Flow metering apparatus for a fluid infusion system

Metering apparatus for use in conjunction with a fluid flow system for infusing fluids at an operator-selected rate into the human body, comprising:

• metering means including valving means, and a syringe-type pump in the flow system having a pump housing and a plunger mounted for reciprocative movement within the housing to provide in cooperation with the valve means alternate fill and pump strokes for establishing fluid flow through the system;
• actuator means including a motor responsive to applied stepping pulses for operatively engaging and reciprocatively driving said plunger;
• motor drive means for providing stepping pulses to said motor, said stepping pulses occurring at a first relatively high predetermined frequency to advance the plunger at a relatively rapid rate during each fill stroke, and at a second relatively low predetermined frequency to advance the plunger at the operator-selected flow rate during each pump stroke, the average flow through the flow system as a result thereof being less than the operator-selected rate as a result of the intervening fill strokes;
• and
• flow compensation means for increasing the frequency of said stepping pulses from said second predetermined frequency to a higher compensating frequency for a first predetermined compensation period immediately following each preceding fill stroke, and for a second predetermined compensation period immediately preceding each succeeding fill stroke, the intervening portion of each pump stroke being at said operator-selected rate, said compensation periods each comprising a substantial portion of a total compensation period during the pump stroke which compensates for the nonoccurrence of pumping action during a fill stroke, whereby the resulting average flow rate through the infusion system comprises the operator-selected rate.

Metering apparatus for use in conjunction with a disposable single-use fluid flow system of the type having valving means, and a syringe-type cassette pump having a pump housing and a plunger mounted for reciprocative movement within the pump housing to provide alternate fill and pump strokes for establishing in cooperation with the valving means fluid flow through the system for infusing fluids at an operator-selected rate into the human body, comprising:

• actuator station means for receiving and fixedly positioning the cassette pump;
• actuator means for operatively engaging and reciprocatively driving the plunger while positioned in said actuator station to provide fill strokes of relatively short duration, and pump strokes of relatively longer duration at the operator-selected flow rate, the average flow through the flow system as a result of the intervening fill strokes being less than the operator-selected rate;
• and
• flow compensation means for increasing the rate of each of said pump strokes from the operator-selected rate to a relatively higher compensation rate for a first predetermined compensation period immediately following each preceding fill stroke, and for a second predetermined compensation period immediately preceding each succeeding fill stroke, the intervening portion of each pump stroke being at the operator-selected rate, said compensation periods each comprising a substantial portion of a total compensation period during the pump strokes which compensates for the non-occurrence of pumping action during a fill stroke, whereby the resulting average flow rate through the flow system comprises the operator-selected rate.

Metering apparatus for use in conjunction with a disposable single-use fluid flow system of the type including valving means, and a syringe-type cassette pump having a pump housing and a plunger mounted for reciprocative movement within the pump housing to provide alternate fill and pump strokes for establishing in cooperation with the valving means fluid flow through the system for infusing fluids at an operator-selected rate into the human body, comprising:

• actuator station means for receiving and fixedly positioning the cassette pump;
• actuator means including a motor responsive to applied stepping pulses for operatively engaging and reciprocatively driving the plunger while positioned in said actuator station;
• motor drive means for providing stepping pulses to said motor, said stepping pulses occurring at a first relatively high predetermined frequency to advance the plunger at a relatively rapid rate during each fill stroke, and at a second relatively low predetermined frequency to advance the plunger at the operator-selected flow rate during each pump stroke, the average flow through the flow system as a result thereof being less than the operator-selected rate as a result of the intervening fill strokes;
• and
• flow compensation means for increasing the frequency of said stepping pulses from said second predetermined frequency to a higher compensating frequency for a first predetermined compensation period immediately following each preceding fill stroke, and for a second predetermined compensation period immediately preceding each succeeding fill stroke, the intervening portion of each pump stroke being at said operator-selected rate, said compensation periods each comprising a substantial portion of a total compensation period during the pump stroke which compensates for the nonoccurrence of pumping action during a fill stroke, whereby the resulting average flow rate through the infusion system comprises the operator-selected rate.