Pneumatic tooth clutches offer the advantage of high torque capacity in small dimensions which can bring significant cost savings to the machine designer. Lenze offer tooth clutches from Mönninghoff who produce a complete range of six basic models and their variants covering torque from 100 to 2200Nm. A clutch with rated torque of 500Nm has an outside diameter of only 166mm which can be compared with pneumatic friction clutches with diameters typically 100% larger. Pneumatic tooth clutches can be run in wet or dry conditions and variable toothforms allow adaption to different types of application.
Pneumatic tooth clutches work by applying an air pressure of 4 to 6bar to an internal piston. Very small volumes are required so the response is rapid. The piston pushes one set of sliding teeth into engagement with a set of fixed teeth, and this teeth engagement transmits the torque. Engagement needs to be at static or low speeds, but disengagement can be at any speed. The torque transmitting teeth can be cut in different forms. Standard is a 20° flank angle which suits torque transmissions in either direction. Saw tooth forms transmit different torques clockwise and counter clockwise. Irregular toothforms can synchronise input to output at 360°, or at several fixed intervals per revolution if required. Shallower tooth forms can be used for torque limiting with the release point being proportional to the pressure applied.
The most popular clutch models have a stationary piston either flange or bearing mounted. The axial force is transmitted to the teeth by a ball bearing. The axial movement of the teeth can be detected by using a proximity switch onto an integrated switch plate. Hence the clutch state and any overload can be monitored. Simpler and lower cost clutches are also available using a rotating union to feed the air supply in through the shaft. This can halve the length of the clutch.
The Mönninghoff range also includes tooth brakes available from 80 to 1000Nm, and spring applied tooth brakes in the same torque range. Tooth brakes are best suited to low speed applications where accidental engagement will not cause tooth damage. Spring applied tooth brakes give a true holding torque until air pressure is applied. Applications include holding barrier arms, and the toothform can be set so that in emergency manual force can open the barrier.
Mönninghoff pneumatic tooth clutches together with electromagnetic clutches are available in the UK through Lenze Ltd who can also provide technical advice. A brochure is available.