Abstract:
A method of applying adhesive to major and minor flaps of a container in a siftproof adhesive pattern. A pair of adhesive dispensing guns are independently moved with respect to the flaps of the container as the container is conveyed past the guns. Electric actuators, such as linear modules or rotatable servo modules, are used to rapidly accelerate the guns in a direction perpendicular to the path of the container along a conveyor. In this manner, rapid packaging takes place and reliable siftproof patterns are achieved using minimal adhesive.

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to methods for sealing containers and, more specifically, to methods of sealing containers in a siftproof manner designed to prevent leakage of particulate contents or infestation by insects. 
     BACKGROUND OF THE INVENTION 
     Many containers, such as cartons, boxes or other less rigid containers, are constructed from paper-based materials and include open ends each having a plurality of flaps. Typically, the flaps at each end include a pair of opposed major flaps and a pair of opposed minor flaps. The containers are usually folded from a flat condition into an erected condition, after which a desired product may be introduced into the container. The flaps are then folded and connected together, typically using an adhesive, to close the opposite ends of the container. The minor flaps are folded down first and the major flaps are folded down next and sealed to upper surfaces of the minor flaps using adhesive. 
     Particulate products, such as granulated or powdered products, require packaging that prevents leakage of the product during shipment and storage. Plastic liners may be used inside the container for this purpose, however, such liners increase packaging costs. To reduce costs, linerless siftproof containers and sealing methods have been developed for storing and shipping particulate products. The end flaps of these siftproof containers must be tightly sealed in a manner that prevents the contents from sifting out between the flaps and which likewise prevents infestation by insects through gaps between the flaps. In the past, all of the flaps have received adhesive deposits in the form of intermittent or continuous adhesive beads to ensure that the seams between the various flaps are sealed in a siftproof manner. 
     As the development of siftproof containers has progressed, certain problems have been addressed relative to siftproof seal integrity and costs associated with the adhesive and the paper construction products. For example, embossments have been used on the various flaps to provide opposed surfaces lying in close relation such that the gap between the flaps does not need to be filled with as much adhesive. Other siftproof containers have been configured to include a modified first major flap that enables direct contact between embossed portions of the minor flaps and a corresponding embossed portion of the second major flap. While these improvements have helped in some regards, modifying containers in these manners can also add expense and some containers cannot have embossed or otherwise modified flaps. 
     Other problems in this art relate to the need for a large of number of adhesive dispensers, or adhesive dispensing nozzles, necessary to place the corresponding number of beads on the container flaps extending in the conveying path of the containers. The increased complexity of the dispensing system increases costs and complicates changeover procedures. In this latter regard, for containers of different configurations and/or sizes, dispensing guns must be removed or added, or nozzles must be removed and plugged or added to accommodate the new configuration or container size. 
     Despite the various developments in the area of siftproof containers, improvements are still needed to maintain siftproof seal integrity while reducing adhesive requirements and general manufacturing costs. In this regard, the use of continuous adhesive sealing beads as opposed to a number of intermittent short and long beads only extending parallel to the conveying path requires much less adhesive and lower manufacturing equipment and changeover costs due to the lower number of necessary adhesive guns. However, applying a continuous adhesive bead in a direction generally perpendicular to the conveying path during high speed packaging operations has been a troublesome problem. Many packaging lines are designed to move at a rate of approximately 400-500 ft./min. or above and, at these high speeds, applying accurate beads of adhesive perpendicular to the direction of the conveying path has been a problem inadequately addressed by prior siftproof packaging systems. With the prior art high speed siftproof packaging methods, beads of adhesive have been applied only in the direction of the conveying path in order to deal with this problem. This results in the use of much more adhesive than necessary to create a siftproof pattern and necessitates the use of multiple side-by-side adhesive dispensing guns and/or nozzles mounted adjacent the conveying path. 
     To solve these and other problems in the art, it would be desirable to provide a method of applying a siftproof pattern of adhesive to the major and minor flaps of a container while using less adhesive and a lower number of adhesive dispensing components while still maintaining a high production rate in a high speed packaging operation. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method of applying adhesive to respective first and second major flaps and first and second minor flaps of a container in a siftproof pattern. The container is moved along a conveying path with the major flaps being folded in an outwardly extending position and the minor flaps being folded in an inwardly extending position. With the container moving along the conveying path, a first gun is moved relative to the container while dispensing a first bead of adhesive therefrom along respective first edges of the first major flap and the first minor flap while moving the first dispensing gun in a direction generally perpendicular to the conveying path. The first bead may be applied starting on the first minor flap and moving onto the first major flap or vice versa. A second gun is moved relative to the container while dispensing a second bead of adhesive therefrom starting along the first edge of the first minor flap and continuing along a first edge of the second major flap in a direction generally perpendicular to the conveying path. With the first bead of adhesive completed and the first gun shut off, the second bead of adhesive is continued with the second gun held stationary. During this time, the container continues to move along the conveying path. The second bead of adhesive is continued along a second edge of second major flap in a direction generally parallel to the conveying path. The second bead of adhesive is then continued along a third edge of the second major flap and extending onto the second minor flap while moving the second dispensing gun again in a direction generally perpendicular to the conveying path. Preferably simultaneously with the dispensing of the second bead of adhesive along the third edge of the second major flap, a third bead of adhesive is dispensed from the first dispensing gun and extends along an edge of the first major flap and onto the second minor flap in a direction generally perpendicular to the conveying path and generally parallel to the first bead of adhesive. Like the first bead of adhesive, this third bead of adhesive may be started on the first major flap and extend onto the second minor flap or vice versa. The major flaps are then folded and sealed to the minor flaps by folding the first major flap onto the minor flaps and then folding the second major flap onto the first major flap. 
     In the preferred embodiment of the invention, only first and second adhesive dispensing guns are necessary in a high speed packaging operation to apply beads of adhesive in a siftproof pattern using minimal adhesive. Quick movements perpendicular to the direction of the conveying path will result in the necessary generally perpendicular beads of adhesive at opposite ends of the major and minor flaps. In the preferred embodiment, electric gun movers, such as linear actuators or servomotors with rotatable outputs, are used to facilitate this quick perpendicular movement. Even with the speed of the container along the conveying path reaching 400-500 ft./min. or above, the adhesive beads necessary in the direction generally perpendicular to the conveying path may be made, while the longer sealing bead extending in the direction of the conveying path is easily placed with the corresponding gun held in a stationary position. 
     In the preferred embodiment, the first and second guns are mounted along a linear guide rod and are initially moved in opposite directions perpendicular to the conveying path to apply respective beads of adhesive extending from the first minor flap onto the respective first and second major flaps. The first gun is then shut off or closed and the second gun is maintained on or opened to dispense a portion of the second bead along an edge which extends parallel to the conveying path. When the end of this portion of the bead is reached, the first dispensing gun is actuated to again dispense a bead of adhesive and each of the dispensing guns is moved toward the other in a direction generally perpendicular to the conveying path to again dispense beads of adhesive that extend from the first and second major flaps onto the second minor flap. This completes the siftproof pattern for the container and this method is repeated for each container continuously moving along the conveying path. 
     In an alternative embodiment, electrically-actuated servomotors with rotatable outputs are used to move the first and second guns in a generally perpendicular direction to the conveying path for the purposes discussed above. The manner of placing the adhesive beads is otherwise the same as discussed above with respect to the preferred embodiment. This alternative embodiment may also have manual adjustment mechanisms for accommodating containers and/or container flaps of different configurations and sizes. In each embodiment, the accommodation of containers and/or flaps of different sizes and configurations also may be made by suitable adjustment in an electrical control controlling the extent of movement for one or both dispensing guns. 
     These and other objects, advantages, and features of the invention will become more readily apparent to those of ordinary skill in the art upon review of the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmented perspective view schematically illustrating an adhesive dispensing system and gun mover for applying a siftproof adhesive pattern to the flaps of a container; 
     FIG. 2 is a top plan view of the container shown in FIG. 1, but schematically illustrating application of the preferred siftproof pattern; and 
     FIG. 3 is a fragmented perspective view showing an alternative apparatus for applying a siftproof pattern in accordance with the inventive concepts. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1 and 2, an adhesive dispensing apparatus  10  is illustrated for applying adhesive beads to a container  12 . Container  12  travels along a conveyor  14  along a path indicated by directional arrows  16 . Conveyor  14  is schematically illustrated as a belt, however, in practice, such conveyors take many different forms depending on the packaging operation and container requirements. Container  12  includes a first major flap  20 , a second major flap  22 , a first minor flap  24  and a second minor flap  26 . Minor flaps  24 ,  26  are folded inwardly toward an interior  28  of container  12 , while major flaps  20 ,  22  are folded outwardly with respect to container interior  28 . This configures container  12  for receipt of the siftproof adhesive bead pattern to be discussed below. 
     Apparatus  10  more specifically includes a pair of vertical support members  30 ,  32  coupled to a horizontal support member  34  and carrying a horizontal guide element  36  in the form of a cylindrical rod. A pair of linear electric motors  40 ,  42  are received on guide element  36  for providing positioning and linear movement of manifolds  44 ,  46  and dispensing guns  48 , 50  in a direction  8  generally perpendicular to conveying path  16 . Electrically actuated and controlled linear motion devices of this type are available as LM Series Linear Modules from Industrial Devices Corporation in Petaluma, Calif. Respective manifolds  44 ,  46  are affixed to linear motors  40 ,  42 . Manifolds  44 ,  46  further carry respective adhesive dispensing guns  48 ,  50  configured to dispense adhesive from nozzles  48   a ,  50   a  in an on/off fashion. Adhesive dispensing guns  48 ,  50  can be pneumatic such as the H200 or H400 Series dispensing guns from Nordson Corporation of Westlake, Ohio, or an electric gun, such as the NORDSON® E350 Series. However, other types of pneumatically or electrically-actuated on/off type guns may be used as well. Adhesive is carried to guns  48 ,  50  through their respective manifolds  44 ,  46  which are in fluid communication with adhesive supply hoses  52 ,  54 . A pair of pressurized air hoses  56 ,  58  feed air to manifolds  44 ,  46 . This air is supplied through manifolds  44 ,  46  to guns  48 ,  50  in order to actuate guns  48 ,  50  between on and off conditions. 
     When guns  48 ,  50  are on or in open positions, pressurized adhesive will flow through hoses  52 ,  54 , manifolds  44 ,  46  and nozzles  48   a ,  50   a  and discharge as respective beads  70 ,  72 ,  74  in accordance with the method of this invention. Bead  70  extends along respective edges  20   a ,  24   a  of first major flap  20  and first minor flap  24 . Bead  74  extends along respective edges  20   c ,  26   c  of first major flap  20  and second minor flap  26 . Bead  72  is comprised of connected portions  72   a ,  72   b ,  72   c . Bead portions  72   a ,  72   b ,  72   c  respectively extend along a first edge  22   a , a second edge  22   b , and a third edge  22   c  of second major flap  22 . Bead portions  72   a ,  72   c  further extend onto respective edges  24   a ,  26   c  of first and second minor flaps  24 ,  26 . 
     Container  12  is shown moving in the direction of arrow  16  along a conveyor  14 . FIG. 2 more specifically illustrates the adhesive application in progress with bead  70 , bead portion  72   a  and part of bead portion  72   b  having been already applied. With container  12  moving in the direction of arrow  16  at a high rate of speed, such as approximately 500 ft./min., and with guns  48 ,  50  respectively turned on directly above starting points  80 ,  82 , linear motors  40 ,  42  rapidly move guns  48 ,  50  in an outward direction away from each other to locations  84 ,  86 . At location  84 , gun  50  is turned off or closed to stop dispensing adhesive and its motion perpendicular to conveying path  16  is also stopped by deactivating motor  42 . At location  86 , the motion of gun  48  perpendicular to conveying path  16  is stopped by deactivating motor  40 , however, gun  48  is maintained on or in an opened condition to continue dispensing adhesive bead portion  72   b  in a substantially parallel direction relative to conveying path  16 . Although guns  48 ,  50  are physically stationary during this part of the process, they move relative to container  12  in the directions of arrows  76 ,  78  due to the physical movement of container  12  in the opposite direction  16 . 
     At locations  88 ,  90 , guns  48 ,  50  are simultaneously moved toward each other via motors  40 ,  42  to points  92 ,  94  in a direction perpendicular to conveying path  16  as indicated by arrows  96 ,  98 . At location  88 , gun  48  is maintained on to apply bead portion  72   c , while gun  50  is turned on at location  90  to apply bead  74 . When locations  92 ,  94  are respectively reached, guns  48 ,  50  are turned off or closed to stop the discharge of adhesive and motors  40 ,  42  are deactivated to stop the perpendicular travel of guns  48 ,  50 . At locations  92 ,  94 , guns  48 ,  50  are located at their respective starting positions ready for the next container and a repeat of the same siftproof adhesive bead application. 
     Preferably, to apply accurate beads of adhesive perpendicular to conveying path  16 , specifically in the form of beads  70  and  74  and bead portions  72   a ,  72   c , the speed of guns  48 ,  50  moving in the perpendicular direction must be sufficient relative to the speed of conveyor  14  to ensure that beads  70 ,  74  and bead portions  72   a ,  72   c  do not curve substantially or become substantially angled away from perpendicular. In the present embodiment, with a conveyor speed in the range of 400-500 ft./min. the speed of guns  48 ,  50  in a direction perpendicular to conveyor  14  should be in the range of 1500-2000 ft./min. In the above-mentioned linear servo module, conventional controls may be used to program the extent that guns  48 ,  50  are moved in the perpendicular direction and also to control the speed of movement. It will be appreciated that these control features may be utilized to accommodate containers of various configurations and sizes, and packaging operations of various speeds. 
     FIG. 3 illustrates an alternative embodiment comprising an apparatus  100  configured to apply the same adhesive bead pattern to a container  12  as discussed above with respect to FIGS. 1 and 2. In FIG. 3, like reference numerals refer to like elements in each embodiment. Apparatus  100  includes respective first and second servomotors  102 ,  104  coupled to support members  108 ,  110 . Support members  108 ,  110  carry first and second manifolds  116 ,  118  and first and second adhesive guns  120 ,  122  with nozzles  120   a ,  122   a  similar to the first embodiment. The adhesive and air hoses have been deleted for clarity. As indicated by arrows  124   a ,  124   b  and  126   a ,  126   b  the physical spacing between guns  120 ,  122  may be changed through the use of a slot  130  in a horizontal support  132 . After the adjustment is made, servomotors  102 ,  104  and support members  108 ,  110  are fixed by suitable fasteners  133 ,  134  to prevent longitudinal movement along slot  130 . However, the connections formed with fasteners  133 ,  134  allow support members  108 ,  110  to rotate about their connection points. For example, suitable bearings may be provided for this purpose. The position of guns  120 ,  122  may be changed in the direction of the conveying path  16 , as indicated by arrows  135 ,  137 , through the use of a second pair of slotted connections between support members  108 ,  110  and manifolds  116 ,  118 . These connections similarly comprise slots  136 ,  138  and fasteners  140 ,  142 . A certain amount of adjustment may also be obtained by electrically controlling the extent of rotation by servomotors  102 ,  104 . 
     Servomotors  102 ,  104  rotate support members  108 ,  110  to move the respective guns  120 ,  122  back-and-forth along an arcuate path, indicated by arrows  144   a ,  144   b  and  146   a ,  146   b  to apply the necessary generally perpendicular beads, illustrated as beads  70 ,  74  and bead portions  72   a ,  72   c  in FIG.  2 . The sequence of bead application is preferably the same as discussed in connection with FIG.  2 . While the motion of guns  48 ,  50  in the first embodiment is in a purely linear direction perpendicular to conveying path  16 , the rotational movement of guns  120 ,  122  in this second embodiment will not adversely affect the integrity of the siftproof seal. That is, the rotation of guns  120 ,  122  occurs through such a short and slight arcuate path that the application of adhesive beads  70 ,  74  and bead portions  72   a ,  72   c  will result in substantially perpendicular beads similar to those shown in FIG.  2 . 
     While the present invention has been illustrated by a description of various preferred embodiments and while these embodiments has been described in some detail, it is not the intention of the Applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The various features of the invention may be used alone or in numerous combinations depending on the needs and preferences of the user. This has been a description of the present invention, along with the preferred methods of practicing the present invention as currently known. However, the invention itself should only be defined by the appended claims, wherein I claim: