Abstract
A screw element for connecting pipes, preferably automotive pipes, wherein the thread is provided with a first coating in at least one area, and wherein at least one thread-free contact surface is provided with a second coating in at least one area, characterized in that the first coating comprises at least 40 wt %, preferably at least 50 wt % and especially at least 60 wt % of at least one epoxy compound, in particular at least one phenol-based epoxy compound and at least one lubricant.
Claims
1. A screw element for connecting pipes, wherein the screw element has at least one thread and at least one thread-free contact surface, wherein the thread is provided with a first coating in at least one area, wherein the at least one thread-free contact surface is provided with a second coating at least one area, and wherein the first coating comprises at least 40 wt % and at least one lubricant.
2. The screw element according to claim 1, wherein the first coating has a first friction coefficient .sub.1, and the second coating has a second friction coefficient .sub.2, wherein the first friction coefficient .sub.1 is greater than the second friction coefficient .sub.2.
3. The screw element according to claim 1, wherein the ratio of the first friction coefficient .sub.1 of the first coating to the second friction coefficient .sub.2 of the second coating (.sub.1/.sub.2) is between 1.1 and 4.0.
4. The screw element according to claim 1, wherein a surface of the screw element, is provided substantially completely with the first coating, and the second coating is applied to the first coating in the at least one area of the at least one thread-free contact surface.
5. The screw element according to claim 1, wherein the screw element is a threaded bolt or a screw fitting, which has a thread configured as an external thread.
6. The screw element according to claim 5, wherein a front end of the threaded bolt or the screw fitting has the at least one thread-free contact surface, which is coated with the second coating in the at least one area.
7. The screw element according to claim 1, wherein the layer thickness of the first coating is 2 to 25 m.
8. The screw element according to claim 1, wherein the lubricant in the first coating is a polymer material and the at least one lubricant is selected from the group of polyolefin, paraffin, waxy material, polyamide, and fluoropolymer.
9. The screw element according to claim 1, wherein the lubricant is present in the amount of 4 to 20 wt % in the first coating.
10. The screw element according to claim 1, wherein the first coating contains 3 to 25 wt %, of at least one filler material.
11. The screw element according to claim 1, wherein the layer thickness of the second coating is 1 to 100 m.
12. The screw element according to claim 1, wherein the layer thickness of the second coating is greater than the layer thickness of the first coating.
13. The screw element according to claim 1, wherein the second coating comprises at least one polymer and at least one lubricant.
14. The screw element according to claim 1, wherein the second coating contains at least one lubricant selected from the group of molybdenum sulfide, graphite, and polytetrafluoroethylene.
15. The screw element according to claim 1, wherein the first coating contains 3 to 20 wt % aluminum.
16. The screw element according to claim 1, wherein the screw element is coated with at least one anti-corrosion coating arranged beneath the first coating.
17. The screw element according to claim 1, wherein at least one passivation layer is applied to the screw element, wherein the passivation layer is arranged beneath the first coating, and wherein the passivation layer is arranged between the anti-corrosion coating and the first coating.
18. A pipe connecting device for connecting pipes having a screw element according to claim 1, wherein a pipe is connected to the screw element and wherein the screw element is configured for connection to a connecting element by means of a screw connection.
19. The pipe connecting device according to claim 18, wherein the screw element is a screw fitting with an axial bore, said axial bore having a piped passing therethrough, wherein the pipe has a flanged on its pipe end, and wherein the thread-free contact surface of the screw fitting, which is provided with the second coating, is in contact with the flange.
20. The screw element according to claim 1, wherein the first coating comprises at least 50% wt of at least one epoxy compound, and wherein the at least one epoxy compound is a phenol-based epoxy compound.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The present disclosure is described in greater detail below on the basis of drawings, which illustrate just one exemplary embodiment. In schematic diagrams:
[0024] FIG. 1 shows a longitudinal section through a pipe connecting device with a screw element according to the present disclosure in the form of a screw fitting,
[0025] FIG. 2 shows a section through a screw element according to the present disclosure designed as a screw fitting, and
[0026] FIG. 3 shows schematically the layer sequence on a screw element according to the present disclosure in the area of a thread-free contact surface.
DETAILED DESCRIPTION
[0027] FIG. 1 illustrates a screw element according to the present disclosure, designed as a screw fitting 1 in a pipe connecting device. In this exemplary embodiment, a pipe 2 passes through the screw fitting 1 in the axial direction, and the pipe 2 has a front element on one end, designed as a flange 10. It is preferably within the scope of the present disclosure in this exemplary embodiment that this is a metal flange 10, which is preferably molded in one piece on the pipe end of the pipe 2. In this exemplary embodiment, the screw fitting 1 is screwed into a connecting element designed as a connecting block 12. Expediently and in this exemplary embodiment, the connecting block 12 here has an integrated second pipe 13. The screw fitting 1 presses the flange 10 with its front sealing surface 11 onto a connecting surface 14 of the connecting block 12. The screw fitting 1 is also screwed into a blind hole 15 in the connecting block 12 with its thread 3, which is designed as an external thread. The thread 3 on the screw fitting 1 is provided with the first coating 7 according to the present disclosure, wherein this first coating 7 preferably has a first friction coefficient .sub.1. The thread-free contact surface 4 is formed on the front end of the screw fitting 1, and this thread-free contact surface 4 in this exemplary embodiment is preferably provided with a second coating 8, which preferably has a second friction coefficient .sub.2. The first friction work .sub.1 is larger than the second friction coefficient .sub.2 in the recommended version and in the exemplary embodiment.
[0028] In the exemplary embodiment according to FIG. 1, the flange 10 of the pipe end of the pipe 2 is designed as an F flange, whose flange rear side is arranged transversely or perpendicular to the longitudinal axis L of the pipe. The front end of the screw fitting 1, which is provided with the second coating 8, has a complementary surface section 17 arranged perpendicular to the longitudinal axis L of the pipe and in form-fitting contact with the flange rear side of the F flange. In tightening the screw fitting 1, the screw fitting 1 with its thread-free contact surface 4 is pressed against the flange 10, i.e., against the flange rear side of the flange 10. Likewise, the front sealing surface 11 of the flange 10 is pressed against the connecting surface 14 of the connecting block 12. This creates a fluid-tight connection between the pipe 2 and a line 13 integrated into the connecting block 12.
[0029] FIG. 2 shows a screw element according to the present disclosure, designed as a screw fitting 1. As already explained above, this screw fitting 1 has a thread 3 and a thread-free contact surface 4 on its front end. The thread 3 is coated with the first coating 7 having the first friction coefficient .sub.1 and is preferably coated completely, i.e., on the complete circumference in this exemplary embodiment. In the recommended version and in the exemplary embodiment, the entire screw fitting 1, i.e., the entire surface of the screw fitting 1 is first provided with the first coating 7 having the first friction coefficient .sub.1. In this exemplary embodiment, the second coating 8 with the second friction coefficient .sub.2 on the thread-free contact surface 4 on the front end of the screw fitting 1 is preferably applied to the first coating 7. The first friction coefficient .sub.1 of the first coating 7 here is expediently greater than the second friction coefficient .sub.2 of the second coating 8.
[0030] FIG. 3 illustrates a very preferred layer sequence for the coating of the screw element or screw fitting 1 according to the present disclosure, namely in the area of the thread-free contact surface 4 on the front end of the screw fitting 1. First, a zinc-nickel layer or a zinc-nickel anti-corrosion coating 9 is applied to the base body 5, i.e., to the metallic base body 5 of the screw fitting 1. The entire screw element or screw fitting 1 according to the present disclosure is preferably provided with this zinc-nickel anti-corrosion coating 5. According to the preferred embodiment of the present disclosure and in the exemplary embodiment, a passivation layer 6, which is expediently arranged on the entire surface of the screw fitting 1 or on the zinc-nickel anti-corrosion coating 9, is provided on the zinc-nickel anti-corrosion coating 9. In this exemplary embodiment, the first coating 7 according to the present disclosure, having the first friction coefficient .sub.1, is preferably applied to the passivation layer 6, in particular over the entire surface of the screw fitting 1. In the area of the thread-free contact surface 4 on the front end of the screw fitting, the second coating 8 having the second friction coefficient .sub.2 in this exemplary embodiment is expediently applied to the first coating 7 having the first friction coefficient .sub.1. In the exemplary embodiment according to FIG. 3, the base body 5 of the screw element or the screw fitting 1 according to the present disclosure is thus provided with a total of four layers in the area of the thread-free contact surface 4 on the front end of the screw fitting 1, namely the zinc-nickel anti-corrosion coating 9, the passivation layer 6, the first coating 7 and the second coating 8.
