Appliance Design - February 2008 - (Page 51) CORDS angle strain relief. In some appliances, the cord might be so rigid that it might not bend for two or three inches and space might not allow for that. Oden points to a microwave that is designed to fit into a space above a stove. Often the appliance is pushed back as far as it will go, and if the cord doesn’t have a right angle or some means of protection, the cord coming out of the back of the microwave could be damaged. Strain reliefs are available in a variety of materials, which is an important factor depending upon the application, says Giglio. He says that Heyco primarily uses Nylon 6/6 for most of its standard products. While Nylon 6/6 resists salt water, weak acids gasoline, alcohol, oil, grease and common solvents, the application may require the use of other materials. For instance, if the application calls for an operating temperature exceeding 105 DegC a Nylon 4/6 can be used. Heyco has also produced products for custom solutions from materials such as: polycarbonate, acetyl, polypropylene, polyethylene, Noryl, and electrically conductive plastics. At Interpower, Ford points to a material that is starting to find uses in strain reliefs called polyvinylidene difluoride. PVDF is a highly non-reactive and pure thermoplastic fluoropolymer that is used in applications requiring the highest purity, strength, and resistance to solvents, acids, and heat and low smoke generation during a fire event. “It is not very common yet, but some of the strain relief manufacturers make these for the equipment end. And, because they are resistant to chemicals, they tend to push those for the medical applications,” Ford says. Ford adds, that depending on Strain relief at the equipment end can protect against damage from excessive pulling and flexing. This Heyco relief can snap into place. and some OEMs, offers strain relief bushings, which are offered for flat and round cables and in flexible and locking versions, and Liquid-Tight Cord Grips. Choosing the correct one often depends on the application, according to Dan Ford, technical support specialist for Interpower Corp., a supplier of cords and cord components. Ford says that the first thing that the cord vendors need to know is the application. For portable appliances, a flex style strain relief might be appropriate. For appliances that are rarely moved or unplugged, a simple dome nut style or strain relief bushing might be a satisfactory approach. In instances, where the power cords are preassembled, the locking versions might be the choice, says Vince Giglio, director of engineering for Heyco Products. Dome nuts are very good for static applications and for a seal to pass a water test. They are less effective for appliances that are moved around during use because they don’t provide for any flex or bend relief. Heyco’s water resistant products are the Liquid-Tight Cord Grips, which come in standard and flexible versions and are offered with a Buna - N or TPE sealing gland. Heyco Cord Grips have a threaded body that can be either threaded into the appropriate hole or used in a clearance www.applianceDESIGN.com hole with a lock nut. In all cases, they provide a liquid-tight seal that would meet a NEMA 6P or IP 68 application. For appliances that are moved around, twisted and turned, or frequently unplugged, then a flexible type strain relief might be a better choice. This type of strain relief has a series of ridges where the cable meets the plug or connector and gently bends with the movement. An alternative might be the flexible version of Heyco’s cord grips. Another less common strain relief is a mesh type relief, which acts much like Chinese finger cuffs and become more resistant as the cable is pulled or flexed. These are often used for larger cables. Within the variety of strain relief types, there are subsets that offer additional features. These features can include electromagnetic interference shielding, fire retardance, multi-cabling capacity, and additional moisture resistance. Additionally, some rigid strain reliefs are available in nickel-plated versions. These can be used for applications in harsh environments where the cord might be subjected to chemicals or other corrosive agents that might other wise harm plastic strain reliefs. These can also be used to improve the product’s aesthetic purposes. Applications that might have limited space can use a 90 Deg Powercords and Related Components Quality service and quality products. Produced in ISO9000 facilities, our UL listed and internationally approved powercords and related components all conform to the highest standards. Upon your next requirement, please keep MEGA in mind. MEGA Electronics Inc. 4B Jules Lane New Brunswick, NJ 08901 tel 732.249.2656 fax 732.249.7442 www.megaelectronics.com sales@megaelectroncis.com For more Information Enter 122 applianceDESIGN February 2008 51 1/11/08 10:12:56 AM AD02084Mega.indd 1 http://www.megaelectronics.com http://www.megaelectronics.com http://www.appliancedesign.com
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