A number of automotive manufacturers have adopted Huco
Dynatork Air Motors to drive the agitators in their paint
shops, with hundreds already in use operating around the
clock in plants across the UK, mainland Europe, North
America and Asia. Piston air motors offer many advantages
over electric or vane type air motors, including energy
efficiency, simple installation, easy maintenance, longevity,
controllability and spark-free operation.
The main purpose of paint agitators is to keep wafer
thin metallic particles evenly distributed in suspension
in the paint. The speed of stirring is critical: too slow
and the particles will settle and form thick clusters at the
bottom of the container, too fast and the particles collapse,
becoming globular instead of flat, resulting in a granular
paint finish. At the automotive paint plants stirring speed can
be controlled directly through the air motors, because the
chosen units have variable-speed capability.
David Lockett, Managing Director with supplier, Huco
Dynatork, an Altra Industrial Motion company, explains:
“With piston air motors, power is related to the supply
pressure and volume air flow, so an inlet valve can be
adjusted to control both speed and torque. The motors can
also be fitted with torque sensors for closed loop feedback.
With a simple arrangement like this, a Huco Dynatork motor
will hold its set speed steadily, almost indefinitely.
“To achieve this with an electric motor you would
need a variable speed drive – which is expensive,
requires installing on site and has to be programmed and
Lockett continues that piston air motors are
significantly different from rotary vane type motors.
“The free-floating piston design of the Huco Dynatork
air motor is intrinsically efficient and consumes far less
compressed air than a conventional vane-type motor, usually
needing less than a quarter of the air supply for the same
power output. Furthermore, the dynamic characteristics of
the motor, including instant start/stop under load, mean that
it can be used in indexing applications, just like a stepper
In operation, air at up to 100 psi is supplied to each
of three pistons in turn via an integral rotary valve. The
free-floating pistons transmit maximum torque on start-up,
which can be adjusted via a pressure regulator. The resulting
performance features high torque, even at low speed;
variable speed control; and very low noise operation.
In the paint shop,
the stirring speed
can be controlled
directly via the air
the models used
here are variable
Because they are supplied only with compressed air and
no electrical cables are required, there is no possibility of
sparking; making the motors intrinsically safe for use in
ATEX Zone 1 applications. Due to the flammable nature of
paint vapors, this feature is a significant benefit to modern
high-throughput paint shops.
“They can even be used completely submerged and are
fine for high pressure washdown,” comments Lockett.
The simplicity of both the air motors and their air
supply system, compared to an electric drive equivalent,
makes installation and maintenance very easy. They are
lightweight and compact, making them easy to lift and
maneuver during routine maintenance. Connecting and
disconnecting the air supply is straightforward.
Furthermore, there is normally no need for a stepdown
gearbox between the motor and stirrer; while an
electric motor would require a gearbox, as would a vanetype
air motor. Even without a step-down gearbox, the Huco
Dynatork motor can run comfortably at output speeds below
100 rpm, the typical range for stirring applications.
“Our motors typically run for many years,” says
Lockett, “…and replacement piston and seal kits can be
fitted to extend motor life almost indefinitely.”
He also notes that service and back-up are fast and
efficient, with components available in the UK direct from
the manufacturer, and through distributors in Europe, Japan
and the USA.
Huco Dynatork motors are available with aluminium,
stainless steel or acetal bodies. Stainless steel and acetal
versions are ideal for use in industries such as food
processing, pharmaceuticals and medical equipment
manufacturing. Three standard sizes are offered, with
maximum torques of up to 16 Nm in direct drive, or up to
550 Nm through a gearbox.