Shifting mechanisms for fluid jet decoking tools

A fluid jet decoking tool comprising:

• a valve body configured to receive a pressurized fluid therein, said body comprising:
• a plurality of cutting fluid passages and a plurality of boring fluid passages formed therein and disposed about an axial centerline thereof;
• a plurality of nozzles each of which is in fluid communication with a respective one of said cutting fluid passages and said boring fluid passages;
• and
• a mode-shifting apparatus coupled to said valve body such that said pressurized fluid received into said valve body is selectively delivered through at least one of said plurality of nozzles, said apparatus comprising:
• a rotatable valve defining a tool-engaging surface thereon;
• a control rod coupled to said rotatable valve such that said control rod and said rotatable valve rotate together;
• a shifting mechanism cooperative with said rotatable valve through said control rod to produce selective rotary movement in said rotatable valve and said control rod, said shifting mechanism comprising:
• a ratcheted biasing apparatus cooperative with said rotatable valve through said control rod such that a pressure-increasing change in decoking fluid pressure within said fluid jet decoking tool produces linearly-downward and rotary movement in said rotatable valve and said control rod while a pressure-decreasing change in decoking fluid pressure within said fluid jet decoking tool produces a linearly-upward movement while not producing rotary movement in said rotatable valve and said control rod;
• and
• a lubricating flowpath defining a lubricating fluid reservoir such that a fluid disposed in said reservoir does not substantially contribute to damping between said rotatable valve and said decoking tool during said linearly-downward movement of said rotatable valve resulting from said pressure-increasing change in decoking fluid pressure;
• and
• a biasing member cooperative with said control rod to temporarily unseat said tool-engaging surface of said rotatable valve from an adjacent non-rotating surface of said valve body during a pressure-decreasing change in said pressurized fluid to establish a friction-reducing gap resulting from said linearly-upward movement.