GB2481418A

GB2481418A - Folding mast

Info

Publication number: GB2481418A
Application number: GB1010503.9A
Authority: GB
Inventors: Timothy Richard Crocker
Original assignee: Tradewind Turbines Ltd
Current assignee: Tradewind Turbines Ltd
Priority date: 2010-06-22
Filing date: 2010-06-22
Publication date: 2011-12-28
Also published as: GB201010503D0

Abstract

A folding mast, e.g. for a wind turbine, comprises lower 1, middle 2 and upper 3 mast sections connected by respective hinged joints 6. The upper section is also connected to the lower by a rigid link 11 which controls the alignment of a longitudinal axes of the upper and lower sections in a parallelogram linkage so that the upper section is always vertical. The link is connected to the sections via gussets and bearing pins 9, 10 and movement effected by an actuator or winch. The mast sections each terminate in a flange which may be bolted or clamped following erection for strength. The link and actuator may be removed for use on subsequent masts. A second set of cable stays may secure the upper section by engaging tangentially with a torque reaction ring on e.g. a vertical axis turbine. The apparatus may be used in a method of erecting a folding mast comprising staying a first mast section 1 before a second mast section 2 is raised into position on top of the first.

Description

I

Folding Mast This invention relates to a folding mast and particularly, although not exclusively relates to a novel method of installation and servicing of wind turbines, particularly those which may need to be installed quickly or temporarily, such as in military or disaster relief situations.

Backci round The power which can be extracted from a turbine presenting a given cross sectional area to the wind is proportional to the cube of the wind speed, and the speed of the wind increases with height above the ground because the friction between the moving air and the ground decreases with increasing height. There is therefore always an advantage in mounting a turbine as high up as practicalities permit.

However the operating elements of a turbine are those which are most complex, and are thus naturally mainly at the top of the structure, whereas for both installation and servicing there is considerable advantage that all work is done as close as possible to ground. This minimises the need for complex and expensive machinery such as raised platforms or cranes, and greatly decreases the cost of measures to allow safe operation.

There is therefore a conflict between the need for height for efficient operation, and the convenience and reduced cost of doing installation and maintenance as close to the ground as possible.

This invention overcomes this conflict. The invention is particularly advantageous when used with turbines which operate with stays which hold the turbine mast vertical and will be described in this mode, however it would also operate advantageously if the turbine is to be mounted from a rigid foundation. It is also described in terms of vertical axis turbines, such as those described in GB0922067.4, G61005557.2 and GB1005564.8, the disclosures of which are hereby incorporated by reference. However, it should be appreciated that the invention is equally applicable to all types of vertical and horizontal axis devices and to masted structures of all kinds.

Statements of inventi

According to a first aspect of the p.esent invention there is provided a folding mast comprising lower, middle and upper mast sections which are connected together by respective hinged joints, the upper mast section also being connected to the lower mast section by means of a rigid link which controls the alignment of a longitudinal axis of the upper mast section relative to a longitudinal axis of the lower mast section.

The hinged joints may comprise pinned joints which resist relative rotation of the respective mast sections. Consequently, due to torsional stiffness in the mast sections and in the nature of the hinged joints, there is control (resistance to rotation) in the axis orthogonal to the axis assured by the rigid link. Consequently, as the mast is assembled the mast upper section rises substantially vertically in both of these planes.

The link and the middle mast section may form bars of a four bar linkage. The link may maintain the longitudinal axis of the upper mast section substantially parallel to the longitudinal axis of the lower mast section through their range of relative movement.

An actuator, such as a hydraulic, pneumatic or electrically operated linear actuator may be provided to fold and unfold the mast. Alternatively a purely mechanical device such as a block and tackle or chain hoist may be used. The actuator may be mounted such that when it is in a first limit position in its range of operation the longitudinal axis of the upper mast section is substantially coincident with the longitudinal axis of the lower mast section and when the actuator is in a second limit position in its range of operation the longitudinal axis of the upper mast section is substantially parallel to but displaced laterally and vertically from the longitudinal axis of the lower mast section.

The actuator may, for example, act between the link and one of the mast sections, or between two mast sections.

According to a second aspect of the present invention there is provided a method of erecting a folding mast comprising at least a first mast section and a second mast section, the method comprising staying the first mast section before the second mast section is raised into position on top of the first mast section. The method may further comprise staying the second mast section.

The method may further comprise the step of erecting a third mast section, simultaneously with erecting the second mast section. It may also include staying the third mast section in addition to or instead of the second mast section.

Staying the mast sections may comprise attaching at least one stay between the respective mast section and a foundation remote from the mast section. The foundation may comprise an anchor, such as a weighted anchor plate, or an earth anchor, pin or shaft driven into the ground.

Alternatively, the foundation may comprise a rigid structure such as a concrete block or pad foundation.

According to third aspect of the present invention, there is provided a wind turbine tower or mast which folds for transport, erection and or servicing. The wind turbine tower or mast may comprise lower, middle and upper mast sections which are connected together by respective hinged joints.

The upper mast section may also be connected to the lower mast section by means of a rigid link which controls the alignment of a longitudinal axis of the upper mast section relative to a longitudinal axis of the lower mast section.

A linear actuator, such as a hydraulic, pneumatic or electrically operated ram may act between the link and one of the mast sections, such that when the linear actuator is in a first position in its range of operation the longitudinal axis of the upper mast section is substantially coincident with the longitudinal axis of the lower mast section and when the actuator is in a second position in its range of operation the longitudinal axis of the upper mast section is substantially parallel to but displaced laterally from the longitudinal axis of the lower mast section.

Brief Description of the Drawinqs

For a better understanding of the present invention and to show how it may be carried into effect, reference will now be made to the accompanying drawings, in which: Figure 1 shows the turbine and mast in a stage in which it is close to the ground either in the last stage of assembly, the first stage of disassembly, or as lowered to the ground for convenient maintenance Figure 2 shows the turbine and mast in an intermediate stage of being raised to working height Figure 3 shows the turbine in a fully raised position.

Figure 4 shows a detail of mounting of a hydraulic ram to allow the turbines to be raised and lowered.

Figure 5 shows a detail of the flanges and locking pins

Detailed Description of Preferred Embodiments

Referring to Figures 1 to 3, the mast of a vertical axis wind turbine 4 consists of a lower mast section 1 a middle section 2 and a upper section 3. The upper section 3 carries the operating mechanism of the vertical axis wind turbine 4 (which is only shown schematically).

Each section of the mast which joins to another part carries a flange or similar arrangement. These flanges can be joined together when the mast is fully vertical using conventional means such as a ring of nuts and bolts, or flange clamps, so that the erected mast has full structural strength.

Conventionally, there may be gussets (not shown) mounted between the flanges and mast sections to reinforce the joint.

The pairs of flanges at each mast joint are hinged together by hinge pins 6, which are arranged such that the mast assembly has torsional strength around the axis of the mast sections. It should be noted that in order that the mast can be raised so that all sections are in line, successive hinge pins 6 are on diagonally opposite sides of the mast (from the viewpoint of the mast in a raised state). The dashed line between the hinge pins 6 shows the line of action between hinge pins 6.

The lower mast section 1 is braced to the ground by tensile stays 7 such as steel or Kevlar cables, which are attached to the ground by conventional ground anchoring techniques, such as by pegs, posts or ground anchors, or by using weighted ground plates which are anchored laterally by pins driven into the ground. The ground plates may be weighted by sand bags' filled locally with any dense material, such as stone or gravel, which is to hand. For example the weighting may be provided by 25 kg bags of building material such as pea gravel. A weight of about 600kg on each of six ground plates, has been shown to provide adequate support for a prototype device.

In a vertical axis wind turbine, wind drives the sails and the sails turn the generators, but power is produced because the generator bodies do not rotate about the mast in response to a reaction torque. This torque can be resisted by a second set of rigging stays taken out to ground anchors.

As viewed from above these stays will attach to the mast essentially tangentially, so as to resist the torque. In order to increase the leverage of the stays, a torque reaction ring which is of larger diameter than the mast may be attached to the mast or to a stationary part of the wind turbine. The tangential stays may then be attached to the torque reaction ring rather than the mast, so that the reaction torque from the wind turbine does not generate excessive tension in the stays. The torque reaction ring may be frustoconical in shape, with a larger diameter end oriented towards the bottom of the mast. The tangential stays may be attached to the larger diameter end of the frustoconiCal torque reaction ring.

The base of the lower mast section 1 may be secured in place, for example by locating it in a metal socket embedded in the ground. When the mast is in the fully vertical position, further ground stays 8 attached to the lower part of the upper mast section 3 can be braced by ground anchoring to give the assembly greater strength against wind loads in operation.

Mounted near the top of the lower mast section 1 and the bottom of upper mast section 3 are two bearing pins 9 and 10, and these are fixed by brackets or gussets 14, 15, to their respective mast sections 1, 2, 3, as is shown schematically in Figures 1 to 3. They lie on a line which is parallel to the line of action between the two hinge pins 6. Mounted between bearing pins 9 and 10 is a rigid spar 11 which is capable of sustaining both compression and tension loads.

It can be seen that this mounting arrangement, with the combination of the parallel action of the spar 11 and the torsional strength of the mast sections and hinge pins 6 constrains lower mast section 1 and upper mast section 3 to remain parallel at all times, and since lower mast section 1 is stayed to the ground the upper section will also remain vertical.

Referring to Figure 4, a linear actuator in the form of a hydraulic ram 12 is fixed between the spar 11 and the middle mast section 2. In order to increase the mechanical advantage of the hydraulic ram 12, a gusset plate 13 is attached to the top of the spar 11.

Figure 5, provides detail of the construction of the gusset 14 and shows the position at which safety pins 16 secure the flanges of the lower and middle mast sections 1, 2 together.

Operation can now be described. For assembly of a turbine on site, the ground anchors and mast base plate are put in place and the lower mast section is raised either by hand or by an actuator.

The stays 7 are then attached to the base plates and tensioned. The components of the vertical axis wind turbine can then be installed. Upper stays are attached to the top mast section 3, but left loose at this stage.

The whole turbine can now be raised by activating the hydraulic ram 12, which can be manual, or may have mechanical or electrical drive. The turbine assembly will thus be raised via the intermediate position shown in Figure 2, into the final position shown by Figure 3. The action of the hydraulic ram as drawn is to contract in length to raise the assembly and to extend in length to lower the assembly. This is advantageous as it keeps the spar 11 largely in tension; however other arrangements could be effective.

The safety pins 16 of Figure 5 can then be inserted, and the flanges can be further strengthened either by nuts and bolts, or via clamps. These operations can be performed by a variety of conventional means, such as by Bosun's chair', or by equipping the mast with climbing rings so that an assembly worker can access the joints directly. Alternatively, the pins 16 can be inserted remotely, for example by electrical, hydraulic of pneumatic means. The upper ground stays 8 and tangential stays can then also be tensioned to make the turbine ready for operation.

The turbine can be lowered for maintenance by simply releasing some of the upper ground stays 8 and tangential stays and venting the hydraulic ram 12. Raising the mast after maintenance is simply a reverse of this procedure, and disassembly is simply a reversal of the assembly procedure.

Means may also be provided to enable removal of some of the components, such as spar 11 and hydraulic ram 12 between raising and lowering operations in order for instance to reduce the cost of equipment across a number of turbines in a locality, or to provide security against un-authorised operation.

In an alternative embodiment, not illustrated, the linear actuator could be replaced by a winch and pulley arrangement. In such an embodiment, a pulley could be fitted to the gusset plate and a winch could be attached to the lower mast section at substantially waist height of an operator. A cable of the winch would then extend from the winch over the pulley and be attached to the rigid link in the region of the bearing pin 10. In order to improve the mechanical advantage of the winch and pulley arrangement, the intermediate pulley may alternatively be fixed to a bracket which forms a bar of the four bar linkage. In such an embodiment, the bracket could be extended vertically upwards and to the left as viewed in Figure 1.

Claims

CLAIMS1. A folding mast comprising lower, middle and upper mast sections which are connected together by respective hinged joints, the upper mast section also being connected to the lower mast section by means of a rigid link which controls the alignment of a longitudinal axis of the upper mast section relative to a longitudinal axis of the lower mast section.
2. A folding mast as claimed in claim 1 in which the hinged joints comprise pinned joints.
3. A folding mast as claimed in claim 1 or 2 in which the link and the middle mast section form bars of a four bar linkage.
4. A folding mast as claimed in any of the preceding claims in which the link maintains the longitudinal axis of the upper mast section substantially parallel to the longitudinal axis of the lower mast section through their range of relative movement.
5. A folding mast as claimed in any of the preceding claims further comprising an actuator, such as a hydraulic, pneumatic or electrically operated actuator, which operates to fold and unfold Q the mast.
6. A folding mast as claimed in claim 5 in which the actuator is mounted such that when it is in its first limit position in its range of operation the longitudinal axis of the upper mast section is substantially coincident with the longitudinal axis of the lower mast section, and when the actuator is in a second limit position in its range of operation the longitudinal axis of the upper mast section is substantially parallel but displaced laterally and vertically from the longitudinal axis of the lower mast section.
7. A folding mast as claimed in claim 6 in which the actuator acts between the link and one of the mast sections, or between two mast sections.
8. A method of erecting a folding mast comprising at least a first mast section and a second mast section, the method comprising staying the first mast section before the second mast section is raised into position on top of the first mast section.
9. A method of erecting a folding mast as claimed in claim 8 further comprising staying the second mast section.
10. A method of erecting a folding mast as claimed in claim 8 or 9 further comprising the step of erecting a third mast section, simultaneously with erecting the second mast section.
11. A method of erecting a folding mast as claimed in any of claims 8 to 10 further including staying the third mast section in addition to or instead of the second mast section.
12. A method of erecting a folding mast as claimed in claim 11 in which staying the mast sections comprises attaching at least one stay between the respective mast section and a foundation remote from the mast section.
13. A method as claimed in claim 12 in which the foundation comprises an anchor such as a weighted anchor plate, an earth anchor, pin or shaft driven into the ground, or a rigid structure such as a concrete block or pad foundation.
14. A folding mast substantially as described herein with reference to and as shown in the accompanying drawings.
15. A method of erecting a folding mast substantially as described herein with reference to the Q accompanying drawings.*.:r: INTELLECTUAL . ... PROPERTY OFFICE Application No: GB 1010503.9 Examiner: James Paddock Claims searched: 1-7,14 Date of search: 20 September 2011 Patents Act 1977: Search Report under Section 17 Documents considered to be relevant: Category Relevant Identity of document and passage or figure of particular relevance to claims X 1-6 AU2004200503 Al BERESFORD See Figures 2,3 and 4. Four component parallel linkage folding wind turbine mast. Turbine bearing upper mast portion D stabilised by bar C relative to lower and mid B portions.X 1-5 DE3405091 A GRAEBER See Figures 1 and 2 and WPI abstract accession No: 1985- 204189 [34]. Parallelogram pin jointed linkage raising wind turbine on mast base.X 1-5 FR2568948 A DODEMAN See Figure 1 and WPI abstract accession No: 1986- 083606 [13]. Lower 1 and upper 5 wind turbine mast portions linked by bar 4 in parallelogram linkage.X 1-5 FR2519710 A BERNARD See Figures 5 and 6 with WPI abstract accession No: 1983- 736811 [33]. Parallelogram wind turbine support linkage.Categories: X Document indicating lack of novelty or inventive A Document indicating technological background and/or state step of the art.Y Document indicating lack of inventive step if P Document published on or after the declared priority date but combined with one or more other documents of before the filing date of this invention.same category.& Member of the same patent family E Patent document published on or after, but with priority date earlier than, the filing date of this application.Field of Search:Search of GB, EP, WO & US patent docjments classified in the following areas of the UKCX: Worldwide search of patent documents classified in the following areas of the IPC EO4H; FO3D The following online and other databases have been used in the preparation of this search report WPI, EPODOC Intellectual Property Office is an operating name of the Patent Office www.ipo.gov.uk *.:r: INTELLECTUAL . ... PROPERTY OFFICE International Classification: Subclass Subgroup Valid From FO3D 0011/04 01/01/2006 EO4H 0012/18 01/01/2006 Intellectual Property Office is an operating name of the Patent Office www.ipo.gov.uk