Device and method for cleaning winding wires of driving roller

Abstract

The embodiment of the invention provides a device and a method for cleaning winding wires of a driving roller, and relates to the technical field of carbon fiber production. The device for cleaning the winding wires of the driving roller comprises a cutting unit which comprises a pulse optical fiber laser and a driving part, and the driving part is used for driving the pulse optical fiber laser to move; the detection unit comprises a visual sensor and a distance measuring sensor, the visual sensor is used for acquiring a driving roller surface image signal, and the distance measuring sensor is used for acquiring a distance signal; the control unit is used for obtaining the wire wrapping width and the wire wrapping thickness according to the surface image signal and the distance signal, and adjusting the output power and the pulse power of the pulse fiber laser; and the waste wire cleaning unit is arranged on the cutting unit and used for cleaning the cut waste wires on the driving roller. According to the device and method for cleaning the winding wires of the driving roller, the problems that at present, the winding wire cleaning efficiency is low, the safety risk is high, and cleaning is not thorough can be solved.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber production technology, and more specifically, to an apparatus and method for cleaning the entanglement of drive rollers. Background Technology

[0002] In the production of carbon fiber precursor, multiple filament bundles are wound in an S-shape around a series of high-speed rotating drive rollers for processes such as drawing and oiling. Due to fluctuations in filament tension and vibrations in the fiber-reducing equipment, the precursor fibers are prone to tangling on the drive rollers, forming entanglement. If entanglement is not addressed promptly, it will rapidly worsen, leading to filament breakage, equipment downtime, and even damage to the surface of the expensive drive rollers, severely impacting production efficiency and product quality.

[0003] Currently, cleaning tangled wires mainly relies on manual operation. Workers need to cut the tangled wire bundles or stop the machine partially before manually cleaning them with special tools. Current methods of cleaning tangled wires suffer from low efficiency, high safety risks, incomplete cleaning, and inability to adapt to high-speed production. Summary of the Invention

[0004] The present invention aims to provide an apparatus and method for cleaning tangled wire on a drive roller, which can improve the current problems of low efficiency, high safety risks, and incomplete cleaning of tangled wire.

[0005] The embodiments of the present invention can be implemented as follows: In a first aspect, the present invention provides an apparatus for cleaning tangled wire on a drive roller, comprising: The cutting unit includes a pulsed fiber laser and a driving component, the driving component being used to drive the pulsed fiber laser to move in the horizontal and vertical directions, so as to drive the pulsed fiber laser closer to or away from the driving roller. The detection unit includes a vision sensor and a distance sensor. The vision sensor is used to acquire image signals of the surface of the drive roller, and the distance sensor is used to acquire distance signals between itself and the drive roller. The control unit is electrically connected to the cutting unit and the detection unit. The control unit is used to obtain the winding width and winding thickness based on the surface image signal and the distance signal, and to adjust the output power and pulse power of the pulsed fiber laser based on the winding width and winding thickness. A waste filament cleaning unit is provided in the cutting unit for cleaning the waste filaments cut on the drive roller.

[0006] In an optional embodiment, the pulsed fiber laser includes a galvanometer scanning system electrically connected to the control unit, which controls the galvanometer scanning system to guide the laser to scan and cut on the surface of the drive roller.

[0007] In an optional embodiment, the drive includes a first cyclic ejection mechanism, with the pulsed fiber laser disposed at the end of the first cyclic ejection mechanism.

[0008] In an optional embodiment, the detection unit further includes an alarm, which is electrically connected to the control unit, and the control unit controls the alarm to be activated when there is wire winding on the drive roller.

[0009] In an optional embodiment, the detection unit further includes a human body sensor, which is disposed on the pulsed fiber laser and electrically connected to the control unit. The human body sensor is used to identify a human body and transmit the human body signal to the control unit. The control unit is used to control the pulsed fiber laser to turn off when it receives the human body signal.

[0010] In an optional embodiment, the waste filament cleaning unit includes a first cleaning component and a second cleaning component, both of which are connected to the cutting unit. The first cleaning component is located above the drive roller for cleaning the upper side of the drive roller, and the second cleaning component is located below the drive roller for cleaning the lower side of the drive roller.

[0011] In an optional embodiment, the first cleaning component includes a rotary joint, a first circulating ejection mechanism, a first telescopic mechanism, and a first scraper. The first circulating ejection mechanism is connected to the cutting unit via the rotary joint. The first telescopic mechanism is disposed on the first circulating ejection mechanism and extends vertically downward. The first scraper is disposed at the bottom end of the first telescopic mechanism.

[0012] In an optional embodiment, the second cleaning component includes a second circulating ejection mechanism, a second telescopic mechanism, and a second scraper. The second circulating ejection mechanism is disposed on the cutting unit, the second telescopic mechanism extends vertically upward, and the second scraper is disposed at the top of the second telescopic mechanism.

[0013] In an optional embodiment, the waste filament cleaning unit further includes a collection box disposed below the second cleaning assembly for collecting tangled filaments that fall from the drive roller.

[0014] Secondly, the present invention provides a method for cleaning tangled wire on a drive roller, comprising the apparatus for cleaning tangled wire on a drive roller as described in any of the foregoing embodiments, including the following steps: A vision sensor monitors the drive roller in real time. When the control unit detects the tangled wire on the drive roller, the distance sensor is activated. The control unit uses a preset algorithm model to control the pulsed fiber laser to scan and cut the winding wire on the drive roller based on the winding thickness signal output by the ranging sensor and the parameter width signal output by the vision sensor. The control unit resets the cutting unit and the detection unit after the wire winding and cutting are completed.

[0015] The beneficial effects of the apparatus and method for cleaning the tangled wire on the drive roller provided in the embodiments of the present invention include: The drive roller is detected in real time by vision sensors and distance sensors. When there is tangled wire on the drive roller, the control unit controls the cutting unit to make precise cuts, realizing the automation of detection and cutting. No machine stoppage is required during high-speed production, improving cleaning efficiency and production efficiency. By using distance and vision sensors to detect the winding width and thickness, precise control of cutting depth and width is achieved, avoiding damage to the drive roller and adjacent normal filament bundles, resulting in low safety risk and good cleaning effect. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the device for cleaning the tangled wire on the drive roller provided in this embodiment.

[0018] Icons: 100-Cutting unit; 110-Pulsed fiber laser; 120-Driver; 130-Galvanometer scanning system; 140-Human body sensor; 200-Detection unit; 210-Vision sensor; 220-Distance sensor; 230-Alarm; 300-Control unit; 400-Waste filament cleaning unit; 410-First cleaning assembly; 411-Rotary joint; 412-First circulating ejection mechanism; 413-First telescopic mechanism; 414-First scraper; 420-Second cleaning assembly; 421-Second circulating ejection mechanism; 422-Second telescopic mechanism; 423-Second scraper; 430-Collection box. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0021] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0022] In the description of this invention, it should be noted that if terms such as "upper," "lower," "inner," or "outer" are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed, they are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0023] Furthermore, the terms "first" and "second" are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0024] It should be noted that, where there is no conflict, the features in the embodiments of the present invention can be combined with each other.

[0025] In the production of carbon fiber precursor, multiple filament bundles are wound in an S-shape around a series of high-speed rotating drive rollers (such as on a 5-roll mill) for processes such as drawing and oiling. Due to factors such as filament tension fluctuations, fuzz, and equipment vibration, the precursor fibers are highly susceptible to tangling on the drive rollers, forming entanglement. If entanglement is not addressed promptly, it will rapidly worsen, leading to filament breakage, equipment downtime, and even damage to the expensive drive roller surface, severely impacting production efficiency and product quality.

[0026] Currently, cleaning tangled wires mainly relies on manual operation. Workers need to cut the tangled wire bundles or stop the machine partially before manually cleaning them using specialized tools. Current methods of cleaning tangled wires suffer from low efficiency, high safety risks, incomplete cleaning, and inability to adapt to high-speed production. For modern production lines with linear speeds as high as 300-400 meters per minute, the window for manual intervention is extremely short, making online processing virtually impossible.

[0027] To address the aforementioned problems, this invention provides an apparatus and method for cleaning tangled wire on a drive roller, thereby improving upon the current methods which suffer from low efficiency, high safety risks, incomplete cleaning, and inability to adapt to high-speed production. The following detailed description, through embodiments and in conjunction with accompanying drawings, outlines the overall structure, working principle, and technical effects of the apparatus for cleaning tangled wire on a drive roller, as well as the detailed steps, implementation principles, and technical effects of the corresponding method.

[0028] Please refer to Figure 1 Taking a typical five-roller carbon fiber production line as an example, multiple drive rollers are arranged in an S-shape, and the fiber bundle passes through the multiple drive rollers at a speed of 350 meters per minute. This invention provides a device for cleaning the entanglement of the drive rollers. The device is installed near the drive rollers via a bracket. Specifically, the device includes a cutting unit 100, a detection unit 200, and a control unit 300. The cutting unit 100 includes a pulsed fiber laser 110 and a driving component 120. The driving component 120 drives the pulsed fiber laser 110 to move horizontally and vertically, thereby moving the pulsed fiber laser 110 closer to or away from the drive rollers. The detection unit 200 includes a vision sensor 210 and a distance sensor 220. The vision sensor 210 continuously monitors and captures images of the drive roller surface, and the distance sensor 220 detects the distance between itself and the drive roller and acquires the distance signal. The control unit 300 is electrically connected to both the cutting unit 100 and the detection unit 200. The vision sensor 210 transmits the acquired surface image signal of the drive roller to the control unit 300, and the distance sensor 220 transmits the distance signal to the control unit 300. Based on the surface image signal and the distance signal, the control unit 300 obtains the winding width and winding thickness through algorithm analysis, and controls the output power and pulse power of the pulsed fiber laser 110 according to the winding width and winding thickness.

[0029] The working process of the device for cleaning the tangled wire on the drive roller provided by this invention is as follows: The vision sensor 210 performs normal detection and imaging on the surface of the drive roller. The image signal is transmitted to the control unit 300 for algorithm analysis. When the raw filament breaks and wraps around the drive roller, forming tangled wire, the vision sensor 210 identifies abnormal image features (such as color and texture changes). The control unit 300 acquires the tangled wire width signal and controls the ranging sensor 220 to start scanning the tangled area and acquire the tangled wire thickness signal. Based on the tangled wire width and thickness, the control unit 300 calculates the required laser power and laser frequency according to a built-in preset model, and controls the drive component 120 to drive the pulsed fiber laser 110 to move to the cutting position to cut the tangled wire on the drive roller. In this embodiment, the ranging sensor 220 is a high-precision laser ranging sensor 220 to improve accuracy.

[0030] The drive roller is monitored in real time by vision sensor 210 and distance sensor 220. When there is tangled wire on the drive roller, the cutting unit 100 is controlled by control unit 300 to perform precise cutting, realizing the automation of detection and cutting. No machine stoppage is required during high-speed production, improving cleaning efficiency and production efficiency. Furthermore, the width and thickness of the tangled wire are detected by distance sensor 220 and vision sensor 210, realizing precise control of cutting depth and cutting width, avoiding damage to the drive roller and adjacent normal wire bundles, with low safety risk and good cleaning effect.

[0031] Please refer to Figure 1 In some optional embodiments, the pulsed fiber laser 110 includes a galvanometer scanning system 130, which is electrically connected to a control unit 300. The control unit 300 controls the galvanometer scanning system 130 to guide the laser to scan and cut on the surface of the drive roller. The high-speed deflecting mirror of the galvanometer scanning system 130 can guide the laser beam to perform rapid trajectory scanning in the winding area and keep up with the production line speed of 300-400 meters per minute of the drive roller. Specifically, in conjunction with the real-time acquisition of the winding thickness and width by the distance sensor 220 and the vision sensor 210, the control unit 300 calculates and outputs corresponding laser parameters through real-time algorithms to ensure that the laser cutting depth is always less than the winding thickness by a safety margin δ, and the cutting path corresponds to the winding width, avoiding interference with adjacent normal filament bundles and achieving precise cutting of the winding. It is understood that the specific value of the safety margin δ is selected according to the actual processing requirements. Please refer to Figure 1To facilitate the movement of the pulsed fiber laser 110, in some optional embodiments, the driving component 120 includes a first circulating ejection mechanism. The pulsed fiber laser 110 is disposed at the end of the first circulating ejection mechanism, and the pulsed fiber laser 110 outputs laser light vertically downward. The first circulating ejection mechanism is pneumatically or electrically driven and can move in the X, Y, and Z axes, and its preset trajectory passes through the drive roller. Thus, by controlling the movement of the first circulating ejection mechanism through the control unit 300, the pulsed fiber laser 110 can be moved to a position opposite to the winding position of the drive roller, so as to facilitate precise cutting of the wound wire.

[0032] Please refer to Figure 1 In some optional embodiments, the detection unit 200 further includes an alarm 230, which is electrically connected to the control unit 300. The control unit 300 activates the alarm 230 when there is wire winding on the drive roller, so as to promptly notify the workers when there is wire winding on the drive roller. The alarm 230 can be a light alarm 230, an audible alarm 230, or an audible and visual alarm 230.

[0033] Please refer to Figure 1 In some optional embodiments, the detection unit 200 further includes a human body sensor 140, which is disposed on the pulsed fiber laser 110 and electrically connected to the control unit 300. The human body sensor 140 is used to identify a human body and transmit the human body signal to the control unit 300. The control unit 300 is used to control the pulsed fiber laser 110 to turn off when a human body signal is received. Specifically, the human body sensor 140 can be an infrared sensor, radar sensor, ultrasonic sensor, image recognition sensor, etc., to detect whether there is a human body around the drive roller, and control the pulsed fiber laser 110 to turn off when a human body is detected, so as to avoid injury to the human body when it approaches the drive roller during the wire winding and cutting process, and improve the safety of the device.

[0034] Please refer to Figure 1 In some optional embodiments, the apparatus for cleaning the tangled wire on the drive roller provided by the present invention further includes a waste wire cleaning unit 400, which includes a first cleaning component 410 and a second cleaning component 420. Both the first cleaning component 410 and the second cleaning component 420 are connected to the cutting unit 100. The first cleaning component 410 is located above the drive roller for cleaning the upper side of the drive roller, and the second cleaning component 420 is located below the drive roller for cleaning the lower side of the drive roller.

[0035] Specifically, please refer to Figure 1The first cleaning assembly 410 includes a rotary joint 411, a first circulating ejection mechanism 412, a first telescopic mechanism 413, and a first scraper 414. The first circulating ejection mechanism 412 is connected to the cutting unit 100 via the rotary joint 411. The first telescopic mechanism 413 is located at the end of the first circulating ejection mechanism 412 and extends vertically downward. The first scraper 414 is located at the bottom end of the first telescopic mechanism 413. The first telescopic mechanism 413 is a tracked telescopic mechanism. Through the cooperation of the first circulating ejection mechanism 412 and the first telescopic mechanism 413, the first scraper 414 moves along the X, Y, and Z axes in space. After the wire winding and cutting is completed, the movement of the first scraper 414 on the drive roller pushes down the waste wire on the upper part of the drive roller, thus cleaning the waste wire on the upper part of the drive roller.

[0036] The second cleaning assembly 420 includes a second circulating ejection mechanism 421, a second telescopic mechanism 422, and a second scraper 423. The second circulating ejection mechanism 421 is disposed in the cutting unit 100, the second telescopic mechanism 422 extends vertically upward, and the second scraper 423 is disposed at the top of the second telescopic mechanism 422. Similar to the first cleaning assembly 410, the second cleaning assembly 420 is disposed below the drive roller. Through the cooperation of the second circulating ejection mechanism 421 and the second telescopic mechanism 422, the second scraper 423 moves along the X, Y, and Z axes, thereby pushing down the waste wire at the bottom of the drive roller after the wire winding and cutting is completed, thus cleaning the waste wire at the bottom of the drive roller.

[0037] Please refer to Figure 1 In some optional embodiments, the waste filament cleaning unit 400 further includes a collection box 430, which is disposed below the second cleaning component 420 for collecting tangled filaments that fall from the drive roller. By providing the collection box 430, waste filaments cleaned from the drive roller by the first cleaning component 410 and the second cleaning component 420 are collected and stored, environmental pollution is avoided and the workload of waste filament cleaning is reduced.

[0038] In summary, the implementation principle of the device for cleaning tangled wire on the drive roller provided by the present invention is as follows: the drive roller is detected in real time by the vision sensor 210 and the distance sensor 220, and when there is tangled wire on the drive roller, the cutting unit 100 is controlled by the control unit 300 to perform precise cutting, thereby realizing the automation of detection and cutting. No machine stop is required during high-speed production, improving cleaning efficiency and production efficiency. Furthermore, based on the detection of the tangled wire width and thickness by the distance sensor 220 and the vision sensor 210, the cutting depth and cutting width are precisely controlled, avoiding damage to the drive roller and adjacent normal wire bundles, resulting in low safety risk and good cleaning effect.

[0039] The present invention also provides a method for cleaning tangled wire on a drive roller, comprising the apparatus for cleaning tangled wire on a drive roller provided in any of the above optional embodiments, including the following steps: In step S100, the vision sensor 210 monitors the drive roller in real time. Specifically, the vision sensor 210 captures images of the drive roller surface in real time and transmits the images to the control unit 300 for processing.

[0040] In step S200, when wire winding is detected on the drive roller, the control unit 300 controls the distance sensor 220 to turn on. When wire winding is detected on the drive roller, the control unit 300 controls the distance sensor 220 to turn on, which is used to detect the thickness of the wire winding.

[0041] In step S300, the control unit 300, based on the winding thickness signal output by the ranging sensor 220 and the parameter width signal output by the vision sensor 210, controls the pulsed fiber laser 110 to scan and cut the winding on the drive roller using a preset algorithm model. According to the winding thickness and width, the pulsed fiber laser 110 is started with the corresponding laser power and pulse frequency. Specifically, the laser cutting path is controlled by the galvanometer scanning system 130, and the cutting depth is set to H-δ, where H is the winding thickness and δwield is the safety margin. By precisely controlling the cutting width and cutting depth, the heat-affected zone during the cutting process is minimized, thus minimizing thermal damage to the drive roller and adjacent normal filament bundles.

[0042] Further, step S300 also includes step S310, whereby the control unit 300 controls the first cleaning assembly 410 to clean the upper side of the drive roller, and the control unit 300 controls the second cleaning assembly 420 to clean the lower side of the drive roller. Specifically, through the cooperation of the first circulating ejection mechanism 412 and the first telescopic mechanism 413, the first scraper 414 is moved to the upper side of the drive roller to be cleaned, and the waste filaments on the upper side of the drive roller are scraped off by the movement of the first scraper 414. Through the cooperation of the second circulating ejection mechanism 421 and the second telescopic mechanism 422, the second scraper 423 is moved to the lower side of the drive roller to be cleaned, and the waste filaments on the lower side of the drive roller are scraped off by the movement of the second scraper 423. The waste filaments scraped off from the drive roller fall into the collection box 430 for collection and storage.

[0043] In step S400, after the wire winding and cutting is completed, the control unit 300 controls the cutting unit 100 and the detection unit 200 to reset. The detection unit 200 and the cutting unit 100 are reset to the normal monitoring mode to wait for the next cutting operation.

[0044] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A device for cleaning tangled wire on a drive roller, characterized in that, include: The cutting unit includes a pulsed fiber laser and a driving component, the driving component being used to drive the pulsed fiber laser to move in the horizontal and vertical directions, so as to drive the pulsed fiber laser closer to or away from the driving roller. The detection unit includes a vision sensor and a distance sensor. The vision sensor is used to acquire image signals of the surface of the drive roller, and the distance sensor is used to acquire distance signals between itself and the drive roller. The control unit is electrically connected to the cutting unit and the detection unit. The control unit is used to obtain the winding width and winding thickness based on the surface image signal and the distance signal, and to adjust the output power and pulse power of the pulsed fiber laser based on the winding width and winding thickness. A waste filament cleaning unit is provided in the cutting unit for cleaning the waste filaments cut on the drive roller.

2. The apparatus for cleaning the tangled wire on the drive roller according to claim 1, characterized in that, The pulsed fiber laser includes a galvanometer scanning system, which is electrically connected to the control unit. The control unit is used to control the galvanometer scanning system to guide the laser to scan and cut on the surface of the drive roller.

3. The apparatus for cleaning the tangled wire on the drive roller according to claim 1, characterized in that, The driving component includes a first cyclic ejection mechanism, and the pulsed fiber laser is disposed at the end of the first cyclic ejection mechanism.

4. The apparatus for cleaning the tangled wire on the drive roller according to claim 1, characterized in that, The detection unit also includes an alarm, which is electrically connected to the control unit. The control unit activates the alarm when there is wire winding on the drive roller.

5. The apparatus for cleaning the tangled wire on the drive roller according to claim 1, characterized in that, The detection unit also includes a human body sensor, which is disposed on the pulsed fiber laser and electrically connected to the control unit. The human body sensor is used to identify a human body and transmit the human body signal to the control unit. The control unit is used to control the pulsed fiber laser to turn off when it receives the human body signal.

6. The apparatus for cleaning the tangled wire on the drive roller according to claim 1, characterized in that, The waste filament cleaning unit includes a first cleaning component and a second cleaning component. Both the first cleaning component and the second cleaning component are connected to the cutting unit. The first cleaning component is located above the drive roller for cleaning the upper side of the drive roller, and the second cleaning component is located below the drive roller for cleaning the lower side of the drive roller.

7. The apparatus for cleaning the tangled wire on the drive roller according to claim 6, characterized in that, The first cleaning component includes a rotary joint, a first circulating ejection mechanism, a first telescopic mechanism, and a first scraper. The first circulating ejection mechanism is connected to the cutting unit through the rotary joint. The first telescopic mechanism is disposed on the first circulating ejection mechanism and extends vertically downward. The first scraper is disposed at the bottom end of the first telescopic mechanism.

8. The apparatus for cleaning the tangled wire on the drive roller according to claim 6, characterized in that, The second cleaning component includes a second circulating ejection mechanism, a second telescopic mechanism, and a second scraper. The second circulating ejection mechanism is disposed on the cutting unit, the second telescopic mechanism extends vertically upward, and the second scraper is disposed at the top of the second telescopic mechanism.

9. The apparatus for cleaning the tangled wire on the drive roller according to claim 6, characterized in that, The waste filament cleaning unit also includes a collection box, which is located below the second cleaning assembly to collect tangled filaments that fall from the drive roller.

10. A method for cleaning tangled wire on a drive roller, characterized in that, The apparatus for cleaning the tangled wire on the drive roller as described in any one of claims 1-9 includes the following steps: A vision sensor monitors the drive roller in real time. When the control unit detects the tangled wire on the drive roller, the distance sensor is activated. The control unit uses a preset algorithm model to control the pulsed fiber laser to scan and cut the winding wire on the drive roller based on the winding thickness signal output by the ranging sensor and the parameter width signal output by the vision sensor. The control unit resets the cutting unit and the detection unit after the wire winding and cutting are completed.

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