Helical gear units

Helical gear units

Helical gears have been an integral part of the KEB Antriebstechnik portfolio for a long time. But how do helical gears work and in which applications are they used? On this page, we shed light on the technical background and explain, among other things, how exactly helical gears transmit rotary motion.

The classic for power transmission

Helical gear units are often used to transfer torque and speed from the motor to a machine component that is to be driven. These consist of two or more interlocking gears. Special feature of the helical gear: the individual gear wheels are arranged on parallel axes to each other. KEB Antriebstechnik manufactures 100 percent of the helical gear units at the motor and gearbox plant in Schneeberg. The result is high-quality gearboxes with a high degree of efficiency, which are used in numerous (customer-specific) applications.

Helical gear motor — Helical gear unit, foot-mounted version in combination with asynchronous motor

At a glance: What are the advantages of a helical gearbox?

Robust: KEB helical gearboxes are particularly resilient and are therefore suitable for use in harsh environments
Compact: Maximum space savings thanks to compact design
Powerful: Minimal losses ensure an excellent efficiency of 94 to 96 percent
Reliable: The long service life of the helical gear units saves costs
High performance: Output torque from 60 Nm to 13,600 Nm
Individual: Specific customer requirements are taken into account thanks to a high level of vertical integration
Precise and quiet: Exact transmission of motion with low noise
Cost-efficient: helical gearboxes are easy to repair

real cutaway model of a helical gear unit with motor made by KEB — Cutaway model of a helical gear unit with motor

What is a helical gear?

A helical gearbox motor traditionally consists of a combination of a gearbox and an electric drive motor. Helical gearboxes are used to transfer torque and speed in numerous fields of application. The gearbox itself is a gear drive and is primarily characterized by an axis-parallel arrangement. This has several advantages: helical gears are compact, so they save as much space as possible while also providing the desired torque ratio and a high speed reduction ratio, i.e. converting a high speed into a lower speed. Ratios of approx. 1:3 up to 1:22,000 are possible.

In the case of spur gears, it can basically be a matter of gears with one, two or even three translation levels. In this type of gearbox, the motor and output shafts are almost on the same level. Combinations of several gears – the helical gears that give them their name – are possible in order to reduce the motor speed and to transfer movements from one shaft to another. The teeth of the gears are designed so that they interlock precisely; they can be arranged straight or in an angle, what is called helical. In KEB, teeth are usually helical. How the gears interlock depends on the individual needs. While straight gear wheels are easier and therefore cheaper to manufacture, helical gear wheels offer quieter running and the option of transferring higher loads. The aim of the helical gearbox is to ensure efficient power transmission.

Engineering drawing as a cutaway model of a helical gear unit made by KEB — Technical drawing as a cutaway model of a helical gear unit with different variants (e.g. bearings and gear wheels)

How do helical gears transfer the rotary motion?

The actual motor speed is usually too fast for many applications and cannot be used without further processing. This is where gearboxes such as the helical gearbox come into play, converting the speed and torque to the appropriate levels for the application. To understand how the helical gearbox transmits rotary motion, we need to take a look at the basic structure of the gearbox. The rotational movement begins at the input shaft. The input shaft is connected to the drive gear. As a result, when the shaft rotates, the drive gear also rotates. The drive gear engages with its gear teeth in the teeth of the output gear, efficiently transmitting the motion. When the drive gear rotates, it forces the output gear to also rotate. The direction of rotation of the output gear is always opposite to the direction of rotation of the drive gear. The rotational motion is finally transmitted to the output shaft, which is connected to the output gear. The output shaft can then transmit the rotational motion to other mechanical components.

The transmission of the rotary motion in a helical gearbox is influenced exclusively by the size and number of teeth of the gears. A smaller gearwheel that drives a larger gearwheel increases the torque while reducing the speed. Conversely, a larger gearwheel that drives a smaller gearwheel results in an increase in speed and a reduction in torque.

Spur gear and Helical gear: What's the difference?

In the machine and plant engineering sector, the terms ‘spur gear’ and ‘helical gear’ are often used synonymously. But what is the difference between the two definitions?

Spur gear: Spur gears are characterised by straight toothing and direct power transmission. They are also distinguished by a particularly simple design.

Helical gear: KEB relies on helical gears in its portfolio. The helical toothing and the comparatively higher quality of the products are typical here.

What is the efficiency of helical gears?

The special feature of KEB helical gear units lies in the relation between power and compact design. Losses occur in the gearbox, for example, due to the friction of the gears when the tooth flanks engage. Due to the high quality of the gearing, the roller bearings and the lubrication of the gearboxes, the helical gearboxes from KEB achieve very good values here. Since the helical gearboxes from the KEB portfolio show hardly any losses, an efficiency of 94 to 96 percent is achieved, depending on the number of stages. The highest possible efficiency means that the motor power that is applied to the gearbox arrives at the output shaft without major power losses. Due to the high efficiency, the spur gearbox is not self-locking.

Which helical gearbox designs does KEB offer?

KEB helical gearboxes are available with power outputs from 0.12 kW to 45 kW. The output torque ranges from 60 Nm to 13600 Nm. The detailed technical data can be found on the corresponding product page. Due to the high production rigidity in the gear and motor plant in Schneeberg, there is always full access to the development process of a helical gear unit. This makes it easy to implement customer-specific requirements and, for example, the output shaft can be designed differently. A special feature of the helical gearboxes is that they are only available with a solid output shaft, i.e. a shaft onto which the customer can attach a coupling, for example.

Customers can choose between foot, flange or foot-flange versions of the helical gearboxes. While the foot-mounted version allows the gearbox to be mounted on a solid surface, the flange-mounted version ensures that the gearbox is attached directly to the customer application.

Foot-mounted helical gear — Foot-mounted version

Flange-mounted helical gear — Flange-mounted version

Foot-flange-mounted helical gear — Foot-flange-mounted version

A helical gearbox with motor underneath a conveyor belt — A helical gearbox underneath a conveyor belt: Intralogistics is a common area of application for the gearboxes

When are helical gear units used?

Helical gear units are in demand in numerous fields of application. In particular, when the greatest possible space savings are desired due to limited installation space. This is precisely where helical gear units are ideal due to the compact arrangement of the gears combined with high efficiency and reliability. Classic areas of application include the automotive industry. Here, helical gear units are often used in manual transmissions to transfer the power of the engine to the wheels of the vehicle. A central task here is to realize different transmission ratios in order to meet the various conditions while driving. And when distributing the rotation to the wheels, helical gears also play an important role as part of differentials. In addition, there are many other fields of application:

KEB has been a partner of mechanical engineering for decades. The helical gears from the motor and gearbox plant of KEB Antriebstechnik are also used in numerous machines and plants. In machine tools, for example, the gears ensure power transmission and optimal load distribution. Due to their high robustness, helical gears are particularly suitable for applications that operate under harsh environmental conditions.

The transmission of high torques is a feature of the gearboxes that is also in demand in conveyor technology, such as conveyor belts. Helical gears are also in demand in textile, plastic, woodworking and packaging machines. In the field of robotics, helical gears are used, for example, in robot links. On the one hand, their compact design makes them the first choice here, and on the other hand, they enable precise movements, which are particularly important for robot and automation applications.

In addition, there are many other areas in which the function of helical gears is relevant. In mechanical watch movements, the gears precisely transfer motion from the spring to the hand, and in agricultural machinery such as tractors, they transfer the power of the engine to attached devices.

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