Appliance Design - February 2009 - (Page 22)

JoINING This sterilization cassette features a polished latch and handle combination from Nielsen Hardware. The hardware had to be easy to grasp and open, and be autoclavable. A flat-screen TV mount from Southco uses positioning technology to allow users to easily tilt or swivel the screen into the optimum-viewing angle. The integrated counterbalance mechanism compensates for the weight of the TV, allowing a 150 lb display to be re-positioned with only a few pounds of effort. doors. These hinges can also incorporate counterbalance mechanisms, damping systems, and other elements to produce a userinteraction. There are a number of critical inputs that go into selecting the appropriate hinge. These include the basic door weight, as well as the anticipated load on the door. As the height, weight, and width of a door increases, the horizontal or vertical stresses on the hinge can also increase (depending on the orientation of the door), and wider hinge spacing or additional hinges might be required to reduce the force. In tandem with that, designers need to look at the overall distance from the hinge, to the point where the operator is going to grab the door. The further the center of gravity is from the pivot, translates into how much operating effort the end user is going to have to use. Another example is ensuring that a constant torque hinge will be strong enough to hold open a lid. Here, what is critical to understand is where the center of gravity is, what kind of hinge moment there is. By understanding the moment, which is force acting at a distance, the amount of torque required to hold the door can be determined. The size of the hinge is based on that torque requirement. Counterbalancing is another way to set a product apart, says Donald Pangborn senior vice president of engineering, Weber Knapp, Jamestown, N.Y. When talking about counterbalancing, a pivoting device is generally what is being discussed. A document handler on a photocopier, for example, may Weber Knapp Company Jamestown, NY 716-484-9135 have one. To raise the document handler and access the glass, the handler is hinged and it has some weight forward of the pivot. Gravity would push the lid down against the glass surface unless there was something to hold it in place. Generally, that would be spring force, the energy generated by a spring combination levered against the Counter-Balance Design Project No.: X31416 Designed By WK Engineer Date - 12/19/2008 Compression Type Adjustable - Yes Cycle Life = 160,000 Friction Lube - Yes W(Lid) = 102 Lbs. W(Supt) = 51.0 Lbs. X_CG = 9.500 in. Y_CG = 2.500 in. B(Max) = 70 deg. Phi = 40 deg. Z = 1.000 in. A = .875 in. B = 5.485 in. K = 420 lbs/in K(Inside) = 140 lbs/in K(Outside) = 280 lbs/in F(Min) = .206 in. F(Max) = 1.348 in. P(Min) = 86.5 lbs. P(Max) = 566.0 lbs. 600 500 400 Torque (In-Lbs) 300 200 100 0 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 Lid Angle (Deg) (Theoretical Data Shown) Lid Torque Spring Torque Spring + Friction Spring - Friction This chart from Weber Knapp looks at lid angles in degrees and the torque requirement for a counterbalance hinge. www.applianceDESIGN.com 22 applianceDESIGN February 2009 http://www.appliancedesign.com

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Appliance Design - February 2009 Contents Editorial Shipments/Forecasts News Watch Force-Sensing Technology Offers Designers an Alternative Approach to Creating Touch-Control Interfaces A Flammable Vapor Sensing Technology that was Originally Developed for use in Water Heaters has Evolved for use in a Broader Array of Applications Latches, Hinges, and Slides Must Reliably Secure Parts Together, Sometimes for Hundreds of Thousands of Cycles. Beyond their Utilitarian Functions, They Can Also Change Consumer Perceptions Elastomeric Electrical Connectors Can Solve Space Constraint Problems in Electronic Products and Provide Some Cost Advantages as Well A Multi-Layer Ceramic Capacitor with a Novel Electrode Design Can Suppress Electromagnetic Interference, Improve Circuit Performance, and Reduce the Number of Needed Components Design Marts Association Report: AHRI Advertisers’ Index

Appliance Design - February 2009

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