A Screw Lifter is another design supporting the basic, tilt and position action necessary for a Lifter to operate. The Carriage is held at its two fulcrum points by supporting arms which are in turn supported by two large vertical support screws. The support arms are moved up and down by the turning action of the vertical support screws. The vertical supports are acted upon by the mechanics at the top of the Lifter. Like other Lifter designs, the tilting mechanism moves back and forth causing the Carriage to tilt through a tilt cycle. When the Carriage is tilted to one side the vertical support screw opposite the direction of tilt turns and raises the supporting arm up to meet the bottom of the tilted Carriage. Upon reversing the Carriage tilt direction, the process is repeated, allowing the other support arm to move up to the bottom of the Carriage.
This design is one of the most stable since the Carriage is supported by two arms extended from the vertical support screws. However, because of the size of the vertical support screws, it may be more expensive. The gears needed to turn the vertical support screws and the tilting mechanism is easily operated from a central rotating shaft, which is ideal for a wind powered source. This allows for gearing up or down the force transferred, easily matching the tilting and turning power requirements of the Lifter.
This design is ideal for very large installations. It moves the support mechanism off of the Carriage and simplifies its overall design while keeping the Tilt Assist Arms and other tilt assist support on the Carriage.
Screw Driven Lifter
Another design using motors can be seen in the section, Powered Lifter: Powered Lifter. The centrally located gear assembly has been replaced with electric motors. This would permit the vertical screws to be stationary and reduce the overall effort needed to position the Fulcrum Support Assembly beneath the Carriage. In addition the tilting can also be accomplished by placing a motor on the Pulley Assembly.
Notice, that, like all Lifters, there is no actual effort used to lift the Carriage. This may seem to be a play on words, but the effort required to tilt is the only force being applied.