It is also called Free Fall Mixer or Gratify Mixer. In this type of mixer, concrete is mixed by lifting the material with the help of a stationary blade inside a rotating drum and then dropping the material by removing the friction between the mix and the blade. Filling and emptying can be done by changing the direction of rotation, opening or tilting of the drum of the mixer. The rotation speed must follow machine-specific instructions carefully and not be too fast so that the free fall of the mixture is not hindered by centrifugal force.
Drum mixer is suitable for concrete that is not too hard; Typically used on construction sites with a drop of up to 50 mm. Truck mixers also use free fall mixing. As the material in the free fall mixer falls from a height, some corrosion of the aggregate occurs.
This type of mixer is used for the production of large quantities of concrete. These mixers are known for high production speed, low maintenance and ideal for slump concrete.
This Drum Mixer is available in following three variants:-
- tilting mixer
- reversible mixer
- non-tilting mixer
1. tilting mixer
Tilting mixers are typically trailer-mounted or otherwise portable, small to medium-sized mixers, used either as the main concrete mixing equipment on smaller sites or as auxiliary equipment on sites served by a concrete plant. Is. The drum has two axes: one around which the drum rotates and the other that serves to change from the loading and mixing position (drum opening) to the discharging position (drum opening down). This position change is done manually by the dump wheel (or handle in small mixers), while drum rotation is electric, gasoline or diesel driven. Drums are traditionally made of steel, but polyethylene drums are now offered for easier cleaning. Most mixers are of the side-dump type, but end-dump mixers are also manufactured. The material is typically loaded directly into the drum manually. There are sizable self-loading units equipped with tilting hoppers. After filling manually at ground level, the hopper is mechanically tilted and dumps the material into the drum. In some models a built-in mechanical drag shovel is optional to facilitate total loading into the hopper.
The drum is conical or bowl-shaped with internal vanes and the discharge is rapid and distinct so that these mixers are suitable for less workable mixtures and larger aggregates. The axis of the drum usually remains at an angle of 15 degrees to the horizontal during mixing.
Tilt Mixer provides consistent mixing with low operating and maintenance costs. Tilting drums are the most common type of drum mixer for small batches.
Tilting mixers can handle larger aggregates more easily and will discharge mixed concrete faster than non-tilting mixers.
2. reversible mixer
Reversible drum mixer is similar to non tilting mixer except that the same opening is used to connect components and discharge aggregate. The drum on a reversible mixer has a horizontal axis around which it rotates. In the mixing position, the drum rotates in one direction; Whereas for discharging, the rotation is reversed.
Typically self-loading, reversible mixers are medium-sized to large-sized units mounted on a two- or four-wheeled trailer for transport between sites. The mixer is equipped with a tilting hopper, as is sometimes found on a tilting mixer, or a hoist-like hopper that moves up and down on a small inclined set of rails and which opens at the bottom of the drum. Dumps the material through. A built-in mechanical skip is optional on many models to facilitate total loading into the hopper.
Most models of this mixer type are equipped with a water tank and meter, and optionally (larger models) with a built-in aggregate batcher.
3. non-tilting mixer
A non tilting drum mixer is one in which the axis of the mixer is always horizontal, and the discharge occurs by inserting a chute into the drum or reversing the direction of rotation of the drum.
Due to the slow rate of discharge, some separation may occur.
There are two openings at each end of the drum: one for feeding the ingredients, the other for discharging the mixture.