Process and machine for wrapping and packaging items in stretchable foil material

Claim 2

A process for wrapping and packaging a tray-like receptacle containing a generally irregularly shaped article in a foil sheet of stretchable plastic material, which receptacle has a flat bottom shallowly recessed from a low, outwardly-curved rim, said process comprising the steps of: a. positioning said receptacle on a support at a wrapping location; b. unreeling a section of a continuous foil web from a storage roll under evenly distributed tensile stress by gripping the leading edge of said foil and translating the foil section to said wrapping location in a direction normal to the leading edge proximate said supported receptacle; c. stretching said foil section by a predetermined amount in at least the dimension transverse to the unreeling direction from locations at opposite sides of said supported receptacle; d. longitudinally holding fast the transversely stretched foil section while severing said section from said storage roll to form a sheet from said foil section; e. bringing said article-containing receptacle into contact with the stretched foil sheet while folding the longitudinally extending edges of the transversely stretched sheet over said rim and onto the bottom surface of said receptacle and simultaneously reducing the transverse tension effected by said stretching in order to maintain the predetermined amount of stretching in said foil; f. folding the leading and trailing edges of said foil sheet over said rim and onto said bottom surface of said receptacle; and g. welding said leading, trailing and longitudinally extending edges to said bottom surface.

Claim 3

The process according to claim 1 wherein step (c) includes clamping said longitudinally extending edges in a state of transverse tension with said foil section oriented substantially horizontal above said supported receptacle; wherein step (e) includes vertically elevating said article-containing receptacle from beneath said sheet to bring said receptacle into contact with said sheet while simultaneously reducing the transverse tension between said longitudinally extending side edges.

Claim 4

The process according to claim 1 wherein step (c) further comprises stretching said foil section in its longitudinal dimension.

Claim 5

The process according to claim 3 wherein the longitudinal stretching of said foil section comprises transversely blocking the unreeling of said foil web at a location upstream of the leading edge of said section while continuing to draw said leading edge in an unreeling direction.

Claim 6

The process of claim 1, wherein said stretching causes an increase of from about 22 to about 30 percent of the initial dimensions of said foil web.

Claim 7

A machine for wrapping and packaging items in sheets of stretchable plastic foil delivered from a storage roll of said material, said machine comprising: a vertically movable lifting plate for supporting an item to be wrapped; operable unreeling means, translatable over a predetermined distance in the delivery direction of said foil, for gripping a transversely extending leading edge of said foil, and selectively unreeling a section of said foil from said storage roll in a downstream to a location above said lifting plate by translating said leading edge over said predetermined distance; a pair of opposed movable clamping means disposed symmetrically along opposite sides of said section of unreeled foil and along opposite sides of said lifting plate for gripping and transversely stretching said section by a predetermined amount; actuable cutting means located downstream of said storage roll and upstream of said opposed clamping means for transversely severing said foil section from said storage roll; actuable braking means disposed downstream of said cutting means and upstream of said opposed clamping means for selectively blocking unreeling of said foil from said storage roll by securing said foil in place; support means integral with said unreeling means; a movable thrusting member; an unloading platform; synchronized drive means, including a drive motor, a drive shaft connected to said motor, and a plurality of cams supported on said drive shaft and conventionally coupled to said unreeling means, said opposed clamping means, said thrusting member, said lifting plate, and said braking means for sequentially: operating said unreeling means; actuating said opposed clamping means to stretch said section by said predetermined amount; actuating said braking means; actuating said cutting means to sever said section from said storage roll; raising said lifting plate with an item to be wrapped supported thereon while gradually releasing the grip by said opposed clamping means to prevent further stretching of said section as said item contacts said section and simultaneously moving said opposed clamping means to a location below the raised item to be wrapped to fold the sides of said foil section under said item; moving said unreeling means to transfer said item onto said support means while folding the leading edge of said foil section under said item; and moving said thrusting member to push said item onto said unloading platform.

Claim 8

A machine for wrapping and packaging items in sheets of stretchable plastic foil delivered from a storage roll of said material, said machine comprising: a vertically movable lifting plate for supporting an item to be wrapped; operable unreeling means, translatable over a predetermined distance in the delivery direction of said foil, for gripping a transversely extending leading edge of said foil, and selectively unreeling a section of said foil from said storage roll in a downstream to a location above said lifting plate by translating said leading edge over said predetermined distance; a pair of opposed movable clamping means disposed symmetrically along opposite sides of said section of unreeled foil and along opposite sides of said lifting plate for gripping and transversely stretching said section by a predetermined amount; actuable cutting means located downstream of said storage roll and upstream of said opposed clamping means for transversely severing said foil section from said storage roll; actuable braking means disposed downstream of said cutting means and upstream of said opposed clamping means for selectively blocking unreeling of said foil from said storage roll by securing said foil in place; support means integral with said unreeling means; a movable thrusting member; an unloading platform; synchronized drive means, including a drive motor, a drive shaft connected to said motor, and a plurality of cams supported on said drive shaft and conventionally coupled to said unreeling means, said opposed clamping means, said thrusting member, said lifting plate, and said braking means for sequentially: operating said unreeling means; actuating said opposed clamping means to stretch said section by said predetermined amount; actuating said braking means; actuating said cutting means to sever said section from said storage roll; raising said lifting plate with an item to be wrapped supported thereon while gradually releasing the grip by said opposed clamping means to prevent further stretching of said section as said item contacts said section and simultaneously moving said opposed clamping means to a location below the raised item to be wrapped to fold the sides of said foil section under said item; moving said unreeling means to transfer said item onto said support means while folding the leading edge of said foil section under said item; and moving said thrusting member to push said item onto said unloading platform.

Claim 9

The machine of claim 6, wherein said unreeling comprises three basic clamps resulting from the combination in the form of an elastic hinge of an extended lower plate with three rectangular upper plates, the two outermost upper plates interacting with a limit stop-release lever, the lower plate being downwardly openable.