The invention relates to a plastic sliding sleeve for a connecting piece in particular for a pressure-tight connection of a pipe to the connecting piece. The invention relates further to a connecting fitting having a connecting piece and such a sliding sleeve.
A plastic sleeve for a connecting piece for connecting pipes is known through prior public use. In case of the known connecting fitting, under extreme conditions, an undesired axial relative movement between the sliding sleeve on the one side and the press-fitted or clamped pipe end section on the other side takes place.
It is an object of the present invention to develop a plastic sliding sleeve of the aforementioned type in such a manner that such an undesired relative movement is avoided in practice.
This object is solved according to the invention by a plastic sliding sleeve with the features specified in the claim 1.
It was found according to the invention that a circumferential rib protruding from the inner diameter results in the desired protection against a relative movement of the sliding sleeve with respect to the pipe end section. The circumferential rib can penetrate into the outer wall of the pipe end piece. At the same time, such a circumferential rib allows the production of the sliding sleeve as injection molding component without the need of a complicated design of an injection molding tool because the circumferential rib can be formed in the region of a core parting plane of the injection molding tool which is necessary anyway. In this case, the injection mold remains free of undercuts.
This represents a significant production cost advantage in comparison to inner profiles of sliding sleeves having undercuts as they are known, for example, from DE 38 13 815 C2. Such a design of the injection molding tool in which the circumferential rib is generated by complementary chamfers on the front end regions of the mold halves opposing each other in the core parting plane can even result in an improved tool life of the injection molding tool because by chamfering the mold halves, an improved wear resistance of the front end wall of the mold halves is exhibited in the region of the core parting plane.
Cross-sectional shapes according to claim 2 can be manufactured cost-effectively.
An edge-free cross-sectional profile according to claim 3 facilitates sliding the sliding sleeve onto the pipe end piece.
Dividing the circumferential rib into sections according to claim 4 results in easing the sliding, in particular if the pipe onto which the sliding sleeve is slid does not have a perfectly round outer wall. By rotating the sliding sleeve on the pipe, a position can be found in which the circumferential rib sections face regions of the pipe which have a reduced diameter with respect to other circumferential regions. The circumferential rib sections can be present on the same axial height, but, in addition to the offset in the circumferential direction, can also be arranged axially offset to each other. Alternatively to the dividing into circumferential rib sections, a continuously extending circumferential rib in particular with a constant cross-section can be provided.
A continuous protrusion contour according to claim 5 prevents the sliding sleeve from getting caught during sliding in the region of circumferential steps on the outer wall of the pipe.
A constant protrusion according to claim 6 can be manufactured in a simple manner.
Surprisingly, it was found that small protrusions according to claim 7 are sufficient for generating the desired axial locking. In particular, the protrusion can be at most 150 μm, at most 100 μm, at most 80 μm or even at most 30 μm.
The advantages of a connecting fitting according to claim 8 correspond to the ones which were described above in reference to the sliding sleeve.
Exemplary embodiments of the invention are illustrated in more detail hereinafter by means of the drawing. In the figures:
The sliding sleeve 3 is made of plastic. In the illustrated embodiment, the sliding sleeve 3 is made of polyvinylidene fluoride (PVDF). Another high-strength polymer material can also be used for forming the sliding sleeve 3. The connecting piece 2 can also be made of PVDF. In the illustrated preferred embodiment, the connecting piece 2 is made of polyphenylsulfone (PPSU). Alternatively, the connecting piece 2 can also be made of metal, for example, of brass or steel. The pipe 4 can involve in particular a reinforced plastic pipe or a metal-plastic composite pipe. Material examples for the pipe 4 are cross-linked polyethylene (PE-X) or polybutylene (PB).
The connecting piece 2 is shown in
On its outer circumferential wall, facing the inner wall of the slid-on pipe end piece 5, the connecting piece 2 has a plurality of circumferential ribs 7 which are axially spaced apart from each other. At its free end facing away from the stop collar 6, the outer circumference of the connecting piece 2 first increases in steps in an end region 8 and then extends conically tapered towards the end, which makes it easier to slide the pipe end piece onto the connecting piece 2.
The sliding sleeve 3 is illustrated in more detail in the
Depending on the embodiment of the sliding sleeve 3, the extension of the conical sections 11 along a longitudinal axis 12 of the sliding sleeve 3 (which axis represents, at the same time, a rotational axis of symmetry of the sliding sleeve) can vary. Also, the cone angle of the conical sections 11 can be different in different embodiments of the sliding sleeve 3.
The middle section 10 of the inner wall of the sliding sleeve 3 has a circumferential rib 13 which protrudes over the remaining inner wall towards the inside, thus towards the longitudinal axis 12. In the embodiment according to
The circumferential rib 13 has a constant protrusion A in the circumferential direction over the middle section 10 of the inner wall of the sliding sleeve 3.
The sliding sleeve 3 is a plastic injection molded component. In
With respect to its axial position along the longitudinal axis 12, the circumferential rib 13 does not run at the central position of the middle section 10 of the inner wall of the sliding sleeve 3, but off-center near a transition 15 between the middle section 10 and the conical section 11 on the left in
The enlarged detail according to
A radial distance between the sliding sleeve 3 and the connecting piece 2 is smaller than a wall thickness of the pipe end piece 5 so that the latter is clamped or press-fitted between the connecting piece 2 and the sliding sleeve 3. Here, the circumferential rib 13 penetrates (see
As an alternative to the triangular cross-section, the circumferential rib 13 can also have another cross-sectional shape, for example a rectangular cross-section or an edge-free cross-section.
The connecting fitting 1 is designed for a pipe 4 with the nominal width 40 mm. Alternative configurations for other nominal widths differ from the described structure merely in their dimensions and, if necessary, in the ratio of the axial extensions of the middle section 10 to the conical sections 11 of the inner wall.
The sliding sleeve 16 has a circumferential rib 17 which, with respect to its radial extension, is illustrated greatly enlarged and not to scale.
The circumferential rib 17 is divided into three circumferential rib sections 18. Each circumferential rib section 18 covers a circumferential angle of 90° about the longitudinal axis 12. Between the circumferential rib sections 18 there is in each case one rib-free circumferential section 18a having a circumferential extension of 30° . Thus, the three circumferential rib sections 18 are offset to each in the circumferential direction and are at the same height in the axial direction. In a non- illustrated embodiment, the circumferential rib sections 18 can also be arranged offset to each other in the axial direction.
In the circumferential direction about the longitudinal axis 12, the circumferential rib sections 18 have a continuously running protrusion over the middle section 10 of the inner wall of the sliding sleeve 16. Viewed in the circumferential direction from the respective middle of a circumferential rib section 18, this protrusion, starting at a central maximum of the protrusion with a protrusion of, for example, 80 μm, decreases continuously in the circumferential direction towards the edges of the circumferential sections 18 until it reaches zero.
The circumferential rib sections 18 are generated during injection molding in correspondingly complementarily shaped intermediate spaces between the mold halves in the region of the core parting plane 14. Said intermediate spaces are shaped by obliquely chamfering the mold halves' front walls that oppose each other in the core parting plane 14.
Dividing the circumferential rib 17 into the circumferential rib sections 18 makes it easier to slide the sliding sleeve 16 onto the pipe 4, in particular if the pipe 4 is not perfectly round with respect to its outer cross-section.
Instead of three circumferential rib sections 18 it is also possible to provide two, four, five or even more circumferential ribs sections.
A different protrusion of the circumferential rib sections 18 over the middle section 10 of the inner wall of the sliding sleeve 16 is also possible, for example, a protrusion of 30 μm.
In a non-illustrated embodiment and alternatively to the configuration of the circumferential rib sections 18 according to the
The sliding sleeve 19 comprises a circumferential rib 20 which, corresponding to the circumferential rib 17 of the embodiment according to the
The maximum protrusion A of the circumferential rib sections 21 over the middle section 10 of the sliding sleeve 19 of the embodiment according to the
Number | Date | Country | Kind |
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20 2008 008 554.3 | Jun 2008 | EP | regional |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP09/04346 | 6/17/2009 | WO | 00 | 12/22/2010 |