Shaped part made from injection-moulded plastic, method for producing the shaped part, insert for carrying out the method, and injection-moulding die for carrying out the method
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- PME FLUIDTEC GMBH
- Filing Date
- 2024-09-27
- Publication Date
- 2026-06-24
AI Technical Summary
In plastic injection molding, achieving a specified minimum wall thickness in curvature sections of molded parts is challenging, particularly when the radius of curvature is small, leading to potential wall thickness reduction below a critical limit, which can result in structural instability and breakage of the molded part.
The use of a shape-stable insert designed as a hollow body, positioned within the cavity of the injection molding tool, which is overmolded with plastic to form the molding wall, ensuring a consistent and minimum wall thickness in curvature sections.
This solution effectively maintains a specified minimum wall thickness in curvature sections, enhancing the structural stability and preventing breakage of the molded part, while also allowing for the production of complex shapes with varying curvature radii.
Smart Images
Figure DE2024100853_03042025_PF_FP_ABST
Abstract
Description
[0001] Title: Plastic injection molded part, process for producing the molded part, insert for carrying out the process and injection mold for carrying out the process
[0002] DESCRIPTION
[0003] The invention is based on a molded part made of plastic injection molding, a method for producing the molded part, an insert and an injection molding tool for carrying out the method.
[0004] During plastic injection molding, a plastic is liquefied and the molten plastic is injected under pressure into an injection mold. The injection mold has a cavity that determines the shape and surface structure of the molded part to be produced. The cavity represents a negative mold of the molded part. In the injection mold, the liquid plastic transforms into a solid state through cooling and / or a crosslinking reaction and solidifies. Finally, the finished molded part is removed from the injection mold. This allows molded parts to be produced cost-effectively in large quantities.
[0005] The molded parts can have almost any shape and surface structure. This also includes molded parts that are designed as dimensionally stable hollow bodies and have a molded part wall that defines a molded part cavity. Such hollow molded parts can also have a curved part section. In plastic injection molding, the molded part is produced by injecting liquid plastic melt into a cavity of an injection molding tool of a plastic injection molding machine. The plastic melt fills the cavity completely or partially. The plastic melt solidifies at the tool wall, while it is still a liquid core inside. To produce a hollow molded part, a fluid is injected into the cavity under pressure using fluid injection technology. This displaces the still liquid plastic melt inside the cavity and creates a cavity. The fluid can be a gas or a liquid, e.g.Water. If the cavity was only partially filled when the plastic melt was introduced, the displacement of the liquid plastic melt by the fluid ensures complete molding of the molded part. If the cavity contains excess plastic melt, this can either be conveyed back into a screw barrel of the plastic injection molding machine via a hot runner using the fluid or pressed into a collecting cavity adjacent to the cavity.
[0006] If the molded part is free of curvatures, the position and size of the cavity can be adjusted during production by adjusting the position of the injectors for the plastic melt and the fluid, as well as by adjusting the process parameters, so that the molded part has a desired wall thickness throughout. However, if the molded part includes one or more curved sections, the liquid plastic melt is displaced in this curved section of the molded part in such a way that the wall thickness in an inner curved section of the molded part, which faces a geometric center of curvature of the molded part, is smaller than in an outer curved section of the molded part, which faces away from the geometric center of curvature of the molded part. The position of the created cavity is shifted inward.Because the radius of curvature in the inner mold part curved section is smaller than the radius of curvature in the outer mold part curved section, the flow velocity of the fluid injected into the cavity is greater inside than outside when displacing the liquid plastic melt. As a result, more plastic melt is removed in the inner mold part curved section than in the outer mold part curved section. The smaller the radius of curvature in the inner mold part curved section, the more plastic melt is removed there, and the more critical the wall thickness of the mold part becomes in this inner mold part curved section. In this case, the wall thickness may fall below a specified limit.If the finished molded part is subjected to significant forces after its production, resulting in tensile, compressive, or transverse stresses, the molded part cannot withstand the stress due to insufficient wall thickness at the inner curved section of the molded part. The result is that the molded part breaks or cracks.
[0007] In addition, when manufacturing a molded part with a curved section, there may be a requirement that the wall thickness in an outer molded part curved section, which is facing away from a geometric molded part curvature center, has a certain specified value, which must not be undercut for reasons of stability.
[0008] The invention is based on the object of providing a dimensionally stable hollow molded part with a molded part curved section as well as a method, an insert and an injection molding tool for producing the molded part, wherein the molded part has a predetermined minimum wall thickness in the molded part curved section, which is not undercut.
[0009] This object is achieved by a molded part having the features of claim 1. The molded part is characterized in that it is equipped with a dimensionally stable insert in the region of the curved section of the molded part. This insert is designed as a dimensionally stable hollow body. It is therefore referred to as a hollow insert body. During production of the molded part, the insert is inserted into the cavity of the injection mold and overmolded with plastic. The insert is positioned in the cavity in such a way that it forms a bond with the overmolded plastic in the curved section of the molded part and, together with the plastic, forms the molded part wall. The molded part wall delimits the molded part cavity.The molded part wall, in the curved section of the molded part, consists entirely or partially of the composite of the insert and the plastic, which is injected into the cavity of the injection mold as a liquid plastic melt during production using the plastic injection molding process. In all other areas of the molded part apart from the insert, the molded part wall is formed from the plastic that is injected into the cavity during plastic injection molding, without these other areas of the molded part enclosing the insert. The insert and plastic are combined into one piece during production, so that the molded part is formed as a single piece.
[0010] In the following, the term "plastic" always refers to the plastic that is injected into the cavity of the injection mold during the production of the molded part and with which the insert is overmolded. If a different plastic is intended, this will be specifically stated.
[0011] Since the molded part is designed as a dimensionally stable hollow body, the molded part wall has an inner side facing the molded part cavity and an outer side facing away from the molded part cavity. Furthermore, the molded part has a curved part section comprising an inner side with a small radius of curvature and an outer side with a larger radius of curvature. The inner side of the curved part section faces a geometric center of curvature of the molded part, while the outer side of the curved part section faces away from the geometric center of curvature of the molded part. If the course of the molded part wall in the curved part section corresponds at least approximately to part of a circle, the geometric center of curvature of the molded part corresponds to the center of this circle. The radius of curvature corresponds to the radius of this circle.To conceptually distinguish the inside of the molded part's curved section from the inside of the molded part's wall, the inside of the molded part's curved section is referred to as the inner molded part's curved section, and the outside of the molded part's curved section is referred to as the outer molded part's curved section. The radius of curvature on the outside of the molded part's curved section is smaller than on the outside of the molded part's curved section. The smallest radius of curvature on the molded part's curved section is referred to as the inner radius of curvature, and the largest radius of curvature on the molded part's curved section is referred to as the outer radius of curvature.
[0012] The insert can be overmolded with plastic only on the inside facing the molded part cavity. Alternatively, the insert can be overmolded with plastic on both the inside and the outside facing away from the molded part cavity.
[0013] The wall thickness of the molded part wall at the curved section corresponds to the sum of the insert wall thickness and the thickness of the plastic layer that forms on the inside of the insert and, if applicable, the outside of the insert during molding. Thus, the wall thickness of the molded part wall corresponds to at least the insert wall thickness. This applies even if the liquid plastic melt is almost completely displaced by the fluid in the inner curved section of the molded part during molding. The insert wall thickness is not exceeded because the insert does not change its shape during overmolding with plastic.
[0014] According to an advantageous embodiment of the invention, the molded part wall is formed throughout the entire curved section of the molded part by the composite insert and plastic. The insert extends over the entire circumference of the curved section of the molded part.
[0015] According to a further advantageous embodiment of the invention, the molded part is produced by means of a combination of plastic injection molding and fluid injection technology.
[0016] According to a further advantageous embodiment of the invention, the insert is overmolded with plastic exclusively on its inner side facing the molded part cavity. The outer side of the insert facing away from the molded part cavity is free of the plastic that is injected into the injection mold during the production of the molded part.
[0017] According to a further advantageous embodiment of the invention, the insert is embedded in the plastic of the molded part in such a way that the molded part is free of any protrusion of the insert beyond an outer surface of the remaining molded part. The insert thus has no influence on the outer geometry of the molded part. It serves exclusively to establish a defined wall thickness in the curved area of the molded part.
[0018] According to a further advantageous embodiment of the invention, the insert on the outside of the molded part is flush with the adjacent sections of the molded part that are free of the insert. The insert does not protrude beyond the rest of the molded part on the outside. The external geometry of the molded part is therefore the same in the area of the insert and in the areas outside the insert. The insert does not lead to any overhang on the molded part. The outer surface of the insert is therefore smooth and also free of steps or projections in the area of the insert. This is advantageous if, after its completion, the molded part is to be inserted into an environment that requires a predetermined external geometry. According to a further advantageous embodiment of the invention, the insert is overmolded with plastic on its inner insert side facing the molded part cavity and on its outer insert side facing away from the molded part cavity.In this case, the insert is embedded in the plastic. It is covered by the plastic on all sides. The insert is therefore not visible from the outside. Furthermore, it is not exposed to the media that flow around the inside and outside of the molded part at its final place of use.
[0019] According to a further advantageous embodiment of the invention, the molded part has an inner molded part curved section, which faces the geometric molded part curvature center, and an outer molded part curved section, which faces away from the geometric molded part curvature center. The insert is overmolded with plastic in such a way that the molded part wall is formed by a composite of the insert and the plastic only in the inner molded part curved section. In this case, the insert can have a distance from the molded part wall in the outer molded part curved section. Alternatively, the molded part wall is formed by a composite of the insert and the plastic only in the outer molded part curved section. In this case, the insert can have a distance from the molded part wall in the inner molded part curved section.
[0020] According to a further advantageous embodiment of the invention, the molded part curved section is L-shaped, U-shaped or C-shaped.
[0021] According to a further advantageous embodiment of the invention, the curved section of the molded part is Y-shaped or T-shaped. The molded part thus has a branching.
[0022] According to a further advantageous embodiment of the invention, the
[0023] The molded part has a first rectilinear molded part section that extends along a first molded part axis L1. Furthermore, the molded part has a second rectilinear molded part section that extends along a second molded part axis L2. The curved molded part section is located between the first molded part section and the second molded part section. The molded part cavity extends continuously through the first molded part section, the curved molded part section, and the second molded part section.
[0024] According to a further advantageous embodiment of the invention, the molded part has a third rectilinear molded part section extending along a third molded part axis L3. The molded part curved section is T-shaped or Y-shaped. The molded part curved section is arranged between the first molded part section, the second molded part section, and the third molded part section. The insert also has a T-shape or Y-shape.
[0025] According to a further advantageous embodiment of the invention, an angle a between L1 and L2 is between 5° and 180°, including the limits. The following applies: 5° < a < 180°.
[0026] According to a further advantageous embodiment of the invention, the radius of curvature at the inner curved section of the molded part is greater than or equal to 0.5 mm. This applies in particular to the inner radius of curvature, which is the smallest radius at the curved section of the molded part. The smaller the inner radius of curvature of the molded part, the more pronounced the edge or corner formed at the curve or deflection of the molded part.
[0027] According to a further advantageous embodiment of the invention, the insert is made of a material that is dimensionally stable under the influence of the temperature and pressure prevailing in the injection mold. This ensures that the insert does not change its shape when hot plastic melt is introduced into the cavity during the production of the molded part and comes into contact with the insert. According to a further advantageous embodiment of the invention, the insert is made of a fiber-reinforced plastic material, wherein the fibers are glass, aramid, carbon, or natural fibers.
[0028] According to a further advantageous embodiment of the invention, the insert consists at least partially of metal.
[0029] According to the inventive method with the features of claim 18, the molded part is produced using a plastic injection molding machine equipped with an injection molding tool. This injection molding tool has a cavity designed as a hollow mold, which represents a negative mold of the molded part and comprises a cavity curved section corresponding to the molded part. The cavity is delimited by a cavity surface, which is part of the injection molding tool. The injection molding tool also has an inlet for the liquid plastic melt and an injector for a fluid. The dimensionally stable insert, which is designed as a hollow insert body, is inserted into the cavity curved section of the injection molding tool. This is done in such a way that the insert at least partially rests against the cavity surface at the cavity curved section and also leaves the cavity free so that the plastic melt can spread.The insert is thus arranged in the curved cavity section without completely filling it. The injection mold is then closed. Liquid plastic melt is then introduced into the cavity under pressure at the inlet, with the plastic melt entering the curved cavity section from the at least one inlet and spreading there. Since the insert does not completely fill the curved cavity section, spreading of the plastic melt in the curved cavity section is possible.A fluid is then introduced into the liquid plastic melt in the cavity in such a way that at least one continuous molded part cavity extending through the molded part's curved section is created in the plastic melt using fluid injection technology. The plastic melt forms the hollow molded part's curved section at the cavity's curved section and the insert arranged there, wherein the insert forms a bond with the plastic melt and forms the molded part wall in this area. The solidifying plastic melt also forms the molded part wall. This process produces a hollow molded part by plastic injection molding, which is reinforced in a molded part's curved section by a plastic-coated insert, such that the wall thickness of the molded part wall in the molded part's curved section corresponds at least to the wall thickness of the insert.
[0030] According to a further advantageous embodiment of the method according to the invention, the insert, together with the solidified plastic melt, forms a circumferentially surrounding composite molded part wall in the molded part curved section.
[0031] According to a further advantageous embodiment of the method according to the invention, the insert lies exclusively on the cavity surface at the inner cavity curvature section and leaves the outer cavity curvature section free, such that the insert, together with the solidified plastic melt, forms a composite molded part wall at the inner molded part curvature section and this is formed integrally with the remaining molded part wall, which consists exclusively of the solidified plastic melt.
[0032] According to a further advantageous embodiment of the method according to the invention, the insert lies exclusively on the cavity surface on the outer cavity curvature section and leaves the inner cavity curvature section free, such that the insert together with the solidified plastic melt forms a composite molded part wall on the outer molded part curvature section and this is formed integrally with the remaining molded part wall, which consists exclusively of the solidified plastic melt.
[0033] According to a further advantageous embodiment of the method according to the invention, the insert is overmolded with plastic melt on its outer side facing the cavity surface and on its inner side facing away from the cavity surface.
[0034] According to a further advantageous embodiment of the method according to the invention, the insert is positioned and held in the cavity by positioning pins. These positioning pins are movably arranged on the injection mold. In a first position, the positioning pins protrude above the cavity surface. They ensure that the insert is spaced from the cavity surface and that plastic can be injected into the space between the insert and the cavity surface. To demold the molded part from the cavity, the positioning pins are moved to a second position, where they are flush with the cavity surface.
[0035] According to a further advantageous embodiment of the method according to the invention, the insert is overmolded with plastic melt exclusively on its inner side facing away from the cavity surface.
[0036] According to a further advantageous embodiment of the method according to the invention, the insert is L-shaped, U-shaped or C-shaped.
[0037] According to a further advantageous embodiment of the method according to the invention, the insert is T-shaped or Y-shaped.
[0038] According to a further advantageous embodiment of the method according to the invention, the insert is a single piece. According to a further advantageous embodiment of the method according to the invention, the insert comprises several insert parts from which it is assembled.
[0039] According to a further advantageous embodiment of the method according to the invention, the plastic melt displaced from the cavity with the fluid is pressed into a collecting cavity which adjoins the cavity.
[0040] According to a further advantageous embodiment of the method according to the invention, the plastic melt displaced from the cavity with the fluid is pressed back into a screw cylinder of the injection molding machine via a hot runner at the inlet. This makes the displaced plastic melt available for another cycle.
[0041] The insert according to the invention with the features of claim 30 is characterized in that it is designed as a dimensionally stable hollow insert body and consists of a material that is dimensionally stable under the influence of the temperature and pressure prevailing in the injection mold. The insert thus retains its shape during the implementation of the method according to the invention.
[0042] According to a further advantageous embodiment of the insert according to the invention, the insert has a wall thickness predetermined by the minimum wall thickness of the molded part.
[0043] According to a further advantageous embodiment of the insert according to the invention, it is L-shaped, U-shaped or C-shaped.
[0044] According to a further advantageous embodiment of the insert according to the invention, it is Y-shaped or T-shaped. According to a further advantageous embodiment of the insert according to the invention, it consists of a fiber-reinforced plastic material, wherein the fibers are glass, aramid, carbon, or natural fibers.
[0045] According to a further advantageous embodiment of the insert according to the invention, it consists at least partially of metal.
[0046] The injection molding tool according to the invention with the features of claim 36 is characterized in that it is equipped with at least one hold-down device by which the insert is held at the position predetermined for it in the injection molding tool.
[0047] According to a further advantageous embodiment of the injection mold according to the invention, the hold-down device is designed as a positioning pin that is movably arranged in the injection mold. In a first extended position, the positioning pin protrudes above the cavity surface and, in a second retracted position, is flush with the cavity surface.
[0048] Further advantages and advantageous embodiments can be found in the following description, the drawing and the claims.
[0049] drawing
[0050] The drawings illustrate exemplary embodiments of the subject matter of the invention. They show: Figure 1 shows a hollow L-shaped molded part not according to the invention in a sectional view,
[0051] Figure 2 first embodiment of a hollow L-shaped molded part with insert in sectional view,
[0052] Figure 3 second embodiment of a hollow L-shaped molded part with insert in sectional view,
[0053] Figure 4 shows a hollow T-shaped molded part not according to the invention in a sectional view,
[0054] Figure 5 third embodiment of a hollow molded part in T-shape with insert in sectional view,
[0055] Figure 6 fourth embodiment of a hollow T-shaped molded part with insert in sectional view,
[0056] Figure 7 shows a hollow L-shaped molded part not according to the invention in a sectional view,
[0057] Figure 8 fifth embodiment of a hollow L-shaped molded part with insert in sectional view,
[0058] Figure 9 sixth embodiment of a hollow L-shaped molded part with insert in sectional view,
[0059] Figure 10 shows a hollow T-shaped molded part not according to the invention in a sectional view,
[0060] Figure 11 seventh embodiment of a hollow T-shaped molded part with insert in sectional view, Figure 12 eighth embodiment of a hollow T-shaped molded part with insert in sectional view,
[0061] Figure 13 first embodiment of a cavity of an injection molding tool for producing a molded part,
[0062] Figure 14 second embodiment of a cavity of an injection mold for producing a molded part,
[0063] Figure 15 embodiment of an injection molding tool with an insert lying against the cavity surface for producing a molded part according to Figure 2,
[0064] Figure 16 Injection molding tool according to Figure 15 with an insert which has a distance from the cavity surface, for producing a molded part according to Figure 3.
[0065] Description of the embodiments
[0066] Figures 1, 4, 7 and 10 show hollow molded parts made of plastic injection molding not according to the invention, having at least one molded part curved section without inserts. The molded part 1 shown in Figure 1 has a first straight molded part section 2, a molded part curved section 3 and a second straight molded part section 4. The molded part curved section 3 is located between the first straight molded part section 2 and the second straight molded part section 4. The first straight molded part section 2 is elongated and extends along a first geometric molded part longitudinal axis L1. The second straight molded part section 4 is also elongated and extends along a second geometric molded part longitudinal axis L2. L1 and L2 are perpendicular to one another.The molded part wall 5 of the molded part 1 defines a molded part cavity 6, which extends continuously through the first straight molded part section 2, the molded part curved section 3, and the second straight molded part section 4. The molded part wall 5 has an inner wall 7 facing the molded part cavity 6 and an outer wall 8 facing away from the molded part cavity 6. The wall thickness of the molded part wall 5 is the same and constant in the first straight molded part section 2 and in the second straight molded part section 4. In the molded part curved section 3, however, the wall thickness is different. In an inner molded part curved section 9, which faces a geometric molded part curvature center 10, the wall thickness is less than in an outer molded part curved section 11 and than in the first and second straight molded part sections 2, 4.The reason for this different wall thickness is the production of the molded part 1 by plastic injection molding, with the molded part cavity 6 being created using fluid injection technology. The fluid flowing through the liquid plastic melt in the cavity of the injection mold removes more liquid plastic melt at the inner molded part curved section 9 than at the outer molded part curved section 11 and than in the straight molded part sections 2, 4. Less plastic melt is removed at the outer molded part curved section 11 because the velocity of the flowing fluid is lower there at the inner molded part curved section 9 and than in the straight molded part sections 2, 4. The molded part curved section 3 has an inner radius of curvature on the outer side of the molded part wall at the inner molded part curved section 9.This inner radius of curvature corresponds to the radius r of the circle 12, which at least approximately describes the course of the outer side of the molded part wall at the inner molded part curved section 9 during the transition from the first straight molded part section 2 to the second straight molded part section 4. The geometric molded part curvature center 10 corresponds to the center point of this circle 12. Furthermore, the molded part curved section 2 has an outer radius of curvature on the outer side of the molded part wall at the outer molded part curved section 11. This outer radius of curvature corresponds to the radius r of the circle 13, which at least approximately describes the course of the outer side of the molded part wall at the outer molded part curved section 11 during the transition from the first straight molded part section 2 to the second straight molded part section 4. The inner radius of curvature is significantly smaller than the outer radius of curvature.The radii of curvature on the inside of the molded part wall in the molded part curvature section are larger than the inner radius of curvature and smaller than the outer radius of curvature.
[0067] Figure 4 shows a second molded part 21 not according to the invention, which, in contrast to the molded part according to Figure 1, has a T-shape. In addition to the first straight molded part section 22 with longitudinal axis L1 and the second straight molded part section 24 with longitudinal axis L2, the molded part 21 has a third straight molded part section 32 with longitudinal axis L3. Between these three straight molded part sections 22, 24, and 32 is the molded part curved section 23. Due to the T-shape, the molded part 21 comprises two inner molded part curved sections 29a and 29b, both of which face their respective geometric molded part curvature centers 30a and 30b. The wall thickness of the molded part wall 25 is smaller in the region of the inner molded part curved sections 29a, 29b than in the straight molded part sections 22, 24, and 32.The outer mold part curved section 31 runs in a straight line in the mold part 21 shown, since the longitudinal axis L2 of the second straight mold part section 24 and the longitudinal axis L3 of the third straight mold part section 32 coincide or enclose an angle of 0°. However, since the flowing fluid has a lower velocity in the outer mold part curved section during the production of the mold part 21 using a combination of plastic injection molding and fluid injection technology than in other sections 22, 24, 29a, 29b, 32 of the mold part, the least amount of liquid plastic melt is displaced in this area. The wall thickness of the mold part wall 25 is therefore greatest in this area. The inner radius of curvature of the two inner mold part curved sections 29a, 29b is identical. Figures 7 and 10 show two further molded parts 41 and 51 not according to the invention, which are essentially similar to the two molded parts 1 and 21 in Figures 1 and 4.The molded part 41 in Figure 7 differs from the molded part 1 in Figure 1 only in that the inner radius of curvature is smaller. A comparison with Figure 1 shows that, due to the smaller inner radius of curvature, the wall thickness of the molded part wall 45 at the inner molded part curved section 49 is even smaller in the molded part 41 than in the molded part 1 in Figure 1. The same applies to the molded part 51 in Figure 10: it differs from the molded part 21 in Figure 4 only in that the inner radius of curvature is smaller, which is why the wall thickness of the molded part wall 55 at the inner molded part curved sections 59a, 59b is smaller.
[0068] Figures 2, 3, 8 and 9 show L-shaped molded parts according to the invention. They differ from the molded parts in Figures 1 and 7 in that they are equipped with an insert. This insert is designed as a hollow body and also has an L shape. It is located on the curved section of the molded part. With regard to the straight molded part sections 2, 4, the molded parts in Figures 2, 3, 8 and 9 correspond to the molded parts in Figures 1 and 7. Therefore, the same reference numerals are given for the straight molded part sections. In the first exemplary embodiment of a molded part 61 according to the invention in Figure 2, an insert 62 designed as a hollow insert is embedded in the plastic on the curved section 63 of the molded part in such a way that the insert 62 forms the outer side 68 of the molded part wall on the curved section 63 of the molded part.The plastic from which the two straight molded part sections 2, 4 are made is located on the inner side of the insert facing the molded part cavity 66. The inner radius of curvature of the molded part 61 in Figure 2 corresponds to the inner radius of curvature of the molded part 1 in Figure 1. Due to the insert 62, the wall thickness of the molded part wall 65 at the inner molded part curved section 69 is significantly greater than the wall thickness at the corresponding position in the molded part 1 in Figure 1. The molded part wall 65 is formed at the molded part curved section by the insert and the plastic on the inside of the insert.
[0069] Figure 3 shows a second embodiment of a molded part 71 according to the invention with an insert 72. The molded part 71 differs from the molded part 61 in that the insert 72 is overmolded with plastic on its inside and outside. The insert 72 is thus embedded in the plastic from the inside and outside. The molded part wall 75 is formed at the molded part curved section 73 by the insert 72 and the plastic on the inside and outside of the insert. The insert 72 does not form the molded part wall outer side 78 at the molded part curved section 73, since the insert is covered by the plastic on its outside.
[0070] The molded part 81 in Figure 8 is similar to the molded part 61 in Figure 2. It differs from the molded part 61 in Figure 2 in that the inner radius of curvature of the inner molded part curved section 89 is smaller. The insert 82 of the molded part 81 has a correspondingly small inner radius of curvature on its outer side. Furthermore, the molded part 61 and the molded part 81 are identical.
[0071] The molded part 91 in Figure 9 is similar to the molded part 71 in Figure 3. It differs from the molded part 71 in Figure 3 in that the inner radius of curvature of the inner molded part curved section 99 is smaller. The insert 92 of the molded part 91 has a correspondingly small inner radius of curvature on its outer side. Furthermore, the molded part 71 and the molded part 91 are identical.
[0072] Figures 5, 6, 11, and 12 show T-shaped molded parts according to the invention. They differ from the molded parts in Figures 4 and 10 in that they are equipped with an insert. This insert is designed as a hollow body and also has a T shape. It is located at the curved section of the molded part. With regard to the straight molded part sections 22, 24, and 32, the molded parts in Figures 5, 6, 11, and 12 correspond to the molded parts in Figures 4 and 10. Therefore, the same reference numbers are given for the straight molded part sections. In the embodiment of a molded part 101 according to the invention in Figure 5, the insert 102 designed as a hollow insert body is embedded in the plastic at the molded part curved section 103 in such a way that the insert 102 forms the molded part wall outer side 108 at the molded part curved section 103.The plastic from which the three straight molded part sections 22, 24, 32 are made is located on the insert inner side facing the molded part cavity 106. The inner radius of curvature of the molded part 101 in Figure 5 corresponds to the inner radius of curvature of the molded part 21 in Figure 4. Due to the insert 102, the wall thickness of the molded part wall 105 at the inner molded part curved sections 109a, 109b is significantly greater than the wall thickness at the corresponding positions in the molded part 21 in Figure 4. The molded part wall 105 is formed at the molded part curved section 103 by the insert 102 and the plastic on the inner side of the insert 102.
[0073] Figure 6 shows a further embodiment of a molded part 111 according to the invention with an insert 112. The molded part 111 differs from the molded part 101 in that the insert 112 is overmolded with plastic on its inside and outside. The molded part wall 115 is formed at the molded part curved section 113 by the insert 112 and the plastic on the inside and outside of the insert 112. The insert 112 does not form the molded part wall outer side 118 at the molded part curved section 113, since the insert is covered by the plastic on its outside.
[0074] The molded part 121 in Figure 11 is similar to the molded part 101 in Figure 5. It differs from the molded part 101 in Figure 5 in that the inner radius of curvature of the inner molded part curved sections 129a, 129b is smaller. The insert 122 of the molded part 121 has a correspondingly small inner radius of curvature on its outer side. Furthermore, the molded part 101 and the molded part 121 are identical.
[0075] The molded part 131 in Figure 12 is similar to the molded part 111 in Figure 6. It differs from the molded part 111 in Figure 6 in that the inner radius of curvature of the inner molded part curved sections 139a, 139b is smaller. The insert 132 of the molded part 131 has a correspondingly small inner radius of curvature on its outer side. Furthermore, the molded part 111 and the molded part 131 are identical.
[0076] Figure 13 shows a first embodiment of a cavity 140 of an injection molding tool in cross-section and in longitudinal section. A possible associated injection molding tool is shown in Figures 15 and 16. The cavity 140 is circular in cross-section and has an L-shape in longitudinal section. It is generally suitable for producing L-shaped molded parts that have an external shape like that in Figures 1, 2, 3, 7, 8 and 9. The cavity represents a negative mold of the molded part not shown in Figure 13. The cavity is delimited by a cavity surface 141, which is part of the associated injection molding tool. The cavity has a first straight cavity section 143, a second straight cavity section 144 and a cavity curved section 145 between the first and the second cavity section.The cavity curvature section 145 comprises an inner cavity curvature section 146, which faces a geometric cavity curvature center 147, and an outer cavity curvature section 148, which faces away from the geometric cavity curvature center 147. An insert 142 with a circular cross-section is arranged in the cavity curvature section 145. The outer diameter of the insert 142 is significantly smaller than the inner diameter of the cavity 140. The insert 142 is arranged in the cavity 140 such that it rests against the cavity surface 141 only in the region of the outer cavity curvature section 148. In the region of the inner cavity curvature section 146, the insert 142 is spaced from the cavity surface 141. Figure 13 does not depict the plastic that is introduced into the cavity 140 to form a molded part.In the position of the insert 142 in the cavity 140 shown in Figure 13, a molded part can be produced in which the molded part wall in an outer molded part curved section is formed by a composite of the insert 142 and the injected plastic and in which the molded part wall in an inner molded part curved section is formed only by the injected plastic.
[0077] All of the aforementioned molded parts have a circular cross-section. The molded part cavity also has a circular cross-section. The aforementioned inserts, which are designed as hollow bodies, also have a circular cross-section.
[0078] Figure 14 shows a second embodiment of a cavity 150 in cross-section and in longitudinal section. The cavity 150 has different cross-sections in different sections. In longitudinal section, the cavity has a Y-shape. The cavity 150 comprises a first straight curved section 153, a second straight curved section 154, a third straight curved section 155, and a cavity curved section 156, which connects the straight curved sections 153, 154, and
[0079] 155. The cross-section of the first straight curved section 153 is circular. The cross-section of the second straight curved section 154 is oval. The cross-section of the third straight curved section 155 is hexagonal. In the cavity curved section
[0080] 156, the cross-sections of the straight cavity sections 153, 154, 155 merge into one another. An insert 152 is arranged in the curved cavity section 156 of the cavity 150. This insert 152 also has a Y-shape with three straight sections and one curved insert section. The cross-section of the insert 152 in the straight sections is adapted to the shape of the corresponding straight cavity sections 153, 154, 155. The insert 152 is arranged in the cavity 150 such that there is essentially an equal distance on all sides between the outer side of the insert 152 and the cavity surface 151. For this purpose, the injection mold (not shown) which encloses the cavity is equipped with hold-down devices. These are also not shown in the drawing.When plastic melt is introduced into the cavity 150 and a cavity is created using a fluid, the insert 152 is embedded in the plastic on its inside and outside. This creates a Y-shaped molded part (not shown), which has different cross-sections in different sections, corresponding to the cavity 150 and the insert 152.
[0081] Figures 15 and 16 show an embodiment of an injection mold 160 with a device 163 for supplying a liquid plastic melt and for supplying a fluid. The opened injection mold is shown with a view of the cavity 161 with the cavity curved section. In Figure 15, an insert 162 is arranged in the cavity 161, the outer side of which rests against the cavity surface. The cavity 161 and the insert 162 are generally suitable for producing a molded part according to Figure 2. In Figure 16, an insert 172 is arranged in the cavity 161, the outer diameter of which is smaller than the diameter of the cavity 161. The cavity 161 and the insert 172 are generally suitable for producing a molded part according to Figure 3.
[0082] All molded parts shown in the drawing are manufactured using a combination of plastic injection molding and fluid injection technology.
[0083] All features can be essential to the invention both individually and in any combination. Reference numbers
[0084] 1 molded part
[0085] 2 First straight molded section
[0086] 3 Molded part curvature section
[0087] 4 Second straight molded section
[0088] 5 molded wall
[0089] 6 molded part cavity
[0090] 7 Moulded wall inside
[0091] 8 Moulded wall exterior
[0092] 9 Inner molded part curvature section
[0093] 10 Geometric molded part curvature center
[0094] 11 Outer molded part curvature section
[0095] 12 Circle
[0096] 13 Circle
[0097] 21 molded part
[0098] 22 First straight molded section
[0099] 23 Molded part curved section
[0100] 24 Second straight molded section
[0101] 25 molded wall
[0102] 29a Inner molded part curved section
[0103] 29b Inner molded part curved section
[0104] 30a Geometric molded part curvature center
[0105] 30b Geometric molded part curvature center
[0106] 31 Outer molded part curvature section
[0107] 32 third straight molded section
[0108] 41 molded part
[0109] 45 molded wall
[0110] 49 inner molded part curvature section
[0111] 51 molded part
[0112] 55 molded wall
[0113] 59a inner molded part curved section 59b inner molded part curved section
[0114] 61 molded part
[0115] 62 inserts
[0116] 63 Molded part curved section
[0117] 65 molded wall
[0118] 66 molded part cavity
[0119] 68 Moulded wall exterior
[0120] 69 Inner molded part curvature section
[0121] 71 molded part
[0122] 72 inserts
[0123] 73 Molded part curved section
[0124] 75 molded wall
[0125] 78 Moulded wall exterior
[0126] 81 molded part
[0127] 82 inserts
[0128] 89 inner molded part curvature section
[0129] 91 molded part
[0130] 92 inserts
[0131] 99 inner molded part curvature section
[0132] 101 molded part
[0133] 102 inserts
[0134] 103 Molded part curved section
[0135] 105 molded wall
[0136] 106 molded part cavity
[0137] 109a inner molded part curvature section
[0138] 109b inner molded part curvature section
[0139] 111 molded part
[0140] 112 inserts
[0141] 113 Molded part curved section
[0142] 118 Moulded wall exterior
[0143] 121 molded part
[0144] 122 Insert a inner molded part curved section b inner molded part curved section
[0145] molded part
[0146] Insert a inner molded part curved section b inner molded part curved section
[0147] cavity
[0148] Cavity surface
[0149] Insert first straight cavity section second straight cavity section
[0150] Cavity curvature section inner cavity curvature section geometric cavity curvature center outer cavity curvature section
[0151] cavity
[0152] Cavity surface
[0153] Insert first straight cavity section second straight cavity section third straight cavity section
[0154] Cavity curvature section
[0155] injection mold
[0156] cavity
[0157] insert
[0158] Device for supplying a liquid plastic melt and a
[0159] Fluids
[0160] insert
Claims
CLAIMS 1. A molded part made of injection-molded plastic, which is designed as a one-piece, dimensionally stable hollow body and has a molded part wall (65, 75, 105) which delimits a molded part cavity (66, 106), wherein the molded part (61, 71, 81, 91, 101, 111, 121, 131) comprises at least one hollow molded part curved section (63, 73, 103, 113), wherein the molded part (61, 71, 81, 91, 101, 111, 121, 131) has an insert (62, 72, 82, 92, 102, 112, 122, 132, 142, 152, 162, 172), which is designed as a dimensionally stable hollow insert body, such that the molded part wall (65, 75, 105) on the molded part curved section (63, 73, 103, 113) is formed at least partially by a composite of the insert (62, 72, 82, 92, 102, 112, 122, 132, 142, 152, 162, 172) and the plastic.
2. Moulded part according to claim 1, characterized in that the moulded part wall (65, 75, 105) in the entire moulded part curved section (63, 73, 103, 113) by the composite of insert (62, 72, 82, 92, 102, 112, 122, 132, 152, 162, 172) and plastic.
3. Molded part according to claim 1 or 2, characterized in that the molded part (61, 71, 81, 91, 101, 111, 121, 131) is produced by means of a combination of plastic injection molding and fluid injection technology.
4. Moulded part according to one of the preceding claims, characterized in that the insert (62, 82, 102, 122, 162) is overmolded with plastic exclusively on its insert inner side facing the moulded part cavity (66, 106).
5. Moulded part according to one of the preceding claims, characterized in that the insert (62, 72, 82, 92, 102, 112, 122, 132, 142, 152, 162, 172) into the plastic of the molded part (61,71,81,91, 101, 111, 121, 131) is embedded, that the molded part (61, 71, 81, 91, 101, 111, 121, 131) is free from a projection of the insert (62, 72, 82, 92, 102, 112, 122, 132, 142, 152, 162, 172) over an outer surface of the molded part (61, 71, 81, 91, 101, 111, 121, 131).
6. Moulded part according to claim 5 insofar as it is dependent on claim 4, characterized in that the insert (62, 82, 102, 122, 162) on the outside of the moulded part is flush with the adjacent sections of the moulded part.
7. Molded part according to one of claims 1, 2, 3 or 5, characterized in that the insert (72, 92, 112, 132) is overmolded with plastic on its inner side facing the molded part cavity and on its outer side facing away from the molded part cavity.
8. Moulded part according to one of the preceding claims, characterized in that the moulded part (61, 71, 81, 91, 101, 111, 121, 131) has an inner moulded part curved section (69, 89, 99, 109a, 109b, 129a, 129b, 139a, 139b) which faces a geometric molded part curvature center (10), and an outer molded part curvature section which faces away from the geometric molded part curvature center (10), that the insert is overmolded with plastic in such a way that the molded part wall is formed only in the inner molded part curvature section by a composite of the insert and the plastic or that the molded part wall is formed only in the outer molded part curvature section by a composite of the insert and the plastic.
9. Molded part according to one of the preceding claims, characterized in that the molded part curved section is L-shaped, egg-shaped or C-shaped.
10. Molded part according to one of claims 1 to 8, characterized in that the molded part curved section has a branch and is Y-shaped or T-shaped.
11. Molded part according to one of the preceding claims, characterized in that the molded part (61, 71, 81, 91, 101, 111, 121, 131) has a first straight molded part section (2, 22) which extends along a first molded part axis L1, that the molded part (61, 71, 81, 91, 101, 111, 121, 131) has a second straight molded part section (4, 24) which extends along a second molded part axis L2, that the molded part curved section (63, 73, 103, 113) is located between the first straight molded part section (2, 22) and the second straight molded part section (4, 24), and that the molded part cavity (66, 106) extends continuously through the first straight molded part section (2, 22), the molded part curved section (63, 73, 103, 113) and the second straight molded part section (4, 24).
12. Moulded part according to claim 11 insofar as it is dependent on claim 10, characterized in that the moulded part (101, 111, 121, 131) has a third straight moulded part section (32) which extends along a third mold part axis L3, that the mold part curved section (103, 113) is T-shaped or Y-shaped and the mold part curved section (103, 113) is arranged between the first straight mold part section (2, 22), the second mold part section (4, 24) and the third mold part section (32).
13. Moulded part according to claim 11 or 12, characterized in that for an angle a between L1 and L2 the following applies: 5° < a < 180°.
14. Molded part according to one of the preceding claims, characterized in that a radius of curvature at the inner molded part curvature section is greater than or equal to 0.5 mm.
15. Moulded part according to one of the preceding claims, characterized in that the insert (62, 72, 82, 92, 102, 112, 122, 132, 142, 152, 162, 172) consists of a material which is dimensionally stable under the influence of the temperature and pressure prevailing in the injection moulding tool.
16. Molded part according to one of the preceding claims, characterized in that the insert (62, 72, 82, 92, 102, 112, 122, 132, 142, 152, 162, 172) consists of a fiber-reinforced plastic material, wherein the fibers are glass, aramid, carbon or natural fibers.
17. Moulded part according to one of the preceding claims, characterized in that the insert (62, 72, 82, 92, 102, 112, 122, 132, 142, 152, 162, 172) consists at least partially of metal.
18. Method for producing the molded part (61, 71, 81, 91, 101, 111, 121, 131) according to one of the preceding claims by means of a plastic injection molding machine, wherein the plastic injection molding machine has an injection molding tool (160) with a cavity (140, 150, 161) designed as a hollow mold, which represents a negative mold of the molded part (61, 71, 81, 91, 101, 111, 121, 131) and corresponding to the molded part (61, 71, 81, 91, 111, 121, 131) comprises a cavity curvature section (145), wherein the cavity (140, 150, 161) is delimited by a cavity surface (141, 151) which is part of the injection molding tool (160), wherein the injection molding tool (160) is equipped with at least one inlet (163) for a liquid plastic melt and with at least one inlet for a fluid, characterized by the following method steps - inserting the dimensionally stable insert (62, 72, 82, 92, 102, 112, 122, 132, 142, 152, 162, 172) designed as a hollow insert body into the cavity curved section (145) of the injection mold (160), such that the insert (62, 72, 82, 92, 102, 112, 122, 132, 142, 152, 162, 172) at least partially bears against the cavity surface at the cavity curved section (145) and, moreover, leaves the cavity (140, 150, 161) free so that the plastic melt can spread, - Closing the injection mold (160), - introducing liquid plastic melt under pressure at the inlet (163) into the cavity (140, 150, 161), wherein the plastic melt passes from the at least one inlet (163) into the cavity curvature section (145), - Introducing a fluid into the liquid plastic melt in the cavity (140, 150, 161) in such a way that at least one continuous mold cavity (66, 106) extending through the molded part curved section (63, 73, 103, 113) is created in the plastic melt by means of fluid injection technology and the plastic melt forms the hollow molded part curved section (63, 73, 103, 113) on the cavity curved section (145) and the insert (62, 72, 82, 92, 102, 112, 122, 132, 142, 152, 162, 172) arranged there, wherein the insert (62, 72, 82, 92, 102, 112, 122, 132, 142, 152, 162, 172) forms a bond with the plastic melt and forms the molded part wall (65, 75, 105) in this area, and the The plastic melt also forms the molded part wall (65, 75, 105).
19. The method according to claim 18, characterized in that the insert (62, 72, 82, 92, 102, 112, 122, 132, 142, 152, 162, 172) together with the solidified plastic melt in the molded part curved section (63, 73, 103, 113) forms a dimensionally stable, circumferentially running composite molded part wall.
20. The method according to claim 18 or 19, characterized in that the insert rests exclusively on the cavity surface at the inner cavity curvature section and leaves the outer cavity curvature section free, such that the insert, together with the solidified plastic melt, forms a composite molded part wall at the inner molded part curvature section and this is formed integrally with the remaining molded part wall, which consists exclusively of the solidified plastic melt.
21. Method according to claim 18 or 19, characterized in that the insert (72, 92, 112, 132, 152, 172) is overmolded with plastic melt on its outer side facing the cavity surface and on its inner side facing away from the cavity surface.
22. The method according to claim 21, characterized in that the insert (62, 72, 82, 92, 102, 112, 122, 132, 142, 152, 162, 172) is positioned and held in the cavity (140, 150, 161) by positioning pins which are arranged on the injection mold (160) and protrude in a first position above the cavity surface (141, 151), and in that the positioning pins are moved into a second position in which they are flush with the cavity surface (141, 151) before the molded part is removed from the injection mold.
23. Method according to one of claims 18 to 20, characterized in that the insert (62, 82, 102, 122) is overmolded with plastic melt exclusively on its inner side facing away from the cavity surface.
24. Method according to one of claims 18 to 23, characterized in that the insert (62, 72, 82, 92, 142, 162, 172) is L-shaped, U-shaped or C-shaped.
25. Method according to one of claims 18 to 22, characterized in that the insert (102, 112, 122, 132, 152) is T-shaped or Y-shaped.
26. Method according to one of claims 18 to 25, characterized in that the insert (62, 72, 82, 92, 102, 112, 122, 132, 142, 152, 162, 172) is one-piece.
27. Method according to one of claims 18 to 25, characterized in that the insert has several insert parts.
28. Method according to one of claims 18 to 27, characterized in that the plastic melt displaced from the cavity with the fluid is pressed into a collecting cavity which adjoins the cavity.
29. Method according to one of claims 18 to 27, characterized in that the plastic melt displaced from the cavity with the fluid is pressed back into a screw cylinder of the injection molding machine via a hot runner at the inlet.
30. Insert for carrying out the method according to one of claims 18 to 29, characterized in that the insert (62, 72, 82, 92, 102, 112, 122, 132, 142, 152, 162, 172) is designed as a dimensionally stable hollow insert body and consists of a material which is dimensionally stable under the influence of the temperature and pressure prevailing in the injection mold.
31. Insert according to claim 30, characterized in that the insert (62, 72, 82, 92, 102, 112, 122, 132, 142, 152, 162, 172) has a wall thickness predetermined by the minimum wall thickness of the molded part.
32. Insert according to claim 30 or 31, characterized in that the insert is L-shaped, U-shaped, C-shaped.
33. Insert according to claim 30 or 31, characterized in that the insert is Y-shaped or T-shaped.
34. Insert according to one of claims 30 to 33, characterized in that it consists of a fiber-reinforced plastic material, wherein the fibers are glass, aramid, carbon or natural fibers.
35. Insert according to one of claims 30 to 34, characterized in that it consists at least partially of metal.
36. Injection molding tool for a plastic injection molding machine for producing a molded part according to one of claims 1 to 17 with a method according to one of claims 18 to 29, characterized in that the injection molding tool is equipped with at least one hold-down device, by means of which the insert (62, 72, 82, 92, 102, 112, 122, 132, 142, 152, 162, 172) according to one of claims 30 to 35 is held at the position predetermined for it in the injection molding tool (160).
37. Injection molding tool according to claim 36, characterized in that the hold-down device is designed as a positioning pin which is movably arranged in the injection molding tool (160), wherein the positioning pin projects beyond the cavity surface (141, 151) in a first extended position and ends flush with the cavity surface (141, 151) in a second retracted position.