GB2080143A - Vacuum cooking appliance - Google Patents

Abstract

A vacuum cooking appliance comprises, for a cooking utensil (1), a closure member (2) therefor capable of withstanding sub-atmospheric pressure; vacuum sealing means (3) between the closure member (2) and said utensil (1); a weighted vacuum vent valve (9, 10, 11, 12, 13) in said closure member (2); and means (14) for evacuating said closure member (2) fitted thereon. Such an appliance enables food- stuffs to be cooked therein in such a way that the natural flavours and nutrient value of the foodstuffs are retained. <IMAGE>

Description

SPECIFICATION Vacuum cooking appliance This invention relates to vacuum cooking appliances and more particularly to means enabling conventional cooking vessels to be converted easily into such vacuum cooking appliances.

Contemporary domestic cooking utensils include those known as pressure cookers" operating under pressure and at elevated temperatures. These, while achieving an accelerated cooking cycle, do so accompanied by a diminished quality of the resulting "pressure cooked" foodstuff.

Other domestic cooking utensils include, for example, saucepans, 'crockpots', frypans and the like which are normally operated under ambient pressure and involve prolonged cooking times with consequent wasteful fuel consumption as well as deleterious effect on the nutritional quality and flavour of the foodstuffs so cooked.

It is therefore an object of the present invention to overcome the above and other disadvantages and to this end there is provided a vacuum cooking appliance comprising, for a cooking utensil, a closure member therefor capable of withstanding sub-atmospheric pressure; vacuum sealing means between said closure member and said utensil; a weighted vacuum vent valve in said closure member; and means for evacuating air from said utensil when said closure member is fitted thereon.

Such an appliance enables foodstuffs to be cooked therein in such a way that the natural flavours and nutrient value of such foodstuffs are retained.

The said closure member may be a lid provided with a strongback-to be hereinafter defined-so that the lid is enabled to be sealingly secured to the utensil.

The evacuating means is preferably a vacuum pump operated either by water pressure or electrically, and may incorporate a vacuum gauge; alternatively such a vacuum pump may be set into the lid.

Ideally, the weighted vacuum vent valve has an annular seal made from material capable of remaining stable at temperatures of up to 1 20 degrees C, and the said subatmospheric pressure is preferably within the range of 0 to 28 inches of mercury.

In order that the reader may obtain a better understanding of the present invention, hereinafter is described a preferred embodiment thereof, by way of example only and with reference to the accompanying drawings in which: Figure 1 is a vertical cross-section through a vacuum cooking appliance according to the present invention; and Figure 2 is a further vertical cross-section but taken at 90 degrees to that shown in Fig.

1.

In the drawings there is shown a conventional cooking utensil 1 which in this case is an electric deep fryer but could, of course, be one of a whole range of domestic or commercial cooking utensils such as saucepans, frypans, pressure cookers, 'crockpots', boilers and the like.

The invention provides a conventional utensil 1 with a lid 2 which has, on its underside, a vacuum sealing means constituted by an Oring 3 which seats in an annular recess 4 in the rim of utensil 1. Lid 2 is provided with a 'strongback' assembly which, together with the lid 2, comprises a closure member for utensil 1. A 'strongback', as it is termed in this art, is a comparatively resilient elongated strip 5 the hooked ends 6 of which engage the underside of the rim of a utensil (conventionally a pressure cooker).Strip 5 may be of bright mild steel and is centrally anchored to lid 2 by stud 7 which has a threaded upper end on which there is a knob 8, usually of plastics; knob 8 is rotatable so as to simultaneously exert an upward force on the underside of the rim and to press lid 2 down into annular recess 4 so as to seal the utensil by means of O-ring 3 on the underside of lid 2.

The above is all as is well known in the pressure cooker art, with the exception that the O-ring 3 replaces the usualy rectanguiarsectioned, annular pressure cooker seal.

Set into lid 2 of the closure member there is a weighted vacuum vent valve comprising a stem 9 on wich is a weight 10 with an integral handle 11. A weight support 1 2 is affixed to lid 2, and between this support 1 2 and weight 10 is an O-ring 1 3 incorporated into a seal and made from material capable of remaining stable at temperatures of up to 1 20 degrees C. The geometry of the stem 9 and of the clearance thereof is such that it will be ensured that the vent valve cannot stick or lock in the housing or be 'blinded' by the product being processed, but at all times of sufficient area to enable pressures above the dead-weight value of the valve (say 5 p.s.i. or 35 Kpa) to vent to atmosphere; weight 10 is to this end, of course, loose.

Also in lid 2 is a means for evacuating air from utensil 1 when the closure member is fitted thereon. Such a means is shown in Fig.

1 and comprises a tee-piece 14, preferably of chrome-plated brass. The evacuation point is achieved by either drilling a clearance hole in lid 2 and securing the tee-piece 14 therein by means of suitable nuts on a threaded spigot 1 5 with the necessary washers interposed to secure an adequate seal, or tapping the hole in lid 2 with a suitable B.S.P. thread to suit the threaded spigot 1 5.

At the upper end of tee-piece 14 is a compound gauge 1 6 with indicia on the dial 1 7 thereof indicating reduced pressures over the range between 0 and 28 inches of mercury, and elevated pressures up to, say 10 p.s.i. or 70 Kpa.

On the centre limb 18 of tee-piece 14 is a pet-cock 1 9-preferably a push-pull cock as shown-leading to the male end of a bayonet fitting 20, the co-operating female fitting being provided on the inlet tube of a vacuum pump. In Fig. 1 this vacuum pump is a mains pressure water-operated venturi 21 preferably made of a plastics material such as nylon. The water inlet end 22 of venturi 21 is connectable to a water faucet (not shown) by means of a conventional tap-fitting, hose and connector assembly.

However, in place of venturi 21 there may be employed an electrically driven vacuum pump with a 'drop-out pot' to collect condensed vapours. Also contemplated is a handoperated vacuum pump where such is obtainable.

In place of its being positioned at the upper end of a tee-piece such as 14, vacuum gauge 1 6 may be separately mounted on lid 2 as may be readily envisaged.

While most conventional cooking utensils will present no danger of implosion under a vacuum of 28 inches of mercury, and indeed are normally capable of substaining the 'perfect 30' inches, the pet-cock 1 9 may be designed to provide control of the degree of vacuum employed to suit the requirements of users, and to meet the design criteria limitations of the various manufacturers of cookware.

Although the present invention has been described in terms of a closure member and its adjuncts for the purpose of converting a conventional cooking utensil as, say, a saucepan, deep fryer, frypan, crockpot or boiler to a vacuum cooking appliance, it will be appreciated by the reader that the abovegoing description also has application to a conversion kit for converting an existing pressure cooker to a vacuum cooker. In order to carry out such a conversion the steam safety valve of the pressure cooker is removed and replaced by the weighted vacuum vent valve as described with reference to Fig. 2. An evacuating means, such as referenced in Fig. 1 by numerals 14 to 22, is fitted to the existing lid of the pressure cooker as previously described with reference to lid 2, and the existing pressure cooker closure is retained.This may not, of course, be composed of a strongback closure as described and illustrated but instead may be on the "taper-lock" principle put out by certain cookware manufacturers at the present time.

A typical example of the cooking or processing cycle possible with a vacuum cooking appliance according to the present invention is as follows: EXAMPLE: Sliced apple pieces are loaded either into the utensil or into an inner basket thereof and the requisite amounts of sugar, perhaps spices and wate (say, a half-cup) added.

The lid is secured onto the utensil by means of the strongback fitting, and the weight fitted into place on the stem. The female bayonet connector together with the venturi is then entered onto the male fitting on the lid. The venturi is connected to a convenient water faucet which is then turned on. The vacuumregulating pet-cock is opened and air is evacuated from the appliance until a vacuum of say, 26 inches of mercury (i.e. 660 mm of mercury) registers on the compound gauge.

The pet-cock is now closed and the venturi disconnected from the vacuum fitting in the lid in order to retain the reduced pressure in the appliance.

At this point, the intercellular gases have already been removed from the apple pieces, thus removing the insulating barriers of air and gases.

The appliance is then placed over the source of heat, or its own heating element is activated, and gradually the vacuum dissipates, the gauge needle returns to zero and a conventional low pressure cooking cycle commences. During the stage in which the degree of vacuum is gradually reduced by the formation of steam, the cooking cycle commences at a much lower temperature than in a conventional cooking process.

It is also possible to cook under vacuum, if a water-operated venturi pump is employed, throughout the total cooking cycle, as the water used to create the vacuum condenses the steam generated.

Moreover, the appliance also allows the contents to be cooled by evaporation to thus halt the cooking cycle at a desired end-point, and to so reduce the time required for air cooling prior to storage in a refrigerator or the like.

Those skilled in the art of food preparation will be likely to appreciate that foodstuffs cooked or otherwise processed under reduced pressure in vacuum cooking appliances according to the present invention retain their nutrient values and, to a considerable degree, also retain colour, shape, texture and taste and thus approach as closely to 'nature' as is possible in cooked foodstuffs.

Claims (8)

1. A vacuum cooking appliance comprising, for a cooking utensil, a closure member therefor capable of withstanding sub-atmospheric pressure; vacuum sealing means between said closure member and said utensil; a weighted vacuum vent valve in said closure member; and means for evacuating air from said utensil when said closure member is fitted thereon.

2. The vacuum cooking appliance as claimed in claim 1, wherein said closure member is a lid provided with a strongback (as hereinbefore defined) whereby said lid is enabled to be sealingly secured to said utensil.

3. The vacuum cooking appliance as claimed in claim 1 or claim 2, wherein said evacuating means is a water-operated vacuum pump or an electrically-driven vacuum pump.

4. The vacuum cooking appliance as claimed in any one of the preceding claims, wherein said evacuating means incorporates a compound gauge.

5. The vacuum cooking appliance as claimed in any one of claims 1 to 3, wherein said closure member is provided with a compound gauge set therein.

6. The vacuum cooking appliance as claimed in any one of the preceding claims, wherein said weighted vacuum vent valve is provided with an annular seal made from material capable of remaining stable at temperatures of up to 1 20 degrees C.

7. The vacuum cooking appliance as claimed in ay one of the preceding claims, wherein said sub-atmospheric pressure is within the range of O to 28 inches of mercury.

8. A vacuum cooking appliance, substantially as hereinbefore described with reference to the accompanying drawings.