RKB Optimized Engineering Solution for Concrete Mixer Gearbox0 pages

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RKB OPTIMIZED ENGINEERING SOLUTION FOR CONCRETE MIXER

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GEARBOX

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RKB TECHNICAL REVIEW - APRIL 2012

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RKB Optimized Engineering Solution for

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Concrete Mixer Gearbox

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Alberto BARILI, Ciprìan RADU, Calalin DANAI LA, Spiridon CRETU

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RKB Beating Industries ■ Department oí Advanced Software Engineering

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Abstract: in an Increasingly competitive sector, the RKB Group, with Executive Headquarters

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and Technological Center in Bolerna (Switzerland!, tías decided heavy investments in

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Reseorch & Development to efficiently satisfy the requirements of the power transmission

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industry, which is becoming more and more demanding in terms of performance and cost-

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effectiveness. The present article illustrates the steps fafcen by the RKB Group to develop a

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customized rolling bearing in co-engineering with a leading European manufacturer of

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gearboxes for concrefe mixers. As usual, the whole engineering process was supported by

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the use of in-house developed software systems ¡MTDS, RRLC and NON-HERTZ¡, 2D and 3D

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CAD tools, and EEM analysis systems. The WOR bearings designed for this special project

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were finally manufactured by RKB using the latest machining iechnofogy and the best raw

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materials and heat treatments.

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Key words: wide ouier ring bearing, concrete mixer, contact pressure, optimization,

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reaction force, von Mises sfress

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i INTRODUCTION

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Concrete mixer gearboxes ore perl of transit nixing t'jeks and transmit the rotational movement from a hydraulic

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motor to the drum. As the concrete payloads are charged into the drum, aiso while traveling to the work site, the

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drum is rotating and confnuously mixes the oad in order to prepare it and avoid its consolidation. During the

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transport, the gearbox rotates the drum in one direction (charge direction] and by using internal helical drum tins the

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concrete load is kept away from the discharge opening. When discharging, the erection of rotation "s reversed.

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The latest generation of gearboxes features innovative solutions that increase reliability, eliminate limitations and

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neffecriveness from the old designs, and reduce cost; ard main"e11 eneo, '.vite ■■"e purpose of ori-.' ng the drum and

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carrying the torque forces and a part of the drum weight, the concrete mixer gearbox represents the key element of

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the application, lhe mair boeri"o rhal support; Iho loed terinilted from —e orurr hai a cucio role in achieving

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maximum performance and reliability. For this reason, the design of the bearing was the main focus of the whole

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engineering process.

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2 APPLICATION DESCRIPTION

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The exploded arrangement in Fig. 1 highlights the main components of the double stage planetary gear speed

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reducer through which a hydra.il c rro'or drives t"e m'xing drum.

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The hydraulic motor transfers the rotational movement to the input pinion shaft 1, that drives the I;l stage planetary

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gear 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

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SRB 8 inside it. The 2f!0 stage planetary carrier 9 couples the crown gear 10 that transmits the torque forces to the

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output flange 14, also absorbing misalignment. The main SRB WOR design 11 is protected against contaminated

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environment by the seal 1 3. The gearbox has to be mounted on a rigid, free distortion support. If the mounting is not

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rigid, it can damage the internal gears, the seals, and finally the bearings.

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The con figura ti or o: this desigr is engineered to withstand the application requisite operating conditions in a safe

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and reliable way. This objective is attained with described gearboxes, which drive and pivotally support the mixing

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CUT. ccr"ipensa"'rg -ne rr-rj-'o- ;;e"wee'" lhe mVng d'um ond the mc"n Peeing case.

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