HK1228987B - Oven exhaust hood methods, devices, and systems - Google Patents

Description

Oven exhaust hood method, device and system

This application is a divisional application of an application filed on January 13, 2011, with application number 201180006171.X and invention name “Oven exhaust hood method, device and system”.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is an international application claiming priority to and the benefit of U.S. Provisional Application No. 61/294,511, filed January 13, 2010, the entire contents of which are incorporated herein by reference.

Background Art

Exhaust systems for ovens are known. Such systems include an exhaust inlet, such as an exhaust hood, which may include a cleanable cartridge filter. A basic exhaust hood uses an exhaust fan to create a negative pressure zone to draw air carrying emissions directly away from the source of the pollution. In a kitchen hood, the exhaust fan typically draws pollutants (which include room air) through a filter and out of the kitchen through a duct system. An exhaust fan, such as a variable speed fan, contained in the exhaust hood is used to remove emissions from the room and is typically located on the inlet side of a filter placed between the source of the pollution and the exhaust fan. Depending on the rate at which emissions are generated and the rate at which emissions accumulate near the source of the pollution, the exhaust fan speed can be manually set to minimize the flow rate to the lowest point that can achieve capture and containment.

The hood uses notches as a buffer to match the fluctuating smoke flow with the constant rate of the exhaust system. The exhaust rate required to achieve complete capture and containment is constrained by the highest instantaneous load pulse that occurs. This requires the exhaust rate to be higher than the average amount of exhaust (which inevitably mixes with the entrained air). Ideally, the oversupply of exhaust should be minimized to avoid wasting energy. The hood works by temporarily capturing sudden emissions that rise into the hood due to thermal convection, and then giving the average exhaust rate time to capture them.

One issue with buffer mode is that the ambient environment can displace flue gases, adding an excessive burden of ambient air to the exhaust stream. This results in flue gases being injected into the already occupied space around the hood. These transients are a persistent problem in hood design and installation. Recesses in the hood provide a buffer zone above the pollution source where buoyancy-driven momentum transients can dissipate before pollutants are drawn in. By managing transients in this way, the effective capture area at the exhaust source can be increased.

U.S. Patent No. 4,066,064 shows a back frame hood with an exhaust air inlet located at a position different from the back end thereof. A short inclined portion rises from the back end of the hood recess and extends at a small angle toward the air inlet.

U.S. Patent No. 3,941,039 shows a back-frame hood having side skirts and sloping walls extending from the rear of the hood to an air inlet located near the middle of the hood. The front of the hood has a horizontal portion (a baffle) extending between approximately 15 percent and approximately 20 percent of the hood's front-to-back dimension. This portion is claimed to direct air in the space above the baffle toward the exhaust inlet and to direct air drawn in from the surrounding space horizontally, thereby diverting rising smoke toward the exhaust inlet.

Summary of the Invention

According to an embodiment, the disclosed subject matter includes a method for containing emissions from one or more ovens, comprising: placing one or more ovens in a cabinet and surrounding the one or more ovens with a cabinet suction area, the cabinet suction area being formed by a continuous space in the cabinet and having an oven front air intake opening facing the cabinet front that is consistent with the front face of the one or more ovens; providing a hood portion of a forward overhang portion and creating a peripheral suction area along the perimeter of the forward overhang hood portion; the forward overhang hood portion having a depth of at least 12 inches and the suction area having a front face and a side face; the forward overhang hood portion being continuous and connected to the cabinet, and the peripheral suction area and the cabinet suction area being created by a negative pressure in a continuous space communicating between the hood portion and the cabinet; the continuous space being in communication with an exhaust connection connected to an exhaust fan to create the negative pressure; the oven front air intake defining at least one side air intake and a top air intake proximately adjacent each of the one or more ovens on a non-hinged side of the one or more ovens; collecting fumes exhausted upon opening a door of the one or more ovens through the oven front air intake and the peripheral suction area and exhausting them through the exhaust connection.

In the method, the collection may include controlling the exhaust flow rate in response to one or more states of one or more ovens by a fan controller or damper. The cabinet may have a substantially constant cross-section and the hood portion may be larger than the cabinet on three sides, forming two opposing side overhangs and a front overhang. The front overhang may be deeper than the side overhang. The hood portion may have at least one downward curtain nozzle. The smoke may be guided by a baffle along the lower surface of the hood portion toward the vertical air inlet collecting door and into the continuous space. The baffle may be lower toward the front side of the hood portion and higher toward the rear side of the hood portion. The oven front air inlet may have an adjustable width. The oven front air inlet may each be formed in an L-shape and include a horizontal portion and a vertical portion. The one or more ovens may be two ovens.

According to an embodiment, the disclosed subject matter includes an exhaust device having a cabinet plenum defined by a cabinet, a front air intake door opening on the front face of the cabinet, the cabinet having support brackets, the support brackets opening on the front face of the cabinet with corresponding support bracket openings, a hood portion at the top of the cabinet having an exhaust plenum communicating with the cabinet plenum, the cabinet and the exhaust plenum communicating with an exhaust outlet having a filter, the hood portion having a front overhang portion that is at least 20 percent of the cabinet depth and is suspended from the front face of the cabinet, the front overhang portion forming a recess covering the cabinet front and in fluid communication with the hood plenum, and a front front air intake door including a horizontal door proximately adjacent each support bracket opening and a first vertical door. The front overhang portion can have a depth of at least 12 inches. The recess can have an inclined baffle at its closed end to direct smoke toward the top of the cabinet and into the air intake opening of the hood plenum. The front front air intake door can form an L-shaped opening. The apparatus may include a second vertical air collecting gate adjacent to each support bracket opening and opposite the first vertical air collecting gate. The first vertical air collecting gate may be larger than the second vertical air collecting gate. The support bracket may be two support brackets, including a lower support bracket and an upper support bracket, with the horizontal air collecting gate adjacent to the lower support bracket having a larger area than the horizontal air collecting gate adjacent to the upper support bracket. The vertical and horizontal air collecting gates may have adjustable widths.

According to an embodiment, the disclosed subject matter includes an exhaust device, an exhaust hood portion having a recess and an inner surface of the recess, a baffle supported below a closed end of the recess to form a gap between an edge of the baffle and the downwardly inclined inner surface of the recess, an exhaust air inlet leading to an air collecting space between the closed end and the baffle, the baffle being movable to enable access to the air inlet, and the gap surrounding at least three sides of the hood portion.

The gap may surround all four sides of the hood portion to form a complete perimeter air intake. According to an embodiment, the disclosed subject matter includes a method for controlling exhaust air flow, comprising receiving at least one signal related to an oven state at a digital controller, controlling the exhaust air flow to increase in response to the at least one signal at a first time, and controlling the exhaust air flow to decrease in response to at least another signal indicating that the oven door is closed at a later time. The at least one signal may include an image signal. The at least one signal may include a digital signal from the oven. The at least one signal may include a signal from a proximity sensor. The at least one other signal may include an image signal. The at least one other signal may include a digital signal from the oven. The at least one other signal may include a signal from a proximity sensor. Control may include coordinated adjustment of fan speed and damper speed. Control may include making a probability estimate of a door open or closed event.

BRIEF DESCRIPTION OF THE DRAWINGS

1 is a front view of an exhaust assembly for exhausting exhaust from a pair of ovens, such as convection ovens or combination (steam/convection combination) ovens, according to an embodiment of the disclosed subject matter.

2 is a partial oblique perspective view of an exhaust assembly for exhausting emissions from a pair of ovens, such as convection ovens or combination (steam/convection combination) ovens, according to an embodiment of the disclosed subject matter.

3 is an oblique perspective view of the exhaust device shown in FIG. 2 , illustrating flow characteristics according to an embodiment of the disclosed subject matter.

4 is a partial side perspective view of an exhaust assembly for exhausting exhaust from a pair of ovens, such as convection ovens or combination (steam/convection combination) ovens, according to an embodiment of the disclosed subject matter.

5 is an elevational view of an exhaust assembly for exhausting emissions from a pair of ovens, such as convection ovens or combination (steam/convection combination) ovens, illustrating flow characteristics in accordance with an embodiment of the disclosed subject matter.

FIG. 6 illustrates a canopy cowl with perimeter air intakes, according to an embodiment of the disclosed subject matter.

FIG7 shows a control system that can be used with any embodiment of the disclosed subject matter.

DETAILED DESCRIPTION

An exhaust hood used over multiple ovens can be used to capture cooking emissions and fumes from the ovens, particularly when the ovens are opened for access. The vertically stacked configuration shown in Figures 1-5 shows a cabinet with a rack of ovens (one, two, or more) having vertical and horizontal air inlets surrounding each oven on all sides. A top-located air inlet exhausts a hood recess overhanging the row of ovens. As shown, the hood section has vertical and horizontal nozzles. Fumes are drawn into an exhaust system and blown away through a treatment system or disposed of in any appropriate manner. The system can also capture heat and/or steam that may be generated by such an oven. Because most fumes are exhausted from the side of the oven away from the oven hinge when the oven door is open, the air inlet can be larger on the side of the oven away from the oven hinge. Similarly, the hood can have a wider overhang on the side of the oven away from the hinge.

The overall exhaust air flow driver behind the exhaust air flow can be controlled to operate based on how the oven is being operated at any given point in time. For a single oven, the air flow can depend on the single oven operating state, which is either off, idle, or cooking, where the door is considered open or closed. While there may be an idle state where the operator may leave the door open, this will generally not result in exhaust gases or smoke being emitted from the oven, but only heat and/or moisture since no cooking is taking place.

For single-oven exhaust airflow levels, no airflow is required if the oven is shut down. During idle (e.g., standby) operation, the oven consumes the energy required to maintain the oven thermostat setpoint—in this case, the lowest exhaust airflow is used to capture heat and/or moisture from the oven. During cooking with the oven door closed, energy input to the device increases to heat the food and maintain the oven temperature. For convection ovens, additional energy is required to drive the air circulation fan. In this cooking condition, in addition to heat and moisture, the oven may also expel grease and smoke during the cooking process. A higher exhaust airflow can be provided for this condition than when the oven is idle. The highest emission is expelled during cooking or when the oven door is opened at the end of a cooking cycle—in this case, heat, smoke, moisture, and grease emissions are not only expelled from the oven exhaust vents but are also physically directed out of the oven by the door opening. This condition may require several times the exhaust airflow to capture the heat and/or moisture compared to cooking with the oven door closed. Thus, for a single oven, there may be five possible control states for the oven: off, idle with door closed, idle with door open, cooking with door closed, and cooking with door open, although the idle state with door open is not often encountered except when food is placed in the oven. In response to a proximity sensor detecting that someone is about to open the oven door, the exhaust air can be gradually increased.

When two ovens are stacked on top of each other, there are potentially ten possible control states, all of which may have different exhaust airflows to properly capture emissions, heat, smoke, and moisture from the ovens. However, for a double-stacked oven, for five of the oven control states, the bottom oven will have significantly higher exhaust airflow than the top oven. This difference in required airflow between the bottom and top ovens is primarily a function of the increased distance between the ovens and the absorption device.

Regarding specific control mechanisms that can be used to monitor oven status, the most straightforward approach is to obtain a signal directly from the oven indicating its operating status. The off operating state must be inferred from the absence of a signal from the oven. Other possible control feedback devices may include a current switch mounted on the convection oven circulation fan that detects when the fan is activated—a device that can distinguish between cooking and idle depending on the oven's control mechanism. For combination ovens (or other ovens that introduce moisture into the oven cavity), a humidity sensor located in the oven vent or hood exhaust plenum can detect when the oven is operating. For ovens (convection ovens), the thermostat is typically able to determine when the oven is in the cooking state or idle state.

Depending on the cooking process, if sufficient smoke is generated during cooking, an optical smoke sensor may be utilized.

1 to 5 , an exhaust device 100 has a hood portion 102 that generates horizontal nozzles (illustrated schematically as circles with an X at 104 entering the page) and vertical nozzles 106 along its perimeter 108. In alternative embodiments, the hood portion 102 may also have only vertical nozzles or only horizontal nozzles.

Cabinet 110 surrounds oven 112, forming upper air inlets 114 and 120 for shelf 1 and shelf 2, as well as first and second side air inlets 116 and 118 for the first and second shelves, respectively. In an alternative embodiment, shelf 1 upper air inlet 114 is omitted. In the illustrated embodiment, shelf 2 upper air inlet 120 is larger than shelf 2 upper air inlet 114. In another alternative embodiment, upper air inlets 114 and 120 are the same size. Hood air inlet 122 is located below baffle 128.

Oven 112 is, for example, a convection oven, a microwave oven, a combination thereof, a steam-convection combination oven, or a conventional oven. In embodiments, the oven can be replaced by another exhaust source, such as a grill, a laboratory cabinet, or another device for exhausting fumes. In certain embodiments, the device exhausts fumes in pulses, or emits fumes more intensely on one side than on the other, as in a side-opening "door" oven. Oven 112 is shown as hinged on the right side and opens from the left, but can be opened from either side. In embodiments, the suction force of all air inlets produces a face velocity of 10-60 cfm per linear ft (ft) on the surface shown with diagonal shading.

As can be seen most clearly in Figure 3, as indicated by curved arrows 210, air is drawn in through the intake plenum 202 and out through the exhaust vents 204. The exhaust vents 204 can be connected to an exhaust system (not shown). The hood portion 102 has a double wall around the front periphery (with a plenum 442 between the double walls as shown in Figure 5) to define a plenum 442 for distributing the airflow, forming vertical and horizontal nozzles. As can be clearly seen in Figure 3, air is drawn through the cabinet 110 through the side and upper air inlets 114, 116, 118 and 120, as shown by arrows 265. The smoke captured by the hood portion 102 rises into the baffle 128 and enters the horizontal air inlet. In this embodiment, the baffle 128 has no gaps along its periphery, and all smoke and air are drawn in through the air inlet area 122. In an alternative embodiment, the air inlet area 122 is omitted and a gap is formed around three sides of the baffle 128 to form a U-shaped passage through which air is drawn upwardly into the intake plenum behind the hood portion 102 .

4 , a filter 250 at the inlet of the filter chamber 260 may be provided to cause air and smoke to flow through the filter 250 before exiting through the exhaust 204. A fan 270 may be provided to pressurize the space between the double walls forming the forward portion of the hood portion 102 to generate the jets 104 and/or 106 (if present).

A hood configuration with a peripheral air inlet (an embodiment in which the air inlet area 122 is omitted and gaps are formed on three sides of the baffle 128) can be used in other configurations, such as a top hood or back frame hood. In such an embodiment, the perimeter can surround the top hood hood instead of just three sides. For example, as shown in FIG6 , the top hood hood has baffles 314 that form an air gap 322 between the edge of the baffles 314 and the inner surface of the hood portion 320. The baffles 314 also form a plenum space 324 between the baffles 314 and the inner surface of the hood portion 320. Arrows 316 symbolically indicate that air flows from under the hood into the peripheral air inlet defined by the air gap 322, passes through the plenum 324, and exits the exhaust port 312. A variation of the back frame hood embodiment shown in FIG6 can have air gaps 322 on three sides of the hood 320 instead of four. In another variation, two air gaps can be provided on adjacent sides or opposite sides forming a corner. The features of FIG. 6 may be combined in various ways with any of the embodiments disclosed herein.

The gap 402 can be used to define the size and shape of the air inlets 114, 116, 118, and 120. A set of variable-sized gaps can be provided to accommodate ovens of different sizes, or the gaps can be variable-sized shutters. Alternatively, adjacent air inlets 114 to 118 can have adjustable flow areas, such as those provided by adjustable air inlet shutters. These can be used to regulate flow or adjust the size of the gaps. The air inlet area can also be a simple open area. The air inlet area can also be formed below the oven, for example, by another gap (as shown in 403). The latter can also be adjustable as described above.

The cabinet 110 may include an adjustable shelf 412. The hood portion 102 may be sized to provide an overhang that is greater on the side 414 where the oven is opened than on the side 416 where the oven hinges. In embodiments, an air guide 446 ( FIG. 4 ) may be provided to direct smoke and air flow toward the filter 250 inlet. In embodiments, the air guide may be omitted.

In an embodiment, the side overhangs 414 and 416 comprise between 5 and 30 percent of the overall width of the shield portion 102. In an embodiment, the front overhang may comprise between 20 and 50 percent of the overall depth of the shield portion 102. In an embodiment, the front overhang 444 is 30 to 40 percent of the shield portion depth. In an embodiment, the overhang 444 is 18 to 30 inches.

FIG7 illustrates a control system that can be used with any embodiment of the disclosed subject matter. A controller 505 can provide control for one or more dampers 510 and a fan speed controller 512 or other flow regulating device (not shown). The controller 505 can receive signals (digital signals, analog signals, etc.) from the oven 112, one or more power sensors 504 that receive an indication of the oven 112's power consumption, one or more proximity sensors 502 configured to detect a person approaching the oven 112, and/or one or more imaging devices 506 configured to detect a person approaching the oven 112. The signal from the oven can provide status information, such as the amount of time remaining until shutdown, as indicated on a timer. The one or more dampers 510 can correspond to a single damper configured to control air flow through the exhaust vent.

Claims (8)

1. A method for controlling exhaust airflow, comprising: Receive at least one signal on the digital controller that is related to the oven status, including the amount of remaining time before the oven is turned off as indicated on the timer; In response to at least one of the signals, the exhaust airflow is controlled to increase; and In response to at least one other signal indicating that the oven door is closed, the exhaust airflow is controlled to decrease, wherein the control includes making a probability estimate of the door opening event. 2. The method according to claim 1, wherein the at least one signal comprises an image signal. 3. The method of claim 1, wherein the at least one signal comprises a digital signal from the oven. 4. The method of claim 1, wherein the at least one signal comprises a signal from a proximity sensor. 5. The method of claim 1, wherein the at least another signal comprises an image signal. 6. The method of claim 1, wherein the at least another signal comprises a digital signal from the oven. 7. The method of claim 1, wherein the at least another signal comprises a signal from a proximity sensor. 8. The method of claim 1, wherein the control includes coordinating the adjustment of fan speed and airlock.