Bicycle shock absorber with combined bearing shaft

Walking on a rigid prosthesis means that shock forces are transmitted directly to the body interface. Amputees attest to the importance of comfort above all other factors as crucial to a successful prosthesis. Daily activities, including golf and travel, involve frequent impact loads and body rotation. A rigid prosthesis transfers these loads directly to the skin as shear forces causing discomfort. The TT Pro absorbs and reduces these shear forces in the resilient rod and spring action. Originally a PTFE infused mesh bearing was moulded into the surface of a carbon fibre tube. This proved difficult to maintain effective tolerances and the bearing surface suffered from wear under load, which in turn produced play unacceptable to an amputee. The Z bearing is pushed into a collar in the shock assembly and moves on a titanium nitride coated stainless steel sleeve bonded onto an aluminium tube. A proprietary shaft seal further protects the bearing. The Z bearing proved to be the only polymer to withstand the high forces produced during not only walking but also sports activities for patients weighing up to 125kg. "The amputees describe the movement action as being 'super smooth'. It also allows the unit to work over a greater duration of the stride."

Clive Smart
Design Engineer
Blatchford Products