There are currently available, wok type cooking devices which are either arranged to sit on a stove or range top or are directly electrically heated by a heating element arranged in a base section. Such wok type cooking devices comprise a base section defining an inverted dome shape cooking region often provided with a loosely fitting lid which is also dome shaped. Such devices or appliances cook satisfactorily in a variety of manners but are relatively slow normally requiring continual attention. There are also commonly available pressure cooker devices usually with a base section having a flat bottom that again either is adapted to sit on a stove or range top or is directly electrically heated by a heating element arranged in the base section. Such pressure cooker devices have a lid with a pressure relief valve arranged therein and a seal arrangement between the lid and the base section so as to maintain a predetermined steam pressure during cooking within a cooking zone inside the pressure cooker device. These pressure cooker devices have the advantage that they cook relatively quickly because the cooking process occurs at a pressure higher than atmosphere but they have the disadvantage that the cooking process always occurs in a high pressure steam atmosphere, thereby limiting the things that might be prepared and cooked therein.

The objective of the present invention is to provide a cooking appliance which is capable of cooking more quickly than conventional cooking devices but which is able to maintain the general cooking flexibility normally associated with non elevated pressure conventional cooking devices.

In accordance with a first aspect of the present invention, there is provided a cooking appliance including a base section having a heating element operably associated therewith, a lid section co-operable with said base section, seal means cooperable between said base section and said lid section whereby in a cooking mode a substantially sealed cooking region is established between said lid section and said base section, pressure control valve means being provided to limit pressure within said sealed cooking region

during a cooking process, and control means adapted to regulate power supply to said heating element to at least two discrete steps with one of said steps limiting power supply levels to a first level substantially less than a second level supplied during a subsequent step while pressure within said cooking zone is maintained substantially greater during said one step than during said subsequent step. Preferably, the appliance includes a steam venting valve adapted to be opened to vent said cooking zone when the control means moves from said first level to said second level. Conveniently the pressure in said cooking zone during said one step is substantially greater than atmospheric pressure and the pressure in said cooking zone during said subsequent step is substantially equal to atmospheric pressure.

Preferably the internal surface of the base section may be dome shaped similar to a wok including at least one depression or recessed region arranged adjacent the heating element for collection of moisture such as condensate or initially introduced water to promote boiling of same during a cooking process.

The depression or recessed region may be located in the lower most region of the base section. Alternatively, the depression or recessed region may be formed by an annular ridge or recess in the lower regions of the base section.

In one preferred arrangement, the base section may be provided with a series of annular steps or may be provided with a separate insert having such annular steps to support food items to be cooked at various levels within the base section. Conveniently, a cooking surface of the base section may be provided with a non-stick surface coating such as now commonly provided in cookware.

In a particularly preferred embodiment, the cooking appliance may be provided with control means adapted to regulate power supply to said heating element to at least two discrete steps, a first one of said steps limiting power supply levels to a first level substantially less than that of a second or further stepped levels. The control means may be such as to be manually moved from said first step to a second or further step after a predetermined period of time dependent upon a moisture quantity level introduced into the cooking region prior to commencing a cooking process. Alternatively, the control means may be such as to automatically move from said first step to the second or further step after the elapse of the predetermined period of time. Preferably the

appliance may further include a steam venting valve that can be operated manually (or automatically) upon the control means moving to the second or further step. In an alternative, rather than providing a steam venting valve for operation at this point, the lid might simply be removed to vent steam from the cooking region. This arrangement allows the cooking appliance to operate like a pressure cooker while the control means is at the lower first step which substantially quickens the cooking cycle, but after this stage, the pressurised steam is released from the cooking region and a higher power level is provided to the heating element to allow the food being cooked to be roasted and/or browned, which is not normally possible in conventional pressure cookers.

The objective of the present invention in a second aspect is to provide an improved form of clamping device for use with any form of pressure cooker.

In accordance with this second aspect of the invention, there is provided a clamping device for a pressure cooker including a pair of opposed jaw elements, each of said jaw elements in use being arranged to engage a lid portion and a base portion of the pressure cooker in a closed configuration, a connecting assembly joining said opposed jaw elements, said connecting assembly including at least a first part and a second part movable relative to each other so as to allow said jaw elements to move toward one another to form a clamping position and to move away from one another to form a release position, a lock plate movable transversely relative to said connecting assembly, said lock plate and/or said connecting assembly further including engagement means co-operable between said lock plate and said connecting assembly whereby in a first transverse position of said lock plate, said engagement means permits movement of said jaw elements away from one another, and in a second transverse position of said lock plate, said engagement means prevents movement of said jaw elements away from one another.

Conveniently when said lock plate is in said second transverse position, the lock plate may be fixed relative to the lid of the pressure cooker. This fixing may occur by registering an aperture in said lock plate with a pressure indicator member located in the lid whereby when pressure in the pressure cooker reaches a predetermined level, said pressure indicator member extends outwardly through the aperture in the lock plate to fix the lock plate in the

second transverse position. Conveniently, the engagement means may comprise a projection means arranged in an L-shaped guide co-operable between the lock plate and the connecting assembly, the projection means being movable along the L-shaped guide to allow transverse movement of the lock plate relative to the connecting assembly and to allow movement of the jaw elements toward or away from one another. Preferably the connecting assembly may include a central member and two opposed end members each of which are connected to a respective said jaw element, the two opposed end members each being movable relative to said central member. Preferably an L- shaped guide and co-operable projection means is provided cooperating between spaced portions of the lock plate and central member and with a respective one of said opposed end members.

Preferred embodiments of the present invention will now be described with reference to the accompanying drawings, in which:- Figure 1 is a schematic cross-sectional view of a wok type cooking appliance according to a preferred embodiment of the present invention; Figures 2 and 3 are partial cross-sectional views similar to Figure 1 showing alternative preferred embodiments; Figure 4 illustrates in schematic cross-section certain details of a pressure regulator/air vent and a preferred mechanism for operating same; Figure 5 is a schematic perspective view of a pressure cooking appliance in accordance with a preferred embodiment of the present invention; Figure 6 is a view similar to Figure 5 but showing the lid clamp released but not removed; Figure 7 is a view similar to Figures 5 and 6 but showing the lid clamp released and removed from the base section of the cooking appliance; Figures 8A and 8B are respectively underneath and upper schematic plan views of the cooking appliance lid and preferred clamp device in an unlocked position of the clamp device; and Figures 9A/9B and 10A/10B are views similar to 8A/8B but showing differing positions of the clamp device.

Referring to Figure 1, the wok type cooking appliance 10 comprises a base section 11 and a lid section 12 with a handle 13. The lid and base sections 12,11 are dome shaped presenting internal domed surfaces 14,15. A heating element 16 is cast into the base section 11 and a supporting stand 17 may be provided to support the base section 11 on a flat surface such as a bench or the like. A conventional demountable seal 18 is provided connecting the peripheral edge 19 of the base section 11 to the peripheral edge 20 of the lid section 12. The seal 18 enables a sealed cooking region 21 to be maintained within the appliance such that a predetermined pressure can be established therein during a cooking process. The lid section 12 may include a conventional pressure relief valve 22 to ensure the pressure within the cooking region 21 does not exceed a predetermined maximum pressure level. Further, the lid section 12 may also include a steam venting valve 23 which may be operated manually or automatically as discussed below.

Control means (not shown) for controlling power input to the heating element may be provided. In one preferred embodiment, the control means may be an electric fry pan type control having a temperature sensing probe adapted to be positioned in a location 24 adjacent the bottom of the base section 11. The control means also includes at least two discrete power input level steps or zones such that in a first zone or level the power input is substantially below that of a second or further zones. This may be achieved by modulating the power supply in the first zone relative to the second zone but any other means of achieving a similar effect might be utilised. The temperature sensing probe provides an on-off type control to maintain the temperature level at or adjacent a selected level.

Referring now to Figure 2, the arrangement may be similar to that shown in Figure 1 except that in this embodiment, a pan shaped depression 25 is formed in the lower part of the base section 11 to collect liquid 26 therein. In Figure 3, an annular liquid collection zone 27 is formed by providing an annular ridge 28. In both cases the liquid collection zones 26,27 are located adjacent the heating element 16 which assists with the boiling of introduced liquid or re- boiling of collecte condensate within the cooking zone 21.

A cooking operation would normally occur as follows. Firstly, the lid section 12 is removed and the desired food to be cooked is placed in the base section 12 with a small predetermined quantity of water. Thereafter, the lid section 12 is replace with the venting valve 23 closed. The control arrangement is set at the first lower level of power input to the heating element and in this mode, steam pressure is built up to the level set by the relief valve 22. Cooking in this pressure mode occurs for a predetermined time period normally sufficient to vaporise all of the introduced liquid. At the end of the predetermined period, the vent valve 23 is opened and the power input level is stepped up to a second higher level. During this cooking mode the food product is roasted or browned in the absence of steam. The foregoing operational steps may occur manually or may automatically occur if a more sophisticated control arrangement is utilised. The initial pressure cooking stage substantially shortens the overall cooking period required but the arrangement still allows preparation and cooking of foods that would normally be prepared and cooked in a wok type cooking appliance.

Reference will now be made to Figure 4 of the accompanying drawings.

Figure 4 shows schematically a cooking appliance in the form of a pressure cooker having a relatively conventional cooking zone formed by internal surfaces of a base section 30 and an internal surface of a lid section 31. The base section 30 may comprise an outer wall 33 and an inner stainless steel housing part 32 in which the cooking process occurs. Suitable lifting handles may be provided attached to the outer wall 33 and a clamping of any conventional type may be provided to enable the lid section 32 to be clamped to the housing part 32 during a cooking operation.

A pressure regulator valve 46 is provided through the lid 31 with the valve 46 including a manually positionable lever 47 such that the valve can, if desired be left permanently in a condition so as to vent the internal cooking zone. The appliance may include a channel shaped housing part 48 (on the lid 31) and a complementary housing part (not shown) on the base 30 which is occupied by control devices and mechanisms for operating the valve 46 as required. Figure 4 illustrates the lid 31 engaged on the base section 30 with a conventional seal 50 actively located there between. The control mechanism

comprises a pivoted lever arm 51, pivoted at 52 with its free end 53 urged by spring 54 away from the lid 31. The lever arm end 53 controls the position of a valve closure member 55 such that when the end 53 is in an elevated position the valve closure member 55 is raised to allow venting of the outer end of passage 56 leading to the interior of the cooking appliance. To close the passage 56 to thereby allow pressure to build up in the interior cooking zone of the appliance, a solenoid 57 pushes the outer free end 58 of the lever arm 51 upwardly against the urging force of the spring 54. In so doing, the valve closure member 55 seats downwardly against the outer end of passage 56.

During a cooking sequence, the solenoid 57 closes the valve 46 for the first cooking stage during which pressure is maintained within the cooking zone.

During the second stage the solenoid 57 is deactivated and the spring 54 opens the valve to vent the cooking zone. The solenoid may be operated by either manual intervention or by some form of timing control device. Alternatively, the solenoid 57 may be activated in response to the cooking appliance transferring from the first cooking stage to the second (or further) cooking stages.

The valve 46 may include an upper level pressure relief valve function to relieve pressure from the cooking zone should it exceed a predetermined level.

Alternatively, a separate pressure relief valve might be provided. As noted above, the lever 47 by rotation about axis 59, may position the valve 46 to either vent the cooking zone fully regardless of the position of the solenoid 57/spring 54 or in a second position of the lever 47, the valve 46 may operate fully under the control of the solenoid 57/spring 54. The operation of the cooking appliance shown in Figure 4 may be similar to that described above with reference to Figures 1 to 3.

The cooker unit may include a controller providing a number of possible control functions including multiple steam pressure selections controlled by temperature control, allowing the unit to run at any desired pressure without exhausting steam into the room. The valve 46 including the upper level pressure relief valve function may be set slightly higher than the pressure/ temperature setting controlled by the controller. At the end of any pre-timed program the controller disables the heater and immediately or within a preset time automatically opens the pressure relief valve 46 so that blow down occurs.

This is important as it stops the cooking process almost immediately, so that food is not overcooked. It also allows new ingredients to be added conveniently and a new cook time to be programmed in. A discrete beep may be sounded every second to indicate that the unit is up to pressure and cooking, as historically the escaping steam gave this indication.

A keep warm feature may be provided adjusting the vessel temperature to a point selected below 100°C so that pressure will not build up inadvertently, and food can be kept warm at the end of any cycle. A browning mode may be provided that allows the unit to run at 180°C to allow pre-browning of onions, condiments, or the like but precludes pressure build up as this temperature equates to very high pressure. A steaming cycle may be provided as with the browning cycle discussed above. (No pressure allowed to build up due to control disabling provision in both these modes.) A control panel for the cooking appliance may include a 2 digit display that has 7 segments in each digit forming the figure 8. Hence 88. The setting key for this allows"cook"time to be set up to 99 minutes and the"delay start" time using the same digits to show up to 99 hours delay. The control then flashes the digits alternately showing cook time selected and then delay time selected. The cook time only decrements after the unit reaches selected temperature as there will be large differences in heat up time and hence cook time depending on the nature of the load.

A second redundant thermostat may be included and this is backed up by a fusible link one shot device. These all act on temperature and as a back up to this system, a mechanical blow-out plug or valve may be provided as an ultimate safety device.

Reference will now be made to Figures 4 to 7 of the accompanying drawings. Figures 5 to 7 show schematically a cooking appliance in the form of a pressure cooker having a relatively conventional cooking zone formed by internal surfaces of a base section 30 and an internal surface of a lid section 31.

The base section 30 may comprise a stainless steel housing part 32 and a phenolic resin base part 33 which includes a control panel 34. Suitable lifting handles 35 may be provided attached to the housing part 32. A clamping device 36 is required which may be conventional in configuration comprising

clamping jaws 37,38, a central bar member 39 and housing portions 40,41 connected to the jaws 37,38 with the housing portions respectively telescopically receiving end zones of the central bar member 39. The parts of the clamp may be made from any suitable material including stainless steel.

Figure 5 shows the parts of the clamping device 36 in a clamping configuration whereas Figures 6 and 7 show the clamping device 36 in various stages of release. Release buttons 42 may be provided to release the device 36 from the position shown in Figure 4. Further pressure indicator apertures 43 are provided to receive a pressure indicator pin (not shown) that will move upwardly through the apertures 43 and corresponding apertures 44 in the member 39 and apertures 45 in the lid (only when in the clamping position and only when a predetermined pressure exists in the internal cooking zone) which both acts as an indicator of pressure in the vessel and locks the clamping device in the clamping position (Figure 5). The pressure indicator pin may have a loose fit shank section that allows air/vapour to escape from the cooking zone until predetermined pressure is built up so as to seal an internal enlarged head portion against the internal regions of the lid.

A pressure regulator valve 46 is provided through the lid 31 with the valve 46 including a manually positionable lever 47 such that the valve can, if desired be left permanently in a condition so as to vent the internal cooking zone. As shown in Figures 5 to 7 the appliance includes a channel shaped housing part 48 (on the lid 31) and a complementary housing part 49 (on the base 30) which is occupied by control devices and mechanisms for operating the valve 46 as required. The control arrangements may be better seen in Figure 4 as described earlier.

Reference will now be made to Figures 8A/8B to 10A/10B which disclose a novel form of clamping device 36 for use with any pressure cooking appliance including those appliances discussed in the preceding description. The clamping device comprises a pair of jaws 60,61 each with a central leg 62,63 extending inwardly. The jaws 60,61 are intended to clamp over and above an outer rim of the led 31 and beneath a top flange of the base 30 so as to maintain the seal 50 operative there between when in use and in the clamped position. The legs 62,63 telescopically engage in a central arm 64 so as to be

capable of moving inwardly from the released position (Figures 8A/8B) to a locked position (Figures 9A/9B). Each leg 62,63 carries an upstanding pin 65 that passes through a longitudinal siot (not illustrated) extending coincident with axis 66 through the central arm 64. The clamping device 36 further includes a lock plate 67 which includes L-shaped slots 68,69 through which a respective one of the pins 65 also extend. One leg 70,71 of the L-shaped slots 68,69 extends parallel to or coincident with the axis 66 and the second legs 72,73 of the L-shaped slots 68,69 extend parallel to a second axis 74 perpendicular to the axis 66. Finally, a rest recess 75,76 is provided adjacent the corners of the L-shaped slots 68,69 for reasons that will be explained in the following. A tension spring 77 is provided acting between the lock plate 67 and the central arm 64 so as to urge the lock plate to move in a direction parallel to the axis 74.

This movement is possible when the pins 65 are within the legs 72,73 but is prevented (as shown in Figure 8B) when the pins are in the legs 70,71 of the L- shaped slots. The lock plate 67 also includes a grip portion 78 to assist in a user moving the plate 67 as required and an aperture 79 which can be brought to register with an aperture 80 in the lid 31 (as shown in Figure 9B) or alternatively, the lock plate 67 will block the lid aperture 80 (as shown in Figure 8B). The lid aperture 80 is intended to carry a pressure indicator member which can move upwardly or downwardly within the aperture 80 over predetermined limits. When a predetermined pressure exists in the cooker appliance, the pressure indicator member will move fully to an outwardly extended position and its inner portions will seal the aperture 80 to allow pressure to further build up in the cooking zone (if desired). This movement of the pressure indicator member to the fully extended position will be possible only if the apertures 79, 80 are aligned and when the pressure indicator member extends fully through both apertures 79,80 the clamping device is locked in the clamped position (Figures 9A/9B). The clamping device cannot be released from this position until such time as the pressure in the cooker appliances drops sufficiently to allow the pressure indicator member to be released from the aperture 78.

In operation, with the clamping device as shown in a released position (Figures 8A/8B), the jaws 60,61 are moved radially inwardly to thereby move the pins 65 inwardly along the slot legs 70,71. When the pins 65 approach the

corner of the slots 68,69, the spring 77 urges the plate 67 laterally upwardiy in the direction of axis 74 to the position shown in Figures 9A/9B. In this position the jaws are fully clamping the lid 31 to the base 30 and the apertures 79,80 are aligned allowing the pressure indicator member to lock the clamping device 36 in this position. To release the clamping device 36 when the pressure in the appliance allows the pressure indicator member to drop out of engagement with the aperture 79, the lock plate 67 is manually moved upwardly (in the drawings) parallel to axis 74 such that the pins 65 can be retained in recesses 75,76 against the urging force of the spring 77 (as shown in Figures 10A/10B).

Thereafter the jaws 60,61 can be moved outwardly back to the position shown in Figures 8A/8B. The pressure indicator member itself may be a loose fit in the aperture 80 so as to allow air to be vented through this aperture during an initial heat up stage.