Decanter centrifuge and gear box with harmonic drive and associated operating method

A gear box for a decanter centrifuge assembly having a bowl and a screw conveyor disposed inside said bowl for rotation at a speed different from an angular velocity of said bowl, comprising:

• a rigid circular spline;
• a first connector coupling said circular spline to the conveyor of the centrifuge assembly;
• a flexible spline rotatably coupled to said circular spline;
• a second connector coupling said flexible spline to the bowl of the centrifuge assembly;
• and
• a wave generator disposed in contact with said flexible spline for distorting said flexible spline and enabling a transmission of rotary power between said flexible spline and said circular spline so that said flexible spline rotates at an angular velocity incrementally differing from an angular velocity of said circular spline, said first connector extending to said circular spline from one side of said wave generator said second connector extending to said flexible spline from an opposite side of said wave generator.

A method for operating a decanter centrifuge assembly having a bowl and a screw conveyor disposed inside said bowl for rotation at a speed different from an angular velocity of said bowl, comprising:

• rotating the bowl of the centrifuge assembley at a first predetermined angular velocity;
• transmitting rotary power from the bowl to a flexible spline of a harmonic drive unit via a transmission coupling extending to a first side of said harmonic drive unit, so that said flexible spline rotates about a rotation axis at said first predetermined angular velocity;
• rotating a circular spline of said harmonic drive unit about said rotation axis at a second predetermined angular velocity differing incrementally from said first predetermined angular velocity;
• distorting said flexible spline via a wave generator disposed in contact with said flexible spline, to place said flexible spline in contact with said circular spline and thereby enable a transmission of rotary power between said flexible spline and said circular spline;
• and
• transmitting rotary force from said circular spline to the conveyor of the centrifuge assembly via a transmission coupling extending to a second side of said harmonic drive unit opposite said first side, to rotate said conveyor at said second predetermined angular velocity.

A decanter centrifuge assembly, comprising:

• a bowl;
• a screw conveyor disposed inside said bowl for rotation at a speed different from an angular velocity of said bowl;
• and
• a harmonic drive unit operatively connected to said conveyor and said bowl, said harmonic drive unit including a wave generator, an outer casing and a shaft coupled to said wave generator and extending along a longitudinal axis of said harmonic drive unit, siad harmonic drive unit having a lubrication system with a skimmer tube for paring lubricating fluid from a pool in said outer casing, said shaft having a channel coaxial with said axis and communicating with said skimmer tube, said lubricating system having at least one spray nozzle communication with said channel and juxtaposed to a bearing surface of said harmonic drive unit for spraying lubricating fluid onto the bearing surface.

A gear box for a decanter centrifuge assembly having a bowl and a screw conveyor disposed inside said bowl for rotation at a speed different from an angular velocity of said bowl, comprising:

• a rigid circular spline;
• a first connector coupling said circular spline to the conveyor of the centrifuge assembly;
• a flexible spline rotatably coupled to said circular spline;
• a second connector coupling said flexible spline to the bowl of the centrifuge assembly;
• a wave generator disposed in contact with said flexible spline for distorting said flexible spline and enabling a transmission of rotary power between said flexible spline and said circular spline so that said flexible spline rotates at an angular velocity incrementally differing from an angular velocity of said circular spline;
• an outer casing;
• a shaft coupled to said wave generator, said shaft extending along a longitudinal axis of said gear box and having a channel coaxial with said axis;
• and
• a lubrication system with a skimmer tube for paring lubricating fluid from a pool in said outer casing, said channel communicating with said skimmer tube, said lubricating system having at least one spray nozzle communicating with said channel and juxtaposed to a bearing surface of said gear box for spraying lubricating fluid onto the bearing surface.