Patent Publication Number: US-2010129480-A1

Title: Multi-anvil cubic machine comprising hemispherical pistons, which is used to generate high pressures and high temperatures

Description:
OBJECT OF THE INVENTION 
     The object of the invention is to provide a high pressure and high temperature machine housed in an industrial reaction chamber which purpose is to obtain diamond, boron nitride and similar substances, by means of cubic multi-anvil action and the action of hemispherical pistons provided with modular locks. 
     BACKGROUND OF THE INVENTION 
     Devices and machines used to generate high pressures and high temperatures have been developed to cover industrial and research needs. Industrial production of diamonds requires the generation of pressures and temperatures similar to those of the innermost depths of earth where natural crystals are formed. Also, the study and simulation of geologic and mining conditions require said conditions. 
     In this sense, multiple variations of devices capable of generating large pressures at high temperatures and to maintain those conditions during many hours, even days, have been developed. Within this group of devices are those known as Belt type and the Mold or Matrix types. In these devices the reaction chamber is confined by a perforated metal disc formed by several cylindrical metal layers adjusted to each other, or in some type of contention mold or matrix designed to sustain the tensions generated. The force is generated by two axially opposed pistons that move toward each other pressing the sample, chamber or capsule, or reaction chamber confined into the mold. Said devices are well known and have been described in the ordinary bibliography on high pressures and crystal synthesis and in various patents. These devices are capable of attaining pressures in the 10 Gpa order of magnitude and above, as well as temperatures of 2000° C. or above. 
     To overcome certain problems related to the enormous internal friction that is generated inside the mold and opposed piston types of machines, and to develop pressures closer to hydrostatic pressure, the apparatuses known as multi-anvil machines have been developed. In these machines, several pistons (or co-anvils) press the sample (capsule or reaction chamber) simultaneously. Generally, there are four pistons arranged in a tetrahedral geometry (tetrahedral machine), six pistons arranged in a cubic geometry (cubic machine) and other simple and ingenious arrangements in one or several layers. The same pistons together with their high pressure joints serve to contain the sample. A good review of these types of machines and their operation can be found, as well as their diverse applications. 
     These types of machines have very good qualities applicable to the synthesis of high pressure and temperature materials; however, they also have some disadvantages that can be improved. The main inconvenience of the multi-anvil machines is their complexity of operation. 
     Most of these machines require the complex assembly of different bodies and joints before beginning the work cycle, or otherwise require a careful adjustment of the linear alignment of their multiple pistons and the adjustment of the force exerted by each piston. 
     Another serious inconvenience is their low productivity, which is generally due to their inability to work with reaction capsules larger than a few cubic centimeters. 
     There is then a need to adapt these types of machines to a productive process that allows a profitable operation in industrial environments and in advance applications of Research and Development, increasing their reliability, and productivity, and making the manufacturing process easier. 
     DESCRIPTION OF THE INVENTION 
     The present invention refers to a multi-anvil machine having the possibility of increasing the pressure inside the reaction chamber by means of one or two hemispherical pistons housed in hemispherical chambers that resolve the problems found in the current state of the art. Said machine is capable of generating large pressures and temperatures, inside a reaction chamber, needed in industrial applications for processes such as the manufacture of diamonds, boron nitride and similar substances. In addition, said conditions are generated in a reproducible manner that is also stable in time. 
     Another objective of the present invention is to provide an easy manufacturable lock capable of containing the force generated by the machine, reducing the size of the assembly parts. Also, said lock is of a modular design, which allows for enlargement of the lock&#39;s size, if the size of the reaction chamber or the necessary pressures so require. 
     Another objective is to provide a multi-anvil machine that can be easily and efficiently operated. 
     The characteristic elements of the invention are:
         Hemispherical pistons: the spherical piston is housed in a spherical chamber that has greater resistance to deformation and fracturing that a cylindrical chamber of the same diameter. This feature translates into two advantages: first, the geometry allows for a design of greater resistance to hydraulic pressure, and generates a greater thrust force with a expenditure of material similar to that of a cylindrical piston. Second, at the same thrust force as that produced by a cylindrical piston the wall of the housing element can be reduced.
           The short piston&#39;s travel path attains great forces to generate high pressures at a minimum hazard, since the volume of hydraulic fluid stored for its operation is very small. Said volume stores a large quantity of energy that is not dangerous even if the housing element was to break. In the event of breakage, the pressure of the hydraulic liquid decreases quickly at the slightest fissure, dissipating all danger before any liquid exits the housing body.   
           Modular lock: the main characteristic of the modular lock is that, because it is configured with the inclusion of the intermediate rings, it facilitates the utilization of reaction chambers of different heights, this characteristic having the advantage that the manufacturing costs are lower than they would be for a whole piece. An additional advantage is that it is possible to regulate the height of the chamber simply by introducing the intermediate pieces and extend the catch ties. This height regulation feature allows designing machines with larger reaction chambers.   Anvils or cylindrical sectors: are of a special design that allows housing other anvils, that once assembled, form a regular octahedron that pushes the reaction chamber from three mutually perpendicular directions (cubic). The number of mobile components has been reduced to facilitate and simplify the assembly process during the operation of each work cycle.       

    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1 : Cross section of a one piston machine 
         FIG. 1   a : Detail A of the piston 
         FIG. 2 : Cross section of a two piston machine 
         FIG. 3 : Cross section of the machine through the edges of the octahedron 
         FIG. 4 : Lock section 
         FIG. 5 : Lock section including an intermediate semi-ring 
         FIG. 6 : Lock section including two supplementary semi-rings 
     
    
    
     PREFERRED EMBODIMENT OF THE INVENTION 
     The machine object of the present invention has the following elements according to the accompanying figures: 
       1 . Nut 
       2 . Tie 
       3 . Upper semi-ring 
       4 . Lower semi-ring 
       5 . Upper cover 
       6 . Chamber 
       7 . Isolated nut 
       8 . Electrode 
       9 . Seal joint 
       10 . Guide 
       11 . Seal joint 
       12 . Abutment 
       13 . Abutment 
       14 . Seal joint 
       15 . High pressure connection 
       16 . Cooling valve 
       17 . Hemispherical pistons 
       18 . Insulating joint plate 
       19 . Cylindrical sector 
       20 . Ring 
       21 . (not in text) 
       22 . Anvil 
       23 . High pressure seal joint 
       24 . Reaction capsule 
       25 . Electrode 
       26 . Intermediate semi-ring 
       27 . Intermediate semi-ring 
       FIG. 1  depicts the machine as having two bodies of, basically, cylindrical geometry, one is an upper body called upper cover  5  and the other is a lower body called chamber  6  that houses a semi-spherical cavity where a semi-spherical piston  17  is adjusted. 
     The design of this spherically shaped chamber supports optimally the hydraulic pressures that can be generated inside it, allowing working conditions in the order of 4,000 and even 6,000 Kgf/sqcm depending on the materials chosen for the design. These two bodies are confined by two semi-locks, that are themselves composed by two upper  3  and lower  4  semi-rings. 
     Said semi-rings are joined by ties  2  threaded in the lower semi-ring and tightened by nuts  1 . In this manner, the semi-locks form a compact but modular unit set that can sustain the force generated by piston  17 , which also thrusts over the upper cover  5  through the set of anvils and capsule as shown in  FIG. 3 . 
       FIG. 1   a  shows a detail of the semi-spherical piston area, where the necessary hydraulic pressures are generated for the operation of the machine as follows: 
     High pressure oil enters the semi-spherical high pressure chamber, where the semi-spherical piston  17  is housed, through the high pressure connection  15 . Said piston moves axially guided by the abutments  13  and a small guide  10  that travels through a cylindrical surface that has a short length compared to its diameter. This travel movement represents the travel path of the semi-spherical piston, that is then, small in relation to its diameter. This short travel path ensures the machine is working in a highly safe manner, since the possible accumulation of energy that could become dangerous in case any of the elements subjected to high pressure were to break, is then reduced to a thin spherical sheet around the piston. This possible failure or breakage of the material would not have severe consequences, since the layer subjected to high pressure is very thin in relation to the piston&#39;s diameter. In case of some type of failure, the volume of the cavity that holds the hydraulic fluid increases quickly, suddenly lowering the pressure to a point of no danger. In other words, it is impossible, in this type of machines for the hydraulic chamber to explode, or for any accident that entails a violent projection of any of the parts that make up the machine to occur. 
     Below the guide  10  there is a high pressure seal joint  11  that confines the hydraulic fluid together with the high pressure joint  14 , preventing escapes. Inside the hemispherical piston there is a cylindrical cavity that houses a series of anvils, called cylindrical sectors  19 .  FIG. 3  shows a detail of the assembly of the cylindrical sectors  19 , centered by the abutments  12 . Also, they are radially supported over rings  20 , both on the semi-spherical piston and on the upper cover. These cylindrical sectors are electrically insulated by insulating joint plate  18 , both radially and axially. The piston exerts a thrust force over the cylindrical sectors  19 , where said cylindrical sectors are designed in such a manner that they themselves house other anvils  22  in a geometrical arrangement such that once assembled they form a regular octahedron. 
     The thrust of the piston over the cylindrical sectors  19  is itself transmitted to these anvils  22  that are separated by high pressure seal joints  23  that confine the reaction chamber  24 . 
     The thrust chain is then the following: 
     The high pressure oil pushes piston  17  that then pushes the cylindrical sectors  19 , that then push anvils  22 , that in turn push the reaction chamber  24  from three mutually perpendicular directions (cubic), enabling an intensification of the pressure inside the reaction chamber  24  due to the geometric relationship of the forces and components that decompose according to the system&#39;s geometry. It is then possible to obtain in reaction chambers of more than 30 cc pressures well above 4 GPa. It is possible, even to obtain pressures above 10 GPa depending on the material used to manufacture the anvils  22  and the contents and size of the reaction chamber. 
     When heating the reaction chamber becomes necessary, the heating is achieved by an electrical resistance that conducts the electric current through the electrodes  7  and  8  that are in contact with the upper cylindrical sectors that transmit the electrical current to the reaction chamber through anvils  22 , all their faces duly insulated, except for the face in contact with the reaction chamber and the corresponding cylindrical sectors. 
     The entire system is cooled by water or cooling fluid that enters through the cooling valve  16 . The cooling system is perfectly pressurized, even during the movement of the hemispherical piston  17 , by seal  9  made of rubber or of any similar elastomer. 
       FIG. 2  shows the arrangement of a two piston machine, having a particularity that distinguishes it from the one piston machine, and that is that the electrical current supply must be provided through horizontal electrodes  25  in order to prevent the electrical current to enter through the area of high pressures generated in the semi-spherical chamber, and is instead done through the space between the lower hemispherical piston and the upper semi-spherical piston. Such arrangement allows duplicating the force generated by the machine object of the present invention in a simple manner, without appreciable modification of the volume and mass of the machine, and particularly indicated when wanting to attain very high pressures in very large reaction chambers. 
     The materials most suited to build these machines are high resistance steels: for the covers and the chamber F-125, F-127 or similar, with the appropriate thermal treatment; for the ties and the nuts, treated F-127 steel or similar, for the semi-rings F-125 or similar, for the semi-spherical pistons F-127, Maragin steel or other high resistance alloyed steels. For the cylindrical sectors F-5318, hardened DIN 1.2379 or similar, and for the anvils wolframium carbide containing between 6% and 10% of ligand (Co) are used. 
       FIG. 4  shows an overview of one of the semi-locks that resist the thrust of the semi-spherical pistons. 
       FIG. 5  shows an example in which an intermediate semi-ring  26  has been introduced, lending height to the lock. This device serves to confine high pressure machines to which intermediate parts have been incorporated, such as for instance multiple reaction chambers of great height if needed. 
     This same model can be repeated in  FIG. 6 , where another supplemental semi-ring  27  is introduced. In this manner, the lock&#39;s modular design allows for the incremental increase of the height when required by the machine design without having to excessively increase the cost of said lock, that does not require employing large parts that would have to be custom made in foundries or produced in very restricted batches.