Actuator belts along with a heavy load

A new modular belt-driven linear actuator for heavy duty applications will compete with rack and pinion drives as much as other actuators.

A new modular belt-driven linear actuator for heavy duty applications will compete with rack and pinion drives as much as other actuators.

The BHD II is developed from Hoerbiger-Origa's original BHD range, and incorporates a precision recirculating ball bearing rail that gives it a load bearing capacity for 2t - ten times that of earlier models.

Modular linear actuators have become a firm favourite with design engineers and machine builders over the last decade or so, being fit-and-forget mechatronic subsystems that save considerable design and installation efforts.

Originally seen as suitable for light and medium duties only, the users are now looking to extend their usage into ever more demanding applications.

Traditionally rack and pinion drives were the technology of choice for high load and/or long stroke requirements.

These have to be built up from basic components, so it is time consuming to develop an optimum configuration for each application.

Also their unenclosed format leaves them somewhat exposed to damage and clogging in typical industrial environments; and dirt can build up on them making them unsuitable for some hygienic applications in food, pharmaceutical, clean room and precision applications.

Another problem associated with rack and pinions is that the drive motor has to be mounted on the moving carriage.

This can add inordinately to the mass being moved and lead to issues with flying leads to power the motor.

Finally there are potential safety issues, in that the meshing of rack and pinion form a potential hazard.

The decision to develop a heavy-duty BHD was based on the observation that some users have overloaded the original medium duty units in preference to using a rack and pinion.

For BHD II Hoerbiger-Origa's development team retained the concepts of a compact low profile actuator, housed in a high strength one-piece aluminium extrusion.

The low profile is achieved by mounting the belt pulleys with vertical axes rather than horizontal, so that the two runs of the belt loop are side-by-side instead of one above the other.

The extruded housing is strong enough to be used as a structural machine element in many applications absorbing any static loads present, including side and bending forces.

The dynamic load being moved by the actuator is carried entirely by the recirculating ball bearing rail for low friction, high dynamic performance.

A stainless steel sliding seal is mounted in the housing to ensure that the belt mechanism is fully protected from ingress of dirt and oil.

Modular mounting options and dovetail slots for adding sensors and other ancillary equipment are also encompassed within the profile of the housing.

The belt is made from a high performance polyurethane reinforced with stainless steel reinforces, being supplied in 20, 25 or 40mm widths depending on the size of the BHD II unit.

The belt requires no maintenance or adjustment throughout its service life which is measured in years for most applications.

BHD II can run at speeds of up to 5m/s, fast enough for +95% of all application requirements and probably more that adequate considering the loads it is likely to be used with.

Acceleration capabilities are up to 30m/s2, which is high so that cycle times on short stroke applications can be reduced.

Stroke length is infinitely variable up to 10m.

It is possible to join two BHD IIs together for even greater strokes, but Hoerbiger-Origa warns that in practice a reduction in speed and thrust performance may be experienced for particularly long strokes.

The decision to develop this long stroke capability was based Hoerbiger-Origa's experience in linear motion engineering which suggests that large loads sometimes need to be transported considerable distances.

In keeping with the modular concept of the BHD range, the drive motor is a plug-and-go unit and can be induction, stepper or servo.

Options available include an integral gearbox and biparting carriages.

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