Self priming and evacuating liquid sterilizing system
Apparatus and method for providing a self priming, self evacuating, cyclicly operating system in which liquid is disposed in a closed, fluid tight heating chamber for sterilization. Only a single parameter, temperature, is monitored to accomplish a desired liquid SAL. A pair of valves are singly and sequentially opened and closed within four phases (steps) to provide for liquid displacement. Operation cycles through four phases which include opening an inlet valve for filling the heating chamber, heating liquid to a predetermined temperature at which the liquid is sterilized to the desired SAL, opening an outlet valve whereby internally generated pressure delivers sterilized liquid to a dispensing container and a delay for keeping valve opening separate.
1. A method for providing and operating a self priming, self evacuating, cyclicly operating, sterilizing apparatus which sterilizes a mass of liquid disposed within a fluid tight, valved chamber by raising the liquid mass to a predetermined critical temperature (CT), which is above the temperature level at which the liquid mass undergoes a state change from liquid to gas, to achieve a predetermined sterility assurance level (SAL), said method comprising the steps of:
providing:
the chamber comprising a liquid constraining volume wherein the mass of liquid is sterilized by being raised to the CT at which the predetermined SAL is achieved;
a pressurized source of the liquid mass to be sterilized, said source comprising a pressure by which liquid is communicated from said source into said chamber;
a liquid communicating pathway between said source and said chamber which comprises a first flow-interrupting normally closed valve;
a reservoir for receiving the so-sterilized liquid mass, said reservoir comprising a hydraulic pressure which is conducive to outlet flow from the chamber to the reservoir;
a fluid communicating pathway between said chamber and said reservoir which comprises a second flow-interrupting normally closed valve;
a heating component by which the liquid mass in said chamber is raised to the critical-sterilizing temperature (CT) consistent with achieving the predetermined SAL;
a temperature meter for measuring temperature within said chamber and for providing a measurable output thereof;
a power source for operating a control system, said power source comprising a power on/power off controller; and
a control system operable to sequencing of valve operation and, thereby, fluid displacement, via separate and distinct steps, as follows:
(a) step one: turning power on, opening said first valve thereby permitting a liquid mass to be displaced from said source into said chamber;
(b) step two: after a delay sufficient to permit the mass of liquid to fill said liquid constraining chamber, closing said first valve thereby heating said liquid mass toward the CT;
(c) step three: when said control system detects temperature of said meter has reached the CT, said control system opening said second valve thereby ending said liquid mass being limited to the liquid constraining volume of said chamber, as when said valves are closed, which results in a state change from liquid, therein, to a volumetrically expanding fluid mixture of liquid and gas, which provides a motive force which overcomes back pressure in said reservoir and, thereby, provides a motive force which displaces liquid and gas from the chamber into the reservoir, such state change and displacement resulting in a drop in measured temperature to a second control level temperature ending step 3 and proceeding immediately to step four; and
(d) step four: said control system then delaying further operation a predetermined period to thereby permit said second valve to fully close and, thereafter, recycling operation to (a) step one.
2. A method for providing and operating a self-priming, self-evacuating, cyclicly operating, sterilizing apparatus according to claim 1 wherein said liquid mass is water.
3. A method for providing and operating a self-priming, self-evacuating, cyclicly operating, sterilizing apparatus according to claim 1 wherein said power source is disposed within said chamber.
4. A method for providing and operating a self-priming, self-evacuating, cyclicly operating, sterilizing apparatus according to claim 1 wherein said control system is operable for determining apparatus failure modes and for removing power from said heating components for ceasing operation.