US2893080A - Apparatus for the continuous casting of metals - Google Patents

Description

APPARATUS FOR THE commuous CASTING 0F METALS July 7, 1959 Filed March 26, 1954 5 Sheets-Sheet 1 INVENTOR NORMAN P. 6088 BY 2 ATTORNEY APPARATUS FOR THE CQNTINUOUS CASTING OF METALS Filed March 26. 1954 July 7, 1959 5 Sheets-Sheet 3 ON mm R O T N E V m N NORMAN E6033 BY 2 ATTORNEY H v I APPARATUS FOR THE CONTINUOUS CASTING OF METALS yiled ua ns. 1954 Q 5 Sfieets-Sheet 4 VINVENTOR v NORMAN P. 6088 ATTORNEY July 7,1959 I N. P. G055 2,893,080

- APPARATUS FOR THE conwmuofis CASTING OF METALS Filed March 26. 1954 5 Sheets-Sheet 5 NORMAN e soss ATTORNEY.

IN V EN TOR.

United States Patent APPARATUS FOR THE CONTINUOUS CASTING OF METALS Norman P. Goss, Mayfield Heights, Ohio Application March 26, 1954, Serial No. 419,014

8 Claims. (Cl. 22-572) This invention pertains to the art of the continuous casting of metals from molten form to a continuous ingot or bar and, more particularly, to apparatus and method for such continuous casting of metals.

In the art of the continuous casting of metals, apparatus is normally provided comprised of one or more water-cooled members or plates defining a mold cavity open at both the top and bottom. The walls of this cavity are usually water cooled by means of water flowing through passages in the plates spaced from the mold cavity forming surfaces. The cavity is first plugged or closed either midway of its length or at the bottom and molten metal is poured thereinto until the cavity is filled. As the molten metal begins to congeal, it is drawn out of the bottom of the mold cavity in a continuous manner and fresh molten metal is then continuously poured into the pool of molten metal in the top of the cavity at a rate equal to the withdrawal of the congealed metal at the bottom of the mold.

In the time for the molten metal to congeal and pass from the top of the mold cavity to the bottom of the cavity, enormous quantities of heat must be removed.

The removal of this heat and the enormous temperature differentials involved have always created extreme problems in the design and maintenance of this type of apparatus. For example, the molten metal, if it is steel, is generally poured at temperatures in excess of 2,700 degrees Fahrenheit while the water flowing on the opposite side of the chill plate; that is, a distance of 1 or 2 inches away from the molten metal, is at a temperature of around 70 degrees Fahrenheit.

As soon as the molten metal strikes the sides of the mold cavity, the members forming the mold cavity are heated to varying degrees. This heating of the walls of the mold cavity causes mechanical expansion to take place therein in all directions and, usually, these expansions are in a nonuniform manner. By nonuniform is meant that the walls of the cavity become warped, in many instances to an extent such as to impede the free movement of the congealing metal through the cavity. When this happens, the ingot hangs up in the mold. This requires a complete shutdown of the apparatus and disassembly of the mold in order to remove the hung-up ingot, an expensive process. Such a process is indeed not continuous or practicable.

The present invention contemplates continuous-casting apparatus of the general type referred to which overcomes the above referred to difliculties, which is relatively simple in construction and which is sure and positive in operation.

In accordance with the present invention, continuouscasting apparatus is provided comprised of a plurality of chill plates arranged about and defining a vertical mold cavity. Each of these chill plates is so supported as to be freely expansible in all directions parallel to its mold-forming surface but fully restrained from any nonuniform movement in a direction transverse to this surface, i.e., warping.

Further, these chill plates are all so arranged relative to each other that their expansion in a direction parallel to the mold-forming surface will have a minimum or no effect on the over-all cross-sectional dimension of the mold cavity.

Further, the chill plates are so arranged as to be and means are provided for continuously oscillating the plates in the plane of the mold surface so as to reduce the frictional contacts between the mold surfaces and the congealing metal, thus assisting in the free passage of the metal through the mold cavity. Likewise, the plates are so mounted as to be and means are provided for quickly pulling the chill plates back away from the mold cavity in order to release an ingot in the event it should stick or hang up for any reason in its passage therethrough.

Further, in accordance with the invention, means are provided in the form of a layer of refractory materials, fluid at the melting temperature of the metal on top of the molten metal for the purpose of protecting the molten metal from oxidation and in lubricating its passage through the mold cavity. Such refractory material is inert to the molten metal but tends to wet it and cling closely thereto as it is carried downwardly through the mold cavity but further has the characteristic of not adhering to the chilled Walls of the mold cavity. Such refractory material must have a solidification temperature substantially under that of the molten steel. Borax is an example of one material which has been found quite satisfactory for this purpose.

Further, in accordance with the invention, the apparatus which must, of necessity, have a substantial vertical height is formed in a plurality of vertically aligned sections, each having its own individual chill plates with the chill plates of one section being in substantially abutting relationship with the chill plates of an adjacent section, the sections being so arranged as to be movable apart to relieve any stresses in the plates and consequent bowing which might result from vertical expansion from the abutting chill plates.

The principal object of the invention is the provision of new and improved apparatus for the continuous casting of metal.

Another object of the invention is the provision of an arrangement for mounting the chill plates of continuous-casting apparatus whereby the chill plates may expand freely in a direction parallel to the cavity-defining surface but are restrained from movement in a direction transverse to such plane.

Another object of the invention is the provision of a new and improved arrangement for the chill plates defining the oavity of continuous-casting apparatus whereby a minimum of change of the dimensions of the mold cavity will occur due to expansion and minimum warpage of the metal forming the walls of the mold cavity.

Still another object of the invention is the provision of a new and improved method of manipulating the chill plates at continuous-casting apparatus whereby a minimum of friction to the movement of the metal through the apparatus will be presented.

Still another object of the invention is the provision of new and improved apparatus for the continuous casting of metal whereby the chill plates may expand in a vertical direction without the imposition of undue mechanical stresses therein.

Still another object of the invention is the provision of continuous-casting apparatus of the type described Where the side chill plates overlap the ends of the end chill plate and are resiliently held in pressure contact at all times.

Still another object of the invention is the provision of a new and improved arrangement for mounting the cooling units of continuous-casting apparatus wherein each cooling unit is mounted from one or a plurality of points of a frame, all of such points being located along a generally horizontal line.

Still another object of the invention is the provision of a mounting for such cooling units wherein the cooling units may expand freely in a horizontal direction relative to such frame.

Another object of the invention is the provision of a new and improved apparatus of the type referred to wherein the chill plates are mounted for free expansion in all directions parallel to the mold surfaces but are restrained against nonuniform movement in a direction transverse to the mold surfaces.

The invention may be embodied in certain parts and arrangement of parts, a preferred embodiment of which will be described in detail in this specification and illustrated-in the accompanying drawings which are a part hereof, and wherein:

Figure 1 is a side elevational view of continuous-casting apparatus constructed in accordance with the present invention;

Figure 2 is a sectional view of Figure 1 taken approximately on the line 2-2 thereof;

Figure 3 is a sectional view of Figure 2 taken approximately on the line 33 thereof;

Figure 4is a sectional view of Figure 2 taken approximately on the line 4--4 thereof;

Figure 5 is a sectional view of Figure 2 taken approximately on the line 55 thereof; and

Figure 6 is a cross-sectional view of Figure 2 taken approximately on the line 65 thereof. Referring now to the drawings wherein the showings are for the purposes of illustrating one form which the invention may take and not for the purposes of limiting the invention, the apparatus shown has a vertically extending rectangular mold cavity 16, open at both the top and bottom and defined on the longer side by pairs of spaced chill plates 11 and, on the shorter side, by pairs of spaced chill plates 12, with the ends of the side chill plates 11 overlapping but in abutting slidable relationship with the ends of the shorter side chill plates 12. With this arrangement, the chill plates 11 which are longer than the chill plates 12 may expand and contract to any degree in the plane of the cavity-forming surface without in any way affecting the over-all dimensions of the mold cavity. On the other hand, the end chill plates 12, which are the shorter, while afiecting the horizontal dimensions of the mold cavity as they expand and contract, willhave a relatively little effect on the over-all dimens'ions of the mold cavity because of their shorter length. Obviously, other arrangements of the chill plates might be employed to hold down the effect on the horizontal dimensions of the mold cavity as the plates expand and contract due to temperature changes by, for example, having the ends of the chill plates alternately overlap and abut against the adjacent chill plate as viewed in a peripheral direction of the mold cavity. The arrangement shown, however, is preferred.

These chill plates 11, 12 are relatively short in vertical height and a plurality of such chill plates in generally vertically aligned relationship are employed to define the entire length of the mold cavity a in the preferred embodiment, the chill plates are preferably fiat slabs of a highly heat-conductive material such as copper or aluminum which, while having the desired high heat conductivity, does not have high structural strength or a great ability to resist warping and the like under the. effects of temperature differentials.

Each chill plate 11 is mounted on a backup plate 14 abutting against the side of the chill plate opposite from the mold cavity forming surface-and fastened thereto by a plurality of bolts 15, 16 and 17 extending through openings' around the perimeter of the backup plate 14 and thricadedly engaged in the chill plate 11. As can be seen clearly from Figure 3, the diameter of the openings in the backup plate 14 through which the shank of the bolts 15, 16 passes in substantially greater than the diameter of this shank so that the chill plate 11 may expand in a direction parallel to the cavity-forming surface thereof without interference from these bolts 15 and 16.

There is one bolt; namely, the bolt 17, which passes through an opening in the backup plate 14 having a diameter substantially equal to the diameter of the shank of the bolt 17. By this construction, the chill plate 11 is fixed in a direction parallel to the cavity-forming surface relative to the backup plate 14 at one point. Generally, this point will be located, and in the preferred embodiment is located, along the upper edge of the chill plate 11. It could be located elsewhere, however. Also, the bolts 16, for reasons which will appear hereinafter, are located only along the upper edge of the chill plate 11 and backup plate 14. Obviously, if desired, the shank of the bolt 17 could also pass through an opening greater than its diameter, allowing the same freedom of movement as exists with the bolts 15 and 16.

The end chill plates 12 are similarly constructed to the side chill plates 11 and similarly mounted. Thus, in the embodiment of the invention shown, the side of the end chill plate 112 remote from the cavity-forming surface thereof abuts against a backup plate 20 and is fastened thereto by means of bolts 21 and 22 extending through openings on the backup plate 211 into the chill plate 12 around the entire perimeter or periphery thereof. In a like manner to that described with reference to the chill plate 11, the bolts 22 pass through openings in the backup plate 20 of a diameter greater than the diameter of the shank of the bolt 22, thus allowing the same freedom of expansion of the chill plate 12 relative to the backup plate 21) in a plane parallel to its cavity-forming surface. In a like manner, the bolt 21 passes through an opening in the backup plate 26 of a diameter generally equal to its own diameter, thus fixing the chill plate 12 relative to its backup plate 20 at one point, there being only one bolt 21 per packup plate 20 and chill plate 12 assembly.

Each backup plate 14 has a recess 24 in its chill-plate facing surface, in which recess 24 is a grid member comprised generally of a plate 25 having a width generally equal to the width of the recess 24 and a vertical height generally less than the vertical height of the recess 24 and with its upper and lower edges spaced from the upper and lower sides of the recess 24. Rib members 26 extend vertically on opposite sides of the plate 25 and beyond the upper and lower edges thereof. These rib members on opposite sides of the plate are generally aligned with each other and the total thickness thereof when considered with the thickness of the plate 25 are such as to completely fill the space between the base of the recess 24- and the back side of the chill plate 11. Such rib members thus serve to provide a solid support from the back side of the chill plate 11 to the backup plate 14.

In practice it has been generally, though not always, found that the chill plates tend to buckle or dish with the concave side thereof facing the mold cavity 10 and with the construction above described; namely, the use of the bolts 15, 16 and 17, fastening the edges or perimeter of the chill plate 11 to the backup plate 14 and the grid disposed in the recess 24, a rigid construction is provided which will prevent this dishing or buckling of the chill plate 11. In this respect, it should be pointed out that the backup plate 14 is preferably madeof a rigid material such as steel having dimensions such that the strength of the backup plate 14 is greater than the yield strength of the material of the chill plate 11. Thus, as the chill plate 11 tends to buckle or dish, it will be restrained from such dishing but will have strains set up therein which ultimately can exceed the yield strength of the material such that no buckling of the chill plates 11 will result.

In a like manner, the backup plate 20 has a recess 28 maintain this spacing of the ends of the plate 29 relative.

to. the ends of the recess 28.

A baflle 32 extends horizontally across the side of the plate 25 on the side remote from the chill plate 11 dividing the recess 24 on this side of the plate into an upper and lower portion. The backup plate 14 is provided with a plurality of openings 34 above the member 32 and a plurality of openings 35 below the member 32 through which cooling water may be circulated respectively into and out of the recess 24. Manifolds 36, 37 are shown communicating with the openings 34, 35 respectively. These manifolds form no part of the present invention and will not be described further. Cooling water fiows inwardly through the manifold 36, the openings 34, thence upwardly around the upper edge of the dividing plate 25, thence downwardly along and in heat-conducting engagement with the side of the chill plate 11 remote from the cavity-forming surface to the lower end of the recess 24, whence it turns upwardly and out through the opening 35 in the manifold 37.

A similar construction exists for the chill plate 12 and backup plate 20 and this construction will not be further described herein.

It will thus appear that the chill plates 11 and 12 are so mounted relative to their backup plates 14 and 20 respectively that they are free to expand in a direction parallel to their respective mold cavity forming surfaces without any physical restraint on such expansion but they are completely restrained from any nonuniform movement in a direction transverse to their mold cavity forming surfaces, i.e., warpage.

It will appreciated that the chill plate is only restrained from such nonuniform movement in a direction such that the cavity-forming surface thereof will become dished or concave. It has been found that in almost all cases, this is the only direction that the chill plates attempts to warp. In the event a chill plate should be found which will warp in the opposite direction, then, obviously, restraining means may extend across the recess 28 generally at the center thereof which are fastened to both the chill plate 11 and the backup plate 14. These restraining means will, thus, be in tension but will restrain the chill plate from a warpage which would make its mold cavity-forming surface convex. Such a convex shape would be equally undesirable to a concave shape.

- In appai'atus of the type to which this invention pertains, the rate of removal of heat from the hot metal is very rapid and the outer surface in contact with the chill plate immediately congeals. As the molten metal cong'eals, it will be appreciated that it will contract and then, as it continues to cool, it continues to contract further. Depending upon the rate of solidification, the contraction coeflicient of the metal or alloy being cast and the casting temperature and the rate of movement of the molten metal through the cavity, the rate of contraction per foot of movement of the metal will also vary. It has been found that if the amount of warpage per foot of vertical length of the chill plate is held below the amount of contraction per foot of movement of the hot metal, it is possible to obtain a free movement of the metal through the mold cavity without the danger of it hanging up.

, It will be appreciated that it is extremely difficult to remove or prevent any warpage of the chill plate surfaces,

so that the present invention contemplates holding this "distortion or warpage to an amount per foot less than'the per-foot contraction of the hot metal as it moves through the mold cavity. For normal continuous-casting apparatus, this contraction of the moten metal per foot of movement has been determined to be approximately .015 inch. Thus, the present invention contemplates holding the warpage to amounts less than this and, preferably, to amounts less than .010 inch. Using the construction of the present invention has permitted the warpages to be held to an amount less than .008 inch per foot of length The chill plate 11 and its backup plate 14 forms a unit which will hereinafter be referred to as cooling unit C. In a like manner, the chill plates 12 and its corresponding backup plate 20 form a unit which will hereinafter be referred to as cooling unit D.

The apparatus shown is generally comprised of three sets of cooling units C and D in vertically aligned relationship and each set of cooling units C and D are mounted on a frame B. Such frame, in the embodiment of the invention shown, is comprised of four vertically extending posts or pillars 40, each arranged in the corner formed by the ends of the cooling units C and D. These posts 40 are structurally joined by upper horizontal side frame members 42 and horizontally extending end frame members 43. The lower ends of these posts 40 are joined by horizontally extending side frame members 44 and horizontally extending end frame members 45. The members in all cases are joined or fastened to the respective posts 40 by means of bolts 46.

The cooling units C are supported or, in effect, hang from the upper side frame member 42 in a manner such that the cooling unit can freely expand or contract due to thermal temperature changes, can move in and out to ward the center of the mold cavity 10 as the end chill plates 12 expand and contract due to thermal temperature changes and so that they can be quickly pulled back from the mold cavity 10 in order to free an ingot as it starts to hang up. Thus, in the preferred embodiment of the invention, the bolts 16 and 17 have elongated heads 48 and 49 which extend horizontally outwardly from the back side of the backup plates 14 through horizontally elongated openings 50 in the side frame members 42. It will be noted that the bolts 16 and the bolts 17 are in horizontal alignment which permits the freedom of horizontal expansion of the cooling units C and also permits a horizontal oscillation of the cooling units C if desired. Such oscillation may be effected by means of a power mechanism consisting of a motor 51, an eccentric 52 and a connecting rod 53 from the eccentric 52 to the cooling unit C. The amount of oscillation of the cooling unit C may be readily adjusted by varying the degree of eccentricity of the eccentric 52. This freedom of movement is permitted by virtue of the heads 48 and 49 extending through the horizontally elongated opening 50.

The oscillation of the two cooling units C may either be in phase or out of phase. Also, the side plates are in good sliding contact with end plates while they are in oscillation. No air gap forms at the joints as is required in some molds of the prior art.

It is to be noted that the bolts 16 and 17 are only located in or along one line of the cooling unit C whereby the cooling unit C is free to expand in a vertical direction without any restraint from the supporting frame B.

The end cooling units D are generally supported at one point only by means of an extension 54 of the bolt 21 extending through the end upper frame member 43.

It will be noted that the ends of the cooling units D are slightly spaced from the sides of the post 40 whereby these cooling units may readily expand in a horizontal direction from the axis of the bolt 21 without interference of the supporting frame. In a like manner, the ends of the cooling units C are also spaced from the sides of the posts 40, permitting both the oscillation above referred to as well as free and unrestrained horizontal expansion. I

-The edges of the'cavity-forming surface of the chill plates -11 abut against the ends of the chill plate 12 in sealing engagement therewith and are resiliently held in such engagement whereby these chill plates may freely expand. It will thus beseen that the outer edge of the cooling units C are'spaced from the inner surface of the horizontal frame members 42. However, resilient members are provided for urging the cooling unit C toward the mold cavity 10. Such resilient means may take any desired form but in the embodiment of the invention shown, comprise a helical coil spring 56 mounted in a horizontal opening in the side frame members 42 and 44. Such spring bears against a follower 57 having a spherical ballbearing 58 positioned between itself and the outer surface of the backup plate 14. A bolt 60 threadably supported in'a boss 61 fastened to the outer side of the side frame member 42 bears against the other end of the spring 56 and provides means for adjusting the compression on the spring-56 and thus the amount of horizontal pressure to be exerted on the cooling unit C.

It will be noted that such resilient means are provided both along the upper and lower edges of the cooling units C. Nosimilar spring means are provided for the end cooling unit D.

As'can be clearly seen from Figure'4, the lower end of one chill plate 11 or 1-2-substantially abuts against the upper end of the adjacent chill plate 11 or 12. Normally, when the apparatus is first assembled, there is a slight clearance provided between these chill plates. However, as the chill plates expands it is important that no substantial restraining forces be exerted to prevent themfrom this expansion. In-some cases, the chill plates expand more than intended; that is, more than enough to just bring the ends into light pressure engagement. In accordance with the invention, means are provided whereby no pressure greater than a light one can exist between these ends. Thus, in the preferred embodiment of the invention, the posts 40 abut at their corresponding upper and lower ends and a dowel pin 65 slidable in aligned openings provided on these ends retains the posts 40 in accurately alignedrelationship but permits the posts 40 to move vertically apart whenever the cooling units expand beyond a predetermined amount. Thus, in no instance will a pressure greater than a predetermined pressure exist between the abutting ends of the chill plates. If desired, mechanical means can be provided for physically retaining the posts 40 in any position to whichthe expansion may cause them to move such as shims or the like and, if desired, or if necessary, counterbalancing means may be-provided to assist the sections in moving a-pait'whene'ver the expansions of the chill plates 11,12 into-abutting engagement so require.

As above pointed out, the cooling units C are movable toward and away from the mold cavity by virtue of the mounting on the side'frame members 42. If desired, mechanical means such as hydraulic cylinders or electrically operatedapparatus or manually operated apparatus may be provided for pulling the cooling unit C back away from the mold cavity against the pressure of the springs 56 in order to quickly release an ingot in case it should tend tohang 'up in the mold cavity 10.

Further, in accordance with the invention, means are provided for assisting in the lubrication of the congealing metalas it passes through the mold cavity. Thus, in accordance Withthe preferred embodiment and ascan be seen in Figure 4, a layer of molten'refractory material 66 is maintained on'top of the molten metal 67 in the mold cavity 10 and the molten metal being poured into the cavity 10 shown schematically at 67 falls through this refractory layer into the molten metal 67 therebelow. As the metal congeals, the refractory material carries down alongsides of the congealing metaland remains molten even-after the metal itself has begun to congeal. molten material conveys or conducts heat from the molten metal to the chill plates 11, 12 while serving the lubricating function. The molten refractory material employed should preferably have the characteristics of having a congealing temperature far below that of the molten metal, an ability to thoroughly Wet the surface of the molten metal and an ability not to wet the cooler surfaces of the chill plates 11, 12. When the congealed ingot leaves the bottom of the mold'cavity 10, this material breaks away from the ingot. In accordance with the preferred embodiment of the invention, the material employed is borax, although other silicates may be employed.

A specific embodiment of the invention above described illustrates only one form which the invention may take. Obviously, physical embodiments differing radically from the one described herein for the purposes of illustrating the invention will occur to others upon a reading and understanding of this specification and it is my intention to include all such modifications and alterations insofar as they come within the scope of the appended claims.

Having thus described my invention, I claim:

1. Continuous-casting apparatus comprising, in combination, a plurality of sections in end-to-end abutting relationship, each section including a plurality of mold-cavity defining members, with the members of one section normally in slightly spaced relationship to members of the adjacent section, said sections being movable apart to compensate for undue expansion of said members.

2. Continuous-casting apparatus comprising a plurality of sections in end-to-end abutting relationship, each section including a frame and a plurality of mold-cavity defining members supported on said frame with the members of one section normally in slightly spaced relationship to the members of the adjacent sections, said frames resting one upon the other with portions thereof in abutting relationship and movable apart and means for guiding said frames and retaining same in aligned relationship when they do move apart.

3. Continuous-casting apparatus comprising a plurality of sections disposed one above the other, said sections being movable apart in a vertical direction one from the other and means for maintaining said sections in aligned relationship when moved apart, each section including a pair of oppositely facing spaced end cooling units and a pair of oppositely facing spaced side cooling units defining a mold cavity open at both the upper and lower end and aligned with the cavity of adjacent cooling units and each unit including a chill plate and a backup plate with each chill plate having a mold cavity defining surface, said side cooling units overlapping the ends of said end cooling units whereby said side cooling units may expand freely in the plane of the mold cavity forming surface, each chill plate being fixed to its backup plate in the plane of its cavity-defining surface at one point only and free to move in said direction elsewhere whereby each chill plate may expand and contract in the plane of the mold cavity surface independently of its backup plate, each backup plate abutting against the side of its respective chill plate opposite from the mold cavity forming surface and having a water-receiving recess in the abutting surface, means in said recess for transmitting forces from said backup plate to said chill plate toprevent the warpage thereof, said cooling units being supported from said sections along a single horizontal line only whereby said cooling units may freely expand in a vertical direction, adjacent cooling units of each section having closed spaced surfaces which may abut as a result of undue thermal expansion, vertical movement of said sections acting, to relieve the forces between the cooling units resulting from such thermal expansion.

4. Continuous-casting apparatus comprising, in combination, a plurality of sections in vertically aligned relationship, means permitting movement of said sections apart while retaining them in said aligned relationship,

each section including two pairs of oppositely facing spaced cooling units, each having a mold cavity defining surface, means for supporting the mold cavity forming surface so as to have a physical distortion of less than the rate of contraction of the metal moving through the mold and means permitting relatively free expansion and contraction of said surfaces in a direction parallel to said surfaces.

5. The combination of claim 2 including counterbalancing means for the lower sections whereby said sections may move apart with a minimum of forces exerted between said members.

6. The combination of claim 2 wherein means are provided for fixing said sections in any relative spacing to which they may move when said members expand and retaining such spacing after said members contract.

7. Continuous casting apparatus comprising in combination a frame, two pairs of mold cavity defining members on said frame, defining a mold cavity having a vertical axis continuously open at the upper and the lower end, at least one of said pairs being mounted for limited movement toward and away from the mold cavity, and power means for pulling said pairs back from said cavity, and means limiting the distance of said pull back, whereby an ingot tends to hang up in said cavity, at least a pair of mold cavity defining members may be instantaneously pulled back from the cavity to assist in releasing the hang up.

8. The combination of claim 7 wherein at least one of said pairs is also mounted on said frame for oscillating horizontal movement in the plane of its mold cavity defining surface, and the combination further includes power means for oscillating said pair.

References Cited in the file of this patent UNITED STATES PATENTS 1,539,110 Carlson May 26, 1925 2,135,183 Junghans Nov. 1, 1938 2,284,704 Welblund et al. June 2, 1942 2,369,233 Hopkins Feb. 13, 1945 2,428,657 Falk et al. Oct. 7, 1947 2,428,658 Falk et al. Oct. 7, 1947 2,428,659 Falk et al. Oct. 7, 1947 2,501,536 Orr Mar. 21, 1950 2,510,100 Goss June 6, 1950 2,527,545 Goss Oct. 31, 1950 2,561,360 Goss July 24, 1951 2,600,772 Horn June 17, 1952 FOREIGN PATENTS 742,180 Germany Nov. 24, 1943 686,413 Great Britain Jan. 21, 19 53

Images