The RO type shaft mounted reducers with hollow low speed shaft are produced by ELLI in ten sizes, with two or three reduction stages.
As far as the two-stage reducers are concerned, the two smaller sizes (210 and 211) have a reduction ratio of 15, while the eight larger sizes (from 212 to 219) are produced with ratios of 15 and 19.
The three-stage reducers are produced in four sizes (from 316 to 319), with reduction ratio of 60, and share the same casing (and therefore the same outer dimensions) of the two-stage reducers of the same size.
The advantage of this type of reducers is their versatility and ease of installation onto the driven machine. In fact, being the reducer directly keyed onto the driven shaft, no baseplate is required, but only a connection to the machine structure, to support the reaction arm. If also the motor foundation needs to be eliminated, the motor can be installed onto the reducer casing, by means of a suitable motor baseplate hinged to the reducer casing.
The usual applications for this type of reducers include:
belt conveyors, screw conveyors, mixers, rotating drums.
The motion transmission between motor and reducer is usually obtained using belts and pulleys, allowing to achieve a broad variety of the total speed reduction ratio between motor and low speed shaft.
For all sizes except the largest, these reducers are stock-produced, and therefore, they are ready for delivery.
Are made of cast iron, in two halves, suitably ribbed; inside them, the gears layout allows for a particularly compact construction. The reducers casings are provided with oil filling/vent plug, level plug and drain plug, so that the correct lubrication is guaranteed in the normal position of installation, i.e. with the high speed shaft below the low speed shaft, as shown in figure A and figure B.
If the reducer must be installed in positions different from the normal, it is absolutely necessary to mention this requirement when ordering the reducer, which will be modified so as to ensure the correct lubrication of all its internal parts.
Reaction arm connection
In all the applications of shaft mounted reducers, a connection to the fixed structure of the driven machine is required, to counteract the rotation of the casing in the direction opposite to that of the low speed shaft, generated by the difference between the torque at the high speed shaft and that at the low speed shaft. This connection can be provided using a rigid beam, hinged at its ends, adjustable by means of threaded rods, or using one or two elastic reaction arms equipped with rubber discs; when using the elastic reaction arm, only one arm is provided (up to size 215 included), while from size 216 (or 316) to size 219 (or 319) two arms are provided, one at each side of the casing.
Pinion and gears
The smallest reducer (size 210) has its pinions and gears nitrided, while all the other reducers of this series have their pinions and gears in alloy steel, case-hardened and tempered, ground on the involute profile after heat treatment. This construction ensures the maximum compactness, together with a high transmissible power, low noise and high efficiency.
Hollow low speed shafts
Are made of steel (Fe 510), and are provided with a groove for a circlip at one end, to keep in position the disc used for installing the reducer (pulling the driven shaft into the reducer hollow shaft) and for removing it from the driven shaft. The torque transmission to the driven shaft is usually performed by means of a key.
Of the tapered rollers and balls type, made by primary manufacturers, designed to allow for a long operating life and calculated according to ISO standard.
Direction of rotation
Normally, rotation in both directions is allowed. Upon request, it is possible to provide a mechanism preventing rotation in the direction opposite to that of normal operation (back-stop device).
Of the oil-splash type; the recommended lubricant types are listed in table, while the oil quantities for the different sizes of reducers are listed in "Type RO2... / RO3...".
For the two-stage reducers the mechanical efficiency is 0.98, while for the three-stage reducers it is 0.97.
Inside every reducer, during normal operation, a certain amount of heat is generated, depending upon the reducer efficiency and the absorbed power. This generated heat causes an increase of the reducer temperature, until an equilibrium temperature is reached, which is higher than the ambient temperature. The thermal rating of a reducer is defined as the power which can be continuously applied to the input shaft without exceeding the maximum allowable reducer temperature, usually 95°C. For all the reducers of this series, the thermal rating is higher than the nominal power listed in Type RO2... / RO3..., which means that the heat exchange towards the outer environment is enough to avoid the danger of overheating, in normal operating conditions. It is apparent that the reducers will reach higher temperatures as the absorbed power increases, as well as the ambient temperature increases
Operation at low temperatures
In case of ambient temperature lower than -20°C, it is necessary to adopt special materials (with high impact strength at low temperatures), and therefore this condition shall be highlighted and discussed when ordering. For ambient temperature lower than 0°C, the oil physical characteristics at start-up conditions shall be considered, foreseeing the use of synthetic lubricants with a particularly low pour point, so as to ensure the necessary fluidity during cold starts.
All the reducers are painted internally and externally with an epoxy primer, which guarantees an excellent anti-oxidation and anti-oil protection.
The outer finishing is performed with one layer of epoxy paint. The standard final color is green RAL 6011. Upon request it is possible to paint with any other final color.
The nominal power and the output torque of the reducers are listed in Type RO2... / RO3..., calculated at different rotating speeds of the low speed shaft (from 10 to 100 rpm); for speeds different from those tabulated, but within this range, it is possible to interpolate the value of the nominal power, while for speeds well outside this range, please contact our technical-sales department for the necessary power calculation and for the check of the operating parameters.
The required service factor depends upon the reducer application and its actual operating conditions; this factor corresponds to the ratio between the reducer nominal power (listed on the catalog) and the power actually absorbed by the reducer during operation. In practice, increasing the service factor means increasing the safety margin of the application with respect to the reducer design limits. Table 1 lists the values of the service factor suggested for the different operating conditions; these values must be multiplied by the coefficients listed in table 2, selected according to the frequency of the start-ups.
Protection for long storage
All the reducers are submitted to a functional no-load running test, filled with their nominal oil quantity, and this ensures the protection of the inner surfaces against corrosion only for a short period. The outer surfaces machined and not painted are usually protected with a corrosion inhibitor which can be easily removed with an industrial thinner when installing the reducer. When a storage period is foreseen, or whenever the reducer installation does not take place within a short time since its delivery, please require the internal protection, which consists in spraying a corrosion inhibitor inside the reducer, ensuring a thorough
protection an not requiring any rinsing before operation, being the protective product soluble in the first oil filling.
When a long storage period in adverse conditions is foreseen (outdoor or in aggressive atmosphere or in particularly humid environment), it is advisable to completely fill the reducer with oil of the same type and grade which will be used for operation, so that the excess oil can be simply drained at the time of the reducer initial start-up. In any case, the reducers are always supplied without oil, but with the first grease charge where necessary.
Upon request, the reducer hollow low speed shaft can be coupled to the driven machine shaft using shrink discs, which operate by means of the elastic deformation of suitable tapered parts, restraining the coupled parts and allowing for the transmission of the mechanical torque (see figure B); in this case, the key-way is not machined. Besides, the hollow shafts can be machined with their inner diameter different from those listed in table 2, so as to comply with particular needs.
In the end, it is also possible to manufacture reducers with special reduction ratios, different from those listed in Type RO2... / RO3....
The reducers weights and the oil quantities are to be intended as indicative, referred to average values; ELLI reserves the right to modify the dimensions indicated on the drawings contained in this catalog.
The assembly of the external parts on the reducer high speed shaft (couplings, pulleys...) as well as the assembly of the reducer on the shaft of the drived machine shall be carried out using tools with controlled force application, such as hydraulic jacks and threaded rods, without hammering the shafts or the parts to be assembled, to avoid damaging the bearings. If no other indication is present, the suggested tolerance for the holes of the parts to be mounted on the high speed shaft ends is H7. In case of rather large bore diameters, it is advisable to warm the parts to be mounted on the high speed shaft up to a temperature of about 100°C to allow for an easy assembly.
It is within the end userís responsibility to make sure that the reducer installation is carried out in compliance with the applicable safety rules, and in particular that the rotating parts are adequately protected and that the necessary alarms and stops are installed and operating.
Before start-up, please check that the reducer shafts are free to rotate without hindrance.
In case the reducer will be assembled in machines to which the EEC Regulation 89/392 Supplement IIB applies, it is forbidden to put it in service before the machine has been declared conforming to the above mentioned Regulation.
As far as any maintenance intervention is concerned, please refer to the operation and maintenance manual, attached to every reducer.
Please pay particular attention to the lubrication prescriptions (quantity and quality of the oil, frequency of the oil changes).
In any case, make sure to carry out the inspection and maintenance operations in full compliance with the applicable safety rules: in particular, cut out the electric supply to the driving motor and remove the external loads before working on the reducer, so as to avoid the risk of accidental starts or unforeseen movements due to external forces acting on the reducer shafts.
Be equipped with the suitable tools for carrying out the planned interventions, with particular attention to the hoisting equipment, and employ personnel which is qualified to operate on precision machinery.
For the purchase of spare parts, please always indicate the reducer serial number (impressed on the plate located on the casing), referring to the Type RO2... / RO3... as far as the parts nomenclature is concerned.
Installation of the reducers onto the drive machine
These reducers can be installed onto the driven equipment shaft by means of a simple disc with a hole, using a threaded bar inserted into the end hole of the driven shaft (see figure A). The same disc is also used as a retaining plate to keep the reducer in place when the installation is completed, axially restraining the hollow shaft together with the circlip.
The choice of the suitable lubricant is made according to table 3, referring to the actual operating conditions of the gearbox, i.e. the ambient temperature and the rotation speed of the low speed shaft; table lists the different brands of lubricants, with the correspondence between them.
ELLI has been operating under certified quality assurance procedures, according to UNI EN ISO 9001 standards, since 1993.
The raw materials are purchased from selected suppliers, complete of the relevant certificates, and are checked at their delivery to our workshop.
The product quality is ensured by a series of tests during manufacturing process of each particular, as well as by the visual and dimensional check on every finished part.
Every reducer, after assembly, is subjected to a final check and to a no-load test.
Thanks to a fifty-years experience in the field of gear reducers for the most varied applications, ELLI can supply the suitable solution to any problem of power transmission by means of gears, guaranteeing the achievement of all the Customerís targets in terms of operation and reliability. Depending upon the requirements, it is possible to design solutions derived from the standard production, as well as develop special units in compliance to the Customerís specifications.
In particular, many reducers have already been designed and manufactured for a number of different applications, including:
- paper industry (shaft mounted reducers for Yankee Dryer drive, suction press cylinders, pulpers, etc.)
- rubber and plastic materials industry (calenders, mixers, extruders, etc.)
- steel industry (reducers for complete lines of stands for hot rolling mills, for coils winders/unwinders, units with speed change and reverser for steel ropes machines, etc.)
- chemical industry (stirrers, mixers and piston pumps drives, etc.)
- sugar industry (screw presses drives, diffusers, etc.)
- lifting and hoisting (winches assemblies complete of reducers, drums, couplings, service and emergency brakes and baseplate, reducers for boom rotation, for carriage movement, for cable-cars, shaft mounted reducers for belt conveyors, etc.)
- material handling (bucket wheel drives for stacker/reclaimers, etc.)
- power stations (reducers for cooling towers fans, speed increasers for hydroelectric generators, reducers for coal pulverizing mills, drives for Ljungstrom type air pre-heaters, etc.)
Reducer selection example
A reducer must be selected for a machine with load subject to moderate shocks, operating for 8 hours a day, with the low speed shaft rotating at 40 rpm; the driving motor has a power of 5.5 kW.
From table 1 comes the recommended service factor for this application, equal to 1.25; hence, the selected reducer must have a nominal power equal or greater than 1.25 x 5.5 = 6.875 kW.
Therefore, from table on page 6, listing the reducers nominal power, at an output speed of 40 rpm, the reducer RO-213 can be selected, with a nominal power of 7.8 kW, corresponding to a service factor of 7.8 / 5.5 = 1.4 referred to the installed power.