Abstract: A pulse damper for use in high-pressure liquid pumping applications such as liquid chromatography comprises a length of flattened polytetrafluoroethylene tubing that can be coupled to the high-pressure liquid flow line. The flattened tubing is enclosed within a liquid-tight housing structure completely filled with a compressible liquid, and the end of the tubing are coupled to the high-pressure flow line by fittings mounted inside the housing structure. When a transient pressure variation occurs in the flow line, the cross-section of the tubing changes from a flattened elliptical configuration to a more rounded configuration as the pressure pulse temporarily overcomes the stresses that tend to maintain the tubing in its flattened configuration. The restoring force of the compressible liquid in the housing structure surrounding the tubing prevents expansion of the tubing beyond a desired limit during a pulse, so that the tubing cannot burst when its cross-sectional configuration changes.

Abstract: A pressure regulating valve for use in a high-pressure fluid flow line, comprises a cylindrical needle-housing structure that is slidable within a bore in a valve body. An external spring urges the needle-housing structure toward a valve seat at a selectable pressure. Contact between the needle-housing structure and the valve seat is prevented by an annular protrusion in the bore. Conduit means through the valve body, connectable to the flow line, permits passage of the flow-line fluid into the needle-housing structure. A cylindrical needle is disposed coaxially within the needle-housing structure, and is urged toward the valve seat by a spring located in the needle-housing structure. When the pressure of the flow-line fluid entering the needle-housing structure exceeds the selected pressure urging the needle-housing structure toward the valve seat, the needle-housing structure assumes a position at which the needle remains spaced apart from the valve seat.

Abstract: A damper for use with a high pressure pumping system, such as a liquid chromatography system, which incorporates a reciprocating pump. The device is a generally enclosed canister including an internally formed flow volume. Inlet and outlet passages through the canister communicate with the flow volume, the inlet passage being connectable to receive the high pressure flow. A compressible body, e.g. of Teflon is positioned in the flow volume. The dimensions of the body are slightly smaller than those of the surrounding volume, whereby the high pressure flow passing between the inlet and outlet flows through the space between the body and the internal canister walls. The compression and decompression of the body in response to the pulsations in the flow dissipate the energy carried by the pulses, thereby damping same.

Abstract: A high pressure liquid chromatography system including a reservoir for a liquid mobile phase, an LC column and detector, a high pressure reciprocating pump for enabling flow from said reservoir through the column, and a positively actuated inlet valve for controlling flow from the reservoir to the pump chamber. The pump is driven by motor means, such as a stepping motor, directly coupled thereto; and the inlet valve is actuated by the power train of the motor and pump, e.g., by an eccentric carried by the pump crank shaft. The pump piston is similarly driven by an eccentric, the pump and inlet valve eccentrics being angularly displaced in their respective positions at the crank shaft, as to delay opening of the inlet valve for a predetermined period following a pump stroke, so as to enable decompression of the liquid in the pump chamber.

Abstract: A liquid chromatography system including a liquid chromatography column, first and second reservoirs for solvents to be utilized as the mobile phase, reciprocating pumping means for flowing the solvents through the column, and motor means for driving the pump through successive pumping cycles including pump and fill subcycles. First and second solenoid-actuated proportioning valves are positioned at the low pressure side of the pump, i.e. between the first and second reservoirs and the pump inlet. Gradient setting means are provided for setting a preselected solvent proportion to be used over a time period. Means responsive to the gradient setting opens one of the said proportioning valves during a predetermined portion of the fill subcycle. The valves are actuated in complementary fashion with respect to opening and closing; hence the fill subcycle is divided between flow proceeding from the first and second valves in accordance with the gradient setting.

Abstract: A liquid chromatography system, including a reservoir for a liquid mobile phase, a liquid chromatography column, reciprocating pumping means for pumping the mobile phase through the column, and motor means for driving the pumping means through successive reciprocation cycles. Means are provided for controlling the rotational speed of the motor throughout the reciprocation cycle of the pump, so as to provide preselected average rotational speeds over predetermined subintervals of each successive reciprocation cycle. Application of the control cycle is synchronized with the pump cycle so that the said speed control is properly applied over each successive reciprocation cycle.