Patent Publication Number: US-2022234832-A1

Title: Trough belt conveyor

Description:
FIELD AND BACKGROUND OF THE INVENTION 
     The invention relates to a trough belt conveyor for conveying bulk material. 
     In a trough belt conveyor a flexible conveyor belt loop is tensioned around a pair of end pulleys at opposite ends of the belt conveyor. The conveyor belt loop has a momentarily upper transport section extending along a transport path over a transport deck and a momentarily lower return section extending under the transport deck. 
     Trough forming guide surfaces extend along the transport section under opposite side edge portions of the transport section. The trough forming guide surfaces are each inclined upward from the transport deck from under the transport section of the conveyor belt in a laterally outward direction transverse to the transport path. The transport section of the conveyor belt rests on the transport deck and on the trough forming guide surfaces with transverse sag so as to form a trough extending along the transport path. 
     Material being transported stays in the trough without requiring side guides that are subject to wear, while closing off or avoiding gaps between the belt and the side guides, through which in particular fine particles can escape, is problematic. Trough belt conveyors are particularly suitable for transporting bulk material that are fine or include a fraction of fine particles, such as sand, gravel, cement and coal. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a trough belt conveyor, which is of simple construction yet versatile, durable and reliable in operation. 
     According to the invention, this object is achieved by providing a belt conveyor according to claim  1 . The trough forming guide surfaces form a simple and reliable support for forming a through having a constant cross-sectional width with very little variation along the length of the transport section. The trough forming guide surface can easily be provided as an option to a side guide, so that a basic belt conveyor system can efficiently be provided in a trough belt version and in a flat belt with side guides version. Because passages are provided at least in the trough forming guide surfaces or in zones of the transport deck along the trough forming guide surfaces, material that is caught between the conveyor belt and the trough forming guide surfaces drops through the guide surfaces or the transport deck when it arrives at one of the passages. Accordingly, the extent to which particles are dragged along between the conveyor belt and the trough forming guide surfaces of the transport deck over long distances and thereby cause wear of the conveyor belt, the guide surfaces and the transport deck as well as additional friction and dust formation, is substantially reduced. 
     In another aspect of the invention, a belt conveyor according to claim  12  is provided. 
     Under a transition from the lower section to the less steep upper section, at least one roller is provided, which has a horizontal axis of rotation perpendicular to the transport path and has a circumference of which a section projects upwardly from the transport deck, so that the trough is locally shallow or absent in a section of the belt above the roller. Thus the belt is allowed to bend from the lower section to the less steep upper section without overstretching over outer portions of the belt. This further contributes to the durability of the belt conveyor. 
     Particular elaborations and embodiments of the invention are set forth in the dependent claims. 
     Further features, effects and details of the invention appear from the detailed description and the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an example of a belt conveyor according to the invention; 
         FIG. 2  is a top plan view of the belt conveyor shown in  FIG. 1 ; and 
         FIG. 3  is a cross-sectional view along the line III-III in  FIG. 2 , leaving out parts remote from the cross-sectional plane. 
     
    
    
     DETAILED DESCRIPTION 
     In the drawings, an example of trough belt conveyor  1  according to the invention is shown. The belt conveyor has a frame  2  to which upper and lower end pulleys  3 ,  4  are rotatably suspended at opposite ends of the belt conveyor  1 . In this example, the upper end pulley  3  is coupled to a drive shaft  5  via which it can be driven as a driven pulley. The motor driving the driven pulley can be part of the belt conveyor  1  or be an external motor. The pulley  4  at the lower end of the belt conveyor  1  is an idler pulley. 
     A flexible conveyor belt loop  6  is tensioned around the end pulleys  3 ,  4 . In  FIGS. 1 and 2 , the conveyor belt  6  is not shown, but only indicated by dash-and-dot lines, to avoid obscuring other parts of the belt conveyor  1  from view. The conveyor belt loop  6  has a momentarily upper transport section  7  extending along a transport path over a transport deck  9  and a momentarily lower return section  10  extending under the transport deck  9 . The transport path  8  is formed by a generally central flat strip of the top surface of the upper transport section  7  from one end of the conveyor belt loop  6  to the opposite end of the conveyor belt loop  6 . In  FIGS. 1 and 2 , the transport path  8  is indicated by dash-and-dot lines. 
     Under opposite side edge portions  11  of the transport section  7 , trough forming guide surfaces  12  extend along the transport path  8 . The trough forming guide surfaces  12  are each inclined upward from the transport deck  9  from under the transport section  7  of the conveyor belt  6  in a laterally outward direction transverse to the transport path  8 . The transport section  7  of the conveyor belt  6  rests on the transport deck  9  and on the trough forming guide surfaces  12  with transverse sag so as to form a trough extending along the transport path  8 . The inclined opposite side edge portions  11  of the transport section  7  of the conveyor belt  6  keep material being transported away from edges  13  of the transport section  7  of the conveyor belt  6 , so that no side guides are needed to keep the material being transported from falling off from lateral sides of the transport section  7  of the conveyor belt  6 . Seen in transverse cross-section, as in  FIG. 3 , the side edge portions  11  of the transport section  7  of the conveyor belt  6  may for instance be oriented at an angle of 5-25°, preferably 10-20° and more preferably about 15° relative to the transport deck  9 . 
     In the trough forming guide surfaces  12 , passages  14  are provided for allowing material caught between the conveyor belt  6  and the trough forming guide surfaces  12  to drop through the guide surfaces  12 . Although the transport section  7  of the conveyor belt  6  forms a trough with inclined side strips  11 , some times some material particles nevertheless fall over one of the side edges  13  of the conveyor belt. When caught between the conveyor belt  6  and the trough forming guide surfaces  12 , such particles are to some extent entrained by the belt  6  and cause friction and wear of the trough forming side surfaces  12 , of the belt  6  and also of the top surface of the transport deck  9  if the particles migrate down to the transport deck  9 . Because the passages  14  are provided, material that is caught between the conveyor belt  6  and the trough forming guide surfaces  12  upstream of the passages  14 , drops through one of the passages  14  when it arrives at that passage, so that the average distance over which the particles are entrained is substantially reduced. Accordingly, the extent to which particles are dragged along between the conveyor belt  6  and the trough forming guide surfaces  12  and thereby cause wear of the conveyor belt, the guide surfaces and the transport deck as well as additional friction and dust formation, is substantially reduced. 
     Such passages may alternatively or additionally also be provided in zones of the transport deck along the trough forming guide surfaces, so that also particles moving inwardly of the trough forming side surfaces can drop away from between the transport section of the conveyor belt and the surface over which the transport section of the conveyor belt slides. 
     In the present example, the transport deck is in the form of a pan  9  which has a top surface which is flat in a horizontal direction transverse to the transport path  8 . Such a flat surface provides an even support of the transport section  7  of the conveyor belt  6  and forms a simple construction, but particles can be dragged along between such a surface and the transport section  7  of the conveyor belt  6  causing considerable friction and wear, so that in particular for a belt conveyor having such a flat pan support of the transport section  7  of the conveyor belt  6 , the presence of passages  14  allowing particles to drop away from between the transport section  7  of the conveyor belt  6  and the surface of which the transport section  7  of the conveyor belt  6  rests is of particular advantage. However, also in a conveyor in which the central portion of the conveyor belt rest on for instance a row or pattern of rollers, passages for allowing particles to drop away quickly from between the transport section of the conveyor belt and supporting trough forming surfaces are advantageous for reducing wear, friction and dust formation. 
     If particles drop through the passages, it is of advantage if these particles do not drop on other parts of the belt conveyor  1 , such as the return section  10  of the belt conveyor  1 . For this purpose, the conveyor according to the present example is provided with chutes  15  below the transport section  7  of the conveyor belt  6 . The chutes are each inclined downward in a direction transverse to the transport path  8  from under the transport section  7  of said conveyor belt  6  to positions laterally outward of the conveyor belt  1 . In particular if there is enough vertical distance between the transport section and the return section of the conveyor belt, it is also possible to provide a single chute sloping downward from outside one side of the conveyor belt  6  to outside of an opposite side of the conveyor belt, so that all particles that have fallen through the openings are led to one side of the belt conveyor only. 
     The chute  15  is a plate section contiguous with the pan  9 , so that the chute also constitutes a stiffening and reinforcement flange for the pan  9 . 
     Because the chute  15  extends along the transport deck  9  in longitudinal direction of the transport path  8  from one end to an opposite end of the transport deck  9 , particles that drop away from between the conveyor belt  6  and the trough forming guide surface  12  or the transport deck  9  are lead away laterally regardless where along the transport deck  9  the particles drop away from between the conveyor belt  6  and the trough forming guide surface  12 . 
     The trough forming guide surfaces  12  mounted with inward edges on top of the transport deck  9  spaced from side edges of the transport deck  9  allow to efficiently manufacture versions of the belt conveyor  1  with a flat transport section of the conveyor belt (for which the transport deck  9  provides a sufficiently wide support) and side guides as well as with a trough shaped transport section of the conveyor belt without side guides. Because the trough forming guide surfaces  12  are removably mounted, the belt conveyor  1  can moreover easily be converted from a trough belt conveyor with a trough shaped transport section of the conveyor belt without side guides into a flat belt conveyor with a flat transport section of the conveyor belt and side guides. 
     For discharging particles caught between the transport section  7  of the conveyor belt  6  and supporting surfaces under that section  7  of the belt  6  particularly effectively, the passages  14  are in the form of recesses in boundaries of the trough forming guide surfaces  12  where the trough forming guide surfaces  12  meet the transport deck  9 . 
     The passages  14  have edges  16  extending to the transport deck  9  in directions oblique relative to a longitudinal direction of the transport path  8 . This causes particles that cling to the belt  6  to be scraped off the moving belt  6  particularly effectively. The directions oblique relative to a longitudinal direction of the transport path  8  are preferably at an angle of 30-60° and more preferably 40-50° relative to the transport path  8 . 
     For ensuring that all particles that are caught between the belt  6  and one of the trough forming guide surfaces  12  or the transport deck can drop away, the passages  14  preferably have a length in longitudinal direction of the transport path  8  of at least 15 cm or, with increasing preference, at least 18 cm or at least 20 cm and/or a width perpendicular to the longitudinal direction of the transport path  8  of at least 5 cm or, with increasing preference, at least 7 cm or at least 8 cm. 
     For providing sufficient support for the transport section  7  of the conveyor belt  6  and avoiding significant scraping of the belt  6  along downstream edges of the opening  6 , the passages  14  have a length in longitudinal direction of the transport path  8  of at most 30 cm or, with increasing preference, at most 27 cm or at most 25 cm and/or a width perpendicular to the longitudinal direction of the transport path  8  of at most 16 cm or, with increasing preference, at most 14 cm or at most 13 cm. 
     The belt conveyor according to the present example has a lower section  17  of the transport path  8  that is steeper than an upper section  18  of the transport path  8  contiguous with that lower section  17 . Under a transition from the lower section  17  to the upper section  18  rollers  19  having a horizontal axis of rotation perpendicular to the transport path  8  and having a circumference of which a section projects upwardly from the transport deck  9  are provided. The trough in the transport section  7  of the conveyor belt  6  is locally shallow or absent in a section of the belt  6  above the rollers  19 , so that the belt  6  is allowed to bend from the lower section  17  to the less steep upper section  18  without overstretching over outer portions of the belt  6 . This further contributes to the durability of the belt conveyor. 
     Several features have been described as part of the same or separate embodiments. However, it will be appreciated that the scope of the invention also includes embodiments having combinations of all or some of these features other than the specific combinations of features embodied in the examples.