Types of shaft couplings

The Oldham, or sliding disc coupling is an economic solution for small drives with shafts 3 to 30mm.  Two aluminium clamp hubs connect through a disc (element) of acetal or nylon.  Torques range from 0.1 to 21Nm and the design with acetal discs is moderately torsionally stiff and free of backlash. Clamp hubs remove the need for keyways.
Manufacturer - RULAND

Beam shaft couplings are constructed in one piece from alloy or stainless steel suiting shafts 3 to 12mm and torques up to 5Nm.  These miniature couplings are torsionally stiff and backlash free with a high radial misalignment capacity.
Manufacturer - RULAND      Type - Flexbeam, MWC, MWS

Bellows shaft couplings are constructed with stainless steel bellows connected to aluminium alloy clamp hubs.  The result is a coupling that is very stiff and ideal for precision drives, reversing drives, tachos and encoders.  Torque range is 2.5 to 45Nm, shafts 3 to 25mm.
Manufacturer RULAND      Type - MBC

The Simplaflex spring type shaft couplings are extremely robust with three layers each of three springs connecting between steel hubs.  They are compact and can run at high speeds, also with a particularly high angular misalignment capacity up to 6 degrees.  Torques range from 2.5 to 900 Nm and shaft sizes up to 75mm.
Type - Simplaflex MM,MF, FF

Curved jaw shaft couplings are simple, inexpensive and very common in European machinery where dimensions have become interchangeable in some cases.  A simple 3 piece coupling will have two cast iron or aluminium hubs and a polyurethane element for torques 11 to 1465Nm, shafts 14 to 90mm.  More sophisticated variants include clamp hubs which can have zero backlash and compact high torque models.  Different grades of element can vary the torsional softness and misalignment capacities.
Type - GR, GESM, GESA

Straight sided jaw shaft couplings are similar to curved jaw types but can be more economical through the use of sintered  iron hubs.  Shaft sizes are 4 to 67mm with torques up to 750Nm.  Different types of element can vary the performance.
Manufacturer - Lovejoy Type - L

Metal disc shaft couplings are bolted assemblies with steel or aluminium hubs connecting through laminated steel flex packs.  To connect two fixed shafts a double flexing design with two packs is needed.  If one shaft is floating, a single flexing design is possible.  Different models suit shafts from 4 to 150 mm, torques up to 9000Nm.  Metal disc couplings are torsionally stiff, backlash free and maintenance free.  Spacer versions up to 5m long are possible.
Manufacturer - Moenninghoff Type - Servoflex 318 & 328,
Arcoflex 314.

Barrel gear shaft couplings use a sleeve with internal splines to connect between two iron hubs.  Small barrel gear couplings for torques 10 to 700Nm and shafts up to 80mm use nylon sleeves.  They are simple and well suited to machines where the axial misalignment is high.  Large gear couplings tend to be replaced by metal disc couplings to avoid lubrication and maintenance.

The Hexaflex rubber disc shaft couplings is a backlash free bolted assembly with high misalignment capacity.  Torques are 100 to 2250Nm with shafts up to 95mm.  The rubber disc has layers of reinforcing cord making it very robust.  Spacer versions and a marine version are possible.
Manufacturer - Monninghoff      Type 313

The Hexaflex BlueLine marine shaft couplings are designed to correct between the gearboxes of diesel engines and the propellor shaft.  They are easy to fit, remove vibrations, and are corrosion protected for a long life.  Torque 100 to 2000Nm.
Manufacturer - Monninghoff Type - BlueLine

Universal joints transmit torque through high values of angular misalignment.  Two single joints or a double joint are needed to accept parallel misalignment and give smooth running.  Telescopic joints are also available for static adjustment of shaft gaps.  Shaft  diameters 6 to 50 mm and dimensions to DIN808.
Types - G, GD, GA, H, HD, & HA

Shaft collars in a range 3 to 50mm are machine elements to provide stops and locations.  Alloy and stainless steel construction is provided with a one piece or two piece clamp action
Manufacturer - RULAND      Type - Nomar

Shaft rigid joints connect shafts of equal diameter rigidly without backlash.  Shafts range from 6 to 50mm and one side should be floating to prevent bearing damage, Construction is in steel or stainless steel with a clamping design to prevent shaft damage.
Manufacturer - RULAND      Type - Nomar

Advice on coupling selection

Flexible shaft couplings accommodate misalignments between shaft ends.  In general, some misalignment will always be present.  If a rigid connection is used  between two shafts each mounted in a pair of bearings, high bearing loads and premature failure will result.

There are three types of shaft misalignment.  Angular misalignment is usually present and typical values are between 1°and 2° although higher figures are possible.  Radial misalignment, also known as parallel misalignment, is the distance between shaft centres.  A well aligned installation might have values better than 0.20mm.  Axial misalignment can be considered as end float.  It is sometimes caused  by thermal expansion or is a result of machine design.  Different types of couplings have different misalignment capacity. See our selection guide for further advice.

Couplings can be with backlash or backlash free.  One piece couplings or those with bolted joints are backlash free and useful for precise positioning, also on reversing drives. Couplings with backlash tend to be lower in cost and easier to assemble.

Couplings with rubber or plastic elements can be considered as torsionally soft, generally having higher misalignment values and the ability to absorb vibration.  Metal couplings tend to be torsionally rigid.  A soft coupling may wind up 5 degrees at  rated torque whilst a rigid one will twist as little as 0.1 degrees.  Soft couplings are generally lower in cost.

Universal joints are not true flexible couplings but can transmit high angular misalignment, up to 45 degrees with a single joint or 90 degrees with a double joint/pair of single joints. They are available in single, double and telescopic versions for shafts 6 to 50m. Universal joints with plain bearings suit speeds below 1000 r/min and lubrication is needed, usually provided by an enclosing gaiter. For higher speeds universal joints with needle roller bearings are used.

For advice in selecting a flexible coupling phone 01234 753200