WO1996013679A2

WO1996013679A2 - Assembly of tubing and method for forming the same

Info

Publication number: WO1996013679A2
Application number: PCT/US1995/014102
Authority: WO
Inventors: John G. Panek; Richard L. Gottorff
Original assignee: Itt Manufacturing Enterprises, Inc.
Priority date: 1994-10-24
Filing date: 1995-10-11
Publication date: 1996-05-09
Also published as: WO1996013679A3

Abstract

A unitary assembly of tubing (10) and an end fitting (16). The end fitting (16) including any fitting appropriate to the end application having a tubular bore extending therethrough. A radiused transition (20) is coaxially provided in the bore (28) at the appropriate interval where the bore (28) constricts. The end of the tubing (10) is coaxially impacted, expanded and sized to an external configuration and dimension that achieves an interference fit relative to the tubular bore (28) through the end fitting (16). The non-expanded end of the tubing (10) is inserted into the largest bore (28) in the end fitting (16) past any transitions and through the smallest bore until it experiences interference from the expansion. The interference is overcome by pressing the expansion into the bore (28) in the end fitting (16) until the expansion is completely seated into the end fitting (16). The expanded tube and end fitting assembly is machined coaxially using a stepped cutting tool. The stepped cutting tool machines the inside diameter of the tube where it has been reduced during end forming, swages the expanded tube into the end fitting bore, machines the female pilot land, machines the sealing surface and machines the visible parting line between the tube and end fitting (16).

Description

METHOD AND APPARATUS FOR A PRESSED ON AND MACHINED TERMINATING FITTING FORMING A UNITARY ASSEMBLY OF TUBING

FIELD OF THE INVENTION

The invention relates to tubing connectors and, more particularly, to such connectors wherein the terminating fitting is impact extruded onto the tubes rather than being brazed, welded or staked onto the associated tube.

BACKGROUND OF THE INVENTION Tubing connectors for threadless pipe, tubing, conduit and the like are generally known and have been widely used in the art. Typically, tubes are mechanically connected by means of a fitting which fits over an expansion on the tube end and are fastened together to clamp the expansion to the mating part.

These known tubing connectors are exemplified by U.S. Patent No. 2,522,194 and U.S. Patent No. 3,494,643. These known tubing connectors have the disadvantage of being susceptible to leaking because significant gaps inherent in the design occur between the expansion or flare and fitting to allow the expansion to deform during assembly. The resultant deformation allows vibration and the like to loosen the fitting assembly and unseat the sealing surfaces, and repeated reassembly and sealing to other identical mating components is rendered impossible.

It is also known to provide tubes with brazed fittings via salt, flame, induction or furnace braze processes, or welded via magnesium inert gas, tungsten inert gas or resistance welding processes. These known processes are exemplified by U.S. Patent No. 4,887,853. These known processes have the disadvantage that each requires the use of large amounts of energy to heat and cool components, pollute the environment and require pretreatment and post treatments and fluxes all of which are considered hazardous, and produce a braze or weld joint that represents a potential leak path in the future.

SUMMARY OF THE INVENTION A unitary assembly of tubing with a terminating fastener is provided. The terminating fastener includes a fitting having a tubular opening therein extending through the fitting along the longitudinal axis thereof. A constriction is provided at a location spaced longitudinally from one end of the fitting. A non- expanded end of an expanded tube is received within the largest opening of the fitting. Insertion continues until expansion and fitting interference has been overcome and the expansion is completely seated in the fitting. The internal characteristics of the tube are machined coaxially using a stepped tool.

The present invention provides a low cost leak- free tube and fitting assembly. The present invention provides a tube and fitting connection with no potential leak path such as a braze or weld joint, and better dimensional and strength characteristics then a step bead that may distort in the area of the O-ring gland and leak. The present invention can be manufactured using a pollution free, low technology process that is also less costly than brazing, welding or impact extrusion. The leak-free characteristics of the present invention eliminate the loss of fluid and increases the reliability of products that use tube and fitting connections. The present technology uses welding, brazing, end forming or impact extrusion. Welding and brazing have inherent leak potential, end forming is structurally and dimensionally inferior and is prone to distortion, while impact extrusion is expensive and not yet commercially viable.

The present invention provides a unitary assembly of tubing with a terminating fastener including a fitting having a tubular opening therein extending along a longitudinal axis and a transition between first and second inner diameters of different dimensions. A tube is also provided having an axial impacted, expanded and sized end for interference fit relative to the opening in the fitting and press fitted in coaxial alignment with the fitting until completely seated. The inside diameter of the tube is finished coaxially with the fitting, so that the tube inside diameter is at least as large as the inside diameter of the tube along substantially its entire longitudinal length. After the tube is swaged into the^' inside of the fitting, the female pilot land, sealing surface and the parting line between the tube and the fitting are machined. The present invention provides a tube and fitting assembly that is superior in form, fit, function and cost competitiveness. Other objects, advantages and applications of the present invention will become apparent to those skilled in the art when the following description of the best mode contemplated for practicing the invention is read in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein:

Figure 1 is a sectional view of a tube after a first hit impaction according to the present invention;

Figure 2 is a sectional view of the tube after a second hit expansion according to the present invention;

Figure 3 is a sectional view of the tube after a third hit sizing according to the present invention;

Figure 4 is a sectional view of a terminating fastener or fitting according to the present invention;

Figure 5 is a sectional view of the terminating fitting pressed onto the end formed on the tubing previously illustrated in Figure 3 according to the present invention; and Figure 6 is a sectional view of a finished tube and fitting assembly according to the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENT In Figure 1 there is shown a tube 10 after a first hit impaction which maintains the original outside diameter of the tube 10, and coaxially constricts the inside diameter and thickens the wall 12 as required. By way of example, and not limitation, the original wall thickness of the tube 10 may be approximately .050 inches thick prior to the first hit impaction, and thereafter having a wall thickness of 0.110 to 0.120 inches inclusive. This differs from the disclosure of the previously filed related application identified as Serial Number 08/155,460 filed November 19, 1993, which is incorporated by reference herein in its entirety. In that application, a thin walled threaded fitting was disclosed as the terminating fitting for pressed on interference fit with an expanded tube having a wall thickness of 0.080 to 0.090 inches. The thin walled threaded terminating fitting required a much closer tolerance of the expanded tube in order to prevent distortion of the thin wall of the threaded fitting during assembly of the tubing and terminating fastener previously disclosed. Figure 2 illustrates a sectional view of an end

14 of the tube 10 after a second hit expansion which coaxially expands the impacted material to a suitable outside diameter relative to the inside diameter of the terminating fitting 16 to provide an interference fit. The interference fit according to the present invention by way of example, and not limitation, can be approximately 0.007 inches interference fit between the expanded outside diameter of the tube and the inside diameter of the fitting 16. The second hit expansion also rough sizes the inside diameter to a machinable condition relative to the dimension of the female pilot land of the finished assembly. A sectional view of the end 14 of the tube 10 is illustrated in Figure 3 after a third hit sizing which sizes and forms the length of the end 14 relative to the transition of the outside diameters and the non-end formed tube end to provide an exact mating surface to the fitting inside diameter and length capability from the shoulder 18 to the opposite end 14.

Referring to Figure 4, there is shown a sectional end view of a terminating fitting 16 including a transition 20 from the major and minor inside diameters coaxial to each other. Preferably, the transition 20 is formed as at least one radius.

Figure 5 illustrates a sectional end view of the tube 10 and fitting 16 assembly where the expanded end 14 extends beyond the mating surface 22 on the fitting 16 so that both may be machined simultaneously. The interference fit eliminates any chance that a gap between tube 10 and fitting 16 will allow the tube 10 to deform into the transition 20. A sectional end view of the finished tube and fitting assembly is shown in Figure 6. A constricted inner portion 24 of the tube 10 is machined open to the minor inside diameter to match the inner diameter of the tube along substantially its entire length. The portion of the tube 26 inside the fitting bore is swaged into the fitting bore 28. The female pilot land area 30, sealing surface 32 and parting surface 34 are appropriately machined for the desired tolerances. The mating seam 36 between the tube 10 and fitting 16 can also be seen in Figure 6. The terminating fitting 16 may include any external characteristics appropriate to the desired end use. The material of the end fitting 16 and tube 10 may include any desired metallic material such as aluminum, copper, steel or the like. The present invention describes a method and apparatus for providing a unitary assembly of tubing and a terminating fitting facilitating, notably, a pressed on and machined tube to fitting assembly and which overcomes the disadvantages of the prior art. It will be appreciated by those skilled in the art, that the present invention provides consistency and reliability of the completed connection heretofore deemed unattainable at a marketable cost. The form of the invention illustrated and described herein is but a preferred embodiment of the teachings. It is shown as an illustration of the inventive concept, however, rather than by way of limitation, and it is pointed out that various modifications and alterations may be indulged in within the scope of the appended claims.

The present invention provides a low cost leak- free tube end fitting assembly. The tube and fitting connection disclosed has no potential leak path such as a braze or weld joint, and provides better dimensional and strength characteristics than a step bead that may distort in the area of the O-ring gland and leak. The unitary assembly can be made using a pollution free, low tech process that is also less costly than brazing, welding or impact extrusion. The leak-free characteristics eliminate the loss of fluid and increases the reliability of tube and fitting connections. The unitary assembly disclosed eliminates the inherent leak potential present in welding and brazing joints, while improving the structural and dimensional characteristics of end forming while reducing distortion and the cost associated with impact extrusion.

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.

Claims

What is claimed is:

1. A method for forming a unitary assembly of tubing with a terminating fastener comprising the steps of: providing a fitting having a tubular opening therein extending through the fitting along a longitudinal axis thereof and an enlarged major inside diameter opening adjacent one end thereof; providing a tube having an enlarged diameter portion adjacent one end thereof; inserting the tube through the enlarged major inside diameter opening of the fitting; and press fitting the enlarged diameter portion of the tube with an interference fit within the enlarged major inside diameter opening of the fitting.

2. The method of claim 1 further comprising the steps of: impacting an end of the tube to increase a wall thickness by approximately three fold; expanding the end of the tube having the thickened wall; and sizing the expanded end of the tube to desired coaxial minor and major diameters with a transition therebetween sufficient to provide interference fit with the enlarged major diameter opening of the fitting.

3. The method of claim 1 further comprising the steps of: inserting a non-expanded end of the tube through the enlarged major inside diameter opening of the fitting until interference is encountered; and pressing the tube into the fitting in coaxial alignment until the fitting is completely seated.

4. The method of claim 1 further comprising the step of finishing an inside diameter of the tube coaxially so that an inside diameter of the tube is consistent over substantially an entire longitudinal length.

5. The method of claim 1 further comprising the step of swaging the tube into an inside of the fitting.

6. The method of claim 1 further comprising the step of machining a female pilot land.

7. The method of claim 1 further comprising the step of machining a sealing surface.

8. The method of claim 1 further comprising the step of machining a parting line surface of the fitting concurrently with the tube.

9. A unitary assembly of tubing with a terminating fastener comprising: a fitting having a tubular opening therein extending through the fitting along a longitudinal axis thereof and an enlarged major inside diameter opening adjacent one end thereof; a tube having an enlarged diameter portion adjacent one end thereof, the tube inserted through the enlarged major inside diameter opening of the fitting and the enlarged diameter portion of the tube press fit with an interference fit within the enlarged major inside diameter opening of the fitting.

10. The unitary assembly of claim 9 further comprising: an end of the tube impacted to increase a wall thickness by approximately three fold, the thickened wall end of the tube expanded and sized to desired coaxial minor and major diameters with a conical transition therebetween sufficient to provide interference fit with the enlarged major diameter opening of the fitting.

11. The unitary assembly of claim 9 further comprising: a non-expanded end of the tube inserted through the enlarged major inside diameter opening of the fitting until interference is encountered and the tube pressed into the fitting in coaxial alignment until the fitting is completely seated.

12. The unitary assembly of claim 9 further comprising: an inside diameter of the tube finished coaxially with the fitting so that an inside diameter of the tube is consistent over substantially an entire longitudinal length.

13. The unitary assembly of claim 9 further comprising: the tube swaged into an inside of the fitting, a female pilot land and a sealing surface machined thereon, and a parting line surface machined on the surface concurrently with the tube.

14. The unitary assembly of claim 9 wherein the fastener comprises: a first portion of the fastener having a through bore with a minor inside diameter and a pair of end faces, and a tubular connecting portion extending from one end face of the first portion and having a through bore with a major inside diameter, the through bores of minor and major inside diameters axially aligned with respect to one another and connected by a coaxial conical transition, the major inside diameter portion of the through bore for receiving a pressed on, interference fit, enlarged end of a tube.

15. The unitary assembly of claim 14 wherein the fastener includes a threaded aperture.