JPH0788940A - Thin-walled bag,production device therefor, and production thereof - Google Patents

Abstract

PURPOSE: To eliminate or substantially relax a defect in conventional technique by forming an inexpensive, reusable and seamless bag from a single thermoplastic film material and providing a reinforcing end edge to the periphery of the opening part of the bag. CONSTITUTION: A reusable and seamless thermoplastic bag 10 has a thick-walled reinforced upper end edge 12 and a main body portion almost uniform in thickness. In an apparatus and method for producing this bag 10, a continuous web of a thermoplastic film is thermoformed while the thickness of the end edge of the bag is kept almost equal to that of the supplied film to obtain the seamless bag 10 uniform in thickness. A circular hollow clamp fixes the end edge of the bag 10 during the formation of the bag 10. The bag 10 ready to form is passed through the region adjacent to the clamp and demarcated by the circular radiation heating element positioned in concentric relation to the clamp to be stretched. A cooling fan is provided so as to be adjacent to the heating element to cool the bag after molding.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a seamless thermoplastic bag and an apparatus and method for making the bag.
More specifically, the present invention defines a plastic bag having reinforced or thickened edges extending around the opening of the bag, and more specifically the present invention defines the body of the bag. A thin seamless bag having a uniform wall thickness, wherein the thick edge portions can maintain the thickness of the original thermoplastic sheet forming the bag.

[0002]

BACKGROUND OF THE INVENTION Plastic bags used to store items such as cosmetics and other consumables are
Devices well known in the art and for mass producing these plastic bags are also well known. Generally, the sizes of these bags range from small sandwich type bags to large disposable garbage and grass clippings bags. These bags are provided with a reinforced edge about their opening to allow the use of various devices to secure them in the open or closed condition. Mechanisms and equipment for making these bags are also well known in the art, as are the various techniques utilized in making these articles. Although the main advantage of this type of bag is its light weight and disposable nature, the construction of these bags generally requires that a seam be formed along at least one edge of the bag, which is why During manufacture, an additional heat-sealing step is required, resulting in weakened parts that are susceptible to breakage and liquid content can leak from the bag.

There are various types of known bags, and various types of devices and methods for making such bags. These methods and devices include various techniques for making bags, and the bags formed are generally similar in shape, but each suffers from disadvantages during manufacture and use of these bags. In the case of, these bags have different structural features that are inconvenient for the user when using these bags.

US Pat. No. 3,175,027 discloses a method of manufacturing a plastic film cap or cover each having an elastic edge formed by heating the edge of a circular plastic film. This method causes the edges to shrink, resulting in a thicker edge that is ten times thicker than the rest of the film. With the contraction of the edge, the edge is blown with a circular film into a cap-shaped product, and the edge contracted by the elastic property of the plastic material forming the cap can be repeatedly stretched and retracted. It has a certain elasticity. The cap-shaped product formed according to this patent is used as a storage bag made of plastic, as the thick edge shrinks, causing distortion of other material parts, especially when heating the edge. Would be unsuitable for U.S. Pat. No. 2,760,233 relates to a method of forming a plastic sheet material on perhaps three different sides. A sheet is formed by polymerizing one or more synthetic resin materials. The sheet is then shaped by heated fluid pressure to finally produce a product for use as a special aircraft plastic laminate. The product is such that the outer edge of the polymeric material is firmly gripped within the pressure forming device and the heated fluid softens the material, which is shaped when pressure is applied. This particular patent discloses a method of forming or shaping a rigid plastic article for use as a high strength material in an aircraft by applying fluid pressure.

US Pat. No. 3,149,017 relates to the manufacture of large polyethylene balloons used in weather observations.
Each balloon is formed from a flat preform having heat sealed or fused edges. The preform body is irradiated with heat, and then the balloon is shaped by the heat blowing method. The result is a balloon with a very large size longitudinal seam.

US Pat. No. 2,377,946 discloses a method and apparatus for forming a thermoplastic article of substantially uniform thickness from a thermoplastic sheet. The sheet of thermoplastic material is clamped across the opening of the negative pressure mold to provide non-uniform infrared irradiation, in which the mold heats the plastic material before vacuum forming the product. The edges of the material are heated to a higher temperature than other parts or regions of the material to compensate for the reduced stretch in the central part of the film and, after shaping of the shaped article, over the entire surface of the product to a uniform thickness. To be able to maintain.

[0007]

The manufacturing devices disclosed in the prior art, and the thermoplastic products formed by these devices, have a number of significant adverse effects on the performance of the formed products and the manufacturing costs of these molded products. There is a drawback. Some prior art publications disclose products such as bags having at least one seam, where the seam is weaker in strength than other parts of the body of the product due to its nature. . Seams generally require reinforcement to hold the edges of the material together and prevent its cracking. Moreover, the formation of the seam generally requires additional steps during manufacturing as the seam is formed by an additional heat sealing step. Such heat sealing, on the other hand, entails shrinkage of the surrounding material, resulting in a less visible appearance of the surrounding plastic material being pulled towards the heat sealing.

Furthermore, prior art bags and similar molded products that can be formed seamlessly have areas of weak strength in the body of the bag due to non-uniform thickness regions during the molding of the bag. It has the drawback. These areas are
When the product is put in the bag, stretching and breakage easily occur.
Furthermore, for bags or products of uniform thickness, these areas must be reinforced, and areas such as near the opening of the bag require more strength during handling by the user. These bags usually require the use of additional plastic material to reinforce these areas,
It is expensive. Therefore, an extra amount of plastic is required for each bag, resulting in a bag that is expensive to manufacture.

[0009]

SUMMARY OF THE INVENTION The present invention forms an inexpensive, reusable and seamless bag from a single sheet of thermoplastic film material, with a reinforced edge around the opening of the bag. This eliminates or substantially alleviates the drawbacks of the prior art.

In accordance with one aspect of the invention, a thin walled bag constructed of a thermoplastic film material comprising a seamless body having a closed end and an open end of the body. And a thicker upper edge, the edge having a wall thickness of about 1.5 to 10 times the thickness of the body.

According to another feature of the invention, a thin walled bag composed of a thermoplastic film material comprising:
A seamless body having two closed ends, and a thicker upper edge including one open end of the body, the thicker upper edge of the thermoplastic film material prior to forming the bag. A bag is provided having a thickness that is approximately equal to the original thickness.

Such a seamless bag has a substantially uniform thickness throughout the entire bag. The reinforced upper edge can accommodate a structure for opening and closing the bag. By its nature, the seamless bag is endowed with special durability and integrity and can be manufactured at low cost. The thermoplastic film material used to mold the bag is transparent and it is desirable to maintain that state even after molding the bag. The bag may be sized for storing consumables, such as cosmetics, for example, in a volume of focus to gallons. Due to the durability of the bag, the bag is reusable and the reinforced edges facilitate opening and closing of the bag without damaging it.

The apparatus for producing a bag and the method for producing a bag according to the present invention enable a production process which can be performed in an efficient and inexpensive manner.

Thus, according to another feature of the invention,
A method of manufacturing a seamless bag formed from a thermoplastic film material, the method comprising securing a circular sheet of the thermoplastic film material in hollow circular clamping means surrounding an outer peripheral edge of the sheet, the bag comprising: At the same time as heating the periphery of the outer surface, thermoforming the sheet to form the bag, and after the thermoforming and heating steps, cooling the bag to lower and stabilize the temperature of the bag, This allows the bag to maintain a thickness along its edges that is equal to the original thickness of the sheet.

According to yet another feature of the invention, an apparatus for producing a seamless bag from a thermoplastic film material, the means for feeding a sheet of said thermoplastic material,
Clamping means having a hollow circular opening for fixing the sheet, further comprising a cutting means for cutting the sheet into a circular film, and a thermoforming means for thermoforming the bag from the sheet, Heating means for heating the bag by radiant heat during thermoforming, the heating means being positioned in a circular shape adjacent to the clamping means about the outer surface of the bag, and adjacent to the heating means. Cooling means for positioning and cooling the bag during thermoforming, such that the bag is formed with an upper edge having a thickness greater than or equal to the thickness of the body of the bag. A device is provided.

The present invention provides a reusable, seamless bag that is inexpensive and lightweight, yet durable due to its substantially uniform thickness.

The bag according to the present invention provides a reinforced edge without increasing the amount of plastic material used, while providing a seamless bag having a substantially uniform thickness throughout the body of the bag. This eliminates the problems associated with prior art bags and thermoformed products. An apparatus for producing such bags maintains the initial thickness of the sheet or film portion forming the upper edge bag surrounding the opening of the bag, while maintaining a uniform thickness throughout the body of the bag. Is guaranteed. Such a bag has a simple structure and can be manufactured relatively inexpensively, which effectively forms a strong, reliable and reusable bag. Of course, the bag must be relatively inexpensive to manufacture, but if the user uses the bag to store a consumable item, the bag will have a sufficient life to allow reuse. Such reusability is
This is the first consideration.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring in detail to the accompanying drawings in which like or identical components are designated by like reference numerals throughout the several views, FIG. 1 shows a reusable seamless thermoplastic according to the present invention. Bag 10 is shown. The bag 1
0 is formed by a conventional blow blow molding method or a vacuum forming method, and has a thick wall portion at the upper edge 12 of the opening 14 of the bag, whereby the bag 10 is reinforced and the bag is opened and closed. Means are provided for. The body 16 of the bag 10 is completely seamless and has a substantially uniform thickness, which increases the stability and strength of the bag. The upper edge 12 has a thickness that can be about 10 times greater than the thickness of the bag body 16, and further, the edge 12 has substantially the same thickness as the original web of thermoplastic film forming the bag. Have During thermoforming, the edge 12 maintains a thickness that is substantially the same as the thermoplastic web of material forming the bag while the body 16 is stretched and molded during thermoforming, so that its thickness is substantially the same. Fall to. The thickness ratio between the edges and the body of the bag is in the range of 10 to 1.5, and in accordance with the preferred embodiment the edges maintain a thickness of about 0.25 mm (10 mils) while the bag maintains The body is thinned to about 0.038 mm (1.5 mil).

2a and 2b, the upper edge 12 of the bag 10 is shown as a cutaway sectional view taken along line 2-2 of FIG. The embodiment of Figure 2a shows an upper edge 12 that is substantially thicker than the body 16, while Figure 2b illustrates the addition of stiffening ribs or bands 18 to assist in opening and closing the bag 10. . Band 18 may be a stainless steel strip secured to edge 12 by heat, adhesive or the like, or may include a device such as a drawstring or closure tie. Further, the band 18 may include additional plastic material reinforcing strips or may include grooves or protrusions used to close the opening 14 of the bag 10 in a lock-tight manner. In FIG.
A device for forming a bag according to the invention is illustrated. A continuous roll 20 of thermoplastic film material, such as polyethylene or polypropylene, is fed from a supply reel 22 to form a seamless bag 10 that is advanced through a thermoforming device 26. After forming the bag 10, a winding reel 24 for winding the roll film 20 is provided. The thermoforming device 26 not only comprises a conventional vacuum forming device or a blow molding device, but also a mechanism for maintaining a uniform thickness of the bag being formed. The mechanism comprises a hollow circular clamp 28 which holds and holds the roll film 20 during the thermoforming process, and a heater and cooling fan device operable during the thermoforming process. The clamp 28 can be constructed of any suitable material, but after the thermoforming process is complete, the roll film 2
It is desirable that the material does not adhere to zero. Clamp 2
As shown in FIG. 4, a roll film 2 is provided with a cutting device 30 to cut the formed bag after the thermoforming process.
It is desirable to be able to remove from zero. Adjacent to and within the clamp 28 is a thermoforming device 26.
A circular radiant heating element 32 concentrically positioned with is further provided. The heating element 32 is positioned on the clamp 28 side in the direction in which the bag is formed. This arrangement provides maximum heating around the edges of the film, where the film has the thickest wall thickness and therefore requires less heating in the center of the film. A suitable air circulator 34, formed of a fan or blower, is positioned adjacent to the heating element 32 but remote from the clamp 28. The radiant heating element 32 preferably comprises a resistive coil element, but can also comprise any radiant heater, such as a quartz heater.

FIG. 4 illustrates the bag 10 being formed in the thermoforming apparatus 26, where the film 2 is formed.
The 0 is carried into the device and secured in the clamp 28. Once the bag is formed, the bag is heated during expansion, expansion and stretching within the region defined by the circular radiant heating element 32. When the bag is stretched, the film is cooled by the air supplied from the air circulator 34 as indicated at 36. The device 34 comprises a heating element 3
Located adjacent to 2 and away from clamp 28. Cooling air contributes to the stability of the bag during the molding process, as described below. After thermoforming, the bag formed with the cutting device 30 is cut, and the bag is released from the clamp 28. The film then advances in the direction of arrow A, allowing continuous bag formation.

During operation, supply roll 22 feeds thermoplastic film 20 into thermoforming device 26. One thermoforming device 2
Although only 6 is shown, several thermoforming devices can be provided in series or side by side so that multiple bags can be manufactured simultaneously. The film 20 advances through a clamp 28, which is circular hollow and the bag 10 can be formed by conventional vacuum forming or blow molding methods. However, when forming the bag, the bag extends in the region formed by the circular heating element 32, which causes the bag to be heated along its edges, where the film has its thickest wall thickness. It becomes a tendency. The center of the film, which is stretched and thus thicker than the rest of the bag, is maintained below the temperature generated at the edges by the heating element 32. The conventional thermoforming method has a drawback that the circular sheet portion being formed is thin near the center thereof. This is because the film stretches at its maximum at this position.

The present invention solves this problem by heating the bag being insufflated by a circular radiant heating element 32 positioned near the clamp as best shown in FIG. The heating element 32 heats the bag to an elevated temperature near the edges where the film tends to be thickest, so that the central portion of the bag receives less radiant heat after the start of the blowing process. The film is cooled during stretching by air from an air circulator 34, which usually comprises a fan or duct type device, which stabilizes the bag as it stretches. The thinner sections of the film are cooled by the more rapid air flow, which lowers the temperature of the sections, making the film stiffer and more stretch resistant. Such a feature tends to compensate for variations in the film, resulting in
The bag comes to have a substantially more uniform thickness.

The ratio of the clamp 28 itself to the film 20 secured within the clamp 28 is relatively low compared to the other parts of the bag that are being formed, so that the film in that part has its own temperature. Substantially maintain the original thickness. Thus, the formed opening of the bag is formed with a "thick portion" that resists breakage and allows the accuracy of the closure means (such as the connection 18) to secure the bag.

[Brief description of drawings]

FIG. 1 is a perspective view of a seamless thermoplastic bag according to the present invention.

2a is a cutaway view of two embodiments of the upper edge of the bag taken along line 2-2 of FIG. 2b is a cutaway view of two embodiments of the upper edge of the bag taken along line 2-2 of FIG.

FIG. 3 is a diagrammatic front view of an embodiment of the device according to the invention for forming a bag of the type according to FIG.

4 is a partially cutaway perspective view of a bag being formed in the apparatus of FIG.

[Explanation of symbols]

 10: Bag 12: Upper edge 14: Opening 16: Bag body 18: Band 20: Roll film 22: Supply roll 24: Take-up reel 26: Thermoforming device 28: Clamp 30: Cutting device 32: Radiant heating device 34 : Air circulation device

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location B29L 22:00 (72) Inventor Gordon Vincent Sharps, Genie, 14450, New York, USA Fairport , Grand View Drive 106

Claims (22)

[Claims] 1. A thin walled bag formed from a thermoplastic film material, comprising a seamless body having a thickened upper edge including one closed end and one open end, said seamless body comprising: The upper edge is substantially 1.5 to 1 of the thickness of the body.
A thin bag having a thickness of 0 times. 2. The bag of claim 1 wherein the body has a thickness of substantially 0.038 mm (1.5 mils). 3. The bag of claim 2 wherein the body has a thickness of substantially 0.25 mm (10 mils). 4. Bag according to any one of claims 1, 2 or 3, characterized in that said upper edge comprises means for sealingly closing said bag. 5. Bag according to claim 4, characterized in that the upper edge comprises a phase lock closure and / or a flexible metal band. 6. A bag according to claim 1, wherein the thickness of the upper edge is substantially equal to the original thickness of the thermoplastic film material before the formation of the bag. Characteristic bag. 7. The bag according to claim 1, wherein the upper edge has sufficient rigidity to maintain the bag in an open or closed position. 8. A bag according to claim 1, wherein the bag has a volume in the range of 1 pint to 1 gallon. 9. A bag according to any one of claims 1 to 8, characterized in that the thermoplastic material is selected from the group consisting of polypropylene and polyethylene. 10. A method of making a seamless bag of thermoplastic film material, the method comprising securing a circular sheet of thermoplastic film material in a hollow circular clamping means including a peripheral edge of the sheet. While heating the bag around its outer surface,
Thermoforming the sheet to form the bag, cooling and stabilizing the bag after the thermoforming and heating steps are completed, and the bag has an initial thickness of the sheet along the peripheral edge; Providing an equal thickness can be maintained. 11. The method of claim 10, wherein the thermoforming step comprises the step of thermally blow molding the sheet through the hollow circular clamping means at a central location on the circular sheet. how to. 12. The method of claim 10, wherein the thermoforming step comprises thermovacuum forming the bag. 13. A method according to claim 10, 11 or 12 wherein the heating step is through a circular radiant heating means positioned adjacent the clamping means about the outer surface of the bag. A method comprising heating the thermoformed bag with radiant heat. 14. A method according to any one of claims 10 to 13 wherein the cooling step comprises exposing the bag to a cooling atmosphere. 15. The method of claim 14, wherein the cooling step comprises circulating air around the bag. 16. An apparatus for producing a seamless bag from a thermoplastic film material, comprising: a feeding means for feeding a sheet of the thermoplastic material; and a clamping means having a hollow circular hole for fixing the sheet, Clamping means having a cutting means for cutting the sheet into a circular film, thermoforming means for thermoforming the bag from the sheet, and heating means for heating the bag by radiant heat during thermoforming, the thermoforming means comprising: A heating means positioned adjacent to the clamping means in a circular shape about the outer surface and a heating means positioned adjacent to the heating means to cool the bag during molding, thereby providing a thicker thickness than the body of the bag. Cooling means to allow the bag to be formed having an upper peripheral edge of the sash. 17. The apparatus of claim 16 wherein said thermoforming means comprises a thermal blow molding apparatus for blow molding said bag. 18. The apparatus of claim 16 wherein the thermoforming means comprises a thermovacuum forming apparatus for vacuum forming the bag. 19. An apparatus according to any one of claims 16, 17 or 18, wherein the heating means concentrically surrounds the bag during thermoforming, and the heating means during thermoforming,
An apparatus comprising a resistive heating element for heating the bag by radiant heat. 20. The apparatus according to claim 16, 17, 18 or 19, wherein the heating means is a quartz type heater. 21. Apparatus according to any of claims 16 to 20, characterized in that said cooling means comprises at least one fan for cooling said thermoformed bag. 22. A thin walled bag of thermoplastic film material having a thicker upper edge enclosing one closed end and one open end, the thicker upper edge comprising:
A bag characterized by having a thickness substantially equal to the initial thickness of the thermoplastic film material prior to forming the bag.