Bridge pipeline inner wall crawling robot and walking method thereof

Abstract

The invention provides a bridge pipeline inner wall crawling robot and a walking method thereof.The bridge pipeline inner wall crawling robot comprises a front robot body and a rear robot body, a steering mechanism is arranged between the front robot body and the rear robot body, the front robot body comprises a plurality of support sets arranged in a circumferential array, each support set comprises two telescopic supporting frames, and each telescopic supporting frame comprises a rotating second guide cylinder; the steering mechanism comprises a plurality of guide discs and a bogie set, and the bogie set comprises a plurality of bogies connected end to end. In the advancing process of the whole structure, the turning direction and angle of the steering mechanism are the same as those of the inner wall of the pipeline, so that the whole structure steers smoothly, and the phenomenon that the whole structure is blocked at the turning position and cannot pass through a complex pipe section smoothly is avoided.

Description

Technical Field

[0001] This invention relates to the field of bridge construction, and in particular to a robot that crawls along the inner wall of a bridge pipe and its walking method. Background Technology

[0002] In the field of bridge construction and operation and maintenance, various pipelines inside the bridge are a key component to ensure the safety of the bridge structure. They need to be inspected regularly by inspection robots. However, existing inspection robots have the following shortcomings.

[0003] First, after long-term use, various obstacles such as scale, debris, and deformed protrusions easily form inside bridge pipelines. Existing inspection robots have poor obstacle-crossing ability when encountering such obstacles, making it difficult to successfully climb over them. This leads to the robot's movement being obstructed and stopping, and there is a risk of the robot tilting or tipping over. As a result, it is impossible to complete the full coverage and blind-spot-free inspection of the pipeline, affecting the integrity of the inspection.

[0004] Secondly, the existing bridge pipelines have different inner diameters, and the existing robots are difficult to adapt to various pipe diameters, lacking flexible pipe diameter adaptation capabilities and unable to meet the inspection needs of bridge pipelines of various specifications.

[0005] Third, bridge pipelines often involve complex conditions such as multiple pipe connections, bends, and diameter changes. Existing inspection robots have insufficient turning and maneuverability, and their turning ability is weak. When entering connected pipelines or bends, they are prone to jamming or getting stuck, making it impossible to pass smoothly through complex pipe sections, which further limits the inspection range and efficiency. Summary of the Invention

[0006] This invention provides a bridge pipeline inner wall crawling robot and its walking method, which solves the problems that existing robots have poor obstacle-crossing ability when encountering pipeline obstacles, making it impossible to successfully climb over them and hindering the robot's movement; existing robots are difficult to adapt to various pipe diameters and cannot meet the inspection needs of bridge pipelines of various specifications.

[0007] Another technical problem solved by this invention is to address the issue that robots have insufficient steering and maneuverability in complex working conditions such as multi-pipe connections, bends, and diameter changes. Their weak steering ability makes them prone to jamming and getting stuck, preventing them from smoothly passing through complex pipe sections.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a bridge pipeline inner wall crawling robot and its walking method, including a front robot and a rear robot, a steering mechanism between the front robot and the rear robot, the front robot including multiple circumferential array support groups, the support groups including two telescopic support frames, the telescopic support frames including a rotating second guide cylinder, the steering mechanism including multiple guide discs and bogie groups, the bogie groups including multiple bogies connected end to end.

[0009] In the preferred embodiment, the front robot includes a support frame with multiple telescopic support assemblies. The telescopic supports slide relative to the support frame. The support frame has multiple mounting plates, and the mounting plates have first cylinders on both sides. The first cylinders are connected to second guide cylinders. The top of the front robot has multiple cameras.

[0010] In a preferred embodiment, the bracket includes two tripods, with multiple guide post groups between the two tripods. Each guide post group includes two guide posts, with a mounting plate between the two guide posts. A mounting bracket is provided on one side of each tripod, and a rotating bidirectional lead screw is provided between the two mounting brackets.

[0011] In a preferred embodiment, a support motor is mounted on one mounting bracket, a deflection motor is mounted on another mounting bracket, and multiple connecting seats are mounted on a tripod at one end.

[0012] In a preferred embodiment, the telescopic support includes a first guide cylinder and a second guide cylinder, which are slidably connected relative to the guide post. The first guide cylinder has long hinged rods that are rotatably connected at both ends, and the second guide cylinder has short hinged rods that are rotatably connected at one end, which are rotatably connected to the long hinged rods.

[0013] In the preferred embodiment, one end of each of the two long hinged rods is provided with a rotating shaft, on which a roller is provided. The front robot is provided with two central frames, which are connected to a bidirectional lead screw. The central frames are connected to multiple first guide cylinders, and the second guide cylinder is connected to a first cylinder. Two connecting rods are provided between two adjacent rotating shafts.

[0014] In the preferred embodiment, both the front and rear robots are equipped with deflection motors, and the output ends of the deflection motors are equipped with top plates. The two top plates are connected to the bogies at both ends respectively. The rear robot is equipped with multiple winches, and steel cables are wound on the winches. The steel cables pass through multiple guide plates, and one end of the steel cable is connected to a connecting seat. The guide plates are equipped with rotating bogies.

[0015] In the preferred embodiment, the guide plate is provided with multiple hole seats, the center of the guide plate is provided with an annular groove, a spring is provided between the hole seats of two adjacent guide plates, a steel cable passes through the hole seat, and the steel cable is connected to the hole seat.

[0016] In a preferred embodiment, the bogie includes a swivel ring, on which a vertical rod is provided, and at both ends of the vertical rod are U-shaped frames. A steering motor is provided on one end of the U-shaped frame, and adjacent bogies are rotatably connected through the U-shaped frames. The swivel ring abuts against the ring groove.

[0017] A walking method for a bridge pipe inner wall crawling robot: S1, open multiple telescopic supports on the front and rear robots so that the rollers abut against the inner wall of the pipe so that the overall structure can crawl on the inner wall of the pipe; S2. When the camera at the end of the robot detects an obstacle and the corresponding roller cannot roll over it, the first cylinder of the corresponding roller is retracted to move the roller away from the obstacle. After the roller passes the obstacle, the first cylinder is reset. S3. The first cylinder corresponding to the rear roller is retracted in sequence. After the rear roller passes the obstacle, the first cylinder is reset. The robot then passes the obstacle in the same way. S4. The camera at the end of the front robot determines whether it encounters a bend inside the pipe. When it encounters a bend, it determines the direction of the bend. S5. Drive the deflection motors on the front and rear robots so that the pre-rotation direction of the multiple bogies is the same as the turning direction. S6. Drive multiple steering motors to rotate multiple bogies, drive multiple winches, the winches closer to the turning direction retract, the winches farther away from the turning direction unwind, and at the same time the front robot and the rear robot move forward until they pass through the pipe.

[0018] The beneficial effects of this invention are as follows: by placing the overall structure inside the pipeline, the support motors of the front and rear robots are driven to open multiple telescopic supports, allowing these supports to abut against the inner wall of the pipeline. The overall structure adapts to pipelines of different diameters, thus meeting the inspection requirements of bridge pipelines of various specifications.

[0019] When an obstacle is encountered, the first cylinder of the foremost telescopic support is activated. The first guide cylinder remains stationary, allowing the second guide cylinder to slide relative to the guide post. This causes the short and long hinge rods to rotate, moving the rollers away from the obstacle. The entire structure continues to move forward until the rollers of the foremost telescopic support have passed the obstacle. The first cylinder then resets. Similarly, the rear telescopic supports pass through the obstacle in the same manner, allowing the front robot to overcome it. Simultaneously, the rear robot passes through the obstacle in the same way. This avoids the problem of existing inspection robots having poor obstacle-crossing ability when encountering such obstacles, failing to successfully overcome them, causing the robot to be obstructed or stalled, and posing a risk of tilting or tipping over, thus preventing the completion of full coverage and blind-spot-free inspection of pipelines.

[0020] When the overall structure encounters multiple interconnected pipes or bends, the deflection motors on the front and rear robots are driven to rotate the two top plates and multiple bogies relative to the central axis of the front robot. This ensures that the pre-rotation direction of the multiple bogies is the same as the bend direction. The steering motors on the multiple bogies are then driven to rotate them, while multiple guide discs deflect. Springs near the bend direction compress, while springs away from the bend direction stretch. Simultaneously, the winch near the bend direction retracts, and the winch away from the bend direction unwinds, ensuring that the steering mechanism's steering direction and angle are the same as the bend direction and angle of the pipe's inner wall. During the overall structure's forward movement, the steering mechanism's bend direction and angle are the same as the bend direction and angle of the pipe's inner wall, allowing the overall structure to turn smoothly and preventing jamming or blockage at bends, which could hinder smooth passage through complex pipe sections. Attached Figure Description

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments; Figure 1 This is an axonometric view of the overall structure of the present invention; Figure 2 This is an axonometric view of the overall structure of the present invention from another perspective; Figure 3 This is an axonometric view of the robot before the invention; Figure 4 This is an axonometric view of the bracket of the present invention; Figure 5 This is an axonometric view of the two telescopic support structures of the present invention; Figure 6 This is an axonometric view of the steering mechanism of the present invention; Figure 7 This is a side view of the steering mechanism of the present invention; Figure 8 This is an axonometric view of a partial structure of the present invention; Figure 9 This is an exploded view of a partial structure of the present invention; Figure 10 This is an axonometric view of the robot following the invention; In the diagram: Front robot 1; Rear robot 2; Steering mechanism 3; Bracket 4; Triangle frame 401; Guide column 402; Mounting frame 403; Two-way lead screw 404; Mounting plate 405; Connecting seat 406; Telescopic support frame 5; First guide cylinder 501; Second guide cylinder 502; Long hinge rod 503; Short hinge rod 504; Rotating shaft 505; Roller 506; Center frame 507; Connecting rod 6; First cylinder 7; Support motor 8; Guide plate 9; Hole seat 901; Ring groove 902; Bogie 10; Rotary ring 1001; Vertical rod 1002; U-shaped frame 1003; Spring 11; Steering motor 12; Top plate 13; Deflection motor 14; Winch 15; Steel cable 16. Detailed Implementation

[0022] Example 1: like Figure 1-10 A bridge pipeline inner wall crawling robot and its walking method are disclosed. The robot includes a front robot 1 and a rear robot 2, with a steering mechanism 3 between them. The front robot 1 includes multiple circumferentially arrayed support groups, each including two telescopic supports 5. Each telescopic support 5 includes a rotating second guide cylinder 502. The steering mechanism 3 includes multiple guide discs 9 and bogie groups, each including multiple bogies 10 connected end-to-end. With this structure, the entire structure is placed inside the pipeline, and the support motors 8 of the front robot 1 and rear robot 2 are driven to open the multiple telescopic supports 5, allowing them to abut against the inner wall of the pipeline. The overall structure adapts to pipelines of different diameters, meeting the inspection needs of multi-specification bridge pipelines.

[0023] When an obstacle is encountered, the first cylinder 7 of the foremost telescopic support 5 is activated. At this time, the first guide cylinder 501 remains stationary, allowing the second guide cylinder 502 to slide relative to the guide post 402. This causes the short hinge rod 504 and the long hinge rod 503 to rotate, moving the roller 506 away from the obstacle. The entire structure continues to move forward until the roller 506 of the foremost telescopic support 5 has passed the obstacle. Then, the first cylinder 7 resets. Similarly, the rear telescopic support 5 passes the obstacle in the same way, allowing the front robot 1 to pass. Simultaneously, the rear robot 2 passes the obstacle in the same manner. This avoids the problem of existing inspection robots having poor obstacle-crossing ability when encountering such obstacles, failing to successfully overcome them, causing the robot's movement to be obstructed or stalled, and posing a risk of tilting or tipping over, thus preventing the completion of full coverage and blind-spot-free inspection of the pipeline.

[0024] When the overall structure encounters multiple pipe connections or bends, the deflection motors 14 on the front robot 1 and the rear robot 2 are driven to rotate the two top plates 13 and multiple bogies 10 relative to the central axis of the front robot 1. This ensures that the pre-rotation direction of the multiple bogies 10 is the same as the bend direction. The steering motors 12 on the multiple bogies 10 are then driven to rotate them. Simultaneously, multiple guide discs 9 deflect, the springs 11 near the bend direction are compressed, and the springs 11 away from the bend direction are stretched. At the same time, the winch 15 near the bend direction retracts, and the winch 15 away from the bend direction unwinds, ensuring that the steering direction of the steering mechanism 3 is the same as the bend direction and angle of the pipe's inner wall. During the overall structure's forward movement, the bend direction and angle of the steering mechanism 3 are the same as the bend direction and angle of the pipe's inner wall, allowing the overall structure to turn smoothly and preventing jamming or blockage at bends, thus avoiding the inability to smoothly pass through complex pipe sections.

[0025] In a preferred embodiment, the front robot 1 includes a support 4, on which multiple telescopic support assemblies are mounted. Telescopic support frames 5 slide relative to the support 4. Multiple mounting plates 405 are mounted on the support 4, and first cylinders 7 are mounted on both sides of each mounting plate 405. The first cylinders 7 are connected to a second guide cylinder 502. Multiple cameras are mounted on the top of the front robot 1. With this structure, the multiple cameras detect the condition of the inner wall of the pipe.

[0026] In a preferred embodiment, the support 4 includes two tripods 401, with multiple guide post groups between the two tripods 401. Each guide post group includes two guide posts 402, with a mounting plate 405 between the two guide posts 402. A mounting bracket 403 is provided on one side of each tripod 401, and a rotating bidirectional lead screw 404 is provided between the two mounting brackets 403. This structure drives the support motor 8 of the front robot 1, causing the first guide cylinder 501 of the multiple telescopic supports 5 to slide relative to the guide posts 402, while the second guide cylinder 502 remains stationary, allowing the multiple telescopic supports 5 to open and abut against the inner wall of the pipe.

[0027] When encountering an obstacle, the first guide cylinder 501 changes its behavior. By driving the first cylinder 7, the second guide cylinder 502 slides relative to the guide post 402, causing the long hinge rod 503 and the short hinge rod 504 to rotate, so that the roller 506 moves away from the inner wall of the pipe. As the overall structure moves forward, the roller 506 passes over the obstacle.

[0028] In a preferred embodiment, a support motor 8 is mounted on one mounting bracket 403, a deflection motor 14 is mounted on another mounting bracket 403, and a plurality of connecting seats 406 are mounted on a tripod 401 at one end. With this structure, the connecting seats 406 are used to mount the spring 11 at the end, and one end of the steel cable 16 passes through the spring 11 and connects to the connecting seat 406.

[0029] In a preferred embodiment, the telescopic support 5 includes a first guide cylinder 501 and a second guide cylinder 502, which are slidably connected relative to the guide post 402. The first guide cylinder 501 has long hinged rods 503 rotatably connected at both ends, and the second guide cylinder 502 has a short hinged rod 504 rotatably connected, with one end of the short hinged rod 504 rotatably connected to the long hinged rod 503. With this structure, a rolling motor is mounted on the roller 506, driving the roller 506 to rotate relative to the rotating shaft 505, allowing the entire structure to crawl against the inner wall of the pipe.

[0030] In the preferred embodiment, one end of each of the two long hinged rods 503 is provided with a rotating shaft 505, on which a roller 506 is mounted. The front robot 1 has two central frames 507, which are connected to a bidirectional lead screw 404 and multiple first guide cylinders 501. A second guide cylinder 502 is connected to a first cylinder 7. Two connecting rods 6 are provided between two adjacent rotating shafts 505. With this structure, when the entire structure is placed inside the pipeline, the support motors 8 of the front robot 1 and the rear robot 2 are driven to rotate the bidirectional lead screw 404, causing the first guide cylinders 501 to slide relative to the guide post 402, thus rotating the long hinged rods 503 and the short hinged rods 504. This causes the multiple telescopic supports 5 to open and abut against the inner wall of the pipeline. The overall structure is adaptable to pipelines of different diameters, meeting the inspection requirements of multi-specification bridge pipelines.

[0031] In the preferred embodiment, both the front robot 1 and the rear robot 2 are equipped with deflection motors 14. The output end of each deflection motor 14 has a top plate 13, which is connected to the bogies 10 at both ends. The rear robot 2 is equipped with multiple winches 15, with steel cables 16 wound around them. The steel cables 16 pass through multiple guide discs 9, with one end connected to a connecting seat 406. The guide discs 9 are equipped with rotating bogies 10. With this structure, the top plate 13 is rotatably connected to the tripod 401, and the top plate 13 is connected to the end bogies 10.

[0032] In a preferred embodiment, the guide disc 9 has multiple seat holes 901, and a ring groove 902 is provided at the center of the guide disc 9. A spring 11 is provided between the seat holes 901 of two adjacent guide discs 9, and a steel cable 16 passes through the seat holes 901 and is connected to the seat holes 901. With this structure, a flexible telescopic hose is provided inside the spring 11, and the steel cable 16 passes through the flexible telescopic hose and is connected to the multiple seat holes 901. Both ends of the spring 11 are connected to the seat holes 901 of different guide discs 9.

[0033] In a preferred embodiment, the bogie 10 includes a swivel ring 1001, a vertical rod 1002 on the swivel ring 1001, and U-shaped frames 1003 at both ends of the vertical rod 1002. A steering motor 12 is mounted on one end of the U-shaped frame 1003. Adjacent bogies 10 are rotatably connected via the U-shaped frames 1003, and the swivel ring 1001 abuts against the annular groove 902. With this structure, the steering motor 12 is mounted on the U-shaped frame 1003, and the output shaft of the steering motor 12 is rotatably connected to the U-shaped frame 1003. The output shaft of the steering motor 12 is also connected to the U-shaped frame 1003 of another bogie 10.

[0034] Example 2: Further explanation based on Embodiment 1: A walking method for a bridge pipe inner wall crawling robot, S1, opening multiple telescopic supports 5 on the front robot 1 and the rear robot 2 so that the rollers 506 abut against the inner wall of the pipe, so that the overall structure can crawl on the inner wall of the pipe; S2. When the camera at the end of the robot 1 determines that an obstacle has been encountered and the corresponding roller 506 cannot roll over it, the first cylinder 7 of the corresponding roller 506 is retracted so that the roller 506 moves away from the obstacle. After the roller 506 passes the obstacle, the first cylinder 7 is reset. S3. The first cylinder corresponding to the rear roller is retracted in sequence. After the rear roller passes the obstacle, the first cylinder is reset. The robot 2 then passes the obstacle in the same way. S4. The camera at the end of the front robot 1 determines whether it encounters a bend inside the pipe. When it encounters a bend, it determines the direction of the bend. S5. Drive the deflection motors 14 on the front robot 1 and the rear robot 2 so that the pre-rotation direction of the multiple bogies 10 is the same as the turning direction. S6. Drive multiple steering motors 12 to rotate multiple bogies 10, drive multiple winches 15, the winches 15 closer to the turning direction retract, the winches 15 away from the turning direction unwind, and at the same time the front robot 1 and the rear robot 2 move forward until they pass through the pipe.

[0035] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A bridge pipeline inner wall crawling robot, characterized in that: The application relates to a robot, which comprises a front robot (1) and a rear robot (2), a steering mechanism (3) is arranged between the front robot (1) and the rear robot (2), the front robot (1) comprises a plurality of circumferentially arranged support groups, each support group comprises two telescopic supports (5), each telescopic support (5) comprises a rotating second guide cylinder (502), the steering mechanism (3) comprises a plurality of guide discs (9) and a plurality of steering frame groups, each steering frame group comprises a plurality of steering frames (10) connected in a head-to-tail mode.

2. The bridge pipeline inner wall crawling robot according to claim 1, characterized in that: The front robot (1) comprises a support (4), a plurality of telescopic support groups are arranged on the support (4), the telescopic supports (5) slide relative to the support (4), a plurality of mounting plates (405) are arranged on the support (4), first air cylinders (7) are arranged on the two sides of each mounting plate (405), the first air cylinders (7) are connected with the second guide cylinders (502), and a plurality of cameras are arranged on the top of the front robot (1).

3. The bridge pipeline inner wall crawling robot according to claim 1, characterized in that: The support (4) comprises two tripods (401), a plurality of guide column groups are arranged between the two tripods (401), each guide column group comprises two guide columns (402), a mounting plate (405) is arranged between the two guide columns (402), each tripod (401) is provided with a mounting frame (403) on one side, and a rotating bidirectional screw rod (404) is arranged between the two mounting frames (403).

4. The bridge pipeline inner wall crawling robot according to claim 3, characterized in that one A supporting motor (8) is arranged on each mounting frame (403), a deflection motor (14) is arranged on the other mounting frame (403), and a plurality of connecting seats (406) are arranged on one end of each tripod (401).

5. The bridge pipeline inner wall crawling robot according to claim 1, characterized in that: Each telescopic support (5) comprises a first guide cylinder (501) and a second guide cylinder (502), the first guide cylinder (501) and the second guide cylinder (502) are slidably connected relative to the guide columns (402), the two ends of the first guide cylinder (501) are provided with rotatingly connected long hinge connecting rods (503), the second guide cylinder (502) is provided with a rotatingly connected short hinge connecting rod (504), and one end of the short hinge connecting rod (504) is rotatably connected with the long hinge connecting rod (503).

6. The bridge pipeline inner wall crawling robot according to claim 5, characterized in that: One end of each long hinge connecting rod (503) is provided with a rotatingly connected rotating shaft (505), the rotating shaft (505) is provided with a roller (506), the front robot (1) is provided with two center frames (507), the center frames (507) are connected with the bidirectional screw rod (404), the center frames (507) are connected with the plurality of first guide cylinders (501), the second guide cylinder (502) is connected with the first air cylinder (7), and two connecting rods (6) are arranged between two adjacent rotating shafts (505).

7. The bridge pipeline inner wall crawling robot according to claim 1, characterized in that: The front robot (1) and the rear robot (2) are both provided with deflection motors (14), the output ends of the deflection motors (14) are provided with top discs (13), the two top discs (13) are connected with the two end steering frames (10) respectively, a plurality of winches (15) are arranged on the rear robot (2), a steel cable (16) is wound on each winch (15), the steel cable (16) penetrates through the plurality of guide discs (9), one end of the steel cable (16) is connected with the connecting seat (406), and the guide disc (9) is provided with a rotating steering frame (10).

8. The bridge pipeline inner wall crawling robot according to claim 1, characterized in that: The guide disc (9) is provided with a plurality of hole seats (901), and a ring groove (902) is arranged at the center of the guide disc (9); the hole seats (901) of two adjacent guide discs (9) are provided with springs (11); the steel cable (16) penetrates through the hole seat (901); and the steel cable (16) is connected with the hole seat (901).

9. The bridge pipeline inner wall crawling robot according to claim 1, characterized in that: The bogie (10) comprises a rotating ring (1001), and the rotating ring (1001) is provided with a vertical rod (1002); the vertical rod (1002) is provided with a U-shaped frame (1003) at both ends; the U-shaped frame (1003) at one end is provided with a steering motor (12); adjacent bogies (10) are rotationally connected through the U-shaped frames (1003); and the rotating ring (1001) abuts against the ring groove (902).

10. The walking method of the bridge pipeline inner wall climbing robot according to any one of claims 1-9, characterized in that: S1, the multiple telescopic supports (5) on the front robot (1) and the rear robot (2) are opened, so that the rollers (506) abut against the inner wall of the pipeline, and the whole structure can climb on the inner wall of the pipeline; S2, the camera at the end of the front robot (1) judges whether an obstacle is encountered; if the corresponding roller (506) cannot roll over the obstacle, the first cylinder (7) corresponding to the roller (506) is retracted, so that the roller (506) is away from the obstacle; and when the roller (506) passes over the obstacle, the first cylinder (7) is reset; S3, the first cylinders corresponding to the rear rollers are retracted in sequence; when the rear rollers pass over the obstacle, the first cylinders are reset; and the rear robot (2) passes over the obstacle in the same way; S4, the camera at the end of the front robot (1) judges whether a turning position in the pipeline is encountered; when the turning position is encountered, the turning direction of the pipeline is judged; S5, the deflection motor (14) on the front robot (1) and the rear robot (2) is driven, so that the pre-rotation directions of the multiple bogies (10) are the same as the turning direction; S6, the multiple steering motors (12) are driven, so that the multiple bogies (10) are rotated; the multiple winches (15) are driven; the winches (15) close to the turning direction are retracted, the winches (15) away from the turning direction are unwound; meanwhile, the front robot (1) and the rear robot (2) advance, until the pipeline is passed through.

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