WO2005012780A1

WO2005012780A1 - Pipe fitting for multilayer tubes

Info

Publication number: WO2005012780A1
Application number: PCT/IT2004/000150
Authority: WO
Inventors: Benedetto Patti
Original assignee: Itap S.P.A.
Priority date: 2003-07-31
Filing date: 2004-03-24
Publication date: 2005-02-10
Also published as: ITBS20030054U1

Abstract

This invention concerns a fitting for multilayer tubes, which includes a tang (14) to be inserted into one end of the tube and a joint (16) for connecting other complementary elements. The tang (14) has an end conical zone (20) acting as a calibrator, an initial cylindrical zone (21) with an external grip threading (24) which engages the internal surface of the tube, and at least one seal (23) between said conical zone and said cylindrical zone. An external sleeve (12) is positioned around the tube to block it in said cylindrical zone when the grip threading is locked in the internal surface of the tube.

Description

"PIPE FITTING FOR MULTILAYER TUBES"

Field of the Invention This invention concerns a fitting for joining tubes, in particular, but not limited to, multilayer tubes made of different materials used in plumbing, sanitaryware and heating systems. The fitting can be straight, at an angle, and T shaped, etc., and is usually made of brass, without excluding however the possibility of it being made out of steel or other materials. Prior Art The multilayer tubes usually have a wall made of alternating layers of metal and polymers; among them, the most popular are those with an aluminium layer between two layers of a plastic material, generally with an external layer which is much thinner than the internal one. When placed in use these tubes are connected using joints which can be of various types and which, in the plumbing sector are usually made of brass, bronze or steel due to their well known reliability. However, if these materials come into direct contact with the aluminium of a multilayer tube the possibility of galvanic corrosion increases. In order to avoid corrosion it is therefore indispensable to prevent the joint fitting from having a part which can penetrate the polymer layers and come into contact with the metal layer of the multilayer tube. When requiring to connect multilayer tubes, fittings known today as "bicono" "double cone", pressure fittings known as "pressure-fittings" , and quick fit fittings are generally used. All these fittings are shaped to engage with the external surface of the multilayer tube and to grip it radially from the outside with the help of a tang inserted into the end of the tube itself. With these systems the risk of the metal fitting coming into contact with the intermediate layer of the multilayer tube, also metallic, increases. This is because the external layer is usually very thin and furthermore it is not easy to adjust tightening and depth of penetration of the gripper elements without them cutting through the external layer, and furthermore the tubes may have defects in thickness making it difficult to establish the exact thickness of the external layer along all its length. In fact, for the joining of some tubes for delivering fluids at high pressure a coupling has been presented which includes a tang with a threaded section which is inserted and is screwed into one end of the tube and which is blocked either by means of a sleeve which is closely fitted or screwed onto the tube. In this case, even if the tang grips onto the inner surface of the tube, the assembly of the fitting requires a sleeve which must be clamped or screwed to the tube itself. Furthermore, neither are there any seals envisaged between the tang and the tube nor is the tang intended and used as a calibrator for the tube it is inserted in, even though it has a conical initial section. Object and Summary of the Invention Starting from this state of the technique, one objective of this invention is to present and achieve a fitting for tubes capable of reliably attaching itself to the internal surface of a tube without having to tighten or screw any element on the outside of the tube. Another objective of this invention is to supply a fitting for tubes which has a mouth acting also as a calibrator of the tube and which has at the same time at least one means of hermetically sealing it against the internal surface of the tube. These objects are reached with an innovative fitting according to the characterising part of claim 1 and having the advantages: - of permanently engaging with the internal layer, generally thicker, of a multilayer tube, - of drastically reducing in this way the probabilities of direct contact with the metal joint with the intermediate metal layer of the tube; - of calibrating the diameter of the tube, removing the irregularities at the moment of joining it to the pipe fitting; and - of ensuring also the hydraulic seal inside the tube. Brief Description of the Invention The enclosed drawing illustrates, indicatively, an example of a practical realisation of the fitting according to the invention and which will be described in more detail in the description to follow. In said drawing the only figure shows a horizontal section of a straight fitting assembled with a multilayer tube. Detailed Description of the Invention As shown, the fitting includes an internal body 11 and an external contrasting sleeve 12, both in metal such as brass, steel or similar. The body 11 may be linear, angular, or T or of some other shape and crossed by a longitudinal hole 13. Said body presents, on one side, a portion in the shape of a tang 14 and, on the other part, a threaded coupling 16, male or female as required, to connect it to other complementary elements with the interposition of a relative seal 16'. The tang portion 14 is made to engage inside the end of the multilayer tube 15 which has, as is known, an intermediate metal layer 17 positioned between two internal layers 18 and an external plastic layer 19.The sleeve 12 is to be fitted on the end of the tube 15, on the outside of the latter concentric to the tang 14. In particular, the tang portion 14 of the body 11 has, from its free end towards the coupling 16, an initial conical zone 12 followed by a first cylindrical zone with an external diameter roughly the same as the internal diameter of the multilayer tube, which is followed by a second cylindrical zone 22 with a diameter greater than the first cylindrical zone 21 and however less than the internal diameter of the intermediate metallic layer 17 of the multilayer tube. Between the initial conical zone 20 and the first cylindrical zone 21 one or more grooves have been cut for the same number of toric seals 23. On the external surface of the first cylindrical zone, threading is cut which is relatively thin and long pitched which goes from a part adjacent to the seals 23 and a part adjacent to the second cylindrical zone 22 of the tang. The first cylindrical zone 21 and the second cylindrical zone 22, which as said above have different diameters, form between them an annular stop shoulder 25. The external sleeve 12 has on one part a flared mouth 12' and on the opposite part an end neck 12" facing radially towards the inside and acting as a rest for a ring seal 26. The fitting described above is assembled with the multilayer tube 15 by fitting it tightly to one end between the tang portion 14 and the external sleeve 12. More precisely, the tang portion 14 is force fitted in the tube by turning it using, for example, a box wrench with which it engages a housing 11' in correspondence with the end of the tang 14 of the fitting 16. Now its initial conical portion 20 acts as a calibrator to reduce any out of round parts and irregularities in the wall of the tube, so as to make the latter cylindrical and compatible with the diameters of the parts it has to join up with. At the same time, the threading 24 in the first cylindrical zone 21 screws into and engages with the internal layer 18 of the tube, facilitating the forward movement of the tang until the end of the tube comes into contact with the annular shoulder stop 25 and with the seal 26 placed against the end neck 12 of the external sleeve 12. On completing assembly the toric seals 23 around the tang 14 ensure the hydraulic seal on the surfaces around the tube. The threading 24 attaches the fitting to the tube without it however interfering with the metallic layer 17 of the tube itself. The stop shoulder 25 rests only against the internal layer 18 of the tube without coming into contact with the metallic layer 17, whereas the end seal 26 prevents any contact of the metallic layer of the tube with the sleeve. In other words, no part of the fitting comes into contact with the metallic layer of the multilayer tube so, as required, any bimetal contact which may become a source of corrosion of the metallic layer of the tube is excluded. Furthermore, the fixing threading 24 which engages the internal layer

18 tends to expand the tube radially towards the external sleeve 12, which due to its resistance reaction and because of its rigidity helps to maintain the grip of the tube around the tang of the fitting and the sealing action of the seals inside the tube. This clamping action on the part of the sleeve also tends to increase in the presence of a force directed at unscrewing and releasing the tube from the fitting or vice versa. Consequently, following any axial movements of the fitting in relation to the tube, the grip threading would tend to cause an even greater expansion of the tube, but the external sleeve stops this expansion making it impossible for the fitting to slip off the tube.

Claims

"PIPE FITTING FOR MULTILAYER TUBES" *****

C L A I M S 1. Fitting for tubes, in particular multilayer tubes, comprising an internal fitting body (11) with a longitudinal hole and an external sleeve (12), where the body of the fitting has, on one side, at least one tang portion (14) to be inserted in one end of the tube and, on the other part, a male or female joint (16) for connection to other complementary elements, characterised in that said tang portion (14) has, an end conical area (20) on its external surface acting as a calibrator, a first cylindrical zone (21) with external grip threading (24) destined to attach itself to the internal surface of the tube, and at least one toric seal (23) between said conical zone and said cylindrical zone for sealing against the internal surface of the tube, and in that the external sleeve (12) is positioned concentric to said tang portion to envelope the tube and clamp it onto said cylindrical zone when the grip threading is gripping the internal surface of the tube, the end of the tube being positioned and firmly held between the tang of said fitting body and said external sleeve. 2. Fitting for tubes according to claim 1 , in which the grip threading (24) of said first cylindrical zone has a long pitch and screws into the innermost layer of the multilayer tube. 3. Fitting for tubes according to claims 1 and 2, in which the first cylindrical zone housing the grip threading (24) is followed, in the opposite direction to the extreme conical portion (20), from a second cylindrical zone with a greater diameter (22) forming with said first cylindrical zone, an annular support shoulder (25) of the end of the multilayer tube on a level with its innermost layer when fitting and tube are assembled. 4. Fitting for tubes according to the previous claims, in which the external sleeve (12) has a flared mouth (12') and on the opposite part an end neck (12") turning radially towards the inside, and in which said neck end is associated with a ring seal (26) supporting the end of the tube when the innermost layer of the latter is resting against said annular shoulder (25).