Methods for positively-driving spiral conveyors

A method of driving a spiral conveyor having a conveyor belt and a drive having a plurality of drive members having a length extending in a vertical direction and that are spaced apart from and rotate about a vertical axis, the method comprising:

• rotating the drive in a drive direction about the vertical axis;
• establishing a point of positive engagement between the conveyor belt and a drive member such that the drive member imparts a non-frictional force to the conveyor belt without slip in the drive direction and such that the conveyor belt is configured to slide vertically along a portion of the length of the drive member as the drive member imparts the non-frictional force to the conveyor belt without slip in the drive direction such that the conveyor belt forms a helical path rotating in the drive direction;
• and
• driving the conveyor belt closer to the vertical axis as the conveyor belt is advanced in the drive direction such that a radial distance between vertical axis and the point of positive engagement of the drive member and the conveyor belt varies along the vertical axis as the point of positive engagement progresses along the helical path.

A method of driving a spiral conveyor about a generally cylindrical drive tower having a vertical axis of rotation, the method comprising:

• a) connecting a plurality of drive members to the drive tower, each drive member having a vertical length and a radial width where the radial width of each drive member varies along the vertical length;
• b) engaging a conveyor belt with the drive members at multiple points along the vertical lengths of the drive members such that the conveyor belt encircles the drive tower so as to form a helical conveying path that is located a first distance from the vertical axis at or after a start of the helical conveying path and is located at a second distance from the vertical axis at the end of the helical conveying path and wherein the first distance is greater than the second distance;
• and
• c) rotating the drive tower such that the drive members maintain positive engagement with the conveyor belt to drive the conveyor belt along the helical conveying path in a conveying direction while simultaneously preventing slip of the conveyor belt in the conveying direction.

A method of driving a spiral conveyor without slip comprising:

• a spiral conveyor having:
• a conveyor drive configured to impart rotational motion about a vertical axis;
• a plurality of drive members, each having a first end and a second end defining a length therebetween and wherein the plurality of drive members are positioned around the vertical axis;
• and
• a conveyor belt long enough to encircle the plurality of drive members a plurality of times;
• wherein the method comprises:
• rotating the drive members about the vertical axis in a drive direction;
• rotating the drive members to successively positively engage a portion of the conveyor belt at points of positive engagement at a first height along the vertical axis such that a plurality of drive members separates the conveyor belt from the vertical axis by a first distance measured between the vertical axis and the point of positive engagement with the drive member;
• continuing to rotate the drive members while the drive members maintain positive engagement with the conveyor belt such that the conveyor belt forms a helix about the vertical axis;
• disengaging each drive member from the conveyor belt at a second height along the vertical axis where each drive member separates the conveyor belt from the vertical axis by a second distance measured between the vertical axis and the point of positive engagement with the drive member just before disengagement;
• and
• wherein the first distance is greater than the second distance.

A method of adapting a cylindrical drive tower to drive a spiral conveyor without slip along a helical path of varying radial distances comprising:

• providing a generally cylindrical drive tower of uniform diameter and having a vertical axis of rotation;
• connecting to the drive tower, in generally parallel vertical orientations, a plurality of drive members, each drive member having a vertical length and a radial width wherein the radial width of each drive member varies along the vertical length;
• encircling the plurality of drive members with a conveyor belt so as to form a helical path about the drive tower wherein the helical path begins at an entrance and ends at an exit;
• and
• rotating the drive tower such that a drive member initially positively engages the conveyor belt at or after the entrance to the helical path such that the radial width of the drive member initially separates the conveyor belt from the vertical axis of rotation by a first radial distance;
• continuing to rotate the drive tower such that the drive member advances the conveyor belt past the entrance through positive engagement with the conveyor belt and allows the conveyor belt to slide vertically along the length of the drive member such that the varying radial width of the drive member separates the conveyor belt from the vertical axis by a second radial distance at a point along the helical path that is between the entrance and the exit;
• continuing to rotate the drive tower such that the drive member advances the conveyor belt to the exit through positive engagement with the conveyor belt and allows the conveyor belt to slide vertically along the length of the drive member such that the varying radial width of the drive member separates the conveyor belt from the vertical axis by a third radial distance at the exit;
• and
• wherein the first radial distance, the second radial distance, and the third radial distance are not all equal to one another.

A method of driving a spiral conveyor, comprising:

• rotating a plurality of drive members having a length extending in a vertical direction about a vertical axis;
• aligning a conveyor belt with an entry segment of at least one of the plurality of drive members;
• establishing positive engagement between the conveyor belt and at least one of the plurality of drive members in the entry segment;
• driving the conveyor belt along a helical path through the entry segment at a first distance from the vertical axis,
• driving the conveyor belt along a helical path through a tapered segment of the plurality of drive members adapted to separate the conveyor belt from the vertical axis by a distance decreasing from the first distance as the drive members rotate;
• driving the conveyor belt along a helical path through an exit segment of the plurality of drive members adapted to separate the conveyor belt from the vertical axis by a second distance, wherein the second distance is less than the first distance;
• disengaging the conveyor belt from at least one of the plurality of drive members.