Cylinder on demand hydraulic device

A variable flow hydraulic device having a plurality of cylinders for varying a flow of hydraulic fluid between a fluid reservoir and a load, the device comprising:

• a housing having the plurality of cylinders with a plurality of corresponding pistons configured for reciprocation of a constant stroke length;
• a main shaft mounted in the housing, such that each of the plurality of corresponding pistons is coupled to and thus driven by rotation of the main shaft by a respective cam of a set of cams mounted on the main shaft, such that at least one piston of the plurality of corresponding pistons is decoupled from the respective cam when the at least one piston is placed into a locked state and the at least one piston is coupled to the respective cam when the at least one piston is placed in an unlocked state, such that when placed in the locked state reciprocation of the at least one piston is inhibited during the rotation and when placed in the unlocked state reciprocation of the at least one piston is facilitated during the rotation;
• an input port of the housing fluidly connected to each cylinder of the plurality of cylinders, the input port facilitating introduction of the hydraulic fluid into said each cylinder;
• an output port of the housing connected to said each cylinder, the output port facilitating the ejection of the hydraulic fluid from said each cylinder during the reciprocation, the output port configured for fluidly coupling said each cylinder to the load;
• the fluid reservoir fluidly connected to the input port by an input fluid pathway and for fluidly connecting to the load by an output fluid pathway, the fluid reservoir containing the hydraulic fluid;
• a charge pump associated with the fluid reservoir such that the charge pump supplies the hydraulic fluid from the fluid reservoir via the input fluid pathway to the input port, such that the charge pump is mechanically coupled to the main shaft and supplies the hydraulic fluid to the input port during both the locked state and the unlocked state of the at least one piston;
• wherein the charge pump supplies at least a portion of the hydraulic fluid to the input port in order to facilitate the reciprocation of one or more of the plurality of corresponding pistons.