【正文】 from the belt line. This feature, which is unique, allows the drive unit and its associated electrical equipment to be located in a position with easy access for maintenance but away from the dust and dirt associated with a conveyor discharge or return belt line. This flexibility also allows the drive unit to be placed at any point in the conveyor, including if necessary on the material carrying run of the drive cables. The other part of the Cable Belt design that is unique is the tensioning system and there is no doubt that this is more plex and takes greater space than would be required in a troughed belt conveyor. There are several reasons for this but the principal reason is the necessity to provide equipment to separately tension each drive cable and the carrying belt. Whilst the tension in the carrying belt is nominal it is still necessary to cater for the drive cable tension movement, particularly in long flat conveyors which, of necessity, are tensioned at or near the drive unit. In such conveyors the tension movement of the drive cables is substantial during the start sequence. Before the whole conveyor is moving the effect is that it is necessary to 39。lift off39。lift off39。 in catenaries to occur. Early Cable Belt Belting Fig 2 Intermediate Cable Belt Belting Fig 3 Modern Cable Belt Belting Fig 4 The Cable Belt is best defined as a belt conveyor with a laterally rigid but longitudinally flexible carrying belt which is supported at or near its edges on two parallel endless looms of drive cable, these cables in turn being supported at intervals by grooved pul1eys. The integral reduction gear and drive unit drives both drive cab1es and incorporates a differential to equalise tensions in the cables. In addition each of the drive cable circuits is separately tensioned to allow for the differential stretch of these during operation. The unique feature of the Cable Belt system is the belt. Originally this was a fabric reinforced rubber belt which had moulded into it spring steel straps at 450 mm intervals. These straps protruded beyond the edges of the bell as illustrated in fig. 2, and had mechanically attached to them a metal shoe with rubber Lining where it gripped the drive cable. This was superseded by a one piece moulded construction shown in fig. 3 where smaller cross section straps at intervals of 100 mm were moulded entirely within the belt and the shoes to grip the drive cables were continuous mouldings along the edge of the belt. Typical 4 Pulley Line Stand Fig 5 Recently a further change was made, illustrated in fig. 4 whereby the shoes which grip the drive cable on the material carrying run have been moved inwards. This increases the stability of the belt when subjected to overloading and in addition allows the use of smaller cross section straps. Angle Station Fig 8 It is normal that on a typical long centre conveyor the eventual replacement of the belt is not for reasons of abrasion of the surface or mechanical damage, but due to the various ageing processes that affect rubber pounds such as heat, sunlight, and ozone. As a result it has been necessary to develop special synthetic rubber pounds that are inherently resistant to ageing. The specification of the drive cables whilst similar superficially to a normal wire rope are specially made to a Cable Belt specification with design criteria laid down for individual wire size, fatigue life and internal lubrication. They are of galvanised construction, Lang39。, without experiencing slipping of the belt on the drive cables. Whilst the Cable Belt conveyor was developed at a time when the powers available of up to 300 kW were regarded as outstanding the basic concept is still retained even when now, single conveyors of 30000 metre length and 8000 kW power are being built. The terminal units are similar to those in a conventional troughed conveyor except that they also serve to separate and rejoin the carrying belt and drive cables. A typical example of a head discharge unit is shown in fig. 6. Obviously the terminals other than the drive unit are more plex than in a conventional troughed conveyor and take up more space particularly in the case of the tensioning arrangements. This is not true of the drive as for a parable power rating it is pact and has the advantage that it can be located remote from the Cable Belt conveyor belt line. Head Discharge Unit Fig 6 As the modulus of elasticity of the drive cables is kept relatively low in order to allow the use of very low starting torques and each drive cable is tensioned, the tension system does require substantial takeup space and is more p