Screw connection for a component made of thermoplastic material

Abstract

The present disclosure relates to a screw connection comprising a support component, an additional component and a screw to affix the support component to the additional component. The support component comprises a tube made of plastic to accommodate the screw in a friction and positive fit, wherein the tube comprises a thermoplastic foam. The screw comprises a blunt-edged screw thread. The foam is compacted as the screw is driven into the tube. The present disclosure further relates to a corresponding screw and to a method of connecting a support component to an additional component using the screw.

Claims

1. A screw connection for connection to an additional component, the screw connection comprising: a support component made of thermoplastic foam, the support component comprising a tube, the tube including an outer layer; and a screw for screwing into the tube and for connecting the support component to the additional component when screwed into the tube, the screw comprising a blunt-edged thread for compacting the thermoplastic foam within the tube to form a friction and positive fit, wherein the outer layer has a shape deformable by the blunt-edged thread of the screw when the screw is screwed into the tube to form the friction and positive fit within the tube, and wherein the screw comprises one or more threads having an outer diameter that is greater than an inner diameter portion of the tube.

2. The screw connection according to claim 1, wherein the threads comprise flank angles of 30-90.

3. The screw connection according to claim 1, wherein the threads comprise flank angles of greater than 60.

4. The screw connection according to claim 1, wherein the threads comprise rounded edges.

5. The screw connection according to claim 1, wherein the threads have a spacing of greater than 2 millimeters.

6. The screw connection according to claim 1, wherein the thermoplastic foam of the tube is produced using one of a chemical or physical foaming process.

7. The screw connection according to claim 6, wherein the thermoplastic foam of the tube is produced using a MuCell process.

8. The screw connection according to claim 1, wherein the outer layer comprises one of an integral foam or a microcellular foam.

9. The screw connection according to claim 1, wherein the tube comprises: the outer layer having a side-wall thickness of 0.1 to 3 millimeters; and a bottom having a thickness of 0.1 to 3 millimeters.

10. The screw connection according to claim 1, wherein the support component comprises a thermoplastic foam produced using one of a chemical or physical foaming process.

11. The screw connection according to claim 10, wherein the thermoplastic foam is produced using a MuCell process.

12. A method of connecting a support component to an additional component using a screw, the method comprising the following steps: forming, using one of a chemical or physical foaming process, the support component with a tube made of thermoplastic foam, wherein the tube includes an outer layer; providing a screw having a plurality of blunt-edged screw threads, the threads having an outer diameter that is larger at least in parts than an inner diameter of the tube; and screwing in the screw in a non-thread-rolling manner through an additional component into the tube, such that the foam of the tube is compacted as the screw is driven in, and wherein the outer layer has a shape deformable by the blunt-edged thread of the screw when the screw is screwed into the tube to form the friction and positive fit within the tube.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Individual embodiments of the present disclosure are explained in greater detail below with reference to the drawings.

(2) In the drawings:

(3) FIG. 1 shows a section through a conventional plastic tube of compact injection molded material with a thread-rolling screw (prior art);

(4) FIG. 2 shows a section through a plastic tube produced using a MuCell process, with a screw according to the present disclosure; and

(5) FIG. 3 shows a section through a plastic tube produced using a MuCell process, with a screw according to the present disclosure, in an additional embodiment.

DETAILED DESCRIPTION

(6) FIG. 1 shows a lateral view of a section through a prior art plastic tube of compact injection molding material, with a conventional thread-rolling screw. When used in plastics, the known, sharp-edged screw has the disadvantage of damaging the plastic on being screwed in by rupturing the screw-in openings or by stress cracking. Additionally, relatively high torque is required to drive the screw.

(7) In screw connections using MuCell injection molded parts the compact layer is destroyed by this type of screw, with the result that a conventional screw completely loses its hold in the remnants of the foam layer.

(8) FIG. 2 shows a lateral view of a section through a plastic tube 4 produced using a MuCell or other similar process, with a screw 3 according to the present disclosure. The outer shape of the screw 3 may be conical. The diameter of the screw is typically between 1 and 8 mm. The tip of the screw may be blunt or sharply pointed. The end of the screw here can have a short, pointed cutting portion that then transitions into a blunt shape. The transition may be continuous or abrupt.

(9) The tube 4 consists of an integral foam or a microcellular foam with a compact outer layer. Giving the screw a profile with blunt thread crests 5 and rounded thread roots enables the compact outer layer of thermoplastic foam to closely adapt its shape by plastic deformation and friction to the screw as it is being screwed in, without being cut. The material displacement or compaction is illustrated directly in FIG. 2. Cracking or rupturing of the tube 4 is avoided.

(10) For example, the transition between the flanks and the thread root here takes place section by section. As the first segment, the outer thread area in FIG. 2 has blunt threads with flank angles of 30-90 and preferably >60. The transition to the second section or segment can be a clean break. The second segment in the transition between the flank and the thread root represents a tangential transition with angles of 145-170. The third segment encompasses the thread root between two flanks and represents a segment of a circle with angles of 170-180.

(11) In another embodiment, FIG. 3 shows a section through a plastic tube 4 produced using a MuCell or a similar process, with a screw 3 according to the present disclosure before and after the driving procedure. The tube 4 shown represents a stress-relief tube that is fundamentally smaller than a compact tube. When it is screwed in, the screw 3 presses itself into the outer layer of the tube 4 or it penetrates all the way through the bottom of the tube.