Abstract: An electrohydraulic control system for an arm assembly of the type described in U.S. Pat. No. 4,364,540 utilizes an electric computer (microprocessor) which receives a nonlinear or harmonic signal from the rotary hydraulic motor of the arm of this assembly and converts the harmonic signal into a linear signal which is applied to a comparator as the value signal for comparison with a command signal from the computer. Similar comparators are provided for each of the hydraulic operators and the sensors thereof can provide direct actual value inputs to these comparators.

Abstract: A muffler for a pneumatic hammer of the type in which a cylinder receives a piston or ram which is pneumatically driven into contact with an anvil, e.g. the rear end of a tool, and in which the discharge of the air is muffled to limit the noise generated by the apparatus. The air to be discharged into the atmosphere is vented into an annular space between an outer wall of a sleeve or head surrounding the cylinder and connected by an elastic suspension thereto.

Abstract: A power cylinder of a hydraulic percussion implement, in whose bore a ram with an enlarged piston head is vertically reciprocable to strike a tool at the lower end of the bore, has a control chamber above the piston head alternately communicating with the high-pressure side and the low-pressure side of a source of hydraulic fluid, an annular recess in the bore being permanently or intermittently connected to high pressure acting upon the underside of the piston head. An annular drainage chamber formed by the bore at a lower level, disposed above an oil seal, collects liquid leaking down from that recess and returns it to the source. A pneumatic buffer lies in or communicates with that drainage chamber for absorbing hydraulic shocks generated when the ram strikes the tool.

Abstract: A mining drill comprising a rail along which a mining drill head is slidably rectilinear, this rail being carried by a hydraulic motor pivotally connected to a rotary head at the end of an arm swingable about a pivot axis which is generally horizontal and is formed by a column or post. A first hydraulic motor is provided to rotate the post about a generally upright axis and hydraulic cylinders can be provided to swing the post about a pivot close to its pedestal. The device is designed to support the rail so that substantially parallel holes can be drilled in a subterranean structure in practically any direction, e.g. with any inclination to the axis of the main gallery, but especially parallel thereto.

Abstract: A percussion tools such as a pneumatic hammer, drill, concrete braker and the like in which a ram is pneumatically reciprocated in a cylinder to drive a tool, has a head provided with the handles gripped by the user and forming a pneumatic cushion with the cylinder. According to the invention, this head carrying the handles is mounted with slight clearance slidably on the cylinder and the pneumatic cushion is formed between the upper end of the cylinder and the interior of the head. A sleeve attached to the head and surrounding the cylinder communicates with the cylinder through the usual reciprocation-producing valve and a portion of the air pressure is bled through the clearance into the cushion. A vent passage of the cylinder communicates with the cushion chamber and can register with a passage in the sleeve opening into the atmosphere.

Abstract: A hydraulic percussion or an impact apparatus for driving rock-breaking tools, drill bits and ramming or tamping tools comprises a body in which an end of the tool is received and a reciprocating mass formed as a piston which is axially displaceable in a cylinder. The cylinder is provided with a distributor member slidable above the piston and of the same diameter as the latter, the distributor being formed as a sleeve having a central portion engaging a collar of a plunger which extends into a piston and forms therewith a suction chamber. The plunger has an extension which is slidable in a bore of the body and is acted upon by the high-pressure fluid.

Abstract: To facilitate the return of a percussion tool by the action of the striking mass, namely, a double-acting piston, without damage to the machine body, the tool is held by a casing attached to the body and the tool. The latter piston defines a chamber with a confronting face of the casing, the chamber being supplied with a liquid under pressure through a check valve. The chamber is connected to a reservoir by a pressure-relief valve.

Abstract: A percussion drill in which a piston or ram is driven against the end of a drill rod comprises a tube extending through the piston and reaching into a bore at the end of the drill rod to deliver a fluid thereto for moving debris formed by the drilling operation. A socket is received in a bore of the drill rod and has a resilient lip which is deflected inwardly by the flared mouth of the drill rod bore while the tube has a tapered end which is engaged by the wall of a tapered bore formed in the socket.