MXPA97000448A - Ventilation system for transportation oven - Google Patents

Abstract

The present invention relates to a ventilation system for a conveyor furnace having a conveyor opening on one of its sides, the combination comprising: an exhaust shield placed on top of the furnace and extending outwardly from the furnace. side of the furnace to form an exhaust channel over the conveyor opening, replacement air means to provide replacement air and transport the replacement air to a location below the conveyor opening, and an air curtain nozzle connected to the replacement air means and positioned below the conveyor opening to direct a replacement air stream upwards along the side of the oven so that the cooking gases flowing out of the conveyor opening are directed upwards and within the channel of esca

Description

VENTILATION SYSTEM FOR CONVEYOR OVEN Background of the Invention The field of the invention is that of ventilation systems for ovens and, more particularly, ovens in which the food is cooked by passing it through the oven chamber on a mobile conveyor. Conveyor ovens are commonly used in fast food restaurants because they ensure uniform cooking conditions. For example, a raw pizza is placed on the conveyor and transported inside the oven chamber where heated convection currents are directed over it by powerful fans. The movement of the conveyor is such that the pizza is properly cooked as it is transported from the cooking chamber. Conveyor ovens produce a large amount of heat and noise and, unlike conventional ovens, are characterized by inlet and outlet openings for the mobile conveyor that are always open towards the cooking chamber. It is common practice to stack two or more conveyor ovens one on top of the other and this multiplies the heat and noise as well as the number of openings inside the cooking chamber. Such furnaces are described, for example, in U.S. Patent Nos. 4,244,285; 4,245,613; 4,363,955; 4,377,109; 4,462,383; 4,554,437; 4,576,090; 4,591,333; 4,626,661; 4,701,340; 4,873,107; 4,951,684; 4,965,435; 4,556,043; 4,960,043; 4,960,100; 4,964,392; 5,025,775; and 5,231,920. The first ventilation systems for conveyor ovens were adaptations of ventilation covers used on conventional cooking equipment. Such systems are described, for example, in U.S. Patent Nos. 4,321,031; 3,900,533; 4,616,562; 4,716,820; 4,738,243 and 4,896,657. These do not significantly reduce the radiant heat produced by conveyor ovens and large amounts of air are expelled to ensure that the heated air emanating from the transportation openings does not escape from the deck. More recently, ventilation systems specifically adapted for conveyor ovens have been used. These systems are characterized by a double-walled enclosure that surrounds most of the furnace. This enclosure reduces the temperature of the surface of the oven and, therefore, the radiated heat inside the room. It also reduces the noise level. In a version of such a ventilation system described in U.S. Patent No. 5,299,557, the replacement air within the enclosure flows over the furnace and down a front panel. The replacement air also flows into panels on each side of the furnace and is blown through the openings located under each conveyor. A cover-type exhaust is located above the conveyor openings on each side of the furnace and the heated air from the cooking chamber mixes with the replacement air and flows upward into the exhaust. Unfortunately, not all cooking gases are trapped with this arrangement and the condensation of grease caused by mixing the cold replacement air in the conveyor openings can be a problem. In another ventilation system described in U.S. Patent Number 5,421,317, the difficulties described above are addressed by a ventilation system in which the exhaust openings are placed very close to each conveyor opening and, the replacement air flows on the top and bottom of the front and rear sides of the oven. By placing exhaust openings near the conveyor openings, it is said that this structure captures more cooking gases loaded with grease and expel them without grease condensation. Unfortunately, this solution is very expensive in its manufacture and the enclosure becomes too hot because both sides of the enclosure and the portions of the front and top convey hot exhaust gases.

Brief Description of the Invention The present invention is a ventilation system for a conveyor furnace or the like in which fresh replacement air flows over the entire front and near all side surfaces of the furnace and is blown over the conveyor openings in such a way that the Cooking gases are trapped by an exhaust shield protruding above each side of the kiln. More specifically, the replacement air is supplied through ducts to a lower side panel which is positioned below the conveyor opening and which includes an air nozzle extending the width of the conveyor opening through which the air is blown upward to provide an air curtain through the conveyor opening that confines the cooking gases emanating therefrom and directs them into the upper exhaust shield. A general object of the invention is to discharge the cooking gases from a conveyor oven and minimize the amount of ambient air expelled by the system. It has been found that cooking gases emanating from the conveyor openings can be confined and directed into a higher exhaust by an upwardly directed replacement air curtain placed below the conveyor opening. The escape shield does not need to extend from the far furnace to ensure capture, but the replacement air is also directed down from the exit shield to aid capture, particularly when several furnaces are stacked. Another object of the invention is to cool the surfaces of the oven. Because the replacement air is introduced adjacent to the conveyor openings, the duct works to transport the cold replacement air that covers the entire front of the furnace as well as substantially both sides. As a result, the hot discharge is confined to the upper exhaust duct and the furnace radiates less heat to the surrounding work site. Even another aspect of the present invention is to efficiently handle the grease that condenses in the upper exhaust. The exhaust duct is simple to build and easily accessible for cleaning. The roof of the exhaust plenum is tilted towards the sides of the oven where a cup of grease is located. Therefore, any grease that condenses in the exhaust will not be collected in areas that are difficult to reach. The foregoing and other objects and advantages of the invention will arise from the following description. In the description, reference is made to the accompanying drawings which are part of it and, in which, a preferred embodiment of the invention is shown by way of example. However, such an embodiment does not necessarily represent the full scope of the invention and therefore, reference is made to the claims herein to interpret the scope of the invention.

Brief Description of the Invention Figure 1 is a perspective view of the oven and the ventilation system employing the preferred embodiment of the invention; Figure 2 is a perspective view of the system of the Figure 1 with parts cut away to show the replacement air duct that is part of the ventilation system; Figure 3 is a cross-sectional view taken through the plane 3-3 shown in Figure 1 to show the exhaust duct; and Figure 4 is a cross-sectional view taken through the plane 4-4 shown in Figure 1; Figure 5 is a partial view of the exhaust duct showing a grease collection assembly; and Figure 6 is a partial view of the grease collection assembly of Figure 5 showing a cup of fat.

Description of the Preferred Modality With particular reference to Figure 1, the conveyor oven with integral ventilation system is constructed around two conveyor ovens 10-12 which are stacked one on top of the other. Each furnace 10 and 12 has a conveyor 14 and 16 respectively, which extends completely through the furnace and extends outward from each side of the furnace a sufficient distance to properly place food products on the conveyor on the inlet side and removes the food products on the outlet side. Each oven 10 and 12 have an oven door 18 and 2o respectively, which provides access to the cooking chamber therein through the front walls of the oven 22 and 24. In the preferred embodiment the conveyor ovens 10 and 12 are the models numbers MT3870, MT3855 and MT3270 manufactured by GS Blodgett Corporation, Burlington Vermont U.S. A., however, other furnaces may also be used, such as those sold under the trademark "Pacesetter 360" manufactured by Middeby Marshall model numbers PS360, PS360WB and PS570. The integral ventilation system virtually encapsulates furnaces 10 and 12 and is comprised of two subsystems: the replacement air subsystem, and the exhaust air subsystem. The exhaust air subsystem is designed to capture the heated cooking gases produced by ovens 10 and 12 and discharge them from the work area through an exhaust duct 30 extending upwards from the top of the kiln system. An exhaust fan (not shown) connects to the exhaust duct 30 and removes a pre-set amount of exhaust air from the work area. In the preferred embodiment, the exhaust system extracts 448 m3 of air per minute. As will be explained in more detail below, the exhaust air subsystem is a relatively simple shield type structure that protrudes above each side of the ovens to capture the cooking gases emanating from the conveyor openings. The replacement air subsystem serves three basic purposes. First, it introduces the non-conditioned outside air through a replacement air duct 32 to supply and significantly reduce the amount of relatively expensive work area of the air that is expelled. In the preferred embodiment a fan (not shown in the drawings) supplies 336 m 3 per minute of replacement air to the work area, leaving 112 m 3 of air conditioning that is removed from the work area by the exhaust subsystem. The second basic purpose of the replacement air subsystem is to cool the surface of ovens 10 and 12. This reduces the heat that radiates into the work area and makes it more comfortable to work near ovens 10 and 12. As will explain in more detail below, the replacement air subsystem in the preferred embodiment encapsulates the front, both sides and most of the upper part of ovens 10 and 12 in a cold replacement air layer. The third basic purpose of the replacement air system is to assist in the capture of heated cooking gases produced by ovens 10 and 12. As will be described in more detail below, the replacement air can be directed within the region. of the conveyor openings so that the cooking gases are reliably confined and directed within the shield of the exhaust system. With particular reference to Figs. 1 and 2, the replacement air indicated by the arrow 34 flows into the replacement air plenum 36 that extends through the top of the ovens adjacent to the front. This replacement air plenum 36 communicates with a number of ducts to distribute the replacement air over the top, sides and front of the ovens. More specifically, the replacement air flows down from the front of the furnaces through the walls 22 and 24 as indicated by the arrows 40. This replacement air enters the work area through the openings (not shown) along the lower edge of the front wall 24. This replacement air flows at a rate of approximately 56 m3 per minute and is directed backward, under the oven 12. Referring particularly to Figs. 2 and 4, the replacement air also flows from the plenum 36 from the horizontal ducts 44 located on top and along each side of the furnace system. As indicated by the ws 46, this replacement air flows into the horizontal ducts 44 and is dispersed in a stream directed downward through the air opening of the shield 48. As will be described in more detail below, the duct horizontal 44 covers the upper part of an exhaust shield generally indicated at 50 and the replacement air 46 flows down from the upper conveyor 14 and bends around and flows into the exhaust shield 50. The replacement air 46 is adjusted to confine the cooking gases, and in the preferred embodiment flows at approximately 42 m3 per minute along each side of the oven. In addition to confining the cooking gases, this replacement air helps to cool the upper part of the exhaust shield 50, significantly reduces the heat radiated within the work area and, minimizes the amount of ambient air discharged by the system. With particular reference to Figs. 1 and 2, the replacement air plenum 36 also delivers replacement air to the vertical ducts 54 and 56 that define the left and right front corners of the furnace system. As indicated by ws 58, the replacement air flows into the top of each vertical duct 54 and 56 from plenum 36 and down to an intermediate side panel 60 and a lower side panel 62. As best shown in FIG. Figs. 2 and 3, the intermediate side panel 60 on the left side is positioned between the conveyors 14 and 16 and extends rearwardly from the vertical duct 54 the total width of the conveyors 14 and 16. The intermediate side panel 60 is a duct air for replacement air 58 which is received from the vertical duct 54 and supplied through the air confinement openings 64 formed along its upper and lower edges. Similarly, the lower side panel 62 is an air duct for replacement air 58 which is received from the vertical duct 54 and supplied through an air curtain nozzle 66 formed along its upper edge. The side panels along the right side of the furnace system (not shown) are identical in construction and operation. As best shown in fig. 3 the intermediate side panel 60 is separated from the side walls of the furnace 68 to form a chimney 70 therebetween. The replacement air 58 from the lower side panel 62 is directed upwardly through the lower conveyor 16 into this chimney 70 and forms an air curtain that "rotates" the cooking gases produced in the lower oven cooking chamber. upward, and into the chimney 70 as indicated by arrow 72. The speed and volume of the replacement air 58 in this air curtain is adjusted to rotate the cooking gases 72 upwardly inside the chimney 70 without causing the cooking gases escape from the exhaust shield 50. In the preferred embodiment, a replacement air flow through the air curtain nozzle 70 m3 per minute on each side of the furnace system is employed. Less replacement air is needed in the intermediate side panel 60 and, in the preferred embodiment, approximately 28 m 3 per minute is supplied on each side to help confine the cooking gases within the chimney 70. It will be apparent from the description above that the replacement air system is designed to provide cold air and to inject most of this air into the region around the conveyor openings on each side. Therefore, this replacement air is used not only to reduce the discharge of air conditioning, but also to cool the exterior of the ovens and to actively confine the cooking gases within the "range" of the exhaust shield. With particular reference to Figs. 1 and 3, the exhaust shield 50 includes exhaust ducts 80 which are formed on top of the furnace 10 and are positioned along each side, above the conveyor 14. The exhaust ducts 80 are joined by a plenum of exhaust 82, which extends through the upper part of the furnace 10 and behind the replacement air plenum 36. The exhaust duct 30 extends upwards from the center of the exhaust plenum 82 and is connected to a blower fan. escape as described before. Referring particularly to Figure 3, the exhaust air indicated by the arrows 84 is drawn from each exhaust duct 80 as indicated by arrow 86. A wide opening is formed along the bottom of each exhaust duct 80 and this opening defines the upper end of a channel 88 formed by a shield side panel 90 and the side wall of the furnace 68. This channel 88 is positioned directly above the chimney 70 to extract the replacement air 58 and the cooking gases 72 in the same. It also removes the replacement air 46 downstream of the shield side panel 90, as well as the cooking gases indicated by the arrow 92 from the baking chamber of the upper oven 94. In the preferred embodiment, approximately 224 m3 per minute are ejected. on each side of the escape shield 50 with the result that part of the air conditioner from the work area is also drawn into each channel 88. As the amount of replacement air and its distribution through the different outlets near the Conveyor openings are the primary variables that are adjusted to ensure that the exhaust shield 50 captures all cooking gases, precise adjustment may be required. As shown in Figure 3, in the preferred embodiment this is achieved by adjusting the size of a flag 100 extending horizontally from the upper edge of the intermediate side panel 60 to the side wall of the oven 68. This flag 100 adjusts to Effectively the size of the chimney 70 is fixed and at a point where all the cooking gases 72 from the lower oven 12 are turned upwards successfully into the chimney 70. However, if the 100 flag is very small , the effective chimney size is very large and the cooking gases will be spilled from below the exhaust shield 50. The cooking gases are typically loaded with grease which condenses against the coldest surfaces. Since the cold replacement air is mixed with the cooking gases in the conveyor openings, the grease will condense on the inner surfaces of the exhaust plenum 82 and the exhaust duct 30.

To facilitate cleaning of the ventilation system the floor of the exhaust plenum 110 is coupled as shown in Figure 3 so that the condensed grease will flow out through the exhaust duct 80. A duct is formed along the rim. external of the inclined floor 110 and, as shown in Figure 5, this duct 112 slopes downwardly through the front of the furnace system. A cup of grease 114 is attached at the front end of the duct 112 and collects the grease flowing through the duct 112 and through a drain hole 116 formed at its forward end. The shield side panel 90 is removable to provide access to the grease cup 114 for regular emptying and to provide access to the exhaust duct 80 and the exhaust plenum 82 for periodic cleaning.

Claims (7)

1 . A ventilation system for a conveyor furnace (10-12) having a conveyor opening on one of its sides, the combination comprising: an exhaust shield (50) placed on top of the furnace and extending outward from the side of the furnace to form an exhaust channel (88) on the conveyor opening; replacement air means (32) for supplying replacement air and transporting the replacement air to a location below the conveyor opening; and an air curtain nozzle (66) connected to the replacement air means and positioned below the conveyor opening to direct a replacement airflow upwards along the side of the furnace (10-12) in a manner that the cooking gases that flow out of the conveyor opening are directed upwards and into the exhaust channel (88).

2. The ventilation system as described in claim 1, wherein a panel (60) is mounted toward the side of the furnace on the conveyor opening and is separated from the side of the furnace to form a chimney (70) which guides the replacement air and cooking gases (92) upwards along the side of the oven. The ventilation system as described in claim 2, wherein the furnace has a second conveyor opening on said side positioned on the chimney (70) and below the exhaust channel (88). The ventilation system as described in claim 2, wherein it includes means (100) for adjusting the size of the chimney (70). The ventilation system as described in claim 2, wherein the replacement air means (32) supplies replacement air to the interior of the panel (60) and the confinement openings (64) are formed as along the top edge of the panel to direct the replacement air upwards thereof. The ventilation system as described in claim 1, wherein the replacement air means (32) transports the replacement air to a location above the exhaust shield (50) and an exhaust shield opening ( 489 directs the replacement air downward along an outer side of the exhaust shield to the exhaust channel (88) 7. A ventilation system for a conveyor furnace (10-12) having a conveyor opening in one of its sides, the combination comprising: an exhaust shield (50) placed on top of the furnace and extending outwardly from the side of the furnace to form an exhaust channel (88) over the conveyor opening, the Exhaust shield (50) including; a) an exhaust plenum (82) connecting the exhaust channel (88) to an exhaust duct (80) extending upward therefrom at a location between the sides of the furnace, and the exhaust plenum (82) ) having a floor (1 10) that is inclined to convey the condensed grease to the exhaust channel (88), and b) grease collection means (1 12, 1 14) formed in the exhaust channel (88) and placed to collect the fat that flows on the floor of the plenum (1 10); and replacement air means (32) to ide replacement air and transport the replacement air to a location adjacent to the conveyor opening where it flows into the air space around the furnace.