Tobacco shred conveying device and constant-flow feeding system

Abstract

The utility model relates to the technical field of tobacco processing, and provides a tobacco shred conveying device and a constant flow feeding system, the tobacco shred conveying device comprises a conveying belt, a metering tube, a transmitting grating, a receiving grating and a controller; an inlet of the metering pipe is communicated with an outlet end of the feeding machine, and an outlet of the metering pipe is positioned at the front end of the conveying belt; the transmitting grating and the receiving grating are oppositely arranged and are arranged on the two sides of the metering tube respectively, and a first gap exists between the bottom of a light beam transmitted by the transmitting grating and the bottom of the metering tube; the transmitting grating and the receiving grating are both in communication connection with the controller, and the controller is used for being in communication connection with a speed adjusting device of the feeding machine. According to the tobacco shred conveying device, the emitting grating and the receiving grating are arranged on the two sides of the metering pipe, and the controller can accurately and continuously monitor the stacking height of materials in the metering pipe and adjust the feeding speed of the feeding machine by detecting changes of signals generated by the gratings, so that the conveying flow is kept constant.

Description

Technical Field

[0001] The utility model relates to the technical field of tobacco processing, in particular to a tobacco shred conveying device and a constant-flow feeding system. Background Art

[0002] In the tobacco industry, a traditional typical constant-flow control system generally consists of a feeder - metering tube (three pairs of photoelectric tubes 3) - electronic belt scale. The control system is shown in the following figure. Materials are fed from the feeder to the metering tube, and after passing through the metering tube, they are transported to the electronic belt scale. After weighing and flow control in the weighing and metering section inside the electronic belt scale, they are transported to the next-level equipment to complete the work of this control system. In the control system, the silo of the feeder is used to store materials, and the lifting belt of the feeder is used to feed materials to the metering tube. Three pairs of high, medium, and low photoelectric tubes are installed on the metering tube to detect the depth of material accumulation in the metering tube. According to the detected material accumulation position, the feeding speed of the lifting belt of the feeder is controlled: when the material accumulation depth is lower than the low level, the feeder feeds at high speed; when the medium level is blocked, the lifting belt feeds at medium speed; when the high level is continuously blocked for 3 seconds, the lifting belt stops feeding to prevent materials from accumulating in the discharge hopper of the lifting belt of the feeder above the metering tube, causing the discharge hopper to be blocked and resulting in production stagnation.

[0003] The existing constant-flow control system only has three levels of high, medium, and low and corresponding three-speed controls. When the change in material accumulation is small, the sensitivity of flow monitoring is insufficient, and it is difficult to maintain a constant flow rate. Summary of the Utility Model

[0004] The utility model provides a tobacco shred conveying device and a constant-flow feeding system to solve the problem that in the existing technology, when the change in material accumulation is small, the sensitivity of flow monitoring of the constant-flow control system is insufficient, and it is difficult to maintain a constant material flow rate.

[0005] In a first aspect, the utility model provides a tobacco shred conveying device, including:

[0006] A conveyor belt;

[0007] A metering tube, the inlet of the metering tube is used to communicate with the outlet end of the feeder, and the outlet of the metering tube is located at the front end of the conveyor belt;

[0008] An emitting grating and a receiving grating arranged oppositely, the emitting grating and the receiving grating are respectively arranged on both sides of the metering tube, and there is a first gap between the bottom of the light beam emitted by the emitting grating and the bottom of the metering tube;

[0009] A controller, both the emitting grating and the receiving grating are communicatively connected to the controller, and the controller is used to communicatively connect with the speed regulating device of the feeder.

[0010] According to the tobacco cuttings conveying device provided by the present utility model, the metering pipe comprises a blanking pipe section and a straight pipe section that are communicated with each other;

[0011] The cross-sectional area of the blanking pipe section gradually decreases from the inlet end to the outlet end; the inlet of the blanking pipe section is used for communicating with the outlet end of the feeder, and the outlet is communicated with the inlet of the straight pipe section;

[0012] The transmitting grating and the receiving grating are respectively arranged on both sides of the straight pipe section.

[0013] According to the tobacco cuttings conveying device provided by the present utility model, the blanking pipe section is a conical pipe or a funnel-shaped pipe.

[0014] According to the tobacco cuttings conveying device provided by the present utility model, a baffle is arranged in the straight pipe section, and the baffle is located directly above the light beam emitted by the transmitting grating.

[0015] According to the tobacco cuttings conveying device provided by the present utility model, it further comprises a vibration assembly, and the vibrating end of the vibration assembly is connected to the blanking pipe section.

[0016] According to the tobacco cuttings conveying device provided by the present utility model, the vibration assembly comprises a power supply, a vibration motor and a photoelectric detection switch. The photoelectric detection switch, the vibration motor and the power supply are connected to form a circuit. The photoelectric detection switch is arranged at the outlet of the blanking pipe section, and the vibration motor is arranged on the blanking pipe section.

[0017] According to the tobacco cuttings conveying device provided by the present utility model, a movable door is arranged at the opening of the metering pipe. The movable door is in transmission connection with a driving member, and the driving member can drive the movable door to move to control the opening size of the metering pipe;

[0018] The driving member is in communication connection with the controller.

[0019] According to the tobacco cuttings conveying device provided by the present utility model, the conveyor belt comprises: an electronic belt weigher;

[0020] The metering pipe is arranged at the front end of the electronic belt weigher, and the electronic belt weigher is in communication connection with the controller.

[0021] In a second aspect, the present utility model provides a constant-flow feeding system, comprising:

[0022] A feeder and the tobacco cuttings conveying device as described in any one of the above;

[0023] The inlet of the metering pipe is communicated with the outlet end of the feeder, and the controller is in communication connection with the speed regulating device of the feeder.

[0024] According to the constant-flow feeding system of the present utility model, the feeder includes an inclined conveying section, the height of the inlet end of the inclined conveying section is lower than the height of the outlet end of the inclined conveying section, and the outlet end of the inclined conveying section is directly above the inlet of the metering pipe.

[0025] For the cigarette tobacco conveying device of the present utility model, by arranging a transmitting grating and a receiving grating on both sides of the metering pipe, the light beam between the transmitting grating and the receiving grating will be blocked when the material in the metering pipe accumulates to a certain height. By detecting the change in the signal generated by the grating caused by the change in the light beam, the controller can accurately and continuously monitor the height of the material accumulation in the metering pipe, and accurately and continuously adjust the feeding speed of the feeder according to the height of the material accumulation, so that the flow rate of the entire material level remains constant and is maintained at the target flow rate. At the same time, by leaving a first gap between the bottom of the light beam and the bottom of the metering pipe, when the accumulated amount of the material in the metering pipe has not reached the bottom of the light beam and the controller monitors that the signal generated by the grating remains at a specific signal, the controller can control the feeder to quickly increase the feeding speed, so that the flow rate of the entire material level quickly increases and approaches the target flow rate. The cigarette tobacco conveying device of the present utility model effectively solves the problem that in the prior art, the constant-flow control system has insufficient sensitivity in flow rate monitoring when the change in the accumulated amount of the material is small, and it is difficult to maintain the constancy of the material flow rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the present utility model or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0027] Figure 1 is a schematic diagram of the cigarette tobacco conveying device provided by an embodiment of the present utility model;

[0028] Figure 2 is a schematic diagram of the transmitting grating and the receiving grating provided by an embodiment of the present utility model;

[0029] Figure 3 is a schematic diagram of the constant-flow feeding system provided by an embodiment of the present utility model.

[0030] Reference Numerals:

[0031] 1. Cigarette tobacco conveying device;

[0032] 11. Metering pipe; 111. Feeding pipe section; 112. Straight pipe section;

[0033] 12. Transmitting grating; 13. Receiving grating; 14. Electronic belt scale;

[0034] 2. Feeder; 21. Inclined conveying section. Detailed implementation manners

[0035] To make the objectives, technical solutions and advantages of the present utility model clearer, the technical solutions in the present utility model will be clearly and completely described below in conjunction with the accompanying drawings in the present utility model. Obviously, the described embodiments are some but not all of the embodiments of the present utility model. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present utility model without making creative efforts fall within the protection scope of the present utility model.

[0036] In the description of the embodiments of the present utility model, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the embodiments of the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the embodiments of the present utility model. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0037] In the description of the present utility model, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "connection", "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific situations.

[0038] The following will be described in conjunction with Figures 1-3 Describe the tobacco cuttings conveying device 1 provided by the present utility model.

[0039] As Figures 1 to 3 shown, the tobacco cuttings conveying device 1 provided by the present utility model includes: a conveyor belt, a metering pipe 11, a transmitting grating 12, a receiving grating 13, and a controller (not shown in the figure); the inlet of the metering pipe 11 is used to communicate with the outlet end of the feeder 2, and the outlet of the metering pipe 11 is located at the front end of the conveyor belt; the transmitting grating 12 and the receiving grating 13 are arranged oppositely, the transmitting grating 12 and the receiving grating 13 are respectively arranged on both sides of the metering pipe 11, and there is a first gap between the bottom of the light beam emitted by the transmitting grating 12 and the bottom of the metering pipe 11; both the transmitting grating 12 and the receiving grating 13 are communicatively connected to the controller, and the controller is used to communicate with the speed regulating device of the feeder 2.

[0040] In this embodiment, by arranging the metering pipe 11 at the outlet end of the feeder 2 and connecting the inlet of the metering pipe 11 with the outlet end of the feeder 2, the feeding of the feeder 2 will enter the metering pipe 11 from the outlet end, so as to measure the material flow rate conveyed by the feeder 2, and reach the conveyor belt through the outlet of the metering pipe 11, and be conveyed by the conveyor belt to the work station of the next process; a transmitting grating 12 and a receiving grating 13 are oppositely arranged on both sides of the metering pipe 11. The light beam emitted by the transmitting grating 12 will pass through the metering pipe 11 and shoot towards the receiving grating 13, be received by the receiving grating 13 and generate corresponding signals. When the material in the metering pipe 11 accumulates to a sufficient height and blocks the light beam of the transmitting grating 12, the height of the light beam received by the receiving grating 13 will also change, and the generated signal will also change. The generated signal is sent to the controller. The controller can determine the accumulation height of the material in the current metering pipe 11 according to the generated signal, calculate the current feeding speed according to the accumulation height of the material in the current metering pipe 11, and thus control the feeding speed of the feeder 2 according to the current feeding speed and the target feeding speed, so that the feeding speed can be maintained at the target feeding speed; the change in the height of the light beam received by the receiving grating 13 and the corresponding change in the generated signal can more accurately and continuously reflect the change in the accumulation height of the material in the metering pipe 11, so that the controller can also more accurately and continuously regulate the feeding speed of the feeder 2, which is beneficial to maintaining a constant speed of the feeding speed of the entire feeding system; in addition, by leaving a first gap between the bottom of the light beam emitted by the transmitting grating 12 and the bottom of the metering pipe 11, a non-detection interval is formed between the bottom of the light beam and the bottom of the metering pipe 11. When the accumulation amount of the material in the metering pipe 11 has not reached the bottom of the light beam, it indicates that the gap between the current feeding speed and the target feeding speed is too large. Adjust the feeding speed of the feeder 2 to the maximum or quickly increase the feeding speed of the feeder 2, so that the feeding speed of the entire system can be quickly increased until the target requirements are met, which can simplify the control device and the control process.

[0041] The tobacco cuttings conveying device 1 of the present utility model is provided with a transmitting grating 12 and a receiving grating 13 on both sides of a metering tube 11. When the material in the metering tube 11 accumulates to a certain height, the light beam between the transmitting grating 12 and the receiving grating 13 will be blocked. By detecting the signal change generated by the grating due to the change of the light beam, the controller can accurately and continuously monitor the material accumulation height in the metering tube 11, and accurately and continuously adjust the feeding speed of the feeder 2 according to the material accumulation height, so as to keep the flow rate of the entire material level constant and maintain it at the target flow rate. At the same time, by leaving a first gap between the bottom of the light beam and the bottom of the metering tube 11, when the material accumulation amount in the metering tube 11 has not reached the bottom of the light beam and the controller monitors that the signal generated by the grating remains at a specific signal, the controller can control the feeder 2 to quickly increase the feeding speed, so that the flow rate of the entire material level quickly increases and approaches the target flow rate. The tobacco cuttings conveying device 1 of the present utility model effectively solves the problem in the prior art that the sensitivity of flow rate monitoring is insufficient when the change of the material accumulation amount is small in the constant flow control system, and it is difficult to maintain the constancy of the material flow rate.

[0042] Specifically, in some embodiments, as Figure 1 shown, the metering tube 11 includes a blanking pipe section 111 and a straight pipe section 112 that are communicated with each other; the cross-sectional area of the blanking pipe section 111 gradually decreases from the inlet end to the outlet end; the inlet of the blanking pipe section 111 is used to communicate with the outlet end of the feeder 2, and the outlet communicates with the inlet of the straight pipe section 112; the transmitting grating 12 and the receiving grating 13 are respectively arranged on both sides of the straight pipe section 112.

[0043] In this embodiment, by dividing the metering tube 11 into a blanking pipe section 111 and a straight pipe section 112, and the cross-sectional area of the blanking pipe section 111 gradually decreases from the inlet end to the outlet end, the cross-sectional area of the inlet end of the blanking pipe section 111 is larger, so as to prevent the material on the feeder 2 from falling outside the pipe when falling from the outlet end, resulting in waste of materials. At the same time, by respectively arranging the transmitting grating 12 and the receiving grating 13 on both sides of the straight pipe section 112, the volume of the material accumulated in the straight pipe section 112 changes uniformly with the height, so as to monitor the volume of the material in the metering tube 11 through the signal change caused by the change of the height between the gratings. The structure is simple, convenient and practical.

[0044] Optionally, in some embodiments, the blanking pipe section 111 is a conical pipe or a funnel-shaped pipe. In this embodiment, both the conical pipe and the funnel-shaped pipe are pipe sections with a large area at the inlet end and a small area at the outlet end, and the inner wall of the pipe between the inlet end and the outlet end is an inclined surface or an arc surface, so that the material falling into the blanking pipe section 111 can slide along the inner wall of the pipe to the outlet end and enter the straight pipe section 112. The structure is simple and practical.

[0045] Optionally, in some embodiments, a baffle is provided in the straight pipe section 112, and the baffle is located directly above the light beam emitted by the emission grating 12.

[0046] In this embodiment, by providing a baffle directly above the light beam, the baffle can block the material, preventing the material from passing through the light beam during the falling process and causing occlusion of the light beam, thereby causing fluctuations in the signal generated by the grating and affecting the control of the speed of the feeder 2 by the controller, making the flow control of the entire feeding system more stable and reliable.

[0047] Optionally, in some embodiments, the tobacco conveying device 1 further includes a vibration assembly, and the vibrating end of the vibration assembly is connected to the blanking pipe section 111.

[0048] In this embodiment, by connecting the vibrating end of the vibration assembly to the blanking pipe section 111, the vibration assembly can drive the blanking pipe section 111 to vibrate slightly, thereby vibrating off the material on the inner wall of the blanking pipe section 111 and enabling the material to slide into the straight pipe section 112, avoiding waste of a small amount of material remaining on the inner wall of the blanking pipe section 111.

[0049] Specifically, in some embodiments, the vibration assembly includes a power supply, a vibration motor, and a photoelectric detection switch. The photoelectric detection switch, the vibration motor, and the power supply are connected to form a circuit. The photoelectric detection switch is disposed at the outlet of the blanking pipe section 111, and the vibration motor is disposed on the blanking pipe section 111.

[0050] In this embodiment, it is easy to understand that the outlet of the blanking pipe section 111 is the thinnest position of the blanking pipe section 111 and is most likely to be blocked. By providing a photoelectric detection switch at the outlet of the blanking pipe section 111 to detect whether the outlet of the blanking pipe section 111 is blocked, when a blockage occurs, the photoelectric detection switch closes, thereby making the circuit formed by the photoelectric detection switch, the vibration motor, and the power supply conductive, the vibration motor is energized to vibrate, driving the blanking pipe section 111 to vibrate slightly, vibrating and loosening the blocked material, and no longer blocking the blanking pipe section 111.

[0051] Optionally, in one embodiment, a movable door is provided at the opening of the metering pipe 11. The movable door is in transmission connection with a driving member, and the driving member can drive the movable door to move to control the opening size of the metering pipe 11; the driving member is in communication connection with the controller.

[0052] In this embodiment, by providing a movable door at the opening of the metering pipe 11, and the driving member of the movable door is in communication connection with the controller, the controller can control the driving member according to the signal of the grating, drive the movable door to adjust the opening size of the metering pipe 11, thereby further controlling the flow rate of the material entering or flowing out of the metering pipe 11, and coordinating with the adjustment of the feeding speed of the feeder 2, the control effect is better.

[0053] It is easy to understand that the movable door can be arranged at the inlet or outlet of the metering pipe 11; preferably, the movable door can be arranged at the outlet of the metering pipe 11. When the movable door is arranged at the inlet of the metering pipe 11, it may block the material and cause the material to fall outside the metering pipe 11, resulting in waste of the material.

[0054] In some embodiments, as Figure 1 shown, the conveyor belt includes: an electronic belt scale 14; the metering pipe 11 is arranged at the front end of the electronic belt scale 14, and the electronic belt scale 14 is communicatively connected with the controller.

[0055] In this embodiment, by arranging the metering pipe 11 at the front end of the electronic belt scale 14, when the material flowing out of the metering pipe 11 passes through the metering section of the electronic belt scale 14, the electronic belt scale 14 can weigh the material and send the weight signal of the material to the controller. The controller can control the feeding speed of the feeder 2 according to the material accumulation amount in the metering pipe 11 and the material weight on the electronic belt scale 14, and can monitor and control the volume flow rate and mass flow rate of the feeding at the same time, so as to better control the feeding flow rate within the range required by the production process and ensure the refined production requirements.

[0056] Based on the above embodiments, according to the production process requirements, the material accumulation height of the metering pipe 11 corresponding to the target flow rate can be used as the reference line, and the lifting belt of the feeder 2 can be PID adjusted based on the material accumulation height in the metering pipe 11. When the material is lower than the target accumulation height, the lifting belt is controlled to accelerate, and the material entering the metering pipe 11 increases, and the accumulation height rises. When the material is higher than the target accumulation height, the lifting belt is controlled to decelerate, and the material entering the metering pipe 11 decreases, reducing the accumulation depth.

[0057] After the preliminary control of the material accumulation height by the metering pipe 11 and the grating, the mass flow rate of the material conveyed to the electronic belt scale 14 is relatively stable. When the material passes through the weighing and metering section of the electronic belt scale 14, the electronic belt scale 14 weighs the material and simultaneously performs PID tracking adjustment of the flow rate. After two PID controls of the material flow rate, a continuous and dynamic balance is formed among the feeding of the feeder 2, the material level control of the metering pipe 11, and the flow rate control of the electronic belt scale 14. Through the above constant flow rate refined control, the fluctuation change of the instantaneous flow rate can be effectively controlled within the range required by the production process, which is beneficial to further ensuring the refined production requirements.

[0058] In a second aspect, the present invention further provides a constant flow rate feeding system, including: a feeder 2 and a tobacco shred conveying device 1 provided in any of the above embodiments; the inlet of the metering pipe 11 is communicated with the outlet end of the feeder 2, and the controller is communicatively connected with the speed regulating device of the feeder 2.

[0059] The constant-flow feeding system of the present utility model, by adopting the tobacco conveying device 1 in the above embodiment, also has the advantages of the tobacco conveying device 1, which will not be elaborated here.

[0060] Specifically, in some embodiments, as Figure 3 shown, the feeder 2 includes an inclined conveying section 21. The height of the inlet end of the inclined conveying section 21 is lower than the height of the outlet end of the inclined conveying section 21, and the outlet end of the inclined conveying section 21 is directly above the inlet of the metering pipe 11.

[0061] In this embodiment, by providing the inclined conveying section 21 on the feeder 2 and making the height of the inlet end of the inclined conveying section 21 lower to receive the materials sent out from the previous process, and the height of the outlet end of the inclined conveying section 21 higher to transport the materials to a higher position so that the materials can fall from the outlet end into the metering pipe 11 for subsequent flow control.

[0062] The embodiments described above are merely illustrative. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art can understand and implement it without creative efforts.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present utility model, not to limit them; although the present utility model has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present utility model.

Claims

1. A cut tobacco conveying device, characterized in that, Comprising: Conveyor belt; Metering pipe, the inlet of the metering pipe is used to communicate with the outlet end of the feeder, and the outlet of the metering pipe is located at the front end of the conveyor belt; Emitter grating and receiver grating arranged oppositely, the emitter grating and the receiver grating are respectively arranged on both sides of the metering pipe, and there is a first gap between the bottom of the light beam emitted by the emitter grating and the bottom of the metering pipe; Controller, both the emitter grating and the receiver grating are communicatively connected to the controller, and the controller is used to communicate with the speed regulating device of the feeder.

2. The cut tobacco conveying device according to claim 1, characterized in that, The metering pipe includes a blanking pipe section and a straight pipe section that communicate with each other; The cross-sectional area of the blanking pipe section gradually decreases from the inlet end to the outlet end; the inlet of the blanking pipe section is used to communicate with the outlet end of the feeder, and the outlet communicates with the inlet of the straight pipe section; The emitter grating and the receiver grating are respectively arranged on both sides of the straight pipe section.

3. The tobacco conveying device according to claim 2, characterized in that, The blanking pipe section is a conical pipe or a funnel-shaped pipe.

4. The cut tobacco conveying device according to claim 2, characterized in that A baffle is arranged in the straight pipe section, and the baffle is located directly above the light beam emitted by the emitter grating.

5. The tobacco cut filler conveying device according to claim 2, wherein, It further includes a vibration assembly, and the vibrating end of the vibration assembly is connected to the blanking pipe section.

6. The cut tobacco conveying device according to claim 5, characterized in that, The vibration assembly includes a power supply, a vibration motor and a photoelectric detection switch. The photoelectric detection switch, the vibration motor and the power supply are connected to form a circuit. The photoelectric detection switch is arranged at the outlet of the blanking pipe section, and the vibration motor is arranged on the blanking pipe section.

7. The cut tobacco conveying device according to claim 1, wherein, An activity door is arranged at the opening of the metering pipe, and the activity door is in transmission connection with a driving member. The driving member can drive the activity door to move to control the opening size of the metering pipe; The driving member is communicatively connected to the controller.

8. The tobacco conveying device according to claim 1, characterized in that, The conveyor belt includes: an electronic belt scale; The metering pipe is arranged at the front end of the electronic belt scale, and the electronic belt scale is communicatively connected to the controller.

9. A constant-flow feeding system, characterized in that, Comprising: A feeder and a cut tobacco conveying device according to any one of claims 1-8; The inlet of the metering pipe communicates with the outlet end of the feeder, and the controller is communicatively connected to the speed regulating device of the feeder.

10. The constant flow feeding system according to claim 9, characterized in that, The feeder includes an inclined conveying section, the height of the inlet end of the inclined conveying section is lower than the height of the outlet end of the inclined conveying section, and the outlet end of the inclined conveying section is located directly above the inlet of the metering pipe.

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