In a percussion drill apparatus for soil drilling with a percussion piston which is moving to and fro within a housing, a control sleeve is mounted on a control tube which protrudes into the percussion piston chamber, the axial position of which determines the direction of movement of the apparatus. In order to make a reversal of movement possible a reversing chamber is connected with a control air line which runs inside the control tube and an approach chamber is connected by way of a drilling with the interior of a control tube which feeds the operating air into the percussion piston chamber. Consequently the control sleeve is moved into one direction with the aid of the control air and in the other direction with the aid of the operating air.

A forward and rearward running ramming device includes: a housing having a percussion head in which a percussion piston a axially displaced by compressed air; a control device for controlling the compressed air so that, during forward running the percussion piston strikes a front side of the housing, and during rearward running the percussion piston strikes a rear side of the housing, the control device interacting with control openings in the percussion piston, which control advancing movement and returning movement of the percussion piston, the control device being seated in a the housing and being connected, through the housing, to an air supply hose; an arresting device, which fixes the control device relative to the housing in individual switching positions, which are set by turning the air supply hose, wherein the arresting device is also a damping device, at least one air chamber, variable in size, being provided as arresting and damping element, the air chamber being bounded at end faces by rear and front terminating rings which are axially displaceable with respect to each other, the rear terminating ring being connected to the control device and the front terminating ring being connected to the housing; two energy accumulating elements, provided between the rings and pressing the rings apart; and a positioning device interacting with the front terminating ring and with the control device, the air chamber being connected to a source of compressed air, so that compressed air prevents inadvertent reversing during forward or rearward running.

An impact borer having a shell and an air drive within the shell. The air drive includes a ram for reciprocation within the shell and a manifold joined to the shell. The manifold defining an inlet passage delivering air to the air drive and an outlet passage exhausting air from the air drive, and a duplicate passage interconnecting the inlet and outlet passages within the manifold.

A method is specified for reversing a compressed air-driven ramming device for its control positions of forward running and rearward running in the earth, wherein, for reversal, a turning is performed against a relatively small detaining force and the force of the operational compressed air is used for locking the control device in the individual control positions and for damping the vibration propagation from a ram housing to the control device. As a result, a reversing of the ramming device during the admission of operational compressed air is reliably prevented.

A pneumatic ground piercing tool has a reversing mechanism than can be operated by remote control but which does not contain a moving valve member inside the tool which become jammed. Such a tool generally includes, as essential components, an elongated tubular housing having a rear opening, a striker disposed for reciprocation within an internal chamber of the housing to impart impacts to a rear impact surface of the anvil for driving the body through the ground, an air distributing mechanism for effecting reciprocation of the striker, a tail assembly mounted in a rear end opening of the housing that secures the striker and air distributing mechanism in the housing, and a reversing mechanism including a supplemental air line capable of supplying compressed air for reverse operation to a radial port in the air distributing mechanism. Opening the supplemental air line to the atmosphere produces a short stroke forward mode of operation useful for operations wherein a less forceful impact is desirable.