The planetary roller screw is divided into four different structural forms:
◆ Fixed Roller Type Nut Motion Type
This form of planetary roller screw consists of the components: long threaded spindle, threaded roller, threaded nut, bearing cap and tooth sleeve. The axial load is transmitted to the threaded nut via the threaded arbor of the threaded roller. The system is synchronized by the teeth on the threaded roller and the two tooth sleeves. Similar to the cage in a ball bearing, the bearing cap ensures the distance between the threaded rollers on the circumference of the screw.
This form of construction of planetary roller screws is used essentially anywhere where high precision, repeatability and high load capacity are required for electromechanical linear drives.
◆ Recirculating Roller Type Nut Movement Type
This type of planetary roller screw consists of the components: long threaded spindle, threaded roller, threaded nut, cage cage and cam retainer. This type of planetary roller screw has a mechanical return function of the threaded roller. With this kinematics (return) it is possible to achieve planetary roller screw couplings with very small lead distances, a robust thread construction and high load capacity. This also allows for smaller lead distances on screws with larger nominal diameters. Similar to the ball in a ball bearing, the threaded roller is held in place by a cage on the spindle circumference. After one revolution of the cage, the threaded roller is lifted radially out of the main screw thread by a cam into a recess in the spindle nut. A cycle is then achieved in this recess by rotating the threaded roller backwards through one revolution on the threaded shaft.
This form of construction is commonly used in electromechanical linear drives that require high load carrying capacity with high accuracy, repeatability and small lead lengths for cyclic roller planetary roller screws. The small spindle lead can achieve very high positioning accuracy under the influence of high loads.
◆ Fixed Roller Type Nut Reversing Type
This form of planetary roller screw consists of components: a threaded spindle with a long optical axis, a threaded roller, a long threaded nut, a bearing cap and a tooth sleeve. The RGTI with reverse design is a reverse version of the RGT. It has essentially the same characteristics as the RGT and also has a high load capacity and positioning accuracy. With this design, the threaded roller on the spindle is kept in the proper position and synchronized through the bearing cover and gear rim compared to the RGT. This reverse design has a smooth cylindrical spindle with no continuous thread profile. This system can therefore be well sealed by a spindle with a radial shaft sealing ring.
This form of construction is mainly integrated as a rotor in hollow shaft motors. It offers a compact electromechanical alternative for hydraulic and pneumatic lifting as well as for linear drives. Depending on the nominal diameter, nuts with a maximum thread length of 800 mm can be manufactured to customer-specific configurations.
◆ Recirculating Roller Nut Reversing Type
This form of planetary roller screw consists of the components: threaded spindle with long optical axis, threaded roller, long threaded nut, cage cage and cam retainer. RGTRI is the reverse design of RGTR. It differs from the RGTR only in that the cage with the threaded roller and the groove for returning the threaded roller are located on the spindle and not in the nut. Thanks to its functional principle of roller return, the RGTRI also features a smaller pitch and a more robust thread profile. Smooth cylindrical spindles are also suitable for sealing systems with this reverse design.
This construction form is mainly integrated as a rotor in hollow shaft motors. It also provides a compact electromechanical alternative for hydraulic and pneumatic lifting and linear drives. The threaded nuts can be manufactured to a nominal diameter with a maximum thread length of 800 mm, depending on the customer’s construction.
Post time: Jan-12-2023
