ReChain positive locking mechanism

This page is part of the ReChain project. Short for Rebar CoreChain Systems. For an index of all pages of this project, see the category page ReChain.

An energetic barrier against loosening of a mechanical connection.
There are many ways to do this both in basic principle and concrete geometry of design.

Macroscale only:

• via magnetic holding forces

Macroscale and nanoscale:

• via clip-locks (may be energetically irreversible snapping or reversibly silent operable)
  

Nanoscale only:

• via van der Waals force (possibly notably simplifying nanomechanical system designs)
  Related: Intercrystolecular snapping modes
• via commensurately interdigitating surfaces acting as indexed notching with energy >>kT,
  (i.e. crystolecule parts melt long before they start slipping on each other in random brownian diffusion like motion)

Concrete designs

Indexed nut positive locking mechanisms

How it works

Prototype of a positive locking mechanism: Here optimized for FFF 3D printing. Locked can only be while tooth index jumps for the nut. Here 1/13th of a revoution. With an FFF printing friendly big thread-pitch of 3.6mm this makes for a bit less than 0.05mm per notch (46.15µm). – Large pitch is also atoms-as-lower-size-limit friendly for future stiff gem based nanosystems.

Prototype of a positive locking mechanism: Here the printed parts are layed out in exploded view. Note that in the alternative case that the screw would have ho frlat "cut off" sides the toothed thick-washer/spacer part needs to lock to the underlying surfaces instead of locking to the screw. This can be naturally and elegantly done e.g. via a hirth joint. No cutoffs from the screw would be natural for nanoscale strained shell helical structures). (wiki-TODO: Add another graphic with arrows / numbers / text … to the pic)

The lock-ring gets pushed up by a spring onto the nut. (Red TPU rubber in pic.)
Thereby reliably preventing the nut from undesired turning and loosening.

The lock-ring is prevented from rotating by rotationally locking to the
(in pic obstructed) spacer below the nut which in turn locks to flat of the screw.

Alternatively the spacer could lock to the the base via a RC/HirthJoint interface.
This seems even better because it does not depend on a flat screw.
(small diamondoid nanoscale screws can't really have their sides cut off)

(TODO: Things to improve from this first prototype: …)
– clearance need to be be given not only radially with a cycloid profile
– spring needs improvements: more clearance, more sturdy, make it twist instead of bulging
– earlier nuts where to weak but this one is too beefy – fatter screw or thinner nut?
– change the spacer to lock to base via a Hirth joint interface rather than locking to the screw

Usage examples

Example usage here as a connector fro parts manufactured (printed) in different orientations. Related topic: Benefits of post assembly over in place manufacturing.

Usage as a ReChain force hydrant
for tensioning a ReChain corechain in a ReCahin strut:

The idea in this specific context is to
avoid using the screw A directly for tensioning to:
– avoid application of high torques to the larger global structure
– avoid the necessity to transmit high forces to a frame assembling end-effector
– avoid the necessity of complex big gearing mechanisms at an frame assembling end-effector

Detailed description:
A specialized robotic end-effector pushes off the lock ring but before release of nut A into "freewheeling" (out of machine phase) the end-effector locks nut A to it's own internal wrench ring A. A second nut B inside the tool/end-effector gets (with no present counter-force) screwed onto the still overtsanding part of the screw (via internal wrench ring B), then gets locked. This second nut B (as part of the (de)tensioning end-effector) will serve as a handle to pull on with high force and thereby remove all tension load that is present on nut, A making it easy to turn. Pulling on screw B (with a counter-push on the lock-ring or the hull segment surface of the frame system behind) can be accomplished by a a high mechanical advantage mechanism inside the specialized (de)tensioning end-effectior (e.g. a nonlinear high mechanical leverage double hinge) Alternating operation of the two nuts A and B allows for arbitrary long range tensioning.

(wiki-TODO: This needs visualizations. Add scan of paper sketch here …)

Clip on indexed nut locking mechanism

(wiki-TODO: Add image and description. Pros & cons.)

Related

• Scale agnostic design principles => Positive locking

---

• ReChain
• ReChain tensioner
• ReChain force hydrant
• ReChain core chain

---

• List of machine elements

External links

• https://en.wikipedia.org/wiki/Positive_locking_device