Servo actuator avoids external gearheads

Inmoco's new Exlar PSA series of geared servo actuators overcomes the requirement for discrete gear reducers to boost torque output levels, by having servo motor and planetary gears in one unit.

The unique design of Inmoco's new Exlar PSA series of geared servo actuators overcomes the costly requirement for discrete gear reducers to boost torque output levels, by the simple expedient of integrating a servo motor and planetary gears in one unit.

The PSA Series, with its patent pending design, is the ideal OEM product, providing a system solution rather than a system component.

The actuator combines the security of single source supply with the advantages of cost competitiveness, compact size and the ability to be used with almost any commercially available servo amplifier.

Because Inmoco supplies the unit complete, customers are relieved of the potential problems of specifying a motor from one company and a gearhead from another.

Instead, they get a single product assembled correctly, with no pinion clamps to cause mounting or misalignment problems, and no worries about specifying motor mounting flanges, so that the gearhead will fit correctly.

The PSA actuator provides 3, 5 and 10 to 1 reductions in a compact package that offers users one of the highest power densities available from any electric actuator system.

The capabilities of the PSA mean that it is extremely useful in applications where high torque and / or power is required while weight and / or space is at a premium.

The key to achieving high levels of performance is synergy of materials and mechanical design.

As regards materials, the brushless PSA motors employ rare earth permanent magnets, of neodymium iron boron, which yield very high power densities and enable high operating speeds to be achieved (up to 5000 rpm).

Complementing this is a mechanical arrangement in which the front motor bearing has been accommodated into the planet carrier, while the rear motor bearing has been located into the motor armature.

Taken together, these initiatives ensure a very compact and rigid design and one which is frequently shorter than many commonly applied servo motors used today.

To ensure maximum strength and torsional stiffness the planet carrier and the output shaft of the PSA actuator are manufactured from a single piece of stainless steel.

These components are designed to operate with a pair of oversized ball bearings to assure long life even in the most demanding applications.

This design integrity also extends to the planet gears, which employ precision caged needle roller bearings.

The arrangement of these bearings, with a rigid shaft forming the inner race, and a planet gear forming the outer race, minimizes run out and bearing play, assuring very low backlash.

The innovative design detail employed on the internals of the PSA actuator is followed through on its case, which is specifically designed to be sealed to enable operation in dirty or corrosive environments.

The rigid IP65 rating, achieved with the help of Viton seals (as standard), also allows the adoption of oil flow cooling and lubrication, without the worry of leaks, in applications where extreme compactness is required, or where zero maintenance is desired.

The space saving achieved by the integrated design of the PSA servo actuator essentially renders right angle reducers obsolete.

Traditionally, right angle reducers have been used to reduce the length which in-line reducers extend out beyond the confines of a machine.

To achieve this, however, they have to employ an additional set of bevel gears to make the 90deg turn.

These gears increase the drive solution cost, complexity, and the total backlash since another mechanism is placed between the load and the motor.

The introduction of the new in-line PSA servo actuator, with a length which is extremely short compared to even non-geared servo motors, can, in almost all cases, overcome this problem and satisfy the application's requirement for overhanging loads.

A wide range of options, including special shafts, bearings, flanges and mounts complements the standard specification of the PSA servo actuator.

The output shaft may be a standard keyless shaft, keyed, or, for special applications, it can be hollow.

A spline shaft or an ISO9409 flange can also be supplied.

Another major option is an integral power-off brake.

With power removed this locks the actuator shaft securing the external load.

The size and performance capabilities of the PSA servo actuator units mean that they are ideally suited to challenging motion applications across a wide range of industries.

A typical list of these includes: Machine Tools, Printing, Process Control, Materials Handling, Automatic Assembly, Web Processing, Robotics Packaging Machinery, Coating, Testing and Aerospace.

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