Water heater tank minus bottom cylinder end

Abstract

The present invention provides a minus bottom cylinder end having a crown portion, a shoulder portion and a peripheral annular skirt, the crown portion being substantially spherical and located at the centre of the minus bottom cylinder end and the shoulder portion being located between a terminus of the crown and said skirt portion, and wherein said shoulder portion substantially conforms, in cross section, to one of the following: a three point spline, or a part elliptical segment.

1 . A minus bottom cylinder end having a crown portion, a shoulder portion and a peripheral annular skirt, the crown portion being substantially spherical and located at the centre of the minus bottom cylinder end and the shoulder portion being located between a terminus of the crown and said skirt portion, and wherein said shoulder portion substantially conforms, in cross section, to one of the following: a three point spline, or a part elliptical segment.  
   
   
       2 . A minus bottom cylinder end as claimed in  claim 1 , wherein the cross section of the shoulder portion conforms to either, the three point spline, or a part elliptical segment, to within 5%.  
   
   
       3 . A minus bottom cylinder end as claimed in  claim 1 , wherein said crown portion conforms to the shape of a sphere to within 5%.  
   
   
       4 . A minus bottom cylinder end as claimed in  claim 1 , wherein the cross section of the shoulder portion conforms to either, the three point spline, or a part elliptical segment, to within 3%.  
   
   
       5 . A minus bottom cylinder end as claimed in  claim 1 , wherein said crown portion conforms to the shape of a sphere to within 3%.  
   
   
       6 . A minus bottom cylinder end as claimed in  claim 1 , wherein said crown portion is spherical.  
   
   
       7 . A minus bottom cylinder end as claimed in  claim 1 , wherein the cross section of the shoulder portion is a three point spline, or a part elliptical segment.  
   
   
       8 . A minus bottom cylinder end as claimed in  claim 1  wherein the three point spline or part elliptical segment has a tangent at the point of intersection with the crown which is equal to the tangent at the terminus of the crown.  
   
   
       9 . A minus bottom cylinder end as claimed in  claim 1 , wherein the three point spline or part elliptical segment has a tangent at the point of intersection with the skirt which makes an angle of between 20° to 35° to the vertical.  
   
   
       10 . A minus bottom cylinder end as claimed in  claim 9 , wherein the three point spline or part elliptical segment has tangent at the point of intersection with the skirt which makes an angle of 30° to the vertical.  
   
   
       11 . A minus bottom cylinder end as claimed in  claim 1 , wherein the skirt has a divergent tapering shape from the top of the skirt to the lower periphery.  
   
   
       12 . A minus bottom cylinder end as claimed in  claim 11 , wherein the skirt tapers at an angle of approximately 3 degrees.  
   
   
       13 . A minus bottom cylinder end as claimed in  claim 1 , which further includes a knuckle portion between the shoulder and the skirt.  
   
   
       14 . A minus bottom cylinder end as claimed in  claim 13 , wherein the knuckle portion has a radius applied to it.  
   
   
       15 . A minus bottom cylinder end as claimed in  claim 14 , wherein the radius is in the range of 15 millimetres to 40 millimetres.  
   
   
       16 . A minus bottom cylinder end as claimed in  claim 1 , which is manufactured from 3.5 mm thick steel.  
   
   
       17 . A minus bottom cylinder end as claimed in  claim 1 , which is manufactured from a steel with a specification the equivalent to a US steel specification UNS G 10100 or G10160.  
   
   
       18 . A minus bottom cylinder end as claimed in  claim 1 , which is 536 mm in diameter and has a theoretical skirt height of 20 mm.  
   
   
       19 . A minus bottom cylinder end as claimed in  claim 1 , wherein the crown has a spherical radius of 490 mm and terminates 126.8 mm from the centre at a height of 113.3 millimetres above the base of the skirt.  
   
   
       20 . A minus bottom cylinder end as claimed in  claim 1 , wherein the three point spline or part elliptical segment intersects the skirt at 268 mm away from the centre and 20 millimetres above the base of the skirt.  
   
   
       21 . A minus bottom cylinder end as claimed in  claim 1 , wherein an intermediate point on the part elliptical segment, or a third point for the three point spline, is located at a radius of 205.7 mm from the centre and 81.6 mm above the base of the skirt.  
   
   
       22 . A method of producing a pressure vessel minus end, said method including the steps of: providing a spherical crown, a peripheral cylindrical or conical skirt and a shoulder connecting the top of said skirt to the terminus of said crown, wherein said shoulder is either an elliptical segment or a three point spline in cross section.  
   
   
       23 . A method as claimed in  claim 22 , further including the step of providing a radiused knuckle portion between said skirt and said shoulder.