Device for injection molding of plastic pipe parts

Abstract

Device for injection molding plastic components comprising at least one tubular section, wherein the device comprises at least two complementary outer mold parts forming a mold cavity (35) and the device comprises at least one core mold part (37, 38, 39, 40), wherein the device comprises an outer main mold (30) and various inserts (36) for injection molding tubular parts of different diameters are provided, which are received by the main mold (30), wherein the inserts (36) each have the same outer contour independent of the diameter of the component to be injection molded and each have a cavity corresponding to the diameter of the component, and wherein the inserts (36) form the outer mold parts of the mold, characterized in that the device is intended for injection molding components for ventilation ductwork.which comprise at least one socket section (11, 12, 17, 19, 23, 24) integrally adjoining the tubular section at its end, wherein separate core molding parts (37, 38) are provided for at least one tubular section of a component to be injection-molded and for at least one socket section (11, 12, 17, 19, 23, 24), and wherein, depending on the material of the component to be injection-molded, at least partially different core molding parts (37, 38, 39, 40) are provided even with the same diameters.

Description

The present invention relates to a device for injection molding plastic components for ventilation pipes, which comprise at least one tubular section and at least one sleeve section adjoining the tubular section integrally at the end, wherein the device comprises at least two complementary outer molded parts, which form a mold cavity and the device comprises at least one core molded part.An apparatus for injection molding pipe bends having the features of the type mentioned at the beginning is described, for example, in DE 44 01 395 C 2. Previously, more complex components of this type, which are required in particular in ventilation technology, have been produced by rotary sintering or by blow molding. The production of such components even by injection molding is technically less difficult if these components can have a greater wall thickness. Such components with a comparatively thick wall thickness can be used when they are water or waste water lines or pressure pipes, for example for gas lines. However, in tubular members having sleeve portions provided for ventilation pipes, thinner wall thickness is required. One of the reasons for this is that a saving in material is sought and a reduction in the weight of this component is aimed at, for example, still enabling the components to be handled during assembly with larger line diameters. However, the injection molding of such thin-walled components is associated with technical difficulties. In particular, depending on the material used, it is difficult to distribute the molten plastic in the mold so uniformly in the melt flow that no defects are produced on the component.A further problem is that comparatively complicated tools are required for the injection molding of plastic components for ventilation pipelines, since on the one hand the outer molded parts are required which form a mold cavity and which define the outer contour of the component to be injected. Moreover, the core molding parts are required which define the inner contour of the component to be injected. If tubular components are injection-molded with sleeve sections, components of similar construction, such as double sleeves, reducing pieces, pipe bends, etc., with different diameters are often required. In order to cover the current range of products, the components must be available in all tube diameters customary on the market. In addition, for example, in the case of reducing pieces which are installed in a pipeline in order to reduce from a larger to a smaller diameter, the diameters can vary on both sides, so that in order to cover all variants occurring in practice, a comparatively large number of these components can be produced in different sizes. If, therefore, for each size variant, a separate complete tool with outer molded parts and core molded parts is produced, this becomes very costly.This is made more difficult by the fact that these components are required for ventilation pipelines for different applications in ventilation technology. These pipes allow, for example, aggressive and corrosive vapors of different compositions to be conducted. This results in different requirements for the choice of material, i.e. the same components must often be produced in different plastics for these different application purposes. For example, the same components are required, once from a polyolefin, and for other applications, for example from PVC or PVDF. These different materials may have different shrinkages on cooling after injection molding in the mold. In the case of the sleeve sections, however, the dimensions to be observed could no longer be ensured due to the narrow tolerance requirements imposed by the standards solely by the shrinkage. This means that according to the prior art, in this case, other tools must be used for components of the same dimensions when injection molding from different plastics, which tools are matched dimensionally to the shrinkage occurring in the material used in each case. This further increases the number of tool variants required.Apparatuses or methods of this type are also known from the publications mentioned below.For example, DE 32 06 433 A1 describes a method for injection molding measuring insert bodies of different sizes made of plastic for water meters of different nominal diameters, the measuring inserts of which are inserted into the meter housing, form the measuring chamber and the throughflow channel with their measuring insert jacket and have one or more bearing points for receiving a measuring blade rotating about its longitudinal axis.DE 104 56 39 A discloses an injection mold for producing molded bodies, in particular closure caps for pharmaceutical tablet tubes, from thermoplastic material, in which one or more helically bent retaining arms are connected at one end in the same axis to the concave side of an internally prismatic cap. The injection mould comprises a smooth mould core which is movable longitudinally with respect to the axial direction of the mould and which is surrounded by a sleeve which is mounted on it so as to be movable in the longitudinal direction and the outer casing of which delimits the inner wall of the cap-shaped part of the injection moulded part and the cavities which form the helically bent holding arms of the injection moulded part are worked into the inner casing of which sleeve. The mold is designed in such a way that after injection molding has taken place, when the mold is opened, the mold core is first pulled out of the sleeve and then the sleeve together with the mold core is pulled out of the cap-shaped part of the injection molding, so that the helically bent arms protrude inward from the depressions of the sleeve.DE 10 2006 042 942 A1 describes a method for producing an intake tract from plastic for internal combustion engines, in which a plurality of intake pipes run parallel and in which throttle valves are located in the intake pipes, which throttle valves are actuated via a common shaft, wherein the shaft is supported by bearings located in the intake pipe walls and wherein an injection tool is used for producing the intake tract, wherein the injection tool has two mandrels for forming the openings for the bearings, such that each mandrel can be pushed in and pulled out from one side of the injection tool, wherein the ends of the mandrels are supported mutually in the injection tool, and wherein each mandrel is formed in a step shape in such a way that in each case larger diameters are provided for the bearing points located further outward than for the adjacent bearing points located inward.US 2002 / 0197428 A1 describes an improved molded plastic bracket, an associated molding apparatus and a manufacturing method. The angle herein defines an internal flow path having a smoothly rounded internal curve and is formed by injecting plastics material into a tubular mould cavity formed by closed mould parts in cooperation with a pair of slidably retractable core units of circular cross-section and having distal ends in mating angularly disposed end-to-end contact to form the internal flow path having a curve formed along its length. Each core unit includes an outer core pin for forming an outer portion of the flowpath and includes a ramped track for slidably mounting an inner slide segment forming an inner portion of the flowpath and further including a curved inner edge for forming a portion of the smoothly rounded inner curve. The initial retraction of each outer core pin from the mold cavity permits relative advancement of the inner slide segment along the ramped path toward a centerline of the flowpath such that the curved inner edge of the inner slide segment releases the rounded inner curve of the molded elbow and thereby permits smooth linear extraction of the core assembly from the molded plastic part.Furthermore, DE 103 47 248 A1 describes a method for producing a tool which serves for producing parts of a ball-head connection by means of plastic injection molding, wherein at least one replacement tool or a replacement negative mold is produced which has slightly different dimensions.Starting from this prior art, it is therefore the object of the present invention to provide a device in which at least parts of the injection mold can be used for the injection molding of a larger number of different components.The solution of this object provides an apparatus for injection molding plastic components for ventilation pipes with the features of claim 1.The device for injection molding plastic components comprising at least one tubular portion comprises at least two complementary external mold parts forming a mold cavity; at least one core mold part; an external master mold, wherein different inserts are provided for injection molding of tubular parts of different diameter received by the master mold, wherein the inserts each have an identical external contour independent of the diameter of the component to be injected and a cavity corresponding to the diameter of the component, and wherein the inserts form the external mold parts of the mold.According to the invention, it is provided that this device is provided for the injection molding of components for ventilation pipelines, which comprise at least one sleeve section adjoining the tubular section in one piece at the end, wherein core molded parts which are separate in each case are provided for at least one tubular section of a component to be injected and for at least one sleeve section, and wherein depending on the material of the component to be injected, core molded parts which are different at least in part are provided in each case even for the same diameters.Due to the solution according to the invention, the outer molded parts are divided into a master mold and at least one insert cooperating with this master mold, whereby the advantage is obtained that the master mold can be used in combination with different inserts, whereby the number of required tool parts for the production of a larger number of injection molded components is reduced. For example, the same master mold can be used for injection molding components of different diameters, with only different inserts being required. Within further size ranges, the same parent form can thus be used. For example, three, four or five different dimensions can be injected in the same master form.According to a further development of the invention, the master mould preferably has at least partially the actuating devices for axially moving the core moulded parts, so that, like the master mould, these actuating devices with the required drives only have to be present once in each case for the master mould and only the insert or the inserts have to be replaced as outer moulded parts and / or the core moulded parts if a similarly shaped component with a different diameter is to be injection moulded.In order to take account of the aforementioned problem of different shrinkage in the case of different materials, different inserts are provided in each case, depending on the material of the component to be injected, even with the same diameters. The same master shape can be used in each case and the respective shrinkage (shrinkage) of the material can be compensated by the specific use. However, it is also possible, for example, to use the same inserts in the case of different materials and to replace only the core molded parts or only certain core molded parts.According to a possible preferred variant of the invention, depending on the material of the component to be injected, it is also possible to provide different core molded parts in each case even with the same diameters, preferably while maintaining the respective inserts as outer molded parts. The respective gap between the inner dimension (cavity) of the insert, which is part of the outer molded part and the outer dimension of the core molded part, then determines the diameter and the wall thickness of the manufactured component in combination with the respective material-specific material shrinkage during injection molding.As a rule, more than two outer molded parts in the form of inserts are provided for the injection molding of a component, that is to say in particular two complementary outer molded parts which complement one another to form a cylindrical or tubularly curved mold cavity which then determines the outer contour of a tubular rectilinear section or of a pipe bend.Furthermore, separate core molded parts are provided for at least one tubular section of a component to be injected and for at least one sleeve section. If a component with at least one tubular section and at least one sleeve section is to be injection molded, for example a double sleeve, different tools can be used for these sections of the same component. Although this initially increases the number of tools required for a single component to be injected, it has the advantage that, for example, the same tools can be used at least partially for the production of identically shaped components from different materials. In this case, independently of the respectively injected plastic, the same tools are used in each case in the region of the tubular sections, that is to say outer molded parts in the form of inserts and core molded parts. For the sleeve sections, however, when the plastic is changed, the corresponding parts of the mold are changed in each case, wherein these are generally core molded parts which are changed. In the region of the tubular section, the different shrinkage of the material in each case due to the different materials used plays no part, since larger dimensional tolerances are acceptable there. However, this is different in the area of the socket section, since there a pipe section must be inserted into the socket section in a fitting manner later during the assembly of the ventilation pipe. Thus, when the material is changed, only the tools for the sleeve section are (partially) changed, while the tools used for a tubular section can be used for components of the same design consisting of different materials. Since the tools for the sleeve sections are usually designed to be comparatively short, this is a cost advantage and ultimately leads to a reduction in the total number of tools required.In a preferred variant of the invention, it is such that at least three, preferably at least four, core moldings are used for the injection molding of a component, of which at least two have cylindrical sections and at least two curved sections. This variant is considered in particular for components such as pipe bends or the like. This facilitates demolding and also makes it possible, in certain applications, to exchange only the core moldings for the cylindrical sections when the injected component is changed, but to leave the core moldings for the arcuate sections. This variant can, however, also be used, for example, for reducing pieces, in which case the core molded parts are then not curved but rather conical. A total of three core molded parts may then be sufficient.Devices of the type according to the invention are provided in particular for the injection molding of components made of PPS, PVC, PP, PE or PVDF, wherein different inserts and / or core molded parts are provided at least partially for these different materials, preferably for the aforementioned reasons in the region of sleeve sections, where it is important to adhere to precise dimensional tolerances.Particularly preferably, a device according to the invention is used for injection molding pipe bends, double sleeves, T-pipe sections, pipe sections with flange, reducing pieces or pipe components with internal throttle valves made of plastic for ventilation pipes.It should be borne in mind that in the relevant standards, for example DIN 1946, DIN 24147 part 1-13, DIN 4740 part 2 for PVC, DIN 4741 part 2 for PP, the dimensions and minimum wall thicknesses for the moldings are fixed, and that according to the invention it is sought in practice to keep the wall thicknesses of the moldings as low as possible in order to achieve a saving in material and a reduction in the weight of the components, but on the other hand, owing to the properties of the material, i.e. its flow behavior in the tool during the injection molding process, limits are set at the minimum wall thicknesses, which additionally vary depending on the material used. In addition, the production of the components by injection molding becomes increasingly difficult with increasing size, since the flow paths which the plastic melt must travel in the mold become larger. If the wall thicknesses are too low, this leads to defects on the component.Preferred developments of the object solution according to the invention are described in the dependent claims. Further advantages of the invention are evident from the following detailed description.The present invention is described in more detail below on the basis of exemplary embodiments with reference to the attached drawings. The following are shown: FIG. 1 shows a sectional view of a double sleeve as an exemplary component which can be produced by means of a device according to the invention; FIG. 2 is a sectional view of a reducer with a sleeve as an exemplary component which can be produced by means of a device according to the invention; FIG. 3 shows a sectional view of a pipe bend with sleeves as an exemplary component, which can be produced by means of a device according to the invention; FIG. 4 is a perspective view of a portion of an exemplary apparatus of the present invention with the parent mold without a replaceable insert; FIG. 5 shows a perspective view of only the interchangeable insert for the master mould according to the exemplary embodiment of FIG. 4 ; FIG. 6 shows a plan view of the master form of FIG. 4 with inserted replaceable insert according to FIG. 5 ; FIG. 7 is a partial longitudinal section through the device of FIG. 6 along the line A-A.In the following, firstly with reference to FIG. 1, a first component which can be produced by means of a device according to the invention is explained by way of example. This is a so-called double sleeve 10, which is a basically tubular component with a sleeve section at each end, which is intended to receive a pipe (not shown here) to be connected of a pipeline. The double sleeve thus serves for connecting two pipe sections of the same diameter. For this purpose, it comprises a first sleeve section 11 and a second sleeve section 12, into each of which the pipe to be connected can be inserted. Centrally between the two sleeve sections 11, 12 is a central web 13 which serves on both sides as a stop for the tubes to be inserted and for this purpose has a respective end-face stop surface 14, 15 on both sides. The inner diameter of the two sleeve sections 11, 12 decreases in a minimally conical manner, as seen from the outside to the inside in the axial direction, so that better clamping of the inserted pipe in the sleeve results when the insertion is deeper.In the following, a further exemplary embodiment of the present invention is explained in more detail with reference to FIG. 2. In this case, it is a reducer 16 for a ventilation pipe which is injection-molded from plastic using a device according to the invention. This reducer 16 comprises a first sleeve portion 17 of smaller diameter into which a pipe of a ventilation pipe of corresponding diameter can be inserted (not shown here). This cylindrical first sleeve section 17 is then adjoined in the axial direction by a section 18 which widens conically in diameter and then merges in turn into a second sleeve section 19 of larger diameter. Between the first sleeve section 17 of smaller diameter and the conical section 18 a small annular circumferential shoulder 20 is formed on the inside, so that here too a tube can be inserted into the sleeve section 17 up to this shoulder serving as a stop. At the other end of the conical section 18, a small shoulder 21 is likewise formed for the inner end of the sleeve section 19 of larger diameter, which shoulder serves as a stop for the larger pipe to be inserted. In this example as well, the two sleeve sections 17 and 19 can taper conically, viewed from the outside to the inside, in the axial direction gradually by a small amount on the inside, in order to clamp the inserted pipe. The reducer 16 shown in FIG. 2 thus serves to reduce a pipe of predetermined diameter (corresponding to the inner diameter of the sleeve portion 19) to a smaller diameter, which corresponds to the inner diameter of the sleeve portion 17.In the following, with reference to FIG. 3, a further component is explained by way of example, which can be injected in a device of the type according to the invention. This is a 45° pipe bend 22, which has sleeve sections 23, 24 at each of the two ends, so that the pipe bend is suitable for deflecting a ventilation pipe in a bend by 45°, the ends of pipe sections (not shown) being inserted into the two sleeve sections 23 and 24, respectively. Both sleeve sections 23, 24 are connected to one another by a pipe bend section 25. At the end of the cylindrical sleeve section 23, a shoulder 26 is formed by a small reduction, which shoulder serves as a front-side stop for the pipe to be inserted there. Likewise, an offset is formed on the other side of the pipe bend piece, in that the sleeve section 24 has a slightly larger diameter on the outside and also on the inside than the pipe bend section 25, as a result of which a shoulder 27 is formed, which serves as a front-side stop for a pipe (not illustrated here) to be inserted. As can be seen in FIG. 3, in this component in the form of a pipe bend 22, the wall thickness is in each case approximately the same both in the pipe bend section 25 and in the two sleeve sections 23 and 24, which is achieved by the respective offset in the region of the transition between pipe bend section 25 and the respective sleeve sections 23 and 24, which is designed such that a jump also occurs on the outer circumference of the component. This achieves a minimum material use on account of the comparatively low wall thickness. Only in the region of the inner bend 28 can the wall thickness be selected to be somewhat greater.In the following, an exemplary device according to the invention for injection molding is explained in more detail with reference to FIGS. 4, 5, 6 to 7. This is a device by means of which 45° pipe bends of the type shown in FIG. 3 can be injected with optionally different diameters. FIG. 4 shows initially in perspective view only a part of the master mould 30, from which the interchangeable insert specific in each case for one diameter has been removed. In addition, only the lower half of the device is shown to a large extent, so that it is possible to see the movable parts 31, 32 of the device which are required in order to move the cores and outer molded parts hydraulically or pneumatically and thus to enable the removal of an injection-molded component. As can be seen, actuating devices 33, 34 engage these movable parts 31, 32 via which the movable parts are moved substantially axially along two axes crossing one another at an angle of 45°. The lower half of the master mould shown has, centrally between the movable parts 31, 32, a cavity 35 which fittingly receives the interchangeable insert 36 shown in FIG. 5. It can be seen in FIG. 5 that this interchangeable insert 36 has a corresponding pentagonal contour.FIG. 5 shows the replaceable insert 36 provided for a specific diameter and removable from the master mould when the dimension is changed, in perspective, the under half of the outer mould 36a for the injection-moulded component being seen. The upper half is again not shown, so that all core molded parts can be seen in the view according to FIG. 5. In the exemplary embodiment shown, these are a total of four core mold parts 37, 38, 39, 40. Between these and the two outer mold parts 36, an annular cavity (gap) is then formed during assembly, which cavity is formed in accordance with the desired shape of the injection-molded component and into which the plastic melt flows.As can be seen from FIG. 5 and in particular also from the sectional illustration according to FIG. 7, the core molded parts 37, 38 and 39, 40 partially engage one another and penetrate one another. The two axially outer core molded parts 37 and 40 assigned to the cylindrical pipe sections of the 45° pipe bend to be produced, the axes of which in the assembled state assume an angle of 45° to one another, each comprise two ring sections of different diameters, wherein the axially inner cylindrical ring sections 37 aand 40 a, respectively, with the respectively smaller diameter, serve for producing the two sleeve sections 23 and 24 of the pipe bend 22 according to FIG. 3. The two curved core formed parts 38 and 39, on the other hand, together serve for producing the pipe bend section 25 of the pipe bend 22 from FIG. 3.In addition to its curved section 38, the core molding 38 has a cylindrical extension 38a of smaller diameter, which passes concentrically through both ring sections of the core molding 37 and in the process projects a certain distance axially beyond the core molding 37, as can be seen in FIG. 5. In the same way, the core molding 39 passes with its cylindrical extension 39a concentrically through the core molding 40. This division of the tool makes it possible, when changing the material but maintaining the diameter and maintaining the basic shape of the component, to exchange only the two core molded parts 37 and 40 defining the sleeve sections, but to continue to use the two other core molded parts 38, 39, since the different shrinkage of the material is critical only in the sleeve sections of the component because of the dimensional precision to be maintained.In FIG. 7, the lower half of the master mould 30 and the interchangeable insert 30 is shown in section. The replaceable insert 36 forms the lower of the outer molded parts and the gap 41 between this outer molded part and three of the core molded parts 37, 38 and 39 can therefore be clearly seen here. During injection molding, the plastic melt flows into this gap, so that after hardening, the injected component, in this case a 45° pipe bend according to FIG. 3, is produced there. This gap between the core molded parts and the outer molded part continues correspondingly upwards when the upper outer molded part (second interchangeable insert), not shown in FIG. 7, is placed on, which has a shape and cavity that is mirror-symmetrical in principle with the lower outer molded part 36 shown and is complemented with the outer molded part 36 shown to form the complete outer shape. The core molded parts 37, 38, 39, 40 also shown in FIG. 5 can each be separately moved axially outwards via the actuating devices 33, 34, in order to remove the mold after the injection molding and remove the finished component.List of reference characters10 Double sleeve 11 First sleeve section 12 Second sleeve section 13 Central web 14 End stop 15 End stop 16 Reducing piece 17 First sleeve section 18 Conical transition section 19 Second sleeve section 20 Shoulder 21 Shoulder 22 Pipe bend 23 Sleeve section 24 Sleeve section 25 Pipe bend section 26 Shoulder 27 Shoulder 28 Inner bend 30 Master mould 31 Movable part 32 Movable part 33 Actuating device 34 Actuating device 35 Cavity 36 Interchangeable insert 37 Core moulded part 37 a Ring section 38 Core moulded part 38 a Cylindrical extension 39 Core moulded part 39 a Cylindrical extension 40 Core moulded part 40 a Ring section 41 Gap

Claims

Device for injection moulding plastics components comprising at least one tubular portion, the device comprising at least two complementary external mould parts forming a mould cavity (35) and the device comprising at least one core mould part (37, 38, 39, 40), the device comprising an external master mould (30) and different inserts (36) being provided for injection moulding tubular parts of different diameter which are received by the master mould (30), the inserts (36) each having an identical external contour which is independent of the diameter of the component to be injected and a cavity which corresponds in each case to the diameter of the component, and the inserts (36) forming the external mould parts of the mould, characterised in that the device is provided for injection moulding components for ventilation pipes which comprise at least one sleeve portion (11, 12, 17, 19, 23, 24) which adjoins the tubular portion on the end side in one piece, wherein separate core moulded parts (37, 38) are provided for at least one tubular section of a component to be injected and for at least one sleeve section (11, 12, 17, 19, 23, 24), and wherein depending on the material of the component to be injected, core moulded parts (37, 38, 39, 40) are provided, at least partially, in each case, even for the same diameters.Device according to claim 1, characterised in that the master mould (30) at least partially comprises the actuating devices (33, 34) for axially moving the core mould parts (37, 38, 39, 40).Device according to one of the preceding claims, characterized in that for the injection moulding of a component at least two complementary outer moulded parts complementary to an outer mould in the form of inserts (36) and at least two core moulded parts (37, 38, 39, 40) are provided, which define the mould for the component.Device according to one of Claims 1 to 3, characterized in that different inserts (36) and / or core mouldings (37, 38, 39, 40) are provided in each case for the injection moulding of components made of PPS, PVC, PP, PE or PVDF, or identical inserts (36) and at least partially different core mouldings (37, 38, 39, 40) are provided in each case.Device according to one of the preceding claims, characterized in that at least three, preferably at least four, core moulding parts (37, 38, 39, 40) are used for the injection moulding of a component, of which at least two have cylindrical sections and at least two curved sections.Device according to one of the preceding claims, characterized in that it serves for injection moulding pipe bends (22), double sleeves (10), T-pipe sections, pipe sections with flange, reducing pieces (16) or pipe components with internal throttle valves.

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