mixture being held under pressure in a preferred embodiment the selective delivery of the pressurized fluid to the fluid chambers of the press is controlled by a servomechanism constantly comparing a reference pressure signal with an actual pressure signal representative of the actual pressure being exerted by the press and actuating a servovalve so as to make the difference between the reference and actual pressure signals zero application_number US 69690385 A description the general organization of the apparatus in accordance with the invention will be understood from a consideration of fig1 included is in this apparatus a fluid operated preferably hydraulic press 10 having an upstanding cylinder 12 a piston 14 is reciprocatively fitted in this cylinder 12 to define a pair of opposed fluid chambers 16 and 18 therein a ram 20 depends from the piston 14 and projects out of the cylinder 12 for acting on a mixture of desired firebrick materials in the form of fine particles contained in a mold not shown a servovalve 22 is provided for selectively placing the opposed fluid chambers 16 and 18 of the press 10 in and out of communication with a hydraulic pump 24 and with a fluid drain or reservoir 26 the servovalve 22 is a four way three position closed center directional control valve capable of infinite positioning a preferred construction of the servovalve.