Plastic pulley for driving drum for washing machine into rotation
A pulley comprising: a central hub; a peripheral crown; a first intermediate section comprising a plurality of radial ribs that radially extend from the hub, and a second intermediate section comprising a plurality of peripheral ribs that end into the peripheral crown and intermediate circular rib concentric with the center of the pulley and having a radius basically equal to half radius of the pulley, the circular intermediate rib separating the first intermediate section from the second intermediate section, the circular intermediate rib comprising connection points of radial ribs and of peripheral ribs, wherein the connection points of radial ribs are distant from those of the peripheral ribs; the peripheral ribs being suitably inclined mutually and with respect to the radial ribs in such way to intersect at least in one crossing point to form a web structure in the second intermediate section.
1. A plastic pulley for driving a drum for a washing machine into rotation, the plastic pulley comprising:
a central hub with a hole or slot to spline a shaft of a drum of washing machine;
a peripheral crown with a housing to receive as driving belt, said peripheral crown being provided with center and radius coinciding with center and radius of the pulley;
a first intermediate section comprising a plurality of radial ribs extending radially from the hub; and
a second intermediate section comprising a plurality of peripheral ribs ending in said peripheral crown, said peripheral ribs being inclined with respect to radial ribs;
wherein the pulley comprises:
a circular intermediate rib concentric with center of the pulley and provided with radius substantially equal to half radius of pulley, said circular intermediate rib separating the first intermediate section from the second intermediate section, said circular intermediate rib comprising connection points of the radial ribs and connection points of the peripheral ribs, wherein said connection points of the radial ribs are distant from said connection points of the peripheral ribs;
said peripheral ribs having suitable inclination both each other and with respect to the radial ribs, in such way that said peripheral ribs intersect each other at least in one crossing point to form a web structure in said second intermediate section.
2. The pulley of claim 1 , wherein each connection point of the peripheral ribs is situated on the circular intermediate rib in intermediate position between two connection points ( 40 b ) of the radial ribs.
3. The pulley of claim 1 , wherein two peripheral ribs with mutual inclination originate from each connection point of the peripheral ribs on the circular rib.
4. The pulley of claim 3 , wherein two peripheral ribs originate from each connection point of the peripheral ribs on the circular rib, being mutually inclined by angle higher than 90°, in such way that each peripheral rib crosses at least two peripheral ribs in two crossing points.
5. The pulley of claim 1 , wherein the pulley comprises at least one plate comprising of a substantially circular plate that covers said first intermediate section of the pulley and extends from the hub to the circular intermediate rib.
6. The pulley of claim 5 , wherein said plate comprises at least one tapered section, in order to obtain taper between the hub and the circular intermediate rib.
7. The pulley of claim 5 , wherein said plate comprises a plurality of openings situated between said radial ribs for air ventilation.
8. The pulley of claim 1 , wherein said peripheral ribs have T-shaped or tapered section from back to front.
9. The pulley of claim 1 , wherein the pulley is made of plastic material with elastic modulus higher than 14,000 MPa, charged with mineral or synthetic charges in percentage from 50 to 70%, preferably 65%.