US3658121A

US3658121A - Die casting apparatus

Info

Publication number: US3658121A
Application number: US97850A
Authority: US
Inventors: William E Douglas
Original assignee: General Motors Corp
Current assignee: Motors Liquidation Co
Priority date: 1970-12-14
Filing date: 1970-12-14
Publication date: 1972-04-25
Anticipated expiration: 1989-04-25

Abstract

Die casting apparatus of the horizontal cold chamber type operative to prevent impurities such as dross and metal foam floating on the surface of the molten metal charge in the shot sleeve from entering the die cavity. The apparatus involves the elimination of the usual vertical runner extending from the end of the shot sleeve adjacent the parting line of the dies to the die cavity, the provision of the overflow cavity above and at the end of the shot sleeve adjacent the parting line of the dies, and the provision of one or more runners extending from the lower portions of the shot sleeve and around the overflow trap whereby when the plunger is caused to move the molten metal to the parting line of the die, the dross and metal foam formed on the surface of the die is trapped in the overflow trap and only clean metal is injected into the die cavity.

Description

United States Patent Douglas [451 Apr. 25, 1972 [54] DIE CASTING APPARATUS [72] Inventor: William E. Douglas, Birmingham, Mich.

[73] Assignee: General Motors Corporation, Detroit,

Mich.

[22] Filed: Dec. 14, 1970 [21] App1.No.: 97,850

[52] U.S.Cl ..164/312, 18/121 [51] Int. Cl ..B22d 17/04 [58] Field of Search ..18/5 BE, 5 B1, 30 EN, 30 FP,

18/30 QM, 30 QB,12 P; 164/47, 62,113,120-127, 136, 257, 284, 303, 306, 309, 312, 313, 314, 316,

Primary Examiner-J. Spencer Overholser Assistant Examiner-John S. Brown Attorney-Peter P. Kozak and Sidney Carter [57] ABSTRACT Die casting apparatus of the horizontal cold chamber type operative to prevent impurities such as dross and metal foam floating on the surface of the molten metal charge in the shot sleeve from entering the die cavity. The apparatus involves the elimination of the usual vertical runner extending from the end of the shot sleeve adjacent the parting line of the dies to the die cavity, the provision of the overflow cavity above and at the end of the shot sleeve adjacent the parting line of the dies, and the provision of one or more runners extending from the lower portions of the shot sleeve and around the overflow trap whereby when the plunger is caused to move the molten metal to the parting line of the die, the dross and metal foam formed on the surface of the die is trapped in the overflow trap and only clean metal is injected into the die cavity.

4 Claims, 2 Drawing Figures PATENTED APR 2 5 m2 INVEN TOR. M71122!!! 5 30119105 DIE CASTING APPARATUS This invention relates to apparatus for forming metallic parts and in particular to pressure die casting apparatus. While the invention is broadly useful in the die casting art it is particularly applicable to die casting of light metals such as aluminum, magnesium and their alloys.

In the manufacture of metallic parts by pressure die casting it has long been recognized that extensive and sometimes prohibitive porosity will occur in die castings. Significant advances in the art of die casting have been made which materially reduce porosity as for example by the die casting apparatus and method disclosed in the U.S. Pats. Nos. 3,270,383 Hall et al. and 3,344,848 Hall et al. These patents disclose a method and apparatus of a horizontal cold chamber type in which the molten metal is injected relatively slowly and nonturbulently into a die cavity from a shot sleeve located below the die cavity and whereby the molten metal is subjected to relatively high pressure after the die cavity is filled to avoid metal turbulence and to compact the molten metal within the cavity to substantially eliminate porosity.

It has been found that in the use of die casting apparatus of the type referred to above wherein the runner is positioned in a vertical plane and leads directly from the top of the shot sleeve to the die cavity, the molten metal charge in the shot sleeve includes small amounts of impurities such as dross and metal foam on the surface thereof. When the molten metal is moved into the die cavity by means of the plunger the dross and metal foam are moved into the die cavity during the ejection procedure to produce imperfections in the cast article. Where it is desired to cast articles such as internal combustion engine blocks even such minor imperfections are objectionable.

It is the basic object of this invention to provide die casting apparatus whereby the impurities such as dross and metal foam floating on the surface of the molten metal in the shot sleeve is trapped during the casting cycle and not permitted to enter into the die cavity whereby such dross and metal foam as a source of casting porosity is effectively and efficiently eliminated.

It is a further object of this invention to provide relatively simple and effective means whereby the aforementioned object is carried out by a relatively simple modification of existing die casting apparatus.

These and other objects are accomplished by the provision of die casting apparatus of the horizontal cold chamber type such as for example as disclosed in the aforementioned patents which is modified to eliminate the usual vertical runner extending from the end of the shot sleeve adjacent the parting line of the dies, to provide an enlarged spaced or enclosed overflow cavity at the end of the shot sleeve adjacent the parting line, and to provide one or more runners extending from the lower portions of the shot sleeve adjacent the parting line around the overflow cavity and to the die cavity. In operation when the shot sleeve is filled with a charge of molten metal and the plunger is caused to move the molten metal toward the parting line of the die the dross and metal foam which are formed on the surface of the molten metal charge are forced into the overflow trap and only clean molten metal is forced from below the trap into the die cavity through the runners.

Other objects and advantages will be apparent from the following detailed description of this invention reference being made to the drawings in which FIG. 1 is a vertical cross-sectional view through the dies and the shot sleeve of die casting apparatus with the dies in a closed position and with the shot sleeve containing a molten metal charge, and

FIG. 2 is a vertical cross-sectional view taken along line 2 2 of FIG. 1.

Referring to the drawings FIG. 1 illustrates die casting apparatus including a cover die attached to a stationary platen l2 and an ejector die 14 including a back plate 15 attached to a movable platen l6 slidably mounted on the tie rods 18 in a manner well known in the art. The movable platen I6 is operative to move the ejector die 14 between a die closed position as shown in FIG. 1 to a die open position by means of toggle links 20 attached to a toggle mechanism (not shown) which in turn is operated by hydraulic means (not shown) well known in the art.

The cover die 10 and ejector die 14 form a die cavity 22 therebetween when in a closed position. The back plate 15 is removable to permit access to conventional ejector pin mechanism (not shown) contained within the ejector die 14 as is well known in the art.

The apparatus includes a shot sleeve 24 extending from outside the stationary platen 12 to the parting line 26 of the dies and having the molten metal charging port 25 and the shot plunger 27. The shot sleeve which is usually of a cylindrical configuration includes the lower horizontal dimension 28 and the upper horizontal dimension 30. These dimensions refer to lower and uppermost horizontal, longitudinal internal surfaces of the shot sleeve. The inner end of the shot sleeve 24 adjacent the parting line 26 is provided with an enlarged portion or overflow trap 32 extending vertically above the upper horizontal dimension 30 of the shot sleeve 24 as shown in FIGS. 1 and 2.

In accordance with this invention the usual vertical runner extending from the shot sleeve to the die cavity is eliminated and the runners 34 and 36 are provided adjacent the parting line 26 which preferably communicate between the die cavity 22 and the shot sleeve 24 from a location as indicated at 38 in the vicinity of the lower horizontal dimension 28 of the shot sleeve and curve about the overflow trap 32. It will be readily apparent to those skilled in the art that this structure may be readily incorporated in existing apparatus by suitably plugging the usual vertical runner as by welding and machining the overflow trap and new runners in the existing dies and shot sleeve.

It may readily be seen that when the shot sleeve 24 is provided with a molten metal charge 40 as shown in FIG. 1, the dross and metal foam will float on the surface 42 ofthe molten metal charge. When the plunger 27 is actuated to inject the molten metal charge 40 into the die cavity 22 the opening 25 of the shot sleeve the die closed and the molten metal is carried forward toward the parting line of the dies with the dross and metal foam floating on top thereof. As the plunger 27 proceeds the dross and foam are collected in the overflow cavity 32 and only clean molten metal is forced into the die cavity through runners 34 and 36 respectively. When the plunger 27 reaches the limit of its travel as indicated by the broken line 46 and the molten metal is solidified, the biscuit formed between the plunger 27 and the die 14 which includes the dross and metal foam solidified in the overflow cavity 32, is removed from the shot sleeve 24, the overflow cavity 32 and the runners 36 with the casting when the dies are opened in a manner well known in the art.

It has been found that the volume of the overflow cavity 32 should be a minimum of 2 percent ofthe volume of the molten metal charge to insure the entrapment of the dross and metal foam floating on the surface of the molten metal charge in the shot sleeve. A volume of bout 5 percent of the molten metal charge in most instances is an optimum to effect entrapment of the impurities referred to and to hold ofial down to a minimum.

While the invention has been shown in simplified form it is to be understood that the invention is particularly adapted to the casting of articles such as engine blocks in which case the runners 34 and 36 would include several branches extending to a plurality of gates at the die cavity to suitably fill the die cavity. Various modifications will be apparent to those skilled in the art in adapting this invention to the casting of specific articles and to various die casting methods and apparatus.

It is claimed:

1. In a die casting apparatus the combination comprising a stationary cover die and a removable ejector die removable between a die open position and a die closed position at a parting line cooperatively defining a die cavity therebetween in said closed position,

a horizontally disposed shot sleeve having an uppermost and a lowermost horizontal dimension and having one end thereof extending into said cover die to said parting line, said shot sleeve having an enlarged portion adjacent said parting line extending upwardly above said upper dimension to form an enclosed overflow cavity,

said cover and said ejector dies defining at said parting line at least one runner extending from a portion of said shot sleeve below said overflow cavity to said die cavity,

a shot plunger in said shot sleeve and an opening means in said shot sleeve for charging said shot sleeve with molten metal,

said overflow cavity, being operative to trap dross and metal foam floating on the surface of a charge of molten metal in said shot sleeve and said runner being operative to convey clean molten metal from a location below said overflow cavity when said plunger is operated to move the molten metal into said die cavity.

2. The die casting apparatus of claim 1 wherein the volume of said overflow cavity is at least 2 percent of the volume of the molten metal charge.

3. In a die casting apparatus the combination comprising a stationary cover die and a removable ejector die removable between a die open position and a die closed position at a parting line cooperatively defining a die cavity therebetween in said closed position,

a horizontal shot sleeve having an uppermost and a lowermost horizontal dimension disposed below said die cavity and having one end thereof extending into said cover die to said parting line, said shot sleeve having an enlarged portion adjacent said parting line extending upwardly above said upper dimension to form an enclosed overflow cavity,

said cover and said ejector dies defining at said parting line at least one runner extending from a portion of said shot sleeve in the vicinity of said lowermost horizontal dimension and below said overflow cavity to said die cavity,

a shot plunger in said shot sleeve and an opening means therein for charging said shot sleeve with molten metal,

said overflow cavity the to trap dross and metal foam floating on t he surface ofa charge of molten metal in said shot sleeve and said runner being operative to convey clean molten metal from a location below said overflow cavity when said plunger is operated to move the molten metal into said die cavity.

4. The die casting apparatus of claim 3 wherein the volume of said overflow cavity is at least 2 percent of the volume of said molten metal charge.

t 1' i i EE-5&3? UNITED STATES PATENT bimibE" v CERTIFICATE CORRECTION Patent No. 3,658 121 Dated April 1972 lnvenw i William E. Douglas It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2,-line S7, "bout" should read about Claim 1, column 2, line 71, after 7 "a" delete "removable" and substitute movable column 2, line 71, after "die" delete "removable" and substitute Claim 3, column 3, line 23, after "a" delete "removable" and substitute movable column 3, line 23, after "die" delete "removable" and substitute movable I Column. 4, line 15, "the" should read being operative i signed and sealed this 12th day of September 1972-. (SEAL) 5 Attest: I

EDWARD M.FLETCHER,JR. I ROBERT GOTISCHALK Attesting Officer Commissioner of Patents

Claims

1. In a die casting apparatus the combination comprising a stationary cover die and a removable ejector die removable between a die open position and a die closed position at a parting line cooperatively defining a die cavity therebetween in said closed position, a horizontally disposed shot sleeve having an uppermost and a lowermost horizontal dimension and having one end thereof extending into said cover die to said parting line, said shot sleeve having an enlarged portion adjacent said parting line extending upwardly above said upper dimension to form an enclosed overflow cavity, said cover and said ejector dies defining at said parting line at least one runner extending from a portion of said shot sleeve below said overflow cavity to said die cavity, a shot plunger in said shot sleeve and an opening means in said shot sleeve for charging said shot sleeve with molten metal, said overflow cavity being operative to trap dross and metal foam floating on the surface of a charge of molten metal in said shot sleeve and said runner being operative to convey clean molten metal from a location below said overflow cavity when said plunger is operated to move the molten metal into said die cavity.

3. In a die casting apparatus the combination comprising a stationary cover die and a removable ejector die removable between a die open position and a die closed position at a parting line cooperatively defining a die cavity therebetween in said closed position, a horizontal shot sleeve having an uppermost and a lowermost horizontal dimension disposed below said die cavity and having one end thereof extending into said cover die to said parting line, said shot sleeve having an enlarged portion adjacent said parting line extending upwardly above said upper dimension to form an enclosed overflow cavity, said cover and said ejector dies defining at said parting line at least one runner extending from a portion of said shot sleeve in the vicinity of said lowermost horizontal dimension and below said overflow cavity to said die cavity, a shot plunger in said shot sleeve and an opening means therein for charging said shot sleeve with molten metal, said overflow cavity the to trap dross and metal foam floating on t he surface of a charge of molten metal in said shot sleeve and said runner being operative To convey clean molten metal from a location below said overflow cavity when said plunger is operated to move the molten metal into said die cavity.