Combination needle flow control and shut-off valve for precision instruments

A combination needle flow control and shut-off valve for precision instruments comprising a body, an elongated opening formed within said body, separated inlet and outlet passages connected with said opening, an elongated cartridge screw threadedly mounted in said body opening for longitudinal movement within said opening to open and close the connection between said inlet and outlet passages, said cartridge having an opening therein connecting said inlet and outlet passages when said cartridge is disposed in open position, an elongated needle member screw threadedly mounted within said cartridge for longitudinal movement within said cartridge, said needle member having a tapered needle longitudinally movable within said opening in said cartridge for precisely controlling the flow of fluid between said inlet and outlet passages, means connected to the outer ends of said cartridge and needle member for rotating and longitudinally moving said members independently from each other, so that said cartridge may be moved between open and closed positions to turn the flow of fluid through the valve completely on and off without affecting the precision flow control setting of said needle, an O-ring mounted adjacent to the end of said cartridge surrounding said cartridge, an inwardly extending portion of said body disposed adjacent to said O-ring, said O-ring being adapted to be compressed into sealing engagement with said inwardly extending portion of said body upon inward movement of said cartridge to close off the connection between said inlet passage and said outlet passage, said cartridge having an inner end engageable with the inner end of said body opening after said O-ring has made sealing engagement with said body to limit further inward movement of said cartridge.