HRP920372A2

HRP920372A2 - Electro-fusion fittings

Info

Publication number: HRP920372A2
Application number: HR920372A
Authority: HR
Inventors: David Michael Anthon Kenworthy; David Bretell; Russel John Kirk; Robin Bryan Carter
Original assignee: Fusion Group Plc
Priority date: 1989-05-03
Filing date: 1992-09-21
Publication date: 1994-10-31
Also published as: SI9010030A

Description

Ovaj se izum odnosi na električno topljive cijevne naglavke i na njihovu proizvodnju. Električno topljivi naglavci se koriste za izradu spojeva termoplastičnih, najčešće polieti1enskih cijevi. Izum se posebno bavi naglavcima namijenjenim za spajanje sučelice dviju cijevi, pri čemu se takvi naglavci nazivaju naglavci ili čahure za zavarivanje. Konvencionalne čahure za zavarivanje sastoje se od šupljeg cilindričnog tijela od termoplastičnog materijala s namotajem elektrootporne žice za zagrijavanje na njegovoj unutrašnjoj površini. Kod primjene, krajevi cijevi se utiskuju u suprotne krajeve čahure i električna struja se dovodi u namotaj za zagrijavanje tako da se materijal cijevi i tijela naglavka topi i međusobno stapa da bi formirao siguran hermetički spoj između krajeva cijevi. This invention relates to electrically fusible pipe caps and their production. Electrically fusible nozzles are used to make joints of thermoplastic, usually polyethylene pipes. The invention is particularly concerned with headers intended for joining the interface of two pipes, whereby such headers are called headers or welding sleeves. Conventional welding ferrules consist of a hollow cylindrical body of thermoplastic material with a coil of electrical resistance heating wire on its inner surface. In application, the ends of the tube are pressed into opposite ends of the sleeve and an electric current is applied to the heating coil so that the material of the tube and body of the cap melts and fuses together to form a secure hermetic joint between the ends of the tube.

Mogu se koristiti različiti postupci za proizvodnju električno topljivih čahura. Najpogodnija je, u slučaju čahura relativno malih promjera, koje zato imaju i tijela relativno male mase, tehnika po kojoj se tijelo proizvodi normalnim postupkom lijevanja ubrizgavanjem. Žica za zagrijavanje, obložena termoplastičnim materijalom, može se namotati na jezgru kalupa za lijevanje ubrizgavanjem, nakon čega se tijelo lijeva ubrizgavanjem na licu mjesta preko namotaja žice. Various processes can be used to produce electrofusible ferrules. In the case of relatively small diameter bushings, which therefore also have bodies of relatively low mass, the most suitable technique is that the body is produced by the normal injection molding process. A heating wire, coated with a thermoplastic material, can be wound onto the injection mold core, after which the body is injection molded in situ over the wire coil.

Ova tehnika nije, međutim, idealna za proizvodnju naglavaka velikih promjera, jer su troškovi za alate veoma veliki a proizvodnost je vrlo mala zbog velike dužine vremena ciklusa (reda veličine 20 minuta) koji se sastoji od vremena potrebnog da se šupljina kalupa ispuni rastopljenom plastičnom masom i zatim vremena stvrdnjavanja potrebno da prođe prije nego što se kalup može otvoriti . Kao rješenje problema ekonomične proizvodnje naglavaka velikih promjera, predloženo je u GB-A-20336518 da se tijelo formira odsijecanjem dijela jedne cijevi od termoplastičnog materijala. Namotaj za zagrijavanje se postavlja u unutrašnjost odsječenog komada cijevi postupkom koji obuhvaća: širenje odsječenog dijela cijevi i umetanje u njega vretena na koje je namotana žica, bilo ogoljena, bilo obložena termoplastičnim materijalom, cijev se skuplja preko vretena i namotaja u nekoj peći, zatim se dovodi električna struja na žicu za zagrijavanje kako bi se navoji žice proširili dok se izvlači vreteno, ili se nastavlja sa skupljanjem odsječenog komada cijevi a termoplastični materijal teče između navojaka, a nakon hlađenja se krajevi žice priključuju na kontaktne klinove koji su ranije postavljeni na odsječeni dio cijevi. Ovaj je postupak složen i još uvijek postoji potreba za pouzdanim i ekonomičnim proizvodnim postupkom. This technique is not, however, ideal for the production of large-diameter heads, because the tooling costs are very high and the productivity is very low due to the long cycle time (of the order of 20 minutes), which consists of the time required to fill the mold cavity with the molten plastic mass and then the hardening time required to pass before the mold can be opened. As a solution to the problem of economical production of large-diameter nozzles, it is proposed in GB-A-20336518 that the body is formed by cutting off a portion of a single tube of thermoplastic material. The heating coil is placed inside the cut-off piece of pipe by a process that includes: expanding the cut-off part of the pipe and inserting into it a spindle on which a wire is wound, either bare or coated with a thermoplastic material, the pipe is gathered over the spindle and coiled in a furnace, then an electric current is applied to the heating wire to expand the threads of the wire as the mandrel is withdrawn, or the cut piece of pipe is continued to shrink and the thermoplastic material flows between the threads, and after cooling the ends of the wire are connected to the contact pins previously placed on the cut section pipes. This process is complex and there is still a need for a reliable and economical production process.

Prema jednom obliku izuma, njime se dobiva električno topljiva cijevna spojnica koja obuhvaća vanjski omotač u obliku jednog samonosećeg cilindra, jedan elektrootporni namot za grijanje koji obuhvaća namotaj žice obložen termoplastičnim materijalom i smješten u omotaču, i sloj termoplastičnog materijala uljeven na licu mjesta između namotaja i omotača a koji pričvršćuje namotaj unutar omotača. According to one form of the invention, it provides an electrically fusible pipe fitting comprising an outer sheath in the form of a self-supporting cylinder, an electrical resistance heating coil comprising a coil of wire coated with a thermoplastic material and housed in the sheath, and a layer of thermoplastic material cast in situ between the coil and of the sheath a which secures the winding inside the sheath.

Kod takve konstrukcije je glavna namjena vanjskog omotača da naglavku da neophodnu jačinu. Iako je preporučljivo da omotač bude napravljen od termoplastičnog materijala, moguće je da bude napravljen i od drugih materijala kao što su metali. Ova mogućnost postoji zbog toga što ne mora biti neophodno da omotač sudjeluje u procesu zavarivanja cijevi, jer lijevani termoplastični materijal u kombinaciji s materijalom obloge namotaja, može biti dovoljan da osigura hermetički spoj između dva kraja cijevi. With such a construction, the main purpose of the outer shell is to give the head the necessary strength. Although it is recommended that the sheath be made of a thermoplastic material, it is possible that it be made of other materials such as metals. This possibility exists because it is not necessary for the casing to participate in the pipe welding process, because the molded thermoplastic material in combination with the coil lining material can be sufficient to ensure a hermetic connection between the two ends of the pipe.

U tijeku faze lijevanja ubrizgavanjem, omotač predstavlja vanjski dio kalupa koji obuhvaća šupljinu kalupa s jezgrom na koju je namotana žica. Na taj način se mogu izbjeći skupi uređaji za lijevanje. Čak i kada je omotač napravljen od termoplastičnog materijala, neće se obavezno ostvariti integralna veza koja spaja omotač i sloj uljevenog materijala u tijeku procesa lijevanja ubrizgavanjem, mada će ova dva dijela biti u neposrednom dodiru. Da bi se spriječilo otkidanje naljevenog sloja, ili raslojavanje s unutrašnje površine omotača zbog skupljanja koje teži da se prirodno javi u tijeku otvrdnjavanja lijevanog materijala, pogodno je da lijevani sloj bude na svakom od krajeva oblikovan s jednim vanjskim ispustom koji naliježe na aksijalno prema van okrenutom uporu koji formira omotač. Upor može predstavljati krajnja, čelna površina omotača,ili jedan žlijeb kod unutrašnjeg ruba krajnje površine. Isto tako, upor može biti nagnut u odnosu na os, ili oblikovan na neki drugi način kako bi se osiguralo sigurno povezivanje s naljevenim slojem. Međutim, veoma zadovoljavajući rezultati ostvareni su pomoću jednog radijalnog upora formiranog jednim prstenastim žlijebom izvedenim u unutrašnjoj površini omotača na maloj udaljenosti od njegovog kraja. During the injection molding phase, the jacket represents the outer part of the mold that encloses the mold cavity with the core on which the wire is wound. In this way, expensive casting devices can be avoided. Even when the casing is made of thermoplastic material, an integral bond connecting the casing and the layer of oiled material will not necessarily be achieved during the injection molding process, although these two parts will be in direct contact. In order to prevent tearing of the cast layer, or delamination from the inner surface of the shell due to shrinkage that tends to occur naturally during the hardening of the cast material, it is convenient for the cast layer to be formed at each of the ends with one external outlet that abuts the axially outward facing the support formed by the envelope. The abutment can be the end, frontal surface of the casing, or one groove at the inner edge of the end surface. Likewise, the abutment can be inclined relative to the axis, or shaped in some other way to ensure a secure connection to the poured layer. However, very satisfactory results were achieved by means of a single radial abutment formed by an annular groove made in the inner surface of the casing at a short distance from its end.

Poželjno je da se lijevani sloj pruža aksijalno od jednog do drugog kraja omotača. Ako je omotač napravljen od termoplastičnog materijala, moguće je ostvariti dva posebna sloja, pri čemu su ti slojevi povezani s dijelovima namotaja predviđenim za istovremeno djelovanje s pripadajućim krajevima cijevi u tijeku procesa zavarivanja. Preferably, the cast layer extends axially from one end of the shell to the other. If the sheath is made of thermoplastic material, it is possible to realize two separate layers, whereby these layers are connected to parts of the winding intended to act simultaneously with the associated pipe ends during the welding process.

Kod svakog od krajeva cijevne spojnice, obloga koju tvori u unutrašnjosti omotača naljeveni sloj može biti zakošena kako bi se napravio uvodni dio za krajeve cijevi koji se spajaju. At each of the ends of the pipe fitting, the lining formed on the inside of the casing by the poured layer can be chamfered to make an introduction for the ends of the pipes to be joined.

Slijedeća je prednost izuma ta, da se ograničavanjem količine ubrizganog materijala dimenzijska točnost gotovog otvora Another advantage of the invention is that by limiting the amount of injected material, the dimensional accuracy of the finished opening is improved

može lakše ostvariti. can more easily be achieved.

Prema jednom drugom poželjnom svojstvu, cijevna spojnica obuhvaća jedan kontaktni klin koji se pruža kroz zid omotača, a ima jedan unutrašnji dio povezan s unutrašnjim dijelom, i predstavlja krajnji priključak. Unutrašnji i vanjski dio spojeni su rastavljivo, na primjer pomoću navoja. Ova konstrukcija ima izvjesne prednosti koje će biti jasne iz slijedećeg opisa. According to another preferred feature, the pipe fitting comprises a contact pin which extends through the wall of the casing, and has an inner part connected to the inner part, and is an end connection. The inner and outer parts are connected releasably, for example by means of threads. This construction has certain advantages that will be clear from the following description.

Prema drugom njegovom obliku, izumom se ostvaruje jedan postupak za izradu električno topljive cijevne spojnice, koji obuhvaća stupnjeve pripremanja jednog cilindričnog omotača, namotavanja namotaja elektrootporne žice za zagrijavanje obložene termoplastičnim materijalom na jezgru kalupa, umetanje jezgre i namotaja na njemu u omotač tako da između njih ostaje jedan radijalni prostor, ubrizgavanje termoplastičnog materijala radi ispunjavanja tog prostora, i uklanjanje jezgre tako da namotaj bude zadržan u omotaču pomoću uljevenog materijala. According to its second form, the invention realizes a process for making an electrically fusible pipe connector, which includes the stages of preparing a cylindrical shell, winding a coil of electro-resistant heating wire coated with thermoplastic material on the core of the mold, inserting the core and the coil on it into the shell so that between them one radial space remains, injection of thermoplastic material to fill that space, and removal of the core so that the coil is held in the sheath by oiled material.

Priprema omotača obuhvaća, poželjno, strojnu obradu omotača pri čemu se kod svakog od njegovih krajeva stvara jedan aksijalno prema van usmjereni upor, tako da sloj materijala koji se potom ulije na licu mjesta u omotač naliježe na upor, a u svrhu koja je ranije objašnjena. Nakon umetanja jezgre u omotač, pogodno je da se jedan kontaktni dio može vezati za kraj žice i umetnuti u jedan radijalni otvor izveden u omotaču, tako da će kontaktni dio biti pričvršćen na svom mjestu naljevenim materijalom. U toku stupnja lijevanja, kontaktni dio može se učvrstiti u svom položaju nekom spravom koja zahvaća kontaktni dio s vanjske strane omotača. Kako su spojevi između kontaktnih dijelova i krajeva žice utopljeni u naljeveni materijal, oni su zaštićeni i ne formiraju ispupčenja za koja bi mogli zapeti krajevi cijevi pri stavljanju u vanjski naglavak. The preparation of the casing includes, preferably, the machining of the casing, whereby an axially outwardly directed abutment is created at each of its ends, so that the layer of material which is then poured on site into the casing abuts the abutment, for the purpose explained earlier. After inserting the core into the jacket, it is convenient that one contact part can be tied to the end of the wire and inserted into one radial hole made in the jacket, so that the contact part will be fixed in place with the poured material. During the casting step, the contact part can be fixed in position by a device that engages the contact part on the outside of the casing. As the connections between the contact parts and the ends of the wire are embedded in the cast material, they are protected and do not form protrusions that could catch the ends of the pipe when inserting it into the outer sleeve.

Poželjno je da žica bude namotana u dva gusto namotana dijela, u kojima su navojci u međusobnom dodiru, s jednim spojnim dijelom koji međusobno povezuje ova dva dijela. It is desirable that the wire is wound in two densely wound parts, in which the threads are in contact with each other, with a connecting part connecting these two parts together.

Prikazani izum je uglavnom namijenjen za proizvodnju električno topljivih naglavaka velikih promjera, ali nema razloga da se ne primijeni i na proizvodnju priključaka malih promjera ako se želi . The presented invention is mainly intended for the production of electrically fusible caps of large diameters, but there is no reason why it should not be applied to the production of small diameter connections if desired.

Najpogodnije je da se omotač pripremi od jednog cjevastog obratka, na primjer odsječenog od jedne termoplastične cijevi izrađene istiskivanjem, ili načinjene od trake dobivene istiskivanjem, kao što će kasnije biti detaljnije prikazano. Poželjno je da materijal obratka bude isti kao i materijal uljeven brizganjem, ali to nije bitno. Unutrašnja površina obratka je strojno obrađena na ravnomjeran promjer, ali je ostavljena gruba, kako bi se poboljšalo prianjanje naljevenog sloja za omotač. It is most convenient for the jacket to be prepared from a single tubular blank, for example cut from a single extruded thermoplastic tube, or made from an extruded strip, as will be shown in more detail later. It is preferable that the workpiece material is the same as the injection molded material, but this is not essential. The inner surface of the workpiece is machined to a uniform diameter, but left rough, to improve the adhesion of the cast layer to the casing.

Prema jednom drugom obliku izuma, izvedena je jezgra kalupa koja će se koristiti u proizvodnji električno topljive čahure, a koja ima dva kružna dijela jezgre, elemente za međusobno povezivanje dijelova jezgre zbog definiranja jedne aksijalno postavljene cilindrične površine za prihvaćanje namotaja elektrootporne žice za zagrijavanje, jedan ulazni otvor za rastopljeni plastični materijal u jednoj vanjskoj krajnjoj površini jednog dijela jezgre, i jedan izlazni otvor za rastopljeni materijal formiran na cilindričnoj površini u ravnini međusobnog dodira jezgre. According to another form of the invention, a mold core to be used in the production of an electrically fusible sleeve is provided, which has two circular core parts, elements for interconnecting the core parts due to the definition of an axially placed cylindrical surface for receiving a coil of electro-resistive heating wire, one an inlet for molten plastic material in one outer end surface of one part of the core, and one outlet for molten material formed on a cylindrical surface in the plane of mutual contact of the core.

Kod jedne preporučljive konstrukcije jezgre, ulazni otvor se pruža aksijalno kroz jedan dio jezgre i povezan je s više radijalnih kanala napravljenih između dva dijela jezgre i povezanih s pripadajućim izlaznim otvorima raspoređenim po cilindričnoj površini. In one preferred core construction, the inlet port extends axially through one part of the core and is connected to a plurality of radial channels made between the two parts of the core and connected to associated outlet ports distributed over the cylindrical surface.

Vanjske površine dijelova jezgre mogu biti izvedene s elementima, na primjer kružnim obodima ili ispustima za držanje namotaja na mjestu prije i u tijeku procesa lijevanja ubrizgavanjem. The outer surfaces of the core parts may be provided with features, for example circular rims or recesses, to hold the windings in place before and during the injection molding process.

Jasno shvaćanje izuma u raznim njegovim oblicima dobiti će se iz slijedećeg detaljnijeg opisa s pozivom na priložene crteže, gdje: A clear understanding of the invention in its various forms will be obtained from the following detailed description with reference to the attached drawings, where:

slika 1 prikazuje uzdužni presjek jednog električno topljivog naglavka u obliku čahure, kojim je ostvaren prikazani izum, figure 1 shows a longitudinal section of an electrically fusible cap in the form of a sleeve, which was used to realize the presented invention,

slika 2 prikazuje povećan detalj naglavka zaokružen na slici 1 , Figure 2 shows an enlarged detail of the head circled in Figure 1.

slika 3 prikazuje pogled na čelnu površinu naglavka prikazanog na slici 1, figure 3 shows a view of the front surface of the cap shown in figure 1,

slika 4 predstavlja, shematski, uzdužan presjek koji prikazuje jedan uređaj za pripremu obratka omotača za izradbu naglavka sa slike 1, figure 4 represents, schematically, a longitudinal section showing a device for the preparation of the shell workpiece for the production of the head from figure 1,

slika 5 predstavlja vodoravnu projekciju uređaja prikazanog na slici 4, figure 5 represents a horizontal projection of the device shown in figure 4,

slika 6 prikazuje bočnu projekciju, djelomično u presjeku duž linije VI-VI na slici 7, jedne jezgre kalupa koja se koristi za izradu naglavka prikazanog na slici 1, Fig. 6 shows a side view, partially in section along line VI-VI in Fig. 7, of one mold core used to make the cap shown in Fig. 1,

slika 7 predstavlja pogled s desne strane na jezgru prikazanu na slici 6, Figure 7 is a right side view of the core shown in Figure 6,

slika 8 prikazuje presjek duž linije VIII—VIII na slici 6, i Fig. 8 shows a section along the line VIII—VIII in Fig. 6, i

slika 9 prikazuje jedan poprečni presjek koji prikazuje jedan sklop električnog kontakta pripremljen za stupanj lijevanja ubrizgavanjem. Figure 9 is a cross-sectional view showing an electrical contact assembly prepared for the injection molding stage.

Na slikama 1 do 3 prikazana je cijevna spojnica u obliku električno topljivog naglavka oblika čahure. Tijelo naglavka sastoji se uglavnom od jednog cilindričnog omotača, ili karkase, 1 na čiju je unutrašnju površinu postavljen jedan namotaj 2 s elektrootporne žice, koji se na mjestu drži umetnutim slojem 3 termoplastičnog materijala uljevenog ubrizgavanjem. Sloj 3 se pruža s kraja na kraj omotača i na svojim krajevima je izveden sa zakošenim površinama 4 koje formiraju uvodni dio za svaki od krajeva cijevi, kako bi se olakšalo umetanje krajeva cijevi koji će se spojiti u čahuri. U središnjoj ravnini sloja 3 postavljeno je više, po obujmu raspoređenih ispusta koji se pružaju prema unutra i tvore graničnike 5 na koje naliježu krajevi cijevi, čime se osigurava pravilno postavljanje unutar čahure kao priprema za proces zavarivanja. Na maloj udaljenosti od svakog kraja urezan je u omotaču 1 prstenasti žlijeb 6, pravokutnog poprečnog presjeka, tako da materijal sloja 3 popunjava taj žlijeb da bi se ostvarilo mehaničko vezanje između omotača i naljevenog sloja. Ta veza sprečava odvajanje sloja 3 od omotača uslijed pojave radijalnog i aksijalnog skupljanja koja se odvija u sloju 3 u tijeku hlađenja kao dijela procesa lijevanja ubrizgavanjem. Figures 1 to 3 show a pipe fitting in the form of an electrically fusible sleeve-shaped cap. The head body consists mainly of a cylindrical shell, or carcass, 1 on the inner surface of which is placed a coil 2 of electro-resistant wire, which is held in place by an inserted layer 3 of injection-oiled thermoplastic material. The layer 3 extends from end to end of the casing and is provided at its ends with beveled surfaces 4 which form an introduction part for each of the pipe ends, to facilitate the insertion of the pipe ends to be joined in the sleeve. In the central plane of the layer 3, there are placed more, according to the volume, distributed outlets that extend inward and form stops 5 on which the ends of the pipes rest, thus ensuring proper placement inside the sleeve in preparation for the welding process. At a short distance from each end, an annular groove 6, with a rectangular cross-section, is cut into the sheath 1, so that the material of the layer 3 fills this groove in order to achieve a mechanical connection between the sheath and the poured layer. This bond prevents separation of layer 3 from the shell due to radial and axial shrinkage occurring in layer 3 during cooling as part of the injection molding process.

Namotaj žice namotan je u obliku dva dijela namotaja koji su povezani jednim integralnim dijelom žice, shematski prikazanim isprekidanim linijama na slici 1. Dijelovi namotaja postavljeni su tako da djeluju usporedno s pripadajućim krajevima cijevi na poznati način. Namotaj je napravljen od žice obložene termoplastičnim materijalom koji je preporučljivo isti kao i materijal sloja 3, a idealno isti kao i materijal omotača 1. U svakom od dijelova namotaja navojci namotaja su raspoređeni u jednom sloju i naliježu jedan uz drugi. Time što je uljeven ubrizgavanjem na licu mjesta, sloj 3 čvrsto prianja na omotač i oblozi namotaja žice, ali nije spojen s njima, tj. sve do procesa zavarivanja, kada toplina razvijena u namotaju električnom strujom koja prolazi kroz njega čini da se termoplastični materijal na graničnim površinama topi i stapa, najmanje u području dva dijela namotaja, pri čemu se dobiva jaki spoj stapanjem između vanjske površine cijevi u čahuri i materijala obloge žice, sloja 3 i omotača 1. The coil of wire is wound in the form of two parts of the coil which are connected by one integral part of the wire, shown schematically by broken lines in Figure 1. The parts of the coil are placed so that they act parallel to the corresponding ends of the pipe in a known manner. The winding is made of wire coated with a thermoplastic material which is preferably the same as the material of layer 3, and ideally the same as the material of sheath 1. In each of the parts of the winding, the turns of the winding are arranged in one layer and abut one another. By being injection oiled in situ, layer 3 adheres firmly to the sheath and cladding of the wire coil, but is not bonded to them, ie until the welding process, when the heat developed in the coil by the electric current passing through it causes the thermoplastic material to it melts and fuses at the boundary surfaces, at least in the area of the two parts of the winding, whereby a strong connection is obtained by fusion between the outer surface of the tube in the sleeve and the material of the wire covering, layer 3 and sheath 1.

Krajevi žice su povezani sa sklopovima kontaktnih klinova za povezivanje namotaja s izvorom električne energije u tijeku procesa zavarivanja. Kao što se vidi na slici 2, stopica 8 s otvorom vezana je za kraj žice deformiranjem, a unutrašnji kontaktni dio 9 s proširenim dijelom pruža se kroz otvor u stopici i jedan radijalni otvor u omotaču 1. Unutrašnji kraj kontaktnog dijela 9 i stopica 8 uljeveni su u sloju 3, tako da ne predstavljaju neku zapreku, i neće biti oštećeni krajem cijevi koji se umeće u čahuru za zavarivanje. Na svom vanjskom kraju kontaktni dio 9 ima jedan priključak s navojem, posebno rupu s navojem u koju se uvrće vanjski kontaktni element 10. Kontaktni element 10 obuhvaća jedan klin na koji je postavljena plastična zaštitna čahura 11, ili je na nju naljevena, tako da okružuje vanjski kontaktni dio klina, dok je unutrašnji kraj klina izveden s navojem radi sprezanja s unutrašnjim kontaktnim dijelom, kako je prikazano. U tijeku procesa zavarivanja cijevi, dva kontaktna naglavka su priključena na jedan izvor električne struje na poznati način. The ends of the wire are connected to the contact pin assemblies for connecting the coil to the source of electricity during the welding process. As seen in Figure 2, the foot 8 with the opening is connected to the end of the wire by deformation, and the inner contact part 9 with the extended part extends through the hole in the foot and one radial hole in the shell 1. The inner end of the contact part 9 and the foot 8 are molded are in layer 3, so they do not represent an obstacle, and will not be damaged by the end of the pipe that is inserted into the welding sleeve. At its outer end, the contact part 9 has a threaded connection, in particular a threaded hole into which the external contact element 10 is screwed. the outer contact part of the pin, while the inner end of the pin is threaded for coupling with the inner contact part, as shown. During the pipe welding process, two contact heads are connected to one source of electric current in a known manner.

Kako je prostor između omotača 1 i električnog namotaja 2 ispunjen slojem 3, nije neophodno da se omotač proizvodi s tijesnim tolerancijama ili da se širi i/ili skuplja dok se namotaj stavlja u omotač. Omotač se može pripremiti od cjevastog obratka odsječenog od plastične cijevi izrađene istiskivanjem, ali je jedan alternativni postupak za izradu cjevastog obratka prikazan na slikama 4 i 5. Konvencionalni uređaj 12 za istiskivanje i alat 13 za istiskivanje koriste se za izradbu plosnate trake 15 u suštini pravokutnog poprečnog presjeka. Traka se dovodi do bubnja 14 za namotavanje i namotava se na bubanj sve dok se ne dobije željena debljina. Pritisni valjak 15 se koristi za pritiskivanje trake na donje slojeve već namotane na bubanj, kako bi se osigurao vrlo tijesan dodir. Ovako dobiveni cilindrični obradak omotača može se podvrgnuti otpuštanju a zatim se strojno obraditi i pripremiti za izradu električno topljivog naglavka. Na obratku se strojno obrađuju unutrašnja i vanjska površina, uključujući izradbu žlijebova 6, i buše se radijalni otvori za prihvaćanje sklopova kontakata. Kao što je već rečeno, omotač se može izraditi sa širokim tolerancijama i strojna obrada treba dati samo približne dimenzije. U stvari je najbolje da unutrašnja površina bude obrađena relativno grubo, na primjer da se napravi jedan zavojni rub, ili ispupčenje, kako bi se povećala ukupna površina, zbog poboljšanja prianjanja sloja naljevenog ubrizgavanjem na tu površinu. As the space between the sheath 1 and the electrical coil 2 is filled with layer 3, it is not necessary for the sheath to be manufactured with close tolerances or to expand and/or contract as the coil is placed in the sheath. The casing can be prepared from a tubular blank cut from an extruded plastic tube, but an alternative process for making the tubular blank is shown in Figures 4 and 5. A conventional extrusion device 12 and extrusion tool 13 are used to produce a flat strip 15 of substantially rectangular shape. cross section. The tape is fed to the winding drum 14 and wound onto the drum until the desired thickness is obtained. The pressure roller 15 is used to press the tape onto the lower layers already wound on the drum, to ensure a very tight contact. The cylindrical shell workpiece obtained in this way can be subjected to loosening and then machined and prepared for the production of an electrically fusible cap. The inner and outer surfaces of the workpiece are machined, including the production of grooves 6, and radial holes are drilled to accept the contact assemblies. As already stated, the casing can be manufactured with wide tolerances and machining should only give approximate dimensions. In fact, it is best to have the inner surface relatively rough, for example to create a single helix, or bulge, to increase the total surface area, to improve the adhesion of the injection-molded layer to that surface.

U stupnju lijevanja ubrizgavanjem, tj. u tijeku formiranja sloja 3, omotač 1 sačinjava vanjski dio kalupa koji ograničava šupljinu kalupa s jezgrom kalupa. Jezgra je prikazana na slikama 6 do 8, ali treba napomenuti da slika 6 ne predstavlja pravi presjek, jer su neki dijelovi, posebno vijak 24 i klinovi 35 prikazani izvan pravih položaja zbog lakšeg prikazivanja. Jezgra ima vanjsku cilindričnu površinu s kružnim krajnjim rubovima 20 za formiranje zakošenih površina 4 kako je naprijed opisano. Na maloj udaljenosti od rubova su slijedeća kružna ispupčenja 21 koja tvore aksijalno prema unutra usmjerene radijalne graničnike koji služe za određivanje položaja vanjskih krajeva pripadajućih dijelova namotaja za zagrijavanje i za držanje istih na njihovom mjestu u tijeku ubrizgavanja lijevanog materijala. Jezgra je napravljena od dvije aksijalne polovine 22, 23 koje se drže zajedno odvojivim vijkom 24. Da bi se osiguralo pravilno koaksijalno poravnavanje polutki jezgre, polutka 23 izvedena je s dva dijametralno suprotno postavljena klina 25 za određivanje položaja koji ulaze u odgovarajuće otvore 26 u polutki 22 jezgre kada se ove dvije polutke spoje. Polutka 22 jezgre izvedena je s aksijalnom vertikalnom čahurom 27 koja stvara ulazni kanal 28 za materijal za lijevanje, pri čemu je unutrašnji kraj kanala povezan sa šest radijalnih kanala 30 ravnomjerno raspoređenih oko osi, koji imaju otvore 31 na cilindričnoj površini jezgre. Kanali su izvedeni između nasuprotnih površina polutki jezgre i otvori su im oblikovani tako da formiraju naprijed spomenute graničnike 5. U udubljenja u vanjskim krajnjim površinama polutki jezgre vijcima 33 su pričvršćene na svojim mjestima ploče 32 za izvlačenje. U svakoj od ploča 32 prorezana su tri proreza 34 u obliku ključanice, koji su podsječeni iza njihovih užih dijelova tako da omogućuju umetanje proširenih glava alata za izvlačenje i malim kutnim zakretanjem istih njihovo sigurno zabravljivanje s pločom za izvlačenje, a time i s polutkom jezgre. Kako su alati za izvlačenje spregnuti s obadvije polutke, ove se mogu razdvojiti i u suprotnim smjerovima izvući iz dovršenog električno topljivog naglavka, pri čemu se, svakako, najprije mora izvaditi vijak 24. Treba napomenuti da je glava vijka 24 postavljena u prorez 35 u ploči za izvlačenje polutke 22 jezgre. Odgovarajući alat za izvlačenje ima ispust koji ulazi u taj prorez i ako zavrtanj 24 nije uklonjen, alat za izvlačenje ne može se sprezati s pločom za izvlačenje. Za oslanjanje i pravilno postavljanje jezgre u stroju za lijevanje ubrizgavanjem, ploče za izvlačenje su izvedene stožastim udubljenjima 36 za određivanje položaja. Treba napomenuti da je okomita čahura pričvršćena u polutki 22 jezgre pomoću njezine ploče 32 za izvlačenje. In the injection molding stage, i.e. during the formation of layer 3, the shell 1 constitutes the outer part of the mold which limits the mold cavity with the mold core. The core is shown in Figures 6 to 8, but it should be noted that Figure 6 is not a true cross-section, as some parts, especially the screw 24 and pins 35, are shown out of true position for ease of display. The core has an outer cylindrical surface with circular end edges 20 to form beveled surfaces 4 as described above. At a short distance from the edges are the following circular protrusions 21 which form axially inwardly directed radial stops which serve to determine the position of the outer ends of the associated parts of the heating coils and to hold them in place during the injection of the cast material. The core is made of two axial halves 22, 23 which are held together by a separable screw 24. To ensure proper coaxial alignment of the core halves, the half-shell 23 is provided with two diametrically opposed locating pins 25 which enter the corresponding holes 26 in the half-shell. 22 cores when these two hemispheres are joined. The half-shell 22 of the core is made with an axial vertical sleeve 27 which creates an inlet channel 28 for the casting material, the inner end of the channel being connected to six radial channels 30 evenly distributed around the axis, which have openings 31 on the cylindrical surface of the core. The channels are made between the opposite surfaces of the core halves and their openings are shaped to form the previously mentioned stops 5. In the recesses in the outer end surfaces of the core halves, the pull-out plates 32 are fixed in place with screws 33. Three keyhole-shaped slots 34 are cut in each of the plates 32, which are undercut behind their narrower parts so as to allow the insertion of the extended heads of the extraction tool and, by turning them at a small angle, their secure locking with the extraction plate and thus with the core half. Since the extraction tools are connected to both halves, they can be separated and pulled out in opposite directions from the completed electrically fusible head, whereby, of course, the screw 24 must be removed first. It should be noted that the head of the screw 24 is placed in the slot 35 in the plate for extracting half of 22 cores. The corresponding puller has a recess that goes into that slot and if the screw 24 is not removed, the puller cannot be engaged with the puller plate. For support and proper placement of the core in the injection molding machine, the draw plates are provided with conical depressions 36 for positioning. It should be noted that the vertical sleeve is fixed in the core half 22 by means of its extraction plate 32.

Polutke jezgre su formirane s odvojivim segmentima 38 jezgre. Kada se jezgra umetne u omotač, ti segmenti, ili bar Core halves are formed with detachable core segments 38. When the core is inserted into the sheath, these segments, or bar

prostor koji normalno zauzimaju, postavljaju se nasuprot otvora izvedenih u omotaču zbog prihvaćanja sklopova kontakata, a iz razloga koji će biti naknadno objašnjeni. the space they normally occupy, they are placed opposite the openings made in the casing to accept the contact assemblies, and for reasons that will be explained later.

Kada je jezgra sklopljena kako je prikazano na crtežima, obložena elektrootporna žica se navija na jezgru da bi formirala dva dijela namotaja, koji svojim vanjskim krajevima naliježu na granične površine rubova 21, pri čemu su krajevi žice ostavljeni da strše van na mjestu pomičnih segmenata 38 jezgre. Jezgra i namotaj se aksijalno umeću u prethodno pripremljen omotač. Segmenti 38 se uklanjaju tako da se stopice 8 s otvorom mogu deformiranjem spojiti s krajevima žice, a unutrašnji kontaktni dijelovi 9 se umeću kroz otvore stopica u otvore u omotaču. Da bi se učvrstili u tijeku procesa lijevanja ubrizgavanjem, čep 39 kalupa (slika 9), obično oblika vijka, uvrće se u svaki od kontaktnih elemenata 9 i služi za njegovo pritezanje uz unutrašnju površinu omotača. Potom se vraćaju segmenti i cijeli sklop omotača i jezgre postavlja se u pogodan stroj za lijevanje ubrizgavanjem. Termoplastični materijal se ubrizgava kroz okomitu čahuru i ulazi u šupljinu formiran između omotača 1 i jezgre preko kanala 30 i otvora 31 , tako da popunjava taj prostor i time formira sloj 3 za držanje namotaja na unutrašnjoj površini omotača. Nakon odgovarajućeg vremena stvrdnjavanja, sklop se vadi iz stroja za lijevanje i polutke 2, 3 jezgre, mogu se vaditi alatima za izvlačenje spregnutim s polutkama jezgre, kako je naprijed objašnjeno. Sve što treba napraviti da bi se dovršio naglavak, jest da se uklone čepovi 39, a na njihovo mjesto postave vanjski kontaktni elementi 10. Ako se želi otkloniti svaka opasnost od oštećenja u tijeku skladištenja i/ili transporta, vanjski kontaktni elementi mogu se postaviti tek onda kada je električno stapanje spremno za upotrebu da bi se pripremio zavareni spoj cijevi. Treba napomenuti da, pored toga što je pogodan sa stanovišta proizvodnje, dvodijelni sklop kontakata ima tu prednost, da se mogu primijeniti različiti vanjski kontaktni elementi, na primjer da odgovaraju posebnim konfiguracijama različitih upravljačkih naprava koje se mogu koristiti za dovod električne struje do naglavka. When the core is assembled as shown in the drawings, a sheathed electroresistive wire is wound on the core to form two winding sections, the outer ends of which rest against the boundary surfaces of the edges 21, the ends of the wire being left to protrude in place of the movable segments 38 of the core . The core and winding are inserted axially into the previously prepared sheath. The segments 38 are removed so that the feet 8 with the opening can be connected to the ends of the wire by deformation, and the internal contact parts 9 are inserted through the openings of the feet into the openings in the sheath. In order to secure them during the injection molding process, the plug 39 of the mold (Fig. 9), usually in the form of a screw, is screwed into each of the contact elements 9 and serves to tighten it against the inner surface of the shell. The segments are then returned and the entire shell and core assembly is placed in a suitable injection molding machine. The thermoplastic material is injected through the vertical sleeve and enters the cavity formed between the sheath 1 and the core through the channel 30 and the opening 31, so that it fills that space and thus forms a layer 3 for holding the winding on the inner surface of the sheath. After a suitable curing time, the assembly is removed from the casting machine and the core halves 2, 3 can be removed with puller tools coupled to the core halves, as explained above. All that needs to be done to complete the cap is to remove the plugs 39 and replace them with the external contact elements 10. If any risk of damage during storage and/or transport is to be eliminated, the external contact elements can only be installed then when the electric fusion is ready to use to prepare the welded joint of the pipe. It should be noted that, in addition to being convenient from the point of view of production, the two-part contact assembly has the advantage that different external contact elements can be applied, for example to match the special configurations of different control devices that can be used to supply electric current to the nozzle.

Podrazumijeva se da su modifikacije moguće, a da se ne odstupa od opsega izuma. Ovdje je kao primjer spomenuto da se drugi oblici priključaka mogu koristiti za povezivanje krajeva žice s kontaktima, radije nego opisane i prikazane stopice s otvorom, ili je, ako su kontakti pogodno izvedeni, moguća neposredna veza sa žicom. Na taj se način kraj žice može umetnuti u poprečni otvor izveden u unutrašnjem kraju kontaktnog dijela 9, i pričvršćeni su u njemu vijkom bez glave uvrnutim u rupu s navojem dijela 9 ispred vanjskog kontaktnog elementa 10. It is understood that modifications are possible without departing from the scope of the invention. It is mentioned here as an example that other forms of connections can be used to connect the ends of the wire to the contacts, rather than the described and shown hole feet, or, if the contacts are suitably designed, a direct connection to the wire is possible. In this way, the end of the wire can be inserted into the transverse opening made in the inner end of the contact part 9, and they are fixed in it with a screw without a head screwed into the threaded hole of the part 9 in front of the external contact element 10.

Claims

1. Electrically fusible pipe cap, which includes an outer coating 1 in the form of a self-supporting cylinder, and an electro-resistant coil 2 for heating, which contains a coil of wire coated with thermoplastic material located in the sheath, characterized by the fact that the layer (3) of thermoplastic material, which is cast in situ between the winding and the casing, secures the winding inside the casing.

2. Pipe cap according to claim 1, characterized in that the wire covering and the layer (3) are made of the same thermoplastic material.

3. Pipe cap according to claim 1 or 2, characterized in that the casing is made of thermoplastic material.

4. Pipe cap according to claim 3, characterized in that the sheath (1) and the layer (3) are made of the same thermoplastic material, for example both of polyethylene.

5. Pipe cap according to claim 3 or 4, characterized in that the casing (1) includes a part of the pipe cut from the thermoplastic pipe obtained by extrusion.

6. Pipe cap according to claim 5, characterized in that the casing is made of several layers of thermoplastic tape (15) made by extrusion, winding continuously layer by layer.

7. Pipe cap according to any one of claims 1 to 6, characterized in that the molded thermoplastic layer (3) extends from end to end of the casing.

8. Pipe cap according to claim 7, characterized in that the thermoplastic layer (3) is formed with beveled surfaces (4) at its ends for guiding the ends of the pipes to be joined.

9. A pipe cap according to claim 7 or 8, characterized in that the molded thermoplastic layer (3) is formed at each end with one external protrusion, wherein this protrusion rests on a single abutment formed on the casing and directed mainly axially from the coil.

10. Pipe head according to claim 9, indicated by the fact that said abutment forms a circular groove (6) on the inner surface of the casing.

11. Pipe head according to any one of claims 1 to 10, characterized in that it includes a contact assembly that extends through an opening in the casing and includes an internal contact part (9) to which one end of the winding wire is attached, and an external contact element (10) connected to the inner part, which represents part of the end connection.

12. Pipe cap according to claim 11, characterized in that the internal contact part (9) is held in place by a cast thermoplastic layer (3).

13. Pipe cap according to claim 11 or 12, characterized in that the inner and outer contact parts (9, 10) have a separable mutual connection.

14. A method for the production of an electrically fusible pipe joint, indicated by the fact that it includes the stages of preparing a cylindrical shell (1), winding a coil (2) of an electro-resistant heating wire coated with a thermoplastic material on the core (22, 23) of the mold, inserting the core and winding on it into the shell, creating a radial space between them, injecting thermoplastic material (3) between the core and the shell to fill said space, and removing the core, so that the coil is held in the shell by the poured material.

15. The method according to claim 14, indicated by the fact that the preparation of the envelope includes machining of the interior of the same in order to form a circular groove on the inner surface of the envelope at each of the ends of the envelope.

16. The method according to claim 14 or 15, characterized in that the sheath is prepared from a thermoplastic material, and the preparation of the sheath includes processing its inner surface so that it has a relatively rough surface treatment.

17. The method according to claim 14, 15 or 16, characterized in that the casing is prepared from a tubular workpiece cut from a plastic pipe obtained by extrusion.

18. The method according to claim 14, 15 or 16, characterized in that the casing is prepared from a tubular workpiece formed by winding a tape (15), obtained by extruding a thermoplastic material, onto a drum (14).

19. The method according to any one of claims 14 to 18, characterized in that the preparation of the casing comprises making at least one opening in the wall to accept the contact assembly.

20. The method according to claim 19, characterized in that the contact part (9) is attached to one end of the wire and inserted into the radial opening and that thermoplastic material is injected to cover the contact part in the interior of the sheath.

21. The method according to claim 20, characterized in that the contact part (9) is temporarily held in place by a fastening device (39) which engages the contact part on the outside of the casing during the injection molding step.

22. The method according to any one of claims 14 to 21, characterized in that the wire wound in two densely wound parts is connected by one connecting part, whereby in both parts the adjacent threads are in contact with each other.

23. The method according to any one of claims 14 to 22, characterized in that the thermoplastic material is injected through the core.

24. The core of the mold used for the production of one electrically fusible pipe connector by the process according to claim 14, characterized by the fact that it includes two circular parts (22, 23) of the core, an element (24) for attaching parts of the core to each other in order to obtain one axially placed cylindrical surface for receiving one coil of electrical resistance heating wire, an inlet (28) for molten plastic material in one outer end surface of one core portion, and one outlet for molten material formed on a cylindrical surface in the plane of abutment of the core portions.

25. The core of the mold according to claim 24, characterized by the fact that several radial channels are formed between the parts of the core and are connected to the associated and outlet openings distributed around the cylindrical surface.

26. Mold core according to claim 25, characterized in that the channels (30) are connected to the mentioned cylindrical surface via openings (31), shaped to form stops (5) on the inner side of the electrically fusible pipe connector.

27. Mold core according to claim 24, 25 or 26, characterized in that said first part of the core has a vertical sleeve (27) which forms said inlet opening (28) which is placed axially therein.

28. A mold core according to any one of claims 24 to 27, characterized in that the core parts have elements (21) on said cylindrical surface for holding the winding in its position thereon.

29. A core according to any one of claims 24 to 28, characterized in that the parts of the core are designed with guide elements (25, 26) which engage to ensure proper alignment of the core.

30. A mold core according to any one of claims 24 to 30, characterized in that at least one of the core parts has a detachable segment (38) at its outer edge to enable the contact part (9) to be connected to one end of the wire coil (2) after the core is placed in the jacket.

31. A mold core according to any one of claims 24 to 30, characterized in that each of the core parts comprises elements (32, 34) for attaching a puller tool thereto for separating and pulling out the core parts after the oiled material has hardened.