WO1999008580A1

WO1999008580A1 - Pressure cooker

Info

Publication number: WO1999008580A1
Application number: PCT/AU1998/000659
Authority: WO
Inventors: Jonathan Bruce Dobson
Original assignee: Jonathan Bruce Dobson
Priority date: 1997-08-18
Filing date: 1998-08-18
Publication date: 1999-02-25
Also published as: AUPO862897A0

Abstract

A pressure vessel which is suitable for use as a pressure cooker (1) which includes a container (2) having a base (3) and at least one wall (4) extending up from a peripheral edge (5) of the base (3). The wall (4) defines an open top of the container (2) on which is removably mounted a lid (7) having a peripheral edge region (8). A retaining formation (10) projecting inwardly from an upper end (11) of the wall (4) retains the lid (7) on the container (2) when pressure within the container (2) increases above atmospheric pressure. One or more vent openings (15) are provided in the lid (7) or the container (2). Excess pressure within the container (2) is relieved by moving or deforming the lid (7) or the container (2) relative to the vent openings (15) to thereby open the vent openings (15) allowing excess pressure to escape. A significant advantage is the elimination of a separate or discrete pressure relief valve.

Description

PRESSURE COOKER

FIELD OF THE INVENTION

The present invention relates to a pressure vessel and relates particularly to a pressure vessel which is suitable for use as a pressure cooker for cooking food. However it is to be clearly understood that it is not to be limited to this example application.

BACKGROUND TO THE INVENTION

Pressure cookers are generally known, comprising an open topped container having a complementary lid for closing off the open top. In use, the lid is sealed to the container and retained against lifting off the container when pressure within the container is increased above atmospheric pressure. Such pressure cookers usually require a relief valve to release pressure within the container when that pressure rises above a predetermined level.

Known pressure cookers are fitted with a discrete relief valve which is typically located in the lid of the container. However, there is considerable expense associated with firstly providing a discrete pressure relief valve and secondly in fitting this to the lid. It would be advantageous if a simpler, cheaper way of providing the necessary pressure relief could be provided.

US 5,641,085 (Lombardo) discloses a safety device for automatically limiting the pressure in a pressure cooker. The device includes an annular seal member which forms a seal between the container and the lid and which is formed with a recess in its exterior surface along a portion of its length. The recess creates an area of reduced cross-section for permitting deformation of the seal member radially outwardly under conditions of excessive pressure. The local deformation of the seal member permits the release in a progressive manner of excess steam by creating a gap in the seal between the seal member and the container. The creation of a localised weakened, or reduced cross section, zone on the seal member avoids the need to modify the lid or container in any way. However, the safety device of Lombardo is only intended to provide a backup in the event of a malfunction of a conventional pressure regulation device provided on the pressure cooker.

The present invention was developed with a view to providing a pressure vessel, such as a pressure cooker, which avoids the need to have a separate or discrete pressure relief valve.

SUMMARY OF THE INVENTION

According to an aspect of this invention there is provided a pressure vessel including:

a container defining an upwardly opening top;

a lid for closing off the open top of the container;

means for retaining the lid in closing engagement with the container;

at least one vent opening provided in the container or lid; and,

means for relieving excess pressure within the container, by moving or deforming the lid or container relative to the vent opening to open the vent opening.

Typically, the container includes a base and at least one wall extending upwardly from the periphery of the base and the lid periphery has a peripheral edge region received within the wall of the container.

Typically, either the wall of the container or the lid is resiliently deformable or bendable such that when pressure within the container is increased above a predetermined level, the wall or lid is moved relative to the other of the wall or lid to open the vent opening. Container or lid deformation or bending is preferably elastic, so that the container or lid returns to its original shape upon relief of the above level internal pressure.

Alternatively, the lid is axially displaceable or moveable relative to the wall and retaining means so as to open the vent opening to relieve pressure within the container.

Typically, the retaining means includes a retaining formation extending radially inwardly in from the wall and passing over at least part of the peripheral edge region of the lid to retain the lid on the container.

Preferably the retaining formation extends axially upwardly and radially inwardly from the wall of the container. Advantageously, the retaining formation includes an extension of the wall of the container. In a preferred form, the retaining formation curls over to form a downwardly facing recess.

Typically, the retaining means includes seal means interposed between the retaining formation and the lid for sealing the lid to the container. The seal means enables pressure to build up within the container to achieve a pressure cooker effect.

Advantageously, the seal means includes a seal member. Preferably, the seal member extends endlessly around the peripheral edge region of the lid.

Typically, the seal member is made of resilient material, for example rubber, and in one form is of O-ring or like shape.

In one preferred form, the seal member is firmly received within the recess defined by the retaining formation, for example with a snug fit.

Typically, the vessel is provided with a plurality of the vent openings. In one arrangement, the vent openings are located in the lid. Such vent openings may be in the peripheral edge region of the lid, and be in the shape of slots, notches or grooves, which may extend generally radially inwardly from the peripheral edge of the lid.

In an alternative arrangement, the vent openings are located in the wall of the container. Such vent openings may comprise holes extending through the wall of the container at a certain level, e.g., adjacent the peripheral edge region of the lid.

Alternatively, those vent openings may comprise recesses or grooves in the retaining formation, particularly in an inwardly facing surface of the retaining formation. Such openings may extend in a radial direction.

In one particularly preferred embodiment, the lid is elastically deformable or bendable, the vent openings are located in the lid, and the seal member provides solely a sealing function.

In another particularly preferred embodiment, the container wall is elastically deformable or bendable, the vent openings are located in the lid, and the seal member provides solely a sealing function.

In a further particularly preferred embodiment, the lid is axially movable relative to the container to achieve pressure release. In this embodiment, the seal member projects outwardly from the retaining formation permitting outward axial movement of the lid, relative to the wall and retaining formation, when the pressure within the container exceeds the resilient force of the seal member. In this embodiment, the vent openings are located in the wall of the container and the axial movement of the lid permitted by the seal member and retaining formation is sufficient to open the vent openings.

A pressure vessel in accordance with this invention may be embodied in a variety of forms. It will be convenient to hereinafter describe in detail four specific embodiments of the invention with reference to the accompanying drawings. It is to be clearly understood that the specific nature of this description does not supersede the generality of the preceding statements.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, where the same reference numerals identify the same or similar features:

Figure 1 is a plan view of a pressure vessel in accordance with a first embodiment of the invention;

Figure 2 is a front view of the pressure vessel of Figure 1;

Figure 3 is a detailed plan view of part of the pressure vessel of Figure 1 showing a vent opening;

Figure 4 is a detailed front view of a corner of the pressure vessel of Figure 1 with the vent opening in a closed position;

Figure 5 is detailed front view of the corner shown in Figure 4 with the vent opening in an open position;

Figure 6 is a plan view of a pressure vessel in accordance with a second embodiment of the invention;

Figure 7 is a front view of the pressure vessel of Figure 6;

Figure 8 is a detailed front view of a corner of the pressure vessel of Figure 6 showing a vent opening in a closed position;

Figure 9 is a detailed front view of the corner shown in Figure 8 with the vent opening in an open position;

Figure 10 is a sectional front view of part of a pressure vessel in accordance with a third embodiment of the invention showing the vent opening in a closed position;

Figure 11 is a sectional front view of the vessel of Figure 10 with the vent opening in an open position;

Figure 12 is a sectional front view of part of a pressure vessel in accordance with a fourth embodiment of the invention showing the vent opening in a closed position; and,

Figure 13 is a sectional front view of the vessel of Figure 12 with the vent opening in an open position.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring initially to the embodiment of Figs.l to 5, there is generally illustrated a pressure vessel in the form of a pressure cooker 1, including a container 2 having a base 3 and at least one wall 4 extending up from a peripheral edge 5 of the base 3. The wall 4 defines an open top of the container 2. The pressure cooker 1 also includes a lid 7, having a peripheral edge region 8, removably mounted on the open top. Typically, the container 2 is of cylindrical configuration and the lid 7 is of a complementary circular shape, although other shapes are envisaged for the cooker 1, for example, an elliptical shape.

In this embodiment, the container 2 is composed of a rigid material, such as stainless steel, whilst the lid 7 is composed of elastically deformable or bendable material, such as injection-moulded plastic material. The container 2 and lid 7 may be made of any suitable materials. It will be appreciated, however, that the lid 7 should be capable of the required elastic deformation or bending at the appropriate pressure levels to be able to vent the container. The cooker 1 also includes retaining means in the form of a retaining formation 10 projecting inwardly from an upper edge 11 of the wall 4 for retaining the lid 7 on the container 2 when pressure within the container 2 increases above atmospheric pressure. In this embodiment, the retaining formation 10 is provided by radially inwardly extending the upper edge 11 of the wall 4. The formation 10 is curled to define a recess 12. It will be clear, however, to a person skilled in the art that the retaining formation 10 may be formed in other ways, and in particular need not be formed integral with the container wall 4.

A seal member 13, such as an O-ring, is received within the recess 12 defined by the curl of the retaining formation 10. The seal member 13 is located between the peripheral edge region 8 of the lid 7, and the container 2 around the periphery thereof to form an airtight seal.

In this embodiment, one or more vent openings 15 are provided in the lid 7. Three such vent openings 15 spaced an equal distance apart around the peripheral edge region 8 of the lid 7 are provided in the illustrated embodiment, although other arrangements are also suitable. Each vent opening 15 includes a longitudinal slot or hole extending radially within the peripheral edge region. The slots are open-ended, opening from the peripheral edge region 8. Figure 3 shows in detail the location and configuration of one such vent opening 15.

In use, food is placed in the container 2 and heat is applied thereto to cook the food. The application of heat generates steam which builds up pressure within the container 2 and assists in cooking the food. Figure 4 shows the cooker 1 in a normal, pressurised condition with the lid 7 being urged sealingly upwardly against the seal member 13. In this condition, the internal pressure is not excessive, so that the lid 7 is not deformed, and the vent openings 15 remain covered and so closed by the seal member 13. However, when the pressure within the container 2 exceeds a predetermined level, the lid 7 deforms axially outwardly as illustrated in Figure 5. This has the effect of displacing the peripheral edge region 8 of the lid 7 radially inwardly relative to the seal member 13 which, in turn, uncovers the vent openings 15 permitting release of pressure built up in the container 2. As the pressure within the container 2 is released, the lid 7 tends to reform, returning to its original position as shown in Figure 4, so closing off the vent openings 15. Hence the lid itself provides a pressure relief function, maintaining the pressure within the cooker 1 at a predetermined maximum level.

A second embodiment of this invention is illustrated in Figures 6 to 9. The structure and functioning of this embodiment is similar to that of the previous embodiment and, therefore, this description will be confined to discussing the only differences between this and the previous embodiment.

The major difference is that the lid 7 is composed of rigid material whilst at least part of the wall 4 of the container 2 is composed of elastically deformable or bendable material and the base 3 is of elliptical shape. In use, when the internal pressure exceeds a predetermined level the container 2 deforms radially outwardly to uncover or open the vent openings 15 rather than the lid 7 deforming. This radially outward deformation of the wall 4 and associated seal member 13 uncovers the radially inner ends of the vent openings 15 enabling pressure to vent from the container 2. Figure 9 shows this outward movement of the wall 4 of the container 2 to open the vent openings 15. As the excess pressure is vented from the container 2 and the internal pressure decreases toward the predetermined level, the wall progressively returns to the position shown in Figure 8 so that the seal member 13 again sealingly covers the vent openings 15.

Figures 10 and 11 illustrate a third embodiment in accordance with this invention. The broad arrangement of container 2 and lid 7 is the same in this embodiment as is in the previous embodiments, although details of the sealing engagement of the container 2 and lid 7 differ. The following description therefore focuses on the features relating to the engagement of the container 2 and lid 7. The retaining formation 10 is formed by an extension of the container wall 4 which curves radially inwardly and then outwardly to form a shoulder 20. In this embodiment, as illustrated, the seal member 13 is provided at the peripheral edge region 8 of the lid 7. To that end, the end region 8 is enlarged to form a bulb-like sealing portion 21 for sealingly engaging against an inner surface 31 of the radially inwardly curving retaining formation 10. As illustrated, the sealing portion 21 is integral with the lid 7. However, in an alternative embodiment (not illustrated) the sealing portion 21 is formed at least in part separate from the lid 7 and connected thereto or carried thereby. Thus, a separate seal member 13 may be provided at the end region 8. The vent openings 15 are provided by radially inwardly extending recesses or grooves 30 in the inner surface 31.

In the position illustrated in Figure 10, where the cooker 1 is normally pressurised but not over pressurised, the seal member 13 at the peripheral edge region 8 of the lid 7 fits snugly into and seals against the curved inner surface 31 of the retaining formation 10. In this position, the seal member 13 extends radially outwardly beyond the grooves 30 and closes those grooves 30. When pressure within the container 2 exceeds a predetermined level, then the lid 7 elastically deforms axially outwardly as in the embodiment of Figures 1 to 5. This draws the seal member 13 on the edge region 8 radially inwardly, as illustrated in Figure 11, allowing pressure to vent through the vent openings 15 defined by the grooves 30. As the pressure drops back towards the predetermined level, the lid 7 progressively returns to its original position, as illustrated in Figure 10, to again cover the vent openings 15.

Figures 12 and 13 illustrate a pressure cooker 1 in accordance with a fourth embodiment of the invention. The overall shape and configuration of the container 2 and lid 7 is broadly similar to that shown in Figs. 1 and 2. However, the mechanism for venting pressure within the cooker 1 through the vent openings 15 is different to that of the other embodiments. In this embodiment, vent openings 15 are in the form of holes extending through the wall 4 of the container 2 adjacent retaining formation 10. The lid 7 is rigid (not elastically deformable) but is axially displaceable relative to the wall 4 and the openings 15. The vent openings 15 are uncovered by this relative movement of lid 7 to wall 4. The retaining formation 10 is provided by an extension of the wall 4 of the container 2 and defines recess 12 in which seal member 13 is received. In this embodiment, the formation 10 has an inverted U cross-sectional shape, although other shapes are envisaged. A free end 40 of the retaining formation 10 is located in spaced relation from the lid 7 as a result of the seal member 13 projecting out of the recess 12 beyond the free end 40.

Figure 12 shows the cooker in a normally pressurised condition where the peripheral edge region 8 of the lid 7 is spaced from the free end 40, and the seal member 13 is axially uncompressed so as to sealingly cover the vent openings 15. As pressure within the container 2 increases toward a predetermined pressure level, the lid 7 progressively compresses the resilient seal member 13 and is moved toward the free end 40 of the retaining formation 10. When the predetermined pressure level is exceeded, as illustrated in Figure 13, the peripheral edge region 8 of the lid 7 has deformed the seal member 13 to an extent that the vent openings 15 are uncovered so that air and steam are permitted to escape from container 2. As the pressure decreases, the lid 7 progressively returns to its position as illustrated in Figure 12 where the seal member 13 again covers the vent openings 15.

An advantage of the pressure cookers described above is that they provide for appropriate pressure relief without requiring a discrete relief valve in the lid of the container. A further advantage is that the pressure cooker can therefore be manufactured relatively simply and inexpensively.

It is to be understood that various alterations, modifications and /or additions may be introduced into the construction and arrangement of the components previously described without departing from the ambit of the invention disclosed therein.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A pressure vessel including:

a container defining an upwardly opening top;

a lid for closing off the open top of the container;

means for retaining the lid in closing engagement with the container;

at least one vent opening provided in the container or lid; and,

means for relieving excess pressure within the container, wherein moving or deforming the lid or container relative to the vent opening opens the vent opening.

2. A pressure vessel as defined in claim 1, wherein the container includes a base and at least one wall extending upwardly from a periphery of the base and wherein a periphery of the lid has a peripheral edge region received within the wall of the container.

3. A pressure vessel as defined in claim 2, wherein either the wall of the container or the lid is resiliently deformable or bendable such that when pressure within the container is increased above a predetermined level, the wall or lid is moved relative to the other of the wall or lid to open the vent opening.

4. A pressure vessel as defined in claim 2, wherein the lid is axially displaceable or moveable relative to the wall and retaining means so as to open the vent opening to relieve pressure within the container.

5. A pressure vessel as defined in claim 2, wherein the retaining means includes a retaining formation extending radially inwardly in from the wall and passing over at least part of the peripheral edge region of the lid to retain the lid on the container.

6. A pressure vessel as defined in claim 5, wherein the retaining formation extends axially upwardly and radially inwardly from the wall of the container.

7. A pressure vessel as defined in claim 6, wherein the retaining formation curls over to form a downwardly facing recess.

8. A pressure vessel as defined in claim 2, wherein the retaining means includes seal means interposed between the retaining formation and the lid for sealing the lid to the container.

9. A pressure vessel as defined in claim 8, wherein the seal means includes a seal member which extends endlessly around the peripheral edge region of the lid.

10. A pressure vessel as defined in claim 9, wherein the seal member is made of resilient material and is of O-ring or like shape.

11. A pressure vessel as defined in claim 10, wherein the seal member is received in close fitting relationship within a recess defined by the retaining means.

12. A pressure vessel as defined in claim 2, wherein the vessel is provided with a plurality of the vent openings.

13. A pressure vessel as defined in claim 12, wherein the vent openings are located in the lid.

14. A pressure vessel as defined in claim 13, wherein the vent openings are in the peripheral edge region of the lid and extend generally radially inwardly from the peripheral edge of the lid.

15. A pressure vessel as defined in claim 12, wherein the vent openings are located in the wall of the container.

16. A pressure vessel as defined in claim 15, wherein the vent openings comprise holes extending through the wall of the container adjacent the peripheral edge region of the lid.

17. A pressure vessel as defined in claim 15, wherein the vent openings comprise recesses or grooves in the retaining formation, particularly in an inwardly facing surface of the retaining formation.

18. A pressure vessel as defined in claim 9, wherein the lid is elastically deformable or bendable, the vent openings are located in the lid, and the seal member provides solely a sealing function.

19. A pressure vessel as defined in claim 9, wherein the container wall is elastically deformable or bendable, the vent openings are located in the lid, and the seal member provides solely a sealing function.

20. A pressure vessel as defined in claim 10, wherein the seal member projects outwardly from the retaining formation permitting outward axial movement of the lid, relative to the wall and retaining formation, when the pressure within the container exceeds the resilient force of the seal member.

21. A pressure vessel as defined in claim 20, wherein the vent openings are located in the wall of the container and the axial movement of the lid permitted by the seal member and retaining formation is sufficient to open the vent openings.