There are two methods of discharging in continuous working—­the sugar is thrown out periodically as the basket fills, or continuously.  In neither case is the speed slackened.  In the first either the upper half of the basket has an upward motion, on the lower half a downward motion (Pat. 252,483); and through the opening thus made the sugar is thrown.  Fig. 22 (R.B.  Palmer & Sons) is a machine of this kind.  The bottom, B, with the cone distributor, a, have downward motion.

[Illustration:  Fig. 22.]

Continuous discharge of the second kind may be brought about by having a scoop fixed to the curb (or casing), extending down into the basket and delivering the sugar over the side (Pat. 144,319).  Another method will be described under “Beet Machines.”

BASKET.—­The construction of the basket is exceedingly important.  Hard experience has taught this.  When centrifugals were first introduced, users were compelled by law to put them below ground; for they frequently exploded, owing to the speed being suddenly augmented by inequalities in the running of the engine or to the basket being too weak to resist the centrifugal force of the overcharge.  Increasing the thickness merely adds to the centrifugal force, and hence to the danger, as even a perfectly balanced basket may sever.

One plan for a better basket was to have more than one wall.  For example, there might be an inner wall of perforated copper, then one of wire gauze, and then another of copper with larger perforations.  Another plan was to have an internal metallic cloth, bearing against the internally projecting ridges of the corrugations of the basket wall.  A further complication is to give this internal gauze cylinder a rotation relative to the basket.

The basket wall has been variously constructed.  In one case it consists of wire wound round and round and fastened to uprights, commonly known as the “wire basket;” in another case of a periphery without perforations, but spirally corrugated and having an opening at the bottom for the escape of the extracted liquid; in still another of a series of narrow bars or rings, placed edgewise, packed as close as desired.  An advantage of this last style is that it is easily cleaned.

The best basket consists of sheet metal with bored perforations and having bands or flanges sprung on around the outside.  The metal is brass, if it is apt to be corroded; if not, sheet iron.  The perforations may be round, or horizontally much longer than wide vertically.  One method for the manufacture of the basket wall (Pat. 149,553) is to roll down a plate, having round perforations, to the required thickness, causing narrowing and elongation of the holes and at the same time hardening the plate by compacting its texture.  Long narrow slots are well adapted to catch sugar crystals, and this is not an unimportant point.  Round perforations are usually countersunk.  Instead of flanges, wire bands have been used, their lapping ends secured by solder.