Abstract:
The invention relates to an improvement for a low pressure gas lamp, and more specifically for a venturi tube in order to furnish a more efficient flame.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of provisional application 60/490,466, dated Jul. 29, 2003. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to an improvement for a gas lamp, and more specifically for a venturi tube in order to furnish a more efficient flame. 
     DESCRIPTION OF THE PRIOR ART 
     Gas lamps are an ancient technology. Modern usage of gas lamps is often found in camping settings or homes without electricity. 
     U.S. Pat. No. 5,971,026 to Beran discloses a Venture tube-like gas-air mixing valve for boilers. 
     U.S. Pat. No. 5,052,920 to Warner discloses a range top gas burner and air mixing apparatus. 
     These burner devices are not appropriate for the low pressure gas used for lighting. 
     SUMMARY OF THE INVENTION 
     The present invention provides an improved venturi tube for maximizing the efficiency of a low-pressure gas lamp. This is particularly important in homes, cabins, and other applications where the gas supply is delivered under relatively low pressures. An embodiment of the present invention uses gas at 11 inches of water column, equivalent to approximately 0.4 pounds per square inch (p.s.i.). This amount is considered low-pressure because it is less than a common required pressure of 10 p.s.i. for similar lamps. At low pressures, it is difficult to get a very bright flame from the slow supply of gas. It is an object of this invention to provide a burner tube to provide a venturi effect and produce the highest efficiency in the lamp. 
     By the design of the tapers and the lengths, the brightness is greatly improved and the pressure of gas required is greatly diminished. The use of low pressure has dramatic benefits for safety in camping and homes using the lamps. 
     The lamp also uses the venturi effect to burn to low-pressure gas more efficiently to produce a flame approximately twice as bright as similar products. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-section of a burner tube of the present invention. 
         FIG. 2  is a cross-section of a burner tube of the present invention showing the taper angles. 
         FIG. 3  is a perspective view of a completed lamp shown without a shade or wick. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in  FIG. 1 , the present invention discloses a burner tube  14  having an inlet section  1 , where gas enters the burner tube. A common gas for this application is propane, however other gases are used. 
     As the gas enters the burner tube, a slightly tapered section  2  narrows the opening of the burner tube. At the narrowest point  3 , the opening begins to open and get wider. This produces a venturi effect on the gas, drawing it through the burner tube and preventing the flame from backing into the supply line. The length of the burner tube should be between approximately 4 and 11 inches from the inlet section  1  to the turning point  12  for maximum efficiency of the venturi effect. 
     As shown in  FIG. 2 , the first tapered section  2  has an angle of taper  7  of 1 to 4 degrees. A preferred taper has been found to be 1.5 degrees. When the gas passes the narrowest point  3 , the burner tube opening should be 0.375 to 0.625 inches in diameter for a typical home gas pressure using a low-pressure system. A preferred opening is approximately 0.5 inches in diameter to achieve the proper air-gas mixture. 
     A long second tapered section  4  expands the diameter of the opening as the gas passes through the burner tube. The angle of the second taper  9  should be approximately 2 degrees for maximum efficiency. A range of 1 to 4 degrees can be utilized with success. 
     After the gas passes the turning point  12 , the opening tapers to slightly smaller than the size of the screen assembly  13  at the outlet  15 . The screen assembly  13  is held in place by notches in the burner tube. Once the opening tapers to its narrowest point at the outlet, a first outlet taper  5  and a second outlet taper  6  help keep the flame from coming back into the burner tube. The first outlet taper angle  10  should be approximately 20 to 40 degrees, with a preferred angle of about 30 degrees. The second outlet angle  11  should be approximately 40 to 70 degrees. A mantle assembly is attached to the end of the burner tube to produce a bright light. 
     By example, an embodiment of the gas lamp  16  as shown in  FIG. 3  was connected to a standard low pressure propane gas system having a pressure of approximately 11 inches of water column or approximately 0.4 p.s.i. The lamp produced 600 lux or 55 foot-candle at a light meter approximately 25 inches from the lamp. The prior art lamp most commonly used in the low pressure system is known as the Humphrey lamp and still sold after more than 90 years. The same testing set up was used on a Humphrey lamp and the resulting light was only approximately 75 lux or 7 foot-candle. 
     The preferred embodiment has been shown and described and minor variations may be made by one skilled in the art. It is intended to cover all such variations as fall withing the scope and spirit of the claims.