Trailer enclosure system with retractable roof frame

An enclosure system for a trailer bed surface comprising,

• a flexible tarpaulin for selectively covering a top,
• a support frame for supporting said tarpaulin between an extended position, wherein said tarpaulin extends substantially over said bed surface, and a retracted position, wherein at least a longitudinal edge portion of said tarpaulin is retracted to a position spaced vertically above said trailer bed to facilitate loading or unloading thereon, the support frame including a laterally extending roof frame section and a support assembly configured for mounting the roof frame section spaced a vertical distance above said trailer bed,
• the roof frame section including,
• a pair of generally parallel spaced elongated rafter support arms, the rafter support arms extending from a first inner end spaced towards said support arm to a second outer end, and a rigid purlin member spanning between and coupled to each rafter support arm second end,
• each rafter support arm being mounted for movement about a pivot axis between a lowered deployed position, wherein said rafter support arms extend laterally over at least part of the top of said bed surface and said purlin member orients substantially above one said trailer bed side, and a raised position, wherein said outer ends of said rafter support arms are inclined angularly upwardly from horizontal at an angle of between about 15° and 90°, and said purlin member is moved laterally inwardly over said top of said trailer bed,
• a lift assembly configured to resiliently bias the rafter support arms from said deployed position to said retracted position against downward forces selected less than a predetermined threshold force,
• an elongated spindle coupled to the longitudinal edge portion of the tarpaulin and being supported for movement in a substantially horizontal orientation,
• a drive for selectively journaling the spindle in rotational movement, whereby rotation of the spindle by the drive coils or uncoils the longitudinal edge portion of the tarpaulin about the spindle to position said tarpaulin between the extended and the retracted positions, and wherein the predetermined threshold force is selected as a downward rotational torque force of a combined weight of said spindle and coiled longitudinal edge portion of said tarpaulin at a force equivalent point along said rafter support arms intermediate said inner and outer ends.