Abstract:
A tube coupling includes a body having a cylindrical projection to engage in a tube to be secured to the body. A grab ring is mounted by arms having openings to snap onto abutments on the coupling body. The grab ring encircles with a clearance the projection and engages an outer surface of a tube pushed onto the projection to grip and resist withdrawal of the tube from the projection.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the priority of United Kingdom Application Serial No. 0603429.2, filed Feb. 21, 2006, which is incorporated herein by specific reference. 
   BACKGROUND OF THE INVENTION 
   1. The Field of the Invention 
   This invention relates to tube couplings and in particular to tube couplings comprising coupling bodies to which a tube is connected. 
   2. The Relevant Technology 
   A number of arrangements are known for securing tubes to tube coupling bodies. For example our UK Patent Specification No. 1520742 discloses a coupling body having a throughway open at one end to receive a tube with a collet having resilient fingers located in the open end of the coupling body and cooperating with an internal cam surface in the coupling body to cause, with movement of the collet outwardly of the coupling body, the collet arms to be forced inwardly into gripping engagement with the tube to lock the tube in the coupling body. We have a number of subsequent patent specifications disclosing further development of this arrangement including UK patent specification no. 1573757, UK patent specification no. 2131903, UK patent specification no. 2167147 and UK patent specification no. 2172948. These arrangements all deploy a collet of one form or another to lock the tube in the coupling body. Arrangements have also been devised in which the tube is locked in the coupling body by a grab ring such as the arrangement shown in our European patent publication no. 0751329. In this arrangement a grab ring is mounted internally in a coupling body to engage the outer surface of a tube in the coupling body to resist withdrawal of the tube. 
   The object of the present invention is to provide a simple arrangement for securing a tube to a coupling body which can easily be disconnected and reassembled when required and also allows the user to see the tube has been correctly secured to the coupling body. 
   SUMMARY OF THE INVENTION 
   This invention provides a tube coupling comprising a coupling body having a cylindrical projection to engage in a tube to be secured to the body, and a grab ring mounted externally of the coupling body and encircling with a clearance the projection to encircle and engage an outer surface of the tube located on the projection to grip and resist withdrawal of the tube from the projection. 
   In a preferred form of the invention the coupling body may have a throughway extending through the projection for flow of a gas or liquid between the tube and coupling body. 
   It is further preferred that the projection has an encircling seal to seal with the internal surface of a tube located on the projection. 
   In the latter case the projection may have an encircling groove and an O-ring seal is located in the groove to engage and seal with the internal surface of a tube located on the projection. 
   In any of the above arrangements the coupling body may have a main portion from which the cylindrical projection extends and an axially facing shoulder encircling the projection to receive an end of a tube located on the projection and the grab ring is mounted on the main portion of the coupling body with the ring spaced from the shoulder to engage and lock with the outer surface of a tube located on the projection at a location spaced from the end of the tube. 
   Also in any of the above arrangements wherein the grab ring may have means to mount the ring on the main portion of the coupling body with the ring spaced along the projection from the main portion. 
   In the latter case the means to mount the grab ring on the main portion of the coupling body may comprise one or more legs extending axially from the grab ring to the main portion of the coupling body. 
   More specifically the grab ring has at least two legs projecting from the ring at spaced locations to the main portion of a coupling body. 
   Furthermore, detent means may be provided between the legs and main portion of the coupling body to retain the grab ring in position around the projection of the coupling body. 
   For example the main portion of the coupling body may have radially projecting lugs spaced around the coupling body and the grab ring has apertures which snap around the lugs to retain the legs and thereby the grab ring in position on the coupling body. 
   In a further arrangement the legs of the grab ring may be integrally molded into the main portion of the coupling body to locate the grab ring around the projection. 
   In any of the above arrangements the grab ring may comprise a cylindrical element having an inturned flange at one end formed with internal teeth to grip and engage a tube inserted through the grab ring on the projection. 
   Also in any of the above arrangements the legs of the grab ring may be molded into the main portion of the coupling body to support the grab ring spaced along the projection from the main portion. 
   According to a further feature of the invention a cap to fit the coupling body and enclosed the projection is provided with an aperture in the top of the cap through which a tube is inserted onto the projection of the coupling body. 
   The arrangement may further include a device to slide along a tube located on the cylindrical projection to release the grab ring from the tube and allow the tube to be withdrawn from the grab ring/projection. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Various embodiments of the present invention will now be discussed with reference to the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. 
       FIG. 1  is an exploded perspective view of a tube coupling comprising a coupling body, a grab ring for securing a tube to the coupling body, and a tube; 
       FIG. 2  is a section view through a tube coupling body with grab ring in situ to receive a tube; 
       FIG. 3  is a similar view to  FIG. 1  showing the tube secured to the coupling body by the grab ring; 
       FIG. 4  is a further view with the tube detached from the coupling body with the grab ring; 
       FIG. 5  is a similar view to  FIG. 1  showing a modified arrangement; and 
       FIG. 6  is a cross-section view through the arrangement of  FIG. 5 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring firstly to  FIG. 1  of the drawings, there is shown a tube coupling body formed as a plastics molding as indicated generally at  10 , a metal grab ring indicated generally at  11  for securing a tube to the coupling body and a portion of a plastics or metal tube  12  for connection to the coupling body. 
   The coupling body has a main body portion  13  of generally cylindrical form having a coaxial cylindrical projection  14  extending from one end of the cylinder with a step  15  between the outer diameter of the cylinder and the outer diameter of the projection. The coupling body has a throughway  16  extending through the body including the projection  14 . 
   The cylindrical projection  14  is intended to receive an end portion of a tube and adjacent the end of the projection there is an annular groove  17  in which an O-ring seal  18  is located to seal with the internal surface of the tube. The dimensions of the internal surface of the tube are such that the tube is a close or interference fit with the outer surface of the projection. Alternatively or in addition, the projection  14  is formed with an annular integral bumper, rib or barbs or is formed as a “fir-tree” to grip inside the tube. 
   The tube  12  is secured in place on the projection  14  by means of the grab ring  11  which is formed in a hard spring metal and comprising a short annular sleeve portion  19  having an in turned flange  20  formed with angled teeth  21  around its inner periphery to receive and grip the tube  12 . The grab ring has axially projecting lugs  22  spaced around the grab ring at diametrically opposite locations formed with elongate rectangular slots  23 . The ends of the lugs have out turned edge portions  24  for a user to lever the lugs outwardly as described later. 
   The main body portion  13  of the coupling body has integral radially outwardly extending abutments  25  which the lugs  22  snap over when the grab ring is located on the main portion of the coupling body with the abutments engaging in the slots in the lugs to hold the grab ring in place on the coupling body around the projection  14  and spaced from the end wall  15 . 
   With the grab ring  11  assembled on the coupling body as shown in  FIG. 2 , a tube  12  is pushed over the projection  14  past the O-ring seal  18  into the grab ring until the end of the tube abuts the end face  15 . The angled teeth  21  of the grab ring engage the outer surface of the tube to lock the tube in place on the projection and the O-ring seal  18  provides a seal against lost fluid or gas from between the tube and projection. The fully assembled position is shown in  FIG. 3 . 
   To release the tube from the coupling body, the lugs  22  are lifted radially outwardly by levering under the out turned ends  24  to disengage from the abutment  25 . The tube can then be drawn off the projection  14  as illustrated in  FIG. 4  of the drawings. 
   Thus the arrangement provides a simple and easily operated arrangement for locating a tube on a tube coupling body which can easily be visually checked to ensure that the tube is correctly positioned on the body and gripped by the grab ring which is on the outside of the fitting body. 
   It will be appreciated that the grab ring can be designed and located on the body in a multitude of ways. In its simplest form, the grab ring could be made tubular and simply cold formed onto the coupling body or could be molded into the coupling body. 
   The grab ring can have more than two legs or clips to locate it on the coupling body and the clips can be designed so that they can easily be released by hand or by a special tool or can be arranged so that they cannot be released to provide a permanent connection of a tube to the coupling body. 
   The grab ring can be specifically designed to allow release of the tube with the use of a tool or “collet cover” which when slid axially towards the connector can engage with and then expand the teeth off the tube allowing removal of the tube but keeping the grab ring mounted on the body. A cap can be provided to fit over the coupling body to conceal the connection of the tube to the coupling body once the correct engagement of the tube with the coupling body has been made. The fitting can be supplied in its component part with or without the cover the latter making it more aesthetically attractive and robust to the environment where necessary. 
   The legs of the grab ring could be molded onto the coupling or the grab ring itself could be molded into the coupling.  FIGS. 5 and 6  show a further arrangement in which the grab ring is formed in a sleeve  30  which is either molded into or crimped onto the coupling. To that end the abutment  25  would be formed as a continuous annular molding for the end of the sleeve to be crimped over. 
   The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.