1. Field to Which the Invention Pertains
This invention relates to the automatic dispensing of flexible and elastic containers from nested stacks of such containers, and particularly to the dispensing of pressed or drawn flanged paperboard containers having a water or grease resistant coating, for example, polyethylene or polyethylene coated with polyester, on the inner wall of the container. Such containers are increasingly being used rather than metal foil containers in the food processing industry for a wide range of products, including pies and other bakery items. A chief advantage of using paperboard for containers rather than metal foil is that foods contained in the paperboard containers can be cooked in a microwave oven as well as in a conventional oven. With metal foil containers, microwave cooking equipment cannot be used.
In many commercial food processing applications, e.g., in continuous pie making machines, containers are automatically dispensed one at a time from the bottom of a nested stack of containers and deposited onto holders on a traveling conveyor. The conveyor carries the containers through the other operations incident to the food processing, including at some point the step of filling the empty containers with food. It is apparent that in such an environment a reliable and accurate method must be employed for automatically dispensing the containers individually one at a time from the bottom of the nested stack of containers and for depositing them on the traveling plate holders or other continuously moving carriers. Moreover, the dispensing apparatus and method should be accurate and reliable at the rapid dispensing speeds required for production line applications, e.g., up to 150 cycles per minute (cpm) per stack of containers.
The method of dispensing metal foil containers which is commonly used in continuous food processing machinery uses continuously rotating cooperating screws or rotors which separate and strip the bottommost plate from a vertical nested container stack, while supporting the penultimate plate and the remainder of the stack. The screws or rotors used with screw-type dispensing apparatus typically comprise flat, annular plates having stepped flanges and channels to separate and dispense the bottommost plate in the stack.
Conventional screw-type dispensing apparatus used for metal foil plates and containers, however, cannot be used without modification for pressed or drawn paperboard containers because of structural differences between the metal and the paperboard containers. Most notable among those differences is the presence in the metal containers of an outstanding bead on the outer perimeter of the flange of the container. When the beaded metal containers are nested and stacked, the beads act as spacers to create a space or cleavage between adjacent flanges. A separator blade carried, for example, by a rotor of a screw-type dispensing machine can easily be inserted into the cleavage between the flanges of the bottommost and penultimate containers to separate the bottommost container from and to support the remainder of the stack. It is not feasible from a manufacturing standpoint to provide beaded flanges on the pressed paperboard containers of the type used with the present invention. Beaded containers, moreover, require more shipping space. Thus there is no bead, and consequently no cleavage, or other space between adjacent flanges of nested drawn or pressed paperboard containers into which a separator blade can easily be inserted.
Paperboard containers, moreover, are generally heavier than metal foil containers, making it even more difficult to insert the separator blade between the flanges of the bottommost and penultimate paperboard containers. That is because, when the nested stack of paperboard containers is supported for dispensing on the rotors of a screw-type dispensing apparatus, the flange of the bottommost container is supported by the rotors. That flange is bent upward at the points of support due to the weight of the stack bearing down on the support points, causing the flange of the bottommost container to touch the flange of the penultimate container at those points. Thus there is no space between the flanges of the bottommost container and the penultimate container into which a separator blade carried by each rotor can be inserted.
And, aluminum and other metal containers can be manufactured to more exact tolerances than pressed or drawn paperboard containers. Thus pressed or drawn paperboard containers exhibit wider variations in diameter, flange size and other dimensions, making them more difficult to dispense reliably than metal containers.
My invention overcomes the above problems inherent in using automatic screw-type dispensing apparatus to dispense pressed or drawn paperboard containers. According to a preferred embodiment of the present invention, the sidewalls of the bottommost container of a vertical stack of nested paperboard containers are inwardly compressed to deform the bottommost container and to cause the remainder of the stack, nested in that bottommost container, to rise vertically. The vertical rise of the stack creates a space or gap between the flanges of the bottommost and penultimate containers into which separator blades are inserted. When the separator blades are inserted, compression is relaxed, and the bottommost container, being elastic, substantially returns to its original shape and is dispensed, i.e., it is released and permitted to drop onto a conveyor-transported holder. When compression is relaxed, the remainder of the stack moves vertically downward and comes to rest upon the separator blade. In a preferred embodiment of my invention, compression is achieved by one or more cammed spacemaker blades which, along with the separator blades, are components of the rotors of a rotating screw-type plate dispensing apparatus.
2. Description of the Prior Art
The art has attempted to solve the problems incident to dispensing drawn or pressed paperboard containers of the type used in my invention principally by resorting to the use of vacuum-type dispensers. In one variation--the vacuum pick and slide method--a suction source carried by a movable arm is placed in contact with the bottommost plate on the stack. The force established between the suction source and the bottommost plate allows the bottommost plate to be separated or "picked" from the stack by automatic movement of the arm. Once separated, the plate is deposited at the top of an inclined ramp, from which the plate slides down and into a plate holder timed to arrive at the bottom of the ramp to receive the plate. In another variation--the vacuum pick and place method--the bottommost plate is picked from the stack by a suction source carried by a movable arm, and placed directly in the plate holder by the moving arm. These vacuum methods are slower, less reliable, and less economical than the screw-type dispenser of my invention. Moreover, my invention can be used with equipment presently using conventional screw-type dispensing apparatus. Add the present invention exploits the structural elasticity of pressed or drawn paperboard containers--a property which aluminum containers do not possess to any significant extent.
I am aware that the art discloses screw-type paper cup dispensing apparatus wherein the beaded rim of the bottommost cup in a nested stack of cups is compressed to overcome the tendency of the bottommost cup to adhere to the rest of the stack, e.g., U.S. Pat. Nos. 1,907,713 and 1,907,714, both to Benson. According to my invention, however, the sidewalls of the containers, not their flanges, are compressed. And in my invention this compression is applied to the walls of the bottommost container in the nested stack to create a space between the flanges for receiving a separator blade, not, as in Benson's patents, to overcome the adhesion force between containers.
The paperboard containers used with my invention have no tendency to adhere to one another, as do Benson's cups. That is because the plates and containers used with my invention, unlike Benson's containters, have walls which slope inwardly from top to bottom, and which are not substantially vertical. Moreover, the polyethylene or polyethylene and polyester with which the inner walls of the containers used with my invention are preferably coated further diminishes the adhesion between the containers.
Moreover, the cups shown in the Benson patents stack with spaces between the beaded flanges of adjacent cups. Thus, contrary to the present invention, Benson does not compress the sidewalls of the bottommost container to create a space for receiving a separator blade.
In summary, prior screw-type dispensing apparatus or methods are not suitable for dispensing flexible, elastic pressed or drawn paperboard containers of the type used in my invention because they do not create a space between the flanges of the bottommost and penultimate containers for receiving a separator blade.