RV / NMRV Series Worm Gear Reducer

Aluminium alloy right-angle worm gear reducer with IEC B5 or B14 motor flange and hollow or solid output shaft. Available in sizes RV025 through RV150 (NMRV025 to NMRV150), covering gear ratios from 5:1 to 100:1 and output torque from 4 N·m to 1,500 N·m. Designed for direct motor-gearbox assembly as a compact right-angle drive unit for conveyors, agitators, packaging machines, and material handling equipment.

Sizes: RV025 – RV150
Ratios: 5:1 – 100:1
Output Torque: 4 – 1,500 N·m
IEC B5 / B14 Flange
Aluminium Alloy Housing
IP54 / IP65 Available

Categoria: Worm Gear Reducers

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Right-Angle Drive

IEC Motor Flange

5:1 to 100:1 Ratio

Self-Locking Above 30:1

Compact Aluminium Body

ISO 9001 Certified

RV NMRV Series Worm Gear Reducer Korea Ever-Power

Worm Gear Reducer CNC Precision Machining

Compact Right-Angle Speed Reducer for IEC Motor Integration

The RV and NMRV series worm gear reducer is a single-stage right-angle gearbox designed for direct assembly with IEC frame motors through a standard B5 or B14 motor input flange. The worm wheel is manufactured from centrifugally cast phosphor bronze, and the worm shaft from case-hardened and ground alloy steel, providing the hard-soft gear pair combination that gives worm gearboxes their characteristic quiet operation and high single-stage reduction ratio capability.

The housing is pressure die-cast from EN AC-46000 aluminium alloy, providing a high strength-to-weight ratio and excellent thermal conductivity for heat dissipation from the worm mesh contact. All sizes from RV025 through RV150 use the same housing alloy and the same surface treatment (chromate conversion coating plus polyurethane topcoat in standard RAL 7001 silver-grey), ensuring a consistent assembly appearance across mixed gearbox sizes in a single installation.

The self-locking characteristic of worm gearboxes at ratios above 30:1 (where the worm helix angle is below the friction angle of the worm-wheel bronze interface) provides natural load holding without a separate brake — a useful property for inclined conveyor drives and positioning applications where the load must stay stationary when the motor is de-energised. At ratios below 30:1, the gearbox is back-driveable and does not provide load holding.

Pair with the Korea Ever-Power motor range at Three-Phase Induction Motors, or explore combined gearmotor assemblies in the Gearmotors section.

RV / NMRV Size and Performance Data

Output torques at standard gear ratios with 4-pole motor input at 1440 rpm. Actual output torque depends on motor power, ratio, and service factor. Efficiency values are for standard worm-bronze mesh at operating temperature.

Size	Centre Distance (mm)	Available Ratios	Max Output Torque (N·m)	Efficiency at 10:1 (%)	Efficiency at 50:1 (%)	IEC Motor Frames	Weight (kg)
RV025	25	5, 7.5, 10, 15, 20, 25, 30, 40, 50	4	85	50	56, 63	0.5
RV030	30	5, 7.5, 10, 15, 20, 25, 30, 40, 50, 60, 80, 100	8	84	48	56, 63, 71	0.8
RV040	40	5, 7.5, 10, 15, 20, 25, 30, 40, 50, 60, 80, 100	18	85	50	71, 80	1.8
RV050	50	5, 7.5, 10, 15, 20, 25, 30, 40, 50, 60, 80, 100	45	86	52	71, 80, 90	3.5
RV063	63	5, 7.5, 10, 15, 20, 25, 30, 40, 50, 60, 80, 100	120	87	53	80, 90, 100	6.5
RV075	75	5, 7.5, 10, 15, 20, 25, 30, 40, 50, 60, 80, 100	210	87	54	90, 100, 112	10.5
RV090	90	5, 7.5, 10, 15, 20, 25, 30, 40, 50, 60, 80, 100	370	88	55	100, 112, 132	18.0
RV110	110	5, 7.5, 10, 15, 20, 25, 30, 40, 50, 60, 80, 100	600	88	56	112, 132, 160	28.5
RV130	130	5, 7.5, 10, 15, 20, 25, 30, 40, 50, 60, 80, 100	1000	89	57	132, 160, 180	45.0
RV150	150	5, 7.5, 10, 15, 20, 25, 30, 40, 50, 60, 80, 100	1500	89	58	160, 180, 200	68.0

Gearbox Specifications

Worm material	20CrMnTi case-hardened
Worm wheel	Phosphor bronze (CC483K)
Housing	EN AC-46000 aluminium
Gear oil	ISO VG 220 worm oil
Lubrication	Splash (all sizes)
Thermal limit	90 °C oil temperature
Protection	IP54 std / IP65 option
Mounting	Any orientation

Input and Output Options

Input flange	IEC B5 or B14
Input shaft	Hollow (motor shaft in)
Output shaft	Solid keyed
Output options	Hollow bore / flange
Right-angle offset	90° standard
Dual output	Available on request
IEC frame range	56 – 200
Standards	ISO 9001 / CE

Typical Applications for RV / NMRV Worm Gear Reducers

NMRV Worm Reducer Food Conveyor Application

Food Processing Conveyors

Belt and slat conveyors in food and beverage production lines use NMRV worm reducers for right-angle drive of conveyor head pulleys in restricted headroom installations. The compact aluminium housing fits within the conveyor frame cross-section, and IP65 protection is available for washdown environments.

Textile and Packaging Machines

Knitting machines, winding frames, and packaging form-fill-seal machines use NMRV worm reducers for their quiet operation, compact right-angle geometry, and high reduction ratio in a single stage — allowing motor speed of 1440 rpm to be reduced to 14 to 144 rpm output without a secondary reduction.

Printing and Paper Handling

Sheet-fed and reel-fed printing presses use NMRV worm reducers for paper web tension roll drives and ink circulation pump drives. The low noise and vibration of the bronze-on-steel worm mesh is critical in printing press installations where mechanical noise can affect product quality.

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Gate and Barrier Drives

Roller shutter door drives, industrial gate openers, and vehicle barrier systems use NMRV worm reducers at ratios of 50:1 to 100:1, where the self-locking property of the worm mesh holds the gate or barrier in position without a separate brake when the motor is de-energised.

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Material Handling Equipment

Roller conveyor line drives, pallet lift tables, and goods lifts use NMRV worm reducers for their inherent load-holding at high ratios, compact right-angle geometry, and the wide availability of mounting configurations for fitting within the mechanical envelope of standard material handling equipment.

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Small Agitators and Mixers

Small vessel agitators, paint mixing machines, and powder mixers in batch production plants use NMRV050 through NMRV090 worm reducers to drive horizontal or angled agitator shafts at 15 to 60 rpm from a standard 4-pole motor, with the right-angle offset minimising the headroom required above the vessel.

Selecting the Correct RV / NMRV Size: Key Criteria

Output Torque and Service Factor

The gearbox size is determined primarily by the required output torque multiplied by the application service factor. For smooth uniform loads (pumps, fans) the service factor is 1.0 to 1.25. For moderate shock loads (conveyors with start-stop) it is 1.5 to 2.0. For heavy shock loads (agitators starting under full viscous load) it is 2.0 to 3.0. The product of required output torque and service factor must be below the maximum rated output torque of the selected gearbox size. Selecting based on motor power alone without applying a service factor is a common sizing error that leads to premature worm wheel bronze wear.

Thermal Power Rating

Worm gearboxes have a thermal power rating in addition to the mechanical torque rating. At high ratios (50:1 to 100:1), efficiency drops to 48 to 58%, meaning that 42 to 52% of input power is dissipated as heat in the worm mesh and must be transferred to the housing surface by convection. The thermal power rating is the maximum continuous input power at which the oil temperature stays below 90 °C in the ambient conditions of the installation. If the mechanical torque requirement is low but the input power is high (high-ratio, fast motor), the thermal rating may be the limiting factor, requiring a larger housing or an external cooling fan.

Self-Locking vs Back-Driveable

At ratios of 30:1 and above, the RV/NMRV worm gearbox is self-locking: the load cannot back-drive the worm shaft through the gear mesh under static conditions. This makes the gearbox suitable for inclined conveyor drives and positioning applications without a separate brake. At ratios below 30:1 (5:1, 7.5:1, 10:1, 15:1, 20:1), the gearbox is back-driveable. For these ratios in applications requiring load holding (gates, lifts), a separate motor brake or external brake must be used. Self-locking should not be relied upon as the sole safety device for human-access lifting equipment, where a rated mechanical safety brake is always required regardless of gear ratio.

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Frequently Asked Questions — RV / NMRV Worm Gear Reducer

What is the difference between the RV and NMRV designations?

RV (Riduttore a Vite, or worm reducer in Italian) and NMRV (Non-Metallic RV — a legacy designation from earlier aluminium body versions) refer to the same product range from Korea Ever-Power. Both designations cover the same gearbox sizes (025 through 150), the same dimensional standards, and the same performance ratings. The NMRV prefix is more common in some markets (particularly East Asian sourcing specifications and older European purchasing specifications); the RV prefix is more common in current IEC-aligned engineering documentation. Korea Ever-Power supplies both prefixes as equivalent; specify either designation when ordering and both will be fulfilled from the same production line.

How often does the gear oil need to be changed?

The initial oil change is recommended at 300 to 500 hours of operation to flush any assembly residues and fine bronze particles from the running-in of the worm wheel. Thereafter, oil changes at 5,000-hour intervals (or every 2 years for intermittent duty) maintain the ISO VG 220 worm gear oil within its useful life. Signs that an oil change is overdue include darkening of the oil, a strong burnt odour, or visible fine bronze particles in the drained oil. For applications with oil temperatures consistently above 80 °C, oil change intervals should be halved. Korea Ever-Power recommends a synthetic PAO-based ISO VG 220 worm gear oil for applications running continuously above 70 °C.

Can I mount the RV gearbox in any orientation?

Yes, but the oil fill and drain plug positions must match the mounting orientation. The RV/NMRV gearbox is shipped in the standard orientation (worm below worm wheel, output shaft horizontal) with the oil fill and drain plugs at the correct positions for this orientation. For non-standard mounting positions (worm above, output shaft vertical upward, output shaft vertical downward), the plug positions must be reassigned before installation using the orientation diagram provided in the instruction manual. Korea Ever-Power can supply gearboxes pre-configured for a specified non-standard mounting orientation on request. Mounting in a non-standard orientation without reassigning plugs risks inadequate lubrication of the worm shaft bearing on the high side.

What are the limits on permissible radial and axial load on the output shaft?

The permissible radial load on the output shaft depends on the shaft diameter, shaft extension length, and the position of the load application point along the shaft. For RV050 to RV090, typical permissible radial loads at the shaft midpoint are 400 to 1,800 N. Permissible axial loads (forces along the shaft axis) are typically 25 to 30% of the permissible radial load. Exceeding these limits causes premature output shaft bearing failure. Korea Ever-Power can provide the permissible load tables for each gearbox size, and can supply output shaft bearings with higher radial capacity for sprocket, chain, or pulley drives on request.

Are two-stage configurations available for ratios above 100:1?

Yes. Two-stage worm configurations (two gearboxes in series) extend the ratio range to 10,000:1, though in practice ratios above 3,000:1 are rarely used. Korea Ever-Power supplies matched two-stage worm assemblies with a mounting plate coupling the output shaft of the first stage to the input of the second stage. The combined efficiency of a two-stage assembly is the product of the individual stage efficiencies; at 50:1 per stage, a 2,500:1 two-stage assembly has an efficiency of approximately 52% x 52% = 27%, meaning nearly three-quarters of the input power is dissipated as heat. For ratios above 100:1, it is often more energy-efficient to use a helical gearbox first stage followed by a worm second stage than to use two worm stages in series.

Request a Quote for RV / NMRV Worm Gear Reducers

Specify gearbox size, ratio, motor frame, output shaft type, and quantity. Learn more about our manufacturing on the About Us page.

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Edited by Cxm

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Editor	Cxm