Tri-lobe flowmeter rotor with partially open core structure

Abstract

There is a gear rotor for use in a positive displacement flowmeter of the type described. The rotor has an external wall profile 8 forming three equally spaced lobes 9 and a partially open core structure inside said profile with internal cavities 15, 15 A defined between webs 13, 14 extending from a central hub 12 of said rotor to said wall profile 8.

1 . A gear rotor of injection moulded engineering plastic for use in a positive displacement flowmeter of the type described, said rotor including a central hub for rotation on an axis, an external wall profile forming three equally spaced lobes arranged symmetrically around said central hub and a partially open core structure inside said wall profile with internal cavities defined between support webs extending between said central hub of the rotor and said wall profile. 
     
     
         2 . The gear rotor as claimed in  claim 1  wherein portions of said external wall profile between said lobes are concave. 
     
     
         3 . The gear rotor as claimed in  claim 2  wherein at least some of said webs extend between said hub and crests of the lobes and run the length of the rotor. 
     
     
         4 . The gear rotor as claimed in  claim 3  wherein others of said webs extend between said central hub and the roots of the profile concavities and run the length of the rotor. 
     
     
         5 . The gear rotor as claimed in  claim 4  wherein pairs of said internal cavities are defined symmetrically within said core structure. 
     
     
         6 . The gear rotor as claimed in  claim 5  wherein the dimensions of the webs and central hub are chosen such that wall thicknesses remain substantially constant throughout the rotor 
     
     
         7 . The gear rotor as claimed in  claim 6  wherein magnets are implanted in one end of the rotor at junctions of the webs and external wall profile. 
     
     
         8 . The gear rotor as claimed in  claim 7  wherein said engineering plastic is Ryton.