DE2053938A1 - Method and device for the manufacture of a see for connecting thermoplastic plastic pipes serving welding sleeve - Google Patents

Description

Berlin, October 26, 1970 Patent Attorneys M / Zi

Dipl.- Ing. W. M eiss π e
Dipl.-Ing. H. Tischer
1 Benin 33 (Grunewald;
Herberts ». 22, TeU S 87 72 37.

Case 25oy

MANNESMANN AKTIENGESELLSCHAFT, 4 Düsseldorf 1, Mannesmannufer

"Method and apparatus for the production of a connection welding socket used for thermoplastic plastic pipes "

The invention relates to a method and a device for producing a non-detachable connection of the ends of thermoplastic Plastic pipe socket made of thermoplastic Plastic, in the inner wall of which a heating wire winding that can be connected to an electrical power source is embedded.

Such welding sockets are used to make pipes made of thermoplastic Material for example at the place of use of the pipes or lines, with each other on simple, also of unskilled workers to firmly connect feasible ways to one another. This is done by inserting the ends of the too connecting pipes into the welding socket and applying a current to the heating wire winding of the socket, whereby the in the sleeve inserted pipes and the sleeve on the surfaces exposed to the heating soften and melt, so that the nested Parts are firmly welded together after switching off the power and cooling.

The previously known way of manufacturing such sleeves is the injection molding process, which, however, is some economical and technical Brings difficulties.

In all current designs, the wire winding is injection-molded with the thermoplastic material and acts to contract of the surrounding plastic during cooling. Included is in the plastic - as long as it is not broken down by relaxation

♦ especially large diameter - 2 -

209818/0932

- a hoop stress is generated which, when the winding is suitably heated, leads to an - albeit limited - passage of the softened thermoplastic leads between the turns of the inner resistance winding. This makes it possible to reduce To absorb diameter differences between pipe and socket and at the same time one for welding pipe and socket to generate favorable welding pressure.

It has now been shown that with large pipe diameters permissible diameter tolerances can no longer be properly controlled by the above-mentioned mechanism.

The present invention enables, among other things, opposite the injection molding process commonly used today to produce sleeves with much greater circumferential stresses, which accordingly also bridge the gap Allow larger diameter tolerances with sufficient welding pressure.

Pipes connected with electrofusion sockets can, depending on the Dimensioning of pipe and socket fail under increased stress. If the failure occurs in the socket, then caused by the notch effect of the inner wire winding, a crack perpendicular to the surface, even with pure internal pressure to the pipe axis, i.e. not in the direction of the maximum stress on the pipe.

It is now known that the creep rupture strength and the notch sensitivity injectable polyethylene types are significantly lower than that for the extrusion of certain higher molecular weight Polyethylene. To avoid the disadvantages described, will proposed according to the invention, the electrofusion socket from for Extruder processing; ; to produce suitable thermoplastics, and in such a way that one from an extruder slot nozzle emerging warm band of thermoplastic material around the of one in rotation; offset mandrel held heating wire winding is wound, whereupon after achieving the desired sleeve thickness the tape is severed, the ends of the sleeve if necessary

209818/0932 _BAD original

be trimmed and this is withdrawn from the mandrel.

It is recommended ο to stretch the thermoplastic tape lengthways su stretch for what the exit speed of the belt of the slot nozzle is set lower than the Uinf to the speed of the mandrel to be wound.

In contrast, for the production of several sleeves at the same time on one with the corresponding number of heating wire windings: provided mandrel wound the tape spirally, the price of the tape, its thickness and the axial Feed the total thickness of the plastic layer; determine.

If only one sleeve is produced, it is advisable to choose a band emerging from the slot die, the width of which, after stretching, slightly exceeds that of the mandrel to be wound, the mandrel executing a pure rotary movement.

By wrapping r.it one: thicker in the middle, thicker at the end thinner band, can also be used after the. according to the invention Process the usual '..' thickness distribution in the socket achieve. This can also be done during the winding of the r.with a heating wire winding Dornes increases the degree of reek of the film and increases its width is decreased.

Ls deserves to be mentioned that there is a disparagement of the stresses in. Endangered cross-section due to thickening of the hoof end wall in the. method according to the invention - in particular even with larger piece weights - can be carried out more cheaply than with injection molding.

Due to the process, there is another possibility to improve the creep behavior by "wrapping" of reinforcing elements. To perform the welding process described above, There is an air gap between the pipe and the socket

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BAD Gf-iiGiNAL

. - ■ - ■ * ■■ -

^: .ΐ- ■. ; 20S3S3B

■ ■ ■. ϊ. ■ /

ΐ contraction of the socket is bridged, not to hinder,

the reinforcement elements only have to be load-bearing in the longitudinal direction,,::; . be "soft" in the circumferential direction. This is achieved in accordance with the i 'further feature of the invention that in'die; Axial positions of the sleeve, distributed over the circumference of the rod : ■. shaped reinforcement elements' are wrapped »some

have a higher modulus of elasticity and a smaller thermal expansion of the sleeve material, for example rods made of glass fiber ¹ 'I ;: reinforced epoxy resin. These rods can be used before inserting

are additionally wetted with liquid resin. It is appropriate., .. * ■ the bars, which can also be profiled., In the manner of a V '■ Summarize rope ladder before wrapping.

. ΐ In the case of thermoplastics that tend to age after long storage ■ ·., .. ν / "and thus to difficulties in welding, a multilayered structure of the plastic wrapping can be selected for C j ■ .-:"■■;'. t, at the inside, i.e. immediately above the wire: ■>■,;■;' : ■ ■. coil a highly stabilized product or a factory ^; ... , ^: j _; ' ; particularly favorable behavior in terms of notch sensitivity

j;. ι ,. ■; · || ir ■.

■■ ' ,, ■' ... - possibility or weldability is used whereas the

: * .-;.,. Outer layer made of a very high molecular weight and relative.

; ,? there is little relaxing product. For low pressure poly

; /; φ; Ethylene is suitable for types with molecular weights

■, ΐ. ■, from 90,000 and above- The two-layer structure can be

^ a. neither by winding de.s

^: ■ Domes with both of them from their own slot nozzle

■■: ■■ :. emerging plastic tapes are made; but it can still

^: The two to work with a slot die,

,: / Extruders fed »the production, a two-shift

■. , Tape allows.

; '.; It is well-known and .proven * the resistance wire: its processing with the plastic forming the sleeve ■■; ■■ or at least a similar one that is welded to this:, to encase the product * where the thickness of the jacket is approximately { ,. can be half the wire diaice. The slope of this-it sheathed wire on the "mandrel" should be in the area

; ' - _s between 2 and 5 χ wire diameter, preferably 3 x wire

diameter lie. The slope can also be enforced in a known manner by winding a wire along with the consists of a material that does not weld with the plastic of the sleeve and after the actual Manufacturing process of the sleeve is removed.

To carry out the method according to the invention, it is proposed with the further features to use a winding mandrel, which has a holding device for the heating wire winding, each of which is detachable from one placed around each end of the mandrel There is steel band, the ends of which are angled and engage in a longitudinal groove of the mandrel, and which on its outside has a wart-shaped projection, which is for receiving each a wire end formed into an eyelet of the heating wire winding is used.

The mandrel expediently consists of two detachably connected to one another Halves, one half of which has a peg-like protrusion into a correspondingly formed recess of the other clip engages, and that the pin-like projection for receiving a pre-fabricated to be wrapped by the thermoplastic tape Stop ring for the pipe ends is used.

An embodiment of the invention is shown in the drawing, namely show:

Figures 1 and 2

a front and side view of the winding mandrel,

Figure 3

a schematic representation of the process,

Figure K

a detail of the extruder die for producing a two-layer ribbon and

Figure 5

a winding mandrel divided into two halves.

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2053838

On a core 2, provided with a longitudinal slot 1, preheated to about 150 °, with a diameter of 200 mm and a length of 150 mm is, a steel band 3 is at the two ends with his angled ends 4 inserted into the longitudinal slot 1 and thus fastened. A wart-shaped elevation 5 of approx. 6 mm in diameter serves as a fastening for the metallic, non-insulated eyelet ends of the resistance wire. The core can be made up of two mutually rotatable and lockable Halves consist. The heating wire is wrapped around the core mechanically with the specified slope. Several cores each provided with a heating wire winding can be used for winding with the Plastic tape can be combined by screwing. This core, which results in several sleeves, is based on a wire- and feed direction 6, which is located below a slot nozzle 7 of 35o mm wide and 1 mm thick, that of a extruder 8, not shown, is fed. The emerging tape made of low-pressure polyethylene with a molecular weight of 100,000 is with the help of a pressure roller 9 and a twice as high peripheral speed as the exit speed from the slot die, wound in several layers until the total layer thickness of the polyethylene body, depending on the intended use, is reached.

As already mentioned, it is also possible to work with the same success in such a way that a single core with a thermoplastic tape is more appropriate Width is wound without axial feed.

Several cores can be arranged on a carousel so that an uninterrupted V / icke Ivorgang is made possible even when the core is changed will. After this operation, the sleeve is trimmed to the right and left, if necessary, cooled and pushed off the winding core and the steel strips remaining in the sleeve with the fastening lugs for the winding are pulled inwards. These Places previously occupied by the warts serve as power supply after drilling through the sleeve wall.

It has been shown that when welding such a sleeve Bridging a gap between the pipe and the pipe that is about twice as high

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BATH ORIGINAL

Socket inner diameter is possible than with the corresponding injection-molded Sleeves and also have significantly improved creep behavior.

In a preferred embodiment, the sleeve with an inner Stop ring 1 provided. This takes place in such a way that a prefabricated stop ring is located between a winding core 12 which is divided in the middle is used and the rest of the procedure is continued as previously described. The stop ring can be made from the same or from .Production reasons are made of a different plastic than the rest of the Fittig.

It is desirable that after being inserted into the split Winding mandrel is facing outward surface of the stop ring, so it is recommended that the 'winding only up to the Execute the stop ring with a normal pitch and the stop ring itself in a groove provided for this purpose To overcome incline.

For the production of sleeves from different layers of material the use of a known Breitschlitiiwerkzeuges IJ is recommended, which of two not shown Extruders with different materials 14 and 15 are fed, which are connected to form a composite film 16 inside the head. To produce a two-layer sleeve, the feeding extruders are operated one after the other and overlapping one another.

- Patent claims 09 818/093? bad ORfGiNAL

Claims (1)

TT ^^ - y-jft {j 1 *} j ^^ jl · -,> -. -4 vj ^ -wi _f _. _1y Claims (1.] A method for producing a permanent connection of the ^ "^ Ends of thermoplastic pipes serving sleeve Made of thermoplastic material, in the inner wall of which a heating wire winding can be connected to an electrical power source embedded, is characterized in that one of a Extruder wide slot nozzle exiting a warm strip of thermoplastic material around the one set in rotation The heating wire winding held in the mandrel is wound, whereupon the tape is cut off after the desired sleeve wall thickness has been achieved and the sleeve is withdrawn from the mandrel, if necessary after trimming its front ends. 2. The method according to claim 1, characterized in that the thermoplastic tape in the longitudinal direction during the winding is stretched, for which the speed of the tape emerging from the nozzle is set lower as the peripheral speed of the mandrel. 5. The method according to claims 1 and 2, characterized in that that the width of the stretched tape is equal to or greater than the length of the wire winding. - 9 -20 9818/093? BAD ORiGiNAL 4. The method according to claims 1 to ~ 5, characterized in that the possibly several heating wire windings carrying rotating mandrel is additionally moved axially during winding and the thickness of the winding is adapted to the respective requirements via the axial advance. 5. Process according to claims 1 to 4, characterized in that that the thermoplastic tape during the winding on the circumference of the heating wire winding or the already wound Layers is pressed, e.g. with rollers or the like. 6. The method according to claims 1 to 5, characterized in that the heating wire winding is wound with two superimposed layers, of which the inner, the heating wire winding facing layer made of a highly stabilized plastic or one with low notch sensitivity, z. B. a copolymer of polyethylene, and the outer layer consists of a high molecular weight plastic, for example low-pressure polyethylene with a molecular weight of over 9 ° · οοο. 7. Process according to Claims 1 to 6, characterized in that that axial rod-shaped reinforcing elements distributed over the circumference of the socket are wrapped in the layers of the socket, which have a higher modulus of elasticity and a smaller thermal expansion of the sleeve material, for example rods made of glass fiber reinforced epoxy resin. 8. mandrel for performing the method according to the claims 1 to 7, characterized in that it has a holding device for the heating wire winding, each of which consists of a Each end of the mandrel is made of detachable steel band, the ends of which are angled and inserted into a longitudinal groove of the mandrel intervene, and which on its outside a wart-shaped Has projection which is used to receive a wire end formed into an eyelet of the heating wire winding. - 1o 209818/093? BATHROOM CRIGiMAL - 1ο - Mandrel according to claim B, characterized in that it consists of two halves detachably connected to one another, of one half with a pin-like projection in a correspondingly formed recess of the other Half engages and that the pin-like projection for receiving one of the thermoplastic tape to be wrapped Stop ring for the pipe ends is used. ^BATH 209818/0932 Blank page