A combined Needle Roller Bearing is a combination of a radial and an axial bearing operating at 90º to each other on a common hub. The radial bearing carries the main load and the axial roller resists “crabbing” or side thrust. Both being cylindrical roller bearings of “cageless” design, the bearings offer maximum load for size. Both bearings are sealed with hybrid rubber/metal seals.
It was originally designed as a roller bearing for fork truck masts but today it is being used to solve many heavy duty track rolling problems.
Heavy Duty – what does that mean?
These products carry loads from tens of kilos up to hundreds of tonnes in both horizontal and vertical linear motion applications.
Mounting?
To mount the combined roller bearing, a hole the same size as the spigot on the rear of the hub is drilled or milled in a steel member. The hub is then welded into place, filling the 45º weld fillet around the circumference of the spigot with weld. There is no need to disassemble the bearing before welding.
Alternatively the bearing can be supplied welded to a mounting plate. The plate is then attached to the assembly using bolt and nut via through holes or machine screws into threaded holes in the plate.
What do they roll on?
In use, the combined roller bearing engages in a ‘C’ or ‘H’ section profiled steel section. The radial roller engages on the flanges of the profiled section and the axial roller engages on the web of the profiled section. These sections are much thicker and heavier than “standard” beams or columns. The profile is formed to exactly match the outer profile of the bearing.
Advantages?
With the combination of the radial and axial bearings, it is very unlikely that the radial bearing will crab or lock in its steel section because any twisting action is immediately counteracted by the axial bearing running into and along the web.
Uses
Whilst some combined roller bearings & steel profiles are still used in fork trucks, most combined roller bearings in the UK find their way into specialised handling equipment.
A typical and very prestigious example of this is the special canitlvered lift mechanism created to lift the 50 tonne wing of the A380. Massive Jumbo Combined bearings and special welded and profiled rails were used to achieve this.
At the other end of the spectrum, a production engineer can use 4 small combined bearings and 2 of the smallest steel profiles to create a low cost slide to move a workpiece from one machine to the next.
Typical Applications
These products are found in:
• Oil Drilling and exploration equipment
• Marine cable and pipe laying equipment
• Palletisers
• Goods lifts
• Vehicle lifts
• Test rigs
• Materials Handling equipment
• Lighting gantries
• Furnace chargers / dischargers
• Manufactured concrete and aggregate conveyors
• Machine tool positioning
• Agricultural equipment
• Specialised Vehicles
• Trailers
• CNC tool storage
• Theatre and film applications
• Brickmaking
• Medical equipment
• Fleet support
• Fork truck attachments
This really is one of those products where the designer’s Thrust Bearing imagination is the only limit to its use.
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