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.

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 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.