Connecting arrangement for a pipe union

Abstract

The invention relates to a connecting arrangement, comprising a pipe piece (1), a connecting body (2) and a union nut (3) for connecting the pipe piece (1) to the connecting body (2), wherein the connecting body (2) has a first cylindrical bore (21) for receiving the pipe piece (1) and a second cylindrical bore (22) which has a reduced diameter and adjoins the first cylindrical bore (21), wherein a pressing surface (23), which is positioned transversely to the first cylindrical bore (21), is provided on the end face, the union nut (3) has a first cylindrical bore (31) for receiving the pipe piece (1), which bore adjoins a second bore (32) which has an enlarged diameter, wherein an internal thread (33) is arranged for being screwed onto an external thread (24) is arranged on the connecting body (2) for this purpose, the pipe piece (1) has a circumferential outwardly projecting section (11) at a distance from its end, wherein the diameter-enlarged second bore (32) of the union nut (3) is cylindrical, as a result of which a stop surface (34) which is positioned transversely with respect thereto is formed, and wherein the outwardly projecting section (11) is formed by a fold of the pipe piece (1) and has two parallel bearing surfaces lying opposite one another for bearing against the stop surface (34) of the union nut (3) on the one side and against the end-face pressing surface (23) of the connecting body (2) on the other side, between which the section (11) is clamped in the mounted state.

Description

[0001] Lawyer's file 25244

[0002] December 4, 2025

[0003] Connection arrangement for a pipe fitting

[0004] The invention relates to a connection arrangement for connecting a cylindrical, thin-walled pipe section to a connecting body according to claim 1.

[0005] Pipe fittings can be essentially divided into three types: cutting ring fittings, tube forming system fittings, and compression fittings. In many hydraulic applications, classic cutting ring fittings are now being replaced by tube forming systems, as described, for example, in EP 2 162 662 B1. Here, as with a cutting ring system, a 45° cone is formed on the pipe, which interacts with a 45° chamfer in the mating nut to secure the pipe in the fitting body. Since the well-known tube forming system is a general hydraulic system also used in high-pressure applications, it is designed for thick-walled hydraulic pipes. The strength of these pipes allows the necessary, sometimes high, torques to be applied to ensure the proper function and leak-tightness of the fitting.

[0006] During the manufacture of railcars and carriages for trains, trams, and subways / light rail systems, long pipelines are installed both beneath and within the vehicles. These pipelines supply and distribute fluids to the braking, air conditioning, and hydraulic systems within the train. The extensive pipelines used for braking systems, in particular, operate with air at a low pressure of 12 bar. Weight reduction to save energy is an increasingly important requirement in the design of vehicles, especially railcars. The low pressure allows for the use of very thin-walled pipes. Cutting ring and compression ring fittings are primarily used in this application.The tube forming system in its known design has only limited stability due to the very thin walls, which leads to an undesirably high degree of compliance when applying torques.

[0007] This is where the present invention comes in. The invention is based on the objective of providing a connection arrangement for attaching a cylindrical, thin-walled pipe section to a connecting body, which is designed to minimize weight and avoids any flex when torque is applied. According to the invention, this objective is achieved by a connection arrangement with the features of claim 1.

[0008] The invention provides a connection arrangement for attaching a cylindrical, thin-walled pipe section to a connecting body. This arrangement is designed to minimize weight and avoids flexion when torque is applied. The outwardly projecting section is formed by folding the pipe section, and the union nut has a 90° contact surface (in contrast to the 45° contact surface found in prior art). This design provides good support for the pipe, which is clamped flat between this contact surface and the end-face contact surface of the connecting body. The connecting body can be configured as a connector for two pipes or as a T-piece. Connections for the further (when configured as a connector) or...The other pipes (when designed as a T-piece) can be designed in the same way or in a known way, for example as a threaded connection.

[0009] In a further development of the invention, the outwardly projecting section (1 1 ) is arranged orthogonally to the pipe axis of the pipe section, wherein the transition between the outer surface of the pipe section and the contact surface of the outwardly projecting section facing the stop surface of the union nut has a circular arc cross-section with a radius R, wherein the transition from the first bore to the second bore with an increased diameter has a circular arc cross-section with a radius substantially corresponding to the radius R. This results in a continuous, flat contact between the contact surface of the outwardly projecting section and the pipe section adjoining it, thereby further increasing the stability of the connection. Particularly good flat contact can be achieved by selecting the largest possible radius of the transition. This, in particular, avoids notch effects.

[0010] In this embodiment of the invention, the outer diameter of the pipe section essentially corresponds to the inner diameter of the first cylindrical bore of the union nut, which in turn essentially corresponds to the inner diameter of the first cylindrical bore of the connecting body into which it is inserted. This results in a uniform pipe diameter on both sides of the outwardly projecting section, thereby further preventing potential cracks caused by stress concentrations. Moreover, this design provides good support for the pipe on both sides of the outwardly projecting section.

[0011] In a further embodiment of the invention, the connecting body has a conical bore extending from its contact surface, to which the first cylindrical bore adjoins and with which it is aligned. Advantageously, a space is defined between the pipe section and the conical bore in which a preferably soft-sealing sealing ring is arranged. The inclined orientation of the conical bore ensures uniform compression of the sealing ring during assembly, thereby achieving a uniform sealing effect.

[0012] In a further embodiment of the invention, the union nut has an external polygonal section, in particular an external hexagonal section, to which a hollow cylindrical guide section with a reduced outer diameter is attached. The external polygonal section serves as a tool engagement. The subsequent hollow cylindrical guide section with a reduced diameter provides extended guidance and thus improved support of the received pipe section while simultaneously reducing weight. Other developments and embodiments of the invention are specified in the remaining dependent claims. An exemplary embodiment of the invention is shown in the drawings and is described in detail below. The drawings show:

[0013] Figure 1: schematic representation of a connection arrangement in longitudinal section and

[0014] Figure 2: a detailed view of section A in Figure 1.

[0015] The connection arrangement chosen as an exemplary embodiment is explained using the example of a pipe screw connection of a thin-walled pipe section with a connecting body according to Figure 1.

[0016] The connection arrangement comprises a thin-walled pipe section 1, a connecting body 2 and a union nut 3 for connecting the pipe section 1 to the connecting body 2.

[0017] The pipe section 1 is hollow and cylindrical and has a circumferential, outwardly projecting section 11 adjacent to its end, which is formed by a fold in the pipe material (see Figure 2). The transitions on both sides of the outwardly projecting section 11 to the outer surface of the pipe section 1 each have an arc-shaped profile.

[0018] The connecting body 2 is essentially hollow and cylindrical and has a first cylindrical bore 21, to which a second cylindrical bore 22 with a reduced diameter is connected, forming a stop 26. A contact surface 23 is provided on the end face of the connecting body 2, which is angled transversely to the first cylindrical bore 21. The contact surface 23 is bounded by a conical bore 25 that merges into the first cylindrical bore 21, with which it is aligned. At its end face, the connecting body 2 has an external thread 24 in the region of the conical bore 25. The union nut 3 is essentially hexagonal and has a cylindrical bore 31 for receiving the pipe section 1, to which a second cylindrical bore 32 is connected. This second bore has a larger inner diameter than the first bore 31, forming a stop surface 34 angled transversely to the second bore 32.The transition from the stop surface 34 to the first bore 31 is rounded, so that an arc-shaped cross-section with a radius R is formed.

[0019] In the second cylindrical bore 32, an internal thread 33 is arranged for screwing onto the external thread 24 of the connecting body 2. A substantially hollow cylindrical guide section 36 adjoins the hexagonal section 35 of the union nut 3, through which the first bore 31 is guided and whose outer diameter is smaller than the outer diameter of the hexagonal section 35.

[0020] A sealing ring 4 is slid onto the end of the pipe section 1, bearing laterally against the outwardly projecting section 1 1. The pipe section 1, thus fitted with the sealing ring 4, is inserted into the first cylindrical bore 21 of the connecting body, with the outwardly projecting section 1 1 bearing against the contact surface 23 of the connecting body 2. In this position, the sealing ring 4 is arranged to seal the space defined between the pipe section 1 and the conical bore 25 of the connecting body 2.

[0021] The union nut 3 is pushed onto the pipe section 1, with the stop surface 34 bearing against the outwardly projecting section 11 of the pipe section 1. The pipe section 1 is guided in the guide section 36 of the union nut. The union nut 3 is screwed onto the external thread 24 of the connecting body 2 with its internal thread 33, thereby clamping the outwardly projecting section 11 of the pipe section 1 between the contact surface 23 of the connecting body 2 and the stop surface 34 of the union nut 3. The radius R of the transition from the stop surface 34 of the union nut to the first bore 31 is selected such that it essentially corresponds to the radius R of the transition from the outwardly projecting section 11 to the outer surface of the pipe section 1, so that the pipe section 1 also bears against the union nut 3 in this area. The pipe section 1 is thus secured within the

[0022] The union nut 3 is well supported, as is the guide section 36.

[0023] This ensures maximum support for the thin-walled pipe section 1 and thus optimizes its bending fatigue strength. For this purpose, the outer diameter of the pipe section 1 essentially corresponds to the inner diameter of the first cylindrical bore 31 of the union nut, which preferably corresponds essentially to the inner diameter of the first cylindrical bore 21 of the connecting piece 2 into which it is inserted.

[0024] In this way, a solid, massive transition is formed between the union nut 2, the folded pipe 1 and the connecting body 2.

Claims

Patent claims 1. Connection arrangement comprising a pipe section (1), a connecting body (2) and a union nut (3) for connecting the pipe section (1) to the connecting body (2), wherein - the connecting body (2) has a first cylindrical bore (21 ) for receiving the pipe section (1 ) and a connection to the first cylindrical bore (21) subsequent, reduced-diameter second cylindrical bore (22) has a contact surface (23) positioned transversely to the first cylindrical bore (21) on the end face, - the union nut (3) has a first cylindrical bore (31) for receiving the pipe section (1), to which a second bore (32) with an increased diameter is connected, wherein an internal thread (33) is arranged for screwing onto an external thread (24) arranged for this purpose on the connecting body (2), - the pipe section (1 ) has a circumferential outwardly projecting section (1 1 ) spaced apart from its end, characterized in that the diameter-enlarged second bore (32) of the union nut (3) is cylindrical, thereby forming a stop surface (34) positioned transversely to it, and that the outwardly projecting section (1 1 ) is formed by a folding of the pipe section (1 ) and has two parallel opposing contact surfaces for contact with the stop surface (34) of the union nut (3) on one side and with the end-face contact surface (23) of the connecting body (2) on the other, between which the section (1 1 ) is clamped in the assembled state.

2. Connection arrangement according to claim 1, characterized in that the outwardly projecting section (11) is arranged orthogonally to the pipe axis of the pipe section (1), wherein the transition between the outer surface of the pipe section (1) and the contact surface of the outwardly projecting section (11) facing the stop surface (34) of the union nut (3) has a circular arc cross-section with a radius R exhibits, wherein the transition from the first bore (31) to the diameter-enlarged second bore (32) has a circular arc cross-section with a radius substantially corresponding to the radius R.

3. Connection arrangement according to claim 1 or 2, characterized in that the outer diameter of the pipe section (1) essentially corresponds to the inner diameter of the first cylindrical bore (31) of the union nut (3), which in turn essentially corresponds to the inner diameter of the first cylindrical bore (21) of the connecting body (2) into which it is inserted.

4. Connection arrangement according to one of the preceding claims, characterized in that the connecting body (2) has a conical bore (25) extending from its contact surface (24), to which the first cylindrical bore (21) is connected and with which it is aligned.

5. Connection arrangement according to claim 4, characterized in that a space is defined between the pipe section (1 ) and the conical bore (25) in which a sealing ring (4) is arranged.

6. Connection arrangement according to one of the preceding claims, characterized in that the union nut (3) has an external polygonal section, in particular an external hexagonal section (35), to which a hollow cylindrical guide section (36) with reduced outer diameter is connected.

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