| 摘要 |
A longitudinally retractable cover system for truck and trailer boxes has travel blocks mounted within a tube containing a rotatable threaded rod. Cover bearing hoops are attached to brackets mounted on the travel blocks. The rearmost hoop is supported on a drive block, the rest on slave blocks. The travel blocks may have wheels or rollers to aid smooth travel. The drive block may itself be threaded or have paired abutting threaded drive blocks. The hoops and cover are retractable under a front housing. When a doghouse is present, angled and level support rods raise the hoops on pulley wheels to clear the doghouse. The cover is a series of sections extending between hoops. Grommet bearing apertures in the sections, correspond to threaded posts in the hoops, to which they are attached by nut and washer. The system is more reliable than previous models and is fully retractable.
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