Abstract:
An oven construction wherein the oven wall forms an oven cavity containing in a lower portion thereof a HTA producing device, wherein a steam generator is provided in the cavity in physically isolated relationship to the device, wherein the steam generator contains a plurality of metal balls which act as a heat sink, and wherein a water reservoir is provided on the outside of the oven and is in water flow communication with the steam generator thru a water feed line.

Description:
[0001]    This application claims priority under 35 U.S.C. 119(e)(1) based on Applicant&#39;s Provisional U.S. Patent Application Serial No. 60/350,521, filed Oct. 25, 2001 and titled “Baking Oven Steam Generator”. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field  
           [0003]    This invention concerns the modification of ovens, primarily of the rack type such as are used in homes, but also is useful in commercial size ovens, wherein the present modifications effect a unique hot air circulation pattern and, in a most preferred embodiment also features a conveniently located and easy to use unique steam generator. The present heated air circulation pattern dramatically improves the oven baking quality and efficiency and the generator provides limited bursts of steam to the oven in an improved manner to assist, e.g., in forming a thick, ruddy brown, crisp crust to bread particularly French bread being baked.  
           [0004]    2. Prior Art  
           [0005]    U.S. Pat. No. 5,680,810, the disclosure of which is hereby incorporated herein by reference in its entirety, discloses a radiant heat toaster oven provided with a steam generating system wherein a water filled tube is placed into contact with an electrical heating element whereby the water is brought to a boil and stem is allowed to escape thru vent holes in the tube.  
         SUMMARY OF THE INVENTION  
         [0006]    The present oven in one preferred embodiment comprises wall means forming a substantially closed cavity means having an upper portion and a lower portion, HTA (high temperature air) supply means mounted in said lower portion of said cavity means for generating a rising HTA flow within said cavity means, and air flow outlet means thru a lower section of said wall means, whereby said HTA from said supply means will rise into said upper portion of said cavity means and then as it becomes cooler will gravitate downwardly into said lower portion of said cavity means and exit thru said outlet means, whereby said HTA will be forced to travel a longer residence path within said cavity means and release a larger amount of heat energy into said cavity means prior to discharge of said HTA therefrom.  
           [0007]    In another preferred embodiment a steam generator means is mounted in said cavity means and comprises water inlet means, heat sink means, steam outlet means, water reservoir means mounted on the exterior of said wall means on an upper portion thereof, and water feed line means passing thru said wall means and into said cavity means and having one end connected to said reservoir means and having its other end juxtaposed said inlet means, whereby a measured amount of water can be poured into said reservoir means and conducted thru said feed line means into said inlet means and into contact with said heat sink means to produce a desired amount of steam. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    The present oven, in its preferred structural embodiments, is shown in FIGS.  1 - 13  wherein the scale and dimensions of the oven and steam generator components are shown for illustration of the invention only and are not intended to represent commercial ovens proportionately in size or configuration, wherein equivalent structure in the figures are numbered the same, and wherein;  
         [0009]    [0009]FIG. 1 is a front view of an oven with portions of the oven front and door, and the steam generator broken away for clarity;  
         [0010]    [0010]FIG. 2 is a side view taken along line  2 - 2  of FIG. 1 with portions broken away for clarity;  
         [0011]    [0011]FIG. 3 is a cross sectional view taken along line  3 - 3  of FIG. 1;  
         [0012]    [0012]FIG. 4 is a cross-sectional view as in FIG. 2 but showing a preferred positioning of the steam generator with respect to the oven heating element;  
         [0013]    [0013]FIG. 5 is an isometric schematic of a portion of the oven interior showing preferred locations of the steam generator, water feed tube and water reservoir;  
         [0014]    [0014]FIG. 6 is an isometric top view of a preferred steam generator tube;  
         [0015]    [0015]FIG. 7 is a cross-sectional view taken along line  7 - 7  of FIG. 6 in the direction of the arrows;  
         [0016]    [0016]FIG. 8 is an isometric view of an upright tube steam generator with portions broken away for clarity;  
         [0017]    [0017]FIG. 9 is a front view of an oven with the front door and the front of the burner housing removed to show a preferred position for the steam generator of FIG. 8; .  
         [0018]    [0018]FIG. 10 is a front view of an oven with the door removed to show how the steam generator feed tube is mounted to enter into the oven cavity;  
         [0019]    [0019]FIG. 11 is an enlarged cross-sectional view taken along line  11 - 11  of FIG. 10;  
         [0020]    [0020]FIG. 12 is a front view of a gas fired oven wherein the various structural components are approximately drawn to scale but with thickness enlarged for clarity, with the door removed and showing a preferred form of steam generator and a preferred positioning of the heated air exhaust or discharge vents; and  
         [0021]    [0021]FIG. 13 is a cross-sectional view taken along line  13 - 13  of FIG. 12. 
     
    
     DETAILED DESCRIPTION  
       [0022]    Referring to the drawings, a typical home oven  10  is shown as having an oven cavity means  49  formed by wall  11  which is spaced from outer wall  12  of the oven cabinet generally designated  23  for heat insulation whereby wall  11  provides a lower high heat portion  13  and an upper cooler air portion  21  in the cavity means  49 . Provided for the oven are the structures of an oven door  14  conventionally hinged at the lower portion  16  of wall  12 , a control panel  17  with control knobs  19  at the upper portion  18  of wall  12 , and a loop-like electrical heating element  20  having its power/ground electrical connection ends  22 ,  24  inserted thru the rear or back portion  15  of cavity wall  11 . Foot members  28  keep the heating element elevated a short distance above the oven floor or baffle plate means  30 . Cabinet  23  as shown in FIGS. 12 and 13 has a front portion  68 , sides  69 , back wall  71  and top  73 .  
         [0023]    The present steam generator generally designated  31 , in one embodiment, comprises a stainless steel open top body  32  having a thick base or flash pan  34 , i.e., about ½ in. thick which functions also as a heat sink. A useful set of dimensions for body  32  is about 3 in. outside height, about 8 in. long on the inside, and about 3 in. wide on the inside. These dimensions can vary depending how much water one wishes to flash into steam and how fast.  
         [0024]    The water is poured as needed into a reservoir  36  of, e.g., about 4-8 oz. capacity, preferably mounted on the front of wall portion  18  and is conducted thru a small metal tube or line  38  such as a ⅛ in. I.D. copper or stainless steel tubing. This line is affixed to the inside of wall  12  and runs, as shown, into the open top of body  32  without contacting heating element  20 . The inlet end  41  or outlet end  42  of line  38  can be pinched as desired to feed the water onto flash pan  34  at a desired rate.  
         [0025]    Referring to FIGS.  4 - 7 , a much preferred steam generating body  44  preferably of tubular stainless steel pipe of, e.g., 1½ in. I.D. and 9 in. length, capped at both ends is employed and is provided with holes  46 , one of which connects with outlet end  42  of line  38  and the others allowing the escape of steam. A bed  48  of ⅛″ to ½″, preferably ¼″ diameter stainless steel balls is positioned in the tube to provide a mass to capture sufficient heat prior to introduction of water to flash the water from the tube when needed.  
         [0026]    The position of the generator as shown in FIG. 5 within the oven cavity  49  is quite significant in that it is juxtaposed but not touching the heating element  20  so that the generator is maximally effective in absorbing radiant heat but doesn&#39;t block the heating element such as to cause a cold spot in the oven.  
         [0027]    Referring to FIGS. 8 and 9 concerning a gas fired oven having gas burners  39 , this particular embodiment  50  of the steam generator comprises a substantially vertically mounted tube  52  of about 12 in. in length, preferably stainless steel, schedule  40 , having a top inlet pipe  54  connected to feed line  38  extending into tube  52  about, e.g., 1½ in., having a plurality of slots  56  of about, e.g., ¾ in. length and {fraction (3/16)} in. width spaced, e.g., 30 degrees around the tube, and being welded to sides  58  of bracket  60 .  
         [0028]    The tube  52  is filled with, e.g., ¼ in, diameter stainless steel balls  62 , preferably up to just below the inner end  55  of pipe  54 . Bracket  60  is mounted, e.g., by welding to the oven base plate or floor  30  such that tube  52  is directly in the path of the HTA rising from burner chamber  63  thru inlet  64  into oven cavity  49 . After circulation of the heated air in cavity  49  it is discharged to the atmosphere thru discharge vents such as  51  thru the back portion  84  of wall  11 .  
         [0029]    In FIGS. 10 and 11 the structure of the entry of water feed line  38  into oven cavity  49  is shown as simply interposing a generally laterally oriented section  66  of the line between a front portion  68  of the oven housing and a conventional compressible seal member  70  which is affixed to the oven door  14  so as to substantially heat and air seal the oven access opening generally designated  72  when the door is shut against the oven housing front. This seal  70  is sufficiently compressible to easily conform around line section  66  to maintain a good heat and air seal when the oven door is closed.  
         [0030]    Referring to FIGS. 12 and 13, a very efficient gas fired oven construction is shown and comprises individually and/or in combination a unique heated air flow pattern and structure within the oven and a unique steam generator structure. The steam generator comprises a plate member which preferably is the oven floor  30  formed with a recess such as  74  which can be V shaped or concavely curved or the like and which can extend for any desired length along the floor, preferably laterally between the gas burners  39  located below the floor  30  in burner chamber  63 . This recess should be dimensioned to hold a substantial quantity of steel balls or the like, preferably at least about two pounds for a typical home use oven.  
         [0031]    The HTA from the burner chamber enters into the oven cavity  49  thru ports  76  in floor  30  of any selected size and number, and fresh air is fed into the burner chamber thru suitable vents such as  78  in the burner chamber floor  80 . In this preferred construction, the heated air discharge vents  82  are provided thru the back portion  84  of wall  11 , substantially adjacent the bottom thereof, e.g., starting 1-6 inches from floor  30 , for venting to the atmosphere. Preferably, vent ducts such as  85  are provided to direct the exhaust air to a desirable vent location such as louvered openings  86  to the atmosphere. This location of the vents  82  ensures that the upward HTA flow and the downward cooler air flow will be forced into a generally circular flow pattern substantially as indicated by the flow arrows in FIG. 12.  
         [0032]    This airflow pattern reduces the heat up time for achieving a baking temperature of, e.g., about 450° F. from about 43 minutes to about 19 minutes and markedly improves the evenness of temperature throughout the oven with or without the use of convection fans. Also, when a steam generator is employed with this unique air flow pattern, more steam is trapped within the oven cavity for a longer period of time which results in more efficient heating in the oven which greatly reduces the duration of the gas burn periods and the bum frequency, and course also reduces the cost of operating the oven.  
         [0033]    This invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications will be effected within the spirit and scope of the invention.