Gearboxes ensure that a machine rotates at the desired speed, even if the electric drive provides a completely different speed. The rotary motion for a machine is usually generated by an electric motor whose shaft rotates at almost 1500 revolutions per minute.
For most applications, this speed is much too high, so it must be adjusted by gears as desired.
In industry, gearboxes with a fixed ratio between the input and output speed are the rule. Manual gearboxes like those in cars are practically non-existent. The ratio between the two speeds is called “gear ratio” or “reduction ratio” (reduction ratio because the output speed is lower than the input speed, i.e. it is reduced), and is designated by the letter “i”. If a gearbox with i=100 is assembled with a motor with a speed of 1500 revolutions per minute, the output shaft of the gearbox rotates a hundred times slower, at 15 revolutions per minute.
Gearboxes are manufactured in various basic forms. For example, the torque can be transmitted to the machine via a solid shaft or a hollow shaft, which is either aligned with the motor shaft, parallel to it, or at right angles to it. Inside a gearbox, external and internal spur gears, bevel gears or worm gears can act. These basic shapes have different advantages, in terms of assembly, efficiency, precision and price, which are detailed below.
MOLL-MOTOR’s experience with gearboxes goes back to the 1970s, and we are manufacturing at our site since 2005. Our sales engineers will be happy to help you to choose the right gearbox!
the manufacturer bonfiglioli
Gearboxes that you can purchase from MOLL-MOTOR come from the traditional Italian brand “Bonfiglioli”, internally also abbreviated to “Bonfi”. Since there is such a wide variety of possible combinations of gears in gearboxes, Bonfiglioli has a philosophy of working with partners. These “BEST” partners are supplied with kits and parts, and final assembly takes place on site, close to the customer. For Austria, MOLL-MOTOR is the exclusive “BEST” partner and manufactures worm gearboxes, spur gearboxes, bevel gearboxes, planetary gearboxes, flat gearboxes and spur worm gearboxes. We can therefore quickly supply a large selection according to your needs. Large quantities for mechanical engineering companies can of course be ordered directly from the factory – with the appropriate lead time. We can also store these products with us, assemble them with motors into subassemblies and deliver them just-in-time when the machine is at the right stage of production.
Only in exceptional cases, when your gearbox cannot be replaced with Bonfiglioli, we work with other manufacturers.
To create the greatest possible modularity, we design most gearboxes with an IEC flange. This flange is used to connect the gearbox to any motor to form a gearmotor. Housing versions for space-saving direct mounting to a motor are available, but the selection of suitable motors is very small, which is why we prefer IEC mounting. Please note for all gearboxes that they may only be operated with oil filling. Mineral oils and synthetic oils are available, and we will be happy to provide information on their properties. Small gearboxes are usually delivered oil-filled. In the case of large gearboxes, oil filling on delivery often has disadvantages, which is why they have to be filled at the customer’s premises. If we deliver a gearbox without oil, it is marked with a warning label.
Different types of gearboxes have different advantages and disadvantages, which are briefly described here.
Spur gearboxes
These gearboxes are particularly widespread. The gear wheels are designed as spur gears and therefore touch each other on the outside. Usually, two or three gear stages, i.e. a total of 4 or 6 differently sized gears, are installed. The gear shaft is always a solid shaft and approximately in line with the motor shaft. The gearboxes are relatively cheap and compact.
worm gearboxes
The structure of worm gears differs significantly from other designs. Instead of a gear wheel, a worm acts on a worm wheel. The output shaft is at right angles to the motor shaft, and is usually designed as a hollow shaft. This design allows the worm gear to be mounted in a very space-saving way. On conveyor belts, for example, the motor can be aligned parallel to the belt. High reduction ratios up to i=100 are possible with only one gear stage, and the movement is transmitted very smoothly. However, the efficiency is significantly lower than with gear drives and a lot of waste heat is generated.
Worm gearboxes can also be combined to form double worm gearboxes, with which very slow output speeds are possible, and which offer the advantage of self-locking. If the motor is stopped, a conveyor belt is prevented from continuing to run or running backwards. Worm gear units can be combined with a spur gear pre-stage and are then called “spur worm gear units”.
Planetary gears and low-backlash planetary gears
Here, various externally toothed gears called “sun gears” and “planet gears” interact with an internally toothed ring gear. Since several gear wheels interact and there are several points of contact, higher torques can be transmitted in a compact design, very high transmission ratios up to i=5234 are possible and it runs very smoothly. Planetary gearheads are the cost-effective alternative when high torques, preferably at low speeds, are to be transmitted in a small space. These gearboxes are assembled in our factory in the most common sizes at short notice.
Planetary gearboxes can be designed with a solid or hollow shaft, the output shaft is exactly in line with the motor shaft. Planetary gearboxes can be combined with a bevel gear pre-stage, which enables output at right angles to the motor shaft.
For precision drives, we offer low-backlash planetary gears.
bevel gearboxes
A bevel gear stage in a gearbox causes the axis of rotation to be deflected by 90°, therefore the output shaft is at right angles to the motor shaft. This allows for very space-saving mounting on machines. Bevel gearboxes are much more efficient than worm gearboxes, which have the same right-angled design, but they are also significantly more expensive. As a rule, a bevel gear stage is combined with at least one spur gear stage, which is why the exact designation is “bevel spur gear”.
angular gearboxes
Angular gears are used if the direction of the rotary axis is to be changed by 90 degrees in an application, but either no transmission ratio or only a small transmission ratio of e.g. i=2 is required. They consist exclusively of a bevel gear stage.
Flat gearboxes
The gears are designed as spur gears, but the gear stages are not arranged one behind the other, but side by side. This makes the flat design that gives the gearbox its name possible. The output shaft is parallel to the motor shaft and can be designed as a solid shaft or a hollow shaft. Due to the centre distance between the two shafts, it is also possible to arrange the motor during assembly in such a way that it is located above or below the machine and requires little space at the side.
Shaft-mounted gearbox
In this gearbox, spur gears work together in a similar way to a flat gear. The output shaft of the gearbox is mounted directly on the machine, but the drive is not provided by a coupled motor. The gearbox has a solid shaft on the input side, which is driven via V-belts and V-belt pulleys by a motor that is usually placed in parallel under the machine.
Other available products in the category Gearboxes:
Gap pole geared motors, extruder gearboxes, screw jacks, planetary gearboxes for hydraulic motors, small geared motors, customised special gearboxes.
