Pneumatics, a subsection of an area called fluid power, is the use of pressurized air to effect mechanical motion.

Pneumatic power is used in industry, where it is common to have industrial factory unit plumbed for compressed air. It also has applications in, among other things, dentistry, construction, and mining. Pneumatic power users need not worry about hazardous leakages as the fuel is commonly just air, although other compressed gases, such as carbon dioxide, may be used.

Pneumatic actuators

A pneumatic actuator converts energy (in the form of compressed air, typically) into motion. The motion can be rotary or linear, depending on the type of actuator. Some types of pneumatic actuators include:

• Tie rod cylinders
• Rotary actuators
• Grippers
• Rodless actuators with magnetic linkage
• Rodless actuators with mechanical linkage
• Pneumatic artificial muscles
• Speciality actuators that combine rotary and linear motion–frequently used for clamping operations
• Vacuum generators

A Pneumatic actuator mainly consists of a piston a cylinder and valves or ports. The piston is covered by a diaphram, which keeps the air in the upper portion of the cylinder, allowing air pressure to force the diaphram downard, moving the piston underneath, which in turn moves the valve stem, which is linked to the internal parts of the valve. Pneumatic actuators only have one spot for a signal input, top or bottom, depending on action requried. Valves require little pressure to operate and usually double or triple the input force. The larger the size of the piston, the larger the output pressure can be. Having a larger piston can also be good if air supply is low, allowing the same forces with less input. These pressures are large enough to crush object in the pipe. On 100 kPa input, you could lift a small car (upwards 10,000 lbs) easily, and this is only a basic, small pneumatic valve. However, the resulting forces required of the stem would be too great and cause the valve stem to fail.

This pressure is transferred to the valve stem, which is hooked up to either the valve plug, butterfly valve etc. Larger forces are required in high pressure or high flow pipelines to allow the valve to overcome these forces, and allow it to move the valves moving parts to control the material flowing inside.

Valves input pressure is the “control signal.” This can come from a variety of measuring devices, and each different pressure is a different set point for a valve. A typical standard signal is 20-100 kPa. For example, a valve could be controlling the pressure in a vessel which has a constant out flow, and a varried in flow. A pressure transmitter will monitor the pressure in the vessel and transmit a signal from 20-100 kPa. 20 kPa means there is no pressure, 100 kPa means there is full range pressure (can be varied by the transmiters calibration points). As the pressure rises in the vessel, the output of the transmitter rises, this increase in pressure is sent to the valve, which causes the valve to stroke downard, and start closing the valve, decreasing flow into the vessel, reducing the pressure in the vessel as excess pressure is evacuated through the out flow. This is called a Direct acting process.

Comparison to hydraulics

Both pneumatics and hydraulics are applications of fluid power. Pneumatics uses air, which is compressible, while hydraulics uses relatively incompressible liquid media such as oil. Most industrial pneumatic applications use pressures of about 80 to 100 pounds per square inch (psi) (500 to 700 kilopascals). Hydraulics applications commonly use from 1,000 to 5,000 psi (7 to 35 MPa), but specialized applications may exceed 10,000 psi (70 MPa).

Advantages of pneumatics

Clean

• Air is used by a machine & is then exhausted to the atmosphere - no return line necessary.
• Any leaks will be of air (which is much less of a problem than oil leaks in Hydraulics).

Availability

• Air is freely available in the pneumatics
• Most factories are pre-plumbed for compressed air distribution - which makes it very easy to set up a manufacturing process

Simplicity of Design And Control

• Machines are easily designed using standard cylinders & other components. Control is as easy as its simple ON - OFF type control

Reliability

• Pneumatic systems tend to have long operating lives and require very little maintenance.
• Because air is compressable, the equipment is less likely to be damaged by shock. The air in pneumatics absorbs excessive force, whereas the fluid of hydraulics directly transfers force.

Storage

• Compressed Air can be stored, allowing the use of machines when electrical power is lost.

Safety

• Very small fire hazard (compared to Hydraulic Oil)
• Machines can be designed to be overload safe.

Advantages of hydraulics

• Fluid does not absorb any of the supplied energy.

• Capable of moving much higher loads and providing much higher forces due to the incompressibility.

• The hydraulic working fluid is basically incompressible, leading to a minimum of spring action. When hydraulic fluid flow is stopped, the slightest motion of the load releases the pressure on the load; there is no need to “bleed off” pressurised air to release the pressure on the load.

An electric motor uses electrical energy to produce mechanical energy. The reverse process, that of using mechanical energy to produce electrical energy, is accomplished by a generator or dynamo. Traction motors used on locomotives often perform both tasks if the locomotive is equipped with dynamic brakes. Electric motors are found in household appliances such as fans, refrigerators, washing machines, pool pumps, floor vacuums, and fan-forced ovens.

The classic division of electric motors has been that of DC types vs AC types. This is more a de facto convention, rather than a rigid distinction. For example, many classic DC motors run happily on AC power.

The ongoing trend toward electronic control further muddles the distinction, as modern drivers have moved the commutator out of the motor shell. For this new breed of motor, driver circuits are relied upon to generate sinusoidal AC drive currents, or some approximation of. The two best examples are: the brushless DC motor, and the stepping motor, both being polyphase AC motors requiring external electronic control.

There is a clearer distinction between a synchronous motor and asynchronous types. In the synchronous types, the rotor rotates in synchrony with the oscillating field or current (eg. permanent magnet motors). In contrast, an asynchronous motor is designed to slip; the most ubiquitous example being the common AC induction motor which must slip in order to generate torque.

A DC motor is designed to run on DC electric power. Two examples of pure DC designs are Michael Faraday’s homopolar motor (which is uncommon), and the ball bearing motor. By far the most common DC motor types are the brushed and brushless types, which use internal and external commutation respectively to create an oscillating AC current from the DC source — so they are not purely DC machines in a strict sense.

Brushed DC motor 

Brushed DC Electric Motor

The classic DC motor design generates an oscillating current in a wound rotor with a split ring commutator, and either a wound or permanent magnet stator. A rotor consists of a coil wound around a rotor which is then powered by any type of battery.

Many of the limitations of the classic commutator DC motor are due to the need for brushes to press against the commutator. This creates friction. At higher speeds, brushes have increasing difficulty in maintaining contact. Brushes may bounce off the irregularities in the commutator surface, creating sparks. This limits the maximum speed of the machine. The current density per unit area of the brushes limits the output of the motor. The imperfect electric contact also causes electrical noise. Brushes eventually wear out and require replacement, and the commutator itself is subject to wear and maintenance. The commutator assembly on a large machine is a costly element, requiring precision assembly of many parts.

Brushless DC motors

Some of the problems of the brushed DC motor are eliminated in the brushless design. In this motor, the mechanical “rotating switch” or commutator/brushgear assembly is replaced by an external electronic switch synchronised to the rotor’s position. Brushless motors are typically 85-90% efficient, whereas DC motors with brushgear are typically 75-80% efficient.

Midway between ordinary DC motors and stepper motors lies the realm of the brushless DC motor. Built in a fashion very similar to stepper motors, these often use a permanent magnet external rotor, three phases of driving coils, one or more Hall effect sensors to sense the position of the rotor, and the associated drive electronics. The coils are activated, one phase after the other, by the drive electronics as cued by the signals from the Hall effect sensors. In effect, they act as three-phase synchronous motors containing their own variable-frequency drive electronics. A specialized class of brushless DC motor controllers utilize EMF feedback through the main phase connections instead of Hall effect sensors to determine position and velocity. These motors are used extensively in electric radio-controlled vehicles. When configured with the magnets on the outside, these are referred to by modelists as outrunner motors.

Brushless DC motors are commonly used where precise speed control is necessary, as in computer disk drives or in video cassette recorders, the spindles within CD, CD-ROM (etc.) drives, and mechanisms within office products such as fans, laser printers and photocopiers. They have several advantages over conventional motors:

• Compared to AC fans using shaded-pole motors, they are very efficient, running much cooler than the equivalent AC motors. This cool operation leads to much-improved life of the fan’s bearings.
• Without a commutator to wear out, the life of a DC brushless motor can be significantly longer compared to a DC motor using brushes and a commutator. Commutation also tends to cause a great deal of electrical and RF noise; without a commutator or brushes, a brushless motor may be used in electrically sensitive devices like audio equipment or computers.
• The same Hall effect sensors that provide the commutation can also provide a convenient tachometer signal for closed-loop control (servo-controlled) applications. In fans, the tachometer signal can be used to derive a “fan OK” signal.
• The motor can be easily synchronized to an internal or external clock, leading to precise speed control.
• Brushless motors have no chance of sparking, unlike brushed motors, making them better suited to environments with volatile chemicals and fuels.
• Brushless motors are usually used in small equipment such as computers and are generally used to get rid of unwanted heat.
• They are also very quiet motors which is an advantage if being used in equipment that is affected by vibrations.

Modern DC brushless motors range in power from a fraction of a watt to many kilowatts. Larger brushless motors up to about 100 kW rating are used in electric vehicles. They also find significant use in high-performance electric model aircraft.

Loctite is a wide-ranging brand of adhesives which includes acrylics, anaerobics, cyanoacrylates, epoxies, hot melts, silicones, urethanes and UV/light curing adhesives. The name Loctite was chosen in 1956 by the daughter-in-law of Dr. Vernon Krieble, inventor of a unique adhesive resin that hardened in the absence of air, as a replacement for less-reliable locking washers when securing bolts and screws. Vernon Krieble is listed as an inventor on a number of patents, including U.S. Patent No. 2,895,950 (July 21, 1959) and U.S. Patent No. 3,046,262 (July 24, 1962).

The Loctite brand is now part of Henkel, a German family company with interests in many chemical and industrial products. Loctite is the market leader in adhesive technology, and although its original anaerobic technology is still core to its business many know Loctite for its superglue (cyanoacrylate) adhesives. Loctite now offers a complete range of adhesives to provide engineering solutions for all industries globally. Loctite products are available in at least 80 countries, and are used throughout the automotive, microelectronics, aerospace and medical industries.

In addition to their consumer and industrial adhesives, other Loctite products include their cleaners, coatings, gasketing and molding products, lubricants, mold releases, sealants, surface treatments and threadlockers.

Some of Loctite’s best-known adhesive products are their threadlockers, used to prevent screws and bolts from loosening, more effectively than a locking washer alone could. They are anaerobic adhesives that are based on methacrylate.

Loctite’s threadlocker products come in different strength grades, to suit the particular application.

Blue Removable No. 242, 243, 246, 248, 2432 & 2440 - Used for things you may want to unscrew with minimal hassle. It cures into a brittle, glassy bond that takes one good twist to break, but removes cleanly after that. Recommended for use with valve covers, water pumps and oil pan bolts.

Red High-Strength No. 271, 262, 266, 268, 272, 277 & 2760 - Used on things that you don’t want to take apart for a long time. It requires heat from a torch or iron (to 250° C) to loosen its grip. It cures into a thicker, sticky bond that holds up better against vibration and shocks. It is typically used in mechanical applications such as nuts and bolts in cars, motorbikes, snowmobiles, and watercraft.

Green - penetrating grade No. 220(blue), 290 & 294 - Used for use on parts that have already been assembled.

Purple - low strength grade No. 222MS & 222 - Used for set screws.

For Plastic threads - No. 425. - Used for small plastic threads.

A ball bearing is a common term referring to either a type of rolling-element bearing (this usage is most commonly used by engineers), or the individual ball used in a ball bearing. The remainder of this entry uses the term ball for the individual component and “ball bearing” or just “bearing” for the assembly.

The purpose of a ball bearing is to reduce rotational friction and support radial  and axial loads. It achieves this by using at least two races to contain the balls and transmit the loads through the balls. Usually one of the races is held fixed. As one of the bearing races rotates it causes the balls to rotate as well. Because the balls are rolling they have a much lower coefficient of friction than if two flat surfaces were rotating on each other.

Deep-groove

A deep-groove radial ball bearing is one in which the race dimensions are close to the dimensions of the balls that run in it. Deep-groove ball bearings have higher load ratings for their size than shallow-groove , but are also less tolerant of misalignment of the inner and outer races. A misaligned shallow-groove ball bearing may support a larger load than a similar deep-groove ball bearing with similar misalignment..

Ball bearings tend to have lower load capacity for their size than other kinds of rolling-element bearings due to the smaller contact area between the balls and races. However, they can tolerate some misalignment of the inner and outer races.

Compared to other bearing types, the ball bearing is the least expensive, primarily because of the low cost of producing the balls used in the bearing.

Although Leonardo da Vinci has been credited with the discovery of the principle behind the mechanics of ball bearings the first patent was awarded to Sven Wingquist from Sweden in 1907. Ball bearings were found on the Roman Nemi ships constructed in about 40 A.D

 Angular contact

An angular contact ball bearing uses axially asymmetric races. An axial load passes in a straight line through the bearing, whereas a radial load takes an oblique path that tends to want to separate the races axially. So the angle of contact on the inner race is the same as that on the outer race. Angular contact Ball Bearings better support “combined loads” (loading in both the radial and axial directions) and the contact angle of the bearing should be matched to the relative proportions of each. The larger the contact angle (typically in the range 10 to 45 degrees), the higher the axial load supported, but the lower the radial load. In high speed applications, such as turbines, jet engines, dentistry equipment, the centrifugal forces generated by the balls will change the contact angle at the inner and outer race. Ceramics such as silicon nitride are now regularly used in such applications due to its low density (40% of steel - and so significantly reduced centrifugal force), its ability to function in high temperature environments, and the fact that it tends to wear in a similar way to bearing steel (rather than cracking or shattering like glass or porcelain

A spherical bearing is a bearing that permits angular rotation about a central point in two orthogonal directions within a specified angular limit based on the bearing geometry. Typically these bearings support a rotating shaft in the [bore] of the inner ring that must move not only rotationally, but also at an angle. Contruction - Construction of spherical bearings can be hydrostatic or strictly mechanical. A spherical bearing by itself can consist of an outer ring and an inner ring and a locking feature that makes the inner ring captive within the outer ring in the axial direction only. The outer surface of the inner ring and the inner surface of the outer ring are collectively considered the raceway and they slide against each other, either with a lubricant or a maintenance-free PTFE [Teflon] based liner. Some spherical bearings incorporate a rolling element such as a race of ball-bearings, allowing lower friction.

 Single-row versus double-row

Most ball bearings are single-row designs. Some double-row designs are available but they need better alignment than single-row bearings.

Plain bearings

A typical plain bearing is made of two parts. For example, a rotary plain bearing can be just a shaft running through a hole. A simple linear bearing can be a pair of flat surfaces designed to allow motion (for example, a drawer and the slides it rests on).

Plain bearings may carry load in one of several ways depending on their operating conditions, load, relative surface speed (shaft to journal), clearance within the bearing, quality and quantity of lubricant, and temperature (affecting lubricant viscosity). If full-film conditions apply, the bearing’s load is carried solely by a film of fluid lubricant, there being no contact between the two bearing surfaces. In this condition, they are known as fluid bearings. In mix or boundary conditions, load is carried partly by direct surface contact and partly by a film forming between the two. In a dry condition, the full load is carried by surface-to-surface contact.

Plain bearings are relatively simple and hence inexpensive. They are also compact, light weight, straightforward to repair and have high load-carrying capacity. However, if operating in dry or boundary conditions, plain bearings may wear faster and have higher friction than rolling element bearings. Dry and boundary conditions may be experienced even in a fluid bearing when operating outside of its normal operating conditions, e.g., at startup and shutdown.

A common plain bearing design utilizes a hardened and polished steel shaft and a soft bronze bushing. In such designs the softer bronze portion can be allowed to wear away, to be periodically renewed.

Plain ’self-lubricating’ bearings utilize porous journals within which a lubricant is held. As the bearing operates and lubricant is displaced from the bearing surface, more is carried in from non-wear parts of the bearing. Dry plain bearings can be made of a variety of materials including PTFE (Teflon), graphite, graphite/metal (Graphalloy) and ceramic. The ceramic is very hard, and sand and other grit which enter the bearing are simply ground to a fine powder which does not inhibit the operation of the bearing.

Solid polymer types

Solid polymer plain bearings are now increasingly popular due to dry-running lubrication-free behaviour. Polymer plain bearings now provide the step from a simple plastic bushing to the proven and tested, and thereby predictable and quickly available, machine component. Solid polymer plain bearings give low weight and corrosion resistance, as well as the freedom from maintenance and lubrication enable a solution for many applications. Designing with solid polymer plain bearings is complicated by the wide range, and non-linearity, of CTE’s (Coefficient of Thermal Expansion). These materials can heat rapidly when subjected to loaded friction.

Managing without lubrication is the dream of every design engineer. With modern materials, polymer plain bearings make this a reality. After research spanning decades, an accurate calculation of the service life of polymer plain bearings is possible today. It is important not to confuse a solid polymer plain bearing with a polymer coated plain bearing, which is a much older technology. Many companies produce bushings which consist of a metal shell which then has a very thin polymer coating (usually PTFE or similar) applied to the inside.

Vee belts (also known as V-belt or wedge Belts) are an early solution that solved the slippage and alignment problem. The V-belt was developed in 1917 by John Gates of the  Gates Rubber Company. The “V” shape of the belt tracks in a mating groove in the pulley (or sheave), with the result that the belt cannot slip off. The belt also tends to wedge into the groove as the load increases — the greater the load, the greater the wedging action — improving torque transmission and making the vee belt an effective solution. They can be supplied at various fixed lengths or as a segmented section ie Nutlink, where the segments are linked (spliced) to form a belt of the required length. For high-power requirements, two or more vee belts can be joined side-by-side in an arrangement called a multi-V, running on matching multi-groove Vee Pulleys. The strength of these belts is obtained by reinforcements with fibers like steel or polyester.

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