Abstract:
Stacking machines, delivery units, and methods suitable for handling and stacking sheets of material, and particularly sheets of magnetizable materials that are relatively heavy and susceptible to damage during a stacking operation. Such a stacking machine includes at least one delivery unit equipped with a belt and a magnetic unit. The belt and magnetic unit are adapted to operate in cooperation with each other to magnetically carry individual sheets of a magnetizable material from one side of the machine to another. The delivery unit may be part of a kit that can be installed as a unit on an existing stacking machine.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. Ser. No. 62/117,238, filed Feb. 17, 2015, the contents of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention generally relates to handling and stacking equipment for sheet-type articles and materials. The invention particularly relates to sheet handling and stacking machines adapted to stack sheets of tin plate and other metallic sheets that are relatively heavy and susceptible to damage during a stacking operation. 
         [0003]    “Tin plate” is a term that is commonly used to refer to metal sheet materials of the type used to produce the outer cylinders of cans, for example, food, beverage, and aerosol cans. Prior to being formed to produce a can, tin plate sheets are typically processed to have a printed surface so that each individual sheet provides the printed information desired or required for the final can product. The sheets are individually printed and stacked prior to being delivered to equipment that forms and welds the sheets and then assembles the resulting cylinder with one or more ends, for example, to produce a three-piece can. 
         [0004]    A particular stacking machine known in industry has been referred to as a Dexter Stacker, which had been manufactured by the Dexter Folder Company and/or its successor, Miehle-Goss-Dexter, Inc. A particular machine of this type is capable of stacking sheets at high rates onto a pallet. However, a problem encountered with such machines is that tin plate and other relatively heavy sheets tend to “dive” as they fall onto the pallet, causing the sheet to scratch the upper surface of the preceding sheet in the stack. In the case of printed tin plate used to produce cans, damage can occur to the printed surface. Because printed tin plate sheets must ordinarily undergo stacking prior to deliver to the forming equipment, there is a need to be able to stack the sheets without scratching their printed surfaces. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0005]    The present invention provides machines and methods suitable for handling and stacking sheets of material, and particularly sheets of magnetizable materials that are relatively heavy and susceptible to damage during a stacking operation. 
         [0006]    According to one aspect of the invention, a stacking machine includes at least one delivery unit comprising a belt and a magnetic means. The belt and magnetic means are adapted to operate in cooperation with each other to magnetically carry individual sheets of a magnetizable material from one side of the machine to another. 
         [0007]    According to another aspect of the invention, a method of stacking individual sheets of a magnetizable material uses a stacking machine to operate a belt and a magnetic means in cooperation with each other to magnetically carry the individual sheets from one side of the machine to another, and then stack the individual sheets on top of each other. 
         [0008]    According to yet another aspect of the invention, a kit is provided for modifying an existing stacking machine adapted to stack individual sheets. The kit comprises a belt and a magnetic means that are adapted to be installed on the stacking machine as a unit, which may be one of any number of units installed on the stacking machine to replace one or more existing delivery mechanisms previously installed on the stacking machine. 
         [0009]    Technical effects of the machines and methods described above preferably include the ability to convey and release individual sheets in a manner that will minimize damage to the sheets, including scratching of their surfaces, as well as minimize damage to sheets already in a stack on which the sheets are being dropped. 
         [0010]    Other aspects and advantages of this invention will be better appreciated from the following detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a perspective view representing a stacking machine equipped with multiple magnetic delivery units in accordance with a nonlimiting embodiment of this invention. 
           [0012]      FIG. 2  is a perspective view of a portion of the machine of  FIG. 1 . 
           [0013]      FIG. 3  is a perspective view of one of the magnetic delivery units of the machine of  FIGS. 1 and 2 . 
           [0014]      FIGS. 4 and 5  represent top and side views of another embodiment of a magnetic delivery unit that can be installed on the stacking machine of  FIGS. 1 and 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]      FIG. 1  represents a stacking machine  10  in accordance with a nonlimiting embodiment of the invention. The machine  10  includes a frame  11  comprising legs  12  for supporting components of the machine  10  that perform certain aspects of a stacking operation. These components include multiple magnetic delivery units  14  suspended beneath a carriage  16 . The carriage  16  and its delivery units  14  are shown in isolation in  FIG. 2 , and an individual delivery unit  14  is shown in isolation in  FIG. 3 .  FIGS. 1 and 2  represent the machine  10  and carriage  16  as having four delivery units  14 , though it should be understood that fewer or more units  14  could be employed. Each delivery unit  14  is effectively a delivery means, which as used herein is defined as serving to deliver a sheet from one side of a stacking machine to another. As discussed below, when adapted to transport sheets formed of a magnetizable material, for example, tin plate, each delivery units  14  is effectively a magnetic delivery means adapted for the same purpose. The term “magnetizable” is used herein to refer to materials that can be magnetized and attracted to a magnet (i.e., ferromagnetic or ferromagnetic materials) including, but not limited to, materials containing iron, nickel, cobalt, and alloys thereof. As an example, tin plate materials typically comprise a base layer formed of a steel, over which an iron-tin alloy layer, a tin layer, and one or more protective layers are often applied. 
         [0016]    Each delivery unit  14  includes a belt  18  and a magnetic bar unit  20 , with each belt  18  (three of which are shown in  FIGS. 1 and 2 ) individually traveling around the longitudinal length of its corresponding magnetic bar unit  20 . Each belt  18  can be formed as any of a wide variety of endless or continuous loop or band of flexible material capable of being used to convey materials or to transfer motion between wheels, pulleys, or shafts. The belts  18  are represented as being driven in unison by a single drive shaft  22 , though it is foreseeable that the belts  18  could be individually driven or subsets of the belts  18  could be driven in unison. 
         [0017]    The carriage  16  supports the individual delivery units  14  so that their individual lateral positions relative to each other can be adjusted as may be desired to convey and stack a particular size of sheet stock. In  FIGS. 1 and 2 , this adjustment is shown as being performed with multiple power screw assemblies engaged with beams  21 A and  21 B that are supported by journal shafts  23  and are adapted to move laterally within the carriage  16 . One such assembly includes a crank wheel  24 , screws  26 , and nuts  28 , for example, two lead screws  26  individually engaged with the nuts  28 , which are each mounted to one of the two beams  21 A that support the two interior delivery units  14  as seen in  FIGS. 1 and 2 . Each of two additional power screw assemblies includes a pair of crank levers  30 , each operating a separate screw  32  engaged with a nut  34  that is mounted in one of the two beams  21 B that support the two outer delivery units  14  as seen in  FIGS. 1 and 2 . In this manner, some of the delivery units  14  may be adjusted while others remain fixed in their positions. Other ways of providing an adjustment capability to the machine  10  are also within the scope of the invention. 
         [0018]    The magnetic bar units  20  are effectively magnetic means adapted to magnetically carry individual sheets (not shown) from one side of the machine  10  to the other. In the particular example of  FIGS. 1 and 2 , sheets enter the machine  10  adjacent the drive shaft  22 , and exit the opposite side of the machine  10 . For illustrative purposes,  FIGS. 1 and 2  depict one of the delivery units  14  without its belt  18  and with the interior of its bar unit  20  exposed.  FIG. 3  represents a more detailed view of the exposed bar unit  20  of  FIGS. 1 and 2 . The bar unit  20  is represented as including a flange  36  and backing plate  38  by which the unit  20  can be mounted to the carriage  16 , and rollers  40  on which a belt  18  (not shown in  FIG. 3 ) travels around a housing  42  in a lengthwise direction of the housing  42 . One of the rollers  40  is represented as being mounted to the backing plate  38  to enable the position of the roller  40  to be adjusted in the lengthwise direction of the housing  42 , enabling the tension of the belt  18  to be adjusted with a suitable adjustment mechanism  44 . The lowermost rollers  40  are represented as being in proximity to the lower wall  46  of the housing  42 , such that the belt  18  is conveyed in close proximity to the lower wall  46 . 
         [0019]      FIG. 3  represents the upper wall of the housing  42  as being formed by a mounting bar  47 , which can be used to secure the housing  42  to the backing plate  38 . In addition,  FIG. 3  represents the housing  42  as containing two magnetic bars  48 , each containing a series of electromagnets  50 . The electromagnets  50  are positioned within the housing  42  and in proximity to its lower wall  46  so that the belt  18  is in sufficiently close proximity to the electromagnets  50  to enable a magnetizable material to be magnetically attracted to the electromagnets  50  through the belt  18 . As such, the belt  18  is permeable to the magnetic fields of the electromagnets  50  or otherwise does not interfere with the ability of a sheet of magnetizable material to be suspended by the magnetic fields of the electromagnets  50  while in contact with the belt  18 . In reference to the use of the machine  10  to deliver tin plate sheets formed of a magnetizable material, the sheets will be attracted upward toward the electromagnets  50  so as to be suspended beneath the housing  42  while simultaneously being conveyed by the belt  18  from one side of the machine  10  to the other. 
         [0020]    According to a preferred aspect of the invention, the machine  10  is operated in combination with a suitable controller  52  ( FIG. 2 ) that causes the electromagnets  50  to be turned on in order to pick up a sheet as it enters the machine  10 , and then turned off when the sheet has been sufficiently carried to the other side of the machine  10  to be released/dropped onto a stack of sheets. According to another preferred aspect of the invention, the belt  18  is also stopped as, just before, or after the electromagnets  50  are turned off in order to better control the trajectory of the sheet as it drops onto a stack of sheets. For this purpose, the belts  18  are preferably servo-driven and the machine  10  preferably utilizes suitable means to determine when to turn the electromagnets  50  on and drive the belts  18  by detecting an individual sheet as it enters the machine  10 , and when to turn the electromagnets  50  off and stop the belts  18  as the sheet is prepared to exit the machine  10 .  FIG. 2  schematically represents a sensor  54  for this purpose, such as one or more proximity sensors. The timing of these events can be tailored to pick up and drop sheets according to their particular characteristics, including size, weight, magnetic properties, etc. It is foreseeable that the electromagnets  50  of each magnetic bar  48  could be operated independently of the other bar(s)  48 , and/or individual electromagnets  50  of an individual bar  48  could be operated independently of other electromagnets  50  of the same bar  48 . 
         [0021]      FIG. 2  further schematically represents the use of a bumper  56  adjacent the exit of the machine  10 , such that sheets exiting the machine  10  gently bump into the bumper  56  as they exit the machine  10  to limit their forward trajectory caused by the movement of the belt  18 . The position of the machine  10  relative to a pallet (not shown) onto which the sheets are to be dropped can also be chosen to promote a desired trajectory for the sheets. In combination, these features described herein can be utilized so that each individual sheet can be conveyed by the belts  18  and released by the bar units  20  in a manner that will minimize damage to the sheet, including scratching of its printed surface, as well as damage to the preceding sheet already in the stack on which the sheet is being dropped. 
         [0022]    According to a nonlimiting aspect of the invention, the frame  11  and its legs  12 , the carriage  16 , and the drive shaft  22  may all be components of an existing stacking machine, for example, one of the aforementioned Dexter Stackers, and the delivery units  14  can be members of a retrofit kit adapted to be manufactured and installed for the purpose of modifying the existing stacking machine. As such, one or more existing delivery mechanisms installed on the machine can be removed from the beams  21 A and/or  21 B of the carriage  16  and one or more delivery units  14  installed in its/their place. As such, the carriage  16 , including the beams  21 A and  21 B, shafts  23 , crank wheel  24 , crank levers  30 , screws  26  and  32 , and nuts  28  and  34  thereof, can all be components of an existing stacking machine that are reused and remain on the machine after installation of the delivery units  14 . 
         [0023]      FIGS. 4 and 5  depict an alternative delivery unit  114  representative of another nonlimiting embodiment of the invention. In view of similarities that the delivery unit  114  shares with the embodiment of  FIGS. 1 through 3 , identical reference numerals will be used in  FIGS. 4 and 5  to denote the same or functionally equivalent elements of the unit  114  as those shown for the units  14  in  FIGS. 1 through 3 , and the following discussion of  FIGS. 4 and 5  will focus primarily on aspects of the delivery unit  114  that differ from the units  14  in some notable or significant manner. Other aspects of the unit  114  not discussed in any detail can be, in terms of structure, function, materials, etc., essentially as was described for the first embodiment. 
         [0024]    The delivery unit  114  is depicted in  FIGS. 4 and 5  with its belt  18  shown in phantom. As more readily evident in  FIG. 5 , the two rolls  40  in closest proximity to the drive shaft  22  are mounted on two legs  58  of a fork  60 , shown as being defined as part of the backing plate  38 . A recess  62  defined between the legs  58  is sized and shaped to accommodate the drive shaft  22  of the machine  10 . As evident in  FIG. 5 , the belt  18  is not routed around the shaft  22 , but instead is forced into engagement with the side of the shaft  22  facing the delivery unit  114 . In this manner, the shaft  22  is not required to be removed from the machine  10  when installing or removing the unit  114  from the machine  10  or when installing or removing the belt  18  from the unit  114 , as is the case with the embodiment of  FIGS. 1 through 3 . The engagement of the belt  18  with the shaft  22  can be adjusted with the adjustment mechanism  44 . 
         [0025]    While the invention has been described in terms of a specific preferred embodiment, it is apparent that other forms could be adopted by one skilled in the art. For example, the machine  10  could differ in appearance and construction from the embodiment shown in the Figures, the functions of each component of the machine  10  could be performed by components of different construction but capable of a similar (though not necessarily equivalent) function, and appropriate materials could be substituted for those noted. Accordingly, it should be understood that the invention is not limited to the specific embodiment illustrated in the Figures. It should also be understood that the phraseology and terminology employed above are for the purpose of disclosing the illustrated embodiment, and do not necessarily serve as limitations to the scope of the invention. Therefore, the scope of the invention is to be limited only by the following claims.