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.

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.(t); and wherein the corrective amplitude Acor is set based on 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.

The liquid feeding device includes a discharge speed calculation part configured to calculate a discharge speed v of the plunger pump so that a converted value L.sub.ATM under an atmospheric pressure of a flow rate L.sub.PRE of the mobile phase discharged to the discharge channel from the pump part becomes a set flow rate L.sub.SET using a volume V of the mobile phase in the pump chamber of the closing pump immediately before the precompression process is started, a volume V reduced due to the precompression process of the mobile phase in the pump chamber of the closing pump, and a feeding pressure P; and a discharge operation controller configured to control a discharge speed of the plunger pump to a discharge speed v calculated by the discharge speed calculation part.

The bellows pump device supplies pressurized air to one air chamber of two hermetic air chambers thereby to cause a bellows to perform expansion operation to suck a transport fluid, and supplies pressurized air to the other air chamber thereby to cause the bellows to perform contraction operation to discharge the transport fluid. The bellows pump device includes: an electropneumatic regulator configured to adjust a first air pressure of the pressurized air to be supplied to the one air chamber, and a second air pressure of the pressurized air to be supplied to the other air chamber; and a control unit configured to control the electropneumatic regulator such that, at least at a time point of end of expansion during expansion operation of the bellows, the first air pressure is lower than the second air pressure.

A liquid feeding device includes a discharge channel, a pump part, a feeding pressure sensor, a non-discharge pressure sensor, a pre-compression part, and a pre-compression speed determination part. The pump part has plunger pumps connected in series or parallel. At least one of the plunger pumps is a closed pump in which communication with the discharge channel is disconnected during a non-discharge time. The pre-compression part causes the closed pump that is after the suction process for sucking the liquid into a pump chamber is completed and during the non-discharge time to execute a pre-compression process to perform a discharge operation until a non-discharge pressure is substantially the same as a feeding pressure based on output of the feeding pressure sensor and output of the non-discharge pressure sensor. The pre-compression speed determination part determines a pre-compression speed of the closed pump in the pre-compression process.

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 method is provided for actively compensating for pressure changes of a working fluid within a conduit. A first cavity is provided in fluid communication with the conduit. A second cavity is in fluid communication with a control fluid. A plunger is in communication with both the first cavity and the second cavity and is movable in response to pressure changes of the working fluid in the conduit. The plunger is re-centered. Re-centering the plunger includes the following steps. Position data representative of movement of the plunger is collected. The position data is analyzed with a control unit to determine an average position of the plunger which is offset relative to a center position. The average position of the plunger is compared, with a control unit, to the center position. A signal is relayed from the control unit to a control valve to urge the plunger toward the center position.

An electro-mechanical actuation system for a piston-driven fluid pump. The electro-mechanical actuation system includes a plurality of electro-mechanical actuators, and a control system electrically connected to the plurality of electro-mechanical actuators. Each electro-mechanical actuator is configured to operatively couple with a piston of the fluid pump. The control system is configured to determine a target output of fluid to be pumped by the fluid pump, individually control a speed and a phase at which each electro-mechanical actuator actuates the piston, such that the plurality of cylinders collectively pump fluid at an actual output that corresponds to the target output, and in response to detecting an operating condition, individually adjust the speed and/or the phase at which one or more of the electro-mechanical actuators actuates the piston based on the operating condition to thereby cause the actual output of the fluid pump to correspond to an updated target output.

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 tube pump system is provided, which includes a pair of roller units which are rotated around the axis line from a contact position to a separate position in a state where the pair of roller units compress the tube, a pair of drive units which rotate the pair of roller units respectively, and a control unit which controls each of the pair of drive units, wherein the control unit controls each of the pair of drive units such that, when one of the pair of roller units passes the separate position, an angular velocity of the other of the pair of roller units toward the separate position is gradually decreased.