The field of the invention is block assemblies for suspending equipment and things with cables and the like.
Block assemblies have long been used to provide a mechanical advantage to reduce the pulling force required to support the load being suspended. For example, when a pair of block assemblies are used together, a 2:1 mechanical advantage is gained. When two pairs of block assemblies are used together, a 4:1 mechanical advantage is provided. Additional mechanical advantage is achieved by increasing the number of block assemblies used. Alternatively, a single block assembly can be used as a pulley to support a load without any mechanical advantage.
In the motion picture industry, especially in the stunt business, equipment and other items are frequently suspended from above with cables or ropes over block assemblies. Typically, the block assembly is high overhead and is not easily seen or inspected. Stunt persons and other actors are also frequently supported by cables using block assemblies. Thus, safety is a great concern, particularly with the reliability of the block assemblies.
When block assemblies are used in the stunt business, there are frequently high performance, reliability and safety demands placed on the equipment used. Thus, there is a need for a block assembly that is capable of supporting very high loads at high rates of speed, while maximizing the safety and reliability of the device.