Stoves and furnaces – Stove hoods
Reexamination Certificate
2002-06-03
2004-06-01
Basichas, Alfred (Department: 3749)
Stoves and furnaces
Stove hoods
C126S29900R, C055SDIG003
Reexamination Certificate
active
06742515
ABSTRACT:
This invention relates to an air extraction apparatus of the kind defined in the preamble of claim
1
.
These days, there often exists, in food service, and especially in food service systems and communal catering in cafeterias and the like, i.e. in situations in which the guests serve themselves, the requirement that cooking, grilling or baking be done right before the guest's eyes. In this so-called up-front cooking there exists the problem that the fumes which are created thereby have to be removed. Because stationary fume extraction hoods are often not available or suitable and transportable fume extraction hoods are often not available or applicable, there has already been developed a mobile cooking station (cf. the SMOKE-STOPP catalog of the Bohner Company for the year 2000) and a stationary kitchen module (cf. the article “Odorless Before The Eyes Of The Guests” in the magazine Cooking Practice and Community Food Supply, October 1999, page 52), which are provided with an air extraction apparatus of the kind defined in the preamble of claim
1
. In the known air extraction apparatus which sometimes involve a grill, the two air openings on both sides of the work station serve for rim extraction. Because extraction is performed at both lateral rims of the work station, the extraction effect above the middle of the work station is naturally relatively slight. Therefore, a large area above the work surface is not efficiently encompassed by the air current drawn in at the rims. A particular disadvantage of rim extraction is that uncleansed room air is drawn partly across the work station. In addition, for integrated odor elimination, the known air extraction apparatus has, in a substructure below the work station, several pre-filters, several fabric filters and several activated carbon filters, between which there is located an exhausting device which provides bidirectional suction. The whole lower surface of the substructure is occupied by a grease-collecting pan. This filter arrangement requires work and is expensive, because the activated carbon filters have to be changed frequently and constitute an environmental burden.
Indeed, an odor extraction apparatus known from DE 2 402 615 A1 can make do with a simpler filter arrangement for grease separation and odor removal, but a suction funnel with a grease retention filter is positioned above the work station, and that requires an upwardly directed air flow in order to produce an air curtain for screening the work station.
From U.S. Pat. No. 3,260,189 there is known a ventilating system in which there is provided, above the work station, an extraction apparatus inclined diagonally with respect to the work station and provided with several grease filters. Air which exits on one side of the work station from a blower slot is thus guided over the work station diagonally upwardly to the extraction device. Furthermore, in this known ventilating system, no special precautions for odor elimination are taken.
The object of the invention is to so improve the extraction in an air extraction apparatus of the kind initially described that the extraction process effectively encompasses the whole work area and that food on the work station does not come into contact with uncleansed ambient air.
This object is achieved according to the invention by an air extraction apparatus having the characteristics stated in claim
1
.
In the air extraction apparatus according to the invention, there is formed an air circulation loop which extends across the whole work station, above which it creates an air curtain. The air curtain is formed by air which flows out of an air opening on one side of the work station and flows into an air opening on the opposite side of the work station. Thus, the air curtain produced by the air extraction apparatus according to the invention covers the whole area above the work station. The air which forms the air curtain is ambient air, i.e. air which flows over the work station only after it has been drawn through the filter arrangement by means of the suction blower, and is therefore cleansed air. The compact housing of the blower and the filter arrangement in a separate space, located in the air circulation loop and connected to the air openings on both sides of the work station, makes it possible for the air extraction apparatus according to the invention to separate, within limited space inside the air loop, grease from the air and simultaneously free it from odors. In the air extraction apparatus according to the invention, the air to be cleansed is drawn in through the grease separating filter and pushed out through the odor filter. Since a grease separating filter and an odor filter have different pressure drops, the inventive arrangement of the two filters, respectively upstream and downstream of the blower, makes it possible to adjust the air velocity optimally for the respective filters.
Since, in the air extraction apparatus according to the invention, the air circulation loop provides an air outlet for a portion of the air from this air circulation loop, a portion of the air in the air circulation loop can be continuously replaced by ambient air which is then also led first through the filter arrangement before it contributes to the formation of the air curtain above the work station.
Because, in an air extraction apparatus according to the invention, the opening of the air outlet can also be adjusted in size, the fraction of fresh ambient air in the air circulation loop can be adjusted as needed. Further, because in the air extraction apparatus according to the invention, the air outlet is located downstream from the blower, the air has passed through the filter arrangement and is therefore already cleansed before it escapes into the ambient. Further, because in the air extraction apparatus according to the invention, the blower is located between at least two filters of the filter arrangement, the blower is protected from becoming dirty. Further, because the filter upstream from the blower is a grease separating filter and the filter downstream from the blower is an odor filter, the blower is especially little adversely affected by air loaded with grease and the ambient air which is led back to the work station is not only grease- but also odor-free.
Indeed, from DE 473883C it is in fact already known to provide, in a system for protecting work spaces from the vapors coming from open vessels and other air uncleanliness, by means of an air curtain, a blower which simultaneously serves to create the air flow and to remove the vapors, whose intake duct segment opens into a funnel located above the edge of a container, whereas its pressure duct segment has a nozzle at the opposite container edge directed toward the funnel from which an outlet duct branches off, but in this known apparatus there are no means at all for grease separation or odor elimination. The air outlet leads simply into open space.
Preferred embodiments of the air extraction apparatus according to the invention are the subject of the dependent claims.
If, in an embodiment of the air extraction apparatus according to the invention, the blower is a centrifugal blower, both structural and flow-technology advantages are achieved in the construction of the air extraction apparatus.
If, in a further embodiment of the air extraction apparatus according to the invention, the grease separating filter is a cyclone filter, as manufactured, for example by the Renchler & Reven Company, 99.5% of the grease entrained in the exhausted air can be separated. Further, such a filter is very maintenance friendly, because it can be simply washed out in a dishwasher and then reinstalled.
If, in a further embodiment of the air extraction apparatus according to the invention, a grease collecting pan is installed below the grease separating filter, the grease separated by the grease separating filter can be collected in simple manner.
If, in a further embodiment of the air extraction apparatus, the odor filter is a zeolite filter, then this odor filter can be ea
Basichas Alfred
Volpe and Koenig P.C.
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