7 according to fig5 or 6 it is thus possible for a single element 16 or a plurality of elements arranged for example in row form on a shaft 31 to be connected to the rotary cylinder 10 via springs 32 33 consequently the elements 16 are urged into their advanced position 23 by spring force during a rotary movement of the rotary cylinder 10 about the axis 11 as a result of the elements 16 striking the skin 21 the elements 16 are urged back against the force of the springs 32 33 approximately parallel to the direction 20 into their retracted position 22 until the elements 16 are no longer opposite the skin 21 on account of the rotary movement in this arrangement the spiral springs 32 in the embodiment of fig5 are arranged approximately parallel to the direction 20 while the leaf springs 33 in the embodiment of fig6 are ranged approximately transverse to the direction 20 in both embodiments the spring force of the springs 32 33 connected to shaft or carrier 31 acts radially outward approximately parallel to the direction 20 so that the elements 16 or u201c flexible protrusions u201d are always urged outward by the springs 32 33 approximately parallel to the direction 20 into the advanced position 23 in addition and or alternatively it is possible in accordance with fig7 to provide a cam track 34 with which the element 16 is coupled and by means of which the reciprocating movement of the element 16 is controlled the cam track 34 results in the element 16 being moved approximately.