Method for detecting the position of at least one bolt end of at least one bolt

Abstract

A method for detecting a position of a bolt end (1) of a bolt (2) disposed in a flange connection (3) by means of a camera (5) comprises the steps of defining a first bolt end level (6) at a first distance (d1) from the flange connection (3), defining a first tolerance range (t1) surrounding the first bolt end level (6), detecting the position of the bolt end (1), determining whether the position of the bolt end (1) is within the first tolerance range (t1), stretching the bolt (2), tightening a locking nut (4) threaded onto the bolt (2), defining a second bolt end level (7) at a second distance (d2) from the flange connection (3) and a second tolerance range (t2), and determining whether the position of the bolt end (1) is within the second tolerance range (t2).

Description

[Technical field]

[0001] The present invention relates to a method for detecting the position of at least one bolt end of at least one bolt of a series of bolts arranged in a linear or curved flange connection by means of a camera movable along the flange connection, the bolt end of the bolt arranged in the flange connection protruding beyond the flange connection. Furthermore, the present invention relates to a tightening device for tightening a series of nuts pre-threaded on the bolts, the tightening device comprising a camera and a computing device connected to the camera, the bolts being arranged in a linear or curved flange connection. [Background technology]

[0002] In the field of modern energy production, wind turbines play an essential role in providing renewable, sustainable and clean energy for the energy market. A wind turbine has a tower, on which a rotor is mounted, which is connected to a generator. The tower can reach heights of 100 meters, 150 meters or even more, depending on the specific requirements arising from the location of the wind turbine, among others. The tower consists of several pipe segments, for example 20 meters or 30 meters long. These segments are connected by circular flange connections on both sides of the pipe segments. During the construction of the wind turbine on site, the pipe segments fit together and are connected by joint circular flange joints, with bolts and nuts. A large number of large bolts, typically several hundred, are necessary to establish the required stiffness and strength of the connections. To achieve the appropriate defined stiffness and strength in the joints, all bolts need to be bolted with a given preload or torque and according to a specific bolt tightening pattern.

[0003] Previously, this action was done manually using a torque wrench or similar tool. The construction of a wind turbine tower was therefore very labor intensive. To speed up the construction, robots were developed that automatically perform the tightening of bolts in sequence. The document EP2607685A1 discloses a robot for bolting a series of nuts and bolts in a circular flange joint of a wind turbine. The robot has at least two wheels, a drive that transports the robot along the series of nuts and bolts, and a tool for bolting the nuts and bolts with a predetermined torque. The drive used in this robot is a belt drive that interacts with the side wall of the tower to drive itself forward. To achieve sufficient friction with the side wall, several electromagnets are provided to press the belt drive against the side wall. Using the side wall as a means for driving the robot forward is beneficial, since on the side wall it cannot hit obstructions such as metal shavings, other tools, or further obstacles.

[0004] However, for such a robot to achieve the desired functionality of automatically torqueing the various bolts of a flange joint to a particular torque, and therefore achieving a predetermined clamping force within the flange joint, the robot needs to automatically grasp and manipulate the various bolts of the bolted joint. The bolts therefore need to be pre-positioned at specific locations within the flange joint. In particular, the upper bolt ends of the various bolts need to be aligned within a particular tolerance range at a level above the flange joint for the robot to function properly.

[0005] This bolt alignment has been previously checked manually, for example, by manually measuring the height of the bolt that protrudes above the flange connection. However, this process is very labor intensive and time consuming, as well as prone to measurement errors. For example, if one bolt is not properly positioned, the process of robotically tightening the bolts may not perform adequately or at all, requiring additional user intervention in the bolt tightening process. Additionally, for quality control purposes, it is desirable to demonstrate the various steps of the tightening process, including proper bolt alignment.

[0006] Furthermore, to check, and preferably also verify, the bolt tightening process according to specifications, it is necessary to determine whether the bolts have been properly tightened to achieve a predetermined amount of clamping force. Simple measurements of the torque values ​​applied to each bolt during tightening are prone to errors due to over- or under-lubrication of the bolt or nut threads, and can also be affected by dirt and contamination of the bolt threads, as well as dimensional deviations of the threads. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] EP2607685A1 Summary of the Invention

[0008] The technical problem of the present invention is therefore to provide a method for detecting the position of at least one bolt end of at least one bolt of a series of bolts arranged in a straight or curved flange connection by a camera movable along the flange connection, the bolt end protruding beyond the flange connection, which method makes it possible to automatically detect the correct placement of the bolt to achieve the correct clamping force for tightening the bolt and to determine whether the bolt has been correctly tightened.

[0009] This problem is solved by providing a method according to the subject matter of claim 1 and a tightening device for tightening a series of nuts pre-threaded onto a bolt according to the subject matter of claim 5.

[0010] A method for detecting the position of at least one bolt end of at least one bolt of a series of bolts disposed within a linear or curved flange connection by a camera movable along the flange connection according to the present invention, the bolt end of the bolt disposed within the flange connection protruding beyond the flange connection, comprising a series of steps including defining a first bolt end level at a first distance from the flange connection and defining a first tolerance range surrounding the first bolt end level.

[0011] Furthermore, the method according to the invention comprises the steps of detecting the position of the bolt end of at least one bolt arranged in the flange connection by means of a camera and determining whether the position of the bolt end of the at least one bolt is within a first tolerance range surrounding a first bolt end level. By carrying out the method according to the invention, the position of the at least one bolt in the flange connection is verified using the camera. By comparing the position of the bolt end of the bolt with a predefined first bolt end level, it is checked whether the bolt protrudes a predefined distance on the flange connection. An advantage of the method according to the invention is that the position of the bolt is verified and can be stored for quality control purposes. Furthermore, it is therefore ensured that the bolt tightening device, when operated manually or automatically, can grip the bolt and perform the desired bolt pulling operation after the position of the bolt has been verified by the method according to the invention.

[0012] According to a preferred embodiment of the method according to the invention, a camera is moved along the flange connection, a position of a bolt end of each bolt of the flange connection is detected by the camera, and it is determined for each bolt of the flange connection whether the position of the bolt end of each bolt is within a first tolerance range surrounding a first bolt end level, thereby allowing the bolts arranged in the flange connection to be tightened in succession and quickly, for example by using a bolt tightening robot.

[0013] The method according to the invention also includes the steps of stretching at least one bolt of the flange connection by applying a force to the bolt in the bolt's axial direction, tightening a locking nut threaded onto the bolt while applying the force to the bolt, and releasing the force on the bolt. This constitutes a bolt tightening procedure utilizing the bolt stretching process. To verify the result of the bolt tightening procedure, the method according to the invention also includes the steps of defining a second bolt end level at a second distance from the flange connection, the second distance being greater than the first distance, tightening the locking nut and releasing the force on the bolt, and detecting the position of the bolt end of the bolt by means of a camera. Furthermore, the method includes the step of determining whether the position of the bolt end is within a second tolerance range surrounding the second bolt end level. By verifying the result of the bolt stretching process in this manner, a reliable documentation of the bolt stretching and tightening procedure can be produced.

[0014] Preferably, each bolt of the flange connection is stretched by applying a force to each bolt in the bolt's axial direction. This is preferably followed by the steps of tightening a lock nut threaded onto each bolt while applying force to each bolt, and releasing the force on each bolt. Thus, each bolt of the flange connection is tightened to ensure a stiff connection and an even distribution of the clamping force along the flange connection.

[0015] According to a preferred embodiment of the method according to the invention, a camera is moved along the flange connection and whether the position of each of the bolt ends of the bolts is within a second tolerance range surrounding a second bolt end level is determined by the camera after each bolt has been stretched, the locking nut has been tightened and the force acting on the bolt has been released. Thus, the stretching and tightening process can be verified using the method according to the invention for each of the bolts of the flange connection.

[0016] The technical problem of the present invention is also solved by a tightening device for tightening a series of nuts pre-threaded on a bolt, which is placed in a straight or curved flange connection, comprising a camera and a computing unit connected to said camera, said computing unit being adapted to execute the method according to the present invention.

[0017] According to a preferred embodiment of the tightening device according to the invention, the tightening device comprises a propulsion unit for moving the tightening device along the flange connection, which enables the tightening device to automatically verify the positioning of each of the bolts before the tightening operation and to verify the result of the tightening operation for each of the bolts.

[0018] The tightening device also preferably has a lock nut tightening unit for tightening a lock nut screwed onto the bolt, and two propulsion units arranged essentially opposite the lock nut tightening unit.

[0019] The method and clamping device according to the present invention, as well as preferred and alternative embodiments, are described below with reference to the figures. [Brief description of the drawings]

[0020] [Figure 1] Shown is a series of three bolts with locking nuts, the bolts having bolt ends positioned at different heights. [Figure 2a] Shown is a bolt with a locking nut. [Figure 2b] FIG. 1b shows the bolt of FIG. 1a after it has been stretched and the lock nut tightened. [Diagram 3] 1 shows a perspective view of a tightening device according to the invention; [Figure 4] 4 shows a cross-sectional view of the clamping device according to FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] A method for detecting the position of at least one bolt end 1 of at least one bolt 2 of a series of bolts 2 arranged in a straight or curved flange connection 3 is described below using figures 1, 2a and 2b. Three bolts 2 depicted in figure 1 each have a bolt end 1 and a locking nut 4 screwed onto each bolt 2. The bolts 2 are arranged in a straight or curved flange connection 3, which is not shown in figure 1 but can be seen in figure 3. The locking nut 4 in figure 1 is not tightened and the bolt ends 1 are placed at different heights, which results in different lengths of threads protruding onto the locking nut 4 and thus onto the flange connection 3 against which the locking nut 4 abuts. The method according to the invention makes use of a camera 5, which is movable along the flange connection 3 and is not shown in figure 1 but can be seen in figure 3. The method according to the invention comprises the steps of defining a first bolt end level 6 at a first distance d1 from the flange connection 3 and defining a first tolerance range t1 surrounding the first bolt end level 6. The first bolt end level 6 and the first tolerance range t1 surrounding the first bolt end reference position 6 are shown in FIG. 1, as is the first distance d1. As can be seen in FIG. 1, the bolt end 1 of the middle bolt 2 is correctly positioned within the tolerance range t1 surrounding the first bolt end level 6, while the position of the bolt end 1 of the left bolt 2 is too low and the position of the bolt end 1 of the right bolt 2 is too high. The position of the bolt end 1 of at least one bolt 2 arranged at the flange connection 3 is detected by the method according to the invention by a camera. Finally, it is determined whether the position of the bolt end 1 of the at least one bolt 2 is within the first tolerance range t1 surrounding the first bolt end level 6. In FIG. 1, only the middle bolt 2 is correctly positioned. By using this method it is possible to provide an easy and simple automatic verification of the position of the bolt 3. The images generated by the camera 5, or the correct or incorrect positioning of the bolt 2, can for example be stored in a memory unit connected to the camera 5.The analysis and determination of whether the position of the bolt end 1 of at least one bolt 2 is within a first tolerance range t1 surrounding a first bolt end level 6 is performed by a computing device connected to the camera 5, which may also have a memory unit, by using image analysis methods such as contrast analysis. Data about the correct positioning of the bolts 2 can be stored, for example, for quality control purposes. Also, if the method according to the invention leads to a determination that at least one bolt 2 in the flange connection 3 is incorrectly positioned, operations can be performed to correct the positioning of the bolts 2. Preferably, in the method according to the invention, the camera 5 is moved along the flange connection 3, the position of the bolt end 1 of each bolt 2 of the flange connection 3 is detected by the camera 5, and it is determined for each bolt 2 of the flange connection 3 whether the position of the bolt end 1 of each bolt 2 is within a first tolerance range t1 surrounding a first bolt end level 6. An advantage of the method according to the invention is that a laborious manual measurement of the length of the bolts 2 protruding from the flange connection 3 is not necessary.

[0022] After the position of the bolt 2 has been verified as described above, the method of the invention comprises the steps of stretching at least one bolt 2 of the flange connection 3 by applying a force to the bolt 2 in the axial direction of the bolt 2, and tightening a locking nut 4 screwed onto the bolt 2 while applying the force to the bolt 2. Finally, the method of the invention comprises the step of releasing the force acting on the bolt 2. Figure 2a shows the bolt 2 with its locking nut 4 before the stretching and tightening process as described above. Figure 2b shows the bolt 2 after the locking nut 4 has been tightened and the force acting on the bolt 2 has been released. This allows a clearly defined torque, by which the locking nut 4 is fixed and the clamping force acting on the flange connection 3 is precisely defined.

[0023] The method according to the invention also comprises a step of defining a second bolt end level 7 at a second distance d2 from the flange connection 3, the second distance d2 being greater than the first distance d1 and defining a second tolerance range t2 surrounding the second bolt end level 7. After stretching the bolt 2, the locking nut 4 is tightened, the force acting on the bolt 2 is released and the position of the bolt end 1 of the bolt 2 is detected by the camera 5. Typically, the difference between the first distance d1 and the second distance d2 is about 1 mm, but it usually depends on the material and the dimensions of the bolt. Finally, according to the invention, it is determined whether the position of the bolt end 1 is within a second tolerance range t2 surrounding the second bolt end level 7. In FIG. 2b it can be seen that the bolt end 1 of the bolt 2 is within the second tolerance range t2. As mentioned above with regard to the positioning of the bolt 2 before the stretching and tightening process, the final result of the stretching and tightening process can be recorded and verified using the method according to the invention, preferably by using a computing device connected to the camera 5 programmed to carry out the method according to the invention. The result can be recorded in a memory device connected to or part of the computing device. Typically, the camera 5 records an image with a resolution of 4000x4000 pixels and a picture height of about 15 cm. One pixel corresponds to 0.0375 mm, which may mean that a stretching of the bolt of 1 mm corresponds to 26-27 pixels.

[0024] Preferably, each bolt 2 of the flange connection 3 is stretched by applying a force to each bolt 2 in the axial direction of the bolt 2, and before releasing the force on each bolt 2, the locking nuts 4 screwed onto each bolt 2 are tightened while applying a force to each bolt 2. This ensures that all locking nuts 4 of the bolts 2 of the flange connection 3 are tightened with the correct torque value. Furthermore, according to a preferred embodiment of the method according to the invention, the camera 5 is moved along the flange connection 3 and it is determined by the camera 5 whether the position of the respective bolt end 1 of the bolts 2 is within a second tolerance range t2 surrounding a second bolt end level 7 after each bolt 2 has been stretched, the locking nuts 4 tightened and the force acting on the bolts 2 released.

[0025] A tightening device 10 according to the invention for tightening a series of locking nuts 4 pre-threaded on bolts 2, the bolts being arranged on a straight or curved flange connection 3, is shown in Figs. 3 and 4 and comprises a camera 5 and a computing device connected to the camera 5, the computing device being arranged to carry out the method according to the invention. As described with respect to the method, the computing device may comprise or be connected to a memory unit. The tightening device 10 according to the invention may also comprise, according to a preferred embodiment, a propulsion unit 11 for moving the tightening device 10 along the flange connection 3. This allows the tightening device 10 to automatically verify the position of each of the bolts 2 before the tightening operation and to verify the result of the tightening operation for each of the bolts 2. Preferably, the tightening device 10 according to the invention also comprises a locking nut tightening unit 12 for tightening the locking nuts 4 screwed on the bolts 2 and two propulsion units 11 arranged essentially opposite the locking nut tightening unit 12. Furthermore, the tightening device 10 may also comprise a bolt tensioning unit 13 for exerting a force on the bolt 2 in the axial direction of the bolt 2 .

Claims

1. A method for detecting the position of at least one bolt end (1) of at least one bolt (2) of a series of bolts (2) arranged in a linear or curved flange connection (3) by means of a camera (5) movable along the flange connection (3), the bolt end (1) of the bolt (2) arranged in the flange connection (3) protruding beyond the flange connection (3), the method comprising: A first distance (d １ ) defining a first bolt end level (6); A first tolerance range (t １ ) detecting the position of the bolt end (1) of the at least one bolt (2) placed in the flange connection (3) by means of the camera (5); The position of the bolt end (1) of the at least one bolt (2) is within the first tolerance range (t １ ) ; and stretching at least one bolt (2) of the flange connection (3) by applying a force to the bolt (2) in an axial direction of the bolt (2); tightening a lock nut (4) threaded onto the bolt (2) while applying the force to the bolt (2); Releasing the force on the bolt (2); A second distance (d ２ ), defining a second bolt end level (7) at said second distance (d ２ ) is the first distance (d １ ) longer than the step, A second tolerance range (t ２ ) detecting the position of the bolt end (1) of the bolt (2) by means of the camera (5) after the steps of stretching the bolt (2), tightening the lock nut (4) and releasing the force on the bolt (2); The position of the bolt end (1) is within the second tolerance range (t ２ ) determining whether A method comprising:

2. The camera (5) is moved along the flange connection (3), and the position of the bolt end (1) of each bolt (2) of the flange connection (3) is detected by the camera (5), and for each bolt (2) of the flange connection (3), the position of the bolt end (1) of each bolt (2) is detected within the tolerance range (t １ 2. The method of claim 1, wherein it is determined whether the first vertex is within the first vertex.

3. stretching each bolt (2) of the flange connection (3) by applying a force to each bolt (2) in an axial direction of the bolt (2); tightening a lock nut (4) threaded onto each of the bolts (2) while applying said force to each of the bolts (2); Releasing the force on each of the bolts (2); The method of claim 1 , comprising:

4. After each of the bolts (2) is stretched, the lock nuts (4) are tightened, and the force acting on the bolts (2) is released, the camera (5) is moved along the flange connection (3) and the position of the bolt end (1) of each of the bolts (2) is measured within the second tolerance range (t ２ 4. The method of claim 3, wherein the camera (5) determines whether the object is within the predetermined range.

5. A tightening device (10) for tightening a series of lock nuts (4) pre-threaded onto a plurality of bolts (2) arranged in a linear or curved flange connection (3), the tightening device having a camera (5) and a computing device connected to the camera (5), A tightening device (10), characterized in that the computing unit (5) is adapted to carry out the method according to any one of claims 1 to 4.

6. The clamping device (10) according to claim 5, characterized in that the clamping device (10) comprises a propulsion unit (11) for moving the clamping device (10) along the flange connection (3).

7. 6. The tightening device (10) according to claim 5, characterized in that the tightening device (10) comprises a lock nut tightening unit (12) for tightening the lock nut (4) screwed onto the bolt (2) and two propulsion units (11) arranged essentially on opposite sides of the lock nut tightening unit (12) for moving the tightening device (10) along the flange connection (3).

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