Modern electronics and high-precision mechanics allow many everyday and industrial items to be miniaturized. The smaller a device can be built, the easier it is to transport, install or integrate into existing systems. One example is micro annular gear pumps for fluid delivery. Their simple, no-valve design allows them to come in a compact size with a virtually non-pulsating, easily adjustable flow.
German manufacturer HNP Mikrosysteme GmbH makes compact, hermetically sealed micro annular gear pumps for continuous dosing. The pump is even able to handle corrosive media.
To achieve a drive compatible with the pump, with dimensions and output tailored to the pump delivery characteristics, HNP worked with Schönaich-based drive expert FAULHABER. The result was a compact pump/drive delivery unit suitable for a number of applications, including the more exotic.
Electronically commutated dc microdrives, which are particularly suitable for driving the micro annular gear pumps, are small in size, and offer high power density and a large speed range with excellent dynamics, enabling high-precision control of flow rates from the smallest volumes to a constant maximum throughput.
The hermetically sealed pump head is driven by means of a powerful rare earth magnetic coupling, which prevents leaks on the drive end. In combination with the materials available, such as nickel-based carbides, stainless steels, ceramics based on aluminum, zirconium oxide or silicon carbide, and plastics such as PTFE, PEEK and FKM, the pumps can be adapted to various media, including corrosive substances.
The pump, 22 mm in diameter and 69 mm long, and weighing around 100 g, is for 24 V operating voltage and can transfer 4.8 to 72 ml/min at up to 5 bar delivery pressure.
Thanks to the annular gear design, the pumpable viscosity range is between 0.3 and 100 mPas, with a pulsation of around 6% and a differential pressure range of 0 to 5 bar. The no-valve annular gear principle guarantees minimal shear forces during pumping.
The pump is driven by an electronically commutated dc motor with integrated speed controller. The brushless design enhances the service life and reliability of the drive. Motor-adapted variable-speed control is guaranteed by a controller that has the same diameter as the motor and is mounted on the rear of the motor. This means that the user can easily adjust the speed through an analog input with 0 – 10 V.
A digital input determines the direction of rotation. For additional monitoring functions, the digital frequency output provides a 15-mA output signal with six pulses per revolution.
The drive supply voltage is 12 or 24 Vdc, while the 22-mm motors achieve around 9 W and feature a torque of up to 59.9 Nm. Supply voltage to the speed controller is 5 to 28 Vdc through a separate flat ribbon cable. The motor efficiency of around 68%, as well as the more than 95% efficiency of the control electronics, allow for long operating times even in battery backed mobile devices.
The rugged stainless steel enclosure and wide temperature range of –40°C to +85°C enable the device to also be used outdoors. The short-term overload capability of the microdrives supports such applications, as this allows increased pump breakaway torques, for example, after overnight temperature drops, and the resulting higher fluid viscosity, to be mastered with ease.
Filed Under: Design World articles, Gears • gearheads • speed reducers, Pumps