DE102013210476B3 - Screw, in particular for use in plastic components and method for producing such a screw - Google Patents

Abstract

The invention relates to a screw, in particular for use in plastic components, comprising a threaded shaft and also a method for producing such a screw. Such a screw has a thread with at least one thread, preferably with several turns with an outer diameter (Da) and with a thread pitch (P), wherein the thread has thread flanks and an intermediate thread root. In addition, the thread is thread-forming or thread-forming. The ratio Q1 = P / Da of the thread pitch (P) based on the outer diameter (Da) is from 0.3 to 0.385 and the thread root has a radius Rg, based on the thread pitch (P) a ratio Q2 = Rg / P is from 0.5 to 1.0, preferably 0.55 to 0.8. Such screws are used in particular for direct screwing.

Description

Technical area

The invention relates to a screw, in particular for use in plastic components, comprising a threaded shaft and also a method for producing such a screw. Such a screw has a thread with at least one thread, preferably with several turns with an outer diameter (Da) and with a thread pitch (P), wherein the thread has thread flanks and an intermediate thread root. In addition, the thread is thread-forming or thread-forming.

Such screws are used in particular for the so-called direct screw connection, in which the screw itself forms a thread in a nut component, which generally has a corresponding through hole or blind hole for receiving the screw.

State of the art

From the EP 0 589 399 A1 a self-tapping screw for thermoplastics is known, which has a ratio between the outer thread diameter and the pitch of less than 3, preferably 2.3. The sections between the thread flanks, referred to as the core section, are conical and taper towards the tip in each case.

From the EP 0 948 719 B1 is screwed into plastic screw known, which may consist of a material due to their geometry, which has lower strength compared to conventional materials for screws for screwing into plastic. The thread root is cylindrical, the ratio between the thread outside diameter and the pitch is between 2.75 and 2.9 or between 2.35 and 2.7.

From the DE 20 2012 000 045 U1 A self-tapping screw is known in which the radius at the transition of the flank into the root of the thread is between 0.15 and 0.25 times the pitch. The core cross section has the shape of a rounded n-corner.

From the DE 24 61 546 A1 is a rolling tool with shaping dies known. In this case, oblique, a conical thread forming tool surfaces are disclosed.

In conventionally produced screws usually a rapid penetration of the rolling tool until the core diameter is reached. Subsequently, a lateral, scraping material displacement takes place at the root of the thread. This type of displacement of the material leads depending on the profile usually to the extent of the thread crest with a closing fold and rolling scales in the thread root, which adversely affects the strength of the thread flanks and the screwing in direct fitting.

The object of the invention is to provide a screw for a direct fitting with a sufficient strength and a favorable flow of material in the component to be screwed on the one hand and the production of such a screw on the other.

Disclosure of the invention

A screw according to the invention has a shaft with a thread with at least one thread, preferably with several turns with an outer diameter (Da) and with a thread pitch (P), wherein the thread has thread flanks and an intermediate thread root. In addition, the thread is thread-forming or thread-forming. The ratio Q1 = P / Da of the thread pitch (P) based on the outer diameter (Da) is from 0.3 to 0.385 and the thread root has a radius Rg, based on the thread pitch (P) a ratio Q2 = Rg / P is from 0.5 to 1.0, preferably 0.55 to 0.8.

It has been found that such a screw is suitable for direct screwing in plastic components, in particular for thermoplastics or thermosetting plastics with a high fiber content, since this design has a positive effect on the flow of material in the component to be screwed.

Advantageously, the transition from the thread root having the radius Rg in the thread flank in an angular range of 25 ° to 45 °, in particular from 28 ° to 38 ° and the flank angle can be in an angular range of 20 ° to 30 °.

It has been found that there is sufficient stability of the thread flanks during penetration into the nut component at these angles.

Advantageously, the material may be a conventional screw material, referred to as tempered steel, or a stainless, non-heat treated material.

Another object of the invention is a method for producing such a screw, wherein starting from a blank, the deformation of the blank takes place in the region of the shaft for producing the screw geometry.

In the method according to the invention for producing the screw, the shank for forming the thread is deformed by means of threads, thread flanks and a thread root by means of a shaping rolling tool having a rolling die. Due to the progress of the rolling jaw length increase the rounding in the thread base while increasing the penetration depth of the forming rolling tool, starting from a profile with an acute angle in the rolling tool to a rounded profile, preferably with a radius RG, there is a formation of tapered thread flanks and a Thread base with a radius RG.

Due to the better material flow of the screw material, this method of production leads to a material flow-optimized thread geometry, since because of the small pitch only relatively little material has to be displaced transversely and the displacement of the screw material takes place both towards the core diameter and laterally. The thread flanks produced in this way are formed almost without a closing fold in the thread crest and the thread root is largely smooth.

Advantageously, the continuous increase of the penetration depth over at least 2/3 of the rolling jaw length used to produce the thread of the screw and / or up to the calibrating section of the rolling jaw and / or up to an outlet lowering of the rolling jaw.

Brief description of the drawings

The inventive method will be explained with reference to the drawing. Show it:

1 a screw according to the invention for the screw in plastic in a side view;

2 the formation of the thread of the screw 1 in detail;

3 a conventional process for creating a thread;

4 an inventive process for generating a thread;

5 a rolling die of a rolling tool as a schematic sketch.

Embodiment (s) of the invention

In the 1 in a side view illustrated screw according to the invention 1 for the screw in plastic has one with a thread 2 provided shaft 3 with an outer diameter Da and a core diameter Dk on. Also shown, but not relevant to this invention, is a head of the screw with internal force application surfaces.

The shaft 3 was used to make the thread 2 with threads 4 , with thread flanks 5 with a flank angle phi and with a thread root 6 deformed, with the thread 2 is formed thread-forming or thread-forming.

2 shows the shape of the thread of the screw 1 in detail. The thread pitch P based on the outer diameter Da has a ratio Q1 = P / Da of 0.3 to 0.385 in such a screw, in the case shown, the ratio is 0.37. Every thread 4 points in the thread 6 between the thread flanks 5 a radius Rg, wherein the radius Rg with respect to the pitch P has a ratio Q2 = Rg / P of 0.5 to 1.0, preferably 0.55 to 0.8, in the illustrated case 0.62.

The flank angle phi of the thread flank 5 may be in an angular range of 20 ° to 30 °, in the illustrated case, the angle phi is 25 °.

In the detailed representation can be further seen that the transition at a transition point 8th with a diameter Dü of the thread root 6 with the radius Rg in the thread flank 5 has an angle alpha, which is in an angular range of 25 ° to 45 °, in particular from 28 ° to 38 ° and in the present case is about 32 °.

The two other diameters min. and max. are not important to the description of the present invention.

In 3 the conventional production of screws is described by way of example n three subfigures. Another part figure shows the blank with the shaft 12 , yet another part figure shows a detail X from the last of the three sub-figures.

There is a rapid penetration of an acute angle having forming rolling tool 11 into a threaded shank 12 a blank until the core diameter DK is reached. Subsequently, the rolling tool widened, resulting in a lateral, scraping material displacement on the thread roots 15 along the core diameter DK leads. This type of displacement of the material usually leads depending on the profile to the extent of the thread crest 13 with a closing fold 14 and to rolling scales in the thread root 15 , This type of screw production by rolling is basically known.

In 4 is shown in three sub-figures, as in the method according to the invention for the preparation of the screw with a progress of the rolling jaw increase in the rounding in the thread root 15 while increasing the penetration depth of the shaping rolling tool 11 into the threaded shank 12 of a blank up to the core diameter DK out. Another part figure shows the blank with the shaft 12 , yet another part figure shows a detail Y from the last of the three sub-figures.

Starting from a lead 18 with a profile with an acute angle and adjoining convex arcs in the rolling tool 11 to achieve the necessary friction for the deformation at the beginning of the displacement is via a continuous change in the profile of the projection 18 ' with a larger angle and widening convex arcs causes a material displacement, which has a favorable flow of material, which, unlike shown, even still a distance to the core diameter DK may be present. This change in the profile is continued until it becomes a fully rounded profile of the projection 18 '' of the rolling tool 11 comes, which corresponds to the radius RG of the thread root and thus the acute angle is gone.

This way, in the shaft 12 tapered thread flanks 13 and a thread root 15 formed with a radius RG.

In 5 is shown that the continuous increase in the penetration depth as well as the change in the shape of the rolling die with its protrusions 18 over a section 16 at least 2/3 of the length of the rolling die of the rolling tool used to make the thread of the screw 11 takes place and in the present case up to a Kalibrierabschnitt 17 of the rolling die, which merges into an outlet lowering of the rolling die extends. The length of the calibration section 17 is preferably at least one turn of the screw.

At the beginning of the deformation of the rolling dies has a narrow projection 18 at an acute angle, represented by the straight line starting from a tip of the projection straight line sections which abut the sheets, which widening progressively, wherein the projection until the end of the deformation, ie at the end of the section 16 widened to the radius RG and rounded in the top, shown as a projection 18 '' ,

Suitable materials for the application of the screw may include: AL die casting, AlMg die casting, Mg die casting, carbon fiber or glass fiber reinforced plastics, such as unsaturated polyester. The screw is also suitable for use in cast or drilled core holes.

Claims (8)

Screw having one with a thread ( 2 ) with at least one thread ( 4 ) provided shaft ( 3 ), whereby the thread ( 2 ) has an outer diameter (Da) and a thread pitch (P) and is thread-forming or thread-forming, characterized in that the ratio Q1 = P / Da of the thread pitch (P) based on the outer diameter (Da) of 0.3 to 0.385 and that the thread root ( 6 ) has a radius Rg which, based on the pitch (P), has a ratio Q2 = Rg / P of 0.5 to 1.0. Screw according to claim 1, characterized in that the material is a conventional screw material, which is referred to as tempered steel or that the screw consists of an austenitic material, in particular according to EN 10269. Screw according to claim 1 or 2, characterized in that the transition ( 8th ) of the thread ( 6 ) in the thread flank ( 5 ) is in an angular range of 25 ° to 45 °, in particular from 28 ° to 38 °, and that the flank angle is in an angular range of 20 ° to 30 °. Screw according to one of claims 1 to 3, characterized in that the thread ( 2 ) several threads ( 4 ) having. Screw according to one of claims 1 to 4, characterized in that the ratio Q2 = Rg / P is 0.55 to 0.8. Method for producing a screw according to one of the preceding claims, wherein the shaft ( 3 ) for producing the thread ( 2 ) with threads ( 4 ), Thread flanks ( 5 ) and a thread root ( 6 ) by means of a rolling die having shaping rolling tool ( 11 ) is deformed, characterized by a progressing with the rolling jaw length increase the rounding in the thread root ( 15 ) while increasing the penetration depth from an acute angle in the rolling tool ( 11 ) to a rounded profile in the rolling tool, so that in the shaft ( 3 ) a formation of a thread ( 2 ) with tapered thread flanks ( 13 ) and with a thread root ( 15 ) with a radius RG. A method according to claim 6, characterized in that the continuous increase in Penetration depth at least 2/3 of that for the production of the thread ( 2 ) of the screw used rolling die length and / or to the calibration section ( 17 ) of the rolling die and / or up to an outlet lowering of the rolling die. Method according to claim 6 or 7, characterized in that the rounded profile ( 18 ) has a radius RG in the rolling tool.

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