US2810169A - Slag-free casting method and a device for the application of this method - Google Patents

Description

0. HOFER Oct. 22, 1957 SLAG-FREE CASTING METHOD AND A DE FOR THE APPLICATION OF THIS METH Filed April 16, 1956 lNVE/VTOR Ozfao Hofer Br ATTYJ.

STAG-FREE CASTING METHOD AND A DEVICE FOR THE APPLICATION OF THIS METHOD This invention relates to certain new and useful improvements in a slag-free casting method and a device for the application of this method and is a continuationin-part of my application Serial No. 290,519, filed May 28, 1952, now abandoned, and embodies improvements in the art thereover.

According to the usual method of casting, the mate rial is poured into a shallow basin. During the casting process the plug, consisting partly of loam and of the casting material, was pulled out of the bath, and the casting material, flowing down into the mould, created eddies which dragged slag along with them, the slag remaining in the cast mass and causing the castings to become defective.

The object of the present invention is a method of casting without slag, and a device for the application of this method. According to the method of this invention, the molten material is dammed back in the bottom of the basin, in front of the passage to the mould, and the plug is lifted only slightly while the material is flowing down. The distance that the plug is lifted is no greater than the height of the darn, so that eddies, which will drag the slag along with them, are avoided in the passage.

The device which is suitable for the application of this method has as its characteristic feature a dam directed upwards, which is provided in the basin at the side of the gate leading to the mould. The gate to the mould is closed by a plug which is suspended from a lever frame and can be lifted a short distance for the purpose of opening the gate.

It is a further object of this invention to provide a method and apparatus of slag-free casting wherein the formation of whirls and eddies around the mould gate will be prevented, but wherein the speed of the casting operation will not be substantially reduced resulting in slag entrapment and casting defects which occur when the flow from the receiving basin to the mould is at a relatively slow rate.

The appended drawing shows the preferred construction of the device for the slag-free method of casting, and

Fig. 1 is a fragmentary, cross-sectional view of the mould apparatus taken on the line II of Fig. 2,

Fig. 2 is a top plan view of the device of the present invention,

Fig. 3 is a fragmentary, vertical cross-sectional view taken on the line IIIIII .of Fig. 2, and

Fig. 4 is a fragmentary, enlarged cross-sectional view taken on the line IVIV of Fig. 2.

In the prior known art, a shallow basin was used for casting. During the casting process, the plug which normally closed the gate into the mould box was completely drawn from the bath, i. e. from the molten material. When the fluid material flowed down into the mould box, eddies were formed which dragged particles of slag along, owing to the suction effect and the turbulence which caused currents and movement in the upper slag layer. The slag particles dragged into the mould renited States Patent 2,810,169 Patented Oct. 22, 1957 mained in the casting and caused it to become defective.

In accordance with the invention, the basin 1 now has a darn 2 as shown in Figures 1 and 2. A plug 3 is provided which includes a tapered shank 12, a rounded head 13 which defines a shoulder 14, and a ring 4 which is positioned at the upper extremity of the tapered shank. The plug 3 is loosely supported by a hook 5' which is formed at the outer end of a plug-lifting lever arm 5, the hook 5 extending through the ring 4. The lever arm 5 is supported on an upstanding bracket arm 20 which is fixed to the mould box casing 9 by any suitable means. The said arm 5 is connected to said bracket by a pin 18 which provides a horizontally disposed pivot for the arm 5. The bracket arm 20 is further provided with an upwardly projecting stop member 19 which is outwardly of and slightly below the pivot pin. The stop member 19 serves to limit the downward movement of the outer end of the lever arm for a purpose which is to be later described.

The dam 2 is preferably provided with an inclined inner side wall 2', as shown in Figure 1, which aids in deflecting and guiding the flow of molten material. In its preferred form the dam is S-shaped in plan view and is provided with tapered ends 2", as clearly shown in Figure 2. The ends 2" terminate short of the side walls of the basin and define passages or channels 21 which permit the final portion of the melt to flow around the dam and outwardly through the gate 8. This insures complete drainage of all the melt from the basin.

The distance c, shown by the arrow in Figure 1, represents the height of the dam taken from the bottom 1 of the basin 1. The distance a also shown by an arrow in Figure 1 represents the depth of the basin, and in accordance with the invention it has been found that the height 0 of the dam should range from approximately one-quarter to one-third the depth a of the basin. These distances have been found to be critical to the invention, since if the top of the dam 2 approaches too closely to the top of the basin 1 the flow of the melt will be too slow for a proper casting. If the top of the darn 2 is too close to the top of the melt and therefore the slag layer, then the flow over the dam will cause entrapment of the slag. If the dam is too low relative to the depth of the basin, then little or no effect will be had on the formation of swirls and eddies.

The mold box body 10 is provided with the usual gate 8 which leads into the mould cavity which is located in the well known manner below the basin 1. It will be noted that the upper portion of the gate 8 has an enlarged bore 8 which defines a seat 7 for the stopper head 13. The said bore 8' is larger than the head 13 of the plug 3 so that an annular space a' will exist around the head 13 when the plug is properly positioned within the bore, and this annular space is made large enough to insure a proper flow of the molten metal around the head into the gate aperture. The gate 8 has a diameter e which is smaller than the head 13 so that the head will properly stop the gate flow when theplug is down. In the preferred form of the invention, the depth b of the bore 8 is slightly greater than the height of the dam 2, as shown in Figure 1.

In the use of the device, the plug 3 is permitted to fall due to its substantial weight, and rest on the seat 7 to close the gate 8. A mass of molten metal is then poured into the basin 1 and the basin is filled to apsaid plug will be lifted. Some variation is permitted in the proportioning of the stop member 19, but it is important and critical that the shoulder 14 of the head 13 not be lifted above the level of n e dam 2.

When the plug is lifted the molten mass flows quickly over the dam 2 and through the bore 8' and the gate 8. The flow path of the mass will be along the basin, then upwardly around the dam and downwardly again around the stopper head 13 and through the gate 8. Repeated tests have shown that the arrangement of the invention prevents the formation of eddies and whirls and the entrapment of slag in the casting, and the casing will be completely free of slag. It has been found that the dam should preferably be S-shaped with tapered ends as shown in the drawings,;and this shape has maximum efficiency in stopping the whirls and eddies. It should be understood, however, that a straight dam will perform the basic function of the invention. It should be pointed out that if the plug is lifted above the dam, whirls and eddies will form and it is the dam in conjunction with the positioning of the plug which provides the novel characteristics of the invention.

While the invention has been described in detail with respect to a preferred example and embodiment of the invention, it will be understood by those skilled in the art after understanding the invention, that various changes and modifications may be made without departing from the spirit and scope of the invention and it is intended, therefore, to cover all such changes and modifications in the appended claims.

Having thus described my invention, I claim as new and desire to secure by Letters Patent:

1. A metal casting device for slag free casting, including a mould block having an upper molten metal receiving basin, said basin having a gate opening in the bottom surface thereof leading into a lower mould cavity, a dam of refractory material adjacent to and around said gate opening and partially separating said receiving basin from said opening, the said dam extending upwardly into said basin for a distance in the range of one-quarter to one" third of the depth of said basin, a vertically movable gate plug positioned above and in alignment with said opening and having a lower head end extending below the top of said dam and cooperable with said opening for selective control of the metal flow from said receiving basin through the gate opening, means for raising and lowering said gate plug, and limit stop means preventing upward movement of the lower head end of said gate plug above the top of said dam when the said plug is raised to empty the basin.

2. A metal casting device for slag free casting, including a mould block having an upper molten metal receiving basin, said basin having a gate opening in the bottom surface thereof leading into a lower mould cavity, the upper end of said gate opening being enlarged to define an upwardly facing gate plug receiving shoulder, a dam of refractory material adjacent to and around said gate opening and partially separating said receiving basin from said opening, the said dam extending upwardly into said basin for a distance in the range of one-quarter to onethird of the depth of said basin, a vertically movable gate plug positioned above and in alignment with said opening and having a lower head end extending below the top of said dam and into the enlarged upper end of said gate opening, the head end having a diameter less than the diameter of said enlarged upper end to define an annular flow passage, means for raising and lowering said gate plug, and limit stop means preventing upward movement of the lower head end of said gate plug above the top of said dam when the said stopper is raised to empty the basin.

3. A metal casting device for slag free casting, including a mould block having an upper molten metal receiving basin, said basin having a gate opening in the bottom surface thereof adjacent one end of said basin, the said opening leading into a lower mould cavity, a dam of refractory material adjacent to said gate opening and extending across the end of said basin to partially separate said receiving basin from said opening, the said dam extending upwardly into said basin for a distance in the range of one-quarter to one-third of the depth of said basin, a vertically movable gate plug positioned above and in alignment with said opening and having a lower head end extending below the top of said dam and cooperable with said opening for selective control of the metal fiow from said receiving basin through the gate opening, means for raising and lowering said gate plug, and limit stop means preventing upward movement of the lower head end of said gate plug above the top of said dam when the said plug is raised to empty the basin.

4. A metal casting device for slag free casting, including a mould block having an upper molten metal receiving basin, said basin having a gate opening in the bottom surface thereof adjacent one end of said basin, the said opening leading into a lower mould cavity, the upper end of said gate opening being enlarged to define an upwardly facing gate plug receiving shoulder, a dam of refractory material adjacent to said gate opening and extending across the end of said basin to partially. separate said receiving basin from said opening, the said dam extending upwardly into said basin for a distance in the range of one-quarter to one-third of the depth of said basin, a vertically movable gate plug positioned above and in alignment with said opening and having a lower head end extending below the top of said dam and into the enlarged upper end of said gate opening, the head end having a diameter less than the diameter of said enlarged upper end to define an annular flow passage, means for raising and lowering said gate plug, and limit stop means preventing upward movement of the lower head end of said gate plug above the top of said dam when the said stopper is raised to empty the basin.

5. A metal casting device as set forth in claim 3 wherein the ends of said dam terminate short of the side walls of said basin.

6. A metal casting device as set forth in claim 3 wherein said dam is generally S-shaped in configuration and wherein the ends of said dam taper to a point and terminate short of the side walls of said basin.

References Cited in the file of this patent UNITED STATES PATENTS 229,953 Caspersson July 13, 1880 343,872 Walker June 14, 1886 618,867 Grittith Feb. 7, 1899 1,321,300 Gathmann Nov. 11, 1919 1,690,749 Moyer Nov. 6, 1928 1,972,684 Jacobson Sept. 4, 1934 2,197,515 Bruce Apr. 16, 1940 2,284,704 Welblund et a1 June 2, 1942 2,409,779 McWane et al. Oct. 22, 1946 FOREIGN PATENTS 383,946 Germany Oct. 19, 1923 1,063,860 France Dec. 23, 1953

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