Load conditioning control apparatus for steam sterilization

• US 4,203,947 A
• Filed: 02/02/1979
• Issued: 05/20/1980
• Est. Priority Date: 11/11/1977
• Status: Expired due to Term

• Current Assignee: American Sterilizer Company (Steris Corporation)
• Original Assignee: American Sterilizer Company (Steris Corporation)
• Inventors: Young, Jack H., Halleck, Frank E.
• Primary Examiner(s): Richman, Barry S.
• Application Number:
  US06/008,925
• Time in Patent Office: 473 Days
• Field of Search: 422/26, 422/110, 422/111, 422/114, 422/116, 422/295, 422/34, 422/27
• US Class Current: 422/114
• CPC Class Codes: A61L 2/07 Steam
• CPC Class Codes: A61L 2/24 Apparatus using programmed or automatic operation

Abstract

Methods and apparatus for steam sterilization in which goods are conditioned by removing air and heating to a desired temperature in sealable chamber. Pressure change in the chamber is monitored and employed to control conditioning. The goods are subjected to a plurality of controlled cyclic pressure pulses below a predetermined supra-atmospheric pressure level by alternate evacuation and vapor pressurization of the chamber. The cyclic pressure pulsing is made responsive to load characteristics which are determined by monitoring pressure change rate in the chamber. In a specific embodiment, air is flushed from the chamber initially by the injection of steam simultaneously with evacuation; the evacuation phase of each pulse continues until both a predetermined time has lapsed and a predetermined vacuum level has been attained; and, the steam pressurization phase of each pulse is continued until a fixed pressure related to sterilization temperature is reached.

Claims

1. Apparatus for conditioning materials forming a load within a sealable sterilizing chamber capable of operation at pressure above atmospheric for steam sterilization without requiring selection of quantity or characteristics of the materials, such conditioning including removal of air, moistening the load, and heating of the load to a desired temperature in preparation for sterilization, the apparatus comprising:

evacuation means operable to evacuate the sterilizing chamber,

vapor injection means operable to inject a vapor having a transferrable latent heat into the sterilizing chamber,

and control means controlling operation of the evacuation means and the vapor injection means to provide cyclic pulsing of chamber pressure to provide a plurality of cyclic pulses of chamber pressure below an upper pressure level related to desired temperature for sterilization,

each cyclic pulse including an evacuating phase during which pressure in the chamber is decreasing during operation of the evacuation means and a vapor injecting phase during which pressure within the chamber is increasing during operation of the vapor injecting means,

pressure sensing means monitoring chamber pressure change during cyclic pulsing,

timing means for measuring the time of the evacuation phase of the cyclic pulses, and

such control means including means responsive to such indication of chamber pressure and evacuation time for determining the rate of evacuation of the chamber and for automatically controlling such cyclic pulsing in response to the determined chamber evacuation rate to complete the conditioning of the load.

2. Apparatus for conditioning materials forming a load within a sealable sterilizing chamber capable of operation at pressure above atmospheric for steam sterilization without requiring selection of quantity or characteristics of the materials, such conditioning including removal of air and heating of the load to a desired temperature for sterilization, the apparatus comprising:

evacuation means operable to evacuate the sterilizing chamber,

steam injection means operable to inject steam into the sterilizing chamber,

means operating the evacuation means and the steam injection means to provide cyclic pulsing of chamber pressure including a plurality of cyclic pulses of chamber pressure below an upper pressure level related to desired temperature for sterilization,

each cyclic pulse including an evacuating phase during which pressure in the chamber is decreasing during operation of the evacuation means and a steam injecting phase during which pressure within the chamber is increasing during operation of the steam injecting means,

pressure sensing means monitoring chamber pressure change during a cyclic pulse,

timing means for measuring the time of each evacuation phase, and

pulse cycle control means for controlling such cyclic pulsing responsive to such indication of chamber pressure and evacuation time,

such control of cyclic pulsing including control of the means operating the evacuation means to continue each evacuation phase of the cyclic pulse until both a predetermined time has lapsed and a predetermined vacuum level is reached in the sterilizing chamber and control of the steam injecting means during cyclic pulsing to heat the load to the desired sterilization temperature and to remove air from throughout the sterilizing chamber irrespective of load size and load characteristics.

3. The apparatus of claim 2 including

means for initiating load conditioning by injecting steam into the chamber while simultaneously evacuating the chamber to flush air from the chamber.

4. An apparatus for conditioning and sterilizing goods within a sterilizing chamber capable of operating at internal pressures above atmospheric for steam sterilization following conditioning of a load of goods in the chamber, the conditioning including the removal of air from the chamber and heating the load to a desired temperature, the apparatus comprising,

steam injector means having a first electrically operated valve means operable between an open and a closed position to respectively pressurize the chamber and stop the flow of steam into the chamber,

evacuating means including suction means and second electrically operated valve means operable between an open and a closed position to respectively connect the chamber to the suction means to evacuate the chamber and disconnect the chamber to stop the evacuation,

the first and second electrically operated valve means being operable to alternately evacuate and inject steam into the chamber to subject a load of goods in the chamber to a plurality of cyclic pressure pulses below an upper pressure level corresponding to the desired sterilization temperature,

control means controlling operation of the steam injection means and the evacuation means, the control means including,

timing means for timing the evacuation of the chamber following each operation of the first electrically operated valve to the open position,

pressure sensing means sensing the pressure within the chamber,

means responsive to both the timing means and the pressure sensing means for maintaining the second electrically operated valve in the open position upon each opening thereof until both a predetermined time has lapsed and a predetermined lower pressure has been attained in the chamber,

means for closing the second electrically operated valve means and opening the first electrically operated valve means to inject steam into and pressurize the chamber after the passing of the predetermined time and the attainment of the predetermined lower pressure,

means responsive to the pressure sensing means for closing the first electrically operated valve means and opening the second electrically operated valve means to again evacuate the chamber, the control means being operable to repeat the evacuating and pressurization phases of the cyclic pressure pulses, and

counting means operable to terminate the cyclic pressure pulsing after a predetermined number of such pulses.

5. The invention as defined in claim 4 wherein the control means further comprises means for initially opening both the first and second electrically operated valve means to simultaneously admit steam into the chamber and evacuate the chamber to thereby purge air from the chamber.

6. The invention as defined in claim 5 further comprising means for closing only the first electrically operated valve means after a predetermined time following the initial opening of both the first and second electrically operated valve means to thereby commence the evacuation phase of the first cyclic pressure pulse.