Abstract:
An infeed system for a can body decorator in which undecorated can bodies are transported from an upstream supply in a conveyor ( 21 ). In the conveyor ( 21 ), the can bodies have a linear pitch as they are touching each other. One or more infeed turrets ( 22, 23; 25, 27; 28, 9, 3 ) separate each can body and change the pitch to the circular pitch of a separator turret and, ultimately to that of the mandrel wheel ( 10 ) in the decorator assembly.

Description:
TECHNICAL FIELD 
       [0001]    This invention relates to an infeed system for supplying undecorated can bodies to a can body decorator. In particular, but not exclusively, it relates to a combination of one or more conveyors, infeed separator turrets and transfer turrets which together change the can pitch to that of a mandrel wheel assembly (sometimes referred to as a “spindle disc”) in the can body decorator. For the avoidance of doubt, the term “decorator” is intended to include the application of any kind of decoration, print, coloured inks or varnish onto a can body which is typically formed from tin free steel, aluminium or other metal. The term “can” is used herein to mean the can body prior to filling and closing to form a finished can. 
       BACKGROUND ART 
       [0002]    U.S. Pat. No. 4,138,041 (COORS CONTAINER COMPANY) describes a gravity infeed through an inclined chute to stationary pockets on a rotatable pocket mandrel wheel. There, the cans are drawn from the pockets and seated by vacuum on mandrels which carry the cans to a printing blanket cylinder. 
         [0003]    As it has become important to increase machine speed, a single stack of cans as in the gravity infeed of U.S. Pat. No. 4,138,041 cannot keep up with the speed of the machine, and cannot rely on gravity alone. Air pressure could be used to force the cans downwards but as the speed increases, the use of more air pressure causes can distortion. 
         [0004]    Decorating machinery has been employed by companies such as 
         [0005]    Rutherford and Alcoa in the printing of metal cans. A known 24 mandrel decorator operates at typically 1800 cans per minute (“cpm”) and a 36 mandrel decorator operates at typically 2000 cpm. The single lane infeed of these decorators has been needed to control the speed of the cans and is a limitation of machine production speed. 
         [0006]    Conventionally, a continuous stream of cans is fed from conveyor track work into the infeed section of the can body decorator. In a conveyor stack, the can bodies have a linear “pitch” which is the distance between their centres, i.e. one can diameter. Individual cans are separated from the conveyor stack by a pocketed single rotating turret wheel. There are two types of infeed separator turret, constant velocity (‘CV’) and ‘tangential’. The type of feed refers to the point where the can is fed from the conveyor stack onto the infeed separator turret. The challenge for a rotary machine infeed system when feeding cans to any container manufacturing process is that the machine takes delivery of cans which are spaced or “pitched” in a linear fashion and the infeed system must change the pitch between the can bodies to that of a circular turret—and larger pitch. 
         [0007]    Following exchange to the separator turret, cans are accelerated up to the peripheral speed of the turret wheel. In known decorators, a further pitch change occurs between the infeed separator turret and mandrel wheel circular pitch. The can body sits in a pocket on this mandrel wheel and is then sucked across using vacuum onto a mandrel. The actual time for this transfer before printing starts is fairly short, especially if the can body is long. The pitch change onto the mandrel wheel has been found to cause can stability problems when misalignment of a can with the corresponding mandrel causes unsuccessful loading. If the can body is not loaded onto the mandrel correctly prior to commencing printing, it has to be blown off. It is apparent that poorly loaded can bodies are rejected and result in spoilage. 
         [0008]    Some machine manufacturers omit the infeed separator turret and guide the can onto a profiled “Can Carrier Pocket” which is mounted in front of a mandrel (the mandrel is part of the mandrel wheel), which has the function of changing can conveyor pitch to that of the mandrel wheel circular pitch. 
         [0009]    A rotary machine infeed system for a can body die necker is described in WO 2011/113710 (CROWN PACKAGING, INC). However, in this prior art system, the can bodies are always already decorated prior to being necked. The skilled man would not consider trying this necker infeed system for handling the undecorated cans of the present invention because undecorated cans do not convey well at high speeds, since the chemicals used in the can washer upstream of the decorator infeed, affect the surface of the cans. This means that the friction properties will vary—strong etching in the washer causes high friction and the cans do not slide against each other as expected. Use of so-called “mobility enhancer” can help, but it is expensive. 
         [0010]    The cans coming into the decorator are “open-ended” or “un-necked” which means that they are not stiff. The cans tend to come into the machine in a long stack of cans which can cause distortion of a can and hang-up on the in-feed guides, and subsequent difficulty in feeding can bodies of unexpected (distorted) shape into the infeed turret. The critical part of an infeed system is when the flexible can body is loaded onto the mandrel. It is therefore desirable that the can body is stable at this point, so as to give minimum spoilage. By having a pitch increase as in conventional infeed systems, the can is not stable and as a result the loading of the can is not 100% reliable. 
         [0011]    It is conventional for current decorator turrets at infeed to hold cans in turret pockets by means of vacuum, applied at the can outside diameter. 
         [0012]    U.S. Pat. No. 3,613,571 (BROWN MACHINE COMPANY OF MICHIGAN, INC.) describes a container printing machine and method of printing which seeks to provide printing machines capable of running at speeds which may print containers at the rate of as much as 400 cans per minute on each side of a mandrel drum. There is no mention as to how cans are held on the infeed starwheel, nor of any can pitch change through the infeed system. 
         [0013]    U.S. Pat. No. 4,048,917 (SUN CHEMICAL CORPORATION) Sep. 20, 1977 is a continuous can printer which is constructed with a worm and star-wheel type input conveyor. Infeed spirals or lead screws such as those described in U.S. Pat. No. 4,048,917 and also U.S. Pat. No. 3,766,851 (SUN CHEMICAL CORPORATION) Oct. 23, 1973, to which U.S. Pat. No. 4,048,917 refers, is old technology and has speed limitations. This is exacerbated by the aspect ratio of some cans. Although U.S. Pat. No. 3,766,851 refers to operation at very high speeds, no actual speed is given and the worm and star-wheel construction of the printer at that time would have prevented its use at line speeds anything like as high as 1000 cans per minute. 
       SUMMARY OF INVENTION 
       [0014]    According to the present invention, there is provided an infeed apparatus for supplying can bodies to a can body decorator, the infeed apparatus comprising: a conveyor which transports can bodies from an upstream supply; a rotatable mandrel wheel which receives each can body in a pocket on the circumference of the wheel; characterised in that the can bodies are supplied undecorated; and the apparatus includes one or more infeed turrets having a circular pitch and a separator turret which separates each can body received from the conveyor, whereby linear can pitch on the conveyor is changed to a circular can pitch on the infeed turret(s); and a transfer turret for transferring can bodies to the mandrel wheel; whereby can pitch between conveyor and mandrel wheel is changed in one or more stages and handling of the undecorated can bodies is controlled. 
         [0015]    An object of the infeed apparatus is to be able to handle undecorated cans at high line speeds, the aim being to handle 1000 cans per minute, or even beyond that, on each conveyor lane, with a fraction of the hardware which is about the mandrel drum of U.S. Pat. No. 3,613,571. Preferably the transfer turret has a circular pitch which is identical to that of the mandrel wheel whereby the can stability is improved for loading. Staging the can pitch change between conveyor and mandrel wheel improves the stack ‘behaviour’ by lowering the magnitude of stack shunting. 
         [0016]    Preferably, the apparatus further comprises two or more conveyors; each conveyor having an accompanying separator turret, which changes the can pitch from that of the conveyor to that of the separator turret, the conveyor and accompanying separator turret providing an independent conveyor lane which feeds directly to the mandrel wheel; each conveyor lane feed being selected to supply a specific sequence of can carrier pockets on the mandrel wheel. 
         [0017]    This embodiment reduces the speed of transfer from each infeed conveyor stack but requires a large pitch change between the infeed conveyor stack and the mandrel wheel circular pitch for a single infeed turret which could be mitigated by the addition of further turrets to accompany each separator turret. Multiple independent conveyor lanes and accompanying infeed turrets feeding directly into the mandrel wheel assembly compromises the mandrel loading time. 
         [0018]    Ideally, the infeed apparatus further comprises: two or more conveyors, each conveyor having an accompanying separator turret, which changes the can pitch from that of the conveyor to that of the separator turret; and each conveyor and accompanying separator turret providing an independent supply lane; each independent supply lane including a further infeed turret which further changes the pitch of the can bodies; a combiner turret which combines the supply lanes together on one turret, the pitch on the combiner turret and the can carrier pocket pitch on the mandrel wheel being identical, such that each conveyor lane supplies a specific sequence of can carrier pockets on the mandrel wheel. 
         [0019]    This final embodiment has the advantages of (i) reducing the speed of the infeed conveyor stack, thus leading to higher machine production speed; (ii) exchanging onto the mandrel wheel assembly (“spindle disc”) without can pitch change between combiner turret and can carrier pocket, thereby improving can stability for mandrel loading; and (iii) not compromising (i.e. optimising) mandrel loading time. 
         [0020]    According to another aspect of the present invention, there is provided a method of feeding can bodies to a can body decorator as defined in the claims. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0021]    Preferred embodiments of the invention will now be described with reference to the accompanying drawings, in which: 
           [0022]      FIG. 1  is a schematic side view of a conventional infeed system; 
           [0023]      FIG. 2  is a schematic side view of a first infeed system according to the invention; 
           [0024]      FIG. 3  is a schematic side view of a second infeed system according to the invention; and 
           [0025]      FIG. 4  is a schematic side view of a third infeed system according to the invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0026]      FIG. 1  shows a known infeed system and associated decorator. The infeed system comprises a conveyor stack  1  in which can bodies are stacked and thereby in contact with each other and having a linear pitch. An infeed separator turret  2  separates and re-pitches the can bodies from the stack  1 . It is apparent from  FIG. 1  that there is a pitch change inherent in the change from the linearly pitched stack to the separator turret  2  and, additionally, in the transfer from the infeed separator turret  2  to the mandrel wheel assembly  10  of the can body decorator. 
         [0027]    Although not featured in the conventional system of  FIG. 1 , some machine manufacturers omit the infeed separator turret and guide the can onto a profiled “can carrier pocket” which is mounted in front of the mandrel. The mandrel is part of the mandrel wheel assembly (cf.  10 ) and the can carrier pocket has the function of changing can conveyor pitch to that of the mandrel wheel circular pitch. 
         [0028]    The remainder of the features shown in  FIG. 1 , including the mandrel wheel assembly or spindle disc  10 , form part of the decorator which is mounted on a machine base represented as rectangular block  19 . 
         [0029]    In the decorator of  FIG. 1 , cans are transferred onto individual mandrels on the spindle disc as noted above. The spindle disc  10  of  FIG. 1  rotates in a clockwise direction and follows a pre-determined cam profile. This decorator includes blanket drum  12  which rotates in the opposite direction to the mandrel wheel assembly so as to bring the blanket drum  12  into contact with plate cylinders. Each plate cylinder rotates and as it does so it receives a thin coat of ink from inker assemblies (“inker stations”)  14 . A single colour of ink is applied to each plate cylinder, with the final printed design being a composite image of all the plate cylinders in use. 
         [0030]    As the different blankets on the drum  12  make contact with individual plate cylinders, the design is applied to each blanket in stages before the blanket makes contact with the can, thereby printing the finished design onto the can. While the can is spinning, the mandrel wheel assembly  10  brings the can into contact with an applicator roll of the over-varnish unit  16  which applies a coat of varnish to protect the printed design. The finished can is then transferred from the spindle disc  10  to a transfer disc (“disc transfer wheel”)  18 . The transfer disc  18  rotates in an anti-clockwise direction and takes the can to a position where it can be transferred to a pin chain discharge  20 . The can is subsequently released and finally transferred to a drying oven (not shown). 
         [0031]      FIGS. 2 to 4  are alternative infeed systems of the present invention. 
         [0032]    Each of  FIGS. 2 to 4  include the same or similar schematic decorator as that of  FIG. 1 , including mandrel wheel assembly  10 . These individual features have been described above and will not be described in any detail hereinafter. 
         [0033]      FIG. 2  infeed system has a single conveyor stack  21  which feeds two or more infeed turrets. In the figure infeed separator turret  22  changes the linear can pitch from the conveyor stack pitch to circular pitch of the separator turret  22  with further increase in circular can pitch at the exchange onto the infeed transfer turret  23 . Additional transfer turrets may be used if further exchange and staged pitch changes are required. The circular pitch of the final transfer turret  23  is identical to that of the mandrel wheel assembly. There is thus no change in the circular pitch of the can when it is transferred from the infeed system to the mandrel wheel assembly of the can body decorator. 
         [0034]    The infeed system of  FIG. 3  uses two or more pairs of infeed conveyor stacks  24 ,  26  and associated separator turrets ( 25  and  27  respectively). Each can undergoes a change in pitch between the stack and associated separator turret. Each combination of stack and separator turret is referred to as an independent “conveyor lane” which feeds directly to the mandrel wheel, with each conveyor lane feed being selected to supply a specific sequence of can carrier pockets on the mandrel wheel  10 . Thus in the two conveyor lanes of  FIG. 3 , cans are transferred into alternate pockets of the mandrel wheel assemble  10 , as shown as black circles around the assembly  10 . In this system, the mandrel loading time is compromised by loading cans at multiple locations. 
         [0035]    The transfer shown in  FIG. 3  uses tangential infeed which does entail a pitch change at the exchange point between the separator turret and mandrel wheel. An alternative would be to use a CV separator turret which would avoid the pitch change at exchange. Whilst not used on decorators at present, this alternative is considered to be within the scope of the present invention. 
         [0036]    An iteration of the infeed system of  FIG. 3  is to use a second infeed turret after each separator turret and a single combiner turret to combine the cans from the conveyor lanes. Thus in  FIG. 4 , there is shown infeed conveyors  24 ,  26  and associated separator turrets  25  and  27  respectively as in  FIG. 3 , plus second infeed turrets  28  and  29  respectively for each conveyor lane. In  FIG. 4 , cans from conveyor lane  1  (conveyor  24 , separator turret  25  and second infeed turret  28 ) are denoted by a cross through the circle whereas cans from conveyor lane  2  (conveyor  26 , separator turret  27  and second infeed turret  29 ) are denoted by a solid circle. 
         [0037]    The combiner turret  30  is loaded with cans alternately from each conveyor lane so as to bring the conveyor lanes together on one turret. This combiner turret has the same pitch as that of the mandrel wheel assembly so that cans are transferred to the pockets of the mandrel wheel assembly without pitch change. 
         [0038]    The system of  FIG. 4  is considered by the Applicant to provide the best possible infeed to a can body decorator. The reduced speed of the conveyor stacks by virtue of using multiple lanes leads to an overall increase in machine production speed. Most importantly at exchange from the combiner turret to can carrier pockets in the mandrel wheel assembly, there is no pitch change hence can stability is optimum during mandrel loading. Each conveyor lane supplies a specific sequence of can carrier pockets on the mandrel wheel and mandrel loading time is not compromised. 
         [0039]    The invention has been described above by way of example only but changes can be made without departing from the scope of the invention as defined by the claims.