Planting unit lockup device for seeding machine

A seeding machine comprising:

• a frame;
• a hopper mounted to the frame;
• a pivot arm having a first end and a second end, the first end of the pivot arm is pivotally mounted to the frame, the pivot arm having a working position, an intermediate non-working position and a transport position;
• a planting unit is mounted to the second end of the pivot arm, when the pivot arm is in its working position the planting unit is in contact with the ground, when the pivot arm is in its intermediate non-working position the planting unit is not in contact with the ground;
• a flexible tube extends between the hopper and the planting unit;
• a rock shaft is rotatably coupled to the frame, wherein the first end of the pivot arm is coupled to the rock shaft, the rock shaft is provided with a driving bell crank, the rock shaft defining a first pivot axis about which the pivot arm is pivoted;
• a linear motor extends between the frame and the driving bell crank, the linear motor has a retracted position, an intermediate extended position and an extended position for rotating the rock shaft relative to the frame and thereby pivoting the pivot arm, the linear motor has a head end and a rod end;
• and
• a detachable U-shaped stop engages the rod end of the linear motor to lock the linear motor in its intermediate extended position and prevent the linear motor from moving into its retracted position.