Frangible Mold Safety Strap to Prevent Bolt Shearing
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Solution Overview
Problem
Existing mold straps, particularly metal ones, suffer from bolt shearing issues during molding cycles, leading to unsafe conditions as they cannot be easily removed from the mold, and plastic straps lack sufficient strength.
Innovation Solution
A mold safety strap with an engineered break point that breaks before the fasteners shear off, featuring a frangible section with reduced material thickness or recesses, ensuring the strap is easily identifiable when broken and can be replaced without disassembling the mold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a metal mold strap is used to secure mold halves together, then the strap has comparable strength to plastic straps, but the bolts holding the strap to the mold halves may shear during operation
Solution Approach 1:
The strap is divided into a strong body portion and a frangible section with reduced material thickness. The frangible section is positioned to break first under excessive load, preventing bolt shearing. This segmentation allows the strap to maintain overall strength while providing a sacrificial weak point that protects the fastening system.
Solution Approach 2:
The frangible section is pre-engineered with reduced material thickness to create a predetermined failure point. This beforehand cushioning mechanism ensures that when overload occurs, the strap breaks at the designed location rather than causing bolt shearing, thereby protecting the more critical fastening components.
2Ease of repair
If a plastic mold strap is used to secure mold halves together, then the strap is easier to replace, but the strap lacks comparable strength to metal straps
Solution Approach 1:
The strap utilizes parameter changes in material thickness along its length. The body portion has full thickness for maximum strength, while the frangible section has reduced thickness to enable controlled breaking. This parameter variation allows the strap to achieve metal-like strength where needed while maintaining ease of replacement through a simple break-and-replace mechanism.
3Reliability
If the strap breaks visibly before bolt shearing, then the failure is evident and replacement can be made, but the strap must be designed with a frangible section that breaks at a specific strain value
Solution Approach 1:
The strap incorporates local quality variations through the frangible section with reduced material thickness. This localized weakening is positioned specifically at the frangible section rather than uniformly throughout the strap. The local quality change creates a predetermined break point that provides visible failure evidence while maintaining overall strap integrity and providing a simple design rather than complex mechanisms.
Data Source
AI summary
A mold safety strap and method of use for securing two mold halves together. The safety strap includes an elongated strap body including two side walls extending between a first end and a second end, and an elongated central opening disposed between the two side walls. The first end is connectable to a first of the mold halves and the second end is connectable to a second of the mold halves. An intended break point is formed in a least one of the two side walls. The break point is frangible at a predetermined breaking strain value. The safety strap is sacrificial and intended to break if left on the mold during use, and at a straining force less than required to shear off the attachment bolts.