Instantaneous acting thread locking mechanism 03 April 2013

Ingenieuruero Wolfgang Weiss (IBW), based in Ottobrunn, Germany, has introduced two innovations that it says offer solutions to specific engineering problems.

Instantaneous acting thread locking mechanism
A threaded fastener joint incorporating the Advanced Thread Locking Mechanism (ATLM) provides failsafe locked fastening for quick installation and de-installation. The ATLM incorporates a freewheel (roller clutch) that is securely installed in one of the two threaded members and detachably coupled with the engaged counterpart. While screwing the threaded members together, the freewheel allows free mating, including torqueing. Once the ATLM fastener is forced to unscrew by occurrence of torque in the undoing direction the freewheel locks instantly. Disengaging the members of the threaded joint requires decoupling of the freewheel by an ejector, preferably implemented in the wrenching socket.

ATLM fasteners have successfully passed the Junker test per DIN 65151 and DIN 25201 Part 4.

IBW points out that in contrast to commonly known self-locking threaded fasteners with integrated locking features, the ATLM fastener mates free running and thus torque values preset in the wrenching tool are not influenced by varying prevailing torque.

The locking of the threaded members takes place automatically, with an instant lock – meaning that there is no loss of preload by unscrewing of threaded members. In addition, the anti-friction coatings on the threads have no influence on locking torque.

The ATLM fastener produces stable retention (locking) torque with no limitation for the number of screw cycles – giving the potential for unlimited use of the fastener in respect to its self-locking capability. No extra locking hardware or retaining compounds are required to install the ATLM fastener.

Positive fit joint with compensation of radial and angular displacement

A shear load fastener subject to multiple installation cycles does not establish positive fit due to the necessary installation clearance. For a shear load joint involving more than one fastener, manufacturing tolerances and thus additionally required play are further detrimental effects on achieving the desired shear load transfer capability.

A core part of the Position Deviation Compensating Positive Fit Joint (PDC-PFJ) is a swivelling, double-spherical ring with corresponding surfaces at the structural (external) and at the fastener (internal) side, which results in each one of the two sphere segments having a differently placed centre at a common axis.

The arrangement of the two spherical radii and their centres is aimed at balancing the moments induced on the double-spherical ring by the lateral forces through shear load, regardless of the angle the double-spherical ring allows for compensating position deviation (radial and/or angular).

Additional benefits from using PDC-PFJ fasteners include:

• Positive fit in multi-fastener joints.

• It is a shear load fastener system free of lateral play.

• No differential movement between joined members.

• Enables fastener size reduction.

• Allows wider manufacturing tolerances (cost reduction).

• Reduces assembly time (cost reduction).

Claire Aldridge Deputy Editor t: +44 (0) 1727 743 889

Having spent a decade in the fastener industry experiencing every facet – from steel mills, fastener manufacturers, wholesalers, distributors, as well as machinery builders and plating + coating companies, Claire has developed an in-depth knowledge of all things fasteners.

Alongside visiting numerous companies, exhibitions and conferences around the world, Claire has also interviewed high profile figures – focusing on key topics impacting the sector and making sure readers stay up to date with the latest developments within the industry.