Load conditioning control method for steam sterilization

Claim 1

A method of conditioning and steam sterilizing materials within a sealable chamber capable of operation at other than atmospheric pressure, such materials forming a load without requiring preselection of load size or material characteristics, such conditioning including removal of air from the load and heating the load to a desired temperature related to sterilizing temperature without requiring sensor contact with load materials, the method comprising the steps of loading such materials into the chamber and sealing the chamber, subjecting the chamber and the materials therein to a plurality of cyclic pressure pulses below an upper pressure level related to the desired sterilization temperature by injecting a condensable vapor having transferable latent heat into the chamber and evacuating the chamber, each cyclic pressure pulse including an evacuating phase during which pressure in the chamber is decreasing and a vapor injecting phase during which the pressure is increasing, measuring the change of chamber pressure in relation to time lapse during at least a portion of the evacuating phase and employing the measured change as an indication of chamber evacuation rate during the evacuating phase, employing the indicated chamber evacuation rate of the evacuation phase to automatically control the termination of that evacuation phase and initiate the succeeding cyclic pressure pulse pressurization phase to complete load conditioning by removing air from the load and heating the load to the desired temperature, and then introducing and maintaining sterilizing steam in the chamber at a pressure level to maintain the desired temperature for a time sufficient to affect desired sterilization of the material in the chamber.

Claim 2

A method of conditioning and steam sterilizing materials within a sealable chamber capable of operation at other than atmospheric pressure, such materials forming a load without requiring preselection of load size or material characteristics, such conditioning including removal of air from the load and heating the load to a desired temperature related to sterilizing temperature without requiring sensor contact with load materials, the method comprising the steps of loading such materials into the chamber and sealing the chamber, subjecting the chamber and the materials therein to a plurality of cyclic pressure pulses below an upper pressure level related to the desired sterilization temperature by injecting a condensable vapor having transferable latent heat into the chamber and evacuating the chamber, each cyclic pressure pulse including an evacuating phase during which pressure in the chamber is decreasing and a vapor injecting phase during which the pressure is increasing, measuring the change of chamber pressure in relation to time lapse during at least a portion of the evacuating phase and employing the measured change as an indication of chamber evacuation rate during the evacuating phase, employing the indicated chamber evacuation rate of the evacuation phase to automatically control the termination of that evacuation phase and initiate the succeeding cyclic pressure pulse pressurization phase to complete load conditioning by removing air from the load and heating the load to the desired temperature, and then introducing and maintaining sterilizing steam in the chamber at a pressure level to maintain the desired temperature for a time sufficient to affect desired sterilization of the material in the chamber.

Claim 12

A method of steam sterilization comprising the steps of: sealing a load of materials to be sterilized within a sterilizing chamber capable of operation at pressure above atmospheric and at a desired temperature for sterilization, the method comprising the steps of: subjecting the chamber and the load to a plurality of cyclic pressure pulses below an upper pressure level related to the desired sterilization temperature by evacuating the chamber and injecting steam into the chamber, each cyclic pressure pulse including an evacuating phase during which pressure in the chamber is decreasing and an injecting phase during which the pressure in the chamber is increasing, controlling the evacuation of the chamber and the injection of steam into the chamber during cyclic pressure pulsing to (a) continue each evacuation phase until both a predetermined time has lapsed and a predetermined low pressure level is reached in the chamber, then (b) terminate the evacuation phase and initiate and continue an injection phase until the chamber pressure is substantially equal to the upper pressure level, (c) terminate the injection phase at the upper pressure level and commence the evacuation phase of the next cyclic pressure pulse, and (d) repeat the controlled evacuating and injecting phases until the chamber and load have been subjected to a predetermined number of cyclic pressure pulses to heat the load to the desired temperature and remove air from throughout the chamber irrespective of the size of characteristics of the load in the chamber, and maintaining the pressure in the chamber at the upper pressure level corresponding to the desired sterilizing temperature for a time interval sufficient to affect sterilization following termination of the pressurizing phase of the final cyclic pressure pulse.

Claim 13

A method of steam sterilization comprising the steps of: sealing a load of materials to be sterilized within a sterilizing chamber capable of operation at pressure above atmospheric and at a desired temperature for sterilization, the method comprising the steps of: subjecting the chamber and the load to a plurality of cyclic pressure pulses below an upper pressure level related to the desired sterilization temperature by evacuating the chamber and injecting steam into the chamber, each cyclic pressure pulse including an evacuating phase during which pressure in the chamber is decreasing and an injecting phase during which the pressure in the chamber is increasing, controlling the evacuation of the chamber and the injection of steam into the chamber during cyclic pressure pulsing to (a) continue each evacuation phase until both a predetermined time has lapsed and a predetermined low pressure level is reached in the chamber, then (b) terminate the evacuation phase and initiate and continue an injection phase until the chamber pressure is substantially equal to the upper pressure level, (c) terminate the injection phase at the upper pressure level and commence the evacuation phase of the next cyclic pressure pulse, and (d) repeat the controlled evacuating and injecting phases until the chamber and load have been subjected to a predetermined number of cyclic pressure pulses to heat the load to the desired temperature and remove air from throughout the chamber irrespective of the size of characteristics of the load in the chamber, and maintaining the pressure in the chamber at the upper pressure level corresponding to the desired sterilizing temperature for a time interval sufficient to affect sterilization following termination of the pressurizing phase of the final cyclic pressure pulse.