Abstract: A device for breaking concrete and similar frangible materials to reduce it to rubble includes a power plunger and a trigger mechanism mounted within a casing. The casing may be carried on and operated by construction equipment such as a back hoe. The trigger mechanism is operative to release the plunger for allowing it to be fired by spring means or dropped by gravity for a preset distance against the concrete. The power plunger has a latch member affixed thereto and forming one element of the trigger mechanism. The element consists of a concave spherical latching edge portion on its underside. The trigger mechanism also includes a releasable trigger having a convex spherical latching edge portion which mates with the concave portion. The trigger initially catches beneath the latch member, and is then pivoted to release the latch member and allow the power plunger to be fired. The mating spherical latching surfaces provide for a smooth, minimal-wear release of the trigger mechanism.

Abstract: A device for breaking concrete and similar frangible materials to reduce it to rubble includes a power plunger and an actuator plunger mounted within a casing. The casing is carried on and operated by construction equipment such as a back hoe. As the back hoe is operated to cock the power plunger by moving the actuator plunger toward the concrete surface, a trigger mechanism affixed to the actuator plunger lifts the power plunger and an associated latch member to load a coil spring associated with the power plunger and presses against the latch member. As the coil is fully compressed, the trigger mechanism engages a trigger operating abutment and releases the latch member. The coil spring then fires the power plunger against the concrete.

Abstract: A housing supports input and output shafts disposed at right angles, and the shafts are connected by a set of reduction gears and a spring biased clutch sleeve splined to the output shaft for axial movement. An electric motor is flange mounted on the housing and has a motor shaft connected to the input shaft which is surrounded by an electrically actuated brake effective to brake the input shaft to the housing. A shift lever operates a control shaft which extends into the housing parallel to the output shaft, and the control shaft supports a rotary cam which moves a spring biased clutch yoke for shifting the clutch sleeve between positive engaged and disengaged positions with respect to a drive gear rotatably supported by the output shaft. The rotary cam provides for spring biased overtravel of the lever operated control shaft and over center action between the engaged and disengaged positions.