In the "Cropp" Mixer—a batch machine— the drum is rotated by gearing which meshes with the teeth on two circumferential racks on the drum. Charging is done at the base of the drum, instead of above its center. In the interior of the drum, in the center, is a V-shaped plow; and fastened to the sides of the drum are blades mounted at an angle, which throw back toward the center the material cast upon them by the central V-shaped plow. The discharge chute, during the mixing process, is covered by a door controlled by a lever on the outside of the drum. By throwing the lever, the door is drawn back across the plate on the wall of the drum, so that the material is lifted by the door and discharged into the chute.
The "Illinois" Mixer is essentially a bateL, machine, but has some features of the continu ous type. It is described by its proprietors as a "continuous automatic batch mixer." The ce ment and aggregates, in properly measured quantities, are shoveled into a hopper operated by a crank piston; this hopper hoists and auto matically dumps them into the mixer proper, where they are cut and turned and mixed by rapidly revolving pugger flukes, which run con tinuously and which push the material along to the discharge.
In the "Multiplex Mixer," the long cylindri cal drum is mounted horizontally, and has a hinged door on its side, the full length of the drum. The drum revolves on roller bearings, and is operated by means of a sprocket chain connecting the sprockets cast on the head of the drum with a small sprocket wheel driven by large and small pinions. The latter are set on
the frame with adjustable bearings for tighten ing OT slackening the chain as the occasion may require. The water tank is mounted in an ele vated position at the head of the drum, and the supply controlled by a stop-cock, the water being spread over the contents of the mixer by two perforated pipes connected with the common pipe outlet to the tank. One end of the mixer is mounted on wheels, while on the opposite end are drop handles. By this arrangement the ma chine can be readily moved like a wheelbarrow.
In the "Baldwin" Improved Hand-Power Mixer, the hollow cylindrical drum is mounted diagonally on its axis of revolution, being op erated by a large rack and small hand-turned pinion.
Among other important types of mixers on the market, are the "Coltrin;" the "Gauntt" (combined type); the "Systematic;" the "Ol sen" Batch; and the "Marsh-Dexter." Concrete Material Washers. Special ma chines are built for the washing of sand, gravel, and crushed stone. They operate somewhat after the manner of mixing machines, by agitat ing the material in an excess of water. In the "Stocker" Washer, which is power-driven, the agitator revolves in a horizontally mounted cylindrical tank.
A concrete mixer may be used for washing sand and other aggregates. The mixer, in such a case, is simply charged with the material, and then water is turned in until it overflows at discharge. The machine is then set in operation, and the supply of water kept up, the impurities being carried off in the overflow.