Ball actuable circulating dump valve

Drilling apparatus comprising:

• a drill pipe housing having a port therein;
• means providing a first abutment at a first point within said housing;
• retaining sleeve means slidably mounted within said housing and having a first opening therein;
• means for holding said retaining sleeve means in a first position wherein said first opening communicates with said port and responsive to a force of selected magnitude to release said retaining sleeve means;
• means providing an abutting surface on said retaining sleeve means;
• piston means mounted within said housing adjacent said abutment and having a second opening therein for communicating with said port, said piston means being slidable to a first position in response to fluid flow wherein said second opening no longer communicates with said port and to a second position wherein said piston means applies force to said abutting surface;
• and
• means for biasing said piston means in a position wherein said opening communicates with said port and yieldable to a force less than or equal to said selected force to enable said piston means to exert said selected force upon said retaining sleeve means.