25 January, 2010

Patently Successful - Variable ratio steering for vehicles

Patently Successful - Variable ratio steering for vehicles

This last column is devoted to the work of one of Australia's most inspiring engineers. Arthur Bishop's inventions and the company he founded based on those inventions, Bishop Technology Group, are models of engineering excellence. Bishop successfully used the patenting system to build a world-renowned engineering design business providing engineers with the flexibility to experiment and drive technology forward.

Bishop started working as an aircraft engineer in the 1940s designing power steered undercarriages for military aircraft. After World War II he applied his skills to developing power steering systems for the automotive industry. In the 1970s he turned to automotive rack-and-pinion systems and started patenting his concepts. One of his most important patents is Australian Patent No. 462,162.

The patent describes a variable ratio steering system mechanism for a vehicle having a rack meshing with a helical pinion, the rack having a group of teeth at its centre of varying form and varying inclinations with respect to the axis of the rack, the teeth of the rack thereby meshing with the teeth of the pinion at varying effective pitch radii in a predetermined manner.

Back in 1971 variable ratio racks meshing with straight-cut (spur) pinions were known, but it was thought that a variable ratio rack meshing with a helical pinion was an impossible geometry. The use of a helical pinion enabled conjugate tooth meshing action to be achieved for up to a 50% ratio change in the rack and pinion steering gear.

Bishop, as can be attested by the number of articles written about him, is an inspiration to young engineers and an example of how thinking outside the square in engineering can drive change. His rack-and-pinion steering systems are now used in many vehicles internationally, including a wide range of Mercedes-Benz vehicles and the locally manufactured Ford Falcon. Bishop Technology Group has filed hundreds of patents for various steering-rated technologies and employs engineers in Australia, the United States, and Germany.

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