Jaw In-Shear Couplings - A Straight Forward Value Add

While Lovejoy's straight jaw coupling is robust, ubiquitous and economical... is is also fail safe & requires no grease/maintenance free. (Fail safe means that if and when the elastomeric spider fails, torque will continued to be transmitted as the jaws of the two hubs interlock directly. Requiring no grease means both greatly reduced environmental leakage risk, which may not be true for grid or gear couplings, and no periodic re-greasing required.)

While being fail safe is great in some applications, is not desirable or valuable for all applications. Additionally, the traditional jaw coupling requires that at least one of the two hubs to be pulled back to replace the elastomeric spider. (Note: There is a fail-safe Snap Wrap version that enables spiders to be radially replaced without moving the hub for lower speed applications.)

The Jaw In-Shear Coupling (pictured right) is a straight forward 4 piece non-fail safe design (meaning the coupling will no longer transmit torque if/after the elastomeric element fails) that is optimized for quick elastomeric element replacement (with neither jaw coupling hub being required to be moved). 

Because the coupling is non-fail safe, the coupling behaves similar to a non-calibrated fuse to prevent equipment damage in the event of torque overloads. (Note: Elastomers are not rated or designed to fail at a specific torque level, so other methods such as rated shear pins or torque limiters should be used if a true fuse is required.) Instead of the spider being compressed between interlocked jaws of each coupling hub (a traditional jaw coupling configuration), the Jaw In-Shear coupling has the hubs drawn apart with jaws aligned axially. The wide spider is thus in a shear-plane.
 
Jaw In-Shear elastomeric spiders, being radially removable, results in saved maintenance time and money. The coupling's retaining ring encloses and secures the In-Shear Spider, using an intuitive twist-lock design that will not work loose and requires no fasteners. Furthermore, the Jaw In-Shear uses Lovejoy's industry-standard L-Type and C-Type jaw coupling hubs which are both cost effective, and quite possibly already installed on the equipment (meaning a retrofit cost will be reduced to the Jaw In-Shear elastomeric spider and retaining ring. The Jaw In-Shear spider is made from a tough Urethane formula offering high durability, chemical resistance, temperature range, and torsional softness. Jaw In-Shear coupling designs are available for jaw coupling hubs with max bores up to 9.0 inches (229 mm) and 183,333 in-lbs (20,714 Nm). 

 

 

Common applications for Jaw In-Shear couplings include rolling mills (pictured at right), electric motors to centrifugal pumps, fans, blowers, gear boxes, and plastic extruding machinery. The Jaw In-Shear solves many maintenance problems and creates on-going savings & environmental risk reduction opportunities in industries like pulp & paper, petrochemical, mining and steel.

Recommended Follow-On Reading: For a full review of jaw couplings, and additional commentary on Jaw In-Shear couplings, please read: Jaw Coupling Overview - Features & Benefits, Design Basics, and Element Options

Popular Jaw Coupling Option - The Snap Wrap Spider Limits Downtime

Changing out an insert from a jaw coupling can be fairly easy or a time consuming process.  A lot depends on the area around the coupling and the ease of access.  Many customer applications have the coupling placed in a restrictive area, which requires a major effort to dissemble the coupling and change the wearable spider insert.  Sometimes the connecting equipment has to be physically moved so that enough clearance is available to move and flange/hub enough so that the spider/sleeve can be replaced.  This is where the Snap Wrap (SW Type) style spider offers a time saving solution!

The Lovejoy Snap Wrap insert has been part of the Lovejoy Jaw product line up for years, but is sometimes forgotten as a solution to easy element replacement.  The spiders are available in the standard Buna-N material, which gives customers the maximum dampening benefits of all of the spider/insert materials.  This design also provides a fail-safe coupling connection that allows torque to be transmitted a short time even after the spider has failed.  The main benefit of the Snap Wrap is that the collar or snap ring that holds the spider in place can be removed and the spider can be replaced without moving either hub.  This feature allows downtime to be kept at a minimum during spider replacement.

The Snap Wrap spider is available in several popular Lovejoy Jaw coupling sizes from L090/095 to L190.  The torque capacities for the Buna-N Snap Wrap range from 144 to 1,728 in-lbs.  The Snap Wrap design is another example of Lovejoy providing the best coupling fit for every application.  

Note: The Snap Wrap is limited to a max RPM of 1750. For increased speeds of up to 3600 RPM, a similar fail-safe jaw coupling design with a collar attachment is available. This coupling type is called an LC Type (pictured at left), and consists of one standard L Type hub, one LC Type hub (which provides collar attachment), one standard snap wrap center, and one collar with screws. And for a non-fail safe design, consider the Jaw In-Shear coupling, which also make use of two common L line hubs.

Recommended Follow-On Reading: For a more complete perspective on jaw couplings in general, inclusive of a second review of elastomeric spider options, please read: Jaw Coupling Overview - Features & Benefits, Design Basics, and Element Options

Author Credit: This article was written by Charlie Mudra (National Accounts Manager, Lovejoy, Inc.).