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Patent Searching and Data


Title:
TUBE CONNECTION
Document Type and Number:
WIPO Patent Application WO/2019/121091
Kind Code:
A1
Abstract:
The invention relates to a Tube connection for example a hose fitting for connection to a tube, which tube connection comprises a body having a through hole with a central axis, a first end, a second end, an internal thread arranged close to the first end and coaxial with the central axis, wherein the internal thread has a constant pitch diameter, wherein the maximum diameter of the thread increases in axial direction from the first end towards the second end and wherein the minimum diameter of the thread decrease in axial direction from the first end towards the second end.

Inventors:
ALTENRATH, Joerg (Kreuzhaeuschen 4b, Lohmar, 53797, DE)
Application Number:
EP2018/084121
Publication Date:
June 27, 2019
Filing Date:
December 10, 2018
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
EATON INTELLIGENT POWER LIMITED (30 Pembroke Road, Dublin 4, 4, IE)
International Classes:
F16L15/06; F16L15/00; F16L33/24; F16L47/16
Foreign References:
US0635636A1899-10-24
GB1133125A1968-11-06
US4488738A1984-12-18
US2580818A1952-01-01
Attorney, Agent or Firm:
EATON IP GROUP EMEA (Route de la Longeraie 7, 1110 Morges, 1110, CH)
Download PDF:
Claims:
Claims

1. Tube connection (1) for example a hose fitting for connection to a tube (8), which tube connection (1) comprises a body (2) having a through hole (3) with a central axis, a first end, a second end, an internal thread (5) arranged close to the first end and coaxial with the central axis, wherein the internal thread (5) has a constant pitch diameter (Dp) ,

characterized in that

the maximum diameter (Dmax) of the thread (5) increases in axial direction from the first end towards the second end and wherein the minimum diameter (Dmin) of the thread (5) decrease in axial direction from the first end towards the second end.

2. Tube connection (1) according to claim 1, wherein the thread (5) starts at a distance from the first end, such that a cylindrical surface (4) is provided in the through hole (3) between the first end and the thread (5) .

3. Tube connection (1) according to claim 2, wherein the diameter of the cylindrical surface (4) is equal to the pitch diameter (Dp) .

4. Tube connection (1) according to any of the preceding claims, wherein the maximum diameter (Dmax) and minimum diameter (Dmin) are equal at the start of the thread (5) .

5. Tube connection (1) according to any of the preceding claims, wherein the minimum diameter (Dmin) decreases at an angle (a) of l2 - 52.

6. Tube connection (1) according to any of the preceding claims, wherein the body (2) comprises a hexagonal prism shape (7), wherein the axis of the hexagonal prism (7) is coaxial with the central axis.

Description:
Tube connection

The invention relates to a tube connection for example a hose fitting for connection to a tube, which tube connection comprises a body having a through hole with a central axis, a first end, a second end, an internal thread arranged close to the first end and coaxial with the central axis, wherein the internal thread has a constant pitch

diameter .

Such a tube connection is known from GB 810628. This publication discloses a body with a through hole and an internal thread, such that a nut like ring is provided. The body is arranged on a tube and maintained at the tube by a ridge arranged in the tube wall. At the tube end, a hose is arranged. Then the nut like ring is rotated onto the hose, such that the thread cuts into the hose and secures the hose to the tube.

The disadvantage is that the tube end needs to be deformed to provide a ridge, which requires special equipment, which is not always available, especially during repairs by a user when a tube part is to be exchanged.

US 4488738 discloses a tube connection wherein the body is provided with a through hole in which a tapering thread is arranged, such that the pitch diameter decreases.

The thread depth starts at virtually zero and increases, such that when a tube is inserted into the through hole by

rotating, a thread is cut into the tube.

The pitch diameter of a particular thread, internal or external, is the diameter of a cylindrical surface, axially concentric to the thread, which intersects the thread flanks at equidistant points, when viewed in a cross-sectional plane containing the axis of the thread, the distance between these points being exactly one half the pitch distance.

Due to the tapering shape of the thread, the

connection is less suitable to take up axial and radial forces. Such forces urge the tube out of the tube connection due to the tapering shape of the though hole and thread. The largest part of the axial forces is to be taken up by the last turn of the thread and as soon as this last turn fails, the connection will come loose.

It is also known to connect a tube to for example a fitting by brazing. Brazing allows for strong connections, which are typically suitable for high pressure applications. However, brazing is time consuming, labor intensive, expensive and prone to errors. Furthermore, long tubes cannot be brazed, as they do not fit in the typical brazing furnace. As a result, the brazing process is typically not suitable, for short term orders or for repairs of damaged connections.

Accordingly, it is an object of the invention to reduce or even remove the above mentioned disadvantages.

This object is achieved according to the invention with a tube connection according to the preamble, which is characterized in that the maximum diameter of the thread increases in axial direction from the first end towards the second end and wherein the minimum diameter of the thread decrease in axial direction from the first end towards the second end.

As the thread of the tube connection has a constant pitch diameter, while the maximum diameter increases and the minimum diameter decreases, a tube, which is inserted in the tube connection by rotation, will have an end being flared outwardly. This is caused by the minimum diameter of the thread which will deform the material of the tube when rotated inwardly in the through hole. The deformed material will be pushed into the space provided by the increasing maximum diameter of the thread.

The resulting shape of the tube end will be flared outwardly, while the shape of the internal thread in the through hole is conical, widening from the first end inwardly toward the second end. As a result a shape defined connection between the tube connection and the tube is provided, which is not only dependent on a single turn of the thread like in US 4488738.

An additional advantage of the invention is that the tube connection can be made without any specialized tools. As long as sufficient torque can be generated to rotate a

straight tube end into the tube connection, a reliable

connection can be achieved.

To ensure a leak tight connection, a special glue can be provided between the tube end and the tube connection, or a soft seal or thermoplastic seal could be arranged in the area of the tube end.

In a preferred embodiment of the tube connection according to the invention the thread starts at a distance from the first end, such that a cylindrical surface is

provided in the through hole between the first end and the thread .

The cylindrical surface provides support for the tube end, such that insertion of the tube end is facilitated, but also for withstanding bending stresses exerted on the tube end. With the cylindrical surface, the bending stresses are exerted on a part of the tube end distal from the part of the tube end provided with the thread, such that the part provided with the thread is virtually only subjected to axial forces.

Preferably, the diameter of the cylindrical surface is equal to the pitch diameter. This allows for a smooth transition from the cylindrical surface towards the threaded part .

In a further preferred embodiment of the tube connection according to the invention, the maximum diameter and minimum diameter are equal at the start of the thread.

This ensures that the thread starts with a thread depth of zero and a tube end with a diameter corresponding to the pitch diameter can be inserted into the tube connection. Then by rotating the tube end and further inserting the tube end into the through hole, the desired flared out shape of the tube end is provided by the internal thread of the tube connection .

In yet a further preferred embodiment of the tube connection according to the invention the minimum diameter decreases at an angle of l 2 - 5 2 .

An angle of l 2 - 5 2 allows for a tube end to be screwed into the tube connection without additional axial force and no additional specialized tools.

In still a further preferred embodiment of the tube connection according to the invention, the body comprises a hexagonal prism shape, wherein the axis of the hexagonal prism is coaxial with the central axis.

With the hexagonal prism shape a typical wrench or spanner can be used to connect the tube connection of the invention with a tube end.

These and other features of the invention will be elucidated in conjunction with the accompanying drawings.

Figure 1 shows an embodiment of a tube connection according to the invention and a tube end in exploded view.

Figure 2 shows the embodiment of figure 1 in

assembled state.

Figure 1 shows a tube connection 1 with a body 2 having a through hole 3. The first end of the through hole 3 is provided with a cylindrical part 4 followed by an internal thread 5.

On the second end, the body 2 is provided on the outer surface 6 with a hose connection. Furthermore, a

hexagonal prism shape 7 is provided on the body 2 to allow engagement of a wrench or spanner.

The thread 5 has a constant pitch diameter D p , while the minimal diameter D min decreases from the cylindrical part 4 towards the second end of the body and the maximal diameter D max increases from the cylindrical part 4 towards the second end .

The minimum diameter D min decreases at an angle a, which is preferably between l 2 and 5 2 , such that no additional axial force is required when a tube end 8 is screwed into the tube connection 1.

The maximum diameter D max increases in the same amount as the minimum diameter decreases D min . This ensures that the pitch diameter D p is constant, but also ensures that the amount of material deformed by the minimum diameter D min can be pushed towards the expanding space as a result of the increasing maximum diameter D max .

The tube end 8 inserted into the tube connection 1 and shown in exploded view in figure 1 has a normal diameter D norm . Due to the shape of the thread 5, the end of the tube end 8 flares out to an expanded diameter D exp , which provides a shaped defined connection of the tube end 8 with the tube connection 1.

Figure 2 shows the tube end 8 and the tube connection 1 is assembled state. The normal diameter D norm corresponds to the pitch diameter D p of the thread. The end of the tube end 8 is flared out to the expanded diameter D exp , which is almost identical to the maximum diameter D max at this position of the thread 5.