Method for sterilizing containers

In a method for sterilizing a container, a valve body (30) is supported by a gas chamber (24) which is under atmospheric pressure. As a result when a pressure difference is present a static condition arises and keeps the valve open or closed. The valve can be used in a variety of way as influx or admission valve or condensate drain valve or as vacuum or condensate drain valve. The control method effects that in each phase the effective valve is kept open also after reaching the negative or positive peak pressure value until the pressure in the autoclave has adjusted itself to a predetermined closing switching pressure.

Sterilizing containers are used to accommodate clinical sterile material 
which must be subjected to a steam sterilization. Said sterilization takes 
place in sterilizers which operate either by the gravitation method (flow 
method) or in modern equipment increasingly by a vacuum method in which 
firstly one or more vacuum phases are provided to extract the air from the 
container, whereafter the container interior is exposed to a steam 
atmosphere under elevated pressure and elevated temperature, the 
sterilizing material thereby being subjected to a sterilization. It is 
advantageous to drain condensate forming so that the material is available 
as dry as possible after the sterilization. After the steam sterilization 
time the container is subjected to a further vacuum treatment to withdraw 
the sterilization steam with any remaining condensate from the container. 
To permit the medium exchange the sterilizing containers are either 
equipped with filters allowing a medium exchange but preventing 
recontamination or valves are disposed in the container wall which close 
after the pressure exchange is completed. As influx or vacuum valves check 
valves according to DE 217,551 or a double valve according to DE 1,217,550 
are frequently used. As condensate draining valve bi-metal valves have 
established themselves which have the advantage over pure check valves 
that an opening of the valve for draining the condensate can take place 
throughout the entire sterilizing stage. 
A valve which can carry out all these functions is known from U.S. Pat. No. 
4,228,914. In this case the gas chamber acting on the valve body is filled 
with steam during the steam influx phase and at the end of the steam 
influx phase, i.e. at the start of the sterilization time, the influx 
opening to the gas chamber is sealed via a shrink hose so that on the 
subsequent pressure reduction expansion of the gas chamber can effect 
closure of the valve. This construction requires that after each 
sterilizing operation the shrink hose must be replaced to ensure the 
sealing function. The sealing function cannot be effected properly if the 
shrink hose does not establish a reliable seal. If a leakage flow takes 
place at the influx opening the seal is jeopardized because the pressure 
difference necessary for the closure pressure cannot form. 
The invention overcomes the problem of providing an operationally safe 
valve system which operates reliably automatically without addition and 
setting of parts and can be used in a variety of ways. 
Due to the fact that the gas volume remains permanently in the chamber and 
need not be replenished on each sterilizing operation as in the prior art 
a reliable and leak-flow-free seal can be achieved in simple manner, and 
said gas volume can be introduced under a defined pressure at 
predetermined temperature, in particular under atmospheric pressure, 
thereby ensuring reliable operation. Conveniently, the differential 
pressure valve function is subjected to a spring bias, the valve opening 
or closing operation thereby being displaced somewhat with respect to the 
atmospheric line. This is however admissible and desirable and the 
temperature-induced pressure differences within the gas chamber can be 
compensated adequately as regards the desired function. 
The particular difference of the invention compared with conventional check 
valves resides in that in this case the control force is not the pressure 
difference acting on the valve disc but a force resulting from the 
compression or elongation of a pressure pickup (roll diaphragms, 
diaphragms, concertina hose, corrugated tube, pressure cylinder, barometer 
cam, etc.) which effects the valve stroke via control rods, control cams, 
levers, or alternatively (preferably) directly. The decisive part for the 
opening and closure condition of the valve is therefore played by the 
pressure present in the sterilizing chamber and not the presence (absence) 
of a pressure difference at the valve itself. The control force generated 
by the pressure pickup can be further intensified by supplementing 
(replacing) part of the gas pressure spring or all of said spring by 
liquid (preferably water) whose boiling point is set to the desired 
switching point (usually about 100.degree. C.) This then gives a 
combination of pressure-dependent and temperature-dependent control. 
The valve according to the invention may be used as influx valve for 
controlling the influx gas jet or as vacuum valve for extracting the steam 
and finally the valve may also be used as condensate drain valve. 
By appropriate valve configuration and arrangement it can be ensured that 
after the last vacuum phase the container is not completely ventilated 
again so that the container content is subjected to a vacuum until made 
available in the operating theater, the penetration of air on opening 
container showing that said vacuum remained present until said opening. 
Other features and advantages of the present invention will become apparent 
from the following description of preferred embodiments of the invention, 
with reference to the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows a sterilizing container of the design described in DE 
3,146,349. Said sterilizing container comprises a container lower portion 
10, a container cover 12 and an intermediate cover 14 carried by the 
latter. The intermediate cover 14 is sealed with respect to the upper edge 
of the container lower portion 10 via a sealing ring 16. The cover 12 is 
detachably secured to the container lower portion 10 via clamp fasteners 
18, the intermediate cover 14 thereby being sealingly biased against the 
lower portion 10 via the supports 19 carrying the intermediate cover 14. 
The intermediate cover 14 is equipped with valves 20 which are only 
indicated schematically in FIGS. 1 and 2. As apparent from FIG. 1 the 
bottom of the container lower portion 10 drops downwardly from all sides 
towards the center where a further valve 22 indicated only schematically 
in FIGS. 1 and 2 is arranged which can serve as condensate drain. Said 
valves 20 and 22 form the subject of the invention and are illustrated in 
various examples of embodiment of the invention in FIGS. 3 to 11. Said 
valves can be used in sterilizing containers of a great variety of types 
and their use is not restricted to the embodiment illustrated in FIGS 1 
and 2. In particular, the valves 20 may be arranged in a container cover 
fitted sealingly on the container lower portion or alternatively in the 
container lower portion. 
Common to all the embodiments is a gas chamber 24 which is sealed all round 
and bordered at least partially by resilient walls and in which a 
predetermined gas volume under predetermined pressure, preferably dry air 
under atmospheric pressure, is enclosed. All the valves are 
rotation-symmetrical with respect to a center axis 26. In all the example 
(apart from the embodiment of FIG. 4) one of the opposing circular chamber 
walls 28 carries a valve body in the form of an encircling sealing bead or 
sealing edge 30 which in the rest state bears on the container wall 
portion 32 which forms the valve seat. Within the surface portion 
surrounded by the sealing bead 30 the wall portion 32 is provided with 
passage holes 34 serving for the exchange of the media. 
The chamber wall 28 is stiffened by an inwardly disposed plate 36 of metal 
or plastic. The opposite chamber wall 38 is likewise stiffened by a plate 
40. The cylindrical side wall 42 between the front wall 28 and the rear 
wall 38 is flexible in such a manner that the spacing between the front 
and rear wall is variable depending on the pressure differences obtaining. 
Said side wall can be made in the manner of a bellows or concertina and 
the chamber wall can be made in one piece or consist of several parts 
which are joined sealingly together. The stiffening plates 36 and 40 also 
serve as spring plates for a biasing helical spring 44 disposed 
therebetween which pushes the two walls 28, 38 apart and tends to increase 
the chamber volume. The gas chamber is surrounded by a housing 46 which is 
provided with openings and which is riveted to the wall portion 32 or 
otherwise secured. The rear wall 38 can be connected to the housing 46 for 
example by riveting. 
In all the examples the gas pressure of the chamber acts directly on the 
valve bodies. This has the advantage that the valves can be accommodated 
compactly on the container wall. If considered expedient in specific cases 
the gas pressure chamber can also be arranged spaced from the valve bodies 
and the supporting can be effected via a hydraulic fluid which in turn is 
supported by the gas spring, for example in a pressure can. 
For sterilization of the sterile material received by a sterilizing 
container in a steam sterilizer the following valve functions are 
necessary, as already mentioned: 
1. Influx valve: Through this valve the steam serving for the sterilization 
must be introduced into the container interior. 
2. Vacuum valve: Through this valve the air originally located in the 
container and subsequently the steam mixed with the residual air must be 
extracted from the container. 
3. Condensate drain valve: Through this valve the condensate which has 
formed in the container, for example in the sterilization of (non-porous) 
instruments, is to be drained. 
The various valves similar in their basic function in the examples 
illustrated can each carry out several functions. However, generally it 
will be expedient to provide several valves in the cover or in the bottom 
and to assign to each of said valves only one or at the most two 
functions. Hereinafter the mode of operation of the individual valves will 
be described with regard to their preferred use but this does not exclude 
any use for a different purpose. 
The valve according to FIG. 3 is primarily suitable as influx or admission 
valve and in this function is conveniently suspended on the wall portion 
32 formed as cover or intermediate cover on the inner side of the 
container. 
Before introduction of the sterilizing container into the sterilizer the 
valve is closed by the bias of the spring 44 and possibly by the bias of 
the gas pressure chamber 24. The gas pressure chamber is filled with air 
under atmospheric pressure (i.e., ambient pressure). Fluctuations in the 
atmospheric pressure do not appreciably affect the operation of the 
invention. In the initial single or repeated extraction of air or the 
steam-residual air content in the vacuum phases 1-2-3 (FIG. 12) the valve 
remains closed because the atmospheric pressure within the chamber 24 is 
positive with respect to the external pressure and is further increased by 
heat. In the now following steam admission phase 3-4 the valve is opened, 
this being done at a point somewhat above atmospheric pressure because of 
the bias of the spring and possibly because of the pressure increase due 
to the temperature increase. However, in contrast to conventional check 
valves the valve according to the invention does not close at the position 
4 of maximum pressure but remains open over the entire sterilizing phase 
4-5 because the gas chamber remains compressed due to the externally 
obtaining excess pressure. When the pressure drops between 5 and 6 (FIG. 
12) the valve still remains open until at a point somewhat above 
atmospheric pressure (due to the spring biasing and heating of the air 
within the chamber) the valve again closes. In the subsequent vacuum phase 
6-7-8-9 the valve remains closed. 
FIG. 4 shows a valve according to the invention in a typical construction 
and use as vacuum valve. In this case the chamber wall 38 together with 
the stiffening plate 40 is secured to the one part of the container 
portion 32 forming the container cover. The stiffening plate 36 bearing in 
this case externally on the opposite chamber wall 28 extends with an 
annular edge 48 outwardly and bears on a sealing ring 50 which is inserted 
into a U-profile 52 fixed on the container cover. The biasing spring 44' 
bears on the plate 36 and on the valve housing 46. 
In all the FIGS. the letter I denotes the container interior and the letter 
A the space disposed outside the sterilizing container (in the autoclave) 
(this applies to the preferred use described; a reversal is conceivable 
for modified construction or modified use). 
In the rest state the valve according to FIG. 4 is closed by the bias of 
the spring 44'. After compensation of the spring bias the valve 4 opens in 
the vacuum phase just below the atmospheric line and remains open during 
the entire vacuum phase 1-2-3, the setting preferably being such that the 
open position is also retained when the internal and external pressures in 
the vacuum region are equal. During the excess pressure phase 3-4-5-6, in 
which the sterilization takes place, the valve remains closed due to the 
externally obtaining excess pressure and opens again in the vacuum phase 
6-7-8-9. 
FIG. 5 shows the invention applied to a typical condensate drain valve. In 
this case the valve is fixed to the inner side of the wall portion 32 
formed by the container bottom 15. The condensate drain valve according to 
FIG. 5 remains in the open position as long as the pressure outside of the 
chamber 24 is higher than the starting pressure within the chamber, i.e. 
during the entire sterilizing phase 3-4-5-6 and not only during the influx 
or admission phase 2-3-4 as is the case with an excess pressure or 
pressure-limiting check valve. Compared with a bi-metal drain valve the 
advantage is achieved that the valve according to the invention operates 
independently of the temperature conditions and has a large stroke and 
higher application pressure. 
The design according to FIG. 6 permits use as influx valve and in this case 
the valve is mounted externally on the cover 14. To ensure opening when 
the outer pressure rises a radially outwardly projecting pressure face 54 
is provided with which the outer pressure raises the valve body 30 and 
when a sealing gap has been formed the outer pressure can engage the 
entire wall face 28. Otherwise the function is as described in conjunction 
with FIG. 3. 
If the valve according to FIG. 6 is to be used as condensate drain it is 
inserted into the container bottom 15 in the manner described and then 
operates in the same manner as the valve described in conjunction with 
FIG. 5. 
FIGS. 7 to 11 illustrate some further modified examples valves according to 
the invention which operate in the arrangement illustrated as steam 
admission valve. However, on corresponding modification use as condensate 
drain valve is also conceivable. 
The valve 7 has the particular feature that the container wall 32 is 
provided with an inwardly projecting edge 56 which surrounds the valve 
body rib 30. The outwardly lying pressure face 54 which effects the 
initial raising is not beveled as in the example of embodiment of FIG. 6 
but made stepped. The container wall is also provided radially outside the 
valve body 30 with an inwardly drawn rib 58. In the embodiment according 
to FIG. 8 said latter portion is made planar and a bean 30' is provided 
instead of the valve body rib. 
In addition, in the examples according to FIGS. 5 and 9 the valve housing 
wall forms at the same time the outer boundary of the gas chamber 24. 
The embodiment of FIG. 10 differs from the remaining examples in the 
arrangement and configuration of the encircling annular wall. In the 
embodiment of FIG. 11 the chamber wall extends outside the valve body rib 
30 in the plane of the cover and perpendicularly thereto, a resilient bead 
60 being formed therebetween. 
FIG. 12 shows the time-dependent pressure variation P within the 
sterilizing container and the valve functions. The step-like form of the 
curves in the region of the zero passage is due to the valve biasing, i.e. 
by the spring pressure and possibly by the gas pressure within the gas 
pressure chamber. 
The sterilizing operation includes the following phases: single or multiple 
vacuum phase (1 to 3), to excess pressure phase (3 to 6) with sterilizing 
phase (4 to 5), after-vacuum phase (5 to 8) ventilation phase (8 to 9). In 
contrast to known devices the valve effective in each phase is also kept 
open after reaching the negative or positive peak pressure value until the 
pressure in the autoclave has adjusted itself to a predetermined closure 
switching pressure (3', 6', 9'). In addition, the valve effective in each 
phase is kept closed until the pressure in the autoclave has adjusted 
itself to a predetermined opening switching pressure (1", 3", 6"). The 
absolute values of the opening switching pressure and closing switching 
pressure are conveniently made of equal magnitude. 
According to the examples illustrated the valves are controlled in 
dependence upon the pressure obtaining in the autoclave. 
Alternatively or additionally the valve control can also take place in time 
dependence on the pressure zero passages (atmospheric pressures) in the 
autoclave or in dependence upon the temperature obtaining in the 
autoclave. A sensor initiating the switching function may be associated 
with each valve arrangement. Finally, it is also possible to control the 
valve arrangement externally. 
FIG. 13 shows a double valve which can be used as admission or influx valve 
or as vacuum valve and furthermore also as condensate drain valve. The 
valve body 82 cooperating with a valve seat 64 of the container wall 
portion 32 is biased by a spring 66 into the closure position. The valve 
body 62 is guided with a cylindrical extension 68 on a bush 70 which is 
carried via a holder 72 by the container wall 32. The valve body 62 
carries an actuating member 74 which has a frusto-conical head 76. The gas 
chamber is surrounded by a bellows 78 which is hermetically sealed and 
connected at one end to a container-fixed block 80. The other end of the 
bellows 78 is secured to a thrust rod 82 which is axially displaceably 
guided in bearing blocks 84. In the region of the actuating member 74 the 
thrust rod 82 comprises a turned-down portion which is defined by two 
conical faces 86 and an intermediate cylindrical portion 88. 
FIG. 13 shows a center position in which the valve is closed. If the outer 
pressure increases the bellows 78 is compressed and the thrust rod 82 
displaced to the right according to FIG. 13. As a result the valve is 
opened via the conical slide faces 86 and 76. 
If however starting from the center position according to FIG. 13 the 
pressure drops then the bellows 78 expand and the thrust rod 82 is 
displaced to the left so that the valve also opens. 
The axial length of the cylindrical portion 88 is somewhat greater than the 
diameter of the head end 76 so that a certain idle movement is 
incorporated and as a result the valve remains closed within a 
predetermined pressure difference range. 
Accordingly, the valve illustrated in FIG. 13 can perform all the valve 
functions because it is controlled by the bellows 78 both in the vacuum 
region and in the excess pressure region. 
In all the examples the gas chamber may be set to the particular 
atmospheric pressure. For this purpose a vent or ventilation valve not 
shown in the drawings may be provided and permits pressure equalization. 
However, generally outer weather-induced air pressure fluctuations need 
not be taken into account and it suffices to provide a pressure 
equalization to the corresponding altitude where the container is to be 
used. For this purpose an opening can be provided which can be permanently 
sealed by a resilient stopper. 
In the embodiment illustrated in FIG. 13 the actuating means 78, 82, 86, 88 
is secured to the container wall via the bearing blocks 80, 84. However, 
the invention also covers the case of separating said actuating means from 
the valve and arranging said means detachably so that the actuating means 
is connected to the valve only in the sterilizer and the sterilizing 
container (outside the sterilizer) can be transported and stored without 
said actuating. 
Although the present invention has been described in connection with 
particular embodiments thereof, many other variations and modifications 
and other uses will become apparent to those skilled in the art. It is 
preferred, therefore, that the present invention be limited not by the 
specific disclosure herein, but only by the appended claims.