Self-lubricating chain

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Self-lubricating chains, also referred to as lube-free chains, are commonly found in both roller chain (ANSI Standards, British Standards, and DIN Standards) and conveyor chain varieties, with specialty self-lubricating chains also available. These chains utilize a bush made of an oil-impregnated sintered metal or plastic to provide continuous lubrication to the chain during drive, eliminating the need for further lubrication. [1]

Contents

History

While some of the earliest self-lubricating bearings were developed by Chrysler [2] the earliest self-lubricating chains were bushed chains, which consisted of pins, plates, and sintered bushes. The loss in strength of the bush required it to be made extra thick. This made the outer diameter so large that it did not allow enough room for a roller. These bushed chains suffer from the drawback of lower allowable load and tensile strength compared to regular roller chain, and the outer diameter of the bushes do not rotate when engaging a sprocket and may suffer faster wear and damage. While various chain manufacturers offered self-lubricating bushed chain designs based on sintered-bush technology since the 1950s, the world's first [3] [ unreliable source? ] self-lubricating roller chain was developed and launched by a Japanese chain manufacturer in 1988. [4] After they made further improvements to the oil impregnation and sintering technologies, they received a patent for their lube-free roller chain, as evidenced by Patent #JP20070237969. [5] In the new design, advancements in powder metal bush technology allowed engineers to design a bush that had a smaller diameter yet was stronger, which allowed room for rollers. These rollers improved performance by allowing the chain to articulate more smoothly into sprockets and protect the sintered bushes. Because of these advancements, the self-lubrication style chains achieved strength on par with regular roller chain, with the added benefit of being lube-free.[ citation needed ] Powdered metal sintered bearings (in the case of roller chain, the bushes) are self-lubricating because their porosity is impregnated with lubricants during the manufacturing process. In use, frictional heat causes the lubricant to expand and flow out of the pores, forming a film between mating parts. Low coefficients of friction, minimal maintenance and trouble-free service life, low cost, and simple installation are the chief advantages of powdered metal bearings. [6] [7]

Construction

An expanded view of a self-lubricating roller chain link Exploded-tsubaki-lambda-chain-link.jpg
An expanded view of a self-lubricating roller chain link

As with standard roller chains, self-lubricating roller chains consist of five basic parts: inner plates, outer plates, pins, bushes, and rollers. However, the bushes for self-lubricating chains are sintered metal, produced using powder metallurgy. Self-lubricating chains can be manufactured cheaply, quickly, and to precision tolerances. [8] To form the bushings, alloyed powdered metal is mixed, compacted, and sintered. The initial compaction to a large degree dictates the density, shape, dimensions, and mechanical properties of the finished part. [7] Sintered materials have inherent porosity, and the pores have both beneficial and detrimental effects on part performance. The pores act as stress concentration zones and reduce mechanical strength and ductility. However, the pores also reduce noise and vibration and serve as lubricant pockets in lubricated contacts. Sintered bearings and gears are used in many applications where the external lubrication is not possible or not preferred. [9] It is essential that the pores form an interconnected system of controlled size and volume, so that oil is supplied to the entire bearing surface. The rate of oil supply increases with temperature and therefore with increasing speeds of rotation, improving performance. [10]

Applications

Self-lubrication is ideal in situations where normal lubrication is difficult, troublesome, or impossible. For example, in paper and food processing, lubrication is undesirable due to product contamination. (Chain companies like Tsubaki and Renold PLC also offer sintered bushes impregnated with food grade lubricant.)

Self-lubricating bushes are used in conveyor chains as well as roller chains for a variety of conveyance applications. These could include not only RS attachment roller chain, but small size conveyor chains and a wide variety of top chains as well.

Related Research Articles

A lubricant is a substance that helps to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. It may also have the function of transmitting forces, transporting foreign particles, or heating or cooling the surfaces. The property of reducing friction is known as lubricity.

<span class="mw-page-title-main">Sintering</span> Process of forming and bonding material by heat or pressure

Sintering or frittage is the process of compacting and forming a solid mass of material by pressure or heat without melting it to the point of liquefaction. Sintering happens as part of a manufacturing process used with metals, ceramics, plastics, and other materials. The nanoparticles in the sintered material diffuse across the boundaries of the particles, fusing the particles together and creating a solid piece.

<span class="mw-page-title-main">Ball bearing</span> Type of rolling-element bearing

A ball bearing is a type of rolling-element bearing that uses balls to maintain the separation between the bearing races.

Fluid bearings are bearings in which the load is supported by a thin layer of rapidly moving pressurized liquid or gas between the bearing surfaces. Since there is no contact between the moving parts, there is no sliding friction, allowing fluid bearings to have lower friction, wear and vibration than many other types of bearings. Thus, it is possible for some fluid bearings to have near-zero wear if operated correctly.

<span class="mw-page-title-main">Bearing (mechanical)</span> Mechanism to constrain relative movement to the desired motion and reduce friction

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.

<span class="mw-page-title-main">Bicycle chain</span> Roller chain that transfers power from the pedals to the drive-wheel of a bicycle

A bicycle chain is a roller chain that transfers power from the pedals to the drive-wheel of a bicycle, thus propelling it. Most bicycle chains are made from plain carbon or alloy steel, but some are nickel-plated to prevent rust, or simply for aesthetics.

<span class="mw-page-title-main">Lubrication</span> The presence of a material to reduce friction between two surfaces.

Lubrication is the process or technique of using a lubricant to reduce friction and wear and tear in a contact between two surfaces. The study of lubrication is a discipline in the field of tribology.

<span class="mw-page-title-main">Powder metallurgy</span> Process of sintering metal powders

Powder metallurgy (PM) is a term covering a wide range of ways in which materials or components are made from metal powders. PM processes can reduce or eliminate the need for subtractive processes in manufacturing, lowering material losses and reducing the cost of the final product.

<span class="mw-page-title-main">Roller chain</span> Type of chain drive

Roller chain or bush roller chain is the type of chain drive most commonly used for transmission of mechanical power on many kinds of domestic, industrial and agricultural machinery, including conveyors, wire- and tube-drawing machines, printing presses, cars, motorcycles, and bicycles. It consists of a series of short cylindrical rollers held together by side links. It is driven by a toothed wheel called a sprocket. It is a simple, reliable, and efficient means of power transmission.

<span class="mw-page-title-main">Plain bearing</span> Simplest type of bearing, comprising just a bearing surface and no rolling elements

A plain bearing, or more commonly sliding contact bearing and slide bearing, is the simplest type of bearing, comprising just a bearing surface and no rolling elements. Therefore, the journal slides over the bearing surface. The simplest example of a plain bearing is a shaft rotating in a hole. A simple linear bearing can be a pair of flat surfaces designed to allow motion; e.g., a drawer and the slides it rests on or the ways on the bed of a lathe.

<span class="mw-page-title-main">Rolling-element bearing</span> Bearing which carries a load with rolling elements placed between two grooved rings

In mechanical engineering, a rolling-element bearing, also known as a rolling bearing, is a bearing which carries a load by placing rolling elements between two concentric, grooved rings called races. The relative motion of the races causes the rolling elements to roll with very little rolling resistance and with little sliding.

<span class="mw-page-title-main">Pillow block bearing</span> Bracket used to provide support to rotating shafts

A pillow block bearing is a pedestal used to provide support for a rotating shaft with the help of compatible bearings and various accessories. The assembly consists of a mounting block which houses a bearing. The block is mounted to a foundation and a shaft is inserted allowing the inner part of the bearing / shaft to rotate. The inside of the bearing is typically 0.025 millimetres (0.001 in) larger diameter than the shaft to ensure a tight fit. Set screws, locking collars, or set collars are commonly used to secure the shaft. Housing material for a pillow block is typically made of cast iron or cast steel.

Grease is a solid or semisolid lubricant formed as a dispersion of thickening agents in a liquid lubricant. Grease generally consists of a soap emulsified with mineral or vegetable oil.

<span class="mw-page-title-main">Grease fitting</span> Metal fitting used in mechanical systems to feed lubricants

A grease fitting, grease nipple, Zerk fitting, grease zerk, or Alemite fitting is a metal fitting used in mechanical systems to feed lubricants, usually lubricating grease, into a bearing under moderate to high pressure using a grease gun.

Dry lubricants or solid lubricants are materials that, despite being in the solid phase, are able to reduce friction between two surfaces sliding against each other without the need for a liquid oil medium.

<span class="mw-page-title-main">Drum motor</span> Electromechanical device

A drum motor is a geared motor drive enclosed within a steel shell providing a single component driving pulley for conveyor belts.

<span class="mw-page-title-main">Conveyor chain</span> Chain designed for chain conveyor systems

A conveyor chain is chain that has been designed specifically for chain conveyor systems. It consists of a series of journal bearings that are held together by constraining link plates. Each bearing consists of a pin and a bush on which the chain roller revolves.

In mechanical engineering, a cam follower, also known as a track follower, is a specialized type of roller or needle bearing designed to follow cam lobe profiles. Cam followers come in a vast array of different configurations, however the most defining characteristic is how the cam follower mounts to its mating part; stud style cam followers use a stud while the yoke style has a hole through the middle.

Oilite is a brand of self-lubricating bearing that is made from metal alloys with pores that channel lubricants between the bearing itself and the shaft. It is manufactured from different types of material. Traditional Oilite is mostly made of copper with approximately 10% tin and up to 1% iron, while both Super Oilite and Super Oilite 16 are primarily made of iron with about 20% copper and, in the case of the latter, up to 1% graphite. Oilite is currently a registered trademark of Beemer Precision, Inc.

Cladding is the bonding together of dissimilar metals. It is different from fusion welding or gluing as a method to fasten the metals together. Cladding is often achieved by extruding two metals through a die as well as pressing or rolling sheets together under high pressure.

References

  1. so that the bearing requires no further lubrication during the whole life of the machine in which it is used, according to "Porous bearings" . Retrieved 27 July 2013.
  2. "Chrysler engineers developed bearings that were made of metal powders forced together under high pressure and heat (a process known as sintering). The ingredients were pure virgin copper (88.5%), tin (10%), and graphite (1.5%). The sintered bearings were so impregnated with oil — with around one third of their volume being oil — that, in most cases, they needed no service attention after installation, although they were seemingly solid. The bearings were dubbed Oilite ®; Oilite bearings would be used in distributors, generators, starters, and ball joints as well as water pump and clutch pilots," according to Zatz, David. "Oilite bearings and the Chrysler Amplex Division". Allpar LLC. Archived from the original on March 25, 2010. Retrieved November 12, 2013.
  3. "Brief History of Lambda Chain" . Retrieved 25 November 2013.
  4. "Lambda Chain" . Retrieved 18 November 2013.
  5. JPgranted JP20070237969,Tanaka Koji,"Lubricant and Oil Non-Feeding Chain",published 2009-04-02, assigned to Tsubakimoto Chain Co
  6. "Specification for Iron-Base Powder Metallurgy (PM) Bearings (Oil-Impregnated)". 2012. doi:10.1520/B0439-12.{{cite journal}}: Cite journal requires |journal= (help)
  7. 1 2 To a large degree, the initial compaction dictates the density, shape, dimensions, and mechanical properties of the finished part, according to Brian James (5 December 2012). "General Description of Production, Properties, and Uses of Sintered Powder Metallurgy Bearings and Structural Parts" (DOC). ASTM. p. 1. Retrieved 2013-11-11.
  8. They are economical, suitable for high production rates and can be manufactured to precision tolerances, according to "2.0 Sintered-Metal Bearings" (PDF). QBC Bearings. 22 May 2008. p. 1. Retrieved 2013-11-11.
  9. The pores act as stress concentration zones and reduce the mechanical strength and ductility, according to Dhanasekaran, S; Gnanamoorthy, G (2004). Development of Self Lubricating Sintered Steels for Tribological Applications (PDF) (Thesis). Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras. Retrieved 11 November 2013.
  10. It is essential that the pores form an interconnected system of controlled size and volume, so that oil is supplied to the entire bearing surface, according to "Porous bearings" . Retrieved 27 July 2013.