Self-lubricating chains, also referred to as lube-free chains, are commonly found in both

roller chain 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, pri ...

( ANSI Standards,

British Standards British Standards (BS) are the standards produced by the BSI Group which is incorporated under a royal charter and which is formally designated as the national standards body (NSB) for the UK. The BSI Group produces British Standards under the a ...

, and DIN Standards) and

conveyor chain 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 c ...

varieties, with specialty self-lubricating chains also available. These chains utilize a bush made of an oil-impregnated

sintered Clinker nodules produced by sintering 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 ...

metal A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typi ...

plastic Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptab ...

to provide continuous

lubrication 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. Lubrication mechanisms such as fluid-lubric ...

to the chain during drive, eliminating the need for further lubrication.so that the bearing requires no further lubrication during the whole life of the machine in which it is used, according to

History

While some of the earliest self-lubricating bearings were developed by Chrysler"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 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 In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. It can also be defined as the longest chord of the circle. Both definitions are also valid fo ...

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 Ultimate tensile strength (UTS), often shortened to tensile strength (TS), ultimate strength, or F_\text within equations, is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials ...

compared to regular roller chain, and the outer diameter of the bushes do not rotate when engaging a

sprocket A sprocket, sprocket-wheel or chainwheel is a profiled wheel with teeth that mesh with a chain, track or other perforated or indented material. The name 'sprocket' applies generally to any wheel upon which radial projections engage a chain pass ...

and may suffer faster

wear Wear is the damaging, gradual removal or deformation of material at solid surfaces. Causes of wear can be mechanical (e.g., erosion) or chemical (e.g., corrosion). The study of wear and related processes is referred to as tribology. Wear in ...

and damage. While various chain manufacturers offered self-lubricating bushed chain designs based on sintered-bush technology since the 1950s, the world's first self-lubricating roller chain was developed and launched by a Japanese chain manufacturer in 1988. 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. In the new design, advancements in powder metal bush technology allowed

engineer Engineers, as practitioners of engineering, are professionals who invent, design, analyze, build and test machines, complex systems, structures, gadgets and materials to fulfill functional objectives and requirements while considering the l ...

s 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. Powdered metal sintered bearings (in the case of roller chain, the bushes) are self-lubricating because their

porosity Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure ...

is impregnated with

lubricant A lubricant (sometimes shortened to lube) 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, t ...

s during the

manufacturing process Manufacturing is the creation or production of goods with the help of equipment, labor, machines, tools, and chemical or biological processing or formulation. It is the essence of secondary sector of the economy. The term may refer to a ...

. In use,

friction Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding (motion), sliding against each other. There are several types of friction: *Dry friction is a force that opposes the relative la ...

heat In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary. A thermodynamic system does not ''contain'' heat. Nevertheless, the term is ...

causes the lubricant to expand and flow out of the pores, forming a film between mating parts. Low coefficients of friction, minimal

maintenance Maintenance may refer to: Biological science * Maintenance of an organism * Maintenance respiration Non-technical maintenance * Alimony, also called ''maintenance'' in British English * Champerty and maintenance, two related legal doctrine ...

and trouble-free

service life A product's service life is its period of use in service. Several related terms describe more precisely a product's life, from the point of manufacture, storage, and distribution, and eventual use. Service life has been defined as "a product's ...

, low cost, and simple installation are the chief advantages of powdered metal bearings.

Construction

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.They are economical, suitable for high production rates and can be manufactured to precision tolerances, according to To form the bushings, alloyed powdered metal is mixed, compacted, and sintered. The initial

compaction Compaction may refer to: * Soil compaction, for mechanically induced compaction near the ground surface * Compaction of ceramic powders * Compaction (geology), part of the process of lithification involving mechanical dewatering of a sediment by ...

to a large degree dictates the

density Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematicall ...

shape A shape or figure is a graphical representation of an object or its external boundary, outline, or external surface, as opposed to other properties such as color, texture, or material type. A plane shape or plane figure is constrained to lie on ...

dimensions In physics and mathematics, the dimension of a mathematical space (or object) is informally defined as the minimum number of coordinates needed to specify any point within it. Thus, a line has a dimension of one (1D) because only one coord ...

, and

mechanical properties A materials property is an intensive property of a material, i.e., a physical property that does not depend on the amount of the material. These quantitative properties may be used as a metric by which the benefits of one material versus another c ...

of the finished part.To a large degree, the initial compaction dictates the density, shape, dimensions, and mechanical properties of the finished part, according to Sintered materials have inherent porosity, and the pores have both beneficial and detrimental effects on part performance. The pores act as

stress concentration In solid mechanics, a stress concentration (also called a stress raiser or a stress riser) is a location in an object where the stress is significantly greater than the surrounding region. Stress concentrations occur when there are irregularit ...

zones and reduce mechanical strength and

ductility Ductility is a mechanical property commonly described as a material's amenability to drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile str ...

. However, the pores also reduce

noise Noise is unwanted sound considered unpleasant, loud or disruptive to hearing. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrations through a medium, such as air or water. The difference aris ...

and

vibration Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point. The word comes from Latin ''vibrationem'' ("shaking, brandishing"). The oscillations may be periodic, such as the motion of a pendulum—or random, suc ...

and serve as lubricant pockets in lubricated contacts. Sintered bearings and

gears A gear is a rotating circular machine part having cut teeth or, in the case of a cogwheel or gearwheel, inserted teeth (called ''cogs''), which mesh with another (compatible) toothed part to transmit (convert) torque and speed. The basic ...

are used in many applications where the external lubrication is not possible or not preferred.The pores act as stress concentration zones and reduce the mechanical strength and ductility, according to It is essential that the pores form an interconnected system of controlled size and

volume Volume is a measure of occupied three-dimensional space. It is often quantified numerically using SI derived units (such as the cubic metre and litre) or by various imperial or US customary units (such as the gallon, quart, cubic inch). Th ...

, so that

oil An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) & lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturate ...

is supplied to the entire

bearing surface A bearing surface in mechanical engineering is the area of contact between two objects. It usually is used in reference to bolted joints and bearings, but can be applied to a wide variety of engineering applications. On a screw the bearing area ...

. The rate of oil supply increases with

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied on ...

and therefore with increasing speeds of

rotation Rotation, or spin, is the circular movement of an object around a '' central axis''. A two-dimensional rotating object has only one possible central axis and can rotate in either a clockwise or counterclockwise direction. A three-dimensional ...

, improving performance.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

Applications

Self-lubrication is ideal in situations where normal lubrication is difficult, troublesome, or impossible. For example, in

paper Paper is a thin sheet material produced by mechanically or chemically processing cellulose fibres derived from wood, Textile, rags, poaceae, grasses or other vegetable sources in water, draining the water through fine mesh leaving the fibre e ...

and

food Food is any substance consumed by an organism for nutritional support. Food is usually of plant, animal, or fungal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals. The substance is ...

processing, lubrication is undesirable due to product contamination. (Chain companies like

Tsubaki Tsubaki (つばき or ツバキ) may refer to: People * , Japanese snowboarder * , the pen name used by a member of the all-female manga-creating team Clamp *Andrew T. Tsubaki (1931-2009), Japanese theatre scholar *, Japanese speed skater * , a ...

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.

References

{{reflist, 1

External links

Tsubaki's Lambda Chain article
Chain drives Mechanical power transmission Mechanical power control