Anti-condensation cover for pressure fryer

A closure for covering the opening of a vessel containing a supply of cooking fluid preferably includes a flexible inner member adapted to cover the opening of the vessel in sealing engagement therewith and an outer member adapted to be positioned above the inner member. A coupling assembly is provided to couple the inner member to the outer member when the closure assembly is removed from the vessel. The coupling assembly permits a portion of the inner member to expand away from the outer member in response to an increase in temperature within the cooking vessel. The inner member is preferably a low thermal conductivity material so that after the inner surface of the inner member, which is exposed to vaporized cooking fluid, reaches the temperature of the vapor condensing thereon, the rate of additional condensation is substantially reduced. The vapor conserved by reduced condensation on the inner surface is used to generate pressure in the vessel more rapidly. The inner member is also preferably selected from a material exhibiting a highly non-linear thermal gradient in response to elevated temperatures.

What is claimed is:

1. A closure for an open top cooking vessel, wherein said vessel includes a plurality of opposed side walls which define the open top, said closure comprising:

a member having a periphery configured and dimensioned to be inserted into said open top and seal against said sidewalls around its periphery,

said member having a predetermined thickness and an inside surface adapted to be subjected to elevated cooking temperatures,

said member having a low thermal conductivity and exhibiting a non-linear thermal gradient through its thickness such that, when subjected to cooking temperatures within said vessel, a first relatively thin portion of said thickness adjacent to the inside surface heats up to the cooking temperature relatively quickly while a second relatively thicker portion of said thickness spaced away from the inside surface by said thin portion remains at a relatively lower temperature such that said member curves convexly in the direction of the inside surface and remains in sealing contact with the side walls when subjected to cooking temperatures within the vessel.

2. The closure according to claim 1, wherein the inside surface of said member is in compression when subjected to the elevated cooking temperature in the vessel.

3. The closure according to claim 1, wherein said member includes seal means disposed around the periphery of said member for sealing against the vessel sidewalls.

4. The closure according to claim 3, wherein said seal means comprises a groove around the periphery of said member and an o-ring seal disposed in said groove.

5. The closure according to claim 1, wherein said member is constructed of a single thermoplastic material exhibiting said low thermal conductivity and non-linear thermal gradient.

6. The closure according to claim 5, wherein said material is polysulfone.

7. The closure according to claim 1, wherein said member comprises a composite construction of at least two materials having different thermal properties.

8. The closure according to claim 1, wherein said member comprises an inner member of a closure assembly, said assembly also comprising:

an outer member positioned above said inner member, said outer member being configured and dimensioned to be received within the vessel open top and seal against said sidewalls; and

means for coupling together said inner and outer members, said coupling means permitting relative movement between said members to allow said convex curvature to form an enlarged space between said members in response to exposure of the inner member to cooking temperatures.

9. The closure according to claim 8, wherein said coupling means are detachable to permit separation of said inner and outer members.

10. The closure according to claim 9, wherein said coupling means comprises:

a plurality of mushroom-like projections, projecting from the outer member toward the inner member, said projections having a shaft portion and a larger head portion; and

a plurality of apertures defined in the inner member, said apertures configured and dimensioned to receive said projections such that relative sliding movement between said members retains the projection heads behind locking abutments which restrain side-to-side motion but not up and down motion as between said members.

11. A closure for a pressure cooking vessel having a top opening and defining a cooking space, said closure comprising:

an inner member adapted to seal the top opening of said vessel and having an inner surface communicating with said cooking space, said inner member constructed of an insulating thermoplastic material exhibiting a non-linear thermal gradient when subjected to elevated cooking temperatures such that it deflects with its central portion moving inward and develops compressive stresses in its inner surface to resist penetration of degradation by vaporized cooking fluids at said elevated temperatures;

an outer member positioned above said inner member in sealing engagement with said vessel; and

means for removably coupling said inner member to said outer member while providing for relative movement between said inner and outer members to allow said deflection of the inner member away from the outer member in the central portion in response to the elevated cooking temperatures in said vessel.