Apparatus for preparation of samples for spectrographic analysis

A programmable hydraulic press for automated, repetitive pressing of sample pellets comprising:

• a) a die cavity to receive a sample of compressible material;
• b) a die member mounted for movement in relation to said die cavity to compress said sample into a pellet;
• c) cyclically operable and depressurizable hydraulic pressurization means to effect said movement between said die cavity and die member and effect compression of said sample;
• d) a manually settable hydraulic control circuit for said hydraulic pressurization means to actuate said cyclic operation and provide a pellet-compression cycle having the following parameters:
• i) a compression step of predetermined duration at a preselected working pressure;
• and
• ii) a bleed-down step wherein said preselected working pressure is bled down over a preselected bleed-down time;
• said control circuit further including data input means for manually effected operator inputs of said preselected working pressure and bleed-down time whereby said press is operable automatically to compress samples into pellets at said preselected working pressure and to relieve said pressure over said preselected bleed-down time.

Sample pelletization apparatus for compressing a sample by hydraulic pressure said apparatus including automated pressure control means and comprising:

• a) a die for receiving said sample in compressible form;
• b) an abutment for holding said sample in a fixed position against said hydraulic pressure;
• c) hydraulic piston-and-cylinder means positioned to drive said die in a direction toward said abutment;
• d) a pump for feeding hydraulic fluid to pressurize said piston-and-cylinder means to a working pressure;
• and
• e) a pressure control valve coupled to said piston-and-cylinder means for controlling the working pressure in said hydraulic cylinder, said pressure control valve comprising:
• i) a sealing member;
• ii) a valve seat defining an outlet configured, dimensioned and positioned to engage said sealing member with said sealing member closing said outlet;
• iii) compressible spring means for urging said sealing member towards said seat, closing said outlet;
• iv) a backing member putting said spring means under compression by maintaining a distance between said backing member and said seat;
• v) mechanical structure for adjusting said distance to actuate said pressure control valve, said mechanical structure comprising a stepper motor rigidly mounted with respect to said seat, said stepper motor having a shaft engageable with said sealing member and indexable to move said sealing member toward and away from said valve seat whereby the compression of said spring means is adjustable;
• f) means for detecting the pressure of hydraulic fluid in said hydraulic cylinder and means for controlling said stepper motor in response thereto;
• and
• g) manually settable control circuit means programmed to cause said shaft of said stepper motor to pull away in a first direction from said seat by a first number of steps which is less than that needed to cause a desired change in said working pressure in the hydraulic cylinder and then proceed in a second direction opposite to said first direction a second number of steps smaller than said first number of steps and then alternate in the first direction and the second direction with numbers of steps resulting in net movement in a desired direction, said control circuit being programmed to cause said shaft to alternately move in said first direction and in said second direction until pressure is reduced to a desired value.

A programmable hydraulic press for the repetitive pressing of sample pellets comprising:

• a) die cavity to receive a sample of compressible material;
• b) a die member movable in said die cavity to compress said sample into a pellet;
• c) hydraulic piston-and-cylinder means coupled to said die member to actuate said die and effect compression of said sample;
• d) hydraulic circuit means connected to said piston-and-cylinder means to pressurize said piston-and-cylinder to a working pressure and to depressurize said piston-and-cylinder;
• e) a pressure controlled relief valve to control said working pressure, said relief valve being settable to a predetermined relief pressure, openable to permit bleed down of said working pressure and comprising a valve sealing member and valve seat, said valve seat defining an outlet configured, dimensioned and positioned to engage said sealing member with said sealing member closing said outlet;
• f) relief valve adjustment means controllable to set said predetermined relief pressure and to open said relief valve to provide controlled bleed down, said valve adjustment means including
• i) adjustable compressible spring means urging said sealing member towards said seat to interengage and close said outlet;
• ii) a backing member movable to adjust said compression spring means, said backing member putting said spring means under compression by maintaining a distance between said backing member and said seat;
• and
• iii) a mechanical structure for adjusting said distance to actuate said pressure control valve, said mechanical structure comprising a stepper motor rigidly mounted with respect to said seat, said stepper motor having a shaft engagable with said sealing member and indexable to move said sealing member toward and away from said valve seat whereby the compression of said spring means may be adjusted;
• g) a control circuit for actuating said relief valve adjustment means, said control circuit being programmed to:
• i) receive operator inputs of desired relief pressure and desired bleed-down time;
• ii) provide a predetermined press duration at said working pressure;
• iii) cause said shaft of said stepper motor to pull away in a first direction from said seat by a first number of steps which is less than that needed to cause a desired change in said working pressure in the hydraulic cylinder and then proceed in a second direction opposite to said first direction a second number of steps smaller than said first number of steps and then alternate in the first direction and the second direction with numbers of steps resulting in net movement in a desired direction, said control circuit being programmed to cause said shaft to alternately move in said first direction and in said second direction until pressure is reduced to a desired value;
• and
• iv) advance the backing member in one direction and to retract it in an opposite direction, said advancing or retracting comprising:
• a) one or more cycles of a plurality of incremental steps in the desired advancing or retracting direction followed by a lesser number of similar incremental steps in the opposite direction;
• whereby, said press is operable automatically to compress samples into pellets at a predetermined operator-selectable working pressure and to release said working pressure with a predetermined operator-selectable bleed-down time.