Worm gearboxes

Due to its mode of operation, a worm gearbox enables high step-down ratios.
In worm gearboxes, both shafts intersect in a defined distance (A).
This centre-to-centre distance is reflected in the specification of the gearbox size.
(Example: S 100 – centre-to-centre distance 100 mm)

Low-noise axial-offset gearboxes

Worm gearboxes are highly precise and powerful axial-offset gearboxes. The high-performance gearboxes cope with today’s high requirements in every respect. They are quiet-running and insensitive to shocks. It is not without reason that they are used worldwide, inter alia, in conveying systems. In everyday language, worm gearboxes are also known as Worms.

 

Product features

  • Robust, powerful, low-noise
  • Housing made of grey cast iron
  • Axial offset between drive and output
  • Maintenance-free

Application examples

  • Stage and theatre technology
  • Separating/Singularization machines
  • Conveying systems
  • Profile processing machines
  • Extrusion machines

Toothing

A gear set consists of worm shaft and worm gear.

Construction types

Due to the modular system, different gearbox construction types can be configured.
The variants differ in the type of the shafts, the rotational direction of the shafts, and the support by bearings.

Threaded mounting holes

The housing surface on the side 1 and the flange surfaces on the sides 5 and 6 are machined and may be used as mounting surfaces.
All flanges always have threaded mounting holes.

You have the following available ordering options:

Gearbox size Ordering options Threaded mounting holes are located in the housing surfaces on the gearbox side Threaded mounting holes are located in the flanges on the gearbox side
040-250 1 1 5,6
040-100 2 1,2 5,6
040-100 3 1,3 5,6
040-100 4 1,4 5,6
040-100 5 1,5 5,6
040-100 6 1,6 5, 6

The standard version of the mounting / fastening has the order code 1.
Please enquire other mounting Options.

Installation position

The installation position is defined by the gearbox side directed downwards during operation and will be indicated by the associated numeral.
The gearboxes can be used in all installation positions.
The technically most favourable and thus recommended installation position is the installation position 1. In this position, the worm shaft is horizontal and located at the bottom.

Please contact us for consultation if the angle of the gearbox side directed downwards deviates more than 15° from the horizontal position. The performance data and torques listed in the selection tables are only valid if the gearboxes are used in the installation positions 1, 5 or 6.
The values must be reduced by 10% if the worm shaft is vertical or located at the top (installation position 3, 4 or 2).

Shaft designation – allocation to the gearbox sides

The worm shaft is the fast-rotating shaft.
It has the speed n1 and is identified by N1.

The slowly rotating shaft has the speed n2 and is identified by N2.
The worm gear is located on this shaft.
The gearbox sides are identified by the numerals 1 to 6.

Rotational direction and gear ratio 

As standard, the worm gearboxes are delivered with right-handed worm shafts.
This results in rotational directions according to Figure 8.2.5‑1.
In the special design, delivery with left-handed gear teeth is also possible.
Please enquire this.
Please refer to the performance tables for the possible gear ratios.
Principally, the actual gear ratio “iist” must be taken into account for the layout.
In some cases, this deviates from the nominal gear ratio i.

Efficiency

The achievable efficiency depends on rotational speed, torque, installation position, sealing, and lubricant type.

Starting Efficiency

The efficiency is always lower during the starting phase and in the cold operating state since the lubricating film is not formed until the sliding motion has started.
Therefore a higher torque is needed.
The starting efficiencies listed below are guidance values and valid for run-in gearboxes.

These starting efficiencies must be taken into account for the layout.

Number of threads Gear ratio range Starting efficiency Pitch
1 83 – 62 0,30 – 0,40 3°-3,5°
1 53 – 30 0,40 – 0,50 5°-6°
2 26 – 15 0,56 – 0,65 10°-12°
4 13 – 7,5 0,68 – 0,75 19°-23°
6 5 0,74 – 0,82 28°-32°

Operating Efficiency

The tooth flanks of worm gearboxes in the as-delivered condition are not yet fully smoothed.
Therefore the gearboxes should be
run in with approx. 50% of the nominal data, if possible, before they are operated under load.
The efficiencies specified in the performance tables relate to the permissible nominal data and are guidance values for run-in gearboxes with standard sealing that have operating temperature, and an oil viscosity of 460 mm2/s.

Step-up drive

Due to the high efficiency of the ATEK worm gear sets it is possible to drive the gearboxes with 4-thread and 6-thread worm shafts also from the worm gear side and thus to generate a stepping-up.

The efficiency with a driving worm gear is calculated by the formula: η´ = 2 – (1 / η)

Self-locking

The self-locking is directly related to the efficiency of the gearbox.
Please refer to chapter 8.2.11 Self-locking for more Information.

Lubrication

Different conditions for the lubrication of the toothing and the roller bearings will arise depending on gearbox size, installation position, rotational speed and on-period.
In order to ensure these optimally, different oil quantities and viscosities are used.

These will be defined by ATEK based on your ordering details (rotational speed, on-period, and ambient temperature).

They will be reflected in the type designation.
You can find the itemisation in the example S 125 10:1 C0 -9.1- 200/A1.
/A1 means:

Abbreviation Explanation Reference
A Oil viscosity 460 Table 9.2.8‑1
1 with venting Table 9.2.8‑2

The worm gearboxes are factory-filled with synthetic polyglycol oil and are normally maintenance-free.

 

Oil viscosity table

Code; numeral 1 Viscosity
A 460
B 220
C not available
D Injection lubrication
F fluid grease

In case of very low rotational speeds, lubrication by fluid grease is also possible.
At operating temperatures over 50°C, high pressure will develop through air expansion in the gearbox.
Then a permanent pressure compensation must be ensured.
To this end, the use of a vent filter is prescribed.

Code numeral 2 Vent filter
0 No
1 Yes

 

Vent filter

If venting is required the gearboxes will be delivered with a vent filter.
The vent bores will be equipped with screw plugs for transport.
The vent filter will be enclosed as a separate item and must be mounted in the intended position prior to commissioning.
An elbow may be required.
Please adhere to the operating instructions!
The position will be specified in the order documents.
Please refer to Figure 8.2.9-1; Installation positions, for the position of the filter.

Here, E4, for example, means: Venting on side 4.

Low-backlash construction

For optimal running, the tooth space in the gear set is manufactured larger than the tooth.
When the direction of rotation is changed, this results in a rotation angle until the counter-rotating tooth flanks contact each other.
This rotation angle is called circumferential backlash.

Circumferential backlash, measuring method

The circumferential backlash is measured after the drive shaft (N1) has been fixed.
A force of around 2% of the nominal torque is applied to the output shaft (N2) in both rotational directions.
A tooth backlash will result between the two final positions. This can be measured as rotation angle and is indicated in minutes of arc [arcmin].

All ATEK worm gearboxes can be delivered as low-backlash types.

The following values can be set with standard gear sets:

Ordering option Gear set 040 – 125 160 -250
/0000 Standard <=30 arcmin <=30 arcmin
/S2 Standard <=10 arcmin u.r.
/S1 Standard <=6 arcmin u.r.
/S0 Sonderradsatz <=3-6 arcmin u.r.

Abbreviation: u.r. – upon request

Self-locking

Worm gearboxes are self-locking if the gearboxes cannot be driven from the worm gear side.

The self-locking is directly related to the efficiency of the gearbox.
If self-locking is demanded the corresponding efficiency of the gearbox with driving worm must be below 0.5.
If a gearbox must be unconditionally self-locking, or alternatively, unconditionally not self-locking, we ask to contact us for consultation, giving a description of the case of application.

Static self-locking

Worm gearboxes are statically self-locking if starting from standstill with driving worm gear is impossible.

The self-locking depends on the pitch of the toothing.
The angle is 2.5° to 5°.
Please enquire this.

Vibrations may override / deactivate the self-locking.
Therefore a self-locking toothing cannot always take the place of a brake or an anti-reversing device.

Dynamic self-locking

Worm gearboxes are dynamically self-locking if, with rotating gearbox mechanism, continued operation is impossible due to torque action on the worm gear (output side) of the gearbox.
The overrun occurring after switching-off depends on the rotating masses on the drive side.
Dynamic self-locking is only possible with very large gear ratios in the range of low driving speeds.
Please enquire this.

Limits

If driven parts have high mass inertia moments no self-locking must occur during the run-down process.
Extremely high load peaks may occur in case of sudden blocking of the gearbox.
In such cases, a gearbox with multistart worm should be used whenever possible.
Also, if a braking motor or a separate brake is used on the drive side, the braking moment must not be too high, and it must be mitigated by using an additional flywheel mass on the drive side