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Contents
1. sed amp Sl ie a NE al OL V ii s S L Ml ZE 47 ra z Z E sA AE A PI od ODO SH SZ E 4 672 996 1 SELF REGULATING VALVE This application is a continuation of application Ser No 722 266 filed Apr 11 1985 now abandoned TECHNICAL FIELD The present invention relates to an improved valve More particularly this invention relates to a valve that opens and closes in response to a change in the physical environment of the valve and that is especially useful as a relief valve Furthermore this invention pertains to a lidded vessel including this improved valve and to uses of this valve BACKGROUND ART As exemplified by A Abu Samra et al Analytical Chemistry 47 1475 1975 and P Barrett et al Analyti cal Chemistry 7 1021 1978 a microwave oven based digestion technigue using an acid digesting agent in an open vessel is known Barrett et al report that this procedure decreases digestion time compared to a hot plate heat source Also known as illustrated by Nadkarni Analytical Chemistry 56 2233 1984 and S A Matthews et al Bureau of Mines Technical Progress Report 120 April 1983 is a microwave oven based digestion technigue using an acid digesting agent in a closed system In Nadkarni s procedure a covered Teflon or polycar bonate beaker was placed in a partially evacuated closed glass desiccator so that acid fumes leaking from the covered beaker2. feature of for example valve 12 may also be used for discharging for purposes of illus tration a pressured fluid such as grease from a hose or conduit on one end of which disc shaped member 14 and a closure element are in place In the preceding description of the present invention there are shown and essentially described only pre 4 672 996 9 ferred embodiments of this invention but as mentioned above it is to be understood that the invention is capa ble of changes or modifications within the scope of the inventive concept expressed herein Several changes or modifications have been briefly mentioned for purposes of illustration INDUSTRIAL APPLICABILITY The improved valve of this invention is useful as a relief valve for example in a microwave system based closed vessel digestion procedure Further uses of the valve in combination with a microwave system include canning a food product sterilizing an object or dispens ing a fluid such as a gas a foam a semi fluid mixture such as a slurry or a liguid such as a semi solid or an emulsion We claim 1 A self opening and self closing relief valve for providing flow out of a closed system in response to a certain internal fluid pressure said relief valve compris ing a a dome shaped pressure deformable wall member having an outlet port and b an abutment integral with a support member therefor said abutment being spaced apart from a center of said supp
3. were trapped within the glass desic cator A polycarbonate bottle with a polypropylene screw cap was used as a closed digestion vessel by Mat thews et al who cautioned against explosion caused by pressure build up within a closed vessel and observed leaking of some acid fumes around the bottle caps dur ing pressure dissolution Matthews et al report that compared to open vessel digestion closed vessel diges tion prevents the introduction of contaminating ele ments and the loss of volatile elements and compounds Accordingly although closed system digestion has been found to have advantages over open vessel diges tion the containing vessel in a closed system could explode under pressure build up with spewing of acid The explosion hazard is enhanced for example if as in tissue digestion gas is generated by the digestion pro cess As a result open vessel digestion is commonly utilized particularly if the digestion process generates gas A lidded digestion vessel suitable for use in a micro wave system based digestion that employs a corrosive digesting agent is available from Savillex Corporation either with or without an outlet port in the lid This lidded vessel is formed of a deformable resilient highly chemically inert thermoplastic material This material is a fluorocarbon copolymer in which the carbon fluo rine backbone in the main chain is connected with per fluoroalkoxy side chains through oxygen links This fluo
4. 1978 Nadkarni Analytical Chemistry 56 2233 1984 Matthews et al Bureau of Mines Technical Progress Report 120 Apr 1983 Operation and Service Manual Microwave Drying Digestion System Model MDS 81 CEM Corpora tion revised Mar 1985 137 859 Primary Examiner Robert G Nilson Attorney Agent or Firm Timothy R Kroboth 57 ABSTRACT The present invention provides an improved valve This valve opens and closes in response to a change in the physical environment of the valve This valve is particularly suited as a relief valve in a microwave sys tem based closed vessel digestion procedure This valve includes a pressure deformable resilient wall member having a fluid vent port and an obstructing member that cooperates with the wall member to open and close the valve Also provided is a lidded vessel employing this improved valve an apparatus that in cludes a microwave system and this lidded vessel and methods using this improved valve 10 Claims 4 Drawing Figures ate Py ww yoy LL D NM DNI U S Patent Jun 16 1987 Sheet 1 of 2 4 672 996 Z MAM MLL ASID OE Sam sr sm A T A LLII TIN I U WAVY VAAVALVAAY A OF VULL NARA TA NE V seo a et a o MO o Z nA Vaja a m II WANA m q U S Patent Jun 16 1987 Sheet 2 of2 4 612 996 J A SS A ISS z VA LSS a eos LJ x de O
5. Signed and Sealed this Twelfth Day of January 1988 Attest DONALD J QUIGG _ Attesting Officer Commissioner of Patents and Trademarks
6. United States Patent 9 Floyd et al 54 75 73 21 22 63 51 52 58 56 SELF REGULATING VALVE Inventors Terry S Floyd Clover S C Wyatt P Hargett Jr Matthews N C Assignee CEM Corporation Matthews N C Appl No 868 171 Filed May 22 1986 Related U S Application Data Continuation of Ser No 722 266 Apr 11 1985 aban doned Int Cle iid u F16K 15 14 WS oj on 137 522 137 468 137 859 220 209 Field of Search 220 209 222 402 21 222 494 137 496 468 859 522 References Cited U S PATENT DOCUMENTS 1 925 926 9 1933 Kunkel sss ennenen 222 494 2 854 996 10 1958 Hughes 137 859 X 2 942 614 6 1960 Lardner 137 859 X 3 160 329 12 1964 Radic 137 859 X 3 265 084 8 1966 Wagner 137 859 X 3 804 113 4 1974 Garcea 137 859 X 3 827 456 8 1974 Sheppard 137 859 4 020 828 5 1977 Steed 137 859 X 4 061 254 12 1977 Nilson ene 222 494 4 400 401 8 1983 Beauvais et al 4 474 211 10 1984 Lucas 4 474 314 10 1984 Roggenburg 222 494 E cho c G LY Ss EVA Patent Number Date of Patent 4 672 996 Jun 16 1987 11 45 4 493 444 1 1985 Del Bon et al FOREIGN PATENT DOCUMENTS 2603712 8 1977 Fed Rep of Germany OTHER PUBLICATIONS Abu Samra et al Analytical Chemistry 47 1475 1975 Barrett et al Analytical Chemistry 7 1021
7. an improved valve More particularly this invention relates to a self regulating valve that opens and closes in response to a change in the physical environment of the valve in particular to a change in internal fluid pres sure In a preferred embodiment this improved valve is also temperature sensitive and therefore able to re spond not only to internal fluid pressure but also to temperature change In this embodiment the compo nents of the valve can amazingly be made of the same material Also in this embodiment the valve is micro wave radiation transparent and is therefore useful as a relief valve in a microwave system based closed vessel digestion technigue even when the digestion generates gas In a very preferred embodiment the improved valve is highly chemically inert and accordingly corro sion resistant Also in a preferred embodiment the im proved valve of this invention can be manually opened Also as explained earlier our invention is directed to a lidded vessel employing this improved valve to an apparatus including a microwave system and this lidded vessel and to methods using the improved valve The term fluid as used in our description of the present invention and in the claims means a liguid gas or vapor and the terms upper lower above below upward and downward are intended to designate relative orientation of the valve as shown in the Figures FIGS 1 3 and 4 de
8. c surface would not strengthen the tight sealing relationship between peak 34 and inner top surface 36 When the disc is flexible the internal pressure reguired for valve opening is less predictable than when the disc is rigid or semi rigid When used with a lidded vessel valve 12 is operable regardless whether a small volume of liguid is used or the lidded vessel is filled to capacity Advantageously valve 12 can be manually opened by exerting finger pressure against an outer wall 47 of sleeve 23 in a direction generaliy perpendicular to the central assembly axis of the valve This type of finger pressure will move inner lid top surface 36 out of the tight sealing relationship with the abutment ring peak Valve 12 can be maintained open by pressure exerted through the outlet port on an upper disc surface 48 FIGS 3 and 4 depict lidded vessel 10 containing in phantom solids 49 and a liquid 50 to which microwave energy is applied by means of a microwave 51 also shown in phantom Solids 49 may be for example a sample to be digested such as a gas generating tissue sample In this case liquid 50 would be a digesting agent such as an acid digesting agent Solids 49 may also be a food product to be canned using microwave energy in which case liquid 50 would contain water or solids 49 may be objects to be sterilized using microwave energy in which case liquid 50 would include water To take advantage of the manual release feature of valv
9. close Thus opening and clos ing of the valve in response to the interna fluid pressure within the lidded vessel recurs as reguired The internal fluid pressure reguired to open valve 12 is controlled by factors including the height and the diameter of abutment ring peak 34 and the flexibility of the lid top For example the greater the height of peak 34 the relatively greater the pressure needed the greater the diameter of the ring peak the relatively greater the pressure reguired and the more flexible the lid top the relatively less pressure needed Accord ingly by selection for example of an appropriate peak height or ring peak diameter the valve can be made to open at a predetermined internal pressure Attention is invited to our later description which illustrates the relationship between diameter of the ring peak and the internal pressure needed to open valve 12 As described later valve 12 is responsive not only to internal fluid pressure but also to temperature change If disc 14 were flexible rather than semi rigid the disc would be seen bowed downwardly in FIG 3 and lid top 16 would show less outward bulging For a constant height of peak 34 and diameter of ring 32 a relatively higher internal pressure would be needed to open valve 12 if the disc were flexible rather than semi rigid If on the other hand the disc were rigid rather than semi rigid internal pressure pushing against central area 43 of the lower dis
10. e 12 lidded vessel 10 could contain a fluid to which microwave energy is applied to heat the fluid and build up internal pressure for manual release of the warm or hot fluid Exemplary fluids include but are not limited to a gas a foam a semi fluid mixture such as a slurry or a liquid such as a semi solid or an emulsion Illustrative semi solids include gels and pastes For example container 20 could be filled with a suit able shaving cream composition and the lidded vessel 4 672 996 7 assembled with disc shaped member 14 in place The contents of the assembled vessel could then be heated by microwave radiation for a desired period of time The lidded vessel could then be inverted and valve 12 manually opened to release a warm or hot shaving cream composition It will be appreciated that the lid ded vessel is refillable as the lid could be removed and additional material could be added to the container for dispensing or discharge It will be noted that the fluid pressure opening valve 12 is in the same upward direction as the mechanical pressure being exerted on deformable lid top 16 Preferably the same material is used to form all com ponents of our improved valve As a result one valve component will not become hotter than another valve component The containers of the lidded vessels of FIGS 1 and 3 6 are preferably formed of the same material as the pressure deformable wall member which results in a vessel protecting
11. ed This improved valve would be especially re markable if the components thereof could be of the same non metallic material Furthermore such an im proved valve would be of enhanced utility if it had a broad range of applications DISCLOSURE OF THE INVENTION It is accordingly an object of the present invention to provide an improved valve that could be used as a pres sure relief valve for explosion prevention in a micro wave system based closed vessel digestion procedure It is a further object of the present invention to pro vide an improved relief valve that is self closing after excess pressure has been relieved and thereby functions as more than a one time pop off valve It is an even further object to provide an improved valve that relieves pressure not only in response to a predetermined internal fluid pressure but also in re sponse to temperature change It is a still further object to provide an improved apparatus for microwave system based closed vessel digestion utilizing this valve 4 672 996 3 It is an additional object to provide an improved valve of this type that can be manually opened It is an even additional object to provide an improved valve the components of which may be non metallic and of the same material It is another object to provide an improved valve having a broad range of applications Additional objects advantages and novel features of the present invention are set forth in the descript
12. effect However in some applications a valve in accordance with the pres ent invention is used with a container formed of a differ ent material For example the valve could be formed of thermoplastic components but the container could be formed of glass For use in a microwave system the improved valve of the present invention should be microwave radiation transparent This characteristic is achieved if the valve is made of a microwave transparent thermoplastic ma terial Preferably the same material is used to form all valve components Exemplary microwave transparent thermoplastic materials include but are not limited to polypropylene polyethylene polypropylene polyethy lene copolymers and the fluorocarbon copolymer de scribed earlier The fluorocarbon copolymer advanta geously provides a high temperature corrosion resis tant valve As later described in more detail a valve in accor dance with the present invention is temperature sensi tive when the pressure deformable wall member thereof is made of a thermoplastic material Illustrative thermo plastic materials for providing a temperature sensitive valve include those just described Advantageously a useful thermoplastic material is moldable and precision machinable An eminently useful microwave system for digestion procedures is characterized by a corrosion resistant interior chamber a corrosion resistant exhaust system capable of providing high volume air flow t
13. el walls being an important limitation on the internal pressure For example we experienced a blow out of a bottom wall of a Savillex lidded digestion vessel at about 150 psi In contrast the prior art closed vessel digestion procedures described earlier experienced leakage at considerably lower pressures High pressure digestions should further reduce digestion time A thermoplastic lidded vessel such as vessel 10 may be heat treated to reduce deformability of the walls thereof Heat treating or annealing is carried out at an appropriate temperature for a suitable period of time to obtain walls having the desired reduced deformability For example lidded vessel 10 could be heated at about 200 C for about 72 hours The self regulating valve of the present invention can be also used with a microwave system for enabling chemical starting materials to be reacted at a desired pressure and temperature and dispensing or discharg ing the reaction product at a desired temperature or for simply dispensing or discharging a fluid at a desired temperature Exemplary fluids include but are not lim ited to a gas a foam a semi fluid mixture such as a slurry or a liquid such as a semi solid or an emulsion Illustrative semi solids include gels and pastes Use of the valve for dispensing or discharging a fluid at a de sired temperature avoids the need for temperature sens ing devices and related temperature actuated devices The manual release
14. hrough the chamber means for absorbing excess reflected radia tion and a computer controlled variable power source A microwave system of this type is commercially avail able under the trademark MDS 81 from CEM Corpora tion Matthews N C Further details of the present invention are now pro vided based on trials carried out in an MDS 81 micro wave system using a valve in accordance with the present invention as a relief valve for a lidded digestion vessel obtained from Savillex Corporation Water is added to the vessel the lid of which is provided with a vent port and the lidded vessel is assembled with semi rigid disc shaped member 14 in place to form valve 12 Member 14 which is made of the thermoplastic fluoro carbon copolymer described earlier has an abutment ring peak that is 0 062 inch high and four apertures equally spaced around the abutment ring each with a diameter of inch The lower disc surface has a diame ter of 1 53 inches When the diameter of the abutment ring peak is gt inch this valve opens at about 60 psi 25 40 45 so 55 60 65 8 internal pressure In comparison if the diameter across the ring peak is 3 inch the valve opens at approximately 80 psi internal pressure and if the ring peak diameter is 2 inch the valve opens at about 95 psi internal pressure A valve in accordance with the present invention in which the pressure deformable resilient wall member is made of a thermo
15. id pressure becomes less than said certain internal fluid pressure 2 The relief valve of claim 1 wherein said abutment support member is semi rigid 3 The relief valve of claim 1 wherein said abutment support member is a disc shaped element 4 The relief valve of claim 1 wherein said abutment is ring shaped 5 The relief valve of claim 1 wherein said abutment support member is formed of a thermoplastic material 6 The relief valve of claim 1 wherein said dome shaped wall member is formed of a thermoplastic mate rial whereby said relief valve is also temperature sensi tive 7 The relief valve of claim 1 wherein said dome shaped wall member and said abutment support member are formed of the same thermoplastic material 8 The relief valve of claim 7 wherein said thermo plastic material is moldable and precision machinable 9 The relief valve of claim 1 wherein said dome shaped wall member is an outer wall member 10 The relief valve of claim 1 wherein said closure element is a lid x x x x k UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENTNO 4 672 996 DATED June 16 1987 INVENTOR S TERRY S FLOYD It is certified that error appears in the above identified patent and that said Letters Patent is hereby corrected as shown below On the Title Page Item 19 Floyd et al should read Floyd Item 75 Inventors should read 75 Inventor Terry S Floyd
16. ion that follows and in part will become apparent to those skilled in the art upon examination of the following description or may be learned by practice of the inven tion The objects and advantages of the invention may be realized and attained by means of instrumentalities and combinations particularly pointed out in the ap pended claims To achieve the foregoing objects and in accordance with the purpose of the present invention as embodied and broadly described herein there is provided a valve responsive to a predetermined internal fluid pressure This valve includes a pressure deformable resilient wall member having a fluid outlet port The valve further includes an obstructing member engaged in a tight seal ing relationship with an inside surface of the wall mem ber or with an inner surface of the outlet port As a result outflow through the outlet port is blocked when internal fluid pressure impinging on the wall member is insufficient to cause deformation thereof that over comes the tight sealing relationship The wall member is sufficiently pressure deformable that the force of the predetermined internal fluid pres sure acting thereon causes deformation thereof that overcomes the tight sealing relationship thereby open ing the valve to permit pressure relief through the outlet port The resiliency of the fluid pressure deformed wall member is sufficient to cause the wall member to reen gage in the tight sealing relationsh
17. ip when internal fluid pressure impinging on the wall member becomes less than the predetermined internal fluid pressure thereby closing the valve Accordingly this valve opens and closes in response to a predetermined internal fluid pressure In a preferred embodiment this valve is sensi tive not only to internal fluid pressure but also to tem perature Also provided by the present invention is a lidded vessel that employs the improved valve of the present invention In addition there is provided an apparatus that in cludes a microwave system and a lidded vessel employ ing the improved valve of the present invention In a preferred embodiment the microwave system includes a corrosion resistant chamber a corrosion resistant exhaust system capable of providing high volume air flow through the chamber an element for absorbing excess reflected radiation and a computer controlled variable power source The lidded vessel is microwave transparent Also provided by the present invention are methods using the improved valve of the present invention These methods include use in canning a food product sterilizing an object and dispensing a fluid at a desired temperature In the drawing and in the detailed description of the invention that follows there are shown and essentially described only preferred embodiments of this invention simply by way of illustration of the best mode contem plated by us of carrying out this invention As wi
18. k of semi rigid disc 14 pushes against flexibly deformable lid top 16 so as to cause the lid top to bulge outwardly Outward bulging of the lid top is seen by comparison to the undis torted lid shown in FIG 2 The point contact provided by the abutment ring peak produces a tight sealing rela tionship between ring 32 and inner lid top surface 36 Peak 34 is appropriately spaced apart from center 30 of the disc such that it surrounds outlet port 22 of the lid thereby obstructing flow through the outlet port The outlet port and abutment ring could be offset from the central assembly axis provided that they are so located relative to one another in the assembled valve that the abutment ring peak surrounds the outlet port As shown in FIGS 3 and 4 disc 14 divides lidded vessel 10 into compartments 40 and 42 Apertures 38 permit internal fluid pressure to be equally exerted against lid top 16 and other walls of the lidded vessel The number of apertures whether one or many is not critical rather the sum of areas A of the apertures should not restrict flow to the cap So long as the force of the internal fluid pressure acting on lid top 16 is less than or only equal to the pressure of abutment ring 32 against the lid top valve 12 remains closed Internal fluid pressure pushing against a centra area 43 of a lower disc surface 44 assists the mechanical pressure exerted by the abutment ring to strengthen the tight sealing relationshi
19. ll be realized this invention is capable of other and different ven 0 20 25 30 35 45 50 55 60 65 4 embodiments and its several details are capable of mod ification in various respects all without departing from the invention Accordingly the drawing and the de tailed description are to be regarded as illustrative in nature and not as restrictive BRIEF DESCRIPTION OF THE DRAWING Reference is now made to the accompanying draw ing which forms a part of the specification of the pres ent invention and which depicts preferred embodi ments of an improved valve in accordance with the present invention and uses of the improved valve FIG 1 is an isometric view of the components of a lidded vessel employing a very highly preferred em bodiment of a valve in accordance with the present invention FIG 2 is a cross sectional view of the lid of the lid ded vessel of FIG 1 along the line 2 2 FIG 3 is a sectional view of the assembled lidded vessel and member 12 of FIG 1 taken in a plane through the central assembly axis showing the valve in closed position and depicting contents in phantom within the lidded vessel and FIG 4 is a sectional view identical to that of FIG 3 except that the valve is shown in open position in re sponse to a certain fluid pressure within the lidded ves sel BEST MODE FOR CARRYING OUT THE INVENTION As explained earlier the present invention is directed to
20. ned by finger pressure exerted against the nozzle Prior work known to us is a beryllium copper spring needle check valve of Lois B Jassie and H M Kings ton This valve attaches to an outlet port of a closed digestion vessel as a pressure relief valve for explosion prevention Because the beryllium copper spring does not absorb microwave radiation this valve is usable in a microwave system based digestion procedure How ever a drawback is that beryllium is oxidizable espe cially in an acid fume environment to beryllium oxide which results in the valve no longer being acceptable for use in a microwave system Moreover beryllium oxide is carcinogenic Therefore there is a need for an improved valve that could be used as a pressure relief valve for explosion prevention in a microwave system based closed vessel digestion procedure Such an improved valve would be of even greater usefulness if it were self closing after excess pressure had been relieved and thereby could function as more than a one time pop off valve Such an improved valve would provide an even greater contri bution to the art if it relieved pressure not only in re sponse to a predetermined internal fluid pressure but also in response to temperature change Such a valve would provide an improved apparatus for microwave system based closed vessel digestion Moreover an improved valve of this type would be especially advantageous if it could also be manually open
21. ort member and having a cir cumferential peak adapted to surround said outlet port and forming a valve seal with an inside surface of said dome shaped wall member when internal fluid pressure impinging on said dome shaped wall member is insufficient to break said valve seal wherein said dome shaped wall member is an integral part of a closure element and said abutment sup port member has a peripheral wall surface that is adapted to interlock with and that is in an inter locking relationship with an inside wall surface of said closure element wherein said abutment support member comprises means for enabling internal fluid pressure impinge ment on said dome shaped wall member said im 0 _ 5 25 35 40 45 so 55 60 65 10 pingement enabling means being located between said abutment and said peripheral wall surface wherein said dome shaped wall member comprises means for manual relief of internal fluid pressure said means for manual relief being a sleeve integral with said dome shaped wall member that extends said outlet port above said dome shaped wall mem ber wherein said dome shaped wall member is suffi ciently fluid pressure deformable that said certain internal fluid pressure acting thereon breaks said valve seal to permit outflow through said outlet port and wherein the fluid pressure deformed wall member is sufficiently resilient that said valve seal is reformed when internal flu
22. p between peak 34 and inner top surface 36 Hence the force of internal fluid pressure is utilized to enhance closure of the valve Central area 43 is defined by a diameter f of the abutment ring peak A donut shaped area 45 which consists of the area of inner lid top surface 36 outside the abutment ring peak is conveniently greater than central area 43 Since the lid top is more flexible than the disc central area 43 could be greater than area 45 If as illustrated in FIG 4 the force of the internal fluid pressure impinging on lid top 16 should exceed the pressure of abutment ring 32 against the lip top the lid top is lifted away from sealing contact with abutment ring peak 34 and valve 12 is opened A gap 46 is created between peak 34 and inner lid top surface 36 through which pressure is released from the lidded vessel via fluid outlet port 22 When a sufficient reduction in the force of the inter nal fluid pressure acting on the lid top has occurred the resiliency of deformable resilient top wall 16 causes disc 14 and inner lid top surface 36 to reseat in a tight sealing relationship thereby closing the valve 20 25 35 40 45 so 55 60 65 6 Should the force of the internal fluid pressure imping ing on the lid top again exceed the pressure of the abut ment ring against the lip top valve 12 will reopen until the fluid pressure within the lidded vessel drops suffi ciently for the valve to re
23. pict a lidded vessel 10 utilizing a very highly preferred embodiment of a valve 12 in accordance with the present invention Valve 12 is formed by a disc shaped member 14 and a deformable resilient top wall 16 of a lid 18 of a hollow receptacle or container 20 Centrally located in the lid is a fluid outlet port 22 Lid 18 includes an upright sleeve 23 that ex tends the outlet port above wall member 16 Preferably disc shaped member 14 and the entirety of lidded vessel 10 are formed of a deformable resilient 4 672 996 5 thermoplastic material that is very preferably the same for each of member 14 the lid and the container Even more preferably this material is the fluorocarbon co polymer described earlier Preferably the cross sec tional thickness of disc 14 imparts semi rigidity to the disc Disc 14 has a peripheral wall surface 24 that con forms to an upper inside wall surface 26 of the lid and enables the disc to be locked in place between the lid and an upper rim 28 of container 20 Encircling and spaced apart from a center 30 of the disc is a raised abutment ring 32 having a peak 34 which provides point contact between the disc and an inner surface 36 of lid top 16 As can best be seen in FIG 1 located between ring 32 and peripheral wall surface 24 are aper tures 38 each having a flow area A defined by a diameter a With reference to FIG 3 which shows valve 12 in closed position the abutment ring pea
24. plastic material is not only pressure sensitive but also temperature sensitive as the tempera ture of the pressure deformable wall member increases elasticity of the material thereof increases and the valve opens at a relatively lower pressure For example as just described when the disc of valve 12 has a ring peak diameter of 3 inch the valve opens at about 60 psi for water In this instance vapors within the lidded vessel result in top wall 16 of the lid being at a temperature of approximately 150 C In contrast if a liquid were used having a boiling point appropriate for producing a lid top temperature of about 60 C the valve would open at approximately 110 psi internal pressure When using valve 12 for closed vessel digestions the manual opening feature of the valve makes it possible to check for high pressure within the closed vessel prior to opening the closed vessel to remove a digested sam ple In carrying out a closed vessel digestion it will gen erally be undesirable for the relief valve to open as digesting agent fumes may escape However when the digestion generates a gas opening and reclosing of the valve will be beneficial As can be seen a valve in accordance with the pres ent invention is capable of containing a high pressure that is a pressure of more than about 50 psi Accord ingly the improved valve makes possible a closed ves sel digestion at high pressure with the strength of the lidded vess
25. rocarbon copolymer is marketed by Dupont Corp under the trademark Teflon PFA Prior art valves are exemplified by U S Pat Nos 4 474 211 to Lucas 4 493 444 to Del Bon et al and 4 400 401 to Beauvais et al The Del Bon et al patent is directed to a self closing valve and lid assembly The Lucas patent pertains to a valve that includes a disc like member through which apertures extend and an aper ture closing device having a pressure responsive flex 0 20 25 30 35 40 45 50 55 60 65 2 web with openings offset from the apertures The Beau vais et al patent relates to a method using microwave energy for sterilizing and canning food products within a nonmetallic enclosure cover having an aperture con trolled by a check valve regulated by a weight Within the enclosure cover a non metallic jar with a nonmetal lic lid having a vent hole closed by a vent closure contains the food product Also known in the prior art is a manually operated dispensing valve formed by an opening in a metallic can lid top a resilient rubber insert located inside the lid top and having an outlet port portion that extends through the lid top and a plastic pin element The plastic pin element has a disc like part with a raised portion that seats against the rubber insert to close the valve and has a pin like part that extends through the outlet port por tion of the rubber insert for engagement with a nozzle The valve is ope
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