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Bearing applications in agricultural machinery

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In this article Schaeffler discusses various bearing types for use on agricultural machinery.

Bearing applications in agricultural machineryUsing its vast experience of supplying reliable, high-quality, maintenance-free bearings to the automotive sector, the Schaeffler Group has also built an enviable reputation for its bearings in agricultural applications.

Heavy-duty agricultural machinery, including tillage and sowing machines, harvesters and tractors, must withstand extremely harsh operating conditions. Key here is the selection of appropriate bearing supports and seals.

Dirt, dust, sand, high humidity levels, heavy soils and shock loads all take their toll on machine components and seals. Operating large machinery often incurs high costs for regular bearing maintenance. Indeed, specialist agricultural machinery contractors are now demanding maintenance-free bearings and seals.

Components on a harvester, for example, have to cope with plant remnants and sap, the acidic contents of which can cause ingress of dirt, leading to seal damage. On a corn harvester, high rotary speeds lead to high mechanical stresses on the bearing. In addition, contamination and acidic corn sap affect the seal. To solve these problems, Schaeffler has developed a ready-to-fit bearing unit with triple-lip sealing, which is similar to automotive wheel bearings. Flingers can also be offered as an additional protective measure against the ingress of dirt and other contaminants. These components are pressed onto the rotating inner ring and use centrifugal forces to transfer contamination away from the bearing.

Grease chamber

Schaeffler's double-row angular contact bearings transmit loads through a solid housing into the adjacent structure. The bearing has an additional grease chamber that protects the bearing from dirt and corn sap. The spherical bearing outer ring and the counter-shaped surface in the housing compensate for any misalignment in the adjacent structure.

Similarly, tillage machines that are used to prepare the field for seed planting also require very robust bearing supports. The bearings are combined with suitable flange housings, which simplify installation.

In plough discs, the inclined position of the disc results in transverse forces and bending moments, as well as radial loads. For these applications, Schaeffler offers double-row angular-contact ball bearings or robust, four-point bearings for applications with limited space. Robust ball bearings are also offered for shaft supports.

For seeders, where the forces involved are lower, Schaeffler offers smaller bearing supports, as well as corresponding bearings for combinations of tillage and seeding machines.

Tractor applications

Increasing working speeds and the higher performance capacity of tractors means that drive and power transmission units are subjected to higher stresses, which places greater demands on the bearing arrangements. For these applications, Schaeffler offers both standard bearing units and custom-designed bearings.

On tractor engines, for example, under its INA brand, Schaeffler offers various belt-drive components, such as tension systems and overrunning clutches, water pump and fan bearings.

Together, Schaeffler's INA and FAG brands offer a wide range of bearings for applications in gears, power transmission systems and axles. This includes needle roller bearings, drawn-cup needle roller bearings and needle roller cages, machined or manufactured by forming. Schaeffler's premium quality X-life bearings boast improved surface and geometrical accuracies, resulting in increased service life.

Full-complement needle roller bearings are offered for maximum load-carrying capacity in tight installation spaces and needle cages with a special, profiled KZK cage are used in high-acceleration applications. Similarly, cylindrical roller bearings with different cage designs (and as full-complement variants) with or without outer ring are other important components for the tractor's drive train.

Schaeffler's X-life tapered roller bearings with large contact angle can be used for high-load applications, with various heat treatment and material coatings available. These types of bearings are often used in transmission-integrated hydro engines, pumps, pinion bearing arrangements and rear axles.

Clutches

For the interface between engine and transmission, Schaeffler can provide its LuK branded clutches, which incorporate specially developed clutch release bearings. Here, effectively sealed bearings with drawn outer and/or inner rings are used, which enable cost-effective overall designs to be executed, while offering high reliability and extended service life.

For supporting slewing, tilting and for the alignment of chassis movements, axle suspensions and load harnesses, Schaeffler's spherical plain bearings and rod ends are available. Spherical plain bearings with complex lubrication groove systems on the outer ring can be used in combination with spring-dampened front axles and chassis.

Stabilisers, damping and hydraulic cylinders are fitted with spherical plain bearings and rod ends. For example, Schaeffler's Elgoglide maintenance-free, heavy-duty spherical plain bearings are used in the wishbone systems of front axles with independent wheel suspension. Maintenance-free Permaglide cylindrical plain bushes can be found in door hinges, engine hood supports, lever sets and rod systems.

Housed bearings

In agricultural machinery, housed bearing units are often used to compensate for static angular misalignment of the shaft of up to 5 degrees for non-lubricating units. The housing bore and bearing outer ring are spherical in shape so that the radial insert ball bearing can align itself in the housing.

In conjunction with the different housing types (cast iron and sheet steel), Schaeffler's radial insert ball bearings form complete units, offering significant rationalisation options at the design stage and during customer manufacturing/assembly. Numerous combinations are possible for every application.

Radial insert ball bearings come with a choice of five seals. Most seals comprise three pieces and are made from zinc-coated outer and inner steel plates with rubber sealing ring. This prevents the ingress of dirt and moisture, while also ensuring the required elasticity and preload of the seal, even after a long period of operation. The deep-drawn outer steel plate protects the sealing ring against mechanical damage. Bearings with R-seals have a larger grease reservoir due to sealing shields that are bent to the outside. All sealing concepts comprise evenly and concentrically abutting rubber lips for increased bearing life, as well as firmly rolled inner and outer caps to ensure easy re-lubrication.

Schaeffler's Corrotect coating can be applied to its radial insert ball bearings, offering customers a corrosion-resistant, low-cost alternative to stainless steel bearings. The inner rings and locking collars are coated against fretting corrosion as standard, which also prevents rust formation at the sealing lip.

 
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