Piezoelectric fluid injector

Claim 1

Apparatus for injecting fluid into a patient at an average prescribed rate over a prolonged period of time comprising: carriage means defining a fluid chamber therein carrying fluid to be dispensed and an outlet from said fluid chamber connected to the patient; a piston slidably mounted in said fluid chamber for forcing fluid from said outlet as said piston is moved toward said outlet; an electrical power supply; electrically operated driving means for moving said piston toward said outlet when said electrically operated driving means is connected to said power supply, said electrically operated driving means constructed and arranged to move said piston only a prescribed distance toward said outlet each time said electrical power supply is connected to said electrically operated driving means regardless of the length of time said electrical power supply is connected to said electrically operated driving means, said piston forcing a volume of the fluid from said outlet much less than the total volume of fluid to be injected over the prolonged period of time each time said piston is moved said prescribed distance; and control means for selectively connecting said electrical power supply to and disconnecting said electrical power supply from said electrically operated driving means at a rate such that fluid is injected into the patient at the desired average rate over the prolonged period of time so that, if said control means fails so as to continuously connect said electrical power supply to said electrically operated driving means, said piston will be moved only said incremental prescribed distance toward said outlet to prevent overdosing the patient, said driving means including a driving member exhibiting a piezoelectric effect and linkage means connecting said driving member to said piston so that the change in volume experienced by said driving member when said control means connects said power supply to said driving member moves said piston toward said outlet.