with a device for applying a coating agent onto a cyclically moved substrate , a uniform coating thickness may be achieved , although the rate of advance not being constant , in that at least one spray valve is provided which is permanently supplied with coating agent and the nozzle opening of which being adjustable with regard to the size of its effective discharge area in case of change of the rate of advance of the substrate according to the dependency , for a constant layer thickness of the coating agent , of the discharge rate of the coating agent out of the spray valve on the rate of advance of the substrate .