22.09.2006
"E" redefined
Linde's new E12 to E20 counterbalanced electric forklift trucks from 1200 to 2000 kg capacity deliver more power with less energy input.
Previously it seemed unlikely to have an electric forklift that could come close to a diesel in terms of performance, but this is now approaching reality.
In collaboration with Bernward Welschof, their colleague from the drives and controls unit, chief design engineers Bernhard Götz and Harald Will elected for a completely new truck concept mutually conditional on several design features and oriented to a single overall scheme in order to provide a comfortable and safe workspace for the operator and at the same time enhance economy on the job. About 80 percent of the truck has been redesigned. Technical innovations include an energy management system incorporating an accurate battery discharge indicator, an on-board battery charger and no less than five battery change options. A further engineering achievement is the maintenance-free enclosed drive axle, in which all main components such as power modules, traction motors and lift motors are integrated. Linde promises users energy savings as high as 25 percent compared to other forklifts of the same category.
All this is supplemented by a number of design elements that first attracted considerable attention when introduced to the market in the 39x Series diesel forklifts: ProtectorFrame with top-mounted tilt jacks, shock isolation of the drive axle or the spacious and comfortable operator compartment equipped with the Linde Load Control joysticks for intuitive control of all mast functions. Entirely new on these electric models is the Linde Driver Assistant, which provides for proportional reduction of travel speed on turns. The range of versions available has also been enlarged, the standard product catalogue numbering 15 different models that efficiently cover all requirements from sporadic light-duty indoor application to multiple-shift operation under harshest working conditions. Customers are given a wide range of choice: five capacity ratings, various battery capacities, low or high truck version, several power options, and center-pivot or combi steer axle. Every user can assemble a fleet precisely matched to the material handling tasks in hand.
The effect of all that's new in performance of the trucks is reflected for instance in their top speed, which is 20 km/h for the four-wheel models. Lift speed is 20 percent higher. "No other truck of this size is able at present to achieve comparably high productivity at such low energy consumption", assures Harald Wozniak head of international marketing and cites delivery truck work cycle figures for confirmation.
Minimizing use of energy, making full use of the energy supplied, and quick charging or change of the battery figure high up on the list of development targets. They have been accomplished first by an accurate battery discharge indicator. A large display directly in front of the operator keeps track of how much energy is left and how long the truck can keep running before the battery needs to be recharged or changed. Battery charge level is measured exactly by a patented method, in which the motor management system detects and interprets both voltage and current data with appropriate sensors. Precise knowledge of battery status allows not only of utilizing energy reserves to the full but also of prolonging battery life and thus reducing operating costs. Harmful deep discharge is avoided by an electronic circuit that restricts travel speed and other truck functions when residual battery capacity drops below 20 percent. The entire life cycle of the battery can be recorded by ordering the optional battery data management system.
Another component of the energy management system is the on-board charger, which Linde says is the first to be installed in a forklift on the European market. This option is located in the counterweight and is precisely matched to the size of battery installed in the truck. A temperature sensor ensures that the battery is recharged at a rate conducive to ensuring a long lifetime. The high-frequency technology employed provides not only fast charging but also for significant energy savings. The flexibility associated with an on-board charger is another advantage, as it enables the battery to be recharged at any available power outlet whenever convenient or necessary. Apart from not having to drive to a fixed charging station, errors due to connecting to the wrong or an unsuitable charger are eliminated.
In applications where battery change is required, fleet owners profit from several options for quick and easy side changeout by opening the sturdy battery compartment door, namely a rollout located under the battery, use of a forklift or hand pallet truck, a fork shoe or a C-hook attached to a hoist to lift the battery out to the side.
In these new trucks Linde uses a compact drive unit with two separate, maintenance-free AC motors. Together with the traction motors, the lift motors and power modules of the truck controller are assembled within the drive axle. The shorter connecting leads this makes possible result in less loss of energy and excellent electromagnetic compatibility. So as to permit maximum traction and lift performance in high ambient temperatures, the axle contains a cooling system with four cooling motors in all, which operate on demand and reliably prevent loss of power.
Since electronic systems are always a potential source of failure, Linde has incorporated adequate redundancy in design of these electric trucks. All safety-related electronic components as well as the electrical signals transmitted are duplicated. The microprocessors are mutually monitored.
As in the 39x Series diesels, overhead guard and frame of the new electric forklift are constructed as a high-strength unit and the tilt jacks are mounted at the top. Stability of the mast is thereby enhanced, allowing use of narrow upright sections to afford better visibility and greater safety for the operator in stacking and retrieval operations.
The compact drive axle is isolated from the chassis by maintenance-free resilient mountings and the mast is fixed to the axle housing. Forces emanating from the mast are therefore transmitted direct to the wheels and not into the chassis. Noise and vibration of the motors and hydraulic transmission are also kept away from the operator compartment. The standard of comfort enjoyed by the operator is superior to any experienced in electric forklift trucks before now.
Simply expressed, the target in design of the operator compartment was to make a good thing better. This is reflected in a lower access height, greater headroom, larger footwell and wider cab and also in controls designed for intuitive operation, a comfort-class seat and options such as cab heater and radio. Linde Load Control is standard for all models. The easy-action joysticks allow responsive, high-precision control of all mast functions through electronic actuation.
