Dust cap assembly and dust cap device for this assembly

A dust cap assembly for a semi-trailer (2) having an underside (20) and adapted to being towed by a towing vehicle (3), the dust cap assembly for closing a king pin (21) which has been bored out with a borehole (22) for an automatic fifth-wheel coupling and which is arranged on the underside (20) of the semi-trailer (2), the king pin (21) serving as a counter bearing for a saddle plate (31) of the towing vehicle (3), the dust cap assembly comprising:

• a dust cap device (1) arranged in contact with the underside (20) of the semi-trailer (2) adjacent to and rotatable around the king pin (21), and
• an annular bearing disc (25) for mounting the dust cap device rotatable about the king pin (21),
• wherein the dust cap device (1) has a dust cap (11) for covering the borehole (22) in the king pin (21),
• wherein the dust cap (11) is designed to be displaceable on the dust cap device (1) during a coupling process with a towing vehicle (3) from a basic position covering the borehole (22) in the king pin (21) into a coupling position that exposes the borehole (22),
• wherein the annular bearing disc (25) comprises a circular bearing seat (26 which is secured coaxially to the king pin (21) on the underside (20) of the semi-trailer (2), and wherein the circular bearing seat (26) has on the annular bearing disc (25) a first sliding bearing edge (261) on an inner circular opening of the circular bearing seat (26) and a second sliding bearing edge (262) on an outer rim of the circular bearing seat (26), in which the dust cap device (1) engages.