One metal replacement application you should avoid

Offering an alternative to heavy metal cuffs, the law enforcement version of the zip tie is making crowd control a slightly simpler matter.

Injection molded handcuffs are already taking hold in the law enforcement market. Jim Reaves, CEO of Milspec Inc. (Asheville, NC), maker of Cobra Cuffs, says the molding material “allowed us to provide a product that is virtually unbreakable and quickly becoming the premier disposable restraint in the market today.” Being foldable helps, too.

By using Sarlink’s TPV, the cuffs can be folded and still retain needed strength. The cuffs are color-coded to identify detainees by the charges against them.

The material is one of the grades of moldable TPV, thermoplastic vulcanizate, made by the global supplier Sarlink (Leominster, MA). Reaves says, “Using Sarlink in our Cobra Cuffs Restraint application gave us the strength we needed along with the flexibility required so that the product could be folded. We could find no other product that offered this balance of properties and could also be processed in a complex tool.”

Sarlink says all its TPVs are based on dynamically vulcanized rubber in a polypropylene matrix that combines excellent elastic properties and the processing ease of thermoplastics. The TPV used to make Cobra Cuffs is Sarlink 3100, a high Shore D, natural-color material with 250-lb tensile strength, good abrasion resistance, and good colorability, which enables color-coding detainees according to the charges against them.

Brian Bubak, Sarlink’s North American marketing manager, says that the entire assembly is injection molded, and that all parts are Sarlink TPV except the locking clip and rivets, which are made of nylon. The complete part is molded in a three-plate tool with a lot of slide action that is fed by a standard cold runner. Parts are robotically picked and the locking clip and rivets are assembled during the folding process. —Rob Neilley