Belt conveyor
Belt reversing mechanisms configured to reverse a belt at an upstream portion and a downstream portion of a return belt of a belt conveyor, includes two sets of pinch rollers spaced apart from each other in a belt movement direction and configured to support the belt, and two sets of guide roller mechanisms spaced apart from each other in the belt movement direction and are configured to guide the belt in a tubular shape from outside between the pinch rollers such that the belt is reversed 180 degrees and twisted to cause a center portion of a span between the pinch rollers so as to form a tubular open cross-section with a dirty surface facing inward; and the belt between the two sets of pinch rollers forms a catenary curve or a curve close to the catenary curve.
1. A belt conveyor comprising:
an endless loop belt which is wrapped around pulleys at both ends thereof and is configured to revolve; and
a first belt reversing mechanism and a second belt reversing mechanism which are provided at an upstream portion and a downstream portion of a return belt, respectively, in a belt movement direction, and are configured to reverse the belt 180 degrees;
wherein each of the first and second belt reversing mechanisms includes two sets of pinch rollers which are provided so as to be spaced apart from each other in a belt movement direction and configured to support the belt, and one or more sets of guide roller mechanisms which are provided so as to be spaced apart from each other in the belt movement direction and are configured to guide the belt in a tubular shape from outside between the pinch rollers such that the belt is reversed 180 degrees and twisted to cause a center portion of a span between the pinch rollers to form a tubular open cross-section with a dirty surface facing inward; and
wherein the belt between the two sets of pinch rollers forms a catenary curve or a curve close to the catenary curve, the catenary curve being defined by a weight of the belt per unit length, a tension applied to the belt, and the span between the pinch rollers, and the guide roller mechanisms are provided at the belt forming the catenary curve or the curve close to the catenary curve.
2. The belt conveyor according to claim 1 ,
wherein the guide roller mechanism includes plural first guide rollers having center axes present in a first reference plane and plural second guide rollers having center axes present in a second reference plane which is spaced a predetermined distance apart from the first reference plane and is parallel to the first reference plane; and
wherein the first and second reference planes are provided to extend in a direction perpendicular to the catenary curve of the belt or a curve close to the catenary curve in a position of the guide roller mechanism.
3. The belt conveyor according to claim 1 , wherein the catenary curve of the belt between the two sets of pinch rollers is defined by the mathematical formula:
Y= ( T/W )×[cos h ( X×W/T )−1];where
T is a tension of the belt, and
W is a weight of the belt per unit length.
4. The belt conveyor according to claim 1 , wherein a center of the curve close to the catenary curve is defined by the mathematical formula:
δ= WL 2 /(8 T ); where
T is a tension of the belt;
W is a weight of the belt per unit length; and
L is a Length of the belt.
5. The belt conveyor according to claim 1 , wherein the catenary curve is formed between the two sets of pinch rollers along a length of the belt.
6. The belt conveyor according to claim 1 , wherein one set of guide roller mechanisms in the one or more sets of guide roller mechanisms is formed by three guide rollers having center axes that are arranged to form an equilateral triangle having a center disposed on the catenary curve formed by a center of the belt.