Injection molding method and apparatus for manufacturing components made of plastic material

Abstract

The embodiments described herein relate to a method and apparatus for manufacturing a component made of a plastic material suitable for use as a container, a housing for a household appliance, or a receptacle, the component comprising a first layer and a second layer covering at least a portion of the first layer.

Description

[Technical Field]

[0001] The embodiments described herein relate to methods and apparatus for manufacturing components having a body with two superimposed layers of plastic material.

[0002] Such a component is particularly suitable for use as a container or housing for a household appliance such as a kettle, a toaster, a vacuum cleaner, a coffee machine, a blender or an iron.

[0003] The invention also relates to a component made of plastic material and to a household appliance or receptacle comprising such a component. [Background technology]

[0004] In the field of household appliances, it is known to manufacture components or finished objects having two or more layers of plastic material that at least partially overlap one another to provide a defined aesthetic appearance. Such components can be used to form the exterior structure of, for example, household appliances or articles or objects such as carafes, bowls, and the like, but the examples of such articles or objects are not limiting.

[0005] It is also known that there is an increasing focus on aesthetic research in the design and manufacture of household appliances to satisfy consumer preferences, in order to provide an attractive and recognizable aesthetic appearance and stand out from similar solutions on the market.

[0006] For example, a component that serves as the container for a kettle is known, which comprises a first layer of a transparent plastic material and a second layer of a metal material, with multiple through-holes formed in the second layer through which the first layer and, by extension, the interior of the kettle itself can be seen.

[0007] However, this solution requires that the first and second layers be fabricated separately and then subsequently bonded together to join them together, which creates problems with bonding and sealing between them.

[0008] The aesthetic research described above has also led to the production of domestic appliances with an external structure made of plastic material consisting of two layers overmolded together.

[0009] Methods for manufacturing components of household appliances are also known in which a first layer of plastic material is injected followed by a second layer of plastic material, for example, the first injected layer can be a transparent material and the second layer can be a colored and / or opaque material.

[0010] In particular, the second layer of material can be injected over only a portion of the outer surface of the part being manufactured, thereby maintaining at least a portion of the first injected layer visible to achieve a desired aesthetically pleasing appearance in the final product. Alternatively, the injected material of the first layer can be colored and / or opaque, while the second layer can be a transparent or translucent material, allowing the injected material of the layer below to be visible.

[0011] Alternatively, the materials used have technical characteristics of mechanical and / or thermal and / or aesthetic type that make them unsuitable for contact with food and therefore cannot be used for the first layer.

[0012] Articles such as bowls or cutlery handles are also known that comprise a first layer of material entirely covered by a second layer of material, the first layer being thicker than the second layer and acting as a structural member while the second layer acts as an aesthetic surface finish.

[0013] Overmolding a second layer of material onto a first layer of material can be problematic. In fact, overmolding a second layer onto a first layer can result in "washing out" of the first layer, leading to aesthetic problems. This problem is particularly noticeable when at least a portion of the outer layer is transparent.

[0014] Overmolding of materials can be even more complicated in the case of so-called bi-injection processes, where the step of injecting a first layer of material is immediately followed by the step of injecting a second layer of material.

[0015] Due to the melting temperature of the second material, there may in fact be undesirable secondary melting of the underlying layer of material already injected at locations where the cooling rate is slow.

[0016] To avoid the problem of remelting of the inner layer, a known solution is to make the inner layer from a material that has a higher melting point than the material used for the outer layer.

[0017] Such a solution may result in the use of more expensive materials for the inner layer that are less open and familiar to users, resulting in higher costs.

[0018] EP 2333421 A1, US 5045268 B1 and JP 2019-202537 A1 describe methods for producing components made of plastic material by two-component injection molding of two materials.

[0019] JP 63-317315 describes a component made of plastic material for manufacturing a cover for a light, which has a diamond-cut finish.

[0020] US Patent Application Publication No. 2010 / 124002 describes a component made of plastic material for a video camera.

[0021] US Patent Application Publication No. 2016 / 374488 describes cutlery made from plastic material.

[0022] The solutions described in the above documents are not suitable for producing components made of plastic material, such as housings or containers for household appliances, in particular kettles or toasters, where the containers are suitable to withstand temperatures above 100°C.

[0023] Therefore, there is a need to develop a method for manufacturing components made of plastic materials that overcomes at least one of the drawbacks of the prior art.

[0024] Another object is to provide a method for manufacturing components made of plastic material that can achieve high productivity and efficiency at high speed.

[0025] Another object of the present invention is to complete a method for manufacturing a component made of plastic material with an inner layer and an outer layer, which makes it possible to avoid any possible "washing out" or remelting of the inner layer.

[0026] Another object is to perfect a method for manufacturing components made of plastic material that allows the production of components with a colored inner layer and a glossy, transparent outer layer that are substantially defect-free.

[0027] Another object is to complete a highly efficient and economical method for manufacturing components made of plastic materials, which method achieves high productivity while simultaneously reducing overall costs.

[0028] The applicant has devised and tested to overcome the shortcomings of the prior art and to achieve these and other objects and advantages and has thus achieved the present invention. Summary of the Invention

[0029] The invention is defined in the independent claims, which describe its features, while the dependent claims describe other features of the invention or variants of its main inventive idea.

[0030] In accordance with the above objectives, the present invention relates to a method and an apparatus for manufacturing a component made of a plastic material suitable for forming a housing, a housing, a shell, an external structure and / or an external body of a household appliance, or at least a part thereof.

[0031] Examples of applications of the components of the present invention may include household appliances such as kettles, toasters, vacuum cleaners, electric brushes, blenders, microwave ovens, electric ovens, fryers, teapots, coffee machines, ice cream makers, kneaders, and hair dryers.

[0032] The component of the present invention has a body made of a plastic material with a first inner layer of a first material and a second outer layer of a second material covering at least a portion of the first inner layer.

[0033] In some embodiments, the second layer covers the entire first layer.

[0034] In some embodiments, the thickness of the outer second layer is greater than the thickness of the inner first layer.

[0035] In some embodiments, the member has a cylindrical shape, which may have a circular, polygonal, or elliptical cross section, or a circumference that combines straight and curved sections. Furthermore, the cross section of the member may be constant or variable along its axial progression, and may have concave or convex portions.

[0036] In some embodiments, the first material can be opaque, or one color, or multiple colors, and the second material can be at least partially transparent, allowing the opaque first layer to be visible through the second material, thereby giving the final part a partially convex, three-dimensional appearance.

[0037] In other embodiments, the transparent outer second layer extends beyond the edge of the inner first layer in at least the axial direction, resulting in the member having a transparent peripheral strip, which provides the effect of transparency and brightness.

[0038] In some embodiments, the outer second layer may extend beyond the edge of the inner layer and itself form one or more portions of the body, such as a spout or handle in the case of a kettle or carafe, or other decorative feature.

[0039] The method for producing a component made of a plastic material of the present invention comprises the steps of: a first injection step of injecting a first plastic material into a first molding volume defined between the punch and the first receiving die at first operating parameters including a first injection temperature and a first injection pressure to create an inner first layer having a first thickness; a second step of injecting a second plastic material into a second molding volume defined between the inner layer obtained in the first step and the second receiving mold at second operating parameters including a second injection temperature and a second injection pressure to produce a second outer layer having a second thickness; and The second thickness is greater than the first thickness of the inner first layer.

[0040] By making the thickness of the outer second layer greater than that of the inner first layer, the resistance to the filling flow of the second material is reduced, thereby reducing the so-called shear stress phenomenon in said material and preventing the formation of aesthetic defects that may be caused by mechanical friction of the second material due to rubbing against the walls of the mold or the material of the first layer.

[0041] By making the thickness of the second layer greater than that of the first layer, it is also possible to obtain a three-dimensional finish on its surface, which gives the plastic material part an exceptional and distinctive aesthetic appearance.

[0042] In some embodiments, the first material and the second material have the same physical properties.

[0043] In a preferred embodiment, the first material is opaque and the second material is at least partially transparent, allowing the first layer to be visible through the second material.

[0044] The combination of opaque and transparent materials can give the final part a partially convex, three-dimensional appearance.

[0045] In some embodiments, the operating parameters of the second injection step are different from the operating parameters of the first injection step.

[0046] In some embodiments, at least one of the second injection temperature or the second injection pressure is lower than the corresponding first injection temperature and first injection pressure.

[0047] Such embodiments reduce the temperature / pressure stresses on the first layer, thereby preventing possible washout or remelting of the first material and thereby preventing possible contamination of the second material.

[0048] In some embodiments, both the second injection temperature and the second injection pressure are lower than the first injection temperature and the first injection pressure, respectively.

[0049] In some embodiments, the second injection temperature is 5-10% lower than the first injection temperature.

[0050] By making the second layer thicker, the injection temperature can be reduced without creating undesirable bond lines because a larger amount of second material is available to retain heat as it fills the second mold volume.

[0051] In some embodiments, the second injection pressure is 10-30% lower than the first injection pressure.

[0052] The above embodiment also allows the second material flow to be generated at a lower pressure, since the thickness of the second forming volume is greater than the thickness of the first forming volume.

[0053] In some embodiments, the method includes cooling a first layer of a first material to a first cooling temperature and cooling a second layer of a second material to a second cooling temperature that is lower than the first cooling temperature.

[0054] The present invention also relates to an apparatus for manufacturing a part made of a plastic material as described above, the apparatus comprising a first moulding assembly having a punch, a first receiving die and a first injection unit, and a second moulding assembly having a second receiving die and a second injection unit, the punch and first receiving die being adapted to define a first moulding volume having a first width between the punch and the first receiving die, the first injection unit being configured to inject a first plastic material into the first moulding volume, the second receiving die being adapted to define a second moulding volume having a second width together with the first layer of material, and the second injection unit being configured to inject a second plastic material into the second moulding volume.

[0055] In one aspect of the invention, the second width is greater than the first width.

[0056] In some embodiments, the first injection unit comprises heating means configured to heat a first plastic material to a first injection temperature and an injection device configured to inject the first material at a first injection pressure, and the second injection unit comprises heating means configured to heat a second plastic material to a second injection temperature and an injection device configured to inject the second material at a second injection pressure.

[0057] In some embodiments, the first and second heating means may be operated and regulated independently of each other.

[0058] In another embodiment, the first molding unit includes a first cooling circuit and the second molding unit includes a second cooling circuit independent of the first cooling circuit, the first cooling circuit and the second cooling circuit being selectively configurable to cool the first plastic material and the second plastic material to respective cooling temperatures, the second cooling temperature being lower than the first cooling temperature.

[0059] These and other aspects, features and advantages of the present invention will become apparent from the following description of some embodiments, which are provided by way of example rather than limitation, and which are considered in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0060] [Figure 1] 1 is a schematic diagram of components of an embodiment of the present invention applied to a household appliance, the household appliance shown in this example being a kettle. [Figure 2] FIG. 2 is a cross-sectional view taken along the line II-II in FIG. [Figure 3] FIG. 3 is an enlarged detail view of a portion of FIG. 2. [Figure 4] 1 is a schematic diagram of components of another embodiment of the present invention applied to another household appliance, in this case the other household appliance being a toaster. [Figure 4a] FIG. 10 is a three-dimensional view of a detail of a component of another embodiment of the present invention. [Figure 4b] FIG. 10 is a three-dimensional view of a portion of a member of another embodiment. [Figure 4c] FIG. 10 is a three-dimensional view of a portion of a member of another embodiment. [Figure 5] 1 is a schematic diagram of an apparatus for manufacturing components made of plastic material according to some embodiments. [Figure 6] 1 is a vertical cross-sectional view of the element of the invention at the end of the first step of injecting the first material; FIG. [Figure 7] 3 is a vertical cross-sectional view of the element of the invention at the end of the second step of injecting the second material; FIG. [Figure 8] FIG. 6 is an enlarged detail view of the apparatus of FIG. 5 during the first injection step. [Figure 9] 9 is a cross-sectional view of the device of FIG. 5 taken along section line IX-IX. [Figure 9a] FIG. 10 is an enlarged detail view of FIG. [Figure 10] FIG. 7 is a cross-sectional view taken along line XX in FIG. 6. [Figure 11] 10 is a cross-sectional view of the device of FIG. 5 taken along section line XI-XI. [Figure 12] A cross-sectional view taken along line XII-XII in Figure 7. DETAILED DESCRIPTION OF THE INVENTION

[0061] Reference will now be made in detail to possible embodiments of the invention. One or more examples of these embodiments are illustrated in the accompanying drawings. Each example is provided by way of illustration of the invention and should not be construed as limiting the invention.

[0062] Before describing these embodiments, it should be made clear that the present invention is not limited in its application to the precise construction and arrangement of parts set forth in the following description, which refers to the accompanying drawings. The following description may provide other embodiments, and may be produced or carried out in various other ways. It should also be made clear that the words and terminology used herein are for descriptive purposes only and should not be construed as limiting the present invention.

[0063] The accompanying drawings are used to illustrate an embodiment of an element 10 made of a plastic material suitable for constituting a housing, a shell, an external structure and / or an external body of a household appliance 50, or at least a part thereof, or other object such as, for example, a bowl, a carafe, a thermos, etc.

[0064] In the following description, household appliances such as a kettle 50A and a toaster 50B are used as examples, however it is understood that the component 10 of the present invention can be a housing or a housing for other types of household appliances such as a vacuum cleaner, an electric brush, a blender, a microwave oven, an electric oven, a fryer, a teapot, a coffee machine, an ice cream maker, a kneader, a hair dryer, an iron, etc.

[0065] The component 10 of the present invention comprises an inner, first layer 11 and a second, outer layer 12 at least partially overlapping the inner, first layer 11 .

[0066] In some embodiments, the member 10 comprises only two layers: a first layer 11 and a second layer 12 .

[0067] In a preferred embodiment, the first layer 11 and the second layer 12 may be made of a plastic material, such as a heat resistant polymeric material.

[0068] In a possible embodiment, the first layer 11 and the second layer 12 may be made of materials with similar properties and characteristics.

[0069] In a possible embodiment, the first layer 11 and the second layer 12 may be made of materials with dissimilar properties and characteristics.

[0070] In some embodiments applicable to, for example, household appliances for food processing, the first layer 11 and the second layer 12 may be made of a resin suitable for food applications, such as polypropylene.

[0071] In a possible embodiment, only the first layer 11 is suitable for food applications, whereas the second layer 12 is not suitable for such applications.

[0072] In other embodiments, depending on the application, the first layer 11 and / or the second layer 12 can be made of thermoplastic resins of different properties.

[0073] In some embodiments, the first layer 11 can be made of an opaque first material or of a single or multiple colors, and the second layer 12 can be made of an at least partially transparent second material, allowing the inner opaque first layer 11 to be visible through the second material.

[0074] A layer is transparent or translucent if it allows optical radiation to pass through the entire thickness of the layer, allowing objects located beyond the layer to be visible.

[0075] This gives the final part 10 a partially convex, three-dimensional appearance.

[0076] In some embodiments, the first layer 11 and the second layer 12 can be made by a two-component injection molding process.

[0077] In some embodiments, the first layer 11 has a first thickness S1 and the second layer 12 has a second thickness S2 that is greater than the first thickness S1.

[0078] In some embodiments, the first thickness S1 and the second thickness S2 can be defined as the maximum thickness of each layer.

[0079] Advantageously, the ratio of the second thickness S2 of the second layer 12 to the first thickness S1 of the first layer 11 may be in the range of 1.05-2.5, more preferably in the range of 1.1-2.

[0080] The first layer 11 has a first surface 13 which forms the inner surface of the member 10 and faces the interior of the household appliance 50 when in use.

[0081] The first layer 11 also has a second surface 14 opposite the first surface 13, with an outer second layer 12 disposed in contact with the second surface 14.

[0082] In some embodiments, the inner first surface 13 can have a smooth, uniform transition without any irregularities.

[0083] The second layer 12 has an outer surface 15 opposite the inner surface 13, which in use becomes the outer surface of the component 10 and thus the outer surface of the household appliance 50 to which the component 10 is applied.

[0084] In some embodiments, the exterior surface 15 has a three-dimensional finish and has at least a portion thereof having a plurality of aesthetic reliefs 16 protruding therefrom, the reliefs 16 being adapted to give the component 10 a pleasing aesthetic appearance.

[0085] The relief in the examples of possible embodiments shown, for example, in Figures 1, 2, 3, 4, 4a and 4b, can include a plurality of parallel ribbed, bubble, hemispherical, diamond-like features, or other geometric or non-geometric aesthetic relief 16.

[0086] In particular, the outer surface 15 has alternating protrusions 17 and recesses 18 which give the member 10, and the household appliance 50 as a whole, a three-dimensional appearance.

[0087] In some embodiments, protrusions 17 and recesses 18 each correspond to areas of different thickness on inner surface 13 of member 10 .

[0088] In a possible embodiment, the projections 17 are formed as vertical ribs that are substantially parallel to and adjacent to one another.

[0089] Possible variations include horizontally or obliquely arranged ribs or projections or reliefs with a spiral or convoluted progression.

[0090] In another embodiment shown in FIG. 4a, the protrusions 17 may be formed as adjacent hemispheres or bubble portions distributed evenly or in a desired arrangement.

[0091] In another embodiment shown in FIG. 4b, the protrusions 17 can be formed in the shape of a polygonal pyramid, and in the case of the rectangular type in this example, can be formed side by side.

[0092] In other variants not shown, the relief 16 can have other shapes and can also have non-geometric shapes, for example, a flower shape, a heart shape, etc.

[0093] In some embodiments, the member 10 can have a cylindrical shape.

[0094] The cross section of member 10 may be circular, polygonal, or elliptical, or may have a perimeter that combines straight and curved sections, depending on the desire or application.

[0095] Furthermore, the cross section of the member 10 may be constant or variable along its axial progression, and may have concave or convex portions.

[0096] In other embodiments, member 10 may be open curved and configured to connect to other similar members 10 to form a housing or enclosure for household appliance 50, or to connect to different members to form a housing or enclosure.

[0097] In some embodiments, the outer second layer 12 covers the entire inner first layer 11 .

[0098] In another possible embodiment, the second layer 12 has an outer edge 23 which extends beyond the inner edge 24 of the first layer 11 in the axial direction X.

[0099] Specifically, in this embodiment, a portion of the second layer 12 actually protrudes from the first layer 11 in the axial direction.

[0100] The component 10 thus has a single-layer peripheral strip 25 made of a second material, which peripheral strip 25 is in particular transparent, which gives the component 10 a bright, three-dimensional appearance.

[0101] In other embodiments, the second layer 12 can extend to the body of the member 10 at other parts, such as the spout 51 or handle 52 of the kettle 50A, to provide an even lighter feel. In some embodiments, the inner first layer 11 has a fill passage or cavity 19 formed in its thickness.

[0102] The shape and location of the fill passage or cavity 19 corresponds to the shape and location of the recess 18 in the outer surface 15 .

[0103] In particular, the filling cavity 19 can be made in the thickness of the first layer 11 corresponding to the second surface 14 so as to follow the shape of the outer surface 15 of the second layer 12 formed by the aesthetic relief 16, i.e., the shape of the outer surface 15 of the second layer 12 formed by alternating protrusions 17 and recesses 18.

[0104] In other words, the second surface 14 of the first layer 11 has flat portions 19a that sandwich the filled cavity 19, the shapes and positions of which correspond to the shapes and positions of the protrusions 17 and recesses 18 of the second layer 12, respectively.

[0105] The first thickness S1 has a minimum value S1 corresponding to the filling cavity 19 that contacts the recess 18. min and the maximum value S1 corresponding to the flat portion 19a corresponding to the convex portion 17 of the second layer 12. max and,

[0106] In the case of the cylindrical member 10, each filling cavity 19 comes into contact with a corresponding recess in the radial direction.

[0107] Depending on the shape and size of the relief 16, the first thickness S1 may be increased to a minimum value S1 min and maximum value S1 max It can vary directly with or take intermediate values.

[0108] In some embodiments, the maximum value S1 max is the minimum value S1 min It can be 20 to 50% larger.

[0109] Advantageously, the filling cavity 19 is able to compensate at least partly for the difference in thickness between the protrusions 17 and the recesses 18 .

[0110] In other words, except for a small deviation from the average value, for example, on the order of 10-20%, the outer second layer 12 is of a substantially constant thickness along the lateral dimension of the member 10, or in any case of a substantially constant average thickness.

[0111] The inner first layer 11 has a varying average thickness across the member 10 .

[0112] In some embodiments, the transition region 20 sandwiched between the portion of the second surface 14 having the fill cavity 19 and the portion of the second surface 14 not having the fill cavity 19 can be beveled, as shown in FIG. 3, for example.

[0113] Advantageously, the beveled transition region 20 can prevent or at least reduce heat concentration during the step of injecting the second material to create the second layer 12, and thus can prevent or at least reduce undesired remelting of the first material that creates the first layer 11.

[0114] In this way, erosion due to mechanical rubbing caused by the flow of the second material is also reduced.

[0115] In some embodiments, the member 10 may include a transparent window 22 suitable for a user to see through.

[0116] For example, in the case of the kettle 50A, the transparent window 22 allows the user to check the level of the water contained in the container made of the member 10.

[0117] In other applications, window 22 may be configured to allow the user to view other possible features of the home appliance, such as the thermostat or timer of toaster 50B.

[0118] In other embodiments, the window 22 may allow a user to view possible internal parts of the household appliance 50 and / or to view products being cooked or the accumulation of dust in the dust collection bin of a vacuum cleaner.

[0119] In some embodiments, the window 22 can be created directly by the outer transparent second layer 12 .

[0120] In particular, the first layer 11 may have an opening 21 or slot having substantially the same shape as the shape of the window 22 that is to be made.

[0121] The second layer 12 which in fact covers the first layer 11 can be made continuous with the outer surface 15 so as to completely cover the opening 21 or slot, in contrast to the first layer 11 .

[0122] In a possible solution, the component 10 can be provided with a different surface finish on the second layer 12 depending on the window 22, such as a substantially flat, smooth finish, to allow for better visibility through the window 22.

[0123] The window 22 made in this way has the advantage that it does not require any specific assembly or any packing or other device that can guarantee its airtight seal. In fact, the window 22 made in this way guarantees maximum sealing, preventing any liquid, vapor or dust that may be inside the domestic appliance from leaking from the inside to the outside, and vice versa.

[0124] The embodiment now described with reference to FIGS. 5 to 12 also relates to an apparatus 26 for manufacturing the component 10. As shown in FIG.

[0125] The apparatus 26 includes a first mold assembly 27 configured to produce the first layer 11 and a second mold assembly 28 configured to produce the second layer 12 .

[0126] In one embodiment of apparatus 26, first mold assembly 27 is positioned adjacent and proximate to second mold assembly 28.

[0127] In some embodiments, the first forming assembly 27 and the second forming assembly 28 can be arranged in series one behind the other and configured to operate in direct temporal sequence to produce the finished component 10 in a single process.

[0128] In some embodiments, the first molding assembly 27 comprises a punch 29, a first molding die 30, and a first injection unit 31, the punch 29 and the first molding die 30 being adapted to cooperate to define a first molding volume V1 therebetween, and the first injection unit 31 being configured to inject a first plastic material into the first molding volume V1.

[0129] In some embodiments, the first molding volume V1 has a first maximum width W1 that corresponds to the first thickness S1 of the first layer 11. max It has.

[0130] In some embodiments, the first injection unit 31 comprises first heating means 53 configured to heat the first plastic material to a first injection temperature T1.

[0131] In some embodiments, punch 29 has a contrast surface 32 configured to be the negative of the shape of inner surface 13 of first layer 11 of member 10 .

[0132] In some embodiments, the contrast surface 32 may be substantially uniform and smooth.

[0133] For example, if the component 10 is suitable for producing a kettle 50A, the punch 29 may be substantially frusto-conical, and if the component 10 is suitable for producing a toaster 50B, the punch 29 may be parallelepiped-shaped with a rectangular cross section.

[0134] The first receiving mold 30 has a first molding surface 33 that is a negative mold of the shape of the second surface 14 of the first layer 11 .

[0135] In some embodiments, the first molding die 30 may have one or more first molding sides 37 that are configured to be positioned adjacent to each other in use to form one first molding surface 33 of the first molding die 30.

[0136] In some embodiments, at least a portion of the first moulding surface 33 has a first moulding ridge 38 that, in use, projects into the first moulding volume V1.

[0137] The first molding ridge 38 is a negative of the shape of the fill cavity 19 that will be formed in the first layer 11 .

[0138] In some embodiments, the second molding assembly 28 includes a second molding die 34 having a second molding surface 35 adapted to form a negative of the shape of the outer surface 15 of the member 10.

[0139] The second forming mold 34 is suitable for cooperating with the second surface 14 of the first layer of material 11 in use to define a second forming volume V2 between the second forming mold 34 and the second surface 14.

[0140] In some embodiments, the second molding volume V1 has a second width W2 that corresponds to a second thickness S2 of the second layer 12. max and a second width W2 max is the first width W1 max Greater than.

[0141] In some embodiments, the second width W2 max and the first width W1 max The ratio is 1.05 to 2.5, preferably 1.1 to 2.

[0142] The second mold assembly 28 further includes a second injection unit 36 configured to inject a second plastic material into the second mold volume V2.

[0143] In some embodiments, the second injection unit 36 comprises second heating means 54 configured to heat the second plastic material to a second injection temperature T2.

[0144] In some embodiments, the first heating means 53 and the second heating means 54 can be operated and regulated independently of each other.

[0145] In some embodiments, the second mold die 34 includes one or more second mold sides 39 .

[0146] In particular, the second forming sides 39 are configured to be positioned adjacent to each other in use to form the second forming surface 35 of one of the second forming molds 34 .

[0147] In some embodiments, at least a portion of the second molding surface 35 is formed with a plurality of cavities 40a alternating with each molding relief 40b.

[0148] In particular, the cavity 40 a and the molded relief 40 b are adapted to be the negative of the shape of the aesthetic relief 16 provided on the outer surface 15 .

[0149] Thus, the shape and size of the cavities 40 a and the molded reliefs 40 b correspond to the shape and final size of the protrusions 17 and recesses 18 on the outer surface 15 .

[0150] The cavity 40 a and molding relief 40 b correspond to the molding ridge 38 of the first molding die 30 .

[0151] In other words, the shape, size and location of the cavities 40 a and molding reliefs 40 b of the second molding die 34 match the shape, size and location of the molding ridges 38 of the first molding die 30 .

[0152] In particular, the shaped relief 40b is located in a position that corresponds to the position of the shaped ridge 38 in use.

[0153] In some embodiments, the first molded side 37 and the second molded side 39 are interchangeable so that members 10 having different aesthetic shapes can be produced with the same apparatus 26 .

[0154] For example, multiple sets of first molded sides 37 and second molded sides 39 may be provided, each with a different surface finish, depending on the final appearance desired for the component 10.

[0155] In another embodiment, the first forming assembly 27 has at least one coupling protrusion 41 that forms an opening 21 or slot or void in the first layer 11 that is free of the first material while simultaneously maintaining the punch 29 and the first receiving die 30 separated from each other.

[0156] In some embodiments, at least one coupling protrusion 41 is provided on one of the first molded sides 37 .

[0157] In particular, the coupling projection 41 is configured to cooperate with the punch 29 to confine and limit a portion of the first forming volume V1 and to prevent the first material from entering this location.

[0158] In some embodiments, the bonding protrusions 41 are formed to minimize bonding contact with the punch 29 in order to preserve the finish and luster of the contrasting surface 32 of the punch 29 .

[0159] In some embodiments, such as those described with reference to Figure 8, the coupling protrusion 41 has at least one protrusion abutment 42 that is suitable for being positioned in contact with the contrast surface 32 of the punch 29 to form an empty space or cavity 43 between the punch 29 and the corresponding first molding surface 33.

[0160] In another embodiment, the coupling protrusion 41 may be provided on the punch 29, and in that case, a cavity 43 may be formed between the punch 29 and the first receiving die 30 of the punch 29, more specifically along the contrast surface 32.

[0161] In some embodiments, such as those described with reference to Figure 10, the coupling protrusion 41 may have a pair of abutment portions 42 or one annular abutment portion suitable for isolating and defining the cavity 43 from the first molding volume V1.

[0162] The abutment portion 42 is configured to bear against the surface 32 of the punch 29 in use to ensure an airtight seal of the cavity 43 .

[0163] In this way, the first molding volume V1 is limited at the corresponding locations of the openings 21 in the first layer 11.

[0164] In some embodiments, the cavity 43 has a height defined as the distance between the opposing surfaces of the punch 29 and the first receiving die 30, and the height is from several tens of micrometers to several hundreds of micrometers.

[0165] In some embodiments, the width of the abutting portion 42 is several hundred micrometers, for example, 0.2 to 1.5 mm.

[0166] A value in the range of 0.2 to 0.9 mm can minimize contact between the punch 29 and the receiving die 30 and obtain a cavity 43 with a larger area.

[0167] A slightly larger width, for example 0.9 to 1.5 mm, has the disadvantage of slightly reducing the area of the cavity 43, but this is the only drawback, and it allows an airtight seal between the punch 29 and the receiving die 30 to be guaranteed even when the closing force is relatively small or when the required processing accuracy is low.

[0168] In some embodiments, one or more coupling protrusions 41 may be provided depending on the shape and size of the opening 21 to be formed, and if there are multiple coupling protrusions 41, they may have the same or different shapes.

[0169] For example, in the case of the component 10 applied to the kettle 50A, a first connecting protrusion 41 (Figure 10) suitable for forming a window 22 for checking the water level, a second connecting protrusion 41 for forming a spout 51, and a third connecting protrusion 41 (Figure 10) for forming a transparent peripheral strip 25 may be provided.

[0170] In some embodiments, the abutment 42 may be shaped to correspond to the shape of the window 22 to be formed in the member 10 .

[0171] In other embodiments, the abutment 42 may be shaped to define the edge 24 of the first layer 11 .

[0172] The cavity 43 between the punch 29 and the first forming die 30 advantageously preserves the finish and gloss of the contrasting surface 32 of the punch 29, even after several forming cycles.

[0173] In some embodiments, the first injection unit 31 and the second injection unit 36 each have at least one injection device 44 and at least one injection passage 45, and the injection passage 45 can fluidly connect each injection device 44 to either the first injection volume V1 or the second injection volume V2.

[0174] In some embodiments, multiple injection devices 44 may be provided for each injection unit 31,36.

[0175] In some embodiments, at least one injection passage 45 is formed in at least one of the first mold sides 37 and at least one of the second mold sides 39 .

[0176] In some embodiments, the apparatus 26 may include a first cooling circuit 46 and a second cooling circuit 47 for each molding assembly 27, 28, respectively.

[0177] In some embodiments, the first cooling circuit 46 and the second cooling circuit 47 are independent of each other and are configured to cool the first layer 11 and the second layer 12 to different corresponding cooling temperatures T3, T4, respectively.

[0178] In some embodiments, the first cooling circuit 46 is configured to cool the first layer 11 to a first cooling temperature T3, and the second cooling circuit 47 is configured to cool the second layer 12 to a second cooling temperature T4 that is lower than the first cooling temperature T3.

[0179] The first cooling circuit 46 comprises one or more cooling passages 48 of known type, not shown in the drawings, and a unit for pumping the coolant or a heat exchanger with a cooling circuit.

[0180] The second cooling circuit 47 comprises one or more cooling passages 49 of known type not shown in the drawings and a unit for pumping the coolant or a heat exchanger with a cooling circuit.

[0181] In some embodiments, the cooling passages 48 , 49 may be formed through at least one of the first forming side 37 and / or the second forming side 39 and / or the punch 29 .

[0182] In particular, the cooling passages 48, 49 are configured to carry a coolant such as water, emulsion and / or oil.

[0183] The embodiments now described with reference to FIGS. 5-12 also relate to methods for manufacturing the component 10. FIG.

[0184] The method comprises a first step of injecting a first plastic material to create a first layer 11 having a first thickness S1; a second injection step in which a second plastic material is injected to create a second layer 12 having a second thickness S2 greater than the first thickness.

[0185] In some embodiments, the method includes ejecting a first material at first operating parameters and ejecting a second material at second operating parameters that are different from the first operating parameters.

[0186] In some embodiments, by fabricating the second layer 12 at a different, larger thickness relative to the first layer 11, lower temperature and pressure processing parameters can be used, which can improve surface stability and brightness, i.e., reduce distortion that may occur during the post-shrinkage step.

[0187] In some embodiments, the method includes positioning a punch 29 and a first forming die 30 relative to each other to define a first forming volume V1 therebetween, and injecting a first material into the first volume V1 thus defined. The first forming volume V1 is defined between a contrast surface 32 and a first forming surface 33 of the punch 29, as shown on the right hand side of FIG. 5 and in FIG. 9.

[0188] In some embodiments, the method injects the first material at defined temperature and pressure parameters.

[0189] In some embodiments, the method injects the first material at a first temperature T1 between 150°C and 260°C (at least for propylene).

[0190] In another embodiment, the first temperature T1 is in the range of 120°C to 240°C, preferably 160°C to 220°C, and more preferably 180°C to 200°C.

[0191] In one embodiment, the method comprises: 2 ~1300kg / cm 2 The first material is injected at a first pressure P1.

[0192] In another embodiment, the first pressure P1 is 750 kg / cm 2 ~1250kg / cm 2 , more preferably 800 kg / cm 2 ~1200kg / cm 2 It can be said that:

[0193] The first injection step makes it possible to obtain the first layer 11 of the component 10 (FIGS. 6 and 10).

[0194] In some embodiments, the method can include cooling the first layer 11 to a first cooling temperature T3 in the first injection step.

[0195] In some embodiments, the method may include circulating a refrigerant in a first cooling circuit 46 to cool at least one of the first receiving mold 30 and / or punch 29 to cool the first layer 11.

[0196] In some embodiments, the method uses a first cooling temperature T3 in the range of 35°C to 55°C, more preferably 40°C to 50°C.

[0197] The method then places the punch 29 with the first layer 11 formed on the surface of the punch 29 into the second forming assembly 28, where the second receiving die 34 is positioned to mate with the second surface 14 of the first layer 11 to define a second forming volume V2.

[0198] A second moulding volume V2 is defined between the second surface 14 of the first layer 11 having the fill cavity 19 and the second moulding surface 35, as shown, for example, on the right hand side of FIG. 7 and in FIG.

[0199] Thereafter, the method comprises a second injection step of injecting a second plastic material into a second mould volume V2 at a second injection temperature T2 and a second injection pressure P2.

[0200] In one possible embodiment, the second injection step immediately follows the first injection step.

[0201] In one embodiment, the method uses a second temperature T2 that is lower than the first injection temperature T1.

[0202] In a preferred embodiment, the second injection temperature T2 is in the range of 0.90 to 0.95 times the first injection temperature T1, in other words, the second injection temperature T2 is 5 to 10% lower than the first injection temperature T1.

[0203] In one embodiment, the second pressure P2 may advantageously be lower than the first pressure P1.

[0204] In one embodiment, the second injection pressure P2 may be in the range of 0.70 to 0.90 times the first pressure P1, in other words, the second pressure P2 is 10 to 30% lower than the first pressure P1.

[0205] The second injection step creates the outer second layer 12 of the component 10 .

[0206] In some embodiments, the method can include cooling the second layer 12 to a second cooling temperature T4 in a second injection step.

[0207] In some embodiments, the method may include circulating a refrigerant in a second cooling circuit 47 to cool at least one of the second receiving mold 34 and / or punch 29 to a second cooling temperature T4 to cool the second layer 12.

[0208] In some embodiments, the second cooling temperature T 4 is the first cooling temperature T 3 It can be reduced by 15% to 25%.

[0209] In a preferred embodiment, the second cooling temperature T4 may be in the range of 25°C to 45°C, more preferably 30°C to 40°C.

[0210] In another embodiment, the method produces an outer second layer 12 having a three-dimensional finish on its outer surface 15 with alternating peaks 17 and valleys 18 .

[0211] In another embodiment, the method creates at least one transparent window 22 .

[0212] To create the window 22, the method forms an opening 21 or slot in the first layer 11 and in a second injection step covers the opening 21 or slot with a second material, which in this example is a transparent material.

[0213] In some embodiments, the method separates the forming punch 29 from the second forming die 35 at the end of the second injection step to remove the part 10 .

[0214] <Example> The applicant has conducted experimental tests and demonstrated that it is possible to vary the injection temperatures T1, T2 and cooling temperatures T3, T4 as well as the injection pressures P1 and P2 within the ranges under consideration depending on the difference between the thickness S1 of the first layer 11 and the thickness S2 of the second layer 12.

[0215] Table 1 below shows possible ratios of processing temperatures and pressures that can be used in the first and second injection steps, corresponding to the ratio of thicknesses S1, S2. [Table 1]

[0216] It will be apparent that modifications and / or additions to individual portions or steps may be made to the component 10, the apparatus 26 and the method described above without departing from the field and scope of the present invention.

[0217] Furthermore, although the present invention has been described with reference to some specific examples, it is clear that those skilled in the art will certainly be able to achieve many other equivalents of the component 10, device 26 and method having the features set forth in the claims, and all such equivalents fall within the scope of protection set forth in the claims.

Claims

1. 1. A method for manufacturing a component (10) made of plastic material having a tubular shape suitable for forming a housing for a household appliance (50), such as a kettle (50A) or a toaster (50B), comprising the steps of: a first injection step of injecting a first plastic material into a first molding volume (V1) defined between a punch (29) and a first receiving die (30) at first operating parameters including a first injection temperature (T1) and a first injection pressure (P1) to produce a first layer (11) having a first thickness (S1); a second injection step of injecting a second plastic material into a second molding volume (V2) defined between the first layer (11) obtained in the first injection step and a second receiving mold (34) at second operating parameters including a second injection temperature (T2) and a second injection pressure (P2) to produce a second layer (12) having a second thickness (S2); and The method, wherein the second injection step occurs immediately after the first injection step, The second thickness (S2) of the second layer (12) is greater than the first thickness (S1) of the first layer (11); at least one of the operating parameters of the second injection step is lower than a corresponding one of the operating parameters of the first injection step; the second injection temperature (T2) is 5 to 10% lower than the first injection temperature (T1), or the second injection pressure (P2) is 10 to 30% lower than the first injection pressure (P1); In the first injection step, the first plastic material in the first molding volume (V1) is cooled to a first cooling temperature (T3), and in the second injection step, the second plastic material in the second molding volume (V2) is cooled to a second cooling temperature (T4) that is 15% to 25% lower than the first cooling temperature (T3). A method characterized by:

2. The first injection temperature (T1) is in the range of 120°C to 260°C, and the second injection temperature (T2) is 5 to 10% lower than the first injection temperature (T1); The method of claim 1.

3. The first injection pressure (P1) is 700 kg / cm ２ ~1300kg / cm ２ and the second injection pressure (P2) is 10 to 30% lower than the first injection pressure (P1).

3. The method according to claim 1 or 2.

4. the first cooling temperature (T3) is 35°C to 55°C, and the second cooling temperature (T4) is 15 to 25% lower than the first cooling temperature (T3); 4. The method according to any one of claims 1 to 3.

5. A single or multiple colored first opaque material and an at least partially transparent second material may be used to allow the inner opaque first layer (11) to be visible through the outer transparent second layer (12).

5. The method according to any one of claims 1 to 4.

6. An apparatus for manufacturing a component (10) made of plastic material having a first layer (11) and a second layer (12), comprising: The device is suitable for carrying out the method according to any one of claims 1 to 5, a first molding assembly (27) including a punch (29), a first receiving die (30) and a first injection unit (31); and a second molding assembly (28) including a second receiving die (34) and a second injection unit (36); The first receiving die (30) has a first width (W1 ｍａｘ a first molding surface (33) adapted to define a first molding volume (V1) having a the first injection unit (31) is configured to inject a first plastic material into the first mould volume (V1) to obtain a first layer (11); The second receiving mold (34) mates with the first layer (11) of the member (10) to form a second width (W2 ｍａｘ a second molding surface (35) adapted to define a second molding volume (V2) having a The apparatus, wherein the second injection unit (36) is configured to inject a second plastic material into the second moulding volume (V2) to obtain a second layer (12), The second width (W2 ｍａｘ ) is the first width (W1 ｍａｘ ) is larger than the first injection unit (31) comprises first heating means (53) configured to heat the first plastic material to the first injection temperature (T1), and the second injection unit (36) comprises second heating means (54) configured to heat the second plastic material to a second injection temperature (T2); at least said first heating means (53) and said second heating means (54) can be operated and adjusted independently of each other; the first mold assembly (27) includes a first cooling circuit (46), and the second mold assembly (28) includes a second cooling circuit (47) independent of the first cooling circuit (46); The first cooling circuit (46) and the second cooling circuit (47) are selectively configurable to cool the first plastic material and the second plastic material to respective cooling temperatures (T3, T4). An apparatus characterized in that

7. The second width (W2) of the second molding volume (V2) ｍａｘ ) and the first width (W1) of the first molding volume (V1). ｍａｘ ) is 1.05 to 2.5, 7. The apparatus of claim 6.

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