Valve assembly and method

A valve assembly for use with a fluid-driven tool comprising:

• an elongated conduit including a bore extending axially therethrough, said bore having a first portion of substantially constant first diameter and a second portion of a second diameter no less than said first diameter, said conduit including an inlet port for connection to the source and communicating with said second portion, said first and second portions and said inlet port being generally coaxial, said conduit including an opening extending radially therethrough;
• an elongated valve member extending axially in said first portion and having proximal and distal ends, said valve member having a chamber defining a seat generally aligned with said opening, an inlet passageway extending from said chamber to said proximal end and communicating with said inlet port upstream from said valve member, and an outlet passageway extending from said seat to said distal end and communicating with said first portion downstream from said valve member;
• a ball in said chamber and having a size to sealingly engage against said seat and being driven into sealing engagement against the seat by the fluid;
• a valve pin slidably received in said opening and having an inner end directed toward said seat and an outer end extending out of said conduit;
• means for moving said valve pin between an outer position with said inner end spaced from the ball, and an inner position with said inner end engaged adjacent said ball for a sufficient distance to move the ball away from said seat and permit passage of the fluid from the source through said inlet port and said inlet passageway into said chamber, and past said seat into said outlet passageway and said bore downstream from said valve member;
• and means for sealing said valve member to said conduit to prevent passage of fluid therebetween.