Press fitting equipped with an annular inside thickness at a free outer edge part of an axially outward press-wall section.

Abstract

A press fitting comprises a socket (2) with an axially outward and inward press-wall section (PWo, Pwi) and a radially outwardly bulging annular sealing ring chamber portion (SRC). An adjacent part (AP) of the outward press-wall section alongside an outer edge part (OEP) has been widened by means of cold-deformation, and the outer edge part has been cold-deformed to locally increase it with an annular inside thickness (IT) that projects radially inwardly to smaller inner dimensions than the widening lying alongside it, wherein the outer edge part has a higher hardness than the adjacent part, such that the axially outward press-wall section is configured to, during pressing action from the non-pressed state towards the pressed state, level / smoothen out the transition between the inside thickness and the at least locally widened adjacent part for coming to lie together radially inwardly deformed against the complementary radially inwardly deformed inserted pipe end.

Description

P37288NLOO / RR Title: Press fitting equipped with an annular inside thickness at a free outer edge part of an axially outward press-wall section. FIELD OF THE INVENTION The present invention relates to press fittings of a type comprising a socket with at least one end configured for a pipe end to be inserted therein, which end has axially outward and inward substantially tube-shaped press-wall sections lying at opposing sides of a radially outwardly bulging annular sealing ring chamber portion. BACKGROUND TO THE INVENTION Over the past years a copper press fitting is successfully commercialized by applicant under the name SudoPress / ApolloPress fitting. The socket hereof starts with a cylindrical- shaped axially outward press-wall section that merges into a radially outwardly bulging sealing ring chamber portion that merges into a cylindrical-shaped axially inward presswall section. A sealing ring is provided inside the sealing ring chamber portion. This is a 'straight' press fitting of which the radially outwardly bulging sealing ring chamber portion is obtained by means of local plastic deformation of copper pipe. The wall thicknesses and dimensions of the cylindrical-shaped press-wall sections are substantially the same as the copper pipe, and are such that a to be connected pipe end of slightly smaller outer dimensions can smoothly and easily be inserted therein with a sliding fit and small circumferential play. In a non-pressed state, a pipe end can be inserted such far into the socket until it comes to abut against an inwardly projecting rim that serves as a depth stop. The pipe end then extends through both the cylindricalshaped axially outward and inward press-wall sections as well as through the sealing ring chamber portion therebetween. The sealing ring may already lie somewhat sealing against the inserted pipe end. Subsequently, the cylindricalshaped press-wall sections get plastically deformed from the non-pressed state towards a pressed state by means of a suitable press tool. During this pressing, a radially inward directed pressing action is exerted by the press tool on outer circumferential walls of the cylindrical-shaped press-wall sections at the opposing sides of the sealing ring chamber portion as well as on the sealing ring chamber portion itself. This causes the cylindrical- shaped presswall sections and the sealing ring chamber portion to radially compress while locally plastically deforming radially inward together with the inserted pipe end. Thus a reliable sealing connection is obtained between the socket and the inserted pipe end. The connection then for example can be used for feeding water through and is suitable for operating pressures of up to 16 bar. However, for some purposes higher operating pressures may occur, like with cooling fluids that are frequently used nowadays for heating, ventilation, air-conditioning and refrigeration (HVAC-R). Those operating pressures then may even arise above 48 bar. This requires special high-pressure press fittings that are well able to withstand such high operating pressures. A first embodiment of such a special high-pressure press fitting is known that is commercialized under the name '>B< MaxiPro' and can be seen in fig. 2 and 3 of W0- 2016 / 067231. This press fitting comprises a socket that here has two symmetrical ends that each start with an axially outward press-wall section that merges into a radially outwardly bulging sealing ring chamber portion that merges into an axially inward presswall section. A sealing ring is provided inside the sealing ring chamber portion. This is a 'flaring' press fitting that is manufactured such that, in the non-pressed state, the axially outward press-wall section gradually widens out towards a free outer edge part, whereas at the same time this free outer edge part of this widening is provided with an annular radially inwardly projecting gripping hook that extends along the entire inner circumference. The transition between the sealing ring chamber portion and the axially outward press- wall section is right angled and directly starts at an innermost diameter that is slightly larger than the outer diameter of a to be inserted pipe end. From there the axially outward press- wall section widens out at such an angle that the annular radially inwardly projecting hook at its free outer edge part, in the non-pressed state, lies at substantially the same innermost diameter that is slightly larger than the outer diameter of a to be inserted pipe end. In the non-pressed state, a pipe end first needs to be manoeuvered with small circumferential play along the annular radially inwardly projecting hook at the free outer edge, then passed by the right angled transition with the sealing ring chamber portion, then passed by the sealing ring and into the axially inward presswall section. Subsequently, the press fitting can get pressed with a suitable press tool acting on outer circumferential walls of the press wall sections at the opposing sides of the sealing ring chamber portion. This causes the 'flaring' axially outward presswall section to radially compress while the annular radially inwardly projecting gripping hook immediately starts to locally deform the inserted pipe end in such a way that an enhanced grip arises. This enhanced grip helps the press fitting to be able to withstand higher operating pressures of for example more than 48 bar of cooling fluids that are used for HVACR after the fitting has been pressed. However, this known high-pressure press fitting still leaves to be improved. For example, the annular radially inwardly projecting gripping hook reduces the contact surface area that can be obtained after pressing between the socket and the inserted pipe end. This might lead to a lower socalled burst pressure. It might even lead to this type of high-pressure press fitting not being able to pass an officially required burst test. The officially required minimal burst pressure lies with a safety factor of 3 times the normally foreseen operating pressure. Thus if the foreseen operating pressure is more than 48 bar, then the minimal burst pressure during a burst test needs to be at least 144 bar. Furthermore it is a disadvantage that the socket of the pressfitting is relative expensive and difficult to accurately manufacture. The making of the right angled transition with the sealing ring chamber, the gradual widening out of the axially outward press-wall section from there at such an angle that the annular radially inwardly projecting gripping hook at the free outer edge comes to lie exactly at the same desired innermost diameter, is time consuming and complex. A second embodiment of such a special high-pressure press fitting is also commercialized under the name '>B< MaxiPro' and can be seen in fig. 1AD of WO 2021 / 185840. This press fitting comprises a socket with two symmetrical ends that each start with a cylindrical-shaped axially outward press-wall section of enlarged inner diameter that merges into a radially outwardly bulging sealing ring chamber portion that merges into an axially inward presswall section. The enlarged diameter for the cylindricalshaped axially outward press-wall section is necessary in order to still be able to equip the free outer edge part thereof with an annular radially inwardly projecting gripping hook that extends along the entire inner circumference, without this gripping hook getting to stand in the way of a pipe end to be inserted. In other words, the annular radially inwardly projecting hook at its free outer edge part, in the nonpressed state, lies at substantially a same innermost diameter as the axially inward presswall section, that is slightly larger than an outer diameter of a to be inserted pipe end. However, this second embodiment still leaves to be improved. The enlarged diameter for the cylindricalshaped axially outward press-wall section further reduces the contact surface area that can be obtained after pressing between the socket and the inserted pipe end compared to the 'flaring' first embodiment. This reduces mechanical grip and thus might lead to an even lower burst pressure. Furthermore it is a disadvantage that the socket of the pressfitting is relative expensive and difficult to accurately manufacture. The making of the two different diameters for the cylindrical-shaped axially outward and inward press-wall sections, may reduce production costs, but is laborious and complex. BRIEF DESCRIPTION OF THE INVENTION The present invention aims to overcome those disadvantages at least partly or to provide a usable alternative. In particular the present invention aims to provide an economic yet truly reliable press fitting that is well able to deal with high-pressures as for example used in HVAC-R, including the obtaining of the officially required threefold safety factor for the officially required minimum burst pressure during testing. According to the present invention this aim is achieved by a press fitting for connecting to a pipe according to claim 1. The press fitting comprises: . a socket that at least at one end comprises a circumferential wall around a central axis delimiting an insertion space for a pipe end to be inserted therein, wherein the circumferential wall has: 0 an axially outward press-wall section delimiting a first portion of the insertion space; 0 an axially inward press-wall section delimiting a second portion of the insertion space; and 0 an intermediate wall section lying in between the press-wall sections and delimiting a radially outwardly bulging annular sealing ring chamber portion; and . a sealing ring placed in the sealing ring chamber portion, wherein the press-wall sections are plastically deformable from a non-pressed state towards a pressed state by means of a radially inward directed pressing action exerted by a press tool on the press-wall sections at opposing sides of the sealing ring chamber portion and causing the presswall sections to radially compress while locally deforming the inserted pipe end radially inward, wherein the axially outward press-wall section has a free outer edge part with an annular inside thickness that projects radially inwardly while delimiting an insertion opening, and wherein the outer edge part has a locally increased wall thickness that is larger than a wall thickness of an adjacent part of the axially outward press-wall section that extends from the location of the annular inside thickness towards and merges with the radially outwardly bulging annular sealing ring chamber portion. According to the inventive thought the adjacent part at least ata position directly alongside of the outer edge part has been widened by means of cold-deformation, and the outer edge part has been colddeformed to locally increase its wall thickness with the annular inside thickness that projects radially inwardly to smaller inner dimensions than the at least locally widened adjacent part lying alongside it, wherein the outer edge part has a higher hardness than the adjacent part, such that the axially outward press-wall section is configured to, during pressing action from the non-pressed state towards the pressed state, level / smoothen out the transition between the inside thickness and the at least locally widened adjacent part for coming to lie together radially inwardly deformed against the complementary radially inwardly deformed inserted pipe end. Thus advantageously an improved highpressure press fitting is obtained. Extensive testing has proven that it is perfectly suitable to be used for high pressures like ones above 48 bars as used in HVAC-R. The colddeformation to at least locally widen the adjacent part alongside the outer edge part and to locally increase the wall thickness of the outer edge part with the annular inside thickness during manufacturing, not only helps to make the outer edge part thicker and stronger relative to the adjacent part in the non-pressed state, but is also prone to locally modify the material structure inside the outer edge part and adjacent part. All in all, the outer edge part with its inside thickness during such cold-deformation becomes of a higher hardness than the at least locally widened adjacent part. Together this leads to specific advantageous deformation behavior during pressing action from the non-pressed state towards the pressed state, that has proven to be able to make the press fitting such strong after a pressing action to its pressed state has taken place, that even a threefold safety factor for officially required minimum burst pressures in HVAC-R of above 3 x 48 = 144 bars, can now truly be reached. At the start of such pressing action, the inside thickness of the hardened outer edge part shall be the first to get pressed against the inserted pipe end. This advantageously results in an initial concentration of pressing forces right underneath the inside thickness of the hardened outer edge part. This concentration of pressing forces underneath the inside thickness eases a beginning of radial inward deforming of the inserted pipe end at that location. This positive effect may even be increased due to the hardened outer edge part having a tendency to tilt radial inward towards the inserted pipe end around the transition towards the at least locally widened adjacent part and / or together with the entire less strong / hard adjacent part around the sealing ring chamber portion. Furthermore, when the hardened outer edge part has reached its pressed state at the end of the pressing action, the fact that it is thicker, stronger and harder shall help it to maintain this pressed state position together with the co-along deformed pipe end. It shall be more difficult for the thicker, stronger and harder outer edge part to get distorted in this pressed state position. Relaxation is thus prevented at the side of the free outer edge part where the radial inward deformation was biggest during pressing action. Due to the outer edge part having been colddeformed to locally increase its wall thickness with the annular inside thickness, also the outer side of the outer edge part have inevitably come to lie at larger outer dimensions in the non-pressed state. This leads to the press tool starting to act on the outer edge part at an earlier stage of a pressing action. This means that the inside thickness of the hardened outer edge part shall also get pressed against the inserted pipe end at an earlier stage of the pressing action, and shall be pressed radial inward while forcing the inserted pipe end to co-deform to a larger degree at that position. The hardened outer edge part locally strengthens the axially outward press-wall section at its most critical part, that is to say at the position furthest away from the sealing ring chamber portion where the deformation during pressing action is biggest. This positive effect is further increased due to the fact that the annular inside thickness at the side of the free outer edge lies at a location where it has maximum leverage during and after pressing relative to a center of the sealing ring chamber. Furthermore, it has appeared that the specific deformation behavior during said pressing action, also leads to the transition that according to the invention is specifically foreseen between the inside thickness and the at least locally widened adjacent part in the non-pressed state, has a tendency to be levelled / smoothened out during said pressing action. This advantageously leads to a much larger contact area to arise between the deformed pipe end and the axially outward press-wall section in the pressed state. Owing to this, after the pressing action has been completed and the pressed state has been reached, not only the inside thickness lies against the pipe end, but also all or almost all of the tailing adjacent part. In other words, the transition between the inside thickness and the adjacent part that was clearly distinguishable in the nonpressed state, shall no longer or hardly be there anymore in the pressed state. The inner surface of the axially outward press wall section, that is formed by the inside thickness and the adjacent part, in the pressed state has become a substantially flat faced angled inner surface that gradually flares inward, starting at the sealing ring chamber portion all the way to the outer edge. This entire inward angled inner surface of the axially outward press wall section now has become contact area between the deformed pipe end and the axially outward presswall section in the pressed state. A socket according to the invention has even been cut through in its pressed state for analysis purposes. There this positive effect could clearly be seen. Thus thanks to the invention, it has become possible to benefit from the presence of the inside thickness right at the beginning of a pressing action without having to suffer from a disadvantage of reduction of contact area in the pressed state that normally goes along with such an inside thickness. In contrast thereto, the invention has proven to be well able to combine optimization of strength of radial inward deformation of the outer edge part with optimization of contact area in the pressed state. This further improves the mechanical grip between the socket and the pipe end, and hence to improve its resistance against pullout force, which adds to the strength, safety and reliability of the press fitting even over long periods of time and / or under harsh circumstances. In a preferred embodiment, the adjacent part may have been widened during manufacturing to larger inner dimensions than the inside thickness over its entire length between the outer edge part and the sealing ring chamber portion. The larger inner dimensions over the entire length of the adjacent part in the non- pressed state advantageously may be obtained by first widening the entire axially outward press-wall section, that is to say including its outer edge part as well as its adjacent part, to a widened cylindrical shape of an inner diameter that is larger than an initial starting diameter of a tube as basic starting material. This can for example be done by forcing a complementary larger sized mandrel in axial direction into a tube having a smaller sized cylindrical-shape of said initial starting diameter. After this widening has been completed, then as a next manufacturing step, an upsetting colddeformation of the outer edge part may be performed to locally increase its wall thickness with the annular inside thickness. This upsetting cold- deformation preferably is performed only the outer edge part, in particular by means of a combined rolling upsetting cold-deformation of the outer edge part. Due to this upsetting after widening, the annular inside thickness then automatically shall come to project radially inwardly to smaller inner dimensions than the widened adjacent part. Preferably, those smaller inner dimensions to which the inside thickness gets upset then are configured to correspond with the initial starting diameter of the tube. It has appeared that the above described specific deformation behavior during said pressing action, then also occurs, that is to say that the stepped transition between the inside thickness and the widened adjacent part gets levelled / smoothened out during said pressing action, thus maximizing the contact area in the pressed state as well as the mechanical grip between the socket and the pipe end. In a further improvement hereof, the adjacent part may not only be widened over its entire length, but at a same time in such a way that it is configured to increasingly widen towards the sealing ring chamber portion in the non-pressed state. Those increasing widened inner dimensions of the adjacent part in axial direction away from the outer edge part in the nonpressed state advantageously may be obtained by not looking up the adjacent part nor sealing ring chamber portion at their outer sides during upsetting cold-deformation of the outer edge part. The manufacturing then may start again with first widening an entire axially outward presswall section to a widened cylindrical shape of larger inner diameter, to then as next manufacturing step, perform the upsetting cold- deformation of the outer edge part while giving the adjacent part and sealing ring chamber portion full freedom to start flaring outward due to axial inward pushing forces that get exerted thereupon during this upsetting while the axially inward presswall section is firmly clamped. This upsetting while leaving free the adjacent part and sealing ring chamber portion at their outer side, then may be configured to have the adjacent part to come to lie at an angle relative to the central axis of between 1-5 degrees during manufacturing, while at a same time the annular inside thickness then automatically may be formed on the outer edge part. Advantageously, in the non-pressed state the adjacent part already angles relative to the central axis in a direction it is foreseen to get increased in the pressed state. Further, it has appeared that this angled orientation of the adjacent part already in the non-pressed state helps to further increase (strength of) radial inward deformation of the outer edge part while also easing the Ievelling / smoothening of the contact area to take place during pressing action. This helps to make it even easier for both the entire adjacent part as well as the inside thickness of the outer edge part to come to lie with maximized contact area and firm mechanical grip against the inserted co-pressed pipe end. In a variant embodiment the adjacent part during manufacturing may only have been locally widened by means of cold-deformation at the position directly alongside of the outer edge part. In that case an indentation is present as locally widened transition alongside the inside thickness in the non-pressed state. The rest of the adjacent part then may lie at a same inner diameter as the inside thickness. This indentation lying as transition alongside the inside thickness, has the advantage that it may be formed simultaneously with an upsetting cold-deformation of the outer edge part. It has appeared that for this variant embodiment also the above described specific deformation behavior occurs during a pressing action. The indentation shall get levelled / smoothened out during a pressing action, thus helping to maximize the contact area in the pressed state as well as the mechanical grip between the socket and the pipe end. In a further preferred embodiment, the hardness of the outer edge part can be configured to be at least twice as high as the hardness of the adjacent part in the non- pressed state. This can be managed by means of cold-deforming the outer edge part to a sufficient high degree. For example a tube that is used as basic starting material for manufacturing may have a hardness of about 30 HRB, whereas the hardness of the outer edge part at the end of manufacturing may have been increased to a hardness of more than 70 HRB due to having been cold deformed to locally increase its wall thickness with at least the annular inside thickness. In a further preferred embodiment, the locally increased wall thickness of the outer edge part at the location of the annular inside thickness can be configured to be at least 1.1 times larger than the wall thickness of the adjacent part in the non-pressed state. Thus advantageously a large enough initial concentration of pressing forces at the beginning of a pressing action and large enough increased degree of radial inward deformation at the end of the pressing action can be obtained. In particular the inside thickness may add about 10-20% to the initial wall thickness in the non-pressed state. Thus keeps the inside thickness thin enough for the smoothening / levelling effect to be able to quickly and efficiently occur. In a further preferred embodiment, the locally increased wall thickness of the outer edge part at the location of the annular inside thickness can be at most 2 times larger than the wall thickness of the adjacent part in the nonpressed state. This maximum dimensioning helps to keep the pressing forces during pressing action within acceptable range, and to keep the outer dimensions of the outer edge part in the non-pressed state to maintain lying within maximum outer dimensions of the sealing ring chamber. In a further preferred embodiment, the annular inside thickness may have an axial length that is smaller than the wall thickness of the adjacent part in the non-pressed state. This helps to obtain the desired deformation behaviour, amongst which the sufficiently concentrating of initial pressing forces underneath the inside thickness at the beginning of the pressing action. In a further preferred embodiment, the adjacent part may have an axial length that is at least twice as long as an axial length of the annular inside thickness in the non-pressed state. Thus a sufficiently long adjacent part is provided that is well able to help obtain the desired deformation behaviour during pressing action, amongst which providing sufficient leverage for the outer edge part relative to the sealing ring chamber portion. In line herewith, an axial distance between a center of the annular inside thickness and a center of the radially outwardly bulging annular sealing ring chamber portion may be at least 4 times the wall thickness of the adjacent part. Th us advantageously the adjacent part of the axially outward presswall section combines leverage as well as flexibility for the outer edge part to have its inside thickness be pressed full force into an inserted pipe end during a pressing action as well as ability to smoothen / Ievel out the transition towards the end of the pressing action. During pressing action, the pressing tool may first start to exert its radially inwards directed pressing force onto the outermost part of the press-wall sections, that is to say on the outer edge part with its annular inside thickness. The lever function of the adjacent part of the axially outward press-wall section then helps the relative strong annular inside thickness to more easily get maximally deformed radially inward together with the inserted pipe end at that locaon. In a further preferred embodiment, the axially inward press-wall section may be cylindrical-shaped extending parallel to the central axis, wherein inner dimensions of the inside thickness then can be configured to be the same as the inner diameter of the cylindrical-shaped axially inward press-wall section in the non-pressed state . The inside thickness may have a smooth inner cylindrical shape, and in particular also the axially inward press-wall section may have such a smooth cylindrical shape of same inner diameter. This makes it possible to insert a pipe end of slightly lesser outer diameter into the insertion space with a smooth sliding fit in the axial direction. The inside thickness is well able to guide this insertion right from the beginning. Furthermore, the combination of the inside thickness and cylindrical-shaped axially inward press-wall section with same inner diameters makes it possible to perfectly neatly align the pipe end during insertion and keep it aligned during and after pressing of the press fitting. In a further preferred embodiment, the axially inward presswall section may have an axial length that is larger than an axial length of the axially outward press-wall section, in particular at least 1,5 times larger, more in particular about 3 times longer. The longer sized axially inward presswall section helps to further increase contact surface with the inserted pipe end after pressing. This further helps to increase the burst pressure, particularly for somewhat larger diameter press fittings according to the invention. In a further preferred embodiment, the axially outward press-wall section with its outer edge part and annular inside thickness and radially outwardly bulging annular sealing ring chamber portion may all have been manufactured by means of cold-deformation of a tube having a cylindrical-shape, in particular a tube already having a same cylindrical shape and inner / outer diameter as the axially inward press-wall section is foreseen to have. Thus advantageously one piece of tube as starting base material then can be used for manufacturing. In a preferred embodiment the socket can be made out of one single metal component. This is advantageous in terms of weight, size, production costs and material costs. The socket can for example be made out of stainless steel. Preferably however, the socket is made out of copper or copper alloy, which is well deformable, which is advantageous both during manufacturing as well as during pressing action of the press fitting. Furthermore, the copper (alloy) material socket is in line with material that is already used in the market, and thus can be used alongside conventional methods. In a further preferred embodiment, the outer edge part may have been cold-deformed during manufacturing to not only locally increase its wall thickness with the inside thickness but also locally increase its wall thickness with an annular outside thickness. The outside thickness then is configured to come to lie at a position opposite the radially inwardly projecting inside thickness while projecting radially outwardly to larger outer dimensions than the at least locally widened adjacent part lying alongside it. For example the inside thickness then may locally increase the wall thickness of the outer edge part with 10-20%, whereas the outside thickness then may locally increase the wall thickness of the outer edge part with 20-30%. Thus the total locally increased wall thickness of the outer edge part at the location of where the annular inside and outside thicknesses lie opposite each other can be between 30-50% larger than the wall thickness of the adjacent part. This helps to make the outer edge part thick, strong and / or hard enough while at a same time make it possible for the transition lying alongside the inside thickness to be kept shallow enough for the smoothening / Ievelling effect to occur during pressing action. Furthermore, the provision of the outside thickness on top of the outer edge part at its position opposite the inside thickness, advantageously leads to the outer dimension of the outer edge part getting to lie at a higher level in the nonpressed state. Thus, the outer edge part shall start to be pressed radially inward at an even earlier stage of a pressing action. In addition thereto, the outside thickness may extend over a length in axial direction that is longer than a length of the inside thickness in the non-pressed state. In particular the outside thickness may be configured to be at least 1,5 times longer than the inside thickness. Thus, the smaller dimensioned inside thickness in combination with the larger dimensioned outside thickness together are well able to sufficiently thicken, strengthen and harden the outer edge part relative to the at least locally widened adjacent part, while the inside thickness can be configured small enough for high concentrating of all exerted pressing forces right underneath the hardened inside thickness onto the inserted pipe end at the beginning of a pressing action. Furthermore, this smaller dimensioning of the inside thickness relative to the outside thickness, shall aid in the desired levelling / smoothening of the transition between the inside thickness and the at least locally widened adjacent part. In addition thereto or in the alternative, the annular outside thickness may have an axial length that is about the same as the locally increased wall thickness of the outer edge part at the location of the annular inside thickness. The invention also relates to a method for pressing the above described press fitting, as well as to a method for manufacturing the above described press fitting. Further preferred embodiments of the invention are stated in the dependent subclaims. DETAILED DESCRIPTION OF THE DRAWINGS The invention shall now be explained in more detail below by means of describing some exemplary embodiments in a non-limiting way with reference to the accompanying drawings, in which: - Fig. 1a shows an assembly of a press fitting according to the invention in a non-pressed state with two insertion ends with a pipe end inserted into the left insertion end; - Fig. 1b shows an enlarged partial view of fig. 1a; Fig. 1c shows the view of fig. 1a with dimension indications; - Fig. 2 shows the left side of the press fitting of fig. 1a and 1c in the pressed state; - Fig. 3a-eshow enlarged partial views of subsequent manufacturing steps of the socket of fig. 1; - Fig. 4a, b show perspective views of the socket respectively the assembly of the socket with a pipe end inserted therein of a variant embodiment in the non-pressed state; Fig. 5a-c and 6 show the views of fig. 1ac and 2 for this first variant embodiment; fig. 7ac shows the pressed state of fig. 6 including a pressing tool; - fig. 8a-f show enlarged partial views of subsequent manufacturing steps of the socket of fig. 5; - Fig. 9a-b show photographs of an axially cut open test assembly according to fig. 4 in the non-pressed respectively pressed state; Fig. 10ab and 11 show the views of fig. 1ab and 2 for a second variant embodiment; Fig. 12a shows a photograph of an axially cut open socket according to this second embodiment according to fig. 10 in the non-pressed state; and Fig. 12b shows a photograph of an axially cut open test assembly according to fig. 10 in the nonpressed state. In fig. 1 a press fitting is shown that has been given the reference numeral 1. The fitting 1 comprises a copper or copper alloy socket 2. The socket 2 has a left and right insertion end that lie mirror-symmetric at opposing sides of insertion depth stop ridges SR. A pipe end 4 has been inserted into the left insertion end such far that it abuts against the stop ridges SR. Both the left and right insertion end of the socket 2 each comprises three subsequent circumferential wall sections of substantially constant wall thickness d around a central axis CA. Starting at the stop ridges SR in the middle of the socket 2, they each start with an axially inward extending presswall section PWi, a radially outwardly bulging intermediate wall section forming a sealing ring chamber portion SRC, and an axially outward extending press- wall section PWo. An elastically deformable sealing ring 5 has been placed inside each sealing ring chamber portion SRC. The axially inward press-wall section PWi is cylindrical-shaped and has a length Li. A wall thickness d, inner diameter Di and outer diameter D0 are constant over this entire length Li. The axially inward presswall section PWi gradually merges into the radially outwardly bulging intermediate wall section. At the inner side, this transition is convexly curved. The sealing ring chamber portion SRC has a same wall thickness d as the cylindrical-shaped axially inward presswall section PWi. The axially outward press-wall section PWo has a length Lo and comprises a free outer edge part OEP and an adjacent part AP. The outer edge part OEP is characterized in that it has an annular inside thickness IT that projects radially inwardly. This inside thickness IT has an inner diameter Dit and an axial length Lit. The inner diameter Dit of the annular inside thickness IT is the same as the inner diameter Di of the cylindrical-shaped axially inward press-wall section PWi. The outer diameter Doep of the outer edge part OEP is larger than the outer diameter D0 of the axially inward press-wall section PWi. At the location of the annular inside thickness IT, the wall thickness d' of the outer edge part OEP is locally increased and larger than the wall thickness d of the adjacent part AP, the sealing ring chamber portion SRC and the cylindrical-shaped axially inward presswall section PWi. The adjacent part AP has been increasingly widened over its entire length Lap in the direction of the sealing ring chamber portion SRC and lies at an angle or relative to the axial direction parallel. At its axially inward end the adjacent part AP gradually merges at a relative wide inner diameter Dapw into the radially outwardly bulging intermediate wall section. At the inner side, this transition is convexly curved. At its axially outward end the adjacent part AP merges at a relative narrow inner diameter Dapn with the outer edge part OEP. At the inner side this transition T is stepped and concavely curved. The adjacent part AP has a same wall thickness d over its length Lap that is substantially equal to the ones of the sealing ring chamber portion SRC and cylindrical-shaped axially inward press-wall section PWi. Both the relative narrow inner diameter Dapn as well as the relative wide inner diameter Dapw are larger than the inner diameter Dit of the annular inside thickness |T respectively the inner diameter Di of the cylindrical-shaped axially inward press-wall section PWi. If for example for a 5 / 8" press fitting, the wall thickness d of the rest of the socket 2 is approximately 1.3 mm, then the locally increased wall thickness d' of the outer edge part OEP an be approximately 1.6 mm. If for example for a 7 / 8" press fitting, the wall thickness d of the rest of the socket 2 is approximately 1.4 mm, then the locally increased wall thickness d' of the outer edge part OEP can be approximately 1.7 mm. Thus, depending on the fitting size, an additional inside thickness IT of about 0.3 mm has been provided, and the locally increased wall thickness d' is about 1.2 times larger than the wall thickness d. The annular inside thickness IT here has a substantial rectangular cross-section and has an axial length Lit that is about half the locally increased wall thickness d'. The center of the annular inside thickness IT lies at an axial distance Lc from the center of the radially outwardly bulging annular sealing ring chamber portion SRC. During pressing this forms a lever. Lc here is about 4-5 times the wall thickness d. In the embodiment of fig. 1, the length Li of the axially inward press-wall section PWi is about 3 times larger than the length Lo of the axially outward press-wall section PWo. Fig. 2 shows the pressed state for the press fitting 1. For this a press tool PT is used of a conventional type, referred to as V-profile, that is already known to be used for the abovementioned SudoPress / ApolloPress, and of which an example is shown in fig. 7a-b. The jaws are profiled such stepped with a semi-circular center maximum grooved portion, semi circular intermediate Ieft and right medium grooved portions, and semi-circular outer left and right press ribs. The semi-circular center maximum grooved portion is configured to fit with a play around the radially outwardly bulging sealing ring chamber portion SRC in the non pressed state. The semicircular outer left and right press ribs are configured that one of them comes to lie against the outer edge part OEP opposite the annular inside thickness IT right at the starting phase of pressing action. The other one of them then still lies spaced over the height ofthe inside thickness IT above the axially inward press-wall section PWi, and only comes to lie against it after the axially outward press-wall section PWo has been radially compressed inwards over this height of the inside thickness IT together with the inserted pipe end 4. From thereon both press-wall sections PWo, PWi as well as the sealing ring chamber portion SRC shall get simultaneously radially compressed inwards by the press tool PT until the pressed state is reached as is shown in fig. 2. In this pressed state, the axially outward press-wall section PWo is deformed into a trapezoid shape of which the entire inner surface has come to lie flat faced flaring inward at an angle ß against the co-deformed pipe end 4. The angle B is larger than the angle d, and the concavely curved stepped transition T has levelled / smoothened out. The inner surfaces of the inside thickness IT and adjacent part (AP) as it were have come to lie in each others prolongation. In fig. 3a-e subsequent manufacturing steps for the socket 1 are shown: STEP 1: Clamping In a first manufacturing step as shown in fig. 3a, an axial inward end oftube base material is fixedly held in position by a clamping mechanism CM whereas an axial outward end of the tube base material is left free around its outer side. The fixedly held axial inward end of the tube base material is destined to form the cylindricalshaped axially inward presswall section PWi. The left free axial outward end of the tube base material is destined to form the sealing ring chamber portion SRC and the free outer edge part OEP and adjacent part AP of the axially outward press-wall section PWo. A front relative narrow section Mns of a mandrel M has a diameter that is substantially equal to Di and has been inserted with a narrow sliding fit into the tube base material. The mandrel M further comprises a back relative wide section Mws of a diameter that is substantially equal to Dapn that lies waiting in front of the tube base material. The back relative wide section Mws ofthe mandrel M is circumvented by a shaping mould SM that delimits an annular widening / shaping chamber WSC around the back relative wide section Mws of the mandrel M. This chamber WSC comprises a concavely curved shaping section WSCs that has a shape substantially complementary to the outer shape of the to be formed sealing ring chamber portion SRC, and a straight widening section WSCW that has a shape substantially complementary to a to be widened frontmost part of the tube base material of an inner diameter that is substantially equal to Doep. STEP 2: Widening and shaping In a second manufacturing step as shown in fig. 3b, the assembly of the mandrel M and shaping mould SM has been pushed towards and against the clamping mechanism CM while forcing the frontmost part of the tube base material to come to lie in the straight widening section WSCw by widening to the larger inner and outer diameters Dapn and Doep for forming the axially outward press-wall section PWo, and while at a same time forcing an intermediate section of the tube base material to radially outwardly bulge into the concavely curved shaping section WSCs for forming the sealing ring chamber portion SRC. STEP 3: Upsetting and flaring In a third manufacturing step as shown in fig. 3c, the mandrel M is positioned such that only the front relative narrow section Mns remains to lie inside the tube. The shaping mould SM has been replaced by an upsetting mould UM that circumvents the relative narrow section Mns of the mandrel M while delimiting an annular upsetting chamber UC around the front relative narrow section of the mandrel M. This chamber UC comprises a straight upsetting section UCu that defines an inner diameter that is substantially equal to Doep such that it is complementary to the outer shape of the outer edge part OEP, whereas the outer diameter of the relative narrow section of the mandrel M is still substantially equal to Di such that it is complementary to the inner shape of the inside thickness IT to be formed on the outer edge part OEP. The arrows in fig. 30 indicates that the upsetting mould UM and mandrel M are rotated during the upsetting of the outer edge part OEP as well as pushed towards the clamping mechanism CM. Due to this the inside thickness IT shall be formed. Owing to the fact that the upsetting mould UM only circumvents the to be formed outer edge part OEP during this rotational upsetting while leaving free a space towards the clamping mechanism CM, the in step 2 already widened wall section has full freedom to start flaring outward due to the large axial inward pushing force that gets exerted thereupon during this upsetting. Fig. 3d shows that the inside thickness IT starts forming. Fig. 3e shows that at the end of the rotational upsetting, not only the hardened, thicker and stronger outer edge part OEP and the entire inside thickness |T are formed, but also the increasingly widening angled adjacent part AP. In fig. 4-9 a first variant embodiment is shown in which same reference indications have been used. This time the outer edge part OEP has been manufactured such that in the upsetting after widening step that not only an inside thickness IT is formed but also an outside thickness OT. For that only the dimensions of the chamber UC in the upsetting mould UM needed to be enlarged. This chamber UC still comprises a straight upsetting section UCu but now one that defines an inner diameter that is substantially equal to Dot such that it is complementary to the outer shape of the to be formed outside thickness OT, whereas the outer diameter of the relative narrow section of the mandrel M is still substantially equal to Di such that it remains complementary to the inside thickness IT to be formed on the outer edge part OEP. With this it is noted that during the rotational upsetting, the outside thickness OT gets formed with a length Lot about twice as large as a length Lit of the inside thickness IT. This has to do with the fact that the outside thickness OT starts forming easier and earlier than the inside thickness IT, as is also shown in fig. 8d and 8e. Fig. 7c shows a variant in which the socket 2 has been made with a larger length Li of its axially inward press-wall section PWi. The insertion depth stop ribs SR then also lie further inwards such that a larger length of pipe 4 can be inserted into the socket 2. As can be seen in fig. 7c this leads to a substantially larger contact surface area between the deformed socket 2 and the inserted pipe end 4 at the axially inward side in the pressed state. In fig. 1012 a second variant embodiment is shown in which same reference indications have been used. This time the outer edge part OEP has been formed without first widening the axially outward presswall section PWo. The dimensions of the chamber UC in the upsetting mould UM are kept the same as in the fig. 4-9 embodiment, such that both an inside thickness IT as well as an outside thickness OT get formed during the upsetting. Further it is noted that here also upsetting mould UM only circumvents the to be formed outer edge part OEP during this rotational upsetting while leaving free a space towards the clamping mechanism CM. This means that the wall section that is destined to form the adjacent part AP has full freedom to locally deform outward due to the large axial inward pushing force that gets exerted thereupon during this upsetting. It appears that without the preceding widening step, the adjacent part AP during manufacturing only gets locally widened by means of cold-deformation at the position directly alongside of the outer edge part OEP. In other words an annular indentation then gets formed alongside the inside thickness IT in the non-pressed state. The rest of the adjacent part AP then may remain lying at a same inner diameter Di as the inside thickness IT. Besides the shown and described embodiments, numerous variants are possible. For example the dimensions and shapes of the various parts can be altered. Also it is possible to make combinations between advantageous aspects of the shown embodiments. Instead of using copper or copper alloy other kinds of metals can be used. All kinds of materials and types of sealing rings can be used. Instead of having the socket comprise two symmetrical insertion ends, it is also possible to have only one insertion end according to the invention provided on the socket, such that the other end can be used for another type of connection. Instead of having an entire sealing ring immediately getting somewhat deformed and coming to lie against an inserted pipe end, it is also possible that this full circumferential sealing is not obtained until after the pressing has taken place. In that way a leak-before-press test option can be provided. It should be understood that various changes and modifications to the presently preferred embodiments can be made without departing from the scope of the invention, and therefore will be apparent to those skilled in the art. It is therefore intended that such changes and modifications are covered by the attached claims. 5 CONCLUSION 1. Press fitting (1) for connection to pipe, comprising: . a sleeve (2) which has a perimeter wall at at least at one end around a central centerline (CA) which limits an insertion space for a tube end to be inserted into it (4), where the perimeter wall is provided with: 0 an axially external press wall section (PWo) which forms a first part of the limited insertion space; or an axially internal press wall section (PWi) which a second part of the limited insertion space; and or an intermediate wall section situated between the press wall sections (PWo, PWi) and a radially outward-protruding annular sealing ring chamber section (SRC) bounded; and . a sealing ring (5) placed in the sealing ring chamber section (SRC), where the press wall sections (PWo, PWi) are plastically deformable of a non- compressed state to a compressed state by means of a radially internally located pressing action exerted by a pressing tool (PT) on the press wall sections (PWo, PWi) on opposite sides of the sealing ring chamber section (SRC) and causing the press wall sections (PWo, PWi) to be radially compressed while the inserted tube end (4) is locally radially deformed inwards, where the axially external press wall section (PWo) is a freely external edge part (OEP) has an immediate annular internal thickening (IT) that radiates to protrudes inside and thereby limits an insertion opening, and where the outer edge section (OEP) has a locally increased wall thickness (d') that is greater than a wall thickness (d) of an adjacent part (AP) of the axially external press wall section (PWo) extending from the location of the annular inner section thickening (IT) into and transitions into the radially outward-protruding ring-shaped sealing ring chamber section (SRC), with the characteristic that the adjacent part (AP) at least at a position directly next to the external part edge part (OEP) is removed by means of cold forming, and the outer edge part (OEP) is cold-formed to locally reduce its wall thickness enlarge with the annular internal thickening (IT) that projects radially inwards to smaller internal dimensions than the at least locally widened adjacent part (AP) that lies next to it, where the outer edge part (OEP) has a higher hardness than the adjacent part (AP), such that the axially external press wall section is designed to, during the pressing from the unpressed state to the pressed state, the transition between the internal thickening (IT) and the at least locally widened adjacent part (AP) to to equalize / flatten so that they lie radially deformed inwards together against the complementary radially inwardly deformed inserted tube end. 2. Press fitting in accordance with claim 1, where the adjacent part (AP) over its entirety length between the outer edge part (OEP) and the sealing ring chamber part (SRC) is widened to larger internal dimensions than the internal thickening (IT). 3. Press fitting in accordance with claim 2, whereby the adjacent part (AP) to the sealing ring chamber section (SRC) becomes increasingly wider, particularly at an angle to relative to the centerline (CA) of between 1-5 degrees. 4. Press fitting in accordance with one of the preceding claims, where the hardness of the outer edge part (OEP) is at least twice as high as the hardness of the adjacent part (AP). 5. Press fitting in accordance with one of the preceding conclusions, where the locally enlarged wall thickness (d') of the outer edge section (OEP) at the location of the ring-shaped internal thickening (IT) is at least 1.1 times greater than the wall thickness (d) of the adjacent part (AP). 6. Press fitting in accordance with one of the preceding conclusions, where the locally enlarged wall thickness (d') of the outer edge section (OEP) at the location of the ring-shaped internal thickening (IT) is at most 2 times greater than the wall thickness (d) of the adjacent part (AP). 7. Press fitting in accordance with one of the preceding claims, where the annular internal thickening (IT) has an axial length (Lit) that is smaller than the wall thickness (d) of the adjacent part (AP). 8. Press fitting in accordance with one of the preceding claims, where the adjacent part (AP) has an axial length (Lap) that is at least twice greater than an axial length (Lit) of the annular internal thickening (IT). 9. Press fitting in accordance with one of the preceding claims, where an axial distance (Lc) between a center of the annular internal thickening (IT) and a center of the radially outward-projecting annular sealing ring chamber section (SRC) at least 4 times the wall thickness (d) of the adjacent part (AP) amounts to. 10. Press fitting in accordance with one of the preceding claims, where the axial internal press wall section (PWi) is cylindrical and parallel to the centerline (CA) extends, and where the internal dimensions (Dit) of the internal thickening (IT) are equal to an inner diameter (Di) of the cylindrical internal press wall section (PWi). 11. Press fitting in accordance with one of the preceding claims, where the axial internal press wall section (PWi) has an axial length (Li) that is greater than an axial length (Lo) of the axially external press wall section (PWo), in particular at least 1.5 times larger, more specifically about 3 times longer. 12. Press fitting in accordance with one of the preceding claims, where the axial external press wall section (PWo) with its external edge section (OEP) and ring-shaped internal thickening (IT) and the radially outward-protruding annular sealing ring chamber section (SRC) are manufactured by means of cold forming a tube with a cylindrical shape, in particular a tube with the same cylindrical shape as the axially internal press wall section (PWi). 13. Press fitting according to one of the preceding claims, where the sleeve (2) is manufactured from copper or copper alloy. 14. Press fitting in accordance with one of the preceding claims, where the external edge section (OEP) is cold-formed to also locally increase its wall thickness by a annular outer thickening (OT) opposite the inner thickening (IT) extends radially outwards to larger external dimensions than the adjacent one, at least locally widened adjacent part (AP). 15. Press fitting in accordance with claim 14, where the outer thickening (OT) is located in axial direction extends over a length that is longer than a length of the internally located thickening (|T), in particular where the outer thickening (OT) is at least 1.5 times so big is. 16. Press fitting according to claim 14 or 15, where the annular outer part thickening (OT) has an axial length (Lot) that is approximately equal to the locally enlarged wall thickness (d') of the outer edge section (OEP) at the location of the ring-shaped internal thickening (IT). 17. Procedure for pressing the press fitting according to one of the preceding conclusions 1-16, comprising the steps of: - inserting a pipe end (4) into the insertion space of the socket (2); - plastic deformation of the press wall sections (PWo, PWi) from a non-pressed state to a compressed state by means of a radially inward-directed pressing action applied by a press tool (PT) to the press wall sections (PWo, PWi) on both sides of the sealing ring chamber section (SRC), whereby the press wall sections (PWo, PWi) be compressed radially and the inserted tube end (4) locally radially towards is deformed inside; where the press tool (PT) is configured to on the side of the axial external press wall section (PWo) a primary part of its radially inwardly directed to exert pressing action directly on the outer edge part with its higher hardness, and whereby the axially external press wall section, during subsequent pressing action from the uncompressed state to the compressed state, the transition between the equalizes / levels the inner thickening (IT) and the adjacent part (AP) to jointly radially inward deformed against the complementary radially inward to come to lie deformed inserted tube end. 18. Method according to conclusion 17, whereby the press tooling (PT) is further configured to a secondary part of on the side of the axially internal press wall section (PWi) to exert its radially inward-directed pressing action directly on an outer side of the axially located internal press wall section (PWi) which in the opposite direction at a distance from the center of the radially outward-protruding annular sealing ring chamber section (SRC) lies, in particular, at the same axial distance (Lc). 19. Method for manufacturing the press fitting according to one of the preceding conclusions 1-16, comprising the steps: - widen the adjacent part (AP) at least at one position directly next to the external edge part (OEP) by cold deformation, and - cold-deforming of the outer edge section (OEP) to locally reduce its wall thickness to be enlarged by the ring-shaped internal thickening (IT) which projects radially inwards to smaller internal dimensions than the at least locally widened adjacent part (AP) that lies next to it, such that the outer edge part (OEP) acquires a higher hardness than the adjacent part (AP), and such that the axially external press wall section is configured to, during compression action from the uncompressed state to the compressed state the at least locally widened broadened transition between the inner thickening (IT) and the adjacent part (AP) equalizes / flattens to jointly radially deformed inwards against the complementary radially inwardly deformed inserted tube end to come into position. g. 1bg. 1a2SR5OEPPWoPWiPWiPWo5SRCITA1APAPSRCOEPIT4OEPSRCAPITαT g. 1cLcdd'LapLoLitLiCADiDoDitDoepDapnddg. 2Dapwβ Fig. 3aFig. 3bFig. 3cMwsMnsMCMWSCwWSCsMwsMnsSMCMPWiPWoSRCMnsMnsUMCMCMUMITUCuFig. 3eFig. 3dOEPOEPAPITAPOEPAPMnsUMCM g. 4bg. 4aSROTSRCAPOTSRCAP411ITAP Fig. 5bFig. 5a2SR4OTPWoPWiPWiPWo5SRCITA1APOEPAPSRCOEPIT4TOT g. 6g. 5cLcdd'LapLoLitLiCADiDoDitDotDapnddDapwβLot g. 7aPTg. 7bPTFig. 7c g.8eFig.8fg.8ag.8cFig.8bFig.8dMwsMnsMCMWSCwWSCsMwsMnsSMCMPWiPWoSRCMnsMnsUMCMCMUMITUCuOEPOEPAPOTAPOEPAPMnsUMCMOTMnsCMUMITOEPAPOT

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