Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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ST~RILIZER
This invention is an improvement on system
disclosed in U.S. Patent Specification No. 3,719,017.
The present invention provides a method of
sterilizing in which an article to be sterilized is
submerged in water, and ozone is bubbled through the ~ater
and over said article while it is submerged.
It is intended to sim~lify the operation and
increase the effectiveness by the concurrent use of
ultrasonic vibration to dislodge bacteria and expose
underlying bacteria to the sterilizing agent.
The invention will be further described by way
of example with reference to the accompanying drawings,
in which:
Fig. 1 is a diagram of a hospital sterilizer;
Fig. 2 is a diagram of a field sterilizer; and
Figs. 3 to 9 show a sterilizing chamber at
various stages in the sterilizing cycle.
In the hospital sterilizer of Fig. 1, the
instruments to be sterilized are carried in a wire mesh
basket 1 which allows free circulation of liquids and gases
over the instruments. The basket is supported in the upper
part of a tank 2 closed by a cover 3 to form the sterilizing
chamber.
During the first stage of sterilization, the tank
is filled with water to the level of drain line 4 connected
to the building vacuum system through line 5. During this
stage, if the water level rises above the line 4, the
excess is drained down to that level. Water is supplied
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to the tank from water line 7, through strainer 8, 2ressure
reducing valve 9, manual valve 10, flow meter 11, solenoid
valve 12, and manual valve 13 discharging to the bottom of
the tank. Oxygen for the generation of ozone is obtained
from line 14 connected to the oxygen supply 15 and feeding
the oxygen through filter 16, pressure reducing valve 17,
manual valve 18, solenoid valve 1~, air drier 20, and flo"
meter 21 to ozone generator 23. Pump 16a is only used when
line pressure is not high enough. The ozone from the
generator leaves through line 24 and enters the tank through
a flat nozzle 25 having a large number of fine perforations
26 in its upper surface through which the ozone bubbles
through the water which is maintained at the level of line
4 during the first stage of sterilization. The bubbling
of the ozone through the water causes the ozone to become
dissolved in the water and also creates a moist ozone vapor
which flows upwardly and over the instruments in the basket
1. The moisture laden ozone is an effective sterilizing
agent for all surfaces with which it comes into contact.
A wetting agent added to the water further increases the
effectiveness of the moist ozone. The ozone is an
effective oxidizing agent which oxidizes or burns the
bacteria or spores at temperatures well below steam
sterilizing temperatures. This means that instruments
~5 which cannot stand steam sterilizing temperatures,
pressures or vacuum can be effectively sterilized by the
moist ozone. The ozone vapor is illustrated in Fig. 4
and takes about 15-25 minutes.
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In the next stage, the valve in drain line 4 is
closed and the valve in drain line 27 is opened and the
liquid level in the tank is raised to the level of drain
line 27, the instruments are immersed in ozonated water
S and ozone bubbles contact the instruments and have a
scrubbing action tending to remove surface bacteria- This
actio~ is important for surfaces carrying more than one
layer of bacteria because an outer layer of bacteria could
protect an inner or underlying layer of bacteria from
sterilization. The sterilization effect is greatest at
the outer surface where the bacteria first comes into
contact with the ozone. This stage is illustrated in
Fig. 5. In the next stage, concurrently with the bubbling
ozone, ultrasonic transducers 30 send ultrasonic vibrations
through the water which have a scrubbing action of the
surfaces of the instruments and furthermore have a pulsing
efect on bacteria lodged in crevices which tend to move
the ozone containing water (a sterilizing agent) into and
out of the crevices and thereby dislodge bacteria which
might otherwise not be reached by the sterilizing agent.
During the ultrasonic cycle the ultrasonic transducers are
turned off and on, being on for one second and off for a
few seconds. This is to get the ultrasonic action and not
to drive out of solution the 03. This second stage takes
about 15 minutes.
At the end of the sterilizing cycle, which is
typically an interval about half the total time required
for steam or gas sterilization, the water in tank 2 is
drained through drain line 31 under the control of solenoid
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valve 32 so as to conduct the water to the hospital vacuum
line 5. There is also an alternative manual drain 33. T~,e
flow of ozone continues for about 5 minutes while the tank
is draining and results in some dryiny of the instrurnents.
Oxygen is then flowed through the tank to finish the drying
and flush out the ozone. At the end of the drying portion
of the sterilizing cycle, the cover is removed and the
instrument tray containinq the sterilized instruments is
lifted ~rom the tank.
By way of example, the following test results are
given to show the effectiveness of the sterilizer. Kill
tests have been run at different concentrations of ozone
on a number of different bacteria. This is a typical group.
Bacteria Kill Time Usinq 2% Ozone
Escherichia coli 4 minutes
Staphylocollus aureus 5 minutes
Streptocollus pyogenes 6 minutes
Candida albicans 4 minutes
Penicilium motatum 3 minutes
Aspergillus niger 6 minutes
Bacillus subtilus var. globigii, a difficult to
kill spore forming bacteria, was set up as a kill standard.
USP has set a kill time for sterilization at 120 minutes
for this bacteria. Commercial sterilizers get a kill time
of 30 to 35 minutes for 100% kill. We are producing 100
kill in 15-20 minutes employing 3.5-4.5~ ozone concentration.
The kill time varies directly with ozone
concentration. It will take 75 minutes to kill Bacillus
globigli with an ozone concentration of 1.5%. At 5%
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concentration, less than 10 minutes exposure is required.
The portable or field sterilizer sho~,~ in Fig. 2
is designed to operate on 110 volts, 60 cycles, or on a 12
volt battery and to use air instead of oxygen and to use
water which is continuously recirculated between the
sterilizing chamber and a holding tank. ~ater from t'ne
holding tank is also circulated through the ozone generator
by pump 35 for cooling.
The portable sterilizer can use the wire basket 1,
tank 2 and cover 3 of the hospital sterilizer shown in Fig.
1. Other parts which are the same are indicated by the same
reference numerals.
Air for the ozone generator 23 enters through a
supply duct 36 manually controlled by a valve 37 and flows
through a filter 38 to a pump 39 haviny its output 40
regulated by a pressure regulator 41 and the flow rate set
by valve 18. The air then flows through an air drier 42 to
remove moisture, through a flow meter 43 and control valve
44 into the ozone generator 23. The air drier 42 is
e~uipped with a heating coil 45 which, when energized, will
heat the drier and drive off the water collected. This
operation is performed after each sterilizer run. Valve
44 is closed when the drier 42 is heated, and valve 46 is
open to let the water vapor escape.
The output of the ozone generator 23 which is a
mixture of air and ozone flows through line 24 and a flow
control valve 48 into submerged tubes 49 adjacent the bottom
of tank 2. The tubes which are made of stainless steel have
fine holes in the upper surface along the length thereof
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through which the ozonated air escapes. The ozonated air
bubbles up through the water and forms a moist ozone
containing vapor which sterilizes the instruments in the
basket l. The ozone also dissolves in the water which
itsel~ becomes a sterilizing agent.
The water for the sterilizer is obtained from a
supnly tank 50 which is filled at 51 through valve 72. The
water preferably contains a wetting agent. Other water
soluble sterilizing agents such as hydrogen peroxide,
hydrogen sulphide, HCN, iodine comuounds, etc., can be added
either as a supplementary or as a sole sterilizing agent.
From the supply tank 50, the water flows through a manually
settable valve 52 which is set at a value which determines
the rate of flow and through a filter 53 to a pump 54 which
discharges through a pressure regulating valve 55a to the
bottom of the sterilizing tank 2. The pump 54 runs
continuously during sterilization. During the first stage,
valve 55 is open and water is continually withdrawn through
line B and valve 55 and recirculated to tne tank through
line 56. This maintains a water level up to line B covering
the nozzles 49 so that ozonated air under pressure bubbles
through the water and creates a moist ozone vapor which
sterilizes the instruments in tray l. The level of water
in the tank 50 is shown by a sight gauge 56a. During this
stage, excess ozone containing air leaves the tank 2 through
line 57 and flows through a filter 58 containing carbon and
a heater 59 which breaks down the ozone and converts it to
C2 which is discharged to the atmosphere through valve 60
and outlet line 61. The first stage of sterilizing lasts
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approximately lS minutes.
At the end of the first stage, the valve 55 is
closed and the pump 54 continues to run. The water level
rises to outlet line A which returns the excess water through
line 56 to the supply tank through valve 51A. During this
stage, the instruments in the tray 1 are immersed in ozone
containing water (a sterilizing agent) and ozone is released
from the water in the form of ozone filled bubbles. The
bubbling of ozone over the instruments has a scrubbing
action whi.ch tends to dislodge surface contamination. The
breaking of the bubbles in contact with the instruments also
causes back and forth movement of ozone containing water into
and out of crevices which might contain harmful bacteria.
During this second stage, which may last an additional
15-30 minutes, ultrasonic generators 62 are intermittently
energized, creating ultrasonic waves which exert a further
scrubbing action on the instruments and also assist in
moving the ozone containing liquid back and forth into and
out of crevices. The ultrasonic generators are preferably
on intermittently for a short interval, such as on one
second and off for four seconds, so that the ultrasonic
waves will not excessively drive the dissolved ozone out of
the water.
At the end of the sterilizing cycle, the valves
48, 55a and 60 are closed and valves 63 and 51a are open.
Pump 5~ is stopped. The water in tank 2 drains through
lines 64 and 56 to storage tank 50. The sterile ozone
containing air in the tank is forced through heated carbon
filter 58 which converts the ozone to C02 and 2 which is
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returned by pump 65 through drier 66 and valve 63 to tank 2
~here it plcks up more ozoné containing air and is recycled
through filter 58 to the tank. It will take about 10 minutes
for the water to drain back into stor~ge tank 50. When the
water is below nozzles 49, the pump 65 starts, valve 69
opens and valve 51a closes, and the heating coil in tan~ 2
at 68 will be energized heating the air. This heating
action will help in drying and will help to kill the ozone.
After 30 minutes, the tank 2 is ozone free and the instrume~s
in the tray 1 ar~ dried and the cover 3 can be removed to
permit removal of the instrument tray. The drying has been
accomplished by recirculating sterile air as required to
remove the ozone. Drying may be accelerated by energizing
the heater 68 which further heats the sterile air in the
tank.
Figs. 3-9 show the sterilizing chamber at
successive stages of the sterilizing cycle.
In Fig. 3, the sterilizing chamber is ready to
receive a load of instruments or other material to be
sterilized.
In Fig. 4, the water is below the instruments and
a mixture of ozone and gas (2 for Fig. l; air for Fig. 2)
is being bubbled through the water to form a high humidity
ozone vapor which is an effective sterilizing agent.
In Fig. 5, the water level has been raised to
submerge the instruments in ozone containing water (a
sterilizing agent) containing bubbles of ozone containing
gas which have a scrubbing action effective to dislodge
surface contamiDation and to penetrate crevices.
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In Fig. 6, intermittent ultrasonic vi~ratlons are
added to increase the scrubbiny action. The ultrasonic
vibrations are used during relatively short intervals to
prevent driving of ozone out of the water. The dissolved
ozone is retained to prevent loss of the sterilizing
properties of the water.
In Fig. 7, draining of the water has started.
The bubbling of the ozone continues so sterilizing action
of the high humidity ozone vapor continues.
Fig. 8 shows the drying cycle. For Fig. 1, the
heating element 68 is on and dry ozonated oxygen is
circulated through the sterilizing chamber 2 to the vacuum
line 5, picking up moisture from the instruments. For
the portable sterilizer of Fig. 2, the heating element 68
is on, the ozonated air in the chamber 2 is recycled through
heated ozone filter 58, drier 66 and back into the chamber
2. The ozonated air is sterile. The recycling does not
contaminate the instruments. At the end of the drying
cycle, the instruments are sterile and dry and the
atmosphere in the sterilizing chamber is ozone free.
For sterilizing loads which are not to be
immersed in water, only the stages illustrated in Figs. 3,
4, 8 and 9 are used.
As shown in Fig. 3, material to be sterilized
is loaded into the chamber which is closed and evacuated
to ensure uniform ~enetration of the sterilizing agent.
As shown in Fig. 4, a moist ozone is injected
into the chamber and withdrawn through an ozone filter 58.
At the end of the sterilizing cycle which typically lasts
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from 30-45 minutes, the water is drained, the sterile
atmosphere in the chamber is heated by heating element 6
and circulated through ozone filter 58 to remove ozone
and is returned to the sterilizing chamber through drier
66 where it picks up moisture from the load and is recycled.
After several minutes of recycling, the load is dry, ozone
free, and ready for removal from the chamber, as shown in
Fig. 9. The recycling also removes chemical germicide
additions.
The invention is not limited to ozone and water.
Other liquids, such as alcohol, naphtha, solvents, etc.,
may be added to or substituted for water. The liquids
may have sterilizing properties. Other sterilizing agents,
such as HCN, hydrogen peroxide, hydrogen sulphide, iodine
compounds, may be used in addition or as a substitute for
ozone. Ozone "kills" HCN, hence where both are to be
used the HCN is to be used first, followed by ozone.
