US3268951A

US3268951A - High pressure press

Info

Publication number: US3268951A
Application number: US313108A
Authority: US
Inventors: Donald H Newhall
Original assignee: Harwood Engineering Co
Current assignee: Harwood Engineering Co
Priority date: 1963-10-01
Filing date: 1963-10-01
Publication date: 1966-08-30
Anticipated expiration: 1983-08-30

Description

Aug. 30, 1966 D. H. NEW/HALL,

HIGH PRESSURE PRESS Filed Oct. 1 1963 INVENTOR. DONALD H. NEWHALL BY w @j sample.

United States Patent 3,268,951 HIGH PRESSURE PRESS Donald H. Newhall, Walpole, Mass., assigner to Harwood Engineering Company, Walpole, Mass., a corporation of Massachusetts Filed Oct. 1, 1963,`Ser. No. 313,108 3 Claims. (Cl. 18-16) The present invention relates to improvements in high pressure presses.

It is a principal object of the invention to provide a novel and improved press of the general type having a ram and an anvil member relatively movable toward and away from one another along a line of thrust which is especially adapted for subjecting wholly enclosed samples of substantial thickness to maximum pressures which can be exerted upon said sample simultaneously from all directions without rupture of the heavily stressed adjacent load bearing portions of both anvil and ram.

More specifically it is an object of the invention to provide a novel and improved construction and arrangement of the ram and anvil elements of a press movable relatively along a single line of thrust, which is especially adapted for building up a maximum pressure upon the enclosed sample with a minimum relative movement of the ram and anvil elements.

The several features of the invention will be readily appreciated by one skilled in the art from the following description taken in connection with the accompanying drawing in which:

The single figure is a view in side elevation partly in section of the anvil and ram elements of a high pressure press constructed in accordance with the invention.

A principal problem encountered in the construction of a high pressure press adapted for subjecting samples of substantial thickness to maximum pressures which may run from 500,000 p.s.i. to 2,000,000 or more p.s.i. consists in providing anvil, ram or punch elements enclosing the sample which are capable of supporting the very great pressures generated. These pressures are concentrated about an enclosure which may be anything up to several inches in diameter, the maximum pressure `being concentrated at the place of contact. The sample engaging press elements which form the sample receiving enclosure of a high pressure press are normally formed with massive base portions which are tapered or reduced to provide relatively small sample engaging tips. It will be evident that tip portions of the tapered punches or anvils will be subjected to maximum pressures and stresses.

The sample to be tested is embedded in a substance as, for example, pyrophylite, or silver chloride which is substantially incompressible, and which will flow freely at the high pressures desired, the prepared sample being thereafter positioned between opposed press surfaces which are relatively moved to compress the prepared Any excess of the -incompressible substance will be forced out from between the opposed press surfaces until the forces of friction set up by the increasing pressure between the presssurfaces Ibecome suiciently great to arrest the flow and thus to form an effective gasket or seal. The distance toward one another through Which the opposed press surfaces must pass to build up a suicient pressure so that a solid gasket is formed, is small, requiring a rapid buildup of pressure within the specimen containing enclosure in order that said pressure within the enclosure may reach the desired level before the sealing portions of the press surfaces referred to reach the limit of their movement toward one another. The arrangement disclosed comprises an anvil having formed therein a hemispherical cavity with outwardly and upwardly sloping adjacent surfaces, in combination with a ram elcment consisting of a spherical contact element having a specimen engaging flat of slightly less size than the perimeter of the hemispherical cavity and a massive cylindrical support therefor. These elements are mounted in a 500 ton jack of ordinary description for movement toward one another. A very small relative movement of the anvil and ram is requi-red to produce pressures in the order of 1,000,000 to 2,000,000 p.s.i.

Referring specifically to the drawing the elements of the press are shown which comprise an anvil anda ram 12 movable relatively to the anvil 10 along the vertical thrust axis. The anvil 10 consists of a pressure vessel 14, which may be of hardened steel, having the shape of a truncated cone which is fitted into a tapered sleeve 16 in turn mounted in a tapered recess 18 formed in a massive support ring 20. The support ring 20 is in turn mounted on a base 22. The pressure vessel 14 is formed with a hemispherical cavity 24 of which the mouth portion is formed with an upwardly and outwardly flanged lip 26. The pressure vessel 14 is preferably made with a taper which is of a suicient angle to avoid locking so that the pressure vessel can be readily removed after usage.

The ram 12 comprises a cylindrical piston 28 of substantial diameter which has press fitted into the lower end thereof la spherical anvil member 30, the lower portion of which is slabbed off to provide a sample engaging face of substantially the same diameter as the cavity 24. It will be noted that the bottom face 32 of the piston 28 is bevelled adjacent its edge t0 follow approximately the corresponding bevelled face 34.

The ultra high pressure press above described operates in the following manner:

The specimen to be studied is embedded in a suitable pressure transmitting medium which may, for example, be pyrophylite or silver chloride shaped to slightly more than fill the hemispherical cavity 24. The jack is then operated to move the ram 12 and lanvil 10 together under great force. The pyrophylite squeezes out Vbetween the sloping `lip 26 of the hemispherical cavity 24 and the opposed rounded portion of the anvil member 30, until the film of pyrophylite has been thinned by the increasing pressure to a point where the forces of friction overcome the tendency to ilow thus forming a gasket of said pyrophylite to prevent further egress ofthe same as the pressure transmitting medium within the hemispherical cavity lis brought to full pressure which in the present example is assumed to be in the order of 800,000 p.s.i. Because of the fact that pressure is applied simultaneously across the open face of the hemispherical cavity a very small movement of the piston suflices to build up a maximum pressure. The rate of increase could be further accelerated by placing a small amount of a relatively incompressible material in the relatively unusable bottom portion of said cavity.

The construction and arrangement of the ram and anvil elements of the press are such as to produce a most efficient distribution of forces in the two cooperating elements and a consequent increase in the load bearing strength of said elements. Pressure exerted against the prepared sample across the open face of the hemispherical cavity is diffused, being directed against all parts of the hemispherically contoured interface between the prepared sample and the walls of the cavity. The sample pressure tends to create tension stresses on the surface of the hemispherical cavity. Because of the conical construction of the support structure with the unsupported base, support pressure develops at the interfaces between the pressure vessel 14, conical sleeve 16 and supporting ring resulting in the development of counter-acting compressive stresses on the cavity surface. The more sample pressure developed, the higher will be these counteracting compressive stresses because of the sliding or wedging action of the conical surfaces. Thus the inner cavity containing pressure vessel 14 is prevented from breaking under the ultra high pressures imposed.

With the present construction the forces set up in the pressure vessel and throughout the anvil assembly by the relative movement of the ram toward the anvil assembly are distributed radially over the entire interface to produce in addition to the usual axial wedging act-ion a large -component of outward thrust which is absorbed directly by the outer supporting ring of the anvil assembly. The support thus afforded to the pressure vessel against the compressive pressures set up within the sample is more efficiently distributed over the entire mass of the anvil assembly thus substantially increasing the strength of the entire anvil assembly. Essentially the interface surface must be a surface of revolution and of smooth contour, since any discontinuities would weaken the structure. The shape of the cavity may be modified without serious loss of strength, for example, to have the shape of a paraboloid or of an ellipsoid. It will be understood that the downard pressure exerted by the ram is diffused radially against all parts of the hemispherical interface through the action of the encasing material of the sample which behaves as a liquid at the very high pressures engendered.

The distribution of forces in the anvil asembly produced by the arrangement of the anvil assembly including the pressure vessel having a hemispherical sample receiving cavity acted against by a ram having an opposed flat sample engaging surface has been found so effective as to permit the use of steel parts in place of the more expensive tungsten carbide elements in the construction of the anvil assembly and ram. While in the preferred form of the invention an anvil assembly employing tapered support with an unsupported base area is employed it is recognized that the more highly efficient sample containing hemispherical cavity is capable of use with other simpler forms of anvil support to obtain very substantial sample engaging pressures Without injury to the anvil parts. The hemispherical sample receiving cavity employed in the combination here set forth including an anvil assembly and a ram movable along a single line of thrust has the advantage that the pressure transmitting medium within which the specimen is embedded is relatively symmetrical in shape, so that any variations of internal pressure Within the sample which might have been brought about by readjustments of the encasing medium against the supporting walls of the cavity are comparatively non-ex-istent, resulting in a uniform gradient free pressure throughout the sample contained in said cavity.

The construction and arrangement of the ram 12 forms also an important feature of applicants improved press. A hardened steel ball 30 is employed which is embedded to a depth of slightly more than one-half its diameter as, for example, by press fitting into a softer steel member 28 which is carefully selected for both strength and ductility. Portions of the embedded surface of the member 30 are preferably flatted as indicated at 36 to prevent the ball from rotating due to a possible unsymmetrcial load in the initial compression of the sample. While, in the example shown the member 30 is made of a hardened steel, it will be understood that other materials suitable for a particular press operation may be employed, such as tool steel or tungsten carbide, glass, sapphire or diamond.

The cooperative relation achieved between the rounded exposed portions of the spherical anvil member 30 and the tapered lip 26 of the pressure Vessel 14 between which excess pyrophylite is extruded and pressed into the form of a gasket seal has the effect of giving the spherical anvil member a substantial additional support at the moment when a maximum load is applied thereagainst, thus permitting the use of the spherical anvil member to pressure loads far in excess of loads which said member could normally be expected to sustain without failure.

It will be understood that the invention in its broadest form is not limited to the specific construction shown and that changes may be made within the scope and spirit of the invention. It will be understood, for example, that applicants anvil assembly including a pressure vessel having formed therein a hemispherical cavity may be employed in combination with a ram of different construction from that shown, in which combination a different conformation of the gasket forming lips may be employed.

The invention having been described what is claimed 1. In a high pressure press for subjecting to ultra high pressure prepared samples comprising specimens encased in a substantially incompressible material ductile at said high pressure, an anvil assembly and a ram assembly relatively movable along a single line of thrust, said anvil assembly comprising an anvil member formed with a hemispherical sample receiving cavity to be filled to excess with said incompressible encasing material and terminating in a gasket forming lip, and said ram assembly comprising an anvil contact member hav-ing a fiat sample engaging surface formed to fit closely into the open face of said cavity, and having adjacent said flat surface a gasket forming lip, said iiat sample engaging surface of the ram being spaced apart from the hemispherical cavity to be moved relatively to a position in which said incompressible material is placed under a maximum pressure, and in which excess incompressible material is extruded between said lips, and said gasket forming lip being spaced apart to be moved clamping between them said extruded material at said maximum pressure to form a frictionally immovable cavity sealing gasket sealing in said incompressible material filled cavity at said maximum pressure.

2. A high pressure press for subjecting to ultra high pressure prepared samples comprising specimens encased in a substantially incompressible material ductile at said high pressure, an anvil assembly and a ram assembly relatively movable along a single line of thrust according to claim 1, in which, said anvil assembly comprises a massive support ring having an internal tapered support surface, and a tapered pressure vessel fitted within said tapered support ring surface, and with the bottom of said pressure vessel unsupported, said pressure vessel having formed in the upper face thereof a hemispherical cavity to be filled to excess with said incompressible encasing material and terminating in its upper edge in said gasket forming lip.

3. In a high pressure press for subjecting to ultra high pressure prepared samples comprising specimens encased in a substantially incompressible material ductile at said high pressure, an anvil assembly and a ram assembly relatively movable along a single line of thrust,

said anvil assembly comprising a massive support ring having a conically tapered aperture, a tapered sleeve ring supported in said aperture, and a conically tapered pressure vessel supported in said tapered sleeve, said pressure vessel having formed in the upper face thereof a hemispherical sample receiving cavity terminating in an upwardly and outwardly sloping gasket forming lip, and said ram assembly comprising a massive support member, and a rounded sample engaging anvil contact member embedded to a depth in excess of one-half its diameter in said support member, said spherical anvil contact member having a at sample Contact surface fitted closely to the open face of said cavity and having the adjacent rounded portions thereof disposed as a gasket forming lip.

References Cited by the Examiner UNITED STATES PATENTS Franz 18-42 X Gillis et al.

Dempsey.

Wells et al. 18-42 X Zeitlin et al.

Scott 18-42 X 10 WILLIAM J. STEPHENSON, Primary Examiner.

Claims

1. IN A HIGH PRESSURE PRESS FOR SUBJECTING TO ULTRA HIGH PRESSURE PREPARED SAMPLES COMPRISING SPECIMENS ENCASED IN A SUBSTANTIALLY IMCOMPRESSIBLE MATERIAL DUCTILE AT SAID HIGH PRESSURE, AN ANVIL ASSEMBLY AND A RAM ASSEMBLY RELATIVELY MOVABLE ALONG A SINGLE LINE OF THRUST, SAID ANVIL ASSEMBLY COMPRISING AND ANVIL MEMBER FORMED WITH A HEMISPHERICAL SAMPLE RECEIVING CAVITY TO BE FILLED TO EXCESS WITH SAID INCOMPRESSIBLE ENCASING MATERIAL AND TERMNATING IN A GASKET FORMING LIP, AND SAID RAM ASSEMBLY COMPRISING AN ANVIL CONTACT MEMBER HAVING A FLAT SAMPLE ENGAGING SURFACE FORMED TO FIT CLOSELY INTO THE OPEN FACE OF SAID CAVITY, AND HAVING ADJACENT SAID FLAT SURFACE A GASKET FORMING LIP, SAID FLAT SAMPLE ENGAGING SURFACE OF THE RAM BEING SPACED APART FROM THE HEMISHPERICAL CAVITY TO BE MOVED RELATIVELY TO A POSITION IN WHICH SAID INCOMPRESSIBLE MATERIAL IS PLACED UNDER A MAXIMUM PRESSURE, AND IN WHICH EXCESS INCOMPRESSIBLE MATERIAL IS EXTRUDED BETWEEN SAID LIPS, AND SAID GASKET FORMING LIP BEING SPACED APART TO BE MOVED CLAMPING BETWEEN THEM SAID EXTRUDED MATERIAL AT SAID MAXIMUM PRESSURE TO FORM A FRICTIONALLY IMMOVABLE CAVITY SEALING GASKET SEALING IN SAID IMCOMPRESSIBLE MATERIAL FILLED CAVITY AT SAID MAXIMUM PRESSURE.