MAST STRUCTURE AND METHOD FOR PRODUCING THE STRUCTURE

Abstract: The invention relates to a mast structure for wireless appliance such as the base station of a mobile phone network. The structure comprises a tubular mast body (1) and at least one fixing spreader frame (22) for support wires (14). The fixing frame forms a structure encircling the tubular body (1) and comprises at least three support wire fix points (23, 24, 25) spaced appart from the tubular body (1) and from each other and e.g. five support wires (14) per frame (22) anchored to the ground for supporting the tubular body (1) via the fixing spreader frame. The structure further comprises means (26, 27) for fastening the fixing spreader frame (22) to the tubular body (1). The invention also concerns a method in relation to a mast structure.

Description: Mast structure and method for producig the structure The present invention relates to a mast structure according to the introductory portion of claim 1 for use as a base station mast for a wireless appliance such as a mobile phone network. The invention also relates to a method relating to a mast structure. The base stations for mobile phones, links or the like wireless appliances commonly use as masts so called lattice structures or lattice masts which provide a sufficiently sturdy mast structure for placing the wireless appliance at a desired altitude without the risk that the mast will fall or break. The height of a mast may generally be over a hundred meters and, accordingly, the strength requirements for the mast body are high. The masts for wireless appliances have therefore been based on solutions wherein the body portion of the mast structure consists of a diagonally supported open lattice structure. The body portion generally has a square or triangular cross section. The diagonals are attached, e.g. fixed by welding or bolting to side beams which extend in the vertical direction and which are set in a square or triangular form and the diagonals extend between the side beams tilted e.g. at an angle of 30° to 60°. The body portion may be supported by suitably positioned supporting wires or chord wires. Even though a sturdy and a sufficiently high mast can be provided by a mast based on diagonals, the solution does have some weaknesses and some deficiencies. Constructing a lattice structure is laborious since it requires the prefabrication of several different parts and the attaching of these to each other by welding, bolting and riveting. This makes the production expensive. The profile of a construction provided by diagonals is relatively broad as viewed from all directions, which makes the construction sensitive to winds. The high and broad structure provided by such diagonals is also clearly discernible in the terrain and especially the increased amount of mobile phone networks has made these negative effects on the landscape more easily recognizable. In addition to being sensitive to winds, the lattice structures have a problem in that they collect snow and ice in the winter. When the ice and hardened snow falls off, it poses a risk for persons underneath. Such falling hard blocks may also break equipment on the mast. Moreover, debris transported by the wind has a tendency to attach to the lattices. Unauthorized climbing in the prior art lattice masts is also common and this causes both a security risk and a risk that the devices mounted on the mast are damaged and/or disappear. The necessary cables and the like remain freely visible, i.e. without any proper protection against snow, ice and sunshine or external shocks. In case protection is provided by special solutions this further increases the complexity and expense of the prior art mast structures. A disadvantage with the prior known mast structures has also been that persons such as installers or service or supervising personnel has been forced to climb up in the mast along ladders provided in connection therewith. The person has not either had access to any handy auxiliary means e.g. for hoisting/lowering of tools and equipment. Instead, he has been forced either to carry the tools in his hands or pockets or in a separate rucksack or bag or the like or make use of various winches, cranes or the like solutions. There is always a job safety risk involved in climbing on ladders, especially in windy, rainy and/or icy surroundings. The object of the present invention is to remedy the defects of the prior art and to provide a totally new kind of mast solution for wireless appliances, such as mobile phone base station equipment. An object of the invention is to provide a solution which offers a mast structure which is narrower than the prior known ones, thus reducing i.a. the sensitivity of the mast to winds. An object is also the provision of a structure which does not collect the same amount of snow, ice and/or debris as the known solutions. An object of the invention is to provide a mast solution which protects cables and the like mounted in connection therewith. An object of the invention is to provide a solution which offers an installer going up the mast a proper working platform and which increases the working comfort and safety of the installer. An object is also to provide a solution which makes it possible to avoid carrying equipment up by hand or with a person climbing a ladder and/or which avoids the use of separate hoisting means. The present invention is based on a basic principle according to which the body portion of a wireless appliance mast is provided of a tubular and substantially slender structure and the body portion is supported in relation to the ground or the like anchoring place in a way which is novel and which differs essentially from the prior art and, thus, a solution is obtained which achieves the objects of the invention. In accordance with an additional embodiment, a lifting platform adapted for movement in connection with the body portion is provided for avoiding the use of ladders etc. More precisely, the structure according to the invention is mainly characterized in that which is presented in the appended claims 1 to 9 and especially in the characterizing portion of claim 1. The characteristic features of the method according to the invention are disclosed in claim 10. The invention provides significant advantages since it enables avoiding the defects of the prior known mast structures. The structure is more simple than those of the prior rt and thus it is also easier and cheaper to produce and erect while still providing a corresponding height, rigidity and load carrying ability. The structure is substantially less sensitive to winds than the prior known solutions. Its tendency to collect snow, ice and debris is also smaller. The cables of the wireless appliance are well supported and protected in the mast structure according to the invention. The cable installation or "drawing" is easy and simple to perform. The mounting rack or lifting platform according to a further embodiment provides a stable and reliable mounting platform for the installers, whose safety can further be increased with safety bars. The rack also avoids the need for a manual hoisting and lowering of accessories. Since the structure lacks fixed ladders and does not enable climbing, the risk for unauthorized climbers and intruders is minimized. The present invention and its other objects and advantages are exemplified in the following by referring to the appended drawing, wherein the numbering in the various Figures refer to corresponding features. Fig. 1 shows a simplified schematic side view of an embodiment according to the invention. Fig. 2 shows the section A- A of Fig. 1. Fig. 3 shows the principle of the fixing spreader frame of the invention. Fig. 4 shows the interior of the tubular mast body according to the invention in a partially dissected schematic drawing. Fig. 5 shows a cross section of the tubular body of Fig. 4. Fig. 6 shows an additional embodiment of the invention seen from above. Fig. 7 shows the embodiment of Fig. 6 from the side. Fig. 1 is a side view of the mast structure 10 of the present invention for carrying a base station 12. The mast 10 comprises a tubular body 1 which may be produced, for instance, of stainless or acid resistant steel or of some other steel material which is protected against corrosion, such as galvanized or otherwise treated steel tubing. The mast structure 10 may be more than a hundred meters high, the height of the depicted mast being 112 m. The structure and the interior of the tubular body 1 is described in greater detail in connection with Figures 4 and 5. In connection with the exemplified tubular body 1 there are provided three special support or chord wire 14 fixing means 20. A separate fixing means 20 is shown in Fig. 3. The fixing means 20 is composed of a triangular fixing spreader frame 22 (see also Figures 2 and 3) surrounding the tubular body 1 with fastening wires 26, 27 extending upwards (26) and downwards (27) from the corners 23, 24 and 25 of the frame 22. The length of one side of the triangle of the exemplified frame 22 is about 5.2 m, whereby the distance from each corner 23 , 24 and 25 of the frame 22 to the center line of the tube 1 is of the order of 3 m. It should be noted that the spreader frame 22 may have another form such as square or circular. It is essential only that the frame 22 extends as a continuous element around the tubular body 1 so that the chord wires 14, which are to be anchored to the ground or the like base, can be attached to the frame 22 of the fixing means 20 instead of being attached directly to the tubular body 1. A total of six wires 26 and 27 extend upwards and downwards from the corners 23-25 of the frame 22, said wires being fastened to the tubular body at points 29 and 28, respectively. The distance between the frame and the fastening points of the wires may be, for instance, 10 meters both upwards and downwards. The wires may be fastened to the tubular body in a manner known per se such as to a band encircling and attached to the tube or to brackets welded to the tube, wire tighteners or locks being suitably used. Between two fixing spreader frames 22 the downwards extending fastening means i.e. the wires 27 of the upper frame and the upwards extending fastening means i.e. the wires 26 of the lower frame are preferably fastened in an interlaced manner so that the fastening point 28 of the upper fram fastening means is at a lower level on the tubular body 1 than the fastening point 29 of the lower frame fastening means. The frame 22 and the fastening wires form an fixing means 20 which provides a cross-framing structure enabling a substantially uniform spreading of the supporting effect of the chord wires 14 along the whole length of the tubular body 1 while at the same time minimizing the number of wires 14 extending all the way to the ground. Fig. 2 illustrates the positioning of the chord wires 14 extending to the ground from the corners 23-25 of the frame 22. Two wires 14 are drawn down from the corner 23 while there is only one wire 14 extending to the ground from each of the other two corners 24 and 25. This arrangement provides a maximally good support while minimizing the number of chords. Moreover, the side 29 of the mast remains more "free" than the other two sides, which is a feature that can be utilized in the way shown in Figures 6 and 7. Figures 4 and 5 show the cables 6 of a radio appliance 12 drawn through the interior of the tubular body 1. In this solution the cables 6 are well protected both against mechanical damage and against weather circumstances and sunshine. Prior to being pulled in, the cables are bound with respect to each other with special binding or supporting dogs 3, which can be applied, for instance, at 1 meter intervals. The binding dogs 3 are in turn attached from their center piece 4 to a special carrying wire 2, which extends in the middle of the tube 1 and which is used for pulling the cable bundle into the tube. The binding dogs 3 may, for instance, be made of plastic. Their structure may be such that they are slightly compressed or bent inwards when they are pulled into the tube 1 , whereby they will press slightly against the walls of the tube 1 in their final position, thus ensuring that the cables 6 remain in place and also restraining any downward movement of the cables. Fig. 5 also shows an additional wire 7 which is intended to be used at a later time for pulling up any additional cables. The wire 7 is not bound to the binding dog 3. There may be more than one additional wire. Fig. 6 shows from above the equipment rail 31 as well as a mounting platform 30 mounted in connection with the mast structure 1 on one side 29 thereof. The platform structure 30 can be hoisted and lowered in relation to the mast structure. This has been achieved by providing the platform structure 30 with wheel means 32 resting against the tubular body 1. The wheel means are adapted for allowing movement of the platform structure as well as for holding and supporting the platform in connection with the tubular body. The wheels may be replaced e.g. by suitable slide rail means or the like solution which enables a simultaneous support and movement between platform 30 and tubular body 1. At least one of the wheel means 22 can preferably be placed in two different operative positions so that it is possible to place the platform structure 30 into connection with the tubular body 1 and to remove it from such connection. This can, for instance, be performed by making one or both of the support bars 34 of the wheel 22 removable or turnable. This makes it possible to remove the platform 30 when it is not needed and thus prevent unauthorized climbing in the mast 10. Moreover, the same platform may be used in connection with different masts, which provides a significant saving in costs. As described above, the platform structure 30 is moved up or down along the tubular body 1 while being supported by the tubular body. The driving force required for the moving may be obtained, for instance, with the aid of a lift wire 36 attached to the platform structure. The lift wire 36 may be threaded into the tubular body 1 as shown in Figures 6 and 7. The upper end if the mast is provided with a pulley drum 37. The mast 10 is further provided e.g. with an electrically powered winch device 38, which winds or releases wire 36 on a reel 39 when the platform 30 is to be hoisted or lowered. According to an alternative embodiment the wire 36 forms an endless loop. One half of the loop link is in place while at the same time the upper and lower ends of the mast is provided with pulley drums 37 enabling rotation of the loop. The platform 30 is attached with a suitable lock or the like fastener to the loop which is rotated with a suitable winch or the like device for moving the wire. The winch device 38 is preferably mounted at the lower part of the mast structure while the wire circulates around the pulley drum 37 mounted in the upper part of the mast and back downwards to the platform structure 30. The winch device may naturally also be located at some other position in the mast structure or even at the platform structure 30. The winch device may also be manually operated or the structure can be provided with an auxiliary manual drive for the case that the winch device 38 breaks down. It should be noted that the platform 30 can be moved also by other means than by being pulled by a wire, such as by arranging a suitable wheel driving mechanism between one wheel means and the tubular body, whereafter the wheel 22 can be rotated with a suitable driving means. The drive may be based on friction, an interconnecting tooth combination or the like. Fig. 6 provides a good illustration of how the platform 30 can move in relation to the tubular body 1, and especially how its movement past the fixing means 20 has been arranged. According to an advantageous alternative, an equipment rail 31 extending from top to bottom of the mast or brackets placed at suitable intervals are attached to the tubular body 1. The fastening wires 26' and 26" extending from the fixing spreader frame 22 are fastened to the rail or to the brackets at a fastening point 29' instead of being fastened directly to the tubular body 1. The platform structure 30 is moreover dimensioned so that it can move on the "free" side of the tubular body. In the exemplified case the platform has a size of 0.6 x 1.2 meters, and it fits into the space inside the bars 22' forming the frame 22 and also inside the fastening wires 26" . The mast structure may also be provided with a safety rail operation (not shown). In this embodiment the mast comprises a grooved rail or T-formed rail to which a person residing on the platform may attach a matching counterpiece provided with a brake. The counter- piece is adapted for movement in the groove or rail in such a way that it cannot become detached therefrom. A rope or wire of the counterpiece is also attached e.g. to a belt or safety jacket of the person. It is preferred to integrate such a rail with the equipment rail 31. Thus, the invention provides a mast structure for wireless appliances which is based on a novel way of thinking and which provides several significant improvements compared to the prior art. It should be noted that the above described examples of embodiments of the invention are not intended to limit the scope of the invention to the specific shown forms but that, on the contrary, the invention is intended to cover all variations, corresponding solutions and alternatives which are included within the spirit and scope of the invention, as defined in the appended claims.

Claims: Claims 1. A mast structure for a wireless appliance such as the base station of a mobile phone network, said structure comprising: a tubular mast body (1) made of a tubular material, at least one fixing structure provided with at least three support wire (14) fix points (23, 24, 25) spaced apart from said mbular body (1) and from each other, fastening means (26, 27; 26', 26") for fastening said fixing structure to said tubular body (1), said fastening means extending both upwards (26, 26', 26") from said fixing structure and downwards (27) from said fixing structure in such a way that said fastening means become fastened to said tubular body (1) or to a protrusion (31) attached thereto both above and below said fixing structure at a point (29, 28; 29') which is at a distance from the position altitude of said fixing structure, characterized in that each fixing structure comprises a fixing spreader frame (22) for said support wires (14), said frame providing a structure encircling said mbular body (1) at a distance therefrom, and in that said mast structure further comprises for any one fixing spreader frame (22), at least five support wires (14) anchored to the ground or the like for supporting said tubular body (1) via said fixing spreader frame (22), the arrangement being such that three of said at least five support wires are attached substantially to the same fix point (23) in said fixing spreader frame (22) and the two other wires are attached to the other fix points (24, 25) of said fixing spreader frame (22). 2. A mast structure according to claim 1, characterized in that between two fixing spreader frames (22) the downwards extending fastening means (27) of the upper fixing spreader frame and the upwards extending fastening means (26; 26', 26") of the lower fixing spreader frame are interlaced so that the fastening point (28) of the fastening means of the upper frame in relation to said tubular body is at a lower level than the fastening point (29; 29') of the fastening means of the lower fixing spreader frame in relation to said tubular body. 3. A mast structure according to claim 1 or 2, characterized in that said fastening means (26, 27; 26', 26") are composed of wires. 4. A mast structure according any one of the preceding claims, characterized in that the cables (6) of said wireless appliance (12) are adapted to extend within said tubular body (1) and that said mast structure further comprises at least one cable support dog (3) mounted within said tubular body for supporting said cables (6), and a support wire (2) for pulling in and supporting said cables (6). 5. A mast structure according to claim 4, characterized in that it comprises an additional wire (7) located within said tubular body (1) for any subsequent cable pulling operation. 6. A mast structure according to any one of the preceding claims characterized in that it additionally comprises a platform structure (30) which can be hoisted and lowered in relation to said mast structure (10) on one side (29) of said mast structure. 7. A mast structure according to claim 6, characterized in that said platform structure (30) comprises wheel means (32) or slide rail means supported against said mbular body (1), said means being adapted for allowing both moving and holding/supporting of said platform structure (30) in connection with said tubular body (1). 8. A mast structure according to claim 7, characterized in that at least one of said wheel means (22) can be placed in two different operational positions so that said platform structure (30) can be brought into and out of connection with said tubular body (1). 9. A mast structure according to any one of the preceding claims, characterized in that it further comprises an equipment rail (31) or other protrusion fastened to one side of said tubular body (1) for displacing said fastening point of said fastening means (26'. 26") of said fixing spreader frame laterally from said mbular body. 10. A method relating to a mast structure (10) for a wireless appliance (12) such as the base station of a mobile phone network, said structure being provided by a tubular body (1) extending from a mounting ground and support wires (14) and fixing means (20) supporting said body and said structure comprising a platform structure (30) for working in said mast structure, said method comprising moving said platform structure (30) up and down along the outer surface of said tubular body (1) and supported by said tubular body.

Inventors: POHJALAINEN AULIS, POHJALAINEN, AULIS
Applicants: EOLE OY, POHJALAINEN AULIS, POHJALAINEN, AULIS
Application year: 1999
Main classification: E04H12
IPC codes: E04H12