Abstract:
A support structure for a conveyor belt which includes two upwardly extending, pivotally mounted, support arms, a garland of conveyor idler rollers suspended between upper ends of the support arms and, for each support arm, respective biasing means which permits pivotal movement of the support arm, towards the other support arm, only when the support arm exerts a force on the respective biasing means in excess of a predetermined load.

Description:
BACKGROUND TO THE INVENTION 
     This invention relates to a support for a conveyor belt. Conveyor belts, at loading points, can be subjected to considerable impact forces. For example a conveyor belt which carries ore may be expected to withstand the impact of rocks with a nominal size in excess of 150 mm falling through heights of up to 4 meters. The impact force on a conveyor belt carrying in excess of 2000 tons per hour may therefore be substantial and, unless adequate measures are taken, the belt or the supporting structure may be damaged. 
     Shock absorbing devices, which are used to overcome the aforementioned adverse effects, must physically be of a size which enable them to be installed in the available space. In certain installations space is at a premium and, as a general rule, it can be said that the width of a shock absorbing system should not exceed the width of the normal supporting structure of the belt. 
     Another factor is that an impact absorbing structure, under normal operating conditions, should not affect the height of a belt once it has been set to a desired or optimum operating level. 
     Furthermore, it is frequently necessary to load a conveyor belt at or near a tail pulley, i.e. in a region where the belt is in transition from the flat tail pulley to the fully troughed carrying condition. A shock absorbing device should, therefore, provide a means of adjustment which takes into account the changing cross-sectional arrangement of the belt in the load zone. 
     SUMMARY OF THE INVENTION 
     The invention provides a support structure for a conveyor belt which includes at least one support member which supports at least one conveyor idler roller, and biasing means, which is biased to a predetermined load, and which acts on the support member in such a way that the support member is movable only when it exerts a force on the biasing means in excess of the predetermined load. 
     The support member may support the conveyor idler roller in any suitable way, directly or indirectly. 
     Means may be provided for adjusting the value or level of the predetermined load. 
     The biasing means may take on any suitable form and, for example, may comprise or include one or more elastomeric or metallic members. 
     In one form of the invention the biasing means includes a plurality of components which are assembled to provide a desired spring characteristic. Each component may for example comprise an elastomeric element. 
     In a preferred form of the invention the biasing means includes a number of elastomeric rings which are axially aligned with each other. 
     In an alternative arrangement use is made of metallic cup washers, or springs of any suitable type. 
     The biasing means may be biased to the said predetermined load by applying an axially directed force, equal to the said predetermined load, to the elastomeric rings. 
     Connection means may be provided between the biasing means and the support member. The connection means may be adjustable relatively to the biasing means to position the support member at a desired orientation. 
     The support member may be mounted to suitable supporting stringers and beams in any appropriate way and, preferably, the support member is pivotally attached thereto. 
     The support structure of the invention is particularly suited for supporting a garland of conveyor idlers although it is to be understood that the scope of the invention is not confined to this particular application. 
     In a preferred embodiment the support structure of the invention includes a base member, at least one support member which is pivotally attached to the base member, means on the support member for engagement, with at least one conveyor idler roller, and biasing means, biased to a predetermined load, which acts between the base member and the support member and which is movable, in a first direction, when the support member exerts a force on the biasing means in excess of the predetermined load. 
     The first direction may be inclined downwards. 
     The support member may be adjustable in length in any suitable way, e.g. telescopically, to accommodate varying belt troughing angles. 
     The support structure may include adjustment means for adjusting the orientation of the support member relatively to the base member. 
     The invention also provides a support structure for a conveyor belt which includes two spaced support members, conveyor idler rollers positioned between, and secured to, upper ends of the support members, means pivotally connecting respective lower ends of the support members to underlying supporting structure, and, for each support member a respective biasing arrangement which is biased to a predetermined load and which permits pivotal movement of the respective support member, in a direction which is downwardly inclined from a side of the belt towards an underside thereof, only when the support member exerts a force on the respective biasing arrangement in excess of the said predetermined load. 
     The invention further extends to a support structure for a conveyor belt which includes two upwardly extending, pivotally mounted, support arms, a garland of conveyor idler rollers suspended between upper ends of the support arms and, for each support arm, respective biasing means which permits pivotal movement of the support arm, towards the other support arm, only when the support arm exerts a force on the respective biasing means in excess of a predetermined load. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is further described by way of examples with reference to the accompanying drawings in which: 
     FIG. 1 is a front view of portion of a support structure according to one form of the invention, and 
     FIG. 2 illustrates a modified support according to the invention. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1 of the accompanying drawings is a front view of a portion of a support structure for a conveyor belt according to one form of the invention. 
     FIG. 1 illustrates a stringer  10  of a conveyor support frame to which is attached a base member  12 . The base member has a downwardly depending connector  14  which is attached to a transversely extending beam  16 . 
     FIG. 1 illustrates a left hand side of the support structure of the invention. It is to be understood that the right hand side has essentially the same arrangement and that the beam  16 , at its right hand side, is connected to a similar connector and base member which are spaced from the illustrated components by a distance which is substantially equal to the width of the belt which is supported by the structure. 
     A support member or arm  18  is attached to the base member  12  at a pivot point  20  and extends upwardly from the base member. At its upper end the support arm has a component  22  from which is suspended, in a known manner, a garland of conveyor idler rollers  24 . 
     A rod  26  extends between a plate  28  which is fixed to the support arm and an inclined face  30  of a plate  32  which is welded to gussets  34  fixed to the base member  12 . The rod is threaded and two nuts  36  which are engaged with the rod secure the rod to the plate  28 . Towards its lower end the rod has a plate  38  engaged with it which bears downwardly on a number of rings  40  which are threaded onto the rod and which rest on the plate  32 . Nuts  42  and  44  are engaged with the rod  26 . The upper nut  42  forces the plate  38  against the rings while the lower nut  44  secures the rod to the plate  32 . By adjusting the nuts  36 ,  42  and  44  the orientation of the support arm  18  can be varied, and by adjusting the nuts  42  and  44  the pressure on the rings can be varied. 
     The rings  40  are, in this example of the invention, made from a suitable elastomeric material with a desired stiffness e.g. rubber with an appropriate hardness. The number of rings which are employed may be varied according to requirement in order to impart to the assembly a desired spring or stiffness characteristic. By rotating the nuts  42  and  44  along the rod the plate  38  can be moved in the axial direction of the rod, relatively to the plate  32 , so that the rings are biased to a greater or lesser extent. The rings on each side of the belt are in practice biased to predetermined loads the sum of which equals the impact load which the garland of idlers may be expected to sustain without movement. 
     The adjustments of the nuts  42  and  44  may alter the orientation of the support arm  18 . If this does occur then the nuts  36  are adjusted to bring the support arm to a desired position. 
     The support structure shown in the accompanying drawing is intended for supporting a conveyor belt, which runs over the garland of idlers, at a loading point, i.e. at a point at which material is discharged onto the belt carried by the garland. When the belt is loaded a force is exerted on the support arm which tends to pivot the support arm in the direction of an arrow  46 , about the pivot point  20 . The support arm is however not able to move in the direction of the arrow until such time as it exerts a force on the rings  40  in excess of the predetermined biasing load. 
     If the sum of the predetermined biasing loads on the two support arms, on opposed sides of the belt, is chosen to correspond with the maximum load which the garland will carry under normal operating conditions of the belt then it is apparent that, for all loads from zero up to the said maximum load, the support arms will not deflect from their normal operating positions. 
     On the other hand if the conveyor belt carried by the garland is subjected to an impact which imparts, via the support arms, loading on the respective sets of biasing rings  40  in excess of the sum of the predetermined biasing forces, then each of the arms will pivot in a direction which is downwardly inclined, from a side of the belt towards an underside thereof and, in so doing, permit the impact load to be absorbed in such a way that the likelihood of the conveyor belt, or the supporting structure for the belt, being damaged, is reduced. 
     The support structure of the invention can be used for supporting a conveyor belt, in its loading area, in the space which is normally available. Thus it is to be noted that the beam  16  extends between opposed stringers  10  and that the support arm  18  extends upwardly in line with the stringer  10 . The support arm, in addition, has a height which is the normal height in that the garland of conveyor idlers  24  is positioned, by means of the support arm, at the height at which the garland would normally be supported. 
     As indicated in the preamble hereof it is also desirable if provision can be made for adjusting shock absorbing or, more generally, conveyor support devices in such a way that adequate support can be provided for a conveyor belt in the transition region between a pulley and a troughed state. It is to be noted that the length of the transition region will vary from installation to installation. The degree of troughing can also vary substantially. It is desirable therefore to provide some mechanism whereby on site adjustment can be effected to take account of variations of this type. 
     FIG. 2 contains two views, at right angles to one another, from the side, of a support arm  18 A which can be used in place of the arm  18  shown in FIG.  1 . The arm has a lower component  60  with a lower pivot point  20 , and an upper component  62  which is telescopically engaged with the lower component. At its upper end the component  62  has a hook-shaped recess  64  which receives one end of a garland of conveyor idlers, not shown. 
     A plate  28  faces obliquely downwardly and is fixed to gussets  66  extending from the lower component  60 . 
     At its upper end the component  60  is split by a longitudinally extending slit  68  and two side-by-side flanges  70  and  72  are respectively positioned on opposed sides of the slit. The flanges have registering holes  74 . 
     The effective length of the support arm  18 A can be adjusted by telescopically moving the upper component  62  relatively to the lower component  60 . Once the arm  18 A has a desired length the components can be locked to each other by means of bolts, not shown, which pass through the holes  74  and which, when tightened, draw the split upper end of the component  60  into tight frictional engagement with the circumscribed portion of the component  62 . 
     As has already been noted the inclination of the arm  18 A can be adjusted pivoting the arm about the point  20  and can be held in a desired angular orientation using a structure which is similar to that shown in FIG.  1 . 
     It thus becomes possible to adjust the support arm in height and in angular orientation to accommodate the exact point at which the arm is installed and to take account of the degree of troughing of the belt which is being supported. This objective can be achieved without affecting the impact absorbing characteristic already referred to. 
     The rubber rings can be replaced by any suitable components e.g. metallic cup washers or coil springs which act between the plates  32  and  38 , hydraulic devices, and any appropriate combination of such suitable components.