Abstract: Two members are locked together by forcing wedge means between mutually facing and converging surfaces of the members, the wedge means causing gripping means to engage one of the members to lock the members together. A fluid pressure is established between the wedge means and at least one surface of one of the members while forcing the wedge means into wedging position between the members to minimize friction between the wedge means and the elements with which they are in contact during movement. When the wedge means is in position, the fluid is terminated to complete the lock.

Abstract: A hydraulically driven hammer is disclosed, along with valve actuation arrangements which operate to switch hydraulic forces on the hammer ram after preselected intervals following application of pressurized pilot fluid flows. These flows pass into a fluid accumulation chamber unitl a predetermined volume is accumulated after which continued pilot fluid flow produces valve actuation.

Abstract: A hydraulically driven hammer is disclosed, along with valve actuation arrangements which operate to switch hydraulic forces on the hammer ram after preselected intervals following application of pressurized pilot fluid flows. These flows pass into a fluid accumulation chamber until a predetermined volume is accumulated after which continued pilot fluid flow produces valve actuation.

Abstract: A hydraulic hammer assembly is disclosed which comprises a stationary piston suspended within a tubular frame or casing and a cylinder locked inside a massive ram within the casing. The cylinder forms a differential hydraulic assembly with the piston and moves up and down along the piston. The cylinder is maintained locked to the ram by the pressure of the hydraulic fluid; and the piston, which is formed of two members, is held in assembly by a continuous hydraulic bias with a special hydraulic balancing arrangement which compensates for the pressure switching in the cylinder to which one portion of the piston assembly is exposed.

Abstract: Method and apparatus for forming piles in the earth with a pile hammer rig having a crane, a hoisting drum carried by the crane, a driving mechanism for driving the drum through a clutch assembly, a braking assembly for the drum, a hoisting rope leading from the drum for lifting a drop-weight, an automatic sensor for sensing the top of the drop-weight stroke for disengaging the clutch mechanism, a second automatic sensor for sensing the bottom of the drop-weight stroke for engaging the drum braking assembly, and in one form of the invention an automatic sensor for sensing the rotation of the hoisting drum for disengaging the braking assembly and engaging the clutch assembly.