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Combinations of these can even be employed within the same bearing. An example is where the cage is made of plastic, and it separates the rollers/balls, which reduce friction by their shape and finish.

Bearings can be lubricated by a ring oiler, a metal ring that rides loosely on the central rotating shaft of the bearing. The ring hangs down into a chamber containing lubricating oil. As the bearing rotates, viscous adhesion draws oil up the ring and onto the shaft, where the oil migrates into the bearing to lubricate it. Excess oil is flung off and collects in the pool again.[23]

However, there are many applications where a more suitable bearing can improve efficiency, accuracy, service intervals, reliability, speed of operation, size, weight, and costs of purchasing and operating machinery.

A recovered example of an early rolling-element bearing is a wooden ball bearing supporting a rotating table from the remains of the Roman Nemi ships in Lake Nemi, Italy. The wrecks were dated to 40 BC.[7][8]

By far, the most common bearing is the plain bearing, a bearing that uses surfaces in rubbing contact, often with a lubricant such as oil or graphite. A plain bearing may or may not be a discrete device. It may be nothing more than the bearing surface of a hole with a shaft passing through it, or of a planar surface that bears another (in these cases, not a discrete device); or it may be a layer of bearing metal either fused to the substrate (semi-discrete) or in the form of a separable sleeve (discrete). With suitable lubrication, plain bearings often give acceptable accuracy, life, and friction at minimal cost. Therefore, they are very widely used.

Factory machines today usually have lube systems, in which a central pump serves periodic charges of oil or grease from a reservoir through lube lines to the various lube points in the machine's bearing surfaces, bearing journals, pillow blocks, and so on. The timing and number of such lube cycles is controlled by the machine's computerized control, such as PLC or CNC, as well as by manual override functions when occasionally needed. This automated process is how all modern CNC machine tools and many other factory machines are lubricated. Similar lube systems are also used on nonautomated machines, in which case there is a hand pump that a machine operator is supposed to pump once daily (for machines in constant use) or once weekly. These are called one-shot systems from their chief selling point: one pull on one handle to lube the whole machine, instead of a dozen pumps of an alemite gun or oil can in a dozen different positions around the machine.

Some applications apply bearing loads from varying directions and accept only limited play or "slop" as the applied load changes. One source of motion is gaps or "play" in the bearing. For example, a 10 mm shaft in a 12 mm hole has 2 mm play.

What originally started life as an ingenious idea by Dr.-Ing. E. h. Georg Schaeffler, has been continuously developed by Schaeffler engineers over the course of 70 years, both in terms of performance and the variety of available types. Compared to a machined needle roller bearing from the 1950s, the operating life for bearings with the same dimensions has increased fifteenfold, and the static load carrying capacity has tripled. The power density, which has been enormously improved thanks to the needle roller and cage assembly, offers considerable downsizing potential for applications that are easier on energy and resources.

There has also been a steady increase in the variety of types: Today, the Schaeffler needle roller bearing portfolio comprises more than 15,000 variants to fulfill a wide variety of requirements. Since the patent application was filed 70 years ago, Schaeffler has sold a total of more than 100 billion needle roller bearings. The length of the wires used in the production of 60 billion needle roller bearings annually would be sufficient to wind around the earth's equator 18 times. Almost 170 million needle rollers are produced from this wire every day.

A second source of motion is elasticity in the bearing itself. For example, the balls in a ball bearing are like stiff rubber and under load deform from a round to a slightly flattened shape. The race is also elastic and develops a slight dent where the ball presses on it.

Stiffness is the amount that the gap varies when the load on the bearing changes, distinct from the friction of the bearing.

Richard Stribeck's extensive research[15][16] on ball bearing steels identified the metallurgy of the commonly used 100Cr6 (AISI 52100),[17] showing coefficient of friction as a function of pressure.

Henry Timken, a 19th-century visionary and innovator in carriage manufacturing, patented the tapered roller bearing in 1898. The following year he formed a company to produce his innovation. Over a century, the company grew to make bearings of all types, including specialty steel bearings and an array of related products and services.

For plain bearings, some materials give a much longer life than others. Some of the John Harrison clocks still operate after hundreds of years because of the lignum vitae wood employed in their construction, whereas his metal clocks are seldom run due to potential wear.

Nonsealed bearings often have a grease fitting, for periodic lubrication with a grease gun, or an oil cup for periodic filling with oil. Before the 1970s, sealed bearings were not encountered on most machinery, and oiling and greasing were a more common activity than they are today. For example, automotive chassis used to require "lube jobs" nearly as often as engine oil changes, but today's car chassis are mostly sealed for life. From the late 1700s through the mid-1900s, industry relied on many workers called oilers to lubricate machinery frequently with oil cans.

The first practical caged-roller bearing was invented in the mid-1740s by horologist John Harrison for his H3 marine timekeeper. In this timepiece, the caged bearing was only used for a very limited oscillating motion, but later on, Harrison applied a similar bearing design with a true rotational movement in a contemporaneous regulator clock.[11][12]

For high-speed and high-power machines, a loss of lubricant can result in rapid bearing heating and damage due to friction. Also, in dirty environments, the oil can become contaminated with dust or debris, increasing friction. In these applications, a fresh supply of lubricant can be continuously supplied to the bearing and all other contact surfaces, and the excess can be collected for filtration, cooling, and possibly reuse. Pressure oiling is commonly used in large and complex internal combustion engines in parts of the engine where directly splashed oil cannot reach, such as up into overhead valve assemblies.[25] High-speed turbochargers also typically require a pressurized oil system to cool the bearings and keep them from burning up due to the heat from the turbine.

The Schaeffler Group has been driving forward groundbreaking inventions and developments in the field of motion technology for over 75 years.

Allowable play varies greatly depending on the use. As an example, a wheelbarrow wheel supports radial and axial loads. Axial loads may be hundreds of newtons force left or right, and it is typically acceptable for the wheel to wobble by as much as 10 mm under the varying load. In contrast, a lathe may position a cutting tool to ±0.002 mm using a ball lead screw held by rotating bearings. The bearings support axial loads of thousands of newtons in either direction and must hold the ball lead screw to ±0.002 mm across that range of loads

Needle cage bearingsizes

Needle roller bearings will continue to play a key role in the future. In e-mobility, needle roller bearings are vital for the function of numerous electrified transmissions. Needle roller and cage assemblies facilitate bearing arrangements with a minimal design envelope, since their section height only corresponds to the diameter of the needle rollers. In addition, they have a high load carrying capacity and are inexpensive compared with other bearing designs. KZK needle roller bearings (crank pin cages) are used, for example, in e-axles with a coaxial design. One application example is the Schaeffler e-axle drive, which has been produced for the Audi e-tron since 2018.

Generally, there is considerable speed range overlap between bearing types. Plain bearings typically handle only lower speeds, rolling element bearings are faster, followed by fluid bearings and finally magnetic bearings which are limited ultimately by centripetal force overcoming material strength.

The term "bearing" is derived from the verb "to bear"; a bearing being a machine element that allows one part to bear (i.e., to support) another. The simplest bearings are bearing surfaces, cut or formed into a part, with varying degrees of control over the form, size, roughness, and location of the surface. Other bearings are separate devices installed into a machine or machine part. The most sophisticated bearings for the most demanding applications are very precise components; their manufacture requires some of the highest standards of current technology.

Bearings played a pivotal role in the nascent Industrial Revolution, allowing the new industrial machinery to operate efficiently. For example, they were used for holding wheel and axle assemblies to greatly reduce friction compared to prior non-bearing designs.

Fluid and magnetic bearings can have practically indefinite service lives. In practice, fluid bearings support high loads in hydroelectric plants that have been in nearly continuous service since about 1900 and show no signs of wear.[citation needed]

In the early 1980s, Pacific Bearing's founder, Robert Schroeder, invented the first bi-material plain bearing that was interchangeable with linear ball bearings. This bearing had a metal shell (aluminum, steel or stainless steel) and a layer of Teflon-based material connected by a thin adhesive layer.[19]

The stiffness of a bearing is how the distance between the parts separated by the bearing varies with the applied load. With rolling element bearings, this is due to the strain of the ball and race. With fluid bearings, it is due to how the pressure of the fluid varies with the gap (when correctly loaded, fluid bearings are typically stiffer than rolling element bearings).

In 1883, Friedrich Fischer, founder of FAG, developed an approach for milling and grinding balls of equal size and exact roundness by means of a suitable production machine, which set the stage for the creation of an independent bearing industry. His hometown Schweinfurt later became a world-leading center for ball bearing production.

Bearing life is often much better when the bearing is kept clean and well-lubricated. However, many applications make good maintenance difficult. One example is bearings in the conveyor of a rock crusher are exposed continually to hard abrasive particles. Cleaning is of little use because cleaning is expensive, yet the bearing is contaminated again as soon as the conveyor resumes operation. Thus, a good maintenance program might lubricate the bearings frequently but not include any disassembly for cleaning. The frequent lubrication, by its nature, provides a limited kind of cleaning action by displacing older (grit-filled) oil or grease with a fresh charge, which itself collects grit before being displaced by the next cycle. Another example are bearings in wind turbines, which makes maintenance difficult since the nacelle is placed high up in the air in strong wind areas. In addition, the turbine does not always run and is subjected to different operating behavior in different weather conditions, which makes proper lubrication a challenge.[32]

Rolling element bearing life is determined by load, temperature, maintenance, lubrication, material defects, contamination, handling, installation and other factors. These factors can all have a significant effect on bearing life. For example, the service life of bearings in one application was extended dramatically by changing how the bearings were stored before installation and use, as vibrations during storage caused lubricant failure even when the only load on the bearing was its own weight;[29] the resulting damage is often false brinelling.[30] Bearing life is statistical: several samples of a given bearing will often exhibit a bell curve of service life, with a few samples showing significantly better or worse life. Bearing life varies because microscopic structure and contamination vary greatly even where macroscopically they seem identical.

There are many methods of mounting bearings, usually involving an interference fit.[27] When press fitting or shrink fitting a bearing into a bore or onto a shaft, it's important to keep the housing bore and shaft outer diameter to very close limits, which can involve one or more counterboring operations, several facing operations, and drilling, tapping, and threading operations.[28] Alternatively, an interference fit can also be achieved with the addition of a tolerance ring.

The first patent for a radial-style ball bearing was awarded to Jules Suriray, a Parisian bicycle mechanic, on 3 August 1869. The bearings were then fitted to the winning bicycle ridden by James Moore in the world's first bicycle road race, Paris-Rouen, in November 1869.[14]

The Schaeffler Group and Vitesco have completed their merger on 1st of October 2024 to become a Leading Motion Technology company.

The cage-guided needle roller bearing is one of Schaeffler’s most important innovations is now an indispensable part of bearing technology. 70 years ago, Dr.-Ing. E. h. Georg Schaeffler had the brilliant idea of equipping the needle roller bearing with a cage to guide the needle rollers. Since the patent was filed in 1950, these bearings have ensured the correct rotation in automotive and industrial applications and also play an extremely important role when it comes to future topics like collaborative robotics and electric mobility.

The first plain and rolling-element bearings were wood, closely followed by bronze. Over their history, bearings have been made of many materials, including ceramic, sapphire, glass, steel, bronze, and other metals. Plastic bearings made of nylon, polyoxymethylene, polytetrafluoroethylene, and UHMWPE, among other materials, are also in use today.

Erich Franke invented and patented the wire race bearing in 1934. His focus was on a bearing design with a cross-section as small as possible and which could be integrated into the enclosing design. After World War II, he founded with Gerhard Heydrich the company Franke & Heydrich KG (today Franke GmbH) to push the development and production of wire race bearings.

The oiling system inside a modern automotive or truck engine is similar in concept to the lube systems mentioned above, except that oil is pumped continuously. Much of this oil flows through passages drilled or cast into the engine block and cylinder heads, escaping through ports directly onto bearings and squirting elsewhere to provide an oil bath. The oil pump simply pumps constantly, and any excess pumped oil continuously escapes through a relief valve back into the sump.

Many bearings in high-cycle industrial operations need periodic lubrication and cleaning, and many require occasional adjustment, such as pre-load adjustment, to minimize the effects of wear.

“The development of this very product is, in itself, an impressive example of what sets us apart: We have utilized all synergies in the cage-guided needle roller bearing, which will allow us to serve all relevant target markets with this innovative product and generate real customer benefits – in both the automotive and the industrial sector.”, says Georg F. W. Schaeffler, Family Shareholder and Chairman of the Supervisory Board.

Bearings are often specified to give an "L10" (US) or "B10" (elsewhere) life, the duration by which ten percent of the bearings in that application can be expected to have failed due to classical fatigue failure (and not any other mode of failure such as lubrication starvation, wrong mounting etc.), or, alternatively, the duration at which ninety percent will still be operating. The L10/B10 life of the bearing is theoretical, and may not represent service life of the bearing. Bearings are also rated using the C0 (static loading) value. This is the basic load rating as a reference, and not an actual load value.

With this invention, my father, Georg Schaeffler, laid the foundation for the rapid growth of our company. The cage-guided needle roller bearing is one of the most important innovations in our company's history as an automotive and industrial supplier.

Although long bearing life is often desirable, it is sometimes not necessary. Harris 2001 describes a bearing for a rocket motor oxygen pump that gave several hours life, far in excess of the several tens of minutes needed.[29]

The service life of the bearing is affected by many factors not controlled by the bearing manufacturers. For example, bearing mounting, temperature, exposure to external environment, lubricant cleanliness, and electrical currents through bearings. High frequency PWM inverters can induce electric currents in a bearing, which can be suppressed by the use of ferrite chokes. The temperature and terrain of the micro-surface will determine the amount of friction by touching solid parts. Certain elements and fields reduce friction while increasing speeds. Strength and mobility help determine the load the bearing type can carry. Alignment factors can play a damaging role in wear and tear, yet overcome by computer aid signaling and non-rubbing bearing types, such as magnetic levitation or air field pressure.[clarification needed]

Leonardo da Vinci incorporated drawings of ball bearings in his design for a helicopter around the year 1500; this is the first recorded use of bearings in an aerospace design. However, Agostino Ramelli is the first to have published roller and thrust bearings sketches.[9] An issue with the ball and roller bearings is that the balls or rollers rub against each other, causing additional friction. This can be reduced by enclosing each individual ball or roller within a cage. The captured, or caged, ball bearing was originally described by Galileo in the 17th century.[10]

Reducing friction in bearings is often important for efficiency, to reduce wear and to facilitate extended use at high speeds and to avoid overheating and premature failure of the bearing. Essentially, a bearing can reduce friction by virtue of its shape, by its material, or by introducing and containing a fluid between surfaces or by separating the surfaces with an electromagnetic field.

It is sometimes assumed that the invention of the rolling bearing, in the form of wooden rollers supporting– or bearing –an object being moved, predates the invention of a wheel rotating on a plain bearing; this underlies speculation that cultures such as the Ancient Egyptians used roller bearings in the form of tree trunks under sleds. There is no evidence for this sequence of technological development.[1][2][3]: 31  The Egyptians' own drawings in the tomb of Djehutihotep show the process of moving massive stone blocks on sledges as using liquid-lubricated runners which would constitute plain bearings.[4][3]: 36 [5]: 710  There are also Egyptian drawings of plain bearings used with hand drills.[6]

The modern, self-aligning design of ball bearing is attributed to Sven Wingquist of the SKF ball-bearing manufacturer in 1907 when he was awarded Swedish patent No. 25406 on its design.

In industry too, where lightweight robots are increasingly in demand, the use of needle bearings permits light and compact joint designs by means of downsizing. The needle bearings provide minimal variability and the highest level of safety. The most recent example is the angular contact needle roller bearing XZU from Schaeffler, which is used both as an articulated arm bearing in lightweight robots and cobots, and as the main bearing arrangement in the new RTWH precision gearbox, a ready-to-install reduction gear unit for robot joints.

A bearing is a machine element that constrains relative motion to only the desired motion and reduces friction between moving parts. The design of the bearing may, for example, provide for free linear movement of the moving part or for free rotation around a fixed axis; or, it may prevent a motion by controlling the vectors of normal forces that bear on the moving parts. Most bearings facilitate the desired motion by minimizing friction. Bearings are classified broadly according to the type of operation, the motions allowed, or the directions of the loads (forces) applied to the parts.

We work to bring about the technologies of the future and, in doing so, create the basis for our innovations to make tomorrow's worldwide mobility even better than it is today.

The first patent on ball bearings was awarded to Philip Vaughan, a British inventor and ironmaster in Carmarthen in 1794. His was the first modern ball-bearing design, with the ball running along a groove in the axle assembly.[10][13]

Today's ball and roller bearings are used in many applications, which include a rotating component. Examples include ultra high-speed bearings in dental drills, aerospace bearings in the Mars Rover, gearbox and wheel bearings on automobiles, flexure bearings in optical alignment systems, and air bearings used in coordinate-measuring machines.

Different bearing types have different operating speed limits. Speed is typically specified as maximum relative surface speeds, often specified ft/s or m/s. Rotational bearings typically describe performance in terms of the product DN where D is the mean diameter (often in mm) of the bearing and N is the rotation rate in revolutions per minute.

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Composite bearings are designed with a self-lubricating polytetrafluorethylene (PTFE) liner with a laminated metal backing. The PTFE liner offers consistent, controlled friction as well as durability, whilst the metal backing ensures the composite bearing is robust and capable of withstanding high loads and stresses throughout its long life. Its design also makes it lightweight-one tenth the weight of a traditional rolling element bearing.[26]

Depending on the customized specifications (backing material and PTFE compounds), composite bearings can operate up to 30 years without maintenance.

Many bearings require periodic maintenance to prevent premature failure, but others require little maintenance. The latter include various kinds of polymer, fluid and magnetic bearings, as well as rolling-element bearings that are described with terms including sealed bearing and sealed for life. These contain seals to keep the dirt out and the grease in. They work successfully in many applications, providing maintenance-free operation. Some applications cannot use them effectively.

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Some bearings use a thick grease for lubrication, which is pushed into the gaps between the bearing surfaces, also known as packing. The grease is held in place by a plastic, leather, or rubber gasket (also called a gland) that covers the inside and outside edges of the bearing race to keep the grease from escaping. Bearings may also be packed with other materials. Historically, the wheels on railroad cars used sleeve bearings packed with waste or loose scraps of cotton or wool fiber soaked in oil, then later used solid pads of cotton.[22]

Watchmakers produce "jeweled" watches using sapphire plain bearings to reduce friction, thus allowing more precise timekeeping.

With the invention Dr.-Ing. E. h. Georg Schaeffler eliminated the serious disadvantages associated with the full complement needle roller bearings that had previously been used as standard: The long needle rollers tended to move in a transverse direction during rotation of the bearing (skewing), which would then cause the bearing to jam. Furthermore, a substantial amount of sliding friction was generated between the counter-rotating needle rollers. The development of the new needle cage overcame these disadvantages and permitted considerably higher speeds and less friction. This allowed engineers to substitute other bearing designs for cage-guided needle roller bearings and significantly improve the performance of their applications.

70 years ago, Dr.-Ing. E. h. Georg Schaeffler revolutionized bearing technology. The first practical tests involving cage-guided needle roller bearings began in February 1950. The results were convincing – the components exhibited extremely low wear and friction. The application for a patent in September 1950 laid the foundation for the product's success. In February 1951, just one year after construction of the first prototype, the first volume production orders were obtained from automotive manufacturers, and use in industrial applications was to follow.

Designed in 1968 and later patented in 1972, Bishop-Wisecarver's co-founder Bud Wisecarver created vee groove bearing guide wheels, a type of linear motion bearing consisting of both an external and internal 90-degree vee angle.[18][better source needed]

Flexure bearings rely on elastic properties of a material. Flexure bearings bend a piece of material repeatedly. Some materials fail after repeated bending, even at low loads, but careful material selection and bearing design can make flexure bearing life indefinite.

Ag bearings

Schaeffler products facilitate and shape mobility - as they have been doing for decades. We have also continued the development of our expertise from "basic" components to complete system solutions.

Even basic materials can have impressive durability. Wooden bearings, for instance, can still be seen today in old clocks or in water mills where the water provides cooling and lubrication.

Bearing design varies depending on the size and directions of the forces required to support. Forces can be predominately radial, axial (thrust bearings), or bending moments perpendicular to the main axis.

A rudimentary form of lubrication is splash lubrication. Some machines contain a pool of lubricant in the bottom, with gears partially immersed in the liquid, or crank rods that can swing down into the pool as the device operates. The spinning wheels fling oil into the air around them, while the crank rods slap at the surface of the oil, splashing it randomly on the engine's interior surfaces. Some small internal combustion engines specifically contain special plastic flinger wheels which randomly scatter oil around the interior of the mechanism.[24]

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Rotary bearings hold rotating components such as shafts or axles within mechanical systems and transfer axial and radial loads from the source of the load to the structure supporting it. The simplest form of bearing, the plain bearing, consists of a shaft rotating in a hole. Lubrication is used to reduce friction. Lubricants come in different forms, including liquids, solids, and gases. The choice of lubricant depends on the specific application and factors such as temperature, load, and speed. In the ball bearing and roller bearing, to reduce sliding friction, rolling elements such as rollers or balls with a circular cross-section are located between the races or journals of the bearing assembly. A wide variety of bearing designs exists to allow the demands of the application to be correctly met for maximum efficiency, reliability, durability, and performance.

In particular, needle roller bearings made an invaluable contribution to the development of small, high-performance, and affordable automobiles. “Without reliable needle roller bearings, modern automotive drives would still be inconceivable today,” says Matthias Zink, CEO Automotive Technologies at Schaeffler. The use of needle roller bearings in mechanical and plant engineering, construction and agricultural machinery, and in conveyor technology, was also being gradually introduced.