Uniaxial eccentric screw pump

Abstract

A uniaxial eccentric screw pump includes a stator having an insertion hole with an inner peripheral surface being internally threaded, and a rotor including shaft placed through the insertion hole in the stator. The insertion hole is, in a cross section, an opening including a middle area and two end areas. An interference amount between an outer peripheral surface of the rotor and the inner peripheral surface of the insertion hole in the stator is smaller in the middle area than in the two end areas.

1 . A uniaxial eccentric screw pump, comprising:
 a stator having an insertion hole with an inner peripheral surface being internally threaded; and   a rotor including a shaft being externally threaded and placed through the insertion hole in the stator,   wherein the insertion hole is, in a cross section, an opening including a middle area and two end areas, and an interference amount between an outer peripheral surface of the rotor and the inner peripheral surface of the insertion hole in the stator is smaller in the middle area than in the two end areas.   
     
     
         2 . The uniaxial eccentric screw pump according to  claim 1 , wherein
 the opening in the stator has an elliptical profile with a ratio of a minor diameter to a major diameter being 0.83 to 0.96 inclusive.   
     
     
         3 . The uniaxial eccentric screw pump according to  claim 1 , wherein
 the opening in the stator has a profile expressed with a single formula defining a condition to cause a smaller interference amount in the middle area than an opening having a profile with a shape of a racetrack including semicircles and straight lines.   
     
     
         4 . The uniaxial eccentric screw pump according to  claim 1 , wherein
 the opening in the stator has a profile expressed with a single formula defining a condition to cause a larger interference amount in the two end areas than an opening having a profile with a shape of a racetrack including semicircles and straight lines.   
     
     
         5 . The uniaxial eccentric screw pump according to  claim 1 , wherein
 the opening in the stator has a profile including, in the middle area, a portion with a first profile and including, in each of the two end areas, a portion with a second profile different from the first profile.   
     
     
         6 . The uniaxial eccentric screw pump according to  claim 5 , wherein
 the opening in the stator has a profile including a part of a perfect circle.   
     
     
         7 . The uniaxial eccentric screw pump according to  claim 5 , wherein
 the opening in the stator has a profile including a part of an ellipse.   
     
     
         8 . The uniaxial eccentric screw pump according to  claim 3 , wherein
 the opening in the stator has, in the middle area, an outwardly curved profile.   
     
     
         9 . The uniaxial eccentric screw pump according to  claim 1 , wherein
 the opening in the stator has a profile including at least one straight portion.   
     
     
         10 . The uniaxial eccentric screw pump according to  claim 9 , wherein
 the at least one straight portion includes parallel straight portions facing each other in the middle area.   
     
     
         11 . The uniaxial eccentric screw pump according to  claim 1 , wherein
 the stator consists of a stator body formed from an elastic material.   
     
     
         12 . The uniaxial eccentric screw pump according to  claim 3 , wherein
 the opening in the stator has a profile including at least one straight portion.   
     
     
         13 . The uniaxial eccentric screw pump according to  claim 3 , wherein
 the stator consists of a stator body formed from an elastic material.   
     
     
         14 . The uniaxial eccentric screw pump according to  claim 3 , wherein
 the opening in the stator has a profile expressed with a single formula defining a condition to cause a larger interference amount in the two end areas than an opening having a profile with a shape of a racetrack including semicircles and straight lines.