US2786247A - Die casting machine pressure chambers - Google Patents

Description

March 26, 1957 M. STERN 2,786,247

DIE CASTING MACHINE PRESSURE CHAMBERS Filed Feb. 3, 1955 IN VEN TOR.

United States Patent 2,786,247 DIE CASTING MACHINE PRESSURE CHAMBERS Marc Stern, Flint, Mich.

Application February 3, 1955, Serial No. 486,011

6 Claims. (Cl.- 227 0) This invention relates to die casting machines and in particular to improved pressure chambers of the submerged type.

Conventional die casting machines of the type to which this invention relates are employed to injection mold low melting point alloy castings, which machines include a stationary pressure chamber submerged into a pot of molten metal. The pressure chamber receives the molten metal by gravity, and, during the injection molding cycle, the molten metal is forced into a die by a plunger operating in the pressure chamber. After the metal has been injected into the die, the plunger retracts and molten metal in the pot again flows by gravity into the pressure chamber filling it prior to the next injection molding cycle.

Stationary pressure chambers of the type presently in general use consist of a cylinder having a plunger reciprocatingly mounted therein and a gooseneck outlet communicating from the bottom of the said cylinder to the injection nozzle of the injection molding machine. An inlet extends from near the top of the cylinder downwardly into the pot of molten metal so that molten metal flowing into the cylinder is withdrawn from the pot .somewhat below the upper level of the molten metal therein. This type of pressure chamber is generally referred to as a gooseneck deriving its name from the shape of the outlet. Such prior art structure .is illustrated in Fig. 1 of Patent No. 2,145,956, issued February 7, 1939, to Marc Stern, the inventor in the instant case.

In an average size commercial die casting machine, the gooseneck weighs as much as 300 pounds and oftentimes more. It requires considerable shaping, boring, contouring and facing in its manufacture. The curved gooseneck type outlet channel limits its manufacture to sand molding. Due to its length and relatively small diameter, it presents a considerable problem in maintaining the sand core in position. A shift in the core will produce a thin wall on one side of the gooseneck causing it to fail under normal operating pressures of about 2500 lbs. per square inch. The shape of the gooseneck channel precludes the removal of the sand core with a rod or drill which necessitates slow pickling in acid to accomplish the core removal. Furthermore, if the supporting rods in the curved core are insufficiently covered with sand, they may fuse to the side walls of the gooseneck. Hence, in the manufacture of goosen'ecks there are many rejects for defective castings. The importance of obtaining a porosity-free casting to withstand rugged use makes the old style gooseneck construction very costly, even before the cost of diflicult machining and finishing operations is added to the basic casting.

Zinc alloys are most commonly used in die casting.

--Their coeflicient of expansion is quite different from cast ice '2 iron, therefore repeated freezing and melting of die cast metal alloys sets up severe strains within the gooseneck which produce unexpected cracks even when the gooseneck is machined from a sound casting. The shape and weight of the gooseneck makes it a slow and difiicult operation to remove it from the pot of molten metal and drain it Whenever it needs replacement either because of insufficient capacity when molds are changed or because it becomes worn or cracked. Obviously, before the gooseneck may be removed from the pot, the plunger must be withdrawn therefrom which involves an additional. relatively diflicult operation.- a

With the foregoing in view, the primary object of this invention is to overcome the above indicated difiiculties by providing a new and improved pressure chamber wherein the gooseneck construction is eliminated and the pressure chamber becomes a movable element. This permits both the pressure chamber cylinder and the plunger'thereof to be made of special steel forgings, but even if these elements were cast, no delicate coring is involved. The improved pressure chamber construction permits most of the finishing to be done by grinding, hence it makes it possible to employ alloys too diflicult to machine which will withstand the wear and corrosive action much better than materials heretofore employed. Furthermore, the improved pressure chamber weighs only a fraction of the weight of a conventional gooseneck of a corresponding capacity, which fact makes the use of costly alloys in the manufacture of pressure chambers embodying the invention no handicap.

The most commonly used metal for die casting consists of a zinc alloy containing 1% to 3% copper. There is a tendency for the copper in die cast metal to settle in the bottom of the melting pot. The turbulence created by the operation of the movable pressure chamber of the improved construction prevents the settling out of components of the die casting alloy.

Furthermore, the instant invention provides an im proved pressure chamber construction, which, unlike the gooseneck, is substantially uniform and symmetrical about its axis.

The molten metal in the old gooseneck construction was required to pass under pressure around a substantially degree bend which was not only inefficient but placed the gooseneck under severe stresses at the sharp bend of the passage therethrough, all of which has been eliminated in the improved pressure chamber.

Because of its symmetry, the improved pressure cham her will retain a truer bore during repeated heating and cooling, and therefore the plunger therein can be held to closer tolerances than heretofore possible. As a result, leakage past the piston can be reduced to a minimum.

It is common practice to remove the plunger from conventional gooseneck construction when the casting machine is permitted to stand idle for any length of time. The plunger otherwise would have a tendency to freeze, and no amount of pressure applied thereto will dislodge it. The present invention completely avoids this problem by the provision of means whereby the whole pressure chamber may be swung clear of the molten metal for the purpose of draining molten metal therefrom when the pressure chamber is hot.

A further object of the invention is to provide an improved pressure chamber assembly which replaces the conventional gooseneck construction arranged and mounted in operating relationship in the pot of a die casting machine in a manner that will cut to a small fraction the time normally expended in changing the old gooseneck type pressure chamber from one capacity to another, thereby cutting to a minimum the usual relatively high percentage of machine down time required in the operation of prior art die casting machines.

Other objects of the invention will become apparent by reference to the following detailed description taken in connection with the accompanying drawing, in which:

Fig. l is a side elevational view with portions shown in section of a pressure chamber embodying the invention.

. Fig. 2 is a front elevational view of the pressure chamber disclosed in Fig. 1.

Fig. 3 is a plan view of the pivot clamp preferably employed to swingably support the pressure chamber on the die cast machine frame.

Fig. 4 is a cross sectional view taken on the line 44 of Fig. 1 showing the pressure clamp preferably employed to connect the outlet of the piston of the pressure chamher to the nozzle of the die cast machine.

Fig. 5 is a front view part in section and part in elevation of the cylinder cage.

Fig. 6 is a top plan view of the cylinder cage turned ninety degrees in respect to the front view thereof shown in Fig. 5.

Fig. 7 is a front view of the cylinder cage trunnion and coupling element employed to couple the cylinder to its power link.

Fig. 8 is a side eleva-tional view of the trunnion and coupling element.

Fig. 9 is a top plan view of the trunnion and coupling element.

Referring now to the drawing wherein like numerals refer to like and corresponding parts throughout the several views, the die casting pressure chamber 10 disclosed for the purpose of illustrating the invention consists of a swingable piston 11 removably pivoted by means of a pivot 12 to the frame 13 of a die casting machine, the said piston 11 being swung against and connected by means of a pin 14 in operating relationship over the butt end of a nozzle 15 of the die casting machine. A cylinder 16 is reciprocatingly mounted on the lower end of the piston 11, the said cylinder 16 being carried by a cage 17 removably connected by means of a combined trunnion and coupling element 18 and link bars 19 to a suitable casting crank arm 20 on the die casting machine.

In a typical die casting machine of a type with which the pressure chamber 10 may be employed, a casting shaft 21 is mounted in pillow blocks 22 and 23 fixed to the cast ing machine frame 13. The casting crank arm 20 is keyed on one end of the said casting shaft 21 while an actuating crank arm 24 is keyed on the other end thereof. The actuating crank arm 24 is moved arcuately by a piston 25 connected thereto by a connecting rod 26. With such or similar construction, the cylinder 16 of the improved die casting pressure chamber 10 is caused to reciprocate. The said cylinder 16, being submerged in a molten metal pot 27 0f the die casting machine, supplies molten die cast metal 270 from the molten metal pot 27 under pressure into the die 28 through the nozzle 15. The said die 23 is supported in any suitable manner on and carried by the die casting machine frame 13.

The. removable pivoting of the upper end of the swingable piston 11 to the frame 13 of the die casting machine is preferably accomplished by such means as the use of a bifurcated pivot block 30 secured to the said frame 13 of the die casting machine. The said pivot block 30 receives the pivot 12 which extends through the upper end of the said swingable piston 11, and the pivot 12 is removably fixed into the said pivot block 30 by means of a keeper block 31 carried by a swinging keeper arm 32 pivoted at one end on a bracket 33 secured to the casting machine frame 13 and anchored at its free bifurcated end 320 under a keeper nut 34 threaded on a stud 35 pivotall'yponnected to a bracket 36 secured to the casting machine frame 13.

The lower end of the swingable piston 11 is bored and counterbored at 37 and 38 and the rear thereof is diagonally bored at 39 to communicate with the molten metal passage 41) in the nozzle 15 of the die casting machine. As best shown in Fig. 1, the rear of the swingable piston 11 is suitably concaved at the bore 39 to accommodate the butt end of the nozzle 15. The front of the swingable piston 11 is provided with a suitable notch to receive the end of the pin 14 carried by a swinging keeper arm 42 pivoted at one end on a bracket 43 secured to the casting machine frame 13 and anchored at its free bifurcated end 420 under a keeper nut 44 threaded on a stud 45 pivotally connected to a bracket 46 secured to the casting machine frame 13. A pair of washers 47 and a spring 48 are interposed between the bifurcated end 420 of the keeper arm 42 and the keeper nut 44 to prevent too great a pressure from being applied on the nozzle 15 of the die casting machine as a result of expansion when the machine is in operation through the pin 14 and swingable piston 11. Studs 49 extending through the brackets 43 and 46 engage the sides of the body of the die casting machine nozzle 15 at suitable dimples formed therein to position it and to prevent it from falling into the molten metal pot 27 when the keeper arm 42 is released.

The foregoing construction permits the pressure chamber 10 to be completely removed from the die casting machine, or, as an alternate, the pressure chamber 10 may be pivoted about the pivot 12 completely out of the molten metal pot 27 whereupon molten metal is drained therefrom through the molten metal passage in the cylinder 16.

The cylinder 16 which is slidably mounted on the lower end of the swingable piston 11 is preferably tapered at 50 at the upper end thereof, and is provided with a pair of diametrically opposite axially facing seats 51, one on each side of the said taper 50 onto which the cylinder return rods 52 are seated. The bottom of the said cylinder 16 is provided with an other-than-round key 53 for the purpose of maintaining the said cylinder 16 in non-rotatable relationship with respect to the cylinder cage 17, the said cylinder cage 17 having a complementary keyway 54 in the bottom thereof to receive the said key 53. The cylinder 16 has an inlet aperture 160 therein near the top thereof through which molten metal flows thereinto from the molten metal pot 27 when the cylinder 16 is retracted downwardly on the piston 11 as shown in Fig. l.

The cage is preferably formed with a tubular body 55 having an internal diameter somewhat larger than the external diameter of the cylinder 16. The cage 17 has a bottom 56 with the aforementioned keyway 54 cut therein to receive the key 53 formed on the bottom of the cylinder 16. The key 53 maintains the cylinder 16 properly oriented in respect to the cage 17 so that the seats 51 on the cylinder 16 are always positioned in alignment with the thrust rods 52 of the trunnion and coupling element 18. The front and rear of the cage 17 are provided with longitudinal slots and the sides thereof have apertures 171 therein, the said slots 174) and apertures 171 being sufiiciently large to assure a free flow of molten metal to, around and into the cylinder 16. The top of the cage 17 has oppositely disposed arcuate members 58 welded thereto and include male bayonet fittings 59 which cooperate with the female bayonet fitting 60 formed on the trunnion and coupling element 18 for the purpose of removably securing the cage 17 to the trunnion and coupling element 18.

The said trunnion and coupling element 18 is preferably formed with a rectangular head block 61 having an aperture 62 therethrough to freely accommodate the piston 11. A pair of oppositely extending trunnions 63 extend laterally from the said head block 61. Below the head block 61 is a circular fitting block 64 into which is cut the female bayonet fitting 60 which receives the male bayonet fittings 5 of the cage 17. Extending downwardly from the fitting block 64 is a pair of cylinder return thrust rods 52 which contact the top of the cylinder 16 at the seats 51 therein. It will be observed that the cylinder 16 is reciprocated by the cage 17 through the link bars 19 pivoted at their upper'ends to the casting crank arm 20 by the pivot 200 and pivoted at their lower ends on the trunnion 63 of the trunnion and coupling element 18. It also will be observed that the cylinder 16 is free within the cage 17 except that it is properly oriented by the key 53 and it is maintained against the bottom of the cage 17 by the thrust rods 52. This means for holding of the cylinder 16 properly in the cage 17 and the employment of the trunnion and coupling element 18 makes the draining and changing of cylinders from one capacity to another extremely simple under the conditions which exist when handling hot pressure chambers of die casting machines.

Although but a single embodiment of the invention has been disclosed and described in detail, it is obvious that many changes may be made in the size, shape, arrangement and detail of the various elements of the invention to accommodate it to the various die casting machines presently in use, all without departing from the spirit and scope of the invention as defined by the appended claims.

I claim:

1. In a die casting machine including a molten metal pot and a nozzle having a passage therethrough through which molten metal is injected into a die, a pressure chamber means for transferring molten metal under pressure from said pot to said nozzle, said pressure chamber means including a piston swingably mounted on said machine and having its lower end submerged in the molten metal in said pot, a cylinder slidably mounted on the lower end of said piston and having an aperture therein through which molten metal enters said cylinder when the said cylinder is in an extended position in respect to the end of said piston, the said piston having a communicating passage from said cylinder located to register with said nozzle passage when said piston is swung thereagainst, pivoted spring loaded lever means removably securing said piston resiliently locked in said swung position whereby to accommodate the assembly to expansion and contraction, and means reciprocating said cylinder in respect to said piston forcing molten metal from said pot through said piston and said nozzle into said die.

2. In a die casting machine including a molten metal pot and a nozzle having a passage therethrough through which molten metal is injected into a die, a pressure chamber means for transferring molten metal under pressure from said pot to said nozzle, said pressure chamber means including a piston and pivot means swingably mounting said pressure chamber and piston on said machine with the lower end of said pressure chamber and piston submerged in the molten metal in said pot, pivoted lever means removably locking said piston pivot means in its swingable position on said machine, a cylinder slidably mounted on the lower end of said piston having an aperture therein through which molten metal enters the cylinder when the said cylinder is in an extended position in respect to the end of said piston, the said piston having a communicating passage from said cylinder located to register with said nozzle passage when said piston is swung against said nozzle, means removably securing said piston in pressure tight relationship against said nozzle, and means reciprocating said cylinder in respect to said piston forcing molten metal from said pot through said piston and said nozzle into said die.

3. In a die casting machine including a molten metal pot and a nozzle leading to a die, a pressure chamber comprising a piston removably and swingably suspended on said machine, a cylinder having an inlet thereto normally submerged in said pot slidably mounted on the lower end of said piston, the said piston having an outlet therefrom communicating with said nozzle, means releasably securing said piston in said piston-to-nozzle communicating position during the operation of the die casting machine, a cage carrying said cylinder, means reciprocating said cage and the cylinder carried thereby in respect to said piston, readily separable connecting means between said cage and said means reciprocating said cage to facilitate removal of said cage and cylinder from said piston, said separable connecting means including thrust rods engaging said cylinder to hold the same in a fixed position against the bottom of said cage, the said piston,

cage and cylinder carried thereby being swingable as a unit out of said molten metal to drain the same when the machine is not in operation.

4. In a die casting machine including a molten metal pot and a nozzle having a passage therethrough through which molten metal is injected into a die, a pressure chamber for transferring molten metal under pressure from said pot to said nozzle, said pressure chamber including a piston swingably mounted on said machine having its lower end submerged in the molten metal in said pot, a cylinder, slidably mounted on the lower end of said piston having an aperture therein through which'molten metal enters said cylinder when the said cylinder is in an extended position in respect to the end of said piston, the said piston having a communicating passage from said cylinder located to register with said nozzle passage when said piston is swung thereagainst, means removably securing said piston in said swung position, a cage carrying said cylinder, means reciprocating said cage and the cylinder carried thereby in respect to said piston whereby to force molten metal to said die, and key means on the bottom of said cylinder registerable with a keyway in the bottom of said cage maintaining said cylinder oriented to present the molten metal aperture therein at the lower side of said cylinder.

5. In a die casting machine including a'molten metal pot and a nozzle having a passage therethrough through which molten metal is injected into a die, a pressure chamber for transferring molten metal under pressure from said pot to said nozzle, said pressure chamber including a piston swingably mounted on said machine having its lower end submerged in the molten metal in said pot, a cylinder slidably mounted on the lower end of said piston having an aperture therein through which molten metal enters said cylinder when the said cylinder is in an extended position in respect to the end of said piston, the said piston having a communicating passage from said cylinder located to register with said nozzle passage when said piston is swung thereagainst, pivoted spring loaded lever means removably securing said piston resiliently locked in said swung position whereby to accommodate the assembly to expansion and contraction, a cage carrying said cylinder, means reciprocating said cage and the cylinder carried thereby in respect to said piston whereby to force molten metal to said die.

6. In a die casting machine including a molten metal pot and a nozzle having a passage therethrough through which molten metal is injected into a die, a pressure chamber for transferring molten metal under pressure from said pot to said nozzle, said pressure chamber including a piston, pivot means swingably mounting said piston on said machine with the lower end of said piston submerged in the molten metal in said pot, pivoted lever means re-. movably locking said piston pivot means in its swingable position on said machine, a cylinder slidably mounted on the lower end of said piston having an aperture therein through which molten metal enters the cylinder when the said cylinder is in an extended position in respect to the end of said piston, the said piston having a cornmunicating passage from said cylinder located to register with said nozzle passage when said piston is swung against said nozzle, spring loaded means removably securing said piston in pressure tight relationship against said nozzle, a cage carrying said cylinder, means reciprocating said cage and the cylinder carried thereby in respect to said piston whereby to force molten metal to said die, readily separable connecting means between said cage and said means reciprocating said cage to facilitate removal of said cage and cylinder from said piston, said connection including thrust rods engaging said cylinder to accomplish its return stroke, and means interconnecting said cylinder and said cage orienting said cylinder Within said cage, to lnaiin tain the. molten metal aperture in said cylinder at the lower side thereof, the said piston, cage and cylinder carried thereby being swingable as a unit out of said References Cited in the file of this patent molten metal to drain the same when the machine is not 10 215 82,029

in operation.

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