According to the US Patent & Trademark Office: “The lifting beam includes an internal counterweight that is adapted to be hydraulically adjusted by use of a manually operated control mechanism.”

It added: “The lifting beam also includes a rigid elongated lifting tower to add stability to the lifting beam and includes a centralised storage cabinet, which stores control mechanism and increases the weight concentration and the overall stability of the beam.”

It also said that storage batteries and hydraulic control equipment are fully encased in the storage cabinet. “As the lifting beam is held by the crane cable and a swivel, the beam can be moved in three dimensions,” the Patent & Trademark Office said.

The inventors were issued US Patent Number 7,017,963 on March 28 2006.

The patent has been assigned to Selby Arm Inc., Bourbonnais, Illinois, US.

The original application was filed on May 17 2004.