Patent Publication Number: US-6663523-B1

Title: Auxiliary chain for drawing assembly in drawing machines

Description:
FIELD OF THE INVENTION 
     This invention concerns an auxiliary chain for drawing assemblies in drawing machines. 
     The drawing assemblies to which the chain according to the invention is applied are of the type comprising two opposite and counter-rotating tracks which collaborate with a product being processed to draw it through a die plate of a drawing machine. 
     The auxiliary chain according to the invention is suitable to be arranged inside a respective track to reduce the friction between the latter and relative rigid supporting means, and to distribute uniformly the forces of thrust which act thereon during the drawing steps. 
     During the operating cycles, very high loads-may affect the tracks according to the reduction in section to be imparted to the products being worked. 
     BACKGROUND OF THE INVENTION 
     The state of the art includes drawing assemblies used in drawing machines and consisting of two counter-rotating tracks opposite each other with respect to the drawing axis, each comprising a plurality of links on each of which respective pads are mounted, suitable to grip and draw the metal product being worked through a draw plate. 
     Motion is supplied to every track by a pair of toothed wheels, normally a drive wheel and a driven wheel, which are mounted at the ends of a rigid supporting plate around which the track itself is closed in a ring. 
     In the state of the art, between the supporting plate and the relative track, an auxiliary chain is provided, wound around the supporting plate, on which the links of the track rest at least in the rectilinear segment of the latter. 
     These auxiliary chains are used to reduce the friction between the tracks and the relative supporting plate, and to discharge uniformly the high forces of thrust which act on the individual links of the tracks, particularly during the operational drawing cycles. 
     In the state of the art, the auxiliary chain is made up of links, and every individual link consists of a containing cage inside which two or more idler rolls are housed. 
     Each link also comprises first pins suitable to associate the different containing cages together, creating the structural connection of the chain, and second pins suitable to associate the individual idler rolls to the relative containing cages. 
     The pins, and particularly the first pins suitable to associate the individual links of the auxiliary chain, are subjected to considerable mechanical stresses since a large proportion of the thrust forces of drawing and compression discharged onto the idler rolls by the tracks of the drawing assembly are in fact discharged onto said pins. 
     The pins of conventional auxiliary chains, therefore, are easily subject to breakages, and when these happen, the machine necessarily has to be stopped for a long time. 
     Another disadvantage of conventional auxiliary chains is that the cages containing the idler rolls are difficult to achieve and assemble, particularly due to the presence of at least three pins for every link. 
     Furthermore, conventional auxiliary chains are not very flexible because each link comprises at least two idler rolls and therefore do not adapt very well to the profile of the supporting plate, particularly in the curved segments of the latter. 
     The present Applicant has devised and embodied this invention to overcome the shortcomings of conventional auxiliary chains and to obtain further advantages as shown hereafter. 
     SUMMARY OF THE INVENTION 
     The main purpose of the invention is to achieve an auxiliary chain for drawing assemblies in drawing machines which will be easy to achieve and assemble, efficient, resistant, unlikely to break or malfunction and suitable to bear very high loads. 
     Another purpose of the invention is to achieve an auxiliary chain suitable to adapt in the best possible way to the curves defined by the profile of the rigid supporting plate on which it is wound. 
     Another purpose of the invention is to achieve an auxiliary chain consisting of a limited number of components and wherein the same pin is used both to support an idler roll and also to couple two adjacent links together. 
     Another purpose is to achieve an auxiliary chain wherein the forces of thrust acting on the idler rolls are discharged uniformly over the entire link, thus reducing the risks of breakages. 
     In accordance with these purposes, an auxiliary chain according to the invention consists of a plurality of links, each comprising an idler roll, a join pin and two connection elements arranged opposite each other respectively on one side and the other of the link, each of which is suitable to cooperate with a respective end of the idler roll. 
     Each connection element is suitable to be arranged at least partly superimposed with respect to at least two adjacent idler rolls of the chain. 
     Each connection element is equipped with two through holes, respectively first and second, and each idler roll is equipped with an axial hole into which the relative pin is inserted. 
     In the auxiliary chain according to the invention, on both sides thereof, two of the adjacent connection elements are suitable to be partly superimposed one on top of the other in such a manner that the first hole of each connection element is suitable to align with the second hole of the adjacent connection element and also with the axial hole of an idler roll. 
     In the three holes thus aligned, the respective join pin is then inserted and left free to rotate but constrained at its ends at least to the more outward of the two, superimposed connection elements. 
     In the preferential embodiment of the invention, the join pin is inserted with a gap inside the axial hole of the relative idler roll, so that the thrust forces and the stresses transmitted by the tracks to the idler rolls do not affect the relative pins. 
     According to a variant, an element of association and constraint, such as, for example, a bushing or similar, is inserted into the first and second aligned holes of two adjacent and partly superimposed connection elements. According to one characteristic of the invention, the thrust forces transmitted by the tracks to the idler rolls are discharged prevalently onto the connection elements in correspondence with the zones of frontal and/or lateral contact between the latter and the idler rolls themselves. These contact zones are studied to discharge the forces acting on the idler rolls in a uniform and well-distributed manner, and absorb most of the stresses so as to preserve the join pins and thus increase the working life of the auxiliary chain. 
     In the preferential embodiment of the invention, the contact zones coincide substantially with the annular portions provided in correspondence with the two ends of every idler roll. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other characteristics of the invention will become clear from the following description of the preferred form of embodiment, given as a non-restrictive example, with reference to the attached drawings wherein: 
     FIG. 1 is a part view of a drawing assembly in a drawing machine using two auxiliary chains according to the invention; 
     FIG. 2 is a side view of a segment of an auxiliary chain according to the invention; 
     FIG. 3 shows a section from III to III of FIG.  2 . 
     FIG. 4 shows a section from IV to IV of FIG.  3 . 
     FIG. 5 is a part view of an exploded section of FIG. 3; 
     FIG. 6 shows an enlarged detail of FIG. 5; 
     FIG. 7 shows another enlarged detail of FIG.  5 . 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
     FIG. 1 is a part view of a drawing assembly  10  of a drawing machine comprising two tracks  11 , counter-rotating and opposite each other, symmetrical to the axis of drawing  12  of a product  13 , in this case a bar. 
     The assembly  10  is suitable to draw the product  13  through a die plate which is not shown in the drawings, located upstream of the drawing assembly  10 . 
     Each track  11  consists of a plurality of links  14  hinged together in correspondence with the relative ends; on each of them a relative pad  15  is solidly mounted, suitable to grip the product  13  in correspondence with the rectilinear segment of the track  11  and draw it. 
     Each track  11  is made to rotate by a driver toothed wheel  16  and returned by a driven toothed wheel, not visible in the drawings, mounted respectively at the opposite ends of a rigid supporting plate  17 . 
     Between the supporting plate  17  and the relative track  11  there is an auxiliary chain  18  according to the invention, on which the respective track  11  is suitable to rest at least in correspondence with its rectilinear segment. 
     The function of the auxiliary chain  18  is to reduce the friction between the track  11  and the relative supporting plate  17 , and to discharge, in a uniform and distributed manner, the thrust forces of drawing and compression acting on the individual links  14  of the tracks  11  during the drawing steps; these thrust forces may even be quite high, depending on the enormous drawing loads needed to obtain the desired reductions in section of the product  13  through the die plate or draw plate. 
     As shown in FIGS. 2-5, the auxiliary chain  18  according to the invention consists of a plurality of links  19  each comprising a roll  20 , two connection elements  21 , a join pin  22  and two bushings  23 . 
     The roll  20  is equipped with an axial hole  24  inside which the respective join pin  22  is inserted in such a manner that the ends  122  of the latter protrude by a defined segment, substantially coinciding with the height of the bushings  23 , from the ends of the roll  20 . 
     As shown in FIG. 6, each connection element  21  has a longitudinal section defined by a first segment  121  and a second segment  221 , substantially parallel, connected together by an intermediate inclined segment  321 . 
     The segments  121  and  221  have the same thickness “s” and are vertically offset with respect to each other by a value “ε” substantially equal to the thickness “s”. 
     With this structure, the first segment  121  of a connection element  21  of a first link  19  is suitable to position itself above the second segment  221  of a connection element  21  of the adjacent link  19 , the second segment  221  being contained in the space between the first segment  121  and a lateral face of the roll  20 . 
     As shown in FIG. 7, each bushing  23  is substantially shaped like a truncated cone, defined by three cylindrical coaxial parts, respectively  123 ,  223  and  323 , with a progressively decreasing section. 
     The first segment  121  of each of the connection elements  21  is equipped with a hole  25  having a first segment  125  and a second segment  225  with a section suitable to house, substantially due to their having the same shape, respectively the cylindrical parts  123  and  223  of the bushing  23 . The second segment  221  of the connection elements  21 , on the contrary, is equipped with a hole  27  suitable to house the cylindrical part  323  of the same bushing  23 . 
     As shown in FIG. 5, the hole  25  of a first connection element  21  is suitable to align with the hole  27  of a second connection element  21  of the adjacent link  19 , the holes  25  and  27  being aligned with the hole  24  of the roll  20  and with an axial hole  26  of the bushing  23 . 
     Inside the axial hole  26 , the end  122  of a respective pin  22  is suitable to be inserted and clamped; since two contiguous connection elements  21  are inserted into the holes  25  and  27 , the pin  22  is thus shared between two adjacent links  19 . 
     To be more exact, as shown in FIG. 7, the hole  26  has a first segment  126  with. a transverse section substantially equal to the transverse section of the pin  22 , a second intermediate segment  226  with a transverse section equal to the narrowest section of the end  122  of the pin  22 , and a third flared segment  326  inside which the end  122  is riveted. 
     The riveting of the ends  122  of the pin  22  (as shown with the line of dashes in FIG.  5 ), therefore, gives a stable connection between the various elements  20 ,  21  and  23  of a single link  19 , and also between two adjacent links  19 ; in this way, we obtain with a single pin  22  the function which in the state of the art is performed by at least two pins. 
     The intermediate segment  321  of each of the connection elements  21  comprises a protrusion  321   a , arranged orthogonal to the plane on which the relative element  21  lies and suitable to be inserted into the space defined between two adjacent rolls  20  (FIG.  3 ). 
     The protrusion  321   a  is suitable to define, together with the rectilinear part of the element  21 , zones of contact  28  cooperating with the corner zones of the opposite faces of the rolls  20  (FIG.  6 ). 
     The rolls  20  of the chain  18  according to the invention cooperate with the inner surface of the links  14  of the respective track  11  and rotate around their own axis, due to the drawing action imparted thereto by the links  14 . 
     According to this characteristic mentioned above, the pins  22  constrain the various elements  20 ,  21  and  23  together, and also connect one link  19  to the adjacent link  19  by means of the connection elements  21 . 
     Unlike what happens in conventional auxiliary chains, the pins  22  are not directly subjected to the considerable thrusts of drawing and compression acting on the rolls  20  and transmitted thereto by the tracks  11  which in turn receive them from the product  13  being drawn. 
     In fact, gaps  29  are defined between the connection elements  21  and the ends of the rolls  20 , just as gaps  30  are defined between the axial hole  24  of each roll  20  and the relative pin  22  (FIG.  3 ). 
     In this way, the thrust forces acting on the rolls  20  are discharged mostly on the connection elements  21  only through the contact zones  28 ; this preserves the pins  22  from dangerous shearing forces. Moreover, since the contact zones  28  are made in a corner zone of the relative connection elements  21 , maximum resistance and maximum absorption of the stresses transmitted by the tracks  11  are obtained. 
     Another advantage of the auxiliary chain  18  according to the invention is that every link  19  comprises a single roll  20  and is therefore suitable to follow in the best possible way the curved segments of the winding path around the relative rigid supporting plate  17 . 
     In fact, every link  19  is suitable to oscillate with respect to the following link  19  since the clamping connection obtained by inserting a single pin  22  into the holes  25  and  27  of two connection elements  21  of two adjacent links  19  does not prevent their reciprocal rotation. 
     It is obvious that modifications and additions may be made to this invention, but these shall remain within the field and scope thereof. 
     For example, there may be no bushings  23  and the holes  25  and  27  may have a section suitable to house the ends  122  of the pin  22  directly. Or another attachment system may be used instead of riveting, such as for example of the type using screws or other removable attachment elements.