【導(dǎo)讀】本文主要探討高速帶式輸送機(jī)設(shè)計方面的問題。帶式輸送機(jī)的輸送量取決于。輸送帶的速度、傳送帶寬度和托輥槽形角。實際條件的限制，在本文有這方面的討論。例如它的能源消耗和它連續(xù)運行的穩(wěn)定性。就是通過考慮運輸過程中的各種能量損耗來進(jìn)行估算的。輸送帶速度的不同使。得安全系數(shù)的要求也各不相同，這也影響輸送帶所要求的強(qiáng)度。輸送帶的寬度隨之變寬，低速輸送機(jī)適于長距離輸送。在這些設(shè)計方法中輸送帶被認(rèn)為是剛性的，靜止的。這增加了輸送機(jī)穩(wěn)定運行的質(zhì)量和也決定了帶式輸送機(jī)各零部件的尺寸。在這種理論中，輸送帶被劃分成一系列的有限元。有限元素的結(jié)構(gòu)性特征能代表輸送帶的流變特征。可靠性，例如托輥組應(yīng)達(dá)到所要求的使用壽命。整體皮帶輸送機(jī)的最低成本在傳送帶寬度到m的系列范圍內(nèi)[2]。第三個方面是帶式輸送機(jī)系統(tǒng)引起的噪聲。對于廠內(nèi)的帶式輸送機(jī)，在受載區(qū)域運行時所受側(cè)抵抗也影響的能源。費用的好處是這個數(shù)字因管理目的而廣泛應(yīng)用。

　　

【正文】 . The recovery of the pressed parts of the belt39。s bottom cover will take some time due to its viscoelastic (time dependent) properties. The time delay in the recovery of the belt39。s bottom cover results in an asymmetrical stress distribution between the belt and the rolls, see Figure 2. This yields a resultant resistance force called the indentation rolling resistance force. The magnitude of this force depends on the viscoelastic properties of the cover material, the radius of the idler roll, the vertical force due to the weight of the belt and the bulk solid material, and the radius of curvature of the belt in curves in the vertical plane. Figure 2: Asymmetric stress distribution between belt and roll [7]. It is important to know how the indentation rolling resistance depends on the belt velocity to enable selection of a proper belt velocity, [11]. Figure 3: Loss factor (tanb) of typical cover rubber [7] Firstly, the indentation rolling resistance depends on the vertical load on the belt, which is the sum of the belt and the bulk material weight. If the vertical load on the belt decreases with a factor 2 then the indentation rolling resistance decreases with a factor (2 ^4/3). The bulk load decreases with increasing belt speed assuming a constant capacity. Therefore, the indentation rolling resistance decreases more than proportionally with increasing belt speed. Secondly, the indentation rolling resistance depends on the size of the idler rolls. If the roll diameter increases with a factor 2 then the indentation rolling resistance decreases with a factor (2 ^2/3). In general the idler roll diameter increases with increasing belt speed to limit the bearing rpm39。s to maintain acceptable idler life. In that case the indentation rolling resistance decreases with increasing belt speed. Thirdly, the indentation rolling resistance depends on the viscoelastic properties of the belt39。s cover material. These properties depend on the deformation rate, see Figure 3. The deformation rate in its turn depends on the size of the deformation area in the belt39。s bottom cover (depending on belt and bulk load) and on the belt speed. In general the indentation rolling resistance increases with increasing deformation rate (and thus belt speed), but only to a relatively small account. Fourthly, the indentation rolling resistance depends on the belt39。s bottom cover thickness. If the bottom cover thickness increases with a factor 2 then the indentation rolling resistance increases with a factor (2 ^1/3). if a bottom cover is increased to account for an increase in belt wear with increasing belt speed, then the indentation rolling resistance increases as well. It should be realized that the indentation rolling resistance, although important, is not the only velocity dependent resistance. The rolling resistance of the idler rolls for example depends on the vertical load as well as on their rotational speed. The effect of the vertical load, which directly depends on the belt speed, is large. The effect of the rotational speed is much smaller. Another resistance occurs due to acceleration of the bulk solid material at the loading point. This resistance increases quadratically with an increase in belt speed assuming that the bulk material falls straight onto the belt. This will affect smaller, in plant belt conveyors in particular. EXAMPLE To illustrate the concept discussed above lets consider a 6 km long conveyor belt with a capacity of 5000 TPH. The trough angle, the surcharge angle and the bulk density are again taken 3539。, 2039。 and 850 kg/m^3 respectively. Figure 4 shows the required belt speed as a function of the belt width to achieve the required capacity of 5000 TPH. This figure is somewhat similar to Figure 1. Figure 4 The figures 5 and 6 show the required belt strength and the required drive power as a function of the belt speed. The required belt strength decreases and the required drive power slowly increases with increasing belt speed as can be seen in those figures. Figure 7 shows the loss factor of transport and the DIN f factor versus belt speed. The loss factor of transport is always higher than the DIN f factor because the DIN f factor takes the mass of the belt into account (in the denominator) whereas the loss factor of transport only accounts for the mass of the bulk solid material. Intuitively, it may be expected that there will be an economically optimum belt speed in the high belt speed range. The determination of the optimum belt speed however, requires more information and is beyond the scope of this paper. Figure 5 Figure 6 Figure 7 RUBBER COMPOUNDS The indentation rolling resistance depends on the viscoelastic properties of the belt39。s bottom cover as discussed in the preceding section. This implies that the rolling resistance can be decreased by selecting a special low indentation rolling resistance (rubber) pound that is available on the market today. A small premium has to be paid for this special pound, but costs can be limited by applying it for the bottom cover only and using a normal wearresistant pound for the carrying top cover. In that case turnovers are required to fully use the energy saving function of the bottom pound. A Quantitative indication of the level of indentation rolling resistance is the indentation rolling resistance indicator tan/E ^1/3, where tan is the loss angle and E39。 the storage modulus of the pound. Compounds with a reasonable indentation rolling resistance performance have indicators below . Figure 8 shows these indicators for typical medium to good performing rubbers. As can be seen in that figure, the choice for a specific rubber pound affects the energy consumption of the belt conveyor, in particular as a function of the ambient temperature. One ment (warning) must