Centralizer

Abstract

A simple centralizer, comprising a mandrel extending between box couplings, a rotor receiving surface between the box couplings, a shoulder on the mandrel defining a first end of the rotor receiving surface; and a collar receiving surface on a second end of the rotor receiving surface. The collar receiving surface may be unthreaded. In use, a collar is press fit on to the collar receiving surface.

1 . A centralizer for rod strings, comprising:
 a mandrel extending between a first coupling and a second coupling, the mandrel having an axis, the first coupling having a first coupling diameter and the second coupling having a second coupling diameter, the first coupling diameter being greater than the second coupling diameter;   a rotor receiving surface between the first coupling and the second coupling;   a shoulder on the mandrel defining a first end of the rotor receiving surface; and   a collar receiving surface at a second end of the rotor receiving surface, the collar receiving surface providing a surface suitable for a press fit of a collar, the collar receiving surface having a diameter smaller than a diameter of the rotor receiving surface.   
     
     
         2 . The centralizer of  claim 1  further comprising a collar press fit on to the collar receiving surface, and a rotor on the rotor receiving surface. 
     
     
         3 . The centralizer of  claim 1  in which one or both of the first coupling and the second coupling is or are a box coupling. 
     
     
         4 . The centralizer of  claim 1  in which the collar receiving surface is smooth. 
     
     
         5 . The centralizer of  claim 1  in which the collar receiving surface has a uniform outer diameter. 
     
     
         6 . The centralizer of  claim 1  in which the collar receiving surface is unthreaded. 
     
     
         7 . (canceled) 
     
     
         8 . The centralizer of  claim 2  in which the rotor comprises a tubular sleeve of non-metallic, soft, resilient, abrasion-resistant material. 
     
     
         9 . The centralizer of  claim 8  in which the rotor comprises polyurethane or high temperature nylon. 
     
     
         10 . The centralizer of  claim 2  in which the rotor fits loosely on the rotor receiving surface. 
     
     
         11 . The centralizer of  claim 1  in which the mandrel comprises steel. 
     
     
         12 . The centralizer of  claim 2  in which the collar comprises steel. 
     
     
         13 . The centralizer of  claim 1  comprising one of a bevel, a taper, or a rise between the collar receiving surface and the rotor receiving surface.