Construction machine

1. A construction machine comprising:

a lower track structure whose left and right crawler track devices are adapted to change in spatial interval;

an upper swing structure swingably mounted above the lower track structure, the upper swing structure including;

a swing frame that forms a support structure,

a counterweight disposed at a rear section of the swing frame,

a seat base supported by the swing frame, disposed at a front side of the counterweight, and forming a swing body support structure in combination with the swing frame,

an operator's seat placed on the seat base, and

a floor panel positioned at a front side of the seat base and the operator's seat and forming an operator's accessway, and

left and right control lever devices arranged respectively to the left and right of the operator's seat on the seat base, wherein the construction machine is configured as a rear ultrasmall-swing machine in which the seat base is disposed so as to shroud devices including an engine and a hydraulic pump, and on a front right side of the swing frame a fuel tank and a hydraulic fluid tank are arranged and that the back end of the counterweight is positioned anterior to the back end of the lower track structure,

a hydraulically actuated cylinder for changing vehicle width, disposed between the left and right crawler track devices, the vehicle width changing cylinder changing the interval between the left and right crawler track devices upon supply and discharge of a hydraulic fluid being controlled by a vehicle width changing control valve, and

a vehicle width changing control lever for operating the vehicle width changing control valve, wherein

the seat base includes a left seat base portion on which the left control lever device is arranged, a right seat base portion on which the right control lever device is arranged, and a middle seat base portion that is placed therebetween and on which the operator's seat is arranged, and an outer peripheral of the left seat base portion is shrouded with an outer cover,

the middle seat base portion includes left and right sidewalls for further separating an internal region of the seat base from the left and right seat base portions, and the left seat base portion includes a partition wall that further splits the internal region of the seat base vertically, and

the left seat base portion has an upper panel that has a back-and-forth elongated lever hole formed at a rear section of the left control lever device, and

the vehicle width changing control lever is configured to extend downward through the back-and-forth elongated lever hole and to be coupled at its lower end to a pivoting section of a linkage mechanism mounted at one end thereof on the partition wall of the left seat base portion via a bracket.

2. The construction machine according to claim 1 ,

wherein the vehicle width changing control lever includes a lever section mounted on the swing body support structure and adapted to tilt back and forth, and a grip section mounted at a distal end of the lever section,

the lever section is bent backward at the distal end where the grip section is mounted, and

the vehicle width changing control lever is disposed at a rear section of the left control lever device such that it does not overstep the swing radius of the upper swing structure.

3. The construction machine according to claim 1 , further comprising:

a lever locking device that locks the vehicle width changing control lever at its neutral position,

wherein the vehicle width changing control lever includes a lever section mounted tiltably back and forth on the swing body support structure, and a grip section mounted at an upper end of the lever section,

the swing body support structure includes an upper panel at where the vehicle width changing control lever is disposed, the upper panel being formed with a back-and-forth elongated lever hole into which the lever section is inserted and encompassing a region in which the vehicle width changing control lever is adapted to move,

the lever locking device includes a movable plate mounted on the upper panel via a hinge and adapted to turn between a horizontally tilted position and a raised position, the movable plate being formed with a notched recess at an edge opposite to the hinge, and

the movable plate, when in the horizontally tilted position, locks the lever section by covering the lever hole and engaging the lever section in the notched recess, and when in the raised position, unlocks the lever section by uncovering the lever hole and releasing the lever section from the notched recess.

4. The construction machine according to claim 3 ,

wherein the lever locking device further includes, at the edge of the movable plate where the notched recess is formed, a holding section disposed so as to rise from the movable plate.

5. The construction machine according to claim 3 ,

wherein the lever locking device further includes a flexible, plate-shaped sealing member on a face of the movable plate, the face adapted to face the lever hole.

6. The construction machine according to claim 4 ,

wherein the lever locking device further includes a flexible, plate-shaped sealing member on a face of the movable plate, the face adapted to face the lever hole.