Tensionless seal apparatus and method

A machine for packaging compressed products in plastic film without inducing tension in the film of the finished package, said machine comprising:

• upper and lower compression belts for advancing a train of products at a given speed and under compression;
• upper and lower continuous webs of plastic film fed relative to said belts so that the products are sandwiched therebetween;
• means for determining the position of advancing products;
• a carriage, disposed longitudinally movable relative to said belts, for reciprocating, first in an advancing and then a reversing direction, responsive to indication of the trailing edge of an advancing product entering said carriage;
• a pair of generally opposing seal bars, disposed on said carriage and downstream from said product detection means, for controllably closing and forming cross-seals in said films between adjacent products;
• and
• pivoting roller frames, mounted on said carriage and controllably pivoting during said reciprocating thereof so as to cause products within said carriage and still held under compression by said roller frames to be pushed relatively back towards said seal bars during their closing, whereby tensionless seals are formed for products packaged under compression.

A machine for packaging under compression and in tensionless plastic film even relatively heavy or thick products, said machine comprising:

• upper and lower compression conveyors for cooperatively transporting a train of products under compression in a defined forward direction at a predetermined speed;
• respective upper and lower plastic film feed rolls for supplying continuous webs of film which enclose the respective tops and bottoms of products transported by said compression conveyors;
• a pair of side sealer means, disposed along at least a portion of respective sides of said compression conveyors, for sealing the sides of said webs of film as they oppose one another outside side edges of said products;
• reciprocating carriage means, including pivotable roller frames with endless belts entrained therearound, for receiving side-sealed products being discharged from said compression conveyors and maintaining such products under compression while longitudinally controllably reciprocating relative to said compression conveyors;
• product detection means for outputting a detection signal responsive to the trailing edge of advancing products entering said carriage means;
• cross-sealer means, mounted on said carriage means for movement therewith, responsive to said detection signal for closing together the respective upper and lower film webs about the product being packaged, and laterally sealing same along a direction perpendicular to said side seals thereof;
• and
• actuation means, mounted on said carriage means for movement therewith, responsive to said closing of said cross-sealer means for pivoting said roller frames so that the forward edges thereof are moved towards each other while the trailing edges thereof are moved away from each other, whereby normally advancing side-sealed products are drawn back against said cross-sealer means by said belts entrained around said frames, so as to remove tension from said film webs being closed and sealed about said products by operation of said cross-sealer means.

A method for packaging articles in relatively tensionless plastic films, comprising the steps of:

• advancing a plurality of spaced-apart articles, to be separately packaged, in a defined forward direction at a predetermined speed;
• feeding plastic films respectively above and below the articles as they are advanced along such forward direction so that they become sandwiched between such films;
• providing sealing means responsive to passage, of articles thereby for drawing together and laterally sealing the pair of respective films, between adjacent articles to be packaged;
• and
• during operation of said sealing means, urging such articles relatively against said forward direction thereof back towards said sealing means, whereby tension is removed in the pair of films as same are drawn together and sealed about the articles.

A method for packaging compressed articles in plastic film without inducing tension in the film of the finished package, comprising the steps of:

• providing upper and lower compression belts for advancing a train of products at a given speed and under compression;
• providing upper and lower continuous webs of plastic film;
• feeding said webs of film relative said belts so that said products are sandwiched therebetween;
• providing a reciprocatable carriage disposed relatively downstream from said belts for receiving and handling said products therefrom substantially in series;
• providing a product detection device disposed adjacent the entrance of said carriage;
• reciprocating said carriage first in an advancing direction at said given speed and then in a reversing direction, beginning such reciprocating responsive to the detection of the trailing edge of an advancing product entering said carriage;
• providing upper and lower seal bars disposed on said carriage for advancing movement therewith at said given speed, and disposed downstream from said product detection device;
• closing said seal bars to draw together and form lateral cross-seals in said films between adjacent products, responsive to product detection by said device therefor;
• providing pivotable frame members mounted on said carriage;
• and
• controllably pivoting such frame members during reciprocating of said carriage so as to cause products within said carriage to be relatively pushed back towards said seal bars as they close, whereby tensionless seals may be formed for products under compression, even for relatively high or heavy products.