Abstract:
A variable volume buffer is employed to conduct a multitude of articles from an elevated supply stream into a container at a lower elevation while maintaining a drop distance for the articles that is shorter than the distance from the source to the bottom of the container. The bottom of the buffer is vertically displaced in response to the height of the articles in the buffer in a continuous or step-wise function to maintain the fill level of the articles in the buffer at substantially a constant drop distance from the source. Upon the bottom of the buffer moving adjacent the bottom of the container, the gate is opened and the buffer is raised to permit the spilling of the articles directly from the buffer and into the container.

Description:
FIELD OF THE INVENTION 
     The present invention relates to transferring items from an elevated supply stream to a container at a lower elevation. More particularly, the invention relates to a variable volume, height adjustable buffer for capturing and retaining a multitude of similar articles and then selectively batch dispensing the items into a container located at a lower elevation. 
     BACKGROUND OF THE INVENTION 
     Although the present invention may be used in conjunction with a variety of items often found in a supply stream such as, for example, food products, building components and manufacturing components, the present application finds particular use with preforms. Preforms are typically formed of a thermoplastic and are the initial material for thin wall containers such as bottles for soft drinks, detergents, etc. produced with blow molding machines. 
     In one method of blow molding plastic containers, such as polyethylene terephthalate (PET) carbonated beverage bottles, a preform first is formed by injection molding followed by reheating and stretch blow molding of such preforms into containers. The preforms are generally cylindrical tubes having a hemispherical closed end and an opposite open end with a ring shaped shoulder and threaded sleeve. Superficially, preforms generally resemble test tubes having a threaded end. 
     Depending upon the size of the container to be blow formed, the preforms have different sizes particularly in length and wall thickness, whereas the diameters are somewhat standardized with reference diameters being 22, 28 and 38 millimeters, measured on the outside of the thread. 
     The preforms are injection molded in large numbers at an injection molding machine, which includes a preform cooling or handling plate. After the preforms are removed from the injection molding machine, they are brought to an elevated position by a conveyor belt and then delivered by a chute to a large corrugated board box normally identified as a “gaylord” for storage and shipment. The preforms merely drop from the chute and into the gaylord. Since a gaylord may be four or more feet tall and the chute discharge is at a still higher elevation, the drop from the chute to the bottom of the gaylord may be five feet or more. 
     Surface damage of the preform typically occurs during dropping through such distances into the gaylord. Such damage is manifest by scratching or scuffing of the surface of the preform and in an extreme case in the chipping of a threaded surface. Since this damage occurs during loading of the articles which is after inspection, the damage often goes undetected. Consequently, such defects on the exterior surface of a preform result in a blow-molded container having an unacceptable surface contusion. 
     A number of methods have been applied to reduce the surface damage to preforms prior to the final blow molding process. 
     Specifically, U.S. Pat. No. 5,509,965 discloses immediately coating preforms after the injection molding of such preforms to prevent damage of the preforms by engagement with one another. 
     However, such processes typically require additional materials as well as processing equipment, thereby adding to the cost. 
     Accordingly, a need exists for a system that can transfer, with a minimum of damage, preforms from the injection mold supply stream at a higher elevation and into a container at a lower elevation for storage and subsequent transport. 
     The need further exists for a such a system for loading a multitude of similar articles into relatively deep containers that minimizes damage to the articles particularly where the articles are dropped from a relatively high elevation relative to the bottom of the container. 
     There is a yet further need for such a system for loading a multitude of similar articles into a deep container wherein the drop or fall distance into the container is kept relatively constant regardless of the container height. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, a vertically oriented buffer is positioned between the discharge of a chute and the bottom of the gaylord. The buffer establishes and maintains a relatively constant drop height so the preforms only drop a short distance into the buffer. In this respect the buffer has expandable sides that allow the base of the buffer to move from a higher elevation to a lower elevation. As preforms accumulate and pile onto the base of the buffer, the buffer sides expand downwardly. In this fashion the base is lowered so the top of the pile of preforms remains at a substantially constant elevation relative to the discharge end of the chute. 
     The buffer is sized and positioned to fit within the gaylord so that as the base is lowered, it extends into the gaylord. When the base of the buffer is at or near the bottom of the gaylord an opening in the base is created so the preforms can be dispensed into the gaylord. The buffer is collapsed by raising the base and this results in a controlled dispensing of the preforms into the gaylord through the open base. 
     Accordingly, the present invention may be characterized in one aspect thereof by an apparatus for maintaining a relatively constant drop distance during the filling a container having an open top and a closed bottom with a multitude of similar articles from a source located at a higher elevation, the apparatus including: 
     a) a vertically expandable buffer disposed intermediate the elevated source and the container for receiving the articles directly into the buffer from the elevated source; 
     b) a top frame at a fixed location defining a buffer inlet; 
     c) a bottom frame defining a buffer outlet including a gate closing the outlet, the bottom frame being sized to fit into the container and being movable between an elevated position adjacent the top frame to a lower position, the bottom frame at the onset of filling being at the elevated position disposed a defined vertical distance below the elevated source that defines an initial drop distance of articles falling from the source and into the buffer; 
     d) expandable sides connecting the top and bottom frames; 
     e) control means for controlling the descent of the bottom frame in response to the entry of articles into the buffer that fill the buffer to a fill level for maintaining a distance between the fill level and the source that is substantially equal to the initial drop distance; and 
     f) means opening the gate responsive to the positioning of the bottom frame at the lower position. 
     In another aspect the present invention may be characterized by a method for filling a container with a multitude of similar articles comprising: 
     a) dispensing the articles from an elevated source and through a defined drop distance into an expandable buffer disposed below the source and above the container; 
     b) expanding the buffer downwardly and into the container as the buffer is filled with the articles so as to maintain substantially the defined drop distance; and 
     c) opening a gate in the buffer when the buffer is expanded to a selected lower level for dispensing the articles into the container by dropping them from the buffer and the distance dropped from the buffer into the container being no greater than the defined drop distance. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view showing the apparatus of the present invention; 
     FIGS. 2-5 are side elevation views partly broken away and in section showing the apparatus at various stages of a filling operation; and 
     FIG. 6 is a schematic view showing a reel arrangement for use in the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, the apparatus of the present invention, generally indicated at  10  is shown in association with other loading apparatus such as a conveyor  12 . As noted hereinabove, the apparatus of the invention is used in a loading system wherein articles are dispensed from an elevated source into gaylord containers. In the present situation the articles are preforms produced by a conventional injection molding machine (not shown). The out put of the injection molding machine, comprising a multitude of similar articles, is delivered to the conveyor lower end  14 . The conveyor carries the articles to a higher elevation and dumps them onto a horizontal conveyor  16 , which in turn delivers the articles to a chute  18 . The articles then drop from the chute and into a gaylord container (not shown in FIG. 1) disposed below the chute. 
     FIG. 1 shows the apparatus  10  to include a generally upright support structure formed by upright legs  20  and a top bracket  22  that connects the legs. The spacing and height of the legs  20  is such that the support structure can accommodate a gaylord container positioned between the legs and below the top bracket. 
     Suspended from the support is an expandable buffer  24 . The buffer includes a top frame  26  and a bottom frame  28 . The top frame  26  is fixed at its ends to the upright legs  20  at an elevation that is just below the level of the discharge of the chute  18 . The bottom frame  28  is vertically adjustable relative to the top frame and is shown in FIG. 1 at or close to its highest position. Extending between the top and bottom frames is an expandable wall  30  forming the sides of the buffer. As the bottom frame is lowered with respect to the top frame, the sides  30  expands downwardly so the volume of the buffer increases responsive to the downward movement of the bottom frame. The expandable wall can take any appropriate form such as telescoping tubes or rectangular sections. A preferred arrangement as disclosed in the Figures is a pleated structure. 
     Any suitable means is attachable to the bottom frame to accomplish a controlled decent of the bottom frame relative to the top frame. In FIG. 1 the control is shown as including a cable  32  attached to each corner of the bottom frame (only one cable being shown for clarity of the Figure). Each cable passes over a pulley  34  attached to the top bracket  22  and then passes onto a motor driven reel or windlass (not shown). 
     FIG. 2 shows the buffer  24  of FIG. 1 on an enlarged scale. The Figure also shows a portion of a container  36  in position between the upstanding legs  20  of the support frame. As can be seen, the top frame  26  of the buffer is in a fixed position above the top edge  38  of the container and the bottom frame  28 , shown near its highest position, can fit into the container. It also should be appreciated that in the position shown, the bottom frame  28  is a measured distance “X” below the discharge end of the chute  18 . 
     The top frame  26  has an opening  40  for receiving articles into the buffer. The bottom frame  28  has a dispensing opening  42  for dispensing articles from the buffer. A trap door or gate  44  closes the dispensing opening. Preferably the gate comprises rigid double doors made of stainless steel or a rigid plastic. Each of the double doors is hinged at one end to the bottom frame  28 . In the closed position, the doors meet and butt together as shown in FIG.  2 . 
     Associated with one of the pulleys  34  is a geared limit switch  35 . The limit switch counts the revolutions of the pulley in order to determine the distance that the bottom frame  28  travels from the top frame  26 . When the geared limit switch travels a selected number of revolutions, it triggers a solenoid  37 . The solenoid in turn is connected to an air valve  39 . When the valve is opened, pressurized air is admitted through a hose  41  connected to a pneumatic cylinder (not shown) that operates the double doors of the gate  44 . 
     To complete the structure, FIG. 6 shows one arrangement for controlling the elevation of the bottom frame. In this respect the arrangement shown is attached to the upright supporting structure of FIG.  1  and includes four pulleys  34 , one associated with each corner of the bottom frame  28 . The cable  32  passing over each pulley is wound onto a reel  48  that is driven by a motor  50 . Operation of the motor acts to reel in or play out the cables  32  in a controlled fashion for raising and lowering the bottom frame  28  of the buffer. 
     Operation is described as beginning with the condition as shown in FIG.  2 . In this condition the bottom frame is at or near its highest elevation and the drop distance “X” is established between the bottom frame  28  and the discharge chute  18 . In this condition articles dropping from the chute have only a relatively short drop as represented by the distance “X” to the bottom frame of the buffer. As articles begin to fill the volume between the top and bottom frames, the motor  50  (FIG. 6) is operated to play out the cables  32  and controllably lower the bottom frame  28 . 
     As the bottom frame descends, the sides  30  of the buffer downwardly expand and the bottom frame passes into the container  36  as shown in FIG.  3 . The descent of the bottom frame is accomplished in a controlled manner so as to maintain the fill level  52  of the articles in the buffer at a substantially constant distance from the discharge of the chute  18 . Preferably this distance corresponds to the distance “X” between the initial elevation of the bottom frame  28  and the chute discharge end as shown in FIG.  2 . The result of the controlled descent of the bottom frame in this manner is that the distance that the articles fall or drop from the chute and onto the pile of the articles within the buffer remains small and substantially constant. This avoids a long drop as measured from the discharge chute to the bottom of the container  36  and reduces the potential of damage to the articles being loaded into the container. 
     As the buffer is filled and expands downwardly, the gear limit switch in effect counts the revolutions of the pulley  34 . At a selected number of revolutions corresponding to the point where the bottom frame  28  is at a desired lower level close to the bottom of the container, the descent of the bottom frame is halted. The geared limit switch then activates the solenoid  37  and valve  39  to pressurize the cylinders that operate the double doors of the gate  44 . 
     As shown in FIG. 4, operating the double doors to open the gate  44  allows the articles in the buffer to release through the opening  42  and into the container  36 . After the gate is opened, the motor  50  (FIG. 6) is reversed to raise the bottom frame  28 . This allows the articles to spill from the buffer in a controlled manner through the opening  42  and into the container as shown in FIG.  5 . In the usual case, the capacity of the buffer is less than the capacity of the container  36 . Accordingly, after the descent of the bottom frame is stopped, the conveyor  16  may continue to deliver articles to the buffer until a desired article count is reached that corresponds to a filled container. At that point, the delivery of articles into the buffer will stop. 
     The gate  44  can be opened when the bottom frame  28  is high enough above the bottom of the container to permit the double doors of the gate to swing completely open. However, in this case the drop distance to the bottom of the container  36  may be greater than the drop distance “X”. Accordingly, to provide a shorter drop to the bottom of the container  36 , the bottom frame  28  may be lowered to a point where the double doors may not swing completely free after opening as shown in FIG.  5 . In this case the double doors will not swing completely open until the buffer is raised some distance as shown in FIG.  5 . 
     When the buffer is elevated to its start position (FIG. 2) pressure on the pneumatic cylinders is reversed and the double doors of the gate  44  are closed so filling of the buffer can begin again. 
     As noted above, the supply stream delivered from the chute  18  typically is the output of a preform molding machine wherein in the newly injected preforms comprise a multitude of similar articles to be transferred to a container for storage and shipment. Although it is preferred that the supply stream be constant so as to deliver a predetermined number of units in a given time, the supply stream may be variable. 
     Generally, the present invention includes a variable volume buffer, a volume adjusting mechanism and a release mechanism. 
     The variable volume buffer as described above has an inlet for receiving the supply stream, an outlet with a gate for selectively passing the accumulated supply stream from the buffer into the container. 
     While shown as a square or rectangular structure, the buffer can have a cross section that is another rectilinear arrangement or it can be circular or oval. The buffer as described is extensible between a collapsed position and a extended position. In a preferred construction, the expandable buffer is formed by a pleated or accordion, non-elastic material. Such materials include canvas or plastic composites or laminates that may have living hinges to form the pleats. 
     In a first configuration, a top frame defines the inlet to the buffer. The top frame preferably is generally set at a fixed location relative to the supply stream such as by fixing it to an upright supporting structure. 
     The outlet of the buffer comprises a bottom frame that can be disposed in a variety of elevations between a lower position and a raised position. The outlet includes a gate moveable between an open position and a closed position. Although the gate may have a variety of dimensions, it is preferably sized to represent a substantial portion, at least greater than 50% of the cross sectional area of the buffer. A gate of such a large cross sectional area provides a large opening to better transfer the accumulated articles in the buffer to the container. In this respect a large opening allows the articles to spill from the buffer so as to uniformly cover the bottom of the container and fill the container evenly as the bottom frame is raised. 
     A preferred release mechanism for selectively permitting movement of the gate from the closed position to the open position is described including a pneumatic cylinder activated by a predetermined expansion of the buffer as determined by the gear limit switch  35 . It should be appreciated that other release mechanisms can be used such as a hydraulic cylinder and opening of the gate can be triggered by other means. For example, a contact or proximity switch  54  located on the bottom frame as shown in FIG. 3 or at the bottom of the container  36  or a manually pulled lanyard can trigger the opening of the gate. The release of articles from the buffer also may be controlled by any of a variety of mechanisms including height dependent, weight, optical or timing and can be located either on the buffer or on the floor of the container. 
     While rigid members described as double doors are preferred for closing the gate  44 , a cloth or cloth-like structure that depends from about the periphery of the opening  42  and is gathered and closed by a releasable clasp also may be used. 
     As described hereinabove, a height adjustment mechanism is connected to the buffer and preferably the bottom frame of the buffer for selectively varying the displacement of the bottom of the buffer relative to the supply stream. Preferably the height adjustment mechanism is responsive to, or corresponds to, or is controlled by, the supply stream rate, weight of material in the buffer, or by optical or mechanical sensing means. 
     While a system of cables is described as the means for controllably lowering the bottom frame  28 , it should be appreciated that the height adjustment mechanism can include pneumatic or hydraulic cylinders, jackscrews, scissors jacks or other appropriate means for controlling the descend and subsequent elevation of the bottom frame. 
     As the operation of the invention is described, the buffer initially is disposed with the bottom frame and the buffer outlet in an elevated position and the gate is closed. This arrangement allows the articles in the supply stream to drop a relatively short distance “X” into the buffer through the inlet. This is because the buffer is in the collapsed position and the bottom of the buffer is adjacent the inlet so a minimum drop height is defined between the bottom of the buffer and the source of the supply stream. The drop distance “X” as described herein is defined as the distance between the average level of articles in the buffer and the discharge of the chute  18 . 
     As the quantity of preforms retained in the buffer increases, the level  52  of the pile of articles in the buffer rises and the drop distance decreases. Accordingly, the height adjustment mechanism is actuated either in steps or in a continuous movement to lower the bottom frame of the buffer thereby increasing the buffer volume to maintain a substantially constant drop distance “X”. If the lowering of the bottom frame is done in a step process, it is preferable to maintain the drop distance within a predetermined maximum value. 
     As the drop distance “X” is at a preferably minimum height, the energy imparted to each article dropping into the buffer is reduced so the available energy for inducing surface defects on the articles as they drop is likewise reduced. Moreover, the eventual drop distance of the articles as they are introduced into the container from the buffer is likewise reduced to a minimum. This is because the outlet (bottom) of the buffer is continually lowered to accommodate additional preforms from the supply stream and the release mechanism is operated only after the bottom of the buffer is at the preselected lower level near the container bottom. 
     Upon operation of the release, the gate is opened and preforms are permitted to pass through the opening  42  in the bottom of the buffer and into the container. The height adjustment mechanism then is actuated to gradually retract the buffer by elevating the bottom frame  28 . As the bottom frame is raised, the retained articles spill and pour through the opening  42  and enter the container without a distinct or discrete vertical drop. 
     After the buffer is emptied, the gate is closed and the buffer is disposed in the retracted position to repeat the process. 
     Thus it should be appreciated that the present invention accomplishes its objects in providing a system for loading a multitude of similar articles into a relatively deep containers that minimizes damage to the articles dropping into the container. The invention further provides for loading a multitudes of articles into a container wherein the drop or fall distance of the articles into the container is kept relatively constant regardless of the container height.