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In a kitchen, a ventilating hood is disposed over a cooking unit and has an
exhaust duct and a return duct, both extending through the roof to the
exterior. An exhaust blower is connected to the exhaust duct and an intake
blower to the intake duct, outside the building. A by-pass duct extends
from the exhaust blower outlet to the intake blower inlet and a damper in
the duct is responsive to temperature sensed in the intake duct to by-pass
a portion of the air handled by the exhaust blower into the intake blower
for return through the hood to the area above the cooking unit. Filtering
means are provided in the hood.
Primary Examiner: Perlin; Meyer
Assistant Examiner: Capossela; Ronald C.
Attorney, Agent or Firm:Woodard, Weikart, Emhardt & Naughton
The invention claimed is:
1. In a ventilating system, the combination comprising:
a working surface;
a hood covering at least a portion of said working surface and having a front;
exhaust means having an outlet coupled to said hood and including an exhaust duct and intake blower means removing air from under said hood;
intake means including a return duct and intake blower means introducing air at the front of said hood;
and by-pass means coupled between said exhaust means and said intake means to take a portion of the air from said exhaust means, prior to discharge of that portion to atmosphere, and return it and reintroduce it at the front of said hood.
2. The combination of claim 1 and further comprising:
temperature sensor means in said return duct;
a damper associated with said by-pass means;
and damper operating means coupled to said sensor means and to said damper and responsive to higher temperatures sensed in said return duct to by-pass a smaller portion of air from said exhaust means.
3. The combination of claim 2 wherein:
said temperature sensor means is located to sense intake air temperature in the intake means between the bypass means and a point where intake air is introduced at the front of said hood.
4. The combination of claim 1 wherein said exhaust blower means establishes a flow of air in a path from said hood to said exhaust blower means, the combination further comprising:
first filter means positioned in the path of air from said hood to said exhaust blower means.
5. The combination of claim 4 wherein said intake blower means establishes a flow of air in a path from said intake blower means to the front of said hood, the combination comprising:
second filter means in the path of air from said intake blower means positioned to the front of said hood.
6. The combination of claim 1 wherein:
said hood and working surface are inside a building, and said work surface is a heat generating cooking surface;
and said blower means are outside the building.
7. The combination of claim 6 wherein:
said blower means include an exhaust blower removing air from under said hood, and intake blower drawing fresh air in from outside the building.
8. A ventilating system comprising:
a vent hood;
exhaust means having an inlet coupled to said hood and including an exhaust duct and exhaust blower means for removing air from under said hood, and of sufficient length between said inlet and a point of discharge to atmosphere to discharge
removed air to the exterior of a building in which said hood may be disposed;
intake means including a return duct and intake blower means introducing air adjacent said hood, said return duct being of sufficient length to enable intake of fresh air from outside a building in which said hood may be disposed;
and by-pass means coupled between said exhaust means and said intake means to take a portion of air from said exhaust means upstream of said point of discharge and return it and reintroduce it adjacent the perimeter of said hood.
9. The combination of claim 8 and further comprising:
temperature sensor means in said return duct;
a damper associated with said by-pass means;
and damper operating means coupled to said sensor means and to said damper and responsive to higher temperatures sensed in said return duct to by-pass a smaller portion of air from said exhaust means to said intake means.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to ventilating systems for buildings, and more particularly to means for removing heat and fumes above a working surface wherein heat and fumes are generated, and returning a mixture of fresh air and a portion of
the removed air through the duct and back to the area over the working surface.
2. Description of the Prior Art
Much has been done in ventilating systems. The problem with which my invention is particularly concerned is that of removing fumes and heat from a working surface in a building, and more particularly a cooking unit in a restaurant kitchen, for
example. Three United States patents of which I am aware and which deal with this subject are as follows:
3,457,850 Sweet et al. July 29, 1969 3,496,704 Bandlow Feb. 24, 1970 3,530,784 Courchesne Sept. 29, 1970
One significant concern of those who pay fuel bills for buildings, is the cost of heating fresh air introduced into the building to make up for air exhausted by various means. The volume of air involved can be particularly large in restaurants
having large hoods with high exhaust capacity for removal of fumes and contaminants from the kitchen. My invention is directed toward minimizing the causes for this concern.
SUMMARY OF THE INVENTION
Described briefly, in a typical embodiment of the present invention, a hood is employed over a working surface where heat and fumes to be exhausted are generated. Exhaust means are connected to the hood for removing air from under the hood and
exhausting it to the atmosphere outside. Intake means are associated with the hood for drawing in fresh air from the outside and introducing it adjacent a portion of the perimeter of the hood. By-pass means are coupled between the exhaust and intake
means to by-pass a portion of the air removed by the exhaust means and return it to the intake means, avoiding the necessity of heating as much fresh air as is removed from the hood. Temperature sensor means are provided in the intake means to control
the damper in the by-pass means and by-pass smaller amounts of air from the exhaust means to the intake means as the intake temperature rises.
BRIEF DESCRIPTION OF THE DRAWING
The single FIGURE of drawing is a sectional view through a kitchen in a building and illustrating a typical embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawing in detail, there is shown a cooking unit 11 in a room 12 of a building, disposed between the floor 13 and roof 14. The cooking unit has a cooking surface 16 thereon which may be heated by electricity, gas, or other
means. A hood 17 is disposed over the cooking unit and has an exhaust duct 18 and an intake or return duct 19 connected therethrough, both ducts extending up through the roof.
An exhaust blower 21 is connected to the exhaust duct 18 and has a discharge outlet to atmosphere at 22. An intake blower 23 has a fresh air inlet 24 and an outlet at 26 connected to the return duct 19.
The assembly as thus far described is capable of removing air from under the hood, through the filter 27 resting over the opening 28 in the partition 29 in the hood, and discharging it to atmosphere at 22. The return or intake blower is capable
of drawing fresh air in from the atmosphere and delivering it through the duct 19 to the chamber 31 over partition 32 in the hood. From chamber 31 it passes through filter 33 and is reintroduced through a slot 34 at the front of the hood. This slot can
be extended around the sides of the hood, if desired, and in certain instances it may be found desirable to extend a slot completely around the entire perimeter of the hood. In any event it is preferable to provide a slot at least along the front
portion of the perimeter of the hood as shown at 34 in the drawing.
According to the main feature of the present invention, a by-pass is provided between the exhaust and intake. In the drawing it is accomplished by the employment of a by-pass duct 36 between the discharge end of the exhaust blower and the intake
of the intake blower. A pivotable damper 37 is provided at the entrance of the by-pass duct and is movable outwardly in the direction of arrow 39 to deflect a portion of the air being discharged from the exhaust blower. The deflected or diverted
portion of the air passes through the by-pass duct in the direction of arrow 41 to the intake of the intake blower where it is mixed with fresh air also entering the intake at opening 24 and reintroduced through the duct 19 and the slot 34 to the area 43
over the cooking surface and under the hood.
Control of the damper 37 is effected by a link or other suitable means 44 connected between a reversible damper control motor 46 and the damper 37. The damper control motor is operated by a temperature sensor 47 in the return duct 19. As the
temperature of the air passing through the return duct 19 increases, the damper control motor is driven in one direction to move the damper 37 in a closing direction opposite arrow 39. Therefore, a larger percentage of fresh air is taken in. As the
temperature in the return duct 19 decreases, the damper control motor 46 is driven in the opposite direction to move the damper in the direction of arrow 39 and increase the amount of air by-passed from the exhaust blower through duct 36 to the intake
blower 23. This tends to raise the temperature in the return duct 19. The arrow 48 in the line between the temperature sensor 47 and the damper control motor 46 represents an adjustment useful to establish the desired temperature range in the return
duct 19, for appropriate damper control motor response thereto. Sensors, and controllers useful for this purpose are well known and commercially available.
From the foregoing description, it can be seen that by diverting part of the heated air taken from the hood and reintroducing it, the need for fresh air through inlet 24 is reduced. Therefore the fuel requirement to heat such fresh air is
reduced. This is particularly beneficial where the building employs a type of heat which is comparatively expensive. I have found that the by-passing of the air is not detrimental to cleanliness of operation and the only requirement is that the filter
27 be kept reasonably clean. Accumulation of foreign matter on filter 33 occurs at a surprisingly slow rate. It should be understood that a variety of types of filters can be employed, including the electrostatic type as well as others. Also the
specific arrangement of ducting can be sufficient from that illustrated, the important aspect being the by-passing of a portion of the exhaust air into the intake system for introduction into the building.
While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has
been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.