Patent Abstract:
A reinforcing and a plastic fitting incorporating such a reinforcing ring are disclosed. The reinforcing ring and plastic fitting have particular utility with respect to fire sprinkler heads in buildings. The reinforcing ring has a single starter thread which is integrally formed with a guide portion which guides a male part to be axially in line with the female fitting.

Full Description:
FIELD OF THE INVENTION 
   This invention relates to a reinforcing ring for a plastic fitting and a plastic fitting incorporating such a reinforcing ring. The invention has particular utility with respect to fire sprinkler heads in buildings, although it will also have utility with other applications. 
   BACKGROUND OF THE INVENTION 
   In the past, plastic fittings have been used for receiving a threaded male part, typically a threaded pipe. Also, in the past, reinforcing rings have been used to reinforce plastic fittings, such as described in U.S. Pat. Nos. 5,582,439 and 6,866,305 to Spears and U.S. Patent Application 2004/0051316 to Spears. Also, U.S. Pat. No. 4,682,797 to Hildner and U.S. Pat. No. 6,186,558 to Komolrochanapom, as well as U.S. Patent Application 2003/0184085 to Thompson, disclose a reinforcing ring used with plastic fittings. 
   Although reinforcing rings that have been made in the past, and used with plastic fittings, there have been problems with such rings and fittings, particularly relating to cross-threading and shearing. Therefore, the present invention provides an improved reinforcing ring and an improved fitting incorporating the reinforcing ring. 
   One problem is that when the male part which is being inserted into the plastic fitting is over-tightened, there is a tendency for the plastic fitting to shear. 
   Also, cross-threading occurs when the thread axis of the male part is not properly aligned relative to the female fitting&#39;s thread axis. All plastic thread design is susceptible to cross-threading. One way of at least reducing the risk of cross-threading is to guide the male part to be axially in line with the female fitting. Another way to lessen the likelihood of cross-threading is to reinforce the first few plastic threads of the fitting with a harder material. The present invention has been able to successfully combine both of these approaches to provide an improved method of reducing the likelihood of cross-threading using only a single starter thread. None of the prior art reinforcing rings use only a single starter thread. 
   SUMMARY OF THE INVENTION 
   Accordingly, it is an object of this invention to at least partially overcome the disadvantages of the prior art. Also, it is an object of this invention to provide an improved reinforcing ring for plastic fittings and an improved plastic fitting incorporating the reinforcing ring. 
   Accordingly, in one of its aspects, this invention resides in providing a reinforcing ring for a plastic fitting, comprising: a first tubular portion; a radial portion extending radially inwardly from a forward end of the tubular portion; a guide portion extending rearwardly from a radially-inner region of the radial portion; and a starter thread extending radially inwardly from a rearward end of the guide portion. 
   In a further aspect, the present invention resides in providing a plastic fitting for receiving a threaded male part, comprising: a plastic body having inner plastic threads for receiving the male part in threaded engagement; and a reinforcing ring as described above wherein the first tubular portion of the reinforcing ring surrounds at least a portion of the plastic body. 
   Further aspects of the invention will become apparent upon reading the following detailed description and drawings which illustrate the invention and preferred embodiments of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, which illustrate embodiments of the invention: 
       FIG. 1  is a perspective view of a preferred embodiment of the reinforcing ring of the invention; 
       FIG. 2  is a top view of a preferred embodiment of the reinforcing ring of the invention; 
       FIG. 3  is a cross-sectional view though line A-A in  FIG. 2  of a preferred embodiment of the reinforcing of the invention; 
       FIG. 4  is another cross-sectional view through line B-B in  FIG. 2  of a preferred embodiment of the reinforcing ring of the invention; 
       FIG. 5  is a detail of a portion “C” from  FIG. 4  of one embodiment of the reinforcing ring of the invention; 
       FIG. 6  is a side view of a preferred plastic fitting of the invention; 
       FIG. 7  is a cross-sectional view through line D-D in  FIG. 6  of a preferred embodiment of a fitting of the invention; 
       FIG. 8  is a detail of a portion “E” from  FIG. 7  of a preferred embodiment of the fitting of the invention; and 
       FIG. 9  shows a metal sheet from which a preferred embodiment of the reinforcing ring of the invention may be stamped. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   As shown in  FIG. 1 , one embodiment of the present invention relates to a reinforcing ring  10  for a plastic fitting  12 . As best seen in  FIG. 3 , the reinforcing ring  10  comprises a first tubular portion  14  and a radial portion  16  which extends radially inwardly from a forward end  18  of the tubular portion  14 . There is also a guide portion  20  extending rearwardly from a radially-inner region  22  of the radial portion  16 . Also, there is a starter thread  24  extending radially inwardly from a rearward end  26  of the guide portion  20 . 
   In one preferred embodiment, the guide portion  20  is tubular. In another preferred embodiment, the guide portion  20  is conical and extends rearwardly and inwardly as seen in  FIG. 3 . 
   Preferably, the tubular portion  14  is conical, preferably at about 86° from horizontal, but the tubular portion  14  may be cylindrical (90° from horizontal). 
   Preferably, the reinforcing ring  10  is stamped from a metal sheet  42  and in a more preferred embodiment the ring is made of stainless steel. 
   Preferably, the reinforcing ring  10  is stamped from the steel sheet  42 , preferably a stainless steel sheet. 
   When the reinforcing ring  10  is stamped in this manner, the starter thread  24  is no more than 360° around the guide portion  20 . In a preferred embodiment, the starter thread  24  is 360° around the guide portion  20 . In another preferred embodiment, the starter thread is less than 360° around the guide portion as seen in  FIG. 2 . 
   As will be seen from the Figures, the reinforcing ring  10 , particularly when stamped from a metal sheet  42 , is dimensioned such that the thickness T of each of the first tubular portion  14 , the radial portion  16  and the guide portion  20  (as best seen in  FIG. 3 ) is relatively small or thin compared to the diameter DIA of the first tubular portion  14  as best seen in  FIG. 2 . Thus, an appropriate thickness T of metal sheet  42  is selected in order to make the reinforcing ring  10  appropriately dimensioned. 
   The plastic fitting  12  is intended to and does receive a threaded male part  28  as seen in  FIG. 7 . Often the male part  28  is made of metal. The plastic fitting has a plastic body  30  which has inner plastic threads  32  for receiving the male part  28  in threaded engagement. 
   Preferably the guide portion  20  of the reinforcing ring  10  forms a guide portion  36  of the fitting  12  for guiding the male part  28  to the starter thread  24 . This reduces the likelihood of cross-threading. 
   Preferably, the starter thread  24  of the reinforcing ring forms a lead face  40  of the first thread  32 A of the threads  32  of the plastic body  30 . 
   Preferably, when the reinforcing ring  10  is properly installed as part of plastic fitting  12 , the radial portion  16  of the reinforcing ring  10  forms a forward protective portion  38  protecting the plastic body  30  from contact with the male part  28  as the male part  28  initially engages the fitting  12 . 
   Preferably, the first tubular portion  14  of the reinforcing ring  10  surrounds at least a portion  34  of the plastic body  30 . 
   Preferably, the plastic fitting  12  is molded with the first tubular portion  14  of the reinforcing ring  10  within and surrounded by a portion  44  the plastic body  30 . 
   Typically there are several inner threads  32  of the plastic body  30 . There will be at least a first inner thread  32 A (as best seen in  FIG. 7 ) closer to the starter thread  24  and a last inner thread  32 B further away from the starter thread  24 . Preferably the tubular portion  14  of the reinforcing ring  10  extends rearwardly to at least the last inner thread  32 B of the plastic body  30 . This will reduce the tendency for shearing the plastic fitting  2  upon over-tightening. 
   More preferably, the first tubular portion  14  extends rearwardly beyond the last thread  32 B of the plastic body  30 . 
   It will be understood that, although various features of the invention have been described with respect to one or another of the embodiments of the invention, the various features and embodiments of the invention may be combined or used in conjunction with other features and embodiments of the invention as described and illustrated herein. 
   Although this disclosure has described and illustrated certain preferred embodiments of the invention, it is to be understood that the invention is not restricted to these particular embodiments. Rather, the invention includes all embodiments which are functional or mechanical equivalents of the specific embodiments and features that have been described and illustrated herein.

Technology Classification (CPC): 5