Lift truck ergonomics move front and center; Reach trucks.
With a primary focus on the operator compartment and controls, lift truck suppliers have made major commitments to easing the stresses and strains of daily use.
By Gary R. Forger -- Modern Materials Handling, 4/1/1998
It wasn't so long ago that a lift truck redesign started with features the engineering department thought needed improvement and finished with the marketing team's evaluation of them. There was usually only minimal attention paid to adapting the design to the people who would eventually use the lift truck.My, but things have changed.
Ergonomics, the science of adapting work conditions to the worker, has taken on steadily increasing importance in lift truck design. And today ergonomic considerations are having a profound influence on lift trucks from controls to operator compartments.
Three examples of the latter are controls contoured to the human hand, multi-functional devices, and adjustable height panels. Ergonomic improvements in operator compartments include larger platforms, vibration damping, and swiveling/reclining seats for optimum driver support during different tasks.
It is important to note that these and other advances are not cosmetic changes. In fact, several are sufficiently dramatic to win international design awards.
There are three primary reasons that the ergonomics of lift trucks should be a concern.
One is worker health and injury avoidance. A second is reduction of workman's compensation claims. And the third is improved profitability for companies using ergonomically improved equipment that increases productivity, reduces absences, and minimizes staff reassignment as well as related turnover.
These issues are being addressed in several ways.
One consideration is the design of lift truck controls and their position in regard to the operator. Both hand controls and foot operated controls are part of the mix.
A second is design of the operator's compartment. This covers the shape, dimensions, and accommodations of the compartment as well as exposure of the driver to operating conditions such as vibration.
Still another focus is the driver's position in the lift truck. This includes the angle of the operator to the load being carried and to the travel direction of the lift truck.
A fourth concern is the operator's view of the warehouse. This focuses on the driver's ability to see where the lift truck is moving and movement of the load from floor level up to the highest storage location.
Determining how lift truck design can best be modified involves an understanding of the stresses and strains on the human body (biomechanics) during a day in the warehouse or plant. Factors commonly evaluated include body posture, muscle activity, and range of motion. The artwork on this page indicates some of the key body motions that can benefit from improved lift truck ergonomics. In fact there are numerous opportunities for improvement.
With an understanding of the key stresses and strains on lift truck operators, ergonomists and designers get to work. Some suppliers bring in specialized ergonomic consultants to help lift truck engineering departments. Others have people on staff who can combine ergonomic principles with evolving lift truck designs. Users are also part of the design process these days.
Many different designs
Although ergonomics is defined by Webster as a science, that does not mean there is only one ergonomically beneficial answer in lift truck design.
As the photos in this article make clear, there are several designs for controls and operator compartments that make lift trucks more user friendly. In fact, these photos are only a sampling of the latest in ergonomic designs for models ranging from stand-up counterbalanced trucks to orderpickers.
With controls in particular, there are three primary focuses of ergonomic design efforts-shape, functionality, and positioning.
One common approach to the shape issue is to better contour the control handle, steering wheel, or switch to the human hand. Regardless of the specific design used, and there are as many as there are lift truck suppliers, the intent is to make each control a more natural extension of the driver's hand. And by extension, these ergonomic improvements also reduce stresses and strains elsewhere on the body.
As a result, the operator can grasp and use the control more comfortably. By positioning functional controls on the handle for ease of access by the thumb or index finger, the operator is better protected from cumulative trauma disorders. Palm and wrist supports are also included on some recent designs.
A compact steering wheel is one control device that has been the focus of several suppliers. By making the steering wheel smaller, operator movement is reduced. In turn, this minimizes the stresses and strains on the arm and shoulder of the driver. In addition to the size of the steering wheel, use of low-resistance electronic technology also improves ergonomics by making it easier to steer.
It is worth noting, however, that for steering controls smaller is not necessarily ergonomically better. The steering handle on one line of center control pallet trucks has been increased in width from 10 in. to 27 in. The design gives the operator better leverage and requires less effort to control. Steering handles are also being slightly angled to better accommodate the natural movements of the driver.
Positioning multiple function controls on a single handle contributes to improved ergonomics also. Most importantly, it reduces the range of movements the operator must make, often limiting motion to a finger rather than the traditional hand and arm movement needed to shift from one control to another.
Positioning of all controls relative to the driver is proving to be an important ergonomic feature too.
One control panel can be either centered in the operator's compartment or shifted 45 deg to one side or the other, depending on the typical standing or leaning position of the driver. Usually, the panel position is selected at the time of purchase and fixed at the factory. It can, however, be modified at the warehouse with some tools in a few minutes.
Another control panel design is even more flexible. It can be raised or lowered 6 in. by drivers to better accommodate differences in height from first shift and second shift operators, for instance.
Even foot controls are being positioned to minimize the operator's leg and foot motion. This is being done on stand-up lift trucks as well as those with seats that allow the operator to sit or stand. In addition, foot controls are being modified to require less pressure for activation, reducing fatigue.
Improving compartments
There are additional opportunities to improve lift truck ergonomics in the operator compartment. The size of the compartment as well as the positioning of the seat figure prominently in models from reach trucks to rider pallet trucks.
Some suppliers have focused on enlarging the operator compartment to allow more unrestricted movement to perform tasks. The compartment on one rider pallet truck is now 21 in., a full 5 in. deeper than before. A related re-design lowers the operator's platform where possible to minimize the step height and related stresses from frequent on/off motions.
Extensive foam rubber padding is another ergonomic feature that is showing up in numerous operator compartments. While some designs are entirely padded, others have opted for strategic placement of pads to protect backs and knees, for instance.
Several different routes have been taken to reduce operator fatigue due to vibration from uneven floors. Padding the floor of the compartment and even the brake pedal is one approach. Another is to float or suspend the floorboard. For some counterbalanced lift trucks, the operator's cell is supported by rubber mounts that reduce the transmission of vibrations.
Even the position of the operator in the compartment is receiving attention. For instance, one reach truck design focuses on fatigue reduction by allowing the operator to sit, lean, or stand depending on preference and tasks.
Another reach truck features a swiveling driver's seat with headrest, automatic seat tilt, and floating arm rest (see photo). The driver can turn the seat forward and backward 30 deg in the direction of travel, minimizing the driver's head movement. The seat tilts back as the forks reach a preset height, allowing a more ergonomic view of the load and its movement. The headrest supports the driver's head, eliminating common neck strains. Meanwhile, the floating arm rest provides support for continued operation of the fingertip controls.
Improved visibility of loads and their movement is possible due to modifications outside of the operator's compartment. Wide-view masts and well-positioned chains, lift cylinders, and hose reeving offer excellent through-mast visibility. Overhead guards have been redesigned to provide maximum view of the load as it is lifted to a high storage position.
Obviously, the age of ergonomics in lift truck design is here. And from all indications, these improvements are only the first go around with many others still to come.
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