US3844148A

US3844148A - Corrosion-resistant flareless tube fitting-ring

Info

Publication number: US3844148A
Application number: US00344125A
Authority: US
Inventors: N Fitzthum; H Patel; A Olejarczyk
Original assignee: Weatherhead Co
Current assignee: Weatherhead Co
Priority date: 1973-03-23
Filing date: 1973-03-23
Publication date: 1974-10-29
Anticipated expiration: 1991-10-29

Abstract

A cutting and sealing sleeve in a tube fitting assembly wherein the sleeve is adapted to be made of the same metal as the tube and, in appropriate applications, the body and nut of the assembly to provide maximum corrosion resistance by elimination of heat treatment for increased hardness which reduces corrosion resistance of certain metals and/or elimination of electrolytic action between dissimilar metals. The area of a cutting and sealing edge in the sleeve is selectively hardened with respect to the remainder of the sleeve by cold working surplus material contiguous to the edge area with the edge being formed by subsequent machining away of this surplus material. Local hardening of only the cutting and sealing edge area insures that the edge will be sufficiently harder than a tube of the same material for reliable ''''bite'''' or cutting and sealing action while the major portion of the sleeve remains relatively soft for minimum wrenching torque in assembly.

Description

United States Patent [191 Patel et al.

[ 1 Oct; 29, 1974 [5 1 CORROSION-RESISTANT FLARELESS TUBE FITTING-RING [75] Inventors: Hiralal V. Patel, Euclid; Anthony J.

Olejarczyk, Cleveland; Nathan J. Fitzthum, Euclid, all of Ohio [73] Assignee: The Weatherhead Company,

Cleveland, Ohio [22] Filed: Mar. 23, 1973 [21] Appl. No.1 344,125

[52] US. Cl 72/70, 72/340, 285/341 [51] Int. Cl B2ld 19/00 [58] Field of Search 72/70, 122, 117, 340; 285/341'; 29/446; 76/104 [56] References Cited UNITED STATES PATENTS 2,810,191 10/1957 Hanna 72/340 2,962,079 11/1960 Wilson 72/117 3,512,812 5/1970 Kreidel et al. 285/341 3,616,712 ll/l97l Eickhorn 76/104 FOREIGN PATENTS OR APPLICATIONS 840,164 7/1960 Great Britain 285/341 Primary Examiner-Lowell A. Larson Attorney, Agent, or Firm-McNenny, Farrington, Pearne & Gordon [5 7] ABSTRACT A cutting and sealing sleeve in a tube fitting assembly wherein the sleeve is adapted to be made of the same metal as the tube and, in appropriate applications, the body and nut of the assembly to provide maximum corrosion resistance by elimination of heat treatment for increased hardness which reduces corrosion resistance of certain metals and/or elimination of electrolytic action between dissimilar metals. The area of a cutting and sealing edge in the sleeve is selectively hardened with respect to the remainder of the sleeve by cold working surplus material contiguous to the edge area with the edge being formed by subsequent machining away of this surplus material. Local hardening of only the cutting and sealing edge area insures that the edge will be sufficiently harder than a tube of the same material for reliable bite or cutting and sealing action while the major portion of the sleeve remains relatively soft for minimum wrenching torque in assembly.

14 Claims, 7 Drawing Figures PATENTEDncr 29 1974 3.844.148

sum 10; 2

CORROSION-RESISTANT FLARELESS TUBE FITTING-RING BACKGROUND OF THE INVENTION PRIOR ART Flareless fittings employing cutting and sealing sleeves are well known and are exemplified by those illustrated in US. Pat. Nos. 2,171,217; 2,823,935 and 3,092,405. When elements of a fitting of this type are assembled, an internal edge of the sleeve is cammed inwardly against a tube surface to shear into the tube to produce an annular ridge or shoulder against which the sleeve locks and seals the tube in the assembly.

For effective cutting and sealing action, the cutting edge of the sleeve should normally be measurably harder than the tube surface. A number of techniques have been used to achieve a suitable differential hardness between the sleeve edge and tube. A direct approach is to produce the entire sleeve from a material harder than the tube, normally, by using a material dissimilar to that of the tube. Other approaches have included forming the sleeve of two parts with the part providing the cutting edge formed of a harder material than the remainder of the sleeve and the tube, work hardening discontinuous portions of a cutting edge by forming cutting teeth in the relevant sleeve area, selectively heat treating only the cutting edge of the sleeve, and heat treating the entire sleeve either to provide a hard case or a through hardness.

While these prior methods of obtaining differential sleeve and tube hardness have been satisfactory in many applications, they are generally unsuitable where corrosive fluids or environments are involved. Dissimilar metals in physical contact, such as between the tube and sleeve, are subject to electrolytic corrosion. Hardening the sleeve or portions of it by heat treatment may reduce its corrosive resistance especially where the sleeve is formed of a chromium nickel stainless steel particularly of the low carbon variety.

SUMMARY OF THE INVENTION The present invention provides an improved cutting and sealing sleeve for flareless fittings which may be formed of the same metal as the .tube to which it is to be fitted. This identity of composition between the sleeve and tube avoids electrolytic corrosion associated with the use of dissimilar metals. Also the absence of any .heat treatment insures against deterioration of corrosion resistance properties of the sleeve material. In accordance with the invention, the sleeve material forming the cutting and sealing edge of the sleeve is seprojecting circumferential rib on the inner surface of a sleeve blank. The rib is progressively deformed or flattened radially outwardly by a roll swaging tool. The sleeve is externally supported by a restrainer die while the rib is swaged to prevent displacement and consequent hardening of sleeve material other than at the rib and closely adjacent areas.

The initial configuration of the rib and adjacent areas of the blank body are preferably arranged to cause the rib to be displaced in an ideal manner whereby the sleeve bore is not affected by flaking or other material failure during the swaging process and whereby an optimum hardness profile is obtained at the edge and adjacent areas.

With a locally hardened cutting and sealing edge, the sleeve may be formed of the same material as a tube, body and nut of a fitting assembly, thus providing resistance to both internal and external electrolytic corrosion. The invention is particularly suited for use with corrosion resistant and work hardenable metals such as the 300 series stainless steels. Selective hardening of the cutting edge and the annular zone contiguous with it leaves the remaining major portion of the sleeve body relatively soft. This provides good bowing characteristics to the sleeve as discussed below and minimizes wrenching forces necessary to effect a fluid tight connection. The selective cold working and edge forming steps, moreover, are readily adapted to high production techniques and tooling so that the sleeve may be produced economically.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal cross-sectional view of a fitting assembly embodying the invention.

FIG. 2 is a longitudinal sectional view of a sleeve blank in an initial stage of formation wherein external surface contours and a preliminary bore are provided.

FIG. 4 is a somewhat enlarged fragmentary sectional view of a forward end of the sleeve blank in initial engagement with an external restraining die and an internal roll swaging tool.

FIG. 5 is an enlarged fragmentary sectional view of a forward portion of the sleeve after the internal rib has been displaced and the adjacent areas work hardened by the roll swaging tool.

FIG. 6 is an enlarged fragmentary view similar to FIG. 5 illustrating a forward end of the sleeve after final finishing operations in which a cutting and sealing edge is formed.

FIG. 7 is a view similar to FIG. 5 which diagramatically illustrates the relative hardness of the sleeve material after the roll swaging operation.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings and in particular to FIG. I there is shown a fitting assembly 10 for connecting a tube 11. The term tube is intended to generically include pipe and similar conduits. The fitting assembly 10 includes a tubular body member 12, an apertured nut 13 and a tube sleeve or ferrule 14.

The fitting body 12 is externally threaded at 16 adjacent a tube receiving forward end 17. The body 12 has a usual enlarged hexagonal portion 18 for engagement by awrench. The interior of the'body 12 is defined by a series of circular bores along an axis 32 of the assembly 10. The internal bores include a conical or camming bore 19 extending with decreasing diameter from the forward end 17 of the body, a cylindrical tube receiving bore 22 and a central bore or passage23. A generally radial surface 24 extends between the

cylindrical bores

22 and 23 and forms an abutment surface against which an end 26 of the tube seats.

The apertured nut 13 is preferably conventionally formed from hexagonally shaped bar stock and is provided with internal threads 28 complementary to the body threads at 16. The nut 13 is formed with a clearance bore or cavity 29 for receiving the sleeve 14 and an internal generally radial end wall or surface 31.

The surface 31, as shown, is preferably inclined slightly, for example, about from a plane normal to the axis 32 of the fitting assembly and extends from the clearance bore 29 inwardly to an aperture 33 dimensioned to provide slight clearance for the tube 11.

The sleeve 14, formedby operations described in detail below, includes a central cylindrical bore 36, a forward annular lip portion 37 and-an internal axially recessed tube cutting and sealing edge 38. Both the sleeve lip 37 and cutting edge 38 are circumferentially continuous. The sleeve 14 also includes a tubular portion 39 of generally uniform wall thickness extending rearwardly from the cutting and sealing edge 38. A rearward end of the sleeve includes a circumferential shoulder 40 having a generally radial end face 41 complementary to the angle of theradial nut surface 31.

The complementary angles of these surfaces provide both a centering action and abutting contact over a substantial area when the sleeve and nut are engaged.

8 Referring now to FIGS. 2 and 3, formation of the sleeve 14 is preferably started by machining round bar stock in a series of surface forming operations. As indicated in FIG. 2, in a first stage a sleeve blank 46 is initially formed by drilling or otherwise boring bar stock 47 to form a provisional bore 48 therein. The exterior of the bar stock 47 is machined or otherwise worked to provide a slightly tapered or conical surface 49 of slightly increasing radius in a direction away from a forward end 51 of the blank 46.

Following formation of the outer tapered surface 49, as illustrated in FIG. 3, the blank 46 is further internally machined to form a counterbore or annular relief 52 at the forward sleeve end 51 and an enlarged axially spaced bore 54 substantially equal to the finished bore 36 of the sleeve 14. Machining of the counterbore 52 and the enlarged bore 54 results in the formation of a continuous circumferential rib 53 extending radially inwardly from these bores. As illustrated, the inner surface of the rib 53 is formed by the remaining surface or land of the provisional bore 48. At a side facing the inner bore 54 the rib 53 is formed with a beveled or conical integral shoulder 56, ideally defining an angle of about 45 with the axis of the blank 46, shown most clearly in the enlarged view of FIG. 4.

In accordance. with a principal feature of the invention, the internal rib 53 of the sleeve blank 46 is provided as excess material which is plastically deformed to locally work harden it and contiguous areas. FIG. 4

illustrates a portion of a suitable tool for engaging and displacing the rib 53 radially outwardly relative to the inner sleeve bore 54. The tool 61 is preferably a roll swaging tool commonly used for swaging boiler tubes. The swaging tool 61 includes a central tapered or conical mandrel 62 and three or more rollers 63 retained on the periphery of the mandrel 62 by suitable retainers 64 on opposite ends of the rollers. Only one of the rollers 63 is illustrated in the view of FIG. 4. The rollers 63 are tapered with an angle complementary to the angle of the mandrel 62 so that each roller 63 presents a line of contact 65 parallel to the axis of the mandrel 62 and the sleeve blank 46. The sleeve blank 46 is radially supported on its exterior by a restraining die 68 having a slightly tapered bore 69 complementary to the conical exterior sleeve surface 49 during working by the swaging tool 61. The taper angle of the surface 49 and bore 69 is provided to prevent the sleeve blank 46 from looking up in the die 68 when the rib 53 is swaged.

During operation of the swaging tool 61, the mandrel 62 is moved axially relative to the rollers 63 and retainers 64, as well as the sleeve blank 46 and restraining die 68. As the mandrel 62 moves axially relative to the rollers 63, the rollers are driven radially outwardly. The mandrel 62 is rotated relative to the sleeve blank 46 and die 68 during this axial movement to cause the rollers 63 to rotate about the inner periphery of the rib 53.

The rollers 63 move progressively radially outward to flatten the rib 53 even with the cylindrical bore 54 as illustrated in FIG. 5. The volume of material of the rib 53 folds overan inner portion 71 of the cylindrical counterbore 52. The working or plastic deformation of the rib 53 is preferably done cold. Plastic displacement of the rib causes the contiguous circumferential area of the sleeve blank 46 to be locally work hardened relative to the remaining portions of the sleeve blank.

As illustrated in FIG. 7, maximum hardness is achieved at or adjacent the inside diameter of the sleeve blank 46 adjacent the base of the material fold at 71. Hardness decreases with distance radially outward from the inside diameter 54 of the sleeve blank 46 and axially rearwardly of the line of fold 71. A series of dots 74 represent points at which micro-hardness readings were taken in a test specimen to generate the relative hardness curves 76 and 77. The horizontally projected curve 76 schematically indicates the variation in hardness in a radial direction while the vertically projected curve 77 schematically illustrates the axial variation in hardness. In tests of a sleeve of type 316 stainless steel of 0.06 carbon material in which a rib having an inner diameter of approximately 0.493 inches, an inner bore diameter of nominally 0.507 inches and a forward counterbore of 0.532 inches, original Rockwell C hardness of about 24.5was increased to approximately 38.0 at the point of maximum hardness. It has been found that a differential hardness between the cutting edge 38 and tube 11 of at least about 10 to 15 points on the Rockwell C" scale is sufficient for satisfactory results.

Subsequent to the roll swaging and selective local hardening of the rib 53 and contiguous areas, the sleeve blank 46 is finish machined. The cutting and sealing edge 38 is formed by removing the excess rib material folded into the counterbore 52. Preferably, the final machining includes the machining away of the original counterbore 52 to form a finish inside counterbore surface or recess 81 (FIG. 6) within. the forward lip portion 37 of the sleeve. A radial wall 83, ideally, is formed axially inward of the original fold line 7l so as to insure structural integrity of the sleeve material in the area of the cutting and sealing edge 38.

The cutting and sealing edge 38 is defined by the intersection of the wall 83 and the finish sleeve bore 36. The finish sleeve bore 36 may be that provided by the inner blank bore 54 or alternatively, the sleeve blank may be machined to a slightly larger finish bore. Subsequent to the roll swaging step, the exterior of the sleeve may also be machined to produce a sleeve of relatively thin wall section by removing the material defining the conical end 49 of the blank and forming a tapered outside lip surface 85 (FIG. 6). The sleeve may be otherwise completely finished before it is severed from the bar stock 47.

The counterbore 52 of the sleeve blank 46 and the integral beveled shoulder 56 of the rib 53 cooperate in controlling the movement of the material forming the rib forwardly into the counterbore such that a minimum amount of flaking or other failure of material in the relevant area is produced so that it is not necessary to remachine the blank bore 54 to provide a smooth surface, or if such machining is desired it is not necessary to remove an excess amount of material.

When the nut 13 is tightened on the body 12, the sleeve is axially compressed between the radial nut surface 31 and body camming surface 19. The tube cutting and sealing edge 38 is cammed inwardly by action of the surface 19 on the lip portion 37 to cut or shear into the outer surface of the tube 11 to form or turn up a ridge thereon in a known manner. The edge 38 engages the ridge to retain the tube 11 in the body and seal the outer periphery of the tube. Simultaneously, the rearward portion of the sleeve is adapted to contact slightly to embrace and support the circumference of the tube 11 at a point axially displaced from the sealing and cutting edge 38. This constriction is provided by a bowing of the sleeve in compression along the tubular portion 39. Such bowing is not restrained as it would otherwise be if the entire sleeve were hardened merely to harden the area of the cutting and sealing edge 38. Consequently, wrenching torque necessary to effect proper bowing and constriction of the sleeve is minimized.

The sleeve 14 may be formed of any homogeneous work hardenable metal but one of the more important applications of the sleeve is in fitting assemblies where the sleeve is formed of the same material of at least the tube and, preferably, the body and nut also. The preferred use of identical materials provides significant advantages in applications where the fitting assembly is subjected to corrosive conditions since the contacting materials are not subject to electrolytic corrosion. One type of material which has been found to be ideally suited for use with the present invention are the 300 series stainless steels and in particular type 3l6 stainless steel. This material, generally, may not be heat treated to increase its hardness without diminishing its corrosion resistance. From the description above it may be understood that the sleeve may be locally hardened in the area of the cutting and sealing edge to a degree sufficient to permit it to reliably cut into a tube of the same material and of approximately the same hardness as that of the major portion of the sleeve.

Although a preferred embodiment of the invention is illustrated, it is to be understood that various modifications and rearrangements of parts may be resorted to without departing from the scope of the invention disclosed and claimed herein.

What is claim is:

1. A method of forming an integral cutting and sealing sleeve for a tube fitting comprising the steps of forming a tubular blank from a body of work hardenable metal, locally work hardening an internal circumferentially continuous zone of material at an end portion of the blank while maintaining the original hardness of the blank material in a major portion of the body, subsequently machining the interior of the sleeve to produce a circumferentially continuous cutting and sealing edge in the work hardened zone whereby the sleeve is adapted to cut and seal a tube having a hardness as great as that of the major portion of the blank.

2. The method as set forth in claim 1 wherein said zone is work hardened by plastically displacing blank material radially outward in the sleeve blank.

3. The method as set forth in claim 2 wherein said blank is originally formed with a circumferential rib adjacent said zone, and said rib providing said plastically displaced material.

4. The method as set forth in claim 3 wherein said rib is plastically deformed by progressive radial movement of a tool in roll contact with an inner periphery of said rib.

5. The method as set forth in claim 4 wherein an annular relief is formed in said blank between said rib and an associated end of the blank.

6. The method as set forth in claim 5 wherein the outer circumferential surface of said blank is restrained by positioning said blank into a restraining die while said rib is plastically deformed.

7. The method as set forth in claim 6 wherein said blank is provided with a tapered outer surface and said die block is provided with a complementary tapered bore whereby lock up of the blank in the die bore is prevented subsequent to displacement of said rib.

8. The method of making a tube coupling sleeve with an integral selectively hardened cutting and sealing edge comprising the steps of forming a tubular blank of work hardenable metal, providing a continuous circumferential zone of excess material on the interior of the blank, plastically displacing said excess material to work harden a contiguous and continuous circumferem tial zone, and subsequently machining said excess material away from said contiguous zone to form an internal cutting and sealing edge.

9. The method as set forth in claim 8 wherein said excess material is originally provided as a circumferential rib extending radially inward from a circular area of said contiguous zone at which said cutting edge is formed.

10. The method as set forth in claim 9 wherein said circumferential rib is plastically deformed by a tool producing radial pressure against said rib.

11. The method as set forth in claim 10 wherein said rib is formed with an integral support shoulder portion at a rearward side whereby said rib is caused to be displaced forwardly as said tool radially engages said rib.

from said relief.

Claims

8. The method of making a tube coupling sleeve with an integral selectively hardened cutting and sealing edge comprising the steps of forming a tubular blank of work hardenable metal, providing a continuous circumferential zone of excess material on the interior of the blank, plastically displacing said excess material to work harden a contiguous and continuous circumferential zone, and subsequently machining said excess material away from said contiguous zone to form an internal cutting and sealing edge.

12. The method as set forth in claim 11 wherein said blank is originally formed with an annular relief to accommodate forward displacement of said rib.

13. The method as set forth in claim 12 wherein said tool means is moved radially outward as it is caused to roll on the inner circumference of said rib.

14. The method as set forth in claim 13 wherein said excess material is machined substantially completely from said relief.