CA1251238A

CA1251238A - Heavy duty tube coupling

Info

Publication number: CA1251238A
Application number: CA000458170A
Authority: CA
Inventors: Ralph G. Ridenour
Original assignee: Ralph G. Ridenour; Universal Tubular Systems, Inc.
Current assignee: Universal Tubular Systems Inc
Priority date: 1983-08-01
Filing date: 1984-07-05
Publication date: 1989-03-14
Also published as: JPS6057089A; GB2144192A; SE8403910L; SE8403910D0; DE3428260A1; AU575841B2; US4585255A; GB8418501D0; AU3115484A; SE458949B; FR2550312B1; FR2550312A1; GB2144192B; DE3428260C2

Abstract

HEAVY DUTY TUBE COUPLING

ABSTRACT OF THE DISCLOSURE

A tube coupling with only a body and a threaded member is disclosed, the threaded member usually being a nut to overlie an outer sleeve and an inner sleeve unitary with the body. These two sleeves define therebetween an annular groove to receive the end of the tube. The method of tightening the nut onto the body provides that a generally conical cam surface on the nut interacts with a shallower taper conical cam follower surface on the outer sleeve to force this cam follower surface radially inwardly and longitudinally inwardly forming annular radially inward bulges on the outer and inner sleeves and on the tube trapped therebetween. This interlocks the tube with the coupling, and provides a fluid seal at three different places, the inner wall of the tube, the outer wall of the tube, and the end of the tube at the bottom of the groove. The foregoing abstract is merely a resume of one general application, is not a complete discussion of all principles of operation or applications, and is not to be construed as a limitation on the scope of the claimed subject matter.

Description

HE~VY DUTY TUBE COUPLING

ACKGROUND OF THE INVENTION

Couplings to connect to a flared end of a tube have often been a two-pact fitting of a body and a nut.
However, th7s ~equirer flaring ~he end of the tubing, and in many case5 thi~ is inconvenient or di~ficult.
Accordingly, st~aight tubing OL non-flared tubing has also been attempted to be secu~ed ~o a coupling, and two-part couplings have been utilized, as in U.S~ Patent No. 927,388, and on small diameter tubes, as in U.S.
Patent No. 3,375,026~ Three-part tube couplings for non-flaLed tubes have been more common, including those disclosed in U.S. Patents Nos. 3,025,086: 3,454,290;
3,834,743: and 4,162,802. Also, The WeatheLhead Company has di~closed a thcee-part flareless tube fitting in its 2600 Series of tube fitting~. Four-par~ tube fittings have also been disclosed, as in ~.S. Patents Nos.
3,493,250 and 3,685,860.
These tube fittings have met with differing degrees of success, usually fo~ low and medium pressure, because at high p~essu~e it was difficult to make ce{tain that the ~ube did not blow out of the tube coupling.
In air conditioning, refrigeration and heat pump units whi~h are sta~ionary units, there is still the problem of vibration and a desire to seal the ~e~rigerant without any leakage. In such a case, the typica~
connection for the refrigerant tubing was to use some form of he~metic seal rathe~ than a threaded coupling seal. Such hermetic seals included ;nert gas brazing or silver solder rather than relying on a ~hreaded coupling which might fail after a long period of use and require a ~6 service call, which was usually qlu;te expensive fo~ the manufacture~ or installer. The rather slight vibration caused by the running of the compressor could cause metal fatigue and failu~e of threaded couplings henceO these were generally avoided.
Automotive air condi~ioning added additional pro~lem~ to try to obtain a leak-free tubing connection, namely: the wide tempe~atuLe range from below o F to above 100 F under the hood of a modern automobile; ~he vibration of the automobile engine: and the ~oad shock6 as the automobile hit chuck holes, etc.
Cryogenic air conditioning apparatus utilized in industry and medical applications created possibly even worse ambient condition6, with temperatures varyi~g widely from ordinary room temperature of 70 F down to -80 F, or even -120 F, together with the vibration from the compressor. As a result, in such automo~ive and cryogenic air conditioninq applications, the practice almost universally has been to utilize some form of hermetic seal on the tubing connections rather than to trust to any form of a threaded connection.
Nevertheless, failure6 have occurred out in the field, where i~ was up to the service man make a repair joint without access to any production equipment as found in the usual manufacturing facility, e.g., without benefit of any inert gas b~azing equipment.
A difficul~y with the two-part hose couplings disclosed in the prio~ art U.S. Patent 927,388 was that the external sleeve thereon was slotted longitudinally to permit the sleeve to be compressed radially inwardly, and thus this effectively cut in half the length of the leakage path, which could be satisfactory for a low pressuce hose but unsatisfactory for a high pressure tube connection. The two-part tube coupling of the prior art U.S. Paten~ 3,375,026 was only for use with very small diametee tubing, e.g., 1/16 inch outside diameter, and the force required ~o longitudinally move the compression ~leeve would be extremely high in larger sizes of tubing. Also, such coupling could be one where vibration would vibrate loose such compression sleeve.
The difficulty with the ~hree-piece tube couplings employing a separa~e external sleeve was that upon turning the nut, the ~riction between the external sleeve and the nut tended to rotate the sleeve, which tended to twist the tube, and if the tube were of ~oft material, the tube could be twisted off before a tight seal was made. Fucther, with aluminum tubing, a small score ma~k, as an annular score around the tube. weakened the tube sufficiently so that subsequent vibratioll could cause metal fatigue and breakage of the tube at such annular score line.
The four-part tube couplings of the prior art were intended for u~e with plastic tubing~ which had little compressive strength in a eadially inward direction and required the insertion of an inner sleeve, yet thi~ created an additional junction whereat leakage could occur rather than minimi~ing the locations where leakage could occur.

SUMMARY OF THE INVENTION

The problem to be solved, therefore, is how to achieve a threaded connection in a flareless tube coupling which can readily be made out in the field with use of simple tools, such as open end wrenches, and yet which will seal high fluid pressure up to the bursting strength of the tube~ withstand ]Large temperature shocks, vibration, and physical shocks.
This problem is solved by a tube coupling consisting of only two pieces: a body and a threaded member; interengageable threads on said body and said threaded member, said body having an aperture for fluid under pressure, a unitary inner sleeve and a un;tary outer sleeve on said body each substantially coaxially surrounding ~aid aperture and defining a metal tube-receiving annulae groove therebetween extending into said body from a first end thereof, ~aid threaded member adapted to have an annular inner surace overlying saîd outer sleeve of said body and to have a first end adjacent said first end of said body in the assembled condition, an annular cam surface on the inner surface of said threaded member reducing in cro~-sectional area toward said first end of said threaded member, an annular cam follower outer ~urface on said outer sleeve of said body reducing to a smalle~ diameter toward said first end of said body, and whereby with a tube in place in said annular groove the threaded member may be tightened on the body to have said cam ~urface and cam follower surface interact and the unitary outer sleeve crushed inwardly onto the outer surface of the tube to form a fluid pressule-tight seal of at least several atmo~pheces between the body and the tube.
This problem is further sclved by a tube coupling having a body with threads and a threaded member threadably connectable thereto, an inner sleeve and an outer sleeve on said body defining an annular groove therebetween to receive the end of a metal tube, a cam on said threaded member and a cam follower on said outer sleeve radially inwardly compressible by the cam to engage the outer surface of the tube for a fluidtight ~'~5~'~3~

~eal, the proYl~ion of ~aid lnner and outer sleeve~ being un~tary with said body for a long fluld leakage path, and ~aid cam and cam follower having relative rotation during threaded tigh~ening of the thceaded member with absence of rotation among the tube and inner and outer sleeve~.
The problem i~ further ~olved by the method of obtaining a fluidtight 6eal in a tube coupling having only a body and an interengaging threaded member, the body having unitary inner and outer ~leevec defining an annular ~ube-receiving groove therebetween extending into a fir~t end of the body, and a cam follower on the outer ~leeve engageable by a cam on the threaded member, said method compri6ing the ~tep~ of inserting an end of a tube longitudinally into the annular groove until the end of the ~ube engage~ the bottom of the groove, and tightening the threaded member to engage the cam with the cam follower and the corre~ponding annular portion of the outer ~leeve compre~ing in a radially inward direction and engaging the outer ~urface of the tube to make a fluid~ight ~eal between the inner sleeve and the inner ~urface of the ~ube, with rela~ive rotation between the cam and follower and an ab~ence of rotation among t~e tube and innec and outer ~leeves.
Accordingly, an object of the inven~ion i6 to pcovide a two-part tube coupling for a flarele~ tube which is easily applied in the field with only t~o open-end wrenche~.
Another object of the invention i6 to provide a two-pact tube coupling with a long leakage path to minimize the pos~ibility of leakage.
A fucther object of the invention is to provide a two-part tube coupling which actually ~eal~ at three diffecent aLeaE to minimize the pos6ibility of leakage.

Othe~ ob3ect~ and a fuller understanding of the invention may be had by refe~ring to the following description and claims, taken in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF l'HE DRAWINGS

FIG. 1 i~ a longitudinal view, partly in ~ection, of the body of a tube coupling embodying the invention, FIG. 2 i~ an end view of the body of FIG, l;

FIGo 3 i~ a longitudinal view, partly in section, of a nut u~ed with the body of FIG. 1:

FIG. 4 is a longitudinal view, partly in section, of a modified tube coupling ~howing partly a~embled and a~6embled condition~; and FIG. 5 i6 a longitudinal view, pa~tially in section, of a ~till further embodiment of the invention.

D _ RIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 illu6trate a body 11 which, together with a nu~ 12 shown in FIG. 3, may be threadably as~embled ~o form a tube coupling 13. Thi~ tube coupling 13 i~ shown in a partly a6~embled condition in the upper half of ~IG. 4 and in a tightened condition in the lower half of ~IG~ 4.

'2~

FIG. 1 illustrate~ that the body 11 ha6 a longitudinal axi~ 14. with a central aperture 15 therein adapted to contain a fluid under pres~uce. The body 11 ha~ a fir~t end 16 and a second end 17. The second end of the body 11 i~ adapted to have an enlarged aperture 18 to receive the outside diameter of a tube, ~uch as a copper tube tnot shown), by mean~ of a brazed OI
~ilver-~oldered connection. A~ 6uch, the body 11 of PIGS. 1 and 2 is adapted to be u~ed as a tran~ition fitting fo~ a tranfi~tion between ~uch copper tube and aluminum tube 21, a~ shown ;~ FIG. 4. To thi~ end, the body 11 may be made of bras6 to be compatible with both the copper tube and the aluminum tube. In FIG. 4, a body llA ifi disclo~ed and the difference from FIGS. 1 and 2 iB
that at the ~econd end of ~hi~ body a taper thread connection 2~ i~ utili~ed in order to p~ovide connection to some other unit, fo~ example, a manifold. In FIG. 5, a body llB i8 di~clo6ed, which i6 a double-ended body and which may be utilized as a 6plice connection between two tube~, ~uch as two aluminum tubes, or between tube6 of differen~ materials, e.g., alu~inum and copper.
Each of the bodie~ 11. llA and 11~ utilize~ a hexagonal wrench pad 25 for engagement by a suitable tool, e,g., an open-end wrench. The bodie~ 11, llA and llB are all identical at the first end 16 thereof, ~o the enlarged view of FIG. 4 will be primarily utilized to describe the con~truction which i8 applicable to all of the embodiment6. The body 11 ifi a one-piece body havLng a unitary inner sleeve 28 and a unitary outer ~leeve 29, each ~ubs~antially coaxial and ~paced apart ~o that an outer surface 30 of the inner ~leeve 2~ and an inner ~urface 31 of the outer sleeve 29 are 6ub~tantially cylindrical and define a cylindrical annular groove 32 extending into the body 11 from ~he first end 16. Thi~

i~ a~ annular groove to receive a metal tube 21, which r has an inner 6ur~ace 33 and an outer surface ~4, and an ~.
end 35 adapted to be inserted until it ~trike~ the bottom J
36 of the groove 32. Preferably, one or the other of the s inner and oute~ ~leeve~ 28 and 29 i6 longer than the r other, to aid insertion of the tube end 35 into the groove 32, in ca6e the end of the tube is not perfectly cylindrical. In the prefer~ed embodiment, the inne~
sleeve 2~ i~ made longer than the outer ~leeve and has a ~' slight chamfer 37, al~o to aid in6ertion of t~e tube.
The nut 12 i~ a threaded member which i~ adapted ;
to threadably engage the body 11. It may have male , threads or female thread~ and, a~ shown, it i~ a nut having female thread~ 40 on an inne~ surface thereof which encircle~ the outer ~leeve 29. Tho~e threads qO ~;' engage male threads 39 on the body 11. The nut 12 carries a cam 6urface 41, which i5 an annular sucface for coaction with an annular cam follower su~face 4Z on the outer sleeve 29. In the preferred em~odiment, this cam 6urface 41 i~ a rathe~ steep cone of about a 45-deg~ee E
angle to coopera~e with prefe~ably a conical cam follower 42 of a le~e~ conical angle~ e.g., 14 deg~ees, each ~elative to the axis 14. A sub6tantially cylindrical extension 43 i6 p~o~ided on the outer sleeve Z9 outboard of the cam followe~ surface 42, and ha6 an outer end 44.
The nut 12 ha6 a ~lightly conical, tapered aperture 45 at the first end 46 the~eof adapted to overlie thi~ ¦
cylindrical exten~ion 43. In the assembled and tightened condition of the tube coupling 13, the fi~st end 46 of the nut is adapted to be adjacent to the fi~st end 16 of the body 11, a6 better ~hown in the lower half of FIG.
4. The nut 12 is adapted to accommodate a tool, and to this end may have a hexagonal w~ench pad 49, e.g., for engagement by an open-end w~ench.

3~3 In operation, the tube coupling 13 may be utilized in many different way6. It may be u~ed as a repair joint for a break in a tube, in which case the body llB of FIG. 5 could be utilized. It may be used a~
a connection to a manifold having threaded apertures, in which ca6e the body llA of FIG. 4 would be used. It may be u~ed a~ a tran~ition joint for connection to another tube of the same or different mate~ial, e.g.~ by ine~t gas brazing or ~ilver ~older~ in which cace the body 11 of FIG. 1 could be used. In all cases, only two simple open-end wrenche~ are required to tighten the tube coupling to its tightened and fluid-~ealed conditiorl.
The tube 21 is cut off perpendicular to the axis thereof, afi by a rotatable hand-operated tube cutter. To avoid having the tube cutter inden~ ~he tube 60 much that the inide surface 33 thereof was deformed to a fimaller diameter at the end 35, 6uch tube cutter may merely sco~e the outer 6urface part way into the wall thickne6s and then the tube repeatedly bent at the ficore line to finap it off. This i6 satisfactory with aluminum tubing, and al60 with copper tubing. The nut lZ i6 61ipped over the end of the tube 21 and the end 35 of the tube 21 i~ then inser~ed into the annular groove 32 until the tube end strikes the bottom 36 of this groove. The tube inner and ou~er surfaces are generally closely received in the 6urfaces defining the groove, but owing to diffecent wall ~hicknessefi on commercially available tubing, there is usually some radial clearance both on the inside and the outside.
The nut i6 then brought up and threaded onto the body 11. The upper half of FIG. 4 illustrates the nut 12 when it hafi been tightened fingertight, and it becomes fingertight when the conical apertu~e 45 frictionally engage6 the outer end of the cylindrical extenslo~ 43 on the oute~ sleeve 29.
U~ually, thi~ is about three or four turns from the fully tightened condition shown in the lower half of FIG. 4.
About one or two mo~e turn~ of the nu~ 12 with a wrench may ea~ily be made until the cam surface 41 on the nut actually begin~ to engage the cam follower surface 42 on the outer ~leeve 29. At thi~ point. the nut 12 becomes proqres~ively harder to turn becau~e metal, primarily that of the cam followec su~face 42, i~ being physically di~placed. The annular volume 51 of metal in the double cros~-hatched area on the upper half of FIG. 4 is generally that which is displaced (compare the upper and lower halves of FIG. 4). The lower half of FIG. 4 show~
the fully tightened condition of the nut 12, whereat the cam 41 has had the inne~ coLne~ 52 generally ~ounded, due to the compression and f~iction. The annular volume 51 of metal immediately inwardly of the cam follower 42 has been displaced generally radially inwardly, but al80 somewha~ longitudinally, away from the first end 16 of the body 12. Thi~ longitudinal di6placement of the tube 21 jam~ the end 35 of the tube against the bottom 36 of the groove and expands the wall thickne~ o the end of the tube so that it completely fills the groove 32. This has been found to be true even though the wall thickness i~ at the thin end of the range of thicknes~es of commercially available tubing. This metal is now displaced inwardly to cause an inward annular bulge 53 on the inner surface 31 of the outer sleeve 29. This bulge takes up any radial clearance between the outer sleeve and the tube 21 and compresses the tube sufficiently so that an inwa~d annular bulge 54 of somewhat larger radius is provided on the inner surface 33 of the tube 21. This bulge 54 D in turn, take~ up any radial clearance between the ir.ner tube wall and the outer sleeve Z~, and cau~es a corresponaing annular bulge 55, again of somewhat larger radius, on the ;nner su~face forming the central aperture 15.
These bulges 53, 54, and 55 accomplish t~o things: a phy~ical interlocking of the tube 21 and tube coupling 13, and a fluidtight seal at three different locations. The physical interlocking of the tube and coupling occurs because the bulges 53 and 54 are in the form of an annular inward deformation of the tube wall, 50 that it effectively interlocks with the body 11. Even if the nut 12 is subsequen~ly unthreaded, the tube 21 cannot be pulled out by hand, or even with any reasonable fo~ce.
When the nut 12 has been tightened as sho~n in the lower half of FIG. 4, the oute~ end 46 of the outer sleeve ~9 is visible and generally flush with the first end 46 of the nut 12. Thifi will vary ~lightly in accordance with the actual thiskness of the tube wall.
For 3/8 inch tube, which i~ the outside diame~er thereof, the tube wall will vary in commeLcially available tubes from .OZ8 inch to .035 inch in thickness. When tubing of the thicker wall, such as .035 inch, i6 used, the firfit end 44 does not usually come out quite to the firs~ end 46 of the nut. The action of the tightening and sealing moves the bulge 53 radially inwardly, but also has a longitudinally inward component which moves the tube Zl longitudinally inwardly to force the tube end 35 tightly again~ the bo~tom of ~he groove 36 to make a seal the~eagainst. Where a thinner wall tube, such as .028 inch wall thickness, is utilized, it will be appreciated that the nut 12 will turn onto the body furthe~ in displacing enouyh volume of metal to create the bulges 53, 54, and 55, and hence usually part of the end of the cylindrical extension 43 is observed pa~t the fir~C end 46 of the nut 12.
Thi~ cyl;ndrical extension 43 i8 no longer cylindrical~ but îs forced into a conical shape, as shswn in the lower half of FIG. 4, and i~ forced tightly against the outer ~urface 34 of the tube 21. The purpose of this is to preclude entrance of moisture between the extension 43 and ~he conical aperture 45, and between the extension 43 and the outer tube wall 34. By ~o precluding entrance of moisture, this moisture cannot freeze, creating ice to possibly damage the tubing 21 or nut 1~ in case the coupling 13 i~ u~ed in air conditioning or the like applications.
The fluidtight seal i~ an e6pecially valuable featuce of the present invention becau6e it has been determined that the fluidtight ~eal occur~ at not only one place but at actually three different location6. It ha~ been deter~ined th~ough te~ts that the fi~st seal is at the bulge 54, the 6econd seal is at the end of the --tube 35, and the third seal is at ~he bulge 53.
To test to determine that there i6 a seal at t~e bulge 54 between the inner ~urface 33 of the tube and the outer surface 30 of the inner sleeve 28, the tube 21 i8 inserted the full depth and then pulled back a short distance, e.g., .025 inch. The nut 12 i~ then tightened down in the usual manner, about until the oute~ end 44 of the outer sleeve 29 is visible and generally flush with the first end 46 of the nut 12.
With the nut 12 tightened, then for te~t purposes, an arcuate slot 58 is cu~ with a circular cutter through the nut 12 at one peripheral location and through a part of the oute~ sleeve 29, as shown in FIG.
5, to pLovide access ~o the bottom 36 of the groove ~2.
Then by using a helium ~niffer connected to a helium mas~

spectrometer and pressurizing the tubing 21 and coupling 13 with helium at up to 1000 psi, it can be deter~ined that there aLe no leaks. This establishes the fact that there is a firs~ seal at the bulge 54 between the tube inner surface 33 and the inner sleeve outer surface 30.
Next, to demonstrate the establishment of the second seal between the tube end 35 and the bottom of the groove 36, a deep, longitudinal score line is scratched into ~he inner surface 33 of the tube wall for the length on one tube diame~er. ~his score line must be deep, e.g.
.020 inch. 5therw~e, the coining of the metal during the tightening can seal a lesseE scratch, e.g., one of only .010 inch deep. Th~ tube 21 i~ bottomed against the bottom of the g~oove 36 for this test, and the nut tightened a~ befoee. Then the arcuate te~t slot 53 is again cut through a part of the nut 12 and the outer fileeve 35 just until the outer surface 34 of the tube 21 is encounte~ed. This deep longitudinal scribe line has established that the first seal at the bulge 54 is ruined. Again, the tube 21 and coupling 13 are pressurized at up to 1000 psi with helium and the sniffe~
on the helium mass spectrometer has again assured in several tests that there is an annular seal established at the tube end 35 and bottom 36 of the groove to withstand high fluld pressures.
The third test to establish the fluidtight seal at the bulge 53 is similar in that the inside wall 33 of the tubing is agaln longitudinally scored deeply, e.g., .020 inch, the tube is inserted the full depth and then moved back a short distance, e.g., .025 inch, and the nut 12 tightened as before. The deep longitudinal score line has assured that the first seal i8 not effectiveO and the retcaction of ~he tube .025 inch has assured that the second seal is not effective. Thus, the only place where ~5~ 8 ' there is an effective seal i5 at the bulge 53. Repeated tests sniffing at the first end of the nut 46 with the sniffer connected to the helium mas~ spectrometer and the tubing 21 and coupling 13 pressurized at up to lOQO psi with helium have demonstrated the effectiveness of such third fluid seal.
The tube couplings constructed i.n accordance with thi~ invention have successsfully passed three succe~ive tests for thermal shock, pressure tes~ing, and vibration, according to the following ~est procedure:

TEST PRO OE DUR~ FOR A~UMIN~ M~CHA~ICAL JOINTS

Vacuum and sniffing with helium ma~s spectrometeL. Senfiitivity on vacuum to be 1 x 10~
~niffing to be done at 1 x 10 8 on expanded ~cale of lower 1/3. No evidence of leak permis~ible.
1. Thermal shock consi~ting of 600 psi, helium, and:
A. Six immersions in liquid nitrogen and boiling water in rapid succession from -320.4 F to ~212 F
B. One te~t wi~h joint ~niffed at -320.4 F
C. One te~t with joint sniffed at ~210 F.

2. Pressure te~ at 1200 p~i hel;um and joint heated to 550~ F fo~ one-half hour.

3. Pre~sure test to 3500 p~i hydraulic, tubing bur~ting ~.050 wall) ~ith no evidence of joint yield, tubing repaired and ~lushed out thoroughly and pressure-te~ted at 1200 psi helium. Thermal shock tet repeated.

4. Pul~ating, hydraulic 6hock at 450 psi for one million cycle~, rete~t at 1200 psi helium and repeat thermal ~hock.

5. Twi~ting torsional te~t with ends held two inches away from the joint and two full turns made. Test at 1200 psi helium and repeat thermal shock.

6. Vibration te~t, 1/4" deflection at 1750 rpm until tubing yield~. Te~t at lZ00 p6i helium and repeat thermal shock.

Test concluded. Sequence of te~t can be altered.

lZS~ 3~

The drawing of FIG. 4 is enlarged, but is approximately to scale according to a 3/8 inch diameter , tubing Zl and fitting 13, which have been actually constructed and tested. For such 3/8 inch diameter tubing, the dimensions of the par~s are in accordance with Table A: .

T~BLE A
Out~ide diameter of tube 21 .375" f Wall thicknes~ of tube 21 .028" to .035"
Inside diameter of aperture lS .Z50"
Outside diameter of inner sleeve 28 .302"
Inside diameter of outer sleeve 29 .382"
Outside diameter of extension 43 .418"
Outside diameter of cam follower 4Z .488"
Angle of cam 41 45 Angle of follower 42 14 Depth of groove 32 .375"
Inside diameter of cam 41 .420"
Inside diameter of nut at end 46 .400"

From the above desc~iption, it will be apparent that the cam surface 41 and the cam follower surface 4Z
are annular surfaces reducing in diameter toward the fi~st end of the nut 46 or body 11. The interaction of these two surfaces establishes that the outer sleeve 29 is crushed o~ compressed generally radially inwardly and also somewhat longitudinally away from the firs~ end of the body 11 in effecting the fluidtight seal~ at the ~ ~s~z~

th~ee different locations of bulge~ 53, 54, and groove bottom 36. The bulges 53, 54, and 55 are ;ntelmediate the length of the outer ~leeve 29 to aia in the physical interlocking of the tube 21 and coupling 13.
The fact that the inner sleeve 28 and outer sleeve 29 are unitary with the body 11 achieves the desicable result of a very long fluid leakage path which is the length of the inner sleeve 28 plus the length of the outer sleeve 29. There are three different annular seal~ achieved along this long fluid leakage path~ and thi~ undoubtedly i8 the reason that the coupling is successful at ealing fluid pressure6 high enough to bu~st the tubing, and despite high vibration and the~mal shocks. The slight longitudinal movement of the vol~me of metal 51 i6 thought to dig into ehe outer surface o the metal tube and cause that metal tube to move longitudinally also. As a test fo~ this longitudinal movement of the tube 21, in the 3/8 O.D. size of tubing 21, the nut 12 ha~ been initially--tightened only until the cam 41 begins to engage the cam follower 42. If a scribe line i~ placed on the outer surface 34 of the tubing 21 at the first end 46 of the nut. and then the nut 12 i8 tightened down until the end 44 of the cylindrical extension 43 is visible. indicating the fully tightened condition. and the distance to the end of the nut to the scribe line is measured, it was found that this distance might be .040 inch as an example. This i6 about one complete rotation of the nut for Z4 th~eads-per-inch of the threads 39 or 40.
Another fitting 13 is prepared with this same tubing wall thicknes and, in this case, af~er the nut has been tightened enough so that the cam 41 just engages the cam follower 42, then a first scribe mark is made on the outer surface 34 of the tube at the nut first end 46. The tube 21 is then pulled out a short distance, e.g~, ~012 inch. The nut i~ then again tightened one full revolu~ion ~o that it i~ in the fully tightened condition, with the end 44 of extension 43 visible at the nut fir~t end 46. One would then expect the scribe line to be .040 ~ .012 inch, or .052 inch away from the first end 46, yet upon actual testing it ha~ been found that the scribe line ;s only .040 inch away from the first end 46, indicating that the tube 21 ha~ been moved inwardly .012 inch during the tightening as caused by the longitudinal displacement of the metal focming the bulges 53, 54, and 55.
The unitary inner and outer sleeve~ 28 and 29 not only provide the long fluid leakage paths, but al~o establish that during tightening of the nut 12, there ~ill be an absence of cotation among the tube and inner and oute~ sleeves. Thi~ i6 quite important in many case~. Where a soft aluminum tube i8 utilized, this tube wa~ often twi~ted by the prior art three-piece fittings because the friction between the nu~ and the separaee outer sleeve tended ~o rotate the outer ~leeve and to frictionally ~otate the tubing as the nut was tightened.
This could twist off the tubing, or at least weaken it sufficiently so that it would be totally unsuitable for use with refrigeration or air conditioning equipment. In the present invention, the relative rotation is only between the cam 41 and cam follower 4Z, and the~e i~ no rotation between the outer sleeve 29 and tube 21, nor between tube 21 and the inner sleeve 2a. The coupling 13 may be used with any tube of malleable material, including plastic, stainless steel, and even titanium.
So long as it is malleable, it will not develop any cracks, even hairline cracks, which could cause leaks.

3~

The present invention provides a highly novel method of obtaining a fluidtight seal in a tube coupling by utilizing only a two-part coupling with a unitary inner and outer sleeve. The tube is inserted into the groove defined between these two sleeves and the tightening of the nut achieves the compression of the outer sleeve in a generally radially inward direction to achieve the fluidtight seal and the unitary inner and outer sleeves assure that these ~wo sleeves and tube will remain stationaryO i.e., non-rotating, during the tightening process.
The present disclosure includes that contained in the appended claims, a~ well as ~hat of the foregoing description. ~lthough this invention ha~ been described in it~ prefe~red form with a certain degree of particularity, it is understood that the present di~closure of the preferred form has been made only by way of example and that numerous changes in the detail~
of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

Claims

WHAT IS CLAIMED IS:

1. A tube coupling consisting of only two pieces:
a body and a threaded member:
interengageable threads on said body and said threaded member:
said body having an aperture for fluid under pressure a unitary inner sleeve and a unitary outer sleeve on said body each substantially coaxially surrounding said aperture and defining a metal tube-receiving annular groove therebetween extending into said body from a first end thereof;
said threaded member adapted to have an annular inner surface overlying said outer sleeve of said body and to have a first end adjacent said first end of said body in the assembled condition;
an annular cam surface on the inner surface of said threaded member reducing in cross-sectional area toward said first end of said threaded member;
an annular cam follower outer surface on said outer sleeve of said body reducing to a smaller diameter toward said first end of said body; and whereby with a tube in place in said annular groove the threaded member may be tightened on the body to have said cam surface and cam follower surface interact and the unitary outer sleeve crushed inwardly onto the outer surface of the tube to form a fluid pressure-tight seal of at least several atmospheres between the body and the tube.

2. A tube coupling as set forth in claim 1 wherein said threaded member is a nut having female threads interengageable with male threads on said body.

3. A tube coupling as set forth in claim 1, wherein one of said cam and cam follower surfaces is conical.

4. A tube coupling as set forth in claim 1, wherein each of said cam and cam follower surfaces is conical, with the cone of the cam surface having a larger conical angle than that of said cam follower surface.

5. A tube coupling as set forth in claim 1, wherein one of said inner and outer sleeves is longer than the other to aid in insertion of a tube end into said groove.

6. A tube coupling as set forth in claim 1, wherein said inner sleeve is longer than said outer sleeve to aid in insertion of a tube end into said groove.

7. A tube coupling as set forth in claim 1, including a substantially cylindrical extension on said outer sleeve at said first end of said body to be visible at said first end of said threaded member upon tightening of said threaded member and body.

8. A tube coupling as set forth in claim 7, including an aperture in said threaded member to overlie said substantially cylindrical extension in the tightened condition of the coupling.

9. A tube coupling as set forth in claim 8.
wherein said aperture in said threaded member has a slight conical angle reducing in size toward said first end of said threaded member to radially inwardly squeeze said outer sleeve substantially cylindrical extension onto the tube in the tightened condition of the coupling to substantially preclude admission of moisture into the annular spaces among the tube, extension, and threaded member.

10. A tube coupling as set forth in claim 1.
wherein said tightening establishes a fluidtight seal at three places, between the tube inner wall and said inner sleeve, between the tube outer wall and said outer sleeve, and between the end of the tube and the bottom of said groove.

11. A tube coupling as set forth in claim 1, wherein said inwardly crushed outer sleeve is at an area substantially radially inwardly of said cam follower surface and is an annular area.

12. A tube coupling as set forth in claim 11, wherein said inwardly crushed area is intermediate that portion of the tube in said annular groove.

13. In a tube coupling having a body with threads and a threaded member threadably connectable thereto, an inner sleeve and an outer sleeve on said body defining an annular groove therebetween to receive the end of a metal tube, a cam on said threaded member and a cam follower on said outer sleeve radially inwardly compressible by the cam to engage the outer surface of the tube for a fluidtight seal, the provision of said inner and outer sleeves being unitary with said body for a long fluid leakage path, and said cam and cam follower having relative rotation during threaded tightening of the threaded member with absence of rotation among the tube and inner and outer sleeves.

14. A tube coupling as set forth in claim 13, wherein said tube coupling consists of only two parts, the body and the threaded member.

15. A tube coupling as set forth in claim 13, wherein said cam is an annular cone on said threaded member and encircling said outer sleeve to compress a cam follower portion of said outer sleeve substantially radially inwardly to deform a corresponding portion of the tube radially inwardly against the inner sleeve.

16. A tube coupling as set forth in claim 15, wherein the inwardly deformed portion of the tube deforms radially inwardly a corresponding portion of said inner sleeve.

17. A tube coupling as set forth in claim 15, wherein the cam has a greater included angle than said cam follower to develop a component of force forcing the longitudinal end of the tube against the bottom of the groove.

18. A tube coupling as set forth in claim 13, wherein the cam follower is a substantially conical portion on said outer sleeve.

19. A tube coupling as set forth in claim 18, including a substantially cylindrical extension on said conical cam follower and the end of which is visible external to said threaded member in the tightened condition of the tube coupling.

20. A tube coupling as set forth in claim 19, including a slightly conical taper on an aperture in said threaded member encircling said cylindrical extension and forcing it into substantially moisture-tight engagement with the outer surface of the tube in the tightened condition of the tube coupling.

21. The method of obtaining a fluidtight seal in a tube coupling having only a body and an interengaging threaded member, the body having unitary inner and outer sleeves defining an annular tube-receiving groove therebetween extending into a first end of the body, and a cam follower on the outer sleeve engageable by a cam on the threaded member, said method comprising the steps of:
inserting an end of a tube longitudinally into the annular groove until the end of the tube engages the bottom of the groove; and tightening the threaded member to engage the cam with the cam follower and the corresponding annular portion of the outer sleeve compressing in a radially inward direction and engaging the outer surface of the tube to make a fluidtight seal between the inner sleeve and the inner surface of the tube, with relative rotation between the cam and follower and an absence of rotation among the tube and inner and outer sleeves.

22. The method as set forth in claim 21, including compressing the annular cam follower generally radially inwardly and forming a fluidtight seal between the outer sleeve and the outer surface of the tube.

23. The method as set forth in claim 21, including forming the cam with a larger included angle than that of the cam follower and generating a component of force from the cam compressing the end of the tube longitudinally against the bottom of the groove forming a fluidtight seal therebetween.