Meeting Changing Demands: Recent Elastomer Coupling Design Advances Improve Product Quality & Safety
Recent elastomer coupling design advances have greatly improved product quality, durability and safety. Design improvements to the elastomer element, hubs, and coupling covers have minimized the harmful effects of misalignment, improved element flexibility and longevity, increased operational safety, and simplified product installation and replacement.
Elastomer Coupling Designs
Elastomer couplings transmit torque between two shafts by means of an elastomeric element that provides flexibility by stretching, compressing or shearing the resilient material. Elastomer element couplings can be grouped into three major design types: shear, compression, or combination (shear and compression) designs.
Shear Designs
Shear type elastomer couplings transmit torque through an elastomeric, cylindrical tube that is attached to each hub by various methods, such as clamping or by intermeshing teeth. (Figure 1) The design accepts misalignment though the deflection and distortion of the elastomer element and through sliding if the element is attached to the hubs through the use of intermeshing teeth.
Compression Designs
Compression design elastomer couplings transmit torque through an elastomer element that is inserted between the axially protruding, intermeshing teeth of the two hubs. (Figure 2) Parallel offset misalignment is accepted via clearances and/or compressive distortion of the elastomer element. Angular misalignment is accepted by sliding or distorting the elastomer material, depending upon the method of securing the material to the hubs.
Combination Designs
The combination design employs shear of a short cylindrical-like flexible element to transmit the torque between the hubs and compression between the hub and flexible element teeth to secure the elastomer element to the hubs. (Figure 3) Misalignment is accommodated primarily by sliding of the elastomer teeth against the hub teeth, similar to a gear coupling.
Elastomer Coupling Design Advances
Design improvements to the elastomer element, hubs, and coupling covers have minimized the negative effects of misalignment, improved element flexibility and longevity, increased operational safety, and simplified product installation and replacement. In particular, four design improvements have recently been incorporated into a combination design shear and compression elastomer coupling: an element compound root radius design, "replace in place" element, hub tooth nose radius design, and coupling cover enhancements.
Element Compound Root Radius Design
A new, patent-pending elastomer element design feature has been incorporated into a combination design elastomer coupling: the element teeth are designed with a compound root radius at the base of the teeth on both flanks to increase the flexibility of the elastomer element. (Figure 4) This radius creates a smooth transition from the base of the element tooth to the outer connecting web of the element, allowing the tooth to flex back and forth to better conform to the hub tooth.
"Replace in Place" Elastomer Element
Recent element design advancements have taken advantage of more flexible elastomer materials and eliminated the need to move hubs or realign motors or drives during the installation or maintenance of the coupling. By incorporating a split in the web of the element, elements can now simply be "replaced in place" by unwrapping and wrapping them about the hubs in a matter of a few minutes. (Figure 5)
Hub Tooth Nose Radius Design
Another new design pertains to the shape of the coupling's hub teeth. (Figure 6) In a unique, patent-pending design, the hub teeth are machined with a smooth, curved nose radius - opposed to the common sharp, flat tooth design - to give the elastomer element a smooth and relatively large curved surface to conform to under load. By improving element tooth-to-hub tooth contact, the torque load is distributed over a larger surface area. Spreading out the load on the element tooth reduces stress on the element for improved load-carrying capacity and longer life.
Coupling Cover Design
To simplify installation and increase operational safety, two coupling cover design improvements have been introduced: a positive retention cover and a cover-locating key.
The positive retention cover design minimizes the potential of element discharge in the event of failure, helping reduce the possibility for damage or personal injury. Two stainless steel button-head cap screws, installed 180° apart on the outside of the coupling cover, engage two holes in the element to provide a positive means of retaining the cover to the element.
The second unique design feature is two integral, tapered locating keys situated 180° apart on the internal diameter of the coupling cover. When installing the cover, the locating keys slide into two matching slots on the outer diameter of the element, assuring that the cover fasteners are properly positioned to engage the holes in the element. (Figure 7)
SummaryRecent advancements in elastomer coupling designs have improved product quality, durability and safety. Design improvements to the elastomer element, hubs and coupling covers have minimized the harmful effects of misalignment, improved element flexibility and longevity, increased operational safety, and simplified product installation and replacement.
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