GB2450851A

GB2450851A - A method and conduit for passing cable through smoothly

Info

Publication number: GB2450851A
Application number: GB0820607A
Authority: GB
Inventors: Jun Xu
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-04-11
Filing date: 2007-04-11
Publication date: 2009-01-07
Anticipated expiration: 2027-04-11
Also published as: GB2450851B; CN1832282A; CN101427433A; GB0820607D0; CN101427433B; WO2007115508A1

Abstract

A method and conduit for passing cable through smoothly, used for passing the cable through soomthly in different directions in one plane or two unparallel planes between two buildings, wherein the method including: choosing the curved path and conduits of the less accumulative bending angle when the equivalent bending radius of them meet the minimum requirement, and choosing the curved path and conduits of the longger equivalent bending radius when the accumulative bending angle is not affected.

Description

A method and conduit for passing cable through smoothly This invention

relates to a method and conduit fittings utilised in building ducting, cabling or decoration engineering, which can make the conduit route smooth. Specifically, the said method and conduit fittings facilitate conduit route in changing its direction smoothly within one building plane or between two unparallel connected planes.

Background

More and more cables and wires have been introduced into modern buildings; and within the operation life cycle of these buildings, it is common to have to change and update cables and wires now and then. These up growing needs have brought with them the higher level requirement and expectation in the quality of design and operation of conduit routes. But the walls and floors of buildings have been becoming thinner than before, which has brought more constrains to the space that conduits could run though.

This invention is intended to solve the following problems: How to achieve a bending with bending radii not less than 10 times of the diameter of the conduit; how to decrease the accumulative bending angle to minimise unnecessary bending.

In terms of bending radius, it is prescribed in the Chinese Building Cabling Code that the bending radius of any in-building conduit should not be less than 6 times of the diameter of the conduit, more than 10 times preferred if possible. It is understandable that the bigger the bending radius, the easier for installing and updating cables and wires, and less damage of them incurred by installation.

However, practically, the walls and floors have a lot of constrains to the space that conduits could run though, therefore it is very difficult, sometimes even impossible, for a conduit route to achieve a bending with bending radius not less than 10 times of the diameter of the conduit.

Figure 1 illustrates a typical bending situation of a vertical flat bend, wherein a and b represent the vertical variation limits of the conduit within two vertically connected building entities, such as a wall and a floor, fli and 112 represent two inner limit planes, the line of their interface is called conjunction line or limit. In Figure 1 limit c is represented by a spot; similarly, the spot h represents the line of two outer limit planes interfacing together. D is diameter, r is an intermediate variant, and then the maximal bending radius, Rmax, of the vertical flat bend is defined by: Rmax = r+ D/2; r2 = (r-a) 2+(r-b) 2 Wherein r?a, rb Figure 2 illustrates a more general situation where the two building entities, e.g. two walls or a wall and a floor, are connected with an angle, not necessary being 900 though this is the most popular case, wherein D is diameter, a and b represent the vertical variation limits of the conduit within two vertically connected building entities, #1, #2 and rare intermediate variants, and then the maximal bending radius, Rmax, of the vertical flat bend is defined by: Rmax = r-i-D/2; 41= #1+412; sine ( #1) = (r-a)/r; sine(#2)=(r-b)/r Whereinra,rb, #190 , #290 When 41=90 , it becomes the simple situation mentioned above.

The following table gives some possible values of a and b, in order to achieve a bending with the bending radius of 10 times of the diameter of the conduit with diameters of 2.0 cm and 2.5cm, respectively. All units in the table are centimetres.

Rmax D a b 2 1 12.9 2 2 10.5 2 3 8.8 2.5 1 16.9 2.5 2 14.2 2.5 3 12.2 It is clear from this table that, in order to achieve a bending with the bending radius of 10 times of the diameter of the conduit with typical diameters of 2.0 and 2.5cm, provided the vertical variation limit of the conduit within the floor is less than 3cm, then the vertical variation limits of the conduit within the wall should not be less than 8.8 and 12.2cm, respectively. Such requirement is very difficult to be fulfilled in practice.

Another problem associated is that different conduit route designs bring different resistant forces to cables and wires, even though they have similar bending radii.

Improvement This invention provides a method and a set of bends and conduit fittings, which can achieve a bending with the bending radius of more than 10 times of the diameter of the conduit; and it may also save unnecessary turning-around which brings resistant forces. These solutions, as a whole, help make the conduit route smoother. In the meantime, the structures of the bends and fittings are optimised to facilitate mass production.

It is necessary to introduce several new terms in order to describe the invention clearly, such as virtual conduit.

Indifferent national building electric codes, there is always a requirement of the minimal bending radius for bending conduits. For theoretically smooth bends, the real bending radius does provide a precise index of their actual bending effects.

But the reality is complicated in that there are always small mal-positions between connected conduits and fittings, various transformations alongside, and unsmooth connections, and these phenomena give birth to so-called odd-spot, where the bending radius is markedly smaller than those of other parts, in particular situation, the bending radius at an odd-spot could be zero.

Figure 3 illustrates a conduit route with odd-spots, wherein odd-spot Si is connecting two straight conduits with angle 0 i, the bending radius at Si is zero; at odd-spot S2, the straight conduit is connected with a bend with a very small bending radius which is smaller than the diameter of the conduit.

The existence of odd-spots makes it rather inaccurate for the bending radius to reflect the real bending effect.

In fact, different odd-spots have different influences on the smoothness of a conduit route, some may be minute, but others could be substantial. The once-popular right-angle elbow is a typical one with a destructive odd-spot; odd-spots at Si and 52 in figure 3, on the other hand, do not influence much of the smoothness, because the angle 01 is very small and the bending angle around 52, which has been amplified in figure 3, is also very small.

The introduction of the term virtual conduit, therefore, is to describe, more accurately, the true bending effect of a bend.

Figure 4 is the profile of a conduit route along the axial line, a virtual conduit L is introduced in the conduit route with odd-spots; the diameter Dv of the virtual conduit L is smaller than the inner diameter of the real conduit. There is no longer any odd-spot in the virtual conduit L, in which Ri, R2, R3 and R4 are the bending radii of different parts of the virtual conduit L. In figure 5, after introducing a virtual conduit L into a bend with odd-spot S3, the odd-spot 53 within the bend is then replaced by a new odd-spot 54 within virtual conduit L. Since there are, theoretically, so many possible virtual conduits within a given conduit route, and their bending radii are different, it is, therefore, necessary to find a virtual conduit with the maximal bending radius to be the representative of them to describe the true bending effect, this representative is called optimum virtual conduit.

The virtual conduit functions as a sieve', which overlooks those odd-spots with little influence on the smoothness; while the diameter of the virtual conduit, or the selection of virtual-real diameter rate, functions as the hole' of the sieve': the bigger the virtual-real diameter rate, the smaller the hole, the fewer odd-spots being overlooked.

With the optimum virtual conduit, we could use its bending radius, which is called equivalent bending radius, to describe the true bending effect of a conduit route.

There is another need to define what a smooth connection is.

It is rather vague to say a connection is smooth. Absolute tangent connection is ideal, but hard to achieve. Therefore it is more practical and usually economical to allow the existence of odd-spots, provided their influence on the smoothness can be overlooked to certain extent, which means that, more accurately, the odd-spots do not make the equivalent bending radius of the whole conduit less than any of the equivalent bending radii of the two parts of the whole conduit.

Furthermore, the above said bending radii should be more than 10 times of the conduit diameter, to fulfil the purpose of this invention. In this way, the bending effect remains the same no matter whether the connection is tangent or with odd-spots. Such a connection is called equivalent smooth-connecting, which helps describe the detailed solutions below.

1. Pseudo-three-dimensional bend A pseudo-three-dimensional bend is a kind of three dimensional bend which comprises two flat bends, within two unparallel planes, connected through equivalent smooth-connecting.

The said flat bends are defined at the end of this specification. Figure 6 illustrates a pseudo-three-dimensional bend, wherein flat bends 1 and 2 have equivalent bending radii of more than 10 times of the diameter of the conduit, and they are connected at spot 0 through equivalent smooth-connecting.

The connection may be rigid or adjustable.

Figure 7 is the three-view drawing of a pseudo-three-dimensional bend, the two flat bends of which are located within two vertically-connected planes. R is bending radius, D is conduit diameter.

Figure 8 illustrates another similar pseudo-three-dimensional bend with adjustable connection, wherein R is bending radius, D is conduit diameter.

Figure 9 illustrates the differing situations of an adjustable pseudo-three-dimensional bend with differing angles.

When the above said angle becomes 1800, then the pseudo-three-dimensional bend becomes an S'-shaped flat bend. Figure 10 illustrates such situation, wherein R is bending radius.

The equivalent bending radius of a pseudo-three-dimensional bend is decided by the equivalent bending radii of the two flat bends, there is no relationship between the bending radii and the vertical variation limits of the conduit.

Because of its simple structure, a pseudo-three-dimensional bend is easy to produce, but there is still obvious weakness in this solution.

Firstly, this solution does not take any advantage of the variation space of walls and floors, i.e. the vertical variation limits of the conduit.

Secondly, when several pseudo-three-dimensional bends have to be installed together in parallel, the minimum distance between them is too big.

Figure 11 illustrate the situation, with front view and top view, where three pseudo-three-dimensional bends are installed together in parallel; the diameter D is equal to 2cm, the bending radius is equal to 20cm, then the minimum distance between these bends is about 9cm. Obviously, this distance is too big to meet the requirement of connecting them with a group of outlets.

2. Three-dimensional bend The three-dimensional bend is intended to take advantage of the variation space of walls and floors, i.e. the vertical variation limits of the conduit.

In order to better understand the improvement, another important index related to the smoothness of the conduit, i.e. accumulative bending angle, has to be introduced and analysed.

Among a group of conduits with the same bending radius, the bigger the accumulative bending angle, the bigger the resistance.

Two examples of L'-shaped bends and S'-shaped bends are examined below.

All bends in figures 12, 13 and 14 are presented as thick lines to simplify the figures; and all bends are flat bends too.

Figure 12 and 13 illustrate several alternatives of L' -shaped vertical bends with the same bending radius R. Bend 81 is the most common bend; its accumulative bending angle is 900 Bend 82 comprises two bends and one straight conduit, its accumulative bending angle is equal to Wi plus W2, i.e. 900 Bends 83 and 64 comprise three sub-bends to achieve 90 direction-changing, their accumulative bending angle are equal to the sum of the three sub-bends' bending angles, i.e. 150 and 210 , respectively.

lfAAl, AA2, AA3 and AA4 represent the accumulative bending angles of 81 to B4, respectively, then AA1=AA2<AA3<AA4.

Provided the other situations are the same, the resistant forces within the four bends have similar relationships. If Zi, Z2, Z3 and Z4 represent the resistant forces within the four bends, then, according experience, Zi Z2<Z3<Z4.

It is clear that, bends Bi and 82 are better than bends 83 and 84.

Figure 14 illustrates several alternatives of S' -shaped vertical bends with the same bending radius R; the extended lines of the two ends are parallel.

For bend 85, its accumulative bending angle is 180 For bend B6, its accumulative bending angle is equal to 2 times of W6. When W6=45 , the accumulative bending angle is 90 . When W6 becomes smaller, the accumulative bending angle becomes smaller too, then the whole 5' -shaped bend becomes less curved.

Theoretically, W6 could approach zero.

Further mathematical analysis could lead to such a statement: The minimal accumulative bending angle of a bend is equal to the angle between the extended lines of the two ends.

For bends with parallel extended lines of the two ends, the minimal accumulative bending angle is just a theoretically extreme value. In practice, a relatively smaller accumulative bending angle is preferred if the route selection is feasible.

Before introducing the three-dimensional bend, let's have a look at the previous vertical flat bend, as illustrated in figure 15. In order to achieve a bigger bending radius, we have to take advantage of the variation space within the walls or floors. However, since the back box 24 behind the outlet cannot be installed too deep, when the bending radius R increases, the accumulative bending angle, which is equal to WOl plus W02, also increases.

After taking advantage of all possible variation space, if the bending radius still does not meet the requirement, or, as a result of such action, the accumulative bending angle becomes too big, then we have to resort to other solutions. As in figure 15, if WOl + WO2 1800, the solution is definitely not a desirable one, even if the bending radius R is expected.

The expected three-dimensional bend must have a smaller accumulative bending angle than that of a pseudo-three-dimensional bend with the same extended directions on both ends.

Figure 16 illustrates a three-dimensional bend.

Figure 17 is the three-view drawing of the three-dimensional bend, wherein Rx, Ry and Rz are the equivalent bending radii of three projections of sub-bend 5, respectively. There is significant difference between the side-views of figures 7 and 17. In figure 17, there is a relationship between Rz and Rmax: 0<Rz Rmax, where Rmax represents the maximal bending radius of a vertical flat bend with vertical variation limits. If R represents the expected equivalent bending radius, and R>Rmax; in addition, assuming that sub-bends 3 and 4 are both flat bends and their equivalent bending radii are R, then it is possible that Rx and Ry are less than R to make sure that the equivalent bending radius of sub-bend 5 is not less than R. It is necessary to flatten the three-dimensional bend to make more comparison. It is relatively easy to flatten a pseudo-three-dimensional bend; in order to flatten a three-dimensional bend, we have to use curved surface.

The above said curved surface comes from extending the axial line along the direction in parallel with the conjunction line of the two connected wall and floor. Figure 18 illustrates the curved surface and the three-dimensional bend within it. It is one of the characteristics of the three-dimensional bend that any tangent line on the axial line is not in parallel with the conjunction line of the two connected walls and floors.

After flattening, the three-dimensional bend becomes a flat bend in figure 19, wherein R is the bending radius; the dotted line represents the conjunction line.

Figure 20 compares the pseudo-three-dimensional bend B7with the three-dimensional bend 88; both them have the same ending directions.

End P7 of bend 87 meets end P8 of bend B8 with the same tangent lines; while tangent lines from ends Q7 and Q8 are parallel. In figure 20, W7= W71 + W72, W8= W81 + W82, where W7 is the accumulative bending angle of the pseudo-three-dimensional bend 87, and W8 is the accumulative bending angle of the flattened three-dimensional bend 88.

Analysed with figure 17 together, increase in Rz may possibly lead to decrease in W8. Even though it is clear that Wi> W8, but the relationship between the real accumulative bending angles of bends B8 and B7 is not clear.

Experiments have proved that there exist uncountable three-dimensional bends with smaller accumulative bending angles than that of a pseudo-three-dimensional bend, but so far it is still difficult to describe accurately the structure of expected three-dimensional bends, which makes mass production impossible.

Therefore, a new solution is needed, which should have simple structure to facilitate mass production, and have similar effect as expected three-dimensional bends.

3. Spinning pseudo-three-dimensional bend The key point of spinning pseudo-three-dimensional bend is to take the advantage of all possible variation space to approach the effect of expected three-dimensional bends.

Figure 21 illustrates a flattened pseudo-three-dimensional bend with bending radius R, wherein the pseudo-three-dimensional bend is presented as a thick line, straight linefis the conjunction line of the two planes, radial m and radial n within the two planes are both vertical to line f and tangent with the two arcs, respectively. The operation of spinning is performed with radials m and n as axes. When spinning with one radial, the other radial shifts within the plane it Sits and remains vertical to linef.

In order to make the situation clear, the connecting Spot 0 and two ends P and Q are highlighted; the circles containing the two flat bends are represented via dotted lines.

The spinning of a pseudo-three-dimensional bend is performed in two steps: spinning along radial n with radial m as axis; then spinning along radial m with radial n as axis.

Figure 22 illustrates a more general situation, wherein only one flat bend OP of a pseudo-three-dimensional bend is presented, bend OP is not necessarily a simple arc, and its equivalent bending radius is R. In order to perform spinning, an arc PPe with bending radius R is introduced, and it connects with bend OP tangentially, the tangent on spot Pe is vertical to linef, and the tangent is just the axis m needed. The arc PPe is called extended arc. As defined at the end of this specification, the extended arc is within the same plane as bend OP. and on the same side as the tangent on spot P. Figure 23 illustrates the front-view and top-view of the post-spinning pseudo-three-dimensional bend in figure 21. The linef in front-view and that in top-view meet together; m and on are spinning angles along axes m and n, respectively. Straight line cand linef are parallel; the distances between line c and the two planes before spinning are vertical variation limits a and b, respectively, which are also the vertical variation limits of the conduit.

After spinning, the two dotted circles become ovals; Bend OP becomes an oval arc in front-view, and a straight line in top-view, while bend OQ becomes an oval arc in top-view, and a straight line in front-view.

Figure 24 is the left-view of the post-spinning pseudo-three-dimensional bend, wherein line fand straight line c become two spots, bends OP and OQ are still oval arcs in this left-view.

It is notable that, after spinning, the conjunction line of the two planes becomesg, and the connecting spots between the pseudo-three-dimensional bend and radials m and n changed from spots P and Q to Pm and Qn, respectively; the tangent directions on spots Pm and Qn after spinning are the same as those on spots P and Q before spinning, which means, after spinning, only a part of the original bend, i.e. the part between spots Pm and Qn, is needed to achieve the same purpose of changing direction of the original bend before spinning. Therefore the redundant parts of PPm and QQn are represented as thick dotted lines in figure 25 and 26.

Figure 25 illustrates the top-views of flat bends OP and OQ within their own planes.

When connecting the two top-views together, with line g and spot 0 in both top-views meet together, then we got figure 26, which illustrates the situation where the post-spinning pseudo-three- dimensional bend is flattened along the new conjunction line g. It is notable that, there are two lines namedf, which are the projections of the real linefon the two planes, the one vertical to radial m is within the same plane as bend OP, the one vertical to radial n is within the same plane as bend OQ.

In figures 25 and 26, Wm and Wn represent the spinning angles of sub-bends OPm and OQn after spinning the pseudo-three-dimensional bend, the accumulative bending angle of the effective part of the pseudo-three-dimensional bend is W, then W = Wm + Wn. Figure 27 helps get the desired relationships between accumulative bending angles and spinning angles, wherein fand g are the same asfand g in figure 23, respectively; m and nare the radials m and n in figure 23, respectively; .m and 6.,n are the spinning angles 6.'m and (i)n in figure 23, respectively; Wm and Wn are the bending angles Wm and Wn in figure 26, respectively. After simple calculation, we got: Cotangent ( 1'n) = tangent (em) X cosine (6n); Cotangent ( Wm) = tangent ( n) >< cosine ( o'm) Where, O cUm<90 , O wn<90 , 0< Wm <900, 0< Wn <90 When m =0, which means there is no spinning with axis m, then Wn=90 ,Wm=90 -(i)fl Then, W=180 -(A)n.

The accumulative bending angle, i.e. W, can be decreased through increasing the values of mand n.

To get the maximal values of &.m and n, the following restrictions are necessary: 0<a<R, 0<b<R, (R -a)2+(R -b)2>R2, 0< m<90 , 0< 6.n<90 When &.m = 0, the maximal value of c..n meets the following equation: (R-a/sine (n))2+(R-b) 2 =R2 When wn = 0, the maximal value of m meets the following equation: (R -b/sine (em)) 2 (R -a) 2 = R2 To analyse a special situation: after spinning, the spot 0 locates exactly on the limit c, which means the distances between spot 0 and the two planes are exactly the vertical variation limits of the conduit, i.e. a and b. In figure 28, R is bending radius, a and bare the distances between spot 0 and the two planes,f is the same as linef in figure 22, n is the same as the radial n in figure 23, 6,n is the same as the spinning angle n in figure 23, Wn is the same as the bending angle Wn in figure 26. Then we got equation: (R-RX cosine ( Wn)) ><sine (en) = a Similarly, we got equation: (R -RX cosine ( Wm)) X sine (wm) = b Combined with the two equations from figure 27, we got the following equations: (R -RX cosine ( Wn)) X sine ( 6n) = a; (R - RX cosine ( Wm)) X sine ( a.m) = Cotangent ( Wn) = tangent ( m) X cosine ( n); Cotangent ( Wm) = tangent ( n) X cosine (em) Where, 0< wm<90 , 0< n<90 , 0< Wm <90 , 0< Wn <90 In this special situation, the accumulative bending angle can be calculated with given values ofR, a and b.

In figure 24, the spot 0 is where the bending radius is the minimum. It is the optimal example of spinning to fit spot 0 with the most difficult place, i.e. limit c.

4. The selection and optimisation of ducting route In the prior solutions, two important indexes are discussed. Then how to balance the two indexes to achieve a desired bending effect in design and installation? ii Given the same bending radius, the smaller the accumulative bending angle, the smoother the conduit; given the same accumulative bending angle, the bigger the bending radius, the smoother the conduit.

Figure 29 illustrates the qualitative relationship between the smoothness of a conduit and its bending radius R and bending angle W, wherein curve ti represents better smoothness, curve t2 represents intermediate smoothness, and curve t3 represents worse smoothness.

When bending angle becomes very big, a larger bending radius will not improve the smoothness much; when bending angle is very small, a smaller bending radius can be reasonably overlooked. The spot S in figure 29 represents the latter situation, which is the same situation with odd-spots, such as 52 in figure 3.

Then the desired method for conduit route design and optimisation is that, choosing the route with less accumulative bending angle provided its equivalent bending radius meets the minimal requirement, and choosing the route with larger equivalent bending radius provided its accumulative bending angle is the same.

List of drawings It is accepted that all the conduits in this invention are round.

Figure 1 and 2 illustrate the vertical flat bends; Figure 3 illustrates a conduit with odd-spots; Figure 4 illustrates the concept of virtual conduit; Figure 5 illustrates the odd-spots within a bend and a virtual conduit; Figure 6 illustrates a pseudo-three-dimensional bend; Figure 7 and 8 illustrate the three-view drawings of pseudo-three-dimensional bends with rigid connection and adjustable connection, respectively; Figure 9 illustrates the differing situations of an adjustable pseudo-three-dimensional bend with differing angles; Figure 10 illustrates a flattened adjustable pseudo-three-dimensional bend; Figure 11 illustrates the situation, with front view and top view, where three pseudo-three-dimensional bends are installed together in parallel; Figure 12, 13 and 14 illustrate several alternatives of L' -shaped and S'-shaped vertical bends with the same bending radius R; Figure 15 illustrates a vertical flat bend, which takes advantage of the variation space within the walls or floors; Figure 16 and 17 illustrate a three-dimensional bend; Figure 18 illustrates the three-dimensional bend within a curved surface; Figure 19 illustrates the flattened three-dimensional bend; Figure 20 illustrates the comparison between a pseudo-three-dimensional bend and a three-dimensional bend; Figure 21 and 22 illustrate two flattened pseudo-three-dimensional bends; Figure 23 illustrates the front-view and top-view of the post-spinning pseudo-three-dimensional bend in figure 21; Figure 24 illustrates the left-view of the post-spinning pseudo-three-dimensional bend; Figure 25 illustrates the top-views of two flat bends within their own planes; Figure 26 illustrates the situation where the post-spinning pseudo-three-dimensional bend is flattened along the new conjunction line; Figure 27 helps get the desired relationships between accumulative bending angles and spinning angles; Figure 28 illustrates a model to calculate the bending angles; Figure 29 illustrates the qualitative relationship between the smoothness of a conduit and its bending radius and bending angle; Figure 30 illustrates 450 flat bend and three types of fittings; Figure 31 illustrates the method to select conduit route.

Methods of implementation The implementation of this invention involves the following considerations: 1. Production of conduits and fittings. 1) Mass production; 2) manual operation with benders.

2. Installation method, especially of how to control the spinning to achieve smaller accumulative bending angle.

3. How to choose proper conduits and fittings to design and optimise the conduit route.

Mass production of pseudo-three-dimensional bends and flat bends can improve the efficiency of engineering projects, and avoid unqualified bends being installed.

Conduit fittings group 1: 30 -450 flat bends and 75 -90 flat bends The bending radii of the bends are recommended to be 10 times, 15 times and 20 times of the conduit diameter. Other specifications between 6 times and 20 times are also

acceptable.

Figure 30 illustrate 45 flat bend and its fittings. Other possible specifications could be 30 ,35 ,40 ,45 ,75 ,80 ,85 and90 The threetypes of fittings are used to connect conduits or bends. Fitting 110 is for connecting concentric bends, fitting 100 is for connecting bend and straight conduit, fitting is for connecting anti-direction bends. In order to avoid the potential resistance at the connection, the cycling separator 130 in the middle of the fittings has been made smooth.

Other three-dimensional fittings to connect two bends within different planes are possible.

It is also possible to label the fittings with marks or grooves to facilitate recognising the bending direction.

There may be a short straight conduit extended from the bend.

There may be a curved or sloping opening at the inner side of the two ends to avoid resistance. In figure 30, there is a sloping opening 61 at one end, and a curved opening 62 at another end.

Conduit fittings group 2: double 45 and double 90 vertical pseudo-three-dimensional bends Double 45 vertical pseudo-three-dimensional bend comprises two 45 fIat bends, which are vertical to each other; double 90 vertical pseudo-three-dimensional bend is similar.

There may be different specifications of bending radii and bending angles as in group 1, and the connection could be rigid or adjustable.

Spinning of three-dimensional bends, if properly applied, may achieve smaller accumulative bending angle.

For pseudo-three-dimensional bends, it is preferred to use the simple spinning method to make the connecting point of the two flat bends to approach the limit.

Figure 31 illustrates three route designs between conduit 30 to conduits 31, 32 and 33, respectively. In figure 31, a pseudo-three-dimensional bend comprises two 45 flat bends 9andlO. The spinning of the pseudo-three-dimensional bend is omitted here. To avoid the concrete block 20, another 45 flat bend is selected to connect the pseudo-three-dimensional bend with conduit 31. The accumulative bending angle from conduit 30 to conduit 31 is 135 Terminology Cables and wires: including electrical wires, optical fibres, control wires, signal wires and communication cables, etc. Conduit: an intact duct route comprised straight ducts, bends and necessary fittings. One conduit has two ends, or openings.

Flat bend: the absolute flat bend is a bend located within one plane. In this invention, a flat bend maybe shift outside the plane a little, provided there is a virtual conduit within the bend and the virtual conduit is an absolute flat bend.

Verticalflat bend: a flat bend, which plane is vertical to both surfaces of the two connected building entities, such as walls and floors.

Bending radius of a bend: is the bending radius of its axis. When there are different bending radii at different parts of the bend, the bending radius of the bend is the smallest one.

Vertical variation limits: come from the constrains, such as the thickness of walls and floors, the structure of the building and installation requirement, which leave somehow confined space for conduit to run through. For a typical modern building, the vertical variation limit in walls is usually about 2-8cm, while in floors it is only 1-3cm.

Limit: limit is the conjunction line of the inner surfaces of two connected building entities.

The corner lines could be the limits provided the conduit is allowed to be near the corner lines.

Maximal bending radius of vertical flat bend: the vertical flat bend takes all the advantage of the variation space.

Three-dimensional bend: there is not such a plane, where all parts of the bend are in this p Ia ne.

Pseudo-three-dimensional bend: a type of three-dimensional bends which comprise two flat bends.

Odd-spot: a place within a conduit, where the bending radius is smaller than the conduit diameter or even equal to zero.

Virtual conduit: there are inevitably odd-spots in the real conduit route; some of these odd-spots have little influence on the smoothness. In order to evaluate the smoothness of a real conduit, a virtual conduit is introduced into the inner space of the real conduit, the thickness of a virtual conduit's wall is zero, and its diameter is less than the inner diameter of the real conduit.

Optimum virtual conduit: given a real conduit, there are usually many possible virtual conduits within the real conduit, the one with the largest bending radius is called optimum virtual conduit.

Equivalent bending radius: the bending radius of an optimum virtual conduit. When using this term, it is common to set a minimal value of the diameter of the virtual conduit.

Virtual-real diameter rate: the rate of virtual conduit diameter to real conduit inner diameter. The maximum of it is 1; the minimum of it is 0. Practically, the virtual-real diameter rate should be from 1/2 to2/3. In this invention, unless otherwise stated, the virtual-real diameter rate of an optimum virtual conduit is 1/2.

Equivalent smooth-connecting: an equivalent smooth-connecting is such that the equivalent bending radius of the whole conduit after the said connecting is not less than any of the two sub-conduits before the said connecting.

Accumulative bending angle: the accumulative bending angle of a conduit is the sum of the different bending angles along the conduit.

Extended arc: the introduction of extended arc is to help describe the spinning of a pseudo-three-dimensional bend. An extended arc from a flat bend is within the same plane, the extended arc is connected to one end of the axial line of the optimum virtual conduit of the flat bend, the connecting is an equivalent smooth-connecting, and the extended arc and optimum virtual conduit are on the same side of the tangent line; the bending radius of the extended arc is the same as that of the optimum virtual conduit.

Claims

Claims 1. A method for passing cable through smoothly, in which the

method is used for conduit route to change its direction within one building plane or between two connected building planes, and its installation meets the requirement of the vertical variation limits within these building entities; the method is to choose conduit route and fittings with smaller accumulative bending angle, provided the equivalent bending radii of every bend meet the minimal radius requirement; and to choose conduit route and fittings with larger equivalent bending radii, provided the accumulative bending angle is not much affected.
2. A method according to claim 1, in which the bends are flat bends with their equivalent bending radii meeting the minimal radius requirement when they are intended to be used for changing directions of the conduit route within one building plane; or the bends are three-dimensional or pseudo-three-dimensional bends with their equivalent bending radii meeting the minimal radius requirement when they are intended to be used for changing directions of the conduit route between two connected building planes; and the conduit route with smaller accumulative bending angle is the effective route after spinning of three-dimensional or pseudo-three-dimensional bends and cutting-off redundant parts when this route is intended to be used for changing directions of the conduit route between two connected building planes.
3. A method according to claim 2, in which the spinning of a pseudo-three-dimensional bend includes two steps of spinning with two tangent lines as axes, respectively, while keeping the pseudo-three-dimensional bend and its necessary extended arcs as a whole connected tangentially with the two planes, and the spinning makes the conjunction spot of the two flat bends approaching the limit of the two connected building entities.
4. A method according to claims 1, 2 or 3, in which the minimal radius requirement is prescribed by national or industrial codes; the larger equivalent bending radii are equal to or greater than 10 times of the conduit diameters.
5. A method according to claims 1, 2 or 3, in which the minimal radius requirement is that equal to or greater than 6 times of the conduit diameter; the larger equivalent bending radii are equal to or greater than 10 times of the conduit diameters.
6. A method according to claim 4, in which the equivalent bending radii are the bending radii of the optimum virtual conduits with their virtual-real diameter rates being 1/2.
7. A method according to claim 4, in which the equivalent bending radii are the bending radii of the optimum virtual conduits with their virtual-real diameter rates being 2/3.
8. A method according to claim 5, in which the equivalent bending radii are the bending radii of the optimum virtual conduits with their virtual-real diameter rates being 1/2.
9. A method according to claim 5, in which the equivalent bending radii are the bending radii of the optimum virtual conduits with their virtual-real diameter rates being 2/3.
10. A set of bends and fittings comprising pseudo-three-dimensional bends, flat bends and corresponding fittings for passing cable through smoothly, the pseudo-three- dimensional bend comprises two flat bends connected through equivalent smooth-connecting and the equivalent bending radii of all the flats bends and corresponding fittings are equal to or greater than 10 times of the conduit diameter.
11. A set of bends and fittings according to claim 10, in which the equivalent smooth-connecting is either rigid or adjustable.
12. A set of bends and fittings according to claim 10, in which the pseudo-three-dimensional bend and the flat bend include straight conduits at both or either ends.
13. A set of bends and fittings according to claim 10, in which the bending angles of the flat bends including the two of the pseudo-three-dimensional bend are from 30 to 45 orfrom75 to9O
14. A set of bends and fittings according to claim 10, in which the equivalent bending radii are the bending radii of the optimum virtual conduits with their virtual-real diameter rates being 1/2.
15. A set of bends and fittings according to claim 10, in which the equivalent bending radii are the bending radii of the optimum virtual conduits with their virtual-real diameter rates being 2/3.
16. A set of bends and fittings according to claim 10, in which the fittings comprise tangentially connected short bends or straight conduits, including concentric short-bends and anti-direction short-bends.
17. A set of bends and fittings according to claim 16, in which the surface of the cycling separator (130) in the middle of the fittings is curved.
18. A set of bends and fittings according to claims 10, 11, 12, 13,14 or 15, in which there are sloping opening (61) or curved opening (62) at both ends of the pseudo-three-dimensional bends and flat bends.
19. A three-dimensional bend used for conduit route to change its direction within one building plane or between two connected building planes, and its installation meets the requirement of the vertical variation limits within these building entities, in which any tangent line on the axial line is not in parallel with the conjunction line of the two connected walls and floors.
20. A three-dimensional bend according to claim 19, in which the equivalent bending radius of the three-dimensional bend is equal to or greater than 10 times of the conduit diameter.
21. A three-dimensional bend according to claims 19 or 20, in which the three-dimensional bend comprises two or more flat bends which are connected through equivalent smooth-con necting.