Plastic dowel for fastening of a rail and combination of such a plastic dowel and a rail screw

Abstract

The present invention relates to a plastic dowel for the fastening of a rail on a solid substrate. The plastic dowel includes an opening, an interior, a shank section, and a holding section, which provides at least one circumferential projection around its circumference. The at least one projection protrudes in a radial direction whereby the upper flank of the projection of the holding section assigned to the dowel opening is aligned at an angle of 903 in relation to a longitudinal axis of the plastic dowel.

Claims

1. A plastic dowel for fastening a rail on a solid substrate, with a dowel opening formed at an end face of the plastic dowel for insertion of a rail screw into the plastic dowel, with a dowel interior space enclosed by the plastic dowel, with a shank section which connects to the dowel opening of the plastic dowel, and with a holding section which connects to the shank section of the plastic dowel and which is provided on an outer side with at least one projection running around its circumference and protruding in a radial direction which, in a finished installed state, engages with a material of the solid substrate enclosing the plastic dowel, wherein the projection of the holding section is formed as an external thread and an upper flank of the projection of the holding section is orientated at an angle of 903 in relation to a longitudinal axis of the plastic dowel, wherein the dowel has an internal thread on an inner side, and a flank of the internal thread is orientated at an angle of 903 in relation to the longitudinal axis of the plastic dowel.

2. The plastic dowel according to claim 1, wherein an inner circumferential face or outer circumferential face of the shank section is smooth.

3. The plastic dowel according to claim 1, wherein a second holding section connects to a first holding section of the plastic dowel, in said second holding section also at least one radially outwardly protruding projection is formed or a respective internal thread is continued, and in that a flank of the projection or of the internal thread in the second holding section is arranged at an angle of more than 93 in relation to the longitudinal axis of the plastic dowel or is rounded.

4. The plastic dowel according to claim 1, wherein the upper flank in a first holding section is orientated in each case at an angle of 901 in relation to the longitudinal axis of the plastic dowel.

5. The plastic dowel according to claim 1, wherein a transition from an underside of a flank of the projection or of an upper flank of the internal thread to a respectively assigned circumferential face of the plastic dowel has a rounded form.

6. The plastic dowel according to claim 1, wherein a lower flank of the projection or of the internal thread has a convex domed form.

7. The plastic dowel according to claim 1, wherein a transition from an underside of the upper flank of the projection or of an upper flank of the internal thread of a second holding section to the flank of an associated projection or of a second holding section to the internal thread has a rounded form.

8. The plastic dowel according to claim 1, wherein on an outer side of the plastic dowel in the area of a first holding section at least one web connected to the shank section and extending in a longitudinal direction of the plastic dowel is formed, the width of said web in a base area being equal to at least a fifteenth of a circumference of the plastic dowel, said web crossing the projection of the first holding section and an apex face of said web extending at most to an imagined prolongation of the envelope of the shank section.

9. The plastic dowel according to claim 8, wherein two or more webs are provided which are arranged at same angular intervals about the longitudinal axis of the plastic dowel.

10. The plastic dowel according to claim 1, wherein in an area of a first holding section a groove-shaped recess extending in a longitudinal direction of the plastic dowel is formed in an inner circumferential face.

11. The plastic dowel according to claim 10, wherein the recess is formed in an area of a web, the web provided in each case on the outer side of the plastic dowel.

12. The plastic dowel according to claim 1, wherein a recess intersects the internal thread.

13. A combination of a rail screw and a plastic dowel formed according to claim 1, wherein the rail screw has a screw head and a threaded screw shank following the screw head in a longitudinal direction of the rail screw, a circulating screw thread being formed on said screw shank, wherein an upper flank of the screw thread is orientated at an angle of 903 in relation to a longitudinal axis of the rail screw.

14. The combination according to claim 13, wherein the upper flank is orientated at an angle of 901 in relation to the longitudinal axis of the rail screw.

15. The combination according to claim 13, wherein a core of the rail screw tapers conically towards a screw tip, at least in an area in which the screw thread is present.

16. The combination according to claim 13, wherein the screw thread extends over an entire length of the screw shank in a radial direction as far as a cylindrically formed envelope of the screw shank.

17. The combination according to claim 13, wherein, between the screw head and the thread section, the rail screw has a shank section whose circumferential face is smooth.

18. The combination according to claim 13, wherein an envelope of a circumferential face of the shank section coincides with a cylindrical envelope of the thread section.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is explained in detail hereinafter with reference to exemplary embodiments. In the figures:

(2) FIG. 1 shows a screw-plastic dowel combination in a perspective exploded view;

(3) FIG. 2 shows the plastic dowel of the screw-plastic dowel combination in perspective view;

(4) FIG. 3 shows the plastic dowel in a first side view;

(5) FIG. 4 shows the plastic dowel in a longitudinal section along the line of intersection A-A shown in FIG. 3;

(6) FIG. 5 shows the plastic dowel in a position rotated through 90 about the longitudinal axis of the plastic dowel compared with the view in FIG. 3 in side view;

(7) FIG. 6 shows the rail screw of the screw-plastic dowel combination in side view;

(8) FIG. 7 shows the rail screw according to FIG. 6 in a longitudinal section;

(9) FIG. 8 shows the screw-plastic dowel combination with rail screw inserted in the plastic dowel and plastic dowel shown in longitudinally cutaway view.

DETAILED DESCRIPTION OF THE INVENTION

(10) The screw-plastic dowel combination K comprises a plastic dowel 1 and a rail screw 2 made from a steel in a conventional manner.

(11) The plastic dowel 1 has a dowel opening 3 delimited by an edge configured in the manner of a collar, a shank section 4 which adjoins the dowel opening 3 in the longitudinal direction LR of the plastic dowel 1, a first holding section 5 which follows the shank section in the longitudinal direction LR of the plastic dowel 1, a second holding section 6 which adjoins the first holding section 5 in the longitudinal direction LR, a dowel tip 7 and a dowel interior 8 which is delimited by the shank section 4 and the holding sections 5, 6. A through-opening 9 aligned coaxially to the longitudinal axis L of the plastic dowel 1 is formed in the dowel tip 7, via which moisture entering into the plastic dowel 1 can flow out.

(12) The outer circumferential surface 10 of the shank section 4 is configured to be cylindrical and smooth so that the circumferential surface 10 coincides with the cylindrical envelope U of the shank section 4.

(13) A projection 11 in the form of an external thread is formed on the first holding section 5, which projection runs around the first holding section 5 in a uniform pitch starting from the boundary between the shank section 4 and the first holding section 5 in the direction of the dowel tip 7. The projection 11 here has an upper flank 12 assigned to the dowel opening 3, which is aligned at an angle 1 of 90 relative to the longitudinal axis L. Accordingly the upper flank 12 encloses the same right angle 1 with the adjoining circumferential wall surface 13 of the plastic dowel 1 aligned axially parallel to the longitudinal axis L. For production technology reasons and in order to avoid a notch effect, the transition 14 between the upper flank 12 and the relevant wall surface 13 is rounded in the manner of a throat.

(14) At its free edge facing away from the circumferential wall surface 13, the upper flank 12 of the projection 11 adjoins an apex surface 15 of the projection 11 which is aligned substantially axially parallel to the longitudinal axis L of the plastic dowel 1. The apex surface 15 here also lies on the cylindrical envelope U of the shank section 4.

(15) The lower flank 16 of the projection 11 assigned to the dowel tip 7 adjoins the apex surface 15. The lower flank 16 of the projection 11 is convexly outwardly rounded here and goes over in a rounded throat into the circumferential wall surface 13 of the plastic dowel 1.

(16) In the region of the holding section 5 the projection configured in the manner of an external thread is interrupted by two webs 17, 18 which extend opposite to one another as an extension of the shank section 4 of the height H1 of the first holding section 5. The webs 17, 18 have a width in their base region which corresponds to approximately 14% of the circumference of the shank section 4. The webs 17, 18 are outwardly curved in a semicircular shape in cross-section, the webs being flattened in their apex region 19 according to the radius of the envelope U. The apex region 19 also lies on the envelope U of the shank section 4 so that the apex region 19 of the webs 17, 18 goes over into the circumferential surface 10 of the shank section 4 in a smooth manner.

(17) In the region of the second holding section 6 the projection 11 of the first holding section 5 configured as an external thread is continued as projection 20 which is also configured as a rounded external thread. Accordingly, the flank of the external thread projection 20 assigned to the dowel opening 3 goes over in a continuous convex outwardly curved curve into the apex region of the projection 20 which in the same way goes over into the flank of the external thread projection 20 associated with the dowel tip 7. In this case, the apex of the projection 20 lies on the cylindrical envelope of the plastic dowel 1.

(18) An internal thread 21 is formed in the inner circumferential surface 23 of the plastic dowel 1 which extends over the first and the second holding section 5, and is formed in the same shape over both holding sections 5, 6.

(19) The upper flank 22 of the internal thread 21 assigned to the dowel opening 3 is in this case aligned at an angle 2 of 90o in relation to the longitudinal axis L of the plastic dowel 1 so that the upper flank 22 encloses the same right angle 2 with the inner circumferential surface 23 of the plastic dowel 1 aligned axially parallel to the longitudinal axis L. The transition 24 between the inner circumferential surface 23 and the upper flank 22 of the internal thread 21 is also rounded here.

(20) At the same time, the upper flank 22 goes over into a continuously convex outwardly curved apex region 25 which is in turn adjoined by a concavely curved lower flank 26 assigned to the dowel tip 7. The lower flank 26 runs out smoothly into the inner circumferential surface 23 of the plastic dowel 1.

(21) In the region of the first holding section 5, the internal thread 21 is interrupted by groove-shaped recesses 27 which extend opposite to the webs 17, 18 on the inner side of the plastic dowel 1 via the height H1 of the first holding section 5. Of the recesses 27 only the recess 27 assigned to the web 18 can be seen as a result of the selected view in FIG. 4. Like the webs 17, 18 the recesses 27 also contribute, in the sense of a lengthening of the smooth inner circumferential surface of the shank section 4, to the minimizing of the spread of transverse forces starting from the first holding section 5 into the solid substrate surrounding the plastic dowel 1 in the installed state.

(22) The shape and dimensions of the upper flank 22, the apex region 25 and the lower flank 26 of the internal thread 21 are designed so that rail screws 2 having differently shaped threads can be screwed into the plastic dowel 1.

(23) Preferably however a rail screw 2 of the type described here is used in the screw-plastic dowel combination K. Such a rail screw 2 has a screw head 30, a shank section 31 connected to the screw head 30 in the longitudinal direction LR of the rail screw 2 and a thread section 32 connected to the shank section 31 in the longitudinal direction LR which carries an external thread 33.

(24) The cylindrically shaped shank section 31 has a smaller diameter than the screw head 30 and a smooth circumferential surface 34 in a manner known per se. It extends over about 24% of the height HS of the rail screw 2.

(25) In the region of the thread section 32 the core 35 of the rail screw 2 tapers in the direction of the tip 36 of the rail screw 2. At the same time, in an upper region 37 adjoining the shank section 31 which occupies about a quarter of the length of the thread section 32, the core 35 initially tapers conically with a greater pitch before tapering conically in the direction of the screw tip 36 with uniform pitch over the remaining length of the thread section 32.

(26) The upper flank 38 of the external thread 33 assigned to the screw head 30 and also the lower flank 39 of the external thread 33 assigned to the screw tip 36 are each aligned at an angle 133 of 90o in relation to the longitudinal axis L of the rail screw. At the same time, the apex region 40 of the external thread 33 connecting the flanks 38, 39 describes a convexly outwardly curved semicircle. The apex of the apex region 40 in this case lies on the cylindrical envelope US of the shank section 31 of the rail screw 2.

(27) As a result of the core 35 tapering conically in the direction of the screw tip 36, when the rail screw 2 is screwed into the plastic dowel 1 an enlarged empty space 41 is formed in the lower region of the dowel interior 8 assigned to the dowel tip 7 in which dirt entering into the plastic dowel 1 can enter without hindering the screwing in and out of the rail screw 2.

(28) The shaping according to the invention has the result that in the installed state in the region of the first holding section 5, forces aligned at most to a minimal extent transversely to the longitudinal axis L of the plastic dowel 1 are guided away from the plastic dowel in the radial direction R into the material surrounding the plastic dowel 1 of the solid substrate accommodating the plastic dowel 1. Accordingly the risk of the formation of cracks in this region is minimised in the same way as in the region of the shank section 4 over the smooth circumferential surface 10 whereof no transverse forces are guided into the material surrounding the plastic dowel 1.

REFERENCE LIST

(29) 1 Plastic dowel 2 Rail screw 3 Dowel opening 4 Shank section of plastic dowel 1 5 First holding section of plastic dowel 1 6 Second holding section of plastic dowel 1 7 Dowel tip of plastic dowel 1 8 Dowel interior of plastic dowel 1 9 Through opening of dowel tip 7 10 Outer circumferential surface of shank section 4 11 Projection formed as external thread on the outer side of the first holding section 5 12 Upper flank of projection 11 13 Circumferential wall surface of plastic dowel 1 14 Transition between the upper flank 12 and the circumferential wall surface 13 15 Apex surface of projection 11 16 Lower flank of projection 11 17, 18 Webs 19 Respective apex region of webs 17, 18 20 Projection of second holding section 6 configured as rounded external thread 21 Internal thread of plastic dowel 1 22 Upper flank of internal thread 21 assigned to dowel opening 3 23 Inner circumferential surface of plastic dowel 1 24 Transition between the inner circumferential surface 23 25 Apex region of internal thread 21 26 Lower flank of internal thread 21 assigned to dowel tip 7 27 Groove-shaped recesses 28 Smooth inner circumferential surface of shank section 4 30 Screw head of rail screw 2 31 Shank section of rail screw 2 32 Threaded section of rail screw 2 33 External thread of rail screw 2 34 Circumferential surface of shank section 31 35 Core of rail screw 2 36 Tip of rail screw 2 37 Region of threaded section 31 adjoining step section 31 38 Upper flank of external thread 33 assigned to screw head 30 39 Lower flank of external thread 33 assigned to screw tip 36 40 Apex region of external thread 33 41 Empty space in plastic dowel 1 when screw is screwed in H1 Height of first holding section 5 HS Height of rail screw 2 K Screw-plastic dowel combination L Longitudinal axis of plastic dowel 1 LR Longitudinal direction R Radial direction 1 Angle enclosed between the longitudinal axis L or the circumferential wall surface 13 aligned coaxially to the longitudinal axis L and the upper flank 12 of the projection 11 2 Angle enclosed between the longitudinal axis L or the inner circumferential surface 23 of the plastic dowel 1 aligned coaxially to the longitudinal axis L 3 Angle at which the upper and the lower flank 38, 39 of the external thread 33 are each aligned in relation to the longitudinal axis LS of the rail screw 2 U Cylindrical envelope U of the shank section 4 and the holding sections 5, 6 US Envelope of the shank section 31