Gearboxes: Basic Design Versions

is the most common gearbox type, also in JE.

Advantages

• simple construction with low costs
• short gearbox length, also for high ratios

Motor shaft is in same direction as gearbox shaft, but usually not coaxial (for comparison see planetary gearbox).

Direction of rotation is being reversed by every gear stage. That means, a gearbox with an odd number of stages reverses the direction.

Ratio per gear stage is in range of 3 … 8.

Higher ratios can be implemented too, but diameter of the secondary gear wheel and thus dimension of the gearbox gets quite large.

Torque load is lowest at motor pinion and highest at the final wheel. For this reason

• size of teeth (gear module) is different.
• material is different

Example: Spur gearbox UGD with Stepper motor

Example: Spur gearbox UGF with DC motor

Motor shaft is perpendicular to gearbox shaft.
The gearmotor has a short length in output shaft direction, which can be advantageous for applications with limited space in axial direction (e.g. window lifters in cars).

Gear ratio can get up to 90.

There is friction between worm and wheel, with effect on

• wear and lifetime.
• transmission efficiency

The higher the ratio the lower the efficiency (can be less than 50%).
Efficiency also depends on lubrication and surface finishing.

The worm wheel is made of softer material than the worm.
It consists of bronze or of plastics, whereas worm is made of steel usually.

The worm produces an axial force (thrust), which must be supported by motor bearings.

Worm gear has high backdriving resistance.
High ratio worm gears are static self blocking. However, possibly not against vibrations.

The gearmotor has small diameter, same or similar to the motor diameter.

Length is rather long, particularly for higher total ratio.

The output shaft is concentric to the housing.

No reverse of direction of rotation, output shaft always rotates in same direction as motor shaft.

Planetary wheels (usually 3 or 4) are driven by a sun wheel and rotate inside a hollow wheel, which is part of the housing.

PG20 with stepper motor, d= 20mm

PG40 with DC motor, d=40mm