DE102024117914A1 - Hollow cylindrical fitting with thread - Google Patents

Abstract

The invention relates to a hollow cylindrical molded part (1) with an annular cross-section, such as a screw, a nut, a socket part, a pipe plug, a pipe connector or the like, wherein the molded part (1) has a hollow cylindrical base body (2) with a mounting section (MA) and with a fastening section (BA) adjoining it in the axial direction (XX), wherein in an inner channel (3) of the base body (2), in particular for the sealing reception of a plug part (4), sections with different functions are arranged one another in the axial direction, and wherein the base body (2) has at least one internal thread and/or one external thread (10) and is produced by injection molding a plasticized thermoplastic polymeric mass containing fibers (F). In order to ensure high strength appropriate to the stress requirements while being technologically easy to manufacture, even at elevated temperatures, and without requiring inserts in the base body (2), it is proposed that the thermoplastic polymer of the plasticized thermoplastic polymeric mass containing fibers (F) be one which, in particular polyarylamide (PARA), has a tensile strength according to ISO 527-2:2012 (test speed: 5 mm/min) of at least 260 MPa in the non-plasticized state.

Description

The present invention relates to a hollow cylindrical molded part with an annular cross-section, such as a screw, a nut, a socket part, a pipe plug, a pipe connector or the like, wherein the molded part has a hollow cylindrical base body with a mounting section and with a fastening section adjacent to it in the axial direction, wherein sections with different functions are arranged in an axial direction in an inner channel of the base body, in particular for the sealing reception of a plug part, and wherein the base body has at least one internal thread and/or one external thread and is produced by injection molding of a plasticized thermoplastic polymeric mass containing fibers.

In particular, if the base body has an external thread in its fastening section, the molded part can have a threadless area with a comparatively small wall thickness in the transition from this fastening section to the axially adjoining assembly section, which usually has a larger diameter than the fastening section and is mostly designed as a flange-like polygon, which is also called a thread relief, and in which a seal is often arranged when making a connection, with the thread relief acting as a sealing groove or sealing channel.

It is well known that, particularly in plug-in systems for compressed air applications, union nuts are usually made of brass. However, polymeric or hybrid molded parts of the type mentioned above, manufactured especially by injection molding, are also known from the prior art. These serve the purpose of replacing brass with plastic, primarily for cost reasons.

In practice, the thread relief groove has often proven problematic when using a plastic for the base body. This is due, on the one hand, to the totality of stress concentrations on the outside of a hollow cylindrical molded part of the type mentioned above, which can reach their maximum in this area, particularly when tightening a molded part designed as a cap screw. Stress concentrations are especially noticeable at changes in diameter, circumferential edges, or radii – both on the outside and on the inner contour of the hollow cylindrical molded part.

Another reason why the thread relief often proves problematic is as follows. Connector components in modern plug-in systems with a hollow cylindrical molded part of the type mentioned earlier are also often made of plastic and have diameters that increase in the opposite direction of mating. The reason for this increasing diameter is that bending or alternating loads acting on the connector are concentrated in a section of the connector located in the upper area, i.e., in the area of the mounting section of the hollow cylindrical molded part, or that protrudes from it. Here, the connector has little or no support. Since the diameter of the inner bore cannot be reduced, the outer diameter of the connector must be increased to ensure sufficient strength.

This in turn means that the inner diameter of the hollow cylindrical component of the type mentioned above, in particular a union nut, must also be chosen to be larger in this area, and if this is the case in the area of the thread relief, the wall thickness in the thread relief can become so small that it cannot withstand the required tightening or loosening torques, so that breakage may occur in the area of the thread relief.

Molded parts of the type mentioned above are, for example, made from the WO 2022/136406 A1 , the WO 2013/092234 A1 and the WO 2009/124994 A1 known. Similar molded parts also describe the WO 2013/124994 A1 and the DE 10 2010 010 651 A1 , in the latter case the special feature is that the base body of the molded part on the one hand and existing thread locking devices and/or circumferential seals on the other hand are manufactured from different polymeric materials in a multi-component injection molding process.

Injection molding is a well-known, discontinuous primary forming process, particularly used for plastics. It allows for the production of large quantities of industrially usable molded parts with high precision. In this process, the respective material or molding compound is plasticized in the injection unit of an injection molding machine and injected into an injection mold.

Modern injection molding machines use a screw that plasticizes the molding compound – supplied, for example, as plastic pellets – conveys it, and finally injects it into the mold. The polymer solidifies in the mold cavity, after which the molded part can be demolded. While volume shrinkage that occurs during solidification can generally be compensated for – but only up to a certain point – by applying a holding pressure before demolding.

Injection molding can be used to process thermoplastics, thermosets, and elastomers. It is also known to use fillers, particularly fibers, in the injection molding of thermoplastics, resulting in higher-strength parts compared to parts without fillers.

According to a report from the WO 2009/124994 A1 In the known method for manufacturing a molded part of the type mentioned above, injection into the cavity is carried out through at least two injection ports such that the fibers align predominantly in the main directions of axial tension and torsion of the molded part. The injection takes place in the axial direction, with the material flowing in a ring-shaped pattern around an inner core of the mold and converging between the injection ports. Weld lines are formed at these points, which generally exhibit lower strength than the rest of the molded part.

A stress-resistant structure of the known molded part consists in the fact that, on the one hand, the proportion of fibers oriented perpendicular to a longitudinal axis of the molded part in the circumferential direction of the annular cross-section, and on the other hand, the proportion of fibers oriented in the axial direction of the molded part, is each less than 50 percent. While the method can surprisingly compensate for a negative weld line effect, at least partially, a disadvantage is that, when hot runner nozzles are used, a reliable and uniform cavity filling cannot always be guaranteed with a known multiple gate as described in the document without additional process stabilizing measures.

It has been shown that in industrial applications, with screw components of the type mentioned above, the importance of the torsional stress on the component often recedes after assembly compared to the importance of the axial tensile stress. However, the maximum torque that can be absorbed without breakage during the insertion or removal of the component plays a significant role. In any case, a multiaxial stress state develops—especially during the assembly of a component of the type mentioned above—particularly in the area of the aforementioned undercut. This results, in particular, not only in the requirement for high tensile strength but also in a requirement for increased shear strength and an increase in the effectiveness of the holding pressure during manufacturing. Effective holding pressure refers specifically to the fact that the applied holding pressure results in a homogeneous filling of the cavity, free of voids and—if weld lines are present—with high weld line strength.

The ones from the WO 2009/124994 A1 and the methods known from the other aforementioned publications for manufacturing molded parts of the type mentioned at the outset as injection-molded plastic parts offer advantageous technical solutions under the aforementioned aspects and have generally proven themselves in practice; however, it has been shown that the various registered designs – with the exception of those according to the WO 2022/136406 A1 - could not always take into account the very high stress profiles that often occur in practice, especially during assembly and disassembly, with sufficient stability.

There are many different reasons for the partial premature failure of the known components, especially those designed as union screws, such as dimensional problems like out-of-roundness, jamming of the threads in the fastening section, shearing of the threads, up to and including the breaking off of a polygon, preferably forming the, in particular flange-like, assembly section, during tightening or loosening.

A complete geometric redesign of a connection, especially a plug connection, using a molded part of the type mentioned above could potentially resolve all these problems, but would then result in entirely different dimensions. However, these types of connections are widespread, with threaded holes in the inner channel, or even the connecting bores, often having specific dimensions, sometimes even being standardized. Furthermore, it is not easily possible, for example, to reduce the inner diameter of plug components to increase their wall thickness, because then the desired or required dimensions would not be achieved. This would result in adverse flow characteristics. For example, the response times of compressed air brakes could be negatively affected.

According to the WO 2022/136406 A1 The task is to provide a screw component that combines the features of previously known technology – e.g., those from the WO 2009/124994 A1 - avoids known disadvantages and in particular features a high applicable torque and low manufacturing tolerance. The document describes a screw component with an annular cross-section, in particular a hollow screw or a nut, comprising a hollow cylindrical base body injection-molded at least partially from a fiber-containing plasticized polymeric mass, wherein the base body has at least one internal thread and/or one external thread and an internal channel for arranging and/or guiding a piping system element in an insertion direction, wherein the internal channel has at least one sealing section for arranging a circumferential seal for sealing between the internal channel and the piping system element and/or at least one support section for supporting and/or guiding the piping system element and/or at least one retaining section for directly or indirectly locking the piping system element, wherein a preferably metallic insert sleeve is arranged coaxially to the internal channel in the base body, which is at least partially overmolded by the polymeric mass, so that the insert sleeve is at least partially surrounded by the polymeric mass radially to the internal channel and radially repelling from the internal channel.

Preferably, the polymeric mass is a thermoset, comprising an epoxy resin (EP), an unsaturated polyester resin (UP), a vinyl ester resin (VE), a phenol-formaldehyde resin (PF), a diallyl phthalate resin (DAP), a methacrylate resin (MMA), a polyurethane (PUR), an amino resin, a melamine resin (MF/MP), or a urea resin (UF). Molded parts with a thermoset matrix cannot be reshaped after curing or crosslinking of the matrix. However, they exhibit a wide operating temperature range and extremely high strength. This is particularly true for heat-curing systems that are cured at high temperatures.

The polymer mass can also consist of a thermoplastic, such as polyamide (PA).

For connectors in plug-in systems with hollow cylindrical molded parts of the type mentioned above, filled polyamide plastics (PA), especially those filled with 50% glass fibers by mass, are often used. Polyamides (PA), which can exist in various compositions depending on their manufacturing process, are generally classified as engineering plastics, a category that also includes polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycarbonate (PC), and polyoxymethylene (POM). For the aforementioned application as connectors, PA 6.6, PA 11, or PA 12 are often chosen, thus ensuring cost-effective manufacturing with regard to overall material usage.

PA 6.6, for example with 50% glass fiber content, absorbs a high degree of water because the polyamide molecular chains contain polar amide groups that attract polar liquids, such as the dipole molecules of water. This leads to a reduction in strength. Therefore, PA 6.6 has proven unsuitable, particularly for the production of union nuts as preferred embodiments of hollow cylindrical molded parts of the type mentioned above in motor vehicles, especially commercial vehicles.

PA 11 or PA 12 plastics provide sufficient strength for connectors and low water absorption, thus reducing the risk of strength loss due to water uptake. However, the strength of these materials decreases relatively significantly at higher temperatures, so that, for example, at a maximum required temperature of 120 °C, sufficient strength for a union nut would no longer be achieved.

This also applies to PPA (polyphthalamide), a further development of PA 6.6, which, while exhibiting high temperature resistance and strength approximately 20% higher than PA 6.6, and not absorbing as much water as PA 6.6, also suffers a significant loss of strength with increasing temperature.

Furthermore, the forces acting on connector components are generally lower than the tightening or loosening torques on screws. Therefore, a material suitable for connectors is not necessarily also suitable for a hollow cylindrical component of the type mentioned earlier. This is also due to the totality of the aforementioned stress concentration factors acting on the outer and inner contours. of a hollow cylindrical component of the type mentioned above, particularly on a union screw. Such stress concentration factors act – as mentioned – at changes in diameter, circumferential edges and/or radii and contribute to the possibility of a hexagon, preferably forming the assembly section, breaking off during tightening or loosening.

Calculating the dimensions of a metal union nut is relatively simple compared to calculating the dimensions of a plastic union nut, as an example of a hollow cylindrical component of the type mentioned earlier. The latter is considerably more difficult because – as already illustrated by the example of the connectors above – many additional parameters must be considered.

As already mentioned, due to the presence of the preferably metallic insert sleeve according to the WO 2022/136406 A1 While the very high stress profiles encountered in practice are adequately addressed, the molded part disclosed therein only offers a partial technical solution to the fundamental objective of reducing manufacturing costs by replacing metallic components, particularly those made of brass, with plastic. Furthermore, the required separate manufacturing and precise placement of the preferably metallic insert sleeve in the injection mold increases the manufacturing effort.

The present invention is therefore based on the objective of creating a hollow cylindrical component with an annular cross-section, such as a nut, a socket, a pipe plug, a pipe connector or the like, of the type mentioned above, which, with technologically simple manufacturability, also ensures high stress-appropriate strength, in particular axial tensile strength, even at elevated temperatures, whereby premature failure – as described above – can be prevented without a complete geometric redesign and without the need for inserts, in particular metallic inserts.

According to the invention, this problem is solved by the fact that the thermoplastic polymer of the fiber-containing plasticized thermoplastic polymer mass is one which, in the non-plasticized state, exhibits a tensile strength according to ISO 527-2:2012 (test speed: 5 mm/min) of at least 260 MPa. In particular, the tensile strength according to ISO 527-2:2012 (test speed: 5 mm/min) can be at least 280 MPa, and particularly preferably at least 300 MPa.

Such polymers are in particular polyarylamides (PARA), which can be described, for example, by the following chemical formula:

Therefore, due to the presence of ring-shaped aryl constituents in the molecule, it is in particular a semi-aromatic - and also partially crystalline - polyamide.

A semi-aromatic polyarylamide is a polyamide-type polymer containing aromatic groups along its polymer chain. In particular, such polymers can be obtained by polycondensation of an aromatic diamine and an aliphatic diacid. For example, semi-aromatic polyarylamides can be obtained by polycondensation of an aliphatic diacid with 3 to 12 carbon atoms, such as adipic acid, and an aromatic diamine, such as xylenediamine and especially metaxylenediamine.

Such polymers are also called semi-crystalline polymers because they comprise a crystalline phase, which corresponds to zones within the solidified polymer matrix where the macromolecules are arranged regularly in space. A second phase is characterized by a disordered (amorphous) arrangement of the macromolecules. This partial crystallinity is advantageous with regard to the optimal absorption of a multiaxial stress state, for example, in the area of the undercut when subjected to a turning or twisting torque.

From the FR 2903591 A1 The use of polyarylamide (PARA) for manufacturing a working section of a single-use surgical instrument, such as a bone rasp, acetabular burr, drill, or reamer, is known – particularly due to the high hardness of polyarylamide, which, however, plays only a minor role in the present invention. Because of the high hardness of a working section made of PARA – for which the material IXEF® 1022 from Solvay is also mentioned – the known surgical instrument is well suited for working with cartilage or bone. Since it is a single-use instrument, long-term strength is not required.

According to the invention, amorphous fibers, such as glass fibers, anisotropic fibers, such as carbon fibers, and/or aramid fibers can be used as fibers.

According to the present invention, the plasticized polymer mass can contain a volume fraction of fillers, in particular fibers, in the range of 2.5 to 75 percent, preferably a mass fraction in the range of 30 to 70 percent, in particular 50, 60 or 65 percent by mass, preferably glass fibers, and particularly preferably flat glass fibers. The filler content increases the strength, in particular the tensile strength. ISO 527-2:2012 , compared to the unfilled polymer, further increased.

The fibers, particularly in the form of glass fibers, preferably flat glass fibers, can have a length in the range of 0.1 mm to 10 mm, preferably in the range of 0.2 mm to 0.5 mm. The fibers can have a mean diameter in the range of approximately 3 µm to 35 µm, preferably in the range of 5 µm to 20 µm. The rectangular cross-sectional shape of flat glass fibers promotes optimal fiber distribution in the injection mold during injection molding and subsequently optimal fiber orientation in the molded part, whereby the fibers in the base body can align themselves predominantly parallel to the axial direction. A flat glass fiber is considered to be one whose wide side in cross-section is 1.5 to 3 times larger than its narrow side. An equivalent mean diameter of the fiber can be easily calculated by dividing the circumference of the cross-section by π.

Different fiber qualities can be used. With amorphous fibers, the advantage of the fiber shape lies almost exclusively in the utilization of the size effect. The elastic modulus of the compact material and the elastic modulus of the fiber are approximately the same, although the general aim should be for the fibers to exhibit a higher elastic modulus and higher tensile strength in their longitudinal direction than the solidified polymer mass. The elongation at break of the matrix should also be higher than that of the fibers. Amorphous fibers drawn from the melt have the advantage that compressive residual stresses develop on their surface during cooling, which can prevent the formation of fiber cracks.

Anisotropic fibers, especially carbon fibers, are used when high strength and stiffness per unit mass are required. Carbon fibers, which typically have a diameter of about 5 to 8 µm and are now predominantly made of polyacrylonitrile, exhibit significantly higher strength and stiffness in the fiber direction than perpendicular to it. Their key characteristic is high tensile strength. The use of commercially available flat fibers is also possible.

According to the invention, aramid fibers can also be used. Aramids, or aromatic polyamides, are defined by the U.S. Federal Trade Commission as long-chain synthetic polyamides in which at least 85 percent of the amide groups are directly bonded to two aromatic rings. This is therefore a similar or identical material to that which is preferably used for the thermoplastic matrix according to the invention. Like carbon fibers, aramid fibers have a negative coefficient of thermal expansion, meaning they shorten when heated. Their specific strength and modulus of elasticity are lower than those of carbon fibers. However, in combination with the positive coefficient of thermal expansion of the matrix material, highly dimensionally accurate molded parts can be produced. Compared to molded parts containing carbon fibers, the compressive strength of such parts is lower, and a potentially similar melting point for the fibers and matrix could also prove problematic.

With PARA, which, for example, has a mass fraction of 50% glass fibers – where, as mentioned, flat glass fiber is particularly suitable for the production of a union screw – a tensile strength of approximately 300 MPa (breaking stress according to [reference missing]) can advantageously be achieved. ISO 527-2:2012 2012 at a test speed of 5 mm/min), thus achieving strengths similar to those of aluminium.

PARA with 50 wt% glass fibers thus has a strength approximately 40% higher than PA 6.6 and is stable up to at least 120 °C, with comparatively low water absorption. Flat glass fibers, in particular, result in excellent strength properties at an angle of 90° to the flow direction during injection molding.

Furthermore, the hollow cylindrical molded part according to the invention can be conditioned, whereby conditioning is understood to mean the controlled absorption of moisture in plastics. The moisture absorption of the individual plastics varies considerably, as already indicated above. Non-polar plastics such as polyolefins, styrene polymers, and fluoropolymers absorb very little moisture. Polar plastics such as polyurethane (PUR) or cellulose esters, on the other hand, absorb more water.

Polyamides – also known as polyarylamides (PARA) – can be conditioned effectively with relatively low water absorption. For example, the base body of a molded part according to the invention, made from polyarylamide, can exhibit a maximum water absorption of 3.7% in a saturated state at 23 °C, as determined according to ISO 62. However, it is not conditioned to its maximum water absorption capacity, but only until an equilibrium with the environment is reached. Once this state is reached, it remains almost constant in the European climate. Even with an initial maximum water absorption, for example, by immersion in water, the base body loses moisture again until equilibrium is reached as soon as it is removed from the water.

This does reduce the strength to some extent, e.g., the tensile strength and flexural strength, but it prevents potential subsequent deterioration of properties during long-term operation under environmental influences. Other properties, such as the modulus of elasticity, toughness, and the friction and wear properties—particularly important for the thread of the hollow cylindrical component according to the invention—remain constant or are even positively influenced. Conditioning can also reduce the loss of preload force after assembly.

Polyarylamides (PARA) also form a very smooth surface when injection molded, which is particularly advantageous from the point of view that frictional forces in the thread when screwing in or out the hollow cylindrical molded part according to the invention can be minimized.

Since the thread is typically produced in two mold halves during the injection molding process, two small burrs inevitably form on the thread, particularly at the points where the mold halves meet. A further technical measure preferred within the scope of the invention addresses this issue. This measure provides a strip-shaped, axially extending flattening of the thread along its entire length in the area where the two mold halves meet, so that any burr formed during injection molding lies within this flattening and thus cannot generate additional frictional forces.

According to the invention, in particular when using PARA as a plastic in the plasticized thermoplastic polymer mass containing the fibers produced by injection molding, the thread is in any case able to bear the axial forces acting on the thread teeth, in particular shear forces, when tightening or loosening.

The inventive design of the base body using a plasticized thermoplastic polymeric mass, in which the polymer in the non-plasticized state exhibits a tensile stress according to ISO 527-2:2012 (Test speed: 5 mm/min) of at least 260 MPa allows for a shortening of the fastening section, and in particular, potentially even a reduction of the thread by at least one compared to the known number of turns, i.e., for example, to three axially consecutive turns instead of four (tooth tips over the thread length) or to four axially consecutive turns instead of five. This, in turn, allows for a shift of the inner contour in the opposite direction of insertion such that the aforementioned extended diameter range of the inner contour moves into the assembly section of the base body, and in particular into the area of a flange-like hexagon of a union nut. The wall thickness in the area of the undercut is thus increased, and stress concentration factors can no longer act in such a way that shearing in the area of the thread undercut is possible at the required tightening and loosening torques. Embedding an insert in the base body or a complete geometric redesign is not necessary.

In the design of the relief groove, it is particularly advantageous if its contour, i.e., the transition from the fastening section to the assembly section, is shaped according to a so-called tree root geometry. The design is based on the well-known "thrust triangle method," preferably with additional rounding, as detailed below.

Injection into the cavity can be carried out in various known ways, for example from the inside by implementing a tunnel, ring, disc, or umbrella gate, wherein at least one two-point gate, preferably up to a five-point gate, and in particular a three-point gate, can be provided in the tunnel gate. Injection into the cavity can be carried out, for example, through at least two injection ports that are uniformly distributed around the circumference of the annular inner cross-section of the molded part.

However, it may also be preferable for the molded part according to the invention to be produced using an injection molding process which, in a manner also known per se, provides only one injection point for injecting the polymeric mass. Reducing the number of necessary injection points reduces the manufacturing effort. Even with only one injection point, a homogeneous distribution of the polymeric mass can be achieved within the base body. In particular, no multiple weld lines form in the polymeric material of the base body during production, which could represent weak points.

For the aforementioned manufacturing process, it is also advantageous if the single injection point for the inner channel of the screw component to be manufactured is located at the end of the mold and angled in such a way that the polymer mass is injected into the closed mold at an angle to the inner channel. Such angled injection offers the advantage that more free space is available for the core component in the area of the inner channel, which is formed by a core component that can be inserted perpendicularly in the insertion direction. This design also makes it possible, in particular, to actively cool the corresponding core component of the mold by means of core cooling. Core cooling advantageously increases the production speed and extends the service life of the mold, especially of the core component.

• Geometrie
  • - Gewindedurchmesser und Steigung;
  • - Maximale Länge des Stecksystems im Innenkanal;
  • - Durchflussquerschnitte von aufgenommenen Steckerteilen;
• Kräfte und Momente
  • - Beispielsweise bei Gewinde M 22 x 1,5: Bruchdrehmoment ca. 30 Nm (zweifache Sicherheit bei einem Anziehdrehmoment 14 - 15 Nm);
  • - Beispielsweise bei Gewinde M 16 x 1,5: Bruchdrehmoment ca. 20 Nm (zweifache Sicherheit bei einem Anziehdrehmoment 10 Nm).

In particular, it can be summarized that, advantageously, the following values commonly used in practice do not need to be changed in a plug connection with a hollow cylindrical molded part according to the invention:

• geometry
  • - Thread diameter and pitch;
  • - Maximum length of the plug-in system in the inner channel;
  • - Flow cross-sections of recorded plug parts;
• Forces and Moments
  • - For example, with thread M 22 x 1.5: breaking torque approx. 30 Nm (double safety factor with a tightening torque of 14 - 15 Nm);
  • - For example, with thread M 16 x 1.5: breaking torque approx. 20 Nm (double safety factor with a tightening torque of 10 Nm).

Further advantageous features of the invention are contained in the dependent claims and in the following description.

• 1 eine Draufsicht auf eine exemplarische Ausführung eines erfindungsgemäßen hohlzylindrischen Formteiles,
• 2 einen Schnitt durch das in 1 dargestellte erfindungsgemäße Formteil entlang der Linie II-II in 1,
• 3 eine perspektivische Darstellung des erfindungsgemäßen Formteils aus 1 und 2,
• 4 eine schematische Darstellung zur Konstruktion eines Übergangs von einem Befestigungsabschnitt zu einem Montageabschnitt eines erfindungsgemäßen Formteils,
• 5 einen Längsschnitt, ähnlich wie in 2, durch ein nicht erfindungsgemäßes Formteil, im Montagezustand mit einem Steckerteil,
• 6 einen Längsschnitt, wie in 5, durch ein erfindungsgemäßes Formteil, im Montagezustand mit einem Steckerteil,
• 7 einen Schnitt, ähnlich wie in 2, durch ein nicht erfindungsgemäßes Formteil,
• 8 zum direkten Vergleich mit 7, einen Schnitt, ähnlich wie in 7, durch ein erfindungsgemäßes Formteil,
• 9 eine Schnittdarstellung wie in 2 bzw. 8, jedoch vergrößert.

The invention will now be explained in more detail using a preferred embodiment. The following are shown:

• 1 a top view of an exemplary embodiment of a hollow cylindrical molded part according to the invention,
• 2 a cut through the in 1 illustrated molded part according to the invention along line II-II in 1 ,
• 3 a perspective view of the molded part according to the invention made of 1 and 2 ,
• 4 a schematic representation for the construction of a transition from a fastening section to an assembly section of a molded part according to the invention,
• 5 a longitudinal section, similar to that in 2 , by means of a non-inventive molded part, in the assembled state with a plug part,
• 6 a longitudinal section, as in 5 , by means of a molded part according to the invention, in the assembled state with a plug part,
• 7 a cut, similar to in 2 , by a non-inventive molded part,
• 8 for direct comparison with 7 , a cut, similar to in 7 , by means of a molded part according to the invention,
• 9 a sectional view as in 2 or 8 , however, enlarged.

Regarding the following description, it is expressly emphasized that the invention is not limited to the exemplary embodiments and not to all or several features of the described combinations of features; rather, each individual partial feature of the exemplary embodiment(s) can have an inventive significance independently of all other partial features described in connection with it, both on its own and in combination with any features of another exemplary embodiment.

In the various figures of the drawing, identical parts are always provided with the same reference symbols, so that they are usually only described once.

1 , 2 , 3 , 6 , 8 and 9 show embodiments of a molded part 1 according to the invention, which - as is shown in particular in the view in 1 This is illustrated – it has a ring-shaped cross-section. In detail, it is a hollow screw that can be manufactured using an injection molding process.

The molded part 1 has a hollow cylindrical base body 2 with a mounting section MA and with a fastening section BA adjacent to it in the axial direction XX, wherein in one, in particular - as in particular 5 and 6 To illustrate, sections with different functions, not further specified in detail, are arranged in the axial direction XX of the base body 2, within an inner channel 3 of the base body 2, designed to provide a sealing connection for a connector part 4, and wherein the base body 2 has at least one internal thread and/or, as shown, an external thread 10 in the mounting section BA. The component 1 according to the invention can be screwed to another component via this external thread 10 in a manner not shown. In the illustrated embodiment, the mounting section MA is designed as a hexagonal flange for possible tool engagement.

A transition area from the assembly section MA to the fastening section BA, which follows in the axial direction X-X, is called a relief groove and is symbolized in the drawing by the reference symbol FS.

The sections in the inner channel 3 can serve to accommodate one or more circumferential seals 5, 6, which may be located particularly on the connector part 4, as well as for the direct or indirect retention and/or locking of the connector part 4 and/or, in a conical or cylindrical form, for supporting and/or guiding the connector part 4, having different inner diameters. It should also be noted that the inner channel 3 tapers in the insertion direction S of the connector part 4, particularly in a stepped or continuous manner, although the inner diameter remains constant in some sections. Thus, with an approximately constant outer diameter in the axial direction X-X, different wall thicknesses result.

To produce a molded part 1 according to the invention, a plasticized polymeric mass containing fibers F is injected through at least one injection opening of a (not shown) mold into a cavity of the mold, and after the polymeric mass has solidified, the molded part 1 is demolded from the mold. The fact that the base body 2 is thus produced from a plasticized thermoplastic polymeric mass containing fibers F by injection molding is indicated by the breakout in 2 visualized.

According to the invention, the thermoplastic polymer of the fiber-containing plasticized thermoplastic polymeric mass is one which, in the non-plasticized state, has a tensile strength according to ISO 527-2:2012 (test speed: 5 mm/min) of at least 260 MPa.

In particular, the polymer of the fiber F containing plasticized thermoplastic polymeric mass can be one which, in the non-plasticized state, has a tensile strength according to ISO 527-2:2012 (test speed: 5 mm/min) of at least 280 MPa, preferably of 300 MPa.

In particular, the polymer of the plasticized thermoplastic polymeric mass containing fibers F can be a polyarylamide (PARA). As already mentioned, the polyarylamide (PARA) can be produced by polycondensation of an aromatic diamine and an aliphatic diacid, in particular by polycondensation of an aliphatic diacid with 3 to 12 carbon atoms, such as adipic acid, and an aromatic diamine, such as xylenediamine, and in particular metaxylenediamine, whereby the polymer of the plasticized thermoplastic polymeric mass containing fibers F is in particular a partially aromatic and/or partially crystalline plastic.

Fiber-reinforced plastics with a thermoplastic matrix can be subsequently formed or welded. After cooling, the molded parts are ready for use, but soften at elevated temperatures. Their tendency to creep decreases with increasing fiber content. The advantage of PARA lies particularly in its high matrix strength and suitability for use under elevated temperature loads.

As already mentioned above, the plasticized polymer mass can contain a volume fraction of fibers F in the range of 2.5 to 75 percent, preferably a mass fraction in the range of 30 to 70 percent, particularly 50, 60, or 65 percent by mass, preferably glass fibers, and especially preferably flat glass fibers. The filler content increases the strength, particularly the tensile strength. ISO 527-2:2012 further increased compared to the unfilled polymer.

The fibers F, particularly in the form of glass fibers, preferably flat glass fibers, can have a length in the range of 0.1 mm to 10 mm, preferably in the range of 0.2 mm to 0.5 mm. The fibers F can have a mean diameter in the range of approximately 3 µm to 35 µm, preferably in the range of 5 µm to 20 µm. Flat glass fibers have an approximately elliptical cross-section (rounded rectangles) and thus possess a major and a minor semi-axis. As a first approximation, the mean diameter can be considered to be half the sum of the two semi-axes.

Examples of such materials are the materials commercially available under the names AKROLOY® PARA GF 50 HU black (8596) and AKROLOY® PARA FGF 50 1 black (8186), both of which are polyarylamides reinforced with 50% glass fiber by mass. Even in their conditioned state, these materials impress with their very high strength due to low moisture absorption. Furthermore, these materials stand out during processing due to their excellent flowability and the high surface quality of the finished product. In the latter material, the PARA is reinforced with flat glass fibers, which further improves the flow properties during injection molding.

Key properties of AKROLOY® PARA GF 50 HU black (8596) are presented as examples in Tables 1 to 3 below – categorized according to general properties (Table 1), mechanical properties (Table 2), and thermal properties (Table 3). For the ISO standards listed in the tables for determining the respective parameters, the versions valid at the time of filing must be observed. For tensile strength and elongation at break, this is version ISO 527-2:2012. Table 1: General Properties Density ISO 1183 23°C 1.65 g/ ^cm³ Moisture absorption equilibrium ISO 1110 70 °C, 62% RH 0.8% Water absorption Saturation ISO 62 23 °C, saturated 3.5% Processing shrinkage along 0.1 - 0.2% ISO 294-4 across 0.2 - 0.4% Table 2: Mechanical properties Train E-module 1 mm/min dry 19700 MPa ISO 527-2 1 mm/min conditioned 19700 MPa Fracture stress 5 mm/min dry 295 MPa ISO 527-2 5 mm/min conditioned 270 MPa Elongation at break 5 mm/min dry 2.0% ISO 527-2 5 mm/min conditioned 2.0% Charpy impact resistance 23 °C dry 78 kJ/ ^m² ISO 179-1/1eU 23 °C conditioned 90 kJ/ ^m² -30 °C dry 60 kJ/ ^m² Charpy 23 °C dry 15 kJ/ ^m² Impact strength 23 °C conditioned 14 kJ/ ^m² ISO 179-1/1eA -30 °C dry 17 kJ/ ^m² Table 3: Thermal properties Heat deflection temperature HDT/A ISO 75 1.8 MPa 230 °C Heat deflection temperature HDT/CISO 75 8 MPa 200 °C Glass transition temperature ISO 11357-2 DSC, 2nd heating 87 °C Melting point ISO 11357-3 DSC, 10K/min 238 °C

The parameters of AKROLOY® PARA FGF 50 1 differ only slightly from those of AKROLOY® PARA GF 50 HU black (8596). In particular, the tensile strength (see Table 2) in the dry state (ISO 527-2:2012 / test speed: 5 mm/min) is completely identical for both materials and is 295 MPa. Conditioning, whereby the maximum water absorption in the saturated state at 23 °C, determined according to ISO 62, can be as low as 3.5% (see Table 1), advantageously results in a strength reduction of no more than 11% for both materials. The melting point according to ISO 11357-3 (DSC, 10 K/min), which can be found in Table 3, makes both materials ideal for processing the plasticized thermoplastic polymer mass, especially in the temperature range of approximately 270 °C to 300 °C.

For high component stability, it has proven advantageous if the injection into the cavity is carried out in such a way—for example, near the end faces of the molded part 1—that the fibers F in the base body 2 align themselves predominantly parallel to the axial direction X-X, i.e., to more than 50 percent in the case of glass fibers, in a manner favorable for the torsional stress that later occurs during screwing in with a screwing tool. This can be verified, for example, by computed tomography X-ray analysis. It should be noted that while a torsional moment is applied by the tool under the aforementioned stress, mechanical axial stresses also arise due to the forces occurring in the thread of the screwing part 1 during screwing in. Therefore, in the area of maximum load near the point of force application, a triaxial stress state with high axial forces occurs.

The in 3 The perspective view of the molded part 1 shown here illustrates an advantageous embodiment of the invention, in which it is provided that, in particular in the In the area of a joint between two mold halves used for injection molding the plasticized thermoplastic polymer mass containing fibers F, a strip-shaped flattening 12 of the thread 10 is provided, extending axially along the length of the thread, so that any burr formed during injection molding lies in this flattening 12. This minimizes axial stress components occurring in the base body during assembly of the molded part 1 according to the invention, and also largely avoids significant frictional forces during screwing in or out.

4 Figure 1 illustrates a previously mentioned construction, preferably to be used within the scope of the invention, for obtaining a so-called tree root geometry for the undercut FS. The construction is carried out—not, as is also known, by means of a circular arc segment, in particular a quarter-circle segment—in the following manner: First, in a first step, a construction line “a” is generated, which is at an angle µ to the mounting section MA, wherein the angle µ can be in particular in the range between 30° and 60°, preferably at 45°. In the second step, a construction line “D” is generated, which originates from the midpoint of the hypotenuse of the triangle formed in the first step. This construction line “b” is led either to the mounting section MA or to the fastening section BA in such a way that another triangle is formed. In the third step, a construction line “c” is generated, which originates from the midpoint of the hypotenuse of the triangle formed in the second step, whereby here again an isosceles triangle is generated, as 4 This construction method is known in itself and is called the "method of draw triangles". In a final fourth step, the endpoints EP and FP of the construction lines "c" and "a" are connected by an arc line, which approximately rounds the polygonal structure formed in the first three steps and then forms the contour of the undercut FS. Several circular arcs that tangentially merge into one another can also be used for this purpose. Examples of such circular arcs with corresponding radii are given in 4 The design is designated by R1, R2, R3, and R4. Likewise, the design is not limited to three design lines; any additional number can be added, preferably depending on the angle µ. Such a contour, which reduces notch stresses, advantageously increases the torsional moment that the inventive component 1 can withstand when screwed into the component by up to approximately 20 percent compared to a component with the conventional simple circular arc shape.

In the 5 and 6 (each with plug 4) as well as 7 and 8 (Each shown separately) are a non-inventive molded part 1' and a molded part 1 according to the invention, each with identical inner and outer diameters and identical lengths L', L, which are not further specified. The reference numerals denote details corresponding to the invention in the non-inventive embodiment.

The non-inventive molded part 1' is according to the teaching of WO 2022/136406 A1 The invention is designed in which the screw part has a hollow cylindrical base body 2' injection-molded from a fiber-containing plasticized polymeric mass, in which a preferably metallic insert sleeve EH is arranged coaxially to its inner channel 3'. With the invention, this feature can be dispensed with, while ensuring high stress-appropriate strength, in particular axial tensile strength, even at elevated temperatures, and preventing premature failure, while also enabling simple manufacturing.

With regard to their position, the non-inventive molded part 1' and the inventive molded part 1 coincide in the plane of the transition from the fastening section BA', BA to the assembly section MA', MA. The inventive design of the base body 2, using a plasticized thermoplastic polymeric mass in which the polymer has a tensile strength according to ISO 527-2:2012 (test speed: 5 mm/min) of at least 260 MPa in the unplasticized state, allows a reduction in the length of the fastening section (from LB' to LB). This, in turn, enables a shift of the inner contour in the opposite direction of insertion, such that an expanded, for example conical, diameter region DE' of the inner contour, which in a non-inventive molded part 1' lies in the area of the transition from the fastening section BA' to the assembly section MA', is shifted into the assembly section MA of the base body 2 by an amount that is 5 /6, which is marked with the reference numeral X, can be displaced (diameter range DE). This brings it, in particular, into the area of the flange-like hexagon of the exemplary union nut. The wall thickness W in the area of the undercut FS is thus increased compared to the known molded part 1'(W' at position FS'), so that a torsional moment required for assembly and/or disassembly, as well as stress concentration factors, can no longer act in such a way as to cause shearing in the area of the thread undercut FS.

While maintaining the overall length L', L of the molded parts 1', 1, which is based on a length of the inner contour that cannot be structurally altered, shortening the fastening section (BA' to BA) can be accompanied by lengthening the assembly section (MA' to MA). Significantly, in the 6 and 8 The fastening sections BA according to the invention (each on the left in the image) are shorter than the fastening sections BA' according to the invention (each on the left in the image). 5 and 7 ), and the assembly sections MA according to the invention (each on the right in the image of 6 and 8 ) are longer than the non-inventive fastening sections BA' (each on the right in the image in 5 and 7 ).

While for a non-inventive molded part 1' the ratio of the length LB' of the fastening section BA' to the total axial length L' (sum of LB' and LM' as the length of the mounting section MA') is in the range of 60% to 80%, preferably about 65%, for a molded part 1 according to the invention the ratio of the length LB of the fastening section BA to the total length L (sum of LB and LM as the length of the mounting section MA') is in the range of only 38% to 57%, preferably about 54%.

In 9 The reference numerals T1 and T2 denote wall thicknesses in the base body 2. The wall thickness T2 is at least 70% of the wall thickness T1 in the fastening section BA from any point of the thread relief FS, wherein the wall thickness T1 in the fastening section BA extends from the root of the thread 10 to the wall surrounding the inner channel 3. In particular, the wall thickness T2, which is also the wall thickness W in 8 The wall thickness T2 corresponds to at least 80%, preferably at least 85%, of the wall thickness T1 in the fastening section BA, wherein the wall thickness T2 extends axially – starting from the end of the thread 10 – in particular over a region of up to at least 20% of a length L1 into the region of the mounting section MA, preferably up to at least 25%, 30% or 40% of the length L1. The length L1 denotes a region in which the mounting section MA is designed as a flange – in particular a multi-sided one.

The invention is not limited to the illustrated embodiments, but also includes all embodiments that have the same effect in the sense of the invention, for example those with an internal thread in the inner channel 3.

Furthermore, the person skilled in the art can provide additional advantageous technical measures without departing from the scope of the invention. For example, in the illustrated embodiment, a particularly delicate outer ring bead 7 is located in a terminal retaining section on the outer circumference of the base body 2, on which a [missing element] is attached for the indirect retention and/or locking of the plug part 4. 5 and 6 The shown, preferably ring-shaped, locking cage 8 is attachable, in particular snap-on, and interacts with at least one locking element 9 on the connector part 4. This indirect fastening and/or locking can be implemented in various ways, with full reference to the following for details. EP 0 913 618 B1 is referred.

The invention is not limited to the combination of features defined in independent claim 1, but can also be defined by any other combination of specific features from all disclosed individual features. This means that, in principle, virtually any individual feature of the independent claim can be omitted or replaced by at least one individual feature disclosed elsewhere in the application. Therefore, the claims should be understood merely as a first attempt at formulating an invention.

Reference symbol list

1

Molded part, according to the invention

1'

Molded part, not according to the invention ( 7 )

2

Basic body of 1

2'

Basic body of 1' ( 7 )

3

Inner channel of 1

3'

Inner channel of 1' ( 7 )

4

Plug part ( 5 , 6 )

5

Perimeter seal

6

Perimeter seal

7

Outer ring bead at 2 ( 8 )

7'

Outer ring bead at 2' ( 7 )

8

Locking cage for 4 ( 5 , 6 )

9

Locking element at 4 ( 5 , 6 )

10

External thread in BA

10'

External thread in BA' ( 7 )

12

Flattening of 10

a, b, c

Construction lines ( 4 )

BA

Fastening section of 1

BA'

Fastening section of 1' ( 7 )

FS

Free cut of 1

DE

Extended inner contour of 1 (diameter range)

DE'

extended inner contour of 1' ( 7 )

EH

Insert sleeve ( 7 )

EP

Endpoint of c ( 4 )

F

Fibers

FP

Endpoint of a ( 4 )

FS'

Free cut of 1' ( 7 )

L

Length of 1

L'

Length of 1' ( 7 )

L1

Length of flange area in MA ( 9 )

LB

Length of BA

LB'

Length of BA' ( 7 )

MA

Assembly section 1

MA'

Assembly section of 1' ( 7 )

R1, R2, R3, R4

Circular arc radii ( 4 )

S

Insertion direction of 4 in 1

S'

Insertion direction of 4 in 1' ( 7 )

T1

Wall thickness in BA

T2

Wall thickness of FS

W

Wall thickness of FS ( 8 )

W'

Wall thickness of FS' ( 7 )

X

shift 5 /6

X-X

Longitudinal axis of 1, 1'

µ

Construction angle ( 4 )

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• WO 2022/136406 A1 [0007, 0014, 0017, 0026, 0076]
• WO 2013/092234 A1 [0007]
• WO 2009/124994 A1 [0007, 0011, 0014, 0017]
• WO 2013/124994 A1 [0007]
• DE 10 2010 010 651 A1 [0007]
• FR 2903591 A1 [0033]
• EP 0 913 618 B1 [0082]

Cited non-patent literature

• ISO 527-2:2012 [0035, 0048, 0067]
• ISO 527-2:2012 2012 [0040]

Claims (16)

A hollow cylindrical fitting (1) with an annular cross-section, such as a screw, a nut, a socket, a pipe plug, a pipe connector, or the like, wherein the fitting (1) has a hollow cylindrical base body (2) with a mounting section (MA) and with a fastening section (BA) adjoining it in the axial direction (XX), wherein sections with different functions are arranged in an axial direction in an inner channel (3) of the base body (2), which is intended in particular for the sealing reception of a plug part (4), and wherein the base body (2) has at least one internal thread and/or one external thread (10) and is produced by injection molding a plasticized thermoplastic polymeric mass containing fibers (F), characterized in that the thermoplastic polymer of the plasticized thermoplastic polymeric mass containing fibers (F) is one which, in the non-plasticized state, exhibits a tensile strength according to ISO 527-2:2012 (test speed: 5 mm/min) of at least 260 MPa. Molded part (1) according to Claim 1 , characterized in that the polymer of the fiber (F) containing plasticized thermoplastic polymeric mass is one which, in the non-plasticized state, has a tensile strength according to ISO 527-2:2012 (test speed: 5 mm/min) of at least 280 MPa, preferably of 300 MPa. Molded part (1) according to Claim 1 or 2 , characterized in that the polymer of the fiber (F) containing plasticized thermoplastic polymeric mass is a polyarylamide (PARA). Molded part (1) according to Claim 3 , characterized in that the polyarylamide (PARA) of the fiber (F) containing plasticized thermoplastic polymeric mass is a polycondensate of an aromatic diamine and an aliphatic diacid, in particular a polycondensate of an aliphatic diacid having 3 to 12 carbon atoms, such as adipic acid, and an aromatic diamine, such as xylenediamine, and in particular metaxylenediamine. Molded part (1) according to one of the Claims 1 until 4 , characterized in that the polymer of the fiber (F) containing plasticized thermoplastic polymeric mass is a semi-aromatic and/or semi-crystalline plastic. Molded part (1) according to one of the Claims 1 until 5 , characterized in that the plasticized polymer mass contains a volume fraction of fibers (F) in the range of 2.5 to 75 percent, preferably a mass fraction in the range of 30 to 70 percent, in particular 50, 60 or 65 mass percent, of glass fibers, preferably in an embodiment as flat glass fibers. Molded part (1) according to one of the Claims 1 until 6 , characterized in that the fibers (F), in particular in an embodiment as glass fibers, preferably in an embodiment as flat glass fibers, have a length in the range of 0.1 mm to 10 mm, preferably in the range of 0.2 mm to 0.5 mm. Molded part (1) according to one of the Claims 1 until 7 , characterized in that the fibers (F) have a mean diameter in the range of about 3 µm to 35 µm, preferably in the range of 5 µm to 20 µm. Molded part (1) according to one of the Claims 1 until 8 , characterized in that the basic body (2) is conditioned. Molded part (1) according to one of the Claims 1 until 9 , characterized in that, in particular in the area of a joint between two mold halves used for injection molding containing the fibers (F), a strip-shaped flattening (12) of the external thread (10) is provided, extending axially over the length of the thread, so that a burr formed during injection molding lies in this flattening (12). Molded part (1) according to one of the Claims 1 until 10 , characterized in that the external thread (10) has three to six turns arranged one behind the other in the axial direction (XX). Molded part (1) according to one of the Claims 1 until 11 , characterized in that in the transition from the fastening section (BA), which in particular has an external thread (10), to the axially adjoining assembly section (MA), which has a larger diameter than the fastening section (BA) and in particular is designed as a flange-like polygon, the base body (2) has a thread-free area which is referred to as the thread relief (FS). Molded part (1) according to Claim 12 , characterized in that the contour of the undercut (FS) is designed according to a so-called tree root geometry using the “method of draw triangles”, preferably with additional rounding. Molded part (1) according to one of the Claims 1 until 13 , characterized in that the ratio of a length (LB) of the fastening section (BA) to an axial total length (L) formed summarily from a length (LB) of the fastening section (BA) and a length (LM) of the mounting section (MA) is in the range of 38% to 57%, preferably around 54%. Molded part (1) according to one of the preceding claims, characterized in that a wall thickness (T2) in the area of a/the thread relief (FS) corresponds to at least 70%, in particular at least 80%, preferably at least 85%, to a wall thickness (T1) in the fastening section (BA), wherein the wall thickness (T1) in the fastening section (BA) extends from the base of the thread (10) to the wall surrounding the inner channel (3). Molded part (1) according to Claim 15 , characterized in that the wall thickness (T2) in the area of the thread relief (FS) - axially starting from the end of the thread (10) - extends over a region of up to at least 20%, preferably up to at least 25%, 30% or 40%, of a length (L1) in the area of the assembly section (MA) in which the assembly section (MA) is designed as a flange.