In prior table-top sterilizing apparatus such as described in U.S. Patent No. 4,865,814, issued September

12, 1989, is it Known to inject water into a sterilization chamber and then to neat the water until it turns to steam which is sufficiently hot to sterilize instruments in the cnamber. A particularly objectionable feature of this prior type of sterilizing apparatus is the length of time required to generate steam at proper sterilizing temperature of 250° F or higher. Sometimes users must wait from fifteen to thirty minutes or more until tiie steam is at proper temperature before the steri ization cycle can begin. Flash sterilization at high temperature of 280°F must await heating times of thirty minutes or or more even though actual sterilization may only require one minute or less for unwrapped instruments.

SUMMARY OF THE INVENTION It is a principle object of the present invention to provide an improved table-top flash autoclave system including a microprocessor controller for automatically controlling a water and steam charging cycle and a plurality of sterilization cycles of different selectable time durations. Another important object is to provide an autoclave system as described, adapted for heating a

autoclave system as described, adapted for heating a sterilization chamber by superheated steam so that instrument sterilization can start shortly after instruments are placed in the chamber. According to the invention the table-top apparatus has a sterilization chamber upon which is mounted a reservoir for distilled water. Under the reservoir is a fill tank and adjacent to the fill rank is a water boiler for generating steam. The fill tank is unique to the present invention for receiving water from the reservoir and for circulating it through the boiler in a closed loop. When the steam reaches proper temperature and pressure, he boiler is isolated from the fill tank , which can be refilled automatically if necessary, while the boiler is connected to the sterilization chamber and supplies it with steam at prescribed temperature. The sterilization chamber can start sterilizing instruments after the instruments are placed in the chamber and the chamber door is locked. Flash sterilization of instruments can take place in approximately three minutes total cycle time. The autoclave is provided with means for selecting sterilization times of one minute, three minutes, ten minutes and thirty minutes, depended on whether instruments are wrapped or unwrapped, and or the quantity of instruments. Each timing parameter has a predetermined temperature of control programmed into a microprocessor. During the thirty minute sterilization time/period, sterilization is performed at a reduced temperature which is advantageous for sterilizing delicate instruments, or liquids. The provision of a boiler outside but adjacent to the sterilization chamber makes it possible to supply steam to the chamber to virtually remove the "come up" (to temperature) time of conventional

tabletop autoclaves.

These and other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagrammatic side view of apparatus embodying the flash autoclave system according to the invention;

Fig. 2 is a block diagram of the flash autoclave system showing mechanical, electrical and electronic components interconnected according to the present invention; and

Figs. 3 and 4 are flow cnarts outlining steps in charging and sterilization cycles utilized in the flash autoclave system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings wherein like reference characters designate like or corresponding parts throughout, there is illustrated in Fig. i , an autoclave housing 20 which contains a sterilizing chamber 25 having an opening closed by a hinged door 26 tnrough which instruments to be sterilized can be inserted and removed. Within the housing 20 is a reservoir 28 comprising a rectangular container designed to hold water. Underneath the fill tank 30 is a boiler 32. In the boiler 32 is generated the steam which is fed to the steriliza ion chamber 25. At the front of the reservoir 28 is a control panel 34 with manually operable control buttons, temperature and pressure gauges described in more detail below in connection with Fig. 2. Adjacent the control panel 34 is an electronic microprocessor controller (MC)

36 which is programmed with a predetermined logic to operate valves, heaters , and other components of the autoclave system shown in Fig. 3.

The autoclave system as shown in Fig . 2 comprises the reservoir 28 in which is a coiled condenser 38 for condensing steam returned to the reservoir 28 from the sterilizing chamber 25, the fill tank 30 and the boiler 32. The reservoir 28 fills the tank 30 with water via a valve 40, a conduit or pipe line 42, a T-joint 44 and two- way line 46. The tank 30 in turn fills the boiler 32 with water via a line 48, a valve 50, a line 52, a T-joint or fitting 54 and a line 56. Steam from the boiler 32 goes to and fills the chamber 25 via a T-joint or fitting 58, line 60 , a valve 62 , and a line 64. The sterilizing chamber 25 discharges excess, spent steam to the condenser coil 38 via a line 66, a T-joint 68, and line 69, a valve 70 and a line 72 to the condenser coil 38. The boiler 32 circulates steam -in a closed loop during the steam generation cycle via the T-joint 58, a line 74 a valve 76, a line 78 a T-joint 80 and a line 79 to fill the tank 30. Tne fill tank 30 returns excess steam to the condenser 38 in the reservoir 28 via a line 79, the T-joint 80, a line 81, a valve 82, a line 83, a T-joint 84 and a T-joint 87. The chamber 25 is connected via the line 66, the T-joint 68, a line 86, a safety relief valve 88 to the reservoir 28, for relieving steam pressure when it exceeds 50 psi. The valve 88 may be set, for example, at 50 PSI (pounds per square inch).

The boiler 32 is connected to a drain via a manually operated valve 89 and a drain line 89' for draining water from the boiler 32. The chamber 25 is connected via a drain line 90, a T-joint 91, a strainer 92, a line 92', a bellows controlled steam trap 93, a line

93', a check valve 94, a T-joint 95, a line 105 and the T- joint 87 to the condenser 38 for draining air and condensate from the chamber 25. Tne boiler 32 is connected via a line 100, to a blow valve 102, a line 104, the T-joint 95, the line 105, the T-joint 's 96 and 87 to the condenser 38 to relieve excess steam pressure to the boiler 32. The boiler 32 is connected to a pressure relief valve 106 via a line 108. The valve 106 is preset to release pressure at a high value, for example 100 PSI. The chamber 25 is connected via a line 110 and the T-joint 91 to the strainer 92.

A line 112 is connected from the cnamber 25 to a pressure sensor at the microprocessor controller (MC) 36. A gauge 116 at the control panel 34 indicates a chamber steam pressure CP. A boiler pressure sensor at the microprocessor controller 36 is connected via a line 114, the T-joint 54, and the line 56 to the boiler 32. A display 118 at the control panel 34 indicates the boiler steam pressure BP. A line 124 is connected from the chamber 25 to a temperature sensor at the microprocessor controller 36 enables a display 122 at the control panel 34 to indicate chamber temperature CT. A display 128 on the panel 34 indicates the time remaining in a seLected cycle. Solenoids 131-136 (SV1-SV6) are connected to the power supply (PS) 140 via electric power lines 142. The solenoids 131-136 respectively control and operate the valves 40,50,76,62,70 and 82. The power supply 140 is connected via control lines 144 to logic elements in the microprocessor controller 36. The control panel 34 is connected via interface control lines 152 to the microprocessor controller 36.

The cnamoer 25 is surrounded by an insulated wire

heater 160 connected to the power supply 140 by wires 162. The heater 160 is used for preheating the chamber 25, and for drying instruments after the sterilization cycle. An electric heater 165 in the boiler 32 is connected by wires 166 to the power supply 140 to heat water in the boiler 32 to boiling to generate pressurized steam which is supplied to the sterilizing chamber 25 via the valve 62 under control of the solenoid (SV3) 133.

The operation of the autoclave system will now be described with particular reference to Figs. 1 and 2 and to the flow charts of Figs. 3 and 4. Initially the reservoir 28 is filled with approximately four gallons of distilled water. This quantity of water is ample for twenty to thirty cycles of sterilization before the reservoir 28 needs refilling , but it is preferable to maintain a full reservoir during the course of running cycles. At the start of the charging cycle (see Fig. 3) the valve 40 between the reservoir 28 and the fill tank 30 is opened and the valve 82 is opened to release air and condensate to the reservoir 28 (Step 1). Trie reservoir the delivers water to fill the tank 30 via the open valve 40 (step 2). Tnen the valves 50, 76 open and the valves 40 and 82 close (step 3). Water then enters the boiler 32 via the line 46, the T-joint 44, the line 48, the valve 50, the T-joint 54 and the line 56 (step 4). The boiler 165 is then energized to heat the water boiling (step 5). At this point a closed circulation path or loop has been constituted from the fill tank 30, through the valve 50, the boiler 32 and the valve 76. Boiler heating continues beyond 212°F while water and steam circulate in a closed loop through the boiler 32 and the tank 30 (step 6). When the steam pressure in the boiler 32 reaches 50 PSI the solenoids (SV1) 131 and (SV2) 132 are energized to

close respected valves 50 and 76 and thereby isolating the boiler 32 which continues to heat alone (step 7). Cutting off the fill tank 30 from the boiler 32 in step 7 affects a reduction of approximately 20% in the volume being heated. The boiler 32 continues heating them stops (step 8) and the pressure is maintained by the switching of the heater power. The charging cycle is now completed and the boiler 32 awaits a call for steam to the chamber 25 to start a sterilization cycle (step 9). The system provides for four selectable sterilization cycles. These cycles occupy respectively 1 minute, 3 minutes , 10 minutes and 30 minutes. At this time the heater 165 in the boiler 32 is controlled by the power supply 140 responsive to the boiler pressure pulses BP applied to a pressure sensor in the microprocessor controller 36. If something should go wrong in the system and if the boiler steam pressure rises as high as 100 PSI the normally closed relief valve 106 will open to discharge steam into the reservoir 28. If necessary normally closed, manually operable valve 102 can be opened to discharge steam from the boiler 32 to the condenser 38.

One Minute Sterilization Cycle

A user of the autoclave system can select a sterilizing cycle of desired duration by pressing one of four buttons 180 accessible at the control panel 34. If button #1 is pressed, this will initiate a steriliza ion cycle for one minute see Fig. 4. This cycle is employed for sterilizing instruments which are unwrapped. Before pressing the button #1, the door 26 will be opened and the unwrapped instruments to be sterilized will be deposited in the chamber 25, (steps 1' and 2'). Then the user will close the door 26 and will press button #1 (steps 3' and

4'). The valve 62 will open (step 5') and steam at 80 psi

will enter the chamber 25 while the steam strap 93 allows air and condensate to escape from the chamber 25 (step 6'). The door 26 will be held closed by a pressure lock and cannot be opened while pressure in the chamber 25 is above 1 psi. The temperature in the chamber 25 rises quickly to 280°F and the timing of the one minute sterilization cycle begins, (step 7'). The temperature of the steam in chamber 25 is kept between 280°F and 285°F by delivery of steam via the valve 62. A safety switch (not shown) on the door 26, connected to the microprocessor controller 36, will allow the solenoid 133 to open the valve 62 only when the door 26 is closed. Steam enters the chamber 25 under 80-85 psi from the boiler 32. When the steam pressure in the chamber 25 begins to rise, the normally open bellows assembly in the steam trap 93 will allow air and condensate to flow from the chamber 25 via the strainer 92 and the valve 94 to the reservoir 28. When saturated steam pressure at 212°F F is sensed by the bellows assembly it closes the steam trap 93 since the air in the chamber 25 has been evacuated. The pressure of the steam in the chamber 25 builds up rapidly when the trap 93 closes. The steam pressure CP and the temperature CT in the chamber 25 are displayed at the pressure indicator 116 and the temperature indicator 122 respectively at the control panel 34. The steam temperature in the chamber 25 is measured at the coldest part of the chamber 25 and guarantees that the chamber is at least the prescribed temperature for flash sterilization. The one minute timing starts when the steam reaches 280 ° F in the chamber (step 7'). The valve 62 closes at the end of one minute, timing stops, and the solenoid (SV4) 134 opens the valve 70 (step 8') to exhaust the chamber 25 through the

valve 70 and the line 72 to the condenser (step 9'). At 1 psi or less of steam pressure in the chamber 25, the transducer (not shown) actuated by the microprocessor controller 36 rings to indicate that the door 26 can be safely opened and the instruments removed (step 10'). A drying phase starts when the pressure reaches 2 PSI or less in the chamber 25 (step 11'). The heater 160 surrounding the housing is a low wattage unit and is always on to keep condensate from forming on the stainless steel walls of the chamber 25. The heater 160 consumes about 250 watts which is sufficient to dry the interior of the chamber 25 without broiling the content s of the chamber 25. When the pressure in the chamber 25 reaches 2 psi a timer at the microprocessor controller 36 starts timing the drying phase while the valve 70 remains open. During the one minute flash sterilization cycle, steam is delivered from the boiler 32 to the chamber 25 via the valve 62 while the valves 52 and 76 are closed. The valve 62 is toggled open and closed to keep the chamber temperature between 280°F and 285°F During the sterilization cycle the valve 82 is opened when the solenoid (SV5) 135 is energized fifteen seconds after the sterilization cycle begins. The steam pressure in the fill tank 30 is then reduced by discharging steam from the fill tank 30 into the reservoir 28 via the valve 82 and the condenser 38. When the pressure in the fill tank 30 reaches 0 PSI the check valve 40 opens so that water can flow from the reservoir 28 via the valve 40 to refill the fill tank 30. Air in the fill tank 30 is displaced via the open valve 82 to the reservoir 28 so that the circulation of water to recharge the fill tank 30 takes place during the sterilization cycle. The fill tank 30 collects water from the reservoir 28 and delivers water

to the boiler 32. The valve 82 is open during the sterilization cycle to connect the fill tank 30 to the reservoir 28. The valve 40 opens when there is 0 psi pressure in the tank 30. The chamber 25 is vented to the reservoir 28 via the valve 70 when the sterilization cycle ends and the valve 70 opens while the valve 62 closes. During the venting phase when the sterilization cycle ends, the valve 82 closes and the valves 50 and 76 open. The closed circulation path including the fill tank 30, the valve 50, the boiler 32, and the valve 76 is reestablished under pressure building conditions.

It will then take about four minutes for the boiler 32 and fill tank 30 to come to pressure equilibrium allowing water and steam to flow in the closed circulation loop or path. This is a four minute lockout phase during which the user cannot start a new cycle. After the four minutes the boiler pressure is checked. If it is above 50 PSI, the valves 50 and 76 are closed. The boiler 32 is alone again and the next cycle can start at 80 psi. If the boiler 32 is not up to 50 PSI, heating and charging of the boiler 32 continues in the closed loop, until a steam pressure of 50 PSI is reached. A new cycle cannot start unless door 26 is closed and locked and there is a steam pressure of at least 80 psi in the boiler 32. There is a possibility that 80 psi can be reached in the boiler 32 while the tank 30 and the boiler 32 are connected in the closed circulation loop or path, but a new sterilization cycle cannot begin until the four minute lockout period has elapsed.

Three Minute Sterilization Cycle The three minutes sterilization cycle is initiated by pressing button #3 at the control panel 34. The cycle

is selected for wrapped instruments which are to be flash sterilized. The three minute cycle takes place in the same manner as described for the one minute flash sterilization cycle, except that steam pressure is released from the chamber 25 at the end of three minutes via the valve 70 and the drying phase starts.

Ten Minute Sterilization Cycle The ten minutes sterilization cycle is initiated by pressing button #10 at the control panel 34. This is termed the standard cycle and is at a steam temperature of 270° F in the chamber 25. This is 10°F below the sterilization temperature employed in the one and three minutes sterilization cycles. By lowering the temperature the sterilization time is prolonged to ten minutes. Instruments may be wrapped or unwrapped. The procedure is the same as described for the one minute flash sterilization cycle, except that steam injection from the boiler takes place via the valve 62 for ten minutes. Then the valve 62 closes, and the valve 70 opens to discharge steam from the chamber 25 to the condenser 38 in the reservoir 28. When the chamber pressure drops to 1 psi or less the door can be opened. The drying phase previously described starts when the pressure in the chamber 25 drops to 2 psi. Thirty Minute Sterilization Cycle

This cycle is initiated by pressing button #30 at the control panel. This is termed the delicate instrument cycle and is at a steam temperature of 250°F in the chamber 25, which is lower than the temperature used in the three shorter sterilization cycles. The steam temperature is kept at 250°F in the chamber 25 by the same means hereinbefore described. In the shorter cycles, the heater 160 is left on

on, but in this longest cycle the heater 160 is turned off and on. The heater 160 is turned off so that it will not cause the steam in the chamber 25 to heat excessively. Steam injection from the boiler 32 via the valve 62 continues during the entire 30 minutes. At the end of the thirty minutes sterilization cycle, steam in the chamber 23 is discharged to the reservoir 28 via the valve 70 which opens while the valve 62 closes to cut off the steam supply. At 1 psi or less in chamber 25 the door 26 can be opened and the sterilized instruments can be removed.

When the valve 62 closes, the valves 50 and 76 open to restart the charging cycle in the closed loop of the fill tank 30, the valve 50, the boiler 32, and the valve 76.

The valve 94 acts as a protection device for the steam trap 93. If the blow valve 102 is opened under pressure in the boiler 32 to drain the boiler 32, a backwash of steam could occur via the line 96 to the steam trap 93. The trap 93 could be damaged by back flow of steam so the check valve 94 prevents such back flow. The strainer 92 protects the inlet of the steam trap 93 from particulate matter, and keeps the system clean. Since the strainer 92 is in the path from the chamber 25 via the line 110, it also stops any particulate matter from the sterilization chamber 25. The present invention employs the reservoir, fill tank and boiler in a cooperating system. This is unique for a table top type of autoclave. Other sterilizers get their steam from an external source or they generate their steam from water injected directly to into the sterilization chamber and boiled there. In the present invention, steam is ready from the boiler in approximately a minute at 280°F for the shorter cycles, at 270°F for the ten minute cycles, and at 250°F for the thirty

13 minutes cycle, once the door 26 is locked and one of the buttons 180 is pressed. In the thirty minutes cycle, steam at 250°F is available in approximately 30 seconds after the door 26 is closed and the button #4 is pressed. This contrasts with prior table-top sterilizers which allow water to flow onto the sterilizing chamber 25 under gravitational pressure. Then the water is heated slowly to boiling in the sterilization chamber. It takes generally 15 to 20 minutes in these prior sterilizers for the steam generated in the sterilizing cycle, in the present invention, embodying the flash sterilizing concept , sterilization starts almost immediately, generally not more than one minute.

The charging cycle outlined in Fig. 3 insures that the sterilization cycle will not start until there is 80 psi pressure of steam in the boiler 32. During the sterilization cycles the boiler 32 is kept between 50 psi and 70 psi which is an optimum steam delivery pressure range. The reservoir 28 is filled most conventionally with distilled water poured through the opening in the top of the reservoir 180. Cool or cold water is added when it goes down about a gallon or more. Tht reservoir holds about four gallons. It takes about eight to fifteen cycles to use a gallon of water.

When the autoclave starts it boils water in the boiler 32 which circulates through the fill tank 30. The valve 40 has a sensitive poppet and closes when pressure in the fill tank 30 is greater than 1 psi. Check valve 40 acts like a steam trap since it only closes under pressure applied by steam generated in the boiler 32. Although a pressure indicator 116 is provided for chamber pressure CP it is only provided for monitoring

purposes. The operation of the sterilization chamoer depends of the chamber temperature CT indicated by indicator 122 at the control panel.

It should be understood that the foregoing relates only to a limited number of preferred embodiments of the invention which have been by way of example only and that it is intended to cover all changes and modifications of the examples of the invention herein chosen for the purpose of the disclosure , which do not constitute departures from the spirit and scope of the invention.