DE1284753B - Pipe screw connection for plastic pipes - Google Patents

Description

The invention relates to a pipe displacement for plastic pipes, consisting of a pipe socket with external thread, a union nut, an in the end of the plastic tube inserted stiffening tube and the plastic tube surrounding ring (pressure ring) between the pipe socket and the union nut, the weakening point formed as an annular groove between its axial ends and when tightening the union nut, narrowing its inside diameter is compressed and thus causes a deformation of the plastic pipe.

Pipe fittings for plastic pipes must take into account the Softness of the pre-material should be such that no excessive indentation of the material is created, as otherwise the plastic could be damaged.

Known (Swedish patent specification 86771) is a pipe screw connection in which the pressure ring can be deformed as far as desired, the deformation resistance not increasing significantly. It is therefore left to the fitter's feeling to effect the correct deformation by feeling. It is clear that this does not guarantee that the optimum sealing pressure will be achieved.

The invention is based on the object; a pipe union of the to train initially mentioned type so that after reaching the optimal sealing pressure further compression of the pressure ring is no longer possible.

This object is achieved in that the walls: the Annular groove in the non-deformed state (A b b.1) of the ring such an inclination to one another have that at least parts of these walls after the desired compression (A. b b. 2) touch each other and thus prevent further deformation of the ring.

If the ring is designed in this way, further deformation occurs so great a resistance against it that the ring by further tightening the Pipe fitting can no longer be deformed. With further deformation would have to firstly the touching wall parts come to flow and secondly inside Part of the cross-section strains occur. For this deformation work. would be but so great forces are necessary that the ring practically turns out to be no longer deformable rigid structure behaves. By appropriately dimensioning the ring groove, one can easily achieve that just such a large deformation up to the abutment of the; Ring groove walls occurs that the plastic pipe is indeed perfectly securely held, however has not yet suffered any harmful deformations.

In an advantageous embodiment of the invention, the annular groove a substantially triangular cross-section, with the groove base being rounded.

Two exemplary embodiments of the invention are given below the drawing described; in this A b b.1 shows the individual parts of a screw connection before tightening the union nut, A b b. 2 shows the state of the screw connection tightening the union nut and A b b. 3 shows a modified embodiment.

In A b b.1 the pipe socket with 1 and the union nut with 6 2 designated. The pipe socket has an external thread for screwing on the nut 2. The plastic pipe is denoted by 3 and pushed onto a reinforcing pipe 4. A ring 5, which has a circumferential groove 6 on its outside from has a substantially triangular cross-section rounded at the bottom. This groove is cut so deep that the diameter D is smaller at the bottom of the groove as the smallest diameter DK of the pressure edges 7 and 8 of the nut 2 or the connector 1, which attack the front edges of the ring. Its front edges are incidentally designed so that they are perpendicular to the pipe axis and above the diameter DK run obliquely to this inclined below this diameter. Against the above lying parts 9 put the pressure edges 7 and 8, while the inner Edges 10 as a stop for the tapered parts 11 and 12 of the nozzle 1 and the Serve mother 2.

A b b. 2 shows the ring after deformation. The inside 13 of the Ring here forms a convex surface instead of the cylindrical one and causes a corresponding deformation of the plastic pipe while avoiding axial stresses of the pipe. Likewise, there are no notch effects and excessive local deformations of the pipe.

When the union nut was tightened, the groove 6 was closed. To When the groove is closed, further deformation of the pressure ring is no longer possible. The shape of the groove wall 6 is chosen so that the groove is closed precisely when when the optimum sealing pressure is reached.

A b b. 3 shows a pipe union in which the nozzle 1 and the Nut 2 have the same dimensions as are usual for steel pipes, where the seal takes place by a so-called cutting ring. Here forms .the inner surface 11 .des Pipe socket 1 has a slim cone. A b b. 3 shows that the ring can also easily can be used for such screw connections, d. H. that these fittings too for connecting plastic pipes are suitable if a ring according to the invention is used.

Claims (2)

Claims: 1. Pipe screw connection for plastic pipes, consisting of a pipe socket with an external thread, a union nut, a stiffening pipe pushed into the end of the plastic pipe and a ring (pressure ring) which surrounds the plastic pipe and is located between the pipe socket and the union nut and which has a ring between its axial ends has a weakening point designed as an annular groove and when the union nut is tightened, its inner diameter is narrowed, thus causing deformation of the plastic pipe, characterized in that the walls of the annular groove (6) in the non-deformed state (A b b. 1) of the ring (5 ) have such an inclination to each other that at least parts of these walls touch each other after the desired compression (Ab b. 2) and thus prevent further deformation of the ring (5). 2. Pipe fitting according to Claim 1, characterized in that the annular groove (6) is essentially triangular Has a cross-section, where .the bottom of the groove is rounded.