Importance

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Abstract

A main frame pivotally supports the forward ends of a laterally spaced apart pair of parallelogram linkage systems. Each linkage system comprises an upper link and a two section lower link, rear ends of which are pivotally interconnected to a rear shackle, the lower end of which has a ground engageable roller. A load platform is pivotally connected along its forward edge to the rear ends of the upper links. The rear sections of the lower links are rigidly interconnected by a lift frame that is fitted at its opposite ends with upstanding crank members. A hydraulic piston cylinder mechanism is mounted adjacent each linkage system with its butt end pivotally connected to the main frame and the piston rod of each cylinder is pivotally connected to one of the upstanding crank members. The forward and rear sections of each lower link are pivotally interconnected by a knuckle pin and each lower link includes stops to bidirectionally limit relative angular displacement of the two sections. The geometry of the mechanism generates moments with respect to the knuckle pin in substantially all elevations of the linkage systems, other than contact of the shackle roller with ground, in the direction tending to align the pair of sections of each lower link. When the platform is lowered to be primarily supported by ground the resultant of the moments tends to misalign the pair of sections of each lower link to effect a ramping action of the platform.

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First Claim