Carbon nano tube discharging device

Abstract

The utility model belongs to the technical field of preparation of carbon nanotubes, and particularly relates to a carbon nanotube discharging device. The discharging device is arranged at the discharging end of the tubular heating furnace and comprises a collecting bin, and a collecting cavity communicating with a discharging opening of the tubular heating furnace is formed in the collecting bin. An operation opening is formed in the collecting bin, a flexible pipeline is connected to the operation opening, and the operation opening is connected with the near end of the flexible pipeline in a sealed mode; at least one operating rod penetrates through the flexible pipeline and extends into the collecting cavity, and the far end of the flexible pipeline is in sealed connection with the operating rod; a discharging connector is arranged at the bottom of the collecting bin. The collecting bin arranged at the discharging end is beneficial to timely removal of flocculent single-walled carbon nanotubes formed in the growth process, furnace tube blockage is prevented, production continuity is guaranteed, and safety is improved. And a flexible pipeline and an operating rod are arranged on the collecting bin, so that an operator can collect the carbon nanotubes under the condition that the normal operation of the heating furnace is not influenced. The winding roller is beneficial to orderly collection of carbon nanotube floccules.

Description

Technical Field

[0001] The utility model belongs to the technical field of the preparation of carbon nanotubes, and particularly relates to a carbon nanotube discharging device. Background Art

[0002] Carbon nanotubes, also known as buckytubes, are one-dimensional quantum materials with special structures. Their radial size is in the nanometer range, and their axial size is in the micrometer range. The two ends of the tubes are basically sealed. Carbon nanotubes are mainly composed of several to dozens of coaxial circular tubes formed by carbon atoms arranged in a hexagonal pattern. The distance between layers is fixed, about 0.34 nm, and the diameter is generally 2 - 20 nm.

[0003] According to the number of graphene layers, carbon nanotubes are divided into two categories: single-walled carbon nanotubes and multi-walled carbon nanotubes. Among them, single-walled carbon nanotubes have more advantages, specifically reflected in: simple structure, stable chemical properties, few structural defects, excellent electrical conductivity, good elasticity, and high mechanical properties.

[0004] In the early stage, the ton-level production of carbon nanotubes was achieved by fixed-bed / moving-bed equipment. In a horizontally placed tubular furnace, through a delicate device, the continuous addition of catalysts and hydrocarbon raw materials and the continuous output of carbon nanotube products were realized, and the production of the first-generation carbon nanotube factories with an annual output of tons to dozens of tons per single device could be achieved.

[0005] The production of single-walled carbon nanotubes or carbon nanotubes using some special raw materials as carbon sources is usually based on the transformation of traditional equipment such as fluidized beds, which can effectively increase the multi-walled output, but the output of single-walled carbon nanotubes is still low, and the actual annual production capacity of a single device is only 30 - 50 KG.

[0006] Currently, in the development and design of larger-scale mass production equipment for single-walled carbon nanotubes, there is still a problem of carbon nanotube flocs. The growth of high-quality carbon nanotubes will form very fluffy flocs. If not removed in time, it will cause furnace tube blockage, increase the internal pressure, and affect the continuous production and the safety of the equipment. The existing carbon nanotube production devices adopt an intermittent collection method, discharging materials according to the output on time, which seriously affects the continuity and output of production, and is very likely to cause the accumulation of carbon nanotube floc products and block the furnace tube. Content of the Utility Model

[0007] Aiming at the deficiencies of the existing technology, the utility model provides a carbon nanotube discharging device.

[0008] The carbon nanotube discharging device provided by the present utility model is arranged at the discharging end of a tubular heating furnace, and includes a collection bin. The interior of the collection bin has a collection cavity communicated with the discharging port of the tubular heating furnace; an operation port is provided on the collection bin, and a flexible pipe is connected to the operation port. The operation port is hermetically connected to the proximal end of the flexible pipe; at least one control rod passes through the flexible pipe and extends into the collection cavity, and the distal end of the flexible pipe is hermetically connected to the control rod; a discharging interface is provided at the bottom of the collection bin.

[0009] As a further optimized solution of the carbon nanotube discharging device, the flexible pipe is an elastic corrugated pipe made of metal.

[0010] As a further optimized solution of the carbon nanotube discharging device, the end of the operation port has a flange port, and the proximal end of the flexible pipe has a flange port. The flange port at the end of the operation port is detachably connected to the flange port at the proximal end of the flexible pipe.

[0011] As a further optimized solution of the carbon nanotube discharging device, the distal end of the operation port has a flange port, and a sealing connection plate is provided on the rod body of the control rod. The flange port at the distal end of the operation port is detachably connected to the sealing connection plate on the control rod.

[0012] As a further optimized solution of the carbon nanotube discharging device, a hook head is provided at one end of the control rod located inside the collection bin, and a handle is provided at the end of the control rod located outside the collection bin.

[0013] As a further optimized solution of the carbon nanotube discharging device, the bottom of the collection bin is conical and a discharge port is provided at the bottom; a sealing bin door is provided on one side of the collection bin facing the discharging port of the tubular heating furnace, and the operation port is arranged on the sealing bin door.

[0014] As a further optimized solution of the carbon nanotube discharging device, at least one observation window is further provided on the collection bin, and the observation window and the operation port are on the same side of the collection bin.

[0015] As a further optimized solution of the carbon nanotube discharging device, a winding roller is rotatably arranged in the collection bin, and the winding roller is driven to rotate by a driving motor installed on the outer side wall of the collection bin.

[0016] As a further optimized solution of the carbon nanotube discharging device, an interlayer space is provided inside the bin wall of the collection bin, and a circulating cooling medium can be maintained in the interlayer space.

[0017] As a further optimized solution of the carbon nanotube discharging device, the distal end and the proximal end of the flexible pipe are of the same size; or the proximal end of the flexible pipe is larger than the distal end, forming a flared shape.

[0018] Beneficial effects

[0019] The carbon nanotube discharging device provided by the utility model provides a feasible discharging solution for large-batch continuous industrial production. The collecting bin arranged at the discharging end helps to timely remove the flocculent single-walled carbon nanotubes formed during the growth process, prevent the furnace tube from being blocked, ensure the continuity of production, and improve safety. The flexible pipe and the control rod arranged on the collecting bin enable the operator to collect the carbon nanotubes without affecting the normal operation of the heating furnace. A rotatable winding roller is arranged inside the collecting bin, which helps to orderly collect the carbon nanotube flocs, avoid material accumulation and chaos, and improve the collection efficiency. Description of the Drawings

[0020] Figure 1 and Figure 2 are the overall structural schematic diagrams of the heating furnace.

[0021] Figures 3 to 6 are the internal structural schematic diagrams of the heating furnace.

[0022] Figure 7 are the internal structural schematic diagrams of the furnace tube.

[0023] Figure 8 are the transverse sectional schematic diagrams of the interior of the heating furnace.

[0024] Figure 9 are the structural schematic diagrams of the feeding end of the furnace tube.

[0025] Figure 10 are the structural schematic diagrams of the collecting bin.

[0026] Figure 11 are the internal structural schematic diagrams of the collecting bin.

[0027] Figure 12 are the structural schematic diagrams of the control rod assembly.

[0028] Figure 13 are the structural schematic diagrams of the winding roller assembly.

[0029] In the figures: 1, furnace tube; 2, heat insulator; 3, cooling cover; 4, cooling jacket; 5, protective shell; 6, collecting bin; 11, intake pipe; 15, conduit; 16, atomizing nozzle; 21, heating chamber; 22, electric heating tube; 31, inner housing; 32, outer housing; 33, cooling chamber; 34, first liquid inlet; 35, first liquid outlet; 41, second liquid inlet; 42, second liquid outlet; 61, operation port; 62, flexible pipe; 63, control rod; 64, sealed bin door; 65, observation window; 66, winding roller; 67, drive motor; 111, preheating section. Detailed Embodiments

[0030] The present utility model will be further illustrated by the following embodiments, aiming to more clearly explain the technical solution of the present utility model and should not be construed as a limitation.

[0031] The preparation of carbon nanotubes is to carry out a high-temperature reaction on a raw material containing hydrogen, a catalyst precursor, a growth promoter precursor, and a carbon source in a heating furnace. The catalyst precursor decomposes and is reduced to catalyst particles through collision. The carbon source decomposes on the surface of the catalyst under the action of the catalyst, dissolves into the catalyst, and then precipitates carbon caps through diffusion. Continuous supply of the carbon source causes the carbon caps to elongate to form carbon nanotubes, which flow towards the tail end of the reaction chamber along with the hydrogen gas flow, and finally form macroscopic single-walled carbon nanotubes growing in different forms such as a film shape or a sponge shape.

[0032] Such as Figures 1 to 6 A tubular heating furnace for preparing carbon nanotubes as shown includes at least one furnace tube 1 and a heat insulator 2 arranged on the outer periphery of the furnace tube 1; the furnace tube 1 is a high-temperature-resistant pipe, which can be one or multiple pipes arranged in parallel. In the figure, two furnace tubes 1 are arranged in parallel in the heat insulator 2 as an example. The heat insulator 2 is made of a high-temperature-resistant heat-insulating material with a low thermal conductivity, and can be integrally formed or spliced. One end of the furnace tube 1 is the feed end, and the other end is the discharge end; there is a gap between the heat insulator 2 and the outer wall of the furnace tube 1, and the gap is divided into a plurality of heating chambers 21 arranged along the length direction of the furnace tube 1, so that the space inside the furnace tube 1 correspondingly forms a plurality of temperature zones; heating elements and temperature detection elements are arranged in the heating chambers 21. Among them, the furnace tube 1 is used to accommodate reactants and provide a heating and reaction space, and the plurality of heating chambers 21 arranged between the heat insulator 2 and the furnace tube 1 can control different heating temperatures. The heating elements heat the heating chambers 21, and the temperature detection elements detect the temperature of the heating chambers 21 to provide a basis for temperature control.

[0033] In some embodiments, the catalyst precursor can be placed in a high-temperature-resistant container such as a crucible or a porcelain boat, and then the high-temperature-resistant container is placed in the furnace tube 1. In some other embodiments, the catalyst precursor can also be gradually introduced into the furnace tube 1 through a pipeline with the gas flow at the feed end.

[0034] In some embodiments, the carbon source gas can be introduced into the furnace tube 1 through a pipeline at the feed end. In some other embodiments, the carbon source gas can also be introduced into the furnace tube 1 from a single point or multiple points on the side wall of the furnace tube 1.

[0035] Preferably, as Figure 6 And Figure 7As shown, a plurality of intake pipes 11 are also led out on the side wall of the furnace tube 1 and along the length direction of the furnace tube 1. Each intake pipe 11 is communicated with the inside of the furnace tube 1 to supply the raw material gas to different parts inside the furnace tube 1. Experiments have found that in the process of growing single-walled carbon nanotubes by the floating catalyst method, the requirements for hydrogen and carbon source are different at different stages. The structure of multi-point intake along the side wall of the furnace tube 1 can just introduce the adapted raw material gas into different temperature zones at different stages, which can significantly improve the utilization rate of the carbon source. The time for the catalyst particles to agglomerate and grow is also shorter before the start of growth, thereby increasing the output of single-walled carbon nanotubes.

[0036] Preferably, as Figure 5 and Figure 6 shown, the heating element is an electric heating tube 22, and an independently controllable heating element is provided in each heating chamber 21. As the heating element, each one or each group of the electric heating tubes 22 can be independently controlled in their respective heating chambers 21, which enables the operator to accurately set different temperature zones along the length direction of the furnace tube 1, thereby optimizing the temperature conditions in the process of growing carbon nanotubes and improving the quality and yield of the products.

[0037] Preferably, as Figure 5 and Figure 6 shown, in each heating chamber 21, the heating elements are arranged along the length direction of the furnace tube 1 to form two rows of symmetric heating element arrays; in each heating chamber 21, a temperature detection element is provided. The temperature detection element is a thermocouple, and the detection end of the thermocouple protrudes from the inner wall of the heat insulation body 2 and points into the heating chamber 21, ensuring the accuracy and real-time performance of temperature measurement, and further providing accurate temperature feedback for temperature control.

[0038] As Figure 7 shown, each intake pipe 11 has a preheating section 111 adjacent to the outer wall of the furnace tube 1. The preheating section 111 passes through the heating chamber 21, so that the gas transported through the pipe can be preheated before entering the furnace tube 1, thereby reducing the temperature fluctuation inside the furnace tube 1 and being beneficial to improving the reaction efficiency.

[0039] As Figure 6 shown, the furnace tube 1 is connected with an intake pipe 11 corresponding to each temperature zone, and each intake pipe 11 has an independent intake end to independently control the supply of the raw material gas in each temperature zone. In this way, the supply of the raw material gas can be accurately controlled according to the different requirements for the growth of carbon nanotubes in different temperature zones. This design improves the utilization efficiency of the carbon source and the growth quality of the carbon nanotubes.

[0040] Preferably, as Figure 3 、 Figure 4 and Figure 8As shown in the figure, the tubular heating furnace further includes a cooling cover 3 disposed outside the heat insulation body 2. The cooling cover 3 includes an inner cover body 31 that envelopes the heat insulation body 2 and an outer cover body 32 that envelopes the inner cover body 31. A cooling cavity 33 for accommodating a cooling medium is formed between the inner cover body 31 and the outer cover body 32. A first liquid inlet 34 and a first liquid outlet 35 are further provided on the outer cover body 32. Both the first liquid inlet 34 and the first liquid outlet 35 are communicated with the cooling cavity 33. An additional cooling system composed of an inner and an outer layer is added outside the heat insulation body 2. The cooling cavity 33 can accommodate the cooling medium. The cooling liquid is injected through the first liquid inlet 34 and discharged from the first liquid outlet 35 after passing through the cooling cavity 33, effectively taking away the excess heat generated during the operation of the heating furnace, protecting external equipment and the environment from the influence of high temperature, and also helping to control the overall temperature distribution of the heating furnace.

[0041] Preferably, as Figure 4 shown, the first liquid inlet 34 is located at the lower part of the cooling cavity 33, and the first liquid outlet 35 is located at the upper part of the cooling cavity 33, which helps cooling media such as water and heat-conducting oil to fully cool the cooling cavity 33, promotes the circulation of the cooling medium, and improves the cooling efficiency.

[0042] Preferably, as Figure 6 、 Figure 7 and Figure 9 shown, at the feed end, a cooling jacket 4 is further wrapped around the outer wall of the furnace tube 1. The cooling jacket 4 can accommodate the cooling medium. A second liquid inlet 41 is provided at the lower part of the cooling jacket 4, and a second liquid outlet 42 is provided at the upper part of the cooling jacket 4. The cooling medium enters from the second liquid inlet 41 at the lower part of the cooling jacket 4, absorbs the heat dissipated by the furnace tube 1, and then flows out from the second liquid outlet 42 at the upper part, which helps to reduce the temperature at the feed end and protect the safety of the operators.

[0043] Preferably, as Figure 1 and Figure 2 shown, a protective shell 5 is further provided outside the cooling cover 3. The protective shell 5 blocks the periphery of the furnace tube 1 and leaves an operation window at the feed end of the furnace tube 1.

[0044] As described above, the catalyst precursor can be placed in a high-temperature resistant container such as a crucible or a porcelain boat, and then the high-temperature resistant container is placed in the furnace tube 1. As the temperature rises, the catalyst precursor gradually volatilizes into the atmosphere in the furnace tube 1 and reacts with the raw material gas to catalyze the carbon source to grow into carbon nanotubes in a specific arrangement. However, in this way, due to the limitations of contact and dispersion, not only the utilization efficiency of the catalyst is not high, but also the catalytic activity is not fully exerted. Therefore, it can be as Figure 7As shown, a conduit 15 extending into the furnace tube 1 is provided at the feed end of the furnace tube 1, and an atomizing nozzle 16 is connected to one end of the conduit 15 inside the furnace tube 1. The catalyst precursor can be evenly dispersed into the reaction atmosphere inside the furnace tube 1 through the atomizing nozzle, increasing the contact between the catalyst and the raw material gas, thereby promoting a more effective catalytic reaction and promoting the efficient and uniform growth of carbon nanotubes. On the other hand, the catalyst precursor is preheated during the flow inside the furnace tube 1, reducing agglomeration and providing more active sites, realizing the growth of single-walled carbon nanotubes with high efficiency and high purity.

[0045] Preferably, the atomizing nozzle 16 is located within a temperature zone near the feed end.

[0046] Preferably, as Figure 9 shown, the feed end of the furnace tube 1 has a flange opening, and a sealing connection plate is provided on the conduit 15. The flange opening at the feed end of the furnace tube 1 is detachably connected to the sealing connection plate on the conduit 15, for example, by means of connecting parts such as bolts and clamps to achieve detachable connection.

[0047] The single-walled carbon nanotubes grown based on the floating catalyst chemical vapor deposition method are in a flocculent shape, with a light material and a large volume, and are easily adhered to the low-temperature area of the reaction chamber, blocking the furnace tube 1, increasing the pressure inside the furnace, and affecting the continuity and safety of production.

[0048] As Figure 1 、 Figure 10 、 Figure 11 and Figure 12 shown, at the discharge end of the tubular heating furnace, a carbon nanotube discharge device is provided. The discharge device includes a collection bin 6. The inside of the collection bin 6 has a collection cavity communicating with the discharge port of the tubular heating furnace, that is, the furnace tube 1 communicates with the collection bin 6; an operation port 61 is provided on the collection bin 6, and a flexible pipe 62 is connected to the operation port 61. The operation port 61 is hermetically connected to the proximal end of the flexible pipe 62; at least one operating rod 63 passes through the flexible pipe 62 and extends into the collection cavity, and the distal end of the flexible pipe 62 is hermetically connected to the operating rod 63; a discharge interface is provided at the bottom of the collection bin 6.

[0049] This discharging device is provided with a collection bin 6 at the discharging port of the furnace tube 1. The operation port 61 is connected through a flexible pipe 62 to at least one operating rod 63 extending into the interior of the collection bin, allowing the operator to safely transfer and collect the flocculent single-walled carbon nanotubes that are likely to cause blockage of the furnace tube during the growth process outside. In addition, a transfer tank can be connected at the discharging interface. When the flocculent carbon nanotubes in the collection bin 6 accumulate to a certain amount, the operator can use the operating rod 63 to dial the flocculent matter into the transfer tank, and then cut off the connection between the discharging interface and the transfer tank, and replace it with a new transfer tank. In this way, the operation of the heating furnace is not affected during the operation, and discharging can be achieved without affecting continuous production, thus solving the problems of continuous production and safety, and improving the mass production capacity of single-walled carbon nanotubes.

[0050] Preferably, the flexible pipe 62 is an elastic corrugated pipe made of metal. The elastic corrugated pipe made of metal not only has good high-temperature resistance and can withstand the high-temperature environment during the operation of the heating furnace, but also has good flexibility and stretchability, can adapt to the position adjustment or slight movement of the collection bin 6, and at the same time allows the operating rod 63 to have a large space for linear movement and rotational movement during the operation. Metal corrugated pipes usually also have high mechanical strength and durability, can effectively prevent deformation or rupture caused by external pressure changes, and ensure the safety and stability of the operation.

[0051] As Figure 12 shown, the sizes of the distal end and the proximal end of the flexible pipe 62 can be the same, forming a pipe with a substantially uniform diameter. More preferably, the size of the proximal end of the flexible pipe 62 can be larger than that of the distal end, forming a flared shape, so that the operating rod 63 can obtain a larger operating space and improve the flexibility of the operating rod 63.

[0052] Preferably, as Figure 12 shown, the end of the operation port 61 has a flange port, and the proximal end of the flexible pipe 62 has a flange port. The flange port at the end of the operation port 61 is detachably connected to the flange port at the proximal end of the flexible pipe 62. For example, the detachable connection can be achieved through connecting parts such as bolts and clamps, which not only ensures the sealing performance, but also enables the operating rod 63 to be easily replaced or taken out as needed, enhancing the operation flexibility of the equipment.

[0053] Preferably, as Figure 12 shown, the distal end of the operation port 61 has a flange port, and a sealing connection plate is provided on the rod body of the operating rod 63. The flange port at the distal end of the operation port 61 is detachably connected to the sealing connection plate on the operating rod 63. Similarly, the detachable connection can also be achieved through connecting parts such as bolts and clamps, which is convenient for quick assembly and disassembly, and is conducive to maintenance and cleaning.

[0054] Preferably, as Figure 12As shown, one end of the joystick 63 located inside the collection bin 6 has a hook, and the end of the joystick 63 located outside the collection bin 6 has a handle. The hook part at the front end of the joystick 63 can be used to hook or move the carbon nanotube flocs inside the collection bin 6, while the handle facilitates the operator to apply force outside the collection bin 6 to control the movement of the joystick 63, improving the operation convenience and safety.

[0055] Preferably, as Figure 11 shown, the bottom of the collection bin 6 is conical and is provided with a discharge port at the bottom; a sealing door 64 is provided on one side of the collection bin 6 opposite to the discharge port of the tube furnace, and the operation port 61 is provided on the sealing door 64.

[0056] Preferably, as Figure 11 shown, at least one observation window 65 is further provided on the collection bin 6, and the observation window 65 and the operation port 61 are located on the same side of the collection bin 6.

[0057] Preferably, as Figure 11 and Figure 13 shown, a winding roller 66 is rotatably provided inside the collection bin 6, and the winding roller 66 is driven to rotate by a driving motor 67 installed on the outer side wall of the collection bin 6. In this way, the prepared carbon nanotube flocs can be wound on the roller in an orderly manner, avoiding the accumulation and chaos of materials. After winding, it is also convenient for the joystick 63 to pick off the carbon nanotube flocs as a whole, facilitating full collection, and improving the collection efficiency and neatness.

[0058] Preferably, as Figure 11 shown, there is an interlayer space inside the wall of the collection bin 6, and a circulating cooling medium can be maintained in the interlayer space to prevent the temperature of the outer wall of the collection bin 6 from being too high.

[0059] The above embodiments are exemplary, and their purpose is to illustrate the technical concept and characteristics of the present invention, so that those skilled in this field can understand the content of the present invention and implement it accordingly. It should not be used to limit the protection scope of the present invention. All equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. A carbon nanotube discharging device, characterized in that: The invention is arranged at the discharge end of the tubular heating furnace, comprising a collecting bin (6), wherein the collecting bin (6) has a collecting cavity in the interior thereof which is connected to the discharge port of the tubular heating furnace; an operating port (61) is arranged in the collecting bin (6), a flexible pipe (62) is connected to the operating port (61), and the operating port (61) is sealedly connected to the proximal end of the flexible pipe (62); at least one operating rod (63) passes through the flexible pipe (62) and extends into the collecting cavity, and the distal end of the flexible pipe (62) is sealedly connected to the operating rod (63); and a discharge interface is arranged at the bottom of the collecting bin (6).

2. The carbon nanotube discharging device according to claim 1, characterized in that: The flexible pipe (62) is an elastic bellows made of metal.

3. The carbon nanotube discharging device according to claim 1, characterized in that: The end of the operation port (61) has a flange opening, and the proximal end of the flexible pipe (62) has a flange opening. The flange opening at the end of the operation port (61) and the flange opening at the proximal end of the flexible pipe (62) are detachably connected.

4. The carbon nanotube discharging device according to claim 1, characterized in that: The operating port (61) has a flange opening at the far end, a sealing connection plate is provided on the rod body of the operating rod (63), and the flange opening at the far end of the operating port (61) is detachably connected to the sealing connection plate on the operating rod (63).

5. The carbon nanotube discharging device according to claim 1, characterized in that: A hook is provided at one end of the operating rod (63) located inside the collecting bin (6), and a handle is provided at one end of the operating rod (63) located outside the collecting bin (6).

6. The carbon nanotube discharging device according to any one of claims 1 to 5, characterized in that: The collecting bin (6) has a conical bottom and is provided with a discharge port at the bottom; a sealed bin door (64) is provided on the side of the collecting bin (6) directly opposite to the discharge port of the tubular heating furnace, and the operating port (61) is provided on the sealed bin door (64).

7. The carbon nanotube discharging device according to claim 6, characterized in that: At least one observation window (65) is also provided on the collection bin (6), and the observation window (65) and the operation port (61) are located on the same side of the collection bin (6).

8. The carbon nanotube discharging device according to claim 6, characterized in that: A winding roller (66) is also rotatably provided in the collection bin (6), and the winding roller (66) is driven to rotate by a driving motor (67) mounted on the outer side wall of the collection bin (6).

9. The carbon nanotube discharging device according to claim 6, characterized in that: The collecting bin (6) has an interlayer space in its wall, and a circulating cooling medium can be maintained in the interlayer space.

10. The carbon nanotube discharging device according to claim 6, characterized in that: The distal end and proximal end of the flexible pipe (62) are of the same size; or the proximal end of the flexible pipe (62) is larger than the distal end, forming a bell-mouth shape.

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