Patent Application
20090029076
The present invention generally relates to, but is not limited to, molding systems, and more specifically the present invention relates to, but is not limited to, (i) a metal-molded article, (ii) a mold for making a metal-molded article.
Examples of known molding systems are (amongst others): (i) the HyPET™ Molding System, (ii) the Quadloc™ Molding System, (iii) the Hylectric™ Molding System, and (iv) the HyMET™ Molding System, all manufactured by Husky Injection Molding Systems (Location: Canada; www.husky.ca).
United States Patent Application Number 2005/0001354 (Inventor: Klocke et al.; Published: 2005 Jan. 6) discloses a process for preparing a composite hollow body article by means of injection molding. The process includes the steps of: (a) providing a hollow body having exterior surfaces and interior surfaces, the interior surfaces of the hollow body defining a hollow interior, the hollow body also having at least one opening which provides fluid communication with the hollow interior thereof, (b) introducing a substantially incompressible fluid into the hollow interior of the hollow body, the hollow interior being substantially filled with the substantially incompressible fluid; and (c) injection molding thermoplastic material onto at least a portion of the exterior surfaces of the hollow body. The object of the present invention is to provide a process for the production of a plastics/metal composite component which consists at least of a hollow body made of metal or plastics material, in which process the hollow body does not become deformed when thermoplastic plastics material is injection molded onto and/or around it. Specifically, paragraph 16 indicates that “the incompressible fluid with which the hollow body is filled according to the invention when the thermoplastic plastics material is injection molded onto or around the hollow body prevents plastic deformation of the hollow body by the injection pressure. The incompressible fluid provides the necessary counter-pressure to the injection pressure. In a preferred embodiment of the process according to the invention, a positive pressure of less than or equal to 130 bar is applied to the incompressible fluid (e.g., a pressure of from 1 bar to 130 bar).” Specifically, paragraph 17 indicates that “the incompressible fluid may be, for example, water, a water/oil mixture, especially an oil-in-water emulsion, a water/glycol mixture or a (mineral) oil. Such fluids are known, for example, as hydraulic fluids of category HFA (oil-in-water emulsions or solutions, which contain more than 80% water), HFB (water-in-oil emulsions having a water content of about 45%) and HFC (polymer/water or water/glycol mixture having a water content of at least 35%). It is additionally possible to use electro-viscous or magneto-viscous fluids.” Specifically, paragraph 21 indicates that the “preferred metals from which the hollow body may be fabricated include steel, nickel, chromium, iron, copper, zinc, titanium, aluminum and magnesium and also alloys of those metals.”
PCT Patent Application Number WO 2005/002825 (Inventor: KLOCKE; Published: 2005 Jan. 13) discloses a method for producing a plastic/metal composite part consisting of at least one metal or plastic hollow body which is provided with at least one aperture and on which injection molding and/or total or partial over-molding with thermoplastic are carried out. The hollow body is entirely filled with an incompressible liquid during injection molding and/or over-molding.
The inventors believe they have arrived at an understanding of the problem that is not known and/or understood to persons skilled in the art. In the conventional die-casting processes, a mold core is extracted after a die-casting operation. The mold core is routinely used to form holes or voids in molded parts. Another molding solution uses an expendable core that is disintegrated (or removed) in a post molding operation, and thereby an internal channel may be formed in a molded article. However, to use a high-pressure injection molding process, a necessity to withstand high injection speeds and high pressures (or impacts) creates a series of problems related to the brittle nature of a molded part. A second problem associated with a molded component having a light metal alloy (such as a magnesium alloy) is the increased reaction and resultant corrosion caused by a cooling media in contact with the magnesium alloy. This is a reason for which forced-cooled molded components made out of the magnesium alloy are not seriously considered by designers of molded parts. The nature of the laminar flow associated with a magnesium injection molding process (along with the high level of automation used) may permit opportunities to create more complex parts without significant added cost in the molding operation.
The method proposed by the inventors, includes insertion of a hollow insert (at least one hollow insert) or a collection of hollow inserts (either interconnected or not interconnected) in a mold prior to injection of a metallic alloy (light metal alloy, such as magnesium) into the mold. The hollow insert is permanently over-molded (at least in part). The hollow insert may be made out of a material that is compatible with the light-metal alloy and the cooling media flowing through the hollow insert during the operation. The hollow nature of the hollow insert will allow a broader choice of materials without a negative impact on the weight of the final part.
A technical effect, amongst other technical effects, of the aspects of the present invention is that the hollow insert may be used to perform a function, such as: cooling, heating, weight saving, fluid transfer, improved strength, etc. Also, removal of heat directly from the part being molded during the molding operation may be performed if it is deemed necessary for reducing cycle time of the injection molding system.
According to a first aspect of the present invention, there is provided a metal-molded article, including: a body molded in association with a mold assembly; and a hollow insert embedded, at least in part, in the body, the body having a light-metal alloy that was injected, under pressure, into the mold assembly.
According to a second aspect of the present invention, there is provided a metal-molding process, including: a positioning operation, including positioning a hollow insert in a mold assembly being couplable with an injection metal-molding system; a closing operation, including closing the mold assembly over the hollow insert at least in part; and an injecting operation, including injecting a light-metal alloy into the mold assembly, the light-metal alloy surrounding, at least in part, the hollow insert, and the light-metal alloy forming into a body of a metal-molded article.
According to a third aspect of the present invention, there is provided a mold assembly for molding a metal-molded article, the mold assembly including: a mold portion, having: a molding surface configured to mold, at least in part, a body; and an insert locator configured to locate, at least in part, a hollow insert, the hollow insert to be embedded, at least in part, in the body, the body having a light-metal alloy that was injected, under pressure, into the mold assembly.
A better understanding of the non-limiting embodiments of the present invention (including alternatives and/or variations thereof) may be obtained with reference to the detailed description of the non-limiting embodiments of the present invention along with the following drawings, in which:
The drawings are not necessarily to scale and are sometimes illustrated by phantom lines, diagrammatic representations and fragmentary views. In certain instances, details that are not necessary for an understanding of the embodiments or that render other details difficult to perceive may have been omitted.
The following is a listing of the elements designated to each reference numeral used in the drawings:
According to variants: the mold portion 22 may include: (i) a boss molding surface 42 configured to locate, at least in part, a boss 44 (depicted in
According to a variant, the hollow insert 100 includes: (i) a tube, (ii) a hollow core, and/or (iii) a network of tubes. According to yet another variant, the light-metal alloy includes a magnesium alloy. Given magnesium's good thermal conductivity, it is in many occasions preferred to plastics in applications where heat removal is a requirement, despite the increased level of complexity posed by magnesium injection molding as compared to plastics. Usually, thermal conduction coupled with natural convection generated at the outside of the part is used to dissipate the heat generated inside casings. Another important feature generated by the magnesium injection process is light-weight components. This is achieved by the low density of the magnesium alloy and a shell design combined with thin wall ribs. The hollow inserts can enhance the light weight requirement in areas where the shell design is not suitable. Providing a liner (that is, a hollow insert) with the desired properties may be an advantage for the parts produced with this method.
According to a variant, the fluid: (i) includes a coolant, and the coolant is compatible with the hollow insert 100, (ii) is configured to exchange heat, at least in part, with the body 60, and/or (iii) is configured to exchange heat, at least in part, with the body 60. By inserting a cooling/heating circuit into a magnesium component, a larger variety of applications may be accommodated and an increased level of complexity of the molded part may be achieved without significant change in the molding process. Examples of the article 10 include: (i) magnesium seat frames, (ii) automobile steering wheels, (iii) engine blocks, etc. According to other non-limiting variants, the hollow insert 100 permits weight reduction of the body 60, and/or the hollow insert 100 permits conveyance of a vacuum.
It will be appreciated that the fluid may be conveyed to and away from the interior of the hollow insert 100 while the mold is closed and clamped shut; if this arrangement is required, then the hollow insert 100 may be extended so that the insert 100 reaches outside of the mold (this arrangement is not depicted); how the fluid is conveyed to and away from the interior of the hollow insert 100 could be achieved by selecting an appropriate arrangement for connecting the fluid to the insert 100.
It will be appreciated that, under some cases, the insert 100 may be relatively fragile enough to require an internal, counter pressure during injection of the surrounding molten alloy molding material, and the timing of when the counter pressure is applied to and withdrawn from the interior of the insert 100 may be determined with some experimentation because otherwise the insert may rupture under excessive pressure during injection of the molten alloy. However, there may be cases where the insert 100 may be able to withstand the injection pressure associated with the molten alloy, and in these cases therefore the counter pressure during injection may not be required. An example of how pressurization of a part may be achieved is described in PCT Patent Application WO 2005/002825(A1).
The description of the non-limiting embodiments provides non-limiting examples of the present invention; these non-limiting examples do not limit the scope of the claims of the present invention. The non-limiting embodiments described are within the scope of the claims of the present invention. The non-limiting embodiments described above may be: (i) adapted, modified and/or enhanced, as may be expected by persons skilled in the art, for specific conditions and/or functions, without departing from the scope of the claims herein, and/or (ii) further extended to a variety of other applications without departing from the scope of the claims herein. It is to be understood that the non-limiting embodiments illustrate the aspects of the present invention. Reference herein to details and description of the non-limiting embodiments is not intended to limit the scope of the claims of the present invention. Other non-limiting embodiments, which may not have been described above, may be within the scope of the appended claims. It is understood that: (i) the scope of the present invention is limited by the claims, (ii) the claims themselves recite those features regarded as essential to the present invention, and (ii) preferable embodiments of the present invention are the subject of dependent claims. Therefore, what is to be protected by way of letters patent are limited only by the scope of the following claims:
