US2437693A

US2437693A - Heat-sealed valve bag

Info

Publication number: US2437693A
Application number: US548393A
Authority: US
Inventors: Hartman Carl Henry
Original assignee: ST Regis Paper Co
Current assignee: ST Regis Paper Co
Priority date: 1944-08-07
Filing date: 1944-08-07
Publication date: 1948-03-16
Anticipated expiration: 1965-03-16

Description

I March 16, 1948. HARTMAN (2,437,693

v HEAT SEALED VALVE BAG Filed Au 7, 1944 2 Sheets-Sheet. 1

gmimw EARL H. HAHTMAN Much m, 1948. H, HAR N 2,437,693

mm SEALED VALVE BAG Filed Aug. 7,1944 2 Sheets-Sheet 2' kg Iii-5 I Y a L I Q1 h i g I "6 I g7 1' L g1 w $49 l l I l 12+ Patented Mar. 16, 1948 UNITED STATES PATENT OFFICE HEAT-SEALED VALVE BAG Carl Henry Hartman, New Rochelle, N. Y., as-

signor to St. Regis Paper Company, New York, N. Y., a corporation of New York v Application August 7, 1944, Serial No. 548,393

This invention relates to sealing bags so as to make them substantially waterand gastight, or to resist chemical, solvent, or other deleterious action of the contents. More particularly, it relates to sealing bags composed of one or more plies of paper and atleast a partial lining of thermoplastic material. The invention is especially applicable to bags closed by a sewn seam, and may be used readily with valve bags.

In sewed end bags, there has been some difficulty encountered in completely avoiding leaks through the needle holes of the seam, and there is always danger of leakage through improperly closed valves of valve bags. It is the primary ob- Ject of this invention to eliminate or minimize these difilculties. Other objects and features of the invention will appear as the description proceeds.

In the accompanying drawings forming a part of this specification Fig. 1 is a side elevation of a valve bag end to which the invention has been applied.

Fig. 2 is a section on the line 2--2 of Fig. 1 through the seam.

Fig. 3 is a section on the line 33 of Fig. 1, but showing the valve closed after the bag has been filled.

Fig. 4 is a view of a sheet adapted toform a sleeve in a valve, and Fig. 5 is a view of the sheet shown in Fig. 4after portions thereof have been folded.

Fig. 6 is a side elevation of the bag end and of a heat-sealing device during the heat-sealing operation.

Fig. '7 is a section on the line 'l--'i of Fig. 6, and

Fig. 8 is a section on the line 88 of Fig. 6.

In the illustrated embodiment of the invention,

it is applied to a gusseted valve bag.

As illustrated, there is a bag In with closure means II at one end, and provided with gussets i2, an inturned valve I3, and a valve sleeve Id. The bag is shown as having two layers l5 of pa per and an inner layer [6 of thermoplastic material of a heat-sealing nature, preferably having appreciable elasticity. The material sold by the Goodrich Company under the trade name of Koroseal has been employed successfully.

A reinforcing tape I1 is applied over the top of the bag and is sewed to the bag, and may be adhered also. As shown in Fig. 2, the bag end is closed by' a sewed seam I8 which passes through the bag walls andthe reinforcing tape.

.The layer It is heat-sealed along the line of the closure. In the drawings, this sealing is indicated at l9, just below the line of stitches. The

sealing may extend along the line of stitches, but preferably should extend somewhat below also. toprevent the contents of the bag from reaching the needle holes, even if those holes are sealed.

Any suitable heat-sealing layer it may be employed, andthe sealing may be done before, after. or simultaneously with the sewing, although sealing prior to sewing and prior to the application of the reinforcing tape has some advantages. The Koroseal, mentioned above, may be pressed in liquid form onto a sheet of paper, so as'to form a lining adhered to the paper, but is a material which maybe reheated to a point where two layers thereof will coalesce without adhering to an ordinary paper surface, which fact is utilized in the manufacture of a sleeved valve bag.

' In the form of valve shown in Fig. 3, the inturned bag walls at I! have their sealing layer It on their side toward the unturned bag walls. but the edges of a sleeve ll are inserted as at 22 between the inner edges of the valve and the unturned bag wall. The sleeve consists of an inner layer of paper 20 having a sealing layer 2| applied thereto. It will be seen that where the edge of the sleeve is turned over at 22, the paper layer is next to the unturned wall and will; not adhere thereto when heat is applied to coalesce layer 2| with layer it at the inner end of the valve, as indicated at 23 in Fig. 3.

Preferably, the outer end of the sleeve is folded in at 24 so layers 2l-.contact and maybe heat sealed at 25 after the bag has been filled. In forming the sleeve, a sheet may be used like that shown in Figs. 4 and 5. This sheet may be folded along longitudinal line. 28, andthen inserted in the bag. The sheet is shown notched at its corners to provide an outer flap 21, and inner flap 28 and side flaps 29.

Flaps

21 and 29 are first folded to bring their paper sides against the paper of the main sheet, while flap 28 is folded in the opposite direction, as shown in Fig. 5.

Then the sheet is folded about line 26, and the" flap 28 inserted at 22 between" the inner end of the valve and the bag walls, as previously .described. The two flaps 29 are then at the upper edge of the sleeve, with their heat-sealing surfacesin contact. The bag at this stage may be heat-sealed as indicatedin Figs. 6 and '7.

Clamp members 30 may be op rated by lugs 3| in any convenient manner to clamp the end of the bag between them. The clamps extend alone the entire length of the seam, and are shaped to fit the bag end. providing for greaterthickness at the gussets and reduced thickness along the top of the sleeve. A downwardlyeatending proaccuse jection 32 is provided at the inner end of the sleeve and valve. Suitable conductors 33 are provided, properly insulated by members 34 from the clamps, and connected by means not shown to any suitable source of high frequencyalternatin current. By this means, sufllcient heat is generated to seal together layers l6 along line i9, including the ends of the gussets, and where there is a sleeve valve, layer 2! is simultaneously sealed to layer It at the inner end of the valve and fiaps 29 are sealed together along the top of the sleeve.

After the bag end has been sealed in this way, a seam as at l8 may be sewed along the end. Also, as previously indicated, the heat-sealing might take lace after or simultaneously with the sewing. If preferred, the heat-sealing might be accomplished by applying heat by electrical or other means progressively across the bag end,

and while for convenience the description has described the operation as taking place at the upper end of the bag, in practice it is immaterial what position the bag is in during the sealing operation. Omission of the valve, and/or the gussets, merely simplifies the sealing operation, which may be otherwise the same as described above.

After the bag has been filled, the outer end of the sleeve may be sealed by applying heat so as to make the cpntacting surfaces of flaps 21 coalesce, thereby completing the sealing of the bag and rendering it waterand airtight. If the bag is to be used for chemical or other material, the lining material is selected so as to retain the contents without injury to the bag.

Where the bag is closed by a sewed seam, it will be understood that the thread holds the bag walls together. If the inner surfaces coalesce below the seam, there is a tendency for the contents to force these surfaces apart. Where the heat-sealing material is elastic, it stretches enough to put the stress on the thread without forming a leakage opening. Less elasticity is required where the coalescence is directly along the line of stitches, especially where dependence is laced upon the material filling the needle holes.

For some purposes, the bag and could be sufficiently sealed by employing a reinforcing tape with heat-sealing materialbetween the tape and the bag. The heat-sealing may be employed with bags which are left entirely open at the top until filled, or those which are only partly closed at the filling end before filling.

While other heating means might result in sealing the bags, the high frequency electric current is especially suitable for the purpose, since it makes possible a very rapid heating of the heat-sealing material without injury .to paper outside thereof, and makes possible the application of the principle to a multiply bag and to the seam where the bag is gusset folded and so comprises many thicknesses of paper through which heat would be conducted very slowly from ordinary external application.

Where the thickness of the bag walls varies widely, suitable variations maybe made in the insulation between the conductor and the bag wall, as indicated in Fig. 8, or variations may be made in the frequency or voltage of the current, so that the sealing will be accomplished in the same time at all points across the bag, or if preferred, the current may be applied for different intervals at different portions.

While for'simplicity acomplete lining of ther- 4 moplastic material has been described, it will be readily understood that the material need be thermoplastic only where it is to be sealed, and any suitable lining material may be employed at other points.

the valve formed of a sheet of paper having its outer side covered with thermoplastic material, its inner end folded outward and the thermoplastic material thereon being heat-sealed to the ba lining material on the inner end of the valve, the longitudinal edges of the sheet being folded inward and their thermoplastic coatings being heatsealed together along the line of said seam and the lining of said bag being heat-sealed the rest of the way along said seam, and the outer end of the sleeve being inturned whereby it may be heat-sealed after the bag has been filled.

2. A plural ply bag comprising an inner ply of pliable plastic material, a surrounding ply of. paper, closure means for an end of the bag con- 1 structecl and arranged 'with a valve at one corner, such valve having an inturned flap formed of said plies, and a valve sleeve therein which includes an inner ply of paper and an outer ply of pliable plastic material, the plastic material of the bag inner ply and of said sleeve being of a type such that contacting layers thereof will coalesce upon heating, surfaces ofthe plastic material along the inner edges of said fiap being brought into contact and heat-sealed with respect to plastic surfaces along the inner end edges of said sleeve, while leaving a filling opening through the sleeve to the exterior of the bag, and the outer end edges of the sleeve being turned inwardly, thus positioning plastic surfaces thereon for contact and heat-sealing of the outer end of the sleeve after the bag is filled.

3. A plural ply paper bag having an initially flattened tubular body portion with end closure means constructed and arranged with a valveat one corner of the bag, the portions of the bag at the region of said end closure at least, having an inner ply of pliable plastic material, said valve having an inturned fiap formed of said plies, and a valve sleeve therein also initially flattened within the bag, said sleeve including 3, ply of paper having at least on its inner end portions an outer ply of pliable plastic material, said plies of plastic material being of a type which will coalesce upon heating when in contact with each other but will not adhere effectively to paper, the inner end edges of said sleeve being folded over to form a cufi-like portion embracing the inner edges of said fiap, and the surfaces of the plastic material along the inner edges of said flap being heat sealed with respect to plastic surfaces along the foldedover edges of said sleeve, while leaving a filling opening through the sleeve to the exterior of the bag, the valve flap and sleeve therein being left free to be generally flattened up against the inside of the closure when the bag is expanded and filled.

4. A plural ply paper bag having a sewn seam end closure means constructed and arranged with a valve at one corner of the bag and the portions of the bag at the region of said end closure at least, having an inner ply of pliable plastic material, said valve having an inturned flap formed of said plies, and a valve sleeve therein which includes an inner ply of paper and an outer ply of pliable plastic material, said plies of plastic material being of a type which will coalesce upon heating when in contact with each other but will not adhere efiectively to paper, the longitudinal edges of the plastic plies forming said sleeve being folded inwardly of the sleeve and coalesced along a line of juncture to form the sleeve as a tube open at both ends, the opposed inner ply surfaces of the bag being heat sealed together along said closure means, and'the inner end edges oi said sleeve being folded over to form a cuff-like portion embracing the inner edges of said flap, and the surfaces of the plastic material along the inner edges of said flap being heat sealed with respect to plastic surfaces along the folded-over edges of said sleeve, while leaving a filling opening through the'sleeve to the exterior of the bag, the valve flap and sleeve therein being left free to be generally flattened up against; the inside of the closure when the bag is expanded and