AU5852590A

AU5852590A - Polymeric tube fitting

Info

Publication number: AU5852590A
Application number: AU58525/90A
Authority: AU
Inventors: Graham Michael Johnson; Paul Edward Nolan; Suzanne Margaret Quigley
Original assignee: Commonwealth Scientific and Industrial Research Organization CSIRO
Current assignee: Commonwealth Scientific and Industrial Research Organization CSIRO
Priority date: 1989-07-03
Filing date: 1990-07-03
Publication date: 1991-01-17
Also published as: WO1991000470A1; EP0479831A1; EP0479831A4

Description

POLYMERIC TUBE FITTING

Technical Field

This invention relates to gas and liquid plumbing fittings and more particularly to polymeric fittings for use with corrosive, reactive or pure fluids.

Background Art

In applications where corrosive, reactive or pure fluids are handled or transported in tubes, special precautions must be taken with the associated vessels, tubing and plumbing. In many instances the fluid must be handled entirely within a non-corrosive environment. Fluorlnated polymers such as TEFLON® have been used in vessels and their linings, tubing and plumbing fittings.

It is known that gas and liquid plumbing fittings such as unions and tees have been fabricated from TEFLON® or other non-corrosive polymers. While such non-corrosive polymeric materials have excellent chemical resistance, they can have poor mechanical properties, including a propensity to cold flow. Where threads are cut Into the material, the threads are weak and are easily cross-threaded. Complex or detailed machining of these mechanically unstable plastics is often difficult and expensive. Further, the fluid pressures that the fittings can with stand 1s limited by the cold flow properties of the polymeric material.

Object of the Invention

Accordingly, 1t is an object of the invention to ameliorate some of the disadvantages of the prior art.

Disclosure of the Invention

According to the teachings of the present invention there is provided a fitting comprising a polymeric plug having a first bore. The first bore is characterised by a relief portion and a tapered section which leads from the relief portion to ar enlarged portion. The polymeric plug is received by a case. The case has a threaded open g leading into th≤ enlarged section. A nut having a second bore and an exterior threaded portion is received by the threaded opening. A polymeric ferrule is provided having a tapered exterior nose which is engageable with the tapered section of the first bore. Brief Description of the Drawings

Figure 1 1s a cross sectional view of a connector incorporating the polymeric fittings of the present Invention.

Figure 2 1s a cross sectional view of an alternate embodiment of a connector Incorporating the polymeric fittings of the present Invention.

Figure 3 1s a prospective view of a polymeric ferrule which 1s used 1n conjunction with the present Invention.

Figure 4 1s a cross sectional view of a nut adapted to receive the polymeric ferrule of Figure 3.

Figure 5 1s an alternate embodiment of the plug and case of the present invention.

Figure 6 is a cross sectional view of a threaded nut, ferrule and grip ring.

Figure 7 1s a cross sectional view of a nut incorporating a gripping blade.

Best Mode and Other Modes for Carrying Out the Invention

As shown 1n Figure 1 a connector 10 may be manufactured with polymeric fittings according to the teachings of the present invention. The connector 10 Includes a polymeric plug 11 Into which has been formed a plug bore 12. The plug bore 12 is perpendicular to the cylindrical axis of the plug 11. The plug bore 12 includes a fluid carrying conduit 13, a relief portion 14, a tapered portion 15 and an enlarged portion 16. Relief portions 14 are a preferred feature of the invention. It should be appreciated that the plug 1s formed from a corrosion resistant polymeric material for example one of the fluorinated hydrocarbon polymers such as TEFLON®, including PTFE grade TEFLON®.

The plug 11 is encircled by a cylindrical metallic case 29. The case includes a threaded opening 60 which is aligned with the enlarged portion 16.

The enlarged portion 16 of the bore is adapted to receive a polymeric ferrule 17. The ferrule includes a central bore 18, a tapered nose 19 and a tapered piloted surface 20. The taper angle L of the nose is less than the taper angle M of the tapered section 15 of the plug bore. The piloted portion 20 of the ferrule co-operates with a tapered forward pilot surface 21 formed in a threaded nut 22. The taper angle of the piloted surface 20 is equal to the nose taper L but may be less than the taper angle of the pilot surface 21. The nut 22 also Includes a central passage 23, exterior threads 24 and flat surfaces 25 for operating the nut.

In operation, a tube 27 is inserted through the passage 23 of the nut and into the central bore 18 of the ferrule. This assembly is pushed through the opening 60 and Into the plug until the nose 19 of the ferrule contacts the tapered section 15 of the plug bore and the tube 27 locates against the Inner end of the relief portion 14. The fitting is tightened by engaging the threads 24 of the nut with matching threads 28 1n the opening 60. Continued tightening of the nut drives the ferrule into the tapered portion 15 and brings together the piloted surface 20 of the ferrule and the pilot surface 21 of the nut. Further tightening of the nut causes a slight plastic deformation of the tapered ends of the ferrule owing to the fact that the taper angles of the ferrule are less than the taper angles of the tapered sectic of the bore 15 or the pilot surface 21. The aforementioned plastic de ormatlon causes radially inward compressive stress at the very tip of the piloted and tapered portions of the ferrule and thus has a clamping or gripping effect on the tube 27 thus providing a better seal. A portion of the tube 27 within the relief portion 14 is not deformed and thus resists being pulled p-: t the compressed inner end of the ferrule. The relief portion may thus be larger than the ferrule Interior diameter to provide accommodation for any outward flaring of the tube. Devices made according to the teachings of the present invention have been successfully pressure tested to 100 p.s.i.g.

When assembled, the fitting provides a joint where the areas in contact with the fluid being handled are all corrosion resistant polymeric material. In the example of Figure 1, two fittings are used to form a connector. It will be appreciated that, for example, three fittings could be joined to a common central fluid conduit 13 thus forming a "T" or "Y". Manifolds which Include four or more fittings would be easily fabricated according to the aforesaid teachings. An alternate embodiment of a connector or coupling incorporating two improved polymeric fittings of the present invention is shown 1n Figure 2. Like the device of Figure 1, a round plug 11 is circumferentially surrounded by an annular case 29, and two similar fittings are aligned along a common axis. The axis is diametrical with regard to the round or circular plug. This arrangement can be easily extended to a coupling Incorporating three or more fittings arranged around the circumference of the plug and case and fluidlcally merging in an area common to each fitting bore. In this embodiment, the polymeric ferrule 30 further Includes an elongated hollow shaft 31. The shaft terminates in a flange 32. The flange 32 and distal portion of the shaft are sub-divided by a plurality of slots 33. The forward pilot section 34 of the nut includes both a tapered portion 35 and an annular r1m 36 for guiding and retaining the ferrule. The slots 33 are provided so that the ferrule may be inserted Into the nut from the forward section 34, and so that the ferrule will be snugly retained by the nut throughout all phases of operation. It will be appreciated that by the provision of the elongated shaft 31 and flange 32, it is possible to visually ascertain whether or not the ferrule has been included In the assembled fitting owing to the obvious presence or absence of the flange 32. Thus it is unnecessary to disassemble the fitting in order to tell whether or not the ferrule has been included. Note that the case 29 may be provided with a threaded opening 60 or other means for attaching the case to a panel or stand. This will further reduce the stresses on the tubing.

Another example of a polymeric ferrule made 1n accordance with the teachings of the invention is depicted in Figure 3. The ferrule includes a flange 32, four slots 33, an elongated shaft 31 and a tapered nose 19. The nose 19 terminates in a flat face 61. However, unlike the ferrule of Figure 2, the piloted surface 37 1s not tapered. Rather, the piloted surface includes a cylindrical shoulder 38 and an annular seat surface 39. This form of piloted surface is adapted for an alternate nut as depicted in Figure 4. The nut 40 in Figure 4 includes an enlarged recess 41 for receiving the shoulder 38. The pilot surface of the nut is in the form of an annular lip 42 which includes a flat face 43 which is adapted to contact the seat 39 of the ferrule's piloted portion. The nut also includes a generally cylindrical exterior surface 44 having exterior threads 45 and two flat surfaces 46 for operating the nut. By compressing the flange 32, the ferrule 1s Inserted into the recessed portion 41 of the nut and Into the nut bore 47. When completely inserted, the flange 32 protrudes from the distal portion 47 of the nut. The ferrule, in Its inserted position, is shown in phantom lines in Figure 4.

A further embodiment of the plug and case are depicted 1n Figure 5. In this instance, the plug 50 1s in the form of a cylinder whose plug bore 51 is axially aligned with the cylindrical axis of the plug 50 rather than perpendicular to it (or diametrical) as .hown In Figures 1 and 2. The plug bore includes a tapered portion 52 which leads from a relief portion 58 into an enlarged section 53. The cylindrical plug 50 terminates 1n a flat face 54. The case 55 Is In the form of a cylinder which is longer than the plug 50. The end face 56 of the cylinder extends beyond the terminal portion 54 of the plug. Thus internal threads 57 may be provided for receiving any one of the nut and ferrule embodiments taught with reference to Figures 1, 2, 3 and 4.

Any of the embodiments disclosed herein may be modified to resist tube pull-out or expulsion if a particular application of the invention is subject to tube tension or high pressures. As shown in Figure 6, the ferrule 61 may be provided with one flat face 62 opposite the tapered nose end 63. A grip ring 64 has a matching tapered end 65 and flat end face 66. The grip ring 64 is preferably provided with a single longitudinal split 67 so that it radially contracts when the nut 68 is tightened. The grip ring may include any variety of Internal projections 69, within its bore, for aiding in the gripping of the tube. The gripping ring is not essential to the fluidic seal, nor does it come into contact with the carried fluid. It may therefore be fabricated from any convenient material Including, but. not limited to, brass, nylon or steel. As shown in Figure 7, a similar gripping effect may be provided by equipping a nut 70 with a blade-like gripper 71 which may be formed from spring steel or hard plastic. The gripper 71 is fitted into a slot 72 formed in the nut 70 so that an inner end 73 of the gripper extends into the bore 74 and is inclined towards the ferrule 17. In a further embodiment the nut 70 and gripper 71 as described with reference to Figure 7 may be used in conjunction with a ferrule having an elongated hollow shaft as shown in Figure 8. The ferrule is similar to the design depicted 1n Figure 3 but also includes an opening or slot 75 in the shaft 31 and flange 32 to provide clearance between the blade-Hke gripper 71 and the ferrule when the ferrule is inserted into nut 70. Thus, the gripper 71 extends into the interior portion of the hollow shaft so that the edge 73 may contact and grip the tube which passes through the ferrule. This configuration provides the benefits of added resistance to tube pull-out from the gripper and the ability to visually ascertain that the ferrule and gripper are in place without disassembly of the fitting.

It should be appreciated that the aforestated embodiments are provided by way of examples and not limitations to the scope of the teachings of the present invention nor of the claims. In particular, it will be appreciated that any number of polymeric materials are suitable for the plug and ferrule. Any polymeric material which is inert or not corroded by the material which it is carrying would be considered suitable. A material would be considered suitable for the case and nut when it provides better strain resistance than the polymeric material, particularly resistance to cold flow, or superior machining qualities such as ease of thread cutting. In addition, 1 is contemplated that any number of fluid or gas handling devices may Incorporate the improved polymeric fittings of the invention without departing from the inventive spirit thereof.

Industrial Applicability The fitting and couplings of the present invention are particularly well adapted to tubes which handle corrosive, reactive or pure fluids. The Invention 1s easily applied to a fitting or coupling in which the gas or liquid contacting parts are made from an inert polymer and yet threads are not required in any of the polymeric parts of said fittings or couplings.

Claims

1. A fitting for a tube, comprising: a polymeric plug having a first bore; the first bore having a relief portion and a tapered section which leads from the relief portion into an enlarged portion; the plug received by a case having at least one opening which communicates with the enlarged portion of the first bore; a nut having a second bore and an exterior portion for engaging the opening which nut may be tightened with respect to the case to engage and compress a polymeric ferrule; the polymeric ferrule having a tapered exterior nose portion engageable with the tapered section of the first bore.

2. The fitting of claim 1, wherein: the tapered section of the first bore is characterized by a first taper angle and the tapered nose portion of the ferrule is characterized by a second taper angle and wherein the first taper angle is grr r than the second.

2. The fitting of claim 1 wherein: the plug is polymeric and the case is metallic.

4. The fitting of claim 1 wherein: the ferrule further comprises a piloted portion which is engageable by a similarly configured forward pilot surface formed on the nut.

5. The fitting of claim 4, wherein: the ferrule further comprises an elongated hollow shaft which extends entirely through the second bore when the piloted portion is actually in contact with the pilot surface of the nut.

6. The fitting of claim 5, wherein: the hollow shaft has forir ¹ therein a )pening; the nut 1s provided with a slot which communicates with the second bore; wherein the slot receives a gripping blade having an edge which extends into the opening formed in the hollow shaft and into the second bore when the piloted ^rtion of the ferrule is actually in contact with the pilot surface of _.,a nut. 7. The fitting of claim 4 wherein the piloted portion and pilot surface are tapered.

8. The fitting of claim 4 wherein the piloted portion comprises a cylindrical shoulder.

9. The fitting of claim 1, wherein: a grip ring 1s provided and is locatable between the ferrule and the nut; the grip ring further comprising a longitudinally sloted body having a central bore, which bore is inscribed with gripping projections.

10. The fitting of claim 9, wherein: the body of the grip ring 1s tapered and is engageable by a similarly tapered forward pilot surface formed on the nut.

11. The fitting of claim 1, wherein: the nut is provided with a slot which communicates with the second bore; the slot receiving a gripping blade having an edge which extends into the second bore.

12. A coupling incorporating at least two of the fittings according to any of claims 1-11.

13. A coupling incorporating two fittings according to any one of claims 1-11 , wherein: the two fittings are aligned along a common axis; the plug is cylindrical and further comprises two end faces; the common axis is aligned with a cylindrical axis of the plug; the case 1s cylindrical and coaxial with respect to the plug wherein the cylindrical case extends beyond both end faces of the plug.

14. A coupling incorporating at least two fittings according to any one of claims 1-11, wherein: two or more fittings are formed radially about a circular plug; and the case is annular and surrounds the plug about a circumferential portion.

15. The fitting of any of claims 1-11, wherein: the plug and ferrule are polymeric and the case is metallic. 16. A fitting for a tube, comprising: a polymeric plug having a first bore; the first bore having a relief ..ortion and a tapered section which leads from the relief portion into an enlarged portion; the plug received by a case having at least one threaded opening which communicates with the enlarged portion of the first bore; a nut having a second bore and an exterior thread for engaging the threaded opening which nut may be tightened with respect to the case to engage and compress a polymeric ferrule; the polymeric ferrule having a tapered exterior nose portion engageable with the tapered section of the first bore; the tapered section of the first bore characterized by a first taper angle and the tapered nose portion of the ferrule is characterized by a second taper angle and wherein the first taper angle 1s greater than the second; the ferrule further comprising a piloted portion which is e-gageable by a similarly configured forward pilot surface formed on the r c.

17. The ^'ttin_d of claim 16, wherein: t\ .rrule further comprises an elongated hollow shaft which e^vtends entirely through the second bore when the piloted portion is .ually in contact with the pilot surface of the nut; and the hollow shaft terminates in a flange which is visible after the nut is thr . ded into the case.

18. A fitting for a tube, comprising: a polymeric plug having a first bore; the first bore having a tapered section which leads towards an enlarged portion; the plug received by a case having at least one threaded opening which communicates with the enlarged portion of the first bore; a nut having a second bore and an exterior thread for engaging the threaded opening which nut may be tightened with respect to the case to engage and compress a polymeric ferrule; the polymeric =rrule having a tapered exterior nose portion engageable with the tape- J section of the first bore; wherein a grip ring is provided and is locatable between the ferrule and the nut; the grip ring further comprising a longitudinally sloted body having a central bore, which bore 1s inscribed with gripping projections.

19. A fitting for a tube, comprising: a polymeric plug having a first bore; the first bore having a tapered section which leads from the relief portion into an enlarged portion; the plug received by a case having at least one threaded opening which communicates with the enlarged portion of the first bore; a nut having a second bore and an exterior thread for engaging the threaded opening which nut may be tightened with respect to the case to engage and compress a polymeric ferrule; the polymeric ferrule having a tapered exterior nose portion engageable with the tapered section of the first bore; the nut provided with a slot which communicates with the second bore; the slot receiving a gripping blade having an edge which extends into the second bore.

20. A fitting for a tube, comprising: a polymeric plug having a first bore; the first bore having a tapered section which leads from the relief portion into an enlarged portion; the plug received by a case having at least one threaded opening which communicates with the enlarged portion of the first bore; a nut having a second bore and an exterior thread for engaging the threaded opening which nut may be tightened with respect to the case to engage and compress a polymeric ferrule; the polymeric ferrule having a tapered exterior nose portion which engages the tapered section of the first bore and an elongated hollow shaft which extends through the nut; the nut provided with a slot which communicates with the second bore; the slot receiving a gripping blade having an edge which extends into the second bore; the gripping blade also extending into the interior of the shaft through an opening formed in the hollow shaft.