The lower parallel flights of the auger within the funnel are produced to a constant pitch so that, when filled, each pitch has a precise and consistent volume. The auger drive rotates the auger at a preset speed to produce a continuous flow of product. The actual filling head comprises of the primary elements illustrated below. By moving the mouse pointer over the names below the illustration, elements within the illustration will change colour to identify each particular part.
1. Hopper containing the product to be dosed
2. Auger rotating vertically through the hopper and funnel to discharge product.
3. Funnel from hopper through which the lower section of the auger doses.
4. Scraper blade to assist powder feed by bringing product into the flights of the auger.
5. Auger drive mechanism.
The scraper blade rotates in the opposite direction to the auger and with the exception of the DigiFill range, is independently driven. Its purpose is to prevent any build-up that generally will form when running non-free flowing powders. The scraper blade extends right down to the neck of the funnel, ensuring that the auger flights are fully filled with product, and preventing cavitation (cavities that can other wise form within the product resulting in poor filling accuracy).
Non-free flowing powders
The auger illustrated is fitted with ‘over-flight’, this can be either a separate detachable component to provide ultimate flexibility, or can be part of the actual auger for dedicated applications.
An over-flight assists the flow of non free flowing products by providing compression into the auger flights, down to the neck of the funnel where the scraper blade feeds the flights of the parallel section of the auger.
With intermediate products, an auger with parallel flights would be normally be selected and no over-flight fitted, as compression could well cause unacceptable damage to the product. These types of product often have the tendency to dribble from the auger once it has stopped and therefore require back pressure to be applied by use of a lip or grid attachment to the bottom of the funnel.
Free flowing powders
Free-flowing powders require a positive means of cut-off to be fitted to the end of the funnel. This can be in the form of a scissor cut-off unit where two horizontal scissor blades close at the end of the funnel immediately a discharge has completed, or a single / double flap attachment (also fitted to outlet of funnel). Either method ensures a clean cut-off at the end of each discharge and prevents product dribble / seepage when the machine is not it a filling cycle. In general, the flap type cut-off is used when the filling machine is mounted above a bag making machine (form, fill & seal machine), allowing the auger and funnel to be extended down through the bag forming tube, and the scissor cut-off is used in applications where the auger filler is dosing into ready made bags / containers.
Spinner plate & Cowl
An alternative tooling option that usually would be fitted for handling particle type products is the Spinner plate & Cowl illustrated below.
Attached to the end of the auger is a spinner plate (disc), this is a saucer shaped disc designed to retain the product flow. All powders have an angle of repose, the angle at which a collapsing heap of powder will come to rest rather than continue to spread outwards. The angle for small smooth beads would be much greater than, for example, vermicelli. The distance between the bottom of the funnel and the spinner plate (the gap needed to allow unrestricted product flow) is defined by the product dose rate. The spinner plate is sized to prevent the powder dribbling over the rim of the disc once the auger has stopped, taking into account this gap and the powder’s angle of repose. As the spinner plate throws the powder outwards, a simple collection cowl funnels it to a size suitable for the aperture of the container to be filled. The use of a spinner plate results in a perfectly clean fill without the requirement for any additional cut-off devices.