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The Latest In Clutches & Couplings

18 March 2013

Ahead of their official launch at the Hannover Fair, CDA takes a look at the latest products from Mönninghoff, a clutch and couplings technology specialist based in Germany's industrial heartland, the Ruhr Valley

When Richard Mönninghoff started his company in 1916, it was as a supplier to the mining industry. It wasn’t until 1952, when an engineer from outside the company approached Mönninghoff with an idea he wanted to develop, that the business became concerned with drive technology. And, as Germany’s mining industry has declined over the years, Mönninghoff ’s activity and expertise in the drive technology sector has increased.

Although much of the company’s output now consists of products specifically customised for the individual application, Mönninghoff has not neglected its regular product ranges. For example, the 450 series of pole face clutches featuring a ‘double flux crossed’ design achieves high torques and operates even in conditions where oil or water are present. Covering torques from 400 to 2000Nm, the 450 clutches are suited to mobile applications, particularly power-take-offs from diesel engines. Clutches are available in three sizes giving backlash free torque transmission with either static or dynamic engagement.

The 450 series clutches are engaged by applying a DC voltage, normally 24V DC, to a stationary coil. This generates magnetic flux which travels into the rotor, a rotating plate that forms one of the two friction surfaces. The flux then crosses an air gap and pulls another plate, the armature, into contact with the rotor generating the torque by friction. The clutch is designed so that the magnetic flux crosses the air gap twice, hence the description ‘double flux crossed’. This doubles the attractive force, increases the torque and leads to compact dimensions. The double flux crossing is achieved by using a two part armature with inner and outer rings, and a rotor where non-magnetic material blocks the flux from travelling radially.

Mönninghoff has also added a new model of metal disc shaft coupling to its range Arcoflex range. Starting at 800Nm, the range now extends to 23000Nm with the new size 120. There are now eight sizes in the range, all torsionally rigid and backlash free, suiting angular misalignments up to 1 degree. Compared to the alternatives of carden shaft universal joints and gear couplings, these metal disc designs give the advantages of being both maintenance and backlash free.

Metal disc couplings are available with one or two disc packs. Each disc pack is constructed with laminations of stainless spring steel, typically 12, bushed together at 6 points for the Arcoflex range. The coupling is assembled with the disc packs connected alternatively left and right with fitted bolts to the hubs and a central spacer. In operation the disc packs flex to take up angular misalignment and also any axial movement, typically a result of thermal expansion. Usually there is also an element of radial misalignment, also known as shaft offset. However if one shaft is self-aligning in a single bearing, then couplings with a single disc pack are suitable.

Addressing the increasingly important issue of energy efficiency, the M1 bi-stable electromagnetic tooth clutch is engaged by applying a pulse of DC current and will only disengage when a second pulse of current is applied. While engaged, the clutch requires no applied current, which is particularly useful for machinery powered from batteries. It also it offers increased safety, meeting the EU directive 2006/42/EG clause 1.2.6 which refers to machinery where the drive must not disengage in case of a power failure. The M1 clutch cannot be released until a further pulse of DC current is applied.

The M1 design adds an extra pair of toothed rings mounted internally, one ring with alternate shallow and deep teeth. Coil springs press these together until an applied DC pulse to the clutch coil causes them to open and index round by one tooth. After the pulse the teeth re-engage, and indexing from a shallow to a deep tooth allows the main tooth rings that transmit the torque to engage. Similarly the next pulse indexes to the shallow tooth which holds the main tooth rings open.

All Mönninghoff products are available in the UK through Techdrives.

Key Points

  • 450 series pole face clutches feature a ‘double flux crossed’ design and operate in difficult environments
  • Arcoflex torsionally rigid flexible coupling range now extends to 23000Nm
  • M1 energy efficient bi-stable electromagnetic tooth clutch also offers increased safety