Patent Publication Number: US-9423180-B2

Title: Disc for industrial plants

Description:
FIELD OF THE INVENTION 
     The invention generally relates to discs for use in industrial applications such as dryers, cookers, coolers or other heat exchangers and particularly, although not exclusively, relates to a disc dryer. 
     BACKGROUND TO THE INVENTION 
     Disc dryers are large industrial dryers used for drying conveyable or flowable materials such as granular and liquid type products. They typically comprise a hollow shaft carrying hollow annular discs at intervals. Each disc comprises a pair of annular plates welded around the periphery to the shaft. The shaft is formed to have apertures through its wall to the hollow interior of each disc. In operation of the dryer steam is fed through the shaft and passes through the apertures into the hollow region formed by the discs heating the surface of the discs. Material to be dried moves through an inlet formed through an outer casing of the disc dryer and along the length of the shaft where it contacts the outer surfaces of the heated discs thereby drying the material. 
     As shown in  FIG. 5 , the discs  41  in a conventional disc dryer  40  have flat surfaces and can be fitted with cross pins  43  that span between the two annular plates  42  forming each disc to prevent the discs from deforming or bursting under steam pressure. At construction of the disc dryer or retrofitting of replacement discs, fitting cross pins to each disc requires drilling or cutting holes through the disc and pressing in and welding of many individual cross pins. This is labour intensive and is carried out when constructing a new disc dryer or retro-fitting an existing dryer with new discs when the existing discs have worn. Other methods for strengthening the discs other than fitting cross-pins are also known in the art but these are also generally labour intensive. 
     The annular plates for forming discs for disc dryers are typically formed by cutting one or more circular sheets from a square sheet of metal leading to significant scrap metal. 
     It is an object of the invention to provide an improved disc for use in industrial applications and/or improved disc dryer, or to at least provide the public with a useful choice. 
     SUMMARY OF THE INVENTION 
     In a first aspect the invention broadly consists in a disc comprising two annular plates connected to one another at an angle around corresponding outer peripheral edges such that corresponding inner peripheral edges of the plates are spaced apart from one another, each plate comprising one or more integral ribs extending between its inner edge and outer edge. 
     In a second aspect the invention broadly consists in an industrial plant comprising:
         a hollow shaft;   one or more hollow discs each comprising two annular plates connected to one another around their outer edges, each plate comprising one or more integral ribs extending between its inner edge and outer edge, the inner edge of each plate being coupled around the shaft and spaced apart from one another so that the disc is coupled to the shaft; and   one or more apertures along the length of the shaft provided between the plates of each disc so that the shaft is in fluid communication with each disc.       

     Preferably, the ribs are formed from folds in the annular plate. 
     Preferably in a first form, the ribs extend radially between the inner edge of the plate and the outer edge of the plate. 
     Preferably, each plate is formed from a length of a sheet of material. More preferably, the sheet of material is formed to integrally comprise the ribs. Even more preferably in a first form, the ribs are formed by rolling and are deeper towards one edge of the sheet of material than the other edge of the sheet of material such that the material curves greater around the deeper ends of the ribs in order to form an annular plate. Even more preferably in a second form, the ribs are formed by crimping or folding. 
     In a third aspect the invention broadly consists in a method of fitting a disc to an industrial plant comprising:
         passing a hollow disc along a hollow shaft so that the interior of the disc is proximal to an aperture provided on the shaft, the disc comprising two annular plates connected to one another around their periphery edges, each plate comprising one or more integral ribs extending between its inner edge and periphery edge;   connecting the inner edge of the first annular plate to the shaft; and   connecting the inner edge of the second annular plate to the shaft and spaced apart from the inner edge of the first annular plate such that the aperture is provided between the inner edges of the annular plates so that the shaft is in fluid communication with the disc.       

     Preferably, each plate is formed from a length of a sheet of material. More preferably, the sheet of material is formed to integrally comprise the ribs. Even more preferably in a first form, the ribs are formed by rolling and are deeper towards one edge of the sheet of material than the other edge of the sheet of material such that the material curves greater around the deeper ends of the ribs in order to form an annular plate. Even more preferably in a second form, the ribs are formed by crimping or folding. 
     In an fourth aspect the invention broadly consists in a method of constructing an industrial plant comprising:
         for each of one or more hollow discs, passing the discs along a hollow shaft so that the interior of the disc is proximal to an associated aperture provided on the shaft, the disc comprising two annular plates connected to one another around their periphery edges, each plate comprising one or more integral ribs extending between its inner edge and periphery edge;   connecting the inner edge of the first annular plate to the shaft; and   connecting the inner edge of the second annular plate to the shaft and spaced apart from the inner edge of the first annular plate such that the aperture is provided between the inner edges of the annular plates so that the shaft is in fluid communication with the disc.       

     In one form of the second, third and fourth aspects the industrial plant is a disc dryer, cooker, cooler or a heat exchanger. 
     Preferably the industrial plant is a disc dryer. 
     In a fifth aspect the invention broadly consists in a method of forming a disc for use in an industrial application comprising connecting the outer periphery edges of two annular plates to one another at an angle around their outer edges such that the inner edges of the plates are spaced apart from one another, each plate comprising one or more integral ribs extending between its inner edge and periphery edge. 
     In a sixth aspect the invention broadly consists in a method of forming an annular plate for use in construction of a disc for an industrial application comprising:
         rolling one or more ribs into a flat length of a sheet of material, the ribs being deeper at one edge of the material than the other edge of the material such that the material curves greater around the deeper ends of the ribs in order to form an annular plate; and   joining the two ends of the sheet of material.       

     Preferably in the fifth and sixth aspects the industrial application is an industrial plant. Preferably the industrial plant is a disc dryer. 
     In a seventh aspect the invention broadly consists in a disc for a disc dryer comprising two annular plates connected to one another at an angle around their outer edges such that the inner edges of the plates are spaced apart from one another, each plate comprising one or more integral ribs extending between its inner edge and outer edge. 
     In an eighth aspect the invention broadly consists in a disc dryer comprising:
         a hollow shaft;   one or more hollow discs each comprising two annular plates connected to one another around their outer edges, each plate comprising one or more integral ribs extending between its inner edge and outer edge, the inner edge of each plate being coupled around the shaft and spaced apart from one another so that the disc is coupled to the shaft; and   one or more apertures along the length of the shaft provided between the plates of each disc so that the shaft is in fluid communication with each disc.       

     The first, fourth, fifth, sixth, seventh and eighth aspects of the invention may include any of the preferable features associated with the second or third aspects of the invention. 
     Preferably for all of the above aspects of the invention, each plate has a central aperture with a radius between 0.2 and 0.5 m. 
     Preferably the radius of each plate is between 0.4 and 1.5 m. 
     Preferably the thickness of each annular plate is between 6 and 12 mm. 
     The term “comprising” as used in this specification means “consisting at least in part of.” When interpreting each statement in this specification that includes the term “comprising”, features other than that or those prefaced by the term may also be present. Related terms such as “comprise” and “comprises” are to be interpreted in the same manner. 
     The term “annular” as used in this specification in relation to the discs and plates includes same with a circular outer peripheral shape but also a non-circular outer peripheral shape such as an oval or square or rectangular outer peripheral shape (typically with radiused corners). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       Preferred embodiments of the invention will be described by way of example only and with reference to the drawings, in which: 
         FIG. 1  is a cut-away, elevation view of a disc dryer of the invention; 
         FIG. 2  is a cross-sectional close up view of a single disc element coupled to the shaft of the dryer of  FIG. 1 , 
         FIG. 3  is a plan view of an annular plate used to form a disc of the disc dryer of  FIG. 1 ; 
         FIG. 4  is a plan view of a partially formed annular plate of  FIG. 3 ; 
         FIG. 5  is a perspective view of a partially formed annular plate of  FIG. 3 ; and 
         FIG. 6  is a cross-sectional close up view of a disc in a conventional disc dryer. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The invention relates to a disc formed from annular plates having one or more integral ribs extending between an inner edge of the plate and an outer edge of the plate. The disc of the invention may be formed for use in a number of industrial applications including, but not limited to industrial plants such as disc dryers, cookers, coolers and other heat exchangers, and also paddle dryers. Such plants typically comprise a hollow shaft on which one or more of the discs of the invention are mounted about. A heating or cooling fluid source is introduced into the main shaft to heat or cool the surfaces of the discs respectively. Material, gas or fluid flowing through the plant (preferably external to but may be within the shaft) is appropriately heated or cooled by the discs before exiting the plant. In accordance with an aspect of the invention, the disc of the invention will be described in detail with reference to a disc dryer. It will be appreciated however that the disc may be used in any industrial application as mentioned. 
     Referring to  FIG. 1  and by way of example, a disc dryer  2  comprises a casing  4  arranged to hold a material  5  to be dried. The casing  4  may be made from a metal or alloy such as aluminium or steel, or any other suitable material. The material may be a pasty material, a sludge-like material, a particulate material, or any other suitable material that can flow through the casing  4  in order to be dried such as food material, grain or meal, coffee beans, chemicals, gluten, or waste-water sludge. The disc dryer  2  may comprise an inlet  6  so that the wet material  5  can enter the casing  4  in order to be dried, and an outlet  8  for removal of dried material  5 . Alternatively, the casing may be provided with a lid or hatch through which material  5  may be introduced into and removed from the disc dryer  2 . 
     The disc dryer comprises a drum, rotor, or shaft  10  extending through the casing  4 . The shaft  10  may be arranged to rotate within the casing  4  for example through actuation from an electric motor coupled to one end. The shaft  10  is hollow so that a heating fluid may flow through the shaft. The shaft  10  may comprise a first connector  12  at one end arranged to be coupled to a heating fluid source, and a second connector  14  at the other end arranged to be coupled to a heating fluid sink. Heating fluid may be may be introduced into the shaft  10  through the first connector  12  so that the heating fluid transfers heat to the shaft  10  which then transfers heat to the material  5 . Preferably, the heating fluid is pressurised steam, however any other suitable heating fluid may be used such as a heated liquid that is pumped into the shaft. The heating fluid may travel the length of the shaft  10 , transferring heat to it on the way, and then be removed at the second connector  14 . The shaft  10  may be constantly replenished with heating fluid from a heating fluid source so that the shaft  10  may constantly provide heat to the material  5 . In applications other than dryers such as in a cooler or heat exchanger the fluid may be a cooling fluid or a fluid which receives heat from the material passing through the plant. 
     The shaft  10  comprises one or more discs  16  provided along its length. The discs  16  are connected to the shaft  10  so that they may rotate with the shaft  10 . For example, the discs  16  may be welded to the shaft  10  or connected to the shaft  10  in any other suitable manner. The shaft  10  and discs  16  may be made from a material with a high thermal conductivity such as a metal or alloy, or any other suitable material. Referring now also to  FIG. 1 a   , the discs  16  are hollow. One or more apertures  17  are provided along the length of the shaft  10  so that the inside  10   a  of the shaft  10  is in fluid communication with the inside  16   a  of each disc  16  as shown by arrow A of  FIG. 1 a   . The apertures  17  are provided so that the heating fluid can move from the shaft  10  to the discs  16  in order to heat the discs  16  and to provide a greater heating area to the material  5 . Each disc coupled around the shaft may be able withstand internal pressure of for example 2-3 Bar, or in some embodiments higher such as up to or over 6 Bar and for example up to 12 Bar without substantially deforming. A heat exchanger may operate at about atmospheric pressure, a cooler at the same or at 2-3 bar for example, and a disc dryer at an internal (steam) pressure of 6 Bar or over, up to 10-12 Bar for example. Preferably, the shaft  10  and discs  16  are closed to the material so that the heating fluid cannot contact the material  5  directly. The material  5  may be heated or dried through contact with the outside surfaces of the shaft  10  and discs  16 . 
     Referring to  FIGS. 1, 2, and 3  the discs  16  are formed from two or more annular plates  18 . Each plate  18  comprises one or more integral ribs  20  on its surface. Preferably, the ribs  20  extend between the inner edge  22  of the annular plate  18  and the outer edge  24  of the annular plate  18 . The ribs  20  may extend radially between corresponding points AA′ on the inner edge  22  and the outer edge  24 . The ribs  20  may extend fully or partially between the inner edge  22  and outer edge  24 . Alternatively, the integral ribs  20  may be provided between and substantially follow the circumferences of the edges  22 ,  24  or at any other orientation but most preferably radially between the inner  22  and outer edge  24  to provide maximum strength. The integral ribs  20  may be provided on the plates  18  in any suitable manner. Preferably, the integral ribs  20  are formed from crimps, bends, creases, stamps, or folds in the plates  18 . However, the integral ribs  20  may be formed from metal strips or bars that are connected to the plates  18 , or in any other suitable manner. The integral ribs  20  may provide structural strength or support to the plates  18  and discs  16 . This may help prevent the discs  16  from deforming or bursting under pressure when in use. This may also mean that a lesser number of plugs, or no plugs, may be required to provide strength to hold the discs  16  together when a pressurised heating fluid is introduced to the disc dryer  2 . 
     A disc  16  may be formed by connecting two plates  18  to one another around their outer edges  24 . The outer edges  24  may be welded to one another, or connected to one another in any suitable manner. The outer edges  24  of the plates  18  are connected to one another at an angle around their entire circumference such that the inner edges  22  of the two plates  18  are spaced apart from one another when the connection is complete. Preferably, the angle is an acute angle. A disc  16  may then be connected to the shaft  10  by connecting each of the inner edges  22  to the shaft  10 , with the inner edges  22  spaced apart from one another. The inner edges  22  may be welded to the shaft  10 , or connected to the shaft  10  in any suitable manner. When a disc  16  is connected to the shaft  10 , the disc  16  may appear convex when viewed from the side (as shown in  FIG. 1 ) due to the angle provided between the outer edges  24  of the two plates  18  and the inner edges  22  being spaced apart from one another. At least one aperture in the shaft  10  is provided between the two inner edges  22  of a disc  16  so that the shaft  10  is in fluid communication with a disc  16  and so that a heating fluid can move between them. 
     Referring to  FIG. 1 , each disc  16  may have one or more shovels  26  connected to a side or periphery of the disc  16 . The shovels  26  may rotate with the shaft  10  and discs  16 . The shovels  26  may move, scoop or push the material  5  within the disc dryer  2  and towards the output  8  in order to dry the material  5 . Alternatively, the discs  16  may be connected to the shaft  10  at a non-right angle so that a screwing effect from the rotating discs  16  encourages movement of the material  5 . 
     Referring to  FIGS. 4 and 5 , in the preferred embodiment, each plate  18  may be formed from a length of a sheet of a suitable material  28  such as steel or any other suitable material. Preferably, the sheet of material  28  has a longer length L than width W. For example, the sheet of material  28  may be 6120 mm long and 550 mm wide. A plate  18  may be formed by rolling the sheet of material  28  in a roll forming mill. The integral ribs  20  may be rolled into the sheet of material  28  as it is passed through the roll forming mill. Each integral rib  20  may be relatively deeper at one long edge (becomes the inner edge  22  of the resultant annular plate  18 ) of the material than the other long edge (becomes the outer edge  24  of the resultant annular plate  18 ) of the material. This may cause the sheet of material  28  to curve greater around the deeper ends of the ribs  20  so that it is formed into an annular shape once it has been entirely passed through the rolling mill. The two ends of the sheet of material  28  may be connected to one another at a joint  30  (shown in  FIG. 3 ) in order to form the completed plate  18 . The two ends may be welded to one another or connected to one another in any other suitable manner. This forms an annular plate  18  having a central aperture (defined by the inner edge  22 ) of sufficient size to fix around the shaft of the disc dryer. 
     The sheet material  28  and in particular the resultant plate  18  should have sufficient dimension for use in industrial applications. In the case of disc dryers, preferably the resultant plate  18  has an inner edge/central aperture radius r 1  (shown in  FIG. 3 ) of at least 0.2 m but more preferably between 0.2 and 0.5 meters, an outer edge radius r 2  (shown in  FIG. 2 ) of at least 0.4 m but more preferably between 0.4 and 1.5 meters, and a thickness t (shown in  FIG. 1 a   ) of at least 6 millimetres but more preferably between 6 and 12 mm. It will be appreciated that other dimensions for the resultant plate or disc may be utilised in disc dryers or other industrial applications and the above dimensions are only exemplary and not intended to limit the scope of the invention. 
     In an alternative embodiment, the plates  18  may be formed from an annular shape cut from a flat sheet of material. The annulus of material may have one or more ribs  20  folded, crimped or punched into its surface in order to form a plate  18  such that the ribs  20  are integral with the plate  18 . 
     The discs  16  and plates  18  may be of shapes other than circular, such as oval or square or rectangular in shape (typically with radiused corners), all of which are included within the term ‘annular’ in this specification and claims. Also, the shaft  10  may have a rectangular cross-section and the plates  18  and discs  16  having corresponding rectangular apertures for fitting the discs  16  around the shaft. 
     As referred to previously the discs in a conventional disc dryer or similar have flat surfaces and are fitted with cross pins that span between the two annular plates forming each disc to prevent the discs from deforming or bursting under steam pressure, as shown in  FIG. 6 . At construction of the disc dryer or retrofitting of replacement discs, fitting cross pins to each disc requires drilling or cutting holes through the disc and pressing in and welding of many individual cross pins which is labour intensive and is carried out when constructing a new disc dryer or retro-fitting an existing dryer with new discs when the existing discs have worn. The need for fitting or replacing such cross pins is removed or at least reduced wuth the construction of the invention. 
     The foregoing description of the invention includes preferred forms thereof. Modifications may be made thereto without departing from the scope of the invention.