Device for producing high pressure in a fluid in miniature

A device for pressurizing fluid, comprising:

• a cylinder;
• a cylindrical hollow piston movable in said cylinder and providing a path for fluid therethrough, wherein an inlet end or an outlet end of said hollow piston includes a widened portion, an inner diameter of said widened portion being greater than the inner diameter of the remainder of said hollow piston, and wherein said inlet end or said outlet end includes an inwardly shaped edge;
• a valve seal provided by said piston;
• a high pressure chamber inside said cylinder;
• and
• a valve operating without any auxiliary force, said valve including,
• a uniaxially rotationally symmetrical valve member including a sealing surface at an inlet end of said valve member to cooperate with said valve seal, said valve member being guided inside said widened portion of said hollow piston, wherein the diameter of said valve member is less than said inner diameter of said widened portion and is greater than said inner diameter of the remainder of said hollow piston, such that said valve member does not extend into the remainder of said hollow piston,
• stop means provided at an outlet end of said widened portion to hold said valve member inside said hollow piston,
• a recess in said stop means or a recess or radially extending indentation in said valve member at an outlet end thereof,
• wherein said valve is closed when said valve member abuts said valve seal and said valve is open when said valve member abuts said stop means.