DE2354554A1 - RESISTANT PLASTIC PIPE CONNECTIONS AGAINST TENSILE FORCE - Google Patents

Description

PATENT LAWYERS

Dipi.-ing. H. Seiler Dipi.-ing. J. Pfenning Dipi.-Phys. K. H. Meinig

4160/4208-B . 1 Berlin 19

• Oldenpurgallee TO

Tel. 030/304 55 21/22

Wireword: rope defense patent

Postal checking account: Berlin-West 59 38 -402

October 29, 1973 Me / Cw / St.

JOHNS-MAFVILLB CORPORATION

22 East 40th Street

New York, N.Y. 10016 / USA

Plastic pipe connection resistant to tensile forces

The invention relates to a socket pipe connection which cannot be released or decoupled by tensile forces and other forces. The invention also relates to a method for producing a socket end provided with grooves and to an apparatus for carrying out this method .

Many methods of connecting plastic pipes are known. Two plastic pipes can, for. B. by means of a socket connection or coupling connected to one another each of these pipe connections a rubber ring connection, a crimp connection or a welded

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connection can be. Although it is known that the rubber ring connection compared to other connections has many advantages, connections of this type have hitherto hardly had any resistance to it a solution of the connection under the action of forces, such as. B. from internal or external tensile forces and forces due to shrinkage, temperature changes, etc. Grumming connections were therefore often required additional means to withstand such forces. If a pipeline z. B. hydraulic fluid contains, pipe connections on elbows are subjected to tensile forces. In many cases you have to to absorb such forces, cement blocks or other suitable means are provided in order to dissolve the Avoid pipe connection due to the resulting forces.

The object of the invention is to create a pipe connection for connecting two plastic pipes such that the pipe connection against forces that a loosening of the pipe connection is resistant, the pipe connection preferably a liquid and / or dust seal having.

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Another object of the invention is to provide a plastic pipe connection with hook-shaped locking parts to secure the pipe connection, "whereby the production and loosening of the pipe connection are uncomplicated.

According to the invention, one serves to solve these problems Plastic pipe connection with a first plastic pipe with socket end, a second plastic pipe with spigot end, the outside diameter of the spigot end being slightly smaller than the inside diameter of the socket end of the first plastic pipe is and with a seal, and this pipe connection is characterized by that the socket end has at least one thread groove in its inner surface, the thread groove has an enlarged portion whose shape

en. corresponds to a locking part and wherein the pin end has at least one thread rib on its Outer surface is formed and protrudes outward therefrom and has a closing part, the The thread rib cooperates with the thread groove of the socket end, um.die plastic pipes to be detachably connected to one another by means of a screw connection

ί --vT

and wherein the pin end has a larger outside diameter than has the plastic pipe molded in one piece with it and also one of its outer surface

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completely circumferential ring groove to accommodate the

Has seal, the base diameter of the

■

! Annular groove essentially equal to the outer diameter of the integrally molded second plastic pipe and the seal is seated in the annular groove.

For making the socket end of the pipe connection According to the invention, a method is used in which an end section of a deformable under the action of heat Plastic pipe is heated to a temperature lying in the thermoplastic range, the heated end portion is pushed over a mandrel, the mandrel having an external shape that is the desired corresponds to the inner shape of the Muffenetades, the end section on a below the thermoplastic

See area lying Thermparatur is cooled, and the plastic pipe with molded socket end is pulled from the mold core, wherein the method is characterized in that the mold core has at least one groove-forming rib protruding from its outer surface, and that the heated end portion of the plastic pipe is thereby removed from the mold core is formed that an inflatable member is provided around the heated end portion and the protruding rib around, the inflatable member is inflated so that it is at least a part of the heated end portion against at least

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a part of the core end portion provided with the rib presses so that the pressed part relative to it Shape exactly matches the rib and the pressurized part of the Kernendabsohnitts, the excellent Rib creates a thread groove in the inner surface of the heated end portion, and that the Pressure medium is drained from the inflatable part after the temperature of the heated end portion has fallen the thermoplastic temperature range has fallen and before the plastic pipe is pulled from the mold core will.

The invention also provides an apparatus for Formation of a thread groove in the inner surface of a heat-deformable tube in the process of the above method, consisting of a cylindrical mandrel, one of its end portions is suitable for receiving an end portion of a heat deformable tube after the pipe end section to a temperature in the thermoplastic Temperature range has been heated, wherein the end portion of the mandrel has an outer shape, which corresponds in terms of its shape to the desired internal shape of the deformed tube, this device is characterized in that the mold core

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has a hip protruding outward from its surface and an annular, inflatable one Part is surrounded, which surrounds the end portion of the mold core and thus the hip, -wherein the inflatable part in the non-inflated state has a radial distance from the core end section, so that the heated end portion of the tube can be pushed therebetween and that a pump is provided which supplies the inflatable part with pressure fluid to inflate it and which the liquid is removed from the inflatable part again.

Several exemplary embodiments of the invention will now be explained with reference to FIGS. 1 to 8. Show it:

1 shows a section through an embodiment of the pipe connection according to the invention;

Fig. 2 is a side view of the pin end according to the invention

5 shows a section through the socket end according to the invention;

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Fig. 4 is a perspective view of a further, preferred embodiment of the invention Pipe connection;

Fig. 5 shows a section through a device according to the invention for forming an internal groove in a plastic pipe that can be deformed by heat;

6 shows a partial section according to FIG. 5 for illustration a step of the method of forming the internal grooves;

FIG. 7 shows a partial section according to FIG. 5 to illustrate a second step of the method for shaping the internal grooves and

■ Fig. 8 is a section through one end of a means Heat deformable plastic pipe having internal grooves formed in accordance with the invention.

Fig. 1 shows an embodiment of an inventive Socket connection 10. The socket connection 10

en has a socket end 12 and a pin end H, wherein both ends are preferably formed from end sections of tubes, which are deformed by means of heat

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material _? such as B. PVC or another

en

Plastic, oestehen. The socket end 12 has an enlarged Sleeve 16, which has a conical inwardly directed shoulder 18 with an undeformed Pipe section 20 of the pipeline is connected.

In a similar way, and for reasons to be explained
The pin end 14 has a somewhat enlarged end section 22 which is connected to an undeformed pipe section 26 of the pipeline via a conically inwardly directed shoulder 24. The outside diameter of the enlarged end section 22 is matched to the inside diameter of the enlarged sleeve 16 in such a way that the pin engages in the sleeve with a close clearance fit.

en

The journal end 14 shown in Fig. 2 has according to the invention a continuous thread rib 28, which is preferably integral with the enlarged end portion 22 is formed and protrudes from its outer surface. As can be seen from the illustration, it winds the thread rib, starting from the front end of the enlarged end portion 22, around the end portion and away from the free end of the same. Although the threaded rib shown has a length of slightly more than one

Has thread turn, the thread rib length

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less than one or more turns, depending on the axial length of the socket joint and depending on the strength required to hold the pipe joint together.

According to a feature of the invention, the threaded rib 28, as can be seen from FIG. 2, has a front flank 30, a rear flank 32 and a ridge 34 which connects the flanks to one another at their outer ends. Both flanks, but in particular the rear flank 32, preferably protrude from this outer surface at an angle between approximately 30 and approximately 90 with respect to the outer surface of the pin. In practical embodiments this angle was between 35 ° and 45 °. The flanks therefore give the outer surface of the pin a fairly sharp profile. This sharp profile increases in a manner still to be explained the resistance of the socket connection against all forces that act on this connection in the sense of a solution of the R ο hiever connection.

In addition to the threaded rib 23, the pin end has an annular groove 36 formed in the outer surface of the pin end between the front end of the threaded rib 28 and the free end of the pin is formed, as from the

- ίο -

Pig. 2 emerges. This ring groove takes one made of rubber

ι or a similar flexible material

j de ring seal 3B. The ring seal is above all therefore in the spigot end and not as usual in the socket

end provided because the annular groove 36 is easier

[ Can be formed on the pin end, especially when using a hydraulic molding process.

As shown in Fig. 1 can be seen when joining

en

Sleeve and spigot ends, the ring seal protruding a little from the outer surface of the .Zapfenendes Inner wall of the enlarged sleeve 16 pressed radially inward. In this way the pipe connection becomes liquid and / or dust tight. As can be seen from Fig. 1, the G-round diameter is the Annular groove 36 equal to the outer diameter of the undeformed Pipe section 26. This is made possible by the enlargement of the end section 22 of the spigot end 14. Palis so the ring seal 33 around the undeformed If the pipe section 26 were lying, it would have the same outer diameter as if it were seated in the annular groove 36.

Palis so enter the improbable pail once should that the pin end H must be separated from the undeformed pipe section 26, the ring seal could 38 are placed around the undeformed pipe section 26,

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the same sealing effect as when seated in the annular groove 36 of the pin would be achieved.

The socket end 12 is shown in Pig = 3, the

j has a continuous thread groove 40 which ! preferably in one piece with the inner surface ! of the enlarged sleeve 16 and suitable for screw connection with the threaded rib 28 is. The G-screw groove 40 according to the invention is limited

j by a front flank 42, a rear flank 44 and iron gutter 46, which connects the two flanks connects. Both planks, but in particular the front flank 42, preferably protrude with an angle between, approx. 30 ° and approx. 90 ° with respect to the inner surface of the enlarged socket 16 into the wall of the same. In practical embodiments this angle was between and 45 · These flanks, similar to the flanks of the thread rib 28, form a fairly sharp one Profile with the inner surface of the socket end.

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As can be seen from FIG. 1, the pin end 14 and socket end 12 are connected to one another.

en bound that the threaded rib 28 of the spigot end

is screwed into the matching thread groove 40 of the socket end. Im screwed together The state of the socket connection is on the trailing edge 32 of the thread rib 28 and front flank 42 of the thread groove 40 against one another. If then Axial forces occur which will cause tensile stress in the pipe joint at least parts of the trailing flank 32 and the leading flank 42 touch one another. There how already mentioned, both the rear flank 32 and the front flank 42 have a sharp profile have, the resistance of the pipe connection to a solution of the Connection enlarged.

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... ■ · _; -235455 *

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FIGS. 9 and 10 show the locking mechanism of the socket joint. Fig. 9 shows a threaded rib ZB with a hook part 54, which is preferably formed in one piece with the outer surface of the pin end 14 and the VPS protrudes outward there. As can be seen from FIG. 9, the hook part 54 extends from the front end of the thread rib 28 away from the free end of the pin, on the other hand FIG. 10 shows an indenut 40 and a locking slot 5.6, which is formed in the inner surface of the enlarged sleeve 16 and extends from the rear end of the threaded groove in the direction of the free end of the sleeve. The closing slot is dimensioned such that it receives the hook part 54 with a tight fit. As can be seen from FIGS. 9 and 10, the width of the thread rib 28 is substantially less than the width of the thread groove 40 Liac part 54 is dimensioned so that it slides along the threaded groove 40 when the screw connection is made. Furthermore, the hook part and the locking slot are designed in such a way that when the hook part engages in the locking slot, the end of the hook part hardly touches the end of the locking slot. In this way it is ensured that the adjacent flanks of the thread groove and thread rib can touch one another.

The front end follows during the assembly of the socket joint the thread rib 28 with the hook part 54 the course

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the threaded part 40 in the socket, the socket connection can SP are designed that the ring seal 38 against a ' circumferential inner shoulder 59, which is provided in the sleeve part 12, is pressed. Like in Pig. 10 is shown the shoulder 59 is provided between the inner end of the threaded groove 40 and the obliquely inwardly directed shoulder 18. At the end of the screwing-together process, the hook part 54 and the locking seat 56 are aligned with one another and the one pressed together The seal acts as a spring and presses the hook part into the locking seat so that the socket part and the pin part together are locked. In order to loosen the pipe connection, the pin part must first be pushed further into the socket after which the hook part and the closing seat can be separated from one another by means of a rotary movement. Normally the two pipe parts are locked together.

The socket end and spigot end can, however, also be dimensioned in such a way that the ring seal in the screwed together state 38 is not compressed. In this case, the hook part 54 only snaps into the locking slot 56 when the Pipe connection is loaded by tensile forces.

Fig. 4 shows a preferred embodiment of a socket connection for pipes made of PVC. or another plastic, the socket joint having a socket end 60 and a

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Has pin end 62. Similar to the one described earlier Sleeve end 12, the sleeve end 60 has an enlarged sleeve 64, which is angled inwardly Shoulder 66 is connected to an undeformed pipe section 68. In contrast to the socket end 12, however, the socket end 60 four different internal thread grooves 70, the length of each thread groove being approximately a quarter of the circumference is, and wherein the flanks of the groove have a similar slope as the flanks of the thread groove 40. The thread grooves 70 are preferably equally spaced on the inner surface of the enlarged sleeve 64, with them . from the free end of the sleeve into this.

The pin end 62, similar to that previously described Spigot end 14, has an enlarged end section 72, which can be slid into the sleeve 64 and via an oblique inwardly directed shoulder 74 into an undeformed pipe section 76 merges, with an outer annular groove for receiving an annular seal 78 made of suitable, flexible material is provided. However, unlike the spigot end 14, the spigot end 62 has four outer threading ribs 80 which, upon insertion of the pin part 62 penetrate into the socket end and, upon subsequent rotation, into the threaded grooves 70. The thread ribs 80 also have - similar to the thread ribs 28 - with respect to the journal end 14, steep flanks.

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The thread grooves 70 and the thread ribs 80 cooperate in a manner similar to that of the thread groove 40 and the thread rib 28.

An important feature of the pipe joint just described is the sharp profile of the threaded groove 40 in the socket, which corresponds to the equally sharp profile of the thread rib 28 on the pin. There has never been an uncomplicated and Economical process for forming such sharply profiled grooves in the inner surface of a by means of heat deformable pipe in general or in particular a socket end of such a pipe.

Figures 5 to 7 show an apparatus for use in the method of making the socket end of the invention Pipe connection. Fig. 5 shows a device 110 for forming sharply profiled, inner grooves in one plastic tube that can be deformed by means of heat. The device has a mandrel 112 and a membrane device 114, which cooperate in a manner to be explained in order to

the end

a PVC or another plastic that can be deformed by means of heat to provide existing plastic pipe with a socket end in such a way that sharply profiled internal grooves in the socket end be formed.

-17- 409818/0969

The mold core 112, which is mounted in a known manner, not shown, has an enlarged hollow cylinder Core 116 with an enlarged socket-shaped section 118 which extends over an obliquely inwardly directed shoulder merges into an end section 122 of smaller diameter, onto which the free end of a heat-deformable tube can be pushed. Several ribs that form grooves 1 24 are on the outer surface of the socket mold section 118 are provided and protrude radially outward. Each of the groove-forming ribs 124 is formed like a thread. In Fig. 5 shows four of these thread ribs. The side flanks 128 of each rib protrude to the extreme at an angle between about 30 and about 90 from the outer surface of the socket molding section 118.

The rib configuration described is due to the shape of the grooves in the socket end shown in FIG. However, the device according to the invention is not limited to the design of this specific exemplary embodiment. Rather, the special rib shape of the mandrel 112 depends exclusively on the one to be produced in the socket end Groove shape. The device according to the invention offers the possibility of using a reliable method a Form internal groove or internal grooves so that the 'grooves are accurate

-13-

4 0 981870969

correspond to the shape of the ribs, with sharply profiled Ribs can also be formed with sharply profiled grooves.

With this method it may also be desirable or necessary, for reasons to be explained, to make the groove-forming ribs 124 movable between a protruding position, as shown in FIG. 5, and a non-protruding position, the outer contour of each rib in the non-protruding position either flush with the outer surface of the socket shape from section 118 or is recessed into the outer surface of that section. The ^s can be accomplished by means of a suitable conventional mechanism.

For example, each of the ribs can be used in a known manner connected to a movable piston 130, so that when Be «·; --— movement of the piston in one direction, the ribs are moved into their outstanding positions and when moving of the piston in the other direction, the ribs are moved into their non-protruding positions.

The device 110 also has a membrane device 114. This device has a membrane support ring 132 which from a front, annular side wall 134, a rear, annular, arranged at an axial distance therefrom Side wall 136 and a hollow cylindrical intermediate part 138

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consists. The front side wall 134 is dimensioned so that its inner diameter is slightly larger than the outer diameter of the socket-forming section 118, so that an annular gap 140 exists between these two parts. As will be explained below, the annular gap serves to push the heated end portion of a heat-deformable tube between the front side wall 134 and the socket-forming portion 118. The rear side wall 136 of the diaphragm support ring 132 is dimensioned such that it is in contact with the free end of the socket molding portion 118, as shown in FIG and is arranged coaxially therewith, so that the annular flange can serve as a stop for the heated end portion of a pipe whose socket end is formed on the mandrel 112.

According to the invention, the membrane device 114 has an annular membrane 146 or a similar, inflatable part, which consists of a suitable, inflatable material. The annular membrane rests against the inner surface of the intermediate part 138 that connects the side walls 134 and 136 of the membrane support ring 132 to one another, the annular membrane in the non-inflated state being like an inner lining of the intermediate part. The annular diaphragm can be in any suitable manner

-20-

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be set in this position as long as a significant part of the annular diaphragm has the freedom to move away from the To remove the inner wall of the intermediate part, wherein a liquid-tight chamber is formed. The ends of the diaphragm For example, as shown in Fig. 5, they can be retained in slots formed in the membrane support ring, so that there is a liquid-tight connection. The inner diameter of the intermediate part 138 is dimensioned so that .The annular membrane in the non-inflated state has such a distance from the socket-shaped section 118 that the heated end section of the tube can accommodate as shown in FIG finds.

The annular diaphragm 146 can be both inflated or unloaded. This is accomplished by a suitable device 148 that can supply and discharge pressure fluid. According to a preferred embodiment of the invention, the fluid used is water and the device 148 has a pump (not usually shown) for supplying the pressurized water and another pump for discharging it Water (not shown) * The water or another suitable liquid is pumped under pressure through a pipe ISO into a channel 152 * which is provided in the intermediate part 138 * The channel 152 extends completely through the intermediate part 13§, see 4a. & Die Liquid, between

Annular diaphragm. 146 and inner surface of the intermediate part. More than one channel can also be provided; in principle, any suitable distribution system can be used will. When the liquid is pumped into this area, the diaphragm is inflated so that it is separated from the Inner wall of the intermediate part removed and approached the socket-forming section 118 and the groove-forming ribs 124, as can be seen from FIG. 7. When the liquid is pumped out, the annular diaphragm returns to its rest position. -.... ■

As can be seen from Fig. 5, the membrane device surrounds 114 the socket molding section in the manner described 118 of the core 116. The membrane device 114 can be held in this position in any suitable manner. According to In a preferred embodiment of the invention, however, it is movably mounted in this position. For example the diaphragm support ring 132 has several radially inwardly outwardly extending flanges 154 which are provided with bores 156 arranged coaxially in the horizontal direction, in which a fixed railΊ58 is slidably arranged is. In this way, the entire membrane device can be displaced in the direction of arrow 170 along the rail. Any other, an axial movement of the diaphragm device The enabling mechanism can instead be preset; will.

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-22-

Any other membrane device can be used instead of the one shown in FIG membrane device 114 shown can be used as long as they are indispensable for the method according to the invention Features.

After the description of the structural design of the device 110 that has now taken place, the invention is now intended to be A method of forming an integrally molded groove in the inner surface of a heat deformable tube described using the device described will. As a first process step, an end section 159 of a thermoplastic plastic pipe 160 (FIGS. 6 and 7) made of PVC or another suitable plastic are heated to a temperature in the thermoplastic Teperaturbereich lies. This heating can be done in any of the known ways.

After the end portion 159 of the plastic pipe 160 has been heated to a thermoplastic temperature, the end portion is pushed over the core 116 so that it approximates the shape of the socket-shaped portion 118 of the shoulder 120 and the ribs 124, as shown in FIG . The heated end section is introduced into the device 110 by the thermoplastic plastic tube 160 and the core 116 being positioned relative to one another.

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-23-be removed.

As already mentioned, the groove-forming ribs can be positioned between the illustrated, outstanding position and be moved in a not excellent position. For example, it may be desirable to retract the ribs as long as possible to hold until the heated end portion 159 of the plastic tube 160 has been pushed completely over the core 116 The ribs can then be moved out into their outstanding positions until the internal grooves have been formed, whereupon the ribs can be retracted to enable the formed tube to be pulled from the core «

Either before the heated end section 159 of a plastic pipe 160 is positioned around the core 116, as shown in FIG. While the heated end portion of the plastic pipe 160 is still deformable, 138 hydraulic fluid is passed between the annular membrane and the intermediate part, in order corresponding to Fig * 7 inflate the membrane * As a result, the diaphragm conforms uniformly to the portion of the heated end portion by which the Mertibifari radially is aligned. Since the membrane is made of a flexible material, it does not only press firmly on the lower lying on it

Part of the heated pipe section., But it adapts itself also the contour of the core and in particular of the ribs 124. In this way, the heated pipe section is equal between the inflated membrane and the groove-forming ribs exactly the rib shape. So if the ribs with If there are sharp contours, the ribs formed in the inner surface of the pipe will also be sharp Have contours. If the ribs have flanks which are at angles between approx. 30 and 90 with the surface of the core have, the flanks of the grooves formed by means of the method according to the invention will also have precisely this rib configuration exhibit.

Thereafter, the membrane can recede, the groove-forming ribs can - if necessary or desired - not in theirs excellent positions are moved back and relative movement between core 116 and shaped end portion 159, the latter is removed from the core. In Fig. 8 is the final product of the method, the plastic pipe 160 having a socket end 162 and internal grooves 164.

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Claims (11)

-25 PATENT CLAIMS Plastic pipe connection with a first plastic pipe with socket end, a second plastic pipe with spigot end, the outside diameter of the spigot end being slightly smaller than the inside diameter of the socket end of the first plastic tube, and with a seal, characterized in that the The socket end (12) has at least one thread groove (40) in its inner surface, the thread groove (40) has an enlarged section, the shape of which corresponds to a closing part, and wherein the spigot end (14) at least one threaded rib (28) formed on and from its outer surface protrudes outwards and has a closing part, wherein the thread rib cooperates with the thread groove of the socket end, to releasably connect the plastic pipes to one another by means of a screw connection, and the Pin end has a larger outer diameter than that with him has one-piece molded plastic tube and an annular groove (36) completely surrounding its outer surface for receiving the seal, the base diameter of the annular groove being essentially equal to the outer diameter of the one-piece molded second plastic tube and the seal is arranged in the annular groove. 409818 / 096-9 ~ ^26u 2. Plastic pipe connection according to claim 1, characterized in that that the enlarged portion of the thread groove is a locking slot (56) leading from the rear end of the thread groove (40) extends out toward its front end 3. Plastic pipe connection according to one of claims 1 or 2, characterized in that the closing part is a raised one Is hook portion (54) provided at the front end of the threaded rib and extending therefrom, wherein the hook part (54) and the locking slot (56) cooperate after being screwed together such that the Pipes are detachably connected to one another. 4. Plastic pipe connection according to one of claims 1 to 3, characterized in that the receiving the seal Annular groove (36) is provided on the second tube in such a way that the seal against a circumferential, on the inner surface the shoulder provided on the first plastic pipe is pressed when the pipes are screwed together, the compression of the seal causing the hook portion (54) to be pressed into the locking slot (56) will. 5. Plastic pipe connection according to one of claims 1 to 4, characterized in that the threaded groove (40) has a front 409818/0969 ~ ²¹ ~ the flank (42) has, with respect to the inner surface of the socket end (12), an angle between approx. 30 and about 90 °. 6. Plastic pipe connection according to one of claims 1 to 5, characterized in that the width of the thread rib (28) is much smaller than the width of the thread groove (40), and that the width of the hook part. (54) is slightly less than the width of the thread groove (40). 7. Plastic pipe connection according to one of claims 1 to 6, characterized in that the threaded rib (28) has a Has rear flank (44) which, with respect to the outer surface of the second plastic pipe, forms an angle between approx. and approximately 90 °, with at least a part of the rear flank (32) under the action of a longitudinal tensile force The front flank (42) of the threaded groove (40) touches. 8. Plastic pipe connection according to one of claims 1 to 7, characterized in that the socket end (60) has four thread grooves (70) which are at equal intervals from each other along the inner circumference of the socket end (60), and that the pin end (62) has four thread ribs (80), which are provided at equal distances from one another along the outer circumference of the pin end. 409818/0969 9. Plastic pipe connection according to claim 8, characterized in that each threaded groove (70) has an enlarged Has section which corresponds in terms of its shape to a closing part, and that each thread rib (80) has a closing part. 10 · Method of making the socket end of the pipe joint according to one of claims 1 to 9, in which an end section of a plastic pipe deformable under the action of heat is heated to a temperature lying in the thermoplastic range, the heated end portion over a mandrel is pushed, the mandrel having an outer shape that corresponds to the desired inner shape of the socket end corresponds, the end section to a temperature below the thermoplastic range is cooled, and the plastic pipe with molded socket end is pulled off the mold core, d a d u r cn characterized in that the mold core (112) has at least one groove-forming rib (124) which consists of its outer surface protrudes, and that the heated end portion (15t) of the plastic tube (160) thereby from Molding core (112) is molded into an inflatable part provided around the heated end portion and the protruding rib, the inflatable member is inflated is so that it is at least part of the heated 409818/0969 - 29 End section (159) presses against at least part of the core end section provided with the rib (124), so that the pressed part is in terms of its shape on the rib and the pressurized part of the core end - section, with the outstanding rib (124) in the inner surface of the heated end portion (159) a threaded groove (164) is created, and that the printing medium from the inflatable part is deflated when the temperature of the heated end portion (159) is below the thermoplastic Temperature range has dropped and before the plastic pipe is pulled from the mold core (112). 11. Device for forming a thread groove in the inner surface a heat-deformable tube for performing the method of claim 10, consisting from a cylindrical mandrel, one of the end portions for receiving an end portion of a by means of heat-deformable tube is suitable after the pipe end section to a temperature in the thermoplastic Temperature range has been heated, wherein the end portion of the mandrel has an outer shape that regarding their shape of the desired inner shape of the corresponds to deformed tube, characterized that the mold core (112) has a rib (124) protruding outward from its surface and 409818/0969. - 30 - is surrounded by an annular, inflatable part, the end portion of the Forrakersn (112) and thus the Surrounds rib (124), wherein the inflatable member in the deflated state has a radial distance from the core end portion, so that the heated end portion (159) of the tube can be inserted, and that a pump is provided that the inflatable part with pressure fluid which can be drained from the inflatable part again 409818/0969 Blank page