Orbit motors

Orbit motors are the standard module when hydraulic pressure needs to be converted into radial motion. They are capable of converting the high pressures of hydraulic systems into powerful torque and are found in all areas where high torque is required without the use of an electric motor as a direct drive.

Design of an orbit motor

Orbit motors consist of:

• Housing
• Internal gear
• Eccentric rotor
• Two ports for incoming and outgoing hydraulic oil
• Optional: Balance piston

Operating principle of an orbit motor

The housing is internally fixed to the internal gear. Often, these are the same component. The flanks of the gears have a strongly curved convex shape. The internal gear has matching concave contours. It moves eccentrically, i.e., in a circular motion offset from the external gear. The internal gear is driven by hydraulic pressure. It transmits its torque to the outside via another internal gear and a connected shaft.

As with all hydraulic systems, the operation of an orbit motor is based on the incompressibility of liquids. The incoming hydraulic pressure forces the internal gear onto its path of motion. In doing so, it exerts just as much pressure on the inlet side as it does suction on the other side. The consistent and highly precise rotation of the output shaft is thus always guaranteed. It is important that the system is always bled and that the technical limits of the orbit motor are not exceeded.

Orbit motor design

The orbit motor is the simplest of all hydraulically operated radial motors. It has only a few components, which also move in a uniform manner relative to each other. This distinguishes it from axial and radial piston motors.

Nevertheless, the orbit motor is only used for small to medium-sized applications. Its technical capacity to absorb hydraulic pressure is limited. Under excessive pressure, it can easily reach ranges where cavitation effects may occur. For this reason, among others, larger orbit motors have replaceable cylinders instead of the convex internal flanks of the internal gear.

Applications of orbit motors

Orbit motors are frequently installed for conveyor systems, industrial drives, locking systems, and all other applications where compact hydraulic motors are required. Larger variants of the motor are found in light construction vehicles and smaller tractors. The displacement and transferable torque of these motor designs are still sufficient for these purposes. For larger construction machinery, however, the more complex but more powerful axial piston motors are more commonly used.

Orbit motors and their advantages

Due to its few components, the orbit motor is very cost-effective, robust, and reliable. As long as it is operated within its technical limits, it can achieve very long service lives. However, it is important that the hydraulic oil is permanently filtered and changed regularly.

The orbit motor can also be manufactured to be very small and compact. Although—like any hydraulic motor—it does not reach high primary speeds at its output shaft, its delivered torque is considerable. A simple gearbox is sufficient to convert this into high rotational speeds.

Due to the high clearance between the drive wheel and the internal gear at the housing wall, the orbit motor is highly thermally resilient. Expanding metal caused by high temperatures does not lead to wear or jamming. This also contributes to the high durability of orbit motors. Service lives of several years are normal for these components. In the event of a repair, replacing the seals is often sufficient.