Abstract:
A fitting for use with corrugated tubing. The fitting includes a first body having a first internal conduit therethrough and a first centerline. The first body has a plurality of fingers integral with the first body. The fingers are positioned radially about a periphery of the first body and each of the fingers is separated from an adjacent finger by a space. A second body which mates with the first body has a second internal conduit therethrough and a second centerline. The second body has a finger deflection surface for contacting the fingers and directing the fingers towards the first centerline.

Description:
BACKGROUND OF THE INVENTION 
     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&#39;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 model codes and 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 INVETION 
     The above-discussed and other drawbacks and deficiencies of the prior art are overcome or alleviated by the fitting of the present invention. The fitting includes a first body having a first internal conduit therethrough and a first centerline. The first body has a plurality of fingers integral with the first body. The fingers are positioned radially about a periphery of the first body and each of the fingers is separated from an adjacent finger by a space. A second body which mates with the first body has a second internal conduit therethrough and a second centerline. The second body has a finger deflection surface for contacting the fingers and directing the fingers towards the first centerline. 
     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: 
     FIG. 1 is a front view of a first body; 
     FIG. 2 is a side view, in partial cross-section, of the first body; 
     FIG. 3 is a cross-sectional view of a portion of FIG. 2; 
     FIG. 4 is a front view of a second body; 
     FIG. 5 is a side view, in partial cross-section, of the second body; 
     FIG. 6 is a cross-sectional view of a portion of FIG. 5; 
     FIG. 7 is a perspective view of a locating sleeve; 
     FIG. 8 is a side view of the locating sleeve; 
     FIG. 9 is a side view, in partial cross section, of the first body partially engaging the second body; and 
     FIG. 10 is a side view, in partial cross section, of the first body fully engaging the second body. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The fitting of the present invention is made up of a first body and a second body. FIG. 1 is an end view of a first body  100  and FIG. 2 is a side view, in partial cross-section, of the first body  100 . First body  100  includes a central conduit  102  and external threads  104  for engaging threads on second body  200 . Formed integral with first body  100  are a plurality of fingers  110  arranged radially about the first body  100 . Adjacent fingers  110  are separated by a space  112 . FIG. 3 is an enlarged, cross sectional view of a finger  110 . Finger  110  includes an outside surface  114 , an inside surface  116  and a front face  118 . The outside diameter of threads  104  is greater than the outside diameter of fingers  110 . 
     The finger  110  has a varying thickness from front face  118  to the base  120  where finger  110  joins the remainder of first body  100 . The finger  110  is thickest at front face  118  and the thickness decreases as the inside surface  116  approaches the base  120 . The inside surface  116  is at an angle a relative to outside surface  114  and relative to the centerline of first body  100 . In an exemplary embodiment, a is  40  degrees. A finger stop surface  122  is provided on the inside of body  100  opposite inside surface  116 . As described herein, finger  110  is bent inwards towards the centerline of body  100  during installation. The finger stop surface  122  serves to stop deflection of finger  110  beyond a certain point. The finger stop surface  122  is at angle β relative to inside surface  116 . In an exemplary embodiment, β is 30 degrees. 
     As shown in FIG. 1, the front face  118  of each finger  110  is trapezoidal. The base of the trapezoid is located towards the outside of the body  100 . When the fingers  110  are deflected inwards during installation, the base of the trapezoidal front face  118  contacts the base of the front face of an adjacent finger. This creates a continuous ring to provide a sealing surface as described herein. 
     FIG. 4 is an end view of a second body  200  and FIG. 5 is a side view, in partial cross-section, of the second body  200 . Second body  200  includes a central conduit  202  which communicates with conduit  102  to allow gas to travel through the fitting. Second body  200  includes internal threads  204  that engage external threads  104  on first body  100 . The inside surface of second body  200  includes a finger deflection surface  206  and a sealing surface  208 . As shown in FIG. 6, the finger deflection surface  206  is frusto-conical and is at an angle γ relative to the centerline of second body  200 . In an exemplary embodiment, γ is  15  degrees. The finger deflection surface  206  has a largest inner diameter greater then the outer diameter of fingers  210 . The internal threads  204  have an inside diameter greater than the largest inside diameter of finger deflection surface  206 . The finger deflection surface  206  contacts finger  110  and deflects the fingers  110  towards the centerline of first body  100 . Sealing surface  208  is used to seal the corrugated tubing as described herein with reference to FIGS. 9-11. Sealing surface  208  is at an angle Δ relative to a normal to the centerline of the second body  200 . In an exemplary embodiment, Δ is 15 degrees. 
     Second body  200  also includes a shoulder  212  which is formed by an area of increased diameter  210  in central conduit  202 . The shoulder  212  serves as a stop to position a locating sleeve  300  (FIGS. 7 and 8) relative to second body  200 . The locating sleeve is similar to that disclosed in U.S. Pat. No. 5,799,989, the contents of which are incorporated herein by reference, and pending application Ser. No. 08/905,373, the contents of which are incorporated herein by reference. The locating sleeve  300  is press fit into second body  200 . Alternatively, the locating sleeve  300  may be formed integral with second body  200 . The locating sleeve  300  is generally cylindrical, and may include a tapered section to facilitate insertion. As described herein, the locating sleeve helps to position the corrugated tubing upon installation of the fitting. 
     Installation of the fitting will now be described with reference to FIGS. 9-10. As shown in FIG. 9, the first body  100  and second body  200  may be partially joined by mating threads  104  with threads  204 . The corrugated tubing  400  is cut in a valley and is snapped into the first body  100  so that fingers  110  are positioned in the first valley adjacent to the cut end of the tubing  400 . The smallest inner diameter of the fingers  110  is less than the outer diameter of peaks on the corrugated tubing but greater than the outer diameter of the valleys of the corrugated tubing. Accordingly, when the corrugated tubing  400  is inserted in first body  100 , a peak of the corrugated tubing  400  engages the fingers  110 . The fingers  110  are resilient and spread outward slightly to allow the peak on the corrugated tubing to clear the fingers  110 . Once the peak of the tubing  400  clears the fingers  110 , the fingers  110  return to their original position and rest in a valley of the tubing. This interference between fingers  110  and the tubing  400  secures first body  100  to the tubing  400 . 
     The outer diameter of the threads  104  and corresponding inner diameter of threads  204  provides a clearance  240  between the threads  204  and the fingers  110 . This clearance allows the fingers  110  to deflect away from the centerline of the first body  100  without interference from the second body  200 . This allows the first body  100  and second body  200  to be partially engaged when the corrugated tubing  400  is snapped into the first body  100 . This facilitates installation in that the first body  100  is partially engaged with second body  200  providing the installer with a single component. 
     The second step is to create a seal by rotating the second body  200  relative to the first body  100  thereby drawing the first body  100  into second body  200 . As first body  100  enters second body  200 , the outside surface  116  of fingers  110  engage finger deflection surface  206 . As the fingers  110  travel along finger deflection surface  206 , the fingers  110  are deflected inwards toward the corrugated tubing  400 . Locating sleeve  300  also enters the tubing  400  to locate the tubing  400  relative to the second body  200 . 
     The first body  100  and second body  200  continue to be tightened until a seal is achieved as shown in FIG.  10 . The fingers  110  have been deflected inwards and two layers of corrugated tubing  400  are compressed between the front face  118  of each finger  110  and the sealing surface  208 . The two layers of tubing, or double flare, provides a metal-to-metal seal that prevents leakage. 
     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.