Twin Shaft Concrete Mixers

Extra-rigid tank
The stiffened frame of the tank eliminates the risk of deformation during the transport (also in container) as well as during the full load operation and guarantees the correct planarity of the shafts’ seals. The metal frame for aggregates hopper and the scales can be laid right on the mixer without additional supports.

Mixing elements
The mixer tank is lined with interchangeable tiles of cast iron with a minimum hardness of 530HB and 15 mm thickness. The mixing arms, with a low profile to avoid material build up, are made by Spheroidal Cast Iron. The mixing blades are made by Ni-Hard Cast Iron of 530HB minimum hardness. The large number of blades, their position and their orientation guarantees the right combination between the effects of rolling and circulation of the material during the mixing action

Gear boxes
The gearboxes of the mixing group are epicyclical type. The first reduction is carried out by a pulley transmission equipped with a constant-velocity universal joint to keep the shafts synchronized. The low input speed to the gearboxes allows the lubrication oil to work at low thermal load. The connection between the gearbox and the tank is made with the exclusive bell housing. This unique feature gives a better rigidity to the coupling between the gearbox and the tank and makes the assembly and the possible maintenance of the bearings and the seals extremely easy.

Shaft supports and seals
The modular support patented by SICOMA is made with two separate housings. The bearing outside of the mixing tank are immersed in a long-lasting oil bath. The shaft seal, based on the exclusive system of the counter-rotating disks, is lubricated with liquid grease under controlled pressure.

Discharge door
The discharge door is driven by a hydraulic power pack system. The closing of the door is guaranteed by the pressure sensor included in the hydraulic circuit. In case of failure or blackout, a manual pump can be operated for an emergency discharge.

The discharge door has a rubber seal that runs along its full perimeter. The eccentric rotation of the door sector guarantees that the rubber seal is always reached and compressed despite its wear and tear.

Automatic lubrication
The grease needed by the seal to keep the counter-rotating surfaces lubricated is supplied by four (4) independent automatic pumps that keep a constant pressure into the housing. They uniformly and accurately dispense the necessary quantity of grease and guarantee a low grease consumption (less than 0.03kg/h) together with a low contamination of the mixing. A high performance filter removes potential impurities that can enter the circuit when the grease container is refilled.

Alarm box
The mixer is equipped with several sensors: thermal sensors for the motors and for the gearboxes, level gauges for the oil of the gearboxes and for the hydraulic power pack, level and pressure sensors for the automatic lubrication system. Upon request, PROTEM can supply a special electronic controller called «MIXER MIND" to which all sensors and the grease system are connected. The controller informs the operator of the type of each possible malfunction or alarm and signals to the plant automation. Through the controller, the operation of the automatic lubrication can also be programmed according to the particularities of each installation.

Mixer’s cover
The high top cover (500mm) is equipped with two hinged hatches and does not have any post. It allows easy access to the mixer for an accurate cleaning at the end of the shift or for both preventive and unscheduled maintenance resulting in a shorter shutdown time of the plant.

The twin shaft MAO series of SICOMA consist of the following available models: 

The mixers MAO can be equipped with the following accessories upon request.

• SKIP HOIST. The loading skip for the aggregates is available for the MAO mixers up to the size of 6000/4000. The hoist has two grooved drums on the same shaft. The skip cable has an anti-free-fall block in case of cable failure while two limit switches constantly check its tension. Upon request, the double speed for ascent and descent is available.
• Discharge Chute
• Dust Collector Bag (Airbag)
• Pre-assembled Feeding system with aggregates holding hopper, cement scale, water scale, complete with the holding frame laying on the four sides of the mixer tank.
• Dual unloading door.
  The mixer can be delivered equipped with two independent discharge doors to unload the concrete at two different points. This way you overcome the most basic limitation of double-axle mixers!
• REDUCED DISCHARGE DOOR. The reduced size of the discharge door allows the use of a small discharge chute. As a consequence, the supporting structure of the mixer can be shorter compared with the standard twin shaft mixers.
• DOUBLE DISCHARGE DOOR. The mixer can be equipped with two independent discharge doors to pour the concrete in two different places. One of the limitations of the twin shaft mixers is then a thing of the past!