Patent Publication Number: US-2018044833-A1

Title: Fluid-driven apparatus for feeding a fabric in a process tumbler

Description:
TECHNICAL FIELD 
     This invention relates to a fluid driven apparatus for feeding a fabric in a process tumbler. 
     Prior Art 
     Currently used in the textile industry are process apparatuses, called “tumblers”, in which fabrics of various kinds are subjected to treatment, for example mechanical and/or heat treatment, to create characteristic and distinctive effects for different types of fabric. The fabric is fed—for example in open-width form and continuously—according to a method known in the industry, by means of an apparatus of this kind, which is equipped with a tubular duct whose transversal cross section is substantially rectangular and whose length is typically at least three times its width. 
     The duct comprises boundary walls which delimit an internal cavity inside the duct itself, ports for the passage of a gaseous fluid in a direction longitudinal to the duct into and out of the internal cavity and at least one lateral opening for the passage of the fluid in a transversal direction towards the internal cavity and made on the top and/or bottom wall of the duct. 
     A supply manifold for directing the fluid towards the tubular duct is abutted against the top and/or bottom opening of the duct, dividing it into two distinct stretches respectively downstream and upstream of its position. 
     Diverters associated with the supply manifold allow diverting the flow of gaseous fluid to one or the other of the two stretches of the duct which, depending on the direction fluid flow, operatively become delivery or suction duct stretches. 
     By effect of movement of the fluid supplied by the supply manifold, diverted and flowing along the duct cavity towards the outlet afforded by one of the two ports, the fabric, at the other port at the opposite end of the duct, is sucked into the duct cavity together with the air and is forced to move along the cavity from one end to the other under the action of, and in the same direction as, the air flow. 
     In the prior art, the tubular duct has walls which are equidistant from each other. That means the cross section of the duct through which the fluid flows is the same at all points of the duct. 
     Although these feed apparatuses are widely used in this industry, they are not free of disadvantages and, depending on the type of fabric processed, can lead to critical conditions which are anything but negligible. 
     In effect, when processing, for example, very stiff, coated fabrics, imitation leather or other material having a high surface friction coefficient, the fabric tends to stick to the duct very easily. Moreover, if the process also involves the use of hot air, the problem becomes even worse. 
     As a result of the difficulty of moving along the duct, the fabric downstream of the manifold which blows air into the duct tends to curl up on itself, to increase its overall dimensions and to gradually reduce the size of the passage through which the air in the duct can flow. 
     The residual flow passing through the duct becomes more and more turbulent, thus dissipating drive power and, as it loses carrying capacity, rapidly becomes unable to support and carry the fabric which eventually stops moving and occludes the duct. 
     DISCLOSURE OF THE INVENTION 
     The aim of this invention is to overcome the above mentioned disadvantages. According to the invention, this aim is achieved by a fluid-driven apparatus for feeding a fabric and whose technical features are defined in the appended claims. 
     Further advantages of the invention will become apparent from the detailed description of a non-limiting example embodiment of such an apparatus, illustrated in the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a schematic longitudinal cross section of a fabric feed apparatus known to operators in the industry; 
         FIG. 2  schematically represents the typical operation of the apparatus of  FIG. 1 ; 
         FIG. 3  is a schematic longitudinal cross section of an apparatus made according to this invention; 
         FIG. 4  schematically represents the typical operation of the apparatus of  FIG. 3  in a scaled-up longitudinal cross section. 
     
    
    
     EMBODIMENTS OF THE INVENTION 
     With reference to the accompanying drawings,  FIGS. 1 and 2  illustrate a prior art pneumatic apparatus for feeding a fabric in a tumbler—not illustrated—which processes fabrics in open-width form and continuously. 
       FIG. 3  shows a fluid-driven apparatus  1  of the kind shown in  FIGS. 1 and 2 , for feeding a fabric  7  and which essentially comprises: a tubular duct  2 ; a manifold  14  for supplying flows  3 , 4  of gaseous fluid into the tubular duct  2 ; and flow diverting means, embodied in this case by two flap valves  8  associated with the manifold  14  and contained therein. 
     More specifically, the duct  2  has a tubular profile with a substantially rectangular cross section and is provided with boundary walls at the top and bottom ( 11   a , 11   b ) and sides (not illustrated) delimiting an internal cavity  12  inside the duct. 
     At opposite open ends of it, the duct is also provided with ports  9  and  10  for the passage of the fluid in the form of flows  5 , 6  directed longitudinally, one into and the other out of the duct  2 . 
     Half way along it, the tubular duct  2  is provided with four further openings  13  formed in opposite pairs, passing through the top and bottom walls  11   a , 11   b , of the duct  2 . Connected to the openings  13  of the duct  2  is the manifold  14  which, thanks to its position—substantially half way along the duct  2 —divides the latter into two component stretches  15   a , 15   b  of equal length, one of which is delimited by the manifold  14  and the port  9  and the other by the manifold  14  and the port  10 . 
     According to the invention, at least one of the two stretches  15   a , 15   b —or preferably both of them—is divergent in shape, with a transversal cross section which increases in size from the manifold  14  to the port  9  or  10  associated with the stretch  15   a  or  15   b  of the duct  2 . 
     Small angles of divergence  16  have been found to be surprisingly optimal. Angles not greater than three sexagesimal degrees are preferable. 
     In  FIGS. 3 and 4 , the divergence of the stretches  15   a , 15   b  of the duct  2  is advantageously obtained by inclining only the top wall  11   a  relative to the bottom wall  11   b . This solution has proved surprisingly more effective than the solution in which the divergence is obtained by inclining the bottom wall  11   b  and keeping the top wall  11   a  horizontal or by inclining both of the walls  11   a , 11   b  at an angle to the horizontal. In a further embodiment, each of the two stretches  15   a , 15   b  of the duct  2  has a constant cross section in a first portion of it adjacent to the manifold  14  and a divergent shape with increasing cross section in the second portion of it. 
     In use, the operation of the apparatus  1  may be described with reference to  FIG. 4 . As may be inferred from  FIG. 4 , the two air flows  3  and  4 —if necessary, thermally conditioned and coming from a central preparation plant—come through the manifold  14  from different directions normal to the duct  2 . Inside the manifold  14 , the two air flows  5  and  6  are intercepted by the flap valves  8  and are diverted into the cavity  12  of the duct  2 , one above the fabric  7  and the other below it, so as to flow through one of the two stretches in the same direction: in the case illustrated, the stretch  15   b  of the duct  2 . By effect of the two flows  6 , the fabric  7  downstream of the manifold  14  is pushed by the two fluid flows  6 . The pushing action causes the fabric  7  to be curled and creased, whilst upstream of the manifold  14  in the stretch  15   a , it is pulled and sucked into the cavity  12  together with the gaseous fluid—outside the duct  2 —through the port  9  associated with the other stretch  15   a  of the duct  2 . 
     It should be noted that the divergence of the stretches  15   a  and  15   b , although only slight, produces a plurality of highly synergic, useful effects which allow the fabric  7  to be pneumatically supported and fed along the duct  2 . 
     In effect, as is clear from  FIG. 4 , the fabric  7  just downstream of the manifold  14 , although it starts curling, does not obstruct the flows  6  of gaseous fluid needed to move it. On the contrary, a virtuous circle is created in this zone of the apparatus  1 , because: thanks to the divergence, the air flow  6  is kept relatively constant and able to support the fabric  7 ; consequently, the fabric becomes less curled and moves more rapidly than it does in conventional apparatuses, where the stretches of duct are provided with equidistant walls. Reduced curling has the further advantage of leaving a wider and more useful gap between the fabric  7  and the walls  11   a , 11   b . This wider useful gap has a twofold benefit. On the one hand, it gives the flow of gaseous fluid a greater capacity to support and carry the fabric; and on the other, by coming between the fabric  7  and the walls  11   a , 11   b , it prevents the fabric  7  from coming into contact therewith, thus limiting friction and allowing it to move forward with much less resistance. 
     In other words, therefore, the divergence of the duct  2 —all other conditions being equal—allows the fabric  7  to be fed much more effectively and under much more favourable conditions of resistance which are particularly useful with coated fabrics or resin-impregnated fabrics with high surface adhesiveness. 
     From  FIGS. 3 and 4 , it may be noted that the apparatus  1  is perfectly reversible, which means that what has been said in relation to the stretch  15   b  of the duct  2  applies also to the other stretch  15   a , obviously if the operation of the process tumbler, that is, if the direction of movement of the fabric  7  therein, is reversed.