Pulley

The specified difference between the pulley and the unit for the transmission or lack of transmission of torque to the shaft is functional in nature. By design and from a technological point of view, the blocks and pulleys are the same and are often called the general term pulley. (Similarly, the shaft and axis are functionally different in moment transfer, and structurally the same).

Classifier ESKD “Classifier of products and design documentation for mechanical engineering and instrumentation” classifies pulleys as 71 class of general machine-building parts - bodies of revolution ^[2] .

In the Russian Federation, the requirements for pulleys are regulated by:

• GOST 20889-88. Pulleys for normal V-belt drive belts. General specifications ^[3]
• GOST R 50640-94. Belt pulleys. General technical requirements. ^[four]
• GOST R 50641-94. Grooved pulleys for conventional and narrow V-belts. A system based on the original width . ^[five]
• GOST 5813-2015 Wedge fan belts and pulleys for automobile engines, tractors and combines. Technical requirements and test methods. ^[6]

Also, they are subject to the general requirements for engineering products.

In the pulleys, you can highlight the hub unit , the disk (for solid) or the spokes (for compound pulleys) and the rim. The recess in the rim is called a belt brook. The rim may have flanges . ^[7]

Pulleys depending on the design can be performed ^[8] :

• whole;
• compound.

Compound pulleys with a wedge-shaped stream can serve to adjust the tension of the belt (by removing the discs or by twisting the threads in the halves of the disc).

A special type of composite wedge pulley is a variator pulley - it controls the cross section of the stream allows you to steplessly change the gear ratio of the gear. The control of the cross section of the stream can be mechanical, hydraulic, electromagnetic. Such belt variators are widespread in mopeds .

By manufacturing technology ^[8] :

• cast ;
• forged ;
• stamped ;
• obtained by machining;
• obtained by 3D printing .

According to the shape of the rim ^{[7] [8]} :

• smooth (in the shape of a stream):
  • flat ^[9] ;
  • wedge ^[10] ;
  • polycline ^[10] ;
  • round.
• toothed (in the shape of a tooth):
  • spongy teeth;
  • trapezoidal;
  • semicircular;
  • involute .

•  

  The shape of the pulley rim (stream): 1 - flat, 2 - wedge, 3 - semicircular, 4 - multi-wedge.

•  

  Smooth (flat, wedge and half round) and toothed pulleys

•  

  Convex Flat Cast Pulley

•  

  Composite stamped-welded pulley (acts as a block, i.e. rotates freely on the axis)

•  

  Variable V-belt pulleys with controlled cross section

Smooth pulleys are used to transmit torque without kinematic compliance requirements, since slippage is inherent in them.

Toothed pulleys are used for kinematic compliance requirements (for example, in the gas distribution mechanism of the internal combustion engine, in the drive of the printer head, etc.).

According to the method of fixing the hub ^[11] :

• tight fit ;
• with dowels ;
• with slots .

For stationary equipment in belt drives for pulleys, the use of classic inexpensive materials continues - gray midrange and malleable cast iron cast iron. A substantial mass of parts, as a rule, does not play a role here, since massive pulleys allow the flywheel to be discarded in the mechanism. Replaced can be stamped steel pulleys. For mechanisms with variable speed, for transport machines, where it is important to reduce the mass and moment of inertia, pulleys made of aluminum alloys are used . Finally, the pulleys of highly responsible aggregates can be made of magnesium or titanium .

In recent years, pulleys made of plastics (for example, capralon ) with the possibility of recycling , especially in household appliances, have been widely introduced. ^[12]

An imbalance of pulleys occurs at the manufacturing stage as a result of mold errors, for example when casting in earthen molds. In the case of new technologies for precision casting or stamping, it is small, but its effect is significant for high-speed pulleys. Pulley balancing is carried out on balancing machines . Unlike cardan shafts or pneumatic wheels assembly, instead of installing balancing weights for pulleys, materials are removed by drilling a group of holes in the imbalance sector. ^[13]

• GOST 20889-88. Pulleys for normal V-belt drive belts. General specifications.
• GOST R 50640-94. Belt pulleys. General technical requirements.
• GOST R 50641-94. Grooved pulleys for conventional and narrow V-belts. A system based on the original width.
• GOST 5813-2015 Wedge fan belts and pulleys for automobile engines, tractors and combines. Technical requirements and test methods
• V.I. Anuryev. Reference designer mechanical engineer. In 3 volumes. Volume 2 .. - M: Mechanical Engineering, 2001. - 912 p. - ISBN 5-217-02964-1 .

• Block
• Belting
• Variable speed drive
• Imbalance