Hybrid gearboxes use planetary and helical bevel technologies

The innovative new Posiplan PH and BPH shaft-mounted gearboxes employ the planetary stages at the input end where higher speed and compactness are a major advantage, and the helical stage at the slower, higher torque output side. The result is a hybrid gearbox offering the best of both worlds and delivering far higher capacities from smaller units, allowing a reduction in size, or a significant increase in capacity over a more traditional design.

Jon Snaith, General manager for sales, states: "In the past some engineers have been reluctant to design a planetary shaft-mounted gearbox into the machine because the driven shaft does not engage all the way through the gearbox. The Posiplan, in contrast, has a helical final stage reduction, thus removing this objection."

Performance matches motors

Available in ten motor-harmonised sizes, the series has been developed not only to deliver more performance, but to also help increase motor efficiency and motor life by working with motor performance curves to optimise the most efficient working input speeds of common frame sized motors.

The high power-to-weight properties of Brevini planetary gearing enables both series of gearboxes to offer OEM designers a lighter and more compact alternative to traditional helical and helical/bevel gearboxes. A modular cast casing and a broad range of mounting options have reduced manufacturing times and design costs, while maintenance engineers and plant managers using the gearboxes in replacement situations will appreciate the use of the latest labyrinth sealing technology and high-performance bearings to guarantee an extended operating life in the harshest of environments.

Offering nominal torque capacities up to 27,000Nm (soon to be extended to 67,00Nm), the Posiplan PH and BPH range of shaft-mounted gearboxes are suitable for use in applications such as bucket elevators, mixers, conveyors and crushers and are suitable for many other industrial applications requiring medium/low speed and high torque.

Using these gearboxes in a shaft-mounted configuration offers the flexibility of fitment in any orientation and they can replace high-wearing/high-maintenance exposed transmission alternatives such as belts, chains and pulleys. Costs can also be reduced over worm/wheel transmissions due to higher-efficiency operation, requiring a smaller motor to drive it as well as the actual units themselves being lower in weight and extremely price competitive.

Benefits and options

The in-line Posiplan PH series provides benefits over traditional helical designs by offering ratios from 12:1 to 2000:1, within the one casing without the need for an additional helical gearbox in the drive train. The units are useful for space- and weight-restricted conveyor or mixer applications where designers need high levels of torque from a low-weight, high-efficiency design. The series achieves torque outputs ranging from 5.8-67KNm via single-, double- or triple-stage planetary inputs and a single-stage helical output for shaft diameters of 70-140mm.

Offering similar levels of performance, the Posiplan BPH series provides reduction ratios of 30:1 up to 1000:1 as standard and are more suited to applications requiring 90-degree operation - such as cranes, crushers, extractors or continuous extruding assemblies. The smallest 29kW, 70mm output shaft version consists of a standard Brevini input with parameter-optimised Gleason bevel gear assembly. A single Brevini planetary stage further reduces transmission speeds to a final helical gear output. However, higher-torque models (BPH20, 23 and 25) are supplied fitted with a single reduction planetary stage input or a two-stage planetary input for maximum speed reduction.

Long life and high-efficiency operation of both gearbox designs is ensured by the specification of high-speed bearings on the input shaft, taper roller bearings in the internal gearing to resist high thrust loads, and oversized bearings on the output shaft to maximise rigidity. Nitrile (NBR) labyrinth seals with a separate grease-filled chamber offer protection against lubricant leakage and contamination, further prolonging the wear life of the gearboxes. The casings are all nodular grade cast iron.

Output options available include hollow shafts (cylindrical with keyway or cylindrical hollow shaft for shrink disc) as well as splined shafts. Input variations include adaptors for IEC, NEMA and hydraulic motors, flexible and fluid couplings, clutches and torque limiters, and belt couplings. Customised versions are available, as well as complete assemblies supplied including motor, coupling and base plate. Units are also offered with torque arms, backstops, brakes and auxiliary drives, as well as oil filtering and cooling systems.