Linear Ball Bearings Offer 50 Per Cent Longer Life

By revising and improving the plastic components and optimising the load plates, Schaeffler has developed a new lightweight range of linear ball bearings that offers smoother running characteristics, higher load carrying capacity and 50 per cent longer operating life.

These bearings are targeted at machine building, automation, control, robotics and general engineering applications.

The KN ..B-PP range is the latest addition to Schaeffler's existing, well-proven KN/KNO series of linear ball bearings, which are designed to compensate for shaft misalignment in a diverse range of applications. The new units comprise a high-strength plastic cage with steel load plates, balls, shields and seals. An external steel retaining ring supports the load plates. The bearings can support high loads, while having a relatively low mass, enabling linear guidance systems to be assembled with unlimited travel.

In developing the KN ..B-PP linear ball bearing, engineers at Schaeffler took the existing KN/KNO series and completely overhauled the design, including optimising the load plates and introducing a 'tapered' lead chamfer entry zone for the balls. Due to the self-alignment function, the balls now run freely into the load zone and load distribution over the whole row of balls is now more uniform. These design improvements result in smoother running characteristics, higher acceleration capability and prevent overloading of the individual balls. In addition, noise levels are reduced and operating life is increased.

With standard linear ball bearings, the raceway plates can sometimes 'rock' about the retaining ring, leading to slippage and undesirable running characteristics. With the KN ..B-PP, the tapered lead chamfer and optimised load and raceway plates ensure that there is no slippage at high acceleration, and the unit is always slightly pre-loaded by the retaining ring. The new robust construction means the KN ..B-PP is self-aligning to +/-30 angular minutes and can operate in temperatures up to 80 degrees C.

KN ..B-PP bearings are available in 'open' or 'closed' variants, the former having a segment cut out for supporting shafts. Highly effective double-lip, polyester-elastomer rings are used on both sides to prevent the ingress of contaminants into the bearing and to retain the grease inside. 'Open' bearings are available with additional sealing strips. The units are maintenance-free for most applications.

Schaeffler can also supply the bearing as a complete support system, comprising a housing and shaft. The housings are made from a high-rigidity, high-strength aluminium alloy that enables the full load carrying capacity of the ball bearings to be utilised. Due to their comparatively low mass, the units are suitable for lightweight designs with high loads and where higher accelerations and travel speeds are required.

The housings, which come in open, closed, slotted or tandem designs (fitted with two linear ball bearings), have threaded and counterbored holes that enable easy mounting.

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