Lines suggesting a technical drawing of a gearbox over a mechanical shaft

Bevel gear units

Whether as foot-mounted, shaft mounted or flange versions, KEB bevel gear units are available in various designs for plant and machine construction and impress with their technical features. But what exactly characterises these gear units? On this page, you will learn everything you need to know about the exciting technology of bevel gearboxes.

The space-saving angular gear

Bevel gear units are a type of angular gear units. This describes one of the key differences between bevel, spur or shaft-mounted gear units. Unlike helical gear units, the output shaft of a bevel gear unit is offset by 90 degrees to the drive axis. This allows the drive to be installed in a particularly space-saving manner. With angular gearboxes, it is possible to design the mounting in a similar way to shaft mounted helical gearboxes. The gearbox can be plugged on, enabling quick and easy installation. As with helical gearboxes, bevel gearboxes can also be designed as foot-mounted versions.

Helical bevel gear unit foot mounted with synchronus motor

At a glance: What are the advantages of a bevel gear unit?

Space-saving: Due to the arrangement of the input and output shafts at an angle to each other
Special feature: Bevel gearboxes enable the rotational movement to be transferred by 90 degrees
Easy installation: Plugging on the customer shaft
Versatile: Various versions such as foot, shaft mounted or flange designs are available from KEB
Efficient: The efficiency of KEB bevel gearboxes is between 94 and 96 percent
Flexible: The arrangement of the gears allows the use of solid shafts and different hollow shafts

Cutaway model of a bevel gear unit. The gears are clearly visible. Special areas are clearly marked for understandig, like the cut areas in yellow — Cutaway model of a bevel gear unit

How does a bevel gearbox work?

Bevel gear units are gear wheels that are used when torque and rotational movement need to be transferred between the driving source (e.g. motor) and the machine. The gear unit consists of two or more gear wheels and can be designed with one or more stages. The unique feature of the bevel gear unit lies in the angular arrangement of the drive shaft and the output shaft in relation to each other. The angle is usually 90 degrees, but other angles are also possible. In most cases, the axes of the respective shafts have a common intersection point. One advantage of the bevel gear design is that the bevel gears roll on top of each other, which results in particularly low frictional resistance during movement. The transmission ratio of KEB bevel gearboxes is between 1:5 and 1:180. In combination with other gearboxes, transmission ratios of up to 1:19,000 and even higher are possible.

The single gear wheels are straight or helical – at KEB, the gearing is helical – and thus transmit the torque with high precision. Specifically, the larger bevel gear (the so-called bevel gear wheel) is driven by a smaller bevel gear (pinion). The helical teeth result in a relatively complex geometry, which is why special machines, fixtures and tools are often required to manufacture the gearboxes.

KEB offers bevel gearboxes in a modular system. This means that different housing designs and output shafts can be selected for each gearbox design. Depending on individual requirements, a shaft mounted version can be selected to benefit from particularly simple installation. Foot versions with solid shafts can also be configured. In addition, the gearboxes can also be fitted with toothed hollow shafts or clamp connections.

Is a bevel gear unit always self-locking?

Bevel gear units are not self-locking. KEB bevel gear units have an efficiency of 94 to 96 percent. This is determined by the number of transmission stages (two-stage or three-stage), as each stage must be taken into account with a loss of around two percent. The rolling of the gears on each other, as described above, and the resulting low frictional resistance ensure high efficiency compared to worm gearboxes.

This high efficiency already indicates that bevel gearboxes are not self-locking, as self-locking is essentially the opposite effect of efficiency. Bevel gearboxes can be moved backwards by a load during operation – an effect that is sometimes desirable and sometimes not. If the gearbox were self-locking, it would not be possible to move it backwards against the load. How does this work in practice? When, for example, a lifting application raises a load, the motor transmits drive power to the gearbox, causing the application to move. If the motor is then switched off, the load can move back down because the bevel gearbox does not have any self-locking properties. KEB's brake portfolio offers suitable solutions for this case. For example, established spring-applied brakes such as the COMISTOP 38 provide reliable holding in lifting applications.

Self-locking gearboxes are generally advantageous when it is important in an application that a load does not move by itself when the drive is switched off. This is the case with worm gear units, for example. Self-locking also depends on several factors. The coefficient of friction between the tooth flanks and the pitch angle of the worm plays an important role. A high coefficient of friction and a small pitch angle favour self-locking. You can find out more about worm gear units on the corresponding technology page.

What bevel gears designs does KEB offer?

Shaft mounted with torque arm + hollow shaft with shrink disc

Shaft mounted with foot area and hollow shaft

Flange mounted with foot area and hollow shaft

The washing units in a train washing system. Clearly visible are also the helical bevel gear units used there — Several bevel gear units in a washing system for locomotives

When are bevel gear boxes used?

KEB drive components are used in numerous areas of plant and machine engineering. The angular design of the bevel gearbox results in compact dimensions – an important advantage in all applications where space is limited. Their ability to be combined with other gearboxes opens up further application possibilities, as double gearboxes are necessary for high reduction ratios or low output speeds.

Against this background, it is not possible to specify general applications for bevel gearboxes, as the most effective gearbox solution for the respective requirements is always selected individually with the experts at KEB. One example where the use of bevel gearboxes is ideal are conveyor belts: if a shaft mounted helical gearbox were to be used here, it would probably protrude too far from the application. An angled bevel gearbox saves installation space because the drive can be placed close to the application.

Another practical example where space-saving gearbox integration is important can be found in intralogistics and the operation of rack serving devices. As a rule, it is important for operators to have the aisles between the high racks as close together as possible. This means that drive solutions are required that can cope with the limited space available. For this reason, bevel gearboxes are often selected for the main drive in this case.