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New regulations overseas that limit machine and vehicle vibrations have encouraged equipment manufacturers to develop all sorts of technologies to improve operator comfort levels. BY MARK CHERRINGTON AND MARY SEARLE.
Last year, the European Union introduced maximum daily vibration limits for operators of new off-road vehicles, with existing vehicles to achieve similar ceilings by 2011 (extended to 2013 in some European countries). These new rules and concerns for workplace safety have encouraged major seat manufacturers to develop ‘active suspension’ type seats that virtually eliminate vibration to the operator – backed up by control technology that allows cabs to be far better isolated from the machine chassis. The US Occupational Health and Safety Authority is also looking at introducing similar legislation to that applying in the EU, and is doing a lot of work with the insurance industry on full-body vibration and soft-tissue injuries, which are in the top four causes of workplace injuries. “At the same time, a key benefit of good suspension is that it allows a vehicle to travel across the ground (farm, quarry, jobsite) a lot faster, thereby improving productivity,” says Anthony Glick from seating manufacturer Sears Manufacturing, which works closely with John Deere in seat development. Glick says there are four levels of suspension: mechanical, which allows vibration through the metal; air, which loses effectiveness with operators weighing over 90 kilograms; semi-active, which uses a vibration reduction system; and active, which uses an independent energy source to actively counter the vibration. “More than 65 percent of John Deere customers in the US pay the extra cost to have our active seats installed as the cost benefit is readily realised,” he says. “Key benefits, aside from increased productivity, is a reduction in harmful vibrations and improved comfort.” Adding to the effectiveness of the latest seat designs is the move towards electro-hydraulic control systems, which eliminate the need to have hydraulic lines in the cab. Eliminating hydraulic lines from within the cab gives significant operator comfort advantages, says Dave Wohlsdorf, the director of product management for Sauer Danfoss. These include reduced noise (hydraulic units generate noise), less heat (hydraulic oil generates heat), and improved visibility, because you can get a smaller operator station. They also allow the cab to be much better isolated from the rest of the machine, so that the only direct connections to the machine are through vibration damping isolation mounts. Electro-hydraulic controls also make it much easier for maintenance, as they allow tilt-up type cabs, which are easier to achieve with just wires, than with wires and hydraulic lines. There are other areas also in the process of evolution, says Wohlsdorf, such as the ‘steer-by-wire’ concept that’s already been adopted by some OEMs, including Komatsu, Cat and Case, to name just a few, which offers some clear advantages. Steer-by-wire also allows OEMs to option of using a steering wheel or joystick controls – which may be a better option for dry hire machines, or where a machine is used by a number of operators. Grammer's vibration meterGerman specialist seat manufacturer Grammer launched its VibroControl vibration “dosimeter” device in the North American market recently, ahead of what it believes is the likely US introduction of regulations limiting whole-of-body vibration. Grammer’s VibroControl attaches to the operator’s seat, and continuously monitors for up to 12 hours – warning when acceptable limits are exceeded. It was developed to meet the requirements of the EU directive, where employers are required to monitor daily vibration levels for each employee – and retain the records for up to 30 years. The data capture by the VibroControl can be exported via a USB port to a computer, documented in an Excel spreadsheet, then saved and archived. Exposure limits are measured both horizontally and vertically with the VibroControl attached to the side of the seat. In addition, while working, operators can tell by glancing at the integrated trend LEDs whether their accumulated vibrations are nearing potentially health-endangering levels. Visual and audible signals alert them if acceptable limits are exceeded.
Contractor Vol.32 No.3 April 2008 |
Excessive vibrations from contraction equipment and vehicles over along period of time can result in lower back injuries and other long-term medical problems.