Patent Publication Number: US-3880062-A

Title: Hood

Description:
1 Apr. 29, 1975 1 1 HOOD [75] Inventors: Clifford Culpepper, Jr.; Robert M.  
 Stuck, both of Charlotte. NC.  
 [73] Assignee: Aero-Dyne Manufacturing. Inc  
 Charlotte. NC.  
 [22] Filed: Nov. 8. 1973 [21] Appl. No.: 413.760  
 U.S. Cl 98/115 K: 55/D1G. 36  
  Int. Cl F23j 11/12 [58] Field of Search 98/115 l\&#39; 115 R; 55/D1G. 36  
 [56] References Cited UNl-TED STATES PATENTS 3.3241129 6/1967 Graswich et al. 98/115 K 3,490.206 1/1971) Doanc 98/115 K 3,731,462 5/1973 Costarella ct alt 98/115 K Primary E.\&#39;aminer-Mc \&#39;er Perlin Assixlanr E.\&#39;umincrRonald C. Capossela Attorney Agwzl, 0r Firm-Parrott. Bell. Seltzer Park 84 Gibson [57 I ABSTRACT Airborne particulate matter is efficiently entrained into an air flow while the volume of air flow required is minimized by a hood which has walls defining an aerodynamically curving flow path with an entrance face having a first cross sectional flow area and a throat zone spaced downstream of the entrance face and having a cross-sectional flow area less than that of the entrance face. The throat zone is defined by the Cooperation of an aerodynamically curving interior forward wall and lower and upper portions of a rear wall which are respectively directed forwardly toward the front wall and rearwardly away from a work surface underlying the interior forward wall.  
 8 Claims. 5 Drawing Figures HOOD  Recent efforts toward control of air pollutants, such as airborne particulate matter, have brought increasing attention to certain problems relating to control of such materials. By way of specific example, airborne particles of grease originating from certain apparatus typically used in fast-service restaurants, such as charbroilers, have in the past been disposed of by arranging a ventilating system to have a hood overlying the work surface of the apparatus and inducing a flovs of air through the hood. Particularly where the hood is located within a building structure where a controlled atmosphere is desired, it is necessary to provide makeup&#34; air to replace the quantity of air withdrawn through the ventilation system. Where high volumes of air are withdrawn, the supply of the necessary quantitites of conditioned make-up air presents difficulty.  
  Yet a further difficulty is encountered where air and entrained airborne particulate matter are delivered from the hood to a disposal device such as an afterburner. It has been discovered that the quantity of fuel required for proper disposal of the air pollutants is determined, at least in part, by the quantity of air necessary to entrain and deliver the particulate matter. Thus, where large volumes of air are required, large quantities of fuel are required and the expense of compliance with requirements for disposal is substantially increased.  
  Having in mind the aforementioned difficulties and deficiencies of prior arrangements, it is an object of this invention to efficiently entrain airborne particulate matter while minimizing the volume of air flow required. In accomplishing this object of the present invention, hood means having wall&#39;means which define a particularly configured flow path for air are provided. Particularly by the cooperation of a front wall defining an aerodynamically curving interior forward wall at least partially overlying a work surface and a rear wall having lower and upper portions which are respectively directed forwardly toward the front wall and rearwardly away from the work surface, a constant acceleration of air flow velocities is achieved between the entrance of air into the hood and a throat zone spaced above the work surface.  
  Some of the objects of the invention having been stated, other objects will appear as the description proceeds, when taken in connection with the accompanying drawings, in which FIG. I is a perspective view, partly broken away, of a ventilation system incorporating the present invention;  
  FIG. 2 is an enlarged side elevation view, partially in section, taken generally along the line 2-2 in FIG. 1;  
  FIG. 3 is a front elevation view of the apparatus of FIGS. 1 and 2;  
  FIG. 4 is a section view taken generally along the line 4-4 in FIG. 2; and  
  FIG. 5 is a section through a portion of the apparatus of FIGS. 1 and 2, taken generally along the line 55 in FIG. 2.  
  A ventilation system and hood means in accordance with the present invention have been illustrated in the accompanying drawing and will be described in the text which follows. The description and drawing refer to the best mode for the practice of this invention contemplated at the time that the description and drawing were prepared. However, it is contemplated that the LII illustration and description of this invention will aid persons skilled in the art of ventilation generally to understand the wide applicability of this invention. For that reason, the illustration and description are to be understood broadly, rather than as restricting the scope of this invention.  
  The present invention has been illustrated in the accompanying drawings in an environment where a charbroiler, generally indicated at 10, is disposed within a building and is used in cooking. As will be understood by persons familiar with such cooking apparatus, particulate grease becomes airborne during the operation of a charbroiler and removal of such airborne particulate matter from the area of the work surface defined by the charbroiler is necessary. As will be recognized, the charbroiler 10 is of known side-to-side and front-torear dimensions.  
  In accordance with this invention, hood means generally indicated at 20 overlies and substantially encloses the work surface, for guiding air flow thereover. The hood means operatively communicates with duct means generally indicated at 21 which in turn operatively communicates with a fan means generally indicated at 22, by which flow of air is induced. Specific details of the duct means 21 and fan means 22 are not here disclosed, as such devices generally may be designed and selected by skilled ventilating engineers.  
  The hood means 20 comprises a plurality of related wall means which together define a flow path for air and entrained matter. In accordance with this inven tion, the flow path is configured for constant acceleration of air flow velocity between an entrance face adjacent the front side of the work surface or charbroiler l0 and a throat zone defined within the path as described more fully hereinafter. By such a constant acceleration of flow velocities, together with the use of aerodynamically curving surfaces, the volume of air flow required for entrainment of airborne particulate matter is minimized.  
  The wall means includes side wall means 30, 31 defining right and left side walls rising from adjacent the right and left sides of the work surface 10 and having front portions 32, 33 and rear portions 34, 35. A front wall means generally indicated at 38 has a lower edge portion 39 spaced upwardly from the work surface 10 and generally overlying the front side thereof (FIGS. 1 and 2). The front wall means 38 defines an aerodynamically curving interior forward wall which rises from the lower edge portion 39 (as best seen in FIG. 2). Together, the lower edge portion 39 of the front wall means 38 and the front portions 32, 33 of the side wall means 30, 31 define with the work surface 10 an entrance face for the hood means 20, through which air flow enters the hood means for entraining airborne particulate matter from above the work surface 10.  
  In accordance with a significant feature of this invention, the front portions 32, 33 of the side wall means 30, 31 and the lower edge portion 39 of the front wall means 38 each define aerodynamically inward curving surfaces adjacent to the entrance face (FIGS. 2 and 5). Such aerodynamic curving of surfaces adjacent the entrance face promotes smooth streamline flow of air entering the hood and avoids turbulent flow which otherwise possibly would result in expulsion of airborne particulate matter from the hood back into the interior of the building adjacent the work surface 10.  
  Cooperating with the front wall means and side wall means is a rear wall means generally indicated at 40 which defines a rear wall rising from adjacent the rear side of the work surface. The rear wall means 40 has a lower portion 41 directed forwardly toward the front wall means 38 and an upper portion 42 directed rearwardly away from the work surface 10. Preferably, and as shown, the lower and upper portions 41, 42 of the rear wall means diverge from a common horizontal edge 44 spaced upwardly from the work surface and the lower edge portion 39 of the front wall means 38. At the horizontal edge 44, the rear wall means 40 and front wall means 38 cooperate to define a throat zone which has a cross-sectional flow area less than the cross-sectional flow area of the entrance face described hereinabove. Further, the upper portion 42, being directed rearwardly away from the work surface 10, defines an expansion zone downstream of the throat zone which has a cross-sectional fiow area greater than the cross-sectional flow area of the throat zone.  
  It is to be noted that the side wall means 30, 31 have lower portions which are parallel one to the other and have upper portions converging toward one another. The upper portions 46, 47 (FIGS. 3 and 4) extend from respective common horizontal bend lines 48, 49 which separate them from the respective lower portions 50, 51. The bend lines 48. 49 of the side wall means 30, 31 are spaced upwardly from the throat zone (F165. 1 and 2) and cooperate with the front and rear wall means in bringing the cross-sectional area of the flow path to a known dimension downstream of the expansion zone discussed hereinabove.  
  It will be noted that, in operation, air entering at the hood means adjacent the lower edge portion 39 of the front wall means 38 passes beneath a generally horizontal entrance face portion of the aerodynamically curved interior forward wall. Air entering near the lower end of the entrance face, immediately adjacent the work surface 10, passes rearwardly over the work surface 10, is heated, and rises toward the rear wall. As such rising air flow encounters the lower portion 41 of the rear wall, the flow is turned toward the throat zone, for mixing with air flow moving along the aerodynamically curved interior forward wall and is accelerated toward the reduced cross-sectional flow area to be found at the throat zone. Thus, efficient entrainment of airborne particulate matter is accomplished, while leakage of such matter back into the building interior is avoided and the volume of air flow required is minimized.  
  In the drawings and specification, there has been set forth a preferred embodiment of the invention, and although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation.  
 That which is claimed is:  
  1. Hood means for efficiently entraining airborne particulate matter, such as originates from a charbroiler during cooking, from above a work surface of known side-to-side and front-to-rear dimensions while minimizing the volume of air flow required, said hood means comprising:  
 side wall means defining right and left side walls rising from adjacent the right and left sides of the overlying the front side thereof, said front wall means defining a smooth aerodynamically curving interior forward wall rising from said lower edge portion for assuring streamline fiow of air therealong and within said hood means,  
 said front portions of said side wall means, said lower edge portions of said front wall means and the work surface together defining an entrance face for said hood means through which air flow enters for entraining airborne particulate matter from above the work surface, and  
 rear wall means defining a rear wall rising from adjacent the rear side of the work surface and having a lower portion directed forwardly toward said front wall means and an upper portion directed rearwardly away from the work surface,  
 said side wall means, front wall means, rear wall means and work surface together defining an at least substantially closed path for air flow, said front wall means and said rear wall means lower and upper portions together defining a throat zone within said air flow path, and the throat zone having a cross-sectional flow area less than the crosssectional flow area of the entrance face.  
  2. Hood means according to claim 1 wherein said wall means together define a flow path for air and entrained matter configured for constant acceleration of flow velocities between the entrance face and the throat zone.  
  3. Hood means according to claim 1 wherein said upper portion of said rear wall means defines with said front wall means and said sidewall means an expansion zone downstream of the throat zone and having a crosssectional flow area greater than the cross-sectional flow area of the throat zone.  
  4. Hood means according to claim 1 wherein said lower and upper portions of said rear wall means diverge from a common horizontal edge spaced upwardly from the work surface and said lower edge portion of said front wall means.  
  5. Hood means according to claim 1 wherein said sidewall means have lower portions parallel one to the other and have upper portions converging toward one another and further wherein said upper and lower portions diverge from respective common horizontal edges which lie in a common horizontal plane spaced upwardly from the throat zone.  
  6. Hood means according to claim 1 wherein said front portions of said sidewall means and said lower edge portions of said front wall means define aerodynamically inwardly curving surfaces at the entrace face.  
  7. Hood means according to claim 1 wherein said interior forward wall defined by said front wall means has a generally horizontal entrance face portion overlying the extreme front edge of the work surface.  
  8. A ventilation system for efficiently entraining airborne particulate matter, such as originates from a charbroiler during cooking, from above a work surface of known side-to-side and front-to-rear dimensions while minimizing the volume of air flow required, the system comprising:  
 duct means for conducting a flow of air and entrained matter,  
 fan means operatively communicating with said duct means for inducing flow of air and entrained matter therethrough, and  
 hood means for overlying the work surface and having wall means for directing air flow relative thereto, said wall means including side wall means defining right and left side walls rising from adjacent the right and left sides of work surface and having front and rear portions,  
 front wall means having a lower edge portion spaced upwardly from the work surface and generally overlying the front side thereof, said front wall means defining a smooth aerodynamically curving interior forward wall rising from said lower edge portion for assuring streamline flow of air therealong and within said hood means,  
 said front portions of said side wall means, said lower edge portions of said front wall means and the work surface together defining an entrance face for said hood means through which air flow enters for entraining airborne particulate matter from above the work surface, and  
 rear wall means defining a rear wall rising from adjacent the rear side of the work surface and having a lower portion directed forwardly toward said front wall means and an upper portion directed rearwardly away from the work surface.  
 said side wall means. front wall means, rear wall means and work surface together defining an at least substantially closed path for air flow into said duct means. said front wall means said rear wall means lower and upper portions together defining a throat zone within said air flow path, and the throat zone having a cross-sectional flow area less than the cross-sectional flow area of the entrance face.