Method of manufacturing a fluid connector and a fluid connector

Abstract

The method is for manufacturing a fluid connector, such as a pneumatic or hydraulic connector, directly onto a metal tube. The metal tube in cross-section has a circular outer periphery defining an i

Description

FIELD OF THE INVENTION The present invention relates to the manufacture of a fluid connector and to a fluid connector formed on a metal tube. BACKGROUND OF THE INVENTION Currently there are a range of fluid connectors in use globally that cover many industries. These connectors are manufactured to meet the specifications of various national and international engineering standards, some examples of such standards include BS5200, SAE J1453, SAE J514, DIN 2353, ISO 6162 and JIS 8363. Connectors are included in fluid carrying systems and are conventionally manufactured using high energy methods, such as being machined from solid bars of metal using oil-based coolants in the machining process in which metal is cut away from the work-piece to produce the desired shape of the connector. These connectors are welded or brazed onto the fluid carrying line which is usually steel tube, or are crimped onto flexible hose and are used in fluid carrying installations. The present invention aims to alleviate, at least partially, some or any of the drawbacks associated with the conventional methods of manufacture and products. SUMMARY OF THE INVENTION According to one aspect there is provided a method of manufacturing a fluid connector directly onto a metal tube, wherein the metal tube in cross-section has a substantially circular outer periphery defining an initial outside diameter and a substantially circular interior defining an initial inside diameter, the method comprising: cold forming an end portion of the tube to: ensure that the interior is substantially concentric with respect to the outer periphery at said end portion; thicken the tube wall so that the outside diameter of the end portion is greater than the initial outside diameter; and shape the end portion of the tube to provide a predetermined connector geometry. According to another aspect there is provided a fluid connector formed integrally and jointlessly on a metal tube, wherein the connector is provided on an end portion of the tube and the connector has a wall thickness that is thicker than the tube wall, and is obtainable by the method of the preceding aspect. Another aspect provides a flexible hose assembly comprising: a length of flexible hose; and at least one fluid connector according to the preceding aspect fitted to an end of the flexible hose. Further optional features of embodiments of the invention are defined in the dependent claims. Specific embodiments of the invention can provide the following advantages: • Reduction in the required number of components used in the manufacture of fluid carrying circuits. • Elimination of welding and brazing processes in the manufacture of fluid carrying circuits which eliminates potential failure point in the fluid carrying systems . • Significant reduction in energy used to produce fluid carrying circuits. • Significant reduction in the use of oil-based coolants in the manufacturing process. The above can all provide significant cost savings. DESCRIPTION OF THE DRAWINGS Embodiments of the invention will now be described, by way of non-limiting example, with reference to the accompanying drawings. The invention may further comprise, in any combination, any features of the embodiments which will now be described. Fig. 1 is a view of the end of a tube, not according to an embodiment of the invention, showing poor concentricity; Fig. 2 is an end-on view of the tube of Fig. 1 after cold forming according to a method embodying the invention; Fig. 3 is a schematic longitudinal section view of a fluid connector formed on a metal tube according to an embodiment of the invention; Fig. 4 is a schematic longitudinal section view of a fluid connector formed on a metal tube according to another embodiment of the invention; Fig. 5 is a schematic longitudinal section view of a fluid connector formed on a metal tube according to a further embodiment of the invention; Fig. 6A is a side view of a fluid connector formed on a metal tube according to another embodiment of the invention; Fig. 6B is longitudinal sectional view of the fluid connector formed on a metal tube of Fig. 6A; and Fig. 7 is a schematic longitudinal sectional view of a fluid connector formed on a metal tube according to another embodiment of the invention. In the drawings, like parts are indicated with like reference numerals, and, for conciseness, description thereof will not be repeated. DETAILED DESCRIPTION OF THE INVENTION Metal tube manufactured for fluid carrying lines typically has a concentricity tolerance that is insufficient to permit directly forming a connector from the tube, and therefore the conventional solution is to weld or braze a pre-machined connector on to the end of the tube. Fig. 1 illustrates schematically tube with poor concentricity (or equivalently expressed as tube with significant eccentricity). The outer periphery of the tube is substantially circular in cross-section and the tube has an initial outside diameter OD. The interior lumen is also substantially circular in cross-section and the tube has an initial inside diameter ID. However, the circles are offset, such that they are not concentric. This means that the wall thickness of the tube is not uniform, being thicker (tl) in some parts and thinner (t2) in other parts. A method according to an embodiment of the invention applies a cold forming process to size, thicken and shape the end portion of the tube to form a connector on the end of the tube that complies with a specified geometry (such as defined in an engineering standard). The resulting connector is provided integrally and jointlessly on the tube. The cold forming is done using a die or dies and / or a swage or swages in an automated process using a form of swaging using commercially available machinery. The cold forming process thickens the tube wall such that the desired connector can be formed or final machined. As can be seen in the end-on view of Fig. 2 after cold forming, the outside diameter ^A is greater than the initial outside diameter OD. Preferably the inside diameter after forming is less than the initial inside diameter ID, but this is not essential, and in some embodiments, the inside diameter can be the same as ID, or even larger than ID. The cold forming can also ensure that the interior of the connector on the end portion of the tube is substantially concentric with respect to the outer periphery of the end portion, as illustrated in Fig. 2. For example, the eccentricity of the connector on the end portion of the tube can be less than a predetermined tolerance. The eccentricity can be defined in various ways, including the absolute difference between the maximum and minimum wall thicknesses, or the ratio of that difference to the mean thickness, or in other ways with various factors and constants, as well known in the art. The cold forming can also, if necessary, correct for any “ovality” or poor circularity of the tube. The cold forming also shapes the end of the tube to a predetermined connector geometry. Examples of connector geometries according to different embodiments of the invention are illustrated in Figs. 3 to 7, all of which have a thickened wall portion 10. Fig. 3 shows a connector geometry with a flat face 12 on the end of the tube for sealing. Fig. 4 shows a connector geometry with a concave conical face 14 on the end of the tube for sealing. Fig. 5 shows a connector geometry with a convex conical face 16 on the end of the tube for sealing. The conical faces 14, 16 of the connectors of Figs. 4 and 5 are each at a specific ‘seat angle’ defined with respect to the axis of the connector / tube, and are designed to mate with a corresponding connector with the opposite concave / convex face to form a tight, but disconnectable, seal. An external thread can also be formed on the thickened portion 10 of the tube wall (such as in any of Figs. 3 to 5). Figs. 6A and 6B show an example of a specific connector geometry including an external thread 20 and an internal concave conical face 14. The presence of an external thread defines the connector as a male connector, which is the preferred embodiment of the invention A groove around the outer periphery of the connector can also be provided in any embodiment of the invention. An example of such a groove is the groove 22 illustrated in Figs. 6A and 6B. Provision of a thread is not the only envisaged feature for joining a connector embodying the invention. Alternatively, a flange 30 can be provided, as shown in Fig. 7. and a clamp known in the art can attach the connector by means of the flange 30 to a flange on the next part of a fluid carrying circuit. Other forms of ‘quick-release’ connection mechanisms are known in the art and can be used in conjunction with embodiments of the invention. A groove for retaining an O-ring, for forming a seal when the connector is joined to the next component, can also be provided in the sealing face of any embodiment of the invention. An example of such an O-ring groove 40 is illustrated in Fig. 7. When applying cold forming in a method according to an embodiment of the invention, the cold forming can be performed as a single process, or alternatively multiple stages of cold forming can be performed, such as thickening and then shaping, either by the same machine or by the successive combination of multiple machines (e.g. commercially available presses / swaging machines). After performing the cold forming, a small amount of final machining may be applied to meet the tolerances of a desired industry standard specification. However, embodiments of the invention remove the need for machining components from scratch and avoid secondary operations such as welding and brazing. Fluid connectors embodying the invention can be formed on ferrous and nonferrous metal tube, comprising for example, but not limited to, steel, carbon steel, stainless steel, brass, aluminium, and alloys of any of the preceding. The outside diameter of a fluid connector according to an embodiment of the invention is typically in the range of from approximately 5 mm to 50 mm (approximately 1 / 4 inch to 2 inches). A fluid connector embodying the invention is formed onto an end portion of a metal tube. The length of the metal tube is typically in the range of from 10 mm to 200 mm if it is for use as a hose fitting. The tube can be straight or can be bent through an angle such as 45 degrees or 90 degrees to provide an elbow connector. Of course, the metal tube can in principle be of any length and shape. A fluid connector according to one embodiment is particularly suitable for use in the manufacture of flexible hose assemblies. A further embodiment provides a flexible hose assembly in which a fluid connector embodying the invention is fitted onto an end of a length of flexible hose. The flexible hose is inserted into the metal tube on which the fluid connector is formed, and then the metal tube is crimped or swaged to form a pressure-tight seal. The flexible hose can be made according to any construction know in the art, such as from rubber, thermoplastic or plastic, and can be single or multi-layered wall, and can optionally include steel wire braid internally and / or externally. Fluid connectors embodying the invention can be used in many industries, including, but not limited to, construction, chemical processing, agriculture, food processing. Fluid connectors embodying the invention can be used with a wide range of fluids, including liquids and gases, and can also be referred to as hydraulic connectors or pneumatic connectors, and can operate with fluids at pressures above and below ambient pressure. The term ‘"connector” has been used herein, but should be considered equivalent to the terms “coupler” or “coupling”.

Claims

1. A method of manufacturing a fluid connector directly onto a metal tube, wherein the metal tube in cross-section has a substantially circular outer periphery defining an initial outside diameter and a substantially circular interior defining an initial inside diameter, the method comprising:cold forming an end portion of the tube to:ensure that the interior is substantially concentric with respect to the outer periphery at said end portion;thicken the tube wall so that the outside diameter of the end portion is greater than the initial outside diameter; andshape the end portion of the tube to provide a predetermined connector geometry.

2. A method according to claim 1, wherein the cold forming is further arranged to thicken the tube wall so that the inside diameter of the end portion is less than the initial inside diameter.

3. A method according to claim 1 or 2, wherein the cold forming is arranged to ensure that the eccentricity of the interior with respect to the outer periphery is less than a predetermined tolerance at said end portion;4. A method according to any preceding claim, wherein the cold forming is performed as a single process or as multiple stages.

5. A method according to any preceding claim, wherein the connector is a male connector.

6. A method according to any preceding claim, further comprising forming an external thread on a thickened portion of the tube wall.

7. A fluid connector formed integrally and jointlessly on a metal tube, wherein the connector is provided on an end portion of the tube and the connector has a wall thickness that is thicker than the tube wall, and is obtainable by the method of any preceding claim.

8. A fluid connector according to claim 7, wherein the connector geometry comprises a flat face on the end of the tube.

9. A fluid connector according to claim 8, wherein the flat face is provided with an O-ring groove.

10. A fluid connector according to any of claims 7 to 9, wherein the connector geometry comprises a concave conical face.

11. A fluid connector according to any of claims 7 to 10, wherein the connector geometry comprises a convex conical face.

12. A fluid connector according to any one of claims 7 to 11, wherein the connector geometry comprises a flange.

13. A fluid connector according to any one of claims 7 to 12, wherein the connector geometry comprises a groove around the outer periphery.

14. A fluid connector according to any one of claims 7 to 13, which is a pneumatic connector or hydraulic connector.

15. A fluid connector according to any one of the claims 7 to 14, which is suitable for use in the manufacture of a flexible hose assembly.

16. A flexible hose assembly comprising: a length of flexible hose; and at least one fluid connector according to any one of the claims 7 to 15 fitted to an end of the flexible hose.

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