rotation of crank disk 54 causes a constantly decreasing angular velocity u03c9 s of spindle 51 so that in the upper stroke range of piston 42 relatively small stroke motions take place when pass through area 48 defines only a narrow circular sector the non linearity of the angular velocity u03c9 s of the lifting spindle 51 depends on the angular deflection u03c6 of link points 55 and 56 from a parallel crank arrangement in the example shown the angular deflection u03b4 u03c6 u00b1 15 u00b0 thus there results an angular velocity progression u03c9 s standardized to the constant drive angular velocity u03c9 h as in fig5 and a linear rate of change of pass through area 48 across the entire control range of hoisting unit correcting element 1 is obtained fig6 and 7 show an additional embodiment with a constant rotational drive motion of the hoisting unit correcting element 1 for changing pass through area 48 linearly as well for this purpose a cam control is used which non linearly displaces piston 42 likewise cut off straight with a circular guiding edge 46 the coupling of the motion of the hoisting unit correcting element 1 to the guiding edge 46 can be done via a suitable linear stepup gearing which drives a cam constructed for the purpose which displaces the piston in the case shown however piston 42 itself is driven at constant angular velocity and is supported in a cushioned fashion on a stationary eccentrically displaced cam 60 cam 60 is inserted into an appropriately shaped depression in.