Pressure cooker

Abstract

The utility model relates to the technical field of household appliances, and discloses a pressure cooker which comprises a cooker body and a cover body arranged on the cooker body in an opening and closing mode, the cooker body comprises a shell and an outer cooker arranged in the shell, a driver is arranged between the side face of the shell and the side face of the outer cooker, the shell is provided with an air outlet and a cold air inlet, and cooling air flows into the driver through the cold air inlet. The cover body is provided with an air inlet, a hot air outlet communicated with the outside and a cooling channel communicated with the air inlet and the hot air outlet, when the pressure cooker is closed, the air outlet and the air inlet are closed to form a cold air through opening, and the driver drives cooling air to flow into the cooling channel through the cold air through opening to exchange heat with the cover body and then flow out of the hot air outlet. According to the pressure cooker, the heat exchange efficiency of the cooling gas is high, and rapid cooling of the pressure cooker can be achieved.

Description

Technical Field

[0001] This utility model relates to the field of household appliance technology, and in particular to a pressure cooker. Background Technology

[0002] An electric pressure cooker is an appliance that uses high pressure to increase cooking temperature and shorten cooking time. To ensure safety, the lid should only be opened after cooking when the internal pressure equals atmospheric pressure. Currently, the main method for rapid pressure reduction in electric pressure cookers is air cooling. For example, Chinese patent CN112716275A discloses a pressure-reducing and heat-dissipating component and pressure cooker. The lid has a heat exchange plate, and the outer shell has an exchange box. A driver is located in the exchange box and connected to a cooling channel. The cooling channel passes through the heat exchange plate of the sealed pressure vessel. The driver fills the cooling medium into the cooling channel, and the cooling medium flows through the heat exchange plate to cool the pressure vessel. However, in the above solution, the exchange box has an inlet for the cooling medium to flow in. After heat exchange with the heat exchange plate, the cooling medium returns to the exchange box through a return air duct and is discharged from a grille on the side of the exchange box. The grille is adjacent to the inlet, causing some of the discharged hot air to re-enter the inlet and participate in the next cooling cycle. This results in poor cooling effect of the cooling medium and slow cooling speed of the pressure cooker. Furthermore, the hot air discharge point is close to the user's operating area, posing a risk of burns and low safety. Utility Model Content

[0003] To address the aforementioned technical problem of slow cooling speed in pressure cookers, this invention provides a pressure cooker that prevents hot air from mixing into the cooling gas, thereby improving the heat exchange efficiency of the cooling gas and achieving rapid cooling of the pressure cooker.

[0004] The specific technical solution of this utility model is as follows: a pressure cooker includes a pot body and a lid that can be opened and closed on the pot body. The pot body includes a shell and an outer pot disposed inside the shell. An actuator is provided between the side of the shell and the side of the outer pot. The shell has an air outlet and a cold air inlet for cooling gas to flow into the actuator. The lid has an air inlet, a hot air outlet communicating with the outside, and a cooling channel communicating with both. When the pressure cooker is closed, the air outlet and the air inlet close together to form a cold air passage. The actuator drives the cooling gas to flow through the cold air passage into the cooling channel to exchange heat with the lid and then flow out from the hot air outlet.

[0005] After cooking is finished, cooling gas continuously flows from the cold air inlet into the actuator, and then, driven by the actuator, flows through the cold air outlet into the cooling channel to exchange heat with the lid. The hot gas after heat exchange flows out from the hot air outlet to quickly reduce the temperature and lower the gas pressure inside the pot, allowing the user to open the lid as soon as possible. The cold air inlet is located on the pot body, and the hot air outlet is located on the lid. The two are spatially separated, preventing the hot air exiting the lid from entering the cold air inlet and participating in the next cooling cycle. This increases the temperature difference between the cooling gas and the pot's interior, improving the heat exchange efficiency of the cooling gas and enabling rapid cooling of the pressure cooker. Compared to having the actuator located at the bottom of the pot, placing the actuator on the side allows the cooling gas to enter directly into the cooling channel after entering through the cold air inlet, avoiding the need for the cooling gas to exchange heat with the pot body first before entering the cooling channel and exchanging heat with the lid. Since lid cooling is more effective at reducing pressure than the side of the pot body, the pressure cooker cools down faster. The hot air outlet is located on the lid, away from the user's operating area, ensuring high safety. The actuator is located inside the pot body, resulting in a compact layout and reducing the overall size of the pressure cooker.

[0006] Preferably, the housing has a receiving cavity for accommodating the driver, and the opening of the receiving cavity is connected to the air outlet.

[0007] In the above technical solution, the space between the driver and the outer pot is sealed, and the cooling gas flows only to the lid, avoiding gas loss caused by the dispersion of the flow. Sufficient cooling gas exchanges heat with the lid, which is conducive to rapid cooling inside the pot.

[0008] Preferably, the housing is provided with a cold air inlet at the position corresponding to the receiving cavity.

[0009] In the above technical solution, the cold air inlet is located on the side wall of the receiving cavity, and the cooling gas can flow directly and horizontally into the driver without the need for a guiding structure, ensuring that a sufficient amount of cooling gas flows into the driver quickly, thereby achieving rapid pressure reduction of the pressure cooker.

[0010] Preferably, the housing is provided with a support surface for supporting the cover, the cover is provided with a contact surface that abuts against the support surface, the air inlet is provided on the contact surface, and the air outlet is provided on the support surface.

[0011] In the above technical solution, the air inlet is located on the contact surface and the air outlet is located on the support surface. The two are closely fitted to form a cold air inlet, which shortens and smooths the flow path of the cooling gas, thereby accelerating the circulation speed of the cooling gas. At the same time, the contact surface is tightly fitted to the support surface, so that the gas can only flow out from the cold air inlet, reducing the leakage of cooling gas and ensuring that a sufficient amount of cooling gas enters the cover to participate in heat exchange, thereby improving the cooling and pressure reduction effect.

[0012] Preferably, the top of the cover is provided with a pressure relief valve exhaust port, and the hot air outlet is located near the pressure relief valve exhaust port.

[0013] The above technical solution takes advantage of users' avoidance of the pressure relief valve's exhaust port by placing the hot air outlet nearby. This allows users to stay away from the exhaust port while avoiding the hot air outlet, reducing the possibility of being burned by hot air and improving the safety of the pressure cooker.

[0014] Preferably, the hot air outlet is located at the top of the cover, away from the air inlet.

[0015] In the above technical solution, the hot gas outlet is located at the top of the cover, away from the air inlet, which extends the cooling path of the cooling gas inside the cover. The cooling gas can flow in a wider area inside the cover, thereby carrying out more sufficient heat exchange and improving the cooling and pressure reduction effect.

[0016] Preferably, the cover includes a shell with a hot air outlet and an air inlet, and an outer cover inside the shell. The outer cover covers the outer pot, and a cooling channel is formed between the shell and the outer cover to allow the cooling gas to exchange heat with the outer cover.

[0017] In the above technical solution, the outer cover is closely connected to the cooking space. The cooling gas carries away the heat from the outer cover, causing it to cool down quickly. This allows the heat in the cooking space to be quickly transferred out through the outer cover, achieving efficient pressure reduction in the cooking space.

[0018] Preferably, the cover includes a cover shell with a hot air outlet and an air inlet, an outer cover inside the cover shell, and an outer cover cover between the cover shell and the outer cover. The outer cover covers the outer pot, the outer cover cover is connected to the cover shell and covers the outer cover, a cooling channel is formed between the outer cover and the outer cover cover, the outer cover cover is provided with a first air outlet communicating with the hot air outlet, and a gap is provided between the outer cover and the outer cover cover to allow cooling gas to flow into the cooling channel, or the outer cover cover is provided with a second air outlet communicating with the air inlet.

[0019] In the above technical solution, since the cover is usually made of plastic, it is easily deformed by heat. An outer cover is set under the cover to prevent hot air from directly contacting the cover and thus prevent the cover from deforming.

[0020] Preferably, the driver is a turbo fan, with the air inlet of the driver facing the air inlet and the air outlet of the driver facing the air outlet.

[0021] In the above technical solution, the turbine fan concentrates the airflow, which can accurately blow the cooling gas to the outlet, eliminating the need for a guide structure, reducing the number of parts, and simplifying the assembly process.

[0022] Preferably, the driver is an impeller fan, with the air inlet of the driver facing the cold air inlet and the air outlet of the driver facing away from the cold air inlet. A guide is provided between the air outlet and the air outlet of the driver to guide the air blown out by the impeller fan to the air outlet.

[0023] In the above technical solution, the impeller fan has a large air volume, and the air guide is set to concentrate the air to the air outlet, so that more cooling gas can enter the cover and improve the cooling efficiency of the cover. At the same time, the impeller fan has a low cost.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] (1) High cooling efficiency: The cold air inlet is located on the side wall of the cavity, and the hot air outlet is located on the lid. The two are far apart in space. The hot air discharged from the lid will not enter the cold air inlet to participate in the next cooling cycle. At the same time, the driver is located on the side to avoid the cooling gas from exchanging heat with the pot body first and then entering the cooling channel to exchange heat with the lid body. Since the lid body cooling has a better effect on pressure reduction than the side of the pot body, the pressure cooker can cool down faster.

[0026] (2) High safety: The hot air outlet is located on the lid and near the pressure relief valve exhaust port. This takes advantage of users' avoidance of the pressure relief valve exhaust port, allowing users to stay away from the exhaust port while avoiding the hot air outlet, reducing the possibility of being burned by hot air and improving the safety of the pressure cooker. Attached Figure Description

[0027] Figure 1 This is a cross-sectional view of the present invention;

[0028] Figure 2 This is a side view of the present invention;

[0029] Figure 3 This is a top view of the present invention;

[0030] Figure 4 This is a top view of the pot body of this utility model. Figure 1 ;

[0031] Figure 5 This is a top view of the pot body of this utility model. Figure 2 ;

[0032] Figure 6 This is a bottom view of the cover of this utility model. Figure 1 ;

[0033] Figure 7 This is a bottom view of the cover of this utility model. Figure 2 .

[0034] The attached figures are labeled as follows: 1. Cover; 11. Hot air outlet; 12. Cover shell; 13. Pressure relief valve exhaust port; 14. Air inlet; 15. Inner cover; 16. Outer cover; 17. Abutment surface; 2. Pot body; 21. Outer pot; 22. Shell; 23. Heating element; 24. Receiving cavity; 25. Cold air inlet; 26. Air outlet; 27. Support surface; 28. Inner pot; 3. Driver; 4. Cold air inlet; 5. Air guide; 6. Cooling channel. Detailed Implementation

[0035] The present invention will be further described below with reference to embodiments. Unless otherwise specified, all devices, connection structures, and methods involved in this invention are known in the art.

[0036] Example 1

[0037] Reference Figures 1 to 7 As shown, this utility model provides a pressure cooker, including a pot body 2 and a lid 1 arranged from bottom to top. The lid 1 is closable and mounted on the pot body 2. The pot body 2 and the lid 1 are screwed together. The pot body 2 includes a shell 22 and an outer pot 21 disposed inside the shell 22. The outer pot 21 is provided with an inner pot 28 and a heating element 23 located below the inner pot 28. After the lid 1 and the pot body 2 are connected, a cooking cavity for cooking food is formed between the lid 1 and the inner pot 28. An actuator 3 is provided between the side of the shell 22 and the side of the outer pot 21. The shell 22 has an air outlet 26 and a cold air inlet 25 for cooling gas to flow into the actuator 3. The cold air inlet 25 is grid-shaped. The lid 1 has an air inlet 14 and a hot air outlet 11 connected to the outside. When the pressure cooker is closed, the air outlet 26 and the air inlet 14 are closed to form a cold air passage 4. The actuator 3 drives the cooling gas to flow into the lid 1 through the cold air passage 4, exchange heat with the lid 1, and then flow out from the hot air outlet 11, carrying away the heat. Understandably, the pot body 2 and the lid body 1 can also be connected using common connection methods such as snap-fit ​​connections.

[0038] After cooking is finished, air continues to flow from the cold air inlet 25 into the driver 3, which generates cooling air. The cooling air flows into the lid 1 through the cold air outlet 4 to exchange heat with the lid 1. The hot air after heat exchange flows out from the hot air outlet 11 to quickly reduce the temperature of the cooking cavity. Then, by utilizing the direct proportional relationship between temperature and pressure, rapid pressure reduction is achieved. The pressure cooker can be opened as soon as cooking is finished, reducing the user's waiting time.

[0039] The cold air inlet 25 is located on the pot body 2, and the hot air outlet 11 is located on the lid 1. The two are spatially far apart, so the hot air discharged from the lid 1 will not enter the cold air inlet 25 to participate in the next cooling cycle. This increases the temperature difference between the cooling gas and the pot, improves the heat exchange efficiency of the cooling gas, and enables the pressure cooker to cool down quickly. Compared with the actuator 3 being located at the bottom of the pot body 2, the actuator 3 is located on the side, which allows the cooling gas to enter from the cold air inlet 25 and flow directly into the cooling channel 6 under the driving action of the actuator 3. This avoids the cooling gas exchanging heat with the pot body 2 first and then entering the cooling channel 6 to exchange heat with the lid 1. Since the cooling effect of the lid 1 on pressure reduction is better than that of the side of the pot body 2, the pressure cooker can cool down faster. The hot air outlet 11 is located on the lid 1, away from the user's operating area, which ensures high safety. The actuator 3 is located inside the pot body 2, which is a compact layout and reduces the volume of the pressure cooker.

[0040] In this embodiment, further, as Figure 1 As shown, the shell 22 has a receiving cavity 24 for accommodating the actuator 3. The receiving cavity 24 and the shell 22 are manufactured by integral casting. The receiving cavity 24 is formed by the internal structure and side walls of the shell 22. There is a gap between the receiving cavity 24 and the outer pot 21. The opening of the receiving cavity 24 is connected to the air outlet 26. A cold air inlet 25 is provided at the corresponding position of the shell and the receiving cavity 24, which allows cooling gas to flow directly into the actuator 3. In this structure, the actuator 3 and the outer pot 21 are sealed, and the cooling gas flows only to the lid 1, avoiding gas loss caused by the dispersion of the flow. Sufficient cooling gas exchanges heat with the lid 1, which is conducive to rapid cooling inside the pot. The cold air inlet 25 is located on the side wall of the receiving cavity 24, and the cooling gas can flow directly and horizontally into the actuator 3 without the need for a guiding structure, ensuring that sufficient cooling gas flows into the actuator 3 quickly, realizing rapid depressurization of the pressure cooker. The receiving cavity 24 and the shell 22 are manufactured by integral casting, reducing the risk of gas leakage.

[0041] In another embodiment, a driver mounting base is installed between the shell 22 and the outer pot 21. After the driver mounting base is connected to the side wall of the shell 22, a receiving cavity 24 is formed. A cold air inlet 25 is provided at the position corresponding to the receiving cavity 24 on the side wall of the shell 22, which simplifies the structure of the shell 22 and facilitates industrial production.

[0042] In this embodiment, the shell 22 is further provided with a support surface 27 for supporting the cover 1, and an air outlet 26 is provided on the support surface 27. The air outlet 26 is located above the opening of the receiving cavity 24. The cover 1 is provided with an abutting surface 17 that abuts against the support surface 27, and an air inlet 14 is provided on the abutting surface 17. The number of air inlets 14 and air outlets 26 are the same and their positions are aligned. When the pressure cooker is closed, the air outlet 26 and the air inlet 14 are combined to form a vertical cold air passage 4. In this structure, the air inlet 14 is provided on the abutting surface 17 and the air outlet 26 is provided on the support surface 27. The two are fitted together to form the cold air passage 4. The cooling gas flow path is short and smooth, which speeds up the cooling gas circulation speed. At the same time, the abutting surface 17 is tightly fitted to the support surface 27, so that the gas can only flow out from the cold air passage 4, reducing cooling gas leakage and ensuring that sufficient cooling gas enters the cover 1 to participate in heat exchange, thereby improving the cooling and pressure reduction effect. Furthermore, a sealing ring is installed on the air inlet 14 or the air outlet 26 to improve the sealing between them and ensure that cooling gas does not leak from the connection point. The pressure cooker should have at least one air inlet 14 and one air outlet 26. When only one air inlet 14 and one air outlet 26 are provided, refer to the following... Figure 4 and Figure 6 The distribution pattern; when multiple air inlets 14 and air outlets 26 are provided, refer to the following: Figure 5 and Figure 7The distribution of the cooling gas is as follows: four air outlets 26 are provided on the support surface 27, and each air outlet 26 is spaced along the inner pot 28. Below each air outlet 26 is a receiving cavity 24 containing the driver 3. The air inlet 14 is aligned with the air outlet 26, increasing the flow rate of the cooling gas and allowing it to enter the lid 1 from different directions for heat exchange, thus improving cooling efficiency. It should be noted that... Figures 4 to 7 As an example only, the number and layout of the air inlet 14 and the air outlet 26 should be flexibly set according to the actual usage requirements and the structural characteristics of the pressure cooker itself.

[0043] In another embodiment, the lid 1 has an air inlet 14 with a concave structure, and the shell 22 has an air outlet 26 with raised ribs around it. When the pressure cooker is closed, the air inlet 14 and the raised ribs around the air outlet 26 form a tight fit to create a closed cold air vent 4. At this time, the lid 1 and the pot 2 are either in contact or have a certain gap. It is understood that the concave air outlet 26 and the air inlet 14 with raised ribs around it can also be configured to form a mating structure.

[0044] In this embodiment, further, as Figure 3 As shown, the top of the lid 1 has four hot air outlets 11, and a pressure relief valve vent 13 is located at the center of the top of the lid 1. The hot air outlets 11 are positioned near the pressure relief valve vent 13, and the hot air outlets 11 are spaced apart along the center of the lid 1. This structure utilizes the user's tendency to avoid the pressure relief valve vent 13 by placing the hot air outlets 11 nearby, allowing the user to avoid the hot air outlets 11 while keeping away from the vent, reducing the possibility of burns from hot air and improving the safety of the pressure cooker. The multiple hot air outlets 11 allow the pressure cooker to release more hot air in the same amount of time, accelerating the release of hot air from the pot and thus improving the cooling speed. The design of several hot air outlets 11 spaced apart along the center of the lid 1 allows hot air to be discharged more evenly from all directions of the lid 1, preventing localized hot air accumulation. It should be noted that the number of hot air outlets 11 can be one or more, depending on actual needs.

[0045] In another embodiment, the hot gas outlet 11 is located at the top of the cover 1 away from the air inlet 14, which extends the cooling path of the cooling gas in the cover 1. The cooling gas can flow in a wider area inside the cover 1, thereby carrying out more sufficient heat exchange and improving the cooling and pressure reduction effect.

[0046] In this embodiment, the cover 1 further includes a cover shell 12 with a hot air outlet 11 and an air inlet 14, and an outer cover 16 disposed inside the cover shell 12. The outer cover 16 covers the outer pot 21, and an inner cover 15 is connected below the outer cover 16. The inner cover 15 seals the inner pot 28. The inner cover 15 has several through holes communicating with the upper and lower spaces of the inner cover 15. A cooling channel 6 is formed between the cover shell 12 and the outer cover 16 to allow the cooling gas to exchange heat with the outer cover 16. In this structure, the outer cover 16 is closely connected to the cooking space. The cooling gas carries away the heat from the outer cover 16, causing it to cool down rapidly, which promotes the rapid transfer of heat from the cooking space through the outer cover 16, achieving efficient depressurization of the cooking space.

[0047] In another embodiment, the cover 1 includes a cover shell 12 with a hot air outlet 11 and an air inlet 14, an outer cover 16 disposed inside the cover shell 12, and an outer cover cover disposed between the cover shell 12 and the outer cover 16. The outer cover 16 covers the outer pot 21, and an inner cover 15 is connected below the outer cover 16. The inner cover 15 seals the inner pot 28. The inner cover 15 has several through holes communicating with the upper and lower spaces of the inner cover 15. The outer cover cover is connected to the cover shell 12 and covers the outer cover 16. A cooling channel 6 is formed between the outer cover 16 and the outer cover cover. The outer cover cover has a first air outlet communicating with the hot air outlet 11, and a gap is provided between the outer cover 16 and the outer cover cover to allow cooling gas to flow into the cooling channel 6. It can be understood that a second air outlet communicating with the air inlet 14 can also be provided on the outer cover cover to allow cooling gas to flow into the cooling channel 6. Since the cover 12 is usually made of plastic, it is easily deformed by heat. An outer cover is set at the bottom of the cover to prevent hot air from directly contacting the cover 12 and thus prevent the cover 12 from deforming.

[0048] In this embodiment, the driver 3 further employs a turbine fan, with its air inlet facing the cooling air inlet 25 and its air outlet facing the air outlet 26. The turbine fan concentrates the airflow, precisely directing the cooling gas towards the air outlet 26, eliminating the need for a guide structure, reducing the number of parts, and simplifying the assembly process.

[0049] In another embodiment, the actuator 3 is an impeller fan. The air inlet of the actuator 3 faces the cold air inlet 25, and the air outlet of the actuator 3 faces away from the cold air inlet 25. An air guide 5 is provided between the air outlet and the air outlet 26 of the actuator 3 to guide the air blown by the impeller fan to the air outlet 26. The impeller fan has a large air volume, and the air guide 5 concentrates the air to the air outlet 26, allowing more cooling gas to enter the cover 1, improving the cooling efficiency of the cover 1. At the same time, the impeller fan has a low cost.

[0050] The above description is merely a preferred embodiment of the present utility model and does not constitute any limitation on the present utility model. Any simple modifications, alterations, or equivalent structural transformations made to the above embodiments based on the technical essence of the present utility model shall still fall within the protection scope of the present utility model.

Claims

1. A pressure cooker comprising a pot body (2) and a cover body (1) which is openably and closably provided on the pot body (2), the pot body (2) comprising a casing (22) and an outer pot (21) which is provided in the casing (22), characterized in that, A driver (3) is provided between the side of the shell (22) and the side of the outer pot (21). The shell (22) has an air outlet (26) and a cold air inlet (25) for cooling gas to flow into the driver (3). The lid (1) has an air inlet (14), a hot air outlet (11) connected to the outside, and a cooling channel (6) connected to both. When the pressure cooker is closed, the air outlet (26) and the air inlet (14) are closed to form a cold air passage (4). The driver (3) drives the cooling gas to flow into the cooling channel (6) through the cold air passage (4) and exchange heat with the lid (1) before flowing out from the hot air outlet (11).

2. A pressure cooker according to claim 1, characterized in that The housing (22) has a receiving cavity (24) for accommodating the driver (3), and the opening of the receiving cavity (24) is connected to the air outlet (26).

3. A pressure cooker according to claim 2, characterized in that, The housing (22) is provided with a cold air inlet (25) at the position corresponding to the receiving cavity (24).

4. A pressure cooker according to claim 1, characterized in that, The housing (22) is provided with a support surface (27) for supporting the cover (1), the cover (1) is provided with a contact surface (17) that abuts against the support surface (27), the air inlet (14) is provided on the contact surface (17), and the air outlet (26) is provided on the support surface (27).

5. A pressure cooker according to claim 1, characterized in that, The top of the cover (1) is provided with a pressure relief valve exhaust port (13), and the hot air outlet (11) is located near the pressure relief valve exhaust port (13).

6. A pressure cooker according to claim 1, characterized in that, The hot air outlet (11) is located at the top of the cover (1) away from the air inlet (14).

7. A pressure cooker according to claim 1, characterized in that, The cover (1) includes a cover shell (12) with a hot air outlet (11) and an air inlet (14) and an outer cover (16) located inside the cover shell (12). The outer cover (16) covers the outer pot (21). A cooling channel (6) is formed between the cover shell (12) and the outer cover (16) to allow the cooling gas to exchange heat with the outer cover (16).

8. A pressure cooker according to claim 1, characterized in that, The cover (1) includes a cover shell (12) with a hot air outlet (11) and an air inlet (14), an outer cover (16) inside the cover shell (12), and an outer cover cover between the cover shell (12) and the outer cover (16). The outer cover (16) covers the outer pot (21). The outer cover cover is connected to the cover shell (12) and covers the outer cover (16). A cooling channel (6) is formed between the outer cover (16) and the outer cover cover to allow the cooling gas to exchange heat with the outer cover (16). The outer cover cover is provided with a first air outlet communicating with the hot air outlet (11). A gap is provided between the outer cover (16) and the outer cover cover to allow the cooling gas to flow into the cooling channel (6) from the air inlet (14). Alternatively, the outer cover cover is provided with a second air outlet for communicating with the cooling channel (6) and the air inlet (14).

9. A pressure cooker according to any one of claims 1 to 8, characterized in that, The driver (3) is a turbine fan, with the air inlet of the driver (3) facing the air inlet (25) and the air outlet of the driver (3) facing the air outlet (26).

10. A pressure cooker according to any one of claims 1 to 8, characterized in that, The driver (3) is an impeller fan. The air inlet of the driver (3) faces the air inlet (25) and the air outlet of the driver (3) is away from the air inlet (25). A guide (5) is provided between the air outlet and the air outlet (26) of the driver (3) to guide the air blown out by the impeller fan to the air outlet (26).

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