Patent ID: 8920291

Claim:
A supporting structure for a treadmill, the treadmill including a foundation lying on the ground and a treadbase swingable with respect to the foundation, the supporting structure being such connected between the foundation and the treadbase that the supporting structure has a viable length and is selectively fixable at a predetermined length to fix an included angle between the foundation and the treadbase, and the supporting structure comprising: an outer tube having an outer-tube pivotal end, an outer-tube telescoping end, an inner wall defining an accommodating space, and a protrusion fixed to the inner wall and jutting out into the accommodating space, wherein the outer tube at where the protrusion exists has an outer-tube internal diameter as r, and the protrusion has a free end that is apart from the inner wall by a vertical distance as L; an inner tube having an inner-tube pivotal end, an inner-tube telescoping end, and a positioning hole for receiving the protrusion, wherein the outer-tube pivotal end and the inner-tube pivotal end are pivotally connected to the foundation and the treadbase, respectively, the inner-tube telescoping end being inserted into the accommodating space from the outer-tube telescoping end, and the inner tube at where the positioning hole exists having an inner-tube external diameter as R, wherein (R+L)<r; and a spring assembly for placing a resilient prestress on the inner tube toward the protrusion; wherein, when the inner tube is substantially parallel to the outer tube and the protrusion faces the positioning hole, the spring assembly pushes the inner tube toward the protrusion, so as to make the protrusion enter the positioning hole, thereby fixing the supporting structure at the predetermined length, and when the inner tube is inclined with respect to the outer tube, the protrusion is disengaged from the positioning hole, so as to allow the inner tube to slide within the accommodating space, thereby varying the length of the supporting structure.