In the storage of bulk materials, considerable flow, capacity and headroom benefits are secured by the use of screw feeders serving extended length of hopper outlet slots and plane flow hopper walls. Plane flow wall angles for mass flow are about 10 degrees less that needed for conical hoppers and reliable flow is secured with slot widths half that needed for cone outlets. The combination of long outlet slots and lower wall inclination also offers increased holding capacity and/or lower headroom needs. However, to secure these advantages, the feeder must extract from the total area of the hopper outlet. Various screw designs are used to obtain ‘live’ flow, by progressively extracting product along the extended length of hopper outlet.
Some feeders used to discharge hoppers are reversible, to serve two different receiving points from a common hopper outlet or reject unsuitable product. These provide considerable headroom savings over bifurcated vales and twin inclined chutes but, unfortunately, existing design features that are used to extract progressively along the length hopper outlet slots adversely affect reverse feeding by excessively compacting the product. A hopper and feeder design can therefore be severely compromised if the feeder is required to reverse such that it was impossible to exploit the flow and storage benefits of an elongated hopper outlet and plane flow hopper section. A further limitation of conventional feeders is that the duty of serving two outlets is that their separate supply are mutually exclusive, the feeder only able to discharge to one or other receiving point. Unique features of the system described is that progressive extraction can be secured from a elongated hopper outlet slot when feeding in either direction in its simplest form and that, in a further arrangement, the feeder can supply either receiving point or both at the same time, without either loss of discharge rate or compromising the ‘live’ extraction from the elongated hopper outlet.
It is often crudely assumed that the axial transfer capacity of a screw is proportional to its swept volume of cross sectional area times pitch. The actual axial movement is also dependent on the frictional relationship between the product and the screw flight face. By varying the flight face friction on the working face of the flight in different axial locations it is practical to secure progressive extraction over an extended length of the screw. When the screw is reversed these surfaces are no longer exerting any influence on the movement of the bulk material and it is therefore practical to vary the contact friction on the ‘back’ face of the screw flights in a different axial location so that progressive extraction is obtained from the hopper outlet when running in either direction.
In a further extension of this development cantilever-mounted twin screws are mounted end-to-end facing each other in a common discharge casing. These have separate drive that each run at full speed when ‘pulling’ materials towards their outlet and half speed when ‘pushing’ the product to the opposing outlet. Treating the screw flights to exhibit variable surface friction on different regions of their front and back faces enables even longer lengths of hopper outlet slots to receive progressive extraction. A further benefit of this arrangement is that discharge can be made to either outlet point independently, or to both the outlets at the same time, without changing the speed of the screws or the rate of discharge made to either receiving point. This unique facility carries many site and operating advantages over present methods.
The attached pdf below shows a comparion of the "Lynflow" reversing feeder with the conventional method.
This invention received the Institute of Mechanical Engineersabout the institution Award for Innovation in 2015.
The Ingenious ‘LynflowTM’ Reversing Screw Feeder by Ajax Equipment Ltd.
The Ingenious ‘LynflowTM’ Reversing Screw Feeder by Ajax Equipment Ltd.
by Lyn Bates339 lyn bates.html,
Managing Director of Ajax Equiment Ltd.
In the storage of bulk materials, considerable flow, capacity and headroom benefits are secured by the use of screw feeders serving extended length of hopper outlet slots and plane flow hopper walls. Plane flow wall angles for mass flow are about 10 degrees less that needed for conical hoppers and reliable flow is secured with slot widths half that needed for cone outlets. The combination of long outlet slots and lower wall inclination also offers increased holding capacity and/or lower headroom needs. However, to secure these advantages, the feeder must extract from the total area of the hopper outlet. Various screw designs are used to obtain ‘live’ flow, by progressively extracting product along the extended length of hopper outlet.
Some feeders used to discharge hoppers are reversible, to serve two different receiving points from a common hopper outlet or reject unsuitable product. These provide considerable headroom savings over bifurcated vales and twin inclined chutes but, unfortunately, existing design features that are used to extract progressively along the length hopper outlet slots adversely affect reverse feeding by excessively compacting the product. A hopper and feeder design can therefore be severely compromised if the feeder is required to reverse such that it was impossible to exploit the flow and storage benefits of an elongated hopper outlet and plane flow hopper section. A further limitation of conventional feeders is that the duty of serving two outlets is that their separate supply are mutually exclusive, the feeder only able to discharge to one or other receiving point. Unique features of the system described is that progressive extraction can be secured from a elongated hopper outlet slot when feeding in either direction in its simplest form and that, in a further arrangement, the feeder can supply either receiving point or both at the same time, without either loss of discharge rate or compromising the ‘live’ extraction from the elongated hopper outlet.
It is often crudely assumed that the axial transfer capacity of a screw is proportional to its swept volume of cross sectional area times pitch. The actual axial movement is also dependent on the frictional relationship between the product and the screw flight face. By varying the flight face friction on the working face of the flight in different axial locations it is practical to secure progressive extraction over an extended length of the screw. When the screw is reversed these surfaces are no longer exerting any influence on the movement of the bulk material and it is therefore practical to vary the contact friction on the ‘back’ face of the screw flights in a different axial location so that progressive extraction is obtained from the hopper outlet when running in either direction.
In a further extension of this development cantilever-mounted twin screws are mounted end-to-end facing each other in a common discharge casing. These have separate drive that each run at full speed when ‘pulling’ materials towards their outlet and half speed when ‘pushing’ the product to the opposing outlet. Treating the screw flights to exhibit variable surface friction on different regions of their front and back faces enables even longer lengths of hopper outlet slots to receive progressive extraction. A further benefit of this arrangement is that discharge can be made to either outlet point independently, or to both the outlets at the same time, without changing the speed of the screws or the rate of discharge made to either receiving point. This unique facility carries many site and operating advantages over present methods.
The attached pdf below shows a comparion of the "Lynflow" reversing feeder with the conventional method.
This invention received the Institute of Mechanical Engineersabout the institution Award for Innovation in 2015.
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Attachments
lynflow_two-way_feeds (PDF)
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