Cam-Driven Variable Displacement Linkage
True Zero DisplacementThis technology improves upon a previous variable linkage variable displacement machine technology, the high efficiency variable displacement pump, which has a crankshaft-driven adjustable six-bar linkage to vary the displacement of a piston. This new technology is a cam-driven adjustable linkage that also varies the displacement of a piston. This highly efficient mechanism reaches true zero displacement. Furthermore, the piston reaches the same top-dead-center position regardless of the displacement, minimizing the unswept volume and resulting compressibility energy losses. The linkages employs low friction pin joints, which further reduces energy losses during operation, and also reduces leakage due to the absence of hydrodynamic bearings. The design incorporates a crosshead bearing, which prevents side loading of the piston. Through design of the cam profile, the piston trajectory can be precisely controlled to minimize the flow and pressure ripple. Furthermore, the use of a multi-lobe cam allows multiple pumping strokes per revolution, creating high power density. A further innovation is a selectable piston chamber area, allowing operation across a wide variety of pressures and flow rates.Higher Power DensityThis new design shares all the advantages of the previous variable displacement pump linkage design but has a higher power density. The compactness makes this technology an excellent fit for mobile applications ranging from human power pumps to robotics to traction motors for construction or agricultural equipment. This improved cam-driven, adjustable linkage machine replaces the crank link and coupler link of the previous mechanism with a cam and follower that is more compact due to allowing multiple pumping strokes per shaft rotation and packaging in a radial configuration. This variable linkage machine uses a crosshead bearing to minimize the piston side loads. An innovative use of this crosshead bearing is to create two different piston areas that are selectable based on the required operating pressure and flow rate of the pump, further extending the range of operation.BENEFITS AND FEATURES:Compact designLow friction and leakage losses = higher energy efficiencyMultiple strokes per revolutionPrecise piston displacement profile control to minimize flow rippleSelectable piston chamber areas based on operating pressure and flowSix-bar linkage varies stroke of a reciprocating engineReplaces crank link and coupler link of previous mechanism with cam-followerReaches true zero displacement positionLow compressibility energy lossesPin joints offer lower friction and energy savingsVariable displacement machineAPPLICATIONS:Hydraulic pumpsCenter for Compact & Efficient Fluid Power (CCEFP) applicationsHuman driven pumpsVariable displacement hydraulic pumps and motorsOther applications such as agriculture, construction, lawn equipment, hydraulic hybrid vehicles, hydrostatic wind power transmission and adjustable linkage applications (e.g., air/gas compressor and engines)Phase of Development - Demonstration prototype
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