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Anglicky v odborných předmětech "Support of teaching technical subjects in English “. Tutorial : Engineering technology Tutorial : Belt drives Prepared by: Ing . Jaroslav Hábl. Projekt Anglicky v odborných předmětech, CZ.1.07/1.3.09/04.0002
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Anglicky v odborných předmětech"Support ofteachingtechnicalsubjects in English“ Tutorial: Engineering technology Tutorial: Belt drives Preparedby: Ing. Jaroslav Hábl Projekt Anglicky v odborných předmětech, CZ.1.07/1.3.09/04.0002 je spolufinancován Evropským sociálním fondem a státním rozpočtem České republiky.
Torque is transmitted by friction forces between pulleys and belt mounted around driving and driven pulley. BELT DRIVES
ADVANTAGES OF BELT DRIVES • Easy and cheap production • Possibility of more shafts driven by one belt • Quiet operation • Damper of operating shocks • Protection to overloading BELT DRIVES
DISADVANTAGES OF BELT DRIVES • Higher bearing load • Belt slippage on pulley • Belt stretcher is necessary • Intolerant to high temperatures BELT DRIVES
GEAR RATIO Rule for friction gears by slip is: ψ = slip coefficient BELT DRIVES
TYPES OF BELTING BELT DRIVES open, b) crossed, c) open with idler pulleys, d) half-crossed
TYPES OF BELTING BELT DRIVES Half-crossed with idler pulleys, b) open with tension pulleys, c) open with more shafts drives
TYPES OF BELTS ACCORDING TO SHAPE • Flat belts – they are used exceptionally today. • V-belts. • - classical cross-section – most common • - narrow – for higher speed • - wide – for disk friction drives • - toothed – for valve train drive of combustion engines • - multiple – they have bigger load wearing capacity than common belts. • Circular cross-section belts – for special use (similarly to rope gears). BELT DRIVES
TENSION MECHANISM Tension mechanism increases pressure force which has to make higher friction force in belt. It eliminates belt lengthening in operation and makes the angle of pulley belting higher. By drive slide on the skids, b) by tension pulley with balance weight, Self-tension reaction momentum– drive is placed on the cradle BELT DRIVES
TENSION MECHANISM • Ways of belt tension: • Belt shortening – used only for flat belts at constant axis distance. Ends of the belt have to be connected after belt shortening by glue sticking or connection fitting. • By tension pulleys – it is advantageous because it makes the belting angle bigger. • By axis distance extension – drive must be placed movably. • By self-tension – drive is placed movably and belt is tensioned by gravitation )force effect of drive). BELT DRIVES
Literature • Stroje a zařízení I, J. Doleček, P. Gajdoš, V. Novák • Strojnictví I, J. Doleček, Z. Holoubek • Strojnictví II, J. Doleček, Z. Holoubek • Moderní strojírenství, Josef Dilinger a kolektiv
Write down the rule for gear ratio. • Name types of belts. • Disadvantages of belt drives?