Enduralock Locking Header Bolt

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The Enduralock Locking Header Bolt is a mechanically locking, high vibration resistant fastener, that for maintenance is easily reversible and reusable. Application (or removal) only requires a standard hex socket. The components are manufactured through a forging and stamping process to greatly reduce the cost in production.

The Enduralock Header Bolt fastener employs a mechanical lock, which does not rely on friction, and it is highly vibration resistant. The washer consists of 3 components. The base component and the middle component have arms and features that allow for interlocking of the components at predefined angles. The angle between the arms is determined at the time of installation by the distance of the fastener to the manifold. An increased angle (arms more separated) is chosen for a smaller distance between the bolt and the manifold. A smaller angle would be chosen if that distance was larger. The assembled 2-arm washer is prevented from rotating during tightening or loosening of the bolt by the 2 arms abutting the manifold. Alternatively, the first and second component could be manufactured as a single component with a fixed angle of the arms for a specific engine block. The third washer component (which comes preassembled to the middle component) consists of 2 circular arms that extend axially away from their base. At the end of these arms there are radially inwardly directed teeth. These teeth engage with teeth on a serrated gear that is keyed into the bolt head (delivered preassembled). The gear component has an axial extension which is radially recessed in relation to the gear’s teeth. When a socket applies axial force, the three-piece washer is flattened. This disengages the teeth of the washer to the bolt’s attached gear by axially deflecting the washer teeth into the gear’s radial recess. The fastener is then free spinning, so an accurate preload can then be applied. As soon as the socket is removed, the third washer component springs back axially and reengages the bolt’s attached gear. This locks the fastener in rotation, as the washer components are locked in rotation (due to their abutment to the manifold) and the bolt’s gear component is locked to the washer’s components. The locking mechanism has been tested for aerospace applications, and in vibration testing it withstood 10X the aerospace requirement for a self-locking nut. It has also been cycled on and off 250 times.

The Enduralock Header Bolt fastener can be supplied either as a locking header bolt or as a stud with a locking nut. This technology can also be applied to other automotive applications such as brake rotor bolts.

In summary, the Enduralock Locking Header Bolt is a mechanically locking header bolt, that is reversible and reusable with a standard hex socket.


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  • Name:
    Harold Hess
  • Type of entry:
    Team members:
    Dr. Harold Hess
    Deeptesh Selvaraj
  • Software used for this entry:
  • Patent status: