Prier art The flexible gas piping (FGP) system, also referred to as corrugated stainless steel tubing (CSST) and formerly Interior Gas Piping (IGP) was developed in Japan and first introduced into that market by Osaka Gas and Tokyo Gas Companies during the early 1980's. The system utilizes stainless steel corrugated tubing supplied in rolls or coils with field attachable fittings to distribute gas from a central supply point such as the meter or regulator to the various appliances within a house or building. The technology, which has likened the process of plumbing a house for gas to wiring a house for electricity, substantially reduces installation time and hence the associated higher cost of labor. The technology was brought to the United States by the Gas Research Institute who saw it as a means of making gas installations more competitive;

thereby increasing the percentage of new construction plumbed for gas and increasing the overall consumption of natural gas on a national basis. The technology was enthusiastically endorsed and supported by major gas utilities who had seen the significant higher cost of installed piping as their single greatest obstacle to selling more gas. Code acceptance required more time and effort to obtain, but the product is now recognized by all national mode codes by ANSI, the National Fire Protection Association/National Fuel Gas Code and is tested and recognized by the American Gas Association. This product will eventually supplant black-iron pipe which accounts for approximately 80% of all fuel gas piping today, as well as copper tube which, while enjoying many of the same advantages of FGP, is being banned from this application at an increasing rate.

There have been three types of fittings originally put into the field. The first fitting introduced into the field used a fiber gasket to make the seal and no special tools were needed to assemble this fitting. This fitting has a higher incidence of leaks than the flared metal to metal seals used by other manufacturers.

The second fitting introduced into the field used first a specialized tool to flatten the convolutions at the end of the CSST tube where the fitting was to be attached and then a second tool was used to put a single flare on the tube end. This product is now off the market due to failures in the tubing caused by work hardening of the stainless steel in the flattening and flaring process.

The third type of fitting was introduced into the field using no special tools to make a metal to metal seal by folding the convolutions of the tube back on itself creating a double flare. After a limited time in the field it was realized that this fitting design was inconsistent in making a leak tight seal. The remedy to the problem was to design an insert type flaring tool; this was used for about three years. A second redesign was conducted, upgrading the insert tool to a socket type flaring tool.

A current problem in installing certain fittings is the number of loose parts that the installer must assemble in the field. In a typical fitting, there is a body, a nut, a gasket and two split ring washers that must be assembled to couple the fitting to the corrugated tubing. This number of parts leads to several disadvantages including

complicated assembly and the need to carry extra parts to compensate for lost or damaged parts.

Summary of the Invention The above-discussed and other drawbacks and deficiencies of the prior art are overcome or alleviated by the preassembled fitting of the present invention. The preassembled fitting includes a body, a nut and a collet positioned within the nut. The nut is threaded on the body a predetermined distanced to allow the installer to snap the corrugated tubing into the nut and engage the collet. The nut is then further tightened to seal the body to the corrugated tubing. A tapered surface on the body engages the cut end of the corrugated tubing and flares the cut end of the corrugated tubing. The fitting will make a metal to metal seal by folding the convolutions of the tubing back against itself creating a double flare reliably without the need for flaring or flattening tools.

The above-discussed and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description and drawings.

Brief Description of the Drawings Referring now to the drawings wherein like elements are numbered alike in the several FIGURES: FIGURE 1 is a perspective view of a body; FIGURE 2 is a side view of the body; FIGURE 3 is an end view of the body; FIGURE 4 is a perspective view of a locating sleeve; FIGURE 5 is a side view of the locating sleeve; FIGURE 6 is a side view of an alternative locating sleeve; FIGURE 7 is a perspective view of a nut; FIGURE 8 is an end view of the nut;

FIGURE 9 is a cross sectional view of the nut taken along line 9-9 of FIGURE 8 ; FIGURE 10 is an end view of a collet; FIGURE 11 is a cross sectional view of the collet taken along line 11-11 of FIGURE 10; FIGURE 12 is a side view, partially in cross section, of the assembled fitting; FIGURE 13 is a side view of corrugated tubing snapped into the fitting; and FIGURE 14 is an enlarged view of a portion of the fitting once fully assembled.

Detailed Descnption of the Invention FIGURE 1 is a perspective view of the body of the fitting, shown generally at 10. The body 10 is similar to the body described in co-pending U. S. patent application Serial No. 08/693,475 which is incorporated herein by reference. Body 10 has external threads 12 that engage internal threads 22 formed in nut 20 as shown in FIGURE 9.

The body 10 includes a tapered surface 16 that seals against the corrugated tubing as described below. The tapered surface 16 has an angle a which in an exemplary embodiment is 55 degrees. A central conduit 14 provides access to the corrugated tubing and the end of the central conduit 14 adjacent the tapered surface 16 has an increased diameter to form a shoulder 18. Shoulder 18 limits the insertion depth of locating sleeve 30 shown in FIGURE 4. FIGURE 3 is an end view of body 10.

FIGURE 4 is a perspective view of the locating sleeve 30. The locating sleeve 30 includes a cylindrical section 32 and a tapered section 34. The tapered section has a decreasing outer diameter away from the cylindrical section 32. The inner diameter of the locating sleeve 30 is preferably constant through both the cylindrical section 32 and the tapered section 34 as shown in FIGURE 5. The tapered section 34 eases positioning the corrugated tubing about the locating sleeve 30 as described below. The locating sleeve 30 does not need to have the tapered section 34. As shown in FIGURE 6, the locating sleeve 30 may be a cylindrical member without any reduction in outside

diameter. The locating sleeve is press fit into the body 10 and engages shoulder 18.

Alternatively, the locating sleeve may be an integral element formed along with body 10.

FIGURE 7 is a perspective view of nut 20. Nut 20 has internal threads 22 that engage external threads 12 formed on body 10. A cavity 24 is formed within nut 20 to receive collet 40 shown in FIGURES 9 and 10. Cavity 24 includes a shoulder 26 that prevents the collet 40 from entering the threaded region of nut 20. The cavity includes a conical section 28 having an angle ß, which in an exemplary embodiment is 40 degrees. A first nut opening 21 has a first inner diameter and a second nut opening 23 has a second inner diameter. The first nut opening 21 and second nut opening 23 are sized so that the collet 40 remains positioned within the nut 20 as described below.

FIGURE 10 is an end view of the collet 40. The collet 40 is an important feature of the invention and helps create a metal to metal seal between the tapered surface 16 on body 10 and the corrugated tubing. The collet 40 snap lockedly receives the corrugated tubing thereby allowing the fitting to be preassembled and facilitating installation of the fitting in the field. Collet 40 is made up of a cylindrical body 42 and a lip 46. The lip 46 is formed at one end of the cylindrical body 42. The lip 46 has an outer beveled surface 43 having an angle of ß and an inner beveled surface having an angle of a. Outer beveled surface 43 engages conical section 28 on nut 20 and inner beveled surface 41 acts in conjunction with tapered surface 16 on body 10 to compress the corrugated tubing and create a metal to metal seal. The other end of the cylindrical body 42 has a ridge 44 of increased thickness. Ridge 44 provides rigidity to the collet 40. A plurality of slots 48 are provided through the lip 46 and along part of the length of the cylindrical body 42 to create a plurality of flexible collet sections 43. This allows the collet 40 to be placed in nut 20 and then expanded, using a tool, so that the collet 40 is held in the nut 20.

FIGURE 12 is a side view, partially in cross-section, of the assembled fitting.

The collet 40 is placed within nut 20 and is expanded so that the flexible collet sections 43 are bent away from the central axis of the collet 40. This expands the outer diameter of lip 46 and retains collet 40 within recess 24 formed in nut 20. Body 10 is threaded

into nut 20. An optional stop 50 may be installed around the external threads on the body 10 to limit the travel of the body 10 relative to the nut 20. This leaves enough room within nut 20 to receive the corrugated tubing as described below. The stop 50 may be a cylindrical, plastic sleeve that includes relief areas (e. g. scored lines). The relief areas cause the stop 50 to separate and become detached from the body 10 upon tightening the body 10 to the nut 20.

FIGURE 13 is a side view, in partial cross-section, illustrating the installation of the corrugated tubing 60 into the fitting. The corrugated tubing 60 is cut in a valley and inserted into the collet 40. The peak on the corrugated tubing 60 spreads the flexible collet sections 43. Once the peak clears the inside of lip 46, the flexible collet sections 43 return back to their position prior to insertion of the corrugated tubing 60 and are positioned within a valley of the corrugated tubing 60. The interference between the lip 46 and the valley of the corrugated tubing 60 holds the corrugated tubing 60 to the fitting. The corrugated tubing 60 is positioned around locating sleeve 30. Locating sleeve 30 aligns the corrugated tubing 60 with the body 10 and facilitates creation of a metal-to-metal seal as described below. Because the body 10 is aligned with the corrugated tubing 60 through the locating sleeve 30, there is no need to use a flaring tool that was previously used in the prior art. This eliminates a step in the installation process and reduces the number of tools the installer must carry.

The installer may now tighten the body 10 relative to nut 20. As the body 10 moves into nut 20, the tapered surface 16 contacts the end of the corrugated tubing and begins to compress the corrugated tubing 60 between tapered surface 16 and inner beveled surface 43 on collet 40. FIGURE 14 is an exploded view of a portion of FIGURE 13. As shown in FIGURE 14, the corrugated tubing 60 is compressed into a double flare as the body 10 is tightened relative to nut 20. Compressing two layers of corrugated tubing provides an enhanced metal-to-metal seal. The two layers of tubing provide for greater compression and a tighter seal.

The present invention provides a preassembled fitting that facilitates installation. The collet includes flexible collet sections which can bend away from the central axis of the collet and return to their original position. This allows the

corrugated tubing to be snapped into the fitting with ease. The corrugated tubing is compressed between the body and the collet thereby creating a metal-to metal seal between the fitting and the corrugated tubing. No tools are needed and the installation procedure is simplified.

While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.

What is claimed is: