CA2152758A1 - Process and apparatus for pressure die-casting - Google Patents
Process and apparatus for pressure die-castingInfo
- Publication number
- CA2152758A1 CA2152758A1 CA002152758A CA2152758A CA2152758A1 CA 2152758 A1 CA2152758 A1 CA 2152758A1 CA 002152758 A CA002152758 A CA 002152758A CA 2152758 A CA2152758 A CA 2152758A CA 2152758 A1 CA2152758 A1 CA 2152758A1
- Authority
- CA
- Canada
- Prior art keywords
- die
- molten metal
- injection
- plunger
- sleeve
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 238000004512 die casting Methods 0.000 title claims abstract description 26
- 238000000034 method Methods 0.000 title claims abstract description 23
- 238000002347 injection Methods 0.000 claims abstract description 113
- 239000007924 injection Substances 0.000 claims abstract description 113
- 239000002184 metal Substances 0.000 claims abstract description 112
- 229910052751 metal Inorganic materials 0.000 claims abstract description 112
- 238000004519 manufacturing process Methods 0.000 claims description 22
- 238000010438 heat treatment Methods 0.000 claims description 12
- 239000012809 cooling fluid Substances 0.000 claims description 11
- 238000006073 displacement reaction Methods 0.000 claims description 8
- 238000005266 casting Methods 0.000 claims description 6
- 238000004140 cleaning Methods 0.000 claims description 6
- 230000002093 peripheral effect Effects 0.000 claims description 6
- 238000009826 distribution Methods 0.000 claims description 5
- 238000004422 calculation algorithm Methods 0.000 claims description 4
- 238000007664 blowing Methods 0.000 claims description 3
- 238000007493 shaping process Methods 0.000 claims description 3
- 238000005058 metal casting Methods 0.000 claims description 2
- 238000005086 pumping Methods 0.000 claims 1
- 230000001105 regulatory effect Effects 0.000 abstract description 10
- 238000012545 processing Methods 0.000 description 16
- 238000001816 cooling Methods 0.000 description 12
- 229910045601 alloy Inorganic materials 0.000 description 10
- 239000000956 alloy Substances 0.000 description 10
- 238000002844 melting Methods 0.000 description 7
- 230000008018 melting Effects 0.000 description 7
- 239000012530 fluid Substances 0.000 description 5
- 150000002739 metals Chemical class 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 230000001276 controlling effect Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 229910001092 metal group alloy Inorganic materials 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 238000004364 calculation method Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000000523 sample Substances 0.000 description 2
- 229910000838 Al alloy Inorganic materials 0.000 description 1
- 101100493705 Caenorhabditis elegans bath-36 gene Proteins 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- 229910001361 White metal Inorganic materials 0.000 description 1
- 239000004411 aluminium Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 238000007596 consolidation process Methods 0.000 description 1
- 239000000498 cooling water Substances 0.000 description 1
- 238000005485 electric heating Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 239000011810 insulating material Substances 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 125000006850 spacer group Chemical group 0.000 description 1
- 238000013022 venting Methods 0.000 description 1
- 239000010969 white metal Substances 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D17/00—Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
- B22D17/20—Accessories: Details
- B22D17/30—Accessories for supplying molten metal, e.g. in rations
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D17/00—Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
- B22D17/20—Accessories: Details
- B22D17/2015—Means for forcing the molten metal into the die
- B22D17/2038—Heating, cooling or lubricating the injection unit
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D17/00—Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
- B22D17/20—Accessories: Details
- B22D17/32—Controlling equipment
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Injection Moulding Of Plastics Or The Like (AREA)
- Molds, Cores, And Manufacturing Methods Thereof (AREA)
- Manufacture Of Alloys Or Alloy Compounds (AREA)
Abstract
A process and an apparatus for the die-casting of pressure-cast metal parts according to which a metered quantity of the molten metal in a furnace is fed, under pressure, into the cavity of a die assembly by means of an injection device operated under controlled pressure and speed conditions; the molten metal is supplied at a pressure ranging between 50 and 350 Atm (4,9 - 34,3 MPa), and under laminar flow conditions by means of a thermally controlled injection device comprising zones thermally regulated at different temperatures for maintaining a condition of axial alignment between the chamber and the plunger of the injection device.
Description
2 21 52 7~ 8 PROCESS AND APPARATUS FOR PRESSURE DIE-CASTING
~ackground of the Invention The present invention relates to the pressure die-casting of metals, in particular light metals or whitemetals, such as for example aluminium, magnesium or other metals and their alloys, and more particularly 5. refers to a process and an apparatus for the pressure die-casting of metal-alloy wheels or pressure-cast pieces in general, by means of wbich injection of the molten metal into the cavity of a die may be performed under controlled temperature, pressure and speed lo. conditions in order to produce high-quality pressure-cast pieces.
In the production of pressure-casting, for example alloy wheels, it is necessary to ensure that the cast piece has optimum resistance and mechanical isotropy 5. characteristics, i.e. is defect-free, has no air inclusions and is able to withstand the high stresses to which this piece is normally subjected during use; in certain cases, such as for example for alloy wheels, it is generally required that there should be a good 20. surface finishing and good pressure sealing properties on the rim of the tyre.
In the production of pressure-cast pieces designed to have optimum mechanical properties, such as for example alloy wheels, currently use is made exclusively of low-pressure die-casting proces~es, according to which the molten metal is fed into the cavity of the die by means of compressed air, at a pressure of the order 5- of about 1 Atm ~101 KPa).
The use of low-pressure die-casting techniques, as compared to high-pressure die-casting processes normally performed with horizontal-type machines which use pressures of the order of 500-800 Atm (49 - 78,4 MPa) or lO. more, has in practice proved necessary in order to avoid air-inclusion phenomena and the formation of blisters which generally tend to weaken the structure of the piece, making it fragile and more prone to breakage under high stresses.
15. Although, with the use of low pressure, pieces having good mechanical properties and an acceptable surface finish are obtained, the low pressure technique nevertheless involves an extremely long operating cycle and low productivity. Moreover, the low pressure 20. requires that the die be formed with metal flow channels and passage~ having a large cross-sectional area in order to ensure that the metal in the molten state r when it comes into contact with the cold walls of the die, does not solidify rapidly, blocking said passage~ and 25. channels totally or partially and preventing total 4 2l ~27~8 filling of the die cavity. With low pre~sure it is therefore necessary to increase considerably the cross-sectional areas of the ducts for flowing of the molten metal, thereby increasing the dimensions of the die, the 5. mass of material and the weight of the cast piece.
Moreover, the surface finish of a piece produced at low pressure is of a fairly poor quality and, in the case of alloy wheels, requires additional finishing operations at the point where the material i8 fed into the die.
lO. Moreover, the pieces obtained by means of low pressure have a low mechanical isotropy such that they must undergo additional heat treatment which is particulary delicate in that they must reach temperatures in the region of or substantially close to 5. the melting point of the metal.
In the production of pressure-cast metal pieces it has therefore been attempted to use high-pressure injection systems; systems of this kind are described for example in ~S-A-4,850,420, US-A-4,583,579, DE-A-20. 3,636,936, DE-A-3,013,226 and DE-A-3,505,554.
According to these known systems the molten metal is fed horizontally into the cavity of the die, exerting a very high pressure, equal to or greater than 500-800 Atm (49 - 78 ~ 4 MPa), and with high speeds, ranging between 40 and 120 m/s, obtaining cast pieces with a 5 21527~8 high surface finish, in extremely fast cycle-times.
However, high pressure in the production of pressure-cast pieces intended to withstand high mechanical stresse~ has proved to be unsuitable owing to the extreme fragility of the pieces themselves as a result of the phenomenon of air-inclusion produced by the high speed and the turbulent movement of the molten metal which is injected.
In high-pressure die-casting operations, with lo. machines of the horizontal type, there is also the problem of inade~uate thermal control of the process and the machine itself, in that the device injecting the molten metal is subiect to extreme and uncontrollable mechanical deformations which result in misalignment 15. between the molten metal collection chamber and the plunger of the said injection device. Typical arrangements of the injection device and molten metal in horizontal pressure die-casting machines are described in the prior documents cited above. In particular, the 20. patent ~S-A-4,583,579 proposes monitoring the expansions of the chamber and the plunger of the injection device in order to calculate the instant when the plunger is to be retracted, depending on the temperatures measured following each injection; this patent also refers 25. generally to the use of means for cooling the plunger and a part of the injection chamber in an entirely uncontrolled manner. This document does not deal with and therefore does not propose any useful solution to the basic problem of pressure die-casting, which 5. consists in obtaining conditions for the injection of molten metal which are controlled and suitable for the production of pressure-cast pieces with optimum mechanical properties and surface finish.
The use of pressure die-casting machines of the lo. vertical type is illustrated in GB-A-489,944, DE-A-1,156,205 and in JP-A 01 178,359; however, these documents also refer to pressure die-casting machines of the high-pressure type which have the drawback~
indicated above. In particular the patents GB-A-489,944 15. and JP-A 01 178,359 relate to a machine with an injection chamber of the "open" type in which the molten metal must be poured from above, causing the well-known phenomena of oxidation of the molten metal owing to its long exposure to air, prior to injection. Therefore, in 20. the production of pressure-cast pieces, in particular alloy wheels or pieces for which optimum mechanical properties are re~uired, high-pressure die-casting, using machines of the horizontal and vertical type, has been entirely abandoned.
25. Moreover, the efficiency of the operating cycle is 7 2I527~8 extremely limited. The patent DE-A-1,156,205 which defines the technological background closest to that of the present invention, as defined in the pre-characterizing part of Claim 1, illustrates a vertical5. pressure die-casting machine of the "closed" chamber type in which the injection device is directly connected, via a duct, to a furnace supplying the molten metal and in which the injection device comprises a vertical injection chamber and a plunger movable inside o. said chamber, between a retracted position, where it uncovers a lateral feed opening for the molten metal, and an advanced position where the molten metal is injected into the cavity of a die. However, this document also does not deal with and solve the basic 5. problem of control of the pressure die-casting process for the production of high-quality metal pieces.
Despite the fact that many ideas have been proposed or suggested for the use of horizontal or vertical type machines in the production of pressure-cast metal pieces, nowadays in practice use must still be made of low-pressure die-casting, along with the limitations and drawbacks which this technology involve~ in terms of the excessive weight and dimensions of the cast pieces, long production times and parts which are often unacceptable zs. from a quality point of view for many applications.
~ackground of the Invention The present invention relates to the pressure die-casting of metals, in particular light metals or whitemetals, such as for example aluminium, magnesium or other metals and their alloys, and more particularly 5. refers to a process and an apparatus for the pressure die-casting of metal-alloy wheels or pressure-cast pieces in general, by means of wbich injection of the molten metal into the cavity of a die may be performed under controlled temperature, pressure and speed lo. conditions in order to produce high-quality pressure-cast pieces.
In the production of pressure-casting, for example alloy wheels, it is necessary to ensure that the cast piece has optimum resistance and mechanical isotropy 5. characteristics, i.e. is defect-free, has no air inclusions and is able to withstand the high stresses to which this piece is normally subjected during use; in certain cases, such as for example for alloy wheels, it is generally required that there should be a good 20. surface finishing and good pressure sealing properties on the rim of the tyre.
In the production of pressure-cast pieces designed to have optimum mechanical properties, such as for example alloy wheels, currently use is made exclusively of low-pressure die-casting proces~es, according to which the molten metal is fed into the cavity of the die by means of compressed air, at a pressure of the order 5- of about 1 Atm ~101 KPa).
The use of low-pressure die-casting techniques, as compared to high-pressure die-casting processes normally performed with horizontal-type machines which use pressures of the order of 500-800 Atm (49 - 78,4 MPa) or lO. more, has in practice proved necessary in order to avoid air-inclusion phenomena and the formation of blisters which generally tend to weaken the structure of the piece, making it fragile and more prone to breakage under high stresses.
15. Although, with the use of low pressure, pieces having good mechanical properties and an acceptable surface finish are obtained, the low pressure technique nevertheless involves an extremely long operating cycle and low productivity. Moreover, the low pressure 20. requires that the die be formed with metal flow channels and passage~ having a large cross-sectional area in order to ensure that the metal in the molten state r when it comes into contact with the cold walls of the die, does not solidify rapidly, blocking said passage~ and 25. channels totally or partially and preventing total 4 2l ~27~8 filling of the die cavity. With low pre~sure it is therefore necessary to increase considerably the cross-sectional areas of the ducts for flowing of the molten metal, thereby increasing the dimensions of the die, the 5. mass of material and the weight of the cast piece.
Moreover, the surface finish of a piece produced at low pressure is of a fairly poor quality and, in the case of alloy wheels, requires additional finishing operations at the point where the material i8 fed into the die.
lO. Moreover, the pieces obtained by means of low pressure have a low mechanical isotropy such that they must undergo additional heat treatment which is particulary delicate in that they must reach temperatures in the region of or substantially close to 5. the melting point of the metal.
In the production of pressure-cast metal pieces it has therefore been attempted to use high-pressure injection systems; systems of this kind are described for example in ~S-A-4,850,420, US-A-4,583,579, DE-A-20. 3,636,936, DE-A-3,013,226 and DE-A-3,505,554.
According to these known systems the molten metal is fed horizontally into the cavity of the die, exerting a very high pressure, equal to or greater than 500-800 Atm (49 - 78 ~ 4 MPa), and with high speeds, ranging between 40 and 120 m/s, obtaining cast pieces with a 5 21527~8 high surface finish, in extremely fast cycle-times.
However, high pressure in the production of pressure-cast pieces intended to withstand high mechanical stresse~ has proved to be unsuitable owing to the extreme fragility of the pieces themselves as a result of the phenomenon of air-inclusion produced by the high speed and the turbulent movement of the molten metal which is injected.
In high-pressure die-casting operations, with lo. machines of the horizontal type, there is also the problem of inade~uate thermal control of the process and the machine itself, in that the device injecting the molten metal is subiect to extreme and uncontrollable mechanical deformations which result in misalignment 15. between the molten metal collection chamber and the plunger of the said injection device. Typical arrangements of the injection device and molten metal in horizontal pressure die-casting machines are described in the prior documents cited above. In particular, the 20. patent ~S-A-4,583,579 proposes monitoring the expansions of the chamber and the plunger of the injection device in order to calculate the instant when the plunger is to be retracted, depending on the temperatures measured following each injection; this patent also refers 25. generally to the use of means for cooling the plunger and a part of the injection chamber in an entirely uncontrolled manner. This document does not deal with and therefore does not propose any useful solution to the basic problem of pressure die-casting, which 5. consists in obtaining conditions for the injection of molten metal which are controlled and suitable for the production of pressure-cast pieces with optimum mechanical properties and surface finish.
The use of pressure die-casting machines of the lo. vertical type is illustrated in GB-A-489,944, DE-A-1,156,205 and in JP-A 01 178,359; however, these documents also refer to pressure die-casting machines of the high-pressure type which have the drawback~
indicated above. In particular the patents GB-A-489,944 15. and JP-A 01 178,359 relate to a machine with an injection chamber of the "open" type in which the molten metal must be poured from above, causing the well-known phenomena of oxidation of the molten metal owing to its long exposure to air, prior to injection. Therefore, in 20. the production of pressure-cast pieces, in particular alloy wheels or pieces for which optimum mechanical properties are re~uired, high-pressure die-casting, using machines of the horizontal and vertical type, has been entirely abandoned.
25. Moreover, the efficiency of the operating cycle is 7 2I527~8 extremely limited. The patent DE-A-1,156,205 which defines the technological background closest to that of the present invention, as defined in the pre-characterizing part of Claim 1, illustrates a vertical5. pressure die-casting machine of the "closed" chamber type in which the injection device is directly connected, via a duct, to a furnace supplying the molten metal and in which the injection device comprises a vertical injection chamber and a plunger movable inside o. said chamber, between a retracted position, where it uncovers a lateral feed opening for the molten metal, and an advanced position where the molten metal is injected into the cavity of a die. However, this document also does not deal with and solve the basic 5. problem of control of the pressure die-casting process for the production of high-quality metal pieces.
Despite the fact that many ideas have been proposed or suggested for the use of horizontal or vertical type machines in the production of pressure-cast metal pieces, nowadays in practice use must still be made of low-pressure die-casting, along with the limitations and drawbacks which this technology involve~ in terms of the excessive weight and dimensions of the cast pieces, long production times and parts which are often unacceptable zs. from a quality point of view for many applications.
The object of the invention is to provide a process and an apparatus for the vertical pressure die-casting of metal parts by means of which it is possible to operate at relatively high pressures, compared to low-5. pressure die-casting, which are nevertheless considerably lower than those normally used for the production of pieces cast using high-pressure techniques, ensuring at the same time fast production cycles and the realization of cast pieces with a high lo. surface quality and good mechanical properties, which cannot be obtained using other known technologies.
A further obiect of the present invention is to provide a process and an apparatus, as defined above, by means of which it is possible to reduce the phenomenon 5. of air inclusion and the formation of oxides in the molten metal, both during feeding of the metal into the injection device and during injection into the die, obtaining cast pieces with a high degree of mechanical isotropy, as a result of which, in certain cases, it is 20. possible to reduce substantially the resistant cross-sectional areas and hence the flow passages for the metals inside the die, achieving in this way cast pieces which are structurally strong, have thin walls and a comparatively very low weight J in extremely short 25. operating cycles; for example, in the case of alloy wheels it is possible to reduce the weight and the production cycle about 3 or 4 times, compared to a wheel normally produced under low pressure, obt~ining wheels with high mechanical and crystallographic properties of 5. the alloy used, as well as a superior finish.
Yet another object of the invention is to provide an apparatus for the production of alloy wheels according to the process mentioned above, substantially devoid of deformation phenomena affecting the parts o. intended to come into contact with the high-temperature molten metal, thus ensuring an operational and processing efficiency and reliability which cannot be achieved with the other known techniques.
A further object of the invention is to provide an 5. apparatus for pressure die-casting which uses in combination an injection device and a die particularly suitable for implementation of a medium-pressure die-casting process, according to the invention, as well a~the production of wheels of a different type, without 20. having to change the entire production die; for the purposes of the present invention "medium pressure" is understood as meaning a pressure for the injection of molten metal into the die ranging between 50 and 350 Atm (4,9 - 34,3 MPa).
lo 2152758 Summary of the Invention The above objects can be achieved by means of a proces~ and an apparatus for the production of metal-alloy pieces, in particular alloy wheel~, according to5. the pre~ent invention more particularly a process for the production of pressure-cast metal pieces has been provided, according to which a metered quantity of molten metal is fed into an injection device comprising a ~leeve defining a vertical injection chamber and a lo. plunger movable inside said chamber between a retracted position, where it uncovers a lateral opening for entry of the molten metal, and an advanced position, where the molten metal is injected into the cavity of a die a~sembly, characterized by:
5. - providing an axially aligned arrangement of the ~leeve and the injection plunger, while maintaining under different temperature controlled conditions the zones of the plunger and the part of the chamber of the injection sleeve located in the vicinity of the 20. pres~ure-casting die assembly, which come into contact with the molten metal;
- detecting the temperatures of the plunger and the injection sleeve in the region of the ~aid temperature controlled zones; and 25. - injecting the molten metal into the cavity of the 11 21$2758 die assembly upon reaching of a predetermined temperature difference between said temperature controlled zones of the sleeve and the injection plunger, at a pressure ranging between 50 and 350 Atm 5. (4,9 - 34,3 MPa), maintaining laminar flow conditions of the molten metal while it is injected and flows into the cavity of the die assembly, ensuring the required axially aligned condition between sleeve and plunger of the injection device.
o. Brief description of the drawin~s These and other objects, features and advantages of the present invention will emerge more clearly from the description, together with the accompanying drawings, in which:
5. Fig. 1 is a general view of the apparatus with some sectioned parts;
Fig. 2 is a side view of the apparatus according to Figure l;
Fig. 3 is a longitudinal sectional view, on a 20. larger scale, of a first embodiment of the device for injecting molten metal into the shaping die;
Fig. 4 is an enlarged detail of the duct connecting the furnace to the molten-metal injection device;
Fig. 5 is a view along the line 5-5 of Figure 4;
Fig. 6 is a longitudinal sectional view of a second 12 21527~8 embodiment of the injection device;
Fig. 7 is a cross-sectional view along the line 7-7 of Figure 6;
Fig. 8 is an enlarged detail of the apparatus 5. according to Figure 1, with the die in the closed condition;
Fig. 9 is a view similar to that of the preceding figure with the die in the open condition.Fig. 10 i8 a general diagram of the ~ystem for temperature-regulation 10. of the injection device;
Fig. 11 is a general diagram of the system for controlling the pressures and speeds of injection of the molten metal into the die during pressure die-casting.
Description of the Invention As shown in Figures 1 and 2, the apparatus comprises a base 10 fixed to the floor opposite a pit 11, from which there emerge four side columns 12 held at the top by cross-beams 35.
A first movable platen 13 supporting the lower part 20. 14 of a die and an upper platen 15 supporting the upper part 16 of the die are movable between a position close to one another, where the die is closed, and a position far from one another, where the die is open, so as to allow respectively the injection of molten metal into the die and the removal of the cast piece, in the manner 13 215275~
illustrated below.
The raising and lowering movement of the lower platen 13 is obtained in a manner known per se by means of a pair of hydraulic cylinders provided in the bottom part of the apparatus, not shown; correspondingly, the movement of the upper platen 15 is obtained by means of a pair of hydraulic cylinders 17. In Figure 2, finally, 18 denotes an auxiliary cylinder supported centrally by the upper platen so as to perform closing and opening lo. operations of the die.
The apparatus comprises, moreover, a device 19 for injecting molten metal, contained in a furnace having a pressurised pot 20, provided movably on one side of the apparatus itself.
5. More precisely, the device 19 for injecting molten metal comprises a cylindrical sleeve 21 defining an injection chamber arranged vertically and centrally with respect to the base 10. Inside the sleeve 21 there slides a plunger 22 connected via a long rod 23 to a 20. hydraulic cylinder 23'.
As shown in Figure 3, the bottom part 21A of the sleeve 21, on one side thereof, has a radial inlet connector 24, downwardly slanted, which may be connected to the duct 25 of the furnace 20, as described further 25. below with reference to Figures 4 and 5 of the accompanying drawings.
The apparatus according to ~igures 1 and 2, on the side opposite to the furnace 20, comprises a service table 26 which may be used both for unloading the cast pieces and for replacing the die. The table 26 is slidably supported on a frame 27 and i8 operated so as to move forwards or backwards by means of a cylinder 28;
the support frame 27, in turn, slides along horizontal guides 29, as schematically shown.
lo. In Figure 1, finally, 30 denotes a tiltable chute for unloading the deadhead 31 which is conveyed away by means of a conveyor 32; the deadhead 31 is removed from the plunger 22 of the injection device, by a lateral pusher 46.
15. In ~igure 2 the reference number 33 denotes a locking member for the upper platen 15, positioned on one side of the cross-members 35 for locking the upper platen 15 in the closed condition of the die during the metal injection phase.
20. The furnace 20 containing the molten metal is of the pot type, i.e. designed to contain a given quantity 36 of a molten metal alloy which is constantly maintained at the melting temperature by means of a suitable heating system, not shown.
25. The furnace 20 is of the pressurised type; the air 215~758 under pressure is fed inside the furnace by a duct 37 connected to a pressurised-air source 38 by a filter 39, a solenoid valve 40 and a pressure regulator 41.
Moreover, in Figure 1, 42 denotes a probe which 5. penetrates inside the furnace so as to provide a signal indicating the height of the molten metal bath 36 and, consequently, an indication of the quantity of metal fed into the injection sleeve 21.
The furnace 20 is supported in a movable manner, lo. for example by means of a system of articulated ~ars 43 provided on a carriage 44 equipped with wheels sliding on rails; the furnace may be operated so as to be raised and lowered by means of a jack 45 or move on the rails by means of a hydraulic cylinder 45A. The movement of 5. raising and/or sliding of the furnace 20 is used to separate the duct 25 supplying the molten metal from the inlet connector 24 of the injection device 19, so as to allow cleaning or prevent the latter from heating excessively, causing dangerous uncontrolled expansion of 20. the injection sleeve 21 with respect to the thrusting plunger 22.
Moreover 47 in Figure 1 indicates, in the form of a solenoid valve symbol, the system for connecting the cylinder 23' to a pressurised-oil source 48. The 25. solenoid valves 40, 47, the probe 42 and suitable devices for controlling pressurisation of the furnace 20 and the temperature of the sleeve 21 and the injection plunger 22, as explained below, are appropriately connected, by means of suitable interface circuits, to a 5. programmable control unit 49 having a microprocessor which governs the entire production cycle.
A first embodiment of the device 19 for injecting molten metal is shown in the enlarged detail of Figure 3; the device 1~ comprise~ a cylindrical sleeve 21 which o. is suitably temperature-regulated by circulation of a diathermal fluid inside an insulating jacket 51 surrounding the sleeve itself. In particular, in the example of Figure 3, the sleeve 21 has two independent temperature-regulation zones, i.e. designed to be heated 5. and/or cooled during the production cycle, as explained below with reference to Figure 10, of which a first zone clo~e to or in the region of the ~haping die is heated and/or cooled by circulating a heating andJor cooling fluid along a first helical channel 50, while the second 20. temperature-regulated zone, located in the region of the lateral inlet opening for the molten metal, is heated and/or cooled by circulation of a heating andJor cooling fluid along a second helical channel 50A. The sleeve 21 terminates at the top in a large annular flange 52, 25. intended to come into contact with the die, which may in 17 21527~8 turn be heated and/or cooled by heat conduction or in another manner. The flange 52 forms a cavity 53 which opens out towards the chamber 54 of the sleeve 21, which cavity, as shown in Figure 6, i8 suitably shaped with a 5. conical or diverging side wall, so as to adapt itself to a corresponding part 70 of the die, with which it defines ducts 74 for distribution of the molten metal which must be fed into the cavity of the die.
Correspondingly, the bottom part 21A of the lo. injection sleeve and its inlet connector 24 may also be temperature-regulated in the same way as the top part of the sleeve 21.
The temperatures, and consequently the expansion of the two parts of the sleeve 21, are detected by suitable 5. heat sensors indicated schematically by 55 for the first upper zone 50, 50B of the injection sleeve 21 and by 55A
for the lower part 21A.
Similarly, the temperatures and the expansion of the plunger 22 are detected and controlled by a heat sensor 56 which penetrates into the body towards the tip of the plunger itself.
According to the present invention, in order to obtain pressure-cast pieces with optimum mechanical properties and a good surface finish, it is advisable to 25. inject the molten metal into the die, under moderately high pressures and under laminar-flow conditions and temperature controlled conditions. Therefore, in addition to temperature-regulation of the injection sleeve 21, from tests and experiments carried out, it 5. has been found that, in addition to temperature-regulation of the injection sleeve it is necessary to perform adequate cooling of the iniection plunger, so that the surfaces intended to come into contact with the molten metal of the plunger 22 and that part of the o. sleeve 21 which delimits the injection chamber close to the die, at the moment of injection, have a temperature difference Dt of predetermined value, i.e. such as to ensure correct axial alignment between plunger 22 and injection sleeve 21 and ade~uate tolerances as regards 5. the gap between the said plunger and the internal wall of the injection chamber.
Therefore the plunger 22 is continuously cooled by the circulation of water or other suitable fluid supplied by a separate cooling circuit. In this 20. connection, according to the example shown in Figure 3, the plunger 22 has an internal cavity 57 inside which water or other cooling fluid supplied by a central duct 58 which extends longitudinally inside the hollow rod 23, coaxially with a duct 59 for recirculation of the 25. cooling fluid, is continuously made to circulate .
The rod 23 of the plunger is provided moreover with a pneumatic cleaning system for cleaning the molten-metal inlet connector 24, this being performed by means of a strong jet of compressed air.
More precisely, as shown in Figure 3, the connector 24 for introducing the molten metal into the injection chamber 54 is arranged on one side of the injection sleeve 21, in the vicinity of the bottom, and is suitably downwardly slanted condition.Therefore, the rod 23 of the plunger 22 on the same side as the inlet 24, in a position underneath the plunger 22, has a blowing nozzle 60 which can be connected to a compressed-air source at 60A under the control of a logic processing unit 49; as explained further below, at the end of the 5. forward movement of the plunger 22, when the nozzle 60 is aligned with the inlet connector 24, it is possible to generate a strong jet of air which cleans the connector 24, ejecting the molten metal residue adhering to its walls.
Figures 4 and 5 show the system for connecting the duct 25 of the furnace to the connector 24 for introducing the molten metal into the injection chamber 54.
As shown, the duct 25 comprises a tubular element 25. 63 which extends inside the furnace 20 nearly as far as the bottom; the tube 63 is surrounded by a collar 61 made of ceramic or other heat-insulating material designed to withstand high temperatures and is kept constantly heated at the metal melting temperature by 5. means of a heating mean~ 64.
The duct 25 terminates in a semi-spherical nozzle which sealingly fits into a corresponding semi-spherical seat at the front end of the inlet connector24. Reference 66 denotes moreover locking members for o. locking the duct 25 to the connector 24, which act again~t a flange 67 at the front end of the connector itself. The locking members 66 are connected to respective actuator~ 68 so as to be moved towards and away from the flange 67 or to rotate through 90, as 15. schematically shown in Figure 5, so as to allow engagement and disengagement of the supply duct 25 with respect to the inlet connector 24.
A rotating closing member 69, schematically shown in Figure 5, serves to close the duct 25 and/or prevent 20. depressurisation of the furnace when it is separated from the injection device 19.
With reference now to Figure~ 6 and 7 we ~hall now de~cribe a second improved embodiment of the device 19 for injecting molten metal into the die, in accordance with the process according to the invention.
Unlike the other systems and the other high-pressure die-casting apparatus, the apparatus operating in accordance with the present invention has proved to be suitable for the production of pressure-cast pieces 5. both of small and large dimensions, obtaining metal castings of 20 or 30 kilograms which in some cases have reached and exceeded 40 kg, with molten-metal contact times of the order of several minutes, at temperatures equal to or slightly less than those for melting of the lo. metal.
In an attempt to obtain the most suitable conditions for injection of the molten metal into the mould, guarantee better results and ensure the required axial alignment between injection sleeve 21 and plunger 5. 22, not only has it proved useful to perform intense varied cooling of the piston 22 and the injection sleeve 21 in the zones intended to remain in contact with the molten metal for a long time, but also to perform injection of the molten metal into the die, upon 20. reaching a predetermined temperature difference Dt, between the plunger head and that part of the injection chamber close to and/or intended to come into contact with the die or part supporting the latter, by preventing jets of molten metal being sprayed from zs. venting holes of the die assembly.
During the tests carried out with an apparatus according to the invention, it has also proved useful, not only to define the dimensions of the injection device so as to obtain rapid and efficient removal of 5- the heat, but also obtain easy and rapid replacement of the worn parts of the injection device which come into direct contact with the molten metal.
Therefore, as shown in Figures 6 and 7, the cylindrical sleeve 21 is made removable from the lO. external jacket 51 and has two different temperature-regulation zones, defined by the ducts 50, 50A forcirculation of the heating and~or cooling fluid, formed directly in the wall of the sleeve. Furthermore, the duct 50 for temperature-regulation of the first zone of 15. the sleeve 21 close to the die continues into a duct 50B
which extends peripherally in the flange 52 intended to come into direct contact with the said die; in Figure 6 the same reference numbers have been used to indicate parts similar or equivalent to those of Figure 3.
20. Correspondingly, the plunger 22 has a removable head 90 of comparatively limited thickness so as to improve the exchange of heat between the external surface of the head 90 intended to come into contact with the molten metal in the injection chamber 54, and 25. the cooling fluid which is made to circulate inside the 23 215Z~58 internal chamber 57 of the plunger 22. The head 90 is fixed removably to the body 22 of the plunger and correspondingly the body of the plunger 22 is fixed removably to the rod 23 by means of a set of locking 5- screws 91 and 92.
Reliable and efficient regulation of the temperature of the plunger may be obtained by providing a cylindrical core 93 inside the chamber 57, provided peripherally with helical fins 94 defining a continuous 0. channel for circulation of the fluid, which is connected to a spiral channel 95 formed between the contact surfaces of the core 93 and the head 90 of the injection plunger. The central duct 58 supplying the fluid extends through the internal core 93, emerging centrally 15. inside the spiral duct 95, while the discharge hole S9 opens out inside the chamber 57 in a position underneath the core 93 and at the point where the helical duct defined by the peripheral fins 94 emerges; in this way the cooling fluid is initially brought into contact with 20. the head 90, cooling it rapidly, and subsequently cools the cylindrical body of the said plunger which thus retains a cylindrical configuration, like the injection chamber 54.
On the basis of the tests carried out, it has been 25. noted that good results are obtained by maintaining a 24 215275g temperature difference between the upper part of the sleeve which defines the injection chamber directed towards the die, and the head 90 of the injection plunger 22, ranging between 10- and 8noc, preferably between 30- and 60-C, for temperature values of the piston between 180 and 280C and for temperatures of the upper part of the injection sleeve between 220- and 320C; obviously these values, experimented on aluminium alloy~, can vary from ca~e to case depending on the lO. melting temperature of the metal used, the dimensions and the materials used for the injection device as well as other process parameters.
With reference now to Figures 8 and 9 we shall describe the features of the die assembly with modular 15. elements, which can be used in combination with the apparatus according to the present invention.
In Figures 8 and 9 the same reference numbers as those of the preceding figures have been used to indicate similar or equivalent parts.
As shown, the die assembly comprises a bottom die part 14 removably fixed to the lower movable surface 13 of the apparatus, and a top die part 16 removably fixed to the upper movable surface 15, as shown.
The bottom die part 14 consists of a bottom die 70 removably fixed, for example by means of bolts (not 2 15 27 S~
shown) to a bottom die-carrier 71 supported by the lower movable surface 13 of the apparatus. The bottom die 70 of the die assembly is provided with a peripheral casting ring 72 formed with a circular seat open 5. downwards, into which the circular flange 52 of the sleeve 21 fits.
Between the die 70 and the casting ring 72 there are formed injection channels 74 which, on one side, open into the cavity 75 of the die assembly defined by o. the bottom die 70 and by the top die 76, while, on the other side, they open downwards and towards a metal distribution chamber defined by the cavity 53 at the top end of the injection sleeve, between the opposing and similarly shaped surfaces of the aforementioned cavity 5. 53 and the bottom die 70.
Correspondingly, the top die part 16 comprise~ the top die 76 removably fixed, for example by means of bolts or other disengageable connecting means ~not shown), to an upper die-holder 77 connected via spacer~
20. 78 to a base plate 79 which in turn is removably fixed to the upper movable surface 15.
The top die part further comprise~ a series of movable side-blocks 80 which are arranged circumferentially around the top die so as to define 25. together with the latter the shaped neck of the wheel onto which a normal tyre is sealingly fitted.
The side-blocks 80, as shown in Figure 7, can be opened radially so a~ to allow extraction of the wheel 81 when the die assembly i8 opened; therefore, the side-5. block~ 80 are connected, via bars 82, to a movable carriage 83 provided between the upper die-holder 77 and the base plate 79. The individual thrusting bars 82 are arranged inclined and diverging downwards, being guided in their sliding travel by respective guide tubes o. 84.
The carriage 83 is connected to the cylinder 18, the rod of which is extended by an extractor 85 suitable guided in a sliding manner through the top die 76 and the respective die-holder 77. The extractor 85 15. terminates in a shaped head 86 defining the hub of the cast wheel. The die as~embly, finally, is completed by the appropriate duct~ for circulation of a cooling fluid.
With reference to Figure 10, we shall now describe the system for temperature-regulation of the sleeve and the plunger of the injection device.
A~ can be seen from said figure, the fir~t temperature-regulation circuit 50, 50B of the iniection sleeve 51 is connected to an oil-type temperature 25. regulator 96 compri~ing electric heating mean~ 97 for 27 21~275~
heating the oil, and cooling means 98 which can be actuated independently of one another, with times and temperatures programmed and controlled by meanY of the central processing unit 49.
More precisely, the diathermic oil cooling means inside the temperature regulator 96 is in the form of a coil for the circulation of a cooling fluid, for example water at 12C, connected to a cooling fluid source via a ~olenoid valve 100 controlled by the processing unit 49, 0. and a first cooler 101, with one or more stages, which in turn is air-cooled.
In a substantially corresponding manner, the second circuit 50A for temperature regulation of the injection sleeve 51 is connected to an oil-type temperature 15. regulator 102 comprising heating means 103 and cooling means 104 in the form of a coil connected to the fluid source 99, via a solenoid valve 105 and the cooler 101 mentioned above. Although the cooling water i8 at the same temperature for both the temperature regulators g6 20. and 102 it is evident that the oil contained in them can be maintained at different temperatures by operating the respective heating mean~, or in some other way, automatically under the control of the processing unit 49 by means of which it is po~sible to program and 25. monitor on a display the values and temperature 28 21S275~
histograms of the various temperature-regulated zones.
In a manner substantially similar to the two temperature-regulation circuits 50 and 50A of the injection sleeve 51, the cooling circuit for the plunger 22 is connected to the water source 99 via a solenoid-valve 106 controlled by the processing unit 49, and an air cooler 107.
As mentioned above, the electronic processing unit 49 comprises memory means which can be programmed with lO. the various operating data and parameters of the machine according to the process of the present invention; in particular it is programmed with the temperatures of the two temperature-regulated zones of the injection sleeve 51, with the cooling temperature of the head of the 5. plunger 22 as well as with the value Dt of the temperature difference between the first temperature-regulated zone 50, 50B of the sleeve 51, in the region of the zone close to or in contact with the pressure-casting die, which values may be read from a special 20. display of the processing unit 49.
Finally, with reference to Figure 11, we shall describe the system for controlling the displacement in time of the piston and the pressure of the oil supplied to the hydraulic cylinder 23' operating the injection 25. device 19 which, indirectly, via special calculation 29 ~152758 algorithms provided in a memory of the electronic processing unit 49, are able to supply corresponding values relating to the speed and pressure injection of the molten metal into the die, to which a laminar flow state of the metal itself corresponds.
As shown, a linear displacement transducer 108 is connected to an arm 108' fixed to the rod 23 of the piston of the hydraulic cylinder 23'.
The displacement S1 detected by the transducer 107 lo. via an interface 109 or in another way is converted into an electrical signal U1 supplied to the inlet of a regulating circuit 110 forming part of the electronic processing unit 49, by means of which it is possible to regulate and convert, via a special calculation 15. algorithm stored in the logic circuit 111 for operation of the machine, the displacement in time of the rod 23 into data indicating the displacement speed of the plunger 22 of the injection device and consequently the maximum injection speed of the molten metal calculated 20. at the point where the ducts supplying and di~tributing the molten metal into the die cavity have the smaller cross-section.
In turn the single-acting cylinder 23' is connected to a pressurised-oil source 48 via a solenoid valve of 25. the proportional type, in turn operationally connected 215~7~
to the logic control circuit 111.
Finally, the pressure P of the oil supplied to the hydraulic cylinder 23', via an interface 112 is converted into a signal U2 supplied to a second data inlet of the regulating circuit 110 which, via another calculation algorithm of the logic circuit 111, is converted into a pressure signal P corresponding to the value of the specific pressure at which the molten metal is injected into the die.
lo. Operation of the pressure die-casting apparatus and the process according to the invention are described hereinbelow.
The molten metal 36 inside the furnace 20 i8 kept at the desired melting temperature by means of the 5. heating system with which the furnace is provided. It is assumed moreover that the die assembly is open with the two surfaces 13 and 15 completely raised in the condition shown in Figure 7 and that the duct 25 supplying the molten metal of the furnace is separated 20. from the inlet connector 24 of the injection chamber.
The plunger 22 is moreover lowered in the condition shown in Figure 1.
Under these conditions, at the start of each working cycle, on the basis of the working program 25. stored in the permanent memory of the electronic processing unit 49, the solenoid valves 100, 105 and the electrical resistances 97 and 103 of the two temperature regulators 99 and 102 are activated 80 as to bring the diathermic oil to a suitable temperature for preheating 5. of the temperature-regulated zones 50 and 50A, for example to temperatures close to that for melting of the metal, or slightly lower, the values of which have been prestored in the processing unit 49. These temperatures are detected by the heat sensor~ or thermocouples 45 and o. 55A and communicated to the logic control unit 49 which compares them with the prestored reference temperatures, so as to avoid sudden jumps in temperature and predispose the said sleeve 21 in the required condition of axial alignment with the plunger 22. At the same 5. time, the plunger 22 is brought to the required temperature which is detected by the heat sensor 21A and communicated to the logic control unit 49 which compares it with the corresponding prestored reference temperature. In the meantime the furnace 20 has been 20. pressurised to a predetermined pre~sure value which will be kept constant, so as to allow, at each working cycle, exact metering of the quantity of molten metal which from time to time will be supplied into the injection ~leeve 21.
25. After closing and preheating the die assembly, bringing it into the condition shown in Figure 8 and after moving up the furnace 20, locking its duct 25 to the inlet connector 24 of the injection chamber, under the control of the processing unit 49 a quantity of pressurised air is supplied into the furnace, sufficient to cause the molten metal inside the duct 25 to rise and partially fill the injection chamber 54, until a predetermined level is reached. In the meantime the cooling systems of the temperature regulators 96 and 102 o. are activated.
As soon as the heat sensors 55, 55A and 56 supply the processing unit 49 with the values of the temperatures detected, indicating the degree of expansion of the sleeve 21 and the plunger 22, and as 5. soon as the difference Dt in temperature detected between the plunger 22, in particular that of its head, and the temperature of the injection sleeve part in contact with the die assembly, has reached a predetermined value, e~ual to a reference value stored 20. in the processing unit 49, the latter supplies a -consent signal for commanding the forward movement of the plunger 22 which is moved a short distance upwards until it closes the inlet connector 24, in view of the fact that the necessary conditions of axial alignment 25. between sleeve 21 and plunger 22 have been achieved.
33 21527~
At this point the furnace 20 is moved away and its supply duct 25 separated from the connector 24, following disengagement of the locking members 66 which previously had been operated so as to maintain a sealed connection between the semi-spherical nozzle 65 of the duct 25 and the corresponding semi-spherical cavity at the end of the connector 24. At the same time the closing member 69 of the furnace duct is brought into the closed condition, after causing the descent of the . molten metal left inside the duct 25 into the furnace.
After separation of the furnace from the injection device, the plunger 22 is made to rise again until the air blowing nozzle 60 coincides with the duct of the connector 24, supplying a strong jet of air in order to 5. clean any molten-metal residue from the connector 24 and thus prevent the said connector from becoming accidentally blocked.
The movement of the plunger 22 continues upward~, with the sleeve 21 and the plunger 22 always being 20. maintained under temperature controlled condition~, until the distribution chamber 53, into which the injection cham~er 54 opens, is completely filled.
During this phase, the position and the speed of displacement of the plunger 22 are detected by the 25. linear transducer 107. Continuing the upward movement 34 21527~
of the plunger 22 under the control of the processing unit 49, the metal material in the molten state is consequently forced to flow along the channels of the bottom die part, supplying the latter at different 5. predetermined injection points, for example along the peripheral edge of the die cavity, at a predetermined pressure, for example ranging between 50 and 350 Atm ~4,9 - 34,3 MPa), and at a speed which are controlled by the control system shown in Figure 11. In this way, 10. conditions of laminar flow of the molten metal are obtained, while the latter is fed into the die cavity;
in this way, dangerous turbulence phenomena and trapping of air in the jet are avoided, which, otherwise, could result in the formation of blisters and a greater degree 5. of fragility.
Therefore, during designing of the die assembly, it is necessary to calculate the appropriate flow cross-sections in accordance with the metal throughput and thepressure exerted on the molten metal, such that the 20. injection speed measured at the point where the metal is introduced into the die cavity i~ in a l~ i n~ r condition with a laminar speed of the flow equal to or less than 12 metres per second.When injection of the metal into the die has been completed and after a sufficient amount 25. of time has lapsed to allow consolidation thereof, the 21S275~
die assembly may be raised and opened, as shown in Figure 7, separating then the deadhead 31 which is dislodged from the plunger and made to fall along the inclined channel 30 onto the conveyor 32. At the same 5. time, the die assembly, as it opens, causes the side-blocks to move apart, freeing the cast piece which thus falls onto the table 26 positioned underneath.
When the operating cycle has been completed, it may be resumed for the production of a new pressure-ca~t o. piece in the manner described above, while at the same time cooling and varied temperature-regulation of the plunger and the sleeve of the injection device are continued.
A further obiect of the present invention is to provide a process and an apparatus, as defined above, by means of which it is possible to reduce the phenomenon 5. of air inclusion and the formation of oxides in the molten metal, both during feeding of the metal into the injection device and during injection into the die, obtaining cast pieces with a high degree of mechanical isotropy, as a result of which, in certain cases, it is 20. possible to reduce substantially the resistant cross-sectional areas and hence the flow passages for the metals inside the die, achieving in this way cast pieces which are structurally strong, have thin walls and a comparatively very low weight J in extremely short 25. operating cycles; for example, in the case of alloy wheels it is possible to reduce the weight and the production cycle about 3 or 4 times, compared to a wheel normally produced under low pressure, obt~ining wheels with high mechanical and crystallographic properties of 5. the alloy used, as well as a superior finish.
Yet another object of the invention is to provide an apparatus for the production of alloy wheels according to the process mentioned above, substantially devoid of deformation phenomena affecting the parts o. intended to come into contact with the high-temperature molten metal, thus ensuring an operational and processing efficiency and reliability which cannot be achieved with the other known techniques.
A further object of the invention is to provide an 5. apparatus for pressure die-casting which uses in combination an injection device and a die particularly suitable for implementation of a medium-pressure die-casting process, according to the invention, as well a~the production of wheels of a different type, without 20. having to change the entire production die; for the purposes of the present invention "medium pressure" is understood as meaning a pressure for the injection of molten metal into the die ranging between 50 and 350 Atm (4,9 - 34,3 MPa).
lo 2152758 Summary of the Invention The above objects can be achieved by means of a proces~ and an apparatus for the production of metal-alloy pieces, in particular alloy wheel~, according to5. the pre~ent invention more particularly a process for the production of pressure-cast metal pieces has been provided, according to which a metered quantity of molten metal is fed into an injection device comprising a ~leeve defining a vertical injection chamber and a lo. plunger movable inside said chamber between a retracted position, where it uncovers a lateral opening for entry of the molten metal, and an advanced position, where the molten metal is injected into the cavity of a die a~sembly, characterized by:
5. - providing an axially aligned arrangement of the ~leeve and the injection plunger, while maintaining under different temperature controlled conditions the zones of the plunger and the part of the chamber of the injection sleeve located in the vicinity of the 20. pres~ure-casting die assembly, which come into contact with the molten metal;
- detecting the temperatures of the plunger and the injection sleeve in the region of the ~aid temperature controlled zones; and 25. - injecting the molten metal into the cavity of the 11 21$2758 die assembly upon reaching of a predetermined temperature difference between said temperature controlled zones of the sleeve and the injection plunger, at a pressure ranging between 50 and 350 Atm 5. (4,9 - 34,3 MPa), maintaining laminar flow conditions of the molten metal while it is injected and flows into the cavity of the die assembly, ensuring the required axially aligned condition between sleeve and plunger of the injection device.
o. Brief description of the drawin~s These and other objects, features and advantages of the present invention will emerge more clearly from the description, together with the accompanying drawings, in which:
5. Fig. 1 is a general view of the apparatus with some sectioned parts;
Fig. 2 is a side view of the apparatus according to Figure l;
Fig. 3 is a longitudinal sectional view, on a 20. larger scale, of a first embodiment of the device for injecting molten metal into the shaping die;
Fig. 4 is an enlarged detail of the duct connecting the furnace to the molten-metal injection device;
Fig. 5 is a view along the line 5-5 of Figure 4;
Fig. 6 is a longitudinal sectional view of a second 12 21527~8 embodiment of the injection device;
Fig. 7 is a cross-sectional view along the line 7-7 of Figure 6;
Fig. 8 is an enlarged detail of the apparatus 5. according to Figure 1, with the die in the closed condition;
Fig. 9 is a view similar to that of the preceding figure with the die in the open condition.Fig. 10 i8 a general diagram of the ~ystem for temperature-regulation 10. of the injection device;
Fig. 11 is a general diagram of the system for controlling the pressures and speeds of injection of the molten metal into the die during pressure die-casting.
Description of the Invention As shown in Figures 1 and 2, the apparatus comprises a base 10 fixed to the floor opposite a pit 11, from which there emerge four side columns 12 held at the top by cross-beams 35.
A first movable platen 13 supporting the lower part 20. 14 of a die and an upper platen 15 supporting the upper part 16 of the die are movable between a position close to one another, where the die is closed, and a position far from one another, where the die is open, so as to allow respectively the injection of molten metal into the die and the removal of the cast piece, in the manner 13 215275~
illustrated below.
The raising and lowering movement of the lower platen 13 is obtained in a manner known per se by means of a pair of hydraulic cylinders provided in the bottom part of the apparatus, not shown; correspondingly, the movement of the upper platen 15 is obtained by means of a pair of hydraulic cylinders 17. In Figure 2, finally, 18 denotes an auxiliary cylinder supported centrally by the upper platen so as to perform closing and opening lo. operations of the die.
The apparatus comprises, moreover, a device 19 for injecting molten metal, contained in a furnace having a pressurised pot 20, provided movably on one side of the apparatus itself.
5. More precisely, the device 19 for injecting molten metal comprises a cylindrical sleeve 21 defining an injection chamber arranged vertically and centrally with respect to the base 10. Inside the sleeve 21 there slides a plunger 22 connected via a long rod 23 to a 20. hydraulic cylinder 23'.
As shown in Figure 3, the bottom part 21A of the sleeve 21, on one side thereof, has a radial inlet connector 24, downwardly slanted, which may be connected to the duct 25 of the furnace 20, as described further 25. below with reference to Figures 4 and 5 of the accompanying drawings.
The apparatus according to ~igures 1 and 2, on the side opposite to the furnace 20, comprises a service table 26 which may be used both for unloading the cast pieces and for replacing the die. The table 26 is slidably supported on a frame 27 and i8 operated so as to move forwards or backwards by means of a cylinder 28;
the support frame 27, in turn, slides along horizontal guides 29, as schematically shown.
lo. In Figure 1, finally, 30 denotes a tiltable chute for unloading the deadhead 31 which is conveyed away by means of a conveyor 32; the deadhead 31 is removed from the plunger 22 of the injection device, by a lateral pusher 46.
15. In ~igure 2 the reference number 33 denotes a locking member for the upper platen 15, positioned on one side of the cross-members 35 for locking the upper platen 15 in the closed condition of the die during the metal injection phase.
20. The furnace 20 containing the molten metal is of the pot type, i.e. designed to contain a given quantity 36 of a molten metal alloy which is constantly maintained at the melting temperature by means of a suitable heating system, not shown.
25. The furnace 20 is of the pressurised type; the air 215~758 under pressure is fed inside the furnace by a duct 37 connected to a pressurised-air source 38 by a filter 39, a solenoid valve 40 and a pressure regulator 41.
Moreover, in Figure 1, 42 denotes a probe which 5. penetrates inside the furnace so as to provide a signal indicating the height of the molten metal bath 36 and, consequently, an indication of the quantity of metal fed into the injection sleeve 21.
The furnace 20 is supported in a movable manner, lo. for example by means of a system of articulated ~ars 43 provided on a carriage 44 equipped with wheels sliding on rails; the furnace may be operated so as to be raised and lowered by means of a jack 45 or move on the rails by means of a hydraulic cylinder 45A. The movement of 5. raising and/or sliding of the furnace 20 is used to separate the duct 25 supplying the molten metal from the inlet connector 24 of the injection device 19, so as to allow cleaning or prevent the latter from heating excessively, causing dangerous uncontrolled expansion of 20. the injection sleeve 21 with respect to the thrusting plunger 22.
Moreover 47 in Figure 1 indicates, in the form of a solenoid valve symbol, the system for connecting the cylinder 23' to a pressurised-oil source 48. The 25. solenoid valves 40, 47, the probe 42 and suitable devices for controlling pressurisation of the furnace 20 and the temperature of the sleeve 21 and the injection plunger 22, as explained below, are appropriately connected, by means of suitable interface circuits, to a 5. programmable control unit 49 having a microprocessor which governs the entire production cycle.
A first embodiment of the device 19 for injecting molten metal is shown in the enlarged detail of Figure 3; the device 1~ comprise~ a cylindrical sleeve 21 which o. is suitably temperature-regulated by circulation of a diathermal fluid inside an insulating jacket 51 surrounding the sleeve itself. In particular, in the example of Figure 3, the sleeve 21 has two independent temperature-regulation zones, i.e. designed to be heated 5. and/or cooled during the production cycle, as explained below with reference to Figure 10, of which a first zone clo~e to or in the region of the ~haping die is heated and/or cooled by circulating a heating andJor cooling fluid along a first helical channel 50, while the second 20. temperature-regulated zone, located in the region of the lateral inlet opening for the molten metal, is heated and/or cooled by circulation of a heating andJor cooling fluid along a second helical channel 50A. The sleeve 21 terminates at the top in a large annular flange 52, 25. intended to come into contact with the die, which may in 17 21527~8 turn be heated and/or cooled by heat conduction or in another manner. The flange 52 forms a cavity 53 which opens out towards the chamber 54 of the sleeve 21, which cavity, as shown in Figure 6, i8 suitably shaped with a 5. conical or diverging side wall, so as to adapt itself to a corresponding part 70 of the die, with which it defines ducts 74 for distribution of the molten metal which must be fed into the cavity of the die.
Correspondingly, the bottom part 21A of the lo. injection sleeve and its inlet connector 24 may also be temperature-regulated in the same way as the top part of the sleeve 21.
The temperatures, and consequently the expansion of the two parts of the sleeve 21, are detected by suitable 5. heat sensors indicated schematically by 55 for the first upper zone 50, 50B of the injection sleeve 21 and by 55A
for the lower part 21A.
Similarly, the temperatures and the expansion of the plunger 22 are detected and controlled by a heat sensor 56 which penetrates into the body towards the tip of the plunger itself.
According to the present invention, in order to obtain pressure-cast pieces with optimum mechanical properties and a good surface finish, it is advisable to 25. inject the molten metal into the die, under moderately high pressures and under laminar-flow conditions and temperature controlled conditions. Therefore, in addition to temperature-regulation of the injection sleeve 21, from tests and experiments carried out, it 5. has been found that, in addition to temperature-regulation of the injection sleeve it is necessary to perform adequate cooling of the iniection plunger, so that the surfaces intended to come into contact with the molten metal of the plunger 22 and that part of the o. sleeve 21 which delimits the injection chamber close to the die, at the moment of injection, have a temperature difference Dt of predetermined value, i.e. such as to ensure correct axial alignment between plunger 22 and injection sleeve 21 and ade~uate tolerances as regards 5. the gap between the said plunger and the internal wall of the injection chamber.
Therefore the plunger 22 is continuously cooled by the circulation of water or other suitable fluid supplied by a separate cooling circuit. In this 20. connection, according to the example shown in Figure 3, the plunger 22 has an internal cavity 57 inside which water or other cooling fluid supplied by a central duct 58 which extends longitudinally inside the hollow rod 23, coaxially with a duct 59 for recirculation of the 25. cooling fluid, is continuously made to circulate .
The rod 23 of the plunger is provided moreover with a pneumatic cleaning system for cleaning the molten-metal inlet connector 24, this being performed by means of a strong jet of compressed air.
More precisely, as shown in Figure 3, the connector 24 for introducing the molten metal into the injection chamber 54 is arranged on one side of the injection sleeve 21, in the vicinity of the bottom, and is suitably downwardly slanted condition.Therefore, the rod 23 of the plunger 22 on the same side as the inlet 24, in a position underneath the plunger 22, has a blowing nozzle 60 which can be connected to a compressed-air source at 60A under the control of a logic processing unit 49; as explained further below, at the end of the 5. forward movement of the plunger 22, when the nozzle 60 is aligned with the inlet connector 24, it is possible to generate a strong jet of air which cleans the connector 24, ejecting the molten metal residue adhering to its walls.
Figures 4 and 5 show the system for connecting the duct 25 of the furnace to the connector 24 for introducing the molten metal into the injection chamber 54.
As shown, the duct 25 comprises a tubular element 25. 63 which extends inside the furnace 20 nearly as far as the bottom; the tube 63 is surrounded by a collar 61 made of ceramic or other heat-insulating material designed to withstand high temperatures and is kept constantly heated at the metal melting temperature by 5. means of a heating mean~ 64.
The duct 25 terminates in a semi-spherical nozzle which sealingly fits into a corresponding semi-spherical seat at the front end of the inlet connector24. Reference 66 denotes moreover locking members for o. locking the duct 25 to the connector 24, which act again~t a flange 67 at the front end of the connector itself. The locking members 66 are connected to respective actuator~ 68 so as to be moved towards and away from the flange 67 or to rotate through 90, as 15. schematically shown in Figure 5, so as to allow engagement and disengagement of the supply duct 25 with respect to the inlet connector 24.
A rotating closing member 69, schematically shown in Figure 5, serves to close the duct 25 and/or prevent 20. depressurisation of the furnace when it is separated from the injection device 19.
With reference now to Figure~ 6 and 7 we ~hall now de~cribe a second improved embodiment of the device 19 for injecting molten metal into the die, in accordance with the process according to the invention.
Unlike the other systems and the other high-pressure die-casting apparatus, the apparatus operating in accordance with the present invention has proved to be suitable for the production of pressure-cast pieces 5. both of small and large dimensions, obtaining metal castings of 20 or 30 kilograms which in some cases have reached and exceeded 40 kg, with molten-metal contact times of the order of several minutes, at temperatures equal to or slightly less than those for melting of the lo. metal.
In an attempt to obtain the most suitable conditions for injection of the molten metal into the mould, guarantee better results and ensure the required axial alignment between injection sleeve 21 and plunger 5. 22, not only has it proved useful to perform intense varied cooling of the piston 22 and the injection sleeve 21 in the zones intended to remain in contact with the molten metal for a long time, but also to perform injection of the molten metal into the die, upon 20. reaching a predetermined temperature difference Dt, between the plunger head and that part of the injection chamber close to and/or intended to come into contact with the die or part supporting the latter, by preventing jets of molten metal being sprayed from zs. venting holes of the die assembly.
During the tests carried out with an apparatus according to the invention, it has also proved useful, not only to define the dimensions of the injection device so as to obtain rapid and efficient removal of 5- the heat, but also obtain easy and rapid replacement of the worn parts of the injection device which come into direct contact with the molten metal.
Therefore, as shown in Figures 6 and 7, the cylindrical sleeve 21 is made removable from the lO. external jacket 51 and has two different temperature-regulation zones, defined by the ducts 50, 50A forcirculation of the heating and~or cooling fluid, formed directly in the wall of the sleeve. Furthermore, the duct 50 for temperature-regulation of the first zone of 15. the sleeve 21 close to the die continues into a duct 50B
which extends peripherally in the flange 52 intended to come into direct contact with the said die; in Figure 6 the same reference numbers have been used to indicate parts similar or equivalent to those of Figure 3.
20. Correspondingly, the plunger 22 has a removable head 90 of comparatively limited thickness so as to improve the exchange of heat between the external surface of the head 90 intended to come into contact with the molten metal in the injection chamber 54, and 25. the cooling fluid which is made to circulate inside the 23 215Z~58 internal chamber 57 of the plunger 22. The head 90 is fixed removably to the body 22 of the plunger and correspondingly the body of the plunger 22 is fixed removably to the rod 23 by means of a set of locking 5- screws 91 and 92.
Reliable and efficient regulation of the temperature of the plunger may be obtained by providing a cylindrical core 93 inside the chamber 57, provided peripherally with helical fins 94 defining a continuous 0. channel for circulation of the fluid, which is connected to a spiral channel 95 formed between the contact surfaces of the core 93 and the head 90 of the injection plunger. The central duct 58 supplying the fluid extends through the internal core 93, emerging centrally 15. inside the spiral duct 95, while the discharge hole S9 opens out inside the chamber 57 in a position underneath the core 93 and at the point where the helical duct defined by the peripheral fins 94 emerges; in this way the cooling fluid is initially brought into contact with 20. the head 90, cooling it rapidly, and subsequently cools the cylindrical body of the said plunger which thus retains a cylindrical configuration, like the injection chamber 54.
On the basis of the tests carried out, it has been 25. noted that good results are obtained by maintaining a 24 215275g temperature difference between the upper part of the sleeve which defines the injection chamber directed towards the die, and the head 90 of the injection plunger 22, ranging between 10- and 8noc, preferably between 30- and 60-C, for temperature values of the piston between 180 and 280C and for temperatures of the upper part of the injection sleeve between 220- and 320C; obviously these values, experimented on aluminium alloy~, can vary from ca~e to case depending on the lO. melting temperature of the metal used, the dimensions and the materials used for the injection device as well as other process parameters.
With reference now to Figures 8 and 9 we shall describe the features of the die assembly with modular 15. elements, which can be used in combination with the apparatus according to the present invention.
In Figures 8 and 9 the same reference numbers as those of the preceding figures have been used to indicate similar or equivalent parts.
As shown, the die assembly comprises a bottom die part 14 removably fixed to the lower movable surface 13 of the apparatus, and a top die part 16 removably fixed to the upper movable surface 15, as shown.
The bottom die part 14 consists of a bottom die 70 removably fixed, for example by means of bolts (not 2 15 27 S~
shown) to a bottom die-carrier 71 supported by the lower movable surface 13 of the apparatus. The bottom die 70 of the die assembly is provided with a peripheral casting ring 72 formed with a circular seat open 5. downwards, into which the circular flange 52 of the sleeve 21 fits.
Between the die 70 and the casting ring 72 there are formed injection channels 74 which, on one side, open into the cavity 75 of the die assembly defined by o. the bottom die 70 and by the top die 76, while, on the other side, they open downwards and towards a metal distribution chamber defined by the cavity 53 at the top end of the injection sleeve, between the opposing and similarly shaped surfaces of the aforementioned cavity 5. 53 and the bottom die 70.
Correspondingly, the top die part 16 comprise~ the top die 76 removably fixed, for example by means of bolts or other disengageable connecting means ~not shown), to an upper die-holder 77 connected via spacer~
20. 78 to a base plate 79 which in turn is removably fixed to the upper movable surface 15.
The top die part further comprise~ a series of movable side-blocks 80 which are arranged circumferentially around the top die so as to define 25. together with the latter the shaped neck of the wheel onto which a normal tyre is sealingly fitted.
The side-blocks 80, as shown in Figure 7, can be opened radially so a~ to allow extraction of the wheel 81 when the die assembly i8 opened; therefore, the side-5. block~ 80 are connected, via bars 82, to a movable carriage 83 provided between the upper die-holder 77 and the base plate 79. The individual thrusting bars 82 are arranged inclined and diverging downwards, being guided in their sliding travel by respective guide tubes o. 84.
The carriage 83 is connected to the cylinder 18, the rod of which is extended by an extractor 85 suitable guided in a sliding manner through the top die 76 and the respective die-holder 77. The extractor 85 15. terminates in a shaped head 86 defining the hub of the cast wheel. The die as~embly, finally, is completed by the appropriate duct~ for circulation of a cooling fluid.
With reference to Figure 10, we shall now describe the system for temperature-regulation of the sleeve and the plunger of the injection device.
A~ can be seen from said figure, the fir~t temperature-regulation circuit 50, 50B of the iniection sleeve 51 is connected to an oil-type temperature 25. regulator 96 compri~ing electric heating mean~ 97 for 27 21~275~
heating the oil, and cooling means 98 which can be actuated independently of one another, with times and temperatures programmed and controlled by meanY of the central processing unit 49.
More precisely, the diathermic oil cooling means inside the temperature regulator 96 is in the form of a coil for the circulation of a cooling fluid, for example water at 12C, connected to a cooling fluid source via a ~olenoid valve 100 controlled by the processing unit 49, 0. and a first cooler 101, with one or more stages, which in turn is air-cooled.
In a substantially corresponding manner, the second circuit 50A for temperature regulation of the injection sleeve 51 is connected to an oil-type temperature 15. regulator 102 comprising heating means 103 and cooling means 104 in the form of a coil connected to the fluid source 99, via a solenoid valve 105 and the cooler 101 mentioned above. Although the cooling water i8 at the same temperature for both the temperature regulators g6 20. and 102 it is evident that the oil contained in them can be maintained at different temperatures by operating the respective heating mean~, or in some other way, automatically under the control of the processing unit 49 by means of which it is po~sible to program and 25. monitor on a display the values and temperature 28 21S275~
histograms of the various temperature-regulated zones.
In a manner substantially similar to the two temperature-regulation circuits 50 and 50A of the injection sleeve 51, the cooling circuit for the plunger 22 is connected to the water source 99 via a solenoid-valve 106 controlled by the processing unit 49, and an air cooler 107.
As mentioned above, the electronic processing unit 49 comprises memory means which can be programmed with lO. the various operating data and parameters of the machine according to the process of the present invention; in particular it is programmed with the temperatures of the two temperature-regulated zones of the injection sleeve 51, with the cooling temperature of the head of the 5. plunger 22 as well as with the value Dt of the temperature difference between the first temperature-regulated zone 50, 50B of the sleeve 51, in the region of the zone close to or in contact with the pressure-casting die, which values may be read from a special 20. display of the processing unit 49.
Finally, with reference to Figure 11, we shall describe the system for controlling the displacement in time of the piston and the pressure of the oil supplied to the hydraulic cylinder 23' operating the injection 25. device 19 which, indirectly, via special calculation 29 ~152758 algorithms provided in a memory of the electronic processing unit 49, are able to supply corresponding values relating to the speed and pressure injection of the molten metal into the die, to which a laminar flow state of the metal itself corresponds.
As shown, a linear displacement transducer 108 is connected to an arm 108' fixed to the rod 23 of the piston of the hydraulic cylinder 23'.
The displacement S1 detected by the transducer 107 lo. via an interface 109 or in another way is converted into an electrical signal U1 supplied to the inlet of a regulating circuit 110 forming part of the electronic processing unit 49, by means of which it is possible to regulate and convert, via a special calculation 15. algorithm stored in the logic circuit 111 for operation of the machine, the displacement in time of the rod 23 into data indicating the displacement speed of the plunger 22 of the injection device and consequently the maximum injection speed of the molten metal calculated 20. at the point where the ducts supplying and di~tributing the molten metal into the die cavity have the smaller cross-section.
In turn the single-acting cylinder 23' is connected to a pressurised-oil source 48 via a solenoid valve of 25. the proportional type, in turn operationally connected 215~7~
to the logic control circuit 111.
Finally, the pressure P of the oil supplied to the hydraulic cylinder 23', via an interface 112 is converted into a signal U2 supplied to a second data inlet of the regulating circuit 110 which, via another calculation algorithm of the logic circuit 111, is converted into a pressure signal P corresponding to the value of the specific pressure at which the molten metal is injected into the die.
lo. Operation of the pressure die-casting apparatus and the process according to the invention are described hereinbelow.
The molten metal 36 inside the furnace 20 i8 kept at the desired melting temperature by means of the 5. heating system with which the furnace is provided. It is assumed moreover that the die assembly is open with the two surfaces 13 and 15 completely raised in the condition shown in Figure 7 and that the duct 25 supplying the molten metal of the furnace is separated 20. from the inlet connector 24 of the injection chamber.
The plunger 22 is moreover lowered in the condition shown in Figure 1.
Under these conditions, at the start of each working cycle, on the basis of the working program 25. stored in the permanent memory of the electronic processing unit 49, the solenoid valves 100, 105 and the electrical resistances 97 and 103 of the two temperature regulators 99 and 102 are activated 80 as to bring the diathermic oil to a suitable temperature for preheating 5. of the temperature-regulated zones 50 and 50A, for example to temperatures close to that for melting of the metal, or slightly lower, the values of which have been prestored in the processing unit 49. These temperatures are detected by the heat sensor~ or thermocouples 45 and o. 55A and communicated to the logic control unit 49 which compares them with the prestored reference temperatures, so as to avoid sudden jumps in temperature and predispose the said sleeve 21 in the required condition of axial alignment with the plunger 22. At the same 5. time, the plunger 22 is brought to the required temperature which is detected by the heat sensor 21A and communicated to the logic control unit 49 which compares it with the corresponding prestored reference temperature. In the meantime the furnace 20 has been 20. pressurised to a predetermined pre~sure value which will be kept constant, so as to allow, at each working cycle, exact metering of the quantity of molten metal which from time to time will be supplied into the injection ~leeve 21.
25. After closing and preheating the die assembly, bringing it into the condition shown in Figure 8 and after moving up the furnace 20, locking its duct 25 to the inlet connector 24 of the injection chamber, under the control of the processing unit 49 a quantity of pressurised air is supplied into the furnace, sufficient to cause the molten metal inside the duct 25 to rise and partially fill the injection chamber 54, until a predetermined level is reached. In the meantime the cooling systems of the temperature regulators 96 and 102 o. are activated.
As soon as the heat sensors 55, 55A and 56 supply the processing unit 49 with the values of the temperatures detected, indicating the degree of expansion of the sleeve 21 and the plunger 22, and as 5. soon as the difference Dt in temperature detected between the plunger 22, in particular that of its head, and the temperature of the injection sleeve part in contact with the die assembly, has reached a predetermined value, e~ual to a reference value stored 20. in the processing unit 49, the latter supplies a -consent signal for commanding the forward movement of the plunger 22 which is moved a short distance upwards until it closes the inlet connector 24, in view of the fact that the necessary conditions of axial alignment 25. between sleeve 21 and plunger 22 have been achieved.
33 21527~
At this point the furnace 20 is moved away and its supply duct 25 separated from the connector 24, following disengagement of the locking members 66 which previously had been operated so as to maintain a sealed connection between the semi-spherical nozzle 65 of the duct 25 and the corresponding semi-spherical cavity at the end of the connector 24. At the same time the closing member 69 of the furnace duct is brought into the closed condition, after causing the descent of the . molten metal left inside the duct 25 into the furnace.
After separation of the furnace from the injection device, the plunger 22 is made to rise again until the air blowing nozzle 60 coincides with the duct of the connector 24, supplying a strong jet of air in order to 5. clean any molten-metal residue from the connector 24 and thus prevent the said connector from becoming accidentally blocked.
The movement of the plunger 22 continues upward~, with the sleeve 21 and the plunger 22 always being 20. maintained under temperature controlled condition~, until the distribution chamber 53, into which the injection cham~er 54 opens, is completely filled.
During this phase, the position and the speed of displacement of the plunger 22 are detected by the 25. linear transducer 107. Continuing the upward movement 34 21527~
of the plunger 22 under the control of the processing unit 49, the metal material in the molten state is consequently forced to flow along the channels of the bottom die part, supplying the latter at different 5. predetermined injection points, for example along the peripheral edge of the die cavity, at a predetermined pressure, for example ranging between 50 and 350 Atm ~4,9 - 34,3 MPa), and at a speed which are controlled by the control system shown in Figure 11. In this way, 10. conditions of laminar flow of the molten metal are obtained, while the latter is fed into the die cavity;
in this way, dangerous turbulence phenomena and trapping of air in the jet are avoided, which, otherwise, could result in the formation of blisters and a greater degree 5. of fragility.
Therefore, during designing of the die assembly, it is necessary to calculate the appropriate flow cross-sections in accordance with the metal throughput and thepressure exerted on the molten metal, such that the 20. injection speed measured at the point where the metal is introduced into the die cavity i~ in a l~ i n~ r condition with a laminar speed of the flow equal to or less than 12 metres per second.When injection of the metal into the die has been completed and after a sufficient amount 25. of time has lapsed to allow consolidation thereof, the 21S275~
die assembly may be raised and opened, as shown in Figure 7, separating then the deadhead 31 which is dislodged from the plunger and made to fall along the inclined channel 30 onto the conveyor 32. At the same 5. time, the die assembly, as it opens, causes the side-blocks to move apart, freeing the cast piece which thus falls onto the table 26 positioned underneath.
When the operating cycle has been completed, it may be resumed for the production of a new pressure-ca~t o. piece in the manner described above, while at the same time cooling and varied temperature-regulation of the plunger and the sleeve of the injection device are continued.
Claims (15)
1. Process for the production of metal pressure die-castings, according to which a metered quantity of molten metal is fed into an injection device comprising a sleeve defining a vertical injection chamber, and a plunger movable inside said chamber between a retracted position, where it uncovers a lateral opening for entry of the molten metal, and an advanced position, where the molten metal is injected into the cavity of a die assembly, characterized by:
- providing an axially aligned arrangement of the sleeve and the injection plunger, while maintaining under different temperature controlled conditions the zones of the plunger and the part of the chamber of the injection sleeve located in the vicinity of the pressure-casting die assembly, which come into contact with the molten metal;
- detecting the temperatures of the plunger and the injection sleeve in the region of the said controlled temperature zones; and, - injecting the molten metal into the cavity of the die assembly upon reaching of a predetermined temperature difference between said temperature controlled zones of the sleeve and the injection plunger, at a pressure ranging between 50 and 350 Atm (4,9 - 34,3 MPa), maintaining laminar flow conditions of the molten metal while it is injected and flows into the cavity of the die assembly, ensuring the required axially aligned condition between sleeve and plunger of the injection device.
- providing an axially aligned arrangement of the sleeve and the injection plunger, while maintaining under different temperature controlled conditions the zones of the plunger and the part of the chamber of the injection sleeve located in the vicinity of the pressure-casting die assembly, which come into contact with the molten metal;
- detecting the temperatures of the plunger and the injection sleeve in the region of the said controlled temperature zones; and, - injecting the molten metal into the cavity of the die assembly upon reaching of a predetermined temperature difference between said temperature controlled zones of the sleeve and the injection plunger, at a pressure ranging between 50 and 350 Atm (4,9 - 34,3 MPa), maintaining laminar flow conditions of the molten metal while it is injected and flows into the cavity of the die assembly, ensuring the required axially aligned condition between sleeve and plunger of the injection device.
2. Process according to Claim 1, in which the molten metal is supplied at peripheral injection points and/or in the central part of the die cavity.
3. Process according to the preceding claim 2, in which the peripheral injection points are positioned along an external edge of the outline of the wheel defined by the die cavity.
4. Apparatus for the pressure die-casting of metal castings, comprising:
- a pot furnace of the pressurised type for containing molten metal;
- a horizontally arranged die assembly, said die assembly having a bottom die part and a top die part movable relative to one another between an open condition, and a closed condition in which said die assembly parts define a shaping cavity corresponding to the piece to be produced, said die assembly having channels for supplying the molten metal which open into the aforementioned cavity;
- an injection device for injecting the molten metal comprising a cylindrical sleeve having a lateral opening for feeding metal, which can be connected to the furnace by a supply duct, and a plunger axially sliding in the aforementioned cylindrical sleeve, the plunger being connected to an operating actuator;
- and pumping means for supplying a metered quantity of molten metal from the furnace to the sleeve of the injection device;
at least a first heat sensor and at least a second heat sensor being provided for detecting the temperatures of that parts of the sleeve and the plunger of the injection device, which are intended to remain in contact with the molten metal;
said first and second sensor being operationally connected to an electronic control unit of the programmable type;
detecting means for detecting the speed of displacement of the injection plunger and the pressure on the metal inside the chamber of the injection sleeve;
said control unit being programmed with data relating to reference pressures, speeds and temperatures so as to command said injection device to supply the molten metal into the cavity of the die assembly, upon reaching of a predetermined temperature difference detected by said first and second sensor, at said reference speed and pressure suitable for maintaining conditions of laminar flow of the molten metal while it is injected and flows into the cavity of the die assembly.
- a pot furnace of the pressurised type for containing molten metal;
- a horizontally arranged die assembly, said die assembly having a bottom die part and a top die part movable relative to one another between an open condition, and a closed condition in which said die assembly parts define a shaping cavity corresponding to the piece to be produced, said die assembly having channels for supplying the molten metal which open into the aforementioned cavity;
- an injection device for injecting the molten metal comprising a cylindrical sleeve having a lateral opening for feeding metal, which can be connected to the furnace by a supply duct, and a plunger axially sliding in the aforementioned cylindrical sleeve, the plunger being connected to an operating actuator;
- and pumping means for supplying a metered quantity of molten metal from the furnace to the sleeve of the injection device;
at least a first heat sensor and at least a second heat sensor being provided for detecting the temperatures of that parts of the sleeve and the plunger of the injection device, which are intended to remain in contact with the molten metal;
said first and second sensor being operationally connected to an electronic control unit of the programmable type;
detecting means for detecting the speed of displacement of the injection plunger and the pressure on the metal inside the chamber of the injection sleeve;
said control unit being programmed with data relating to reference pressures, speeds and temperatures so as to command said injection device to supply the molten metal into the cavity of the die assembly, upon reaching of a predetermined temperature difference detected by said first and second sensor, at said reference speed and pressure suitable for maintaining conditions of laminar flow of the molten metal while it is injected and flows into the cavity of the die assembly.
5. Apparatus according to Claim 4, in which the chamber of said injection sleeve terminates in an enlarged cavity, said enlarged cavity defining with a corresponding opposing surface of the bottom die part, a distribution chamber for the flow of molten metal into the cavity of the die assembly.
6. Apparatus according to Claim 4, in which the supply duct of the furnace terminates in a semi-spherical nozzle which sealingly fits into a corresponding semi-spherical seat at the front end of a connector for introducing the molten metal into the sleeve of the injection device, and in which disengageable connecting means are provided to sealingly connect said semi-spherical nozzle to the semi-spherical seat of the inlet connector.
7. Apparatus according to Claim 4, in which said sleeve of the injection device comprises an inlet connector for the molten metal, radially and downwardly oriented, and in which pneumatic cleaning means are provided for cleaning the aforementioned connector.
8. Apparatus according to Claim 4, in which said pneumatic cleaning means comprise a blowing nozzle connected to a compressed-air source, in an underlying position and sliding together with said plunger of the injection device.
9. Apparatus according to Claim 4, comprising means for circulating a heating and/or cooling fluid for keeping the sleeve of the injection device at a thermostatic temperature different from the thermostatic temperature of the plunger of the said injection device.
10. Apparatus according to Claim 4, comprising means for detecting the displacement of the injection plunger and means for detecting the pressure of the oil supplied to the hydraulic cylinder actuating the injection device, and in that said electronic control unit comprises a memory programmed with calculation algorithms for providing data indicating the speed of injection and flow of the molten metal into the die assembly, and the pressure exerted on the molten metal of said injection device.
11. Apparatus according to Claim 4, in which the die assembly is provided with a bottom die part and a top die part, said apparatus comprising a first movable platen supporting the bottom die part, a second movable platen supporting the top die part, and actuating means for moving said surfaces with the respective parts of the die assembly, between a raised position where the die assembly is open, and a lowered position where the die assembly is closed and connected to the aforementioned injection device.
12. Apparatus according to Claim 11, in which said bottom die part and said top die part each comprise a shaping part defining the die cavity, removably fixed to a support part.
13. Apparatus according to Claim 12, in which the bottom part of the die assembly further comprises an annular element arranged peripherally around said forming die, so as to define peripheral channels for injecting molten metal into the cavity of the die assembly, respectively comprising a seat for sealingly seating the top end of the sleeve of the injection device in a chamber for distribution of the metal flow.
14. Apparatus according to Claim 11, comprising a series of radially movable side-blocks which peripherally surround the die of the top die part.
15. Apparatus according to Claim 14, in which said movable side-blocks are connected to diverging bars sliding in guide collars and supported by a carriage axially slideable with respect to said top die part.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| ITMI941387A IT1270059B (en) | 1994-07-04 | 1994-07-04 | PROCESS AND EQUIPMENT FOR THE MOLDING OF METALLIC ALLOY PIECES |
| ITMI94A001387 | 1994-07-04 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2152758A1 true CA2152758A1 (en) | 1996-01-05 |
Family
ID=11369211
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002152758A Abandoned CA2152758A1 (en) | 1994-07-04 | 1995-06-27 | Process and apparatus for pressure die-casting |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0691166A1 (en) |
| CN (1) | CN1127174A (en) |
| CA (1) | CA2152758A1 (en) |
| IT (1) | IT1270059B (en) |
| TW (1) | TW267958B (en) |
Families Citing this family (18)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100357048C (en) * | 2004-03-30 | 2007-12-26 | 马自达汽车株式会社 | Casting method and casting apparatus |
| JP4015139B2 (en) * | 2004-06-28 | 2007-11-28 | ファナック株式会社 | Servo motor control device for forging machine |
| JP4688145B2 (en) * | 2005-06-09 | 2011-05-25 | 日本碍子株式会社 | Die casting apparatus and die casting method |
| WO2008040129A1 (en) * | 2006-10-06 | 2008-04-10 | Bühler Druckguss AG | Method for cooling casting pistons |
| US7886807B2 (en) | 2007-06-15 | 2011-02-15 | Die Therm Engineering L.L.C. | Die casting control method |
| US8356655B2 (en) * | 2011-02-09 | 2013-01-22 | United Technologies Corporation | Shot tube plunger for a die casting system |
| CN102218523A (en) * | 2011-04-21 | 2011-10-19 | 华南理工大学 | Method and system for adjusting temperature of extruding and casting pressure chamber |
| JP5935776B2 (en) * | 2013-09-03 | 2016-06-15 | トヨタ自動車株式会社 | Die casting method and die casting apparatus |
| ES2819773T3 (en) * | 2015-05-20 | 2021-04-19 | Alustrategy S R L | Improvements relating to equipment for the manufacture of light alloy or similar articles |
| CN106623839B (en) * | 2015-11-03 | 2020-01-14 | 广东科达洁能股份有限公司 | Casting forming machine |
| FR3044943B1 (en) * | 2015-12-11 | 2020-12-04 | Adm28 S Ar L | INJECTION TIP FOR A CASTING MACHINE, MACHINE AND CASTING PROCESS USING SUCH A TIP |
| ITUB20159255A1 (en) * | 2015-12-28 | 2017-06-28 | Stefano Beretta | LIQUID FORGING APPARATUS AND ITS METHOD |
| CN105655595B (en) * | 2016-03-14 | 2019-08-06 | 上海福万得物资有限公司 | A kind of device of the quick roll casting accumulator cell lead mesh sheet of energy |
| PT3645192T (en) * | 2017-09-11 | 2023-03-15 | Bux Ralf | Method, casting mold and device for producing a vehicle wheel |
| CN113814373B (en) * | 2021-10-19 | 2023-04-14 | 芜湖舜富精密压铸科技有限公司 | Integrated processing equipment of die casting production usefulness |
| CN116618603B (en) * | 2023-07-17 | 2023-09-19 | 合肥亚明汽车部件有限公司 | Aluminum alloy die-casting conveying, positioning and clamping integrated device |
| CN117428156B (en) * | 2023-12-21 | 2024-03-15 | 福建申利卡铝业发展有限公司 | High-efficient wheel hub casting equipment |
| CN118122991A (en) * | 2024-05-08 | 2024-06-04 | 福建远拓电气科技有限公司 | Die casting equipment is used in production of automatically controlled cabinet organism |
Family Cites Families (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB489944A (en) | 1937-02-03 | 1938-08-03 | Josef Polak | Improvements in or relating to pressure casting apparatus |
| FR902392A (en) * | 1943-04-01 | 1945-08-29 | Mahle Werk Gmbh | Casting mold for injection and pressure molding machines |
| DE1156205B (en) | 1959-02-11 | 1963-10-24 | Eckert G M B H Geb | Die casting machine |
| DE3013226A1 (en) | 1980-04-03 | 1981-10-15 | Nippon Light Metal Co. Ltd., Tokyo | Cooling of injection plunger in pressure die casting machine - where cooling water and air are circulated for controlled times through hollow plunger |
| JPS59215259A (en) * | 1983-05-19 | 1984-12-05 | Ube Ind Ltd | Injection device in vertical type die casting machine |
| JPS6030567A (en) * | 1983-07-25 | 1985-02-16 | Nippon Light Metal Co Ltd | Die casting method |
| DE3505554A1 (en) | 1983-08-17 | 1986-08-21 | Ortwin Prof. Dr.-Ing. Hahn | Method for controlling a die-casting machine |
| JPS6092060A (en) * | 1983-10-26 | 1985-05-23 | Toshiba Mach Co Ltd | Method for correcting pouring rate in die-casting machine |
| JPS62110855A (en) | 1985-11-08 | 1987-05-21 | Toshiba Mach Co Ltd | Casting apparatus |
| DE3636936A1 (en) | 1986-10-30 | 1988-05-05 | Buehler Ag Geb | Sensor-controlled evaluation circuits for die casting machines - allows measurement of several parameters from one sensor probe improving control |
| JPH0716779B2 (en) | 1987-12-29 | 1995-03-01 | トヨタ自動車株式会社 | Lower pressure type high pressure casting equipment |
-
1994
- 1994-07-04 IT ITMI941387A patent/IT1270059B/en active IP Right Grant
-
1995
- 1995-06-27 CA CA002152758A patent/CA2152758A1/en not_active Abandoned
- 1995-06-27 TW TW084106566A patent/TW267958B/zh active
- 1995-06-28 EP EP95110065A patent/EP0691166A1/en not_active Ceased
- 1995-07-04 CN CN95115001.4A patent/CN1127174A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| IT1270059B (en) | 1997-04-28 |
| TW267958B (en) | 1996-01-11 |
| EP0691166A1 (en) | 1996-01-10 |
| ITMI941387A1 (en) | 1996-01-04 |
| ITMI941387A0 (en) | 1994-07-04 |
| CN1127174A (en) | 1996-07-24 |
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| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |