APPARATUS FOR THE INJECTION OF METALS OR ALLOYS WITH A LOW MELTING POINT INTO A POLYMERIC MOULD OF AN ELASTOMER TYPE, THE POLYMERIC MOULD OF AN ELASTOMER TYPE EMPLOYED, AND A METHOD FOR THE OPERATION OF THE ASSEMBLY

Abstract

The present invention discloses a new process for the injection of metallic materials into polymer-based moulds, the mould itself required for a process of this nature, and the apparatus which will execute the process and will employ the mould, in such a way that moulds with greater or lesser properties of flexibility are subjected to a pressurised injection of metal thereon, it being possible to adjust and coordinate the parameters of pressure, flowrate, closure of the mould, and the conditions of the material, thanks to a new polymer-based mould which adapts its configuration to the rest of the system and to the pressurised injection of the material.

Claims

1. A method for the injection of metals or alloys with a low melting point into a polymeric mould of an elastomer type of the type which employ injection pressure control system and are equipped with a vacuum system, wherein the method comprises at least the following stages: choice of the mould to be employed in accordance with the item it is desired to produce; its identification and insertion into the injection equipment; once in the injection equipment, the mould is placed in the supporting and closure device, wherein it is positioned and locked at the set pressure; and this will be the projected area pressure, to which a pressure depending on the hardness of the mould and a corrective coefficient will be added; the transfer and injection device of the injection equipment collect the metal under the ideal conditions from said furnace/crucible, these being the melting point temperature of said metal or higher, so that said metal is conveyed to the pressure system in order to perform the injection; as well as the correct stirring of said material, so that once the filling stage commences, the pressure system may have in the chamber of said pressure system the corresponding metal, thus to exert pressure thereon and to perform the injection stage; prior to the commencement of the injection process itself, and/or during the metal injection itself, a vacuum is performed on the mould in order to extract the air from the channels and spaces for the formation of items by the vacuum system, which are sealed coupled to said mould via an aperture provided for that purpose, wherein this vacuum system is controlled by the regulation and control system; next, the injection of the metal on the polymer-based mould is performed, at a pressure and flowrate enabling the moulding of the items in said mould; the flowrate of the metal at the inlet of the item is configured to be between 0.05 m/s and 10 m/s, so the regulation of the pressure of the pressure system will be between 0.1 bar and 50 bar, and being said injection stage divided into various sub-stages wherein the injection flowrate into the mould is adjusted in accordance with whether it is the commencement of the injection, the filling or the compaction, it being possible to divide this into more stages, all coordinated with the regulation and control system; said injection of metal applied and the solidification time are adjusted for each type of piece and material injected; on conclusion thereof proceeding with the opening of the mould supporting and closure device, for its manual or automatic extraction, and the insertion of a new empty mould for the next metal injection process; wherein said process features means for the control and adjustment of the operating parameters of the systems included in the equipment, performing a static adjustment prior to each injection method in accordance with the mould, the material to be injected and the item to be obtained, and a dynamic adjustment during the injection process in accordance with the current stage, synchronising and varying the mould closure force with the injection flowrates at each stage, and activating or deactivating the vacuum generation system.

2. The method for injection according to claim 1, wherein the operating parameters to be controlled are at least: the temperature and stirring parameters of the material to be injected while in the supply device; that is, temperature and stirring; the force exerted by the supporting and closure device on the mould; the injection pressure and flowrate; control of the quantity, flowrate, pressure, temperature, etc. of the material injected and of the transfer means; the mould cooling temperature and solidification time parameters; the pressure of the vacuum system.

3. The method for injection according to claim 1, wherein the injection stage comprises different sub-stages which are controlled and regulated by the control system, and in coordination/synchronisation with the mould supporting and closure device and the vacuum generation system, synchronising the intensity of the force exerted on the mould, there being an approach stage, an injection stage, a slowing stage and a compaction stage, synchronising the intensity of the force, position and flowrate of the pressure system acting upon the metal to be injected, depending on whether it is at the approach stage, wherein there is a slight acceleration of the piston to convey the metal to the mould (11) inlet at a low flowrate, while at the commencement of the filling of the mould, during the injection stage, a great acceleration is performed, with a high flowrate of metal into the mould, which will be slowed after a period of time determined by the volumes of each item to be produced, reducing the flowrate prior to the filling of the items, in order that it may be a lower flowrate which performs the final filling at the compaction stage; all the aforesaid, synchronised with the pressure exerted by the mould closure device and likewise synchronised with the creation of the vacuum in such a way that it will be activated at the commencement of the injection stage and will conclude at the commencement of the compaction stage.

4. The method for injection according to claim 1, wherein the stage of selecting the mould to be used in the process and the identification of the same is performed automatically, by means of a rotating system holding the different moulds to be used in the production process.

5. (canceled)

6. An apparatus for the injection of metals or alloys with a low melting point into a polymeric mould of an elastomer type, of the type which executes a method such as that described in claim 1, and contains a supply of metal, whether incorporated in this equipment or as auxiliary equipment, wherein the apparatus for the injection of metals or alloys with a low melting point into a polymeric mould, this being of a high-temperature vulcanised elastomeric or Liquid Silicone Rubber (LSR) type, disposing: a device for the transfer and injection of the metal or alloy with a low melting point to be injected, supplied by the material supply device, wherein said device are constituted at least by device for the displacement through the same of said metal, and by a pressure system entrusted with the injection of the metal on the polymer-based mould; a mould supporting and closure device formed at least by a mould positioning/centring system, formed by centring devices, to locate said mould in the correct position for its coupling, and by a closure system with adjustable pressure; a system for the generation of a vacuum within the mould; a polymeric mould of a high-temperature vulcanised elastomeric or Liquid Silicone Rubber (LSR) type, which is inserted into the supporting and closure device, equipped with an sealed coupling between said mould and the transfer and injection device; a regulation and control system of the equipment, which may be manual or automatic, which control and regulate at least the device for the maintenance of the conditions of the metal in the material supply device, the transfer and injection device, the mould supporting and closure device, and the operation of the vacuum system.

7. The apparatus according to claim 6, characterised in that the regulation and control device of the equipment regulate and adjust, statically prior to each injection method in accordance with the mould, the material to be injected and the item to be obtained, and dynamically during the injection process, at least the following parameters: the temperature and stirring parameters of the material to be injected while in the supply device; the force exerted by the supporting and closure device on the mould; the pressure, piston travel and, therefore, the injection flowrate into the mould; control of the quantity, flowrate, pressure, temperature, etc. of the material injected and of the transfer and injection device; the mould cooling temperature and solidification time parameters; the pressure of the vacuum system, wherein, it being possible to perform multiple divisions or stages, as many as may be required, for the coordinated control of said parameters.

8. The apparatus according to claim 6, wherein the vacuum system is formed by a system with a vacuum pump, a vacuum reservoir, measuring elements, filters for particulates and possible contaminants, and the corresponding valves and ducts.

9. The apparatus according to claim 6, wherein the vacuum system is sealed coupled to the mould via an aperture in said mould, wherein said joint between the two is sealed.

10. The apparatus according to claim 6, wherein the metal transfer and injection device has an injection chamber upstream of the mould, which is filled with the material to be injected coming from the furnace or crucible, and wherein the pressure system acts.

11. according to claim 10, wherein the metal transfer and injection device are formed by a heated gooseneck partially inserted into the molten metal to be injected.

12. The apparatus according to claim 6, wherein the pressure system of the metal transfer and injection device is based on an assembly of impulsion elements for the material to be injected into the mould, these being formed by a mechanical device, (pneumatic piston, hydraulic piston, auger, etc.) controlled by the adjustment and control system with regard to the pressure, travel, stage and flowrate of the material to be injected, adjusted manually or automatically by said adjustment and control system and synchronised with the mould supporting and closure device and the vacuum generation system.

13. The apparatus according to claim 6, wherein the supporting and closure device are provided with a seal, integrated in the mould or independent therefrom, which facilitates the closing action at lower pressures.

14. The apparatus according to claim 6, wherein the injection of the metal into the mould is performed on a slope for the collection by gravity of the surplus material.

15. according to claim 6, characterised in that it features a mould cooling system by means of ventilated tables or the cooling of the supporting and closure device.

16. (canceled)

17. A polymeric mould of an elastomer type, of the type employed in processes of the pressurised injection of metals or alloys with a low melting point such as that mentioned in claim 1, constituted by two separable sections for the unmoulding of the pieces, wherein the mould features: in at least one of said sections, elements for the ingress of the material injected, leading from said inlet through the distribution channels to the cavities which form the items; elements for the ingress of metal, sealed coupled to the metal transfer and injection device of the injection equipment; its own distribution elements, in said inlet elements, located at the point of branching/distribution of the incoming flow from the transfer and injection device, toward the filling channels of the mould, being specific to each mould for direct distribution to each channel; an aperture for the sealed coupling of the vacuum system, provided with independent or specific channels which communicate with all the channels and internal spaces which will receive the metal injected under pressure.

18. The polymeric mould according to claim 17, wherein the distribution piece integrated in the mould is manufactured from a material with a greater resistance than that of the elastomer forming the mould, such as metallic or ceramic materials or an elastomer with a greater resistance than that of the mould, resistant to the pressures and temperatures employed and to the flow of metal at said pressure.

19. The polymeric mould according to claim 17, wherein the mould is provided with internal protections or new distribution elements at the points of impact of the material injected or of its branching, and also at the inlet from the transfer and injection device, having a greater resistance than that of the elastomer chosen for the mould itself, such as metallic or ceramic materials.

20. The polymeric mould according to claim 17, wherein the mould is of a hybrid nature, featuring therein totally rigid, fixed or removable parts subjected to the impact of the material injected or its branching, using materials resistant to distortion, wear and/or breakage.

21. The polymeric mould according to claim 17, wherein the connection between the vacuum system and the cavities destined for the formation of the items is performed via a minimal cross-section which at most shall be of four mm.sup.2, to prevent the passage of the metal.

22. The polymeric mould according to claim 17, wherein in the mould a heating or cooling layer or element is inserted to facilitate the exchange of heat with the material injected, based on electric elements or cooling/heating channels.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0074] For the better understanding of the above, a set of drawings is attached wherein, schematically and by way of a non-limitative example, a practical embodiment is portrayed.

[0075] FIG. 1 is a perspective view of the equipment for injection into a polymeric mould, with the transfer and injection device partially submerged in the furnace of molten metal.

[0076] FIG. 2 is an elevational view of the injection system, wherein the detail of the coupling between the mould, the closure device and the injection device is marked.

[0077] FIG. 3 is a view of the detail of the coupling between the polymeric mould, the closure device and the injection device.

[0078] FIG. 4 is an elevational view of the gooseneck-type injection system.

[0079] FIG. 5 is an upper plan view of a polymeric mould, seen from within.

[0080] FIG. 6 is a view of the detail of the coupling between the closure device and the injection device, using thermally insulated contact areas.

DESCRIPTION OF A PREFERRED EMBODIMENT

[0081] In one of the preferred embodiments of the present invention, as may be seen in FIGS. 1 to 5, the new apparatus (10) for injection into a polymer-based mould features a number of systems forming the same, including supporting and closure device (12) of the mould (11), metal transfer and injection device (13) and vacuum generation system, not portrayed in the figures, all governed by regulation and control system (15), which in the present embodiment are considered to be automatic.

[0082] The injection apparatus (10) requires a supply of molten metal under the ideal conditions of temperature and stirring for its injection into the mould (11), for example Zamak 5 at approximately 400-480 C. In the present embodiment, this molten metal will be supplied by a furnace (16) featuring parameters for the regulation of said conditions of temperature and stirring and equipped with its own regulation and control system, although alternatively, said regulation and control system of the furnace (16) may be connected to those of the injection apparatus (10) so that it also is governed therefrom in a centralised manner; in other embodiments, the furnace (16) may even be part of the injection system (10) itself.

[0083] The transfer and injection device (13) are formed by a number of gooseneck-type ducts, which in the present embodiment are heated, and through which the metal will flow, wherein said device (13) are partially inserted into the molten metal in the furnace (16), the lower part of the gooseneck remaining submerged; that is, the area for the filling of the impulsion chamber (21), so that it is always fed with metal via the aperture (22). This aperture is formed by communicating vessels, and as the impulsion chamber (21) of the gooseneck is in communication with the molten metal in the furnace (16), and with the piston (24) in a raised position, freeing said impulsion chamber (21), the metal flows therein (21). If the level of the metal in the furnace (16) falls, a regulation system may be used to give the piston longer displacement, as the metal will not be so high in the impulsion chamber as metal will have entered from a lower level.

[0084] The pressure system to perform the injection of the metal on the mould (11) is actuated by the action of a piston (24), which as it moves forward provides conditions of pressure and flowrate on the metal to be injected, wherein said forward movement, travel, pressure and flowrate of the pressure system are controlled and regulated by the system (15), by being aware of the position of said piston and of the previous parameters. The flowrate of the metal at the entrance to the piece will be configured to be between 0.05 m/s and 10 m/s; therefore, the regulation of the pressure in the pressure system will be between 0.1 bar and 50 bar.

[0085] As has been mentioned, this embodiment features a transfer and injection device (13), located within the supply means or furnace (16), although alternatively these injection device (13) may be external, of the cold-chamber type, and the molten metal must be supplied via a transfer system which fills the corresponding pressure system.

[0086] The extremity of the transfer and injection device, formed by an injector nozzle (23), must be sealed coupled to the supporting and closure device (12) containing the mould (11). Said sealed coupling is executed by the part-to-part pressurised contact between the nozzle (23) and the support (12) of the mould or the mould (11) itself. This airtight coupling system features complementary shapes so that, on entering into contact and under pressure, the metal injected under pressure cannot leak through said joint, the coupling being of a conical shape, opening towards the mould, to enable the expulsion of the solidified sprue.

[0087] This coupling system may be executed directly; metal part of the nozzle (23) against metal part of the mould (11) support (12), as portrayed in FIG. 3, but alternatively, as portrayed in FIG. 6, in the event of desiring thermal insulation of the nozzle (23) area, to prevent the solidification of the metal during injection, contact areas (100) of a rubber-like material are inserted in the coupling shapes; furthermore, due to their certain flexibility, these act as a seal between the bodies coupled under pressure.

[0088] This coupling is executed at a slope of 10 degrees to the horizontal in order to collect by gravity any surplus amount of the material injected. Alternatively, this slope may be varied, on condition that this return of molten metal toward the heated area of the injection system is achieved.

[0089] The injection apparatus (10) has a supporting and closure device (12) into which the mould (11) to be used in accordance with the type of item to be manufactured must be inserted. In the present embodiment, the choice of mould (11) is performed manually, and said mould will be identified at the regulation and control system (15) for the characteristics of said mould (11) and item to be known, and for any necessary adjustments to closing pressures, flowrates and injection pressures to be made, likewise the quantity of product, all this being performed automatically.

[0090] In alternative embodiments, there will be an automated mould (11) supply device, based on a rotating system whereon the moulds to be used during the production period, and which will be used in the injection apparatus (10), are placed. The supply of said moulds to the injection equipment is performed in an automated process by recognition and monitoring of mould references device and a transport/interchange system for the same.

[0091] The supporting and closure device (12) are formed by two parallel closure plates (31, 32), capable of relative displacement between the two, by means of displacement guide elements on the structure of the equipment, in order to insert the corresponding mould (11) between said plates (31, 32) and to close the same by exerting a specific closing pressure on the mould (11). In the present embodiment, one of said plates (31), which is stationary, is anchored to the structure (33) communicating with the transfer and injection device (13), having a slight displacement in order to receive the closing pressure of the plate (32) on the mould (11) located on said stationary plate (31). This placement of the mould (11) on the stationary plate (31) is performed by means of centring devices (60) which are coupled in a particular position to complementary shapes in the mould, ensuring the correct placement of the mould on the plate (31) and therefore the correct coupling of the assembly.

[0092] The plates (31, 32) may also feature perimetral walls locking the mould (11), to prevent the lateral expansion of the same (11) at the time of exerting the closing pressure.

[0093] The value of the closing pressure of the mould (11) exerted by the plates (31, 32) is that corresponding to the projected area pressure, as items with a greater volume will have a greater projected area and will require a greater closure pressure than smaller items; to this, a pressure corresponding to the hardness of the mould is added, in order to prevent excessive distortion of the same, and a corrective coefficient; the global result varying between values slightly higher than the injection pressure to values of higher closing pressures, with no need to reach the closing pressures for injection into metallic moulds. These closing pressures, which are governed automatically, are synchronised with the execution of the different stages of the injection process, said stages of the injection process being synchronised in turn with the vacuum system, thanks to the regulation and control system (15), which coordinate the values of the pressure exerted by the supporting and closure device (12) of the mould (11) with the real-time position and the values of flowrate and pressure of the piston (24) of the injection system, and the generation of a vacuum within said mould (11).

[0094] The correspondence between the generation of vacuum and the injection stages correspond to the table/diagram below, where it may be seen that the generation of vacuum commences at the beginning of the injection stage and will conclude at the beginning of the compaction stage.

[0095] The stationary plate (31) features an aperture which coincides with the position and size of the injector nozzle (23) for its sealed coupling, and also coincides with the inlet aperture (43) of the mould (11).

[0096] The vacuum generation system are located behind the closure plate (32) of the supporting and closure device (12), so that via the corresponding aperture in said plate (32), the mould (11) may be sealing coupled to the aperture (44) destined for the extraction of air from the channels of the mould (11).

[0097] The parameters of closing pressure, approach and flowrate of the injection pressure system, and therefore, the parameters of injection of the material, of the conditions of said material, of the vacuum pressures of the mould and the cooling parameters of the moulds are governed by the regulation and control system (15) of the injection apparatus (10), aided by the corresponding sensors of the temperature conditions, pressure, travel regulators, identification of the mould and of the piece to be manufactured, etc. This control and regulation system (15) automatically configures the above parameters in a coordinated manner, in accordance with the stages occurring.

[0098] The mould (11) employed in the apparatus (10) is polymer-based, thus featuring elastic properties, which vary in accordance with its composition and treatment. For its application in metal injection processes and equipment, of the two parts (41, 42) into which the mould (11) may be divided to perform its unmoulding, in the part (41) whereby the inflow of injected material is performed, an aperture (43) is foreseen for this purpose, communicating with the channels (45) which will convey the metal to the cavities (46) wherein the pieces are formed. Upstream of the branching of the inlet aperture (43) into the different channels (45), a distribution elements (47), of a more resistant material than that of the elastomer employed in the mould, preferably metallic or ceramic, capable of resisting distortion due to the pressure of the material injected and of resisting the multiple injection processes to which the mould (11) will be subjected, is to be found in the interior of the mould (11), solidarily therewith, specifically designed thereto and to the specific configuration of its channels (45).

[0099] The shape of said distribution elements (47) is such that it prevents as much as possible the loss of load at the metal inlet, and conveys said pressurised metal to the channels (45), it being the commencement of said channels (45), preventing the mould from damage at the area where it receives the impact of the injection, distortions affecting the useful life of the mould and the correct injection of the material, likewise the correct formation of the pieces.

[0100] The mould (11) features sprues (48) to house the air displaced by the metal which may remain after creating the vacuum.

[0101] The mould (11) features vacuum channels (50) which communicate with the vacuum generation means and which in turn connect with the cavities (46) and the channels (45) for the extraction of the air therein, and that which enters subsequently upon the entry of the metal into the injection system, displacing the air existing in said injection system.

[0102] The mould (11) may include a number of channels for cooling and/or heating fluid, which in the case of siliconized moulds or moulds composed of resins with high thermal insulation properties, may provide the necessary conditions for the process of obtaining the items, in addition to maintaining the conditions of temperature of the mould, in order to maintain its properties of hardness, which may vary according to the variations in temperature.

[0103] In alternative embodiments, with a rotating mould supply system, once the mould (11) has been extracted from the injection apparatus (10), mould (11) cooling means are provided, based on the ventilation of the same.

[0104] With regard to the method followed by the injection apparatus (10), once the mould (11) has been inserted into the supporting and closure device (12), and said mould (11) and the piece to be manufactured have been identified at the regulation and control means, the following stages and configurations are performed: [0105] The supporting and closure device carry out the coupling between the closure plate (32) and the mould (11), which is in its correct position due to the centring devices (60) which prevent incorrect coupling, and is aligned with the nozzle (23) to perform the airtight coupling between mould (11) and nozzle (23). [0106] The mould is closed at a pressure governed by the regulation and control means (15), in accordance with the identification of the type of mould (11) and the injection parameters to be applied during the process, all the above automatically; this will be the projected area pressure, to which a pressure depending on the hardness of the mould and a corrective coefficient will be added. [0107] The transfer means (13), which are partially inserted into the molten metal in the furnace (16), collect the molten metal in the impulsion chamber (21) via the aperture of communicating vessels, the piston (24) being at its highest position, enabling the ingress of metal into said chamber (21). [0108] The generation of a vacuum in the mould (11) for the extraction of air from the channels (45) and the cavities (46) for the formation of items, is performed by the vacuum means which are sealed coupled to said mould (11) via an aperture provided for this purpose, wherein this vacuum system is controlled by the regulation and control system, which will activate it at the commencement of the injection stage and will deactivate it at the commencement of the compaction stage. [0109] Next, the injection of the metal on the polymer-based mould (11) is performed, at a pressure and flowrate which enables the moulding of the pieces in said mould (11), regulating the parameters of piston (24) travel and the pressure exerted by said piston, in order to achieve the desired acceleration of the same. This stage is divided into various sub-stages, these being: an approach stage, an injection stage, a slowing stage and a compacting stage, and in coordination/synchronisation with the mould supporting and closure device and the vacuum generation system, synchronising the intensity of the force, position and flowrate of the pressure system, acting upon the metal to be injected, depending on whether it is at the approach stage, wherein there is a mild acceleration of the piston to convey the metal to the mould (11) inlet at a low flowrate, while at the commencement of the filling of the mould, during the injection stage, a great acceleration is performed, with a high flowrate of metal into the mould, which will be slowed after a period of time determined by the volumes of each item to be produced, reducing the flowrate prior to the filling of the items, in order that it may be a lower flowrate which performs the final filling at the compaction stage. All of the above, as has been stated, synchronised with the pressure exerted by the mould closure system, also synchronising with the creation of the vacuum or otherwise in each stage, as required. [0110] Said injection of metal and the solidification time, likewise the action of the mould heating/cooling elements, are adjusted for each type of item and material injected; once completed, proceeding with the opening of the supporting and closure device (12) of the mould (11), for its manual or automatic extraction and the insertion of a new empty mould (11) for the next metal injection process.

[0111] The system (15) for the control and adjustment of the operating parameters of the systems included in the appartus (10) perform a static adjustment prior to each injection method in accordance with the mould (11), the material to be injected and the item to be obtained, and a dynamic adjustment during the injection process in accordance with the current stage, controlling: [0112] the parameters of the metal to be injected within the supply device (16); that is, temperature and stirring; [0113] the force exerted by the supporting and closure device (12) on the mould (11); [0114] the pressure and displacement of the piston (24), and consequently the injection flowrate into the mould (11). [0115] the quantity, flowrate, pressure, temperature, etc. of the material injected and of the transfer means (13). [0116] the mould (11) cooling parameters and solidification time. [0117] the vacuum system parameters.

[0118] Although reference has been made to a specific embodiment of the invention, it is evident to an expert skilled in the art that the invention described is susceptible to numerous variations and modifications, and that all the details mentioned may be substituted by other technically equivalent details, without departing from the scope of protection defined by the appended claims.