sensors 30 are arranged in a heat permeable housing 32 which extends across the width c of the cylinder 4 and is fixed to the extension bends 19 a 19 b the temperature sensors 30 1 30 2 are arranged radially spaced from and facing the edge region 4 e i and the temperature sensors 30 6 30 7 not shown are arranged radially spaced from and facing the edge region 4 e ii in this way the heat output of the heating devices 27 1 27 2 and 27 6 27 7 in the edge regions 4 e i and 4 e ii can be adjusted to increase outwards in the embodiment of fig6 seven inductive heating units 27 1 to 27 7 which are connected to the open loop and closed loop control device 31 see fig5 are arranged side by side across the entire width c of the cylinder 4 the heat output of the heating units 27 1 to 27 7 independently of or in addition to the embodiment illustrated in fig3 and 5 can be effected uniformly across the width c of the machine so that the carding gap a see fig2 is uniformly altered across the width c the carding nip a can be made smaller by energy input and enlarged by throttling the energy input in this way it is possible for example to adjust a desired narrow carding nip a the cylinder surface is advantageously heated in zones the temperature gradient across the working width is minimised by the roller heating unit and hence thermal expansion is evened out the heating unit is divided into several zones across the working width so that different.