Patent ID: 7828310

Claim:
A chassis structure for a mid-wheel drive power wheelchair comprising: a frame comprising a front section, two side sections, and three connecting rods, the three connecting rods being pivotally connected to the front section and the two side sections, respectively; a transverse pipe having two ends and a middle section between the two ends, the middle section being connected with the connecting rod on the front section of the frame; a pair of front wheel rods each having a first end, a second end and a first connecting portion between the first end and the second end, the first end being connected with a front wheel; a pair of driving units each secured to the second end of a relative front wheel rod and comprising a driving wheel and a second connecting portion; a pair of connecting racks each having a first end and a second end, the first end being pivotally connected to the first connecting portion of a relative front wheel rod, the second end being connected with to a press cylinder, the press cylinder having a third connecting portion, the pair of connecting racks being secured to the two ends of the transverse pipe, respectively; a pair of restricting racks each comprising a first restricting plate and a second restricting plate, the first restricting plate having a first end, a second end and a first slot at a central portion thereof, the second restricting plate having a first end, a second end and a second slot at a central portion thereof, a first fixing member inserting through the second end of the first restricting plate and the second slot of the second restricting plate, a second fixing member inserting through the second end of the second restricting plate and the first slot of the first restricting plate, the first restricting plate and the second restricting plate overlapping for extending and restricting with each other, the first end of the first restricting plate being pivotally connected to the second connecting portion of a relative driving unit; and a pair of rear wheel rods each having a first end and a second end, the first end being connected with a rear wheel, the second end having a fourth connecting portion and a fifth connecting portion and being connected with an action rod, the action rod having a first end and a second end, the connecting rod on a relative side section of the frame being inserted through the first end of the action rod and pivotally connected to the fourth connecting portion of the second end of a relative rear wheel rod, the second end of the action rod being secured to a relative connecting rack, the action rod having a sixth connecting portion, the sixth connecting portion being pivotally connected to the first end of the second restricting plate of a relative restricting rack, the fifth connecting portion of the second end of the rear wheel rod being connected to the third connecting portion of a relative press cylinder.