Chains

Chain

  A chain is regarded in between the gear drive and the belt drive. Like gears, chains are made of metal and, therefore, occupy lesser space and give constant velocity ratios. Like belts, they are used for longer centre distances.

Sprocket and chain

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Classification of chains

Chains have been classified into hoisting chains, conveyor chains and power-transmission chains.  Each type has been discussed below:

1. Hoisting Chains 

    Hoisting chains include oral link and stud - link chains.  An oval - link chain is a common form of hoisting chain [Fig. (a)].  It consists of oval links and is also known as coil chain.  Such chains are used for lower speeds only.  Figure (b) shows a stud - link chain.  This does not link or tangle easily.

Hoisting chain

2. Conveyor Chains 

   Conveyor chains may be of detachable or hook - joint type [Fig. (a)], or of the closed - end pintle type [Fig. (b)].  The sprocket teeth are so shaped and spaced that the chain should run onto and off the sprocket smoothly and without interference.  Such chains are used for low - speed agricultural machinery.  The material of the links is usually.  malleable cast iron. The motion of the chain is not very smooth.

Conveyor chain

3. Power Transmissions Chains 

   These chains are made of steel in which the wearing parts are hardened.  They are accurately machined and run on carefully designed sprockets.  These are of three types

   

Power transmission chain

     (i) Block Chain 

  This type of chain [Fig. (a)] is mainly used for transmission of power at low speeds.  Sometimes, they are also used as conveyor chains in place of malleable conveyor chains.

    (ii) Roller Chain  

   A common form of roller chain is shown in [Fig. (b)], bushing is fixed to the inner link where as the outer link has a pin fixed to it.  There only sliding motion between the pin and the bushing. The roller is made up the hardened material and is free to turn on the bushing.  Figure shows this type of chain in place on the sprocket good roller chain is quieter and wears less as compared to a block chain.  

  (iii) silent chain (Inverted Tooth Chain)  

   Though roller chains can run quietly at fairly high speeds, the silent chains or inverted tooth chains are used where maximum quietness is desired.  Silent chains do not have rollers.  The links are so shaped as to engage directly with the sprocket teeth.  The included angle is either 60 ° or 75 ° [Fig. (c)].