Patent ID: 7407150

Claim:
A hoist and suspension system for raising and lowering a load comprising: first and second rigid supports, one on each side of the load; a first inextensible line fastened to said first rigid support and passing over and under a plurality n a of pulleys including a pulley connected at a first end of a rigid beam which supports the load, said first line extending along said beam beneath the load, said first line passing to another plurality n b of pulleys including a pulley at said second end of said rigid beam and thence to a power source fixed to said second rigid support to which said first line is connected; a second inextensible line spaced adjacent said first line and fastened to said first rigid support and passing over and under the plurality m a of pulleys including a pulley connected at the first end of said beam, said second line extending along said beam and beneath the load, said second line passing to the plurality m b of pulleys including a pulley at a second end of said beam and thence to said power source fixed on said second rigid support to which said second line is connected; said first and second lines and corresponding pulleys producing mechanical advantages n a and m a on the first side of the load and mechanical advantages n b and m b on the other side of the load, respectively; said total mechanical advantage n a and n b of said first line being equal to said total mechanical advantage of m a and m b said second line expressed as: m a +m b =n a +n b said ratio of said mechanical advantages of one line being unequal to said ratio of said mechanical advantages of said other line expressed as: m a /m b ≠n a /n b whereby said load is raised and lowered by said power source without said lines or said beam passing over the load, and without rotation of the load about a horizontal axis perpendicular to said rigid beam, with a positive resistance to rotation that increases expressed as: |n a m b −n b m a |.