Hydraulic coupling bush

A hydraulic coupling bush for coupling to a hydraulic coupling plug, comprising:

• a coupling housing
• a bush body which configured to be displaced within the coupling housing, and configured to be actuated in order to close or open the coupling, the bush body including
• a plug space configured to receive at least sections of the coupling plug and configured for fluidic connection of said coupling plug,
• a supply space configured to be fluidically connected to an external supply channel,
• a low pressure space configured to be fluidically connected to a pressure medium sink, and
• an interior space fluidically connected to the supply space;
• a supply seat valve device via the actuation of which a supply flow path is configured between the supply space and the plug space;
• a relief seat valve device via a first actuation of which the interior space is relieved of pressure toward the low pressure space, and via a second actuation of which, which is dependent on the pressure in the interior space, the pressure in the interior space is limited, wherein the relief seat valve device has an actuable first valve body with an associated first valve seat for the pressure relief, and a second valve body which is actuated in a manner which is dependent on the pressure in the interior space and has an associated second valve seat for the pressure limiting, wherein the first and second valve seats are arranged coaxially.