JPS643503B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to reliable, skilled and precisely monitored steam sterilization involving removal of air and heating of the items to be sterilized. In particular, the present invention relates to automated sterilizer control that conditions the charge with optimal efficiency of time and energy.

Steam sterilization requires contact of the steam with all parts of the charge to be sterilized (Health Sciences, 2nd edition, 3rd printing, Charles C., Springfield, Illinois).
“Principles and
Methods of Sterilization,” pages 110-114). Therefore, proper conditioning of a charge containing fabric eliminates air pockets and thus prevents the charge from filling throughout its volume. In order to heat an object, it is necessary to substantially completely remove air from the interstices of the cloth.

Conditioning non-hermetically sealed charges in conventional steam sterilization has generally relied on high pre-vacuum treatments and pulsing of steam.
High prevacuum treatment uses a vacuum as high as a few millimeters of Hg to substantially completely remove air from the charge prior to introducing steam. This approach is expensive, both in equipment and operation, as it requires high power vacuum pumping equipment and the entire system must be of high vacuum integrity. Also, especially when using cloth foil type charges, considerable time is required to obtain the high vacuum levels used.

Various water vapor pulse generation methods have been taught (see above).
Health Science, “Principles and Methods of
Sterilization” pages 150-152; U.S. Patent No.
3,409,389; and US Pat. No. 3,494,725), examples of which are supra-atmospheric water vapor pulsing, sub-atmospheric water vapor pulsing, and combinations of supra-atmospheric and sub-atmospheric pulsing. the above
Health Science, “Principles and Methods of
Sterilization”, page 151 states: “The time required for a pulse-generating system to heat the charge to sterilization temperature is a function of the number of pulses and the time spent on each pulse. The effectiveness of the pulse, or in other words the number of pulses required, in turn depends on the amplitude or excursion of the pulse and the ratio of the maximum and minimum absolute pressure of each pulse.The time spent on the pulse is , is a function of the rate of delivery and release of steam and the pressure of maximum and minimum pulse generation with respect to atmospheric pressure.'' In the past, the conditioning portion of the steam cycle has been the most difficult to encounter in a particular sterilizer. based on the requirements for heating the normal charge. In practice, the sterilizer was preset to perform the most difficult conditioning cycle and heat the charge, ignoring the characteristics and size of the charge to be sterilized. In water vapor pulse generation methods, timer controls and pressure controls that function in a fixed manner are based on fixed pulse durations and fixed pressure excursions. Such an approach is useful when using fixed time cycles to sterilize partial charges or charges containing minimal fabric, and when using fixed pressure cycles to sterilize complete charges. cycle may be insufficient. Operator charge pre-judgment and operator conditioning cycle selection or monitoring of charge conditioning as an alternative to the cycles in which it is most difficult to heat the charge. For this purpose, there is the use of conditioning sensors (eg temperature sensors) which are placed manually within the charge. Such alternative measures require operator steps and/or judgment and therefore introduce oversights and errors that good hospital practice attempts to avoid.

The present invention is a unique automated and precise conditioning control that provides charge monitoring without placing a charge sensor in contact with the charge and without requiring operator prejudgment. provide ideas. The present invention evaluates the charge by the rate of change of pressure during cyclic pulsing to provide reliable and complete conditioning while saving time and energy. The ideas and methods of the present invention can be applied to any standard size of sterilizer in commercial use and provide complete conditioning to facilitate the desired sterilization in the shortest implementation time and lowest vacuum level. provide.

Partial or minimal fabric loads present the greatest difficulty in automatically obtaining adequate air removal and complete conditioning. For example, with a single cloth foil charge, the pressure in the chamber will drop rapidly, so if the evacuation is stopped at a fixed vacuum level, any air adsorbed or adhered to the cloth foil will be adequately removed. Therefore, proper exposure to vacuum may not be possible. Therefore, fixed pressure variations during pulsing may not provide the desired effectiveness or efficiency of a reasonable number of pulses when working with all types of charges. With a full cloth foil charge, the pressure in the chamber will drop slowly, so the desired vacuum level will depend on the fixed evacuation time when evacuation is stopped.
Unreachable.

The present invention enables automated and precise conditioning control without requiring operator preliminary judgment about the charge and without sensor contact with the charge. Provide data showing the characteristics of The present invention teaches the use of the slope of the drop curve during cyclic pulses to evaluate the charge. The particular method taught balances the measurements of the rate of descent, which provides the control logic with functional inputs for the necessary parameters for proper conditioning of the charge. In this way, suitable air removal vacuum exposure automatically and reliably provides effective and efficient conditioning of both partial and complete fabric charges. It can be provided with sex.

Cyclic pulsing of conditioning is provided by alternating chamber evacuation and steam pressurization. Since the purpose is to heat the charge, the steam should transfer high latent heat upon condensation. Water vapor is the most commonly used condensable vapor with transferable latent heat, but other vapors such as organic solvents, alcohols, etc.
Ketone and ether vapors can be used in combination with water vapor. During the evacuation portion of the cyclic pulse, the slope of the draw-down curve is used to
Accurate evaluation of the characteristics of the charge can be made which allows automatic control of the response of the charge. draw·
The slope of the down curve can be obtained by measuring the change in chamber pressure versus time. Charge contact monitors are not required; data can only be obtained by measuring chamber pressure and time;
That is, the data is obtained by reliable measurements under the harsh conditions of the sterilizer environment.

The ideas of the present invention include the critical analysis of air removal for proper charge conditioning for steam thermal sterilization. That is, the air must be removed before water vapor can penetrate and condense and heat the charge. However, what is so unique about the present invention is the realization of the interrelationship of the properties associated with the various fabrics for the properties of the charge. For example, the percentage of cloth foil in the charge, chamber volume utilization, and packing method all have effects related to cloth foil. This effect appears as a compound effect, which most closely characterizes the charge for the purpose of proper control of the conditioning cycle, without the use of sensors actually in contact with the charge. This combined effect of the properties associated with the fabric of a particular charge is most evident during evacuation of the chamber, and in measuring the rate of pressure change between selected portions of such evacuation. It has thus been found that it is most accurately determined and related to the conditioning of the charge.

In the conditioning of cloth foil type charges, it has been found that a functional relationship exists between the slope of the pressure curve of the exhaust phase and the composite properties of the charge. Also, the gradient of the exhaust phase curve and the perfect combination of cloth foil and heavy cargo (hardgoods)
It has been determined that a functional relationship exists between the percentage of cloth foil in the charge or the fraction of the charge occupied by cloth foil in the complete or partial charge. It was done. Moreover, these two functional relationships correspond closely to each other, so that for control purposes, the composite properties of any charge or partial charge are compared to the complete charge made up of cloth foils. It was decided that it could be related to or thought of as a percentage of something.

A functional relationship between the slope of the pressure-time curve of the evacuation phase and the percentage of fabric can be established experimentally for any sterilizer using a given evacuation system. This relationship can then be used to relate the slope of any such curve to the percentage of fabric, which is then used to determine the appropriate conditioning cycle and/or for any charge. Alternatively, the pressure-time parameters of the exhaust phase of the conditioning cycle can be selected.
For example, a curve representing this functional relationship can be obtained by plotting the percentage of fabric foil against the slope of the pressure-time curve of the exhaust phase of a charge having various known percentages of fabric. Can be established. By monitoring the conditioning of the test charge using charge contact sensors and measurements using known test methods, a curve representing the functional relationship is established and the conditioning You can determine the pressure and time requirements for.

The experimentally established functional relationships can be provided as program inputs to the control logic for the sterilizer. The control logic uses this input to automatically control the conditioning of the charge.
It can include a computer or microprocessor. To accomplish this, the monitored time and pressure inputs to the control logic can be used to calculate the slope of the pressure-time curve of the exhaust phase, which can be compared to the functionally related program inputs to determine the condition. Determine the required cycle and/or pressure-time parameters. This information can also be used in other phases of the entire sterilization cycle, e.g.
It can be used during drying that the cloth foil content of the charge has a direct bearing on the required drying time.

Minimum cloth-foilized charges do not require very long or very high vacuum treatments for air removal during conditioning because the pressure drop within the chamber is very rapid for such charges. Sometimes. Conversely, a relatively low pressure drop within the chamber containing the fabric charge will lengthen the vacuum exposure, so that lower vacuum levels will provide adequate air removal. For example, for a complete cloth load in a standard 36 inch sterilizer, up to 5 minutes or more of evacuation time may be required to bring the pressure in the chamber to a vacuum of 10 inches Hg; For the smallest cloth load in the same sterilizer, a vacuum of 10 inches Hg will be reached in less than 1 minute.

Conditioning can be controlled according to the invention by controlling time or pressure excursions, although a combination of both can also be used. For example, a time-minimum cloth foil charge, such as a material that requires less than 1 minute to reach a vacuum of 10 inches Hg during evacuation,
and the pressure can be used to control the exhaust phase of the charge where the slope of the exhaust pressure-time curve exhibits a high percentage of cloth flakes. This method does not require the use of complex and expensive vacuum measurement equipment that can provide an analog output.

Pressure and time measurements can also be used directly for control without fixing either value. In certain embodiments, a minimum time and level of exhaust is established for each cyclic pulse. During the cyclic pulses, only the upper pressure level and eventually the upper temperature level have a preselected or fixed value. Evacuation time and lower pressure level can be varied in a controlled manner.

Because of the data available in use of the teachings of the present invention, conditioning cycles can be optimized and the need for high vacuum levels can be eliminated.
Minimizing vacuum power requirements makes an important contribution in allowing the use of effective, more economical, and less complex ejector devices in place of vacuum pumps. Both initial costs and operating power requirements are reduced. This minimum contribution to the vacuum force requirement can be increased by flushing air from the chamber prior to cyclic pulsing. Such early addition of steam increases the efficiency of the ejector device due to air removal and steam disintegration, and also contributes to rapid and efficient heating of the charge.

Other aspects, contributions and advantages of the invention will be described with reference to the accompanying drawings.

In accordance with one aspect of the invention, minimum evacuation time and minimum Both vacuum conditions must be satisfied during the evacuation portion of the pulse before evacuation of the chamber stops and pressurization of the cycle begins. For example, sterilizers of the type and size commonly used in hospitals are
Can be programmed to require an evacuation time of minutes and a vacuum level of at least 10 inches Hg. Under these conditions, chamber evacuation continues for 1 minute, ignoring the pumping speed and the vacuum level achieved. At the end of the preselected 1 minute time period, the chamber pressure is checked and if the vacuum is greater than or equal to 10 inches Hg, evacuation is stopped and pressurization begins immediately.

However, if the pumping speed is such that the vacuum level is less than 10 inches Hg at the end of one minute, the pumping will continue until this desired vacuum level is reached, regardless of time. be done. Thus, for large fabric charges, the evacuation phase of the pulse of the cycle can last for more than 4 minutes before the desired subatmospheric pressure is reached; For cloth foil charges, the pressure in the chamber can be reduced to a minimum level before the expiration of one minute. When a greater vacuum is achieved by continuing the evacuation for the predetermined time required for the minimum cloth charge,
As a result, the air within the charge will have an opportunity to escape and the pressure will become more even throughout the charge and chamber before steam pressurization.

The present invention can be practiced using conventional sterilizer chamber shapes and sizes. As shown in Figure 1,
The double-walled chamber construction, indicated generally at 10, includes an internal end-open container 12 which together with an end closure or door 14 forms a sterile chamber.
Container 12 is supported within an outer wall 18 that is spaced outwardly and surrounds a major portion of container 12. wall 18
The open end of the flange 20 connects to the adjacent end of the inner container 12.
2 to form a water vapor jacket 22 between the inner and outer walls.

Door 14 may be hinged or otherwise attached to one side of the open end of the duplex to facilitate opening and closing of chamber 16. A conventional lock assembly, such as a cam lock assembly including an actuating lever or wheel 24 and a locking cam 26, may be used for the door 14;
During the sterilization process, lock the door tightly and close chamber 1.
6 can be tightly sealed.

Jacket 22 and chamber 12 are connected separately for evacuation purposes, but are interconnected during feeding to provide certain benefits in charge control. A drain pipe 28 connects the jacket 22 to a water-cooled heat exchanger 29 which drains into a suitable drain. Heat exchanger 29 is supplied with cooling water which mixes with steam and hot condensate from the jacket to adjust the effluent temperature to a level acceptable for discharge to a conventional sewer drain. Steam trap 3 connected to drain pipe 28
0 removes condensate from jacket 22, while check valve 31 prevents possible backflow into the jacket through line 28.

The second drain pipe 32 is connected to the container 12 and the heat exchanger 2.
Connect between 9 and 9. A steam trap 33 and one-way check valve 34 connected to the drain pipe 32
regulates the flow of water vapor, condensate, or other fluid exiting chamber 16 through heat exchanger 29 . A thermometer 36 is mounted upstream of the steam trap 33 and adjacent the outer chamber wall 18 for regulating the supply of steam during sterilization.
The temperature of the water vapor flowing from the sterilization chamber 16 is measured.

A main steam supply line or conduit 37 connects a steam source, such as a boiler 38, to the steam jacket 22. A check valve 39, a solenoid operated shutoff valve 40, and a pressure regulator 42, in turn, are connected in the main steam line 37 to regulate the flow of steam into the jacket 22. Steam line 37 can have multiple branches (not shown) for supplying steam to multiple locations on the jacket. The pressure regulator 42 is connected to the water vapor trap 31
In conjunction with this, the pressure, and therefore the temperature, within the jacket 22 is maintained substantially constant.

Water vapor flows from the water vapor jacket 22 to the chamber 1.
Supply to 6. To achieve this, pipe 44
is connected to the outer wall 18 by connecting its inlet to the steam jacket and its outlet to the sterilization chamber 1.
Connect to the inside of 6. A solenoid operated valve 45 is connected in pipe 44 to regulate flow from the jacket to the sterilization chamber. Providing water vapor from the jacket to the chamber avoids many of the problems of poor quality water vapor often encountered in sterilizer operation. Condensate etc. are collected in the jacket and are finally discharged from the bottom through the drain pipe 28, so that only substantially saturated water vapor enters the chamber 16.

Evacuation of the chamber is accomplished through an evacuation conduit 46 which connects to the drain line 32 upstream of the steam trap 33. The conduit 46 has an inlet connected to a water ejector 48
is connected to. Ejector 48 connects pipe 50 and solenoid operated shutoff valve 5 at uniform pressure.
Water is supplied through step 2. The flow of water through ejector 48 creates suction at the end of conduit 46, thereby evacuating sterilization chamber 16.
The water supply line 50 discharges into a suitable drain, and the water vapor exhausted from the chamber 16 is cooled with water.
It is condensed in water and then discharged. The exhaust of the exhaust system can be provided as a cooling fluid input to the heat exchanger 29 to conserve water. Flow through exhaust conduit 46 is regulated by solenoid operated valve 54 and one-way check valve 56.

Air supply line 58 connects to steam pipe 44 via valve 4
connected at a point downstream of 5. Air at atmospheric pressure is supplied to chamber 16 through air line 58 and filter 60 upon completion of the sterilization cycle. Filter 60 is of a type that effectively removes bacteria, dust, etc. from the air, and may also include an air sterilizer. Flow through the filter and air line is regulated by a solenoid operated shut-off valve 62 and a one-way check valve 64.

A pressure sensing assembly 66 is mounted within chamber 16 that is capable of sensing pressures above and below atmospheric. Pressure sensing assembly 66 is connected via suitable conductors, generally indicated at 68, to a master logic controller 70 which controls the operation of the sterilizer.

The operation of a sterilizer with cycle pulses adjusted to have a minimum evacuation time and to reach a selected vacuum level is outlined in the flowchart of FIG. The cycles alternately first purge air from the chamber by evacuating the chamber and pressurizing it with conditioning steam, then subjecting the material to a certain number of cycle pulses below a predetermined upper level. can include exposure to As a result of the conditioning pulse, the chamber is pressurized with water vapor to a level that produces the desired sterilization temperature and is maintained at this temperature for a period of time (this is achieved by measuring the pressure in the absence of air). can). The sterilization chamber is then evacuated and a relatively high vacuum is maintained for a period of time, eg, 5 minutes, to dry the material. Finally, air is introduced to bring the chamber to atmospheric pressure by passing it through a bacterial filtration system.

Preferably, conditioning is initiated by introducing water vapor at a pressure above atmospheric pressure into the sterilization chamber and simultaneously activating the exhaust system. When air is purged from the chamber in this manner, the pressure within the chamber initially increases such that the increased fraction of water vapor in the steam-air mixture that is being evacuated increases the efficiency of the selected ejector system by increasing the pressure in the chamber. increase to the point where it begins to decrease.

As part of the process depicted in FIG. 2, this decrease in pressurization rate can be sensed and used to generate a signal to close the steam valve 45, with or without a time delay. Alternatively, a purge timer can be started at the beginning of steam injection or evacuation. After the purge step, the exhaust should be at a predetermined sub-atmospheric pressure, e.g. 10 in.
Continue until pressure sensor 66 senses that Hg has been reached and time requirements are met.
When both of these conditions are met, the conditioning pressure pulse counter is updated, the exhaust system is turned off, and the steam valve 45 opens to admit steam from the jacket 22 into the chamber. to the predetermined upper pressure level.

The conditioning phase of the cycle ends when the conditioning pulse counter signals that the charge has been exposed to the appropriate number of pressure pulses. If the counter indicates that this number has not been reached, the steam valve 45 is closed, the exhaust system is turned on, and the exhaust draw town
The timer is restarted, exposing the system to another pressure pulse as just described. In the particular embodiment described, the charge is exposed to a plurality of predetermined pressure pulses. Pulse counting can occur at lower or upper pressure levels.

During the sterilization phase after the cycle, the water vapor pressure within the chamber is maintained at a desired level, e.g., 26-30 psig, to maintain the required sterilization temperature for a predetermined period of time. At the end of the sterilization period, the evacuation system is turned on and run for a predetermined period of time, preferably maintaining the vacuum at the highest level attainable by evacuation of the system, to effectively remove the material within the chamber. to dry. A solenoid-operated valve 62 in air line 58 opens to admit evacuated air into the chamber. The cycle is completed when the pressure in the chamber equals the surrounding atmospheric pressure,
Door 14 can be opened.

Pressure sensor assembly 66 can be a conventional transducer capable of conducting an electrical signal that is proportional to the chamber pressure continuously and spontaneously. This signal can then be used in system control logic to control the operation of various process phases by determining the rate of pressure change, or pressure-time curve. Alternatively, the pressure sensor assembly 66 can contain a plurality of contact sets, one of which indicates that the pressure within the chamber is below a predetermined atmospheric pressure, e.g., 10 inches Hg.
and the second of them is activated at sterilization pressure, for example 26 psig. These signals, in combination with time signals from appropriate conventional timers within control logic 70, can be used to automate the control of time and pressure parameters during the conditioning phase. Charge responsiveness is thus provided by the vacuum level and time required to reach the level as determined by the nature of the charge.

The electronic control of the system shown in FIG. 3 includes a conventional up-down counter 72, which is counted up by a signal on the "count" line when the "control" line is in a certain state. , and is counted down by the signal on the "count" line when the "control" line is in a different constant state. Before the process begins, up-down counter 72 is preloaded by a number corresponding to the number of chamber pumps to be used.

Counter 72 can be loaded by depressing button 74 on pulse selector 76. Pulse selector 76 can be a conventional pulse generator arranged so that the number of times button 74 is pressed appears in display window 78.
Each time button 74 is depressed, pulse selector 76 is effective in generating a signal for input to counter 72 on both the count line and the control line, and the counter indicates that the signal is present on the control line. It is arranged to count up when. In the illustrated embodiment, button 74 has been pressed to load the number 3 into counter 72. Since up-down counter 72 is automatically preloaded with the required fixed number, up-down counter 73 is automatically preloaded with the required fixed number. It can be configured to be input. With this configuration, errors due to operator's erroneous operations will not occur.

The starting signal is generated by known means, for example, by closing a conventional on/off switch connected in the main power circuit. When air is purged from the chamber, the start signal initiates the purge phase. Although the purge length and maximum pressure reached during the purge phase can be controlled in many ways, as described above, Figures 3-5 illustrate the simplest control method, i.e., a predetermined time. are doing.

The start signal is thus effective to start the purge timer 80, which can be an ordinary timer such as a digital timer, and the signal is supplied to the "start" input line. Afterwards, it is arranged to issue a signal on the "end" output line for a predetermined period of time. The start signal input is also electrically connected to electrical control solenoid means for exhaust system valves 52 and 54 (FIG. 1) and to steam supply valve 45 to open these valves. Water vapor is introduced and the chamber is evacuated at the same time. After a predetermined period of time, purge timer 80 times out;
A signal is issued on the "end" output line which is effective to close the steam valve 45.

Referring to FIG. 3, the "end" output line of purge timer 80 also
2 to the “Start” input line. The evacuation phase of the conditioning phase of the cycle is continued until at least a predetermined vacuum level is reached and a predetermined period of time has elapsed.
Continuous. In this embodiment, the draw down
Timer 82 can be started at the beginning of the steep negative slope of the pressure curve of FIGS. 4 and 5, which corresponds to the time of closure of steam valve 45. Other points can be used; starting the draw down timer at about 4 psig is typical.

Draw down timer 82 is similar to purge timer 80 for the minimum parameter aspects described.
, and outputs a signal on its output (or termination) line for a predetermined period of time after it is applied to its input line. draw·
The output signal of down timer 82 is applied to a set input of flip-flop 84.

As previously discussed, the pressure sensing assembly 66 includes a first set of contacts for providing a signal when the upper front reaches or exceeds a selected pressure and a lower front for reaching a selected pressure level. or a second set that generates a signal when the signal is exceeded.
As shown in FIG. 3, the signals are placed on respective output lines, and the assembly 66 can consist of two separate pressure responsive switches or other sensing devices connected to respective signal generating circuits. When the lower front reaches the selected pressure,
The signal applied to the set input terminal of flip-flop 88 is placed on line 86.

Set-reset flip-flops 84 and 88 provide output signals on their respective output lines when a signal is received on the set input line, and hold said signals on the output lines until the flip-flops are reset. Therefore, it is effective. The output of the flip-flop is connected to the input of an "AND" gate 90, and when both flip-flops are set at the same time, the "AND" gate 90 is used to provide a signal to the "count" input of the up-down counter 72. It is valid. This only occurs when the pressure reaches or exceeds the predetermined lower level and the draw down timer 82 times out, and this means that the negative slope portion of the cycle was previously Indicates that it has been interrupted for the determined minimum time. When only one of these two states exists, there will be an output on only one of the flip-flops, and eventually there will be no output signal at the output of the "AND" gate 90.

The output of the "and" gate 90 is also connected to the steam valve 45 and exhaust valve 54 and is effective to open the steam valve and close the exhaust valve, respectively, so that both exhaust time and pressure parameters are satisfied. Then, water vapor enters the chamber and pressurizes it.

Assuming up-down counter 72 is not at zero, when the previously selected upper pressure is exceeded, sensor 66 is activated and sends an output signal to line 92.
This line 92 is also connected to exhaust valve 54 and steam valve 45. This signal opens the exhaust valve and closes the steam valve, respectively.
Reduce chamber pressure. When a signal is generated on line 92, it also sets a draw down timer 82 which, as previously described, sets the output signal to its "end" when a predetermined period of time has elapsed. line and reset flip-flops 84 and 88.

The cyclic pulses continue in the manner described above until a preselected number of cyclic pulses have occurred. The output of up-down counter 72 is connected to decoder 94, each of whose output lines represent a fixed number. Thus, when the first number of pulses is loaded into the counter 72, the decoder 9
The four corresponding output lines carry signals. When this initial number of pulses counts down to zero, the zero output line of decoder 92 has a signal. This indicates the end of the conditioning phase and is connected to sterilization timer 96. The signal at the zero line output of the decoder indicates the sterilization phase.

Sterilization timer 96 maintains an output signal on a line connected to a control solenoid of steam valve 45 in conduit 44 between jacket 22 and chamber 16. The timer includes temperature level control means connected in line to valve 45 to regulate the flow of water vapor into the chamber. The temperature level control means includes a temperature sensor 36 which transmits a signal proportional to the temperature of the water vapor flowing from the chamber. Using the signal from this temperature sensor 36,
By controlling the opening and closing of normally closed valve 45, the temperature within the chamber is maintained at a desired level within predetermined limits.

The pressure within chamber 16 can also be used to control the opening and closing of valve 15 during the sterilization phase of the cycle. However, temperature sensing means are generally preferred for economic reasons to regulate the sterilizing steam flow.

When the sterilization timer 96 times out, a signal is placed on its end line to start the dry phase timer 98.
start. At the same time, the water vapor phase 45 closes and the vacuum valve 54 opens. Drying timer 98 maintains this system for a predetermined amount of time available to dry the charge. When dry timer 98 times out, it signals its end line to close exhaust system valves 52,54. At the same time, air valve 62 opens, allowing evacuated air into chamber 16 to complete the cycle.

Figures 4 and 5 are graphs of chamber pressure plotted against time during operation of the aforementioned apparatus according to the method of the invention, in which the purge phase of the sterilization cycle is stopped after a predetermined time; It is. Figure 4 represents the purge and conditioning phases of the cycle used to sterilize the minimum cloth charge, and Figure 5 depicts the same sterilizer with the highest cloth charge. Represents driving.

At the beginning of the cycle depicted in both FIGS. 4 and 5, water vapor under pressure is introduced into the chamber 16.
, and simultaneously operating the evacuation means, a relatively sharp initial increase in pressure occurs. Using the minimum fabric charge depicted in FIG. 4, before the ejector device can stop the pressure increase at point 100 on the pressure curve,
Pressure increases rapidly to over 20 psig. At this point, the pressure gradually decreases under the influence of the ejector,
Meanwhile, water vapor is continued to be introduced. The purge timer 80, which has been set to a purge time of 1 minute, has a point of 1.
02, and the steam valve 45 is closed. At the same time, draw down timer 82 can be started.

The pressure is measured along curved section 104 from point 102 to the minimum vacuum level at point 106 (which is 10 inches).
(preset to Hg). In the illustrated embodiment, it takes approximately 1.8 minutes to reach the minimum vacuum level from point 102 after the purge phase. Thus, draw down timer 8
2 times out at the end of one minute and issues a signal to flip-flop 84, flip-flop 88 has not yet received the signal from the low pressure contact in pressure sensor 66. When this low pressure is sensed, a signal is generated along line 86 to flip-flop 88 and "and" gate 90
passed a signal to the up-down counter 72 and counted it down by one count, simultaneously issuing a signal to close the exhaust valve 54 and open the steam valve 45. Exhaust valve 54 was closed and steam valve 45 was maintained open along curve section 108 from minimum vacuum point 106 to maximum chamber pressure of approximately 27 psig at point 110. Point 10
It should be noted that the pressure increase between 6 and point 110 is very rapid, almost linear, and takes slightly less than 0.5 minutes. The slope of the repressurization curve can be considered to be indicative of the heat absorption properties of the charge, while the slope of the exhaust phase is generally considered to be more indicative of air removal properties.

When maximum pressure is sensed, sensor 66 connects line 9
2 simultaneously opens exhaust valve 54, closes steam valve 45, starts draw down timer 82, and resets flip-flops 84 and 88. In this condition, the exhaust continued along curved section 112 from point 110 to lower pressure point 114. However, point 114 is approximately 16 inches Hg vacuum, or approximately 6 inches Hg less than point 106.
It should be noted that this is low. The reason this happens is that when sensor 66 senses the preset low pressure of 10 inches Hg and sends a signal along line 86 to flip-flop 88, draw down timer 82 has not yet timed out and the flip-flop The problem lies in the fact that they did not send a signal. Continuing the evacuation for one full minute exposes the charge within the chamber to an increased vacuum, which adequately removes air from the interstices of the fabric charge.

This operation is repeated for three complete pressurization and evacuation pulses of the conditioning phase, upon completion of which the up-down counter indicates that the pressure in the chamber has reached point 116 on the curve. At that time, it was counted down four times. At this point, decoder 94 issues a signal to start sterilization timer 96 and open steam valve 45 to increase the pressure and temperature within the sterilizer to the desired sterilization temperature. The chamber pressure curve for the remainder of the cycle is not shown in FIGS. 4 or 5, as its shape is clear from the previous description.

Comparing the curved section 104a of FIG. 5 with the corresponding section 104 of FIG. 4 reveals the automatic selection of conditioning depending on the particular charge.
That is, for the complete fabric charge of FIG. 5, from point 102a, after one minute of evacuation time, the pressure in chamber 16 has only dropped to approximately atmospheric pressure. Additional 2.6 minutes or 3.6 minutes total pumping time
It took 1.3 minutes to reach a vacuum of approximately 21 psig to 10 inches Hg for the minimum fabric charge, compared to 9.5 psig required to reach a vacuum of 10 inches Hg. Compared to the minimum cloth charge,
The relatively slow rise in chamber pressure during the flash phase for a complete cloth charge is due to the different absorption characteristics of the charges.

Similarly, the substantially greater evacuation time required in FIG. 5 requires increased time to draw air through the interstices of the complete fabric charge, especially during the initial pulse. Particularly because of this. Air removal becomes more efficient when the charge is evacuated for an increased period of time without a complete cloth. However, such additional evacuation time is unnecessary and is not used for minimal fabric charges. The resulting savings in time and operating costs are obvious. Also, as is clear, a gradient in time for the exhaust phase can exist between a minimal cloth charge and a full cloth charge, and the appropriate time for a particular charge is Automatically selected by this aspect.

The charge response aspect of the present invention allows relatively low levels of vacuum to be used while ensuring adequate air removal and heating throughout the charge. Fifth
As shown, a partial vacuum of only 10 inches Hg is satisfactory for the practice of the present invention;
The exhaust phase of each pressure pulse then ends at this level. However, as shown in Figure 4, when this embodiment is used for conditioning a minimal fabric charge, this minimum vacuum level does not adequately remove air from any fabric present. and, according to the invention, the charge is exposed to continuous vacuum, preferably at increasing levels, for a predetermined minimum time.

The charge-dependent aspect of the invention is also evident from the pressurization phase following the initial air flash. That is, the lower level point 106a at the beginning of FIG.
From to the initial maximum or high pressure level 110a, the curve section 108a takes slightly more than 2.5 minutes, compared to the corresponding pressure phase of the smallest fabric charge in FIG. It's slightly shorter than 0.5 minutes. In addition, steam pressurization for 1 minute during flashing,
The total time required to complete the conditioning phase, including three complete pressurization-evacuation pulses, is slightly less than 7 minutes for the minimal fabric charge compared to a complete It should be noted that most cloth foil charges require approximately 20 minutes.

Relatively low vacuum levels (e.g., 10 in.
In addition to facilitating the use of ejector devices instead of vacuum pumps, there are advantages in selecting Hg). Such low levels of vacuum increase the overall efficiency of the sterilizer and conserve energy by minimizing heat loss. High vacuum evacuation as the charge is being heated by steam removes heat from the charge and the sterilizer walls. It is therefore advantageous in reducing heat losses to be able to condition the charge using as low a vacuum as possible consistent with rapid heating and adequate air removal.

A pressure transducer can be used to monitor the pressure in the chamber to obtain information indicative of the characteristics of the charge and, according to the invention, can be used to automatically select the conditioning pressure and/or time. Pressure transducers can be used to select cycles for conditioning the charge. A functional relationship between the slopes of the exhaust phase pressure-time curves for various charges processed in a particular sterilizer with a constant exhaust system is programmed into the control logic and combined with the collected data. , of the desired conditioning pressure-time parameters based on comparison with experimentally derived functional relationships from data previously established or objectified from the charge over a range of properties. Can be used for selection. Programming experimentally established functional relationships into control logic,
It is then used as a basis for comparison of exhaust phase gradients calculated from the monitored pressure input from the transducer and the time input from conventional time signal generation means in the control logic.

Comparison of gradients for conditioning control is preferably carried out at near atmospheric pressure in the exhaust phase, but it is also possible to use the average gradient over a long section in all of the exhaust phases. For example, for a standard 36-inch sterilizer, when the slope of the evacuation pressure curve indicates a rate greater than about 9 psi/min, the chamber pressure is less than 1 min when determined between about 4 and 0 psig during the evacuation phase. It was determined that a vacuum level of 10 inches Hg would be reached in a short period of time, and control logic decisions could then be made to continue the complete 1 minute evacuation phase. Conversely, gradients exhibiting pumping speeds lower than 9 psi/min
When indicating that it will take longer than 1 minute to reach a vacuum level of 10 inches Hg,
The control logic is to stop the evacuation phase of the pulse only when this minimum vacuum level is reached.

Test loads for the venting of the present invention included a challenge pack of sheets, a challenge pack of towels, a surgical pack of clothing, and a hardgoods pack.

Several criteria were evaluated in the conditioning sterilization suitability test according to the present invention. The efficiency of sterilization was demonstrated in complete loads and single packs of cloth, wrapped heavy goods and unwrapped heavy goods. As an example of one test procedure, in each of five consecutive cycles, the biological indicator had to be sterilized to a proven and appropriate safety margin. The condition of the sterile charge is dry, undamaged, and substantially free of visible wet spots on the outer packaging or dirt or stains on metal surfaces when recommended practices are followed. There should be virtually no residue present. The above criteria were that all applicable garment testing standards be met. For example, for a 24 inch x 36 inch x 60 inch sterilizer, Federal Standard GG-S-1343A
specifies specific size charges of surgical packs, and heavy cargo, and also specifies the allowable total cycle time for all such charges. Other sterilization criteria, drying criteria, pressure and temperature tolerances were met.

While these criteria are met, the performance characteristics, production costs, and economics of operation, when related to the practicalities encountered in normal operation,
All were found to compare favorably with currently available sterilizers on the market.

During testing, temperature was measured with T-type (copper constantan) Teflon insulated thermocouples and pressure was monitored with a Viatran absolute pressure measurement transducer. Temperature and pressure were continuously monitored and recorded.

Carefully tested biological and chemical indicators were manufactured by American Sterilizer Company, Erie, Pennsylvania.
SPORDI biological spore strips manufactured by Sterilizer Company. The chemical indicator used was from American Sterilizer Company.
It was a CHEMDI test indicator. These chemical indicators change color to indicate complete charge conditioning and water vapor penetration.

For compliance testing purposes, a thermocouple was placed in the center of the pack near the chemical indicator and biological test strips to monitor the temperature of the pack along with the temperature of the chamber. For heavy cargo, the thermocouple was placed in direct metal-to-metal contact with the heaviest instrument or component of the pack, and the chemical and biological indicators were distributed throughout the pack contents. Times were checked in duplicate with a stopwatch and times were compared to ensure repeatability.

In five consecutive tests of single packs and complete charges of packaged heavy cargo, towel packs, sheet challenge packs, and 10 sheet clothing packs, sterility was observed in all test specimens processed. occurred. All processed packs are 5
There was no evidence of water spots on the outer packaging after cycling for a drying period of minutes. All cloth foil challenge packs performed well within acceptable standards for drying efficiency.

The temperature at the center of the complete charge and the minimum charge is determined before the completion of the conditioning phase of the cycle.
The temperature was substantially equal to that of the chamber.

A test cycle was performed in which the sterilization phase was extended to the full recommended 4 minutes and a shortened period. The processed biological test stops indicated sterilization for both full and shortened cycles and showed adequate safety margins. Chemical indicators showed that water vapor had penetrated through the charge in each case.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a sterilization device using the present invention. FIG. 2 is a process flowchart for implementing a sterilization cycle according to the present invention using the apparatus of FIG. FIG. 3 is a schematic diagram of the control logic of a control device according to the invention. FIG. 4 is a graph of the pulse shape achieved during charge conditioning of a minimal foil type charge according to the present invention. FIG. 5 is a graph of the pulse shape achieved during charge conditioning of a full cloth foil type charge according to the present invention. 16... Chamber, 20... Flange, 22...
...Steam jacket, 28...Drain pipe, 2
9...Heat exchanger, 31...One-way check valve, 32...
...Second drain pipe, 34...One-way check valve, 3
6...Temperature sensor, temperature sensor, 37...Steam supply pipe, 39...One-way check valve, 40...Solenoid operation cut-off valve, 45...Solenoid operation valve, steam valve, 46...Exhaust pipe, 48...Ejecta, 5
4...Solenoid operated valve, 58...Air supply line, 64...One-way check valve, 66...Pressure sensor assembly, 70...Master logic controller, control logic, 72...Up/down counter , 76... Pulse selector, 78... Display window, 90... "AND" gate.

Claims (1)

[Scope of Claims] 1. Conditioning and steam sterilization of materials in a hermetically sealed chamber operable at pressures other than atmospheric pressure, such that such materials have a predetermined charge size or material properties. This conditioning removes air from the charge and the desired temperature relative to the sterilization temperature without the need for contacting the sensor with the charge material. Conditioning and steam sterilization methods that involve heating a charge include charging such material into a chamber, sealing the chamber, and introducing condensable vapor having transferable latent heat into the chamber. exposing the chamber and the material therein to a plurality of cyclic pressure pulses below the above pressure level associated with the desired sterilization temperature by injecting and evacuating the chamber, each cyclic pressure the pulse includes an evacuation phase in which the pressure in the chamber decreases and a steam injection phase in which the pressure increases; and measuring a change in chamber pressure over time during at least a portion of the evacuation phase; using the change as an indication of the chamber pumping speed during the pumping phase, and using the indicated chamber pumping speed of the pumping phase to automatically control the termination of that pumping phase and subsequent cyclic pressure pulse pressurization. starting the phase, completing the conditioning of the charge by removing air from the charge and heating the charge to the desired temperature, and then introducing sterilizing steam into the chamber. , maintaining a pressure level sufficient to maintain the desired temperature for a sufficient period of time to effect the desired sterilization of the material within the chamber. 2. The method of claim 1, wherein the step of automatically controlling the shutdown of the exhaust phase comprises automatically controlling the chamber exhaust pressure level. 3. The method of claim 1, wherein the step of automatically controlling the stoppage of the evacuation phase comprises automatically controlling the evacuation time of the chamber. 4. The method of claim 1, wherein the pressure range of the cyclic pulses of chamber pressure extends above and below atmospheric pressure. 5. The method of claim 4, wherein conditioning the charge comprises continuing the evacuation phase of each cyclic pressure pulse until both a minimum vacuum level and a minimum time are reached. . 6. The method of claim 5, wherein controlling the conditioning further comprises selecting the number of cyclic pulses. 7. Charge conditioning is initiated by purging air from the chamber by injecting condensable steam into the chamber and simultaneously exhausting such steam and air from the chamber. The method according to claim 1. 8. The method of claim 1, wherein evacuation of the chamber comprises creating a vacuum by ejector means and exposing the sealable chamber to such vacuum. 9. The method of claim 1, wherein the condensable vapor comprises water vapor. 10 Conditioning of the charge is carried out by automatically controlling the evacuation of the chamber and the injection of steam into the chamber during cyclic pressure pulses to ensure that (a) a predetermined period of time has elapsed and the chamber successively evacuation phases of each cyclic pulse until a predetermined lower pressure level is reached within the
then (b) by stopping the evacuation phase and beginning the steam injection phase of each cyclic pulse until the pressure in the chamber is substantially equal to the predetermined upper pressure level; Then,
A method according to claim 9 for controlling. 11. By sealing the charge of material to be sterilized in a sterilization chamber operable at a pressure above atmospheric pressure and at the desired temperature for sterilization, evacuating the chamber and injecting water vapor into the chamber, exposing the chamber and charge to a plurality of cyclic pressure pulses below an upper pressure level associated with the desired sterilization temperature;
each cyclic pressure pulse includes an evacuation phase in which the pressure in the chamber decreases and an injection phase in which the pressure in the chamber increases; in a controlled manner: (a) continuing each evacuation phase until a predetermined time period has elapsed and a predetermined low pressure level is reached in the chamber, and then (b) stopping the evacuation phase;
and begins the injection phase, which continues until the pressure in the chamber is substantially equal to the upper pressure level;
(c) stopping the injection phase at the upper pressure level and starting the exhaust phase of the next cyclic pressure pulse;
and (d) repeating the controlled evacuation and injection phases.
The chamber and charge are exposed to a predetermined number of cyclic pressure pulses to heat the charge to the desired temperature and to evacuate the air, regardless of the size or characteristics of the charge in the chamber. sterilization by removing the entire chamber and maintaining the pressure in the chamber at a pressure level above the desired sterilization temperature for a sufficient period of time to effect sterilization after the cessation of the pressurization phase of the last cyclic pressure pulse. A steam sterilization method characterized by comprising. 12. The method of claim 11, wherein the low pressure level achieved during the evacuation phase is below atmospheric pressure. 13. The method of claim 12, wherein the chamber and charge are exposed to a minimum of four cyclic pressure pulses, each pulse consisting of an evacuation phase and a steam injection phase. 14. The method of claim 11, further comprising the step of purging air from the chamber by injecting water vapor into the chamber and simultaneously evacuating water vapor and air from the chamber prior to the initiation of cyclic pressure pulse generation. Method. 15 The step of purging air from the chamber consists of simultaneously evacuating the chamber and injecting water vapor into the chamber for a predetermined time interval, and at the end of that interval stopping the injection of water vapor while continuing to evacuate the chamber. 15. The method of claim 14, further comprising starting the evacuation phase of the first cyclic pressure pulse. 16. Claim 15, wherein the step of purging air from the chamber initially comprises injecting water vapor into the chamber at a rate such that the pressure within the chamber is substantially increased and the chamber is simultaneously evacuated.
The method described in section. 17. The step of purging air from the chamber involves first injecting water vapor into the chamber at a rate that rapidly increases the pressure in the chamber, then substantially decreasing the rate of pressurization of the chamber, and evacuating the chamber; 17. The method of claim 16, comprising: sensing a change in chamber pressurization rate; and ceasing water vapor injection in response to the sensed decrease in chamber pressurization rate. 18 The process of purging air from the chamber consists of injecting water vapor into the chamber at a rate that first substantially increases the pressure in the chamber and then gradually decreases the pressure in the chamber, and then evacuating the chamber to reduce the pressure in the chamber. 17. The method of claim 16, comprising sensing the decrease and stopping the injection of water vapor in response to the sensed decrease in pressure. 19 Conditioning the material forming the charge in a sealable sterilization chamber operable at superatmospheric pressure for steam sterilization, without having to select the amount or properties of the material, and Conditioning involves removing air, moistening the charge,
and heating of the charge to a desired temperature in preparation for sterilization, an evacuation means for evacuating the sterilization chamber, and a steam operable to inject into the sterilization chamber steam having transferable latent heat. injection means, and controlling the operation of the evacuation means and the steam injection means to generate cyclic pulses of chamber pressure for multiple cycles of chamber pressure below the above pressure level related to the desired temperature for sterilization. and control means for generating cyclic pulses, each cyclic pulse comprising an evacuation phase in which the pressure in the chamber decreases during operation of the evacuation means, and a steam injection phase in which the pressure in the chamber increases during operation of the steam injection means. and further comprising pressure sensing means for monitoring changes in pressure in the chamber during generation of the cyclic pulses, and timing means for measuring the duration of the exhaust phase of the cyclic pulses, such control means comprising: the pressure and pumping time of such a chamber to determine the chamber pumping speed and to control such cyclic pulsing to control charge conditioning in response to the chamber pumping speed; A conditioning device comprising means for responding to an indicator. 20 Conditioning the materials forming the charge in a sealable sterilization chamber operable at supra-atmospheric pressure for steam sterilization, without having to select their quantities or properties; Conditioning involves the removal of air and heating of the charge to the desired temperature for sterilization.In the conditioning equipment, there is an evacuation means for evacuating the sterilization chamber, and a steam injection means for injecting water vapor into the sterilization chamber. and means for manipulating the evacuation means and the steam injection means to generate cyclic pulses of chamber pressure comprising a plurality of cyclic pulses of chamber pressure below an upper pressure level related to a desired temperature for sterilization. each cyclic pulse comprises an evacuation phase in which the pressure in the chamber decreases during operation of the evacuation means, a steam injection phase in which the pressure in the chamber increases during operation of the steam injection means, and further comprising: pressure sensing means for monitoring changes in chamber pressure during the time; timing means for measuring the time of each evacuation phase; and pulses for controlling such cyclic pulses in response to such indications of chamber pressure and evacuation time. cycle control means, the pulse cycle control means comprising: cyclic pulses such that each evacuation phase continues until a predetermined time period has elapsed and a predetermined vacuum level is achieved within the sterilization chamber; means for controlling the means for activating said evacuation means to continue each evacuation phase; and during said cyclic pulses, controlling said steam injection means to heat the charge to the desired sterilization temperature and discharge the charge; and means for removing air from the entire sterilization chamber irrespective of article size and charge characteristics. 21. The apparatus of claim 20, including means for initiating conditioning of the charge by injecting steam into the chamber and simultaneously evacuating the chamber to flush air from the chamber. 22. Conditioning and sterilizing the charge in a portable sterilization chamber at an internal pressure above atmospheric pressure for steam sterilization, following conditioning of the charge of goods in the chamber; Conditioning involves the removal of air from the chamber and the heating of the charge to a temperature that includes, in conditioning and sterilization equipment operating between open and closed positions, respectively. a steam injector having first electrically operated valve means capable of pressurizing the chamber and stopping the flow of steam into the chamber; and a steam injector operable between an open position and a closed position, respectively. evacuation means including a suction means and a second electrically operated valve means capable of connecting the chamber to a suction means to evacuate the chamber and isolating the chamber to stop evacuation; a steam injection means and an evacuation means; a control means for controlling operation of the means, the control means comprising a timing means for timing evacuation of the chamber after each operation of the first electrically operated valve to an open position; pressure sensing means for sensing the pressure of the second electrically operated valve in its open position each time the second electrically operated valve is in its open position in response to the timing means and the pressure sensing means; and closing the second electrically operated valve means until the predetermined time period has elapsed and a predetermined low pressure is reached in the chamber.
means for opening the electrically operated valve means to inject water vapor into the chamber and pressurize it after a predetermined period of time has elapsed and a predetermined low pressure has been reached; responsive to the pressure sensing means, closing the first electrically operated valve means and opening the second electrically operated valve means to evacuate the chamber again to correspond to the desired sterilization temperature; means for operating the control means to alternate between evacuation and pressurization phases to expose the charge in the chamber to a plurality of cyclic pressure pulses below an upper pressure level; and counting means for ceasing the generation of cyclic pressure pulses after a predetermined number of pulses. 23. The control means initially opens both the first and second electrically operated valve means to simultaneously introduce water vapor into the chamber and evacuate the chamber;
23. The apparatus of claim 22, further comprising means for thereby purging air from the chamber. 24 After a predetermined period of time after both the first and second electrically operated valve means are first opened, only the first electrically operated valve means is closed, thereby 24. The apparatus of claim 23, further comprising means for initiating the evacuation phase of the first cyclic pressure pulse.