Abstract: A pressure cooker has a pressure regulating control mounted on the cover handle thereof, the control, except when in its zero pressure position, acting to lock a locking mechanism supported within the top handle to prevent attachment removal of the cover from the main body of the pressure cooker.

Abstract: A disc-shaped inner member engages the valve stem. The inner member has a smooth uninterrupted exterior surface, except for a pair of spaced conical projections. An annular outer member is freely rotatably mounted around the inner member and has two peripheral slots. The actuator has a cap assembly receiving cavity including a pair of conical recesses adapted to engage the projections. Inwardly extending parts from spaced side portions are adapted to pass through the peripheral slots in the outer member and lodge thereunder to permit rotation of the valve stem.

Abstract: A safety lock for a pivoted door (16) closing an opening in a pressure vessel (10) to prevent the door from being opened when pressure in the vessel is above a selected level. A handle (44) is pivotably supported relative to the opening and movable to a locked position in which the door cannot be opened. A pressure lock housing (50) extends from the pressure containment vessel, the housing having a cylindrical opening therein, the axis of which intersects the plane of pivotation of the handle. A piston member (102) is received in the cylindrical opening (98) and has a portion extending externally of the housing. A tubular member (122) carried by the handle is engaged by the piston member when the handle is in the locked position, and pressure within the containment vessel forces the piston member outwardly to thereby prevent the handle from being moved towards the unlocked position. The piston member is automatically retracted when the pressure in the containment vessel is below a safe level.

Abstract: The invention relates to a saucepan lid having a lid handle detachably secured thereto, particularly for a steam pressure cooker, including monitoring elements disposed within said lid handle. Means are provided for permitting said handle to be detached from said lid without technical difficulties and to be safely re-attached thereto. To this effect the lid and lid handle are provided with projections and engagement recesses at locations permitting them to be brought into mutual engagement for attaching the handle to the lid and to be readily released from such engagement for detaching the handle, at least one such projection forming a movable component of a locking closure means. In a preferred embodiment the locking closure means is designed as a snap-engagement locking means (FIG. 1).

Abstract: A pressure compensating container having a cavity and including an open end. A closure lid is provided for sealing the open end of the container. A pressure regulating device is operatively connected to the container for regulating the pressure within the cavity. The base portion and the lid portion are constructed of a microwave permeable material. A safety pressure relief valve is provided having a manually operated pressure relief button for relieving the pressure within said cavity of said pressure compensating container.

Abstract: The present invention relates to an improved apparatus for retaining a valve body in secure engagement with the valve neck of a pressurized container. The apparatus assembly of the present invention incorporates a unique design which makes the retaining arrangement tamperproof since the retaining ring or rings which keep the valve body in place within the valve neck cannot be removed through the use of any ordinary tool. It will take a special tool designed especially to remove the retaining ring or rings in order to accomplish the removal process. As a result, product safety is assured with a significant reduction in product liability.

Abstract: An improved pressure-activated interlock system for a pressure vessel such as a pressure fryer, the interlock system includes a safety lock which cooperates with a latching mechanism to prevent opening of the pressure vessel while potentially hazardous pressure levels exist within the vessel. The safety lock includes a pin and associated solenoid actuator mounted on an arm which both mounts the latching mechanism and also serves to lift the lid of the pressure vessel. The existence of pressure conditions of a given level within the pressure vessel causes the solenoid to force the pin into engagement with one of a plurality of spaced radial slots formed in a hub portion of the latching mechanism, thereby preventing operation of the latching mechanism and thus opening of the pressure vessel. The solenoid is actuated by means of a pressure switch which directly senses the pressure within the pressure vessel.

Abstract: A steam pressure cooker has a--readily exchangeable--cooking goods container with a uniformly extending rim and a divided lid. The one lid component is a central hood surrounded by a concentric frame down underneath which extends the hood, making contact with the lip of a profiled gasket which is arranged between the lid and the cooking goods container. Besides, the hood and the frame of the lid form the operating device for the locking mechanism of the steam pressure cooker.

Abstract: The present invention provides apparatus which operates the door of a chamber that is capable of maintaining pressure within the chamber. The invention includes an improved closure for cooperating to move the door among positions in which it confronts the opening of the chamber, seals the chamber and allows access to the interior of the chamber. The preferred embodiment of the present invention includes a driving member and an operating member which have surfaces which cooperate to move the operating member in two separate directions. Movement of the operating member in the first direction secures the door in its position in which it confronts the chamber opening but in which it cannot seal the chamber. Movement of the operating member in the second direction causes the door to be secured against the perimeter of the chamber opening, thus sealing the chamber against fluid flow from between the perimeter opening and the door.

Abstract: A shipping container for radioactive or other hazardous materials which has a conical-shaped closure containing grooves in the conical surface thereof and an O-ring seal incorporated in each of such grooves. The closure and seal provide a much stronger, tighter and compact containment than with a conventional flanged joint.

Abstract: A sealable pressure vessel 5 has a closure member 8 held on by means of a bayonet fixing member which is movable between two positions while retaining the mechanical linkage between the vessel 5 and the closure member 8 forming a container 1. The bayonet fixing comprises a vessel lug 19 which co-operates with a stepped slot 18 in a locking ring 9 secured to the closure member. In one position of the lug 19 in the slot 18 the closure member is sealed on the vessel and the container is closed to atmosphere while in another position the seal is broken and the container is open to atmosphere. The closure member 8 incorporates a sliding valve 29 which has a spring urged piston 32 carrying a locking pin 33 to lock the lug 19 within the slot 18 when the container is closed to atmosphere.

Abstract: A pressure activated safety device includes a body structure defining an internal chamber having a partition movably disposed within the chamber. Pressure from a pipeline, pressure vessel, etc., acts upon the partition and positions it at a locking position preventing a venting seal from being released. A seal releasing element is movable relative to the body structure and is manually forced into an unlocking position against the bias of pressure acting upon the partition. The partition is pressure responsive such that it is manually movable from the locking position only upon the occurrence of a negligible pressure condition within the pressure chamber, thus providing for movement of a mechanical object only under an internal pressure condition that renders the apparatus safe.

Abstract: A closure assembly is provided for high pressure applications. It includes a hollow cylindrical member having a beveled end for welding to a pressure vehicle and a threaded end for receiving a cap. An annular projection extends from the threaded end and includes a O-ring for sealing purposes. The projection has relatively thin walls which allow it to dilate under pressure and provide an excellent seal.

Abstract: A pressure cooker is disclosed having a safety interlock including a resilient gasket interposed between flat sealing surfaces of a receptacle and a cover, and configured to form a seal against the surfaces when they are spaced by a first distance, and to prevent formation of the seal when the surfaces are spaced by a second, smaller distance. The receptacle and cover are provided with interlocking lugs which are engageable in two different conditions to determine the first and second distances respectively. The gasket comprises an annular body having inwardly directed, axially diverging leg portions terminating in lip portions to seal against the sealing surfaces, and has faces with peripherally spaced bosses engageable by the sealing surfaces when at the second distance to decrease the divergence of the leg portions and so prevent seal formation. Y-shaped, V-shaped, and W-shaped cross sections for the gasket are shown.

Abstract: The invention relates to a pressure indicator on a steam pressure cooker or similar container. This pressure indicating device is simple in construction and assembly, having a constant pressure display dependable in its functioning with little subject to fouling, and includes a membrane. Under action of the internal pressure of the container, the membrane brings about relative movement in an axial direction between a twist-giver nut and a twist spindle from which there follows a rotation of one of these members, and thereby a proportional pressure display by a pointer or marking connected to the one rotating member.

Abstract: A lid-latching and pressure-relieving device for a steam pressure cooker, the device enabling a lid (1) to be latched on to a saucepan of the cooker and having a valve (2) to relieve pressure in the cooker. The pressure-relief and lid-latching functions of the device are so coupled that the valve (2) is operatively connected to an actuating member (4) and the valve being responsive to pressure in the cooker when the lid is latched on the saucepan and being movable by the actuating member from a first position, in which the lid is latched on the saucepan and pressure exists in the cooker to enable cooking under pressure to take place, to a second position in which pressure in the cooker can be relieved through the valve without unlatching the lid, and to a third position in which the lid can be unlatched by the actuating member, the third position only being attainable upon discharge of the pressure in the cooker.

Abstract: A steam pressure cooking apparatus includes a connectible pot and lid with respective radially projecting handles thereon, the lid handle lying above the pot handle when the pot and lid are interconnected. A pressure discharge valve is provided in the lid and is controlled by a cam surface on a knob rotatably supported on the lid handle. A cam plate rotated by the knob has a further cam surface thereon which controls a spring-biased locking slide supported on the lid handle and engageable with a cam on the pot handle to prevent relative movement of the handles.

Abstract: An accumulator having a housing, a spring-loaded liquid inlet-outlet valve, a gas charging and release valve, and a gas-liquid separator in which a top is provided releasably connected to the housing for servicing the accumulator from the top. The top is slidably insertable into the top of the housing and a releasable lock is positioned externally of the top for locking the top in the housing. The lock is prevented from releasing while the top is held in an upward position by pressure in the housing and can only be released when the pressure in the housing is reduced and the top is moved downwardly. The locking means includes a notch in the exterior of the housing, a locking ring, and a backup shoulder on the exterior of the top. An anti-extrusion ring is bonded on the bottom edge of the top and slidably engages the interior of the housing for preventing damage to the separator. Preferably the top includes a dome and an annular flange extending around the lower end of the dome.

Abstract: In order to reduce the risk of inadvertent removal from an internally-pressurized cask or keg of a valve-type closure through which the contents are discharged, the valve body (15, 16) has rotationally-mounted on it an axially-trapped sleeve (23) which is threaded into the usual fixed socket (11) on the cask or keg. As the sleeve is screwed in, a peg (24) on the body enters a channel (25) in the socket to guide the body axially into the socket. On attempted removal of the sleeve (23) without a special tool to restrain rotation of the body in the unscrewing direction, the body tends to rotate in the unscrewing direction and the peg (24) enters a blind-ended passage (27) so preventing removal of the closure. However, the body moves axially sufficiently to open a gas-relief passage from the cask or keg to atmosphere.

Abstract: The body member and cover member of a pressure cooker are adapted to be held together by means of inter-engageable pairs of lugs arranged on each member. One or more selected pairs of lugs are constructed so that a shoulder on a first lug or lugs can interact with either of two linearly arranged projections carried by a second lug or lugs. The interaction of the selected pair of lugs produces two locking positions of the body and cover. The pressure cooker preferably incorporates a further safety mechanism, such as a gasket off-set device which prevents pressurization of the vessel if there is only partial overlap of the body and cover lugs.

Abstract: A vessel includes a body having a chamber normally containing pressurized gas and enclosed by a removable closure provided with a gas charging valve. Inadvertent disassembly of the closure when the chamber contains pressurized gas is precluded by a planar cover plate captively retained by the charging valve and normally masking tool-receiving members on the closure. Removal of the valve/cover plate unit initially releases a resilient seal carried by the inner face of the valve juxtaposed the outer face of the closure and subsequently progressively exposes to the atmosphere a gas bleeding passage formed in the attachment stem of the valve to gradually release all pressurized gas from the vessel chamber. The closure is only accessible for disassembly following complete removal of the unitary valve and cover plate after which all gas under pressure in the chamber has been relieved.

Abstract: A locking device for connectors or closures which device prevents rotation of the means for holding a pair of members in engagement wherein the locking device includes a shield which overlies all surfaces on the locking device which might be engaged by a wrench to rotate the locking device while the closure is subjected to pressure. The locking device includes a pressure responsive member exposed to pressure within the closure which carries the shield and positions the shield to overlie all surfaces on the device on which a wrench may be placed and when there is no pressure differential across the pressure responsive member permits the shield to be moved to an out of the way position exposing a wrench surface.

Abstract: A pressure fryer having a vessel adapted to cook a food product within a bath of cooking oil. A cover seals the vessel in a pressure-tight condition and, as pressure builds up in the vessel, the cover automatically locks an opening-closing actuator to prevent the cover from being opened. When the pressure is relieved, the cover unlocks the actuator to permit opening of the cover.

Abstract: Apparatus secures in its closed position the door of a chamber capable of maintaining pressure within the chamber. The present invention includes apparatus disposed on the chamber for cooperating to move the door to and from its closed position including at least two members, one of which is movable relative to the chamber. The door is in its closed position when the stationary member and the door are separated from each other by a predetermined distance. The movable member can be forced between the door and the stationary member to separate the door and the stationary member from each other by a predetermined distance. Further, the present invention includes apparatus for preventing the door from assuming its closed position until the movable member is forced between the door and the stationary member.

Abstract: A food product is cooked under pressure and within a bath of hot cooking oil in a vessel when the vessel is sealed closed by a cover. The pressure in the vessel is controlled by an exhaust valve which must be located in an open position before the cover may be closed and sealed. As long as the exhaust valve is closed, it is not possible to open a drain valve and drain the oil from the vessel.

Abstract: An improved valve system for obtaining access to a container of fluid. In a container of fluid, and particularly a keg for beer, a valve assembly receiving member or keg neck extends from the top of the container. A sealing mechanism is provided to secure the valve assembly in sealed relationship with the keg neck and to allow access to the fluid contained by actuation of the valves. More specifically, the valve neck has a groove in its inner surface to receive a resilient retainer ring which maintains the valve assembly in place. In addition, a safety feature is provided to prevent inadvertent expulsion of the valve assembly should the retainer ring be dislodged while the keg is pressurized. A siphon tube extends from the valve assembly to a position adjacent the bottom of the keg when the valve is secured within the keg neck.

Abstract: A steam pressure cooker having a lid with a retainer body, such as a grip member or a valve housing for containing safety and monitoring devices releasably affixed thereto by means of a sealed fastener element. For protection of said devices against contamination from inside or outside the cooker, such as during cleaning thereof, all of said devices are located in cavities formed in said retainer body and sealed against the interior of the cooker, said sealing being accomplished by means of a diaphragm. The fastener element is releasable independently of the remaining components.

Abstract: A pressure cooker particularly adapted for use as a pressure fryer. The cooker's tank is electrically heated by a novel electrical resistance heater and heat reflector structure. The cooker also includes a novel cover and cover hold-down mechanism.

Abstract: A rotatable pressure vessel has an opening and an internal movable cover therefor attached to a lever which is pivoted to the exterior of the vessel. For closing the cover, there is an actuating element movable to engage the lever, and mounted on a stationary support adjacent the vessel.

Abstract: A closure for a chamber having an interior which can contain a fluid under pressure provides apparatus for latching the door of the chamber in its closed position and locking it in that position when the positive pressure within the chamber reaches a predetermined level. The closure includes a door that is moved by positive pressure within the chamber and, through appropriate mechanisms, activates locking apparatus that prevents the door from leaving its closed position as long as such pressure is present within the chamber.

Abstract: A system for dispensing fluid from a container. The container is pressurized by supplying gas into the container thereby forcing the fluid out of the container through a siphon tube and an outlet valve in the container. The system utilizes a valve assembly having two valves, one for enabling the flow of the gas into the container and the second for allowing the flow of the fluid out of the container. The valve assembly is mounted in a neck member that is secured to an opening in one of the walls of the container. Arranged within the neck is a deformable seal that is compressed between a body portion of the valve assembly and an inner surface of the neck member. A non-threaded retaining ring holds the valve body portion of the valve assembly within the neck member and serves to apply the force to the valve body portion for compressing the seal.

Abstract: An automatic locking device for the lid-closing lever of a pressure-cooker.The lever is provided with an engaging portion designed for engaging a locking pin which is operated in response to the pressure within the pressure-cooker. The pin is mounted directly on the lid and interferes with the lid-closing lever in the lowered condition of the latter, in order to prevent said lever from rotating, and therefore prevent the opening when there is some pressure in the cooker.

Abstract: A pressure device is provided with a cover member which is removably attached thereto by a pair of clamping rings which are hydraulically actuated laterally outwardly and inwardly relative to flanges on the pressure device and cover member to respectively release the cover and interengage the cover with the device. The clamping rings are pivotally interconnected with the device such that lateral outward displacement of the clamping rings is accompanied by radial outward displacement of the pivot axis to provide clearance for removal of the cover member. The clamping ring members are guided during a portion of the lateral inward and outward displacement thereof, and the guide arrangement supports the clamping rings in the laterally outermost positions thereof.

Abstract: A tamperproof cap assembly for a hydrant having a valve stem rod which in one embodiment is displaceable in elevation within the hydrant housing without rotation of the valve stem rod about its axis. The assembly includes a cap adapted to cover the outlet port in the hydrant housing. The cap is provided with a stem. A locking means secured to the valve stem rod engages the cap stem when the valve stem rod is in a first position and the cap stem is displaced toward the valve stem rod. The locking means releases the cap stem when the valve stem rod is displaced in elevation from the first position to a second position without rotation of the valve stem rod about its axis. The cap is provided with a pair of unthreaded facing annular walls which define an annular channel for receiving the hydrant nozzle.

Abstract: A pressure cooker particularly adapted for use as a pressure fryer. The cooker's tank is electrically heated by a novel electrical resistance heater and heat reflector structure. The cooker also includes a novel cover and cover hold-down mechanism.

Abstract: A safety closure system for a tank comprises(a) complementary sections of a tank adapted to contain pressurized fluid, said sections having annular flanges which are subject to relative separation as the tank sections relatively separate due to said fluid pressurization,(b) said flanges respectively having oppositely facing annular surfaces which extend in relatively divergent relation away from the tank interior, and(c) clamp means assembled onto said flanges and having channel shape with webs extending in complementary relation in said divergent surfaces to engage the flanges and block said relative separation of the flanges at which time removal of the clamp means off the flanges is also blocked by said divergent surfaces.

Abstract: A pressure-cooker comprising a pot and a lid each having flange portions for interconnection thereof through rotation of the lid relative to the pot, with locking means formed in the flanges for preventing reverse relative rotation of the lid if pressure of a predetermined value is present in the pressure-cooker. A spring actuated relief valve provided in the lid and a timer mechanism for loading the spring for a designated period of time whereby pressure of a predetermined value is maintained in the pressure-cooker during such period of time.

Abstract: A pressure cooker has a cooking container, a cover retainable on the container by a bayonet lock and having a sealing ring, a radially extending handle on the cover, and a combined valve and safety device arranged in the handle and having valve elements, safety elements and one common operating element interdependently adjusting and actuating the valve and safety elements. The valve elements of the device include a pressure limiting valve simultaneously forming a safety valve and one slider arranged to adjust the pressure limiting valve. The safety elements of the device include two further sliders one of which is formed as a ventilating slider and arranged for lifting of the sealing ring of the cover whereas the other of the sliders is formed as a locking slider and arranged for mechanical locking of the cover on the container.

Abstract: A closure for a pressure cooker pot which includes a lid with a lateral keyway in the center, and a standpipe fixed to the lid, a key fitting in the keyway and removable lid locking means fixed to the key and reacting between the key and the pot. A pressure regulator when in position on the standpipe prevents the separation of the locking means from the lid by blocking the removal of the key.

Abstract: An improved valve system for obtaining access to a container of fluid. In a container of fluid, and particularly a keg for beer, a valve assembly receiving member or keg neck extends from the top of the container. A sealing mechanism is provided to secure the valve assembly in sealed relationship with the keg neck and to allow access to the fluid contained by actuation of the valves. More specifically, the valve neck has a groove in its inner surface to receive a resilient retainer ring which maintains the valve assembly in place. In addition, a safety feature is provided to prevent inadvertent expulsion of the valve assembly should the retainer ring be dislodged while the keg is pressurized. A siphon tube extends from the valve assembly to a position adjacent the bottom of the keg when the valve is secured within the keg neck.

Abstract: A pressure cooker has a cover which is removably secured in pressure-tight relation to the cooker body. The cover has a centrally disposed valve, which regulates pressure development in the cooker, and an over-pressure release plug in the cover margin adjacent a cover handle, which separates from the cover in response to excessive pressure development in the cooker is captivated by an overhang portion of the cover handle which directs the escaping fluids away from the hand grip portion of the handle. The cooker also has a pressure-actuated interlock in the margin of its cover opposite the cover handle which inhibits removal of the cover when the cooker is in a pressurized condition, and prevents pressure build up in the cooker when the cover is incompletely locked to the cooker body.

Abstract: A cover effective to be applied to pots, casseroles and similar kitchen containers is described, which is of such size and structural characteristics as to allow use as part of a "pressure pot." The cover comprises an outwardly projecting edge, a cup-like portion which is provided with a rim which extends downwardly to a level lower than said outwardly projecting edge; an essentially annular component, for instance a gasket, located about the rim and capable of contracting or shrinking. The annular component has preferably a segmented perimetral outline, alternately of smaller and larger diameter, the small diameter parts circumscribing, as the component is in the contracted condition, a circle having a diameter lesser than that defined by the projecting edge.

Abstract: A lid catch on a container driven with superpressure is disclosed. A prestressed spring catch bolt is held in an engaged position due to the pressure exerted on an inner lid of the container which is transmitted by a counterpoise to the bolt. Therefore, releasing of the lid when the container is pressurized is impossible.

Abstract: A safety interlock for a pressure vessel having a shell portion, a door portion and an opening in one of the portions, the interlock including a collar affixed to the outside of the pressure vessel surrounding the opening, the collar having a bore therethrough with an enlarged section extending partway toward the pressure vessel opening, a resilient ring seal disposed within the enlarged section of the bore, a guide bushing positioned within the enlarged section of the bore in contact with the seal, a support bracket affixed to another portion of the pressure vessel, a movable shear bolt carried by the support bracket, and means for advancing the shear bolt when the bolt is aligned with the pressure vessel opening through the guide bushing, ring seal and collar into contact with the opening of the pressure vessel and maintaining the end of the bolt tightly against the pressure vessel opening so a pressure can selectively be maintained within the vessel.

Abstract: The hold-down bolts on the cover of a pressure vessel cannot be loosened until a pressure relief valve has been opened to relieve the pressure in the vessel and to release a safety member positioned over the bolts.

Abstract: Disclosed is a safety closure apparatus for a pressure vessel, particularly for a vessel such as a pump stabilizer which has a gas compartment and a liquid compartment therein, both of which are normally pressurized. The apparatus includes a safety head configured to cover the closure means of the vessel to prevent its actuation; a liquid pressure bleed valve which must be removed before the safety hood can be moved off of the closure means, thereby insuring depressurization of the liquid compartment prior to opening; and gas pressure bleed means automatically operable upon movement of the safety hood off of the closure means, thereby also insuring depressurization of the gas compartment before access can be had to the closure means to actuate it to open the vessel.

Abstract: A sterilizing container having a lid with an outer flange which cooperates with the upper edge of a base and a resilient member for sealing the container. The lid contains a mechanism for automatically moving the lid into sealing engagement with the base. Located on both the outer flange of the lid and the upper edge of the base are locking means which interact to place the lid in a sealing engagement with the base when the lid is moved by the moving mechanism on the lid. The container is designed to receive articles such as medical instruments which are sterilized when the container is placed in an autoclave, subjecting the instruments or articles to a sterilizing environment. The moving mechanism on the lid includes means responsive to the sterilizing environment to automatically bring the lid into sealing contact with the base prior to the return of the surrounding environment to ambient conditions, preserving the sterilized instruments until needed for use.

Abstract: A pressure cooker has a vent opening in its cover in which a sealing plug rises in response to pressure developed in the cooker and the cover handle has a slidably mounted lock member which is manually movable into an "open" position when its abutment portion overlies the vent opening to prevent rise of the plug and thereby development of pressure within the cooker. The lock member can be moved out of said "open" position into a "cook" position where its abutment portion is clear of the vent opening and the plug is free to rise and seal the vent opening to permit pressure development within the cooker. The lock member, however, has a catch portion which, in the cook position of the lock member, catches with a cooker body handle so that the cover cannot be rotated relative to the cooker body, as is required to remove the cover from the cooker.

Abstract: A locking mechanism for a door of an autoclave made up of a vent plate, a diaphragm, and a seat and a pressure plate that engages a locking mechanism on the side of the diaphragm remote from the pressure side.The seat has a counterbore adjacent to its inner edge defining a shoulder. The diaphragm is clamped to the seat outwardly of the counterbore and the pressure plate can move into engagement with the flat surface defined by the counterbore when gas is under pressure in the chamber forcing the pressure plate against the door locking mechanism. The surface of the seat between the outer flat surface and the shoulder is contoured providing a smooth surface for the diaphragm to engage.

Abstract: An autoclave, to be used as a pressure cooker or a sterilizer, has a cylindrical vessel centered on a horizontal axis with open ends rimmed by radially inwardly projecting shoulders reinforced by rings with axially outwardly converging resilient external flanges and axially inwardly diverging resilient internal flanges forming small-diameter outer annular seats and large-diameter inner annular seats. A carriage, axially slidable along a base supporting the vessel, rigidly interconnects an upright internal lid and two upright external lids which are axially separated by a distance corresponding to the spacing of the two end flanges of the vessel, the internal lid coming to rest against one or the other inner seat while a respective external lid lies against the opposite outer seat to seal the vessel, the development of steam pressure within the vessel exerting upon these lids a differential force holding them firmly in their closure position.