is mounted at the end 20 of the actuation rod 14 facing the plane 20 on the one hand and is articulated to the base 12 on the other all joints 21 are designed to be as freely moving as possible possibly as convex spherical caps in hollow spherical shells since all joints 21 are pivoted about mutually parallel axes oriented transverse to the drawing plane in case of the introduction of force into the actuation rod 14 they can also be executed as rolling contact joints 21 the central rod 16 and the coupling rod 19 are each supported against their two pivoting directions free of play against pressure sensors 22 responding almost without displacement pressure sensors 22 are subjected to stress over a wide area via pressure plates 23 which in turn are subjected to force in their central areas according to the transverse and flexural forces currently being introduced manually from bulger or transfer ball 24 into the actuation rod 14 because of the always identical direction of force introduction this results in a high constancy of the sensor characteristics the joints 21 act as lever rotation points with regard to which the levers in the form of the central rod 16 and the coupling rod 19 are counterbalanced by counterweights 25 to an indifferent equilibrium this brings about a high response sensitivity of the sensors 22 to manual force introduction.