Actuator has ten times better load capacity

.Five to ten years ago, machines used to be designed on one common drive technology. Today, there is an increasing demand to develop machines and equipment that match the drive technology to a specific machine axis, hence the converging technology trend in linear motion. There is also a trend towards outsourcing the complete system design as machine builders no longer wish to procure separate machine elements from different suppliers, then integrate it all together and hope it does the job. With all this in mind, linear motion supplier Hoerbiga-Origa has developed a new modular belt-driven linear actuator for heavy duty applications that should save designers considerable design and installation effort and will compete against rack and pinion drives and other actuators. The BHD II incorporates a precision recirculating ball bearing rail that gives it a load bearing capacity of two tonnes - ten times that of earlier BHD models. For high load and long stroke applications, rack and pinion drives would normally be specified by design engineers. But these have to be built up from basic components and the whole system configuration optimised, which is time consuming. And a rack and pinion's 'unenclosed' design leaves the unit somewhat exposed to damage and clogging in typical industrial environments. This is particularly the case in hygienic applications such as food, pharmaceutical and clean rooms. And, with rack and pinions, the drive motor has to be mounted on the moving carriage, which can add inordinately to the mass being moved and lead to issues with flying leads to power the motor. Even safety can be a problem here, as the meshing of rack and pinion can form a potential hazard. Hoerbiga-Origa developed the BHD II series in response to users that were overloading the original BHD medium duty units in preference to using a rack and pinion. The 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 for low friction, high dynamic performance. Nigel Smith, product manager at Hoerbiga-Origa told Eureka: "The unit can run at speeds of up to 5m/s, fast enough for 95% of all application requirements, which is probably more than enough considering the loads it is likely to be used with. Acceleration is up to 30m/s2 which is high so that cycle times on short stroke applications can be reduced." The housing has a stainless steel sliding seal inside which ensures the belt is protected from ingress of dirt and oil. Modular mounting options and dovetail slots for adding sensors and other ancillaries are also included in the housing profile. The belt itself is manufactured from a high performance polyurethane reinforced with stainless steel. According to Jones, "the belt requires no maintenance or adjustment throughout its service life which is measured in years for most applications." He also said that in some applications, belts were outliving the machine they were driving. The drive motor is a plug-and-go unit and can be induction, stepper or servo and there is an integral gearbox option and bi-parting cartridges. Stroke length is infinitely varaible up to 10m and it is possible to join two units together for even greater strokes. Jones advised that other possible application areas for the BHD II unit were in: mechanical handling; high speed reciprocating; and long stroke lifting. Jones even said that tyre manufacturer Pirelli was using the units as bi-part clamps to trim tyres to width on its production lines in the UK.