NL2015414B1 - Press fitting for pipes having a helical wound split spacer ring with overlapping windings. - Google Patents

Abstract

A press fitting for pipes comprises a socket 1 with an insertion space for a pipe end 4. The insertion space has a press region 3 which is delimited by a press wall part 10. An annular groove-shaped space is present in the press wall part. A sealing ring 16, spacer ring and gripping ring 17 are placed in the groove-shaped space. The press region is deformable from a non-compressed towards a compressed state during a radially inward directed pressing action causing the press wall part to radially compress and the gripping ring to grip the pipe end while the sealing ring lies sealing against the pipe end. The spacer ring is a helical wound split ring 18 having at least partially overlapping windings which increase their overlap when radially compressed during the pressing action such that an inner and outer diameter of the spacer ring decreases.

Description

Title: Press fitting for pipes having a helical wound split spacer ring with overlapping windings.

The present invention relates to press fittings for pipes which have sockets with compressible press regions such that pipe ends can be inserted therein after which the press fittings can be press fitted from a non-compressed state into a compressed state by means of a suitable pressing action exerted upon those press regions by complementary pressing tools.

Such press fittings are known in a wide variety of embodiments. For example EP- 0.955.493 discloses a press fitting which comprises a socket with a central insertion opening into which a complementary pipe end can be inserted. The central insertion opening has an insert region and a press region. The insert region lies axially inwards, is relative thick-walled and is dimensioned such that an inserted pipe end can come to lie abutting therein with only a minimum amount of circumferential play. The press region lies axially outwards, is relative thin-walled and presents a widened annular groove-shaped space in which a first sealing ring, a spacer ring, a second sealing ring and a gripping ring are placed. At its axial outward end the groove-shaped space is delimited by a radially inwards flared edge of the press region. At its axial inward end the groove-shaped space is delimited by a transitional wall part which extends between the insert region and press region. In the non-compressed state, radial inner dimensions of the rings are such that an inserted pipe end can come to lie therein with only a minimum amount of circumferential play. The press region is compressible from the non-compressed state towards the compressed state by a radially inward directed pressing action exerted upon an outer wall of the press region. In the compressed state, grasping teeth of the gripping ring get to couple with the inserted pipe end and the sealing rings get to lie sealing against the inserted pipe end. With this the spacer ring, which is made of a polymeric material, has the object of ensuring a positioning of the sealing rings within the press fitting. A disadvantage herewith is that, during the pressing action, the spacer ring may quickly get fully locked up between an inner circumferential wall of the press region and an outer circumferential wall of the pipe end. Further pressing action then requires relative large forces and, more importantly, shall force the spacer ring to deform in one or both axially sideways directions. The way the spacer ring deforms is rather unpredictable. The spacer ring may even get damaged. At least it forces the spacer ring against one or both sealing rings. All in all this results in unpredictable deformation behaviour or even a damaging of the sealing rings, making it more difficult to guarantee a leak free press fitting.

Another example of a press fitting is disclosed in WO 2010/089188. Here the press fitting comprises a socket with an annular groove-shaped space present inside a widened thin-walled press region. At its axial outward end the groove-shaped space is delimited by a plurality of interspaced inwardly projecting stop segments. At its axial inward end the grooveshaped space is delimited by a transitional wall part which extends between the insert region and press region. A sealing ring, a spacer ring and a gripping ring are placed side by side in the groove-shaped space. The spacer ring is used for fixing the gripping ring at its axial inward side and to keep sharp-edged grasping teeth of the gripping ring separated from the sealing ring. The spacer ring here is dimensioned such that both in the non-compressed state as well as in the compressed state it does not lie or come to lie against an outer circumferential wall of the pipe end. Both in the non-compressed state as well as in the compressed state, a space keeps on lying in between them. A disadvantage here is that the deformation behaviour of the spacer ring during a pressing action is still rather unpredictable and thus still may lead to the spacer ring and/or the sealing ring to get damaged. Another disadvantage is that the sealing ring during the pressing action deforms such that it gets to partially extend to inside said space in between the spacer ring and the pipe end. This enlarges the risk of the sealing ring getting damaged during a pressing action. Furthermore it is noted that, in cases of the sealing ring getting damaged during use, for example by getting burned in case of fire, said space which keeps on lying in between the spacer ring and the pipe end in the compressed state, immediately may result in large amounts of possibly dangerous transportation gases or fluids being forcedly blown out of the press fitting via the press region. In case of highly combustible media being transported through the pipes this may lead to very dangerous situations. EP 2 623 832 shows a stopper grip ring for a press fitting for plumbing pipes. The stopper grip ring is made as a finite ring with free outer ends. It comprises a cross-sectional C-shape with one leg of the C-shape forming a stopper portion and the other leg forming an O-ring supporting portion. The stopper portion is formed by a row of slanted inward bent sharpened teeth for gripping into an inserted pipe end after the press fitting has been compressed by a pressing action with a press tool. The stopper portion extends over less than a full turn. It comprises a spacing between its outer ends. The O-ring supporting portion is formed by a radially inward bent circumferential wall that is destined to come to lie against an O-ring of the press fitting both in the non-compressed and in the compressed state. The O-ring supporting portion has one slanted end part that projects past by its corresponding outer end of the stopper portion and one opposing slanted end part that does not project past by its corresponding outer end of the stopper portion. During compressing of the press fitting, the opposing slanted end parts of the O-ring supporting portion slide alongside each other while increasing their overlap. A disadvantage here is that in case the O-ring gets damaged during use, for example by getting burned in case of fire, a large space that remains lying between the O-ring supporting portion and the inserted pipe end in the compressed state, immediately leads to large amounts of possibly dangerous transportation gases or fluids starting to flow out of the press fitting. Another disadvantage is that the radial space between the O-ring supporting portion and an inserted pipe end is so large, more than one third of the height of the stopper gripping ring, that the O-ring during the pressing action might get bulged into the space between the O-ring supporting portion and the inserted pipe end. This entails a risk of the O-ring getting damaged between the O-ring supporting portion and the inserted pipe end during the pressing action. When pressurized, the rubber of the O-ring behaves like a fluid, because of which the O-ring might even get blown out of its aimed sealing position if the space between the O-ring supporting portion and the inserted pipe end is too large during the compression or remains too large in the compressed state. It is noted that it is not possible to reduce the radial space between the O-ring supporting portion and the inserted pipe end far enough for those negative effects to no longer be able to occur. Because the O-ring supporting portion and the stopper portion are combined into one single integral component, a reduction of the inner diameter of the O-ring supporting portion would immediately have a negative limiting impact on the maximum compressibility of the teeth of the stopper portion. Those teeth then may be prematurely stopped from getting further compressed and thus may be unable to bite sufficiently far into the inserted pipe end during a pressing action. Furthermore, it is noted that the stopper grip ring is difficult and expensive to manufacture.

The present invention aims to at least partially overcome the above disadvantages or to provide a usable alternative. In particular the present invention aims to provide a user-friendly reliable press fitting which is able to provide a predictable and reliable deformation behaviour during a pressing action.

This aim is achieved by a press fitting according to claim 1. The press fitting comprises a socket with an insertion space for having a pipe end inserted therein. The insertion space has a press region which is delimited by a substantially cylindrical press wall part. An annular groove-shaped space is present in the press wall part. A sealing ring, a spacer ring and a gripping ring are placed in the annular groove-shaped space. The spacer ring is made as a separate distinctive component, that is not integral with the gripping ring, making it possible for the spacer ring and gripping ring to independently move/deform from each other. The spacer ring preferably lies in between the sealing ring and the gripping ring. The press wall part is configured such that it is deformable from a non-compressed state towards a compressed state during a radially inward directed pressing action which causes the press wall part to get radially compressed, which in turn causes the gripping ring to grip onto or into an inserted pipe end while the sealing ring comes to lie or remains to lie sealing against this inserted pipe end. According to the inventive thought the spacer ring is a helical wound split ring which has at least partially overlapping windings which lie adjacent each other. The at least partially overlapping windings are able to increase their overlap by means of the windings starting to slide along and/or over each other, when the spacer ring gets radially compressed during the pressing action. Because the overlaps of the windings are able to increase, the diameter of the spacer ring is able to decrease. The height of the windings is such that in the compressed state the helical wound split ring lies with radially inner circumferential edge parts of its windings substantially against an inserted pipe end and with radially outer circumferential edge parts of its windings substantially against the press wall part. Thus, in the compressed state, the windings together form a blocking wall inside the press region by fully extending in between the pipe end and the press wall part. The increasable overlap between the windings while being able to form a blocking wall inside the press region offers important advantages to the pressing behaviour of the press fitting as well as for the reliability of the fitting during use. First of all, the helical wound split spacer ring now is able to truly follow the compression of the press wall part without getting damaged itself. The spacer ring no longer gets forced to start deforming in a rather unpredictable manner. It simply can reduce its diameter along with the reducing press region during a pressing action of the press fitting. This has the advantage that the spacer ring both in the non-compressed state as well as in the compressed state, can keep on limiting a uniform space for the sealing ring to lie inside.

Should the sealing ring for whatever reason get damaged during use, for example get burned in a fire, then the helical wound split spacer ring advantageously is well able to prevent large blow outs of transported media via the press region. This is because owing to the present invention it can be obtained that the helical wound split spacer ring, in the compressed state, lies both substantially all around against an inner circumferential wall of the press wall part as well as substantially all around against an outer circumferential wall of an inserted pipe end. This makes the press fitting for example optimally usable in a gas installation or the like, where a certain degree of closure/sealing now can be maintained under all circumstances by the spacer ring, even when the sealing ring may have been burned away.

Secondly, the helical wound split spacer ring makes it possible to easily place it inside the groove-shaped space of the press fitting. During assembly it is advantageously possible to temporarily reduce the diameter of the spacer ring in order to have it pass by for example a radially inwardly projecting edge which delimits the groove-shaped space at its axial outer end. Finally it is noted that the overlapping windings add axial stability to the spacer ring.

The press fitting according to the invention has the pressing action exerted by a pressing tool. This pressing tool gets placed around the press fitting merely during the pressing action itself and gets removed again from the press fitting as soon as the compressed state has been achieved. Furthermore the press fitting according to the invention has the pressing action result in a plastic deformation of the press wall part, such that it is able to maintain the compressed state of the press fitting, including that of the gripping and spacer ring, after the press tool has been removed again as soon as the compressed state has been achieved.

It is noted that EP 0 551 582 shows a collar fitting for connecting two pipe ends to each other, which makes use of a permanently tensioned external collar clamp for maintaining a locked state. Such a collar fitting is different from the press fitting according to the invention. In particular it does not make use of plastic deformation, but of a contractible tensionable collar clamp. As soon as the collar clamp gets released again, the various components of the fitting release back to their original shapes and the inserted pipe ends can be taken out of the clamp again. It is further noted that although this known collar fitting comprises support rings in between the sealing ring and two gripping rings, it is unable to prevent large blow outs of transported media, should its sealing ring get damaged or burned. It is not foreseen or possible for the support rings to, in the locked state, form a blocking wall between the inserted pipe ends and the collar clamp. For example, the contractible collar clamp is not and cannot be circumferentially closed, but has a large angular spacing of more than 60 degrees between its outer ends. Should this angular spacing not be foreseen then it would be impossible to sufficiently tension the collar clamp from a released state towards its locked state and vice versa. The sealing ring thus is the one and only component that is able to perform a sealing function between the two pipe ends in this type of collar fitting. Should the sealing ring get damaged or burned, then no sealing at all would be accomplished.

In a preferred embodiment according to the present invention the helical wound split spacer ring is made out of a spring material, in particular spring steel. This makes it able to have the diameter of the helical wound split spacer ring temporarily reduced during assembly of the spacer ring into the groove-shaped space, while having it automatically spring back radially outwards into the groove-shaped space after being released again. In this assembled non-compressed state, the helical wound split spacer ring preferably has an inner diameter which is larger than the outer diameter of the pipe end to be inserted. Thus the pipe end is not blocked by it during insertion.

In a further preferred embodiment the helical wound split ring of spring material is dimensioned such that the windings in the non-compressed state lie biased with outer circumferential edge parts substantially against the press wall part. This can be obtained by manufacturing the helical wound split spacer ring with an outer diameter which is larger than the outer diameter of the groove-shaped space which is delimited by the press wall part.

This has the advantage that the helical wound split spacer ring, after being released again during assembly, automatically springs back to a to a position in which it comes to lie biased against an inner circumferential wall of the press wall part. During a subsequent pressing action, the radially outwards directed biasing force of the helical wound split spacer ring in the groove-shaped space helps to keep it lying substantially sealing against the press wall part.

The helical wound split spacer ring can be made out of all kinds of materials, for example plastic or metal. In a preferred embodiment the helical wound split spacer ring is made out of metal. This gives the split spacer ring sufficient rigidity to keep the sealing ring properly separated from the gripping ring. At the same time it helps to make the press fitting sufficiently resistant to excessive heat, like in the case of fire.

In a particular embodiment the windings in the compressed state lying with radially inner and radially outer circumferential edge parts substantially against an inserted pipe end and press wall part respectively, is obtained by choosing the height of the windings such that this winding height results in an aimed initial radial play between the windings and an inserted pipe end in the non-compressed state, over which aimed initial play the press region can subsequently be compressed from the non-compressed state towards the compressed state.

In a variant or in addition thereto, individual cross sectional profiles of the overlapping windings can be made elastically deformable inwards in the radial direction. In particular this can be done by providing each winding with a suitable cross-sectional profile. This makes it possible, to not only have the windings increase their overlap during the pressing action and thus decrease the radius of the entire ring, but also to have the individual windings get elastically radially deformed and thus decrease their radial height dimensions. The elastic radial deformation of the individual windings offers an important advantage. As soon as the pressing action has ended, the press region shall have a tendency to slightly spring back. The individual windings are now able to easily follow this relaxation by springing back. This can now easily be followed by the individual windings also springing back radially outwards, owing to the amount of elastic deformation which they received during the pressing action. Thus the ring keeps on lying neatly biased with outer circumferential edge parts substantially against the press wall part, even when the pressing force is taken away after the pressing action has been completed. During a first stage of the pressing action, the press wall part gets pushed against radial outer edges of the windings. The windings then shall start to slide along each and/or over each other, until the ring gets pushed with a radial inner edge against the pipe end. Then during a second stage of the pressing action, the cross-sectional profiles of the windings get elastically deformed in the radial inwards direction. When subsequently the pressing action is ended, the press region may spring slightly back to a larger radial dimension, while at the same time the cross-sectional profiles of the windings also may spring slightly back to a larger radial dimension.

This cross-sectional profile for example can comprise slanted, curved or bend parts.

In the embodiment with the slanted parts, the helical wound split ring may have a dish-shape of which the windings extend slanting relative to the radial and axial direction. This is relative cheap and simple to manufacture, and has deformation behaviour during the pressing action which is well predictable. The dish-shaped spacer ring is particularly advantageous because it is able to tilt during the pressing action. This helps to prevent that the pressing force that is required for the pressing action could become too high. The inner and outer circumferential edge parts do not need to start biting themselves into the pipe end and press wall part as soon as the spacer ring has come to lie with its inner and outer circumferential edge parts against the inserted pipe end and press wall part respectively owing to a sliding of its windings over one another. Instead the spacer ring then is able to start tilting by increasing its angle relative to the radial direction, thus making it possible for the press wall part to get compressed further until its aimed compressed state has been achieved. Should this tilting during the second part of the compression not be possible, then this could otherwise have led to a large increase in the required pressing force. The required pressing force then even might have become larger than possible for the press tool to deliver, which would have led to the pressing action not getting completed and the compressed state not being sufficiently attained. This could then have led to a bad connection between the press fitting and the pipe end, and might even have led to leakages starting to occur or the fitting to collapse.

In a further embodiment the windings preferably extend slanting relative to the radial direction under an angle of less than 45°, in particular between 5-15°, more in particular about 10°. This has appeared to provide the desired tilting behaviour for the spacer ring.

In the embodiment with the curved or bend parts the elastic radial deformation behaviour can be achieved by having free inner and outer ends of those curved or bend parts get pushed somewhat towards each other during the pressing action causing the curvature or bend to get elastically flattened somewhat.

In an embodiment the helical wound split ring is made out of substantially flat strip material, in particular metal strip. This makes it possible for the windings to form a blocking with a substantial uniform wall thickness which delimits the sealing ring at one side. Also it helps for the respective windings to more easily slide along and/or over each other during a pressing action. If desired the windings can even be provided with a suitable friction reducing coating for this.

The overlapping windings preferably lie against each other in a sideways axial direction, independent of the amount of compression which it is given. This gives the helical wound split spacer ring sideways stability during pressing and during use.

In a particular embodiment outermost ones of the windings have been given an initial overlap in the non-compressed state inside the groove-shaped space such that after being compressed towards the compressed state they have received an overlap of between substantially 10-100%. This advantageously prevents the ring from getting too thick during compression, while at the same time it gives the split spacer ring sufficient rigidity and freedom to increase its overlap during the pressing action.

The split spacer ring can have a plurality of windings. In order to keep its total thickness minimized, the helical wound split ring in the non-compressed state preferably comprises less than two windings and/or has a thickness for each of its windings in the axial direction of at most 1 mm, in particular at most 0.7 mm.

The windings can be given all kinds of overlaps. In order to give it sufficient freedom to get compressed before reaching a full overlap in the compressed state, outermost ones of the windings may be given an initial overlap in the non-compressed state of at most 90%. In order to give it sufficient freedom to get assembled without becoming in a situation of less than zero overlap, outermost ones of the windings may be given an initial overlap in the non-compressed state of at least 10%.

In a variant the annular groove-shaped space at its outer end is delimited by a substantially continuous radially inwardly projecting edge of the press wall part, in particular one which has been made integral therewith. This is advantageously possible owing to the fact that the split spacer ring can easily be reduced to a smaller diameter in order to be able to pass by such an edge during assembly into the groove-shaped space. The substantially continuous radially inward projecting edge makes the enclosing of the rings inside the groove shaped space stronger and is well able to remain intact without turning over even for large diameter press fittings and/or for high pressure use.

Advantageously a cross-sectional height of the windings in the radial direction is chosen to be substantially equal to a cross-sectional height of the gripping ring in the radial direction. In this way it can be guaranteed that the spacer ring during its deformation towards the compressed state can quickly come and maintain to lie against the pipe end and press wall part with its circumferential edge parts.

Further preferred embodiments are stated in the dependent subclaims.

The invention also relates to an assembly of the inventive press fitting and an inserted pipe end, as well as to a method for pressing the inventive press fitting.

The invention shall be explained in more detail with reference to the accompanying drawings, in which: - Fig. 1 is a schematic perspective view of a press fitting according to the invention in a non-compressed state having a pipe end inserted therein and part of a pressing tool distanced from the fitting; - Fig. 1 a is a partially cut-open view of fig. 1; - Fig. 2 is a sectional view of fig. 1 with the part of the pressing tool ready for pressing; - Fig. 2a is an enlarged partial view of fig. 2; - Fig. 3 shows the assembly of fig. 1 with a socket of the press fitting shown in a sectional view with only a spacer ring shown in a groove-shaped space of a pressing region; - Fig. 4a-e show a perspective, side, front, cross-sectional, and enlarged partial cross-sectional view of the spacer ring of fig. 2-3; - Fig. 5 is a view according to fig. 2 in a compressed state; - Fig. 5a is an enlarged partial view of fig. 5; - Fig. 6 is a view according to fig. 3 in the compressed state; - Fig. 7 is an exploded view of the press fitting; - Fig. 8 shows a first variant of the spacer ring in a perspective, side and enlarged partial cross-sectional view; and - Fig. 9 shows a second variant of the spacer ring in a perspective, side and enlarged partial cross-sectional view.

The press fitting comprises a steel socket which has been given the reference numeral 1 in fig. 1-7. The socket 1 comprises an insert region 2 and a press region 3. A pipe end 4 has been inserted into an insertion space of the insert and press regions 2, 3.

The insert region 2 is delimited by a substantially cylindrical insert wall part 7 which has an inner diameter Dir which is slightly larger than an outer diameter Dpe of the pipe end 4, such that the pipe end 4 could be easily inserted therein until it came to abut against an abutment edge 8.

The press region 3 is formed by a substantially cylindrical press wall part 10. This press wall part 10 forms a widened section relative to the insert wall part 7. Inside the press wall part 10, a groove-shaped space 11 is present. See in particular fig. 2 and 3. The groove-shaped space 11 has been manufactured in the press wall part 10 by means of a machining operation in which metal has been removed from the inside of the press wall part 10. With this the press wall part 10 before machining had a substantially same wall thickness as the insert wall part 7, but after machining has a reduced wall thickness compared thereto. The machining operation has been performed over almost the entire length of the press region 3. Only at the free end of the press region 3 the machining operation has not taken place such that a radially inwardly projecting edge 12 is formed there. This edge 12 delimits the groove-shaped space 11 towards a free end of the socket 1. At an axial inward side the groove-shaped space 11 is delimited by a transitional wall part 14 which extends between the insert wall part 7 and the press wall part 10.

In the groove-shaped space 11 a sealing ring 16 and a gripping ring 17 are placed. A separate distinctive spacer ring 18 is placed in between the sealing ring 16 and the gripping ring 17. Furthermore a check ring 19 has been clicked onto the gripping ring 17.

The sealing ring 16 here is formed by an O-ring with two radially inwardly projecting circumferential ridges 16’. Between those ridges 16’ a concave hollow is present. The ridges 16’ give the sealing ring 16 sideways stability against rolling during assembly. Furthermore they make it possible for the sealing ring 16 to properly seal against irregularities which might be present on the inserted pipe end 4. Finally they give the sealing ring 16 more volume compared to a conventional O-ring and thus more stability and sealing capacities.

The gripping ring 17 is equipped with two rows of pairs of grasping teeth 17’. Each pair has oppositely slanting grasping teeth 17’. The grasping teeth are slanted outwards away from each other. This has the advantage that the most important row of teeth 17’, that is to say the one which points slanted inwards and thus needs to prevent that the pipe end 4 can be pulled out of the socket 1, lies at a greater distance of the free outer end of the socket 1 compared to the other row of teeth 17’, that is to say where the socket 1 is stronger.

According to the invention the spacer ring 18 is formed by a helical wound split spacer ring. In the embodiment shown, the split spacer ring 18 in a non-compressed state has approximately 1.75 windings, that is to say one full winding which overlaps sideways with an approximately three quarter winding (about 75% overlap). The split spacer ring 18 is made out of steel spring strip material having a height h of a few mm and a thickness t of between about 0.2-0.8 mm. The overlapping windings lie flat against each other in an axial sideways direction. The split spacer ring 18 is able to reduce its inner and outer diameter Dsri and Dsro by having its windings slide along each other such that the amount of overlap is increased.

The split spacer ring 18 here is formed with a dish-shape, that is to say its windings extend slanting under an angle a relative to the radial direction. This angle a here is a sharp angle of less than 45°, in particular about 10°.

The press fitting with the pipe end 4 inserted therein is shown in fig. 1-3 in its non-compressed state. In this non-compressed state, inner diameters of the sealing ring 16, gripping ring 17, split spacer ring 18 and check ring 19 are slightly larger than an outer diameter Dpe of the pipe end 4, such that the pipe end 4 could be easily inserted therein until it came to abut against the abutment edge 8. In the embodiment shown, the split spacer ring 18 in this non-compressed state lies with its outer circumferential edge parts free from the machined press wall part 10. It may however also lie somewhat pre-biased against it.

The press region 3 of the press fitting of fig. 1-3 can now be compressed from the non-compressed state into the compressed state by means of a press tool 22. This press tool 22, of which only a part has been schematically shown in fig. 1 and 2, is designed to exert a radially inward directed pressing action on the outer side of the press wall part 10. Because of this the press wall part 10 starts to deform and gets radially compressed to a smaller diameter. This can clearly be seen when comparing fig. 2 and 5 resp. 3 and 6. In the compressed state the gripping ring 17 has gotten to grip with its grasping teeth 17’ into the pipe end 4. The sealing ring 16 has gotten deformed such that it substantially fills up the entire space between the pipe end 4, the transitional wall part 14, the press wall part 10 and the spacer ring 18.

Furthermore, during the deforming of the press region 3, the windings of the split spacer ring 18 have increased their overlap. In the situation shown in fig. 5-7 this overlap has become about 80%. Owing to the increasing overlap, the inner and outer diameter Dsri and Dsro of the split spacer ring 18 have decreased during the pressing action. Owing to the decreasing inner and outer diameter Dsri and Dsro, the split spacer ring 18 in the compressed state has come to lie biased against both the pipe end 4 and the press wall part 10.

Furthermore, during the last stage of the deforming of the press region 3, the windings of the spacer ring 18 may have been forced to tilt towards a larger angle a. This elastic deformation causes the individual windings to lie even more biased against both the pipe end 4 and the press wall part 10.

As soon as the pressing tool 22 is removed at the end of the pressing action, the press wall part 10 is deemed to undergo a slight amount of relaxation. Owing to the two-fold biasing forces inside the spacer ring 18, the windings advantageously are able to slightly spring back and thus keep on substantially lying both against the pipe end 4 and the press wall part 10.

In fig. 5 it can be seen that the check ring 19 during the pressing action gets divided in three distinctive parts 26, 28 and 32. Together they make it able to perform a visual check that the pressing action indeed has been properly performed.

In fig. 8 a variant of the split spacer ring has been shown in which the windings have been formed with a gutter-like kinked or bended cross-sectional shape of which the gutter opens out sideways in the axial direction. This shape also makes the cross-sectional profiles of the overlapping windings elastically deformable in the radial direction during the pressing action. For similar reasons fig. 9 shows a variant with a gutter-like curved cross-sectional shape for the windings of the split spacer ring.

Besides the embodiments shown numerous variants are possible. For example the types, shapes and dimensions of the sealing ring and gripping ring can be changed. Instead of the split spacer ring having between one and two overlapping windings, it is also possible to provide it with more windings of which only the outermost ones need to increase their overlaps during a pressing action. The split spacer ring can also be given other cross sectional shapes and dimensions, and can be made out of other materials. Instead of the groove-shaped space being machined into the socket it can also be formed by a widened wall part with an inwardly flared outer edge. The socket can be closed at the side of the insert region, or be provided with means for connecting a pipe end or the like thereto. For example it can also be equipped with a second set of a press and insert region according to the invention for inserting and connecting another pipe end thereto in a similar manner as described above. The gripping ring can also be provided with other means for gripping into or onto the pipe end, and for example may also comprise merely one row of grasping teeth or the like.

Thus the invention provides a press fitting which can easily be assembled and which after a pipe end has been inserted into it, can easily and reliably be pressed into a compressed state in which not only the sealing ring but also the split spacer ring add in properly sealing the socket relative to the pipe end and keeping it sealed.

Claims (16)

A compression fitting for pipes, comprising: a sleeve (1) with an insertion space for inserting a pipe end (4) therein, the insertion space having a pressing area (3) bounded by a substantially cylindrical pressing wall part (10); an annular groove-shaped space (11) provided in the pressing wall portion (10); and a sealing ring (16), a spacer ring (18) and a gripping ring (17) disposed in the annular groove-shaped space (11), the pressing region (3) being plastically deformable from a non-compressed state to a compressed state during a radially inwardly directed pressing action exerted by a pressing tool (22) which causes the pressing wall part (10) to compress radially and the gripring ring (17) grips a inserted pipe end while the sealing ring (16) sealingly abuts against the inserted pipe end (4) wherein the spacer ring (18) has at least partially overlapping windings that increase their overlap when radially compressed during the pressing action such that an inner and outer diameter (Dsri, Dsro) of the spacer ring (18) decreases, characterized in that the spacer ring (18) is a helically wound split ring that is separate from the grip ring (17), the windings having a height in the radial direction that is arranged such that, in the compressed state, the helically wound split ring is capable of substantially peripheral edge portions of its windings with radially inner and radially outer edges of a wound pipe end (4) or pressing wall part (10) for the joint by forming the windings of a blocking wall within the pressing area (3) by fully extending between the tube end (4) and the pressing wall part (10) in the compressed state. 2. Press fitting as claimed in any of the foregoing claims, wherein the helically wound split ring is made from a spring material, in particular spring steel. 3. Press fitting as claimed in claim 2, wherein the helically wound split ring is dimensioned such that the windings with circumferential edge parts located in radial direction lie substantially resiliently against the pressing wall part (10). 4. Press fitting as claimed in any of the foregoing claims, wherein cross-sectional profiles of the overlapping windings are elastically deformable in the radial direction during the pressing action. The press fitting of claim 4, wherein the helically wound split ring has a dish shape whose windings are inclined with respect to the radial and axial directions. Press fitting according to claim 5, wherein the windings extend obliquely with respect to the radial direction at an angle of less than 45 °, in particular between 5-15 °, more in particular approximately 10 °. Press fitting as claimed in any of the foregoing claims, wherein the screw-wound split ring is made from a substantially flat strip material, in particular metal strip. A press fitting according to any one of the preceding claims, wherein the overlapping windings abut each other in an axial direction. The press fitting of any one of the preceding claims, wherein outer windings have an initial overlap in the non-compressed state of at least 10%. 10. Press fitting as claimed in any of the foregoing claims, wherein the helically wound split ring comprises in the non-compressed state between one and two windings. A press fitting according to any one of the preceding claims, wherein each winding has a thickness of at most 1 mm. A press fitting according to any one of the preceding claims, wherein the annular groove-shaped space (11) is bounded at its outer end by a substantially continuous edge (12) of the press wall part (10) protruding in radial direction. A press fitting according to any one of the preceding claims, wherein a cross-sectional height of the windings in the radial direction is substantially equal to a cross-sectional height of the gripping ring (17) in the radial direction. Assembly of a press fitting according to one of the preceding claims and a pipe end inserted therein. Method for pressing a press fitting according to one of the preceding claims, comprising the steps of: inserting a pipe end (4) into the insertion space of the sleeve (1); plastically deforming the pressing area (3) from a non-compressed state to a compressed state by means of a radially inwardly directed pressing action exerted by a pressing tool (22) which causes the pressing wall part (10) to compress in the radial direction and the gripring (17) engages the inserted pipe end (4) while the sealing ring (16) is sealingly abutting against the inserted pipe end (4), wherein, during deformation of the pressing area (3), the at least partially overlapping turns of the spacer ring (18) ) increase their overlap such that an inner and outer diameter (Dsri, Dsro) decreases from the spacer ring (18), and wherein the press fitting becomes deformed to the compressed state such that the helically wound split ring with radially inner and radial direction outer peripheral edge portions of its windings substantially abut against the inserted pipe end (4), respectively k press wall part (10). A method according to claim 15, wherein cross-sectional profiles of the windings become elastically deformed during deformation of the pressing area (3).