The S-Flex (sleeve) coupling has 5 primary flange types, each with their own benefits.
 |
| J Type |
J Type
The first four sizes of flanges (size 3J to 6J) are available in this type which differs from the S Type in that the J Type does not have as great a length-thru-bore. This is due to the absence of a projection in the cast material on the J-type flange at the inner face. Thus, where both J and S flanges are available (sizes 5 and 6 couplings), the S flange has a greater maximum bore capacity than the J.
This flange is very economical and provides a coupling which is only slightly more expensive than a comparable jaw coupling. Due to the high torque of the Hytrel sleeves, the J-type flanges can only be used with EPDM or Neoprene sleeves.
 |
| S Type (with E Sleeve) |
S Type
The S Type covers the 11 coupling sizes from 5S through 16S. These flanges all have the projection at the inner face of the casting which provides for greater shaft engagement. The S-type flanges can be used with any of the sleeve materials.
B Type
The B Type flange is modified to accept the industry-standard QD bushing, and is offered in sizes 6B through 16B. The use of bushings limits the bore capacity of the coupling, but provides a very firm grip on the shaft and can simplify the stock room of many customers (if they use bushings on other power transmission components). Due to the torque limits of the QD bushing, B Type flanges cannot be used with Hytrel sleeves.
T Type
Similar to the B Type for QD bushings, the T Type is a standard flange modified to accept the style of bushing called Taper-Lock. There are two ways to mount the bushing to the flange, from the serration side (Rear) or from the same side of the flange as the shaft is inserted initially (Front). We call these versions the TR for Taper-Lock/Rear and the TF for Taper-Lock/Front. Be sure to determine if the bushing being used has either UNC threads (which have a 60° thread angle) or B.S.W. (55° thread). As with the B Flanges, the T Type cannot be used with Hytrel sleeves due to the limits of the Taper-Lock bushing ratings.
 |
| SC Type Coupling |
SC Type
These meet standard API (American Petroleum Institute) spacing requirements for pump disassembly. One of the other benefits to the S-Flex spacer couplings is that the various components can be mixed/matched in combinations to achieve dozens of other shaft separations beyond the API standards of 3 1/2", 5", and 7".
 |
| SC Type Flange |
The SC Type spacer coupling is achieved by using a Spacer Flange (with nomenclature such as 8SC35 or 8SC44) to which is bolted a Spacer Hub (8SCH for example). There are usually three lengths of Spacer Flanges available in each size coupling. The Spacer Hub has the finished bore and keyway for the driver/driven shaft. Each half of the full spacer coupling uses a Spacer Flange/Hub combination. Half-spacer couplings are possible, as well as combining different lengths of Spacer Flanges.
 |
| SC Type Hub |
S-Flex spacer couplings are available from size 5 through size 14 couplings. Any of the sleeve materials can be used with the SC Type coupling. The Spacer Hub is bolted to the Spacer Flange with four hex head cap screws. By removing these screws, the center section of the coupling can be dropped out.
To get technical specifications fo S-Flex couplings, please visit Lovejoy's website product page or download the S-Flex pdf catalog. Detailed installation instructions and videos for these products can also be found here.
To keep learning about S-Flex couplings on this blog, go to:
Gear
couplings like all other shaft coupling devices perform the basic
functions of connecting two shafts to transmit torque and compensate for
misalignment. Gear couplings though are the king of the coupling types.
While each type of coupling has its own niche, gear couplings are more
power intensive, have more modifications, and a wider size, torque, and
bore range than all the others. Gear couplings can also perform at
extremely high rates of speed. As inferred by the name, gear couplings
use the meshing of gear teeth to transmit the torque and to provide for
misalignment.
To give you some idea of the differences between
gear couplings and other types look at the sales by size and the torque
capability per pound of coupling. While some may argue that the sale of
gear couplings is not growing compared to other types, there are so many
gear couplings installed in rotating machinery that the replacement
business keeps the product sales robust. Actually gear couplings can do
things that many other couplings cannot do or can only do with
difficulty or with expensive modifications and de-rating. Gear couplings
have axial slide capability, low speed high torque capability, shifter
capability and spindle capability not found in other couplings. They are
easily modified to shear pin service, floating shaft type, vertical
type, insulated type, limited end float, and can have a brake drum or
disc features added. While those latter items may be available on other
couplings, it is usually easier and less costly to modify the gear
couplings.
Gear couplings are power intensive. That means more
torque transmitted per pound of coupling weight and per cubic inch of
space consumed. That allows space and weight for attachments without
having the coupling grow to unusable proportions. Power intensity and
space savings mean the original equipment manufacturer (OEM) can bury
the coupling in small out of the way places. When the OEM does that, it
can be done with the confidence that the coupling will not fail. The
gear coupling has more torque capability than the shaft can transmit.
The gear coupling eventually wears without a spectacular failure. Gear
couplings can be sized to make sure that wear life is consistent with
the rest of the machine's design. The Sier-Bath "C" or continuous sleeve gear coupling has long been a champion of OEM service for its small size, easy installation, and large torque ratings, and the HercuFlex "CX" continuous sleeve gear coupling promised to take this performance to the next level.
Gear
couplings have been likened to a one-to-one gear box, that is, torque
transfers from hub teeth to sleeve teeth and across the shaft gap with
no change in RPM. The gear coupling can be configured with two flex
planes to achieve parallel misalignment as well as angular and axial, or
it can be configured with one flex plane and one rigid plane to limit
the misalignment to angular and axial only. The two flex plane version
is the most popular, but there are many applications for the single flex
plane. Those applications appear in three bearing systems or in
floating shafts. Many times the single flex coupling is used in series
with another single flex unit to give much more parallel misalignment
capability.
Gear couplings achieve their misalignment capability
through backlash in the teeth, and crowning on the tooth faces. Gear
couplings also utilize a major diameter fit which helps the misalignment
and assembly capability. Teeth on gear couplings normally use a 20°
pressure angle but can also be made with 25° and 40°. The 20° tooth
evolved over the years as the most wear resistant and strongest form.
The 25° tooth is used on spindles to improve the strength at some
sacrifice in wear, and the 40° tooth form is the strongest but is rarely
offered anymore.
To keep learning, go to:
Note:
This article series is an updated & modified version of a legacy
Lovejoy training document. The blog writer is not the original source
author.
