Lift truck design: vital to operator comfort, safety
Testing this lift truck operator, instrumented with sensors to measure muscle strength and fatigue, allows ergonomists to determine body stress levels. Analysis of the data gathered helps refine truck design.
By Staff -- Modern Materials Handling, 1/1/1998
Editor's note: As these two stories involving the lift trucks from two manufacturers indicate, attention to good design is important, especially when it comes to features that foster ergonomics and accident-free operation. Ergonomics and safety will continue to be a vital element of design.Forklift operator survives 40 ft fall
Dale Butler, an employee of Lanter Company, St. Louis, Mo., was operating his Clark CGC-25 forklift recently when the building he was in collapsed. Rescue personnel had to work four-and-a-half hours to free Butler from a tangled web of concrete and steel.
Butler, who was wearing a seat belt, survived with only bruises, scratches, and a fractured leg.
According to the forklift's manufacturer, Clark Material Handling Company, rescue personnel attributed Butler's survival to the safety features of the lift truck's operator compartment. "It looks like that saved his life," Clark quoted Capt. Duane Greer of the St. Louis Fire Department as saying.
Just prior to the accident, Butler was moving a pallet load of air conditioning compressors on the fourth floor of the warehouse. A portion of the roof caved in, causing a 80 ft by 120 ft section of the floor to collapse. Butler and the Clark forklift he was in fell some 40 ft to the ground. The forklift came to rest on its side, with the operator's compartment providing protection from debris that completely covered the lift truck.
"Our forklift design provided effective protection," says Clark vp Kevin Reardon. "Safety features of the operator compartment-an overhead guard, seat belt, and winged safety seat-worked together and made a difference.''
Building better trucks with ergonomic analysis
Today, many companies focus on ergonomic features when they design lift trucks. One company taking ergonomics to new levels is Yale Materials Handling Corporation, based in Flemington, N.J.
Yale has used the services of a well-known consulting firm, Ergonomic Technologies Corporation (ETC), Oyster Bay, N.Y., to help develop several new truck models. ETC's partners are certified professional ergonomists with industrial or mechanical engineering backgrounds and training in biomechanics and human physiology.
Applying ETC's expertise begins in the concept design stage. A Yale design team works with ETC to interview and obtain feedback from lift truck operators on comfort and lift truck efficiency factors. The data are analyzed and used in the design of an initial prototype. ETC then validates ergonomic features based on a number of measures, says John Piccolo, Yale product manager.
Tests are conducted by ETC, for example, to determine the stress levels on the body of operators instrumented with sensors measuring muscle strength and fatigue (photo). Included are tests of muscle activity, body posture, contact pressure, and whole body vibrations transmitted to the operator.
Once test validation and simulations are complete, further refinements to the prototypes are made. Yale's product group may then conduct customer reviews, which includes administering surveys-a comfort checklist, for example-to lift truck operators. Thorough evaluation by a sample of operators and purchasing managers often precedes final production.
One of the latest trucks ETC looked at was Yale's next generation reach truck. ETC evaluated the control handle position, brake pedal location, the position of the buttons, the armrest height and the width of the compartment. The reach truck was redesigned with larger buttons placed on the multi-function control handle as a result. This made accessibility to the buttons easier, especially for operators who often use gloves. Another redesign involved development of an adjustable control handle giving better accessibility to people of varying heights.
Another Yale truck with an ergonomic redesign is a 6,000 to 8,000 lb center control pallet truck. It now has a larger operator compartment, increasing from 16 in. to a full 21 in. in depth. Operators were increasingly using this truck for cross-aisle order picking. What was needed was to allow the operator to pass through the compartment with greater ease. The addition of a full one-inch-thick floor pad from a half-inch also improved operator comfort.
And a wider steer handle, increased from 10 in. to 27 in., on this truck provides a more natural steering position, giving the operator better leverage with less steer effort.
Ergonomic analysis also revealed that adding rear mounted controls for lift, lower, and horn would improve operator productivity. These controls allow the operator to maneuver the truck more easily while entering and exiting pallets or traveling forks first. By positioning the optional controls on the inside of the load support plate slightly below the arm rest, this truck offers the operator greater comfort and im-proved maneuverability, while maintaining a grip on the arm rest and having a clear view of the forks.
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