A tube fitting of the push-pull type wherein the tube end is connected to the fitting by a simple inward insertion thereof, and withdrawal of the tube is effected by a simple withdrawal movement thereof upon manual rearrangement of the fitting components. The fitting includes a spring finger locking element adapted to engage the tube end when inserted and effectively prevent outward axial withdrawal movement of the tube end. A manipulating device is provided for selectively disengaging the spring finger from the tube end to permit axial withdrawal of the tube end when desired. The disengaging device is a one-piece element and is associated with suitable seals for providing an accurately preselected prestressing thereof against the tube end and body to provide an improved seal of the tube end to the body. The spring fingers are defined by an annular element. In one form, additional structure is provided for providing different spring constants relative to axial outward and inward movement of the spring fingers.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to tube fittings and in particular to push-pull type 
tube fittings arranged for facilitated installation and removal of tube 
ends. 
2. Description of the Prior Art 
One improved form of quick-connect type tube fitting is shown in U.S. Pat. 
No. 3,062,240, of George E. Franck, which patent is owned by the assignee 
hereof. Therein, a pivotable pawl is provided for locking the tube against 
axial withdrawal. The pawl carries a biting edge which digs into the tube 
automatically to prevent such withdrawal. When it is desired to release 
the tube, however, the pawl is manipulated by means of a knob portion 
thereof to move the pawl slightly radially outwardly and away from contact 
with the tube wall surface. 
In U.S. Pat. No. 3,291,510, of Joseph D. Kody, which patent is also owned 
by the assignee hereof, a tube fitting is shown to include an annular 
springy retainer for effectively positively gripping the tubing and a 
sealing and gripping ring cooperating with the retainer for sealingly 
retaining the tube in the fitting. The fitting provides a positive 
retention of the tube notwithstanding the presence of severe vibrations 
and high pressure while permitting limited axial and transverse 
displacement of the tube without loosening of the connection. 
Jacob J. Hamburg, in U.S. Pat. No. 3,633,944, discloses a tube coupling of 
the slip-in type generally similar to that of the Kody patent in providing 
a sequential arrangement of a spring retainer ring and a resilient sealing 
ring. 
Jacques Sapy et al show in U.S. Pat. No. 3,653,689, a releasable coupling 
having a clamping member provided with a plurality of flexible jaws. The 
clamping member has an inclined surface cooperating with a conical surface 
of a collar to force the jaws inwardly to clamp a tube received in the 
socket. A packing ring is retained inwardly of the jaws. 
In U.S. Pat. No. 3,909,046, of Andre Legris, a connector for fluid conduits 
is shown which is generally similar to the Sapy et al patent in providing 
a clamp having pipe-engaging jaws and an inner sealing ring. 
In German Pat. No. 005711/75, of Willy Gassert, a fitting is shown having a 
springy retainer outwardly of means for positioning a plurality of sealing 
rings. 
A number of other tube fittings are known in the prior art. Illustratively, 
a tube fitting known as the "Sogeclip" tube fitting is shown in a sales 
leaflet to include a springy retainer radially outwardly of a pair of 
tubular elements compressing therebetween an O-ring. The springy retainer 
includes an outer portion extending between the O-ring and body and a 
variable compression of the O-ring is effected by applying force to the 
outer tubular element. 
In a sales leaflet of Virgo Fluid-Power Corporation, Norton, Massachusetts, 
a fitting is shown to include a depressible latch locking the latch to the 
fitting body with the fitting being maintained locked to the tubing at all 
times. 
In the German sales leaflet of Martonair, D1400, a Lynfitting Series 3000 
is shown to have a plurality of jaws outwardly of an O-ring for use in 
connecting a nylon tube to the fitting. 
SUMMARY OF THE INVENTION 
The present invention comprehends an improved tube fitting of the push-pull 
type including a carrier through which the tube end is inserted into the 
fitting body recess. 
Sealing means are carried by the carrier for maintained accurately 
prestressed sealing of the tube end to the body and in the illustrated 
embodiment, include an inner seal ring engaging the tube end and an outer 
seal ring engaging the fitting body. 
The seal rings may be received in annular grooves in the carrier accurately 
sized to provide the desired prestressing of the seal rings. 
An annular retainer provided with inwardly projecting spring fingers is 
provided axially inwardly of the carrier. The spring fingers are arranged 
in a frustoconical array angled radially and axially inwardly so as to 
permit the tube end to move readily therepast to the fully inserted 
position within the fitting recess. 
The distal end of the spring fingers defines a biting edge biased into 
engagement with the outer surface of the tube wall. An urging of the tube 
end axially outwardly from the recess causes the spring fingers to bite 
into the tube wall and thereby effectively lock the tube wall against 
axial outward displacement. 
In one form, a back-up spring is provided to provide a spring constant in 
the tube withdrawal-preventing action greater than the spring constant in 
the tube inserting action. 
The retainer may be locked in the recess by a suitable locking ring, and in 
the modified form, the back-up ring may serve as the locking means. 
The tube end may be withdrawn axially outwardly from the recess when 
desired by simple inward movement of the carrier to cause an actuator 
portion at the inner end thereof to engage the spring fingers and urge 
them outwardly away from the tube wall. 
The illustrated spring finger retainer comprises a generally flat annular 
washer-type retainer of relatively simple and inexpensive construction. 
In the present invention, the carrier synergistically defines means for 
providing maintained accurate prestressed sealing of the tube to the body, 
provides means for selectively releasing the tube locking means, and 
provides means for maintaining axial alignment of the tube end with the 
fitting bore. As the locking means is releasably connected to the tube 
end, the tube end may be readily withdrawn and a substitute tube end 
inserted if desired. 
The tube fitting of the present invention is extremely simple and 
economical of construction while yet providing the highly desirable 
features discussed above.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the exemplary embodiment of the invention as disclosed in the drawing, a 
tube fitting generally designated 10 is shown to include a body 11, a 
carrier 12, and a locking means generally designated 13. Fitting 10 is 
adapted to be sealingly connected to a tube end 14 such as formed of 
relatively soft material, such as synthetic resin. The fitting is adapted 
to provide a push-pull type connection and disconnection of the tube end 
thereto. 
Body 11 defines an inner end 15 having an externally threaded connecting 
portion 16 and an axially outer tube-engaging portion 17 defining a 
plurality of flats 18. The body is provided with a through bore generally 
designated 19 having an axially inner portion 20 and an axially outer 
enlarged recess portion 21. At its inner end, the recess 21 is defined by 
a planar annular shoulder 22 adapted to be engaged by the distal end 23 of 
the tube end when the tube end is fully inserted into the recess 21, as 
shown in FIG. 3. 
When so installed in recess 21, the tube end 14 is sealed to the body 11, 
as shown in FIG. 3, by an improved sealing means including an outer seal 
ring 24 and an inner seal ring 25 carried by the carrier 12 in a radially 
outwardly opening outer annular recess 26 and a radially inwardly opening 
annular inner recess 27, respectively. Bore recess 21 includes an outer 
portion 28 and an inner portion 29 with an intermediate planar radial 
shoulder 30 therebetween. Seal ring 24 and recess 26 are preselected to 
provide a prestressed sealing engagement of the O-ring with the body 
portion in recess portion 28, and seal ring 25 and annular recess 27 are 
preselected to provide a prestressed sealed engagement with the tube end 
14. 
As indicated briefly above, locking means 13 are provided for effectively 
positively retaining tube end 14 in the fitting in the assembled 
arrangement, as shown in FIG. 3. More specifically, the locking means 
comprises an annular retainer, which, as shown in FIGS. 5 and 6, includes 
an outer annular flat ring portion 31 and a plurality of axially and 
radially inwardly projecting spring fingers 32. In the illustrated 
embodiment, the spring fingers are spaced equiangularly about the axis 33 
of the retainer. As shown in FIG. 5, the spring fingers define a 
frustoconical array extending at an angle of greater than 45.degree. to 
the axis 33 so that effectively, the retainer defines a flat annular 
washer-type retainer of low cost and simple construction. 
As shown in FIG. 2, in the undeflected arrangement, the spring fingers 
extend into the path of movement of the tube end 14 through the tubular 
bore 34 of the carrier into abutment with shoulder 22 of the body. Distal 
end 23 of the tube end deflects the spring fingers radially outwardly in 
moving therepast so that the distal end 35 of the spring fingers slides 
along the outer surface of the tube end. 
Distal end 35 of the spring fingers defines a biting edge adapted to bite 
into the tube end wall as an incident of urging of the tube end wall 
axially outwardly away from shoulder 22 in the installed arrangement of 
the fitting, as shown in FIG. 3. As further shown therein, the outer 
portion 31 of the retainer is retained against shoulder 30 of recess 21 by 
a locking ring 36 which may be staked into an annular groove 37 in the 
body portion defining recess portion 28 to secure the retainer 13 in the 
recess. Thus, tube end 14 is effectly positively retained against 
undesirable axial outward withdrawal in the installed arrangement. 
As further indicated briefly above, carrier 12 synergistically further 
defines means for effecting release of the tube end when desired. For this 
purpose, the carrier is provided with an axially inner actuator portion 38 
adapted to engage the spring fingers 32 of the retainer 13 and urge them 
radially outwardly from the wall of tube end 14 as an incident of an 
axially inward movement of the carrier, as shown in FIG. 4. The carrier 
may be readily moved inwardly by a fingertip manipulation of an outer 
outturned flange 39 thereof. 
The carrier may be axially retained within axially outer portion 17 of body 
11 by the reception of an inturned flange 40 on the body received within 
an outwardly opening annular recess 41 at the outer end of the carrier. 
Seal rings 24 and 25 may comprise conventional O-rings formed of suitable 
resilient material. While providing a preselected accurately prestressed 
sealing of the tube end to the body, the seal rings further provide, 
synergistically, an augmented retention of the tube end in the assembled 
arrangement of FIG. 3. The prestressing, however, is preselected to permit 
facilitated withdrawal of the tube end upon release of the locking ring 
13, as discussed above. 
The carrier further serves as means for preventing undesirable angular 
deflection of the tube end 14 in providing a relatively long support 
surface defined by the carrier bore 34. Additionally, the outer end of 
bore 34 may be defined by a rounded, outwardly flaring surface 42 for 
preventing notching of the tube end 14 thereat. 
The invention further comprehends, as shown in FIG. 7, the provision of 
means for providing a double spring constant in the action of the locking 
ring 13. More specifically, as shown in FIG. 7, a back-up spring 43 may be 
provided having a frustoconical inner portion 44 spaced outwardly of the 
biting edge 35 so as to clear the actuator portion 38 of the carrier and 
thus permit release of the biting edge 35 from the wall of tube end 14 in 
the manner discussed above. However, the back-up spring 43 provides an 
additional resistance to the axial outward displacement of biting edge 35 
so as to provide increased resistance to the axial withdrawal of the tube 
end 14. 
Synergistically, back-up spring 43 may further define the means for locking 
the retaining ring 13 in recess 21. More specifically, the outer portion 
45 of the back-up spring 43 may comprise a split annular portion adapted 
to be received in an inwardly opening axial groove 46 of the body. 
Thus, back-up spring 43 provides a further improved retention of the tube 
end in the fitting while yet providing a similar low cost extremely simple 
construction of the fitting providing facilitated push-pull installation 
of the tube end 14 therein. 
The foregoing disclosure of specific embodiments is illustrative of the 
broad inventive concepts comprehended by the invention.