COUPLING PIECE WITH FLANGE, CONDUIT SYSTEM WITH AT LEAST ONE SUCH COUPLING PIECE, METHOD FOR CONNECTING A CONDUXT AND A COUPLING PIECE, AND CONNECTING DEVICE

The present invention relates to diverse aspects related to plastic conduit systems (PCS) .

A PCS is used in the known art for many applications, such as discharge of water, supply of water, gas and chemical substances. PCSs have been used increasingly in the Dutch building industry in the last 10 years as an alternative to steel and copper. PCS for drainage is generally known, among other ways through the introduction of PVC. Partly in view of the required pressure resistance, only copper conduits were used up until recently for the supply of hot and cold water and gas and central heating and drinking water. Owing to the high price of copper, and also due to the theft of copper from construction sites, there has been a rapid increase in the use of PCS to which no end is in sight. Simplifications in PCS in respect of fitting thereof has also resulted in PCS being accepted by the regulatory bodies and being used more and more by fitters. It is noted that PCS has already been applied in many countries for mains water because the quality thereof is sometimes so limited that the use of metal in conduits is undesirable.

PCS can comprise different types of plastic, optionally with a base of for instance aluminium embedded in plastic for the purpose of improving the pressure resistance. Thermoplastic plastics are mostly used, such as polypropylene (PP), polyethylene (PE), polybutylene (PB) and sometimes PVC. The installing of a system comprises of forming combinations of conduit and connecting pieces, couplings and/or fittings. The type of fitting also determines the nature of the tool that has to be used. An increasing number of systems are otherwise

emerging for which no tool need be used at all, the so-called push couplings.

The following division can be made in systems most applied in Europe and the world:

Of the above PCSs the most used are the multilayer conduits (PE conduits with aluminium base layer, usually embedded in the plastic on the outside and on the inside) .

With an estimated market share of 60%, these systems are the most used in the built environment. The great advantage of these systems is that they can bend in form-retaining manner, just as copper conduits, but that they are much lighter in

weight and less expensive. The drawback of these known systems is that the fittings or couplings are expensive. The seal, even under pressure, is obtained by means of an O-ring on the coupling piece. The coupling piece is inserted or pushed into the conduit or pipe. The coupling piece is then squeezed shut with great force over the conduit or pipe by means of a sleeve.

In another known example the conduit is produced with a thicker conduit wall, whereby an axial press connection can be made: the conduit is flared, the fitting is inserted therein and a thick brass sleeve is then pushed over the conduit, whereby the fitting acquires its clamping force.

All such known systems have the common feature that a diversity of tools must be used, and the high price of the coupling piece or the fitting. A limited advantage of such systems is that no O-ring is used, whereby these PCSs have a "secure" appearance.

For the last two years push connections have also been available for the conduits or pipes with an aluminium base. While these are practical, they are on the other hand expensive and there is, as well as the apparent convenience, a not inconsiderable risk of leakage as a result of the O-ring. They are not to be recommended in concrete-like floors. All these PCSs thus have connections of metal with plastic and/or 0- rings.

As also shown in the table, polypropylene conduits and coupling pieces and fittings are also applied. A possibility of realizing this is by using welded fittings. These fittings are welded onto the conduit using a laser device (polyfusion welding) . An advantage hereof is that the coupling piece will form one whole with the conduit or pipe. In addition, hardly any narrowing occurs. This provides high certainty. The conduit or pipe cannot however be deformed by hand, so that work generally takes place with a rigid conduit. Partly for this reason use is generally made of a flexible conduit in the final

finishing (above the concrete) . It is therefore always necessary to work with a welding device if connection to the PP conduit is required. A conduit or pipe of PP is usually not oxygen-tight, making them less suitable for central heating systems.

At the moment these conduits are increasingly being applied as alternative to steel conduits for heat and for cooling ceilings in offices. The connection is rapid and relatively inexpensive and is highly suitable for prefabrication. The most interesting development relates to polyethylene conduits which are provided with an aluminium inner layer comprising a layer of polyethylene on either side. Such conduits are flexible and have a proven strength for the intended applications. Particularly interesting are conduits based on PE-RT (PE-Raised Temperature, a product of Dowlex) , which can withstand temperatures of 90-95 ⁰ C and can be applied up to pressures of 10 bar.

According to the present invention as now presented and defined in the appended claims, a coupling piece, a conduit system, a method and a device have been developed.

The invention as defined in claim 1 comprises a coupling piece for plastic conduits, this coupling piece being manufactured from thermoplastic material chosen from polyethylene (PE), reinforced PE, and PE-RT (PE-Raised Temperature, a product of Dowlex) . This coupling piece is provided on the inner side with a flange, which can also be seen as an additional sleeve or inner sleeve.

When a conduit is inserted into the coupling piece, after heating of the conduit and the coupling piece, the end surface of the conduit inserted into the coupling piece is covered over the width of the flange, for instance 3.5 mm, and thus protected by this flange. When both the inner side of this coupling piece and the flange or collar or additional sleeve are heated, as well as the inner and outer side of the conduit

or pipe, the conduit and the coupling piece will thus be adhered to each other in very reliable manner. When conduits having an aluminium base layer are coupled, an optimum adhesion and protection of the aluminium layer is created after connection of the coupling piece and the likewise heated conduit .

Such a protection is necessary in such an embodiment since corrosion of the aluminium in the conduit otherwise occurs, and this corrosion would damage the base layer of aluminium more and more until a leakage occurs. The inner adhesion at the flange is also desirable, usually even necessary, in order to ensure a sufficient tensile strength. If the flange were not used for this purpose, the fitting would be adhered only to the outer side of the conduit, and this may be insufficient in some circumstances when taking into account the thin layer of thermoplastic plastic over or on the aluminium base layer.

This is a particular problem in newly developed PE conduits which enable an increasingly thinner layer of PE on either side of the aluminium layer compared to current dimensioning. A PERT conduit with aluminium base layer can for instance allow an outer layer of PE-RT of 0.3 mm at a diameter of 16 mm. The inner layer of PE-RT is 1.2 mm, and the overall wall thickness of the conduit including adhesive layers is 2.0 mm. Such relatively thin layers of thermoplastic material thus make greater demands of the coupling. When the coupling piece is of PE and is used for a PE conduit, the best possible fusing of thermoplastic material is then achieved in that the melting points are substantially the same and a homogenous connection of the same material is created. This moreover simplifies the steps of heating the components for fusing, since it is not necessary to work at varying temperatures.

The coupling piece according to the invention preferably comprises a stop between the socket and the flange. The stop guarantees a good positioning of the parts to be fused relative

to each other, and moreover provides thermoplastic material for the fusing process.

The coupling piece according to the invention more preferably comprises a stop from the same thermoplastic material as the flange. The parts for fusing thus have the same melting point, and can be formed integrally.

In a preferred embodiment of the coupling piece the socket, stop and flange together enclose a wedge-shaped space. It has been found that an intimate contact can thus be achieved between the inserted outer end of a conduit and the stop. A wedge shape essentially increases the contact surface of the stop, thereby increasing the resistance to tensile forces and protecting the aluminium base layer over a larger surface area.

In a subsequent aspect the invention relates to a conduit system comprising at least one conduit formed substantially from plastic and a coupling piece according to the invention for connection to the conduit, wherein at least the inner side of the socket, the flange and the inner and outer wall of the conduit are formed from thermoplastic material chosen from the group of: polyethylene (PE), reinforced PE and PE-RT (PE-Raised Temperature) . Such a system has the above stated advantages of a homogenous fusion due to the use of PE for the parts for fusing, this resulting in a strong connection between conduit and coupling piece and an optimum sealing of the aluminium base layer when it is received in the conduit.

The conduit system according to the invention preferably comprises a coupling piece, of which the socket, stop and flange together enclose a wedge-shaped space, and the outer end of the conduit connected to the coupling piece has a corresponding wedge shape for receiving in the wedge-shaped space. Such an embodiment minimizes the deformation of the components to be fused when the conduit is inserted as far as the stop of the coupling piece. The less the components are

deformed, the higher the quality of the connection after fusion.

The conduit system can also be embodied as according to either of the claims 7 or 8, whereby by means of the coupling piece conduits can lie at different angles to each other.

In a following aspect the invention relates to a method according to claim 9, wherein the components of coupling piece and conduit to be heated are formed from thermoplastic material chosen from the group of: polyethylene (PE), reinforced PE and PE-RT (PE-Raised Temperature) . As already stated above, an optimal connection is thus obtained in simple manner, this connection simultaneously being able to comply with requirements such as apply for PE-RT.

In the method according to the invention the inner diameter of the socket is preferably greater during heating than the outer diameter of the conduit. When the conduit is inserted inside the socket, the occurrence of high shear forces is thus prevented between the outer side of the conduit and inner side of the socket. Since it is the case that PE conduits with aluminium base layer have an outer layer of PE which can be very thin, is important to minimize such shear forces. This therefore prevents the aluminium base layer becoming exposed during the method due to deformation of the outer layer of PE of the conduit.

It is more preferably the case here that in cold state the outer diameter of the conduit is greater than or equal to the inner diameter of the socket. It is thus necessary to heat until the conduit and coupling piece fit into each other, and it is possible using heating to set precisely the difference in diameter desired for insertion.

Finally, the invention relates to a device for connecting a coupling piece according to the invention and at least one conduit comprising thermoplastic plastic, comprising means for heating the inner side and the outer side of the conduit, and

means for heating the inner side of the socket and the flange in order to form a connection therebetween after joining together the conduit and the socket and after allowing the thus obtained assembly to cool in fused state.

The conduit and the coupling piece are heated with at least one welding device, but usually with two welding mandrels: one for the fitting and one for the conduit. The welding mandrels form part of the system, and the method can also be realized therewith. The welding mandrels can have a form adapted to respectively the conduit and to the coupling piece, so that the conduit and the coupling piece are heated in the correct form. This need not necessarily be desired or practical under all conditions.

The invention combines the advantages of a form-retaining but flexible or at least bendable conduit or pipe of for instance PE, optionally with an aluminium base layer therein, and the advantages of a welded connection. A certain and reliable connection can be realized without having to make use of metal couplings with O-rings. The price, particularly in the case of conduits of large diameters, is furthermore a factor of 10 cheaper.

An embodiment of the present invention will be described hereinbelow on the basis of and with reference to the accompanying figures, this embodiment not being limitative for the present invention, and in which the same reference numerals can be and are used in the various separate figures and views for the same or similar components, elements and aspects, and in which:

Fig. 1 shows schematically a method for assembling a coupling piece and a conduit for the purpose of forming a conduit system;

Fig. 2 shows the assembly of a conduit as according to arrow II;

Fig. 3A and 3B show steps in a method for connecting a coupling piece to a conduit according to the present invention;

Fig. 4 shows a cross-sectional side view along the line IV- IV in fig. 3B;

Fig. 5, 6 and 7 show detail views of variants of the general embodiment of Fig. 4.

Fig. 1 shows a coupling piece 1 according to the present invention, which is connected with a method according to the present invention to a conduit 2 for the purpose of forming a conduit system as assembly of coupling pieces and conduits according to the present invention, wherein use can be made of a device, likewise according to the present invention, of which several main components are shown in fig. 3A.

Coupling piece 1 is thus shown in fig. 1. It is sleeve-like or tubular. A stop 3 is arranged in the middle of the interior of tubular coupling piece 1, but can also be displaced over a desired distance relative to the middle of coupling piece 1. Arranged on the stop are a flange 4 extending in rearward direction in fig. 1 and a flange 5 extending in forward direction in fig. 1. Flanges 4, 5 therefore extend from stop 3 in opposing directions.

The outermost edge of a conduit 2 can be inserted under flanges 4, 5 and against stop 3. This is because conduit 2 has a slightly smaller diameter 6 than the inner diameter 7 of coupling piece 1. The wall thickness 8 of conduit 2 closely corresponds to the distance between the inner wall of coupling piece 1 and flanges 4, 5, so that conduit 2 can be inserted under flange and against stop 3 in the direction of arrow A.

An inspection hole 18 can be provided in coupling piece 1 in order to visually assess whether conduit 2 has been pushed sufficiently deeply into coupling piece 1 after heating. It is recommended that inspection hole 18 be situated in the vicinity of the middle of coupling piece 1 such that the inner part of flange 4,5 becomes visible at the position of stop 3. A

plurality of inspection holes can be provided on both sides of stop 3.

Fig. 2 shows the assembly of a conduit 2 as can be applied in a possible embodiment of the present invention. A base layer 9 therein is manufactured from aluminium having on either side thereof layers 10, 11 with adhesive or glue or the like, and the inner surface of the conduit and the outer surface of conduit 2 are each covered with layers 12, 13 of thermoplastic material, in particular polyethylene, for instance PE-RT (Polyethylene-Raised Temperature) . Because the outer edge 14 of conduit 2 is to be inserted under the protrusion of at least one of the flanges 4, 5 in fig. 1, particularly the aluminium of base layer 9 is well protected and covered and enclosed by thermoplastic plastic, which is substantially inert to corrosion and other harmful influences. The coupling piece according to the invention can of course also be applied with conduits without aluminium base layer 9 or with a layer of other material. A good sealing can moreover be obtained, for instance with the method to be described below.

As shown in fig. 3A, each of coupling piece 1 and conduit 2 can be placed on a respective heating element. Coupling piece 1 can be placed on a heating element 15, which is bush-shaped and has the same dimensions as conduit 2. The inner surface of coupling piece 1 can hereby be heated to a plastic state. If heating element 15, which is connected to for instance a voltage source for the purpose of generating the required heat, has the same thickness as conduit 2, at least one of the flanges 4, 5 can also be heated herewith to a plastic state. For this purpose coupling piece 1 can be placed in the direction of double arrow B on heating element 15 or pushed thereover, or heating element 15 can be pushed into coupling piece 1. Coupling piece 1 and heating element 15 are subsequently separated from each other again.

Simultaneously, or shortly before or after, conduit 2 is inserted into or between two heating elements 16, 17 which are both bush-shaped or cylindrical and disposed concentrically. Heating elements 16 and 17 are further each connected to a voltage source for supplying electric power and bringing heating elements 16 and 17 to higher temperature. When conduit 2 is then inserted between heating elements 16 and 17, the temperature of the inner surface and of the outer surface of conduit 2 can be heated to a temperature where the materials on the inner surface and on the outer surface become plastic. A double arrow C is also shown here to make clear that a relative movement takes place of the assembly of heating elements 16, 17 relative to conduit 2, and the heated outer ends of coupling piece 1 and conduit 2 are subsequently directed toward each other as according to respective arrows D and E. There then follows the movement shown in fig. 3B. That is, conduit 2 is then inserted into coupling piece 1 in the direction of arrow F, or coupling piece 1 is pushed over the free outer end of conduit 2. This situation is further shown in fig. 4.

Fig. 4 shows that conduit 2 comprises an aluminium base layer 9 per conduit. This base layer 9 is covered on the inside and on the outside with layers 12, 13 of thermoplastic material, in particular polyethylene. In the situation of fig. 4 the inner surface of coupling piece 1 and at least one of the flanges 4 are heated, wherein stop 3 or even the other of the flanges 5 can possibly also be brought into a plastic state. Layers 12, 13 of conduit 2 are likewise brought into a plastic state. Before the diverse materials have once again cooled to a temperature lower than the lower limit for the plastic state, coupling piece 1 and conduit 2 are brought together. The free outer end of conduit 2 herein comes to lie between the inner surface of coupling piece 1 and flange 4, possibly even against stop 3. The outer layer 12 of conduit 2 will here adhere to the inner surface of coupling piece 1, and an annular inner surface

of the material of inner layer 13 of conduit 2 will adhere to flange 4. In combination with flange 5 and stop 3, flange 4 has an anchor shape. A good engagement or clamping of the free outer end of conduit 2 can thus be realized. The angular tips on the outer ends of flanges 4, 5 can also penetrate into the plasticized material of the inner covering layer 13 of conduit 2 in order to realize an even better seal. In a specific embodiment of a method according to the invention the end surface of conduit 2, before being pushed between heating element 16, 17, is calibrated and chamfered to an angle K. After heating, the angle K moves as according to arrow F (fig. 4) into the cavity which can have the same angle as the chamfered side. The reason for this is to obtain a larger welding surface (Pythagoras' s theorem = chamfered side provides a larger surface) . Another reason is that flange 4 may have a maximum size such that no narrowing occurs in the connection if heating takes place for a (too) long period of time.

Fig. 5 shows a lengthwise section of a part of coupling piece 1 and the outer end of a conduit 2 to be inserted, constructed from a respective PE outer and inner layer 12, 13 and an aluminium base layer 9. Stop 3, flange 4,5 and socket 1 enclose a wedge-shaped space 51. The outer end of conduit 2 is chamfered in a corresponding wedge shape 53. It will be apparent that the outer end is thus oriented optimally toward space 51 of stop 3, thereby achieving an optimal connection between conduit and coupling piece.

Fig. 6 shows a variant of fig. 5, wherein the form of space 61 in the coupling piece and outer end 63 of the conduit are pointed. This provides advantages similar to the embodiment of fig. 5.

Fig. 7 shows a subsequent variant which is essentially a reversal of the wedge shape of fig. 5, with wedge-shaped space 71 and wedge-shaped outer end 73 of the conduit.

After examination of the foregoing many alternative and additional embodiments will occur to the skilled person, all of which lie within the scope of the present invention, at least to the extent they comply with the letter and spirit of the definitions in the appended claims. The stop need not be a continuous ring, but serves only to hold flanges 4, 5 a distance from the inner surface of coupling piece 1. Coupling piece 1 does not have to be a socket in order to define a continuous passage. Coupling piece 1 can also be an end cover, or a T-junction or any other random connecting element. Coupling piece 1 can on one hand also be provided with screw thread in order to form a connection with for instance an external component, for instance the screw thread on the outer side of a tap, wherein screw thread can then be arranged on one side in the interior of coupling piece 1. It is also possible to arrange an element with screw thread over coupling piece 1, wherein counter screw thread can then be defined in the outer surface of coupling piece 1. Of the device for realizing the method according to the invention only the heating elements are shown, which are as it were negatives of the elements and components to be heated, in particular the coupling piece and the conduit. Other components and aspects of such a device lie well within the reach and ability of the person with usual or ordinary skill in the relevant technical field, so a further consideration or description thereof is omitted here. It will nevertheless be apparent that a device for realizing the method, and then in combination with a coupling piece according to the present invention, optionally in combination with a conduit, lies within the scope of the present invention as defined in the appended claims.