NZ247855A

NZ247855A - Ribs spaced around internal circumference of cable tube and extending longitudinally in waveshape with predetermined parameters for efficient sliding in of cable

Info

Publication number: NZ247855A
Application number: NZ247855A
Authority: NZ
Inventors: Horst Vogelsang
Original assignee: Dipl
Priority date: 1992-06-13
Filing date: 1993-06-11
Publication date: 1995-12-21
Also published as: AU4010193A; NO932116D0; ATE147899T1; NO304720B1; GB9311475D0; BR9302294A; FI932685A0; GR3022486T3; HRP930969B1; GB2268002B; CZ110593A3; HU9301711D0; TW227618B; MY109227A; CA2098219A1; DE4219403A1; AU657221B2; JPH06311623A; YU41193A; DK0578959T3

Abstract

A cable guiding device having at least one cable guiding pipe (conduit) of thermoplastic synthetic material, which cable guiding pipe has a cable guiding duct with a duct inner wall (which is circular in cross-section and has the pipe internal radius r), and which has sliding ribs which are arranged on the duct inner wall and are formed out of the thermoplastic synthetic material of the synthetic material pipe. The sliding ribs run at a predetermined rotation angle a with respect to the internal circumference. Contact surfaces having the rib contact width b result in a cable guiding pipe, which is arranged in a straight line, with a cable (which is to be inserted) at the contact points between the sliding ribs and the cable sheath of the cable which is to be inserted. The sliding ribs run in a corrugated shape and form reversing regions between sections having a constant rotation angle a. The rib contact width b, the number of sliding ribs which are distributed equidistantly over the circumference of the duct inner wall, the pipe internal radius r and the length LK of the rib contact sections between the reversing regions satisfy the equation Ar = 0.16 b<2>z LK. A defines the contact area of the cable sheath at the intersections with the sliding ribs in the rib contact sections. The angle g, measured in radians, of the pitch of the sliding ribs, measured on the duct inner wall, satisfies the equation g = ra/LK.

Description

<div class="application article clearfix" id="description"> 24 7855 ^ Priority Dais(s): i Compete S?-;c (;.:;:iU.n Rbd: ltlUfl.3 Class: ©..B.Q2&3./.OU.h...£j12. Publication Date: 2..1..BE.G...1995. ^P.O. Journal No: NEW ZEALAND PATENTS ACT, 1953 No.: Date: COMPLETE SPECIFICATION CABLE CONDUIT ASSEMBLY WITH AT LEAST ONE CABLE CONDUIT TUBE MADE OF THERMOPLASTIC PLASTICS We, DIPL.-ING. DR. ERNST VOGELSANG GMBH & CO. KG, a German company, Industriestrasse 2, D-4352 Herten, Westf., Germany hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- - 1 -(followed by page la) N.Z. PATENT OK • | 1 1 JUN 1993 RECEIVED 247 85 5 — 1 3 — The invention relates to a cable conduit assembly with at least one cable conduit tube made of thermoplastic plastics, the tube having an inner wall defining a cable conduit through the tube, the inner wall being substantially circular in cross section with a tube inside radius r, there being sliding ribs moulded from the thermoplastic plastics of the tube arranged on the inner wall which, referred to the circumference of the inner wall, extend with a given angle of rotation a, whereby in a linearly arranged cable conduit tube with a cable to be fed into the conduit, contact faces of rib contact width b arise at contact points between the sliding ribs and a cable jacket of the cable to be fed. Such cable conduit assemblies are typically used underground. Cables are later fed into the cable conduit tube and cable conduit tubes respectively. "Cable" within the scope of the invention defines standard telecommunications cables as used especially in postal services, power supply cables and the like. Individual or several cables or cable bundles can be fed into a cable conduit tube of the cable conduit assembly. Individual cables are single-core 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 (cf. Hiitte "The Engineer's Pocket Book" I, Theoretical Foundations, 28th Edition, Ernst & Sohn, Berlin, Page 157 - available on request). According to this theory, a helical line is defined as follows: 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 along the axis, are proportional to the angles around which the straight line turns, any of its points draws a normal helical line. Tke—erfui1 yniyri fluffed ' *1 N.Z. OFFICE 9 - NOV 1995 RECEIVED 247 85 5 - 2 - 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 tube. The tangent of the helix angle at a point of a sliding rib is the first derivation of the mathematical equation for the helical line which corresponds at that point to the sliding rib. Standard cable diameters are in the range from 10 to 90 mm, e.g. 10, 28, 35 or 90 mm. The 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 A1 -available on request) but also cable conduit tubing aggregates (cf. DE 32 17 401 A1 - available on request). Individual or several cable conduit tubes of the cable conduit assembly accommodate individual cables or cable bundles which must be fed by pushing or pulling. In a known cable conduit assembly (DE 35 29 541 A1 - available on request), 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 angle of rotation 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, a feature turned out to be useful in many applications which facilitates 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 a cable or cable bundle, it may rhappen thinf 247 8 5 5 - 3 - troubling influences occur as a result of the interaction of a cable or a cable bundle with the sliding ribs, namely that torsion forces are imparted to the cable and cable bundle respectively and substantially brake the cable or the cable bundle by the twisting action, whereby the 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 - available on request) . 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 A1 - available on request, Figs. 1, 4 and 5). N.Z. PATENT OFFICE 9 - NOV 1995 247 8 5 5 4 The invention is based on the object to arrange a cable conduit assembly of the above described structure in such a way that the pulling forces are extremely low under any pulling conditions in service, and even when the cable conduit assembly is laid in curves. To accomplish this object, the invention teaches the combination 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 about the circumference of the conduit tube inner wall, the tube inside radius r, and a length LK of rib contact sections between reversal zones satisfy the equation 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 sliding ribs' lead, measured on the tube inner wall, satisfies the equation Ar = 0.16 b2z Lk, g = ra / Lk 9 - HOV 1995 RECEIVED 24 7 8 5 - 5 - and ranges numerically from 0.001 to 1.2 rad, where r between 12 and 100 mm and LK between 500 and 10,000 mm are selected, and the cable(s) to be fed has/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. Reversal zones of sliding ribs, which run sinusoidally 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. Reference is made to Fig. 1 and its 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 above-defined and dimensioned cable conduit tubes and cables, provided that measures have been taken to replace dry friction by a friction that approximates lubrij^aifrfcZfgicgdicsnQpp|Qg 9 - NOV 1995 24 7 8 5 5 - 6 - 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 the friction 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 optional 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 that 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 absolute 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 amd^carefully in 24 7 8 5 5 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 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 plurality of particularly significant designs for cable conduit assemblies with cable conduit tubes having standard diameters as listed in the following table: Design Parameters Cable Conduit Tube Designation Outside Diameter 32(x3.0) 50(x4.6) 110(x6.3) 225(x!2 -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 7. 65 angle of rotation C). 180 180 180 180 Rib contact width (mm) 0.1 0.1 0.1 0. 1 Length of rib contact sections (mm) 1275 2000 4775 9775 Length of connecting sections (mm) 2 2 2 2 ™T 24 7 8 5 5 8 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°. For optimal results in many applications the rib contact width b, the number z of the sliding ribs equidistantly distributed about the circumference of the tube inner wall, the tube inside radius r, the angle of rotation a and the length 1^ of the rib contact sections between reversal zones and parallel to the tube axis should satisfy the equation: Especially favourable results concerning pulling forces can be achieved where between each two adjacent sections which have a constant angle of rotation there is a connecting section of length Ly where the sliding ribs lie substantially parallel to the tube axis, and the rib contact width b, the number z of sliding ribs equidistantly distributed about the circumference of the tube inner wall, the tube inside radius r, the angle of rotation a, thfe length LK of the rib contact sections as well as the length Ly of the connecting sections satisfy the equation The invention will now be described in more detail by means of the accompanying drawings which represents an embodiment example only, wherein: Fig. 1 shows schematically in perspective Ar = 0.16 b2z (0.0003 r2a2 + Lk2) 1/2 Ar = 0.16 b2z (0.0003 r2a2 + LK2)1/2 + 4Lvbr having a circular cross section of 247 8 5 5 - 9 - tube with some geometrical symbols associated with the technical features of the invention, Fig. 2 is a graph to explain the term "Contact Face", Fig. 3 shows an unwinding of the conduit tube inside wall with sliding ribs according to the invention and intimated cable, Fig. 4 is a large-scale view of a partial longitudinal section through a cable conduit tube according to the invention with cable, and Fig. 5 is a large-scale view of a partial cross section through a cable conduit tube according to the invention. The cable conduit tube inner wall 1, circular in cross section as shown in Fig. 1, belongs to a cable conduit tube 2 which is part of a cable conduit assembly according to the invention. The tube has inside radius r and sliding ribs 3 arranged on the tube 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 tube inner wall 1 and, in supported position, a pulled-in cable 5, the jacket of which belongs to zone 4. In Figs. 2 and 3 can be seen that in linear arrangement of a cable conduit tube 2 with fa'puTled^n--'-cable 5 rhombic-shaped contact faces K with rib contact-width- I . 24 7 8 5 5 10 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 rotation a. The rib contact width b, the number z of the sliding ribs 3 equidistantly distributed about the circumference of the tube inner wall 1 , the tube inside radius r and the length LK of rib contact sections between reversing zones 7 satisfy the equation specified 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 tube inner wall 1 also satisfies the equation specified in claim 1. The disclosed relationships are authentic and tried and tested by extensive experiments, if r is in the range from 12 to 100 mm, if Lr 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 embodiment example and preferably be approx. 180°, although it is shown as 90° in the example illustrated by Fig. 1. Fig. 4 shows an enlarged segment of a longitudinal section 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 fiction condition will be established by the fused mass 8 . p«—» 9 - my 1995 247 85 5 - 1 1 - As seen in Fig. 5, the conduit tube inner wall 1 exhibits between adjacent sliding ribs 3 a groove shape 9 concave to the tube inner wall, which runs on both sides into the ridge 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 xf of the cable jacket 10 as measured from the bottom of groove shape 9 between sliding ribs 3. </div>

Claims

1. 24 7 £ - 12 - WHAT WE CLAIM IS:

1 . A cable conduit assembly with at least one cable conduit tube made of thermoplastic plastics, the tube having an inner wall defining a cable conduit through the tube, the inner wall being substantially circular in cross section with a tube inside radius r, there being sliding ribs moulded from the thermoplastic plastics of the tube arranged on the inner wall which, referred to the circumference of the inner wall, extend with a given angle of rotation a, whereby in a linearly arranged cable conduit tube with a cable to be fed into the conduit, contact faces of rib contact width b arise at contact points between the sliding ribs and a cable jacket of the cable to be fed, whereby the combination of the following features is realized: 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 about the circumference of the conduit tube inner wall, the tube inside radius r, and a length LK of rib contact sections between reversal zones satisfy the equation Ar = 0.16 b2z Lk, where A defines the contact face of ^ the cable jacket at intersecting points with sliding*ribs' 'in r 24 7 8 5 5 - 13 - rib contact sections, and is numerically in the range from 4.5 to 32 mm2, 3) the angle g, measured in radians, of the sliding 5 ribs' lead, measured on the tube inner wall, satisfies the equation g = ra / Lk 10 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 mm are selected, and the cable(s) to be fed has/have an outside radius in the 15 range from 5 to 45 mm.

2. A cable conduit assembly according to claim 1, whereby the tube inner wall between adjacent sliding ribs is provided with a concave groove which runs on both sides 20 into the ridges of the sliding ribs.

3. A cable conduit assembly according to claim 1 or 2, whereby the angle of rotation a is selected in the range between 4 5° and 340°. 25

4. A cable conduit assembly according to claim 3, whereby the angle of rotation is selected to be about 180°.

5. A cable conduit assembly according to any one of claims 30 1 to 4, whereby the rib contact width b, the number z of the sliding ribs equidistantly distributed about the circumference of the tube inner wall, the tube inside radius r, the angle of rotation a and the._lenath L„ of N.2. PA1CNT OFFICE "I 9 - NOV 1995 24 7 8 5 5 - 14 - the rib contact sections between reversal zones and parallel to the tube axis satisfy the equation

A cable conduit assembly according to any one of claims 1 to 5, whereby between each two adjacent sections which have a constant angle of rotation there is a connecting section of length Lv where the sliding ribs lie substantially parallel to the tube axis, and the rib contact width b, the number z of sliding ribs equidistantly distributed about the circumference of the tube inner wall, the tube inside radius r, the angle of rotation a, the length LK of the rib contact sections as well as the length Ly of the connecting sections satisfy the equation Ar = 0.16 b2z (0.0003 r2a2 + LK2)^ + 4Lybr

A method for pulling a cable or cables into a cable conduit tube or into cable conduit tubes of a cable conduit assembly according to any one of claims 1 to 6, whereby the pull-in speed of the cable(s) to be fed is so selected that the contact faces are melted to a fused mass by friction heat, and a lubricant friction condition is provided by the fused mass.

A cable conduit assembly substantially as herein described with reference to any embodiment shown in the accompanying drawings. Ar = 0.16 b2z (0.0003 r2a2 + LK2)^. 9 - NOV 1995 RECEIVED 24 7 8 5 5 - 15 -

9. A method according to claim 7 and substantially as herein described with reference to any embodiment disclosed.

10. A cable conduit assembly having had a cable or cables pulled through a cable conduit tube thereof by the method of claim 7 or 9. Dipl..- INC, ftp, VQCB^A|sC By the authorised agents 9cD A. J Park & Son !■_ _2FFICE 9 - NOV 1995 RECEIVED