Fitting for smooth wall tubes

A fitting for mounting to the ends of smooth wall tubes, the fitting having an entry for the tube and a collet which grips on the outside diameter of the tube by means of a mechanical spring. The fitting also seals on the inside diameter of the tube. A passageway extends through the fitting such that the tube is in fluid communication with a supply source, the fluid being able to flow between the supply source and the tube. The fluid pressure activates a piston in the fitting which causes the collet to engage the tube more securely and also increases the seal within the inside diameter of the tube.

BACKGROUND AND SUMMARY OF THE PRESENT INVENTION 
The fitting of the present invention is generally related to those types of 
fittings disclosed in U.S. Pat. Nos. 3,738,688; 3,779,587; 3,868,132; 
4,154,465; and 4,225,159. 
The fittings disclosed in the above-mentioned U.S. patents are generally of 
two types. The first type grasps the tube by means of a collet around the 
outside of the smooth wall tube and compresses a tubular plug against the 
outer diameter of the tube upon translation of a ram element within the 
housing thereof. This type of fitting provides a good seal and holding 
action so that fluids passing through the smooth wall tube may be sealed 
by the fitting, or may be conveyed out of the fitting into auxiliary 
tubing mounted thereto. The second type of fitting is mounted to the ends 
of the tube by compressing a plug against the inner diameter of the tube 
upon translation of a ram element while a collet grasps a outer diameter 
of the tube. These types of fittings are especially useful on thin walled 
tubing wherein the gripping force of the collet is counter-balanced by the 
sealing of the plug. Both types of fittings utilize a manually operated 
torque transmitting lever to translate a ram element which seals and holds 
the smooth wall tube. 
The present invention provides a fitting that grips on the outside diameter 
and also seals on the inside diameter. The gripping on the outside 
diameter is accomplished by the operation of a piston forced into 
operation by a fluid, the piston forcing a collet operator to cause a 
split collet to grasp the outside diameter of the tube. The fluid is under 
pressure and flows through the fitting to the smooth wall tube which is 
connected to the device to be tested. A fluid pressure further causes the 
seal on the inside diameter of the tube to compress around an elongated 
seal screw having a passage which allows the fluid to flow through the 
fitting. Initial gripping and sealing of the tube into the fitting is 
accomplished by a mechanical spring. 
A fitting is applicable for use on a wide range of tube sizes, but has 
generally been found most applicable to tube ends with a minimum inside 
diameter of 0.295 inches. The fitting's configuration is designed for use 
on condensor and evaporator cores or other high pressure cores which 
periodically should be tested. 
Accordingly, it is an object of the present invention to provide improved 
fittings for mounting to the ends of smooth wall tubes. 
More particularly, it is an object to provide such a fitting which is 
semi-automatic and does not require manual operation of a lever or other 
handle-type torque transmitting device to accomplish the installation of 
the fitting. 
It is an additional object to provide a fitting which is operable by fluid 
means while having the initial gripping and sealing accomplished by 
spring-loaded mechanical pressure.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to FIG. 1, a tube fitting 10 is illustrated which comprises a 
body 14 with a threaded upper end 15. At the other or lower end of the 
body 14 is a collet operator 16 which is secured to the fitting 10, as 
will be more fully described below. A shaft 20 extends longitudinally 
through the body 14 and into the collet operator 16. The upper end of the 
shaft 20 is firmly secured into an axial bore 22 within the body 14. 
Securing can be done by means of press fitting or other similar methods. 
An elongated seal screw 24 having an enlarged head 26 has a resilient 
sealing member 28 disposed about it, and the sealing member 28 is retained 
between a pair of seal stops 30 and 32 which are likewise disposed on the 
elongated seal screw, with one of the seal stops engageable with the 
enlarged head 26. there is a passage 33 provided through the seal screw 
24, and its purpose will be described more fully below. 
A tube stop 34 also is disposed about the seal screw 24, atop the seal stop 
32. It may be noted that the seal stops 30 and 32, and the tube stop 34 
are all of washer-type construction, with the diameter of the tube stop 34 
being slightly larger than the diameter of the seal stops 30 and 32. The 
resilient sealing member 28 may be made of rubber or other like material, 
and is generally of a cylindrical configuration. The end of the seal screw 
24 opposite the enlarged head 26 is threadedly secured to the shaft 20 by 
threadedly engaging its end within a threaded cavity 36 in the end of the 
shaft 20. 
A split collet 38 is slidably engaged within the opened lower end of the 
collet operator 16. The collet operator 16 and the split collet 38 have 
complimentary conical-shaped cam surfaces 40 and 42 on them, respectively, 
for operating the collet 40 to grip the tube end, as will be more fully 
described below. The collet 40 also has an annular flange formed on its 
interior wall 44 which forms an annular shoulder or stop 46. A helical 
spring 48 is disposed about the seal screw 24 and disposed within the 
collet 38 and the collet operator 16. One end of the spring 48 bears 
against a shaft stop plate 50 which is in the upper interior portion of 
the collet 38. The other end of the spring 48 bears against the annular 
stop 46 on the collet 38. The spring 48 normally urges the collet 38 out 
of the collet operator 16, but the collet 38 is restrained therein by the 
annular stop 46 which engages against the tube stop 34. 
The collet operator 16 has at its upper end a reduced portion 52 which 
forms an internal bore 53 surrounding the lower portion of the shaft 20. 
The body 14 has a flange area 54 at its lower end. The flange area 54 
receives a cylindrical piston 56 disposed about the shaft 20. Between the 
flange area 54 and the piston 56 is a sealing ring 58 within ring seal 
seat 60. Similarly, between the piston 56 and the shaft 20 is an O ring 62 
in a ring seal seat 64. Within piston 56 is a top spring stop 65 
encompassing shaft 20. A helical piston spring 66 is positioned against 
the stop 65 with the lowermost portion of the spring 66 resting in a 
bottom spring stop 67 located in the top portion of the collet operator 
16. When the fitting 10 is to be used, the shaft 20 and the elongated seal 
screw 24 are screwed together. As the seal screw 24 moves into the 
threaded cavity 36, the spring 66 is placed in compression. This places an 
initial force against the collet operator 16 which forces the collet 38 to 
grasp the outer wall of a tube 76. 
The fitting 10 has a fluid inlet channel or passage 68 to allow the 
introduction of a fluid generally under pressure. The shaft 20 has a shaft 
fluid channel 70 in fluid communication with the fluid inlet channel 68. 
Within the shaft 20 and generally perpendicular to the shaft fluid channel 
70 is a shaft fluid chamber 72 to receive the fluid therefrom. At the top 
of the piston 56 is a piston chamber 74 also in fluid communication with 
the shaft fluid chamber 72. 
In using the fitting 10, the initial pressure exerted on the split collet 
38 is relieved by gripping the collet operator 16 by hand and pulling it 
upward (as illustrated). This releases the initial pressure that the 
collet operator 16 applied to the split collet 38, and the latter opens 
sufficiently to permit the end of a smooth wall tube 76 to be fitted into 
the split collet 38, about the end of the seal screw 24, with the seal 
stops 30 and 32 and the seal 28 disposed within the tube 76. The end of 
the tube 76 is urged onto or about the end of the seal screw 24, until the 
end of the tube 76 engages and is stopped by the tube stop 34. The minimum 
inside diameter of the tube 76 should be about 0.295 inches. 
The collet operator 16 then is released, and the helical spring 66 forces 
the collet operator 16 in a downward direction such that the 
conical-shaped cam surfaces 40, 42 engage and force the split collet 38 to 
grasp the end of the tube 76. Simultaneously, the sealing member 28 is 
slightly compressed between seal stops 30 and 32 and into sealing 
engagement with the tube 76. 
The threaded upper end 15 of the body 14 is connected to a high-pressure 
fluid supply source or from the component being tested. The high-pressure 
fluid passes through the fluid inlet channel 68, through the shaft fluid 
channel 70, into the shaft fluid chamber 72 and then to the piston chamber 
74. This fluid pressure exerted on the top of the piston 56 forces it 
downward into engagement with the collet operator 16 and the latter is 
thereby forced downwardly against the split collet 38. This forces the 
split collet 38 to more securely grip or clamp the tube 76. As the 
pressure increases, the collet operator further closes the collet and 
simultaneously increases the sealing of the resilient sealing member 28 
within the tube. 
It will thus be seen that the objects set forth above, among those made 
apparent from the preceding description, are officially attained, and 
certain changes may be made in carrying out the above construction. 
Accordingly, it is intended that all matter contained in the above 
description or shown in the accompanying drawings, shall be interpreted as 
illustrative and not in a limiting sense.