FI64250C - FARING REQUIREMENTS FOR ELECTRICAL CABLE WITH DRAGAVLASTNING - Google Patents

Description

il Awll-I Γβ1 ADVERTISEMENT „, JSTa ^ (11) UTLÄGGNINGSSKRIFT 64250 • jpig cw 1; ·; 3 ^ ^ (51) Kv.Ht?/i ].a.3 Η 01 Β 13/14 FINLAND — FINLAND (2.1 ) iwttit »k« mu.-PK *> tti »eknta1 Τ73920 (22) H * k * mtap« hft — AmBkidngadag 23-12.77 (23) AlkupUvt — GlMgfcttdf 23-12-77 (41) Translators JulVlffc »l - BUyH offancMg 21.07. J8

Mnttl. ) · Registries (44) ΝΙΜΜωρβιβη ‘’

Patent- och registeretyrelaen λ 'AmMcmutkgd odiutijkrifnn pub «c« rad ju.uo.o ^ (32) (33) (31) Fyy ^ nty «ueikeit — Begird priority 20.01.77

Federal Republic of Germany-Förbundsrepubliken lysklancL (DE) P 2702182.5 (71) lynenwerk GmbH & Co. KG. KG, Durener Strasse, 5l80 Eschweiler,

Federal Republic of Germany-Förbundsrepubliken lyskland (DE) (72) Robert Ney, Langerwehe, Federal Republic of Germany-FÖrbundsrepubliken llyskland (DE) (7 ^) Oy Kolster Ab (5 ^) Method of manufacturing an electric cable with strain relief -; For the production of electrical cables with dragging

The invention relates to a method of manufacturing an electric cable with strain relief, in which, for example, endless, high-tensile strain relief devices in the form of wires or ropes are spaced apart from the cable core concentrically from the strain relief device corrugates as it exits the extruder.

German patent application 16 40 929 relates to a cable of this type with strain relief, namely a self-supporting overhead cable, and German patent application 23 44 577 describes in detail a corresponding cable manufacturing method. Even Kuroma's article assumes that the strain relief devices are non-impregnated glass silk fiber bundles, and German patent application 2 64250 23 44 577 proposes polyethylene as a sheath material. This material has the property of generating, immediately after cooling the extruder, immediately in the longitudinal direction of the cable, a tensile stress which results in the corrugation of the endless strain relief device. The corrugation improves the adhesive bond between the glass fibers and the sheath material. The cables in question, in particular self-supporting aerial cables, have proved to be good in practice and have reached a high level of use.

However, polyethylene material has the disadvantage of easy combustibility, and this material is not permitted today, for example in mining. But this is where electrical cables with strain relief are needed, for example in mining shafts or in the excavation of steep or even semi-steep layers. Permissible cable sheath materials for such purposes include, for example, polyvinyl chloride and certain low-flammability rubber elastomers. However, these materials do not have the shrinkage property of polyethylene, and thus do not provide the corrugation caused by the shrinkage stress of said cable sheath.

As developments have shown, crimping the strain relief device is such a well-suited means of making, as far as possible, an internal adhesive connection between the strain relief device and the sheath material that its benefits cannot be denied. This applies not only to self-supporting aerial cables with their own slacking problem between the columns and the fire resistance of said mining cables, but also to special cable installations where the strain relief arrangement acts as a traction aid, making it possible to route longer cables to e.g. side effects on the cable core.

You can also install a specific cable by installing it on the ground. This creates traces on the cable which, due to the complex construction of the modern cable core, are not suitable.

According to German patent applications 16 40 929 and 23 44 577, in addition to glass silk fibers, high-tensile fibers with mechanical properties which meet the specific requirements for such cables are also suitable as strain relief devices for said cables. removal devices by mechanically crimping the cable sheath.

With this in mind, it is an object of the invention to provide such a method, which quite generally achieves the creasing of strain relief devices in practically any cable sheath material. In this case, the size of the individual corrugations must be consciously adjustable in order to achieve the flexibility of the cable and the optimal adhesion effect, while at the same time keeping the outer surface of the cable sheath perfect.

The solution according to the most preferred embodiment of the present invention appears from the characterizing part of the appended claim.

When manufacturing cable sheaths in an extrusion machine, the injection molding method must take into account the phenomenon known as "thread expansion" or "memory effect", in which the cable sheath easily expands after the extruder mold (cf. BASF "Kunststoff-Physik im Gespräch", 1966, pages 97-102). This phenomenon is reinforced in certain cases by selecting the outer mold smaller than the designed cable diameter, for example, to complete the filling of the nozzle with sheath material as the outer surface of the core progresses, so as not to damage the circular cross-section of the finished cable. Also, when the outer mold is a few tenths of a millimeter larger than the outer diameter of the cooled cable sheath, there is another pressure spraying method in which, depending on the sheath material, the outer diameter The contrast of the pressure spraying method is the so-called draft spraying method, in which a thin jacket mimicking the shape of a heart is obtained. The two methods differ mainly in the mass velocities of the cable core and the viscous sheath material as they pass through the outer mold, with the mass velocity of the pulp around the outer mold being greater than the withdrawal rate of the shaped cable sheath.

The invention takes advantage of the principles of the pressure injection method and creates some dimension between the movement of the introduced strain relief devices and the movement of the cable core and viscose sheath mass inside and immediately after the extruder to determine the operating conditions immediately after provide a certain type of compression that affects the corrugation of the strain relief devices. In this case, it must be taken into account that this compressibility does not follow spontaneously as when polyethylene is used as a material, but rather that the compressibility is the result of phenomena occurring in the desired and surprisingly large range in the spray head or in the spray head outlet area. This is due - simply put - to the control of the speeds of the various structural elements of the cable in such a way that the desired corrugation occurs regardless of the raw material to be sprayed.

The method according to the invention thus makes it possible to use any thermoplastic and elastomer as a cable sheath in which crimped strain relief devices are embedded.

An embodiment of the method according to the invention will now be described with reference to the drawing.

Figure 1 schematically shows an axial longitudinal section of a spraying head of a cable coating machine in which a cable is to be manufactured.

Fig. 2 schematically shows a perspective view of a cable end, with its partially exposed strain relief devices, whereby their corrugation can be seen.

The injection head 10 has an opening 11 for connecting a coil part (not shown) of the extruder. A prefabricated insulated electrical conductors of the cable core 13 turned in the direction of arrow 12, the injection head 10 in which it is injected into the outer casing around 1 * +, and the completed cable 15 leaves the injection pressure and is cooled immediately in the usual manner. Figure 2 shows what the cross-section of the finished cable 15 can look like. In particular, it can be identified from a cable core consisting of insulated conductors 16, five four-conductor four-threads 19 and a plastic core 21. Around the twisted elements 19 there is still an ordinary sheath 22 made of plastic strips.

At the spraying head, an outer sheath 14 is sprayed with the cable core 13 onto the sheath 22 of the spraying head 22, in which a varying number of strain relief devices 23 are arranged. is dimensioned according to the number of double conductors 19, the minimum required breaking strength of the cable, the distance between the bundles and the distance from the inner sheath of the bundles, as further described in German patent application 23 44 577. It is essential that the strain relief devices 23 are not quite straight in the direction of the cable axis (core 21) in the outer sheath 14, but more or less evenly corrugated, i.e. corrugated, as can be seen in Figure 2. Thus, an internal adhesive attachment is obtained between the strain relief devices and the sheath material.

At the injection head 10, the cable core 13 passes through the inner nipple 25 and then enters a hollow space, the front of which further opens with channels 26 arranged concentrically with the incoming cable core 13, of which only two channels are shown in Fig. 1. In front of the outer (rear) inlet of each channel 26 at a certain distance therefrom, a pre-preparation site for strain relief devices is arranged, comprising primarily coils 27 in wires or ropes 28 in a rack (not shown) with an outer mold 29, also called a mouthpiece. the cable 15 comes from the spray head 10.

The hollow space between the inner nipple 25 and the outer mold 29 is indicated by reference numeral 30; its shape is funnel-shaped, in which the strain relief devices 23 are placed in the jacket material. This material - thermoplastic or elastomer - flows here, coming from the helix connection opening 11, in the direction of the mouthpiece 29 and passes through it at a certain speed depending on the diameter of the outer mold and the pulp pressure, while the cable core 13 travels at the same speed. In contrast, the propagation speed of the strain relief devices 23 differs from the drawing speed of the cable 15 and thus of the propagation speed of the core 13, and is slightly higher and is essentially the same as the flow rate of the sheath material around the outer mold 29. In this way, the length of the strain relief device 23 per unit length of the cable 15 6 64250 is greater than this unit dimension, which is flattened so that immediately after entering the outer mold 39 the devices 23 crimp in the cable sheath 14 (Fig. 2). This corrugation or corrugation of the strain relief devices 23 takes place in particular around the outer mold 29 of the spray head 10 as a result of the tuning of the magnitude and speed conditions. The dimensions of the waves can be influenced and controlled immediately with this tuning, as shown in the following table: 7 64250

C/O

3 3 co co co co co 3 3 3 3 • H 3 3 3 3 O co co co co

-P -H * H * H -H

-H o O O O

(0 4J 4J + J + J

Frt TO r-H r-H r — I i — I

TO TO TO TO

gj · TO TO TO TO

· Η Ή * H · Η · Η S 44 C G H Ρ 3 (0 <U Q> 3 3 0) --H -H 3 3

44 ϋ Λ CO CO., LTD

I -S3> i _ r-ι to o σι vo m m »3 .μ Jg & IN 1- r- rr

Ito +4 44 3 I CO

R n § .5 cnocnoo TOC-P & E r- <N <N <- T- 2 8>

C CN

co 8 S mmminm

g'g ^ oi CN CN CN CN CN

I CO

S 3 m m m m m u "5 vo vo vo vo vo

• h 3> M

l, & G ω CO TO · Η r-

-5 3 * G O O O O O

r-H $ H M S -H (N CN CN (N CN

iro <D: 0 CL g ap -h> ι a CU 44 CL G

A; -rt fg

Qj 3 P * ^ * »*» ^

ff E E CM CM <N CM CM

1¾ - - -

B

r-H

: TO & E

coE E · ** · **. * -H · γΗ Γ · * "Γ * ^ Γ **

WC TSL

m O U U O O

e>>>>>

T | CL CL CL CL CL

8 vo ro vo <T \ rr m oo cn o in * in m oo oo vo Ä • TO1 9 1— cn en Tf in

Z C

8 64250 A total of five samples are entered in this table. For simplicity, in these examples, the dimensions of the mouthpiece 29 and the flow rates of the viscose sheath mass of the cable are constant in all five cases, while the tensile speed of the finished cable 15 varies. But similar results can be obtained by changing the diameter of the mouthpiece and / or the velocity of the mass. An important result can be deduced from the samples that the outer diameter of the coated cable 15, immediately after coming from the outer mold 29, must be larger than the inner diameter of the mouthpiece when the optimal corrugation of the strain relief devices 23 is to be obtained. This is due to the swelling of the jacket material immediately after the mouthpiece, which is typical of the injection method. This expansion is a consequence of the injection pressure and thus the velocity of the mass with respect to the pulling speed of the cable around the outer mold 29.

The relatively different cable speeds at the time of the formation of the cable sheath provide a somewhat faster moving strain relief device 28, 23 from the cable core 13 of the component to be left, forcing them to corrugate. It now depends on the careful tuning of the factors to avoid that the strain relief devices tend to retract or wrap around themselves to a certain extent, and thus themselves make S-shaped loops inside the cable sheath 14, which would undoubtedly have corresponding thickenings on the outer surface of the cable 15. The opposite extreme case would be the omission of each pulling moment so that the strain relief devices 23 are pulled tight on the sheath 14, which is also undesirable, because then, for example, the flexibility of the cable decreases. It is this important feature of a cable with strain relief devices that increases considerably due to the corrugation, because due to the corrugation, a traction harmonic-like effect is created, which enables correspondingly strong bends.

It is practically possible for a person skilled in the art to tune the individual values of the various sheath substances and the substances of the strain relief devices once he has experienced the dependence of the phenomena of the invention.

The features disclosed in this specification, drawings, and claim of the subject matter of the application may be in individual or arbitrary combinations to practice the invention in its various applications.