US2932865A - Cold chamber shot end with loose piece arrangement - Google Patents

Description

April 19, 1960 A. F. BAUER & 3

COLD CHAMBER SHOT END WITH LOOSE PIECE ARRANGEMENT Filed Jan. 25. 1957 3 Sheets -Sheet 1 /JV///////////// lfl/////////// ,9

Fig. 2. /0' /6` /7 Fiq 3 ,5 o

INVENTOR Alfred F. Bauer Aprl 19, 1960 A. F. BAUER COLD CHAMBER SHOT END WITH LOOSE PIECE ARRANGEMENT Filed Jan; 23, 1957 3 Sheets-Sheet 2 INVENTOR Alfred F. Bauer BY m {g 44 NEY A. F. BAUER April 19, 1960 COLD CHAMBER SHOT END WITH LOOSE PIECE ARRANGEMENT Filed Jan.'23, 1957 5 Sheets-Sheet 3 Fig. o.

INVENTOR Alfred F. Bauer ORNEY COLD CHAMBER SHUT END WITH LOOSE PECE ARRANGEMENT Application January 23, 1957, Serial No. &35,765 8 Claims. (Cl. 22--200) This invention relates to die casting techniques and improvements therein.

In the cold chamber process of pressure die casting, one of the inherent diificulties is mantaining a proper working fit between the shot sleeve and the plunger reciprocable therein. The ideal fit of plunger and sleeve would be one which provides enough clearance so that the sliding motion of the plunger in the sleeve would result in no binding, galling or freezing of the two surfaces and at the same time prevents the seepage of molten metal past the face of the plunger into the clearance space between plunger and sleeve. This ideal condition cannot be attained in actual practice, however. Since the molten metal is subjected to a pressure of several thousand pounds per square inch, so that it Will be injected into the die cavity properly, some seepage past the plunger face will be encountered regardless of how small a clearance space is provided. Any metal entering this clearance space does not remain molten but chills quickly and solidifies and clings to the surface of the plunger causing galling and binding of the plunger in the sleeve. This constant wear and tear of shot sleeve and plunger is the biggest maintenance problem of all cold chamber die casting machines. With improvements in machine structure and casting methods leading to the production of larger castings requiring the injection of larger volumes of metal, this problem of obtaining and maintaining the proper working fit becomes an increasingly difiicult one.

The larger quantities of metal per shot, of necessity, require the use of larger shot sleeves and plungers. Adequate clearance must be provided between the plunger and sleeve at room temperature so that the two will not stick or freeze when the machine is first started. It is customary to provide cooling facilities for the plunger in order to solidify the biscuit of casting metal remaining in the sleeve. Even though the sleeve may also be provided with cooling facilities to help equalze the temperature between them, the temperature of the two parts Will fiuctuate during operation of the machine. This temperature fiuctuation will cause a change in the amount of clearance between plunger and sleeve and will lead to excessive galling and sticking as the size of these parts is increased. i

i Another inherent problem associated with cold chamber die casting is that of providing proper lubrication for the plunger and sleeve because of the direct contact of these parts With molten metal. The temperature encountered in these parts are quite high and, therefore, no material has been found which aiiords satisfactory lubrication to the sliding condition existing between plunger and sleeve. Any decrease in the amount of clearance caused by temperature diiferences of plunger and sleeve magnes the lubrication problem as does any accumulation of metal which has seeped past the plunger face. It has been found that operators frequently keep their machine Operating longer by using an excess amount of lubricant. This excess lubricant, however, is detri- States atnt O mental to the quality of the casting because it stains its surface, increases porosity and decreases the physical properties of the casting.

Another factor present in the cold chamber process and one which is dfiicult to evaluate is that of friction between the plunger and the shot sleeve. Regardless of the excess amounts of lubricant used, the surfaces of the plunger and sleeve of currently used machines become grooved from wear due to dirt and small bits of metal. The longer the machine is operated, the more these conditions build up resulting in increased friction between plunger and sleeve. As the f'iction increases, more and more of the hydraulic pressure available for the shot is used in overcoming the friction. There is no way of determining exactly how much of the available pressure is used for this purpose and how much is left for injecting the molten metal into the die cavity. On present day machines, the operator continues running until the plunger seizes in the sleeve or until a visibly bad casting is produced. There is no way for the operator to know when friction between plunger and sleeve has increased to the point where the machine should be stopped and sleeve and plunger overhauled in order to guarantee high quality castings. In the present cold chamber machines the pressure with which the metal is injected Varies as the friction condition gradually changes, resulting in large Variations in the quality of cold chamber die castings.

It is, therefore, an object of this invention to provide an improved cold chamber shot sleeve and plunger assembly wherein an interchangeable loose piece or plunger seal separates the plunger tip from the molten metal thus avoiding any gallng or sticking of the plunger tip in the sleeve.

Another object of this invention is to provide a cold chamber shot sleeve and plunger assembly with a separate sealing member of a shape deformable by the molten metal during the injection interval so as to positively assure a tight seal against the shot sleeve and prevent seepage.

Still another object of this invention is to provide an assemblage in conformity with the foregoing object, wherein the plunger is finished to a size such that its diameter is materially less than the inside diameter of the shot sleeve so as to eliminate the possibility of the plunger galling and freezing in the shot sleeve.

Another object of this invention is to provide a separate plunger seal in conformity with the foregoing objects by means of which lubrication tor the shot sleeve and plunger can be easily provided and accurately controlled by applying the iubricant to the plunger seal so as to obviate the present practice of overlubricatiou with its resultant ill effects.

Yet another object of this invention is to provide a shot sleeve and plunger assembly wherein a separate scaling member or plunger seal is empioyed in conformity with the foregoing objects so as to obviate an increase in frictional resistance with succeeding injection Operations of the plunger.

A further object of this invention is to provide a shot sleeve and plunger assembly wherein a die cast sealing member or plunger seal is inserted in the shot sleeve in the as-cast condition and the `flash is removed therefrom by the cooperating action of plunger and sleeve thus eliminating a separate trimmng operation.

A still further object of this invention is to provide a shot sleeve and plunger assembly wherein wear and tear of plunger tip and shot sleeve are eliminated.

In the drawings:

Fig. 1 is a sectional view through a portion of a cold chamber die casting machine, showing details of the chamber as constructed in accordance with this inven- Patented Apr.. 19, 1960 tion and illustrating in full and dottcd lincs, respectively, the separate loose piece or scaling member being inserted and in place;

Fig. 2 is a View similar to Fig. 1 but showing the plunger seal in place and the die casting metal being ladled into the shot chamber;

Fig. 3 is a view similar to Figs. i and 2 but showing the plungcr in position upon completion of its stroke;

Fig. 4 is an enlarged sectional View illustrating the def ormation of the scaling member to cffcct the scaling cngagcment with the inner wall of the shot sle-eve;

Figs. 5-9 are enlarged partial sections illustrating modi- 'ed forms of scaling members;

' Fig. is a longitudinal section taken through a modifred form of shot chamber assembiy with end loading mechanism; v

Fig. 11 is a pe'spectve view showing an end portion of the shot sleeve with end loading mechanism for the separate plunger seal;

Fig. 12 is a vertical section taken along the plane of section line 12-12 inFig. 10;

Fig. 13 is a pcrspcctive view showing a plunger seal as removed from the die having the gate and flash still attac ed;

Fig. 14 is a perspective view of an alternate modification of the end loading mechanism of the shot sleeve; and

Fig. 15 is a Vertical section taken along the plane of section line 15--15 in Fig. 14.

in Pig. l, the reference numeral 10 indicates the fixed die half whereas reference numeral 11 illustrates the movable die half, and reference numcral 12 indicates a gatc ormed between the two die halves for introduction of the casting metal into the die cavity. The fixed die half in the specific embodiment shown in Fig. 1, tor eX- ample, has an opening 13 therethrough which receives the inner end 14 of the shot sleevc which is indicated generally by the reference character 15. The shot sleevc has an annular collar portion 16 which bears against the outer face of the fixed die half 10 and is held rigidly thcreagainst by means of a front machine plate 17. Reciprocable within the sleeve 15 is a plunger assembly indicated generally by the reference character 1 .8 which includes the usual plunger rod 19 and an enlarged plunger head portion 20, the rod being connected at its free end, not shown, to a source of powersuch as a hydraulic ram or the like.

It is to be understood that the particular construction of the die halves and the manner of securing the shot sleeve to the die halves may take any convcntional form and the particular structure shown in the drawings is for illustrative purposes only, with respect to these parts.

l`his invention contemplates the use of a separate scaling member or plunger seal which is preierably made from the same or a closely similar metal as is being die cast. Since the cold chamber method of die casting is commonly used for aluminum, the separate'plunger seal will preferably be made of aluminum or an aluminum alloy. l-lowever, it is contemplated that plnngcr seals made of metals entirely dissmilar from that being cast may be used. For example, a ferrous metal or bronze plunger seal may be used with aluminum cold chamber die castmg.

The separate scaling member or plunger seal in the form of a free floating piston is indicated generally by the reference character 21 which is insertable within the shot sleeve through the usual opening 22 thereir. Fig. l illustrates in full line position the plunger seal or sealing member !21 in the process oftbeing inserted within the shot siec /e whcreas the dotted line position shows the seal in place, and Fig. 2 shows in full lines the ultimate position of the separate plunger seal before the plunger is reciprocated to efiect the injection of the molten metal.

With the seal 21 in place, as in Fig. 2, the molten metal 2; is introduced into the chamber by any suitable means,

such as the ladle iudicated by the reference character 24, and when proper charge of metal has been poured into the shot chamber, mechanism is opcrated for moving the plunger head 20 in Fig. 3, Fig. 3 showing the position of the plunger at the end of its stroke and at the completion of the shot.

As shown more clearly in Fig. 4, thesealing member or separate plunger seal may be formed as to provide a disc-like main body portion 25 and`on one side thcreof an annular lip or rim 26 which projects forwardly there- 'from to provide the central depresson 27 in the piston. Preferably, the lip'26 is so formed that it is thicker in the region 28 where it joins the main body 25 than at the free edge portion 29 thereof, the purpose of which will be presently apparent. The outer surface of the plunger seal is cylindrical and is initially formed to loosely fit within the shot slccve 15.* For the purpose of lubrication, the outer surface of the plunger seal maybe provided with one or more lubrication'grooves 30 and it is preferred that a suitable lubricant be utilized to coat the piston at least on the outcr cylindrical surface thereor", some of which lu bricant will, of course, be rctained within the lubrication groovcs 30 to prevent undue wear of the shot slccve during the casting operation.

During the injection interval the injcction 'pressui'e is excrted by the plunger on the casting metal 23 and, be-

ing in the molten or"1iquid state, this pressure is exertcd equally in all directions throughout the body of molten metal. This prcssure acting on the lip or rim 26 ot the plungcr seal will cause it to be deformed outwardly inthe manner illustrated by solid lines in Fig. 4 so that the outer surface of the plunger seal, at least in the region of the lip or rim, will be in close contact with the shot slecve and thus prevent seepage of'mctal pastthe separate plunger seal. Since the plunger seal is of thinnest section at the free edge 29 of the lip or rim 26, this portion will be aorded the most deformation and the seal will hcncc be most effectively produced at this point, the pressure of thc molten metal 2.3 acting over the entire inner surface area 31 of the lip or rim 26 to efiect the deformation thereof.

Prefcrably, the lubrication coating on plunger seal 21 and the scaling members hercinafter described is etlected by dipping these parts in an aqueous solution of lubricant while they are hot. 'In thisjmanner, a coat of dry lubricant will be formed on the surface of the scaling members. Since these scaling members can easily be made by die casting, the lubrication coat can be conveniently applied by dipping the pieccs as soon as" they are removed from the die and while they are still hot. Thus, the liquid carrier for thelubricant will driven dit' and a dry coating or lubricant will remain. This eliminatcs the formaton of oil or similar vapors, when the scaling mem: bers are used in making a shot, which are produced with the lubricants as conventionally used. One present method of lubrication involves the use of a graphite in a liquid carrier, usually oil, the carrier being used primarily not for any lubricating value since it is vaporized by the molten metal, but as means by which the graphite is applied in a liquid state. It would, ot course,'be incon-V venent and difficult to apply graphite alonein the dry state.

The use of the separate plunger seal 21 permits the plunger head 20 to be made of material smaller :diameter than the inside diameter of the shot sleeve 15, thus eliminating any wear between plunger and sleeve. In Fig. 4, the initial clearance between the plunger seal and shot sleeve as well as the dcformation of the plunger seal has been exaggerated for the purpose of clarity, although it is to be understood thatthe same principle of operation applied under actual conditions.

Each plunger seal 21 is preferably used only once and then is removed from the machine at the same time that the solidificd biscuit 36 of casting metal, a-s shown in Fig. 3, is removed from the shot sleeve. The plunger seal the solidified biscuit and reused several times. Of course,`

if the plunger seal is of some metal dissimilar to that being cast, it will preferably be reused for a considerable time. This plunger seal may be fed into the shot sleeve either manually or mechanically as desired.

In actual operation, the plunger seals or sealing members 21 will-permit the use of much larger cold chambers than has previously been practicable. For example, the maximum diameter of shot sleeves conventional now in the art is perhaps 4 inches, whereas with the use of scaling members such as are disclosed above, the diameter may be increased to 6, 7 or more inches, thus permitting much larger castings to be made than were heretofore known.

The reason for this, of course, stems directly from the fact that the plunger seal or sealing member efiectively seals against molten metal leakage past the plunger regardless of the amount of clearance between the plunger and sleeve. At the same time, the lubricating means on the plunger seal provides all of the lubrication that is necessary for proper operation and the attainment of castings having consistently good quality.

The use of the plunger seal eliminates the variable of friction of the plunger in the shot sleeve since the same amount of friction is present with every shot. The plunger seal, being of softer metal than the sleeve, will receive any grooves formed during the injection or ramming operation of the plunger and since a new piece is used for each shot, identical conditions will be present during each shot. No increased friction is cncountered on subsequent shots since there is no contact between the plunger and shot sleeve and, the plunger seal prevents the seepage of molten metal into the clearance between plunger and sleeve and consequently there is no build-up of metal particles to retard the movement of the plunger.

' Fgs. 5-9 illustrate modified forms of sealing mernbers for the plunger. In Figs. 6, 7, 8 and 9, the sealing members are of annular form and in general these forms are to be preferred by virtue of the fact that they allow the molten metal to come in contact with the plunger. This is of importance when the plunger is provided with means of internal cooling. After the shot of metal has `been injected into the die, with the metal in the sleeve directly Contacting the end surface of the plunger, the coolant in the interier of the plunger absorbs enough heat from the molten metal to solidify the biscut of metal remaining in the sleeve, which biscuit is removed with the casting and gate. In all its forms, the plunger seal is z of such a shape as to prevent a V-shaped annular groove in contact with the molten metal so that, as hereinbefore described, the pressure in the molten metal presses the plunger seal against the plunger while deforming its lips and thus creating a perfect seal against the seepage of molten metal.

The plunger seal of Fig. S is of full piston form with the main body portion or hub 42 forming the center of the piston and with an outer cylindrcal rim or lip 37 having its thinnest section at the leading edge 39. The inner surface 38 of the rim or lip is tapered and it together with the flared web 40 form the V-shaped annular'groove previously mentioned. Flared web 4@ joins the main body portion or hub 42 to present a continuous surface between the molten casting metal and plunger 2051. The plunger Zla terminates in the tapered surface 46 intersecting the radial shoulder 45 and has a shape similar to that of the rear face of the plunger seal. Also, the plunger may be hollow to provide a coolant chamber 47. In this form, the rim under pressure, will be de- 6 formed into sealing contact with the inner surface of shot sleeve 15. The position of the parts in Fig. 5 illustrate the position of the plunger at the end of the shot x when the gate of the casting will fill the gate runner 12.

The seal of Fig. 6 is similar to that shown in Fig. 5 except that it is annular in form having a cylindrical rim with a tapered' inner surface 51 from its leading edge 52 toward the rear edge 53 where it is joined with the central hub section 54 which -tapers in the reverse direction as shown to form the V-shaped groove. In both cases the plunger 20:: is the same.

The plunger seal of Fig. 7 is annular in' general form having an outer cylindrical rim or lip 57 with its thinnest section at leading edge 5 9. The V-shaped groove is formed by the tapered inner surface 58 of the rim and the flared web 60. Flared web 60 terminates at its inner edge in a circular hub 61 which under the pressure in jthe molten metal forms a seal against step 64 of plunger Zttb :to prevent seepage of the casting metal between the plunger seal and plunger. It will be noted that tip 62 of plunger 2017 is rounded to increase the cooling area and is provided with step 65 and tapered surface 66 against which the plunger seal is pressed during the injection operation; i

In the form shown in Fig. 8, the rim 71 tapers inwardly from both the leading and traling edges 72 and 73 and intermediate such edges is formed the inturned radial hub 74 which bears against the front face of plunger 206, the end of such plunger being shaped to fit the plunger seal as shown.

The plunger seal shown in Fig. 9 consists of an annular band 76 fitting around the reduced end portion of plunger 20d and hearing against shoulder '78. The inner surface of the band at leading edge 79 is chamfered as at 81 and this together with chamfered edge 863 of the plunger present an annular space within which the molten metal under pressure may react against the inner surface of the band to expand it and form the proper seal.

Fgs. 10-13 illustrate the principle of automatic flash removal. In Fig. 10, 11 is the movable die half, 10 the fixed die half and 12 the gate runner. The plunger is designated by the numeral 20 and the pouring opening into sleeve 15a by numeral 22::.

As previously mentoned, the forming of the plunger seal lends itself readily to a die casting operation. Such a plunger seal 81 is shown in Fig. 13, with the gate 82 still attached and having the flash 84 thereon. The plunger seals may be formed in dies especially made for this purpose or one or more plunger seals may be formed in conjunction with production run castings, in which case the regular production dies would be formed with one or more plunger seal cavities attached to the regular casting by means of additional gate runners. In any case, the plunger seals thus formed are preferably used in the as-cast condition without the benefit of any separate trimming operation, such trimrning being performed at the time that the plunger seal is used.

For this purpose, the plunger 20 is movable between its bottomed position and the position in Fig. 10 where it is completely withdrawn from the sleeve or cylinder. When withdrawn, the plunger rests upon a semi-circular combined guide and support 85 attached to the sleeve by a pair of forwardly projecting arms 86 and 87. An end view showing the location of these projecting arms is shown in Fig. 12. The top of the sleeve at its free end is notched inwardly as at 88 leaving the rearwardly projecting step 89 upon which the plunger seal rests. The guide 85 is spaced from the rear edge of the sleeve to provide clearance for the flash 84 and those portions of the arms 86 and 87 bridging such gap are bulged outwa'rdly as shown at 90 and 91 in Fig. 11. The plunger must, of course, be capable of withdrawal to such a point to permit the plunger seal to be inserted.

After the plunger seal has been inserted, the plunger is moved inwardly past the notch 88, after which the.

i the shot sleeve may be modified to accomplish the task of trimming the flash from the plunger seal without; the necessity of performing this step on a separate machine.

As in the aforementioned modification, when withdrawn, the plunger rests 'upon the semi-circular guide and' support 105. attached to sleeve 15b by a pair of arms 1313 and '115. sleeve end 106 is in a plane which is normal to the bore of the sleeve and said sleeve end is provided with three lugs 108, 116 and 112, Fig. 15, which project on the axis of the sleeve. The said lugs perform the 'dual purpose of acting' as locating blocks for the plunger seal and also serving as a means to shear off sections of the flash and preventing a circular ring of 'fiash'being formed by the shearing action as the plunger, seal is pushed by the plunger into the end of the sleeve. The guide 185 is spaced from the rear ends of the lugs to provide a clearance space 118 for the flash and those portions of arms 113 and 115 bridging such clearance space are bulged outwardly as shown, at 114- and 116.

' As previously mentioned, the njection of a shot of metal is accomplished by a two-step operation. After the plunger seal has been inserted so that it rests upon the locating lugs, the plunger is moved inwardly far enough to push the plungenseal past the free end of the sleeve, after which the shot of metal is poured' into the sleeve and rammed home. movement of the plunger causes the flash to'be sheared from the outer diameter of the plunger seal obviating a separate trimming operation.

it is to be understood that' the separate plunger seal or sealing member may be of a shape other than the Again the preliminary specific examples shown which are for the purpose of illustration andare not meant to limit the scope of the following claims.

I claim:

1. in the art of pressure die' casting in which a multiplicty, more than three, of identical parts are made, the method of produ cing castings including the steps of placing a separate deformable plunger seal into a shot sleeve ahead of the plunger at each cycle of operation of the machine ntroducing molten metal of the same base metal composition as said seal into said shot sleeve ahead of said plunger seal, exerting pressure upon said plunger, moving said deformable plunger seal and plunger under pressure exerted on the plunger 'forward into' the shot sleeve, deforming the plunger seal by the pressure of the liquid metal into scaling contact with the inner surface of said sleeve 'and thereby preventing the backward passageofmolten metal between plunger and sleeve, continuing to exert pressure on said plunger and plunger seal whereby molten metal is forced into the die cavity and solidified therein, and withdrawing said plunger away from said seal and said' soiidied charge, whereby said plunger seal remains as a part of the soiidified charge.

2. A shot chamber assembly for cold chamber die casting machines, comprising a shot sleeve adapted for connection at one end to a die casting machine, a plunger within said sleeve and mova'ole between one position completely withdrawn from and spaced from the outer end of the sleeve a sufiicient distance to permit the insertion of a plunger seal into the sleeve and a position innermost within the sleeve, the outer edge of said sleeve being cooperabie with the plunger to shear flash'metal from the periphery of a plunger seal as the plunger is moved from its oneposition into the sleeve, andvmeans for supporting said plunger in an outer position and to guide the same into thevsleeve, said supportingmeans shaped i comprising a semi-circular guide and support memberattached to the shot sleeve' by a pair of arms.

3. In the art of pressure die casting, the steps of pl'acing a separate deformable plunger seal of metal selected from' the group consisting of aluminum and aluminum alloy.

into a shot sleeve ahead of the plunger, introducing molten metal of substantially the same composition as the deformable plunger seal into said shot sleeve, exerting pressure upon said plunger, moving said deformable plunger seal and plunger under pressure exerted on the plunger forward into the shot sleeve, deforming the plunger seal by the pressure of the liquid metal into scaling contact with the inner surface of said sleeve and thereby preventing the backward passage'of nolten metal between the plunger' and sleevecontinuing' to exert pressure on said plunger and plunger seal-whereby molten metal is forced into the die cavity and solidified therein, and withdrawing said plunger away from said plunger seal and said solidified charge, whereby said plunger seal remains as a part of the solidified charge.

4. In the art of pressure die casting, the method of producing a casting including the steps of placing a separate deformable plunger seal constructed of metal selected from the group consisting of aluminum and aluminum alioy into a shot sleeve ahead of the plunger,introducing molten metal of substantially the same composition as the deformable plunger seal into said shot sleeve, exerting pressure upon said plunger, moving said deformable,

er seal by the pressure of the liquid metal into scaling;

contact with the inner surface of said sleeve and'thereby preventing the backward passage of molten metal be.- twe'en plunger and sleeve and continuing to eXert pressure on said plunger and plunger seal whereby molten metal'is forced into the die cavity stopping'the forward rnotion of the plunger while a portion of said molten' metal remains in the gate area of the apparatus, permittng the molten metal to solidify thereby to form a die' casting, and. withdrawing said plunger away from said plunger seal and said solidied metal, the plunger seal adhering to the molten metal in the gate areaas it solidifies and being removed from 'the die casting apparatus therewith, a separate deformable'plurger seal being placed into the shot sleeve as described and the casting steps repeated as previously described.

5. In combination, a cold chamber shot sleeve,7 a plunger reciprocable within said sleeve, a separate metallic plunger seal engaged against the forward face of said plunger, said seal engagement with the inner end of said sleeve during injection of metal into a die, and having a frusto-concal 'web joining a rear, edge of said rim and forming a V- channel with the inner surface of said rim, said V-shaped channel being in contact with molten metal 'in said sleeve and subject to deformation by pressure exerted during an injection operation 6. The combination defined in claim 5 wherein the:

plunger seal is provided with a disc-like central portion joining said web. p V

7. A method of pressure die casting a metallic object which includes, introducing a first deforrnable plunger seal into the shot sleeve of a die casting machine ahead' of a plunger therein, introducing a charge of molten etal into said sleeve ahead of said plunger seal, forcing said plunger and plunger seal forwardly in said sleeve to expel said charge of metal while still liquid from said sleeve into a die having a cavity for a production casting and a communicating cavity for a second plunger seal, deforming said first plunger seal into scaling contact with the inner surface of said'sleeve by the pressure of said liquid metal during the travel of said plunger, solidifying said charge of molten metal to form a production casting and a second plunger seal, and subsequently with draw- 'ing said plunger away from saidfirst plunger seal aud including a cylindrical rim for scaling' said solidied charge, whereby said first plunger seal remains as a part of the solidied charge, and introducing the second plunger seal formed in said communicating die cavity ahead of said plunger for a succeeding stroke of said plunger as the first step in a subsequent die casting operation.

8. A method of pressure die casting a metallic object which includes, introdueng a first deformable plunger seal into the shot sleeve of a die casting machine ahead of a plunger therein, introducing a charge of molten metal into said sleeve' ahead of said plunger seal, forcng said plunger and plunger seal forwardly in said sleeve to expel said charge of metal while still liquid from said sleeve into a die having a cavity for a production casting and a communicating cavity for a second plunger seal, deforming said first plunger seal into sealng contact with the inner surface of said sleeve by the pressure of said liquid metal during the travel of said plunger, solidifying said charge of molten metal to form a production casting and a second plunger seal, and subsequently withdrawing said plunger away from said first plunger seal and said solidied charge, Whereby said first plunger seal remains as a part of the solidied charge, and introducing the second plunger seal forned in said communcating die cavity ahead of said plunger for the next succeedng 10 stroke of said plunger as the first step in. a subsequent die casting operation.

References Cited in the file of this patent UNITED STATES PATENTS 312,693 Ziegler Feb. 24, 1885 1,730,469 Millspaugh Oct. 8, 1929 1,781,143 Williams Nov. 11, 1930 1,859,355 Crowther May 24, 1932 1,935,059 Pack Nov. 14, 1933 1,983,558 Morin Dec. 11, 1934 2,057,669 Brauchler Oct. 20, 1936 2,375,486 Morin May 8, 1945 2,468,322 Cook Apr. 26, 1949 2,473,366 Galliano June 14, 1949 2,496,131 Morin Ian. 31, 1950 2,564,885 Sternberg Aug. 21, 1951 2,575,162 Sternberg Nov. 13, 1951 2,620,528 Sternberg Dec. 9, 1952 2,804,666 Saives Sept. 3, 1957 2,816,608 Farnwald Dec. 17, 1957 2,836,474 Mosher May 27, 1958 FOREIGN PATENTS 855.010 France Feb. 5, 1940 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Now &932,865 April 19, 1960 Alfred Ferdinand Bauer It is hereby Certified that error appears in the printed specification of the above numbered patent requiring correction and that 'the said Letters Patent should read` as corrected below.

Column 4` line 64 for "material" read materially column 5 line 56, for "prevent" read present Signed and sealed this 20th day of September 1960.

(SEAL) Attest:

KARL H. AXLINE ROBERT c. WATSN Attesting Oficer Commissioner of Patents

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