EP1751378A1

EP1751378A1 - A mast construction

Info

Publication number: EP1751378A1
Application number: EP05735667A
Authority: EP
Inventors: Alvar Palmcrantz
Original assignee: Sutoria Trading AB
Current assignee: Sutoria Trading AB
Priority date: 2004-04-26
Filing date: 2005-04-25
Publication date: 2007-02-14
Also published as: SE0401068L; SE0401068D0; WO2005103417A1; SE527017C2

Abstract

ABSTRACT The present invention relates to a mast construction that includes at least three tubular legs which are releasably fastened to a base (2) disposed at ground level by means of fastening devices. According to the invention, the legs are comprised of a plurality of tubular sections wherein the number of tubular leg sections is chosen in accordance with the desired height of the mast construction. The mast construction also includes a plurality of bracing units (8,9,10,11,12,13) and the legs are mutually connected with the aid of said bracing units (8,9,10,11,12,13). The bracing units (8,9,10,11,12,13) are spaced at a suitable distance in a vertical direction, depending on the height of the mast. The mast construction also includes a wire (16) which is connected to the uppermost bracing unit (13) and a lowermost bracing unit (8) with the wire (16) located in the space between the space. (Fig. 1)

Description

A mast construction

Field of invention

The present invention relates to a mast construction which is realisably secured at ground level, in accordance with the preamble of claim 1. The invention relates in particular to a mast construction intended for mobile telephone networks and radio networks, although other areas of use are conceivable.

Background of the invention

Wireless, or cordless, communication is a rapidly growing field of activity at present. Because the development of timesharing and co-use of mast constructions in this field of activity is constricted due to the fact that the various activities that shall share one and the same mast construction interfere with one another, and because the consensus of opinion leads away from these types of construction and leans, rather, towards a development of smaller and therewith also less radiating structures, the demands placed on masts for transmitting and receiving telephone and radio signals for instance have increased to a corresponding degree. Moreover, smaller masts require less space and thus cause less damage to the environment and are less discriminating from an aesthetic sense. It is therefore desirable that a mast structure will take-up but a small ground area and that it will be more attractive aesthetically than those used today and will also be inexpensive and simple to construct. It is also desirable that a mast will fulfil maintenance, stability and safety requirements and that it can be taken down, e.g. for recycling purposes, and assembled, preferably on site, both quickly and easily.

WO 91/18163 describes a conventional mast construction. In order to be able to withstand the stresses and strains to which the mast is subjected by workers climbing up and down the mast and also to withstand the effect of weather and wind, the ground-level secured mast construction is comprised of legs and latticework that provide a stable structure in the absence of bracing lines or wires. This places high requirements on the choice of material used and also on the complex construction. The complex construction of the mast, the comprehensive transport planning and the onsite erection of the mast involved, together with the requirement of additional measures, such as the provision of cranes for assembling the mast, makes this type of mast expensive.

US 5832688 describes a collapsible mast structure of the latticework type which comprises base fastener means, a base bracing element, a base lattice structure comprised of steel wires, a central tubular spacing element, and an upper bracing element. Because of the complex construction of the mast, the mast is erected at its place of manufacture prior to being transported to and erected at its intended site. One drawback with this type of mast construction is that it takes a long time to assemble and requires comprehensive planning for transportation to and erection on said site. In total, this makes the mast construction both expensive and difficult to manage.

Prior publication Us 4212015, US 4146897, US 5233809 and US 5832688 all describe some type of mast construction that includes external bracing lines. This type of mast is also expensive due to the cost of the external bracing lines. This type of mast also requires a large erection area in order to provide place for the braced tower.

Object of the invention

The object of the present invention is to provide an extremely light mast construction that can be transported, positioned, erected and collapsed readily substantially at any desired site and in the absence of any additional measures, such as the use of cranes and the construction of roads.

Another object of the invention is to provide a mast construction that requires less ground space by virtue of the fact that no external bracing elements are required and that also has lower manufacturing costs than traditional systems. Summary of the invention

The aforesaid objects are achieved by means of the present invention defined in the independent claim 1. Suitable embodiments of the invention are made apparent in the dependent claims.

Accordingly, there is defined a mast construction according to the present invention that comprises at least three tubular legs which are fastened releasably to a base disposed at ground level by means of fastening devices, wherein the invention is characterized in that the legs are comprised of a plurality of tubular sections, wherein the number of tubular sections of respective legs is chosen according to the intended height of the mast; in that the mast construction includes a variable number of bracing units; in that the legs are mutually joined with the aid of said bracing units; in that the bracing units are placed at an appropriate distance apart with respect to height and in accordance with the desired height of the mast; in that the mast construction includes a wire that is connected to the uppermost bracing unit or to the lowermost bracing unit respectively; and in that the wire is located in the space between the mast legs.

Because of its simplicity, the inventive mast construction has the benefit of being able to be assembled readily on site and then raised manually to its upright position. Because the mast structure can be raised and collapsed there is no reason for the mast to be equipped with climbing facilities, meaning that the mast need not satisfy climbing safety requirements, therewith affording economical benefits from the aspect of material among other things. Placement of the wire between the legs of the mast obviates the need for external bracing lines and the mast construction will therewith require less space on the ground plane and will have a less detrimental effect on the surroundings.

According to one beneficial embodiment of the invention, the wire may be tension able. When the wire is stretched, tensions are beneficially obtained in the construction therewith rendering mast construction resistant to stresses in all directions which, in combination with the cohering effect of the bracing units and therewith the stabilizing ability achieved, enables the mast construction to be held compact and also to be adapted to the weight or load to be carried, for instance weight in the form of antennas for mobile and radial networks. The wire is conveniently fastened at least to either the uppermost bracing unit or to the lowermost bracing unit with the aid of at least one bottlescrew with which the wire can be tensioned. The tension in the wire is preferably held constant with the aid of a spring element.

The tubular sections forming the mast legs may conveniently be joined together with the aid of splicing elements. This enables the height of the mast construction to be readily adjusted, by first lowering the mast and then lengthening the mast legs by joining together a desired number of tubular sections to form the mast legs, with the aid of said splicing elements. The mast may, of course, also be shortened in this way, by first lowering the mast and then removing the appropriate number of tubular sections from the mast legs accordingly.

The splicing elements are conveniently glued to respective tubular sections. This enables the mast construction to be assembled quickly and simply and its height adjusted on site. Alternatively, in order to enable the mast to be moved relatively often, for instance for military purposes, the tubular sections are not glued and the construction is held together solely by the wire.

The bracing units of the inventive mast construction may have different designs. For example, the mast construction may have at least one bracing unit in the form of a first variant, comprising outer bracing elements that extend from one leg to an adjacent leg. These outer bracing elements need not necessarily sit together, but shall, nevertheless, be seen as a unit by virtue of their function. The mast structure is held compact and rigid in this way. Alternatively, the mast construction may include at least one bracing unit designed in accordance with a second variant that includes inner bracing elements that extend from respective legs in towards the centre of the mast, where they are connected together. According to another alternative, the mast construction may include at least one bracing unit that consists in a combination of inner and outer bracing elements, which constitutes a third variant. It will be understood that one and the same mast construction may include bracing units that represent more than one of the aforesaid variants. The legs and bracing elements of the mast construction may beneficially comprise high alloy steel that can be fully recycled. This results in a light, strong and maintenance free mast construction with which no surface treatment is required and with which the accompanying negative influence of the environment has been eliminated, which is also beneficial economically. Moreover, the tubular members have a very smooth and glossy surface which conveniently reduces the risk of icing as distinct from the case when galvanized pipes are used.

According to further attributes, the invention is characterized in that the fastener devices of at least one leg are pivotal so as to enable the mast to be lowered and raised respectively without needing to loosen said at least one leg from its fastening device. The benefit afforded by this embodiment is that the fastening device will have the form of a pivot shaft that enables the mast construction to be raised and lowered around said shaft.

Brief description of the drawings

The invention will now be described in more detail with reference to exemplifying embodiments thereof and also with reference to the accompanying drawings, in which

Figure 1 is a perspective view of one embodiment of the mast construction according to the present invention; Figure 2 is a perspective view of part of a first variant of a bracing unit that includes outer bracing elements according to the present invention;

Figure 3 is a perspective view of part of a second variant of a bracing unit having inner bracing elements in accordance with the present invention;

Figure 4 is a perspective view of part of a third variant of a bracing unit that includes outer and inner bracing elements in accordance with the present invention;

Figure 5 is a perspective view of the uppermost bracing unit of the mast construction according to said embodiment; and

Figure 6 is a diagrammatic side view of the wire fastened to a bottlescrew. Detailed description of the invention

Figures 1-6 illustrate and exemplifying embodiment of the present invention applied to a mast construction intended for mobile telephone and/or radio networks. It will be emphasized immediately that the invention is no way restricted to this type of mast construction, but can be applied to any type of mast construction whatsoever.

Figure 1 is a perspective view of the mast construction 1 according to one embodiment thereof. In the case of the illustrated embodiment, each of the mast legs is comprised of five tubular sections 3,4,5,6,7 which are joined together with the aid of splicing elements. Each leg is ref fastened releasably at its bottom to a base 2 disposed at ground level, with the aid of a pivotal attachment 17,18,19, and is connected to the other legs through the medium of six bracing units 8,9,10,11 ,12,13. In order to provide a stable mast construction, a wire 16 is tensioned between an uppermost bracing unit and a lowermost bracing unit 8. The wire 16 is fastened in the lowermost bracing unit 8 with the aid of a bottlescrew 15 with which the wire 16 can be tensioned to the extent desired said tension in the wire 16 being held constant within reasonable limit with the aid of a mechanical spring pack 15. The wire 16 is placed in the centre of the mast, between the mast legs.

Figure 2 is an illustration of a bracing unit according to a first variant that comprises outer bracing elements 25,26,27. The outer bracing elements 25,26,27 extend from one leg to an adjacent leg. The outer bracing elements 25,26,27 of this bracing unit need not necessarily sit together but shall only be seen as a unit with regard to their function. For example, the bracing units may be connected to the legs via splicing elements.

Figure 3 illustrates a second variant of a bracing unit according to said example, wherewith the lower bracing unit comprises inner bracing elements 28,29,30. The inner bracing elements 28,29,30 extend from respective legs in towards the centre of the mast where they are joined together, for instance with the aid of splicing elements.

Figure 4 is a perspective view of part of a third variant of a bracing unit comprising a combination of outer bracing elements 25,26,27 and inner bracing elements 28,29,30. The outer bracing elements 25,26,27 extend from one leg to an adjacent leg and the inner bracing elements 28,29,30 extend from respective legs in towards the centre of the mast, where they are joined together. The outer bracing elements 25,26,27 in this bracing unit need not necessarily be seated together but shall only be seen as a unit by virtue of their function. For example the bracing units may be connected to the legs via splicing elements.

As will be evident from the mast construction according to the embodiment shown in figure 1 , one and the same mast may include bracing units of mutually different design. The illustrated mast includes a combination of bracing units in the form of variant 2 and variant 3 respectively. In addition, an uppermost bracing unit 13 has its own particular design in the form of a plate.

Figure 5 is a top view of the upper most bracing unit 13 of the mast construction according to the embodiment of figure 1 in the form of a plate. Located in the centre of the bracing unit is a hole 20 through which the wire 16 is intended to run to be fastened. The corners of the bracing unit respectively include recesses 21 ,22,23 for fastening of the mast legs. The upper most bracing unit thus has a design that differs from other bracing units. This is primarily because the need to be able to fasten the wire and to support the legs.

Figure 6 illustrates an embodiment of the wire 16 and the bottlescrew. The wire 16 is fastened to the bottlescrew with the aid of a wirelock 14. It will be understood that the use of other devices for fastening and tensioning the wire are conceivable.

Claims

1. A mast construction comprising at least three tubular legs which are releasably fastened to a base disposed at ground level by means of fastening devices, characterized

- in that the legs are comprised of a number of tubular sections, said number being chosen in accordance with the desired height of the mast construction;

- in that the mast construction includes a various number of bracing units;

- in that the legs are connected together with the aid of said bracing units, wherein said bracing units are placed at a suitable distance apart with respect to height and also with respect to the height of the mast; and

- in that the mast construction includes a wire which is connected to the uppermost bracing unit and the lowermost bracing unit respectively and is located in the space between the legs of the mast.

2. A mast construction according to claim 1 , characterized in that the wire can be tensioned.

3. A mast construction according to claim 2, characterized in that the wire is fastened at least to either of the uppermost bracing unit and the lowermost bracing unit with the aid of at least one bottlescrew and can be tensioned with the aid of said screw.

4. A mast construction according to any of the preceding claims, characterized by a spring element that functions to maintain the tension in the wire constant.

5. A mast construction according to any of the preceding claims, characterized in that the tubular sections forming the mast legs are joined together with the aid of splicing elements

6. A mast construction according to claim 5, characterized in that the splicing elements are glued to the tubular sections.

7. A mast construction according to any of the preceding claims, characterized in that at least one bracing unit has outer bracing elements that extend from one leg to an adjacent leg.

8. A mast construction according to any of the preceding claims, characterized in that at least one bracing unit has inner bracing elements that extend from respective legs in towards the centre of the mast where they are connected together.

9. A mast construction according to any of the preceding claims, characterized in that the legs of the mast construction and its bracing elements are made of recyclable high alloy steel.

10. A mast construction according to any of the preceding claims, characterized in that the fastener device of at least one leg is pivotal so as to enable the mast to be lowered and raised respectively without loosening at least said one leg.