The benefits of jaw-in-shear couplings

Krister K. Meister

Fact: The manufacturing sector has always been concerned about the amount of downtime incurred for scheduled and unscheduled maintenance. The dollars lost to unscheduled maintenance can be quite substantial.

Fact: All industrial facilities use some type of flexible coupling for pumps, compressors, conveyors and other machinery. These flexible couplings all require some measure of maintenance.

What are your coupling and related maintenance options?

Gear- and grid-type flexible couplings require lubrication. To lubricate these types of couplings, the lubrication plugs first must be removed and then the coupling filled with grease.

Various elastomeric-type flexible couplings require periodic change of the elastomeric element. The difficulty level for different types of elastomeric couplings can vary widely. Some, like the standard jaw product, require that one of the hubs be moved back on the shaft to allow for the element to be changed out. Machinery may need to be moved to allow for this hub movement, which can be very time-consuming. Other elastomeric designs have many fasteners and parts to be disassembled for element changeout.

In either case, the time that it takes to change this element is critical for maintenance personnel. This is where the advantages of a jaw-in-shear design can provide a solution to plant downtime.


Photo 1. The jaw-in-shear element can be changed without having to move either hub.

The basic components of a jaw-in-shear coupling are two standard jaw hubs, a jaw-in-shear element and a retaining ring. The jaw-in-shear element is designed to be changed without having to move either hub, as would be needed with the standard jaw coupling. Additionally, there are no fasteners to worry about as a result of the jaw-in-shear retaining ring. The ring can simply be removed and the element replaced in minutes. This saves a substantial amount of time. Not only is the element a "pit stop"-style changeout, but it eliminates the need of moving either hub or the equipment that the coupling is connecting. The time savings when compared with other elastomeric-type couplings is at least 50 percent.

Due to the ease of assembly and disassembly with the jaw-in-shear design, anyone can perform the required coupling maintenance. Another benefit is that it offers twice the amount of angular misalignment compensation over the standard jaw products. The urethane element has 1.5 times the torque rating of the standard Buna-N rubber element. This provides an additional service factor for applications that had originally used the standard rubber spider.

To reiterate, the jaw-in-shear design provides advantages in time for element changeout, ease of assembly (no specialized personnel required), double the misalignment capacity over the standard jaw product and 1.5 times the torque rating of the standard Buna-N spider material.

Excess inventory is a concern for manufacturers. Companies are always looking for a way to economize their inventory to get the most bang for the buck. Any time a facility can reduce or minimize the amount of stock-keeping units (SKUs) or Universal Product Code (UPC) numbers that it inventories, it saves inventory space and money.

The jaw-in-shear coupling allows plants the benefit of utilizing the industry-standard jaw coupling hub with a wrapping elastomeric spider and retaining ring. This means adding only two new SKUs or UPC numbers for plants that already use the industry-standard jaw product. The result is less additional inventory dollars and space to allow for the upgrade from the industry-standard jaw product.

The jaw-in-shear design gives plant maintenance personnel a solution that addresses plant downtime. By utilizing both economy of inventory and the advantage of the jaw-in-shear design, substantial savings can be realized in many applications plant-wide.

With the cost of plant downtime increasing every day, this solution gives maintenance personnel a way to save resources without sacrificing response time.

Krister K. Meister is the marketing manager for Lovejoy Inc., a manufacturer of heavy-duty couplings. To learn more, visit, call 630-852-0500 or e-mail

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