AUTOCLAVE

AUTOCLAVE

English Abstract

An autoclave 10 has a first vessel 12 in which objects are
heated, and a second vessel 14 in which the objects are cooled
down. A container 24 containing the objects is introduced via
a preheating chamber 30 into a chamber 20, and thence into the
cavity 16 of the vessel 12. Similarly, at the downstream end of
the second vessel 14, a container is removed from a cavity 18 via
a chamber 22. Transfer of containers is effected lock fashion
to limit loss of pressure. When a container is thus removed and
a fresh container is loaded, containers in the cavity 16 are
advanced upwardly and containers in the cavity 18 are advanced
downwardly. A container at the top of the cavity 16 is laterally
displaced to the top of the cavity 18, via a chamber 19. The
autoclave is thus operated continuously, stepwise. Pressures and
temperatures are monitored via an interface 32 and a computer 34.
Sterilization values for the objects are computed and advance of
the containers are dependant on appropriate sterilization values
being obtained.

Claims

21
CLAIMS
1. A method of operating an autoclave for sequentially
heating separate objects under pressure and cooling said objects,
the method including
providing an autoclave having, lock fashion, a pre-transfer
chamber and a post-transfer chamber, means selectively to
communicate respectively the pre-transfer chamber and the post-
transfer chamber with and to isolate respectively the pre-
transfer chamber and the post-transfer chamber from an operative
cavity of the autoclave, and means for selectively pressurizing
and depressurizing the respective pre-transfer chamber and post-
transfer chamber;
loading an object to be treated into the autoclave by,
sequentially, isolating the pre-transfer chamber from the
autoclave cavity, depressurizing the pre-transfer chamber,
introducing the object into the pre-transfer chamber, isolating
the pre-transfer chamber from atmosphere, pressurizing the pre-
transfer chamber, communicating the pre-transfer chamber with the
autoclave cavity and transferring the object from the pre-
transfer chamber into the autoclave cavity; and
unloading another object which has been treated from the
autoclave by, sequentially, isolating the post-transfer chamber
from atmosphere, pressurizing the post-transfer chamber,

22
communicating the post-transfer chamber with the autoclave
cavity, transferring said other object into the post-transfer
chamber, isolating the post-transfer chamber from the autoclave
cavity, depressurizing the post-transfer chamber and removing
said other object from the post-transfer chamber.
2. A method as claimed in Claim 1 in which isolating the
respective pre-transfer chamber and post-transfer chamber from
the autoclave cavity is by closing pressure tight closures
between the respective pre-transfer chamber and post-transfer
chamber and the autoclave cavity, in which communicating the
respective pre-transfer chamber and post-transfer chamber with
the autoclave cavity is by opening said pressure tight closures,
and in which transferring the respective objects is via openings
left open by opening of said pressure tight closures.
3. A method as claimed in Claim 1 in which pressurizing
each respective chamber is by intercommunicating it via a
restrictive passage with the autoclave cavity.
4. A method as claimed in Claim 1 in which loading and
unloading are synchronized to take place simultaneously.
5. A method as claimed in Claim 1 in which the autoclave
is a composite autoclave which includes a first vessel and a
second vessel, the pre-transfer chamber being associated with the
first vessel and the post-transfer chamber being associated with
the second vessel, the method including progressively moving

23
objects from the pre-transfer chamber through the first vessel,
heating said objects in the first vessel, intermittently
transferring said objects to the second vessel, cooling said
objects in the second vessel and progressively moving said
objects through the second vessel toward the post-transfer
chamber.
6. A method as claimed in Claim 5, in which intermittently
transferring said objects from the first vessel to the second
vessel is via an intermediate transfer chamber, the method
including isolating the intermediate transfer chamber from the
second vessel, communicating the intermediate transfer chamber
with the first vessel, transferring a respective object from the
first vessel to the intermediate transfer chamber, isolating the
intermediate transfer chamber from the first vessel,
communicating the intermediate transfer chamber with the second
vessel and transferring said respective object from the
intermediate transfer chamber to the second vessel.
7. A method as claimed in Claim 6 which includes operating
the second vessel at a pressure different to the pressure of the
first vessel.
8. A method as claimed in Claim 7 which includes, after
isolating the intermediate transfer chamber from the first
vessel, and before communicating the intermediate transfer
chamber with the second vessel, equalizing pressures between the
second vessel and the intermediate chamber.

24
9. A method as claimed in Claim 8 in which equalizing
pressures is effected by exposing the intermediate transfer
chamber to the second vessel via a restricted passage.
10. A method as claimed in Claim 1, in which introducing
said object into the pre-transfer chamber is via a pre-heating
chamber, the method including the steps of introducing a
respective object into the pre-heating chamber, pre-heating said
respective object in the pre-heating chamber, and in which
depressurizing the pre-transfer chamber includes isolating the
pre-heating chamber from atmosphere, exposing the pre-transfer
chamber to the pre-heating chamber, and relieving the pre-
transfer chamber into the pre-heating chamber.
11. A method as claimed in Claim 1 which includes
measuring, at predetermined time intervals, a temperature in the
autoclave cavity, comparing the measured temperature with a
predetermined base temperature, and adjusting energy input into
the autoclave cavity appropriately in response to the difference
between the measured temperature and the predetermined base
temperature.
12. A method as claimed in Claim 1 which includes
establishing repeatedly, at predetermined time intervals, a
temperature of a respective object, computing a sterilization
value Fo for said object in accordance with the formula
Fo= <IMG>

in which
.DELTA.T is a convenient time interval;
ti is the average temperature of a product in the i-th
time interval;
tref is a reference temperature;
n is determined such that the sterilization value F0 is
bigger than a pre-defined set-point value,
comparing the computed value for F0 with a predetermined base
value for F0, and unloading said respective object only when the
calculated value for F0 of said respective object is at least
equal to the base value for F0.
13. A method as claimed in Claim 12 which includes
measuring the average steam temperature, in the or each chamber
or cavity in which the respective objects are heated, repeatedly
at predetermined time intervals, and computing the value of ti in
accordance with the formula
ti = <IMG>
in which
ti is the average temperature of a product in the i-th
time interval;
.DELTA.T is a convenient time interval;
tsteami is the average steam temperature as measured in
the i-th time interval;
C is an experimentally determined parameter;
ti-1 is the average temperature of a product in the i-1
interval.
14. A method as claimed in Claim 12 which includes
recording the F0 value of each object and identifying each object
with said F0 value.

26
15. A method as claimed in Claim 12 which includes
advancing the objects through the autoclave under control of a
computer in accordance with predetermined criteria in respect of
positions of respective objects in the autoclave and the values
of Fo of the respective objects.
16. A method as claimed in Claim 1 in which each object is
in the form of a product contained in a container forming part
of the autoclave.
17. An autoclave for heating, under pressure, separate
objects, the autoclave including, lock-fashion, a pre-transfer
chamber and a post-transfer chamber, means selectively to
communicate each of the pre-transfer chamber and post-transfer
chamber with and to isolate each of the pre-transfer chamber and
post-transfer chamber from atmosphere and from an operative
cavity of the autoclave, pressurizing means for selectively
pressurizing and depressurizing means for selectively
depressurizing the respective pre-transfer chamber and post-
transfer chamber, loading means suitable for loading the objects
into the pre-transfer chamber, unloading means suitable for
unloading the objects from the post-transfer chamber, and
transport means suitable for transporting the objects from the
pre-transfer chamber through the autoclave cavity to the post-
transfer chamber.
18. An autoclave as claimed in Claim 17 which is a
composite autoclave and which includes a first vessel and a

27
second vessel, the operative cavity being defined as sub-cavities
in said first vessel and said second vessel, the pre-transfer
chamber being associated with the first vessel, and the post-
transfer chamber being associated with the second vessel, the
autoclave including an intermediate transfer chamber arranged to
operate lock-fashion intermediate the first vessel and the second
vessel, and means selectively respectively to communicate the
intermediate transfer chamber with each of the first vessel and
the second vessel and to isolate the intermediate transfer
chamber from each of the first vessel and the second vessel.
19. An autoclave as claimed in Claim 18 in which the second
vessel is adapted selectively to be operated at a pressure
different to the pressure of the first vessel, the autoclave
having pressure equalizing means selectively operable between the
intermediate transfer chamber and the second vessel.
20. An autoclave as claimed in Claim 18 which includes a
plurality of containers suitable to contain the objects, the
transport means being adapted for progressively, intermittently
in stepped manner, transporting the containers from the pre-
transfer chamber through the first vessel, and thence via the
intermediate transfer chamber to the second vessel and through
the second vessel to the post-transfer chamber.
21. An autoclave as claimed in Claim 20 in which the
transport means is arranged to effect transport along the first
vessel upwardly and to effect transport along the second vessel

28
downwardly, the intermediate transfer chamber being arranged
intermediate the first vessel and the second vessel at a high
level.
22. An autoclave as claimed in Claim 17 in which the
pressurizing means includes pressurizing passages between the
autoclave cavity and respectively the pre-transfer chamber and
post-transfer chamber and valve means selectively to open and
close said pressurizing passages.
23. An autoclave as claimed in Claim 17 in which the means
selectively to communicate each
of the pre-transfer chamber and the post-transfer chamber with
and to isolate each of the pre-transfer chamber and the post-
transfer chamber from the operative cavity of the autoclave is
in the form of openable closures, which are pressure-tight when
closed, intermediate the autoclave cavity and respectively the
pre-transfer chamber and the post-transfer chamber.
24. An autoclave as claimed in Claim 17 which includes a
pre-heating chamber upstream of the pre-transfer chamber,
isolating means arranged selectively to isolate the pre-heating
chamber from atmosphere, and lock means arranged selectively to
communicate the pre-heating chamber and the pre-transfer chamber
and to isolate the pre-heating chamber from the pre-transfer
chamber.

29
25. An autoclave as claimed in Claim 17 which includes
temperature measuring means arranged to measure temperature
repeatedly, at predetermined time intervals, in the autoclave,
computing means for computing sterilization values F0 for objects
being sterilized in accordance with the formula
F0 = <IMG>
in which
.DELTA.T is a convenient time interval;
ti is the average temperature of a product in the i-th
time interval;
tref is a reference temperature;
n is determined such that the sterilization value F0 is
bigger than a pre-defined set-point value,
and comparing means for comparing the computed value for F0 with
a predetermined base value for F0, the unloading means being
adapted in response to the result of comparing the computed and
base values for F0, to unload the object only when the computed
value for F0 is at least equal to the base value for F0.
26. An autoclave as claimed in Claim 25 in which the
computing means is adapted to compute a value for ti in
accordance with the formula
ti = <IMG>
27. An autoclave as claimed in Claim 25 which includes
computerized control means adapted to actuate the transport means
to advance the objects through the autoclave in accordance with
predetermined criteria in respect of positions of respective

objects in the autoclave and the values of Fo of the respective
objects.
28. An autoclave as claimed in Claim 17 which includes a
plurality of containers.

Description

2I2751~
THIS INVENTION relates to an autoclave.
In an autoclave, matter is heated to high temperature
under conditions of high pressure. In one kind of application,
matter or objects are thus heated to sterilize the matter or
objects.
When an autoclave is batch operated, it is charged with
the matter or filled with the objects, closed, and pressurized
and heated. After the pressurizing and heating operation, the
autoclave is cooled and depressurized, opened and then unloaded.
In continuous operated autoclaves known to the
Inventor, flowable matter is continuously pumped under high
pressure into the autoclave while flowable matter is
correspondingly continuously exhausted out of the autoclave.
In accordance with this invention, broadly, there is
provided a method of operating an autoclave for sequentially

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heating separate objects under pressure and cooling said objects,
the method including
providing an autoclave having, lock fashion, a pre-transfer
chamber and a post-transfer chamber, means selectively to
communicate respectively the pre-transfer chamber and the post-
transfer chamber with and to isolate respectively the pre-
transfer chamber and the post-transfer chamber from an operative
cavity of the autoclave, and means for selectively pressurizing
and depressurizing the respective pre-transfer chamber and post-
transfer chamber;
loading an object to be treated into the autoclave by,
sequentially, isolating the pre-transfer chamber from the
autoclave cavity, depressurizing the pre-transfer chamber,
introducing the object into the pre-transfer chamber, isolating
the pre-transfer chamber from atmosphere, pressurizing the pre-
transfer chamber, communicating the pre-transfer chamber with the
autoclave cavity and transferring the object from the pre-
transfer chamber into the autoclave cavity; and
unloading another object which has been treated from the
autoclave by, sequentially, isolating the post-transfer chamber
from atmosphere, pressurizing the post-transfer chamber,
communicating the post-transfer chamber with the autoclave
cavity, transferring said other object into the post-transfer
chamber, isolating the post-transfer chamber from the autoclave
cavity, depressurizing the post-transfer chamber and removing
said other object from the post-transfer chamber.

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It is to be appreciated that in respect of both of the
pre-transfer chamber and the post-transfer chamber, pressurizing
is to a pressure substantially equal to the prevailing pressure
in the autoclave cavity.
Isolating the respective pre-transfer chamber and post-
transfer chamber from the autoclave cavity may be by closing
pressure tight closures between the respective pre-transfer
chamber and post-transfer chamber and the autoclave cavity.
Communicating the respective pre-transfer chamber and post-
transfer chamber with the autoclave cavity may be by opening said
pressure tight closures, and transferring the respective objects
may thus be via openings left open by opening of said pressure
tight closures.
Pressurizing each respective chamber may be by
intercommunicating it via a restrictive passage with the
autoclave cavity.
Advantageously, loading and unloading may be
synchronized to take place simultaneously.
In a preferred method, applied in a composite autoclave
which includes a first vessel and a second vessel, the pre-
transfer chamber being associated with the first vessel and the
post-transfer chamber being associated with the second vessel,
the method may include progressively moving objects from the pre-
transfer chamber through the first vessel, heating said objects

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in the first vessel, intermittently transferring said objects to
the second vessel, cooling said objects in the second vessel and
progressively moving said objects through the second vessel
toward the post-transfer chamber.
Such intermittently transferring said objects from the
first vessel to the second vessel may be via an intermediate
transfer chamber. The method may thus include isolating the
intermediate transfer chamber from the second vessel,
communicating the intermediate transfer chamber with the first
vessel, transferring a respective object from the first vessel
to the intermediate transfer chamber, isolating the intermediate
transfer chamber from the first vessel, communicating the
intermediate transfer chamber with the second vessel and
transferring said respective object from the intermediate
transfer chamber to the second vessel.
If desired or if required, the method may include
operating the second vessel at a pressure different to the
pressure of the first vessel. Then, the method may include,
after isolating the intermediate transfer chamber from the first
vessel, and before communicating the intermediate transfer
chamber with the second vessel, equalizing pressures between the
second vessel and the i~termediate chamber. Equalizing pressures
may be effected by exposing the intermediate transfer chamber to
the second vessel via a restricted passage.

2127-514
By way of development, introducing said object into the
pre-transfer chamber may be via a pre-heating chamber. The
method may thus include the steps of introducing a respective
object into the pre-heating chamber and pre-heating said
respective object in the pre-heating chamber. Depressurizing the
pre-transfer chamber may include isolating the pre-heating
chamber from atmosphere, exposing the pre-transfer chamber to the
pre-heating chamber, and relieving the pre-transfer chamber into
the pre-heating chamber.
The method may include measuring, at predetermined time
intervals, a temperature in the autoclave cavity, comparing the
measured temperature with a predetermined base temperature, and
adjusting energy input into the autoclave cavity appropriately
in response to the difference between the measured temperature
and the predetermined base temperature.
Further by way of advantageous development, the method
may include establishing repeatedly, at predetermined time
intervals, a temperature of a respective object, computing a
sterilization value Fo for said object in accordance with the
formula
~ t; - t~
n \ 10 J
Fo = ~T * ~ 10
i=1
in which
~T is a convenient time interval, for example 10
seconds;
ti is the average temperature of a product in the i-th
time interval;
t~ is a reference temperature namely 121.1C;

~_ 21~7!~1~
n is determined such that the sterilization value Fo is
bigger than a pre-defined set-point value,
comparing the computed value for Fo with a predetermined base
value for Fo~ and unloading said respective object only when the
calculated value for Fo of said respective object is at least
equal to the base value for Fo~
The method may include measuring the average steam
temperature in the or each chamber or cavity in which the
respective objects are heated, i.e. in the preheating chamber and
in the cavity of the first vessel, repeatedly at predetermined
time intervals, and computing the value of t; in accordance with
the formula
(tj_l + C * ~T * tS~m i)
t; =
(1 + C * ~T)
in which
t; is the average temperature of a product in the i-th
time interval;
~T is a convenient time interval, for example 10
seconds;
tS~m; is the average steam temperature as measured in
the i-th time interval;
C is an experimentally determined parameter;
tjl is the average temperature of a product in the i-1
interval.
The method may include recording the Fo value of each
object and identifying each object with said Fo value.
The method may then include advancing the objects
through the autoclave under control of a computer in accordance
with predetermined criteria in respect of positions of respective

` 212751~
objects in the autoclave and the values of Fo of the respective
objects.
Each object may be in the form of a product contained
in a container forming part of the autoclave.
The invention extends to an autoclave for heating,
under pressure, separate objects, the autoclave including, lock-
fashion, a pre-transfer chamber and a post-transfer chamber,
means selectively to communicate each of the pre-transfer chamber
and post-transfer chamber with and to isolate each of the pre-
transfer chamber and post-transfer chamber from atmosphere and
from an operative cavity of the autoclave, pressurizing means for
selectively pressurizing and depressurizing means for selectively
depressurizing the respective pre-transfer chamber and post-
transfer chamber, loading means suitable for loading the objects
into the pre-transfer chamber, unloading means suitable for
unloading the objects from the post-transfer chamber, and
transport means suitable for transporting the objects from the
pre-transfer chamber through the autoclave cavity to the post-
transfer chamber.
Advantageously, the autoclave may be a composite
autoclave which includes a first vessel and a second vessel, the
operative cavity being defined as sub-cavities in said first
vessel and said second vessel, the pre-transfer chamber being
associated with the first vessel, and the post-transfer chamber
being associated with the second vessel, the autoclave including

~1275~
an intermediate transfer chamber arranged to operate lock-fashion
intermediate the first vessel and the second vessel, and means
selectively respectively to communicate the intermediate transfer
chamber with each of the first vessel and the second vessel and
to isolate the intermediate transfer chamber from each of the
first vessel and the second vessel.
The second vessel may be adapted selectively to be
operated at a pressure different to the pressure of the first
vessel, the autoclave having pressure equalizing means
selectively operable between the intermediate transfer chamber
and the second vessel.
The autoclave may include a plurality of containers
suitable to contain the objects, the transport means being
adapted for progressively, intermittently in stepped manner,
transporting the containers from the pre-transfer chamber through
the first vessel, and thence via the intermediate transfer
chamber to the second vessel and through the second vessel to the
post-transfer chamber. The transport means may be arranged to
effect transport along the first vessel upwardly and to effect
transport along the second vessel downwardly, the intermediate
transfer chamber being arranged intermediate the first vessel and
the second vessel at a high level.
The pressurizing means may include pressurizing
passages between the autoclave cavity and respectively the pre-
transfer chamber and post-transfer chamber and valve means
selectively to open and close said pressurizing passages.

` ~l27sl 1
The means selectively to communicate each of the pre-
transfer chamber and the post-transfer chamber with and to
isolate each of the pre-transfer chamber and the post-transfer
chamber from the operative cavity of the autoclave may be in the
form of openable closures, which are pressure-tight when closed,
intermediate the autoclave cavity and respectively the pre-
transfer chamber and the post-transfer chamber.
By way of development, the autoclave may include a pre-
heating chamber upstream of the pre-transfer chamber, isolating
means arranged selectively to isolate the pre-heating chamber
from atmosphere, and lock means arranged selectively to
communicate the pre-heating chamber and the pre-transfer chamber
and to isolate the pre-heating chamber from the pre-transfer
chamber.
By way of advantageous development, the autoclave may
include temperature measuring means arranged to measure
temperature repeatedly, at predetermined time intervals, in the
autoclave, computing means for computing a sterilization value
Fo for an object in accordance with the formula
~ ti - t~f~
n ~ 10 J
Fo = ~T * ~ 10
i=1
in which
~T is a convenient time interval, for example 10
seconds;
tj is the average temperature of a product in the i-th
time interval;
t~f is a reference temperature namely 121.1C;
n is determined such that the sterilization value Fo is
bigger than a pre-defined set-point value,

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and comparing means for comparing the computed value for Fo with
a predetermined base value for Fo/ the unloading means being
adapted in response to the result of comparing the computed and
base values for Fo~ to unload the object only when the computed
value for Fo is at least equal to the base value for Fo~
The computing means may be adapted to compute a value
for t; in accordance with the formula
(tjl + C * ~T * tS,e~ ;)
t; = .
(1 + C * ~T)
in which
t; is the average temperature of a product in the i-th
time interval;
~T is a convenient time interval, for example 10
seconds;
tS~m; is the average steam temperature as measured in
the i-th time interval;
C is an experimentally determined parameter;
tj1 is the average temperature of a product in the i-1
interval.
The autoclave may include computerized control means
adapted to actuate the transport means to advance the objects
through the autoclave in accordance with predetermined criteria
in respect of positions of respective objects in the autoclave
and the values of Fo of the respective objects.
The autoclave may include a plurality of containers.
The invention is now described by way of example with
reference to the accompanying diagrammatic drawing which shows,

212751~
12
schematically, in side view, an autoclave in accordance with this
invention.
With reference to the drawing, an autoclave in
accordance with the invention is generally indicated by reference
numeral 10. The autoclave 10 is a composite autoclave comprising
a first pressure vessel 12 and a second pressure vessel 14. The
vessels 12, 14 respectively enclose autoclave cavities generally
indicated respectively by reference numerals 16 and 18 which
cavities are adapted to be operated under pressure at high
temperature. In the embodiment shown, the autoclave is adapted
to be operated with steam.
A transversely extending intermediate transfer chamber
19 interconnects the first and second vessels 12, 14 at positions
toward upper ends of the vessels.
The vessel 12, more specifically associated with the
cavity 16, incorporates heating means for heating the cavity 16.
The vessel 14, more specifically associated with the cavity 18,
incorporates cooling means for cooling the cavity 18.
Pressurizing means (not shown) is provided to
pressurize the vessels 12, 14.
External to and adjacent to the vessel 12, at a low
level and associated with a lower end of the first vessel 12,
there is provided a pre-transfer chamber 20. Likewise, external

21~751~
13
to, and adjacent to the second vessel 14 and associated with a
lower end thereof, there is provided a post-transfer chamber 22.
The autoclave 10 has displacement means including a
plurality of drawer-like containers 24 and mechanized transport
means progressively to displace the containers upwardly in the
cavity 16, into the intermediate transfer chamber 19,
transversely along the intermediate transfer chamber 19 to the
top of the cavity 18 and downwardly along the cavity 18 to the
post-transfer chamber 22. For use with small or flat objects,
a container may be divided in upper and lower compartments, each
compartment then containing one or more objects.
The pre-transfer chamber 20 and post-transfer chamber
22 are shaped commensurate with and such as to contain containers
24. The containers 24 in use contain objects which are to be
heated under pressure in the autoclave 10. Such objects may, for
example, be surgical instruments which are to be sterilized for
use in an operating theatre, drip bags containing water to be
sterilized, and the like.
Each of the pre-transfer chamber 20 and the post-
transfer 22 has a pressure-tight, openable closure 26.1, 26.2
selectively to open the respective chambers externally or to
atmosphere respectively to allow a container 24 to be introduced
or loaded into the pre-transfer chamber 20 and such a container
to be removed or unloaded from the post-transfer chamber 22.

~ 7 5 1 ~
14
Furthermore, intermediate the respective autoclave
cavities 16, 18 and respectively the pre-transfer chamber 20 and
the post-transfer chamber 22, there are provided openable
closures 26.3, 26.4 which are pressure tight and which, when
open, afford communication between the respective autoclave
cavities and respectively the pre-transfer chamber 20 and the
post-transfer chamber 22.
It is to be appreciated that, when closed, all of the
closures mentioned above are substantially pressure tight.
Pressurizing means is provided in the form of
pressurizing passages between the respective autoclave cavities
16, 18 and respectively the pre-transfer chamber 20 and the post-
transfer chamber 22 together with valve means selectively to
render the passages open and closed. Similarly, depressurizing
means is provided in the form of depressurizing passages leading
respectively from the pre-transfer chamber 20 and from the post-
transfer chamber 22 to vent the respective chambers. The
depressurizing passages are provided together with valve means
selectively to render the depressurizing passages open and
closed.
When objects to be heated under pressure are to be
introduced into the autoclave 10, they are placed within the
container 24. The containers 24 are progressively loaded into
the autoclave 10. Visualize a specific container 24 containing
objects. It is introduced or loaded via the pre-transfer chamber

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20 into the cavity 16. In synchronization, a similar container
is removed or unloaded from the lower end of the cavity 18 via
the post-transfer chamber 22 to remove objects 26 which have
already undergone heating under pressure.
Assume that the pre-transfer chamber 20 is in
communication with the autoclave cavity 16 and is isolated from
atmosphere while the pos~-transfer chamber 22 is isolated from
the autoclave cavity 18 and is open to atmosphere. As a first
step, the post-transfer chamber is isolated from atmosphere and
the pre-transfer chamber 20 is isolated from the autoclave cavity
16.
To effect loading, the pre-transfer chamber 20 is
depressurized by opening the respective depressurizing passage.
The openable closure 26.1 giving external access is then opened,
the container 24 is introduced into the chamber 20 and the
closure 26.1 is closed.
Unloading is effected by venting the autoclave cavity
18 via the pressurizing passage into the post-transfer chamber
22. When the pressures have been equalized, the closure 26.4
giving access from the autoclave cavity 18 into the chamber 22
is opened, and a container 24 is displaced from a bottom of the
cavity 18 into the chamber 22. The closure 26.4 is closed.

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At that stage, both the chamber 20 and the chamber 22
contain containers and both are isolated from the respective
autoclave cavities 16, 18 and from atmosphere.
The pre-transfer chamber 20 is then pressurized to
autoclave pressure via the respective pressurizing passage by
venting the autoclave cavity 16 into the chamber 20. When
pressures are equal, the closure 26.3 intermediate the autoclave
cavity 16 and the chamber 20 can be-opened and the container 24
containing the objects 26 is introduced into the autoclave cavity
16 at the bottom thereof.
More or less simultaneously, the chamber 22 is
depressurized by venting it to atmosphere and the drawer is
unloaded by opening the external closure 26.2.
Associated with loading and unloading, in the cavity
16, the containers 24 have been moved up one position each and
the containers 24 in the cavity 18 have been moved down one
position each. The top container in the cavity 16 has been
displaced into the intermediate transfer chamber 19, has been
displaced laterally through the intermediate transfer chamber 19
and has been displaced downwardly to the top of the second
portion 16. Such displacing is effected lock-fashion via the
closures 26.5 and 26.6 and, if required, by equalizing pressures
firstly between the chamber 19 and the cavity 16, and secondly
between the chamber 19 and the cavity 18.

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The above procedure is intermittently repeated, to
introduce containers containing fresh objects into the autoclave
and to remove containers containing treated objects from the
autoclave. The procedure is controlled, as described below, to
ensure the required degree of sterilizing.
The autoclave cavity is repressurized from time to time
to maintain its pressure within predetermined limits. Heating
is controlled to maintain appropriately high temperatures.
By way of development, there is provided a preheating
chamber 30 upstream of the pre-transfer chamber 20. The
preheating chamber 30 has capacity to contain a plurality of
containers 24. The closure 26.1 is arranged selectively to
communicate the preheating chamber 30 and the pre-transfer
chamber 20, and to isolate them. In addition, there is provided
a closure 26.7 intermediate the preheating chamber 30 and
atmosphere.
Thus, by closing the closure 26.1, the preheating
chamber 30 is isolated from the autoclave 10 to allow loading of
fresh containers 24. After loading, the preheating chamber 30
is isolated from atmosphere by closing the closure 26.7 to allow
the containers in waiting to be preheated prior to being loaded
into the autoclave 10 via the pre-transfer chamber 20.
Preheating is effected, if desired, by providing
heating means associated with the preheating chamber. Preheating

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18
is facilitated conveniently by depressurizing the pre-transfer
chamber 20 via an appropriate passage and valve means into the
preheating chamber 30 to re-use the energy which would otherwise
have been lost.
Apart from using waste energy, the use of the
preheating chamber has the advantages that the thermal shock on
the autoclave cavity 16 when loading takes place is diminished
and that the objects preheated are brought to elevated
temperatures in the cavity 16 quicker than would otherwise have
been possible thus enhancing the capacity of the autoclave 10.
The Inventor regards it as extremely important that
operation of the autoclave 10 is managed or controlled
automatically by means of a computer. The Inventor further
regards it as of paramount importance that such control is based
primarily on computing a sterilization value Fo (as described
above) in respect of the objects in each container and
controlling advance of the objects or the containers through the
autoclave on actual sterilization values achieved in use.
Furthermore, temperature control in the autoclave cavity 16 is
based on the sterilization values measured in comparison to base
sterilization values.
Thus, control of operation of the autoclave 10 is via
an interface 32 by means of a computer 34.

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Control commences with compiling of information
regarding pressure and temperature at strategic positions through
the autoclave, more specifically, in respect of temperature, in
the preheating chamber, in the autoclave cavity 16, and the
autoclave cavity 18. Monitoring of pressure is important in
respect of transport, lock fashion, of the containers and is
monitored in the autoclave cavity 16, the intermediate transfer
chamber 19, the autoclave cavity 18 and the post-transfer chamber
22.
As described above, the sterilization value or Fo value
for each container is computed based on data actually measured
and progression of the sterilization process, or advance of the
containers through the autoclave 10, is controlled in accordance
with comparisons between actual sterilization values achieved and
predetermined base values fcr sterilization values which are
predetermined.
By means of the computer 34, via the interface 32, the
valves for controlling pressurization and depressurization,
hydraulic or pneumatic cylinders for opening and closing
closures, and the transport means, are controlled.
It is an advantage of the invention that an autoclave
in accordance with the invention can receive fresh objects and
can exhaust treated objects on a substantially continuous albeit
stepwise fashion. It is further an advantage that less energy
is required to maintain the pressure in the autoclave cavity as,

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first, only a relatively small chamber is depressurized and
pressurized in respect of each loading and unloading operation.
It is an important advantage that the autoclave can be operated
on a continuous basis as opposed to batch operation.
It is further an advantage that objects to be sterilized are
advanced and are ultimately unloaded from the autoclave only in
response to appropriate results obtained from automated
monitoring of the sterilization value to ensure adequate or
appropriate sterilization of the products.

Representative Drawing