A handheld hair dryer

Abstract

The present invention discloses a handheld hair dryer, which comprises a hair dryer body and a handle. The hair dryer body includes a body housing part and an internal flow guiding structure. The body housing part and the internal flow guiding structure form an internal annular cavity and a through air outlet channel around the central axis of the hair dryer body. A heating unit is arranged in the annular cavity, and the annular cavity is provided with an air outlet, and the air outlet is an annular gap for guiding the flowing air in the annular cavity to the air outlet channel. The body housing part includes an air inlet opening part, and the air inlet opening part is communicated with one end of the handle. The handle is a hollow structure, and the hollow structure is an air inlet channel. A fan unit and a single-chip microcomputer control unit are arranged in the hollow structure. A filtering device is arranged at one end of the handle far away from the hair dryer body. The present invention can reduce the loss of wind speed and wind pressure, generate the Coanda effect, so that the wind speed is greater and more stable, up to 20 m / s, and the hair can be dried more quickly.

Description

Technical Field

[0001] The invention relates to the field of hair dryers, and in particular to a handheld high-speed motor and fan blade driven electrically heated hot air hair dryer, such as a hair dryer and a hair dryer in the field of small household appliances. Background Art

[0002] Electric hair dryers are mainly used for drying and shaping hair. They can also be used for local drying, heating and treatment in laboratories, physiotherapy rooms, industrial production, and art.

[0003] Typically, a motor and a fan blade are provided, which draw air into the body, which is then blown out after being heated by a heating wire. Typically, such hair dryers are provided with an air collecting port or a diffusion nozzle, which can be connected to or removed from the hair dryer and changes the speed and direction of the air flow discharged from the hair dryer.

[0004] Patent CN201621361236.9 discloses a handheld product using a high-speed motor. The motor speed in this technical solution is between 75,000 and 110,000 revolutions per minute. This handheld product allows the fan unit composed of a high-speed motor installed in the handle to drive air into the body cavity and blow it out quickly from a 2mm wide annular outlet. It uses air multiplication technology and the wind speed can reach 17m / s, which is unattainable by ordinary hair dryers. Although it is already a very high wind speed, the airflow direction of the handle will change by about 90° when the air flows to the body cavity, which will cause losses in wind speed and wind pressure. In the prior art, this loss is usually reduced by setting an air guide structure.

[0005] Another disadvantage of the bladeless high-speed hair dryer technology solution currently on the market is that the circuit board is placed at the rear end of the top of the hair dryer, where the air flow is not very smooth, and heat dissipation has always been a big problem.

[0006] Currently, the technical solutions for bladeless high-speed hair dryers on the market usually install a filter device at the air inlet end of the hair dryer. However, after long-term use, the filter device and the filter net are covered with dust, which is not easy to detect. Dust and other reasons often cause increased noise, unreasonable shutdown or overheating protection failure, which reduces the consumer experience.

[0007] Patent application number CN201710809640.0 discloses a handheld smooth hair dryer. The technical solution includes an air multiplier device, characterized in that the air guide element is provided with at least one annular air outlet cutout, and the width of the annular air outlet cutout should be within 1.3 to 1.4 mm. I have not seen the actual product on the market, so I don't know how effective it is. Summary of the invention

[0008] The object of the present invention is to provide a new structure of an electric hair dryer, which has a more reasonable structure, a greater and more stable wind speed, up to 20 m / s, and can dry hair more quickly.

[0009] To achieve the above object, the present invention provides the following technical solution: A hand-held electric hair dryer, comprising a hair dryer body and a handle. The hair dryer body includes a body housing part and an internal flow guiding structure. The body housing part and the internal flow guiding structure form an internal annular cavity and a through air outlet channel around the central axis of the hair dryer body. A heating unit is arranged in the annular cavity, and the annular cavity is provided with an air outlet, and the air outlet is an annular gap. The annular gap communicates the annular cavity and the air outlet channel. The body housing part includes an air inlet opening part, and the air inlet opening part is connected to one end of the handle, and the annular cavity and the handle are communicated to form a hollow structure, and the hollow structure is an air inlet channel. A fan unit and a single-chip microcomputer control unit are arranged in the hollow structure, and a filtering device is arranged at one end of the handle far away from the hair dryer body.

[0010] Preferably, the width of the annular gap is 1.5 mm to 3 mm, and the included angle between the annular gap and the central axis of the air inlet channel is not less than 90°.

[0011] Preferably, the internal flow guiding structure at least includes a flared component and an air outlet guiding component;

[0012] The flared component forms a partial covering surface of the annular cavity. The large end of the flared component is the fixed end, and the small end is the open end. The fixed end is connected to the body housing part, and the open end and the air outlet guiding component form the annular gap of the air outlet.

[0013] Preferably, the air outlet guiding component includes an internal wall curved surface. The internal wall curved surface sequentially includes an annular gap forming section curved surface, an annular gap guiding section curved surface and an exhaust guiding section along the air outlet direction. The annular gap forming section curved surface is arranged staggered with the open end of the flared component to form the annular gap of the air outlet; the annular gap guiding section curved surface is a smooth arc, including a throat curved surface forming the narrowest air outlet channel. The included angle between the throat curved surface and the horizontal central axis is 5° to 30°, and the minimum diameter of the throat curved surface is 22 mm to 26 mm. The exhaust guiding section is horizontally arranged.

[0014] Preferably, the annular gap forming section curved surface is an inclined surface or a smooth arc surface, and the open end is a smooth arc shape. The annular gap forming section curved surface of the smooth arc surface is arranged parallel to the smooth arc shape of the open end.

[0015] Preferably, a support structure is arranged in the annular cavity, and a heating unit is arranged inside the support structure.

[0016] Preferably, it includes a support member, and the support member includes at least 3 support points, and the support points are evenly arranged in a circle in the annular gap.

[0017] Preferably, the single-chip microcomputer control unit is placed at one end of the handle close to the filtering device.

[0018] Preferably, the power system of the fan unit is a forward and reverse variable frequency motor.

[0019] Preferably, the filtering device includes an outer cylindrical coarse filtering device and an inner fine filtering device.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] The main air entering the handle is driven by the fan unit after passing through the air at the inlet of the filtering device and is sent into the annular cavity, and is ejected from the annular slit-shaped air outlet. The air from the outside of the tail of the hair dryer body is entrained by the fast air flow ejected from the annular slit-shaped air outlet through the air outlet channel, generating the Coanda effect. The ejected air flow and the entrained air flow form a total air flow that shoots forward from the throat surface. That is, the Coanda effect is generated at the inner wall surface of the annular slit-shaped air outlet, so that there is a certain air amplification effect on the air volume of the hair dryer appliance, which can effectively improve the air volume. Among them, the setting of the annular slit-shaped exhaust port has an amplifying effect on the air flow. When the air flows out from the annular slit-shaped exhaust port, according to the Coanda effect, this part of the air (referred to as the first air flow) will adsorb on the inner wall curved surface of the air outlet guiding component and flow along the inner wall curved surface. Therefore, a certain negative pressure is generated in the central area of the annular inner wall curved surface, so that a large amount of surrounding air is inhaled. After the first air flow and the surrounding air flow converge, a fast and high-capacity air flow flows out, realizing the air amplification effect. In addition, the air flow direction of the handle of the present invention is a direct current direction when flowing into the annular cavity of the hair dryer body, reducing the loss of wind speed and wind pressure, so that the wind speed is greater and more stable, up to 20 m / s, and the hair can be dried more quickly.

[0022] The unique design of the air flow amplification air duct of the present invention uses all the air volume inhaled by the scroll fan brushless motor to drive the air flow amplifier, and takes all the inhaled air flows as the power source for the hair dryer body to amplify and then inhale the make-up air behind the air outlet channel, further improving the air flow multiplication effect; in addition, after the air flow amplification multiple increases, the hot air flow blown out is mixed with a large proportion of cold air, effectively avoiding the phenomenon of high-temperature burning of the hair and drying and protecting the hair at a safe and comfortable temperature. Description of the Drawings

[0023] Figure 1 is the front view of the handheld hair dryer according to Embodiment 1 of the present invention;

[0024] Figure 2 is Figure 1 the rear view of;

[0025] Figure 3 is Figure 1 the side view of;

[0026] Figure 4 is Figure 1 A cross-sectional view taken along the A-A direction;

[0027] Figure 5 is a schematic explosion diagram of the present invention;

[0028] Figure 6 is a schematic cross-sectional diagram of the hand-held hair dryer according to Embodiment 2 of the present invention;

[0029] In the figure: 1, hair dryer body, 11, body housing part, 111, air inlet opening part, 12, internal flow guiding structure, 121, flared component, 1211, fixed end, 1212, open end, 122, air outlet guiding component, 1221, curved surface of the annular gap forming section, 1222, curved surface of the annular gap leading-out section, 1223, exhaust leading-out section, 1224, throat curved surface, 13, annular cavity, 131, support structure, 14, annular gap, 15, air outlet channel, 2, handle, 21, air inlet channel, 22, control on / off, 3, heating unit, 4, fan unit, 41, motor, 42, fan blade, 5, single-chip microcomputer control unit, 6, filtering device, 61, outer cylindrical coarse filtering device, 62, inner fine filtering device, 7, honeycomb component, 10, support point. Specific embodiments

[0030] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0031] Such as Figures 1 to 5As shown in the figure, a handheld hair dryer includes a hair dryer body 1 and a handle 2. The handle 2 is circular tubular. The hair dryer body 1 includes a body housing part 11 and an internal flow guiding structure 12. The body housing part 11 is circular tubular, and the outer wall diameter of the circular tube is 82 mm. The body housing part 11 and the internal flow guiding structure 12 form an internal annular cavity 13 and a through air outlet channel 15 around the central axis of the hair dryer body 1. The average thickness of the cavity wall of the annular cavity 13 is generally between 1 mm and 5 mm, preferably between 1 mm and 3 mm, which is beneficial to reducing the resistance of air flow and reducing the loss of air flow. A heating unit 3 is arranged in the annular cavity 13. An air outlet is arranged on the inner ring surface of the annular cavity 13. The air outlet is an annular gap 14, which is used to lead the flowing air in the annular cavity 13 to the air outlet channel 15. The annular gap 14 is located at the middle position of the air outlet channel 15. Even if the front end outlet position of the air outlet channel 15 is blocked, the air flow can blow backward through the hollow air outlet channel 15, ensuring smooth internal air flow, and further ensuring that no high temperature will be generated inside the hair dryer body 1 and at the outlet, ensuring safety. The above structure also solves the problem of the air outlet of the traditional hair dryer being at the front end of the hair dryer. Once the air outlet is blocked, due to the unsmooth air flow, the air flow will reverse, and it is extremely easy to generate temperature sensing inside the hair dryer and at the outlet, posing a huge safety hazard. The width of the annular gap 14 is 1.5 mm to 3 mm, preferably between 2 mm and 2.6 mm. Through experimental tests, the above annular gap 14 structure combined with the hair dryer body 1 and handle 2 structures of this embodiment can best produce the Coanda effect and the Coandă effect, achieving the best use effect. The body housing part 11 includes an air inlet opening part 111. The air inlet opening part 111 is communicated with one end of the handle 2. The handle 2 is a hollow structure, and the hollow structure is an air inlet channel 21. The included angle between the annular gap 14 and the central axis of the air inlet channel 21 is not less than 90°. A fan unit 4 and a single-chip microcomputer control unit 5 are arranged in the hollow structure. A filtering device 6 is arranged at one end of the handle 2 away from the hair dryer body 1.

[0032] In a preferred embodiment, the internal flow guiding structure 12 at least includes a flared component 121 and an air outlet guiding component 122; the flared component 121 constitutes a partial covering surface of the annular cavity 13. The large end of the flared component 121 is a fixed end 1211, and the small end is an open end 1212. The fixed end 1211 is connected to the body housing part 11, and the open end 1212 and the air outlet guiding component 122 form the annular gap 14 of the air outlet. The fixed end 1211 and the body housing part 11 are connected by threads, or other connection methods, and are configured with a sealing rubber ring for sealing; it can also be derived that the fixed end 1211, the body housing part 11 and the outer shell of the handle 2 are integrally formed. And the outer shell of the flared component 121, the outer shell of the body housing part 11 and / or the outer shell of the handle 2 are made of plastic material and sprayed with rubber paint, which not only improves the aesthetic appearance of the overall hair dryer, but also improves the overall texture of the hair dryer and enhances the user experience.

[0033] In a preferred embodiment, the air outlet guiding member 122 is connected to or integrally formed with the main body housing portion 11. The air outlet guiding member 122 includes an inner wall curved surface. The inner wall curved surface sequentially includes an annular gap forming section curved surface 1221, an annular gap guiding section curved surface 1222, and an air exhaust guiding section 1223 in accordance with the air outlet direction. The annular gap forming section curved surface 1221 is staggeredly arranged with the open end 1212 of the flared member 121 to form an annular gap 14 of the air outlet. The width of the exhaust port of the annular gap 14 is 2.5 mm. The annular gap guiding section curved surface 1222 is a smooth arc, including a throat curved surface 1224 that forms the narrowest air outlet channel 15. The angle α between the throat curved surface 1224 and the horizontal central axis is 5° to 30°, preferably between 15° and 25°. The minimum diameter of the throat curved surface 1224 is 22 mm to 26 mm, preferably between 23 mm and 25 mm. The air exhaust guiding section 1223 is horizontally arranged. The annular gap forming section curved surface 1221 is an inclined surface or a smooth arc surface, and the open end 1212 is a smooth arc shape. The smooth arc-shaped annular gap forming section curved surface 1221 is arranged in parallel with the smooth arc shape of the open end 1212. The air exhaust guiding section 1223 is horizontally arranged, with a length of approximately 11.54 mm and an inner diameter of 36 mm. The horizontal distance between the front end surface of the air exhaust guiding section 1223 and the fixed end 1211 of the flared member 121 is 30 mm.

[0034] In a preferred embodiment, the cross-section of the annular cavity 13 passing through the central axis presents a quasi-inverted triangular structure. A support structure 131 is arranged in the annular cavity 13, and a heating unit 3 is arranged inside the support structure 131. The heating unit 3 is used to heat the air flow in the annular cavity 13 and convey it to the front end of the hair dryer body 1 through the exhaust port of the annular gap 14. At the same time, the relative positions of the main body housing portion 11, the flared member 121, and the air outlet guiding member 122 are supported and fixed by the support structure 131, thereby keeping the structure and size of the annular gap 14 fixed.

[0035] In a preferred embodiment, a control on / off 22 and an indicator light are arranged on the handle 2. The control on / off is set as a push-pull type switch or a button type switch. The PCB 100 of the single-chip microcomputer control unit 5 is assembled in the handle 2, and is arranged near the main air inlet for better heat dissipation. The PCB 100 of the single-chip microcomputer control unit 5 controls parameters such as the temperature of the heating unit 3 and the rotation speed of the fan unit 4. Internal wiring (not shown) electrically connects the PCB 100 to the heating unit 3, the fan unit 4, and the cable. The control on / off 22 is provided and connected to the PCB 100. The user can select four temperature settings (natural wind / first gear temperature (low temperature) / second gear temperature (medium temperature) / third gear temperature (high temperature)) and three wind speed settings (first gear wind speed (low speed) / second gear wind speed (medium speed) / third gear wind speed (high speed)).

[0036] In a preferred embodiment, the fan unit 4 is arranged in the hollow structure of the handle 2, and the fan unit 4 is composed of a motor 41 and a fan blade 42. The fan unit 4 draws air through the main air inlet, and the air flows through the air inlet channel of the handle 2 and enters the hair dryer body 1. After being heated around the electric heating core unit, the air is quickly discharged through the annular gap 14 exhaust port. The power system of the fan unit 4 is a forward and reverse frequency brushless motor, which can be reversed regularly to remove dust from the filter screen, and at the same time, it plays a role in heat dissipation for the single-chip control unit 5, reducing the probability of unexplained shutdown or overheating shutdown. The fan adopts a turbofan, and all the air volume sucked by the fan unit drives the airflow amplifier, and all the sucked airflow is used as the power source for the hair dryer body to amplify and then suck in the air supply at the rear of the air outlet channel, which further improves the airflow multiplication effect; in addition, after the airflow amplification factor is increased, a large proportion of cold air is mixed in the high-temperature airflow blown out, which effectively avoids the phenomenon of high temperature burning the hair, and keeps the hair dry and hair care at a safe and comfortable temperature.

[0037] In a preferred embodiment, in order to isolate external impurities and improve the diversion effect on the incoming and outgoing air, the filter device 6 includes an outer layer cylindrical coarse filter device 61 and an inner layer fine filter device 62 arranged at the air inlet. The outer layer cylindrical coarse filter device 61 and the inner layer fine filter device 62 can be removed and can be cleaned by wiping or brushing.

[0038] In a preferred embodiment, a honeycomb component 7 is provided inside the tubular interior of the handle 2. The honeycomb component 7 is integrally connected to the inner wall of the handle 2 to support and strengthen the handle 2 and reduce resistance to incoming wind.

[0039] In a preferred embodiment, the outer wall of the exhaust outlet section 1223 is provided with a recess for placing an iron ring. The design here is used to magnetically connect an external air collection nozzle or a diffuser nozzle.

[0040] Working principle: The main air entering the handle 2 passes through the air at the inlet of the filtering device 6 and is sent to the annular cavity 13 after being driven by the fan unit 4, and is ejected by the air outlet of the annular gap 14. The air from the outside of the tail of the hair dryer body 1 is entrained by the fast air flow discharged from the air outlet of the annular gap 14 through the air outlet channel 15, generating the Coanda effect. The ejected air flow and the entrained air flow form the total air flow that shoots forward from the throat curved surface 1224. That is, the Coanda effect is generated at the inner wall surface of the air outlet of the annular gap 14, enabling a certain air amplification effect on the air volume of the hair dryer appliance, and effectively improving the air volume. Among them, the setting of the air outlet of the annular gap 14 has an amplifying effect on the air flow. When the air flows out from the air outlet of the annular gap 14, according to the Coanda effect, this part of the air (referred to as the first air flow) will adsorb on the inner wall curved surface of the air outlet guiding member 122 and flow along the inner wall curved surface. As a result, a certain negative pressure is generated in the central region of the annular inner wall curved surface, causing a large amount of surrounding air to be inhaled. After the first air flow and the surrounding air flow converge, they form a fast and high-capacity air flow to flow out, realizing the air amplification effect. In addition, the air flow direction of the handle 2 of the present invention to the annular cavity 13 of the hair dryer body 1 is a direct current direction, reducing the loss of wind speed and wind pressure, so that the wind speed is greater and more stable, up to 20 m / s, and the hair can be dried more quickly. Embodiment

[0041] As Figure 6 shown, the difference from Embodiment 1 is that the component surface of the internal diversion structure 12 surrounding the annular cavity 13 is a smooth arc surface, and the structure and size of the annular gap 14 are supported by setting support members. The support members can include 3, 4, 6 or 8 support points 10, and the support points 10 are evenly arranged on the circumference in the annular gap 14.

[0042] For Embodiment 1, an experimental test was conducted on a handheld hair dryer with the support member including 3 support points 10 as follows:

[0043] Wind speed: Remove the nozzle. On the axis of the air outlet cylinder, at positions 0 mm, 100 mm, and 200 mm away from the air outlet, measure the maximum wind speed with an anemometer.

[0044] Air volume: Remove the nozzle. On the axis of the air outlet cylinder, at positions 10 mm, 100 mm, and 200 mm away from the air outlet, measure the wind force (i.e., air volume) with an electronic scale.

[0045] Measuring range of the electronic scale: 0 - 500 g·s;

[0046] Measuring range of the anemometer: 0.3 m / s - 45 m / s;

[0047] Ambient temperature: 26.8°.

[0048] Experimental results:

[0049] The present invention Annular slit opening gap (1.6 mm) Annular slit opening gap (2.5 mm) Annular slit opening gap (5 mm) Other hair dryers Gear Highest gear Highest gear Highest gear Highest gear Blowing force at a distance of 10 mm 108 g 120 g 80 g Blowing force at a distance of 10 mm 102 g Blowing force at a distance of 100 mm 103 g 116 g 70 g Blowing force at a distance of 100 mm 110 g Blowing force at a distance of 200 mm 85 g 108 g 40 g Blowing force at a distance of 200 mm 95 g Wind speed measured at 0 mm, 18 m / s 20.5 m / s 18.5 m / s Wind speed measured at 0 mm 16.86 m / s Wind speed measured at 100 mm, 17 m / s 16.5 m / s 15 m / s Wind speed measured at 100 mm 16.8 m / s Wind speed measured at 200 mm, 12 m / s 13 m / s 12 m / s Wind speed measured at 200 mm 14.5 m / s

[0050] The experimental results show that:

[0051] The maximum wind speed measured by other hair dryers is 16.86 m / s, which is basically consistent with the publicity (17 m / s) and the values in online evaluations (16 - 17 m / s), indicating that our measurement method is reliable.

[0052] After a large number of prototype tests, we finally demonstrated that when the gap of the annular gap 14 is 2.5 mm, the air outlet effect of the hair dryer is the best.

[0053] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A handheld hair dryer, comprising a hair dryer body and a handle, characterized in that: The hair dryer body includes a body housing part and an internal flow guiding structure. The body housing part and the internal flow guiding structure form an internal annular cavity and a through air outlet channel around the central axis of the hair dryer body. A heating unit is arranged in the annular cavity. The annular cavity is provided with an air outlet, and the air outlet is an annular gap. The annular gap communicates the annular cavity and the air outlet channel. The body housing part includes an air inlet opening part, and the air inlet opening part is connected to one end of the handle. The annular cavity and the handle are in a hollow structure, and the hollow structure is an air inlet channel. A fan unit and a single-chip microcomputer control unit are arranged in the hollow structure. A filtering device is arranged at one end of the handle away from the hair dryer body. The included angle between the annular gap and the central axis of the air inlet channel is greater than 90°. The cross-section of the annular cavity passing through the central axis presents a quasi-inverted triangular structure. The annular gap is located at the middle position of the air outlet channel, so that the air flow direction of the handle to the annular cavity of the hair dryer body is a direct current direction.

2. The hand-held hair dryer according to claim 1, wherein: The width of the annular gap is 1.5 mm to 3 mm.

3. A hand-held hair dryer according to claim 1, characterized in that: The internal flow guiding structure at least includes a flared component and an air outlet guiding component; The flared component forms a partial covering surface of the annular cavity. The large end of the flared component is the fixed end, and the small end is the open end. The fixed end is connected to the body housing part, and the open end and the air outlet guiding component form the annular gap of the air outlet.

4. A hand-held hair dryer according to claim 3, characterized in that: The air outlet guiding component includes an internal wall curved surface. The internal wall curved surface sequentially includes an annular gap forming section curved surface, an annular gap guiding section curved surface, and an exhaust guiding section along the air outlet direction. The annular gap forming section curved surface is arranged staggeredly with the open end of the flared component to form the annular gap of the air outlet. The annular gap guiding section curved surface is a smooth arc, including a throat curved surface forming the narrowest air outlet channel. The included angle between the throat curved surface and the horizontal central axis is 5° to 30°, and the minimum diameter of the throat curved surface is 22 mm to 26 mm. The exhaust guiding section is horizontally arranged.

5. A handheld hair dryer according to claim 4, characterized in that: The annular gap forming section curved surface is an inclined surface or a smooth arc surface, and the open end is a smooth arc shape. The annular gap forming section curved surface of the smooth arc surface is arranged parallel to the smooth arc shape of the open end.

6. A handheld hair dryer according to claim 1, characterized in that: A support structure is arranged in the annular cavity, and the heating unit is arranged inside the support structure.

7. A hand-held electric hair dryer according to any one of claims 1 to 6, characterized in that: It includes a support member, and the support member includes at least 3 support points. The support points are evenly arranged in a circle in the annular gap.

8. A handheld electric hair dryer according to claim 1, characterized in that: The single-chip microcomputer control unit is placed at one end of the handle close to the filtering device.

9. A hand-held electric hair dryer according to claim 1, wherein: The power system of the fan unit is a forward and reverse variable frequency motor.

10. A hand-held electric hair dryer according to claim 1, characterized in that: The filtering device includes an outer cylindrical coarse filtering device and an inner fine filtering device.

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