NEFF-bevel gearboxes have strong grey cast iron housing, hardened bevel gears lapped in pairs with spiral toothing and adequately dimensioned roller bearings. Spiral bevel gears offer the decisive advantage of very favorable engagement ratios (high degree of overlap).
They are therefore predestinated for applications under high stresses, coupled with optimum smooth running characteristics and high transmission accuracy. The arc shaped teeth are more resistant to bending than straight or diagonal teeth. A further advantage is the relative insensitivity to elastic deformation of gear wheels, shafts and bearings. The gears can therefore also transmit extreme shock loads. Three standard designs are available. 22 further variations are possible as auxiliary drives. The gearboxes can be used in all installation positions and provided with various mounting holes. Cover and flanges are generally provided with mounting holes.
The following standard transmission ratios are available: 1:1, 1.5:1, 2:1, 3:1, 4:1, 5:1 and 6:1. All transmission ratios are mathematically precise. The gearboxes can be used as step-up and step-down gearboxes. Customer specific transmission ratios are available. Please enquiry.
The efficiency off the NEFF bevel gearboxes is 94—98%, depending on speed, installation position, sealing and type of lubricant. The efficiencies refer to the rated performances of the gearboxes. In certain installation positions the bevel gears are fully immersed into the lubricant. In case of larger gearboxes and high peripheral speeds of the gear wheels, the churning losses cannot be neglected and NEFF must be consulted. Note that the stat-up efficiency is always smaller than the operational efficiency. The resultant increased breakaway torque must be considered in the design of the drive performance.
As standard the gearboxes have a circumferential backlash of 10 to 30 angular minutes, depending on the size of the transmission and the transmission ratio. However, all NEFF bevel gearboxes can be supplied in a low-backlash version. The circumferential backlash at the slow running shaft is measured with the drive shaft blocked on a lever arm of 100mm with measuring force of 3% of the nominal torque and given as the torsion angle. The following values are adjustable with normal gear wheel sets:
Version S1: i=1:1 to 2:1 < 6 angular minutes
Version S2: i=3:1 to 6:1 < 10 angular minutes
Tighter values require select, HPGS-toothed or polished gear wheel sets – please enquire.
In principle NEFF gearboxes can be driven in both directions of rotation. Together with the direction of rotation, the spiral direction of a gear wheel, set determines the internal load ratios of the gearbox. If one selects the direction of rotation of the small gear contrary to its spiral direction (viewed from the shaft end face to the center of the gearbox), then the axial force acts outwards. As a result the gear wheel set is pressed apart and causes a lowering of the noise level by 1-2 dBA. NEFF manufactures the pinion as a left-hand spiral; the preferable direction of rotation is thus clockwise.
NEFF bevel gearboxes are delivered with an oil filling and are maintenance-free under normal operating conditions. In case of extreme requirements or increased service life requirements, we recommend an oil change approx. every 15.000 hours of operation.