This invention relates to packaging of articles, and particularly to the packaging of fresh produce such as lettuce, cauliflower, and the like. More specifically, the invention relates to an apparatus and method for stretch-wrapping fresh produce in a transparent film at the point of harvest.
Fresh produce is harvested and packaged so that it can be stored and transported to arrive in a fresh condition at remote destinations. Iceberg lettuce, for example, is manually cut and placed by hand in a pre-formed standard lettuce bag that is vented to promote effective vacuum cooling. The bag is manually taped closed, and twenty-four to thirty heads of the bagged lettuce are packed in cases to achieve a minimum gross carton weight of about fifty pounds. This process typically requires a team of twenty-four to twenty-eight people organized into groups of two cutters and one taper/packer. A team can pack an average of two hundred fifty cases per hour on an average production day. The teams work behind a harvester machine comprising two elongate wings projecting from opposite sides of a trailer, with each wing incorporating a plurality of bagging and taping stations. The machine is moved through a lettuce field in spanning relation to rows of lettuce, which is harvested by the team as the machine advances through the field. This method of harvesting iceberg lettuce has remained basically unchanged over the past thirty years.
The cartons of bagged lettuce are palletized by hand, put on a trailer, and sent to a plant to be vacuum cooled prior to storage in a cold storage facility and subsequent shipment to a point of sale, where the bagged lettuce will arrive fresh and ready for display and sale.
Efforts have been made in the prior art to at least partially automate the process of harvesting and bagging lettuce, as exemplified, for example, by U.S. Pat. No. 3,245,198 to Schmied, U.S. Pat. No. 3,851,440 to Horsky, U.S. Pat. No. 4,525,983 to Libow, and U.S. Pat. No. 5,794,410 to Harper. These patents all relate to at least partially automated bagging equipment which functions to push a head of lettuce against a plastic film wrap so that the head of lettuce is enclosed by the wrap, rotate the bagged head of lettuce to twist and gather excess wrap material above the head of lettuce, sever the wrap above the twisted portion, and then heat seal it by applying heat to the gathered twisted portion of wrap. Although these prior art systems should help reduce the labor requirements of harvesting and bagging lettuce, they are not entirely satisfactory because they either use too much material, and/or produce an unsightly package, and/or take an excessive amount of time due to the steps required, and/or damage the produce by applying heat and/or excessive force to it.
To date, no commercially viable packaging system has been designed to address the packer's desires for increased productivity, reduced labor costs, improved package appearance, and reduction in the amount of plastic used.
The present invention provides an apparatus and method for packaging articles, and especially freshly harvested produce in a way to achieve increased productivity, reduced labor costs, improved package appearance, and reduction in the amount of plastic used.
The apparatus of the invention is designed so that it can be mounted to a conventional harvester in place of the conventional bagging devices that are currently used. It includes means for holding and supplying under tension a unique stretch wrap film, means for advancing the film to a wrapping station, means for holding the film in place, means for pushing the article, e.g. head of lettuce, against the film to stretch it and form a bag-like enclosure around the head of lettuce, means for gathering the film behind the head of lettuce, and means for sealing the gathered film, severing it, and conveying the shrink wrapped head of lettuce away from the wrapping station.
More specifically, the apparatus comprises a frame having means for mounting it to a conventional harvester. A roller is positioned to support a roll of stretch film, which is unwound from the roller and fed under a dancer bar and an unwind roller and attached at its leading edge to a film feed gripper. The dancer bar and unwind roller maintain a predetermined light tension on the strip of film. The film feed gripper is cycled forwardly, carrying the strip of film with it to a wrapping station, where the film is gripped and held in place by clamps fore and aft and at opposite sides of the wrapping station to define a rectangularly shaped web of the film having a size predetermined to be sufficient to stretch wrap a head of lettuce. The film feed gripper then releases the film and returns to its home position where it grips the strip of film in preparation for another cycle. The strip of film is then severed at a position between the film feed gripper and the clamps.
A freshly cut head of lettuce is placed on a holder, and an operator then presses a cycle button to move the head of lettuce into position centered over the clamped film web. A ram then moves against the head of lettuce, pressing it against the film web, while the holder moves out of the way. The ram continues to press the head of lettuce against the film, stretching it to a point approximately twelve inches below its at-rest position. The ram and holder then return to their home positions in preparation for another cycle.
The stretched overwrap film is then gathered in two stages, by a pair of gathering arms which first move toward one another in a first direction against the film to gather it into a relatively wide flattened condition, and then by a sealing and trimming unit and U-channel which move in a direction transverse to the first direction toward one another against the partially gathered film to further gather the film into a narrow, necked down condition. A heated block in the sealing and trimming unit then closes onto the gathered neck of the film, both sealing it and severing it from the excess film above the seal. A pair of pinch fingers grips the excess film and pulls it away for release to a collection system such as, e.g., a vacuum, and the sealing unit releases the wrapped lettuce to a take-away conveyor.
Simultaneously with release of the wrapped lettuce, the film feed gripper again advances a strip of film to the wrapping station, where the film is clamped by the clamps in preparation for wrapping another head of lettuce.
The film is a mostly polyethylene based seven layer composition with an outer polypropylene layer for added gloss, slip and clarity, and has a 300% stretch capability. It is FDA approved for direct food contact, and has an anti-fog additive for moisture dissipation during temperature fluctuations. In the preferred embodiment, the film has a width of sixteen inches and is thirteen microns thick.
A label insert mechanism can be provided for inserting a label onto the strip of film as it is advanced to the wrapping station. Further, a film perforating mechanism can be positioned to form small holes in the stretched film before it is gathered and sealed. The holes are formed slightly above the center of the lettuce head, where the stretched film is spaced from the lettuce prior to the film being gathered and sealed, and in the finished package permit the product to be vacuum cooled.
The apparatus of the invention can cycle sixteen times per minute to automatically shrink wrap a head of lettuce with a fifteen inch by fifteen inch web of ultra clear, anti-fogging, highly stretchable film FDA approved for direct contact with the lettuce. Use of the invention would enable a reduction of 21.5% in the number of field workers required, with a concomitant reduction of 38% in labor costs per case, while achieving a 30% increase in the rate of harvester production, with a 37% reduction in the amount of film needed to wrap a head of lettuce. The cost associated with taping the wrapped head of lettuce would also be eliminated, and the final appearance of the wrapped head of lettuce would be greatly improved, with a high gloss, ultra clear film that has anti-fogging properties and is superior to conventional industry standard LDPE lettuce packaging.
The film itself, the film advancing and clamping means, and the film gathering, sealing and severing means are all unique and result in an economical and efficient packaging system which produces a package with superior appearance and performance characteristics.
The foregoing as well as other objects and advantages of the invention will become apparent from the following detailed description when considered in conjunction with the accompanying drawings, wherein like reference characters designate like parts throughout the several views, and wherein:
A conventional lettuce harvesting machine is indicated generally at 10 in
As schematically depicted in
Two film feed grippers 33 and 34 are positioned to the rear of rear clamp 28 at opposite sides of the film for feeding the strip of film forwardly over the opening, and a heated film severing wire 35 is positioned between the rear clamp and the film feed grippers for severing the section of film held over the opening from the strip of film.
Opposed sets of pivoted fingers 36 are supported at the near end of the housing, forward of the opening 26, for receiving and supporting a head of lettuce or other article. The arms are movable into and out of position centered over the opening, and are pivotable to release the lettuce or other article onto the web of film held across the opening.
A ram 37 is supported above the center of the opening and is movable downwardly to engage a head of lettuce placed on the film and to push the lettuce downwardly through the opening, stretching the film to form a bag-like enclosure tightly surrounding the lower hemisphere of the head of lettuce.
Opposed gathering arms 38 and 39 of generally open rectangular configuration are supported below the opening 26 in positions fore and aft of the opening, and are movable toward and away from one another in a direction parallel to the length of film to gather the excess film above the head of lettuce into a generally flattened condition.
A U-channel member 40 is supported at one side of the opening, generally midway between the opposed gathering arms, and a sealing and trimming unit 41 is supported in opposed relationship to the U-channel 40. The sealing unit and U-channel are movable toward and away from one another in a direction transverse to the direction of movement of the gathering arms 38 and 39, for compressing the flattened excess film into a narrow neck immediately above the head of lettuce. A heated sealing element 42 (see
A control panel 43 is mounted adjacent the near or forward end of the apparatus for access by an operator.
Further details of the film advancing and clamping means can be seen with particular reference to
With particular reference to
As soon as the grippers are retracted, the rear clamp 28, side clamps 29 and 30, and center side clamps 31 and 32 all lower onto the film, securely clamping it all around the opening 26. The cut-off wire 35 then lowers onto the film in the space between the rear clamp and the grippers, severing the strip of film at this location. A head of lettuce L is then carried by the pivoted fingers 36 into a centered position over the section of film held over the opening 26, at which time the fingers pivot downwardly to release the head of lettuce onto the film. Ram 37 then lowers onto the head of lettuce, pushing it downwardly against the film and through the opening to a predetermined distance below the opening (typically about 12 inches), stretching the film and partially forming a bag-like enclosure around the lettuce, with the film tightly engaging the lettuce over its lower hemisphere and stretched upwardly therefrom to the clamps. The ram is then withdrawn, and the front, rear and side clamps raise away from the film, releasing it except at the center of the opposite sides of the opening, where the center side clamps remain lowered against the film.
The film gathering, sealing and trimming means then operates, as seen best with reference to
As seen best in
A perforating means 60 for making small holes in the film to facilitate vacuum cooling can be provided, if desired, as shown in
Although particular embodiments of the invention are illustrated and described in detail herein, it is to be understood that various changes and modifications may be made to the invention without departing from the spirit and intent of the invention as defined by the scope of the appended claims.