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A new-generation toroidal worm drive device that replaces the single-enveloping worm gear pair with a plane-secondary-enveloping toroidal worm pair. Higher load capacity, higher transmission efficiency and longer service life than a conventional worm reducer in the same centre distance.
National Second Prize for Invention — Planar Secondary Enveloping Toroidal Worm DrivePlane secondary enveloping toroidal worm drive — how it differs from a standard worm reducer
A standard cylindrical worm meshes with a cylindrical worm wheel along a single contact line. Load concentrates on a small number of teeth at any instant, so torque capacity is limited and the oil film between the worm and wheel breaks down easily under heavy load.
The toroidal worm envelope is generated by a plane acting as the mother surface, then the worm gear tooth surface is generated in turn by the worm tooth surface. This produces a meshing zone where multiple teeth engage simultaneously with instantaneous double-line contact. The contact line is long, the contact area exceeds 70%, and the load is distributed across many teeth rather than concentrated on one.
Each point maps to a measurable improvement over a conventional worm gearbox
The multi-tooth contact and small sliding angle between the contact line and relative velocity direction allow an easy-to-form hydrodynamic oil film. Less heat is generated at the mesh, less oil needs to be pumped through the unit, and less energy is lost compared with a standard worm reducer of the same centre distance.
The oil film is retained more effectively on the small-sliding-angle mesh. Wear is reduced at the tooth surface, so the gear pair keeps its dimensional accuracy for far longer than a conventional worm gear pair operating at the same load.
The number of teeth engaging at the same time is larger than in a standard worm pair. Load is spread across many teeth rather than concentrated on one line, so the unit can transmit higher torque without increasing the gearbox size.
The toroidal worm envelope wraps around the worm wheel over a wider angle than a cylindrical worm. Instantaneous double-line contact means the total contact line length is longer and the contact area can exceed 70% of the theoretical maximum.
Because several teeth share the load and the contact transition happens gradually, the mesh produces less vibration and less audible noise than a conventional worm pair operating at the same speed and load. Important for equipment installed in production halls or near operators.
Worm shaft made from 40Cr, 42CrMo or 38CrMoAl, quenched and ion-nitrided. Worm gear made from ZCuSn10Pb1 tin bronze, centrifugal cast. The two materials are matched to each other: the hardened worm shaft resists surface fatigue while the bronze worm gear maintains a stable tooth surface against the hardened worm.
The machining process matches the forming principle of the toroidal worm envelope, so tooth profile accuracy is high and the final meshing clearance is uniform around the worm. This makes the gearbox suitable for applications that need consistent output speed rather than approximate reduction.
Worm shaft and worm gear materials are matched to each other, not selected independently
Compared with a conventional cylindrical worm gear pair of the same centre distance
Applications where higher load capacity or longer service life justifies the upgrade over a standard worm reducer
Servo-driven positioning axes where transmission accuracy and low backlash matter. The multi-tooth contact pattern keeps the output shaft tracking the input command without the accumulated backlash of a conventional worm pair.
Conveyor and hoist drives that run continuously under load. Higher contact ratio means less heat generated at the mesh and less oil degradation over a long duty cycle.
Valve actuators where the gearbox must hold position under torque and release smoothly. The higher torsional rigidity and zero-backlash tendency of the mesh make the actuator response predictable.
Winch and lifting applications where overload capacity is the limiting factor. Torque capacity in the same envelope is higher than a standard worm reducer, so the operator can either lift a heavier load or derate the gearbox for longer service life.
Packaging lines and printing presses where consistent output speed and quiet operation are required. Lower mesh noise and uniform speed reduce vibration transmitted into the machine frame.
Heavy construction and mining drives operating in dusty or high-temperature environments. The retained oil film on the low-sliding-angle mesh tolerates poorer lubrication conditions than a conventional worm pair.
Factory-direct supply with documented material and heat treatment records
The TPU / PWU series reducer is manufactured under a documented process covering the casting of the bronze worm gear, the ion-nitriding of the worm shaft, precision grinding of the tooth flank and the final meshing check. Each unit ships with material certificates for the worm shaft and the worm gear on request. OEM and private-label production available. Review our factory, inspection equipment and why customers choose us.
Buyers sourcing a TPU / PWU reducer often combine the order with these items
Technical questions buyers ask before placing the first order
What is a planar double enveloping worm gearbox, and how is it different from a standard worm reducer?
A standard worm reducer uses a cylindrical worm meshing with a cylindrical worm wheel along a single contact line. A planar double enveloping worm gearbox uses a toroidal worm that wraps around the worm wheel, so multiple teeth engage at the same time with instantaneous double-line contact. The result is a longer total contact line, a contact area exceeding 70% of the theoretical maximum, and higher torque capacity in the same gearbox envelope. The technology was recognised with the National Second Prize for Invention.
What materials are used for the worm shaft and the worm gear?
The worm shaft is made from 40Cr, 42CrMo or 38CrMoAl, quenched and ion-nitrided to a surface hardness above HRC 58, then precision ground to a surface roughness of Ra 0.8. The worm gear is made from ZCuSn10Pb1 tin bronze, centrifugal cast. The two materials are matched to each other — the hardened worm shaft resists surface fatigue while the bronze worm gear holds a stable tooth surface under load.
What torque capacity and ratios are available for the TPU / PWU series?
Torque capacity and ratio depend on the specific model within the TPU / PWU series. Send us your required output torque, input speed, centre distance and mounting position, and we will recommend the correct model and confirm the exact ratio available. Custom ratios can be quoted if the standard range does not match your drive.
Why is the contact area important for a worm gearbox?
The contact area determines how much load is carried per unit area of tooth surface. A larger contact area means lower contact stress per tooth, which extends gear life and reduces the risk of surface pitting. In the planar double enveloping worm pair, multiple teeth share the load simultaneously and the contact area exceeds 70%, which is significantly higher than a conventional worm gear pair of the same centre distance.
What is the MOQ and lead time for the TPU / PWU series reducer?
MOQ depends on the specific model and whether it is a standard configuration or a custom build. Send us your required model, quantity and destination port, and our sales team will confirm MOQ, unit price and production schedule in writing. Standard models generally ship faster than customized builds.
Can the reducer be supplied under our own brand?
Yes. OEM and private-label production is available. We can apply your brand nameplate, custom paint colour and branded packaging. Share your branding requirement and we will confirm feasibility and any additional lead time.
Send us your required output torque, input speed, centre distance and mounting position. We will reply with the correct TPU / PWU model, ratio, materials, price and lead time.
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