Abstract:
The corrugating roller ( 7; 9 ) for machines to produce corrugated cardboard, comprises: a hollow cylindrical body ( 7 B;  9 B), with an outer ( 7 D;  9 D) surface provided with corrugations ( 7 C;  9 C); a circuit for a heat-carrying fluid; and a pair of necks ( 7 E,  7 F;  9 E,  9 F), through at least a first ( 7 E;  9 E) of which said heat-carrying fluid is supplied. The body ( 7 B) and the necks ( 7 E,  7 F) are produced in a single block machined by removal.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is a divisional application under 37 CFR 1.53(b) of prior application Ser. No. 10/860,500 filed Jun. 3, 2004, now abandoned. 

   FIELD OF THE INVENTION 
   The present invention pertains to a corrugating roller to produce corrugated cardboard. 
   The invention also relates to a “single facer” machine to produce corrugated cardboard, comprising a pair of corrugating rollers, between which a sheet of corrugated cardboard passes, and a pressure system to couple the sheet of corrugated cardboard with a sheet of smooth cardboard. 
   BACKGROUND OF THE INVENTION 
   The corrugated cardboard is composed of a plurality of sheets of cardboard, alternately smooth and corrugated, glued to one another. To produce this type of cardboard, corrugating or “single facer” machines are used, wherein a pair of corrugating rollers, provided with longitudinal grooves that mesh together, form a nip through which a first sheet of cardboard passes, which is corrugated and provided with a glue on the crests of the flutes. The corrugated sheet is then glued to a smooth sheet or “cover”. The product thus obtained can be provided with a second smooth sheet, or cover. Differently, several products coming from a corrugating machine can be superimposed and glued to obtain a corrugated cardboard with several layers. 
   Corrugating machines of this type are described in EP-A-870598, EP-A-601528, U.S. Pat. No. 6,068,701, EP-A-786329, EP-A-1086805, US-A-20010047850, U.S. Pat. No. 5,415,720, EP-A-734849. 
   Corrugating rollers are relatively complex components. In fact, they have an internal heating circuit through a heat-carrying fluid, typically steam. The heat-carrying fluid circuit has an internal duct and a series of external ducts, in proximity to the cylindrical surface of the roller, to obtain efficient heat exchange. 
   Due to their complex nature, currently known corrugating rollers are produced with several components. For example, U.S. Pat. No. 4,917,664 describes a corrugating roller constituted by two head ends on which the shanks or necks to support the roller are provided. The head ends are connected to a hollow cylindrical body, on the outer surface of which ribs or grooves are produced to perform corrugation of the cardboard, and in the cylindrical wall of which ducts are produced parallel to the axis of the roller for circulation of the heat-carrying fluid. The ducts are disposed to allow the heat-carrying fluid to flow alternately in one direction and in the opposite direction. 
   ES-B-2070726 describes a corrugating roller comprising a interchangeable external cylindrical jacket, on which grooves or corrugations are produced, fitted on a grooved and radially perforated central core. Once the jacket has been mounted on the central core, these grooves form longitudinal ducts for circulation of the heat-carrying fluid. The core is axially perforated to define an inlet duct and an outlet duct of the heat-carrying fluid. It forms, with its ends, the end necks or shanks of the roller. 
   ES-A-2110871 describes a corrugating roller comprising a hollow cylindrical body, at the ends of which two portions forming the shanks or necks of the roller are inserted. One of the two portions has an inlet duct and an outlet duct for the heat-carrying fluid, which circulates in an interspace with an annular section formed by the inner wall of the hollow cylindrical body and by a pipe coaxial to said body. 
   EP-B-657275 describes a corrugating roller comprising a hollow cylindrical body, in the wall of which circulation ducts for the heat-carrying fluid are produced. The ducts are fed through head ends forming the necks or shanks supporting the roller. The head ends are inserted into the axial cavity of the cylindrical body. 
   U.S. Pat. No.5,899,264 and EP-A-1962590 describe a corrugating roller constituted by a hollow cylindrical body, in the wall of which ducts for circulation of the heat-carrying fluid are produced. The fluid is fed through an axial hole produced in one head end of the roller, fixed to the central cylindrical body and passes through a duct coaxial to the cylinder, extending through the hollow cylindrical body thereof, to the opposite head end from which the fluid is distributed radially to the peripheral ducts produced in the cylindrical wall of the body of the roller. Radial holes in the first head end collect the spent heat-carrying fluid and convey it outside. 
   All the constructional solutions described in the aforesaid documents are complex and costly and in some cases somewhat inefficient from a thermal point of view, as they do not allow efficacious heating of the outer surface of the corrugating roller. 
   SUMMARY OF THE INVENTION 
   The object of the present invention is the production of a corrugating roller for corrugating machines to produce corrugated cardboard which is simple and inexpensive to produce, maintaining a high level of thermal efficiency, that is high characteristics of heat exchange between the heat-carrying fluid and the roller towards the outer surface thereof. 
   Essentially, according to the invention, a corrugating roller is provided for machines to produce corrugated cardboard, comprising: a hollow cylindrical body, with an outer surface provided with corrugations; a circuit for a heat-carrying fluid; and a pair of necks, through at least a first of which said heat-carrying fluid is supplied. Characteristically, according to the invention, the body and the necks are produced in a single block machined by removal. This simplifies and reduces the construction costs of the corrugating rollers. 
   According to a practical embodiment, the corrugating roller comprises an axial cavity extending through a first of said two necks and essentially for the entire axial extension of the cylindrical body of the roller, and a plurality of peripheral longitudinal ducts, parallel to the axis of the roller in proximity to the cylindrical surface of said body, in communication with the axial cavity through a first series of essentially radial ducts and a second series of essentially radial ducts for flow of the heat-carrying fluid from the axial cavity into said peripheral longitudinal ducts and therefrom back into the axial cavity. The axial cavity, the longitudinal ducts and the radial ducts are advantageously obtained by boring. 
   Further advantageous characteristics and embodiments of the roller according to the invention are indicated in the attached dependent claims. 
   The invention also relates to a corrugating machine comprising two corrugating rollers, one of which or preferably both of which are produced by a single block of material machined by mechanical removal. 
   The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which the preferred embodiment of the invention is illustrated. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
       FIG. 1  shows a side view of a corrugating machine; 
       FIGS. 2 and 3  show longitudinal sections of the two corrugating rollers, respectively lower and upper, of the machine in  FIG. 1 ; 
       FIG. 3A  shows an enlargement of an end portion of a roller; and 
       FIGS. 4 and 5  show cross sections according to IV-IV and V-V in  FIGS. 2 and 3  respectively. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to the drawings in particular,  FIG. 1  shows a corrugating machine or “single facer” in which the invention may be incorporated. The machine, indicated as a whole with  1 , has a load-bearing structure  3 , inserted into which is a unit  5  comprising a first corrugating roller  7  and a second corrugating roller  9 . 
   On its cylindrical surface the corrugating roller  7  has a plurality of ribs or corrugations  7 C, meshing with corresponding corrugations or ribs  9 C of the second corrugating roller  9 . A web material N, such as a sheet of paper or cardboard, is made to pass through the nip defined between the two rollers  7  and  9 , where the ribs  7 C and  9 C mesh with each other, to be subjected to corrugation between the two rollers  7  and  9  and remains adherent, upon delivery from the nip between said rollers, to the first corrugating roller  7 . 
   The first corrugating roller  7  rotates about an axis  7 A according to the arrow f 7 , the axis  7 A being essentially fixed with respect to the unit  11  that supports the rollers  7  and  9 . Differently, the second corrugating roller  9  is carried by a pair of arms  13  hinged about an axis of oscillation  15 , parallel to the axis  7 A of the first corrugating roller  7  and to the axis  9 A about which the second corrugating roller  9  rotates according to the arrow f 9 . The second corrugating roller  9  is stressed against the first corrugating roller  7  by a pair of actuators (in the example shown a pair of “torpress”) indicated with  17  and acting on the two end arms  13  supporting the axis  9 A of the corrugating roller  9 . 
   A gluing unit, indicated as a whole with  31 , is fastened to the structure  3  of the machine. The gluing unit  31  is hinged about an axis of oscillation B parallel to the axes  7 A and  9 A of the corrugating rollers  7  and  9 . 
   The gluing unit  31  bears a glue tank  37 , from which glue is collected by a transfer cylinder  39  rotating according to the arrow f 39 . The transfer cylinder  39  is tangent to a gluing cylinder  41  rotating according to f 41  in the same direction as the transfer cylinder  39  and in contact therewith. In this way glue is transferred from the tank  37  to the cylindrical surface of the gluing cylinder  41  and therefrom to the crests of the web material N driven about the first corrugating roller  7  and previously deformed in the nip between the corrugating roller  7  and the corrugating roller  9 . 
   Along the extension of the corrugating roller  7 , downstream of the gluing area defined by the position of the gluing cylinder  41 , a pressure roller  55  is provided, supported by a pair of arms  57  hinged in  59  to the fixed structure  3  and stressed by actuators  61  so as to press the pressure roller  55  against the corrugating roller  7 . A second continuous web material, for example a sheet of paper material indicated with N 2 , guided by a cylinder  63 , is driven about the pressure roller  55 . The web material N 2  is applied with pressure by the roller  55  on the crests of the web material N previously provided with glue by means of the gluing cylinder  41 . The second web material N 2  constitutes the “cover” of the corrugated cardboard produced by the machine. Said cardboard, indicated with CO, is thus constituted by the corrugated web material N glued to the smooth web material N 2 . In a per se known way, this material is subsequently fed to another machine for a second smooth sheet to be applied to the opposite side and, if necessary, combined with other sheets of corrugated cardboard. 
   The corrugating rollers  7  and  9  are heated internally by circulation of a heat-carrying fluid, typically steam. Characteristically, according to the present invention, the corrugating rollers are produced in a single piece, that is “monobloc”, and the channels for fluid circulation, and the supporting necks are produced by machine removal from a single block. 
   The configuration of the two rollers  7  and  9  is represented in  FIGS. 2 to 5 . In particular, the roller  7  ( FIG. 3 ) has a cylindrical body  7 B with an essentially cylindrical side surface  7 D provided with corrugations  7 C. In proximity to the head ends of the roller the cylindrical surface  7 D has two essentially smooth bands or annular areas, that is without corrugations. 
   Two necks  7 E,  7 F produced in one piece by turning from the same metal block forming the main cylindrical body  7 B, are integral with the main cylindrical body  7 B. 
   An axial cavity  7 G extends through the neck  7 E, also extending along the axis of the cylindrical body  7 B until it is in proximity to the neck  7 F. Moreover, peripheral longitudinal ducts  7 H are produced in the cylindrical body  7 B, distributed (see  FIG. 5 ) with their axes on a geometrical cylindrical surface coaxial to the cylindrical surface  7 D of the corrugating roller  7 . The peripheral longitudinal ducts  7 H are produced by means of perforation of the cylindrical body  7 B and emerge on the opposed and parallel base surfaces  7 I of the roller. The peripheral longitudinal ducts  7 H are closed at their ends by caps  7 J. 
   Two series of essentially radial ducts, indicated with  7 K and  7 L, are produced by means of perforation from the outside in proximity to the head ends of the cylindrical body  7 B, at the level of the two smooth bands of the outer surface  7 D. Each radial duct intersects a corresponding peripheral longitudinal duct  7 H and emerges in the axial cavity  7 G. The surface holes produced to create the radial ducts  7 K and  7 L are closed with caps  7 M and  7 N. 
   At the level of the caps  7 N elements  7 P are inserted in the radial ducts  7 L to discharge the steam condensate that forms in the peripheral longitudinal ducts  7 H. These elements are visible in particular in the enlargement in  FIG. 3A  and their function is per se known and therefore does not require a detailed description. 
   A distributor element  7 Q is inserted into the axial cavity  7 G inside the neck  7 E, the structure of which is visible in particular in the enlarged detail in  FIG. 3A . The distributor element  7 Q has an essentially cylindrical extension, with an internal passage  7 R coaxial to the cavity  7 G, inside which a small tube  7 S is inserted. The small tube forms a fluid passage for delivery of the heat-carrying fluid, coming from a rotating manifold, not shown and per se known, towards the inside of the cavity  7 G. A fluid passage with an annular section  7 T, in which the radial ducts  7 L emerge, through inclined holes  7 V produced in the cylindrical wall of the distributor element  7 Q, is defined between the outer wall of the small tube  7 S and the surface of the inner passage  7 R of the distributor element  7 Q. The spent heat-carrying fluid coming from the radial ducts  7 L is collected through the fluid passage with annular section  7 T. 
   Therefore, by means of mechanical machining of a single metal block, a channel is formed in the roller  7  for the heat-carrying fluid which from the distributor element  7 Q makes the heat-carrying fluid circulate from the neck  7 E into the cavity  7 G, through the radial ducts  7 K, in the peripheral longitudinal ducts  7 H and therefrom through the radial ducts  7 L back towards the distributor element  7 Q and herefrom to the rotating manifold, not shown. The heat-carrying fluid yields the majority of its heat to the outer cylindrical surface  7 D and to the ribs or corrugations  7 C of the roller. 
   As can be seen in the drawing, the axial cavity  7 G has a relatively small diameter with respect to the diameter of the cylindrical surface  7 D of the roller and the peripheral longitudinal ducts are positioned closer together with respect to said surface  7 D. In this way heat distribution is optimized through a heat-carrying fluid that enters the cavity  7 G and circulates therefrom into the peripheral longitudinal ducts  7 H and by conduction heats the surface  7 D and in particular the corrugations or ribs  7 C. In particular, the diameter of the axial cavity  7 G can be from a fourth to an eighth of the diameter of the cylindrical surface  7 D. Differently, the diameter of the geometrical cylindrical surface on which the peripheral longitudinal ducts lie is equal to or greater than more or less two thirds and preferably equal to or greater than three quarters of the diameter of the cylindrical surface  7 D, so that the ducts are located in proximity to the outer surface of the roller. 
     FIGS. 2 and 4  show the structure of the roller  9 . This structure is conceptually identical to the structure of the roller  7  with the exception of the different dimensions, as the roller  9  has an essentially smaller diameter. The various parts of the roller  9  shown in  FIGS. 2 and 4  are indicated with the number  9  followed by the same letter utilized in  FIGS. 3 ,  3 A and  5  for the corresponding parts of the roller  7 . It can be seen in the drawing that in this case the diameter of the internal cavity  9 G is greater with respect to the diameter of the cylindrical outer surface  9 D of the roller, the diameter of the cavity  9 G being more or less equal to a quarter of the outer diameter of the cylindrical surface. This is in view of the fact that the cross section of the cavities  7 G and  9 G must be essentially equal or similar to have the same flow rate of heat-carrying fluid. 
   The longitudinal axes of the peripheral longitudinal ducts are on an ideal cylindrical surface with a diameter approximately equal to three quarters of the outer diameter of the cylindrical surface  9 D and therefore in proximity to said surface to optimizie heat exchange. 
   In the example shown, the inlet and outlet of the steam for heating the roller are disposed on the same side of the roller. Nonetheless, it must be understood that the inlet and outlet could also be disposed on opposite sides of the roller. 
   The drawing purely shows a practical embodiment of the invention, which may vary in shapes and layouts without however departing from the scope of protection defined by the claims. Any reference numbers in the claims are provided purely for the purpose of facilitating reading in the light of the description and drawings and do not limit the scope of protection. 
   While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.