GB2519663A

GB2519663A - Tower construction

Info

Publication number: GB2519663A
Application number: GB1417377.7A
Authority: GB
Inventors: Sean Prendergast; Steve Graham Williams; Andrew Michael Ibbotson; Jeff Pomeroy
Original assignee: Babcock Networks Ltd
Current assignee: Morrison Energy Services Transmission Networks Ltd
Priority date: 2013-10-04
Filing date: 2014-10-01
Publication date: 2015-04-29
Also published as: GB201317591D0; WO2015049520A1; GB201417377D0

Abstract

Apparatus to align modular sections during construction of a tower (e.g. electricity pylon) comprising first and second guide plate assemblies 310,320, arranged orthogonally to each other, each comprising respective first and second ramps 312,322, assemblies mountable on the upper leg 1A of a first tower section onto which the lower leg 2A of a second tower section may be lowered. The modular tower sections may be constructed on a ground based fixture away from the towers installation site (figure 1). The fixture may have adjustment means to accommodate four legs of a mast section during construction. Each section may be transported via helicopter to the site to avoid the need to build roads or crane platforms in inaccessible areas (e.g. farmland), where the ramps guide each lower leg to the desired location to be connected to corresponding upper leg via splice plates 314 and/or clamp plates 330. Also disclosed is a system comprising one guide assembly mounted on an upper leg, and a guide stop mounted on a corresponding lower leg (figures 16-18).

Description

TOWER CONSTRUCTION

[0001] This invention relates to the field of apparatus and methods for the construction of towers, in particular but not exclusively electrical transmission line towers which are used to support electricity transmission lines.

BACKGROUND

[0002] Transmission line towers support the electrical conductors which form the basis of an electricity transmission and distribution network. In the United Kingdom alone there are in the region of 50000 steel lattice overhead transmission line towers, 23000 of these forming the National Grid Transco (NGT) 275/400kv "supergrid", with the remainder forming a lower (132kv) distribution network.

[0003] Transmission line towers typically have four orthogonally spaced legs, each rigidly set into a foundation structure. Each leg typically has a generally [-shaped cross section, the L-shape being formed by two leg elements abutting, typically, at an angle of approximately 90 degrees. The two leg elements may be equal or unequal in length. Whilst the foundation design can vary from structure to structure, almost all towers connect to a foundation "stub" steelwork via a butt-joint connection which is held in place with bolted "splice plates".

[0004] The construction of new transmission line towers or replacement of existing towers with new towers is a costly and time-consuming process. Traditionally, the individual component parts of the tower are delivered to the site by lorry. A crane is provided on site which assembles the component parts together and installs them in place to form the tower. This process is repeated at each individual tower site.

[0005] In view of the extensive tower network, many tower sites are relatively inaccessible to vehicles and require access to privately-owned land. A specially-constructed stone road or the like is often required in order to provide vehicular access for the crane and delivery lorries. A specially-constructed platform needs to be built on-site to provide support for the crane, sometimes referred to as a "crane pad".

[0006] Instead of using a crane, it may be more cost-effective to part-assemble modules of the tower at a remote location and deliver the modules or other component parts to the site by helicopter. This obviates the need for the crane pad (and possibly the need for road access entirely). However, whether modules or components are assembled onto the tower by crane or by helicopter, difficulties arise in adequately and effectively aligning each module or component onto those which have already been installed.

[0007] A further difficulty arises in part-assembling modules of the tower in a remote location in that it can be problematic to assemble modules of the correct dimensions and within acceptable tolerances at a location remote from the actual installation site where immediate measurements and real-time adjustments could otherwise be made.

[0008] The invention described herein attempts to mitigate the problems of the prior art.

SUMMARY OF THE INVENTION

[0009] According to a first aspect of the invention there is provided apparatus for construction of a tower in which it is desired to align and assemble a second tower component with a first tower component by lowering the second component onto the first component from above, the first tower component having at least one upper leg having a substantially L-shaped cross section formed by two leg elements and the second tower component having at least one lower leg having a substantially [-shaped cross section formed by two leg elements, the apparatus comprising: a first guide plate assembly, mountable on an upper leg element of the first tower component, and having an upper portion comprising a first ramp leading to a desired end location for said lower leg of the second tower component; a second guide plate assembly, mountable another upper leg element of the first tower component, and having an upper portion comprising a second ramp leading to the desired end location for the lower leg of the second tower component; the first and second ramps being orthogonally arranged with respect to one another so that they are capable of guiding the lower leg of the second tower component to the desired location by limiting movement of the [-shaped lower leg in two orthogonal directions in an X-Y plane.

[0010] In another aspect of the invention there is provided apparatus for construction of a tower in which it is desired to align and assemble a second tower component with a first tower component by lowering the second component onto the first component from above, the first tower component having at least one upper leg having a substantially [-shaped cross section formed by two leg elements and the second tower component having at least one lower leg having a substantially [-shaped cross section formed by two leg elements, the apparatus comprising: a guide plate assembly, mountable on an upper leg element of the first tower component, and having an upper portion comprising a first ramp leading to a desired end location for said lower leg of the second tower component; a guide stop assembly, mountable on the lower leg of the second tower component, including a generally horizontal stop plate to limit downward movement of the lower leg of the second tower component when the stop plate abuts the upper leg of the first tower component, in use; the guide plate assembly and guide stop assembly together being capable of guiding the lower leg of the second tower component to the desired location by limiting movement of the L-shaped lower leg in two orthogonal directions.

[0011] The apparatus may include a further guide plate assembly, mountable on another upper leg element of the first tower component, and having an upper portion comprising a further ramp leading to the desired end location for the L-shaped lower leg of the second tower component.

[0012] In another aspect, there is provided apparatus comprising: a first tower element having at least one upper leg having a substantially L-shaped cross section formed by two leg elements; a second tower element having at least one lower leg having a substantially L-shaped cross section formed by two leg elements; apparatus as claimed in any of claims 1-3 mounted on at least two of said legs, the orientation of the guide plate assemblies relative to one another on adjacent legs being rotated through 90 degrees in order to further limit movement of the second tower component in the X-Y plane when the second tower component is lowered onto the first tower component from above.

[0013] In an embodiment, the first tower component has four of said upper legs and wherein apparatus as described above is mounted on all four of said upper legs.

[0014] In an embodiment, the first and second guide plate assemblies each include a lower portion which is removably fixable to an upper leg element of the first tower component, the lower portion being substantially parallel with the upper leg element to which it is fixed. Preferably, the apparatus further comprises a strengthening brace between the lower portion and the upper portion of the guide plate assembly.

[0015] In an embodiment, the leg elements forming the substantially [-shaped cross section of a leg are unequal in length.

[0016] Preferably, the guide plate assemblies are removably fixable to the upper legs of the first tower component using bolts.

[0017] Further preferably, the upper portion of the guide plate assembly includes a hole through which a rope or the like can be passed, in use, for manipulation by an operator or a tutor.

[0018] When in the desired end location, the lower leg of the second tower component preferably abuts the upper leg of the first tower component and the apparatus further comprises a clamp plate through which bolts can attach the lower leg and upper leg together. Alternatively, when in the desired end location, the lower leg of the second tower component overlaps with the upper leg of the first tower component, and the lower leg and upper leg can be attached together using bolts through the overlapping section.

[0019] The apparatus preferably further comprises one or more splice plates for attaching the lower leg and upper leg together. The splice plate may include a hole alignable with a hole in the guide plate assembly and through which a bolt can be received.

Preferably, the hole in the guide plate assembly is of a larger diameter than the hole in the splice plate sufficient to allow a splice plate bolt to pass entirely therethrough. The splice plate may be pivotable about a bolt therethrough in order to move it from an initial position to a final position in which it can be used to attach the lower leg and upper leg together.

[0020] In an embodiment, the apparatus further comprises a solenoid-operated shot bolt for attaching the lower leg and upper leg together.

[0021] The apparatus may also include at least one video camera in the vicinity of the guide plate assemblies for providing visual feedback to an operator.

[0022] In a further aspect of the invention there is provided a method of assembling a second tower component by lowering it onto a first tower component using apparatus as described in any of the preceding paragraphs, the first tower component having at least one upper leg having a substantially [-shaped cross section formed by two leg elements and the second tower component having at least one lower leg having a substantially L-shaped cross section formed by two leg elements, the method comprising the steps of: attaching said guide plate assemblies to the upper legs of the first tower component; optionally attaching clamp plates and splice plates to the upper legs of the first tower component, the splice plates being in their initial position; optionally attaching guide stop assemblies to the lower legs of the second tower component; lowering the second tower component towards the first tower component, until the lower legs of the second tower component approach the ramps of the guide assemblies; continuing to lower the second tower component as the lower legs thereof travel down the ramps of the guide assemblies to their desired end location; optionally pivoting at least one of said splice plates from its initial position to its final position; using bolts to fix the legs of the first and second tower components together; removing bolts holding the guide assemblies in place so that the guide plate assemblies can be removed.

[0023] Preferably, the second tower component is lowered towards the first tower component using a helicopter, crane or derrick.

[0024] In a further aspect there is provided a method of constructing a modular tower comprising the steps of: providing a ground-based fixture on which a tower module can be constructed, the fixture including a plurality of stubs fixed to support beams and spaced according to the desired tower module dimensions; constructing the tower module on the plurality of stubs; separating the constructed tower module from the fixture; transporting the tower module to an installation site remote from the fixture.

installing the tower module at the installation site.

Preferably, the tower module is transported by helicopter.

[0025] In an embodiment, a second tower module is constructed on the first tower module before separation from the fixture.

[0026] Preferably, the tower module is installed using apparatus as described in any of the preceding paragraphs. The installation step preferably comprises: attaching said guide plate assemblies to the upper legs of the first tower component; optionally attaching clamp plates and splice plates to the upper legs of the first tower component, the splice plates being in their initial position; optionally attaching guide stop assemblies to the lower legs of the second tower component; lowering the second tower component towards the first tower component, until the lower legs of the second tower component approach the ramps of the guide assemblies; continuing to lower the second tower component as the lower legs thereof travel down the ramps of the guide assemblies to their desired end location; optionally pivoting at least one of said splice plates from its initial position to its final position; using bolts to fix the legs of the first and second tower components together; removing bolts holding the guide assemblies in place so that the guide plate assemblies can be removed.

[0027] Further features are defined in the appended claims.

[0028] Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination.

Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Embodiments of the invention are described hereinafter by way of example only with reference to the accompanying drawings, in which: Figure 1 shows an isometric view of a fixture for construction of towers thereupon; Figure 2 shows an enlarged view of a guide bracket for positioning towers on a fixture; Figure 3 shows an enlarged view of packers for adjusting the height of a fixture; Figures 4A-4D are schematic views showing how a tower can be built up from a plulality of stacked modules; Figure 5 is a perspective view of apparatus used to facilitate the connection of one module to another; Figure 6 is an exploded view of the apparatus shown in Figure 5; Figure 7 shows two legs A, B with the relative positions of their respective guide plate assemblies; Figure 8 shows all four legs A, B, C, D with the relative positions of their respective guide plate assemblies; Figures 9-15 are a sequence of views illustrating how a second leg 2A is aligned with and attached to a first leg 1A; Figures 16-18 are perspective views of another embodiment of the invention; Figures 19-22 are perspective views of another embodiment of the invention; and Figures 23 and 24 are perspective views of an adjustable stub.

DETAILED DESCRIPTION

[0030] In some embodiments the present invention relates to a fixture 100 for construction of one or more structures 200 theleupon. The fixture is configured to provide a solid, temporary, base for construction of structures, which structures may be complete towers or modules which are tower sub-assemblies which can be subsequently assembled together to form towers. The fixture may be especially well suited to providing a temporary base for the construction of towers, or modules thereof, for use in electricity transmission.

[0031] Figure 1 shows a fixture 100 for construction of structures 200 thereupon. The fixture includes a base comprising a plurality of base beams 102 arranged generally parallel to one another. Concrete blocks 103 are disposed on top of the base beams to stabilise the base. In one embodiment the concrete blocks 103 are disposed upon support plates 104, which plates are disposed at both ends of base beams 102. Each plate is supported at opposite edges by two generally parallel base beams, and the base comprises either one such arrangement or two or more such arrangements disposed at opposite ends of the base and arranged generally parallel to one another.

[0032] The fixture further comprises a plurality of support beams 105 disposed on top of the base beams and arranged generally perpendicular to the base beams. The support beams are bolted to the base beams and the number and spacing of the support beams can be adjusted based on the requirements of the structure, or structures, to be built upon the fixture. The support beams may be spaced apart by a distance equal to the planned spacing between adjacent legs 1A-D in a structure to be built.

[0033] The height of the support beams above the base beams can be adjusted by placing packers 106 between the base beams and the support beams, as shown in figure 2. The angular orientation of the support beams may also be adjusted by placing packers between the base beams and the support beams. This may be useful if the base of the fixture is not level. Bolts 108 attach the support beams to the base beams and allow the support beams to be positioned at any location along the base beam. Both the support beams and the base beams may advantageously be "I" beams, i.e. beams having a generally I-shaped cross section formed by upper and lower flanges connected by a central plate arranged perpendicular to the flanges. In this embodiment the beams can be easily bolted together by providing bolts whose heads partially overlap one of the flanges of both the support beam and the base beam, as shown in figure 2. This obviates the need for drilling holes in the beams to bolt them together.

[0034] Stubs 107 are bolted on top of support beams 105 by bolts 115, as shown in enlarged view in figure 2. Stubs can be bolted to support beams at any position along the length of support beams. In this way the relative positioning of the stubs may be separately controlled in two mutually perpendicular dimensions; the relative positioning in a first dimension can be adjusted by changing the spacing between support beams and the relative positioning in a second dimension can be adjusted by changing the position of the stubs on the support beams.

[0035] Stubs 107 comprise a base plate 109 for bolting onto support beams 105 and having two plates llOa, 11Db projecting therefrom. The plates llOa, 11Db may project from the base plate in a plane arranged perpendicular to the base plate, or may project on a plane which is angled by more or less than 900 relative to the base plate. Plates 11 0a, 11 Ob are arranged generally perpendicular to one another and share a common edge. One or more holes 111 are provided in the surface of each plate 110 to allow legs 1A-D to be bolted to the stub. The relative positions of the stubs 107 on the fitting 100 determine the distances between legs of a structure built on the fixture. The angle of the plates 110 relative to the base plate of the stub 109 determines the angle of the legs 1A-D relative to the fixture.

[0036] In an alternative embodiment, one or more of the fixed stubs 107 can be replaced by an adjustable stub that can be used to construct a wide variety of tower structures having different leg dimensions and leg angles, obviating the need for bespoke stubs 107 for each specific tower structure. The adjustable stub is fully adjustable on pillow block bearings for a range of tower leg angles (typically 0-15 degrees) by adjustment of a turnbuckle on the inside of the stub angle. The stub angle would be set using an inclinometer for the specific tower structure required.

An example of an adjustable stub is shown in Figures 23 and 24.

[0037] In addition to bolts, release pins 112 may be disposed in holes 111, and the release pins may attach the legs to the stubs.

[0038] In other embodiments the invention relates to a method for assembling a tower structure on top of a fixture as described herein. In such embodiments the stubs 107 may be placed into predetermined relative positions so that the distances between the stubs are substantially equal to the planned distances between the end points of the legs of a structure to be built.

[0039] Once the stubs are positioned correctly components of a structure may be assembled, starting with legs 1A-D, on top of a fixture as described herein to form a structure. Alternatively, the components may first be assembled into sub-assemblies or modules which may be subsequently attached to a fixture as described herein and further assembled to form a structure, or a combination of components and modules may be assembled on a fixture as described herein. In any event, the assembly of the components and/or modules may be performed using a crane or a helicopter.

[0040] Once the structure is assembled it may be removed from the fixture and transported to a remote location, for example by helicopter, and then mounted upon a permanent foundation. To detach the structure from the fixture, bolts 113 attaching the legs 1A-D to the stubs 107 are removed. With the bolts 113 removed the structure is held in place by triangular stop blocks 114 and release pins 112.

The release pins are left in place until immediately before the structure is removed from the fixture, which is typically done by lifting the structure off the fixture using a helicopter.

[0041] In another embodiment the invention relates to a method for building a tower in which a plurality of modules are sequentially built and the modules are then assembled to form a tower. In this embodiment a first, lowermost, module is assembled as described herein and then removed from the fixture and mounted upon a permanent foundation. The stubs 107 are then repositioned and a second module is assembled on the fixture, and then removed from the fixture and mounted on top of the first module. Further modules may also be formed in a similar way, depending on the planned number of modules in the tower to be formed. The removal of the modules may be performed in the manner described above.

[0042] In another embodiment, sufficient fixtures can be provided so that all the individual tower modules can be simultaneously constructed. This avoids the need to reposition the stubs for the next sequential construction once the first module has been airlifted to the tower installation site, giving substantial time and cost savings, particularly important if a helicopter is being used.

[0043] The modules can be delivered to the installation site by helicopter, whereupon they need to be assembled together to form the complete tower. The complete tower may typically comprise three or four stacked modules, each module having four orthogonally placed legs for securing to a foundation (in the case of the lowermost module) or for securing on top of an already-installed module. For convenience, in the following description, the four legs of the first tower module will be referred to as first legs 1A, 18, 1C, 1 D, the four legs of the second tower module will be referred to as second legs 2A, 2B, 20, 2D, the four legs of the third tower module will be referred to as third legs 3A, 3B, 30, 3D etc. Each leg comprises two generally perpendicular leg elements, such that the leg has a generally L-shaped cross-section.

[0044] Figures 4A-4D show schematically how the tower is built up from stacked modules.

[0045] A conventional tower foundation will have been constructed on-site, comprising four orthogonally spaced stubs A, B, C, D embedded in concrete. The stubs are located at the corners of what will be the footprint of the tower. The stubs are upwardlyextending, readyto receivethe legs 1A, 1B, 1C, 1D ofthefirsttower module thereon and angled inwardly i.e. towards the middle of the footprint. Figure 4A shows the tower foundation and two of the stubs.

[0046] A first tower module can be installed onto the stubs in the same manner as set out below for the second and later modules.

[0047] Referring to Figure 5, a second tower module is assembled onto the first tower module by connecting the second legs 2A, 2B, 2C and 20 respectively with first legs 1A, 13, 1C and 1D. In Figure 5 can be seen the top of first leg 1A and the bottom of second leg 2A which approaches downwardly from above, lowered into place by helicopter, for example.

[0048] The legs 1A, 2A are substantially L-shaped in cross-section, making it harder to align them with one another than would be the case if each leg were substantially planar as they need to be correctly aligned in two transverse dimensions in the X-Y plane, as well as being delivered at the correct height. To facilitate the alignment of the legs in the X-Y plane, two guide plate assemblies 310, 320 are provided: an outer guide plate assembly 310 and an inner guide plate assembly 320. Each guide plate assembly comprises a lower portion 311, 321 which in use is substantially parallel with the legs 1A, 2A and an upper portion 312, 321 which in use is angled away from the legs 1A, 2A in the manner of a "funnel" or ramp leading to the desired location. The upper and lower portions are connected by one or more strengthening braces 313, 323. Further details of the assemblies are visible in the exploded view of Figure 6. The upper portion 312 may be provided with a hole 318 through which a rope or the like can be passed to facilitate guiding and manipulation of the assembly by an operator on the ground or positioned on the tower. Alternatively, instead of an operator, one or more tirfors could be used to pull the ropes in tight from the helicopter. The rope extends up to the helicopter via the hole 318. Use of the tirfor or ground-based operator improves initial contact between the downwardly moving leg and the upper portion of the guide plate assembly.

[0049] A substantially L-shaped clamp plate 330 (may be referred to in the art as a "bosom angle") is bolted to the inner surfaces of the two leg elements comprising the top of the first leg 1A. This plate will ultimately receive the fixings for connecting the two legs 1A and 2A together, once the legs are properly aligned as set out below. A first splice plate 314 and a second splice plate 324 are provided on the outer surfaces of the first leg 1A whose function will be described further below. In another embodiment (not illustrated) the clamp plate 330 may be replaced by one or two inner splice plates, fixed to the interior surfaces of the first leglA.

[0050] Each of the four legs is provided with two guide plate assemblies 310, 320 (one attached to each respective leg element) but, as shown in Figure 7, their relative positioning on adjacent legs 1A, lB is as images of one another rotated through 90 degrees, most obvious by the different orientation of upper portions 312A and 312B and 322A and 322B seen in Figure 7.

[0051] FigureS shows all four legs A, B, C, D with the relative positions of their respective guide plate assemblies.

[0052] The outer guide plate assembly 310 is initially bolted to the clamp plate 330, through the outer surface of the leg 1A and the splice plate 314 (see "B" in Figure 8). The inner guide plate assembly 320 is initially bolted to the inner surface of the leg 1A through the clamp plate 330 (see "0" in Figure 8).

[0053] Figures 9-15 are a sequence of views illustrating how a second leg 2A is aligned with and attached to a first leg 1A [0054] Figure 9 is equivalent to Figure 5 except shown from a different angle. The second leg 2A is approaching the first leg 1A from above, delivered by helicopter in the downward Z direction. It is necessary to accurately align the second leg 2A in the X and Y plane to enable it to properly abut the top of the first leg 1A. A skilled helicopter pilot may be able to align the second leg 2A to within a few centimetres by eye alone. This is accurate enough to enable the bottom of second leg 2A to engage one or both of the upper portions 312, 322 of the guide plate assemblies.

[0055] The sloping upper portions 312, 322 guide the second leg 2A as it travels further downwardly until the position shown in Figure 10 is reached. The bottom of the second leg 2A abuts the top of the first leg 1A and the two legs are now in a suitable position to be connected together.

[0056] The guide plate assembly 310 is fixed to the first leg 1A by means of bolts 315 and 316. These bolts pass through the guide plate assembly 310, the splice place 314, the first leg 1A and the clamp plate 330 (not visible in Figure 10).

[0057] To begin the fixing process, bolt 315 is removed so that splice plate 314 can be pivoted upwardly about bolt 316 in the direction of the arrow in Figure 10, to reach to the position illustrated in Figure 11. Holes in the splice plate 314 align with holes 317 in guide plate assembly 310, ready to receive fixings. Note that holes 317 are of a larger diameter than the holes in which bolts 315, 316 are located.

[0058] As shown in Figure 12, fixing bolts 317' are then placed through holes 317 to rigidly fix the splice plate 314, first leg 1A, second leg 2A and clamp plate 330 together.

[0059] Holes 317 are of a large enough diameter to allow passage therethrough of bolt 316. In the position shown in Figure 12, bolt 316 is the only means holding guide plate assembly 310 in place and therefore simple removal of bolt 316 permits easy and complete removal of the guide plate assembly 310 to reach the condition illustrated in Figure 13. The guide plate assembly 320 can also be unbolted and removed to reach the condition illustrated in Figure 14.

[0060] The second splice plate 324 is attached to the leg 1A by means of a single bolt 327. The splice plate 324 can be pivoted about bolt 327 in the direction indicated by the arrow in Figure 14 to reach the position shown in Figure 15.

[0061] As shown in Figure 15, further bolts 327 can be provided to firmly fix splice plate 324, resulting in legs 1A and 2A firmly fixed together by means of splice plates 314, 324, with the guide plate assemblies removed.

[0062] The guide plate assembly arrangement described herein is suitable for use with all conventional splice plated joints. Although described above in relation to a tower module, the guide plate assembly arrangement could equally be used to assemble individual legs, panels or any other components where it is desired to correctly "land" a downwardly approaching component in the X-Y plane. Site staff may select whether to use one or other of the guide plate assemblies only, or indeed none of them depending on the size, shape and nature of the component concerned. In particular, when installing a first module onto the foundation stubs, the absence of working at height (staff on the ground) makes it easy to manually guide the module into position with ropes.

[0063] Figures 16-18 illustrate another embodiment in which no splice plates are required.

In this embodiment, instead of legs 1A and 2A being brought together to abut one another and then being fixed together by splice plates, the second leg 2A is brought down to overlap with and nest inside the first leg 1A so that the two leg elements of each respective leg can be directly bolted together.

[0064] Figure 16 shows the top of a first leg 1A and the bottom of a second leg 2A approaching from above. A guide plate assembly 400 is provided, of a type similar to guide plate assembly 310 described above. The guide plate assembly 400 comprises a lower portion 411 which in use is substantially parallel with the legs 1A, 2A and an upper portion 412 which in use is angled away from the legs 1A, 2A in the manner of a funnel" or ramp leading to the desired location. The upper and lower portions are connected by one or more strengthening braces 413. The guide plate assembly 400 is bolted to the first leg 1A by means of bolts 414.

[0065] Only one guide plate assembly 400 is used in this embodiment. Further guidance is provided by a clamp stop assembly 420 which is bolted to the second leg 2A.

Referring to Figure 16, the second leg 2A approaches the first leg 1A from above in the direction indicated by the arrow. Since the second leg is going to overlap with and nest inside the first leg, it is necessary to ensure that the second leg 2A can be guided inwardly towards the centre of the tower footprint (out of the page toward a viewer of Figure 16). The sloping upper portion 412 of the guide plate assembly will guide the second leg to nest inside the first leg 1A but this can be facilitated by attaching a rope or the like to eye 421 on the clamp stop assembly 420 so that the second leg can be pulled inwardly towards the centre of the tower footprint as the second leg is moved downwardly by the crane or helicopter. This inward pulling of the second leg can be achieved by shackling the eye 421 of one second leg to the eye of the diagonally opposite second leg of the tower module by a rope, chain or the like in tension.

[0066] Figures 17 and 18 show further perspective views of the Figure 16 embodiment.

Referring particularly to Figure 18, a generally horizontal stop plate 422 is provided as part of the clamp stop assembly 420 to limit downward travel of the second leg 2A. Downward travel of the second leg 2A is limited to ensure that the holes 424 in the first and second legs align properly so that fixings can be inserted. The desired downward travel distance required to achieve alignment of the holes 424 is measured before arrival of the second leg 2A so that the clamp stop assembly 420 (and therefore the stop plate 422) can be bolted at the required location on leg 2A.

In use, downward travel of the second leg 2A is limited by stop plate 422 abutting the top of leg 1A.

[0067] When second leg 2A is nested inside first leg 1A with stop plate 422 abutting the first leg, the two legs 1A, 2A can be bolted together through a suitable number of overlapping holes 424. Once the legs are safely bolted together, the clamp stop assembly can be removed by removing bolts 423 and the guide plate assembly 400 can be removed by removing bolts 414 (see Figure 17).

(0068] Figures 19-22 are perspective views of another embodiment of the invention using four splice plates and no clamp plate.

(0069] In any of the above embodiments, one or more video cameras could be used in the region of the guide plate assemblies to assist the helicopter pilot or other operators during installation. Video cameras may obviate entirely the need for ground-based staff at the installation site, with the concomitant safety benefit.

(0070] Although the above description relates to embodiments in which a plurality of modules or sub-assemblies are assembled together to form a tower, it is envisaged that the apparatus and methods could equally be used to facilitate the alignment and installation of a complete tower (in one piece) on a foundation. As already mentioned above, the apparatus and methods could equally be used to assemble any individual legs, panels or any other components where it is desired to correctly "land" a downwardly approaching component in the X-Y plane.

(0071] It will be understood that a tower or tower structure can comprise one or more modules or subassemblies or structures. A module/subassembly/structure can comprise one or more legs or panels or components. Each leg/component/panel has at least a part having generally L-shaped cross section, the L-shape being formed by two leg elements abutting, typically, at an angle of approximately 90 degrees. The two leg elements may be equal or unequal in length.

(0072] The apparatus and methods are equally applicable to installation performed by means of a helicopter or by an on-site crane or derrick.

(0073] Throughout the description and claims of this specification, the word bolt" is used as an example only of the type of fixing that could be used. Any other suitable fixing could alternatively be used.

(0074] Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of them mean "including but not limited to", and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0075] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0076] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

Claims

CLAIMS1. Apparatus for construction of a tower in which it is desired to align and assemble a second tower component with a first tower component by lowering the second component onto the first component from above, the first tower component having at least one upper leg having a substantially [-shaped cross section formed by two leg elements and the second tower component having at least one lower leg having a substantially [-shaped cross section formed by two leg elements, the apparatus comprising: a fiist guide plate assembly, mountable on an upper leg element of the first tower component, and having an upper portion comprising a first ramp leading to a desired end location for said lower leg of the second tower component; a second guide plate assembly, mountable another upper leg element of the first tower component, and having an upper portion comprising a second ramp leading to the desired end location for the lower leg of the second tower component; the first and second ramps being orthogonally arranged with respect to one another so that they are capable of guiding the lower leg of the second tower component to the desired location by limiting movement of the [-shaped lower leg in two orthogonal directions in an X-Y plane.
2. Apparatus for construction of a tower in which it is desired to align and assemble a second tower component with a first tower component by lowering the second component onto the first component from above, the first tower component having at least one upper leg having a substantially [-shaped cross section formed by two leg elements and the second tower component having at least one lower leg having a substantially [-shaped cross section formed by two leg elements, the apparatus comprising: a guide plate assembly, mountable on an upper leg element of the first tower component, and having an upper portion comprising a first ramp leading to a desired end location for said lower leg of the second tower component; a guide stop assembly, mountable on the lower leg of the second tower component, including a generally horizontal stop plate to limit downward movement of the lower leg of the second tower component when the stop plate abuts the upper leg of the first tower component, in use; the guide plate assembly and guide stop assembly together being capable of guiding the lower leg of the second tower component to the desired location by limiting movement of the L-shaped lower leg in two orthogonal directions.
3. Apparatus as claimed in claim 2 further comprising a further guide plate assembly, mountable on another upper leg element of the first tower component, and having an upper portion comprising a further ramp leading to the desired end location for the L-shaped lower leg of the second tower component.
4. Tower construction apparatus comprising: a first tower element having at least one upper leg having a substantially L-shaped cross section formed by two leg elements; a second tower element having at least one lower leg having a substantially L-shaped cross section formed by two leg elements; apparatus as claimed in any of claims 1-3 mounted on at least two of said legs, the orientation of the guide plate assemblies relative to one another on adjacent legs being rotated through 90 degrees in order to further limit movement of the second tower component in the X-Y plane when the second tower component is lowered onto the first tower component from above.
5. Apparatus as claimed in claim 4 wherein the first tower component has four of said upper legs and wherein apparatus as claimed in any of claims 1-3 is mounted on all four of said upper legs.
6. Apparatus as claimed in any of the preceding claims wherein the first and second guide plate assemblies each include a lower portion which is removably fixable to an upper leg element of the first tower component, the lower portion being substantially parallel with the upper leg element to which it is fixed.
7. Apparatus as claimed in claim 6 further comprising a strengthening brace between the lower portion and the upper portion of the guide plate assembly.
8. Apparatus as claimed in any of the preceding claims wherein the leg elements forming the substantially L-shaped cross section of a leg are unequal in length.
9. Apparatus as claimed in any of the preceding claims wherein the guide plate assemblies are removably fixable to the upper legs of the first tower component using bolts.
10. Apparatus as claimed in any of the preceding claims wherein the upper portion of the guide plate assembly includes a hole through which a rope or the like can be passed, in use, for manipulation by an operator or a tirfor.
11. Apparatus as claimed in any of the preceding claims wherein, when in the desired end location, the lower leg of the second tower component abuts the upper leg of the first tower component and the apparatus further comprises a clamp plate through which bolts can attach the lower leg and upper leg together.
12. Apparatus as claimed in any of claims 1-10 wherein, when in the desired end location, the lower leg of the second tower component overlaps with the upper leg of the first tower component, and the lower leg and upper leg can be attached together using bolts through the overlapping section.
13. Apparatus as claimed in any of the preceding claims further comprising one or more splice plates for attaching the lower leg and upper leg together.
14. Apparatus as claimed in claim 13 wherein the splice plate includes a hole alignable with a hole in the guide plate assembly and through which a bolt can be received.
15. Apparatus as claimed in claim 14 wherein the hole in the guide plate assembly is of a larger diameter than the hole in the splice plate sufficient to allow a splice plate bolt to pass entirely therethrough.
16. Apparatus as claimed in any of claims 13-15 wherein the splice plate is pivotable about a bolt therethrough in order to move it from an initial position to a final position in which it can be used to attach the lower leg and upper leg together.
17. Apparatus as claimed in any of the preceding claims further comprising a solenoid-operated shot bolt for attaching the lower leg and upper leg together.
18. Apparatus as claimed in any of the preceding claims further comprising at least one video camera in the vicinity of the guide plate assemblies for providing visual feedback to an operator.
19. Apparatus for construction of a tower substantially as described herein with reference to and as illustrated in any appropriate combination of the accompanying drawings.
20. Method of assembling a second tower component by lowering it onto a first tower component using apparatus as claimed in any of claims 1-19, the first tower component having at least one upper leg having a substantially L-shaped cross section formed by two leg elements and the second tower component having at least one lower leg having a substantially [-shaped cross section formed by two leg elements, the method comprising the steps of: attaching said guide plate assemblies to the upper legs of the first tower component; optionally attaching clamp plates and splice plates to the upper legs of the first tower component, the splice plates being in their initial position; optionally attaching guide stop assemblies to the lower legs of the second tower component; lowering the second tower component towards the first tower component, until the lower legs of the second tower component approach the ramps of the guide assemblies; continuing to lower the second tower component as the lower legs thereof travel down the ramps of the guide assemblies to their desired end location; optionally pivoting at least one of said splice plates from its initial position to its final position; using bolts to fix the legs of the first and second tower components together; removing bolts holding the guide assemblies in place so that the guide plate assemblies can be removed.
21. Method as claimed in claim 20 wherein the second tower component is lowered towards the first tower component using a helicopter, crane or derrick.
22. Method of constructing a modular tower comprising the steps of: providing a ground-based fixture on which a tower module can be constructed, the fixture including a plurality of stubs fixed to support beams and spaced according to the desired tower module dimensions; constructing the tower module on the plurality of stubs; separating the constructed tower module from the fixture; transporting the tower module to an installation site remote from the fixture.installing the tower module at the installation site.
23. Method as claimed in claim 22 wherein the tower module is transported by helicopter.
24. Method as claimed in claim 22 or claim 23 wherein a second tower module is constructed on the first tower module before separation from the fixture.
25. Method as claimed in any of claims 22-24 wherein the tower module is installed using apparatus as claimed in any of claims 1-19.
26. Method as claimed in claim 25 wherein the installation step comprises: attaching said guide plate assemblies to the upper legs of the first tower component; optionally attaching clamp plates and splice plates to the upper legs of the first tower component, the splice plates being in their initial position; optionally attaching guide stop assemblies to the lower legs of the second tower component; lowering the second tower component towards the first tower component, until the lower legs of the second tower component approach the ramps of the guide assemblies; continuing to lower the second tower component as the lower legs thereof travel down the ramps of the guide assemblies to their desired end location; optionally pivoting at least one of said splice plates from its initial position to its final position; using bolts to fix the legs of the first and second tower components together; removing bolts holding the guide assemblies in place so that the guide plate assemblies can be removed.
27. Method of constructing a tower substantially as described herein with reference to any appropriate combination of the accompanying drawings.