GB2180452A

GB2180452A - A sterilising vessel

Info

Publication number: GB2180452A
Application number: GB08622259A
Authority: GB
Inventors: William Derek Bradford
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-09-17
Filing date: 1986-09-16
Publication date: 1987-04-01
Also published as: GB8622259D0; GB8522922D0

Abstract

A sterilising vessel has a container (20) in which the objects to be sterilised are placed. The container is placed inside a pressure-tight jacket (10) which contains a small volume of water (18). The water is heated until it boils, and the resulting steam passes up a gap between the jacket and the container and then into the container from above. The steam then displaces the air which initially is present inside the vessel downwardly through a valve (28) and this valve is arranged so that it closes once all the air has been displaced and steam starts to be vented. Because the exit opening from the container for the air or the steam is at the lower part of the container, one can be sure that all the air has been displaced from the container once steam starts to pass through the valve (28). <IMAGE>

Description

SPECIFICATION A sterilising vessel This invention relates to a sterilising vessel, and particularly to a small scale sterilising vessel which can be used, for example, by small doctor's surgeries or dentists.

A problem with known small sterilising vessels is that air is trapped inside. Because air is displaced downwardly by steam, and because the vent valve in the known vessels is at the top, the air can never escape. As a result the sterilising efficiency is impaired.

According to the present invention, there is provided sterilising vessel comprising a container for containing objects to be sterilised, the container having an opening at its upper part and an opening at its lower part, a valve which can allow the passage of air and can be closed once steam starts to pass through and which is connected to the lower opening, and a pressure jacket surrounding the container, the jacket being adapted to hold a volume of water externally of the container and having a pressure tight lid, so that when the water in the jacket boils, the steam produced rises into the lid of the jacket and then displaces air downwardly in the container so that the air leaves the container through the lower opening.

The valve preferably closes automatically once steam starts to pass through. In this way, objects to be sterilised can be placed inside the container and sterilised by being completely surrounded by steam in the absence of air. The use of a valve which closes in the prssence of steam e.g. a so-called steam condensate valve, connected to the lower opening means that the valve remains open whilst air is being vented, but closes once steam starts to be vented. The valve therefore stays open until all the air is removed and then closes.

The pressure jacket is preferably constructed so that water is contained in a recess in the bottom of the jacket. The gap between the outer walls of the container and the inner surface of the walls of the jacket is preferably as small as possible.

The lower opening may be formed by a hole in the floor, or by leaving one wall of the container open.

In either case, the floor preferably slopes towards the opening.

The lid of the jacket may contain a pressure relief valve and can be sealed to the jacket itself by means of any conventional pressure vessel seal known for this purpose. The container can suitably be made from stainless steel whilst the jacket can be made from aluminium.

The vessel may include its own heater which is preferably constructed so that it heats only the water-containing space in the bottom of the jacket.

The vessel can have a vertical axis, with the container having an open top, a hole in the centre of the floor and an annular water-containing space below the container. The lid can be at the top of the vessel so that the container can be withdrawn upwards.

In order to charge the water-containing space in the bottom of the jacket with water, a one-way valve can be provided in the base of the container through which water can be introduced to the space and which closes as soon as water rises to the level of the valve.

In an alternative construction, the vessel can have a horizontal axis with the container having an open side. The water-containing space can be bounded by an internal wall which also forms a support for one end of the container. The lid can be at one end of the vessel so that the container can be withdrawn horizontally.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure lisa section through a first embodiment a sterilising vessel in accordance with the invention, Figures 2 and 3 both show a section through a second embodiment of sterilising vessel in accordance with the invention, with the container being absent in Figure 2 and present in Figure 3; Figure 4 is a perspective view of the vessel of Figures 2 and 3; and Figures 5 and 6 are, respectively, sections taken on the lines V-V and VI--VI from Figures 2 and 4.

The vessel shown in Figure 1 has a vertical axis and includes a pressure jacket 10 with a lid 12. The lid is removable and the pressure tight seal between the two is shown schematically at 14. A portion of the base of the jacket 10 is removed, and an inverted cup-like member 16 is welded to the edges of the opening of the base and forms the inner boundary to an internal annular space 18 in the jacket 10.

An open-topped container 20 fits within the jacket 10 with a narrow annular gap 22 between the walls of the jacket 10 and the container 20. The container sits on the cup-like member 16, and objects to be sterilised are placed inside the container 20.

A heater 24, which may be an electrically operated Monel heater is mounted beneath the vessel.

In operation, the annular space 18 is filled with water. Objects to be sterilised are placed inside the container 20 and the lid 12 is fitted. The heater 24 then heats the water in the space 18 such that the water boils and steam passes up the annular gap 22 into the lid 12. As the volume and the pressure of the steam increases inside the vessel, so air is driven down into the container 20 and out through a vent pipe 26. The pipe 26 leads to a steam condensate valve 28 which allows air to pass through but closes when steam, at a highertemperature, begins to pass through. When the valve 28 closes one can be sure that the space inside the container 20 contains steam only and that therefore proper sterilisation will be effected.It is therefore important that any air inside the container, as well as the air passing along the vent pipe is kept at a relatively low temperature and therefore is kept away from the heat source. The uses of the cup-like member to support the container 20 ensures that the air is not heated to too high a temperature.

The base of the container 20 slopes down towards the position where the vent pipe 26 is taken off so that all the (heavier) air passes into the pipe 26 before any steam. In a practical embodiment, the base of the container 20 would be of uniform thickness suitably formed so as to produce a slope leading to the vent pipe 26.

A spigot 30 depends from the centre of the container 20 and passes through an aperture 32 in the cup-like member 16. This spigot is externally threaded and receives a nut 34 which is tightened to pull the container down onto the member 16. A conventioanl pipe union 36 is then used to connect a further length of vent pipe. The pipe has to pass through the centre of the heater 24, but the centre hole through which it passes is provided with an internal insulating collar 38 because it is important that no undesired heat is transferred to the contents of the vent pipe which might cause the steam valve 28 to operate earlier than desired.

For the same reason, it may be desirable to include some insulation between the spigot 30 and the cup-like member 16. This insulation could perhaps take the form of an insulating washer underneath the nut 34.

Before operation it is necessary to fiil the space 18 with water. Since the gap 22 is so narrow and the container 20 is permanently fixed in place, it is necessary to provide an inlet 40 through the base of the container 20. This inlet is closed with a one way valve 42 which can be opened by inserting the nozzle end of a suitable reservoir. The valve 42 is preferably of a type which will close as soon as the water level reaches the level of the valve itself. Thus the volume of water introduced into the space will always be constant and the water level will not rise above the bottom of the container 20.

For the best efficiency, it is desirable for the heater 24 to be in close contact with the base of the jacket 10. This can be achieved by mounting the vessel and the heater in a single frame and then providing screws below the heater which can be screwed up to press the heater against the bottom of the jacket.

The use of such a frame can strengthen the jacket 10.

Figures 2-6 illustrate an alternative embodiment of sterilising vessel. In this embodiment, the vessel comprises a cylindrical pressure jacket 50 which is arranged with its primary axis horizontal. The jacket is closed by a lid 52 which fits at one end of the jacket. Within the jacket are two supports for a container. The first support is a shelf 54 at the end of the jacket opposite the lid 52. The other support is a wall 56 located towards the lid 52. The wall 56, as can be seen from Figure 4, has a horizontal upper edge and fits against the shape of the internal wall of the jacket 50, so that a space for containing a body of water 58 is created.

Figure 3 shows how the container 60 fits into the jacket, and more details of this arrangement can be seen from Figure 4.

It will be seen from Figure 4 that the jacket 50 is of cylindrical form. The container 60, however, has a flattened floor 62 which allows the container to be properly supported on the shelf 54 and on the upper, horizontal edge of the wall 56. The length of the container 60 should be such that it just fits comfortably on these two supports, as can be seen in Figure 3.

At its right hand end, the container 60 has an outwardly extending flange 64. The lower part of this flange limits the extent to which the container can be pushed into the jacket, when it butts against the wall 56. The remainder of this flange is a snug fit against the inside of the jacket for reasons which will become apparent when the operation of this embodiment is discussed later. In the top of the container 60 are a number of holes 66 which will allow air and steam to pass into open the interior 68 of the container.

In use, the water space 58 is filled with water as shown in Figure 2. The articles to be sterilised are placed in the space 68 inside the container 60, and the container is then ioaded into the jacket 50. The lid 52 is secured in place with an air-tight seal. Next, the water 58 is heated so that it boils. This heating can be carried out by either an internal or an external heater. The heater may be part of the vessel or separate. The water is heated until it boils, and the steam thus generated passes up into the gap between the container 60 and the jacket 50, displacing air as it goes, and then passes down into the container through the holes 66. The steam is prevented from flowing to the right, past the righthand end of the container by the tight fit between the flange 64 and the inner wall of the jacket. The steam thus passes into the interior 68 of the container, and displaces air as it does so.

The displaced air is vented through a passage 70 and through a valve 72. The valve 72 is of a type which remains open whilst air is passed through it but closes as soon as steam begins to pass through.

Sterilising of the articles in the container 60 then takes place in the same manner as already described for the embodiment of Figure 1.

The steam condensate valve will shut at about 101"C, and a pressure relief valve 44 in the lid will be set so that sterilising takes place in the vessel, as is known, between 121 and 135 C.

Claims

1. A sterilising vessel comprising a container for containing objects to be sterilised, the container having an opening at its upper part and an opening at its lower part, a valve which can allow the passage of air and can be closed once steam starts to pass through and which is connected to the lower opening, and a pressure jacket surrounding the container, the jacket being adapted to hold a volume of water externally of the container and having a pressure tight lid, so that when the water in the jacket boils, the steam produced rises into the lid of the jacket and then displaces air downwardly in the container so that the air leaves the container through the lower opening.

2. A sterilising vessel as claimed in claim 1, wherein the valve closes automatically once steam starts to pass through.

3. A sterilising vessel as claimed in claim 1 or claim 2, wherein the pressure jacket is constructed so that the water is contained in a recess in the bottom of the jacket

4. A sterilising vessel as claimed in any preceding claim wherein the gap between the outer walls of the container and the inner surface of the walls of the jacket is as small as possible.

5. A sterilising vessel as claimed in any preceding claim, wherein the lower opening is formed by a hole in the floor.

6. A sterilising vessel as claimed in claim 5, wherein the floor slopes towards the opening.

7. A sterilising vessel as claimed in any preceding claim, which has a vertical axis and wherein the container has a hole in the centre of the floor forming the lower opening, and wherein there is an annular water-containing space below the container.

8. A sterilising vessel as claimed in claim 7, wherein the lid is at the top of the vessel so that the container can be withdrawn upwards.

9. A sterilising vessel as claimed in claim 7 or claim 8, wherein a one-way valve is provided in the base of the container through which water can be introduced to the space and which closes as soon as water rises to the level of the valve.

10. A sterilising vessel as claimed in any one of claims 1 to 4, wherein the lower opening is formed by leaving one wall of the container open.

11. A sterilising vessel as claimed in claims 10, wherein the vessel has a horizontal axis, the container has an open side and the water-containing space is bounded by an internal wall which also forms a support for one end of the container.

12. A sterilising vessel as claimed in claims 10 or 11, wherein the lid is at one end of the vessel so that the container can be withdrawn horizontally.

13. A sterilising vessel as claimed in any preceding claim, wherein the lid of the jacket contains a pressure relief valve.

14. A sterilising vessel as claimed in any preceding claim, including a heater for heating to boiling point a volume of water in the jacket.

15. A sterilising vessel substantially as herein described with reference to any one embodiment shown in the acompanying drawings.