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Ergonomics02 - Unit Eight One of the most important...

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Unformatted text preview: Unit Eight One of the most important considerations, of course, is human diver- sity. It may not be sufficient to base a design on the needs of the“ average” . person. For example, if a non-adjustable chair was designed to accommo- date a 170 cm person, then anyone With a stature more that a few centime- tres more or less would be uncomfortable' 111 that chair. In this example, the design would not be successful even though it was developed for “average” body stature. What you probably recognize is that many workstation designs now incorporate adjustable features—the computer station, for example, with adjustable height for the keyboard, adjustable screen height, and adjustable screen angle or the Office chair with adjustable “just about everything.” Have you ever stapped to consider what the limits of the adjustments are or what they should be based upon? The following examples should provide you with answers to this and other important questions facing the er- gonomist. Of course, you will probably end up with many questions of your own, which you may only be able to answer with further training in this exciting, dynamic field of study. - AChairforAll Reasons The ergonomist must consider a few basic fundamentals in designing a chair. It has to be comfortable over a period of time, physiologically satis- factory (i. e. cause no undue stress or fatigue on the legs or back), and appropriate for the task or activity for which it 15 created. To do this, the de— signer must consider the wide variation that exists in human shape and proportion, In order fer the chair to provide a satisfactory fit for most users, the designer has to rely on anthropometric tables that summarize the full range of body dimensions. Such tables provide data for individual measures and values for the 5th percentile (small or short), the 50th per- centile (median or average), and the 95th percentile (large or tall) Important measures for chair design might include stature (height), sitting height, sitting'shoulder height (for neck rest), sitting elbow height (for arm rest), buttock-to-knee length, hip breadth, and knee height. These anthropometric data would then be incorporated into seat height, seat depth, dimensions of the backrest, backrest angle, seat width, seat angle or tilt, seat surface, armrests, and leg room Fundamental to the design 15 the intended use of the chair—is it to be part of a computer workstation,a formal lounge chair, an easy chair, or is it to provide seating in a board- room or at a dining room table. For example, Figure 8—2 shows the basic adjustable features of an ergonomically designed office chair. 168 ...
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