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A roller bearing, also known as a rolling contact bearing, is one type of rolling element bearings, which is used to create the appropriate environment for a rotary shaft by reducing the friction that may be produced when the shaft performs either axial or radial motion, in order to smooth the mechanism in the connected machine or device.
The roller bearings reduce the friction between the rotary shaft, which is wrapped by the bearing, and the outer component by utilizing the rolling elements inside the outer and the inner rings or races, to prevent the rotary shaft from directly contacting the outer part of the mechanism.
Bearings are the peripheral equipments that are wrapped around the rotary shafts on the machines. The rotary shafts are used in the transmission of motion, either directly or indirectly. The direct transmission of motion with the rotary shafts can be seen on the positive displacement pump, for example.
This type of pump makes use of the differentiation of the given pressure to cause the piston to move forward and backward, so as to pump out the media of the pumps. In this application, the rotary shaft is required to allow the piston to travel through the pump when the pressure is given or released.
At this time, the rotary shaft itself is performing the radial movement. As the piston is driven by the differentiation of the pressure inside the pump, the axial movement is thus facilitated. Therefore, a bearing would be adopted around the shaft, in order to relieve the load or thrust against the shaft and the outer component, and thus less friction is produced during the operation.
These bearings, depending on the required applications, can be made as two main forms. One is the plain bearing, and the other form, which is what we discuss here, is the bearings that are quipped with the rolling elements. Among these rolling element bearings, the roller bearings are usually compared with their counterpart, which are the ball bearings.
The most obvious difference between these two must be the shapes of the rolling elements. The rolling elements on the ball bearings are one or two rows of balls and that on the roller bearings are replaced with cylindrical rollers, which allow for greater radial loads than the balls on the ball bearings.
Depending on the design of the rollers and their own properties, these bearings can be differentiated into four main types, including cylindrical roller bearings, spherical roller bearings, tapered roller bearings, and needle roller bearings.
In addition to the design of the configuration of each roller, the numbers of the rows also determine the load and thrust capacities that the bearings have. In general, the more rows of rollers the bearing, the greater the load and thrust capacities. This makes another parameter to be considered when it is necessary to choose the right type of bearing for the compatible application.
● Cylindrical roller bearings
The cylindrical roller bearings have cylindrical rollers that are secured by the cages in between the inner and the outer rings. The basic single-row cylindrical rollers replace the single row of balls, so as to provide higher radial load capacity as the rotary shaft works at a high speed.
● Spherical roller bearings
This type usually comes in two rows of spherical rollers around the races of the bearings. Unlike the balls on the ball bearings, which have no edges and are supported by the point of pivot, the spherical rollers have round edges on the sides of the cylinders. These bearings are self-aligning, and are capable of carrying heavier loads in the circumstances when the alignment of their applications is difficult.
● Tapered roller bearings
The rollers on this type of bearing are designed as tapered cylinders, which are able to withstand both radial or axial loads, or the combination of the two, in order to provide the firm and stable secure for the rotary shafts that they are adopted for.
● Needle roller bearings
The needle roller bearings, as the name implies, are equipped with cylindrical rollers that are relatively thinner than others, which are suitable for radial loads of applications with high loads and speed.
As the above introduction has mentioned, the roller bearings, or the rolling element bearings, are widely adopted for a variety of applications, such as the positive displacement pumps.
However, there is another type, the plain bearings that provides even higher load and thrust capacities, and better shock resistant ability due to the larger contacting surfaces between the plain bearings and their applications.
The concern may exist in whether to choose the rolling element bearings or the plain bearings, but in fact, one can never completely replace another. Since what the rolling element bearings have may not be equipped on the plain bearings, such as the space for lubrication to be fed in. Therefore, what’s important is that if the bearings that the customers choose can fit for the applications, rather than comparing their own properties to decide which one is better.
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