ASSEMBLIES

Background of the Invention

The invention relates to a self-centering machine for manipulating a series of nut and bolt assemblies for interconnecting components of a mechanical structure.

Manipulating a nut and bolt assembly can include, for example, tightening, inspecting, adjusting and/or releasing a nut, which is screwed on a bolt or wire end, also called stud, of an already existing bolted flange connection, but also one or more steps in the placement of a bolted flange connection at the location of a bolt hole present for this purpose in a perforated flange.

When in the present specification and claims reference is made to a bolted connection it must be understood that, unless explicitly stated otherwise, this term also includes an intended bolt connection, which has not yet been realized, but for which, for example, a bolt hole has already been provided.

Accordingly, when used in this specification and claims, the term manipulating a nut and bolt assembly includes any rotation of the nut relative to the bolt, or bolt relative to the nut, for tightening, un tightening and/or re-tightening of the nut and bolt assembly, as well as stretching the bolt.

When used in this specification and claims the terms bolt, and nut and bolt assembly also include assemblies where a nut is screwed on a threaded end of a cylindrical rod or stud which is at another end screwed into a female screw thread in a flange or otherwise rigidly secured to one of the interconnected flanges or components and which rod or stud does not comprise a bolt head that can be clamped and turned by a wrench head, tongue or other mechanical tool head.

Furthermore the terms bolt, and nut and bolt assembly also include assemblies where a pair of nuts is screwed at opposite threaded ends of a cylindrical rod or stud which passes through a pair of aligned bolt holes in adjacent flanges or other components of a mechanical structure.

Bolted connections for interconnecting components of a mechanical structure typically comprise nut and bolt assemblies that are spaced at regular circumferential intervals along the circumference of a circular or curved flange assembly and are generally used to clamp together flanged components of a mechanical structure, such as flanged components interconnecting successive hull parts of a mast, in particular a mast for a wind turbine, transmission tower, oil platform, watchtowers or similar tall structures, or interconnecting successive flanged tubular sections of a pipeline or interconnecting parts of swing bearings of crane housings. These are relatively heavy constructions that often require working in hard-to-reach places to establish, maintain, inspect and/or control the intended bolted connection.

Wind turbines also comprise bolted flange connections between the rotor blades and a central rotor hub that is rotatably connected to a nacelle which is rotatably mounted on a tower to swing the rotor blades towards the wind. The nut and bolt assemblies between the rotor blades and the central hub may be subject to extremely high loads, vibrations and fatigue due to centrifugal loads induced by spinning of the turbine. This requires precise tightening and regular inspection, re-tightening and replacement of the nut and bolt assemblies.

The nut and bolt assemblies between the wings and a central hub of a wind turbine, and all other nut and bolt assemblies such as between tower or pipeline sections, must be tightened at an accurate prestressing to prevent bolt fatigue. By mechanically checking and electronically registering the tightening process parameters and possibly checking the prestressing of the bolts ultrasonically, a conclusive and traceable registration of each bolt’s tightening parameters in the flange connection can be obtained. Human errors such as, for example, skipping a bolt or inaccurate tightening has to be prevented. A more reliable connection made by an automatic or partially automatic or robot assisted bolting machine also results in cost savings on maintenance because bolt checks can be saved during the service life. In addition, a mechanization of the realization and control of flange connections limits the manpower required to handle the often heavy tools and man-hours can be saved for what will often be repetitive work. Automation of the flange connection process can therefore save on both installation costs and maintenance costs.

Robotic bolting machines are known from European patent specifications EP2607685, EP3163071, EP3195974, EP3195991, EP3550139 , International patent applications WO2016193297, WO2019110061 and WO2020/212323, US patent application US2011/232071, US patents 9,457,439 and 11,148,240, Korean patent application KR20130026039 and Japanese patent application JP H01 103240. The robotic bolting machines known from these prior art references generally are heavy and complex devices with complex robot motion mechanisms to move the machine along the circumference of the flanges, which mechanisms need to be adjusted to the curvature of the flanges and to the pitch or circumferential spacing between the circumferentially spaced nut and bolt assemblies.

The known robot motion mechanisms also require electronic positioning and navigation sensors to accurately align the tool head or tool heads to the manipulated nut and bolt assemblies. Such electronic positioning and navigation sensors need regular calibration and are fragile and damage prone components that can easily cause malfunctioning or even inhibit any further utilization of the faulty bolting machine.

For example, the robotic bolting machine known from EP 2607685 comprises a robot that allows a series of nuts to be tightened on a corresponding number of bolts of a bolted flange connection of a wind turbine. To this end, the robot is equipped with a drive to feed the robot over the flange connection along a series of bolt nuts and the robot has a tool with which a bolt nut can be tightened with a predefined tightening torque. By means of an optical position sensor, the robot must find its way to position the tool above the bolt nut in question. The position sensor exchanges such position information with a robot control system, which controls the tool and records bolt data.

Although this well-known robotic device thus offers a step forward in further automation and standardization of such a flange connection, the position sensors used therein are sensitive to contamination and disturbance which can lead to wrong positioning of the tool head misaligned with a bolt nut and inhibit any further utilization of the faulty bolting machine. In addition, due to the stability of the applied wagon, the well-known robot device requires that a set of electromagnets from the drive system always together with a complicated roller assembly will be in contact with a wall of the relevant hull segment, which cannot always be achieved in practice.

The bolting robot known from US patent 11 ,148,240 and European patent EP3550139 comprises a travel controller to stop a traction drive that moves the rotatable tool head to a next to be manipulated nut and bolt assembly after reaching a predefined travel length along the circumference of a flange, which length is a target variable and the positioning accuracy is dependent on a wheel, which may slip or be lifted from the flange if the flange has an irregular or slippery surface. In such case this known travel controller does not accurately align the tool head with the to be manipulated nut and bolt assembly and the tool cannot tighten the nut and bolt assembly.

The bolting robot known from W02020/212323 comprises a tool head that can be maneuvered into alignment with a to be manipulated nut and bolt assembly by a lift and swing mechanism, on the basis of navigation and positioning data acquired by electronic navigation and positioning sensors, which are fragile and require frequent maintenance, inspection, recalibration and replacement.

This known bolting robot comprises a tool head lifting crane with a vertical tower that is clamped around a nut and bolt assembly and a curved crane arm with a guide rail from which the tool head carrier body and fool head are suspended, such that they can be lifted up and down to move the tool head from an already tightened to a nearby nut and bolt assembly that is to be tightened. This crane arm and guide rail have a curvature which has to be identical to the curvature of the ring of circumferentially spaced nut and bolt assemblies. If this known robot is to be used to manipulate nut and bolt assemblies that are arranged in a ring with another curvature, then the crane arm needs to be replaced by another arm with a guide rail that also has this other curvature.

This known crane is also a relatively tall structure since the tool head carrier body and tool head are suspended below the arm and need to be lifted up and down to successive nut and bolt assemblies that are to be manipulated. Due to this tall configuration and long guide rail this known bolting robot is a relatively large and heavy structure that is rather unstable if it is temporarily clamped around a nut and bolt assembly and that is not suitable for use at non-horizontal flange assemblies in which case the robot will rotate about the tilted or horizontal axis of a bolt due to gravity and loose the alignment of the curved arm with the curved bolt rows.

European patents EP3195974, EP3195991 disclose robotic bolting machines with guide rails that slide along opposite sides of already tightened nut and bolt assemblies and a chain wheel that rolls over these assemblies to monitor the circumferential position of the tool head. The tool head has a frusto-conical alignment section that is lowered onto a to be manipulated nut and bolt assembly when the rotation of the guide wheel indicates that the tool head is located in the vicinity of the to be manipulated nut and bolt assembly. A disadvantage of these known robotic bolting machines is that the distance between the guide rails and their orientation needs to be adjusted to different sizes and radii of nut and bolt assemblies and that the guide wheel needs to be replaced by a differently dimensioned guide wheel if the radii of and/or pitches between and/or sizes of adjacent nut and bolt assemblies are changed. A further disadvantage of these known bolting machines is that if nut and bolt assemblies are arranged within oversized bolt holes, they are arranged at slightly different circumferential pitches and at slightly different radial distances from a central axis of the flange, in which case the guide rails and guide wheel will not accurately align the tool head with the next to be manipulated nut and bolt assembly.

European patent application EP 3550139 discloses the self-centering robotic bolting machine according to the preamble of claim 1. This known machine comprises a carriage that carries a tool head for tightening the nut and bolt assembly. The carriage is mounted on wheels that run along the circumference of the flange assembly so that it does not comprise a stepping mechanism and the tool head is aligned with an upper end of a to be manipulated nut and bolt assembly by an U-shaped guide nose which is pressed in a radial direction against a lower end of the to be manipulated nut and bolt assembly which is located at an opposite side of the flange assembly. The known U-shaped guide nose and tool head are iteratively moved in a radial direction relative to the carriage whilst the carriage is rolled tangentially from a manipulated nut and bolt assembly to a next to be manipulated nut and bolt assembly and the U-shaped guide nose does not interrupt this tangential movement of the carriage.

Disadvantages of this and the other known bolting machines are that they are complex and heavy pieces of equipment with fragile components and sensors, which increase the chance of the known robots to misaligning the tool head with a to be manipulated nut and bolt assembly, leading to inhibit any further utilization of the robots and wrongly tightened nut and bolt assemblies which may lead to collapsing of the bolted structure.

Thus, there is a need for a more robust, reliable, compact, light-weight, portable and damage proof improved machine for manipulating a bolted connection in a flange connection, which machine is self-centering and can, without replacing components, be easily adapted to different flange diameters and to different pitches at which adjacent nut and bolt assemblies are mutually spaced and which machine is configured to steer itself to each of a series of nut and bolt assemblies that are to be manipulated, also at non-horizontal flange assemblies, and thereby alleviate disadvantages of the known bolting robots and which improved bolting machine can be carried and manually installed at a flange assembly by a person and which can operate with a minimum of, and optionally without, position, navigation and other fragile wear and damage prone sensors.

Summary of the Invention in accordance with the invention there is provided a seif-centering machine for- manipulating a series of nut and bolt assemblies for clamping together components of a mechanical structure, the machine comprising:

- a tool head which is rotatably connected to a tool head carrier body, such that, when in use, the tool head can be removably arranged around a nut of a manipulated nut and bolt assembly and be rotated about an axis of rotation relative to the tool head carrier body to manipulate the nut of the manipulated nut and bolt assembly:

- a traction mechanism, which is configured to, when in use, sequentially release the tool head from the manipulated nut and bolt assembly and to move the tool head towards a next to be manipulated nut and bolt assembly; and

- a guide nose, which is connected to the traction mechanism and is configured to interrupt the movement of the tool head and to guide, prior to the interruption, the axis of rotation of the tool head into axial alignment with a central axis of the next to be manipulated nut and bolt assembly;

- wherein the guide nose has a V- or U-shaped, semi-circular or other bifurcated concave funneling surface, which is configured to slide prior to the interruption of the movement of the tool head along an outer contour of the next to be manipulated nut and boit assembly or of another nut and bolt assembly nearby the next to be manipulated nut and bolt assembly and to thereby guide the axis of rotation of the tool head into substantial alignment with the central axis of the next to be manipulated nut and bolt assembly;

- characterized in that the traction mechanism comprises:

- a stepping shoe which is configured to be reieasably positioned around another nut and bolt assembly that is located nearby the manipulated nut and bolt assembly; and

- a stepping mechanism, which connects the stepping shoe to the tool head carrier body and which is configured to, when in use, alternatingly release the tool head from the manipulated nut and bolt assembly and the stepping shoe from the other nut and bolt assembly and to induce during one step the tool head to step towards a next to be manipulated nut and bolt assembly and to induce during another step the stepping shoe to be moved towards another nut and bolt assembly that is located nearby the next to be manipulated nut and bolt assembly; and

- wherein the stepping mechanism is configured to alternatingly vary during said one step a distance between the stepping shoe and the tool head, and the guide nose is configured to rotate the carrier frame and the stepping mechanism and the tool head carrier body relative to the stepping shoe such that the tool head is directed into substantial alignment with the next to be manipulated nut and bolt assembly.

Suitable embodiments of the self-centering machine according to the invention are claimed m the accompanying sub-claims 2-14 and a method of using the self-centering machine according to the invention is claimed in the accompanying claim 15.

Brief Description of the Drawings

The invention will be explained in more detail below on the basis of a number of execution examples and accompanying drawings.

In the drawings:

Figure 1 shows the self-centering machine according to the invention during a step when the tool head is rotated to manipulate a to be manipulated nut and bolt assembly and a stepping shoe is positioned around a nearby nut and bolt assembly;

Figure 2 shows the self-centering machine of Figure 1 during a next step when, during or after manipulating of the selected nut and bolt assembly the stepping shoe is released from the nearby nut and bolt assembly;

Figures 2, 3 and 4 show how the stepping shoe is moved towards and lowered onto another nearby nut and bolt assembly;

Figure 5 shows how the tool head is subsequently lifted from the manipulated nut and bolt assembly for movement to another to be manipulated nut and bolt assembly; and

Figures 6-9 show an alternative embodiment of the self-centering machine according to the invention wherein the guide nose is pivotably or slidably connected to the tool head carrier body or stepping mechanism, and wherein: Figure 6 is a side view of the pivotable guide nose, when it is pivoted down and faces the nut and bolt assembly which is to be manipulated;

Figure 7 is a top view of the guide nose in the pivoted down position shown in Figure 6;

Figure 8 is a side view of the guide nose of Figures 6 and 7, after it has pivoted up and away from the nut and boit assembly which is to be manipulated;

Figure 9 is a top view of the guide nose in the pivoted up position shown in Figure 8;

Figures 10-14 show yet another alternative embodiment of the seif-centering machine according to the invention wherein a guide nose is pivotably connected to the stepping mechanism; and wherein:

Figure 10 shows how the guide nose is pressed against a to be manipulated nut and bolt assembly to accurately align the too! head with the to be manipulated nut and bolt assembly;

Figure 11 shows how after the alignment an electromagnetic disk maintains the tool head aligned with the to be manipulated nut and bolt assembly whilst the guide nose is pivoted up and away from the to be manipulated nut and boit assembly;

Figure 12 shows the self-centering machine of Figure 11 after the guide nose has been pivoted up into a vertical position to allow lowering of the tool head onto the to be manipulated nut and bolt assembly;

Figure 13 shows the self-centering machine of Figure 12 whilst the tool head is being lowered onto the to be manipulated nut and bolt assembly; and Figure 14 is a more detailed three-dimensional view of the self-centering machine of Figures 10-13 after aligning the tool head to another nut and bolt assembly whilst the electromagnetic disk maintains the tool head aligned with the to be manipulated nut and bolt assembly and the guide nose is being pivoted up to lower and engage the tool head with the to be manipulated nut and bolt assembly as also shown in Figure 11 .

Incidentally, it should be noted that the figures are drawn purely schematically and not always on (the same) scale. Corresponding parts may be identified In different figures with the same reference sign.

Detailed Description of the Depicted Embodiments

Figures 1-5 show an exemplary embodiment of the self-centering machine 1 for manipulating nut and bolt assemblies according to the invention, wherein a tool head 2 is rotatably mounted within a tubular tool head carrier body 3 and can be rotated relative to the tool head carrier body 3 as illustrated by arrow 4 in Figure 1 to manipulate a nut and bolt assembly 5H (shown in dotted lines Figures 1-4, and fully shown in Figure 5) of a series of circumferentially spaced nut and bolt assemblies, of which nut and bolt assemblies 5A-5N are shown in Figures 1-5. The depicted nut and bolt assemblies 5A-5N and non-depicted nut and bolt assemblies are configured to clamp together components, usually with adjacent flanges, of which flange segment 6 is shown in Figures 1-5, of flanged components of a mechanical structure, such as a tower section of a wind turbine or a blade to a hub. In Figures 1-5 the tool head 2 is shown in dotted lines since it is surrounded by the tubular tool head carrier body 3, which carrier body may be provided with a bolt tensioning device that manipulates the nut and bolt assembly by stretching the bolt to reduce friction during the tightening of the nut, such as a bolt tensioning device known from European patent EP 3894138 of Tentec Ltd, or a bolt torquing device which manipulates the nut and bolt assembly by rotating the nut to stretch the bolt.

Figures 1-5 also show that the self-centering machine 1 furthermore comprises a stepping shoe 7 A-D with a lower part 7A that is rotatably connected to an upper part 7B, which upper part comprises a pair of alignment toes 7C and 7D, and that the upper part 7B of the stepping shoe 7 is connected to the tool head carrier body 3 by a traction mechanism comprising a stepping mechanism 9, which comprises a pair of parallel stepping legs 10A, 10B that are each at a lower end thereof pivotably connected to the stepping shoe 7 and at an upper end thereof pivotably connected to a horizontal lift arm 11 B of an L-shaped lift body 11 , which also comprises a vertical tower 11 A that is slidably connected to a guide rail 12 at an outer surface of the tool head carrier body 3.

Figures 1-5 also show that a bifurcated, for example concave V- or U-shaped, guide nose 13 is slidably connected to the vertical tower 11 A of the L-shaped lift body 11 , such that during said one step the concave guide nose 13 is pressed by actuating legs 10A and 10B against the substantially cylindrical outer contour of the nut and bolt assembly 5G nearby the manipulated nut and bolt assembly 5H that is to be manipulated and the concave guide nose 13 thereby rotates, as illustrated by arrows 52 in Figure 5, the upper part 7B relative to the lower part 7A of the stepping shoe. The upper part 7B of the stepping shoe 7 thereby rotates the stepping mechanism 9, the tool head carrier body 3 and the tool head 2 relative to the nearby nut and bolt assembly around which the lower part 7A of the stepping shoe 7 is releasably positioned in such a manner that the tool head 2 is brought into axial alignment with the central axis 14 of the next nut and bolt assembly 5H that is to be manipulated.

Figures 1-5 furthermore show that the substantially parallel stepping legs 10A, 10B have substantially the same length, and thereby create a transformable stepping frame that can be transformed from parallelogrammical shape, as shown in Figures 1 , 2, and 5 into a substantially rectangular shape as shown in Figures 3 and 4, using some sort of actuation, which actuation may be manual, robotic, robot-assisted and/or gravity assisted.

Figures 1-5 also show that the pair of alignment toes 7C and 7D are configured to be arranged, when in use, at opposite sides of a substantially cylindrical outer contour of a nut and bolt assembly 5D, which is located adjacent to the nut and bolt assembly 5E (not shown in Figure 1, but shown in Figures 2-4) to which the stepping shoe 7 is releasably positioned. Figure 2 shows that the alignment toes 7C and 7D are mutually spaced at a spacing S, which is larger than the diameter D of the outer contour of the nut and bolt assemblies 5A-5N such that the pair of alignment toes 7C, 7D restrict the rotation of the stepping mechanism 9, the tool head carrier body 3 and the tool head 2 relative to the nut and bolt assembly 5E (not shown in Figure 1, but shown in Figures 2-4) around which the stepping shoe 7 is releasably positioned, to prevent guide nose 13 coming out of reach from self-centering on the next nut and bolt assembly.

Figures 1-5 furthermore show that a power and/or signal transmission umbilical 15 is connected to the tool head carrier body 3 for providing the machine 1 with electric, hydraulic and/or pneumatic power and for transmitting manipulation and stepping actuation signals to the machine 1 and for transmitting manipulation and stepping monitoring signals to and from the machine 1 to and from an at least partially automated and computerized bolt manipulation monitoring and control unit (not shown).

Figure 1 shows the machine 1 in a nut manipulation mode, wherein the tool head 2 is arranged around the to be manipulated nut 5H, which is not shown since it is surrounded by the tool head 2 and the tool head carrier body 3, and nut 5H rotated about an axis of rotation 14 relative to tool head carrier body 3 as illustrated by arrow 4 to manipulate nut 5H.

In Figure 1 the vertical tower 11A of the L-shaped lift body 11 is located near a lower end of the guide rail 12, such that the guide nose 13 faces and is pressed against the cuter contour of the nut or bolt of the nut and bolt assembly 5G and the lower part 7A of the stepping shoe 7 surrounds and is optionally clamped to the nut and bolt assembly 5E.

Figure 2 shows that, after completion of the nut manipulation operation shown in Figure 1 , the tower 11A of the L-shaped lift body 11 is induced by an actuator to slide upwards along the guide rail 12 as illustrated by arrow 20 and that as a result of the upward movement the guide nose 13 is lifted above the nut and bolt assembly 5G and the stepping shoe 7 is lifted from the nut and bolt assembly 5E.

Figure 3 shows that after lifting the L-shaped lift body 11 upwards the parallel stepping legs 10A and 10B are actuated, which actuation may be robotic, manual or robot- and/or gravity-assisted, and pivot from the parallelogrammical shape shown in Figure 2 towards the rectangular shape shown in Figure 3 thereby moving, as illustrated by arrow 31, the lower part 7A of the stepping shoe 7 above and in substantial alignment with a central axis of another nut and bolt assembly 5F,

Figure 4 shows how the stepping shoe 7 is subsequently lowered onto and positioned around nut and bolt assembly 5F, whereupon the tool head carrier body 3 is lifted upwards as illustrated by arrow 40 by sliding the tool head carrier body in upward direction by actuating guide rail 12 relative to the vertical tower 11A of the L-shaped lift body 11.

Figure 5 shows how subsequently the stepping legs 10A, 10B are pivoted relative to the stepping shoe 7 such that the stepping legs 10A, 10B pivot from the rectangular shape shown in Figures 3 and 4 into the parallelogrammical shape shown in Figures 1, 2 and 5, thereby moving the L-shaped lift body 11 and the tool head carrier body 3 and tool head 2 in a substantially circumferential direction towards a next to be manipulated nut and bolt assembly 51 as illustrated by arrow 50,

During the substantially circumferential movement illustrated by arrow 50 the concave guide nose 13 is lowered relative to the tower 11A of the lift body 11 as illustrated by arrow 51 to press the guide nose 13 against the outer contour of nut and bolt assembly 5H and to thereby rotate the stepping mechanism 9, the tool head carrier body 3 and the tool head 2 relative to nut and bolt assembly 5F to which the stepping shoe 7 is positioned as illustrated by arrows 52, allowed by a bearing between the lower part 7A and the upper part 7B of the stepping shoe 7.

After the substantially circumferential movement of the stepping mechanism 9, and the carrier body 3 illustrated by arrow 50 and the downward movement of the guide nose 13 illustrated by arrow 51 and subsequently of the tool carrier body 3 and tool head 2 along the guide rail 12 as illustrated by arrow 52 the self- centering machine 1 is brought into the same position as illustrated in Figure 1 , but now with the stepping shoe positioned around nut and bolt assembly 5F and with the tool head 2 positioned around nut and bolt assembly 51, which is subsequently to be manipulated.

Figure 5 also shows that the bearing between the lower part 7A and the upper part 7B of the stepping shoe 7 allows the upper part 7B to rotate or swing relative to the nut and bolt assembly 5F, wherein the alignment toes 7C and 7D, which are spaced at a larger spacing S than the diameter D of the nut and bolt assembly to restrict the rotation to a limited angle as illustrated by arrows 52. The swinging motion illustrated by arrows 52 is induced by the movement of the concave guide nose 13 along the outer contour of the nut and bolt assembly 5H and serves to align the tool head 2 with the next nut and bolt assembly 5I that is to be manipulated without the necessity of using a complex and fragile electronic navigation and steering assembly or sensors, which can break down in a harsh environment such as a wind turbine, and stop the machine from functioning and potentially causing collapse of the to be bolted structure.

Figure 3 shows that also the carrier body 3 may be pivotably connected to the guide rail 12 such that the self-centering machine 1 can swing over a limited angle relative to the central axis 14 of the recently manipulated nut and bolt assembly 5H as illustrated by arrows 30. This swinging motion allows accurate alignment of the stepping shoe 7 with the central axis of the nut and bolt assembly 5F onto which the stepping shoe 7 is lowered during the step illustrated by arrow 31 in Figure 3.

It will be understood that the concave guide nose 13 and the stepping mechanism 9 with a pivotable stepping shoe 7 with alignment toes 7C and 7D and a carrier body 3, which is slidably connected to the guide rail 12 can be easily adjusted to different diameters of the flange assembly 6 and to different mutual distances, or pitches, between adjacent nut and bolt assemblies 5A-5N, by having a stroke in the stepping legs 10A and 10B, large enough to reach the next bolt, and having guide nose 13 wide enough to self-center onto the next nut and bolt assembly on varying diameters and allow sufficient rotation of arrows 52 and 30 to accommodate for varying flange diameters.

The guide nose 13 shown in Figures 1-5 provides a robust mechanical tool head steering, navigation and support assembly that does not require use of wear prone electronic tool head navigation and positioning sensors or any pre- programmed bolt to bolt distances as disclosed in EP3550139.

Figures 6-9 show an alternative embodiment of the guide nose 63 of the self- centering machine 1 according to the invention, wherein the guide nose 63 faces the nut and bolt assembly 65 which is to be manipulated. The guide nose 63 is connected by a pivot 66, which pivot 66 may be replaced by a sliding element, to the carrier body 67 or stepping mechanism 70, which also carries the tool head 68 and which may be connected by a bearing assembly 69 to a stepping mechanism 70, which may be substantially similar to the stepping mechanism 9 shown in Figures 1-5.

Figure 6 is a side view of the concave guide nose 63 when it faces the substantially tubular outer contour 71 of the nut and bolt assembly 65 which is to be manipulated and Figure 7 is a top view of the guide nose 63 in the position shown in Figure 6, and which shows that the concave guide nose 63 has a V- shaped bifurcated concave surface 72 that is shaped such that it guides a central axis 73 of the tool head 68 into axial alignment with a central axis 74 of the nut and bolt assembly 65 which is to be manipulated.

In this way, the central axis 73 of tool head 68 is aligned first with the central axis 74 of the nut and bolt assembly, before lowering the tool head 68 onto the nut and bolt assembly, contrary to what is disclosed in EP3195991. There, the tool is aligned with the nut and bolt assembly by lowering it onto the nut and bolt assembly and thereby initiating a complex pivoting guide mechanism.

Figure 8 is a side view of the guide nose 63 of Figures 6 and 7, after it has pivoted, or slid away from the nut and bolt assembly 65 which is to be manipulated, as illustrated by arrow 75 and after the tool head 68 has been lowered onto and around the nut and bolt assembly 65, which is to be manipulated as illustrated by arrow 76.

Figure 9 is a top view of the guide nose 63 in the position shown in Figure 8. Figures 6-9 also show that the nut and bolt assembly 65 comprises a pair of nuts 65A and 65B with interna! screw threads (not shown) and a cylindrical rod 65C which has a generally cylindrical outer contour 71 into which an external screw thread (not shown) has been machined. The nut and bolt assembly 65 is configured to clamp together a pair of flanges 80A and 80B of a flange assembly 80 that interconnects flanged components 81A and 81 B of a mechanical structure 81 , such as a wing and a central wing carrier hub or two tower sections of a wind turbine.

An advantage of the pivotable guide nose 63 shown in Figures 6-9 is that the stepping mechanism can be more compact, stable and light-weight than the stepping mechanism 9 shown in Figures 1-5 since there is no need to always maintain one nut and bolt assembly between the manipulated nut and bolt assembly 5H and the nut and bolt assembly 5E around which the stepping shoe 7 is positioned. In addition, if nut and bolt assemblies are arranged within oversized bolt holes, they are arranged at slightly different circumferential pitches and at slightly different radial distances from a central axis of the flange, in which case the guide nose 63 aligns the tool head accurately onto the nut and bolt assembly.

Figures 10-14 show an alternative embodiment of a self-centering machine 101 according to the invention, which carries a tool head 102, shown in dashed lines, that can be rotated relative to a tool head carrier body 103 by an electric motor 128 to sequentially tighten a series of circumferentially spaced nut and bolt assemblies 105A-K of a ring shaped flange assembly 106 of a mechanical structure. The nuts of these nut and bolt assemblies 105A-K each comprise a hexagonal upper part that is configured to fit into the hexagonal inner surface of the tool head 102 and a cylindrical lower part 130.

The self-centering machine 101 furthermore comprises a stepping shoe 107A-D with a tubular heel section 107A that is rotatably arranged around a nut and bolt assembly 105D, and an U-shaped toe section 107B comprising a pair of alignment toes 107C and 107D. The tubular heel section 107A of the stepping shoe 107A-D is pivotably connected to two pairs of parallel stepping legs 110A, 110B, 110C and 110D of a stepping mechanism 109, which legs 110A-D are each at an upper end thereof pivotably connected to a horizontal lift arm 111B of an L -shaped lift body 111 , which also comprises a vertical tower 111 A that is slidably connected to a guide rail (not shown) at an outer surface of a tool head carrier body 103 to which the tool head 102 is rotatably connected. The machine 101 is furthermore provided with a lift motor 129 to move the tool head carrier body 103 up and down along the guide rail ( not shown). The lift motor 129 could be an electric, hydraulic or another power source. Figure 10 shows that a bifurcated, for example concave V- or U-shaped, or otherwise funneling guide nose 113 (which is shown in more detail in Figure 14) is pivotably connected to the vertical tower 111A of the L- shaped lift body 111, such that the concave guide nose 113 is pressed by rotating the stepping legs 110A-D by means of a linear actuator 120 against the substantially cylindrical outer contour of the to be manipulated nut and bolt assembly 105G in such a manner that the tool head carrier body 103 and the tool head 102 are brought into axial alignment with a central axis of the to be manipulated nut and bolt assembly 105G.

Figures 11 and 14 show how after the alignment an electromagnetic disk 121 maintains the tool head 102 aligned with the to be manipulated nut and bolt assembly 105G whilst the guide nose 113 is pivoted up and away from the to be manipulated nut and bolt assembly 105G, as illustrated by arrow 131.

Figure 12 shows the self-centering machine 101 of Figures 10, 11 and 14 after the guide nose 121 has been pivoted up into a vertical position to allow lowering of the tool head 102 onto the to be manipulated nut and bolt assembly 105G.

Figure 13 shows the self-centering machine 101 of Figures 10-12 and 14 whilst the tool head carrier body 103 and the tool head 102 are being lowered onto the to be manipulated nut and bolt assembly 105G as illustrated by arrow 132.

Figures 10-14 furthermore show that the substantially parallel stepping legs 110A- D have substantially the same length, and thereby create a transformable stepping mechanism 109 that can be transformed from parallelogrammical shape into a substantially rectangular shape by extending or contracting the linear actuator 120 or another sort of actuation, which may be manual, robotic, robot- assisted and/or gravity assisted.

Figures 10-14 also show that the pair of alignment toes 107C and 107D are mutually spaced at a spacing, which is larger than the diameter of the outer contour of the nut and bolt assemblies 105A-105K such that the pair of alignment toes 107C, 107D restrict the rotation of the stepping mechanism 109, the tool head carrier body 103 and the tool head 102 relative to the nut and bolt assembly 105D around which the tubular heel section 107A of the stepping shoe 107 A-D is releasably positioned, to prevent guide nose 113 missing the next nut and bolt assembly 105G during a stepping motion. In the absence of the alignment toes 107C and 107D, the stepping mechanism 109 and the V-shaped guide nose 113 could over rotate about the stepping shoe 107A and thereby V- shaped guide nose 113 comes out of reach of, and be prevented from self- centering on, the to be manipulated nut and bolt assembly 105G.

Figures 10-14 also show that after accurate alignment of the tool head 102 with the to be manipulated nut and bolt assembly 105G an electromagnetic disk 121 is magnetized and fixed by magnetic forces to the upper end of the previously manipulated nut and bolt assembly 105F, which comprises a ferromagnetic material. The electromagnetic disk 121 is vertically slidably connected to the vertical tower 111A of the L-shaped lift body 111 so that after magnetizing the electromagnetic disk 121 the guide nose 113 can be lifted up and away from the to be manipulated nut and bolt assembly 105G whilst the alignment of the tool head 102 and tool head carrier body 103 with the to be manipulated nut and bolt assembly 105G remains preserved by the magnetized electromagnetic disk 121. The electromagnetic disk 121 , which may be substituted by a permanently magnetized disk, a clamp or another alignment fixation device, thereby blocks forward / backward motion of stepping mechanism 109, as well as it locks rotation of the carrier frame and the stepping mechanism and the tool head carrier body relative to the stepping shoe in order to maintain the aligned position of tool head 102 with the to be manipulated nut and bolt assembly 105G while the guide nose 113 is pivoted up as illustrated by arrow 131 in Figures 11 and 14.

This blocking allows the pivoting up of the guide nose 113 as illustrated by arrow 131 in Figures 11 and14 to a substantially vertical position as illustrated in Figures 12 and 13, thereby giving clearance for the vertical lowering of the tool head 102 and tool head carrier body 103 along the vertical tower 111 A of the L- shaped lift body 111 to engage with the to be manipulated nut and bolt assembly 105G without the need for re-alignment of tool head 102 onto nut and bolt assembly 105G while lowering tool head carrier body 103.This is contrary to the teachings of EP3195991 B1, where the tool head is aligned to the next to be bolted nut and bolt assembly by lowering the tapered tool head onto the next to be bolted nut and bolt assembly. This is also contrary to the teachings of WO2020212323A1 , where the tool head is aligned to the next to be bolted nut and bolt assembly by sliding it along a sliding arm with a curvature matching the curvature of the flange assembly 106. it is observed that the bolts of the nut and bolt assemblies 105 need to be inserted into bolt holes that have a larger diameter than the outer diameter of the bolts in order to allow smooth insertion of the bolts into these bolt holes penetrating the flange assembly 106. Due to this necessary oversizing of the bolt holes relative to the bolts, adjacent nut and bolt assemblies 105 may be spaced at slightly different mutual spacings, wherein the difference in spacing is associated with the oversize of the bolt holes relative to the outer diameter of the bolts and additional manufacturing tolerances. In order to press the V-shaped guide nose 113 against the next nut and bolt assembly 105G, the linear actuator 120 optionally can have a pre-programmed maximum stroke, which is slightly larger than the maximum spacing between adjacent nut and bolt assemblies, or multiple times this spacing in case of skipping one or multiple nut and bolt assemblies during said one step. In such case the V-shaped guide nose 113 may be pressed against and be aligned with the to be manipulated nut and bolt assembly 105G, and thereby has mechanically aligned tool head 102 with the to be manipulated nut and bolt assembly 105G before the linear actuator has reached its pre-programmed maximum stroke. Once the V-shaped guide nose 113 is pressed against the to be manipulated nut and bolt assembly 105G and thereby mechanically aligns tool head 102 with nut and bolt assembly 105G, an electric motor, which actuates the linear actuator 120 will generate a peak current since its motion is blocked by the aligned V~guide 113. This peak current may act as a signal to the operating system that mechanical alignment of tool head 102 with nut and bolt assembly 105G is completed and that the motor is to be deactivated. This is contrary to the teachings of EP2607685B1 where a positioning sensor provides feedback information to actively align a tool head with a to be manipulated nut and bolt assembly.

Optionally or alternatively a spring (not shown) can be mounted at an end of the linear actuator 120 such that the linear actuator 120 is during each step of the stepping mechanism 109 extended by a pre-programmed maximum stroke and the spring is compressed once the guide nose 113 has aligned itself to a nut and bolt assembly 105 and the guide nose 113 is not moved further during the remaining stroke of the linear actuator 120 due to the progressing compression of the spring. Therefore alignment of tool head 102 with the to be manipulated nut and bolt assembly 105G happens mechanically and without any feedback signal to the operating system. In the light of the foregoing it will be understood that the stepping motion of the stepping mechanism 109 may be interrupted and locked in various ways after alignment of the tool head 102 with the next to be manipulated nut and bolt assembly 105G by the guide nose 113, which thereby preserves, together with locking of the rotation of stepping shoe 107 A, the aligned position of tool head 102 with the next to be manipulated nut and bolt assembly 105 after hinging the guide nose 113 up as illustrated in Figures 11-13 by arrow 131.

The tool head carrier body 103 shown in Figures 10-14 may be provided with a bolt stretching device similar to the bolt stretching device shown in Figures 1-9, or a bolt torquing device. When the bolt 105G is stretched by this bolt stretching device the tool head carrier body 103 will exert a significant compression force on the flange assembly 106 which may compress the flange assembly 106 such that the next to be manipulated nut and bolt assembly 105H may be lifted from the flange assembly 106 and thereby be inadvertently loosened. To avoid such inadvertent loosening the tool head carrier body 103 carries an impact wrench carrier body 123 that carries an impact wrench tool head 122, which is actuated to slightly tighten the next to be manipulated nut and bolt assembly 105H to avoid its loosening whilst the bolt stretching device is actuated to stretch the to be manipulated nut and bolt assembly 105G. The to be bolted nut and bolt assembly needs to be tightened slightly before engaging tool head 102, to avoid the risk of wrong or no engagement between tool head 102 and nut and bolt assembly 105G due to uncontrolled nut and bolt assembly motions or rotations while engaging the tool head 102 with the nut and bolt assembly 105.

It is observed that in the embodiment shown in Figures 11-14 all nut and bolt assemblies 105 are initially slightly tightened after insertion into the bolt holes, so that the bolt tightening involves a three step process, wherein:

- the first step takes place when the nut and bolt assemblies 105 are inserted into the bolt holes,

- the second step involves the slight further tightening of each next to be tightened nut and bolt assembly 105H by the impact wrench 122 and

- the third step involves the tightening of each to be bolted nut and bolt assembly 105G to its final predetermined tightening force by tool head 102. In order to save time, the second and third step of the above described three step process can be executed simultaneously by self-centering machine 101.

It is also observed that In the embodiment shown in Figures 11-14 the stepping mechanism 109 may iteratively move the L-shaped lift body 111 back and forward along the circumference of the flange assembly while pivoting the guide nose 113 down to allow the guide nose 113 to be lowered down between adjacent nut and bolt assemblies 105G and 105H without hitting the upper ends of these adjacent nut and bolt assemblies 105G and 105H. A gap 125 at the foot of the pivotable guide nose 113 further reduces the risk of inadvertent contact between the foot of the guide nose 113 and the adjacent nut and bolt assemblies 105G and 105H during the stepping motion.

The V-shaped guide nose 113 can be equipped with rollers on its bifurcated concave surface in order to lower friction between the V-shaped guide nose 113 and the nut and bolt assembly when the V-shaped guide nose 113 is pressed against the to be manipulated nut and bolt assembly 105G for alignment of tool head 102 therewith.

The tool head 102 may have different configurations, where in one configuration it is configured to engage with the thread of the bolt of to be manipulated nut and bolt assembly 105G, whereas in another configuration, it is configured to engage with the nut of the to be bolted nut and bolt assembly 105G.

It will be understood that the self-centering machine 101 shown in Figures 10-14 provides a light weight and user friendly bolt manipulation device that is able to accurately tighten or otherwise manipulate a series of nut and bolt assemblies 105 that are arranged with small mutual spacings around the circumference of a flange assembly 106 of a mechanical structure.

It is also observed that the stepping motion of the stepping mechanism 109 shown in Figures 10-14 is substantially similar to the stepping motion of the stepping mechanisms shown in Figures 1-9.

Figures 11-13 also show that the L-shaped lift body 111 may comprise two lift body parts 111A and 111 B, which may hinge and rotate with respect to each other about axis 126, up to a maximum hinge angle 127 of at most 15 degrees, wherein the hinging motion may also be blocked by a brake (not shown), Such hinging about axis 126 is desired to allow stepping shoe 107A, during each step of the stepping mechanism 109, to align with a next nut and bolt assembly 105D on the circumference of flange assembly 106, Once stepping shoe 107A is aligned with and clamped around a nut and bolt assembly 105D and tool head carrier body 103 and tool head 102 are lifted upwards, rotation 127 is reversed by a straightening device, such as a torsion spring (not shown) which brings lift body parts 111A and 111 B in parallel alignment with each other again.

Thereafter, rotation about axis 126 is blocked by the brake(not shown) such that lift body part 111 A and guide nose 113 are aligned and parallel with the stepping mechanism 100. Prior to lowering the stepping shoe 107A to a nut and bolt assembly 105, the brake is released to reallow rotation of lift body parts 111A and 111 B relative to each other about axis 126 such that stepping shoe 107A can align itself with a next nut and bolt assembly 105.

The stepping motion of the stepping mechanism 109 is preferably executed while tool head 102 is manipulating a nut and bolt assembly to save time of moving to the next nut and bolt assembly 105.

A prototype of the self-centering machine 101 shown in Figures 10-14 was built and tested. The machine 101 had a weight of about 40 Kg and could be divided into two parts which each had a weight of about 20Kg. These parts were carried by a person to a flange that was provided with hand tightened nut and bolt assemblies 105. This person assembled these two parts on site to the selfcentering machine 101 shown in Figures 10-14, which was configured to be activated and operated in the manner shown in Figures 10-14.

Although the invention has been explained in more detail on the basis of only a few execution examples, it is clear that the invention is in no way limited to these examples.

On the contrary, many variations and appearances are still possible for an average craftsman within the framework of the invention. For example, the implementation examples are based on a linear step mechanism, but a curved step mechanism can also be used for this purpose that follows the contour of the flange connection. Also, bolt pre-tension measuring, inspection, manipulation and other tools other than those mentioned can similarly be self-centered with the nut and bolt assembly, including intended bolted connections and cavities. When no nut and bolt assembly is present, the stepping shoe will then clamp or position itself inside a bolt hole. The stepping shoe may also be configured such that it can be adjusted to different sizes of nut and bolt assemblies.

The concave guide nose 13 shown in Figures 1-4 and the guide noses 63 and 113 shown in Figures 6-14 may also be configured to engage a nut of one of the nut and bolt assemblies. In such case the guide nose 13, 63, 113 may have a concave surface 72 having a generally circular or otherwise rounded shape.

The guide nose 13, 63, 113 may also be magnetic and/or be shaped and/or be provided with a surface with a high friction coefficient such that it prevents the bolt or stud from rotating when the nut is manipulated, thereby preventing inadequate manipulation of the nut and bolt assembly. it is also observed that the guide nose 13, 63,113 may also be used to self- center a tool head of a robotic or manually operated machine where the tool head is moved manually and/or by a wheel supported carriage along the circumference of a flange.

Furthermore, it is observed that features and embodiments shown in the accompanying drawings and/or described in this specification, abstract and claims may be combined in several ways.