Patent ID: 8029250
Filing Date: 2011-10-04
Classification: A61M,F03G,F04B,F05C,G01F

Abstract:
1. A pump comprising: a chamber; a piston within the chamber; a shape memory element that drives the piston from a first position to a second position, such that a fluid is drawn into the chamber when the piston is moved from the first position to the second position; a stroke length equal to the maximum distance of travel between the first position and the second position; a position sensing mechanism that senses a position of the piston including the first position and the second position, wherein the position sensing mechanism is configured to detect a fault when the piston does not travel the entire stoke length; a positioning system configured to move the piston in increments less than the stroke length toward at least one of the first position and the second position when the fault is detected, resulting in a partial piston stroke; and a processor programmed to increase a frequency of the piston movement, wherein the frequency is based on the partial piston stroke, wherein the processor is further programmed to measure a first time period, wherein the first time period is the time it takes for the piston to complete the partial piston stroke, to compare the first time period to a predetermined time period, and to determine that the pump is not primed when the first time period is below the predetermined time period by a threshold amount of time.