Dispensing measured quantities of materials for mixing into a larger batch

A method of mixing a plurality of different materials in small amounts into a bulk material comprising:

• providing a duct;
• providing a plurality of hoppers each containing a respective one of the different materials to be mixed;
• connecting each hopper to the duct so that material can be dispensed from the hopper to the duct;
• generating an air flow through the duct to carry the materials from the hoppers along the duct;
• controlling flow of material from each hopper to the duct through a respective air lock valve which prevents flow of air from the duct to the respective hopper and which is arranged to supply material from the hopper to the duct in an unmeasured stream to an unmeasured volume;
• providing a separator container in the duct such that the material in the duct carried by the air flow passes to the separator container;
• in the separator container separating the material from the air flow to deposit the material into the container while the air flow is discharged from the container;
• providing a mixing container;
• providing in the mixing container the bulk material into which the different material from the separator container are to be mixed;
• generating in the separator container a batch of at least one of the different materials to be mixed by:
• selecting a required one of the hoppers;
• operating the air lock valve of the selected hopper to supply material from the hopper to the duct in the unmeasured stream;
• controlling the air lock valve of the selected hopper so as to continue to discharge the material in the unmeasured stream up to a predetermined required weight as determined by the weighing of the material in the separator container;
• and when the predetermined weight is reached, as determined by the weighing of the material in the separator container, operating the air lock valve to halt the supply of material from the hopper to the duct in the unmeasured stream;
• and discharging the deposited material from the separator container into the mixing container for mixing with the bulk material therein.