US3182685A - Closure valve for the outlet port of a pressure vessel - Google Patents

Description

May 11,1965 J. MEhClER X 3,182,685

- CLOSURE VALVE FOR THE OUITLET PORT OF A PRESSURE VESSEL Original Filed May 27, 1959 4 Sheets-Sheet 1 /6 A 22 t ,9 mmm'z.

y 1, 1965 J. MERCIER E 3,182,685

CLOSURE VALVE FOR THE OUTLET PORT OF A PRESSURE VESSEL Original Filed May 27 1959 4 Sheets-Sheet 2 INVQVTOR.

.1549 MERC/ER y 11, 9 J. MERCIER 3,182,685

CLOSURE VALVE FOR THE OUTLET PORT OF A PRESSURE VESSEL Original Filed May 2'7. 1959 4 Sheets-Sheet 3 y 1965 .1. MERCIER 3,182,685

I CLOSURE VALVE FOR THE OUTLET PORT OF A PRESSURE VESSEL Original Filed May 2'7, 1959 4 Sheets-Sheet 4 r h g 04 ,2. I I IOJ Original application May 27, 1959,-Sen No, 816,114.

United States Patent "ice Divided and this application Dec. 12,1962, Ser. No.

Claims priority, application France June 3, 1958 18 Claims. (Cl. 138-30) This invention'relates to the closure of the outlet port of a container for fluid and more particularly to a closure valve for a pressure accumulator of the type having a rigid container to be filled with fluid, usually oil and air under pressure and having a deformable partition intervening between such fluids.

When oil is pumped into the outlet port of the container on one side of the partition, it will deform the latter and compress the air previously charged into the container on the other side of the partition. In use of the accumulator, a control valve in the line between the outlet port and the hydraulic device to be operated, is, opened and the partition in expanding will force such oil from the container through the closure valve.

Unless the closure valve remains open until substantially all the oil in the container is expelled, the trapped oil will not be available for useful purposes. Also, where the partition when expanding is' forced against and extrudes past the closure valve, it is likely to become pinched or torn with resultant failure of the equipment.

Where, to retain the valve'opened so that substantially all of the oil may be expelled from the container, a relatively strong spring is used to react against the valve head, if such spring also keeps the valve open even when the container is substa'ntiallyempty, the partition maybe extruded past the valve head with resultant injury thereto.

Where, to insure that the valve head will close before the partition can be extruded, a relatively weak spring is used, then the expanding partition, when it engages the valve head, will immediately'overcome the force of the 'spring and close the valve while the container is still charged with a considerable quantity of oil. Furthermore,

in the event a large rate of flow of liquid is desired dur ing any short period of time, such as, for example, to

operate a hydraulic brake, the flow of such fluid would result in a low pressure area beneath the valve head and a high pressure area in the container. As a result, the

relatively weak spring would not be able to overcome the differential pressure on both sides of the valve head and the latter may close almost immediately after the flow of fluid begins, thereby to prevent proper functioning of the equipment to be operated. a

It is accordingly among the objects of the invention .to provide a closure valve for the outlet port of a presof the accumulator, which open initial engagement by the expanding partition will only partially close the liquid "port to prevent extrusion of the partition and only when substantially all of the liquid has been'expelled;from the accumulator by the expanding partition, will completely close the liquid port'of said accumulator.

l Another object is to provide a valve for the liquid port "of the accumulator which will provide a greater-flow in ,one direction thanqthe other, through said'po rt ,and will Another object is to provide a valve for the liquid port Q 3,182,685 Patented May 11, less close only when substantially all the liquid has been expelled from the accumulator by the expanding partition.

This application is a division of copending application Serial No. 816,114, filed May 27, 1959, now abandoned.

According to the invention these objects are accomplished by the arrangement and combination of elements hereinafter described and particularly recited in the claims.

In the accompanying drawings in which are shown one Mixture of the various possible embodiments of the several features of the invention,

FIG. 1 is a longitudinal sectional view of an accumulator having one embodiment of the invention incorporated therewith;

FIG. 2 is a fragmentary sectional view similar to FIG. 1 of another embodiment of the invention;

FIG. 3 is an expanded view of the embodiment of FIG. 2;

FIG. 4 is a plan view taken along line 44 of FIG. 2;

' FIGS. 5, 6 and 7 are fragmentary views of other embodiments of the invention, and

FIG. 8 is a longitudinal sectional view of still another embodiment of the invention.

Referring now to the drawings, in FIG. 1 there is shown a pressure accumulator comprising a container or pressure vessel 10, preferably of strong rigid material such as steel, cast aluminum or the like, capable of withstanding high pressures. The container may be spherical or cylindro-spherical as desired, and has a deformable partition 11 intervening between axially aligned openings 12 and 13 therein. Preferably the partition is a collapsible and expansible bladder which desirably is of resilient material such as rubber or synthetic plastic of like physical characteristics, which in undistended but substantially unstretched condition is smaller than the cavity of the container and the opening 12, which defines the gas inlet port, leads into the bladder 11 and is controlled by a valve 14.

Means are provided to close the opening 13. Such means desirably comprises an outlet closure assembly 15' which may include cylindrical member 16 secured as by welding in said opening 13.

According to the illustrative embodiment of the invention shown in FIG. 1, the cylindrical member 16 desirably has a plurality of passageways 17 leading from its inner end 18 adjacent its periphery to an axial bore 19 therethrough, the latter defining the liquid port. A very flexible valve member, preferably of spring steel, in the form of a resilient normally fiat disc 21 is aflixed by a rivet 22to such inner end 1'8 so that the center of the disc is clamped thereagainst.

The diameter of disc 21 is such that its periphery 23 will extend laterallybeyond the inner ends 24 of the passageways 17 and such periphery 23 isnormally spaced from such inner ends 24. As shown in FIG. 1, this is accomplished by providing an annular groove 25 in the inner end 18 of the member 16 of depth such that it may accommodate acoil spring 26, which reacts against the undersurface of the flexible disc 21 between the axis of the disc and its periphery, to deflect said periphery away from the passageways 17, the disc" thus retaining its flexibility at its periphery. As the disc 21 is very flexible, it will assume the cup-shaped contour shown in FIG. 1 without substantial crinkling.

Thus, when any portion of the periphery 23 of the disc 21 is engaged-by the expanding bladder 11 in operation of the unit, it will readily be moved downwardly compressing the coil spring 26 and will react on the inner end 18 of the tubular member 16 closing the ends of the passageways 17 to prevent extrusion of the bladder 11 therethrough.

It is to be noted that during the closing of the valve,

the reactions exerted by the peripheral zone of thedisc against the partition is partically negligible, as the parti- '3 tion works against the resilient means 26 through a continuous surface and not against the periphery of the disc 21 which is practically free to yield.

The closure assembly shown in FIGS. 2, 3 and 4 is substantially identical to the one shown in FIG. 1 and corresponding elements have the same reference 7 numerals primed.

In this embodiment, however, instead of the single coil spring'26 shown in FIG. 1,.a plurality of coil springs 31 are provided each positioned in an associated recess 32 in the inner end 18 of tubular member 16, the recesses desirably being arranged in a ring concentric with the rivet 22 as shown in FIG. 4 and alternating with the passageways 17'.

The disc 21 secured to the inner end 18' of the tubular member 16' by the rivet 22' has a plurality of openings 33 designed to avoid counter-pressure between the disc 21' and the inner end of the tubular member 16' as fluid flows through the passageways 17 so that such counter-pressure will not interfere with the action of the coil springs 31. p r r In the embodiment shown in FIG; 5, the inner end 18' of the tubular member 16 has an annular groove 41 with a shoulder 42 at the inner periphery of the groove and a shoulder 43 at a level higher than shoulder 42 at the outer periphery of the groove 41.

The very flexible disc 21' is secured by rivet 22' to the inner end of the tubular member 16 and the periphery23' of the disc is urged inwardly, away from the inner ends 24 of passageways 17' by a pair of Belleville washers 45, 46, the shoulders 42 and 43 preventing excessive flexure of the washers when they are cornpressed. r

The Belleville washers are springsof the negative? type, i.e., over a predetermined range of deformation thereof caused by the force exerted by the expanding bladder in direction to move thejperiphery 23 of the disc 21' downwardly, the washers 42, 43 will provide a progressively increasing force opposing the force causing such deformation and thereafter when such deformation exceeds a predetermined amount it provides a progressively decreasing force opposing the force causing such of the tubular member 16 has an annular groove 41 with a seat 51 at its outer periphery and with passageways 52 leading into said groove 41 adjacent its outer periphery from bore 19. V

A disc 21' which has a plurality of openings 33 therethrough is secured by a rivet 22 to the inner end 18 of the tubular member 16' and its outer periphery 23 extends over the inner ends 53 of a series of passageways 17' extending through the tubular member 16 into the bore 1% thereof and positioned outwardly of passageways 52.

Positioned beneath the disc 21' is an idly mounted disc 56, the periphery 57 of which is adapted to seat on shoulder 51 to close passageways 52.

The disc 56 is urged inwardly by a Belleville washer 58 and a plurality of coil springs '59 positioned in recesses 61 in said tubular member 16" react against said disc 21' between its peripheral zone and its central mount 22 to urge said periphery inwardly.

The springs 59 and the Belleville washer 58 are of tension such that the periphery of disc 56 will move onto its seat 51 to close passageway 52 by a counter pressure resulting from outflow of fluid greater than a predetermined value, the disc 21 closing onlyby direct action of the expanding bladder thereagainst.

It is of course to be understood that when the accumulator empties at a rate such that the outflow of fluid does not exceed such predetermined amount, the bladder reacting against disc 21' will not only close the passageways 17 but by the action of the disc 21 against disc 56 the latter will close the passageways 52.

With the above arrangement a largevvolume of fluid may flow into the accumulator in a relatively short time and the output from the accumulator will be moderate.

It is to be noted that the peripheral zone of the disc 21 of FIG; 7, not only is very flexible due to'the location of the springs 59, but further that the action of the Belleville washer 58, exerted through disc '56 against deformation so that the periphery of the disc 21' will'- rapidly seat to seal the passageways 17 and but little force is required to keep the disc'seated.

- In the embodiment shown in FIG. 6, the inner end 18' of the tubular member 16' has an annular groove 41' with a shoulder 42 at its inner periphery and a shoulder 43 at its outer periphery at a higher level than shoulder 42. A plurality of passageways 17' extend through the floor of the groove 41' into the bore'19' of the tubular member 16', said passageways 17' being arranged in a circle outwardly of the shoulder 43.

.The very flexible disc 21 of FIG. 6 is secured by the rivet 22' to the inner endof tubular member 16' and the periphery 23' of the disc 21 is urged inwardly away from the periphery 47 of the tubular member 16 by a pair of Belleville washers 45, 46 which have the characteristics previously described, the shoulders 42, 43 preventing excessive flexure of the washers when they are'compressed.

' Interposed between'the washers 45, 46 is a resilient. disc 48 the periphery 49 of which extends partially over the inner end of passageways 17. 7

It is to be noted that the disc 48 is free to move and when liquid enters the accumulator through the passageways- 17', the periphery 49 of the disc 48will be raised so that flow of liquid into the accumulatorwill not be restricted. However, when liquid is forced out of the accumulator through the passageways 17' the disc 48 will be forced against the shou1der 43 as shown, to reduce the flow through passageways 17.

the disc 21 when the partition closes the openings 33', will be exerted against a zone of said disc 21' further off the peripheral zone of said disc 21'. Consequently, the pressure to be exerted by the partition to close the valve will be decreasing from the central part of disc 21' toward its peripheral zone.

. reduced diameter as at 78 outwardly of its inner end 79 which defines a valve seat 81. A plurality of bores 82 extendparallel to bore 77 toprovide communication between the upper and lower portions 83vand 84 thereof, said bores 82 having ports 85 and 86 at each end respectively.

Secured in the upper end of the reduced diameter por- .tion78 of bore 77 is a bushing 87 which slidably mounts Thus thedisc 48 serves jas a valve to permit large 1 flowinto the accumulator and restricted flow out of the V latter,

a valve stem 88. The upper end of the valve stem 88 has a valve head 89 preferably formed integral there with which is normally retained against valve seat 81 by a coil spring 91, compressed between the outer end of bushing 87 and an annular flange 92, at the outer end of the valve stem 88. e

The valve stem 88 has an axial bore 93 in which is slidablymounted a rod 94. The Valve head 89 has an axial bore 94" in communication with said axial bore .93 and of larger diameterthan the latter, the lower end of said bore 94 defining a seat 95 to receive a ball valve 96 normally retained on its seat by a relatively weak'coil spring 97. I

A very flexible plate 98is secured at 9 as by a rivet to. the valve means and extends over theinner end of bore 943a coil spring 101 positionedv in a recess in the valve head reacting against said plate 98 between the outer edge zone thereof and its mount zone, to space the outer edge zone from its seat.

The valve stem 88 has a transverse bore 102 leading into the bore 93 of the valve stem 88 and adapted to provide communication between the bore 94', the portion 83 of bore 77 and the bores 82.

The lower end of the rod 94 extends through an axial bore 105 in a plug 106 secured in the outer end of bore 77 and reacts against the head 107 of a button 108 slidably mounted in the bore 109 of a screw 111 threaded into the lower end of the bore 77.

A passageway 112 extends through the tubular member 71 leading into the bore 82 and is controlled by a valve 113.

A transverse bore 114 extends through the tubular member 71 into the portion 84 of bore 77 and a coupling 115 is connected to said bore 114.

In the operation of the unit when oil under pressure flows through coupling 115 it will pass into portion 84 of bore 77, through ports 86, bores 82, bore portion 83 to react against the valve head 89 to lift the latter off its seat 81 so that a large opening will be provided for admission of fluid into the accumulator. In addition, the fluid under pressure will also pass through transverse bore 102 to react against ball valve 96 to move the latter off its seat 95 against the tension of coil spring 97 so that a small quantity of fluid will also pass through bore 94' into the accumulator.

When the admission of fluid into the accumulator through coupling 115 has been completed and the flow has stopped, the coil spring 91 will move the valve head 89 onto its seat, the ball valve 96 also closing at this time under the action of coil spring 97.

If it is desired to empty the accumulator it is merely necessary to press button 108 which, through rod 94, will lift the ball valve 96 off its seat, so that fluid may flow beneath the plate 98 through bores 94' and 102, bores 82 out of the coupling 115.

It is apparent that such flow will be relatively small due to the small size of passageway 102.

When the accumulator is empty, the expanding bladder will press against plate 98 to move the latter downwardly to close the bore 94' so that the flow of fluld will be stopped.

If desired, the accumulatpr may also be charged through the valve 113.

With the constructions above described, a closure member is provided which will dependably retain the outlet port of a pressure accumulator open until substantially all of the oil is expelled therefrom regardless of the rate of flow of oil from the accumulator, yet with assurance that when substantially all of such oil is discharged, the outlet port will be closed without likelihood of extrusion of the bladder.

As many changes could be made in the above constructions, and many apparently widely different embodiments of this invention could be made without departing from the scope of the claims, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

l. A pressure vessel comprising a rigid container wlth an inlet port for a first fluid and an outlet port for a second fluid and a deformable partition intervening between said ports, valve means controlling said outlet port, said valve means comprising a valve seat having an associated passageway, a flexible plate rigidly mounted with respect to said seat and movableto close said passageway, and resilient means comprising a negative spring reacting against said .plate between the peripheral zone thereof and the mounted portion thereof to space the portion of the plate outwardly from its affixed portion on said seat,

whereby the reaction of the peripheral zone of the plate against the partition is negligible, said peripheral zone being substantially free to yield and said partition reacting against a continuous surface to overcome said resilient means to move said plate to close said passageway.

2. The combination set forth in claim 1 in which the flexible plate is mounted at its central portion on its seat, and the resilient means comprises a Belleville washer reacting against said plate between said central portion and said peripheral zone.

3. The combination set forth in claim 2 in which a shoulder limits the compression of said Belleveille washer.

4. A pressure vessel comprising a rigid container with an inlet port for a first fluid and an outlet port for a second fluid and a deformable partition intervening between said ports, valve means controlling said outlet port, said valve means comprising a valve seat having an associated passageway, a flexible plate rigidly mounted at its central portion with respect to said seat and movable to close said passageway, and resilient means comprising a coil spring concentric with said central portion and reacting against said plate between the peripheral zone thereof and the mounted portion thereof to space the portion of the plate outwardly from its afiixed portion on said seat, whereby the reaction of the peripheral zone of the plate against the partition is negligible, said peripheral zone being substantially free to yield and said partition reacting against a continuous surface to overcome said resilient means to move said plate to close said passageway.

5. A pressure vessel comprising a rigid container with an inlet port for a first fluid and an outlet port for a second fluid and a deformable partition intervening between said ports, valve means controlling said outlet port, said valve means comprising avalve seat having an associated passageway, a flexible plate rigidly mounted with respect to said seat and movable to close said passageway, and resilient means reacting against said plate between the peripheral zone thereof and the mounted portion thereof to space the portion of the plate outwardly from its affixed portion on said seat, whereby the reaction of the peripheral zone of the plate against the partition is negligible, said peripheral zone being substantially free to yield and said partition reacting against a continuous surface to overcome said resilient means to move said plate to close said passageway, and a second flexible plate is provided between the first plate and the said seat, and partially closes said passageway when the fluid flows in one direction and offers unrestricted flow through said passageway when the fluid flows in the opposite direction.

6. The combination set forth in claim 5 in which said plates are designed to be moved outwardly from said seat upon flow of fluid in said opposite direction.

7. The combination set forth in claim 5 in which resilient means are associated with said second flexible plate and a passageway is associated with each of said plates.

8. The combination set forth in claim 7 in which said first flexible plate has a diameter greater than the diameter of said second flexible plate.

9. The combination set forth in claim 7 in which the second flexible plate is adapted to close the associated passageway by the action of the fluid flow in overcoming the associated resilient means and the resilient means associated with the first flexible plate is overcome by the force exerted by the partition.

10. A pressure vessel comprising a rigid container with a port for a first fluid and an outlet port for a second fluid and a deformable and expansible partition intervening between said ports, valve means controlling said outlet port, said valve means comprising a cylindrical member positioned in said outlet port having its inner end in said container, said member having passageways therethrough adjacent its outer periphery, said outer periphery defining a valve seat axially aligned with said outlet port, a valve member in the form of a disc of flexible material in said container, said disc being secured at its axis to the inner end of said cylindrical member, said disc being rigidly mounted with respect thereto, said passageways having ports aligned with the periphery of said disc, and resilient means comprising at least one Belleville washer positioned between the disc and the inner end of said tubular member and reacting against said disc between its peripheral zone and the mount zone normally to space said peripheral zone from said valve seat, Whereby when the expanding partition initially engages a portion of the periphery of the disc when the latter is spaced from its seat, such portion will move toward the seat to engage the latter only at the region of engagement of the disc by the partition, to prevent extrusion of the partition past the valve seat yet permitting flow of fluid.

11. The combination set forth in claim 10 in which an annular shoulder extends inwardly from the inner end of said tubular member and the periphery of said Belleville washer is adapted to abut against said shoulder to limit the flexure of said Belleville washer.

12. The combination set forth in claim 10 in which a resilient disc of diameter less than said first disc is positioned between said washer and the inner end of said tubular member, said second disc being secured at its axis to said tubular member and having its periphery extending partially over the ports of said passageways.

13. A pressure vessel comprising a rigid container with a port for a first fluid and an outlet port for a second fluid and a deformable and expansible partition intervening between said ports, valve means controlling said outlet port, said valve means comprising a cylindrical member positioned in said outlet port having its inner end in said container, said member having passageways therethrough adjacent its outer periphery, said outer periphery defining a valve seat axially aligned with said outlet port, a valve member in the form of a disc of flexible material in said container, said disc being secured at its axis to the inner end of said cylindrical member, said disc being rigidly mounted with respect thereto, said passageways having ports aligned with the periphery of said disc, and

resilient means comprises a plurality of coil springs reacting against said disc between its peripheral zone and the mount zone, a very flexible disc of diameter less than that of said first disc positioned between said first disc and e inner end of said tubular member, said second disc being secured at its axis to said tubular member, a Belleville washer positioned between the second disc and the inner end of the tubular member and reacting against said second disc etween its peripheral zone and the mount zone, said inner end of said tubular member having additional passageways therethrough positioned inwardly of of said first passageways and having ports aligned with the periphery of said second disc, the periphery of said second disc being movable against the tension of said Washer to close the ports of said additional passageways, thereby to prevent extrusion of the partition past the valve seat yet permitting flow of fluid.

14. A pressure vessel comprising a rigid container with a port for a first fluid and an outlet port for a second fluid and a deformable and expansible partition intervening between said ports, valve means controlling said outlet port, said valve means comprising a cylindrical member positioned in said outlet port having its inner end in said container, said member having passageways therethrough adjacent its outer periphery, said outer periphery defining a valve seat, axially aligned with said outlet port, a V

' valve member in the form of a disc of flexible material in said container, said disc being secured at its axis to 8 said groove reacting against said disc between its peripheral zone and the mount zone, whereby when the expanding partition initially engages a portion of the periphery of the disc when the latter is spaced from its seat, such portion will move toward the seat to engage the latter only at the region of engagement of the disc by the partition, to prevent extrusion of the partition past the valve seat, yet permitting flow of fluid.

15. A pressure vessel comprising a rigid container with an inlet port for a first fluid and an outlet port for a second fluid and a deformable partition intervening between said ports, a tubular member positioned in said outlet port having its inner end in said container, the inner end of said member defining a valve seat, said tubular member having a central bore and an additional bore extending substantially parallel to said central bore and positioned outwardly thereof, a valve stem slidably mounted in said central bore, said stem having a valve head at its inner end, resilient means reacting against said stem normally retaining said valve head on its seat, said stem and said valve head having an axial bore therethrough, a transverse bore'leading into said axial bore in said stem, the bore in said valve head defining a valve seat, a valve memher in said bore, a very flexible plate secured to the valve head and extending over the bore therein, resilient means in said valve head bore reacting against said plate between the outer edge zone thereof and the mount zone to space the outer edge zone from its seat, and means to move said valve member off its seat for flow of fluid through said valve bore into said additional bore.

16. The combination set forth in claim 15 in which a coil spring is positioned between the periphery of said plate and the valve head to urge said periphery away from the bore in said valve head.

17. The combination set forth in claim 15 in which a rod is slidably mounted in the bore of said valve stem and reacts against said valve member to move the latter off its seat.

'18. A pressure vessel comprising a rigid container with an inlet port for a first fluid and an outlet port for a second fluid and a deformable partition intervening between said ports, valve means controlling said outlet port, said valve means comprising a valve seat having an associated passageway, a flexible plate rigidly mounted with respect to said seat and movable to close said passageway, and resilient means of the type providing a substantially constant force opposing the force causing deformation thereof and reacting against said plate between the peripheral zone thereof and the mounted portion thereof to space the portion of the plate outwardly from its afiixed portion on said seat, whereby the reaction of the peripheral zone of the plate against the partition is comparatively small, said peripheral zone being substantially free to yield and said partition reacting against a continuous surface to overcome said resilient means to move said plate to close said passageway.

References Gated hy the Examiner UNITED STATES PATENTS 1,956,836 5/34 Rosenow 251-303 2,299,599 18/ 42 Shultz 251--3 03 2,310,570 2/43 Briggs 137-525.5 2,385,016 9/45 Mercier l3830 2,390,320 12/45 Overbeke l3830 2,401,791 6/46 Overbeke 13830 2,786,488 3/57 Mercier 138-30 2,885,178 7 5/59 Mott 251 -303 2,932,322 4/60 Mercier 138-3() Y FOREIGN PATENTS 472,033 6/52 Italy.

EDWARD v. BENHAM, Primary Examiner.

Claims (1)

1. A PRESSURE VESSEL COMPRISING A RIGID CONTAINER WITH AN INLET PORT FOR A FIRST FLUID AND AN OUTLET PORT FOR A SECOND FLID AND A DEFORMABLE PARTITION INTERVENING BETWEEN SAID PORTS, VALVE MEANS CONTROLLING SAID OUTLET PORT, SAID VALVE MEANS COMPRISING A VALVE SEAT HAVING AN ASSOCIATED PASSAGEWAY, A FLEXIBLE PLATE RIGIDLY MOUNTED WITH RESPECT TO SAID SEAT AND MOVABLE TO CLOSE SAID PASSAGEWAY, AND RESILIENT MEANS COMPRISING A NEGATIVE SPRING REACTING AGAINST SAID PLATE BETWEEN THE PERIPHERAL ZONE THEREOF AND THE MOUNTED PORTION THEREOF TO SPACE THE PORTION OF THE PLATE OUTWARDLY FROM ITS AFFIXED PORTION ON SAID SEAT, WHEREBY THE REACTION OF THE PERIPHERAL ZONE OF THE PLATE AGAINST THE PARTITION IS NEGLIGIBLE, SAID PERIPHERAL ZONE BEING SUBSTANTIALLY FREE TO YIELD AND SAID PARTITION REACTING AGAINST A CONTINUOUS SURFACE TO OVERCOME SAID RESILIENT MEANS TO MOVE SAID PLATE TO CLOSE SAID PASSAGEWAY.

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