Abstract:
A coupling for tubes with a body with a neck ( 14 ) provided with two or more longitudinal recesses ( 15 ) and each of which is positioned a jaw ( 12 ) able to move radially between an expanded release position and a contracted lock position. The jaws can move from one position to the other by means of cam surfaces ( 24 ) provided inside a tightening nut ( 13 ) assembled and susceptible to partial rotation on the neck of the coupling body. Furthermore the nut has means for interacting with the neck to block it and prevent it from turning in the release direction.

Description:
FIELD OF THE INVENTION 
   This invention concerns a coupling for metal, plastic or multi-layer tubes for plumbing, both in sanitation and heating systems. 
   STATE OF THE TECHNIQUE 
   The type of coupling here considered can be straight, female or male, straight intermediate, an elbow joint, T or Y etc., used to be connected together or to other components of pipes used in water systems but not only. At present there are many and well known types available on the market, for example threaded couplings, compression joints, press-fittings, rapid fittings and so on. Usually these couplings have at least one ring locking element to tighten around the end of the pipe, with the help of a conical threaded nut or press-fitting to enable it to grip on the external surface of the pipe. 
   Usually, with pipes with a metal core and at least one external coating, tightening of the blocking element must be adjusted so that it only partially cuts into the covering and does not cut through it and come into contact with the metal part of the pipe. Furthermore with these types of tube it is necessary to avoid contact with the fluid flowing through the metal pipe, the free end of which is normally bare. 
   OBJECTS AND SUMMARY OF THE INVENTION 
   A first object of this invention is to provide a coupling for pipes which has a new concept and has a simple, rapid and efficient block/release system, involving only a partial rotation of one component on and with respect to another. 
   A second object of the invention is to provide a new, original coupling for pipes using gripping elements that engage the pipe to be blocked only for a part of its length without however encompassing it. 
   A further object of the invention is to provide a coupling for pipes that can be made not only of metal, such as brass or steel, but also totally or partially of a synthetic material, produced by molding or some other forming technique. 
   Another object of the invention is to provide a coupling suitable both for metal and plastic material pipes, but in particular for connecting multilayer pipes, the coupling being equipped with physical means to limit the level of tightening of the gripping elements, so that they do not cut through the layer of external coating in that type of pipe. 
   Another object of the invention is to provide a coupling which is reliable when in use in that it cannot be accidentally released and moreover its sealing capacity increases when operating under high pressure. 
   Yet another object of the invention is to provide a coupling which is easy to use in as much as its components always maintain their correct position even when the coupling is released and is packed and handled. 
   Said objects and subsequent practical and functional advantages are reached, according to the invention, by a coupling for tubes that includes jaws that move in a radial direction of a hollow cylindrical body of a coupling body. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will however be described more in detail with reference to the enclosed indicative and not limiting drawings, in which: 
       FIG. 1  shows a view in perspective of only the coupling body; 
       FIGS. 2 and 3  show, respectively, a side view and a longitudinal section of the coupling body; 
       FIG. 4  shows a cross section level with the neck of the coupling body of  FIG. 1 ; 
       FIG. 5  shows a view in perspective of the tightening nut; 
       FIGS. 6 and 7  show the tightening nut seen from one end and a longitudinal section respectively of  FIG. 5 ; 
       FIG. 8  shows a view in perspective of a jaw; 
       FIGS. 9 and 10  show, respectively, a longitudinal section and a cross section of the jaw in  FIG. 8 ; 
       FIG. 11  shows a view in perspective of the coupling assembled complete with pipe; 
       FIGS. 12 and 13  show, respectively, a side view and a longitudinal section of the assembly in  FIG. 11 ; 
       FIG. 14  shows a view in perspective of a construction variation of the jaw, and 
       FIGS. 15 and 16  show, respectively, the side views and cross section of the jaw in  FIG. 14 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The coupling subject of this invention comprises a coupling body  11 , at least two jaws  12  and a tightening nut  13 . 
   The body  11  can be straight, an elbow, a T, a Y coupling or the like. In the example shown it is straight (as shown in  FIGS. 1-4 ) and has, in one part of it, a hollow, cylindrical neck  14  in the walls of which are machined, longitudinal recesses  15  spaced at an angle to each other. In the case in question there are two diametrally opposite recesses  15 , and the neck  14  forms a housing  14 ′ with an internal diameter compatible with the diameter of the pipe  16  to be connected. On the other side, the body  11  can have a completely similar neck (thus forming a double coupling) or a threaded female section  11 ′ as shown or a male threaded section. In any case, the body  11  can also have an external polygonal part  11 ″, better if hexagonal, to facilitate gripping with a tool. 
   The jaws  12  are rectilinear and each one is housed in a recess  15  of the neck  14  of the coupling body  11  with the possibility of moving radially between an expanded release position and a contracted locking one. In the release position the jaws are moved towards the outside of the neck and when in the locked position towards the axis of the neck. 
   Each jaw  12  (as shown in  FIGS. 8 and 14 ) has the shape of a cylindrical section with a diameter compatible with that of the pipe  16  to be blocked. It has a smooth external surface  17  and a toothed internal one with a series of serrated gripper teeth  18 , parallel to each other and oriented crossways to the jaw itself. 
   On each of the longitudinal sides, that is from opposite sides of the teeth  18 , each jaw  12  has a supporting plane  19  made to rest on a facing locator step  20  cut along each side of every recess  15  so as to set the maximum movement position of the jaw towards the contracted locking position. 
   Furthermore, each longitudinal side of each jaw  12  has at least one tab  112  made to fit into a corresponding indent  115  provided in the relative side of the recess  15  so as to prevent the jaw from moving, tilting and falling inside the neck, which would prevent the pipe from entering, thus obstructing the immediate use of the coupling on the part of the user. 
   The tightening nut  13  is placed around the neck  14  of the coupling body  11  and has in preference a hexagonal external surface to facilitate gripping by a maneuvering tool. It is held axially on the neck  14 , but has the possibility to turn, between an annular shoulder  21  at the base of the neck and the radial locking lugs  22  at the free end of the neck itself. 
   Internally, the tightening nut  13  has lengthwise, as many grooves  23  as jaws  12  associated with the neck  14  of the coupling body  11 . Starting from each groove  23 , the tightening nut  13  has also a cam thrust surface  24  provided to engage with the external surface  17  of each jaw  12 . 
   On the head of the tightening nut  13  in the area between the grooves  23 , there is at least one upward ramp  113  terminating in a front anti-release indent  113 ′. Preferably the ramps  113  are the same number as the radial locking lugs  22  of the neck  14  of the coupling body. 
   All the components  11 ,  12 ,  13  of the coupling can advantageously be made of a suitable plastic material. However, where it is considered necessary and opportune, al least the jaws  12  can be made out of a metal, such as for example brass or steel. 
   The gripper teeth  18  are triangular in shape for assembly and bidirectional use of the jaws. However in the case of steel serrated gripper teeth  18  they can be a different shape and made by shearing and bending as shown in  FIGS. 14-16 . 
   In practice, when the tightening nut  13  is turned and its internal grooves  23  coincide with the jaws  12 , the latter can expand into the locking position. In such a condition, the pipe  16  in question can be connected to the coupling or, if already connected can be disconnected. 
   The pipe is connected to the coupling by inserting one of its ends into the neck  14 , where it is seal fitted with the help of at least one annular seal  25 . The pipe  16  is then blocked in the coupling body following a partial turn of the tightening nut  13 . By turning in this way, the internal cam  24  surfaces of the tightening nut  13  push the jaws  12  radially towards the pipe or the contracted blocking position where their serrated gripper teeth  18  engage the external surface of the pipe, blocking it firmly without it having the possibility either to turn or to slip out axially even in the presence of a fluid under pressure passing through the pipe. However the maximum gripping depth of the pipe by the serrated teeth  18  will be limited by the support of the lateral plane surface  19  of the jaws  12  on the lateral locator steps  20  of the indents  115  which house them to prevent the serrated teeth  18  from cutting through the pipe protective coating when the pipe is multilayer with an external coating. 
   Following the rotation the lugs  22  at the end of the neck begin to move up the upward ramps  113  on the head of tightening nut  13  until they fit into the anti locking  113 ′ indents, compelling the body of the coupling to fit completely and tightly on the pipe. These indents stop the nut from turning backwards in the releasing direction, ensuring the coupling-pipe joint. 
   It should also be noted that on the bottom of the housing  14 ′ which receives the pipe, a seal  114 ′ is provided to act against the end of the pipe. This seal, due to its elasticity, forms a seal on the end of the pipe even when the pipe moves backwards when it is subjected to operating pressure. Furthermore, in the case of multilayer pipes, this seal  114 ′ also helps to prevent the fluid coming into contact with the metal core of the pipe as is required by regulations.