WO2012033395A1

WO2012033395A1 - Tube fitting

Info

Publication number: WO2012033395A1
Application number: PCT/MY2008/000183
Authority: WO
Inventors: Christiaan Reijmer
Original assignee: Christiaan Reijmer
Priority date: 2008-12-12
Filing date: 2008-12-12
Publication date: 2012-03-15

Abstract

A tube fitting (20) for a tube (10) or a tube end has a first (30) and a second coupling member (70) in an assembly with a tube gripping element (40), a compression ring (50) and a resilient seal (60). After insertion of tube (10) in tube fitting (20), tightening the assembly moves compression ring (50) into a contiguous position with a tapered internal surface (73) of second coupling member (70), thereby deforming seal (60) between compression ring (50), tapered internal surface (73) of second coupling member (70) and tube (10), and tube gripping element (40) is compressed by first coupling member (30), compression ring (50) and tube (10), effectively sealing and gripping tube (10) in tube fitting (20).

Description

TUBE FITTING

FIELD OF INVENTION

The subject invention is generally directed to the art of tube fittings.

BACKGROUND OF INVENTION Tube fittings are used to join a tube end to another tube end, or to a device that needs to be in fluid communication with the tube end, for example a compressor, a pump or a valve. Another application of tube fittings is to seal and grip a tubular member that extends completely through the tube fitting, such as a cable or a pressure sensor.

As used herein the term 'lube" is intended to include flexible walled conduits as well as rigid walled conduits such as polyurethane or polyethylene tubing, plastic or rubber hose, molded cable, glass tube and metal pipe or tube.

Tubes are generally manufactured to a certain outer diameter within a certain tolerance. For instance small-diameter metric tube with an outer diameter of up to 20 mm is manufactured with a diameter tolerance of plus 0.05 mm and minus 0.1 mm. As used herein the term that a body is designed "to receive" a tube indicates the body has an axial bore with an inner diameter larger than the largest diameter in a certain tube tolerance class.

Tube fittings in general serve a dual purpose: the tube fitting has to provide a fluid tight seal against fluid leakage, and the tube fitting has to grip the tube or tube end in order to prevent tube blow out. Many types of tube fittings are known in the art, each designed for the characteristics of the tube to be fitted and the application in which the tube fitting is to be used, and each with its respective strengths and weaknesses.

Push type tube fittings such as the tube fitting disclosed in US patent 5,584,513, are generally used for plastic tube in a low pressure application, and use a retaining ring or collet held by a tapered surface to grip the tube, and a seal such as an O-ring to provide a fluid tight seal. As the seal is not elastically deformed in this type of tube fitting, these tube fittings tend to leak when side loading of the fitted tube occurs during operation.

Tube fittings that do elastically deform an O-ring seal by tightening of the tube fitting, such as the tube fitting disclosed in US patent 4,776,618, tend to destroy the O-ring after repeated use. Elastomeric seal material behaves like an incompressible fluid, and tightening the tube fitting extrudes the seal in the clearances between tube and tube fitting components, ripping it apart.

Ferrule type tube fittings such as the tube fitting disclosed in US patent 3,103,373 are generally used for metal walled tube, and tightening of the tube fitting compresses one or more ferrules, which plastically deform and grip and seal the tube. These tube fittings are effective but sensitive to tolerance fluctuations of the outer diameter of the tube, difficult to re-use and relatively expensive to manufacture.

There is a need for a tube fitting that allows a wide range of tube materials and dimensions, delivers an effective seal under high pressure even under side loading of the tube or vibrating operating conditions, is suited for repeated use without wearing out the seal, and that can be manufactured in high volume at relatively low cost. SUMMARY OF THE INVENTION

A tube fitting for a tube or tube end is provided with a first and second coupling member, a tube gripping element, a compression ring and a resilient seal that achieves an excellent tube seal and grip function suited for repeated use without wearing out the seal. Additionally, a method to seal a tube or tube end in a tube fitting is provided. The sealing function is achieved by tightening the first coupling member in the second coupling member whereby the compression ring is moved into a contiguous position with a tapered internal surface of the second coupling member. As a result the compression ring elastically deforms the resilient seal in a conical cavity between the compression ring, the tapered internal surface of the second coupling member and the external surface of the tube, with a design volume slightly larger than the volume of the seal itself, thereby preventing the seal to be destroyed when tightening the tube fitting to the required design torque to guarantee adequate grip. With the compression ring and tapered internal surface in a contiguous position, tightening the tube fitting to its design torque causes the tube gripping element to be compressed between the first coupling member, the compression ring and the tube wall, as a result of which the tube gripping element grips the tube.

These and other aspects of the present invention will be apparent to those skilled in the art from the following description of the preferred embodiments in view of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings constitute part of this specification and include exemplary or preferred embodiments of the invention, which may be embodied in various forms. Therefore, the features (not to scale) disclosed herein are not to be interpreted as limiting, but merely as the basis for the claims and for teaching one skilled in the art of the invention. The invention will now be described by reference to the accompanying drawings, in which:

FIG. 1 is a cross-sectional view through a tube fitting according to an embodiment of the present invention, in an open position before a tube is inserted.

FIG. 2 is a cross-sectional view through a tube fitting according to an embodiment of the present invention, in an open position with a tube inserted.

FIG. 3 is a cross-sectional view through a tube fitting according to an embodiment of the present invention, in a closed position with a tube inserted.

FIG. 4 is a detail of a cross sectional view of a tube fitting according to the present invention in a closed position with a tube inserted. FIG. 5 is a cross-sectional view through a tube fitting according to another embodiment of the present invention, in a closed position with a tube inserted.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention relates to a tube fitting device. Hereinafter, this specification will describe the present invention according to the preferred embodiments of the invention. However, it is to be understood that limiting the description to the preferred embodiments of the invention is merely to facilitate discussion of the present invention and it is envisioned that those skilled in the art may devise various modifications and equivalents without departing from the scope of the appended claims.

The following detailed description of the preferred embodiments will now be described in accordance with the attached drawings, either individually or in combination. FIG. 1 shows a cross-sectional view through a tube fitting (20) according to an embodiment of the present invention, consisting of a first coupling member (30), a tube gripping element (40), a compression ring (50), a resilient seal (60) and a second coupling member (70). Tube fitting (20) in the figure is in an open position, and is designed to accommodate tubes of a certain outer diameter. First coupling member (30) has a tightening means (32) such as a knurled or nut-like perimeter on the rear outside perimeter, for tightening first coupling member (30). Threads (33) are designed to engage a companion threaded second coupling member (70). First coupling member (30) has a bore (34) designed to receive tube (10), and a front portion with a tube gripping element (40) such as axially extending teeth. First coupling member (30) includes male threads that mate with female threads of second coupling member (70). Alternatively, first coupling member (30) includes female threads that mate with male threads of second coupling member (70). Compression ring (50) has an outer diameter (55) to be received in first bore (71 ) of second coupling member (70), and a rear portion with a tapered internal surface (51 ) designed to deflect tube gripping element (40) radially inwards when tube fitting (20) is tightened. Preferably, the axial length of tapered internal surface (51 ) is longer than the axial length of tube gripping element (40). Preferably, the axial angle of tapered internal surface (51 ) is between 20 and 30 degrees. Bore (52) is designed to receive tube (10). The front portion of compression ring (50) ends in a flat surface (53) with a filleted rim (54) designed to move flush against and elastically deform seal (60). Rim (54) minimizes extrusion of seal (60) in the clearance between compression ring (50) and external surface (11 ) of an inserted tube and facilitates installing tube (10) through seal (60).

In the figure tube gripping element (40) is an attachment of first coupling member (30), which is compressed by tapered mouth (51) of compression ring (50). Tube gripping element (40) can also be a separate insert designed to receive tube (10), which is then compressed by a tapered mouth of either first coupling member (30) or of compression ring (50), or both. Another option is to have tube gripping element (40) attached to compression ring (50), which is then compressed by a tapered mouth of first coupling member (30). Tube gripping element (40) can either have axially extended teeth, or have a ferrule-like shape. Seal (60) has a circular internal surface (62) and is designed to receive tube (10), and is made of an elastomeric material such as neoprene, nitrile, Teflon, or other types of pliable synthetic material. The outer diameter of seal (60) is designed to be received in first bore (71 ) of second coupling member (70). Preferably, seal (60) is an O-ring. To minimize extrusion of seal (60) in the clearance between an inserted tube (10) and compression ring (50), the shore hardness of the material of seal (60) is preferably 80 or larger. However the material of seal (60) should be pliable enough to permit uniform deformation of seal (60) when it is elastically deformed by compression ring (50).

Second coupling member (70) has a rear portion with a first bore (71) with female threads (72) designed to fit companion threads (33) of first coupling member (30). First bore (71) is designed to receive compression ring (50) and seal (60). Second coupling member (70) has a tapered internal surface (73) terminated by an annular step (74) with a flat surface, designed to elastically deform seal (60), and a second circular bore 75 designed to receive tube (10). Preferably tapered internal surface (73) of second coupling member (70) has an axial angle between 10 and 20 degrees. The figure shows a third bore (76), which can be a port permitting fluids to flow from an inserted tube through bore (76) to another location. Also, bore (76) can be connected to a tube, a coupling, tube, valve, housing, another tube fitting or be a tube. Annular step (77) functions as a positive stop for an inserted tube (10). When used for fitting cables or other tubular male members adapted to extend completely through tube fitting (20), third bore (76) and annular step (77) are omitted.

Depending on the required performance level and operating conditions under which tube fitting (20) has to perform, first coupling member (30), tube gripping element (40), compression ring (50) and second coupling member (70) can be made of a variety of materials, ranging from engineering plastics such as polyvinyl, polycarbonate or glass filled nylon to metals including alloy steel, aluminum alloys, brass, copper-nickel alloys, nickel, stainless steel 304, 316, 321 , 347, carbon steel, tantalum, titanium, zirconium alloys and like materials.

Herein below operation of tube fitting (20) is described. FIG. 1 shows tube fitting (20) in a pre-assembled, open position, with first (30) and second coupling member (70) in finger-tight threaded engagement, and with tube gripping element (40), compression ring (50) and resilient seal (60) aligned and pre- installed. Tube gripping element (40) is in contact with but not stressed by tapered internal surface (51 ) of compression ring (50), and seal (60) is moved away from tapered internal surface (73) towards first bore (71 ).

As all components of tube fitting (20) are designed to receive tube (10), the pre- assembled tube fitting (20) allows direct insertion of tube (10), and subsequent tightening of tube fitting (20) completes the installation. This avoids the necessity of disassembling tube fitting (20) in order to install tube (10).

FIG. 2 shows tube fitting (20) in an open position after insertion of a tube (10).

Tube fitting (20) is closed by tightening first coupling member (30) and second coupling member (70). FIG. 3 shows a tube fitting (20) with an inserted tube (10) in a closed position. As first coupling member (30) is tightened with second coupling member (70), tube gripping element (40) engages tapered internal surface (51 ) of compression ring (50), and pushes compression ring (50) towards tapered internal surface (73), which causes seal (60) to be elastically deformed between flat surface (53) of compression ring (50), first bore (71 ), tapered internal surface (73) and annular step (74) of second coupling member (70) and external surface (1 1 ) of tube (10). Once the outer diameter (55) of compression ring (50) engages tapered internal surface (73), further movement of compression ring (50) is prevented and seal (60) is at maximum elastic deformation. With compression ring (50) and tapered internal surface (73) in a contiguous position, further tightening of first coupling member (30) in second coupling member (70) causes tube gripping element (40) to be deflected radially inwards by the tapered internal surface (51) of compression ring (50), as a result of which tube gripping element (40) grips tube (10).

Depending on the application, operating conditions and tube material involved, the design torque required to ensure proper grip of tube (10) deforms tube gripping element (40) between first coupling member (30), tapered internal surface (51 ) of compression ring (50) and the external surface (1 1 ) of tube (10), either elastically or plastically. Depending on the design torque and the tube wall material, as a result tube wall (12) may be deformed as well, either elastically or plastically.

FIG. 4 shows a detail of a cross section of tube fitting (20) in a closed position, with a tube (10) inserted and with compression ring (50) and tapered internal surface (73) of second coupling member (70) in a contiguous position. The figure shows resilient seal (60) deformed in the cavity between inserted tube (10), compression ring (50) and second coupling member (70). The cavity boundaries are formed by external surface (1 1 ) of tube (10), flat surface (53) and rim (54) of compression ring (50), and tapered internal surface (73) and annular step (74) of second coupling member (70). The figure also shows the clearances between external surface (1 1 ) of tube (10) and second bore (75), and between external surface (1 1 ) of tube (10) and bore (52) of compression ring (50), and the point where the outer diameter (55) of compression ring (50) engages tapered internal surface (73). As resilient seal (60) is radially compressed and axially stretched in the cavity, high contact stress between resilient seal (60) and flat surface (53), rim (54), tapered internal surface (73), annular step (74) and external surface (1 1) of tube (10) tightly seals tube (10) in tube fitting (20) even under side loading of tube (10) or vibrating operating conditions. By design, the volume of the cavity enclosed by contiguous flat surface (53) of compression ring (50) and tapered internal surface (73), rim (54), annular step (74) and external surface (1 1 ) of tube (10) is slightly larger than the volume of seal (60). As a result it is impossible to destroy seal (60) by over-tightening tube fitting (20).

FIG. 5 shows another embodiment of tube fitting (20) with an additional locking nut (80) assembled on first coupling member (30). Locking nut (80) has threads to matingly engage on threads of first coupling member (30). Once tube fitting (20) is tightened to its design torque, the assembly can be locked by tightening locking nut (80), to prevent the assembly loosening during operation.

Referring to FIG.3 and FIG.5, loosening of first coupling member (30) and second coupling member (70) causes tube gripping element (40) to move away from tapered internal surface (51 ) of compression ring (50), and seal (60) to move away from tapered internal surface (73) pushing compression ring (50) towards first bore (71 ) of second coupling member (70), and tube (10) can be pulled out of tube fitting (20), after which tube fitting (20) again allows insertion of a tube (10).

Claims

1 . A tube fitting (20) to grip and seal a tube (10) or a tube end, comprising: a first coupling member (30) having a circular bore (34) to receive tube (10); a tube gripping element (40) having a circular bore to receive tube (10); a compression ring (50) having a circular bore (52) to receive tube (10), and having a front portion with a flat surface (53); a resilient seal (60) having a circular inner diameter that allows seal (60) to receive tube(10); a second coupling member (70) joined with first coupling member (30), having a first circular bore (34) to receive tube gripping element (40), compression ring (50) and resilient seal (60), and having a tapered internal surface (73) terminated by an annular step (74), and having a second circular bore (75) to receive tube (10); and wherein assembly of tube gripping element (40), compression ring (50) and resilient seal (60) in second coupling member (70) with first coupling member (70) to a tightened condition causes compression ring (50) to be moved into a contiguous position with tapered internal surface (73) of second coupling member (70), and as a result resilient seal (60) is elastically deformed between contiguous flat surface (53) and tapered internal surface (73), annular step (74), and external surface (11 ) of tube (10), effectively sealing the tube (10) in the tube fitting (20), and further causes tube gripping element (40) and tube wall (12) to be elastically or plastically deformed as tube gripping element (40) is compressed between first coupling member (30), compression ring (50) and tube wall (12), as a result of which the tube gripping element (40) grips tube (10).

2. Tube fitting (20) of claim 1 wherein tube gripping element (40) has axially extending teeth.

3. Tube fitting (20) of claim 1 wherein tube gripping element (40) is a ferrule.

4. Tube fitting (20) of claim 1 wherein tube gripping element (40) is attached to first coupling member (30) or to compression ring (50).

5. Tube fitting (20) of claim 1 wherein compression ring (50) has a front portion with a tapered internal surface (51) having an axial angle between 20 and 30 degrees.

6. Tube fitting (20) of claim 1 wherein flat surface (53) of compression ring (50) ends in a filleted rim (54) around the inner diameter.

7. Tube fitting (20) of claim 1 wherein resilient seal (60) is an O-ring

8. Tube fitting (20) of claim 1 wherein tapered internal surface (73) of second coupling member (70) has an axial angle between 10 and 20 degrees.

9. Tube fitting (20) of claim 1 further comprising a second annular step (77) and a third bore (76) in second coupling member (70), wherein second annular step (77) provides a positive stop for an inserted tube (10).

10. Tube fitting (20) of claim 1 wherein second coupling member (70) is connected to a coupling, tube, valve, housing or another tube fitting.

1 1. Tube fitting (20) of claim 1 wherein first coupling member (30) includes male threads (33) that mate with female threads (72) of second coupling member (70).

12. Tube fitting (20) of claim 1 wherein first coupling member (30) includes female threads (33) that mate with male threads (72) of second coupling member (70).

13. Tube fitting (20) of claims 1 1 and 12 further comprising a locking nut (80), which is tightened after assembly of first coupling member (30) with second coupling member (70) to a tightened condition in order to prevent the assembly loosening during use.

14. Tube fitting (20) of claim 1 , wherein the volume of the cavity enclosed by contiguous flat surface (53) of compression ring (50) and tapered internal surface (73), annular step (74) and external surface (1 1) of tube (10) is larger than the volume of resilient seal (60).

15. A method of sealing a tube (10) or a tube end in a tube fitting (20) comprising the steps of: providing a first coupling member (30) having a circular bore (34) to receive tube (10); providing a compression ring (50) having a circular bore (52) to receive tube (10), and having a front portion with a flat surface (53); providing a resilient seal (60) having a circular inner diameter that allows seal (60) to receive the tube (10); providing a second coupling member (70), having a first circular bore (71 ) to receive compression ring (50) and resilient seal (60), and having a tapered internal surface (73) terminated by an annular step (74), and having a second circular bore (75) to receive tube (10); assembling compression ring (50) and resilient seal (60) in second coupling member (70) with first coupling member (30); installing a tube (10) or a tube end in tube fitting (20); and tightening tube fitting (20) to move compression ring (50) in a contiguous position with tapered internal surface (73) of second coupling member (70) causing resilient seal (60) to be elastically deformed between contiguous flat surface (53) and tapered internal surface (73), annular step (74) and external surface (1 1 ) of tube (10), effectively sealing tube (10) in tube fitting (20).

16. The method as claimed in claim 15, wherein tapered internal surface (73) of second coupling member (70) has an axial angle between 10 and 20 degrees.

17. The method as claimed in claim 15, wherein the volume of the cavity enclosed by contiguous flat surface (53) and tapered internal surface (73), annular step (74) and external surface (1 1 ) of tube (10) is larger than the volume of resilient seal (60).

18. The method as claimed in claim 15, wherein coupling member (70) is an integral part of another device.