Hollow bolt comprising a longitudinal bore and manufacturing method thereof

European).

Description [001] The invention relates to a method for producing a hollow bolt which is provided with circumferential notches (indentations) and to a hollow bolt or borehole bolt made according to this method.

[002] The hollow bolt with circumferential notches may be a screw bolt or a bolt with notches / ring notches, such as are used, for example, to latch fasten any plastic elements provided with a matching hole.

[003] Pins provided with a longitudinal hole, so-called hollow pins are often used in screw joints that require subsequent adjustment of a structural element held by the pin; for this purpose, the adjustable screw connection is operated, e.g. with a screwdriver, which is inserted through the longitudinal hole in the hollow bolt. The production of such hollow or hole pins provided with circumferential notches is difficult if the notches (indentations), and in particular the thread, are to be rolled on a hollow pin. In this case, due to significant pressures (pressures) occurring at the same time, the hollow pin tends to radial deformations, because due to the longitudinal hole in its interior there is no necessary material that could absorb these significant pressures (pressures). For this reason, hollow pins with a rolled thread are produced in such a way that first the thread is rolled into a solid semi-finished product and then a longitudinal hole is made in the pin by drilling. It is an additional operation that significantly irritates the production of this type of hollow pins.

[004] DE 1 921 229 A1 describes and describes a vibration-resistant screw in which an intermediate formed of three round bars placed symmetrically, closely next to each other, is braided into a braid, the three round bars being adjacent like a thread, after which a screw thread is extruded on this material, which then has internal springing properties, which in the thread of the nut into which this type of screw is screwed, they claw to some extent like claws and make the screw resistant to vibration. There is no through hole in this screw for passing a tool through it.

[005] At the heart of the invention is the task of creating a pin provided with a longitudinal hole, in which circumferential notches can be made on the blank by rolling without risking deformation of the intermediate provided with the longitudinal hole. According to the invention, this is done in such a way that the bolt blank with a longitudinal hole surrounded by an annular wall is provided with longitudinal grooves between the elevations defining the diameter of the bolt and that the hollow bolt provided with longitudinal grooves and elevations is circumferential notches (indentations) rolled, the grooves longitudinal sections have such a cross section that some of the material displaced when rolling the notches flows into the longitudinal grooves without deforming the annular wall.

[006] Due to the longitudinal grooves that extend along the hollow pin initially still free from notches, pressure rolling is created on the deformed hollow pin material that can escape into the free spaces created by the longitudinal grooves, thereby reducing pressure accordingly (pressure ) exerted by rolling tools acting on the hollow pin material. This reduction in pressure is so great that, despite its longitudinal hole, the hollow pin does not deform during this operation. The material escaping when rolling the notches is shifted to the areas of the longitudinal grooves, so in practice thread threads or rings are obtained without prolonged interruption by the longitudinal grooves. A short recess or groove of thread turns is even desirable here, especially when it comes to self-cutting thread without chipping, because because of the recesses or furrows, edges are formed in the rolled thread that facilitate the cutting of the thread of the nut. The material of the nut thread can still flow into these cavities, which further increases the loosening torque of this type of screw.

[007] Rolling the thread onto a bolt onto which the helical grooves with a large pitch were rolled before rolling the thread is known per se from 2,562,516. Helical grooves, which in many places have the US-PS description interrupting the later rolled thread, serve to create cutting teeth in the thread, which are to facilitate the threading through the thread bolt in the nut. The pin itself is made of solid material, i.e. it has no longitudinal hole. Therefore, the patent specification also does not disclose how the specific conditions of the hollow bolt provided with the longitudinal hole are to be taken into account.

[008] The invention also relates to a hollow pin with circumferential notches, which has a longitudinal bore surrounded by an annular wall and is formed from a blank which is provided with longitudinal grooves that run between the elevations defining the diameter of the pin, and on which the pin hollow notches with longitudinal grooves are rolled peripheral notches, with longitudinal grooves having such a cross-section, that part of the material displaced when rolling the notches (indents) flows into the longitudinal grooves.

[009] The notches may be primarily threaded, although it is also possible to shape the notches so that they form rings. Application examples are also known for this.

[0010] There are many different possibilities for forming the longitudinal grooves. The longitudinal grooves can be arranged so that they run parallel to the hollow pin axis. However, it is also possible to arrange the longitudinal grooves at an oblique angle to the axis of the hollow pin. In either case, the longitudinal grooves cross the rolled notches, regardless of whether they form a thread or rings.

[0011] The figures show embodiments of the invention. They show:

Figure 1 - a hollow pin with oblique longitudinal grooves, without circumferential notches (indentations);

Figure 2 - a similar hollow pin with longitudinal grooves extending parallel to its axis;

Figure 3 - the hollow bolt according to figure 1 with a rolled thread;

Figure 4 - the hollow pin according to figure 2 with rolled rings;

[0012] In Figure 1, a hollow pin 1 with a shaft 2 and a head 3 is shown. On the shaft 2, longitudinal grooves 4 are made which lie between the elevations 5. The outer surface of these elevations defines the diameter of the shaft of the pin 2. A longitudinal hole extends through the hollow pin 1 6, which is surrounded by a corresponding annular wall 7.

[0013] The longitudinal grooves 4 can be made on the shank 2 in any way, e.g. by rolling or pressing. In the course of the further production process, which will be described in more detail below, the hollow pin produced in this way is provided with notches, as shown in connection with figures 3 and 4.

[0014] the figure shows a similar form of the hollow bolt 8, which differs from the hollow bolt 1 according to figure 1 in that the longitudinal grooves 9 extend parallel to the axis of the shaft 10 of the hollow bolt 8.

[0015] The hollow pins according to figures 1 and 2 form a kind of blank for the further process of manufacturing the hollow pin according to the invention, which in its final form is shown in figures 3 and 4.

[0016] The hollow bolt 1 shown in figure 3 was formed by rolling a thread onto the hollow bolt 1 according to figure 1, for which the thread which formed the threads 11 was rolled on the hollow bolt 1 according to figure 1. When rolling these threads hollow pin material 1 is formed into individual threads 11 that wind around the shaft 2 of the hollow pin 1 and have short cavities or grooves 12 that result from the longitudinal grooves 4 made. The material flow gives the effect that the longitudinal grooves 4 shrink, forming cavities 12 shortened in width, which results from the fact that when rolling a thread with 11 thread turns, the material of the pin flows into the longitudinal grooves 4 and thus leaves free cavities 12 shortened compared to the width of the longitudinal grooves 4. The wider the longitudinal grooves, the longer the notches form. In particularly narrow longitudinal grooves, the notches close enough that they practically close. With the flow flow thus allowed, the notches shrink completely.

of the material results from the aforementioned reduction in pressure of the rolling tools on the hollow pin 1, which leads to the fact that the annular surrounding of the hole 6 corresponding to the surface 7 is not deformed.

[0017] The hollow pin 8 according to figure 4 provided with rolled notches is derived from the hollow pin shown in figure 2, which is provided with longitudinal grooves 9 parallel to the axis. When rolling the notches shown in figure 4, these longitudinal grooves led to the formation of annular lodges 13 which are interrupted by cavities or furrows 14 (similar to cavities 12 according to figure 3). Regarding the creation of cavities 13 and their effects, we refer to the explanation above for figure 3.

[0018] It should also be noted that annular elevations 13 are of course also possible in the case of the hollow bolt 1 according to figure 1, and therefore in the case of the hollow bolt with indents 4 oblique.

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EP 1 891 341 B1 into the grooves defining the hollow (1) diameter of the pin