Omnidirectional vent cap

Abstract

An omnidirectional vent cap for venting holding tanks is provided. Current vent caps seldom exhaust gasses and create higher rather than lower pressure above the vent. By providing a 360 degree channel, the present invention can use a small movement of air to significantly reduce the air pressure above the exhaust port to draw out vapors. Since the device is symmetrical about the central axis the movement of air can be from any direction relative to the device.

1 . A vent cap for venting an exhaust gas passage, comprising: 
 i) a generally circular base having a central opening for communicating with said exhaust gas passage and a generally circular perimeter, and an upper ramp surface extending between said perimeter and said central opening, said ramp surface having an increasing slope as the distance from the central opening decreases;    ii) a top cover element supported above said base and having an outer edge and providing a convex lower surface extending at its lowest point below said outer edge to thereby in combination with said base cause a low pressure effect above said exhaust gas passage when air moves through said cap; and    iii) means for supporting said top cover element above said base.    
   
   
       2 . The vent cap of  claim 1  further comprising a plurality of spaced, radially extending vanes projecting upwardly from said upper ramp surface.  
   
   
       3 . The vent cap of  claim 2  wherein said vanes extend above said ramp surface a distance which is 5% to 10% of the length of said ramp surface.  
   
   
       4 . The vent cap of  claim 1  wherein said top cover element comprises a convex upper surface.  
   
   
       5 . The vent cap of  claim 1  wherein said top cover element and said base have a minimum separation of approximately ½ the length of said ramp surface.  
   
   
       5 . The vent cap of  claim 1  wherein said ramp surface is curved with a smoothly increasing tangential angle  
   
   
       6 . The vent cap of  claim 1  wherein said ramp surface is approximately horizontal at its outer edge and is about 80 degrees at the central opening.  
   
   
       7 . The vent cap of  claim 1  wherein said ramp surface rises about one-half its surface distance over the curvature of the ramp from outer to inner edge.  
   
   
       8 . The vent cap of  claim 1  wherein the radial length of said ramp surface is approximately the same as the radius of said central opening.  
   
   
       9 . The vent cap of  claim 1  wherein said means for supporting said top cover element above said base comprise a plurality of legs.  
   
   
       10 . A vent cap for venting an exhaust gas passage, comprising: 
 i) a generally circular base having a central opening for communicating with said exhaust gas passage and a generally circular perimeter, and an upper ramp surface extending between said perimeter and said central opening, said ramp surface having an increasing slope as the distance from the central opening decreases;    ii) a top cover element supported above said base and having an outer edge and providing a convex lower surface extending at its lowest point below said outer edge to thereby in combination with said base cause a low pressure effect above said exhaust gas passage when air moves through said cap;    iii) means for supporting said top cover element above said base; and    iv) a plurality of spaced, radially extending vanes projecting upwardly from said upper ramp surface.    
   
   
       11 . The vent cap of  claim 10  wherein said vanes extend above said ramp surface a distance which is 5% to 10% of the length of said ramp surface.  
   
   
       12 . The vent cap of  claim 10  wherein said top cover element comprises a convex upper surface.  
   
   
       13 . The vent cap of  claim 10  wherein said top cover element and said base have a minimum separation of approximately ½ the length of said ramp surface.  
   
   
       14 . The vent cap of  claim 10  wherein said ramp surface is curved with a smoothly increasing tangential angle  
   
   
       15 . The vent cap of  claim 10  wherein said ramp surface is approximately horizontal at its outer edge and is about 80 degrees at the central opening.  
   
   
       16 . The vent cap of  claim 10  wherein said ramp surface rises about one-half its surface distance over the curvature of the ramp from outer to inner edge.  
   
   
       17 . The vent cap of  claim 10  wherein the radial length of said ramp surface is approximately the same as the radius of said central opening.  
   
   
       18 . The vent cap of  claim 10  wherein said means for supporting said top cover element above said base comprise a plurality of legs.