Power transmission systems form the backbone of nearly every industrial process. Assembly lines are driven by mechanical propulsion systems and they are the most common method for mass production of products, from automobiles to consumer goods. Liquids are moved in chemical processes by pumps that make gasoline, diesel, heating oil, and plastics and specialty chemicals. In the home, compressors can be found in the back of every refrigerator to run the refrigeration cycle that keeps our food fresh and in the air conditioners that cool our homes. Commercial appliances, farm equipment, and business equipment all use power transmission systems to run businesses and make our lives easier.
Power transmission systems break down into sub-systems, motors, drive systems, and bearings. In this article, we will examine each sub-system and analyze the choices and applications available for industry.
Motors That Drive Industry
Motors are ubiquitous in industry. Converting energy, be it electrical, steam, or compressed air, into work is the paradigm that runs manufacturing. They are the essential part of power transmission systems and are thus seen in every facet of life even outside of manufacturing.
Motors can be used to move air by driving fans. Fan blades can either be attached directly to the motor's shaft, or a drive system, typically a belt, can link the power generated to the fan blades. In order to compress gases, motors run compressors. Pressurized gases are the working fluid for refrigeration systems. Every piece of food that is kept cold and every air conditioner utilize a motor driven compressor. Pressurizing air is another widely used application for powering tools.
Motor driven pumps are the essential component when moving liquids. Centrifugal pumps use a motor to spin an impeller, which accelerates the movement of liquid. It then flows through a volute or diffuser to increase the liquid pressure. Positive displacement pumps pressurize liquids by trapping them in a chamber and then using a motor to apply a force. Imagine a piston in a cylinder, similar to a car engine.
Motors are found practically everywhere, from cars and refrigerators to industry and business.
Powering Mechanical Drive Systems
In a power transmission system, where the motors generate power, drive systems transfer that power to perform work. In a technical sense, drive systems convert a motor's cyclical power into linear motion. This is how a motor can spin in a circle, but provides the power to run a conveyor belt in a straight line.
The most simple drive system is a direct coupling. Take a spinning motor shaft and weld fan blades onto the end to create a fan to move air. Centrifugal pumps' impeller fans are also directly coupled, as well as sealed to contain liquid, to the drive shaft of the motor. While simple in design, direct coupling is limited to one device operated per motor, and the need to have many motors.
To transfer linear motion to a device that is not directly coupled to a motor, belt and pulley systems are often used. Belts have been in use since the 18th century in water-powered textile mills. The concept is that the motor turns a pulley with a belt attached that runs to a series of pulleys and bushings all attached to other equipment. In this way, one motor can drive multiple machines, as its power is transferred via the belt. Belt and pulley systems can also be synchronized, like the system in a car engine that uses power from the engine to run the alternator, air conditioner, and power steering.
Chain systems are another form of power transmission of linear motion. Often seen in conveyor belts, chain systems transfer a motor's power directly into work, such as moving an assembly line. Mass production facilities utilize this direct application of power as their means of production.
The Right Bearings To Maintain Operation
With all of these heavy metal components in motion, lubrication is needed to ensure smooth movement and power transmission as well as to reduce the load that friction will apply to materials. Bearings are used as the essential method for ensuring that metal does not grind against metal, destroying the machinery. They consist of a set of concentric rings with ball bearings and lubricating fluid set between them. Bearings will support a load in any direction depending on their configuration so they can be used in rotary and linear motion applications.
Linear motion bearings are commonly seen as rollers that will guide material along a specific path. Radial bearings support loads that run perpendicular to the axis of rotation and thrust bearings support loads that run parallel. A full set will support a motor shaft and prevent excessive vibration, friction, and material wear. Advanced bearings will include ports that allow a steady flow of fresh lubricant to enter the bearings and provide a cooling effect for high temperature applications. Ultimately, bearings can be custom made to even support non-uniform shapes.
When all of the components of a power transmission system are designed with integration in mind, work is accomplished more effectively with less down time. Motors that are properly supported by bearings and a drive system that transfers energy into work are the cornerstones of manufacturing processes.
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