The image shows a CAD model of a regulator for steam engines, developed and applied for a patent by the Siemens brothers, which is absolutely different from preliminary centrifugal regulators.
This regulator is based on the difference of the velocity of a circular pendulum and of the velocity of the steam engine, which has to be controlled.
The control mechanism was implemented in remarkably different ways.
Here is shown the solution by use of three interlocking bevel gears.