EP1744103A2

EP1744103A2 - Exhaust hood

Info

Publication number: EP1744103A2
Application number: EP06000918A
Authority: EP
Inventors: Seung-Jo Baek; Sang-Bum Sohn; Sung-Bae Song
Original assignee: LG Electronics Inc
Current assignee: LG Electronics Inc
Priority date: 2005-07-12
Filing date: 2006-01-17
Publication date: 2007-01-17
Also published as: KR20070008002A; KR100741783B1

Abstract

An exhaust hood comprising: a hood main body 110 provided with a canopy 111 having an inlet 117 and an exhaustion portion 123 connected to the canopy 111 and having an exhaustion passage 123 therein; and a nozzle unit 140 disposed at a front side of the hood main body 110, and provided with a curved shape portion 143, an air supply nozzle 141 disposed at an upper side of the curved shape portion 143 along a circumferential direction of the curved shape portion 143 for discharging air, and an air suction nozzle 141 disposed at a lower side of the curved shape portion 143 along the circumferential direction of the curved shape portion 143 for sucking air, whereby contaminated air flowing toward a front region of the exhaust hood without being sucked therein can effectively be induced to the inlet to thus be collected. Also, when a supplementary nozzle unit 140is additionally provided, the contaminated air flowing toward a lateral region of the exhaust hood without being sucked therein can effectively be collected, to thus enable creating of more comfortable cooking circumstances and experimental environment.

Description

The present invention relates to an exhaust hood, and particularly, to an exhaust hood having an improved efficiency for collecting contaminated air.
In general, an exhaust hood is disposed above a cooker such as a gas range or a laboratory table that generate materials causing air pollution like smoke, smells and grease vapor.
Figure 1 is a side sectional view that illustrates one example of an exhaust hood according to the conventional art. Referring to Figure 1, the conventional exhaust hood includes a canopy 21 installed above a cooker 10 having a plurality of burners 11a and 11b spaced at a predetermined distance therebetween, and an exhaust part 31 communicating with the canopy 21 and upwardly protruding from the canopy 21 to a predetermined height.
An inlet 23 is formed at the bottom of the canopy 21, through which the polluted air including pollutants like smoke, smells and grease vapor generated from the cooker 10 is drawn in. Also, a grease filter 24 that can collect pollutants is mounted at the inlet 23.
An exhaust path 33 is formed in the exhaust part 31, through which the polluted air having been introduced through the inlet 23 is exhausted to the outside. An exhaust fan 34 for forcibly taking in the air is installed under the exhaust path 33.
The polluted air including smoke, smells and grease vapor generated as burners 11a and 11b of the cooker heat food items is in a buoyancy jet form and increases in width as it ascends.
Thusly, only a portion of the polluted air is exhausted to the outside via the grease filter 24 installed at the inlet 23 and the exhaust path 33, and most of the polluted air is moved to the outside along a bottom surface of the canopy 21, contaminating the ambient air. Such a phenomenon greatly occurs when a food item is heated on the burner 11a disposed at the front side of the cooker 10.
To prevent the phenomenon, a method of increasing a rotation rate of the exhaust fan 34 and thusly increasing an intake force may be used. However, even though the rotation rate of the exhaust fan 34 is increased to increase the intake force, the intake performance is not improved in proportion to the increased rotation force. For this reason, only the intake force of the exhaust fan 34 used in such a method is not enough to guide the polluted air, which is moved to outside along the bottom surface of the canopy 21, to the inlet 23.
Consequently, the conventional exhaust hood cannot prevent the polluted air from moving out from the canopy 21, polluting an upper region (A) of the front side of the canopy 21 and spreading to a room to thus pollute a surrounding environment.
In order to solve the aforementioned problems, an exhaust hood illustrated in Figure 2 has been devised.
Figure 2 is a side sectional view that illustrates another example of a conventional exhaust hood. Referring to Figure 2, the conventional exhaust hood in accordance with another example includes a hood body 51 disposed above a cooker 10 at a predetermined distance therebetween, and a nozzle part 81 installed at a front region of the hood body 51 and downwardly discharging the air.
The hood body 51 includes a canopy 61 installed above the cooker 10, which has a plurality of burners 11a and 11b, at a predetermined distance therebetween, and an exhaust part 71 communicating with the canopy 61 and upwardly protruding from the canopy 61 to a predetermined height.
The nozzle part 81 is formed at a front region of a bottom surface of the canopy 61 and discharges the air downwardly. An air supply fan 83 for blowing the air to the nozzle part 81 is installed in the canopy 61.
A curve shape portion 85 having an arc shaped section which is convex downwardly is formed at a lower side of the front surface of the canopy 61, so that a portion of the air discharged through the nozzle part 81 can flow to a region of the inlet 63 by the so-called coanda effect. By the curved shape portion 85, the polluted air cannot be moved outside the canopy 61 but is guided to the inlet 63.
In the exhaust hood illustrated in Figure 2, the nozzle part 81 is formed at a spot inwardly spaced apart from the front end of the canopy 61 at a predetermined distance. Thusly, the polluted air having ascended inside the canopy 61 can be guided to the inlet 63 by the air discharged through the nozzle part 81. However, the method does not solve the problem that the polluted air ascending to the front end of the canopy 61 is moved out from the front end of the canopy 61 and pollutes an upper region (B).
Therefore, an object of the present invention is to provide an exhaust hood having an improved collecting efficiency of contaminated air.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided an exhaust hood comprising: a hood main body 110 provided with a canopy 111 having an inlet 117 and an exhaustion portion 123 connected to the canopy 111 and having an exhaustion passage 123 therein; and a nozzle unit 140 disposed at a front side of the hood main body 110, and provided with a curved shape portion 143, an air supply nozzle 141 disposed at an upper side of the curved shape portion 143 along a circumferential direction of the curved shape portion 143 for discharging air, and an air suction nozzle 141 disposed at a lower side of the curved shape portion 143 along the circumferential direction of the curved shape portion 143 for sucking air.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.
In the drawings:

Fig. 1 is a lateral sectional view illustrating an embodiment of an exhaust hood according to a related art;
Fig. 2 is a lateral sectional view illustrating another embodiment of the exhaust hood according to the related art;
Fig. 3 is a perspective view illustrating an exhaust hood in accordance with a first embodiment of the present invention;
Fig. 4 is a sectional view taken along the line IV-IV of Fig. 3;
Fig. 5 is an enlarged view of a part C of Fig. 4;
Fig. 6 is a lateral sectional view illustrating an exhaust hood in accordance with a second embodiment of the present invention;
Fig. 7 is a lateral sectional view illustrating an exhaust hood in accordance with a third embodiment of the present invention;
Fig. 8 is a lateral sectional view illustrating an exhaust hood in accordance with a fourth embodiment of the present invention;
Fig. 9 is a bottom view illustrating a canopy shown in Fig. 8; and
Fig. 10 is a perspective view illustrating an exhaust hood in accordance with a fifth embodiment of the present invention.

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.
Fig. 3 is a perspective view illustrating an exhaust hood in accordance with a first embodiment of the present invention, Fig. 4 is a sectional view taken along the line IV-IV of Fig. 3, and Fig. 5 is an enlarged view of a part C of Fig. 4
Referring to Figs. 3 and 4, an exhaust hood in accordance with a first embodiment of the present invention may include a hood main body 110 and a nozzle unit 140 disposed at a front side of the hood main body 110 for discharging and sucking air. Arrows indicate an air flow.
The hood main body 110 may include a canopy 111 disposed at an upper side of a cookware 10 (refer to Fig. 1) having a plurality of burners 11a and 11b with a particular distance therebetween, and an exhaustion portion 121 connected to the canopy 111 and protruding to an upper side of the canopy 111 by a particular height.
The canopy 111 is formed in a rectangular plate, and provided with an inlet 117 formed at a bottom surface thereof for sucking air, and a grease filter 118 mounted in the inlet 117 for collecting contaminated materials.
An air supply fan 135 is installed within the canopy 111 so as to blow air to the nozzle unit 140 and simultaneously to suck air through the nozzle unit 140, and an air supply motor 136 is also disposed within the canopy 111 so as to drive the air supply fan 135.
An air supply passage 137 is formed at a left side of the air supply fan 135 to thus allow air blown by the air supply fan 135 to move to the nozzle unit 140. In more detail, the air supply passage 137 is formed horizontally along an inner upper side of the canopy 111. An air suction passage 147 is formed at a lower side of the air supply motor 136 to thus allow flowing of the air sucked through the nozzle unit 140 by the air supply fan 135. In more detail, the air suction passage 147 is formed horizontally along an inner lower side of the canopy 111. At this time, a height (h) of the air suction passage 147 is preferably 0.05 to 0.3 times as great as the diameter (D) of the curved shape portion 143 so as to suck air into the air suction passage.
A through hole 148 is formed at an upper portion of the air supply passage 147 to communicate the air suction passage with the air supply passage 137. A filter 149 is mounted in the through hole 148 to thus remove impurities included in the air.
An exhaustion passage 123 is formed at an upper side of the exhaustion portion 121 to thus discharge air from which impurities are removed (filtered) by passing through the grease filter 118 to the exterior. An exhaustion fan 124 for forcibly sucking air and an exhaustion motor 125 for driving the exhaustion fan 124 are mounted below the exhaustion passage 123.
As illustrated in Figs. 4 and 5, the nozzle unit 140 may include the curved shape portion 143, an air supply nozzle 141 disposed at an upper side of the curved shape portion 143 along a circumferential direction of the curved shape portion 143 for discharging air, and an air suction nozzle 145 disposed at a lower side of the curved shape portion 143 along the circumferential direction of the curved shape portion 143 for sucking air.
The curved shape portion 143 has a cylindrical bar or a cylindrical pipe of which circular section has a diameter of 40 to 65 mm. The curved shape portion 143 is disposed at the front side of the canopy 111.
The air supply nozzle 141 is separately or integrally formed at an end of the air supply passage 137, and disposed at an upper side of the curved shape portion 143 along a radius direction of the curved shape portion 143 with a gap (d1) of about 2 to 4 mm therebetween. At this time, an internal angle θ1 formed between a virtual line L1 connecting an end of the air supply nozzle 141 and a center O of the curved shape portion 143 and a perpendicular line Lv passing through the center O of the curved shape portion 143 is preferably 0° to 30° in order to maximize a coanda effect. Also, a speed of air discharged (blown) through the air supply nozzle 141 is preferably 3 to 5 m/sec in order to maximize the coanda effect.
The air supply nozzle 145 is separately or integrally formed at an end of the air suction passage 147, and disposed at a lower side of the curved shape portion 143 along the radius direction of the curved shape portion 143 with a gap (d2) corresponding to about d1 to 3*d1 therebetween. At this time, an internal angle θ3 formed between a virtual line L3 connecting an end of the air suction nozzle 145 and the center O of the curved shape portion 143 and the perpendicular line Lv passing through the center O of the curved shape portion 143 is preferably 0° to 30° in order to maximize the coanda effect. As the air suction nozzle 145 for sucking air therein is formed at the lower side of the curved shape portion 143, the air is separated and thus the coanda effect can continuously be maintained even at the lower side of the curved shaped portion 143 at which the coanda effect is difficult to be maintained.
Hereinafter, an operation of the exhaust hood in accordance with the first embodiment will now be explained.
Referring to Figs. 4 and 5, when the exhaustion fan 124 rotates, air flows in through the grease filter 118 mounted in the inlet 117. At this time, contaminated materials included in the air is filtered by the grease filter 118. The air from which the contaminated materials are filtered is discharged to the exterior via the exhaustion passage 123.
When the air supply fan 135 rotates, on the other side, the air having passed through the inlet 117 is integrated with the air having passed through the through hole 148 to be discharged through the air supply nozzle 141 via the air supply passage 137.
While the air discharged through the air supply nozzle 141 by the coanda effect partially flows in an anticlockwise direction along an upper circumferential surface of the curved shape portion 143, the air forms a negative pressure region S1 having a minus (-) gauge pressure at an upper surface and a front surface of the curved shape portion 143. A progressive path of the contaminated air which is intended to flow away from the exhaust hood is curved by the negative pressure region S1 and thus the air is induced back into the inlet 117.
The air discharged from the air supply nozzle 141 is partially sucked into the air suction passage 147 through the air suction nozzle 145 to thus continuously maintain the coanda effect. Afterwards, the air sucked into the air suction passage 147 passes through the air supply passage 137 again via the through hole 148 to thereafter be discharged through the air supply nozzle 141. Such processes are repeatedly performed. Accordingly, the contaminated air which flows toward the front region of the exhaust hood without being sucked therein can effectively be collected by being induced to the inlet 117.
Hereinafter, an exhaust hood in accordance with a second embodiment will now be explained. The same reference numerals are provided to the same parts and components as those in the aforementioned and illustrated construction, and thus a detailed explanation therefor would be omitted.
Fig. 6 is a lateral sectional view illustrating an exhaust hood in accordance with a second embodiment of the present invention. With reference to Fig. 6, in the second embodiment unlike in the first embodiment, the air having passed through the grease filter 118 mounted in the inlet 117 is not supplied to the air supply nozzle 141. Rather, the air passing through the exhaustion passage 123 is partially supplied as air to be discharged through the air supply nozzle 141. For this, a reflux flow path 161 of which one end is connected to the exhaustion passage 123 and the other end is connected to the air supply passage 137 is formed within the exhaustion portion 121. Accordingly, the air supply fan 135 (refer to Fig. 4) and the air supply motor 136 (refer to Fig. 4) are not required any more, which results in a reduction of cost thereof.
According to the aforementioned construction, when the exhaustion fan 124 rotates, the air passing through the exhaustion passage 123 is partially discharged through the air supply nozzle 141 via the reflux flow path 161 and the air supply passage 137. The operation and effect of the discharged air have already been explained in the first embodiment and the explanation therefor will be omitted.
The air discharged through the air supply nozzle 141 is partially sucked into the air suction passage 147 via the air suction nozzle 145 to thus continuously maintain the coanda effect. Afterwards, the air sucked into the air suction passage 147 flows along the air supply passage 137 again via the through hole 148, thereafter being discharged through the air supply nozzle 141. such processes are repeatedly performed. Accordingly, the contaminated air flowing toward the front region of the exhaust hood without being sucked therein can effectively be collected by being induced to the inlet 117.
Hereinafter, an exhaust hood in accordance with a third embodiment of the present invention will now be explained. The same reference numerals are provided to the same parts and components as those in the aforementioned and illustrated construction, and thus a detailed explanation therefor would be omitted.
Fig. 7 is a lateral sectional view illustrating an exhaust hood in accordance with a third embodiment of the present invention. As illustrated in Fig. 7, in the third embodiment unlike in the first embodiment, air having passed through the grease filter 118 mounted in the inlet 117 is not supplied to the air supply nozzle 141. Rather, air having passed through a grease filter 155 mounted in an upper inlet 153 of the canopy 111 is supplied as air to be discharged through the air supply nozzle 141.
Also, in order to allow the partial air sucked into the air suction passage 147 not to be flowed into the air supply passage 137 again through the through hole 148 (refer to Fig. 4), the through hole 148 is removed. A filter 149 for filtering contaminated materials included in the air, on the other side, is mounted in the air suction passage 147 in a direction that air flows.
In the aforementioned construction, when the air supply fan 135 rotates, air of an upper side of the canopy 111 is sucked inside through the grease filter 155 mounted in the upper inlet 153. The sucked air is discharged through the air supply nozzle 141 via the air supply passage 137. Afterwards, the operation and effect of the discharged air have already been explained in the first embodiment and thus the explanation therefor would be omitted.
The air discharged through the air supply nozzle 141 is partially sucked into the air suction passage 147 through the air suction nozzle 145 to thus continuously maintain the coanda effect. Afterwards, the air sucked into the air suction nozzle 147 all flows into the exhaustion passage 123 through the filter 149 to be then discharged to the exterior.
Hereinafter, an exhaust hood in accordance with a fourth embodiment of the present invention will now be explained. The same reference numerals are provided to the same parts and components as those in the aforementioned and illustrated construction, and thus a detailed explanation therefor would be omitted.
Fig. 8 is a lateral sectional view illustrating an exhaust hood in accordance with a fourth embodiment of the present invention, and Fig. 9 is a bottom view illustrating a canopy of Fig. 8.
In the fourth embodiment unlike in the third embodiment, a plurality of slits 148 are disposed at a bottom surface of the air suction passage 147 with a constant interval therebetween. Accordingly, a suction force of the exhaustion fan 124 can also be transferred to the slits 148, and thus the contaminated air of the lower side of the air suction passage 147 can be induced to the exhaustion passage 123 through the slits 148 more effectively.
In the aforementioned construction, when the air supply fan 135 rotates, air of an upper side of the canopy 111 is sucked inside through the grease filter 155 mounted in the upper inlet 153. The sucked air is discharged through the air supply nozzle 141 via the air supply passage 137. Afterwards, the operation and effect of the discharged air have already been explained in the first embodiment and thus the explanation therefor would be omitted.
The air discharged through the air supply nozzle 141 is partially sucked into the air suction passage 147 through the air suction nozzle 145 to thus continuously maintain the coanda effect. Afterwards, the air sucked into the air suction nozzle 147 is all induced to the exhaustion passage 123 to be then discharged to the exterior. Also, the contaminated air in the lower side of the air suction passage 147 is partially induced to the exhaustion passage 123 through the slits 148 and the filter 149 to be then discharged to the exterior.
Hereinafter, an exhaust hood in accordance with a fifth embodiment of the present invention will now be explained. The same reference numerals are provided to the same parts and components as those in the aforementioned and illustrated construction, and thus a detailed explanation therefor would be omitted.
Fig. 10 is a lateral sectional view illustrating an exhaust hood in accordance with a fifth embodiment of the present invention.
As illustrated in Fig. 10, an exhaust hood in accordance with a fifth embodiment may include the nozzle unit 140 for preventing the contaminated air from flowing toward the front region of the canopy 111 without being sucked therein, and a plurality of supplementary nozzle units 170 for preventing the contaminated air from flowing toward both lateral regions of the canopy 111 without being sucked therein.
The construction and the operation of the nozzle unit 140 has already been explained in the first embodiment and thus the explanation therefor will be omitted.
The supplementary nozzle unit 170 may include a lateral curved shape portion 173, a lateral air supply nozzle 171 for discharging air at an upper side of the lateral curved shape portion 173 along a circumferential direction thereof, and a lateral air suction nozzle 175 for sucking air at a lower side of the lateral curvved shape portion 173 along the circumferential direction thereof.
The construction and operation of the lateral curved shape portion 173, the lateral air supply nozzle 171 and the lateral air suction nozzle 175 of the supplementary nozzle unit 170 are the same as those of the curved shape portion 143, the air supply nozzle 141 and the air suction nozzle 145 of the nozzle unit 140, and thus the explanation therefor will be omitted. Such supplementary nozzle unit 170 is provided such that the contaminated air flowing toward the lateral region of the canopy 111 without being sucked therein can be collected to thus increase a collecting efficiency of the exhaust hood.
The exhaust hood according to the aforementioned embodiments of the present invention may have the following advantages.
First, the nozzle unit having the curved shape portion, the air supply nozzle and the air suction nozzle is provided such that the contaminated air flowing toward the front region of the exhaust hood without being sucked therein can be effectively induced to the inlet to thus be collected, thereby creating more comfortable cooking circumstances and experimental environment. In particular, as the air suction nozzle for sucking air is formed at the bottom side of the curved shape portion, the air is separated and thus the coanda effect can continuously be maintained even at the lower side of the curved shaped portion at which the coanda effect is difficult to be maintained. Accordingly, the collecting efficiency of the contaminated air of the exhaust hood can be increased.
Second, when the supplementary nozzle unit is additionally provided, the contaminated air flowing toward the lateral region of the exhaust hood without being sucked therein can effectively be collected, to thus enable creating of more comfortable cooking circumstances and experimental environment.
As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalence of such metes and bounds are therefore intended to be embraced by the appended claims.

Claims

An exhaust hood comprising:
a hood main body (110) provided with a canopy (111) having an inlet (117) and an exhaustion portion (123) connected to the canopy (111) and having an exhaustion passage (123) therein; and

a nozzle unit (140) disposed at a front side of the hood main body (110), and provided with a curved shape portion (143), an air supply nozzle (141) disposed at an upper side of the curved shape portion (143) along a circumferential direction of the curved shape portion (143) for discharging air, and an air suction nozzle (141) disposed at a lower side of the curved shape portion (143) along the circumferential direction of the curved shape portion (143) for sucking air.
The exhaust hood of claim 1, further comprising;
an air supply passage (137) of which one end is connected to the inlet (117) and the other end is connected to the air supply nozzle (114); and

an air suction passage (147) for inducing the air sucked through the air suction nozzle (145) to the air supply passage (137) again.
The exhaust hood of claim 2, wherein a through hole (148) is formed at an upper portion of the air suction passage (147) to communicate the air suction passage (147) with the air supply passage (147), and a filter (149) is mounted in the through hole (148).
The exhaust hood of claim 1, 2 or 3, further comprising:
a reflux flow path (161) of which one end is connected to the exhaustion passage (123) and the other end is connected to the air supply passage (137); and

an air suction passage (147) for inducing the air sucked through the air suction nozzle (145) to the air supply passage (137) again.
The exhaust hood of claim 4, wherein a through hole (148) is formed at an upper portion of the air suction passage (147) to be communicated with the air supply passage (137), and a filter (149) is mounted in the through hole (148).
The exhaust hood of any of claims 1 to 5, further comprising:
an upper inlet (153) formed at an upper surface of the canopy (111);

an air supply passage (137) of which one end is connected to the upper inlet (153) and the other end is connected to the air supply nozzle (141); and

an air suction passage (147) for inducing the air sucked through the air suction nozzle (145) to the exhaustion passage (123).
The exhaust hood of claim 6, wherein a filter (149) is mounted in the air suction passage (147).
The exhaust hood of claim 6, wherein a plurality of slits (148) are formed at a bottom surface of the air suction passage (147).
The exhaust hood of any of claims 2 to 8, wherein a height(h) of the air suction passage (147) is 0.05 to 0.3 mm as great as a diameter(D) of the curved shape portion (143).
The exhaust hood of any of claims 1 to 9, wherein the curved shape portion (143) has a cylindrical bar or a cylindrical pipe of which circular section has a diameter(D) of 40 to 65 mm.
The exhaust hood of any of claims 1 to 10, wherein the air supply nozzle (141) is disposed at the upper side of the curved shape portion (143) along a radius direction of the curved shape portion (143) in order to have a gap (d1) corresponding to 2 to 4 mm with the curved shape portion (143).
The exhaust hood of claim 11, wherein an internal angle(θ 1) formed between a virtual line(L1) connecting an end of the air supply nozzle (141) and a center(O) of the curved shape portion (143) and a perpendicular line(Lv) passing through the center of the curved shape portion (143) is 0° to 30°.
The exhaust hood of claim 11, wherein a speed of air discharged through the air supply nozzle (141) is 3 to 5 m/sec.
The exhaust hood of claim 11, wherein the air suction nozzle (145) is disposed at the lower side of the curved shape portion (143) along the radius direction of the curved shape portion (143) in order to have a gap(d2) corresponding to the gap (d1) to 3*d1 with the curved shape portion (143).
The exhaust hood of claim 14, wherein an internal angle(θ 3) formed between a virtual line(L2) connecting an end of the air suction nozzle (145) and the center(O) of the curved shape portion (143) and the perpendicular line (Lv) passing through the center(O) of the curved shape portion (143) is 0° to 30°.
An exhaust hood comprising:
a hood main body (110) provided with a canopy (111) having an inlet (117) and an exhaustion portion (121) connected to the canopy (111) and having an exhaustion passage (123) therein; and

a nozzle unit (140) disposed at a front side of the hood main body (110), and provided with a curved shape portion (143), an air supply nozzle (141) disposed at an upper side of the curved shape portion (143) along a circumferential direction of the curved shape portion (143) for discharging air, and an air suction nozzle (145) disposed at a lower side of the curved shape portion (143) along the circumferential direction of the curved shape portion (143) for sucking air; and

a plurality of supplementary nozzle units (170) installed at both lateral sides of the hood main body (110), and provided with a lateral curved shape portion (173), a lateral air supply nozzle (171) for discharging air at an upper side of the lateral curved shape portion (173) along a circumferential direction of the lateral curved shape portion (173), and a lateral air suction nozzle (175) for sucking air at a lower side of the lateral curved shape portion (173) along the circumferential direction of the lateral curved shape portion (173).