Novel auxiliary device and method for guiding rope to penetrate through tackle window

Abstract

The invention discloses a novel auxiliary device and method for a guide rope to penetrate through a tackle window, and belongs to the technical field of power transmission and transformation. The novel auxiliary device comprises an unmanned aerial vehicle provided with a multi-angle visual observation system, the lower end of the unmanned aerial vehicle is fixedly connected with a mounting frame, and the other end of the mounting frame is fixedly connected with a threading execution module; the middle of the threading execution module is fixedly connected with a butt joint adsorption assembly, and the two ends of the threading execution module are connected to the two sides of the pulley frame in a bridging mode through the butt joint adsorption assembly. The device has the advantages that the unmanned aerial vehicle can independently enable the guide rope to penetrate through the pulley window, and the device is suitable for most existing single-wheel and multi-wheel pulleys.

Description

Technical Field

[0001] The invention relates to the technical field of power transmission and transformation, and in particular to a novel auxiliary device and method for a guide rope to pass through a pulley window. Background Art

[0002] When laying out overhead transmission lines, the primary guide rope, traction rope, and conductor are laid out step by step. Laying out the Dyneema guide rope is the first step. The large multi-rotor drones that have appeared in recent years have the characteristics of long flight distance, large load, and flexible maneuverability. They are more suitable for laying out the primary guide ropes of long-distance overhead transmission lines and large-span transmission lines.

[0003] At present, the use of drones to deploy guide ropes at home and abroad is mostly carried out by workers on the tower to assist the operation. The drone carries the guide rope and deploys it to the cross arm of the tower. The construction workers on the tower cut the guide rope, bypass the wire pulley, and reconnect it. The drone continues to fly to the next tower to repeat the deployment operation. The deployment accuracy is high, and it gets rid of the restrictions of complex terrain conditions on construction. The requirements for drone operators are low, but the construction process requires the cooperation of high-altitude personnel, which has high safety risks. In addition, the guide rope passing the pulley operation requires the drone to hover and wait for manual operation, and the construction efficiency is not significantly improved.

[0004] In order to improve the disadvantage that the UAV guide rope deployment requires manual operation on the tower, and to realize the continuous operation of the UAV guide rope deployment, the research of relevant domestic and foreign companies and research institutions is currently focused on the modification of the line-laying pulley and the UAV structure.

[0005] For example, Chinese patents CN2018112089353, CN2019112424093, and CN2023111160639 propose to modify the pulley structure, add a guide mechanism, and guide the guide rope into the pulley under the traction of the drone.

[0006] However, the disadvantages of these solutions are that they require modification of a wide variety of pulley structures that are themselves subject to heavy loads, resulting in a low safety factor and high modification costs, and they are not applicable to a large number of pulleys in existing inventory. Summary of the invention

[0007] The present invention aims to solve the technical problems mentioned in the above background technology. On the first aspect, it provides a new auxiliary device for the guide rope to pass through the pulley window, which enables the UAV to pass the guide rope through the pulley window alone and is suitable for most existing single-wheel and multi-wheel pulleys without the need for structural modifications to the existing pulleys.

[0008] The second aspect provides a method, which is applied to the first aspect to provide a novel auxiliary device for guiding a guide rope to pass through a pulley window.

[0009] According to the subject of the first aspect, the technical solution provided by the present invention is: a novel auxiliary device for guiding a guide rope to pass through a pulley window, comprising a drone equipped with a multi-angle visual observation system, a mounting frame fixedly connected to the lower end of the drone, a threading execution module fixedly connected to the other end of the mounting frame, a docking adsorption assembly fixedly connected to the middle of the threading execution module, and the two ends of the threading execution module are bridged to the two sides of the pulley frame through the docking adsorption assembly; The threading execution module includes a fixed disk, one side of the fixed disk is provided with an opening, the lower end of the fixed disk is rotatably connected to a rotating ring, one side of the rotating ring is also provided with an opening, a rack is provided on the outer circumference of the rotating ring, and a plurality of vertically downward driving members are installed at intervals on the outer circumference of the fixed disk, and the lower end output shaft of the driving member is connected to a gear that meshes with the rack for transmission.

[0010] In some embodiments, the lower end circumference of the fixed plate is vertically connected to more than three guide wheels for rotation, and the multiple guide wheels are evenly arranged along the inner side of the lower end circumference of the fixed plate, and an annular groove is provided in the middle of the guide wheel, and the inner circumference of the rotating ring is provided with a sliding rail that matches the annular groove of the guide wheel. The rotating ring is sleeved on the outer side of the multiple guide wheels and maintains a sliding connection with the guide wheels.

[0011] In some embodiments, at least two driving members are provided and are mounted on both ends of a diameter of the fixed disk by screws.

[0012] In some embodiments, a position sensor is provided on one side of the opening of the fixed disk, and a sensing device is installed at a position on the one side of the opening of the rotating ring corresponding to the position sensor.

[0013] In some embodiments, one side of the opening of the rotating ring is fixedly connected to the guide rope.

[0014] In some embodiments, the docking adsorption assembly includes an electromagnet seat, one end of which is provided with a slot that is clamped in the opening of the fixed disk, and the slot is provided with a fastener, which fixes the electromagnet seat to the fixed disk, and the other end of the electromagnet seat is fixedly connected to the electromagnet.

[0015] In some embodiments, the mounting frame is in a ladder-shaped structure, and a plurality of openings are provided inside the mounting frame to reduce weight.

[0016] According to the subject of the second aspect, the present invention provides a method comprising: S1. Check and confirm that all aspects of each equipment are in working condition; S2, control the UAV to hover on one side of the pulley frame after taking off, and control the docking adsorption component to be electromagnetically adsorbed on the side of the pulley frame after being powered on; S3, start the driving member, the driving member drives the gear to rotate, thereby driving the rotating ring to rotate along the guide wheel, so that the rotating ring rotates one circle after passing through the pulley window; S4. Start the drone and keep it hovering, and control the docking adsorption component to cut off the power, then control the drone to fly away from the current pulley. During the process of controlling the drone to fly away from the current pulley, the drone needs to be kept flying horizontally and fly in the direction of the pulley threading.

[0017] Further; S1. Check and confirm that all aspects of each equipment are in working condition; S11. Check and confirm that the information feedback of the control system is quick and that each mechanical transmission part is smooth; S12. Tie the guide rope and the rotating ring securely; S13. Before takeoff, keep the openings of the rotating ring and the fixed plate on the same side; S2. Control the drone to hover on one side of the pulley frame after takeoff, control the docking adsorption component to be electromagnetically adsorbed on the side of the pulley frame after power is turned on, and keep the threading execution module as far away from the pulley as possible, that is, to ensure that the guide rope can pass through the pulley window smoothly, and the guide rope is not easily caught in the gap, and to ensure that there is no interference between the equipment and surrounding objects during the threading process.

[0018] Further; S3, start the driving member, the driving member drives the gear to rotate, thereby driving the rotating ring to rotate along the guide wheel, so that the rotating ring rotates one circle after passing through the pulley window. In this process, the guide rope is straightened as much as possible and maintained at a suitable height that is not easily clamped; S31, the driving member of the threading execution module is started, the driving member drives the gear to rotate, the gear and the rack are meshed for transmission, thereby driving the rotating ring to rotate counterclockwise along the guide wheel; S32, when the rotating ring rotates one circle to the initial position, the position sensor detects the sensing device and outputs a signal, and the driving part stops working. At this time, the guide rope head is brought through the pulley window.

[0019] Compared with the prior art, the advantages of the present invention are: 1. It eliminates the need for workers to perform auxiliary threading operations at high altitudes; 2. There is no need to make large-scale structural modifications to existing pulleys, thereby reducing costs; 3. The device has a simple structure, is small and light, has good maneuverability, is easy to maintain, and information exchange during construction operations is timely, accurate, and convenient, which can improve construction efficiency, reduce construction costs, and reduce labor intensity and safety hazards of personnel.

[0020] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic diagram of a novel auxiliary device for a guide rope to pass through a pulley window according to an embodiment of the present invention; Figure 21 is a schematic diagram of the maximum occupancy of the auxiliary device for the new guide rope to pass through the pulley window according to an embodiment of the present invention; Figure 3 yes Figure 1 The schematic diagram of the mounting bracket shown in FIG. Figure 4 yes Figure 1 Schematic diagram of the docking adsorption component shown in; Figure 5 yes Figure 1 The schematic diagram of the threading execution module shown in ; Figure 6 yes Figure 5 Schematic diagram of the rotating ring shown in; Figure 7 is a schematic diagram of the initial position state of the auxiliary device for the new guide rope passing through the pulley window of this embodiment; Figure 8 1 is a schematic diagram of the appropriate height of the auxiliary device for the new guide rope passing through the pulley window of the embodiment when adsorbing the pulley; Fig. 9 This is a schematic diagram of the threading execution module of the embodiment of the present invention when starting threading; Fig.10 yes Fig. 9 An enlarged schematic diagram of the A part shown in FIG. Fig.11 This is a schematic diagram of the threading execution module of the embodiment of the present invention when threading is completed; Fig.12 yes Fig.11 An enlarged schematic diagram of the B portion shown in FIG. Fig.13 This is a schematic diagram of the auxiliary device for the new guide rope passing through the pulley window of this embodiment when the threading is completed and the rope flies away; In the attached figure: 1. wire-laying pulley; 2. drone; 3. mounting frame; 4. docking adsorption assembly; 5. threading execution module; 6. guide rope; 41. magnet seat; 42. electromagnet; 51. Fixed plate; 52. Rotating ring; 53. Guide wheel; 54. Gear; 55. Driving member; 56. Position sensor; 57. Induction device; 521, rack; 522, slide rail; 100. A new auxiliary device for the guide rope to pass through the pulley window. DETAILED DESCRIPTION

[0022] The present invention is described in further detail below.

[0023] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0024] Combination Figure 1 As shown, this embodiment is a new auxiliary device 100 for guiding the rope to pass through the pulley window, equipped with a drone 2 with a multi-angle visual observation system, and the power supply of the threading execution module 5 and the docking adsorption component 4 is a 24V power supply, which is provided by the power supply of the drone 2.

[0025] The theoretical weight of the mechanical part of the threading auxiliary device in this embodiment is estimated to be 3.5Kg. Considering the weight of the equipment control components and power supply, and the safety factor of 1.2-1.5, the load of the drone 2 is estimated to be 10Kg. The X6-10L drone 2 is selected, the operating system is the Yunzhuo H12 large-screen remote control, and the three-body camera is used for real-time feedback. The battery is standard 12S-16000 mAh. The drone 2 occupies a plane when working. Figure 2 shown.

[0026] Combination Figure 3 , Figure 4 As shown, the lower end of the drone 2 is connected to a mounting frame 3 by screws, the other end of the mounting frame 3 is connected to a threading execution module 5 by screws, the middle part of the threading execution module 5 is connected to a docking adsorption component 4 by screws, and the two ends of the threading execution module 5 are bridged to the two sides of the pulley frame through the docking adsorption component 4.

[0027] Combination Figure 3 As shown, the mounting frame 3 is in a ladder-shaped structure, and a plurality of openings are provided inside the mounting frame 3 to reduce weight.

[0028] Combination Figure 4 As shown, the docking adsorption assembly 4 includes an electromagnet seat 41, one end of which is provided with a slot that is clamped in the opening of the fixed disk 51, and the slot is provided with a fastener, through which the electromagnet seat 41 is fixedly connected to the fixed disk 51, and the other end of the electromagnet seat 41 is fixedly connected to the electromagnet 42, and the model of the electromagnet 42 is ELE-P6ELE-P60-30-25.

[0029] Combination Figure 5 , Figure 6 As shown, the threading execution module 5 includes a fixed disk 51, which is a three-quarter fan-shaped disk structure. An opening is provided on one side of the fixed disk 51 close to the pulley, and a docking adsorption component 4 is installed in the opening of the fixed disk 51.

[0030] The rotating ring 52 is in the shape of a three-quarter circular ring. A slide rail 522 is disposed on the inner circumference of the rotating ring 52 , and a rack 521 is disposed on the outer ring surface of the rotating ring 52 .

[0031] The lower end of the fixed plate 51 is vertically connected to four guide wheels 53, and an annular groove is provided in the middle of the guide wheel 53. The rotating ring 52 is sleeved on the outer sides of the four guide wheels 53, and the slide rail 522 of the rotating ring 52 is provided in the annular groove of the guide wheel 53, so that the rotating ring 52 and the guide wheel 53 maintain a sliding connection.

[0032] Two vertically downward driving members 55 are installed at intervals on the outer circumference of the fixed plate 51. The lower output shaft of the driving member 55 is connected to a gear 54 meshing with the rack 521. The driving member 55 is a DC reduction motor with a model of JGA25-370, an input voltage of 24V, a motor speed of 8500RPM, a speed ratio of 171:1, a rated output speed of 40RPM, a rated torque of 4Kgf.cm, and a rated power of 4.8W.

[0033] Combination Figure 2 As shown, four guide wheels 53 are located at the four corners of the lower end of the fixed plate 51, and a pair of guide wheels 53 are provided on each side. A driving member 55 is provided between the pair of guide wheels 53 on the left, and another driving member 55 is provided between the pair of guide wheels 53 on the right. The guide wheels 53 cooperate with the gears 54 to limit the rotating ring 52.

[0034] Position sensors 56 are provided on both the left and right sides of the opening of the fixed plate 51 , and sensing devices 57 are installed at the positions corresponding to the position sensors 56 on the left and right sides of the opening of the rotating ring 52 .

[0035] The following is a description of the materials of the various components of the threading auxiliary device of this embodiment: Drone 2 (equipped with a multi-angle visual observation system): purchased from an external manufacturer; Mounting seat: high-strength engineering plastic; Docking adsorption component 4: metal accessories assembly; Electromagnet seat 41: aluminum; Electromagnet 42: metal part; Threading execution module 5: metal accessories & non-metal accessories assembly; Fixed plate 51: high-strength engineering plastic; Rotating ring 52: high-strength engineering plastic; Guide wheel 53: high-strength engineering plastic + deep groove ball bearing; Driving pinion 54: high-strength engineering plastic; DC reduction motor (drive part 55): outsourced standard parts; Position sensor 56: outsourced standard parts; Guide rope 6 (Dyneema rope): high-strength polyethylene fiber; The connection relationship of each component of this embodiment is described below: Drone 2 (equipped with a multi-angle visual observation system): fixed to the associated components with screws; Mounting base: Use screws to fix it to the drone 2; Docking adsorption component 4: fixedly connected with threading execution module 5 by screws; Electromagnet seat 41: fixedly connected to the fixing plate 51 by screws; Electromagnet 42: fixedly connected to the electromagnet seat 41 by screws; Threading execution module 5: fixedly connected to the mounting base using screws; Fixed plate 51: fixedly connected to the mounting seat by screws; Rotating ring 52: mounted in the grooves of four guide wheels 53, and the teeth thereof mesh with the teeth of two gears 54; Guide wheel 53: The guide wheel 53 is sleeved on the support shaft (the guide wheel 53 can rotate), and the support shaft is fixedly connected to the bottom of the fixed plate 51 by screws; Driving gear 54: sleeved on the output shaft of the DC reduction motor; DC reduction motor: fixed on the fixing plate 51 by screw lock; Position sensor 56: is fixed on the fixing plate 51 by using a nut.

[0036] When this embodiment is used, Figure 2 As shown in (unit: mm), ensure that there is no interference around the current pulley in the plane occupied by the drone 2, and pay special attention to the posture of the Dyneema rope during the construction process to prevent the Dyneema rope from falling into the gap of the pulley and getting stuck. The solution is to keep the Dyneema rope in proper tension during use and use auxiliary tools to make the Dyneema rope fall properly into the wheel groove of the pulley.

[0037] The steps to use are as follows: S1. Check and confirm that all aspects of each equipment are in working condition; S11. Check and confirm that the information feedback of the control system is quick and that each mechanical transmission part is smooth; S12, securely tying the guide rope 6 and the rotating ring 52; S13, before takeoff, keep the openings of the rotating ring 52 and the fixed plate 51 on the same side, that is, Figure 7 Initial position shown; S2, control the drone 2 to hover on one side of the pulley frame after taking off, control the docking adsorption component 4 to be electromagnetically adsorbed on the side of the pulley frame after being powered on, and keep the threading execution module 5 as far away from the pulley as possible (such as Figure 8 As shown), that is, to ensure that the guide rope 6 can smoothly pass through the pulley window, and the guide rope 6 is not easily caught in the gap, and to ensure that there is no interference between the equipment and surrounding objects during the threading process; S3, start the driving member 55, the driving member 55 drives the gear 54 to rotate, thereby driving the rotating ring 52 to rotate along the guide wheel 53, so that the rotating ring 52 rotates one circle after passing through the pulley window. In this process, the guide rope 6 is straightened as much as possible and maintained at a suitable height that is not easily clamped; S31, the driving member 55 of the threading execution module 5 is started, the driving member 55 drives the gear 54 to rotate, the gear 54 is meshed with the rack 521 for transmission, thereby driving the rotating ring 52 to rotate counterclockwise along the guide wheel 53, as shown in FIG. Fig. 9 , Fig.10 As shown; S32, when the rotating ring 52 rotates one circle to the initial position, the position sensor 56 detects the sensing device 57 and outputs a signal, and the driving member 55 stops working. At this time, the rope head of the guide rope 6 is brought through the pulley window, such as Fig.11 , Fig.12 As shown; S4, start the drone 2 to keep it hovering, control the docking adsorption component 4 to cut off the power, and then control the drone 2 to fly away from the current pulley. During the process of controlling the drone 2 to fly away from the current pulley, the drone 2 needs to be kept flying horizontally and fly in the direction of the pulley threading, such as Fig.13 shown.

[0038] The wire threading auxiliary device of this embodiment can replace the following existing construction techniques in the construction process of tension wire stringing of power transmission lines: 1. Rely on manual deployment of guide ropes on the line; 2. Use a drone combined with a sky pulley to deploy the guide rope (this method requires manual assistance); 3. Use drones in combination with a new type of overhead pulley (a drone-based line-releasing pulley in which the guide rope can directly fall into the wheel groove of the line-releasing pulley); When laying out power transmission lines in plains, mountains, hills, deserts, forests, rivers, lakes, seas, plantations, densely-networked areas, villages, cities, etc., the device can be used to intelligently pass the guide rope of the traction rope through the pulley window on the iron tower one by one; The threading auxiliary device of this embodiment is highly integrated, simple in structure, easy to operate, small in size and light in weight, easy to maintain, and information exchange during construction operations is timely, accurate, and convenient.

[0039] Using this device to replace the existing construction method can improve construction efficiency, reduce construction costs, reduce labor intensity and safety hazards of personnel, has strong adaptability to complex terrain and harsh environment, and improves the safety factor of personnel when working.

[0040] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A novel auxiliary device (100) for guiding a guide rope to pass through a pulley window, comprising a drone (2) equipped with a multi-angle visual observation system, characterized in that: The lower end of the drone (2) is fixedly connected to a mounting frame (3), the other end of the mounting frame (3) is fixedly connected to a threading execution module (5), the middle of the threading execution module (5) is fixedly connected to a docking adsorption component (4), and the two ends of the threading execution module (5) are bridged to the two sides of the pulley frame through the docking adsorption component (4); The threading execution module (5) comprises a fixed disk (51), one side of which is provided with an opening, the lower end of the fixed disk (51) is rotatably connected to a rotating ring (52), one side of which is also provided with an opening, a rack (521) is provided on the outer circumference of the rotating ring (52), and a plurality of vertically downward driving members (55) are installed at intervals on the outer circumference of the fixed disk (51), and the lower end output shaft of the driving member (55) is connected to a gear (54) meshing with the rack (521) for transmission.

2. The novel auxiliary device (100) for guiding the guide rope to pass through the pulley window according to claim 1 is characterized in that: The lower end circumference of the fixed plate (51) is vertically rotatably connected to more than three guide wheels (53); the plurality of guide wheels (53) are evenly spaced along the inner side of the lower end circumference of the fixed plate (51); an annular groove is provided in the middle of the guide wheel (53); the inner circumference of the rotating ring (52) is provided with a slide rail (522) adapted to the annular groove of the guide wheel (53); the rotating ring (52) is sleeved on the outer sides of the plurality of guide wheels (53) and maintains a sliding connection with the guide wheels (53).

3. The novel auxiliary device (100) for guiding the guide rope to pass through the pulley window according to claim 1 is characterized in that: At least two driving members (55) are provided and are mounted on both ends of a diameter of the fixing plate (51) by means of screws.

4. The novel auxiliary device (100) for guiding the guide rope to pass through the pulley window according to claim 1 is characterized in that: A position sensor (56) is provided on one side of the opening of the fixed disk (51), and a sensing device (57) is installed at a position on one side of the opening of the rotating ring (52) corresponding to the position sensor (56).

5. The novel auxiliary device (100) for guiding the guide rope to pass through the pulley window according to claim 1 is characterized in that: One side of the opening of the rotating ring (52) is fixedly connected to a guide rope (6).

6. The novel auxiliary device (100) for guiding the guide rope to pass through the pulley window according to claim 1 is characterized in that: The docking adsorption assembly (4) comprises an electromagnet seat (41), one end of the electromagnet seat (41) being provided with a notch which is clamped in an opening of a fixed disk (51), the notch being provided with a fastener, the electromagnet seat (41) being fixedly connected to the fixed disk (51) by the fastener, and the other end of the electromagnet seat (41) being fixedly connected to an electromagnet (42).

7. The novel auxiliary device (100) for guiding the guide rope to pass through the pulley window according to claim 1 is characterized in that: The mounting frame (3) is in a ladder-shaped structure, and a plurality of openings are provided inside the mounting frame (3) for reducing weight.

8. A method, characterized in that: The auxiliary device (100) for the new guide rope passing through the pulley window according to any one of claims 1 to 7 comprises: S1. Check and confirm that all aspects of each equipment are in working condition; S2, controlling the drone (2) to hover on one side of the trolley frame after taking off, and controlling the docking adsorption component (4) to be electromagnetically adsorbed on the side of the trolley frame after being powered on; S3, starting the driving member (55), the driving member (55) drives the gear (54) to rotate, thereby driving the rotating ring (52) to rotate along the guide wheel (53), so that the rotating ring (52) rotates one circle after passing through the pulley window; S4, start the drone (2) to keep it hovering, control the docking adsorption component (4) to cut off the power, and then control the drone (2) to fly away from the current pulley. In the process of controlling the drone (2) to fly away from the current pulley, the drone (2) needs to be kept in level flight and fly in the direction of the pulley threading.

9. The method according to claim 8, characterized in that The following steps are involved: S1. Check and confirm that all aspects of each equipment are in working condition; S11. Check and confirm that the information feedback of the control system is quick and that each mechanical transmission part is smooth; S12, securely tying the guide rope (6) and the rotating ring (52); S13, before takeoff, keep the openings of the rotating ring (52) and the fixed plate (51) on the same side; S2. Control the drone (2) to hover on one side of the pulley frame after takeoff, control the docking adsorption component (4) to be electromagnetically adsorbed on the side of the pulley frame after power is turned on, and keep the threading execution module (5) as far away from the pulley as possible, that is, to ensure that the guide rope (6) can pass through the pulley window smoothly, and the guide rope (6) is not easily caught in the gap, and to ensure that there is no interference between the equipment and surrounding objects during the threading process.

10. The method according to claim 8, characterized in that: S3, starting the driving member (55), the driving member (55) drives the gear (54) to rotate, thereby driving the rotating ring (52) to rotate along the guide wheel (53), so that the rotating ring (52) rotates one circle after passing through the pulley window. In this process, the guide rope (6) is straightened as much as possible and maintained at a suitable height that is not easily clamped; S31, the driving member (55) of the threading execution module (5) is started, the driving member (55) drives the gear (54) to rotate, the gear (54) and the rack (521) are meshed and transmitted, thereby driving the rotating ring (52) to rotate counterclockwise along the guide wheel (53); S32, when the rotating ring (52) rotates one circle to the initial position, the position sensor (56) detects the sensing device (57) and outputs a signal, and the driving member (55) stops working. At this time, the rope head of the guide rope (6) is brought through the pulley window.

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