US2320326A - Manufacture of heat sealed bags - Google Patents

Description

May 25, 1943.

T. M. AVERY MANUFACTURE OF HEAT SEALED BAGS Filed April 29, 1940 -'-I-r-r Patented May 25, 1943 MANUFACTURE OF HEAT SEALED BAGS True M. Avery, Glens Falls, N. Y., assignor to Union Bag & Paper Corporation, Hudson Falls, N. Y., a corporation of New Jersey Application April 29, 1940, Serial No. 332,388

18 Claims.

' together, thereby obviating the use of an adhesive and its attendant objections. 1 The invention is applicable more particularly to the manufacture of bags of the so-called square" type having pleats or tucks along their side edges which open or expand and the bottoms of which assume a square or rectangular form when the bags are filled, and the more particular object of the invention is to provide a method of heat sealing the inner surfaces of the lower comers of the front and back walls of the bag to the opposed inner surfaces of the adjacent pleats whereby, when the bag isfllled, the material is excluded from the triangular pockets formed at the corners of the bag bottom as the pleats are opened or expanded, thus allowing the bottom of the filled bag to assume a flat form.

A further object of the invention is to provide a novel method of heat sealing such inner surfaces of bags which is applicable to the manfacture of bags rapidly on bag machines of the kinds commonly employed commercially in the making of bags.

In the accompanying drawing:

Figure 1 is a diagrammatic view in side elevation of one form of bag machine to which the present invention is applicable and with the aid of which the method may be carried out;

Figure 2 is a top plan view of the apparatus shown in Fig. 1;

Figure 3 is a view of a length of a bag tube showing the steps of the method;

Figure 4 is a perspective view, showing dia- I grammatically the step of heat sealing at one edge of the bag tube; Figureb is a perspective view of a completed bag made in accordance with the improved method and Figure 6 is a view of a severed end of the tube, indicating the lines on which the tube is heat sealed.

Similar parts are designated by the same reference characters in the several views.

The method according to the present inventionis applicable generally to the manufacture of bags from a heat seala'ble strip such, for example,

the pleats as paper coated on one or both surfaces with a waxy or other heat scalable substance, or regenerated cellulose such as transparent Cellophane of the well known waterproof variety coated on one or both surfaces with a substance which is heat sealable, or thin rubber sheeting such for example as transparent Pliofilm" which is vulcanizable or fusible by heat and thereby heat sealable.

The material from which the bags are to be made is conveniently fed in the form of a continuous sheet or strip 9 from a supply roll Ill preferably to a machine which forms the strip into a pleated bag tube, it being led in the present instance over a guide roller H and then beneath a former I2 supported in fixed position in the machine. As the strip travels along the former, its side edges are folded inwardly by suitable me'ans such, for example, as a pair of folding blades l3 and 14 such as those commonly used in bag machines, the strip being thus formed into a tube andits longitudinal edges being thus brought into overlapping relation to form a longitudinal seam l5. Also, as the tube is being formed over the former, its sides are tucked inwardly, as by a pair of tucking blades I6 and H, to form infolded pleats in its sides, one of these pleats comprising folds l8 and I9 adjacent and connected to the top and bottom walls 20 and 2| respectively of the tube, and the other pleat comprising folds 22 and 23 adjacent and connected to the top and bottom walls 20 and 2| respectively of the tube. The strip may be drawn continuously from the supply roll and over the former by continuously driven draw rolls 24 such as those commonly used in bag machines and which engage the edges of the bag tube after it passes from the former. After the bag tube passes the draw rolls, it passes between a pair of continuously revolving delivery rolls 25, and the bag/tube is cut off beyond the delivery rolls, by knives 26 or other suitable severing means, into bag sections of the desired length. The parts just described-may be similar to those commonly used in well known forms of be machines.

material which is heated, preferably by an electric heating unit, and presses on the seam while the latter is supported on thetop of the former. thereby sealing this scam along the line 3|.

Before the bag tube passes between the draw rolls and near the end of the former, the upper inner surfaces of the upper folds l3 and 22 of the pleats are heat sealed against the inner Surface of the top wall of the tube and the lower inner surfaces of the lower folds I9 and 23 of the pleats are sealed against the inner surface of the bottom wall 2| of the tube. This heat sealing operation is performed, while the tube is advancing, preferably by upper and lower pairs of metal or other suitable blades 32 and 33 which are revoluble in unison so that the upper and lower blades simultaneously engage the upper and lower sides of the tube, and are heated preferably by electric heating units, these heated blades pressing between them the edges of the tube to substantially the width of the pleats in its respective edges and operating to heat seal or vulcanize the inner surfaces of the top and bottom walls of the tube to the opposed inner surfaces of the adjacent folds of the pleats. The sealing blades extend helically, with those of each pair having a pitch.

in opposite directions and arranged to register with those of the other pair, and they heat seal or vulcanize the inner surface of the top wall 20 of the tube to the opposed inner surfaces of the folds l8 and 22 of the pleats and the inner surface of the bottom wall 2| of the tube to the opposed inner surfaces of the folds l9 and 23 of the pleats along oppositely inclined lines 34 and which will diverge upwardly from the bottom of the completed bag and outwardly at angles of substantially degrees to the outer fold lines of the pleats, as shown in Fig. 5, thereby closing off from the interior of the bag the triangular corners formed in the bag bottom when opened or expanded, and thus preventing entrance of material into these corners during the filling of the bag. When the bags are made of rubber sheeting such'as Pliofilm or of paper or Cellophane which is coated and heat scalable on both sides, heat resisting means such as the tucking blades l6 and I! are arranged to extend into the pleats in the regions of operation of the. sealing blades 32 and 33 to avoid heat sealing or vulcanizing together the outer surfaces of the pleats, thus leaving the pleats free to expand when the bottom of the bag is opened during filling, but when the bags are made of a strip or sheet which is heat sealable only on one surface arranged inside of the tube, such heat resisting means may be omitted and the sealing blades-32 an'd33 may press the top and bottom walls of the tube and the interposed pleats directly together to effect the heat sealing, as the outer surfaces of the pleats will not, in that case, be heat sealed to one another.

The bottom seal which closes the bag bottom,

is made by heat sealing or vulcanlzing the top and bottom of the tube together and to the adjacent folds of the pleats on a line 36 extending at a right angle entirely across the tubeand adjacent to or intersecting the inner ends of the pleat- sealing lines 34 and 35, which will ordinarily be sufllcient, but if desired the bottom seal may include an additional sealing line 36. This bottom sealing operation may be performed after the bag has been severed from the tube and immediately prior to its delivery, but preferably and as shown, this sealing operation is performed on the tube before it is severed, by a revoluble sealing blade 31 of metalor other suitable material which is heated preferably by an electric heating unit and compresses the tube between it and an opposed roller 38 which supports the tube while this sealing blade is performing its heat scaling or vulcanizing operation thereon along the line 36, and an additional similarly heated revoluble blade 3! may be employed to seal the bag bottom along the line 36 also, if additional strength for the bag bottom seal is desired. When the bags are made of Pliofilm or other material which is heat sealable on both sides, the bottom seal will not only seal the inner surfaces of the front and back walls of the bag to each other and to the inner surfaces of the adjacent folds of the pleats, but will also seal together directly the outer surfaces of the pleats along the line of the bottom seal, thus increasing the strength of the bottom of the bag.

The knives or other severing means cut off the bag section from the tube beyond but adjacent to the bottom seal, and the portion of the bag beyond the bottom seal may project therefrom, as shown in Fig. 5, as the security of the bottom seal renders folding thereof unnecessary. and the resulting fin left projecting beneath the bottom seal is not objectionable as it will lie flatwise against the flat bottom of the bag when the latter is filled.

The method provided by the present invention enables the inner surfaces of the lower corners of the front and back walls of bags made from a scalable strip to be sealed to the inner opposed surfaces of the adjacent pleats, and also the longitudinal seam and the bottom of the bag to be sealed, without requiring the application of an adhesive the use of which would not only be objectionable, due to its tendency to stick to parts of the machine and thus interfere with the operation thereof, but is also unsatisfactory due to the ineffectiveness of the usual adhesives to secure heat sealable materials of the kinds hereinbefore referred to. As it is unnecessary to apply adhesive, the sealing together of the interior surfaces of the bag may be effected readily after the strip of bag material has been formed into a tube, and the method is applicable to the manufacture of bags upon bag machines of the usual and well known forms without reducing the speed of o eration of such machines.

I claim as my invention:

1. The method of making pleated bags, comprising forming a heat scalable sheet into a tube having pleats in its edges and between its opposite walls, and heat sealing the inner surfaces of said walls of the tube to the inner surfaces of the adjacent pleats on lines which diverge outwardly to the edges of said walls while holding the outer surfaces of the pleats in the regions of said lines in non-sealing relation.

2. The method of making pleated bags, comprising forming a heat sealable sheet into a tube having pleats in its edges and between its opposite walls, and heatsealing the inner surfaces of said walls of the tube to the inner surfaces of the adjacent pleats on lines which diverge outwardly to the edges of said walls while the outer surfaces of the pleats are shielded from sealing together on said lines.

3. The method of making pleated bags, comprising forming a heat sealable strip into a tube having pleats in its edges and between its opposite walls, and heat sealing the inner surfaces of said walls of the tube to the inner surfaces of the adjacent pleats on lines which diverge outwardly to the edges of said walls while holding the outer surfaces of the pleats in the regions of said lines in separated relation.

4. The method of'making pleated bags, comprising forming a heat sealable strip into a tube having pleats in its edges and between its opposite walls, heat sealing the inner surfaces of said walls of the tube to the inner surfaces of the adjacent pleats on lines which diverge outwardly to the edges of said walls while the .outer surfaces of the pleats are shielded from sealing together on said lines, and sealing said walls of the tube to one another and to the adjacent folds of the pleats on a line extending transversely of the tube adjacent to said diverging lines.

5. The method of making pleated bags, comprising forming a sheet of material heat sealable on both sides into a tube having pleats in its edges and between its opposite walls, heat sealing the inner surfaces of said walls of the tube to the inner surfaces of the adjacent pleats on lines which diverge outwardly to the edges of said walls while holding the outer surfaces of the pleats in the regions of said lines in separated relation, heat sealing the inner surfaces of said walls of the tube to one another and to the opposed inner surfaces of the adjacent folds of the pleats and the outer surfaces of the pleats to one another on a line extending transversely of the tube adj acent to said diverging lines, and severing the tube along a line extending transversely of the tube adjacent to but beyond said transverse heat sealing line.

6. The method of making pleated bags, comprising the steps of forming and folding a sheet of material heat sealable on both sides to overlap its edges and form a pleated tube the inner and outer surfaces of which are heat sealable, heat sealing said overlappededges to form a longitudinal seam in the tube, heat sealing the inner surfaces of opposite walls of the tube to the inner 'surfaces of the adjacent folds of the pleats on lines which diverge outwardly to the edges of said walls while holding the outer surfaces of the pleats in non-sealing relation along said lines,

heat sealing the inner surfaces of said walls to one another and to the inner surfaces of the adjacent folds of the pleats on a line extending transversely across the tube adjacent to the inner ends of said diverging lines, and severing the tube along a line extending transversely across the tube adjacent to but beyond said transverse heat sealing line.

7. Apparatus for making heat sealed pleated bags, comprising means including a former for forming a heat sealable strip into a tube having pleats in its edges, heated sealing means operative upon the pleated edges of the tube to heat seal the inner surfaces of the pleats to the inner surfaces of the adjacent walls of the tube on lines which diverge outwardly to the edges of. said walls, and means for shielding the outer surfaces of the pleats from sealing together on said lines.

8. Apparatus for making heat sealed pleated bags, comprising means including a former for forming a heat sealable strip into a tube having pleats in its edges, and opposed pairs of heated helical blades operative upon the pleated edges of the tube to heat seal the inner surfaces of the pleats to the inner surfaces of the adjacent walls of the tube.

iii

9. Apparatus for making heat sealed pleated bags, comprising means including a former for forming a heat sealable strip into a tube having pleats in its edges, and opposed pairs of rotatable heated helical blades operativeupon the pleated edges of the tube, the blades of each pair being of reverse pitch, said blades operating to heat seal faces of the adjacent walls of the tube on outwardly diverging lines.

10; Apparatus for making heat sealed pleated bags, comprising means including a former for forming a heat sealable strip into a tube having pleats in its edges, heated members spaced laterally of the former and operative upon the respective pleated edges of the tube to heat seal the inner surfaces of the pleats to the inner surfaces of the adjacent walls of the tube on outwardly diverging lines, and a heated blade operated on and across the width of the tube beyond said members to heat seal the inner surfaces of the opposing walls of the tube to one another and to the opposing inner surfaces of the adjacent folds of the pleats.

11. Apparatus for making heat sealed pleated bags, comprising means including a. former for forming a heat sealable strip into a. tube having pleats in its edges, heated members beyond the former and operative upon the pleated edges of the tube to heat'seal the inner surfaces of the pleats to the inner surfaces of the adjacent walls of the tube, and means for holding the outer surfaces of the pleats opposite to said members in separated relation to prevent heat sealing of said outer surfaces.

12. Apparatus for making heat sealed pleated bags, comprising means including a former for forming a heat sealable strip into a tube having a longitudinal seam and pleats in its edges, a heated seam sealing member operative on said longitudinal seam to heat seal it, laterally spaced heated pleat sealing members operative upon the pleated edges of the tube to heat seal the inner surfaces of the pleats to the inner surfaces of the respectively adjacent opposed walls of the tube on outwardly diverging lines, and a heated bottom sealing member operative on the tube across its width to heat seal the inner surfaces of the opposed walls of the tube to one another and to the opposing inner surfaces of the pleats.

13. Apparatus for making heat sealed pleated bags, comprising means including a former for forming a heat sealable strip into a tube having pleats in its edges, heated members operative upon the pleated edges of the tube to heat seal the inner surfaces of the pleatsto the inner surfaces of the respectively adjacent opposed walls of the tube, shielding means in the regions of operation of said members for holding the outer surfaces of the pleats in non-sealing relation, a heated bottom sealing member beyond said shielding means and operative on the tube across its width to heat seal the inner surfaces of the opposed walls of the tube to one another and to the-opposing inner surfaces of the pleats, and severing means operative to sever the tube.

14. The method of making pleated bags, comprising forming a heat sealable strip into a tube the inner surface of which is heat sealable throughout its area and having pleats in its edges and between its opposite walls, and applying heat and pressure to the pleated edges of the tube on definite lines which diverge outwardly to the edges of said walls to thereby heat seal the inner surfaces of said walls of the tube to the inner surfaces of the adjacent pleats on said lines and to leave adjacent areas of said heat sealable surfaces unsealed.

15. The method of making pleated bags, com- [prising forming a sheet, at least one surface of the inner surfaces of the pleats to the inner surwhich throughout its area is heat sealable, into a tube having said heat sealable surface on its inner side and pleats in its edges between its opposite walls, and applying heat and pressure to the pleated edges of the tube on definite lines which diverge outwardly to the edges of said walls to thereby heat seal the inner surfaces of said walls of the tube to the inner surfaces of the adjacent pleats on said lines, leaving the outer surfaces of the pleats unsealed on said lines.

16. The method of making pleated bags, comprising forming a sheet, at least one surface of which is heat sealable, into .a tube having said heat sealable surface on its inner side and having pleats in its edges and between its opposite walls, applying heat and pressure to the tube adjacent to its edges to substantially the width of the respectivepleats and on lines which diverge outand applying heat and pressure to the opposite wardly to the edges of the opposite walls of the tube to thereby heat seal the inner surfaces of said walls of the tube to the inner surfaces of the adjacent pleats on said lines but leaving the outer heat sealing the inner surfaces of said opposite walls of the tube to one another and to the opposed inner surfaces of the adjacent folds of the pleats on a line extending transversely of the tube adjacent to said diverging lines.

17. The method of making pleated bags, comprising forming a strip, which is heat sealable on both sides, into' a tube having heat sealable inner and outer surfaces and pleats in its edges and between its opposite walls, applying heat and pressure to the opposite walls of the tube adjacent to their edges to substantially the width of the respective pleats on lines which diverge outwardly to the edges of said walls to thereby heat seal the inner surfaces of said walls of the pleats to the inner surfaces of the adjacent pleats on said lines while the outer surfaces of the pleats in the regions of said lines are in non-sealing relation,

walls of the tube on a line extending transversely across the tube adjacent to the inner ends of said diverging lines while the outer surfaces of the pleats are in sealing relation along said transverse line to heat seal the inner surfaces of the opposite walls of the tube to one another and to the op-' posed inner surfaces ofthe pleats on said transverse line and to heat seal the outer surfaces of the pleats to one another on said transverse line,

18. The method of making pleated bags, com prising forming a sheet of material heat sealable on both sides into a tube having heat sealable inner and outer surfaces and pleats in its edges and between its opposite walls, applying heat and pressure to said opposite walls of the tube adjacent to their edges to substantially the width of the pleats on lines which diverge outwardly to the edges of said walls while maintaining the outer surfaces of the pleats on said lines in non-sealing relation to thereby heat seal the inner surfaces of said opposite walls of thetube to the inner surfaces of the adjacent pleats on said lines while leaving the outer surfaces of the pleats unsealed on said lines, applying heat and pressure to said opposed walls of the tube along a line extending transversely across the tube adjacent to the inner ends of said diverging lines while the outer surfaces of the pleats along said transverse line are in sealing relation to heat seal the inner surfaces of said opposite walls of the tube to one another and to the opposed inner surfaces of the adjacent folds of the pleats on said transverse line and to heat seal the outer surfaces of the pleats to one another on said transverse line,'and severing the tube along a line extending transversely across the tube adjacent to said transverse heat sealing line.

' TRUE M. AVERY.

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