ENERGY TRANSPORTATION MAST WITH DIFFERENT CONICITIES
FIELD OF THE INVENTION
The invention relates to an energy transportation mast for being placed on the ground, which may be configured for connecting to a crossbar for carrying and guiding electric cables. The invention further relates to a method of manufacturing such mast from com posite material.
BACKGROUND OF THE INVENTION It is known to use energy transportation masts that are conical shaped, wherein the coni cal mast is the carrying element in transportation and distribution of (electric) energy. The conical masts are generally used to adapt the mast dimensions to the forces that occur at different positions along the mast in operational use. The lateral forces (for example due to wind) applied at the topside of the mast require that the bending section modulus at the bottom end of the mast is much higher than at the top end of the mast. These known masts are manufactured in separate conical sections, where the sections are connected by placing them over each other. By playing with the dimensions and conicity the desired overlap between said conical sections can be set. The current applicant runs a business of energy transportation masts that are made of composite material and in one piece. The current applicant filed an earlier patent application in Norway NO2016151 1 , wherein a first development was disclosed. In this application the focus was to make a one-piece composite mast having a cylindrical upper portion to facilitate placing a crossbar adaptor on top of the mast, no matter at which height the mast was cut off within the cylindrical upper portion.
Still there is a need to further develop the energy transportation mast, in particular mast made of one-piece in composite material.
SUMMARY OF THE INVENTION The invention has for its object to remedy or to reduce at least one of the drawbacks of the prior art, or at least provide a useful alternative to prior art.
The object is achieved through features, which are specified in the description below and in the claims that follow.
The invention is defined by the independent patent claims. The dependent claims define advantageous embodiments of the invention.
In a first aspect the invention relates to an energy transportation mast for being placed on a ground. The mast comprises: i) a first section having a first conicity having a first conicity value, the first section being configured to be coupled to the ground or to an adapter mod ule for fixing the mast to the ground, and ii) a second section connected to the first sec- tion, the second section being connectible to a crossbar for carrying and guiding electric cables, the second section having a second conicity having a second conicity value, the second conicity value being smaller than the first conicity value.
The effects of the energy transportation mast in accordance with the invention are as fol lows. The advantage of having only conical sections in the energy transportation mast is that the conicity is exploited best such that the bottom part of the mast is widest at a pre defined length of the mast. This results in the best bending section modulus (bending re sistance) of the mast.
In order to facilitate understanding of the invention one or more expressions are further defined hereinafter. Wherever the wording“mast” is used, this is to be seen as equivalent to words like tower, pylon, and pole.
In an embodiment of the energy transportation in accordance with the invention the mast is further provided with a further section in between the first section and the second sec tion, wherein the further section has a further conicity having a further conicity value, wherein the further conicity value lies in between the first conicity value and the second
conicity value. This embodiment is advantageous particularly when the difference in conic- ity between the most upper section and the most lower section is large. When a further section is formed in between these sections, this section may be advantageously de signed with a further conicity having a value in between the values of the other conicities. In an embodiment of the energy transportation in accordance with the invention the sec ond conicity value is less than or equal to 2 millimeters per meter length. The advantage of using such low conicity for the second section (the upper section in operational use) is that such a low conicity in practice means that the upper section may be cut at whatever height without making the connection to a crossbar through a crossbar adapter more diffi- cult, i.e. the same adapter fits at different heights/lengths.
In an embodiment of the energy transportation in accordance with the invention the first conicity value is between 10 and 25 millimeters per meter length. The advantage of choosing this conicity for the first section (the lowest section in operational use) is that fixation to the ground is easier, either by placing the mast straight into the ground or via an adapter module.
In an embodiment of the energy transportation in accordance with the invention the further conicity value is between 2 and 20 millimeters per meter length. This conicity value lies conveniently in between the conicities of the other parts and will render the manufactura bility of the mast easier, particularly when it is manufactured from one piece and from composite material.
In an embodiment of the energy transportation in accordance with the invention the mast comprises at least four different sections having different conicities having different conici ty values that that the conicity of the mast reduces from a bottom end to a top end of the mast. The advantage of this embodiment is that it extends the idea of the invention such that even wider diameters of the mast at the bottom end (the first section) are possible, while using the same diameter at the top end (the second section).
In an embodiment of the energy transportation in accordance with the invention the transi tion between said conicities is smoothened. The advantage of smooth transitions between the separate sections is that the manufacturability and robustness of the mast increases. This embodiment also includes the variant where the conicity within the sections gradually changes.
In an embodiment of the energy transportation in accordance with the invention all sec-
tions are formed in one-piece. Masts that are manufactured from one-piece are mechani cally stronger than when they are formed from multiple pieces.
In an embodiment of the energy transportation in accordance with the invention the mast comprises composite material. In this embodiment the invention finds it strongest impact. Manufacturability of composite masts is by definition more challenging than when other materials are used, yet it renders the mast very cheap and also much more processable.
In a second aspect the invention relates to the mast is made by a filament winding pro cess, wherein a rotating mandrel used in the filament winding process defines the inside form of the mast to be manufactured. Filament winding is a process that is known to the person skilled in the art. It is the inventor’s insight that such process can be used to make tubular objects having non-constant radius over its length. The main idea is to use a rotat ing mandrel which defines the inside form of the (hollow) mast to be formed.
BRIEF INTRODUCTION OF THE DRAWINGS In the following is described an example of a preferred embodiment illustrated in the ac companying drawings, wherein:
Fig. 1 shows a side view of an energy transportation mast in accordance with an embodiment of the invention, and
Fig. 2 shows a top view of the mast of Fig. 1 .
DETAILED DESCRIPTION OF THE EMBODIMENTS
Various illustrative embodiments of the present subject matter are described below. In the interest of clarity, not all features of an actual implementation are described in this specifi- cation. It will of course be appreciated that in the development of any such actual embod iment, numerous implementation-specific decisions must be made to achieve the devel opers’ specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be ap preciated that such a development effort might be complex and time-consuming, but
would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.
The present subject matter will now be described with reference to the attached figures. Various systems, structures and devices are schematically depicted in the drawings for purposes of explanation only and so as to not obscure the present disclosure with details that are well known to those skilled in the art. Nevertheless, the attached drawings are included to describe and explain illustrative examples of the present disclosure. The words and phrases used herein should be understood and interpreted to have a meaning consistent with the understanding of those words and phrases by those skilled in the rele- vant art. No special definition of a term or phrase, i.e., a definition that is different from the ordinary and customary meaning as understood by those skilled in the art, is intended to be implied by consistent usage of the term or phrase herein. To the extent that a term or phrase is intended to have a special meaning, i.e., a meaning other than that understood by skilled artisans, such a special definition will be expressly set forth in the specification in a definitional manner that directly and unequivocally provides the special definition for the term or phrase.
Fig. 1 shows a side view of an energy transportation mast 10 in accordance with an em bodiment of the invention. Fig. 2 shows a top view of the mast of Fig. 1. The mast 10 in accordance with this embodiment comprises three sections 10-1 , 10-2, 10-3, but it could have been two sections, four sections, or more in accordance with other embodiments. What is important is that these sections 10-1 , 10-2, 10-3 each have a different conicity. Values of the respective conicities are referred to as a1 , a2 and a3, respectively. The first conicity of the first section (bottom section) 10-1 here has the highest value a1 . The sec ond conicity of the second section (top section) 10-3 here has the lowest value a3. The third conicity of the third section (middle section) 10-2 has a third value a2 that here lies in between the values of the first value a1 and the second value a2.
The bottom section 10-1 of the mast 10 has a first length L1 , which may be between 4 m and 8 m (for example 6,5m). The middle section 10-2 of the mast 10 has a second length L2, which may be between 1 m and 4 m (for example 2,5m). The top section 10-3 has a third length L3, which may be between 2 m and 6 m (for example 4m). As a result, the mast 10 may have a total length L123 between 4 m and 14 m (for example 12m). It must be stressed that deviations from these values are also possible, which do not depart from the scope of the invention as claimed.
The conicity of the bottom section 10-1 may typically have a value between 10 and 25 mm per meter length (for example 18 mm/m). The conicity of the middle section 10-2 may typ ically have a value between 2 and 20 mm per meter length (for example 10 mm/m). The conicity of the top section 10-3 may typically have a value between 2 mm per meter length or smaller (for example 2 mm/m). It must be stressed that the mast sections 10-1...10-3 may also have local deviations or transitions in diameter, for example to facilitate mount ing of objects in the mast or to facilitate higher lengths of the mast.
Designing the mast as illustrated in Fig. 1 with clear conical sections is advantageous for the manufacturing process, particularly when a filament winding process is used. In a fur- ther variation the conical sections 10-1 ..10-3 may have smooth transitions in conicity or may even have a gradually changing conicity themselves. Alternatively, there may be four or more different conical sections in the mast such that the transitions in conicity become smaller.
As mentioned earlier the second section (upper section) 10-2 of the mast is configured for carrying and guiding electric cables. There is different ways of achieving this function for the upper section 10-2.
A first way is to provide a crossbar (not shown) on the upper section 10-2 of the mast 10. Such crossbar may be mounted to the upper section 10-2 by means of a crossbar adapter (not shown). To this end the upper section 10-2 may need to be configured for being able to receive the crossbar adapter. Subsequently, the electric cable (not shown) may be mounted to the crossbar via known fastening means (not shown).
A second way is to provide said fastening means directly to the upper section 10-2 of the mast 10 and mount the electric cables thereto. In that case no crossbar or crossbar adapter is necessary. The figures and description above do not disclose any details about a possible crossbar adapter to be placed on the mast for placing the cross-bar on the mast. This knowledge is considered known to the person skilled in the art. Reference is made to the non- prepublished patent application mentioned in the introductory part of this specification for more details. The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. For example, the method steps set forth
above may be performed in a different order. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope of the inven- tion. Accordingly, the protection sought herein is as set forth in the claims below.
It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodi ments without departing from the scope of the appended claims. In the claims, any refer ence signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a com bination of these measures cannot be used to advantage. In the device claims enumerat- ing several means, several of these means may be embodied by one and the same item of hardware.