An implement unit comprising a position securing apparatus (30a, 30b) for securing an agricultural working implement which can be mounted to an agricultural working machine by way of a coupling device in position to a transport carriage comprising: a sensor, a receiving device having a first functional portion which is provided at a first longitudinal side of two longitudinal sides (LT1, LT2) of the transport carriage, that face away from each other and extend along a longitudinal direction thereof, and a second functional portion which is provided at a first longitudinal side of two longitudinal sides (LA1, LA2) of the working implement, that face away from each other and extend along a longitudinal direction thereof, wherein the first and second functional portions (33a, 33b) can be brought into engagement with each other to provide a support mounting so that the first longitudinal side of the working implement is supported at the first longitudinal side of the transport carriage, wherein the second longitudinal side of the working implement faces in the same direction as the second longitudinal side of the transport carriage, a locking device which can be selectively moved into a locking condition in which it prevents release of the engagement of the two functional portions (33a, 34a) and an unlocking condition in which it allows release of the engagement of the two functional portions (33a, 34a), and a drive device which is connected to the sensor to be actuated by same and is connected to the locking device, characterised in that the sensor, the locking device and the drive device are arranged on the working implement and the sensor is provided on the part of the working implement on the coupling device and is adapted to detect a coupled condition and an uncoupled condition of the coupling device to drive the locking device so that it is moved into the locked condition when the sensor detects the uncoupled condition and is moved into the unlocked condition when the sensor detects the coupled condition. a sensor, a receiving device having a first functional portion which is provided at a first longitudinal side of two longitudinal sides (LT1, LT2) of the transport carriage, that face away from each other and extend along a longitudinal direction thereof, and a second functional portion which is provided at a first longitudinal side of two longitudinal sides (LA1, LA2) of the working implement, that face away from each other and extend along a longitudinal direction thereof, wherein the first and second functional portions (33a, 33b) can be brought into engagement with each other to provide a support mounting so that the first longitudinal side of the working implement is supported at the first longitudinal side of the transport carriage, wherein the second longitudinal side of the working implement faces in the same direction as the second longitudinal side of the transport carriage, a locking device which can be selectively moved into a locking condition in which it prevents release of the engagement of the two functional portions (33a, 34a) and an unlocking condition in which it allows release of the engagement of the two functional portions (33a, 34a), and a drive device which is connected to the sensor to be actuated by same and is connected to the locking device, characterised in that the sensor, the locking device and the drive device are arranged on the working implement and the sensor is provided on the part of the working implement on the coupling device and is adapted to detect a coupled condition and an uncoupled condition of the coupling device to drive the locking device so that it is moved into the locked condition when the sensor detects the uncoupled condition and is moved into the unlocked condition when the sensor detects the coupled condition.