Abstract: A motor-driven hand drill includes a housing, in which between a motor and a drill receptacle, a safety coupling for limiting a torque, applied to a drill, is positioned. For specific conditions, for example for drilling in armoring iron, the torque applied to the drill must be increased. The drill is provided with an electro-magnetic device which is operatively connected to the safety coupling to adjust the limiting torque applied to the drill. The magnetic device is actuated by means of a pushbutton positioned in the same gripping region as the pushbutton for actuating an electric motor of the drill to switch the same on and off.

Abstract: A speed limiter for setting the speed of an air tool has a flow passage body which screws into the air inlet of the tool. The body defines an axial air flow path therethrough with an annular land adjacent to internal threads. An adjusting insert is threaded to the internal threads and has a pair of opposed axially extending grooves formed in its periphery which extend further radially inward than the land. The size of the air flow passage and therefore the speed of the tool is varied by adjusting the insert toward or away from the land.

Abstract: An automatic shift drill for rotationally driving a bit into a laminated workpiece at one of two speeds according to the depth of the bit in the workpiece is disclosed. A cam block element has flag sections and gap sections corresponding to the various layers of the workpiece. The cam block element is mounted on a spindle of the drill to move in translation with the bit. A vent element has an orifice which is adapted to be closed when it is adjacent to one of the flag sections and open when it is adjacent to one of the gap sections. Shifting means responsive to pneumatic pressurization changes the rotational speed of the bit from one speed to the other speed. The orifice vents the shifting means when it is adjacent to a gap section to drive the bit at the appropriate speed through the corresponding layer and seals the shifting means when it is adjacent to a flag section to drive the bit at the other speed appropriate for the layer corresponding to the flag section.

Abstract: A pair of rotating flywheels which engage a ram for moving a tool which impacts a part, such as a nail to be driven, are rotated in opposite directions from a single motor or other rotating means, through a pair of substantially identical gears, one of which drives one flywheel and the other of which drives the other flywheel. The drive connection between the respective gears and each of the flywheels may include a belt and pulley arrangement, so that each flywheel may be driven directly by the respective belt but the flywheels are pivoted toward and away from the ram so that when the flywheel moves toward the corresponding side of the ram, the connection between the belt and the corresponding pulley will tend to slacken. A special flywheel pulley has an inner V-shaped groove and parallel side walls for guiding the belt into the groove when full tension occurs.

Abstract: A percussive-action pneumatic tool comprising a handle-carrying frame having successively accommodated therein a shock-absorber and a housing with the percussion mechanism therein, connected through a gas distribution system to a compressed air source. The frame has a length sufficient for abutting against the surface of a material being worked and has a guide which receives the housing with the percussion mechanism. The shock-absorber includes a receptacle mounted on the frame and communicating via a controllable valve alternatively with the compressed air source and the atmosphere, a rod being mounted in this receptacle, adapted to act upon the housing with the percussion mechanism, to move the housing relatively to the frame as compressed air is supplied into the receptacle.

Abstract: An impact device comprises a cylindrical casing accommodating a hammer piston imparting blows to a working tool, which reciprocates under the action of compressed air admitted from a compressed air line through a control valve air distribution arrangement and a mechanism for automatically starting the device. The mechanism for automatically starting the device comprises a hollow two-step cylinder secured to the cylindrical casing accommodating a two-step piston which incorporates a valve co-operating with a tappet. The two-step piston is mounted in the hollow two-step cylinder in such a manner that an annular chamber is defined between the outer surface of the piston and the inner surface of the cylinder, the piston co-operating with the valve.

Abstract: A bolt-setting and rock-drilling apparatus has a rail which can be swung about and axis and axially displaced therealong to position a drilling carriage and a bolt-setting carriage alternately with respect to a rock wall in which the bolt is to be lodged. The carriages are slidable on opposite sides of the rail and, in the upper end thereof, in alignment with the drill holder, is an opening drill through which the main drill passes. The opening drill, which is of a configuration enabling it to form a conical mouth to the hole bored, by the main drill, is displaceable parallel to the main drill when its holder engages a clutch member carrying the opening drill. The conical mouth facilitates subsequent insertion of the bolt.

Abstract: An apparatus for removably mounting a hand-held tool such as a pavement breaker or tamper releasably on the wrist linkage of the bucket for a backhoe attachment for a tractor or truck including an attachment member having a slide rail, a carriage slidably mounted on the slide rail, a biasing member mounted on the attachment member biasing the carriage to a tool nonoperating position and a control member mounted on the attachment member adapted for engaging the tool operating lever.

Abstract: A throttle valve construction for a pneumatic paving breaker and other types of percussion tools employing a reciprocating piston to impart blows to a work steel or the like is disclosed, wherein partial movement of the control lever of the tool from a fully depressed position to a partially depressed position permits the throttle valve to shift to a position which substantially reduces the quantity of air under pressure being supplied to the operating cylinder of the tool so that the reciprocation frequency and kinetic energy of the piston are reduced. The amplitude and frequency of the vibrations generated by the tool and transmitted to the operator thereof are likewise substantially reduced when the tool is operating in this mode, and a significant reduction in the level of the sound emitted by the tool is also obtained.