Patent ID: 8683720

Claim:
A tractor-scraper machine comprising: a tractor drive vehicle having a propulsion system and a hydraulic fluid pump; a towed scraper; and a cushion hitch that couples the towed scraper to the tractor drive vehicle, the cushion hitch including; first and second pivotable links coupled between the towed scraper and the tractor drive vehicle; and a suspension system, the suspension system having; a hydraulic cylinder with an extendable rod, the hydraulic cylinder and the rod coupled between the first and second pivotable links; a control valve fluidly coupled between the hydraulic cylinder and the fluid pump, the control valve configured to adjust an extension length of the rod; a variable orifice fluidly coupled between the hydraulic cylinder and the control valve, the variable orifice configured to adjust resistance to extension and retraction of the rod; a first fixed restrictive element fluidly coupled in series with the variable orifice to dissipate energy as the rod extends; and a second fixed restrictive element fluidly coupled in series with the variable orifice to dissipate energy as the rod retracts.