If, for example, a supermarket does not have a ramp for delivering goods, a lorry with a lift platform is necessary. The tailboard of the vehicle is pivoted into a horizontal position and then lowered so that the cargo can be loaded or unloaded safely and as quickly as possible. Moisture and corrosion, improper handling and insufficient maintenance are the reasons why the company MBB Palfinger uses igus plastic plain bearings on its tail lifts.
Hoykenkamp near Bremen – the construction of helicopters started here on the premises of today’s MBB Palfinger GmbH in 1937. In the course of the war and during the post-war years, among other things the production of parts for aircraft construction went ahead with a focus on hydraulics. In the mid-1960s the construction of lift platforms began here, which became the main business activity over the years. At the beginning of the 1980s, the company “Vereinigte Flugtechnische Werke GmbH” (“VFW”) was integrated into Messerschmitt-Bölkow-Blohm (“MBB”) and was taken over in 2008 by the Austrian company Palfinger AG. Today, 15,000 lift platforms are manufactured here each year for an international clientele.
“A lift platform is located just behind a lorry in a difficult environment – just everything rusts here,” says Eike Rulfs, Head of Design & Development at MBB Palfinger, describing the application environment. “With frequent moisture or even road salt on the street, lack of lubrication at the bearing points leads to the failure of the lift platforms, which must absolutely be avoided.” If the function of a lift platform is not guaranteed, goods cannot, for example, be delivered to the supermarket or even patients cannot be safely taken away from the accident site.
Demand for rust-free components
There are twelve bearing points on each hoist of a lift platform. If metallic bearings are used here, it is absolutely necessary to relubricate them continuously. “Who is supposed to do this work, for example with different drivers per vehicle in transport companies or even in rental vehicles?” Eike Rulfs recalls. “Or where should a grease gun for lubrication be stored in an ambulance or a lorry for foodstuffs?” Another big problem is the pollution caused by lubricants. Maintenance-free property and corrosion-resistance were therefore the required criteria for the components in a new project.
This order was for the construction of tail lifts for ambulances in Great Britain. “There, it is legally stipulated that every patient must be brought into the ambulance by means of a lifting aid,” explains construction manager Rulfs. “The vehicles are box vans with twin wheels on the rear axle and a vehicle weight of five tons.” The customer of MBB Palfinger was not satisfied with the previous solution offered by a competitor and was looking for a new, maintenance-free solution. Here, the company opted to place stainless steel bolts on the lift platforms. “We were already acquainted with the igus plain bearing products,” says Eike Rulfs. “With the change to stainless steel bolts came a good opportunity and so here we dared to switch to the plastic plain bearings.”
New material for new solution
The new material iglidur Q290 from igus was launched on the market at the right time for the construction of the lift platform of the ambulance. Like all plain bearing materials made of igus high-performance plastics, this is also optimised for friction and wear, and is used without external lubrication. The compatibility of the plain bearings was very important to MBB Palfinger – the bearings should fit into the existing housings of the structure. igus introduced a new dimension for the material iglidur Q290, which is available exclusively for MBB Palfinger.
The iglidur Q290 also has excellent friction and wear values on stainless steel shafts and therefore fits very well with the new MBB Palfinger bolts. The material is well suited for forces up to 55 MPa and gets along very well with edge loads. With metallic bearings this would lead to problems. Compared to metallic bearings there is no risk of damaging bearings and shaft with the flexible iglidur material. This doesn’t happen even with a single-sided loading of the platform and the resulting edge loads, or when used for other purposes, for example, when a lorry with a tail lift is used as a snow plow.
“The maintenance-free property and corrosion resistance as well as the price difference compared to metallic bearings are not the only advantages offered to us by the igus bearings,” explains Eike Rulfs of MBB Palfinger. “Our industry is so tightly calculated that it is also very valuable if whole work steps can be saved during assembly, when bearings can be pressed in easily and no longer have to be lubricated. All these combined benefits have endeared us to the igus bearings.”