DEVICE FOR CONNECTING A COMPOSITE PIPE WITH A METALLIC INNER LAYER

Description

[0001] The invention relates to a device for connecting a composite pipe with a metallic layer to a connection nipple of a press fitting, with a profiled connection nipple which receives at least one sealing ring in a sealing ring groove of the connection nipple, wherein the connection nipple has a profiled cylindrical base body, and wherein, viewed in the axial direction of the connection nipple, on both sides of the sealing ring groove with the sealing ring, a cylindrical jacket section of the base body adjoins which is delimited by a pipe receiving groove on at least one side facing away from the sealing ring groove and wherein the web width of the cylindrical jacket section is greater than or equal to the sealing ring groove width.

[0002] Such a device is known, for example, from DE29721224U1. Another alternative is disclosed in EP 0 390 747 B1. Pressing is currently a predominant connection technique in heating and plumbing installations. Copper, steel, or multi-layer composite pipes are pressed together using press fittings with the aid of hand-operated pressing tongs or electric pressing machines. Examples of such press fittings are known, for example, from EP 2 672 159 A, EP 2 154 411 A, and AT 507 566 A. Before pressing, the pipes are placed on the connection nipple. A sealing ring inserted into a sealing ring groove in the connection nipple subsequently ensures proper tightness. When the pipe connection is pressed onto the connection nipple, pipe material penetrates into the connection nipple profiles, such as grooves or claws, and thus ensures that the pipe is held securely on the connection nipple.

[0003] Known fittings are well suited for multi-layer composite pipes with a metallic core, particularly an aluminum core layer, and an inner and outer layer made of plastic. However, these fittings are not suitable for multi-layer composite pipes with a metallic inner layer, particularly a stainless steel inner layer and a plastic outer layer. During compression, the metallic inner layer, particularly a stainless steel layer, folds, forming open channels running axially and distributed around the circumference. These folds form in those areas where the pipe is deformed radially and mean that the fitting cannot be made tight even with the use of sealing rings, since each fold corresponds to an open flow channel. The more free volume there is between the connection nipple and the metallic inner layer, the greater the tendency for folds to form.Connection nipple profiles with sharp edges can also puncture and damage the very thin metallic inner layer of composite pipes. Composite pipes with a metallic inner layer are disclosed, for example, in DE 10 2005 023751 A1.

[0004] The invention is therefore based on the object of creating a simple device of the type described at the outset, which allows a tight press connection of a composite pipe with a metallic inner layer to a connection nipple of the device.

[0005] The invention solves the stated problem by providing a multi-layer composite pipe with a metallic inner layer and an outer layer made of plastic as the composite pipe and by providing the pipe receiving groove with a circular shape.

[0006] It is essential that the connection nipple has a profiled, cylindrical base body whose outer diameter is adapted as precisely as possible to the inner diameter of the composite pipe with its metallic inner layer. There should be just enough play or a transition fit between the composite pipe and the connection nipple to allow the pipe to be pushed onto the connection nipple without force. Viewed in the axial direction of the connection nipple, a cylindrical jacket section of the base body adjoins the sealing ring groove on both sides. These cylindrical jacket sections of the base body form a press fit for the pipe during pressing, which is held deformation-free in the area of ​​the cylindrical jacket sections. The pipe is therefore not radially compressed in these areas. The cylindrical jacket section of the base body is delimited on the side facing away from the sealing ring groove by a pipe receiving groove or, in turn, a sealing ring groove.Thus, two or more sealing ring grooves can be provided. However, at least one additional pipe receiving groove is always provided, which adjoins a cylindrical shell section of the base body and is preferably located between two cylindrical shell sections of the base body.

[0007] During pressing, pipe material penetrates this pipe receiving groove, which runs particularly around the circumference of the connection nipple. In this area of ​​the pipe receiving groove, the pipe can penetrate and form folds to prevent it from being pulled out. However, since a cylindrical jacket section of the base body is provided on both sides of the sealing ring groove, which forms a press fit for the pipe during pressing, the folds cannot form in these cylindrical jacket sections of the base body, thus ensuring the tightness of the device and a firm connection between pipe and connection nipple. The function of the sealing ring is fully retained. In addition, the cylindrical jacket sections of the base body, in conjunction with the metallic inner layer, act as a gap seal, which relieves the load on the sealing ring.In order to reliably prevent the formation of wrinkles in the cylindrical shell sections, the web width of the cylindrical shell section is greater than or equal to the sealing ring groove width.

[0008] To ensure a secure hold of the pressed pipe on the fixture, the pipe receiving groove width can be greater than or equal to the sealing ring groove width. According to the invention, the pipe receiving groove is circular. It is also recommended that the depth of the pipe receiving groove be smaller than the depth of the sealing ring groove. This also keeps wrinkling in the area of ​​the pipe receiving groove within acceptable limits.

[0009] If at least 15%, preferably at least 30%, of the connection nipple length is formed by a cylindrical shell section of the base body, a highly effective gap seal is created in addition to the sealing ring.

[0010] The drawing shows an example of the subject matter of the invention. Fig. 1 a connection nipple with attached pipe in pressed state above the pipe axis and in unpressed state below the pipe axis and Fig. 2 the device from Fig. 1 with partially cut-out connection nipple below the pipe axis.

[0011] The device according to the invention for connecting a composite pipe 1 with a metallic inner layer 2 and a plastic outer layer 3, which are connected via an adhesion promoter, to a connection nipple 4 of a press fitting 5 comprises a profiled connection nipple 4 which receives at least one sealing ring 6 in a sealing ring groove 7 of the connection nipple.

[0012] In order to be able to press composite pipes with a metallic inner layer 2 securely and tightly with the connection nipple 4, the connection nipple 4 has a profiled cylindrical base body 8, wherein, viewed in the axial direction of the connection nipple 4, on both sides of the sealing ring groove 7 with the sealing ring 6, a cylindrical jacket section 9 of the base body 8 adjoins, which is delimited on its side facing away from the sealing ring groove 7 by a pipe receiving groove 10.

[0013] In the illustrated embodiment, the web width s of the cylindrical shell section 9 is slightly larger than the sealing ring groove width b. The pipe receiving groove width r is in turn larger than the sealing ring groove width b. In addition, the pipe receiving groove 10 is circular, and the depth t / d of the pipe receiving groove tr is smaller than the depth td of the sealing ring groove 7.

[0014] The thickness of the metallic stainless steel inner layer of the composite pipe 1 is in particular between 70-100 µm. A polymer cover layer is bonded to this layer via an adhesion promoter. The polymer cover layer is, for example, between 1.5 and 3.5 mm thick, in particular between 2.00 and 2.50 mm thick, and is made of polyethylene with increased temperature resistance (PE-RT). The device for connecting the composite pipe 1 and the connection nipple 4 can be made of metal, in particular also stainless steel, or a suitable plastic.

Claims

1. Device for connecting a composite pipe (1) with a metallic layer to a connecting nipple (4) of a press fitting (5), with a composite pipe (1), with a profiled connecting nipple (4) which receives at least one sealing ring (6) in a sealing ring groove (7) of the connecting nipple, wherein the connecting nipple (4) has a profiled cylindrical base body (8), and wherein, viewed in the axial direction of the connecting nipple (4), on both sides of the sealing ring groove (7) with the sealing ring (6) a cylindrical jacket section (9) of the base body (8) adjoins, which is bounded on at least one side facing away from the sealing ring groove (7) by a pipe receiving groove (10) and wherein the web width (s) of the cylindrical jacket section (9) is greater than or equal to the sealing ring groove width (b), characterized, in that the composite pipe (1) is a multilayer composite pipe with a metallic inner layer (2) and an outer layer of plastic (3) and in that the pipe receiving groove (10) is circular in longitudinal section.

2. Device according to claim 1, characterized in that the pipe receiving groove width (r) is greater than or equal to the sealing ring groove width (b).

3. Device according to claim 1 or 2, characterized in that the depth (tr) of the pipe receiving groove is smaller than the depth (td) of the sealing ring groove (7).

4. Device according to one of claims 1 to 3, characterized in that at least 15%, preferably at least 30%, of the connecting nipple length is formed by a cylindrical jacket section (9) of the base body (8).