Liquid nitrogen drip irrigation device

Abstract

The invention relates to the technical field of quick cooling equipment, and provides a liquid nitrogen drip irrigation device which comprises a mounting frame, a liquid nitrogen storage box, a drip irrigation pipe, a flow guide pipe and a cold insulation cover. The liquid nitrogen storage box is mounted on the mounting frame, and the drip irrigation pipe is communicated with the liquid nitrogen storage box and used for releasing liquid nitrogen to materials; the cold insulation cover sleeves the drip irrigation pipe, a cooling gap is formed between the inner wall of the cold insulation cover and the outer wall of the drip irrigation pipe, one end of the flow guide pipe is communicated with the nitrogen overflow port of the liquid nitrogen storage box, and the other end of the flow guide pipe is communicated with the cooling gap. According to the liquid nitrogen drip irrigation device provided by the invention, the surface of the material can be quickly frozen to quickly shape the pattern on the surface of the material, and meanwhile, the liquid nitrogen released in the drip irrigation pipe can be always injected to the surface of the material in a liquid form, so that the stability and the reliability of the drip irrigation liquid nitrogen of the drip irrigation pipe are ensured.

Description

Technical Field

[0001] The invention relates to the technical field of rapid cooling equipment, and in particular to a liquid nitrogen drip irrigation device. Background Art

[0002] Liquid nitrogen freezing is a technology that uses the extremely low temperature characteristics of liquid nitrogen for rapid freezing. It achieves rapid cooling through the evaporation and conduction of liquid nitrogen. It is widely used in the field of food processing. Liquid nitrogen can freeze the surface of soft food and quickly shape it.

[0003] At present, when using liquid nitrogen to freeze materials, the materials are usually placed in liquid nitrogen and frozen by dipping. Alternatively, a special liquid nitrogen quick-freezing device is used to first set up a liquid nitrogen protection and closed area in a certain area, and a large amount of liquid nitrogen is used to pre-cool and reduce the temperature of this area. After the liquid nitrogen slows down its volatilization, the liquid nitrogen is sprayed onto the surface of the frozen material. Both methods require a large amount of liquid nitrogen, resulting in a waste of liquid nitrogen. Summary of the invention

[0004] The invention provides a liquid nitrogen drip irrigation device, which is used to solve the problem that a large amount of liquid nitrogen needs to be consumed in the liquid nitrogen freezing device in the prior art, resulting in waste of liquid nitrogen.

[0005] The present invention provides a liquid nitrogen drip irrigation device, comprising: a mounting frame, a liquid nitrogen storage box, a drip irrigation pipe, a flow guide pipe and a cold preservation cover; The liquid nitrogen storage box is installed on the mounting frame, and the drip irrigation pipe is connected to the liquid nitrogen storage box to release liquid nitrogen to the material; The cold-keeping cover is sleeved on the drip irrigation pipe, a cooling gap is provided between the inner wall of the cold-keeping cover and the outer wall of the drip irrigation pipe, one end of the guide pipe is communicated with the nitrogen overflow port of the liquid nitrogen storage box, and the other end of the guide pipe is communicated with the cooling gap.

[0006] According to a liquid nitrogen drip irrigation device provided by the present invention, the end of the cold-keeping cover is closer to the surface of the material than the liquid outlet of the drip irrigation pipe.

[0007] A liquid nitrogen drip irrigation device provided according to the present invention further includes a switch assembly, and the switch assembly is used to control the opening and closing of the liquid outlet of the drip irrigation pipe.

[0008] According to a liquid nitrogen drip irrigation device provided by the present invention, the switch assembly comprises: a moving rod and a driving member; the driving member is installed on the mounting frame and is transmission-connected with the moving rod; Under the drive of the driving member, the moving rod can be movably arranged in the liquid nitrogen storage box and the drip irrigation pipe, and the end of the moving rod seals the liquid outlet or is exposed at the liquid outlet.

[0009] According to a liquid nitrogen drip irrigation device provided by the present invention, one end of the moving rod is cone-shaped, and the small end of the moving rod faces the liquid outlet.

[0010] According to a liquid nitrogen drip irrigation device provided by the present invention, the cold-keeping cover is provided with a multi-layer structure, and the multi-layer structure comprises an inner layer, an outer layer and a heat-insulating layer sandwiched between the inner layer and the outer layer.

[0011] A liquid nitrogen drip irrigation device provided by the present invention also includes a compressed air source and a delivery pump, and a blowing pipe is installed at one end of the guide pipe close to the liquid nitrogen storage box; the compressed air source is connected to the blowing pipe through the delivery pump.

[0012] According to a liquid nitrogen drip irrigation device provided by the present invention, the liquid nitrogen storage box is connected to the liquid nitrogen storage container through a liquid nitrogen pipeline, and a throttle valve is provided on the liquid nitrogen pipeline.

[0013] According to the liquid nitrogen drip irrigation device provided by the present invention, the liquid nitrogen storage box can be lifted and installed on the mounting frame.

[0014] According to a liquid nitrogen drip irrigation device provided by the present invention, the mounting frame is provided with a liquid nitrogen storage box, a plurality of drip irrigation pipes, a plurality of flow guide pipes and a plurality of cold preservation covers; The plurality of drip irrigation pipes are arranged corresponding to the conveying positions of the materials, and the plurality of drip irrigation pipes, the plurality of flow guide pipes and the plurality of cold preservation covers are arranged one by one correspondingly.

[0015] The liquid nitrogen drip irrigation device provided by the present invention drips liquid nitrogen onto the surface of a material by arranging a drip irrigation pipe connected with a liquid nitrogen storage box, so as to quickly freeze the surface of the material so as to quickly shape the surface pattern of the material. Meanwhile, a cold preservation cover is arranged on the drip irrigation pipe, and a nitrogen overflow port of the liquid nitrogen storage box is connected with the cold preservation cover through a guide pipe, so that low-temperature nitrogen volatilized in the liquid nitrogen storage box is introduced into the cold preservation cover, so as to ensure that the cooling gap between the cold preservation cover and the drip irrigation pipe is kept at a low temperature, so that the liquid nitrogen released in the drip irrigation pipe can always be added to the surface of the material in a liquid form, thereby ensuring the stability and reliability of the drip irrigation liquid nitrogen of the drip irrigation pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 It is a schematic cross-sectional structural diagram of the liquid nitrogen drip irrigation device provided by the present invention.

[0018] Figure 2 The present invention provides Figure 1 Enlarged view of the K part.

[0019] Figure 3 It is a schematic diagram of the appearance of the liquid nitrogen drip irrigation device provided by the present invention.

[0020] Reference numerals: 1. Liquid nitrogen drip irrigation device; 11. Mounting frame; 12. Liquid nitrogen storage box; 13. Drip irrigation pipe; 14. Flow guide pipe; 15. Cold preservation cover; 16. Switch assembly; 17. Blowing pipe; 131. Liquid outlet; 161. Moving rod; 162. Driving member; 2. Materials. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are 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.

[0022] Combine the following Figure 1-Figure 3 , the liquid nitrogen drip irrigation device provided by the embodiment of the present invention is described in detail through specific embodiments and application scenarios.

[0023] like Figure 1 and Figure 2 As shown, this embodiment provides a liquid nitrogen drip irrigation device 1, including: a mounting frame 11, a liquid nitrogen storage box 12, a drip irrigation pipe 13, a guide pipe 14 and a cold preservation cover 15.

[0024] The liquid nitrogen storage box 12 is installed on the mounting frame 11 , and the drip irrigation pipe 13 is connected to the liquid nitrogen storage box 12 for releasing liquid nitrogen to the material 2 .

[0025] The cold-keeping cover 15 is sleeved on the drip irrigation pipe 13, and a cooling gap is provided between the inner wall of the cold-keeping cover 15 and the outer wall of the drip irrigation pipe 13. One end of the guide pipe 14 is connected to the nitrogen overflow port of the liquid nitrogen storage box 12, and the other end of the guide pipe 14 is connected to the cooling gap.

[0026] The liquid nitrogen drip irrigation device 1 of this embodiment is arranged at the rear side of the flat plate filling machine. The material that is filled by the flat plate filling machine can be a soft material such as cup ice cream. After the material 2 is poured and formed, the surface has a complex pattern structure. If it is exposed to the air for a long time, the pattern structure is easy to melt and become limp and sink, causing the surface of the material 2 to deform and lose its aesthetics. The filled material 2 is transported to the lower side of the mounting frame 11 by a conveyor belt, and the drip irrigation pipe 13 drips liquid nitrogen onto the surface of the material 2 to quickly cool and shape the material 2.

[0027] Liquid nitrogen has the characteristic of absorbing heat at ultra-low temperatures. When liquid nitrogen is in contact with food, a strong heat exchange is carried out with a temperature difference of more than 200K, and the freezing speed is extremely fast. Since liquid nitrogen freezes at low temperatures in a short period of time, small and evenly distributed ice crystals are formed inside the food, which causes little damage to cells and reduces the loss of juice after thawing, thus maintaining the nutrition, taste and original flavor of the food. Liquid nitrogen quickly freezes material 2, freezing the surface of material 2 to a hard shell, so that the surface pattern structure of material 2 can be maintained during the transmission process from the flat filling machine to the freezing tunnel, ensuring the beauty of material 2.

[0028] The boiling point of nitrogen at normal pressure is -196.56°C, and it is very easy to produce gasification at room temperature. In order to prevent the liquid nitrogen dripping from the drip irrigation pipe 13 from gasifying before it contacts the surface of the material 2, a cold-keeping cover 15 is provided on the outer side of the drip irrigation pipe 13 in this embodiment. Specifically, the cold-keeping cover 15 forms a cooling gap outside the drip irrigation pipe 13, and the cooling gap is connected to the nitrogen overflow port of the liquid nitrogen storage box 12 through the guide pipe 14. After the liquid nitrogen evaporates at room temperature, it is sent into the cooling gap from the nitrogen overflow port through the guide pipe 14. Since the temperature of the newly volatilized nitrogen is also close to the boiling point of nitrogen, the temperature inside the cold-keeping cover 15 is reduced to a lower temperature, and then the temperature around the drip irrigation pipe 13 is lowered, preventing the liquid nitrogen in the drip irrigation pipe 13 from gasifying rapidly, ensuring that the liquid nitrogen can be added to the surface of the material 2 in a liquid state, and having a better freezing effect on the material 2.

[0029] The liquid nitrogen drip irrigation device 1 provided by the present invention drips liquid nitrogen onto the surface of the material 2 by arranging a drip irrigation pipe 13 connected to a liquid nitrogen storage tank 12, so as to quickly freeze the surface of the material 2 so that the surface pattern of the material 2 can be quickly fixed. At the same time, a cold preservation cover 15 is arranged to be sleeved on the drip irrigation pipe 13, and the low-temperature nitrogen volatilized in the liquid nitrogen storage tank 12 is introduced into the cold preservation cover 15, so as to ensure that the cooling gap between the cold preservation cover 15 and the drip irrigation pipe 13 is in a low-temperature state, so that the liquid nitrogen released in the drip irrigation pipe 13 can always be added to the surface of the material 2 in a liquid form, thereby ensuring the stability and reliability of the drip irrigation liquid nitrogen of the drip irrigation pipe 13.

[0030] In some embodiments, Figure 1 and Figure 2As shown, the end of the cold-keeping cover 15 of this embodiment is closer to the surface of the material 2 than the liquid outlet 131 of the drip irrigation pipe 13 .

[0031] The higher the coverage rate of the cooling gap between the inner wall of the cold-keeping cover 15 and the outer wall of the drip irrigation pipe 13 on the outer wall of the drip irrigation pipe 13, the better. To this end, the end of the cold-keeping cover 15 of this embodiment is closer to the surface of the material 2 than the liquid outlet 131 of the drip irrigation pipe 13, so that the cooling space formed by the end of the cold-keeping cover 15 and the surface of the material 2 completely covers the drip irrigation pipe 13, thereby improving the cooling effect of the drip irrigation pipe 13 and ensuring the stability of the liquid nitrogen in the drip irrigation pipe 13.

[0032] In some embodiments, Figure 1 As shown, the liquid nitrogen drip irrigation device 1 of this embodiment further includes a switch assembly 16 , and the switch assembly 16 is used to control the opening and closing of the liquid outlet 131 of the drip irrigation pipe 13 .

[0033] In order to control the drip irrigation amount of the liquid nitrogen drip irrigation device 1, the liquid nitrogen drip irrigation device 1 of this embodiment is further provided with a switch assembly 16, which can switch the opening and closing state of the drip irrigation pipe 13. When the material 2 is transported to the lower side of the drip irrigation pipe 13, the switch assembly 16 is turned on to drip irrigate the material 2; when the material 2 is dripped, the switch assembly 16 is turned off to avoid waste of liquid nitrogen.

[0034] Specifically, the switch assembly 16 may be a baffle plate provided on the drip irrigation pipe 13, and the switch assembly 16 is controlled by opening and blocking the liquid outlet 131 of the drip irrigation pipe 13. Alternatively, the switch assembly 16 may also be a solenoid valve, and the on-off control of the liquid nitrogen is realized by controlling the solenoid valve.

[0035] In this embodiment, by providing a switch assembly 16 in the liquid nitrogen drip irrigation device 1, the on-off switching of the liquid outlet 131 of the drip irrigation pipe 13 is realized, ensuring that the liquid nitrogen is drip-irrigated only when the material 2 is located at the lower side of the drip irrigation pipe 13 and the material 2 has not completed the liquid nitrogen drip irrigation, and the drip irrigation state of the liquid nitrogen is accurately controlled, which not only ensures the drip irrigation effect of the liquid nitrogen, but also avoids the waste of the liquid nitrogen.

[0036] In some embodiments, Figure 1 As shown, the switch assembly 16 of this embodiment includes: a moving rod 161 and a driving member 162 ; the driving member 162 is installed on the mounting frame 11 and is transmission-connected with the moving rod 161 .

[0037] Driven by the driving member 162 , the moving rod 161 can be moved to penetrate the liquid nitrogen storage box 12 and the drip irrigation pipe 13 , and the end of the moving rod 161 seals the liquid outlet 131 or is exposed at the liquid outlet 131 .

[0038] When the end of the moving rod 161 seals the liquid outlet 131, the liquid outlet 131 is blocked by the moving rod 161, and the moving rod 161 closes the drip irrigation pipe 13, and the drip irrigation pipe 13 does not drip liquid nitrogen. When the end of the moving rod 161 is exposed at the liquid outlet 131, the gap between the liquid outlet 131 and the moving rod 161 can allow liquid nitrogen to drip, the liquid outlet 131 of the drip irrigation pipe 13 is opened, and the drip irrigation pipe 13 drips liquid nitrogen.

[0039] Furthermore, the driving member 162 drives the moving rod 161 to move relative to the liquid nitrogen storage tank 12 and the drip irrigation pipe 13 to switch the position state of the end of the moving rod 161 relative to the liquid outlet 131 , thereby controlling the opening and closing of the liquid outlet 131 .

[0040] Specifically, the driving member 162 may be a linear motor or a cylinder.

[0041] In this embodiment, a moving rod 161 and a driving member 162 are provided in the switch assembly 16, and the driving member 162 drives the position of the moving rod 161 relative to the liquid outlet 131 to adjust the opening and closing of the liquid outlet 131 of the drip irrigation pipe 13, and the structure is simple and the adjustment method is convenient.

[0042] In some embodiments, Figure 1 and Figure 2 As shown, one end of the moving rod 161 of this embodiment is in a cone shape, and the small end of the moving rod 161 faces the liquid outlet 131.

[0043] One end of the moving rod 161 is arranged in a cone shape. As the moving rod 161 moves relative to the drip irrigation pipe 13, the position of the side wall of the cone relative to the liquid outlet 131 changes, so that the size of the annular gap formed between the outer wall of the end of the moving rod 161 and the liquid outlet 131 of the drip irrigation pipe 13 changes, thereby adjusting the drip irrigation flow of the drip irrigation pipe 13. Since the area difference of the cone is small, the area change of the annular gap formed by the liquid outlet 131 and the cone is also small, so that the flow of liquid nitrogen drip irrigation can be accurately controlled by moving the moving rod 161.

[0044] In some embodiments, Figure 1 As shown, the cold-keeping cover 15 of this embodiment has a multi-layer structure, which includes an inner layer, an outer layer and a heat-insulating layer sandwiched between the inner layer and the outer layer.

[0045] In order to ensure the cooling effect of the cold-keeping cover 15, the cold-keeping cover 15 can be provided with a multi-layer structure. An insulating layer is sandwiched between the inner layer and the outer layer, and the insulating layer can reduce the transfer of heat, so that less heat is lost to the environment in the cooling gap, so that the effect of maintaining the low temperature in the cooling gap is better.

[0046] Optionally, the inner layer and the outer layer may be made of plastics; the heat insulating layer may be made of foam plastics, vacuum insulation panels or aluminosilicate wool panels.

[0047] In some embodiments, Figure 1 As shown, the liquid nitrogen drip irrigation device 1 of this embodiment also includes a compressed air source and a delivery pump. A blowing pipe 17 is installed at one end of the guide pipe 14 close to the liquid nitrogen storage box 12; the compressed air source is connected to the blowing pipe 17 through the delivery pump.

[0048] Optionally, the blowing pipe 17 is a U-shaped pipe, the inlet end of the blowing pipe 17 is arranged perpendicular to the radial direction of the guide pipe 14, and the outlet end of the blowing pipe 17 is arranged along the axial direction of the guide pipe 14. When compressed air is introduced into the guide pipe 14 through the blowing pipe 17, the blowing pipe 17 blows the compressed air toward the end of the guide pipe 14 away from the liquid nitrogen storage box 12, thereby generating a negative pressure at the nitrogen overflow port, so that the nitrogen at the nitrogen overflow port can flow faster toward the cold preservation cover 15. Therefore, by introducing compressed air into the guide pipe 14, the flow speed of the low-temperature nitrogen in the guide pipe 14 can be accelerated, avoiding excessive loss of liquid nitrogen cooling in the guide pipe 14, and optimizing the cold preservation effect in the cold preservation cover 15.

[0049] If the flow rate of the compressed air in the blowing pipe 17 is too high, the compressed air will quickly bring nitrogen to the cold-keeping cover 15, causing excessive volatilization of liquid nitrogen and resulting in waste. If the flow rate of the compressed air in the blowing pipe 17 is too low, the cold-keeping cover 15 cannot be replenished with low-temperature nitrogen in time, resulting in poor cold-keeping effect of the cold-keeping cover 15, thereby affecting the drip irrigation of liquid nitrogen. Therefore, it is necessary to control the flow rate of the compressed air in the blowing pipe 17. To this end, the present embodiment provides a regulating valve on the connecting pipeline between the compressed air source and the blowing pipe 17. The flow rate of the compressed air in the connecting pipeline is adjusted by the regulating valve so that the compressed air introduced into the guide pipe 14 is maintained within a suitable flow rate and flow rate range.

[0050] In some embodiments, Figure 1 As shown, the liquid nitrogen storage box 12 of this embodiment is connected to the liquid nitrogen storage container through a liquid nitrogen pipeline, and a throttle valve is provided on the liquid nitrogen pipeline.

[0051] The liquid nitrogen storage tank 12 stores only a small amount of liquid nitrogen. When the liquid nitrogen level in the liquid nitrogen storage tank 12 is low, the liquid nitrogen in the liquid nitrogen storage container is replenished into the liquid nitrogen storage tank 12 through the liquid nitrogen pipeline. In this embodiment, by setting a throttle valve on the liquid nitrogen pipeline, the liquid nitrogen pipeline can be controlled to be on and off, thereby controlling the liquid level of the liquid nitrogen storage tank 12. The drip irrigation speed of the liquid nitrogen can also be adjusted by changing the pressure in the liquid nitrogen storage tank 12. Therefore, the throttle valve of this embodiment can also adjust the pressure in the liquid nitrogen storage tank 12 by controlling the flow rate in the liquid nitrogen pipeline, thereby adjusting the drip irrigation speed of the liquid nitrogen.

[0052] In some embodiments, Figure 1 As shown, the liquid nitrogen storage box 12 of this embodiment can be lifted and installed on the mounting frame 11.

[0053] When drip irrigation of liquid nitrogen is performed on the material 2, the lower end of the cold preservation cover 15 needs to be brought close to the surface of the material 2. Since the types of materials 2 filled by the flat-plate filling machine are different and the volumes of different materials 2 are also different, it is necessary to adjust the height of the liquid nitrogen storage box 12 for different materials 2 to adjust the distance between the liquid outlet 131 of the drip irrigation pipe 13 and the material 2. The liquid nitrogen storage box 12 of this embodiment can be lifted and installed on the mounting frame 11, so as to facilitate the adjustment of the height of the liquid outlet 131 of the drip irrigation pipe 13 according to the type of material. In addition, when in use, if the material 2 is in a conveying state, the liquid nitrogen storage box 12 can be raised to a higher position of the mounting frame 11 to avoid interference with the conveying of the material 2; if the material 2 is in a liquid nitrogen drip irrigation state, the liquid nitrogen storage box 12 is lowered to a lower position to facilitate the liquid nitrogen drip irrigation operation on the surface of the material 2.

[0054] Specifically, a track and a linear drive may be provided on the mounting frame 11, and a driving end of the linear drive is connected to the liquid nitrogen storage box 12. The linear drive drives the liquid nitrogen storage box 12 to move up and down on the mounting frame 11 along the track to adjust the position of the liquid nitrogen storage box 12 in the height direction.

[0055] In this embodiment, the liquid nitrogen storage box 12 is escalably mounted on the mounting frame 11. For different materials 2 and different operating states of the materials 2, the height position of the liquid outlet 131 of the drip irrigation pipe 13 can be adjusted in time, which is more conducive to the liquid nitrogen drip irrigation operation of the drip irrigation pipe 13 on the materials 2.

[0056] In some embodiments, Figure 3 As shown, a liquid nitrogen storage box 12, a plurality of drip irrigation pipes 13, a plurality of flow guide pipes 14 and a plurality of cold-keeping covers 15 are provided on the mounting frame 11 of the present embodiment.

[0057] The plurality of drip irrigation pipes 13 are arranged in one-to-one correspondence with the conveying positions of the plurality of materials 2, and the plurality of drip irrigation pipes 13, the plurality of flow guide pipes 14 and the plurality of cold preservation covers 15 are arranged in one-to-one correspondence.

[0058] According to the number of conveying positions of the flat-plate filling machine, the number of drip irrigation pipes 13 equal to the number of conveying positions is selected so that the material 2 on each conveying position can be drip-irrigated with liquid nitrogen in time. Multiple drip irrigation pipes 13 perform liquid nitrogen drip irrigation at the same time, which improves the efficiency of liquid nitrogen drip irrigation on the surface of the material 2 and avoids deformation of the flower pattern of the material 2 caused by untimely drip irrigation.

[0059] For example, a liquid nitrogen storage box 12, four drip irrigation pipes 13, four guide pipes 14 and four cold-keeping covers 15 are provided on the mounting frame 11. The four drip irrigation pipes 13 correspond to the four conveying positions of the material 2, and liquid nitrogen drip irrigation can be performed synchronously on the four materials 2. Of course, two, three or other numbers of drip irrigation pipes 13 can also be installed on one liquid nitrogen storage box 12.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A liquid nitrogen drip irrigation device, characterized in that: include: Mounting rack, liquid nitrogen storage tank, drip irrigation pipe, flow guide pipe and cold shield; The liquid nitrogen storage box is installed on the mounting frame, and the drip irrigation pipe is connected to the liquid nitrogen storage box to release liquid nitrogen to the material; The cold-keeping cover is sleeved on the drip irrigation pipe, a cooling gap is provided between the inner wall of the cold-keeping cover and the outer wall of the drip irrigation pipe, one end of the guide pipe is communicated with the nitrogen overflow port of the liquid nitrogen storage box, and the other end of the guide pipe is communicated with the cooling gap.

2. The liquid nitrogen drip irrigation device according to claim 1, characterized in that: The end of the cold-keeping cover is closer to the surface of the material than the liquid outlet of the drip irrigation pipe.

3. The liquid nitrogen drip irrigation device according to claim 1, characterized in that: It also includes a switch component, which is used to control the opening and closing of the liquid outlet of the drip irrigation pipe.

4. The liquid nitrogen drip irrigation device according to claim 3, characterized in that: The switch assembly comprises: a moving rod and a driving member; the driving member is mounted on the mounting frame and is transmission-connected with the moving rod; Under the drive of the driving member, the moving rod can be movably arranged in the liquid nitrogen storage box and the drip irrigation pipe, and the end of the moving rod seals the liquid outlet or is exposed at the liquid outlet.

5. The liquid nitrogen drip irrigation device according to claim 4, characterized in that: One end of the moving rod is in a cone shape, and the small end of the moving rod faces the liquid outlet.

6. The liquid nitrogen drip irrigation device according to claim 1, characterized in that: The cold-keeping cover is provided with a multi-layer structure, and the multi-layer structure comprises an inner layer, an outer layer and a heat-insulating layer sandwiched between the inner layer and the outer layer.

7. The liquid nitrogen drip irrigation device according to claim 1, characterized in that: It also includes a compressed air source and a delivery pump. A blowing pipe is installed at one end of the guide pipe close to the liquid nitrogen storage box; the compressed air source is connected to the blowing pipe through the delivery pump.

8. The liquid nitrogen drip irrigation device according to claim 1, characterized in that: The liquid nitrogen storage box is connected to the liquid nitrogen storage container through a liquid nitrogen pipeline, and a throttle valve is provided on the liquid nitrogen pipeline.

9. The liquid nitrogen drip irrigation device according to claim 1, characterized in that: The liquid nitrogen storage box can be lifted and installed on the mounting frame.

10. The liquid nitrogen drip irrigation device according to claim 1, characterized in that: The mounting frame is provided with a liquid nitrogen storage box, a plurality of drip irrigation pipes, a plurality of flow guide pipes and a plurality of cold preservation covers; The plurality of drip irrigation pipes are arranged corresponding to the conveying positions of the materials, and the plurality of drip irrigation pipes, the plurality of flow guide pipes and the plurality of cold preservation covers are arranged one by one correspondingly.

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