Chains And Sprockets

UN DER STAND IN G THE FUND AM EN TALS OF CHA IN & SP ROC KET

Submitted By Balraj - 007 Devesh - 008 Debajyoti - 009

Chains Definition A chain is a reliable machine component, which transmits power by means of tensile forces, and is used primarily for power transmission and conveyance systems(for material handling purpose). As a transmission, chain drives can operate efficiently at high loads and they may be used where precise speed ratios are required.

Features of Chain Drives     

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Features of Chain Drives: Speed reduction/increase of up to seven to one can be easily accommodated. Chain can accommodate long shaft-center distances (less than 4 m), and is more versatile. It is possible to use chain with multiple shafts or drives with both sides of the chain. Standardization of chains under the American National Standards Institute (ANSI), the International Standardization Organization (ISO), and the Japanese Industrial Standards (JIS) allow ease of selection. It is easy to cut and connect chains. The sprocket diameter for a chain system may be smaller than a belt pulley, while transmitting the same torque.

Types of chains Roller chains

Chains Conveyor chains

Inverted Tooth chains

Roller Chains A length of roller chain is made up from a number of links and each chain link comprise side plates, pins, bushes and rollers. The ends of a chain are joined together when in mesh with the drive and driven sprocket. As the sprocket teeth engage with the rollers, rolling rather than sliding contact occurs - thus making this a very efficient form of transmission element. Roller chains are available in various standard forms, including stainless steel, plastic (for their self lubricating qualities) and various forms (especially for use on agricultural and conveying applications).

Components of roller chain A roller chain consists of a number of inner link assemblies in which adjacent pairs are connected by outer links.  An inner link assembly is made up of a pair of inner plates connected by two riveted bushes spaced a set distance apart called the pitch. A roller is free to rotate on either bush.  The outer links comprise a pair of outer plates which are attached via a pair of riveted bearing pins which are spaced a pitch distance apart.  These pins are free to fit inside the inner link bushes and connect inner links as shown in Figure. 

Conveyer Chain 

Roller chains which are specifically manufactured for use on material handling and conveyor equipment are called ‘Conveyer Chain’.

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Such chains are widely used in the textile, food processing, mining and agricultural industries, for escalators, elevators and also on modern machine tools.

Inverted Tooth Chain 

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Inverted Tooth chain has teeth formed in the links and these engage with the teeth in the sprockets. Their sprockets can be likened to gears but instead of meshing with each other they connect across a greater centre distance by means of a chain. Due to the compliance of individual links, there is less impact force when a link first engages with sprocket teeth and consequently an inverted tooth chain drive can operate more quietly and at higher speed than roller chain of comparable size.

Lubrication 

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Chains are usually prelubricated with rustprevention oil before shipping. Nevertheless, it is essential to lubricate roller chain. Properly lubricated chain has a longer wear life and is less likely to develop rust. Lubricate the chain where the tension is minimal, applying the lubricant in the clearance between the link plates

 

Lubrication

Method Manual Application. Oil is applied with an oil filler or brush on the slack side of the chain.

Drip Lubrication. A simple case can be used. Oil from the oil cup is supplied by drip feeding

Oil Bath Lubrication. The chain is installed in a leak free casing.

Application 

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Chain drives are a very widely used transmission system and can be found extensively in all mechanical industries and even on some civil engineering projects. Applications range from machine tool, marine and aerospace drives, motor cycle and bicycle transmissions. They are also widely used in the nuclear, mining and food industries and on conveying and packaging machinery. For example, in many motor vehicle and ships engines, the cam shaft is driven by a chain. Chain drives are used on civil aircraft such as Concorde and military aircraft.

Sprockets A sprocket is a profiled wheel with teeth that meshes with a chain, track or other perforated or indented material. It is distinguished from a gear in that sprockets are never meshed together directly, and from a pulley by not usually having a flange at each side.

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The sprocket looks like a gear but differs in three important ways: Sprockets have many engaging teeth; gears usually have only one or two. The teeth of a gear touch and slip against each other; there is basically no slippage in a sprocket. The shape of the teeth are different in gears and sprockets.

Types of Sprockets There are four types of sprocket; 3. 4. 5. 6.

Type A: Plain Plate sprockets Type B: Hub on one side Type C: Hub on both sides Type D: Detachable hub

Application Sprockets are used in bicycles, motorcycles, cars, tanks, and other machinery either to transmit rotary motion between two shafts where gears are unsuitable or to impart linear motion to a track, tape etc.  In the case of vehicles with caterpillar tracks the engine-driven toothed-wheel transmitting motion to the tracks is known as the drive sprocket and may be positioned at the front or back of the vehicle, or in some cases, both.  Sprockets are used in the film transport mechanisms of movie projectors and movie cameras. In this case, the sprocket wheels engage film perforations in the film stock.  Sprocket feed was also used for punched tape and is used for paper feed to some computer printers. 

Bibliography  www.chain-guide.com  www.google.com  www.wikipedia.com

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