on said circular surfaces, and means for yieldably resisting radially inward movement of said wedges.

3. A collapsible mold core comprising three similar substantially segmental circumferentially arranged metal sections hollowed to permit circulation of a cooling medium therethrough, and having outer circular surfaces and inner plane substantially chordal surfaces, a metal wedge between each adjoining pair of segmental sections hollowed to permit circulation of a cooling medium therethrough, said wedge having inclined plane surfaces seated on the inner chordal surfaces of said pair of adjoining segmental sections and slidable therealong to permit said sections to move radially, the inclination of said Wedge surfaces being such as to cause said wedges to move radially inwardly upon application of compressive pressure on said circular surfaces, a block in the interior space conjointly defined by said sections and said wedges, and springs between said block and said wedges urging said wedges radially outwardly.

4. A collapsible mold core comprising four similar quadrantly arranged sections having outer circular surfaces respectively, and each having a pair of converging inner plane surfaces extending away from its corresponding curved surface, a wedge between each adjoining pair of sections having inclined plane surfaces seated on the inner plane surfaces of said adjoining sections and slidable therealong to permit said sections to move radially, the inclination of said wedge surfaces being such as to allow said wedges and said sections to move radially inwardly out of molding position upon application of compressive pressure on said curved surfaces by shrinking cast metal, and spring means urging said wedges radially outwardly.

ROBERT K. HOPKINS.

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