EP0670758B1

EP0670758B1 - Cold chamber die casting machine injection system

Info

Publication number: EP0670758B1
Application number: EP93924481A
Authority: EP
Inventors: Guido Perrella; Nicolas Bigler
Original assignee: Unicast Technologies Inc
Current assignee: Unicast Technologies Inc
Priority date: 1992-11-17
Filing date: 1993-11-17
Publication date: 1998-09-16
Anticipated expiration: 2013-11-17
Also published as: BR9307460A; KR950704074A; KR100307908B1; CA2083082C; AU685403B2; EP0670758A1; DE69321137T2; ES2125355T3; JP3386466B2; AU5415894A; JPH08505323A; ATE171093T1; CA2083082A1; DE69321137D1; WO1994011136A1; DK0670758T3

Abstract

An injection unit for a cold chamber die casting machine having dies which close on a part line, the injection unit being comprised of an open upwardly inclined injection sleeve (29), an injection plunger (28), means to advance and retract the injection plunger (28) and means to control the extent of advance or retraction of the injection plunger (28), the top of the injection sleeve (29) being disposed at or proximate the part line during die casting.

Description

This invention relates to a top filling injection unit in accordance with the preamble to the attached Claim 1 and to a method of injecting metal in accordance with the preamble to Claim 6.

The injection unit includes an upwardly disposed injection sleeve having an open top which is adapted to be top filled with molten metal. The volume of the injection sleeve is varied by adjusting the lower position of the plunger in the injection sleeve. The injection unit is used with a die casting machine having a fixed die attached to a fixed platen. The top of the injection sleeve is proximate or on the part line at which the dies close. The plunger in the injection sleeve is adapted to force the hot metal into the die cavity after the dies are locked.

An injection sleeve receiver adapted to receive the injection sleeve is connected to the fixed platen immediately below the fixed die which is also connected to the fixed platen. The injection sleeve may be withdrawn from the injection sleeve receiver for servicing and returned to the injection sleeve receiver, where it remains during casting operations.

In preparation for top filling the injection sleeve with molten metal, the dies are opened, the top of the injection sleeve extends into an injection sleeve receiver which is fastened to the fixed die so as to present an open cylinder adapted to receive hot metal by ladle or other means. The volume of the injection sleeve is controlled by controlling the position of the injection plunger in the injection sleeve. The position of the injection plunger is controlled so that the size of the metal shot required for a particular casting will substantially top up the injection sleeve when the injection sleeve is filled with molten metal.

The extent of retraction of the injection plunger is adjusted relative to the volume of molten metal required to complete the metal casting. For a large metal casting requiring considerable metal, the injection plunger is retracted deeply into the injection sleeve whereas for a smaller casting requiring less metal, the plunger is retracted less deeply into the injection sleeve. It is desirable that the injection sleeve be top filled by ladling or other means approximately to the top of the injection sleeve to minimize air inclusion during the casting operation.

After the injection sleeve is filled with metal the moving platen and moving die are closed on the part line, clamping pressure is applied to the moving platen and die, the injection plunger is advanced driving the molten metal through a runner in the face of the moving die into the cavity. When the casting is sufficiently solid the injection plunger is retracted, the clamping pressure is released and the moving platen and die are opened. The casting and biscuit are simultaneously removed with the opening of the moving die. When the dies are open, molten metal may be ladled or otherwise transferred into the injection sleeve prior to the next cycle.

The injection system of this invention avoids any ninety degree turns between the injection sleeve and the dies in which the casting is effected. The forcing of molten metal into the dies through a combination of turns may result in pressure drops causing the metal to cool or in the alternative introducing the molten metal at a higher temperature to allow for temperature loss. The instant injection system without any ninety degree turns between the injection sleeve and the runner or dies is consistent with maintaining a suitable time cycle per shot.

One problem in some existing die casting machines is caused by air entrapment associated with ninety degree turns between the injection sleeve and the dies in which casting is effected. Air entrapment is caused by wave fronts created as the metal approaches and travels around a ninety degree turn into the runners and cavity. Transferring molten metal around ninety degree turns also causes unwanted load losses and turbulence.

Some metals such as liquid aluminum used in cold chamber die casting are very corrosive. In prior die casting machines for casting aluminum, the aluminum travelled a substantial distance before reaching the cavities in the mold. Being highly corrosive the longer the distance the liquid aluminum has to travel, the greater the wear on the delivery system. In this invention the injection sleeve when in operative position is immediately adjacent the part line. The aluminum or other corrosive metal has a very short distance to travel during injection.

In the processes of filling the injection sleeve the liquid metal is ladled, poured or otherwise transferred directly into the top of the injection sleeve, which is open when the dies of the die casting machine are opened. The opening at the top of the injection sleeve is closed by the closing of the moving platen and moving die. The injection unit is disposed either below the dies or at an angle up to 15° below the horizontal centerline through the dies. The instant invention has the advantage of easy top ladling or transfer by robot of molten metal into the top opening of the injection sleeve. Metal filling of the injection sleeve close to the top of the injection sleeve results in less entrapped air in the injection sleeve when the top of the injection sleeve is closed by the moving die.

The avoidance of any ninety degree angles between the sleeve of the injection unit and the cavity of the dies results in less entrapped air.

The injection unit of the instant invention includes an injection plunger which displaces the molten metal from the injection sleeve through a short runner directly into the die cavity. The die filling is less affected by gravity than most existing machines. The injection system for a die casting machine disclosed herein has a metal to air ratio of 80/90% compared with 30% for some conventional machines.

The applicant's earlier Canadian Patent Application No. 2 045 879-8 entitled Die Casting Machine disclosed an improved die casting machine which has a frame comprising two opposed fixed end platens separated by two connecting rods, a moving platen being mounted on said connecting rods. The moving platen and the opposed fixed platen have dies mounted thereon for closing and clamping prior to casting. The patent application also discloses a novel and an improved injection system in which said injection system is disposed in close proximity to the fixed die so that the injection nozzle may be inserted in the bottom portion of the fixed die below the cavity.

The injection unit of this invention differs in important respects from the invention disclosed in the earlier application referred to above. In the invention which is the subject matter of this invention, the liquid metal is ladled or otherwise transferred directly into the opening at the top of the injection unit receiver of the injection sleeve. The volume of the liquid metal which must be injected varies from casting to casting. To minimize air entrapment, the bottom position of the injection plunger is adjusted so that the volume of the interior of the injection sleeve is substantially topped up with molten metal whether the casting calls for a small volume or larger volume of metal. Other differences include temperature control of the injection plunger and temperature control of the injection sleeve. A still further difference is the projecting shape of the injection plunger head which is so shaped as to reduce the size of the biscuit left cooling in the top of the injection sleeve when the casting is cooled. The injection plunger is retracted as soon as the metal has solidified. The biscuit cooling on the top of the injection sleeve remains attached to the runner and casting and is removed from the part line with the withdrawal of the moving platen and moving die. The biscuit and runner are subsequently trimmed from the casting during the trimming operation. The fact that the biscuit is limited in size and is removed with the moving die leaves the top of the injection sleeve free of debris and ready for filling for the next shot.

UK Patent Application GB-2 123 326-A discloses an injection unit for a cold chamber die casting machine in which an inclined cylindrical passage is formed in the fixed mould and fixed platen. An injection mould cylinder is inserted in the inclined cylindrical passage through the fixed platen but not through the fixed mould. A drive piston is located in the injection mould cylinder. The injection mould cylinder includes a molten metal inlet located in the injection mould cylinder a substantial distance below the fixed platen. The drive piston is withdrawn below the molten metal inlet and molten metal is supplied to the injection mould cylinder through the molten metal inlet until there is sufficient molten metal in the injection mould cylinder for the next casting. As will be seen in the drawings of GB-2 123 326-A, the molten metal poured into the molten metal inlet settles in the injection mould cylinder but not in the cylindrical passage in the fixed mould. In contrast, in the invention of this application, the molten metal is top filled through the fixed die such that the molten metal is proximate the face of the fixed die. In the invention of this application the bottom or retracted position of the piston is controlled so that the void in the top of the injection cylinder is substantially equal to the molten metal required for the next casting. The injection cylinder is substantially filled leaving very little space for air at the top of the injection cylinder.

United States Patent 4 006 774 to Mikulski comes closest to the inventions according to Claims 1 and 6 and discloses a Die Casting Apparatus Which Eliminates Shot Sleeve Metal Contact. The patent discloses vertical shot sleeves or inclined shot sleeves in which the shot sleeves extend through both the fixed platen and the fixed die to the part plane. The shot sleeves serve as a cylinder for a reciprocating piston which delivers the molten metal to the narrow runner and die cavity. The reciprocating plunger features an upper face cavity which is adapted to receive sufficient molten metal to fill the runners and the die cavity. Molten metal is poured into the upper face cavity of the reciprocating piston through a pour hole in the shot sleeve positioned a substantial distance below the fixed platen and fixed die. The invention of U.S. Patent 4 006 774 does not disclose top filling of the injection sleeve at the part line such that the molten metal is proximate the runners and the opening in the dies adapted to receive the molten metal. A further difference between the invention of this application and that of US Patent 4 006 774 lies in the fact that in the instant application, larger or smaller volumes of molten metal may be retained proximate the top of the injection sleeve by controlling the lower position of the injection piston. US Patent 4 006 774 would require piston heads with substantial cavities to receive the molten metal required for large castings. The instant invention does not require air vents running through the fixed platen and fixed dies to vent air above the pour vent when the plunger is advanced upwardly in the injection sleeve.

One embodiment of the invention is an injection unit for a cold chamber die casting machine having a part line on which the dies meet, the injection unit being comprised of an open upwardly inclined injection sleeve, an injection plunger, means to advance and retract the injection plunger and means to control the extent of retraction of the injection plunger, the top of the injection sleeve being disposed at or proximate the part line.

Additional embodiments of the invention are defined in dependent Claims 2 - 5.

The invention also relates to a method of injecting molten metal in a cold chamber die casting machine having a moving die and a fixed die, the fixed die fastened to a fixed platen, the fixed die and the moving die meeting on the part line, a cylindrical passage in the fixed die, a top filling injection sleeve located within the cylindrical passage disposed at a vertical or inclined angle located in the injection sleeve, the top of the injection sleeve is located at or proximate the part line, an injection piston to control the bottom position of the injection plunger in the injection sleeve, the injection plunger being adapted to receive or dispel molten metal from the injection sleeve, the method comprising locating the bottom position of the injection plunger in the injection sleeve so that the volume of the void in the top portion of the injection sleeve corresponds to the volume of hot metal required for the next shot, opening the moving die a sufficient distance to top fill the injection sleeve at the part line, top filling the injection sleeve substantially to the top with molten metal, closing the moving die on the fixed die, operating the piston and injection plunger to inject the molten metal into the dies.

Figure 1 is a side elevation view of a cold chamber die casting machine with an injection unit connected to the end of the machine to which the fixed platen and fixed die are connected.

Figure 2 is a perspective view of the injection unit connected to the machine base at one end of the cold chamber die casting machine.

Figure 3 is a cross-sectional view along the longitudinal centerline of the injection unit showing the injection plunger in retracted position adapted to receive hot liquid metal.

Figure 4 is a cross-sectional view along the longitudinal centerline of the top of injection unit showing the relationship of the injection unit to the closed left and right hand side dies during the injection step.

Figure 5 is a cross-sectional view along the longitudinal centerline of the injection unit showing a protruding cooled nose extending from the face of the left hand side die in close proximity to an injection plunger with a flat face.

Figure 6 is a side elevation view of a 4-tie bar cold chamber die casting machine with toggles.

Figure 7 is a cross-sectional view through a cold chamber die casting machine in which the injection unit is disposed in a bevel sleeve in an aperture in the base of the fixed die.

Referring to Figure 1, there is shown a cold chamber die casting machine 1 with an injection unit 2 mounted on the right hand end of the cold chamber die casting machine 1. The cold chamber die casting machine 1 is comprised of a die casting machine base 3. A fixed right hand platen 4 is mounted towards the right hand end of die casting machine base 3 and a fixed left hand side platen 5 is mounted above the left hand end of die casting machine base 3. The fixed right and

left hand platens

4,5 have rods 6,7 mounted therethrough. A moving platen 8 is mounted on rods 6,7 for movement towards the fixed right hand platen 4 or withdrawal from fixed right hand platen 4. The moving platen 8 is moved towards fixed left hand side platen 5 or withdrawn from fixed left hand side platen 5 by hydraulics, toggles or other mechanical means known in the art represented by number 9. Cooling base 10 and moving die 11 are mounted on moving platen 8. Fixed platen cooling base 12 and fixed die 14 are mounted on fixed right hand side platen 4.

As seen in Figures 1 and 2, injection unit 2 is mounted by front and rear brackets 20,21 and injection

unit support arms

22,23 to the right hand end of die casting machine base 3 and fixed right hand side platen 4 respectively.

The injection unit 2 is comprised of an injection cylinder 24 having a piston 25 mounted near the base of the injection cylinder 24 for movement of the injection plunger 28 towards and away from the fixed right hand side platen 4, cooling base 12 and fixed die 14. A piston rod 26 is connected at one end to the piston 25 and at the other end to the piston rod-injection plunger connecting link 27. The piston rod-injection plunger connecting link 27 is connected at its upper end to injection plunger 28.

As seen in Figure 1, the moving die 11 is mounted on cooling base 10 which in turn is mounted on moving platen 8. As seen in Figure 4, the face of moving die 11 closes on the part line immediately prior to injection, and remains on the part line during injection and until the injected metal solidifies sufficiently to withdraw the moving platen 8, cooling base 10 and moving die 11 away from the fixed die 14 mounted on fixed platen cooling base 12. The face of moving die 11 attached to cooling base 10 attached to the moving platen 8 includes a runner 30 through which the molten metal 31 travels to the cavity 32 between moving die 11 and fixed die 14.

Figure 5 discloses an injection plunger 28 having a flat face as opposed to the nose of the injection plunger 28 shown in Figure 4. The left hand die 11 has a protruding cooled nose 37 which extends across the part line between the left hand die 11 and right hand die 14 when the dies are closed. When the dies are opened after the casting has solidified, the casting, runner and biscuit 35 are withdrawn with the left hand die 11 which is connected to the left side moving platen 8.

Referring to Figure 4, an injection unit receiver 33 is mounted below the fixed die 14. In the event of corrosion or damage to the injection unit receiver 33, the injection unit receiver 33 may be replaced without replacing the fixed die 14. The injection unit receiver 33 has a cylindrical passage 34 adapted to receive injection sleeve 29.

Referring to Figure 7, a fixed die 14 is disclosed which has a cylindrical passage 34 adapted to receive injection sleeve 29. In Figure 7 the injection sleeve 29 is inserted directly into the cylindrical passage 34 in the fixed die 14 as opposed to being inserted in an injection unit receiver 33 as shown in Figure 4. As shown in Figure 7, the injection sleeve 29 extends upwardly substantially to the part die.

Referring to Figures 1 and 4, the piston 25, piston rod 26 and piston rod-injection plunger connecting link 27 may be withdrawn from the injection sleeve 29 if the piston 25, piston rod 26 and piston rod-injection plunger connecting link 27 require adjustment or repair. The injection sleeve 29 is inserted and retained in the cylindrical passage 34 in fixed die 14. The range of movement of piston 25 in injection cylinder 24 is adjusted with each die so as to reduce air at the top of the injection sleeve 29 to a minimum during filling of the injection sleeve 29 with molten metal and secondly to limit the size of the biscuit 35 remaining above the injection plunger 28 when the casting 36 cools.

While the injection unit 2 is shown in Figures 1 to 3 mounted on the right hand end of the cold chamber die casting machine 1 in such a manner that the injection unit 2 extends upwardly at forty-five degrees relative to the right hand end of the cold chamber die casting machine 1, it will be appreciated by those skilled in the art that the angle of the injection unit 2 relative to the dies may extend from vertical, where the injection power unit 2 would be located under the part line on which the moving die 11 and the fixed die 14 meet anywhere up to approximately 20° relative to horizontal, where the benefits of gravity and control of air entrapment are greater.

As seen in Figures 1 and 3, the moving platen 8 is withdrawn from the fixed right hand side platen 4. The top of the injection sleeve 29 is open at the part line and adapted to receive molten metal. The injection plunger 28 has been withdrawn within the injection sleeve to a position such that when the injection sleeve 29 is filled with molten metal, the injection sleeve 29 will be substantially topped up with metal decreasing air entrapment during the injection cycle. When the injection sleeve 29 is filled, the moving left hand side platen is moved towards the part line until the moving die 11 closes on the fixed die 14, as shown in Figure 4. Following the closing of the moving die 11 and fixed die 14, the dies are clamped shut prior to injection of the molten liquid. After clamping, the injection plunger 28 is advanced towards the part line driving the molten liquid in the injection sleeve 29 into the runner 30 and cavity 32 between the moving die 11 and the fixed die 14. When the molten liquid has solidified into a casting the injection plunger 28 is withdrawn within the injection sleeve 29, and the left side moving platen 8 and moving die 11 are withdrawn from the part line. The casting, runner and biscuit 35 are withdrawn with the moving die 11 which is connected to the left side moving platen 8. The casting, runner and biscuit 35 are subsequently removed from the moving die 11 and runner 30 by ejection pins prior to commencement of the next cycle. The injection plunger 28 is withdrawn within injection sleeve 29 prior to the addition of molten metal to the injection sleeve 29 as part of the next cycle.

Claims

A top filling injection unit (2) for a cold chamber die casting machine (1),

the cold chamber die casting machine (1) having a fixed platen (4), a moving platen (8), a fixed die (14) and a moving die (11),

the fixed die (14) is mounted on the fixed platen (4) and the moving die (11) is mounted on the moving platen (8),

a part line on which the moving die (11) and fixed die (14) meet,

the top filling injection unit (2) consisting of an open upwardly inclined injection sleeve (29), an injection plunger (28), an injection plunger-piston connecting link (27), an injection cylinder (24) and an injection piston (25),

the injection plunger (28) connected by the injection plunger-piston connecting link (27) to the injection piston (25),

the injection piston (25) located in the injection cylinder (24),
characterized by an aperture in the fixed die (14) defining an opening,

the injection sleeve (29) is secured in the opening in the fixed die (14) with the top of the injection sleeve (29) proximate the part line,

the injection plunger (28) having a variable retracted filling position,

the injection piston (25) having an upper injection position in which the position of the connected injection plunger (28) is proximate the part line.
The top filling injection unit (2) for a cold chamber die casting machine (1) of Claim 1 having a fixed die (14), a moving die (11) and an injection unit receiver (33) substituted for the lower part of fixed die (14), the injection unit receiver (33) having a cylindrical passage (34) therein, the injection unit receiver (33) is disposed below a truncated fixed die (14) and is adapted to receive the upwardly inclined injection sleeve (29) in the cylindrical passage (34) therein.
The top filling injection unit (2) for a cold chamber casting machine (1) of Claim 1, in which the top of the injection plunger (28) has an upwardly and outwardly extending surface.
The top filling injection unit (2) for a cold chamber die casting machine (1) of Claim 2 including injection unit support means (20,21,22,23), the injection unit (2) is connected to the die casting machine base (3) and the fixed platen (4) by injection unit support means (20,21,22,23).
The top filling injection unit (2) for a cold chamber die casting machine (1) of Claim 1, in which the moving die (11) has a protruding cooled nose (37), which extends across the part line between the moving and fixed die (11,14) when the dies are closed.
A method of injecting molten metal in a cold chamber die casting machine (1) having a moving die (11) and a fixed die (14), the fixed die (14) fastened to a fixed platen (4), the fixed die (14) and moving die (11) meeting on the part line a cylindrical passage (34) in the fixed die (14), a top filling injection sleeve (29) located within the cylindrical passage (34) disposed at a vertical or inclined angle located in the injection sleeve (29), the top of the injection sleeve (29) is located at or proximate the part line, an injection piston (24) to control the bottom position of the injection plunger (28) in the injection sleeve (29), the injection plunger (28) being adapted to receive or dispel molten metal from the injection sleeve (29), the method being characterized by

locating the bottom position of the injection plunger (28) in the injection sleeve (29) so that the volume of the void in the top portion of the injection sleeve (29) corresponds to the volume of hot metal required for the next shot,

opening the moving die (11) a sufficient distance to top fill the injection sleeve (29) at the part line,

top filling the injection sleeve (29) substantially to the top with molten metal,

closing the moving die (11) on the fixed die (14),

operating the piston (25) and injection plunger (28) to inject the molten metal into the dies (11,14).