What are gear couplings and how do they work?

Gear couplings are designed to transmit torque between two shafts that are not collinear. They typically consist of two flexible joints&#;one fixed to each shaft&#;which are connected by a spindle, or third shaft. The gear coupling connects the drive motor to the gearbox in hoist mechanisms, but it can also connect the gearbox directly to smaller wire rope drums using a flanged half.

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In terms of their design, gear couplings transmit torque via hubs with crowned gear teeth that are in permanent mesh with the straight gear teeth of the sleeves&#;a design that provides the highest torque transmission for the smallest size. They also run at high speeds, conform to the AGMA bolting pattern and compensate for angular, radial and axial shaft misalignment.

Design, Attributes and Specifications

Guides

Gear couplings are three-piece flexible shaft couplings that are used to connect driving and driven shafts in mechanical power transmission assemblies. Flexible shaft couplings are used to counter the inevitable misalignment that occurs between connected shafts. Other coupling styles included Oldham, Schmidt, chain, disc, bellows, grid, and beam, about which more may be found in our Couplings Buyers Guide.

Gear Coupling Design

Gear couplings consist of identical left and right hand external toothed elements that are connected through an internal toothed sleeve having a matching number of teeth. The meshed teeth transmit torque between the coupled shafts while allowing some misalignment to exist between them. Generally, the elements are made from steel, although nylon is sometimes used for the sleeve portion. Some designs use a split sleeve, flanged design that is bolted together at installation. Special coupling bolts are used to transmit power between flanges or, sometimes, to effect a friction transfer between adjoining flange faces. Bolt heads may be shrouded or exposed, but in either case, a coupling guard is generally required.

Shaft attachment is usually by way of set screw and keyway, splines, or matched tapers. To function correctly, the coupling must maintain some clearance between the faces of the external tooth elements. The teeth themselves are usually crowned to provide for angular misalignment. An interference fit between shaft and hub is generally recommended for critical applications.

Gear couplings require lubrication at regular intervals and will fail prematurely if deprived of grease or oil. Shaft seals &#; usually O-rings &#; keep lubricant in place. Special coupling grease is required to prevent oil and soap from separating due to centrifugal effects &#; high-speed couplings will sometimes employ flooded oil lubrication as a way around this phenomenon. Wear is a normal aspect of gear couplings but with proper lubrication, it can be managed over the life of the coupling.

An advantage of gear couplings over many other designs is their ability to tolerate axial growth. An important attribute is the distance between shaft ends, which specifies the distance between shaft faces of the driven and driving equipment. In some cases, the distance may be varied by reversing one or both external gear elements on the shafts.

Gear Coupling Applications

Gear couplings are commonly employed on large, industrial machines such as pumps, blowers, compressors, mixers, etc. They can be used in smaller motion control systems, mostly with a polymer sleeve as a means of reducing backlash but other zero-backlash coupling designs are usually better suited to these applications. Backlash is necessary for metal gear couplings as it provides for misalignment compensation in addition to providing clearance for lubrication to flow between meshing teeth.

For standard power transmission applications, gear couplings can be purchased in a broad range of shaft sizes and torque capacities, with typical bore diameters up to 40 in. and torque capacities up to 70 million in.-lbs. available. The largest sizes are generally special order as their use is infrequent and usually restricted to lower speed machinery. Gear couplings in the standard sizes are intended for serious levels of torque transfer and high-speed operation. A variety of special arrangements are available including spool sections, electrical isolators, and designs incorporating shear pins for overload protection.

Specifying a gear coupling requires knowing the required bore, calculating the transmitted torque, then applying a multiplier supplied by the manufacturer that rates the severity of the service, usually by machine type. Manufacturers often have on-line calculators to help specifiers in selecting couplings.

As with any coupling, gear couplings are rated for maximum angular and parallel misalignment. Gear couplings are generally capable of managing 1-1/2° of angular misalignment for each meshing pair. A single mesh is inadequate for accommodating parallel misalignment. Greater parallel misalignment capacity can be had by increasing the span between meshes with a spacer. Spacers are generally available in standard incremental lengths which vary by machine type, i.e., pump, compressor, etc.

Gear couplings are often used in power transmission applications where motors may be larger than 200 HP, in which the use of journal bearings is common. Couplings can be manufactured that are capable of limiting the amount of float that a shaft operating in such bearings manifests.

Attributes and Specifications

Gear coupling specifications include the following parameters and attributes

• Bore size or diameter &#; the diameter of the coupling bore that accepts the connecting shaft. Bore sizes may be identical or different on each side of the coupling, depending on the model.
• Overall length &#; the end-to-end length of the coupling as measured from the two end faces of the coupling.
• Coupling diameter &#; the overall diameter of the coupling.
• Allowable speed &#; the maximum rpm of the coupling.
• Service factor &#; a multiplier applied to account for harsh duty such as high peak loads or frequent starts and stops. Calculated torque times the service factor must be less than the maximum rated torque.
• Gap &#; the space that must be maintained between coupled shafts.
• Maximum rated torque &#; the maximum rating of the coupling for peak torque rating.
• Lateral offset &#; also called parallel misalignment, represents the maximum tolerable distance of shaft misalignment along the axial dimension that can be accommodated by the coupling.
• Angular offset &#; also called angular misalignment, represents the maximum angular deviation of shaft misalignment along the radial dimension that can be accommodated by the coupling.
• Axial offset &#; represents the maximum axial deviation along the shaft axes that can be accommodated by the coupling.
• Shaft coupling fastening method &#; the means by which the coupling attaches to the drive or driven shaft.

Considerations

Gear couplings are said to be power-intensive, meaning they can transmit greater torques than other couplings for the same weight and volume. Their smaller sizes can be an advantage where space for the coupling is limited. With proper lubrication intervals, gear couplings may last as long as the equipment on which they are installed. Unlike jaw couplings, which can fail catastrophically with the destruction of the flexible element, gear couplings will generally reach an unusable condition gradually, at which point the entire coupling is replaced.

Unlike the jaw coupling, the gear coupling is less adept at handling high shock loads because of the metal-on-metal contact of the coupling teeth.

Misalignment is defined along two planes, parallel and angular, and it usually occurs as some combination of the two. A single mesh gear coupling will accommodate angular misalignment, defined as two connecting shafts whose axes intersect at an angle less than 180°. A double mesh gear coupling is necessary to handle parallel misalignment, where shaft axes run parallel to each other but not collinearly.

Procedures for aligning machine trains vary from manual rule-and-feeler-gage techniques to high-end laser-based systems. Alignment services are a common offering of many rotating-equipment service organizations.

Summary

This article presented a brief discussion of gear couplings including their design, applications, specifications, and selection considerations. For more information on related products, consult our other guides or visit the Thomas Supplier Discovery Platform to locate potential sources of supply or view details on specific products.

Other Couplings and Related Articles

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Types of Gear Coupling With Working Principles

Different types of gear coupling are critical since they all make gear coupling but in different machines. A gear coupling is designed to convey high torques and has a seat with a kind of gender coupling. There are several types of gear coupling available depending on the application. You will read about what gear couplings really are. You will also find different types of gear coupling. Follow us in Linquip.

What are Gear couplings?

To answer this question, we must first define what coupling is. A coupling, at the simplest, is a power transmitter. Couplings serve as connecting components between any two shafts. The type of complexity of connectivity, the power to be transferred, and the field of operation all play a significant role in the coupling type collection. Gear couplings fall into the heading of flexible couplings and can relay extremely high torques. You can also find more types of a gear coupling.

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Gear couplings, often known as gear couplings, are a form of coupling that is often used in high-torque, high-power applications. Gear couplings can normally tolerate more torque than universal joints, whereas universal joints produce less vibration. A gear coupling is made up of two hubs with external and internal teeth and a one- or two-piece sleeve.

Gear couplings have a general misalignment capability of 0.01-0.02 inches in parallel and 2 degrees in angular. They are sometimes used in pairs of spacer shafts to bridge the gap between driving and driven machinery. They are usually lubricant-required, but some are designed for lighter-duty use of lubricant-free nylons or other polymers for the center sleeve.

Types of gear coupling

There are various types of gear couplings utilized in various kinds of machines, such as:

Full Gear Couplings

The double engagement forged steel coupling is the regular series 100 complete gear coupling and is used in the majority of industrial applications. It has a large end float capability and can compensate for both parallel (offset) shaft misalignment and angular misalignment.

Half Gear Half Rigid Couplings

The Series 100 Half Gear Coupling is made up of a flexible and rigid half. The open half is a regular Series 100 half coupling with an outer sleeve and an inner hub, while the rigid half has a flanged hub.

Rigid Couplings

A type of coupling used to connect shafts that are aligned. Among types of gear coupling, the rigid coupling is the simplest kind. Rigid couplings are used where exact shaft alignment is required; shaft misalignment can affect the coupling&#;s performance as well as its existence.

Floating shaft assemblies

This makes for long-distance shaft connections. For example, if you have an engine that needs to power a fan 15 feet away but there is no place to install connecting shaft supports, a floating shaft assembly is a good solution.

Slide couplings

These are used where any axial movement is needed and thermal shaft expansion must also be considered.

Shear pin couplings

Next to the above types of gear coupling, shear pin couplings are suitable for applications that often overrun or get clogged. When the pin inside the coupling breaks, the equipment stops working. This avoids damage by shutting down the machine as loads get dangerously high.

Disconnect couplings

These are similar to shear pin couplings in that they can easily disconnect depending on the case. Disconnect couplings are suitable for both medium- and high-speed applications.

Flanged gear couplings

Flanged gear couplings are made up of short sleeves surrounded by a perpendicular flange. For each pole, one sleeve is placed such that the two flanges match up face to face. The flanges are held together by a series of screws or bolts.

Continuous sleeve gear couplings

To wrap up the different types of gear coupling, we mention continuous sleeve gear couplings that have shaft ends that are joined together and abutted against each other before being enclosed in a sleeve. These sleeves are usually made of copper, but they may also be made of nylon.

In this article, we learned that gear coupling is a mechanical mechanism that transmits torque between two non-collinear axes. Couplings are usually made up of two flexible joints that are attached to each shaft. This joint is often linked by a third axis known as a spindle. The majority of joints are made up of a pair of internal or external gears. To allow angular displacement between the two gears, the gear side and outer ring are crowned.

We also discovered different types of gear coupling. This is all about some types of a gear coupling. If you have any queries regarding this article, ask by commenting. Also, if you like this article, don&#;t forget to share it on social networks. Subscribe to Linquip for more about types of a gear coupling. Thanks for reading it.

Half Gear Coupling Function

Rokee® is a well-known high-quality half gear coupling supplier from china, learn more about half gear coupling function, pls contact Rokee technology. Rokee has been established in China since , over the years, with excellent quality, we have been continuously providing many half gear coupling products of various categories and uses complying with multiple standards and a full range of services, from the half gear coupling selection to final installation and operation, for the industry fields of ferrous metallurgy, nuclear power, gas turbine, wind power, ropeway construction, lifting transportation, general equipment, etc.

The half gear coupling is a specially designed advanced gear coupling. Its outer teeth are made into a sphere, with the center of the sphere on the axis of the gear. The teeth clearance is slightly larger than the general products and can transfer a greater torque and allow greater angular displacement, enjoying excellent performance and longer life.

Half Gear Coupling Products

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