Lead screw device

Claim 1

A hydrostatically supported lead screw assembly comprising: a rotatable lead screw having a plurality of internal passages therein, one set of internal passages passing longitudinally along the length of said lead screw radially inwardly of the threaded portion thereof, a second set of internal passages extending in a generally radial direction outwardly from said longitudinal passages and terminating in outlets on the faces of the threads of said lead screw for supplying a hydrostatic support fluid to the interface between cooperating threads; a grooved block, the grooves of which form a cooperating thread portion for cooperating with the threaded portion of said lead screw; said lead screw being rotatable relative to said grooved block to cause relative axial movement between said lead screw and said grooved block by the engagement of the threaded portions thereof; a plurality of recesses formed in the respective side walls of said grooves of said grooved block for containing hydrostatic support fluid flowing from said outlets from said second set of internal passages formed within said lead screw; and a distributor valve formeD circumferentially about the longitudinal axis of said lead screw, said distributor valve having a plurality of longitudinal passages formed therein, one end of said longitudinal passages in said distributor valve being connected with a hydrostatic fluid pressure source, said distributor valve further including a plurality of radial passages extending outwardly from said longitudinal passages in said distributor valve in the direction of the grooves in said ground block; said longitudinal passages formed in said lead screw adapted to be communicated with said radial passages formed in said distributor valve when said longitudinal passages are adjacent said recesses formed in the side walls of said grooves, whereby hydrostatic fluid pressure can be distributed to said recesses to provide an even pressure to be maintained between the threads and the grooves, with the hydrostatic fluid pressure supply to a given longitudinal passage being cut off when said passage moves away from said recesses during rotation of said lead screw.