Spindle Pulleys

What is a pulley?
Pulley is a simple machine used in a number of machinery work or machine parts to reduce the amount of force required to do a work. Usually a pulley consists of a wheel with a grooved rim in which a rope or chain is run. What pulleys actually do is that they change the direction of force applied on the load to do the required work. Pulleys work in a similar way like gears but they are not directly joined but linked by tubular springs, elastic bands or some flexible but strong material which is referred to as a belt pulley.


Advantages & disadvantages of pulleys over gears
The main advantage of pulley over gear is that it is simple to make and can be used at a distance from each other whereas gear needs to touch to work. The disadvantage of the pulley is that it works by friction and can slip.

Uses of pulleys
Pulleys are used in belt driven spindles. They are used as single or in combination to transmit energy and motion. In belt driven spindles, they are attached to the shafts at their axes. The power is transferred between the shafts by means of endless belts running over these pulleys. Pulleys are used to change the spindle speed and feed rate.

Materials used in making pulleys

• Fiberglass
• Plastic
• Polyester
• Steel
• Cast iron etc.

Styles of pulley
There are two pulley styles:

• Solid: They use belts that have a uniform thickness along the radius.
  
  
• Spoke, Thin or ribbed: They are designed for applications that require a reduction in pulley weight.

Types of pulleys in belt driven spindles

• V-belt spindle pulley
• Flat belt spindle pulley

V-belt pulleys
V belt pulleys are attached with drive belts in several power transmission applications. They are efficient and cost-effective. These type of pulleys have a triangular or trapezoidal cross-section. They are available in both single groove and multiple groove devices. They differ in terms of pulley size, belt width, belt angle, shaft mounting, operating temperature, and pulley web style. There are different types of V belt pulleys.

• Standard V belt pulleys: They have one or more grooves and are used for general-purpose applications.
  
  
• Variable speed pulleys: They have faces or flanges which can adjust axially to vary pitch diameter.
  
  
• Idler pulleys: They are used as belt tensioners and contain bearings allowing free rotation.
  
  
• Companion pulleys: This type has ribbed webs for high strength-to-weight ratios.
  
  
• Multiple-size pulleys: They use step-down or cone configurations.
  
  
• Poly-V pulleys: They are the most common belts used in spindles and used with mating belts for high-speed power transmission.

Flat belt pulleys
These type of pulleys are used in transmission systems that are driven by flat belts, typically used in high-speed, low-power applications. Flat belts are smaller than V belts because they are thinner by 25% or more. They require flat pulleys and flat pulley idlers and not necessarily grooved flat belt pulleys. They apply motive power to the belt.