US3231935A

US3231935A - High pressure apparatus

Info

Publication number: US3231935A
Application number: US396811A
Authority: US
Inventors: Brayman Jacob
Original assignee: Barogenics Inc
Current assignee: Barogenics Inc
Priority date: 1964-09-10
Filing date: 1964-09-10
Publication date: 1966-02-01
Anticipated expiration: 1983-02-01

Description

Feb. 1, 1966 J. BRAYMAN 3,231,935

HIGH PRESSURE APPARATUS Original Filed Nov. 21, 1963 2 Sheets-Sheet 1 INVENTOR 76 JACOB BRAYMAN H mi;

his A TTOR/VEYS Feb. 1, 1966 J, BRAYMAN 3,231,935

HIGH PRESSURE APPARATUS Original Filed Nov. 21, 196-3 2 Sheets-Sheet 2 INVENTOR.

JACOB FIR/21mm BYAQHMQHVLI 7L4),

W 'PDDWLW his ATTORNEYS United States Patent 3,231,935 HIGH PRESSURE APPARATUS Jacob Brayman, Staten Island,N.Y., assignor to Barogeniles, Inc., Mt. Vernon, N.Y., a corporation of New Yor Continuation of application Ser. No. 325,364, Nov. 21, 1963. This application Sept. 10, 1964, Ser. No. 396,811

11 Claims. (CI. 18-16) This application is a continuation of my copending application Serial No. 325,364, filed November 21, 1963, and now abandoned.

This invention relates generally to apparatus for containing and/or exerting a high or ultra high pressure.

More particularly, this invention relates to" apparatus of apparatus embody the same general concept which is as follows.

A cylindrical member composed of a single cylinder or a plurality of nested cylinders is used to contain the material to be subjected to pressure. At each end of the cylinder (or at only one end, if the other end is closed) are close fitting pistons (or pressure-multiplying punches) which, when driven inward, generate the required pressure on the contained material.

For low to moderate pressures (e.g., up to 100,000 p.s.i.), the pressure container may be in the form of a monoblock or a single-piece cylinder. The effect on the monoblock of the pressure therein isto develop in the monoblock a hoop tension which creates a tensile stress having a stress distribution which peaks sharply at the bore and rapidly diminishes toward the outside. Such peak stress is substantially greater than the stress value which would be obtained if the stress were to have a uniform distribution throughout the monoblock. Increasing the wall thickness of the monoblock does not proportionately drop the peak tensile stress. In fact, even if the walls of the monoblock were to be infinitely thick, the peak tensile stress would still equal the internal pressure.

The trend of modern technology has been towards ever-increasing pressure for the production of synthetic diamonds and for other purposes. Monoblock structures are incapable of containing those increased pressures because the stress which would be induced in the monoblock by the contained pressure would exceed the safe stress level that even the strongest steels can safely eX- perience without failure. Therefore, in order to increase the permissible internal pressures, it has become common practice to use a pressure container providedby an assemblage of concentric or nested cylinders. Any number of nested cylinders may be used, although three are used most often. The purpose of using several cylinders is to induce at the inner wall of each of the one or more inner cylinders a compressive pre-stress which operably opposes and oifsets the tensile stress created in those cylinders by the contained pressure. This pre-stressing is accomplished by shrinking around each inner cylinder another cylinder which squeezes the inner cylinder to generate a compressive stress therein see Timoshenko, Strength of Materials, vol. II).

When the internal pressure is not too high, a two piece cylinder assembly may be all that is necessary. When further strength is needed, however, a third cylinder is shmnkonto two inner cylindersto thereby increase ice the compressive stress in the innermost, and, simultaneously, to reduce the tensile stress in the intermediate cylinder. More than three cylinders may be used. Because, however, the etfect of each additional cylinder is only a fraction of the eflfect of the preceding one, there is ordinarily no advantage in increasing the number of cylinders beyond about three.

Although a nested cylinder container serves to reduce the peak tensile stress developed in the container, the maximum stress is still a tensile stress which, irrespective of the number of cylinders employed, occurs at the inner wall of either the inner cylinder or the second cylinder. Further, when operating pressures become very high (e.g., 200,000 p.s.i. and above), there is a rapid increase in the amount of shrinkage required between the several cylinders which make up the nest. One often encountered consequence of such requirement is an inability to effect a shrinking of an outer cylinder onto an inner one because it is not possible to expand and to contract theouter and inner cylinders, respectively, in amounts sufii-cient to assemble the two together. Other consequences which often arise are that the tensile stress induced in the outer cylinder is of a magnitude causing such cylinder to fail without the application of any further load, and that the compressive pre-stress induced in the inner cylinder is of a magnitude causing buckling or fracture of that inner cylinder.

It is, accordingly, an object of my invention to provide apparatus for containing pressure (or for both exerting and containing pressure) which is adapted to contain a higher internal-pressure than that safely containable by the described prior art structures. Another object of my invention is to provide apparatus of such sort in which the inner portions or components of the pressure container are not subjected to any tensile stress.

These and other objects are realalized according to the invention by providing a container structure wherein the pressure within a central cavity is contained byan array of separate cavity closure means circumferentially disposed around the cavity. Since those means are separate, no hoop tension can be set up therein by the pressure in the cavity. Accordingly, none of such means are subjected to any tensile stress.

The cavity closure elements, are however, subjected to outward pressure from the cavity. To maintain them in place against such pressure, each element has an outwardly projecting wedge portion received in a corresponding wedge-shaped notch provided by a backing means which contains the entire array of elements. By virtue of such wedge connections between the cavity closure elements and the backing means therefor, the outward pressure from the cavity is dissipated in the container structure in a manner whereby the safe stress values for the constituent parts of the structure are not exceeded in the presence of a cavity pressure which would rupture a pressure container of conventional design.

For a better understanding of the invention, reference is made to the following description of representative enibodiments thereof and to the accompanying drawings wherein:

FIG. 1 is a plan view in cross section of a pressure exerting and pressure containing apparatus embodying the present invention; 7

FIG. 2 is a side elevation in cross section of the FIG. 1 apparatus, the cross section being taken as indicated b the arrows 2-2 in FIG. 1;

FIGS. 3 and 4 are diagrams of the pressure distribution on certain of the elements of the FIG. 1 apparatus;

FIG. 5 is a plan view in cross section of 'a modification of the apparatus of 'FIG. 1.

Referring now to FIGS. 1 and 2, the reference numeral designates the central cavity of an ultra high pressure apparatus. As shown, the cavity 10 is of uniform equilateral triangular cross section in planes normal to the cavity axis 11 (FIG. 2). The shape of the cavity is not critical. Thus, for example, the cavity 10 may be a prismatic cavity of which the cross section is that of any regular polygon. Alternatively, the cavity may (as later explained) he, say, a cylindrical cavity of circular cross section.

Within the cavity 10 is a pressure-receiving assembly 12 having a configuration matching that of the cavity. As is conventional in ultra high apparatus, the assembly 12 comprises a central charge 13 to be compressed and a casing 14 around that charge. The charge 13 may be a collocation of elements and constituents for producing synthetic diamonds, a workpiece to be subjected to ultra high pressure, etc. The casing 14 is constituted of a material which is solid at low pressure but behaves plastically under applied pressure of relatively low value to thereby act as a hydrostatic or near hydrostatic medium for transmitting the applied pressure to the central charge 13. Materials suitable for the casing 14 are pyrophyllite (preferred), silver chloride, certain metals such as brass, etc.

Pressure receiving assemblies of the same type as the shown assembly 12 are disclosed, in for example, US. Patents 2,968,837, 3,044,113 and 3,080,609.

It is to be understood that the pressure receiving con- .tainer 12 may include a sample tube for charge 13, a

heating sheath around that charge, conductors for leading heating current or other electrical current from the exterior of assembly 12 to charge 13, and other ancillary elements not shown herein.

The circumference of the cavity 10 is defined by an array of three

anvils

30a, 30b, and 30c which are of a passive character in that they are subjected to an internal pressure from the cavity rather than being the agencies which subject the material in the cavity to pressure. For lower pressures generated in cavity 10 (e.g., 2,000,- 000 p.s.i.), the three anvils may be made of steel. For high cavity pressures (e.g. 50 kilobars and up), the anvils are preferably made of cemented tungsten carbide. Since all three anvils are identical, only the anvil 30a will be described in detail.

At the front of anvil 30a is an inner vertical planar rectangular end face 31a providing a closure wall for the cavity 10. Extending radially outward from face 31a are a pair of planar

rectangular side walls

32a, 33a each parallel to axis 11 and disposed on opposite sides of an anvil tapered portion 34a which diverges away from the mentioned face. Radially outward from that tapered portion, the anvil 30a has a wedge portion 35a formed by a pair of oppositely disposed planar

rectangular side walls

36a, 37a intersecting with, respectively, the

walls

32a and 33a of the tapered portion. The

walls

36a, 37a are each parallel to axis 11 and converge towards each other in the radially outward direction to render the smaller end of wedge portion 35a radially outwards of the larger end thereof. The anvil 30a is symmetrical about a plane which passes through axis 11 and bisects the anvil.

The

anvils

30a, 30b and 30c are so shaped that their tapered portions are in side to side registration around the cavity 10. As illustrated, that registration is of such character that the three anvils are separated from each other by three inter-anvil gaps 40a, 40b and 400 which permit access from the side to the pressure-receiving assembly 12 for electrical lead-ins and the like. When, however, such access is not needed, the gaps 40a-40c may be closed by bringing into flat contact with each other the anvil side walls which were previously on opposite sides of those gaps.

Disposed radially outward of the anvil array is a configuration of

backing members

45a, 45b, 45c made of steel or of a like material which need not have the same compressive strength as the anvil material. If desired, the three shown backing members may be split along their respective centerplanes 46a, 46b, 460 to provide six such members. All three of the members 45a45c being substantially identical, only member 45a will be described in detail.

The center plane 46a of the member 45a bisects the inter-anvil gap a, wherefore the front surface of member a extends transversely of and faces toward the radially outward end of that gap. Directly opposite such gap end, the member 45a has formed therein an axially running recess 50:: which permits electrical conductors or the like to be lead in from the exterior of the apparatus to the pressure receiving assembly 12. That is, one or more of such conductors may be passed from the top or bottom side of member 45a through the recess 50a and then through the gap 40a to the assembly. The recess 50a may be reduced or enlarged in size in dependence on the room needed therein for the lead-in elements. If no such elements are contemplated, the recess 50a may be eliminated entirely.

To the opposite sides of recess 50a, the backing member 45a has a pair of rectangular planar front faces 51a, 52a extending adjacent to and parallel with, respectively, the side wall 36a of anvil wedge portion 35a and the side wall 37c of anvil wedge portion 350. Each of the other backing members has similar front faces. Thus, between the three backing members there are formed three wedge-shaped notches 55a, 55b and 550. As will be noted, each of those notches widens in the radially inward direction and is defined at the Zone of proximity between an adjacent two backing members by the respective front faces on those members which are nearest to each other at that zone. As will be further noted, the notches 55a-55c have the same angle of taper as the anvil wedge portions 35a-35c, and each of those notches has a respective one of such wedge portions received in the notch with a wedging fit. Sheets 56 of Teflon or other anti-friction material are inserted in each notch between the sides thereof and the sides of the received wedge portion to reduce friction between that wedge portion and the two backing members between which the notch is formed.

Outward movement of the wedge portions 35a-35c in the notches 55a-55c is limited by three stop blocks 69a, 50b, 600 of which there is one in each notch. For many applications, those stop blocks are unnecessary. Radially outwards of the stop blocks, the sides of the notches become parallel to form three slots 61a, 61b, 61c which peripherally separate the three backing members. If desired, the width of such slots may be reduced to zero.

'In the FIG. 1 apparatus, the backing members 45a- 450 are operably restrained from radially outward movement by a pressure shell 70 which girdles the configuration of members so that the bacle surface of each is in pressure communicating relation over its entire area (or most of its area) with the inner wall of the shell. While the shape of the shell is not critical (e.g., it may be a triangular frame which is hinged along its edges in the manner described in US. Patent 3,080,609), conveniently it is of the shown cylindrical form. As illustrated, the shell 70 may be monoblock ring. Alternatively, the shell 70 may be a nested cylindrical structure in which an inner one or more cylinders are compressively prestressed by shrink fitting on each inner cylinder of the adjacent outward cylinder. Moreover, the shell 70 may be designed to be shrink fitted onto the anvils 3011-300 and backing members 45a-45c so as to close the gaps 40a40c, 61a-61c and to apply some compressive prestressing to those anvils and hacking members.

As shown in FIG. 2, the cavity 10 is open at each of its two axially opposite ends. Pressure is applied to the assembly 12 within cavity 10 by relative movement to- Wards the center of the cavity of each of a pair of active pressure-multiplying anvils or rams 75, 75' made of steel (for lower pressure) or of cemented tungsten carbide (for higher pressures). The

rams

75, 75 are in the form of

cylinders

76, 76 which are chamfered at their front ends to form equilateral triangular planar front faces 77, 77 of slightly smaller dimension than thecross section of the cavity. Such rams and the means for driving them are well known in the art and are described in detail in, for example, U.S. Patent 2,968,837.

In operation, the

rams

75, 75" are driven inwardly to exert pressure on the assembly 12. As the applied pressure increases, some of the material of casing 14 flows into the inter-anvil gaps 40a-40c to there resolidify as bulges 80. Those budges form a gasket which holds in the pressure developed in the rest of the casing material. The formation of the gasket may be facilitated by coating the gap-bordering walls of the anvils with a high friction material such as rouge (iron oxide) or by restraining the bulging of the casing material into the gaps by flexible stretchable diaphragm (not shown) in the manner taught in my copending application Serial Number 240,049 filed November 26,1962, now Patent Number 3,154,619. Y

The driving in of the

rams

75,75, develops a more or less uniform hydrostatic field in the material of casing 14 which is not forced into the inter-anvil gaps. The pressure of that field acts both inwardly on the central charge 13 (to subject it to high pressure) and outwardly on the inner end faces on anvils 3011-300 to compressively stress those anvils. Since the anvils form around the cavity a pressure-containing structure which is circumferentially discontinuous at the gaps 40a-40c, no

hoop tension can be set up in such structure by the pressure generated in the cavity. Hence, the anvils 30a30c are not subjected to any tensile stress. The

advantage derived from the absence of any tensile stress in the anvils is that the strongest present day materials wedged in, the anti-friction sheets 56 reduce the sliding' friction and prevent galling or pitting of the mating surfaces of the anvils and the backing members. The sheets 56 may, in addition, act as electrical insulators which isolate the anvils'from each other to thereby allow their use as carriers of current on the way to the charge 13 in the pressure receiving assembly 12. I

FIG. 3 shows the compressive loading by pressure of the anvils 30a (the other anvils 30b and 30c being similarly loaded). As indicated, the high pressure end face 31a of anvil 30a is loaded by pressure exerted outwardly by the hydrostatic medium of the casing 14. In addition, the gasket bulges 80 of the medium apply to the anvil side faces 32a, 33: a lesser pressure loading which falls off to zero with distance away from the cavity 10. The

anvil side walls

36a, 37a are loaded by reactive pressure developed by the backing members 45a, 45b and transmitted from those members through the intervening sheets 56 to the wedge portion 35a. As is evident, the anvil 30a is loaded almost wholly in compression, and the distribution of compressive stress around the anvil periphery is more or less uniform. Thus, because the anvil 30a is stronger in compressive stress than in tensile stress, it is able to contain without failure a cavity pressure which would rupture the anvil if itwere to develop of the backing member 45a (there being a similar pattern of loading on the other backing members 45b and 450). The front faces 51a and 52a of member 45a are loaded as shown, by, respectively, the

anvils

30c and 30a. Such anvil loading is opposed by reactive loading distributively exerted on the rear face 71a of member 4541 from the inner wall of the pressure-restraining ring 70. It will be noted that the member 45a is loaded wholly in compression. The loaded area of the rear face 71a is at least twice as large as the total area of faces 51a and 52a on which anvil loading is exerted. Consequently, the backing member 45a is subjected to an average compressive stress less than that developed in the anvils, wherefore member 45a (and the other backing members as well) may be made of lower strength material than the anvils.

The outer ring 70 is, of course, subjected to tensile stress from the hoop tension developed by the outward pressure exerted on the ring from the rear faces of the backing members. Even so, the tensile stress at the inner wall of the ring is far less than the tensile stress which the same cavity pressure would produce at the inner wall of a conventional cylinder container. For example, assuming a cavity pressure of 1,500,000 p.s.i., a one inch spacing of the inner faces of the anvils from axis 11 and a ten inch inside diameter for ring 70, the tensile stress at the inner wall of the ring 70 would be 1,500,000x or 15,000 p.s.i. Such a stress can be readily handled by a conventional material such as steel.

As compared to conventional nested cylinder containers, the presently described container structure affords the advantages (besides elimination of tensile stress in its parts nearest the high pressure cavity) of (1) absence of the necessity of making shrink fits, (2) ease of manufacture and assembly, (3) ready accessibility to the central cavity for electrical lead-ins and the like. An additional advantage of the presently described container is that it minimizes blow-outs of the gasket bulges in interanvil gaps 40a-40c during the release of pressure on the central pressure-receiving assembly 12. In an ordinary multi-axial ultra high pressure apparatus, such blow-outs often occur because the withdrawal of the anvils (to release the pressure) is accompanied by a widening of the inter-anvil gaps and a consequent loss within those gaps of the friction developed between the gasket material and the anvil side walls. In the presently described structure, however, the release of pressure (by withdrawal of rams 75, 75') causes the previously compressed anvils 30a-30c to be wedged forward from the gaps 55a55c and to themselves expand so as to narrow rather than to widen the inter-anvil gaps Mia- 40c. Such gap narrowing increases the friction grip of the anvil side walls on the gasket material, and, accordingly, blow-out of the gasket is inhibited.

The FIG. 1 apparatus can be modified as shown in FIG. 5 to apply a pressure of up to about 200,000 p.s.i. on a liquid or gaseous body 85. The liquid or gaseous material is contained Within a relatively thin walled cylinder 86 externally supported by an array of eight anvils 87 generally similar to the anvils 30a-30c of FIG. 1. As shown, each of the anvils 87 has a concave inner end face mating with a corresponding portion of the outer surface of the cylinder 86. If access from the side to the cylinder 86 is not needed, the diverging tapered portions 88 of the anvils 87 can be brought in contact with each other so as to eliminate the illustrated gap separations between those portions.

The anvils 87 of FIG. 5 are shaped like the FIG. 1 anvils to have radially outward wedge portions 89. Those wedge portions are received with a wedging fit in corresponding wedge-shaped notches 90 formed between adjacent twos of eight backing members 91 externally restrained by a cylindrical pressure-restraining ring 92. As before, sheets 93 of anti-friction material (e.g., Tefion) may be inserted in such notches between the anvil wedge portions and the backing members. In the case of FIG. 5, the pressure-multiplying rams 75, 75' (FIG. 2) are replaced by a pair of pistons (not shown) which enter cylinder 86 at its axially opposite ends, and which carry 0 rings or other sealing devices to provide a fluid-tight seal between each piston and the inner wall of the cylinder. The FIG. 5 structure is otherwise generally similar to that of the already discussed FIG. 1 apparatus and, therefore, need not be described herein in further detail.

The above-described embodiments being exemplary only, it is to be understood that additions thereto, modifications thereof and omissions therefrom can be madewithout departing from the spirit of the invention, and that the invention comprehends embodiments differing in; form and/ or detail from those specifically described. For example, instead of having vertical planar inner faces, the described anvils may have inner faces which (as seen from axis 11) are convex in the vertical plane in the manner taught in US. Patent 3,061,877 to Custers et al.

Accordingly, the invention is not to be considered as limited save as is consonant with the recitals of the following claims.

I claim:

1. Pressure containing apparatus comprising, an array of cavity closure means circumferentially disposed around the axis of a central cavity and having wedge portions disposed outwards of said cavity with the small ends of said portions outwards of the larger ends thereof, and backing means radially outwards of and containing said array and providing towards it a plurality of wedge shaped notches: which widen inwardly, and which have said wedge portions received therein with a wedging fit.

2. Apparatus as in claim 1 in which a sheet of antifriction material is interposed between each side wall of each wedge shaped portion and the corresponding side face of the notch in which such wedge portion is received.

3. Apparatus as in claim 1 in which each of said notches has received therein a stop block disposed radially outward of the wedge portion received in such notch.

4. Pressure containing apparatus comprising, an array of cavity closure means circumferentially disposed around the axis of a central cavity and having wedge portions disposed outwards of said cavity with the small ends of said portions outwards of the larger ends thereof, a configuration of circumferentially adjacent backing members radially outward of and containing said array and providing towards it at zones of proximity of said members a plurality of wedge shaped notches of which each is formed between an adjacent two of said members to widen radially inwards, said notches having said wedge portions received therein with a wedging fit, and means restraining said members from moving outwardly.

5. Apparatus as in claim 4 in which said restraining means comprises a pressure shell radially outward of and girdling said configuration of members.

6. Apparatus as in claim 4 in which said restraining means comprises a plurality of dowel means disposed at said zones of proximity and fitted in axial channels of which each is formed half in one and half in another of an adjacent two backing members.

7. Pressure containing apparatus comprising, an array of cavity closure anvils circumferentially disposed around a central cavity, each of said anvils having an inner end face towards said cavity and a tapered portion diverging from said face and a wedge portion converging from said tapered portion to have its small end outwards, said anvils at their respective tapered portions being in side to side registration around said cavity, and backing means radially outwards of and containing said array and providing towards it a plurality of wedge shaped notches which widen radially inwards, and which have said wedge portions received therein with a wedging fit.

8. Apparatus as in claim 7 in which said anvils are separated around said cavity by inter-anvil gaps between the tapered portions of said anvils.

9. Pressure containing app-anatus comprising, an array of cavity closure anvils circumferentially disposed around a central cavity, each of said anvils having an inner end face towards said cavity and a tapered portion diverging from said face and a wedge portion converging from said tapered portion to have its small end outwards, said anvils at their respective tapered portions being in side to side registration around said cavity, a configuration of circumferentially adjacent backing members radially outwards of and containing said array and providing towards it at zones of proximity of said members a plurality of wedge shaped notches of which each is formed between an adjacent two of said members to widen radially inwards, said notches having said wedge portions received therein with a wedging fit, and means restraining said members from moving outwardly.

10. Apparatus as in claim 9, in which said anvils are separated around said cavity by inter-anvil gaps and surface portions of said members face towards and extend "transversely of the radially outward ends of said gaps, and in which said surface portions are characterized by axially-running recesses which register with said gap ends.

11. Pressure exerting apparatus comprising, an array of cavity closure means circumferentially disposed around the axis of a central cavity which is open at axially opposite ends, said closure means having wedge portions disposed outwards of said cavity with the small ends of said portions being outwards of the larger ends thereof, backing means radially outward of and containing said array and providing towards it a plurality of wedge shaped notches which widen radially inwards, and which have said wedge portions received therein with a wedging fit, and a pair of pressure-multiplying rams disposed at the axially opposite ends of said cavity, said rams being relatively movable towards the center of said cavity.

References Cited by the Examiner UNITED STATES PATENTS 3,091,804 6/1963 Gerard et al. 3,093,862 6/1963 Gerard et al. 3,118,177 1/1964 Von Platen.

WILLIAM J. STEPHENSON, Primary Examiner,

Claims

1. PRESSURE CONTAINING APPARATUS COMPRISING, AN ARRAY OF CAVITY CLOSURE MEANS CIRCUMFERENTIALLY DISPOSED AROUND THE AXIS OF A CENTRAL CAVITY AND HAVING WEDGE PORTIONS DISPOSED OUTWARDS OF SAID CAVITY WITH THE SMALL ENDS OF SAID PORTIONS OUTARDS OF THE LARGER ENDS THEREOF, AND BACKING MEANS RADIALLY OUTWARDS OF AND CONTAINING SAID ARRAY AND PROVIDING TOWARDS IT A PLURALITY OF WEDGE SHAPED NOTCHES WHICH WIDEN INWWARDLY, AND WHICH HAVE SAID WEDGE PORTIONS RECEIVED THEREIN WITH A WEDGING FIT.