Screw conveyors, augers, and flighting for use therein

Apparatus for producing continuous rolled flighting suitable for use in screw conveyors and augers, the flighting including a continuous helical blade having radially spaced inner and outer helical edges, the continuous helical blade being formed integrally by (i) an inner helical portion which extends radially from the inner helical edge to a predetermined intermediate radius, (ii) an intermediate helical portion which extends radially from the predetermined intermediate radius portion and (iii) an outer helical portion , the transverse thickness of the continuous helical blade in the inner helical portion decreasing gradually from a maximum value at the outer edge to a minimum value at the intermediate helical portion, and the thickness of the continuous helical blade in the outer helical portion tapering outwardly to at least 150% of the minimum thickness of the flighting between the inner and outer edge of the helical blade;

• the apparatus comprising:
• (a) a pair of opposed, mutually-inclined conical rolls of which at least a first of the conical rolls has a stepped conical rolling surface divided by graduated diameter-reducing steps progressing from an apex conical section of the rolling surface to an intermediate conical section of the rolling surface to a base conical section of the rolling surface thereby upon rolling a helical blade from a metal strip to produce pressure differentials in adjoining inner, intermediate and outer helical portions respectively of the helical blade;
• (b) a driver for rotating the conical rolls in complementary directions;
• (c) an introducer for introducing a continuous metal strip of substantially rectangular cross section and substantially constant height between the rotating conical rolls thereby causing the metal strip to be converted by the rotating conical rolls and the pressure differentials exerted on the metal strip into a helical blade constituting said continuous rolled flighting, the inner helical portion being formed by the apex conical section of the stepped rolling surface, the intermediate helical portion being formed by the intermediate conical section and the outer helical portion being formed by the base conical section of the stepped rolling surface and projecting outwardly on at least one side of the helical blade relative to an adjacent surface of the intermediate portion of the helical blade;
• and
• (d) a receiver for receiving and supporting the flighting upon emerging from the conical rolls;
• wherein the conical rolls and the diameter-reducing steps of the first conical roll are constructed and arranged such that the conical rolls alone convert the continuous metal strip into said continuous helical blade, without substantially reducing the height of the metal strip and without a simultaneous application to the metal strip of pressures directed transversely to the pressures exerted on the metal strip by the conical rolls.

A method of producing continuous rolled flighting, the flighting including a continuous helical blade having radially spaced inner and outer helical edges, the continuous helical blade being formed integrally by (i) an inner helical portion which extends radially from the inner helical edge to a predetermined intermediate helical portion, (ii) the intermediate helical portion having a generally constant thickness and (iii) an outer helical portion increasing in thickness less gradually than the inner helical portion and which extends from the intermediate helical portion to the outer helical edge, the transverse thickness of the continuous helical blade in the inner helical portion decreasing gradually from a maximum value at the outer helical edge to a minimum value at the intermediate helical portion, and the thickness of the continuous helical blade in the outer helical portion tapering outwardly to at least 150% of the minimum thickness of said flighting in said intermediate helical portion;

• the method comprising the steps of:
• (a) providing a pair of opposed, mutually-inclined conical rolls having their respective axes of rotation disposed in transversely offset planes with the axes of rotation having no common point of intersection of which at least a first of the conical rolls has a stepped conical rolling surface divided by graduated diameter-reducing steps progressing from an ‘apex’ conical section of the rolling surface to an intermediate conical section and said intermediate conical section progressing to a ‘base’ conical section of the rolling surface thereby upon rolling a helical blade from a metal strip to produce pressure differentials in adjoining inner, intermediate and outer helical portions respectively of the helical blade;
• (b) rotating the conical rolls in complementary directions;
• (c) introducing a continuous metal strip of substantially rectangular cross section and substantially constant height between the rotating conical rolls thereby causing the metal strip to be converted by the rotating conical rolls into a helical blade constituting said continuous rolled flighting, the inner helical portion being formed by the apex conical section of the stepped rolling surface, the intermediate helical portion being formed by the intermediate conical section and the outer helical portion being formed by the base conical section of the stepped rolling surface and projecting outwardly on at least one side of the helical blade relative to an adjacent surface of the intermediate portion of the helical blade;
• and
• (d) receiving and supporting the flighting upon emerging from the conical rolls;
• the conical rolls and the diameter-reducing steps of the first conical roll being operative such that in performing step (c) the continuous metal strip is converted by the conical rolls alone into said continuous helical blade, without substantially reducing the height of the metal strip and without a simultaneous application to the metal strip of pressures directed transversely to the pressures exerted on the metal strip by the conical rolls.