Linear mechanical drive with precise end-of-travel load positioning

A linear mechanical drive with precise end-of-travel load positioning comprising:

• a drive shaft having a threaded portion intermediate two non-threaded portions;
• motor drive means for reversibly turning said drive shaft;
• a threaded load carrier including load connecting means axially displaceable on said shaft from one to another of said non-threaded portions responsive to rotation of said shaft, said carrier disengaging from said threaded portion at said non-threaded portions to thereby precisely determine the end-of-travel positions of the carrier irrespective of drive shaft rotation;
• and
• thread follower means on said carrier, said follower means remaining in engagement with said threaded shaft section after disengagement of said carrier at one or both of said non-threaded sections for bringing said carrier into reengagement with said threaded section upon rotation of said shaft in one sense and for maintaining said disengaged carrier spaced from said shaft threads to avoid thread wear during shaft rotation in the opposite sense.

A linear mechanical drive with precise end-of-travel load positioning comprising:

• a drive shaft having a threaded portion intermediate two non-threaded portions;
• motor drive means for reversibly turning said drive shaft;
• a threaded load carrier including load connecting means axially displaceable on said shaft from one to another of said non-threaded portions responsive to rotation of said shaft, said carrier disengaging from said threaded portion at said non-threaded portions to thereby precisely determine the end-of-travel positions of the carrier irrespective of drive shaft rotation;
• carrier stop means on said shaft;
• thread follower means on said carrier comprising spring means in thread following engagement with said shaft, said spring means disengaging from said shaft thread during shaft rotation urging said carrier against said stop means, said follower spring means remaining in engagement with said threaded shaft section after disengagement of said carrier at one or both of said non-threaded sections for bringing said carrier into reengagement with said threaded section upon rotation of said shaft in one sense and for maintaining said disengaged carrier spaced from said shaft threads to avoid thread wear during shaft rotation in the opposite sense.

A linear mechanical drive with precise end-of-travel load positioning comprising:

• a drive shaft having a threaded portion intermediate two non-threaded portions;
• motor drive means for reversibly turning said drive shaft;
• a threaded load carrier including load connecting means axially displaceable on said shaft from one to another of said non-threaded portions responsive to rotation of said shaft, said carrier disengaging from said threaded portion at said non-threaded portions to thereby precisely determine the end-of-travel positions of the carrier irrespective of continued drive shaft rotation;
• first means for bringing said carrier into reengagement with said threaded shaft portion at each of said non-threaded portions;
• said carrier comprising two axially connected threaded segments, said load connecting means being attached to one of said segments, and means for adjusting the axial spacing between said segments so as to vary the effective length of said carrier, thereby to adjust at least one of the end-of-travel positions of said load connecting means in relation to the shaft axis;
• and
• means for adjusting the threading on one of said segments in relation to the other of said segments thereby to match the shaft threading during said axial spacing adjustment.

A linear mechanical drive with precise end-of-travel load positioning comprising:

• a drive shaft having a threaded portion intermediate two non-threaded portions;
• drive shaft support means for mounting said drive shaft to a supporting structure;
• motor drive means for reversibly turning said drive shaft;
• a threaded load carrier including load connecting means axially displaceable on said shaft from one to another of said non-threaded portions responsive to rotation of said shaft, said carrier disengaging from said threaded portion at said non-threaded portions to thereby precisely determine the end-of-travel positions of the carrier irrespective of drive shaft rotation;
• first means for bringing said carrier into reengagement with said threaded shaft portion at each of said non-threaded portions;
• and
• means for engaging said load connecting means to said supporting structure at one or both of said end-of-travel positions thereby to relieve said carrier of a load on said load connecting means while at said end-of-travel position.

In a transport vehicle having a cargo enclosure and a pull-up type door slidable within guide tracks between a closed and an open position for access to the cargo enclosure, the improvement comprising:

• a drive shaft rotatably mounted to said cargo enclosure, said shaft having a threaded portion intermediate two non-threaded portions;
• motor drive means for reversibly turning said drive shaft;
• a threaded load carrier including load connecting means connected to said door, said carrier being axially displaceable on said shaft between a first and a second of said non-threaded portions responsive to rotation of said shaft, said first position corresponding to said closed position of said door and said second position corresponding to said open position of said door;
• said carrier disengaging from said threaded portion at said non-threaded portions to thereby precisely position said door at said closed and open positions irrespective of continued drive shaft rotation;
• and
• first means for bringing said carrier into reengagement with said threaded shaft portion at each of said non-threaded portions.