| 摘要 |
<p>ROTATABLE DRIVE MEMBER FORMED FROM INJECTION MOLDED PLASTICS MATERIAL WITH PREFORM INSERT A rotary drive member such a gear or pulley that can be mounted on a shaft is formed by injection molding plastics material to envelop selected portions of at least one preform insert. Preferably two metal preform inserts are used to form a pulley that is a combination plastic and metal structure. One of the metal preform inserts is a tubular sleeve that defines portions of a hub of the pulley. The other of the metal preform inserts is an annular disc that defines portions of a radially extending web for rigidly connecting hub and rim portions of the pulley. The injection molded plastics material envelopes peripheral portions of the tubular sleeve as well as inner and outer edge portions of the annular disc, and defines a drive formation on the rim for engaging another drive member such as a gear or an endless belt. The annular disc has inner edge portions that extend into close proximity with outer surface portions of the tubular sleeve, and outer edge portions that extend into close proximity with the drive formation of the rim. The inner and outer edge portions of the annular disc, and the outer surface portions of the tubular sleeve have formations that help to establish rigid driving connections with the enveloping plastics material to provide a rotary drive member that can be formed quite inexpensively as a combination of metal and plastics materials, and yet is capable of transmitting relatively high torque for example between a shaft on which the member is mounted and a drive element that engages the drive formation of the rim.</p> |
