Thumb screws, wing nuts or knobs are usually hand tightened to secure parts that do not require large clamping forces. However, they are subject to undesirable loosening due to vibration.
There is a need for a more reliable hand tightened fastener that does not loosen.
The applied asymmetric thread design features a continuously inclined surface (a) (Fig.1) and a cylindrical profile that works with standard threads, providing secure, self-locking, vibration resistant connections, while eliminating the potential for fatigue failure.
A significant feature of this thread is its shallow incline. This incline (a) forms a wedge-like feature to hold parts in place when an axial force (clamping) is applied.
The asymmetric thread allows the mating fastener with standard threads to spin freely until a clamp load is applied. At that point, the crest of the standard thread slides against the ramp along the entire thread engagement length.
As the clamp load increases, the incline of the ramp is drawn tightly against the standard thread crest, eliminating the radial clearance. This results in a self-locking arrangement.
The VRTS eliminates the need for additional locking devices that hinder assembly or maintenance. It is also reusable.
This fastening arrangement (asymmetric thread coupled with a standard thread) is not limited to thumb screws, wing nuts or knobs. It can be applied to nuts and bolts (Fig. 2 and 3) in a wide range of industries where low clamping loads are applicable.
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