Flexible Fastener


  • General Construction
  • Seismic Retrofits
  • Medical Devices/Implants

In October 2005, Cal Poly was granted patent number 6,955,513 for a flexible fastener that embodies this revolutionary bolt and its applications. In July 31, 2007 additional claims were granted to Cal Poly for this invention under U.S. Patent number 7,249,923. The fastener is made up of a flexible shank which may be made up of any strong, yet flexible material, including torque-transmitting coupling material, Kevlar, nylon, steel cable, and rope. The threads encircle the core material and are bonded to it at two ends, along with a bolt head. As a result, the bolt can carry axial loads, and therefore, can be tightened like any other bolt. However, it is laterally compliant, allowing it to bend or move in shear when needed.

The bolt may be manufactured to be less or more flexible. This is a function of the flexibility of the core material as well as how tightly the threads are wound around the core material. It can be made in many different sizes, as small as 3/16th inch in diameter to as large as desired.

The fastener can be used for many different applications in different fields. In construction, it can be used for attaching parts that have non-parallel surfaces without a need for countersinks like in a truss. It can be used in repairing and re-furbishing of products and structures where holes do not line-up or are misplaced, and it can be used for retrofitting building for earthquake. It can also be used in earthquake-resistant buildings to allow lateral motions of structural components in response to earthquake-induced motions.

The flexible fastener can also be used in robotics applications where simultaneous lateral compliance and axial stiffness is desired in assembly operations. Similarly, the fastener can be used in medical applications such as in artificial knees, where bending is desired between different parts while they remain attached.

Please contact Jim Dunning at 805-756-5551 or jdunning@calpoly.edu in the Office of Research and Economic Development for more information or if you are interested in licensing this product.

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