PROPELLER SHAFT OF HYDRAULIC DOWNHOLE MOTOR Russian patent published in 2012 - IPC E21B4/02 F16D3/16 

FIELD: engines and pumps.

SUBSTANCE: propeller shaft comprises central shaft and two half-couplings each embracing central shaft edge while line of balls is arranged between each half-coupling and central shaft edge. One side of said balls is fitted in semispherical recesses of propeller shaft and opposite side is located in lengthwise semispherical grooves of half-coupling. Every said line of balls between central shaft and half-coupling makes linkwork to transmit torque. Every edge of central shaft is provided with lengthwise toothed ledges each accommodated inside lengthwise semispherical groove of half-coupling. Maximum height of said ledge equals ball diameter. Half of semispherical recess on central shaft edge located opposite the plane of symmetry crossing central lengthwise axis of central shaft and ball center and half of lengthwise semispherical groove of half-coupling feature depth increased by the height of lengthwise toothed ledge. Lateral surface of every lengthwise toothed ledge on central shaft edge and half-coupling groove wall directed thereto are arranged with annular lateral clearance, its maximum size being equal to ball diameter.

EFFECT: longer life, higher reliability.

4 cl, 7 dwg