Abstract: Pile driving apparatus comprises first and second sets of eccentric members mounted in a housing for opposing rotation. A phase shifting arrangement connects the sets of eccentric members for controlling coordinated rotation thereof, and comprises a limiting device between the first and second sets of eccentric members for shifting between a first condition wherein the eccentric members are constrained to rotate out of phase to negate generation of vibration and a second condition wherein the eccentric members are constrained to rotate in phase to generate vibration. Two motors are connected with the limiting device for alternatively driving rotation thereof. A control arrangement selectively drives the limiting device predominantly by the first motor for shifting the limiting device into the first condition thereof for preventing vibration or predominantly by the second motor for shifting the limiting device into the second condition for generating vibration in the housing.

Abstract: A method and apparatus for driving and extracting piles that includes a vibration/tension load absorber assembly mounted between a housing and the vibratory unit which includes shear-type vibration absorbers connected between the housing and the vibratory unit and operating in combination with at least one compression-type vibration absorber positioned to be compressed between first and second compression plates when the tension load reaches a predetermined level.

Abstract: An impact hammer having a non-mechanical connection between the driving piston rod and the impact ram. The non-mechanical connection includes an annular body portion connected to the lower end of the piston rod which is received in a cavity in the top surface of the impact ram, and an elastomeric ring is held in facing grooves in the cavity and the annular body member to constitute the sole connecting element between the piston rod and the impact ram.

Abstract: A power hammer for driving piles and the like which includes a housing having a ram carried therein for reciprocating vertical movement to strike, during its downward movement, an anvil slidably carried within the lower portion of the housing. The portion of the housing in which the anvil is carried is formed with an annular recess, and the anvil includes an annular flange projecting into the recess to form an enclosed chamber beneath such flange. Air pressure generated by the ascendency of the ram is transmitted to the enclosed chamber to impose an upwardly directed force on the anvil whereby the weight of the anvil is utilized to oppose the upwardly directed force imposed on the power hammer during the ascending movement of the ram.