US 3268152 A
Description (OCR text may contain errors)
3, 1966 H. D. SWARTZ 3,268,152
SELF-SEALING VALVE BAG Filed NOV. 27, 1964 3 Sheets-Sheet 1 INVENTOR. HENRY D. SWARTZ ATTORNEYS Aug. 23, 1966 H. D. SWARTZ 3,268,152
SELF-SEALING VALVE BAG Filed Nov. 27, 1964 5 Sheets-Sheet 5 INVENTOR.
HENRY D. SWARTZ ATTORNEYS United States Patent Ofiice 3,268,152 Patented August 23, 1966 3,268,152 SELF-SEALING VALVE BAG Henry D. Swartz, Brooldine, Mass., assignor t Thermoplastic Industries, Inc., Brockton, Mass, a corporation of Massachusetts Filed Nov. 27, 1964, Ser. No. 414,072 8 Claims. (Cl. 22.9-62.5
This invention relates generally to containers of the type that are filled through self-closing valves and more particularly is directed towards a container of the sort constructed at least in part with heat scalable panels and having a flexible self-sealing valve of a heat sealable material attached thereto. This invention is also directed towards a novel method for producing self-sealing containers of the foregoing type in a simple and efficient manner.
In my US. Patent No. 3,089,636, there is disclosed a self-sealing container which, in its principal embodiment, comprises a bag formed from plies of a heat sealable material, such as polyethylene for example, and having attached to one wall thereof a flat sleeve type valve located inwardly of the bag edges and which is adapted to close automatically under pressure. This type of container and valve have been found to be particularly useful in packaging, storing and shipping a wide variety of materials both granular and liquid insofar as the bag is extrmely rugged, inexpensive and seals tightly. In fact, it has been found that the greater the pressure on the bag, as when a number of bags are stacked on a pallet, the greater is the sealing action and this feature makes the bag particularly suitable for stacking a number of bags for storage and shipment.
It is one object of the present invention to provide improvements in self-sealing containers of the sort disclosed in my above patent.
A more specific object of this invention is to provide improvements in self-sealing bags of heat sealable material.
Another object of this invention is to provide a selfsealing container of simple design and one which lends itself to quick and easy assembly by mass production techniques.
A further object of this invention is to provide a novel method for fabricating self-sealing containers.
More particularly, this invention features a self-sealing container comprising a container and valve assembly wherein the container is formed with at least one wall of heat sealable material to which is bonded a sleeve also of heat scalable material. The sleeve is mounted flat against the wall and is formed from two or more plies of flexible heat sealable material, the ply adjacent the container wall being formed with an opening in register with an opening in the container wall and through which the container is filled. The sleeve plies are characterized by different heat sealing points with the ply bonded to the container wall having a lower softening point than the opposing sleeve ply. In this fashion a heating die may be employed against the outer surface of the container walls with the sleeve placed in register with the die to simultaneously bond the low temperature sleeve ply to the container wall and form the opening therein without affecting the opposing sleeve ply.
This invention also features a novel method of assembling a self-sealing container comprising the steps of marginally bonding two plies of flexible heat sealable material of different heat softening characteristics to form a flexible sleeve, placing the sleeve within a partly formed container with the sleeve ply of lower softening characteristics flat against a heat scalable wall of the container, applying heat from the outer surface of the container Wall and over a predetermined design in register with the sleeve underlying said wall for a sufficient period and at a suflicient temperature and pressure to thermally bond the low-temperature sleeve ply to the panel wall and simultaneously form a common opening therein without altering the opposing sleeve ply, and finally sealing the remaining portion of said container.
However, these and other features of the invention along with further objects and advantages thereof, will become more fully apparent from the following etailed description of preferred embodiments of the invention, with reference being made to the accompanying drawings, in which:
FIG. 1 is a view in perspective of a self-sealing container made according to the invention,
FIG. 2 is a cross-sectional detailed view taken along the line 22 of FIG. 1,
FIG. 3 is a top plan view of a valve element prior to assembly,
FIG. 4 is a sectional view in side elevation of the FIG. 3 valve,
FIG. 5 is a view in perspective showing a gusseted flexible tube used in fabricating a flexible valve bag,
FIG. 6 is a top plan view showing the valve sleeve element assembled in the FIG. 5 tube prior to the heat sealmg operation,
FIG. 7 is a view in perspective of a heat sealing device employed in the invention,
FIG. 8 is a sectional view in side elevation showing an apparatus for simultaneously attaching the valve element and sealing the tube ends,
FIG. 9 is a view in perspective showing a modification of the invention,
FIG. 10 is a view in perspective showing another modification of the invention,
FIG. 11 is a view in perspective showing a further modification of the invention,
FIG. 12 is a sectional view of the FIG. 11 modification,
FIG. 13 is a detail sectional view of a still further modification.
FIG. 14 is a perspective view partly broken of still another modification, and
FIG. 15 is a perspective view of a still further modification of the invention.
Referring now to the drawings, the reference character 10 generally indicates a bag which may be of single or multiwall construction and typically is formed from a heat scalable material such as sheet polyethylene or the like. The bag itself preferably is formed from tubular material which may be gusseted at 12 and its end sealed along heat sealing lines 14 and 16 to form a closed container.
A self-sealing valve 18 is mounted to the inner face of one wall 19 of the bag 10 and typically is located in the upper right hand corner as shown to permit filling of the bag with conventional automatic loading machines. Quite obviously, the valve could be located at any other suitable position depending upon particular applications. In any event, the valve is attached to the inner face of one wall of the bag along a delta shaped sealing line 20. A curved slit opening 22 is formed in the bag wall and through the valve with a heat sealing line 24 extending thereabout. The inner free end of the valve 18 is unattached as at 25 to provide a loose flap which is adapted to fold over against itself once the bag has been filled to form a tight seal which positively prevents escape of the bag contents.
As best shown in FIGS. 3 and 4 the valve element 18 prior to assembly is essentially a sleeve or pocket formed by bonding two or more plies 26 and 28, which may be rectangular or other useful shapes, along three marginal edges by heat seal line 36, so that an end 32 is open.
In the practice of this invention the valve plies 26 and 28 are made of materials having dilferent heat sealing characteristics with the ply 26 which underlies the bag wall 19 being formed from a material having a relatively low temperature heat sealing characteristic and generally similar to the heat sealing characteristics of the bag wall. The valve ply 28, on the other hand, is formed from a material having a relatively high temperature heat sealing characteristic. With this arrangement, the valve element may be quickly and easily mounted and the bag completed in a minimum number of steps. In practice, the blank valve element 18, as shown in FIGS. 3 and 4, is inserted in the open ended tube 11 and positioned in the desired mounting position in the manner suggested in FIG. 6. The low-temperature ply 26 of the valve element should be facing against the tube wall 19 to which the valve element will be bonded. When the valve element 18 is assembled in the manner described the tube 11 and valve element are placed on a flat support 34 with the valve element 18 in register with a heating die 36 and sealing dies 38 disposed oppositely the ends of the tube 11. The die 36, as best shown in FIG. 7, is provided with relatively Wide heating elements 40 corresponding to the outline of the heat sealing lines 20 and 24 shown best in FIG. 1. The die is also provided with a relatively narrow heating element 42 corresponding to the shape of the slit opening 22 shown in FIG. 1. The sealing dies 38 are provided with straight line relatively wide heating elements 44 which span the width of the tube 11 to make the heat sealing lines 14 and 16 which seal the bag ends.
When the die 36 comes down against the outer surface of the tube wall opposite the valve element, it is held in position long enough to form the heat seal lines 20 and .24 which attach the valve element to the tube Wall. At the same time, the heating element 42 cuts through the tube wall 19 and the ply 26 to form the valve opening. Simultaneously the heating elements 38 seal the ends of the tube to form the bag. When the dies are withdrawn the bag is completed with the valve in its proper assembled position.
The function of the high temperature valve ply 28 is to prevent the heat of the die 36 from causing the ply 28 to bond itself to either the opposite wall of the bag or to the ply 26 to which it has been joined along the previously formed sealing lines 30. In this fashion the valve is assembled in the proper position and the valve itself is attached only by means of the ply 26. Thus the bag may be filled by inserting a nozzle in the slit opening 22 and injecting the fill in the bag. Once the bag is filled the valve plies 26 and 28 will close against one another and both will lay flat at least in part against the bag Wall. Very frequently the free end of the valve will fold back to form an even more effective seal in the manner described in my above patent.
Referring now more particularly to FIG. of the drawings, there is illustrated a modification of the invention and in this embodiment a container such as a flexible plastic bag 46 is provided with a bellows type valve 48 attached to the inner face of one wall thereof. This valve comprises two plies 50 and 52 with the ply 50 being of a material having a relatively low softening point and bonded to the bag wall along heat sealing lines 54 and 56. An opening 58 is formed through the bag wall in register with the valve opening through the ply 50 and the opening is sealed around its periphery by the heat seal line 56.
The ply 50' is folded to define gussets 60 with the edges being marginally bonded to the ply 52 along seal line 62. It will be understood that the ply 52 is formed from a material having a relatively high softening point so that when a heating die is brought down against the outer surface of the bag wall oppositely the prepositioned valve element 48 the valve will be bonded to the bag wall only by the ply 58 since the ply 52 serves as an insulator for the opposite wall of the bag and also, since its sealing characteristics are different from those of the ply 50, is will not 'be heat sealed either to the ply St) or to the front wall of the bag.
It will be understood that the valve opens up as a bel lows when the bag is filled through the opening 58 and, once filled, the interior pressure will cause the bellows valve 48 to close with the ply 52 being pressed fiat against the ply 50 and completely sealing the opening 58. This type of valve bag is particularly Well adapted for use with a rigid supporting container such as a corrugated carton 53 as shown in FIG. 14. This carton is formed with a prepunched filler opening 55 which registers with the valve opening 58.
Referring now more particularly to FIGS. 11 and 1 2, there is illustrated another modification of the invention and in this embodiment a multi-wall bag 64 is provided with a self-sealing valve 66 such as that illustrated in FIG. 10. The bag may be gusseted as suggested in FIG. 11 or the sides may be conventional in shape. In any event, the bag is of multi-wall construction having an inner ply 68 and an outer ply 70. Both plies are formed with a number of small perforations 72 and 74 arranged in spaced rows with the perforations 72 in the outer ply being arranged in rows that are offset from the perforations 74 in the inner ply 68. In this fashion, the perforations will permit the free escape of air entrapped within the bag. This is particularly important when filling the bags by automatic loading machines since considerable pressure may build up within the bag as the fill is injected unless some means is provided to relieve the air. With the air relieving arrangement described above, the air will pass out through the openings 74, between the bag walls and then out to the atmosphere through the openings 72. As the bag fills up, presusre within the bag caused by the fill will close off the openings by forcing the two plies against one another. This prevents bag leakage and yet oflers a convenient means to relieve air. This consideration makes possible faster filling of the bag without danger of building up excessive air pressure within the bag. These bags may also be made with walls comprising three, four or more plies as suggested in FIG. 13. As before, the perforations in one ply will be offset from those in adjacent ply. It will be understood that a definite control over air escapement is achieved by additional plies in the bag wall.
Referring now more particularly to FIG. 9, there is illustrated a modification of the invention and in this embodiment a container such as a flexible bag 76 of heat sealable material and similar to the bag 10 in the principal embodiment is provided with a self-closing valve 78 also similar to the valve 18 described in connection with FIG. 1. In this instance, the valve opening 80 may be fully sealed to provide a positive barrier to the entrance of vermin or the like by means of a pressure sensitive adhesive flap 82. This flap is provided With a protective stratum 84 which covers the adhesive coated free end of the flap until ready for use. As shown, the flap is prepositioned with one end of the flap attached to the outer surface of the bag wall immediately adjacent the valve opening 80 and the stratum 84 has a free hanging tab 86 which an operator may grasp once the bag is to be sealed. It will be understood that once the bag is filled, it is necessary for the operator only to pull the tab 86 to the left as viewed in FIG. 1 to peel oif the protective stratum from the adhesive covered flap. In doing so, he may also pull it against the surface of the bag so that in one motion the pressure sensitive adhesive will be exposed and the flap will be pressed down over the opening.
As illustrated in FIG. 15 valve bags of the foregoing type may be connected end-to-end by a perforated tear line 90 and wrapped into a roll 92. With this arrangement the bags may be unwound from the roll past a filling unit 94 having multiple nozzles 96 for filling several bags simultaneously. The bags may be separated by tearing them apart along tear line 90.
By way of specific example and without limiting the generality of foregoing disclosure, in one particularly advantageous form of the embodiment of FIGS. 1 to 8: bag 10 and valve ply 26 both are composed of low density polyethylene ranging in thickness from 0.001 to 0.006 mil, in specific gravity from 0.910 to 0.925 and in softening point from 250 to less than 325 F.; and valve ply 28 is composed of high density polyethylene ranging in thickness from 0.001 to 0.006 mil, in specific gravity from 0.941 to 0.965 and in softening point from greater than 325 to 400 F. Thus, a selected sealing temperature of 350 F. causes welding of valve ply 26 to bag 10 but no welding of valve ply 28 to bag 10.
While the invention has been described with particular reference to the illustrated embodiments, it will be understood that numerous modifications thereto will appear to those skilled in the art. Accordingly, the above description and accompanying drawings should be taken as illustrative of the invention and not in a limiting sense.
Having thus described the invention, what I claim and desire to obtain by Letters Patent of the United States is:
1. A self-sealing container, comprising (a) walls forming a container,
(b) at least one of said walls being formed from a plastic material having one heat sealing characteristic,
(c) said one wall being formed with an opening therein,
((1) a valve bonded to the inner face of said wall and across said opening,
(e) said valve comprising a pair of flexible plastic panels joined about portions of their margins,
(f) one of said panels having a heat sealing characteristic similar to that of said wall,
(g) said one panel being formed with an opening in register with said wall opening and being bonded thereto at least about said opening,
(h) the other of said panels being formed from a material having a heat sealing characteristic higher than that of said wall or said other panel.
2. A self-sealing container according to claim 1 wherein said walls are flexible.
3. A self-sealing container according to claim 1 wherein said valve panels form an open-ended sleeve, said open end being free from said wall.
4. A self-sealing container according to claim 3 wherein said sleeve is gusseted.
5. A self-sealing container according to claim 1 wherein said container is a flexible tube sealed at both ends.
6. A self-sealing container, comprising (a) walls forming a container,
(b) at least one of said walls being formed with an opening therein,
(c) a valve bonded to the inner face of said wall and across said opening,
(d) said valve comprising a pair of flexible plastic panels joined about portions of their margins,
(e) one of said panels being formed with an opening in register with said wall opening and being bonded thereto at least about said opening,
(f) a flexible tab attached at one end to the outer face of said wall adjacent said opening, and
(g) a stratum of pressure sensitive adhesive coating one side of the free end of said tab whereby said free end may be pressed over said opening and attached to said wall to seal said opening.
'7. A self-sealing container according to claim 6 including a protective ply detachably covering said adhesive coated side and adapted to be removed prior to sealing said opening.
8. A self-sealing container, comprising (a) planar walls of uniformly thick flexible heat sealable material connected to define a bag,
(b) a valve attached to said bag,
(0) each of said walls being fabricated with at least two plies of said material,
(d) each of said plies being formed with a plurality of spaced perforations,
(e) the perforations in one ply being offset from the perforations in another ply to permit entrained air to escape from said bag While said bag is being filled and to seal said bag when said bag is filled by said plies being forced into face to face contact over their full extent.
References Cited by the Examiner UNITED STATES PATENTS 2,593,328 4/1952 Meaker 229- 3,089,636 5/1963 Swartz 229-625 3,116,002 12/1963 Crawford et al. 229-17 3,180,558 4/1965 Quaadgrass et a1. 229-625 JGSEPH R. LECLAIR, Primary Examiner. D. M. BOCKENEK, Assistant Examiner.