Fluid delivery system and method

An infusion system comprising:

• a first flow sensor that receives a first fluid from a first fluid source and delivers the first fluid to a tube attached to a human subject, the first flow sensor comprising a first freestanding tube portion through which the first fluid flows, first means for vibrating the first freestanding tube portion at a resonant frequency thereof that varies with the density of the first fluid flowing therethrough, first means for sensing movement of the first freestanding tube portion, the first movement-sensing means producing a first output signal based on the resonant frequency of the first freestanding tube portion and a second output signal based on the degree of twist of the first freestanding tube portion, the Coriolis effect causing the first freestanding tube portion to twist while being vibrated at resonance, the first freestanding tube portion exhibiting a degree of twist that varies with the mass flow rate of the first fluid flowing therethrough;
• a plurality of second flow sensors arranged in fluidic parallel, the second flow sensors delivering at least a second fluid from at least a second fluid source to the tube, each of the second flow sensors comprising a second freestanding tube portion through which the second fluid flows, second means for vibrating the second freestanding tube portion at a resonant frequency thereof that varies with the density of the second fluid flowing therethrough, second means for sensing movement of the second freestanding tube portion, the second movement-sensing means producing a first output signal based on the resonant frequency of the second freestanding tube portion and a second output signal based on the degree of twist of the second freestanding tube portion, the Coriolis effect causing the second freestanding tube portion to twist while being vibrated at resonance, the second freestanding tube portion exhibiting a degree of twist that varies with the mass flow rate of the second fluid flowing therethrough;
• means for measuring elapsed time during which the first and second fluids have flowed through the first and second flow sensors;
• and
• means for stopping flow of the first and second fluids through the first and second flow sensors, respectively, in response to either of the first and second output signals from the first and second movement-sensing means, wherein the flow-stopping means is operable to stop the flow of the second fluid if, based on the elapsed time determined by the time-measuring means and the second output signal of the second movement-sensing means, a specified amount of the second fluid has passed through any one or more of the second flow sensors.

A fluid delivery method comprising the steps of:

• flowing a fluid through a freestanding tube portion;
• vibrating the freestanding tube portion at a resonant frequency thereof that varies with the density of the fluid flowing therethrough, the Coriolis effect causing the freestanding tube portion to twist while being vibrated at resonance, the freestanding tube portion exhibiting a degree of twist that varies with the mass flow rate of the fluid flowing therethrough;
• sensing movement of the freestanding tube portion and producing a first output signal based on the resonant frequency of the freestanding tube portion and a second output signal based on the degree of twist of the freestanding tube portion;
• measuring elapsed time during which the fluid has flowed through the freestanding tube portion;
• and
• stopping flow of the fluid through the freestanding tube portion in response to either of the first and second output signals, wherein flow of the fluid is stopped if, based on the elapsed time and the second output signal, a specified amount of the fluid has passed through the freestanding tube portion.

An infusion method comprising the steps of:

• flowing a first fluid from a first fluid source through a first flow sensor to a tube attached to a human subject, the first flow sensor comprising a first freestanding tube portion through which the first fluid flows, first means for vibrating the first freestanding tube portion at a resonant frequency thereof that varies with the density of the first fluid flowing therethrough, first means for sensing movement of the first freestanding tube portion, the first movement-sensing means producing a first output signal based on the resonant frequency of the first freestanding tube portion and a second output signal based on the degree of twist of the first freestanding tube portion, the Coriolis effect causing the first freestanding tube portion to twist while being vibrated at resonance, the first freestanding tube portion exhibiting a degree of twist that vanes with the mass flow rate of the first fluid flowing therethrough;
• flowing a second fluid from a second fluid source through a second flow sensor to the tube, the second flow sensor comprising a second freestanding tube portion through which the second fluid flows, second means for vibrating the second freestanding tube portion at a resonant frequency thereof that varies with the density of the second fluid flowing therethrough, second means for sensing movement of the second freestanding tube portion, the second movement-sensing means producing a first output signal based on the resonant frequency of the second freestanding tube portion and a second output signal based on the degree of twist of the second freestanding tube portion, the Coriolis effect causing the second freestanding tube portion to twist while being vibrated at resonance, the second freestanding tube portion exhibiting a degree of twist that varies with the mass flow rate of the second fluid flowing therethrough;
• measuring elapsed time during which the first and second fluids have flowed through the first and second flow sensors, respectively;
• and
• stopping flow of the first and second fluids through the first and second flow sensors, respectively, in response to either of the first and second output signals from the first and second movement-sensing means, wherein the flow of the second fluid is stopped if, based on the elapsed time determined by the time-measuring means and the second output signal of the second movement-sensing means, a specified amount of the second fluid has passed through the second flow sensor.