| 摘要 |
A pedal drive for a bicycle having a driven wheel rotatably mounted to a frame, including a first sprocket rotatably mounted to the frame; a second sprocket rotatably mounted to the frame below the first sprocket and in planar alignment with it at a location spaced apart from the first sprocket; an endless chain extending about and interconnecting the first and second sprockets; a third sprocket rotatably mounted to the frame for rotary movement in response to the rotary movement of the first and second sprockets; an endless chain extending about and interconnecting the third sprocket and a sprocket attached to the driven wheel; left and right upper crank arms attached to the first sprocket and extending in generally opposite directions from each other; left and right lower crank arms attached to the second sprocket and extending in opposite directions from each other; a left pedal arm carrying a left pedal and pivotally connected to the left upper crank arm; a right pedal arm carrying a right pedal and pivotally connected to the right upper crank arm; a left link pivotally connected to the left pedal arm and pivotally connected to the left lower crank arm; and a right link pivotally connected to the right pedal arm and pivotally connected to the right lower crank arm. The upper and lower left-side crank arms are rotationally displaced from each other by at least 60 degrees, as are the upper and lower right-side crank arms, with the lower crank arms rotationally leading the upper crank arms. The left and right links have a length exceeding the left and right lower crank arms, and the left and right pedal arms exceed the left and right upper crank arms.
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