Torque-limiting coupling

A torque limiting coupling, comprising:

• a shaft formed with a conical connector;
• a coupling ring arranged coaxially with said shaft, said coupling ring having a lateral surface in contact with a lateral surface of said shaft;
• said coupling ring having a double-walled section with an internal annular pressure fluid chamber, configured to increase a radial thickness of said section when said fluid chamber is filled with pressurized fluid and to thereby increase pressure forces and friction forces between the lateral surface of said coupling ring and the lateral surface of said shaft in order to enable a torque transfer, and wherein said coupling ring transfers substantially no torque, when said fluid chamber is not filled with pressurized fluid;
• said coupling ring having a shear tube configured to close said pressure fluid chamber to hold pressure in said pressure fluid chamber;
• a shear plate and a central bolt fixedly connecting said shear plate to said shaft;
• said shear plate being configured to cut off a tip of said shear tube in order to open said pressure fluid chamber when said shaft slips relatively to said coupling ring when the torque is higher than a predefined maximum transferable torque given by the pressure in said pressure fluid chamber and a design of the torque limiting coupling;
• and
• a conical bushing connected to, or forming part of, said shear plate, and wherein said shear plate is fixed to said shaft by said central bolt pressing said conical bushing against said conical connector of said shaft.