Patent Description:
The present invention relates to pipe connection, in particular, to the connection of tubes, such as plastic pipes or pipes made of plastic and metal, for the flow of fluids. More specifically, the present description relates to a fitting assembly for pipe connection.

Fittings for connecting pipes such as plastic pipes especially of the multilayer type used, for example, in plumbing installations consisting of two polyethylene layers between which a layer of metal, plastic, etc. is arranged, joined together by an adhesive layer are widely known.

Joining of said type of conduits is usually carried out by means of a fitting that comprises a sleeve with a bushing intended to be pressed radially onto the conduit, tube, or pipe using a suitable jaw. In such known fittings, sealing elements, such as O-rings, fitted around the sleeve, are used to prevent fluid leakage.

Such pipe connection technique by pressing a bushing is known as press fitting. In order to carry out joining, suitable radial pressure is applied through a jaw on the bushing of the fitting causing the bushing to deform. The deformation of the bushing results in a deformation of the pipe, with a portion of the pipe material being inserted into the sleeve, applying pressure on the sealing elements. As a result, by virtue of the aforementioned sealing elements, a mechanically tight pipe connection is obtained in a rapid manner as compared to other types of pipe connections such as, for example, welded connections.

As described above, pipe fittings known in the art make use of sealing elements, such as O-rings, which are provided around the sleeve, inserted in one or more annular grooves formed therein, as disclosed, for example, in <CIT> and <CIT>.

The problem with these fittings is that, when the pipe is inserted into the fitting, the O-rings may become damaged and even at least partially removed out of the annular groove of the sleeve where they are received. This may result in leaks that may not be detected in an installation pressure test, which is undesirable.

Several approaches to the above problem have been proposed in the art, such as the one disclosed in <CIT> where a configuration is provided in which the O-ring does not protrude over the flank of the sleeve annular groove. However, provision of O-rings is still conducive to the occurrence of leakage at the pipe connection when the fitting is assembled.

<CIT> discloses a fitting assembly for connecting tubes that comprises a sleeve with at least one circumferential groove configured to house a sealing gasket. Flanks of different diameter adjacent the circumferential groove are defined in the sleeve. The sleeve is adapted to receive a bushing intended to be radially pressed to compress one end of a tube against the sleeve.

Therefore, there still remains the need for a fitting for pipe connection, in particular a fitting for joining plastic and metal multilayer pipes, having a simple configuration and which ensures tightness of the assembly once the joint has been made.

A pipe connection fitting assembly is described hereinbelow, which has been found to effectively overcome the above-mentioned problem and that further provides a number of additional advantages, in particular, for joining multilayer pipes (e.g., consisting only of plastic layers, or consisting of plastic layers and metal layers) and/or monolayer pipes (e.g., consisting of cross-linked polyethylene) for conducting domestic hot and cold water, heating applications, and many others, as will be shown hereinafter.

In the present disclosure, the terms tube and pipe will be used interchangeably to designate conduits or parts of conduits conducting fluids that can be connected to each other.

The pipe connection fitting assembly disclosed herein comprises a sleeve having at least one outer profile of a given length. Said at least one sleeve outer profile extends from a first end of the sleeve to a second end or free end of the sleeve, opposite said first end. As used herein, the second end or free end of the sleeve refers to an end or terminal portion of the sleeve which, when the sleeve is inserted into the bushing when assembling the fitting, is the one which first passes through the inside of the bushing.

The sleeve outer profile includes an outer surface where at least two toothed areas are formed. More specifically, the sleeve outer profile includes at least one first toothed area having at least two teeth, such as, for example, three or more teeth, and at least one second toothed area having at least one tooth, such as, for example, two or more teeth.

The sleeve outer profile further includes a curved area. In particular, the curved area is concave, that is, it has a curvature towards the inside of the assembly, towards the longitudinal axis of the sleeve, i.e., it is a depth wise recessed area. The height of such curved area is lower than the height of the teeth of the first and second toothed area. Said curved area is formed between the first toothed area and the second toothed area in a substantially central position of the sleeve outer profile. The two toothed areas of the present fitting assembly are thus spaced away by said curved area. The curved area may have protrusions formed at the ends thereof. The height of said protrusions in the curved area may be lower than or equal to the height of the teeth.

The present fitting assembly for pipe connection further comprises a bushing. The bushing is intended to be mounted around said sleeve and on a coupling part intended to hold the bushing on the sleeve. The above-mentioned first end of the sleeve outer profile is located closer to said coupling part than the second end or free end of the sleeve outer profile, while the above mentioned second end or free end of the sleeve outer profile is located furthest from the coupling part than the first end of the sleeve outer profile.

The sleeve outer profile, as described above, thus defines areas where the positioning of the bushing and coupling thereof by means of the bushing coupling part is to be performed. In the mounting position, a gap is defined between the bushing and the sleeve profile, suitable for a tube to be inserted there through.

As described above, the sleeve has one or more outer profiles, which may be curved or straight. If the sleeve is made up of several outer profiles, the outer profiles may be the same or different from each other, and they may be arranged in different ways. For example, the outer profiles may be aligned with each other, they may be arranged at an angle to each other, such as <NUM>°, forming an elbow shape, a T-shape, or other angles. The sleeve outer profile(s) may include threaded areas.

The teeth of the first toothed area and the teeth of the second toothed area of the sleeve outer profile have rounded ridges. The ridges of the teeth of the first toothed area have a radius of curvature of <NUM>. It is preferred that the ridges of the teeth in the second toothed area have a radius of curvature of <NUM>.

Each tooth formed in the toothed areas has two flanks. One flank, which is located furthest from the free end of the sleeve, defines an angle with the outer surface of the sleeve outer profile which has a value other than <NUM>°. That is, a flank is formed in each tooth furthest from the free end of the sleeve having an inclination with respect to the outer surface of the sleeve outer profile, i.e., it is not perpendicular. Examples of values of such angle between the flank furthest from the free end of the sleeve and the outer surface of the sleeve outer profile are between <NUM>° and <NUM>°, more specifically a value between <NUM>° and <NUM>°. The other flank defining the tooth, i.e., the one located closer to the free end of the sleeve, defines an angle with the outer surface of the sleeve outer profile which also has a value other than <NUM>°.

In operation, that is, in an assembly position, the tube is arranged sandwiched between the bushing and the sleeve, so that the tube is in close contact with the sleeve and the bushing, as the bushing is pressed against the sleeve through a suitable jaw, by applying a proper radial pressure thereon.

Between the flanks of each tooth, i.e., their lateral surfaces, an angle may be defined which preferably has a value other than <NUM>°. In particular, it is preferred that the angle defined between the flanks in each tooth has a value between <NUM>° and <NUM>°, specifically a value between <NUM>° and <NUM>°.

The curved area formed between the two toothed areas is positioned so that the center thereof is at a distance from a free end of the sleeve. Said distance is preferably <NUM>-<NUM>% of the length of the sleeve outer profile.

The first toothed area may extend along a first length and the second toothed area may extend along a second length preferably shorter than or equal to the first length. That is, the first toothed area has an extension greater than or equal to the extension of the second toothed area.

Between contiguous tooth ridges of the first toothed area a distance is defined which preferably corresponds to <NUM>-<NUM>% of the above mentioned first length. Between contiguous tooth ridges of the second toothed area a distance is defined which preferably is equal to or shorter than said distance between contiguous tooth ridges of the first toothed area.

A support area may be provided on the sleeve outer profile. Said support area is configured to receive the aforementioned coupling part for holding the bushing and positioning a jaw to properly press the bushing onto the pipe against the sleeve.

With a fitting assembly having the specific geometry of the sleeve outer profile as described above, consisting of two toothed areas separated by a curved area with protrusions, it has been found that an advantageous optimization of the contact pressure between the pipe and the sleeve profile, with values of the order of <NUM> to <NUM> MPa, is obtained, which makes it possible to hold the pipe to the fitting assembly, once the latter has been pressed tightly together without the need for either O-rings or any other sealing element. The design of toothed areas with rounded ridged teeth provides excellent contact pressure performance as compared to conventional tooth designs with flat or ridged areas. The described fitting assembly makes it possible to avoid the use of sealing elements and the provision of radial contact pressure between the pipe material, usually a multilayer pipe, the sleeve, and the bushing such that no fluid leakage occurs.

As stated above, the described fitting assembly advantageously eliminates the need for sealing elements, such as ethylene propylene diene monomer (EPDM) O-rings, nitrile butadiene rubber (NBR), etc., which are employed in most commercially available fittings. The lack of sealing elements results in simplifying assembly, reducing costs, and maintaining effectiveness. The described fitting assembly also reduces the risk of seal winding up during assembly, thus advantageously avoiding subsequent leaks.

This results in a very efficient pipe fitting assembly by press fitting, which overcomes currently existing problems in prior art fittings, avoiding the use of sealing elements, providing high performance in joining of multilayer plastic-metal pipes, ensuring tightness throughout the service life of the fitting and the installation.

The described fitting assembly is compact, light, safe, and cost effective due to the simplification of parts, in particular the absence of sealing elements. In addition, the fitting assembly allows LBP (Leak Before Press) function to be carried out, which makes it possible to easily detect leaks due to lack of pressing when pressure testing the installation, even at very low fluid pressures, of the order of <NUM>-<NUM> bar. This advantageously makes it possible to easily identify unpressed fittings before starting up the installation.

The described fitting assembly further allows a great ease of pressing through manual tools, such as radial pressing machines with conventional jaws.

A further important advantage from the particular specific geometry of the above described sleeve outer profile is that the assembly is watertight, especially when used for joining multilayer pipes such as, for example, pipes consisting of two layers of plastic material and one layer of aluminium. The layers of plastic material in such multilayer pipes may be made of polyethylene of raised temperature resistance (PERT) or cross-linked polyethylene (PEX), interchangeably.

Additional advantages and features of the fitting assembly for pipe connection will become apparent to those skilled in the art upon examination of the description or may be learned by practice thereof.

Particular embodiments of a fitting assembly for pipe connection will be described in the following with reference to the appended drawings, in which:.

The non-limiting examples described below correspond to a fitting assembly <NUM> for connecting conduits. The conduits to be joined may be multilayer pipes or tubes <NUM> made of plastic, or plastic and metal, for conducting of fluids in plumbing, heating, etc. The multilayer pipes <NUM> to which the present fitting assembly <NUM> is intended may be, for example, cross-linked polyethylene and metal pipes for conducting of domestic hot and cold water, as well as for heating applications.

The fitting assembly <NUM> described herein comprises a sleeve <NUM> which may be made, for example, of brass and/or polyphenylsulfone (PPSU).

The sleeve <NUM> has one or more outer profiles 110a, 110b, 110c as shown in <FIG> of the drawings. As it will be described in greater detail further below, <FIG> show examples where the sleeve <NUM> is provided with a single outer profile 110a, <FIG> show examples where the sleeve <NUM> is provided with two outer profiles 110a, 110b, and <FIG> shows one example where the sleeve <NUM> is provided with three outer profiles 110a, 110b, 110c.

Each outer profile 110a, 110b, 110c of the sleeve <NUM> has a given length L, shown in <FIG>. Each outer profile 110a, 110b, 110c of the sleeve <NUM> extends from a first end <NUM> of the sleeve <NUM> to a free end <NUM> of the sleeve <NUM> opposite said first end <NUM>.

A first toothed area <NUM> and a second toothed area <NUM> are formed on the outer surface <NUM> of each outer profile 110a, 110b, 110c of the sleeve <NUM>. A central curved area <NUM> is formed between the first toothed area <NUM> and the second toothed area <NUM> of each outer profile 110a, 110b, 110c of the sleeve <NUM>. As it can be seen from <FIG> and <FIG> of the drawings, the central curved area <NUM> has a concave curvature formed towards the inside of the sleeve <NUM>.

The curved central area <NUM> has protrusions <NUM>, <NUM> formed at the ends thereof that promote the sealing of the fitting assembly <NUM>. It has been shown experimentally that, at least in one of said protrusions <NUM>, <NUM> of the curved central area <NUM>, maximum contact pressure is obtained between the sleeve <NUM> and the pipe <NUM>. The curved central area <NUM> coincides with a central area <NUM> of a jaw <NUM>, one example of which is shown in detail in <FIG> of the drawings. The jaw <NUM> is configured to radially press the bushing <NUM> against the sleeve <NUM>, with the pipe <NUM> sandwiched there between, as shown in <FIG>. During the pressing operation, material from the pipe <NUM> flows into the central curved area <NUM> and into the toothed areas <NUM>, <NUM> of the sleeve <NUM> and adheres to the protrusions <NUM>, <NUM> thereof. The curved central area <NUM> allows the material to flow better when pressed by the jaw <NUM>.

In the non-limiting example illustrated in <FIG> and <FIG> of the drawings, the first toothed area <NUM> of the outer profile 110a, 110b, 110c of the sleeve <NUM> has three teeth <NUM> and the second toothed area <NUM> of the outer profile 110a, 110b, 110c of the sleeve <NUM> has two teeth <NUM>. Other configurations are possible provided that the first toothed area <NUM> has at least two teeth <NUM> and the second toothed area <NUM> has at least one tooth <NUM>.

The height of the protrusions <NUM>, <NUM> of the aforementioned curved central area <NUM> is lower than or equal to the height of the teeth <NUM>, <NUM>.

As stated above, and as shown in <FIG> and <FIG> of the drawings, the curved central area <NUM> separating the first toothed area <NUM> and the second toothed area <NUM> is located at a substantially central part of the length L of the outer profile 110a, 110b, 110c of the sleeve <NUM>. Moreover, as also shown in the aforementioned figures, the height of said central curved area <NUM> is lower than the height of the teeth <NUM>, <NUM> of the first and second toothed area <NUM>, <NUM>. This configuration promotes an even contact pressure distribution at the mounting position, shown in <FIG>, promoting material creeping in pressing.

With continued reference to <FIG>, the fitting assembly <NUM> further comprises a bushing <NUM>. The bushing <NUM> may be made, for example, of reduced thickness AISI <NUM> stainless steel deep drawing. The bushing <NUM> is intended to be mounted around the sleeve <NUM>.

There is also provided a coupling part <NUM> intended for suitably holding the bushing <NUM> in the sleeve <NUM>. The coupling part <NUM> of the bushing <NUM> is preferably made of plastic, such as PP. Other materials are possible.

As it can be seen from <FIG>, the first end <NUM> of the outer profile 110a, 110b, 110c of the sleeve <NUM> is located closer to the coupling part <NUM> than the free end <NUM> of said outer profile 110a, 110b, 110c of the sleeve <NUM>. In turn, the free end <NUM> of the outer profile 110a, 110b, 110c of the sleeve <NUM> is located furthest from the coupling part <NUM> than the first end <NUM> of said outer profile 110a, 110b, 110c of the sleeve <NUM>.

The outer profile 110a, 110b, 110c of the sleeve <NUM>, depending on its configuration according to <FIG>, is configured for the positioning of the bushing <NUM> and the coupling of the coupling part <NUM> of said bushing <NUM>. A gap suitable for the pipe <NUM> to be inserted through said sleeve 110a, 110b, 110c, is defined, in the mounting position, between the bushing <NUM> and the outer profile 110a, 110b, 110c of the sleeve <NUM>. Thus, in operation or in an assembly position, as shown in <FIG>, the pipe <NUM> is sandwiched between the bushing <NUM> and the sleeve <NUM>. When radial pressure is applied to the bushing <NUM> through the use of the jaw <NUM>, the bushing <NUM> is deformed and the pipe <NUM> is becomes trapped between the bushing <NUM> and the sleeve <NUM>, with the pipe <NUM> being in close contact with the sleeve <NUM>.

<FIG> show several examples of the sleeve <NUM>. In particular, in the example of <FIG>, the sleeve <NUM> is formed by a single straight outer profile 110a. In the example of <FIG>, the sleeve <NUM> is formed by two aligned straight outer profiles 110a, 110b. In the example of <FIG>, the sleeve <NUM> is formed by a straight outer profile 110a and a threaded profile <NUM> aligned with said straight outer profile 110a. In the example of <FIG>, the sleeve <NUM> is formed by two straight outer profiles 110a, 110b, arranged to form an angle of <NUM>° there between defining an elbow configuration. <FIG> is a perspective view of one example of a sleeve formed by three straight profiles 110a, 110b, 110c with two of them being arranged aligned and forming an angle of <NUM>° with each other defining a T-shaped configuration.

As it can be seen from <FIG> and <FIG> of the drawings, in all the teeth <NUM>, <NUM> in both toothed areas <NUM>, <NUM>, the ridge, i.e., the outer part intended to be in contact with the outer surface of the pipe <NUM> is rounded.

In the example described and illustrated in <FIG> and <FIG>, the outer profile 110a, 110b, 110c of the sleeve <NUM> includes a support area <NUM> that is configured to receive the coupling part <NUM> for holding the bushing <NUM> and positioning the jaw <NUM> to properly press the bushing <NUM> onto the pipe <NUM> against the sleeve <NUM>.

The inventors have found that, with a fitting assembly <NUM> as described above, with a defined design meeting the parameters that are given below, an efficient and watertight radial press joint of multilayer pipes <NUM> is possible to be carried out through a suitable jaw <NUM>. When applying the jaw <NUM>, a suitable radial contact pressure is generated between the pipe <NUM> and the sleeve <NUM> such that, in operation, no fluid leakage occurs, avoiding the use of sealing elements such as O-rings.

The above mentioned parameters defining the design of the present fitting assembly <NUM> are those cited below with reference to <FIG> and, in particular, to the enlarged view of <FIG> of the drawings showing the detail of the area S of <FIG>:.

It has been found that the above described parameters applied to the fitting assembly <NUM>, in combination with a sleeve <NUM> with two distinct tooth areas <NUM>, <NUM> without sharp edges or flat portions on the tooth ridge <NUM>, <NUM>, separated by a curved central area <NUM> with protrusions <NUM>, <NUM>, allow the contact pressure distribution of the assembly <NUM> to be advantageously optimized, with values between <NUM> and <NUM> MPa, without the use of sealing elements to keep the pipe <NUM> attached to the fitting <NUM> once the radial pressing through the jaw <NUM> has been carried out, without fluid leakage.

The inventors carried out a temperature cycling test for the above described fitting assembly <NUM>. The test consisted of cycling cold water, at <NUM>, and hot water, at <NUM>, alternately every <NUM> minutes. The total number of cycles was <NUM>, with each cycle lasting <NUM>. The system pressure was maintained at <NUM> bar. This test characterized the long-term performance of the joints with the above described fitting assembly <NUM>. The installation successfully passed the test without any leakage, thus validating the above described geometry, which was considered optimal for the design of the outer profile 110a, 110b, 110c of the sleeve <NUM> of the fitting assembly <NUM> described herein.

Claim 1:
Fitting assembly (<NUM>) for connecting pipes (<NUM>), the fitting assembly (<NUM>) comprising:
- a sleeve (<NUM>) having at least one outer profile (110a, 110b, 110c) with a length (L) extending from a first end (<NUM>) of the sleeve (<NUM>) to a free end (<NUM>) of the sleeve (<NUM>), opposite said first end (<NUM>), said outer profile (110a, 110b, 110c) including an outer surface (<NUM>) where at least a first toothed area (<NUM>) is formed having at least two teeth (<NUM>), at least a second toothed area (<NUM>) having at least one tooth (<NUM>), and a curved area (<NUM>) having a height lower than the height of the teeth (<NUM>, <NUM>) of the first and second toothed areas (<NUM>, <NUM>), the curved area (<NUM>) being formed between the first toothed area (<NUM>) and the second toothed area (<NUM>), at a substantially central position of said at least one outer profile (110a, 110b, 110c) of the sleeve (<NUM>);
- a bushing (<NUM>) intended to be mounted around the sleeve (<NUM>); and
- a coupling part (<NUM>) intended to hold the bushing (<NUM>) to the sleeve (<NUM>),
characterized in that the teeth (<NUM>, <NUM>) of the first and second toothed areas (<NUM>, <NUM>) have rounded ridges, wherein an angle (β) defined between a flank of each tooth (<NUM>, <NUM>), said flank being located furthest from the free end (<NUM>) of the sleeve (<NUM>), and said outer surface (<NUM>) of the outer profile (110a, 110b, 110c) of the sleeve (<NUM>) has a value other than <NUM>°, and wherein, in operation, the sleeve (<NUM>) and the bushing (<NUM>) are arranged with the pipe (<NUM>) sandwiched therebetween, the pipe (<NUM>) being in close contact with the sleeve (<NUM>) and the bushing (<NUM>), as the bushing (<NUM>) is pressed against the sleeve (<NUM>) through a jaw (<NUM>), and the tooth ridges (<NUM>) of the first toothed area (<NUM>) have a radius of curvature (R<NUM>) of <NUM>.