DRIVE SHAFT TO CONNECT SCREW GEROTOR HYDROMACHINE WITH SPINDLE Russian patent published in 2006 - IPC E21B4/02 F16D3/16 

FIELD: rotary drilling, particularly fluid rotary type drives to be arranged in well.

SUBSTANCE: drive shaft comprises central rod and two bodies. Each body encloses central rod end. Ball row is located between each body and central rod end. The first ball sides are inserted in semispherical depressions formed, for instance, in central rod. The second ball sides are located in longitudinal semicylindrical grooves made in body. Each ball row defines joint assembly between central rod and body. Summary number or balls grouped in two rows and equally spaced along a circle is equal to that of balls arranged in single row of single-row joint assembly. Double ball row defines joint assembly, which functions practically as constant-velocity ball joint. Balls of each two rows are arranged along central rod axis and spaced apart predetermined distance equal to at least screw gerotor hydromachine rotor eccentricity with respect to stator thereof.

EFFECT: increased reliability and service life, namely improved uniformity of contact stress distribution in each joint assembly between central rod and body, decreased wear, contact stresses and backlash of joint assemblies due to two rows of balls usage and reduced amplitude of transversal resonance oscillations of screw downhole motor body.

3 cl, 5 dwg