Volumetric CH and gravimetric CHW, CHY dosers are suitable machines to dose various kinds of powder products, even if they are poorly flowing, cohesive and sticky. They can be used also for granular products or flakes, pellet and fibers with particle size up to 20mm. 

The dosing tool is constituted by an horizontal screw. Different types of screws are available, they are interchangeable, to be chosen according to the dosing products characteristics. The carpentry made dosing screws can have different shapes, obtained using square or round section spirals and flat helix, also with welded central shaft. The dosing screws can be manufactured with different pitch geometry: square, long or reduced and with single or double principle so allowing to optimize the doser performances even using products with different characteristics .

Machined out manufactured dosing screws are also available with full flight profile, lowered diameter or concave geometry . Also in this case it is possible to have different pitch geometry types: square, long, reduced, with single or double principle. 

The front side of the doser from which the product comes out has an outlet tube, which contains the terminal part of the dosing screw. The tube is flanged to the body of the doser and it can be removed to allow the dosing screw dismantling. The dosing screw is fixed to the gear motor shaft through a threaded or bayonet connection. 

The body of the doser has a trough shape with a specific geometry suitable to house both the dosing screw and a horizontal agitator. This last one action is fundamental to avoid the formation of bridges that can occur mostly with compact and poorly flowing products. The horizontal agitator also feeds the dosing screw regularly and constantly, which is very important in order to have a good dosing repeatability. 

There are different horizontal agitator models to choose according to the product characteristics. They can be equipped with different stirring tools such as blades, ploughshares, combs, helix and combination of these types. 

The body of the doser is completely openable removing the front flange which is tightened with nuts and bolts. In this way it is possible to have access to the dosing screw and to the horizontal agitator that can be easily removed to be cleaned and sanitized. 

Are also available versions equipped with knobs and safety microswitch, instead of bolts and nuts, that allow to open the body of the doser more quickly. This arrangement is useful when the cleaning operations are frequent, as it happens for example in the food sector or in all the cases where the contamination among different products is not allowed. 

Vertical T spouts complete the set of this kind of dosers. They are mounted at the end of the front outlet tube to vertically guide the product falling down while dosing. Discharges equipped with automatic plug, slide or butterfly valves are also available. These devices have the function to intercept the product while falling down. In the batch dosages they are particularly suggested to obtain the maximum accuracy and in general to avoid the spontaneous product leakage, especially if very free flowing , when the doser is on break. 

The transmission groups that move the dosing screw and the horizontal agitator are constituted by worm type gearboxes and three-phase electric motors. In cases where a very wide throughput range is required (the range between the minimum and maximum dosage capacity is more than 1 to 10) brushless type motors are used, that allow very slow rotation speed so as to achieve very small capacities. 

The shaft mechanical seals are made with shielded bearings and dust tight rings available in various materials such as NBR, SILICONE, PTFE and VITON. Air flushed sealing groups are also available for the hardest cases. 

Atex certified motors are available eventually equipped with a temperature probe and an anti-condensation heating devices when it is requested. 

The dosing screw motor can be controlled by a frequency converter, and can be eventually servoventilated. The brushless type motors are controlled by their specific digital servo-drive. Using these controlling devices it is possible to regulate the rotation speed of the dosing screw in order to obtain the wanted capacity in a predefined minimum and maximum range. The real achievable capacity range depends also on the characteristics of the product to dose. Using asynchronous motors generally it can be covered a range from 1 to 8 between minimum and maximum. The adjustment range can increase until 1 to 30 using brushless motors. 

The transmission groups can be equipped with a device for detecting the direction of rotation of the dosing screws and of the horizontal agitator. The device is made of an inductive sensor and a flap keyed on the slow shaft of the gear motor. Everything is protected by an aluminum restraint box with a transparent polycarbonate sight glass. 

The entire dosers range CH, CHW and CHY is constituted by 12 standard sizes that allow to cover a range from a minimum 0,1 Kg/h to a maximum of 10.000Kg/h. 

It is possible to associate to the dosers a wide variety of standard loading hoppers with different capacities. 

The hoppers can have a polygonal or truncated conical, symmetrical or skewed shape and their design ensure a correct out flow and complete emptying even with poorly flowing products. The polygonal hoppers have rounded corners to allow a complete and easy cleaning; they can be equipped with wide transparent polycarbonate sight glasses and inspection window as needed. The hoppers truncated conical shaped can have a vertical agitator, which is useful for particularly compact products, that stick to the walls and have to be forced to come down the dosing body. Agitators with different geometric shape are available to choose according to the product characteristics. 

The hoppers can be manually or automatically loaded. 

The hoppers loaded manually have a completely removable lid or semi-openable with hinges. Inside it there is a safety grid which protects from the risk of contact with moving parts of the doser and prevents the accidental access of foreign matter that could damage the doser. 

The hoppers automatically loaded have bolted lids with a round inlet and a vent socket equipped with a bag in polyester filtering fabric sleeve. 

As accessories of the hoppers there are level sensors, to detect the presence of product, and pneumatic vibrators or moto vibrators to prevent the formation of bridges. The most used sensors are capacitive types, rotary level sensors, vibrating level switches to choose according to the product characteristics. 

In the gravimetric version, the doser can be installed on a proper platform scale(CHW) or hung to load cells with its hopper (CHY). The load cells are off-center or flexion type, made in aluminium or in stainless steel with protection grade up to IP67, available also with Atex certification when requested. 

The most used construction materials are stainless steel Aisi 304 and 316L, but it is also possible to provide carbon steel on request. 

The surfaces in contact with the product can be easily pickled or mirror polished in case of poorly flowing products. It is possible to have certifications of the contact materials on request. 

The external surfaces are satin finished 180 mesh. It is possible to have them glass bead blasted or electro-polished on request. 

The gaskets are made in dust-tight rubber , such as SBR or NBR. They are available also with FDA certification on request. 

Both volumetric CH and gravimetric CHW and CHY dosers can be Atex 21/22 and Atex 21/21 certified, if required. 

Electrical control panels can also be supplied including software specifically designed according to the requested functionality.