threaded insert

Abstract

Threaded insert which has a head (1) at one end, to which a shaft (3) is connected, which extends to the end of the threaded insert facing away from the head (1), wherein an internal thread (6) is introduced into the shaft (3), characterized in that the shaft (3) is provided with flattened portions (8) between which cylindrical sections (9) are formed, into which notches (10) are introduced.

Description

[0001] The invention relates to a threaded insert which has a head at one end, to which a shaft is connected, which extends to the end of the threaded insert facing away from the head, wherein an internal thread is introduced into the shaft.

[0002] In many applications, plastic components are often used instead of metal components. Different plastics are used depending on the application and load requirements. Glass fiber or carbon fiber reinforced plastics are also used, particularly for applications subject to high mechanical stress. Both thermosetting plastics and thermoplastics are considered as base materials.

[0003] When connecting plastic components with screws, the screws can be screwed directly into the plastic. This can be done using self-tapping threads or by cutting a thread and then screwing in the screw.

[0004] Joining non-reinforced plastics with screws is often problematic because such plastics have a low modulus of elasticity and low strength. Consequently, only lower forces can be transmitted with a screw connection. For components made of glass fiber or carbon fiber reinforced plastics, joining with screws often poses a problem because, while such components have high strength, they are also quite brittle.

[0005] Threaded inserts have been developed to overcome these problems. These threaded inserts are used to connect two plastic components using screws. These threaded inserts are made of metal and increase the strength of the connection between the components.

[0006] The threaded inserts can be pressed into the plastic part after the injection molding process. This involves using threaded inserts that do not have any undercuts on the outside. The threaded inserts are connected to the respective component by frictional engagement. However, this limits the force that can be transmitted via the screw connection.

[0007] Alternatively, the threaded inserts are inserted into the injection mold and overmolded prior to injection molding. The threaded inserts are sufficiently rigid and will not deform during the injection molding process or a subsequent assembly process. The threaded inserts typically have undercuts or similar features on the outside, which creates a positive connection in both the axial and radial directions. This allows higher forces to be transmitted through the screw connection.

[0008] A threaded insert of the type considered here is known, for example, from EP 2 542 792 B1. This insert has projections on its shaft that form a waterfall-shaped thread and extend from the head of the threaded insert to the end facing away from the head. Although the known threaded insert meets the requirements placed on it, its production is complex due to the complex design of the projections.

[0009] The invention aims to remedy this situation. The invention is based on the object of creating a threaded insert that can be manufactured cost-effectively and simultaneously meets the requirements for positive locking in the axial and radial directions. According to the invention, this object is achieved with the features of claim 1.

[0010] The invention provides a threaded insert that can be manufactured cost-effectively and simultaneously meets the requirements for positive locking in the axial and radial directions. This is made possible by the fact that the flats, the cylindrical sections, and the notches form a positive connection with the overmolded plastic. The notches form undercuts that prevent axial positional changes, while the flats formed between the cylindrical sections prevent rotation of the threaded insert in the plastic.

[0011] It is advantageous to have six flats and six cylindrical sections on the shaft. Tests have shown that this number of flats and cylindrical sections represents an optimal compromise between the manufacturing costs of the threaded insert and the desired form fit with the plastic.

[0012] Preferably, six notches are formed per cylindrical section. This design also provides an optimal balance between manufacturing costs and form fit.

[0013] In a further development of the invention, the notches are each introduced into the cylindrical sections in the manner of a secant. This offers the advantage that the notches at the lateral ends of the cylindrical sections are shallower than those in their center. This facilitates the entry of the plastic during injection into the injection mold, ensuring reliable entry.

[0014] Further developments and refinements of the invention are specified in the remaining subclaims. An embodiment of the invention is illustrated in the drawings and described in detail below. They show: Fig. 1 is a plan view of a threaded insert according to the invention; Fig. 2 the view of the Fig. 1 threaded insert shown; Fig. 3 the section along the line CC in Fig. 2; Fig. 4 the underside of the Fig. 1 threaded insert shown; Fig. 5 the section along the line DD in Fig. 4; Fig. 6 the enlarged view of detail E in Fig. 5; Fig. 7 the three-dimensional representation of the threaded insert according to the invention.

[0015] The threaded insert chosen as the example is made of steel. It can also be made of other metallic materials as a modification of the example.

[0016] The threaded insert has a circular head 1 at one end. Adjacent to the head is a recess 2, which is followed by a shank 3 that extends to the end of the threaded insert facing away from the head 1. At its end facing away from the head 1, the shank 3 has a chamfer 4.

[0017] The shaft 3 of the threaded insert is provided internally with a blind hole 5 into which an internal thread 6 is inserted. The blind hole 5 has a countersink 7 at its free end.

[0018] The shaft 3 has a substantially round cross-section, which is provided with flats 8. The flats 8 extend in the axial direction from the undercut 2 to the chamfer 4. Between the flats 8, cylindrical sections 9 are formed, which also extend in the axial direction. The imaginary extension of the cylindrical sections 9 over the flats 8 leads to a circular line, as shown in Fig. 4. In the exemplary embodiment, six flattened portions 8 and six cylindrical portions 9 are formed on the shaft 3. A different number of flattened portions 8 and cylindrical portions 9 is possible.

[0019] Notches 10 are formed in the cylindrical sections 9. In the exemplary embodiment, six notches 10 are formed per cylindrical section 9. The notches 10 are each formed in the cylindrical sections 9 in the manner of a secant. In the exemplary embodiment, the notches 10 are pressed into the cylindrical sections 9. Other manufacturing processes are of course possible.

[0020] The threaded insert according to the invention is ideally suited for molding into plastic components. For this purpose, the threaded insert is positioned in a plastic injection mold. The mold is then closed, and the hot plastic is injected into the mold. The threaded insert is overmolded in the plastic such that the head 1 is either flush with the surface of the plastic component or rests against the component. In any case, it is ensured that the opening of the blind hole 5 with the internal thread 6 is not covered by the plastic, thus allowing a screw to be screwed in later.

[0021] Due to the inventive design of the shaft 3 with the flattened portions 8 and the cylindrical sections 9 and notches 10 formed therebetween, the threaded insert forms a positive connection with the plastic. The notches 10 form undercuts that prevent axial positional changes. The flattened portions 8 formed between the cylindrical sections 9 also prevent rotation of the threaded insert in the plastic.

[0022] Overall, the threaded insert is characterized by properties at least as good as those of threaded inserts known from the prior art. At the same time, the threaded insert according to the invention is significantly more cost-effective to manufacture because the three-dimensional design of the shaft 3 with the flattened portions 8, the cylindrical sections 9, and the notches 10 can be produced in a single operation by pressing in a forming machine. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 2 542 792 B1

[0008]

Claims

[1] Threaded insert having at one end a head (1) to which a shaft (3) is connected, which extends to the end of the threaded insert facing away from the head (1), wherein an internal thread (6) is introduced into the shaft (3), characterized by that the shaft (3) is provided with flattened portions (8) between which cylindrical sections (9) are formed, into which notches (10) are made. [2] Threaded insert according to claim 1, characterized by that the flats (8) and the cylindrical sections (9) extend in the axial direction of the shaft (3). [3] Threaded insert according to claim 1 or 2, characterized by that six flats (8) and six cylindrical sections (9) are formed on the shaft (3). [4] Threaded insert according to one of the preceding claims, characterized by that six notches (10) are formed per cylindrical section (9). [5] Threaded insert according to one of the preceding claims, characterized by that the notches (10) are each introduced into the cylindrical sections (9) in the manner of a secant.

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