A high pressure pump including a linear actuator having a servo motor to axially rotate a hollow rotor shaft in alternating directions, the servo motor having a stator positioned co-axially around the hollow rotor shaft with an interior of the rotor shaft being co-axially coupled to a drive member to convert axial rotation into reciprocal displacement, the drive member being constrained against linear movement and supporting a shaft. At least one piston is coupled to the shaft and the piston is arranged within a cylinder to define a pumping chamber, whereby alternating rotation of the rotor shaft causes reciprocal linear displacement of the piston to pressurize fluid in the pumping chamber. A drive mechanism includes a controller coupled to a servomotor and an encoder to measure movement of the hollow rotor or output shaft and send a feedback signal proportional to the movement to the controller.

The present invention relates to a method of operating a pump generating a flow of a fluid with a pressure, the method comprising operating the pump with a pump speed S satisfying the equation S=S.sub.simple(1+COR(t)); wherein S is the pump speed, S.sub.simple is the pump speed disregarding any compression and/or expansion of the fluid, t is a time, and COR(t) is a time dependent correction function; wherein the time dependent correction function COR(t) is a product of a corrective amplitude A.sub.cor and a time-dependent function f(t), i.e., COR(t)=A.sub.cor.Math.f (t); and wherein the corrective amplitude A.sub.cor is set by means of a measure for the flow and a measure for the pressure. The present invention also relates to a corresponding use, a pump, a pump system and an HPLC system.

A control device of a piston pump unit comprising at least two piston-cylinder units that operate in a phase-shifted manner for the purpose of liquid chromatography and to a piston pump unit is described. The control device corrects fluctuations of the system pressure while switching from one piston cylinder unit to the respective other piston cylinder unit. The fluctuations can occur as a result of the cooling of the liquid medium that is heated in an adiabatic manner during a pre-compression phase in the working piston. The control unit controls the piston speed of at least one piston-cylinder unit during the transition phase depending on at least one characteristic, which is ascertained from chronologically previously detected pressure values, such that variations of the system pressure as a result of the cooling of the adiabatically heated medium are at least partially compensated for.

A fuel supply device for supplying fuel into a combustion chamber of an internal combustion engine is provided. The device includes: a low pressure fuel supply pipe to which a low pressure fuel is supplied; a high pressure fuel supply pipe to which high pressure fuel to be supplied into the combustion chamber is supplied; fuel supply units provided between the low pressure fuel supply pipe and the high pressure fuel supply pipe, each of the fuel supply units being configured to boost the fuel in the low pressure fuel supply pipe and supply the boosted fuel to the high pressure fuel supply pipe; and a control unit configured to control the fuel supply units. The control unit controls the fuel supply units such that a total amount of ejection of the fuel ejected from the fuel supply units per unit time is close to a constant value.

A positive displacement pump includes at least two pumping chambers and associated plungers. Each plunger is driven by an associated variable speed motor, such as a stepper motor, in a reciprocating motion. The stepper motor varies speed during each stroke of the plunger. A controller controls speed and direction of each stepper motor. Each stepper motor is coupled to a leadscrew having an associated guide rod mounted on the leadscrew to move along the leadscrew as the leadscrew rotates and actuate an associated plunger. The controller varies the speed, displacement and duration of the stepper motors' steps to maintain a constant outflow without pulses.

A solvent supply system for supplying a composite solvent is described. The solvent supply system comprises a first supply flow path with a first pump unit, the first supply flow path being adapted for supplying a flow of a first solvent to a mixing unit, the first pump unit operating periodically, and a second supply flow path with a second pump unit, the second supply flow path being adapted for supplying a flow of a second solvent to the mixing unit, the second pump unit operating periodically. The mixing unit is adapted for mixing the first and the second solvent and for supplying a composite solvent. The solvent supply system further comprises a control unit adapted for controlling operation of the first and the second pump unit, the control unit being adapted to prevent at least one of a predefined phase relation and a predefined frequency relation between the first pump unit and the second pump unit.

A plant for delivering a fluid in a conduit (10) comprises a prime mover (2), for example a gas turbine, which is configured to drive one or more fluid delivery systems (34a-c, 35a1-c1, 35a2-c2) for delivering a fluid in the conduit (10). A first sensor (16) is configured for sensing pressure variations in the pipe (10) and is connected to a first controller (7). The first controller (7) is configured to provide control signals to control valves (36a-c, 37a-c) for at least one fluid delivery system and to a control system (4, 3) for the prime mover (2). One or more hydraulic pumps (9a-c) are configured to operate the fluid delivery systems and are driven by the prime mover, whereby interaction between the hydraulic pumps and the prime mover is controlled based on sensed pressure in the pipe (10).

A liquid feeding apparatus has a primary side pump and a secondary side pump, and an outlet part of the primary side pump and an inlet part of the secondary side pump are connected to each other via a check valve. A temporary side pump pressure sensor for detecting the pressure inside the pump chamber of the primary side pump and a secondary side pressure sensor for detecting the pressure inside the pump chamber of the secondary side pump are provided. The signal of the primary side pressure sensor and the signal of the secondary side pressure sensor are acquired after the suction operation of the primary side pump is terminated and before the discharge operation of the secondary side pump is terminated.

A fuel supply device for supplying fuel into a combustion chamber of an internal combustion engine is provided. The device includes: a low pressure fuel supply pipe to which a low pressure fuel is supplied; a high pressure fuel supply pipe to which high pressure fuel to be supplied into the combustion chamber is supplied; fuel supply units provided between the low pressure fuel supply pipe and the high pressure fuel supply pipe, each of the fuel supply units being configured to boost the fuel in the low pressure fuel supply pipe and supply the boosted fuel to the high pressure fuel supply pipe; and a control unit configured to control the fuel supply units. The control unit controls the fuel supply units such that a total amount of ejection of the fuel ejected from the fuel supply units per unit time is close to a constant value.

A positive displacement pump for pumping a fluid mastic comprises a plurality of cylinders each having a piston arranged for reciprocal motion within the cylinder. Movement of the piston in a first direction draws the fluid into the cylinder and movement in a second, opposite direction pumps the fluid out of the cylinder. A variable speed electric motor is drivingly coupled to a cam arrangement providing a reciprocating drive to the pistons. The cam arrangement comprises cams shaped and arranged to drive each piston in the first direction over less than half of a rotational cycle and to drive each piston in the second direction over the remainder of the rotational cycle. The cams are arranged to drive the pistons out of phase with one another.