Abstract:
A conveyor belt ( 1 ) includes a metallic net belt ( 8 ) functionally driven by at least a traction drum ( 5 ), tensioned by at least a return drum ( 12 ) and supported by a plurality of independent transversal rollers ( 13 ). Belt ( 1 ) supports individually a plurality of plates ( 2 ) partially overlapping one another, so as to form a flat continuous transport surface as a mobile reliable plane that is resistant to extreme mechanical stress. Each of said plates ( 2 ) is suitably shaped so that an upper portion of one plate overlaps a lower portion of the following plate.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is the National Stage of International Application Serial No. PCT/IB2006/002589, filed on Sep. 20, 2008, the disclosure of which is incorporated herein by reference in its entirety. 
     FIELD OF INVENTION 
     The present invention is about a metallic conveyor belt with overlapping planar surface plates. 
     BACKGROUND OF INVENTION 
     It is common practice, by now, in transporting difficult material, especially at high temperatures, use of a kind of metallic belt conveyor comprising a metallic net traction element supporting a plurality of partially overlapping steel plates, such as to form an almost sealed load bearing channel. Each plate is subsequently individually fixed by a plurality of bolts, screws or rivets inserted in corresponding bored plaques, each of these plaques being in turn inserted inside the meshes of the traction net conveyor belt. The conveyor belt thus comprised is operated by a traction drum, it is tensioned by a transmission drum, ensuring the necessary tension, and is supported by a plurality of independent transversal rollers, supporting the conveyor belt on its load bearing section, and by wheels supporting the belt in its return section. Examples of conveyor belts of this kind are disclosed in U.S. Pat. Nos. 3,633,737 and 3,749,228, where material holding means overlap each other to form a continuous channel in which the material can be held and carried. However, the transport surface is not planar, having steps corresponding to the overlapping zone of the material holding means. 
     In conveyor belts according to prior art, the overlapping of plates generates a non planar surface, caused by partial imbricated overlapping of the plates in the direction of motion. Such embodiment constitutes a limit to the increase in thickness of the plates and therefore to the sturdiness of the assembly, due to the growing difficulty with the thickness of the plates, to slide on the return wheels. The presence of small ste 
     causes a waste of power due to the energy absorbed to raise the conveyor belt at every passage of the small steps on the return wheels. This energy waste, besides, produces vibrations or noise. 
     The non planar surface of the conveyor belt on the load bearing section causes, in practice, hindrance to positioning deviators on the conveyor belt to laterally discharge transported materials, which would get stuck between the small steps formed by the overlapping of the plates and the deviator. 
     For similar reasons, it is impossible to create more channels on the same conveyor belt for the possible choice and separation of the transported material. 
     SUMMARY OF INVENTION 
     Moreover, an example of conveyor characterized by a planar transport surface is disclosed in U.S. Pat. No. 3,311,222, where load carrying members are bracketed to cables at each side of the conveyor frame, said carrying members having marginal side portions that allow meshing on the driving sprocket drum. This kind of conveyor is not dependable for continuous operation and extreme mechanical stress. In fact even the failure of only one of the two connection cables stops the conveyor operation. This occurrence is not possible for a metallic belt conveyor. 
     The above mentioned limits are overcome by the conveyor belt of the present invention, whose planar surface, does not create obstacles in applying deviation and/or separation devices and is able to operate as a mobile work plane, attaining handling reliabilty even in the presence of extreme mechanical stress. 
     In everyday practice of vertical mould lines, the cooling of the casting in mould parts, as it requires to be performed in absence of any vibration, rubber conveyor belts are used positioned just downstream of the casting point of the cast iron. During transport of the mould parts, the rubber belt undergoes severe early deterioration caused by the leakage of the cast iron which spills out in case of possible damage of the mould parts, with resulting production down time. These problems can be totally eliminated by the conveyor belt object of this invention, whose planar high temperature proof transport surface and its absence of vibration allow for a safe transport of the mould parts, without damaging them. 
     The absolute stiffness of the plane, the absence of vibrations and the perfectly flat planar surface make this invention fit to be used as a moving walkways, possibly even in association with working performed by personnel transported by the conveyor belt. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The innovative features, aims and advantages of the present invention will become apparent from the following description and attached drawings, relating to non limitative embodiments, in which: 
         FIG. 1  is a partial sectional view of the conveyor belt according to the present invention, including the traction and return drums and load bearing rollers; 
         FIG. 1A  is a view in detail of the plates of the conveyor belt of  FIG. 1 ; 
         FIG. 2  represents a schematic view of the conveyor belt wrapping on the drum; 
         FIG. 2B  is a view in detail of the wrapping phase of  FIG. 2 ; 
         FIG. 3  is a cross sectional view of the conveyor belt according to the invention; 
         FIG. 4  is a front sectional view of the conveyor belt with its support calibrated; and 
         FIG. 5  represents a schematic view of the close roller pitch. 
     
    
    
     In this respect it is hereby noted that identical reference numbers in the various figures indicate identical or equivalent parts. 
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     The conveyor belt  1  object of this invention, compared to a conveyor belt of known construction, provides a particular construction of the plates  2  such as the relative position between two consecutive plates makes the transport surface planar and continuous, turning it into a sturdy and reliable moving plane. This is particularly evident with reference to  FIG. 1  of the attached drawings. 
     The conveyor belt  1  according to the present invention is able to operate even in the presence of extreme mechanical stress, deriving for example from the impact of heavy weights on the belt or mechanical stress due to working performed on the belt. 
     The conveyor belt  1  comprises a metallic net belt  8  ( FIGS. 1A and 1B ) representing the principal traction element, to which the plates  2  are fixed by means of screws  7 , bolts or rivets and corresponding bored plaques  9 , each of these bored plaques  9  being thereby inserted inside a mesh of the traction net  8 . The shape of each plate  2 , partially overlapping the following one, allows to attain a planar and continuous transport surface, keeping it closed to protect the supporting belt  8  even during rotation on the traction drum  5  and the return drum  12 . 
     The conveyor belt  1  thus set up is operated by the traction drum  5 , it is tensioned by the return drum  12 , the latter assuring the necessary constant tension, and is supported by a plurality of transversal independent rollers  13 , supporting the belt on the upper section, and by wheels (not shown), supporting the belt on the return section. 
     The planarity of the transport surface allows for the application of one or more deviators  11  and/or separation baffles  16 , allowing to differentiate the transported material according to production requirements, avoiding the material to get stuck between the belt and the deviators  11 , with subsequent abrupt stops of the conveyor belt. 
     An advantage deriving from the planarity of the transport surface and absence of vibrations is the possibility to transport components, like mould parts of the vertical moulding line during the cooling phase of cast iron, without damaging the mould part, nor the conveyor belt due to accidental spilling of cast iron during transport. 
     Additionally, the absolute sturdiness of the plane, the absence of vibrations and the perfectly planar surface without protrusions cause the conveyor belt according to the invention to be fit to be used as a mobile walkway, possibly even in association with working performed by personnel transported by the belt. 
     A possible embodiment of the conveyor belt  1  is obtained by coupling two plates  3  and  4  of different shape, fixing them by couples by means of bolts, screws or rivets  7  to corresponding bored plaques  9  inserted inside the metal net  8 , where the upper plate  3  results partially overlapping over the following base plate  4 . Plates  3  and  4  thus coupled stay integral and form a single body even when wrapping on drums  5 . The bores on the lower plate  4  are slotted to allow for a differential expansion between the plates  3  and  4  due to different thermal conditions. 
     In case of such realization of plates  2 , elements  3  and  4  may be of different thickness and different material from each other, allowing for both the ideal choice for the material in contact with the product to be transported, and the choice of the total thickness necessary to convey sturdiness to the conveyor belt according to transport needs. 
     For this reason, the conveyor belt object of this invention can be considerably sturdier than those according to prior art, because this configuration with coupled plates  3  and  4  fixed to the net traction belt  8  allows to use considerable thickness without any difficulty in sliding on the return wheels  14 . The close pitch of the load bearing rollers  13  gives sturdiness and reliability to the conveyor belt  1 , absorbing possible impacts deriving for example by heavy weights hitting the conveyor belt  1 . 
     The resistance to mechanical stress of the high thickness overlapping plates  3  and  4  system, with close load bearing rollers  13 , is further increased adopting supports  15  of the load bearing rollers provided with a breaking up point  14  with a calibrated resistance. these supports  15  allow to protect belt  1  from any mechanical stress, as they brake at the predetermined point when admitted stress is exceeded. 
     Since the pitch of the load bearing  13  is close, the possible break up of one or more supports  15  will be non influential on the normal running of the conveyor belt  1  and the substitution of supports  15  and relevant rollers  13  can be performed without the necessity to stop the conveyor belt  1 . 
     Another possible embodiment of the conveyor belt  1  is that of making the plates  2  in one single piece, by machining or moulding, and they can further be made of plastic material, for example high density polyethylene, when it is necessary to warrant a low friction coefficient and when the materials to be transported are cold and not excessively abrasive. 
     According to transport needs and kind of material, the conveyor belt I can provide for lateral tabs  10  constituting extensions of the plates  2  which are turned either upwards ( FIG. 4 ) or downwards ( FIG. 1 ). In particular, the function of tabs  10  turned upwards ( FIG. 4 ) is suitable to contain the transported material in case it is loose or small sized. The configuration with tabs  10  turned downwards ( FIG. 1 ) is suitable in case a lateral discharge is required, by applying suitable deviators  11  or by action of the operator, allowing to simply push the workpieces towards the discharge points without the necessity to lift them. 
     It is apparent that to the embodiments described in this application by way of example and in a non limitative way, many modifications, adaptations, integrations, changes and substitutions of elements with functionally equivalent others may be performed, without falling out of the scope as defined by the following claims.