As a start:

http://www.oldselevator.com/downloads.php

Regards,

Lyle ■

It is good to learn that you are studying the important subject of materials handling and would wish to give you my best assistance. Bulk materials handling has to take account of the behaviour of the material, so it is not as straightforward as mechanical normal engineering.

The Old's elevator has two main mechanisms that affect both the elevating rate and the power consumption. The rotor at the inlet scoops the particulate material into the casing whilst material on the blades of the static screw material moves up the axis, driven by frictional drag of the material lining the space between the tips of the screw flights and the inner wall of the casing. The latter mechanism limits what the elevator can transport, so if the rotor tries to gather in excess of this amount it wastes energy. Designing the optimum balance is determined by the manufacturer, but certain clear principles apply.

Considering the elevating mechanism of the screw, interface boundary friction between the material lining the casing and that moving up the inclined flight determines the driving force whereas the resisting force is contact friction on the face of the screw flight. The energy adsorbs by flight face contact friction of moving up an inclined plane is one component of the work content of elevating and the gain in potential energy is another. The swept volume of the screw flight is the maximum volume that can be in motion, there being no back-leakage as with conventional screw elevators but the axial advance per revolution of the casing is determined by the combination of the flight tip helix angle and the angle of contact friction with the flight face. ( Note that the value of the internal angle of friction of the bulk material determines the power lost in shear at the boundary interface, which transfers the elevating power requirements, but does not influence the helix angle at which the screw contents move.

The inlet scoop has to shear through the bed of material in the feed hopper and move the product inwards to the screw. The shear stress depends on the hopper feed over-pressures, material characteristics and geometry of the device, and is separate from the elevating power requirement. These features preclude standard drive calculations being published, but pose an interesting exercise for students in bulk technology.

A paper outlining the mechanics of helical screw mechanics is given in an early paper I presented at a Boston conference. ‘Entrainment pattern of screw feeders’ published in the A.I.Mech.E. Jrnl of Engrs for Ind.. 1969 PP 205 – 302

I include some notes by email on the operating features involved with this equipment that I hope is useful and would be pleased to learn of your work on this topic as I may be able to send some background notes on bulk handling generally.

, ■