RKB Optimized Engineering Solution for Concrete Mixer Gearbox0 pages
RKB OPTIMIZED ENGINEERING SOLUTION FOR CONCRETE MIXER
nnnnGEARBOX
nnnnRKB TECHNICAL REVIEW - APRIL 2012
nnnnRKB Optimized Engineering Solution for
nnnnConcrete Mixer Gearbox
nnnnAlberto BARILI, Ciprìan RADU, Calalin DANAI LA, Spiridon CRETU
nnnnRKB Beating Industries ■ Department oí Advanced Software Engineering
nnnnAbstract: in an Increasingly competitive sector, the RKB Group, with Executive Headquarters
nnnnand Technological Center in Bolerna (Switzerland!, tías decided heavy investments in
nnnnReseorch & Development to efficiently satisfy the requirements of the power transmission
nnnnindustry, which is becoming more and more demanding in terms of performance and cost-
nnnneffectiveness. The present article illustrates the steps fafcen by the RKB Group to develop a
nnnncustomized rolling bearing in co-engineering with a leading European manufacturer of
nnnngearboxes for concrefe mixers. As usual, the whole engineering process was supported by
nnnnthe use of in-house developed software systems ¡MTDS, RRLC and NON-HERTZ¡, 2D and 3D
nnnnCAD tools, and EEM analysis systems. The WOR bearings designed for this special project
nnnnwere finally manufactured by RKB using the latest machining iechnofogy and the best raw
nnnnmaterials and heat treatments.
nnnnKey words: wide ouier ring bearing, concrete mixer, contact pressure, optimization,
nnnnreaction force, von Mises sfress
nnnni INTRODUCTION
nnnnConcrete mixer gearboxes ore perl of transit nixing t'jeks and transmit the rotational movement from a hydraulic
nnnnmotor to the drum. As the concrete payloads are charged into the drum, aiso while traveling to the work site, the
nnnndrum is rotating and confnuously mixes the oad in order to prepare it and avoid its consolidation. During the
nnnntransport, the gearbox rotates the drum in one direction (charge direction] and by using internal helical drum tins the
nnnnconcrete load is kept away from the discharge opening. When discharging, the erection of rotation "s reversed.
nnnnThe latest generation of gearboxes features innovative solutions that increase reliability, eliminate limitations and
nnnnneffecriveness from the old designs, and reduce cost; ard main"e11 eneo, '.vite ■■"e purpose of ori-.' ng the drum and
nnnncarrying the torque forces and a part of the drum weight, the concrete mixer gearbox represents the key element of
nnnnthe application, lhe mair boeri"o rhal support; Iho loed terinilted from —e orurr hai a cucio role in achieving
nnnnmaximum performance and reliability. For this reason, the design of the bearing was the main focus of the whole
nnnnengineering process.
nnnn2 APPLICATION DESCRIPTION
nnnnThe exploded arrangement in Fig. 1 highlights the main components of the double stage planetary gear speed
nnnnreducer through which a hydra.il c rro'or drives t"e m'xing drum.
nnnnThe hydraulic motor transfers the rotational movement to the input pinion shaft 1, that drives the I;l stage planetary
nnnngear 3. with deep groove ball bearing;, A Iho: re"c¡lc lhe pi-ion snef" 6 of the 2' ' s "age p anclary goor 7 sustained by
nnnnSRB 8 inside it. The 2f!0 stage planetary carrier 9 couples the crown gear 10 that transmits the torque forces to the
nnnnoutput flange 14, also absorbing misalignment. The main SRB WOR design 11 is protected against contaminated
nnnnenvironment by the seal 1 3. The gearbox has to be mounted on a rigid, free distortion support. If the mounting is not
nnnnrigid, it can damage the internal gears, the seals, and finally the bearings.
nnnnThe con figura ti or o: this desigr is engineered to withstand the application requisite operating conditions in a safe
nnnnand reliable way. This objective is attained with described gearboxes, which drive and pivotally support the mixing
nnnnCUT. ccr"ipensa"'rg -ne rr-rj-'o- ;;e"wee'" lhe mVng d'um ond the mc"n Peeing case.
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