ANTENNA TOWER IN THE FORM OF A TREE

Abstract: An antenna tower, generally indicated at 10, includes a trunk (11), branches (12) and antennae (13, 14). The branches (12) are made of metal and diverge from antennae mounting position to leave clear arcs of approximately 120 DEG C. The antennae mountings are vertical offset allowing 360 DEG cover.

Description: ANTENNA TOWER IN THE FORM OF A TREE This invention relates to support structures for antennae and in particular, but not exclusively, such structures for use in mobile telephone communication systems . With the explosion of mobile telephone usage and the increase in the number of operators, the need to provide local antennae support structures has correspondingly grown. These towers support a plurality of antenna to provide 360° coverage between the mast and users in the local area and also support microwave dish antennae for communicating with the network as a whole. The antennae are normally located in visually very prominent positions, because of the need to try to achieve direct line of sight between the user and an antenna. Unfortunately the towers and antennae are in most people's eyes, extremely ugly and, particularly in sensitive rural areas, planning authorities are becoming increasingly concerned about the appearance of such structures . There have been a number of proposals to disguise antenna struc- cures such as masts and towers. In urban settings they have been represented as telephone boxes and lamp posts, whilst in rural settings artificial trees have been used. In one current tree disguise there is a steel trunk which carries a frame work extending around and coaxial with εhe trunk for supporting the antennae. In order to disguise this fairly substantial construction, plastic branches and leaves are mounted on the trunk TO extend around the frame work and antennae and as far as possible hide them from sight. These plastic branches are expensive to fabricate and it is quite difficult to manufacture a tree which is at all convincing when there has to be a high density of foliage around the cylinder of space occupied by the framework and antenna. Often, this means that a great deal of other foliage has to be carried at other levels by the tree in order to make a realistic looking shape. There are also significant restrictions on the size of canopy that can be achieved. SUMMARY OF INVENTION From one aspect the present invention consists in a support structure for antennae in the form of a tree having a trunk, branches and means for mounting an antenna characterised in that the means for mounting the antenna are disposed on the trunk and in that the adjacent branches diverge outwardly from the means for mounting to leave a clear arc of sight . Particularly conveniently there are three means for mounting spaced around the trunk and these may be vertically o fset . With this arrangement it is possible to provide 120° coverage with each antenna without a bare ring around the crunk at antennae level and the antennae can be mounted close to the trunk and painted or otherwise decorated tc blend in with the trunk. It will thus be appreciated that the amount of foliage required is greatly reduced. The mam portions of the branches may now be made of metal, because they no longer extend across the line of sight of the antennae and so will not have any detrimental effect on the signals being received or transmitted by the antennae. This can both increase strength and significantly reduce cost . In particular it can reduce the wind loading on the structure and hence allow for reduced trunk diameter. Conveniently these main portions of the branch may be made of sections of metal tubing, each succeeding section, as the branch extends from the trunk, being of a smaller diameter than its immediately preceding section. In this case, the outward end of at least some sections may be curved inwardly to provide a transition between the diameters. From a distance this arrangement provides an authentic looking tapering branch, without tne necessity for complex forming of tubing. The branches may include leaf portions comprising leaves and twigs and these may be formed from wires twisted on to or to form a central core with their free ends diverging progressively, layer by layer towards the tip so as to provide the constant bifurcation seen m nature. These portions may be coated m sibriolated propopylene (MI ON) to enhance strength and appearance and then dipped m chlorinated rubber paint . The trunk may be formed by a metal tune, which preferably tapers, and the brancnes may extend tr.rough the trun to be fixed to the other side either cirectly or via sockets . The structure may further comprise dish antennae mounting means locatable at the top of the trunk and comprising at least a pair of divergent upwardly extended branches, each defining vertical portion to provide a dish antenna mounting. Preferably the mounting dish antenna means may be locatable at at least a range of rotational orientations relative to the trunk to allow for a variety of combinations of line of shoot, for the microwave antennae, and branch location. The trunk may define a cable housing and access doors may be provided m the trunk. The trunk may also define or carry step locations up at least part of its length. In certain cases the stress locations may be removable. The tower may further comprise dual polarised antennae mounted on the trunk by respective mounting means and these may be painted or otherwise decorated to blend m with the trunk. It is particularly preferred that tnese antennae are formed as set out m our co-pendmg European Patent Application No. 95303611.8. The tower may further comprise respective dish antenna, which may be mounted on the disπ antenna mountings mentioned above. From a further aspect the invention consists m a support structure for antennae m the form of tree having a trunk and branches characterised m that tne tower further comprises dish antenna mounting means locatable on the top of tne trunk and comprising at least a pair of diverging upwardly extending branches each defining a vertical portion to provide a dish antenna mounting. When the trunk is hollow, the dish antenna mounting means may include a stub portion for insertion m or around the upper end of the trunk. This or other location arrangements preferably allow a variety of rotational orientations of the mounting means relative to the trunk to be achieved. Although the invention has been defined above, it is to be understood it includes any inventive combination of the features set out above or m the following description. The invention may be formed m various ways and a specific embodiment will now be described, by way of example, with reference to the accompanying drawings, m which: Figure 1 is a plan view of a tower for antennae ; Figure 2 is an elevation on the arrow A m figure 1; and Figure 3 is an elevation on the arrow B. A support structure m the form of an antennae tower, generally indicated at 10, includes a trunk 11, branches 12 and antennae 13 and 14. The trunk 11 comprises a stack of tapering sections 15- IS, each of which are m the form of hollow steel tube. The Dotto section 15 has an annular flange 19 through which oolts (not shown) can be fixed into a concrete foundation 20 The trunk sections would normally be sleeved onto or slipped onto each other but they may be welded together o erection, or connected by any suitable attachment mechanisrr may t>e used. The trunk sections may be painted or otherwise coated to be provided with a bark-like appearance either oefore or after erection. After erection the application of which occurs between trunk sections. The paint may be Micaceous Iron Oxide (MIO) and may be applied by hand. The bottom section 15 has an access door 21 to allow cables to be inspected and a cable insertion door 22. A corresponding door is provided at 23 in section 17 to provide a feed line exit. Sections 15 and 16 and 17 may be provided with locations 24 for steps to enable the trunk to be climbed. A permanent or replaceable climbing ladder section may be provided on 18. The branches 12, which are shown on sections 16 and 17, simply have the function of making the tree life like and it would be seen that some of these branches may be in the form of cut off or broken branches as are often seen on the lower trunk portions of pines. In contrast the branches at the top of the trunk 11 are formed and located in a way which reflects the purpose of the tower 10. However, m all cases the branches are fabricated m accordance with the same principle. Thus the main branch portions 25 consist of successive tubes 26 of decreasing diameter the further the tubes are away from the trunk 11. Each tube is made of steel or other suitable metal . Some of the tubes 26 have side tubes or branches 27 to increase the branch like structure. From these side tubes 27 and the end of the final main tube 26, project twigs and leaf portions 28. These portions 28 may be formed m any suitable fashion and will depend on the type of tree which is being imitated. However, for example, for a Scots pine, the twigs may be formed by winding layers of metal wires around a central core, or together to form a central core, and then progressively diverging the free ends of those wires so that the portion 28 gets thinner towards its end and the diverged wires form small twigs for carrying artificial pine needles. The wire structure may be coated with εibriolated propopyl- ene (MILON) to enhance strength and appearance and then dipped m chlorinated rubber paint. The branches 26 and sub-branches 27 can be rotated to vary the appearance of the structure to suite particular circumstances. The mam portions 26, which actually contacts the trunk, may be supported by sockets 29, with or without associated flanges or simply by flanges. Additionally or alternatively, they may extend through the trunk (forming a small stub on the other side) and be welded to that other side to give good structural strength and location. The remainder of the branch 25 may be removable from the ma portion 26 for repair and maintenance. Section 18 carries three suitable antenna mounting means 13a, which may be brackets, bolt holes or the like, depending on the nature of the antenna to be mounted. These are preferably spaced at 120° and vertically offset by at least a small amount to enable the arcs to be present without a bare section appearing around the trunk. Branches 12 extend out radially between the mounting positions 13a so that they more or less bisect tne arc between those positions. In this way it is possible to achieve an effective 360° line of sight for the combination of antennae 13 mounted on the mounting means without interference arising from the fact that the branches 12 are made of metal . The antenna 13 are m the form of elongate rectangles and can be decorated to blend in with the trunk. Only three antennae are needed, because dual polarisation antennae are utilised. If more antennae were required, greater vertical offset may be needed to achieve the same result . As has been explained above these antennae 13 receive and transmit the signals to and from the mobile phones. Further dish microwave antenna 14 are required to communicate with the network as a whole . These tend to have to be mounted on vertical tubes and can be particulary difficult to disguise effectively. The applicants have cleverly disguised the necessary vertical tubes 30 as part of a bifurcated branch structure 31, which has a dependent stub (not shown) that is sleeved inside the open end of trunk section 18. This arrangement lifts the dish antennae above the metallic sections of other branches 12, whilst enhancing the tree like appearance of the tower 10.

Claims: CLAIMS 1. A support structure for antennae in the form of a tree having a trunk, branches and means for mounting antenna characterised in that the means for mounting the antenna are disposed on the trunk and in that the adjacent branches diverge outwardly from the means for mounting to leave a clear arc of sight. 2. A structure as claimed in claim 1 comprising three means for mounting spaced around the trunk. 3. A structure as claimed in claim 1 or claim 2 wherein the means for mounting are vertical offset. 4. A structure as claimed in any one of the preceding claims wherein at least the main portion of the branches are metal . 5. A structure as claimed in any one of the preceding claims wherein the main portions of the branches are made of sections of metal tubing, each succeeding section, as the branch extends from the trunk, being of a smaller diameter than its immediately preceding section. 6. A structure as claimed in claim 5 wherein the outward end of at least some sections are curved inwardly to provide a transition between diameters. 7. A structure as claimed in any one of the preceding claims wherein the branches include leaf portions comprising imitation leaves and twigs. 8. A structure as claimed in any one of the preceding claims wherein the trunk is formed by a metal tube or tubes and wherein the branches extend through the trunk are fixed to the other side. 9. A structure as claimed in claim 8 wherein the thick end of the branch extends through the other side of the trunk and is welded or otherwise fixed thereto. 10. A structure as claimed in any one of the preceding claims further comprising dish antennae mounting means locatable on the top of the trunk and comprising at least a pair of divergent upwardly extending branches each defining a vertical portion to provide a dish antenna mounting. 11. A structure as claimed in any one of the preceding claims wherein the trunk defines a cable housing and access doors are provided in the trunk. 12. A structure as claimed in claim 11 wherein the trunk defines or carry step ladder locations up at least part of its length. 13. A structure as claimed in any one of the preceding claims wherein the trunk is formed from tapering sections. 14. A structure as claimed in any one of the preceding claims further comprising three dual polarised antennae mounted on the trunk by respective mounting means. 15. A structure as claimed m claim 14 wherein the dual polarised antennae are painted to blend in with the trunk. 16. A structure as claimed in claim 14 or claim 15 further comprising respective dish antennae. 17. A structure as claimed in claim 16 as dependent on claim 10 wherein the dish antennae are mounted a respective dish antenna mountings. 18. A support structure for antennae m the form of a tree having a trunk and branches characterised that mast further comprises dish antennae mounting means locatable on the top of the trunk and comprising at least a pan of divergent upwardly extending branches each defining a vertical portion to provide a dish antenna mounting. 19. A support structure as claimed m claim 18 wherein the trunk is nollow and the dish antennae mounting means includes a stub portion for insertion m the upper end of the trunk.

Inventors: ALLCOCK GEORGE, ALLCOCK, GEORGE
Applicants: ALAN DICK & COMPANY LIMITED, ALLCOCK GEORGE, ALLCOCK, GEORGE
Application year: 1998
Main classification: H01Q1
IPC codes: H01Q1