Patent Publication Number: US-2013240329-A1

Title: Conveyor Device For Conveyance Of Workpieces

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application is based upon and claims the benefit of PCT/EP2011/068764, filed 26 Oct. 2011; which is based on German patent application no. 10 2010 060 425.6, filed 9 Nov. 2010. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to a conveyor device for conveyance of blanks to a shaping machine. 
     BACKGROUND OF THE INVENTION 
     The invention relates to a conveyor device for conveyance of blanks and especially of bowls or cups to a shaping machine, such as a press. These bowls or cups have a pot-like shape with an essentially cylinder-shaped surface area and a base. In the shaping machine, the bowl is first held with the aid of a blank holder that engages the bowl. With the aid of a coaxial drawing punch that moves through inside the blank holder, the bowl is then shaped into a can body consisting of a can bottom and a can wall joined to the can bottom without joints. The applicant knows of such a shaping machine, for example, from German Patent Application 10 2010 019 323.2-14. 
     Known conveyor devices for shaping machines for example have a rotary table which have a plurality of recesses distributed across their circumference, each recess being able to engage a pot-like blank. By rotating this rotary table in steps, it is always possible to move one of the blanks into the desired working position in the shaping machine. 
     SUMMARY OF THE INVENTION 
     The blanks must be fed to the shaping machine. To this end, it is important that the conveyor device delivers the blanks or workpieces with adequate speed and high precision into a position in which the blank holder and drawing punch of the shaping machine or press can engage the bowl exactly. The shaping machine operates at stroke rates of approximately 400 to 500 strokes per minute. At such stroke rates, the conveyor device must convey a blank into position underneath the blank holder or underneath the drawing punch approximately every 120 to 150 milliseconds. In addition, the very thin-walled blank may not be damaged. If the wall of the blank is bent, this could otherwise cause the blank holder to no longer engage the blank but to instead mount onto the top edge of the wall and destroy the blank instead of clamping it into the desired position for the drawing punch. 
     Proceeding from the above, the present invention creates a conveyor device which guarantees a sufficiently high conveying capacity, ensures exact positioning of the blanks to be transported and prevents damage to the blank. 
     The conveyor device has the following characteristics. The conveyor device for conveyance of blanks ( 14 ), preferably has a drivable conveyor spindle ( 11 ), which has a spiral-like conveyor groove ( 20 ) on its exterior, has a guide element ( 28 ), which is arranged separated from the longitudinal axis ( 12 ) of the conveyor spindle ( 11 ) and extends along the conveyor spindle ( 11 ), wherein the inclination (α) of the conveyor groove ( 20 ) changes in the conveying direction (R) of the conveyor system ( 11 ). 
     The conveyor device has a drivable conveyor spindle, which is preferably operated at constant rotational speed. On its exterior, a spiral-like conveyor groove is provided in the conveyor spindle. In addition, a guide element, which extends along the conveyor spindle in the conveying direction, is arranged separated from the exterior of the conveyor spindle and thus separated from the conveyor groove. When the conveyor spindle rotates, the blanks arrive between the guide element and the spiral-like conveyor groove. The rotation moves them in the conveying direction between the conveyor spindle and the guide element in the conveying direction until they reach their end position, wherein the blanks rest against both the conveyor groove on the conveyor spindle and also against the guide element. 
     According to the invention, the course of the conveyor groove is chosen so that its inclination or pitch changes in the conveying direction. The conveying speed and clearance between two blanks along the conveyor path can be varied in this manner. This can ensure the achievement of a uniform conveyance of blanks out of a conveyor channel running toward the conveyor spindle on the one hand and ensure that a separation of the blanks can occur along the conveyor path of the conveyor spindle on the other hand. This separation is necessary because only one blank, which can also be called a bowl or cup, can be conveyed into the end position within a very short time window during the excess movement of the shaping machine in order to then be shaped into the can body by the shaping machine. 
     The drive of the conveyor spindle can occur at a constant rotational speed. The conveyor spindle can be driven by a special electrical drive device, such as a servomotor. Alternatively, it is also possible to embody the drive device of the conveyor spindle as an auxiliary drive of the shaping machine. The conveyor spindle provides for continuous feeding of blanks conveyed from the congestion to the conveyor spindle and into the working position or end position in the shaping machine. Exact positioning of the blanks is guaranteed. Furthermore, appropriate choice of the inclination of the conveyor groove and the rotational speed of the conveyor spindle will optimally exploit the smooth running of the shaping machine. 
     Preferably, the inclination of the conveyor groove is constant on a front end section as viewed in the conveying direction. The blanks conveyed in congestion in a conveyor channel are seized by the conveyor spindle within this front end section. In the front end section, the diameter of the conveyor spindle can be smaller than that in the subsequent sections in the conveying direction. 
     It is furthermore advantageous for the inclination of the conveyor groove in a center section joined to the front end section in the conveying direction to be larger than in the front end section. The inclination or pitch of the conveyor groove in the center section consequently increases in relation to the front end section. In the center section it can continuously rise in the conveying direction. The blanks are separated in this center section. Their clearance increases as viewed in the conveying direction. The diameter of the conveyor spindle and/or the depth of the conveyor groove can increase if the inclination or pitch of the conveyor groove rises. The blanks are encompassed within a larger circumferential range due to the increasing depth of the conveyor groove. Since the conveying speed of the blanks increases as the pitch increases, this ensures reliable and damage-free transport of the blanks. 
     It is furthermore advantageous for the inclination of the conveyor groove in a rear end section joined to the center section to decrease in the conveying direction. After the separating, the conveying speed along the conveyor path can thereby be reduced before the end position is reached. In the preferred embodiment example, the blanks are conveyed out of a conveyor channel along a straight conveyor path and into their end position. 
     As viewed in the conveying direction, the conveyor groove in a rear end section of the conveyor spindle terminates in a circular circumferential recess running around the longitudinal axis of the conveyor spindle. When a blank reaches the circumferential recess, linear conveying movement is no longer generated even during continuous rotation of the conveyor spindle. The blank remains in this end position. A positioning means adjoining the circumferential recess in the conveying direction can be present to establish this end position precisely. A blank sits in its end position on this positioning means. The positioning means can be an end flange of the conveyor spindle for example or a stop element separate from the conveyor spindle. This stop element preferably has a prismatic stop face. 
     Changing the pitch or inclination of the conveyor groove accelerates or slows down the transported blanks. In this process, the change in pitch of the conveyor groove is set so that the positive or negative acceleration of the blanks that it causes, as viewed in the conveying direction, does not have a jump discontinuity. The time derivative of the acceleration of the blanks along the linear conveyor path in the conveying direction is therefore continuous. In this manner, a gentle transport of the blanks without jerks therefore takes place. 
     In one embodiment example, the guide element can be embodied as another, second conveyor spindle. The blanks are then transported into their end position between the two conveyor spindles. The two conveyor spindles each have a conveyor groove. They synchronously rotate in opposite direction to one another. In another embodiment, the guide element can be embodied as a guide rail having an essentially flat guide surface. 
     Advantageous embodiments of the conveyor device arise from the dependent claims and the description. The description is limited to essential characteristics of the invention and other facts. 
    
    
     
       IN THE DRAWINGS 
       The drawing is to be considered supplementary. The drawing shows:  FIGS. 1 through 3  each an embodiment example of the conveyor device in schematic top view along the conveying direction. 
         FIG. 1  depicts a first embodiment example of conveyor device  10  having conveyor spindle  11 . 
         FIG. 2  shows a second embodiment conveyor device  10 .  FIG. 2  essentially corresponds to the first embodiment except that stop element  32  is configured separately from conveyor spindle  11  and has a stop face  33 . 
         FIG. 3  shows a third embodiment of conveyor device  10  including a second conveyor spindle identified as supplementary conveyor spindle  35 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The above detailed description of the present invention is given for explanatory purposes. It will be apparent to those skilled in the art that numerous changes and modifications can be made without departing from the scope of the invention. Accordingly, the whole of the foregoing description is to be construed in an illustrative and not a limitative sense, the scope of the invention being defined solely by the appended claims. 
       FIG. 1  depicts a first embodiment example of a conveyor device  10  having a conveyor spindle  11 . The conveyor spindle  11  is driven around its longitudinal axis  12  preferably with constant rotational speed. A conveyor drive  13  of the conveyor device  10  serves this purpose. The conveyor drive  13  can be embodied as a separate electrical drive of the conveyor device  10  or as an auxiliary drive of a shaping machine, such as a press, not illustrated in detail. In any case, the conveyor drive  13  runs synchronously with the cycle of the shaping machine. 
     In the first embodiment example, the conveyor device  10  is assigned to a shaping machine for producing can bodies. The conveyor spindle  11  transports bowls  14  from a stowage area  15  into a conveyor channel  16  along a conveyor path S into an end position P. The blank  14  has a pot-like shape and will hereinafter be called a bowl or cup  14 . The end position P can also be called a working position. In this end position P, the bowl  14  is located in the shaping machine, which is not illustrated in detail, for further shaping into a can body. In particular, it is positioned flush coaxial to a blank holder or drawing punch of the shaping machine. In this process, the pot opening of the bowl points toward the blank holder or drawing punch. 
     The conveyor spindle  11  moves the bowls  14  straightly along the conveyor path S into their end position P. For this purpose, the conveyor spindle  11  has a spiral-like conveyor groove  20  which is provided on its exterior surface and is outwardly open. The inclination or pitch G changes along the conveyor path S in the conveying direction R. The conveyor spindle  11  has a front end section  21  which is assigned to the stowage area  15  of the conveyor channel  16 . Inside this front end section  21 , the pitch G or inclination α of the conveyor groove  20  is constant. The pitch G is essentially adapted to the size of the bowls  14 . In this front end section  21 , the bowls  14  are transported along the conveyor path S with very small clearance. The clearance between two adjacent conveyed bowls  14  is smaller than the diameter or smaller than the radius of the base of one bowl  14 . 
     The inclination α of the conveyor groove  20  is the angle that encloses the conveyor groove  20  in relation to a plane running perpendicular to the longitudinal axis  12 . A center section  22  of the conveyor spindle  11  is joined to the front end section  21  in a conveying direction R. In this center section  22 , the inclination α and thereby also the pitch G of the conveyor groove  20  increases in comparison to the inclination α or the pitch G in the front end section  21 . In the embodiment example, the diameter D of the conveyor spiral  11  also becomes larger with increasing inclination α or pitch G of the conveyor groove  20 . In  FIG. 1  it is evident that the diameter D 1  in the front end section  21  is smaller than the diameter D 2  in the opposite rear end section  23 . In the center section  22  located therebetween, the diameter D increases with the inclination α or the pitch G. The groove depth of the conveyor groove  20  also rises with the increase of the diameter D. The groove depth of the conveyor groove  20  is therefore larger for a larger inclination α. The transport speed of the bowl  14  along the linear conveyor path S also rises with increasing inclination α or increasing pitch G of the conveyor groove  20 . To prevent damage, the groove depth of the conveyor groove  20  increases with increasing pitch G so that the bowl  14  to be transported rests against the conveyor spindle  11  inside the conveyor groove  20  along a larger circumferential range. 
     In one embodiment example of the conveyor device  10 , the inclination α and thereby also the pitch G of the conveyor groove  20  increases in comparison to the inclination α or the pitch G in the front end section  21  as previously described only in a first subsection of the center section  22  adjacent to the front end section  21 . In the further course of the center section  22 , the inclination α and thereby also the pitch G of the conveyor groove  20  can then be constant. This second subsection with constant inclination is optional and as a rule is provided for larger conveyor paths. 
     The rear end section  23  of the conveyor spindle  11  is joined to the center section  22 . In this rear end section  23 , the conveyor groove  20  flows into a circumferential recess  24 . The circumferential recess  24  is incorporated circularly coaxial to the longitudinal axis  12  of the conveyor spindle  11  in its exterior. The pitch G or inclination α of the conveyor groove  20  can be smaller in the rear end section  23  than in the center section  22 . The inclination α of the guide groove  23  in the rear end section  23  decreases in the direction of the circumferential recess  24  in order to reduce the transport speed of the bowl  14  along the conveyor path S before reaching the end position P. The change of the inclination α or pitch G can also affect only one portion of a rotation of the spiral of the conveyor groove  20  around the longitudinal axis  12  of the conveyor spindle  11 . 
     A guide element  28  extends along the conveyor path S separated from the exterior of the conveyor spindle  11  or conveyor groove  20 . The guide element  28  is embodied rail-like in the first two embodiment examples of the conveyor device  10  according to  FIGS. 1 and 2 . It has an essentially flat guide surface  29  which faces the conveyor spindle  11 . During the transport of the bowls  14  along the conveyor path S, the bowls  14  rest against a circumferential section on the guide groove  20  of the conveyor spindle  11  and, on their opposite side, rest against the guide surface  29  of the guide element  28 . The bowl  14  carries out a relative motion during its transport along the conveyor path S both relative to the conveyor spindle  11  and also relative to the guide element  28 . During this relative motion, the bowl  14  can slide along the guide element  28  or roll on it. 
     The cross-sectional shape of conveyor groove  21  is adapted for example to the cylindrical contour of the pot-like bowls  14 . Viewed in cross section, this can have a circular-arc-shaped course, particularly in the region of the largest groove depth, the radius of this course preferably corresponding approximately to that of the bowl  14 . But alternatively, the groove  14  can also have any other desired contour so that the conveyor groove  20  is not adapted to the contour of the bowl  14 . The bowl can be embodied as a polygon in cross section, particularly a regular polygon, a square for example, or as an oval or in any other shape. 
     A positioning means  30  is provided adjacent to the circumferential recess  24 . The positioning means  30  serves for setting the end position P of a bowl  14  at the end of the conveyor path S. In the first embodiment example of the conveyor device  10  according to  FIG. 1 , the positioning means  30  is formed by an end flange  31  of the conveyor spindle  11 . The end flange  31  borders the circumferential recess  24  in the conveying direction R so that the circumferential recess  24  forms an annular groove arranged coaxial to the longitudinal axis  12 . 
     The first embodiment example of the conveyor device  10  according to  FIG. 1  operates as follows: 
     A number of bowls  14  lined up one after another in a row are situated in the stowage area  15  of the conveyor channel  16 . A corresponding inclination of the conveyor channel  16  for example feeds them to the front end section  21  of the of the conveyor spindle  11 . The conveyor drive  13  rotates the conveyor spindle  11  around its longitudinal axis  12  with constant rotational speed. The open end of the conveyor groove  20  captures one bowl  14  after another out of the stowage area  15  on the front end section  21 . The bowls  14  move along the conveyor path S due to the rotation of the conveyor spindle  11  and the inclination α of the conveyor groove  20 . The inclination α of the conveyor groove  20  is constant in the front end section  21 . The bowls  14  therefore also move at a constant speed along the conveyor path S. 
     In the center section  22 , the inclination α of the conveyor groove  20  increases in the first subsection adjacent to the front end section, thereby accelerating the bowls  14  and raising the conveying speed. At the same time, the pitch G of the conveyor groove  20  and the clearance between two adjacent conveyed bowls  14  increases. The bowls  14  are separated so to say. In a second subsection of the center section  22  joined thereto, the inclination of the conveyor groove can be constant. 
     Before reaching the circumferential recess  24  and therefore the end position P, the inclination α of the conveyor groove  20  decreases in the rear end section  23  and the transport speed of the bowls  14  drops. The bowls  14  therefore move gently into the end position P. As soon as the bowls  14  reach the circumferential recess  24 , they are in their end position P at the end of the conveyor path S. In this position, they are situated in the position inside a shaping machine in which they are seized by a blank holder or drawing punch of the shaping machine and are shaped. 
     The changes in inclination of the conveyor groove  20  or the changes in pitch are embodied so that the thereby caused transport movement of the bowls  14  occurs without jerks. This means that the change in acceleration of the bowls  14  along the straight transport path S is continuous. The acceleration of the bowls  14  does not have any jumps. Jump discontinuities in the acceleration of a body are observed as a jerk. The relatively thin-walled bowls  14  could thereby be damaged and bent in particular. This can lead to destruction of the bowl  14  in the subsequent processing by the shaping machine. 
       FIG. 2  shows a second embodiment example of conveyor device  10 .  FIG. 2  essentially corresponds to the first embodiment example according to  FIG. 1 . In contrast to the first embodiment example, the positioning means  30  configured as a stop element  32  which is configured separately from the conveyor spindle  11  and has a stop face  33 . In the embodiment example according to  FIG. 2 , the stop face  33  has a prismatic shape, so that the cylindrical exterior surface of the bowls  14  rests against the stop face  33  in at least two locations and defines the end position P. The stop element  32  is arranged in a straight extension of the conveyor path S. 
     Another difference of the second embodiment example relative to the first embodiment example consists of the fact that the circumferential recess  24  of the conveyor spindle  11  is open not only radially outwards, but is also open in the conveying direction R. In the second embodiment example, the stop element  32  is provided in place of the end flange  31 . In other respects, the second embodiment example according to  FIG. 2  corresponds to the first embodiment example according to  FIG. 1  in construction and function. To this extent reference is made to the preceding description of the first embodiment example. 
       FIG. 3  shows a third embodiment of conveyor device  10 .  FIG. 3  shows a second conveyor spindle, called a supplementary conveyor spindle  35  for better discriminability, spindle  35  is provided in place of rail-like guide element  28 . The conveyor path S runs between the conveyor spindle  11  and the supplementary conveyor spindle  35 . The two spindles  11 ,  35  are synchronously driven in opposite directions. The arrangement is symmetrical along the conveyor path S between the two spindles  11 ,  35  relative to a center longitudinal plane. The inclination α of the two spindles  11 ,  35  is therefore opposite but of equal size along the conveyor path S. 
     Also the clearance and therefore the gap between the two spindles  11 ,  35  varies depending on the diameter D of the two spindles  11 ,  35 . The longitudinal axis  12  of the conveyor spindle  11  and the longitudinal axis  36  of the supplementary conveyor spindle  35  are aligned parallel to one another. The conveyor spindle  11  corresponds to the conveyor spindle of the first embodiment example according to  FIG. 1 . The supplementary conveyor spindle  35  is constructed analogously to it, wherein there is provided only an oppositely wound conveyor groove  20 . The end position P of the conveyor path S is provided between the two circumferential recesses  24  of the conveyor spindle  11  on one side and the supplementary conveyor spindle  35  on the other side. The conveyor spindle  11  and the supplementary conveyor spindle  35  can each be driven around their respective longitudinal axis  12  or  36  by separate drive devices or by a common drive device. Here too, the drive device can be embodied as an auxiliary unit of the shaping machine as explained in connection with the first embodiment example. 
     In the third embodiment example, it is understood that a stop element  32  could be arranged as positioning means  30  at the end of the conveyor path S in place of the end flange  31  of the conveyor spindle  11  and the supplementary conveyor spindle  31 . The end flange  31  is nevertheless preferred for reasons of space. 
     In all embodiment examples, the drive device  13  of the conveyor spindle  11  or of the supplementary conveyor spindle  35  can also simultaneously serve for actuating a holding means  14 , which in  FIG. 1  is schematically indicated only in the form of an arrow. The holding means  40  can be used to keep the bowl  14 , which is in its end position P, from prematurely falling into a mold of the shaping machine. The holding means  40  releases the bowl  14 , which is in the end position P, only at a defined time when the plunger of the shaping machine is supposed to shape the bowl  14 . For sake of example, a movable disc or the like can serve as holding means  40 . 
     The invention relates to a conveyor device  10  for conveyance of bowls  14  from a stowage area  15  into a predetermined end position P. In this end position P, the bowl  14  is positioned so that it can be shaped into a can body by the stroke of the plunger of the shaping machine. The conveyor device  10  has a conveyor spindle  11  which has a conveyor groove  20  on its external circumference. On the front end area  21  assigned to the stowage area  15 , the inclination α and the pitch G of the conveyor groove  20  are constant. The front end section  21  is joined to a section  22  in which the inclination α of the conveyor groove  20  is larger than in front end area  21 . The conveyor spindle  11  is preferably driven at constant rotational speed and ensures that the bowls  14  are transported in a straight line along the conveyor path S. In the process, the conveyor spindle  11  slides along the bowl  14  to be transported. 
     List of Reference Characters 
     
         
           10  conveyor device 
           11  conveyor spindle 
           12  longitudinal axis of  11   
           13  conveyor drive 
           14  bowl 
           15  stowage area 
           16  conveyor channel 
           20  conveyor groove 
           21  front end section 
           22  center end section 
           23  rear end section 
           24  circumferential recess 
           28  guide element 
           29  guide flange 
           30  positioning means 
           31  end flange 
           32  stop element 
           33  stop face 
           35  supplementary conveyor spindle 
           36  longitudinal axis of  35   
           40  holding means 
         α inclination 
         G pitch 
         P end position 
         R conveying direction 
         S conveyor path