Joint for connecting pipes .

The present invention relates to a joint for connecting pipes composed of a body provided at least at an end with an outer thread; a cylindrical seat for inserting the pipe inside said body; a ring nut intended to be screwed at the end of said body on the thread, said ring nut being provided with an inner conical surface; at least a clamping ring with an outer shell surface that is at least partially conical and intended to cooperate with the inner conical surface of said ring nut and which ring internally has teeth intended to grip the end of the pipe inserted in the joint and said ring having the possibility of being tightened by means of a radial restriction caused by the ring nut being screwed on the body, at least a seal between the cylindrical seat of the joint and the outer wall of the pipe. Joints of this type are known and widely used.

The joint is assembled and then tightened on the pipe generally according to the following sequence of steps:

According to a first step, the pipe is introduced into the joint which is in its pre-assembly condition and with the tightening ring nut already screwed on the thread. The tightening ring nut is in an initial screwing condition wherein the clamping ring is not compressed against the pipe for clamping it into the joint yet, while the seal has such a diameter to allow

the pipe to slide inside it generating a frictional resistance that can be easily overcome by a manually applied force. Therefore the pipe can slide inside the clamping ring and the seal being brought in the proper coupling position into the joint body.

Once the pipe has reached the complete coupling position, it is mechanically clamped by screwing the tightening ring nut acting on the clamping ring by means of respective conical surfaces . In some cases , it can be also provided for the tightening ring nut to exert an axial compression on the seal by means of the axial movement along the joint body that is transmitted to the clamping ring and in this case it acts also as seal pushing means . In all above mentioned variants , the inner conical surface of the ring nut is pushed to contact the conical surface of the end of the clamping ring so when the ring nut is screwed the axial advance of the ring nut causes a radial constriction of the clamping ring gripping the pipe wall by a series of conical inner teeth due to the relative sliding motion of two conical surfaces of the above mentioned two parts .

Although these joints serve their function in a satisfactory way, they have some drawbacks, particularly when the joint is inserted and clamped on the pipe .

Joints for pipes commercially available, have a type of clamping ring, whose inner diameter is slightly smaller than the outer diameter of the pipe therefore said ring is elastically deformed, i.e. it is slightly

widened, when the pipe is inserted in the joint and such deformation causes an intrinsic force for the elastic returning action in the original/not stressed position to be generated by means of which, inner teeth of the ring, by gripping the outer surface of the pipe allow the ring to be firmly tightened thereon.

The above clamping ring carries out its function by its physical structure/shape, being composed of a ring, usually a plastic one, having an axial open slot at both head sides.

Therefore the clamping ring is inserted by forcing it on the pipe and this leading to: both a certain difficulty for inserting the pipe in the joint, and the fact that, when the pipe is taken out from the joint, such ring remains clamped on the pipe, since the gripping action of teeth thereof does not allow the ring to slide on the outer surface of the pipe, towards the end thereof housed in the joint.

Therefore for removing the clamping ring from the pipe, it is necessary not only to unscrew the ring nut from the body and to take off the pipe with the ring still gripped thereon, but it requires an external operation by the user, i.e. the application of a certain force, particularly intended for widening the ring. Said force has to be applied between the two ends of the ring generated by the axial slot in order to oppose and overcome the elastic return force that, on the basis also of the size of the pipe and consequently of the thickness of the clamping ring, can be difficult to be opposed by the user. In addition to this there is

also the fact that even only the simple gripping action for applying a sufficient force is difficult, the axial slot being somewhat narrow, and it is often necessary the help of some tools for levering the two ends of said slot.

A further drawback of joints actually on the market, is the fact that the clamping action by the ring on the pipe cannot be easily reproduced. This drawback, is caused by two facts: the first one is that the ring is clamped on the pipe by two forces: an intrinsic elastic return force, previously described, that can clamp the ring on the pipe in a wrong position, and a tightening force by the radial restriction deriving from the tightening/pressing action determined by screwing the ring nut on the body. The second fact is that due to the coupling action the clamping ring/ring nut that is generally made with a conicity of about 8-10 degrees causes also a very high screwing length on the body. That causes also high positioning allowances between the ring nut, the clamping ring, the pipe and the body with a low repetitiveness of the same relative position of said parts in the optimal condition tightening and clamping the pipe. Therefore it is not possible to provide effective references for the right positioning for screwing the ring nut on the body and the pipe can take various positions for the axial insertion in the body in various possible clamping conditions, pipes being also variable in their outer diameter even if within specific tolerances regarding both size and

ovalization.

By screwing the ring nut on the body the conical inner surface of said ring nut interacts with the conical outer shell surface of the clamping ring, and such interaction causes the ring to be tightened, consequently leading to a more firm clamping action of the ring on the joint. However the above tightening action, deriving from the ring nut being screwed, as it is easy to understand, depends on how much such ring nut is screwed on the body, and consequently, it is a force that depends directly on the sensitiveness of the person using the joint, which is a characteristic fully subjective as it can be obviously understand.

The angle of inclination of conical walls with respect to the central axis of the cone defined by said conical walls defines the travel of the ring nut necessary to tighten the pipe in its clamped condition. An acute angle, so wherein the conicity is relatively small, i.e. conical surfaces are slightly inclined with respect to the central axis of the cone defined by said conical walls results in a relatively low torque for screwing the ring nut, but the travel necessary for obtaining a sufficient tightening action is relatively long so the ring nut has to be turned a lot of time when screwing it.

The increase in the conicity and so in the inclination of conical walls with reference to above mentioned definitions of said inclination results in a shorter tightening travel, but a greater tightening torque is necessary.

Therefore the choice of the inclination is generally a compromise in comparison with joint functionalities .

On one hand the fact of having the highest tightening and so clamping effect of the pipe into the joint is desired, but without the need of a too high effort being possible to exert it even only manually for a large range of pipe diameters, and i.e. without using tools . Concerning the conical shape, for such reasons as mentioned above the clamping action of the ring on the pipe cannot be perfectly reproduced thus leading to the fact that often the joint does not work in its optimal conditions . Under strong pressures of the fluid and/or pulling actions on the pipe, prior art joints do not guarantee the pipe to be retained inside the joint in the sealing condition. When the fluid pressure is very high or when a pulling action is exerted on the pipe for withdrawing it from the joint, the pipe can slide into the joint to a position wherein the sealing action of the seal fails and possibly the force acting on the pipe can cause the pipe to be withdrawn out of the joint by causing it to be also mecahnically released from the tightening action of the clamping ring.

The aim of the present invention is to provide a joint for connecting pipes able to overcome in a simple and inexpensive way above drawbacks of commercially used joints, by making the joint behaviour as an optimal one both as regards the fact of being able to

reproduce optimal tightening conditions and as regards an effective retaining action in opposition to forces acting for withdrawing the pipe from the joint.

The invention achieves the above aims by providing a joint whose clamping ring has an intrinsic elastic force for firmly maintaining a condition wherein its inner diameter is slightly greater than the outer diameter of the pipe or however it is such that the latter can be inserted by an axial sliding action without any impediments in the clamping ring, and said clamping ring can be elastically deformed narrowing the inner port delimited by the ring against the action of said elastic force in a condition with the diameter reduced with respect to the diameter in its resting condition, at such an extent that teeth of the ring grip the outer surface/wall of the pipe by firmly clamping it inside the joint, said reduction being generated by the action of the conical surface of the ring nut on the conical surface of the clamping ring, while the conical surface of the tightening ring nut at the end having the shortest diameter, ends by a step annular shoulder abutting against the corresponding head end of the clamping ring.

By such characteristic, the axial pushing force is shared not only by the conical surface of the ring nut, but also on a surface perpendicular to the axis . Thus the stress of the conical surface is partially relieved and the ring nut can be made with a wall having a shortest thickness. Advantageously the clamping ring has a radial

abutment shoulder cooperating with a corresponding opposite radial abutment surface of the tightening ring nut at the two ends of the conical surface, that is of the end having shortest diameter and greatest diameter. The distance between radial abutment shoulders provided on the clamping ring and corresponding annular abutment surfaces of the ring nut is the same, the inner shortest diameter and the inner greatest diameter of the conical portion of the ring nut, the shortest outer diameter and the greatest outer diameter of the conical portion of the clamping ring and the inner diameter of the clamping ring being such that, with the ring nut in its screwed condition, which screwing condition corresponds to the condition with the clamping ring tightened on the pipe and to a condition with the pipe tightened into the joint body thus generating the sealing action, radial abutment shoulders provided on the clamping ring and corresponding annular abutment surfaces of the ring nut are spaced apart, so when into the pipe there are high pressures of the fluid the clamping ring being grasped to the pipe is dragged by it more and more against the ring nut cone increasingly grasping the pipe during its longitudinal sliding and contemporaneous clamping travel till stopping said travel contemporaneously with annular radial abutment shoulders against the two annular abutment surfaces of the ring nut.

By the above arrangement, in said condition wherein the pipe moves in the withdrawing direction, dragging the clamping ring in the position abutting the

annular radial abutment shoulders against the two annular abutment surfaces of the ring nut, due to the fluid pressure or to a pulling action for withdrawing the pipe, the further grasping action caused by cooperating conical surfaces and by the fact that the clamping ring is inserted deeper between the conical surface of the ring nut and the outer shell surface of the pipe is enough for preventing the pipe from being withdrawing anyway from the clamping ring therefore the further pulling effect of the pipe can be taken up by the two radial abutment shoulders leading to advantages of a lower thickness of the ring nut.

The outer conical surface of the clamping ring has the same inclination or an inclination consistent with the inner conical surface of the ring nut with which it interacts when it is screwed on the joint body.

According to a further characteristic of the present joint the clamping ring on its inner surface, at the end intended to clamp the pipe in the joint, has one or more teeth that make one or more series of crowns of teeth.

A first advantageous embodiment of the present invention, provides mutual abutting conical surfaces and that is the inner one of the ring nut and the outer one of the clamping ring provided at the end thereof outside the seat of the pipe in the body of the joint, to have a relatively abrupt inclination and comprised between 10 and 18°, preferably about 15°. By this relatively abrupt inclination of the conical surface, (corresponding to an opening angle of the cone of 30°)

it is possible to obtain a sealing tightening of the joint on the pipe by a screwing rotation of the ring nut of about one turn. This is particularly advantageous as regards the speed of intervention especially under uncomfortable working conditions . Obviously the short rotation of one turn is also for loosening the joint from the tightened condition of the pipe to freely take out the pipe from the joint.

According to a further characteristic of the present joint there is provided a seal of the pipe inside the joint, which seal is housed in a suitable seat obtained inside the body, and in the resting condition, i.e. with the joint not tightened on the pipe, it has an inner diameter greater than the outer diameter of the pipe or substantially equal to the outer one of the pipe said inner diameter of the seal being such that it allows the pipe to be freely slidably inserted in the joint without any impediments, while with the joint tightened on the pipe, caused by the ring nut screwed on the body, said seal is elastically deformed such that its inner diameter is smaller than the outer diameter of the pipe so that in said deformed conditions it tightly adheres against the outer surface of the pipe, guaranteeing the desired hydraulic sealing effect, while when the joint is released from the pipe, said seal has such an intrinsic elasticity that it elastically recovers its original resting shape spontaneously due also to the particular conical shape of the sealing seat tending to refuse the seal from being retained into the seat and partially

due to the dragging action of the pipe when it is taken out from the joint and under said condition it allows the pipe to slide in the direction for taking it out from the joint without interfering with said seal such to avoid undesired frictional effects .

According to an advantageous characteristic, the clamping ring cooperates with a pushing ring axially interposed between the axial end of the clamping ring faced towards the seal and said seal and which pushing ring has an head side abutting against the head surface of the clamping ring and an annular surface axially compressing and pushing the seal provided at the opposite head side of the pushing ring.

Advantageously the pushing ring at the head side faced towards the clamping ring has an outer radial shoulder abutting with an annular abutment surface of the ring nut, said annular abutment shoulder of the pushing ring and the cooperating annular abutment surface of the ring nut being provided in an axial position with respect to cooperating head sides of the clamping ring and pushing ring, so that when the ring nut is screwed on the body, the clamping ring is pushed with its head side faced towards the pushing ring abutting the opposite head side of the pushing ring and the abutment surface of the ring nut intended to cooperate with the annular abutment shoulder of the pushing ring contact each other and after completely screwing the ring nut up to the abutment the o-ring seal axially and radially moves from the preassembling seat to the sealing seat and the grasping ring clamps

the pipe for obtaining its first mechanical clamping on the pipe, therefore the fact of completely screwing the ring nut up to the abutment causes the pipe to be completely hydraulically and mechanically sealed into the joint.

In order to guarantee a univocal and repeatable complete screwing position of the ring nut corresponding to the pipe in its optimal tightening condition both as regards the mechanical clamping point of view and the sealing point of view, the body and the ring nut are provided with cooperating limit stops for screwing the ring nut.

Such screwing limit stops are composed of one or more surface abutment projections constituting indicators and/or limiting means of the screwing travel of the ring nut on the body, which indicators and/or limiting means allow the user of the joint to tighten the ring nut on the body such to always guarantee the optimal operation of the joint. According to a preferred embodiment of the present joint the body can be provided with means for temporary positioning and retaining the ring nut partially screwed on the joint body and wherein the pipe can be inserted into the joint through the ring nut, the clamping ring and the seal that, under such partial screwing condition, have an inner diameter greater than or substantially equal to the one of the pipe and being such to allow it to freely pass through, which means retain the ring nut under said partial screwing condition in a temporary way and by means of a force

that can be manually overcome .

According to a preferred embodiment, said means are composed of at least a radial projection in the trajectory corresponding to the peak of an outer thread of the coupling union for the pipe, which projection can be elasically deformed by a predetermined manual force and which projection cooperates with engaging nothces or grooves provided at the head side of the tightening ring nut faced towards the joint body. Advantgeously, said projection or projections have a protrusion slightly greater than the depth of grooves of the inner thread on the tightening ring nut, therefore the engaging interaction of said projection or projections is in the area of the head side of the tightening ring nut, while once said projections penetrate into the ring nut thread they freely move into grooves of said inner thread being elastically bent and resulting in a slight friction.

Again according to a further characteristic of the invention that can be provided as an alternative or in combination with one or more of previous characteristics, the joint of the present invention is provided with anti-rotational means preventing the ring nut from being unscrewed once it reaches the predetermined tightening stop position.

In this case said anti-rotational means are composed of one or more radial teeth having the front faces faced towards the ring nut at a radial plane that is slightly upstream than the radial plane where the head side of the tightening ring nut faced towards the

joint body falls once the ring nut is in the final tightening position, said radial anti-rotational tooth or teeth being engaged in corresponding recesses or nothces provided in the head side of the tightening ring nut, said teeth being provided beyond the end of the threaded portion.

Particularly anti-rotational teeth have a lower elastic deformability than projections temporary positioning and retaining the ring nut in its partial screwed condition, while engaging recesses or nothces of the ring nut can be the same cooperating both with temporary retaining projections and with anti- rotational teeth .

By such arrangement, with the ring nut completely screwed till it abuts on the joint body, which condition is clearly indicated and can always be reproduced, the ring pushing the seal in the sealing condition against the pipe is firmly retained by the ring nut, so if the pipe slides in the withdrawing direction due to a pulling action on the pipe or to the fluid pressure it has no effect on the seal and so on the sealing condition, while the clamping ring that is separated by the pushing ring is dragged by the pipe in the withdrawing direction and by means of cooperating conical surfaces of said clamping ring and ring nut narrowing their diameter in the withdrawing direction of the pipe as well as of annular abutment surfaces between ring nut and clamping ring, the pipe is axially stopped and the withdrawing axial thrust is taken up by the ring nut by means of the two abutment surfaces

cooperating with annular, radial shoulders of the clamping ring.

Advantageously in order to prevent the clamping ring or the pushing ring to be lost if the ring nut is completely screwed, both said clamping ring and said pushing ring have movable snap means engaging inside the ring nut and the joint body respectively.

According to a variant embodiment of the invention, the annular seal for example is of the 0- ring type or the like. Said annular seal is housed in a widening of the seat for the insertion of the pipe with cylindrical wall .

An embodiment of the invention provides the seat of said annular seal of the 0-ring type or the like to be composed of a radial widening of the seat of the pipe in the body of the joint which widening has a cylindrical seat for positioning the seal and a slightly conical hydraulic sealing seat with a shorter diameter, such seat has a slightly conical shell surface which conical shell surface ends by an annular shoulder at the end opposite to the one for inserting the pipe. However the smallest diameter of said hydraulic sealing seat is greater than the outer diameter of the pipe and the conical shell surface has an axial length that is slightly greater than the diameter of the cross section of the 0-ring annular seal. With the joint in its not tightened conditions, the annular seal is housed in cylindrical portion having the greatest diameter. When the joint is tightened on the pipe by screwing the tightenend ring

nut, axial pushing means, i.e. the pushing ring, provided in the joint act on the seal, are automatically driven by the tightening movement of the ring nut and they push the seal against the annular shoulder at the end having the smallest diameter of the conical shell surface of the hydraulic sealing seat of the seal, while diametric size of the o-ring seat, of the pipe and of the seal are such that with under the not tightened condition the pipe can freely axially slide in the seal and with the joint in its tightened condition the seal is tightly forces in the narrowing portion between the pipe and the wall of said narrowing or hydraulic sealing seat and it is elastically circumferentially deformed so that its inner diameter is smaller than the outer diameter of the pipe.

When the joint is released from the pipe, i.e. the ring nut is unscrewed, the seal of the O-ring type or the like can elastically return in its initial position i.e. in the cylindrical narrowing portion having the greatest diameter and such elastic return occurs either spontaneously, or at least partially by means of the drawing action of the pipe when it is taken out from the joint. When the pipe is taken out from the joint a friction between the annular seal with the pipe and the opposing sealing seat, the fact of being conical in the direction withdrawing the pipe, helps in making the seal slide into the positioning cylindrical seat. As previously described, the configuration of said seat of the annular seal of the O-ring type being slightly conical and having a length close to the diameter of

the longitudinal section of the annular seal, when the pipe is taken out from the joint, said seal recovers its initial position i.e. near the region of the cylindrical shell surface characterized by the greatest diameter, thus allowing the pipe to be freely taken out from the joint. In conventional joints, on the contrary there is provided a seat of the annular seal having a cylindrical shell surface and/or an axial extension of said shell surface that is really greater than the diameter of the cross section of the annular seal of the 0-ring type. Therefore due to such configuration, when the pipe is taken out from the joint, the seal remains embedded against the annular shoulder and/or it is subjected to a kind of unnatural twisting due to the friction with the outer surface of the pipe and the wall of seat of the seal . Due to above effects , in known joints it is necessary to position again the annular seal in order to give it its original shape if the pipe is desired to be again inserted in its seat of the joint after it has been previously taken out, since the deformed seal or embedded in the seat has an inner diameter smaller than the one of the pipe and so it cannot be inserted. By means of the above configuration of the present joint on the contrary such repositioning of the seal is not necessary since as previously mentioned the annular seal recovers its initial position without any external operations , thus allowing the free sliding in the direction for re-inserting the pipe in the joint. When the joint is undamped from the pipe, on the

contrary, said seal can elastically take again its original resting shape either in a spontaneous manner or at least partially by means of the action dragging the pipe when it is withdrawn from the joint and under such condition it allows the pipe to slide in the direction withdrawing it from the joint without interacting with said seal thus not deforming it.

From the above it is clear that one of the main advantages of the present invention is the joint tightened on the pipe being intended to absorb axial movements due to such high pressures of the fluid and also to use them and said withdrawing movements in order to generate a condition increasing the clamping force and/or the sealing condition. According to an advantageous improvement allowing the seal to elastically return from the compressed condition to the resting, not compressed condition, in a more effective way, the joint body has a seat for housing the 0-ring seal composed of an axial sequence of two radial widenings having different diameters and a first radial widening is provided at the side faced towards the end of the joint body for inserting the pipe and has a substantially cylindrical shell wall with such a diameter that the 0-ring is in its resting condition and susbtantially it is not compressed against the pipe, while the second radial widening housing the seal is axially adjacent to the first one and has a shorter diameter the shell wall of the second radial widening being connected to the shell wall of the first radial widening by a narrowing step, said

second radial widening ending by an annular radial abutment surface and said shell wall of said second radial widening having a shape conically tapering in the direction introducing the pipe into the joint body for at least a part of its total axial length and diameters of said second radial widening being such to generate a radial compression of the seal against the outer shell of the pipe and contemporaneously a compression against the shell wall and/or the terminal end wall of the second radial widening.

The first radial cylindrical widening for housing the seal advantageously is connected to the conical portion up to the opening of the joint body for introducing the pipe . The second radial widening for at least a part of the axial extension has a conical shell wall and such a greatest diameter that the 0-ring seal is wedged between the outer wall of the pipe, the annular radial shoulder and the at least partially conical shell wall of the second radial widening and thus said seal is elastically compressed against the pipe when it passes from the first to the second radial widening by means of axial pushing means acting on the o-ring seal and operated such to axially slide pushing or releasing the o-ring seal by means of the rotation of the tightening ring nut.

Advantageously in order to guarantee the automatic elastic return action from the second radial widening to the first radial widening, the axial extension of the second annular widening between the step portion

narrower with respect to the first radial widening and the annular radial shoulder delimiting the seal seat at the side of said seat opposite to the opening for introducing the pipe into the joint, is similar to the diameter of the o-ring seal in its not compressed condition, while it is slightly shorter than the extension in the axial direction of said seal when the latter is wedged between the second radial widening and the outer wall of the pipe. According to an improvement, the radial depth of the radial widening is lower than the diameter of the o-ring seal.

Moreover in order to again allow better the o-ring to automatically pass from the condition in which it is wedged into the second radial widening to the condition in which it is housed into the first radial widening once the axial pushing action of the seal stops, the shell wall of the second radial widening for a first portion directly adjacent to the narrowing step provided between the first and the second radial widening has a conical shape, ending at about half of the axial extension of the second widening, while between said first conical-shaped portion of the shell wall of the second radial widening a second portion is connected that is cylindrical and it ends by the annular radial shoulder .

Said cylindrical portion has a diameter corresponding to the shortest diameter of the first conical portion of the shell surface of the second widening and an axial length that is shorter than the

diameter of the cross-section of the o-ring seal particularly it is shorter than or preferably similar to the radius of the cross-section of the o-ring seal.

By such arrangement, the pipe being absent, when the axial pushing action exerted by pushing means such as the clamping ring or other separate pushing means is not applied or stops and the seal is disengaged the latter has enough elasticity to automatically release or move out from the second radial widening into the first one where the seal is in its resting condition and the inner diameter is such that the pipe can slide inside the seal .

A variant embodiment of the joint according to the present invention provides the annular seal to be of the lip type or the like.

Said lip seal has a base ring and an extension/lip attached to an end of the inner surface of the base ring.

In this case the seat of the annular lip seal is composed of a cylindrical wall and an annular axial abutting shoulder of the base ring.

The inner surface of the base ring is cylindrical or if necessary slightly conical for allowing the elasticity to increase and also the elasticity to be adjusted. Said abutting shoulder of the base ring of the lip seal has an abutting surface that is preferably slightly inclined with the inclination having a direction equal to the direction of the conical surface of the ring nut. According to a further characteristic of the

present joint the base ring of the lip seal has a cross section that resembles a right-angled trapezium which oblique side has such an inclination to be complementary with the annular abutting shoulder of the seal on the body.

Advantageously the inner diameter of the base ring of the lip seal, when it is not stressed, is greater than the outer diameter of the pipe, while the inner port delimited by the lip of said seal, has an inner diameter smaller than the outer diameter of the pipe, but it is such that when the pipe is inserted in the body the lip of the seal cooperates with the outer surface of the pipe but only by means of a slipping action so that the lip, of said lip seal, does not lead to a physical impediment for inserting the pipe in the body of the joint so it is freely inserted in the joint. This is also in the case if the joint is not thightened when the pipe is taken out from the joint.

By inserting the pipe in the joint, but with the joint not tightened on the pipe, the radially outer surface of the lip of the lip of the seal, overlaps the radially inner surface of the base ring of said seal , thus forming a kind of circular space with a wedge- shaped cross section between said two surfaces; at the same time the radially inner surface of the lip, rests against the outer surface of the pipe without preventing it to be easily taken out from the body, while with the joint tightened on the pipe, the pushing ring axially acts on the base ring of the seal by pushing it against the annular abutting shoulder of the

body and by circumferentially expanding it, which espansion leads to a pressure on the lip of the seal allowing the inner surface of said lip to adhere by a pressing action against the outer surface of the pipe so to generate the desired hydraulic sealing effect.

According to a further characteristic of the present joint, when the joint is tightened on the pipe, the inclination of the surface of the annular abutting shoulder, makes a kind of compression such that, the elastic deformation of the base ring following it leads to a deformation of the inner surface of the base ring of the seal .

In the operating condition of the joint, i.e. with the joint in its tightened condition on the pipe and with the fluid passing in the pipe, the circular space having a wedge-shaped section is flooded by the fluid, that, by acting on the inner surface of the lip of the seal, pushes said lip against the outer surface of the pipe, thus coopoerating with the pushing action of the base ring following the elastic deformation thereof made by the pushing ring, thus increasing the hydraulic sealing effect of the seal .

Moreover it results that the intensity of the action of the fluid on the inner surface of the lip, of the lip seal, it substantially directly proportional to the pressure of the fluid inside the pipe therefore an increase of the action of the liquid pressure on the lip can be associated to an increase in the pressure of the fluid in the pipe consequently increasing the hydraulic sealing effect.

According to a further characteristic of the present joint when the pipe is released from the joint the lip seal can elastically and spontaneously recover its initial shape under not stressed conditions, thus allowing the pipe to be taken out from the joint without any mechanical and/or excessive friction impediments .

Even in the embodiment wherein the seal is a lip seal type, as in the case of o-ring seal, the ring pushing the seal cooperates with the ring nut by means of the clamping ring when the ring nut is tightened by a screwing action thereon and by means of cooperating conical surfaces of the ring nut and clamping ring. After screwing the ring nut on the body, the clamping ring is elastically circumferentially tightened against the outer surface of the pipe and at the same time it is axially pushed inside the body against the pushing ring. The axial movement of the clamping ring inside the body leads the ring to be axially pushed/compressed against the annular seal. With the ring nut in its screwed condition and with the pipe tightened into the joint, the ring nut directly abuts against the ring pushing the seal.

According to a technical solution of the present joint, obviously the material composing the clamping ring has an hardness greater than the one of the material composing the pipe. Such technical solution is absolutely necessary for causing teeth of the axial crowns of the clamping ring to grip the outer surface of the pipe.

Obviously the use of the seal both the 0-ring type or the like, and the lip type, as well as of manufacturing arrangements regarding the inner configuration of the body of the joint, particularly as regards the seat of said annular seals, leaves out of consideration the use of the particular type of clamping ring and pushing ring previously described and made according to the present invention.

Above described characteristics of the joint regarding the seal can be used by providing also the use of simple clamping rings currently on the market.

Such types of seals and parallely inner configurations of the body, particularly as regards the seat of said seals , allow to overcome a series of problems regarding the step inserting and taking out the pipe in/from the joint. By using conventional seals , which have an inner diameter slightly smaller than the outer diameter of the pipe, when the pipe is inserted in the joint there is the risk of making a too high effort for introducing the pipe particularly for coupling diameters greater than 63 mm, running the risk of damaging the seal, since as it is easy to understand the pipe is inserted by elastically forcing it in the seal housed in its seat. Due to the action inserting the pipe in the joint, the edge of the outer surface of the pipe acts by a cutting action against the inner surface of the seal, since said edge of the pipe, resulting from cutting the pipe, can be particularly sharp or slightly chipped. Moreover still in the step inserting the pipe in the joint, due to the fact that

the pipe interacts by a considerably sliding action on the inner surface of the seal by a friction intereference between the two walls , often there is the risk of giving bending or twisting effects to the seal such to damage it for these reasons not guaranteeing a suitable hydraulic effect. In order to partially overcome above drawbacks the pipe needs to be bevelled and/or lubricated sometimes by improvised lubricants using not consistent tools or products both as regards technical efficacy and sanitary regulations. The risk of giving the seal the above unnatural twisting effects , without lubricants , is also present when the pipe is taken out from the joint.

On the contrary as previously mentioned, said problems do not exist by using seals and inner configurations of the body of the joint according to the present invention.

Moreover the body of the joint, on its outer shell surface, precisely on the side opposite to the threaded one intended for screwing the ring nut, is provided with suitable fastening/anchoring means, generally represented by a further thread, which fastening means allow the joint to interact with other devices for example valves, or T or elbow joints, or still other joints of the type previously described, and of the type commercially available in order to allow two final sections of pipes having different sections or composed of different material to be coupled.

According to a further characteristc of the present joint, the body thereof is internally made such

to have at least two abutting shoulders of the pipe end having an inner diameter slightly smaller one with respect to the other. Due to this inner configuration of the body, the same joint can be used for pipes having different diameters without changing neither the clamping ring, nor the annular seal, since due to the characteristics of the joint that have been previously described, both the clamping ring, and the annular seal have the possibility to change, within material limits allowed thereto, their inner port, thus to be adapated to clamp/retain also pipes having different diameters .

The fact of freely introducing and withdrawing the pipe into the joint allows also to make a repair joint that in combination with all the above has the further characteristic of having a sleeve-like joint body that is longer and free from stop abutment for introducing the pipe into the joint body. That allows the joint body to slide on the pipe to be repaired without the need of disassembling ring nuts and clamping rings from the joint body and so making repair actions considerably more easier.

Therefore unlike joints actually on the market the present joint has the possibility of being used not for only one pipe having a specific outer diameter, but is can be used for at least two pipes having different outer diameters , even if slightly differing one from the other .

These and other characteristics and advantages of the present invention will be more clear from the following description of some embodiments shown in

annexed drawings wherein:

Fig. IA is a section view of a first embodiment according to the invention taken according to a diametral plane and wherein the joint is disassembled, that is with the ring nut unscrewed from the joint body and with the pushing ring, also called rubber-pusher retained inside the joint body, the seal going back into the wider seat portion corresponding to a first annular, radial inner widening of the tubular body of the joint.

Fig. IB is an enlarged detail of figure IA. Fig.2A like figure 1 is the joint of figure 1 in the assembled condition and being ready for receiving the pipe, denoted by position 1, and wherein the pipe is just introduced into the tubular body of the joint passing through the ring nut screwed on the joint body in a loose position, and through the clamping ring in the condition wherein it is free from radial compression, as well as through the pushing ring and the seal the latter being also not radially compressed since it is housed into the first radial widening.

Fig2B is a enlarged detail of the area of the seal seat, wherein the pushing ring and the seal are in the position corresponding to figure 2A. Fig.3 like figures 1 and 2, is the joint with the ring nut partially screwed on the body and it is such a condition that the seal is pushed in a position partially going over the step connecting the first radial widening and the second radial widening of the seal seat denoted by position 2.

Fig.4 like figure 3 is the joint of figure 3 with the ring nut completely screwed and the pipe tightened into the joint, such condition is defined as position 3 limit stop means for screwing the ring nut cooperating one with the other and acting between the head of the ring nut and the joint body.

Fig. 4B is an enlarged detail of figure 4A. Fig.5 like previous figures is the condition of the joint with the pipe moved in the withdrawing direction for example because of a pulling action exerted thereon or because of fluid pressure and in such condition denoted by position 4 , the pipe has dragged also the clamping ring in the withdrawing direction which has been further tightened against the pipe by means of cooperating conical surfaces of the clamping ring and ring nut and wherein the ring nut and the clamping ring are in a mutual abutment condition by means of corresponding, respective annular abutment surfaces and annular abutment shoulders . Reaching the abutment is the highest constriction and clamping usually necessary for the clamping ring, further greater pushing actions of pressure or pulling forces are relieved on radial abutments without burdening too much on the conical portion of the ring nut. Fig.6 is a variant embodiment of the invention providing a lip seal and wherein the lip seal position is with the pipe not inserted in the joint.

Fig.7 is the position of the lip seal with the pipe in the inserted condition wherein the joint is not tightened on the pipe.

Fig. 8 particularly is the position of the lip seal with the joint tightened on the pipe.

Fig.9 is a perspective view of the sleeve forming the joint body and wherein limit stop abutment means provided on the joint body and means for temporary stopping the free rotation of the ring nut on the thread of the joint body by a frictional locking action can be seen.

Fig.10 is an enlarged detail of the area of limit stop and preventive retaining projections in the partially screwing condition on the body 1.

The body 1 of the joint has a union 101 for coupling the pipe 5 having an outer thread 201. The union 101 has an inner shoulder 301 being a radial abutment surface for an annular seal 11 of the 0-ring type. The inner annular shoulder 301 is also a side wall of a seat housing said annular seal in the form of a groove made in the inner surface of the coupling union 101. The seat housing the seal 11 is composed of two radial portions widener with respect to the inner diameter of the tubolar body 1 of the joint that is like a sleeve 101. A first annular, radial widening 50 is provided at the side of the body 1 faced towards the end for introducing the pipe 5 into said body 1 and it extends towards the opposite end of the body 1 of the joint by a second annular, radial widening 60 having an inner diameter shorter than the inner diameter of the first annular radial widening 50 and being connected thereto by a step 70 making an annular, radial

shoulder. The first annular, radial widening is partially the seat for the o-ring seal under its resting condition and it extends, by an introduction cone, up to the head end intended for introducing the pipe 5 into the joint body 1, while the second annular, radial widening 60 ends at the side opposite than the one for the connection to the first annular, radial widening 50 with an annular radial inner shoulder 301, by which the inner diameter of the sleeve 101 forming the tubolar joint body 1 becomes narrower up to a diameter slightly greater than the diameter of the pipe 5. At the head side of the joint body 1 opposite to the head side for introducing the pipe there is provided an annular, radial inner shoulder 901 for stopping introducing the pipe 5 in said body 1.

The seal 11 housed in the first annular radial widening 50 of the body 1 with the joint in its disassembled and not tightened position cooperates with a pushing ring 20 axially sliding inside the joint body 1 and whose inner diameter is greater than the outer diameter of the pipe 5. The pushing ring 20 cooperates with the seal 11, by means of its head annular surface 320 at the end faced in the direction introducing the pipe 5 into the tubular body 1. The pushing ring 20 has movable snap engaging means acting by means of the intrinsic elasticity of the material the body 1 and the pushing ring 20 itself are made of. Such means allow the pushing ring 20 to be retained in a position axially adjacent to the seal 11 when the latter is housed into the first annular,

radial widening 50 , thus avoiding the pushing ring to go outside the joint body 1 under the disassembled condition of the joint as shown in figure 1. Particularly said means are composed of an outer radial tooth 120 engaging in the back of an inner radial annular tooth 150 provided at an intermediate area of the first annular radial widening 50, with reference to the direction withdrawing the pushing ring 2 from the joint body 1. The inner radial annular tooth 150 provided on the shell surface of the first annular, radial widening 50 of the joint 1 is provided at a distance from the step narrowing 70 by which it is connected to the second annular, radial widening 60 of the body 1 intended to receive the seal 11 with the joint in its tightened condition on the pipe 5, which distance is similar to the diameter of the cross-section of the seal 11.

As it can be seen in figure 3, the inner diameter of the first annular, radial widening 50 in the area between the tooth 150 retaining the pushing ring 2 and the annular step narrowing 70 for the connection to the second narrowing substantially corresponds to or is slightly greater than the outer diameter of the seal 11, and however it is such that when the seal 11 is housed in said first annular, radial widening 50, the pipe 5 can slide freely or by a slight slipping action inside the seal, without dragging it. Anyway the pushing ring 20 snap engaged with the joint body 1 is prevented from axially slipping in the withdrawing direction and so it is a stop limiting the axial

movement of the seal 11 by its head annular surface intended to contact the seal 11 even when the joint is in its loosened condition and i.e. when it is not tightened on the pipe 5. The annular step narrowing 70 by which the first annular, radial widening 50 is connected to the second annular, radial widening 60 has a radial height that is lower than the radius of a branch of the cross-section of the seal 11. On the contrary the second annular, radial widening 60 has an axial length similar to the diameter of a branch of the cross-section of the seal 11, between said step narrowing 70 and the annular, inner, radial shoulder 301 at the head side opposite to the one for the connection to the first annular, radial widening 50. The shell surface of said second annular, radial widening 60 has a first conical portion 160 and a second cylindrical portion 260. The first conical portion 160 has an axial length greater than the second cylindrical portion 260, while the first conical portion has an axial length greater than the radius of a branch of the cross-section of the seal 11. The second cylindrical portion 260 has an axial length substantially equal to or slightly shorter than the radius of a branch of the cross-section of the seal 11. Particularly the axial length of the cylindrical portion 260 is equal to the diameter of a branch of the cross-section of the seal 11 divided by 2,2. As regards diameters, the first conical portion 160 has its greatest diameter at the annular step narrowing 70 and it becomes narrower towards the second cylindrical

portion 260 by an inclination from 5 to 15 ° . The inner diameter of the conical portion in the area of the greatest radius is shorter than the outer diameter of the not compressed seal 11 in a way corresponding to twice the radial thickness of the step narrowing 70 which radial thickness is lower than the radius of a branch of the cross-section of the seal 11. The inner diameter of the cylindrical portion 260 is shorter than the outer diameter of the seal and is slightly greater than the diameter of the seal 11 measured at the centres of the two diametrically opposite cross- sections of the seal 11. That is to say, the diameter of the cylindrical portion 260 of the second annular, radial widening 60 , with respect to the outer diameter of the seal 11, is shorter than twice an amount lower than the radius of a branch of the cross-section of the seal 11.

The conical portion 160 of the second annular, radial widening 60 is connected to the radial surface of the annular radial step narrowing 70 by a conically beveled or rounded leading portion 170. The cylindrical portion 260 of the second annular, radial widening 60 is connected to the annular, radial shoulder 301 by a rounded portion. The conical leading surface 170 obtained by bevelling the annular step narrowing 70 aids in obtaining a firm supporting position of the seal 11 preventing it from being moved when the pipe 5 is inserted. The cylindrical portion 260 of the shell surface

of the second annular, radial widening 60 makes an outer unstable support for the 0-ring seal 11 in the compressed condition inside the second annular, radial widening 60 and it helps the release in the backward position from said second annular, radial widening 60 to the first annular, radial widening 50 wherein the O- ring seal 11 is in its resting condition, when the joint is opened or loosened and the pipe is withdrawn therefrom. The section defined by the second annular, radial step widening 60 and comprised between the shell surface of the pipe 5, the head surface 520 of the pushing ring 20 in its axially inwardly pushed position compressing the seal 11 inside the second annular, radial widening 60 approximately corresponds to the cross-section of the branch of the seal 11 compressed inside said second annular, radial widening 60.

The pipe is mechanically retained in place inside the joint by a clamping ring 2 by an intrinsic elastic force firmly keeping it under a condition wherein its inner diameter is slightly greater than the outer diameter of the pipe 5, in its resting condition, i.e. with the pipe not tightened into the joint. Therefore the pipe can be inserted into the clamping ring 2 with no physical obstacles.

The clamping ring 2 is tightened on the pipe by means of a tightening ring nut 4 whose inner thread can be screwed on the outer thread 201 of the coupling union 101. The clamping ring is made as an open one, i.e. it

has an axial cut passing through one head side to the other head side of the clamping ring and also radially passing through the outer shell surface to the inner one like prior art clamping rings . The clamping ring has one or more crown of teeth 6. These teeth 6 have no interaction or slightly scrape against the outer surface of the pipe 5 when the joint is in its not tightened condition so that upon the introduction of the pipe 5, it is not subjected to any physical impediments by the clamping ring 2.

From figures 1 to 6 it is clear that the external shell surface of the clamping ring 2 has a wedge-shaped or conical surface 102 that, during the step screwing the ring nut 4, just cooperates with an inner conical surface portion 104 of the ring nut 4.

Still from figures 1 to 5 it is clear that the clamping ring 2 has two annular, radial surfaces 502, 602 abutting against corresponding inner annular shoulders 604, 704 of the ring nut 4. Advantageously said annular shoulders are provided at the two opposite head ends of conical portions 104, 102 of the tightening ring nut 4 and clamping ring 2 respectively which have the same conicity in the shown embodiment. As it is clear from the sequence of figures 1 to 5 , with the joint in its tightened condition, i.e. the condition with the ring nut 4 screwed on the body 1 wherein the pipe is mechanically tightened and clamped by the clamping ring 2 and the seal 11 is compressed by the pushing ring 20 into the second annular, radial widening 60 such that it sealingly adheres into said

annular, radial widening 60 and against the outer shell wall of the pipe thus generating the sealing effect, said two annular radial surfaces 502 and 602 of the clamping ring and cooperating inner annular abutment shoulders are axially spaced apart and the clamping ring 2 is at an intermediate position in the overall axial length of the conical portion 104 of the ring nut 4.

On the contrary, such as shown in figure 5 , when the pipe 5 is moved in the withdrawing direction with respect to the joint i.e. to the body 1 and the ring nut 4 screwed thereon, due to inner pressure or a pulling action withdrawing the pipe 5, the pipe 5 has dragged the clamping ring 2 in the withdrawing direction and further wedging it between its outer shell wall and the inner conical surface 104 of the ring nut 4. All this by the fact that annular crowns or annular teeth 6 are penetrated into the thickness of the wall of the pipe 5, so the clamping ring 2 is coupled to the pipe wall. Moreover the movement of the clamping ring 2 in the withdrawing direction cause the clamping ring 2 to be more wedged between the pipe and the ring nut by means of conical surfaces 102 of the clamping ring 2 and the ones 104 of the ring nut 4. The axial withdrawing movement of the pipe 5 together with the clamping ring 2 being contemporaneously dragged is limited by annular abutment shoulders and abutment surfaces of the clamping ring 2 and ring nut 4 respectively acting for creating an abutment preventing the clamping ring 2

from being withdrawn from the joint when there are high pressures of the fluid. To this end the axial distance between radial abutment shoulders 502, 602 provided on the clamping ring 2 and corresponding annular abutment surfaces 604, 704 of the ring nut 4 is the same. The inner shorter diameter and the inner greater diameter of the conical portion 104 of the ring nut 4, the shorter outer diameter and the greater outer diameter of the conical portion 102 of the clamping ring 2 and the inner diameter of the clamping ring being such that, with the ring nut 4 in its screwed condition, which screwing condition corresponds to the condition with the clamping ring 2 tightened on the pipe 5 and to a condition with the pipe 5 tightened into the joint body 1 thus generating the sealing action, radial abutment shoulders 502 , 602 provided on the clamping ring 2 and corresponding annular abutment surfaces 604, 704 of the ring nut 4 are spaced apart. So when into the pipe there are high pressures of the fluid the clamping ring being grasped to the pipe is dragged by it more and more against the ring nut cone increasingly grasping the pipe during its longitudinal sliding and contemporaneous clamping travel till stopping said travel contemporaneously with annular radial abutment shoulders against the two annular abutment surfaces of the ring nut.

In this case the withdrawing pushing action is absorbed by two annular surfaces so a large abutment surface is obtained keeping reduced the thickness of the ring nut 4 and so the overall outer diameter of the

ring nut 4 and joint.

Advantageously the annular inner shoulder 704 of the ring nut 4 is made at an intermediate step widening of the inner conical portion 104 of the tightening ring nut 4. The conicity that is the inclination of the conical surface is the same on the two sides of the step widening 104' , while the conical portion at the side of the end of the tightening ring nut 4 opposite to the direction introducing the pipe into the joint has the radial inner abutment surface 604 at the side with the shortest diameter. The axial length of the conical surface portion between the two inner, radial, annular abutment surfaces 604 and 704 corresponds to the axial length of the conical portion 102 of the clamping ring 2. So the conical portion 102 of the clamping ring 2 can be fully inserted in the conical portion of the end of the tightening ring nut 4 while contemporaneously radial abutment surfaces 502 and 602 abut against inner annular shoulders 604, 704 of the ring nut 4.

The second radial, annular abutment surface 602 of the clamping ring 2 is composed of a terminal annular flange at the end with the greatest diameter of said conical portion 102 of the clamping ring 2. Said flange has a predetermined axial thickness and the peripheral edge of said flange is conical at least for a part of said axial thickness and at the opposite side with reference to the direction introducing the pipe into the joint. The conicity is substantially the same of the conical portion downstream of the conical widening

step of the ring nut 4. The conical surface portion 104 of the ring nut 4 ends by a conical narrowing 804 constituting a tooth for movably retaining the clamping ring 2 into the ring nut, while said clamping ring 2 abuts against said conical narrowing 804 by a corresponding conical abutment surface 802 of the peripheral edge of the annular flange forming the annular radial abutment surface 602 of the clamping ring 2. Still according to an advantageous characteristic, the clamping ring 2 on one side cooperates with the tightening ring nut 4 and on the other side with the pushing ring 20 that in turn acts as a means axially pushing the seal 11. The pushing ring also called rubber-pusher 20 has an annular abutment surface for the abutment with an opposing annular radial surface of the clamping ring 2. With reference to the shown embodiment, the annular head surface of the pushing ring 20 is intended for cooperating with the opposing annular head surface of the clamping ring 2 provided downstream of the annular flange forming the annular, radial abutment shoulder 602.

Still according to a further characteristic, the pushing ring 20 has an annular, radial shoulder 220 abutting against a cooperating annular, radial abutment surface 904 of the tightening ring nut 4.

When the ring nut 4 is screwed for being tightened on the thread 201 of the joint body 1, the clamping ring 2 is both tightened and axially pushed in the direction introducing the pipe and it abuts against the

head side 302 of the pushing ring 20 by the head side 902 (fig.3) . When the ring nut 4 is further screwed the latter pushes axially forwards the clamping ring 2 being contemporaneously clamped against the pipe 5 thus pushing axially forwards the pushing ring 20. The latter by its opposite head side pushes in turn the seal 11 in the direction axially introducing the pipe 5 progressively passing from the first annular, radial widening 50 to the second annular, radial widening 60 passing over the step narrowing 70 (fig.3 and fig.4) . Thus the seal 11 is pushed in a condition wedged between walls of the second annular, radial widening 60, the annular, radial, inner shoulder 301 and the outer shell wall of the pipe 5 so the sealing effect is generated.

As it results from figures 4 and 5, in the final screwing condition of the ring nut 4 that is univocally and repeatable defined by screwing limit stop means which means will be described below more in details , the annular, radial, inner abutment surface 904 of the ring nut 4 cooperates with the annular, radial, outer shoulder 220 of the pushing ring 20, thus it is firmly retained in position compressing the seal 11 in its wedging condition into the second annular, radial widening 60 as described above in details . All the above occurs even when, such as shown in figure 5 , the pipe 5 with the clamping ring move in the withdrawing direction and are retained by the particular arrangement of conical surfaces of the ring nut and clamping ring and of annular, radial abutment surfaces

and cooperating annular, radial shoulders of the ring nut and clamping ring due to a pulling action exerted on the pipe in the direction withdrawing the joint from the pipe or the pipe from the joint or to the fluid pressures acting on the pipe, leading to an effect equal to the pulling action exerted on the pipe . In this case, the pushing ring 20 is retained by the ring nut 4 by means of the annular, radial abutment surface 904 provided thereon and cooperating with the annular, radial, outer shoulder 220 of the pushing ring 20, so the axial movement of the pipe does not affect the conditions of the seal 11 and so the sealing effect. The two rings i.e. the clamping one and the pushing one, are axially disengaged one with respect to the other, so when into the pipe there are high pressures of the fluid the clamping ring 2 grasped to the pipe is dragged by it more and more against the conical surface 104 of the ring nut 4 increasingly grasping the pipe 5 during its axial sliding and contemporaneous clamping travel till stopping said travel contemporaneously against the two abutments of the ring nut 604 and 704. So the obtained grasping action is enough to prevent the pipe from being withdrawn from the clamping ring so the further pulling action exerted on the pipe is absorbed by the two abutments 604 and 704 with advantages of providing a ring nut with a lower thickness .

With reference to figures 1 to 5 and particularly to the enlarged view of figure 4B, with the joint in its tightened condition the pushing ring 20 is retained

in the axial position with reference not only to an axial movement in the withdrawing direction, but it is tightened between two opposite annular, radial walls of the ring nut 4 and of the body 1. Particularly, the annular, radial outer shoulder 220 abuting against the annular, radial inner surface 904 of the ring nut 4 is the side face of an annular outer flange, whose opposite face faced in the direction introducing the pipe 5 into the body 1 is an annular, radial shouder 420 abutting against an annular, radial abutment surface 110 of the body 1 that in the shown embodiment is the annular head side of the tubolar body 1 at the end for introducing the pipe 5 therein. Therefore, with the ring nut 4 completely tightened on the body 1 , the ring 20 is tightened with the outer radial flange making the two opposite annular, radial abutment shoulders 220 and 420 between the two opposite annular, radial abutment surfaces 904 and 110 of the tightening ring nut 4 and of the joint body 1. Still according to an improvement, the pushing ring 20 has such an axial length that the annular head surface 520 acting against the seal 11 abuts against the step narrowing 70 connecting the two widenings 50 and 60 forming the seat housing the seal 11, when the pushing ring 20 is in said condition tightened between the ring nut 4 and the head side of the joint body 1. Under such conditions the pushing ring is firmly retained such that it cannot move in any directions .

Said shown embodiment is particularly suitable for joints to use with large diameter pipes that is with a

diameter greater than 50mm.

The shown pipe joint is of the type wherein, the pipe can be inserted and withdrawn from the joint with the seal , clamping ring 2 tightening ring nut 4 assembled on and/or into the coupling union 101. In this case with the tightening ring nut 4 partially screwed, the clamping ring 2 and the 0-ring seal 11 have such an inner diameter that the pipe can slide into said parts with a frictional resistence against sliding that can be overcome by a manually applied force and without any effort and without mechanically damaging the pipe and/or said two parts 2 and 11.

With reference to the seal 11 it can be provided with such a diameter that even with the ring nut partially screwed it has an inner diameter greater than the pipe diameter to such an extent that the head side of the pipe upon introduction into the coupling union 101 even if inserted in an offset way can laterally contact the seal 11 that is anyhow prevented from sliding in the introduction direction by the annular shoulder 170. In the withdrawing direction the seal 11 is prevented from sliding by the head wall of the pushing ring 20 the seal being already in the greater seat Figures 6 to 8 show a variant embodiment of the joint providing a so called lip seal instead of an O- ring seal .

Fig. 6 shows a section plane/cross section of the joint having inside the body 1 a lip seal 12, with the joint in its not tightened condition and with the pipe

5 (shown by the broken line) not inserted in said joint.

It can be noted that the lip seal 12 is composed of a base ring 13 having an inner diameter slightly greater than the outer diameter of the pipe and of an extension/lip 14, secured to an end of the inner surface of the base ring 13 in which the inner port delimited by said lip, has an inner diameter smaller than the outer diameter of the pipe. Moreover it can be noted that the section of said lip seal 12, or better to say the section of the base ring 13 of said seal 12 resembles to a right-angled trapezium whose oblique side has such an inclination to be complementary to the inclination of the annular abutting shoulder, which with the inner cylindrical wall of the body 1 constitutes the seat of said seal 12.

In fig. 6 the pushing ring 20 is further shown. Fig. 7 shows a section plane/cross section of the joint 1 having inside the body 1 a lip seal 12, with the joint in its not tightened condition and with the pipe 5 inserted in said joint.

As it can be noted the lip 14 of the seal 12 cooperates with the outer surface of the pipe 5 when it is introduced in the joint but only by a slipping action by the inner surface 15 of said lip 14 without preventing to easily take out the sealing body, therefore even by using lip seals of the type described hereinbefore, the pipe can be freely introduced in the joint without any mechanical and/or excessive frition

impediments .

Moreover as it can be noticed, after having inserted the pipe 5 in the joint, the outer surface 16 of the lip 14 comes to overlap the inner surface of the base ring 13 thus arising a space 17 having a wedge- shaped cross section.

Fig. 8 shows a section plane/cross section of the joint 1 having a lip seal 12 inside the body 1, with the joint tightened on the pipe 5. After the ring nut 4 has been screwed on the body 1 the clamping ring 2 pushes against the pushing ring 20 that, such as previously described, is subjected to an axial movement towards the inside of the body 1 and such movement causes said pushing ring to act against the annular lip seal 12.

Due to said axial movement of the pushing ring 20, the seal 12 is pushed against the annular abutting shoulder 301 and following said pushing action the seal 12 is circumeferentially widened. More precisely, the annular abutting shoulder being slightly inclined, a kind of compression of seal 12 occurs therefore it results that the base ring 13 of said seal 12 is subejcted to the deformation, and such deformation results in the inner surface of the base ring to be circumferentially widened.

After said circumferential widening, the inner surface of the base ring 13 pushes against the outer surface 16 of the lip 14 pushing/forcing the inner surface 15 of the lip 14 to tightly adhere against the outer surface of the pipe 5.

In the operating condition of the joint 1, i.e. with the joint in its tightened condition on the pipe 5 and with the fluid passing in the pipe, the circular space 17 having a wedge-shaped section is flooded by the fluid which exters a pressure on the outer surface 16 of the lip 14, which pressure pushes the inner surface 15 of said lip 14 towards the outer surface of the pipe 5 thus cooperating with the pushing action of the base ring 13 following the elastic deformation thereof.

Obviously the pushing action of the fluid against the outer surface 16 of the lip 14 of the seal 12 is substantially directly proportional to the pressure of the fluid inside the pipe, so by increasing the pressure, as a consequence the hudraulic sealing effect of the seal 12 increases .

When the joint is released from the pipe, as previously said, the pushing ring 20 spontaneously recovers its original position, such as shown in fig.7 and consequently, the lip seal can elastically recover its initial/original shape under not stressed conditions, either in a spontaneous way or also at least partially by the pipe being drawn when it is taken out from the joint. With reference to shown and described examples and to possible variants, the invention allows to leave the joint in its ready condition to insert the pipe, with the seal housed in the seat and with the pipe freely moving inside it; the clamping ring already fitted in its seat and in its opened condition like a flower

allowing the pipe to freely slide inside it and with the ring nut screwed on the body of the joint with the conical face abutting against the conical face of the clamping ring at the beginning of the predetermined screwing travel necessary for mechanically clamping the pipe and the desired hydraulic tight seal . Therefore the user has only to insert the pipe in the joint and so to tighten the joint by a simple rotation of the ring nut that is of minimum extent and that can be indicated by a reference between the body and the ring nut.

Advantageously such as shown in more details figures 9 and 10, in order to identify more easily the proper position for partially screwing the tightening ring nut 4 on the coupling union 101, with the clamping ring 2 and seal 11 allowing at least to introduce and/or also to withdraw the pipe from the joint said parts being in the assembled condition, the invention provides a radial projection 701 or two or more radial projections in the trajectory at one peak of a thread 201 of the coupling union 101 arising from said area in the trajectory of the peak of said thread 201 and which projection or projections are engaged into a corresponding notch or recess or in a crown of notches or recesses 204 provided at the head side of the tightening ring nut 4 faced towards the coupling union 101 that is in the front with reference to the direction for introducing the pipe 5 into the joint or screwing said tightening ring nut 4. Said notches or recesses 204 are open both at the head side and at the

inner surface of said end of the tightening ring nut 4.

Radial projections 701 at the bottom of the thread 201 have such a protrusion to project with a slight interaction inside grooves 304 between threads 404 of the tightening ring nut 4 that can be elastically deformed, and to project more beyond the radial inner edge 504 of front recesses 204. Upon screwing, therefore, interactions between projections 701 and front recesses 204 occur causing the ring nut 4 to move forward by steps which can be easily manually overcome, by holding it in the partial screwing position with respect to the coupling union 101. By further rotationally screwing the tightening ring nut 4 , projections 701 are elastically deformed and come out from front recesses 204 passing inside the groove 304 of the thread where there is some friction obtained by the slight interaction between the projection or projections 701 and the groove 201 preventing the ring nut from freely rotating holding its predetermined preassembly position.

Therefore the action provides to temporary hold the tightening ring nut in a predetermined screwing position. Particularly the thread 201 on the coupling union 101 is provided in an axial position of said coupling union 101 corresponding to a partial screwing position of the tightening ring nut 4 wherein the clamping ring 2 and the seal 11 allow the pipe to be inserted and/or in case withdrawn by sliding inside the clamping ring 2 and the seal 11. So the tightening ring nut 4 is temporary effectively retained in its starting

position which can be overcome by a simple manual force. Particularly it has to be noted that also the arrangement of the tightening ring nut 4 and the clamping ring 2 cause the choice of the readiness position with the ring nut temporary retained in the partial screwing position (preassembly) on the coupling union 101 to be such that the rotation necessary to completely tighten the ring nut 4 in order to sealingly clamp the joint on the pipe is very small, approximately from half a turn to one complete turn of the ring nut, so the joint is tightened on the pipe by a minimum and precise travel and by a very simple and quick movement.

Still according to a further advantageous characteristic, there are provided limit stop means for the screwing tightening travel of the tightening ring nut 4 on the pipe preventing also the tightening ring nut 4 from being unintentionally rotated.

Said means advantageously are composed of a radial tooth 801 or two radial teeth or a crown of more radial teeth. Such radial tooth or teeth 801 are provided on the coupling union 101 in an axial position with respect to the axial position of the tightening ring nut 4 being screwed on said coupling union 101 corresponding to the joint being completely tightened on the pipe 5 , so when the ring nut reaches said axial position the radial tooth or teeth of the ring nut 204 engage into corresponding front recess or recesses 204 of the tightening ring nut 4. This can be obtained by means of elasticity of teeth provided on the ring nut

teeth that can be also the intrinsic elasticity of the material itself. Under such condition, the rotation of the tightening ring nut 4 unscrewing and so opening the joint needs a certain force to be overcome for disengaging radial tooth or teeth 801 from front recess or recesses 204 of the ring nut, so effectively it is not possible to unintentionally loosen or unscrew the tightening ring nut 4. Moreover the correct condition for screwing the tightening ring nut 4 corresponding to the correct condition for tightening the joint on the pipe is indicated to the user. All this leads to the fact that upon the tightening action, the ring nut is prevented from being uselessly screwed too much by leaving to possible high pressures or pulling actions exerted on the plant a further automatic/dynamic sliding action of the seal pipe and clamping ring assembly on conical surfaces of the ring nut, allowing high pressures of the fluid to be used in order to increase both the clamping condition and the sealing effect under such pressure conditions.

The radial tooth or teeth 801 are composed of radial axially oriented ribs having such a circumferential thickness which thickness is lower than the corresponding size of front recess or recesses 204 of the ring nut.

With reference to a further characteristic, the limit stop for the introduction of the pipe denoted by 901 in figures can be omitted and the body 1 of the joint can have an inner diameter that is always slightly greater than the pipe diameter. So together

with the characteristic for introducing and withdrawing the pipe into the joint without too much friction a repair joint can be obtained that is a joint particularly suitable for making repairs . The longer joint body 1 free from inner annular abutment shoulder 901 of the pipe allows the joint to slide inside the pipe to be repaired, without the need of disassembling ring nuts and clamping rings from the body 1 and so making repair actions considerably more easier. A further not binding novel characteristic is the maximum repairing distance between pipe and pipe that due to clearness and semplicity reasons is exactly like the diameter of the corresponding pipe and it is clearly shown on the outside of the joint.