Shrinkage Compensating Seismic Restraint Device
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Solution Overview
Problem
Existing seismic restraint systems in wood building construction, particularly those using ratcheting split nut devices, fail to maintain a tight connection due to inherent slack and lack of constant restraint force, unlike spring-activated devices which provide continuous tension through shrinkage compensation.
Innovation Solution
Combining the principles of spring-activated and ratcheting split nut devices by attaching the split nut housing to the upper end of a spring-operated TUD, allowing the split nut to be slid down over a threaded rod in a ratcheting fashion, with relative rotation of cylindrical components to maintain full thread engagement and constant restraint force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a ratcheting split nut device is used, then installation is simplified and the device can be slid down easily, but inherent slack remains and constant restraint force is not maintained
Solution Approach 1:
The patent combines a spring-activated TUD mechanism with a ratcheting split nut device into a single integrated unit. The spring-activated portion provides continuous tension and eliminates slack through shrinkage compensation, while the ratcheting split nut portion maintains ease of installation by allowing the device to be slid down easily. The two mechanisms work together synergistically to resolve the contradiction between installation simplicity and connection tightness.
2Reliability
If a spring-activated TUD is used, then constant restraint force is maintained through shrinkage compensation, but the device complexity increases with threaded cylinders and spring mechanisms
Solution Approach 1:
The patent merges the spring-activated TUD mechanism with a ratcheting split nut device, where the split nut housing is attached to the upper end of the spring-operated TUD. This integration allows the complex spring mechanism to be housed within a simpler external structure that resembles a conventional ratcheting device, reducing the perceived complexity while maintaining the constant restraint force functionality.
3Manufacturing precision
If relative rotation of cylindrical components is used, then thread registry is maintained and shrinkage is taken up, but the mechanism requires precise alignment and activation pin removal
Solution Approach 1:
The activation pin is pre-installed in the aligned holes of the inner and outer cylinders during manufacturing, ensuring precise alignment is already achieved before installation. The pin prevents premature rotation during handling and installation. The installer simply needs to remove the pin (a single simple action) to activate the shrinkage compensation mechanism, rather than needing to perform complex alignment procedures on-site.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The combined device ensures tighter connections and eliminates slack by utilizing relative rotation and expansion to maintain thread registry, effectively taking up wood component shrinkage over time, simplifying installation and maintaining consistent tension.
Implementation Method 1
A coil spring is tightly wound and connected to the two cylinders in a way tending to cause relative rotation of the cylinders, rotating the inner cylinder along the threads so as to extend upwardly and outwardly from the outer cylinder.
Implementation Method 2
A threaded nut on the rod is tightened to bear down against the inner cylinder
Implementation Method 3
tension is applied via a threaded rod through the height of several floors
Data Source
AI summary
A shrinkage compensating device for seismic restraint in wood building construction combines a spring-operated take-up device (TUD) with a ratcheting split nut. The split nut, attached to or formed as part of a rotatable component of the TUD, acts as the securing nut for the TUD and allows the TUD with the split nut to be slipped over the top of a threaded rod and pulled down along the rod into place against a structural member. Several forms of attachment of the split nut to the spring-operated TUD are disclosed, as is a simplified rotatable split nut version.