Bi-stable tooth clutch is both safe and efficient
11 February 2013
Mechanical drives specialist, Moenninghoff is relatively small by German 'Mittelstand' standards - just 140 employees and a current turnover of 12.5 million Euros. But it is certainly 'big' in terms of its technological know-how; “we sell engineering - the hardware is a bonus” is a favourite mantra of the Moenninghoff sales team.
A good example of this engineering capability is a totally new concept in electromagnetic tooth clutches, which the company plans to launch at this year's Hannover Fair in April.
The M1 bi-stable electromagnetic tooth clutch is engaged by applying a short current pulse, and it only disengages when a second pulse of current is applied. This gives two significant advantages. Firstly, it is much more energy efficient than a conventional electromagnetic clutch as, once engaged, it requires no applied current - particularly useful for machinery powered by batteries or reliant upon battery back-up.
Secondly, it offers increased safety. The EU directive 2006/42/EG clause 1.2.6 refers to machinery where the drive must not disengage in case of a power failure. The M1 clutch is fully compliant with this clause as it cannot be released until a further current pulse is applied. The M1 is the result of 40 years worth of development work by Moenninghoff in the production of electromagnetic tooth clutches.
The patented 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 current 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. Effectively, engagement and disengagement of this clutch is achieved with very short energy pulses, and no energy is consumed in either engaged or disengaged positions.
The M1 bi-stable clutch is currently available in a range of four sizes to meet torque requirements from 50 to 500Nm and shaft diameters 20 to 50mm. Clutch engagement can be made statically or at low speeds, with dis-engagement possible at any speed.
Apart from battery driven systems mentioned above, potential applications of the MI clutch are likely to take advantage of one or other, or both of its key features: energy efficiency and 2006/42/EG safety compliance. Clearly, higher energy savings will be obtained from systems whose clutch engagement times are longer.
Of course, the MI comes at a price premium, but at the time of writing, the pricing structure was not available. Moenninghoff will no doubt be in a position to go into details at the Hannover launch, and further information will shortly be available from exclusive UK distributor, Techdrives.
In common with many specialised suppliers to the German machine building sector, Moenninghoff has had to adapt to both technological and economic change. Founded in 1916 to serve the huge coal mining industries of the Ruhr, it responded to the post-war growth of the German machine building sector by applying its resources to the design and production of precision power transmission components - principally clutches, brakes and shaft couplings.
With the growth of alternative electronic drive systems affecting many of its traditional markets, such as printing and machine tools, and economic decline in certain European sectors such as textile machinery, Moenninghoff has sought new markets for its products. Growth sectors, including access control, ski-lift systems and aerospace, have opened up new opportunities for the company.
Aerospace, in particular, is proving fertile ground, given Moenninghoff’s proven capabilities in delivering purpose-built, high-precision, high-reliability products. Recent examples include helicopter rotor linkages and aircraft nose-wheel drives that hold promise of big fuel savings from airline operators.
All of Moenninghoff’s products, together with the innovative new M1 clutch, are available exclusively in the UK from Lenze UK subsidiary, Techdrives.
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