GB2268002A

GB2268002A - Cable conduit

Info

Publication number: GB2268002A
Application number: GB9311475A
Authority: GB
Inventors: Horst Vogelsang
Original assignee: Ernst Vogelsang GmbH and Co KG
Current assignee: Ernst Vogelsang GmbH and Co KG
Priority date: 1992-06-13
Filing date: 1993-06-03
Publication date: 1993-12-22
Anticipated expiration: 2013-06-03
Also published as: RU2128389C1; DE9208873U1; HUT64649A; KR940001505A; EP0578959B1; TR26974A; TW227618B; HRP930969A2; CA2098219A1; GB2268002B; UA41257C2; IL105884A; AU657221B2; NO932116L; DE59305113D1; NO932116D0; SK57293A3; LT3010B; SK281827B6; CZ110593A3

Abstract

A cable conduit of thermoplastics material has internal ribs of serpentine longitudinal shape to allow cables to slide easily over the internal surface. The conduit has an internal radius r set at a given angle of rotation a. In a linearly arranged cable conduit with a cable to be fed contact faces of rib contact width b arise at contact points between sliding ribs and cable jacket of the cable to be fed. The sliding ribs extend in waveshape and form reversal zones between sections with constant angle of rotation a. The rib contact width b, the number of sliding ribs equidistantly distributed over the circumference of the conduit inner wall, the tube inside radius r, and the length LK of the rib contact sections between reversal zones satisfy the equation Ar = 0.16 b<2>z LK. The angle g, measured in radians, of the gliding ribs' lead as measured on the conduit inner wall, satisfies the equation g = ra/LK. <IMAGE>

Description

2268002 Cable Conduit Assembly with at least one cable conduit tube made

of Thermoplastic Plastics

Specification

The invention relates to a cable conduit assembiv with at least one cable conduit tube made of thermoolas-lt.-.-!c plas- tics, which includes a cable conduit having a conduit inner wall circular in cross section with a tube inside radius r and sli'ding ribs moulded from the thermoplastics of the plastic tube arranged on the conduit inner wall wh-Jc',-.,. referred to the inside circumference, extend with a given angle of rotation a, whereby in a linearly arranged cable conduit with a cable to be fed contact faces of rib contact width b arise at contact points between sliding ribs and cable jacket of the cable to be fed. Such cable conduit assem blies are typically used underground. Cables are later fred J_ -ube and cable conduit tubes resDec- into the cable conduit 4t..

tively. ",--able" within the scope of the invention defines standard telecommunications cables as used especial-1v in postal services, power supply cables and the 'like. Individual or several cables or cable bundles can be fed inno a cable conduit tube of the cable conduit assembly. Individual cables are single-care or multi-core cables and have a cable jacket made of rubber or plastics. Sliding ribs have a rib height of more than 0.1 mm, preferably -from 0.3 to 3 mm. As far as the term "angle of rotation" is concerned, reference is made to the Helical Line Theory Mit-te "The Englrjeerls Pocket Book" 1, Theoret-ical Foundations, 28th Edition, Ernst & Sohn, Berlin, Page 157). According r_o this theory, a helical line is defined as foilews: Provided that a straight line moves in such a way that it always intersects a fixed axis vertically and the distances, by which the fixed intersecting point on the straIght line moves awav from the axis, are proportional to the angles around which the straight line turns, any of its points draw a normal helical line. The aforementioned angles are the angles of rotation opposite the initial direction of the straight line. This dimension refers to a specified linear extension of the axis. Sliding ribs extend with a specified lead relative to the inner wall of the con duit. The tangent of the helix angle at a point of a slid ing rib is the first derivation of the mathematical equa tion for the helical line which corresponds at that point to the sliding rib. Standard cable diameters are in t-he range from 10 to 90 mm, e.cr. 10, 28, 35 or 90 '.1.h.e inside diameter of standard cable conduit tubes of a cable conduit assembly according to the invention ranges from 26 to 200 mm.

The term "Cable Conduit Assembly" means for instance individual tubes for cable conduits (cf. DE 35 29 541 All) but a_so cable conduit tubing aggregates (cf. DE 32 17 401- A1). Tndvidual or several cable conduit tubes of the cable con- duit assembly accom=date individual cables or cable bundles which must be fed by pushing or pulling. In a known cable conduit assembly (DE 35 29 541 A1), the sliding ribs have a constant direction relative to the cable conduit axis and in direction of the cable conduit axis. They extend for instance helicoidally as well as along the entire length of the cable conduit assembly with equal,ngle of foatation in left-hand rotation or right-hand rotation.

The friction resistance which encounters a cable or a cable bundle when fed into such a cable conduit assembly will be substantially reduced by these sliding ribs, afeature turned out to be useful in many applications which J --'a c 1 11 1 - tates pulling and pushing of cables and cable bundles respectively. Within the scope of the invention, the term "Pulling" will be used for both operations. Depending on the design of cable or cable bundle, it may happen that troubling influences occur as a result of the interaction of a Gable or a cable bundle with the sliding ribs, namely that torsion forces are imparted to cable and cable bundle respectively and substantially brake the cable or the cable bundle by the twisting action, whereby cable or cable bundle may, so to speak, climb up the sliding ribs. Such interferences can be reduced - as is also known by arranging the sliding ribs in alternating direction relative to the cable conduit axis and in direction of the cable conduit axis (DE 40 31 783 A1). Alternating direction means that the sliding. ribs' sense of rotation changes, e.g. once from left to right, once from right to left. In other words, the angle- of rotation is first positive and then negative etc., whereby the sliding ribs may in addition evidence a lead which varies in sections in direction of the cable conduit axis. Surprisingly, no interfering torsion forces are imparted any more to a cable to be pulled- in or pushed-in or to a cable bundle to be pulled-in or pushed-in with such design and formation of the cable conduit assembly. The forces resulting from the frictional interaction of a cable and a cable bundle respectively with sliding ribs prevent interfering twistings of the cable and the cable bundle respectively and cancel each other completely depending on design. With pulling a cable or a cable bundle into a cable conduit, however, considerable linear pulling forces must be applied which overcome the linear friction resistance in longitudinal direction of the cable conduit. Suitable means must be provided. All that applies, too, if the sliding ribs run in serpentines in a special case of this known embodiment without any special guiding means and particular design (DE 40 31 783 Al, Figs. 1, 4 and 5).

The invention is based on the object to arrange a cable conduit assemblv of the above described structure in such a wav 'hat the pulling forces are extremely low under any pulling conditions in service, and even then i.-L' the cable conduit assembly is laid in curves.

To accomplish this object, the invention teaches the comb-i- natIon of the following features:

1) The sliding ribs run in waveshape and form reversal zones between sections with constant angle of rotation, 2) the rib contact width b, the number z of sliding ribs equidistantly distributed over the circum ference of the conduit inside wall, the tube inside radius r, and a length of rib contact sections between reversal zones, identified as LKI sa-'Ls.'L--y the eauation Ar 0.16 b 2 z LK, where A defines the contact face of the cable jacket at intersecting points with sliding ribs in rib contact sections, and is numerically inthe range from 4.5 to 32 mm2, 3) the angle g measured in radians of the sliding ribs' - lead, measured on the condult inside wall, satisfies the ecruation - g = ra / LK and ranges numerically from 0.001 to 1.2 rad, where r between 12 and 100 mm and LK between 500 and 10,000 are selected, and the cables to be fed have an outside radius between 5 and 45 mm. Thereby, the specified dimension of the angle of rotation relates to the longitudinal section of the conduit axis between reversal zones. 10 Reversal zones of sliding ribs, which run s-,,,7iuso--'da-3-ly in unwinding of the conduit inside wall into the plane, are the highest points of wave peaks and the lowest points of wave valleys respectively of sinus curves. The reversal zones then become a reversal point. The feature 1) in the embodiment with reversal zones shrunk to reversal points is known as such as described in the introduction. However, sliding rib sections, which extend in direction of surface lines of the conduit inside wall and define relatively long reversal zones, can also be inserted in the area of wave peaks and wave valleys respectively. The faces of the cable jacket that contact individual sliding ribs have in plan view a more or less rhomboidal shape the geometry of which is defined by the rib contact width, i.e. the width of the sliding ribs at the contact point on the cable jacket. Re-ference is made to Fig. 1 and it's description for further explanation of the terms appearing in the teaching of technical dealing discussed above.

The invention is based on the knowledge that a considerable reduction of pulling forces can be achieved in the abovedefined and dimensioned cable conduits and cables, provided that measures have been taken to replace dry friction by a friction that approximates lubricant friction, which, as is well known, has substantially lower friction coefficients than dry friction, in case of occurrence of interferingly high pulling forces during pulling work to be performed. To achieve this, no special lubricant is required according to the invention. According to the method included in the scope of the invention, pulling speed and/or pushing speed of the cable or cable bundle to be fed into the conduit are rather so selected that the contact faces undergo a temperature increase which surprisingly reduces tInie resistance. The preferred work is such that the contact faces will be molten by friction heat, and a condition of true lubricant friction generated by the molten mass. Until now, this possibility has not been taken into account. Thereby, the sliding rib cross section is to a large extent oDtional within the limits indicated above. According to the invention, the given numerical parameters are adapted in such a way that the lubricant friction condition can be achieved always and without any difficulties, provided zL-.at the cable conduit assembly is made of thermoplastic plastics customary for such applications, and cables and standard cable jackets have the normal weight per length unit. Even though the invention provides such a possibility, the scope of the invention permits nevertheless to arrange lubricants in the groove-shaped cavities between sliding ribs. This, however, is not required. Cable jackets may also be provided with a coating acting as sliding means. it is understood that the pulling forces relating to the abso- lute size increase proportionally to the length of the cable conduit assembly in a cable conduit assembly according to the invention. This applies also to providing a lubricant friction by melting the sliding ribs or, to be more exact, the ridges of sliding ribs according to the described method. The scope of the invention permits in addition to pull slowly and carefully in such a way that lubricant friction must not be generated, and also does not occur.

Even though the sliding rib cross section is optional to a large extent, one embodiment stands out in which the cable 1.0 conduit inside wall provides between adjacent sliding ribs a groove shape concave to the cable conduit and running on both sides into the ridge of the sliding ribs.

Realizing the teaching of the invention results in a plu rality of particularly significant designs for cable con duit assemblies with cable conduit tubes having standard diameters as listed in the following table:

Design Parameters Cable Conduit Tube Designation 32(x3.0) Outside Diameter 50(x4.6) 110(x6.3) 225(x12.8) outside diameter (MM) 32.0 50.0 110.0 225.0 Wall thickness (MM) 3.0 4.6 6.3 12.8 Inside diameter (MM) 26.0 40.8 97.4 199.4 Number of sliding ribs 26 40 40 82 Sliding rib distance (mm) 3.14 3.20 7.65 11.65 angle of rotati - on (0). 180 180 180 180 Rib contact width (MM) 0.1 0.1 0.1 0.1 Length of rib contact (mm) 1275 2000 4775 9775 sections Length of connecting (MM).2 2 2 2 sections There are several possibilities for additionally shaping and designing cable -conduit assemblies according to the invention: The angle of rotation should regularly be in the range from 45 to 340', preferably approx. 180. Realizing the measures according to claim 4 results in optimizing many applications. Realizing the characteristics of claim 5 entails especially favourable results concerning pulling forces, if connecting zones are arranged between two sections with constant angle of rotation in a cable conduit tube of a cable conduit assembly according to the invention.

The invention will now be described in more detail by means 0-10 the accompanying drawing which represents an embodiment example only, wherein: 15 Fig. 1 shows schematically in perspective a conduit inside wall havina a circular cross section of a cable conduit tube with some geometrical symbols associated with the technical features of the inven20 tion, Fig. 2 is a graph to explain the term "Contact Face", Fig. 3 shows an unwinding of the conduit inside wall with 25 sliding ribs according to the invention and mated cable, Fig. 4 is a large-scale v--ew of a partiall longitud-L-n.a-' section through a cable conduit tube according to 30 the invention with cable, and 9 Fig. 5 is a large-scale view of a partial cross section through a cable conduit tube according to the invention.

The cable conduit inner wall 1 circular in cross section shown in Fig. 1 belongs to a cable conduit tube 2 which is part of a cable conduit assembly according to the inven -,L-.ion. The tube inside radius r and sliding ribs 3 arranged on the conduit inner wall 1 and mainly represented by plain lines that extend with a specified pitch angle a relative to the inside circumference are clearly discernible.

Figure 2 is a diagrammatic plan view of a sliding rib 3 offset to level, on which a striped zone 4 of the cable jacket of a pulled-in cable is resting. Fig. 3 is a partial view of an unwinding of the conduit inner wall 1 and, in supported position, a pulled-in cable 5, the jacket of which belongs to zone 4. Tn Figs. 2 and 3 can be seen that in linear arrangement of a cable conduit 1Cube 2 with a -oulled-in cable 5 rhombic-shaped contact faces K with rib contact width b arise at contact points between sliding ribs 3 and zones 4 of the cable jacket of the cable 5 to be fed. Fig. 3 shows clearly that the sliding ribs extend in waveform. They form reversing zones 7 between sections 6 with constant angle of rotatioln a. The rib contact width b, the number z of the sliding ribs 3 equidistantly distributed over the circumference of the conduit inner wall 1, the tube rad-I-Jus r and the length LK Of rib contact sec tions between reversing zones 7 satisfy the equation speci- fied in claim 1. In Fig. 3, the length of sections 6 corresponds to the length LK. The angle g intimated in Fig. 1 and measured in radian measure of the lead of sliding ribs 3 as measured on the conduit inner wall 1 also satis fies the equation specified in claim 1. The disclosed rela tionships are authentic and tried and tested by extensive experiments, if r is in the range from 12 to 100 mm, if LK is selected in the range from 500 to 10,000 mm, and if the cables 5 to be pulled in have an outside radius in the range from 5 to 45 mm. The angle of rotation a may in the embodi ment example and preferably be approx. 180'.

-'0 Fig. 4 shows an enlarged segment of a longitudinal seczion taken approx. in direction A-A of Fig. 2 with a cable 5 resting on a cut sliding rib 3 in the zone of a contact face K. A dot-shaded line intimates that the sliding rib 3 has been molten, to be precise by friction heat generated during pulling the cable 5. The reference mark 8 identifies the fused mass. Fig. 4 is intended to make clear that a lubricant friction condition will be established bv the mass 8.

As seen in Fig. 5, the cable conduit inner wall 1 exhibits between adjacent sliding ribs 3 a groove shape 9 concave to the cable conduit, which runs on both sides into the r-'dae of the sliding ribs 3. The represented dimensions are typical for many applications. The rib height hR is about twice as large as the free distance xp of the cable jacket 10 as measured from the bottom of groove shape 9 between sliding ribs 3.

Claims

C 1 a i m s A cable conduit assembly with at least one cable con duit tube made of thermoplastic plastics, which includes a cable conduit having a conduit inner wall circular in cross section with the tube inside radius r and sliding ribs moulded from the thermoplastic plas tics of the plastic tube arranged on the conduit inner wall which, referred to the inside circumference, extend with a given angle of rotation a, whereby in a line arly arranged cable conduit tube with a cable to be fed contact faces of rib contact width b arise at contact points between sliding ribs and cable jacket of the cable to be fed, whereby the combination of the follow ing features is realized:

1) The sliding ribs run in waveshape and form reversal zones between sections with constanr_ angle- of rotation, 2) the rib contact width b, the number z of slid ing ribs equidistantly distributed over t_he circumference of the conduit inside wall, the tube inside radius r, and a length of rib con tact sections between reversal zones, identl fied as LKI satisfy the equation Ar = 0.16 b 2 z LK, where A defines the contact face of the cable jacket at intersecting points with sliding ribs in rib contact sections, and is numerically in the range from 4,5 to 32 MM2, 3) the angle g, measured in radians, of the slid ing ribs ' lead, measured on the conduit inside wall, satisfies the equation g = ra / LK and ranges numerically from 0.001 to 1.2 rad, where r in the range from 12 and 100 mm and LK in the range from 500 and 10,000 are selected, and thle cables to be fed have an outside radius in the range from 5 to 45 mm.

2. A cable conduit assembly according to claim 1, whereby the cable conduit inner wall between adjacent sliding ribs is provided with a groove shape concave to the cable conduit which runs on both sides into the ridge of the sliding ribs.

3. A cable conduit assembly according to one of claims 1 or 2, whereby the angle of-rotation a is selected in the range between-45' and 3400, preferably at approx. 180'.

4. A cable conduit assembly according to any of claims 1 to 3, whereby the rib contact width b, the number z of the sliding ribs equidistantly distributed over t-he circumference of the - conduit inner wall, the IC-ube inside radius r, theangle of ratation-a and the length L K of - 13 the rib contact sections between reversal zones satisfy the equation Ar = 0.16 b 2 Z (0.0003 r2a2 + LK 2)1/2

5. A cable conduit assembly according to any of claims 1 to 4, whereby between two sections with constant angle of rotation connecting sections of the length LV arranged, in which the sliding ribs continue in parallel to the tube axis, J. 0 and the rib contact width b, the number z of sliding ribs equidistantly distributed over the circumference of the conduit inner wall, the tube inside radius r, the angle of rotation a, the length L K of the rib contact sections as well as the length LV of the connecting sections satisfy the equation Ar = 0.16 b 2 Z (0.0003 r 2 a 2 + LK 2) 1/2 + 4LVbr

6. A Method for pulling cables into cable conduit tubes 20 according to any of claims 1 to 5, whereby the pull-in speed of the cable to be fed is so selected that tChe contact faces are molten by friction heat, and a lubricant friction condition is provided by the fused mass.