WO1990006779A1

WO1990006779A1 - Jacket control for steam sterilizers

Info

Publication number: WO1990006779A1
Application number: PCT/US1989/005247
Authority: WO
Inventors: Ronald P. Krahe
Original assignee: American Sterilizer Company
Priority date: 1988-12-22
Filing date: 1989-11-20
Publication date: 1990-06-28
Also published as: ES2019511A6; CA2005768A1

Abstract

A steam sterilizer having an improved jacket control comprises a steam chamber for receiving materials to be sterilized. A steam jacket substantially surrounds the steam chamber. Means are provided for admitting steam into the jacket. A chamber valve is connected between the steam jacket and the chamber for controllably admitting steam into the chamber from the jacket. A control circuit controls the operation of the means for admitting steam and the chamber valve such that the pressure in the steam chamber follows the pressure in the steam jacket.

Description

JACKET CONTROL FOR STEAM STERILIZERS

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention is directed generally to steam sterilizers and more particularly to steam sterilizers having a steam jacket surrounding the sterilization chamber.

Description of the Prior Art

Currently available steam sterilizers which have a steam jacket surrounding the steam chamber are provided with piping which separately provides steam to both the chamber and the steam jacket. On many commercially available units,^' a manually adjustable steam regulator (hi-low valve) is used to control the steam pressure in the steam jacket. It is the operator's responsibility to manually set the jacket pressure before a cycle is run. For example, if a 270-F (134-C) cycle is to be run, the pressure regulator must be turned to the "hi" position, which is about thirty four psig. If a 250~F (121-C) cycle is to be run, the pressure regulator must be turned to the "lo" position, which is about twenty one psig. If any other lower temperature cycle is to be run, a service adjustment is required which entails repositioning a lower stop ring of the pressure regulator. Thereafter, the operator must manually adjust the regulator by referring to the jacket pressure gauge.

Although currently available steam sterilizers function extremely well and are very reliable, an operator's failure to properly set the pressure regulator can lead to problems such as superheating. Additionally, it is an inconvenience to require a service call each time a lower temperature cycle is to be run. Thus, the need exists for a steam sterilizer having an improved jacket control.

SUMMARY OF THE INVENTION The present invention is directed to a steam sterilizer having an improved jacket control comprising a steam chamber for receiving materials to be sterilized. A steam jacket substantially surrounds the steam chamber. Means are provided for admitting steam into the jacket. A chamber valve is connected between the steam jacket and the chamber for controUably admitting steam into the chamber from the jacket. A control circuit controls the operation of the means for admitting steam into the chamber and the chamber valve such that the pressure in the steam chamber follows the pressure in the steam jacket.

According to one embodiment of the present invention, the means for admitting steam into the jacket includes a pressure transducer and a steam to jacket valve. According to another embodiment of the present invention, the means for admitting steam into the jacket includes a fixed pressure regulator and a steam to jacket valve.

The present invention also includes a method of operating a steam sterilizer having an improved jacket control which is comprised of the steps of operating a jacket valve to control the admission of steam to a steam jacket surrounding a steam chamber adapted to receive materials to be sterilized and operating a chamber valve connected between the steam jacket and the steam chamber so as to control the admission of steam into the chamber from the jacket such that the pressure in the steam chamber follows the pressure in the steam jacket. According to one embodiment of the present invention, when a sterilization phase of a sterilization cycle is to be run, the chamber valve remains open while the jacket valve is opened and closed according to the dictates of the sterilization cycle. In that manner, the pressure in the chamber follows the pressure in the steam jacket.

The apparatus and method of the present invention provide a steam sterilizer in which the chamber pressure follows the pressure in the steam jacket. Because of that, liquid loads can be cooled faster, and other loads can be dried faster. Additionally, there is no need for operator adjustment of the pressure regulator prior to running a cycle. That eliminates superheating problems associated with improperly set pressure regulators. Finally, a cost savings can be effected by using a less costly fixed pressure regulator. Those and other advantages and benefits of the present invention will be apparent from the Description of a Preferred Embodiment hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS In order that the present invention may be easily understood and readily practiced, a preferred embodiment will now be described, by way of example only, in connection with the figures wherein:

FIG. 1 illustrates a jacket control for a steam sterilizer constructed according to the teachings of the present invention; and FIG. 2 is a graph illustrating the status of the two valves illustrated in FIG. 1 during a sterilization cycle. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT In FIG. 1, a steam sterilizer 10 is illustrated having a steam chamber 12 substantially surrounded by a steam jacket 14^' in a known manner. The steam chamber 12 is capable of receiving materials which are to be subjected to a sterilization or decontamination cycle.

Steam is admitted into the jacket 14 through a fixed pressure regulator 16 and a steam to jacket valve 18. The steam to jacket valve 18 may be a solenoid type of valve which is under the control of a microprocessor based control circuit 20. Steam is controUably admitted from the steam jacket 14 into the chamber 12 through a chamber valve 22. The chamber valve 22 is also under the control of the control circuit 20.

The control circuit 20 may be programmed in a known manner to carry out a sterilization cycle made up of several phases as illustrated in FIG. 2. In order fo the sterilizer 10 to perform such a sterilization cycle, the control circuit 20 controls the status, i.e. opened or closed, of the steam to jacket valve 18 and the chamber valve 22. For example, the steam jacket 14 may be maintained at a pressure of thirty four psig during a standby phase, or at a higher pressure depending upon the pressure at which the sterilizer 10 can be safely run per ASME standards, by opening the steam to jacket valve 18 fro time t_n to time t.. During that time, the chamber valve 22 is closed. When the sterilization cycle is started, the steam to chamber valve 22 is opened to begin the conditioning purge. That valve remains open throughout the condition and sterilization phases, except as explained below under preva conditions. During the condition and sterilization phases, from time t to time t , the steam pressure to the jacket 1 and chamber 12 is controlled by the steam to jacket valve

18. During sterilization, that valve is opened and closed

(or otherwise controlled according to the desired cycle) t control both the jacket 14 and chamber 12 pressures and , temperatures. Such control may be based on signals input from known types of pressure and temperature sensors 24 an

26, respectively, which are input to the control circuit 20

During an exhaust/dry phase from time t to time t , the steam to jacket valve 18 is open and the steam to chamber valve 22 is closed. That provides some heat for drying. During a solution cooling exhaust phase, from time t4. to time t5._,' the steam to jacket valve 18 is closed while the steam to chamber valve 22 can be opened or closed. Tha reduces heating of the load from the inner jacket walls and speeds solution cooling with less liquid loss due to evaporation.

During a complete phase after time ₅, and before the load is removed from the chamber, the steam to jacket valve 18 may be kept closed to keep from reheating the load or degrading wrapping materials. The steam to chamber valve 2 can be opened or closed. After the chamber door is opened and the load is removed, the control circuit 20 returns to the standby condition.

The method and apparatus of the present invention eliminate the need for operator action with respect to adjusting the setting of the pressure regulator 16. Therefore, the pressure regulator 16 may be a fixed type of regulator thereby reducing equipment costs. Additionally, because of the present invention, the pressure within the chamber 12 closely follows the pressure of the jacket 14, thereby eliminating superheating problems.

Although not all steam sterilizers have the ability to perform a prevac or isothermal cycles, the present inventio can also work with such cycles. During prevac pulses, the steam to chamber valve 22 can remain open throughout the condition phase from time t to time t_, and the steam to jacket valve 18 can be used to control steam flow to both the jacket 14 and the chamber 12. The steam to chamber valve 22 would then be closed during an evacuate phase (not shown) and opened during a steam charge phase (not shown) . Such operation could reduce superheating of chamber steam from hot inner jacket walls. Alternatively, if superheating is not a problem, the steam to jacket valve 18 can remain open throughout conditioning, and the steam to chamber valve 22 can be used to control steam flow to the chamber, closed during an evacuation phase, and opened during a steam charge phase. That could reduce the additional time required to^' evacuate and recharge the jacket. According to another embodiment of the present invention, a pressure transducer 28 is provided in the jacket 14 which provides a signal input to the control circuit 20 representative of the pressure in the steam jacket 14. In that embodiment, when a cycle is run at a given temperature, the control circuit 20 will automaticall regulate the pressure in the steam jacket 14 to the appropriate value based on the cycle temperature and the reading from the transducer 28. Thus, the pressure regulator 16 can be eliminated in that embodiment. Additionally, the operator need not make any mand pair of lenses through which said intensified image passes after passing through one of said filters; and means associated with said cylinder for alternatively and repetitively directing said input image from each said lens of said first pair of lenses onto one of said filters as said filters are brought into alignment with said image intensifier, and for alternatively and repetitively directing said intensified image from said filters as said filters are brought into alignment with said t. All such modifications and variations are intended to be covered by this disclosure and the following claims.

Claims

What is claimed is:

1. A steam sterilizer having an improved jacket control, comprising: a steam chamber for receiving materials to be sterilized; a steam jacket substantially surrounding said steam chamber; means for admitting steam into said jacket; chamber valve means connected between said steam jacket and said chamber for controllable admitting steam into said chamber from said jacket; and control means for controlling the operation of said means for admitting and said chamber valve means such that the pressure in said steam chamber follows the pressure in said steam jacket.

2. The steam sterilizer of claim 1 wherein said means for admitting steam into said steam jacket includes a pressure transducer and a steam to jacket valve means.

3. The steam sterilizer of claim 1 wherein said means for admitting steam into said steam jacket includes a pressure regulator and a steam to jacket valve means.

4. The steam sterilizer of claim 3 wherein said control means opens and closes said jacket valve means during sterilization to control the pressure in said jacket and wherein said control means opens said chamber valve means during sterilization such that the pressure in said chamber follows the pressure in said steam jacket.

5. A steam sterilizer having an improved jacket control, comprising: a steam chamber for receiving materials to be sterilized; a steam jacket substantially surrounding said steam chamber; steam to jacket valve means connecting said steam jacket to a source of steam; pressure transducer means responsive to the pressure i said chamber; chamber valve means connecting said chamber to a sourc of steam; and control means for controlling the operation of said steam to jacket valve means and said chamber valve means in response to said pressure transducer means such that the pressure in said steam chamber follows the pressure in said steam jacket.

6. The steam sterilizer of claim 5 wherein said steam jacket is the source of steam for said chamber.

7. A method of operating a steam sterilizer having an improved jacket control, comprising the steps of: operating a jacket valve to control the admission of steam to a steam jacket surrounding a steam chamber adapted to receive materials to be sterilized; and operating a chamber valve connected between said steam jacket and said steam chamber so as to control the admissio of steam into said chamber from said jacket such that the pressure in said steam chamber follows the pressure in said steam jacket.

8. The method of claim 7 wherein said jacket valve and said chamber valve are opened to effect a conditioning phase.

9. The method of claim 8 wherein said jacket valve is opened and closed to effect a sterilization phase and wherein said chamber valve is opened during said sterilization phase such that the pressure .in said steam chamber follows the pressure in said steam jacket.