Guidable bogie truck for mobile cranes

A guidable bogie truck for use with a mobile crane, said guidable bogie truck comprising a frame;

• two pairs of wheel means, one pair being connected to one end of the frame and the second pair being connected to the opposite end of the frame, one of said two pairs of wheel means being respectively connected to pivotable wheel axles so as to enable this pair of wheel means to constitute guide wheel means;
• four support legs movably connected to the frame, each support leg being attached to the frame near a respective wheel means and each support leg including a footplate;
• lifting means connected to each of said four support legs so as to extend them towards the ground and enable their associated footplates to contact the ground or retract them upwardly towards the frame;
• at least one wheel drive means for turning said wheel means;
• at least one adjustment motor means connected to said pivotable wheel axles to cause them to pivot and thus the associated guide wheel means to turn, thereby steering the bogie truck;
• and a common control device to which each of said wheel drive means, each adjustment motor means and each lifting means is connected, said common control device including at least one shift element for controlling said wheel drive means and at least one direction-setting element for selecting the pivot position of said pivotable wheel axles, said common control device being constructed in such a manner that whenever the direction-setting element is actuated, it first guides at least the two support legs located nearest said pivotable wheel axles into an extended position by their associated lifting means such that the footplates thereof contact the ground and cause the guide wheels to be lifted away from the ground, then it causes said adjustment motor means to pivot said pivotable wheel axles such that the associated guide wheel means are aimed in the desired new direction of travel, and it then causes said adjustment motor means to discontinue operation.