Connection system

Abstract

The present invention relates to a connection system for a mechanically detachable connection, in particular of plastic components, with a threaded insert that can be screwed into a hole and has an external thread and an internal thread. In order to create a connection system (1) of the aforementioned type while solving the problem of unscrewing, it is proposed that the connection system has the threaded insert (2) and a locking device to prevent the threaded insert (2) from being unscrewed from a corresponding recess, wherein the external thread (4) of the threaded insert (2) has a recess (6) extending substantially parallel to a longitudinal axis (M) of the external thread (4), in which a locking element (3) can be inserted as a locking device after the threaded insert (2) has been screwed into the hole.

Description

[0001] The present invention relates to a connection system for a mechanically detachable connection, in particular of plastic components, with a threaded insert which can be screwed into a hole and which has an external thread and an internal thread.

[0002] Currently, in addition to wood, plastic components in particular, which are to be connected to other components via threads, are provided with a threaded insert at a predetermined location. Such a threaded insert, also known to those skilled in the art as a screw-in nut, screw-in sleeve, threaded sleeve or using well-known brands of the respective manufacturers, usually consists of a hollow metal cylinder with a metric internal thread and a usually coarse external thread, e.g. a wood screw. As a rule, both threads are right-hand threads. When an internally screwed fastening screw is loosened, the threaded insert remains firmly in its position. This is because the loosening torque of the threaded insert is greater than the reaction torque required when loosening the fastening screw with its smaller diameter, due to the comparatively larger diameter with the coarse external thread, and the lower friction of its fine thread.

[0003] Although threaded inserts are particularly common in furniture construction, they are also used in many other materials such as wood, stone, plastic, and metal. In addition to the shape of their thread contour, thread inserts are differentiated by various pitches, flank angles, and thread profiles. A key advantage of threaded inserts is that, where access via the outside of a component is difficult, installation can be carried out from the same side from which a machine screw or bolt with a fine thread will later be screwed in. The threaded insert therefore does not necessarily require a visible and therefore usually undesirable through-hole in the surface of the component's outside. Rather, a recess of the appropriate diameter and depth in the form of a blind hole or a recess produced in another way is sufficient.

[0004] Compared to a drive-in nut or press-in nut, the threaded insert is distinguished by the fact that the screwing depth into a recess can be continuously selected and varied within certain limits without the recess in question having to be specially prepared, e.g. chemically, thermally or in any other way, or complex adjustments to a tool being necessary. This means that a threaded insert can be screwed in flush with a surface of the component for aesthetic reasons. On the other hand, a projection of the threaded insert above the surface of the component can be used to create a defined distance between the components to be connected. It is also possible to screw a threaded insert deeper into an appropriately sized hole in order to reliably shield the threaded insert from the outside after the components to be fastened to it have been assembled.All of these possible applications can be realized in a predetermined and reproducible manner using a depth control, e.g. on a screwing device.

[0005] In addition, a threaded insert in a plastic component offers greater holding power due to its positive and frictional engagement, as well as its larger effective diameter of the external thread, than threads cut directly into the plastic by cutting, rolling, or other methods. Ensat® bushings have proven effective as self-tapping threaded inserts, which lock into a pre-drilled hole via a self-tapping external thread in the surrounding plastic in an improved manner. An Ensat® threaded insert with a cutting slot can be used to create highly resilient, wear-resistant, and vibration-proof screw connections, even in materials with low shear strength. This threaded insert is therefore also suitable for installation in: - aluminum and aluminum alloys, - magnesium alloys, - Brass, bronze and - Thermosets and - Thermoplastics with the exception of soft rubber thermoplastics.

[0006] Even with a threaded insert with a self-tapping external thread, static friction alone prevents the threaded insert from unscrewing itself out of the plastic when a screw inserted into such a threaded insert is unscrewed. Reinserting the threaded insert into an existing hole is very difficult, and the holding force of the threaded insert in the plastic is also significantly reduced in this case. In this case, the product in which the threaded insert was located can therefore no longer be used safely. This causes major problems, especially with materials that have a low coefficient of static friction between the material of the thread insert and a plastic, such as a combination of fluoroplastics and steel, if the internal thread of the threaded insert is intended for multiple use, with the screw inserted into the internal thread being screwed in and out, etc.

[0007] The problem of unintentional unscrewing when removing a screw located in the respective threaded insert is well known to those skilled in the art. For example, DE 2415941 A1, DE 3725974 A1, DE 4033650 A1, DE 19903254 A1, or DE 102014213610 A1 disclose designs of threaded inserts for more secure fixation in a component. The unscrewing force is attempted here, for example, by conical expansions and / or interruptions in the threads of the respective threaded insert, in order to prevent the threaded insert from unscrewing when loosening a screw connection.

[0008] The present invention has the object of creating a connection system of the type mentioned while solving the problem of unscrewing the threaded insert in question.

[0009] This object is achieved according to the invention by the features of claim 1. Accordingly, a connection system for a mechanically detachable connection, in particular of plastic components, with a threaded insert that can be screwed into a hole and has an external thread and an internal thread is characterized in that the connection system comprises the threaded insert and a lock to prevent the threaded insert from being unscrewed from the hole of the plastic component. The external thread of the threaded insert has a recess into which a locking element can be inserted after the threaded insert has been screwed into the hole. The locking element thus acts as a block within the thread and prevents the threaded insert from being unscrewed.

[0010] A further advantage of a device according to the invention is that a threaded insert of known design only needs to be slightly adapted in the area of ​​the external thread to accommodate a locking element. Furthermore, only one additional component is required, which is comparatively small and easy to manufacture and acts as a locking element inserted into the external thread, preventing the threaded insert from being unscrewed.

[0011] Advantageous further developments are the subject of the dependent claims. Accordingly, the recess is designed to run essentially parallel to a longitudinal axis of the external thread. Such a recess is very easy to manufacture, for example, by sawing or milling after the external thread has been completed.

[0012] The locking element is preferably designed as an elongated element, in particular made of metal. In a preferred embodiment of the invention, the locking element is designed as a piece of wire.

[0013] The length of the locking element essentially corresponds to the height of the threaded insert. This ensures that the threaded insert and the elongated element are flush with a freely accessible external surface. Depending on the application, it is also possible for a connection system according to the invention to protrude beyond the surface of a component in a defined manner, or to be countersunk into the hole by a certain amount below the surface, particularly to protect the connection system against corrosive substances during intended use of the connected components.

[0014] The locking element can generally be a piece of wire with a round cross-section that is cut to length directly upon insertion. In a preferred embodiment of the invention, the locking element has a rectangular, in particular square, cross-section. In one embodiment of the invention, the locking element can be cut to length from, for example, a wound wire upon completion of the connection system, according to the respective requirements of a particular application, preferably after insertion into the recess on the external thread of the threaded insert already screwed into the hole.

[0015] Preferably, the recess in the area of ​​the external thread of the threaded insert has a 90° angle. Together with a locking element with a rectangular, particularly square, cross-section, this results in an elongated edge of the locking element, which extends from the threaded insert through the thread cut into the plastic component into the solid material of the plastic component. This not only ensures a secure hold of the locking element but also creates a very strong locking effect against unscrewing the threaded insert.

[0016] In a particularly preferred embodiment of the invention, the at least one recess on the threaded insert is designed as a self-tapping screw. The recess thus fulfills two functions: that of a self-tapping screw and that of a receptacle for the locking element.

[0017] In one embodiment of the invention, a slot for screwing in using a slotted screwdriver is provided on one end of the threaded insert, which is preferably aligned with the recess in the area of ​​the external thread of the threaded insert. The slot for screwing in the threaded insert can thus be used when positioning the locking element.

[0018] Further features and advantages of embodiments of the invention are explained in more detail below with reference to exemplary embodiments based on the drawings. In these, the following are shown: Fig. 1: a perspective view of a connection system consisting of a threaded insert with a locking element; Fig. 2: a top view of the connection system of Fig. 1 with two shapes of slots to represent different locking elements and Fig. 3: a sectional view of the connection system of Fig. 2 in a plane AA when inserted into a plastic component.

[0019] Throughout the various illustrations of the drawing, the same reference numerals are used for identical elements. Without limiting the invention, only one use of a connection system for a mechanically detachable connection to a plastic component is illustrated and described below, because the problem of unwanted unscrewing of the thread insert is particularly significant when using a plastic component made of PTFE in conjunction with a stainless steel thread insert.

[0020] Fig. 1 shows a perspective view of a connection system 1 for a mechanically detachable connection to a plastic component (not shown in detail). The connection system 1 comprises a threaded insert 2 that can be screwed into a hole in this plastic component, and a locking element 3. The threaded insert 2, as a metallic hollow cylinder, has an external thread 4 and an internal thread 5. The connection system 1 is secured against unscrewing from the plastic component by the fact that the threaded insert 2 has a recess 6 on the external thread 4, into which the locking element 3 can be inserted after the threaded insert 2 has been screwed in. The recess 6 runs essentially parallel to a longitudinal or central axis M of the external thread 4 of the threaded insert 2.

[0021] A slot 7 adapted to a slotted screwdriver is provided for screwing in the threaded insert 2 using a screwdriver. In this embodiment, the slot 7 is aligned with the recess 6 in the area of ​​the external thread 4 of the threaded insert 2.

[0022] In a manner not further illustrated, the locking element 3 is provided with at least a roughened surface and advantageously embossed serrations. This significantly increases the resistance of the locking element 3 to being pulled out, even from a plastic component.

[0023] Fig. 2 is a plan view of the connection system of Fig. 1. It can be seen here that, with little effort, a second recess 6 can also be provided on the threaded insert 2 in the area of ​​the external thread 4. This is particularly advantageous in the manufacture of such a threaded insert 2 if the recesses 6 are also designed as self-tapping tools for the threaded insert 2. Those skilled in the art know that, to produce shorter chips when cutting threads, more than one cutting edge designed as a self-tapping tool is advantageous. Thus, more than one locking element 3 could also be used for securing within a connection system 1 according to the invention.

[0024] In Fig. 2 shows two embodiments of recesses 6. In the upper area, the recess 6 has a 90° angle and acts as a triangular notch; in the lower area, a recess 6 with two 90° angles is provided in the form of a milled groove. The locking element 3 has a round cross-section in the lower embodiment. Inserted into the recess 6 in the area of ​​the external thread 4 of the threaded insert 2, this locking element 3 very effectively blocks the thread cut into the surrounding material. Indicated in dashed line in the locking element 3 with a rectangular cross-sectional area, which can also engage beyond the cut thread into the plastic.

[0025] In the second embodiment of Fig. 2, the recess 6 in the area of ​​the external thread 4 of the threaded insert 2 encompasses only a 90° angle. Thus, the locking element 3, which here has a square cross-section and is inserted into the recess 6, protrudes with one edge into the thread cut by the threaded insert 2 and even beyond it into the surrounding plastic of the component. This creates a particularly strong locking effect, preventing any unscrewing of the threaded insert 2, while reducing the force required when inserting the locking element 3 into the recess 6.

[0026] Fig. 3 shows a sectional view through the connection system of Fig.2 in a plane AA when inserted flush into a blind bore 8 of a plastic component K. Here, an embodiment is shown in which the locking element 3 engages into the plastic component K beyond the thread cut by the threaded insert 2. Furthermore, it is clearly visible that the slot 7 for screwing in using a slotted screwdriver is aligned with the recess 6 in the area of ​​the external thread 4 of the threaded insert 2. To facilitate inserting the threaded insert 2 into a blind bore 8 as a recess in a plastic component K, the threaded insert 2 has a chamfer 9 at an end opposite the screw slot 7.

[0027] The threaded insert 2 is generally screwed into a hole designed as a blind bore 8 in a plastic component K, which in one embodiment is made of PTFE and, after the thread has been cut during the screwing in of the threaded insert 2, has particularly low friction between the threaded insert 2 and the plastic of the component K. As a result, the threaded insert 2 can be unscrewed from the plastic particularly easily, which is very effectively prevented by inserting a locking element 3 into a recess 6 of the connection system 1 designed according to the invention. A self-tapping thread cutter was used as the recess 6. In the same way, however, a connection system can also be inserted into a through-bore, wherein the person skilled in the art adapts an axial length of the connection system 1 to a thickness of the component in question. List of reference symbols 1 connection system 2 threaded inserts 3 locking element 4 external threads 5 internal threads 6 Recess on the external thread 4 / Cutting edge of the self-tapping tool of the thread insert 2 7 Slot for screwing in using a slotted screwdriver 8 Blind hole / hole in the component K made of plastic 9 Chamfer on the threaded insert 2 M central axis K Plastic component 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] DE 2415941 A1

[0007] DE 3725974 A1

[0007] DE 4033650 A1

[0007] DE 19903254 A1

[0007] DE 102014213610 A1

[0007]

Claims

[1] Connection system for a mechanically detachable connection, in particular of plastic components, with a threaded insert which can be screwed into a hole and which has an external thread and an internal thread, characterized by that the connection system (1) has the threaded insert (2) and a safety device against unscrewing the threaded insert (2) from the hole in the plastic component, wherein the external thread (4) of the threaded insert (2) has a recess (6) into which a locking element (3) can be inserted as a safety device after the threaded insert (2) has been screwed into the hole in the plastic component. [2] Connection system (1) according to the preceding claim, characterized by that the recess (6) is designed to run substantially parallel to a longitudinal axis (M) of the external thread (4). [3] according to one of the preceding claims, characterized by that the locking element (3) is designed as an elongated element, preferably made of metal. [4] Connection system (1) according to one of the preceding claims, characterized by that the locking element (3) is designed as a piece of wire. [5] Connection system (1) according to one of the preceding claims, characterized by that the locking element (3) has a length which essentially corresponds to a height (H) of the threaded insert (2). [6] Connection system (1) according to one of the preceding claims, characterized by that the blocking element (3) has a rectangular, in particular square, cross-section. [7] Connection system (1) according to one of the preceding claims, characterized by that the locking element (3) has a rough surface, preferably with embossed teeth. [8] Connection system (1) according to one of the preceding claims, characterized by that the recess (6) in the area of the external thread (4) of the threaded insert (2) has a 90° angle. [9] Connection system (1) according to one of the preceding claims, characterized by that the recess (6) is designed as a self-tapping screw. [10] Connection system (1) according to one of the preceding claims, characterized by that a slot (7) for screwing in using a slotted screwdriver is aligned with the recess (6) in the area of the external thread (4) of the threaded insert (2).

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