The human shoulder joint allows the arm to rotate 360 degrees, and the hip joint allows the thigh to swing freely forward, backward, left, and right. Without joints, bones are just stiff sticks, unable to complete any complex movements.
Devices also face the same problem.
The arm of the excavator needs to swing up and down, the boom of the crane needs to be adjusted in pitch, and the support of the bridge needs to expand and contract with the temperature - between these moving parts, a connection is needed that can swing freely and bear the load. Ordinary rolling bearings are good at rotation, but not good at swinging and tilting. When there is an angular error between the shaft and the bearing seat, or when the component needs to swing back and forth within a certain angle range, ordinary bearings will not be able to do what they want.
Is there a kind of bearing that can allow the connected parts to swing and tilt freely like human joints?
Yes. It's called a spherical bearing.
01 Structural design of spherical bearings
The core design of the spherical bearing is hidden in its structure - the spherical surface.
The outer surface of its inner ring is spherical, and the inner surface of the outer ring is also spherical. The inner and outer rings are in spherical contact, forming a sliding group that can swing freely.
This structure is exactly the same as the human joint.
The humeral head of the shoulder joint is spherical and is embedded in the glenoid fossa of the scapula. The spherical contact surface allows the arm to rotate in any direction—front and back, left and right, in circles, it’s all possible.
The same goes for spherical bearings. The spherical fit gives it a self-aligning function - even if there is an installation error or deflection between the shaft and the bearing seat, the bearing can automatically compensate and maintain normal operation.
The inner and outer rings of deep groove ball bearings are fixed cylindrical surfaces. Once the shaft deflects, the rolling elements will be subject to abnormal loads, accelerated wear and even failure.
The spherical surface design of the spherical plain bearing fundamentally solves this problem.
The load-bearing characteristics of spherical plain bearings are also unique - they can bear both radial loads and axial loads. The spherical contact area is large, the load is evenly distributed, and the load-bearing capacity far exceeds that of rolling bearings of the same size.
In addition, spherical plain bearings are also suitable for complex motion conditions such as swinging, tilting, and low-speed rotation. In these scenarios, the rolling elements of rolling bearings are prone to slippage and wear, while the sliding contact of spherical bearings is more stable and reliable.
02 Spherical bearing classification
Force direction
Classification by load direction: Under GB/T 304.1-2017, spherical plain bearings are mainly classified by nominal contact angle into radial spherical plain bearings, thrust spherical plain bearings, and angular contact spherical plain bearings. Radial spherical plain bearings have a nominal contact angle τ of 0° to 30° and primarily carry radial loads, while also accommodating some axial load. Thrust spherical plain bearings have a nominal contact angle τ of 30° to 90° and primarily carry axial loads. Angular contact spherical plain bearings have a nominal contact angle between the above two types, usually 30°, and can simultaneously carry substantial combined radial and axial loads.
Lubrication method
Spherical bearings can be divided into lubricating type and self-lubricating type according to the lubrication method. Lubricated spherical bearings require regular replenishment of grease or oil and are suitable for clean and easy-to-maintain environments. Self-lubricating spherical bearings are inlaid with self-lubricating material on the friction surface of the inner ring or outer ring, so there is no need to replenish lubricant. They are suitable for situations where refueling is not possible or contamination is not allowed.
Structural form
According to the structural form, spherical plain bearings can be divided into integral outer rings, split outer rings and rod end spherical plain bearings. The outer ring of the integral outer ring spherical plain bearing has an integral structure, has good rigidity, and is suitable for heavy-load applications. The outer ring of the split outer ring spherical plain bearing is composed of two or more lobes, which can be clamped by bolts to facilitate installation and gap adjustment. It is suitable for large or occasions that require adjustment. Rod end spherical bearings integrate the bearing and rod end structure, with internal or external threads, and are often used in connecting rod mechanisms.
03 Supporting industries
●Construction machinery: excavator stick connection, crane boom connection, loader working device connection - spherical plain bearings are the bones of construction machinery.
●Water conservancy and hydropower: gate support hinges and hoist connections - long-term stable operation in underwater environments.
●Robot: six-axis robot wrist/elbow joint, welding, spraying and handling scenarios, micron-level precision.
As a leading bearing company in China, Renben Co., Ltd. has a complete product series and technology accumulation in the field of spherical bearings. From material formulation to finished product testing, the entire industry chain is independently controllable to ensure that every spherical plain bearing can withstand the test of working conditions.
04 Let the device move freely like a human
The joints of the human body make bones no longer rigid sticks, but flexible movement systems.
Spherical bearings make equipment connections no longer rigid fixed points, but flexible nodes that can swing freely and self-align.
From the bucket arm of the excavator to the bearings of the bridge, from the steering system of the car to the landing gear of the aircraft - spherical plain bearings work quietly in every place that requires swinging and alignment.
It is not only a bearing, but also a commitment - to allow every piece of equipment to move freely like a human being.
(Source: C&U human bearing)