Abstract:
A knife for trimming comprising a circular blade adapted for attachment to a rotating flange at a point away from the center of the blade, such that said blade rotates eccentrically when said flange is rotated.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates generally a knife, and more particularly a rotating knife for trimming a plastic container.  
         [0003]     2. Related Art  
         [0004]     Current knives used for trimming plastic containers have a single or dual D-shaped blade. Such blades have a point formed where the curved edge meets the straight edge. When used in a trimming operation, the point first encounters the container, piercing the plastic. As a result, there is significant wear-and-tear on the knife point(s). The chipping of the knife point leads to a reduction in the life of the knife. Further, depending on the thickness of the plastic, a particular knife would not be suitable for all cutting/trimming jobs. Additionally, the device must be very carefully positioned so that the knife point meets the plastic at each rotation and the curved portion cuts through the entire thickness of the plastic.  
         [0005]     Since existing knives only cut at a single point, proper positioning can be tedious take a significant amount of time to complete. An improperly positioned blade can dent the container instead of cutting it. This not only damages the appearance of the container, but can also result in an ineffective seal when a lid is placed on the container, due to the gap that now exists between the container and the lid. Ultimately, the denting creates a defective product, causing a loss in productivity.  
         [0006]     What is needed then is an improved knife, with a blade less susceptible to chipping, which lasts longer than knives that are currently available in the art. What is further needed is a knife that can penetrate plastic containers of varying thickness, without having to be meticulously positioned in order to ensure proper cutting.  
       BRIEF SUMMARY OF THE INVENTION  
       [0007]     The present invention is a rotating knife comprising a circular blade which is fixed to a base, such as a flange, at a point away from the center of the blade. For the purpose of this specification, the term knife includes the blade and any additional related components. The blade can optionally include an opening for attachment to the base. This off-center attachment results in an eccentric rotation of the blade.  
         [0008]     This invention improves over prior art knives in having no single knife point. Rather, the invention utilizes an eccentrically rotating circular blade, which cuts along the entire blade circumference. This eliminates the problem of chipping of the knife point. The blade also allows for flexibility in positioning. In the prior art, the knife must be positioned such that the knife point meets the object to be cut. The present invention has no such positioning requirement because the blade cuts along a wider path.  
         [0009]     This invention satisfies a long felt need for a knife used for trimming plastic that does not chip, can be used to cut plastic of varying thicknesses, and need not be strictly positioned in order to accomplish cutting.  
         [0010]     The present invention speaks to an apparatus having a circular blade attached to a rotating flange, and a means for rotating the flange. The flange can be driven by a motor through a direct connection, or the flange also can be connected to the motor by a belt and pulley arrangement, for example. The apparatus can further include a conveyor to position an object within the rotational path of the blade. The blade, in conjunction with the flange and a rotating means, is referred to in this specification as a knife system.  
         [0011]     In another embodiment of the invention, the apparatus utilizes a dual knife system with a second circular blade attached to a second rotatable flange at a point away from the center of the blade. The two blades are substantially parallel and can be positioned to define opposite ends of a cylinder. Alternative positions are possible and are also contemplated by the invention. Further, the apparatus can contain more than two knife systems. Additionally, the apparatus can include a conveyor for positioning a container log in the rotational path of the two blades.  
         [0012]     The container log can be composed of a first and second container joined by a moil region and can be positioned by the conveyor such that the two containers are simultaneously separated from the moil by the two blades. Alternatively, single or multiple blades can be used to separate the two containers sequentially.  
         [0013]     The apparatus in any of its embodiments can be used for trimming or demoiling a plastic container, and further can be used to trim or demoil containers of varying thicknesses. The term trimming as used in this specification includes separating an object from a waste portion, for example demoiling a plastic container, cutting, making an incision, and other similar actions.  
         [0014]     The invention further speaks to a knife for trimming, including a circular blade adapted for attachment to a rotating flange at a point away from the center of the blade. Thus, the blade rotates eccentrically when the flange is rotated.  
         [0015]     The present invention also speaks to a method for trimming or demoiling containers of varying thicknesses by eccentrically rotating a circular blade. This method can further involve attaching the blade to a rotatable flange at point away from the center of the blade, and rotating the flange to rotate the blade.  
         [0016]     The method can also include positioning an object in the rotational path of the blade to trim an object. This object can be a plastic container or a container log comprising multiple containers, each separated by a waste portion. This method can additionally include removing the waste portion by simultaneously or sequentially separating the containers. The waste portion can further contain a moil, and the claimed method of demoiling includes separating each container from the moil.  
         [0017]     Further objectives and advantages, as well as the structure and function of preferred embodiments will become apparent from a consideration of the description, drawings, and examples. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]     The foregoing and other features and advantages of the invention will be apparent from the following, more particular description of exemplary embodiments of the invention, as illustrated in the accompanying drawings wherein like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements.  
         [0019]      FIG. 1  depicts a top view of an exemplary embodiment of a blade according to the present invention and a plastic container;  
         [0020]      FIG. 2  depicts a side view of an exemplary embodiment of an apparatus according to the present invention;  
         [0021]      FIG. 3  depicts the trimming process according to an exemplary embodiment the present invention; and  
         [0022]      FIG. 4  depicts the trimming process according an exemplary embodiment the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]     Embodiments of the invention are discussed in detail below. In describing embodiments, specific terminology is employed for the sake of clarity. However, the invention is not intended to be limited to the specific terminology so selected. While specific exemplary embodiments are discussed, it should be understood that this is done for illustration purposes only. A person skilled in the relevant art will recognize that other components and configurations can be used without parting from the spirit and scope of the invention. All references cited herein are incorporated by reference as if each had been individually incorporated.  
         [0024]      FIG. 1  depicts the knife  100  of the present invention cutting a plastic container log,  110 . A container log is one or more containers with scrap or waste material attached. Typically the container log is brought into contact with the blade using a conveyor (not shown), which positions the container log  110  and knife  100  for contact throughout the trimming process. The blade  102  has an area of attachment  103  to a flange  104  (see  FIG. 2 ). As the flange rotates, the blade pivots about the point of attachment. A locating dowel, S, is present to keep the blade and flange together and prevent slippage of the blade as it rotates.  
         [0025]     Because the blade  102  is circular, the blade can cut into the container  110  at every point of contact. This eliminates the strict knife positioning requirement of the prior art, thus decreasing the amount of time it takes to change or mount knives in a trimmer apparatus.  
         [0026]     During the trimming process, the plastic object/container,  110  also rotates. This way the blade  102  does not have to penetrate through the entire container; the blade  102  need only cut through a path greater than the thickness T of the container ( FIG. 3D ). The knife can penetrate plastic containers of varying wall thickness because the blade is positioned off-center. Hence, the cutting path of the circular blade is greater than in the prior art, and a greater effective “knife length” can be achieved (See  FIG. 3A -C).  
         [0027]     After the container  110  has completed a minimal number of rotation cycles, the trimming process is complete, i.e., the container  110  is separated from any waste or moil portion.  
         [0028]     In  FIG. 2 , the rotation of the knife blade  102  is driven by the flange  104  through its connection to a shaft  106 . The shaft can be directly rotated by a motor (not shown) or the shaft  106  can be connected to the flange  104  by a belt  111 . In another embodiment, the belt can be driven by the motor to turn a pulley connected to the shaft.  
         [0029]      FIG. 3A-3C  illustrate sequentially the trimming process as the plastic container, is moved into the rotational path of the blade  107 . As the container  110  moves along its own rotational path  109 , the container enters the rotational path of the blade  107  ( FIG. 3A ). However, the blade and the container are not yet in contact.  
         [0030]     The distance between the point of attachment  103  and the rotational path of the blade defines the blade length, L 1 . As a result of the blade&#39;s eccentric rotation, blade length varies and is referred to as the effective blade length. Note that in  FIG. 3A , L 1  is not long enough to penetrate the container.  
         [0031]     A conveyor is typically used to bring the knife  100  and container  110  into contact. Thus the conveyor is responsible for the positioning of the container and knife for contact throughout the trimming process.  
         [0032]     Due to the eccentric rotation of the knife blade  102 , the container  110  can be within the rotational path without being in contact with the blade itself. As the blade rotates ( FIG. 3B ), the container  110  contacts the blade and is trimmed. Here the effective length of the blade, L 2 , is sufficient to penetrate the container  110 .  
         [0033]     Unlike prior art knives, the present knife does not have a point and therefore does not pierce the container by jabbing or stabbing, but cuts with a slicing motion. This smoothing of the initial cutting results in force being extended over a larger surface of the blade and container. As a result there is less tendency to chip the blade or cause deformation of the container.  
         [0034]     When the container  110  is positioned for deepest penetration ( FIG. 3C ), the blade is fully engaged, and at its longest effective length, L 3 . The blade is at its deepest penetration point, which extends beyond the inner wall  112  of the container  110 . D notes the portion of  FIG. 3C  that is enlarged (see  FIG. 3D ) to more clearly show the extension of the knife through the inner wall  112  of the container  110 . Because of the eccentric nature of the blade, the blade can be adjusted to move more deeply within the container, and thus can be used to trim containers with varying thicknesses. In a preferred embodiment, the plastic object is a plastic bottle that is separated from a waste portion, such as a moil.  
         [0035]      FIG. 4  illustrates an embodiment of the invention having a dual knife system. In this embodiment two knife systems are arranged in parallel and define opposite ends of a cylinder. Other parallel placements (i.e. where the knives are not directly opposite each other) are contemplated by the invention. Each knife system contains a circular blade, a flange, and means for rotating the flange to rotate the blade. The illustrated embodiment contains a first circular blade  402  attached at an off-center point  403  to a rotating flange  404 , coupled to a means for rotating  406 . Directly opposite the first knife system is a second knife system having a second circular blade  422  attached to a second flange  424  at an off-center point  423 , where the second flange  424  is coupled to the same means for rotating  406  the flange  424  and blade  422 . Alternatively, the knives can be driven by a member  426  between the blades  402  and  422 . The member  426  can be rotated by, for example, a belt or other drive mechanism connected to a motor. In another embodiment, each blade flange can be coupled to a separate rotating means. In the dual-knife system depicted in  FIG. 4 , container log  430  includes a first container  410  and a second container  420  connected by a moil region  418 . As the container log  430  approaches the rotational paths of the blades, the container log  430  rotates and continues to do so until both the first container  410  and second container  420  are each separated from the moil region  418 . Using this arrangement, the first container  410  and second container  420  are separated simultaneously from the moil.  
         [0036]     The embodiments illustrated and discussed in this specification are intended only to teach those skilled in the art the best way known to the inventors to make and use the invention. Nothing in this specification should be considered as limiting the scope of the present invention. All examples presented are representative and non-limiting. The above-described embodiments of the invention may be modified or varied, without departing from the invention, as appreciated by those skilled in the art in light of the above teachings. It is therefore to be understood that, within the scope of the claims and their equivalents, the invention may be practiced otherwise than as specifically described.