Control valve unit

A control valve unit comprising a valve rod which is sealed from a valve housing via a seal assembly, the seal assembly having a packing, which is received axially between a pressure sleeve and a counter bearing on the valve housing, which pressure sleeve is movably mounted in the axial direction relative to the valve housing and transmits a pressing force, which is applied to the pressure sleeve by a spring element via a pressure element, to the packing, and which spring element is supported on a pretensioning device, the distance of which to the counter bearing can be adjusted, whereby the pressing force of the spring element acting on the pressure sleeve can be adjusted, characterized in that the spring element is arranged axially between a first stop and a second stop of the pretensioning device, wherein, in a preinstalled state of the pretensioning device, the spring element is supported on the first stop and on the second stop under pretension, wherein, in an operating state of the control valve unit, the second stop is arranged at a fixed distance to the first stop in the direction of the counter bearing and wherein the change in the axial position of the pressure sleeve is limited by the second stop which is arranged at a distance to the pressure element in the direction of the counter bearing.