Patent Publication Number: US-8522589-B2

Title: Machine of variable linear structure for the formation of tubes

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention refers to a machine for the formation of tubes, called “of variable linear structure”, which comprises a plurality of forming stations, placed in series with each other, which progressively bend a strip of sheet metal to form a tube, followed by at least one finishing station which further brings together the edges of the bent strip of sheet metal in view of the final welding. 
     2. Description of the Related Art 
     Machines for forming tubes by means of continuous bending of sheet metal are well known to the art and comprise, in series with each other, a plurality of stations in which the strip of sheet metal is progressively deformed by pairs of rollers having matching profiles. 
     These machines of the prior art have the drawback of making it necessary to replace the pair of rollers when it is desired (or necessary) to change the diameter of the tube produced, which leads to more or less long machine downtimes which reduce the productivity of the plant. 
     BRIEF SUMMARY OF THE INVENTION 
     To overcome this serious drawback, machines for forming tubes by means of continuous bending of sheet metal have been proposed (such as, for example, that described in European patent EP 1 393 830 in the name of the Applicant) in which the two pairs of rollers with matching profiles belonging to a station can make rototranslational movements of the same amplitude but in opposite directions, making it possible to use the same pairs of rollers to produce tubes whose diameter falls within a more or less broad range of values. 
     Object of the present invention is to realise a machine “of variable linear structure” for the formation of tubes, which improves the performance of machines of the type described, for example, by the aforementioned European patent since it allows the range of values of the diameter of the tubes to be widened without having to replace the pairs of rollers. 
     This object is achieved by means of a machine which has the characterising features indicated in independent claim  1 . 
     Further advantageous characteristics of the invention form the subject matter of the dependent claims. 
     A machine for continuous formation of tubes realised according to the invention comprises, in series with each other, forming stations which progressively bend a strip of sheet metal and at least one finishing station which further brings together the edges of the bent strip of sheet metal in view of the final welding. 
     Each forming station comprises two pairs of idle forming rollers which make rototranslational movements of the same amplitude but in opposite directions and the at least one finishing station comprises four idle forming rollers able to make movements of the same amplitude and direction according to 90° axes. 
     The profile of the lower rollers of each forming station is elliptical with a decreasing curvature from the outer edge to the inner edge of said roller, that of the upper rollers of the first forming station is elliptical with an increasing curvature from the outer edge to the inner edge of said roller, that of the upper rollers of the forming stations subsequent to the first one (hereafter called “second forming stations”) is circular and that of the forming rollers of the at least one finishing station is concave with a constant curvature. 
     The radius of the circular profile of the upper rollers of each second forming station preferably corresponds to the minimum radius of curvature of the bent strip of sheet metal in correspondence of said second forming station and the curvature of the concave profile of the forming rollers of the at least one finishing station corresponds to the maximum curvature of the bent strip of sheet metal in correspondence of said finishing station. 
     A machine according to the invention is called “of variable linear structure” since (as indicated very diagrammatically in  FIGS. 5 and 7 ) makes it possible to produce tubes of different diameters by changing the reciprocal positions of the two pairs of rollers and those of each of the rollers of each pair. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described with reference to purely exemplifying (and therefore non limiting) embodiments thereof illustrated in the appended figures, wherein: 
         FIG. 1  shows diagrammatically a perspective view of a machine for the formation of tubes realised according to the invention; 
         FIG. 2  shows diagrammatically a side view of the machine of  FIG. 1 ; 
         FIG. 3  shows diagrammatically a front view and an enlarged detail ( FIG. 3   a ) of the first forming station of the machine of  FIG. 1 ; 
         FIG. 4  shows diagrammatically, enlarged, a pair of forming rollers belonging to the first forming station of  FIG. 3 ; 
         FIG. 5  shows diagrammatically, enlarged, the position assumed by the two pairs of forming rollers of the first forming station of  FIG. 3  to produce three tubes of different diameters; 
         FIG. 6  shows diagrammatically a front view and an enlarged detail ( FIG. 6   a ) of a second forming station of the machine of  FIG. 1 ; 
         FIG. 7  shows diagrammatically, enlarged, the position assumed by the two pairs of forming rollers of the second forming station of  FIG. 6  to produce the three tubes of different diameters of  FIG. 5 ; 
         FIG. 8  shows diagrammatically a front view and an enlarged detail ( FIG. 8   a ) of one of the containment stations situated downstream of the first forming station and of each of the second forming stations; 
         FIG. 9  shows diagrammatically a front view ( FIG. 9   a ), a side view ( FIG. 9   b ) sectioned along the plane F-F of  FIG. 9   a  and an enlarged detail ( FIG. 9   c ) of a finishing station belonging to the machine of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the appended figures corresponding elements will be identified by means of the same reference numerals. 
       FIG. 1  shows diagrammatically a perspective view of a machine  1  according to the invention for the formation of tubes  2  which comprises, in series with each other, traction means  13  for the strip of sheet metal  4  (which enters the machine  1  in the direction of the arrow I), a first forming station  3 , second forming stations  3 ′, containment stations  12  (each of which is situated downstream of a forming station), at least one finishing station  5  and at least one welding station (per se known and omitted in  FIGS. 1 and 2 ), from which the tube  2  exits in the direction of the arrow U. 
     In the embodiment illustrated in  FIGS. 1 and 2  the machine  1  comprises five second forming stations  3 ′, six containment stations  12  (visible in the side view of  FIG. 2 ) situated downstream of the forming stations ( 3   3 ′) and two finishing stations  5  but, without departing from the scope of the invention, the number of second forming stations  3 ′ (and, consequently, that of containment stations  12 ) and finishing stations  5  can vary to meet the particular requirements of a specific machine  1 . 
     The traction means  13  will not be described because they are per se known. The first forming station  3  will be described with reference to  FIGS. 3-5 , a second forming station  3 ′ will be described with reference to  FIGS. 6-7 , a containment station  12  will be described with reference to  FIG. 8  and a finishing station  5  will be described with reference to  FIG. 9 . 
       FIG. 2  shows diagrammatically a side view of the machine  1  of  FIG. 1 , which makes it possible to see more clearly the containment stations  12  situated downstream of a forming station ( 3 ,  3 ′). 
       FIG. 3  shows diagrammatically a front view of the first forming station  3  of the machine  1 , symmetrical with respect to the midline, which comprises two vertical uprights  31  which support two horizontal traverses  32 , sliding along the uprights  31 ; along each traverse  32  slide two shoes  33 , on each of which is present a pivot  34  which acts as a fulcrum for rotation of a unit  35  that carries one of the forming rollers ( 8 ,  8 ′). 
     The pivots  34  and the units  35 , which can be seen better in  FIG. 3A , have not been designated with the corresponding reference numerals in  FIG. 3  for the sake of clarity of the graphic representation. 
     This supporting structure ( 32 ,  33 ,  34 ) allows the axes of the forming rollers ( 8 ,  8 ′) to perform a rototranslational movement, in the vertical plane, inside the forming station  3  that allows a considerable freedom in positioning and orienting the rollers ( 8 ,  8 ′) of each pair, whilst always keeping them in contact with each other, to adapt them to the diameter of the tube to be produced, as schematically indicated in  FIG. 5 , which shows the position assumed by the two pairs in rollers ( 8 ,  8 ′) for three diameters of the tube  2  coming within the tubes  2  that can be produced without replacing the forming rollers ( 8 ,  8 ′). 
     The sliding movements of the horizontal traverses  32  along the uprights  31  and of the shoes  33  along the traverses  32  and the rotation of the units  35  around the relative pivots  34  are of the same amplitude and opposite direction, take place along guides indicated schematically with dashed lines in  FIG. 3  and are realised by means of activating means not described herein because they are per se known and not explicitly indicated in  FIG. 3  for the sake of simplicity of the graphic representation. 
       FIG. 3A  shows diagrammatically, enlarged, the area of the first forming station  3  comprising the two pairs of rollers ( 8 ,  8 ′), supported by the units  35 , which deform the outermost area of the strip of sheet metal  4 . 
       FIG. 4  shows diagrammatically, enlarged, a pair of forming rollers ( 8 ,  8 ′), realised according to the invention, belonging to the first forming station  3 ; from  FIG. 4  it can be seen that the profile of the lower rollers  8 ′ is elliptical with a curvature decreasing from the outer edge to the inner edge of the roller  8 ′, whereas the profile of the upper rollers  8  is elliptical with a curvature increasing from the outer edge to the inner edge of the roller  8 . 
     The ellipses to which the profiles of the rollers  8  and  8 ′ belong have been indicated with dashed lines in  FIG. 4 . 
       FIG. 5  shows diagrammatically, enlarged, the position assumed by the two pairs of forming rollers ( 8 ,  8 ′) of the first forming station  3  to produce three tubes  2  of different diameter coming within the tubes  2  that can be produced without replacing the forming rollers ( 8 ,  8 ′): the elliptical profiles of the rollers  8  and  8 ′ allow the radius of curvature of the outermost areas of the strip of sheet metal  4  to be modified by modifying only the position and orientation of the rollers ( 8 ,  8 ′). 
       FIG. 6  shows diagrammatically a front view of one of the second forming stations  3 ′ of the machine  1 , situated downstream of the first forming station  3 , from which it differs essentially in that the upper rollers  8 ″ have a circular profile whose radius corresponds to the minimum radius of curvature (within the range of tubes  2  that can be produced without replacing the forming rollers  8 ′ and  8 ″) of the bent strip of sheet metal  4  in correspondence of said second forming station  3 ′ and in that the pairs of forming rollers ( 8 ′,  8 ″) belonging to the second forming stations  3 ′ deform the inner part of the strip of the sheet metal  4 . 
     The pivots  34  and the units  35 , seen better in  FIG. 6   a , have not been designated in  FIG. 6  with the corresponding reference numerals for the sake of clarity of the graphic representation. 
       FIG. 6   a  shows diagrammatically, enlarged, a pair of forming rollers ( 8 ″,  8 ′), realised according to the invention, belonging to a second forming station  3 ; from  FIG. 6   a  it can be seen that the profile of the lower rollers  8 ′ is elliptical with a curvature decreasing from the outer edge to the inner edge of the roller  8 ′, whereas the profile of the upper rollers  8 ″ is circular. 
       FIG. 7  shows diagrammatically, enlarged, the position assumed by the two pairs of forming rollers ( 8 ′,  8 ″) of the second forming station  3 ′ of  FIG. 6  to produce the three tubes of different diameter of  FIG. 5 : the elliptical profile of the lower rollers  8 ′ allows the radius of curvature of the inner part of the strip of sheet metal  4  to be modified by modifying only the position and orientation of the forming rollers  8 ′ and  8 ″. 
     The amplitude of the rototranslational movements permitted to the forming rollers ( 8 ,  8 ′,  8 ″) by the supporting structure ( 32 ,  33 ,  34 ) and the particular profiles of the forming rollers ( 8 ,  8 ′,  8 ″) allow the range of values of the diameter of the tubes which can be produced without having to replace the forming ( 8 ,  8 ′,  8 ″) to be increased with respect to machines of the prior art. 
     Moreover, from the foregoing description it is obvious that, in the machine of the present invention, the strip of sheet metal  4  is not deformed by pairs of forming rollers ( 8 ,  8 ′,  8 ″) having matching profiles: this represents an obvious feature able to differentiate the machine of the present invention from machines of the prior art including that described in European patent EP 1 393 830. 
       FIG. 8  shows diagrammatically a front view of one of the containment stations  12  situated downstream of the forming stations  3  and  3 ′. 
     This station  12 , symmetrical with respect to the midline, consists of two guides  81 , fixed to uprights  31 , each of which allows translation along an inclined axis of a shoe  82  which supports an idle roller  83 , having a concave profile, which guides and supports the strip of sheet metal  4  between two adjacent forming stations ( 3 ,  3 ′). 
     The containment stations  12  can be omitted without departing from the scope of the invention. 
     The upper part of each rollers  83  presents a protruding disc element  84  (seen better in  FIG. 8   a , which shows diagrammatically an enlarged detail of the containment station  12 ), which protrudes with respect to the body of the roller  83  to contain the edge  6  of the strip of sheet metal  4 . 
       FIG. 9   a  shows diagrammatically a front view ( FIG. 9   a ) and a side view sectioned along the plane F-F of  FIG. 9   a  ( FIG. 9   b ) of a finishing station  5  belonging to the machine  1 , which differs from the forming stations ( 3 ,  3 ′) previously described essentially in that each of the units  35  carries a forming roller  91  acting on the outer surface of the strip of sheet metal  4  bent to form the tube  2  and in that it further comprises a roller  92 , the position of which between the edges  6  of the strip of sheet metal  4  forming the tube  2  is adjustable by means of a lever  93  operated in a per se known manner. 
     The units  35  and the rollers  91  and  92 , seen better in  FIG. 9   c , have not been designated with the corresponding reference numerals in  FIG. 9   a  for the sake of clarity of the graphic representation. 
     The forming rollers  91  have a concave profile, with a constant curvature equal to the maximum value of the curvature presented by the strip of bent sheet metal  4  in correspondence to the finishing station  5  during production of one of the tubes  2  that can be produced without replacing the forming rollers ( 8 ,  8 ′,  8 ″) of the forming stations ( 3 ,  3 ′); the roller  92  has a convex V-shaped profile. 
     In  FIG. 9   b  the strip of sheet metal  4 , one of the forming rollers  91 , the roller  92  inserted in the strip of sheet metal  4  and the lever  93  which adjusts the position of the roller  92  can be seen. 
       FIG. 9   c  shows diagrammatically an enlarged detail of the finishing station  5  of  FIG. 9   a , where the forming rollers  91  acting on the outer surface of the strip of sheet metal  4  bent to form the tube  2  and the roller  92  situated between the edges  6  of the strip of sheet metal  4  can be seen better. 
     Without departing form the scope of the invention, a person skilled in the art can make to the above described machine with variable linear structure all the modifications and improvements suggested by normal experience and/or by the natural evolution of the art.