Patent Description:
In many applications, the rapidity of the formation of a sufficiently secure sealing is an important factor affecting the effectiveness and productivity of the plumbing work. Shrinkage performance of the pipe materials typically depend on the ambient temperature: the formation of the sealed connection may become undesirably slow in cold conditions. In this sense, the design and way of operation of the tool used for expanding the pipe end, and the design of the connecting part of the pipe fitting, may be key factors for the feasibility of the cold expansion fittings especially in cold conditions.

Techniques related to various pipe connections are disclosed e.g. in <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, and <CIT>. For example, <CIT> discloses a coupling element with a shoulder at one end and a series of annular radially projecting barbs on its outer diameter.

In first aspect, a pipe fitting is implemented according to claim <NUM> for forming a cold expansion pipe connection, the pipe fitting comprising a tubular connecting part extending substantially in an axial direction DA and a shoulder extending radially outwards from one end of the connecting part; the tubular connecting part being configured to be inserted into a pipe end section of a pipe expanded by an expanding tool head comprising a plurality of radially movable outer spreading surfaces, the outer spreading surfaces comprising a first circumferential groove crossing each of the outer spreading surfaces and leaving, during expansion of a pipe end section, a first circumferential intact sealing region on the inner surface of the pipe end section at a first distance from the end of the pipe; whereby the tubular connecting part comprises a first radially outwards extending circumferential sealing barb positioned for engaging, when in use, with the circumferential intact sealing region during shrinkage of the pipe end section for forming a sealing between the pipe fitting and the pipe.

The sealing barb has a wedge-shape longitudinal section in the axial direction with a first facet with a first slope on the side of the free end of the tubular connecting part, and a second facet with a second slope steeper than the first slope on the side of the shoulder, the first and the second facets being connected via a tip. The tip has a radius of curvature in the range of <NUM>,<NUM> to <NUM>,<NUM> (<NUM> to <NUM> inches).

The tubular connecting part has a wall thickness which is substantially constant outside the sealing barb.

In an embodiment, the radially movable outer spreading surfaces comprises a second circumferential groove crossing each of the outer spreading surfaces and leaving, during expansion of a pipe end section, a second circumferential intact sealing region on the inner surface of the pipe end section at a second distance, larger than the first distance, from the end of the pipe; whereby the tubular connecting part comprises a second radially outwards extending circumferential sealing barb positioned for engaging, when in use, with the second circumferential intact sealing region during shrinkage of the pipe end section for forming a sealing between the pipe fitting and the pipe.

In an embodiment, one of the first and the second sealing barbs lies at the free end of the tubular connecting part lying opposite to the shoulder.

In an embodiment, the first slope forms, or the first facet lies at, an angle of <NUM> to <NUM> degrees, for example, an angle of <NUM> to <NUM> degrees, with respect to the axial direction DA of the tubular connecting part.

In an embodiment, the second slope forms, or the second facet lies at, an angle of <NUM> to <NUM> degrees, for example, an angle of <NUM> to <NUM> degrees, with respect to the axial direction DA of the tubular connecting part.

In an embodiment, the radially movable outer spreading surfaces comprises an additional circumferential groove crossing each of the outer spreading surfaces and leaving, during expansion of a pipe end section, a circumferential intact retaining region on the inner surface of the pipe end section preferably between the end of the pipe and the first circumferential intact sealing region; whereby the tubular connecting part comprises a radially outwards extending circumferential retaining barb positioned for engaging, when in use, with the inner surface of the pipe end section behind the circumferential intact retaining region so as to prevent the pipe fitting from escaping out of the pipe during and/or after shrinkage of the pipe end section.

In an embodiment, the tubular connecting part has a chamfer enlarging the inner diameter of the tubular connecting part towards the free end thereof lying opposite to the shoulder.

In an embodiment, the pipe fitting is configured for forming a cold expansion pipe connection with a pipe having a pipe inner diameter outside the pipe end section, wherein the tubular connecting part has a connecting part inner diameter outside the possible chamfer that is substantially equal to or larger than the pipe inner diameter.

In another aspect, a pipe connection, which may be a cold expansion pipe connection, may be implemented which comprises: a pipe fitting in accordance with any of those of the first aspect discussed above; and a pipe; the tubular connecting part of the pipe fitting being inserted into a pipe end section of the pipe having a first circumferential intact sealing region on the inner surface of the pipe end section; the first radially outwards extending circumferential sealing barb of the tubular connecting part being engaged with the first circumferential intact sealing region to form a sealing between the pipe fitting and the pipe.

In an embodiment, the pipe has a pipe inner diameter outside the pipe end section, and the tubular connecting part has a connecting part inner diameter outside the possible chamfer that is substantially equal to or larger than the pipe inner diameter.

In yet another aspect, a cold expansion pipe connection system may be implemented which comprises: a pipe fitting in accordance with any of those of the first aspect discussed above; and a pipe to be connected to the pipe fitting at a pipe end section thereof.

In one embodiment, the pipe has a pipe inner diameter outside the pipe end section, and the tubular connecting part has a connecting part inner diameter outside the possible chamfer that is substantially equal to or larger than the pipe inner diameter.

In yet another aspect, a cold expansion pipe connection equipment may be implemented which comprises: an expanding tool head for expanding a pipe end section of a pipe, the expanding tool head comprising a plurality of radially movable outer spreading surfaces, the outer spreading surfaces comprising a first circumferential groove crossing each of the outer spreading surfaces and leaving, during expansion of a pipe end section, a first circumferential intact sealing region on the inner surface of the pipe end section; and a pipe fitting in accordance with any of those of the first aspect discussed above.

In an embodiment, the expanding tool head is configured to expand a pipe end section of a pipe having a pipe inner diameter outside the pipe end section, and the tubular connecting part has a connecting part inner diameter outside the possible chamfer that is substantially equal to or larger than the pipe inner diameter.

In yet another aspect, a cold expansion pipe connection method may be implemented which comprises: expanding a pipe end section of a pipe by an expanding tool head comprising a plurality of radially movable outer spreading surfaces, the outer spreading surfaces comprising a first circumferential groove crossing each of the outer spreading surfaces and leaving, during expansion of a pipe end section, a first circumferential intact sealing region on the inner surface of the pipe end section; inserting a pipe fitting in accordance with the first aspect above into the expanded pipe end section, the first radially outwards extending circumferential sealing barb being positioned for engaging, when in use, with the circumferential intact sealing region during shrinkage of the pipe end section; and letting the expanded pipe end section shrink to form a sealing between the pipe fitting and the pipe.

In an embodiment, the pipe has a pipe inner diameter outside the pipe end section, and the tubular connecting part has, outside a possible chamfer on its inner surface enlarging the inner diameter of the tubular connecting part towards the free end thereof lying opposite to the shoulder, a connecting part inner diameter that is substantially equal to or larger than the pipe inner diameter.

The drawings of <FIG> are schematic and not necessarily to scale.

The detailed description provided below in connection with the appended drawings is intended as a description of a number of embodiments and is not intended to represent the only forms in which the embodiments may be constructed, implemented, or utilized.

The pipe fitting <NUM> of <FIG> may be used to form a cold expansion pipe connection. "Expansion" refers basically to the pipe connecting techniques which are based on mechanically expanding a pipe end section, followed by letting the expanded pipe end section shrinkage towards its original dimensions after a pipe fitting having been inserted into the expanded pipe end section. In "cold expansion" techniques, such expanding can be carried out purely mechanically, without heating the pipe end section. Also the shrinkage may take place without any activation by heat, thus automatically on the basis of the so called memory properties of the pipe material. Thus, a cold expansion pipe connection may be formed completely without applying external heat to the pipe end section to be heated.

A "pipe" refers basically to any tubing, thus a tubular structure with an internal flow channel for a fluid such as water. The flow channel may have substantially circular cross section.

A "pipe end section" refers to a section of a pipe extending from an end of the pipe to a predetermined distance therefrom. A pipe end section may be the section to be expanded when forming a cold expansion pipe connection.

A pipe to be used in forming a cold expansion pipe connection may be formed of any material, such as cross linked polyethylene PEX and its different variants, having appropriate memory properties for providing sufficient compressive force on the pipe fitting to ensure secure sealing. A reinforcing or clamping ring, also formed of a material such as cross-linked polyethylene having sufficient memory properties, may be used as positioned over the pipe end section during the expansion and shrinkage thereof. Such ring may further strengthen and secure the pipe connection.

The pipe fitting of <FIG> comprises a tubular connecting part <NUM>. The connecting part has a first end <NUM> at which a shoulder <NUM> extends outwards from the connecting part, and a second or free end <NUM> lying opposite to the shoulder.

The connecting part <NUM> extends substantially in an axial direction DA. The axial direction refers to the longitudinal direction of the connecting part, i.e. the direction in which the tubular connecting part has a length. Basically, said direction may also refer to the direction of a central axis of a tubular connecting part. The shoulder <NUM> extending "outwards" extends in a radial direction, i.e. perpendicularly to said axial direction DA.

The pipe fitting <NUM> of <FIG> is configured to be used in connection with a pipe end section which has been expanded by a specific type of expanding tool head. Such expanding tool head may be in accordance with that illustrated in <FIG>, and also basically in accordance with the expanding tool head illustrated in <FIG>.

Drawing A of <FIG> shows the pipe fitting <NUM> with its tubular connecting part <NUM> inserted into such expanded pipe end section <NUM> of a pipe <NUM>. Drawing B illustrates the situation after the initially expanded pipe end section has shrunk so that it is pressed against the tubular connecting part. The situation of drawing B of <FIG> showing the pipe end section shrunk so as to be pressed against the tubular connecting part may be considered as an illustration of a cold expansion pipe connection. It is possible that after the situation illustrated in drawing B, the pipe end section is still shrunk further. Then, it may become more conformal with the outer surface of the tubular connecting part.

An "expanding tool head" refers to a mechanical assembly which may be used as a releasable part of, or be integrated in, an expanding tool to expand pipe end sections. The expanding tool head then serves as the member of the tool assembly which actually contacts the pipe end section inner surface during the expanding operation.

The expanding tool head <NUM> of <FIG> comprises a plurality of spreading elements <NUM> which are radially movable in relation to a center longitudinal axis x of the tool head.

The spreading elements <NUM> have a starting position I illustrated in drawing A of <FIG>, at which position the spreading elements lie close to said axis x and adjacent to each other. With the spreading elements in this starting position, the expanding tool head may be inserted into a pipe end section to be expanded.

The spreading elements <NUM> have also an outwardly extended expansion position II illustrated in drawing B of <FIG>, at which position the spreading elements are radially distanced from said axis x to expand the pipe end section.

The expanding tool head may be actuated, i.e. the spreading elements may be transferred between the starting position and the expansion position by any appropriate means. For example, the spreading elements may have beveled inner surfaces, and the expander tool may have a piston with a tapered end configured to engage with and slide along those beveled surfaces. Then, the radial movement of the spreading elements may be effected by axial movement of the piston.

Each of the spreading elements has an outer spreading surface <NUM>. In the example of <FIG>, each outer spreading surface is an nth part of a substantially cylindrical surface, wherein n is the number of the spreading elements <NUM>. When in use, during expansion of a pipe end section, the outer spreading surfaces may be pressed against the inner surface of the pipe end section.

As can be seen in <FIG>, with the spreading elements <NUM> in their outwardly extended expansion position, the outer spreading surfaces are separated from each other by lateral gaps <NUM>.

Due to said lateral gaps, the expansion of the pipe end section is effected by pressing the inner surface of the expanded pipe end section at discrete regions along the circumference of the inner surface only. Therefore, the expanded pipe end section may have an alternating inner radius or diameter. This is illustrated in <FIG> as the cross section A of the pipe end section <NUM>.

The outer spreading surfaces <NUM> comprise a first circumferential groove <NUM> which extends circumferentially so that it crosses each outer spreading surface in the circumferential direction. During expansion, there is no contact between the expanding tool head <NUM> and the inner surface <NUM> of the pipe end section at the location of the first circumferential groove. Therefore, this groove leaves a first circumferential intact, non-contacted and therefore undamaged sealing region <NUM> on the inner surface of the pipe end section. At the location of this sealing region, the expanded pipe end section may advantageously have a constant inner radius or diameter. This is illustrated in <FIG> as the cross section B.

<FIG> thus shows two cross sections of the expanded pipe end section <NUM>. Cross section A represents the situation at the location in the axial direction of the pipe outside any circumferential groove. Cross section B represents the situation at the location of the first circumferential groove of the expanding tool head.

In the cross-section A of <FIG>, the inner radius or diameter of the connecting part changes along the circumference of the connecting part. Those regions <NUM> of the inner surface <NUM> of the pipe end section where the outer spreading surfaces pressed the inner surface of the pipe end section have been forced farther from the center longitudinal axis (x) than the regions <NUM> of the inner surface <NUM> of the pipe end section formed at the locations of the lateral gaps <NUM> between the adjacent outer spreading surfaces <NUM> of the expanding tool head.

Such non-uniform radius or diameter, meaning a non-circular circumference of the inner surface, make different regions of the inner surface circumference engage with the connecting part <NUM> of the pipe fitting <NUM> at different times during the shrinkage of the pipe end section <NUM>. Those non-contacted regions <NUM> resulted from the lateral gaps reach the outer surface of the connecting part <NUM> first. After this engaging, the shrinkage may slow down, and it may therefore take a long time before the inner surface <NUM> of the pipe end section <NUM> is pressed on the connecting part throughout its circumference.

In the cross-section B, instead, the inner radius or diameter of the connecting part is substantially constant and the first circumferential sealing region is thus substantially circular.

In addition to the outer spreading surface, each spreading element <NUM> of the expanding tool head <NUM> of <FIG> has further a radial stop face <NUM>.

The first circumferential groove <NUM> is located so that when using the expanding tool <NUM> at its intended way of use, the first circumferential intact sealing region <NUM> is formed at a first distance D<NUM> from the end <NUM> of the pipe. Said intended way of use may comprise, for example, positioning the end <NUM> of the pipe or, possible end of a clamping or reinforcing ring positioned on the pipe end section and extending beyond the end of the pipe, against the radial stop faces <NUM> of the spreading elements <NUM> of the expanding tool head. In the example of <FIG>, such extension beyond the end <NUM> of the pipe <NUM> is defined by the thickness of the stop edge <NUM> of the clamping or reinforcing ring <NUM>. Thus, the first circumferential groove <NUM> may lie at the first distance, or at a distance of the first distance D<NUM> plus the possible extension of an end of a clamping ring beyond the end of the pipe, from the radial stop faces <NUM> of the spreading elements <NUM> of the expanding tool head.

In the example of <FIG>, a stop face <NUM> of is formed in each of the spreading elements. In other embodiments, a stop face may be arranged in an expanding tool head separately from the radially movable spreading surfaces.

Referring back to <FIG>, the connecting part <NUM> of the pipe fitting <NUM> comprises a first radially outwards extending circumferential sealing barb <NUM>'.

A "barb" refers to a rib or ridge structure. A sealing barb has, for ensuring reliable sealing, preferably substantially constant height in the radial direction.

The first radially outwards extending circumferential sealing barb <NUM>' is advantageously positioned so that when using the expanding tool at its intended way of use, this first sealing barb engages with the first circumferential intact sealing region <NUM> during shrinkage of the pipe end section <NUM>. Said intended way of use may comprise, for example, inserting the connecting part <NUM> into the pipe end section <NUM> so far that the end <NUM> of the pipe or, end of a possible clamping or reinforcing ring positioned on the pipe end section and extending beyond the end of the pipe, is set against the radial stop face <NUM> of the shoulder <NUM> of the pipe fitting <NUM>. Thus the first radially outwards extending circumferential sealing barb <NUM>' may lie at the first distance D<NUM>, or at a distance of the first distance plus the possible extension of an end of a clamping ring beyond the end of the pipe, from the radial stop face <NUM> of the shoulder <NUM> of the pipe fitting <NUM>.

Due to the substantially circular first circumferential intact sealing region <NUM>, the sealing barb <NUM>' may contact the pipe inner surface <NUM> substantially at the same time throughout the circumference thereof. This may enable a rapid formation of a sealed connection already before the pipe end section <NUM> have been shrunk so as to make the entire inner surface <NUM> thereof being pressed against the connecting part of the pipe fitting. This may facilitate forming cold expansion connections, in particular, in low assembling temperatures.

In the example of <FIG>, there is also a second circumferential groove <NUM> extending circumferentially so as crossing each of the outer spreading surfaces <NUM> and leaving, during expansion of a pipe end section <NUM>, a second circumferential intact sealing region <NUM> on the inner surface <NUM> of the pipe end section. The second circumferential groove is located so that when using the expanding tool at its intended way of use, the second circumferential intact sealing region is formed at a second distance D<NUM> from the end of the pipe. Thus, the second circumferential groove may lie at the second distance, or at a distance of the first distance plus the possible extension of an end of a clamping ring beyond the end <NUM> of the pipe <NUM>, from the radial stop faces <NUM> of the spreading surfaces <NUM> the expanding tool head <NUM>.

The second distance D<NUM> is larger than the first distance. So, the second circumferential groove lies farther from the stop faces of the spreading surfaces <NUM> than the first circumferential groove.

Referring again back to <FIG>, the connecting part <NUM> of the fitting comprises also a second radially outwards extending circumferential sealing barb <NUM>". This second sealing barb is advantageously positioned so that when using the expanding tool at its intended way of use, this sealing barb engages with the second circumferential intact sealing region <NUM> during shrinkage of the pipe end section <NUM>. Thus, the second radially outwards extending circumferential sealing barb may lie at the second distance D<NUM>, or at a distance of the second distance plus the possible extension of an end of a clamping ring beyond the end <NUM> of the pipe, from the radial stop face <NUM> of the shoulder <NUM> of the pipe fitting <NUM>.

The second radially outwards extending circumferential sealing barb <NUM>" may operate similarly to the first radially outwards extending circumferential sealing barb <NUM>'. Thereby, it may further secure rapid formation of a sealed pipe connection.

In the example of <FIG>, the second sealing barb <NUM>" lies at the free end <NUM> of the tubular connecting part <NUM>. This positioning may advantageously serve as a guiding member facilitating insertion of the connecting part of the pipe fitting into an expanded pipe end section. Further, it may serve as a stabilizer to reduce side to side rocking or motion during the shrinkage of the pipe end section.

In other embodiments, a second radially outwards extending circumferential sealing barb may lie elsewhere, between a first radially outwards extending circumferential sealing barb and the free end of the tubular connecting part.

In the example of <FIG>, each of the sealing barbs <NUM>', <NUM>" has, in a longitudinal section plane along the center longitudinal axis of the pipe fitting, a wedge-shape cross section. The wedge shape has a first facet <NUM>' with a first slope on the side of the free end <NUM> of the tubular connecting part. A second facet <NUM>" with a second slope which is steeper than the first slope lies on the side of the shoulder <NUM> of the pipe fitting. Said basic configuration of the barbs may allow inserting of the connecting part properly into the pipe end section.

The facets are connected via a tip <NUM> at the top of the wedge shape. The tip is substantially or nearly sharp. It has a radius of curvature r in the range of <NUM>,<NUM> to <NUM>,<NUM> (<NUM> to <NUM> inches). Appropriate sharpness, i.e. suitable radius of curvature, of the tip may facilitate formation of a sealed connection between the sealing barb and the sealing region of the inner surface of the pipe end section. Thereby, a rapid formation of a sealed pipe connection may be achieved.

In the example of <FIG>, to ensure proper performance of the fitting, the first facet lies at an angle α of about <NUM> degrees, and the second slope lies at an angle β of about <NUM> degrees, with respect to the axial direction DA. Said angles are defined as the smaller angles formed between the slopes of the facets and the axial direction. In other embodiments, the first facet may lie at an angle of <NUM> to <NUM> degrees, for example, an angle of <NUM> to <NUM> degrees, and/or the second facet may lie at an angle of <NUM> to <NUM> degrees, for example, an angle of <NUM> to <NUM> degrees, with respect to the axial direction DA of the tubular connecting part.

The expanding tool head <NUM> of <FIG> differs from that of <FIG> in that the radially movable outer spreading surfaces <NUM> of the expanding tool head <NUM> comprise further an additional circumferential groove <NUM> which crosses each of the outer spreading surfaces. This additional groove lies substantially at the end of the outer spreading surfaces <NUM> where the stop faces <NUM> of the spreading elements <NUM> lie. This additional groove leaves, during expansion of a pipe end section, a circumferential intact retaining region <NUM> on the inner surface <NUM> of the pipe end section <NUM> substantially at the end of the pipe as illustrated in <FIG>. In other embodiments, an additional groove may be positioned to leave such retaining region at some other location, preferably between the end of the pipe and the first circumferential intact sealing region.

In the example of <FIG>, the expanding tool head <NUM> of <FIG> is connected to an expander tool <NUM>. The expander tool comprises a radially movable piston <NUM>. The piston has a tapered end configured to engage with beveled inner surfaces <NUM> of the spreading elements <NUM> to control radial movement thereof by axial movement of the piston.

Referring again back to <FIG>, the connecting part <NUM> of the pipe fitting <NUM> comprises correspondingly a radially outwards extending circumferential retaining barb <NUM>‴. This retaining barb is advantageously positioned so that when using the expanding tool head at its intended way of use, this retaining barb engages, during shrinkage of the pipe end section, the inner surface <NUM> of the pipe end section <NUM> behind the circumferential intact retaining region <NUM>. In the example of <FIG>, said positioning is achieved by having the tip of the cross section of the retaining ring lying at a distance from the stop face of the shoulder which is equal to the thickness of the stop edge of the clamping ring plus the width of the circumferential intact retaining region. In other embodiments, corresponding positioning of a retaining barb behind a circumferential intact retaining region may be achieved differently, depending on the position and width of the retaining region and the presence of a clamping ring on the pipe end section extending beyond the end of the pipe.

The retaining barb <NUM>‴ positioned behind the circumferential intact retaining region <NUM> may retain the connecting part <NUM> within the pipe end section, thus prevent the pipe fitting from escaping out of the pipe end section, during and/or after the shrinkage of the pipe end section. Thereby, it may facilitate ensuring that the sealing barbs are positioned as properly aligned with the intact sealing regions of the inner surface of the pipe end section.

In the example of <FIG>, the retaining barb <NUM>‴ has the same wedge-shaped cross section as the sealing barbs. In other embodiments, retaining barbs may be used with any appropriate longitudinal sectional shape suitable for providing said retaining function.

In the example of <FIG>, there is a chamfer <NUM> on the inner surface of the tubular connecting part at the free end of the connecting part. The chamfer enlarges the inner diameter of the tubular connecting part towards the free end thereof lying opposite to the shoulder. The chamfer may advantageously reduce disturbances to the flow of a fluid between the pipe and the pipe fitting connected to it. In other embodiments, pipe fittings may be implemented without any chamfer.

Differently from the example of <FIG>, other embodiments may be implemented with different number and/or of sealing and/or retaining barbs in the connecting part of a pipe fitting. For example, there may be only one, thus "first" sealing barb. Alternatively, connecting parts may have more than two retaining barbs. Preferably, at least one sealing barb lies in a middle section of the tubular connecting part between the ends thereof. Also the number of retaining barbs may vary; connecting pieces may be implemented without any retaining barb, or with two or more retaining barbs. In such other embodiments, one or more of the possibly several sealing barbs may be in accordance with any of the tip and facet/slope configurations discussed above.

Such pipe fittings differing form that of <FIG> may be configured to be inserted into pipe end sections expanded by expanding tool heads having a circumferential groove configuration correspondingly differing from that of <FIG>.

In the example of <FIG>, outside the first and the second sealing barb and the retaining barb and the chamfer, the wall thickness of tX the tubular connecting part is substantially constant. Also in other embodiments, irrespective of the number and positioning of various sealing and/or retaining barbs, the wall thickness may be substantially constant outside the sealing barb(s), possible retaining barb (s), and possible chamfer.

Said substantially constant wall thickness may enable maximizing the volume of the flow channel formed within the tubular connecting part, as discussed further below.

Pipe fittings may be provided for different pipe sizes so that there is a specific pipe fitting size with specific outer diameter of the connecting part for each pipe inner diameter. Thereby, cold expansion pipe connection systems may be implemented for different pipe sizes, each such system comprising a pipe fitting and a pipe to be connected to the pipe fitting at a pipe end section thereof. An example of such system is illustrated in <FIG>.

On the other hand, expanding tool heads may be provided for different pipe sizes so that there is a specific expanding tool head size with specific outer diameter of cylinder formed by the outer spreading surfaces for each pipe inner diameter. Thereby, cold expansion pipe connection equipment may be implemented for each pipe sizes, each such system comprising an expanding tool head as discussed above with reference to <FIG> or <FIG>, and a pipe fitting.

In the example of <FIG>, the tubular connecting part is configured so that the connecting part inner diameter IDF outside possible chamfer is substantially equal to the pipe inner diameter IDP. In other embodiments, it may be even slightly larger. Equal or larger inner diameter may advantageously contribute to reducing disturbances to the flow of a fluid between the pipe and the pipe fitting connected to it.

Pipe inner diameter refers to the inner diameter of the pipe outside the pipe end section thereof.

Pipe fittings and/or expanding tool heads may be provided, for example, for pipe inner diameters in the range of <NUM> to <NUM> or <NUM> to <NUM> inches.

Any of the pipe fittings discussed above may also be used in connection with an expanded pipe end section expanded by using an expanding tool head different from those discussed above with reference to <FIG> and <FIG>. This is the case especially as far as after the expansion, the expanded pipe end section comprises on its inner surface a first possibly intact circumferential sealing region and possibly also a second possibly intact circumferential sealing region and/or a possibly intact circumferential retaining region corresponding to the first sealing barb and possible second sealing barb and/or retaining barb of the pipe end section, respectively.

In the method <NUM> of <FIG>, any of the expanding tool heads and corresponding pipe fittings and pipes discussed above may be used.

In the method, a pipe end section of a pipe, possibly together with a clamping or retaining ring positioned over the pipe end section, is expanded by an expanding tool head in step <NUM>. Then, the tubular connecting part of a pipe fitting is inserted into the expanded pipe end section in step <NUM>. The expanded pipe end section is then let shrink in step <NUM> so that it is pressed against the tubular connecting part of the pipe fitting, whereby a sealed pipe connection is formed between the pipe fitting and the pipe.

Steps <NUM> and <NUM> may be carried out at least partially simultaneously so that the shrinkage of the pipe end section may already have been initiated when the connecting part of the pipe fitting is inserted into the initially expanded pipe section.

Claim 1:
A pipe fitting (<NUM>) for forming a cold expansion pipe connection, comprising a tubular connecting part (<NUM>) extending substantially in an axial direction DA and a shoulder (<NUM>) extending radially outwards from one end (<NUM>) of the tubular connecting part; the tubular connecting part being configured to be inserted into a pipe end section (<NUM>) of a pipe (<NUM>) expanded by an expanding tool head (<NUM>) comprising a plurality of radially movable outer spreading surfaces (<NUM>), the outer spreading surfaces comprising a first circumferential groove (<NUM>) crossing each of the outer spreading surfaces and leaving, during expansion of a pipe end section (<NUM>), a first circumferential intact sealing region (<NUM>) on the inner surface (<NUM>) of the pipe end section (<NUM>) at a first distance (D<NUM>) from the end (<NUM>) of the pipe (<NUM>); the tubular connecting part comprising a first radially outwards extending circumferential sealing barb (<NUM>') positioned for engaging, when in use, with the first circumferential intact sealing region during shrinkage of the pipe end section for forming a sealing between the pipe fitting and the pipe, wherein the sealing barb (<NUM>') has a wedge-shape longitudinal section in the axial direction with a first facet (<NUM>') with a first slope on the side of the free end (<NUM>) of the tubular connecting part (<NUM>), and a second facet (<NUM>") with a second slope steeper than the first slope on the side of the shoulder (<NUM>), the first and the second facet being connected via a tip (<NUM>), characterized in that the tip (<NUM>) has a radius of curvature r in the range of <NUM>,<NUM> to <NUM>,<NUM> (<NUM> to <NUM> inches), and wherein the tubular connecting part (<NUM>) has a wall thickness (tW) which is substantially constant outside the sealing barb.