Pressure sensing type backflushing valve for mud separation backflushing system

Abstract

The invention discloses a pressure sensing type backflushing valve for a mud separation backflushing system, and belongs to the technical field of control valves, the pressure sensing type backflushing valve comprises a valve body, a valve cover is fixedly mounted on the upper surface of the valve body through bolts, an input pipe and an output pipe are respectively mounted on the outer surface of the valve body in a communicating manner, a knocking assembly is arranged on the inner wall of the valve cover, and a pressure sensor is arranged on the inner wall of the knocking assembly. A collecting assembly is arranged on the inner wall of the bottom face of the valve body. According to the device, the knocking assembly is arranged, the backflushing system is automatically started when the pipeline is blocked, the situation that the pipeline is damaged or exploded due to blockage can be effectively avoided, meanwhile, backflushing silt flushes up slag at the bottom of the slurry storage tank, slurry is more uniform, the probability of later-stage blockage is reduced, and the service life of the pipeline is prolonged. After the backflushing valve is used, silt in the valve body is automatically cleaned and collected, the situation that the backflushing valve is damaged due to the fact that the backflushing valve is blocked by too much silt in the backflushing valve is avoided, corrosion of the silt to the inner wall of the backflushing valve can be reduced, and the service life of the backflushing valve is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of control valves, and in particular relates to a pressure sensing recoil valve for a mud separation recoil system. Background Art

[0002] Mud is a semi-colloidal suspension formed by tiny particles of clay dispersed in water and mixed with water. In colloid chemistry, solid clay is called dispersed phase or solid phase, and water is called medium or liquid phase. If the solid phase is dispersed into molecules or ions, and there is no interface between the solid and liquid phases, it is called a true solution, such as a solution of salt dissolved in water. If the particles dispersed in the liquid phase are composed of many molecules, although the particles are very small, there is an interface. Such a mixture is called a colloidal solution. Various commonly used glues belong to this category. In order to extract the sediment in the mud, the mud will be separated.

[0003] The prior art discloses a valve, which includes a valve body formed with a material channel, and also includes a sealing disk, an upper valve seat, a lower valve seat and a driving mechanism. The upper valve seat and the lower valve seat are arranged in the valve body and block the material channel. The sealing disk can be rotatably clamped around its own axis and formed with an upper end surface and a lower end surface that are tightly matched with the bottom surface of the upper valve seat and the top surface of the lower valve seat. The upper valve seat and the lower valve seat are respectively formed with first through holes arranged opposite to each other, and the sealing disk is formed with a second through hole that can be aligned with the first through hole. The driving mechanism can drive the sealing disk to rotate to adjust the relative position of the first through hole and the second through hole, thereby controlling the flow and switch of the valve. The upper valve seat can be movably arranged in the valve body up and down, and an elastic upper pressure ring is arranged between the valve body and the upper valve seat. The elastic upper pressure ring applies a downward elastic force to the upper valve seat, so that the bottom surface of the upper valve seat is tightly matched with the upper end surface of the sealing disk. Mud may become clogged during the separation process. In order to avoid long-term clogging of mud and excessive pressure in the pipeline, a recoil system is set up to allow the mud to flow back to the slurry storage tank when the pressure is too high, thereby impacting the slag. However, mud and sand are easily adhered to the inner wall of the recoil valve during use. As the use time increases, the inside of the recoil valve will cause wear, thereby reducing the sealing effect of the recoil valve. For this purpose, a pressure-sensing recoil valve for a mud separation recoil system is provided. Summary of the invention

[0004] The purpose of the present invention is to provide a pressure sensing recoil valve for a mud separation recoil system, which solves the problem that the current recoil valve is easily worn by mud and sand, resulting in reduced sealing effect.

[0005] In order to achieve the above-mentioned object, the present invention adopts the following technical scheme: a pressure sensing recoil valve for a mud separation recoil system, comprising a valve body, a valve cover is fixedly installed on the upper surface of the valve body by bolts, an input pipe and an output pipe are respectively connected and installed on the outer surface of the valve body, a knocking assembly is arranged on the inner wall of the valve cover, a collecting assembly is arranged on the inner wall of the bottom surface of the valve body, and a sealing assembly is arranged on the inner wall of the shell cavity of the input pipe and the output pipe; The knocking assembly includes a rotating rod, one end of which is rotatably connected to the inner wall of the top surface of the valve cover, a transmission gear is fixedly installed on the outer surface of the rotating rod, and a rotating disk is fixedly installed on the other end of the rotating rod.

[0006] As a further description of the above technical solution: A knocking rod is rotatably mounted on the lower surface of the rotating disk via a rotating shaft, a limiting sleeve is slidably mounted on the outer surface of the knocking rod, and one end of the limiting sleeve is fixedly connected to the inner side wall of the valve cover.

[0007] As a further description of the above technical solution: A turning handle is rotatably mounted on the upper surface of the valve cover, one end of the turning handle extends to the interior of the valve cover and is fixedly mounted with a connecting rod, a driving gear is fixedly mounted on the outer surface of the connecting rod, the driving gear is meshingly connected with the transmission gear, and the diameter of the driving gear is larger than that of the transmission gear.

[0008] As a further description of the above technical solution: One end of the connecting rod extends to the interior of the valve body, a supporting rod is fixedly mounted on one end of the connecting rod, a baffle is fixedly mounted on the outer surface of the supporting rod, and the outer surface of the baffle is in contact with the inner wall of the valve body.

[0009] As a further description of the above technical solution: The collecting assembly comprises a travel groove and a sealing cover. The travel groove is arranged on the inner wall of the bottom surface of the valve body. A threaded opening is arranged on the inner wall of the travel groove. A collecting box is threadedly mounted on the outer surface of the threaded opening.

[0010] As a further description of the above technical solution: The upper surface of the sealing cover is fixedly connected to the lower surface of the baffle, the outer surface of the sealing cover is slidably connected to the inner wall of the travel groove, and the sealing cover is adapted to the travel groove and the threaded opening.

[0011] As a further description of the above technical solution: The sealing assembly includes a movable plate, a connecting spring is fixedly installed on the side wall of the movable plate, one end of the connecting spring is fixedly connected to the inner wall of the shell cavity of the input pipe, and an extrusion rod and a push rod are respectively fixedly installed on the other side wall of the movable plate.

[0012] As a further description of the above technical solution: An extrusion ring is fixedly mounted on one end of the extrusion rod, and the extrusion ring extends to the outside of the input pipe. A sealing ring is fixedly mounted on one end of the push rod, and the sealing ring extends to the outside of the input pipe.

[0013] As a further description of the above technical solution: A positioning rod is fixedly mounted on the inner wall of the movable plate, one end of the positioning rod extends to the outside of the movable plate, and a mounting plate is rotatably mounted on one end of the positioning rod.

[0014] As a further description of the above technical solution: One end of the mounting plate is fixedly connected to the inner wall of the shell cavity of the input pipe, the extrusion ring and the sealing ring are both made of rubber material, and a pressure sensor is fixedly installed on the inner wall of the input pipe.

[0015] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. In the present invention, a knocking assembly is provided. With the transportation of mud, the input pipe may be blocked. When the pressure sensor senses that the pressure in the input pipe is too high, it will automatically control the turning handle to rotate. At this time, the turning handle will drive the support rod to rotate through the connecting rod. At this time, the support rod will drive the baffle to rotate. When the baffle is perpendicular to the pipe openings of the input pipe and the output pipe, it is in a fully open state. At this time, the mud will flow into the slurry storage tank through the output pipe, and the slag that has sunk to the bottom of the slurry storage tank will be flushed up, thereby avoiding the accumulation of slurry in the slurry storage tank due to long-term use. After the recoil is completed, the recoil valve will be closed. During the closing process, the connecting rod will drive the driving gear to rotate, and the driving gear will drive the rotating rod to rotate on the inner wall of the top surface of the valve cover, and the rotating gear will drive the rotating rod to rotate. The rod will drive the rotating disk to rotate. At this time, the knocking rod will knock on the inner wall of the valve cover under the limit of the limit sleeve. The knocked valve cover will drive the valve body to vibrate synchronously. The mud and sand adhered to the inner wall of the vibrated valve body will flow into the collection box through the threaded port. When the pipeline is blocked, the recoil system will be automatically turned on to effectively prevent the pipeline from being damaged or burst due to blockage. At the same time, the recoiled mud and sand will flush up the slag at the bottom of the slurry storage tank, making the mud more uniform and reducing the probability of later blockage. After the recoil valve is used, the mud and sand inside the valve body will be automatically cleaned and collected, avoiding blockage caused by excessive mud and sand in the recoil valve, thereby damaging the recoil valve. It can also reduce the corrosion of the inner wall of the recoil valve caused by mud and sand, thereby increasing the service life of the recoil valve.

[0016] 2. In the present invention, by providing a collecting assembly, when the recoil valve is opened next time, the baffle will drive the sealing cover to move in the stroke groove to seal the threaded opening, thereby preventing the mud from carrying away the silt in the collection box when the mud flows. When the silt in the collection box reaches a certain amount, the collection box is removed and cleaned under the action of the thread, and the silt in the recoil valve is collected, which is convenient for unified treatment later. At the same time, it can also prevent the silt from adhering to the internal surface of the recoil valve, causing wear on the baffle in the valve body, and reducing the sealing of the recoil valve.

[0017] 3. In the present invention, a sealing assembly is provided to connect the input pipe with the output end of the slurry pump, and the output pipe is communicated with the side wall of the slurry storage tank. When the input pipe and the output pipe are connected, the extrusion ring will be squeezed, thereby moving toward the shell cavity of the input pipe and the output pipe. As the extrusion ring moves, one end of the movable plate will be squeezed through the extrusion rod. At this time, the other end of the squeezed movable plate will be tilted under the limitation of the positioning rod and the mounting plate, so that the sealing ring will move toward the outside of the input pipe and the output pipe under the action of the push rod. Since the extrusion ring and the sealing ring are both made of rubber material, the connection will be sealed. Under the double sealing of the extrusion ring and the sealing ring, the sealing property of the connection of the recoil valve is improved, which effectively avoids leakage at the connection during the recoil process and improves the stability of the recoil valve during use. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a three-dimensional structural schematic diagram of a pressure sensing recoil valve for a mud separation recoil system.

[0019] Figure 2 The figure is a schematic diagram of the internal structure of a pressure sensing recoil valve for a mud separation recoil system.

[0020] Figure 3 The schematic diagram of the exploded structure of the knocking assembly in a pressure sensing recoil valve for a mud separation recoil system is shown in FIG.

[0021] Figure 4 The schematic diagram is a decomposed structure of a collecting component in a pressure sensing recoil valve for a mud separation recoil system.

[0022] Figure 5 A pressure sensing recoil valve for a mud separation recoil system Figure 2 Schematic diagram of the enlarged structure at point A in the middle.

[0023] Figure 6 The present invention is a schematic diagram of a partial three-dimensional structure of a sealing component in a pressure sensing recoil valve for a mud separation recoil system.

[0024] Figure 7 A pressure sensing recoil valve for a mud separation recoil system Figure 6Schematic diagram of the enlarged structure at point B in the middle.

[0025] Legend: 1. Valve body; 2. Valve cover; 3. Input pipe; 4. Output pipe; 5. Pressure sensor; 6. Knocking assembly; 61. Rotating rod; 62. Transmission gear; 63. Rotating disk; 64. Knocking rod; 65. Limit sleeve; 7. Collecting assembly; 71. Travel groove; 72. Discharge port; 73. Collecting box; 74. Sealing cover; 8. Baffle; 9. Connecting rod; 10. Turning handle; 11. Driving gear; 12. Support rod; 13. Sealing assembly; 131. Movable plate; 132. Connecting spring; 133. Extrusion rod; 134. Extrusion ring; 135. Push rod; 136. Sealing ring; 137. Mounting plate; 138. Positioning rod. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] See also Figure 1-7 The present invention provides a technical solution: a pressure sensing recoil valve for a mud separation recoil system, comprising a valve body 1, a valve cover 2 is fixedly installed on the upper surface of the valve body 1 by bolts, an input pipe 3 and an output pipe 4 are connected and installed on the outer surface of the valve body 1, a knocking component 6 is arranged on the inner wall of the valve cover 2, a collecting component 7 is arranged on the inner wall of the bottom surface of the valve body 1, and a sealing component 13 is arranged on the inner wall of the shell cavity of the input pipe 3 and the output pipe 4; The knocking assembly 6 includes a rotating rod 61, one end of which is rotatably connected to the inner wall of the top surface of the valve cover 2, a transmission gear 62 is fixedly installed on the outer surface of the rotating rod 61, a rotating disk 63 is fixedly installed on the other end of the rotating rod 61, a knocking rod 64 is rotatably installed on the lower surface of the rotating disk 63 through a rotating shaft, a limiting sleeve 65 is slidably installed on the outer surface of the knocking rod 64, one end of the limiting sleeve 65 is fixedly connected to the inner side wall of the valve cover 2, and a turning handle 10 is rotatably installed on the upper surface of the valve cover 2 One end of the turning handle 10 extends to the interior of the valve cover 2 and is fixedly installed with a connecting rod 9. A driving gear 11 is fixedly installed on the outer surface of the connecting rod 9. The driving gear 11 is meshingly connected with the transmission gear 62. The diameter of the driving gear 11 is larger than the transmission gear 62. One end of the connecting rod 9 extends to the interior of the valve body 1. A support rod 12 is fixedly installed on one end of the connecting rod 9. A baffle 8 is fixedly installed on the outer surface of the support rod 12. The outer surface of the baffle 8 is in contact with the inner wall of the valve body 1.

[0028] The specific implementation example is as follows: with the transportation of mud, the input pipe 3 may be blocked. When the pressure sensor 5 senses that the pressure in the input pipe 3 is too high, it will automatically control the turning handle 10 to rotate. At this time, the turning handle 10 will drive the support rod 12 to rotate through the connecting rod 9. At this time, the support rod 12 will drive the baffle 8 to rotate. When the baffle 8 is perpendicular to the pipe openings of the input pipe 3 and the output pipe 4, it is in a fully open state. At this time, the mud will flow into the slurry storage tank through the output pipe 4, and the slag that has sunk to the bottom of the slurry storage tank will be flushed up, thereby avoiding the slurry storage tank from being blocked due to long-term use. The recoil valve will be closed after the recoil is over, and the connecting rod 9 will drive the driving gear 11 to rotate during the closing process, and the rotating rod 61 will be driven by the transmission gear 62 to rotate on the inner wall of the top surface of the valve cover 2, and the rotating rod 61 will drive the rotating disk 63 to rotate. At this time, the knocking rod 64 knocks on the inner wall of the valve cover 2 under the limit of the limit sleeve 65, and the knocked valve cover 2 will drive the valve body 1 to vibrate synchronously, and the mud and sand adhered to the inner wall of the vibrated valve body 1 will flow into the collection box 73 through the threaded port.

[0029] The collecting assembly 7 includes a travel groove 71 and a sealing cover 74. The travel groove 71 is arranged on the inner wall of the bottom surface of the valve body 1. A threaded opening is arranged on the inner wall of the travel groove 71. A collecting box 73 is threadedly installed on the outer surface of the threaded opening. The upper surface of the sealing cover 74 is fixedly connected to the lower surface of the baffle 8. The outer surface of the sealing cover 74 is slidably connected to the inner wall of the travel groove 71. The sealing cover 74 is adapted to the travel groove 71 and the threaded opening.

[0030] The specific implementation method is as follows: when the recoil valve is opened next time, the baffle 8 will drive the sealing cover 74 to move in the stroke groove 71 to seal the threaded opening, thereby preventing the mud from carrying away the mud in the collection box 73 when flowing. When the mud in the collection box 73 reaches a certain amount, the collection box 73 is removed and cleaned under the action of the thread.

[0031] The sealing assembly 13 includes a movable plate 131, on the side wall of which a connecting spring 132 is fixedly installed, one end of which is fixedly connected to the inner wall of the shell cavity of the input pipe 3, and an extrusion rod 133 and a push rod 135 are fixedly installed on the other side wall of the movable plate 131, respectively, one end of which is fixedly installed with an extrusion ring 134, which extends to the outside of the input pipe 3, one end of which is fixedly installed with a sealing ring 136, which extends to the outside of the input pipe 3, a positioning rod 138 is fixedly installed on the inner wall of the movable plate 131, one end of which extends to the outside of the movable plate 131, and a mounting plate 137 is rotatably installed on one end of the positioning rod 138, one end of which is fixedly connected to the inner wall of the shell cavity of the input pipe 3, the extrusion ring 134 and the sealing ring 136 are both made of rubber, and a pressure sensor 5 is fixedly installed on the inner wall of the input pipe 3.

[0032] The specific implementation example is as follows: the input pipe 3 is connected to the output end of the slurry pump, and the output pipe 4 is communicated with the side wall of the slurry storage tank. When the input pipe 3 and the output pipe 4 are connected, the extrusion ring 134 will be squeezed, thereby moving into the shell cavity of the input pipe 3 and the output pipe 4. As the extrusion ring 134 moves, one end of the movable plate 131 will be squeezed through the extrusion rod 133. At this time, the other end of the squeezed movable plate 131 will be tilted under the limitation of the positioning rod 138 and the mounting plate 137, so that the sealing ring 136 will move to the outside of the input pipe 3 and the output pipe 4 under the action of the push rod 135. Since the extrusion ring 134 and the sealing ring 136 are both made of rubber, the connection will be sealed.

[0033] Working principle: The input pipe 3 is connected to the output end of the slurry pump, and the output pipe 4 is connected to the side wall of the slurry storage tank. When the input pipe 3 and the output pipe 4 are connected, the extrusion ring 134 will be squeezed, so that it moves into the shell cavity of the input pipe 3 and the output pipe 4. As the extrusion ring 134 moves, it will squeeze one end of the movable plate 131 through the extrusion rod 133. At this time, the other end of the squeezed movable plate 131 will be tilted under the limit of the positioning rod 138 and the mounting plate 137, so that the sealing ring 134 is pressed under the action of the push rod 135. 36 moves to the outside of the input pipe 3 and the output pipe 4. Since the extrusion ring 134 and the sealing ring 136 are made of rubber, the connection will be sealed. With the transportation of mud, the input pipe 3 may be blocked. When the pressure sensor 5 senses that the pressure in the input pipe 3 is too high, it will automatically control the turning handle 10 to rotate. At this time, the turning handle 10 will drive the support rod 12 to rotate through the connecting rod 9. At this time, the support rod 12 will drive the baffle 8 to rotate. When the baffle 8 is aligned with the input pipe 3 and the output pipe 4, the baffle 8 will rotate. When the pipe mouth is vertical, it is in a fully open state. At this time, the mud will flow into the slurry storage tank through the output pipe 4, and the slag that has settled at the bottom of the slurry storage tank will be flushed up, thereby avoiding the accumulation of slurry in the slurry storage tank due to long-term use. After the recoil is completed, the recoil valve will be closed. During the closing process, the connecting rod 9 will drive the driving gear 11 to rotate, and the rotating rod 61 will be driven by the transmission gear 62 to rotate on the inner wall of the top surface of the valve cover 2. The rotating rod 61 will drive the rotating disk 63 to rotate. At this time, the knocking rod 64 is in the limit sleeve 65. The inner wall of the valve cover 2 is knocked under the limit, and the knocked valve cover 2 will drive the valve body 1 to vibrate synchronously. The mud and sand adhered to the inner wall of the vibrated valve body 1 will flow into the collection box 73 through the threaded opening. When the recoil valve is opened next time, the baffle 8 will drive the sealing cover 74 to move in the stroke groove 71 to seal the threaded opening, thereby preventing the mud from carrying away the mud in the collection box 73 when flowing. When the mud in the collection box 73 reaches a certain amount, the collection box 73 is removed for cleaning under the action of the thread.

[0034] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A pressure sensing recoil valve for a mud separation recoil system, comprising a valve body (1), characterized in that: A valve cover (2) is fixedly mounted on the upper surface of the valve body (1) by means of bolts, an input pipe (3) and an output pipe (4) are respectively connected and mounted on the outer surface of the valve body (1), a knocking assembly (6) is arranged on the inner wall of the valve cover (2), a collecting assembly (7) is arranged on the inner wall of the bottom surface of the valve body (1), and a sealing assembly (13) is arranged on the inner walls of the shell cavities of the input pipe (3) and the output pipe (4); The knocking assembly (6) comprises a rotating rod (61), one end of the rotating rod (61) being rotatably connected to the inner wall of the top surface of the valve cover (2), a transmission gear (62) being fixedly mounted on the outer surface of the rotating rod (61), and a rotating disk (63) being fixedly mounted on the other end of the rotating rod (61).

2. A pressure sensing recoil valve for a mud separation recoil system according to claim 1, characterized in that: A knocking rod (64) is rotatably mounted on the lower surface of the rotating disk (63) via a rotating shaft, and a limiting sleeve (65) is slidably mounted on the outer surface of the knocking rod (64), wherein one end of the limiting sleeve (65) is fixedly connected to the inner side wall of the valve cover (2).

3. A pressure sensing recoil valve for a mud separation recoil system according to claim 2, characterized in that: A turning handle (10) is rotatably mounted on the upper surface of the valve cover (2), one end of the turning handle (10) extends into the interior of the valve cover (2) and is fixedly mounted with a connecting rod (9), a driving gear (11) is fixedly mounted on the outer surface of the connecting rod (9), the driving gear (11) is meshingly connected with the transmission gear (62), and the diameter of the driving gear (11) is larger than that of the transmission gear (62).

4. A pressure sensing recoil valve for a mud separation recoil system according to claim 3, characterized in that: One end of the connecting rod (9) extends into the interior of the valve body (1), a support rod (12) is fixedly mounted on one end of the connecting rod (9), a baffle (8) is fixedly mounted on the outer surface of the support rod (12), and the outer surface of the baffle (8) is in contact with the inner wall of the valve body (1).

5. A pressure sensing recoil valve for a mud separation recoil system according to claim 4, characterized in that: The collecting assembly (7) comprises a travel groove (71) and a sealing cover (74); the travel groove (71) is arranged on the inner wall of the bottom surface of the valve body (1); a threaded opening is arranged on the inner wall of the travel groove (71); and a collecting box (73) is threadedly mounted on the outer surface of the threaded opening.

6. A pressure sensing recoil valve for a mud separation recoil system according to claim 5, characterized in that: The upper surface of the sealing cover (74) is fixedly connected to the lower surface of the baffle (8), the outer surface of the sealing cover (74) is slidably connected to the inner wall of the travel groove (71), and the sealing cover (74) is adapted in size to the travel groove (71) and the threaded opening.

7. A pressure sensing recoil valve for a mud separation recoil system according to claim 6, characterized in that: The sealing assembly (13) comprises a movable plate (131), a connecting spring (132) being fixedly mounted on a side wall of the movable plate (131), one end of the connecting spring (132) being fixedly connected to an inner wall of a shell cavity of the input pipe (3), and an extrusion rod (133) and a push rod (135) being fixedly mounted on the other side wall of the movable plate (131).

8. A pressure sensing recoil valve for a mud separation recoil system according to claim 7, characterized in that: An extrusion ring (134) is fixedly mounted on one end of the extrusion rod (133), and the extrusion ring (134) extends to the outside of the input pipe (3); a sealing ring (136) is fixedly mounted on one end of the push rod (135), and the sealing ring (136) extends to the outside of the input pipe (3).

9. A pressure sensing recoil valve for a mud separation recoil system according to claim 8, characterized in that: A positioning rod (138) is fixedly mounted on the inner wall of the movable plate (131), one end of the positioning rod (138) extends to the outside of the movable plate (131), and a mounting plate (137) is rotatably mounted on one end of the positioning rod (138).

10. A pressure sensing recoil valve for a mud separation recoil system according to claim 9, characterized in that: One end of the mounting plate (137) is fixedly connected to the inner wall of the shell cavity of the input pipe (3); the extrusion ring (134) and the sealing ring (136) are both made of rubber material; and a pressure sensor (5) is fixedly mounted on the inner wall of the input pipe (3).

Images